updates

.env.example

@@ -9,6 +9,9 @@ APP_PASSWORD=change-me
 SESSION_TTL_HOURS=720
 # Data dir: holds kisassistant.db (SQLite: users, sessions, chats, shares)
 DATA_DIR=./data
+# Local file CDN (avatars today, more namespaces tomorrow).
+# Dev default is a folder next to the codebase; NixOS points it under state dir.
+CDN_DIR=./cdn
 
 # Per-driver debug logging to stdout ([driver:name] lines).
 DRIVER_DEBUG=true

.gitignore

@@ -1,7 +1,8 @@
-data/
+/data/
+/cdn/
 node_modules/
 dist/
-public/
+/public/
 .env
 *.log
 *.db

docs/ARCHITECTURE.md

@@ -63,9 +63,24 @@ conversations → sessions → user) inside a transaction.
   **returned once** at creation/regeneration. Regeneration also wipes the
   account's sessions.
 
-## Drivers
+## Local file CDN
 
-`src/drivers/`: `LLMDriver` interface (`listModels`, `chat`, `chatStream`),
+`src/cdn.ts` + routes in `index.ts`. Generic namespaced layout
+(`PUT /cdn/<ns>/<key>` authed, `GET /cdn/<ns>/<key>.<ext>` public) so future
+file kinds plug into `CDN_NAMESPACES` without new routes. Today only `avatar`
+exists: key = account id (`/cdn/avatar/<id>.png`), ownership enforced.
+
+- Type safety by **magic bytes** (JPEG `FF D8 FF`, PNG signature, `RIFF…WEBP`);
+  only `jpg`/`png`/`webp` are representable, the stored extension is always
+  detected, everything else is `415`. Route regex charsets make traversal
+  unmatchable (attempts fall through to the SPA fallback).
+- Per-namespace limits: `avatar` = 5 MB max (`413`), 5 uploads / 2 h /
+  account (`429` + `Retry-After`), counted on success. Re-upload replaces all
+  stored variants for the key.
+- Served with detected `Content-Type`, `X-Content-Type-Options: nosniff`,
+  `Cache-Control: public, max-age=3600`.
+
+## Drivers`src/drivers/`: `LLMDriver` interface (`listModels`, `chat`, `chatStream`),
 `DriverRegistry` with global priority
 `ollama → mistral → puppeteer-openai (stub) → deepseek → anthropic → openai`.
 Models are addressed as `"driver:model"` (split on the first `:`).

docs/FRONTEND.md

@@ -39,7 +39,8 @@ read-only `SharePage` (no auth), everything else renders the authenticated app.
   share button), message list (`Markdown` for assistant, emerald bubble for
   user), rounded composer (Enter to send, Shift+Enter for newline).
 - `dialogs.tsx` — `ConvEditDialog` (title + topic), `ShareModal` (public link,
-  copy, unshare), `SettingsModal` (display name, avatar URL, theme).
+  copy, unshare), `SettingsModal` (display name, avatar upload box with
+  drag & drop, avatar URL, theme).
 - `AdminPanel.tsx` — No-KYC account management: create (key shown once),
   regenerate (revokes sessions), edit, delete with confirm.
 - `SharePage.tsx` — public read-only view, fetches `/api/share/:id` unauthenticated.
@@ -52,3 +53,12 @@ Tailwind `darkMode: "class"`. `applyTheme()` in `App.tsx` toggles the `dark`
 class from the account theme (`auto` follows `prefers-color-scheme` with a
 live media-query listener). Accent: emerald; shapes: `rounded-2xl/3xl`
 everywhere; every surface needs a `dark:` variant. UI text is English only.
+
+## Mobile
+
+Below the `md` breakpoint the sidebar becomes a slide-in drawer (backdrop tap
+or swipe-left closes it, hamburger in the chat header opens it). Modals render
+as bottom sheets with a drag handle — pull down past the threshold to dismiss
+(tap backdrop or Escape works too). Composer respects
+`env(safe-area-inset-bottom)`. No separate mobile codebase: same components,
+responsive Tailwind classes + minimal touch handlers.

