fix(studio): Code Agent stream interruptions when navigating Studio

[htolentino-nvidia]

Summary by CodeRabbit

• Bug Fixes
  • Improved Claude Code chat stability by detecting premature/unexpected stream completion and showing a clearer “connection interrupted” message.
  • Added periodic server SSE keepalives when events are idle to prevent the stream from appearing stalled.
  • Reduced unnecessary rerenders during chat run handling by removing render-time path capture.
• Tests
  • Updated Claude Code chat streaming tests to consistently signal completion with explicit stream-done handling.
• Refactor
  • Simplified a chat runtime message conversion helper while keeping behavior unchanged.

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📥 Commits

Reviewing files that changed from the base of the PR and between 19e4366 and 9ace72f.

📒 Files selected for processing (4)

• services/studio/src/nmp/studio/coding_agents.py
• web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.test.ts
• web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.ts
• web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useCustomAssistantChatRuntime.ts

💤 Files with no reviewable changes (4)

• web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useCustomAssistantChatRuntime.ts
• web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.ts
• services/studio/src/nmp/studio/coding_agents.py
• web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.test.ts

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📝 Walkthrough

Walkthrough

Claude Code streaming now tracks explicit stream completion, the backend emits SSE keepalives on idle queue waits, and the custom assistant runtime reuses a named convertMessage helper. Tests were updated to complete mocked streams with onDone().

Changes

Claude Code streaming onDone handling

Layer / File(s)	Summary
Runtime: studioPathname ref and onDone completion check web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.ts	Adds studioPathnameRef, passes it to streamClaudeCodeMessage, throws an interruption error when onDone was not received, and removes the direct studioPathname dependency from handleRun.
Tests: drive mock streams via handlers.onDone() web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.test.ts	Adds onDone to test handler interfaces and updates permission, input, and AskUserQuestion stream mocks to complete via handlers.onDone().

MCP keepalive emission

Layer / File(s)	Summary
Timed queue wait and keepalive emit services/studio/src/nmp/studio/coding_agents.py	Changes _stream_claude to time out on queue.get() and emit ":\n\n" before continuing.

convertMessage extraction

Layer / File(s)	Summary
Named convertMessage helper web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useCustomAssistantChatRuntime.ts	Extracts the inline converter into a named convertMessage constant and reuses it in the runtime object.

Sequence Diagram(s)

sequenceDiagram
  participant UI
  participant handleRun
  participant streamClaudeCodeMessage

  UI->>handleRun: trigger run
  handleRun->>streamClaudeCodeMessage: stream(studioPathnameRef.current, handlers)
  streamClaudeCodeMessage-->>handleRun: onDone()
  alt onDone missing and not aborted
    handleRun->>UI: throw interruption Error
  end

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Possibly related PRs

• NVIDIA-NeMo/nemo-platform#144: Directly overlaps with the Claude Code runtime’s onDone-based streaming completion flow.
• NVIDIA-NeMo/nemo-platform#459: Modifies the same useClaudeCodeChatRuntime streaming wiring and handleRun flow.
• NVIDIA-NeMo/nemo-platform#551: Touches the same Studio↔Claude Code MCP streaming loop in coding_agents.py.

Suggested reviewers: dmariali

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title matches the main change: fixing Code Agent stream interruptions while navigating Studio.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.

✨ Finishing Touches

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🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch studio-code-agent-fix-disconnections/htolentino

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🧹 Nitpick comments (2)

web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.test.ts (1)

247-251: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Repeated inline handler types instead of shared interfaces.

These tests redefine { onPermissionRequest/onInputRequest; onDone } inline, duplicating the already-defined PermissionRequestTestHandlers/InputRequestTestHandlers interfaces used elsewhere in this file.

Also applies to: 304-308, 417-421, 550-554, 654-658

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In
`@web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.test.ts`
around lines 247 - 251, The test callbacks in useClaudeCodeChatRuntime.test.ts
are repeating inline handler object types instead of reusing the existing shared
interfaces. Update the affected async handler signatures to use the
already-defined PermissionRequestTestHandlers and InputRequestTestHandlers types
(and their shared onDone shape where applicable) so the tests stay consistent
and avoid duplicated type definitions.

web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.ts (1)

393-396: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Ref sync during render — minor nit.

Assigning studioPathnameRef.current in the render body works but technically mutates outside the commit phase. Fine in practice for this "latest ref" pattern; consider moving to a layout effect if strict-mode purity ever becomes a concern.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In
`@web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.ts`
around lines 393 - 396, The latest-value ref sync for studioPathnameRef is being
done during render, which mutates state outside the commit phase. Update
useClaudeCodeChatRuntime to keep the ref in sync inside a layout effect instead
of assigning studioPathnameRef.current directly in the render body, and preserve
the existing onSessionIdChange/studioPathname handling around that ref.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In
`@web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.test.ts`:
- Around line 247-251: The test callbacks in useClaudeCodeChatRuntime.test.ts
are repeating inline handler object types instead of reusing the existing shared
interfaces. Update the affected async handler signatures to use the
already-defined PermissionRequestTestHandlers and InputRequestTestHandlers types
(and their shared onDone shape where applicable) so the tests stay consistent
and avoid duplicated type definitions.

In
`@web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.ts`:
- Around line 393-396: The latest-value ref sync for studioPathnameRef is being
done during render, which mutates state outside the commit phase. Update
useClaudeCodeChatRuntime to keep the ref in sync inside a layout effect instead
of assigning studioPathnameRef.current directly in the render body, and preserve
the existing onSessionIdChange/studioPathname handling around that ref.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: e58ac827-acf1-4946-9afc-bae363cf4208

📥 Commits

Reviewing files that changed from the base of the PR and between bd70579 and 57c3b2f.

📒 Files selected for processing (3)

• web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.test.ts
• web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useClaudeCodeChatRuntime.ts
• web/packages/studio/src/routes/agents/ClaudeCodeChatRoute/useCustomAssistantChatRuntime.ts

[github-actions]

Suite	Lines Covered	Line Rate	Branch Rate
Unit Tests	23089/30221	76.4%	61.3%
Integration Tests	13258/28901	45.9%	19.1%