diff --git a/docs/troubleshooting.md b/docs/troubleshooting.md
index 9506859a..d06b4dc7 100644
--- a/docs/troubleshooting.md
+++ b/docs/troubleshooting.md
@@ -74,6 +74,18 @@ This guide provides solutions to common issues and debugging tips, including top
   - **Cause:** The `DEBUG` and `DEBUG_MODE` variables are automatically excluded from project `.env` files to prevent interference with gemini-cli behavior.
   - **Solution:** Use a `.gemini/.env` file instead, or configure the `excludedProjectEnvVars` setting in your `settings.json` to exclude fewer variables.
 
+## Exit Codes
+
+The Gemini CLI uses specific exit codes to indicate the reason for termination. This is especially useful for scripting and automation.
+
+| Exit Code | Error Type                 | Description                                                                                         |
+| --------- | -------------------------- | --------------------------------------------------------------------------------------------------- |
+| 41        | `FatalAuthenticationError` | An error occurred during the authentication process.                                                |
+| 42        | `FatalInputError`          | Invalid or missing input was provided to the CLI. (non-interactive mode only)                       |
+| 44        | `FatalSandboxError`        | An error occurred with the sandboxing environment (e.g., Docker, Podman, or Seatbelt).              |
+| 52        | `FatalConfigError`         | A configuration file (`settings.json`) is invalid or contains errors.                               |
+| 53        | `FatalTurnLimitedError`    | The maximum number of conversational turns for the session was reached. (non-interactive mode only) |
+
 ## Debugging Tips
 
 - **CLI debugging:**
diff --git a/packages/cli/index.ts b/packages/cli/index.ts
index 6b7e87a5..e247b095 100644
--- a/packages/cli/index.ts
+++ b/packages/cli/index.ts
@@ -8,9 +8,18 @@
 
 import './src/gemini.js';
 import { main } from './src/gemini.js';
+import { FatalError } from '@google/gemini-cli-core';
 
 // --- Global Entry Point ---
 main().catch((error) => {
+  if (error instanceof FatalError) {
+    let errorMessage = error.message;
+    if (!process.env['NO_COLOR']) {
+      errorMessage = `\x1b[31m${errorMessage}\x1b[0m`;
+    }
+    console.error(errorMessage);
+    process.exit(error.exitCode);
+  }
   console.error('An unexpected critical error occurred:');
   if (error instanceof Error) {
     console.error(error.stack);
diff --git a/packages/cli/src/config/sandboxConfig.ts b/packages/cli/src/config/sandboxConfig.ts
index 182176bb..2b0a5dc8 100644
--- a/packages/cli/src/config/sandboxConfig.ts
+++ b/packages/cli/src/config/sandboxConfig.ts
@@ -5,6 +5,7 @@
  */
 
 import type { SandboxConfig } from '@google/gemini-cli-core';
+import { FatalSandboxError } from '@google/gemini-cli-core';
 import commandExists from 'command-exists';
 import * as os from 'node:os';
 import { getPackageJson } from '../utils/package.js';
@@ -51,21 +52,19 @@ function getSandboxCommand(
 
   if (typeof sandbox === 'string' && sandbox) {
     if (!isSandboxCommand(sandbox)) {
-      console.error(
-        `ERROR: invalid sandbox command '${sandbox}'. Must be one of ${VALID_SANDBOX_COMMANDS.join(
+      throw new FatalSandboxError(
+        `Invalid sandbox command '${sandbox}'. Must be one of ${VALID_SANDBOX_COMMANDS.join(
           ', ',
         )}`,
       );
-      process.exit(1);
     }
     // confirm that specified command exists
     if (commandExists.sync(sandbox)) {
       return sandbox;
     }
-    console.error(
-      `ERROR: missing sandbox command '${sandbox}' (from GEMINI_SANDBOX)`,
+    throw new FatalSandboxError(
+      `Missing sandbox command '${sandbox}' (from GEMINI_SANDBOX)`,
     );
-    process.exit(1);
   }
 
