diff --git a/tests/unit/cliproxy/account-registry-optional-nickname.test.ts b/tests/unit/cliproxy/account-registry-optional-nickname.test.ts
new file mode 100644
index 00000000..04ef857a
--- /dev/null
+++ b/tests/unit/cliproxy/account-registry-optional-nickname.test.ts
@@ -0,0 +1,101 @@
+import { describe, expect, it } from 'bun:test';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { runWithScopedCcsHome } from '../../../src/utils/config-manager';
+
+async function loadAccountManager() {
+  return import(`../../../src/cliproxy/account-manager?optional-nickname=${Date.now()}`);
+}
+
+async function withIsolatedHome<T>(fn: () => Promise<T> | T): Promise<T> {
+  const testDir = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-optional-nickname-'));
+  try {
+    return await runWithScopedCcsHome(testDir, fn);
+  } finally {
+    fs.rmSync(testDir, { recursive: true, force: true });
+  }
+}
+
+describe('registerAccount optional nickname flow', () => {
+  it('uses a filename-derived id when Kiro/GHCP nickname is omitted', async () => {
+    const account = await withIsolatedHome(async () => {
+      const { registerAccount } = await loadAccountManager();
+      return registerAccount('kiro', 'kiro-github-ABC123.json');
+    });
+
+    expect(account.id).toBe('github-ABC123');
+    expect(account.nickname).toBe('github-ABC123');
+  });
+
+  it('falls back to provider-scoped sequential ids when the filename is not descriptive', async () => {
+    const { first, second } = await withIsolatedHome(async () => {
+      const { registerAccount } = await loadAccountManager();
+      return {
+        first: registerAccount('kiro', 'kiro-nomail.json'),
+        second: registerAccount('kiro', 'kiro-second.json'),
+      };
+    });
+
+    expect(first.id).toBe('kiro-1');
+    expect(first.nickname).toBe('kiro-1');
+    expect(second.id).toBe('kiro-2');
+    expect(second.nickname).toBe('kiro-2');
+  });
+
+  it('keeps user nicknames optional metadata separate from internal ids', async () => {
+    const account = await withIsolatedHome(async () => {
+      const { registerAccount } = await loadAccountManager();
+      return registerAccount('ghcp', 'ghcp-amazon-XYZ789.json', undefined, 'work');
+    });
+
+    expect(account.id).toBe('amazon-XYZ789');
+    expect(account.nickname).toBe('work');
+  });
+
+  it('preserves an existing custom nickname when the same token file is re-registered', async () => {
+    const reauthenticated = await withIsolatedHome(async () => {
+      const { registerAccount } = await loadAccountManager();
+      registerAccount('kiro', 'kiro-github-ABC123.json', undefined, 'work');
+      return registerAccount('kiro', 'kiro-github-ABC123.json');
+    });
+
+    expect(reauthenticated.id).toBe('github-ABC123');
+    expect(reauthenticated.nickname).toBe('work');
+  });
+
+  it('rejects nickname collisions against existing account ids and nicknames', async () => {
+    await withIsolatedHome(async () => {
+      const { registerAccount, renameAccount } = await loadAccountManager();
+      registerAccount('kiro', 'kiro-github-ABC123.json');
+      const second = registerAccount('kiro', 'kiro-google-XYZ789.json', undefined, 'personal');
+
+      expect(() =>
+        registerAccount('kiro', 'kiro-google-NEW123.json', undefined, 'github-ABC123')
+      ).toThrow(/already exists/i);
+      expect(() => renameAccount('kiro', second.id, 'github-ABC123')).toThrow(/already used/i);
+    });
+  });
+
+  it('avoids auto-generated ids that would collide with an existing nickname', async () => {
+    const added = await withIsolatedHome(async () => {
+      const { registerAccount } = await loadAccountManager();
+      registerAccount('kiro', 'kiro-github-ABC123.json', undefined, 'google-XYZ789');
+      return registerAccount('kiro', 'kiro-google-XYZ789.json');
+    });
+
+    expect(added.id).toBe('kiro-1');
+    expect(added.nickname).toBe('kiro-1');
+  });
+
+  it('does not resolve ambiguous nickname prefixes to the first generated account', async () => {
+    const match = await withIsolatedHome(async () => {
+      const { registerAccount, findAccountByQuery } = await loadAccountManager();
+      registerAccount('kiro', 'kiro-github-ABC123.json');
+      registerAccount('kiro', 'kiro-github-DEF456.json');
+      return findAccountByQuery('kiro', 'github');
+    });
+
+    expect(match).toBeNull();
+  });
+});
diff --git a/tests/unit/cliproxy/oauth-handler-paste-callback.test.ts b/tests/unit/cliproxy/oauth-handler-paste-callback.test.ts
index 1b8da8a9..9ad75161 100644
--- a/tests/unit/cliproxy/oauth-handler-paste-callback.test.ts
+++ b/tests/unit/cliproxy/oauth-handler-paste-callback.test.ts
