What changed? Why?

Two SKILL.md files have argument-hint: values whose first non-whitespace character is [. In YAML, an unquoted value starting with [ is a flow sequence (array), not a string. This makes the frontmatter fail validation in tools that expect argument-hint to be a string.

The most immediate example is GitHub Copilot CLI 1.0.65, which rejects the file with a schema error when argument-hint parses as an array. The same latent issue has been reported against Claude Code (see anthropics/claude-code#22161).

Fix: quote the two affected values so YAML parses them as strings.

Root cause (required for bugfixes)

YAML 1.2 flow-style sequences begin with [. Any plain scalar whose first character is [ is interpreted as the start of a flow sequence, not a string. Quoting the whole value forces string parsing regardless of the contents.

Files changed:

• .claude/skills/git.detect-breaking-changes/SKILL.md
  • Before: argument-hint: [Number of commits to review]
  • After: argument-hint: "[Number of commits to review]"
• .claude/skills/research.component-libs/SKILL.md
  • Before: argument-hint: [research goal (e.g. "theming architecture", ...)]
  • After: argument-hint: '[research goal (e.g. "theming architecture", ...)]' (single-quoted because the value contains embedded double quotes)

Other SKILL.md files in .claude/skills/ were audited:

• deprecate-cds-api/SKILL.md, cds-migrator-transform/SKILL.md — already single-quoted strings. No change.
• components.styles/SKILL.md, components.write-docs/SKILL.md, git.backport/SKILL.md — start with <, which is a valid first character for a YAML plain scalar (parses as string). No change.

UI changes

None. This change only affects the YAML frontmatter of two .claude/skills/*/SKILL.md files (developer-tooling metadata); no runtime code, no user-facing UI.

Testing

How has it been tested?

• Unit tests
• Interaction tests
• Pseudo State tests
• Manual - Web
• Manual - Android (Emulator / Device)
• Manual - iOS (Emulator / Device)

Verified with a YAML parser that the argument-hint field now parses as str rather than list in both files:

$ python3 -c "import yaml; ..."
.claude/skills/git.detect-breaking-changes/SKILL.md -> str '[Number of commits to review]'
.claude/skills/research.component-libs/SKILL.md -> str '[research goal (e.g. "theming architecture", "progress bar component API", "styling solutions")]'

Testing instructions

1. Open either affected SKILL.md file in a YAML-schema-aware tool (e.g. GitHub Copilot CLI 1.0.65).
2. Confirm the file is accepted and argument-hint is treated as a string.

Illustrations/Icons Checklist

Not applicable — no files under packages/illustrations/** or packages/icons/** are changed.

Change management

type=routine
risk=low
impact=sev5

automerge=false

References

• Latent instance in Claude Code: [BUG] argument-hint YAML frontmatter with brackets causes React error #31 and unrecoverable TUI hang anthropics/claude-code#22161