diff --git a/lib/logger.dart b/lib/logger.dart
index c914698..d2bfe57 100644
--- a/lib/logger.dart
+++ b/lib/logger.dart
@@ -49,4 +49,5 @@
 /// - **stderr**: WARNING, ERROR, CRITICAL, ALERT, EMERGENCY
 library;
 
-export 'src/logger/logger.dart';
+export 'src/logger/logger.dart'
+    hide createLogger, projectIdZoneKey, traceIdZoneKey;
diff --git a/lib/src/common/environment.dart b/lib/src/common/environment.dart
new file mode 100644
index 0000000..6b48b59
--- /dev/null
+++ b/lib/src/common/environment.dart
@@ -0,0 +1,128 @@
+// Copyright 2026 Firebase
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:meta/meta.dart';
+
+/// Provides unified access to environment variables, emulator checks, and
+/// Google Cloud / Firebase configuration.
+class FirebaseEnv {
+  FirebaseEnv() : environment = mockEnvironment ?? Platform.environment;
+
+  @visibleForTesting
+  static Map<String, String>? mockEnvironment;
+
+  final Map<String, String> environment;
+
+  /// Whether running within a Firebase emulator environment.
+  bool get isEmulator {
+    // Explicit functions emulator flag
+    return environment['FUNCTIONS_EMULATOR'] == 'true' ||
+        // Generic fallback: check if any common emulator hosts are configured
+        _emulatorHostKeys.any(environment.containsKey);
+  }
+
+  /// Timezone setting.
+  String get tz => environment['TZ'] ?? 'UTC';
+
+  /// Whether debug mode is enabled.
+  bool get debugMode => environment['FIREBASE_DEBUG_MODE'] == 'true';
+
+  /// Whether to skip token verification (emulator only).
+  bool get skipTokenVerification => _getDebugFeature('skipTokenVerification');
+
+  /// Whether CORS is enabled (emulator only).
+  bool get enableCors => _getDebugFeature('enableCors');
+
+  bool _getDebugFeature(String key) {
+    if (environment['FIREBASE_DEBUG_FEATURES'] case final String json) {
+      try {
+        if (jsonDecode(json) case final Map<String, dynamic> m) {
+          return switch (m[key]) {
+            final bool value => value,
+            _ => false,
+          };
+        }
+      } on FormatException {
+        // ignore
+      }
+    }
+    return false;
+  }
+
+  /// Returns the current Firebase project ID.
+  ///
+  /// Checks standard environment variables in order:
+  /// 1. FIREBASE_PROJECT
+  /// 2. GCLOUD_PROJECT
+  /// 3. GOOGLE_CLOUD_PROJECT
+  /// 4. GCP_PROJECT
+  ///
+  /// If none are set, throws [StateError].
+  String get projectId {
+    for (final option in _projectIdEnvKeyOptions) {
+      final value = environment[option];
+      if (value != null && value.isNotEmpty) return value;
+    }
+
+    throw StateError(
+      'No project ID found in environment. Checked: ${_projectIdEnvKeyOptions.join(', ')}',
+    );
+  }
+
+  /// The port to listen on.
+  ///
+  /// Uses the [PORT] environment variable, defaulting to 8080.
+  int get port => int.tryParse(environment['PORT'] ?? '8080') ?? 8080;
+
+  /// The name of the Cloud Run service.
+  ///
+  /// Uses the `K_SERVICE` environment variable.
+  ///
+  /// See https://cloud.google.com/run/docs/container-contract#env-vars
+  String? get kService => environment['K_SERVICE'];
+
+  /// The name of the target function.
+  ///
+  /// Uses the `FUNCTION_TARGET` environment variable.
+  ///
+  /// See https://docs.cloud.google.com/run/docs/configuring/services/environment-variables#additional_reserved_environment_variables_when_deploying_functions
+  String? get functionTarget => environment['FUNCTION_TARGET'];
+
+  /// Whether the functions control API is enabled.
+  ///
+  /// Uses the `FUNCTIONS_CONTROL_API` environment variable.
+  ///
+  /// This is part of the contract with `firebase-tools`.
+  bool get functionsControlApi =>
+      environment['FUNCTIONS_CONTROL_API'] == 'true';
+}
+
+/// Common project ID environment variables checked in order.
+const _projectIdEnvKeyOptions = [
+  'FIREBASE_PROJECT',
+  'GCLOUD_PROJECT',
+  'GOOGLE_CLOUD_PROJECT',
+  'GCP_PROJECT',
+];
+
+/// Common emulator host keys used to detect emulator environment.
+const _emulatorHostKeys = [
+  'FIRESTORE_EMULATOR_HOST',
+  'FIREBASE_AUTH_EMULATOR_HOST',
+  'FIREBASE_DATABASE_EMULATOR_HOST',
+  'FIREBASE_STORAGE_EMULATOR_HOST',
+];
diff --git a/lib/src/firebase.dart b/lib/src/firebase.dart
index c72e352..99c20d1 100644
--- a/lib/src/firebase.dart
+++ b/lib/src/firebase.dart
@@ -13,7 +13,6 @@
 // limitations under the License.
 
