fix: add graceful shutdown to UI server

[AmanGIT07]

Summary

The UI server now shuts down gracefully on the process stop signal,
draining in-flight requests within the grace period.

Changes

• ServeUI builds a dedicated http.Server instead of calling the
  package-level http.ListenAndServe, and shuts it down when the
  context is cancelled.
• UI routes register on a local http.ServeMux instead of the global
  DefaultServeMux, so the UI port serves only its own routes.
• Flattened a redundant else block (the branch above it returns).
• Added tests for shutdown on context cancel and the disabled-port case.

Technical Details

ListenAndServe runs in a goroutine reporting into a buffered channel;
the main flow selects between server failure and context cancellation.
On cancellation it calls Shutdown bounded by the existing grace
period, so ServeUI returns only after in-flight requests finish. A
startup failure logs and returns, and the app keeps running since the
UI is optional.

Test Plan

• Added TestServeUIReturnsAfterShutdownOnContextCancel (starts the
  real server, polls /configs, cancels, asserts clean return)
• Added TestServeUIReturnsWhenPortNotConfigured
• go test -race ./pkg/server/... passes
• golangci-lint run pkg/server/ reports 0 issues

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
frontier	Ready	Preview, Comment	Jul 10, 2026 12:18pm

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: c53c92d6-f187-40e7-8e52-9b24fd0e3d0c

📥 Commits

Reviewing files that changed from the base of the PR and between bcfcf0f and 98fa948.

📒 Files selected for processing (1)

• pkg/server/server.go

🚧 Files skipped from review as they are similar to previous changes (1)

• pkg/server/server.go

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Improved UI server shutdown so it exits promptly when its context is canceled.
  • UI startup now returns quickly when no UI port is configured.
  • UI routing is handled by an isolated request handler, with graceful shutdown behavior that won’t affect other HTTP handlers.
• Tests
  • Added tests covering shutdown behavior on context cancel and prompt return when the UI port is not configured.

Walkthrough

Changes

ServeUI lifecycle

Layer / File(s)	Summary
Dedicated server and graceful shutdown pkg/server/server.go	ServeUI uses a dedicated mux and HTTP server, registers UI and proxy routes, runs asynchronously, and performs graceful shutdown on context cancellation.
Lifecycle test coverage pkg/server/serve_ui_test.go	Tests verify the configs endpoint, prompt return after cancellation, and prompt return when no port is configured; UI asset-dependent coverage is skipped when assets are unavailable.

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

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

---

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

pkg/server/server.go (1)

107-110: 🔒 Security & Privacy | 🔵 Trivial | ⚡ Quick win

Add ReadHeaderTimeout to the UI HTTP server.

The newly constructed http.Server has no read, write, or idle timeouts, leaving it vulnerable to Slowloris-style resource exhaustion. Setting at least ReadHeaderTimeout bounds how long the server waits for request headers. Consider adding WriteTimeout and IdleTimeout as well, bearing in mind that overly aggressive write timeouts can interrupt large SPA asset responses.

🛡️ Proposed fix

 	server := &http.Server{
 		Addr:    fmt.Sprintf(":%d", uiConfig.Port),
 		Handler: mux,
+		ReadHeaderTimeout: 10 * time.Second,
 	}

Source: Linters/SAST tools

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 5d952878-b233-4d10-88a7-f499119869dc

📥 Commits

Reviewing files that changed from the base of the PR and between cd6b070 and a5f9b4a.

📒 Files selected for processing (2)

• pkg/server/serve_ui_test.go
• pkg/server/server.go

[coveralls]

Coverage Report for CI Build 29092121671

Coverage decreased (-0.009%) to 44.867%

Details

• Coverage decreased (-0.009%) from the base build.
• Patch coverage: 49 uncovered changes across 1 file (0 of 49 lines covered, 0.0%).
• 5 coverage regressions across 1 file.

Uncovered Changes

File	Changed	Covered	%
pkg/server/server.go	49	0	0.0%

Coverage Regressions

5 previously-covered lines in 1 file lost coverage.

File	Lines Losing Coverage	Coverage
pkg/server/server.go	5	2.91%

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Coverage Stats

Relevant Lines:	37665
Covered Lines:	16899
Line Coverage:	44.87%
Coverage Strength:	12.53 hits per line

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💛 - Coveralls