Log the prompt token count of every LLM round

Asks llama-server for usage in the stream, so the log shows how full
the model's context is; history, tool definitions and tool results all
count.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/AGENTS.md b/AGENTS.md
index 395fed6..77313ac 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -393,6 +393,23 @@ phase 2.
 - Whisper wrote "build system" as two words; the model mapped it to the
   VM name `buildsystem` without help.
 
+### Context size (2026-09-26)
+
+Gemma's context is 32768 tokens. Measured against the running model:
+system prompt + question 106 prompt tokens, + the 10 tool definitions
+946, + a full 20-message history of typical exchanges 1576. Worst case
+per question is ~9k (20 long history messages ~3k, up to 3 tool rounds
+of 2000-character results ~4k), so the 20-message window and the
+2000-character tool cap keep it well inside; each extra tool costs ~85.
+
+- The assistant logs `context: N prompt tokens` for every LLM round
+  (`stream_options.include_usage`). Live: a weather question 969, then
+  1115 with the tool result.
+- The server log (`/var/log/llama-server/server.log`) also prints
+  `stop processing: n_tokens = N, truncated = 0` per request, but it is
+  shared with every router client, so it cannot be attributed to the
+  assistant. `truncated = 1` there would mean an overflow.
+
 ### Barge-in (2026-09-26)
 
 A button press cuts the current reply. A global `turn` counter goes up on