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Sweep 22 Oct 2026 · 21:04Z Build v2.1.309 528 read Stable v2.1.308 Latest v2.1.309 Next v2.1.309 Feeds RSS JSON llms.txt llms-full.txt Unofficial

Claude Code v2.1.300 ·

The Bash tool description Claude reads was rewritten

Claude's instructions for the Bash tool were rewritten, including how background commands and waiting work

Group of 2 You'll notice Internal Changes
JSON All of v2.1.300
You'll noticeTier: how much it should matter to you
1Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
Bash ToolArea: what it touches
Internal ChangesKind: in v2.1.300,
ImprovementsSection of the release

Unclear Which part of the Bash instructions changed, and so what Claude now does differently, is not clear.

What

The Bash tool is how Claude runs commands on your computer, and Claude reads a description of how to use it. That description was rewritten in this release, as measured on the prompt the running client sends:

  • Main prompt: changed for the interactive Claude Code prompt, with and without an account, across 13 captured model setups. Another set of model setups got a different edit. The new text includes: 'Foreground sleep is blocked; use Monitor with an until-loop to wait on a condition.'
  • Agent prompt: changed in the agent-claude prompt. The new text includes: 'You will be notified when it exits - do not poll its output file while waiting.'

The longest version of the description captured under this release is 9,857 characters.

Why

These are Claude's own instructions, so changes here can change how Claude runs commands, particularly when it waits for something or runs a command in the background. What the change does in practice is a reading of the text, not something measured.

How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtWhich part of the Bash instructions changed, and so what Claude now does differently, is not clear.

See this entry in the whole of v2.1.300 →

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