From b08f9821d8f61ea8f66e974d7ce95591c603b543 Mon Sep 17 00:00:00 2001
From: Spencer <spencertang@google.com>
Date: Thu, 12 Mar 2026 21:37:17 +0000
Subject: [PATCH] fix(core): improve terminal heuristics

---
 packages/core/src/utils/compatibility.test.ts | 58 +++++--------------
 packages/core/src/utils/compatibility.ts      | 22 +------
 2 files changed, 15 insertions(+), 65 deletions(-)

diff --git a/packages/core/src/utils/compatibility.test.ts b/packages/core/src/utils/compatibility.test.ts
index 45c81bc9a1..372401537f 100644
--- a/packages/core/src/utils/compatibility.test.ts
+++ b/packages/core/src/utils/compatibility.test.ts
@@ -13,7 +13,6 @@ import {
   isGnuScreen,
   isLowColorTmux,
   isDumbTerminal,
-  getTerminalNameFromEnv,
   supports256Colors,
   supportsTrueColor,
   getCompatibilityWarnings,
@@ -128,21 +127,31 @@ describe('compatibility', () => {
   });
 
   describe('isLowColorTmux', () => {
-    it('should return true when TERM=screen and COLORTERM is not set', () => {
+    it('should return true when TERM=screen, COLORTERM is not set, and TMUX is set', () => {
       vi.stubEnv('TERM', 'screen');
       vi.stubEnv('COLORTERM', '');
+      vi.stubEnv('TMUX', 'dummy');
       expect(isLowColorTmux()).toBe(true);
     });
 
-    it('should return false when TERM=screen and COLORTERM is set', () => {
+    it('should return false when TERM=screen, COLORTERM is set, and TMUX is set', () => {
       vi.stubEnv('TERM', 'screen');
       vi.stubEnv('COLORTERM', 'truecolor');
+      vi.stubEnv('TMUX', 'dummy');
       expect(isLowColorTmux()).toBe(false);
     });
 
-    it('should return false when TERM=xterm-256color', () => {
+    it('should return false when TERM=xterm-256color and TMUX is set', () => {
       vi.stubEnv('TERM', 'xterm-256color');
       vi.stubEnv('COLORTERM', '');
+      vi.stubEnv('TMUX', 'dummy');
+      expect(isLowColorTmux()).toBe(false);
+    });
+
+    it('should return false when TMUX is not set', () => {
+      vi.stubEnv('TERM', 'screen');
+      vi.stubEnv('COLORTERM', '');
+      vi.stubEnv('TMUX', '');
       expect(isLowColorTmux()).toBe(false);
     });
   });
@@ -164,46 +173,6 @@ describe('compatibility', () => {
     });
   });
 
-  describe('getTerminalNameFromEnv', () => {
-    it('should prioritize TERM_PROGRAM', () => {
-      vi.stubEnv('TERM_PROGRAM', 'iTerm.app');
-      expect(getTerminalNameFromEnv()).toBe('iTerm.app');
-    });
-
-    it('should use JETBRAINS_IDE if TERM_PROGRAM is missing', () => {
-      vi.stubEnv('TERM_PROGRAM', '');
-      vi.stubEnv('TERMINAL_EMULATOR', 'JetBrains-JediTerm');
-      vi.stubEnv('JETBRAINS_IDE', 'PyCharm');
-      expect(getTerminalNameFromEnv()).toBe('PyCharm');
-    });
-
-    it('should use TMUX if other vars are missing', () => {
-      vi.stubEnv('TERM_PROGRAM', '');
-      vi.stubEnv('TERMINAL_EMULATOR', '');
-      vi.stubEnv('JETBRAINS_IDE', '');
-      vi.stubEnv('TMUX', 'some-socket');
-      expect(getTerminalNameFromEnv()).toBe('tmux');
-    });
-
-    it('should use STY if other vars are missing', () => {
-      vi.stubEnv('TERM_PROGRAM', '');
-      vi.stubEnv('TERMINAL_EMULATOR', '');
-      vi.stubEnv('JETBRAINS_IDE', '');
-      vi.stubEnv('TMUX', '');
-      vi.stubEnv('STY', 'some-session');
-      expect(getTerminalNameFromEnv()).toBe('GNU screen');
-    });
-
-    it('should return Unknown if no vars are set', () => {
-      vi.stubEnv('TERM_PROGRAM', '');
-      vi.stubEnv('TERMINAL_EMULATOR', '');
-      vi.stubEnv('JETBRAINS_IDE', '');
-      vi.stubEnv('TMUX', '');
-      vi.stubEnv('STY', '');
-      expect(getTerminalNameFromEnv()).toBe('Unknown');
-    });
-  });
-
   describe('supports256Colors', () => {
     it.each<{
       depth: number;
@@ -340,6 +309,7 @@ describe('compatibility', () => {
     it('should return low-color tmux warning when detected', () => {
       vi.stubEnv('TERM', 'screen');
       vi.stubEnv('COLORTERM', '');
+      vi.stubEnv('TMUX', 'dummy');
 
       const warnings = getCompatibilityWarnings();
       expect(warnings).toContainEqual(
diff --git a/packages/core/src/utils/compatibility.ts b/packages/core/src/utils/compatibility.ts
index d19b07dc75..aacabd3546 100644
--- a/packages/core/src/utils/compatibility.ts
+++ b/packages/core/src/utils/compatibility.ts
@@ -52,7 +52,7 @@ export function isGnuScreen(): boolean {
  */
 export function isLowColorTmux(): boolean {
   const term = process.env['TERM'] || '';
-  return term.startsWith('screen') && !process.env['COLORTERM'];
+  return isTmux() && term.startsWith('screen') && !process.env['COLORTERM'];
 }
 
 /**
@@ -63,26 +63,6 @@ export function isDumbTerminal(): boolean {
   return term === 'dumb' || term === 'vt100';
 }
 
-/**
- * Detects the terminal name from environment variables.
- */
-export function getTerminalNameFromEnv(): string {
-  const env = process.env;
-  if (env['TERM_PROGRAM'] && env['TERM_PROGRAM'] !== 'Unknown') {
-    return env['TERM_PROGRAM'];
-  }
-  if (isJetBrainsTerminal()) {
-    return env['JETBRAINS_IDE'] || 'JetBrains IDE';
-  }
-  if (isTmux()) {
-    return 'tmux';
-  }
-  if (isGnuScreen()) {
-    return 'GNU screen';
-  }
-  return env['TERM_PROGRAM'] || 'Unknown';
-}
-
 /**
  * Detects if the current terminal is the default Apple Terminal.app.
  */