fix(diff): disambiguate duplicate comment anchors

cmd/opencodereview/emit_run_result_test.go

@@ -319,6 +319,44 @@ func TestEmitRunResult_JSONWithComments(t *testing.T) {
 	}
 }
 
+func TestEmitRunResult_DoesNotResolveAmbiguousCommentToFirstMatch(t *testing.T) {
+	ag := &mockResultProvider{
+		filesReviewed: 1,
+		diffs: []model.Diff{{
+			NewPath: "main.go",
+			Diff: `@@ -1,6 +1,8 @@
+ func first() {
++	target()
+ }
+ func second() {
++	target()
+ }
+`,
+		}},
+	}
+	comments := []model.LlmComment{{
+		Path:         "main.go",
+		Content:      "ambiguous repeated code",
+		ExistingCode: "target()",
+	}}
+
+	got := captureStdout(t, func() {
+		if err := emitRunResult(context.Background(), ag, comments, time.Now(), "json", "developer", nil, nil, nil); err != nil {
+			t.Fatalf("emitRunResult: %v", err)
+		}
+	})
+	var out jsonOutput
+	if err := json.Unmarshal([]byte(got), &out); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if len(out.Comments) != 1 {
+		t.Fatalf("comments = %d, want 1", len(out.Comments))
+	}
+	if out.Comments[0].StartLine != 0 || out.Comments[0].EndLine != 0 {
+		t.Fatalf("comment lines = %d-%d, want unresolved 0-0", out.Comments[0].StartLine, out.Comments[0].EndLine)
+	}
+}
+
 func TestEmitRunResult_JSONWithResumeInfo(t *testing.T) {
 	ag := &mockResultProvider{
 		filesReviewed: 2,

internal/config/template/prompts/candidate_re_location_task_system.md

@@ -0,0 +1 @@
+You are a code location assistant. Given a review comment and candidate code locations, choose the single candidate that the comment targets. /no_think

internal/config/template/prompts/candidate_re_location_task_user.md

@@ -0,0 +1,41 @@
+A review comment's existing_code matched multiple locations. Choose the one location the comment actually targets.
+
+Rules:
+1. Use the review comment, suggestion, optional reasoning, and candidate context to decide.
+2. Return ONLY one JSON object, no Markdown and no explanation.
+3. If no candidate is clearly correct, return {"candidate_id":null}.
+4. Candidates are provided as a JSON array. Use only a candidate_id value from that array.
+
+Output schema:
+{"candidate_id":1}
+
+Examples:
+
+Input candidates:
+[{"candidate_id":"1"},{"candidate_id":"2"}]
+Correct output when candidate 2 is the target:
+{"candidate_id":2}
+
+Input candidates:
+[{"candidate_id":"1"},{"candidate_id":"2"}]
+Correct output when neither candidate is clearly the target:
+{"candidate_id":null}
+
+Review comment:
+{suggestion_content}
+
+Original existing_code:
+```
+{existing_code}
+```
+
+Suggestion:
+```
+{suggestion_code}
+```
+
+Reviewer reasoning:
+{thinking}
+
+Candidates:
+{candidates}

internal/config/template/task_template.json

@@ -29,6 +29,12 @@
       { "role": "user", "prompt_file": "re_location_task_user.md" }
     ]
   },
+  "CANDIDATE_RE_LOCATION_TASK": {
+    "messages": [
+      { "role": "system", "prompt_file": "candidate_re_location_task_system.md" },
+      { "role": "user", "prompt_file": "candidate_re_location_task_user.md" }
+    ]
+  },
   "MAX_TOOL_REQUEST_TIMES": 30,
   "PLAN_MODE_LINE_THRESHOLD": 50,
   "MAX_TOKENS": 58888

internal/config/template/template.go

@@ -20,11 +20,12 @@ type Template struct {
 	MaxTokens             int              `json:"MAX_TOKENS"`
 	// MaxCompletionTokens is a runtime-only output cap. When zero, callers
 	// retain the template's historical MaxTokens behavior.
-	MaxCompletionTokens   int              `json:"-"`
-	MaxToolRequestTimes   int              `json:"MAX_TOOL_REQUEST_TIMES"`
-	PlanModeLineThreshold int              `json:"PLAN_MODE_LINE_THRESHOLD"`
-	ReLocationTask        *LlmConversation `json:"RE_LOCATION_TASK,omitempty"`
-	ReviewFilterTask      *LlmConversation `json:"REVIEW_FILTER_TASK,omitempty"`
+	MaxCompletionTokens     int              `json:"-"`
+	MaxToolRequestTimes     int              `json:"MAX_TOOL_REQUEST_TIMES"`
+	PlanModeLineThreshold   int              `json:"PLAN_MODE_LINE_THRESHOLD"`
+	ReLocationTask          *LlmConversation `json:"RE_LOCATION_TASK,omitempty"`
+	CandidateReLocationTask *LlmConversation `json:"CANDIDATE_RE_LOCATION_TASK,omitempty"`
+	ReviewFilterTask        *LlmConversation `json:"REVIEW_FILTER_TASK,omitempty"`
 }
 
