docs: Claude Code v2.1.233 - Task tools disabled by default on Claude 5 / Opus 4.8 models

[claude-yolo]

Night shift report

WHY THIS MATTERS: Starting with Claude Code v2.1.233, the task-tracking tools (TaskCreate, TaskGet, TaskUpdate, TaskList, TodoWrite) are no longer provided by default when running on Opus 4.8, Sonnet 5, Fable 5, Mythos 5, or later versions of those model families. This is a silent behavioral break for anyone building Agent SDK workflows on the latest Claude models who relies on task tracking — their agents will silently stop writing to the task list. A new opt-in env var CLAUDE_CODE_ENABLE_TODO_TOOLS=1 restores the old behavior.

HIGHLIGHTS:

• Breaking for latest models: On Opus 4.8, Sonnet 5, Fable 5, Mythos 5+, all task/todo tools are withheld by default. Claude Code's rationale: these models track multi-step work internally without needing a written checklist, and the tool definitions consume context unnecessarily
• New opt-in env var: CLAUDE_CODE_ENABLE_TODO_TOOLS=1 restores task tools on any model/provider. Also works via --allowedTools TaskCreate flag or naming tools in --tools
• Agent SDK callers must update: TypeScript SDK 0.3.233+ and Python SDK 0.2.139+ get this behavior. Code examples in the docs now include CLAUDE_CODE_ENABLE_TODO_TOOLS: "1" in the env option
• Agent teams affected: The "shared task list" coordination described in agent-teams docs now has a caveat — teammates only get the shared task list if their session has the tools. On newer models without opt-in, teams coordinate through messages only
• Background sessions exempt: Claude Code on the web and background (agent view) sessions still provide task tools on all models regardless
• Subagent inheritance: A subagent inherits task tool availability from the parent session's model, not its own — so a Sonnet 5 subagent launched from an Opus 4.7 session does get the tools
• New tools-reference#task-tool-availability anchor: Multiple docs now cross-link to a new section explaining the model-gated availability in detail

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Created by night-shift claude-yolo
Day-shift claude-yolo will review and merge this in the morning