fix(ce-compound): quote YAML array items starting with reserved indicators (#613)

Co-authored-by: Nathan Vale <hi@nathanvale.com>

plugins/compound-engineering/skills/ce-compound/SKILL.md

@@ -216,7 +216,7 @@ The orchestrating agent (main conversation) performs these steps:
    - Tag session-sourced content with "(session history)" so its origin is clear to future readers
    - If findings are thin or "no relevant prior sessions," proceed without session context
 4. Assemble complete markdown file from the collected pieces, reading `assets/resolution-template.md` for the section structure of new docs
-5. Validate YAML frontmatter against `references/schema.yaml`
+5. Validate YAML frontmatter against `references/schema.yaml`, including the YAML-safety quoting rule for array items (see `references/yaml-schema.md` > YAML Safety Rules)
 6. Create directory if needed: `mkdir -p docs/solutions/[category]/`
 7. Write the file: either the updated existing doc or the new `docs/solutions/[category]/[filename].md`
 
@@ -340,7 +340,7 @@ The orchestrator (main conversation) performs ALL of the following in one sequen
 1. **Extract from conversation**: Identify the problem and solution from conversation history. Also scan the "user's auto-memory" block injected into your system prompt, if present (Claude Code only) -- use any relevant notes as supplementary context alongside conversation history. Tag any memory-sourced content incorporated into the final doc with "(auto memory [claude])"
 2. **Classify**: Read `references/schema.yaml` and `references/yaml-schema.md`, then determine track (bug vs knowledge), category, and filename
 3. **Write minimal doc**: Create `docs/solutions/[category]/[filename].md` using the appropriate track template from `assets/resolution-template.md`, with:
-   - YAML frontmatter with track-appropriate fields
+   - YAML frontmatter with track-appropriate fields, applying the YAML-safety quoting rule for array items (see `references/yaml-schema.md` > YAML Safety Rules)
    - Bug track: Problem, root cause, solution with key code snippets, one prevention tip
    - Knowledge track: Context, guidance with key examples, one applicability note
 4. **Skip specialized agent reviews** (Phase 3) to conserve context

plugins/compound-engineering/skills/ce-compound/assets/resolution-template.md

@@ -8,6 +8,8 @@ Choose the template matching the problem_type track (see `references/schema.yaml
 
 Use for: `build_error`, `test_failure`, `runtime_error`, `performance_issue`, `database_issue`, `security_issue`, `ui_bug`, `integration_issue`, `logic_error`
 
+<!-- YAML safety: array items (symptoms, applies_when, tags, related_components) starting with ` [ * & ! | > % @ ? or containing ": " must be wrapped in double quotes. See references/yaml-schema.md > "YAML Safety Rules". -->
+
 ```markdown
 ---
 title: [Clear problem title]
@@ -54,6 +56,8 @@ tags: [keyword-one, keyword-two]
 
 Use for: `best_practice`, `documentation_gap`, `workflow_issue`, `developer_experience`
 
+<!-- YAML safety: array items (symptoms, applies_when, tags, related_components) starting with ` [ * & ! | > % @ ? or containing ": " must be wrapped in double quotes. See references/yaml-schema.md > "YAML Safety Rules". -->
+
 ```markdown
 ---
 title: [Clear, descriptive title]

plugins/compound-engineering/skills/ce-compound/references/schema.yaml

@@ -228,3 +228,4 @@ validation_rules:
   - "date must match YYYY-MM-DD format"
   - "rails_version, if provided, must match X.Y.Z format and only applies to bug-track docs"
   - "tags should be lowercase and hyphen-separated"
+  - "Array-of-strings frontmatter items (symptoms, applies_when, tags, related_components, or any future array field) must be wrapped in double quotes when the value starts with a YAML reserved indicator (`, [, *, &, !, |, >, %, @, ?) or contains the substring `: ` — otherwise strict YAML parsers reject the file"

plugins/compound-engineering/skills/ce-compound/references/yaml-schema.md

@@ -89,3 +89,30 @@ Docs created before the track system may have `symptoms`/`root_cause`/`resolutio
 7. Array fields must respect min/max item counts.
 8. `date` must match `YYYY-MM-DD`.
 9. `rails_version`, if present, must match `X.Y.Z` and only applies to bug-track docs.
+
+## YAML Safety Rules
+
+Strict YAML 1.2 parsers (`yq`, `js-yaml` strict, PyYAML) reject array items
+that start with a reserved indicator character as unquoted scalars. When
+writing items for any array-of-strings field (`symptoms`, `applies_when`,
+`tags`, `related_components`, or any future array field), wrap the value in
+double quotes if it starts with any of:
+
+`` ` ``, `[`, `*`, `&`, `!`, `|`, `>`, `%`, `@`, `?`
+
+Also quote if the value contains the substring `": "` — that punctuation
+confuses flow-style parsers.
+
+Example — before (breaks strict YAML):
+
+    symptoms:
+      - `sudo dscacheutil -flushcache` does not restore in-container mDNS
+
+Example — after (parses cleanly):
+
+    symptoms:
+      - "`sudo dscacheutil -flushcache` does not restore in-container mDNS"
+
+This rule applies to all array-of-strings frontmatter fields. Scalar string
+fields like `description:` have their own quoting rules (see plugin
+`AGENTS.md` under "YAML Frontmatter").