Denying "slash_tmp" breaks Codex

What version of Codex CLI is running?

codex-cli 0.149.0

What subscription do you have?

Business

Which model were you using?

GPT‑5.6

What platform is your computer?

Linux 7.0.0-28-generic x86_64 x86_64

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

kitty 0.32.2

Codex doctor report

~ ❯ codex doctor --json                                                                                                                              16:21:41
{
  "schemaVersion": 1,
  "generatedAt": "1787322162s since unix epoch",
  "overallStatus": "ok",
  "codexVersion": "0.149.0",
  "checks": {
    "app_server.status": {
      "id": "app_server.status",
      "category": "app-server",
      "status": "ok",
      "summary": "background server is not running",
      "details": {
        "control socket": "/home/jja/.codex/app-server-control/app-server-control.sock",
        "daemon state dir": "/home/jja/.codex/app-server-daemon",
        "mode": "ephemeral",
        "pid file": "/home/jja/.codex/app-server-daemon/app-server.pid (missing)",
        "settings": "/home/jja/.codex/app-server-daemon/settings.json (missing)",
        "status": "not running",
        "update-loop pid file": "/home/jja/.codex/app-server-daemon/app-server-updater.pid (missing)"
      },
      "remediation": null,
      "durationMs": 0
    },
    "auth.credentials": {
      "id": "auth.credentials",
      "category": "auth",
      "status": "ok",
      "summary": "auth is configured",
      "details": {
        "auth file": "/home/jja/.codex/auth.json",
        "auth storage mode": "File",
        "stored API key": "false",
        "stored ChatGPT tokens": "true",
        "stored agent identity": "false",
        "stored auth mode": "chatgpt"
      },
      "remediation": null,
      "durationMs": 0
    },
    "config.load": {
      "id": "config.load",
      "category": "config",
      "status": "ok",
      "summary": "config loaded",
      "details": {
        "CODEX_HOME": "/home/jja/.codex",
        "config.toml": "/home/jja/.codex/config.toml",
        "config.toml parse": "ok",
        "cwd": "/home/jja",
        "enabled feature flags": "shell_tool, view_image, unified_exec, shell_snapshot, code_mode_host, terminal_resize_reflow, sqlite, hooks, enable_request_compression, unbounded_connection_retries, multi_agent, apps, tool_search_always_defer_mcp_tools, tool_suggest, plugins, in_app_browser, in_app_chat, in_app_dictation, in_app_updates, browser_use, browser_use_full_cdp_access, browser_use_external, computer_use, remote_plugin, plugin_sharing, image_generation, resize_all_images, item_ids, skill_mcp_dependency_install, skill_search, mentions_v2, steer, guardian_approval, goals, collaboration_modes, tool_call_mcp_elicitation, auth_elicitation, personality, fast_mode, tui_app_server, remote_compaction_v2, workspace_dependencies",
        "feature flag overrides": "none",
        "feature flags enabled": "42",
        "log dir": "/home/jja/.codex/log",
        "mcp servers": "0",
        "model": "<default>",
        "model provider": "openai",
        "sqlite home": "/home/jja/.codex"
      },
      "remediation": null,
      "durationMs": 0
    },
    "git.environment": {
      "id": "git.environment",
      "category": "git",
      "status": "ok",
      "summary": "git version 2.43.0",
      "details": {
        "PATH git #1": "/usr/bin/git",
        "PATH git #2": "/bin/git",
        "PATH git entries": "2",
        "git build options": "git version 2.43.0; cpu: x86_64; no commit associated with this build; sizeof-long: 8; sizeof-size_t: 8; shell-path: /bin/sh",
        "git exec path": "/usr/lib/git-core",
        "git version": "git version 2.43.0",
        "repo detected": "false",
        "selected git": "/usr/bin/git"
      },
      "remediation": null,
      "durationMs": 55
    },
    "installation": {
      "id": "installation",
      "category": "install",
      "status": "ok",
      "summary": "installation looks consistent",
      "details": {
        "PATH codex #1": "/home/jja/.local/bin/codex",
        "PATH codex #2": "/home/jja/.local/bin/codex",
        "PATH codex entries": "2",
        "current executable": "/home/jja/.codex/packages/standalone/releases/0.149.0-x86_64-unknown-linux-musl/bin/codex",
        "install context": "standalone (unix, package /home/jja/.codex/packages/standalone/releases/0.149.0-x86_64-unknown-linux-musl, bin /home/jja/.codex/packages/standalone/releases/0.149.0-x86_64-unknown-linux-musl/bin, resources /home/jja/.codex/packages/standalone/releases/0.149.0-x86_64-unknown-linux-musl/codex-resources, path /home/jja/.codex/packages/standalone/releases/0.149.0-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": 1
    },
    "mcp.config": {
      "id": "mcp.config",
      "category": "mcp",
      "status": "ok",
      "summary": "no MCP servers configured",
      "details": {},
      "remediation": null,
      "durationMs": 0
    },
    "network.env": {
      "id": "network.env",
      "category": "network",
      "status": "ok",
      "summary": "network-related environment looks readable",
      "details": {
        "managed proxy": "not configured",
        "proxy env vars": "none",
        "respect system proxy": "disabled"
      },
      "remediation": null,
      "durationMs": 0
    },
    "network.provider_reachability": {
      "id": "network.provider_reachability",
      "category": "reachability",
      "status": "ok",
      "summary": "active provider endpoints are reachable over HTTP",
      "details": {
        "ChatGPT inference URL": "https://chatgpt.com/backend-api/<redacted> reachable (HTTP 405)",
        "reachability mode": "ChatGPT auth"
      },
      "remediation": null,
      "durationMs": 170
    },
    "network.websocket_reachability": {
      "id": "network.websocket_reachability",
      "category": "websocket",
      "status": "ok",
      "summary": "Responses WebSocket handshake succeeded",
      "details": {
        "DNS": "2 IPv4, 2 IPv6, first IPv4",
        "auth mode": "chatgpt",
        "connect timeout": "15000 ms",
        "endpoint": "wss://chatgpt.com/backend-api/<redacted>",
        "handshake result": "HTTP 101 Switching Protocols",
        "model provider": "openai",
        "provider name": "OpenAI",
        "proxy env vars": "none",
        "reasoning header": "false",
        "server model present": "false",
        "supports websockets": "true",
        "wire API": "responses"
      },
      "remediation": null,
      "durationMs": 707
    },
    "runtime.provenance": {
      "id": "runtime.provenance",
      "category": "runtime",
      "status": "ok",
      "summary": "running standalone on linux-x86_64",
      "details": {
        "commit": "unknown",
        "current executable": "/home/jja/.codex/packages/standalone/releases/0.149.0-x86_64-unknown-linux-musl/bin/codex",
