#119 fix(browser): auto-connect provisioned sessions

Summary

• auto-connect a disconnected process-scoped Session before browser_execute runs a snippet when BU_CDP_WS or BU_CDP_URL is configured
• deduplicate concurrent first calls with one per-Session in-flight connection promise
• preserve explicit-connect behavior when neither provisioned endpoint variable is present
• propagate the original connection failure instead of wrapping it as a snippet exception

Why

V4 provisions the browser and sets BU_CDP_WS, but a fresh worker still begins with a disconnected in-process Session. In a recent ordered production cohort, all 28 exact Not connected. Call session.connect(...) first. snippets reached CDP before executing a connection; 26/28 later recovered with successful browser calls. Initialization should be deterministic instead of model-dependent.

Semantics and tradeoffs

• auto-connect runs only at the tool-call boundary; a snippet that closes its socket mid-execution still controls and must perform any same-snippet reconnect itself
• an already-connected explicit replacement endpoint is left untouched
• after an explicit close, a later tool call reconnects the fixed provisioned endpoint unless the snippet explicitly reconnects first within the same call
• an expired or rejected provisioned endpoint is not retried or replaced here; its real WebSocket/endpoint error is returned
• without BU_CDP_WS/BU_CDP_URL, local BrowserCode behavior is unchanged

Tests

• first raw CDP snippet auto-connects and subsequent snippets reuse one socket
• both BU_CDP_WS and BU_CDP_URL trigger the behavior
• parallel first calls share one connection attempt
• explicit close plus explicit reconnect remains under snippet control
• non-cloud sessions still fail raw CDP until explicitly connected
• failed auto-connect surfaces the original connection error and never runs the snippet

Validation:

• cd packages/bcode-browser && bun typecheck
• cd packages/bcode-browser && bun test — 23 passed, 8 live/smoke tests skipped, 0 failed
• root filtered bun run typecheck — 16 packages passed
• targeted oxlint — 0 errors; 5 pre-existing warnings in browser-execute.ts

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Summary by cubic

Auto-connects provisioned cloud sessions in browser_execute when BU_CDP_WS or BU_CDP_URL is set, eliminating "Not connected" errors. Deduplicates concurrent first connections, keeps local sessions explicit-connect, and returns the original connect error on failure.

• Bug Fixes
  • Connect the process-scoped Session before a snippet runs when a provisioned endpoint is present; reuse one socket across calls.
  • Share one in-flight connect per Session to avoid race conditions.
  • Leave already-connected or local sessions unchanged; do not retry or mask endpoint errors.