[yaacovcorcos]

What Changed

• Reconnecting no longer cancels a runtime install. ProviderRuntimeManager.start did all of its startup in the WebSocket request's fiber: planning (which includes a PATH lookup), the plan-revision check, the lifecycle reservation, the first runtime-state read and the "preparing" publication. Only after that did it hand off to a background supervisor. The whole startup now runs in a manager-owned fiber (Effect.forkIn(managerScope)), and the request just joins it. A reload or disconnect only detaches the request; cancel and manager shutdown still end it. This is the same pattern ProviderConnectionManager uses for sign-in since fix(antigravity): reliable Google sign-in on Windows; app-owned sign-in page opening #595. The old body is unchanged, renamed startup.
• A stalled first runtime-state read can't hold the provider busy. Before the operation is published, nothing can cancel it. That read now gives up after two minutes with "Scient could not read the provider runtime state in time. Try again." and releases the reservation.

Why

Seen in the dev app on Windows: installing the Scient Agent runtime from Settings was cancelled. The trace shows server.startProviderRuntime → ProviderRuntimeManager.plan → shell.resolveCommandPath running for 34 s on a heavily loaded machine. The window's connection dropped meanwhile, and when it reconnected at 15:37:37 the request fiber was interrupted, taking the install with it.

Both files are Scient-owned; no upstream-owned code changes.

Documentation Impact

Documentation impact: Updated — docs/internals/provider-lifecycle.md

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

Tests: ProviderRuntimeManager.test.ts 32/32.

• New: the caller disconnects during planning, and the change still runs to succeeded and releases its reservation.
• New: a stalled first runtime-state read releases the reservation after two minutes.
• New: an interrupted initial publication releases its own reservation with the manager still open.
• Three tests that used caller interruption to reach startup cleanup now use manager shutdown, the only thing that can still interrupt a startup.
• Each new test fails with its fix removed.
• ProviderConnectionManager.test.ts 52/52 and ManagedRuntimeSystemSwitch.test.ts 28/28 on the first commit; server typecheck clean.

Review: Codex, two rounds. Round 1 found no problem with the fork/join interruption semantics or the handoff race. It asked for the bounded first read and the isolated publication-cleanup test. Round 2 approved with no findings.

Not verified: a real WebSocket drop during an install in the desktop app; the behaviour is covered at the manager level.

🤖 Generated with Claude Code

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	5.6 KiB	5.6 KiB	0 B (0.0%)	6.8 KiB	✅
Codex	Thread snapshot wire	4.3 KiB	4.3 KiB	0 B (0.0%)	4.9 KiB	✅
Codex	Live turn WebSocket wire	1.3 KiB	1.3 KiB	0 B (0.0%)	2.0 KiB	✅
Codex	Live turn WebSocket decoded	26.2 KiB	26.2 KiB	0 B (0.0%)	29.3 KiB	✅
Codex	Live turn messages	2	2	0 (0.0%)	8	✅
Claude	Total thread wire	5.6 KiB	5.6 KiB	0 B (0.0%)	6.8 KiB	✅
Claude	Thread snapshot wire	4.3 KiB	4.3 KiB	0 B (0.0%)	4.9 KiB	✅
Claude	Live turn WebSocket wire	1.3 KiB	1.3 KiB	0 B (0.0%)	2.0 KiB	✅
Claude	Live turn WebSocket decoded	26.6 KiB	26.6 KiB	0 B (0.0%)	29.3 KiB	✅
Claude	Live turn messages	2	2	0 (0.0%)	8	✅

Baseline: 15893fa · PR result: 46bc6a8 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.
Full compact HTTP snapshot with live cursor.

• Codex decoded thread snapshot: 133.1 KiB
• Claude decoded thread snapshot: 133.4 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.