perf: fix model reload thrash and cut time-to-first-token

Ollama reloaded the chat model mid-message because plan/summary/router
calls sent divergent runner options (no num_ctx/num_batch) and omitted
keep_alive — the main cause of perceived slowness.

- share one keep-alive httpx.AsyncClient for all Ollama calls
- unify runner options (runner_options) + keep_alive on every model
  call, embeddings included
- drop the blocking LLM routing fallback (pure lexical heuristic)
- run RAG recall + plan + code-model pick in parallel inside the SSE
  stream, after the start event
- RAG cosine scoring off the event loop; cache /api/tags 30s and
  nvidia-smi 5s; frontend polls 2s->5s, warm poll backoff, dedup
  config fetch

feat: working session menu in TopBar (switch/create/rename/delete)
feat: workspace file deletion (DELETE /api/files + UI trash buttons)
docs: recommended Ollama env vars (KEEP_ALIVE, MAX_LOADED_MODELS...)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/components/Icon.tsx

@@ -85,6 +85,12 @@ export const DownloadIcon = ({ size = 14, className }: Props) => (
   </svg>
 );
 
+export const TrashIcon = ({ size = 14, className }: Props) => (
+  <svg {...base(size, className)} strokeWidth={1.9}>
+    <path d="M4 7h16M10 7V5h4v2M9 7l.8 13h4.4L15 7M6.5 7l.7 13h9.6l.7-13" />
+  </svg>
+);
+
 export const CopyIcon = ({ size = 14, className }: Props) => (
   <svg {...base(size, className)} strokeWidth={1.7}>
     <rect x="9" y="9" width="11" height="11" rx="2" />

