diff --git a/src/audit/audit-session.ts b/src/audit/audit-session.ts
index 6e09133..7e8cc6a 100644
--- a/src/audit/audit-session.ts
+++ b/src/audit/audit-session.ts
@@ -17,21 +17,11 @@ import { MetricsTracker } from './metrics-tracker.js';
 import { initializeAuditStructure, type SessionMetadata } from './utils.js';
 import { formatTimestamp } from '../utils/formatting.js';
 import { SessionMutex } from '../utils/concurrency.js';
+import type { AgentEndResult } from '../types/index.js';
 
 // Global mutex instance
 const sessionMutex = new SessionMutex();
 
-interface AgentEndResult {
-  attemptNumber: number;
-  duration_ms: number;
-  cost_usd: number;
-  success: boolean;
-  model?: string | undefined;
-  error?: string | undefined;
-  checkpoint?: string | undefined;
-  isFinalAttempt?: boolean | undefined;
-}
-
 /**
  * AuditSession - Main audit system facade
  */
diff --git a/src/audit/metrics-tracker.ts b/src/audit/metrics-tracker.ts
index 4462d90..89cdf2b 100644
--- a/src/audit/metrics-tracker.ts
+++ b/src/audit/metrics-tracker.ts
@@ -18,7 +18,7 @@ import {
 import { atomicWrite, readJson, fileExists } from '../utils/file-io.js';
 import { formatTimestamp, calculatePercentage } from '../utils/formatting.js';
 import { AGENT_PHASE_MAP, type PhaseName } from '../session-manager.js';
-import type { AgentName } from '../types/index.js';
+import type { AgentName, AgentEndResult } from '../types/index.js';
 
 interface AttemptData {
   attempt_number: number;
@@ -30,7 +30,7 @@ interface AttemptData {
   error?: string | undefined;
 }
 
-interface AgentMetrics {
+interface AgentAuditMetrics {
   status: 'in-progress' | 'success' | 'failed';
   attempts: AttemptData[];
   final_duration_ms: number;
@@ -68,21 +68,10 @@ interface SessionData {
     total_duration_ms: number;
     total_cost_usd: number;
     phases: Record<string, PhaseMetrics>;
-    agents: Record<string, AgentMetrics>;
+    agents: Record<string, AgentAuditMetrics>;
   };
 }
 
-interface AgentEndResult {
-  attemptNumber: number;
-  duration_ms: number;
-  cost_usd: number;
-  success: boolean;
-  model?: string | undefined;
-  error?: string | undefined;
-  checkpoint?: string | undefined;
-  isFinalAttempt?: boolean | undefined;
-}
-
 interface ActiveTimer {
   startTime: number;
   attemptNumber: number;
@@ -326,9 +315,9 @@ export class MetricsTracker {
    * Calculate phase-level metrics
    */
   private calculatePhaseMetrics(
-    successfulAgents: Array<[string, AgentMetrics]>
+    successfulAgents: Array<[string, AgentAuditMetrics]>
   ): Record<string, PhaseMetrics> {
-    const phases: Record<PhaseName, AgentMetrics[]> = {
+    const phases: Record<PhaseName, AgentAuditMetrics[]> = {
       'pre-recon': [],
       'recon': [],
       'vulnerability-analysis': [],
diff --git a/src/audit/utils.ts b/src/audit/utils.ts
index 4b024d3..6e91964 100644
--- a/src/audit/utils.ts
+++ b/src/audit/utils.ts
@@ -15,6 +15,10 @@ import fs from 'fs/promises';
 import path from 'path';
 import { fileURLToPath } from 'url';
 
+// Import and re-export file I/O utilities from canonical location
+import { ensureDirectory, atomicWrite, readJson, fileExists } from '../utils/file-io.js';
+export { ensureDirectory, atomicWrite, readJson, fileExists };
+
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = path.dirname(__filename);
 
@@ -93,65 +97,6 @@ export function generateWorkflowLogPath(sessionMetadata: SessionMetadata): strin
   return path.join(auditPath, 'workflow.log');
 }
 
-/**
- * Ensure directory exists (idempotent, race-safe)
- */
-export async function ensureDirectory(dirPath: string): Promise<void> {
-  try {
-    await fs.mkdir(dirPath, { recursive: true });
-  } catch (error) {
-    // Ignore EEXIST errors (race condition safe)
-    if ((error as NodeJS.ErrnoException).code !== 'EEXIST') {
-      throw error;
-    }
-  }
-}
-
-/**
- * Atomic write using temp file + rename pattern
- * Guarantees no partial writes or corruption on crash
- */
-export async function atomicWrite(filePath: string, data: object | string): Promise<void> {
-  const tempPath = `${filePath}.tmp`;
-  const content = typeof data === 'string' ? data : JSON.stringify(data, null, 2);
-
-  try {
-    // Write to temp file
-    await fs.writeFile(tempPath, content, 'utf8');
-
-    // Atomic rename (POSIX guarantee: atomic on same filesystem)
-    await fs.rename(tempPath, filePath);
-  } catch (error) {
-    // Clean up temp file on failure
-    try {
-      await fs.unlink(tempPath);
-    } catch {
-      // Ignore cleanup errors
-    }
-    throw error;
-  }
-}
-
-/**
- * Read and parse JSON file
- */
-export async function readJson<T = unknown>(filePath: string): Promise<T> {
-  const content = await fs.readFile(filePath, 'utf8');
-  return JSON.parse(content) as T;
-}
-
-/**
- * Check if file exists
- */
-export async function fileExists(filePath: string): Promise<boolean> {
-  try {
-    await fs.access(filePath);
-    return true;
-  } catch {
-    return false;
-  }
-}
-
 /**
  * Initialize audit directory structure for a session
  * Creates: audit-logs/{sessionId}/, agents/, prompts/, deliverables/
diff --git a/src/session-manager.ts b/src/session-manager.ts
index 5733740..4e7fced 100644
--- a/src/session-manager.ts
+++ b/src/session-manager.ts
@@ -4,14 +4,7 @@
 // it under the terms of the GNU Affero General Public License version 3
 // as published by the Free Software Foundation.
 
-import type { AgentName } from './types/index.js';
-
-// Agent definition interface
-interface AgentDefinition {
-  name: AgentName;
-  displayName: string;
-  prerequisites: AgentName[];
-}
+import type { AgentName, AgentDefinition } from './types/index.js';
 
 // Agent definitions according to PRD
 export const AGENTS: Readonly<Record<AgentName, AgentDefinition>> = Object.freeze({
diff --git a/src/types/audit.ts b/src/types/audit.ts
new file mode 100644
index 0000000..efa9326
--- /dev/null
+++ b/src/types/audit.ts
@@ -0,0 +1,24 @@
+// 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.
+
+/**
+ * Audit system type definitions
+ */
+
+/**
+ * Result data passed to audit system when an agent execution ends.
+ * Used by both AuditSession and MetricsTracker.
+ */
+export interface AgentEndResult {
+  attemptNumber: number;
+  duration_ms: number;
+  cost_usd: number;
+  success: boolean;
+  model?: string | undefined;
+  error?: string | undefined;
+  checkpoint?: string | undefined;
+  isFinalAttempt?: boolean | undefined;
+}
diff --git a/src/types/index.ts b/src/types/index.ts
index 9d7088d..8968dd3 100644
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -11,3 +11,4 @@
 export * from './errors.js';
 export * from './config.js';
 export * from './agents.js';
+export * from './audit.js';