fix(agent): detect case-insensitive Windows configuration collisions

src/agent/configurator.ts

@@ -990,21 +990,29 @@ function writeTarget(path: string): string {
   }
 }
 
+export function configurationTargetIdentity(
+  targetPath: string,
+  platform: NodeJS.Platform = process.platform,
+): string {
+  return platform === 'win32' ? targetPath.toLowerCase() : targetPath;
+}
+
 function hasWeakPermissions(mode: number): boolean {
   return process.platform !== 'win32' && (mode & 0o077) !== 0;
 }
 
 function assertDistinctConfigurationTargets(prepared: PreparedAgentFile[]): void {
   const targets = new Set<string>();
   for (const file of prepared) {
-    if (targets.has(file.targetPath)) {
+    const identity = configurationTargetIdentity(file.targetPath);
+    if (targets.has(identity)) {
       throw new CLIError(
         `Multiple agent configuration paths resolve to ${file.targetPath}.`,
         ExitCode.GENERAL,
         'No files were changed. Use distinct configuration paths and retry.',
       );
     }
-    targets.add(file.targetPath);
+    targets.add(identity);
   }
 }
 

test/agent/configurator.test.ts

@@ -21,6 +21,7 @@ import { parse as parseYaml } from 'yaml';
 
 import {
   applyAgentConfigurations,
+  configurationTargetIdentity,
   prepareAgentConfigurations,
 } from '../../src/agent/configurator';
 import { AGENT_IDS, type AgentId, type AgentSetupOptions } from '../../src/agent/types';
@@ -462,6 +463,26 @@ describe('agent configurator', () => {
     expect(existsSync(shared)).toBe(false);
   });
 
+  it('compares configuration target paths case-insensitively on Windows', () => {
+    expect(configurationTargetIdentity('C:\\Users\\Alice\\settings.json', 'win32'))
+      .toBe('c:\\users\\alice\\settings.json');
+    expect(configurationTargetIdentity('/Users/Alice/settings.json', 'linux'))
+      .toBe('/Users/Alice/settings.json');
+  });
+
+  it('rejects duplicate targets that differ only by case on Windows', () => {
+    if (process.platform !== 'win32') return;
+
+    const shared = join(home, 'shared-agent-config');
+    mkdirSync(shared, { recursive: true });
+    const differentlyCased = shared.replace('shared-agent-config', 'SHARED-AGENT-CONFIG');
+
+    expect(() => prepareAgentConfigurations(setupOptions(
+      ['claude-code', 'pi'],
+      { env: { CLAUDE_CONFIG_DIR: shared, PI_CODING_AGENT_DIR: differentlyCased } },
+    ))).toThrow('Multiple agent configuration paths');
+  });
+
   it('removes the setup lock when installation receives an exit signal', async () => {
     if (process.platform === 'win32') return;
     const configuratorUrl = pathToFileURL(