diff --git a/packages/cli/src/config/config.test.ts b/packages/cli/src/config/config.test.ts
index 180f461749..263c7938d9 100644
--- a/packages/cli/src/config/config.test.ts
+++ b/packages/cli/src/config/config.test.ts
@@ -999,6 +999,7 @@ describe('Hierarchical Memory Loading (config.ts) - Placeholder Suite', () => {
       }),
       200, // maxDirs
       ['.git'], // boundaryMarkers
+      undefined, // workspaceRootOverride
     );
   });
 
@@ -1029,6 +1030,7 @@ describe('Hierarchical Memory Loading (config.ts) - Placeholder Suite', () => {
       }),
       200,
       ['.git'], // boundaryMarkers
+      undefined, // workspaceRootOverride
     );
   });
 
@@ -1058,6 +1060,7 @@ describe('Hierarchical Memory Loading (config.ts) - Placeholder Suite', () => {
       }),
       200,
       ['.git'], // boundaryMarkers
+      undefined, // workspaceRootOverride
     );
   });
 });
diff --git a/packages/cli/src/config/config.ts b/packages/cli/src/config/config.ts
index 213c22120e..3cec5c54fb 100755
--- a/packages/cli/src/config/config.ts
+++ b/packages/cli/src/config/config.ts
@@ -8,6 +8,7 @@ import yargs from 'yargs';
 import { hideBin } from 'yargs/helpers';
 import process from 'node:process';
 import * as path from 'node:path';
+import { existsSync, statSync } from 'node:fs';
 import { execa } from 'execa';
 import { mcpCommand } from '../commands/mcp.js';
 import { extensionsCommand } from '../commands/extensions.js';
@@ -107,6 +108,7 @@ export interface CliArgs {
   rawOutput: boolean | undefined;
   acceptRawOutputRisk: boolean | undefined;
   isCommand: boolean | undefined;
+  workspace?: string;
 }
 
 /**
@@ -124,6 +126,25 @@ const coerceCommaSeparated = (values: string[]): string[] => {
   );
 };
 
+/**
+ * Pre-parses the command line arguments to find the workspace flag.
+ * Used for early setup before full argument parsing with settings,
+ * since settings are loaded from the workspace directory.
+ */
+export function getWorkspaceArg(argv: string[]): string | undefined {
+  const result = yargs(hideBin(argv))
+    .help(false)
+    .version(false)
+    .option('workspace', { type: 'string' })
+    .strict(false)
+    .exitProcess(false)
+    .parseSync();
+
+  return typeof result.workspace === 'string'
+    ? path.resolve(result.workspace.trim())
+    : undefined;
+}
+
 /**
  * Pre-parses the command line arguments to find the worktree flag.
  * Used for early setup before full argument parsing with settings.
@@ -305,6 +326,13 @@ export async function parseArguments(
             return trimmed;
           },
         })
+        .option('workspace', {
+          type: 'string',
+          nargs: 1,
+          description:
+            'Use this directory as the workspace root. Prevents the CLI from walking upward to find .git, GEMINI.md, or .gemini directories.',
+          coerce: (value: string): string => path.resolve(value.trim()),
+        })
         .option('sandbox', {
           alias: 's',
           type: 'boolean',
@@ -526,7 +554,26 @@ export async function loadCliConfig(
   argv: CliArgs,
   options: LoadCliConfigOptions = {},
 ): Promise<Config> {
-  const { cwd = process.cwd(), projectHooks } = options;
+  const { cwd: cwdOption = process.cwd(), projectHooks } = options;
+
+  // --workspace takes priority over the default cwd. Resolve symlinks and
+  // validate it is an existing directory before using it for anything else.
+  if (argv.workspace) {
+    const resolvedWorkspace = resolveToRealPath(argv.workspace);
+    if (!existsSync(resolvedWorkspace)) {
+      throw new FatalConfigError(
+        `--workspace directory does not exist: ${argv.workspace}`,
+      );
+    }
+    if (!statSync(resolvedWorkspace).isDirectory()) {
+      throw new FatalConfigError(
+        `--workspace path is not a directory: ${argv.workspace}`,
+      );
+    }
+    argv.workspace = resolvedWorkspace;
+  }
+
+  const cwd = argv.workspace ?? cwdOption;
   const debugMode = isDebugMode(argv);
 
