Preserve exact JSON validation semantics

engine_test.go

@@ -2424,6 +2424,60 @@ func TestWithProfilesRejectsCyclicExtraParams(t *testing.T) {
 	}
 }
 
+func TestPreparedStructuredOutputRetainsExactSchemaNumbers(t *testing.T) {
+	const schema = `{
+  "type": "number",
+  "const": 9007199254740993,
+  "minimum": 0.123456789012345678901234567890,
+  "maximum": 1e400,
+  "multipleOf": 0.0000000000000000001
+}`
+	engine, err := promptkit.NewEngine(promptkit.Config{},
+		promptkit.WithPromptFS(publicStructuredPromptFS("exact.schema.prompt", "events.schema.json"), "prompts"),
+		promptkit.WithSchemaFS(fstest.MapFS{
+			"schemas/events.schema.json": &fstest.MapFile{Data: []byte(schema)},
+		}, "schemas"),
+		promptkit.WithProfiles(promptkit.Profile{
+			ID: "contract-fast", Endpoint: "http://example.test/v1", Model: "exact-model",
+		}),
+	)
+	if err != nil {
+		t.Fatalf("construct engine: %v", err)
+	}
+
+	prepared, err := engine.Prepare(context.Background(), promptkit.RunRequest{
+		PromptID: "exact.schema.prompt",
+		Inputs: map[string]promptkit.ArtifactRef{
+			"transcript": promptkit.Inline("Rin opens the gate."),
+		},
+	})
+	if err != nil {
+		t.Fatalf("prepare structured prompt: %v", err)
+	}
+	if prepared.StructuredOutput == nil || prepared.StructuredOutput.JSONSchema == nil {
+		t.Fatalf("structured output = %#v, want JSON Schema", prepared.StructuredOutput)
+	}
+	document, ok := prepared.StructuredOutput.JSONSchema.Schema.(map[string]any)
+	if !ok {
+		t.Fatalf("public schema = %#v, want object", prepared.StructuredOutput.JSONSchema.Schema)
+	}
+	want := map[string]string{
+		"const":      "9007199254740993",
+		"minimum":    "0.123456789012345678901234567890",
+		"maximum":    "1e400",
+		"multipleOf": "0.0000000000000000001",
+	}
+	for name, wantNumber := range want {
+		got, ok := document[name].(json.Number)
+		if !ok {
+			t.Fatalf("public schema field %q = %#v, want json.Number", name, document[name])
+		}
+		if got.String() != wantNumber {
+			t.Fatalf("public schema field %q = %q, want %q", name, got, wantNumber)
+		}
+	}
+}
+
 func TestRunStructuredOutputWorksWithSchemaFS(t *testing.T) {
 	fake := &fakeLLMClient{response: &promptkit.GenerateResponse{Content: `{"events":[]}`}}
 	engine, err := promptkit.NewEngine(promptkit.Config{