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diff --git a/.gitignore b/.gitignore
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--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+HANDOFF.md
diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 100644
index 0000000..9d4cd5f
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1,153 @@
+# sbo-dockerbuild
+
+Docker-based toolchain for test-building [SlackBuilds.org (SBo)](https://slackbuilds.org)
+packages on Slackware, on both `-current` and `15.0`, in throwaway containers.
+
+Extracted from the `.extras/` dir of the **sbo-slackbuilds** package repo (danix's
+SBo maintenance mirror) once it grew from a helper into a standalone tool. Git
+history starts fresh here; the original 41-commit log is preserved in
+[HISTORY.md](HISTORY.md) (those hashes refer to sbo-slackbuilds, not this repo).
+
+## What this repo is (and is not)
+
+This is the **tooling**, not packages. It builds and consumes docker images to
+verify that a SlackBuild still builds; it does not itself contain SlackBuilds.
+The packages live in the maintenance repo (sbo-slackbuilds) and other repos.
+
+Two cooperating tools, one shared set of images:
+
+- **`test-build`** — verify a single SlackBuild builds cleanly in a container.
+- **`image-builder/`** — build the images `test-build` consumes.
+
+## Layout
+
+```
+test-build                 the test-build tool (single bash script)
+install.sh                 copy test-build into ~/bin (BINDIR= to override)
+test-logic.sh              pure-logic self-check for test-build (no docker)
+test-build-config.example  copy to ~/.config/sbo-testbuild/config and edit
+overrides.example          current-vs-stable dep overrides (optional)
+image-builder/             bootstrap.sh, build-full-image.sh,
+                           build-sbo-testbuild.sh, lib.sh, config,
+                           test-image-builder.sh, README
+docs/specs, docs/plans     design specs and implementation plans
+```
+
+Everything is at the repo root (flat), not under `.extras/` — that nesting was a
+sbo-slackbuilds convention and does not apply here.
+
+## test-build
+
+Resolves and builds a SlackBuild in a disposable Slackware container, then lints
+it. The **target** is the local SlackBuild under edit; its **dependencies** come
+from a configured SBo tree. These are two different sources — do not conflate
+them (an earlier bug resolved the target from the tree, testing the published
+version instead of the edit).
+
+### Target resolution (`resolve_target_dir`)
+
+Repo-agnostic, driven by where you are:
+
+- a **path** (absolute, `./x`, or containing `/`): that directory
+- a **bare name**: `./<name>/` under CWD, else CWD itself if it *is* `<name>/`
+
+So `cd pkgdir && test-build <name>`, `test-build /path/to/pkg`, and
+`test-build ./pkg` all work.
+
+### Dependency resolution
+
+Deps are resolved from the SBo tree in the config (`SBO_TREE_CURRENT` /
+`SBO_TREE_STABLE`), topologically sorted, cycle-checked. A dep is satisfied by:
+
+1. building it from the tree (recursively), or
+2. `installed_in_base` — already present in the full-install image (queried once
+   per run from the image's `/var/log/packages`), or
+3. an override (see below).
+
+Deps build first and are cached; the target always rebuilds (that is the test).
+
+### current-vs-stable overrides
+
+`~/.config/sbo-testbuild/overrides` (see `overrides.example`), applied **only on
+-current** (15.0 is the SBo baseline). Verbs:
+
+- `drop: <dep>` — a 15.0-only SBo dep whose payload the -current base already
+  ships (e.g. `rust-opt`, `google-go-lang`, `cmake-opt`, `llvm-opt`,
+  `python3-installer`, `python3-build`). Satisfied at resolution: not built, not
+  UNMET.
+- `rename: <old> -> <new>` — dep renamed on -current.
+- `fetch: <prog>` — dep removed from the -current tree; built via `sbopkg` in
+  the container.
+
+### The build container
+
+One `docker run --rm -i` per package (the `-i` is required — without it `bash -s`
+gets no stdin and the heredoc is silently discarded). Inside, as root:
+installs already-built deps, sources `/etc/profile.d/*.sh` (so dep-provided env
+like google-go-lang's `GOROOT`/`PATH` is live in the non-login shell), builds the
+SlackBuild, `installpkg`s it, and runs `sbopkglint` **in-container** (it shells
+out to sudo, which only works as root here; never lint on the host). The host
+reads a `LINT-CLEAN`/`LINT-FINDINGS` marker from the log.
+
+### Dep cache
+
+Host dir (`PKG_CACHE`), namespaced `<variant>-<image-digest>/`. An image rebuild
+changes the digest and self-invalidates the cache. Each run prunes superseded
+digests **of the same variant only**, so a `--current` run does not wipe the
+`15.0` cache (both live caches survive; testing both trees back-to-back reuses
+built deps). Only **deps** are cached, never the target.
+
+### Flags
+
+`--stable` (15.0), `--dry-run`, `--yes`, `--no-cache`, `--keep` (copy the built
+target `.txz` to `<data>/kept/` so it can be installed on the host, e.g. to
+regenerate post-install artifacts), `--no-color`.
+
+## image-builder
+
+Three chained scripts build the images, each self-gated so an unchanged night is
+a cheap no-op:
+
+- `bootstrap.sh` → `sbo-base:{ver}` FROM scratch (gated on the mirror's
+  `ChangeLog.txt` hash)
+- `build-full-image.sh` → `sbo-full:{ver}` all series (gated on base digest;
+  `--force` prunes the build cache first)
+- `build-sbo-testbuild.sh` → `sbo-testbuild:{ver}` + sbopkg + maintainer-tools
+  (gated on full digest + tools `.txz` hash)
+
+All settings in `image-builder/config`. Full setup (NFS mirror mounts, LAN
+registry, prebuilt pkgs, cron) is in `image-builder/README`.
+
+**Main-loop gotcha:** each script runs its `build_variant` in an `if ! (...)`
+condition, which suppresses `set -e` inside the subshell. So `docker build` /
+`docker push` failures are caught with **explicit** `if ! ...; return 1` checks,
+not by relying on `set -e`. Keep that pattern when editing.
+
+## Testing
+
+Pure-logic self-checks, no docker, no network:
+
+```bash
+bash test-logic.sh                       # test-build resolver/overrides/cache
+bash image-builder/test-image-builder.sh # image-builder lib.sh logic
+```
+
+Non-trivial logic changes get a check here. The docker build path itself is
+verified by running `test-build` against a real image.
+
+## Conventions
+
+- Plain bash, single-file scripts where practical, minimal dependencies.
+- `set -euo pipefail` in executables; guard `set -e` around subshell conditions
+  (see the image-builder gotcha).
+- GPLv2-only. Every source file carries a short GPL header notice.
+- No em dashes in prose.
+
+## Deployment
+
+The image-builder scripts run on the docker host VM (`docker.noland.dnx`,
+reached via the `docker` SSH host alias, root login), deployed under
+`/opt/sbo-testbuild/image-builder/`. A nightly cron rebuilds both variants after
+the repo syncs. Treat the VM as outward-facing: confirm before deploying, and
+inspect a target before overwriting it. After editing a script here, sync it to
+the VM so the cron runs the current version.
diff --git a/HISTORY.md b/HISTORY.md
new file mode 100644
index 0000000..8e12890
--- /dev/null
+++ b/HISTORY.md
@@ -0,0 +1,54 @@
+# History
+
+This project began as a side-project inside the **sbo-slackbuilds** repository
+(danix's SlackBuilds.org maintenance mirror), under `.extras/`. It grew from a
+throwaway docker test-build helper into a structured, self-maintaining toolchain,
+so it was extracted here to be developed on its own.
+
+Git history starts fresh in this repo. The 41 commits below are the original
+development history from sbo-slackbuilds, preserved here as a record. The hashes
+refer to the sbo-slackbuilds repository, not this one.
+
+## Original commits (from sbo-slackbuilds, oldest first)
+
+- `b4c286e` 2026-07-13 — docs: test-build design spec; refine CLAUDE.md purpose and docker workflow
+- `1e42a7f` 2026-07-13 — docs: test-build implementation plan
+- `eb74944` 2026-07-13 — test-build: scaffold script + self-check
+- `1a39e22` 2026-07-13 — test-build: config, arg parsing, version selection
+- `b828163` 2026-07-13 — test-build: port SBo lookup + dependency resolver
+- `3680234` 2026-07-13 — test-build: current-vs-stable override engine
+- `5d1fb3a` 2026-07-13 — test-build: port dep cache, namespaced by image digest
+- `f4dff4e` 2026-07-13 — test-build: port BLOCKED-BY-DEP propagation
+- `44f0338` 2026-07-13 — test-build: container build step (build_one via docker)
+- `4a3d6a6` 2026-07-13 — test-build: run_target orchestration + summary + confirm
+- `7c7e549` 2026-07-13 — test-build: wire main, image-presence check, target lookup
+- `11153a8` 2026-07-13 — test-build: fix empty-order corruption when all deps dropped
+- `71b58e1` 2026-07-13 — test-build: document installed_in_base deferral
+- `d9cd1ad` 2026-07-13 — image-builder: add design spec
+- `4db7f46` 2026-07-13 — image-builder: add implementation plan
+- `b844135` 2026-07-13 — image-builder: config + lib.sh helpers
+- `8b4c556` 2026-07-13 — image-builder: curl -sS in fetch for http error diagnostics
+- `3e79c1b` 2026-07-13 — image-builder: lib.sh self-check
+- `b4f19b7` 2026-07-13 — image-builder: bootstrap.sh base image from NAS
+- `b954189` 2026-07-13 — image-builder: bootstrap.sh cleanup trap on EXIT not RETURN
+- `88f399e` 2026-07-13 — image-builder: build-full-image.sh
+- `160ab1f` 2026-07-13 — image-builder: build-sbo-testbuild.sh
+- `0b42333` 2026-07-13 — image-builder: guard FULL_DIGEST recompute against set -e abort
+- `26674aa` 2026-07-13 — image-builder: per-variant isolation, non-zero exit on failure
+- `bb67cd4` 2026-07-13 — image-builder: README with VM setup checklist
+- `7363f45` 2026-07-13 — image-builder: mark scripts executable
+- `e513a3e` 2026-07-13 — image-builder: require_mount in changelog gate so unmounted NAS fails loud
+- `f273077` 2026-07-13 — image-builder: accept any Slackware pkg extension (*.t?z) not just .txz
+- `416ea5d` 2026-07-13 — image-builder: fix false GPG-update warning from SIGPIPE on yes pipe
+- `e887d1e` 2026-07-13 — image-builder: feed full build from LAN NFS mirror over HTTP, fix GPG verify
+- `5e93772` 2026-07-14 — test-build: implement installed_in_base from image package db
+- `d839dd4` 2026-07-14 — test-build: make drop: satisfy a dep at resolution time
+- `be7880b` 2026-07-14 — test-build: fix container stdin and move lint in-container
+- `3a99bb5` 2026-07-14 — test-build: auto-pull the image from the LAN registry when missing
+- `7df4fdf` 2026-07-14 — image-builder: README cron matches deployed 06:00/06:20/08:00 schedule
+- `78db185` 2026-07-14 — image-builder: cron gates both variants, add 15.0, drop --force
+- `e4edbf2` 2026-07-14 — image-builder: cron moved to 03:00/05:00 (trees now sync 01:00/02:00)
+- `e129f08` 2026-07-14 — test-build: target the local SlackBuild (CWD/path), deps from the tree
+- `2b75214` 2026-07-14 — image-builder: catch build/push failures, prune cache on --force
+- `b50ad87` 2026-07-14 — test-build: variant-namespace the dep cache and prune stale digests
+- `4cf9fe4` 2026-07-14 — test-build: add --keep to save the built target package
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..9efa6fb
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,338 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
+
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+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, the commands you use may
+be called something other than `show w' and `show c'; they could even be
+mouse-clicks or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Moe Ghoul>, 1 April 1989
+  Moe Ghoul, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..c52d4d2
--- /dev/null
+++ b/README.md
@@ -0,0 +1,85 @@
+# sbo-dockerbuild
+
+Docker-based toolchain for test-building SlackBuilds.org (SBo) packages on
+Slackware, on both `-current` and `15.0`, without touching a real system.
+
+Two tools that share the same set of images:
+
+- **`test-build`** — verify a SlackBuild (the one you are editing, wherever it
+  lives) builds cleanly in a throwaway container. Resolves and builds its SBo
+  deps from a configured tree, caches built deps per image digest, lints the
+  target with `sbopkglint`, and reports per-package status.
+- **`image-builder/`** — build the images `test-build` consumes
+  (`sbo-base` → `sbo-full` → `sbo-testbuild`, per Slackware version) from a
+  mirror of the Slackware package trees, pushed to a LAN registry.
+
+This started as a helper under `.extras/` in the **sbo-slackbuilds** package
+repository and was extracted here to be maintained on its own. See
+[HISTORY.md](HISTORY.md) for the original development log.
+
+## Layout
+
+```
+test-build                 the test-build tool
+test-logic.sh              pure-logic self-check for test-build (no docker)
+test-build-config.example  copy to ~/.config/sbo-testbuild/config and edit
+overrides.example          current-vs-stable dep overrides (optional)
+image-builder/             the image-build scripts + their self-check
+docs/specs, docs/plans     design specs and implementation plans
+```
+
+## Install
+
+Copy the `test-build` CLI into `~/bin` (on your `$PATH`):
+
+```bash
+./install.sh                     # -> ~/bin/test-build
+BINDIR=/usr/local/bin ./install.sh
+./install.sh --uninstall
+```
+
+It copies the file, so re-run after editing `test-build`. The `image-builder/`
+scripts are not installed; they run on the docker host from their own checkout.
+
+## Quick start
+
+Test-build a package you are editing (from its dir, or by path):
+
+```bash
+cd some-slackbuild-dir && test-build <name>        # -current
+test-build --stable <name>                         # 15.0
+test-build --keep <name>                           # also keep the built .txz
+```
+
+Build the images (on the docker host; see `image-builder/README`):
+
+```bash
+cd image-builder
+./bootstrap.sh           --version current --force
+./build-full-image.sh    --version current --force
+./build-sbo-testbuild.sh --version current --force
+```
+
+## Requirements
+
+- Docker with a reachable LAN registry for the built images.
+- A local mirror of the Slackware package tree(s) for the image build, and a
+  checkout of the SBo tree(s) for dependency resolution.
+- `sbo-maintainer-tools` (baked into the images for `sbopkglint`).
+
+See the specs under `docs/specs/` for the full design.
+
+## License
+
+Released under the GNU General Public License, version 2 (v2 only). See
+[LICENSE](LICENSE). Each source file carries a short header notice.
+
+Copyright (C) 2026 Danilo M. &lt;danix@danix.xyz&gt;
+
+## Development Approach
+
+This project is developed using AI-assisted tools. Code is generated with the help of AI based on human-provided specifications, design decisions, and iterative feedback.
+
+All contributions are reviewed, tested, and curated by the maintainer before being included in the codebase. AI is used as a productivity and exploration tool, while human oversight remains central to all decisions.
+
+The goal is to combine the flexibility of AI-assisted development with standard open-source practices such as transparency, review, and accountability.
diff --git a/docs/plans/2026-07-13-docker-test-build.md b/docs/plans/2026-07-13-docker-test-build.md
new file mode 100644
index 0000000..6195de9
--- /dev/null
+++ b/docs/plans/2026-07-13-docker-test-build.md
@@ -0,0 +1,1579 @@
+# Docker test-build Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** A single bash script `.extras/test-build` that verifies an already-published SBo package still builds cleanly on `-current` or `15.0` inside a throwaway docker container, resolving and building its SBo deps from the local tree, caching built deps per image digest, and reporting per-package status + lint.
+
+**Architecture:** Host resolves the dep tree from the local SBo tree (logic ported from `sbo-batch-test`), applies current-vs-stable override rules, prints the build order and confirms, then runs one `docker run --rm` that builds deps (or installs them from a host cache) and the target, lints the target, and streams results back. The container is the disposable environment (no overlayfs). Images are built by a separate job and consumed by tag.
+
+**Tech Stack:** Bash, docker, Slackware `installpkg`/`makepkg`, `sbo-maintainer-tools` (`sbopkglint`). Self-check is plain bash (`test-logic.sh`), no framework.
+
+---
+
+## Reference source
+
+Port from `/home/danix/Programming/GIT/sbo-batch-tester/sbo-batch-test`. These
+functions are lifted with minimal change (they are pure or host-side):
+
+- `find_slackbuild_dir`, `category_of`, `pkg_key`, `read_requires`,
+  `version_of`, `installed_in_base`
+- resolver: `_resolve_visit`, `resolve_target`, globals `RESOLVED_ORDER`,
+  `UNMET`, `CYCLES`, `HAS_README`, `_vstate`
+- cache: `_cache_ver_of`, `cache_decision`, `cache_path`, `cache_store`,
+  `cache_label`
+- `depends_on_failed`, `print_summary`, `lint_pkg`, `init_color`
+- self-check patterns from
+  `/home/danix/Programming/GIT/sbo-batch-tester/test-logic.sh`
+
+What is NEW or CHANGED in this repo:
+
+- overlay lifecycle (`setup_overlay`/`teardown_overlay`/`cleanup_trap`) is
+  REMOVED. The container replaces it.
+- `build_one` is rewritten to run its build steps via `docker run` instead of
+  `chroot`.
+- image + tree selection by version (`--stable`).
+- override engine (drop / rename / fetch) applied to the resolved order.
+- cache namespaced by image digest.
+- config keys differ (see Task 2).
+
+## File Structure
+
+- Create: `/home/danix/Programming/GIT/sbo-slackbuilds/.extras/test-build`
+  (the script, executable)
+- Create:
+  `/home/danix/Programming/GIT/sbo-slackbuilds/.extras/test-build-config.example`
+  (config template)
+- Create:
+  `/home/danix/Programming/GIT/sbo-slackbuilds/.extras/overrides.example`
+  (override-rules template)
+- Create:
+  `/home/danix/Programming/GIT/sbo-slackbuilds/.extras/test-logic.sh`
+  (self-check)
+
+All work happens in `.extras/`. Run every command from the repo root
+`/home/danix/Programming/GIT/sbo-slackbuilds`.
+
+Note on committing: this repo has a pre-commit hook that runs `sbolint` on
+staged packages. `.extras/` files are not packages, but to be safe every
+commit in this plan uses `SBOLINT=no git commit ...`. Commits are GPG-signed
+automatically; do not disable signing.
+
+---
+
+## Task 1: Scaffold the script + smoke self-check
+
+**Files:**
+- Create: `.extras/test-build`
+- Create: `.extras/test-logic.sh`
+
+- [ ] **Step 1: Write the failing self-check**
+
+Create `.extras/test-logic.sh`:
+
+```bash
+#!/bin/bash
+#
+# Logic self-check for .extras/test-build. Covers the pure, host-side parts:
+# dependency resolution, override application, unknown-dep -> UNMET, cache
+# decisions, and BLOCKED-BY-DEP propagation. No docker.
+#
+# Run: bash .extras/test-logic.sh
+#
+set -uo pipefail
+
+SCRIPT="$(dirname "$0")/test-build"
+T=$(mktemp -d)
+BASE_DB=$(mktemp -d); mkdir -p "$BASE_DB"
+
+cleanup() { rm -rf "$T" "$BASE_DB"; }
+trap cleanup EXIT
+
+# Source the script without running main(). Sourcing re-runs the CONFIG block,
+# so set test vars AFTER the source.
+LIB=$(mktemp)
+sed '/^main "\$@"$/d' "$SCRIPT" > "$LIB"
+# shellcheck disable=SC1090
+source "$LIB" 2>/dev/null
+rm -f "$LIB"
+
+pass=0; fail=0
+ok()  { echo "  ok: $1"; ((pass++)); return 0; }
+bad() { echo "  FAIL: $1"; ((fail++)); return 0; }
+
+# Placeholder assertion so this file runs before any logic exists.
+ok "script sources without executing main"
+
+echo
+echo "$pass passed, $fail failed"
+[[ $fail -eq 0 ]] || exit 1
+echo "ALL LOGIC CHECKS PASS"
+```
+
+- [ ] **Step 2: Run it to verify it fails**
+
+Run: `bash .extras/test-logic.sh`
+Expected: FAIL. `$SCRIPT` does not exist yet, `sed`/`source` on a missing file
+errors, no "ALL LOGIC CHECKS PASS".
+
+- [ ] **Step 3: Write the minimal script skeleton**
+
+Create `.extras/test-build`:
+
+```bash
+#!/bin/bash
+#
+# test-build - verify an already-published SBo package still builds on a target
+# Slackware version inside a throwaway docker container. Resolves + builds its
+# SBo deps from the local tree, caches built deps per image digest, reports
+# per-package status and lints the target.
+#
+# Dependency-resolution, cache, and summary logic are adapted from sbo-batch-test
+# (github: danixland). The overlay chroot is replaced by a docker container: the
+# container IS the disposable environment, so no overlayfs.
+#
+# No em dashes in prose by author convention.
+
+# =============================================================================
+# CONFIG (do not edit here; real values live in the external config file)
+# =============================================================================
+SBO_TREE_CURRENT=""
+SBO_TREE_STABLE=""
+IMAGE_CURRENT=""
+IMAGE_STABLE=""
+LOG_ROOT="/var/log/sbo-test-build"
+PKG_CACHE=""
+
+TB_CONFIG="${TB_CONFIG:-$HOME/.config/sbo-testbuild/config}"
+if [[ -f "$TB_CONFIG" ]]; then
+  # shellcheck disable=SC1090
+  source "$TB_CONFIG"
+fi
+
+TB_OVERRIDES="${TB_OVERRIDES:-$HOME/.config/sbo-testbuild/overrides}"
+
+# =============================================================================
+set -uo pipefail
+# Not -e: a package build failing is a handled outcome, not a script crash.
+
+main() {
+  :
+}
+
+main "$@"
+```
+
+- [ ] **Step 4: Run the self-check to verify it passes**
+
+Run: `bash .extras/test-logic.sh`
+Expected: PASS, ending `ALL LOGIC CHECKS PASS`.
+
+- [ ] **Step 5: Commit**
+
+```bash
+chmod +x .extras/test-build
+git add .extras/test-build .extras/test-logic.sh
+SBOLINT=no git commit -m 'test-build: scaffold script + self-check'
+```
+
+---
+
+## Task 2: Config, arg parsing, version selection
+
+**Files:**
+- Modify: `.extras/test-build`
+- Create: `.extras/test-build-config.example`
+- Test: `.extras/test-logic.sh`
+
+- [ ] **Step 1: Write the failing test**
+
+Append to `.extras/test-logic.sh` before the `--- result ---` block (the
+`echo; "$pass passed..."` lines at the end):
+
+```bash
+# --- version selection ------------------------------------------------------
+SBO_TREE_CURRENT="/trees/current"
+SBO_TREE_STABLE="/trees/stable"
+IMAGE_CURRENT="sbo-testbuild:current"
+IMAGE_STABLE="sbo-testbuild:15.0"
+
+VERSION_ID="current"; select_version_paths
+[[ "$ACTIVE_TREE" == "/trees/current" ]] && ok "current -> current tree" || bad "current tree wrong: [$ACTIVE_TREE]"
+[[ "$ACTIVE_IMAGE" == "sbo-testbuild:current" ]] && ok "current -> current image" || bad "current image wrong: [$ACTIVE_IMAGE]"
+
+VERSION_ID="15.0"; select_version_paths
+[[ "$ACTIVE_TREE" == "/trees/stable" ]] && ok "15.0 -> stable tree" || bad "stable tree wrong: [$ACTIVE_TREE]"
+[[ "$ACTIVE_IMAGE" == "sbo-testbuild:15.0" ]] && ok "15.0 -> stable image" || bad "stable image wrong: [$ACTIVE_IMAGE]"
+```
+
+- [ ] **Step 2: Run test to verify it fails**
+
+Run: `bash .extras/test-logic.sh`
+Expected: FAIL, `select_version_paths: command not found`.
+
+- [ ] **Step 3: Implement config globals, flags, parse_args, select_version_paths**
+
+In `.extras/test-build`, replace the `main() { : }` line and everything up to
+`main "$@"` with the flags/globals and functions below (keep the CONFIG block
+above untouched):
+
+```bash
+# ---- flags / globals --------------------------------------------------------
+USE_COLOR=1        # --no-color or non-TTY disables
+DRY_RUN=0          # --dry-run: resolve + print order, do not build
+ASSUME_YES=0       # --yes: skip the confirm prompt (still prints the order)
+USE_CACHE=1        # --no-cache disables the dep cache for one run
+VERSION_ID="current"   # "current" | "15.0"; set by --stable
+TARGET_ARG=""
+
+ACTIVE_TREE=""     # selected SBo tree (by version)
+ACTIVE_IMAGE=""    # selected image tag (by version)
+RUN_DIR=""         # timestamped log dir for this run
+
+# Status tracking. Keyed by "category/prog". Parallel assoc arrays.
+declare -A ST_STATUS=()
+declare -A ST_REASON=()
+declare -A ST_TIME=()
+declare -A ST_README=()
+
+usage() {
+  cat <<'EOF'
+test-build - verify an SBo package builds on a target Slackware in docker
+
+USAGE:
+  test-build [OPTIONS] <program-name>
+
+OPTIONS:
+  -h, --help    This text.
+  --stable      Target Slackware 15.0 (image + tree). Default is -current.
+  --dry-run     Resolve, apply overrides, print the build order, do not build.
+  --yes         Skip the confirm prompt (the order is still printed first).
+  --no-cache    Rebuild all deps this run, ignore/refresh the cache.
+  --no-color    Disable ANSI color (auto-disabled when stdout is not a TTY).
+EOF
+}
+
+parse_args() {
+  while [[ $# -gt 0 ]]; do
+    case "$1" in
+      -h|--help) usage; exit 0 ;;
+      --stable|15.0) VERSION_ID="15.0"; shift ;;
+      --dry-run) DRY_RUN=1; shift ;;
+      --yes) ASSUME_YES=1; shift ;;
+      --no-cache) USE_CACHE=0; shift ;;
+      --no-color) USE_COLOR=0; shift ;;
+      -*) echo "Unknown option: $1" >&2; usage >&2; exit 2 ;;
+      *)
+        if [[ -n "$TARGET_ARG" ]]; then
+          echo "Only one target accepted (got '$TARGET_ARG' and '$1')." >&2
+          exit 2
+        fi
+        TARGET_ARG="$1"; shift ;;
+    esac
+  done
+  if [[ -z "$TARGET_ARG" ]]; then
+    echo "No target given." >&2; usage >&2; exit 2
+  fi
+}
+
+init_color() {
+  if [[ $USE_COLOR -eq 1 && -t 1 ]]; then
+    C_RED=$'\e[31m'; C_GRN=$'\e[32m'; C_YEL=$'\e[33m'; C_RST=$'\e[0m'
+  else
+    C_RED=""; C_GRN=""; C_YEL=""; C_RST=""
+  fi
+}
+
+# Map VERSION_ID to the active tree + image. No I/O, unit-testable.
+select_version_paths() {
+  if [[ "$VERSION_ID" == "15.0" ]]; then
+    ACTIVE_TREE="$SBO_TREE_STABLE"; ACTIVE_IMAGE="$IMAGE_STABLE"
+  else
+    ACTIVE_TREE="$SBO_TREE_CURRENT"; ACTIVE_IMAGE="$IMAGE_CURRENT"
+  fi
+}
+
+# require_config: the external config must exist and set the version's paths.
+require_config() {
+  if [[ ! -f "$TB_CONFIG" ]]; then
+    cat >&2 <<EOF
+No config file: $TB_CONFIG
+Copy the example and edit it:
+
+  mkdir -p "\$(dirname "$TB_CONFIG")"
+  cp .extras/test-build-config.example "$TB_CONFIG"
+  \${EDITOR:-vi} "$TB_CONFIG"
+EOF
+    exit 1
+  fi
+  select_version_paths
+  if [[ -z "$ACTIVE_TREE" || -z "$ACTIVE_IMAGE" ]]; then
+    echo "Config $TB_CONFIG is missing the tree/image for version '$VERSION_ID'." >&2
+    exit 1
+  fi
+  if [[ ! -d "$ACTIVE_TREE" ]]; then
+    echo "SBo tree for '$VERSION_ID' does not exist: $ACTIVE_TREE" >&2
+    exit 1
+  fi
+}
+
+main() {
+  parse_args "$@"
+  init_color
+  require_config
+}
+
+main "$@"
+```
+
+- [ ] **Step 4: Run test to verify it passes**
+
+Run: `bash .extras/test-logic.sh`
+Expected: PASS (the new version-selection checks included).
+
+- [ ] **Step 5: Write the config example**
+
+Create `.extras/test-build-config.example`:
+
+```bash
+# test-build config. Copy to ~/.config/sbo-testbuild/config and edit.
+# Override the path with the TB_CONFIG environment variable.
+
+# Local SBo trees, one per target Slackware version.
+SBO_TREE_CURRENT="/home/danix/SBo/current"
+SBO_TREE_STABLE="/home/danix/SBo/15.0"
+
+# Ready image tags (built by a separate job, consumed here by tag).
+IMAGE_CURRENT="sbo-testbuild:current"
+IMAGE_STABLE="sbo-testbuild:15.0"
+
+# Where per-run logs land.
+LOG_ROOT="/home/danix/.cache/sbo-test-build"
+
+# Dependency package cache (host dir). Empty disables caching.
+# Namespaced internally by image digest, so it self-invalidates on image update
+# and keeps current vs 15.0 separate.
+PKG_CACHE="/home/danix/.cache/sbo-test-build/pkgcache"
+```
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add .extras/test-build .extras/test-build-config.example .extras/test-logic.sh
+SBOLINT=no git commit -m 'test-build: config, arg parsing, version selection'
+```
+
+---
+
+## Task 3: Port the SBo-tree lookup + resolver + self-check
+
+**Files:**
+- Modify: `.extras/test-build`
+- Test: `.extras/test-logic.sh`
+
+- [ ] **Step 1: Write the failing test**
+
+Append to `.extras/test-logic.sh` before the result block:
+
+```bash
+# --- resolution -------------------------------------------------------------
+# Fake SBo tree under one category. mk <prog> "<REQUIRES>".
+mk() { mkdir -p "$T/cat/$1"; echo "REQUIRES=\"$2\"" > "$T/cat/$1/$1.info"; }
+mk c ""
+mk b "c"
+mk a "b %README%"
+mk d "nonexistentpkg"
+mk e "f"
+mk f "e"
+mk g "b"
+
+SBO_TREE_ROOTS=("$T")   # resolver reads this global (set by select in real runs)
+
+resolve_target "$T/cat/a"
+order=""; for x in "${RESOLVED_ORDER[@]}"; do order+="$(basename "$x") "; done
+order="${order% }"
+[[ "$order" == "c b a" ]] && ok "topo order c b a" || bad "topo order, got: [$order]"
+[[ "${HAS_README[$T/cat/a]:-}" == "1" ]] && ok "%README% recorded" || bad "%README% not recorded"
+[[ ${#UNMET[@]} -eq 0 ]] && ok "no false unmet" || bad "unexpected unmet"
+
+resolve_target "$T/cat/d"
+[[ ${#UNMET[@]} -eq 1 ]] && ok "unmet-dep caught" || bad "unmet-dep missed"
+
+resolve_target "$T/cat/e"
+[[ ${#CYCLES[@]} -ge 1 ]] && ok "cycle caught" || bad "cycle missed"
+```
+
+Note: the base-installed check (`installed_in_base`) is exercised in real runs
+against the container, not here. In the self-check `BASE_DB` is empty, so a dep
+that is neither in the tree nor a known override reads as UNMET (which is the
+behavior we test with `d`).
+
+- [ ] **Step 2: Run test to verify it fails**
+
+Run: `bash .extras/test-logic.sh`
+Expected: FAIL, `resolve_target: command not found`.
+
+- [ ] **Step 3: Implement lookup + resolver (ported)**
+
+Add to `.extras/test-build` above `main()`:
+
+```bash
+# =============================================================================
+# SBo tree lookup
+# =============================================================================
+# In this tool there is one active tree per run, but the resolver reads an array
+# named SBO_TREE_ROOTS so the ported logic and its self-check match sbo-batch-test.
+# main() sets SBO_TREE_ROOTS=("$ACTIVE_TREE") after require_config.
+declare -a SBO_TREE_ROOTS=()
+
+find_slackbuild_dir() {
+  local prog="$1" root d
+  for root in "${SBO_TREE_ROOTS[@]}"; do
+    [[ -d "$root" ]] || continue
+    for d in "$root"/*/"$prog"; do
+      if [[ -d "$d" && -f "$d/$prog.info" ]]; then
+        echo "$d"; return 0
+      fi
+    done
+  done
+  return 1
+}
+
+category_of() { basename "$(dirname "$1")"; }
+pkg_key() { echo "$(category_of "$1")/$(basename "$1")"; }
+
+read_requires() {
+  local info="$1"
+  # shellcheck disable=SC1090
+  ( set +u; source "$info"; echo "${REQUIRES:-}" )
+}
+
+version_of() {
+  local dir="$1"
+  local info="$dir/$(basename "$dir").info"
+  [[ -f "$info" ]] || return
+  local v; v="$(grep -m1 '^VERSION=' "$info" | cut -d'"' -f2)"
+  echo "$v"
+}
+
+# =============================================================================
+# DEPENDENCY RESOLUTION (topo sort + cycle detection, LOCAL tree only)
+# =============================================================================
+declare -a RESOLVED_ORDER=()
+declare -A UNMET=()
+declare -a CYCLES=()
+declare -A HAS_README=()
+declare -A _vstate=()
+
+# Is a prog already present in the container base? Overridden at build time to
+# consult the image; in resolution we treat "in base" as a callback so the pure
+# topo logic stays testable. Default: not in base (self-check has no base db).
+installed_in_base() { return 1; }
+
+_resolve_visit() {
+  local dir="$1" parent="$2"
+  local key; key="$(basename "$dir")"
+
+  if [[ "${_vstate[$dir]:-}" == "1" ]]; then return 0; fi
+  if [[ "${_vstate[$dir]:-}" == "0" ]]; then
+    CYCLES+=("cycle involving $key (pulled in via $parent)")
+    return 1
+  fi
+  _vstate["$dir"]=0
+
+  local info="$dir/$(basename "$dir").info"
+  local req tok depdir rc=0
+  req="$(read_requires "$info")"
+  for tok in $req; do
+    if [[ "$tok" == "%README%" ]]; then
+      HAS_README["$dir"]=1
+      continue
+    fi
+    if depdir="$(find_slackbuild_dir "$tok")"; then
+      _resolve_visit "$depdir" "$key" || rc=1
+    elif installed_in_base "$tok"; then
+      :
+    else
+      UNMET["$tok"]="needed by $key"
+      rc=1
+    fi
+  done
+
+  _vstate["$dir"]=1
+  RESOLVED_ORDER+=("$dir")
+  return $rc
+}
+
+resolve_target() {
+  local dir="$1"
+  RESOLVED_ORDER=()
+  CYCLES=()
+  UNMET=()
+  _vstate=()
+  _resolve_visit "$dir" "(top)"
+}
+```
+
+Update `main()` to set the resolver's tree array after `require_config`:
+
+```bash
+main() {
+  parse_args "$@"
+  init_color
+  require_config
+  SBO_TREE_ROOTS=("$ACTIVE_TREE")
+}
+```
+
+- [ ] **Step 4: Run test to verify it passes**
+
+Run: `bash .extras/test-logic.sh`
+Expected: PASS (topo order, %README%, unmet, cycle checks green).
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add .extras/test-build .extras/test-logic.sh
+SBOLINT=no git commit -m 'test-build: port SBo lookup + dependency resolver'
+```
+
+---
+
+## Task 4: Override engine (drop / rename / fetch) + UNMET stop
+
+**Files:**
+- Modify: `.extras/test-build`
+- Create: `.extras/overrides.example`
+- Test: `.extras/test-logic.sh`
+
+The override file encodes current-vs-stable deltas. It is applied ONLY when
+`VERSION_ID == current` (15.0 is the SBo baseline). Rules:
+
+- `drop:   <prog>`            remove from the build order (already in -current base)
+- `rename: <old> -> <new>`    rewrite the dep name before it is looked up
+- `fetch:  <prog>`            mark this dep to come from sbopkg in-container, not the local tree
+
+- [ ] **Step 1: Write the failing test**
+
+Append to `.extras/test-logic.sh` before the result block:
+
+```bash
+# --- overrides --------------------------------------------------------------
+OV=$(mktemp)
+cat > "$OV" <<'EOF'
+# comment ignored
+drop:   dropme
+rename: oldname -> newname
+fetch:  fetchme
+EOF
+TB_OVERRIDES="$OV"
+load_overrides
+
+[[ "${OV_DROP[dropme]:-}" == "1" ]] && ok "override drop parsed" || bad "drop not parsed"
+[[ "${OV_RENAME[oldname]:-}" == "newname" ]] && ok "override rename parsed" || bad "rename not parsed"
+[[ "${OV_FETCH[fetchme]:-}" == "1" ]] && ok "override fetch parsed" || bad "fetch not parsed"
+
+# rename maps a token
+[[ "$(apply_rename oldname)" == "newname" ]] && ok "apply_rename maps" || bad "apply_rename wrong: [$(apply_rename oldname)]"
+[[ "$(apply_rename untouched)" == "untouched" ]] && ok "apply_rename passthrough" || bad "apply_rename mangled untouched"
+
+# drop filters the order (build a fake order of dirs; dropme is removed)
+mk dropme ""
+mk keepme ""
+RESOLVED_ORDER=("$T/cat/dropme" "$T/cat/keepme")
+apply_overrides_to_order
+kept=""; for x in "${RESOLVED_ORDER[@]}"; do kept+="$(basename "$x") "; done
+kept="${kept% }"
+[[ "$kept" == "keepme" ]] && ok "drop removes from order" || bad "drop failed, order=[$kept]"
+rm -f "$OV"
+
+# overrides only apply on current; on 15.0 they are a no-op
+VERSION_ID="15.0"
+TB_OVERRIDES="$OV"   # file gone; must not error, must clear maps
+load_overrides
+[[ ${#OV_DROP[@]} -eq 0 ]] && ok "overrides inert on 15.0" || bad "overrides applied on 15.0"
+VERSION_ID="current"
+```
+
+- [ ] **Step 2: Run test to verify it fails**
+
+Run: `bash .extras/test-logic.sh`
+Expected: FAIL, `load_overrides: command not found`.
+
+- [ ] **Step 3: Implement the override engine**
+
+Add to `.extras/test-build` above `main()`:
+
+```bash
+# =============================================================================
+# current-vs-stable overrides. Parsed from $TB_OVERRIDES. Applied only when
+# targeting -current (15.0 is the SBo baseline, no deltas).
+# =============================================================================
+declare -A OV_DROP=()      # prog -> 1
+declare -A OV_RENAME=()    # old  -> new
+declare -A OV_FETCH=()     # prog -> 1
+
+load_overrides() {
+  OV_DROP=(); OV_RENAME=(); OV_FETCH=()
+  # 15.0 is the baseline: no overrides.
+  [[ "$VERSION_ID" == "15.0" ]] && return
+  [[ -f "$TB_OVERRIDES" ]] || return
+  local line kind rest
+  while IFS= read -r line; do
+    line="${line%%#*}"                       # strip comments
+    line="${line#"${line%%[![:space:]]*}"}"  # ltrim
+    [[ -z "$line" ]] && continue
+    kind="${line%%:*}"; rest="${line#*:}"
+    kind="${kind//[[:space:]]/}"
+    rest="${rest#"${rest%%[![:space:]]*}"}"  # ltrim value
+    case "$kind" in
+      drop)   OV_DROP["${rest//[[:space:]]/}"]=1 ;;
+      fetch)  OV_FETCH["${rest//[[:space:]]/}"]=1 ;;
+      rename)
+        # rest is "old -> new"
+        local old new
+        old="${rest%%->*}"; new="${rest##*->}"
+        old="${old//[[:space:]]/}"; new="${new//[[:space:]]/}"
+        [[ -n "$old" && -n "$new" ]] && OV_RENAME["$old"]="$new" ;;
+      *) echo "WARN: unknown override rule: $line" >&2 ;;
+    esac
+  done < "$TB_OVERRIDES"
+}
+
+# Map a dep token through rename rules (identity if no rule).
+apply_rename() {
+  local tok="$1"
+  echo "${OV_RENAME[$tok]:-$tok}"
+}
+
+# Remove dropped packages from RESOLVED_ORDER in place.
+apply_overrides_to_order() {
+  local d prog keep=()
+  for d in "${RESOLVED_ORDER[@]}"; do
+    prog="$(basename "$d")"
+    [[ "${OV_DROP[$prog]:-}" == "1" ]] && continue
+    keep+=("$d")
+  done
+  RESOLVED_ORDER=("${keep[@]:-}")
+}
+```
+
+Wire `apply_rename` into the resolver so renamed deps look up under the new
+name. In `_resolve_visit`, change the dep-lookup line:
+
+```bash
+  for tok in $req; do
+    if [[ "$tok" == "%README%" ]]; then
+      HAS_README["$dir"]=1
+      continue
+    fi
+    tok="$(apply_rename "$tok")"          # <-- add this line
+    if [[ "${OV_FETCH[$tok]:-}" == "1" ]]; then
+      FETCH_DEPS["$tok"]=1                 # satisfied via sbopkg at build time
+      continue
+    fi
+    if depdir="$(find_slackbuild_dir "$tok")"; then
+      _resolve_visit "$depdir" "$key" || rc=1
+    elif installed_in_base "$tok"; then
+      :
+    else
+      UNMET["$tok"]="needed by $key"
+      rc=1
+    fi
+  done
+```
+
+Add the `FETCH_DEPS` global with the other resolver globals:
+
+```bash
+declare -A FETCH_DEPS=()   # prog -> 1: resolve via sbopkg in-container
+```
+
+And reset it in `resolve_target`:
+
+```bash
+resolve_target() {
+  local dir="$1"
+  RESOLVED_ORDER=()
+  CYCLES=()
+  UNMET=()
+  FETCH_DEPS=()
+  _vstate=()
+  _resolve_visit "$dir" "(top)"
+}
+```
+
+Load overrides in `main()` (before any resolve happens, after tree setup):
+
+```bash
+main() {
+  parse_args "$@"
+  init_color
+  require_config
+  SBO_TREE_ROOTS=("$ACTIVE_TREE")
+  load_overrides
+}
+```
+
+- [ ] **Step 4: Run test to verify it passes**
+
+Run: `bash .extras/test-logic.sh`
+Expected: PASS (all override checks green).
+
+- [ ] **Step 5: Write the overrides example**
+
+Create `.extras/overrides.example`:
+
+```
+# current-vs-stable dep overrides for test-build.
+# Copy to ~/.config/sbo-testbuild/overrides and edit. Applied only when
+# targeting -current (15.0 is the SBo baseline). One rule per line.
+#
+#   drop:   <prog>            dep is in 15.0 but already in the -current base
+#   rename: <old> -> <new>    dep was renamed on -current
+#   fetch:  <prog>            dep was removed from the -current tree; pull via sbopkg
+#
+# Start light: add rules only when a real package needs them.
+
+# drop:   rust
+# rename: python3-foo -> foo
+# fetch:  somelib
+```
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add .extras/test-build .extras/overrides.example .extras/test-logic.sh
+SBOLINT=no git commit -m 'test-build: current-vs-stable override engine'
+```
+
+---
+
+## Task 5: Port the dep cache, namespaced by image digest
+
+**Files:**
+- Modify: `.extras/test-build`
+- Test: `.extras/test-logic.sh`
+
+The cache is the ported sbo-batch-test cache with one change: the cache root
+seen by `cache_*` is `$PKG_CACHE/<image-digest>`, computed once per run. A new
+digest gives a fresh namespace (old deps ignored), which is the invalidation.
+
+- [ ] **Step 1: Write the failing test**
+
+Append to `.extras/test-logic.sh` before the result block:
+
+```bash
+# --- cache ------------------------------------------------------------------
+PKG_CACHE=$(mktemp -d)
+CACHE_ROOT="$PKG_CACHE/sha256-deadbeef"   # simulate a resolved digest namespace
+mkc() { mkdir -p "$CACHE_ROOT/$1/$2"; : > "$CACHE_ROOT/$1/$2/$3"; }
+
+mkc net libfoo "libfoo-1.1-x86_64-1_danix.txz"
+[[ "$(cache_decision net libfoo 1.1)" == "cached" ]] && ok "cache hit on version match" || bad "cache_decision got [$(cache_decision net libfoo 1.1)]"
+[[ "$(cache_decision net libfoo 1.2)" == "bump:1.1:1.2" ]] && ok "cache bump reported" || bad "cache bump got [$(cache_decision net libfoo 1.2)]"
+[[ "$(cache_decision net libbar 1.0)" == "new" ]] && ok "cache new for absent" || bad "cache new got [$(cache_decision net libbar 1.0)]"
+
+hit="$(cache_path net libfoo 1.1)"
+[[ "$hit" == "$CACHE_ROOT/net/libfoo/libfoo-1.1-x86_64-1_danix.txz" ]] && ok "cache_path returns hit" || bad "cache_path got [$hit]"
+[[ -z "$(cache_path net libfoo 9.9)" ]] && ok "cache_path empty on miss" || bad "cache_path not empty on miss"
+
+srctmp=$(mktemp -d); : > "$srctmp/libfoo-1.2-x86_64-1_danix.txz"
+cache_store net libfoo "$srctmp/libfoo-1.2-x86_64-1_danix.txz"
+count=$(find "$CACHE_ROOT/net/libfoo" -name '*.t?z' | wc -l)
+[[ "$count" -eq 1 ]] && ok "cache_store evicts to one file" || bad "cache_store left $count files"
+[[ -e "$CACHE_ROOT/net/libfoo/libfoo-1.2-x86_64-1_danix.txz" ]] && ok "cache_store stored new file" || bad "cache_store did not store"
+rm -rf "$srctmp"
+
+# disabled cache -> new
+CACHE_ROOT_SAVE="$CACHE_ROOT"; USE_CACHE=0
+[[ "$(cache_decision net libfoo 1.2)" == "new" ]] && ok "--no-cache disables (new)" || bad "disabled cache got [$(cache_decision net libfoo 1.2)]"
+USE_CACHE=1; CACHE_ROOT="$CACHE_ROOT_SAVE"
+```
+
+- [ ] **Step 2: Run test to verify it fails**
+
+Run: `bash .extras/test-logic.sh`
+Expected: FAIL, `cache_decision: command not found`.
+
+- [ ] **Step 3: Implement the cache (ported, keyed on CACHE_ROOT + USE_CACHE)**
+
+Add to `.extras/test-build` above `main()`:
+
+```bash
+# =============================================================================
+# Dependency cache. Layout: $CACHE_ROOT/<cat>/<prog>/<prog>-<ver>-...txz where
+# CACHE_ROOT = $PKG_CACHE/<image-digest> (set per run by resolve_cache_root).
+# Key is prog+version. --no-cache (USE_CACHE=0) or empty PKG_CACHE disables.
+# =============================================================================
+CACHE_ROOT=""   # set by resolve_cache_root once the image digest is known
+
+# True when the cache is usable this run.
+_cache_on() { [[ $USE_CACHE -eq 1 && -n "$PKG_CACHE" && -n "$CACHE_ROOT" ]]; }
+
+_cache_ver_of() {
+  local prog="$1" base="$2"
+  base="${base#"$prog"-}"
+  echo "${base%%-*}"
+}
+
+# cache_decision <cat> <prog> <version> -> cached | bump:OLD:NEW | new
+cache_decision() {
+  local cat="$1" prog="$2" version="$3"
+  _cache_on || { echo new; return; }
+  local dir="$CACHE_ROOT/$cat/$prog"
+  local f newest=""
+  for f in "$dir/$prog"-*.t?z; do
+    [[ -e "$f" ]] || continue
+    [[ -z "$newest" || "$f" -nt "$newest" ]] && newest="$f"
+  done
+  [[ -z "$newest" ]] && { echo new; return; }
+  local have; have="$(_cache_ver_of "$prog" "$(basename "$newest")")"
+  if [[ "$have" == "$version" ]]; then echo cached; else echo "bump:$have:$version"; fi
+}
+
+cache_path() {
+  local cat="$1" prog="$2" version="$3"
+  _cache_on || return
+  local dir="$CACHE_ROOT/$cat/$prog"
+  local f newest=""
+  for f in "$dir/$prog"-*.t?z; do
+    [[ -e "$f" ]] || continue
+    [[ -z "$newest" || "$f" -nt "$newest" ]] && newest="$f"
+  done
+  [[ -z "$newest" ]] && return
+  [[ "$(_cache_ver_of "$prog" "$(basename "$newest")")" == "$version" ]] && echo "$newest"
+}
+
+cache_store() {
+  local cat="$1" prog="$2" src="$3"
+  _cache_on || return
+  local dir="$CACHE_ROOT/$cat/$prog"
+  mkdir -p "$dir"
+  rm -f "$dir"/*.t?z
+  cp -a "$src" "$dir/"
+}
+
+cache_label() {
+  local dir="$1" is_target="$2"
+  local cat prog ver dec
+  cat="$(category_of "$dir")"; prog="$(basename "$dir")"; ver="$(version_of "$dir")"
+  dec="$(cache_decision "$cat" "$prog" "$ver")"
+  local label
+  case "$dec" in
+    cached)   label="cached ($ver)" ;;
+    bump:*)   label="rebuild: ${dec#bump:}"; label="${label/:/ -> }" ;;
+    *)        label="build (new)" ;;
+  esac
+  if [[ "$is_target" == "1" ]]; then
+    case "$dec" in
+      cached) label="build (cached $ver, rebuilt as target)" ;;
+    esac
+    echo "target, $label"
+  else
+    echo "$label"
+  fi
+}
+
+# Compute CACHE_ROOT from the image's digest. Falls back to the tag if the
+# digest cannot be read (still isolates per image reference).
+resolve_cache_root() {
+  [[ -z "$PKG_CACHE" ]] && { CACHE_ROOT=""; return; }
+  local digest
+  digest="$(docker image inspect --format '{{index .Id}}' "$ACTIVE_IMAGE" 2>/dev/null)"
+  [[ -z "$digest" ]] && digest="tag-${ACTIVE_IMAGE//[^a-zA-Z0-9._-]/_}"
+  digest="${digest//[^a-zA-Z0-9._-]/_}"
+  CACHE_ROOT="$PKG_CACHE/$digest"
+  mkdir -p "$CACHE_ROOT"
+}
+```
+
+- [ ] **Step 4: Run test to verify it passes**
+
+Run: `bash .extras/test-logic.sh`
+Expected: PASS (all cache checks green).
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add .extras/test-build .extras/test-logic.sh
+SBOLINT=no git commit -m 'test-build: port dep cache, namespaced by image digest'
+```
+
+---
+
+## Task 6: BLOCKED-BY-DEP propagation (ported)
+
+**Files:**
+- Modify: `.extras/test-build`
+- Test: `.extras/test-logic.sh`
+
+- [ ] **Step 1: Write the failing test**
+
+Append to `.extras/test-logic.sh` before the result block:
+
+```bash
+# --- BLOCKED-BY-DEP (depends_on_failed) -------------------------------------
+dead=(b)
+if depends_on_failed "$T/cat/g" dead; then ok "g blocked when b dead"; else bad "g should block on b"; fi
+if depends_on_failed "$T/cat/a" dead; then ok "a blocked when b dead (direct)"; else bad "a should block on b"; fi
+
+dead=(c)
+if depends_on_failed "$T/cat/a" dead; then bad "a wrongly blocked on c"; else ok "a not directly blocked by c"; fi
+if depends_on_failed "$T/cat/b" dead; then ok "b blocked when c dead"; else bad "b should block on c"; fi
+
+dead=()
+if depends_on_failed "$T/cat/a" dead; then bad "a blocked with empty dead"; else ok "no block when nothing dead"; fi
+
+dead=("%README%")
+if depends_on_failed "$T/cat/a" dead; then bad "%README% treated as dep"; else ok "%README% not treated as dep"; fi
+```
+
+- [ ] **Step 2: Run test to verify it fails**
+
+Run: `bash .extras/test-logic.sh`
+Expected: FAIL, `depends_on_failed: command not found`.
+
+- [ ] **Step 3: Implement depends_on_failed (ported)**
+
+Add to `.extras/test-build` above `main()`:
+
+```bash
+# Does SlackBuild dir $1 directly require any prog in the dead list (nameref $2)?
+# Direct-requires check only; transitive blocking works because run_target
+# iterates in topo order, propagating a failure one hop per package.
+depends_on_failed() {
+  local dir="$1"; local -n failed="$2"
+  local info="$dir/$(basename "$dir").info"
+  local req tok f
+  req="$(read_requires "$info")"
+  for tok in $req; do
+    [[ "$tok" == "%README%" ]] && continue
+    for f in "${failed[@]:-}"; do
+      [[ "$tok" == "$f" ]] && return 0
+    done
+  done
+  return 1
+}
+```
+
+- [ ] **Step 4: Run test to verify it passes**
+
+Run: `bash .extras/test-logic.sh`
+Expected: PASS.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add .extras/test-build .extras/test-logic.sh
+SBOLINT=no git commit -m 'test-build: port BLOCKED-BY-DEP propagation'
+```
+
+---
+
+## Task 7: The container build step (build_one via docker)
+
+**Files:**
+- Modify: `.extras/test-build`
+
+No self-check here (docker/build is out of the pure-logic reach, same boundary
+as sbo-batch-test). Verified by a real run in Task 10.
+
+- [ ] **Step 1: Implement build_one + lint_pkg**
+
+Add to `.extras/test-build` above `main()`.
+
+`lint_pkg` is ported verbatim:
+
+```bash
+# lint_pkg <txz> <logf> -> run sbopkglint on a built package. Host-side, target
+# only, fail-soft (skip if absent, never change SUCCESS).
+lint_pkg() {
+  local txz="$1" logf="$2"
+  if ! command -v sbopkglint >/dev/null 2>&1; then
+    echo "  sbopkglint not installed on host, skipping lint"
+    return 0
+  fi
+  echo "  sbopkglint $(basename "$txz") ..."
+  echo "===== sbopkglint: $(basename "$txz") =====" >> "$logf"
+  local out rc
+  out="$(sbopkglint "$txz" 2>&1)"; rc=$?
+  printf '%s\n' "$out" >> "$logf"
+  if [[ $rc -eq 0 ]]; then
+    echo "  lint: ${C_GRN}clean${C_RST}"
+  else
+    echo "  lint: ${C_RED}findings${C_RST} (see $(basename "$logf")):"
+    printf '%s\n' "$out" | sed 's/^/    /'
+  fi
+}
+```
+
+`build_one` runs the same download/md5/build/installpkg steps as sbo-batch-test,
+but inside a container via `docker run` instead of `chroot`. The container gets:
+the SlackBuild dir mounted read-only, a work dir for output, and (for deps) the
+cached .txz mounted in. `sbopkglint` runs host-side on the copied-out package.
+
+```bash
+# build_one <slackbuild-dir> <is_target 0|1> [container-name]
+# Runs the build in a throwaway container. Sets ST_STATUS/ST_REASON/ST_TIME.
+# Successful builds copy their package to a host workdir; deps are cached and
+# the target is linted. Returns 0 on SUCCESS/CACHED, 1 otherwise.
+build_one() {
+  local dir="$1" is_target="${2:-0}"
+  local prog cat key
+  prog="$(basename "$dir")"; cat="$(category_of "$dir")"; key="$cat/$prog"
+  local logf="$RUN_DIR/${cat}_${prog}.log"
+  local start; start=$(date +%s)
+  local version; version="$(version_of "$dir")"
+
+  [[ "${HAS_README[$dir]:-}" == "1" ]] && ST_README["$key"]=1
+
+  # Dep with a version-matching cached package: installpkg it into the shared
+  # dep-package dir; no build. The target never takes this path.
+  if [[ "$is_target" != "1" ]]; then
+    local cached; cached="$(cache_path "$cat" "$prog" "$version")"
+    if [[ -n "$cached" ]]; then
+      cp -a "$cached" "$DEPS_DIR/"
+      {
+        echo "===== test-build: $prog (from cache) ====="
+        echo "cached package: $(basename "$cached")"
+      } >> "$logf"
+      ST_TIME["$key"]=$(( $(date +%s) - start ))
+      ST_STATUS["$key"]="CACHED"
+      return 0
+    fi
+  fi
+
+  # Build in a container. Mounts:
+  #   $dir           -> /sbo/pkg    (ro, the SlackBuild)
+  #   $DEPS_DIR      -> /sbo/deps   (rw, already-built dep .txz to installpkg first)
+  #   $BUILD_OUT     -> /sbo/out    (rw, where the built package is copied out)
+  # The in-container script installs any deps present, then builds the target,
+  # writes a status token to /sbo/out/$prog.status, and copies the package out.
+  local statf="$BUILD_OUT/$prog.status"
+  rm -f "$statf"
+
+  # fetch deps (removed from -current tree): let the container's sbopkg build
+  # them first. FETCH_DEPS is the set collected during resolution.
+  local fetch_list=""
+  local fp
+  for fp in "${!FETCH_DEPS[@]}"; do fetch_list+="$fp "; done
+
+  docker run --rm \
+    -v "$dir":/sbo/pkg:ro \
+    -v "$DEPS_DIR":/sbo/deps \
+    -v "$BUILD_OUT":/sbo/out \
+    -e PROG="$prog" \
+    -e FETCH_LIST="$fetch_list" \
+    "$ACTIVE_IMAGE" /bin/bash -s >>"$logf" 2>&1 <<'CONTAINER_EOF'
+set -uo pipefail
+prog="$PROG"
+statf="/sbo/out/$prog.status"
+
+# 0. install already-built dependency packages (order guaranteed by the host).
+for d in /sbo/deps/*.t?z; do
+  [[ -e "$d" ]] || continue
+  installpkg --terse "$d" || { echo "INSTALL-FAILED (dep $d)"; echo INSTALL-FAILED > "$statf"; exit 1; }
+done
+
+# 0b. fetch-from-SBo deps via sbopkg (removed from the -current tree).
+for f in $FETCH_LIST; do
+  echo "sbopkg-building fetch dep: $f"
+  sbopkg -B -i "$f" || { echo "BUILD-FAILED (fetch dep $f)"; echo BUILD-FAILED > "$statf"; exit 1; }
+done
+
+# copy the SlackBuild out of the read-only mount so it can write there.
+cp -a /sbo/pkg /sbo/build
+cd /sbo/build || { echo BUILD-FAILED > "$statf"; exit 1; }
+. ./"$prog".info
+
+export OUTPUT=/sbo/out
+mkdir -p "$OUTPUT"
+
+echo "===== test-build: $prog ====="
+echo "PRGNAM=${PRGNAM:-$prog} VERSION=${VERSION:-?} BUILD=${BUILD:-?} TAG=${TAG:-?}"
+echo "uname -m: $(uname -m)   OUTPUT=$OUTPUT"
+echo "REQUIRES=${REQUIRES:-}"
+echo "================================="
+
+if [ "$(uname -m)" = "x86_64" ] && [ -n "${DOWNLOAD_x86_64:-}" ] && [ "${DOWNLOAD_x86_64}" != "UNSUPPORTED" ] && [ "${DOWNLOAD_x86_64}" != "UNTESTED" ]; then
+  DL="$DOWNLOAD_x86_64"; MD="$MD5SUM_x86_64"
+else
+  DL="$DOWNLOAD"; MD="$MD5SUM"
+fi
+
+for u in $DL; do
+  wget -c --tries=3 "$u" || { echo DOWNLOAD-FAILED > "$statf"; exit 1; }
+done
+
+set -- $MD
+for u in $DL; do
+  f="$(basename "$u")"
+  want="$1"; shift
+  got="$(md5sum "$f" | cut -d' ' -f1)"
+  if [ "$got" != "$want" ]; then
+    echo "MD5 mismatch on $f: want $want got $got"
+    echo MD5-MISMATCH > "$statf"; exit 1
+  fi
+done
+
+chmod +x ./"$prog".SlackBuild
+if ! ./"$prog".SlackBuild; then
+  echo BUILD-FAILED > "$statf"; exit 1
+fi
+
+pkg="$(ls -t "$OUTPUT"/"$prog"-*.t?z 2>/dev/null | head -n1)"
+if [ -z "$pkg" ]; then
+  echo "No package produced in $OUTPUT"
+  echo BUILD-FAILED > "$statf"; exit 1
+fi
+if ! installpkg --terse "$pkg"; then
+  echo INSTALL-FAILED > "$statf"; exit 1
+fi
+echo "===== installed files: $(basename "$pkg") ====="
+pkgname="$(basename "$pkg")"; pkgname="${pkgname%.t?z}"
+cat "/var/log/packages/$pkgname" 2>/dev/null || echo "(package db entry not found)"
+echo "================================="
+echo SUCCESS > "$statf"
+CONTAINER_EOF
+
+  local status="BUILD-FAILED"
+  [[ -f "$statf" ]] && status="$(cat "$statf")"
+  ST_TIME["$key"]=$(( $(date +%s) - start ))
+  ST_STATUS["$key"]="$status"
+
+  if [[ "$status" == "SUCCESS" ]]; then
+    # locate the built package copied to the host workdir
+    local built newest=""
+    for built in "$BUILD_OUT/${prog}"-*.t?z; do
+      [[ -e "$built" ]] || continue
+      [[ -z "$newest" || "$built" -nt "$newest" ]] && newest="$built"
+    done
+    if [[ -n "$newest" ]]; then
+      if [[ "$is_target" != "1" ]]; then
+        cache_store "$cat" "$prog" "$newest"
+        # make the dep available to later builds in this run
+        cp -a "$newest" "$DEPS_DIR/"
+      else
+        lint_pkg "$newest" "$logf"
+      fi
+    fi
+    return 0
+  fi
+  ST_REASON["$key"]="see $(basename "$logf")"
+  return 1
+}
+```
+
+- [ ] **Step 2: Sanity-check bash syntax**
+
+Run: `bash -n .extras/test-build`
+Expected: no output (syntax OK).
