diff --git a/backend/main.py b/backend/main.py
index fb3fcc4..71422c2 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -735,6 +735,22 @@ FRONTEND_DIR = Path(__file__).resolve().parent.parent / "frontend"
 # Path safety helper
 # ---------------------------------------------------------------------------
 
+def _content_disposition(disposition: str, filename: str) -> str:
+    """Build a header-safe Content-Disposition value.
+
+    HTTP header values must be ASCII. Unicode filenames are sent per
+    RFC 5987 via ``filename*`` (percent-encoded UTF-8) with a pure-ASCII
+    ``filename`` fallback. This avoids a UnicodeDecodeError / HTTP 500 when
+    the filename contains accented characters (e.g. 'Bière blonde…pdf').
+    """
+    from urllib.parse import quote
+    ascii_name = "".join(c for c in filename if c.isascii() and (c.isalnum() or c in " _-.")).strip() or "file"
+    ext = Path(filename).suffix
+    if ext and not Path(ascii_name).suffix:
+        ascii_name = ascii_name + ext
+    return f"{disposition}; filename=\"{ascii_name}\"; filename*=UTF-8''{quote(filename)}"
+
+
 def _resolve_safe_path(vault_root: Path, relative_path: str) -> Path:
     """Resolve a relative path safely within the vault root.
 
@@ -2801,13 +2817,13 @@ async def api_pdf_stream(
                 "Content-Range": f"bytes {start}-{end}/{file_size}",
                 "Accept-Ranges": "bytes",
                 "Content-Length": str(chunk_size),
-                "Content-Disposition": f'inline; filename="{file_path.name}"',
+                "Content-Disposition": _content_disposition("inline", file_path.name),
             },
         )
 
     return FileResponse(str(file_path), media_type="application/pdf", headers={
         "Accept-Ranges": "bytes",
-        "Content-Disposition": f'inline; filename="{file_path.name}"'})
+        "Content-Disposition": _content_disposition("inline", file_path.name)})
 
 
 @app.get("/api/file/{vault_name}/pdf/info")
diff --git a/docs/ISSUES_TODOLIST.md b/docs/ISSUES_TODOLIST.md
index 10d92b2..14d7643 100644
--- a/docs/ISSUES_TODOLIST.md
+++ b/docs/ISSUES_TODOLIST.md
@@ -107,9 +107,8 @@ Avant de corriger quoi que ce soit, un agent IA doit :
 
 | # | Titre | Statut | Priorité | Scope | Assigné | Zone (fichier) | Cmd de repro | Correctif / Commit | Notes |
 |---|---|---|---|---|---|---|---|---|---|
-| *BUG-001* | L'ouverture des fichier PDF ne fonctionne pas et donne l'erreur Internal Server Error | 🔴 ouvert | P1 | fichier PDF | IA |  | 
-https://og.dracodev.net/api/file/Recettes/pdf/stream?path=98_Boite_Outils%2F98.2_Attachments%2FBi%C3%A8re%20blonde%20envoy%C3%A9%20par%20Desja.pdf| — | l'erreur se retrouve dans la section network de la console web et dans l'interface web lors du chargement d'un pdf |
-| *BUG-002* | l'ouverture d'un fichier .excalidraw ne fonctionne pas et affiche toujours Loading *Excalidraw…* | 🔴 ouvert | P1 | fichier .excalidaw  | IA | |  | — | test d'accès réaliser via cloudflare et réseau local démontre que ce problème est au 2 endroits |
+| *BUG-001* | L'ouverture des fichier PDF ne fonctionne pas et donne l'erreur Internal Server Error | 🟢 corrigé | P1 | fichier PDF | IA | `backend/main.py` | `GET /api/file/{vault}/pdf/stream?path=…(pdf à nom accentué)` | `backend/main.py` : Content-Disposition encodé RFC 5987 (helper `_content_disposition`) | 500 car nom Unicode brut dans l'en-tête → header invalide. Vérifié: stream 200 / Range 206 + test `tests/test_pdf_stream.py` |
+| *BUG-002* | l'ouverture d'un fichier .excalidraw ne fonctionne pas et affiche toujours Loading *Excalidraw…* | 🟢 corrigé | P1 | fichier .excalidraw | IA | `frontend/excalidraw-editor.html` | Ouvrir un fichier `.excalidraw` | `frontend/excalidraw-editor.html` : alias esm.sh supprimé (408 jotai) + React 19 cohérent + prop `excalidrawAPI` | 2 causes: 408 esm.sh sur `?alias` + prop legacy `excalidrawRef` inopérante en 0.18. Vérifié navigateur: Loading masqué + cycle save OK |
 |  | | | | | | | | | |
 
