fix(tui): harden terminal dimming and multiplexer copy (#14906)

- disable ANSI dim on VTE terminals by default so dark-background reasoning and accents stay readable
- suppress local multiplexer OSC52 echo while preserving remote passthrough and add regression coverage

ui-tui/packages/hermes-ink/src/ink/components/Text.test.ts

@@ -0,0 +1,18 @@
+import { describe, expect, it } from 'vitest'
+
+import { shouldUseAnsiDim } from './Text.js'
+
+describe('shouldUseAnsiDim', () => {
+  it('disables ANSI dim on VTE terminals by default', () => {
+    expect(shouldUseAnsiDim({ VTE_VERSION: '7603' } as NodeJS.ProcessEnv)).toBe(false)
+  })
+
+  it('keeps ANSI dim enabled elsewhere by default', () => {
+    expect(shouldUseAnsiDim({ TERM: 'xterm-256color' } as NodeJS.ProcessEnv)).toBe(true)
+  })
+
+  it('honors explicit env override', () => {
+    expect(shouldUseAnsiDim({ HERMES_TUI_DIM: '1', VTE_VERSION: '7603' } as NodeJS.ProcessEnv)).toBe(true)
+    expect(shouldUseAnsiDim({ HERMES_TUI_DIM: '0' } as NodeJS.ProcessEnv)).toBe(false)
+  })
+})

ui-tui/packages/hermes-ink/src/ink/components/Text.tsx

@@ -3,6 +3,9 @@ import React from 'react'
 import { c as _c } from 'react/compiler-runtime'
 
 import type { Color, Styles } from '../styles.js'
+
+const ENV_ON_RE = /^(?:1|true|yes|on)$/i
+const ENV_OFF_RE = /^(?:0|false|no|off)$/i
 type BaseProps = {
   /**
    * Change text color. Accepts a raw color value (rgb, hex, ansi).
@@ -62,6 +65,20 @@ type WeightProps =
     }
 export type Props = BaseProps & WeightProps
 
+export function shouldUseAnsiDim(env: NodeJS.ProcessEnv = process.env): boolean {
+  const override = (env.HERMES_TUI_DIM ?? '').trim()
+
+  if (ENV_ON_RE.test(override)) {
+    return true
+  }
+
+  if (ENV_OFF_RE.test(override)) {
+    return false
+  }
+
+  return !env.VTE_VERSION
+}
+
 const memoizedStylesForWrap: Record<NonNullable<Styles['textWrap']>, Styles> = {
   wrap: {
     flexGrow: 0,
@@ -143,6 +160,7 @@ export default function Text(t0: Props) {
   const strikethrough = t3 === undefined ? false : t3
   const inverse = t4 === undefined ? false : t4
   const wrap = t5 === undefined ? 'wrap' : t5
+  const effectiveDim = dim && shouldUseAnsiDim()
 
   if (children === undefined || children === null) {
     return null
@@ -174,11 +192,11 @@ export default function Text(t0: Props) {
 
   let t8
 
-  if ($[4] !== dim) {
-    t8 = dim && {
-      dim
+  if ($[4] !== effectiveDim) {
+    t8 = effectiveDim && {
+      dim: effectiveDim
     }
-    $[4] = dim
+    $[4] = effectiveDim
     $[5] = t8
   } else {
     t8 = $[5]