Desktop UI polish: link chips, sidebar arc, tab strip rule

apps/desktop/src/app/chat/sidebar/session-row.tsx

@@ -163,7 +163,9 @@ export function SidebarSessionRow({
         style={style}
         {...rest}
       >
-        {sessionShowsRunningArc({ isWorking, needsInput }) && <span aria-hidden="true" className="arc-border" />}
+        {sessionShowsRunningArc({ isWorking, needsInput }) && (
+          <span aria-hidden="true" className="arc-border arc-row" />
+        )}
         <SidebarRowBody
           className={cn('z-0 group-hover:pr-12', branchStem && 'pl-3.5')}
           // Middle-click = open in a new tab (browser muscle memory). Swallow

apps/desktop/src/components/assistant-ui/directive-text.tsx

@@ -510,7 +510,7 @@ export const SessionRefLink: FC<{
 
   return (
     <a
-      className="font-semibold text-foreground underline underline-offset-4 decoration-current/20 wrap-anywhere"
+      className="link-chip font-semibold wrap-anywhere"
       href="#"
       onClick={event => {
         event.preventDefault()

apps/desktop/src/components/assistant-ui/markdown-text.tsx

@@ -100,7 +100,7 @@ function OpenMediaButton({ kind, path }: { kind: 'audio' | 'video'; path: string
   return (
     <span className="block">
       <button
-        className="mt-2 bg-transparent text-xs font-medium text-muted-foreground underline underline-offset-4 decoration-current/20 hover:text-foreground"
+        className="mt-2 link-chip bg-transparent text-xs font-medium text-muted-foreground hover:text-foreground"
         onClick={open}
         type="button"
       >
@@ -196,7 +196,7 @@ function MediaAttachment({ path }: { path: string }) {
   return (
     <span className="wrap-anywhere">
       <a
-        className="font-semibold text-foreground underline underline-offset-4 decoration-current/20 wrap-anywhere"
+        className="link-chip font-semibold wrap-anywhere"
         href="#"
         onClick={event => {
           event.preventDefault()
@@ -246,10 +246,7 @@ function MarkdownLink({ children, className, href, ...props }: ComponentProps<'a
   if (!target || !/^https?:\/\//i.test(target)) {
     return (
       <a
-        className={cn(
-          'font-semibold text-foreground underline underline-offset-4 decoration-current/20 wrap-anywhere',
-          className
-        )}
+        className={cn('link-chip font-semibold wrap-anywhere', className)}
         href={href}
         rel="noopener noreferrer"
         target="_blank"
@@ -324,7 +321,7 @@ function MarkdownImage({ className, src, alt, ...props }: ComponentProps<'img'>)
       <span className="my-2 block text-sm text-muted-foreground">
         Couldn&apos;t load {name}.{' '}
         <button
-          className="bg-transparent font-medium text-foreground underline underline-offset-4 decoration-current/20 hover:text-foreground"
+          className="link-chip bg-transparent font-medium text-foreground hover:text-foreground"
           onClick={open}
           type="button"
         >

apps/desktop/src/components/assistant-ui/tool/fallback.tsx

@@ -26,6 +26,7 @@ import { ZoomableImage } from '@/components/chat/zoomable-image'
 import { Button } from '@/components/ui/button'
 import { Codicon } from '@/components/ui/codicon'
 import { CopyButton } from '@/components/ui/copy-button'
+import { DisclosureCaret } from '@/components/ui/disclosure-caret'
 import { FadeText } from '@/components/ui/fade-text'
 import { FileTypeIcon } from '@/components/ui/file-type-icon'
 import { GlyphSpinner } from '@/components/ui/glyph-spinner'
@@ -96,6 +97,44 @@ const TOOL_EXPANDED_SHELL_CLASS = 'rounded-[0.3125rem] border border-(--ui-strok
 
 const TOOL_SECTION_PRE_CLASS = cn(TOOL_SECTION_SURFACE_CLASS, 'font-mono text-[0.7rem] leading-relaxed')
 