   const worktreeSettings =
@@ -647,6 +694,7 @@ export async function loadCliConfig(
       memoryFileFiltering,
       settings.context?.discoveryMaxDirs,
       settings.context?.memoryBoundaryMarkers,
+      argv.workspace,
     );
     memoryContent = result.memoryContent;
     fileCount = result.fileCount;
diff --git a/packages/cli/src/config/workspace-arg.test.ts b/packages/cli/src/config/workspace-arg.test.ts
new file mode 100644
index 0000000000..9ed82d3171
--- /dev/null
+++ b/packages/cli/src/config/workspace-arg.test.ts
@@ -0,0 +1,165 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import * as path from 'node:path';
+import * as fs from 'node:fs';
+import { getWorkspaceArg, loadCliConfig, type CliArgs } from './config.js';
+import { FatalConfigError } from '@google/gemini-cli-core';
+import { createTestMergedSettings } from './settings.js';
+
+vi.mock('./trustedFolders.js', () => ({
+  isWorkspaceTrusted: vi.fn(() => ({ isTrusted: true, source: 'file' })),
+}));
+
+vi.mock('./sandboxConfig.js', () => ({
+  loadSandboxConfig: vi.fn(async () => undefined),
+}));
+
+vi.mock('../commands/utils.js', () => ({
+  exitCli: vi.fn(),
+}));
+
+// ---------------------------------------------------------------------------
+// getWorkspaceArg
+// ---------------------------------------------------------------------------
+describe('getWorkspaceArg', () => {
+  it('returns undefined when --workspace is not provided', () => {
+    expect(getWorkspaceArg(['node', 'gemini'])).toBeUndefined();
+    expect(
+      getWorkspaceArg(['node', 'gemini', '--prompt', 'hello']),
+    ).toBeUndefined();
+  });
+
+  it('returns the resolved absolute path when --workspace is provided', () => {
+    const result = getWorkspaceArg([
+      'node',
+      'gemini',
+      '--workspace',
+      './my_dir',
+    ]);
+    expect(result).toBe(path.resolve('./my_dir'));
+  });
+
+  it('resolves relative paths to absolute', () => {
+    const result = getWorkspaceArg([
+      'node',
+      'gemini',
+      '--workspace',
+      '../sibling',
+    ]);
+    expect(result).toBe(path.resolve('../sibling'));
+  });
+
+  it('handles an already-absolute path', () => {
+    const absPath = path.resolve('/tmp/workspace');
+    const result = getWorkspaceArg(['node', 'gemini', '--workspace', absPath]);
+    expect(result).toBe(absPath);
+  });
+
+  it('trims whitespace from the path', () => {
+    const result = getWorkspaceArg([
+      'node',
+      'gemini',
+      '--workspace',
+      '  ./my_dir  ',
+    ]);
+    expect(result).toBe(path.resolve('./my_dir'));
+  });
+
+  it('ignores unrelated flags', () => {
+    const result = getWorkspaceArg([
+      'node',
+      'gemini',
+      '--prompt',
+      'hello',
+      '--workspace',
+      './ws',
+      '--yolo',
+    ]);
+    expect(result).toBe(path.resolve('./ws'));
+  });
+});
+
+// ---------------------------------------------------------------------------
+// loadCliConfig: --workspace validation
+// ---------------------------------------------------------------------------
+describe('loadCliConfig --workspace validation', () => {
+  let tmpDir: string;
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(path.resolve('.'), 'workspace-test-'));
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+    vi.restoreAllMocks();
+  });
+
+  const baseArgv = (): CliArgs => ({
+    query: undefined,
+    model: undefined,
+    sandbox: undefined,
+    debug: false,
+    prompt: undefined,
+    promptInteractive: undefined,
+    yolo: false,
+    approvalMode: undefined,
+    policy: undefined,
+    adminPolicy: undefined,
+    allowedMcpServerNames: undefined,
+    allowedTools: undefined,
+    extensions: undefined,
+    listExtensions: undefined,
+    resume: undefined,
+    listSessions: undefined,
+    deleteSession: undefined,
+    includeDirectories: undefined,
+    screenReader: undefined,
+    useWriteTodos: undefined,
+    outputFormat: undefined,
+    fakeResponses: undefined,
+    recordResponses: undefined,
+    rawOutput: undefined,
+    acceptRawOutputRisk: undefined,
+    isCommand: undefined,
+    workspace: undefined,
+  });
+
+  it('throws FatalConfigError when --workspace directory does not exist', async () => {
+    const argv = {
+      ...baseArgv(),
+      workspace: path.join(tmpDir, 'does-not-exist'),
+    };
+    const settings = createTestMergedSettings();
+    await expect(loadCliConfig(settings, 'session-id', argv)).rejects.toThrow(
+      FatalConfigError,
+    );
+  });
+
+  it('throws FatalConfigError when --workspace path is a file, not a directory', async () => {
+    const filePath = path.join(tmpDir, 'notadir.txt');
+    fs.writeFileSync(filePath, 'hello');
+    const argv = { ...baseArgv(), workspace: filePath };
+    const settings = createTestMergedSettings();
+    await expect(loadCliConfig(settings, 'session-id', argv)).rejects.toThrow(
+      FatalConfigError,
+    );
+  });
+
+  it('does not throw when --workspace is a valid directory', async () => {
+    const argv = { ...baseArgv(), workspace: tmpDir };
+    const settings = createTestMergedSettings();
+    // Should not throw — we just verify it reaches the point past validation.
+    // It may fail later for unrelated reasons (missing auth etc.) in unit tests,
+    // so we only assert no FatalConfigError from workspace validation.
+    try {
+      await loadCliConfig(settings, 'session-id', argv);
+    } catch (err) {
+      expect(err).not.toBeInstanceOf(FatalConfigError);
+    }
+  });
+});
diff --git a/packages/cli/src/gemini.test.tsx b/packages/cli/src/gemini.test.tsx
index 5b31d153fe..404d168a7e 100644
--- a/packages/cli/src/gemini.test.tsx
+++ b/packages/cli/src/gemini.test.tsx
@@ -202,6 +202,7 @@ vi.mock('./config/config.js', () => ({
   isDebugMode: vi.fn(() => false),
   getRequestedWorktreeName: vi.fn(() => undefined),
   getWorktreeArg: vi.fn(() => undefined),
+  getWorkspaceArg: vi.fn(() => undefined),
 }));
 