 // ScanTemplate holds the full-file scan task template configuration loaded
@@ -82,14 +83,15 @@ type manifestConversation struct {
 }
 
 type templateManifest struct {
-	MainTask              manifestConversation  `json:"MAIN_TASK"`
-	PlanTask              *manifestConversation `json:"PLAN_TASK,omitempty"`
-	MemoryCompressionTask manifestConversation  `json:"MEMORY_COMPRESSION_TASK"`
-	MaxTokens             int                   `json:"MAX_TOKENS"`
-	MaxToolRequestTimes   int                   `json:"MAX_TOOL_REQUEST_TIMES"`
-	PlanModeLineThreshold int                   `json:"PLAN_MODE_LINE_THRESHOLD"`
-	ReLocationTask        *manifestConversation `json:"RE_LOCATION_TASK,omitempty"`
-	ReviewFilterTask      *manifestConversation `json:"REVIEW_FILTER_TASK,omitempty"`
+	MainTask                manifestConversation  `json:"MAIN_TASK"`
+	PlanTask                *manifestConversation `json:"PLAN_TASK,omitempty"`
+	MemoryCompressionTask   manifestConversation  `json:"MEMORY_COMPRESSION_TASK"`
+	MaxTokens               int                   `json:"MAX_TOKENS"`
+	MaxToolRequestTimes     int                   `json:"MAX_TOOL_REQUEST_TIMES"`
+	PlanModeLineThreshold   int                   `json:"PLAN_MODE_LINE_THRESHOLD"`
+	ReLocationTask          *manifestConversation `json:"RE_LOCATION_TASK,omitempty"`
+	CandidateReLocationTask *manifestConversation `json:"CANDIDATE_RE_LOCATION_TASK,omitempty"`
+	ReviewFilterTask        *manifestConversation `json:"REVIEW_FILTER_TASK,omitempty"`
 }
 
 func resolveConversation(m manifestConversation) (LlmConversation, error) {
@@ -147,6 +149,9 @@ func LoadDefault() (*Template, error) {
 	if tpl.ReLocationTask, err = resolveOptionalConversation(m.ReLocationTask, "RE_LOCATION_TASK"); err != nil {
 		return nil, err
 	}
+	if tpl.CandidateReLocationTask, err = resolveOptionalConversation(m.CandidateReLocationTask, "CANDIDATE_RE_LOCATION_TASK"); err != nil {
+		return nil, err
+	}
 	if tpl.ReviewFilterTask, err = resolveOptionalConversation(m.ReviewFilterTask, "REVIEW_FILTER_TASK"); err != nil {
 		return nil, err
 	}

internal/config/template/template_test.go

@@ -93,6 +93,9 @@ func TestLoadDefault_FieldsPopulated(t *testing.T) {
 	if tpl.ReLocationTask == nil {
 		t.Fatal("ReLocationTask is nil, expected non-nil")
 	}
+	if tpl.CandidateReLocationTask == nil {
+		t.Fatal("CandidateReLocationTask is nil, expected non-nil")
+	}
 	if tpl.ReviewFilterTask == nil {
 		t.Fatal("ReviewFilterTask is nil, expected non-nil")
 	}
@@ -124,6 +127,11 @@ func TestLoadDefault_PlaceholdersPresent(t *testing.T) {
 		{"MemoryCompression user has context", tpl.MemoryCompressionTask.Messages[1].Content, "{{context}}"},
 		{"ReviewFilter user has comments", tpl.ReviewFilterTask.Messages[1].Content, "{{comments}}"},
 		{"ReLocation user has diff (single brace)", tpl.ReLocationTask.Messages[1].Content, "{diff}"},
+		{"CandidateReLocation user has suggestion content", tpl.CandidateReLocationTask.Messages[1].Content, "{suggestion_content}"},
+		{"CandidateReLocation user has candidates", tpl.CandidateReLocationTask.Messages[1].Content, "{candidates}"},
+		{"CandidateReLocation user has existing_code", tpl.CandidateReLocationTask.Messages[1].Content, "{existing_code}"},
+		{"CandidateReLocation user has suggestion_code", tpl.CandidateReLocationTask.Messages[1].Content, "{suggestion_code}"},
+		{"CandidateReLocation user has thinking", tpl.CandidateReLocationTask.Messages[1].Content, "{thinking}"},
 	}
 
 	for _, tt := range tests {