fix: chat session reliability, cost, and hygiene (empty-response guard, tool truncation, delete, titles)

- Empty/refusal responses retried once, then surfaced as errors instead of silent blanks
- Chinese refusal boilerplate detected via denylist + non-ASCII heuristic
- Bulk-tool preference added to SOUL.md (list_lxcs over per-entity get_lxc_state)
- Tool results truncated to 4KB on persist; get_state_snapshot filters null-state entities
- Session delete (DELETE /sessions/{id} + confirm-on-second-click UI)
- Session titles auto-generated from assistant answer instead of raw user message

web/src/lib/api.ts

@@ -31,6 +31,11 @@ export async function fetchMessages(sessionId: string): Promise<Message[]> {
   return data.messages ?? []
 }
 
+export async function deleteSession(sessionId: string): Promise<boolean> {
+  const res = await fetch(`${BASE}/sessions/${sessionId}`, { method: 'DELETE' })
+  return res.ok
+}
+
 export interface ChatEvent {
   type: string
   data: any

web/src/lib/components/SessionRail.svelte

@@ -1,20 +1,39 @@
 <script lang="ts">
   import { onMount } from 'svelte'
-  import { sessions, currentSession, loadSessions, loadSessionMessages, newChat } from '$lib/stores/chat'
+  import { sessions, currentSession, loadSessions, loadSessionMessages, newChat, deleteSession } from '$lib/stores/chat'
   import { relativeTime } from '$lib/utils'
   import { Button } from '$lib/components/ui/button'
   import { ScrollArea } from '$lib/components/ui/scroll-area'
   import PlusIcon from '@lucide/svelte/icons/plus'
+  import Trash2Icon from '@lucide/svelte/icons/trash2'
 
   onMount(() => {
     loadSessions()
   })
 
-  // Pick up sessions created/renamed elsewhere (e.g. after a turn completes).
   $effect(() => {
     void $currentSession
     loadSessions()
   })
+
+  let confirmDelete = $state<string | null>(null)
+
+  function handleDelete(e: MouseEvent, id: string) {
+    e.stopPropagation()
+    if (confirmDelete === id) {
+      deleteSession(id)
+      confirmDelete = null
+    } else {
+      confirmDelete = id
+      // Hide confirmation after 3s
+      setTimeout(() => { if (confirmDelete === id) confirmDelete = null }, 3000)
+    }
+  }
+
+  function handleClick(sessionId: string) {
+    confirmDelete = null
+    loadSessionMessages(sessionId)
+  }
 </script>
 
 <aside class="flex h-full w-56 shrink-0 flex-col gap-2 overflow-y-auto border-r bg-card/50 p-2">
@@ -27,10 +46,23 @@
       {#each $sessions as session (session.id)}
         <button
           type="button"
-          class="flex flex-col items-start gap-0.5 rounded-md border px-2 py-1.5 text-left text-xs transition-colors hover:bg-muted/60 {$currentSession === session.id ? 'border-primary bg-muted/50' : 'border-transparent'}"
-          onclick={() => loadSessionMessages(session.id)}
+          class="group flex flex-col items-start gap-0.5 rounded-md border px-2 py-1.5 text-left text-xs transition-colors hover:bg-muted/60 {$currentSession === session.id ? 'border-primary bg-muted/50' : 'border-transparent'}"
+          onclick={() => handleClick(session.id)}
         >
-          <span class="w-full truncate font-medium">{session.title || 'Untitled'}</span>
+          <span class="flex w-full items-center justify-between gap-1">
+            <span class="min-w-0 truncate font-medium">{session.title || 'Untitled'}</span>
+            <span
+              class="shrink-0 rounded p-0.5 opacity-0 transition-opacity group-hover:opacity-100 hover:bg-destructive/20 hover:text-destructive"
+              onclick={(e) => handleDelete(e, session.id)}
+              title={confirmDelete === session.id ? 'Click again to confirm delete' : 'Delete session'}
+            >
+              {#if confirmDelete === session.id}
+                <span class="text-[10px] font-semibold text-destructive">Sure?</span>
+              {:else}
+                <Trash2Icon class="size-3" />
+              {/if}
+            </span>
+          </span>
           <span class="text-[11px] text-muted-foreground">{relativeTime(session.last_active_at)}</span>
         </button>
       {:else}

web/src/lib/stores/chat.ts

@@ -1,5 +1,5 @@
 import { writable, get } from 'svelte/store'
-import { streamChat, fetchSessions, fetchMessages } from '$lib/api'
+import { streamChat, fetchSessions, fetchMessages, deleteSession as apiDeleteSession } from '$lib/api'
 import type { ChatEvent, Session, Message } from '$lib/api'
 