 vi.mock('read-package-up', () => ({
diff --git a/packages/cli/src/gemini.tsx b/packages/cli/src/gemini.tsx
index 6e257270d7..41d2d324a0 100644
--- a/packages/cli/src/gemini.tsx
+++ b/packages/cli/src/gemini.tsx
@@ -269,8 +269,12 @@ export async function main() {
   slashCommandConflictHandler.start();
   registerCleanup(() => slashCommandConflictHandler.stop());
 
+  // Pre-parse --workspace before loading settings, since project settings
+  // (.gemini/settings.json) are loaded relative to the workspace directory.
+  const workspaceArg = cliConfig.getWorkspaceArg(process.argv);
+
   const loadSettingsHandle = startupProfiler.start('load_settings');
-  const settings = loadSettings();
+  const settings = loadSettings(workspaceArg ?? process.cwd());
   loadSettingsHandle?.end();
 
   // If a worktree is requested and enabled, set it up early.
diff --git a/packages/cli/src/gemini_cleanup.test.tsx b/packages/cli/src/gemini_cleanup.test.tsx
index 2df1ab4d82..8bc9f445cf 100644
--- a/packages/cli/src/gemini_cleanup.test.tsx
+++ b/packages/cli/src/gemini_cleanup.test.tsx
@@ -80,6 +80,7 @@ vi.mock('./config/config.js', () => ({
   isDebugMode: vi.fn(() => false),
   getRequestedWorktreeName: vi.fn(() => undefined),
   getWorktreeArg: vi.fn(() => undefined),
+  getWorkspaceArg: vi.fn(() => undefined),
 }));
 
 vi.mock('read-package-up', () => ({
diff --git a/packages/core/src/utils/memoryDiscovery.test.ts b/packages/core/src/utils/memoryDiscovery.test.ts
index 9e18a41f66..1c7fdff88b 100644
--- a/packages/core/src/utils/memoryDiscovery.test.ts
+++ b/packages/core/src/utils/memoryDiscovery.test.ts
@@ -1361,6 +1361,112 @@ included directory memory
     });
   });
 
