Preserve public error categories from collaborators

engine_test.go

@@ -915,6 +915,12 @@ func TestArtifactReaderFailuresPreserveArtifactLoadErrors(t *testing.T) {
 			}},
 			wantNested: context.Canceled,
 		},
+		{
+			name:       "public reader error",
+			ctx:        context.Background(),
+			reader:     &recordingArtifactReader{err: scriptorium.ErrInvalidRequest},
+			wantNested: scriptorium.ErrInvalidRequest,
+		},
 	}
 
 	for _, tc := range tests {
@@ -936,6 +942,26 @@ func TestArtifactReaderFailuresPreserveArtifactLoadErrors(t *testing.T) {
 	}
 }
 
+func TestRunAddsLLMGenerateToCollaboratorPublicError(t *testing.T) {
+	engine := newContractEngineWithOptions(t, frameworkSchemaDir,
+		scriptorium.WithLLMClient(&fakeLLMClient{err: scriptorium.ErrArtifactLoad}),
+	)
+
+	_, err := engine.Run(context.Background(), scriptorium.RunRequest{
+		PromptID: frameworkMarkdownSummaryPromptID,
+		Inputs: map[string]scriptorium.ArtifactRef{
+			"transcript": scriptorium.Inline("Rin opens the gate."),
+			"glossary":   scriptorium.Inline("gate: A guarded passage."),
+		},
+	})
+	if !errors.Is(err, scriptorium.ErrLLMGenerate) {
+		t.Fatalf("expected ErrLLMGenerate, got %v", err)
+	}
+	if !errors.Is(err, scriptorium.ErrArtifactLoad) {
+		t.Fatalf("expected preserved ErrArtifactLoad, got %v", err)
+	}
+}
+
 func TestPrepareWithoutProfileMatchesSpecificPublicError(t *testing.T) {
 	promptDir := t.TempDir()
 	writePublicPromptFile(t, promptDir, "profile-required", "")