diff --git a/bun.lockb b/bun.lockb
index 4ee602c..a3cb5e8 100755
Binary files a/bun.lockb and b/bun.lockb differ
diff --git a/src/agents/agent.test.ts b/src/agents/agent.test.ts
index 5bd39b7..769a4ff 100644
--- a/src/agents/agent.test.ts
+++ b/src/agents/agent.test.ts
@@ -8,6 +8,7 @@ import { WorkflowAgents } from ".";
 import { tool } from "ai";
 import { z } from "zod";
 import { getAgentsApi } from "./task.test";
+import { WORKFLOW_PROTOCOL_VERSION } from "../constants";
 
 describe("agents", () => {
   const openaiToken = nanoid();
@@ -105,6 +106,7 @@ describe("agents", () => {
                 "upstash-callback-forward-upstash-workflow-stepid": "1",
                 "upstash-callback-forward-upstash-workflow-stepname": "Call Agent my agent",
                 "upstash-callback-forward-upstash-workflow-steptype": "Call",
+                "upstash-callback-forward-upstash-workflow-sdk-version": WORKFLOW_PROTOCOL_VERSION,
                 "upstash-callback-workflow-calltype": "fromCallback",
                 "upstash-callback-workflow-init": "false",
                 "upstash-callback-workflow-runid": workflowRunId,
@@ -172,6 +174,7 @@ describe("agents", () => {
                 "upstash-callback-forward-upstash-workflow-stepid": "2",
                 "upstash-callback-forward-upstash-workflow-stepname": "Call Agent my agent",
                 "upstash-callback-forward-upstash-workflow-steptype": "Call",
+                "upstash-callback-forward-upstash-workflow-sdk-version": WORKFLOW_PROTOCOL_VERSION,
                 "upstash-callback-retries": "5",
                 "upstash-callback-workflow-calltype": "fromCallback",
                 "upstash-callback-workflow-init": "false",
@@ -238,6 +241,7 @@ describe("agents", () => {
               "upstash-callback-forward-upstash-workflow-stepid": "3",
               "upstash-callback-forward-upstash-workflow-stepname": "Call Agent manager llm",
               "upstash-callback-forward-upstash-workflow-steptype": "Call",
+              "upstash-callback-forward-upstash-workflow-sdk-version": WORKFLOW_PROTOCOL_VERSION,
               "upstash-callback-retries": "5",
               "upstash-callback-workflow-calltype": "fromCallback",
               "upstash-callback-workflow-init": "false",
diff --git a/src/agents/task.test.ts b/src/agents/task.test.ts
index baa6062..5ce4a15 100644
--- a/src/agents/task.test.ts
+++ b/src/agents/task.test.ts
@@ -7,6 +7,7 @@ import { WorkflowAgents } from ".";
 import { tool } from "ai";
 import { z } from "zod";
 import { DisabledWorkflowContext } from "../serve/authorization";
+import { WORKFLOW_PROTOCOL_VERSION } from "../constants";
 import { createAnthropic } from "@ai-sdk/anthropic";
 import { createOpenAI } from "@ai-sdk/openai";
 
@@ -118,6 +119,7 @@ describe("tasks", () => {
               "upstash-callback-forward-upstash-workflow-stepid": "1",
               "upstash-callback-forward-upstash-workflow-stepname": "Call Agent my agent",
               "upstash-callback-forward-upstash-workflow-steptype": "Call",
+              "upstash-callback-forward-upstash-workflow-sdk-version": WORKFLOW_PROTOCOL_VERSION,
               "upstash-callback-workflow-calltype": "fromCallback",
               "upstash-callback-workflow-init": "false",
               "upstash-callback-workflow-runid": workflowRunId,
@@ -196,6 +198,7 @@ describe("tasks", () => {
               "upstash-callback-forward-upstash-workflow-stepid": "1",
               "upstash-callback-forward-upstash-workflow-stepname": "Call Agent Manager LLM",
               "upstash-callback-forward-upstash-workflow-steptype": "Call",
+              "upstash-callback-forward-upstash-workflow-sdk-version": WORKFLOW_PROTOCOL_VERSION,
               "upstash-callback-workflow-calltype": "fromCallback",
               "upstash-callback-workflow-init": "false",
               "upstash-callback-workflow-runid": workflowRunId,
@@ -262,6 +265,7 @@ describe("tasks", () => {
               "upstash-callback-feature-set": "LazyFetch,InitialBody",
               "upstash-callback-forward-upstash-workflow-callback": "true",
               "upstash-callback-forward-upstash-workflow-concurrent": "1",
+              "upstash-callback-forward-upstash-workflow-sdk-version": "1",
               "upstash-callback-forward-upstash-workflow-contenttype": "application/json",
               "upstash-callback-forward-upstash-workflow-stepid": "1",
               "upstash-callback-forward-upstash-workflow-steptype": "Call",
diff --git a/src/context/context.test.ts b/src/context/context.test.ts
index d83bda8..d973b42 100644