        "install method": "standalone (unix, package /home/jja/.codex/packages/standalone/releases/0.149.0-x86_64-unknown-linux-musl, bin /home/jja/.codex/packages/standalone/releases/0.149.0-x86_64-unknown-linux-musl/bin, resources /home/jja/.codex/packages/standalone/releases/0.149.0-x86_64-unknown-linux-musl/codex-resources, path /home/jja/.codex/packages/standalone/releases/0.149.0-x86_64-unknown-linux-musl/codex-path)",
        "platform": "linux-x86_64",
        "version": "0.149.0"
      },
      "remediation": null,
      "durationMs": 1
    },
    "runtime.search": {
      "id": "runtime.search",
      "category": "search",
      "status": "ok",
      "summary": "search is OK (bundled)",
      "details": {
        "search command": "/home/jja/.codex/packages/standalone/releases/0.149.0-x86_64-unknown-linux-musl/codex-path/rg",
        "search command readiness": "file exists",
        "search provider": "bundled"
      },
      "remediation": null,
      "durationMs": 0
    },
    "sandbox.helpers": {
      "id": "sandbox.helpers",
      "category": "sandbox",
      "status": "ok",
      "summary": "sandbox configuration is readable",
      "details": {
        "approval policy": "OnRequest",
        "codex-linux-sandbox helper": "/home/jja/.codex/tmp/arg0/codex-arg08VmbEq/codex-linux-sandbox",
        "execve wrapper helper": "/home/jja/.codex/tmp/arg0/codex-arg08VmbEq/codex-execve-wrapper",
        "filesystem sandbox": "restricted",
        "network sandbox": "restricted"
      },
      "remediation": null,
      "durationMs": 0
    },
    "security.endpoint": {
      "id": "security.endpoint",
      "category": "security",
      "status": "ok",
      "summary": "endpoint protection is not inspected on this platform",
      "details": {
        "endpoint products": "not inspected on this platform"
      },
      "remediation": null,
      "durationMs": 0
    },
    "state.paths": {
      "id": "state.paths",
      "category": "state",
      "status": "ok",
      "summary": "state paths and databases are inspectable",
      "details": {
        "CODEX_HOME": "/home/jja/.codex (dir)",
        "active rollout files": "262 files, 92828809 total bytes, 354308 average bytes",
        "archived rollout files": "0 files, 0 total bytes, 0 average bytes",
        "goals DB": "/home/jja/.codex/goals_1.sqlite (file)",
        "goals DB integrity": "ok",
        "log DB": "/home/jja/.codex/logs_2.sqlite (file)",
        "log DB integrity": "ok",
        "log dir": "/home/jja/.codex/log (missing)",
        "memories DB": "/home/jja/.codex/memories_1.sqlite (file)",
        "memories DB integrity": "ok",
        "queue DB": "/home/jja/.codex/queue_1.sqlite (file)",
        "queue DB integrity": "ok",
        "sqlite home": "/home/jja/.codex (dir)",
        "standalone release cache": "2 entries in /home/jja/.codex/packages/standalone/releases",
        "state DB": "/home/jja/.codex/state_5.sqlite (file)",
        "state DB integrity": "ok",
        "thread history DB": "/home/jja/.codex/thread_history_1.sqlite (file)",
        "thread history DB integrity": "ok"
      },
      "remediation": null,
      "durationMs": 2114
    },
    "state.rollout_db_parity": {
      "id": "state.rollout_db_parity",
      "category": "threads",
      "status": "ok",
      "summary": "rollout files and state DB thread inventory agree",
      "details": {
        "default model provider": "openai",
        "rollout DB active files": "262",
        "rollout DB active rows": "262",
        "rollout DB archive mismatches": "0",
        "rollout DB archived files": "0",
        "rollout DB archived rows": "0",
        "rollout DB duplicate DB paths": "0",
        "rollout DB duplicate rollout thread ids": "0",
        "rollout DB malformed file names": "0",
        "rollout DB missing active rows": "0",
        "rollout DB missing archived rows": "0",
        "rollout DB model providers": "openai=262",
        "rollout DB rows": "262",
        "rollout DB scan cap reached": "false",
        "rollout DB scan errors": "0",
        "rollout DB sources": "vscode=153, cli=92, subagent:thread_spawn=17",
        "rollout DB stale rows": "0"
      },
      "remediation": null,
      "durationMs": 290
    },
    "system.disk": {
      "id": "system.disk",
      "category": "disk",
      "status": "ok",
      "summary": "sufficient free disk space (270.1 GiB)",
      "details": {
        "CODEX_HOME available": "270.1 GiB",
        "failure threshold": "1.0 GiB",
        "warning threshold": "5.0 GiB",
        "worktree available": "270.1 GiB"
      },
      "remediation": null,
      "durationMs": 0
    },
    "system.environment": {
      "id": "system.environment",
      "category": "system",
      "status": "ok",
      "summary": "OS language en",
      "details": {
        "EDITOR": "set",
        "LANG": "en_US.UTF-8",
        "LC_ALL": "en_US.utf8",
        "LESS": "set",
        "PAGER": "set",
        "VISUAL": "not set",
        "os": "Ubuntu 24.4.0 (noble) [64-bit]",
        "os language": "en",
        "os type": "Ubuntu",
        "os version": "24.4.0"
      },
      "remediation": null,
      "durationMs": 14
    },
    "terminal.env": {
      "id": "terminal.env",
      "category": "terminal",
      "status": "ok",
      "summary": "terminal metadata was detected",
      "details": {
        "COLORTERM": "truecolor",
        "DISPLAY": "present",
        "TERMINFO": "/usr/lib/kitty/terminfo (dir)",
        "color output": "enabled",
        "effective locale": "en_US.utf8",
        "stderr is terminal": "true",
        "stdin is terminal": "true",
        "stdout is terminal": "true",
        "terminal": "kitty",
        "terminal size": "158x49"
      },
      "remediation": null,
      "durationMs": 0
    },
    "terminal.title": {
      "id": "terminal.title",
      "category": "title",
      "status": "ok",
      "summary": "terminal title default",
      "details": {
        "terminal title activity": "true",
        "terminal title items": "activity, project-name",
        "terminal title project source": "cwd",
        "terminal title project value": "jja",
        "terminal title source": "default"
      },
      "remediation": null,
      "durationMs": 0
    },
    "updates.status": {
      "id": "updates.status",
      "category": "updates",
      "status": "ok",
      "summary": "update configuration is locally consistent",
      "details": {
        "cached latest version": "0.149.0",
        "check for update on startup": "true",
        "last checked at": "2026-08-21T10:58:22.748509757Z",
        "latest version": "0.149.0",
        "latest version status": "current version is not older",
        "update action": "standalone installer",
        "version cache": "/home/jja/.codex/version.json"
      },
      "remediation": null,
      "durationMs": 888
    }
  }
}

