fix(cli): gracefully handle --resume when no sessions exist

[SandyTao520]

Summary

Running gemini -r (or --resume) in a directory with no previous sessions crashes with Error resuming session: No previous sessions found for this project. and exits with a fatal error code. This PR makes it gracefully fall back to starting a fresh session and displays the message as a startup warning in the UI instead.

Details

• SessionSelector.resolveSession() was throwing a generic Error when no sessions existed. Changed it to use the existing SessionError.noSessionsFound() factory, which returns a typed SessionError with code NO_SESSIONS_FOUND.
• In gemini.tsx, the --resume error handler now checks for SessionError with NO_SESSIONS_FOUND specifically: instead of calling process.exit(), it pushes a high-priority startup warning and continues with a fresh session. All other session errors (invalid ID, corrupt session, etc.) still exit as before.

Related Issues

How to Validate

1. Navigate to a directory with no previous Gemini CLI sessions
2. Run gemini -r
3. Before: CLI crashes with an error and exits
4. After: CLI starts a fresh session and shows a warning: "No previous sessions found for this project."

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-cli]

Hi @SandyTao520, 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!

[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 enhances the robustness and user experience of the Gemini CLI by improving how the --resume command operates. Previously, attempting to resume a non-existent session would cause the application to crash. The changes introduce a more graceful fallback mechanism, where the CLI now starts a fresh session and provides a clear warning to the user, ensuring a smoother workflow without abrupt terminations.

Highlights

• Improved --resume command behavior: The gemini --resume command now gracefully handles cases where no previous sessions exist, preventing a crash and instead starting a new session with a warning.
• Standardized session error handling: SessionSelector.resolveSession() now throws a specific SessionError.noSessionsFound() when no sessions are found, allowing for more granular error handling.
• Enhanced error handling in gemini.tsx: The main gemini.tsx file was updated to specifically catch SessionError.noSessionsFound() and display a high-priority startup warning, while other session errors still result in an exit.
• Added new test coverage: New tests were added to ensure the --resume command behaves as expected when no sessions are found, verifying it doesn't crash and emits the correct warning.

Changelog

• packages/cli/src/gemini.test.tsx
  • Added a new test case should start normally with a warning when no sessions found for resume to verify the new behavior.
  • Modified the vi.mock call for sessionUtils.js to use importOriginal for better mocking practices.
• packages/cli/src/gemini.tsx
  • Imported SessionError from sessionUtils.js.
  • Updated the try-catch block for resolveSession to specifically check for SessionError with code NO_SESSIONS_FOUND.
  • If NO_SESSIONS_FOUND error is caught, a high-priority startup warning is pushed, and the application continues.
  • Other SessionError types or generic errors still trigger an application exit.
• packages/cli/src/utils/sessionUtils.test.ts
  • Added a new test case to ensure SessionSelector.resolveSession('latest') throws SessionError with NO_SESSIONS_FOUND when no sessions exist.
• packages/cli/src/utils/sessionUtils.ts
  • Changed the error thrown in resolveSession from a generic Error('No previous sessions found for this project.') to SessionError.noSessionsFound() when sessions.length is zero.

Activity

• No specific activity (comments, reviews, progress updates) has been recorded for this pull request yet.

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[github-actions]

Size Change: -171 B (0%)

Total Size: 26 MB

ℹ️ View Unchanged

Filename	Size	Change
./bundle/gemini.js	25.5 MB	-171 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}

[gemini-code-assist]

Code Review

This pull request gracefully handles the case where --resume is used without any existing sessions, preventing a CLI crash. This is achieved by introducing a typed SessionError and specifically handling the NO_SESSIONS_FOUND case to show a warning and start a fresh session. The changes are well-implemented and include corresponding tests. I've identified a minor redundancy in one of the new tests that could be improved for better maintainability.