fix: show 'Session started' immediately instead of empty chat on startup

Previously claude_started was suppressed and the first visible message
only appeared on system_init, which fires after the first user input —
leaving the chat empty until then. Now claude_started renders a
"Session started" system message immediately.

Also resets _lastReportedModel on process start so the model info
message always appears on system_init, even across process restarts.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: alari76

server/session-lifecycle.ts

@@ -172,6 +172,9 @@ export class SessionLifecycle {
 
     cp.start()
     session.claudeProcess = cp
+    // Reset so the next system_init always broadcasts the model message,
+    // even if the model hasn't changed since the previous process.
+    session._lastReportedModel = undefined
     this.deps.globalBroadcast?.({ type: 'sessions_updated' })
 
     const startMsg: WsServerMessage = { type: 'claude_started', sessionId }

src/hooks/useChatSocket.hook.test.ts

@@ -554,12 +554,14 @@ describe('useChatSocket hook', () => {
       unmount()
     })
 
-    it('claude_started is suppressed (no message added)', () => {
+    it('claude_started shows Session started message', () => {
       const { result, unmount } = setupConnected()
       act(() => MockWebSocket.latest().simulateMessage({
         type: 'claude_started', sessionId: 's1',
       } as WsServerMessage))
-      expect(result.current.messages).toHaveLength(0)
+      expect(result.current.messages).toHaveLength(1)
+      expect(result.current.messages[0].type).toBe('system')
+      expect((result.current.messages[0] as any).text).toBe('Session started')
       unmount()
     })
 

src/hooks/useChatSocket.test.ts

@@ -158,9 +158,11 @@ describe('processMessage', () => {
       expect((result[0] as any).model).toBe('claude-opus-4-6')
     })
 
-    it('claude_started is suppressed (init shown on system_init instead)', () => {
+    it('claude_started shows Session started message', () => {
       const result = processMessage(empty(), { type: 'claude_started', sessionId: '123' } as WsServerMessage)
-      expect(result).toHaveLength(0)
+      expect(result).toHaveLength(1)
+      expect(result[0].type).toBe('system')
+      expect((result[0] as any).text).toBe('Session started')
     })
   })
 
@@ -347,11 +349,13 @@ describe('rebuildFromHistory', () => {
     expect((result[0] as any).text).toBe('User input')
   })
 
-  it('claude_started is suppressed in history rebuild', () => {
+  it('claude_started shows Session started in history rebuild', () => {
     const result = rebuildFromHistory([
       { type: 'claude_started', sessionId: 's1' } as WsServerMessage,
     ])
-    expect(result).toHaveLength(0)
+    expect(result).toHaveLength(1)
+    expect(result[0].type).toBe('system')
+    expect((result[0] as any).text).toBe('Session started')
   })
 
   it('builds tool_group from tool_active', () => {
@@ -447,15 +451,17 @@ describe('rebuildFromHistory', () => {
       { type: 'result' } as WsServerMessage,
     ]
     const result = rebuildFromHistory(buffer)
-    expect(result).toHaveLength(5)
-    expect(result[0].type).toBe('system')       // system_message (claude_started suppressed)
-    expect(result[1].type).toBe('user')          // user_echo
-    expect(result[2].type).toBe('assistant')     // "Sure, I can help." (incomplete — tool_active broke the chain)
-    expect((result[2] as any).text).toBe('Sure, I can help.')
-    expect((result[2] as any).complete).toBe(false)
-    expect(result[3].type).toBe('tool_group')    // Read tool
-    expect(result[4].type).toBe('assistant')     // "Here it is." — marked complete by result
-    expect((result[4] as any).text).toBe('Here it is.')
-    expect((result[4] as any).complete).toBe(true)
+    expect(result).toHaveLength(6)
+    expect(result[0].type).toBe('system')       // claude_started → "Session started"
+    expect((result[0] as any).text).toBe('Session started')
+    expect(result[1].type).toBe('system')       // system_message init
+    expect(result[2].type).toBe('user')          // user_echo
+    expect(result[3].type).toBe('assistant')     // "Sure, I can help." (incomplete — tool_active broke the chain)
+    expect((result[3] as any).text).toBe('Sure, I can help.')
+    expect((result[3] as any).complete).toBe(false)
+    expect(result[4].type).toBe('tool_group')    // Read tool
+    expect(result[5].type).toBe('assistant')     // "Here it is." — marked complete by result
+    expect((result[5] as any).text).toBe('Here it is.')
+    expect((result[5] as any).complete).toBe(true)
   })
 })

src/hooks/useChatSocket.ts

@@ -68,10 +68,8 @@ function applyMessageMut(messages: ChatMessage[], msg: WsServerMessage): boolean
       return true
 
     case 'claude_started':
-      // Process spawned — don't show a message yet.  The actual "Session started"
-      // is shown when system_init arrives (system_message subtype=init), proving
-      // the process is fully initialized and ready for input.
-      return false
+      messages.push({ type: 'system', subtype: 'init', text: 'Session started', key: nextKey() })
+      return true
 
     case 'tool_active':
       if (last && last.type === 'tool_group') {