diff --git a/src/cli.ts b/src/cli.ts
index 7fc4c203..e27fec95 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -13,6 +13,7 @@ import { getSessionManager } from './session-manager.js';
 import { getTaskQueue } from './task-queue.js';
 import { getRalphLoop } from './ralph-loop.js';
 import { getStore } from './state-store.js';
+import { getErrorMessage } from './types.js';
 
 const program = new Command();
 
@@ -40,7 +41,7 @@ sessionCmd
       console.log(`  Working directory: ${session.workingDir}`);
       console.log(`  PID: ${session.pid}`);
     } catch (err) {
-      console.error(chalk.red(`✗ Failed to start session: ${(err as Error).message}`));
+      console.error(chalk.red(`✗ Failed to start session: ${getErrorMessage(err)}`));
       process.exit(1);
     }
   });
@@ -54,7 +55,7 @@ sessionCmd
       await manager.stopSession(id);
       console.log(chalk.green(`✓ Session stopped: ${id}`));
     } catch (err) {
-      console.error(chalk.red(`✗ Failed to stop session: ${(err as Error).message}`));
+      console.error(chalk.red(`✗ Failed to stop session: ${getErrorMessage(err)}`));
       process.exit(1);
     }
   });
@@ -474,7 +475,7 @@ program
       console.log(chalk.green(`\n✓ Web interface running at http://localhost:${port}`));
       console.log(chalk.gray('  Press Ctrl+C to stop\n'));
     } catch (err) {
-      console.error(chalk.red(`✗ Failed to start web server: ${(err as Error).message}`));
+      console.error(chalk.red(`✗ Failed to start web server: ${getErrorMessage(err)}`));
       process.exit(1);
     }
   });
@@ -496,7 +497,7 @@ program
         port,
       });
     } catch (err) {
-      console.error(chalk.red(`✗ Failed to start TUI: ${(err as Error).message}`));
+      console.error(chalk.red(`✗ Failed to start TUI: ${getErrorMessage(err)}`));
       process.exit(1);
     }
   });
diff --git a/src/ralph-loop.ts b/src/ralph-loop.ts
index 695b483a..a996886f 100644
--- a/src/ralph-loop.ts
+++ b/src/ralph-loop.ts
@@ -19,7 +19,7 @@ import { getTaskQueue, TaskQueue } from './task-queue.js';
 import { getStore, StateStore } from './state-store.js';
 import { Session } from './session.js';
 import { Task } from './task.js';
-import { RalphLoopStatus } from './types.js';
+import { RalphLoopStatus, getErrorMessage } from './types.js';
 
 /**
  * Events emitted by RalphLoop
@@ -304,10 +304,10 @@ export class RalphLoop extends EventEmitter {
 
       this.emit('taskAssigned', task.id, session.id);
     } catch (err) {
-      task.fail((err as Error).message);
+      task.fail(getErrorMessage(err));
       session.clearTask();
       this.taskQueue.updateTask(task);
-      this.emit('taskFailed', task.id, (err as Error).message);
+      this.emit('taskFailed', task.id, getErrorMessage(err));
     }
   }
 
diff --git a/src/screen-manager.ts b/src/screen-manager.ts
index 98df15ea..c6b443a0 100644
--- a/src/screen-manager.ts
+++ b/src/screen-manager.ts
@@ -19,7 +19,7 @@ import { spawn, execSync } from 'node:child_process';
 import { existsSync, readFileSync, writeFileSync, mkdirSync } from 'node:fs';
 import { dirname, join } from 'node:path';
 import { homedir } from 'node:os';
-import { ScreenSession, ProcessStats, ScreenSessionWithStats } from './types.js';
+import { ScreenSession, ProcessStats, ScreenSessionWithStats, getErrorMessage } from './types.js';
 
 /** Path to persisted screen session metadata */
 const SCREENS_FILE = join(homedir(), '.claudeman', 'screens.json');
@@ -213,7 +213,7 @@ export class ScreenManager extends EventEmitter {
 
       return screen;
     } catch (err) {
-      throw new Error(`Failed to create screen: ${(err as Error).message}`);
+      throw new Error(`Failed to create screen: ${getErrorMessage(err)}`);
     }
   }
 