+
+- [ ] **Step 3: Run the self-check still passes (no regression)**
+
+Run: `bash .extras/test-logic.sh`
+Expected: PASS (build_one is not exercised, but sourcing must not break).
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add .extras/test-build
+SBOLINT=no git commit -m 'test-build: container build step (build_one via docker)'
+```
+
+---
+
+## Task 8: run_target orchestration + summary
+
+**Files:**
+- Modify: `.extras/test-build`
+
+- [ ] **Step 1: Implement run_target + print_summary + confirm**
+
+Add to `.extras/test-build` above `main()`. `print_summary` is ported verbatim
+(status set is the same). `run_target` replaces the overlay lifecycle with the
+per-run docker workdirs and adds the printed-order + Y/n confirm.
+
+```bash
+# confirm_order: print the resolved order (overrides marked) and ask to proceed.
+# --yes skips the prompt but the order is still printed. --dry-run never reaches
+# here. Returns 0 to proceed, 1 to abort.
+confirm_order() {
+  local target_dir="$1"
+  echo "  build order (${VERSION_ID}):"
+  local d
+  for d in "${RESOLVED_ORDER[@]}"; do
+    local it=0; [[ "$d" == "$target_dir" ]] && it=1
+    local rdm=""; [[ "${HAS_README[$d]:-}" == 1 ]] && rdm="  [%README%]"
+    printf "    %-30s %s%s\n" "$(pkg_key "$d")" "$(cache_label "$d" "$it")" "$rdm"
+    echo "$(pkg_key "$d")" >> "$RUN_DIR/build-order.txt"
+  done
+  # note fetch deps (built via sbopkg in-container, not in the order list)
+  local fp
+  for fp in "${!FETCH_DEPS[@]}"; do
+    printf "    %-30s %s\n" "$fp" "fetch (sbopkg in container)"
+  done
+  [[ $ASSUME_YES -eq 1 ]] && return 0
+  local reply
+  read -rp "  Proceed? [Y/n] " reply
+  [[ -z "$reply" || "$reply" =~ ^[Yy]$ ]]
+}
+
+# run_target <target-slackbuild-dir>
+run_target() {
+  local target_dir="$1"
+  local tkey; tkey="$(pkg_key "$target_dir")"
+
+  echo
+  echo "=== Target: $tkey (${VERSION_ID}) ==="
+  resolve_target "$target_dir"
+  apply_overrides_to_order
+
+  # Hard resolution failures: report and stop, do not build.
+  if [[ ${#CYCLES[@]} -gt 0 || ${#UNMET[@]} -gt 0 ]]; then
+    local why=""
+    if [[ ${#UNMET[@]} -gt 0 ]]; then
+      local u
+      for u in "${!UNMET[@]}"; do why+="unmet:$u(${UNMET[$u]}) "; done
+    fi
+    [[ ${#CYCLES[@]} -gt 0 ]] && why+="${CYCLES[*]}"
+    ST_STATUS["$tkey"]="UNMET-DEP"
+    ST_REASON["$tkey"]="$why"
+    echo "  resolution failed: $why"
+    echo "  add an override rule ($TB_OVERRIDES) and rerun, or fix the tree." >&2
+    return
+  fi
+
+  if [[ $DRY_RUN -eq 1 ]]; then
+    echo "  build order (dry-run):"
+    local d
+    for d in "${RESOLVED_ORDER[@]}"; do
+      local it=0; [[ "$d" == "$target_dir" ]] && it=1
+      local rdm=""; [[ "${HAS_README[$d]:-}" == 1 ]] && rdm="  [%README%]"
+      printf "    %-30s %s%s\n" "$(pkg_key "$d")" "$(cache_label "$d" "$it")" "$rdm"
+      echo "$(pkg_key "$d")" >> "$RUN_DIR/build-order.txt"
+    done
+    local fp
+    for fp in "${!FETCH_DEPS[@]}"; do
+      printf "    %-30s %s\n" "$fp" "fetch (sbopkg in container)"
+    done
+    return
+  fi
+
+  if ! confirm_order "$target_dir"; then
+    echo "  aborted."
+    ST_STATUS["$tkey"]="ABORTED"
+    return
+  fi
+
+  # Per-run docker workdirs (host side, discarded after the run).
+  DEPS_DIR="$RUN_DIR/deps"; BUILD_OUT="$RUN_DIR/out"
+  mkdir -p "$DEPS_DIR" "$BUILD_OUT"
+
+  local d failed_progs=()
+  for d in "${RESOLVED_ORDER[@]}"; do
+    local key; key="$(pkg_key "$d")"
+    local prog; prog="$(basename "$d")"
+
+    if depends_on_failed "$d" failed_progs; then
+      ST_STATUS["$key"]="BLOCKED-BY-DEP"
+      ST_REASON["$key"]="blocked by failed dep"
+      [[ "${HAS_README[$d]:-}" == "1" ]] && ST_README["$key"]=1
+      echo "  $key: BLOCKED-BY-DEP"
+      failed_progs+=("$prog")
+      continue
+    fi
+
+    local it=0; [[ "$d" == "$target_dir" ]] && it=1
+    echo "  building $key ..."
+    if build_one "$d" "$it"; then
+      echo "  $key: ${ST_STATUS[$key]} (${ST_TIME[$key]}s)"
+    else
+      echo "  $key: ${ST_STATUS[$key]} (${ST_TIME[$key]}s)"
+      failed_progs+=("$prog")
+    fi
+  done
+}
+
+# =============================================================================
+# SUMMARY (ported)
+# =============================================================================
+print_summary() {
+  local total=$SECONDS
+  local succ=0 fail=0 blocked=0 cached=0
+  local summary="$RUN_DIR/summary.log"
+
+  {
+    echo "test-build run summary"
+    echo "target: $TARGET_ARG  version: $VERSION_ID"
+    echo
+  } > "$summary"
+
+  echo
+  echo "================ SUMMARY ================"
+  local key
+  for key in "${!ST_STATUS[@]}"; do
+    local st="${ST_STATUS[$key]}" rsn="${ST_REASON[$key]:-}" t="${ST_TIME[$key]:-0}"
+    local rd=""; [[ "${ST_README[$key]:-}" == "1" ]] && rd=" [%README%]"
+    local col="$C_YEL"
+    case "$st" in
+      SUCCESS) col="$C_GRN"; ((succ++)) ;;
+      CACHED)  col="$C_GRN"; ((cached++)) ;;
+      BLOCKED-BY-DEP|UNMET-DEP|ABORTED) col="$C_YEL"; ((blocked++)) ;;
+      *) col="$C_RED"; ((fail++)) ;;
+    esac
+    printf "%s%-30s %-16s%s %s%s (%ss)\n" "$col" "$key" "$st" "$C_RST" "$rsn" "$rd" "$t"
+    printf "%-30s %-16s %s%s (%ss)\n" "$key" "$st" "$rsn" "$rd" "$t" >> "$summary"
+  done
+  echo "----------------------------------------"
+  printf "%s%d succeeded%s, %s%d failed%s, %s%d blocked%s, %s%d cached%s, total %ss\n" \
+    "$C_GRN" "$succ" "$C_RST" "$C_RED" "$fail" "$C_RST" "$C_YEL" "$blocked" "$C_RST" \
+    "$C_GRN" "$cached" "$C_RST" "$total"
+  echo "logs: $RUN_DIR"
+  if [[ $fail -eq 0 && $blocked -eq 0 ]]; then
+    echo "${C_GRN}All green.${C_RST} Safe to build the SBo submission tarball on the host."
+  fi
+  {
+    echo
+    echo "$succ succeeded, $fail failed, $blocked blocked, $cached cached, total ${total}s"
+    echo "logs: $RUN_DIR"
+  } >> "$summary"
+}
+```
+
+Add the two workdir globals near the other globals (top of the flags block):
+
+```bash
+DEPS_DIR=""        # per-run host dir of built dep .txz, mounted into the container
+BUILD_OUT=""       # per-run host dir where built packages are copied out
+```
+
+- [ ] **Step 2: Sanity-check syntax**
+
+Run: `bash -n .extras/test-build`
+Expected: no output.
+
+- [ ] **Step 3: Self-check no regression**
+
+Run: `bash .extras/test-logic.sh`
+Expected: PASS.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add .extras/test-build
+SBOLINT=no git commit -m 'test-build: run_target orchestration + summary + confirm'
+```
+
+---
+
+## Task 9: Wire main(), image presence check, target lookup
+
+**Files:**
+- Modify: `.extras/test-build`
+
+- [ ] **Step 1: Implement the full main()**
+
+Replace the current `main()` in `.extras/test-build` with:
+
+```bash
+# Verify the selected image exists locally. It is built by a separate job; this
+# script only consumes it. (Later: a local-registry docker pull slots in here.)
+require_image() {
+  if ! docker image inspect "$ACTIVE_IMAGE" >/dev/null 2>&1; then
+    cat >&2 <<EOF
+Image not found locally: $ACTIVE_IMAGE
+It is produced by the separate image-builder job (full Slackware $VERSION_ID +
+sbo-maintainer-tools + sbopkg), stored on the NAS / local registry. Load or
+pull it, then rerun. This script does not build images.
+EOF
+    exit 1
+  fi
+}
+
+main() {
+  parse_args "$@"
+  init_color
+  require_config
+  SBO_TREE_ROOTS=("$ACTIVE_TREE")
+  load_overrides
+
+  # image + cache namespace (skip the image check on a pure dry-run so the order
+  # can be inspected without the image present).
+  if [[ $DRY_RUN -eq 0 ]]; then
+    command -v docker >/dev/null 2>&1 || { echo "docker not found in PATH." >&2; exit 1; }
+    require_image
+  fi
+  resolve_cache_root
+
+  RUN_DIR="$LOG_ROOT/$(date +%Y-%m-%d_%H-%M-%S)"
+  mkdir -p "$RUN_DIR"
+  : > "$RUN_DIR/build-order.txt"
+
+  # Single-package mode: resolve the name in the active tree.
+  local tdir
+  if ! tdir="$(find_slackbuild_dir "$TARGET_ARG")"; then
+    echo "Program not found in the SBo tree ($ACTIVE_TREE): $TARGET_ARG" >&2
+    exit 1
+  fi
+
+  run_target "$tdir"
+  print_summary
+}
+```
+
+- [ ] **Step 2: Sanity-check syntax**
+
+Run: `bash -n .extras/test-build`
+Expected: no output.
+
+- [ ] **Step 3: Dry-run smoke test against the real tree (no docker needed)**
+
+This needs a real config. If `~/.config/sbo-testbuild/config` is not set up,
+create a throwaway one pointing at an existing local SBo tree, then:
+
+Run: `.extras/test-build --dry-run <some-pkg-in-that-tree>`
+Expected: prints `=== Target: ... ===`, a build order, exits 0, no docker call.
+
+- [ ] **Step 4: Self-check no regression**
+
+Run: `bash .extras/test-logic.sh`
+Expected: PASS.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add .extras/test-build
+SBOLINT=no git commit -m 'test-build: wire main, image-presence check, target lookup'
+```
+
+---
+
+## Task 10: Real end-to-end build (user-run) + README
+
+**Files:**
+- Modify: `.extras/test-build` (only if the real run surfaces a bug)
+- Create: `.extras/README.test-build` (short usage note)
+
+This task needs a real image and the buildsystem. Per repo rules the throwaway
+docker build is Claude-OK, but the IMAGE must exist first (separate job, not yet
+built). So this task is: document usage, and record the end-to-end run as a
+manual verification step the user performs once an image is available.
+
+- [ ] **Step 1: Write the usage README**
+
+Create `.extras/README.test-build`:
+
+```markdown
+# test-build
+
+Verify an already-published SBo package still builds on a target Slackware
+version inside a throwaway docker container.
+
+## Setup
+
+    mkdir -p ~/.config/sbo-testbuild
+    cp .extras/test-build-config.example ~/.config/sbo-testbuild/config
+    cp .extras/overrides.example        ~/.config/sbo-testbuild/overrides
+    $EDITOR ~/.config/sbo-testbuild/config
+
+Set the two SBo tree paths, the two image tags, LOG_ROOT, and PKG_CACHE.
+
+The images (`sbo-testbuild:current` / `:15.0`) are FULL Slackware installs plus
+`sbo-maintainer-tools` and `sbopkg`, built by a separate job (not this script).
+The script errors if the tagged image is not present locally.
+
+## Usage
+
+    .extras/test-build <pkg>            # build on -current (default)
+    .extras/test-build --stable <pkg>   # build on 15.0
+    .extras/test-build --dry-run <pkg>  # show the build order, no build
+    .extras/test-build --yes <pkg>      # skip the confirm (order still shown)
+    .extras/test-build --no-cache <pkg> # rebuild all deps this run
+
+A green run means it is safe to build the SBo submission tarball on the host.
+
+## current-vs-stable overrides
+
+`~/.config/sbo-testbuild/overrides` (see `overrides.example`) encodes deltas
+that only apply when building on -current:
+
+    drop:   <prog>            already in the -current base
+    rename: <old> -> <new>    renamed on -current
+    fetch:  <prog>            removed from the -current tree; built via sbopkg
+
+Start light; add rules only when a real package needs them.
+
+## Self-check
+
+    bash .extras/test-logic.sh
+```
+
+- [ ] **Step 2: Commit the docs**
+
+```bash
+git add .extras/README.test-build
+SBOLINT=no git commit -m 'test-build: usage README'
+```
+
+- [ ] **Step 3: Manual end-to-end verification (user, once an image exists)**
+
+Documented for the user to run when a `sbo-testbuild:*` image is available:
+
+```bash
+# pick a small already-published package with a dep, e.g. one already in the repo
+.extras/test-build --yes <pkg>
+```
+
+Expected: build order printed, deps built (or CACHED on a second run), target
+built, `sbopkglint` result shown, summary green, `All green.` line printed.
+A second run of the same package should show its deps as `CACHED`.
+
+Record the outcome. If a real bug surfaces (mount path, sbopkg invocation,
+package glob), fix it in `.extras/test-build` and re-run; add a self-check case
+if the bug was in pure logic.
+
+---
+
+## Self-Review
+
+Run this checklist against the spec after the plan is written:
+
+**1. Spec coverage:**
+- purpose / one-target-per-run: Task 2 (`parse_args`), Task 9 (`main`) - covered
+- two versions, current default: Task 2 (`--stable`, `select_version_paths`) - covered
+- resolve local tree + topo: Task 3 - covered
+- overrides drop/rename/fetch + UNMET stop: Task 4, stop in Task 8 `run_target` - covered
+- external config + overrides file: Task 2, Task 4 - covered
+- external image, presence check, no bake: Task 9 `require_image` - covered
+- container build (download/md5/build/installpkg): Task 7 - covered
+- fetch via sbopkg: Task 7 (`FETCH_LIST` loop) - covered
+- dep cache, digest-namespaced, --no-cache, target always fresh: Task 5, wired Task 7/8 - covered
+- target lint: Task 7 `lint_pkg`, called in Task 7 build_one - covered
+- confirm order + --yes still prints: Task 8 `confirm_order` - covered
+- --dry-run: Task 8 `run_target`, Task 9 skips image check - covered
+- report + logs (per-pkg, summary, build-order): Task 8 `print_summary`, Task 7 logs - covered
+- status values incl CACHED: Task 8 `print_summary` - covered
+- self-check parity: Tasks 1-6 - covered
+
+**2. Placeholder scan:** no TBD/TODO in code steps; every code step shows full
+code. The one deferred item (real end-to-end run) is explicit and gated on an
+external image, not a placeholder.
+
+**3. Type consistency:** function + global names match across tasks:
+`RESOLVED_ORDER`, `FETCH_DEPS`, `OV_DROP/OV_RENAME/OV_FETCH`, `CACHE_ROOT`,
+`ACTIVE_TREE/ACTIVE_IMAGE`, `DEPS_DIR/BUILD_OUT`, `cache_decision/cache_path/
+cache_store/cache_label`, `select_version_paths`, `apply_overrides_to_order`,
+`apply_rename`, `load_overrides`, `resolve_cache_root`, `require_image`,
+`build_one(dir,is_target)`, `run_target`, `confirm_order`, `print_summary`.
+Consistent.
+
+## Notes on deliberate simplifications
+
+- Single-package mode only (no category-folder / all / queue modes). This repo
+  bumps one package at a time. Extension point is `main`'s target lookup.
+- `-j` parallelism dropped entirely (was a no-op stub upstream). Builds serial.
+- fetch deps are not topo-ordered among themselves; sbopkg resolves their own
+  deps. Start light per the spec; revisit if a fetch dep needs another fetch dep.
+```
+
diff --git a/docs/plans/2026-07-13-image-builder.md b/docs/plans/2026-07-13-image-builder.md
new file mode 100644
index 0000000..0c61051
--- /dev/null
+++ b/docs/plans/2026-07-13-image-builder.md
@@ -0,0 +1,790 @@
+# sbo-testbuild image builder — Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Build the three chained bash scripts that produce `sbo-testbuild:current` / `sbo-testbuild:15.0` docker images from NAS Slackware trees and push them to a LAN registry, consumed by `.extras/test-build`.
+
+**Architecture:** Adapt the forge `slackware/docker-images` scripts (`bootstrap.sh`, `build-full-image.sh`) into `.extras/image-builder/`. Add a third `build-sbo-testbuild.sh` layer. Share config + helpers via `config` and `lib.sh`. Pure-logic helpers are unit-tested with an assert-based self-check; the docker chain is verified manually on the VM.
+
+**Tech Stack:** bash, docker, slackpkg/installpkg (Slackware), `registry:2`.
+
+**Reference:** design spec at `.extras/docs/specs/2026-07-13-image-builder-design.md`. Forge originals cloned at (scratchpad) `docker-images/scripts/` — re-clone with `git clone slackware_forge:slackware/docker-images.git` if gone.
+
+---
+
+## File Structure
+
+```
+.extras/image-builder/
+├── config                    REGISTRY, MIRROR, VARIANTS, PKGDIR (sourced by all)
+├── lib.sh                    _log/_warn/_err, fetch(), txz_hash(), require_mount()
+├── bootstrap.sh              base image FROM scratch (root; installpkg from NAS)
+├── build-full-image.sh       full image FROM base (slackpkg all series)
+├── build-sbo-testbuild.sh    testbuild image FROM full (installpkg sbopkg + tools)
+├── test-image-builder.sh     assert-based self-check for lib.sh logic
+└── README                    VM-side setup checklist
+```
+
+Responsibilities:
+- **config** — the only place hostnames/paths/variants live. No script hardcodes them.
+- **lib.sh** — all shared, testable logic. Sourced by the three build scripts and by the test. No side effects at source time (only function defs + nothing else).
+- **bootstrap/full/testbuild** — one image each, thin: guard, gate, generate Dockerfile, build, push.
+- **test-image-builder.sh** — sources lib.sh, exercises fetch/txz_hash/require_mount with asserts. No docker.
+
+---
+
+## Task 1: config + lib.sh skeleton
+
+**Files:**
+- Create: `.extras/image-builder/config`
+- Create: `.extras/image-builder/lib.sh`
+
+- [ ] **Step 1: Write config**
+
+Create `.extras/image-builder/config`:
+
+```sh
+# Shared configuration for the sbo-testbuild image builder.
+# Sourced by bootstrap.sh, build-full-image.sh, build-sbo-testbuild.sh, tests.
+
+REGISTRY="docker.noland.dnx:5000"
+MIRROR="file:///mnt/nas"
+VARIANTS=(current 15.0)              # x86_64 only for now
+PKGDIR="/opt/sbo-testbuild/pkgs"     # sbopkg + sbo-maintainer-tools .txz
+HASH_DIR="/var/cache/sbo-testbuild"  # ChangeLog hashes for rebuild gating
+```
+
+- [ ] **Step 2: Write lib.sh with logging + require_mount**
+
+Create `.extras/image-builder/lib.sh`:
+
+```sh
+# Shared helpers for the image builder. Source, do not execute.
+# Sourcing must have no side effects beyond defining functions.
+
+_log()  { echo "[$(date '+%Y-%m-%d %H:%M:%S')] [${LOG_TAG:-image-builder}] $*"; }
+_warn() { echo "[$(date '+%Y-%m-%d %H:%M:%S')] [${LOG_TAG:-image-builder}] WARNING: $*" >&2; }
+_err()  { echo "[$(date '+%Y-%m-%d %H:%M:%S')] [${LOG_TAG:-image-builder}] ERROR: $*" >&2; exit 1; }
+
+# mirror_path MIRROR RELPATH
+# Join a MIRROR (file:///... or http(s)://...) with a relative path.
+mirror_path() {
+    local mirror="$1" rel="$2"
+    printf '%s/%s' "${mirror%/}" "${rel#/}"
+}
+
+# is_local_mirror MIRROR -> 0 if file:// or bare absolute path, else 1
+is_local_mirror() {
+    case "$1" in
+        file://*) return 0 ;;
+        http://*|https://*) return 1 ;;
+        /*) return 0 ;;
+        *) return 1 ;;
+    esac
+}
+
+# strip_scheme URL -> filesystem path for a file:// or bare-local URL
+strip_scheme() {
+    local u="$1"
+    case "$u" in
+        file://*) printf '%s' "${u#file://}" ;;
+        *) printf '%s' "$u" ;;
+    esac
+}
+
+# fetch SRC DEST
+# Copy SRC (a full mirror URL) to DEST. Local mirror -> cp, http -> curl.
+# Returns non-zero on failure; caller decides whether that is fatal.
+fetch() {
+    local src="$1" dest="$2"
+    if is_local_mirror "$src"; then
+        local path; path="$(strip_scheme "$src")"
+        [[ -f "$path" ]] || return 1
+        cp "$path" "$dest"
+    else
+        curl -sSfL --connect-timeout 60 "$src" -o "$dest"
+    fi
+}
+
+# txz_hash DIR
+# Stable hash of the set of .txz files in DIR (names + contents), order
+# independent. Empty/absent dir -> empty string.
+txz_hash() {
+    local dir="$1"
+    [[ -d "$dir" ]] || { printf ''; return 0; }
+    local files; files=$(find "$dir" -maxdepth 1 -name '*.txz' -type f | sort)
+    [[ -n "$files" ]] || { printf ''; return 0; }
+    # Hash sorted "name  sha256" lines so reordering does not change output.
+    while IFS= read -r f; do
+        printf '%s  %s\n' "$(basename "$f")" "$(sha256sum "$f" | cut -d' ' -f1)"
+    done <<< "$files" | sha256sum | cut -d' ' -f1
+}
+
+# require_mount VERSION
+# Assert the NAS tree for VERSION is mounted (file:// mirror only).
+# x86_64 tree dir is slackware64-${VERSION}.
+require_mount() {
+    local version="$1"
+    is_local_mirror "$MIRROR" || return 0   # http mirror: nothing to check
+    local base; base="$(strip_scheme "$MIRROR")"
+    local dir="${base}/slackware64-${version}"
+    [[ -d "$dir" ]] || _err "NAS tree not mounted: ${dir}"
+}
+```
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add .extras/image-builder/config .extras/image-builder/lib.sh
+git commit -m 'image-builder: config + lib.sh helpers'
+```
+
+---
+
+## Task 2: lib.sh self-check
+
+**Files:**
+- Create: `.extras/image-builder/test-image-builder.sh`
+
+- [ ] **Step 1: Write the test**
+
+Create `.extras/image-builder/test-image-builder.sh`:
+
+```sh
+#!/bin/bash
+# Assert-based self-check for lib.sh pure logic. No docker, no network.
+# Run: bash .extras/image-builder/test-image-builder.sh
+set -u
+cd "$(dirname "$0")"
+source ./lib.sh
+
+pass=0 fail=0
+check() { # DESC EXPECTED ACTUAL
+    if [[ "$2" == "$3" ]]; then pass=$((pass+1));
+    else fail=$((fail+1)); echo "FAIL: $1"; echo "  expected: [$2]"; echo "  actual:   [$3]"; fi
+}
+check_rc() { # DESC EXPECTED_RC ACTUAL_RC
+    if [[ "$2" == "$3" ]]; then pass=$((pass+1));
+    else fail=$((fail+1)); echo "FAIL: $1 (rc expected $2 got $3)"; fi
+}
+
+tmp="$(mktemp -d)"
+trap 'rm -rf "$tmp"' EXIT
+
+# --- mirror_path ---
+check "mirror_path trailing slash" \
+    "file:///mnt/nas/slackware64-current/PACKAGES.TXT" \
+    "$(mirror_path 'file:///mnt/nas/' 'slackware64-current/PACKAGES.TXT')"
+check "mirror_path no trailing slash" \
+    "file:///mnt/nas/x/y" "$(mirror_path 'file:///mnt/nas' '/x/y')"
+
+# --- is_local_mirror ---
+is_local_mirror "file:///mnt/nas"; check_rc "is_local file://" 0 $?
+is_local_mirror "/mnt/nas";        check_rc "is_local bare abs" 0 $?
+is_local_mirror "https://x/y";     check_rc "is_local https" 1 $?
+
+# --- strip_scheme ---
+check "strip_scheme file://" "/mnt/nas" "$(strip_scheme 'file:///mnt/nas')"
+check "strip_scheme bare" "/mnt/nas" "$(strip_scheme '/mnt/nas')"
+
+# --- fetch: local file resolves ---
+echo hello > "$tmp/src.txt"
+fetch "file://$tmp/src.txt" "$tmp/dst.txt"; check_rc "fetch local ok" 0 $?
+check "fetch local content" "hello" "$(cat "$tmp/dst.txt" 2>/dev/null)"
+
+# --- fetch: missing local file errors ---
+fetch "file://$tmp/nope.txt" "$tmp/x.txt"; check_rc "fetch local missing" 1 $?
+
+# --- txz_hash: stable + content-sensitive ---
+mkdir -p "$tmp/pkgs"
+printf a > "$tmp/pkgs/sbopkg-1.txz"
+printf b > "$tmp/pkgs/tools-1.txz"
+h1="$(txz_hash "$tmp/pkgs")"
+h2="$(txz_hash "$tmp/pkgs")"
+check "txz_hash stable" "$h1" "$h2"
+printf c > "$tmp/pkgs/tools-1.txz"   # change content
+h3="$(txz_hash "$tmp/pkgs")"
+check_rc "txz_hash changes on content" 0 "$([[ "$h1" != "$h3" ]] && echo 0 || echo 1)"
+check "txz_hash empty dir" "" "$(txz_hash "$tmp/empty-nope")"
+
+# --- require_mount: missing mount errors (subshell to catch _err exit) ---
+MIRROR="file://$tmp/no-such-root"
+( require_mount current ) 2>/dev/null; check_rc "require_mount missing" 1 $?
+mkdir -p "$tmp/mnt/slackware64-current"
+MIRROR="file://$tmp/mnt"
+( require_mount current ) 2>/dev/null; check_rc "require_mount present" 0 $?
+MIRROR="https://example/x"
+( require_mount current ) 2>/dev/null; check_rc "require_mount http skips" 0 $?
+
+echo "----"
+echo "PASS: $pass  FAIL: $fail"
+[[ "$fail" -eq 0 ]]
+```
+
+- [ ] **Step 2: Run — expect PASS**
+
+Run: `bash .extras/image-builder/test-image-builder.sh`
+Expected: final line `PASS: N  FAIL: 0`, exit 0.
+
+If any FAIL, fix `lib.sh` (the test encodes the intended behavior).
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add .extras/image-builder/test-image-builder.sh
+git commit -m 'image-builder: lib.sh self-check'
+```
+
+---
+
+## Task 3: bootstrap.sh (base image)
+
+**Files:**
+- Create: `.extras/image-builder/bootstrap.sh`
+- Reference: forge `docker-images/scripts/bootstrap.sh`
+
+This is the forge `bootstrap.sh` adapted: source `config`+`lib.sh`, drop i586,
+`file://` fetch via `fetch()`, LAN registry, `sbo-base` name, mount guard.
+
+- [ ] **Step 1: Write bootstrap.sh**
+
+Create `.extras/image-builder/bootstrap.sh`. Start from the forge original and apply exactly these changes; everything else (the `download_pkgtxt`, `find_package`, rootfs configuration, cleanup, Dockerfile-from-scratch blocks) is copied verbatim from the forge script:
+
+1. Header block:
+
+```sh
+#!/bin/bash
+# bootstrap.sh — build the sbo-base:{ver} image FROM scratch from NAS trees.
+# Run as root (installpkg). Adapted from forge slackware/docker-images.
+set -euo pipefail
+HERE="$(cd "$(dirname "$0")" && pwd)"
+source "${HERE}/config"
+LOG_TAG=bootstrap
+source "${HERE}/lib.sh"
+
+REGISTRY_IMAGE="${REGISTRY}/sbo-base"
+[[ "${EUID}" -eq 0 ]] || _err "run as root."
