desktop: keep slash popover live while typing args

The trigger regex `(?:^|[\s])([@/])([^\s@/]*)$` stopped matching the moment
the user typed a space after a slash command, so the popover never showed arg
completions for `/personality`, `/tools`, etc. — even though the backend's
`complete.slash` already returns them with a `replace_from` indicator.

Split the trigger detection so `/` allows args (`/cmd arg1 arg2`) while `@`
keeps the strict no-space behavior. Restrict the slash command name to
`[a-zA-Z][\w-]*` so file paths like `src/foo/bar` don't accidentally trigger
the popover.

Rewrite arg-completion items in useSlashCompletions to insert the full
`/personality alice` token instead of stranding `/alice`: when `replace_from`
is past the command base, prepend the existing prefix to each item's text so
the chip serializer produces a coherent replacement.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop/src/app/chat/composer/hooks/use-slash-completions.ts

@@ -67,10 +67,30 @@ export function useSlashCompletions(options: { gateway: HermesGateway | null }):
           return { items, query }
         }
 
-        const result = await gateway.request<{ items?: CompletionEntry[] }>('complete.slash', { text })
+        const result = await gateway.request<{ items?: CompletionEntry[]; replace_from?: number }>(
+          'complete.slash',
+          { text }
+        )
+
+        // Arg-completion items (replace_from > 1) carry just the arg stub —
+        // e.g. complete.slash returns `{text: "alice"}` for `/personality alic`
+        // with replace_from = 14. Rewrite those entries so the popover inserts
+        // the full `/personality alice` token instead of stranding `/alice`.
+        const replaceFrom = typeof result.replace_from === 'number' ? result.replace_from : 1
+        const isArgCompletion = replaceFrom > 1
+        const prefix = isArgCompletion ? text.slice(0, replaceFrom) : ''
 
         const items = (result.items ?? [])
-          .filter(item => isDesktopSlashSuggestion(item.text))
+          .map(item => {
+            if (!isArgCompletion) {
+              return item
+            }
+
+            const argText = typeof item.text === 'string' ? item.text : ''
+
+            return { ...item, text: `${prefix}${argText}` }
+          })
+          .filter(item => isArgCompletion || isDesktopSlashSuggestion(item.text))
           .map(item => ({
             ...item,
             meta: desktopSlashDescription(item.text, textValue(item.meta))

apps/desktop/src/app/chat/composer/text-utils.test.ts

@@ -22,6 +22,33 @@ describe('detectTrigger', () => {
   it('returns null for plain text', () => {
     expect(detectTrigger('hello there')).toBeNull()
   })
+
+  it('keeps the slash trigger live while typing args', () => {
+    expect(detectTrigger('/personality ')).toEqual({
+      kind: '/',
+      query: 'personality ',
+      tokenLength: 13
+    })
+    expect(detectTrigger('/personality alic')).toEqual({
+      kind: '/',
+      query: 'personality alic',
+      tokenLength: 17
+    })
+    expect(detectTrigger('/tools enable foo')).toEqual({
+      kind: '/',
+      query: 'tools enable foo',
+      tokenLength: 17
+    })
+  })
+
+  it('does not treat file-style paths as slash triggers', () => {
+    expect(detectTrigger('src/foo/bar')).toBeNull()
+    expect(detectTrigger('/path/to/file')).toBeNull()
+  })
+
+  it('still anchors at-mention triggers strictly at the token edge', () => {
+    expect(detectTrigger('@file:path with space')).toBeNull()
+  })
 })
 
 describe('extractClipboardImageBlobs', () => {

apps/desktop/src/app/chat/composer/text-utils.ts

@@ -6,7 +6,13 @@ export interface TriggerState {
   tokenLength: number
 }
 
-const TRIGGER_RE = /(?:^|[\s])([@/])([^\s@/]*)$/
+// `@` triggers stop at the first whitespace — `@file:path` and `@diff` are
+// single tokens. `/` triggers keep going so the popover stays live while the
+// user types args (`/personality alic` → arg completer suggests `alice`).
+// Restricting the slash command name to `[a-zA-Z][\w-]*` avoids matching file
+// paths like `src/foo/bar`.
+const AT_TRIGGER_RE = /(?:^|[\s])(@)([^\s@/]*)$/
+const SLASH_TRIGGER_RE = /(?:^|[\s])(\/)((?:[a-zA-Z][\w-]*(?:\s+\S*)*)?)$/
 
 /** Stable key for paste dedupe — `items` and `files` often mirror the same image as different objects. */
 export function blobDedupeKey(blob: Blob): string {
@@ -97,11 +103,17 @@ export function textBeforeCaret(editor: HTMLDivElement): string | null {
 }
 
 export function detectTrigger(textBefore: string): TriggerState | null {
-  const match = TRIGGER_RE.exec(textBefore)
+  const slash = SLASH_TRIGGER_RE.exec(textBefore)
 
-  if (!match) {
-    return null
+  if (slash) {
+    return { kind: '/', query: slash[2], tokenLength: 1 + slash[2].length }
   }
 
-  return { kind: match[1] as '@' | '/', query: match[2], tokenLength: 1 + match[2].length }
+  const at = AT_TRIGGER_RE.exec(textBefore)
+
+  if (at) {
+    return { kind: '@', query: at[2], tokenLength: 1 + at[2].length }
+  }
+
+  return null
 }