docs/OPERATIONS.md

@@ -10,6 +10,7 @@ Copy `.env.example` to `.env`. Full list:
 | `APP_PASSWORD` | *(required)* | **admin** access key — generate with `openssl rand -base64 24` |
 | `SESSION_TTL_HOURS` | `720` | Bearer session lifetime (30 days) |
 | `DATA_DIR` | `./data` | holds `kisassistant.db` (SQLite) |
+| `CDN_DIR` | `./cdn` | local file CDN storage (avatars; NixOS: under state dir) |
 | `WIKI_URL` | `https://git.kisakay.com/k/chat/wiki` | remote docs wiki — `GET /wiki` redirects (302) there |
 | `RATE_LIMIT_MAX` / `RATE_LIMIT_WINDOW_MIN` | `5` / `10` | login rate limit per IP |
 | `OLLAMA_HOST` / `OLLAMA_ENABLED` | `http://10.66.66.4:11434` / `true` | local-model driver |
@@ -35,11 +36,25 @@ unshare. See `AGENTS.md`.
 1. Log in as `admin` with the `APP_PASSWORD` key.
 2. Open **Accounts** → *New account* → username (+ display name).
 3. Copy the one-time `ka_…` key and hand it to the owner (chat, QR code, …).
-4. Users set their display name, avatar URL (upload e.g. to `catbox.moe`, paste
-   the direct link) and theme in the profile settings.
+4. Users set their display name, avatar (upload box in profile settings, or a
+   remote URL e.g. from `catbox.moe`) and theme in the profile settings.
 5. Rotate a compromised key with the regenerate button (old sessions die);
    delete removes the account with all its chats and shares.
 
+## Local file CDN (avatars)
+
+`PUT /cdn/<ns>/<key>` (Bearer) / `GET /cdn/<ns>/<key>.<ext>` (public), e.g.
+`/cdn/avatar/<account-id>.png`. Namespaces live in `CDN_NAMESPACES`
+(`src/cdn.ts`) — add one to extend (future usage).
+
+- Allowed types **only** `jpg`/`png`/`webp`, verified by **magic bytes**, never
+  by extension (client filename is ignored; the stored extension comes from
+  detection). Everything else → `415`, unknown namespace/ext → `404`.
+- `avatar` rules: 5 MB max (`413` above), **5 uploads max per 2 h per account**
+  (`429` + `Retry-After`), ownership enforced (own id, or admin).
+- Served with fixed `Content-Type`, `nosniff`, `Cache-Control: public,
+  max-age=3600`. No listing, no traversal (strict charsets + SPA fallback).
+
 ## NixOS deployment (`chat.kisakay.com`)
 
 `flake.nix` exposes `packages.<system>.default` (backend + prebuilt frontend)

flake.lock

@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1789785513,
+        "narHash": "sha256-B44WL6h0XoLjJ41bUPJk0X5SDinLCII//6EcBLXKiJ0=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "20b1ddd1aa5ace70c9468305030aa4f9ef79671b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -5,19 +5,47 @@
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
   };
 
-  outputs = { self, nixpkgs }: {
+  outputs = { self, nixpkgs }:
+    let lib = nixpkgs.lib; in {
     nixosModules.default = import ./module.nix;
     packages.x86_64-linux.default =
       let
         pkgs = nixpkgs.legacyPackages.x86_64-linux;
-        # Frontend: built offline from the npm lockfile. If the build fails
-        # with a hash mismatch, replace npmDepsHash with the suggested one.
-        frontend = pkgs.buildNpmPackage {
-          pname = "kisassistant-frontend";
         version = "0.2.0";
+
+        # Frontend: two-phase bun build.
+        # Phase 1 (fixed-output, has network): populate node_modules from
+        # frontend/bun.lock. If the build fails with a hash mismatch, paste
+        # the "got: sha256-…" value into bunDepsHash below.
+        bunDeps = pkgs.stdenv.mkDerivation {
+          pname = "kisassistant-frontend-bun-deps";
+          inherit version;
           src = ./frontend;
-          npmDepsHash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
-          npmBuildScript = "build";
+          nativeBuildInputs = [ pkgs.bun ];
+          buildPhase = ''
+            export HOME=$TMPDIR
+            export BUN_INSTALL_CACHE_DIR=$TMPDIR/bun-cache
+            bun install --frozen-lockfile --ignore-scripts
+          '';
+          installPhase = ''
+            cp -r node_modules $out
+          '';
+          outputHashAlgo = "sha256";
+          outputHashMode = "recursive";
+          outputHash = "sha256-0AhK5sK0FmqxTb1kedUDPH9aOiYKN7z1jWQVFsnb1hs=";
+        };
+
+        # Phase 2 (offline): vite build against the pre-fetched node_modules.
+        frontend = pkgs.stdenv.mkDerivation {
+          pname = "kisassistant-frontend";
+          inherit version;
+          src = ./frontend;
+          nativeBuildInputs = [ pkgs.bun ];
+          buildPhase = ''
+            export HOME=$TMPDIR
+            ln -s ${bunDeps} node_modules
+            bun run build
+          '';
           installPhase = ''
             mkdir -p $out
             cp -r dist/* $out/
@@ -25,7 +53,7 @@
         };
       in pkgs.stdenv.mkDerivation {
         pname = "kisassistant";
-        version = "0.2.0";
+        inherit version;
         src = ./.;
         nativeBuildInputs = [ pkgs.bun ];
         buildPhase = ''

