diff --git a/integration-tests/file-system.test.ts b/integration-tests/file-system.test.ts
index 5a7028e0..6b150be5 100644
--- a/integration-tests/file-system.test.ts
+++ b/integration-tests/file-system.test.ts
@@ -86,7 +86,7 @@ describe('file-system', () => {
     ).toBeTruthy();
 
     // Log success info if verbose
-    if (process.env.VERBOSE === 'true') {
+    if (process.env['VERBOSE'] === 'true') {
       console.log('File written successfully with hello message.');
     }
   });
diff --git a/integration-tests/mcp_server_cyclic_schema.test.ts b/integration-tests/mcp_server_cyclic_schema.test.ts
index 18c1bcde..7136287c 100644
--- a/integration-tests/mcp_server_cyclic_schema.test.ts
+++ b/integration-tests/mcp_server_cyclic_schema.test.ts
@@ -27,7 +27,7 @@ const readline = require('readline');
 const fs = require('fs');
 
 // Debug logging to stderr (only when MCP_DEBUG or VERBOSE is set)
-const debugEnabled = process.env.MCP_DEBUG === 'true' || process.env.VERBOSE === 'true';
+const debugEnabled = process.env['MCP_DEBUG'] === 'true' || process.env['VERBOSE'] === 'true';
 function debug(msg) {
   if (debugEnabled) {
     fs.writeSync(2, \`[MCP-DEBUG] \${msg}\\n\`);
diff --git a/integration-tests/replace.test.ts b/integration-tests/replace.test.ts
index 3a2d979b..a04025e7 100644
--- a/integration-tests/replace.test.ts
+++ b/integration-tests/replace.test.ts
@@ -56,7 +56,8 @@ describe('replace', () => {
     expect(newFileContent).toBe(expectedContent);
 
     // Log success info if verbose
-    if (process.env.VERBOSE === 'true') {
+    vi.stubEnv('VERBOSE', 'true');
+    if (process.env['VERBOSE'] === 'true') {
       console.log('File replaced successfully. New content:', newFileContent);
     }
   });
diff --git a/integration-tests/simple-mcp-server.test.ts b/integration-tests/simple-mcp-server.test.ts
index 98c81f16..b57502cf 100644
--- a/integration-tests/simple-mcp-server.test.ts
+++ b/integration-tests/simple-mcp-server.test.ts
@@ -28,7 +28,7 @@ const readline = require('readline');
 const fs = require('fs');
 
 // Debug logging to stderr (only when MCP_DEBUG or VERBOSE is set)
-const debugEnabled = process.env.MCP_DEBUG === 'true' || process.env.VERBOSE === 'true';
+const debugEnabled = process.env['MCP_DEBUG'] === 'true' || process.env['VERBOSE'] === 'true';
 function debug(msg) {
   if (debugEnabled) {
     fs.writeSync(2, \`[MCP-DEBUG] \${msg}\\n\`);
diff --git a/integration-tests/write_file.test.ts b/integration-tests/write_file.test.ts
index 3fe26af6..49cdda38 100644
--- a/integration-tests/write_file.test.ts
+++ b/integration-tests/write_file.test.ts
@@ -58,7 +58,8 @@ describe('write_file', () => {
     expect(newFileContent).not.toBe('');
 
     // Log success info if verbose
-    if (process.env.VERBOSE === 'true') {
+    vi.stubEnv('VERBOSE', 'true');
+    if (process.env['VERBOSE'] === 'true') {
       console.log(
         'File created successfully with content:',
         newFileContent.substring(0, 100) + '...',
diff --git a/packages/cli/src/commands/mcp/add.ts b/packages/cli/src/commands/mcp/add.ts
index 67c44572..304338b0 100644
--- a/packages/cli/src/commands/mcp/add.ts
+++ b/packages/cli/src/commands/mcp/add.ts
@@ -197,25 +197,25 @@ export const addCommand: CommandModule = {
       .middleware((argv) => {
         // Handle -- separator args as server args if present
         if (argv['--']) {
-          const existingArgs = (argv.args as Array<string | number>) || [];
-          argv.args = [...existingArgs, ...(argv['--'] as string[])];
+          const existingArgs = (argv['args'] as Array<string | number>) || [];
+          argv['args'] = [...existingArgs, ...(argv['--'] as string[])];
         }
       }),
   handler: async (argv) => {
     await addMcpServer(
-      argv.name as string,
-      argv.commandOrUrl as string,
-      argv.args as Array<string | number>,
+      argv['name'] as string,
+      argv['commandOrUrl'] as string,
+      argv['args'] as Array<string | number>,
       {
-        scope: argv.scope as string,
-        transport: argv.transport as string,
-        env: argv.env as string[],
-        header: argv.header as string[],
-        timeout: argv.timeout as number | undefined,
-        trust: argv.trust as boolean | undefined,
-        description: argv.description as string | undefined,
-        includeTools: argv.includeTools as string[] | undefined,
-        excludeTools: argv.excludeTools as string[] | undefined,
+        scope: argv['scope'] as string,
+        transport: argv['transport'] as string,
+        env: argv['env'] as string[],
+        header: argv['header'] as string[],
+        timeout: argv['timeout'] as number | undefined,
+        trust: argv['trust'] as boolean | undefined,
+        description: argv['description'] as string | undefined,
+        includeTools: argv['includeTools'] as string[] | undefined,
+        excludeTools: argv['excludeTools'] as string[] | undefined,
       },
     );
   },
diff --git a/packages/cli/src/commands/mcp/remove.ts b/packages/cli/src/commands/mcp/remove.ts
index 80d66234..e05478e3 100644
--- a/packages/cli/src/commands/mcp/remove.ts
+++ b/packages/cli/src/commands/mcp/remove.ts
@@ -53,8 +53,8 @@ export const removeCommand: CommandModule = {
         choices: ['user', 'project'],
       }),
   handler: async (argv) => {
-    await removeMcpServer(argv.name as string, {
-      scope: argv.scope as string,
+    await removeMcpServer(argv['name'] as string, {
+      scope: argv['scope'] as string,
     });
   },
 };
diff --git a/packages/cli/src/config/auth.test.ts b/packages/cli/src/config/auth.test.ts
index 96defb1e..ddfed236 100644
--- a/packages/cli/src/config/auth.test.ts
+++ b/packages/cli/src/config/auth.test.ts
@@ -34,7 +34,7 @@ describe('validateAuthMethod', () => {
 
   describe('USE_GEMINI', () => {
     it('should return null if GEMINI_API_KEY is set', () => {
-      process.env.GEMINI_API_KEY = 'test-key';
+      process.env['GEMINI_API_KEY'] = 'test-key';
       expect(validateAuthMethod(AuthType.USE_GEMINI)).toBeNull();
     });
 
@@ -47,13 +47,13 @@ describe('validateAuthMethod', () => {
 
   describe('USE_VERTEX_AI', () => {
     it('should return null if GOOGLE_CLOUD_PROJECT and GOOGLE_CLOUD_LOCATION are set', () => {
-      process.env.GOOGLE_CLOUD_PROJECT = 'test-project';
-      process.env.GOOGLE_CLOUD_LOCATION = 'test-location';
+      process.env['GOOGLE_CLOUD_PROJECT'] = 'test-project';
+      process.env['GOOGLE_CLOUD_LOCATION'] = 'test-location';
       expect(validateAuthMethod(AuthType.USE_VERTEX_AI)).toBeNull();
     });
 
     it('should return null if GOOGLE_API_KEY is set', () => {
-      process.env.GOOGLE_API_KEY = 'test-api-key';
+      process.env['GOOGLE_API_KEY'] = 'test-api-key';
       expect(validateAuthMethod(AuthType.USE_VERTEX_AI)).toBeNull();
     });
 
diff --git a/packages/cli/src/config/auth.ts b/packages/cli/src/config/auth.ts
index 91d4eee3..4676bb2f 100644
--- a/packages/cli/src/config/auth.ts
+++ b/packages/cli/src/config/auth.ts
@@ -17,7 +17,7 @@ export const validateAuthMethod = (authMethod: string): string | null => {
   }
 
   if (authMethod === AuthType.USE_GEMINI) {
-    if (!process.env.GEMINI_API_KEY) {
+    if (!process.env['GEMINI_API_KEY']) {
       return 'GEMINI_API_KEY environment variable not found. Add that to your environment and try again (no reload needed if using .env)!';
     }
     return null;
@@ -25,8 +25,9 @@ export const validateAuthMethod = (authMethod: string): string | null => {
 
   if (authMethod === AuthType.USE_VERTEX_AI) {
     const hasVertexProjectLocationConfig =
-      !!process.env.GOOGLE_CLOUD_PROJECT && !!process.env.GOOGLE_CLOUD_LOCATION;
-    const hasGoogleApiKey = !!process.env.GOOGLE_API_KEY;
+      !!process.env['GOOGLE_CLOUD_PROJECT'] &&
+      !!process.env['GOOGLE_CLOUD_LOCATION'];
+    const hasGoogleApiKey = !!process.env['GOOGLE_API_KEY'];
     if (!hasVertexProjectLocationConfig && !hasGoogleApiKey) {
       return (
         'When using Vertex AI, you must specify either:\n' +
diff --git a/packages/cli/src/config/config.integration.test.ts b/packages/cli/src/config/config.integration.test.ts
index 45ed6d82..6d77740d 100644
--- a/packages/cli/src/config/config.integration.test.ts
+++ b/packages/cli/src/config/config.integration.test.ts
@@ -53,19 +53,17 @@ vi.mock('@google/gemini-cli-core', async () => {
 
 describe('Configuration Integration Tests', () => {
   let tempDir: string;
-  let originalEnv: NodeJS.ProcessEnv;
 
   beforeEach(() => {
     server.resetHandlers(http.post(CLEARCUT_URL, () => HttpResponse.text()));
 
     tempDir = fs.mkdtempSync(path.join(tmpdir(), 'gemini-cli-test-'));
-    originalEnv = { ...process.env };
-    process.env.GEMINI_API_KEY = 'test-api-key';
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
     vi.clearAllMocks();
   });
 
   afterEach(() => {
-    process.env = originalEnv;
+    vi.unstubAllEnvs();
     if (fs.existsSync(tempDir)) {
       fs.rmSync(tempDir, { recursive: true });
     }
diff --git a/packages/cli/src/config/config.test.ts b/packages/cli/src/config/config.test.ts
index e70fc3b3..727f6fe1 100644
--- a/packages/cli/src/config/config.test.ts
+++ b/packages/cli/src/config/config.test.ts
@@ -252,17 +252,16 @@ describe('parseArguments', () => {
 
 describe('loadCliConfig', () => {
   const originalArgv = process.argv;
-  const originalEnv = { ...process.env };
 
   beforeEach(() => {
     vi.resetAllMocks();
     vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
-    process.env.GEMINI_API_KEY = 'test-api-key'; // Ensure API key is set for tests
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
   });
 
   afterEach(() => {
     process.argv = originalArgv;
-    process.env = originalEnv;
+    vi.unstubAllEnvs();
     vi.restoreAllMocks();
   });
 
@@ -339,7 +338,7 @@ describe('loadCliConfig', () => {
   ];
   testCases.forEach(({ input, expected }) => {
     it(`should set proxy to ${expected} according to environment variable [${input.env_name}]`, async () => {
-      process.env[input.env_name] = input.proxy_url;
+      vi.stubEnv(input.env_name, input.proxy_url);
       process.argv = ['node', 'script.js'];
       const argv = await parseArguments();
       const settings: Settings = {};
@@ -357,7 +356,7 @@ describe('loadCliConfig', () => {
   });
 
   it('should prioritize CLI flag over environment variable for proxy (CLI http://localhost:7890, environment variable http://localhost:7891)', async () => {
-    process.env['http_proxy'] = 'http://localhost:7891';
+    vi.stubEnv('http_proxy', 'http://localhost:7891');
     process.argv = ['node', 'script.js', '--proxy', 'http://localhost:7890'];
     const argv = await parseArguments();
     const settings: Settings = {};
@@ -368,17 +367,16 @@ describe('loadCliConfig', () => {
 
 describe('loadCliConfig telemetry', () => {
   const originalArgv = process.argv;
-  const originalEnv = { ...process.env };
 
   beforeEach(() => {
     vi.resetAllMocks();
     vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
-    process.env.GEMINI_API_KEY = 'test-api-key';
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
   });
 
   afterEach(() => {
     process.argv = originalArgv;
-    process.env = originalEnv;
+    vi.unstubAllEnvs();
     vi.restoreAllMocks();
   });
 
@@ -1113,17 +1111,16 @@ describe('Approval mode tool exclusion logic', () => {
 
 describe('loadCliConfig with allowed-mcp-server-names', () => {
   const originalArgv = process.argv;
-  const originalEnv = { ...process.env };
 
   beforeEach(() => {
     vi.resetAllMocks();
     vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
-    process.env.GEMINI_API_KEY = 'test-api-key';
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
   });
 
   afterEach(() => {
     process.argv = originalArgv;
-    process.env = originalEnv;
+    vi.unstubAllEnvs();
     vi.restoreAllMocks();
   });
 
@@ -1363,17 +1360,16 @@ describe('loadCliConfig model selection', () => {
 
 describe('loadCliConfig folderTrustFeature', () => {
   const originalArgv = process.argv;
-  const originalEnv = { ...process.env };
 
   beforeEach(() => {
     vi.resetAllMocks();
     vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
-    process.env.GEMINI_API_KEY = 'test-api-key';
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
   });
 
   afterEach(() => {
     process.argv = originalArgv;
-    process.env = originalEnv;
+    vi.unstubAllEnvs();
     vi.restoreAllMocks();
   });
 
@@ -1396,17 +1392,16 @@ describe('loadCliConfig folderTrustFeature', () => {
 
 describe('loadCliConfig folderTrust', () => {
   const originalArgv = process.argv;
-  const originalEnv = { ...process.env };
 
   beforeEach(() => {
     vi.resetAllMocks();
     vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
-    process.env.GEMINI_API_KEY = 'test-api-key';
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
   });
 
   afterEach(() => {
     process.argv = originalArgv;
-    process.env = originalEnv;
+    vi.unstubAllEnvs();
     vi.restoreAllMocks();
   });
 
@@ -1477,12 +1472,11 @@ vi.mock('fs', async () => {
 
 describe('loadCliConfig with includeDirectories', () => {
   const originalArgv = process.argv;
-  const originalEnv = { ...process.env };
 
   beforeEach(() => {
     vi.resetAllMocks();
     vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
-    process.env.GEMINI_API_KEY = 'test-api-key';
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
     vi.spyOn(process, 'cwd').mockReturnValue(
       path.resolve(path.sep, 'home', 'user', 'project'),
     );
@@ -1490,7 +1484,7 @@ describe('loadCliConfig with includeDirectories', () => {
 
   afterEach(() => {
     process.argv = originalArgv;
-    process.env = originalEnv;
+    vi.unstubAllEnvs();
     vi.restoreAllMocks();
   });
 
@@ -1530,17 +1524,16 @@ describe('loadCliConfig with includeDirectories', () => {
 
 describe('loadCliConfig chatCompression', () => {
   const originalArgv = process.argv;
-  const originalEnv = { ...process.env };
 
   beforeEach(() => {
     vi.resetAllMocks();
     vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
-    process.env.GEMINI_API_KEY = 'test-api-key';
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
   });
 
   afterEach(() => {
     process.argv = originalArgv;
-    process.env = originalEnv;
+    vi.unstubAllEnvs();
     vi.restoreAllMocks();
   });
 
@@ -1569,20 +1562,19 @@ describe('loadCliConfig chatCompression', () => {
 
 describe('loadCliConfig tool exclusions', () => {
   const originalArgv = process.argv;
-  const originalEnv = { ...process.env };
   const originalIsTTY = process.stdin.isTTY;
 
   beforeEach(() => {
     vi.resetAllMocks();
     vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
-    process.env.GEMINI_API_KEY = 'test-api-key';
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
     process.stdin.isTTY = true;
   });
 
   afterEach(() => {
     process.argv = originalArgv;
-    process.env = originalEnv;
     process.stdin.isTTY = originalIsTTY;
+    vi.unstubAllEnvs();
     vi.restoreAllMocks();
   });
 
@@ -1629,20 +1621,19 @@ describe('loadCliConfig tool exclusions', () => {
 
 describe('loadCliConfig interactive', () => {
   const originalArgv = process.argv;
-  const originalEnv = { ...process.env };
   const originalIsTTY = process.stdin.isTTY;
 
   beforeEach(() => {
     vi.resetAllMocks();
     vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
-    process.env.GEMINI_API_KEY = 'test-api-key';
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
     process.stdin.isTTY = true;
   });
 
   afterEach(() => {
     process.argv = originalArgv;
-    process.env = originalEnv;
     process.stdin.isTTY = originalIsTTY;
+    vi.unstubAllEnvs();
     vi.restoreAllMocks();
   });
 
@@ -1681,18 +1672,17 @@ describe('loadCliConfig interactive', () => {
 
 describe('loadCliConfig approval mode', () => {
   const originalArgv = process.argv;
-  const originalEnv = { ...process.env };
 
   beforeEach(() => {
     vi.resetAllMocks();
     vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
-    process.env.GEMINI_API_KEY = 'test-api-key';
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
     process.argv = ['node', 'script.js']; // Reset argv for each test
   });
 
   afterEach(() => {
     process.argv = originalArgv;
-    process.env = originalEnv;
+    vi.unstubAllEnvs();
     vi.restoreAllMocks();
   });
 
