fix(kitchen-sink): default mock agent to local endpoint

[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

[NathanFlurry]

• fix(pegboard): align drain grace defaults with stop threshold #4958 : 2 dependent PRs (#4960 , #4966 )
• fix(rivetkit): preserve bridge error messages #4959
• fix(rivetkit): fire abort signal on shutdown finalize #4957
• fix(rivetkit): use startup kv preload #4956
• fix(client): flatten skipReadyWait option #4955
• ci(publish): add manual preview publish flow #4954
• fix(depot): add ltx decode diagnostics #4953
• fix(universaldb): preserve plain set values #4952
• fix(universaldb): align versionstamp operand encoding #4951
• fix(rivetkit): export database provider types #4950
• wip: kitchen sink agentic loop finish #4949
• chore(rivetkit): note duplicate admission logic #4948
• test(rivetkit): cover bypass fetch header forwarding #4947
• feat(kitchen-sink): add actor probe controls #4946
• fix(gateway): split actor response wait errors #4945
• fix(guard): handle bypass preflight before query parse #4944
• feat(kitchen-sink): add mock agent event log copy #4943
• fix(kitchen-sink): default mock agent to local endpoint #4942 👈 (View in Graphite)
• test(rivetkit): enable driver lifecycle regressions #4941
• test(rivetkit): verify cached websocket db refs exceed grace #4940
• fix(rivetkit-core): keep sleeping actors reachable during grace #4939
• test(rivetkit): cover async websocket close db access #4938
• fix(rivetkit): keep actors awake until keepAwake work finishes #4937
• fix(rivetkit): persist native onSleep state on errors #4936
• fix(rivetkit-core): allow dispatch during sleep grace #4935
• fix(rivetkit): make duplicate sleep requests idempotent #4934
• main

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[claude]

PR Review: fix(kitchen-sink): default mock agent to local endpoint

Overview

This PR makes two main changes to the kitchen-sink example:

1. Endpoint defaulting: The mock agentic loop panel now defaults to http://127.0.0.1:6420 (a local dev server) instead of rivetEndpoint (the app's RivetKit backend). The VITE_RIVET_ENDPOINT env var is also wired into the mock-agentic-loop.ts script as a fallback.
2. Async handler cleanup: The void (async () => {...})() IIFE pattern in the WebSocket message handler is replaced with a direct async event handler.

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Code Quality

Positive changes:

• The IIFE-to-async-handler refactor in mock-agentic-loop.ts is a clean simplification. Both patterns are functionally equivalent here (the try/catch covers all async operations, so no unhandled rejections), but the new form is easier to read.
• Splitting import.meta.env.VITE_RIVET_ENDPOINT into viteRivetEndpoint avoids repeating the env access and makes the intent clearer.
• The close handler now uses await recordDebugEvent(...) instead of void recordDebugEvent(...), which is more semantically honest.

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Issues and Suggestions

1. Orphaned localStorage entries (minor)

The storage key for the mock agentic loop endpoint now embeds the endpoint value:

const mockAgenticLoopEndpointStorageKey = `kitchen-sink:mock-agentic-loop:endpoint:${mockAgenticLoopEndpoint}`;

When VITE_RIVET_ENDPOINT changes between environments or sessions, the old key is abandoned in localStorage and never cleaned up. Minor leak in a dev tool, but worth noting.

2. DEFAULT_ON_SLEEP_DELAY_MS = 0 in actor source

The actor-side default in src/actors/testing/mock-agentic-loop.ts is changed from 15s to 0ms. This is a production actor file, not just a script default. If ON_SLEEP_DELAY_MS defaults to 0 in deployed environments, actors will immediately proceed on sleep with no delay. Worth confirming this actor is only used in kitchen-sink dev/testing contexts, or that 0ms is safe for the sleep logic.

3. Async close handler

The close handler is now async with await. Since the RivetKit WebSocket API is not a standard EventTarget, it's worth confirming whether the runtime awaits the returned Promise from the close handler. If not, behavior is identical to the prior void pattern (which is fine), but sets a slightly misleading expectation.

---

No Issues Found

• The try/catch in the async message handler covers all branches. No new unhandled-rejection risk.
• The VITE_RIVET_ENDPOINT fallback in scripts/mock-agentic-loop.ts is a sensible DX improvement.
• No CLAUDE.md conventions are violated.

---

Summary

Low-risk, clean PR. The main thing to confirm is whether DEFAULT_ON_SLEEP_DELAY_MS = 0 in the actor source is intentional for all environments, and whether the storage key migration (orphaning old localStorage keys) is acceptable for this dev tool.

[github-actions]

Preview packages published to npm

Install with:

npm install rivetkit@pr-4942

All packages published as 0.0.0-pr.4942.d6aaad8 with tag pr-4942.

Engine binary is shipped via @rivetkit/engine-cli on linux-x64-musl, linux-arm64-musl, darwin-x64, and darwin-arm64. Windows users should use the release installer or set RIVET_ENGINE_BINARY.

Docker images:

docker pull rivetdev/engine:slim-d6aaad8
docker pull rivetdev/engine:full-d6aaad8

Individual packages

npm install rivetkit@pr-4942
npm install @rivetkit/react@pr-4942
npm install @rivetkit/rivetkit-napi@pr-4942
npm install @rivetkit/workflow-engine@pr-4942