Windows: browser runtime fails before bootstrap with `failed to write kernel assets` (os error 3)

What version of the Codex App are you using (From “About Codex” dialog)?

OpenAI.Codex 26.820.9563.0

Browser/Chrome-control plugin: 26.820.71523
Runtime manifest: 0.0.9/20260825190732-1bc5ee2d44ce-pr-1350514
Bundled Node: 24.19.0

What subscription do you have?

ChatGPT Pro

What platform is your computer?

Windows 11 Pro 24H2, build 26100.9168, x64

What issue are you seeing?

The governed browser runtime fails before browser binding, troubleshooting documentation, or profile discovery with:

failed to write kernel assets: The system cannot find the path specified. (os error 3)

This is reproducible with the smallest browser-runtime initialization call and occurs before any website navigation or authentication.

The execution tool does not return a stack trace or the calculated kernel-assets destination, so the failing path cannot be identified safely from the installed runtime.

This blocks the documented browser bootstrap/troubleshooting path itself because setupBrowserRuntime() never returns an agent.

Minimal reproduction

const { setupBrowserRuntime } = await import(
  'C:/Users/<user>/.codex/plugins/cache/openai-bundled/chrome/26.820.71523/scripts/browser-client.mjs'
);
const agent = await setupBrowserRuntime();

Expected: browser runtime initializes so documentation and browser discovery APIs can be used.

Actual:

failed to write kernel assets: The system cannot find the path specified. (os error 3)

One fresh reproduction was performed for this report at approximately 2026-08-28T16:13:04Z–16:13:05Z.

Environment / component evidence

Browser client:

C:\Users\<user>\.codex\plugins\cache\openai-bundled\chrome\26.820.71523\scripts\browser-client.mjs
size: 149148 bytes
SHA-256: 2158647076eed887c7591cca0957da78747ab9155819d64409d6b895e84ed99b

Runtime executable:

C:\Users\<user>\AppData\Local\OpenAI\Codex\runtimes\cua_node\57937f104cca4dc5\bin\node_repl.exe
size: 31939248 bytes
SHA-256: 4a81e940919a2b4773ab0b12c2085f261b9ae6449c4bde13f7da7a1d12c8fb70

Runtime manifest:

C:\Users\<user>\AppData\Local\OpenAI\Codex\runtimes\cua_node\57937f104cca4dc5\manifest.json
SHA-256: 8a8f26e805af7b5c668977b43889b68da8a8ab554d967e6999574745ad7d5a09

Selected Codex executable:

C:\Users\<user>\AppData\Local\OpenAI\Codex\bin\d5f4c71927a04589\codex.exe

The runtime manifest explicitly declares:

{
  "node_path": "bin/node.exe",
  "node_modules": "bin/node_modules",
  "node_repl_path": "bin/node_repl.exe",
  "node_archive_path": "v24.19.0/node-v24.19.0-win-x64.zip",
  "runtime_archive_name": "cua-node-0.0.9-20260825190732-1bc5ee2d44ce-pr-1350514-windows-x64.zip"
}

The manifest-referenced installed paths exist:

• bin/node.exe
• bin/node_modules
• bin/node_repl.exe

Relevant shell environment paths also exist (TEMP, TMP, LOCALAPPDATA, APPDATA, USERPROFILE). The failing tool process's inherited environment was not separately exposed, so that remains unknown.

Relevant log context

Earlier application log entry:

[BrowserUseThreadConfig] browser_use_runtime_paths_selected
codexCliPathSource=bundled-or-dev
nodePathSource=bundled-or-dev
nodeReplPathSource=bundled-or-dev
nodeVersionError=undefined
nodeVersionMajor=24
nodeVersionStatus=ok
nodeVersionValue=v24.19.0
platform=win32

No matching failure stack or calculated write path appeared in the inspected logs.

Path evidence

The installed browser-client source does not expose the kernel-assets write destination. The literal error text is embedded in node_repl.exe, but no usable source-level path construction or calculated destination is visible.

TARGET PATH NOT EXPOSED BY INSTALLED RUNTIME

No speculative directory creation, permission changes, runtime reset, profile reset, or reinstall was attempted.

Boundary / impact

• Failure occurs before browser binding.
• bootstrap-troubleshooting cannot be retrieved because runtime initialization itself fails.
• Browser/profile discovery is not reached.
• This is not evidence that Chrome is disconnected or a specific Chrome profile is missing.
• No Microsoft/Azure authentication is involved.
• Governed workflows that require verified browser-profile routing cannot proceed.

What is the expected behavior?

setupBrowserRuntime() should initialize successfully and return an agent so the documented bootstrap/troubleshooting and browser discovery APIs can be called.

If initialization fails, diagnostic output should expose a sanitized calculated kernel-assets destination and failing filesystem operation so the problem can be repaired without guessing paths or modifying unrelated browser/profile state.

Additional information / request

Please identify the missing/incorrect kernel-assets write destination or packaging/path-resolution defect and provide the supported repair/update procedure.

There are older reports containing the same error text, including #29137 and a broader Windows sandbox report #21470, but this report captures the current 26.820.9563.0 / browser plugin 26.820.71523 environment and isolates the failure to pre-bootstrap runtime initialization.

Start with setupBrowserRuntime() in the installed browser-client.mjs and the runtime manifest and node_repl.exe paths described in the report. Reproduce the Windows failure, trace the kernel-assets write destination and filesystem operation, then verify that initialization succeeds or reports a sanitized actionable path.