diff --git a/packages/core/src/utils/compatibility.test.ts b/packages/core/src/utils/compatibility.test.ts
index dfa9ffb14f..45c81bc9a1 100644
--- a/packages/core/src/utils/compatibility.test.ts
+++ b/packages/core/src/utils/compatibility.test.ts
@@ -94,6 +94,8 @@ describe('compatibility', () => {
       },
       { env: {}, expected: false, desc: 'no env vars set' },
     ])('should return $expected when $desc', ({ env, expected }) => {
+      vi.stubEnv('TERMINAL_EMULATOR', '');
+      vi.stubEnv('JETBRAINS_IDE', '');
       for (const [key, value] of Object.entries(env)) {
         vi.stubEnv(key, value);
       }
@@ -140,6 +142,7 @@ describe('compatibility', () => {
 
     it('should return false when TERM=xterm-256color', () => {
       vi.stubEnv('TERM', 'xterm-256color');
+      vi.stubEnv('COLORTERM', '');
       expect(isLowColorTmux()).toBe(false);
     });
   });
@@ -230,6 +233,8 @@ describe('compatibility', () => {
       process.stdout.getColorDepth = vi.fn().mockReturnValue(depth);
       if (term !== undefined) {
         vi.stubEnv('TERM', term);
+      } else {
+        vi.stubEnv('TERM', '');
       }
       expect(supports256Colors()).toBe(expected);
     });
@@ -278,6 +283,14 @@ describe('compatibility', () => {
 
   describe('getCompatibilityWarnings', () => {
     beforeEach(() => {
+      // Clear out potential local environment variables that might trigger warnings
+      vi.stubEnv('TERMINAL_EMULATOR', '');
+      vi.stubEnv('JETBRAINS_IDE', '');
+      vi.stubEnv('TMUX', '');
+      vi.stubEnv('STY', '');
+      vi.stubEnv('TERM', 'xterm-256color'); // Prevent dumb terminal warning
+      vi.stubEnv('TERM_PROGRAM', '');
+
       // Default to supporting true color to keep existing tests simple
       vi.stubEnv('COLORTERM', 'truecolor');
       process.stdout.getColorDepth = vi.fn().mockReturnValue(24);
diff --git a/packages/core/src/utils/compatibility.ts b/packages/core/src/utils/compatibility.ts
index 0b902c064d..d19b07dc75 100644
--- a/packages/core/src/utils/compatibility.ts
+++ b/packages/core/src/utils/compatibility.ts
@@ -160,7 +160,7 @@ export function getCompatibilityWarnings(options?: {
     warnings.push({
       id: 'jetbrains-terminal',
       message:
-        '⚠️  JetBrains terminal detected — alternate buffer mode may cause scroll wheel issues and rendering artifacts. If you experience problems, disable it in /settings → "Use Alternate Screen Buffer".',
+        'Warning: JetBrains terminal detected — alternate buffer mode may cause scroll wheel issues and rendering artifacts. If you experience problems, disable it in /settings → "Use Alternate Screen Buffer".',
       priority: WarningPriority.High,
     });
   }
@@ -169,7 +169,7 @@ export function getCompatibilityWarnings(options?: {
     warnings.push({
       id: 'tmux-alternate-buffer',
       message:
-        '⚠️  tmux detected — alternate buffer mode may cause unexpected scrollback loss and flickering. If you experience issues, disable it in /settings → "Use Alternate Screen Buffer".\n    Tip: Use Ctrl-b [ to access tmux copy mode for scrolling history.',
+        'Warning: tmux detected — alternate buffer mode may cause unexpected scrollback loss and flickering. If you experience issues, disable it in /settings → "Use Alternate Screen Buffer".\n    Tip: Use Ctrl-b [ to access tmux copy mode for scrolling history.',
       priority: WarningPriority.High,
     });
   }
@@ -178,7 +178,7 @@ export function getCompatibilityWarnings(options?: {
     warnings.push({
       id: 'low-color-tmux',
       message:
-        '⚠️  Limited color support detected (TERM=screen). Some visual elements may not render correctly. For better color support in tmux, add to ~/.tmux.conf:\n      set -g default-terminal "tmux-256color"\n      set -ga terminal-overrides ",*256col*:Tc"',
+        'Warning: Limited color support detected (TERM=screen). Some visual elements may not render correctly. For better color support in tmux, add to ~/.tmux.conf:\n      set -g default-terminal "tmux-256color"\n      set -ga terminal-overrides ",*256col*:Tc"',
       priority: WarningPriority.High,
     });
   }
@@ -187,7 +187,7 @@ export function getCompatibilityWarnings(options?: {
     warnings.push({
       id: 'gnu-screen',
       message:
-        '⚠️  GNU screen detected. Some keyboard shortcuts and visual features may behave unexpectedly. For the best experience, consider using tmux or running Gemini CLI directly in your terminal.',
+        'Warning: GNU screen detected. Some keyboard shortcuts and visual features may behave unexpectedly. For the best experience, consider using tmux or running Gemini CLI directly in your terminal.',
       priority: WarningPriority.Low,
     });
   }
@@ -196,7 +196,7 @@ export function getCompatibilityWarnings(options?: {
     warnings.push({
       id: 'dumb-terminal',
       message:
-        '⚠️  Basic terminal detected (TERM=dumb). Visual rendering will be limited. For the best experience, use a terminal emulator with truecolor support.',
+        'Warning: Basic terminal detected (TERM=dumb). Visual rendering will be limited. For the best experience, use a terminal emulator with truecolor support.',
       priority: WarningPriority.High,
     });
   }