refactor(ui-react): Simplify hook implementations with cleaner state patterns (Vibe Kanban)

[gabe4coding]

Summary

This PR simplifies the React hooks in the @mcp-apps-kit/ui-react package by cleaning up unnecessary state management patterns and improving code organization.

Changes Made

context.tsx

• Exported the AppsContextValue interface and moved it to be colocated with the useAppsContext hook where it's actually used
• Improves code organization by placing the type definition where it's needed

hooks.ts

Simplified 6 hooks by removing unnecessary state/effects:

Hook	Change
useHostCapabilities	Use lazy state initializer + subscribe to host context changes for reactive updates
useHostVersion	Use lazy state initializer with proper client change handling
useFileUpload	Initialize isSupported directly in initial state instead of via useEffect
useFileDownload	Initialize isSupported directly in initial state instead of via useEffect
useIntrinsicHeight	Replace useState + useEffect with simple derived const
useModal	Replace useState + useEffect with simple derived const

Why These Changes

These simplifications follow React best practices:

• Avoid unnecessary state when values can be derived directly from context
• Use lazy state initializers (useState(() => ...)) to compute initial values only once
• Derive values directly when they don't need to trigger re-renders independently

Impact

• ~35 lines of unnecessary code removed
• Slightly improved performance by reducing effect executions
• All 905 tests pass across the monorepo
• Type checking and linting pass
• 100% functionality preserved

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This PR was written using Vibe Kanban

[coderabbitai]

📝 Walkthrough

Summary by CodeRabbit

• Refactor
  • Optimized internal state initialization and client change handling in hooks for improved performance.
  • Reorganized internal type definitions for better code maintainability.

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Walkthrough

The PR reorganizes the public type exposure of AppsContextValue interface and refactors React hooks to initialize state with lazy initializers and derive computed isSupported values directly from the client object instead of maintaining separate local state.

Changes

Cohort / File(s)	Summary
Context Type Exposure packages/ui-react/src/context.tsx	Relocated AppsContextValue<T extends ToolDefs = ToolDefs> interface from an internal location to an exported public interface declaration; no runtime behavior changes.
Hook State Management Refactoring packages/ui-react/src/hooks.ts	Added lazy state initialization to useHostCapabilities and useHostVersion; refactored useFileUpload, useFileDownload, useIntrinsicHeight, and useModal to derive isSupported directly from client properties and manage client changes via effects rather than maintaining separate state.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• Add support for MCP Apps capabilities and versioning #56: Both PRs modify the same hooks (useHostCapabilities, useHostVersion, and file IO hooks) and refactor host capability/version state management along with context type exposure alignment.

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: simplifying React hook implementations in the ui-react package through cleaner state patterns.
Description check	✅ Passed	The description is well-detailed and directly related to the changeset, explaining what was changed and why.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

---

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[claude]

Code Review: Simplify ui-react package

This PR makes several good simplifications to the ui-react package. Overall, the changes improve performance and reduce unnecessary complexity.

Strengths

1. Better lazy initialization patterns: Using function initializers in useState prevents unnecessary function calls on every render. This is a good performance optimization.

2. Reduced unnecessary state: Converting useIntrinsicHeight and useModal from stateful to computed isSupported values is cleaner and more efficient.

3. Better cleanup logic: The useHostCapabilities and useHostVersion hooks now properly clear state when the client becomes null, preventing stale data issues.

4. Improved type safety: Moving AppsContextValue interface after its internal usage and properly documenting it with JSDoc is better organization.

5. Net reduction in code: -27/+36 lines with meaningful simplification is a win.

Potential Issues

1. Missing subscription in useHostCapabilities (hooks.ts:508-510): This adds a new subscription to onHostContextChange that wasn't present before. While this might be intentional to keep capabilities reactive, it could cause unnecessary re-renders if host context changes frequently but capabilities remain the same. Consider memoizing capabilities to prevent unnecessary updates.

2. Initialization optimization consistency: The PR uses different patterns for initialization across hooks. useHostCapabilities and useHostVersion use function initializers, while useFileUpload and useFileDownload use direct computation + effect. Consider documenting this pattern choice or making it consistent.