--- a/src/context/context.test.ts
+++ b/src/context/context.test.ts
@@ -330,6 +330,7 @@ describe("context tests", () => {
                   "application/x-www-form-urlencoded",
                 "upstash-callback-forward-upstash-workflow-invoke-count": "7",
                 "upstash-forward-upstash-workflow-invoke-count": "7",
+                "upstash-callback-forward-upstash-workflow-sdk-version": WORKFLOW_PROTOCOL_VERSION,
                 "upstash-callback-forward-upstash-workflow-stepid": "1",
                 "upstash-callback-forward-upstash-workflow-stepname": "my-step",
                 "upstash-callback-forward-upstash-workflow-steptype": "Call",
@@ -393,6 +394,7 @@ describe("context tests", () => {
                 "upstash-callback-forward-upstash-workflow-callback": "true",
                 "upstash-callback-forward-upstash-workflow-concurrent": "1",
                 "upstash-callback-forward-upstash-workflow-contenttype": "application/json",
+                "upstash-callback-forward-upstash-workflow-sdk-version": WORKFLOW_PROTOCOL_VERSION,
                 "upstash-callback-forward-upstash-workflow-stepid": "1",
                 "upstash-callback-forward-upstash-workflow-stepname": "my-step",
                 "upstash-callback-forward-upstash-workflow-steptype": "Call",
@@ -557,6 +559,7 @@ describe("context tests", () => {
                 "upstash-callback-forward-upstash-workflow-callback": "true",
                 "upstash-callback-forward-upstash-workflow-concurrent": "1",
                 "upstash-callback-forward-upstash-workflow-contenttype": "application/json",
+                "upstash-callback-forward-upstash-workflow-sdk-version": WORKFLOW_PROTOCOL_VERSION,
                 "upstash-callback-forward-upstash-workflow-stepid": "1",
                 "upstash-callback-forward-upstash-workflow-stepname": stepName,
                 "upstash-callback-forward-upstash-workflow-steptype": "Call",
@@ -640,11 +643,11 @@ describe("context tests", () => {
                 "upstash-callback-forward-upstash-workflow-callback": "true",
                 "upstash-callback-forward-upstash-workflow-concurrent": "1",
                 "upstash-callback-forward-upstash-workflow-contenttype": "application/json",
-                "upstash-callback-forward-upstash-workflow-invoke-count": "5",
-                "upstash-forward-upstash-workflow-invoke-count": "5",
+                "upstash-callback-forward-upstash-workflow-sdk-version": WORKFLOW_PROTOCOL_VERSION,
                 "upstash-callback-forward-upstash-workflow-stepid": "1",
                 "upstash-callback-forward-upstash-workflow-stepname": stepName,
                 "upstash-callback-forward-upstash-workflow-steptype": "Call",
+                "upstash-callback-forward-upstash-workflow-invoke-count": "5",
                 "upstash-callback-retries": "2",
                 "upstash-callback-workflow-calltype": "fromCallback",
                 "upstash-callback-workflow-init": "false",
@@ -653,6 +656,7 @@ describe("context tests", () => {
                 "upstash-feature-set": "WF_NoDelete,InitialBody",
                 "upstash-forward-authorization": `Bearer ${openAIToken}`,
                 "upstash-forward-content-type": "application/json",
+                "upstash-forward-upstash-workflow-invoke-count": "5",
                 "upstash-method": "POST",
                 "upstash-retries": "0",
                 "upstash-workflow-calltype": "toCallback",
@@ -721,6 +725,7 @@ describe("context tests", () => {
                 "upstash-callback-forward-upstash-workflow-callback": "true",
                 "upstash-callback-forward-upstash-workflow-concurrent": "1",
                 "upstash-callback-forward-upstash-workflow-contenttype": "application/json",
+                "upstash-callback-forward-upstash-workflow-sdk-version": WORKFLOW_PROTOCOL_VERSION,
                 "upstash-callback-forward-upstash-workflow-stepid": "1",
                 "upstash-callback-forward-upstash-workflow-stepname": stepName,
                 "upstash-callback-forward-upstash-workflow-steptype": "Call",
@@ -811,11 +816,11 @@ describe("context tests", () => {
                 "upstash-callback-forward-upstash-workflow-callback": "true",
                 "upstash-callback-forward-upstash-workflow-concurrent": "1",
                 "upstash-callback-forward-upstash-workflow-contenttype": "application/json",
-                "upstash-callback-forward-upstash-workflow-invoke-count": "3",
-                "upstash-forward-upstash-workflow-invoke-count": "3",
