diff --git a/pyrit/prompt_target/http_target/httpx_api_target.py b/pyrit/prompt_target/http_target/httpx_api_target.py
index bbf993928..393f947ba 100644
--- a/pyrit/prompt_target/http_target/httpx_api_target.py
+++ b/pyrit/prompt_target/http_target/httpx_api_target.py
@@ -105,6 +105,8 @@ async def send_prompt_async(self, *, message: Message) -> list[Message]:
             if isinstance(possible_path, str) and os.path.exists(possible_path):
                 logger.info(f"HTTPXApiTarget: auto-using file_path from {possible_path}")
                 self.file_path = possible_path
+        elif not os.path.exists(self.file_path):
+            raise FileNotFoundError(f"File not found: {self.file_path}")
 
         if not self.http_url:
             raise ValueError("No `http_url` provided for HTTPXApiTarget.")
@@ -129,6 +131,7 @@ async def send_prompt_async(self, *, message: Message) -> list[Message]:
                         method=self.method,
                         url=self.http_url,
                         headers=self.headers,
+                        params=self.params,
                         files=files,
                         follow_redirects=True,
                     )
@@ -139,7 +142,7 @@ async def send_prompt_async(self, *, message: Message) -> list[Message]:
                         method=self.method,
                         url=self.http_url,
                         headers=self.headers,
-                        params=self.params if self.method in {"GET", "HEAD"} else None,
+                        params=self.params,
                         json=self.json_data if self.method in {"POST", "PUT", "PATCH"} else None,
                         data=self.form_data if self.method in {"POST", "PUT", "PATCH"} else None,
                         follow_redirects=True,
diff --git a/tests/unit/target/test_http_api_target.py b/tests/unit/target/test_http_api_target.py
index c67919fe1..ad98884b3 100644
--- a/tests/unit/target/test_http_api_target.py
+++ b/tests/unit/target/test_http_api_target.py
@@ -45,6 +45,34 @@ async def test_send_prompt_async_file_upload(mock_request, patch_central_databas
     os.unlink(file_path)
 
 
+@pytest.mark.asyncio
+@patch("httpx.AsyncClient.request")
+async def test_send_prompt_async_file_upload_preserves_query_params(mock_request, patch_central_database):
+    with tempfile.NamedTemporaryFile(delete=False) as tmp:
+        tmp.write(b"This is a mock PDF content")
+        tmp.flush()
+        file_path = tmp.name
+
+    message_piece = MessagePiece(role="user", original_value="mock", converted_value=file_path)
+    message = Message(message_pieces=[message_piece])
+
+    mock_response = MagicMock()
+    mock_response.content = b'{"message": "File uploaded successfully"}'
+    mock_request.return_value = mock_response
+
+    target = HTTPXAPITarget(
+        http_url="http://example.com/upload/",
+        method="POST",
+        params={"alpha": "1"},
+        timeout=180,
+    )
+    await target.send_prompt_async(message=message)
+
+    assert mock_request.call_args.kwargs["params"] == {"alpha": "1"}
+
+    os.unlink(file_path)
+
+
 @pytest.mark.asyncio
 @patch("httpx.AsyncClient.request")
 async def test_send_prompt_async_no_file(mock_request, patch_central_database):
@@ -70,6 +98,55 @@ async def test_send_prompt_async_no_file(mock_request, patch_central_database):
     assert "Sample JSON response" in response_text
 
 
+@pytest.mark.asyncio
+@patch("httpx.AsyncClient.request")
+async def test_send_prompt_async_preserves_query_params_for_post(mock_request, patch_central_database):
+    message_piece = MessagePiece(role="user", original_value="mock", converted_value="non_existent_file.pdf")
+    message = Message(message_pieces=[message_piece])
+
+    mock_response = MagicMock()
+    mock_response.content = b'{"status": "ok"}'
+    mock_request.return_value = mock_response
+
+    target = HTTPXAPITarget(
+        http_url="http://example.com/data/",
+        method="POST",
+        params={"alpha": "1"},
+        json_data={"payload": "value"},
+        timeout=180,
+    )
+    await target.send_prompt_async(message=message)
+
+    mock_request.assert_called_once_with(
+        method="POST",
+        url="http://example.com/data/",
+        headers={},
+        params={"alpha": "1"},
+        json={"payload": "value"},
+        data=None,
+        follow_redirects=True,
+    )
+
+
+@pytest.mark.asyncio
+@patch("httpx.AsyncClient.request")
+async def test_send_prompt_async_missing_explicit_file_path_raises(mock_request, patch_central_database):
+    message_piece = MessagePiece(role="user", original_value="mock", converted_value="trigger")
+    message = Message(message_pieces=[message_piece])
+
+    target = HTTPXAPITarget(
+        http_url="http://example.com/upload/",
+        method="POST",
+        file_path="/definitely/missing/file.pdf",
+        timeout=180,
+    )
+
+    with pytest.raises(FileNotFoundError, match="File not found"):
+        await target.send_prompt_async(message=message)
+
+    mock_request.assert_not_called()
+
+
 @pytest.mark.asyncio
 @patch("httpx.AsyncClient.request")
 async def test_send_prompt_async_validation(mock_request, patch_central_database):