getsentry · vsolano9 · Aug 10, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed simulator build, build-and-run, and test MCP calls silently discarding explicit project, scheme, destination, and configuration arguments when session defaults were set. Explicit values now override defaults, and `test_sim` accepts typed `onlyTesting` and `skipTesting` selectors ([#509](https://github.com/getsentry/XcodeBuildMCP/issues/509)).
+
 ### Changed
 
 - Dictionary-shaped MCP inputs now use client-compatible wire representations ([#491](https://github.com/getsentry/XcodeBuildMCP/issues/491)). The `env` and `testRunnerEnv` inputs on build, launch, test, and session-default tools are arrays of `{ "key": "...", "value": "..." }` entries, while `xcode_ide_call_tool.arguments` is a JSON object string. XcodeBuildMCP converts these values to their existing internal objects only after MCP input validation.

diff --git a/src/mcp/tools/simulator/__tests__/build_run_sim.test.ts b/src/mcp/tools/simulator/__tests__/build_run_sim.test.ts
@@ -48,7 +48,7 @@ describe('build_run_sim tool', () => {
       expect(typeof handler).toBe('function');
     });
 
-    it('should expose only non-session fields in public schema', () => {
+    it('should expose optional session defaults for explicit overrides', () => {
       const schemaObj = z.strictObject(schema);
 
       expect(schemaObj.safeParse({}).success).toBe(true);
@@ -64,16 +64,36 @@ describe('build_run_sim tool', () => {
         }).success,
       ).toBe(true);
 
-      expect(schemaObj.safeParse({ derivedDataPath: '/path/to/derived' }).success).toBe(false);
+      expect(
+        schemaObj.safeParse({
+          workspacePath: '/path/to/workspace.xcworkspace',
+          scheme: 'ExplicitScheme',
+          simulatorName: 'iPhone 17',
+          configuration: 'Release',
+          derivedDataPath: '/path/to/derived',
+          preferXcodebuild: false,
+        }).success,
+      ).toBe(true);
       expect(schemaObj.safeParse({ extraArgs: [123] }).success).toBe(false);
       expect(schemaObj.safeParse({ launchArgs: [123] }).success).toBe(false);
-      expect(schemaObj.safeParse({ preferXcodebuild: false }).success).toBe(false);
+      expect(schemaObj.safeParse({ preferXcodebuild: 'false' }).success).toBe(false);
 
       const schemaKeys = Object.keys(schema).sort();
-      expect(schemaKeys).toEqual(['extraArgs', 'launchArgs']);
-      expect(schemaKeys).not.toContain('scheme');
-      expect(schemaKeys).not.toContain('simulatorName');
-      expect(schemaKeys).not.toContain('projectPath');
+      expect(schemaKeys).toEqual(
+        [
+          'configuration',
+          'derivedDataPath',
+          'extraArgs',
+          'launchArgs',
+          'preferXcodebuild',
+          'projectPath',
+          'scheme',
+          'simulatorId',
+          'simulatorName',
+          'useLatestOS',
+          'workspacePath',
+        ].sort(),
+      );
     });
   });
 

diff --git a/src/mcp/tools/simulator/__tests__/build_sim.test.ts b/src/mcp/tools/simulator/__tests__/build_sim.test.ts
@@ -29,7 +29,7 @@ describe('build_sim tool', () => {
       expect(typeof handler).toBe('function');
     });
 
-    it('should have correct public schema (only non-session fields)', () => {
+    it('should expose optional session defaults for explicit overrides', () => {
       const schemaObj = z.strictObject(schema);
 
       expect(schemaObj.safeParse({}).success).toBe(true);
@@ -40,15 +40,41 @@ describe('build_sim tool', () => {
         }).success,
       ).toBe(true);
 
