diff --git a/src/utils/validation.ts b/src/utils/validation.ts
index 6240e15..3ea318a 100644
--- a/src/utils/validation.ts
+++ b/src/utils/validation.ts
@@ -107,3 +107,26 @@ export function safeValidateIdentifier(
   }
   return { success: false, error: result.error.issues[0]?.message ?? 'Validation failed' };
 }
+
+/**
+ * Validation schema for Tangled-specific DID (did:plc: format only)
+ */
+export const tangledDidSchema = z
+  .string()
+  .regex(/^did:plc:[a-z0-9]+$/, 'Invalid Tangled DID format. Expected: did:plc:...');
+
+/**
+ * Check if a string is a valid AT Protocol handle
+ * Returns true/false without throwing
+ */
+export function isValidHandle(handle: string): boolean {
+  return handleSchema.safeParse(handle).success;
+}
+
+/**
+ * Check if a string is a valid Tangled DID (did:plc: format)
+ * Returns true/false without throwing
+ */
+export function isValidTangledDid(did: string): boolean {
+  return tangledDidSchema.safeParse(did).success;
+}
diff --git a/tests/utils/validation.test.ts b/tests/utils/validation.test.ts
index 05379f7..aa6eef5 100644
--- a/tests/utils/validation.test.ts
+++ b/tests/utils/validation.test.ts
@@ -1,5 +1,7 @@
 import { describe, expect, it } from 'vitest';
 import {
+  isValidHandle,
+  isValidTangledDid,
   safeValidateDid,
   safeValidateHandle,
   safeValidateIdentifier,
@@ -136,3 +138,36 @@ describe('App Password Validation', () => {
     });
   });
 });
+
+describe('Boolean Validation Helpers', () => {
+  describe('isValidHandle', () => {
+    it('should return true for valid handles', () => {
+      expect(isValidHandle('user.bsky.social')).toBe(true);
+      expect(isValidHandle('markbennett.ca')).toBe(true);
+      expect(isValidHandle('sub.domain.example.com')).toBe(true);
+    });
+
+    it('should return false for invalid handles', () => {
+      expect(isValidHandle('invalid')).toBe(false);
+      expect(isValidHandle('.starts-with-dot.com')).toBe(false);
+      expect(isValidHandle('ends-with-dot.com.')).toBe(false);
+      expect(isValidHandle('has space.com')).toBe(false);
+      expect(isValidHandle('')).toBe(false);
+    });
+  });
+
+  describe('isValidTangledDid', () => {
+    it('should return true for valid Tangled DIDs (did:plc: format)', () => {
+      expect(isValidTangledDid('did:plc:b2mcbcamkwyznc5fkplwlxbf')).toBe(true);
+      expect(isValidTangledDid('did:plc:abc123xyz')).toBe(true);
+    });
+
+    it('should return false for invalid Tangled DIDs', () => {
+      expect(isValidTangledDid('did:plc:')).toBe(false);
+      expect(isValidTangledDid('did:plc:ABC123')).toBe(false); // uppercase not allowed
+      expect(isValidTangledDid('did:web:example.com')).toBe(false); // wrong method
+      expect(isValidTangledDid('not-a-did')).toBe(false);
+      expect(isValidTangledDid('')).toBe(false);
+    });
+  });
+});