Add a separate exec doc

README.md

@@ -83,6 +83,7 @@ Codex CLI supports a rich set of configuration options, with preferences stored
 - [**Authentication**](./docs/authentication.md)
   - [Auth methods](./docs/authentication.md#forcing-a-specific-auth-method-advanced)
   - [Login on a "Headless" machine](./docs/authentication.md#connecting-on-a-headless-machine)
+- [**Non-interactive mode**](./docs/exec.md)
 - [**Advanced**](./docs/advanced.md)
   - [Non-interactive / CI mode](./docs/advanced.md#non-interactive--ci-mode)
   - [Tracing / verbose logging](./docs/advanced.md#tracing--verbose-logging)

docs/advanced.md

@@ -1,51 +1,5 @@
 ## Advanced
 
-## Non-interactive / CI mode
-
-Run Codex head-less in pipelines. Example GitHub Action step:
-
-```yaml
-- name: Update changelog via Codex
-  run: |
-    npm install -g @openai/codex
-    codex login --api-key "${{ secrets.OPENAI_KEY }}"
-    codex exec --full-auto "update CHANGELOG for next release"
-```
-
-### Resuming non-interactive sessions
-
-You can resume a previous headless run to continue the same conversation context and append to the same rollout file.
-
-Interactive TUI equivalent:
-
-```shell
-codex resume             # picker
-codex resume --last      # most recent
-codex resume <SESSION_ID>
-```
-
-Compatibility:
-
-- Latest source builds include `codex exec resume` (examples below).
-- Current released CLI may not include this yet. If `codex exec --help` shows no `resume`, use the workaround in the next subsection.
-
-```shell
-# Resume the most recent recorded session and run with a new prompt (source builds)
-codex exec "ship a release draft changelog" resume --last
-
-# Alternatively, pass the prompt via stdin (source builds)
-# Note: omit the trailing '-' to avoid it being parsed as a SESSION_ID
-echo "ship a release draft changelog" | codex exec resume --last
-
-# Or resume a specific session by id (UUID) (source builds)
-codex exec resume 7f9f9a2e-1b3c-4c7a-9b0e-123456789abc "continue the task"
-```
-
-Notes:
-
-- When using `--last`, Codex picks the newest recorded session; if none exist, it behaves like starting fresh.
-- Resuming appends new events to the existing session file and maintains the same conversation id.
-
 ## Tracing / verbose logging
 
 Because Codex is written in Rust, it honors the `RUST_LOG` environment variable to configure its logging behavior.

docs/exec.md

@@ -0,0 +1,105 @@
+## Non-interactive mode
+
+Use Codex in non-interactive mode to automate common workflows.
+
+```shell
+codex exec "count the total number of lines of code in this project"
+```
+
+In non-interactive mode, Codex does not ask for command or edit approvals. By default it runs in `read-only` mode, so it cannot edit files or run commands that require network access.
+
+Use `codex exec --full-auto` to allow file edits. Use `codex exec --sandbox danger-full-access` to allow edits and networked commands.
+
+
+### JSON output mode
+
+`codex exec` supports a `--json` mode that streams events to stdout as JSON Lines (JSONL) while the agent runs.
+
+Supported event types:
+- `thread.started` - when a thread is started or resumed.
+- `turn.started` - when a turn starts. A turn encompasses all events between the user message and the assistant response.
+- `turn.completed` - when a turn completes; includes token usage.
+- `turn.failed` - when a turn fails; includes error details.
+- `item.started`/`item.updated`/`item.completed` - when a thread item is added/updated/completed.
+
+Supported item types:
+- `assistant_message` - assistant message.
+- `reasoning` - a summary of the assistant's thinking.
+- `command_execution` - assistant executing a command.
+- `file_change` - assistant making file changes.
+- `mcp_tool_call` - assistant calling an MCP tool.
+- `web_search` - assistant performing a web search.
+
+Typically, an `assistant_message` is added at the end of the turn.
+
+Sample output:
+```jsonl
+{"type":"thread.started","thread_id":"0199a213-81c0-7800-8aa1-bbab2a035a53"}
+{"type":"turn.started"}
+{"type":"item.completed","item":{"id":"item_0","item_type":"reasoning","text":"**Searching for README files**"}}
+{"type":"item.started","item":{"id":"item_1","item_type":"command_execution","command":"bash -lc ls","aggregated_output":"","status":"in_progress"}}
+{"type":"item.completed","item":{"id":"item_1","item_type":"command_execution","command":"bash -lc ls","aggregated_output":"2025-09-11\nAGENTS.md\nCHANGELOG.md\ncliff.toml\ncodex-cli\ncodex-rs\ndocs\nexamples\nflake.lock\nflake.nix\nLICENSE\nnode_modules\nNOTICE\npackage.json\npnpm-lock.yaml\npnpm-workspace.yaml\nPNPM.md\nREADME.md\nscripts\nsdk\ntmp\n","exit_code":0,"status":"completed"}}
+{"type":"item.completed","item":{"id":"item_2","item_type":"reasoning","text":"**Checking repository root for README**"}}
+{"type":"item.completed","item":{"id":"item_3","item_type":"assistant_message","text":"Yep — there’s a `README.md` in the repository root."}}
+{"type":"turn.completed","usage":{"input_tokens":24763,"cached_input_tokens":24448,"output_tokens":122}}
+```
+
+### Structured output
+
+By default, the agent responds with natural language. Use `--output-schema` to provide a JSON Schema that defines the expected JSON output.
+
+The JSON Schema must follow the [strict schema rules](https://platform.openai.com/docs/guides/structured-outputs).
+
+Sample schema:
+
+```json
+{
+    "type": "object",
+    "properties": {
+        "project_name": { "type": "string" },
+        "programming_languages": { "type": "array", "items": { "type": "string" } }
+    },
+    "required": ["project_name", "programming_languages"],
+    "additionalProperties": false
+}
+```
+
+```shell
+codex exec "Extract details of the project" --output-schema ~/schema.json
+...
+
+{"project_name":"Codex CLI","programming_languages":["Rust","TypeScript","Shell"]}
+```
+
+Combine `--output-schema` with `-o` to only print the final JSON output. You can also pass a file path to `-o` to save the JSON output to a file.
+
+### Git repository requirement
+
+Codex requires a Git repository to avoid destructive changes. To disable this check, use `codex exec --skip-git-repo-check`.
+
+
+### Resuming non-interactive sessions
+
+Resume a previous non-interactive session with `codex exec resume <SESSION_ID>` or `codex exec resume --last`. This preserves conversation context so you can ask follow-up questions or give new tasks to the agent. 
+
+```shell
+codex exec "Review the change, look for use-after-free issues"
+codex exec resume --last "Fix use-after-free issues"
+```
+
+Only the conversation context is preserved; you must still provide flags to customize Codex behavior. 
+
+```shell
+codex exec --model gpt-5-codex --json "Review the change, look for use-after-free issues"
+codex exec --model gpt-5 --json resume --last "Fix use-after-free issues"
+```
+
+## Authentication
+
+By default, `codex exec` will use the same authentication method as Codex CLI and VSCode extension. You can override the api key by setting the `CODEX_API_KEY` environment variable.
+
+```shell
+CODEX_API_KEY=your-api-key-here codex exec "Fix merge conflict"
+```
+
+NOTE: `CODEX_API_KEY` is only supported in `codex exec`.