The Stagehand block (Run Agent operation) fails immediately when it tries to open a Browserbase browser session. The run errors out after ~1s and no navigation actions are ever recorded — the browser never launches.
Environment
Workspace ID: 87354126-e3c3-4093-a07b-76df681ab4c9
Workflow: vinted-login-test (d6a50651-f4aa-4c61-96a8-65156e71e8c3)
Block: vintedLogin — type stagehand, operation agent, mode hybrid, provider anthropic
Steps to reproduce
- Create a workflow: Start → Stagehand (Run Agent).
- Configure provider anthropic with a valid ANTHROPIC_API_KEY, startUrl=https://www.vinted.cz, a login task, and variables for email/password.
- Run the workflow.
- Block fails after ~1s with Unexpected server response: 101.
Expected
Stagehand opens the Browserbase session and begins navigating.
Actual
WebSocket/CDP upgrade to Browserbase fails with Unexpected server response: 101; browser session never starts. Consistent across retries (not transient).
Ruled out (verified on the workspace side)
ANTHROPIC_API_KEY is valid — starts with sk-ant-, 108 chars, no whitespace; the block accepts it (the earlier Invalid Anthropic API key format error is gone).
VINTED_EMAIL / VINTED_PASSWORD are stored and correctly substituted at runtime.
Workflow lints clean: Start → vintedLogin, no orphans, no unresolved references.
Likely cause
HTTP 101 is actually the successful WebSocket upgrade response. The ws client is rejecting a successful upgrade — a known symptom of a Bun-vs-Node runtime incompatibility (Bun's ws polyfill doesn't handle the upgrade/unexpected-response events), or a reverse proxy not forwarding Upgrade/Connection headers to wss://connect.browserbase.com. Missing/invalid Browserbase credentials would return 401/403, not 101, so this points to server-side runtime/proxy config for the Stagehand↔Browserbase connection rather than user error.
The Stagehand block (Run Agent operation) fails immediately when it tries to open a Browserbase browser session. The run errors out after ~1s and no navigation actions are ever recorded — the browser never launches.
Environment
Workspace ID: 87354126-e3c3-4093-a07b-76df681ab4c9
Workflow: vinted-login-test (d6a50651-f4aa-4c61-96a8-65156e71e8c3)
Block: vintedLogin — type stagehand, operation agent, mode hybrid, provider anthropic
Steps to reproduce
Expected
Stagehand opens the Browserbase session and begins navigating.
Actual
WebSocket/CDP upgrade to Browserbase fails with Unexpected server response: 101; browser session never starts. Consistent across retries (not transient).
Ruled out (verified on the workspace side)
ANTHROPIC_API_KEY is valid — starts with sk-ant-, 108 chars, no whitespace; the block accepts it (the earlier Invalid Anthropic API key format error is gone).
VINTED_EMAIL / VINTED_PASSWORD are stored and correctly substituted at runtime.
Workflow lints clean: Start → vintedLogin, no orphans, no unresolved references.
Likely cause
HTTP 101 is actually the successful WebSocket upgrade response. The ws client is rejecting a successful upgrade — a known symptom of a Bun-vs-Node runtime incompatibility (Bun's ws polyfill doesn't handle the upgrade/unexpected-response events), or a reverse proxy not forwarding Upgrade/Connection headers to wss://connect.browserbase.com. Missing/invalid Browserbase credentials would return 401/403, not 101, so this points to server-side runtime/proxy config for the Stagehand↔Browserbase connection rather than user error.