diff --git a/packages/core/src/agents/local-executor.test.ts b/packages/core/src/agents/local-executor.test.ts
index 2ecd305a04..32fc93f690 100644
--- a/packages/core/src/agents/local-executor.test.ts
+++ b/packages/core/src/agents/local-executor.test.ts
@@ -198,6 +198,27 @@ vi.mock('../utils/promptIdContext.js', async (importOriginal) => {
   };
 });
 
+vi.mock('../config/scoped-config.js', async (importOriginal) => {
+  const actual =
+    await importOriginal<typeof import('../config/scoped-config.js')>();
+  return {
+    ...actual,
+    runWithScopedWorkspaceContext: vi.fn(actual.runWithScopedWorkspaceContext),
+    createScopedWorkspaceContext: vi.fn(actual.createScopedWorkspaceContext),
+  };
+});
+
+import {
+  runWithScopedWorkspaceContext,
+  createScopedWorkspaceContext,
+} from '../config/scoped-config.js';
+const mockedRunWithScopedWorkspaceContext = vi.mocked(
+  runWithScopedWorkspaceContext,
+);
+const mockedCreateScopedWorkspaceContext = vi.mocked(
+  createScopedWorkspaceContext,
+);
+
 const MockedGeminiChat = vi.mocked(GeminiChat);
 const mockedGetDirectoryContextString = vi.mocked(getDirectoryContextString);
 const mockedPromptIdContext = vi.mocked(promptIdContext);
@@ -396,6 +417,8 @@ describe('LocalAgentExecutor', () => {
       );
     mockedLogAgentStart.mockReset();
     mockedLogAgentFinish.mockReset();
+    mockedRunWithScopedWorkspaceContext.mockClear();
+    mockedCreateScopedWorkspaceContext.mockClear();
     mockedPromptIdContext.getStore.mockReset();
     mockedPromptIdContext.run.mockImplementation((_id, fn) => fn());
 
@@ -885,6 +908,55 @@ describe('LocalAgentExecutor', () => {
     });
   });
 
+  describe('run (Workspace Scoping)', () => {
+    it('should use runWithScopedWorkspaceContext when workspaceDirectories is set', async () => {
+      const definition = createTestDefinition();
+      definition.workspaceDirectories = ['/tmp/extra-dir'];
+      const executor = await LocalAgentExecutor.create(
+        definition,
+        mockConfig,
+        onActivity,
+      );
+
+      // Mock a simple complete_task response so run() terminates
+      mockModelResponse([
+        {
+          name: COMPLETE_TASK_TOOL_NAME,
+          args: { finalResult: 'done' },
+          id: 'c1',
+        },
+      ]);
+
+      await executor.run({ goal: 'test' }, signal);
+
+      expect(mockedCreateScopedWorkspaceContext).toHaveBeenCalledOnce();
+      expect(mockedRunWithScopedWorkspaceContext).toHaveBeenCalledOnce();
+    });
+
+    it('should not use runWithScopedWorkspaceContext when workspaceDirectories is not set', async () => {
+      const definition = createTestDefinition();
+      const executor = await LocalAgentExecutor.create(
+        definition,
+        mockConfig,
+        onActivity,
+      );
+
+      // Mock a simple complete_task response so run() terminates
+      mockModelResponse([
+        {
+          name: COMPLETE_TASK_TOOL_NAME,
+          args: { finalResult: 'done' },
+          id: 'c1',
+        },
+      ]);
+
+      await executor.run({ goal: 'test' }, signal);
+
+      expect(mockedCreateScopedWorkspaceContext).not.toHaveBeenCalled();
+      expect(mockedRunWithScopedWorkspaceContext).not.toHaveBeenCalled();
+    });
+  });
+
   describe('run (Execution Loop and Logic)', () => {
     it('should log AgentFinish with error if run throws', async () => {
       const definition = createTestDefinition();
diff --git a/packages/core/src/agents/local-executor.ts b/packages/core/src/agents/local-executor.ts
index 83e3ee69b1..50a93ec7ff 100644
--- a/packages/core/src/agents/local-executor.ts
+++ b/packages/core/src/agents/local-executor.ts
@@ -73,6 +73,10 @@ import {
   formatBackgroundCompletionForModel,
 } from '../utils/fastAckHelper.js';
 import type { InjectionSource } from '../config/injectionService.js';
+import {
+  createScopedWorkspaceContext,
+  runWithScopedWorkspaceContext,
+} from '../config/scoped-config.js';
 import { CompleteTaskTool } from '../tools/complete-task.js';
 import { COMPLETE_TASK_TOOL_NAME } from '../tools/definitions/base-declarations.js';
 
