fix(google): stop leaked Gemini planning from spreading through replayed history

[lidge-jun]

Summary

Gemini models, most visibly Gemini 4 Argon on Antigravity at high effort, sometimes skip the thinking channel on a tool-calling turn and plan in the visible progress text instead. The planning arrives as ordinary text parts with no thought flag, so it reaches every client as answer text. A captured live response looked like this:

앞선 배치에서 잘린 google.ts(580~1700줄) ... 를 마저 읽겠습니다. Let's read google.ts 580-1700 first.

The real problem is that the leak spreads. Once a turn like that goes back to Gemini as history, the model copies the pattern on the turns that follow. In one live Codex session, every turn after the first leak leaked too, across Chat Completions, Messages and Responses clients.

The fix is on the history side only. When messagesToGeminiFormat replays an assistant turn that contains a tool call to a Gemini model, the text before the first call is sent as its lead sentence (src/adapters/google-progress-history.ts). The split uses punctuation only: ASCII terminators followed by whitespace, full-width CJK terminators, or a line break. Closing quotes and Markdown emphasis stay with the sentence, and leading list markers and e.g.-style abbreviations are skipped. It never looks at wording.

The following are replayed unchanged: text after a tool call, turns Codex marks phase: "final_answer", final answers, non-Gemini models such as Claude on Antigravity, and tool calls with their signatures. What clients receive is never rewritten. A leak in the current response is still delivered once; the trim stops it from repeating in later turns. The trade-off is that facts a model states only in pre-call text, beyond its first sentence, are not sent back to it. The call, its result and any final answer still are.

How the cause was found:

• Raw CCA SSE from live Argon sessions, captured through a fetch tee on a local dev proxy, showed that the leaked sentences are unmarked text parts. Turns that leaked had no thoughtsTokenCount, so the model had skipped thinking on those turns. The thought: true classifier is correct; test(google): guard Argon thought separation across client protocols #7188 already covers it, and an extra synthetic check with marked thoughts interleaved after visible text also kept them separate.
• We replayed one recorded 300K-token gemini-4-argon-high request against live CCA with different changes:
  • Unchanged: 10/12 and 5/6 leaked.
  • Stronger system-prompt wording against thinking out loud: 6/9 and 7/9 leaked.
  • Adding an explicit thinkingLevel or thinkingBudget: 3/6 leaked each.
  • Trimming replayed tool-turn text to its lead sentence with this module: 0/12 leaked, at both the first and the review-fixed head, and the model still wrote a progress line each time.
  • Dropping that text entirely also gave 0/9, but the model stopped writing progress lines.
• Other proxies use the same rule for thoughts: CLIProxyAPI, Antigravity-Manager, antigravity-claude-proxy, opencode-antigravity-auth, gemini-cli, LiteLLM, cc-switch and new-api all classify reasoning by the thought flag, and none treats a signature as a visibility marker. gemini-cli's reports of Code Assist history contamination (bug: Code Assist session resume leaks [Thought: true] as literal text in model responses google-gemini/gemini-cli#23046, #23525) match the self-reinforcing pattern seen here.

Verification

• tests/adapters/google/gemini-progress-history.test.ts (new, 5 tests) covers CCA Argon and AI Studio Gemini history trimming, the final_answer and Claude-on-Antigravity exemptions, text after a call, final answers left whole, and the language-neutral split, including short lead sentences, CJK, Markdown emphasis and abbreviations.
• An independent read-only review found three issues: text after a call and final_answer turns were being trimmed, short lead sentences were skipped, and Markdown emphasis hid sentence ends. All three are fixed in the second commit.
• bun run test:changed on Bun 1.4.3 at the final head: 17,195 pass / 0 fail across 711 files. Layout, file-size and structure gates: 87 pass. Focused Google adapter and test(google): guard Argon thought separation across client protocols #7188 boundary tests: 132 pass.
• bun run typecheck, bun run structure:check and bun run privacy:scan all pass.
• Full bun run test on Bun 1.4.3: 48,763 tests across 2,436 files, with 3 failures that are not caused by this change:
  • claude-desktop-remote-hub fails the same way on unmodified dev.
  • optional-desktop-upstream timed out under host load and passes on its own (26/26).
  • bun-runtime refuses to clean up fixtures because this checkout lives under the real Codex home.
• Live check: two high-effort Argon Codex sessions on the patched proxy ran 55 upstream turns, up to a 354K-token prompt, with no leaks. In those runs the model thought on every turn, so they do not show the fix working. The controlled replay above is the evidence for that.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed. (structure/providers/google.md, docs-site providers guide)
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults. No auth or credential paths changed. The live captures used the maintainer's own Antigravity session and stayed in local scratch space; none are committed.