+  describe('workspaceRootOverride (--workspace flag)', () => {
+    it('should not traverse above the workspace root even when a parent has .git', async () => {
+      // Layout:
+      //   testRootDir/
+      //     parent/          ← has .git, GEMINI.md (should NOT be picked up)
+      //       workspace/     ← the --workspace dir, has GEMINI.md (should be picked up)
+      //         src/         ← cwd
+      const parent = await createEmptyDir(path.join(testRootDir, 'parent'));
+      await createEmptyDir(path.join(parent, '.git'));
+      const workspace = await createEmptyDir(path.join(parent, 'workspace'));
+      const src = await createEmptyDir(path.join(workspace, 'src'));
+
+      const parentMemory = await createTestFile(
+        path.join(parent, DEFAULT_CONTEXT_FILENAME),
+        'Parent memory — should NOT appear',
+      );
+      const workspaceMemory = await createTestFile(
+        path.join(workspace, DEFAULT_CONTEXT_FILENAME),
+        'Workspace memory — should appear',
+      );
+
+      const result = flattenResult(
+        await loadServerHierarchicalMemory(
+          src,
+          [],
+          new FileDiscoveryService(workspace),
+          new SimpleExtensionLoader([]),
+          true,
+          'tree',
+          undefined,
+          200,
+          ['.git'],
+          workspace, // workspaceRootOverride
+        ),
+      );
+
+      expect(result.filePaths).toContain(normalizePath(workspaceMemory));
+      expect(result.filePaths).not.toContain(normalizePath(parentMemory));
+    });
+
+    it('should include GEMINI.md files inside the workspace (downward scan)', async () => {
+      // Layout:
+      //   workspace/
+      //     GEMINI.md        ← picked up
+      //     src/
+      //       GEMINI.md      ← picked up (downward scan)
+      const workspace = await createEmptyDir(
+        path.join(testRootDir, 'workspace_down'),
+      );
+      const src = await createEmptyDir(path.join(workspace, 'src'));
+
+      const wsMemory = await createTestFile(
+        path.join(workspace, DEFAULT_CONTEXT_FILENAME),
+        'Workspace root memory',
+      );
+      const srcMemory = await createTestFile(
+        path.join(src, DEFAULT_CONTEXT_FILENAME),
+        'Src memory',
+      );
+
+      const result = flattenResult(
+        await loadServerHierarchicalMemory(
+          workspace,
+          [],
+          new FileDiscoveryService(workspace),
+          new SimpleExtensionLoader([]),
+          true,
+          'tree',
+          undefined,
+          200,
+          ['.git'],
+          workspace, // workspaceRootOverride
+        ),
+      );
+
+      expect(result.filePaths).toContain(normalizePath(wsMemory));
+      expect(result.filePaths).toContain(normalizePath(srcMemory));
+    });
+
+    it('should behave identically to the default when no override is given', async () => {
+      // Verify the new optional parameter does not alter behaviour when absent.
+      await createEmptyDir(path.join(projectRoot, '.git'));
+      const projMemory = await createTestFile(
+        path.join(projectRoot, DEFAULT_CONTEXT_FILENAME),
+        'Project memory',
+      );
+      const cwdMemory = await createTestFile(
+        path.join(cwd, DEFAULT_CONTEXT_FILENAME),
+        'CWD memory',
+      );
+
+      const withoutOverride = flattenResult(
+        await loadServerHierarchicalMemory(
+          cwd,
+          [],
+          new FileDiscoveryService(projectRoot),
+          new SimpleExtensionLoader([]),
+          true,
+        ),
+      );
+
+      expect(withoutOverride.filePaths).toContain(normalizePath(projMemory));
+      expect(withoutOverride.filePaths).toContain(normalizePath(cwdMemory));
+    });
+  });
+
   it('refreshServerHierarchicalMemory should refresh memory and update config', async () => {
     const extensionLoader = new SimpleExtensionLoader([]);
     const config = new Config({
diff --git a/packages/core/src/utils/memoryDiscovery.ts b/packages/core/src/utils/memoryDiscovery.ts
index f59aed4460..6cd574a3b8 100644
--- a/packages/core/src/utils/memoryDiscovery.ts
+++ b/packages/core/src/utils/memoryDiscovery.ts
@@ -214,6 +214,7 @@ async function getGeminiMdFilePathsInternal(
   fileFilteringOptions: FileFilteringOptions,
   maxDirs: number,
   boundaryMarkers: readonly string[] = ['.git'],
+  workspaceRootOverride?: string,
 ): Promise<{ global: string[]; project: string[] }> {
   const dirs = new Set<string>([
     ...includeDirectoriesToReadGemini,
@@ -237,6 +238,7 @@ async function getGeminiMdFilePathsInternal(
         fileFilteringOptions,
         maxDirs,
         boundaryMarkers,
+        workspaceRootOverride,
       ),
     );
 
