diff --git a/pkg/workflow/compiler_activation_jobs.go b/pkg/workflow/compiler_activation_jobs.go
index 6d6d7a3b14e..fa68aaa9e43 100644
--- a/pkg/workflow/compiler_activation_jobs.go
+++ b/pkg/workflow/compiler_activation_jobs.go
@@ -434,8 +434,9 @@ func (c *Compiler) buildActivationJob(data *WorkflowData, preActivationJobCreate
 		if data.SafeOutputs != nil && data.SafeOutputs.Messages != nil {
 			messagesJSON, err := serializeMessagesConfig(data.SafeOutputs.Messages)
 			if err != nil {
-				compilerActivationJobsLog.Printf("Warning: failed to serialize messages config for activation job: %v", err)
-			} else if messagesJSON != "" {
+				return nil, fmt.Errorf("failed to serialize messages config for activation job: %w", err)
+			}
+			if messagesJSON != "" {
 				steps = append(steps, fmt.Sprintf("          GH_AW_SAFE_OUTPUT_MESSAGES: %q\n", messagesJSON))
 			}
 		}
diff --git a/pkg/workflow/compiler_yaml_main_job.go b/pkg/workflow/compiler_yaml_main_job.go
index e21cdeb1d6a..961e1bb03df 100644
--- a/pkg/workflow/compiler_yaml_main_job.go
+++ b/pkg/workflow/compiler_yaml_main_job.go
@@ -76,10 +76,9 @@ func (c *Compiler) generateMainJobSteps(yaml *strings.Builder, data *WorkflowDat
 			// Convert to JSON array for the script
 			repoImportsJSON, err := json.Marshal(data.RepositoryImports)
 			if err != nil {
-				compilerYamlLog.Printf("Warning: failed to marshal repository imports: %v", err)
-			} else {
-				fmt.Fprintf(yaml, "          GH_AW_REPOSITORY_IMPORTS: '%s'\n", string(repoImportsJSON))
+				return fmt.Errorf("failed to marshal repository imports for merge step: %w", err)
 			}
+			fmt.Fprintf(yaml, "          GH_AW_REPOSITORY_IMPORTS: '%s'\n", string(repoImportsJSON))
 		}
 
 		// Set agent import spec if present (legacy path)