fix(plan): keep approved plan during chat compression

[ruomengz]

Summary

This PR ensures that approved implementation plans are preserved during chat history compression. When the conversation history grows too large and needs to be distilled into a <state_snapshot>, the model is now explicitly instructed to keep the plan's file path, step completion status, and any relevant user feedback.

Details

• Updated PromptProvider to retrieve and pass the approved plan path (if any) to the history compression prompt.
• Modified both modern (snippets.ts) and legacy (snippets.legacy.ts) compression prompts to include a new ### APPROVED PLAN PRESERVATION section when a plan is active.
• This prevents the agent from "forgetting" its current progress on a plan after a compression event, which previously led to redundant work or lost context on the overall goal.

Related Issues

Fixes #17796

How to Validate

1. Start a session that generates an approved plan.
2. Force or wait for history compression (simulated via tests).
3. Verify that the compression prompt now includes the ### APPROVED PLAN PRESERVATION section.
4. Run the new tests: npm test -w @google/gemini-cli-core -- src/prompts/promptProvider.test.ts

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical issue where the system would lose context of an approved implementation plan during chat history compression. By explicitly instructing the model to preserve plan details like file path, step completion, and user feedback, the agent can maintain its progress and avoid redoing work, significantly improving the continuity and efficiency of long-running tasks.

Highlights

• Approved Plan Preservation: Ensured that approved implementation plans are explicitly preserved during chat history compression, preventing loss of context and redundant work.
• PromptProvider Update: Modified the PromptProvider to retrieve and pass the approved plan's file path to the history compression prompt.
• Compression Prompt Modification: Updated both modern and legacy compression prompts to include a dedicated '### APPROVED PLAN PRESERVATION' section when an active plan is present, instructing the model to retain critical plan details.
• New Test Coverage: Added new unit tests to verify that plan preservation instructions are correctly included or excluded in the compression prompt based on the presence of an approved plan path, covering both modern and legacy model scenarios.

Changelog

• packages/core/src/prompts/promptProvider.test.ts
  • Added new test suite for getCompressionPrompt to validate plan preservation logic.
  • Included tests to confirm plan preservation instructions are present when an approved plan path is provided.
  • Added tests to confirm plan preservation instructions are absent when no approved plan path is provided.
  • Verified correct behavior for legacy models regarding plan preservation in compression prompts.
• packages/core/src/prompts/promptProvider.ts
  • Updated getCompressionPrompt to pass the result of config.getApprovedPlanPath() to the active snippets' getCompressionPrompt method.
• packages/core/src/prompts/snippets.legacy.ts
  • Modified getCompressionPrompt to accept an optional approvedPlanPath parameter.
  • Implemented conditional logic to append an '### APPROVED PLAN PRESERVATION' section to the prompt if approvedPlanPath is provided, detailing what plan information to preserve.
• packages/core/src/prompts/snippets.ts
  • Modified getCompressionPrompt to accept an optional approvedPlanPath parameter.
  • Implemented conditional logic to append an '### APPROVED PLAN PRESERVATION' section to the prompt if approvedPlanPath is provided, detailing what plan information to preserve.

Activity

• Related issue Handle plan awareness during chat compression #17796 has been fixed.
• New tests have been added and updated to cover the changes.
• The changes have been validated on MacOS.

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[gemini-code-assist]

Code Review

This pull request implements a mechanism to preserve the state of an approved plan during chat history compression by modifying the prompt provider to pass the plan path and updating prompt snippets. However, a prompt injection vulnerability was identified in getCompressionPrompt in both snippets.ts and snippets.legacy.ts. The approvedPlanPath is directly interpolated into the prompt string without sanitization, which could allow manipulation of the LLM's behavior if a malicious path is provided. It is recommended to properly escape or quote the path, or use returnDisplay if the path is for display purposes, to prevent such injections.

[github-actions]

Size Change: +474 B (0%)

Total Size: 26 MB

ℹ️ View Unchanged

Filename	Size	Change
./bundle/gemini.js	25.5 MB	+474 B (0%)
./bundle/node_modules/@google/gemini-cli-devtools/dist/client/main.js	221 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/_client-assets.js	227 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/index.js	11.5 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/types.js	132 B	0 B
./bundle/sandbox-macos-permissive-open.sb	890 B	0 B
./bundle/sandbox-macos-permissive-proxied.sb	1.31 kB	0 B
./bundle/sandbox-macos-restrictive-open.sb	3.36 kB	0 B
./bundle/sandbox-macos-restrictive-proxied.sb	3.56 kB	0 B
./bundle/sandbox-macos-strict-open.sb	4.82 kB	0 B
./bundle/sandbox-macos-strict-proxied.sb	5.02 kB	0 B

_{compressed-size-action}

[jerop]

lgtm to me, looping in IQ workstream

[abhipatel12]

LGTM, thanks for adding!