@@ -521,6 +525,27 @@ export class LocalAgentExecutor<TOutput extends z.ZodTypeAny> {
    * @returns A promise that resolves to the agent's final output.
    */
   async run(inputs: AgentInputs, signal: AbortSignal): Promise<OutputObject> {
+    // If the agent definition declares additional workspace directories,
+    // wrap execution in a scoped workspace context. All calls to
+    // Config.getWorkspaceContext() within this scope will see the extended
+    // directories, without mutating the shared Config.
+    const dirs = this.definition.workspaceDirectories;
+    if (dirs && dirs.length > 0) {
+      const scopedCtx = createScopedWorkspaceContext(
+        this.context.config.getWorkspaceContext(),
+        dirs,
+      );
+      return runWithScopedWorkspaceContext(scopedCtx, () =>
+        this.runInternal(inputs, signal),
+      );
+    }
+    return this.runInternal(inputs, signal);
+  }
+
+  private async runInternal(
+    inputs: AgentInputs,
+    signal: AbortSignal,
+  ): Promise<OutputObject> {
     const startTime = Date.now();
     let turnCounter = 0;
     let terminateReason: AgentTerminateMode = AgentTerminateMode.ERROR;
diff --git a/packages/core/src/agents/memory-manager-agent.test.ts b/packages/core/src/agents/memory-manager-agent.test.ts
index c4f9879e8f..a917a415c4 100644
--- a/packages/core/src/agents/memory-manager-agent.test.ts
+++ b/packages/core/src/agents/memory-manager-agent.test.ts
@@ -150,4 +150,11 @@ describe('MemoryManagerAgent', () => {
     const agent = MemoryManagerAgent(createMockConfig());
     expect(agent.modelConfig.model).toBe('flash');
   });
+
+  it('should declare workspaceDirectories containing the global .gemini directory', () => {
+    const agent = MemoryManagerAgent(createMockConfig());
+    const globalGeminiDir = Storage.getGlobalGeminiDir();
+    expect(agent.workspaceDirectories).toBeDefined();
+    expect(agent.workspaceDirectories).toContain(globalGeminiDir);
+  });
 });
diff --git a/packages/core/src/agents/memory-manager-agent.ts b/packages/core/src/agents/memory-manager-agent.ts
index 1687da6d1f..95ef382ea3 100644
--- a/packages/core/src/agents/memory-manager-agent.ts
+++ b/packages/core/src/agents/memory-manager-agent.ts
@@ -131,6 +131,7 @@ reply with what you need, and exit. Do not search the codebase for the missing c
     modelConfig: {
       model: GEMINI_MODEL_ALIAS_FLASH,
     },
+    workspaceDirectories: [globalGeminiDir],
     toolConfig: {
       tools: [
         READ_FILE_TOOL_NAME,
diff --git a/packages/core/src/agents/registry.ts b/packages/core/src/agents/registry.ts
index 36fe970cdf..7ff547fba9 100644
--- a/packages/core/src/agents/registry.ts
+++ b/packages/core/src/agents/registry.ts
@@ -281,21 +281,11 @@ export class AgentRegistry {
     }
 
     // Register the memory manager agent as a replacement for the save_memory tool.
+    // The agent declares its own workspaceDirectories (e.g. ~/.gemini) which are
+    // scoped to its execution via runWithScopedWorkspaceContext in LocalAgentExecutor,
+    // keeping the main agent's workspace context clean.
     if (this.config.isMemoryManagerEnabled()) {
       this.registerLocalAgent(MemoryManagerAgent(this.config));
-
-      // Ensure the global .gemini directory is accessible to tools.
-      // This allows the save_memory agent to read and write to it.
-      // Access control is enforced by the Policy Engine (memory-manager.toml).
-      try {
-        const globalDir = Storage.getGlobalGeminiDir();
-        this.config.getWorkspaceContext().addDirectory(globalDir);
-      } catch (e) {
-        debugLogger.warn(
-          `[AgentRegistry] Could not add global .gemini directory to workspace:`,
-          e,
-        );
-      }
     }
   }
 
diff --git a/packages/core/src/agents/types.ts b/packages/core/src/agents/types.ts
index a7d921453b..6cf30bcfb4 100644
--- a/packages/core/src/agents/types.ts
+++ b/packages/core/src/agents/types.ts
@@ -215,6 +215,18 @@ export interface LocalAgentDefinition<
   // Optional configs
   toolConfig?: ToolConfig;
 
