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Sweep 22 Oct 2026 · 04:32Z Build v2.1.308 527 read Stable v2.1.308 Latest v2.1.308 Next v2.1.308 Feeds RSS JSON llms.txt llms-full.txt Unofficial

Claude Code v2.1.251 ·

Eval-authoring guidance now requires mocking MCP servers

The eval-writing skill now requires stubbing MCP calls so evals never hit real services.

You'll notice New Features
JSON All of v2.1.251
You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
SkillsArea: what it touches
New FeaturesKind: in v2.1.251,
New FeaturesSection of the release
What

The built-in skill for writing evals gained a required step telling authors to stub every MCP tool call an eval can make, so evals never reach real MCP services.

Details
  • each tool gets a mock file under mocks/<server>/<tool>.md
  • flows that make several calls can use a single _server.md agent mock with an abort_when: list
Evidence

Step 3a — Mock the MCP servers

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

See this entry in the whole of v2.1.251 →

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