Run Claude Code programmatically

The Agent SDK gives you the same tools, agent loop, and context management that power Claude Code. It’s available as a CLI for scripts and CI/CD, or as Python and TypeScript packages for full programmatic control.

The CLI was previously called “headless mode.” The -p flag and all CLI options work the same way.

To run Claude Code programmatically from the CLI, pass -p with your prompt and any CLI options:

claude -p "Find and fix the bug in auth.py" --allowedTools "Read,Edit,Bash"

This page covers using the Agent SDK via the CLI (claude -p). For the Python and TypeScript SDK packages with structured outputs, tool approval callbacks, and native message objects, see the full Agent SDK documentation.

Basic usage

Add the -p (or --print) flag to any claude command to run it non-interactively. All CLI options work with -p, including:

--continue for continuing conversations
--allowedTools for auto-approving tools
--output-format for structured output

This example asks Claude a question about your codebase and prints the response:

claude -p "What does the auth module do?"

Start faster with bare mode

Add --bare to reduce startup time by skipping auto-discovery of hooks, skills, plugins, MCP servers, auto memory, and CLAUDE.md. Without it, claude -p loads the same context an interactive session would, including anything configured in the working directory or ~/.claude. Bare mode is useful for CI and scripts where you need the same result on every machine. A hook in a teammate’s ~/.claude or an MCP server in the project’s .mcp.json won’t run, because bare mode never reads them. Only flags you pass explicitly take effect. This example runs a one-off summarize task in bare mode and pre-approves the Read tool so the call completes without a permission prompt:

claude --bare -p "Summarize this file" --allowedTools "Read"

In bare mode Claude has access to the Bash, file read, and file edit tools. Pass any context you need with a flag:

To load	Use
System prompt additions	`--append-system-prompt`, `--append-system-prompt-file`
Settings	`--settings <file-or-json>`
MCP servers	`--mcp-config <file-or-json>`
Custom agents	`--agents <json>`
A plugin	`--plugin-dir <path>`, `--plugin-url <url>`

Bare mode skips OAuth and keychain reads. Anthropic authentication must come from ANTHROPIC_API_KEY or an apiKeyHelper in the JSON passed to --settings. Bedrock, Vertex, and Foundry use their usual provider credentials.

--bare is the recommended mode for scripted and SDK calls, and will become the default for -p in a future release.

Examples

These examples highlight common CLI patterns. For CI and other scripted calls, add --bare so they don’t pick up whatever happens to be configured locally.

Pipe data through Claude

Non-interactive mode reads stdin, so you can pipe data in and redirect the response out like any other command-line tool. This example pipes a build log into Claude and writes the explanation to a file:

cat build-error.txt | claude -p 'concisely explain the root cause of this build error' > output.txt

With --output-format json, the response payload includes total_cost_usd and a per-model cost breakdown, so scripted callers can track spend per invocation without consulting the usage dashboard.

As of Claude Code v2.1.128, piped stdin is capped at 10MB. If you exceed the cap, Claude Code exits with a clear error and a non-zero status. To work with larger inputs, write the content to a file and reference the file path in your prompt instead of piping it.

Add Claude to a build script

You can wrap a non-interactive call in a script to use Claude as a project-specific linter or reviewer. This package.json script pipes the diff against main into Claude and asks it to report typos. Piping the diff means Claude doesn’t need Bash permission to read it, and the escaped double quotes keep the script portable to Windows:

{
  "scripts": {
    "lint:claude": "git diff main | claude -p \"you are a typo linter. for each typo in this diff, report filename:line on one line and the issue on the next. return nothing else.\""
  }
}

Get structured output

Use --output-format to control how responses are returned:

text (default): plain text output
json: structured JSON with result, session ID, and metadata
stream-json: newline-delimited JSON for real-time streaming

This example returns a project summary as JSON with session metadata, with the text result in the result field:

claude -p "Summarize this project" --output-format json

To get output conforming to a specific schema, use --output-format json with --json-schema and a JSON Schema definition. The response includes metadata about the request (session ID, usage, etc.) with the structured output in the structured_output field. This example extracts function names and returns them as an array of strings:

claude -p "Extract the main function names from auth.py" \
  --output-format json \
  --json-schema '{"type":"object","properties":{"functions":{"type":"array","items":{"type":"string"}}},"required":["functions"]}'

Use a tool like jq to parse the response and extract specific fields:

# Extract the text result
claude -p "Summarize this project" --output-format json | jq -r '.result'

# Extract structured output
claude -p "Extract function names from auth.py" \
  --output-format json \
  --json-schema '{"type":"object","properties":{"functions":{"type":"array","items":{"type":"string"}}},"required":["functions"]}' \
  | jq '.structured_output'

Stream responses

Use --output-format stream-json with --verbose and --include-partial-messages to receive tokens as they’re generated. Each line is a JSON object representing an event:

claude -p "Explain recursion" --output-format stream-json --verbose --include-partial-messages

The following example uses jq to filter for text deltas and display just the streaming text. The -r flag outputs raw strings (no quotes) and -j joins without newlines so tokens stream continuously:

claude -p "Write a poem" --output-format stream-json --verbose --include-partial-messages | \
  jq -rj 'select(.type == "stream_event" and .event.delta.type? == "text_delta") | .event.delta.text'

When an API request fails with a retryable error, Claude Code emits a system/api_retry event before retrying. You can use this to surface retry progress or implement custom backoff logic.