   // look for seatbelt, docker, or podman, in that order
@@ -80,11 +79,10 @@ function getSandboxCommand(
 
   // throw an error if user requested sandbox but no command was found
   if (sandbox === true) {
-    console.error(
-      'ERROR: GEMINI_SANDBOX is true but failed to determine command for sandbox; ' +
+    throw new FatalSandboxError(
+      'GEMINI_SANDBOX is true but failed to determine command for sandbox; ' +
         'install docker or podman or specify command in GEMINI_SANDBOX',
     );
-    process.exit(1);
   }
 
   return '';
diff --git a/packages/cli/src/gemini.test.tsx b/packages/cli/src/gemini.test.tsx
index b1e3c3b6..16a2d60f 100644
--- a/packages/cli/src/gemini.test.tsx
+++ b/packages/cli/src/gemini.test.tsx
@@ -4,7 +4,6 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import stripAnsi from 'strip-ansi';
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 import {
   main,
@@ -16,6 +15,7 @@ import type { SettingsFile } from './config/settings.js';
 import { LoadedSettings, loadSettings } from './config/settings.js';
 import { appEvents, AppEvent } from './utils/events.js';
 import type { Config } from '@google/gemini-cli-core';
+import { FatalConfigError } from '@google/gemini-cli-core';
 
 // Custom error to identify mock process.exit calls
 class MockProcessExitError extends Error {
@@ -75,7 +75,6 @@ vi.mock('./utils/sandbox.js', () => ({
 }));
 
 describe('gemini.tsx main function', () => {
-  let consoleErrorSpy: ReturnType<typeof vi.spyOn>;
   let loadSettingsMock: ReturnType<typeof vi.mocked<typeof loadSettings>>;
   let originalEnvGeminiSandbox: string | undefined;
   let originalEnvSandbox: string | undefined;
@@ -97,7 +96,6 @@ describe('gemini.tsx main function', () => {
     delete process.env['GEMINI_SANDBOX'];
     delete process.env['SANDBOX'];
 
-    consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
     initialUnhandledRejectionListeners =
       process.listeners('unhandledRejection');
   });
@@ -126,7 +124,7 @@ describe('gemini.tsx main function', () => {
     vi.restoreAllMocks();
   });
 
-  it('should call process.exit(1) if settings have errors', async () => {
+  it('should throw InvalidConfigurationError if settings have errors', async () => {
     const settingsError = {
       message: 'Test settings error',
       path: '/test/settings.json',
@@ -158,28 +156,7 @@ describe('gemini.tsx main function', () => {
 
     loadSettingsMock.mockReturnValue(mockLoadedSettings);
 
-    try {
-      await main();
-      // If main completes without throwing, the test should fail because process.exit was expected
-      expect.fail('main function did not exit as expected');
-    } catch (error) {
-      expect(error).toBeInstanceOf(MockProcessExitError);
-      if (error instanceof MockProcessExitError) {
-        expect(error.code).toBe(1);
-      }
-    }
-
-    // Verify console.error was called with the error message
-    expect(consoleErrorSpy).toHaveBeenCalledTimes(2);
-    expect(stripAnsi(String(consoleErrorSpy.mock.calls[0][0]))).toBe(
-      'Error in /test/settings.json: Test settings error',
-    );
-    expect(stripAnsi(String(consoleErrorSpy.mock.calls[1][0]))).toBe(
-      'Please fix /test/settings.json and try again.',
-    );
-
-    // Verify process.exit was called.
-    expect(processExitSpy).toHaveBeenCalledWith(1);
+    await expect(main()).rejects.toThrow(FatalConfigError);
   });
 