 import 'dart:async';
-import 'dart:io';
 
 import 'package:dart_firebase_admin/dart_firebase_admin.dart';
 import 'package:google_cloud_firestore/google_cloud_firestore.dart' as gfs;
@@ -22,6 +21,7 @@ import 'package:shelf/shelf.dart';
 
 import 'alerts/alerts_namespace.dart';
 import 'common/cloud_run_id.dart';
+import 'common/environment.dart';
 import 'database/database_namespace.dart';
 import 'eventarc/eventarc_namespace.dart';
 import 'firestore/firestore_namespace.dart';
@@ -39,7 +39,7 @@ import 'test_lab/test_lab_namespace.dart';
 ///
 /// Provides access to all function namespaces (https, pubsub, firestore, etc.).
 class Firebase {
-  Firebase() {
+  Firebase() : _env = FirebaseEnv() {
     _initializeAdminSDK();
   }
 
@@ -48,18 +48,7 @@ class Firebase {
 
   /// Initialize the Firebase Admin SDK
   void _initializeAdminSDK() {
-    // Get project ID from environment
-    final projectId =
-        Platform.environment['GCLOUD_PROJECT'] ??
-        Platform.environment['GCP_PROJECT'] ??
-        'demo-test'; // Fallback for emulator
-
-    // Check if running in emulator
-    final firestoreEmulatorHost =
-        Platform.environment['FIRESTORE_EMULATOR_HOST'];
-    final isEmulator = firestoreEmulatorHost != null;
-
-    if (isEmulator) {
+    if (_env.isEmulator) {
       // TODO: Implement direct REST API calls to emulator
       // For now, we'll skip document fetching in emulator mode
       return;
@@ -71,7 +60,7 @@ class Firebase {
       _adminApp = FirebaseApp.initializeApp(
         options: AppOptions(
           credential: Credential.fromApplicationDefaultCredentials(),
-          projectId: projectId,
+          projectId: _env.projectId,
         ),
       );
 
@@ -82,6 +71,8 @@ class Firebase {
     }
   }
 
+  final FirebaseEnv _env;
+
   /// Get the Firestore instance
   gfs.Firestore? get firestoreAdmin => _firestoreInstance;
 
@@ -260,3 +251,9 @@ abstract class FunctionsNamespace {
   const FunctionsNamespace(this.firebase);
   final Firebase firebase;
 }
+
+/// Internal extension to access private members of Firebase.
+@internal
+extension FirebaseInternal on Firebase {
+  FirebaseEnv get $env => _env;
+}
diff --git a/lib/src/https/https_namespace.dart b/lib/src/https/https_namespace.dart
index 3f49f3c..87a7882 100644
--- a/lib/src/https/https_namespace.dart
+++ b/lib/src/https/https_namespace.dart
@@ -14,7 +14,6 @@
 
 import 'dart:async';
 import 'dart:convert';
-import 'dart:io';
 
 import 'package:meta/meta.dart';
 import 'package:shelf/shelf.dart';
@@ -26,20 +25,6 @@ import 'callable.dart';
 import 'error.dart';
 import 'options.dart';
 
