> ## Documentation Index
> Fetch the complete documentation index at: https://docs.tryreplicas.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Claude Code

> Run Claude Code agents in Replicas workspaces.

Replicas runs [Claude Code](https://code.claude.com/docs/en) inside isolated workspace VMs, with access to your repository, environment configuration, and integrations.

## Setup

Choose one authentication method:

* **Claude OAuth:** Run `replicas claude-auth` to connect an existing Claude subscription.
* **Anthropic API key:** Add a key under [Organization → Coding Agents](https://tryreplicas.com/dashboard/agents).
* **Microsoft Foundry:** Add a Foundry API key, resource name, and optional Claude deployment names under [Organization → Coding Agents](https://tryreplicas.com/dashboard/agents).
* **AWS Bedrock:** Add AWS credentials and a region under [Organization → Coding Agents](https://tryreplicas.com/dashboard/agents).

Pass `--user` to `replicas claude-auth` to save OAuth credentials to your account instead of sharing them with the organization. Personal credentials take priority over organization defaults. See [Credentials](/admin/credentials) for details.

## Models

Replicas supports Claude Fable, Opus, Sonnet, and Haiku models. Set the organization default under [Organization → Settings → Preferences](https://tryreplicas.com/dashboard/settings?tab=defaults), or choose a model for an individual chat.

The available models depend on the authentication method and model access on the connected Anthropic or Bedrock account.

## Using Claude Code in Workspaces

In a workspace, use the composer's harness/model picker to choose **Claude Code** and start or continue a session. Claude Code can:

* Read and edit files and run shell commands
* Use environment [skills and MCP servers](/features/environments)
* Create branches, commits, and pull requests
* Run background Bash, Agent, and Monitor tasks
* Use [Plan Mode](/features/workspaces/plan-mode)

Background task status and output appear in the transcript and can continue across turns. See [Workspace background tasks](/features/workspaces/overview#background-tasks).

### Fast Mode

[Fast Mode](/features/workspaces/fast-mode) is available for Claude Opus models. Start a message with `/fast` or use the lightning toggle in the composer.

### Thinking levels

Use **Ultracode** in the thinking picker to combine `xhigh` effort with Claude Code dynamic workflows when supported by the connected model and plan.

### Chat history

Claude Code sessions persist across turns and workspace sleep. Send `/compact` to compact the active session without starting a new one, or use `replicas read` from the [CLI](/features/cli) to inspect transcript history.

## Programmatic Use

Select Claude Code anywhere Replicas accepts a coding agent:

| Surface                                                                                                      | How to choose Claude Code                                                 |
| ------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------- |
| [CLI](/features/cli)                                                                                         | `-a claude` on `replicas create` and `replicas send`                      |
| [API](/features/api)                                                                                         | `"coding_agent": "claude"` on create and message requests                 |
| [MCP](/features/mcp)                                                                                         | `"coding_agent": "claude"` on `create_replica` and `send_replica_message` |
| [Automations](/features/automations)                                                                         | Set **Coding agent** to Claude Code                                       |
| [Slack](/features/slack), [Linear](/features/linear), [GitHub](/features/github), [GitLab](/features/gitlab) | Set Claude Code as the [default coding agent](/admin/defaults)            |

```bash theme={null}
replicas create fix-checkout \
  -e frontend \
  -a claude \
  -m "Fix the checkout validation error"
```

## When to Use Claude Code

Claude Code is a strong fit when you want Anthropic-native agent behavior, long-running background tasks, or Claude skills and commands. Use Codex when you need Codex goal mode or OpenAI-native models; use Cursor or Opencode when you prefer their model and authentication ecosystems.