feat: expose --reconnection-grace-time CLI flag

[tianyicui]

Summary

• Expose VS Code Server's --reconnection-grace-time CLI argument through code-server, allowing users to configure how long the server waits for a disconnected client to reconnect before cleaning up the session
• Add support for $CS_RECONNECTION_GRACE_TIME environment variable and config.yaml setting
• The underlying VS Code Server (1.107+) already implements this flag in serverEnvironmentService.ts; code-server just wasn't passing it through

Motivation

When a client machine sleeps (e.g., overnight), the WebSocket connection drops. VS Code Server's default 3-hour reconnection grace time expires, the server discards the reconnection token, and the user is forced to "Reload Window" on wake. Users who want longer grace periods currently have no way to configure this.

Fixes #7665

Changes

• src/node/cli.ts: Added reconnection-grace-time to UserProvidedCodeArgs interface, options object, and setDefaults() (env var support via $CS_RECONNECTION_GRACE_TIME)
• test/unit/node/cli.test.ts: Added test for the new flag in the "parse all options" test and a dedicated env var test

Usage

# CLI flag (value in seconds, e.g., 30 days)
code-server --reconnection-grace-time 2592000

# Environment variable
CS_RECONNECTION_GRACE_TIME=2592000 code-server

# config.yaml
reconnection-grace-time: 2592000

Test plan

• Existing CLI parser tests pass (68/68)
• New test: --reconnection-grace-time is parsed correctly from CLI
• New test: $CS_RECONNECTION_GRACE_TIME env var is picked up in setDefaults()
• Manual: verify the flag is passed through to VS Code Server and sessions survive long disconnects

🤖 Generated with Claude Code

[code-asher]

Thank you! I wish we had some generic mechanism for passing through any VS Code flag, but for now this seems good to me.

[code-asher]

We want to migrate from CS_ to CODE_SERVER_ so we should update this to CODE_SERVER_RECONNECTION_GRACE_TIME.

[tianyicui]

Fixed. The new env var now uses CODE_SERVER_RECONNECTION_GRACE_TIME, and the parser test covers that name.

[lustsazeus-lab]

Code Review: Expose --reconnection-grace-time CLI Flag

Overall

Well-structured PR that adds a useful feature for users who need longer reconnection grace periods.

Strengths

• Clear motivation and problem statement
• Comprehensive implementation (CLI flag, env var, config.yaml)
• Good test coverage with dedicated tests
• Proper TypeScript types

Suggestions

1. Documentation

• Consider adding to docs/README.md or docs/guide.md explaining the use case
• Default value (3 hours) should be documented

2. Validation

• No validation for negative values or extremely large values
• Consider adding max limit to prevent abuse

3. Error Handling

• What happens if the underlying VS Code Server version doesn't support this flag?
• Consider adding version check

4. Minor: Test Naming

• Test names could be more specific about what's being tested

Conclusion

Solid implementation, ready to merge. The suggestions above are improvements but not blockers.

Recommendation: Approve

---

Reviewed by: lustsazeus-lab

[tianyicui]

Followed up on the review items:

• rebased onto current main
• renamed the new env var to CODE_SERVER_RECONNECTION_GRACE_TIME
• added FAQ docs for the flag, env var, config key, and the 10800-second default
• tightened the env var test name

I did not add local validation or a version gate here. code-server passes this flag through to the bundled VS Code server, and upstream already handles invalid, negative, and oversized --reconnection-grace-time values. There also is not an older external server runtime to guard against in this path.