+// Raw args/result dump — reference material, so a notch smaller than a body.
+const TOOL_PAYLOAD_PRE_CLASS = cn(TOOL_SECTION_SURFACE_CLASS, 'font-mono text-[0.65rem] leading-relaxed')
+
+/**
+ * Technical-mode raw payload, behind a chevron disclosure.
+ *
+ * Collapsed by default — in technical mode every tool row carries one, and
+ * expanding them all buries the transcript. Uses `DisclosureCaret` rather than
+ * a native `<details>`, whose marker is a browser-drawn triangle matching
+ * nothing else here.
+ */
+function ToolPayloadDisclosure({ args, result }: { args: unknown; result: unknown }) {
+  const [open, setOpen] = useState(false)
+
+  return (
+    // `py-0.5` tops up the parent's `p-1.5` to an even block on both edges.
+    <div className="max-w-full py-0.5">
+      <button
+        aria-expanded={open}
+        className={cn(
+          TOOL_SECTION_LABEL_CLASS,
+          'mb-0 flex items-center gap-1 bg-transparent transition-colors hover:text-(--ui-text-secondary)'
+        )}
+        onClick={() => setOpen(value => !value)}
+        type="button"
+      >
+        <DisclosureCaret className="text-(--ui-text-tertiary)" open={open} size="0.625rem" />
+        Tool payload
+      </button>
+      {open && (
+        <pre className={cn(TOOL_PAYLOAD_PRE_CLASS, 'mt-1 whitespace-pre-wrap wrap-anywhere')}>
+          {technicalTrace(args, result)}
+        </pre>
+      )}
+    </div>
+  )
+}
+
 interface ToolStatusCopy {
   statusDone: string
   statusError: string
@@ -616,19 +655,7 @@ function ToolEntry({ part }: ToolEntryProps) {
                 )}
               </div>
             ))}
-          {toolViewMode === 'technical' && !(isFileEdit && view.inlineDiff) && (
-            <pre className={cn(TOOL_SECTION_PRE_CLASS, 'whitespace-pre-wrap wrap-anywhere')}>
-              {technicalTrace(part.args, part.result)}
-            </pre>
-          )}
-          {toolViewMode === 'technical' && isFileEdit && view.inlineDiff && (
-            <details className="max-w-full">
-              <summary className={cn(TOOL_SECTION_LABEL_CLASS, 'mb-0 cursor-pointer')}>Tool payload</summary>
-              <pre className={cn(TOOL_SECTION_PRE_CLASS, 'mt-1 whitespace-pre-wrap wrap-anywhere')}>
-                {technicalTrace(part.args, part.result)}
-              </pre>
-            </details>
-          )}
+          {toolViewMode === 'technical' && <ToolPayloadDisclosure args={part.args} result={part.result} />}
         </div>
       )}
     </div>

apps/desktop/src/components/chat/compact-markdown.tsx

@@ -2,7 +2,7 @@ import type { ComponentProps, ElementType, FC } from 'react'
 import { memo } from 'react'
 import { Streamdown } from 'streamdown'
 
-import { ExternalLink, ExternalLinkIcon } from '@/lib/external-link'
+import { ExternalLink } from '@/lib/external-link'
 import { cn } from '@/lib/utils'
 
 // Compact markdown renderer for tool detail bodies. Same Streamdown pipeline
@@ -42,20 +42,15 @@ function tagged<T extends keyof typeof TAG_CLASSES>(Tag: T) {
 function MarkdownAnchor({ children, className, href, ...rest }: ComponentProps<'a'>) {
   if (!href || !/^https?:\/\//i.test(href)) {
     return (
-      <a
-        className={cn('font-medium underline underline-offset-4 decoration-current/20', className)}
-        href={href}
-        {...rest}
-      >
+      <a className={cn('link-chip font-medium', className)} href={href} {...rest}>
         {children}
       </a>
     )
   }
 
   return (
-    <ExternalLink className={cn('decoration-current/20', className)} href={href} showExternalIcon={false}>
+    <ExternalLink className={className} href={href}>
       {children}
-      <ExternalLinkIcon />
     </ExternalLink>
   )
 }

apps/desktop/src/components/chat/generated-image-result.tsx

@@ -96,7 +96,7 @@ export const GeneratedImage: FC<{ aspectRatio?: string; result?: unknown }> = ({
   if (failed && image) {
     return (
       <a
-        className="mt-2 inline-block font-semibold text-foreground underline underline-offset-4 decoration-current/20 wrap-anywhere"
+        className="mt-2 link-chip inline-block font-semibold wrap-anywhere"
         href="#"
         onClick={event => {
           event.preventDefault()

apps/desktop/src/components/ui/pane-tab.tsx

@@ -12,17 +12,23 @@ export const PANE_TAB_STRIP_LINE_RIGHT = 'shadow-[inset_-1px_0_0_var(--ui-stroke
 const TAB =
   'group/tab relative flex shrink-0 items-center border-transparent bg-(--tab-bg) text-[0.6875rem] font-medium [-webkit-app-region:no-drag]'
 
