fix(core): strip redundant plan directory prefix in plan mode

This fix updates `resolveAndValidatePlanPath` to detect and strip redundant prefixes from file paths when the agent provides a path that begins with the basename of the plans directory (e.g., stripping `conductor/` when writing to `conductor/product.md` inside the `conductor` plan directory).

 This prevents the creation of nested directories (e.g., `conductor/conductor/product.md`) while maintaining path compatibility between Plan Mode and Execution Mode.

packages/core/src/utils/planUtils.test.ts

@@ -8,7 +8,11 @@ import { describe, it, expect, beforeEach, afterEach } from 'vitest';
 import path from 'node:path';
 import * as fs from 'node:fs';
 import os from 'node:os';
-import { validatePlanPath, validatePlanContent } from './planUtils.js';
+import {
+  validatePlanPath,
+  validatePlanContent,
+  resolveAndValidatePlanPath,
+} from './planUtils.js';
 
 describe('planUtils', () => {
   let tempRootDir: string;
@@ -29,6 +33,56 @@ describe('planUtils', () => {
     }
   });
 
+  describe('resolveAndValidatePlanPath', () => {
+    it('should strip redundant prefix matching plansDir basename', () => {
+      const result = resolveAndValidatePlanPath('plans/test.md', plansDir);
+      expect(result).toBe(path.join(plansDir, 'test.md'));
+    });
+
+    it('should strip redundant prefix when path starts with ./', () => {
+      const result = resolveAndValidatePlanPath('./plans/test.md', plansDir);
+      expect(result).toBe(path.join(plansDir, 'test.md'));
+    });
+
+    it('should strip redundant prefix matching plansDir basename (with nested path)', () => {
+      const result = resolveAndValidatePlanPath(
+        'plans/nested/test.md',
+        plansDir,
+      );
+      expect(result).toBe(path.join(plansDir, 'nested/test.md'));
+    });
+
+    it('should handle standard paths without the prefix', () => {
+      const result = resolveAndValidatePlanPath('test.md', plansDir);
+      expect(result).toBe(path.join(plansDir, 'test.md'));
+    });
+
+    it('should handle standard paths with ./ prefix', () => {
+      const result = resolveAndValidatePlanPath('./test.md', plansDir);
+      expect(result).toBe(path.join(plansDir, 'test.md'));
+    });
+
+    it('should throw if path is empty after stripping prefix', () => {
+      expect(() => resolveAndValidatePlanPath('plans', plansDir)).toThrowError(
+        /must include a filename/,
+      );
+      expect(() => resolveAndValidatePlanPath('plans/', plansDir)).toThrowError(
+        /must include a filename/,
+      );
+      expect(() =>
+        resolveAndValidatePlanPath('./plans', plansDir),
+      ).toThrowError(/must include a filename/);
+    });
+
+    it('should handle mixed separators', () => {
+      const result = resolveAndValidatePlanPath(
+        'plans\\windows-style.md',
+        plansDir,
+      );
+      expect(result).toBe(path.join(plansDir, 'windows-style.md'));
+    });
+  });
+
   describe('validatePlanPath', () => {
     it('should return null for a valid path within plans directory', async () => {
       const planPath = 'test.md';

packages/core/src/utils/planUtils.ts

@@ -39,7 +39,33 @@ export function resolveAndValidatePlanPath(
     throw new Error('Plan file path must be non-empty.');
   }
 
-  const resolvedPath = path.resolve(plansDir, trimmedPath);
+  // Normalize separators to forward slashes for easier manipulation
+  const normalizedInput = trimmedPath.replace(/\\/g, '/');
+
+  // Prevent redundant nesting if the agent includes the plans directory name in the path.
+  // E.g. plansDir='/repo/conductor', planPath='conductor/test.md' -> we want '/repo/conductor/test.md'
+  // Also handle './conductor/test.md' or 'conductor/nested/test.md'
+  let normalizedPlanPath = normalizedInput;
+  const plansDirName = path.basename(plansDir);
+
+  // Split into segments and remove empty or '.' segments from the beginning
+  const segments = normalizedInput.split('/').filter((s) => s !== '');
+  if (segments[0] === '.') {
+    segments.shift();
+  }
+
+  if (segments[0] === plansDirName) {
+    // Strip the redundant prefix.
+    segments.shift();
+    normalizedPlanPath = segments.join('/');
+
+    // If the path was EXACTLY just the directory name (e.g. "conductor"), it's invalid for a file.
+    if (!normalizedPlanPath) {
+      throw new Error('Plan file path must include a filename.');
+    }
+  }
+
+  const resolvedPath = path.resolve(plansDir, normalizedPlanPath);
   const realPath = resolveToRealPath(resolvedPath);
   const realPlansDir = resolveToRealPath(plansDir);