 export interface ChatMessage {
@@ -177,3 +177,12 @@ export function cancelStream() {
     streaming.set(false)
   }
 }
+
+export async function deleteSession(sessionId: string) {
+  const ok = await apiDeleteSession(sessionId)
+  if (!ok) return
+  if (get(currentSession) === sessionId) {
+    newChat()
+  }
+  loadSessions()
+}

web/src/pages/Sessions.svelte

@@ -1,29 +1,59 @@
 <script lang="ts">
-  import { sessions, loadSessions, loadSessionMessages, messages, currentSession } from '$lib/stores/chat'
+  import { sessions, loadSessions, loadSessionMessages, deleteSession, currentSession } from '$lib/stores/chat'
   import { onMount } from 'svelte'
+  import Trash2Icon from '@lucide/svelte/icons/trash2'
 
   onMount(() => {
     loadSessions()
   })
+
+  let confirmDelete = $state<string | null>(null)
+
+  function handleDelete(e: MouseEvent, id: string) {
+    e.stopPropagation()
+    if (confirmDelete === id) {
+      deleteSession(id)
+      confirmDelete = null
+    } else {
+      confirmDelete = id
+      setTimeout(() => { if (confirmDelete === id) confirmDelete = null }, 3000)
+    }
+  }
 </script>
 
 <div class="sessions-page">
   <h2>Sessions</h2>
   <div class="session-list">
     {#each $sessions as session (session.id)}
-      <button
-        class="session-card"
+      <div
+        class="session-card group"
         class:active={$currentSession === session.id}
-        onclick={() => {
-          loadSessionMessages(session.id)
-          location.hash = '#/chat'
-        }}
       >
-        <div class="session-title">{session.title || 'Untitled'}</div>
-        <div class="session-meta">
-          {new Date(session.last_active_at).toLocaleString()}
-        </div>
-      </button>
+        <button
+          class="session-content"
+          onclick={() => {
+            loadSessionMessages(session.id)
+            location.hash = '#/chat'
+          }}
+        >
+          <div class="session-title">{session.title || 'Untitled'}</div>
+          <div class="session-meta">
+            {new Date(session.last_active_at).toLocaleString()}
+          </div>
+        </button>
+        <button
+          class="session-delete"
+          onclick={(e) => handleDelete(e, session.id)}
+          title={confirmDelete === session.id ? 'Click again to confirm delete' : 'Delete session'}
+          aria-label="Delete session"
+        >
+          {#if confirmDelete === session.id}
+            <span class="confirm-text">Delete?</span>
+          {:else}
+            <Trash2Icon class="icon" />
+          {/if}
+        </button>
+      </div>
     {:else}
       <div class="empty">No sessions yet. Start chatting with Nomos.</div>
     {/each}
@@ -54,15 +84,12 @@
     display: flex;
     justify-content: space-between;
     align-items: center;
-    padding: 0.75rem 1rem;
     background: var(--bg-surface);
     border: 1px solid var(--border);
     border-radius: 8px;
-    cursor: pointer;
     color: var(--text);
     font-family: inherit;
     font-size: 0.875rem;
-    text-align: left;
     transition: border-color 0.15s;
   }
 
@@ -75,6 +102,58 @@
     background: var(--bg-hover);
   }
 
+  .session-content {
+    flex: 1;
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    padding: 0.75rem 1rem;
+    background: none;
+    border: none;
+    cursor: pointer;
+    color: inherit;
+    font-family: inherit;
+    font-size: inherit;
+    text-align: left;
+  }
+
+  .session-delete {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    width: 32px;
+    height: 32px;
+    margin-right: 4px;
+    padding: 0;
+    background: none;
+    border: none;
+    border-radius: 6px;
+    cursor: pointer;
+    color: var(--text-muted);
+    opacity: 0;
+    transition: opacity 0.15s, background 0.15s;
+  }
+
+  .group:hover .session-delete {
+    opacity: 1;
+  }
+
+  .session-delete:hover {
+    background: var(--destructive-bg-subtle, rgba(239, 68, 68, 0.1));
+    color: var(--destructive, #ef4444);
+  }
+
+  .confirm-text {
+    font-size: 0.65rem;
+    font-weight: 700;
+    color: var(--destructive, #ef4444);
+  }
+
+  .icon {
+    width: 16px;
+    height: 16px;
+  }
+
   .session-title {
     font-weight: 500;
   }