backend/__init__.py eagerly imported the whole framework (manifest, egress,
git-gate, env, workspace, agent-provider), so importing ANY backend.* submodule
paid ~32 modules just to run the package init. Split it:
- backend/base.py — the abstract contract (BottleSpec, BottlePlan,
BottleCleanupPlan, ExecResult, ActiveAgent, Bottle,
BottleImages, BottleBackend). Carries the framework
imports; loaded only when a caller needs the contract.
- backend/selection.py — backend registry / selection / enumeration
(get_bottle_backend, _get_backends, _auto_select_backend,
has_backend, known_backend_names, enumerate_active_agents).
Concrete backends still imported lazily inside.
- backend/__init__.py — thin: a __getattr__ that resolves the public names
from those submodules on first access (+ a TYPE_CHECKING
block for checkers). Existing `from bot_bottle.backend
import X` and patch.object call-sites keep working.
`import bot_bottle.backend` drops from 32 -> 2 bot_bottle modules. Repointed the
backend-selection test's patch targets to the `selection` module (the functions
reference each other there now; the FirecrackerBottleBackend class-method
patches are unchanged — same class object).
Note: backend.docker.util is still heavy because backend/docker/__init__ eagerly
imports DockerBottleBackend — slimming the three sub-package inits is the
follow-up that makes the leaves cheap.
Full unit suite green (2243).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