frontend/src/App.tsx

@@ -36,6 +36,7 @@ export function App() {
   const [streaming, setStreaming] = useState("");
   const [sending, setSending] = useState(false);
   const [sidebarCollapsed, setSidebarCollapsed] = useState(false);
+  const [mobileNav, setMobileNav] = useState(false);
   const [editConv, setEditConv] = useState<Conversation | null>(null);
   const [shareConv, setShareConv] = useState<Conversation | null>(null);
   const [deleteConv, setDeleteConv] = useState<Conversation | null>(null);
@@ -191,15 +192,17 @@ export function App() {
         activeId={activeId}
         collapsed={sidebarCollapsed}
         onToggle={() => setSidebarCollapsed(true)}
-        onNew={newChat}
-        onSelect={setActiveId}
+        onNew={() => { newChat(); setMobileNav(false); }}
+        onSelect={(id) => { setActiveId(id); setMobileNav(false); }}
         onRename={setEditConv}
         onTopic={setEditConv}
         onShare={setShareConv}
         onDelete={setDeleteConv}
-        onOpenSettings={() => setSettingsOpen(true)}
-        onOpenAdmin={() => setAdminOpen(true)}
+        onOpenSettings={() => { setSettingsOpen(true); setMobileNav(false); }}
+        onOpenAdmin={() => { setAdminOpen(true); setMobileNav(false); }}
         onLogout={logout}
+        mobileOpen={mobileNav}
+        onCloseMobile={() => setMobileNav(false)}
       />
       <Chat
         user={user}
@@ -214,6 +217,7 @@ export function App() {
         onShare={() => active && setShareConv(active)}
         sidebarCollapsed={sidebarCollapsed}
         onExpandSidebar={() => setSidebarCollapsed(false)}
+        onOpenNav={() => setMobileNav(true)}
       />
 
       <ConvEditDialog

frontend/src/components/Chat.tsx

@@ -1,5 +1,5 @@
 import { useEffect, useRef, useState } from "react";
-import { BookOpen, Bot, Cpu, PanelLeftOpen, SendHorizontal, Share2, User as UserIcon } from "lucide-react";
+import { BookOpen, Bot, Cpu, Menu, PanelLeftOpen, SendHorizontal, Share2, User as UserIcon } from "lucide-react";
 import type { ChatMessage, Conversation, DriverModel, User } from "../lib/types.ts";
 import { Avatar, IconButton, LOGO_URL, Logo, Picker, type PickerGroup, Spinner } from "./ui.tsx";
 import { Markdown } from "./Markdown.tsx";
@@ -42,6 +42,7 @@ export function Chat({
   onShare,
   sidebarCollapsed,
   onExpandSidebar,
+  onOpenNav,
 }: {
   user: User;
   conv: Conversation | null;
@@ -55,6 +56,7 @@ export function Chat({
   onShare: () => void;
   sidebarCollapsed: boolean;
   onExpandSidebar: () => void;
+  onOpenNav: () => void;
 }) {
   const [draft, setDraft] = useState("");
   const boxRef = useRef<HTMLDivElement>(null);
@@ -95,10 +97,15 @@ export function Chat({
   return (
     <div className="flex h-full min-w-0 flex-1 flex-col">
       <header className="flex items-center gap-2 border-b border-stone-200/70 px-4 py-2.5 backdrop-blur dark:border-zinc-800">
+        <IconButton title="Open chats" onClick={onOpenNav} className="md:hidden">
+          <Menu size={18} />
+        </IconButton>
         {sidebarCollapsed && (
+          <span className="hidden md:inline">
             <IconButton title="Expand sidebar" onClick={onExpandSidebar}>
               <PanelLeftOpen size={18} />
             </IconButton>
+          </span>
         )}
         <span className="hidden items-center gap-2 font-semibold sm:flex">
           <Logo size={24} className="rounded-lg" />
@@ -154,7 +161,7 @@ export function Chat({
         </div>
       </div>
 
-      <div className="px-4 pb-2 sm:px-8">
+      <div className="px-4 pb-[max(0.5rem,env(safe-area-inset-bottom))] sm:px-8">
         <form onSubmit={submit} className="mx-auto flex w-full max-w-3xl items-end gap-2 rounded-[1.75rem] border border-stone-200 bg-white p-2 pl-5 shadow-lg dark:border-zinc-700 dark:bg-zinc-900">
           <textarea
             ref={taRef}

frontend/src/components/Sidebar.tsx

@@ -1,4 +1,4 @@
-import { useState } from "react";
+import { useRef, useState } from "react";
 import {
   MessageSquarePlus,
   MoreVertical,
@@ -9,6 +9,7 @@ import {
   Tag,
   Trash2,
   Users,
+  X,
 } from "lucide-react";
 import type { Conversation, User } from "../lib/types.ts";
 import { Avatar, Button, ContextMenu, IconButton } from "./ui.tsx";
@@ -35,6 +36,8 @@ export function Sidebar({
   onOpenSettings,
   onOpenAdmin,
   onLogout,
+  mobileOpen,
+  onCloseMobile,
 }: {
   user: User;
   convs: Conversation[];
@@ -50,8 +53,11 @@ export function Sidebar({
   onOpenSettings: () => void;
   onOpenAdmin: () => void;
   onLogout: () => void;
+  mobileOpen: boolean;
+  onCloseMobile: () => void;
 }) {
   const [menu, setMenu] = useState<MenuState | null>(null);
+  const touchX = useRef<number | null>(null);
 
   function openMenu(e: React.MouseEvent, conv: Conversation) {
     e.preventDefault();
@@ -59,18 +65,40 @@ export function Sidebar({
     setMenu({ x: e.clientX, y: e.clientY, conv });
   }
 