-const TAB_HORIZONTAL = 'h-full min-w-0 max-w-48 border-b not-first:border-l not-first:border-l-(--ui-stroke-quaternary)'
+// Stop 1px short: the strip's rule is an INSET shadow painted in the
+// container's own last pixel row, so a full-height tab covers it and reads as
+// overhanging the bar. The container owns the line; nothing redraws it.
+const TAB_HORIZONTAL =
+  'h-[calc(100%-1px)] min-w-0 max-w-48 not-first:border-l not-first:border-l-(--ui-stroke-quaternary)'
 
 const TAB_VERTICAL =
   'w-full max-h-48 justify-center not-first:border-t not-first:border-t-(--ui-stroke-quaternary) [writing-mode:vertical-rl]'
 
-const TAB_ACTIVE = 'text-foreground [--tab-bg:var(--pane-tab-active-bg,var(--ui-editor-surface-background))]'
+// Full height, so the active tab alone covers that row and cuts the rule.
+const TAB_ACTIVE =
+  'h-full text-foreground [--tab-bg:var(--pane-tab-active-bg,var(--ui-editor-surface-background))]'
 
-// Inactive = gutter. Hover = 4% translucent wash (VS Code/GitHub alpha hover),
-// not an opaque recolor — and never touch borders.
+// Inactive = gutter. Hover DARKENS: active is the lighter content surface, so a
+// lightening wash made the two nearly indistinguishable.
 const TAB_IDLE =
-  'text-(--ui-text-tertiary) [--tab-bg:var(--pane-tab-strip-bg,var(--theme-card-seed))] hover:shadow-[inset_0_0_0_100vmax_color-mix(in_srgb,var(--ui-base)_4%,transparent)] hover:text-(--ui-text-secondary)'
+  'text-(--ui-text-tertiary) [--tab-bg:var(--pane-tab-strip-bg,var(--theme-card-seed))] hover:shadow-[inset_0_0_0_100vmax_color-mix(in_srgb,#000_var(--ui-tab-hover-darken),transparent)] hover:text-(--ui-text-secondary)'
 
 interface PaneTabProps extends React.ComponentProps<'div'> {
   active?: boolean
@@ -66,17 +72,17 @@ export const PaneTab = React.forwardRef<HTMLDivElement, PaneTabProps>(function P
   },
   ref
 ) {
-  // Content-facing edge: horizontal cuts the bottom strip line; vertical cuts
-  // the side that faces the editor (left rail → right edge, right rail → left).
-  const edge = vertical ? (side === 'right' ? 'border-l' : 'border-r') : 'border-b'
+  // Vertical rails only. Horizontal tabs draw no bottom border — the strip owns
+  // that rule, and a per-tab border stacked a second translucent line over it.
+  const edge = vertical ? (side === 'right' ? 'border-l' : 'border-r') : undefined
 
   return (
     <div
       className={cn(
         TAB,
         vertical ? TAB_VERTICAL : TAB_HORIZONTAL,
         edge,
-        active ? TAB_ACTIVE : cn(TAB_IDLE, `${edge}-(--ui-stroke-tertiary)`),
+        active ? TAB_ACTIVE : cn(TAB_IDLE, edge && `${edge}-(--ui-stroke-tertiary)`),
         className
       )}
       data-active={active}

apps/desktop/src/lib/external-link.test.tsx

@@ -112,11 +112,24 @@ describe('external link helpers', () => {
     expect(openExternal).toHaveBeenCalledWith('https://example.com/path/to/resource')
   })
 
-  it('shows a trailing external-link icon', () => {
+  it('hides the trailing external-link icon by default', () => {
     installDesktopBridge()
 
     render(<ExternalLink href="https://example.com/path/to/resource">Example link</ExternalLink>)
 
+    const link = screen.getByRole('link', { name: 'Example link' })
+    expect(link.querySelector('svg')).toBeNull()
+  })
+
+  it('shows a trailing external-link icon when opted in', () => {
+    installDesktopBridge()
+
+    render(
+      <ExternalLink href="https://example.com/path/to/resource" showExternalIcon>
+        Example link
+      </ExternalLink>,
+    )
+
     const link = screen.getByRole('link', { name: 'Example link' })
     expect(link.querySelector('svg')).toBeTruthy()
   })

apps/desktop/src/lib/external-link.tsx

@@ -215,14 +215,14 @@ export function ExternalLink({
   className,
   href,
   onClick,
-  showExternalIcon = true,
+  showExternalIcon = false,
   ...rest
 }: ExternalLinkProps) {
   const target = normalizeExternalUrl(href)
 
   return (
     <a
-      className={cn('font-semibold text-foreground underline underline-offset-4 decoration-current/20', className)}
+      className={cn('link-chip font-semibold', className)}
       href={target}
       onClick={event => {
         event.stopPropagation()