+  /**
+   * Optional additional workspace directories scoped to this agent.
+   * When provided, the agent receives a workspace context that extends
+   * the parent's with these directories. Other agents and the main
+   * session are unaffected. If omitted, the parent workspace context
+   * is inherited unchanged.
+   *
+   * Note: Filesystem root paths (e.g. `/` or `C:\`) are rejected at
+   * runtime to prevent accidentally granting access to the entire filesystem.
+   */
+  workspaceDirectories?: string[];
+
   /**
    * Optional inline MCP servers for this agent.
    */
diff --git a/packages/core/src/config/config.ts b/packages/core/src/config/config.ts
index d9ab9e597c..3d967c0fa7 100644
--- a/packages/core/src/config/config.ts
+++ b/packages/core/src/config/config.ts
@@ -132,6 +132,7 @@ import type { GenerateContentParameters } from '@google/genai';
 export type { MCPOAuthConfig, AnyToolInvocation, AnyDeclarativeTool };
 import type { AnyToolInvocation, AnyDeclarativeTool } from '../tools/tools.js';
 import { WorkspaceContext } from '../utils/workspaceContext.js';
+import { getWorkspaceContextOverride } from './scoped-config.js';
 import { Storage } from './storage.js';
 import type { ShellExecutionConfig } from '../services/shellExecutionService.js';
 import { FileExclusions } from '../utils/ignorePatterns.js';
@@ -2001,7 +2002,7 @@ export class Config implements McpContext, AgentLoopContext {
   }
 
   getWorkspaceContext(): WorkspaceContext {
-    return this.workspaceContext;
+    return getWorkspaceContextOverride() ?? this.workspaceContext;
   }
 