-  if (collapsed) return null;
+  if (collapsed && !mobileOpen) return null;
 
   return (
-    <aside className="flex h-full w-72 shrink-0 flex-col gap-2 border-r border-stone-200/70 bg-white/70 p-3 backdrop-blur dark:border-zinc-800 dark:bg-zinc-900/70">
+    <>
+      {mobileOpen && (
+        <div className="fixed inset-0 z-30 bg-black/40 md:hidden" onClick={onCloseMobile} aria-hidden="true" />
+      )}
+      <aside
+        onTouchStart={(e) => { touchX.current = e.touches[0]!.clientX; }}
+        onTouchEnd={(e) => {
+          if (touchX.current === null) return;
+          const dx = e.changedTouches[0]!.clientX - touchX.current;
+          touchX.current = null;
+          if (dx < -60) onCloseMobile(); // swipe left closes the drawer
+        }}
+        className={cn(
+          "fixed inset-y-0 left-0 z-40 flex h-full w-72 shrink-0 flex-col gap-2 border-r border-stone-200 bg-white p-3 shadow-2xl transition-transform duration-200",
+          "md:static md:z-auto md:shadow-none dark:border-zinc-800 dark:bg-zinc-900 md:dark:bg-zinc-900/70 md:bg-white/70 md:backdrop-blur",
+          mobileOpen ? "translate-x-0" : "-translate-x-full",
+          "md:translate-x-0",
+          collapsed && "md:hidden",
+        )}
+      >
         <div className="flex items-center gap-1">
           <Button variant="secondary" size="sm" className="flex-1" onClick={onNew}>
             <MessageSquarePlus size={16} />
             New chat
           </Button>
-        <IconButton title="Collapse sidebar" onClick={onToggle}>
+          <IconButton title="Collapse sidebar" onClick={onToggle} className="hidden md:inline-flex">
             <PanelLeftClose size={18} />
           </IconButton>
+          <IconButton title="Close chats" onClick={onCloseMobile} className="md:hidden">
+            <X size={18} />
+          </IconButton>
         </div>
 
       <div className="flex-1 space-y-1 overflow-y-auto py-1">
@@ -148,5 +176,6 @@ export function Sidebar({
         </div>
       </div>
       </aside>
+    </>
   );
 }

frontend/src/components/dialogs.tsx

@@ -1,6 +1,7 @@
-import { useEffect, useState } from "react";
-import { Globe, Link2, Pencil, Settings2, Tag, Unplug } from "lucide-react";
+import { useEffect, useRef, useState } from "react";
+import { Globe, ImagePlus, Link2, Pencil, Settings2, Tag, Unplug } from "lucide-react";
 import { api } from "../lib/api.ts";
+import { cn } from "../lib/cn.ts";
 import type { Conversation, User } from "../lib/types.ts";
 import { Avatar, Button, CopyButton, Field, Input, Modal, Picker, Spinner } from "./ui.tsx";
 
@@ -130,6 +131,10 @@ export function SettingsModal({
   const [theme, setTheme] = useState("auto");
   const [busy, setBusy] = useState(false);
   const [error, setError] = useState("");
+  const [uploading, setUploading] = useState(false);
+  const [uploadError, setUploadError] = useState("");
+  const [dragOver, setDragOver] = useState(false);
+  const fileRef = useRef<HTMLInputElement>(null);
 
   useEffect(() => {
     if (user) {
@@ -137,9 +142,32 @@ export function SettingsModal({
       setAvatarUrl(user.avatarUrl);
       setTheme(user.theme);
       setError("");
+      setUploadError("");
     }
   }, [user]);
 
