fix(stagehand): wait for Stagehand to register a page before using it#3865
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Stagehand launches the browser and we attach a second Playwright handle to it over CDP, so pages we create with `context.newPage()` are unknown to Stagehand until it processes its own `Target.attachedToTarget` event. Its AI methods resolve pages by main frame id, so calling `extract()` inside that window fails with 'Failed to resolve V3 Page from Playwright page'. Stagehand's own `newPage()` polls until the target is registered; we bypassed it. The window was normally hidden by navigation happening before the request handler runs, which is why this only surfaced as a flaky e2e test. Wait for the page to be resolvable before handing it out, mirroring what Stagehand does. This also surfaces a clear error when Stagehand skips registration for good (it does that when it cannot install its helper script into the page's CDP session) instead of failing later inside the handler.
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StagehandCrawlerintermittently fails withFailed to resolve V3 Page from Playwright pagewhen a page's AI methods (extract()/act()/observe()) run right after the page is created — most visibly under concurrency, where it looks like a "poisoned" browser instance whose every request keeps failing.Stagehand learns about pages from CDP
Target.attachedToTargetevents on its own connection and maps them by main frame id. Because we create pages through a separateconnectOverCDP()handle,context.newPage()can resolve before Stagehand has processed that event, leaving the page unresolvable for a short window. Stagehand's ownnewPage()polls for exactly this reason.The fix makes
_newPage()wait until Stagehand has registered the page (resolving it by main frame id) before returning it, with a 10s timeout. If registration never happens — e.g. Stagehand couldn't install its helper script into the page's CDP session — the page is closed and an error is thrown rather than handed back in an unusable state.