 ### TODOs techniques (améliorations / nouvelles tâches)
@@ -130,6 +129,7 @@ https://og.dracodev.net/api/file/Recettes/pdf/stream?path=98_Boite_Outils%2F98.2
 | Date | ID(s) traité(s) | Action | Fichiers modifiés | Résumé | Statut après |
 |---|---|---|---|---|---|
 | *(exemple)* 2026-06-15 | BUG-001 | Correction | `frontend/app.js` | Réécriture de `renderFile()` pour préserver le DOM dashboard | 🟢 corrigé (en attente vérif) |
+| 2026-09-09 | BUG-001, BUG-002 | Correction | `backend/main.py`, `frontend/excalidraw-editor.html`, `tests/test_pdf_stream.py` | BUG-001: Content-Disposition RFC 5987 (nom PDF accentué ne casse plus l'en-tête → plus de 500). BUG-002: suppression alias esm.sh (408 jotai) + React 19 cohérent + prop `excalidrawAPI` → Loading masqué, save OK. Vérifié: 534 tests backend verts + E2E navigateur. | 🟢 corrigé (en attente vérif utilisateur) |
 
 ---
 
diff --git a/frontend/excalidraw-editor.html b/frontend/excalidraw-editor.html
index 57eeaef..a9faddd 100644
--- a/frontend/excalidraw-editor.html
+++ b/frontend/excalidraw-editor.html
@@ -92,26 +92,20 @@
     <button id="btn-export-svg" title="Export SVG">📐 SVG</button>
   </div>
 
-  <!-- Import map: force ALL modules (Excalidraw + sub-deps) to use React 18.3.1 -->
-  <script type="importmap">
-  {
-    "imports": {
-      "react": "https://esm.sh/react@18.3.1",
-      "react-dom": "https://esm.sh/react-dom@18.3.1",
-      "react-dom/": "https://esm.sh/react-dom@18.3.1/"
-    }
-  }
-  </script>
-
-  <!-- Single module script -->
+  <!-- Excalidraw is loaded from esm.sh WITHOUT the `?alias=react:…` query.
+       The alias gets propagated by esm.sh to every transitive dependency; for
+       range-version deps (e.g. jotai@>=2.9.2) esm.sh then tries to rebuild the
+       range + alias variant and times out (HTTP 408) → the whole import fails →
+       the diagram stays stuck on "Loading Excalidraw…". Dropping the alias lets
+       esm.sh resolve a consistent React 19 (Excalidraw 0.18's default), which
+       loads reliably. -->
   <script type="module">
-    import React from "react";
-    import ReactDOM from "react-dom/client";
+    import React from "https://esm.sh/react@^19.2.0?target=es2022";
+    import { createRoot } from "https://esm.sh/react-dom@^19.2.0/client?target=es2022";
     import { decompressFromBase64 } from "https://esm.sh/lz-string@1.5.0";
-    import * as ExcalidrawLib from "https://esm.sh/@excalidraw/excalidraw@0.18.0?alias=react:react@18.3.1,react-dom:react-dom@18.3.1";
+    import * as ExcalidrawLib from "https://esm.sh/@excalidraw/excalidraw@0.18.0";
 
     window.React = React;
-    window.ReactDOM = ReactDOM;
     window.EXCALIDRAW_ASSET_PATH = "https://esm.sh/@excalidraw/excalidraw@0.18.0/dist/prod/";
     window.ExcalidrawLib = ExcalidrawLib;
 
@@ -186,7 +180,11 @@
     function App({ initialData, theme }) {
       const [appState, setAppState] = React.useState(null);
 