diff --git a/src/types.ts b/src/types.ts
index 1e6299d6..ddcde499 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -615,3 +615,43 @@ export function createInitialState(): AppState {
     config: { ...DEFAULT_CONFIG },
   };
 }
+
+// ========== Error Handling Utilities ==========
+
+/**
+ * Type guard to check if a value is an Error instance
+ * @param value The value to check
+ * @returns True if the value is an Error instance
+ */
+export function isError(value: unknown): value is Error {
+  return value instanceof Error;
+}
+
+/**
+ * Safely extracts an error message from an unknown caught value.
+ * Handles the TypeScript 4.4+ unknown error type in catch blocks.
+ *
+ * @param error The caught error (type unknown in strict mode)
+ * @returns A string error message
+ *
+ * @example
+ * ```typescript
+ * try {
+ *   await riskyOperation();
+ * } catch (err) {
+ *   console.error('Failed:', getErrorMessage(err));
+ * }
+ * ```
+ */
+export function getErrorMessage(error: unknown): string {
+  if (isError(error)) {
+    return error.message;
+  }
+  if (typeof error === 'string') {
+    return error;
+  }
+  if (error && typeof error === 'object' && 'message' in error) {
+    return String((error as { message: unknown }).message);
+  }
+  return 'An unknown error occurred';
+}
diff --git a/src/web/server.ts b/src/web/server.ts
index 30d1791f..58eec2ff 100644
--- a/src/web/server.ts
+++ b/src/web/server.ts
@@ -23,19 +23,20 @@ import { ScreenManager } from '../screen-manager.js';
 import { getStore } from '../state-store.js';
 import { generateClaudeMd } from '../templates/claude-md.js';
 import { v4 as uuidv4 } from 'uuid';
-import type {
-  CreateSessionRequest,
-  RunPromptRequest,
-  SessionInputRequest,
-  ResizeRequest,
-  CreateCaseRequest,
-  QuickStartRequest,
-  CreateScheduledRunRequest,
-  QuickRunRequest,
-  ApiResponse,
-  SessionResponse,
-  QuickStartResponse,
-  CaseInfo,
+import {
+  getErrorMessage,
+  type CreateSessionRequest,
+  type RunPromptRequest,
+  type SessionInputRequest,
+  type ResizeRequest,
+  type CreateCaseRequest,
+  type QuickStartRequest,
+  type CreateScheduledRunRequest,
+  type QuickRunRequest,
+  type ApiResponse,
+  type SessionResponse,
+  type QuickStartResponse,
+  type CaseInfo,
 } from '../types.js';
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
@@ -376,7 +377,7 @@ export class WebServer extends EventEmitter {
         this.broadcast('session:updated', { session: session.toDetailedState() });
         return { success: true, message: 'Interactive session started' };
       } catch (err) {
-        return { error: (err as Error).message };
+        return { error: getErrorMessage(err) };
       }
     });
 
@@ -399,7 +400,7 @@ export class WebServer extends EventEmitter {
         this.broadcast('session:updated', { session: session.toDetailedState() });
         return { success: true, message: 'Shell session started' };
       } catch (err) {
-        return { error: (err as Error).message };
+        return { error: getErrorMessage(err) };
       }
     });
 
@@ -580,7 +581,7 @@ export class WebServer extends EventEmitter {
           respawnStatus: controller.getStatus(),
         };
       } catch (err) {
-        return { error: (err as Error).message };
+        return { error: getErrorMessage(err) };
       }
     });
 
@@ -694,7 +695,7 @@ export class WebServer extends EventEmitter {
       } catch (err) {
         // Clean up session on error too
         await this.cleanupSession(session.id);
-        return { success: false, sessionId: session.id, error: (err as Error).message };
+        return { success: false, sessionId: session.id, error: getErrorMessage(err) };
       }
     });
 
@@ -809,7 +810,7 @@ export class WebServer extends EventEmitter {
 
         return { success: true, case: { name, path: casePath } };
       } catch (err) {
-        return { success: false, error: (err as Error).message };
+        return { success: false, error: getErrorMessage(err) };
       }
     });
 
@@ -868,7 +869,7 @@ export class WebServer extends EventEmitter {
         this.broadcast('case:linked', { name, path: expandedPath });
         return { success: true, case: { name, path: expandedPath } };
       } catch (err) {
-        return { success: false, error: (err as Error).message };
+        return { success: false, error: getErrorMessage(err) };
       }
     });
 
@@ -944,7 +945,7 @@ export class WebServer extends EventEmitter {
 
           this.broadcast('case:created', { name: caseName, path: casePath });
         } catch (err) {
-          return { success: false, error: `Failed to create case: ${(err as Error).message}` };
+          return { success: false, error: `Failed to create case: ${getErrorMessage(err)}` };
         }
       }
 
@@ -996,7 +997,7 @@ export class WebServer extends EventEmitter {
       } catch (err) {
         // Clean up session on error to prevent orphaned resources
         await this.cleanupSession(session.id);
-        return { success: false, error: (err as Error).message };
+        return { success: false, error: getErrorMessage(err) };
       }
     });
 
@@ -1026,7 +1027,7 @@ export class WebServer extends EventEmitter {
         writeFileSync(settingsPath, JSON.stringify(settings, null, 2));
         return { success: true };
       } catch (err) {
-        return { error: (err as Error).message };
+        return { error: getErrorMessage(err) };
       }
     });
 
@@ -1415,7 +1416,7 @@ export class WebServer extends EventEmitter {
         // Small pause between iterations
         await new Promise(r => setTimeout(r, 2000));
       } catch (err) {
-        addLog(`Error: ${(err as Error).message}`);
+        addLog(`Error: ${getErrorMessage(err)}`);
         this.broadcast('scheduled:updated', run);
 
         // Clean up the session on error too