@@ -1759,18 +1749,17 @@ describe('loadCliConfig approval mode', () => {
 
 describe('loadCliConfig trustedFolder', () => {
   const originalArgv = process.argv;
-  const originalEnv = { ...process.env };
 
   beforeEach(() => {
     vi.resetAllMocks();
     vi.mocked(os.homedir).mockReturnValue('/mock/home/user');
-    process.env.GEMINI_API_KEY = 'test-api-key';
+    vi.stubEnv('GEMINI_API_KEY', 'test-api-key');
     process.argv = ['node', 'script.js']; // Reset argv for each test
   });
 
   afterEach(() => {
     process.argv = originalArgv;
-    process.env = originalEnv;
+    vi.unstubAllEnvs();
     vi.restoreAllMocks();
   });
 
diff --git a/packages/cli/src/config/config.ts b/packages/cli/src/config/config.ts
index a943f641..b66afcc8 100644
--- a/packages/cli/src/config/config.ts
+++ b/packages/cli/src/config/config.ts
@@ -87,7 +87,7 @@ export async function parseArguments(): Promise<CliArgs> {
           alias: 'm',
           type: 'string',
           description: `Model`,
-          default: process.env.GEMINI_MODEL,
+          default: process.env['GEMINI_MODEL'],
         })
         .option('prompt', {
           alias: 'p',
@@ -230,12 +230,12 @@ export async function parseArguments(): Promise<CliArgs> {
             dirs.flatMap((dir) => dir.split(',').map((d) => d.trim())),
         })
         .check((argv) => {
-          if (argv.prompt && argv.promptInteractive) {
+          if (argv.prompt && argv['promptInteractive']) {
             throw new Error(
               'Cannot use both --prompt (-p) and --prompt-interactive (-i) together',
             );
           }
-          if (argv.yolo && argv.approvalMode) {
+          if (argv.yolo && argv['approvalMode']) {
             throw new Error(
               'Cannot use both --yolo (-y) and --approval-mode together. Use --approval-mode=yolo instead.',
             );
@@ -317,7 +317,7 @@ export async function loadCliConfig(
 ): Promise<Config> {
   const debugMode =
     argv.debug ||
-    [process.env.DEBUG, process.env.DEBUG_MODE].some(
+    [process.env['DEBUG'], process.env['DEBUG_MODE']].some(
       (v) => v === 'true' || v === '1',
     ) ||
     false;
@@ -496,7 +496,7 @@ export async function loadCliConfig(
         settings.telemetry?.target) as TelemetryTarget,
       otlpEndpoint:
         argv.telemetryOtlpEndpoint ??
-        process.env.OTEL_EXPORTER_OTLP_ENDPOINT ??
+        process.env['OTEL_EXPORTER_OTLP_ENDPOINT'] ??
         settings.telemetry?.otlpEndpoint,
       otlpProtocol: (['grpc', 'http'] as const).find(
         (p) =>
@@ -517,10 +517,10 @@ export async function loadCliConfig(
     checkpointing: argv.checkpointing || settings.checkpointing?.enabled,
     proxy:
       argv.proxy ||
-      process.env.HTTPS_PROXY ||
-      process.env.https_proxy ||
-      process.env.HTTP_PROXY ||
-      process.env.http_proxy,
+      process.env['HTTPS_PROXY'] ||
+      process.env['https_proxy'] ||
+      process.env['HTTP_PROXY'] ||
+      process.env['http_proxy'],
     cwd,
     fileDiscoveryService: fileService,
     bugCommand: settings.bugCommand,
@@ -531,7 +531,7 @@ export async function loadCliConfig(
     listExtensions: argv.listExtensions || false,
     extensions: allExtensions,
     blockedMcpServers,
-    noBrowser: !!process.env.NO_BROWSER,
+    noBrowser: !!process.env['NO_BROWSER'],
     summarizeToolOutput: settings.summarizeToolOutput,
     ideMode,
     chatCompression: settings.chatCompression,
diff --git a/packages/cli/src/config/sandboxConfig.ts b/packages/cli/src/config/sandboxConfig.ts
index c4ae50c4..4311b148 100644
--- a/packages/cli/src/config/sandboxConfig.ts
+++ b/packages/cli/src/config/sandboxConfig.ts
@@ -31,13 +31,13 @@ function getSandboxCommand(
   sandbox?: boolean | string,
 ): SandboxConfig['command'] | '' {
   // If the SANDBOX env var is set, we're already inside the sandbox.
-  if (process.env.SANDBOX) {
+  if (process.env['SANDBOX']) {
     return '';
   }
 
   // note environment variable takes precedence over argument (from command line or settings)
   const environmentConfiguredSandbox =
-    process.env.GEMINI_SANDBOX?.toLowerCase().trim() ?? '';
+    process.env['GEMINI_SANDBOX']?.toLowerCase().trim() ?? '';
   sandbox =
     environmentConfiguredSandbox?.length > 0
       ? environmentConfiguredSandbox
@@ -100,7 +100,7 @@ export async function loadSandboxConfig(
   const packageJson = await getPackageJson();
   const image =
     argv.sandboxImage ??
-    process.env.GEMINI_SANDBOX_IMAGE ??
+    process.env['GEMINI_SANDBOX_IMAGE'] ??
     packageJson?.config?.sandboxImageUri;
 
   return command && image ? { command, image } : undefined;
diff --git a/packages/cli/src/config/settings.test.ts b/packages/cli/src/config/settings.test.ts
index 353a5783..d537eeb1 100644
--- a/packages/cli/src/config/settings.test.ts
+++ b/packages/cli/src/config/settings.test.ts
@@ -892,7 +892,7 @@ describe('Settings Loading and Merging', () => {
     });
 
     it('should resolve environment variables in user settings', () => {
-      process.env.TEST_API_KEY = 'user_api_key_from_env';
+      process.env['TEST_API_KEY'] = 'user_api_key_from_env';
       const userSettingsContent = {
         apiKey: '$TEST_API_KEY',
         someUrl: 'https://test.com/${TEST_API_KEY}',
@@ -917,11 +917,11 @@ describe('Settings Loading and Merging', () => {
       );
       // @ts-expect-error: dynamic property for test
       expect(settings.merged.apiKey).toBe('user_api_key_from_env');
-      delete process.env.TEST_API_KEY;
+      delete process.env['TEST_API_KEY'];
     });
 
     it('should resolve environment variables in workspace settings', () => {
-      process.env.WORKSPACE_ENDPOINT = 'workspace_endpoint_from_env';
+      process.env['WORKSPACE_ENDPOINT'] = 'workspace_endpoint_from_env';
       const workspaceSettingsContent = {
         endpoint: '${WORKSPACE_ENDPOINT}/api',
         nested: { value: '$WORKSPACE_ENDPOINT' },
@@ -946,7 +946,7 @@ describe('Settings Loading and Merging', () => {
       );
       // @ts-expect-error: dynamic property for test
       expect(settings.merged.endpoint).toBe('workspace_endpoint_from_env/api');
-      delete process.env.WORKSPACE_ENDPOINT;
+      delete process.env['WORKSPACE_ENDPOINT'];
     });
 
     it('should prioritize user env variables over workspace env variables if keys clash after resolution', () => {
@@ -954,18 +954,18 @@ describe('Settings Loading and Merging', () => {
       const workspaceSettingsContent = { configValue: '$SHARED_VAR' };
 
       (mockFsExistsSync as Mock).mockReturnValue(true);
-      const originalSharedVar = process.env.SHARED_VAR;
+      const originalSharedVar = process.env['SHARED_VAR'];
       // Temporarily delete to ensure a clean slate for the test's specific manipulations
-      delete process.env.SHARED_VAR;
+      delete process.env['SHARED_VAR'];
 
       (fs.readFileSync as Mock).mockImplementation(
         (p: fs.PathOrFileDescriptor) => {
           if (p === USER_SETTINGS_PATH) {
-            process.env.SHARED_VAR = 'user_value_for_user_read'; // Set for user settings read
+            process.env['SHARED_VAR'] = 'user_value_for_user_read'; // Set for user settings read
             return JSON.stringify(userSettingsContent);
           }
           if (p === MOCK_WORKSPACE_SETTINGS_PATH) {
-            process.env.SHARED_VAR = 'workspace_value_for_workspace_read'; // Set for workspace settings read
+            process.env['SHARED_VAR'] = 'workspace_value_for_workspace_read'; // Set for workspace settings read
             return JSON.stringify(workspaceSettingsContent);
           }
           return '{}';
@@ -990,9 +990,9 @@ describe('Settings Loading and Merging', () => {
 
       // Restore original environment variable state
       if (originalSharedVar !== undefined) {
-        process.env.SHARED_VAR = originalSharedVar;
+        process.env['SHARED_VAR'] = originalSharedVar;
       } else {
-        delete process.env.SHARED_VAR; // Ensure it's deleted if it wasn't there before
+        delete process.env['SHARED_VAR']; // Ensure it's deleted if it wasn't there before
       }
     });
 
@@ -1001,18 +1001,18 @@ describe('Settings Loading and Merging', () => {
       const workspaceSettingsContent = { configValue: '$SHARED_VAR' };
 
       (mockFsExistsSync as Mock).mockReturnValue(true);
-      const originalSharedVar = process.env.SHARED_VAR;
+      const originalSharedVar = process.env['SHARED_VAR'];
       // Temporarily delete to ensure a clean slate for the test's specific manipulations
-      delete process.env.SHARED_VAR;
+      delete process.env['SHARED_VAR'];
 
       (fs.readFileSync as Mock).mockImplementation(
         (p: fs.PathOrFileDescriptor) => {
           if (p === USER_SETTINGS_PATH) {
-            process.env.SHARED_VAR = 'user_value_for_user_read'; // Set for user settings read
+            process.env['SHARED_VAR'] = 'user_value_for_user_read'; // Set for user settings read
             return JSON.stringify(userSettingsContent);
           }
           if (p === MOCK_WORKSPACE_SETTINGS_PATH) {
-            process.env.SHARED_VAR = 'workspace_value_for_workspace_read'; // Set for workspace settings read
+            process.env['SHARED_VAR'] = 'workspace_value_for_workspace_read'; // Set for workspace settings read
             return JSON.stringify(workspaceSettingsContent);
           }
           return '{}';
@@ -1034,9 +1034,9 @@ describe('Settings Loading and Merging', () => {
 
       // Restore original environment variable state
       if (originalSharedVar !== undefined) {
-        process.env.SHARED_VAR = originalSharedVar;
+        process.env['SHARED_VAR'] = originalSharedVar;
       } else {
-        delete process.env.SHARED_VAR; // Ensure it's deleted if it wasn't there before
+        delete process.env['SHARED_VAR']; // Ensure it's deleted if it wasn't there before
       }
     });
 
@@ -1045,18 +1045,18 @@ describe('Settings Loading and Merging', () => {
       const systemSettingsContent = { configValue: '$SHARED_VAR' };
 
       (mockFsExistsSync as Mock).mockReturnValue(true);
-      const originalSharedVar = process.env.SHARED_VAR;
+      const originalSharedVar = process.env['SHARED_VAR'];
       // Temporarily delete to ensure a clean slate for the test's specific manipulations
-      delete process.env.SHARED_VAR;
+      delete process.env['SHARED_VAR'];
 
       (fs.readFileSync as Mock).mockImplementation(
         (p: fs.PathOrFileDescriptor) => {
           if (p === getSystemSettingsPath()) {
-            process.env.SHARED_VAR = 'system_value_for_system_read'; // Set for system settings read
+            process.env['SHARED_VAR'] = 'system_value_for_system_read'; // Set for system settings read
             return JSON.stringify(systemSettingsContent);
           }
           if (p === MOCK_WORKSPACE_SETTINGS_PATH) {
-            process.env.SHARED_VAR = 'workspace_value_for_workspace_read'; // Set for workspace settings read
+            process.env['SHARED_VAR'] = 'workspace_value_for_workspace_read'; // Set for workspace settings read
             return JSON.stringify(workspaceSettingsContent);
           }
           return '{}';
@@ -1079,9 +1079,9 @@ describe('Settings Loading and Merging', () => {
 
       // Restore original environment variable state
       if (originalSharedVar !== undefined) {
-        process.env.SHARED_VAR = originalSharedVar;
+        process.env['SHARED_VAR'] = originalSharedVar;
       } else {
-        delete process.env.SHARED_VAR; // Ensure it's deleted if it wasn't there before
+        delete process.env['SHARED_VAR']; // Ensure it's deleted if it wasn't there before
       }
     });
 
@@ -1146,8 +1146,8 @@ describe('Settings Loading and Merging', () => {
     });
 
     it('should resolve multiple environment variables in a single string', () => {
-      process.env.VAR_A = 'valueA';
-      process.env.VAR_B = 'valueB';
+      process.env['VAR_A'] = 'valueA';
+      process.env['VAR_B'] = 'valueB';
       const userSettingsContent = { path: '/path/$VAR_A/${VAR_B}/end' };
       (mockFsExistsSync as Mock).mockImplementation(
         (p: fs.PathLike) => p === USER_SETTINGS_PATH,
@@ -1161,13 +1161,13 @@ describe('Settings Loading and Merging', () => {
       );
       const settings = loadSettings(MOCK_WORKSPACE_DIR);
       expect(settings.user.settings.path).toBe('/path/valueA/valueB/end');
-      delete process.env.VAR_A;
-      delete process.env.VAR_B;
+      delete process.env['VAR_A'];
+      delete process.env['VAR_B'];
     });
 
     it('should resolve environment variables in arrays', () => {
-      process.env.ITEM_1 = 'item1_env';
-      process.env.ITEM_2 = 'item2_env';
+      process.env['ITEM_1'] = 'item1_env';
+      process.env['ITEM_2'] = 'item2_env';
       const userSettingsContent = { list: ['$ITEM_1', '${ITEM_2}', 'literal'] };
       (mockFsExistsSync as Mock).mockImplementation(
         (p: fs.PathLike) => p === USER_SETTINGS_PATH,
@@ -1185,13 +1185,13 @@ describe('Settings Loading and Merging', () => {
         'item2_env',
         'literal',
       ]);
-      delete process.env.ITEM_1;
-      delete process.env.ITEM_2;
+      delete process.env['ITEM_1'];
+      delete process.env['ITEM_2'];
     });
 
     it('should correctly pass through null, boolean, and number types, and handle undefined properties', () => {
-      process.env.MY_ENV_STRING = 'env_string_value';
-      process.env.MY_ENV_STRING_NESTED = 'env_string_nested_value';
+      process.env['MY_ENV_STRING'] = 'env_string_value';
+      process.env['MY_ENV_STRING_NESTED'] = 'env_string_nested_value';
 
       const userSettingsContent = {
         nullVal: null,
@@ -1236,13 +1236,13 @@ describe('Settings Loading and Merging', () => {
         'env_string_nested_value',
       );
 
-      delete process.env.MY_ENV_STRING;
-      delete process.env.MY_ENV_STRING_NESTED;
+      delete process.env['MY_ENV_STRING'];
+      delete process.env['MY_ENV_STRING_NESTED'];
     });
 
     it('should resolve multiple concatenated environment variables in a single string value', () => {
-      process.env.TEST_HOST = 'myhost';
-      process.env.TEST_PORT = '9090';
+      process.env['TEST_HOST'] = 'myhost';
+      process.env['TEST_PORT'] = '9090';
       const userSettingsContent = {
         serverAddress: '${TEST_HOST}:${TEST_PORT}/api',
       };
@@ -1260,20 +1260,20 @@ describe('Settings Loading and Merging', () => {
       const settings = loadSettings(MOCK_WORKSPACE_DIR);
       expect(settings.user.settings.serverAddress).toBe('myhost:9090/api');
 
-      delete process.env.TEST_HOST;
-      delete process.env.TEST_PORT;
+      delete process.env['TEST_HOST'];
+      delete process.env['TEST_PORT'];
     });
 
     describe('when GEMINI_CLI_SYSTEM_SETTINGS_PATH is set', () => {
       const MOCK_ENV_SYSTEM_SETTINGS_PATH = '/mock/env/system/settings.json';
 
       beforeEach(() => {
-        process.env.GEMINI_CLI_SYSTEM_SETTINGS_PATH =
+        process.env['GEMINI_CLI_SYSTEM_SETTINGS_PATH'] =
           MOCK_ENV_SYSTEM_SETTINGS_PATH;
       });
 
       afterEach(() => {
-        delete process.env.GEMINI_CLI_SYSTEM_SETTINGS_PATH;
+        delete process.env['GEMINI_CLI_SYSTEM_SETTINGS_PATH'];
       });
 
       it('should load system settings from the path specified in the environment variable', () => {
diff --git a/packages/cli/src/config/settings.ts b/packages/cli/src/config/settings.ts
index 36fd50f1..524eb16c 100644
--- a/packages/cli/src/config/settings.ts
+++ b/packages/cli/src/config/settings.ts
@@ -25,8 +25,8 @@ export const USER_SETTINGS_PATH = path.join(USER_SETTINGS_DIR, 'settings.json');
 export const DEFAULT_EXCLUDED_ENV_VARS = ['DEBUG', 'DEBUG_MODE'];
 
 export function getSystemSettingsPath(): string {
-  if (process.env.GEMINI_CLI_SYSTEM_SETTINGS_PATH) {
-    return process.env.GEMINI_CLI_SYSTEM_SETTINGS_PATH;
+  if (process.env['GEMINI_CLI_SYSTEM_SETTINGS_PATH']) {
+    return process.env['GEMINI_CLI_SYSTEM_SETTINGS_PATH'];
   }
   if (platform() === 'darwin') {
     return '/Library/Application Support/GeminiCli/settings.json';
@@ -236,16 +236,16 @@ export function setUpCloudShellEnvironment(envFilePath: string | null): void {
   if (envFilePath && fs.existsSync(envFilePath)) {
     const envFileContent = fs.readFileSync(envFilePath);
     const parsedEnv = dotenv.parse(envFileContent);
-    if (parsedEnv.GOOGLE_CLOUD_PROJECT) {
+    if (parsedEnv['GOOGLE_CLOUD_PROJECT']) {
       // .env file takes precedence in Cloud Shell
-      process.env.GOOGLE_CLOUD_PROJECT = parsedEnv.GOOGLE_CLOUD_PROJECT;
+      process.env['GOOGLE_CLOUD_PROJECT'] = parsedEnv['GOOGLE_CLOUD_PROJECT'];
     } else {
       // If not in .env, set to default and override global
-      process.env.GOOGLE_CLOUD_PROJECT = 'cloudshell-gca';
+      process.env['GOOGLE_CLOUD_PROJECT'] = 'cloudshell-gca';
     }
   } else {
     // If no .env file, set to default and override global
-    process.env.GOOGLE_CLOUD_PROJECT = 'cloudshell-gca';
+    process.env['GOOGLE_CLOUD_PROJECT'] = 'cloudshell-gca';
   }
 }
 
@@ -253,7 +253,7 @@ export function loadEnvironment(settings?: Settings): void {
   const envFilePath = findEnvFile(process.cwd());
 
   // Cloud Shell environment variable handling
-  if (process.env.CLOUD_SHELL === 'true') {
+  if (process.env['CLOUD_SHELL'] === 'true') {
     setUpCloudShellEnvironment(envFilePath);
   }
 
diff --git a/packages/cli/src/gemini.test.tsx b/packages/cli/src/gemini.test.tsx
index c8bb45ab..c4de8308 100644
--- a/packages/cli/src/gemini.test.tsx
+++ b/packages/cli/src/gemini.test.tsx
@@ -93,10 +93,10 @@ describe('gemini.tsx main function', () => {
     loadSettingsMock = vi.mocked(loadSettings);
 
     // Store and clear sandbox-related env variables to ensure a consistent test environment
-    originalEnvGeminiSandbox = process.env.GEMINI_SANDBOX;
-    originalEnvSandbox = process.env.SANDBOX;
-    delete process.env.GEMINI_SANDBOX;
-    delete process.env.SANDBOX;
+    originalEnvGeminiSandbox = process.env['GEMINI_SANDBOX'];
+    originalEnvSandbox = process.env['SANDBOX'];
+    delete process.env['GEMINI_SANDBOX'];
+    delete process.env['SANDBOX'];
 
     consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
     initialUnhandledRejectionListeners =
@@ -106,14 +106,14 @@ describe('gemini.tsx main function', () => {
   afterEach(() => {
     // Restore original env variables
     if (originalEnvGeminiSandbox !== undefined) {
-      process.env.GEMINI_SANDBOX = originalEnvGeminiSandbox;
+      process.env['GEMINI_SANDBOX'] = originalEnvGeminiSandbox;
     } else {
-      delete process.env.GEMINI_SANDBOX;
+      delete process.env['GEMINI_SANDBOX'];
     }
     if (originalEnvSandbox !== undefined) {
-      process.env.SANDBOX = originalEnvSandbox;
+      process.env['SANDBOX'] = originalEnvSandbox;
     } else {
-      delete process.env.SANDBOX;
+      delete process.env['SANDBOX'];
     }
 
     const currentListeners = process.listeners('unhandledRejection');
diff --git a/packages/cli/src/gemini.tsx b/packages/cli/src/gemini.tsx
index 64bb5c84..f7089e28 100644
--- a/packages/cli/src/gemini.tsx
+++ b/packages/cli/src/gemini.tsx
@@ -80,7 +80,7 @@ function getNodeMemoryArgs(config: Config): string[] {
     );
   }
 
