diff --git a/pf/schema_sidecar.go b/pf/schema_sidecar.go
new file mode 100644
index 0000000..e3aa556
--- /dev/null
+++ b/pf/schema_sidecar.go
@@ -0,0 +1,124 @@
+//
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+//
+
+package pf
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+const (
+	// SinkSchemaSidecarFileName is the schema sidecar file consumed by the generic runtime.
+	SinkSchemaSidecarFileName = "sink.schema.json"
+
+	// SchemaTypeNone disables the sink schema sidecar.
+	SchemaTypeNone = "none"
+	// SchemaTypeBytes disables the sink schema sidecar.
+	SchemaTypeBytes     = "bytes"
+	SchemaTypeJSON      = "json"
+	SchemaTypeAvro      = "avro"
+	SchemaTypeString    = "string"
+	SchemaTypeBool      = "boolean"
+	SchemaTypeInt8      = "int8"
+	SchemaTypeInt16     = "int16"
+	SchemaTypeInt32     = "int32"
+	SchemaTypeInt64     = "int64"
+	SchemaTypeFloat     = "float"
+	SchemaTypeDouble    = "double"
+	SchemaTypeDate      = "date"
+	SchemaTypeTime      = "time"
+	SchemaTypeTimestamp = "timestamp"
+)
+
+// SinkSchema describes the sink schema definition written to the runtime sidecar file.
+// SchemaType should use one of the SchemaType* constants for JSON, Avro, or
+// primitive schemas. Empty, none, and bytes schema types do not need sidecars.
+type SinkSchema struct {
+	SchemaType string
+	Name       string
+	SchemaData string
+	Properties map[string]string
+}
+
+type sinkSchemaSidecarPayload struct {
+	SchemaType string            `json:"schemaType"`
+	Name       string            `json:"name"`
+	SchemaData string            `json:"schemaData"`
+	Properties map[string]string `json:"properties"`
+}
+
+// StartWithSinkSchema writes the sink schema sidecar before starting the function.
+func StartWithSinkSchema(funcName interface{}, schema SinkSchema) {
+	if _, err := WriteSinkSchemaSidecar(schema); err != nil {
+		panic(err)
+	}
+	Start(funcName)
+}
+
+// WriteSinkSchemaSidecar writes sink.schema.json next to the current executable.
+func WriteSinkSchemaSidecar(schema SinkSchema) (string, error) {
+	executable, err := os.Executable()
+	if err != nil {
+		return "", err
+	}
+	return writeSinkSchemaSidecarToDir(filepath.Dir(executable), schema)
+}
+
+func writeSinkSchemaSidecarToDir(workDir string, schema SinkSchema) (string, error) {
+	schemaType := strings.TrimSpace(schema.SchemaType)
+	sidecarPath := filepath.Join(workDir, SinkSchemaSidecarFileName)
+	if isNoSchemaType(schemaType) {
+		if err := os.Remove(sidecarPath); err != nil && !os.IsNotExist(err) {
+			return "", err
+		}
+		return "", nil
+	}
+
+	properties := schema.Properties
+	if properties == nil {
+		properties = map[string]string{}
+	}
+	payload := sinkSchemaSidecarPayload{
+		SchemaType: schemaType,
+		Name:       schema.Name,
+		SchemaData: schema.SchemaData,
+		Properties: properties,
+	}
+	content, err := json.Marshal(payload)
+	if err != nil {
+		return "", err
+	}
+
+	if err := os.WriteFile(sidecarPath, content, 0644); err != nil {
+		return "", err
+	}
+	return sidecarPath, nil
+}
+
+func isNoSchemaType(schemaType string) bool {
+	switch strings.ToLower(strings.TrimSpace(schemaType)) {
+	case "", SchemaTypeBytes, SchemaTypeNone:
+		return true
+	default:
+		return false
+	}
+}
diff --git a/pf/schema_sidecar_test.go b/pf/schema_sidecar_test.go
new file mode 100644
index 0000000..44cd3e9
--- /dev/null
+++ b/pf/schema_sidecar_test.go
@@ -0,0 +1,169 @@
+//
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+//
+
+package pf
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestWriteSinkSchemaSidecarToDirWritesCommonSidecar(t *testing.T) {
+	workDir := t.TempDir()
+	schema := SinkSchema{
+		SchemaType: SchemaTypeJSON,
+		Name:       "example.Student",
+		SchemaData: `{"type":"record","name":"Student","fields":[]}`,
+		Properties: map[string]string{
+			"custom": "value",
+		},
+	}
+
+	sidecarPath, err := writeSinkSchemaSidecarToDir(workDir, schema)
+	if err != nil {
+		t.Fatalf("writeSinkSchemaSidecarToDir returned error: %v", err)
