feat(check): make check fails when a service imports another service's sdk at startup

template/{{ part_dir }}/Makefile.jinja

@@ -30,7 +30,8 @@ check:
 	uv run ruff format --check
 	uv run ruff check
 	uv run ty check
-{% if svc_modules %}
+{% if svc_modules %}	uv run python scripts/check_imports.py
+{% endif %}{% if svc_modules %}
 build:
 	$(COMPOSE) build {{ svc_modules[0] }}
 

template/{{ part_dir }}/scripts/{% if backend_services %}check_imports.py{% endif %}.jinja

@@ -0,0 +1,60 @@
+import os
+import subprocess
+import sys
+
+HEAVY = ["aiogram", "pyrogram", "fastapi", "google.genai"]
+SERVICES = {
+{%- if 'api' in backend_services %}
+    "api": (["api.app"], {"fastapi"}),
+{%- endif %}
+{%- if 'aiogram_bot' in backend_services %}
+    "bot": ({% if include_payments %}["bot"]{% else %}["bot.common", "bot.handlers"]{% endif %}, {"aiogram"}),
+{%- endif %}
+{%- if 'kurigram_userbot' in backend_services %}
+    "userbot": (["userbot.runner", "userbot.handlers"], {"pyrogram"}),
+{%- endif %}
+{%- if 'taskiq_worker' in backend_services %}
+    "worker": (["worker.broker", "worker.tasks"], {% if 'api' in backend_services %}{"fastapi"}{% else %}set(){% endif %}),
+{%- elif 'scheduler' in backend_services %}
+    "scheduler": (["scheduler"], set()),
+{%- endif %}
+}
+PROBE = """
+import importlib, sys
+for module in sys.argv[1].split(","):
+    importlib.import_module(module)
+print(" ".join(name for name in sys.argv[2:] if name in sys.modules))
+"""
+{%- if 'aiogram_bot' in backend_services %}
+ENV = {**os.environ, "BOT__TOKEN": "1:check"}
+{%- else %}
+ENV = dict(os.environ)
+{%- endif %}
+
+
+def loaded(modules: list[str]) -> tuple[set[str], str]:
+    result = subprocess.run(  # noqa: S603
+        [sys.executable, "-c", PROBE, ",".join(modules), *HEAVY],
+        capture_output=True,
+        text=True,
+        cwd="src",
+        env=ENV,
+        check=False,
+    )
+    error = (result.stderr.strip().splitlines() or ["exit code"])[-1]
+    return set(result.stdout.split()) & set(HEAVY), error if result.returncode else ""
+
+
+def main() -> int:
+    failed = False
+    for service, (modules, allowed) in SERVICES.items():
+        found, error = loaded(modules)
+        extra = sorted(found - allowed)
+        status = error or ("imports " + ", ".join(extra) if extra else "")
+        print(f"{service:10s} {'FAIL: ' + status if status else 'ok'}")
+        failed |= bool(status)
+    return int(failed)
+
+
+if __name__ == "__main__":
+    sys.exit(main())

template/{{ part_dir }}/{% if layout == 'part' %}CLAUDE.md{% endif %}

@@ -5,3 +5,9 @@ ruff format
 ruff check --fix
 ty check
 ```
+
+## Imports
+Every service imports only what it needs to start. `make check` runs `scripts/check_imports.py`, which fails when a service loads a heavy package it is not allowed; `SERVICES` there is the contract, extend it on purpose.
+- Package `__init__` files don't re-export clients or SDKs.
+- An SDK used by one function is imported inside it. On an async path load it first with `await preload("<module>")` from `utils.imports`, so the event loop never waits on the import.
+- Types used in Dishka provider signatures and `FromDishka[...]` stay real top-level imports.