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Sweep 06 Nov 2026 · 01:32Z Build v2.1.319 537 read Stable v2.1.311 Latest v2.1.318 Next v2.1.319 Feeds RSS JSON llms.txt llms-full.txt Unofficial
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Claude Code v2.1.296 ·

Hooks gain an on_failure field, and cloud launches report built-in tool count

Hook commands accept an on_failure value of continue or block that cloud hook comparison now includes, and cloud launches report built-in tool count

Group of 3 Use it now Internal Changes
JSON All of v2.1.296
Use it nowTier: how much it should matter to you
5Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
Cloud SessionsArea: what it touches
Internal ChangesKind: in v2.1.296,
What probably matters to youSection of the release

Unclear Whether onFailure is something you can set on your own hooks is not known.

What

Hooks are commands you configure to run automatically at certain points, for example before a tool runs.

  • Hook commands accept a new on_failure field, set to continue or block. It can be left out, and an invalid value falls back to block. What reads this field at runtime was not traced, so its effect is not confirmed.
  • The signature Claude Code uses to compare cloud hooks now includes onFailure, unless it is block. Before, it only left out cloud.
  • When a headless cloud session (one running on Anthropic's servers without the interactive screen) is launched, its launch report now includes builtin_tools_count, the number of built-in tools passed in.

Why

The new field suggests hook authors may be able to choose whether a failing hook stops the action or lets it continue. Until it is confirmed to have an effect, treat block as the behaviour you get.

Read from
Names in the bundleonFailure
Since it was published

The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.

Added since A small documentation edit on Agent SDK reference - TypeScript touched a line naming onFailure after this was published. onFailure?: "continue" | "block"; // "block" blocks the action when a callback fails agent-sdk/typescript see the edit
Confirmed since Anthropic's documentation has since written up onFailure, on MCP, plugins, skills, and hooks. A [`PreToolUse`](https://code.claude.com/docs/en/hooks#pretooluse) hook that runs this way and has no `onFailure` field blocks the tool call when it fails or times out. The hook error that Claude receives includes `blocking because Git Bas… third-party/claude-desktop/extensions see the edit
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 doubtWhether `onFailure` is something you can set on your own hooks is not known.
Anthropic's documentation agreesAnthropic's documentation has since written up onFailure, on MCP, plugins, skills, and hooks.

See this entry in the whole of v2.1.296 →

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