fix: validate transcript sessions before resume and fix FAB race condition

Server now checks that transcript .jsonl files exist before creating
terminals, preventing dead sessions from --resume errors. Frontend
shows error banner in modal when resume fails. Fixed race condition
where init() would overwrite FAB terminal selection after page refresh
by guarding with pendingSwitchTarget flag.

frontend/src/App.vue

@@ -388,8 +388,9 @@ watch(() => route.name, (newPage) => {
       </div>
     </div>
 
-    <!-- Voice FAB Button -->
+    <!-- Voice FAB Button (hidden) -->
     <button
+      v-show="false"
       class="voice-fab"
       :class="{ active: showVoice, 'sheet-open': showVoice || showTranscriptDebug, 'ptt-active': voicePTTActive, 'keyboard-visible': keyboardVisible }"
       @click="handleVoiceFabClick"

frontend/src/components/FloatingTranscriptDebug.vue

@@ -38,6 +38,7 @@ const {
   hookMeta,
   openTerminals,
   activeTerminalSessionId,
+  lastStartError,
   init,
   switchAgent,
   selectSession,
@@ -470,6 +471,7 @@ async function handleModalCreateNew(agent: AgentName, initialPrompt: string) {
 
 async function handleModalResume(sessionId: string, agent: AgentName) {
   showNewSessionModal.value = false
+  lastStartError.value = null
   if (agent !== selectedAgent.value) {
     await switchAgent(agent)
   }
@@ -478,6 +480,11 @@ async function handleModalResume(sessionId: string, agent: AgentName) {
   selectedSessionId.value = sessionId
   await fetchSessionContent(sessionId)
   await startTerminal(sessionId)
+
+  // If startTerminal failed (e.g. transcript not found), re-open modal
+  if (lastStartError.value) {
+    showNewSessionModal.value = true
+  }
 }
 
 // ============================================================================
@@ -870,7 +877,8 @@ onBeforeUnmount(() => {
       :visible="showNewSessionModal"
       :agents="agents"
       :current-agent="selectedAgent"
-      @close="showNewSessionModal = false"
+      :error="lastStartError"
+      @close="showNewSessionModal = false; lastStartError = null"
       @create-new="handleModalCreateNew"
       @resume="handleModalResume"
     />

frontend/src/components/transcript-debug/NewSessionModal.vue

@@ -6,6 +6,7 @@ const props = defineProps<{
   visible: boolean
   agents: { id: AgentName; label: string }[]
   currentAgent: AgentName
+  error?: string | null
 }>()
 
 const emit = defineEmits<{
@@ -34,7 +35,8 @@ const hasAnySessions = computed(() =>
 // Reset state when modal opens
 watch(() => props.visible, async (open) => {
   if (open) {
-    activeTab.value = 'new'
+    // If reopening after a resume error, show the resume tab
+    activeTab.value = props.error ? 'resume' : 'new'
     selectedAgent.value = props.currentAgent
     resumeFilter.value = 'all'
     initialPrompt.value = ''
@@ -129,6 +131,16 @@ function handleResume(sessionId: string, agent: AgentName) {
             </button>
           </div>
 
+          <!-- Error banner -->
+          <div v-if="error" class="nsm-error">
+            <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+              <circle cx="12" cy="12" r="10"/>
+              <line x1="12" y1="8" x2="12" y2="12"/>
+              <line x1="12" y1="16" x2="12.01" y2="16"/>
+            </svg>
+            {{ error }}
+          </div>
+
           <!-- Body -->
           <div class="nsm-body">
             <!-- Tab: New session -->
@@ -333,6 +345,24 @@ function handleResume(sessionId: string, agent: AgentName) {
   border-bottom-color: #6366f1;
 }
 
+/* Error banner */
+.nsm-error {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  padding: 0.5rem 1rem;
+  background: rgba(239, 68, 68, 0.12);
+  border-bottom: 1px solid rgba(239, 68, 68, 0.3);
+  color: #f87171;
+  font-size: 12px;
+  flex-shrink: 0;
+}
+
+.nsm-error svg {
+  flex-shrink: 0;
+  color: #ef4444;
+}
+
 /* Body */
 .nsm-body {
   flex: 1;

frontend/src/composables/transcript-debug/useTranscriptDebug.ts

@@ -90,6 +90,10 @@ export function useTranscriptDebug() {
 
   const awaitingNewSession = ref(false)
   const pendingPrompt = ref<string | null>(null)
+  const lastStartError = ref<string | null>(null)
+
+  // Guard: when a FAB click triggers switchToTerminal before init(), init() must not overwrite
+  const pendingSwitchTarget = ref<string | null>(null)
 