   it('should log unhandled promise rejections and open debug console on first error', async () => {
diff --git a/packages/cli/src/gemini.tsx b/packages/cli/src/gemini.tsx
index 21a7b55b..66892e09 100644
--- a/packages/cli/src/gemini.tsx
+++ b/packages/cli/src/gemini.tsx
@@ -34,6 +34,7 @@ import {
   logIdeConnection,
   IdeConnectionEvent,
   IdeConnectionType,
+  FatalConfigError,
 } from '@google/gemini-cli-core';
 import { validateAuthMethod } from './config/auth.js';
 import { setMaxSizedBoxDebugging } from './ui/components/shared/MaxSizedBox.js';
@@ -173,15 +174,12 @@ export async function main() {
 
   await cleanupCheckpoints();
   if (settings.errors.length > 0) {
-    for (const error of settings.errors) {
-      let errorMessage = `Error in ${error.path}: ${error.message}`;
-      if (!process.env['NO_COLOR']) {
-        errorMessage = `\x1b[31m${errorMessage}\x1b[0m`;
-      }
-      console.error(errorMessage);
-      console.error(`Please fix ${error.path} and try again.`);
-    }
-    process.exit(1);
+    const errorMessages = settings.errors.map(
+      (error) => `Error in ${error.path}: ${error.message}`,
+    );
+    throw new FatalConfigError(
+      `${errorMessages.join('\n')}\nPlease fix the configuration file(s) and try again.`,
+    );
   }
 
   const argv = await parseArguments(settings.merged);
diff --git a/packages/cli/src/nonInteractiveCli.test.ts b/packages/cli/src/nonInteractiveCli.test.ts
index f7fc00e4..7de83930 100644
--- a/packages/cli/src/nonInteractiveCli.test.ts
+++ b/packages/cli/src/nonInteractiveCli.test.ts
@@ -38,7 +38,6 @@ describe('runNonInteractive', () => {
   let mockCoreExecuteToolCall: vi.Mock;
   let mockShutdownTelemetry: vi.Mock;
   let consoleErrorSpy: vi.SpyInstance;
-  let processExitSpy: vi.SpyInstance;
   let processStdoutSpy: vi.SpyInstance;
   let mockGeminiClient: {
     sendMessageStream: vi.Mock;
@@ -49,9 +48,6 @@ describe('runNonInteractive', () => {
     mockShutdownTelemetry = vi.mocked(shutdownTelemetry);
 
     consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
-    processExitSpy = vi
-      .spyOn(process, 'exit')
-      .mockImplementation((() => {}) as (code?: number) => never);
     processStdoutSpy = vi
       .spyOn(process.stdout, 'write')
       .mockImplementation(() => true);
@@ -202,7 +198,6 @@ describe('runNonInteractive', () => {
     expect(consoleErrorSpy).toHaveBeenCalledWith(
       'Error executing tool errorTool: Execution failed',
     );
-    expect(processExitSpy).not.toHaveBeenCalled();
     expect(mockGeminiClient.sendMessageStream).toHaveBeenCalledTimes(2);
     expect(mockGeminiClient.sendMessageStream).toHaveBeenNthCalledWith(
       2,
@@ -228,12 +223,9 @@ describe('runNonInteractive', () => {
       throw apiError;
     });
 
-    await runNonInteractive(mockConfig, 'Initial fail', 'prompt-id-4');
-
-    expect(consoleErrorSpy).toHaveBeenCalledWith(
-      '[API Error: API connection failed]',
-    );
-    expect(processExitSpy).toHaveBeenCalledWith(1);
+    await expect(
+      runNonInteractive(mockConfig, 'Initial fail', 'prompt-id-4'),
+    ).rejects.toThrow(apiError);
   });
 
   it('should not exit if a tool is not found, and should send error back to model', async () => {
@@ -272,7 +264,6 @@ describe('runNonInteractive', () => {
     expect(consoleErrorSpy).toHaveBeenCalledWith(
       'Error executing tool nonexistentTool: Tool "nonexistentTool" not found in registry.',
     );
-    expect(processExitSpy).not.toHaveBeenCalled();
     expect(mockGeminiClient.sendMessageStream).toHaveBeenCalledTimes(2);
     expect(processStdoutSpy).toHaveBeenCalledWith(
       "Sorry, I can't find that tool.",
@@ -281,9 +272,10 @@ describe('runNonInteractive', () => {
 
