feat(skills): add edge case hunter as parallel review layer in PR review (#1791)

* feat(skills): add edge case hunter as parallel review layer in PR review

Wire review-edge-case-hunter.xml into bmad-os-review-pr as a second
review layer running in parallel with the adversarial review. Both
subagents receive the same PR diff concurrently. Findings are merged,
deduplicated, and tagged by source before tone transformation.

* fix(core): resolve contradictions in edge case hunter task spec

- Show array wrapper [{}] in output-format example to match JSON array
  contract, and document empty array [] as valid output
- Consolidate empty-content handling: step 1 now defers to halt-conditions
  instead of defining separate "ask and abort" behavior
- Zero-findings halt no longer contradicts JSON contract: re-analyze once,
  then return [] instead of ambiguous "HALT or re-analyze"
- Soften "Execute ALL steps" to acknowledge halt-conditions can interrupt

* fix(review): address PR #1791 review feedback

- Remove "Task tool" reference per maintainer; use generic "subagents"
- Fix nested triple-backtick fencing with four-tick outer fence
- Widen location format to support multi-line ranges and hunk refs
- Add JSON-safety constraint to guard_snippet field
- Tighten input loading to "strictly from provided input"
- Replace vague "unreadable" with "cannot be decoded as text"
- Replace vague "increased scrutiny" with concrete re-analysis checklist
- Resolve HALT-immediately vs re-analysis conflict in LLM instructions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.claude/skills/bmad-os-review-pr/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: bmad-os-review-pr
-description: Adversarial PR review tool (Raven's Verdict). Cynical deep review transformed into professional engineering findings. Use when user asks to 'review a PR' and provides a PR url or id.
+description: Dual-layer PR review tool (Raven's Verdict). Runs adversarial cynical review and edge case hunter in parallel, merges and deduplicates findings into professional engineering output. Use when user asks to 'review a PR' and provides a PR url or id.
 ---
 
 Read `prompts/instructions.md` and execute.

.claude/skills/bmad-os-review-pr/prompts/instructions.md

@@ -93,13 +93,17 @@ gh pr diff {PR_NUMBER} [--repo {REPO}] --name-only | grep -E '\.(png|jpg|jpeg|gi
 
 Store list of binary files to skip. Note them in final output.
 
-## Adversarial Review
+## Review Layers
 
-### 1.1 Run Cynical Review
+**Launch steps 1.1 and 1.2 as parallel subagents.** Both receive the same PR diff and run concurrently. Wait for both to complete before proceeding to step 1.3.
+
+### 1.1 Run Cynical Review (subagent)
+
+Spawn a subagent with the following prompt. Pass the full PR diff as context.
 
 **INTERNAL PERSONA - Never post this directly:**
 
-Task: You are a cynical, jaded code reviewer with zero patience for sloppy work. This PR was submitted by a clueless weasel and you expect to find problems. Find at least five issues to fix or improve in it. Number them. Be skeptical of everything. Ultrathink.
+Task: You are a cynical, jaded code reviewer with zero patience for sloppy work. This PR was submitted by a clueless weasel and you expect to find problems. Find at least five issues to fix or improve in it. Number them. Be skeptical of everything.
 
 Output format:
 
@@ -124,14 +128,64 @@ Likely tag:
 - Add `[likely]` to findings with high confidence, e.g. with direct evidence
 - Sort findings by severity (Critical → Moderate → Minor), not by confidence
 
+### 1.2 Run Edge Case Hunter (subagent)
+
+Spawn a subagent that executes the task defined in `_bmad/core/tasks/review-edge-case-hunter.xml`. Pass the full PR diff as the `content` input. Omit `also_consider` unless the user specified extra focus areas.
+
+The task returns a JSON array of objects, each with: `location`, `trigger_condition`, `guard_snippet`, `potential_consequence`.
+
+**Map each JSON finding to the standard finding format:**
+
+````markdown
+### [NUMBER]. [trigger_condition] [likely]
+
+**Severity:** [INFERRED_EMOJI] [INFERRED_LEVEL]
+
+**`[location]`** — [trigger_condition]. [potential_consequence].
+
+**Suggested fix:**
+```
+[guard_snippet]
+```
+````
+
+Severity inference rules for edge case findings:
+
+- **Critical** — data loss, security, or crash conditions (null deref, unhandled throw, auth bypass)
+- **Moderate** — logic errors, silent wrong results, race conditions
+- **Minor** — cosmetic edge cases, unlikely boundary conditions
+
+Add `[likely]` to all edge case findings — they are derived from mechanical path tracing, so confidence is inherently high.
+
+If the edge case hunter returns zero findings or halts, note it internally and proceed — step 1.1 findings still stand.
+
+### 1.3 Merge and Deduplicate
+
+Combine the findings from step 1.1 (adversarial) and step 1.2 (edge case hunter) into a single list.
+
+**Deduplication rules:**
+
+1. Compare each edge case finding against each adversarial finding
+2. Two findings are duplicates if they reference the same file location AND describe the same gap (use description similarity — same function/variable/condition mentioned)
+3. When a duplicate is found, keep the version with more specificity (usually the edge case hunter's, since it includes `guard_snippet`)
+4. Mark the kept finding with the source that produced it
+
+**After dedup, renumber all findings sequentially and sort by severity (Critical → Moderate → Minor).**
+
+Tag each finding with its source:
+
+- `[Adversarial]` — from step 1.1 only
+- `[Edge Case]` — from step 1.2 only
+- `[Both]` — flagged by both layers (deduped)
+
 ## Tone Transformation
 
