diff --git a/skyvern/exceptions.py b/skyvern/exceptions.py
index 935f75ea..01275de6 100644
--- a/skyvern/exceptions.py
+++ b/skyvern/exceptions.py
@@ -715,3 +715,11 @@ class MissingBrowserSessionError(SkyvernHTTPException):
 class MissingBrowserAddressError(SkyvernException):
     def __init__(self, browser_session_id: str) -> None:
         super().__init__(f"Browser session {browser_session_id} does not have an address.")
+
+
+class BrowserSessionNotFound(SkyvernHTTPException):
+    def __init__(self, browser_session_id: str) -> None:
+        super().__init__(
+            f"Browser session {browser_session_id} does not exist or is not live.",
+            status_code=status.HTTP_404_NOT_FOUND,
+        )
diff --git a/skyvern/forge/agent.py b/skyvern/forge/agent.py
index 18753623..103d5ed7 100644
--- a/skyvern/forge/agent.py
+++ b/skyvern/forge/agent.py
@@ -27,6 +27,7 @@ from skyvern.constants import (
     ScrapeType,
 )
 from skyvern.exceptions import (
+    BrowserSessionNotFound,
     BrowserStateMissingPage,
     DownloadFileMaxWaitingTime,
     EmptyScrapePage,
@@ -223,6 +224,15 @@ class ForgeAgent:
     async def create_task(self, task_request: TaskRequest, organization_id: str) -> Task:
         webhook_callback_url = str(task_request.webhook_callback_url) if task_request.webhook_callback_url else None
         totp_verification_url = str(task_request.totp_verification_url) if task_request.totp_verification_url else None
+        # validate browser session id
+        if task_request.browser_session_id:
+            browser_session = await app.DATABASE.get_persistent_browser_session(
+                session_id=task_request.browser_session_id,
+                organization_id=organization_id,
+            )
+            if not browser_session:
+                raise BrowserSessionNotFound(browser_session_id=task_request.browser_session_id)
+
         task = await app.DATABASE.create_task(
             url=str(task_request.url),
             title=task_request.title,
diff --git a/skyvern/forge/sdk/workflow/service.py b/skyvern/forge/sdk/workflow/service.py
index ebcf282a..508c84b2 100644
--- a/skyvern/forge/sdk/workflow/service.py
+++ b/skyvern/forge/sdk/workflow/service.py
@@ -10,6 +10,7 @@ from skyvern import analytics
 from skyvern.config import settings
 from skyvern.constants import GET_DOWNLOADED_FILES_TIMEOUT, SAVE_DOWNLOADED_FILES_TIMEOUT
 from skyvern.exceptions import (
+    BrowserSessionNotFound,
     FailedToSendWebhook,
     InvalidCredentialId,
     MissingValueForParameter,
@@ -779,6 +780,15 @@ class WorkflowService:
         organization_id: str,
         parent_workflow_run_id: str | None = None,
     ) -> WorkflowRun:
+        # validate the browser session id
+        if workflow_request.browser_session_id:
+            browser_session = await app.DATABASE.get_persistent_browser_session(
+                session_id=workflow_request.browser_session_id,
+                organization_id=organization_id,
+            )
+            if not browser_session:
+                raise BrowserSessionNotFound(browser_session_id=workflow_request.browser_session_id)
+
         return await app.DATABASE.create_workflow_run(
             workflow_permanent_id=workflow_permanent_id,
             workflow_id=workflow_id,