-      const excalidrawRef = React.useCallback((api) => {
+      // Excalidraw 0.18 exposes its imperative API through the `excalidrawAPI`
+      // prop, called with the API object once mounted (NOT the legacy
+      // `excalidrawRef` name). Without this the loading overlay never hides
+      // and save/export stay dead.
+      const onReady = React.useCallback((api) => {
         if (api) {
           excalidrawAPI = api;
           loadingEl.classList.add("hidden");
@@ -201,7 +199,7 @@
       }, []);
 
       return React.createElement(Excalidraw, {
-        excalidrawRef: excalidrawRef,
+        excalidrawAPI: onReady,
         initialData: initialData,
         onChange: onChange,
         theme: theme,
@@ -247,10 +245,10 @@
             setTheme(currentTheme);
 
             try {
-              if (typeof ReactDOM.createRoot !== "function") {
-                throw new Error("ReactDOM.createRoot is not available — check react-dom/client import");
+              if (typeof createRoot !== "function") {
+                throw new Error("createRoot is not available — check react-dom/client import");
               }
-              ReactDOM.createRoot(document.getElementById("root")).render(
+              createRoot(document.getElementById("root")).render(
                 React.createElement(App, {
                   initialData: initialData,
                   theme: currentTheme,
diff --git a/tests/test_pdf_stream.py b/tests/test_pdf_stream.py
new file mode 100644
index 0000000..86a6e71
--- /dev/null
+++ b/tests/test_pdf_stream.py
@@ -0,0 +1,62 @@
+# tests/test_pdf_stream.py — Regression tests for BUG-001 (PDF stream HTTP 500)
+#
+# BUG-001: opening a PDF whose filename contains accented characters
+# (e.g. "Bière blonde envoyé par Desja.pdf") returned HTTP 500 because the raw
+# Unicode name was injected into the Content-Disposition header, producing an
+# invalid (non-ASCII) header value. /pdf/info worked because it sets no
+# filename header.
+#
+# Fix: RFC 5987 header encoding (ASCII `filename` fallback + `filename*=UTF-8''…`).
+import os
+from pathlib import Path
+
+# Minimal valid PDF so pypdf/stream treats the bytes as a real PDF.
+MIN_PDF = (
+    b"%PDF-1.4\n"
+    b"1 0 obj<</Type/Catalog/Pages 2 0 R>>endobj\n"
+    b"2 0 obj<</Type/Pages/Kids[3 0 R]/Count 1>>endobj\n"
+    b"3 0 obj<</Type/Page/Parent 2 0 R/MediaBox[0 0 612 792]>>endobj\n"
+    b"xref\n0 4\n0000000000 65535 f \n"
+    b"trailer<</Size 4/Root 1 0 R>>\nstartxref\n0\n%%EOF\n"
+)
+
+
+def _create_pdf_with_unicode_name():
+    vault = Path(os.environ["VAULT_1_PATH"])
+    sub = vault / "98_Boite_Outils" / "98.2_Attachments"
+    sub.mkdir(parents=True, exist_ok=True)
+    pdf = sub / "Bière blonde envoyé par Desja.pdf"
+    pdf.write_bytes(MIN_PDF)
+    return "98_Boite_Outils/98.2_Attachments/Bière blonde envoyé par Desja.pdf"
+
+
+class TestPdfStreamUnicodeFilename:
+    def test_full_stream_ok(self, client):
+        rel = _create_pdf_with_unicode_name()
+        resp = client.get("/api/file/TestVault/pdf/stream", params={"path": rel})
+        assert resp.status_code == 200, resp.text
+        assert resp.headers["content-type"] == "application/pdf"
+        cd = resp.headers.get("content-disposition", "")
+        # Content-Disposition must be RFC 5987 encoded (ASCII-safe)
+        assert "filename*=UTF-8''" in cd, cd
+        # UTF-8 percent-encoded accented name present (é -> %C3%A8)
+        assert "%C3%A8re%20blonde" in cd
+
+    def test_range_request_ok(self, client):
+        rel = _create_pdf_with_unicode_name()
+        resp = client.get(
+            "/api/file/TestVault/pdf/stream",
+            params={"path": rel},
+            headers={"Range": "bytes=0-99"},
+        )
+        assert resp.status_code == 206
+        assert resp.headers.get("content-range", "").startswith("bytes 0-99/")
+
+    def test_disposition_ascii_safe(self, client):
+        rel = _create_pdf_with_unicode_name()
+        resp = client.get("/api/file/TestVault/pdf/stream", params={"path": rel})
+        cd = resp.headers.get("content-disposition", "")
+        # Every header field value must be ASCII-encodable (no UnicodeEncodeError)
+        cd.encode("ascii")
+        # ASCII fallback filename present
+        assert 'filename="' in cd