refactor(core): harden skill frontmatter parsing #16705

NTaylorMullen · 2026-01-15T02:28:51Z

Summary

This PR adds a 'hardening' pass on top of the recently merged fix for issue #16323. It makes the simple frontmatter parser more resilient to variations in user formatting.

Details

Regex-based matching: Replaced string prefix checks with regex to allow for leading whitespace and missing spaces after colons (e.g., name:foo).
Improved Multi-line Joining: Refined the array-based approach to ensure clean joining of indented lines without accidental leading spaces.
Safety Checks: Added a null check for the skill body to prevent crashes if a SKILL.md file contains frontmatter but no subsequent content.
Expanded Test Suite: Added 6 new test cases covering edge cases like empty values, indented fields, and missing spaces.

Related Issues

Related to #16323

How to Validate

Run the updated test suite:

npx vitest run packages/core/src/skills/skillLoader.test.ts

Verified that all 13 tests pass, including the 6 new edge case scenarios.

Pre-Merge Checklist

Added/updated tests (if needed)
Validated on required platforms/methods:
- MacOS
  - npm run

This commit adds a 'hardening' pass on top of the initial fix for issue #16323: - Use regex for more flexible name and description field matching - Support missing space after colons in frontmatter (e.g. 'name:foo') - Support indented field names in frontmatter - Add safety check for missing body in SKILL.md - Add comprehensive test cases for frontmatter edge cases

gemini-code-assist · 2026-01-15T02:29:03Z

Summary of Changes

Hello @NTaylorMullen, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly improves the robustness and flexibility of the skill frontmatter parsing mechanism. By adopting more adaptive matching techniques and enhancing error handling, the system can now gracefully process a wider range of user formatting styles, preventing issues that might arise from non-standard input.

Highlights

Robust Frontmatter Parsing: The skill frontmatter parser has been enhanced to use regular expressions for matching 'name' and 'description' fields, making it more resilient to variations like leading whitespace and missing spaces after colons.
Improved Multi-line Description Handling: The logic for parsing multi-line descriptions has been refined to correctly join indented continuation lines without introducing accidental leading spaces.
Null Safety for Skill Body: A null check was added for the skill body content, preventing potential crashes if a SKILL.md file contains only frontmatter without any subsequent body text.
Expanded Test Coverage: Six new test cases have been introduced to cover various edge cases, including empty name/description values, indented fields, and missing spaces after colons, ensuring the parser's reliability.

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abhipatel12

LGTM

github-actions · 2026-01-15T02:31:37Z

Size Change: +74 B (0%)

Total Size: 23.1 MB

ℹ️ View Unchanged

Filename	Size	Change
`./bundle/gemini.js`	23 MB	+74 B (0%)
`./bundle/sandbox-macos-permissive-closed.sb`	1.03 kB	0 B
`./bundle/sandbox-macos-permissive-open.sb`	890 B	0 B
`./bundle/sandbox-macos-permissive-proxied.sb`	1.31 kB	0 B
`./bundle/sandbox-macos-restrictive-closed.sb`	3.29 kB	0 B
`./bundle/sandbox-macos-restrictive-open.sb`	3.36 kB	0 B
`./bundle/sandbox-macos-restrictive-proxied.sb`	3.56 kB	0 B

_{compressed-size-action}

gemini-code-assist

Code Review

This pull request effectively hardens the frontmatter parsing for skills by using regular expressions to handle formatting variations like leading whitespace and missing spaces after colons, and adds a crucial safety check to prevent crashes when a skill file lacks a body. The accompanying tests are comprehensive and cover the new edge cases well. To further improve the parser's resilience, consider making the key matching case-insensitive for name and description fields.

gemini-code-assist · 2026-01-15T02:31:56Z

packages/core/src/skills/skillLoader.ts

-    if (line.startsWith('name:')) {
-      name = line.substring(5).trim();
+    // Match "name:" at the start of the line (optional whitespace)
+    const nameMatch = line.match(/^\s*name:\s*(.*)$/);


The regex for matching the name field is case-sensitive. To be more resilient to user formatting variations, as is the goal of this refactor, consider making it case-insensitive. A user might write Name: which would currently fail to be parsed by this fallback parser.

Suggested change

const nameMatch = line.match(/^\s*name:\s*(.*)$/);

const nameMatch = line.match(/^\s*name:\s*(.*)$/i);

gemini-code-assist · 2026-01-15T02:31:56Z

packages/core/src/skills/skillLoader.ts

-    if (line.startsWith('description:')) {
-      const descLines = [line.substring(12).trim()];
+    // Match "description:" at the start of the line (optional whitespace)
+    const descMatch = line.match(/^\s*description:\s*(.*)$/);


The regex for matching the description field is case-sensitive. To be more resilient to user formatting variations, consider making it case-insensitive. A user might write Description: which would currently fail to be parsed by this fallback parser.

Suggested change

const descMatch = line.match(/^\s*description:\s*(.*)$/);

const descMatch = line.match(/^\s*description:\s*(.*)$/i);

NTaylorMullen requested a review from a team as a code owner January 15, 2026 02:28

NTaylorMullen enabled auto-merge January 15, 2026 02:29

abhipatel12 approved these changes Jan 15, 2026

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gemini-code-assist bot reviewed Jan 15, 2026

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NTaylorMullen added this pull request to the merge queue Jan 15, 2026

github-merge-queue bot removed this pull request from the merge queue due to failed status checks Jan 15, 2026

NTaylorMullen added this pull request to the merge queue Jan 15, 2026

Merged via the queue into main with commit d0bbc7f Jan 15, 2026
25 checks passed

NTaylorMullen deleted the ntm/skill-parser-hardening branch January 15, 2026 02:54

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refactor(core): harden skill frontmatter parsing #16705

refactor(core): harden skill frontmatter parsing #16705

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	const nameMatch = line.match(/^\sname:\s(.*)$/);
	const nameMatch = line.match(/^\sname:\s(.*)$/i);

	const descMatch = line.match(/^\sdescription:\s(.*)$/);
	const descMatch = line.match(/^\sdescription:\s(.*)$/i);

refactor(core): harden skill frontmatter parsing #16705

refactor(core): harden skill frontmatter parsing #16705

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NTaylorMullen commented Jan 15, 2026

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