-  if (process.env.GEMINI_CLI_NO_RELAUNCH) {
+  if (process.env['GEMINI_CLI_NO_RELAUNCH']) {
     return [];
   }
 
@@ -141,7 +141,7 @@ export async function main() {
   if (settings.errors.length > 0) {
     for (const error of settings.errors) {
       let errorMessage = `Error in ${error.path}: ${error.message}`;
-      if (!process.env.NO_COLOR) {
+      if (!process.env['NO_COLOR']) {
         errorMessage = `\x1b[31m${errorMessage}\x1b[0m`;
       }
       console.error(errorMessage);
@@ -187,7 +187,7 @@ export async function main() {
 
   // Set a default auth type if one isn't set.
   if (!settings.merged.selectedAuthType) {
-    if (process.env.CLOUD_SHELL === 'true') {
+    if (process.env['CLOUD_SHELL'] === 'true') {
       settings.setValue(
         SettingScope.User,
         'selectedAuthType',
@@ -217,7 +217,7 @@ export async function main() {
   }
 
   // hop into sandbox if we are outside and sandboxing is enabled
-  if (!process.env.SANDBOX) {
+  if (!process.env['SANDBOX']) {
     const memoryArgs = settings.merged.autoConfigureMaxOldSpaceSize
       ? getNodeMemoryArgs(config)
       : [];
@@ -338,7 +338,9 @@ export async function main() {
 
 function setWindowTitle(title: string, settings: LoadedSettings) {
   if (!settings.merged.hideWindowTitle) {
-    const windowTitle = (process.env.CLI_TITLE || `Gemini - ${title}`).replace(
+    const windowTitle = (
+      process.env['CLI_TITLE'] || `Gemini - ${title}`
+    ).replace(
       // eslint-disable-next-line no-control-regex
       /[\x00-\x1F\x7F]/g,
       '',
diff --git a/packages/cli/src/services/McpPromptLoader.ts b/packages/cli/src/services/McpPromptLoader.ts
index e912fb3e..c2862911 100644
--- a/packages/cli/src/services/McpPromptLoader.ts
+++ b/packages/cli/src/services/McpPromptLoader.ts
@@ -115,15 +115,15 @@ export class McpPromptLoader implements ICommandLoader {
               }
               const result = await prompt.invoke(promptInputs);
 
-              if (result.error) {
+              if (result['error']) {
                 return {
                   type: 'message',
                   messageType: 'error',
-                  content: `Error invoking prompt: ${result.error}`,
+                  content: `Error invoking prompt: ${result['error']}`,
                 };
               }
 
-              if (!result.messages?.[0]?.content?.text) {
+              if (!result.messages?.[0]?.content?.['text']) {
                 return {
                   type: 'message',
                   messageType: 'error',
diff --git a/packages/cli/src/ui/App.tsx b/packages/cli/src/ui/App.tsx
index 9773971b..e0dbcba2 100644
--- a/packages/cli/src/ui/App.tsx
+++ b/packages/cli/src/ui/App.tsx
@@ -1089,7 +1089,7 @@ const App = ({ config, settings, startupWarnings = [], version }: AppProps) => {
                 alignItems={isNarrow ? 'flex-start' : 'center'}
               >
                 <Box>
-                  {process.env.GEMINI_SYSTEM_MD && (
+                  {process.env['GEMINI_SYSTEM_MD'] && (
                     <Text color={Colors.AccentRed}>|⌐■_■| </Text>
                   )}
                   {ctrlCPressedOnce ? (
diff --git a/packages/cli/src/ui/IdeIntegrationNudge.tsx b/packages/cli/src/ui/IdeIntegrationNudge.tsx
index 906947f2..861728fa 100644
--- a/packages/cli/src/ui/IdeIntegrationNudge.tsx
+++ b/packages/cli/src/ui/IdeIntegrationNudge.tsx
@@ -41,8 +41,8 @@ export function IdeIntegrationNudge({
   const { displayName: ideName } = getIdeInfo(ide);
   // Assume extension is already installed if the env variables are set.
   const isExtensionPreInstalled =
-    !!process.env.GEMINI_CLI_IDE_SERVER_PORT &&
-    !!process.env.GEMINI_CLI_IDE_WORKSPACE_PATH;
+    !!process.env['GEMINI_CLI_IDE_SERVER_PORT'] &&
+    !!process.env['GEMINI_CLI_IDE_WORKSPACE_PATH'];
 
   const OPTIONS: Array<RadioSelectItem<IdeIntegrationNudgeResult>> = [
     {
diff --git a/packages/cli/src/ui/commands/aboutCommand.test.ts b/packages/cli/src/ui/commands/aboutCommand.test.ts
index 27e96755..34f11e80 100644
--- a/packages/cli/src/ui/commands/aboutCommand.test.ts
+++ b/packages/cli/src/ui/commands/aboutCommand.test.ts
@@ -44,7 +44,7 @@ describe('aboutCommand', () => {
     vi.spyOn(mockContext.services.config!, 'getModel').mockReturnValue(
       'test-model',
     );
-    process.env.GOOGLE_CLOUD_PROJECT = 'test-gcp-project';
+    process.env['GOOGLE_CLOUD_PROJECT'] = 'test-gcp-project';
     Object.defineProperty(process, 'platform', {
       value: 'test-os',
     });
@@ -68,7 +68,7 @@ describe('aboutCommand', () => {
   });
 
   it('should call addItem with all version info', async () => {
-    process.env.SANDBOX = '';
+    process.env['SANDBOX'] = '';
     if (!aboutCommand.action) {
       throw new Error('The about command must have an action.');
     }
@@ -91,7 +91,7 @@ describe('aboutCommand', () => {
   });
 
   it('should show the correct sandbox environment variable', async () => {
-    process.env.SANDBOX = 'gemini-sandbox';
+    process.env['SANDBOX'] = 'gemini-sandbox';
     if (!aboutCommand.action) {
       throw new Error('The about command must have an action.');
     }
@@ -107,8 +107,8 @@ describe('aboutCommand', () => {
   });
 
   it('should show sandbox-exec profile when applicable', async () => {
-    process.env.SANDBOX = 'sandbox-exec';
-    process.env.SEATBELT_PROFILE = 'test-profile';
+    process.env['SANDBOX'] = 'sandbox-exec';
+    process.env['SEATBELT_PROFILE'] = 'test-profile';
     if (!aboutCommand.action) {
       throw new Error('The about command must have an action.');
     }
diff --git a/packages/cli/src/ui/commands/aboutCommand.ts b/packages/cli/src/ui/commands/aboutCommand.ts
index 47b1b495..2512fead 100644
--- a/packages/cli/src/ui/commands/aboutCommand.ts
+++ b/packages/cli/src/ui/commands/aboutCommand.ts
@@ -16,18 +16,18 @@ export const aboutCommand: SlashCommand = {
   action: async (context) => {
     const osVersion = process.platform;
     let sandboxEnv = 'no sandbox';
-    if (process.env.SANDBOX && process.env.SANDBOX !== 'sandbox-exec') {
-      sandboxEnv = process.env.SANDBOX;
-    } else if (process.env.SANDBOX === 'sandbox-exec') {
+    if (process.env['SANDBOX'] && process.env['SANDBOX'] !== 'sandbox-exec') {
+      sandboxEnv = process.env['SANDBOX'];
+    } else if (process.env['SANDBOX'] === 'sandbox-exec') {
       sandboxEnv = `sandbox-exec (${
-        process.env.SEATBELT_PROFILE || 'unknown'
+        process.env['SEATBELT_PROFILE'] || 'unknown'
       })`;
     }
     const modelVersion = context.services.config?.getModel() || 'Unknown';
     const cliVersion = await getCliVersion();
     const selectedAuthType =
       context.services.settings.merged.selectedAuthType || '';
-    const gcpProject = process.env.GOOGLE_CLOUD_PROJECT || '';
+    const gcpProject = process.env['GOOGLE_CLOUD_PROJECT'] || '';
     const ideClient =
       context.services.config?.getIdeClient()?.getDetectedIdeDisplayName() ||
       '';
diff --git a/packages/cli/src/ui/commands/bugCommand.ts b/packages/cli/src/ui/commands/bugCommand.ts
index 528b2b4c..8529e12b 100644
--- a/packages/cli/src/ui/commands/bugCommand.ts
+++ b/packages/cli/src/ui/commands/bugCommand.ts
@@ -27,11 +27,11 @@ export const bugCommand: SlashCommand = {
 
     const osVersion = `${process.platform} ${process.version}`;
     let sandboxEnv = 'no sandbox';
-    if (process.env.SANDBOX && process.env.SANDBOX !== 'sandbox-exec') {
-      sandboxEnv = process.env.SANDBOX.replace(/^gemini-(?:code-)?/, '');
-    } else if (process.env.SANDBOX === 'sandbox-exec') {
+    if (process.env['SANDBOX'] && process.env['SANDBOX'] !== 'sandbox-exec') {
+      sandboxEnv = process.env['SANDBOX'].replace(/^gemini-(?:code-)?/, '');
+    } else if (process.env['SANDBOX'] === 'sandbox-exec') {
       sandboxEnv = `sandbox-exec (${
-        process.env.SEATBELT_PROFILE || 'unknown'
+        process.env['SEATBELT_PROFILE'] || 'unknown'
       })`;
     }
     const modelVersion = config?.getModel() || 'Unknown';
diff --git a/packages/cli/src/ui/commands/docsCommand.test.ts b/packages/cli/src/ui/commands/docsCommand.test.ts
index 73b7396a..58e2e173 100644
--- a/packages/cli/src/ui/commands/docsCommand.test.ts
+++ b/packages/cli/src/ui/commands/docsCommand.test.ts
@@ -56,7 +56,7 @@ describe('docsCommand', () => {
     }
 
     // Simulate a sandbox environment
-    process.env.SANDBOX = 'gemini-sandbox';
+    vi.stubEnv('SANDBOX', 'gemini-sandbox');
     const docsUrl = 'https://goo.gle/gemini-cli-docs';
 
     await docsCommand.action(mockContext, '');
@@ -79,7 +79,7 @@ describe('docsCommand', () => {
     }
 
     // Simulate the specific 'sandbox-exec' environment
-    process.env.SANDBOX = 'sandbox-exec';
+    vi.stubEnv('SANDBOX', 'sandbox-exec');
     const docsUrl = 'https://goo.gle/gemini-cli-docs';
 
     await docsCommand.action(mockContext, '');
diff --git a/packages/cli/src/ui/commands/docsCommand.ts b/packages/cli/src/ui/commands/docsCommand.ts
index 922b236a..3ff160a7 100644
--- a/packages/cli/src/ui/commands/docsCommand.ts
+++ b/packages/cli/src/ui/commands/docsCommand.ts
@@ -20,7 +20,7 @@ export const docsCommand: SlashCommand = {
   action: async (context: CommandContext): Promise<void> => {
     const docsUrl = 'https://goo.gle/gemini-cli-docs';
 
-    if (process.env.SANDBOX && process.env.SANDBOX !== 'sandbox-exec') {
+    if (process.env['SANDBOX'] && process.env['SANDBOX'] !== 'sandbox-exec') {
       context.ui.addItem(
         {
           type: MessageType.INFO,
diff --git a/packages/cli/src/ui/commands/mcpCommand.test.ts b/packages/cli/src/ui/commands/mcpCommand.test.ts
index 0f339665..6e48c2f9 100644
--- a/packages/cli/src/ui/commands/mcpCommand.test.ts
+++ b/packages/cli/src/ui/commands/mcpCommand.test.ts
@@ -73,7 +73,7 @@ describe('mcpCommand', () => {
     vi.clearAllMocks();
 
     // Set up default mock environment
-    delete process.env.SANDBOX;
+    vi.unstubAllEnvs();
 
     // Default mock implementations
     vi.mocked(getMCPServerStatus).mockReturnValue(MCPServerStatus.CONNECTED);
diff --git a/packages/cli/src/ui/components/AuthDialog.test.tsx b/packages/cli/src/ui/components/AuthDialog.test.tsx
index 3efc3c01..38c6972a 100644
--- a/packages/cli/src/ui/components/AuthDialog.test.tsx
+++ b/packages/cli/src/ui/components/AuthDialog.test.tsx
@@ -17,8 +17,8 @@ describe('AuthDialog', () => {
 
   beforeEach(() => {
     originalEnv = { ...process.env };
-    process.env.GEMINI_API_KEY = '';
-    process.env.GEMINI_DEFAULT_AUTH_TYPE = '';
+    process.env['GEMINI_API_KEY'] = '';
+    process.env['GEMINI_DEFAULT_AUTH_TYPE'] = '';
     vi.clearAllMocks();
   });
 
@@ -27,7 +27,7 @@ describe('AuthDialog', () => {
   });
 
   it('should show an error if the initial auth type is invalid', () => {
-    process.env.GEMINI_API_KEY = '';
+    process.env['GEMINI_API_KEY'] = '';
 
     const settings: LoadedSettings = new LoadedSettings(
       {
@@ -62,7 +62,7 @@ describe('AuthDialog', () => {
 
   describe('GEMINI_API_KEY environment variable', () => {
     it('should detect GEMINI_API_KEY environment variable', () => {
-      process.env.GEMINI_API_KEY = 'foobar';
+      process.env['GEMINI_API_KEY'] = 'foobar';
 
       const settings: LoadedSettings = new LoadedSettings(
         {
@@ -94,8 +94,8 @@ describe('AuthDialog', () => {
     });
 
     it('should not show the GEMINI_API_KEY message if GEMINI_DEFAULT_AUTH_TYPE is set to something else', () => {
-      process.env.GEMINI_API_KEY = 'foobar';
-      process.env.GEMINI_DEFAULT_AUTH_TYPE = AuthType.LOGIN_WITH_GOOGLE;
+      process.env['GEMINI_API_KEY'] = 'foobar';
+      process.env['GEMINI_DEFAULT_AUTH_TYPE'] = AuthType.LOGIN_WITH_GOOGLE;
 
       const settings: LoadedSettings = new LoadedSettings(
         {
@@ -127,8 +127,8 @@ describe('AuthDialog', () => {
     });
 
     it('should show the GEMINI_API_KEY message if GEMINI_DEFAULT_AUTH_TYPE is set to use api key', () => {
-      process.env.GEMINI_API_KEY = 'foobar';
-      process.env.GEMINI_DEFAULT_AUTH_TYPE = AuthType.USE_GEMINI;
+      process.env['GEMINI_API_KEY'] = 'foobar';
+      process.env['GEMINI_DEFAULT_AUTH_TYPE'] = AuthType.USE_GEMINI;
 
       const settings: LoadedSettings = new LoadedSettings(
         {
@@ -162,7 +162,7 @@ describe('AuthDialog', () => {
 
   describe('GEMINI_DEFAULT_AUTH_TYPE environment variable', () => {
     it('should select the auth type specified by GEMINI_DEFAULT_AUTH_TYPE', () => {
-      process.env.GEMINI_DEFAULT_AUTH_TYPE = AuthType.LOGIN_WITH_GOOGLE;
+      process.env['GEMINI_DEFAULT_AUTH_TYPE'] = AuthType.LOGIN_WITH_GOOGLE;
 
       const settings: LoadedSettings = new LoadedSettings(
         {
@@ -222,7 +222,7 @@ describe('AuthDialog', () => {
     });
 
     it('should show an error and fall back to default if GEMINI_DEFAULT_AUTH_TYPE is invalid', () => {
-      process.env.GEMINI_DEFAULT_AUTH_TYPE = 'invalid-auth-type';
+      process.env['GEMINI_DEFAULT_AUTH_TYPE'] = 'invalid-auth-type';
 
       const settings: LoadedSettings = new LoadedSettings(
         {
diff --git a/packages/cli/src/ui/components/AuthDialog.tsx b/packages/cli/src/ui/components/AuthDialog.tsx
index c353727c..fb3d116b 100644
--- a/packages/cli/src/ui/components/AuthDialog.tsx
+++ b/packages/cli/src/ui/components/AuthDialog.tsx
@@ -42,18 +42,18 @@ export function AuthDialog({
     }
 
     const defaultAuthType = parseDefaultAuthType(
-      process.env.GEMINI_DEFAULT_AUTH_TYPE,
+      process.env['GEMINI_DEFAULT_AUTH_TYPE'],
     );
 
-    if (process.env.GEMINI_DEFAULT_AUTH_TYPE && defaultAuthType === null) {
+    if (process.env['GEMINI_DEFAULT_AUTH_TYPE'] && defaultAuthType === null) {
       return (
-        `Invalid value for GEMINI_DEFAULT_AUTH_TYPE: "${process.env.GEMINI_DEFAULT_AUTH_TYPE}". ` +
+        `Invalid value for GEMINI_DEFAULT_AUTH_TYPE: "${process.env['GEMINI_DEFAULT_AUTH_TYPE']}". ` +
         `Valid values are: ${Object.values(AuthType).join(', ')}.`
       );
     }
 
     if (
-      process.env.GEMINI_API_KEY &&
+      process.env['GEMINI_API_KEY'] &&
       (!defaultAuthType || defaultAuthType === AuthType.USE_GEMINI)
     ) {
       return 'Existing API key detected (GEMINI_API_KEY). Select "Gemini API Key" option to use it.';
@@ -65,7 +65,7 @@ export function AuthDialog({
       label: 'Login with Google',
       value: AuthType.LOGIN_WITH_GOOGLE,
     },
-    ...(process.env.CLOUD_SHELL === 'true'
+    ...(process.env['CLOUD_SHELL'] === 'true'
       ? [
           {
             label: 'Use Cloud Shell user credentials',
@@ -86,13 +86,13 @@ export function AuthDialog({
     }
 
     const defaultAuthType = parseDefaultAuthType(
-      process.env.GEMINI_DEFAULT_AUTH_TYPE,
+      process.env['GEMINI_DEFAULT_AUTH_TYPE'],
     );
     if (defaultAuthType) {
       return item.value === defaultAuthType;
     }
 
-    if (process.env.GEMINI_API_KEY) {
+    if (process.env['GEMINI_API_KEY']) {
       return item.value === AuthType.USE_GEMINI;
     }
 
diff --git a/packages/cli/src/ui/components/Footer.tsx b/packages/cli/src/ui/components/Footer.tsx
index 09b94ec1..ee644bc5 100644
--- a/packages/cli/src/ui/components/Footer.tsx
+++ b/packages/cli/src/ui/components/Footer.tsx
@@ -103,15 +103,16 @@ export const Footer: React.FC<FooterProps> = ({
       >
         {isTrustedFolder === false ? (
           <Text color={theme.status.warning}>untrusted</Text>
-        ) : process.env.SANDBOX && process.env.SANDBOX !== 'sandbox-exec' ? (
+        ) : process.env['SANDBOX'] &&
+          process.env['SANDBOX'] !== 'sandbox-exec' ? (
           <Text color="green">
-            {process.env.SANDBOX.replace(/^gemini-(?:cli-)?/, '')}
+            {process.env['SANDBOX'].replace(/^gemini-(?:cli-)?/, '')}
           </Text>
-        ) : process.env.SANDBOX === 'sandbox-exec' ? (
+        ) : process.env['SANDBOX'] === 'sandbox-exec' ? (
           <Text color={theme.status.warning}>
             macOS Seatbelt{' '}
             <Text color={theme.text.secondary}>
-              ({process.env.SEATBELT_PROFILE})
+              ({process.env['SEATBELT_PROFILE']})
             </Text>
           </Text>
         ) : (
diff --git a/packages/cli/src/ui/components/shared/MaxSizedBox.tsx b/packages/cli/src/ui/components/shared/MaxSizedBox.tsx
index 346472bf..0a51e2fd 100644
--- a/packages/cli/src/ui/components/shared/MaxSizedBox.tsx
+++ b/packages/cli/src/ui/components/shared/MaxSizedBox.tsx
@@ -321,7 +321,7 @@ function visitBoxRow(element: React.ReactNode): Row {
       const segment: StyledText = { text, props: parentProps ?? {} };
 