apps/desktop/src/styles.css

@@ -317,6 +317,10 @@
        :root.dark bumps the alpha since a dark card swallows shadow. Removed on
        focus (the focus border carries the state). */
     --dt-input-inset: inset 0 1px 1px color-mix(in srgb, #000 10%, transparent);
+    /* Hovered inactive tab: deepen it AWAY from the lighter active surface, so
+       hover can never be mistaken for selected. Dark mode needs more — black
+       over a dark gutter shows less. */
+    --ui-tab-hover-darken: 2.5%;
     --dt-ring: var(--ui-stroke-primary);
     --dt-midground: var(--theme-midground);
     --dt-composer-ring: var(--ui-base);
@@ -446,6 +450,7 @@
     --backdrop-invert-mul: 0;
     /* Dark mode: a dark card needs a stronger black inset to show the recess. */
     --dt-input-inset: inset 0 1px 1px color-mix(in srgb, #000 38%, transparent);
+    --ui-tab-hover-darken: 6%;
     /* Dark needs a lighter resting border than light mode. */
     --dt-input-border: 4%;
 
@@ -514,6 +519,32 @@
   background: repeating-conic-gradient(currentColor 0% 25%, transparent 0% 50%) 0 0 / 0.125rem 0.125rem;
 }
 
+/* Inline content links: a small tinted chip instead of an underline. Tint is
+   currentColor-relative (the old `decoration-current/20` idiom), so text and
+   fill share a hue on every theme from one `color` declaration. */
+.link-chip {
+  --link-chip-tint: 8%;
+
+  /* `ch`/`em` so the chip tracks the text at any size. Block padding is
+     asymmetric because an inline box's content area is ascent+descent — equal
+     padding paints the glyphs high. Keep it small: `padding-block` doesn't grow
+     the line box, so an over-padded chip creeps into the line above. */
+  padding: 0.05ch 0.5ch 0.2ch;
+  border-radius: 0.25rem;
+  color: var(--dt-primary);
+  background: color-mix(in srgb, currentColor var(--link-chip-tint), transparent);
+  /* Explicit: the base layer underlines every `a` (see the :where(a, …) reset). */
+  text-decoration: none;
+  /* A wrapped link gets a chip per line fragment, not one ragged box. */
+  -webkit-box-decoration-break: clone;
+  box-decoration-break: clone;
+  transition: background-color 0.12s ease;
+}
+
+.link-chip:hover {
+  --link-chip-tint: 15%;
+}
+
 /* Hover-reveal suppression — the shared, declarative escape hatch.
    A collapsed pane slides in when the pointer dwells on its thin edge trigger.
    Controls that sit over that edge gutter would drag the panel in by accident.
@@ -610,14 +641,19 @@
   --arc-c2: var(--dt-background);
   --arc-angle: 160deg;
   --arc-width: 0.078125rem;
-  --arc-inset: -0.125rem;
+  /* How far the ring stands off its host, per side. */
+  --arc-standoff: 0.125rem;
+  /* An outset ring is only concentric when its radius grows by the standoff
+     (r = r_host + gap); `border-radius: inherit` leaves the corner pinched.
+     Defaults to the shared `rounded-md`; a host on another radius sets it. */
+  --arc-radius: var(--radius-md);
   --arc-duration: 2.23s;
 
   pointer-events: none;
   position: absolute;
   overflow: hidden;
-  border-radius: inherit;
-  inset: var(--arc-inset);
+  border-radius: calc(var(--arc-radius) + var(--arc-standoff));
+  inset: calc(var(--arc-standoff) * -1);
   padding: var(--arc-width);
   mask:
     linear-gradient(#000 0 0) content-box,
@@ -719,6 +755,23 @@
   --arc-duration: 3.27s;
 }
 
+/* Sidebar session row — a thin, clipped, single-line host, so it differs twice
+   from the default ring:
+
+   1. Flush, not outset. The sidebar scroller is `overflow-x-hidden` and rows sit
+      `gap-px` apart, so an outset ring loses its left/right runs to the clip.
+
+   2. A visible tail. `--arc-c2` defaults to `--dt-background` — invisible
+      against the sidebar. With c0 a transparent sentinel and c2 invisible, only
+      the bright c1 stop survives each pass, and the gradient has three of them:
+      three moving dots instead of an arc. Tying c2 to c1 gives each spike a
+      falloff. (`arc-nous` already overrides c2, so the hero is unaffected.) */
+.arc-border.arc-row,
+:root.dark .arc-border.arc-row {
+  --arc-standoff: 0rem;
+  --arc-c2: color-mix(in srgb, var(--arc-c1) 45%, transparent);
+}
+
 @media (prefers-reduced-motion: reduce) {
   .arc-border::before {
     animation: none;