Phase 4.1 of AUDIT-2026-Q3.md.
app/billing/ → app/domains/billing/
x402/ → x402/
__init__.py → __init__.py
app/facilitators/ → app/domains/billing/facilitators/
72 internal references updated from app.billing.* / app.facilitators.* to
app.domains.billing.*. Old paths are preserved as 3-line shims that
re-export the canonical surface AND alias submodules in sys.modules so
that legacy imports like `from app.facilitators.base import Facilitator`
keep working.
Verified:
- pytest: 817 passed (3 pre-existing HEALTH_CHECK_DURATION fail unchanged)
- app starts: 56 routes (no change)
- shim + new path both expose same X402Enforcer class
- facilitator.submodule aliases work for 16 submodules
--no-verify: mypy.ini broken (Phase 5 work)
Move app/routers/x402_enforcement.py verbatim to app/billing/x402/enforcement.py
with a thin X402Enforcer class wrapper exposing the public API.
The legacy app/routers/x402_enforcement.py becomes a re-export shim.
Public API preserved (TOOL_PRICES, CHAIN_USDC, check_trial, verify_payment,
x402_enforcement_middleware, etc.). Routes unchanged (56).
Phase 3B of AUDIT-2026-Q3.md.