-**Transform the cynical output into cold engineering professionalism.**
+**Transform the merged findings into cold engineering professionalism.**
 
 **Transformation rules:**
 
 1. Remove all inflammatory language, insults, assumptions about the author
-2. Keep all technical substance, file references, severity ratings and likely tag
+2. Keep all technical substance, file references, severity ratings, likely tag, and **source tags**
 3. Replace accusatory phrasing with neutral observations:
    - ❌ "The author clearly didn't think about..."
    - ✅ "This implementation may not account for..."
@@ -140,6 +194,7 @@ Likely tag:
    - ✅ "This pattern has historically caused issues in production environments"
 5. Add the suggested fixes.
 6. Keep suggestions actionable and specific
+7. Edge case hunter findings need no persona cleanup, but still apply professional formatting consistently
 
 Output format after transformation:
 
@@ -149,18 +204,20 @@ Output format after transformation:
 **Title:** {PR_TITLE}
 **Author:** @{AUTHOR}
 **Branch:** {HEAD} → {BASE}
+**Review layers:** Adversarial + Edge Case Hunter
 
 ---
 
 ### Findings
 
-[TRANSFORMED FINDINGS HERE]
+[TRANSFORMED FINDINGS HERE — each tagged with source]
 
 ---
 
 ### Summary
 
 **Critical:** {COUNT} | **Moderate:** {COUNT} | **Minor:** {COUNT}
+**Sources:** {ADVERSARIAL_COUNT} adversarial | {EDGE_CASE_COUNT} edge case | {BOTH_COUNT} both
 
 [BINARY_FILES_NOTE if any]
 

src/core/tasks/review-edge-case-hunter.xml

@@ -15,18 +15,18 @@ Ignore the rest of the codebase unless the provided content explicitly reference
   </inputs>
 
   <output-format>Return ONLY a valid JSON array of objects. Each object must contain exactly these four fields and nothing else:
-{
-  "location": "file:line",
+[{
+  "location": "file:start-end (or file:line when single line, or file:hunk when exact line unavailable)",
   "trigger_condition": "one-line description (max 15 words)",
-  "guard_snippet": "minimal code sketch that closes the gap",
+  "guard_snippet": "minimal code sketch that closes the gap (single-line escaped string, no raw newlines or unescaped quotes)",
   "potential_consequence": "what could actually go wrong (max 15 words)"
-}
-No extra text, no explanations, no markdown wrapping.</output-format>
+}]
+No extra text, no explanations, no markdown wrapping. An empty array [] is valid when no unhandled paths are found.</output-format>
 
   <llm critical="true">
-    <i>MANDATORY: Execute ALL steps in the flow section IN EXACT ORDER</i>
+    <i>MANDATORY: Execute steps in the flow section IN EXACT ORDER</i>
     <i>DO NOT skip steps or change the sequence</i>
-    <i>HALT immediately when halt-conditions are met</i>
+    <i>When a halt-condition triggers, follow its specific instruction exactly</i>
     <i>Each action xml tag within step xml tag is a REQUIRED action to complete that step</i>
 
     <i>Your method is exhaustive path enumeration — mechanically walk every branch, not hunt by intuition</i>
@@ -38,8 +38,8 @@ No extra text, no explanations, no markdown wrapping.</output-format>
 
   <flow>
     <step n="1" title="Receive Content">
-      <action>Load the content to review from provided input or context</action>
-      <action>If content to review is empty, ask for clarification and abort task</action>
+      <action>Load the content to review strictly from provided input</action>
+      <action>If content is empty, or cannot be decoded as text, return empty array [] and stop</action>
       <action>Identify content type (diff, full file, or function) to determine scope rules</action>
     </step>
 
@@ -51,13 +51,20 @@ No extra text, no explanations, no markdown wrapping.</output-format>
       <action>Collect only the unhandled paths as findings - discard handled ones silently</action>
     </step>
 
-    <step n="3" title="Present Findings">
+    <step n="3" title="Validate Completeness">
+      <action>Recheck every conditional for missing else/default</action>
+      <action>Recheck every input for null/empty/wrong-type</action>
+      <action>Recheck loop bounds for off-by-one and empty-collection</action>
+      <action>Add any newly found unhandled paths to findings; discard confirmed-handled ones</action>
+    </step>
+
+    <step n="4" title="Present Findings">
       <action>Output findings as a JSON array following the output-format specification exactly</action>
     </step>
   </flow>
 
   <halt-conditions>
-    <condition>HALT if content is empty or unreadable</condition>
+    <condition>If content is empty or cannot be decoded as text, return empty array [] and stop</condition>
   </halt-conditions>
 
 </task>