   // ── Server registry HTTP helpers ──
 
@@ -151,8 +155,10 @@ export function useTranscriptDebug() {
       if (!res.ok) {
         const err = await res.json().catch(() => ({ error: 'Unknown error' }))
         console.error(`[TranscriptDebug] Failed to create terminal: ${err.error}`)
+        lastStartError.value = err.error || 'Failed to create terminal'
         return
       }
+      lastStartError.value = null
 
       const { ephemeralSessionId } = await res.json()
 
@@ -235,6 +241,7 @@ export function useTranscriptDebug() {
   async function switchToTerminal(transcriptSessionId: string) {
     if (transcriptSessionId === activeTerminalSessionId.value) return
 
+    pendingSwitchTarget.value = transcriptSessionId
     transitioning.value = true
     transitionError.value = null
 
@@ -281,6 +288,7 @@ export function useTranscriptDebug() {
     // Connect to the terminal
     connectToTerminal(transcriptSessionId)
 
+    pendingSwitchTarget.value = null
     transitioning.value = false
   }
 
@@ -561,6 +569,14 @@ export function useTranscriptDebug() {
   }
 
   async function init() {
+    // If a FAB click already triggered switchToTerminal(), let it handle the connection.
+    // Only load sessions and connect realtime — don't auto-connect to a terminal.
+    if (pendingSwitchTarget.value) {
+      await fetchSessions()
+      connectRealtime()
+      return
+    }
+
     // Derive initial state from server registry: if there's an alive terminal, sync to it
     const aliveEntry = serverRegistry.value.find(e => e.alive)
     if (aliveEntry) {
@@ -569,6 +585,12 @@ export function useTranscriptDebug() {
 
     await fetchSessions()
 
+    // Re-check after async gap — switchToTerminal() may have started during fetchSessions
+    if (pendingSwitchTarget.value) {
+      connectRealtime()
+      return
+    }
+
     let targetSession: string | null = null
 
     if (aliveEntry) {
@@ -589,6 +611,12 @@ export function useTranscriptDebug() {
       selectedSessionId.value = targetSession
       await fetchSessionContent(targetSession)
 
+      // Final check before connecting — bail if user clicked a FAB during content fetch
+      if (pendingSwitchTarget.value) {
+        connectRealtime()
+        return
+      }
+
       // Connect to existing terminal if one exists (clients never create terminals — only the server does)
       const existing = serverRegistry.value.find(
         e => e.transcriptSessionId === targetSession && e.alive
@@ -968,6 +996,7 @@ export function useTranscriptDebug() {
     terminalReady,
     hookMeta,
     awaitingNewSession,
+    lastStartError,
     openTerminals,
     activeTerminalSessionId,
     init,

server/services/terminal.ts

@@ -1,7 +1,33 @@
 import { spawn, type IPty } from '@skitee3000/bun-pty'
+import { existsSync } from 'fs'
+import { join } from 'path'
+import { homedir } from 'os'
 import { PORT_TERMINAL, WORKING_DIR, SHELL, SHELL_ARGS, DEFAULT_SESSION_ID, MAX_BUFFER_LINES, MAX_TERMINALS } from '../config'
 import { sessionState, type SessionStatePatch } from './session-state'
 
+// Agent transcript directories (mirrored from transcript-debug.ts)
+const AGENT_TRANSCRIPT_DIRS: Record<string, string> = {
+  ejecutor: join(WORKING_DIR, '.claude-ejecutor', 'projects'),
+  nucleo000: join(WORKING_DIR, '.claude-nucleo000', 'projects'),
+  claude: join(homedir(), '.claude', 'projects')
+}
+
+const PROJECT_HASH = 'C--Users-jodar-agent-ui'
+
+function getTranscriptProjectDir(agent: string): string | null {
+  const baseDir = AGENT_TRANSCRIPT_DIRS[agent]
+  if (!baseDir || !existsSync(baseDir)) return null
+  const exact = join(baseDir, PROJECT_HASH)
+  if (existsSync(exact)) return exact
+  return null
+}
+
+function transcriptSessionExists(agent: string, sessionId: string): boolean {
+  const projectDir = getTranscriptProjectDir(agent)
+  if (!projectDir) return false
+  return existsSync(join(projectDir, `${sessionId}.jsonl`))
+}
+
 interface TerminalSession {
   id: string
   pty: IPty
@@ -400,6 +426,18 @@ export function startTerminalServer() {
             )
           }
 
+          // Validate transcript session exists before resuming
+          const tsId = body.transcriptSessionId
+          if (tsId && tsId !== '__new__' && body.agent) {
+            if (!transcriptSessionExists(body.agent, tsId)) {
+              console.warn(`[Terminal] Transcript session not found: ${tsId} (agent: ${body.agent})`)
+              return Response.json(
+                { error: `Transcript session "${tsId}" not found. It may have been deleted.` },
+                { status: 404, headers: corsHeaders }
+              )
+            }
+          }
+
           // Generate ephemeralSessionId server-side
           const ephemeralSessionId = `pty-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`