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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 v2.1.221 ·

Agent SDK rejects skill names containing parentheses, commas or control characters

Skill names with parentheses, commas or control characters now fail validation immediately instead of silently breaking.

You'll notice Improvements
JSON All of v2.1.221
You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
0Signal: worth watching, 1 to 5
SkillsArea: what it touches
ImprovementsKind: in v2.1.221,
ImprovementsSection of the release
What

Skill-name validation gained a rule blocking (, ), , and C0/C1 control characters, so those names now fail up front rather than producing a name that cannot match a directory.

Details
  • Sits on top of the existing unpaired-surrogate, whitespace and wildcard rules.
  • The error explains that skill names must match the skill's directory name.
  • Applies to everyone on this build.
Evidence

parentheses, commas, and control characters are not allowed in skill names

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

See this entry in the whole of v2.1.221 →

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