Hardened the proposal modules to skip malformed proposals rather than hard failing the entire run

internal/framework/proposal_generation/generate.go

@@ -44,6 +44,16 @@ type StructuredCorrectionSet struct {
 	Corrections []StructuredCorrectionProposal `json:"corrections"`
 }
 
+type DroppedCandidate struct {
+	ProposalIndex   int     `json:"proposal_index"`
+	TargetSegmentID int     `json:"target_segment_id"`
+	OriginalText    string  `json:"original_text"`
+	CorrectedText   string  `json:"corrected_text"`
+	Confidence      float64 `json:"confidence"`
+	ReasonCode      string  `json:"reason_code"`
+	Message         string  `json:"message"`
+}
+
 // Request captures reusable proposal-generation inputs for future modules.
 type Request struct {
 	ModuleKey         string                      `json:"module_key"`
@@ -62,12 +72,14 @@ type Request struct {
 	Scheduler         contracts.LLMScheduler
 	DiagnosticsDir    string
 	DiagnosticsWriter InteractionDiagnosticsWriter
+	OnDroppedCandidate func(dropped DroppedCandidate)
 }
 
 // Result contains generated candidate proposals and optional diagnostics paths.
 type Result struct {
 	Corrections []proposals.CorrectionProposal         `json:"corrections"`
 	Enriched    []proposals.EnrichedCorrectionProposal `json:"enriched"`
+	Dropped     []DroppedCandidate                     `json:"dropped,omitempty"`
 	Artifacts   InteractionArtifacts                   `json:"artifacts,omitempty"`
 }
 
@@ -161,7 +173,9 @@ func GenerateCandidates(ctx context.Context, req Request) (Result, error) {
 
 	corrections := make([]proposals.CorrectionProposal, 0, len(response.Corrections))
 	enriched := make([]proposals.EnrichedCorrectionProposal, 0, len(response.Corrections))
+	dropped := make([]DroppedCandidate, 0)
 	for i, raw := range response.Corrections {
+		proposalIndex := req.StartIndex + i
 		candidate := proposals.CorrectionProposal{
 			TargetSegmentID: raw.TargetSegmentID,
 			OriginalText:    raw.OriginalText,
@@ -169,14 +183,27 @@ func GenerateCandidates(ctx context.Context, req Request) (Result, error) {
 			Confidence:      raw.Confidence,
 		}
 		if err := candidate.Validate(); err != nil {
-			return Result{}, fmt.Errorf("invalid structured correction at index %d: %w", i, err)
+			record := DroppedCandidate{
+				ProposalIndex:   proposalIndex,
+				TargetSegmentID: raw.TargetSegmentID,
+				OriginalText:    raw.OriginalText,
+				CorrectedText:   raw.CorrectedText,
+				Confidence:      raw.Confidence,
+				ReasonCode:      "invalid_structured_correction",
+				Message:         fmt.Sprintf("invalid structured correction at index %d: %v", i, err),
+			}
+			dropped = append(dropped, record)
+			if req.OnDroppedCandidate != nil {
+				req.OnDroppedCandidate(record)
+			}
+			continue
 		}
 
 		corrections = append(corrections, candidate)
 		enrichedCandidate := proposals.EnrichedCorrectionProposal{
 			CorrectionProposal: candidate,
 			ProposalMetadata: proposals.ProposalMetadata{
-				ProposalIndex:  req.StartIndex + i,
+				ProposalIndex:  proposalIndex,
 				ModuleKey:      req.ModuleKey,
 				ModuleInstance: req.ModuleInstance,
 			},
@@ -191,6 +218,7 @@ func GenerateCandidates(ctx context.Context, req Request) (Result, error) {
 	return Result{
 		Corrections: corrections,
 		Enriched:    enriched,
+		Dropped:     dropped,
 		Artifacts:   artifacts,
 	}, nil
 }

internal/framework/proposal_generation/generate_test.go

@@ -229,7 +229,7 @@ func TestGenerateCandidatesMalformedStructuredResponse(t *testing.T) {
 		responses: []StructuredCorrectionSet{
 			{
 				Corrections: []StructuredCorrectionProposal{
-					{TargetSegmentID: 1, OriginalText: "x", CorrectedText: "", Confidence: 0.9},
+					{TargetSegmentID: 0, OriginalText: "x", CorrectedText: "", Confidence: 0.9},
 				},
 			},
 		},
@@ -237,9 +237,18 @@ func TestGenerateCandidatesMalformedStructuredResponse(t *testing.T) {
 	req := defaultRequest(t)
 	req.LLMClient = client
 
-	_, err := GenerateCandidates(context.Background(), req)
-	if err == nil || !strings.Contains(err.Error(), "invalid structured correction") {
-		t.Fatalf("expected structured response validation failure, got %v", err)
+	got, err := GenerateCandidates(context.Background(), req)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(got.Corrections) != 0 || len(got.Enriched) != 0 {
+		t.Fatalf("expected invalid proposal to be dropped, got %+v", got)
+	}
+	if len(got.Dropped) != 1 {
+		t.Fatalf("expected one dropped candidate, got %+v", got.Dropped)
+	}
+	if got.Dropped[0].ReasonCode != "invalid_structured_correction" {
+		t.Fatalf("unexpected dropped reason: %+v", got.Dropped[0])
 	}
 }