@@ -269,6 +271,7 @@ async function getGeminiMdFilePathsInternalForEachDir(
   fileFilteringOptions: FileFilteringOptions,
   maxDirs: number,
   boundaryMarkers: readonly string[] = ['.git'],
+  workspaceRootOverride?: string,
 ): Promise<{ global: string[]; project: string[] }> {
   const globalPaths = new Set<string>();
   const projectPaths = new Set<string>();
@@ -305,17 +308,29 @@ async function getGeminiMdFilePathsInternalForEachDir(
         resolvedCwd,
       );
 
-      const projectRoot = await findProjectRoot(resolvedCwd, boundaryMarkers);
+      // When an explicit workspace root is provided via --workspace, use it
+      // directly as the project root. This prevents any upward traversal
+      // above the user-specified directory boundary.
+      const projectRoot = workspaceRootOverride
+        ? normalizePath(workspaceRootOverride)
+        : await findProjectRoot(resolvedCwd, boundaryMarkers);
       debugLogger.debug(
         '[DEBUG] [MemoryDiscovery] Determined project root:',
         projectRoot ?? 'None',
+        workspaceRootOverride ? '(from --workspace override)' : '',
       );
 
       const upwardPaths: string[] = [];
       let currentDir = resolvedCwd;
-      const ultimateStopDir = projectRoot
-        ? normalizePath(path.dirname(projectRoot))
-        : normalizePath(path.dirname(resolvedHome));
+      // When a workspace root override is provided, the upward walk stops AT
+      // the workspace dir (it is included, but nothing above it is scanned).
+      // Without an override, the walk stops at the parent of the project root
+      // (the original behaviour).
+      const ultimateStopDir = workspaceRootOverride
+        ? normalizePath(workspaceRootOverride)
+        : projectRoot
+          ? normalizePath(path.dirname(projectRoot))
+          : normalizePath(path.dirname(resolvedHome));
 
       while (
         currentDir &&
@@ -647,6 +662,7 @@ export async function loadServerHierarchicalMemory(
   fileFilteringOptions?: FileFilteringOptions,
   maxDirs: number = 200,
   boundaryMarkers: readonly string[] = ['.git'],
+  workspaceRootOverride?: string,
 ): Promise<LoadServerHierarchicalMemoryResponse> {
   // FIX: Use real, canonical paths for a reliable comparison to handle symlinks.
   const realCwd = normalizePath(
@@ -680,6 +696,7 @@ export async function loadServerHierarchicalMemory(
       fileFilteringOptions || DEFAULT_MEMORY_FILE_FILTERING_OPTIONS,
       maxDirs,
       boundaryMarkers,
+      workspaceRootOverride,
     ),
     Promise.resolve(getExtensionMemoryPaths(extensionLoader)),
   ]);