   it('should exit when max session turns are exceeded', async () => {
     vi.mocked(mockConfig.getMaxSessionTurns).mockReturnValue(0);
-    await runNonInteractive(mockConfig, 'Trigger loop', 'prompt-id-6');
-    expect(consoleErrorSpy).toHaveBeenCalledWith(
-      '\n Reached max session turns for this session. Increase the number of turns by specifying maxSessionTurns in settings.json.',
+    await expect(
+      runNonInteractive(mockConfig, 'Trigger loop', 'prompt-id-6'),
+    ).rejects.toThrow(
+      'Reached max session turns for this session. Increase the number of turns by specifying maxSessionTurns in settings.json.',
     );
   });
 
diff --git a/packages/cli/src/nonInteractiveCli.ts b/packages/cli/src/nonInteractiveCli.ts
index 9f9ffd1c..73e8ae23 100644
--- a/packages/cli/src/nonInteractiveCli.ts
+++ b/packages/cli/src/nonInteractiveCli.ts
@@ -11,6 +11,8 @@ import {
   isTelemetrySdkInitialized,
   GeminiEventType,
   parseAndFormatApiError,
+  FatalInputError,
+  FatalTurnLimitedError,
 } from '@google/gemini-cli-core';
 import type { Content, Part } from '@google/genai';
 
@@ -53,8 +55,9 @@ export async function runNonInteractive(
     if (!shouldProceed || !processedQuery) {
       // An error occurred during @include processing (e.g., file not found).
       // The error message is already logged by handleAtCommand.
-      console.error('Exiting due to an error processing the @ command.');
-      process.exit(1);
+      throw new FatalInputError(
+        'Exiting due to an error processing the @ command.',
+      );
     }
 
     let currentMessages: Content[] = [
@@ -68,10 +71,9 @@ export async function runNonInteractive(
         config.getMaxSessionTurns() >= 0 &&
         turnCount > config.getMaxSessionTurns()
       ) {
-        console.error(
-          '\n Reached max session turns for this session. Increase the number of turns by specifying maxSessionTurns in settings.json.',
+        throw new FatalTurnLimitedError(
+          'Reached max session turns for this session. Increase the number of turns by specifying maxSessionTurns in settings.json.',
         );
-        return;
       }
       const toolCallRequests: ToolCallRequestInfo[] = [];
 
@@ -126,7 +128,7 @@ export async function runNonInteractive(
         config.getContentGeneratorConfig()?.authType,
       ),
     );
-    process.exit(1);
+    throw error;
   } finally {
     consolePatcher.cleanup();
     if (isTelemetrySdkInitialized()) {
diff --git a/packages/cli/src/utils/sandbox.ts b/packages/cli/src/utils/sandbox.ts
index 3b328e4b..dc4ef3bd 100644
--- a/packages/cli/src/utils/sandbox.ts
+++ b/packages/cli/src/utils/sandbox.ts
@@ -17,6 +17,7 @@ import {
 } from '../config/settings.js';
 import { promisify } from 'node:util';
 import type { Config, SandboxConfig } from '@google/gemini-cli-core';
+import { FatalSandboxError } from '@google/gemini-cli-core';
 import { ConsolePatcher } from '../ui/utils/ConsolePatcher.js';
 
 const execAsync = promisify(exec);
@@ -198,8 +199,9 @@ export async function start_sandbox(
     if (config.command === 'sandbox-exec') {
       // disallow BUILD_SANDBOX
       if (process.env['BUILD_SANDBOX']) {
-        console.error('ERROR: cannot BUILD_SANDBOX when using macOS Seatbelt');
-        process.exit(1);
+        throw new FatalSandboxError(
+          'Cannot BUILD_SANDBOX when using macOS Seatbelt',
+        );
       }
 
