fix: stop deleting the signed contract when it is downloaded

backend/app/routers/pdf.py

@@ -5,7 +5,7 @@
 import logging
 
 from fastapi import (
-    APIRouter, BackgroundTasks, Depends, File,
+    APIRouter, Depends, File,
     Form, HTTPException, UploadFile, status,
 )
 from fastapi.responses import FileResponse
@@ -154,7 +154,6 @@ async def sign_pdf(
 async def download_signed(
     task_id: str,
     token: str,
-    background: BackgroundTasks,
     ss: StorageService = Depends(get_storage_service),
 ) -> FileResponse:
 
@@ -180,11 +179,11 @@ async def download_signed(
     if not path.is_file():
         _raise_http(SignedPdfNotReadyError())
 
-    background.add_task(
-        ss.remove_task,
-        task_id,
-    )
-
+    # The task dir is deliberately NOT removed after download. A signed
+    # internship agreement is a lasting record: the dashboard previews it, the
+    # coordinator may re-download it, and it is emailed to the candidate. The
+    # delete-after-download behaviour here came from this service's one-shot
+    # PDF-signing origins and destroyed contracts on first download.
     return FileResponse(
         path=str(path),
         media_type="application/pdf",

backend/tests/test_api.py

@@ -55,6 +55,50 @@ def test_missing_application_returns_404():
     assert client.get("/applications/9999").status_code == 404
 
 
+def _upload_and_sign() -> str:
+    """Upload a blank PDF, sign it, and return the download URL."""
+    doc = fitz.open()
+    doc.new_page()
+    pdf_buf = io.BytesIO()
+    doc.save(pdf_buf)
+    pdf_buf.seek(0)
+
+    upload = client.post(
+        "/pdf/upload",
+        files={"file": ("sample.pdf", pdf_buf, "application/pdf")},
+    )
+    assert upload.status_code == 201
+    task_id = upload.json()["task_id"]
+
+    img = Image.new("RGBA", (50, 20), (255, 0, 0, 255))
+    img_buf = io.BytesIO()
+    img.save(img_buf, format="PNG")
+    img_buf.seek(0)
+
+    signed = client.post(
+        "/pdf/sign",
+        data={"task_id": task_id, "page": 0, "x": 10, "y": 10, "w": 50, "h": 20},
+        files={"image": ("sig.png", img_buf, "image/png")},
+    )
+    assert signed.status_code == 200
+    return signed.json()["download_url"]
+
+
+def test_signed_contract_survives_download():
+    """Regression test: /pdf/download used to schedule remove_task() as a
+    background task, wiping the whole task directory the first time the file was
+    fetched. The dashboard opens that link automatically right after signing, so
+    a signed internship agreement — which is previewed, re-downloaded and
+    emailed to the candidate — was destroyed on first download. Downloading
+    twice must keep working.
+    """
+    download_url = _upload_and_sign()
+
+    assert client.get(download_url).status_code == 200
+    # The file must still be there for the preview / email / re-download paths.
+    assert client.get(download_url).status_code == 200
+
+
 def test_sign_pdf_download_url_is_reachable():
     """Regression test: /pdf/sign previously returned a download_url prefixed
     with settings.api_prefix ("/api/v1/pdf/download/..."), but routers are