Windows sandbox fails parsing deny_read_acl_state.json containing 22 NUL bytes

Unsent support draft: Windows sandbox ACL-state parse failure

Prepared locally; not submitted or uploaded. Paths are sanitized.

The approved Computer Use entry point fails before a screenshot or ordinary input. Sandboxed shell/file helpers also fail. Current log cause:

parse deny-read ACL state .codex.sandbox\deny_read_acl_state.json
expected value at line 1 column 1

Read-only inspection confirms this file is readable, 22 bytes long and contains exactly 22 NUL bytes. SHA-256: 6A4875DDACEAA91FB3369F0F6D962F77442DAF1B1D97733457D12BCABDF79441.
Last write: 2026-09-08 09:45:29.3876012 UTC. Corruption origin is unknown. No ACL access-denied Win32 code appears in this failure chain.

Environment: Codex desktop MSIX 26.901.6511.0, process ChatGPT.exe; actual desktop child codex.exe reports codex-cli 0.153.4, cache 8e5b6932251c2c1c. This version was read from the running host child's executable, not a separate PATH CLI. CUA runtime 0.0.9/20260829001140-68931e022688, cache b474a88d5d105afa, Node 24.19.0, @oai/sky 0.6.26, Computer Use skill 26.901.51231. Windows 10 Pro 22H2 x64, build 19045.6456, native elevated mode configured. Host newly started at 2026-09-09 05:10:27 UTC.

Reproduce in the prescribed node_repl tool:

if (!globalThis.sky) {
const { sky } = await import("@oai/sky");
globalThis.sky = sky;
}

At 05:12:44 UTC this returned node_repl kernel exited unexpectedly, PID 4852, exit 1, stderr: windows sandbox failed: helper_unknown_error: apply deny-read ACLs; reason stdout_eof. One tool invocation triggered two internal setup attempts. No manual reset loop or alternate backend was used. Earlier sessions had the same high-level error; their underlying cause was not inspected here.

sandbox-log-sanitized.txt covers only 05:11:45–05:13:13 UTC; native display timestamps use UTC+05:00. The actual log is sandbox.2026-09-09.log; undated sandbox.log is absent. Approved read-only escalated diagnostics work; default sandbox initialization fails. No approval-review rejection occurred. C:/system/runtime temp had 17,056,231,424 bytes free and project E: 106,504,192; the current setup failure has no disk-full error.

Please provide a supported recovery/host fix that preserves actual deny-read ACL boundaries and safely restores the malformed tracking state. Setup refresh itself fails while parsing this file. We have not edited/deleted the state, changed ACLs/security modes or used another input backend.

Guidance reviewed: Troubleshooting and Windows sandbox. Neither establishes an exact repair for this all-NUL file. Only the compact sanitized diagnostic archive is proposed for sharing; no raw sessions or sandbox secrets are included.

FZ10_RUNTIME_DIAGNOSTICS_FOR_SUPPORT.zip

FZ10_RUNTIME_DIAGNOSTICS_FOR_SUPPORT (1).zip

Start by reviewing the sanitized sandbox log and reproducing the prescribed node_repl failure around parsing .codex.sandbox\deny_read_acl_state.json containing 22 NUL bytes. Trace the Windows sandbox initialization path that reads this state, then verify that recovery preserves deny-read ACL boundaries and safely handles the malformed file without requiring manual deletion or ACL changes.