.github/workflows/test-1.md:1:1: error: failed to parse frontmatter:
[9:1] missing ':' after key — YAML mapping entries require 'key: value' format
>  9 | engine copilot
       ^
```

_Source trace_: `frontmatter_content.go:67` wraps the goccy error string in `fmt.Errorf("failed to parse frontmatter:\n%s", formattedErr)`. This is NOT a `FormattedParserError`, so `compiler.go:96` calls `formatCompilerError(markdownPath, "error", err.Error(), err)` which hard-codes position `1:1`.

#### Evaluation Scores

| Dimension | Score | Rating |
|-----------|-------|--------|
| Clarity | 18/25 | Good |
| Actionability | 20/25 | Good |
| Context | 13/20 | Limited |
| Examples | 3/15 | Poor |
| Consistency | 9/15 | Inconsistent |
| **Total** | **63/100** | **Acceptable** |

#### Strengths
- ✅ Excellent YAML error translation: "missing ':' after key — YAML mapping entries require 'key: value' format" (from `yaml_error.go` translation table)
- ✅ Goccy-style source context with `^` pointer embedded in message body
- ✅ Correct inner line reference `[9:1]` visible in message

#### Weaknesses
- ❌ **Outer IDE position is wrong**: `file:1:1:` instead of `file:9:1:` — IDE "click-to-jump" navigates to the wrong line. Root cause: `frontmatter_content.go:67` uses `fmt.Errorf` (not `FormattedParserError`), so `compiler.go:96` falls back to `1:1`
- ⚠️ Generic wrapper `"failed to parse frontmatter:"` adds noise without value
- ⚠️ Mixed format: outer `file:N:M:` style and inner `[line:col]` goccy style in same output
- ⚠️ No example of correct syntax (`engine: copilot`)

#### Improvement Suggestions

1. **Fix outer position by returning `FormattedParserError` from frontmatter parser**:
   Instead of `fmt.Errorf("failed to parse frontmatter:\n%s", formattedErr)`, extract the line/column from the goccy error and return a `FormattedParserError` with the exact position, so the compiler gets a properly-positioned error at `file:9:1:` not `file:1:1:`.

2. **Remove the "failed to parse frontmatter:" wrapper**:
   The goccy output already contains full context. The wrapper message is redundant noise.

3. **Add a corrected syntax example** (following the `mcp.go` pattern):
   ```
   Correct usage:
     engine: copilot
   ```

</details>

<details>
<summary>Test Case 2: Invalid Engine Name (typo) — Score: 76/100 ✅</summary>

#### Test Configuration

**Workflow**: `.github/workflows/agentic-observability-kit.md` (265 lines, medium)
**Error Type**: Category B – Configuration error (invalid value)
**Error Introduced**: `engine: copiilot` (double-`i` typo)

#### Predicted Compiler Output

```
.github/workflows/test-2.md:11:1: error: 'engine' (line 11, col 1): value must be one of 'claude', 'codex', 'copilot', 'gemini'. Did you mean 'copilot'?
   9 | permissions:
  10 |   contents: read
  11 | engine: copiilot
     ^^^^^^
  12 | strict: true
  13 | tracker-id: agentic-observability-kit
```

_Source trace_: `validateWithSchemaAndLocation` → `cleanOneOfMessage` strips the `oneOf` jargon → `LocateJSONPathInYAMLWithAdditionalProperties` finds the precise line → `generateSchemaBasedSuggestions` computes Levenshtein distance between "copiilot" and enum values (distance 1 to "copilot") → returns `Did you mean 'copilot'?`

#### Evaluation Scores

| Dimension | Score | Rating |
|-----------|-------|--------|
| Clarity | 21/25 | Excellent |
| Actionability | 22/25 | Excellent |
| Context | 17/20 | Good |
| Examples | 5/15 | Minimal |
| Consistency | 11/15 | Generally consistent |
| **Total** | **76/100** | **Good** |

#### Strengths
- ✅ "Did you mean 'copilot'?" — highly actionable, pinpoints the fix instantly
- ✅ Lists all valid engine names in the error message
- ✅ Precise line/column with source context and `^` pointer
- ✅ IDE-parseable format (`file:line:col:`)

#### Weaknesses
- ⚠️ **Redundant position** in message body: `'engine' (line 11, col 1):` duplicates what the IDE-format prefix already shows. When there is only one failure the `formatSchemaFailureDetail` path-prefix adds noise
- ⚠️ "value must be one of" is JSON-schema vocabulary; plainer phrasing (e.g. "unknown engine") would be more accessible
- ⚠️ No pointer to documentation or custom engine reference

#### Improvement Suggestions

1. **Suppress the `'field' (line N, col M):` prefix when there is only a single failure** — it duplicates the IDE prefix and clutters the message
2. **Replace "value must be one of" with plain language**, e.g. `invalid engine 'copiilot'. Valid engines: claude, codex, copilot, gemini`
3. **Add documentation link**: "For custom engines see: https://github.com/github/gh-aw#custom-engines"

</details>

<details>
<summary>Test Case 3: Invalid Permissions Scope — Score: 66/100 ⚠️</summary>

#### Test Configuration

**Workflow**: `.github/workflows/security-compliance.md` (301 lines, complex)
**Error Type**: Category C – Semantic / unknown property
**Error Introduced**: `unknown-scope: read` added to `permissions:` block

#### Predicted Compiler Output

```
.github/workflows/test-3.md:N:3: error: 'permissions/unknown-scope' (line N, col 3):
Unknown property: unknown-scope (Valid permission scopes: actions, all, attestations,
checks, contents, deployments, discussions, id-token, issues, metadata, models,
organization-projects, packages, pages, pull-requests, repository-projects,
security-events, statuses, vulnerability-alerts) See: https://docs.github.com/....
Valid fields are: actions, all, attestations, checks, contents, deployments,
discussions, id-token, issues, metadata, ...
[context lines + ^ pointer]