fix(vercel): anchor vercelignore patterns so app/evals is not stripped from the bundle

Author: codebybilal18

.vercelignore

@@ -1,28 +1,33 @@
 # Keep the serverless bundle under the 250 MB unzipped limit.
 #
-# Only api/ and app/ are needed at runtime. Everything below is development,
-# CI, or deployment tooling that would otherwise be uploaded and counted
-# against the limit.
+# Every pattern here is ANCHORED with a leading slash, and that is not stylistic.
+# .vercelignore uses gitignore semantics: an unanchored `evals/` matches a
+# directory of that name at ANY depth, so it silently excluded `app/evals/` —
+# a package the request path imports — and the function died at cold start with
+# FUNCTION_INVOCATION_FAILED while the build itself reported success.
+#
+# Only api/ and app/ are needed at runtime.
 
-tests/
-k8s/
-.github/
-scripts/
+/tests/
+/k8s/
+/.github/
+/scripts/
 
-Dockerfile
-docker-compose.yml
-.dockerignore
+/Dockerfile
+/docker-compose.yml
+/.dockerignore
 
-# Migrations run from a developer machine or CI, never from the function —
-# two concurrent instances racing the same migration is worse than a manual
-# step. The golden set and corpus are eval fixtures, not runtime data.
-alembic.ini
-evals/
+# Migrations run from a developer machine or CI, never from the function — two
+# concurrent instances racing the same migration is worse than a manual step.
+# /evals/ holds the golden set and corpus: eval fixtures, not runtime data.
+# (app/evals/ is source code and must ship — hence the leading slash.)
+/alembic.ini
+/evals/
 
-requirements-local.txt
-requirements-dev.txt
+/requirements-local.txt
+/requirements-dev.txt
 
-README.md
-.venv/
-.ruff_cache/
-.pytest_cache/
+/README.md
+/.venv/
+/.ruff_cache/
+/.pytest_cache/

api/index.py

@@ -1,15 +1,32 @@
 """Vercel serverless entrypoint.
 
-Vercel's @vercel/python runtime looks for a module-level ASGI callable named
-`app`. Everything else in this file exists to make the repo root importable,
-since Vercel executes this module from inside api/ rather than the project root.
+Vercel's Python runtime looks for a module-level ASGI callable named `app`.
+Everything else here exists because this module is executed from inside api/
+rather than the project root, so the repo root has to be put on sys.path before
+`app` is importable.
 """
 
 import os
 import sys
 
-sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+sys.path.insert(0, ROOT)
 
-from app.main import create_app  # noqa: E402
+try:
+    from app.main import create_app
+except ModuleNotFoundError as exc:  # pragma: no cover - deployment diagnostics
+    # A missing package here is almost always a packaging problem, not a code
+    # one: something excluded `app/` or a subpackage from the bundle. The raw
+    # traceback surfaces only as FUNCTION_INVOCATION_FAILED with the build
+    # reporting success, which sends you looking in entirely the wrong place —
+    # so say what is actually on disk.
+    present = sorted(p for p in os.listdir(ROOT) if not p.startswith("."))
+    raise RuntimeError(
+        f"Could not import {exc.name!r} from the deployment bundle. "
+        f"Project root {ROOT} contains: {present}. "
+        "If 'app' is absent or incomplete, check .vercelignore — its patterns "
+        "use gitignore semantics, so an unanchored directory name matches at "
+        "every depth."
+    ) from exc
 
 app = create_app()