What issue are you seeing?

When starting codex there is an error:

~ ❯ codex                                                                                                                                            16:24:07
Error: Failed to start a fresh session through the app server: thread/start failed during TUI bootstrap: thread/start failed: error creating thread: Fatal error: Failed to initialize session: failed to load AGENTS.md instructions for environment `local`: fs sandbox helper failed with status exit status: 1: bwrap: Can't mkdir /tmp/codex-bwrap-synthetic-mount-targets-1000: Read-only file system (code -32603)`

What steps can reproduce the bug?

/etc/codex/requirements.toml:

default_permissions = "repro"

[allowed_permission_profiles]
"repro" = true

[permissions.repro]
extends = ":workspace"

[permissions.repro.filesystem]
":minimal" = "read"
":slash_tmp" = "deny"

[permissions.repro.filesystem.":workspace_roots"]
"." = "write"

What is the expected behavior?

Codex CLI starts.

Additional information

Issue was introduced after upgrading to v0.149.0.

Start by reproducing the failure with the reported restricted filesystem sandbox and the codex-linux-sandbox helper shown in the doctor report. Check how denying slash_tmp affects startup or command execution; done means Codex continues working while slash_tmp remains denied. No source file or test is identified in the report, so locating the sandbox implementation and its tests is part of the work.