fix: tighten desktop slash command edge cases

Desktop slash command handling needed a few follow-up guards after adding
CLI parity. Bare /clear remains a local desktop reset, but /clear with
arguments is rejected instead of silently discarding user text. Clear also
resets cached slash commands, compact boundaries preserve CLI-provided text,
and the help panel now discloses when the More section is truncated.

Constraint: Preserve the desktop /clear fast path without accepting accidental arguments
Rejected: Let /clear arguments fall through to the CLI | the CLI command still clears context and would keep the footgun
Confidence: high
Scope-risk: narrow
Directive: Keep desktop-local slash command guards in sync with CLI command argument semantics
Tested: cd desktop && bun run test src/stores/chatStore.test.ts src/__tests__/pages.test.tsx --run -t "clears local desktop chat state|ActiveSession routes /help"
Tested: bun test src/server/__tests__/conversations.test.ts
Tested: cd desktop && bun run lint
Tested: git diff --check
Not-tested: Full pages.test.tsx because unrelated locale-sensitive assertions are already present in that file

desktop/src/__tests__/pages.test.tsx

@@ -474,7 +474,13 @@ describe('Content-only pages render without errors', () => {
           tokenUsage: { input_tokens: 0, output_tokens: 0 },
           elapsedSeconds: 0,
           statusVerb: '',
-          slashCommands: [{ name: 'cost', description: 'Show token usage and costs' }],
+          slashCommands: [
+            { name: 'cost', description: 'Show token usage and costs' },
+            ...Array.from({ length: 14 }, (_, index) => ({
+              name: `extra-${index + 1}`,
+              description: `Extra command ${index + 1}`,
+            })),
+          ],
           agentTaskNotifications: {},
           elapsedTimer: null,
         },
@@ -492,6 +498,7 @@ describe('Content-only pages render without errors', () => {
     expect(screen.getByText('Slash commands')).toBeInTheDocument()
     expect(screen.getByText('/clear')).toBeInTheDocument()
     expect(screen.getByText('/cost')).toBeInTheDocument()
+    expect(screen.getByText('13 more commands available. Type / to search the full command list.')).toBeInTheDocument()
 
     useTabStore.setState({ tabs: [], activeTabId: null })
     useSessionStore.setState({ sessions: [], activeSessionId: null, isLoading: false, error: null })

desktop/src/components/chat/LocalSlashCommandPanel.tsx

@@ -319,6 +319,10 @@ function HelpPanel({
   const otherCommands = (commands ?? [])
     .filter((command) => !groupedNames.has(command.name))
     .slice(0, 12)
+  const hiddenOtherCommandCount = Math.max(
+    0,
+    (commands ?? []).filter((command) => !groupedNames.has(command.name)).length - otherCommands.length,
+  )
 
   const renderCommand = (command: SlashCommandOption) => (
     <div key={command.name} className="flex min-w-0 items-start gap-3 border-t border-[var(--color-border)] px-4 py-3 first:border-t-0">
@@ -355,6 +359,11 @@ function HelpPanel({
             <div className="overflow-hidden rounded-2xl border border-[var(--color-border)] bg-[var(--color-surface)]">
               {otherCommands.map(renderCommand)}
             </div>
+            {hiddenOtherCommandCount > 0 && (
+              <p className="mt-2 text-xs leading-5 text-[var(--color-text-tertiary)]">
+                {hiddenOtherCommandCount} more commands available. Type / to search the full command list.
+              </p>
+            )}
           </section>
         )}
       </div>

desktop/src/stores/chatStore.test.ts

@@ -224,7 +224,7 @@ describe('chatStore history mapping', () => {
           tokenUsage: { input_tokens: 0, output_tokens: 0 },
           elapsedSeconds: 0,
           statusVerb: '',
-          slashCommands: [],
+          slashCommands: [{ name: 'old-command', description: 'Old command' }],
           agentTaskNotifications: {},
           elapsedTimer: null,
         },
@@ -519,6 +519,7 @@ describe('chatStore history mapping', () => {
     expect(session?.streamingText).toBe('')
     expect(session?.chatState).toBe('idle')
     expect(session?.tokenUsage).toEqual({ input_tokens: 0, output_tokens: 0 })
+    expect(session?.slashCommands).toEqual([])
     expect(clearTasksMock).toHaveBeenCalled()
   })
 

desktop/src/stores/chatStore.ts

@@ -785,6 +785,7 @@ export const useChatStore = create<ChatStore>((set, get) => ({
             elapsedSeconds: 0,
             statusVerb: '',
             tokenUsage: { input_tokens: 0, output_tokens: 0 },
+            slashCommands: [],
           }))
           useCLITaskStore.getState().clearTasks()
           useSessionStore.getState().updateSessionTitle(sessionId, 'New Session')

src/server/__tests__/conversations.test.ts

@@ -235,7 +235,7 @@ describe('WebSocket Chat Integration', () => {
     }
   }
 
-  async function runTurn(sessionId: string, content: string): Promise<any[]> {
+  async function runTurn(sessionId: string, content: string, allowError = false): Promise<any[]> {
     const messages: any[] = []
     const ws = new WebSocket(`${wsUrl}/ws/${sessionId}`)
 
