Widen #90001's compaction-time strip to cover the gaps #89965 identified,
applied at compaction only per the cache ruling (request-time eviction
changes the per-call prefix and breaks prompt caching; compaction is the
one sanctioned cache break):
- Rule 1b: the opening attachment (anchor == 0) ages out once a newer
tool-result image supersedes it. The reported session opened with a
~200KB poster that previously survived every compaction. The row keeps
a non-empty text placeholder, so the zero-user-turn guard (#58753) and
role alternation are untouched.
- Native {_multimodal: True, content: [...]} dict envelopes now both
anchor (newest is kept) and strip (older collapse to their
text_summary via _strip_images_from_tool_msg, which also drops the
stale api_content sidecar per #97125's drop_stale_api_content).
- All three wire shapes (Chat Completions image_url, Responses
input_image, Anthropic-native image) were already matched by
_IMAGE_PART_TYPES; tests now pin each shape explicitly, plus
determinism (double-run is a no-op returning the same object).
Refs #89938, #89965
_strip_historical_media anchors on the newest image-bearing USER message and
returns the list untouched when that anchor is index 0 or does not exist. A
session whose images arrive from tools rather than attachments therefore has
nothing to be "before": twenty vision_analyze results keep multi-MB of base64
in every request body, the provider answers 413, and the 413 handler's
recovery compaction lands right back in this function and frees nothing. The
reporter saw seven compactions in thirteen minutes, all below 200K tokens.
Age tool-result images on their own timeline: keep the newest one, since that
is the image the model is reasoning about, and strip every older one wherever
it sits, including inside the protected tail. The tail exists to preserve
conversational continuity, not to pin bytes the model has already moved past.
User-message images keep today's treatment exactly. The user anchor is
checked first, so a tool result that is the newest of its kind but still sits
before that anchor is stripped as it always has been, and the anchor message
itself is still kept byte-for-byte - test_compressor_zero_user_guard depends
on that.
Refs #89938
After context compression, the protected tail messages retain their
original image parts. When those include multi-MB pasted screenshots,
every subsequent API request re-ships the same base-64 blobs forever —
which can push the request past provider body-size limits and wedge the
session even though compression 'succeeded'.
Add _strip_historical_media() to agent/context_compressor.py. After the
summary is built, find the newest user message that carries an image
part and replace image parts in every earlier message with a short
text placeholder ('[Attached image — stripped after compression]').
The newest image-bearing user turn keeps its media so the model can
still analyse what the user just sent.
Handles all three multimodal shapes:
- OpenAI chat.completions image_url
- OpenAI Responses API input_image
- Anthropic native {type: image, source: ...}
Includes 27 unit tests covering the helpers and the end-to-end
compress() integration, plus a manual E2E check confirming a ~4MB
two-image conversation shrinks to ~2MB after compression.
Teknium