+mkdir -p "${HASH_DIR}"
+```
+
+2. Argument parsing: keep `--force` and `--version` only; **remove `--arch`**
+   (x86_64 fixed). Variant list comes from config:
+
+```sh
+FORCE=false
+OPT_VERSION=""
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --version) OPT_VERSION="$2"; shift 2 ;;
+        --force)   FORCE=true;       shift   ;;
+        *) _err "unknown argument: $1" ;;
+    esac
+done
+if [[ -n "${OPT_VERSION}" ]]; then
+    BUILD_VARIANTS=("${OPT_VERSION}")
+else
+    BUILD_VARIANTS=("${VARIANTS[@]}")
+fi
+```
+
+3. Copy the forge `PACKAGES=( ... )` array verbatim (lines 80–187 of the forge
+   original — the full base package list).
+
+4. Replace `changelog_changed`: read ChangeLog via `fetch` from the NAS,
+   x86_64-only repo key:
+
+```sh
+# changelog_changed VERSION -> 0 if changed (or --force), else 1
+changelog_changed() {
+    local version="$1"
+    local repo_key="slackware64-${version}"
+    local hash_file="${HASH_DIR}/${repo_key}.sha256"
+    local url; url="$(mirror_path "${MIRROR}" "${repo_key}/ChangeLog.txt")"
+    local tmp; tmp="$(mktemp)"
+    if ! fetch "${url}" "${tmp}"; then
+        rm -f "${tmp}"
+        _warn "${repo_key}: cannot read ChangeLog (${url}); skipping."
+        return 1
+    fi
+    local live; live=$(sha256sum "${tmp}" | cut -d' ' -f1); rm -f "${tmp}"
+    if [[ "${FORCE}" == "true" ]]; then
+        echo "${live}" > "${hash_file}"; return 0
+    fi
+    local stored=""; [[ -f "${hash_file}" ]] && stored=$(cat "${hash_file}")
+    if [[ "${live}" == "${stored}" ]]; then
+        _log "${repo_key}: ChangeLog unchanged; skipping."; return 1
+    fi
+    _log "${repo_key}: ChangeLog changed."; echo "${live}" > "${hash_file}"; return 0
+}
+```
+
+5. Copy `download_pkgtxt` and `find_package` verbatim from the forge original,
+   but change the two `curl -sfL ... "${URL}" -o "${DEST}"` download lines in
+   `download_pkgtxt` to `fetch "${URL}" "${DEST}"` (drops the http assumption).
+
+6. `build_variant`: take `VERSION` only (no ARCH). Set:
+
+```sh
+build_variant() {
+    local VERSION="$1"
+    require_mount "${VERSION}"
+    local REPO_KEY="slackware64-${VERSION}"
+    local PKG_PATH; PKG_PATH="$(mirror_path "${MIRROR}" "${REPO_KEY}")"
+    local TAG="${REGISTRY_IMAGE}:${VERSION}"
+    local SLACKPKG_MIRROR="https://slackware.nl/slackware/slackware64-${VERSION}/"
+    ...
+}
+```
+
+   The `SLACKPKG_MIRROR` written into the image stays an https slackware.nl URL
+   (it is used later by slackpkg inside the container, which has internet; the
+   NAS `file://` mount only feeds the host-side build). Keep the rest of the
+   forge `build_variant` body verbatim, except:
+   - the package **download loop** uses `fetch "${URL}" "${PKGCACHE}/${FILENAME}"`
+     instead of `curl`.
+   - the final `docker build ... && docker push` targets `${TAG}` as above.
+
+7. Main loop over `BUILD_VARIANTS`, one arg:
+
+```sh
+for VERSION in "${BUILD_VARIANTS[@]}"; do
+    if changelog_changed "${VERSION}"; then
+        build_variant "${VERSION}"
+    fi
+done
+```
+
+- [ ] **Step 2: Syntax check**
+
+Run: `bash -n .extras/image-builder/bootstrap.sh`
+Expected: no output, exit 0.
+
+- [ ] **Step 3: shellcheck (if available)**
+
+Run: `shellcheck -x .extras/image-builder/bootstrap.sh || true`
+Expected: no errors (warnings about unreachable `_err` exit are fine). If shellcheck absent, skip.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add .extras/image-builder/bootstrap.sh
+git commit -m 'image-builder: bootstrap.sh base image from NAS'
+```
+
+---
+
+## Task 4: build-full-image.sh
+
+**Files:**
+- Create: `.extras/image-builder/build-full-image.sh`
+- Reference: forge `docker-images/scripts/build-full-image.sh`
+
+Forge `build-full-image.sh` adapted: source config+lib, drop i586, LAN
+registry, `sbo-base`→`sbo-full` names.
+
+- [ ] **Step 1: Write build-full-image.sh**
+
+Create `.extras/image-builder/build-full-image.sh`. From the forge original, apply exactly:
+
+1. Header:
+
+```sh
+#!/bin/bash
+# build-full-image.sh — sbo-full:{ver} FROM sbo-base:{ver}, all series.
+# Adapted from forge slackware/docker-images. No root needed.
+set -euo pipefail
+HERE="$(cd "$(dirname "$0")" && pwd)"
+source "${HERE}/config"
+LOG_TAG=full
+source "${HERE}/lib.sh"
+
+BASE_IMAGE="${REGISTRY}/sbo-base"
+FULL_IMAGE="${REGISTRY}/sbo-full"
+DIGEST_LABEL="sbo.full.base-digest"
+```
+
+2. Arg parsing: `--force` and `--version` only (no `--arch`), variant list from
+   config — identical shape to bootstrap Task 3 Step 1.2, but `BUILD_VARIANTS`.
+
+3. `derive_tags VERSION`:
+
+```sh
+derive_tags() {
+    local VERSION="$1"
+    BASE_TAG="${BASE_IMAGE}:${VERSION}"
+    FULL_TAG="${FULL_IMAGE}:${VERSION}"
+}
+```
+
+4. Keep `needs_rebuild` verbatim from the forge original (it already takes
+   BASE_TAG/FULL_TAG args and uses `_log`/`_warn`/`FORCE`).
+
+5. `build_variant VERSION`: drop the ARCH/ARCH_SUFFIX lines; call
+   `derive_tags "${VERSION}"`. Keep the forge Dockerfile heredoc **verbatim**
+   (the `slackpkg update` + all-series install + cleanup + labels). Only the
+   `LABEL org.opencontainers.image.title/description` strings lose the
+   `(${ARCH})` suffix; leave them or hardcode `(x86_64)`.
+
+6. Main loop over `BUILD_VARIANTS`:
+
+```sh
+for VERSION in "${BUILD_VARIANTS[@]}"; do
+    build_variant "${VERSION}"
+done
+```
+
+- [ ] **Step 2: Syntax check**
+
+Run: `bash -n .extras/image-builder/build-full-image.sh`
+Expected: exit 0.
+
+- [ ] **Step 3: shellcheck (if available)**
+
+Run: `shellcheck -x .extras/image-builder/build-full-image.sh || true`
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add .extras/image-builder/build-full-image.sh
+git commit -m 'image-builder: build-full-image.sh'
+```
+
+---
+
+## Task 5: build-sbo-testbuild.sh
+
+**Files:**
+- Create: `.extras/image-builder/build-sbo-testbuild.sh`
+
+New script (no forge equivalent). FROM sbo-full, installpkg the two .txz,
+gate on full digest AND .txz-set hash.
+
+- [ ] **Step 1: Write build-sbo-testbuild.sh**
+
+Create `.extras/image-builder/build-sbo-testbuild.sh`:
+
+```sh
+#!/bin/bash
+# build-sbo-testbuild.sh — sbo-testbuild:{ver} FROM sbo-full:{ver}.
+# Adds sbopkg + sbo-maintainer-tools from prebuilt .txz in PKGDIR.
+# Rebuilds when the full image OR the .txz set changes.
+set -euo pipefail
+HERE="$(cd "$(dirname "$0")" && pwd)"
+source "${HERE}/config"
+LOG_TAG=testbuild
+source "${HERE}/lib.sh"
+
+FULL_IMAGE="${REGISTRY}/sbo-full"
+TB_IMAGE="${REGISTRY}/sbo-testbuild"
+DIGEST_LABEL="sbo.testbuild.full-digest"
+PKGS_LABEL="sbo.testbuild.pkgs-hash"
+
+FORCE=false
+OPT_VERSION=""
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --version) OPT_VERSION="$2"; shift 2 ;;
+        --force)   FORCE=true;       shift   ;;
+        *) _err "unknown argument: $1" ;;
+    esac
+done
+if [[ -n "${OPT_VERSION}" ]]; then
+    BUILD_VARIANTS=("${OPT_VERSION}")
+else
+    BUILD_VARIANTS=("${VARIANTS[@]}")
+fi
+
+# Verify the required .txz are present before doing anything.
+require_pkgs() {
+    [[ -d "${PKGDIR}" ]] || _err "PKGDIR missing: ${PKGDIR}"
+    compgen -G "${PKGDIR}/sbopkg-*.txz" >/dev/null \
+        || _err "no sbopkg-*.txz in ${PKGDIR}"
+    compgen -G "${PKGDIR}/sbo-maintainer-tools-*.txz" >/dev/null \
+        || _err "no sbo-maintainer-tools-*.txz in ${PKGDIR}"
+}
+
+# needs_rebuild FULL_TAG TB_TAG PKGS_HASH -> 0 if rebuild needed
+needs_rebuild() {
+    local full_tag="$1" tb_tag="$2" pkgs_hash="$3"
+    [[ "${FORCE}" == "true" ]] && { _log "  --force."; return 0; }
+
+    local full_digest
+    full_digest=$(docker inspect --format '{{index .RepoDigests 0}}' \
+        "${full_tag}" 2>/dev/null || echo "")
+    [[ -n "${full_digest}" ]] || { _warn "  no full digest; rebuilding."; return 0; }
+
+    local rec_digest rec_pkgs
+    rec_digest=$(docker inspect \
+        --format "{{index .Config.Labels \"${DIGEST_LABEL}\"}}" \
+        "${tb_tag}" 2>/dev/null || echo "")
+    rec_pkgs=$(docker inspect \
+        --format "{{index .Config.Labels \"${PKGS_LABEL}\"}}" \
+        "${tb_tag}" 2>/dev/null || echo "")
+
+    if [[ "${full_digest}" == "${rec_digest}" && "${pkgs_hash}" == "${rec_pkgs}" ]]; then
+        _log "  full image and .txz set unchanged; skipping."
+        return 1
+    fi
+    _log "  full image or .txz set changed; rebuilding."
+    return 0
+}
+
+build_variant() {
+    local VERSION="$1"
+    local FULL_TAG="${FULL_IMAGE}:${VERSION}"
+    local TB_TAG="${TB_IMAGE}:${VERSION}"
+    _log "=== ${TB_TAG} ==="
+
+    _log "  Pulling ${FULL_TAG}..."
+    docker pull "${FULL_TAG}"
+
+    local PKGS_HASH; PKGS_HASH="$(txz_hash "${PKGDIR}")"
+
+    if ! needs_rebuild "${FULL_TAG}" "${TB_TAG}" "${PKGS_HASH}"; then
+        return 0
+    fi
+
+    local FULL_DIGEST
+    FULL_DIGEST=$(docker inspect --format '{{index .RepoDigests 0}}' "${FULL_TAG}")
+
+    local WORKDIR; WORKDIR="$(mktemp -d /tmp/sbo-testbuild.XXXXXX)"
+    trap "rm -rf '${WORKDIR}'" RETURN
+    mkdir -p "${WORKDIR}/pkgs"
+    cp "${PKGDIR}"/sbopkg-*.txz "${PKGDIR}"/sbo-maintainer-tools-*.txz "${WORKDIR}/pkgs/"
+
+    cat > "${WORKDIR}/Dockerfile" <<DOCKERFILE
+FROM ${FULL_TAG}
+LABEL maintainer="danix <danix@danix.xyz>"
+COPY pkgs/*.txz /tmp/pkgs/
+RUN installpkg /tmp/pkgs/*.txz && rm -rf /tmp/pkgs
+RUN /sbin/ldconfig
+LABEL org.opencontainers.image.created="$(date -u +%Y-%m-%dT%H:%M:%SZ)"
+LABEL org.opencontainers.image.title="SBo test-build env ${VERSION} (x86_64)"
+LABEL org.opencontainers.image.description="Slackware ${VERSION} full + sbopkg + sbo-maintainer-tools"
+LABEL slackware.version="${VERSION}"
+LABEL ${DIGEST_LABEL}="${FULL_DIGEST}"
+LABEL ${PKGS_LABEL}="${PKGS_HASH}"
+CMD ["/bin/bash"]
+DOCKERFILE
+
+    local BUILD_FLAGS=()
+    [[ "${FORCE}" == "true" ]] && BUILD_FLAGS+=(--no-cache)
+    _log "  Building ${TB_TAG}..."
+    docker build "${BUILD_FLAGS[@]}" -t "${TB_TAG}" "${WORKDIR}"
+    _log "  Pushing ${TB_TAG}..."
+    docker push "${TB_TAG}"
+    _log "=== Done: ${TB_TAG} ==="
+}
+
+require_pkgs
+for VERSION in "${BUILD_VARIANTS[@]}"; do
+    build_variant "${VERSION}"
+done
+```
+
+- [ ] **Step 2: Syntax check**
+
+Run: `bash -n .extras/image-builder/build-sbo-testbuild.sh`
+Expected: exit 0.
+
+- [ ] **Step 3: shellcheck (if available)**
+
+Run: `shellcheck -x .extras/image-builder/build-sbo-testbuild.sh || true`
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add .extras/image-builder/build-sbo-testbuild.sh
+git commit -m 'image-builder: build-sbo-testbuild.sh'
+```
+
+---
+
+## Task 6: per-variant isolation
+
+The spec requires one variant failing not to block the other, non-zero exit at
+the end. Add this to all three scripts' main loops.
+
+**Files:**
+- Modify: `.extras/image-builder/bootstrap.sh` (main loop)
+- Modify: `.extras/image-builder/build-full-image.sh` (main loop)
+- Modify: `.extras/image-builder/build-sbo-testbuild.sh` (main loop)
+
+- [ ] **Step 1: Wrap each main loop**
+
+In each script, replace the plain `for VERSION ...` main loop with an
+isolation wrapper. For **bootstrap.sh** (which also has the changelog gate):
+
+```sh
+rc=0
+for VERSION in "${BUILD_VARIANTS[@]}"; do
+    if changelog_changed "${VERSION}"; then
+        if ! ( build_variant "${VERSION}" ); then
+            _warn "variant ${VERSION} failed; continuing."
+            rc=1
+        fi
+    fi
+done
+exit "${rc}"
+```
+
+For **build-full-image.sh** and **build-sbo-testbuild.sh** (no changelog gate):
+
+```sh
+rc=0
+for VERSION in "${BUILD_VARIANTS[@]}"; do
+    if ! ( build_variant "${VERSION}" ); then
+        _warn "variant ${VERSION} failed; continuing."
+        rc=1
+    fi
+done
+exit "${rc}"
+```
+
+Note: `build_variant` runs in a subshell `( )` so a `set -e` abort inside it
+(or an `_err` exit) is contained and the loop proceeds to the next variant.
+For build-sbo-testbuild.sh keep the `require_pkgs` call **before** the loop
+(a missing .txz is fatal for all variants, not per-variant).
+
+- [ ] **Step 2: Syntax check all three**
+
+Run: `for f in bootstrap build-full-image build-sbo-testbuild; do bash -n .extras/image-builder/$f.sh; done`
+Expected: exit 0, no output.
+
+- [ ] **Step 3: Re-run lib self-check (unaffected, sanity)**
+
+Run: `bash .extras/image-builder/test-image-builder.sh`
+Expected: `FAIL: 0`.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add .extras/image-builder/bootstrap.sh .extras/image-builder/build-full-image.sh .extras/image-builder/build-sbo-testbuild.sh
+git commit -m 'image-builder: per-variant isolation, non-zero exit on failure'
+```
+
+---
+
+## Task 7: README
+
+**Files:**
+- Create: `.extras/image-builder/README`
+
+- [ ] **Step 1: Write README**
+
+Create `.extras/image-builder/README` with the VM-side setup, verbatim:
+
+```
+sbo-testbuild image builder
+===========================
+
+Builds the docker images that .extras/test-build consumes:
+  docker.noland.dnx:5000/sbo-testbuild:current
+  docker.noland.dnx:5000/sbo-testbuild:15.0
+
+Three scripts, chained (see .extras/docs/specs/2026-07-13-image-builder-design.md):
+  bootstrap.sh           sbo-base:{ver}       FROM scratch, base pkgs from NAS
+  build-full-image.sh    sbo-full:{ver}       FROM base, all series
+  build-sbo-testbuild.sh sbo-testbuild:{ver}  FROM full, + sbopkg + tools
+
+All settings live in ./config.
+
+VM setup (docker.noland.dnx, Slackware x86_64, 4 vCPU / 4 GB / 80 GB)
+--------------------------------------------------------------------
+1. Install docker; enable the daemon.
+
+2. NFS-mount the two NAS trees read-only, named to match:
+     /mnt/nas/slackware64-current   -> -current mirror tree
+     /mnt/nas/slackware64-15.0      -> 15.0 mirror tree
+   Each is a full mirror (PACKAGES.TXT, ChangeLog.txt, slackware64/, patches/,
+   extra/). Root must be able to read them (bootstrap runs installpkg as root).
+
+3. Run a LAN registry:
+     docker run -d --restart=always -p 5000:5000 \
+       -v /opt/registry/data:/var/lib/registry --name registry registry:2
+
+4. Mark the registry insecure (plain HTTP) on the VM AND every pulling client
+   (this dev box, the buildsystem VM). In /etc/docker/daemon.json:
+     { "insecure-registries": ["docker.noland.dnx:5000"] }
+   then restart docker.
+
+5. Drop the two prebuilt packages (built once, re-drop on upstream bumps):
+     /opt/sbo-testbuild/pkgs/sbopkg-*.txz
+     /opt/sbo-testbuild/pkgs/sbo-maintainer-tools-*.txz
+
+6. Install the nightly cron (root):
+      0 4 * * *  /path/to/.extras/image-builder/bootstrap.sh           >> /var/log/sbo-testbuild.log 2>&1
+     15 4 * * *  /path/to/.extras/image-builder/build-full-image.sh    >> /var/log/sbo-testbuild.log 2>&1
+     30 4 * * *  /path/to/.extras/image-builder/build-sbo-testbuild.sh >> /var/log/sbo-testbuild.log 2>&1
+
+7. Ensure docker.noland.dnx resolves on the LAN (static IP or DNS).
+
+Manual first run
+----------------
+   ./bootstrap.sh --version current --force
+   ./build-full-image.sh --version current --force
+   ./build-sbo-testbuild.sh --version current --force
+Then confirm:
+   docker pull docker.noland.dnx:5000/sbo-testbuild:current
+   docker run --rm docker.noland.dnx:5000/sbo-testbuild:current sbopkg -V
+
+Flags: --force (rebuild unconditionally), --version <current|15.0> (one variant).
+
+Tests
+-----
+   bash test-image-builder.sh     # pure-logic self-check, no docker
+```
+
+- [ ] **Step 2: Commit**
+
+```bash
+git add .extras/image-builder/README
+git commit -m 'image-builder: README with VM setup checklist'
+```
+
+---
+
+## Task 8: executable bits + final check
+
+**Files:**
+- Modify (mode): the four `.sh` scripts
+
+- [ ] **Step 1: chmod +x the scripts**
+
+```bash
+chmod +x .extras/image-builder/bootstrap.sh \
+         .extras/image-builder/build-full-image.sh \
+         .extras/image-builder/build-sbo-testbuild.sh \
+         .extras/image-builder/test-image-builder.sh
+```
+
+- [ ] **Step 2: Run the self-check once more**
+
+Run: `bash .extras/image-builder/test-image-builder.sh`
+Expected: `PASS: N  FAIL: 0`, exit 0.
+
+- [ ] **Step 3: Syntax-check all four**
+
+Run: `for f in .extras/image-builder/*.sh; do bash -n "$f" || echo "SYNTAX FAIL: $f"; done`
+Expected: no `SYNTAX FAIL` lines.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add .extras/image-builder
+git commit -m 'image-builder: mark scripts executable'
+```
+
+---
+
+## Deferred (not in this plan)
+
+- **Real end-to-end chain** on the VM (bootstrap→full→testbuild producing a
+  pushed `sbo-testbuild:current`): the user runs it once the VM/registry/mounts
+  exist, and reports back. Mirrors `.extras/test-build` Task 10.
+- **`installed_in_base`** in `.extras/test-build`: now unblockable (query the
+  built image's package db) but tracked separately in the project memory
+  `test-build-image-builder-todo`.
+- **i586** variants.
+- **Registry auth/TLS** (LAN plain HTTP for now).
+```
diff --git a/docs/specs/2026-07-13-docker-test-build-design.md b/docs/specs/2026-07-13-docker-test-build-design.md
new file mode 100644
index 0000000..9f14d1e
--- /dev/null
+++ b/docs/specs/2026-07-13-docker-test-build-design.md
@@ -0,0 +1,258 @@
+# Docker test-build script - design
+
+Date: 2026-07-13
+
+## Purpose
+
+A single bash script that verifies an already-published SBo package still
+builds cleanly on a target Slackware version, inside a throwaway docker
+container. This is the "test-build" step of this repo's maintenance loop
+(track upstream -> bump -> **test-build** -> make tarball).
+
+The container is disposable, so unlike a real `slackrepo build` this runs
+directly (no host install), and Claude may run it (per the repo's
+`Who builds SlackBuilds` exception).
+
+## Scope and non-goals
+
+- One target package per run: `test-build <pkg>`.
+- Two Slackware targets: `-current` (default) and `15.0` (`--stable`).
+- Resolves the target's SBo dependency tree from the LOCAL SBo tree, builds
+  deps then target in the container, reports, discards everything.
+- NOT a redistributable-package builder. The container's built `.txz` is
+  throwaway; the SBo submission tarball is made separately (post-commit hook)
+  only after a green run.
+- Does NOT wrap slackrepo or sbo-batch-test. It REUSES sbo-batch-test's
+  resolver + build logic, adapted, but is an independent script.
+- Shares the host kernel (docker). No kernel-module build claims.
+
+## Why not the overlay approach (sbo-batch-test)
+
+`sbo-batch-test` already resolves deps + builds + reports, but against a
+LOCAL overlayfs over a 15.0 base. In docker the container IS the disposable
+base, and overlayfs-over-docker-storage (itself overlayfs) is fragile. So we
+drop the overlay layer and build directly in the container. We port
+sbo-batch-test's dep resolver and its `build_one` chroot heredoc
+(download -> md5 -> build -> installpkg -> status token) into a `docker run`.
+
+## Architecture
+
+Single self-contained bash script (`test-build`, location TBD in
+implementation - likely `.extras/`). Host does resolution + orchestration;
+the container does the actual building.
+
+```
+host: parse args, load config
+host: pick version -> image tag + SBo tree
+host: resolve dep tree (local tree, topo sort)   [ported from sbo-batch-test]
+host: apply current-vs-stable overrides
+host: print final build order, Y/n confirm       (--yes: still prints first)
+  docker run --rm -v <tree>:ro -v <pkg>:ro -v <cache/digest>:ro <image>:
+    for each dep in order:
+      cache hit (version match) -> installpkg from cache  (CACHED)
+      else                      -> download/md5/build/installpkg + cache
+    target:                     download/md5/build/installpkg (always fresh)
+    target: sbopkglint on the built .txz
+host: collect per-package results, print color summary
+container discarded (--rm)
+```
+
+### Images (external input, not built by this script)
+
+The script does NOT build images. It consumes a ready image per version,
+tagged locally:
+
+- current: `sbo-testbuild:current`
+- 15.0:    `sbo-testbuild:15.0`
+
+Each image is a FULL, patched Slackware install (SBo tests against a full
+install; a minimal base causes false "missing dependency" results, a lesson
+from sbo-batch-tester) plus `sbo-maintainer-tools` (for `sbopkglint`) and
+`sbopkg` configured to that version's SBo repo (`:current` -> -current repo,
+`:15.0` -> 15.0 repo).
+
+**How the images are produced is out of scope for this script.** A separate
+nightly job (a LAN machine, images stored on the NAS, later served from a
+local registry) builds and refreshes them. That builder is its own tool,
+specced separately.
+
+For now the script assumes the tagged image is present locally: it runs
+`docker run` against the tag and errors with a clear message if the image is
+missing (pointing at the image-builder job). When the local registry exists,
+a `docker pull` of the tag slots in ahead of the run via the same config,
+no other change.
+
+Per-run cost is just the SlackBuild's own build time + ~1s container start.
+
+### Config (external file)
+
+`~/.config/sbo-testbuild/config`, empty defaults in-script, sourced if
+present (same pattern as sbo-batch-test). Keys:
+
+```sh
+SBO_TREE_CURRENT=/path/to/SBo-current   # local SBo tree, -current
+SBO_TREE_STABLE=/path/to/SBo-15.0       # local SBo tree, 15.0
+IMAGE_CURRENT=sbo-testbuild:current     # ready image tag (built elsewhere)
+IMAGE_STABLE=sbo-testbuild:15.0
+LOG_ROOT=/path/to/logs
+PKG_CACHE=/path/to/cache                 # dep cache; empty = disabled
+```
+
+The version flag selects BOTH the image and the tree together (default
+current; `--stable` / `15.0` switches both), so tree and image never mismatch.
+
+### current-vs-stable overrides
+
+A data file next to the config, `~/.config/sbo-testbuild/overrides`. It
+encodes the known deltas between building on 15.0 and on -current. Applied
+ONLY when the target version is `-current` (15.0 is the SBo baseline). Three
+rule kinds:
+
+```
+# dep present in 15.0 but already in -current base -> drop from order
+drop:   rust
+# dep renamed on -current -> map old -> new before lookup
+rename: python3-foo -> foo
+# dep removed from the -current tree -> fetch from SBo instead of local tree
+fetch:  somelib
+```
+
+Format: one rule per line, `kind: value` (rename uses `old -> new`), `#`
+comments and blank lines ignored.
+
+### Dependency resolution + unknown deps
+
+Resolver is ported from sbo-batch-test (`resolve_target` / `_resolve_visit`,
+DFS topo sort + cycle detection, `installed_in_base` check). Runs on the host
+against the selected tree.
+
+After resolving and applying overrides, every dep must be accounted for:
+in base, in the tree, or covered by a `fetch:` rule. If a dep is none of
+those (and no rule covers it), the script **stops before building**, reports
+it as UNMET, and asks the user to add an override rule and rerun, or abort.
+Never silently skip or guess.
+
+### Confirmation
+
+Always print the final build order before building, with overrides marked
+(dropped / renamed / fetch). Then `Y/n` to proceed. `--yes` skips the prompt
+for non-interactive/agent runs but STILL prints the order first.
+
+`--dry-run` resolves, applies overrides, prints the order, and exits without
+building (no confirm).
+
+### Build in container (ported from build_one)
+
+Deps then target, in order. For each package, inside the container:
+
+1. download sources (arch-specific `DOWNLOAD_x86_64`/`MD5SUM_x86_64` when
+   present, else `DOWNLOAD`/`MD5SUM`)
+2. verify md5
+3. `bash <pkg>.SlackBuild` with `OUTPUT` forced to a known dir
+4. `installpkg` the resulting `.txz`
+5. write a status token read back by the host
+
+`fetch:` deps (removed from the -current tree) are pulled via the baked-in
+`sbopkg`, which points at the image's matching SBo repo; everything else
+builds from the mounted local tree. Start light: handle only the few known
+`fetch:` cases, add rules as real packages need them.
+
+### Dependency cache
+
+Ported from sbo-batch-tester (`cache_decision`/`cache_path`/`cache_store`/
+`version_of`). A host dir caches built dep packages so consecutive runs reuse
+them instead of rebuilding the whole tree.
+
+- Config `PKG_CACHE=/path` enables it; empty (default) disables. `--no-cache`
+  forces a full rebuild for one run.
+- Bind-mounted read-only into the container; a cached dep is `installpkg`ed
+  instead of built (status `CACHED`). Storing is host-side: a freshly built
+  package is written to `OUTPUT` (a mounted dir the host reads back), and the
+  host copies it into the cache after the build (`cache_store`), so the cache
+  mount stays read-only. The **target always builds fresh** and refreshes its
+  own cache entry; it is never `CACHED`.
+- Key = prog + version (build/arch/tag ignored). Layout mirrors the SBo tree:
+  `$PKG_CACHE/<image-digest>/<category>/<prog>/<prog>-<ver>-...txz`, one .txz
+  per prog.
+- **Invalidation by image digest.** The cache is namespaced by the running
+  image's digest. When the digest changes (image updated by the nightly job),
+  the old namespace is stale: its deps were built against the previous image,
+  so they are ignored and rebuilt once under the new digest. This also keeps
+  the `:current` and `:15.0` caches separate (different images, different
+  digests). Old digest namespaces can be pruned.
+- A per-dep version bump (`bump: OLD -> NEW`) rebuilds and re-caches that dep.
+- Build-order line shows the outcome per dep: `cached (1.1)`,
+  `rebuild: 1.0 -> 1.1`, or `build (new)`; `--dry-run` shows the same without
+  building.
+
+### Target lint
+
+After the target builds, run `sbopkglint` on its `.txz` (tool baked into the
+image). Fail-soft: findings reported but do not change SUCCESS; missing tool
+prints a skip note. Target only (deps are vetted).
+
+### Report
+
+Per-package status + a color summary (screen) and a plain-text log under
+`LOG_ROOT/<timestamp>/`:
+
+```
+<timestamp>/
+  <prog>.log          per-package full build/install output
+  summary.log         plain recap
+  build-order.txt     the resolved+overridden order actually used
+```
+
+Status values (from sbo-batch-test):
+`SUCCESS CACHED DOWNLOAD-FAILED MD5-MISMATCH BUILD-FAILED INSTALL-FAILED
+BLOCKED-BY-DEP UNMET-DEP`. `CACHED` = a dep installed from the cache instead
+of rebuilt (target is never CACHED). `%README%` deps flagged as a reminder,
+not built.
+
+A fully green run tells the user it is safe to make the SBo submission tarball
+on the host (the container is no longer needed).