-/// Checks if token verification should be skipped (emulator mode).
-bool _shouldSkipTokenVerification() {
-  final debugFeatures = Platform.environment['FIREBASE_DEBUG_FEATURES'];
-  if (debugFeatures == null) {
-    return false;
-  }
-  try {
-    final features = jsonDecode(debugFeatures);
-    return features['skipTokenVerification'] as bool? ?? false;
-  } catch (_) {
-    return false;
-  }
-}
-
 /// HTTPS triggers namespace.
 ///
 /// Provides methods to define HTTP-triggered Cloud Functions.
@@ -115,7 +100,7 @@ class HttpsNamespace extends FunctionsNamespace {
       }
 
       // Extract auth and app check tokens
-      final skipVerification = _shouldSkipTokenVerification();
+      final skipVerification = firebase.$env.skipTokenVerification;
       final tokens = await checkTokens(
         request,
         skipTokenVerification: skipVerification,
@@ -195,7 +180,7 @@ class HttpsNamespace extends FunctionsNamespace {
       final body = await request.json as Map<String, dynamic>?;
 
       // Extract auth and app check tokens
-      final skipVerification = _shouldSkipTokenVerification();
+      final skipVerification = firebase.$env.skipTokenVerification;
       final tokens = await checkTokens(
         request,
         skipTokenVerification: skipVerification,
diff --git a/lib/src/identity/identity_namespace.dart b/lib/src/identity/identity_namespace.dart
index a3e20e3..e2bd0ce 100644
--- a/lib/src/identity/identity_namespace.dart
+++ b/lib/src/identity/identity_namespace.dart
@@ -17,7 +17,6 @@ library;
 
 import 'dart:async';
 import 'dart:convert';
-import 'dart:io';
 
 import 'package:meta/meta.dart';
 import 'package:shelf/shelf.dart';
@@ -276,45 +275,24 @@ class IdentityNamespace extends FunctionsNamespace {
   /// certificates. In emulator mode (when FUNCTIONS_EMULATOR=true or
   /// skipTokenVerification debug feature is enabled), verification is skipped.
   Future<Map<String, dynamic>> _decodeAndVerifyJwt(String jwt) async {
-    // Get environment configuration
-    final env = Platform.environment;
-    final isEmulator = env['FUNCTIONS_EMULATOR'] == 'true';
-    final skipVerification = _shouldSkipTokenVerification(env);
-
     // Get project ID
-    final projectId =
-        env['GCLOUD_PROJECT'] ??
-        env['GCP_PROJECT'] ??
-        env['FIREBASE_PROJECT'] ??
-        'demo-test';
+    final projectId = firebase.$env.projectId;
 
     // Create verifier
     final verifier = AuthBlockingTokenVerifier(
       projectId: projectId,
-      isEmulator: isEmulator || skipVerification,
+      isEmulator:
+          firebase.$env.isEmulator || firebase.$env.skipTokenVerification,
     );
 
     // Determine audience based on platform
     // Cloud Run uses "run.app", GCF v1 uses default
-    final kService = env['K_SERVICE']; // Cloud Run service name
+    final kService = firebase.$env.kService; // Cloud Run service name
     final audience = kService != null ? 'run.app' : null;
 