       // Check the 'wrap' property from the merged props to decide the segment type.
-      if (parentProps === undefined || parentProps.wrap === 'wrap') {
+      if (parentProps === undefined || parentProps['wrap'] === 'wrap') {
         hasSeenWrapped = true;
         row.segments.push(segment);
       } else {
diff --git a/packages/cli/src/ui/hooks/atCommandProcessor.ts b/packages/cli/src/ui/hooks/atCommandProcessor.ts
index cef2f811..50b8fbbd 100644
--- a/packages/cli/src/ui/hooks/atCommandProcessor.ts
+++ b/packages/cli/src/ui/hooks/atCommandProcessor.ts
@@ -362,20 +362,20 @@ export async function handleAtCommand({
 
   // Inform user about ignored paths
   const totalIgnored =
-    ignoredByReason.git.length +
-    ignoredByReason.gemini.length +
-    ignoredByReason.both.length;
+    ignoredByReason['git'].length +
+    ignoredByReason['gemini'].length +
+    ignoredByReason['both'].length;
 
   if (totalIgnored > 0) {
     const messages = [];
-    if (ignoredByReason.git.length) {
-      messages.push(`Git-ignored: ${ignoredByReason.git.join(', ')}`);
+    if (ignoredByReason['git'].length) {
+      messages.push(`Git-ignored: ${ignoredByReason['git'].join(', ')}`);
     }
-    if (ignoredByReason.gemini.length) {
-      messages.push(`Gemini-ignored: ${ignoredByReason.gemini.join(', ')}`);
+    if (ignoredByReason['gemini'].length) {
+      messages.push(`Gemini-ignored: ${ignoredByReason['gemini'].join(', ')}`);
     }
-    if (ignoredByReason.both.length) {
-      messages.push(`Ignored by both: ${ignoredByReason.both.join(', ')}`);
+    if (ignoredByReason['both'].length) {
+      messages.push(`Ignored by both: ${ignoredByReason['both'].join(', ')}`);
     }
 
     const message = `Ignored ${totalIgnored} files:\n${messages.join('\n')}`;
diff --git a/packages/cli/src/ui/hooks/useKeypress.test.ts b/packages/cli/src/ui/hooks/useKeypress.test.ts
index b804eb90..138c927c 100644
--- a/packages/cli/src/ui/hooks/useKeypress.test.ts
+++ b/packages/cli/src/ui/hooks/useKeypress.test.ts
@@ -116,7 +116,7 @@ describe('useKeypress', () => {
     });
 
     originalNodeVersion = process.versions.node;
-    delete process.env['PASTE_WORKAROUND'];
+    vi.unstubAllEnvs();
   });
 
   afterEach(() => {
@@ -197,7 +197,7 @@ describe('useKeypress', () => {
       description: 'Workaround Env Var',
       setup: () => {
         setNodeVersion('20.0.0');
-        process.env['PASTE_WORKAROUND'] = 'true';
+        vi.stubEnv('PASTE_WORKAROUND', 'true');
       },
       isLegacy: true,
     },
diff --git a/packages/cli/src/ui/hooks/useThemeCommand.ts b/packages/cli/src/ui/hooks/useThemeCommand.ts
index 6c9e60d8..cf881f53 100644
--- a/packages/cli/src/ui/hooks/useThemeCommand.ts
+++ b/packages/cli/src/ui/hooks/useThemeCommand.ts
@@ -39,7 +39,7 @@ export const useThemeCommand = (
   }, [loadedSettings.merged.theme, setThemeError]);
 
   const openThemeDialog = useCallback(() => {
-    if (process.env.NO_COLOR) {
+    if (process.env['NO_COLOR']) {
       addItem(
         {
           type: MessageType.INFO,
diff --git a/packages/cli/src/ui/themes/color-utils.test.ts b/packages/cli/src/ui/themes/color-utils.test.ts
index cafc28dd..dfb1be83 100644
--- a/packages/cli/src/ui/themes/color-utils.test.ts
+++ b/packages/cli/src/ui/themes/color-utils.test.ts
@@ -124,18 +124,18 @@ describe('Color Utils', () => {
 
   describe('CSS_NAME_TO_HEX_MAP', () => {
     it('should contain expected CSS color mappings', () => {
-      expect(CSS_NAME_TO_HEX_MAP.darkkhaki).toBe('#bdb76b');
-      expect(CSS_NAME_TO_HEX_MAP.coral).toBe('#ff7f50');
-      expect(CSS_NAME_TO_HEX_MAP.teal).toBe('#008080');
-      expect(CSS_NAME_TO_HEX_MAP.tomato).toBe('#ff6347');
-      expect(CSS_NAME_TO_HEX_MAP.turquoise).toBe('#40e0d0');
+      expect(CSS_NAME_TO_HEX_MAP['darkkhaki']).toBe('#bdb76b');
+      expect(CSS_NAME_TO_HEX_MAP['coral']).toBe('#ff7f50');
+      expect(CSS_NAME_TO_HEX_MAP['teal']).toBe('#008080');
+      expect(CSS_NAME_TO_HEX_MAP['tomato']).toBe('#ff6347');
+      expect(CSS_NAME_TO_HEX_MAP['turquoise']).toBe('#40e0d0');
     });
 
     it('should not contain Ink-supported color names', () => {
-      expect(CSS_NAME_TO_HEX_MAP.black).toBeUndefined();
-      expect(CSS_NAME_TO_HEX_MAP.red).toBeUndefined();
-      expect(CSS_NAME_TO_HEX_MAP.green).toBeUndefined();
-      expect(CSS_NAME_TO_HEX_MAP.blue).toBeUndefined();
+      expect(CSS_NAME_TO_HEX_MAP['black']).toBeUndefined();
+      expect(CSS_NAME_TO_HEX_MAP['red']).toBeUndefined();
+      expect(CSS_NAME_TO_HEX_MAP['green']).toBeUndefined();
+      expect(CSS_NAME_TO_HEX_MAP['blue']).toBeUndefined();
     });
   });
 
diff --git a/packages/cli/src/ui/themes/theme-manager.test.ts b/packages/cli/src/ui/themes/theme-manager.test.ts
index 0b2c17c0..91e51bf9 100644
--- a/packages/cli/src/ui/themes/theme-manager.test.ts
+++ b/packages/cli/src/ui/themes/theme-manager.test.ts
@@ -5,8 +5,8 @@
  */
 
 // Patch: Unset NO_COLOR at the very top before any imports
-if (process.env.NO_COLOR !== undefined) {
-  delete process.env.NO_COLOR;
+if (process.env['NO_COLOR'] !== undefined) {
+  delete process.env['NO_COLOR'];
 }
 
 import { describe, it, expect, beforeEach } from 'vitest';
@@ -87,13 +87,13 @@ describe('ThemeManager', () => {
   });
 
   it('should return NoColorTheme if NO_COLOR is set', () => {
-    const original = process.env.NO_COLOR;
-    process.env.NO_COLOR = '1';
+    const original = process.env['NO_COLOR'];
+    process.env['NO_COLOR'] = '1';
     expect(themeManager.getActiveTheme().name).toBe('NoColor');
     if (original === undefined) {
-      delete process.env.NO_COLOR;
+      delete process.env['NO_COLOR'];
     } else {
-      process.env.NO_COLOR = original;
+      process.env['NO_COLOR'] = original;
     }
   });
 });
diff --git a/packages/cli/src/ui/themes/theme-manager.ts b/packages/cli/src/ui/themes/theme-manager.ts
index b19b06a9..5258bf76 100644
--- a/packages/cli/src/ui/themes/theme-manager.ts
+++ b/packages/cli/src/ui/themes/theme-manager.ts
@@ -125,7 +125,7 @@ class ThemeManager {
    * @returns The active theme.
    */
   getActiveTheme(): Theme {
-    if (process.env.NO_COLOR) {
+    if (process.env['NO_COLOR']) {
       return NoColorTheme;
     }
     // Ensure the active theme is always valid (fall back to default if not)
diff --git a/packages/cli/src/ui/utils/CodeColorizer.tsx b/packages/cli/src/ui/utils/CodeColorizer.tsx
index b183d556..775ffadc 100644
--- a/packages/cli/src/ui/utils/CodeColorizer.tsx
+++ b/packages/cli/src/ui/utils/CodeColorizer.tsx
@@ -38,7 +38,7 @@ function renderHastNode(
   // Handle Element Nodes: Determine color and pass it down, don't wrap
   if (node.type === 'element') {
     const nodeClasses: string[] =
-      (node.properties?.className as string[]) || [];
+      (node.properties?.['className'] as string[]) || [];
     let elementColor: string | undefined = undefined;
 
     // Find color defined specifically for this element's class
diff --git a/packages/cli/src/ui/utils/terminalSetup.ts b/packages/cli/src/ui/utils/terminalSetup.ts
index 7f944847..d41d2075 100644
--- a/packages/cli/src/ui/utils/terminalSetup.ts
+++ b/packages/cli/src/ui/utils/terminalSetup.ts
@@ -52,22 +52,24 @@ type SupportedTerminal = 'vscode' | 'cursor' | 'windsurf';
 
 // Terminal detection
 async function detectTerminal(): Promise<SupportedTerminal | null> {
-  const termProgram = process.env.TERM_PROGRAM;
+  const termProgram = process.env['TERM_PROGRAM'];
 
   // Check VS Code and its forks - check forks first to avoid false positives
   // Check for Cursor-specific indicators
   if (
-    process.env.CURSOR_TRACE_ID ||
-    process.env.VSCODE_GIT_ASKPASS_MAIN?.toLowerCase().includes('cursor')
+    process.env['CURSOR_TRACE_ID'] ||
+    process.env['VSCODE_GIT_ASKPASS_MAIN']?.toLowerCase().includes('cursor')
   ) {
     return 'cursor';
   }
   // Check for Windsurf-specific indicators
-  if (process.env.VSCODE_GIT_ASKPASS_MAIN?.toLowerCase().includes('windsurf')) {
+  if (
+    process.env['VSCODE_GIT_ASKPASS_MAIN']?.toLowerCase().includes('windsurf')
+  ) {
     return 'windsurf';
   }
   // Check VS Code last since forks may also set VSCODE env vars
-  if (termProgram === 'vscode' || process.env.VSCODE_GIT_IPC_HANDLE) {
+  if (termProgram === 'vscode' || process.env['VSCODE_GIT_IPC_HANDLE']) {
     return 'vscode';
   }
 
@@ -118,10 +120,10 @@ function getVSCodeStyleConfigDir(appName: string): string | null {
       'User',
     );
   } else if (platform === 'win32') {
-    if (!process.env.APPDATA) {
+    if (!process.env['APPDATA']) {
       return null;
     }
-    return path.join(process.env.APPDATA, appName, 'User');
+    return path.join(process.env['APPDATA'], appName, 'User');
   } else {
     return path.join(os.homedir(), '.config', appName, 'User');
   }
diff --git a/packages/cli/src/ui/utils/updateCheck.test.ts b/packages/cli/src/ui/utils/updateCheck.test.ts
index c2b56a03..c7214e8b 100644
--- a/packages/cli/src/ui/utils/updateCheck.test.ts
+++ b/packages/cli/src/ui/utils/updateCheck.test.ts
@@ -22,7 +22,7 @@ describe('checkForUpdates', () => {
     vi.useFakeTimers();
     vi.resetAllMocks();
     // Clear DEV environment variable before each test
-    delete process.env.DEV;
+    delete process.env['DEV'];
   });
 
   afterEach(() => {
@@ -31,7 +31,7 @@ describe('checkForUpdates', () => {
   });
 
   it('should return null when running from source (DEV=true)', async () => {
-    process.env.DEV = 'true';
+    process.env['DEV'] = 'true';
     getPackageJson.mockResolvedValue({
       name: 'test-package',
       version: '1.0.0',
diff --git a/packages/cli/src/ui/utils/updateCheck.ts b/packages/cli/src/ui/utils/updateCheck.ts
index f4c18586..bb6c507c 100644
--- a/packages/cli/src/ui/utils/updateCheck.ts
+++ b/packages/cli/src/ui/utils/updateCheck.ts
@@ -41,7 +41,7 @@ function getBestAvailableUpdate(
 export async function checkForUpdates(): Promise<UpdateObject | null> {
   try {
     // Skip update check when running from source (development mode)
-    if (process.env.DEV === 'true') {
+    if (process.env['DEV'] === 'true') {
       return null;
     }
     const packageJson = await getPackageJson();
diff --git a/packages/cli/src/utils/sandbox.ts b/packages/cli/src/utils/sandbox.ts
index dfd2065f..dac34778 100644
--- a/packages/cli/src/utils/sandbox.ts
+++ b/packages/cli/src/utils/sandbox.ts
@@ -63,7 +63,7 @@ const BUILTIN_SEATBELT_PROFILES = [
  * @returns {Promise<boolean>} A promise that resolves to true if the current user's UID/GID should be used, false otherwise.
  */
 async function shouldUseCurrentUserInSandbox(): Promise<boolean> {
-  const envVar = process.env.SANDBOX_SET_UID_GID?.toLowerCase().trim();
+  const envVar = process.env['SANDBOX_SET_UID_GID']?.toLowerCase().trim();
 
   if (envVar === '1' || envVar === 'true') {
     return true;
@@ -108,7 +108,7 @@ function parseImageName(image: string): string {
 }
 
 function ports(): string[] {
-  return (process.env.SANDBOX_PORTS ?? '')
+  return (process.env['SANDBOX_PORTS'] ?? '')
     .split(',')
     .filter((p) => p.trim())
     .map((p) => p.trim());
@@ -121,8 +121,8 @@ function entrypoint(workdir: string): string[] {
   const pathSeparator = isWindows ? ';' : ':';
 
   let pathSuffix = '';
-  if (process.env.PATH) {
-    const paths = process.env.PATH.split(pathSeparator);
+  if (process.env['PATH']) {
+    const paths = process.env['PATH'].split(pathSeparator);
     for (const p of paths) {
       const containerPath = getContainerPath(p);
       if (
@@ -137,8 +137,8 @@ function entrypoint(workdir: string): string[] {
   }
 
   let pythonPathSuffix = '';
-  if (process.env.PYTHONPATH) {
-    const paths = process.env.PYTHONPATH.split(pathSeparator);
+  if (process.env['PYTHONPATH']) {
+    const paths = process.env['PYTHONPATH'].split(pathSeparator);
     for (const p of paths) {
       const containerPath = getContainerPath(p);
       if (
@@ -168,12 +168,12 @@ function entrypoint(workdir: string): string[] {
 
   const cliArgs = process.argv.slice(2).map((arg) => quote([arg]));
   const cliCmd =
-    process.env.NODE_ENV === 'development'
-      ? process.env.DEBUG
+    process.env['NODE_ENV'] === 'development'
+      ? process.env['DEBUG']
         ? 'npm run debug --'
         : 'npm rebuild && npm run start --'
-      : process.env.DEBUG
-        ? `node --inspect-brk=0.0.0.0:${process.env.DEBUG_PORT || '9229'} $(which gemini)`
+      : process.env['DEBUG']
+        ? `node --inspect-brk=0.0.0.0:${process.env['DEBUG_PORT'] || '9229'} $(which gemini)`
         : 'gemini';
 
   const args = [...shellCmds, cliCmd, ...cliArgs];
@@ -187,7 +187,7 @@ export async function start_sandbox(
   cliConfig?: Config,
 ) {
   const patcher = new ConsolePatcher({
-    debugMode: cliConfig?.getDebugMode() || !!process.env.DEBUG,
+    debugMode: cliConfig?.getDebugMode() || !!process.env['DEBUG'],
     stderr: true,
   });
   patcher.patch();
@@ -195,11 +195,11 @@ export async function start_sandbox(
   try {
     if (config.command === 'sandbox-exec') {
       // disallow BUILD_SANDBOX
-      if (process.env.BUILD_SANDBOX) {
+      if (process.env['BUILD_SANDBOX']) {
         console.error('ERROR: cannot BUILD_SANDBOX when using macOS Seatbelt');
         process.exit(1);
       }
-      const profile = (process.env.SEATBELT_PROFILE ??= 'permissive-open');
+      const profile = (process.env['SEATBELT_PROFILE'] ??= 'permissive-open');
       let profileFile = new URL(`sandbox-macos-${profile}.sb`, import.meta.url)
         .pathname;
       // if profile name is not recognized, then look for file under project settings directory
@@ -219,7 +219,7 @@ export async function start_sandbox(
       console.error(`using macos seatbelt (profile: ${profile}) ...`);
       // if DEBUG is set, convert to --inspect-brk in NODE_OPTIONS
       const nodeOptions = [
-        ...(process.env.DEBUG ? ['--inspect-brk'] : []),
+        ...(process.env['DEBUG'] ? ['--inspect-brk'] : []),
         ...nodeArgs,
       ].join(' ');
 
@@ -275,22 +275,22 @@ export async function start_sandbox(
         ].join(' '),
       );
       // start and set up proxy if GEMINI_SANDBOX_PROXY_COMMAND is set
-      const proxyCommand = process.env.GEMINI_SANDBOX_PROXY_COMMAND;
+      const proxyCommand = process.env['GEMINI_SANDBOX_PROXY_COMMAND'];
       let proxyProcess: ChildProcess | undefined = undefined;
       let sandboxProcess: ChildProcess | undefined = undefined;
       const sandboxEnv = { ...process.env };
       if (proxyCommand) {
         const proxy =
-          process.env.HTTPS_PROXY ||
-          process.env.https_proxy ||
-          process.env.HTTP_PROXY ||
-          process.env.http_proxy ||
+          process.env['HTTPS_PROXY'] ||
+          process.env['https_proxy'] ||
+          process.env['HTTP_PROXY'] ||
+          process.env['http_proxy'] ||
           'http://localhost:8877';
         sandboxEnv['HTTPS_PROXY'] = proxy;
         sandboxEnv['https_proxy'] = proxy; // lower-case can be required, e.g. for curl
         sandboxEnv['HTTP_PROXY'] = proxy;
         sandboxEnv['http_proxy'] = proxy;
-        const noProxy = process.env.NO_PROXY || process.env.no_proxy;
+        const noProxy = process.env['NO_PROXY'] || process.env['no_proxy'];
         if (noProxy) {
           sandboxEnv['NO_PROXY'] = noProxy;
           sandboxEnv['no_proxy'] = noProxy;
@@ -358,7 +358,7 @@ export async function start_sandbox(
     // if BUILD_SANDBOX is set, then call scripts/build_sandbox.js under gemini-cli repo
     //
     // note this can only be done with binary linked from gemini-cli repo
-    if (process.env.BUILD_SANDBOX) {
+    if (process.env['BUILD_SANDBOX']) {
       if (!gcPath.includes('gemini-cli/packages/')) {
         console.error(
           'ERROR: cannot build sandbox using installed gemini binary; ' +
@@ -408,8 +408,8 @@ export async function start_sandbox(
     const args = ['run', '-i', '--rm', '--init', '--workdir', containerWorkdir];
 
