ci: add agent session drift check workflow

[adamfweidman]

Summary

Adds a GitHub Actions workflow that posts a non-blocking warning comment on PRs when one file in a known legacy/agent-session pair is modified without its counterpart. Initial scope is nonInteractiveCli.ts ↔ nonInteractiveCliAgentSession.ts; designed to be extended with one-line entries as other pairs (local/remote invocation, etc.) enter the migration.

Details

During the AgentSession migration, legacy implementations run alongside session-based ones behind feature flags. Silent drift between the two creates bugs that only surface when the flag is flipped. This workflow makes drift visible without blocking legitimate one-sided changes (bug fixes, protocol-only features).

Design notes:

• Modular PAIRS array — to cover a new pair, append one object ({legacy, session, label}) and add both paths to the paths: filter. Nothing else changes.
• Warning, not failing check — legitimate one-sided changes exist; a comment is visible but non-blocking.

Conformance with existing workflows (pr-contribution-guidelines-notifier.yml, eval-pr.yml, links.yml, issue-opened-labeler.yml):

• Ratchet-pinned action SHA with # ratchet:actions/github-script@v8 comment (same pin as pr-contribution-guidelines-notifier.yml, issue-opened-labeler.yml)
• Job-level permissions: { contents: read, pull-requests: write }
• concurrency group with cancel-in-progress

Related Issues

Relates to #22700

How to Validate

1. On a test branch off main, modify only packages/cli/src/nonInteractiveCli.ts. Open a PR → expect a warning comment naming the non-interactive pair.
2. Push a follow-up commit that also modifies packages/cli/src/nonInteractiveCliAgentSession.ts → expect the comment to be deleted (drift resolved).
3. Open a PR that touches neither file → the workflow should not run at all (filtered by paths:).
4. Open a PR that touches both files in the pair from the start → no warning comment created.

Pre-Merge Checklist

• Updated relevant documentation and README (if needed) — N/A, workflow-only change
• Added/updated tests (if needed) — N/A, validated manually per "How to Validate"
• Noted breaking changes (if any) — none
• Validated on required platforms/methods — N/A, GitHub Actions workflow (runs on ubuntu-latest)

[gemini-code-assist]

Note

Gemini is unable to generate a summary for this pull request due to the file types involved not being currently supported.

[gemini-cli]

Hi @adamfweidman, thank you so much for your contribution to Gemini CLI! We really appreciate the time and effort you've put into this.

We're making some updates to our contribution process to improve how we track and review changes. Please take a moment to review our recent discussion post: Improving Our Contribution Process & Introducing New Guidelines.

Key Update: Starting January 26, 2026, the Gemini CLI project will require all pull requests to be associated with an existing issue. Any pull requests not linked to an issue by that date will be automatically closed.

Thank you for your understanding and for being a part of our community!

[github-actions]

Size Change: -4 B (0%)

Total Size: 34.1 MB

Filename	Size	Change
./bundle/chunk-33UIFPTA.js	0 B	-3.54 MB (removed)	🏆
./bundle/chunk-6I76Y3RE.js	0 B	-14.9 MB (removed)	🏆
./bundle/chunk-HBMSOQ7Y.js	0 B	-3.8 kB (removed)	🏆
./bundle/core-YAMYRDWY.js	0 B	-46.5 kB (removed)	🏆
./bundle/devtoolsService-3JECW5A3.js	0 B	-28.4 kB (removed)	🏆
./bundle/gemini-ZUI6AOP4.js	0 B	-553 kB (removed)	🏆
./bundle/interactiveCli-A3VCBUJ7.js	0 B	-1.29 MB (removed)	🏆
./bundle/oauth2-provider-OUQQVSXE.js	0 B	-9.16 kB (removed)	🏆
./bundle/chunk-KENNKL2X.js	14.9 MB	+14.9 MB (new file)	🆕
./bundle/chunk-LPYQR3CT.js	3.54 MB	+3.54 MB (new file)	🆕
./bundle/chunk-YHHZMWEC.js	3.8 kB	+3.8 kB (new file)	🆕
./bundle/core-6GVEXJAG.js	46.5 kB	+46.5 kB (new file)	🆕
./bundle/devtoolsService-IPACK63O.js	28.4 kB	+28.4 kB (new file)	🆕
./bundle/gemini-CTLNLO65.js	553 kB	+553 kB (new file)	🆕
./bundle/interactiveCli-B4KDWPLP.js	1.29 MB	+1.29 MB (new file)	🆕
./bundle/oauth2-provider-AAYNVSDE.js	9.16 kB	+9.16 kB (new file)	🆕

ℹ️ View Unchanged

Filename	Size	Change
./bundle/bundled/third_party/index.js	8 MB	0 B
./bundle/chunk-34MYV7JD.js	2.45 kB	0 B
./bundle/chunk-5AUYMPVF.js	858 B	0 B
./bundle/chunk-5PS3AYFU.js	1.18 kB	0 B
./bundle/chunk-664ZODQF.js	124 kB	0 B
./bundle/chunk-DAHVX5MI.js	206 kB	0 B
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./bundle/chunk-QM5IP3NK.js	1.97 MB	0 B
./bundle/chunk-RJTRUG2J.js	39.8 kB	0 B
./bundle/cleanup-E6EPHKUQ.js	0 B	-932 B (removed)	🏆
./bundle/devtools-36NN55EP.js	696 kB	0 B
./bundle/dist-T73EYRDX.js	356 B	0 B
./bundle/events-XB7DADIJ.js	418 B	0 B
./bundle/gemini.js	4.97 kB	0 B
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./bundle/getMachineId-win-6KLLGOI4.js	1.72 kB	0 B
./bundle/memoryDiscovery-MYQ3ZWKM.js	980 B	0 B
./bundle/multipart-parser-KPBZEGQU.js	11.7 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/client/main.js	222 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/_client-assets.js	229 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/index.js	13.4 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
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./bundle/sandbox-macos-strict-proxied.sb	5.02 kB	0 B
./bundle/src-QVCVGIUX.js	47 kB	0 B
./bundle/tree-sitter-7U6MW5PS.js	274 kB	0 B
./bundle/tree-sitter-bash-34ZGLXVX.js	1.84 MB	0 B
./bundle/cleanup-6WSALSXM.js	932 B	+932 B (new file)	🆕

_{compressed-size-action}

[github-actions]

⚠️ Invocation Drift Warning

The following file pairs should generally be kept in sync during the AgentSession migration:

• non-interactive CLI: packages/cli/src/nonInteractiveCliAgentSession.ts was modified but packages/cli/src/nonInteractiveCli.ts was not.

If this is intentional (e.g., a bug fix specific to one implementation), you can ignore this comment.

This check will be removed once the legacy implementations are deleted.