feat: MPP credits/billing for ARES with a guaranteed-profit model

[daemon-blockint-tech]

Context

Turn ARES into a paid service: meter each audit's LLM usage, charge it in credits, and guarantee a profit on every run. Settlement of pay-as-you-go usage uses the Machine Payments Protocol (MPP) — the HTTP-402 machine-to-machine payment standard. Fully opt-in: with BILLING_ENABLED unset, nothing here runs, so default audits and the hermetic test suite are untouched.

The model

audit → token usage → provider $ (pricing.ts)
                     → × markup   (profit.ts, margin floored)
                     → credits    (credits.ts: system → on-demand)
                     → MPP settle overflow (mpp.ts, HTTP-402)

• pricing.ts — per-model USD/MTok rate table (Anthropic/OpenRouter rates incl. prompt-cache multipliers and $10/1k web search), plus cost computation. Normalizes OpenRouter ids (anthropic/claude-3.5-sonnet, dotted versions) to canonical keys.
• credits.ts — two-tier ledger: prepaid system credits drawn first, then pay-as-you-go on-demand overflow (optionally capped), with a full audit trail. 1 credit = $0.01 by default (100 credits = $1).
• mpp.ts — MPP protocol shapes (Challenge → Credential → Receipt) with a hermetic LocalMppClient; a real HTTP-402 client attaches behind MPP_ENDPOINT, off by default like the CUA analyzer.
• profit.ts — the profit guarantee. The effective markup is floored at 1 + BILLING_MIN_MARGIN_PCT, credits are rounded up, and every audit is billed at least BILLING_MIN_CHARGE_CREDITS. A run can never settle below provider cost, even if BILLING_MARKUP is misconfigured below 1. Each settlement reports cost / revenue / profit / margin.
• meter.ts + usage.ts — accumulate token usage from LangChain responses and settle a run; index.ts wires a metering chat wrapper and prints the bill after each audit.
• config.ts — all knobs from env (BILLING_*, MPP_*), documented in .env.example.

Verification

typecheck ✓ · lint ✓ · test ✓ (11 files, 85 tests — +34) · build ✓
npm ci (npm 10.8.2, runner version) ✓

Verified end-to-end against the live audit graph: usage was metered across the run and settled at a positive margin — $0.1044 provider cost → $0.14 revenue → $0.0356 profit (25.4% gross margin) — drawn from prepaid credits, with on-demand overflow settling through MPP in the on-demand test. The margin-floor, minimum-charge, and below-cost-markup cases are all covered by tests.

Notes

• No new runtime dependencies (reuses uuid), so the lockfile is unchanged and npm ci stays green.
• Opt-in by design — BILLING_ENABLED defaults off; the hermetic graph/test suite runs exactly as before.

🤖 Generated with Claude Code

https://claude.ai/code/session_017ZB4NjNJZ6zWTqypbSiihy

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Generated by Claude Code