Address backend implementation review findings

engine_test.go

@@ -2357,6 +2357,11 @@ func TestExtraParamsTypedNestedValuesAreCopiedAcrossPublicBoundary(t *testing.T)
 }
 
 func TestRunRejectsInvalidExtraParams(t *testing.T) {
+	cyclicMap := map[string]any{}
+	cyclicMap["self"] = cyclicMap
+	cyclicSlice := []any{nil}
+	cyclicSlice[0] = cyclicSlice
+
 	tests := []struct {
 		name        string
 		extraParams map[string]any
@@ -2368,42 +2373,10 @@ func TestRunRejectsInvalidExtraParams(t *testing.T) {
 		{name: "nan", extraParams: map[string]any{"bad": math.NaN()}},
 		{name: "positive infinity", extraParams: map[string]any{"bad": math.Inf(1)}},
 		{name: "negative infinity", extraParams: map[string]any{"bad": math.Inf(-1)}},
-	}
-	for _, tc := range tests {
-		t.Run(tc.name, func(t *testing.T) {
-			fake := &fakeLLMClient{response: &promptkit.GenerateResponse{Content: "ok"}}
-			engine := newContractEngineWithOptions(t, frameworkSchemaDir, promptkit.WithLLMClient(fake))
-
-			_, err := engine.Run(context.Background(), promptkit.RunRequest{
-				PromptID: frameworkMarkdownSummaryPromptID,
-				Inputs: map[string]promptkit.ArtifactRef{
-					"transcript": promptkit.Inline("Rin opens the gate."),
-					"glossary":   promptkit.Inline("gate: A guarded passage."),
-				},
-				Execution: &promptkit.ExecutionTargetOverride{ExtraParams: tc.extraParams},
-			})
-			if !errors.Is(err, promptkit.ErrInvalidRequest) {
-				t.Fatalf("expected ErrInvalidRequest, got %v", err)
-			}
-			if len(fake.requests) != 0 {
-				t.Fatalf("expected invalid request to fail before LLM call, got %d requests", len(fake.requests))
-			}
-		})
-	}
-}
-
-func TestRunRejectsCyclicExtraParams(t *testing.T) {
-	cyclicMap := map[string]any{}
-	cyclicMap["self"] = cyclicMap
-	cyclicSlice := []any{nil}
-	cyclicSlice[0] = cyclicSlice
-
-	tests := []struct {
-		name        string
-		extraParams map[string]any
-	}{
-		{name: "map", extraParams: cyclicMap},
-		{name: "slice", extraParams: map[string]any{"cycle": cyclicSlice}},
+		{name: "cyclic map", extraParams: cyclicMap},
+		{name: "cyclic slice", extraParams: map[string]any{"cycle": cyclicSlice}},
+		{name: "malformed JSON number", extraParams: map[string]any{"value": json.Number("+1")}},
+		{name: "empty nested key", extraParams: map[string]any{"nested": map[string]any{"": true}}},
 	}
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {