diff --git a/src/temporal/workflow-errors.ts b/src/temporal/workflow-errors.ts
new file mode 100644
index 0000000..3062080
--- /dev/null
+++ b/src/temporal/workflow-errors.ts
@@ -0,0 +1,94 @@
+// Copyright (C) 2025 Keygraph, Inc.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License version 3
+// as published by the Free Software Foundation.
+
+/**
+ * Workflow error formatting utilities.
+ * Pure functions with no side effects — safe for Temporal workflow sandbox.
+ */
+
+/** Maps Temporal error type strings to actionable remediation hints. */
+const REMEDIATION_HINTS: Record<string, string> = {
+  AuthenticationError:
+    'Verify ANTHROPIC_API_KEY or CLAUDE_CODE_OAUTH_TOKEN in .env is valid and not expired.',
+  ConfigurationError: 'Check your CONFIG file path and contents.',
+  BillingError:
+    'Check your Anthropic billing dashboard. Add credits or wait for spending cap reset.',
+  GitError: 'Check repository path and git state.',
+  InvalidTargetError: 'Verify the target URL is correct and accessible.',
+  PermissionError: 'Check file and network permissions.',
+  ExecutionLimitError: 'Agent exceeded maximum turns or budget. Review prompt complexity.',
+};
+
+/**
+ * Walk the .cause chain to find the innermost error with a .type property.
+ * Temporal wraps ApplicationFailure in ActivityFailure — the useful info is inside.
+ *
+ * Uses duck-typing because workflow code cannot import @temporalio/activity types.
+ */
+function unwrapActivityError(error: unknown): {
+  message: string;
+  type: string | null;
+} {
+  let current: unknown = error;
+  let typed: { message: string; type: string } | null = null;
+
+  while (current instanceof Error) {
+    if ('type' in current && typeof (current as { type: unknown }).type === 'string') {
+      typed = {
+        message: current.message,
+        type: (current as { type: string }).type,
+      };
+    }
+    current = (current as { cause?: unknown }).cause;
+  }
+
+  if (typed) {
+    return typed;
+  }
+
+  return {
+    message: error instanceof Error ? error.message : String(error),
+    type: null,
+  };
+}
+
+/**
+ * Format a structured error string from workflow catch context.
+ * Segments are delimited by | for multi-line rendering by WorkflowLogger.
+ */
+export function formatWorkflowError(
+  error: unknown,
+  currentPhase: string | null,
+  currentAgent: string | null
+): string {
+  const unwrapped = unwrapActivityError(error);
+
+  // Phase context (first segment)
+  let phaseContext = 'Pipeline failed';
+  if (currentPhase && currentAgent && currentPhase !== currentAgent) {
+    phaseContext = `${currentPhase} failed (agent: ${currentAgent})`;
+  } else if (currentPhase) {
+    phaseContext = `${currentPhase} failed`;
+  }
+
+  const segments: string[] = [phaseContext];
+
+  if (unwrapped.type) {
+    segments.push(unwrapped.type);
+  }
+
+  // Sanitize pipe characters from message to preserve delimiter format
+  segments.push(unwrapped.message.replaceAll('|', '/'));
+
+  if (unwrapped.type) {
+    const hint = REMEDIATION_HINTS[unwrapped.type];
+    if (hint) {
+      segments.push(`Hint: ${hint}`);
+    }
+  }
+
+  return segments.join('|');
+}
diff --git a/src/temporal/workflows.ts b/src/temporal/workflows.ts
index 6fbadeb..4950f6c 100644
--- a/src/temporal/workflows.ts
+++ b/src/temporal/workflows.ts
@@ -41,10 +41,10 @@ import {
   type AgentMetrics,
   type ResumeState,
 } from './shared.js';
-import type { VulnType } from '../services/queue-validation.js';
-import type { AgentName } from '../types/agents.js';
+import type { AgentName, VulnType } from '../types/agents.js';
 import { ALL_AGENTS } from '../types/agents.js';
 import { toWorkflowSummary } from './summary-mapper.js';
+import { formatWorkflowError } from './workflow-errors.js';
 
 // Retry configuration for production (long intervals for billing recovery)
 const PRODUCTION_RETRY = {
@@ -102,90 +102,6 @@ const preflightActs = proxyActivities<typeof activities>({
   retry: PREFLIGHT_RETRY,
 });
 
-/** Maps Temporal error type strings to actionable remediation hints. */
-const REMEDIATION_HINTS: Record<string, string> = {
-  AuthenticationError:
-    'Verify ANTHROPIC_API_KEY or CLAUDE_CODE_OAUTH_TOKEN in .env is valid and not expired.',
-  ConfigurationError: 'Check your CONFIG file path and contents.',
-  BillingError:
-    'Check your Anthropic billing dashboard. Add credits or wait for spending cap reset.',
-  GitError: 'Check repository path and git state.',
-  InvalidTargetError: 'Verify the target URL is correct and accessible.',
-  PermissionError: 'Check file and network permissions.',
-  ExecutionLimitError: 'Agent exceeded maximum turns or budget. Review prompt complexity.',
-};
-
-/**
- * Walk the .cause chain to find the innermost error with a .type property.
- * Temporal wraps ApplicationFailure in ActivityFailure — the useful info is inside.
- *
- * Uses duck-typing because workflow code cannot import @temporalio/activity types.
- */
-function unwrapActivityError(error: unknown): {
-  message: string;
-  type: string | null;
-} {
-  let current: unknown = error;
-  let typed: { message: string; type: string } | null = null;
-
-  while (current instanceof Error) {
-    if ('type' in current && typeof (current as { type: unknown }).type === 'string') {
-      typed = {
-        message: current.message,
-        type: (current as { type: string }).type,
-      };
-    }
-    current = (current as { cause?: unknown }).cause;
-  }
-
-  if (typed) {
-    return typed;
-  }
-
-  return {
-    message: error instanceof Error ? error.message : String(error),
-    type: null,
-  };
-}
-
-/**
- * Format a structured error string from workflow catch context.
- * Segments are delimited by | for multi-line rendering by WorkflowLogger.
- */
-function formatWorkflowError(
-  error: unknown,
-  currentPhase: string | null,
-  currentAgent: string | null
-): string {
-  const unwrapped = unwrapActivityError(error);
-
-  // Phase context (first segment)
-  let phaseContext = 'Pipeline failed';
-  if (currentPhase && currentAgent && currentPhase !== currentAgent) {
-    phaseContext = `${currentPhase} failed (agent: ${currentAgent})`;
-  } else if (currentPhase) {
-    phaseContext = `${currentPhase} failed`;
-  }
-
-  const segments: string[] = [phaseContext];
-
-  if (unwrapped.type) {
-    segments.push(unwrapped.type);
-  }
-
-  // Sanitize pipe characters from message to preserve delimiter format
-  segments.push(unwrapped.message.replaceAll('|', '/'));
-
-  if (unwrapped.type) {
-    const hint = REMEDIATION_HINTS[unwrapped.type];
-    if (hint) {
-      segments.push(`Hint: ${hint}`);
-    }
-  }
-
-  return segments.join('|');
-}
-
 /**
  * Compute aggregated metrics from the current pipeline state.
  * Called on both success and failure to provide partial metrics.