-      expect(schemaObj.safeParse({ derivedDataPath: '/path/to/derived' }).success).toBe(false);
+      expect(
+        schemaObj.safeParse({
+          projectPath: '/path/to/project.xcodeproj',
+          scheme: 'ExplicitScheme',
+          simulatorName: 'iPhone 17',
+          configuration: 'Release',
+          derivedDataPath: '/path/to/derived',
+          preferXcodebuild: false,
+        }).success,
+      ).toBe(true);
       expect(schemaObj.safeParse({ extraArgs: [123] }).success).toBe(false);
-      expect(schemaObj.safeParse({ preferXcodebuild: false }).success).toBe(false);
+      expect(schemaObj.safeParse({ preferXcodebuild: 'false' }).success).toBe(false);
       expect(
         schemaObj.safeParse({
           buildForTesting: true,
           testProductsPath: '/tmp/MyApp.xctestproducts',
         }).success,
       ).toBe(true);
+
+      expect(Object.keys(schema).sort()).toEqual(
+        [
+          'buildForTesting',
+          'configuration',
+          'derivedDataPath',
+          'extraArgs',
+          'preferXcodebuild',
+          'projectPath',
+          'scheme',
+          'simulatorId',
+          'simulatorName',
+          'testProductsPath',
+          'useLatestOS',
+          'workspacePath',
+        ].sort(),
+      );
     });
 
     it('should reject testProductsPath without buildForTesting', () => {

diff --git a/src/mcp/tools/simulator/__tests__/test_sim.test.ts b/src/mcp/tools/simulator/__tests__/test_sim.test.ts
@@ -18,7 +18,7 @@ describe('test_sim tool', () => {
       expect(typeof handler).toBe('function');
     });
 
-    it('should expose only non-session fields in public schema', () => {
+    it('should expose optional session defaults for explicit overrides', () => {
       const schemaObj = z.strictObject(schema);
 
       expect(schemaObj.safeParse({}).success).toBe(true);
@@ -31,12 +31,41 @@ describe('test_sim tool', () => {
 
       expect(schemaObj.safeParse({ derivedDataPath: 123 }).success).toBe(false);
       expect(schemaObj.safeParse({ extraArgs: ['--ok', 42] }).success).toBe(false);
-      expect(schemaObj.safeParse({ preferXcodebuild: true }).success).toBe(false);
+      expect(
+        schemaObj.safeParse({
+          projectPath: '/path/to/project.xcodeproj',
+          scheme: 'ExplicitScheme',
+          simulatorName: 'iPhone 17',
+          configuration: 'Release',
+          preferXcodebuild: true,
+          onlyTesting: ['MyTests/LoginTests/testSuccess'],
+          skipTesting: ['MyTests/LoginTests/testFailure'],
+        }).success,
+      ).toBe(true);
+      expect(schemaObj.safeParse({ preferXcodebuild: 'true' }).success).toBe(false);
+      expect(schemaObj.safeParse({ onlyTesting: [42] }).success).toBe(false);
       expect(schemaObj.safeParse({ testRunnerEnv: { FOO: 123 } }).success).toBe(false);
 
       const schemaKeys = Object.keys(schema).sort();
       expect(schemaKeys).toEqual(
-        ['extraArgs', 'progress', 'testProductsPath', 'testRunnerEnv', 'xctestrunPath'].sort(),
+        [
+          'configuration',
+          'derivedDataPath',
+          'extraArgs',
+          'onlyTesting',
+          'preferXcodebuild',
+          'progress',
+          'projectPath',
+          'scheme',
+          'simulatorId',
+          'simulatorName',
+          'skipTesting',
+          'testProductsPath',
+          'testRunnerEnv',
+          'useLatestOS',
+          'workspacePath',
+          'xctestrunPath',
+        ].sort(),
       );
     });
   });

diff --git a/src/mcp/tools/simulator/build_run_sim.ts b/src/mcp/tools/simulator/build_run_sim.ts
@@ -509,16 +509,8 @@ export function createBuildRunSimExecutor(
   };
 }
 
-const publicSchemaObject = baseSchemaObject.omit({
-  projectPath: true,
-  workspacePath: true,
+const publicSchemaObject = baseSchemaObject.partial({
   scheme: true,
-  configuration: true,
-  simulatorId: true,
-  simulatorName: true,
-  useLatestOS: true,
-  derivedDataPath: true,
-  preferXcodebuild: true,
 } as const);
 
 export async function build_run_simLogic(

diff --git a/src/mcp/tools/simulator/build_sim.ts b/src/mcp/tools/simulator/build_sim.ts
@@ -187,16 +187,8 @@ export async function prepareBuildSimExecution(
   };
 }
 