+  async function uploadFile(f: File) {
+    if (!user) return;
+    if (f.size > 5 * 1024 * 1024) {
+      setUploadError("File too large (max 5MB).");
+      return;
+    }
+    if (!/^image\/(jpeg|png|webp)$/.test(f.type)) {
+      setUploadError("Only jpg, png or webp images are accepted.");
+      return;
+    }
+    setUploading(true);
+    setUploadError("");
+    try {
+      const res = await api.uploadAvatar(user.id, f);
+      setAvatarUrl(res.url); // applied when you press Save
+    } catch (err) {
+      setUploadError(err instanceof Error ? err.message : "Upload failed");
+    } finally {
+      setUploading(false);
+    }
+  }
+
   async function save(e: React.FormEvent) {
     e.preventDefault();
     if (!user || busy) return;
@@ -161,7 +189,54 @@ export function SettingsModal({
       <form onSubmit={save} className="space-y-4">
         <div className="flex items-center gap-3">
           <Avatar name={displayName || "?"} url={avatarUrl || undefined} size={52} />
-          <p className="text-sm opacity-60">@{user?.username}</p>
+          <div className="min-w-0 flex-1">
+            <p className="truncate text-sm font-medium">{displayName || "…"}</p>
+            <p className="truncate text-xs opacity-60">@{user?.username}</p>
+          </div>
+        </div>
+        <div>
+          <span className="mb-1.5 block text-sm font-medium opacity-80">Avatar upload</span>
+          <div
+            role="button"
+            tabIndex={0}
+            aria-label="Upload avatar"
+            onClick={() => fileRef.current?.click()}
+            onKeyDown={(e) => e.key === "Enter" && fileRef.current?.click()}
+            onDragOver={(e) => { e.preventDefault(); setDragOver(true); }}
+            onDragLeave={() => setDragOver(false)}
+            onDrop={(e) => {
+              e.preventDefault();
+              setDragOver(false);
+              const f = e.dataTransfer.files?.[0];
+              if (f) uploadFile(f);
+            }}
+            className={cn(
+              "flex cursor-pointer items-center gap-3 rounded-3xl border-2 border-dashed px-4 py-3.5 transition",
+              dragOver
+                ? "border-emerald-500 bg-emerald-500/10"
+                : "border-stone-200 hover:border-emerald-500/60 hover:bg-stone-50 dark:border-zinc-700 dark:hover:bg-zinc-800/60",
+            )}
+          >
+            <span className="grid h-10 w-10 shrink-0 place-items-center rounded-full bg-emerald-600/10 text-emerald-600 dark:text-emerald-400">
+              {uploading ? <Spinner size={17} /> : <ImagePlus size={17} />}
+            </span>
+            <span className="min-w-0 flex-1 text-sm">
+              <span className="block font-medium">{uploading ? "Uploading…" : dragOver ? "Drop it!" : "Drop an image or click to upload"}</span>
+              <span className="block text-xs opacity-60">jpg · png · webp — max 5MB — 5 changes per 2h</span>
+            </span>
+          </div>
+          <input
+            ref={fileRef}
+            type="file"
+            accept="image/jpeg,image/png,image/webp"
+            className="hidden"
+            onChange={(e) => {
+              const f = e.target.files?.[0];
+              if (f) uploadFile(f);
+              e.target.value = "";
+            }}
+          />
+          {uploadError && <p className="mt-1.5 text-sm text-red-600 dark:text-red-400">{uploadError}</p>}
         </div>
         <Field label="Display name">
           <Input value={displayName} onChange={(e) => setDisplayName(e.target.value)} maxLength={60} required />

frontend/src/components/ui.tsx

@@ -256,17 +256,45 @@ export function Modal({
     return () => window.removeEventListener("keydown", h);
   }, [open, onClose]);
 
+  // Bottom-sheet drag state (mobile): pull the handle down to dismiss.
+  const [dragY, setDragY] = useState(0);
+  const dragStart = useRef<number | null>(null);
+  useEffect(() => {
+    if (!open) {
+      setDragY(0);
+      dragStart.current = null;
+    }
+  }, [open ]);
+
   if (!open) return null;
   const Icon = icon;
   return (
-    <div className="fixed inset-0 z-50 flex items-center justify-center p-4" role="dialog" aria-modal="true">
+    <div className="fixed inset-0 z-50 flex items-end justify-center sm:items-center sm:p-4" role="dialog" aria-modal="true">
       <div className="absolute inset-0 bg-black/50 backdrop-blur-sm" onClick={onClose} />
       <div
         className={cn(
-          "relative max-h-[85vh] w-full overflow-y-auto rounded-3xl border border-stone-200 bg-white p-6 shadow-2xl dark:border-zinc-700 dark:bg-zinc-900",
-          wide ? "max-w-2xl" : "max-w-md",
+          "relative max-h-[92vh] w-full overflow-y-auto rounded-b-none rounded-t-[1.75rem] border border-stone-200 bg-white p-6 pt-3 shadow-2xl sm:max-h-[85vh] sm:rounded-3xl sm:pt-6 dark:border-zinc-700 dark:bg-zinc-900",
+          wide ? "sm:max-w-2xl" : "sm:max-w-md",
         )}
+        style={dragY > 0 ? { transform: `translateY(${dragY}px)` } : undefined}
       >
+        {/* drag handle — mobile only */}
+        <div
+          className="sticky top-0 z-10 -mx-6 px-6 pb-3 pt-1 sm:hidden"
+          onTouchStart={(e) => { dragStart.current = e.touches[0]!.clientY; }}
+          onTouchMove={(e) => {
+            if (dragStart.current === null) return;
+            const dy = e.touches[0]!.clientY - dragStart.current;
+            setDragY(dy > 0 ? dy : 0);
+          }}
+          onTouchEnd={() => {
+            if (dragY > 110) onClose(); // snap shut past threshold…
+            setDragY(0); // …otherwise snap back
+            dragStart.current = null;
+          }}
+        >
+          <div className="mx-auto h-1.5 w-12 rounded-full bg-stone-300 dark:bg-zinc-600" />
+        </div>
         <div className="mb-4 flex items-center gap-2.5">
           {Icon && (
             <span className="grid h-9 w-9 place-items-center rounded-full bg-emerald-600/10 text-emerald-600 dark:text-emerald-400">
@@ -339,11 +367,14 @@ export function ContextMenu({ x, y, items, onClose }: { x: number; y: number; it
     return () => window.removeEventListener("keydown", h);
   }, [x, y, onClose]);
 
