feat: deliver billable usage to Polar idempotently

[kang-heewon]

Outcome

Polar can now deliver durable journaled billable usage through typed meter bindings. Each event carries a replay-safe Polar external ID; inserted and duplicate acknowledgements both resolve the local claim without a second provider increment. Delivery stays outside request handling, claims one bounded event at a time, and retains retryable or terminal failures with stable recovery Problems.

Usage delivery is bounded by a five-second provider attempt timeout, a 15-second provider retry window, and a minimum 30-second journal lease. Missing meter mappings and customers provide replay guidance, and a credential-gated live certification covers a deliberate usage event.

Fixes #1522

Verification

• pnpm --filter @croco/billing-polar test — 98 passed; 3 credential-gated live tests skipped.
• pnpm --filter @croco/billing-polar typecheck, lint, and build — passed.
• pnpm public-api:check, pnpm problem-registry:check, pnpm docs:catalog:check, and pnpm docs:api-triggers:check — passed.
• Pre-push workspace gates — 234/234 test tasks and 233/233 typecheck tasks passed.

Review notes

• Live Polar certification is opt-in and requires the documented POLAR_USAGE_* environment variables; it was not run without credentials.

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 61698ad5-4ae2-40db-97d9-9f6ffe4bb275

📥 Commits

Reviewing files that changed from the base of the PR and between 7b1505b and 5d3b90b.

⛔ Files ignored due to path filters (2)

• packages/problems-core/src/generated/problem-code-registry.ts is excluded by !**/generated/**
• pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

📒 Files selected for processing (31)

• .changeset/polar-usage-delivery.md
• docs/problem-code-registry.json
• packages/billing-polar/README.md
• packages/billing-polar/package.json
• packages/billing-polar/src/index.ts
• packages/billing-polar/src/libs/PolarBillingProviderProfile.ts
• packages/billing-polar/src/libs/PolarUsageBillingGateway.ts
• packages/billing-polar/src/libs/PolarUsageDeliveryWorker.ts
• packages/billing-polar/src/libs/problems/PolarBillingProblems.ts
• packages/billing-polar/src/tests/PolarBillingDiagnosticsProvider.spec.ts
• packages/billing-polar/src/tests/PolarBillingGateway.spec.ts
• packages/billing-polar/src/tests/PolarBillingProviderProfile.spec.ts
• packages/billing-polar/src/tests/PolarLiveSmoke.spec.ts
• packages/billing-polar/src/tests/PolarUsageBillingGateway.spec.ts
• packages/billing-polar/tsconfig.json
• packages/billing-polar/vitest.config.ts
• packages/docs/src/content/docs/api/billing-polar/src/classes/PolarUsageBillingGateway.md
• packages/docs/src/content/docs/api/billing-polar/src/classes/PolarUsageCustomerNotFoundProblem.md
• packages/docs/src/content/docs/api/billing-polar/src/classes/PolarUsageDeliveryWorker.md
• packages/docs/src/content/docs/api/billing-polar/src/classes/PolarUsageMeterMappingProblem.md
• packages/docs/src/content/docs/api/billing-polar/src/functions/bindPolarUsageMeter.md
• packages/docs/src/content/docs/api/billing-polar/src/functions/normalizePolarBillingError.md
• packages/docs/src/content/docs/api/billing-polar/src/type-aliases/PolarUsageDeliveryRunResult.md
• packages/docs/src/content/docs/api/billing-polar/src/type-aliases/PolarUsageDeliveryWorkerOptions.md
• packages/docs/src/content/docs/api/billing-polar/src/type-aliases/PolarUsageMeterBinding.md
• packages/docs/src/content/docs/api/billing-polar/src/variables/POLAR_BILLING_PROVIDER_PROFILE.md
• packages/docs/src/content/docs/api/problems-core/src/classes/Problem.md
• packages/docs/src/content/docs/api/problems-core/src/variables/CROCO_PROBLEM_CODE_REGISTRY.md
• packages/docs/src/content/docs/en/reference/problem-recovery-cookbook.md
• packages/docs/src/content/docs/en/reference/provider-maturity.md
• public-api-surface.snapshot.json

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[github-actions]

📊 Benchmark Results

✅ All benchmarks passed

Benchmark	p75	Threshold	Baseline	vs Baseline	Status	Notes
CrocoApp constructor	38.1μs	30.0ms	8.2μs	+366.1%	❌	-
CrocoApp lambdaHandler (10 controllers)	2.3ms	50.0ms	258.4μs	+784.5%	❌	-
Lambda cold-start simulation	1.8ms	80.0ms	418.1μs	+331.0%	❌	-
Lambda cold-start with headers	1.6ms	80.0ms	369.7μs	+342.5%	❌	-
Lambda cold-start with binary body	1.7ms	80.0ms	339.1μs	+394.0%	❌	-
Lambda cold-start with query params	1.6ms	80.0ms	301.3μs	+434.2%	❌	-
Lambda cold-start with authorizer context	1.6ms	80.0ms	299.8μs	+435.7%	❌	-
Lambda cold-start realistic scenario	1.6ms	80.0ms	299.2μs	+430.2%	❌	-
EventBusConfig.start (10 handlers)	1.9μs	10.0ms	1.4μs	+32.8%	❌	-
EventPublisher.publishNow single event	2.1μs	2.0ms	1.7μs	+26.2%	❌	-
DefaultHandlerResolver.resolve × 10	0.1μs	5.0ms	0.1μs	-12.5%	✅	-
Container.get singleton (cold)	76.9μs	5.0ms	70.3μs	+9.5%	✅	-
Container.register × 50 components	3.5ms	10.0ms	3.2ms	+9.4%	✅	-
Container.validate (50 components)	3.9ms	20.0ms	3.4ms	+15.6%	✅	-
Container.get singleton (warm)	1.9μs	500.0μs	1.6μs	+17.6%	✅	-
TelemetryRuntime.init (lambda preset)	2.3μs	200.0ms	1.1ms	-99.8%	✅	-
lambdaPreset config creation	1.5μs	2.0ms	1.4μs	+6.7%	✅	-

_{Updated: 2026-08-02T15:06:02.304Z · Commit: 60156ed}