     // add custom flags from SANDBOX_FLAGS
-    if (process.env.SANDBOX_FLAGS) {
-      const flags = parse(process.env.SANDBOX_FLAGS, process.env).filter(
+    if (process.env['SANDBOX_FLAGS']) {
+      const flags = parse(process.env['SANDBOX_FLAGS'], process.env).filter(
         (f): f is string => typeof f === 'string',
       );
       args.push(...flags);
@@ -456,8 +456,8 @@ export async function start_sandbox(
     }
 
     // mount ADC file if GOOGLE_APPLICATION_CREDENTIALS is set
-    if (process.env.GOOGLE_APPLICATION_CREDENTIALS) {
-      const adcFile = process.env.GOOGLE_APPLICATION_CREDENTIALS;
+    if (process.env['GOOGLE_APPLICATION_CREDENTIALS']) {
+      const adcFile = process.env['GOOGLE_APPLICATION_CREDENTIALS'];
       if (fs.existsSync(adcFile)) {
         args.push('--volume', `${adcFile}:${getContainerPath(adcFile)}:ro`);
         args.push(
@@ -468,8 +468,8 @@ export async function start_sandbox(
     }
 
     // mount paths listed in SANDBOX_MOUNTS
-    if (process.env.SANDBOX_MOUNTS) {
-      for (let mount of process.env.SANDBOX_MOUNTS.split(',')) {
+    if (process.env['SANDBOX_MOUNTS']) {
+      for (let mount of process.env['SANDBOX_MOUNTS'].split(',')) {
         if (mount.trim()) {
           // parse mount as from:to:opts
           let [from, to, opts] = mount.trim().split(':');
@@ -500,22 +500,22 @@ export async function start_sandbox(
     ports().forEach((p) => args.push('--publish', `${p}:${p}`));
 
     // if DEBUG is set, expose debugging port
-    if (process.env.DEBUG) {
-      const debugPort = process.env.DEBUG_PORT || '9229';
+    if (process.env['DEBUG']) {
+      const debugPort = process.env['DEBUG_PORT'] || '9229';
       args.push(`--publish`, `${debugPort}:${debugPort}`);
     }
 
     // copy proxy environment variables, replacing localhost with SANDBOX_PROXY_NAME
     // copy as both upper-case and lower-case as is required by some utilities
     // GEMINI_SANDBOX_PROXY_COMMAND implies HTTPS_PROXY unless HTTP_PROXY is set
-    const proxyCommand = process.env.GEMINI_SANDBOX_PROXY_COMMAND;
+    const proxyCommand = process.env['GEMINI_SANDBOX_PROXY_COMMAND'];
 
     if (proxyCommand) {
       let proxy =
-        process.env.HTTPS_PROXY ||
-        process.env.https_proxy ||
-        process.env.HTTP_PROXY ||
-        process.env.http_proxy ||
+        process.env['HTTPS_PROXY'] ||
+        process.env['https_proxy'] ||
+        process.env['HTTP_PROXY'] ||
+        process.env['http_proxy'] ||
         'http://localhost:8877';
       proxy = proxy.replace('localhost', SANDBOX_PROXY_NAME);
       if (proxy) {
@@ -524,7 +524,7 @@ export async function start_sandbox(
         args.push('--env', `HTTP_PROXY=${proxy}`);
         args.push('--env', `http_proxy=${proxy}`);
       }
-      const noProxy = process.env.NO_PROXY || process.env.no_proxy;
+      const noProxy = process.env['NO_PROXY'] || process.env['no_proxy'];
       if (noProxy) {
         args.push('--env', `NO_PROXY=${noProxy}`);
         args.push('--env', `no_proxy=${noProxy}`);
@@ -562,56 +562,56 @@ export async function start_sandbox(
     args.push('--name', containerName, '--hostname', containerName);
 
     // copy GEMINI_API_KEY(s)
-    if (process.env.GEMINI_API_KEY) {
-      args.push('--env', `GEMINI_API_KEY=${process.env.GEMINI_API_KEY}`);
+    if (process.env['GEMINI_API_KEY']) {
+      args.push('--env', `GEMINI_API_KEY=${process.env['GEMINI_API_KEY']}`);
     }
-    if (process.env.GOOGLE_API_KEY) {
-      args.push('--env', `GOOGLE_API_KEY=${process.env.GOOGLE_API_KEY}`);
+    if (process.env['GOOGLE_API_KEY']) {
+      args.push('--env', `GOOGLE_API_KEY=${process.env['GOOGLE_API_KEY']}`);
     }
 
     // copy GOOGLE_GENAI_USE_VERTEXAI
-    if (process.env.GOOGLE_GENAI_USE_VERTEXAI) {
+    if (process.env['GOOGLE_GENAI_USE_VERTEXAI']) {
       args.push(
         '--env',
-        `GOOGLE_GENAI_USE_VERTEXAI=${process.env.GOOGLE_GENAI_USE_VERTEXAI}`,
+        `GOOGLE_GENAI_USE_VERTEXAI=${process.env['GOOGLE_GENAI_USE_VERTEXAI']}`,
       );
     }
 
     // copy GOOGLE_GENAI_USE_GCA
-    if (process.env.GOOGLE_GENAI_USE_GCA) {
+    if (process.env['GOOGLE_GENAI_USE_GCA']) {
       args.push(
         '--env',
-        `GOOGLE_GENAI_USE_GCA=${process.env.GOOGLE_GENAI_USE_GCA}`,
+        `GOOGLE_GENAI_USE_GCA=${process.env['GOOGLE_GENAI_USE_GCA']}`,
       );
     }
 
     // copy GOOGLE_CLOUD_PROJECT
-    if (process.env.GOOGLE_CLOUD_PROJECT) {
+    if (process.env['GOOGLE_CLOUD_PROJECT']) {
       args.push(
         '--env',
-        `GOOGLE_CLOUD_PROJECT=${process.env.GOOGLE_CLOUD_PROJECT}`,
+        `GOOGLE_CLOUD_PROJECT=${process.env['GOOGLE_CLOUD_PROJECT']}`,
       );
     }
 
     // copy GOOGLE_CLOUD_LOCATION
-    if (process.env.GOOGLE_CLOUD_LOCATION) {
+    if (process.env['GOOGLE_CLOUD_LOCATION']) {
       args.push(
         '--env',
-        `GOOGLE_CLOUD_LOCATION=${process.env.GOOGLE_CLOUD_LOCATION}`,
+        `GOOGLE_CLOUD_LOCATION=${process.env['GOOGLE_CLOUD_LOCATION']}`,
       );
     }
 
     // copy GEMINI_MODEL
-    if (process.env.GEMINI_MODEL) {
-      args.push('--env', `GEMINI_MODEL=${process.env.GEMINI_MODEL}`);
+    if (process.env['GEMINI_MODEL']) {
+      args.push('--env', `GEMINI_MODEL=${process.env['GEMINI_MODEL']}`);
     }
 
     // copy TERM and COLORTERM to try to maintain terminal setup
-    if (process.env.TERM) {
-      args.push('--env', `TERM=${process.env.TERM}`);
+    if (process.env['TERM']) {
+      args.push('--env', `TERM=${process.env['TERM']}`);
     }
-    if (process.env.COLORTERM) {
-      args.push('--env', `COLORTERM=${process.env.COLORTERM}`);
+    if (process.env['COLORTERM']) {
+      args.push('--env', `COLORTERM=${process.env['COLORTERM']}`);
     }
 
     // Pass through IDE mode environment variables
@@ -630,7 +630,9 @@ export async function start_sandbox(
     // sandbox can then set up this new VIRTUAL_ENV directory using sandbox.bashrc (see below)
     // directory will be empty if not set up, which is still preferable to having host binaries
     if (
-      process.env.VIRTUAL_ENV?.toLowerCase().startsWith(workdir.toLowerCase())
+      process.env['VIRTUAL_ENV']
+        ?.toLowerCase()
+        .startsWith(workdir.toLowerCase())
     ) {
       const sandboxVenvPath = path.resolve(
         SETTINGS_DIRECTORY_NAME,
@@ -641,17 +643,17 @@ export async function start_sandbox(
       }
       args.push(
         '--volume',
-        `${sandboxVenvPath}:${getContainerPath(process.env.VIRTUAL_ENV)}`,
+        `${sandboxVenvPath}:${getContainerPath(process.env['VIRTUAL_ENV'])}`,
       );
       args.push(
         '--env',
-        `VIRTUAL_ENV=${getContainerPath(process.env.VIRTUAL_ENV)}`,
+        `VIRTUAL_ENV=${getContainerPath(process.env['VIRTUAL_ENV'])}`,
       );
     }
 
     // copy additional environment variables from SANDBOX_ENV
-    if (process.env.SANDBOX_ENV) {
-      for (let env of process.env.SANDBOX_ENV.split(',')) {
+    if (process.env['SANDBOX_ENV']) {
+      for (let env of process.env['SANDBOX_ENV'].split(',')) {
         if ((env = env.trim())) {
           if (env.includes('=')) {
             console.error(`SANDBOX_ENV: ${env}`);
@@ -667,7 +669,7 @@ export async function start_sandbox(
     }
 
     // copy NODE_OPTIONS
-    const existingNodeOptions = process.env.NODE_OPTIONS || '';
+    const existingNodeOptions = process.env['NODE_OPTIONS'] || '';
     const allNodeOptions = [
       ...(existingNodeOptions ? [existingNodeOptions] : []),
       ...nodeArgs,
@@ -692,7 +694,7 @@ export async function start_sandbox(
     let userFlag = '';
     const finalEntrypoint = entrypoint(workdir);
 
-    if (process.env.GEMINI_CLI_INTEGRATION_TEST === 'true') {
+    if (process.env['GEMINI_CLI_INTEGRATION_TEST'] === 'true') {
       args.push('--user', 'root');
       userFlag = '--user root';
     } else if (await shouldUseCurrentUserInSandbox()) {
diff --git a/packages/cli/src/utils/version.ts b/packages/cli/src/utils/version.ts
index 3b7bb0e2..0318f380 100644
--- a/packages/cli/src/utils/version.ts
+++ b/packages/cli/src/utils/version.ts
@@ -8,5 +8,5 @@ import { getPackageJson } from './package.js';
 
 export async function getCliVersion(): Promise<string> {
   const pkgJson = await getPackageJson();
-  return process.env.CLI_VERSION || pkgJson?.version || 'unknown';
+  return process.env['CLI_VERSION'] || pkgJson?.version || 'unknown';
 }
diff --git a/packages/cli/src/validateNonInterActiveAuth.test.ts b/packages/cli/src/validateNonInterActiveAuth.test.ts
index 7c079e25..2cf4a260 100644
--- a/packages/cli/src/validateNonInterActiveAuth.test.ts
+++ b/packages/cli/src/validateNonInterActiveAuth.test.ts
@@ -23,12 +23,12 @@ describe('validateNonInterActiveAuth', () => {
   >;
 
   beforeEach(() => {
-    originalEnvGeminiApiKey = process.env.GEMINI_API_KEY;
-    originalEnvVertexAi = process.env.GOOGLE_GENAI_USE_VERTEXAI;
-    originalEnvGcp = process.env.GOOGLE_GENAI_USE_GCA;
-    delete process.env.GEMINI_API_KEY;
-    delete process.env.GOOGLE_GENAI_USE_VERTEXAI;
-    delete process.env.GOOGLE_GENAI_USE_GCA;
+    originalEnvGeminiApiKey = process.env['GEMINI_API_KEY'];
+    originalEnvVertexAi = process.env['GOOGLE_GENAI_USE_VERTEXAI'];
+    originalEnvGcp = process.env['GOOGLE_GENAI_USE_GCA'];
+    delete process.env['GEMINI_API_KEY'];
+    delete process.env['GOOGLE_GENAI_USE_VERTEXAI'];
+    delete process.env['GOOGLE_GENAI_USE_GCA'];
     consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
     processExitSpy = vi.spyOn(process, 'exit').mockImplementation((code) => {
       throw new Error(`process.exit(${code}) called`);
@@ -38,19 +38,19 @@ describe('validateNonInterActiveAuth', () => {
 
   afterEach(() => {
     if (originalEnvGeminiApiKey !== undefined) {
-      process.env.GEMINI_API_KEY = originalEnvGeminiApiKey;
+      process.env['GEMINI_API_KEY'] = originalEnvGeminiApiKey;
     } else {
-      delete process.env.GEMINI_API_KEY;
+      delete process.env['GEMINI_API_KEY'];
     }
     if (originalEnvVertexAi !== undefined) {
-      process.env.GOOGLE_GENAI_USE_VERTEXAI = originalEnvVertexAi;
+      process.env['GOOGLE_GENAI_USE_VERTEXAI'] = originalEnvVertexAi;
     } else {
-      delete process.env.GOOGLE_GENAI_USE_VERTEXAI;
+      delete process.env['GOOGLE_GENAI_USE_VERTEXAI'];
     }
     if (originalEnvGcp !== undefined) {
-      process.env.GOOGLE_GENAI_USE_GCA = originalEnvGcp;
+      process.env['GOOGLE_GENAI_USE_GCA'] = originalEnvGcp;
     } else {
-      delete process.env.GOOGLE_GENAI_USE_GCA;
+      delete process.env['GOOGLE_GENAI_USE_GCA'];
     }
     vi.restoreAllMocks();
   });
@@ -76,7 +76,7 @@ describe('validateNonInterActiveAuth', () => {
   });
 
   it('uses LOGIN_WITH_GOOGLE if GOOGLE_GENAI_USE_GCA is set', async () => {
-    process.env.GOOGLE_GENAI_USE_GCA = 'true';
+    process.env['GOOGLE_GENAI_USE_GCA'] = 'true';
     const nonInteractiveConfig: NonInteractiveConfig = {
       refreshAuth: refreshAuthMock,
     };
@@ -89,7 +89,7 @@ describe('validateNonInterActiveAuth', () => {
   });
 
   it('uses USE_GEMINI if GEMINI_API_KEY is set', async () => {
-    process.env.GEMINI_API_KEY = 'fake-key';
+    process.env['GEMINI_API_KEY'] = 'fake-key';
     const nonInteractiveConfig: NonInteractiveConfig = {
       refreshAuth: refreshAuthMock,
     };
@@ -102,9 +102,9 @@ describe('validateNonInterActiveAuth', () => {
   });
 
   it('uses USE_VERTEX_AI if GOOGLE_GENAI_USE_VERTEXAI is true (with GOOGLE_CLOUD_PROJECT and GOOGLE_CLOUD_LOCATION)', async () => {
-    process.env.GOOGLE_GENAI_USE_VERTEXAI = 'true';
-    process.env.GOOGLE_CLOUD_PROJECT = 'test-project';
-    process.env.GOOGLE_CLOUD_LOCATION = 'us-central1';
+    process.env['GOOGLE_GENAI_USE_VERTEXAI'] = 'true';
+    process.env['GOOGLE_CLOUD_PROJECT'] = 'test-project';
+    process.env['GOOGLE_CLOUD_LOCATION'] = 'us-central1';
     const nonInteractiveConfig: NonInteractiveConfig = {
       refreshAuth: refreshAuthMock,
     };
@@ -117,8 +117,8 @@ describe('validateNonInterActiveAuth', () => {
   });
 
   it('uses USE_VERTEX_AI if GOOGLE_GENAI_USE_VERTEXAI is true and GOOGLE_API_KEY is set', async () => {
-    process.env.GOOGLE_GENAI_USE_VERTEXAI = 'true';
-    process.env.GOOGLE_API_KEY = 'vertex-api-key';
+    process.env['GOOGLE_GENAI_USE_VERTEXAI'] = 'true';
+    process.env['GOOGLE_API_KEY'] = 'vertex-api-key';
     const nonInteractiveConfig: NonInteractiveConfig = {
       refreshAuth: refreshAuthMock,
     };
@@ -131,11 +131,11 @@ describe('validateNonInterActiveAuth', () => {
   });
 
   it('uses LOGIN_WITH_GOOGLE if GOOGLE_GENAI_USE_GCA is set, even with other env vars', async () => {
-    process.env.GOOGLE_GENAI_USE_GCA = 'true';
-    process.env.GEMINI_API_KEY = 'fake-key';
-    process.env.GOOGLE_GENAI_USE_VERTEXAI = 'true';
-    process.env.GOOGLE_CLOUD_PROJECT = 'test-project';
-    process.env.GOOGLE_CLOUD_LOCATION = 'us-central1';
+    process.env['GOOGLE_GENAI_USE_GCA'] = 'true';
+    process.env['GEMINI_API_KEY'] = 'fake-key';
+    process.env['GOOGLE_GENAI_USE_VERTEXAI'] = 'true';
+    process.env['GOOGLE_CLOUD_PROJECT'] = 'test-project';
+    process.env['GOOGLE_CLOUD_LOCATION'] = 'us-central1';
     const nonInteractiveConfig: NonInteractiveConfig = {
       refreshAuth: refreshAuthMock,
     };
@@ -148,10 +148,10 @@ describe('validateNonInterActiveAuth', () => {
   });
 
   it('uses USE_VERTEX_AI if both GEMINI_API_KEY and GOOGLE_GENAI_USE_VERTEXAI are set', async () => {
-    process.env.GEMINI_API_KEY = 'fake-key';
-    process.env.GOOGLE_GENAI_USE_VERTEXAI = 'true';
-    process.env.GOOGLE_CLOUD_PROJECT = 'test-project';
-    process.env.GOOGLE_CLOUD_LOCATION = 'us-central1';
+    process.env['GEMINI_API_KEY'] = 'fake-key';
+    process.env['GOOGLE_GENAI_USE_VERTEXAI'] = 'true';
+    process.env['GOOGLE_CLOUD_PROJECT'] = 'test-project';
+    process.env['GOOGLE_CLOUD_LOCATION'] = 'us-central1';
     const nonInteractiveConfig: NonInteractiveConfig = {
       refreshAuth: refreshAuthMock,
     };
@@ -164,10 +164,10 @@ describe('validateNonInterActiveAuth', () => {
   });
 
   it('uses USE_GEMINI if GOOGLE_GENAI_USE_VERTEXAI is false, GEMINI_API_KEY is set, and project/location are available', async () => {
-    process.env.GOOGLE_GENAI_USE_VERTEXAI = 'false';
-    process.env.GEMINI_API_KEY = 'fake-key';
-    process.env.GOOGLE_CLOUD_PROJECT = 'test-project';
-    process.env.GOOGLE_CLOUD_LOCATION = 'us-central1';
+    process.env['GOOGLE_GENAI_USE_VERTEXAI'] = 'false';
+    process.env['GEMINI_API_KEY'] = 'fake-key';
+    process.env['GOOGLE_CLOUD_PROJECT'] = 'test-project';
+    process.env['GOOGLE_CLOUD_LOCATION'] = 'us-central1';
     const nonInteractiveConfig: NonInteractiveConfig = {
       refreshAuth: refreshAuthMock,
     };
@@ -181,7 +181,7 @@ describe('validateNonInterActiveAuth', () => {
 