-  return (
+  // Rendered in a portal: the sidebar's backdrop-blur would otherwise turn
+  // into a containing block, breaking the fullscreen overlay and offsetting
+  // the menu (text showing through / misplaced over the composer).
+  return createPortal(
     <div className="fixed inset-0 z-50" onClick={onClose} onContextMenu={(e) => { e.preventDefault(); onClose(); }}>
       <div
         ref={ref}
-        className="absolute w-52 overflow-hidden rounded-2xl border border-stone-200 bg-white p-1.5 shadow-xl dark:border-zinc-700 dark:bg-zinc-900"
+        className="fixed z-50 w-52 overflow-hidden rounded-2xl border border-stone-200 bg-white p-1.5 shadow-2xl dark:border-zinc-700 dark:bg-zinc-900"
         style={{ left: pos.x, top: pos.y }}
         onClick={(e) => e.stopPropagation()}
       >
@@ -363,7 +394,8 @@ export function ContextMenu({ x, y, items, onClose }: { x: number; y: number; it
           </button>
         ))}
       </div>
-    </div>
+    </div>,
+    document.body,
   );
 }
 

frontend/src/lib/api.ts

@@ -73,6 +73,23 @@ export const api = {
 
   models: () => req<{ models: DriverModel[] }>("/api/models"),
 
+  /** Avatar upload to the local CDN. Returns the public /cdn/… URL. */
+  uploadAvatar: async (userId: string, file: File): Promise<{ url: string }> => {
+    const res = await fetch(`/cdn/avatar/${userId}`, {
+      method: "PUT",
+      headers: { Authorization: `Bearer ${getToken()}`, "Content-Type": file.type || "application/octet-stream" },
+      body: file,
+    });
+    if (res.status === 401) {
+      clearToken();
+      window.location.reload();
+      throw new ApiError(401, "Session expired.");
+    }
+    const data = (await res.json().catch(() => ({}))) as { error?: string; url?: string };
+    if (!res.ok) throw new ApiError(res.status, data.error || `Upload failed (${res.status})`);
+    return { url: data.url! };
+  },
+
   /** Streaming chat. Calls onToken per token; resolves with the full text. */
   chatStream: async (
     args: { model: string; messages: ChatMessage[]; conversationId?: string },

module.nix

@@ -48,6 +48,7 @@ in {
         PORT = toString cfg.port;
         HOST = cfg.host;
         DATA_DIR = "${cfg.dataDir}/data";
+        CDN_DIR = "${cfg.dataDir}/cdn";
         OLLAMA_HOST = cfg.ollamaHost;
       } // cfg.extraEnv;
       serviceConfig = {