       const profile = (process.env['SEATBELT_PROFILE'] ??= 'permissive-open');
@@ -214,10 +216,9 @@ export async function start_sandbox(
         );
       }
       if (!fs.existsSync(profileFile)) {
-        console.error(
-          `ERROR: missing macos seatbelt profile file '${profileFile}'`,
+        throw new FatalSandboxError(
+          `Missing macos seatbelt profile file '${profileFile}'`,
         );
-        process.exit(1);
       }
       // Log on STDERR so it doesn't clutter the output on STDOUT
       console.error(`using macos seatbelt (profile: ${profile}) ...`);
@@ -325,13 +326,12 @@ export async function start_sandbox(
           console.error(data.toString());
         });
         proxyProcess.on('close', (code, signal) => {
-          console.error(
-            `ERROR: proxy command '${proxyCommand}' exited with code ${code}, signal ${signal}`,
-          );
           if (sandboxProcess?.pid) {
             process.kill(-sandboxProcess.pid, 'SIGTERM');
           }
-          process.exit(1);
+          throw new FatalSandboxError(
+            `Proxy command '${proxyCommand}' exited with code ${code}, signal ${signal}`,
+          );
         });
         console.log('waiting for proxy to start ...');
         await execAsync(
@@ -366,11 +366,10 @@ export async function start_sandbox(
     // note this can only be done with binary linked from gemini-cli repo
     if (process.env['BUILD_SANDBOX']) {
       if (!gcPath.includes('gemini-cli/packages/')) {
-        console.error(
-          'ERROR: cannot build sandbox using installed gemini binary; ' +
+        throw new FatalSandboxError(
+          'Cannot build sandbox using installed gemini binary; ' +
             'run `npm link ./packages/cli` under gemini-cli repo to switch to linked binary.',
         );
-        process.exit(1);
       } else {
         console.error('building sandbox ...');
         const gcRoot = gcPath.split('/packages/')[0];
@@ -403,10 +402,9 @@ export async function start_sandbox(
         image === LOCAL_DEV_SANDBOX_IMAGE_NAME
           ? 'Try running `npm run build:all` or `npm run build:sandbox` under the gemini-cli repo to build it locally, or check the image name and your network connection.'
           : 'Please check the image name, your network connection, or notify gemini-cli-dev@google.com if the issue persists.';
-      console.error(
-        `ERROR: Sandbox image '${image}' is missing or could not be pulled. ${remedy}`,
+      throw new FatalSandboxError(
+        `Sandbox image '${image}' is missing or could not be pulled. ${remedy}`,
       );
-      process.exit(1);
     }
 
