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code-mode.md 2026-11-12 23:02 UTC to 2026-11-13 23:02 UTC

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2026
Fri 13 23:02

Run tool calls from code with Code Mode

Try Code Mode, an experimental feature in which Claude writes JavaScript that makes several tool calls in one step.

Code Mode changes how Claude uses its tools. Without Code Mode, Claude asks for tool calls such as Bash, Read, or Edit directly and reads each result before it decides what to do next. With Code Mode, Claude writes a piece of JavaScript that makes the tool calls, and Claude Code runs that code in your session.

[!NOTE]

Code Mode is experimental and off by default. It may change or be removed in any release. To share feedback, run /feedback.

How Code Mode works

In a Code Mode session, you still describe your task in a prompt, and Claude writes JavaScript to carry it out. One piece of code can run commands in parallel, use one result in the next call, and return the part of the output that Claude needs to read.

For example, if you ask Claude to raise a retry limit, Claude might write this code to find the file, edit it, and run the tests. The last line returns the file's path and the test output to Claude:

const files = await $`rg -l "function retryPolicy" src`.text();
const target = files.trim().split("\n")[0];
await edit(target, "maxAttempts: 3", "maxAttempts: 5");
({ edited: target, tests: $`npm test -- retryPolicy`.nothrow() });

In the conversation, you see the tool calls, such as the edit's diff, and not the code. To read the code, press Ctrl+O to open the transcript viewer. Each piece of code appears there as a collapsed Code row, with a hint for how to expand it.

When to use Code Mode

Try Code Mode on tasks that take many related tool calls, such as:

  • A change that repeats across many files
  • A search whose results need filtering before Claude reads them
  • Several independent commands that can run at the same time

Code Mode limitations

Before you turn on Code Mode, check that you can accept these limits:

Requirements

  • Version: Claude Code v2.1.323 or later, on either release channel. An older version starts without Code Mode, with or without the reason it isn't open to your account yet
  • Account: a Claude subscription or Console account. You can't use Code Mode through a gateway, Amazon Bedrock, Claude Platform on AWS, Google Cloud's Agent Platform, or Microsoft Foundry
  • Organization: your organization doesn't use the HIPAA configuration or zero data retention
  • Model: Claude Opus 5.5, Sonnet 5.5, Haiku 5.5, or Fable 5.2
  • Surface: an interactive claude session in a terminal. Code Mode doesn't work with -p, the Agent SDK, the VS Code panel, the Desktop app, or cloud sessions
  • Installation: the native build of Claude Code
  • Windows: Git for Windows is installed

You also can't start Code Mode with some settings on, such as an API key helper, agent teams, OpenTelemetry export, or DISABLE_TELEMETRY. For the fix for each, see Code Mode doesn't start.

Try Code Mode

Turn on Code Mode, give Claude a task, and look at the code that Claude wrote.

1. Check your version

Run claude --version. If the version is older than v2.1.323, run claude update. If you're on the stable channel and the update doesn't reach v2.1.323, wait for stable to catch up or switch to latest.

2. Start Claude Code with Code Mode on

Set the CLAUDE_CODE_EXPERIMENTAL_CODE_MODE environment variable to 1. To try Code Mode, set it in your shell. To turn on Code Mode for every new session, set it in your user settings.

[tab] macOS, Linux, WSL

CLAUDE_CODE_EXPERIMENTAL_CODE_MODE=1 claude

[tab] Windows PowerShell

$env:CLAUDE_CODE_EXPERIMENTAL_CODE_MODE = "1"
claude

[tab] settings.json

Save this env block in ~/.claude/settings.json and start claude:

{
  "env": {
    "CLAUDE_CODE_EXPERIMENTAL_CODE_MODE": "1"
  }
}

Claude Code ignores this variable in a project's settings files, so a repository you clone can't turn on Code Mode for you.

3. Confirm that you want Code Mode

Claude Code asks you to confirm before your first Code Mode session. Select Yes, turn on Code Mode. Claude Code restarts and shows this line near the top of the session:

Code Mode (experimental) is on · this session can be resumed only with Code Mode on

If you see a different line or none, see Code Mode doesn't start.

4. Give Claude a task with many tool calls

In a project you know, send a prompt such as this one:

Read every Markdown file in this project and list the links that point to local files that don't exist.

5. Read the code Claude wrote

Press Ctrl+O and expand a Code row to see the JavaScript behind the tool calls. Press Ctrl+O again to return to the conversation.

[!WARNING]

To resume a Code Mode session later, keep CLAUDE_CODE_EXPERIMENTAL_CODE_MODE set to 1 when you run claude --continue or claude --resume. With Code Mode off, Claude Code refuses to resume the session. Sessions that you started without Code Mode resume without Code Mode, even with the variable set.

Turn off Code Mode

Remove CLAUDE_CODE_EXPERIMENTAL_CODE_MODE from your shell and from ~/.claude/settings.json, then start a new session. You can also keep the variable and change its value to 0 in either place. With a 0 in one place, Code Mode stays off even if you set 1 in the other.

Block Code Mode for your organization

Add CLAUDE_CODE_EXPERIMENTAL_CODE_MODE with the value 0 to your managed settings so that nobody in your organization can use Code Mode:

{
  "env": {
    "CLAUDE_CODE_EXPERIMENTAL_CODE_MODE": "0"
  }
}

Users who are in a Code Mode session stay in it until they exit or restart Claude Code. After that, your users start without Code Mode and can't resume their Code Mode sessions while the 0 is in place. You can't turn on Code Mode for your users from managed settings.

