Fix malformed snapshot Unicode

[monadoid]

why

BYOK/direct provider calls reject when page snapshot text we passed in contained malformed UTF-16. I

what changed

Normalize captured accessibility snapshot strings with toWellFormed() at the snapshot boundary and add unit/integration coverage for lone-surrogate page text.

test plan

Red/greened the new unit and local SDK observe regressions, and the focused unicode-well-formed integration test.

---

Summary by cubic

Fixes malformed Unicode in accessibility snapshots by normalizing text with String.prototype.toWellFormed() at capture and during frame merge, so both local SDK and provider prompts always get well-formed UTF-16. Adds tests that confirm lone surrogates are repaired to U+FFFD in prompts.

• Bug Fixes

  • Normalize outline strings during capture and frame merge; per-frame and combined trees are well-formed before prompting.
  • Add integration test asserting U+FFFD appears in the model prompt and a unit test verifying combined tree repair.

• Dependencies

  • Add changeset to publish a patch for @browserbasehq/stagehand.

^{Written for commit 143ac0e. Summary will update on new commits.}

[changeset-bot]

🦋 Changeset detected

Latest commit: 143ac0e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@browserbasehq/stagehand	Patch
@browserbasehq/stagehand-evals	Patch
@browserbasehq/stagehand-server-v3	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[cubic-dev-ai]

Review completed against the latest diff

Confidence score: 5/5

• Safe to merge after the addressed issues were fixed.

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>