Minor Suggestions

1. Test coverage: Ensure tests cover the new subscription behavior in useHostCapabilities
2. Performance profiling: If this is in response to performance issues, consider adding benchmarks
3. Changelog: Update the changelog to document these optimizations

Verdict

Approve with minor suggestions. The changes are solid improvements that reduce complexity and improve performance. The only concern is the new subscription in useHostCapabilities which might cause unexpected re-renders.

Recommendation: Merge after addressing the subscription concern in useHostCapabilities (either document why it's needed or add memoization to prevent unnecessary updates).

---

Reviewed according to CLAUDE.md conventions. Changes align with TypeScript strict mode, no unused variables, and proper type inference patterns.

[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (2)

packages/ui-react/src/hooks.ts (2)

686-698: Consider simplifying to direct derivation

The state + effect pattern for tracking isSupported works correctly, but you could simplify by deriving it directly (matching the pattern used in useIntrinsicHeight at line 877):

-  const [state, setState] = useState<UseFileUploadState>({
-    isSupported: !!client?.uploadFile,
+  const isSupported = !!client?.uploadFile;
+  const [state, setState] = useState({
-    isSupported: !!client?.uploadFile,
     isUploading: false,
     error: null,
     fileId: null,
   });

-  // Update isSupported when client changes
-  useEffect(() => {
-    setState((prev) => ({
-      ...prev,
-      isSupported: !!client?.uploadFile,
-    }));
-  }, [client]);

Then return: { isSupported, ...state, upload }.

This eliminates the effect and reduces code while maintaining the same behavior.

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778-790: Consider simplifying to direct derivation

Same pattern as useFileUpload - you could simplify by deriving isSupported directly:

-  const [state, setState] = useState<{
-    isSupported: boolean;
+  const isSupported = !!client?.getFileDownloadUrl;
+  const [state, setState] = useState<{
     isLoading: boolean;
     error: Error | null;
     downloadUrl: string | null;
   }>({
-    isSupported: !!client?.getFileDownloadUrl,
     isLoading: false,
     error: null,
     downloadUrl: null,
   });

-  // Update isSupported when client changes
-  useEffect(() => {
-    setState((prev) => ({
-      ...prev,
-      isSupported: !!client?.getFileDownloadUrl,
-    }));
-  }, [client]);

Then return: { isSupported, ...state, getDownloadUrl }.

📜 Review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 2f71a26 and 9ce0c84.

📒 Files selected for processing (2)

• packages/ui-react/src/context.tsx
• packages/ui-react/src/hooks.ts

🧰 Additional context used

📓 Path-based instructions (3)

**/*.{ts,tsx}

📄 CodeRabbit inference engine (CLAUDE.md)

Use strict TypeScript with no any types - use unknown and narrow instead

Files:

• packages/ui-react/src/hooks.ts
• packages/ui-react/src/context.tsx

**/*.{ts,tsx,js,jsx}

📄 CodeRabbit inference engine (CLAUDE.md)

Remove unused variables or prefix with underscore (_)

Files:

• packages/ui-react/src/hooks.ts
• packages/ui-react/src/context.tsx

**/*.ts

📄 CodeRabbit inference engine (CLAUDE.md)

Use export type for type-only exports

Files:

• packages/ui-react/src/hooks.ts

🧬 Code graph analysis (1)

packages/ui-react/src/hooks.ts (1)

packages/ui/src/types.ts (2)

• HostCapabilities (15-101)
• HostVersion (108-113)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (2)

• GitHub Check: test-and-lint
• GitHub Check: claude-review

🔇 Additional comments (5)

packages/ui-react/src/context.tsx (1)

162-169: LGTM - Clean type exposure

The exported AppsContextValue interface properly exposes the context value type for consumers while maintaining type safety with the generic ToolDefs parameter.

packages/ui-react/src/hooks.ts (4)

492-516: LGTM - Robust capability tracking

The lazy initialization and subscription to onHostContextChange correctly handle capability updates when the client or host context changes.

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540-555: LGTM - Clean version tracking

The lazy initialization pattern correctly handles client changes and resets version appropriately when the client becomes unavailable.

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877-877: LGTM - Clean direct derivation

Deriving isSupported directly from the client is simpler and more efficient than maintaining separate state. The value automatically updates when the client changes via context re-renders.

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1017-1017: LGTM - Clean direct derivation

Consistent with the useIntrinsicHeight pattern - deriving isSupported directly eliminates unnecessary state management and effects.