   getAgentRegistry(): AgentRegistry {
diff --git a/packages/core/src/config/scoped-config.test.ts b/packages/core/src/config/scoped-config.test.ts
new file mode 100644
index 0000000000..59689e25a9
--- /dev/null
+++ b/packages/core/src/config/scoped-config.test.ts
@@ -0,0 +1,206 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
+import * as os from 'node:os';
+import * as fs from 'node:fs';
+import * as path from 'node:path';
+import {
+  createScopedWorkspaceContext,
+  runWithScopedWorkspaceContext,
+  getWorkspaceContextOverride,
+} from './scoped-config.js';
+import { Config } from './config.js';
+
+vi.mock('../utils/paths.js', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('../utils/paths.js')>();
+  return {
+    ...actual,
+    resolveToRealPath: vi.fn((p) => p),
+    isSubpath: (parent: string, child: string) => child.startsWith(parent),
+  };
+});
+
+describe('createScopedWorkspaceContext', () => {
+  let tempDir: string;
+  let extraDir: string;
+  let config: Config;
+
+  beforeEach(() => {
+    tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'scoped-config-'));
+    extraDir = fs.mkdtempSync(path.join(os.tmpdir(), 'scoped-extra-'));
+
+    config = new Config({
+      targetDir: tempDir,
+      sessionId: 'test-session',
+      debugMode: false,
+      cwd: tempDir,
+      model: 'test-model',
+    });
+  });
+
+  afterEach(() => {
+    fs.rmSync(tempDir, { recursive: true, force: true });
+    fs.rmSync(extraDir, { recursive: true, force: true });
+  });
+
+  it('should include parent workspace directories', () => {
+    const scoped = createScopedWorkspaceContext(config.getWorkspaceContext(), [
+      extraDir,
+    ]);
+    const dirs = scoped.getDirectories();
+
+    expect(dirs).toContain(fs.realpathSync(tempDir));
+  });
+
+  it('should include additional directories', () => {
+    const scoped = createScopedWorkspaceContext(config.getWorkspaceContext(), [
+      extraDir,
+    ]);
+    const dirs = scoped.getDirectories();
+
+    expect(dirs).toContain(fs.realpathSync(extraDir));
+  });
+
+  it('should not modify the parent workspace context', () => {
+    const parentDirsBefore = [...config.getWorkspaceContext().getDirectories()];
+
+    createScopedWorkspaceContext(config.getWorkspaceContext(), [extraDir]);
+
+    const parentDirsAfter = [...config.getWorkspaceContext().getDirectories()];
+    expect(parentDirsAfter).toEqual(parentDirsBefore);
+    expect(parentDirsAfter).not.toContain(fs.realpathSync(extraDir));
+  });
+
+  it('should throw when parent context has no directories', () => {
+    const emptyCtx = { getDirectories: () => [] } as unknown as ReturnType<
+      typeof config.getWorkspaceContext
+    >;
+    expect(() => createScopedWorkspaceContext(emptyCtx, [extraDir])).toThrow(
+      'parent has no directories',
+    );
+  });
+
+  it('should return parent context unchanged when additionalDirectories is empty', () => {
+    const parentCtx = config.getWorkspaceContext();
+    const scoped = createScopedWorkspaceContext(parentCtx, []);
+    expect(scoped).toBe(parentCtx);
+  });
+
+  it('should throw when adding a filesystem root directory', () => {
+    expect(() =>
+      createScopedWorkspaceContext(config.getWorkspaceContext(), ['/']),
+    ).toThrow('Cannot add filesystem root');
+  });
+});
+
+describe('runWithScopedWorkspaceContext', () => {
+  let tempDir: string;
+  let extraDir: string;
+  let config: Config;
+
+  beforeEach(() => {
+    tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'scoped-run-'));
+    extraDir = fs.mkdtempSync(path.join(os.tmpdir(), 'scoped-run-extra-'));
+
+    config = new Config({
+      targetDir: tempDir,
+      sessionId: 'test-session',
+      debugMode: false,
+      cwd: tempDir,
+      model: 'test-model',
+    });
+  });
+
+  afterEach(() => {
+    fs.rmSync(tempDir, { recursive: true, force: true });
+    fs.rmSync(extraDir, { recursive: true, force: true });
+  });
+
+  it('should override Config.getWorkspaceContext() within scope', () => {
+    const scoped = createScopedWorkspaceContext(config.getWorkspaceContext(), [
+      extraDir,
+    ]);
+
+    runWithScopedWorkspaceContext(scoped, () => {
+      const ctx = config.getWorkspaceContext();
+      expect(ctx).toBe(scoped);
+      expect(ctx.getDirectories()).toContain(fs.realpathSync(extraDir));
+    });
+  });
+
+  it('should not affect Config.getWorkspaceContext() outside scope', () => {
+    const scoped = createScopedWorkspaceContext(config.getWorkspaceContext(), [
+      extraDir,
+    ]);
+
+    runWithScopedWorkspaceContext(scoped, () => {
+      // Inside scope — overridden
+      expect(config.getWorkspaceContext()).toBe(scoped);
+    });
+
+    // Outside scope — original
+    const ctx = config.getWorkspaceContext();
+    expect(ctx.getDirectories()).not.toContain(fs.realpathSync(extraDir));
+  });
+
+  it('should allow paths within scoped directories via Config.isPathAllowed()', () => {
+    const scoped = createScopedWorkspaceContext(config.getWorkspaceContext(), [
+      extraDir,
+    ]);
+    // Use realpathSync because WorkspaceContext resolves symlinks internally
+    const filePath = path.join(fs.realpathSync(extraDir), 'test.md');
+
+    // Outside scope — not allowed
+    expect(config.isPathAllowed(filePath)).toBe(false);
+
+    // Inside scope — allowed
+    runWithScopedWorkspaceContext(scoped, () => {
+      expect(config.isPathAllowed(filePath)).toBe(true);
+    });
+
+    // After scope — not allowed again
+    expect(config.isPathAllowed(filePath)).toBe(false);