     return verifier.verifyToken(jwt, audience: audience);
   }
 
-  /// Checks if token verification should be skipped based on debug features.
-  bool _shouldSkipTokenVerification(Map<String, String> env) {
-    final debugFeatures = env['FIREBASE_DEBUG_FEATURES'];
-    if (debugFeatures == null) return false;
-
-    try {
-      final features = jsonDecode(debugFeatures) as Map<String, dynamic>;
-      return features['skipTokenVerification'] as bool? ?? false;
-    } on FormatException {
-      return false;
-    }
-  }
-
   /// Validates the auth response for invalid claims.
   void _validateAuthResponse(
     AuthBlockingEventType eventType,
diff --git a/lib/src/logger/logger.dart b/lib/src/logger/logger.dart
index 6afe200..f8c3b96 100644
--- a/lib/src/logger/logger.dart
+++ b/lib/src/logger/logger.dart
@@ -16,6 +16,8 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:io' as io;
 
+import 'package:meta/meta.dart';
+
 /// Log severity levels for Cloud Logging.
 ///
 /// See [LogSeverity](https://cloud.google.com/logging/docs/reference/v2/rest/v2/LogEntry#logseverity).
@@ -42,17 +44,6 @@ enum LogSeverity {
 /// of the logged entry.
 typedef LogEntry = Map<String, Object?>;
 
-/// Zone key for propagating trace IDs through async operations.
-///
-/// Set this in a [Zone] to automatically include trace context in log entries:
-/// ```dart
-/// runZoned(
-///   () { logger.info('traced!'); },
-///   zoneValues: {traceIdKey: 'abc123'},
-/// );
-/// ```
-const Symbol traceIdKey = #firebaseTraceId;
-
 /// Removes circular references from an object graph for safe JSON
 /// serialization.
 ///
@@ -128,6 +119,15 @@ bool _isStderrSeverity(String severity) => switch (severity) {
   _ => false,
 };
 
+/// Creates a new [Logger] instance.
+///
+/// [stdoutWriter] and [stderrWriter] can be provided for testing.
+@internal
+Logger createLogger({
+  void Function(String line)? stdoutWriter,
+  void Function(String line)? stderrWriter,
+}) => Logger._(stdoutWriter: stdoutWriter, stderrWriter: stderrWriter);
+
 /// Structured logger for Cloud Logging, compatible with the Firebase
 /// Functions Node.js SDK `logger` namespace.
 ///
@@ -152,11 +152,11 @@ bool _isStderrSeverity(String severity) => switch (severity) {
 /// // Low-level structured entry
 /// logger.write({'severity': 'NOTICE', 'message': 'Custom', 'code': 42});
 /// ```
-class Logger {
+final class Logger {
   /// Creates a [Logger] instance.
   ///
   /// Custom [stdoutWriter] and [stderrWriter] can be provided for testing.
-  Logger({
+  Logger._({
     void Function(String line)? stdoutWriter,
     void Function(String line)? stderrWriter,
   }) : _stdoutWriter = stdoutWriter ?? _defaultStdoutWriter,
@@ -171,17 +171,19 @@ class Logger {
   /// Writes a [LogEntry] to stdout or stderr depending on severity.
   ///
   /// The entry must contain a `severity` key. If a trace ID is available
-  /// in the current [Zone] (via [traceIdKey]), it is automatically added
+  /// in the current [Zone] (via [traceIdZoneKey]), it is automatically added
   /// to the entry.
   void write(LogEntry entry) {
     // Add trace context if available.
-    final traceId = Zone.current[traceIdKey] as String?;
-    if (traceId != null) {
-      final project = io.Platform.environment['GCLOUD_PROJECT'];
-      if (project != null) {
-        entry['logging.googleapis.com/trace'] =
-            'projects/$project/traces/$traceId';
-      }
+
+    final projectId = Zone.current[projectIdZoneKey] as String?;
+    final traceId = Zone.current[traceIdZoneKey] as String?;
+
+    if (projectId != null && traceId != null) {
+      assert(projectId.isNotEmpty, 'projectIdZoneKey value must not be empty');
+      assert(traceId.isNotEmpty, 'traceIdZoneKey value must not be empty');
+      entry['logging.googleapis.com/trace'] =
+          'projects/$projectId/traces/$traceId';
     }
 