Summary by CodeRabbit

• Improvements
  • Gemini requests now replay only the first sentence of assistant progress text before the first tool call from earlier turns. Text after a tool call and final answers continue to be replayed in full, and client-visible output remains unchanged.
• Documentation
  • Updated the Gemini provider guides with details on how progress text is handled.

[github-actions]

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[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-16T15:31:16.941331Z	15422a8	PR opened

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Reviewing files that changed from the base of the PR and between 68c80ca and 276c67a.

📒 Files selected for processing: 3

• src/adapters/google-progress-history.ts
• structure/providers/google.md
• tests/adapters/google/gemini-progress-history.test.ts

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📝 Walkthrough

For eligible Gemini assistant turns with tool calls, the Google adapter now retains only the lead sentence from the first usable text part before the first tool call. Final answers, text after tool calls, and client-visible output remain unchanged. Tests and provider documentation describe the behavior.

Changes: Gemini progress-history handling

Layer / File(s)	Summary
Lead extraction src/adapters/google-progress-history.ts, tests/adapters/google/gemini-progress-history.test.ts	Adds case-insensitive Gemini model detection and lead extraction. It recognizes punctuation and line-break boundaries, skips boundaries that close a leading list marker or common abbreviation, and returns no lead for blank text or a lead that starts with a code fence. Tests cover sentence extraction.
Adapter integration and validation src/adapters/google.ts, tests/adapters/google/gemini-progress-history.test.ts, structure/providers/google.md, docs-site/src/content/docs/guides/providers.md, scripts/test-layout/layout.json, tests/fixtures/test-layout-expected.json	For eligible Gemini assistant turns with tool calls, the adapter keeps the lead sentence from the first usable pre-call text part and skips later pre-call text parts. Tests cover history replay. Provider documentation and test-layout mappings are updated.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 276c6

The change trims replayed Gemini pre-call progress text to its lead sentence and leaves final answers, post-call text, and other models unchanged. No actionable merge-blocking risk remains.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 3 files. (1 skipped: 1…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: preventing leaked Gemini planning text from spreading through replayed history in the Google adapter.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 3 files. (1 skipped: 1 unsupported.)

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

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[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 15422a8b46

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Actionable comments posted: 1

---

• 🪄 Fix comments: Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @src/adapters/google-progress-history.ts:
- Line 44: Update the lead-boundary detection to allow a short completed
sentence such as “Done.” to end the lead before planning text, while continuing
to skip list markers such as “1.”; add a regression case for a short progress
sentence followed by planning.

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📥 Commits

Reviewing files that changed from the base of the PR and between a02cecd and 15422a8.

📒 Files selected for processing: 7

• docs-site/src/content/docs/guides/providers.md
• scripts/test-layout/layout.json
• src/adapters/google-progress-history.ts
• src/adapters/google.ts
• structure/providers/google.md
• tests/adapters/google/gemini-progress-history.test.ts
• tests/fixtures/test-layout-expected.json

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[lidge-jun]

Maintainer integration into dev under MAINTAINERS.md. Exact head 276c67a: 22 required checks pass, 8 skipped by policy (no macOS/Windows PR jobs). CodeRabbit re-review of this head has no actionable comments. The Codex P2 (other-script sentence terminators) and the CodeRabbit short-sentence finding are fixed in 276c67a and 14adb27. No release or deployment is included.