diff --git a/tests/test_build_user_content_pdf_marker.py b/tests/test_build_user_content_pdf_marker.py
new file mode 100644
index 0000000..9cc9166
--- /dev/null
+++ b/tests/test_build_user_content_pdf_marker.py
@@ -0,0 +1,57 @@
+"""Regression: build_user_content must strip the '[PDF content]:' wrapper with
+the prefix-safe helper, not str.lstrip(chars).
+
+The PDF-attach path at build_user_content used
+`_process_pdf(path).lstrip("\\n[PDF content]:")`, which treats the argument as a
+set of characters and keeps eating leading body characters (so a page that
+begins "Page 1 text]: to the board" lost its "P"/"to"). The other call sites
+were switched to `strip_pdf_content_marker` (str.removeprefix); this one wasn't.
+"""
+import os
+import tempfile
+
+import src.document_processor as dp
+import src.pdf_forms as pdf_forms
+import src.pdf_form_doc as pdf_form_doc
+
+
+class _FakeUploadHandler:
+    def is_image_file(self, name, mime):
+        return False
+
+    def is_audio_file(self, name, mime):
+        return False
+
+    def is_document_file(self, name, mime):
+        return True
+
+    def _inside_upload_dir(self, path):
+        return True
+
+
+def test_pdf_body_marker_stripped_without_eating_text(monkeypatch, tmp_path):
+    pdf_path = tmp_path / "doc.pdf"
+    pdf_path.write_bytes(b"%PDF-1.4 fake")
+
+    # Shape _process_pdf actually returns: marker, then a page-text marker, then body.
+    raw = "\n\n[PDF content]:\n\n[Page 1 text]:\nto the board, the agenda is set"
+    monkeypatch.setattr(dp, "_process_pdf", lambda path: raw)
+    monkeypatch.setattr(pdf_forms, "has_form_fields", lambda path: False)
+    monkeypatch.setattr(pdf_form_doc, "create_plain_pdf_document", lambda **kw: "doc-123")
+
+    resolved = {"fid1": {"path": str(pdf_path), "mime": "application/pdf", "name": "doc.pdf"}}
+    content = dp.build_user_content(
+        text="here is a pdf",
+        attachment_ids=["fid1"],
+        upload_dir=str(tmp_path),
+        upload_handler=_FakeUploadHandler(),
+        session_id="s1",
+        resolved_uploads=resolved,
+    )
+
+    body = content[0]["text"] if isinstance(content, list) else content
+    # The leading page text must survive intact.
+    assert "[Page 1 text]:" in body
+    assert "to the board, the agenda is set" in body
+    # The old lstrip(chars) corruption ate "[P" then "to" -> "age 1 text]: the board".
+    assert "age 1 text" not in body