fix(plan): isolate plan files per session (#18757)

docs/cli/plan-mode.md

@@ -99,7 +99,7 @@ These are the only allowed tools:
 - **MCP Tools (Read):** Read-only [MCP tools] (e.g., `github_read_issue`,
   `postgres_read_schema`) are allowed.
 - **Planning (Write):** [`write_file`] and [`replace`] ONLY allowed for `.md`
-  files in the `~/.gemini/tmp/<project>/plans/` directory.
+  files in the `~/.gemini/tmp/<project>/<session-id>/plans/` directory.
 - **Skills:** [`activate_skill`] (allows loading specialized instructions and
   resources in a read-only manner)
 

packages/cli/src/config/policy-engine.integration.test.ts

@@ -336,9 +336,9 @@ describe('Policy Engine Integration Tests', () => {
 
           // Valid plan file paths
           const validPaths = [
-            '/home/user/.gemini/tmp/a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2/plans/my-plan.md',
-            '/home/user/.gemini/tmp/a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2/plans/feature_auth.md',
-            '/home/user/.gemini/tmp/new-temp_dir_123/plans/plan.md', // new style of temp directory
+            '/home/user/.gemini/tmp/a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2/session-1/plans/my-plan.md',
+            '/home/user/.gemini/tmp/a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2/session-1/plans/feature_auth.md',
+            '/home/user/.gemini/tmp/new-temp_dir_123/session-1/plans/plan.md', // new style of temp directory
           ];
 
           for (const file_path of validPaths) {
@@ -365,7 +365,6 @@ describe('Policy Engine Integration Tests', () => {
             '/project/src/file.ts', // Workspace
             '/home/user/.gemini/tmp/a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2/plans/script.js', // Wrong extension
             '/home/user/.gemini/tmp/a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2/plans/../../../etc/passwd.md', // Path traversal
-            '/home/user/.gemini/tmp/a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2/plans/subdir/plan.md', // Subdirectory
             '/home/user/.gemini/non-tmp/new-temp_dir_123/plans/plan.md', // outside of temp dir
           ];
 

packages/core/src/config/config.ts

@@ -823,7 +823,7 @@ export class Config {
       (params.shellToolInactivityTimeout ?? 300) * 1000; // 5 minutes
     this.extensionManagement = params.extensionManagement ?? true;
     this.enableExtensionReloading = params.enableExtensionReloading ?? false;
-    this.storage = new Storage(this.targetDir);
+    this.storage = new Storage(this.targetDir, this.sessionId);
 
     this.fakeResponses = params.fakeResponses;
     this.recordResponses = params.recordResponses;

packages/core/src/config/storage.test.ts

@@ -154,12 +154,24 @@ describe('Storage – additional helpers', () => {
     expect(Storage.getGlobalBinDir()).toBe(expected);
   });
 
-  it('getProjectTempPlansDir returns ~/.gemini/tmp/<identifier>/plans', async () => {
+  it('getProjectTempPlansDir returns ~/.gemini/tmp/<identifier>/plans when no sessionId is provided', async () => {
     await storage.initialize();
     const tempDir = storage.getProjectTempDir();
     const expected = path.join(tempDir, 'plans');
     expect(storage.getProjectTempPlansDir()).toBe(expected);
   });
+
+  it('getProjectTempPlansDir returns ~/.gemini/tmp/<identifier>/<sessionId>/plans when sessionId is provided', async () => {
+    const sessionId = 'test-session-id';
+    const storageWithSession = new Storage(projectRoot, sessionId);
+    ProjectRegistry.prototype.getShortId = vi
+      .fn()
+      .mockReturnValue(PROJECT_SLUG);
+    await storageWithSession.initialize();
+    const tempDir = storageWithSession.getProjectTempDir();
+    const expected = path.join(tempDir, sessionId, 'plans');
+    expect(storageWithSession.getProjectTempPlansDir()).toBe(expected);
+  });
 });
 
 describe('Storage - System Paths', () => {

packages/core/src/config/storage.ts

@@ -20,11 +20,13 @@ const AGENTS_DIR_NAME = '.agents';
 
 export class Storage {
   private readonly targetDir: string;
+  private readonly sessionId: string | undefined;
   private projectIdentifier: string | undefined;
   private initPromise: Promise<void> | undefined;
 
-  constructor(targetDir: string) {
+  constructor(targetDir: string, sessionId?: string) {
     this.targetDir = targetDir;
+    this.sessionId = sessionId;
   }
 
   static getGlobalGeminiDir(): string {
@@ -242,9 +244,19 @@ export class Storage {
   }
 
   getProjectTempPlansDir(): string {
+    if (this.sessionId) {
+      return path.join(this.getProjectTempDir(), this.sessionId, 'plans');
+    }
     return path.join(this.getProjectTempDir(), 'plans');
   }
 
+  getProjectTempTasksDir(): string {
+    if (this.sessionId) {
+      return path.join(this.getProjectTempDir(), this.sessionId, 'tasks');
+    }
+    return path.join(this.getProjectTempDir(), 'tasks');
+  }
+
   getExtensionsDir(): string {
     return path.join(this.getGeminiDir(), 'extensions');
   }

packages/core/src/policy/policies/plan.toml

@@ -53,4 +53,4 @@ toolName = ["write_file", "replace"]
 decision = "allow"
 priority = 70
 modes = ["plan"]
-argsPattern = "\"file_path\":\"[^\"]+/\\.gemini/tmp/[a-zA-Z0-9_-]+/plans/[a-zA-Z0-9_-]+\\.md\""
+argsPattern = "\"file_path\":\"[^\"]+/\\.gemini/tmp/[a-zA-Z0-9_-]+/[a-zA-Z0-9_-]+/plans/[a-zA-Z0-9_-]+\\.md\""