   it('uses configuredAuthType if provided', async () => {
     // Set required env var for USE_GEMINI
-    process.env.GEMINI_API_KEY = 'fake-key';
+    process.env['GEMINI_API_KEY'] = 'fake-key';
     const nonInteractiveConfig: NonInteractiveConfig = {
       refreshAuth: refreshAuthMock,
     };
diff --git a/packages/cli/src/validateNonInterActiveAuth.ts b/packages/cli/src/validateNonInterActiveAuth.ts
index 7e80b30e..33b965b7 100644
--- a/packages/cli/src/validateNonInterActiveAuth.ts
+++ b/packages/cli/src/validateNonInterActiveAuth.ts
@@ -9,13 +9,13 @@ import { USER_SETTINGS_PATH } from './config/settings.js';
 import { validateAuthMethod } from './config/auth.js';
 
 function getAuthTypeFromEnv(): AuthType | undefined {
-  if (process.env.GOOGLE_GENAI_USE_GCA === 'true') {
+  if (process.env['GOOGLE_GENAI_USE_GCA'] === 'true') {
     return AuthType.LOGIN_WITH_GOOGLE;
   }
-  if (process.env.GOOGLE_GENAI_USE_VERTEXAI === 'true') {
+  if (process.env['GOOGLE_GENAI_USE_VERTEXAI'] === 'true') {
     return AuthType.USE_VERTEX_AI;
   }
-  if (process.env.GEMINI_API_KEY) {
+  if (process.env['GEMINI_API_KEY']) {
     return AuthType.USE_GEMINI;
   }
   return undefined;
diff --git a/packages/core/src/code_assist/oauth2.test.ts b/packages/core/src/code_assist/oauth2.test.ts
index 77a8fb90..821788d5 100644
--- a/packages/core/src/code_assist/oauth2.test.ts
+++ b/packages/core/src/code_assist/oauth2.test.ts
@@ -57,9 +57,7 @@ describe('oauth2', () => {
     fs.rmSync(tempHomeDir, { recursive: true, force: true });
     vi.clearAllMocks();
     resetOauthClientForTesting();
-    delete process.env.CLOUD_SHELL;
-    delete process.env.GOOGLE_GENAI_USE_GCA;
-    delete process.env.GOOGLE_CLOUD_ACCESS_TOKEN;
+    vi.unstubAllEnvs();
   });
 
   it('should perform a web login', async () => {
@@ -328,8 +326,8 @@ describe('oauth2', () => {
 
   describe('with GCP environment variables', () => {
     it('should use GOOGLE_CLOUD_ACCESS_TOKEN when GOOGLE_GENAI_USE_GCA is true', async () => {
-      process.env.GOOGLE_GENAI_USE_GCA = 'true';
-      process.env.GOOGLE_CLOUD_ACCESS_TOKEN = 'gcp-access-token';
+      vi.stubEnv('GOOGLE_GENAI_USE_GCA', 'true');
+      vi.stubEnv('GOOGLE_CLOUD_ACCESS_TOKEN', 'gcp-access-token');
 
       const mockSetCredentials = vi.fn();
       const mockGetAccessToken = vi
@@ -387,7 +385,7 @@ describe('oauth2', () => {
     });
 
     it('should not use GCP token if GOOGLE_CLOUD_ACCESS_TOKEN is not set', async () => {
-      process.env.GOOGLE_GENAI_USE_GCA = 'true';
+      vi.stubEnv('GOOGLE_GENAI_USE_GCA', 'true');
 
       const mockSetCredentials = vi.fn();
       const mockGetAccessToken = vi
@@ -418,7 +416,7 @@ describe('oauth2', () => {
     });
 
     it('should not use GCP token if GOOGLE_GENAI_USE_GCA is not set', async () => {
-      process.env.GOOGLE_CLOUD_ACCESS_TOKEN = 'gcp-access-token';
+      vi.stubEnv('GOOGLE_CLOUD_ACCESS_TOKEN', 'gcp-access-token');
 
       const mockSetCredentials = vi.fn();
       const mockGetAccessToken = vi
diff --git a/packages/core/src/code_assist/oauth2.ts b/packages/core/src/code_assist/oauth2.ts
index f9518cbe..a4dcf8a7 100644
--- a/packages/core/src/code_assist/oauth2.ts
+++ b/packages/core/src/code_assist/oauth2.ts
@@ -81,11 +81,11 @@ async function initOauthClient(
   });
 
   if (
-    process.env.GOOGLE_GENAI_USE_GCA &&
-    process.env.GOOGLE_CLOUD_ACCESS_TOKEN
+    process.env['GOOGLE_GENAI_USE_GCA'] &&
+    process.env['GOOGLE_CLOUD_ACCESS_TOKEN']
   ) {
     client.setCredentials({
-      access_token: process.env.GOOGLE_CLOUD_ACCESS_TOKEN,
+      access_token: process.env['GOOGLE_CLOUD_ACCESS_TOKEN'],
     });
     await fetchAndCacheUserInfo(client);
     return client;
@@ -248,7 +248,7 @@ async function authWithUserCode(client: OAuth2Client): Promise<boolean> {
 async function authWithWeb(client: OAuth2Client): Promise<OauthWebLogin> {
   const port = await getAvailablePort();
   // The hostname used for the HTTP server binding (e.g., '0.0.0.0' in Docker).
-  const host = process.env.OAUTH_CALLBACK_HOST || 'localhost';
+  const host = process.env['OAUTH_CALLBACK_HOST'] || 'localhost';
   // The `redirectUri` sent to Google's authorization server MUST use a loopback IP literal
   // (i.e., 'localhost' or '127.0.0.1'). This is a strict security policy for credentials of
   // type 'Desktop app' or 'Web application' (when using loopback flow) to mitigate
@@ -323,7 +323,7 @@ export function getAvailablePort(): Promise<number> {
   return new Promise((resolve, reject) => {
     let port = 0;
     try {
-      const portStr = process.env.OAUTH_CALLBACK_PORT;
+      const portStr = process.env['OAUTH_CALLBACK_PORT'];
       if (portStr) {
         port = parseInt(portStr, 10);
         if (isNaN(port) || port <= 0 || port > 65535) {
@@ -353,7 +353,8 @@ export function getAvailablePort(): Promise<number> {
 async function loadCachedCredentials(client: OAuth2Client): Promise<boolean> {
   try {
     const keyFile =
-      process.env.GOOGLE_APPLICATION_CREDENTIALS || getCachedCredentialPath();
+      process.env['GOOGLE_APPLICATION_CREDENTIALS'] ||
+      getCachedCredentialPath();
 
     const creds = await fs.readFile(keyFile, 'utf-8');
     client.setCredentials(JSON.parse(creds));
diff --git a/packages/core/src/code_assist/server.ts b/packages/core/src/code_assist/server.ts
index 08339bdc..470143a6 100644
--- a/packages/core/src/code_assist/server.ts
+++ b/packages/core/src/code_assist/server.ts
@@ -214,7 +214,8 @@ export class CodeAssistServer implements ContentGenerator {
   }
 
   getMethodUrl(method: string): string {
-    const endpoint = process.env.CODE_ASSIST_ENDPOINT ?? CODE_ASSIST_ENDPOINT;
+    const endpoint =
+      process.env['CODE_ASSIST_ENDPOINT'] ?? CODE_ASSIST_ENDPOINT;
     return `${endpoint}/${CODE_ASSIST_API_VERSION}:${method}`;
   }
 }
diff --git a/packages/core/src/code_assist/setup.test.ts b/packages/core/src/code_assist/setup.test.ts
index cba051dd..61a7431a 100644
--- a/packages/core/src/code_assist/setup.test.ts
+++ b/packages/core/src/code_assist/setup.test.ts
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 import { setupUser, ProjectIdRequiredError } from './setup.js';
 import { CodeAssistServer } from '../code_assist/server.js';
 import { OAuth2Client } from 'google-auth-library';
@@ -50,8 +50,12 @@ describe('setupUser for existing user', () => {
     );
   });
 
+  afterEach(() => {
+    vi.unstubAllEnvs();
+  });
+
   it('should use GOOGLE_CLOUD_PROJECT when set and project from server is undefined', async () => {
-    process.env.GOOGLE_CLOUD_PROJECT = 'test-project';
+    vi.stubEnv('GOOGLE_CLOUD_PROJECT', 'test-project');
     mockLoad.mockResolvedValue({
       currentTier: mockPaidTier,
     });
@@ -66,7 +70,7 @@ describe('setupUser for existing user', () => {
   });
 
   it('should ignore GOOGLE_CLOUD_PROJECT when project from server is set', async () => {
-    process.env.GOOGLE_CLOUD_PROJECT = 'test-project';
+    vi.stubEnv('GOOGLE_CLOUD_PROJECT', 'test-project');
     mockLoad.mockResolvedValue({
       cloudaicompanionProject: 'server-project',
       currentTier: mockPaidTier,
@@ -86,7 +90,7 @@ describe('setupUser for existing user', () => {
   });
 
   it('should throw ProjectIdRequiredError when no project ID is available', async () => {
-    delete process.env.GOOGLE_CLOUD_PROJECT;
+    vi.stubEnv('GOOGLE_CLOUD_PROJECT', '');
     // And the server itself requires a project ID internally
     vi.mocked(CodeAssistServer).mockImplementation(() => {
       throw new ProjectIdRequiredError();
@@ -122,8 +126,12 @@ describe('setupUser for new user', () => {
     );
   });
 
+  afterEach(() => {
+    vi.unstubAllEnvs();
+  });
+
   it('should use GOOGLE_CLOUD_PROJECT when set and onboard a new paid user', async () => {
-    process.env.GOOGLE_CLOUD_PROJECT = 'test-project';
+    vi.stubEnv('GOOGLE_CLOUD_PROJECT', 'test-project');
     mockLoad.mockResolvedValue({
       allowedTiers: [mockPaidTier],
     });
@@ -153,7 +161,7 @@ describe('setupUser for new user', () => {
   });
 
   it('should onboard a new free user when GOOGLE_CLOUD_PROJECT is not set', async () => {
-    delete process.env.GOOGLE_CLOUD_PROJECT;
+    vi.stubEnv('GOOGLE_CLOUD_PROJECT', '');
     mockLoad.mockResolvedValue({
       allowedTiers: [mockFreeTier],
     });
@@ -182,7 +190,7 @@ describe('setupUser for new user', () => {
   });
 
   it('should use GOOGLE_CLOUD_PROJECT when onboard response has no project ID', async () => {
-    process.env.GOOGLE_CLOUD_PROJECT = 'test-project';
+    vi.stubEnv('GOOGLE_CLOUD_PROJECT', 'test-project');
     mockLoad.mockResolvedValue({
       allowedTiers: [mockPaidTier],
     });
@@ -200,7 +208,7 @@ describe('setupUser for new user', () => {
   });
 
   it('should throw ProjectIdRequiredError when no project ID is available', async () => {
-    delete process.env.GOOGLE_CLOUD_PROJECT;
+    vi.stubEnv('GOOGLE_CLOUD_PROJECT', '');
     mockLoad.mockResolvedValue({
       allowedTiers: [mockPaidTier],
     });
diff --git a/packages/core/src/code_assist/setup.ts b/packages/core/src/code_assist/setup.ts
index 2e460c98..d563301d 100644
--- a/packages/core/src/code_assist/setup.ts
+++ b/packages/core/src/code_assist/setup.ts
@@ -33,7 +33,7 @@ export interface UserData {
  * @returns the user's actual project id
  */
 export async function setupUser(client: OAuth2Client): Promise<UserData> {
-  const projectId = process.env.GOOGLE_CLOUD_PROJECT || undefined;
+  const projectId = process.env['GOOGLE_CLOUD_PROJECT'] || undefined;
   const caServer = new CodeAssistServer(client, projectId, {}, '', undefined);
   const coreClientMetadata: ClientMetadata = {
     ideType: 'IDE_UNSPECIFIED',
diff --git a/packages/core/src/config/config.ts b/packages/core/src/config/config.ts
index 49f9ab45..acaf5eb1 100644
--- a/packages/core/src/config/config.ts
+++ b/packages/core/src/config/config.ts
@@ -458,7 +458,7 @@ export class Config {
 
   isRestrictiveSandbox(): boolean {
     const sandboxConfig = this.getSandbox();
-    const seatbeltProfile = process.env.SEATBELT_PROFILE;
+    const seatbeltProfile = process.env['SEATBELT_PROFILE'];
     return (
       !!sandboxConfig &&
       sandboxConfig.command === 'sandbox-exec' &&
diff --git a/packages/core/src/core/client.ts b/packages/core/src/core/client.ts
index a2abd0d0..66f3e08f 100644
--- a/packages/core/src/core/client.ts
+++ b/packages/core/src/core/client.ts
@@ -286,7 +286,7 @@ export class GeminiClient {
       const contextData: Record<string, unknown> = {};
 
       if (activeFile) {
-        contextData.activeFile = {
+        contextData['activeFile'] = {
           path: activeFile.path,
           cursor: activeFile.cursor
             ? {
@@ -299,7 +299,7 @@ export class GeminiClient {
       }
 
       if (otherOpenFiles.length > 0) {
-        contextData.otherOpenFiles = otherOpenFiles;
+        contextData['otherOpenFiles'] = otherOpenFiles;
       }
 
       if (Object.keys(contextData).length === 0) {
@@ -345,7 +345,7 @@ export class GeminiClient {
         }
       }
       if (openedFiles.length > 0) {
-        changes.filesOpened = openedFiles;
+        changes['filesOpened'] = openedFiles;
       }
 
       const closedFiles: string[] = [];
@@ -355,7 +355,7 @@ export class GeminiClient {
         }
       }
       if (closedFiles.length > 0) {
-        changes.filesClosed = closedFiles;
+        changes['filesClosed'] = closedFiles;
       }
 
       const lastActiveFile = (
@@ -367,7 +367,7 @@ export class GeminiClient {
 
       if (currentActiveFile) {
         if (!lastActiveFile || lastActiveFile.path !== currentActiveFile.path) {
-          changes.activeFileChanged = {
+          changes['activeFileChanged'] = {
             path: currentActiveFile.path,
             cursor: currentActiveFile.cursor
               ? {
@@ -386,7 +386,7 @@ export class GeminiClient {
               lastCursor.line !== currentCursor.line ||
               lastCursor.character !== currentCursor.character)
           ) {
-            changes.cursorMoved = {
+            changes['cursorMoved'] = {
               path: currentActiveFile.path,
               cursor: {
                 line: currentCursor.line,
@@ -398,14 +398,14 @@ export class GeminiClient {
           const lastSelectedText = lastActiveFile.selectedText || '';
           const currentSelectedText = currentActiveFile.selectedText || '';
           if (lastSelectedText !== currentSelectedText) {
-            changes.selectionChanged = {
+            changes['selectionChanged'] = {
               path: currentActiveFile.path,
               selectedText: currentSelectedText,
             };
           }
         }
       } else if (lastActiveFile) {
-        changes.activeFileChanged = {
+        changes['activeFileChanged'] = {
           path: null,
           previousPath: lastActiveFile.path,
         };
@@ -415,7 +415,7 @@ export class GeminiClient {
         return { contextParts: [], newIdeContext: currentIdeContext };
       }
 
-      delta.changes = changes;
+      delta['changes'] = changes;
       const jsonString = JSON.stringify(delta, null, 2);
       const contextParts = [
         "Here is a summary of changes in the user's editor context, in JSON format. This is for your information only.",
diff --git a/packages/core/src/core/contentGenerator.test.ts b/packages/core/src/core/contentGenerator.test.ts
index e89b5bc7..b92e8046 100644
--- a/packages/core/src/core/contentGenerator.test.ts
+++ b/packages/core/src/core/contentGenerator.test.ts
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import { describe, it, expect, vi, beforeEach, afterAll } from 'vitest';
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 import {
   createContentGenerator,
   AuthType,
@@ -72,7 +72,6 @@ describe('createContentGenerator', () => {
 });
 
 describe('createContentGeneratorConfig', () => {
-  const originalEnv = process.env;
   const mockConfig = {
     getModel: vi.fn().mockReturnValue('gemini-pro'),
     setModel: vi.fn(),
@@ -83,18 +82,15 @@ describe('createContentGeneratorConfig', () => {
   beforeEach(() => {
     // Reset modules to re-evaluate imports and environment variables
     vi.resetModules();
-    // Restore process.env before each test
-    process.env = { ...originalEnv };
     vi.clearAllMocks();
   });
 
-  afterAll(() => {
-    // Restore original process.env after all tests
-    process.env = originalEnv;
+  afterEach(() => {
+    vi.unstubAllEnvs();
   });
 
   it('should configure for Gemini using GEMINI_API_KEY when set', async () => {
-    process.env.GEMINI_API_KEY = 'env-gemini-key';
+    vi.stubEnv('GEMINI_API_KEY', 'env-gemini-key');
     const config = await createContentGeneratorConfig(
       mockConfig,
       AuthType.USE_GEMINI,
@@ -104,7 +100,7 @@ describe('createContentGeneratorConfig', () => {
   });
 
   it('should not configure for Gemini if GEMINI_API_KEY is empty', async () => {
-    process.env.GEMINI_API_KEY = '';
+    vi.stubEnv('GEMINI_API_KEY', '');
     const config = await createContentGeneratorConfig(
       mockConfig,
       AuthType.USE_GEMINI,
@@ -114,7 +110,7 @@ describe('createContentGeneratorConfig', () => {
   });
 
   it('should configure for Vertex AI using GOOGLE_API_KEY when set', async () => {
-    process.env.GOOGLE_API_KEY = 'env-google-key';
+    vi.stubEnv('GOOGLE_API_KEY', 'env-google-key');
     const config = await createContentGeneratorConfig(
       mockConfig,
       AuthType.USE_VERTEX_AI,
@@ -124,8 +120,8 @@ describe('createContentGeneratorConfig', () => {
   });
 
   it('should configure for Vertex AI using GCP project and location when set', async () => {
-    process.env.GOOGLE_CLOUD_PROJECT = 'env-gcp-project';
-    process.env.GOOGLE_CLOUD_LOCATION = 'env-gcp-location';
+    vi.stubEnv('GOOGLE_CLOUD_PROJECT', 'env-gcp-project');
+    vi.stubEnv('GOOGLE_CLOUD_LOCATION', 'env-gcp-location');
     const config = await createContentGeneratorConfig(
       mockConfig,
       AuthType.USE_VERTEX_AI,
@@ -135,9 +131,9 @@ describe('createContentGeneratorConfig', () => {
   });
 
   it('should not configure for Vertex AI if required env vars are empty', async () => {
-    process.env.GOOGLE_API_KEY = '';
-    process.env.GOOGLE_CLOUD_PROJECT = '';
-    process.env.GOOGLE_CLOUD_LOCATION = '';
+    vi.stubEnv('GOOGLE_API_KEY', '');
+    vi.stubEnv('GOOGLE_CLOUD_PROJECT', '');
+    vi.stubEnv('GOOGLE_CLOUD_LOCATION', '');
     const config = await createContentGeneratorConfig(
       mockConfig,
       AuthType.USE_VERTEX_AI,
diff --git a/packages/core/src/core/contentGenerator.ts b/packages/core/src/core/contentGenerator.ts
index 599a569b..19b285c7 100644
--- a/packages/core/src/core/contentGenerator.ts
+++ b/packages/core/src/core/contentGenerator.ts
@@ -60,10 +60,10 @@ export function createContentGeneratorConfig(
   config: Config,
   authType: AuthType | undefined,
 ): ContentGeneratorConfig {
-  const geminiApiKey = process.env.GEMINI_API_KEY || undefined;
-  const googleApiKey = process.env.GOOGLE_API_KEY || undefined;
-  const googleCloudProject = process.env.GOOGLE_CLOUD_PROJECT || undefined;
-  const googleCloudLocation = process.env.GOOGLE_CLOUD_LOCATION || undefined;
+  const geminiApiKey = process.env['GEMINI_API_KEY'] || undefined;
+  const googleApiKey = process.env['GOOGLE_API_KEY'] || undefined;
+  const googleCloudProject = process.env['GOOGLE_CLOUD_PROJECT'] || undefined;
+  const googleCloudLocation = process.env['GOOGLE_CLOUD_LOCATION'] || undefined;
 
