Opt into the built-in Browserbase extension

[miguelg719]

Summary

• request the image-owned Stagehand extension through browserSettings.extensions
• select resident auto-attach for Browserbase sources
• preserve and deduplicate other requested built-in extensions
• preserve top-level extensionId for customer-uploaded extensions
• remove per-session Stagehand extension upload and deletion
• keep local and custom-CDP extension loading unchanged

Scope

Stack 2/6, based on the init-first protocol PR. This PR changes Browserbase session provisioning and source selection only.

Rollout note

The Browserbase smoke remains opt-in until the corresponding private browser image and Core support are deployed. Unit coverage for exact request construction remains active.

Validation

• complete TypeScript/package/rule suite on this branch
• Browserbase session, browser-source, and client-schema tests
• generated protocol/Python model checks
• pnpm check

---

Summary by cubic

Opt into Browserbase’s built-in Stagehand extension via browserSettings.extensions and auto-attach resident connections for Browserbase sources. Unify Browserbase settings and validation across the protocol, TS, and Python SDKs.

• New Features

  • Add extensions to Browserbase browser settings (protocol JSON/TS types and Python/TS SDKs) with BrowserbaseExtension enum: onepassword, browser-events, stagehand.
  • Always append stagehand, dedupe, and preserve order.
  • Auto-attach resident connections in the Browserbase browser source.

• Refactors

  • Remove per-session Stagehand upload/cleanup; drop helper and tests using @browserbasehq/sdk. Remove the packaged extension archive and build copy; update package contract to not assert the zip.
  • Keep top-level extensionId for uploaded customer extensions; reject nested browserSettings.extensionId.
  • Make Browserbase browser settings strict (no extra properties) across protocol, TS, and Python; validate built-in names.
  • Switch smoke opt-in flag to BROWSERBASE_RESIDENT_SMOKE until image/Core rollout.

^{Written for commit 0c2fb5f. Summary will update on new commits.}

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Latest commit: 0c2fb5f

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