+
+## Options (planned)
+
+| Option | Effect |
+|--------|--------|
+| `--stable` / `15.0` | Target 15.0 (image + tree). Default is -current. |
+| `--dry-run` | Resolve + apply overrides + print order, no build. |
+| `--yes` | Skip the Y/n confirm (still prints the order). |
+| `--no-cache` | Rebuild all deps this run, ignore/refresh the cache. |
+| `--no-color` | Disable ANSI (auto-off when not a TTY). |
+| `-h`, `--help` | Usage. |
+
+## Self-check
+
+A `test-logic.sh` (host, no docker) covering the pure logic:
+
+- dep topo order + cycle detection (ported tests from sbo-batch-test)
+- override application: drop removes, rename maps, fetch marks source
+- unknown-dep -> UNMET stop
+- BLOCKED-BY-DEP propagation
+- cache decision: `cached`/`rebuild: OLD -> NEW`/`build (new)`, digest
+  namespacing, version-bump eviction (ported from sbo-batch-tester's tests)
+
+Docker/build/installpkg paths are out of the self-check's reach (verified by
+running a real target), same boundary as sbo-batch-test.
+
+## Resolved decisions
+
+- **Image**: a ready FULL-install image per version (full pkg set +
+  `sbo-maintainer-tools` + `sbopkg` on that version's repo), built by a
+  separate nightly job, NOT by this script. Script consumes it by tag.
+- **Missing image**: error clearly, point at the image-builder job. A local
+  registry `docker pull` slots in later via the same tag, no script change.
+- **`fetch:`**: via the image's `sbopkg` (per-version repo). Start with only
+  the few known cases; grow the override rules as needed.
+- **Script location**: `.extras/` (a tool, not a package).
+
+## Out of scope / later
+
+- The nightly image-builder (full-install + tools + sbopkg per version, NAS
+  storage, local registry). Its own tool, specced when the LAN machine is set
+  up.
+- Local registry pull step in this script (slots into the same config tag).
+```
+
diff --git a/docs/specs/2026-07-13-image-builder-design.md b/docs/specs/2026-07-13-image-builder-design.md
new file mode 100644
index 0000000..9ee1a11
--- /dev/null
+++ b/docs/specs/2026-07-13-image-builder-design.md
@@ -0,0 +1,216 @@
+# sbo-testbuild image builder — design
+
+Date: 2026-07-13
+Status: approved (design)
+
+## Purpose
+
+Produce and serve the docker images the `.extras/test-build` tool consumes.
+`.extras/test-build` verifies a published SBo package still builds on a target
+Slackware version inside a throwaway container; it does **not** build the
+images, it only checks image presence by tag and errors if absent. This is the
+missing image-builder job.
+
+Images produced (x86_64 only for now):
+
+- `sbo-testbuild:current` — Slackware -current, full install + sbopkg +
+  sbo-maintainer-tools
+- `sbo-testbuild:15.0` — Slackware 15.0, same
+
+Served from a LAN docker registry so `.extras/test-build`'s `require_image`
+can `docker pull` them, and so `installed_in_base` can later query the image's
+package db.
+
+## Infrastructure
+
+Self-hosted on a Slackware VM (proxmox node), fully offline from the public
+internet for the Slackware bits:
+
+- **Host**: `docker.noland.dnx` (LAN DNS), Slackware x86_64, 4 vCPU / 4 GB RAM
+  / 80 GB disk.
+- **NAS trees**: two standard Slackware mirror trees NFS-mounted read-only:
+  - `/mnt/nas/slackware64-current`
+  - `/mnt/nas/slackware64-15.0`
+  Each is a full mirror tree (`PACKAGES.TXT`, `ChangeLog.txt`, `slackware64/`
+  series dirs, `patches/`, `extra/`).
+- **Registry**: `registry:2` container on the VM, port 5000, plain HTTP (LAN
+  only). Pull path `docker.noland.dnx:5000/sbo-testbuild:{tag}`.
+- **Local .txz drop**: `/opt/sbo-testbuild/pkgs/` holds `sbopkg-*.txz` and
+  `sbo-maintainer-tools-*.txz`, provided by the user (sbopkg packaged from the
+  user's SBo repo). Installed into the image, not built in it (hermetic, no
+  build-time deps).
+
+Both `docker.noland.dnx` and every client that pulls (this dev box, the
+`buildsystem` VM) need the registry marked insecure in
+`/etc/docker/daemon.json`:
+`{"insecure-registries":["docker.noland.dnx:5000"]}`, then `docker` restarted.
+
+i586 is out of scope for now; the variant list is written to extend to it
+later without restructuring.
+
+## Architecture
+
+Three scripts, chained, adapted from the forge repo
+`slackware/docker-images` (`scripts/bootstrap.sh`, `build-full-image.sh`,
+`build-builder-image.sh`). The forge `build-builder-image.sh` is **not** used:
+the full image already ships the toolchain (series d, kde, x, etc.), so a
+separate builder layer is redundant here.
+
+```
+bootstrap.sh              FROM scratch; installpkg base pkgs read from NAS
+  → sbo-base:{ver}          via file://; configure rootfs for container use.
+
+build-full-image.sh       FROM sbo-base:{ver}; slackpkg install every series
+  → sbo-full:{ver}          (a ap d e f k kde l n t tcl x xap xfce y).
+
+build-sbo-testbuild.sh    FROM sbo-full:{ver}; installpkg sbopkg +
+  → sbo-testbuild:{ver}     sbo-maintainer-tools from /opt/sbo-testbuild/pkgs.
+```
+
+All three push to `docker.noland.dnx:5000`.
+
+### Namespacing
+
+Forge scripts push to `registry.slackware.nl/slackware/slackware*`. Re-namespace
+to the LAN registry with our own image names:
+
+- `docker.noland.dnx:5000/sbo-base:{ver}`
+- `docker.noland.dnx:5000/sbo-full:{ver}`
+- `docker.noland.dnx:5000/sbo-testbuild:{ver}`
+
+`sbo-base` and `sbo-full` are intermediate; `.extras/test-build` only pulls
+`sbo-testbuild`.
+
+## Configuration
+
+Single shared file `config`, sourced by all scripts and the test:
+
+```sh
+REGISTRY=docker.noland.dnx:5000
+MIRROR=file:///mnt/nas
+VARIANTS=(current 15.0)          # x86_64 only for now
+PKGDIR=/opt/sbo-testbuild/pkgs   # sbopkg + sbo-maintainer-tools .txz
+```
+
+The forge scripts hardcode `MIRROR=https://slackware.nl/slackware` and
+`REGISTRY=registry.slackware.nl/...`; both move to the shared config.
+
+### NAS path mapping
+
+bootstrap derives the per-variant repo dir as `slackware64-${VERSION}` for
+x86_64 (`DIRSUFFIX=64`). With `MIRROR=file:///mnt/nas` this resolves to
+`file:///mnt/nas/slackware64-current/...` and `.../slackware64-15.0/...`,
+matching the mount points. Mounts must be named to match.
+
+## Patches to the forge scripts
+
+1. **`file://`-aware fetch.** Forge downloads `PACKAGES.TXT` and packages with
+   `curl` over http. Replace with one helper in `lib.sh` that detects a
+   `file://` (or bare-local) MIRROR and uses `cp`, otherwise `curl`. curl's
+   own `file://` support is unreliable across builds, so branch explicitly.
+2. **Drop i586.** `ALL_VARIANTS` becomes the config `VARIANTS` (x86_64 only).
+   All the `ARCH_SUFFIX`/`-i586` machinery collapses to the x86_64 path.
+3. **Re-namespace + LAN registry** (see Namespacing).
+4. **MIRROR → `file:///mnt/nas`** (see config).
+
+## Data flow and rebuild gating
+
+Nightly cron on the VM (root; `bootstrap` needs `installpkg`):
+
+```cron
+ 0 4 * * *  bootstrap.sh
+15 4 * * *  build-full-image.sh
+30 4 * * *  build-sbo-testbuild.sh
+```
+
+Rebuild gating (kept from the forge scripts, extended):
+
+- **bootstrap**: sha256 of the NAS `ChangeLog.txt` (read via `file://`)
+  compared to a stored hash under `HASH_DIR`; skip the variant if unchanged.
+- **build-full-image**: base image digest recorded as a label on the full
+  image; pull base, compare, skip if unchanged.
+- **build-sbo-testbuild**: full image digest label, same pattern; **plus** a
+  hash of the `.txz` set in `PKGDIR`, so a sbopkg / sbo-maintainer-tools bump
+  forces a rebuild even when the full image is unchanged.
+
+Net effect: a quiet NAS tree makes the whole chain no-op in seconds; a
+-current churn cascades base → full → testbuild.
+
+### Local-registry digest consistency
+
+The forge scripts read the base/full digest via `docker inspect RepoDigests`
+after `docker pull`. Self-hosted, those intermediate images live in the LAN
+registry, so pull-then-inspect must target `docker.noland.dnx:5000`. Since
+every image name is derived from `REGISTRY`, re-namespacing handles this with
+no extra logic.
+
+## Error handling
+
+- `set -euo pipefail` in every script (forge already has it).
+- **Missing NAS mount**: guard `[[ -d /mnt/nas/slackware64-$ver ]]` first;
+  `_err` if absent.
+- **Missing `.txz`**: `build-sbo-testbuild` errors before building if
+  `PKGDIR` lacks a `sbopkg-*.txz` or `sbo-maintainer-tools-*.txz` — never push
+  a testbuild image missing sbopkg.
+- **Registry unreachable**: `docker push` fails under `set -e`; the chain
+  aborts. The base/full may already be built locally; cron retries next night.
+  Acceptable.
+- **Per-variant isolation**: one variant failing (e.g. current) must not block
+  the other (15.0). Each variant runs wrapped; log the failure, continue, and
+  exit non-zero at the end so cron logs surface it.
+
+## Testing
+
+Pure-logic pieces get a `test-image-builder.sh` self-check, matching the
+existing `.extras/test-build` pattern (`.extras/test-logic.sh`, assert-based,
+no framework). No docker daemon in tests — hermetic.
+
+- **`file://` fetch helper**: local file resolves via cp; missing local file
+  errors; an http MIRROR still routes to curl.
+- **`.txz`-set hash**: stable across file reordering; changes when a file's
+  content changes.
+- **variant guard**: a missing mount dir yields non-zero.
+
+The real end-to-end chain is verified by a manual first run on the VM (the user
+runs it and reports back), the same division of labor as `.extras/test-build`
+Task 10.
+
+## Layout
+
+```
+.extras/image-builder/
+├── config                    REGISTRY, MIRROR, VARIANTS, PKGDIR
+├── lib.sh                    shared: _log/_warn/_err, fetch, txz_hash, guards
+├── bootstrap.sh              base image (root; installpkg from NAS)
+├── build-full-image.sh       full image (slackpkg all series)
+├── build-sbo-testbuild.sh    testbuild image (installpkg sbopkg + tools)
+├── test-image-builder.sh     pure-logic self-check
+└── README                    VM-side setup, reproducible
+```
+
+Lives in `.extras/` for now (per the user), relocatable later.
+
+The README carries the user-side checklist so it is reproducible and not
+trapped in chat:
+
+- VM specs (4/4/80), Slackware x86_64, docker installed.
+- Two NFS mounts (ro), root-readable, named `slackware64-current` /
+  `slackware64-15.0` under `/mnt/nas`.
+- `registry:2` container: `-v /opt/registry/data:/var/lib/registry`,
+  `--restart=always`, port 5000.
+- `/etc/docker/daemon.json` insecure-registry entry on the VM **and** on every
+  pulling client (this dev box, `buildsystem`), docker restarted.
+- Drop `sbopkg-*.txz` and `sbo-maintainer-tools-*.txz` into
+  `/opt/sbo-testbuild/pkgs/`.
+- Install the three cron lines.
+- VM static IP / LAN DNS for `docker.noland.dnx`.
+
+## Out of scope
+
+- i586 images (extensible later via `VARIANTS` / arch machinery).
+- Building sbopkg / sbo-maintainer-tools from source in the image (installed
+  from prebuilt `.txz`).
+- The forge `build-builder-image.sh` toolchain layer (redundant with full).
+- `installed_in_base` implementation in `.extras/test-build` — unblocked by
+  this work (queries the built image's package db) but tracked separately.
+- Registry auth / TLS (LAN-only plain HTTP).
diff --git a/image-builder/README b/image-builder/README
new file mode 100644
index 0000000..8711b1d
--- /dev/null
+++ b/image-builder/README
@@ -0,0 +1,69 @@
+sbo-testbuild image builder
+===========================
+
+Builds the docker images that test-build consumes:
+  docker.noland.dnx:5000/sbo-testbuild:current
+  docker.noland.dnx:5000/sbo-testbuild:15.0
+
+Three scripts, chained (see docs/specs/2026-07-13-image-builder-design.md):
+  bootstrap.sh           sbo-base:{ver}       FROM scratch, base pkgs from NAS
+  build-full-image.sh    sbo-full:{ver}       FROM base, all series
+  build-sbo-testbuild.sh sbo-testbuild:{ver}  FROM full, + sbopkg + tools
+
+All settings live in ./config.
+
+VM setup (docker.noland.dnx, Slackware x86_64, 4 vCPU / 4 GB / 80 GB)
+--------------------------------------------------------------------
+1. Install docker; enable the daemon.
+
+2. NFS-mount the two NAS trees read-only, named to match:
+     /mnt/nas/slackware64-current   -> -current mirror tree
+     /mnt/nas/slackware64-15.0      -> 15.0 mirror tree
+   Each is a full mirror (PACKAGES.TXT, ChangeLog.txt, slackware64/, patches/,
+   extra/). Root must be able to read them (bootstrap runs installpkg as root).
+
+3. Run a LAN registry:
+     docker run -d --restart=always -p 5000:5000 \
+       -v /opt/registry/data:/var/lib/registry --name registry registry:2
+
+4. Mark the registry insecure (plain HTTP) on the VM AND every pulling client
+   (this dev box, the buildsystem VM). In /etc/docker/daemon.json:
+     { "insecure-registries": ["docker.noland.dnx:5000"] }
+   then restart docker.
+
+5. Drop the two prebuilt packages (built once, re-drop on upstream bumps):
+     /opt/sbo-testbuild/pkgs/sbopkg-*.txz
+     /opt/sbo-testbuild/pkgs/sbo-maintainer-tools-*.txz
+
+6. Install the nightly cron (root). The NAS repos sync at 01:00 and 02:00, so
+   the chain runs after and both variants are ready well before the ~09:00 work
+   start. No --force: each script self-gates (bootstrap on the ChangeLog hash,
+   full-image on the base-image digest, build-sbo-testbuild on the full-image
+   digest + tools .txz hash), so an unchanged night is a cheap no-op. -current
+   moves daily and rebuilds most nights; 15.0 is frozen stable and rebuilds only
+   on a real repo update. Deployed schedule on docker.noland.dnx:
+      # -current (ready ~04:35)
+      0  3 * * *  /path/to/sbo-dockerbuild/image-builder/bootstrap.sh           --version current >> /var/log/sbo-testbuild.log 2>&1
+     20  3 * * *  /path/to/sbo-dockerbuild/image-builder/build-full-image.sh    --version current >> /var/log/sbo-testbuild.log 2>&1
+     30  4 * * *  /path/to/sbo-dockerbuild/image-builder/build-sbo-testbuild.sh --version current >> /var/log/sbo-testbuild.log 2>&1
+      # 15.0 (ready ~06:35)
+      0  5 * * *  /path/to/sbo-dockerbuild/image-builder/bootstrap.sh           --version 15.0 >> /var/log/sbo-testbuild.log 2>&1
+     20  5 * * *  /path/to/sbo-dockerbuild/image-builder/build-full-image.sh    --version 15.0 >> /var/log/sbo-testbuild.log 2>&1
+     30  6 * * *  /path/to/sbo-dockerbuild/image-builder/build-sbo-testbuild.sh --version 15.0 >> /var/log/sbo-testbuild.log 2>&1
+
+7. Ensure docker.noland.dnx resolves on the LAN (static IP or DNS).
+
+Manual first run
+----------------
+   ./bootstrap.sh --version current --force
+   ./build-full-image.sh --version current --force
+   ./build-sbo-testbuild.sh --version current --force
+Then confirm:
+   docker pull docker.noland.dnx:5000/sbo-testbuild:current
+   docker run --rm docker.noland.dnx:5000/sbo-testbuild:current sbopkg -V
+
+Flags: --force (rebuild unconditionally), --version <current|15.0> (one variant).
+
+Tests
+-----
+   bash test-image-builder.sh     # pure-logic self-check, no docker
diff --git a/image-builder/bootstrap.sh b/image-builder/bootstrap.sh
new file mode 100755
index 0000000..273afc8
--- /dev/null
+++ b/image-builder/bootstrap.sh
@@ -0,0 +1,564 @@
+#!/bin/bash
+#
+# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# bootstrap.sh — build the sbo-base:{ver} image FROM scratch from NAS trees.
+# Run as root (installpkg). Adapted from forge slackware/docker-images.
+set -euo pipefail
+HERE="$(cd "$(dirname "$0")" && pwd)"
+source "${HERE}/config"
+LOG_TAG=bootstrap
+source "${HERE}/lib.sh"
+
+REGISTRY_IMAGE="${REGISTRY}/sbo-base"
+[[ "${EUID}" -eq 0 ]] || _err "run as root."
+mkdir -p "${HASH_DIR}"
+
+# ============================================================================
+# Package list
+#
+# Names only - the version and build suffix are resolved automatically
+# from PACKAGES.TXT for the x86_64 target architecture.
+#
+# slackpkg and its runtime dependencies (perl, gnupg2, gpgme) are included
+# so users can run slackpkg inside the container without extra setup.
+# ============================================================================
+
+PACKAGES=(
+    # Base system
+    aaa_base
+    coreutils
+    aaa_glibc-solibs
+    aaa_libraries
+    aaa_terminfo
+    pam
+    cracklib
+    libpwquality
+    acl
+    attr
+    bash
+    bin
+    brotli
+    bzip2
+    c-ares
+    cpio
+    curl
+    cyrus-sasl
+    devs
+    dialog
+    diffutils
+    duktape
+    elvis
+    etc
+    file
+    findutils
+    flex
+    gawk
+    gnutls
+    grep
+    groff
+    gzip
+    iproute2
+    iptables
+    jansson
+    less
+    libcgroup
+    libpsl
+    librsvg
+    libtermcap
+    mtr
+    ncurses
+    net-tools
+    network-scripts
+    nghttp2
+    nghttp3
+    ngtcp2
+    nvi
+    openssh
+    patch
+    pcre2
+    pinentry
+    pkgtools
+    polkit
+    procps-ng
+    quota
+    rsync
+    screen
+    sed
+    elogind
+    shadow
+    sharutils
+    strace
+    sudo
+    sysfsutils
+    sysvinit
+    sysvinit-scripts
+    tar
+    time
+    tree
+    eudev
+    usbutils
+    utempter
+    util-linux
+    wget
+    which
+    whois
+    xz
+    zlib
+    # Package management - series ap
+    slackpkg
+    # Perl runtime required by slackpkg - series d
+    perl
+    # e2fsprogs provides libcom_err.so.2 required by perl on 15.0
+    e2fsprogs
+    # libunistring - Unicode string library required by gnupg2 dependencies
+    libunistring
+    # gnupg2 runtime libraries (series l) - required for gpg to start at all
+    libgpg-error
+    libgcrypt
+    libassuan
+    libksba
+    npth
+    sqlite
+    icu4c
+    # GPG/PKCS support for slackpkg (series l)
+    gpgme
+    # GnuPG binaries (series n)
+    # gnupg  = version 1, called by slackpkg on Slackware 15.0
+    # gnupg2 = version 2, called by slackpkg on -current
+    gnupg
+    gnupg2
+    # Full OpenSSL and CA bundle - required for HTTPS inside the container
+    openssl
+    ca-certificates
+)
+
+# ============================================================================
+# Argument parsing
+# ============================================================================
+
+FORCE=false
+OPT_VERSION=""
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --version) OPT_VERSION="$2"; shift 2 ;;
+        --force)   FORCE=true;       shift   ;;
+        *) _err "unknown argument: $1" ;;
+    esac
+done
+if [[ -n "${OPT_VERSION}" ]]; then
+    BUILD_VARIANTS=("${OPT_VERSION}")
+else
+    BUILD_VARIANTS=("${VARIANTS[@]}")
+fi
+
+# ============================================================================
+# ChangeLog tracking
+# ============================================================================
+
+# changelog_changed VERSION -> 0 if changed (or --force), else 1
+changelog_changed() {
+    local version="$1"
+    require_mount "${version}"   # loud fail if NAS unmounted, not silent skip
+    local repo_key="slackware64-${version}"
+    local hash_file="${HASH_DIR}/${repo_key}.sha256"
+    local url; url="$(mirror_path "${MIRROR}" "${repo_key}/ChangeLog.txt")"
+    local tmp; tmp="$(mktemp)"
+    if ! fetch "${url}" "${tmp}"; then
+        rm -f "${tmp}"
+        _warn "${repo_key}: cannot read ChangeLog (${url}); skipping."
+        return 1
+    fi
+    local live; live=$(sha256sum "${tmp}" | cut -d' ' -f1); rm -f "${tmp}"
+    if [[ "${FORCE}" == "true" ]]; then
+        echo "${live}" > "${hash_file}"; return 0
+    fi
+    local stored=""; [[ -f "${hash_file}" ]] && stored=$(cat "${hash_file}")
+    if [[ "${live}" == "${stored}" ]]; then
+        _log "${repo_key}: ChangeLog unchanged; skipping."; return 1
+    fi
+    _log "${repo_key}: ChangeLog changed."; echo "${live}" > "${hash_file}"; return 0
+}
+
+# ============================================================================
+# Package discovery via PACKAGES.TXT
+#
+# Search order: patches/ -> main repo -> extra/
+# This mirrors Slackware's own install priority: a patched package in
+# patches/ always takes precedence over the same package in the main tree.
+# ============================================================================
+
+# download_pkgtxt PKGTXT_DIR PKG_PATH
+# Downloads PACKAGES.TXT from patches/, the repo root, and extra/ into
+# PKGTXT_DIR. Sets global associative array PKGTXT[loc] -> local file path.
+# Uses -L to follow HTTP redirects (some mirrors use them) and checks that
+# the downloaded file is non-empty before marking it as available.
+declare -gA PKGTXT=()
+
+download_pkgtxt() {
+    local PKGTXT_DIR="$1"
+    local PKG_PATH="$2"
+    mkdir -p "${PKGTXT_DIR}"
+    PKGTXT=()
+    local LOC URL DEST
+    for LOC in patches main extra; do
+        case "${LOC}" in
+            patches) URL="${PKG_PATH}/patches/PACKAGES.TXT" ;;
+            main)    URL="${PKG_PATH}/PACKAGES.TXT"         ;;
+            extra)   URL="${PKG_PATH}/extra/PACKAGES.TXT"   ;;
+        esac
+        DEST="${PKGTXT_DIR}/${LOC}.txt"
+        if fetch "${URL}" "${DEST}"                 && [[ -s "${DEST}" ]]; then
+            PKGTXT["${LOC}"]="${DEST}"
+            _log "  PACKAGES.TXT [${LOC}]: $(wc -l < "${DEST}") lines"
+        else
+            rm -f "${DEST}"
+            _log "  PACKAGES.TXT [${LOC}]: not available at ${URL}"
+        fi
+    done
+}
+
+# find_package NAME
+# Searches PKGTXT files in order: patches -> main -> extra.
+# Prints the path relative to PKG_PATH, e.g.:
+#   slackware64/a/bash-5.2-x86_64-1.txz
+#
+# Base name extraction uses the Slackware convention: the filename has the
+# form PKGBASE-VERSION-ARCH-BUILD.txz where VERSION, ARCH and BUILD are
+# guaranteed to contain no dashes. Reversing, cutting the last three fields,
+# and reversing again always yields the correct PKGBASE:
+#   echo aaa_glibc-solibs-2.42-x86_64-1.txz | rev | cut -d- -f4- | rev
+#   -> aaa_glibc-solibs
+find_package() {
+    local PKG="$1"
+    [[ "${#PKGTXT[@]}" -gt 0 ]] || {
+        _warn "find_package called with empty PKGTXT array - PACKAGES.TXT not loaded"
+        return 1
+    }
+    for LOC in patches main extra; do
+        [[ -v "PKGTXT[${LOC}]" ]] || continue
+        local RESULT
+        RESULT=$(awk -v want="${PKG}" '
+            /^PACKAGE NAME:/ {
+                filename = $NF
+                # PKGBASE = all fields except the last three (VERSION ARCH BUILD)
+                n = split(filename, parts, "-")
+                base = parts[1]
+                for (i = 2; i <= n-3; i++) base = base "-" parts[i]
+                if (base == want) found = filename
+            }
+            /^PACKAGE LOCATION:/ && found {
+                loc = $NF; sub(/^\.\//, "", loc)
+                print loc "/" found
+                found = ""; exit
+            }
+        ' "${PKGTXT[${LOC}]}")
+        if [[ -n "${RESULT}" ]]; then
+            echo "${RESULT}"
+            return 0
+        fi
+    done
+    return 1
+}
+
+# ============================================================================
+# Build one variant
+# ============================================================================
+
+build_variant() {
+    local VERSION="$1"
+    require_mount "${VERSION}"
+    local REPO_KEY="slackware64-${VERSION}"
+    local PKG_PATH; PKG_PATH="$(mirror_path "${MIRROR}" "${REPO_KEY}")"
+    local TAG="${REGISTRY_IMAGE}:${VERSION}"
+    # Bake the LAN HTTP mirror into the base image: the full-image build serves
+    # the NFS mirror over HTTP on the bridge (see build-full-image.sh), rooted
+    # at the variant's mirror tree, so slackpkg pulls from LAN not the internet.
+    # The URL is variant-agnostic (the server's --directory selects the tree).
+    local SLACKPKG_MIRROR="http://${HTTP_MIRROR_HOST}:${HTTP_MIRROR_PORT}/"
+
+    _log "=== Building ${TAG} from ${PKG_PATH} ==="
+
+    local WORKDIR
+    WORKDIR="$(mktemp -d /tmp/slackware-bootstrap.XXXXXX)"
+    # shellcheck disable=SC2064
+    trap "rm -rf '${WORKDIR}'" EXIT
+
+    local ROOTFS="${WORKDIR}/rootfs"
+    local PKGCACHE="${WORKDIR}/packages"
+    local PKGTXT_DIR="${WORKDIR}/pkgtxt"
+    mkdir -p "${ROOTFS}" "${PKGCACHE}"
+
+    # --- Download PACKAGES.TXT index files ---
+    download_pkgtxt "${PKGTXT_DIR}" "${PKG_PATH}"
+
+    # --- Download packages ---
+    _log "Locating and downloading packages..."
+    local PKG RELPATH FILENAME URL
+    for PKG in "${PACKAGES[@]}"; do
+        RELPATH=$(find_package "${PKG}") || {
+            _warn "  '${PKG}' not found in any PACKAGES.TXT - skipping"
+            continue
+        }
+        FILENAME="${RELPATH##*/}"
+        URL="${PKG_PATH}/${RELPATH}"
+        _log "  ${FILENAME}"
+        fetch "${URL}" "${PKGCACHE}/${FILENAME}" || {
+            _warn "  Failed to download ${URL}"
+        }
+    done
+
+    # --- Install packages ---
+    _log "Installing packages..."
+    for PKG in "${PKGCACHE}"/*.txz; do
+        [[ -f "${PKG}" ]] || continue
+        ROOT="${ROOTFS}" installpkg --terse "${PKG}"
+    done
+
+    # --- Run ldconfig to create library symlinks ---
+    # Some packages (notably aaa_libraries on stable releases) install
+    # versioned library files (e.g. libtinfo.so.6.3) and rely on ldconfig
+    # to create the unversioned symlinks (e.g. libtinfo.so.6).  On -current
+    # the symlinks are included in the package tarballs directly; on 15.0
+    # they are not.  Running ldconfig here ensures the symlinks exist before
+    # any chroot operations and before the dependency check below.
+    _log "Running ldconfig..."
+    chroot "${ROOTFS}" /sbin/ldconfig
+
+    # --- Check for missing library dependencies ---
+    # Run ldd on key binaries inside the chroot and report anything missing
+    # before it surfaces as a runtime failure inside the container.
+    _log "Checking for missing library dependencies in key binaries..."
+    local DEPCHECK_OK=true
+    for BIN in /usr/bin/gpg /usr/bin/gpg2 /usr/sbin/slackpkg                /usr/bin/perl /bin/wget /usr/bin/openssl; do
+        [[ -f "${ROOTFS}${BIN}" ]] || continue
+        local MISSING_LIBS
+        MISSING_LIBS=$(chroot "${ROOTFS}" ldd "${BIN}" 2>/dev/null                        | grep "not found" || true)
+        if [[ -n "${MISSING_LIBS}" ]]; then
+            _warn "${BIN} has unresolved dependencies:"
+            while IFS= read -r lib; do
+                _warn "  ${lib}"
+            done <<< "${MISSING_LIBS}"
+            DEPCHECK_OK=false
+        fi
+    done
+    if [[ "${DEPCHECK_OK}" == "true" ]]; then
+        _log "Dependency check passed."
+    else
+        _warn "Add the missing packages to PACKAGES and rebuild with --force."
+    fi
+
+    # --- Prepare rootfs for container use ---
+    _log "Configuring rootfs for container use..."
+
+    # Remove the empty update.d hook directory so that update-ca-certificates
+    # does not look for run-parts (which ships with dcron, not installed here).