Field	Type	Description
`type`	`"system"`	message type
`subtype`	`"api_retry"`	identifies this as a retry event
`attempt`	integer	current attempt number, starting at 1
`max_retries`	integer	total retries permitted
`retry_delay_ms`	integer	milliseconds until the next attempt
`error_status`	integer or null	HTTP status code, or `null` for connection errors with no HTTP response
`error`	string	error category: `authentication_failed`, `oauth_org_not_allowed`, `billing_error`, `rate_limit`, `invalid_request`, `server_error`, `max_output_tokens`, or `unknown`
`uuid`	string	unique event identifier
`session_id`	string	session the event belongs to

The system/init event reports session metadata including the model, tools, MCP servers, and loaded plugins. It is the first event in the stream unless CLAUDE_CODE_SYNC_PLUGIN_INSTALL is set, in which case plugin_install events precede it. Use the plugin fields to fail CI when a plugin did not load:

Field	Type	Description
`plugins`	array	plugins that loaded successfully, each with `name` and `path`
`plugin_errors`	array	plugin load-time errors, each with `plugin`, `type`, and `message`. Includes unsatisfied dependency versions and `--plugin-dir` load failures such as a missing path or invalid archive. Affected plugins are demoted and absent from `plugins`. The key is omitted when there are no errors

When CLAUDE_CODE_SYNC_PLUGIN_INSTALL is set, Claude Code emits system/plugin_install events while marketplace plugins install before the first turn. Use these to surface install progress in your own UI.

Field	Type	Description
`type`	`"system"`	message type
`subtype`	`"plugin_install"`	identifies this as a plugin install event
`status`	`"started"`, `"installed"`, `"failed"`, or `"completed"`	`started` and `completed` bracket the overall install; `installed` and `failed` report individual marketplaces
`name`	string, optional	marketplace name, present on `installed` and `failed`
`error`	string, optional	failure message, present on `failed`
`uuid`	string	unique event identifier
`session_id`	string	session the event belongs to

For programmatic streaming with callbacks and message objects, see Stream responses in real-time in the Agent SDK documentation.

Auto-approve tools

Use --allowedTools to let Claude use certain tools without prompting. This example runs a test suite and fixes failures, allowing Claude to execute Bash commands and read/edit files without asking for permission:

claude -p "Run the test suite and fix any failures" \
  --allowedTools "Bash,Read,Edit"

To set a baseline for the whole session instead of listing individual tools, pass a permission mode. dontAsk denies anything not in your permissions.allow rules or the read-only command set, which is useful for locked-down CI runs. acceptEdits lets Claude write files without prompting and also auto-approves common filesystem commands such as mkdir, touch, mv, and cp. Other shell commands and network requests still need an --allowedTools entry or a permissions.allow rule, otherwise the run aborts when one is attempted:

claude -p "Apply the lint fixes" --permission-mode acceptEdits

Create a commit

This example reviews staged changes and creates a commit with an appropriate message:

claude -p "Look at my staged changes and create an appropriate commit" \
  --allowedTools "Bash(git diff *),Bash(git log *),Bash(git status *),Bash(git commit *)"

The --allowedTools flag uses permission rule syntax. The trailing * enables prefix matching, so Bash(git diff *) allows any command starting with git diff. The space before * is important: without it, Bash(git diff*) would also match git diff-index.

User-invoked skills like /commit and built-in commands are only available in interactive mode. In -p mode, describe the task you want to accomplish instead.

Customize the system prompt

Use --append-system-prompt to add instructions while keeping Claude Code’s default behavior. This example pipes a PR diff to Claude and instructs it to review for security vulnerabilities:

gh pr diff "$1" | claude -p \
  --append-system-prompt "You are a security engineer. Review for vulnerabilities." \
  --output-format json

See system prompt flags for more options including --system-prompt to fully replace the default prompt.

Continue conversations

Use --continue to continue the most recent conversation, or --resume with a session ID to continue a specific conversation. This example runs a review, then sends follow-up prompts:

# First request
claude -p "Review this codebase for performance issues"

# Continue the most recent conversation
claude -p "Now focus on the database queries" --continue
claude -p "Generate a summary of all issues found" --continue

If you’re running multiple conversations, capture the session ID to resume a specific one:

session_id=$(claude -p "Start a review" --output-format json | jq -r '.session_id')
claude -p "Continue that review" --resume "$session_id"

Next steps

Agent SDK quickstart: build your first agent with Python or TypeScript
CLI reference: all CLI flags and options
GitHub Actions: use the Agent SDK in GitHub workflows
GitLab CI/CD: use the Agent SDK in GitLab pipelines

Agents

Tools and plugins

Automation

Troubleshooting

Run Claude Code programmatically

Basic usage

Start faster with bare mode

Examples

Pipe data through Claude

Add Claude to a build script

Get structured output

Stream responses

Auto-approve tools

Create a commit

Customize the system prompt

Continue conversations

Next steps

Agents

Tools and plugins

Automation

Troubleshooting

Documentation Index

​Basic usage

​Start faster with bare mode

​Examples

​Pipe data through Claude

​Add Claude to a build script

​Get structured output

​Stream responses

​Auto-approve tools

​Create a commit

​Customize the system prompt

​Continue conversations

​Next steps

Basic usage

Start faster with bare mode

Examples

Pipe data through Claude

Add Claude to a build script

Get structured output

Stream responses

Auto-approve tools

Create a commit

Customize the system prompt

Continue conversations

Next steps