codex/docs/config.md

Configuration

For basic configuration instructions, see this documentation.

For advanced configuration instructions, see this documentation.

For a full configuration reference, see this documentation.

Connecting to MCP servers

Codex can connect to MCP servers configured in ~/.codex/config.toml. See the configuration reference for the latest MCP server options:

• https://developers.openai.com/codex/config-reference

MCP tools default to serialized calls. To mark every tool exposed by one server as eligible for parallel tool calls, set supports_parallel_tool_calls on that server:

[mcp_servers.docs]
command = "docs-server"
supports_parallel_tool_calls = true

Only enable parallel calls for MCP servers whose tools are safe to run at the same time. If tools read and write shared state, files, databases, or external resources, review those read/write race conditions before enabling this setting.

MCP tool approvals

Codex stores approval defaults and per-tool overrides for custom MCP servers under mcp_servers in ~/.codex/config.toml. Set default_tools_approval_mode on the server to apply a default to every tool, and use per-tool approval_mode entries for exceptions:

[mcp_servers.docs]
command = "docs-server"
default_tools_approval_mode = "approve"

[mcp_servers.docs.tools.search]
approval_mode = "prompt"

Spawned agent defaults

Use [agents.spawn] to set defaults for newly spawned agents. mcp_servers is an optional allowlist of MCP server names; omit it to inherit all effective MCP servers, or set it to an empty list to disable MCP servers in spawned agents. inject_skills_message controls whether spawned agents receive the skills developer message.

[agents.spawn]
mcp_servers = ["docs"]
inject_skills_message = false

The spawn_agent tool can override either setting per spawned agent. Full history forks inherit the parent session settings and reject these overrides.

Apps (Connectors)

Use $ in the composer to insert a ChatGPT connector; the popover lists accessible apps. The /apps command lists available and installed apps. Connected apps appear first and are labeled as connected; others are marked as can be installed.

Notify

Codex can run a notification hook when the agent finishes a turn. See the configuration reference for the latest notification settings:

• https://developers.openai.com/codex/config-reference

When Codex knows which client started the turn, the legacy notify JSON payload also includes a top-level client field. The TUI reports codex-tui, and the app server reports the clientInfo.name value from initialize.

JSON Schema

The generated JSON Schema for config.toml lives at codex-rs/core/config.schema.json.

SQLite State DB

Codex stores the SQLite-backed state DB under sqlite_home (config key) or the CODEX_SQLITE_HOME environment variable. When unset, WorkspaceWrite sandbox sessions default to a temp directory; other modes default to CODEX_HOME.

Custom CA Certificates

Codex can trust a custom root CA bundle for outbound HTTPS and secure websocket connections when enterprise proxies or gateways intercept TLS. This applies to login flows and to Codex's other external connections, including Codex components that build reqwest clients or secure websocket clients through the shared codex-client CA-loading path and remote MCP connections that use it.

Set CODEX_CA_CERTIFICATE to the path of a PEM file containing one or more certificate blocks to use a Codex-specific CA bundle. If CODEX_CA_CERTIFICATE is unset, Codex falls back to SSL_CERT_FILE. If neither variable is set, Codex uses the system root certificates.

CODEX_CA_CERTIFICATE takes precedence over SSL_CERT_FILE. Empty values are treated as unset.

The PEM file may contain multiple certificates. Codex also tolerates OpenSSL TRUSTED CERTIFICATE labels and ignores well-formed X509 CRL sections in the same bundle. If the file is empty, unreadable, or malformed, the affected Codex HTTP or secure websocket connection reports a user-facing error that points back to these environment variables.

Notices

Codex stores "do not show again" flags for some UI prompts under the [notice] table.

Plan mode defaults

plan_mode_reasoning_effort lets you set a Plan-mode-specific default reasoning effort override. When unset, Plan mode uses the built-in Plan preset default (currently medium). When explicitly set (including none), it overrides the Plan preset. The string value none means "no reasoning" (an explicit Plan override), not "inherit the global default". There is currently no separate config value for "follow the global default in Plan mode".

Realtime start instructions

experimental_realtime_start_instructions lets you replace the built-in developer message Codex inserts when realtime becomes active. It only affects the realtime start message in prompt history and does not change websocket backend prompt settings or the realtime end/inactive message.

Ctrl+C/Ctrl+D quitting uses a ~1 second double-press hint (ctrl + c again to quit).