     final sanitized = removeCircular(entry);
@@ -269,4 +271,17 @@ LogEntry _entryFromArgs(
 /// logger.info('Hello');
 /// logger.warn('Something is off', {'requestId': 'abc'});
 /// ```
-final logger = Logger();
+final logger = Logger._();
+
+/// Standard HTTP header used by
+/// [Cloud Trace](https://cloud.google.com/trace/docs/setup).
+@internal
+const cloudTraceContextHeader = 'x-cloud-trace-context';
+
+/// Zone key for propagating trace IDs.
+@internal
+final Object traceIdZoneKey = Object();
+
+/// Zone key for propagating project ID.
+@internal
+final Object projectIdZoneKey = Object();
diff --git a/lib/src/server.dart b/lib/src/server.dart
index e9254a5..92f141a 100644
--- a/lib/src/server.dart
+++ b/lib/src/server.dart
@@ -16,12 +16,13 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
+import 'package:meta/meta.dart';
 import 'package:shelf/shelf.dart';
 import 'package:shelf/shelf_io.dart' as shelf_io;
-
 import 'package:stack_trace/stack_trace.dart' show Trace;
 
 import 'common/cloud_run_id.dart';
+import 'common/environment.dart';
 import 'common/on_init.dart';
 import 'firebase.dart';
 import 'logger/logger.dart';
@@ -29,47 +30,6 @@ import 'logger/logger.dart';
 /// Callback type for the user's function registration code.
 typedef FunctionsRunner = FutureOr<void> Function(Firebase firebase);
 
-/// Firebase emulator environment detection and configuration.
-class EmulatorEnvironment {
-  EmulatorEnvironment(this.environment);
-  final Map<String, String> environment;
-
-  /// Whether running in the Firebase emulator.
-  bool get isEmulator => environment['FUNCTIONS_EMULATOR'] == 'true';
-
-  /// Timezone setting.
-  String get tz => environment['TZ'] ?? 'UTC';
-
-  /// Whether debug mode is enabled.
-  bool get debugMode => environment['FIREBASE_DEBUG_MODE'] == 'true';
-
-  /// Whether to skip token verification (emulator only).
-  bool get skipTokenVerification {
-    if (!environment.containsKey('FIREBASE_DEBUG_FEATURES')) {
-      return false;
-    }
-    try {
-      final features = jsonDecode(environment['FIREBASE_DEBUG_FEATURES']!);
-      return features['skipTokenVerification'] as bool? ?? false;
-    } on FormatException {
-      return false;
-    }
-  }
-
-  /// Whether CORS is enabled (emulator only).
-  bool get enableCors {
-    if (!environment.containsKey('FIREBASE_DEBUG_FEATURES')) {
-      return false;
-    }
-    try {
-      final features = jsonDecode(environment['FIREBASE_DEBUG_FEATURES']!);
-      return features['enableCors'] as bool? ?? false;
-    } on FormatException {
-      return false;
-    }
-  }
-}
-
 /// Starts the Firebase Functions runtime.
 ///
 /// This is the main entry point for a Firebase Functions application.
@@ -87,23 +47,37 @@ class EmulatorEnvironment {
 /// ```
 Future<void> fireUp(List<String> args, FunctionsRunner runner) async {
   final firebase = Firebase();
-  final emulatorEnv = EmulatorEnvironment(Platform.environment);
+  final env = firebase.$env;
+  final projectId = env.projectId;
+
+  await runZoned(zoneValues: {projectIdZoneKey: projectId}, () async {
+    // Run user's function registration code
+    await runner(firebase);
+
+    // Build request handler with middleware pipeline
+    final handler = const Pipeline()
+        .addMiddleware(_corsMiddleware(env))
+        .addHandler((request) {
+          final traceId = extractTraceId(
+            request.headers[cloudTraceContextHeader],
+          );
 