+    rm -rf "${ROOTFS}/etc/ca-certificates/update.d"
+
+    # Disable init scripts that manage hardware absent in a container
+    local SVC
+    for SVC in rc.acpid rc.pcmcia rc.setterm rc.udev; do
+        [[ -f "${ROOTFS}/etc/rc.d/${SVC}" ]] && chmod -x "${ROOTFS}/etc/rc.d/${SVC}"
+    done
+
+    # Each container generates its own SSH host keys on first start
+    rm -f "${ROOTFS}"/etc/ssh/*key*
+
+    # /etc/mtab should reflect the container's actual mounts
+    rm -f "${ROOTFS}/etc/mtab"
+    ln -s /proc/mounts "${ROOTFS}/etc/mtab"
+
+    # No hardware clock in a container
+    sed -i -e '/^if \[ -x \/sbin\/hwclock/,/^fi$/s/^/#/' \
+        "${ROOTFS}/etc/rc.d/rc.S" 2>/dev/null || true
+
+    # The filesystem write-check would drop the container into a recovery shell
+    sed -i -e '/^if touch \/fsrwtestfile/,/^fi$/s/^/#/' \
+        "${ROOTFS}/etc/rc.d/rc.S" 2>/dev/null || true
+
+    # Skip all filesystem checks at boot
+    touch "${ROOTFS}/etc/fastboot"
+
+    # setterm is not useful in a container
+    sed -i -e '/\/bin\/setterm/s/^/# /' \
+        "${ROOTFS}/etc/rc.d/rc.M" 2>/dev/null || true
+
+    # Cannot write to the hardware clock at shutdown
+    sed -i -e '/systohc/s/^/# /' \
+        "${ROOTFS}/etc/rc.d/rc.6" 2>/dev/null || true
+
+    # Container-appropriate fstab
+    cat > "${ROOTFS}/etc/fstab" <<'FSTAB'
+devtmpfs         /dev             devtmpfs  defaults                        0   0
+devpts           /dev/pts         devpts    gid=5,mode=620                  0   0
+tmpfs            /dev/shm         tmpfs     defaults,nodev,nosuid,mode=1777 0   0
+FSTAB
+
+    # No TTYs in a container; disable agetty and reduce console definitions
+    sed -i -e '/agetty/s/^c/#c/' \
+        "${ROOTFS}/etc/inittab" 2>/dev/null || true
+    sed -i -e '/^c3\|^c4\|^c5\|^c6/s/^/# /' \
+        "${ROOTFS}/etc/inittab" 2>/dev/null || true
+
+    # Invalidate the root password (containers use other means of access)
+    sed -i -e '/^root/s/^root::/root:!:/' \
+        "${ROOTFS}/etc/shadow" 2>/dev/null || true
+
+    # Terminal configuration
+    printf 'export TERM=linux\n' > "${ROOTFS}/etc/profile.d/term.sh"
+    chmod +x "${ROOTFS}/etc/profile.d/term.sh"
+
+    # Source /etc/profile from .bashrc so interactive sessions are fully
+    # initialised (Docker sets / as the home directory for root in containers)
+    printf '. /etc/profile\n' > "${ROOTFS}/.bashrc"
+
+    # DNS resolver
+    printf 'nameserver 1.1.1.1\nnameserver 8.8.4.4\n' \
+        >> "${ROOTFS}/etc/resolv.conf"
+
+    # Configure slackpkg for silent non-interactive use in a container
+    if [[ -f "${ROOTFS}/etc/slackpkg/slackpkg.conf" ]]; then
+        sed -i 's/DIALOG=on/DIALOG=off/'     "${ROOTFS}/etc/slackpkg/slackpkg.conf"
+        sed -i 's/POSTINST=on/POSTINST=off/' "${ROOTFS}/etc/slackpkg/slackpkg.conf"
+        sed -i 's/SPINNING=on/SPINNING=off/' "${ROOTFS}/etc/slackpkg/slackpkg.conf"
+        sed -i 's/WGETFLAGS="--passive-ftp/& --no-verbose/' \
+            "${ROOTFS}/etc/slackpkg/slackpkg.conf"
+    fi
+
+    # Configure the slackpkg mirror
+    [[ -f "${ROOTFS}/etc/slackpkg/mirrors" ]] && \
+        printf '%s\n' "${SLACKPKG_MIRROR}" >> "${ROOTFS}/etc/slackpkg/mirrors"
+
+    # slackpkg requires an explicit opt-in for -current
+    if [[ "${VERSION}" == "current" ]]; then
+        mkdir -p "${ROOTFS}/var/lib/slackpkg"
+        touch "${ROOTFS}/var/lib/slackpkg/current"
+    fi
+
+    # Set a predictable locale for all chroot operations.
+    # Without this, perl emits locale warnings when the host locale
+    # (e.g. en_US.UTF-8) is not installed in the minimal rootfs.
+    export LC_ALL=C
+
+    # Rebuild the CA certificate database inside the rootfs.
+    # Without this, wget cannot verify Let's Encrypt certificates and every
+    # HTTPS download by slackpkg fails with an SSL error.  That SSL error in
+    # turn causes the interactive "do you want to import the GPG key?" prompt
+    # even when -batch=on -default_answer=y is set.
+    _log "Refreshing CA certificate database..."
+    chroot "${ROOTFS}" /usr/sbin/update-ca-certificates --fresh 1>/dev/null ||         _warn "CA certificate update failed; SSL verification may not work correctly."
+
+    # Import the Slackware GPG key and update the package list.
+    # 'yes YES |' feeds a pre-emptive answer to the interactive import prompt
+    # as a safety net; with the CA database now valid the prompt should not
+    # appear because the download succeeds on the first attempt.
+    _log "Importing Slackware GPG key via slackpkg..."
+    # Check slackpkg's own exit status, not the pipeline's: 'yes' takes SIGPIPE
+    # when slackpkg exits first, which can make the pipeline non-zero even on
+    # success (false "GPG update failed" warning). Wrapping in 'if' exempts the
+    # pipeline from set -e/pipefail so we can read PIPESTATUS[1] (slackpkg's own
+    # status) instead of the SIGPIPE-poisoned pipeline status.
+    local gpg_rc
+    if yes YES | chroot "${ROOTFS}" /usr/sbin/slackpkg         -batch=on -default_answer=y update gpg
+    then gpg_rc="${PIPESTATUS[1]}"; else gpg_rc="${PIPESTATUS[1]}"; fi
+    [[ "${gpg_rc}" -eq 0 ]] ||         _warn "slackpkg GPG update failed; check the output above."
+
+    _log "Updating slackpkg package list..."
+    chroot "${ROOTFS}" /usr/sbin/slackpkg         -batch=on -default_answer=y update ||         _warn "slackpkg update failed; cache will build on first container run."
+
+    # --- Clean up ---
+    _log "Cleaning up rootfs..."
+    rm -f  "${ROOTFS}"/boot/*
+    rm -f  "${ROOTFS}"/tmp/[A-Za-z]*
+    rm -f  "${ROOTFS}"/var/mail/*
+    rm -rf "${ROOTFS}"/dev/*
+    rm -rf "${ROOTFS}"/usr/share/locale/*
+    rm -rf "${ROOTFS}"/usr/info/*
+    rm -rf "${ROOTFS}"/usr/man/*
+    (cd "${ROOTFS}/usr/doc" 2>/dev/null && \
+        find . -type d -mindepth 2 -maxdepth 2 | grep -v '/cups-' | \
+        xargs rm -rf) || true
+    rm -rf "${ROOTFS}"/usr/doc/*/html
+    rm -f  "${ROOTFS}"/usr/doc/*/*.{pdf,db,gz,bz2,xz,txt,TXT} 2>/dev/null || true
+    rm -rf "${ROOTFS}"/usr/share/gtk-doc
+    rm -rf "${ROOTFS}"/usr/share/help
+    find   "${ROOTFS}"/usr/share/ -type d -name doc | xargs rm -rf
+    # Keep only the terminfo entries the container actually needs
+    find "${ROOTFS}"/usr/share/terminfo/ -type f \
+        ! -name 'linux' ! -name 'xterm' ! -name 'screen.linux' \
+        -delete 2>/dev/null || true
+    find "${ROOTFS}"/usr/share/terminfo/ -xtype l -delete 2>/dev/null || true
+    # gpg-agent socket files left behind by slackpkg in the chroot.
+    # tar cannot archive Unix domain sockets; removing them eliminates
+    # the "socket ignored" warnings when the image tarball is created.
+    rm -f "${ROOTFS}"/root/.gnupg/S.*
+
+    # Kernel-specific content has no meaning in a container
+    rm -rf "${ROOTFS}"/usr/src
+    rm -rf "${ROOTFS}"/lib/modules
+    rm -rf "${ROOTFS}"/lib64/modules 2>/dev/null || true
+
+    # --- Build Docker image ---
+    _log "Creating image tarball..."
+    tar -C "${ROOTFS}" -czf "${WORKDIR}/rootfs.tar.gz" .
+
+    local BUILD_DATE
+    BUILD_DATE="$(date -u +%Y-%m-%dT%H:%M:%SZ)"
+
+    cat > "${WORKDIR}/Dockerfile" <<DOCKERFILE
+FROM scratch
+LABEL maintainer="Eric Hameleers <alien@slackware.com>"
+ADD rootfs.tar.gz /
+ENV container=docker
+ENV PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+LABEL org.opencontainers.image.created="${BUILD_DATE}"
+LABEL org.opencontainers.image.title="Slackware Linux ${VERSION} (x86_64)"
+LABEL org.opencontainers.image.description="Slackware Linux ${VERSION} base container image (x86_64)"
+LABEL org.opencontainers.image.vendor="Slackware Linux"
+LABEL org.opencontainers.image.licenses="GPL-2.0-or-later AND LGPL-2.1-or-later"
+LABEL org.opencontainers.image.url="http://www.slackware.com"
+LABEL org.opencontainers.image.source="https://forge.slackware.nl/slackware/docker-images"
+LABEL org.opencontainers.image.revision="${VERSION}"
+LABEL slackware.version="${VERSION}"
+LABEL slackware.arch="x86_64"
+CMD ["/bin/bash"]
+DOCKERFILE
+
+    # Explicit exit checks: build_variant runs in an `if ! (...)` condition
+    # (see Main), which suppresses `set -e` in this subshell, so a failed build
+    # would otherwise push a nonexistent tag and log "Done".
+    _log "Building and pushing ${TAG}..."
+    if ! docker build --no-cache -t "${TAG}" "${WORKDIR}"; then
+        _warn "build failed for ${TAG}; not pushing."
+        return 1
+    fi
+    if ! docker push "${TAG}"; then
+        _warn "push failed for ${TAG}."
+        return 1
+    fi
+    _log "=== Done: ${TAG} ==="
+}
+
+# ============================================================================
+# Main
+# ============================================================================
+
+rc=0
+for VERSION in "${BUILD_VARIANTS[@]}"; do
+    if changelog_changed "${VERSION}"; then
+        if ! ( build_variant "${VERSION}" ); then
+            _warn "variant ${VERSION} failed; continuing."
+            rc=1
+        fi
+    fi
+done
+exit "${rc}"
diff --git a/image-builder/build-full-image.sh b/image-builder/build-full-image.sh
new file mode 100755
index 0000000..a2fdb18
--- /dev/null
+++ b/image-builder/build-full-image.sh
@@ -0,0 +1,245 @@
+#!/bin/bash
+#
+# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# build-full-image.sh — sbo-full:{ver} FROM sbo-base:{ver}, all series.
+# Adapted from forge slackware/docker-images. No root needed.
+set -euo pipefail
+HERE="$(cd "$(dirname "$0")" && pwd)"
+source "${HERE}/config"
+LOG_TAG=full
+source "${HERE}/lib.sh"
+
+BASE_IMAGE="${REGISTRY}/sbo-base"
+FULL_IMAGE="${REGISTRY}/sbo-full"
+DIGEST_LABEL="sbo.full.base-digest"
+
+# ============================================================================
+# Argument parsing
+# ============================================================================
+
+FORCE=false
+OPT_VERSION=""
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --version) OPT_VERSION="$2"; shift 2 ;;
+        --force)   FORCE=true;       shift   ;;
+        *) _err "unknown argument: $1" ;;
+    esac
+done
+if [[ -n "${OPT_VERSION}" ]]; then
+    BUILD_VARIANTS=("${OPT_VERSION}")
+else
+    BUILD_VARIANTS=("${VARIANTS[@]}")
+fi
+
+# ============================================================================
+# Tag derivation
+# ============================================================================
+
+# derive_tags VERSION
+# Sets globals BASE_TAG and FULL_TAG for the given variant.
+derive_tags() {
+    local VERSION="$1"
+    BASE_TAG="${BASE_IMAGE}:${VERSION}"
+    FULL_TAG="${FULL_IMAGE}:${VERSION}"
+}
+
+# ============================================================================
+# Rebuild detection
+#
+# After pulling the latest base image, its digest is compared with the
+# digest stored in the DIGEST_LABEL on the current full image.  If
+# they differ the base image has been updated and the full must be
+# rebuilt to incorporate slackpkg package updates shipped with the new base.
+# ============================================================================
+
+needs_rebuild() {
+    local BASE_TAG="$1" FULL_TAG="$2"
+
+    if [[ "${FORCE}" == "true" ]]; then
+        _log "  --force specified; rebuilding unconditionally."
+        return 0
+    fi
+
+    # Digest of the base image we just pulled
+    local BASE_DIGEST
+    BASE_DIGEST=$(docker inspect --format '{{index .RepoDigests 0}}' \
+                  "${BASE_TAG}" 2>/dev/null || echo "")
+    if [[ -z "${BASE_DIGEST}" ]]; then
+        _warn "  Could not determine base image digest; rebuilding to be safe."
+        return 0
+    fi
+
+    # Digest recorded in the full image's label (empty if image doesn't exist)
+    local RECORDED_DIGEST
+    RECORDED_DIGEST=$(docker inspect \
+                      --format "{{index .Config.Labels \"${DIGEST_LABEL}\"}}" \
+                      "${FULL_TAG}" 2>/dev/null || echo "")
+
+    if [[ "${BASE_DIGEST}" == "${RECORDED_DIGEST}" ]]; then
+        _log "  Base image unchanged (${BASE_DIGEST:0:40}...); skipping."
+        return 1
+    fi
+
+    _log "  Base image changed; rebuilding."
+    _log "    Was : ${RECORDED_DIGEST:0:60}..."
+    _log "    Now : ${BASE_DIGEST:0:60}..."
+    return 0
+}
+
+# ============================================================================
+# Build one variant
+# ============================================================================
+
+build_variant() {
+    local VERSION="$1"
+    local REPO_KEY="slackware64-${VERSION}"
+    require_mount "${VERSION}"   # NFS must be up: we serve it over HTTP below
+    derive_tags "${VERSION}"
+
+    _log "=== ${FULL_TAG} ==="
+
+    # Pull the latest base image so digest comparison is against the current
+    # state of the registry, not a stale local cache.
+    _log "  Pulling base image ${BASE_TAG}..."
+    docker pull "${BASE_TAG}"
+
+    if ! needs_rebuild "${BASE_TAG}" "${FULL_TAG}"; then
+        return 0
+    fi
+
+    # Record the base image digest for the label
+    local BASE_DIGEST
+    BASE_DIGEST=$(docker inspect --format '{{index .RepoDigests 0}}' "${BASE_TAG}")
+
+    local WORKDIR
+    WORKDIR="$(mktemp -d /tmp/slackware-full.XXXXXX)"
+
+    # Serve the NFS mirror over HTTP on the docker bridge for the duration of
+    # the build, so slackpkg in the build container fetches packages from LAN
+    # instead of the internet. Killed (with WORKDIR cleanup) on any exit.
+    local MIRROR_ROOT; MIRROR_ROOT="$(strip_scheme "$(mirror_path "${MIRROR}" "${REPO_KEY}")")"
+    [[ -f "${MIRROR_ROOT}/PACKAGES.TXT" ]] \
+        || _err "mirror root has no PACKAGES.TXT: ${MIRROR_ROOT}"
+    python3 -m http.server "${HTTP_MIRROR_PORT}" \
+        --bind "${HTTP_MIRROR_HOST}" --directory "${MIRROR_ROOT}" \
+        >/dev/null 2>&1 &
+    local HTTP_PID=$!
+    # shellcheck disable=SC2064
+    trap "kill ${HTTP_PID} 2>/dev/null; rm -rf '${WORKDIR}'" EXIT
+    # Wait for the server to accept connections before building.
+    local i
+    for i in 1 2 3 4 5 6 7 8 9 10; do
+        curl -sf -o /dev/null "http://${HTTP_MIRROR_HOST}:${HTTP_MIRROR_PORT}/PACKAGES.TXT" && break
+        [[ $i -eq 10 ]] && _err "HTTP mirror did not come up on ${HTTP_MIRROR_HOST}:${HTTP_MIRROR_PORT}"
+        sleep 0.5
+    done
+
+    # Generate the Dockerfile for this variant
+    cat > "${WORKDIR}/Dockerfile" <<DOCKERFILE
+FROM ${BASE_TAG}
+LABEL maintainer="Eric Hameleers <alien@slackware.com>"
+
+# Import the Slackware GPG key against THIS mirror first: without it slackpkg
+# cannot verify CHECKSUMS.md5 and silently installs almost nothing (only the
+# packages already in base). 'yes YES |' answers the import prompt.
+RUN yes YES | LC_ALL=C slackpkg -batch=on -default_answer=y update gpg
+
+# Update the slackpkg package list before installing so that we always
+# get the versions current at build time, not the versions cached in the
+# base image.
+RUN LC_ALL=C slackpkg -batch=on -default_answer=y update
+
+# Download and install each individual package (thanks aclemons):
+RUN sed -i 's/DOWNLOAD_ALL=on/DOWNLOAD_ALL=off/' /etc/slackpkg/slackpkg.conf
+
+# We don't care about a big firmware package:
+RUN mv /etc/slackpkg/blacklist{,.keep} && \\
+  echo kernel-firmware > /etc/slackpkg/blacklist
+
+# Install the full Slackware:
+# All packages are installed in a single RUN layer to keep the image lean.
+RUN export LC_ALL=C && \\
+  for series in a ap d e f k kde l n t tcl x xap xfce y ; do \\
+  slackpkg -delall=on -batch=on -default_answer=y install "\$series"/* ; done
+
+# And back to defaults:
+RUN sed -i 's/DOWNLOAD_ALL=off/DOWNLOAD_ALL=on/' /etc/slackpkg/slackpkg.conf
+RUN mv /etc/slackpkg/blacklist{.keep,}
+
+
+# Delete package cache:
+RUN rm -rf /var/cache/packages/*
+
+# Rebuild the linker cache after adding new libraries
+RUN /sbin/ldconfig
+
+LABEL org.opencontainers.image.created="$(date -u +%Y-%m-%dT%H:%M:%SZ)"
+LABEL org.opencontainers.image.title="Slackware Linux ${VERSION} full (x86_64)"
+LABEL org.opencontainers.image.description="Slackware Linux ${VERSION} full image with all packages installed (x86_64)"
+LABEL org.opencontainers.image.vendor="Slackware Linux"
+LABEL org.opencontainers.image.licenses="GPL-2.0-or-later AND LGPL-2.1-or-later"
+LABEL org.opencontainers.image.url="http://www.slackware.com"
+LABEL org.opencontainers.image.source="https://forge.slackware.nl/slackware/docker-images"
+LABEL org.opencontainers.image.revision="${VERSION}"
+LABEL slackware.version="${VERSION}"
+LABEL slackware.arch="x86_64"
+LABEL ${DIGEST_LABEL}="${BASE_DIGEST}"
+CMD ["/bin/bash"]
+DOCKERFILE
+
+    local BUILD_FLAGS=()
+    [[ "${FORCE}" == "true" ]] && BUILD_FLAGS+=(--no-cache)
+
+    # Explicit exit checks: build_variant runs in an `if ! (...)` condition
+    # (see Main), which suppresses `set -e` inside this subshell, so a failed
+    # docker build would otherwise fall through to push a nonexistent tag and
+    # log "Done". Check each step and return non-zero on failure.
+    _log "  Building ${FULL_TAG}..."
+    if ! docker build "${BUILD_FLAGS[@]}" \
+        -t "${FULL_TAG}" \
+        "${WORKDIR}"; then
+        _warn "  build failed for ${FULL_TAG}; not pushing."
+        return 1
+    fi
+
+    _log "  Pushing ${FULL_TAG}..."
+    if ! docker push "${FULL_TAG}"; then
+        _warn "  push failed for ${FULL_TAG}."
+        return 1
+    fi
+
+    _log "=== Done: ${FULL_TAG} ==="
+}
+
+# ============================================================================
+# Main
+# ============================================================================
+
+# A --force build passes --no-cache, so the stale build cache is dead weight:
+# it still loads the containerd snapshotter's lease/lock bookkeeping and has
+# raced the layer export ("failed to open writer: ref ... locked ... unavailable").
+# Prune it first to shrink that surface. Best-effort; never fail the build on it.
+if [[ "${FORCE}" == "true" ]]; then
+    _log "  --force: pruning build cache before rebuild"
+    docker builder prune -f >/dev/null 2>&1 || _warn "  builder prune failed (ignored)"
+fi
+
+rc=0
+for VERSION in "${BUILD_VARIANTS[@]}"; do
+    if ! ( build_variant "${VERSION}" ); then
+        _warn "variant ${VERSION} failed; continuing."
+        rc=1
+    fi
+done
+exit "${rc}"
diff --git a/image-builder/build-sbo-testbuild.sh b/image-builder/build-sbo-testbuild.sh
new file mode 100755
index 0000000..a246b79
--- /dev/null
+++ b/image-builder/build-sbo-testbuild.sh
@@ -0,0 +1,143 @@
+#!/bin/bash
+#
+# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# build-sbo-testbuild.sh — sbo-testbuild:{ver} FROM sbo-full:{ver}.
+# Adds sbopkg + sbo-maintainer-tools from prebuilt .txz in PKGDIR.
+# Rebuilds when the full image OR the .txz set changes.
+set -euo pipefail
+HERE="$(cd "$(dirname "$0")" && pwd)"
+source "${HERE}/config"
+LOG_TAG=testbuild
+source "${HERE}/lib.sh"
+
+FULL_IMAGE="${REGISTRY}/sbo-full"
+TB_IMAGE="${REGISTRY}/sbo-testbuild"
+DIGEST_LABEL="sbo.testbuild.full-digest"
+PKGS_LABEL="sbo.testbuild.pkgs-hash"
+
+FORCE=false
+OPT_VERSION=""
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --version) OPT_VERSION="$2"; shift 2 ;;
+        --force)   FORCE=true;       shift   ;;
+        *) _err "unknown argument: $1" ;;
+    esac
+done
+if [[ -n "${OPT_VERSION}" ]]; then
+    BUILD_VARIANTS=("${OPT_VERSION}")
+else
+    BUILD_VARIANTS=("${VARIANTS[@]}")
+fi
+
+# Verify the required packages (*.t?z) are present before doing anything.
+require_pkgs() {
+    [[ -d "${PKGDIR}" ]] || _err "PKGDIR missing: ${PKGDIR}"
+    compgen -G "${PKGDIR}/sbopkg-*.t?z" >/dev/null \
+        || _err "no sbopkg-*.t?z in ${PKGDIR}"
+    compgen -G "${PKGDIR}/sbo-maintainer-tools-*.t?z" >/dev/null \
+        || _err "no sbo-maintainer-tools-*.t?z in ${PKGDIR}"
+}
+
+# needs_rebuild FULL_TAG TB_TAG PKGS_HASH -> 0 if rebuild needed
+needs_rebuild() {
+    local full_tag="$1" tb_tag="$2" pkgs_hash="$3"
+    [[ "${FORCE}" == "true" ]] && { _log "  --force."; return 0; }
+
+    local full_digest
+    full_digest=$(docker inspect --format '{{index .RepoDigests 0}}' \
+        "${full_tag}" 2>/dev/null || echo "")
+    [[ -n "${full_digest}" ]] || { _warn "  no full digest; rebuilding."; return 0; }
+
+    local rec_digest rec_pkgs
+    rec_digest=$(docker inspect \
+        --format "{{index .Config.Labels \"${DIGEST_LABEL}\"}}" \
+        "${tb_tag}" 2>/dev/null || echo "")
+    rec_pkgs=$(docker inspect \
+        --format "{{index .Config.Labels \"${PKGS_LABEL}\"}}" \
+        "${tb_tag}" 2>/dev/null || echo "")
+
+    if [[ "${full_digest}" == "${rec_digest}" && "${pkgs_hash}" == "${rec_pkgs}" ]]; then
+        _log "  full image and .txz set unchanged; skipping."
+        return 1
+    fi
+    _log "  full image or .txz set changed; rebuilding."
+    return 0
+}
+
+build_variant() {
+    local VERSION="$1"
+    local FULL_TAG="${FULL_IMAGE}:${VERSION}"
+    local TB_TAG="${TB_IMAGE}:${VERSION}"
+    _log "=== ${TB_TAG} ==="
+
+    _log "  Pulling ${FULL_TAG}..."
+    docker pull "${FULL_TAG}"
+
+    local PKGS_HASH; PKGS_HASH="$(txz_hash "${PKGDIR}")"
+
+    if ! needs_rebuild "${FULL_TAG}" "${TB_TAG}" "${PKGS_HASH}"; then
+        return 0
+    fi
+
+    local FULL_DIGEST
+    FULL_DIGEST=$(docker inspect --format '{{index .RepoDigests 0}}' "${FULL_TAG}" 2>/dev/null || echo "")
+
+    local WORKDIR; WORKDIR="$(mktemp -d /tmp/sbo-testbuild.XXXXXX)"
+    # shellcheck disable=SC2064
+    trap "rm -rf '${WORKDIR}'" EXIT
+    mkdir -p "${WORKDIR}/pkgs"
+    cp "${PKGDIR}"/sbopkg-*.t?z "${PKGDIR}"/sbo-maintainer-tools-*.t?z "${WORKDIR}/pkgs/"
+
+    cat > "${WORKDIR}/Dockerfile" <<DOCKERFILE
+FROM ${FULL_TAG}
+LABEL maintainer="danix <danix@danix.xyz>"
+COPY pkgs/ /tmp/pkgs/
+RUN installpkg /tmp/pkgs/* && rm -rf /tmp/pkgs
+RUN /sbin/ldconfig
+LABEL org.opencontainers.image.created="$(date -u +%Y-%m-%dT%H:%M:%SZ)"
+LABEL org.opencontainers.image.title="SBo test-build env ${VERSION} (x86_64)"
+LABEL org.opencontainers.image.description="Slackware ${VERSION} full + sbopkg + sbo-maintainer-tools"
+LABEL slackware.version="${VERSION}"
+LABEL ${DIGEST_LABEL}="${FULL_DIGEST}"
+LABEL ${PKGS_LABEL}="${PKGS_HASH}"
+CMD ["/bin/bash"]
+DOCKERFILE
+
+    local BUILD_FLAGS=()
+    [[ "${FORCE}" == "true" ]] && BUILD_FLAGS+=(--no-cache)
+    # Explicit exit checks: build_variant runs in an `if ! (...)` condition
+    # (see Main), which suppresses `set -e` in this subshell, so a failed build
+    # would otherwise push a nonexistent tag and log "Done".
+    _log "  Building ${TB_TAG}..."
+    if ! docker build "${BUILD_FLAGS[@]}" -t "${TB_TAG}" "${WORKDIR}"; then
+        _warn "  build failed for ${TB_TAG}; not pushing."
+        return 1
+    fi
+    _log "  Pushing ${TB_TAG}..."
+    if ! docker push "${TB_TAG}"; then
+        _warn "  push failed for ${TB_TAG}."
+        return 1
+    fi
+    _log "=== Done: ${TB_TAG} ==="
+}
+
+require_pkgs
+rc=0
+for VERSION in "${BUILD_VARIANTS[@]}"; do
+    if ! ( build_variant "${VERSION}" ); then
+        _warn "variant ${VERSION} failed; continuing."
+        rc=1
+    fi
+done
+exit "${rc}"
diff --git a/image-builder/config b/image-builder/config
new file mode 100644
index 0000000..8b52313
--- /dev/null
+++ b/image-builder/config
@@ -0,0 +1,15 @@
+# Shared configuration for the sbo-testbuild image builder.
+# Sourced by bootstrap.sh, build-full-image.sh, build-sbo-testbuild.sh, tests.
+
+REGISTRY="docker.noland.dnx:5000"
+MIRROR="file:///mnt/nas"
+VARIANTS=(current 15.0)              # x86_64 only for now
+PKGDIR="/opt/sbo-testbuild/pkgs"     # sbopkg + sbo-maintainer-tools .txz
+HASH_DIR="/var/cache/sbo-testbuild"  # ChangeLog hashes for rebuild gating
+
+# During the full-image build, packages are served to the build container off
+# the local NFS mirror (MIRROR) over HTTP on the docker bridge, so slackpkg
+# fetches from LAN instead of the internet. The bridge-gateway IP is what the
+# build container sees as the host; the port is ephemeral to this host.
+HTTP_MIRROR_HOST="172.17.0.1"        # docker0 bridge gateway (host from container)
+HTTP_MIRROR_PORT="8099"
diff --git a/image-builder/lib.sh b/image-builder/lib.sh
new file mode 100644
index 0000000..dfb076b
--- /dev/null
+++ b/image-builder/lib.sh
@@ -0,0 +1,84 @@
+#
+# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# Shared helpers for the image builder. Source, do not execute.
+# Sourcing must have no side effects beyond defining functions.
+
+_log()  { echo "[$(date '+%Y-%m-%d %H:%M:%S')] [${LOG_TAG:-image-builder}] $*"; }
+_warn() { echo "[$(date '+%Y-%m-%d %H:%M:%S')] [${LOG_TAG:-image-builder}] WARNING: $*" >&2; }
+_err()  { echo "[$(date '+%Y-%m-%d %H:%M:%S')] [${LOG_TAG:-image-builder}] ERROR: $*" >&2; exit 1; }
+
+# mirror_path MIRROR RELPATH
+# Join a MIRROR (file:///... or http(s)://...) with a relative path.
+mirror_path() {
+    local mirror="$1" rel="$2"
+    printf '%s/%s' "${mirror%/}" "${rel#/}"
+}
+
+# is_local_mirror MIRROR -> 0 if file:// or bare absolute path, else 1
+is_local_mirror() {
+    case "$1" in
+        file://*) return 0 ;;
+        http://*|https://*) return 1 ;;
+        /*) return 0 ;;
+        *) return 1 ;;
+    esac
+}
+
+# strip_scheme URL -> filesystem path for a file:// or bare-local URL
+strip_scheme() {
+    local u="$1"
+    case "$u" in
+        file://*) printf '%s' "${u#file://}" ;;
+        *) printf '%s' "$u" ;;
+    esac
+}
+
+# fetch SRC DEST
+# Copy SRC (a full mirror URL) to DEST. Local mirror -> cp, http -> curl.
+# Returns non-zero on failure; caller decides whether that is fatal.
+fetch() {
+    local src="$1" dest="$2"
+    if is_local_mirror "$src"; then
+        local path; path="$(strip_scheme "$src")"
+        [[ -f "$path" ]] || return 1
+        cp "$path" "$dest"
+    else
+        curl -sSfL --connect-timeout 60 "$src" -o "$dest"
+    fi
+}
+
+# txz_hash DIR
+# Stable hash of the set of Slackware package files (*.t?z) in DIR (names +
+# contents), order
+# independent. Empty/absent dir -> empty string.