frontend/src/components/SessionMenu.tsx

@@ -0,0 +1,174 @@
+import { useEffect, useRef, useState } from "react";
+import { useStore } from "../store/useStore";
+import { ChevronDown, PlusIcon, TrashIcon } from "./Icon";
+import { relTime } from "../lib/time";
+
+/** Sélecteur de session de la barre supérieure : titre courant + menu déroulant
+ *  (nouvelle session, liste, renommage inline, suppression). */
+export function SessionMenu() {
+  const {
+    sessions,
+    currentSessionId,
+    streamingSessionId,
+    newSession,
+    openSession,
+    removeSession,
+    renameSession,
+  } = useStore();
+  const [open, setOpen] = useState(false);
+  const [editingId, setEditingId] = useState<string | null>(null);
+  const [draft, setDraft] = useState("");
+  const rootRef = useRef<HTMLDivElement>(null);
+
+  const current = sessions.find((s) => s.id === currentSessionId);
+
+  // Fermeture au clic extérieur + Escape.
+  useEffect(() => {
+    if (!open) return;
+    const onDown = (e: MouseEvent) => {
+      if (rootRef.current && !rootRef.current.contains(e.target as Node)) {
+        setOpen(false);
+        setEditingId(null);
+      }
+    };
+    const onKey = (e: KeyboardEvent) => {
+      if (e.key === "Escape") {
+        setOpen(false);
+        setEditingId(null);
+      }
+    };
+    document.addEventListener("mousedown", onDown);
+    document.addEventListener("keydown", onKey);
+    return () => {
+      document.removeEventListener("mousedown", onDown);
+      document.removeEventListener("keydown", onKey);
+    };
+  }, [open]);
+
+  const commitRename = async (id: string) => {
+    const title = draft.trim();
+    setEditingId(null);
+    if (title) await renameSession(id, title);
+  };
+
+  return (
+    <div ref={rootRef} className="relative">
+      <button
+        onClick={() => setOpen((o) => !o)}
+        className="flex cursor-pointer items-center gap-2 text-[13px] text-on-dark hover:text-white"
+        title="Sessions"
+      >
+        <span className="max-w-[220px] truncate">
+          {current?.title ?? "Nouvelle session"}
+        </span>
+        <ChevronDown className="text-on-dark-3" />
+      </button>
+
+      {open && (
+        <div
+          className="absolute left-0 top-[calc(100%+9px)] z-30 w-[300px] border-[3px] border-line bg-chrome-2 shadow-hard"
+          style={{ borderRadius: 7 }}
+        >
+          <button
+            onClick={async () => {
+              setOpen(false);
+              await newSession();
+            }}
+            className="flex w-full cursor-pointer items-center gap-2 border-b-[3px] border-chrome-3 px-3 py-2.5 text-[13px] font-bold text-accent hover:bg-chrome-3"
+          >
+            <PlusIcon />
+            Nouvelle session
+          </button>
+
+          <div className="scr max-h-[320px] overflow-auto">
+            {sessions.length === 0 && (
+              <div className="px-3 py-4 text-center text-[12px] text-on-dark-3">
+                Aucune session enregistrée.
+              </div>
+            )}
+            {sessions.map((s) => {
+              const active = s.id === currentSessionId;
+              const working = s.id === streamingSessionId;
+              return (
+                <div
+                  key={s.id}
+                  onClick={() => {
+                    if (editingId === s.id) return;
+                    setOpen(false);
+                    void openSession(s.id);
+                  }}
+                  className={`group cursor-pointer border-b-2 border-chrome-3 px-3 py-2 last:border-b-0 ${
+                    active ? "bg-chrome-3" : "hover:bg-chrome-3"
+                  }`}
+                >
+                  <div className="flex items-center gap-1.5">
+                    {editingId === s.id ? (
+                      <input
+                        autoFocus
+                        value={draft}
+                        onChange={(e) => setDraft(e.target.value)}
+                        onClick={(e) => e.stopPropagation()}
+                        onKeyDown={(e) => {
+                          if (e.key === "Enter") void commitRename(s.id);
+                          if (e.key === "Escape") {
+                            e.stopPropagation();
+                            setEditingId(null);
+                          }
+                        }}
+                        onBlur={() => setEditingId(null)}
+                        className="min-w-0 flex-1 border-2 border-line bg-card-deep px-1.5 py-0.5 text-[13px] text-white outline-none"
+                      />
+                    ) : (
+                      <span
+                        className={`min-w-0 flex-1 truncate text-[13px] ${
+                          active ? "text-white" : "text-on-dark"
+                        }`}
+                      >
+                        {s.title}
+                      </span>
+                    )}
+                    {working && (
+                      <span
+                        className="flex-none border-2 border-line bg-accent px-1 py-0.5 text-[9px] leading-none text-white"
+                        title="Session en cours de travail"
+                      >
+                        EN COURS
+                      </span>
+                    )}
+                    <button
+                      onClick={(e) => {
+                        e.stopPropagation();
+                        setEditingId(s.id);
+                        setDraft(s.title);
+                      }}
+                      className="hidden flex-none text-[11px] text-on-dark-3 hover:text-white group-hover:block"
+                      title="Renommer la session"
+                    >
+                      ✎
+                    </button>
+                    <button
+                      onClick={(e) => {
+                        e.stopPropagation();
+                        if (window.confirm("Supprimer cette session ?")) {
+                          void removeSession(s.id);
+                        }
+                      }}
+                      className="hidden flex-none text-on-dark-3 hover:text-accent group-hover:block"
+                      title="Supprimer la session"
+                    >
+                      <TrashIcon size={12} />
+                    </button>
+                  </div>
+                  <div className="mt-0.5 text-[11px] text-on-dark-3">
+                    {relTime(s.updated_at)} · {s.message_count ?? 0} message
+                    {(s.message_count ?? 0) > 1 ? "s" : ""}
+                  </div>
+                </div>
+              );
+            })}
+          </div>
+        </div>
+      )}
+    </div>
+  );
+}

frontend/src/components/TopBar.tsx

@@ -1,8 +1,9 @@
 import { useEffect, useState } from "react";
 import { useStore } from "../store/useStore";
 import { getVersion } from "../api/client";
-import { ChevronDown, LokiMark } from "./Icon";
+import { LokiMark } from "./Icon";
 import { ModelSelector } from "./ModelSelector";
+import { SessionMenu } from "./SessionMenu";
 
 /** Barre supérieure sombre : logo, fil d'Ariane, statut Ollama, sélecteur. */
 export function TopBar() {
@@ -33,10 +34,7 @@ export function TopBar() {
 
       <div className="h-6 w-[3px] bg-chrome-3" />
 
-      <div className="flex items-center gap-2 text-[13px] text-on-dark">
-        <span>Nouvelle session</span>
-        <ChevronDown className="text-on-dark-3" />
-      </div>
+      <SessionMenu />
 
       <div className="flex-1" />