     // use interactive mode and auto-remove container on exit
@@ -484,17 +482,15 @@ export async function start_sandbox(
           mount = `${from}:${to}:${opts}`;
           // check that from path is absolute
           if (!path.isAbsolute(from)) {
-            console.error(
-              `ERROR: path '${from}' listed in SANDBOX_MOUNTS must be absolute`,
+            throw new FatalSandboxError(
+              `Path '${from}' listed in SANDBOX_MOUNTS must be absolute`,
             );
-            process.exit(1);
           }
           // check that from path exists on host
           if (!fs.existsSync(from)) {
-            console.error(
-              `ERROR: missing mount path '${from}' listed in SANDBOX_MOUNTS`,
+            throw new FatalSandboxError(
+              `Missing mount path '${from}' listed in SANDBOX_MOUNTS`,
             );
-            process.exit(1);
           }
           console.error(`SANDBOX_MOUNTS: ${from} -> ${to} (${opts})`);
           args.push('--volume', mount);
@@ -665,10 +661,9 @@ export async function start_sandbox(
             console.error(`SANDBOX_ENV: ${env}`);
             args.push('--env', env);
           } else {
-            console.error(
-              'ERROR: SANDBOX_ENV must be a comma-separated list of key=value pairs',
+            throw new FatalSandboxError(
+              'SANDBOX_ENV must be a comma-separated list of key=value pairs',
             );
-            process.exit(1);
           }
         }
       }
@@ -776,13 +771,12 @@ export async function start_sandbox(
         console.error(data.toString().trim());
       });
       proxyProcess.on('close', (code, signal) => {
-        console.error(
-          `ERROR: proxy container command '${proxyContainerCommand}' exited with code ${code}, signal ${signal}`,
-        );
         if (sandboxProcess?.pid) {
           process.kill(-sandboxProcess.pid, 'SIGTERM');
         }
-        process.exit(1);
+        throw new FatalSandboxError(
+          `Proxy container command '${proxyContainerCommand}' exited with code ${code}, signal ${signal}`,
+        );
       });
       console.log('waiting for proxy to start ...');
       await execAsync(
diff --git a/packages/core/src/code_assist/oauth2.ts b/packages/core/src/code_assist/oauth2.ts
index fc401655..f71f5a0f 100644
--- a/packages/core/src/code_assist/oauth2.ts
+++ b/packages/core/src/code_assist/oauth2.ts
@@ -18,7 +18,7 @@ import open from 'open';
 import path from 'node:path';
 import { promises as fs } from 'node:fs';
 import type { Config } from '../config/config.js';
-import { getErrorMessage } from '../utils/errors.js';
+import { getErrorMessage, FatalAuthenticationError } from '../utils/errors.js';
 import { UserAccountManager } from '../utils/userAccountManager.js';
 import { AuthType } from '../core/contentGenerator.js';
 import readline from 'node:readline';
@@ -142,7 +142,9 @@ async function initOauthClient(
       }
     }
     if (!success) {
-      process.exit(1);
+      throw new FatalAuthenticationError(
+        'Failed to authenticate with user code.',
+      );
     }
   } else {
     const webLogin = await authWithWeb(client);
@@ -166,7 +168,7 @@ async function initOauthClient(
         console.error(
           'Failed to open browser automatically. Please try running again with NO_BROWSER=true set.',
         );
-        process.exit(1);
+        throw new FatalAuthenticationError('Failed to open browser.');
       });
     } catch (err) {
       console.error(
@@ -174,7 +176,7 @@ async function initOauthClient(
         err,
         '\nPlease try running again with NO_BROWSER=true set.',
       );
-      process.exit(1);
+      throw new FatalAuthenticationError('Failed to open browser.');
     }
     console.log('Waiting for authentication...');
 
diff --git a/packages/core/src/utils/errors.ts b/packages/core/src/utils/errors.ts
index a57186b2..a02399ea 100644
--- a/packages/core/src/utils/errors.ts
+++ b/packages/core/src/utils/errors.ts
@@ -25,6 +25,41 @@ export function getErrorMessage(error: unknown): string {
   }
 }
 
+export class FatalError extends Error {
+  constructor(
+    message: string,
+    readonly exitCode: number,
+  ) {
+    super(message);
+  }
+}
+
+export class FatalAuthenticationError extends FatalError {
+  constructor(message: string) {
+    super(message, 41);
+  }
+}
+export class FatalInputError extends FatalError {
+  constructor(message: string) {
+    super(message, 42);
+  }
+}
+export class FatalSandboxError extends FatalError {
+  constructor(message: string) {
+    super(message, 44);
+  }
+}
+export class FatalConfigError extends FatalError {
+  constructor(message: string) {
+    super(message, 52);
+  }
+}
+export class FatalTurnLimitedError extends FatalError {
+  constructor(message: string) {
+    super(message, 53);
+  }
+}
+
 export class ForbiddenError extends Error {}
 export class UnauthorizedError extends Error {}
 export class BadRequestError extends Error {}