-  // Run user's function registration code
-  await runner(firebase);
+          if (traceId == null) {
+            return _routeRequest(request, firebase, env);
+          }
 
-  // Build request handler with middleware pipeline
-  final handler = const Pipeline()
-      .addMiddleware(_corsMiddleware(emulatorEnv))
-      .addHandler((request) => _routeRequest(request, firebase, emulatorEnv));
+          return runZoned(zoneValues: {traceIdZoneKey: traceId}, () {
+            return _routeRequest(request, firebase, env);
+          });
+        });
 
-  // Start HTTP server
-  final port = int.tryParse(Platform.environment['PORT'] ?? '8080') ?? 8080;
-  await shelf_io.serve(handler, InternetAddress.anyIPv4, port);
+    // Start HTTP server
+    await shelf_io.serve(handler, InternetAddress.anyIPv4, env.port);
+  });
 }
 
 /// CORS middleware for emulator mode.
-Middleware _corsMiddleware(EmulatorEnvironment env) =>
+Middleware _corsMiddleware(FirebaseEnv env) =>
     (innerHandler) => (request) {
       // Handle preflight OPTIONS requests
       if (env.enableCors && request.method.toUpperCase() == 'OPTIONS') {
@@ -136,7 +110,7 @@ Middleware _corsMiddleware(EmulatorEnvironment env) =>
 FutureOr<Response> _routeRequest(
   Request request,
   Firebase firebase,
-  EmulatorEnvironment env,
+  FirebaseEnv env,
 ) {
   final functions = firebase.functions;
   final requestPath = request.url.path;
@@ -152,15 +126,14 @@ FutureOr<Response> _routeRequest(
     return _handleQuitQuitQuit(request);
   }
 
-  if (requestPath == '__/functions.yaml' &&
-      env.environment['FUNCTIONS_CONTROL_API'] == 'true') {
+  if (requestPath == '__/functions.yaml' && env.functionsControlApi) {
     // Manifest endpoint for function discovery
     return _handleFunctionsManifest(request, firebase);
   }
 
   // FUNCTION_TARGET mode (production): Serve only the specified function
   // This matches Node.js behavior where each Cloud Run service runs one function
-  final functionTarget = env.environment['FUNCTION_TARGET'];
+  final functionTarget = env.functionTarget;
   if (functionTarget != null && functionTarget.isNotEmpty) {
     return _routeToTargetFunction(request, firebase, env, functionTarget);
   }
@@ -176,7 +149,7 @@ FutureOr<Response> _routeRequest(
 FutureOr<Response> _routeToTargetFunction(
   Request request,
   Firebase firebase,
-  EmulatorEnvironment env,
+  FirebaseEnv env,
   String functionTarget,
 ) {
   final functions = firebase.functions;
@@ -700,3 +673,21 @@ bool _matchesRefPattern(String refPath, String pattern) {
 
   return true;
 }
+
+final _traceIdRegExp = RegExp(r'^[a-f0-9]{32}$', caseSensitive: false);
+
+/// Extracts the 32-character hexadecimal trace ID from an [x-cloud-trace-context] header.
+///
+/// Expected format: `TRACE_ID/SPAN_ID;o=TRACE_TRUE`
+@visibleForTesting
+String? extractTraceId(String? header) {
+  if (header == null || header.isEmpty) return null;
+  final parts = header.split('/');
+  if (parts.isNotEmpty) {
+    final traceId = parts[0];
+    if (_traceIdRegExp.hasMatch(traceId)) {
+      return traceId;
+    }
+  }
+  return null;
+}
diff --git a/test/unit/error_logging_test.dart b/test/unit/error_logging_test.dart
index 5ba62a6..75935f5 100644
--- a/test/unit/error_logging_test.dart
+++ b/test/unit/error_logging_test.dart
@@ -14,6 +14,7 @@
 
 import 'dart:convert';
 