+txz_hash() {
+    local dir="$1"
+    [[ -d "$dir" ]] || { printf ''; return 0; }
+    local files; files=$(find "$dir" -maxdepth 1 -name '*.t?z' -type f | sort)
+    [[ -n "$files" ]] || { printf ''; return 0; }
+    # Hash sorted "name  sha256" lines so reordering does not change output.
+    while IFS= read -r f; do
+        printf '%s  %s\n' "$(basename "$f")" "$(sha256sum "$f" | cut -d' ' -f1)"
+    done <<< "$files" | sha256sum | cut -d' ' -f1
+}
+
+# require_mount VERSION
+# Assert the NAS tree for VERSION is mounted (file:// mirror only).
+# x86_64 tree dir is slackware64-${VERSION}.
+require_mount() {
+    local version="$1"
+    is_local_mirror "$MIRROR" || return 0   # http mirror: nothing to check
+    local base; base="$(strip_scheme "$MIRROR")"
+    local dir="${base}/slackware64-${version}"
+    [[ -d "$dir" ]] || _err "NAS tree not mounted: ${dir}"
+}
diff --git a/image-builder/test-image-builder.sh b/image-builder/test-image-builder.sh
new file mode 100755
index 0000000..525ea8f
--- /dev/null
+++ b/image-builder/test-image-builder.sh
@@ -0,0 +1,80 @@
+#!/bin/bash
+#
+# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# Assert-based self-check for lib.sh pure logic. No docker, no network.
+# Run: bash test-image-builder.sh
+set -u
+cd "$(dirname "$0")"
+source ./lib.sh
+
+pass=0 fail=0
+check() { # DESC EXPECTED ACTUAL
+    if [[ "$2" == "$3" ]]; then pass=$((pass+1));
+    else fail=$((fail+1)); echo "FAIL: $1"; echo "  expected: [$2]"; echo "  actual:   [$3]"; fi
+}
+check_rc() { # DESC EXPECTED_RC ACTUAL_RC
+    if [[ "$2" == "$3" ]]; then pass=$((pass+1));
+    else fail=$((fail+1)); echo "FAIL: $1 (rc expected $2 got $3)"; fi
+}
+
+tmp="$(mktemp -d)"
+trap 'rm -rf "$tmp"' EXIT
+
+# --- mirror_path ---
+check "mirror_path trailing slash" \
+    "file:///mnt/nas/slackware64-current/PACKAGES.TXT" \
+    "$(mirror_path 'file:///mnt/nas/' 'slackware64-current/PACKAGES.TXT')"
+check "mirror_path no trailing slash" \
+    "file:///mnt/nas/x/y" "$(mirror_path 'file:///mnt/nas' '/x/y')"
+
+# --- is_local_mirror ---
+is_local_mirror "file:///mnt/nas"; check_rc "is_local file://" 0 $?
+is_local_mirror "/mnt/nas";        check_rc "is_local bare abs" 0 $?
+is_local_mirror "https://x/y";     check_rc "is_local https" 1 $?
+
+# --- strip_scheme ---
+check "strip_scheme file://" "/mnt/nas" "$(strip_scheme 'file:///mnt/nas')"
+check "strip_scheme bare" "/mnt/nas" "$(strip_scheme '/mnt/nas')"
+
+# --- fetch: local file resolves ---
+echo hello > "$tmp/src.txt"
+fetch "file://$tmp/src.txt" "$tmp/dst.txt"; check_rc "fetch local ok" 0 $?
+check "fetch local content" "hello" "$(cat "$tmp/dst.txt" 2>/dev/null)"
+
+# --- fetch: missing local file errors ---
+fetch "file://$tmp/nope.txt" "$tmp/x.txt"; check_rc "fetch local missing" 1 $?
+
+# --- txz_hash: stable + content-sensitive ---
+mkdir -p "$tmp/pkgs"
+printf a > "$tmp/pkgs/sbopkg-1.txz"
+printf b > "$tmp/pkgs/tools-1.txz"
+h1="$(txz_hash "$tmp/pkgs")"
+h2="$(txz_hash "$tmp/pkgs")"
+check "txz_hash stable" "$h1" "$h2"
+printf c > "$tmp/pkgs/tools-1.txz"   # change content
+h3="$(txz_hash "$tmp/pkgs")"
+check_rc "txz_hash changes on content" 0 "$([[ "$h1" != "$h3" ]] && echo 0 || echo 1)"
+check "txz_hash empty dir" "" "$(txz_hash "$tmp/empty-nope")"
+
+# --- require_mount: missing mount errors (subshell to catch _err exit) ---
+MIRROR="file://$tmp/no-such-root"
+( require_mount current ) 2>/dev/null; check_rc "require_mount missing" 1 $?
+mkdir -p "$tmp/mnt/slackware64-current"
+MIRROR="file://$tmp/mnt"
+( require_mount current ) 2>/dev/null; check_rc "require_mount present" 0 $?
+MIRROR="https://example/x"
+( require_mount current ) 2>/dev/null; check_rc "require_mount http skips" 0 $?
+
+echo "----"
+echo "PASS: $pass  FAIL: $fail"
+[[ "$fail" -eq 0 ]]
diff --git a/install.sh b/install.sh
new file mode 100755
index 0000000..8be02f0
--- /dev/null
+++ b/install.sh
@@ -0,0 +1,41 @@
+#!/bin/bash
+#
+# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# Install the test-build CLI into ~/bin (override with BINDIR=...). Copies the
+# file, so re-run after editing. The image-builder scripts are NOT installed:
+# they run on the docker host from their own checkout.
+#
+#   ./install.sh              install to ~/bin
+#   BINDIR=/usr/local/bin ./install.sh
+#   ./install.sh --uninstall  remove it
+
+set -euo pipefail
+HERE="$(cd "$(dirname "$0")" && pwd)"
+BINDIR="${BINDIR:-$HOME/bin}"
+PROG=test-build
+
+if [[ "${1:-}" == "--uninstall" ]]; then
+  rm -f "$BINDIR/$PROG" && echo "removed $BINDIR/$PROG"
+  exit 0
+fi
+
+[[ -f "$HERE/$PROG" ]] || { echo "$PROG not found in $HERE" >&2; exit 1; }
+mkdir -p "$BINDIR"
+install -m 0755 "$HERE/$PROG" "$BINDIR/$PROG"
+echo "installed $BINDIR/$PROG"
+
+case ":$PATH:" in
+  *":$BINDIR:"*) ;;
+  *) echo "note: $BINDIR is not in \$PATH; add it (e.g. in ~/.bashrc):"
+     echo "      export PATH=\"$BINDIR:\$PATH\"" ;;
+esac
diff --git a/overrides.example b/overrides.example
new file mode 100644
index 0000000..e9d89e9
--- /dev/null
+++ b/overrides.example
@@ -0,0 +1,16 @@
+# current-vs-stable dep overrides for test-build.
+# Copy to ~/.config/sbo-testbuild/overrides and edit. Applied only when
+# targeting -current (15.0 is the SBo baseline). One rule per line.
+#
+#   drop:   <prog>            dep is a 15.0-only SBo package whose payload the
+#                             -current base already ships; skipped at resolution
+#                             (not built, not flagged UNMET). e.g. rust-opt:
+#                             15.0 needs the SBo rust-opt, current has rust in base.
+#   rename: <old> -> <new>    dep was renamed on -current
+#   fetch:  <prog>            dep was removed from the -current tree; pull via sbopkg
+#
+# Start light: add rules only when a real package needs them.
+
+# drop:   rust-opt
+# rename: python3-foo -> foo
+# fetch:  somelib
diff --git a/test-build b/test-build
new file mode 100755
index 0000000..eb4009f
--- /dev/null
+++ b/test-build
@@ -0,0 +1,876 @@
+#!/bin/bash
+#
+# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+#
+# test-build - verify an already-published SBo package still builds on a target
+# Slackware version inside a throwaway docker container. Resolves + builds its
+# SBo deps from the local tree, caches built deps per image digest, reports
+# per-package status and lints the target.
+#
+# Dependency-resolution, cache, and summary logic are adapted from sbo-batch-test
+# (github: danixland). The overlay chroot is replaced by a docker container: the
+# container IS the disposable environment, so no overlayfs.
+#
+# No em dashes in prose by author convention.
+
+# =============================================================================
+# CONFIG (do not edit here; real values live in the external config file)
+# =============================================================================
+SBO_TREE_CURRENT=""
+SBO_TREE_STABLE=""
+IMAGE_CURRENT=""
+IMAGE_STABLE=""
+LOG_ROOT="/var/log/sbo-test-build"
+PKG_CACHE=""
+
+TB_CONFIG="${TB_CONFIG:-$HOME/.config/sbo-testbuild/config}"
+if [[ -f "$TB_CONFIG" ]]; then
+  # shellcheck disable=SC1090
+  source "$TB_CONFIG"
+fi
+
+TB_OVERRIDES="${TB_OVERRIDES:-$HOME/.config/sbo-testbuild/overrides}"
+
+# =============================================================================
+set -uo pipefail
+# Not -e: a package build failing is a handled outcome, not a script crash.
+
+# ---- flags / globals --------------------------------------------------------
+USE_COLOR=1        # --no-color or non-TTY disables
+DRY_RUN=0          # --dry-run: resolve + print order, do not build
+ASSUME_YES=0       # --yes: skip the confirm prompt (still prints the order)
+USE_CACHE=1        # --no-cache disables the dep cache for one run
+KEEP_TARGET=0      # --keep: copy the built target package out to KEEP_DIR
+VERSION_ID="current"   # "current" | "15.0"; set by --stable
+TARGET_ARG=""
+
+ACTIVE_TREE=""     # selected SBo tree (by version)
+ACTIVE_IMAGE=""    # selected image tag (by version)
+RUN_DIR=""         # timestamped log dir for this run
+DEPS_DIR=""        # per-run host dir of built dep .txz, mounted into the container
+BUILD_OUT=""       # per-run host dir where built packages are copied out
+
+# Status tracking. Keyed by "category/prog". Parallel assoc arrays.
+declare -A ST_STATUS=()
+declare -A ST_REASON=()
+declare -A ST_TIME=()
+declare -A ST_README=()
+
+usage() {
+  cat <<'EOF'
+test-build - verify an SBo package builds on a target Slackware in docker
+
+USAGE:
+  test-build [OPTIONS] <program-name>
+
+OPTIONS:
+  -h, --help    This text.
+  --stable      Target Slackware 15.0 (image + tree). Default is -current.
+  --dry-run     Resolve, apply overrides, print the build order, do not build.
+  --yes         Skip the confirm prompt (the order is still printed first).
+  --no-cache    Rebuild all deps this run, ignore/refresh the cache.
+  --keep        Copy the built target package out to a kept/ dir (path is
+                printed), so it can be installed on the host. The build is
+                otherwise throwaway.
+  --no-color    Disable ANSI color (auto-disabled when stdout is not a TTY).
+EOF
+}
+
+parse_args() {
+  while [[ $# -gt 0 ]]; do
+    case "$1" in
+      -h|--help) usage; exit 0 ;;
+      --stable|15.0) VERSION_ID="15.0"; shift ;;
+      --dry-run) DRY_RUN=1; shift ;;
+      --yes) ASSUME_YES=1; shift ;;
+      --no-cache) USE_CACHE=0; shift ;;
+      --keep) KEEP_TARGET=1; shift ;;
+      --no-color) USE_COLOR=0; shift ;;
+      -*) echo "Unknown option: $1" >&2; usage >&2; exit 2 ;;
+      *)
+        if [[ -n "$TARGET_ARG" ]]; then
+          echo "Only one target accepted (got '$TARGET_ARG' and '$1')." >&2
+          exit 2
+        fi
+        TARGET_ARG="$1"; shift ;;
+    esac
+  done
+  if [[ -z "$TARGET_ARG" ]]; then
+    echo "No target given." >&2; usage >&2; exit 2
+  fi
+}
+
+init_color() {
+  if [[ $USE_COLOR -eq 1 && -t 1 ]]; then
+    C_RED=$'\e[31m'; C_GRN=$'\e[32m'; C_YEL=$'\e[33m'; C_RST=$'\e[0m'
+  else
+    C_RED=""; C_GRN=""; C_YEL=""; C_RST=""
+  fi
+}
+
+# Map VERSION_ID to the active tree + image. No I/O, unit-testable.
+select_version_paths() {
+  if [[ "$VERSION_ID" == "15.0" ]]; then
+    ACTIVE_TREE="$SBO_TREE_STABLE"; ACTIVE_IMAGE="$IMAGE_STABLE"
+  else
+    ACTIVE_TREE="$SBO_TREE_CURRENT"; ACTIVE_IMAGE="$IMAGE_CURRENT"
+  fi
+}
+
+# require_config: the external config must exist and set the version's paths.
+require_config() {
+  if [[ ! -f "$TB_CONFIG" ]]; then
+    cat >&2 <<EOF
+No config file: $TB_CONFIG
+Copy the example and edit it:
+
+  mkdir -p "\$(dirname "$TB_CONFIG")"
+  cp test-build-config.example "$TB_CONFIG"
+  \${EDITOR:-vi} "$TB_CONFIG"
+EOF
+    exit 1
+  fi
+  select_version_paths
+  if [[ -z "$ACTIVE_TREE" || -z "$ACTIVE_IMAGE" ]]; then
+    echo "Config $TB_CONFIG is missing the tree/image for version '$VERSION_ID'." >&2
+    exit 1
+  fi
+  if [[ ! -d "$ACTIVE_TREE" ]]; then
+    echo "SBo tree for '$VERSION_ID' does not exist: $ACTIVE_TREE" >&2
+    exit 1
+  fi
+}
+
+# =============================================================================
+# SBo tree lookup
+# =============================================================================
+# In this tool there is one active tree per run, but the resolver reads an array
+# named SBO_TREE_ROOTS so the ported logic and its self-check match sbo-batch-test.
+# main() sets SBO_TREE_ROOTS=("$ACTIVE_TREE") after require_config.
+declare -a SBO_TREE_ROOTS=()
+
+find_slackbuild_dir() {
+  local prog="$1" root d
+  for root in "${SBO_TREE_ROOTS[@]}"; do
+    [[ -d "$root" ]] || continue
+    for d in "$root"/*/"$prog"; do
+      if [[ -d "$d" && -f "$d/$prog.info" ]]; then
+        echo "$d"; return 0
+      fi
+    done
+  done
+  return 1
+}
+
+category_of() { basename "$(dirname "$1")"; }
+pkg_key() { echo "$(category_of "$1")/$(basename "$1")"; }
+
+# Resolve the TARGET to test from CWD or a path (repo-agnostic). The target is
+# the SlackBuild you are editing, wherever it lives; its deps come from the
+# configured SBo tree (see find_slackbuild_dir), NOT the other way around.
+#   - a path (absolute, or containing '/', or '.'/'./x'): use that dir directly
+#   - a bare name: ./<name>/ under CWD, else CWD itself if it IS <name>/
+# Prints the resolved absolute dir on success; returns 1 (with a message) if the
+# dir has no matching <name>.info.
+resolve_target_dir() {
+  local arg="$1" dir prog
+  if [[ "$arg" == /* || "$arg" == .* || "$arg" == */* ]]; then
+    dir="${arg%/}"; prog="$(basename "$dir")"
+  elif [[ -f "./$arg/$arg.info" ]]; then
+    dir="./$arg"; prog="$arg"
+  elif [[ "$(basename "$PWD")" == "$arg" && -f "./$arg.info" ]]; then
+    dir="."; prog="$arg"
+  else
+    echo "Target '$arg' not found: no ./$arg/$arg.info, and CWD is not $arg/." >&2
+    return 1
+  fi
+  if [[ ! -f "$dir/$prog.info" ]]; then
+    echo "Target dir '$dir' has no $prog.info (expected a SlackBuild package dir)." >&2
+    return 1
+  fi
+  ( cd "$dir" && pwd )   # emit absolute path
+}
+
+read_requires() {
+  local info="$1"
+  # shellcheck disable=SC1090
+  ( set +u; source "$info"; echo "${REQUIRES:-}" )
+}
+
+version_of() {
+  local dir="$1"
+  local info="$dir/$(basename "$dir").info"
+  [[ -f "$info" ]] || return
+  local v; v="$(grep -m1 '^VERSION=' "$info" | cut -d'"' -f2)"
+  echo "$v"
+}
+
+# =============================================================================
+# DEPENDENCY RESOLUTION (topo sort + cycle detection, LOCAL tree only)
+# =============================================================================
+declare -a RESOLVED_ORDER=()
+declare -A UNMET=()
+declare -a CYCLES=()
+declare -A HAS_README=()
+declare -A _vstate=()
+declare -A FETCH_DEPS=()   # prog -> 1: resolve via sbopkg in-container
+
+# Is a prog already present in the container base? Kept as a callback so the
+# pure topo logic stays testable.
+#
+# Populated lazily from the active image's package db on first call: each entry
+# in /var/log/packages is named <name>-<ver>-<arch>-<build>, so strip the last
+# three dash-fields to get the bare package name and match the SBo token
+# against that. TB_BASE_PKGS can be pre-seeded by tests to bypass docker.
+declare -A TB_BASE_PKGS=()
+TB_BASE_LOADED="${TB_BASE_LOADED:-0}"
+
+load_base_pkgs() {
+  [[ "$TB_BASE_LOADED" == "1" ]] && return 0
+  TB_BASE_LOADED=1
+  [[ -n "$ACTIVE_IMAGE" ]] || return 0
+  local entry name
+  while IFS= read -r entry; do
+    [[ -n "$entry" ]] || continue
+    # strip trailing -<ver>-<arch>-<build>
+    name="${entry%-*-*-*}"
+    TB_BASE_PKGS["$name"]=1
+  done < <(docker run --rm "$ACTIVE_IMAGE" \
+             /bin/sh -c 'ls /var/log/packages' 2>/dev/null)
+}
+
+installed_in_base() {
+  load_base_pkgs
+  [[ -n "${TB_BASE_PKGS[$1]:-}" ]]
+}
+
+_resolve_visit() {
+  local dir="$1" parent="$2"
+  local key; key="$(basename "$dir")"
+
+  if [[ "${_vstate[$dir]:-}" == "1" ]]; then return 0; fi
+  if [[ "${_vstate[$dir]:-}" == "0" ]]; then
+    CYCLES+=("cycle involving $key (pulled in via $parent)")
+    return 1
+  fi
+  _vstate["$dir"]=0
+
+  local info="$dir/$(basename "$dir").info"
+  local req tok depdir rc=0
+  req="$(read_requires "$info")"
+  for tok in $req; do
+    if [[ "$tok" == "%README%" ]]; then
+      HAS_README["$dir"]=1
+      continue
+    fi
+    tok="$(apply_rename "$tok")"
+    # drop: satisfied by the -current base (e.g. a 15.0-only dep like rust-opt
+    # whose payload ships in current's full-install image). Skip it entirely:
+    # no recurse, no UNMET, no order entry. Inert on 15.0 (overrides are).
+    if [[ "${OV_DROP[$tok]:-}" == "1" ]]; then
+      continue
+    fi
+    if [[ "${OV_FETCH[$tok]:-}" == "1" ]]; then
+      FETCH_DEPS["$tok"]=1
+      continue
+    fi
+    if depdir="$(find_slackbuild_dir "$tok")"; then
+      _resolve_visit "$depdir" "$key" || rc=1
+    elif installed_in_base "$tok"; then
+      :
+    else
+      UNMET["$tok"]="needed by $key"
+      rc=1
+    fi
+  done
+
+  _vstate["$dir"]=1
+  RESOLVED_ORDER+=("$dir")
+  return $rc
+}
+
+resolve_target() {
+  local dir="$1"
+  RESOLVED_ORDER=()
+  CYCLES=()
+  UNMET=()
+  FETCH_DEPS=()
+  _vstate=()
+  _resolve_visit "$dir" "(top)"
+}
+
+# =============================================================================
+# current-vs-stable overrides. Parsed from $TB_OVERRIDES. Applied only when
+# targeting -current (15.0 is the SBo baseline, no deltas).
+# =============================================================================
+declare -A OV_DROP=()      # prog -> 1
+declare -A OV_RENAME=()    # old  -> new
+declare -A OV_FETCH=()     # prog -> 1
+
+load_overrides() {
+  OV_DROP=(); OV_RENAME=(); OV_FETCH=()
+  # 15.0 is the baseline: no overrides.
+  [[ "$VERSION_ID" == "15.0" ]] && return
+  [[ -f "$TB_OVERRIDES" ]] || return
+  local line kind rest
+  while IFS= read -r line; do
+    line="${line%%#*}"                       # strip comments
+    line="${line#"${line%%[![:space:]]*}"}"  # ltrim
+    [[ -z "$line" ]] && continue
+    kind="${line%%:*}"; rest="${line#*:}"
+    kind="${kind//[[:space:]]/}"
+    rest="${rest#"${rest%%[![:space:]]*}"}"  # ltrim value
+    case "$kind" in
+      drop)   OV_DROP["${rest//[[:space:]]/}"]=1 ;;
+      fetch)  OV_FETCH["${rest//[[:space:]]/}"]=1 ;;
+      rename)
+        # rest is "old -> new"
+        local old new
+        old="${rest%%->*}"; new="${rest##*->}"
+        old="${old//[[:space:]]/}"; new="${new//[[:space:]]/}"
+        [[ -n "$old" && -n "$new" ]] && OV_RENAME["$old"]="$new" ;;
+      *) echo "WARN: unknown override rule: $line" >&2 ;;
+    esac
+  done < "$TB_OVERRIDES"
+}
+
+# Map a dep token through rename rules (identity if no rule).
+apply_rename() {
+  local tok="$1"
+  echo "${OV_RENAME[$tok]:-$tok}"
+}
+
+# Remove dropped packages from RESOLVED_ORDER in place.
+apply_overrides_to_order() {
+  local d prog keep=()
+  for d in "${RESOLVED_ORDER[@]}"; do
+    prog="$(basename "$d")"
+    [[ "${OV_DROP[$prog]:-}" == "1" ]] && continue
+    keep+=("$d")
+  done
+  # Assign without "${keep[@]:-}": under set -u that fallback yields a
+  # one-element array holding an empty string when keep is empty (all deps
+  # dropped), which the build loop would then iterate over as d="". Guard it.
+  if [[ ${#keep[@]} -eq 0 ]]; then
+    RESOLVED_ORDER=()
+  else
+    RESOLVED_ORDER=("${keep[@]}")
+  fi
+}
+
+# =============================================================================
+# Dependency cache. Layout: $CACHE_ROOT/<cat>/<prog>/<prog>-<ver>-...txz where
+# CACHE_ROOT = $PKG_CACHE/<image-digest> (set per run by resolve_cache_root).
+# Key is prog+version. --no-cache (USE_CACHE=0) or empty PKG_CACHE disables.
+# =============================================================================
+CACHE_ROOT=""   # set by resolve_cache_root once the image digest is known
+
+# True when the cache is usable this run.
+_cache_on() { [[ $USE_CACHE -eq 1 && -n "$PKG_CACHE" && -n "$CACHE_ROOT" ]]; }
+
+_cache_ver_of() {
+  local prog="$1" base="$2"
+  base="${base#"$prog"-}"
+  echo "${base%%-*}"
+}
+
+# cache_decision <cat> <prog> <version> -> cached | bump:OLD:NEW | new
+cache_decision() {
+  local cat="$1" prog="$2" version="$3"
+  _cache_on || { echo new; return; }
+  local dir="$CACHE_ROOT/$cat/$prog"
+  local f newest=""
+  for f in "$dir/$prog"-*.t?z; do
+    [[ -e "$f" ]] || continue
+    [[ -z "$newest" || "$f" -nt "$newest" ]] && newest="$f"
+  done
+  [[ -z "$newest" ]] && { echo new; return; }
+  local have; have="$(_cache_ver_of "$prog" "$(basename "$newest")")"
+  if [[ "$have" == "$version" ]]; then echo cached; else echo "bump:$have:$version"; fi
+}
+
+cache_path() {
+  local cat="$1" prog="$2" version="$3"
+  _cache_on || return
+  local dir="$CACHE_ROOT/$cat/$prog"
+  local f newest=""
+  for f in "$dir/$prog"-*.t?z; do
+    [[ -e "$f" ]] || continue
+    [[ -z "$newest" || "$f" -nt "$newest" ]] && newest="$f"
+  done
+  [[ -z "$newest" ]] && return
+  [[ "$(_cache_ver_of "$prog" "$(basename "$newest")")" == "$version" ]] && echo "$newest"
+}
+
+cache_store() {
+  local cat="$1" prog="$2" src="$3"
+  _cache_on || return
+  local dir="$CACHE_ROOT/$cat/$prog"
+  mkdir -p "$dir"
+  rm -f "$dir"/*.t?z
+  cp -a "$src" "$dir/"
+}
+
+cache_label() {
+  local dir="$1" is_target="$2"
+  local cat prog ver dec
+  cat="$(category_of "$dir")"; prog="$(basename "$dir")"; ver="$(version_of "$dir")"
+  dec="$(cache_decision "$cat" "$prog" "$ver")"
+  local label
+  case "$dec" in
+    cached)   label="cached ($ver)" ;;
+    bump:*)   label="rebuild: ${dec#bump:}"; label="${label/:/ -> }" ;;
+    *)        label="build (new)" ;;
+  esac
+  if [[ "$is_target" == "1" ]]; then
+    case "$dec" in
+      cached) label="build (cached $ver, rebuilt as target)" ;;
+    esac
+    echo "target, $label"
+  else
+    echo "$label"
+  fi
+}
+
+# Compute CACHE_ROOT from the image's digest, namespaced by variant. Falls back
+# to the tag if the digest cannot be read (still isolates per image reference).
+# The dir is "<variant>-<digest>", so an image rebuild changes the digest and
+# self-invalidates the cache (deps built against the old base are never reused).
+#
+# Prune stale digests of THIS variant on the way in: a base update leaves the
+# old <variant>-<olddigest> dir orphaned, so drop it. Scoped to the variant so a
+# --current run does not wipe the 15.0 cache (both live caches survive, and
+# testing both trees back-to-back still reuses built deps).
+resolve_cache_root() {
+  [[ -z "$PKG_CACHE" ]] && { CACHE_ROOT=""; return; }
+  local digest
+  digest="$(docker image inspect --format '{{index .Id}}' "$ACTIVE_IMAGE" 2>/dev/null)"
+  [[ -z "$digest" ]] && digest="tag-${ACTIVE_IMAGE//[^a-zA-Z0-9._-]/_}"
+  digest="${digest//[^a-zA-Z0-9._-]/_}"
+  local name="${VERSION_ID}-${digest}"
+  CACHE_ROOT="$PKG_CACHE/$name"
+  mkdir -p "$CACHE_ROOT"
+
+  # drop superseded caches for this variant only
+  local d
+  for d in "$PKG_CACHE/${VERSION_ID}-"*; do
+    [[ -d "$d" ]] || continue
+    [[ "$(basename "$d")" == "$name" ]] && continue
+    rm -rf "$d"
+  done
+}
+
+# Does SlackBuild dir $1 directly require any prog in the dead list (nameref $2)?
+# Direct-requires check only; transitive blocking works because run_target
+# iterates in topo order, propagating a failure one hop per package.
+depends_on_failed() {
+  local dir="$1"; local -n failed="$2"
+  local info="$dir/$(basename "$dir").info"
+  local req tok f
+  req="$(read_requires "$info")"
+  for tok in $req; do
+    [[ "$tok" == "%README%" ]] && continue
+    for f in "${failed[@]:-}"; do
+      [[ "$tok" == "$f" ]] && return 0
+    done
+  done
+  return 1
+}
+
+# build_one <slackbuild-dir> <is_target 0|1> [container-name]
+# Runs the build in a throwaway container. Sets ST_STATUS/ST_REASON/ST_TIME.
+# Successful builds copy their package to a host workdir; deps are cached and
+# the target is linted. Returns 0 on SUCCESS/CACHED, 1 otherwise.
+build_one() {
+  local dir="$1" is_target="${2:-0}"
+  local prog cat key
+  prog="$(basename "$dir")"; cat="$(category_of "$dir")"; key="$cat/$prog"
+  local logf="$RUN_DIR/${cat}_${prog}.log"
+  local start; start=$(date +%s)
+  local version; version="$(version_of "$dir")"
+
+  [[ "${HAS_README[$dir]:-}" == "1" ]] && ST_README["$key"]=1
+
+  # Dep with a version-matching cached package: installpkg it into the shared
+  # dep-package dir; no build. The target never takes this path.
+  if [[ "$is_target" != "1" ]]; then
+    local cached; cached="$(cache_path "$cat" "$prog" "$version")"
+    if [[ -n "$cached" ]]; then
+      cp -a "$cached" "$DEPS_DIR/"
+      {
+        echo "===== test-build: $prog (from cache) ====="
+        echo "cached package: $(basename "$cached")"
+      } >> "$logf"
+      ST_TIME["$key"]=$(( $(date +%s) - start ))
+      ST_STATUS["$key"]="CACHED"
+      return 0
+    fi
+  fi
+
+  # Build in a container. Mounts:
+  #   $dir           -> /sbo/pkg    (ro, the SlackBuild)
+  #   $DEPS_DIR      -> /sbo/deps   (rw, already-built dep .txz to installpkg first)
+  #   $BUILD_OUT     -> /sbo/out    (rw, where the built package is copied out)
+  # The in-container script installs any deps present, then builds the target,
+  # writes a status token to /sbo/out/$prog.status, and copies the package out.
+  local statf="$BUILD_OUT/$prog.status"
+  rm -f "$statf"
+
+  # fetch deps (removed from -current tree): let the container's sbopkg build
+  # them first. FETCH_DEPS is the set collected during resolution.
+  local fetch_list=""
+  local fp
+  for fp in "${!FETCH_DEPS[@]}"; do fetch_list+="$fp "; done
+
+  # -i is required: without it docker does not attach stdin, so `bash -s` reads
+  # nothing and the heredoc script is silently discarded (exit 0, empty log).
