# Claude Code v2.1.221: system prompt

> 1 added and 1 removed, of 224 lines, about 2 words, in the prompt 17 of 27 arms receive. 3 other prompts also changed. Compared against v2.1.220.

The two arm counts on this page measure different things: 17 arms receive the prompt the headline is about, and the widest edit below reached 27, because the same changed lines sit in more than one prompt.

Web version: https://changelogs.core-directive.com/prompts/2.1.221?arm=sdk-cli

## What this version holds
- model strings captured: 27
- tool descriptions: 24
- compared against: v2.1.220
- system prompt edits: 1
- widest system prompt edit: +1/-1 lines
- tool descriptions changed: 0

## What moved

### System prompt (+1/-1 lines)

This edit reached all 27 arms.

The same edit landed in 11 other copies of this prompt, which differ from this one only in text interpolated per model.

```diff
@@ from line 68 @@
  - Assistant knowledge cutoff is January 2026.
  - The most recent Claude models are the Claude 5 family and Haiku 4.5. Model IDs — Fable 5: 'claude-fable-5', Opus 5: 'claude-opus-5', Sonnet 5: 'claude-sonnet-5', Haiku 4.5: 'claude-haiku-4-5-20251001'. When building AI applications, default to the latest and most capable Claude models.
  - Claude Code is available as a CLI in the terminal, desktop app (Mac/Windows), web app (claude.ai/code), and IDE extensions (VS Code, JetBrains).
- - Fast mode for Claude Code uses Claude Opus with faster output (it does not downgrade to a smaller model). It can be toggled with /fast and is available on Opus 5/4.8/4.7.
+ - Fast mode for Claude Code uses Claude Opus with faster output (it does not downgrade to a smaller model). It can be toggled with /fast and is available on Opus 5/4.8.
 
 # Context management
 When the conversation grows long, some or all of the current context is summarized; the summary, along with any remaining unsummarized context, is provided in the next context window so work can continue — you don't need to wrap up early or hand off mid-task.
```

## Tool descriptions
- Agent: https://changelogs.core-directive.com/prompts/2.1.221/tools/Agent.txt?arm=sdk-cli
- Bash: https://changelogs.core-directive.com/prompts/2.1.221/tools/Bash.txt?arm=sdk-cli
- CronCreate: https://changelogs.core-directive.com/prompts/2.1.221/tools/CronCreate.txt?arm=sdk-cli
- CronDelete: https://changelogs.core-directive.com/prompts/2.1.221/tools/CronDelete.txt?arm=sdk-cli
- CronList: https://changelogs.core-directive.com/prompts/2.1.221/tools/CronList.txt?arm=sdk-cli
- Edit: https://changelogs.core-directive.com/prompts/2.1.221/tools/Edit.txt?arm=sdk-cli
- EnterWorktree: https://changelogs.core-directive.com/prompts/2.1.221/tools/EnterWorktree.txt?arm=sdk-cli
- ExitWorktree: https://changelogs.core-directive.com/prompts/2.1.221/tools/ExitWorktree.txt?arm=sdk-cli
- NotebookEdit: https://changelogs.core-directive.com/prompts/2.1.221/tools/NotebookEdit.txt?arm=sdk-cli
- Read: https://changelogs.core-directive.com/prompts/2.1.221/tools/Read.txt?arm=sdk-cli
- ReportFindings: https://changelogs.core-directive.com/prompts/2.1.221/tools/ReportFindings.txt?arm=sdk-cli
- ScheduleWakeup: https://changelogs.core-directive.com/prompts/2.1.221/tools/ScheduleWakeup.txt?arm=sdk-cli
- SendMessage: https://changelogs.core-directive.com/prompts/2.1.221/tools/SendMessage.txt?arm=sdk-cli
- Skill: https://changelogs.core-directive.com/prompts/2.1.221/tools/Skill.txt?arm=sdk-cli
- TaskCreate: https://changelogs.core-directive.com/prompts/2.1.221/tools/TaskCreate.txt?arm=sdk-cli
- TaskGet: https://changelogs.core-directive.com/prompts/2.1.221/tools/TaskGet.txt?arm=sdk-cli
- TaskList: https://changelogs.core-directive.com/prompts/2.1.221/tools/TaskList.txt?arm=sdk-cli
- TaskOutput: https://changelogs.core-directive.com/prompts/2.1.221/tools/TaskOutput.txt?arm=sdk-cli
- TaskStop: https://changelogs.core-directive.com/prompts/2.1.221/tools/TaskStop.txt?arm=sdk-cli
- TaskUpdate: https://changelogs.core-directive.com/prompts/2.1.221/tools/TaskUpdate.txt?arm=sdk-cli
- WebFetch: https://changelogs.core-directive.com/prompts/2.1.221/tools/WebFetch.txt?arm=sdk-cli
- WebSearch: https://changelogs.core-directive.com/prompts/2.1.221/tools/WebSearch.txt?arm=sdk-cli
- Workflow: https://changelogs.core-directive.com/prompts/2.1.221/tools/Workflow.txt?arm=sdk-cli
- Write: https://changelogs.core-directive.com/prompts/2.1.221/tools/Write.txt?arm=sdk-cli

## Full text
- system prompt: https://changelogs.core-directive.com/prompts/2.1.221/system.txt?arm=sdk-cli