src/cdn.ts

@@ -0,0 +1,133 @@
+import { mkdir } from "node:fs/promises";
+import { join } from "node:path";
+import { config } from "./config.ts";
+
+// --- local file CDN -----------------------------------------------
+// Generic, future-proof layout:
+//
+//   PUT /cdn/<ns>/<key>          (auth)   -> { url: "/cdn/<ns>/<key>.<ext>" }
+//   GET /cdn/<ns>/<key>.<ext>    (public)
+//
+// <ns> is a registered namespace (see CDN_NAMESPACES — `avatar` today,
+// more tomorrow). <key> is namespaced client-chosen id ([A-Za-z0-9_-]).
+// The stored extension ALWAYS comes from magic-byte detection, never from
+// the client. Everything else is systematically blacklisted.
+
+export type ImageExt = "jpg" | "png" | "webp";
+
+export interface CdnNamespace {
+  maxBytes: number;
+  windowMs: number;
+  maxUploads: number;
+}
+
+export const CDN_NAMESPACES: Record<string, CdnNamespace> = {
+  // Avatar rules (spec): 5 MB max, 5 changes max per 2 h per account.
+  avatar: { maxBytes: 5 * 1024 * 1024, windowMs: 2 * 3600_000, maxUploads: 5 },
+};
+
+export const CDN_EXTS: ImageExt[] = ["jpg", "png", "webp"];
+
+const CDN_MIME: Record<ImageExt, string> = {
+  jpg: "image/jpeg",
+  png: "image/png",
+  webp: "image/webp",
+};
+
+export function cdnMime(ext: ImageExt): string {
+  return CDN_MIME[ext];
+}
+
+export function validNamespace(ns: string): boolean {
+  return /^[a-z0-9]{1,16}$/.test(ns) && ns in CDN_NAMESPACES;
+}
+
+export function validKey(key: string): boolean {
+  return /^[A-Za-z0-9_-]{1,64}$/.test(key);
+}
+
+export function validExt(ext: string): ext is ImageExt {
+  return (CDN_EXTS as string[]).includes(ext);
+}
+
+function cdnDir(): string {
+  return config.cdnDir;
+}
+
+export function cdnPath(ns: string, key: string, ext: ImageExt): string {
+  return join(cdnDir(), ns, `${key}.${ext}`);
+}
+
+export async function cdnFile(ns: string, key: string, ext: ImageExt): Promise<{ path: string; exists: boolean }> {
+  const path = cdnPath(ns, key, ext);
+  return { path, exists: await Bun.file(path).exists() };
+}
+
+/**
+ * Detect the real image type from magic bytes (first bytes of the file).
+ * Extension alone is NEVER trusted.
+ *   JPEG: FF D8 FF
+ *   PNG:  89 50 4E 47 0D 0A 1A 0A
+ *   WEBP: "RIFF"...."WEBP" (bytes 0-3 and 8-11)
+ */
+export function detectImageType(buf: Uint8Array): ImageExt | null {
+  if (buf.length >= 3 && buf[0] === 0xff && buf[1] === 0xd8 && buf[2] === 0xff) return "jpg";
+  if (
+    buf.length >= 8 &&
+    buf[0] === 0x89 && buf[1] === 0x50 && buf[2] === 0x4e && buf[3] === 0x47 &&
+    buf[4] === 0x0d && buf[5] === 0x0a && buf[6] === 0x1a && buf[7] === 0x0a
+  ) {
+    return "png";
+  }
+  if (
+    buf.length >= 12 &&
+    buf[0] === 0x52 && buf[1] === 0x49 && buf[2] === 0x46 && buf[3] === 0x46 && // RIFF
+    buf[8] === 0x57 && buf[9] === 0x45 && buf[10] === 0x42 && buf[11] === 0x50 // WEBP
+  ) {
+    return "webp";
+  }
+  return null;
+}
+
+/** Remove every stored variant for a key (used before replacing an avatar). */
+export async function removeCdnVariants(ns: string, key: string): Promise<void> {
+  const { unlink } = await import("node:fs/promises");
+  for (const ext of CDN_EXTS) {
+    try {
+      await unlink(cdnPath(ns, key, ext));
+    } catch {
+      // missing — fine
+    }
+  }
+}
+
+export async function writeCdnFile(ns: string, key: string, ext: ImageExt, data: Uint8Array): Promise<string> {
+  await mkdir(join(cdnDir(), ns), { recursive: true });
+  await removeCdnVariants(ns, key);
+  await Bun.write(cdnPath(ns, key, ext), data);
+  return `/cdn/${ns}/${key}.${ext}`;
+}
+
+// --- per-account upload rate limiter (sliding window) ---
+
+const uploads = new Map<string, number[]>();
+
+export function uploadAllowed(userId: string, ns: string): { ok: boolean; retryAfterSec: number } {
+  const cfg = CDN_NAMESPACES[ns]!;
+  const now = Date.now();
+  const k = `${ns}:${userId}`;
+  const list = (uploads.get(k) ?? []).filter((t) => t > now - cfg.windowMs);
+  uploads.set(k, list);
+  if (list.length >= cfg.maxUploads) {
+    const retryAfterSec = Math.ceil((list[0]! + cfg.windowMs - now) / 1000);
+    return { ok: false, retryAfterSec: Math.max(retryAfterSec, 1) };
+  }
+  return { ok: true, retryAfterSec: 0 };
+}
+
+export function recordUpload(userId: string, ns: string): void {
+  const k = `${ns}:${userId}`;
+  const list = uploads.get(k) ?? [];
+  list.push(Date.now());
+  uploads.set(k, list);
+}

src/config.ts

@@ -44,6 +44,11 @@ export const config = {
 
   // Per-driver debug logging to stdout ([driver:name] lines).
   driverDebug: envBool("DRIVER_DEBUG", true),
+
+  // Local file CDN (avatars today, more namespaces tomorrow).
+  // Dev default is a folder next to the codebase; NixOS module points it
+  // under the service state dir.
+  cdnDir: env("CDN_DIR", "./cdn"),
 };
 