-const publicSchemaObject = baseSchemaObject.omit({
-  projectPath: true,
-  workspacePath: true,
+const publicSchemaObject = baseSchemaObject.partial({
   scheme: true,
-  configuration: true,
-  simulatorId: true,
-  simulatorName: true,
-  useLatestOS: true,
-  derivedDataPath: true,
-  preferXcodebuild: true,
 } as const);
 
 export function createBuildSimExecutor(

diff --git a/src/mcp/tools/simulator/test_sim.ts b/src/mcp/tools/simulator/test_sim.ts
@@ -79,6 +79,14 @@ const baseSchemaObject = z.object({
   configuration: z.string().optional().describe('Build configuration (Debug, Release, etc.)'),
   derivedDataPath: z.string().optional(),
   extraArgs: z.array(z.string()).optional(),
+  onlyTesting: z
+    .array(z.string())
+    .optional()
+    .describe('Test identifiers to include (for example, Target/Suite/testMethod)'),
+  skipTesting: z
+    .array(z.string())
+    .optional()
+    .describe('Test identifiers to exclude (for example, Target/Suite/testMethod)'),
   useLatestOS: z
     .boolean()
     .optional()
@@ -118,12 +126,26 @@ interface PreparedTestSimExecution {
   warningMessage?: string;
 }
 
+function resolveExtraArgs(params: TestSimulatorParams): string[] | undefined {
+  const selectorArgs = [
+    ...(params.onlyTesting ?? []).map((selector) => `-only-testing:${selector}`),
+    ...(params.skipTesting ?? []).map((selector) => `-skip-testing:${selector}`),
+  ];
+
+  if (!params.extraArgs && selectorArgs.length === 0) {
+    return undefined;
+  }
+
+  return [...(params.extraArgs ?? []), ...selectorArgs];
+}
+
 async function prepareTestSimExecution(
   params: TestSimulatorParams,
   executor: CommandExecutor,
   fileSystemExecutor: FileSystemExecutor,
 ): Promise<PreparedTestSimExecution> {
   const preparedTestSource = hasPreparedTestSource(params);
+  const extraArgs = resolveExtraArgs(params);
   const configuration = preparedTestSource ? undefined : params.configuration;
   const inferred = await inferPlatform(
     {
@@ -182,7 +204,7 @@ async function prepareTestSimExecution(
           workspacePath: params.workspacePath,
           scheme: params.scheme!,
           configuration,
-          extraArgs: params.extraArgs,
+          extraArgs,
           destinationName,
         },
         fileSystemExecutor,
@@ -264,7 +286,7 @@ export function createTestSimExecutor(
         simulatorName: params.simulatorName,
         configuration: resolved.configuration,
         derivedDataPath: params.derivedDataPath,
-        extraArgs: params.extraArgs,
+        extraArgs: resolveExtraArgs(params),
         useLatestOS: false,
         preferXcodebuild: params.preferXcodebuild ?? false,
         platform: resolved.platform,
@@ -294,29 +316,9 @@ export async function test_simLogic(
   setXcodebuildStructuredOutput(ctx, 'test-result', result, '3');
 }
 
-const publicSchemaObject = baseSchemaObject.omit({
-  projectPath: true,
-  workspacePath: true,
-  scheme: true,
-  simulatorId: true,
-  simulatorName: true,
-  configuration: true,
-  useLatestOS: true,
-  derivedDataPath: true,
-  preferXcodebuild: true,
-} as const);
+const publicSchemaObject = baseSchemaObject;
 
-const mcpPublicSchemaObject = mcpFullSchemaObject.omit({
-  projectPath: true,
-  workspacePath: true,
-  scheme: true,
-  simulatorId: true,
-  simulatorName: true,
-  configuration: true,
-  useLatestOS: true,
-  derivedDataPath: true,
-  preferXcodebuild: true,
-} as const);
+const mcpPublicSchemaObject = mcpFullSchemaObject;
 
 export const schema = getSessionAwareToolSchemaShape({
   sessionAware: publicSchemaObject,

diff --git a/src/smoke-tests/__tests__/e2e-mcp-sessions.test.ts b/src/smoke-tests/__tests__/e2e-mcp-sessions.test.ts
@@ -145,6 +145,71 @@ describe('MCP Session Management (e2e)', () => {
     expect(buildCommand).toContain('SessionScheme');
   });
 
