/fork leaves parent thread with active writer, preventing resume in another terminal

What version of Codex CLI is running?

codex-cli 0.147.0

What subscription do you have?

Pro

Which model were you using?

gpt-5.6-sol

What platform is your computer?

Linux 5.15.167.4-microsoft-standard-WSL2 x86_64 x86_64

What terminal emulator and version are you using (if applicable)?

WSL

Codex doctor report

{
  "schemaVersion": 1,
  "generatedAt": "1786518424s since unix epoch",
  "overallStatus": "warning",
  "codexVersion": "0.147.0",
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      "status": "ok",
      "summary": "background server is not running",
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        "control socket": "/home/[REDACTED_USER]/.codex/app-server-control/app-server-control.sock",
        "daemon state dir": "/home/[REDACTED_USER]/.codex/app-server-daemon",
        "mode": "ephemeral",
        "pid file": "/home/[REDACTED_USER]/.codex/app-server-daemon/app-server.pid (missing)",
        "settings": "/home/[REDACTED_USER]/.codex/app-server-daemon/settings.json (missing)",
        "status": "not running",
        "update-loop pid file": "/home/[REDACTED_USER]/.codex/app-server-daemon/app-server-updater.pid (missing)"
      },
      "remediation": null,
      "durationMs": 0
    },
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      "id": "auth.credentials",
      "category": "auth",
      "status": "ok",
      "summary": "auth is configured",
      "details": {
        "auth env vars present": "OPENAI_API_KEY",
        "auth file": "/home/[REDACTED_USER]/.codex/auth.json",
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        "feature flags enabled": "41",
        "log dir": "/home/[REDACTED_USER]/.codex/log",
        "mcp servers": "[REDACTED: MCP server names]",
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      "summary": "git version 2.43.0",
      "details": {
        ".git entry": "[REDACTED: repository metadata]",
        "PATH git #1": "/usr/bin/git",
        "PATH git #2": "/bin/git",
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        "git branch": "[REDACTED: branch name]",
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        "git exec path": "/usr/lib/git-core",
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    "installation": {
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      "details": {
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        "PATH codex #2": "/home/[REDACTED_USER]/.local/bin/codex",
        "PATH codex #3": "/home/[REDACTED_USER]/.local/bin/codex",
        "PATH codex #4": "/home/[REDACTED_USER]/.local/bin/codex",
        "PATH codex #5": "/home/[REDACTED_USER]/.local/bin/codex",
        "PATH codex #6": "/home/[REDACTED_USER]/.local/bin/codex",
        "PATH codex #7": "/mnt/c/nvm4w/nodejs/codex",
        "PATH codex #8": "/mnt/c/nvm4w/nodejs/codex",
        "PATH codex entries": "8",
        "current executable": "/home/[REDACTED_USER]/.codex/packages/standalone/releases/0.147.0-x86_64-unknown-linux-musl/bin/codex",
        "install context": "standalone (unix, package /home/[REDACTED_USER]/.codex/packages/standalone/releases/0.147.0-x86_64-unknown-linux-musl, bin /home/[REDACTED_USER]/.codex/packages/standalone/releases/0.147.0-x86_64-unknown-linux-musl/bin, resources /home/[REDACTED_USER]/.codex/packages/standalone/releases/0.147.0-x86_64-unknown-linux-musl/codex-resources, path /home/[REDACTED_USER]/.codex/packages/standalone/releases/0.147.0-x86_64-unknown-linux-musl/codex-path)",
        "managed by bun": "false",
        "managed by npm": "false",
        "managed by pnpm": "false",
        "managed package root": "not set"
      },
      "remediation": null,
      "durationMs": 23
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    "mcp.config": {
      "id": "mcp.config",
      "category": "mcp",
      "status": "ok",
      "summary": "MCP configuration is locally consistent",
      "details": {
        "configured servers": "[REDACTED: MCP server names]",
        "disabled servers": "[REDACTED: MCP server names]",
        "stdio servers": "[REDACTED: MCP server names]",
        "streamable_http servers": "[REDACTED: MCP server names]"
      },
      "remediation": null,
      "durationMs": 3481
    },
    "network.env": {
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      "category": "network",
      "status": "ok",
      "summary": "network-related environment looks readable",
      "details": {
        "proxy env vars": "[REDACTED: proxy configuration]"
      },
      "remediation": null,
      "durationMs": 0
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    "network.provider_reachability": {
      "id": "network.provider_reachability",
      "category": "reachability",
      "status": "ok",
      "summary": "active provider endpoints are reachable over HTTP",
      "details": {
        "openai API base URL": "https://api.openai.com/v1 reachable (HTTP 404)",
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      "summary": "Responses WebSocket handshake succeeded",
      "details": {
        "DNS": "[REDACTED: DNS result]",
        "auth mode": "chatgpt",
        "connect timeout": "15000 ms",
        "endpoint": "wss://chatgpt.com/backend-api/<redacted>",
        "handshake result": "HTTP 101 Switching Protocols",
        "model provider": "openai",
        "models etag present": "true",
        "provider name": "OpenAI",
        "proxy env vars": "[REDACTED: proxy configuration]",
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    "runtime.provenance": {
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      "summary": "running standalone on linux-x86_64",
      "details": {
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        "current executable": "/home/[REDACTED_USER]/.codex/packages/standalone/releases/0.147.0-x86_64-unknown-linux-musl/bin/codex",
        "install method": "standalone (unix, package /home/[REDACTED_USER]/.codex/packages/standalone/releases/0.147.0-x86_64-unknown-linux-musl, bin /home/[REDACTED_USER]/.codex/packages/standalone/releases/0.147.0-x86_64-unknown-linux-musl/bin, resources /home/[REDACTED_USER]/.codex/packages/standalone/releases/0.147.0-x86_64-unknown-linux-musl/codex-resources, path /home/[REDACTED_USER]/.codex/packages/standalone/releases/0.147.0-x86_64-unknown-linux-musl/codex-path)",
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          "remedy": null,
          "fields": []
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        "check for update on startup": "true",
        "last checked at": "2026-08-12T06:19:22.738664369Z",
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        "version cache": "/home/[REDACTED_USER]/.codex/version.json"
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    }
  }
}

What issue are you seeing?

/fork leaves the parent session with an active writer, so the parent session cannot be resumed in another terminal.

I am using Codex CLI 0.147.0.

Steps to reproduce:

1. Start working in a Codex CLI session.
2. Run:

/fork

1. Codex switches to a new forked session.
2. Run:

/status

The result confirms that the current TUI is attached to the new forked session:

Session:              019ff4b6-6708-7830-8f43-11ce2495c89f
Forked from:          019ff4a0-1d4d-79a3-a456-ab7187a79d02

After /fork, Codex also prints:

To continue this session, run codex resume 019ff4a0-1d4d-79a3-a456-ab7187a79d02

1. In another terminal, run exactly that command:

codex resume 019ff4a0-1d4d-79a3-a456-ab7187a79d02

Instead of resuming the parent session, Codex fails with:

Error: Failed to resume session from /home/pavel/.codex/sessions/2026/08/12/rollout-2026-08-12T11-19-21-019ff4a0-1d4d-79a3-a456-ab7187a79d02.jsonl: thread/resume failed during TUI bootstrap: thread/resume failed: thread 019ff4a0-1d4d-79a3-a456-ab7187a79d02 already has an active writer (code -32600)

What steps can reproduce the bug?

Uploaded thread: 019ff4b6-6708-7830-8f43-11ce2495c89f

What is the expected behavior?

_No response_

Additional information

_No response_