@@ -102,3 +102,54 @@ describe('resolvePasteCallbackAuthUrl', () => {
     expect(request.headers['Authorization']).toBe('Bearer test-mgmt-key');
   });
 });
+
+describe('getCliAuthNicknameError', () => {
+  it('allows omitted nicknames for no-email providers', async () => {
+    const { getCliAuthNicknameError } = await import(
+      `../../../src/cliproxy/auth/oauth-handler?cli-nickname-empty=${Date.now()}`
+    );
+
+    expect(getCliAuthNicknameError('kiro', undefined, [])).toBeNull();
+    expect(getCliAuthNicknameError('ghcp', undefined, [])).toBeNull();
+  });
+
+  it('rejects invalid supplied nicknames before OAuth starts', async () => {
+    const { getCliAuthNicknameError } = await import(
+      `../../../src/cliproxy/auth/oauth-handler?cli-nickname-invalid=${Date.now()}`
+    );
+
+    expect(getCliAuthNicknameError('kiro', 'bad nickname', [])).toBe(
+      'Nickname cannot contain whitespace'
+    );
+  });
+
+  it('rejects supplied nicknames that collide with existing ids or nicknames', async () => {
+    const { getCliAuthNicknameError } = await import(
+      `../../../src/cliproxy/auth/oauth-handler?cli-nickname-conflict=${Date.now()}`
+    );
+    const existingAccounts = [
+      { id: 'github-ABC123', nickname: 'work' },
+      { id: 'ghcp-2', nickname: 'personal' },
+    ];
+
+    expect(getCliAuthNicknameError('ghcp', 'github-ABC123', existingAccounts)).toBe(
+      'Nickname "github-ABC123" is already in use. Choose a different one.'
+    );
+    expect(getCliAuthNicknameError('ghcp', 'work', existingAccounts)).toBe(
+      'Nickname "work" is already in use. Choose a different one.'
+    );
+  });
+
+  it('allows reauth when the supplied nickname already belongs to the same account', async () => {
+    const { getCliAuthNicknameError } = await import(
+      `../../../src/cliproxy/auth/oauth-handler?cli-nickname-reauth=${Date.now()}`
+    );
+    const existingAccounts = [
+      { id: 'github-ABC123', nickname: 'work' },
+      { id: 'amazon-XYZ789', nickname: 'personal' },
+    ];
+
+    expect(getCliAuthNicknameError('kiro', 'work', existingAccounts, 'github-ABC123')).toBeNull();
+    expect(getCliAuthNicknameError('kiro', 'github-ABC123', existingAccounts, 'github-ABC123')).toBeNull();
+  });
+});
diff --git a/tests/unit/web-server/cliproxy-auth-routes-manual-callback.test.ts b/tests/unit/web-server/cliproxy-auth-routes-manual-callback.test.ts
new file mode 100644
index 00000000..eb7ccb03
--- /dev/null
+++ b/tests/unit/web-server/cliproxy-auth-routes-manual-callback.test.ts
@@ -0,0 +1,145 @@
+import { afterAll, afterEach, beforeAll, beforeEach, describe, expect, it } from 'bun:test';
+import express from 'express';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import * as http from 'http';
+import type { Server } from 'http';
+import cliproxyAuthRoutes from '../../../src/web-server/routes/cliproxy-auth-routes';
+import { restoreFetch, mockFetch } from '../../mocks';
+
+describe('cliproxy-auth-routes manual callback nickname persistence', () => {
+  let server: Server;
+  let baseUrl = '';
+  let tempHome = '';
+  let originalCcsHome: string | undefined;
+
+  beforeAll(async () => {
+    const app = express();
+    app.use(express.json());
+    app.use('/api/cliproxy/auth', cliproxyAuthRoutes);
+
+    await new Promise<void>((resolve, reject) => {
+      server = app.listen(0, '127.0.0.1');
+      const onError = (error: Error) => reject(error);
+      server.once('error', onError);
+      server.once('listening', () => {
+        server.off('error', onError);
+        resolve();
+      });
+    });
+
+    const address = server.address();
+    if (!address || typeof address === 'string') {
+      throw new Error('Unable to resolve test server port');
+    }
+
+    baseUrl = `http://127.0.0.1:${address.port}`;
+  });
+
+  afterAll(async () => {
+    await new Promise<void>((resolve) => server.close(() => resolve()));
+  });
+
+  beforeEach(() => {
+    tempHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-cliproxy-manual-callback-'));
+    originalCcsHome = process.env.CCS_HOME;
+    process.env.CCS_HOME = tempHome;
+  });
+
+  afterEach(() => {
+    restoreFetch();
+
+    if (originalCcsHome === undefined) {
+      delete process.env.CCS_HOME;
+    } else {
+      process.env.CCS_HOME = originalCcsHome;
+    }
+
+    fs.rmSync(tempHome, { recursive: true, force: true });
+  });
+
+  async function postJson(route: string, body: Record<string, unknown>) {
+    return await new Promise<{ status: number; body: unknown }>((resolve, reject) => {
+      const payload = JSON.stringify(body);
+      const url = new URL(`${baseUrl}${route}`);
+      const request = http.request(
+        {
+          method: 'POST',