+  it('explicit simulator build arguments override session defaults', async () => {
+    await harness.client.callTool({
+      name: 'session_set_defaults',
+      arguments: {
+        scheme: 'DefaultScheme',
+        projectPath: '/default/project.xcodeproj',
+        simulatorId: 'AAAAAAAA-1111-2222-3333-444444444444',
+        configuration: 'Debug',
+      },
+    });
+
+    harness.resetCapturedCommands();
+    const result = await harness.client.callTool({
+      name: 'build_sim',
+      arguments: {
+        scheme: 'ExplicitScheme',
+        projectPath: '/explicit/project.xcodeproj',
+        simulatorName: 'iPhone 17 Pro',
+        configuration: 'Release',
+      },
+    });
+
+    expectContent(result);
+    const commandStrs = harness.capturedCommands.map((command) => command.command.join(' '));
+    const buildCommand = commandStrs.find(
+      (command) => command.includes('xcodebuild') && command.includes('-scheme'),
+    );
+    expect(buildCommand).toBeDefined();
+    expect(buildCommand).toContain('ExplicitScheme');
+    expect(buildCommand).toContain('/explicit/project.xcodeproj');
+    expect(buildCommand).toContain('iPhone 17 Pro');
+    expect(buildCommand).toContain('Release');
+    expect(buildCommand).not.toContain('DefaultScheme');
+    expect(buildCommand).not.toContain('/default/project.xcodeproj');
+  });
+
+  it('accepts typed simulator test selectors', async () => {
+    await harness.client.callTool({
+      name: 'session_set_defaults',
+      arguments: {
+        scheme: 'SessionScheme',
+        projectPath: '/session/project.xcodeproj',
+        simulatorId: 'AAAAAAAA-1111-2222-3333-444444444444',
+      },
+    });
+
+    harness.resetCapturedCommands();
+    const result = await harness.client.callTool({
+      name: 'test_sim',
+      arguments: {
+        onlyTesting: ['MyTests/LoginTests/testSuccess'],
+        skipTesting: ['MyTests/LoginTests/testFailure'],
+      },
+    });
+
+    expectContent(result);
+    const commandStrs = harness.capturedCommands.map((command) => command.command.join(' '));
+    const testCommand = commandStrs.find(
+      (command) => command.includes('xcodebuild') && command.includes(' test'),
+    );
+    expect(testCommand).toBeDefined();
+    expect(testCommand).toContain('-only-testing:MyTests/LoginTests/testSuccess');
+    expect(testCommand).toContain('-skip-testing:MyTests/LoginTests/testFailure');
+  });
+
   it('updating session defaults changes subsequent tool behavior', async () => {
     // Set initial defaults
     await harness.client.callTool({

diff --git a/src/snapshot-tests/__fixtures__/mcp-contracts/session-defaults-disabled/test_sim.json b/src/snapshot-tests/__fixtures__/mcp-contracts/session-defaults-disabled/test_sim.json
@@ -11,12 +11,22 @@
         "items": {"type":"string"},
         "type": "array"
       },
+      "onlyTesting": {
+        "description": "Test identifiers to include (for example, Target/Suite/testMethod)",
+        "items": {"type":"string"},
+        "type": "array"
+      },
       "preferXcodebuild": {"type":"boolean"},
       "progress": {"description":"Show detailed test progress output (MCP defaults to true, CLI defaults to false)","type":"boolean"},
       "projectPath": {"description":"Path to .xcodeproj file. Provide EITHER this OR workspacePath, not both","type":"string"},
       "scheme": {"description":"The scheme to use in source mode","type":"string"},
       "simulatorId": {"description":"UUID of the simulator (from list_sims). Provide EITHER this OR simulatorName, not both","type":"string"},
       "simulatorName": {"description":"Name of the simulator (e.g., 'iPhone 17'). Provide EITHER this OR simulatorId, not both","type":"string"},
+      "skipTesting": {
+        "description": "Test identifiers to exclude (for example, Target/Suite/testMethod)",
+        "items": {"type":"string"},
+        "type": "array"
+      },
       "testProductsPath": {"description":"Path to a prepared .xctestproducts package. Cannot be combined with source inputs","type":"string"},
       "testRunnerEnv": {
         "description": "Environment variables to pass to the test runner (TEST_RUNNER_ prefix added automatically)",