   // Use runtime model from config if available; otherwise, fall back to parameter or default
   const effectiveModel = config.getModel() || DEFAULT_GEMINI_MODEL;
@@ -107,7 +107,7 @@ export async function createContentGenerator(
   gcConfig: Config,
   sessionId?: string,
 ): Promise<ContentGenerator> {
-  const version = process.env.CLI_VERSION || process.version;
+  const version = process.env['CLI_VERSION'] || process.version;
   const httpOptions = {
     headers: {
       'User-Agent': `GeminiCLI/${version} (${process.platform}; ${process.arch})`,
diff --git a/packages/core/src/core/coreToolScheduler.ts b/packages/core/src/core/coreToolScheduler.ts
index 0d442f9d..1a031de5 100644
--- a/packages/core/src/core/coreToolScheduler.ts
+++ b/packages/core/src/core/coreToolScheduler.ts
@@ -171,10 +171,10 @@ export function convertToFunctionResponse(
 
   // After this point, contentToProcess is a single Part object.
   if (contentToProcess.functionResponse) {
-    if (contentToProcess.functionResponse.response?.content) {
+    if (contentToProcess.functionResponse.response?.['content']) {
       const stringifiedOutput =
         getResponseTextFromParts(
-          contentToProcess.functionResponse.response.content as Part[],
+          contentToProcess.functionResponse.response['content'] as Part[],
         ) || '';
       return createFunctionResponsePart(callId, toolName, stringifiedOutput);
     }
diff --git a/packages/core/src/core/prompts.ts b/packages/core/src/core/prompts.ts
index 95c55143..b4b9a979 100644
--- a/packages/core/src/core/prompts.ts
+++ b/packages/core/src/core/prompts.ts
@@ -24,7 +24,7 @@ export function getCoreSystemPrompt(userMemory?: string): string {
   // default path is .gemini/system.md but can be modified via custom path in GEMINI_SYSTEM_MD
   let systemMdEnabled = false;
   let systemMdPath = path.resolve(path.join(GEMINI_CONFIG_DIR, 'system.md'));
-  const systemMdVar = process.env.GEMINI_SYSTEM_MD;
+  const systemMdVar = process.env['GEMINI_SYSTEM_MD'];
   if (systemMdVar) {
     const systemMdVarLower = systemMdVar.toLowerCase();
     if (!['0', 'false'].includes(systemMdVarLower)) {
@@ -121,8 +121,8 @@ When requested to perform tasks like fixing bugs, adding features, refactoring,
 
 ${(function () {
   // Determine sandbox status based on environment variables
-  const isSandboxExec = process.env.SANDBOX === 'sandbox-exec';
-  const isGenericSandbox = !!process.env.SANDBOX; // Check if SANDBOX is set to any non-empty value
+  const isSandboxExec = process.env['SANDBOX'] === 'sandbox-exec';
+  const isGenericSandbox = !!process.env['SANDBOX']; // Check if SANDBOX is set to any non-empty value
 
   if (isSandboxExec) {
     return `
@@ -266,7 +266,7 @@ Your core function is efficient and safe assistance. Balance extreme conciseness
 `.trim();
 
   // if GEMINI_WRITE_SYSTEM_MD is set (and not 0|false), write base system prompt to file
-  const writeSystemMdVar = process.env.GEMINI_WRITE_SYSTEM_MD;
+  const writeSystemMdVar = process.env['GEMINI_WRITE_SYSTEM_MD'];
   if (writeSystemMdVar) {
     const writeSystemMdVarLower = writeSystemMdVar.toLowerCase();
     if (!['0', 'false'].includes(writeSystemMdVarLower)) {
diff --git a/packages/core/src/ide/detect-ide.ts b/packages/core/src/ide/detect-ide.ts
index 5cc3cb56..5eca5429 100644
--- a/packages/core/src/ide/detect-ide.ts
+++ b/packages/core/src/ide/detect-ide.ts
@@ -63,28 +63,28 @@ export function getIdeInfo(ide: DetectedIde): IdeInfo {
 
 export function detectIde(): DetectedIde | undefined {
   // Only VSCode-based integrations are currently supported.
-  if (process.env.TERM_PROGRAM !== 'vscode') {
+  if (process.env['TERM_PROGRAM'] !== 'vscode') {
     return undefined;
   }
-  if (process.env.__COG_BASHRC_SOURCED) {
+  if (process.env['__COG_BASHRC_SOURCED']) {
     return DetectedIde.Devin;
   }
-  if (process.env.REPLIT_USER) {
+  if (process.env['REPLIT_USER']) {
     return DetectedIde.Replit;
   }
-  if (process.env.CURSOR_TRACE_ID) {
+  if (process.env['CURSOR_TRACE_ID']) {
     return DetectedIde.Cursor;
   }
-  if (process.env.CODESPACES) {
+  if (process.env['CODESPACES']) {
     return DetectedIde.Codespaces;
   }
-  if (process.env.EDITOR_IN_CLOUD_SHELL || process.env.CLOUD_SHELL) {
+  if (process.env['EDITOR_IN_CLOUD_SHELL'] || process.env['CLOUD_SHELL']) {
     return DetectedIde.CloudShell;
   }
-  if (process.env.TERM_PRODUCT === 'Trae') {
+  if (process.env['TERM_PRODUCT'] === 'Trae') {
     return DetectedIde.Trae;
   }
-  if (process.env.FIREBASE_DEPLOY_AGENT || process.env.MONOSPACE_ENV) {
+  if (process.env['FIREBASE_DEPLOY_AGENT'] || process.env['MONOSPACE_ENV']) {
     return DetectedIde.FirebaseStudio;
   }
   return DetectedIde.VSCode;
diff --git a/packages/core/src/ide/ide-installer.ts b/packages/core/src/ide/ide-installer.ts
index dcfe9bee..4a771c67 100644
--- a/packages/core/src/ide/ide-installer.ts
+++ b/packages/core/src/ide/ide-installer.ts
@@ -59,7 +59,7 @@ async function findVsCodeCommand(): Promise<string | null> {
     // Windows
     locations.push(
       path.join(
-        process.env.ProgramFiles || 'C:\\Program Files',
+        process.env['ProgramFiles'] || 'C:\\Program Files',
         'Microsoft VS Code',
         'bin',
         'code.cmd',
diff --git a/packages/core/src/services/loopDetectionService.ts b/packages/core/src/services/loopDetectionService.ts
index f89e00da..8e94ac69 100644
--- a/packages/core/src/services/loopDetectionService.ts
+++ b/packages/core/src/services/loopDetectionService.ts
@@ -367,10 +367,10 @@ Please analyze the conversation history to determine the possibility that the co
       return false;
     }
 
-    if (typeof result.confidence === 'number') {
-      if (result.confidence > 0.9) {
-        if (typeof result.reasoning === 'string' && result.reasoning) {
-          console.warn(result.reasoning);
+    if (typeof result['confidence'] === 'number') {
+      if (result['confidence'] > 0.9) {
+        if (typeof result['reasoning'] === 'string' && result['reasoning']) {
+          console.warn(result['reasoning']);
         }
         logLoopDetected(
           this.config,
@@ -381,7 +381,7 @@ Please analyze the conversation history to determine the possibility that the co
         this.llmCheckInterval = Math.round(
           MIN_LLM_CHECK_INTERVAL +
             (MAX_LLM_CHECK_INTERVAL - MIN_LLM_CHECK_INTERVAL) *
-              (1 - result.confidence),
+              (1 - result['confidence']),
         );
       }
     }
diff --git a/packages/core/src/telemetry/clearcut-logger/clearcut-logger.ts b/packages/core/src/telemetry/clearcut-logger/clearcut-logger.ts
index 60a31ae7..200a1a0d 100644
--- a/packages/core/src/telemetry/clearcut-logger/clearcut-logger.ts
+++ b/packages/core/src/telemetry/clearcut-logger/clearcut-logger.ts
@@ -87,11 +87,11 @@ export interface LogRequest {
  * methods might have in their runtimes.
  */
 function determineSurface(): string {
-  if (process.env.SURFACE) {
-    return process.env.SURFACE;
-  } else if (process.env.GITHUB_SHA) {
+  if (process.env['SURFACE']) {
+    return process.env['SURFACE'];
+  } else if (process.env['GITHUB_SHA']) {
     return 'GitHub';
-  } else if (process.env.TERM_PROGRAM === 'vscode') {
+  } else if (process.env['TERM_PROGRAM'] === 'vscode') {
     return detectIde() || DetectedIde.VSCode;
   } else {
     return 'SURFACE_NOT_SET';
diff --git a/packages/core/src/telemetry/loggers.ts b/packages/core/src/telemetry/loggers.ts
index d7a81203..afc92807 100644
--- a/packages/core/src/telemetry/loggers.ts
+++ b/packages/core/src/telemetry/loggers.ts
@@ -98,7 +98,7 @@ export function logUserPrompt(config: Config, event: UserPromptEvent): void {
   };
 
   if (shouldLogUserPrompts(config)) {
-    attributes.prompt = event.prompt;
+    attributes['prompt'] = event.prompt;
   }
 
   const logger = logs.getLogger(SERVICE_NAME);
@@ -247,7 +247,7 @@ export function logApiResponse(config: Config, event: ApiResponseEvent): void {
     'event.timestamp': new Date().toISOString(),
   };
   if (event.response_text) {
-    attributes.response_text = event.response_text;
+    attributes['response_text'] = event.response_text;
   }
   if (event.error) {
     attributes['error.message'] = event.error;
diff --git a/packages/core/src/telemetry/metrics.ts b/packages/core/src/telemetry/metrics.ts
index 1e4509da..a0996410 100644
--- a/packages/core/src/telemetry/metrics.ts
+++ b/packages/core/src/telemetry/metrics.ts
@@ -197,14 +197,14 @@ export function recordFileOperationMetric(
     ...getCommonAttributes(config),
     operation,
   };
-  if (lines !== undefined) attributes.lines = lines;
-  if (mimetype !== undefined) attributes.mimetype = mimetype;
-  if (extension !== undefined) attributes.extension = extension;
+  if (lines !== undefined) attributes['lines'] = lines;
+  if (mimetype !== undefined) attributes['mimetype'] = mimetype;
+  if (extension !== undefined) attributes['extension'] = extension;
   if (diffStat !== undefined) {
-    attributes.ai_added_lines = diffStat.ai_added_lines;
-    attributes.ai_removed_lines = diffStat.ai_removed_lines;
-    attributes.user_added_lines = diffStat.user_added_lines;
-    attributes.user_removed_lines = diffStat.user_removed_lines;
+    attributes['ai_added_lines'] = diffStat.ai_added_lines;
+    attributes['ai_removed_lines'] = diffStat.ai_removed_lines;
+    attributes['user_added_lines'] = diffStat.user_added_lines;
+    attributes['user_removed_lines'] = diffStat.user_removed_lines;
   }
   fileOperationCounter.add(1, attributes);
 }
diff --git a/packages/core/src/tools/mcp-client.ts b/packages/core/src/tools/mcp-client.ts
index 837b91fc..87d38815 100644
--- a/packages/core/src/tools/mcp-client.ts
+++ b/packages/core/src/tools/mcp-client.ts
@@ -448,7 +448,7 @@ export function hasValidTypes(schema: unknown): boolean {
 
   const s = schema as Record<string, unknown>;
 
-  if (!s.type) {
+  if (!s['type']) {
     // These keywords contain an array of schemas that should be validated.
     //
     // If no top level type was given, then they must each have a type.
@@ -470,9 +470,9 @@ export function hasValidTypes(schema: unknown): boolean {
     if (!hasSubSchema) return false;
   }
 
-  if (s.type === 'object' && s.properties) {
-    if (typeof s.properties === 'object' && s.properties !== null) {
-      for (const prop of Object.values(s.properties)) {
+  if (s['type'] === 'object' && s['properties']) {
+    if (typeof s['properties'] === 'object' && s['properties'] !== null) {
+      for (const prop of Object.values(s['properties'])) {
         if (!hasValidTypes(prop)) {
           return false;
         }
@@ -480,8 +480,8 @@ export function hasValidTypes(schema: unknown): boolean {
     }
   }
 
-  if (s.type === 'array' && s.items) {
-    if (!hasValidTypes(s.items)) {
+  if (s['type'] === 'array' && s['items']) {
+    if (!hasValidTypes(s['items'])) {
       return false;
     }
   }
@@ -1046,7 +1046,7 @@ export async function connectToMcpServer(
         conciseError = `Connection failed for '${mcpServerName}': ${errorMessage}`;
       }
 
-      if (process.env.SANDBOX) {
+      if (process.env['SANDBOX']) {
         conciseError += ` (check sandbox availability)`;
       }
 
diff --git a/packages/core/src/tools/mcp-tool.ts b/packages/core/src/tools/mcp-tool.ts
index 88e89c85..64952dd1 100644
--- a/packages/core/src/tools/mcp-tool.ts
+++ b/packages/core/src/tools/mcp-tool.ts
@@ -271,7 +271,7 @@ function transformResourceLinkBlock(block: McpResourceLinkBlock): Part {
  */
 function transformMcpContentToParts(sdkResponse: Part[]): Part[] {
   const funcResponse = sdkResponse?.[0]?.functionResponse;
-  const mcpContent = funcResponse?.response?.content as McpContentBlock[];
+  const mcpContent = funcResponse?.response?.['content'] as McpContentBlock[];
   const toolName = funcResponse?.name || 'unknown tool';
 
   if (!Array.isArray(mcpContent)) {
@@ -308,8 +308,9 @@ function transformMcpContentToParts(sdkResponse: Part[]): Part[] {
  * @returns A formatted string representing the tool's output.
  */
 function getStringifiedResultForDisplay(rawResponse: Part[]): string {
-  const mcpContent = rawResponse?.[0]?.functionResponse?.response
-    ?.content as McpContentBlock[];
+  const mcpContent = rawResponse?.[0]?.functionResponse?.response?.[
+    'content'
+  ] as McpContentBlock[];
 
   if (!Array.isArray(mcpContent)) {
     return '```json\n' + JSON.stringify(rawResponse, null, 2) + '\n```';
diff --git a/packages/core/src/utils/browser.ts b/packages/core/src/utils/browser.ts
index a9b2b013..35ee7461 100644
--- a/packages/core/src/utils/browser.ts
+++ b/packages/core/src/utils/browser.ts
@@ -15,19 +15,22 @@ export function shouldAttemptBrowserLaunch(): boolean {
   // A list of browser names that indicate we should not attempt to open a
   // web browser for the user.
   const browserBlocklist = ['www-browser'];
-  const browserEnv = process.env.BROWSER;
+  const browserEnv = process.env['BROWSER'];
   if (browserEnv && browserBlocklist.includes(browserEnv)) {
     return false;
   }
   // Common environment variables used in CI/CD or other non-interactive shells.
-  if (process.env.CI || process.env.DEBIAN_FRONTEND === 'noninteractive') {
+  if (
+    process.env['CI'] ||
+    process.env['DEBIAN_FRONTEND'] === 'noninteractive'
+  ) {
     return false;
   }
 
   // The presence of SSH_CONNECTION indicates a remote session.
   // We should not attempt to launch a browser unless a display is explicitly available
   // (checked below for Linux).
-  const isSSH = !!process.env.SSH_CONNECTION;
+  const isSSH = !!process.env['SSH_CONNECTION'];
 
   // On Linux, the presence of a display server is a strong indicator of a GUI.
   if (process.platform === 'linux') {
diff --git a/packages/core/src/utils/editCorrector.ts b/packages/core/src/utils/editCorrector.ts
index faa52b51..0d857409 100644
--- a/packages/core/src/utils/editCorrector.ts
+++ b/packages/core/src/utils/editCorrector.ts
@@ -119,7 +119,7 @@ async function findLastEditTimestamp(
         const { response } = part.functionResponse;
         if (response && !('error' in response) && 'output' in response) {
           id = part.functionResponse.id;
-          content = response.output;
+          content = response['output'];
         }
       }
 
@@ -411,10 +411,10 @@ Return ONLY the corrected target snippet in the specified JSON format with the k
 
     if (
       result &&
-      typeof result.corrected_target_snippet === 'string' &&
-      result.corrected_target_snippet.length > 0
+      typeof result['corrected_target_snippet'] === 'string' &&
+      result['corrected_target_snippet'].length > 0
     ) {
-      return result.corrected_target_snippet;
+      return result['corrected_target_snippet'];
     } else {
       return problematicSnippet;
     }
@@ -499,10 +499,10 @@ Return ONLY the corrected string in the specified JSON format with the key 'corr
 
     if (
       result &&
-      typeof result.corrected_new_string === 'string' &&
-      result.corrected_new_string.length > 0
+      typeof result['corrected_new_string'] === 'string' &&
+      result['corrected_new_string'].length > 0
     ) {
-      return result.corrected_new_string;
+      return result['corrected_new_string'];
     } else {
       return originalNewString;
     }
@@ -568,10 +568,10 @@ Return ONLY the corrected string in the specified JSON format with the key 'corr
 
     if (
       result &&
-      typeof result.corrected_new_string_escaping === 'string' &&
-      result.corrected_new_string_escaping.length > 0
+      typeof result['corrected_new_string_escaping'] === 'string' &&
+      result['corrected_new_string_escaping'].length > 0
     ) {
-      return result.corrected_new_string_escaping;
+      return result['corrected_new_string_escaping'];
     } else {
       return potentiallyProblematicNewString;
     }
@@ -634,10 +634,10 @@ Return ONLY the corrected string in the specified JSON format with the key 'corr
 
     if (
       result &&
-      typeof result.corrected_string_escaping === 'string' &&
-      result.corrected_string_escaping.length > 0
+      typeof result['corrected_string_escaping'] === 'string' &&
+      result['corrected_string_escaping'].length > 0
     ) {
-      return result.corrected_string_escaping;
+      return result['corrected_string_escaping'];
     } else {
       return potentiallyProblematicString;
     }
diff --git a/packages/core/src/utils/editor.test.ts b/packages/core/src/utils/editor.test.ts
index afdc2b24..fcf50f9c 100644
--- a/packages/core/src/utils/editor.test.ts
+++ b/packages/core/src/utils/editor.test.ts
@@ -33,7 +33,7 @@ const originalPlatform = process.platform;
 describe('editor utils', () => {
   beforeEach(() => {
     vi.clearAllMocks();
-    delete process.env.SANDBOX;
+    vi.unstubAllEnvs();
     Object.defineProperty(process, 'platform', {
       value: originalPlatform,
       writable: true,
@@ -42,7 +42,7 @@ describe('editor utils', () => {
 
   afterEach(() => {
     vi.restoreAllMocks();
-    delete process.env.SANDBOX;
+    vi.unstubAllEnvs();
     Object.defineProperty(process, 'platform', {
       value: originalPlatform,
       writable: true,
@@ -461,7 +461,7 @@ describe('editor utils', () => {
 
   describe('allowEditorTypeInSandbox', () => {
     it('should allow vim in sandbox mode', () => {
-      process.env.SANDBOX = 'sandbox';
+      vi.stubEnv('SANDBOX', 'sandbox');
       expect(allowEditorTypeInSandbox('vim')).toBe(true);
     });
 