@@ -254,7 +254,11 @@ describe('WebSocket Chat Integration', () => {
         if (msg.type === 'error') {
           clearTimeout(timeout)
           ws.close()
-          reject(new Error(msg.message))
+          if (allowError) {
+            resolve()
+          } else {
+            reject(new Error(msg.message))
+          }
         }
         if (msg.type === 'message_complete') {
           clearTimeout(timeout)
@@ -544,6 +548,33 @@ describe('WebSocket Chat Integration', () => {
     expect(body.messages).toEqual([])
   })
 
+  it('should reject /clear arguments without clearing the desktop session', async () => {
+    const createRes = await fetch(`${baseUrl}/api/sessions`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ workDir: process.cwd() }),
+    })
+    expect(createRes.status).toBe(201)
+    const { sessionId } = await createRes.json() as { sessionId: string }
+
+    await runTurn(sessionId, 'message before invalid clear')
+
+    const clearTurn = await runTurn(sessionId, '/clear please keep this', true)
+    expect(
+      clearTurn.some(
+        (m) => m.type === 'error' && m.code === 'INVALID_SLASH_COMMAND_ARGS',
+      ),
+    ).toBe(true)
+    expect(
+      clearTurn.some(
+        (m) => m.type === 'system_notification' && m.subtype === 'session_cleared',
+      ),
+    ).toBe(false)
+
+    const nextTurn = await runTurn(sessionId, 'message after invalid clear')
+    expect(nextTurn.some((m) => m.type === 'message_complete')).toBe(true)
+  })
+
   it('should prewarm the CLI before the first user turn and reuse that process', async () => {
     const createRes = await fetch(`${baseUrl}/api/sessions`, {
       method: 'POST',

src/server/ws/handler.ts

@@ -219,7 +219,18 @@ async function handleUserMessage(
   sessionStopRequested.delete(sessionId)
   clearPrewarmState(sessionId)
 
-  if (getDesktopSlashCommandName(message.content) === 'clear') {
+  const desktopSlashCommand = getDesktopSlashCommand(message.content)
+  if (desktopSlashCommand?.commandName === 'clear' && desktopSlashCommand.args.trim()) {
+    sendMessage(ws, {
+      type: 'error',
+      message: 'The /clear command does not accept arguments.',
+      code: 'INVALID_SLASH_COMMAND_ARGS',
+    })
+    sendMessage(ws, { type: 'status', state: 'idle' })
+    return
+  }
+
+  if (desktopSlashCommand?.commandName === 'clear') {
     await handleDesktopClearCommand(ws)
     return
   }
@@ -1080,7 +1091,7 @@ function translateCliMessage(cliMsg: any, sessionId: string): ServerMessage[] {
         return [{
           type: 'system_notification',
           subtype: 'compact_boundary',
-          message: 'Context compacted',
+          message: getCompactBoundaryMessage(cliMsg),
           data: cliMsg.compact_metadata ?? cliMsg,
         }]
       }
@@ -1107,9 +1118,10 @@ function sendError(ws: ServerWebSocket<WebSocketData>, message: string, code: st
   sendMessage(ws, { type: 'error', message, code })
 }
 
-function getDesktopSlashCommandName(content: string): string | null {
+function getDesktopSlashCommand(content: string): ReturnType<typeof parseSlashCommand> {
   const parsed = parseSlashCommand(content.trim())
-  return parsed?.commandName ?? null
+  if (!parsed || parsed.isMcp) return null
+  return parsed
 }
 
 function extractLocalCommandOutput(content: unknown): string | null {
@@ -1139,6 +1151,16 @@ function extractTaggedContent(raw: string, tag: string): string | null {
   return match?.[1]?.trim() ?? null
 }
 
+function getCompactBoundaryMessage(cliMsg: any): string {
+  const message = typeof cliMsg?.message === 'string' ? cliMsg.message.trim() : ''
+  if (message) return message
+
+  const content = typeof cliMsg?.content === 'string' ? cliMsg.content.trim() : ''
+  if (content) return content
+
+  return 'Context compacted'
+}
+
 function rebindSessionOutput(
   sessionId: string,
   ws: ServerWebSocket<WebSocketData>,