Model
By default,deepagents uses "claude-sonnet-4-5-20250929". You can customize this by passing any LangChain model object.
System prompt
Deep agents come with a built-in system prompt inspired by Claude Code’s system prompt. The default system prompt contains detailed instructions for using the built-in planning tool, file system tools, and subagents. Each deep agent tailored to a use case should include a custom system prompt specific to that use case.Tools
Just like tool-calling agents, a deep agent gets a set of top level tools that it has access to.write_todos– Update the agent’s to-do listls– List all files in the agent’s filesystemread_file– Read a file from the agent’s filesystemwrite_file– Write a new file in the agent’s filesystemedit_file– Edit an existing file in the agent’s filesystemtask– Spawn a subagent to handle a specific task
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