+	}
+
+	if sidecarPath != filepath.Join(workDir, SinkSchemaSidecarFileName) {
+		t.Fatalf("sidecarPath = %q, want %q", sidecarPath, filepath.Join(workDir, SinkSchemaSidecarFileName))
+	}
+
+	content, err := os.ReadFile(sidecarPath)
+	if err != nil {
+		t.Fatalf("read sidecar: %v", err)
+	}
+	var payload map[string]interface{}
+	if err := json.Unmarshal(content, &payload); err != nil {
+		t.Fatalf("unmarshal sidecar: %v", err)
+	}
+
+	if payload["schemaType"] != "json" {
+		t.Fatalf("schemaType = %v, want json", payload["schemaType"])
+	}
+	if payload["name"] != "example.Student" {
+		t.Fatalf("name = %v, want example.Student", payload["name"])
+	}
+	if payload["schemaData"] != `{"type":"record","name":"Student","fields":[]}` {
+		t.Fatalf("schemaData = %v, want record schema", payload["schemaData"])
+	}
+	properties, ok := payload["properties"].(map[string]interface{})
+	if !ok {
+		t.Fatalf("properties = %T, want object", payload["properties"])
+	}
+	if properties["custom"] != "value" {
+		t.Fatalf("properties[custom] = %v, want value", properties["custom"])
+	}
+}
+
+func TestWriteSinkSchemaSidecarToDirSkipsNoSchemaTypesAndRemovesStaleSidecar(t *testing.T) {
+	tests := []struct {
+		name       string
+		schemaType string
+	}{
+		{name: "empty", schemaType: ""},
+		{name: "bytes", schemaType: SchemaTypeBytes},
+		{name: "uppercase bytes", schemaType: "BYTES"},
+		{name: "none", schemaType: SchemaTypeNone},
+		{name: "uppercase none", schemaType: "NONE"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			workDir := t.TempDir()
+			sidecarFile := filepath.Join(workDir, SinkSchemaSidecarFileName)
+			if err := os.WriteFile(sidecarFile, []byte("stale"), 0644); err != nil {
+				t.Fatalf("write stale sidecar: %v", err)
+			}
+
+			sidecarPath, err := writeSinkSchemaSidecarToDir(workDir, SinkSchema{SchemaType: tt.schemaType})
+			if err != nil {
+				t.Fatalf("writeSinkSchemaSidecarToDir returned error: %v", err)
+			}
+			if sidecarPath != "" {
+				t.Fatalf("sidecarPath = %q, want empty", sidecarPath)
+			}
+			if _, err := os.Stat(sidecarFile); !os.IsNotExist(err) {
+				t.Fatalf("sidecar stat error = %v, want not exist", err)
+			}
+		})
+	}
+}
+
+func TestWriteSinkSchemaSidecarToDirTrimsSchemaTypeAndPreservesCasing(t *testing.T) {
+	workDir := t.TempDir()
+
+	sidecarPath, err := writeSinkSchemaSidecarToDir(workDir, SinkSchema{
+		SchemaType: " JSON ",
+		SchemaData: `{"type":"record","name":"Student","fields":[]}`,
+	})
+	if err != nil {
+		t.Fatalf("writeSinkSchemaSidecarToDir returned error: %v", err)
+	}
+
+	content, err := os.ReadFile(sidecarPath)
+	if err != nil {
+		t.Fatalf("read sidecar: %v", err)
+	}
+	var payload struct {
+		SchemaType string `json:"schemaType"`
+	}
+	if err := json.Unmarshal(content, &payload); err != nil {
+		t.Fatalf("unmarshal sidecar: %v", err)
+	}
+	if payload.SchemaType != "JSON" {
+		t.Fatalf("schemaType = %q, want JSON", payload.SchemaType)
+	}
+}
+
+func TestSchemaTypeBoolUsesPulsarBooleanName(t *testing.T) {
+	if SchemaTypeBool != "boolean" {
+		t.Fatalf("SchemaTypeBool = %q, want boolean", SchemaTypeBool)
+	}
+}
+
+func TestWriteSinkSchemaSidecarToDirWritesEmptyPropertiesObject(t *testing.T) {
+	workDir := t.TempDir()
+
+	sidecarPath, err := writeSinkSchemaSidecarToDir(workDir, SinkSchema{
+		SchemaType: SchemaTypeString,
+		SchemaData: "",
+	})
+	if err != nil {
+		t.Fatalf("writeSinkSchemaSidecarToDir returned error: %v", err)
+	}
+
+	content, err := os.ReadFile(sidecarPath)
+	if err != nil {
+		t.Fatalf("read sidecar: %v", err)
+	}
+	var payload struct {
+		Properties map[string]string `json:"properties"`
+	}
+	if err := json.Unmarshal(content, &payload); err != nil {
+		t.Fatalf("unmarshal sidecar: %v", err)
+	}
+	if payload.Properties == nil {
+		t.Fatal("properties is nil, want empty object")
+	}
+	if len(payload.Properties) != 0 {
+		t.Fatalf("properties length = %d, want 0", len(payload.Properties))
+	}
+}