 export function assertConfig(): void {

src/index.ts

@@ -37,6 +37,18 @@ import {
 } from "./db.ts";
 import type { ChatMessage } from "./drivers/types.ts";
 import { DriverRegistry } from "./drivers/registry.ts";
+import {
+  CDN_NAMESPACES,
+  cdnFile,
+  cdnMime,
+  detectImageType,
+  recordUpload,
+  uploadAllowed,
+  validExt,
+  validKey,
+  validNamespace,
+  writeCdnFile,
+} from "./cdn.ts";
 
 assertConfig();
 const registry = new DriverRegistry();
@@ -92,6 +104,8 @@ function validAvatar(v: unknown): string | null {
   if (typeof v !== "string") return null;
   const t = v.trim();
   if (t.length > 2048) return null;
+  // Local CDN avatar (uploaded via PUT /cdn/…) or remote http(s) URL.
+  if (/^\/cdn\/[a-z0-9]{1,16}\/[A-Za-z0-9_-]{1,64}\.(jpg|png|webp)$/.test(t)) return t;
   if (!/^https?:\/\//i.test(t)) return null;
   return t;
 }
@@ -142,6 +156,66 @@ const server = Bun.serve({
       return Response.redirect(config.wikiUrl, 302);
     }
 
+    // --- public: local file CDN (avatars today, more namespaces tomorrow) ---
+    // GET /cdn/<ns>/<key>.<ext> — serves stored images, nothing else.
+    const cdnGet = path.match(/^\/cdn\/([a-z0-9]{1,16})\/([A-Za-z0-9_-]{1,64})\.([a-z0-9]{1,8})$/);
+    if (cdnGet && req.method === "GET") {
+      const [, ns, key, ext] = cdnGet as [string, string, string, string];
+      if (!validNamespace(ns) || !validKey(key) || !validExt(ext)) {
+        return new Response("not found", { status: 404 });
+      }
+      const f = await cdnFile(ns, key, ext);
+      if (!f.exists) return new Response("not found", { status: 404 });
+      return new Response(Bun.file(f.path), {
+        headers: {
+          "Content-Type": cdnMime(ext),
+          "Cache-Control": "public, max-age=3600",
+          "X-Content-Type-Options": "nosniff",
+        },
+      });
+    }
+
+    // --- authed (non-/api/): CDN upload ---
+    // PUT /cdn/<ns>/<key> with the raw file bytes as body. The stored
+    // extension always comes from magic-byte detection, never the client.
+    const cdnPut = path.match(/^\/cdn\/([a-z0-9]{1,16})\/([A-Za-z0-9_-]{1,64})$/);
+    if (cdnPut && req.method === "PUT") {
+      const user = requireAuth(req);
+      if (!user) return json({ error: "unauthorized" }, 401);
+      const [, ns, key] = cdnPut as [string, string, string];
+      if (!validNamespace(ns) || !validKey(key)) return json({ error: "unknown namespace or key" }, 404);
+      const rules = CDN_NAMESPACES[ns]!;
+      // Avatar ownership: your own account id, unless admin.
+      if (ns === "avatar" && key !== user.id && !user.isAdmin) {
+        return json({ error: "forbidden" }, 403);
+      }
+      const declared = Number(req.headers.get("content-length") || "0");
+      const maxMb = (rules.maxBytes / (1024 * 1024)).toFixed(0);
+      if (declared > rules.maxBytes) return json({ error: `file too large (max ${maxMb}MB)` }, 413);
+      let buf: Uint8Array;
+      try {
+        buf = new Uint8Array(await req.arrayBuffer());
+      } catch {
+        return json({ error: "unreadable body" }, 400);
+      }
+      if (buf.length < 16) return json({ error: "empty file" }, 400);
+      if (buf.length > rules.maxBytes) return json({ error: `file too large (max ${maxMb}MB)` }, 413);
+      const ext = detectImageType(buf);
+      if (!ext) {
+        return json({ error: "unsupported file type: only jpg/png/webp images are accepted (verified by content, not extension)" }, 415);
+      }
+      const rl = uploadAllowed(user.id, ns);
+      if (!rl.ok) {
+        return new Response(
+          JSON.stringify({ error: `rate limited: ${rules.maxUploads} uploads per ${rules.windowMs / 3600_000}h`, retryAfterSec: rl.retryAfterSec }),
+          { status: 429, headers: { "Content-Type": "application/json", "Cache-Control": "no-store", "Retry-After": String(rl.retryAfterSec) } },
+        );
+      }
+      const url = await writeCdnFile(ns, key, ext, buf);
+      recordUpload(user.id, ns);
+      return json({ url }, 201);
+    }
+
     // --- auth: login (rate limited) ---
     if (path === "/api/auth/login" && req.method === "POST") {
       const ip = clientIp(req, server);