fix(native-compaction): retain image-only user content

[andrexibiza]

Problem

#91477 repaired native-compaction summary provenance, but pre-checkpoint pruning still dropped an image-only user message. The normalized Responses item has a valid input_image part and no measurable text, so the text-only extraction path returned None and pruning discarded the message before retention accounting.

Repair

• Keep _extract_item_text() text-only.
• Grant retention authority only to the adapter-owned normalized input_image shape with a non-empty string image_url.
• Retain the original user-message object verbatim at one-token cost and preserve the explicit retention budget.
• Reject empty, malformed, and unknown multipart placeholders instead of treating any non-empty list as durable history.
• Do not claim file-only support: the current chat-to-Responses adapter does not emit input_file.

Proof

The regression suite proves text extraction remains text-only, valid image-only user content survives a replayed compaction checkpoint verbatim, zero budget still drops it, malformed or unknown multipart content is not promoted, and the production _chat_messages_to_responses_input() path carries the image-only message across the checkpoint.

Exact green object

The branch contains one commit only. Superseded red objects are no longer part of the PR history.

• Head: 039e26994fa5b7f37a387721055519b531c32f5b
• Tested base: 2584b7c4eca82ada05f16eba08936d157b483329
• GitHub merge candidate: 24c2bc4e5cd456799729b51b20a1c4b2295ad764
• CI 32508623713 — success
• Docker 32508622727 — success
• Nix 32508622749 — success
• Topology — one commit, two intended files, open, non-draft, mergeable

The final object republishes the identical source tree after an unrelated focus-redraw timing failure on the superseded object; there is no source delta between the two objects.

Interlocks

#90976 → merged #91477 → #91557. This is a distinct post-merge regression repair, not a reopening or repeat review of #90975.

[andrexibiza]

Exact-head review complete at fca470be7cf50d3ff4f6f0dc9a873f5f6b8e4609: no remaining blocker.

This head closes the residual post-#91477 non-text loss without broadening arbitrary multipart content into durable history:

• _extract_item_text() remains text-only;
• only the adapter-owned normalized input_image shape with a non-empty image_url receives attachment retention authority;
• the original user message is retained verbatim and still consumes the explicit retention budget;
• empty, malformed, and unknown multipart placeholders remain non-retainable;
• the production _chat_messages_to_responses_input() conversion path is exercised across an actual compaction checkpoint, rather than fabricating only a pruner-local shape.

The earlier unsupported file-only claim is correctly removed because the current adapter does not emit input_file.

Fresh exact-head hosted evidence is green: CI 32499632201, Docker 32499631402, and Nix 32499631392. The PR is open, non-draft, and mergeable against current main. No source, review, exact-head CI, or mergeability blocker remains.

[andrexibiza]

Final status

This is the authoritative current-state receipt after the branch cleanup.

• Head: 039e26994fa5b7f37a387721055519b531c32f5b
• Tested base: 2584b7c4eca82ada05f16eba08936d157b483329
• GitHub merge candidate: 24c2bc4e5cd456799729b51b20a1c4b2295ad764
• Topology: one commit, two intended files, open, non-draft, mergeable

Exact-object verification

• CI 32508623713 — success
• Docker 32508622727 — success
• Nix 32508622749 — success

The repair is deliberately narrow: valid normalized input_image user content survives native-compaction checkpoint pruning verbatim; text extraction remains text-only; malformed or unknown multipart placeholders are not promoted; zero retention budget still drops the item; and no unsupported input_file claim is made.

The final object republishes the identical source tree after an unrelated timing failure on the superseded object. No source delta was introduced during the history cleanup. No source, exact-head CI, base-alignment, or mergeability blocker remains. The remaining repository transition is upstream acceptance and merge.

Interlock: #90976 → merged #91477 → #91557.

[Enough1122]

AI code review — automated review for reference, author can ignore or act on any point.

Good catch on what looks like a comment-vs-code regression: the old inline comment promised "Image-only user messages … Don't skip them just because text is falsy", but the guard above it (if text is None: continue) ran first — an image-only message has no text parts, _extract_item_text returns None, and the item was dropped before the sympathetic branch could ever fire. This restores the documented contract, and doing it via a positive has_retainable_image signal instead of loosening the None-check is the right structure: junk stays dropped by default and images earn retention explicitly.

Points:

1. The strict predicate matches reality — pin that coupling. I checked agent/codex_responses_adapter.py: every image emit site produces exactly {"type": "input_image", "image_url": <str>} (no file_id variants), so _has_retainable_image_content's narrow shape test covers all producible inputs today, and its fail-closed stance against malformed/empty parts is correct — "non-empty list" was far too weak to justify durable history. Since correctness depends on the adapter never growing a new image shape without updating this predicate, consider a one-line comment on _has_retainable_image_content pointing at the adapter's emit sites (or vice versa) so the two evolve together.

2. Test suite is exemplary — verbatim retention asserted with identity (pruned[1] is image_only, not just equality), budget obedience at zero (so images can't smuggle past a tight budget), the malformed-matrix ({}, empty URL, unknown type), and an end-to-end conversion test proving the chat-completions image_url → Responses input_image handoff survives across a checkpoint. All behavior contracts, nothing snapshot-shaped.

3. Two scope notes worth a docstring line each: (a) retention is user-only (is_user and …) — assistant/tool items carrying images are still pruned; presumably intentional (matches main's accounting) but stating it prevents "why not symmetric?" follow-ups. (b) A mixed [input_text(""), input_image] message falls through with text="" rather than the image path — fine either way, just confirming it's considered.

4. Nit: the new if text is None: text = "" coercion reads slightly odd directly under a continue that already excluded None-without-image; folding it into the first condition (if text is None and not has_retainable_image: continue / text = text or "") would be marginally tighter — purely stylistic.