+import 'package:firebase_functions/src/common/environment.dart';
 import 'package:firebase_functions/src/common/utilities.dart';
 import 'package:firebase_functions/src/firebase.dart';
 import 'package:firebase_functions/src/https/error.dart';
@@ -24,6 +25,10 @@ import 'package:shelf/shelf.dart';
 import 'package:test/test.dart';
 
 void main() {
+  setUpAll(() {
+    FirebaseEnv.mockEnvironment = {'FIREBASE_PROJECT': 'demo-test'};
+  });
+
   group('Error logging utilities', () {
     group('logInternalError', () {
       test('returns InternalError', () {
diff --git a/test/unit/https_namespace_test.dart b/test/unit/https_namespace_test.dart
index c568b38..3a2f26f 100644
--- a/test/unit/https_namespace_test.dart
+++ b/test/unit/https_namespace_test.dart
@@ -14,6 +14,7 @@
 
 import 'dart:convert';
 
+import 'package:firebase_functions/src/common/environment.dart';
 import 'package:firebase_functions/src/firebase.dart';
 import 'package:firebase_functions/src/https/callable.dart';
 import 'package:firebase_functions/src/https/error.dart';
@@ -32,6 +33,10 @@ FirebaseFunctionDeclaration? _findFunction(Firebase firebase, String name) {
 }
 
 void main() {
+  setUpAll(() {
+    FirebaseEnv.mockEnvironment = {'FIREBASE_PROJECT': 'demo-test'};
+  });
+
   group('HttpsNamespace', () {
     late Firebase firebase;
     late HttpsNamespace https;
diff --git a/test/unit/logger_test.dart b/test/unit/logger_test.dart
index 18a1b44..7759667 100644
--- a/test/unit/logger_test.dart
+++ b/test/unit/logger_test.dart
@@ -27,7 +27,7 @@ void main() {
     setUp(() {
       lastStdout = '';
       lastStderr = '';
-      testLogger = Logger(
+      testLogger = createLogger(
         stdoutWriter: (line) => lastStdout = line,
         stderrWriter: (line) => lastStderr = line,
       );
@@ -293,7 +293,7 @@ void main() {
 
     group('trace context', () {
       test(
-        'should add trace header when traceId is in Zone',
+        'should add trace header when both projectId and traceId are in Zone',
         () {
           runZoned(
             () {
@@ -306,13 +306,26 @@ void main() {
               });
             },
             zoneValues: {
-              traceIdKey: 'abc123',
-              // Simulate GCLOUD_PROJECT env var via a zone-aware override
+              projectIdZoneKey: 'test-project',
+              traceIdZoneKey: 'abc123',
             },
           );
         },
-        skip: 'Requires GCLOUD_PROJECT env var to be set',
       );
+
+      test('should not add trace header when projectId is missing in Zone', () {
+        runZoned(() {
+          testLogger.write({'severity': 'INFO', 'message': 'traced'});
+          expect(parseStdout(), {'severity': 'INFO', 'message': 'traced'});
+        }, zoneValues: {traceIdZoneKey: 'abc123'});
+      });
+
+      test('should not add trace header when traceId is missing in Zone', () {
+        runZoned(() {
+          testLogger.write({'severity': 'INFO', 'message': 'traced'});
+          expect(parseStdout(), {'severity': 'INFO', 'message': 'traced'});
+        }, zoneValues: {projectIdZoneKey: 'test-project'});
+      });
     });
   });
 
diff --git a/test/unit/remote_config_test.dart b/test/unit/remote_config_test.dart
index 90abf8c..4faa989 100644
--- a/test/unit/remote_config_test.dart
+++ b/test/unit/remote_config_test.dart
@@ -15,6 +15,7 @@
 import 'dart:convert';
 
 import 'package:firebase_functions/src/common/cloud_event.dart';
+import 'package:firebase_functions/src/common/environment.dart';
 import 'package:firebase_functions/src/firebase.dart';
 import 'package:firebase_functions/src/remote_config/config_update_data.dart';
 import 'package:firebase_functions/src/remote_config/remote_config_namespace.dart';
@@ -71,6 +72,10 @@ Request _createRemoteConfigRequest({
 }
 
