fix(rivetkit): move ActorInspector init to constructor body

[NathanFlurry]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[railway-app]

🚅 Deployed to the rivet-pr-4124 environment in rivet-frontend

Service	Status	Web	Updated (UTC)
website	❌ Build Failed (View Logs)	Web	Feb 5, 2026 at 8:37 am
frontend-cloud	❌ Build Failed (View Logs)	Web	Feb 5, 2026 at 8:36 am
frontend-inspector	❌ Build Failed (View Logs)	Web	Feb 5, 2026 at 8:36 am
mcp-hub	✅ Success (View Logs)	Web	Feb 5, 2026 at 8:36 am

[NathanFlurry]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• fix(rivetkit): move ActorInspector init to constructor body #4124 👈 (View in Graphite)
• feat: use cases #4100 : 1 other dependent PR (#3666 )
• refactor(rivetkit): migrate granularly to zod v4 #4121 : 1 other dependent PR (#4119 )
• fix(rivekit): stub traces in browser #4120
• main

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[claude]

Code Review

Summary

This PR moves the ActorInspector initialization from a class field initializer to the constructor body in ActorInstance. This is a small but important fix that addresses a potential initialization order issue.

Analysis

What Changed:

• Before: #inspector = new ActorInspector(this) (field initializer)
• After: #inspector!: ActorInspector (field declaration) + initialization in constructor body

Why This Matters:

1. Initialization Order: In TypeScript/JavaScript, class field initializers run before the constructor body executes. When ActorInspector is initialized as a field, it receives this before the constructor has finished setting up the instance.

2. Incomplete State: The ActorInspector constructor accesses actor.config.run and actor.queueManager. If these properties are not fully initialized when the field initializer runs, it could lead to undefined behavior.

3. Proper Fix: Moving initialization to the constructor body (after this.#config = config) ensures that all dependencies are properly set up before ActorInspector is created.

Code Quality: ✅ Good

• Correct pattern: Uses the definite assignment assertion (!) appropriately
• Follows conventions: Matches the pattern used for other fields like #schedule, #traces
• Minimal change: Touches only what is necessary

Potential Issues: ✅ None Found

• No bugs identified
• No race conditions or timing issues
• The inspector getter will work correctly since it is only called after construction

Performance: ✅ Neutral

• No performance impact - just reordering initialization

Security: ✅ No Concerns

Test Coverage: ⚠️ Consider Adding

Recommendation: Consider adding a test that verifies the inspector is properly initialized with the correct config and queue state. This would prevent regression if someone moves the initialization back to a field initializer.

Verdict: ✅ LGTM

This is a solid bug fix that prevents potential initialization order issues. The change is minimal, correct, and follows existing patterns in the codebase.

Minor Suggestion: Consider adding a comment explaining why this initialization happens in the constructor rather than as a field initializer to help prevent future refactoring from reintroducing the issue.

[pkg-pr-new]

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commit: 6d0f317