Permissions and long-running code

Your permission mode decides how Claude's code is checked and whether you can talk to Claude while the code runs.

Permission checks

Each tool call that Claude's code makes goes through your deny and ask permission rules and your PreToolUse hooks. You don't need to change a rule or matcher for a tool such as Bash. Beyond rules and hooks, a classifier reviews the code in auto mode, and you answer prompts in the modes that ask:

  • Auto mode: the classifier reviews each piece of code before it runs, not each tool call. It doesn't see values computed at run time, such as a path taken from search output, so keep rules or hooks for calls you must control. You can still be prompted when new code starts while earlier code runs
  • Other permission modes: the code starts without a review, and you're prompted for each tool call that would prompt you in that mode

To check the code itself, write a PreToolUse hook that matches REPL, the tool that runs Claude's code, and read the JavaScript from tool_input.code.

[!WARNING]

Bash rules match command text, so Claude can run a denied command in a form the rule doesn't match, with or without Code Mode. For limits that don't depend on command text, see sandboxing.

Long-running code

While code runs a long build or test, Claude either waits for it or lets it continue in the background:

  • Waiting: Claude answers after the code finishes, and the code stops after ten minutes, including time you spend at permission prompts
  • Background: you can keep talking to Claude, and the code can run for up to two hours

For background code, start your session in auto or bypassPermissions mode. If Claude still waits, check your current mode and how you started the session:

  • You switched to another mode: press Shift+Tab until you're back in the mode you started in
  • You started in another mode, or picked the session from the claude --resume list: if auto mode is available to you, exit, then run claude --continue --permission-mode auto with Code Mode on
  • You passed tool names to --tools: start again in auto mode without that flag

Troubleshooting

Code Mode doesn't start

Code Mode (experimental) isn't available near the top of the session means that Claude Code started without Code Mode. The reason follows on the same line, and /status shows it too. Find the reason in this table, make the change, and start a new session. For a reason that isn't listed, check the requirements.

Reason includes What to do
it isn't open to your account yet If your version is older than v2.1.323, update. Otherwise, check your network connection and start again. If the reason stays, try again another day
it only works with the Anthropic API Remove the settings that route requests through a cloud provider, a gateway, or a custom ANTHROPIC_BASE_URL
it doesn't work with an API key helper Remove apiKeyHelper, ANTHROPIC_AUTH_TOKEN, and any Authorization or X-Api-Key header in ANTHROPIC_CUSTOM_HEADERS. Then sign in or set ANTHROPIC_API_KEY
it only works with Opus 5.5, Sonnet 5.5 and later models Start with a supported model, for example with --model opus. Haiku 5.5 and Fable 5.2 also work
it doesn't work in background jobs Start in the foreground, without --remote-control
it needs settings that Claude Code downloads from Anthropic Unset the variable that turns off feature-flag fetching, such as DISABLE_TELEMETRY
OpenTelemetry is on Unset CLAUDE_CODE_ENABLE_TELEMETRY and ENABLE_BETA_TRACING_DETAILED if you can work without OpenTelemetry export
it doesn't yet work with an installed mod Turn off the mod that checks tool calls
it can't be used together with agent teams yet Unset CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS
this launch's tool options Start without --restricted, add REPL to --tools, and remove REPL from --disallowedTools and your deny rules
couldn't save your answer Make ~/.claude.json writable
your organization's settings don't allow it Ask your administrator about the managed setting

If you see no line about Code Mode, run claude --version. If your version is older than v2.1.323, update. Then check that CLAUDE_CODE_EXPERIMENTAL_CODE_MODE is 1 in your shell or user settings, and remove any 0 from those and from any --settings file.

Permission prompt with a countdown

When Claude starts more code in auto mode while earlier code is still running, the earlier code loses its classifier review. Claude Code then asks you about the earlier code's remaining calls that would need a review. With no IDE connected, the prompt shows a countdown:

Claude Code will automatically block this request in 1:59, to avoid holding up an unattended session

Answer before the countdown ends. Otherwise that call is refused, and later calls that would show a countdown are refused without a prompt. To see the prompts again, send Claude a message.

Tool call refused by a hook

If Claude reports a refused tool call, ask it for the error text. These errors mean that a PreToolUse hook didn't give a decision, which refuses the call even when onFailure is unset:

  • the hook failed: on a call from Claude's code, your hook couldn't start, was killed, exited with 126, 127, or a code above 128, or returned an HTTP error or invalid output. Fix the hook
  • the hook did not finish: your hook timed out on a call from Claude's code, or on any other tool call once Claude has run code in the session. Raise the hook's timeout

To let calls go ahead when a command or http hook fails or times out, set "onFailure": "continue" on it. If a command hook exits with an ordinary code such as 1, the call goes ahead unless you set "onFailure": "block".

Code output withheld by a hook

If Claude reports a hook's block reason where you expected output from Claude's code, check your UserPromptSubmit hooks. When code can run in the background, command, http, and mcp_tool hooks on that event also run on code output. To let the output through, change the hook so that it doesn't block when source in its input is poll_event.