 void main() {
+  setUpAll(() {
+    FirebaseEnv.mockEnvironment = {'FIREBASE_PROJECT': 'demo-test'};
+  });
+
   group('RemoteConfigNamespace', () {
     late Firebase firebase;
     late RemoteConfigNamespace remoteConfig;
diff --git a/test/unit/scheduler_namespace_test.dart b/test/unit/scheduler_namespace_test.dart
index 2058a9b..229185e 100644
--- a/test/unit/scheduler_namespace_test.dart
+++ b/test/unit/scheduler_namespace_test.dart
@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+import 'package:firebase_functions/src/common/environment.dart';
 import 'package:firebase_functions/src/common/options.dart';
 import 'package:firebase_functions/src/firebase.dart';
 import 'package:firebase_functions/src/scheduler/options.dart';
@@ -30,6 +31,10 @@ FirebaseFunctionDeclaration? _findFunction(Firebase firebase, String name) {
 }
 
 void main() {
+  setUpAll(() {
+    FirebaseEnv.mockEnvironment = {'FIREBASE_PROJECT': 'demo-test'};
+  });
+
   group('SchedulerNamespace', () {
     late Firebase firebase;
     late SchedulerNamespace scheduler;
diff --git a/test/unit/server_test.dart b/test/unit/server_test.dart
new file mode 100644
index 0000000..71def4a
--- /dev/null
+++ b/test/unit/server_test.dart
@@ -0,0 +1,53 @@
+// Copyright 2026 Firebase
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import 'package:firebase_functions/src/server.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('server', () {
+    group('extractTraceId', () {
+      test('extracts valid trace ID with span and option', () {
+        const header = '4bf92f3577b34da6a3ce929d0e0e4736/12345;o=1';
+        expect(extractTraceId(header), '4bf92f3577b34da6a3ce929d0e0e4736');
+      });
+
+      test('extracts valid trace ID with uppercase hex', () {
+        const header = '4BF92F3577B34DA6A3CE929D0E0E4736/12345;o=1';
+        expect(extractTraceId(header), '4BF92F3577B34DA6A3CE929D0E0E4736');
+      });
+
+      test('extracts valid trace ID without span or option', () {
+        const header = '1234567890abcdef1234567890abcdef';
+        expect(extractTraceId(header), '1234567890abcdef1234567890abcdef');
+      });
+
+      test('handles null and empty', () {
+        expect(extractTraceId(null), isNull);
+        expect(extractTraceId(''), isNull);
+      });
+
+      test('rejects malformed traces', () {
+        // Too short
+        expect(extractTraceId('1234/567;o=1'), isNull);
+
+        // Too long
+        expect(extractTraceId('1234567890abcdef1234567890abcdef0/5'), isNull);
+
+        // Invalid hex
+        expect(extractTraceId('1234567890xyzdef1234567890abcdef/5'), isNull);
+      });
+    });
+  });
+}
diff --git a/test/unit/storage_test.dart b/test/unit/storage_test.dart
index 4bc7f7b..50913fa 100644
--- a/test/unit/storage_test.dart
+++ b/test/unit/storage_test.dart
@@ -14,6 +14,7 @@
 
 import 'dart:convert';
 
+import 'package:firebase_functions/src/common/environment.dart';
 import 'package:firebase_functions/src/firebase.dart';
 import 'package:firebase_functions/src/storage/storage_event.dart';
 import 'package:firebase_functions/src/storage/storage_namespace.dart';
@@ -72,6 +73,10 @@ Request _createStorageRequest({
 }
 
 void main() {
+  setUpAll(() {
+    FirebaseEnv.mockEnvironment = {'FIREBASE_PROJECT': 'demo-test'};
+  });
+
   group('StorageNamespace', () {
     late Firebase firebase;
     late StorageNamespace storage;