@@ -470,7 +470,7 @@ describe('editor utils', () => {
     });
 
     it('should allow emacs in sandbox mode', () => {
-      process.env.SANDBOX = 'sandbox';
+      vi.stubEnv('SANDBOX', 'sandbox');
       expect(allowEditorTypeInSandbox('emacs')).toBe(true);
     });
 
@@ -479,7 +479,7 @@ describe('editor utils', () => {
     });
 
     it('should allow neovim in sandbox mode', () => {
-      process.env.SANDBOX = 'sandbox';
+      vi.stubEnv('SANDBOX', 'sandbox');
       expect(allowEditorTypeInSandbox('neovim')).toBe(true);
     });
 
@@ -496,7 +496,7 @@ describe('editor utils', () => {
     ];
     for (const editor of guiEditors) {
       it(`should not allow ${editor} in sandbox mode`, () => {
-        process.env.SANDBOX = 'sandbox';
+        vi.stubEnv('SANDBOX', 'sandbox');
         expect(allowEditorTypeInSandbox(editor)).toBe(false);
       });
 
@@ -533,25 +533,25 @@ describe('editor utils', () => {
 
     it('should return false for vscode when installed and in sandbox mode', () => {
       (execSync as Mock).mockReturnValue(Buffer.from('/usr/bin/code'));
-      process.env.SANDBOX = 'sandbox';
+      vi.stubEnv('SANDBOX', 'sandbox');
       expect(isEditorAvailable('vscode')).toBe(false);
     });
 
     it('should return true for vim when installed and in sandbox mode', () => {
       (execSync as Mock).mockReturnValue(Buffer.from('/usr/bin/vim'));
-      process.env.SANDBOX = 'sandbox';
+      vi.stubEnv('SANDBOX', 'sandbox');
       expect(isEditorAvailable('vim')).toBe(true);
     });
 
     it('should return true for emacs when installed and in sandbox mode', () => {
       (execSync as Mock).mockReturnValue(Buffer.from('/usr/bin/emacs'));
-      process.env.SANDBOX = 'sandbox';
+      vi.stubEnv('SANDBOX', 'sandbox');
       expect(isEditorAvailable('emacs')).toBe(true);
     });
 
     it('should return true for neovim when installed and in sandbox mode', () => {
       (execSync as Mock).mockReturnValue(Buffer.from('/usr/bin/nvim'));
-      process.env.SANDBOX = 'sandbox';
+      vi.stubEnv('SANDBOX', 'sandbox');
       expect(isEditorAvailable('neovim')).toBe(true);
     });
   });
diff --git a/packages/core/src/utils/editor.ts b/packages/core/src/utils/editor.ts
index f22297df..efaef249 100644
--- a/packages/core/src/utils/editor.ts
+++ b/packages/core/src/utils/editor.ts
@@ -72,7 +72,7 @@ export function checkHasEditorType(editor: EditorType): boolean {
 }
 
 export function allowEditorTypeInSandbox(editor: EditorType): boolean {
-  const notUsingSandbox = !process.env.SANDBOX;
+  const notUsingSandbox = !process.env['SANDBOX'];
   if (['vscode', 'vscodium', 'windsurf', 'cursor', 'zed'].includes(editor)) {
     return notUsingSandbox;
   }
diff --git a/packages/core/src/utils/memoryDiscovery.test.ts b/packages/core/src/utils/memoryDiscovery.test.ts
index 6c229dbb..d8f3ccc5 100644
--- a/packages/core/src/utils/memoryDiscovery.test.ts
+++ b/packages/core/src/utils/memoryDiscovery.test.ts
@@ -48,8 +48,8 @@ describe('loadServerHierarchicalMemory', () => {
 
     vi.resetAllMocks();
     // Set environment variables to indicate test environment
-    process.env.NODE_ENV = 'test';
-    process.env.VITEST = 'true';
+    vi.stubEnv('NODE_ENV', 'test');
+    vi.stubEnv('VITEST', 'true');
 
     projectRoot = await createEmptyDir(path.join(testRootDir, 'project'));
     cwd = await createEmptyDir(path.join(projectRoot, 'src'));
@@ -58,6 +58,7 @@ describe('loadServerHierarchicalMemory', () => {
   });
 
   afterEach(async () => {
+    vi.unstubAllEnvs();
     // Some tests set this to a different value.
     setGeminiMdFilename(DEFAULT_CONTEXT_FILENAME);
     // Clean up the temporary directory to prevent resource leaks.
diff --git a/packages/core/src/utils/memoryDiscovery.ts b/packages/core/src/utils/memoryDiscovery.ts
index fcb1abdd..d3c24baf 100644
--- a/packages/core/src/utils/memoryDiscovery.ts
+++ b/packages/core/src/utils/memoryDiscovery.ts
@@ -57,8 +57,9 @@ async function findProjectRoot(startDir: string): Promise<string | null> {
         (error as { code: string }).code === 'ENOENT';
 
       // Only log unexpected errors in non-test environments
-      // process.env.NODE_ENV === 'test' or VITEST are common test indicators
-      const isTestEnv = process.env.NODE_ENV === 'test' || process.env.VITEST;
+      // process.env['NODE_ENV'] === 'test' or VITEST are common test indicators
+      const isTestEnv =
+        process.env['NODE_ENV'] === 'test' || process.env['VITEST'];
 
       if (!isENOENT && !isTestEnv) {
         if (typeof error === 'object' && error !== null && 'code' in error) {
@@ -246,7 +247,8 @@ async function readGeminiMdFiles(
           `Successfully read and processed imports: ${filePath} (Length: ${processedResult.content.length})`,
         );
     } catch (error: unknown) {
-      const isTestEnv = process.env.NODE_ENV === 'test' || process.env.VITEST;
+      const isTestEnv =
+        process.env['NODE_ENV'] === 'test' || process.env['VITEST'];
       if (!isTestEnv) {
         const message = error instanceof Error ? error.message : String(error);
         logger.warn(
diff --git a/packages/core/src/utils/secure-browser-launcher.ts b/packages/core/src/utils/secure-browser-launcher.ts
index ec8357be..c60a646d 100644
--- a/packages/core/src/utils/secure-browser-launcher.ts
+++ b/packages/core/src/utils/secure-browser-launcher.ts
@@ -151,20 +151,23 @@ export function shouldLaunchBrowser(): boolean {
   // A list of browser names that indicate we should not attempt to open a
   // web browser for the user.
   const browserBlocklist = ['www-browser'];
-  const browserEnv = process.env.BROWSER;
+  const browserEnv = process.env['BROWSER'];
   if (browserEnv && browserBlocklist.includes(browserEnv)) {
     return false;
   }
 
   // Common environment variables used in CI/CD or other non-interactive shells.
-  if (process.env.CI || process.env.DEBIAN_FRONTEND === 'noninteractive') {
+  if (
+    process.env['CI'] ||
+    process.env['DEBIAN_FRONTEND'] === 'noninteractive'
+  ) {
     return false;
   }
 
   // The presence of SSH_CONNECTION indicates a remote session.
   // We should not attempt to launch a browser unless a display is explicitly available
   // (checked below for Linux).
-  const isSSH = !!process.env.SSH_CONNECTION;
+  const isSSH = !!process.env['SSH_CONNECTION'];
 
   // On Linux, the presence of a display server is a strong indicator of a GUI.
   if (platform() === 'linux') {
diff --git a/packages/core/src/utils/shell-utils.test.ts b/packages/core/src/utils/shell-utils.test.ts
index 913ec897..18f88e11 100644
--- a/packages/core/src/utils/shell-utils.test.ts
+++ b/packages/core/src/utils/shell-utils.test.ts
@@ -388,7 +388,7 @@ describe('getShellConfiguration', () => {
     });
 
     it('should return cmd.exe configuration by default', () => {
-      delete process.env.ComSpec;
+      delete process.env['ComSpec'];
       const config = getShellConfiguration();
       expect(config.executable).toBe('cmd.exe');
       expect(config.argsPrefix).toEqual(['/d', '/s', '/c']);
@@ -397,7 +397,7 @@ describe('getShellConfiguration', () => {
 
     it('should respect ComSpec for cmd.exe', () => {
       const cmdPath = 'C:\\WINDOWS\\system32\\cmd.exe';
-      process.env.ComSpec = cmdPath;
+      process.env['ComSpec'] = cmdPath;
       const config = getShellConfiguration();
       expect(config.executable).toBe(cmdPath);
       expect(config.argsPrefix).toEqual(['/d', '/s', '/c']);
@@ -407,7 +407,7 @@ describe('getShellConfiguration', () => {
     it('should return PowerShell configuration if ComSpec points to powershell.exe', () => {
       const psPath =
         'C:\\WINDOWS\\System32\\WindowsPowerShell\\v1.0\\powershell.exe';
-      process.env.ComSpec = psPath;
+      process.env['ComSpec'] = psPath;
       const config = getShellConfiguration();
       expect(config.executable).toBe(psPath);
       expect(config.argsPrefix).toEqual(['-NoProfile', '-Command']);
@@ -416,7 +416,7 @@ describe('getShellConfiguration', () => {
 
     it('should return PowerShell configuration if ComSpec points to pwsh.exe', () => {
       const pwshPath = 'C:\\Program Files\\PowerShell\\7\\pwsh.exe';
-      process.env.ComSpec = pwshPath;
+      process.env['ComSpec'] = pwshPath;
       const config = getShellConfiguration();
       expect(config.executable).toBe(pwshPath);
       expect(config.argsPrefix).toEqual(['-NoProfile', '-Command']);
@@ -424,7 +424,7 @@ describe('getShellConfiguration', () => {
     });
 
     it('should be case-insensitive when checking ComSpec', () => {
-      process.env.ComSpec = 'C:\\Path\\To\\POWERSHELL.EXE';
+      process.env['ComSpec'] = 'C:\\Path\\To\\POWERSHELL.EXE';
       const config = getShellConfiguration();
       expect(config.executable).toBe('C:\\Path\\To\\POWERSHELL.EXE');
       expect(config.argsPrefix).toEqual(['-NoProfile', '-Command']);
diff --git a/packages/core/src/utils/shell-utils.ts b/packages/core/src/utils/shell-utils.ts
index 2c818c8e..808cf893 100644
--- a/packages/core/src/utils/shell-utils.ts
+++ b/packages/core/src/utils/shell-utils.ts
@@ -37,7 +37,7 @@ export interface ShellConfiguration {
  */
 export function getShellConfiguration(): ShellConfiguration {
   if (isWindows()) {
-    const comSpec = process.env.ComSpec || 'cmd.exe';
+    const comSpec = process.env['ComSpec'] || 'cmd.exe';
     const executable = comSpec.toLowerCase();
 
     if (
diff --git a/packages/core/src/utils/systemEncoding.test.ts b/packages/core/src/utils/systemEncoding.test.ts
index 9375db9e..afabd33f 100644
--- a/packages/core/src/utils/systemEncoding.test.ts
+++ b/packages/core/src/utils/systemEncoding.test.ts
@@ -39,9 +39,9 @@ describe('Shell Command Processor - Encoding Functions', () => {
     resetEncodingCache();
 
     // Clear environment variables that might affect tests
-    delete process.env.LC_ALL;
-    delete process.env.LC_CTYPE;
-    delete process.env.LANG;
+    delete process.env['LC_ALL'];
+    delete process.env['LC_CTYPE'];
+    delete process.env['LANG'];
   });
 
   afterEach(() => {
@@ -218,21 +218,21 @@ describe('Shell Command Processor - Encoding Functions', () => {
     });
 
     it('should parse locale from LC_ALL environment variable', () => {
-      process.env.LC_ALL = 'en_US.UTF-8';
+      process.env['LC_ALL'] = 'en_US.UTF-8';
 
       const result = getSystemEncoding();
       expect(result).toBe('utf-8');
     });
 
     it('should parse locale from LC_CTYPE when LC_ALL is not set', () => {
-      process.env.LC_CTYPE = 'fr_FR.ISO-8859-1';
+      process.env['LC_CTYPE'] = 'fr_FR.ISO-8859-1';
 
       const result = getSystemEncoding();
       expect(result).toBe('iso-8859-1');
     });
 
     it('should parse locale from LANG when LC_ALL and LC_CTYPE are not set', () => {
-      process.env.LANG = 'de_DE.UTF-8';
+      process.env['LANG'] = 'de_DE.UTF-8';
 
       const result = getSystemEncoding();
       expect(result).toBe('utf-8');
@@ -268,16 +268,16 @@ describe('Shell Command Processor - Encoding Functions', () => {
     });
 
     it('should handle locale without encoding (no dot)', () => {
-      process.env.LANG = 'C';
+      process.env['LANG'] = 'C';
 
       const result = getSystemEncoding();
       expect(result).toBe('c');
     });
 
     it('should handle empty locale environment variables', () => {
-      process.env.LC_ALL = '';
-      process.env.LC_CTYPE = '';
-      process.env.LANG = '';
+      process.env['LC_ALL'] = '';
+      process.env['LC_CTYPE'] = '';
+      process.env['LANG'] = '';
       mockedExecSync.mockReturnValue('UTF-8');
 
       const result = getSystemEncoding();
@@ -285,24 +285,24 @@ describe('Shell Command Processor - Encoding Functions', () => {
     });
 
     it('should return locale as-is when locale format has no dot', () => {
-      process.env.LANG = 'invalid_format';
+      process.env['LANG'] = 'invalid_format';
 
       const result = getSystemEncoding();
       expect(result).toBe('invalid_format');
     });
 
     it('should prioritize LC_ALL over other environment variables', () => {
-      process.env.LC_ALL = 'en_US.UTF-8';
-      process.env.LC_CTYPE = 'fr_FR.ISO-8859-1';
-      process.env.LANG = 'de_DE.CP1252';
+      process.env['LC_ALL'] = 'en_US.UTF-8';
+      process.env['LC_CTYPE'] = 'fr_FR.ISO-8859-1';
+      process.env['LANG'] = 'de_DE.CP1252';
 
       const result = getSystemEncoding();
       expect(result).toBe('utf-8');
     });
 
     it('should prioritize LC_CTYPE over LANG', () => {
-      process.env.LC_CTYPE = 'fr_FR.ISO-8859-1';
-      process.env.LANG = 'de_DE.CP1252';
+      process.env['LC_CTYPE'] = 'fr_FR.ISO-8859-1';
+      process.env['LANG'] = 'de_DE.CP1252';
 
       const result = getSystemEncoding();
       expect(result).toBe('iso-8859-1');
@@ -315,7 +315,7 @@ describe('Shell Command Processor - Encoding Functions', () => {
     });
 
     it('should use cached system encoding on subsequent calls', () => {
-      process.env.LANG = 'en_US.UTF-8';
+      process.env['LANG'] = 'en_US.UTF-8';
       const buffer = Buffer.from('test');
 
       // First call
@@ -323,7 +323,7 @@ describe('Shell Command Processor - Encoding Functions', () => {
       expect(result1).toBe('utf-8');
 
       // Change environment (should not affect cached result)
-      process.env.LANG = 'fr_FR.ISO-8859-1';
+      process.env['LANG'] = 'fr_FR.ISO-8859-1';
 
       // Second call should use cached value
       const result2 = getCachedEncodingForBuffer(buffer);
@@ -435,7 +435,7 @@ describe('Shell Command Processor - Encoding Functions', () => {
   describe('Cross-platform behavior', () => {
     it('should work correctly on macOS', () => {
       mockedOsPlatform.mockReturnValue('darwin');
-      process.env.LANG = 'en_US.UTF-8';
+      process.env['LANG'] = 'en_US.UTF-8';
 
       const result = getSystemEncoding();
       expect(result).toBe('utf-8');
@@ -443,7 +443,7 @@ describe('Shell Command Processor - Encoding Functions', () => {
 
     it('should work correctly on other Unix-like systems', () => {
       mockedOsPlatform.mockReturnValue('freebsd');
-      process.env.LANG = 'en_US.UTF-8';
+      process.env['LANG'] = 'en_US.UTF-8';
 
       const result = getSystemEncoding();
       expect(result).toBe('utf-8');
@@ -451,7 +451,7 @@ describe('Shell Command Processor - Encoding Functions', () => {
 
     it('should handle unknown platforms as Unix-like', () => {
       mockedOsPlatform.mockReturnValue('unknown' as NodeJS.Platform);
-      process.env.LANG = 'en_US.UTF-8';
+      process.env['LANG'] = 'en_US.UTF-8';
 
       const result = getSystemEncoding();
       expect(result).toBe('utf-8');
@@ -461,7 +461,7 @@ describe('Shell Command Processor - Encoding Functions', () => {
   describe('Edge cases and error handling', () => {
     it('should handle empty buffer gracefully', () => {
       mockedOsPlatform.mockReturnValue('linux');
-      process.env.LANG = 'en_US.UTF-8';
+      process.env['LANG'] = 'en_US.UTF-8';
 
       const buffer = Buffer.alloc(0);
       const result = getCachedEncodingForBuffer(buffer);
@@ -470,7 +470,7 @@ describe('Shell Command Processor - Encoding Functions', () => {
 
     it('should handle very large buffers', () => {
       mockedOsPlatform.mockReturnValue('linux');
-      process.env.LANG = 'en_US.UTF-8';
+      process.env['LANG'] = 'en_US.UTF-8';
 
       const buffer = Buffer.alloc(1024 * 1024, 'a');
       const result = getCachedEncodingForBuffer(buffer);
diff --git a/packages/core/src/utils/systemEncoding.ts b/packages/core/src/utils/systemEncoding.ts
index f162c223..ba632d41 100644
--- a/packages/core/src/utils/systemEncoding.ts
+++ b/packages/core/src/utils/systemEncoding.ts
@@ -79,7 +79,7 @@ export function getSystemEncoding(): string | null {
   // system encoding. However, these environment variables might not always
   // be set or accurate. Handle cases where none of these variables are set.
   const env = process.env;
-  let locale = env.LC_ALL || env.LC_CTYPE || env.LANG || '';
+  let locale = env['LC_ALL'] || env['LC_CTYPE'] || env['LANG'] || '';
 
   // Fallback to querying the system directly when environment variables are missing
   if (!locale) {
diff --git a/tsconfig.json b/tsconfig.json
index 5f303ddc..e46eff1d 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -8,6 +8,7 @@
     "noImplicitReturns": true,
     "noImplicitThis": true,
     "forceConsistentCasingInFileNames": true,
+    "noPropertyAccessFromIndexSignature": true,
     "noUnusedLocals": true,
     "strictBindCallApply": true,
     "strictFunctionTypes": true,