+                "upstash-callback-forward-upstash-workflow-sdk-version": WORKFLOW_PROTOCOL_VERSION,
                 "upstash-callback-forward-upstash-workflow-stepid": "1",
                 "upstash-callback-forward-upstash-workflow-stepname": stepName,
                 "upstash-callback-forward-upstash-workflow-steptype": "Call",
+                "upstash-callback-forward-upstash-workflow-invoke-count": "3",
                 "upstash-callback-retries": "2",
                 "upstash-callback-workflow-calltype": "fromCallback",
                 "upstash-callback-workflow-init": "false",
@@ -825,6 +830,7 @@ describe("context tests", () => {
                 "upstash-forward-x-api-key": anthropicToken,
                 "upstash-forward-anthropic-version": "2023-06-01",
                 "upstash-forward-content-type": "application/json",
+                "upstash-forward-upstash-workflow-invoke-count": "3",
                 "upstash-method": method,
                 "upstash-retries": "0",
                 "upstash-workflow-calltype": "toCallback",
diff --git a/src/context/steps.ts b/src/context/steps.ts
index ab185f2..799b654 100644
--- a/src/context/steps.ts
+++ b/src/context/steps.ts
@@ -19,7 +19,13 @@ import { WorkflowError } from "../error";
 import { getWorkflowRunId } from "../utils";
 import { WorkflowContext } from "./context";
 import { getHeaders, prepareFlowControl } from "../qstash/headers";
-import { WORKFLOW_FEATURE_HEADER, WORKFLOW_INIT_HEADER, WORKFLOW_URL_HEADER } from "../constants";
+import {
+  WORKFLOW_FEATURE_HEADER,
+  WORKFLOW_INIT_HEADER,
+  WORKFLOW_PROTOCOL_VERSION,
+  WORKFLOW_PROTOCOL_VERSION_HEADER,
+  WORKFLOW_URL_HEADER,
+} from "../constants";
 import { getTelemetryHeaders, HeadersResponse } from "../workflow-requests";
 
 type StepParams = { context: WorkflowContext } & Pick<HeaderParams, "telemetry"> &
@@ -450,6 +456,7 @@ export class LazyCallStep<TResult = unknown, TBody = unknown> extends BaseLazySt
         "Upstash-Callback-Workflow-Url": context.url,
         "Upstash-Callback-Feature-Set": "LazyFetch,InitialBody",
 
+        [`Upstash-Callback-Forward-${WORKFLOW_PROTOCOL_VERSION_HEADER}`]: WORKFLOW_PROTOCOL_VERSION,
         "Upstash-Callback-Forward-Upstash-Workflow-Callback": "true",
         "Upstash-Callback-Forward-Upstash-Workflow-StepId": step.stepId.toString(),
         "Upstash-Callback-Forward-Upstash-Workflow-StepName": this.stepName,
diff --git a/src/serve/serve-many.test.ts b/src/serve/serve-many.test.ts
index a2a234d..d4adadb 100644
--- a/src/serve/serve-many.test.ts
+++ b/src/serve/serve-many.test.ts
@@ -279,6 +279,7 @@ describe("serveMany", () => {
                 "upstash-callback-forward-upstash-workflow-stepid": "1",
                 "upstash-callback-forward-upstash-workflow-stepname": "call other workflow",
                 "upstash-callback-forward-upstash-workflow-steptype": "Call",
+                "upstash-callback-forward-upstash-workflow-sdk-version": "1",
                 "upstash-callback-workflow-calltype": "fromCallback",
                 "upstash-callback-workflow-init": "false",
                 "upstash-callback-workflow-runid": "wfr_id",
diff --git a/src/serve/serve.test.ts b/src/serve/serve.test.ts
index ed7c446..7238e21 100644
--- a/src/serve/serve.test.ts
+++ b/src/serve/serve.test.ts
@@ -640,6 +640,7 @@ describe("serve", () => {
                 "upstash-callback-forward-upstash-workflow-concurrent": "1",
                 "upstash-callback-forward-upstash-workflow-contenttype": "application/json",
                 "upstash-callback-forward-upstash-workflow-stepid": "1",
+                "upstash-callback-forward-upstash-workflow-sdk-version": "1",
                 "upstash-callback-forward-upstash-workflow-stepname": "call step",
                 "upstash-callback-forward-upstash-workflow-steptype": "Call",
                 "upstash-callback-retries": "2",
diff --git a/src/workflow-requests.test.ts b/src/workflow-requests.test.ts
index 1baf733..df4e22b 100644
--- a/src/workflow-requests.test.ts
+++ b/src/workflow-requests.test.ts
@@ -563,6 +563,7 @@ describe("Workflow Requests", () => {
         "Upstash-Callback-Forward-Upstash-Workflow-StepId": stepId.toString(),
         "Upstash-Callback-Forward-Upstash-Workflow-StepName": stepName,
         "Upstash-Callback-Forward-Upstash-Workflow-StepType": "Call",
+        "Upstash-Callback-Forward-Upstash-Workflow-Sdk-Version": WORKFLOW_PROTOCOL_VERSION,
         "Upstash-Callback-Workflow-CallType": "fromCallback",
         "Upstash-Callback-Workflow-RunId": workflowRunId,
         "Upstash-Callback-Workflow-Init": "false",