diff --git a/README.md b/README.md
index 38ea526..a69d740 100644
--- a/README.md
+++ b/README.md
@@ -123,5 +123,5 @@ Each request creates a folder under `runs/<run_id>/` containing:
 -   `original.*` (your upload)
 -   `diagram.tex`
 -   `diagram.pdf` (if LaTeX compilation succeeded)
--   `preview.png` (if ImageMagick rendering succeeded)
+-   `diagram.png` (if ImageMagick rendering succeeded)
 -   `run.log.txt` (all logs: LLM + pdflatex + magick)
diff --git a/main.py b/main.py
index a3b90e2..8e3b2fa 100644
--- a/main.py
+++ b/main.py
@@ -448,7 +448,7 @@ def _compile_pdflatex(
 
 
 def _render_png_with_magick(
-    run_dir: Path, pdf_path: Path, run_logger: RunLogger, section_title: str, png_name: str = "preview.png"
+    run_dir: Path, pdf_path: Path, run_logger: RunLogger, section_title: str, png_name: str = "diagram.png"
 ) -> Optional[Path]:
     png_path = run_dir / png_name
 
@@ -551,7 +551,7 @@ def _compile_phase(
     allowed, reason, digest = _should_compile(run_dir, tex_text, cooldown_s=COMPILE_COOLDOWN_SECS)
 
     pdf_path_existing = run_dir / Path(tex_path.name).with_suffix(".pdf").name
-    png_path_existing = run_dir / "preview.png"
+    png_path_existing = run_dir / "diagram.png"
     svg_path_existing = run_dir / "diagram.svg"
 
     if not allowed:
@@ -857,11 +857,11 @@ async def get_run_result(request: Request, run_id: str, warn: str | None = None)
 
     tex_path = run_dir / "diagram.tex"
     pdf_path = run_dir / "diagram.pdf"
-    png_path = run_dir / "preview.png"
+    png_path = run_dir / "diagram.png"
     svg_path = run_dir / "diagram.svg"
 
     tex = tex_path.read_text(encoding="utf-8", errors="replace") if tex_path.exists() else ""
-    png_url = f"{BASE_PATH}/runs/{run_id}/{png_path.name}" if png_path.exists() else None
+    png_url = f"{BASE_PATH}/d/{run_id}/files/{png_path.name}" if png_path.exists() else None
 
     original_candidates = sorted(run_dir.glob("original.*"))
     original_path = original_candidates[0] if original_candidates else (run_dir / "original")
@@ -879,7 +879,7 @@ async def get_run_result(request: Request, run_id: str, warn: str | None = None)
     error_text = _read_run_error(run_dir) or None
 
     def file_url(name: str) -> str:
-        return f"{BASE_PATH}/runs/{run_id}/{name}"
+        return f"{BASE_PATH}/d/{run_id}/files/{name}"
 
     download_pdf_url = file_url(pdf_path.name) if pdf_path.exists() else file_url("diagram.pdf")
     download_svg_url = file_url(svg_path.name) if svg_path.exists() else file_url("diagram.svg")
@@ -905,7 +905,7 @@ async def get_run_result(request: Request, run_id: str, warn: str | None = None)
             "download_original_url": file_url(original_path.name),
             "download_tex_url": file_url(tex_path.name),
             "download_pdf_url": download_pdf_url,
-            "download_png_url": file_url("preview.png"),
+            "download_png_url": file_url("diagram.png"),
             "download_svg_url": download_svg_url,
             "error": error_text,
             "base_path": BASE_PATH,
@@ -1221,7 +1221,7 @@ async def delete_run(request: Request, run_id: str):
     return RedirectResponse(url=f"{BASE_PATH}/", status_code=303)
 
 
-@app.get("/runs/{run_id}/{filename}")
+@app.get("/d/{run_id}/files/{filename}")
 async def get_run_file(run_id: str, filename: str):
     path = _safe_join_run_file(run_id, filename)
     if path is None or not path.exists() or not path.is_file():
diff --git a/templates/edit.html b/templates/edit.html
index d852709..040b573 100644
--- a/templates/edit.html
+++ b/templates/edit.html
@@ -8,7 +8,7 @@
         <meta property="og:description" content="View and edit the LaTeX/TikZ code for diagram {{ run_id }}." />
         <meta property="og:type" content="website" />
         <meta property="og:url" content="{{ base_path }}/d/{{ run_id }}" />
-        <meta property="og:image" content="{{ base_path }}/d/{{ run_id }}/preview.png" />
+        <meta property="og:image" content="{{ base_path }}/d/{{ run_id }}/files/diagram.png" />
         <link rel="preconnect" href="https://fonts.googleapis.com" />
         <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
         <link