+  });
+
+  it('should still allow parent workspace paths within scope', () => {
+    const scoped = createScopedWorkspaceContext(config.getWorkspaceContext(), [
+      extraDir,
+    ]);
+    const filePath = path.join(fs.realpathSync(tempDir), 'src/index.ts');
+
+    runWithScopedWorkspaceContext(scoped, () => {
+      expect(config.isPathAllowed(filePath)).toBe(true);
+    });
+  });
+
+  it('should work with async functions', async () => {
+    const scoped = createScopedWorkspaceContext(config.getWorkspaceContext(), [
+      extraDir,
+    ]);
+
+    await runWithScopedWorkspaceContext(scoped, async () => {
+      // Simulate async work
+      await new Promise((resolve) => setTimeout(resolve, 1));
+      const ctx = config.getWorkspaceContext();
+      expect(ctx).toBe(scoped);
+    });
+  });
+
+  it('should return undefined from getWorkspaceContextOverride outside scope', () => {
+    expect(getWorkspaceContextOverride()).toBeUndefined();
+  });
+
+  it('should return scoped context from getWorkspaceContextOverride inside scope', () => {
+    const scoped = createScopedWorkspaceContext(config.getWorkspaceContext(), [
+      extraDir,
+    ]);
+
+    runWithScopedWorkspaceContext(scoped, () => {
+      expect(getWorkspaceContextOverride()).toBe(scoped);
+    });
+  });
+});
diff --git a/packages/core/src/config/scoped-config.ts b/packages/core/src/config/scoped-config.ts
new file mode 100644
index 0000000000..90cdea2da6
--- /dev/null
+++ b/packages/core/src/config/scoped-config.ts
@@ -0,0 +1,86 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { AsyncLocalStorage } from 'node:async_hooks';
+import * as path from 'node:path';
+import { WorkspaceContext } from '../utils/workspaceContext.js';
+
+/**
+ * AsyncLocalStorage for scoped workspace context overrides.
+ *
+ * When a subagent declares additional workspace directories, its execution
+ * runs inside this store. `Config.getWorkspaceContext()` checks this store
+ * first, allowing per-agent workspace scoping without mutating the shared
+ * Config instance.
+ *
+ * This follows the same pattern as `toolCallContext` and `promptIdContext`.
+ */
+const workspaceContextOverride = new AsyncLocalStorage<WorkspaceContext>();
+
+/**
+ * Returns the current workspace context override, if any.
+ * Called by `Config.getWorkspaceContext()` to check for per-agent scoping.
+ */
+export function getWorkspaceContextOverride(): WorkspaceContext | undefined {
+  return workspaceContextOverride.getStore();
+}
+
+/**
+ * Runs a function with a scoped workspace context override.
+ * Any calls to `Config.getWorkspaceContext()` within `fn` will return
+ * the scoped context instead of the default.
+ *
+ * @param scopedContext The workspace context to use within the scope.
+ * @param fn The function to run.
+ * @returns The result of the function.
+ */
+export function runWithScopedWorkspaceContext<T>(
+  scopedContext: WorkspaceContext,
+  fn: () => T,
+): T {
+  return workspaceContextOverride.run(scopedContext, fn);
+}
+
+/**
+ * Creates a {@link WorkspaceContext} that extends a parent's directories
+ * with additional ones.
+ *
+ * @param parentContext The parent workspace context.
+ * @param additionalDirectories Extra directories to include.
+ * @returns A new WorkspaceContext with the combined directories.
+ */
+export function createScopedWorkspaceContext(
+  parentContext: WorkspaceContext,
+  additionalDirectories: string[],
+): WorkspaceContext {
+  if (additionalDirectories.length === 0) {
+    return parentContext;
+  }
+
+  const parentDirs = [...parentContext.getDirectories()];
+  if (parentDirs.length === 0) {
+    throw new Error(
+      'Cannot create scoped workspace context: parent has no directories',
+    );
+  }
+
+  // Reject overly broad directories (filesystem roots) to prevent
+  // accidentally granting access to the entire filesystem.
+  for (const dir of additionalDirectories) {
+    if (path.resolve(dir) === path.parse(path.resolve(dir)).root) {
+      throw new Error(
+        `Cannot add filesystem root "${dir}" as a workspace directory`,
+      );
+    }
+  }
+
+  // WorkspaceContext's first constructor argument is the primary targetDir.
+  // getDirectories() returns targetDir first, so parentDirs[0] is always it.
+  return new WorkspaceContext(parentDirs[0], [
+    ...parentDirs.slice(1),
+    ...additionalDirectories,
+  ]);
+}
diff --git a/packages/core/src/policy/policies/memory-manager.toml b/packages/core/src/policy/policies/memory-manager.toml
index b1b1b4ddd9..3794871be3 100644
--- a/packages/core/src/policy/policies/memory-manager.toml
+++ b/packages/core/src/policy/policies/memory-manager.toml
@@ -1,10 +1,20 @@
 # Policy for Memory Manager Agent
 # Allows the save_memory agent to manage memories in the ~/.gemini/ folder.
 
+# Read-only tools: allow access to anything under .gemini/
 [[rule]]
 subagent = "save_memory"
-toolName = ["read_file", "write_file", "replace", "list_directory", "glob", "grep_search"]
+toolName = ["read_file", "list_directory", "glob", "grep_search"]
 decision = "allow"
 priority = 100
 argsPattern = "(^|.*/)\\.gemini/.*"
 denyMessage = "Memory Manager is only allowed to access the .gemini folder."
+
+# Write tools: only allow .md files under .gemini/
+[[rule]]
+subagent = "save_memory"
+toolName = ["write_file", "replace"]
+decision = "allow"
+priority = 100
+argsPattern = "(^|.*/)\\.gemini/.*\\.md\""
+denyMessage = "Memory Manager is only allowed to write .md files in the .gemini folder."