+          hostname: url.hostname,
+          port: url.port,
+          path: url.pathname,
+          headers: {
+            'Content-Type': 'application/json',
+            'Content-Length': Buffer.byteLength(payload),
+          },
+        },
+        (response) => {
+          let responseBody = '';
+          response.setEncoding('utf8');
+          response.on('data', (chunk) => {
+            responseBody += chunk;
+          });
+          response.on('end', () => {
+            resolve({
+              status: response.statusCode || 0,
+              body: responseBody ? JSON.parse(responseBody) : null,
+            });
+          });
+        }
+      );
+
+      request.on('error', reject);
+      request.write(payload);
+      request.end();
+    });
+  }
+
+  it('persists the supplied nickname for Kiro social start-url flows after callback submission', async () => {
+    mockFetch([
+      {
+        url: /\/v0\/management\/kiro-auth-url\?is_webui=true&method=google$/,
+        response: {
+          auth_url: 'https://auth.example.com/authorize?state=state-123',
+          state: 'state-123',
+        },
+      },
+      {
+        url: /\/v0\/management\/oauth-callback$/,
+        method: 'POST',
+        response: { status: 'ok' },
+      },
+    ]);
+
+    const startResponse = await postJson('/api/cliproxy/auth/kiro/start-url', {
+        nickname: 'work',
+        kiroMethod: 'google',
+      });
+    expect(startResponse.status).toBe(200);
+
+    const tokenDir = path.join(tempHome, '.ccs', 'cliproxy', 'auth');
+    fs.mkdirSync(tokenDir, { recursive: true });
+    fs.writeFileSync(
+      path.join(tokenDir, 'kiro-github-ABC123.json'),
+      JSON.stringify({ type: 'kiro' }),
+      'utf8'
+    );
+
+    const callbackResponse = await postJson('/api/cliproxy/auth/kiro/submit-callback', {
+        redirectUrl: 'http://localhost/callback?code=abc123&state=state-123',
+      });
+
+    expect(callbackResponse.status).toBe(200);
+
+    const registryPath = path.join(tempHome, '.ccs', 'cliproxy', 'accounts.json');
+    const registry = JSON.parse(fs.readFileSync(registryPath, 'utf8')) as {
+      providers: {
+        kiro: {
+          accounts: Record<string, { nickname?: string }>;
+        };
+      };
+    };
+
+    expect(registry.providers.kiro.accounts['github-ABC123']?.nickname).toBe('work');
+  });
+});
diff --git a/tests/unit/web-server/cliproxy-auth-routes.test.ts b/tests/unit/web-server/cliproxy-auth-routes.test.ts
index 9314f32c..ec2ce8d3 100644
--- a/tests/unit/web-server/cliproxy-auth-routes.test.ts
+++ b/tests/unit/web-server/cliproxy-auth-routes.test.ts
@@ -1,6 +1,7 @@
 import { describe, expect, it } from 'bun:test';
 import {
   getStartAuthFailureMessage,
+  getStartAuthNicknameError,
   getStartUrlUnsupportedReason,
 } from '../../../src/web-server/routes/cliproxy-auth-routes';
 
@@ -43,3 +44,44 @@ describe('cliproxy-auth-routes start failure messaging', () => {
     expect(getStartAuthFailureMessage('kiro')).toBe('Authentication failed or was cancelled');
   });
 });
+
+describe('cliproxy-auth-routes nickname validation', () => {
+  it('allows Kiro and GHCP start requests without a nickname', () => {
+    expect(getStartAuthNicknameError('kiro', undefined, [])).toBeNull();
+    expect(getStartAuthNicknameError('ghcp', undefined, [])).toBeNull();
+  });
+
+  it('rejects invalid supplied nicknames for no-email providers', () => {
+    expect(getStartAuthNicknameError('kiro', 'bad nickname', [])).toEqual({
+      error: 'Nickname cannot contain whitespace',
+      code: 'INVALID_NICKNAME',
+    });
+  });
+
+  it('rejects nicknames that collide with an existing account id or nickname', () => {
+    const existingAccounts = [
+      { id: 'github-ABC123', nickname: 'work' },
+      { id: 'ghcp-2', nickname: 'personal' },
+    ];
+
+    expect(getStartAuthNicknameError('ghcp', 'github-ABC123', existingAccounts)).toEqual({
+      error: 'Nickname "github-ABC123" is already in use. Choose a different one.',
+      code: 'NICKNAME_EXISTS',
+    });
+
+    expect(getStartAuthNicknameError('ghcp', 'work', existingAccounts)).toEqual({
+      error: 'Nickname "work" is already in use. Choose a different one.',
+      code: 'NICKNAME_EXISTS',
+    });
+  });
+
+  it('allows reauth when the nickname already belongs to the same account', () => {
+    const existingAccounts = [
+      { id: 'github-ABC123', nickname: 'work' },
+      { id: 'ghcp-2', nickname: 'personal' },
+    ];
+
+    expect(getStartAuthNicknameError('kiro', 'work', existingAccounts, 'github-ABC123')).toBeNull();
+    expect(getStartAuthNicknameError('kiro', 'github-ABC123', existingAccounts, 'github-ABC123')).toBeNull();
+  });
+});