fix(core): improve headless mode detection for flags and query args (#18855)

packages/core/src/utils/headless.test.ts

@@ -99,16 +99,50 @@ describe('isHeadlessMode', () => {
     expect(isHeadlessMode({ prompt: true })).toBe(true);
   });
 
-  it('should return false if query is provided but it is still a TTY', () => {
-    // Note: per current logic, query alone doesn't force headless if TTY
-    // This matches the existing behavior in packages/cli/src/config/config.ts
-    expect(isHeadlessMode({ query: 'test query' })).toBe(false);
+  it('should return true if query is provided', () => {
+    expect(isHeadlessMode({ query: 'test query' })).toBe(true);
+  });
+
+  it('should return true if -p or --prompt is in process.argv as a fallback', () => {
+    const originalArgv = process.argv;
+    process.argv = ['node', 'index.js', '-p', 'hello'];
+    try {
+      expect(isHeadlessMode()).toBe(true);
+    } finally {
+      process.argv = originalArgv;
+    }
+
+    process.argv = ['node', 'index.js', '--prompt', 'hello'];
+    try {
+      expect(isHeadlessMode()).toBe(true);
+    } finally {
+      process.argv = originalArgv;
+    }
+  });
+
+  it('should return true if -y or --yolo is in process.argv as a fallback', () => {
+    const originalArgv = process.argv;
+    process.argv = ['node', 'index.js', '-y'];
+    try {
+      expect(isHeadlessMode()).toBe(true);
+    } finally {
+      process.argv = originalArgv;
+    }
+
+    process.argv = ['node', 'index.js', '--yolo'];
+    try {
+      expect(isHeadlessMode()).toBe(true);
+    } finally {
+      process.argv = originalArgv;
+    }
   });
 
   it('should handle undefined process.stdout gracefully', () => {
     const originalStdout = process.stdout;
-    // @ts-expect-error - testing edge case
-    delete process.stdout;
+    Object.defineProperty(process, 'stdout', {
+      value: undefined,
+      configurable: true,
+    });
 
     try {
       expect(isHeadlessMode()).toBe(false);
@@ -122,8 +156,10 @@ describe('isHeadlessMode', () => {
 
   it('should handle undefined process.stdin gracefully', () => {
     const originalStdin = process.stdin;
-    // @ts-expect-error - testing edge case
-    delete process.stdin;
+    Object.defineProperty(process, 'stdin', {
+      value: undefined,
+      configurable: true,
+    });
 
     try {
       expect(isHeadlessMode()).toBe(false);