A 413 is a byte-size error, but the recovery loop scored compression
progress with estimate_messages_tokens_rough, which deliberately prices
every image at a flat per-image token cost (so screenshots don't trigger
premature compaction). When the payload is image-dominated that check can
never pass: in the reporting session two vision_analyze results were
5,627,202 bytes (96.6% of the request body) but ~3K of the ~80K token
estimate, so every attempt reported no_progress, the budget burned, and
the session wedged permanently with 'max compression attempts (3)
reached' at 13% context usage.
Post-#97160, the 413 path already routes into compaction and compaction's
historical-media aging genuinely frees the image bytes — but the
token-scored yardstick could not see the megabytes it freed. Add
serialized_messages_bytes() (exact serialized payload size, measured
identically before and after each pass — a measurement, not an estimate)
and score the 413 progress check with it. Tokens remain for status
display only; the context-overflow branch keeps its token yardstick,
because that error IS a token-budget error.
Images are never evicted from live history outside compaction (cache
invariant); the original strip-from-history mechanism in this PR was
superseded by #97160's compaction-time aging and is dropped in salvage.
Salvaged from #88960. Fixes#47339.
Brian
b855f86bc8