+  docker run --rm -i \
+    -v "$dir":/sbo/pkg:ro \
+    -v "$DEPS_DIR":/sbo/deps \
+    -v "$BUILD_OUT":/sbo/out \
+    -e PROG="$prog" \
+    -e FETCH_LIST="$fetch_list" \
+    -e IS_TARGET="$is_target" \
+    "$ACTIVE_IMAGE" /bin/bash -s >>"$logf" 2>&1 <<'CONTAINER_EOF'
+set -uo pipefail
+prog="$PROG"
+statf="/sbo/out/$prog.status"
+
+# 0. install already-built dependency packages (order guaranteed by the host).
+for d in /sbo/deps/*.t?z; do
+  [[ -e "$d" ]] || continue
+  installpkg --terse "$d" || { echo "INSTALL-FAILED (dep $d)"; echo INSTALL-FAILED > "$statf"; exit 1; }
+done
+
+# 0b. fetch-from-SBo deps via sbopkg (removed from the -current tree).
+for f in $FETCH_LIST; do
+  echo "sbopkg-building fetch dep: $f"
+  sbopkg -B -i "$f" || { echo "BUILD-FAILED (fetch dep $f)"; echo BUILD-FAILED > "$statf"; exit 1; }
+done
+
+# copy the SlackBuild out of the read-only mount so it can write there.
+cp -a /sbo/pkg /sbo/build
+cd /sbo/build || { echo BUILD-FAILED > "$statf"; exit 1; }
+. ./"$prog".info
+
+export OUTPUT=/sbo/out
+mkdir -p "$OUTPUT"
+
+echo "===== test-build: $prog ====="
+echo "PRGNAM=${PRGNAM:-$prog} VERSION=${VERSION:-?} BUILD=${BUILD:-?} TAG=${TAG:-?}"
+echo "uname -m: $(uname -m)   OUTPUT=$OUTPUT"
+echo "REQUIRES=${REQUIRES:-}"
+echo "================================="
+
+if [ "$(uname -m)" = "x86_64" ] && [ -n "${DOWNLOAD_x86_64:-}" ] && [ "${DOWNLOAD_x86_64}" != "UNSUPPORTED" ] && [ "${DOWNLOAD_x86_64}" != "UNTESTED" ]; then
+  DL="$DOWNLOAD_x86_64"; MD="$MD5SUM_x86_64"
+else
+  DL="$DOWNLOAD"; MD="$MD5SUM"
+fi
+
+for u in $DL; do
+  wget -c --tries=3 "$u" || { echo DOWNLOAD-FAILED > "$statf"; exit 1; }
+done
+
+set -- $MD
+for u in $DL; do
+  f="$(basename "$u")"
+  want="$1"; shift
+  got="$(md5sum "$f" | cut -d' ' -f1)"
+  if [ "$got" != "$want" ]; then
+    echo "MD5 mismatch on $f: want $want got $got"
+    echo MD5-MISMATCH > "$statf"; exit 1
+  fi
+done
+
+# Source /etc/profile.d so dep-provided env is live (google-go-lang sets GOROOT
+# + PATH to its go here, rust-opt sets cargo, etc.). This heredoc runs in a
+# non-login shell, which does NOT read profile.d, so a bare `go build` would
+# otherwise pick the system gccgo instead of the installed google-go-lang.
+set +u   # profile.d scripts routinely reference unset vars
+for pf in /etc/profile.d/*.sh; do
+  [ -r "$pf" ] && . "$pf"
+done
+set -u
+
+chmod +x ./"$prog".SlackBuild
+if ! ./"$prog".SlackBuild; then
+  echo BUILD-FAILED > "$statf"; exit 1
+fi
+
+pkg="$(ls -t "$OUTPUT"/"$prog"-*.t?z 2>/dev/null | head -n1)"
+if [ -z "$pkg" ]; then
+  echo "No package produced in $OUTPUT"
+  echo BUILD-FAILED > "$statf"; exit 1
+fi
+if ! installpkg --terse "$pkg"; then
+  echo INSTALL-FAILED > "$statf"; exit 1
+fi
+echo "===== installed files: $(basename "$pkg") ====="
+pkgname="$(basename "$pkg")"; pkgname="${pkgname%.t?z}"
+cat "/var/log/packages/$pkgname" 2>/dev/null || echo "(package db entry not found)"
+echo "================================="
+
+# lint the target here in the container: sbopkglint is baked into the image and
+# runs as root, so it needs no host sudo. Fail-soft: findings never fail the build.
+if [ "${IS_TARGET:-0}" = "1" ] && command -v sbopkglint >/dev/null 2>&1; then
+  echo "===== sbopkglint: $(basename "$pkg") ====="
+  if sbopkglint "$pkg"; then
+    echo "LINT-CLEAN"
+  else
+    echo "LINT-FINDINGS"
+  fi
+  echo "================================="
+fi
+echo SUCCESS > "$statf"
+CONTAINER_EOF
+
+  local status="BUILD-FAILED"
+  [[ -f "$statf" ]] && status="$(cat "$statf")"
+  ST_TIME["$key"]=$(( $(date +%s) - start ))
+  ST_STATUS["$key"]="$status"
+
+  if [[ "$status" == "SUCCESS" ]]; then
+    # locate the built package copied to the host workdir
+    local built newest=""
+    for built in "$BUILD_OUT/${prog}"-*.t?z; do
+      [[ -e "$built" ]] || continue
+      [[ -z "$newest" || "$built" -nt "$newest" ]] && newest="$built"
+    done
+    if [[ -n "$newest" ]]; then
+      if [[ "$is_target" != "1" ]]; then
+        cache_store "$cat" "$prog" "$newest"
+        # make the dep available to later builds in this run
+        cp -a "$newest" "$DEPS_DIR/"
+      else
+        # lint ran in-container (see IS_TARGET block); surface its verdict from
+        # the log so the host summary can show clean/findings.
+        if grep -q '^LINT-FINDINGS$' "$logf" 2>/dev/null; then
+          echo "  lint: ${C_RED}findings${C_RST} (see $(basename "$logf"))"
+        elif grep -q '^LINT-CLEAN$' "$logf" 2>/dev/null; then
+          echo "  lint: ${C_GRN}clean${C_RST}"
+        fi
+        # --keep: copy the built target package to a durable dir (sibling of the
+        # logs tree, not inside a throwaway run dir) so it can be installed on
+        # the host, e.g. to regenerate post-install artifacts.
+        if [[ $KEEP_TARGET -eq 1 ]]; then
+          local keepdir; keepdir="$(dirname "$LOG_ROOT")/kept"
+          mkdir -p "$keepdir"
+          cp -a "$newest" "$keepdir/"
+          echo "  kept: $keepdir/$(basename "$newest")"
+        fi
+      fi
+    fi
+    return 0
+  fi
+  ST_REASON["$key"]="see $(basename "$logf")"
+  return 1
+}
+
+# confirm_order: print the resolved order (overrides marked) and ask to proceed.
+# --yes skips the prompt but the order is still printed. --dry-run never reaches
+# here. Returns 0 to proceed, 1 to abort.
+confirm_order() {
+  local target_dir="$1"
+  echo "  build order (${VERSION_ID}):"
+  local d
+  for d in "${RESOLVED_ORDER[@]}"; do
+    local it=0; [[ "$d" == "$target_dir" ]] && it=1
+    local rdm=""; [[ "${HAS_README[$d]:-}" == 1 ]] && rdm="  [%README%]"
+    printf "    %-30s %s%s\n" "$(pkg_key "$d")" "$(cache_label "$d" "$it")" "$rdm"
+    echo "$(pkg_key "$d")" >> "$RUN_DIR/build-order.txt"
+  done
+  # note fetch deps (built via sbopkg in-container, not in the order list)
+  local fp
+  for fp in "${!FETCH_DEPS[@]}"; do
+    printf "    %-30s %s\n" "$fp" "fetch (sbopkg in container)"
+  done
+  [[ $ASSUME_YES -eq 1 ]] && return 0
+  local reply
+  read -rp "  Proceed? [Y/n] " reply
+  [[ -z "$reply" || "$reply" =~ ^[Yy]$ ]]
+}
+
+# run_target <target-slackbuild-dir>
+run_target() {
+  local target_dir="$1"
+  local tkey; tkey="$(pkg_key "$target_dir")"
+
+  echo
+  echo "=== Target: $tkey (${VERSION_ID}) ==="
+  resolve_target "$target_dir"
+  apply_overrides_to_order
+
+  # Hard resolution failures: report and stop, do not build.
+  if [[ ${#CYCLES[@]} -gt 0 || ${#UNMET[@]} -gt 0 ]]; then
+    local why=""
+    if [[ ${#UNMET[@]} -gt 0 ]]; then
+      local u
+      for u in "${!UNMET[@]}"; do why+="unmet:$u(${UNMET[$u]}) "; done
+    fi
+    [[ ${#CYCLES[@]} -gt 0 ]] && why+="${CYCLES[*]}"
+    ST_STATUS["$tkey"]="UNMET-DEP"
+    ST_REASON["$tkey"]="$why"
+    echo "  resolution failed: $why"
+    echo "  add an override rule ($TB_OVERRIDES) and rerun, or fix the tree." >&2
+    return
+  fi
+
+  if [[ $DRY_RUN -eq 1 ]]; then
+    echo "  build order (dry-run):"
+    local d
+    for d in "${RESOLVED_ORDER[@]}"; do
+      local it=0; [[ "$d" == "$target_dir" ]] && it=1
+      local rdm=""; [[ "${HAS_README[$d]:-}" == 1 ]] && rdm="  [%README%]"
+      printf "    %-30s %s%s\n" "$(pkg_key "$d")" "$(cache_label "$d" "$it")" "$rdm"
+      echo "$(pkg_key "$d")" >> "$RUN_DIR/build-order.txt"
+    done
+    local fp
+    for fp in "${!FETCH_DEPS[@]}"; do
+      printf "    %-30s %s\n" "$fp" "fetch (sbopkg in container)"
+    done
+    return
+  fi
+
+  if ! confirm_order "$target_dir"; then
+    echo "  aborted."
+    ST_STATUS["$tkey"]="ABORTED"
+    return
+  fi
+
+  # Per-run docker workdirs (host side, discarded after the run).
+  DEPS_DIR="$RUN_DIR/deps"; BUILD_OUT="$RUN_DIR/out"
+  mkdir -p "$DEPS_DIR" "$BUILD_OUT"
+
+  local d failed_progs=()
+  for d in "${RESOLVED_ORDER[@]}"; do
+    local key; key="$(pkg_key "$d")"
+    local prog; prog="$(basename "$d")"
+
+    if depends_on_failed "$d" failed_progs; then
+      ST_STATUS["$key"]="BLOCKED-BY-DEP"
+      ST_REASON["$key"]="blocked by failed dep"
+      [[ "${HAS_README[$d]:-}" == "1" ]] && ST_README["$key"]=1
+      echo "  $key: BLOCKED-BY-DEP"
+      failed_progs+=("$prog")
+      continue
+    fi
+
+    local it=0; [[ "$d" == "$target_dir" ]] && it=1
+    echo "  building $key ..."
+    if build_one "$d" "$it"; then
+      echo "  $key: ${ST_STATUS[$key]} (${ST_TIME[$key]}s)"
+    else
+      echo "  $key: ${ST_STATUS[$key]} (${ST_TIME[$key]}s)"
+      failed_progs+=("$prog")
+    fi
+  done
+}
+
+# =============================================================================
+# SUMMARY (ported)
+# =============================================================================
+print_summary() {
+  local total=$SECONDS
+  local succ=0 fail=0 blocked=0 cached=0
+  local summary="$RUN_DIR/summary.log"
+
+  {
+    echo "test-build run summary"
+    echo "target: $TARGET_ARG  version: $VERSION_ID"
+    echo
+  } > "$summary"
+
+  echo
+  echo "================ SUMMARY ================"
+  local key
+  for key in "${!ST_STATUS[@]}"; do
+    local st="${ST_STATUS[$key]}" rsn="${ST_REASON[$key]:-}" t="${ST_TIME[$key]:-0}"
+    local rd=""; [[ "${ST_README[$key]:-}" == "1" ]] && rd=" [%README%]"
+    local col="$C_YEL"
+    case "$st" in
+      SUCCESS) col="$C_GRN"; ((succ++)) ;;
+      CACHED)  col="$C_GRN"; ((cached++)) ;;
+      BLOCKED-BY-DEP|UNMET-DEP|ABORTED) col="$C_YEL"; ((blocked++)) ;;
+      *) col="$C_RED"; ((fail++)) ;;
+    esac
+    printf "%s%-30s %-16s%s %s%s (%ss)\n" "$col" "$key" "$st" "$C_RST" "$rsn" "$rd" "$t"
+    printf "%-30s %-16s %s%s (%ss)\n" "$key" "$st" "$rsn" "$rd" "$t" >> "$summary"
+  done
+  echo "----------------------------------------"
+  printf "%s%d succeeded%s, %s%d failed%s, %s%d blocked%s, %s%d cached%s, total %ss\n" \
+    "$C_GRN" "$succ" "$C_RST" "$C_RED" "$fail" "$C_RST" "$C_YEL" "$blocked" "$C_RST" \
+    "$C_GRN" "$cached" "$C_RST" "$total"
+  echo "logs: $RUN_DIR"
+  if [[ $fail -eq 0 && $blocked -eq 0 ]]; then
+    echo "${C_GRN}All green.${C_RST} Safe to build the SBo submission tarball on the host."
+  fi
+  {
+    echo
+    echo "$succ succeeded, $fail failed, $blocked blocked, $cached cached, total ${total}s"
+    echo "logs: $RUN_DIR"
+  } >> "$summary"
+}
+
+
+# Ensure the selected image is available locally. It is built by a separate job
+# (the image-builder) and pushed to the LAN registry; this script only consumes
+# it. If it is not already local, pull it once (ACTIVE_IMAGE is a fully-qualified
+# registry ref). A stale local tag is not refreshed here.
+# ponytail: pull-if-missing only. If the registry's :current is rebuilt, the
+#   local copy goes stale silently. Add a --pull force-flag if that bites.
+require_image() {
+  docker image inspect "$ACTIVE_IMAGE" >/dev/null 2>&1 && return 0
+  echo "Image not present locally, pulling: $ACTIVE_IMAGE" >&2
+  docker pull "$ACTIVE_IMAGE" >&2 && return 0
+  cat >&2 <<EOF
+Image not found and pull failed: $ACTIVE_IMAGE
+It is produced by the image-builder job (full Slackware $VERSION_ID +
+sbo-maintainer-tools + sbopkg) and pushed to the LAN registry. Check the
+registry is reachable and the tag exists, then rerun. This script does not
+build images.
+EOF
+  exit 1
+}
+
+main() {
+  parse_args "$@"
+  init_color
+  require_config
+  SBO_TREE_ROOTS=("$ACTIVE_TREE")
+  load_overrides
+
+  # image + cache namespace (skip the image check on a pure dry-run so the order
+  # can be inspected without the image present).
+  if [[ $DRY_RUN -eq 0 ]]; then
+    command -v docker >/dev/null 2>&1 || { echo "docker not found in PATH." >&2; exit 1; }
+    require_image
+  fi
+  resolve_cache_root
+
+  RUN_DIR="$LOG_ROOT/$(date +%Y-%m-%d_%H-%M-%S)"
+  mkdir -p "$RUN_DIR"
+  : > "$RUN_DIR/build-order.txt"
+
+  # The target is the local SlackBuild under test (CWD or a path); its deps are
+  # resolved from the configured SBo tree during _resolve_visit.
+  local tdir
+  if ! tdir="$(resolve_target_dir "$TARGET_ARG")"; then
+    exit 1
+  fi
+
+  run_target "$tdir"
+  print_summary
+}
+
+main "$@"
diff --git a/test-build-config.example b/test-build-config.example
new file mode 100644
index 0000000..a07b2c1
--- /dev/null
+++ b/test-build-config.example
@@ -0,0 +1,18 @@
+# test-build config. Copy to ~/.config/sbo-testbuild/config and edit.
+# Override the path with the TB_CONFIG environment variable.
+
+# Local SBo trees, one per target Slackware version.
+SBO_TREE_CURRENT="/home/danix/SBo/current"
+SBO_TREE_STABLE="/home/danix/SBo/15.0"
+
+# Ready image tags (built by a separate job, consumed here by tag).
+IMAGE_CURRENT="sbo-testbuild:current"
+IMAGE_STABLE="sbo-testbuild:15.0"
+
+# Where per-run logs land.
+LOG_ROOT="/home/danix/.cache/sbo-test-build"
+
+# Dependency package cache (host dir). Empty disables caching.
+# Namespaced internally by image digest, so it self-invalidates on image update
+# and keeps current vs 15.0 separate.
+PKG_CACHE="/home/danix/.cache/sbo-test-build/pkgcache"
diff --git a/test-logic.sh b/test-logic.sh
new file mode 100644
index 0000000..da50513
--- /dev/null
+++ b/test-logic.sh
@@ -0,0 +1,227 @@
+#!/bin/bash
+#
+# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+#
+# Logic self-check for test-build. Covers the pure, host-side parts:
+# dependency resolution, override application, unknown-dep -> UNMET, cache
+# decisions, and BLOCKED-BY-DEP propagation. No docker.
+#
+# Run: bash test-logic.sh
+#
+set -uo pipefail
+
+SCRIPT="$(dirname "$0")/test-build"
+T=$(mktemp -d)
+BASE_DB=$(mktemp -d); mkdir -p "$BASE_DB"
+
+cleanup() { rm -rf "$T" "$BASE_DB"; }
+trap cleanup EXIT
+
+# Source the script without running main(). Sourcing re-runs the CONFIG block,
+# so set test vars AFTER the source.
+LIB=$(mktemp)
+sed '/^main "\$@"$/d' "$SCRIPT" > "$LIB"
+# shellcheck disable=SC1090
+source "$LIB" 2>/dev/null
+rm -f "$LIB"
+
+pass=0; fail=0
+ok()  { echo "  ok: $1"; ((pass++)); return 0; }
+bad() { echo "  FAIL: $1"; ((fail++)); return 0; }
+
+# Placeholder assertion so this file runs before any logic exists.
+ok "script sources without executing main"
+
+# --- version selection ------------------------------------------------------
+SBO_TREE_CURRENT="/trees/current"
+SBO_TREE_STABLE="/trees/stable"
+IMAGE_CURRENT="sbo-testbuild:current"
+IMAGE_STABLE="sbo-testbuild:15.0"
+
+VERSION_ID="current"; select_version_paths
+[[ "$ACTIVE_TREE" == "/trees/current" ]] && ok "current -> current tree" || bad "current tree wrong: [$ACTIVE_TREE]"
+[[ "$ACTIVE_IMAGE" == "sbo-testbuild:current" ]] && ok "current -> current image" || bad "current image wrong: [$ACTIVE_IMAGE]"
+
+VERSION_ID="15.0"; select_version_paths
+[[ "$ACTIVE_TREE" == "/trees/stable" ]] && ok "15.0 -> stable tree" || bad "stable tree wrong: [$ACTIVE_TREE]"
+[[ "$ACTIVE_IMAGE" == "sbo-testbuild:15.0" ]] && ok "15.0 -> stable image" || bad "stable image wrong: [$ACTIVE_IMAGE]"
+
+# --- resolution -------------------------------------------------------------
+# Fake SBo tree under one category. mk <prog> "<REQUIRES>".
+mk() { mkdir -p "$T/cat/$1"; echo "REQUIRES=\"$2\"" > "$T/cat/$1/$1.info"; }
+mk c ""
+mk b "c"
+mk a "b %README%"
+mk d "nonexistentpkg"
+mk e "f"
+mk f "e"
+mk g "b"
+
+SBO_TREE_ROOTS=("$T")   # resolver reads this global (set by select in real runs)
+
+resolve_target "$T/cat/a"
+order=""; for x in "${RESOLVED_ORDER[@]}"; do order+="$(basename "$x") "; done
+order="${order% }"
+[[ "$order" == "c b a" ]] && ok "topo order c b a" || bad "topo order, got: [$order]"
+[[ "${HAS_README[$T/cat/a]:-}" == "1" ]] && ok "%README% recorded" || bad "%README% not recorded"
+[[ ${#UNMET[@]} -eq 0 ]] && ok "no false unmet" || bad "unexpected unmet"
+
+resolve_target "$T/cat/d"
+[[ ${#UNMET[@]} -eq 1 ]] && ok "unmet-dep caught" || bad "unmet-dep missed"
+
+# --- resolve_target_dir (target from CWD/path, NOT the SBo tree) -------------
+# Local package dir, separate from the fake SBo tree above.
+LOCALREPO=$(mktemp -d); mkdir -p "$LOCALREPO/mypkg"
+echo 'REQUIRES=""' > "$LOCALREPO/mypkg/mypkg.info"
+# 1. absolute path
+got="$(resolve_target_dir "$LOCALREPO/mypkg" 2>/dev/null)"
+[[ "$got" == "$LOCALREPO/mypkg" ]] && ok "target: absolute path" || bad "abs path got [$got]"
+# 2. bare name resolved under CWD (./mypkg/)
+got="$(cd "$LOCALREPO" && resolve_target_dir "mypkg" 2>/dev/null)"
+[[ "$got" == "$LOCALREPO/mypkg" ]] && ok "target: bare name in CWD" || bad "bare-in-cwd got [$got]"
+# 3. CWD itself is the package
+got="$(cd "$LOCALREPO/mypkg" && resolve_target_dir "mypkg" 2>/dev/null)"
+[[ "$got" == "$LOCALREPO/mypkg" ]] && ok "target: CWD is the package" || bad "cwd-is-pkg got [$got]"
+# 4. missing -> failure
+resolve_target_dir "nosuchpkg" >/dev/null 2>&1 && bad "missing target should fail" || ok "target: missing fails"
+rm -rf "$LOCALREPO"
+
+resolve_target "$T/cat/e"
+[[ ${#CYCLES[@]} -ge 1 ]] && ok "cycle caught" || bad "cycle missed"
+
+# --- installed_in_base ------------------------------------------------------
+# Pre-seed the base pkg set (TB_BASE_LOADED=1 bypasses docker). Names are the
+# bare package name; installed_in_base must match a REQUIRES token against it.
+TB_BASE_LOADED=1
+TB_BASE_PKGS=([python3]=1 [libfoo]=1)
+installed_in_base python3 && ok "base pkg matched" || bad "base pkg not matched"
+installed_in_base notthere && bad "absent pkg wrongly matched" || ok "absent pkg not matched"
+
+# a dep present in the base resolves as met, not UNMET
+mk h "python3"
+resolve_target "$T/cat/h"
+[[ ${#UNMET[@]} -eq 0 ]] && ok "base-provided dep not unmet" || bad "base dep flagged unmet"
+TB_BASE_LOADED=0; TB_BASE_PKGS=()
+
+# --- overrides --------------------------------------------------------------
+VERSION_ID="current"   # reset: left at 15.0 by the version-selection checks above
+OV=$(mktemp)
+cat > "$OV" <<'EOF'
+# comment ignored
+drop:   dropme
+rename: oldname -> newname
+fetch:  fetchme
+EOF
+TB_OVERRIDES="$OV"
+load_overrides
+
+[[ "${OV_DROP[dropme]:-}" == "1" ]] && ok "override drop parsed" || bad "drop not parsed"
+[[ "${OV_RENAME[oldname]:-}" == "newname" ]] && ok "override rename parsed" || bad "rename not parsed"
+[[ "${OV_FETCH[fetchme]:-}" == "1" ]] && ok "override fetch parsed" || bad "fetch not parsed"
+
+# rename maps a token
+[[ "$(apply_rename oldname)" == "newname" ]] && ok "apply_rename maps" || bad "apply_rename wrong: [$(apply_rename oldname)]"
+[[ "$(apply_rename untouched)" == "untouched" ]] && ok "apply_rename passthrough" || bad "apply_rename mangled untouched"
+
+# drop satisfies an external (no-dir) dep during resolution: not UNMET, absent
+# from the order. mk k requires a dropme that has no dir in the tree.
+OV_DROP=([extdrop]=1)
+mk k "extdrop"
+resolve_target "$T/cat/k"
+[[ ${#UNMET[@]} -eq 0 ]] && ok "drop satisfies external dep (not unmet)" || bad "dropped external dep still unmet"
+seen=""; for x in "${RESOLVED_ORDER[@]}"; do seen+="$(basename "$x") "; done
+[[ "$seen" != *extdrop* ]] && ok "dropped dep absent from order" || bad "dropped dep in order: [$seen]"
+load_overrides   # restore OV_DROP[dropme] for the order-filter test below
+
+# drop filters the order (build a fake order of dirs; dropme is removed)
+mk dropme ""
+mk keepme ""
+RESOLVED_ORDER=("$T/cat/dropme" "$T/cat/keepme")
+apply_overrides_to_order
+kept=""; for x in "${RESOLVED_ORDER[@]}"; do kept+="$(basename "$x") "; done
+kept="${kept% }"
+[[ "$kept" == "keepme" ]] && ok "drop removes from order" || bad "drop failed, order=[$kept]"
+
+# all entries dropped -> RESOLVED_ORDER must be truly empty (not one "" element)
+OV_DROP=([dropme]=1 [keepme]=1)
+RESOLVED_ORDER=("$T/cat/dropme" "$T/cat/keepme")
+apply_overrides_to_order
+[[ ${#RESOLVED_ORDER[@]} -eq 0 ]] && ok "all-dropped -> empty order" || bad "all-dropped left ${#RESOLVED_ORDER[@]} elem(s): [${RESOLVED_ORDER[*]}]"
+OV_DROP=()
+rm -f "$OV"
+
+# overrides only apply on current; on 15.0 they are a no-op
+VERSION_ID="15.0"
+TB_OVERRIDES="$OV"   # file gone; must not error, must clear maps
+load_overrides
+[[ ${#OV_DROP[@]} -eq 0 ]] && ok "overrides inert on 15.0" || bad "overrides applied on 15.0"
+VERSION_ID="current"
+
+# --- cache ------------------------------------------------------------------
+PKG_CACHE=$(mktemp -d)
+CACHE_ROOT="$PKG_CACHE/sha256-deadbeef"   # simulate a resolved digest namespace
+mkc() { mkdir -p "$CACHE_ROOT/$1/$2"; : > "$CACHE_ROOT/$1/$2/$3"; }
+
+mkc net libfoo "libfoo-1.1-x86_64-1_danix.txz"
+[[ "$(cache_decision net libfoo 1.1)" == "cached" ]] && ok "cache hit on version match" || bad "cache_decision got [$(cache_decision net libfoo 1.1)]"
+[[ "$(cache_decision net libfoo 1.2)" == "bump:1.1:1.2" ]] && ok "cache bump reported" || bad "cache bump got [$(cache_decision net libfoo 1.2)]"
+[[ "$(cache_decision net libbar 1.0)" == "new" ]] && ok "cache new for absent" || bad "cache new got [$(cache_decision net libbar 1.0)]"
+
+hit="$(cache_path net libfoo 1.1)"
+[[ "$hit" == "$CACHE_ROOT/net/libfoo/libfoo-1.1-x86_64-1_danix.txz" ]] && ok "cache_path returns hit" || bad "cache_path got [$hit]"
+[[ -z "$(cache_path net libfoo 9.9)" ]] && ok "cache_path empty on miss" || bad "cache_path not empty on miss"
+
+srctmp=$(mktemp -d); : > "$srctmp/libfoo-1.2-x86_64-1_danix.txz"
+cache_store net libfoo "$srctmp/libfoo-1.2-x86_64-1_danix.txz"
+count=$(find "$CACHE_ROOT/net/libfoo" -name '*.t?z' | wc -l)
+[[ "$count" -eq 1 ]] && ok "cache_store evicts to one file" || bad "cache_store left $count files"
+[[ -e "$CACHE_ROOT/net/libfoo/libfoo-1.2-x86_64-1_danix.txz" ]] && ok "cache_store stored new file" || bad "cache_store did not store"
+rm -rf "$srctmp"
+
+# disabled cache -> new
+CACHE_ROOT_SAVE="$CACHE_ROOT"; USE_CACHE=0
+[[ "$(cache_decision net libfoo 1.2)" == "new" ]] && ok "--no-cache disables (new)" || bad "disabled cache got [$(cache_decision net libfoo 1.2)]"
+USE_CACHE=1; CACHE_ROOT="$CACHE_ROOT_SAVE"
+
+# resolve_cache_root prunes stale digests of the SAME variant, keeps the other.
+# No docker here, so the digest falls back to the tag-derived name; seed sibling
+# dirs and confirm only the active-variant orphan is removed.
+PRUNE_CACHE=$(mktemp -d)
+PKG_CACHE="$PRUNE_CACHE"; ACTIVE_IMAGE="sbo-testbuild:current"; VERSION_ID="current"
+mkdir -p "$PRUNE_CACHE/current-oldstale" "$PRUNE_CACHE/15.0-keepme"
+resolve_cache_root
+[[ -d "$CACHE_ROOT" ]] && ok "cache root created" || bad "cache root missing"
+[[ ! -e "$PRUNE_CACHE/current-oldstale" ]] && ok "prune drops stale same-variant digest" || bad "stale current digest survived"
+[[ -d "$PRUNE_CACHE/15.0-keepme" ]] && ok "prune keeps other-variant cache" || bad "15.0 cache wrongly pruned"
+rm -rf "$PRUNE_CACHE"
+VERSION_ID="current"; CACHE_ROOT="$CACHE_ROOT_SAVE"
+
+# --- BLOCKED-BY-DEP (depends_on_failed) -------------------------------------
+dead=(b)
+if depends_on_failed "$T/cat/g" dead; then ok "g blocked when b dead"; else bad "g should block on b"; fi
+if depends_on_failed "$T/cat/a" dead; then ok "a blocked when b dead (direct)"; else bad "a should block on b"; fi
+
+dead=(c)
+if depends_on_failed "$T/cat/a" dead; then bad "a wrongly blocked on c"; else ok "a not directly blocked by c"; fi
+if depends_on_failed "$T/cat/b" dead; then ok "b blocked when c dead"; else bad "b should block on c"; fi
+
+dead=()
+if depends_on_failed "$T/cat/a" dead; then bad "a blocked with empty dead"; else ok "no block when nothing dead"; fi
+
+dead=("%README%")
+if depends_on_failed "$T/cat/a" dead; then bad "%README% treated as dep"; else ok "%README% not treated as dep"; fi
+
+echo
+echo "$pass passed, $fail failed"
+[[ $fail -eq 0 ]] || exit 1
+echo "ALL LOGIC CHECKS PASS"