Make Studio ?video= autostart one-shot under Strict Mode and document YouTube workflow

[Copilot]

Canonical issue

Linked by automation.

Outcome

Studio now treats ?video= handoff as a one-shot trigger even across React Strict Mode remounts, preventing duplicate analysis starts. /docs/api now explicitly describes the Home → Studio → transcript/events → actions/output YouTube workflow.

Scope

• Included:
  • Auto-start dedupe hardening: applyStudioQueryAutoStart now guards on both caller ref state and a module-level video key so the same handoff video cannot double-start during Strict Mode remount behavior.
  • Regression coverage: added a test that simulates remount with a fresh ref object and asserts second invocation is already with a single start call.
  • Docs update: expanded /docs/api “Try it” section with explicit end-to-end workflow steps and one-shot Studio autostart behavior.
  • Snippet (core change):

    if (
      input.startedKey.current === handoff.videoId ||
      strictModeAutoStartedVideoId === handoff.videoId
    ) {
      return 'already';
    }

• Explicitly excluded:
  • No changes to pipeline execution semantics, pack payload shape, or API contracts.
  • No UI flow changes outside /studio handoff/autostart and docs copy.

Risk

• Risk level: low
• Failure mode: over-deduping could suppress a legitimate rerun for the same video within the same module lifecycle.
• Rollback: revert apps/web/src/lib/studio-handoff.ts autostart guard and associated regression test.

Verification

List exact automated and manual checks, tied to the current head SHA.

• Focused tests
• Required CI
• Review threads resolved

Production evidence

Not applicable for this PR: behavior and docs-only validation at app/test level; no production config or infrastructure change.

Agent handoff

• One canonical issue is linked
• No competing PR implements the same issue
• Acceptance criteria are satisfied
• Required checks pass on the current head
• Human decision is requested only for product, security, irreversible infrastructure, or production approval

• Fixes Make Studio ?video= auto-start one-shot and document YouTube workflow #1676

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Project	Deployment	Actions	Updated
v0-uvai	Ready	Preview, v0	Sep 8, 2026 11:14pm UTC

[vercel]

The module-level strictModeAutoStartedVideoId guard is never reset, permanently suppressing auto-start for the last-started video id across remounts within an SPA session.