fix(rivetkit): restore hibernatable sockets and hydrate serverless starts

[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]

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.
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• chore(rivetkit): remove inline tests #4668
• fix(guard): serialize gateway actor keys correctly #4655
• fix(api): subscribe before namespace workflow dispatch #4654
• fix(rivetkit): restore hibernatable sockets and hydrate serverless starts #4658 👈 (View in Graphite)
• fix(rivetkit-native): expose full hibernation metadata to JS #4657
• fix(pegboard): persist and replay hibernating requests #4656
• fix(rivetkit): keep internal error exposure behavior consistent #4661
• test(rivetkit): stabilize actor db driver tests #4664
• fix(test): stabilize lifecycle, sleep, queue, and run edge cases #4660 : 1 other dependent PR (#4665 )
• test(rivetkit): re-enable gateway URL and direct-registry coverage #4659
• fix(rivetkit): add lifecycle error retry and gateway HTTP routing #4666
• chore(engine): publish engine bases in ci #4649 : 2 other dependent PRs (#4650 , #4652 )
• chore: lockfile lefthook #4647
• fix(rivetkit): surface native sqlite kv errors to callers #4645
• fix(rivetkit): prevent sleep races during disconnect and db work #4644
• fix(rivetkit): isolate engine envoys and propagate startup failures #4643
• test(rivetkit): remove wasm sqlite-only fixtures and coverage #4642
• chore(sqlite-vfs): remove wasm sqlite packages and workspace wiring #4641
• chore(rivetkit): remove wasm sqlite runtime #4614
• fix(sqlite-native): restore native startup kv preload #4639
• fix(sqlite-native): delete metadata before chunk range #4638
• fix(sqlite-native): keep truncate cache coherent #4637
• fix(sqlite-vfs): use delete range for truncate cleanup #4636
• fix(sqlite-native): restore kv error hook #4635
• perf(sqlite-native): avoid cloning cached read chunks #4634
• perf(sqlite-native): gate kv operation labels #4633
• perf(sqlite-native): reuse read cache for partial writes #4632
• perf(sqlite-native): remove delete file existence probe #4631
• fix(sqlite-native): gate native read cache behind env var #4630
• fix(pegboard): isolate runner config dc lookup failures #4625 : 1 other dependent PR (#4626 )
• docs(pegboard): note runner config upsert split write risk #4624
• fix(pegboard): unpack global runner config keys correctly #4623
• fix(pegboard-gateway): enforce tunnel message state #4622
• fix(pegboard-runner): clear terminal tunnel routes #4621
• fix(pegboard): skip protocol version keys in runner pool backfill #4620
• fix(pegboard): create missing normal runner configs #4619
• fix(epoxy): reuse cached optimistic value #4618
• main

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[claude]

PR Review: fix(rivetkit): restore hibernatable sockets and hydrate serverless starts

Note: This PR is currently in DRAFT state.

Overview

This PR fixes two related hibernation issues in the engine actor driver:

1. Hibernatable socket restoration - Properly rebinds in-flight WebSocket connections when an actor wakes from hibernation.
2. Serverless start hydration - Hydrates the CommandStartActor payload with persisted hibernating-socket metadata at serverless start time.

It also refactors the test suite to use retry-based polling (readAfterSleepCycle) instead of fixed waitFor delays, and updates gateway routing test paths from /api/hello to /request/api/hello.

---

actor-driver.ts

Good patterns:

• The new disposeDynamicRuntime and disposeAllDynamicRuntimes methods replace a bare .clear() call with proper async dispose() calls.
• Force-stopping remaining actors when ENVOY_STOP_WAIT_MS expires prevents the process from hanging indefinitely.
• The detach pattern on binding objects cleanly decouples listener registration from binding lifetime.

Issues and suggestions:

1. Error path leaves dangling binding in bindHibernatableConnectSocket - If routeWebSocket throws, the binding is stored in hibernatableConnectBindings with no listeners. Consider wrapping in try/catch and calling deleteHibernatableConnectBinding + websocket.close on failure.

2. changed mutation inside Promise.all - Setting changed = true inside async callbacks is safe but non-obvious. Consider deriving it after Promise.all resolves: commands.some((c, i) => c !== decoded.val[i]).

3. O(n) scan in rebind methods - Both rebindHibernatableConnectSockets and rebindDynamicHibernatableRunnerWebSockets filter all bindings for a single actorId. With many actors this is O(n). Consider indexing by actorId.

4. Stale proxyToActorWs between rebinds - When isRestoringHibernatable and event.reason === dynamic.runtime.disposed, onProxyClose returns early. The old proxyToActorWs may remain open between rebinds.

5. Logging inconsistency - One log site uses err: instead of error: (around the dynamic hibernating requests restore block). All other log sites use error:.

---

Test changes (actor-sleep.ts, actor-conn-hibernation.ts)

Good patterns:

• readAfterSleepCycle with bounded retries replaces fragile fixed-wait waitFor calls.
• The invariant startCount === sleepCount + 1 is more correct than the old startCount === 2 && sleepCount === 1.
• Making the hibernation suite .sequential prevents shared-state race conditions.
• Adding a 90-second suite timeout avoids silent hangs.

Minor observations:

1. waitForHibernatableRegistration magic number - The 100ms wait is undocumented. A brief comment explaining what it is waiting for would help future readers.

2. readAfterSleepCycle retries on all errors - The function always retries maxAttempts times regardless of error type. For permanent failures this wastes time.

3. alarms keep actor awake test semantic change - The original asserted exactly sleepCount === 1, verifying that the alarm delayed the first sleep. The new version asserts sleepCount >= 1. Probably fine, but a comment noting this trade-off would be helpful.

---

gateway-routing.ts

All URL changes consistently add a /request/ prefix segment. No issues, but the PR description could note what router change this corresponds to.