diff --git a/skyvern/forge/sdk/routes/agent_protocol.py b/skyvern/forge/sdk/routes/agent_protocol.py
index 0add3b12..8d34c4ae 100644
--- a/skyvern/forge/sdk/routes/agent_protocol.py
+++ b/skyvern/forge/sdk/routes/agent_protocol.py
@@ -18,11 +18,16 @@ from fastapi import (
 )
 from fastapi import status as http_status
 from fastapi.responses import ORJSONResponse
+from pydantic import ValidationError
 
 from skyvern import analytics
 from skyvern._version import __version__
 from skyvern.config import settings
-from skyvern.exceptions import CannotUpdateWorkflowDueToCodeCache, MissingBrowserAddressError
+from skyvern.exceptions import (
+    CannotUpdateWorkflowDueToCodeCache,
+    MissingBrowserAddressError,
+    SkyvernHTTPException,
+)
 from skyvern.forge import app
 from skyvern.forge.prompts import prompt_engine
 from skyvern.forge.sdk.api.llm.exceptions import LLMProviderError
@@ -826,6 +831,9 @@ async def update_workflow_legacy(
         ) from e
     except WorkflowParameterMissingRequiredValue as e:
         raise e
+    except (SkyvernHTTPException, ValidationError) as e:
+        # Bubble up well-formed client errors so they are not converted to 500s
+        raise e
     except Exception as e:
         LOG.exception(
             "Failed to update workflow",
@@ -897,6 +905,9 @@ async def update_workflow(
         raise HTTPException(status_code=422, detail="Invalid YAML")
     except WorkflowParameterMissingRequiredValue as e:
         raise e
+    except (SkyvernHTTPException, ValidationError) as e:
+        # Bubble up well-formed client errors so they are not converted to 500s
+        raise e
     except Exception as e:
         LOG.exception(
             "Failed to update workflow",
diff --git a/skyvern/forge/sdk/workflow/service.py b/skyvern/forge/sdk/workflow/service.py
index 2ce0a083..36c9338a 100644
--- a/skyvern/forge/sdk/workflow/service.py
+++ b/skyvern/forge/sdk/workflow/service.py
@@ -3339,7 +3339,9 @@ class WorkflowService:
                     loop_over_parameter = parameters[trimmed_key]
 
             if loop_over_parameter is None and not block_yaml.loop_variable_reference:
-                raise Exception("Loop value parameter is required for for loop block")
+                raise InvalidWorkflowDefinition(
+                    f"For loop block '{block_yaml.label}' requires either loop_over_parameter_key or loop_variable_reference"
+                )
 
             return ForLoopBlock(
                 **base_kwargs,
@@ -3458,7 +3460,9 @@ class WorkflowService:
             )
 
             if not block_yaml.complete_criterion and not block_yaml.terminate_criterion:
-                raise Exception("Both complete criterion and terminate criterion are empty")
+                raise InvalidWorkflowDefinition(
+                    f"Validation block '{block_yaml.label}' requires at least one of complete_criterion or terminate_criterion"
+                )
 
             return ValidationBlock(
                 **base_kwargs,
@@ -3479,7 +3483,7 @@ class WorkflowService:
             )
 
             if not block_yaml.navigation_goal:
-                raise Exception("empty action instruction")
+                raise InvalidWorkflowDefinition(f"Action block '{block_yaml.label}' requires navigation_goal")
 
             return ActionBlock(
                 **base_kwargs,