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Windows browser control fails before initialization: sandbox setup refresh hits sharing violation on node_repl.exe

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
20/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
node.js
Domain
devtools, security

Research direction

The failure sits in the Windows sandbox setup refresh, which runs an ACL update on the cua_node runtime's node_repl.exe under LOCAL_APP_DATA; the log names the 'open ACL target for root-only update' step and the os error 32 sharing violation. Start by locating where the sandbox setup refresh and its root-only ACL update are implemented in the repository, and identify what could hold a lock on that file. Done would mean the refresh completes without errors on a restarted machine, with a test or reproduction showing the sharing violation no longer occurs.

Written by the indexing model from the issue text.

Description

app browser bug sandbox windows-os

Environment

  • Windows desktop, Codex app.
  • Local execution uses workspace-write sandbox and automatic approval review.
  • Browser control tool: cua_repl.
  • Reproduced on 2026-10-09 after a full computer restart.
  • Exact current desktop app version not freshly verified; avoid inferring it from the bundled CLI or package directory.

Steps to reproduce

  1. Open the desktop app after restarting the computer.
  2. Ask the assistant to connect to an existing website tab using the supported browser control tool.
  3. The in-app browser connection fails before returning tool documentation or page state.
  4. Reset the tool session and try the supported Chrome fallback. It fails at the same initialization stage.

Expected result

Browser control initializes and returns a page snapshot, or reports a browser-specific connection problem.

Actual result

Both entry points fail before any page interaction:

node_repl kernel exited unexpectedly
kernel_status: exited(code=1)
kernel_stderr_tail: windows sandbox failed: helper_unknown_error: setup refresh had errors
reason: stdout_eof

Sanitized sandbox log excerpt:

runtime read/execute validation failed:
validate runtime read/execute access on
<LOCAL_APP_DATA>\OpenAI\Codex\runtimes\cua_node\<runtime-id>\bin\node_repl.exe:
open ACL target for root-only update:
another program is using this file; the process cannot access it. (os error 32)
setup refresh completed with errors
setup error: setup refresh had errors

The log excerpt corresponds to local attempts around 09:07–09:08, UTC+08:00 on 2026-10-09.

Impact and attempted recovery

  • Browser automation is unavailable; no generation/form-submission action was performed.
  • Restarting the desktop app previously did not resolve it; a full computer restart also did not resolve the current reproduction.
  • Resetting the browser-control tool and testing the supported Chrome fallback did not resolve it.
  • Standard sandboxed shell initialization also failed with setup-refresh errors, while explicitly approved elevated read-only diagnostics succeeded.
  • This localizes the observed failure to initialization rather than website authentication. The process holding the file and the underlying root cause are not established by this excerpt.
  • No sandbox protections were disabled and no ACL settings were changed.

Privacy

This report excludes customer assets, project details, account credentials, session transcripts, real user paths, and complete raw logs. Sharing the full conversation or raw log is not authorized by this report.

Dominant language
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Avg merge
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Merged PRs (30d)
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