feat(customcurrencies): add configuration flag

[turip]

Summary

Adds an explicit credits.customCurrenciesEnabled opt-in for the experimental custom-currency flow.

When enabled, the setting initializes custom-currency support for flat-fee, usage-based, and credit-purchase charges and allows custom currencies and their cost bases to be created through the API. It remains disabled by default, while quickstart and e2e opt in so the flow can be exercised in development and automated coverage.

The example configuration includes a prominent warning that the feature is experimental and can cause database inconsistencies until the full implementation is complete.

Validation

• make lint-go-fast
• focused Go tests and vet for config, wiring, charge services, and currency handlers
• make test-nocache (6,288 tests; only the out-of-scope Svix connectivity test failed because the local Svix service was not running)

Greptile Summary

Adds an opt-in configuration flag for experimental custom-currency support.

• Defaults custom-currency mutations and charge creation to disabled.
• Propagates the flag through both API surfaces and all three charge-service implementations.
• Enables the feature in quickstart and end-to-end configurations and documents its experimental status.

Confidence Score: 5/5

The PR appears safe to merge with the custom-currency opt-in consistently applied across API mutations and production charge services.

The disabled default is preserved, both API constructions receive the configured value, and server, billing-worker, and jobs wiring propagate it to flat-fee, usage-based, and credit-purchase services without an uncovered production path.

Important Files Changed

Filename	Overview
app/config/credits.go	Adds the disabled-by-default custom-currency configuration field and Viper default.
app/common/charges.go	Propagates the configured flag into all three production charge-service constructors.
api/v3/handlers/currencies/handler.go	Stores the feature setting on currency handlers for mutation gating.
api/v3/handlers/currencies/create.go	Rejects custom-currency creation when the experimental feature is disabled.
api/v3/handlers/currencies/create_cost_basis.go	Rejects cost-basis creation when the experimental feature is disabled.
openmeter/billing/charges/flatfee/service/service.go	Initializes flat-fee custom-currency support from configuration.
openmeter/billing/charges/usagebased/service/service.go	Initializes usage-based custom-currency support from configuration.
openmeter/billing/charges/creditpurchase/service/service.go	Initializes credit-purchase custom-currency support from configuration.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    Config[credits.customCurrenciesEnabled] --> V1[v1 currency handler]
    Config --> V3[v3 currency handler]
    Config --> Registry[charges registry]
    Registry --> FlatFee[flat-fee service]
    Registry --> Usage[usage-based service]
    Registry --> Purchase[credit-purchase service]
    V1 --> Mutations[custom currency and cost-basis mutations]
    V3 --> Mutations
    FlatFee --> Charges[custom-currency charge creation]
    Usage --> Charges
    Purchase --> Charges

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_{Reviews (1): Last reviewed commit: "feat(customcurrencies): add configuratio..." | Re-trigger Greptile}

Context used:

• Knowledge Base — API Server: Request Routing, Auth, and Handler Dispatch
• Knowledge Base — Billing: Invoices, Charges, Tax, and Currency

Summary by CodeRabbit

• New Features

  • Added a configuration option to enable or disable custom-currency support.
  • Custom-currency creation and cost-basis operations now return a validation error when the feature is disabled.
  • Enabled custom-currency support in quickstart and end-to-end configurations.

• Bug Fixes

  • Ensured custom-currency settings are consistently applied across billing services and API handlers.

• Documentation

  • Added configuration guidance and warnings noting that custom currencies are experimental.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 39c14327-4b92-46ac-b6b9-c76760dae480

📥 Commits

Reviewing files that changed from the base of the PR and between fab8c28 and ab0d023.

📒 Files selected for processing (19)

• .agents/skills/charges/SKILL.md
• api/v3/handlers/currencies/create.go
• api/v3/handlers/currencies/create_cost_basis.go
• api/v3/handlers/currencies/handler.go
• api/v3/handlers/currencies/handler_test.go
• api/v3/handlers/currencies/list_test.go
• api/v3/server/server.go
• app/common/charges.go
• app/config/config_test.go
• app/config/credits.go
• config.example.yaml
• e2e/config.yaml
• openmeter/billing/charges/creditpurchase/service/service.go
• openmeter/billing/charges/flatfee/service/service.go
• openmeter/billing/charges/service/creditpurchase_test.go
• openmeter/billing/charges/service/invoicable_test.go
• openmeter/billing/charges/usagebased/service/service.go
• openmeter/server/router/router.go
• quickstart/config.yaml

---

📝 Walkthrough

Walkthrough

Changes

Custom-currency enablement is now configured through credits.customCurrenciesEnabled, propagated into charge services and currency handlers, and enforced on currency mutation endpoints. Disabled mutations return validation errors before parsing. Tests and configuration examples reflect enabled and disabled environments.

Custom currency configuration

Layer / File(s)	Summary
Configuration contract app/config/credits.go, app/config/config_test.go, config.example.yaml, e2e/config.yaml, quickstart/config.yaml	Adds the customCurrenciesEnabled credits setting, defaults it to false, and configures it for example, e2e, and quickstart environments.
Charge service initialization app/common/charges.go, openmeter/billing/charges/*/service.go, openmeter/billing/charges/service/*_test.go, .agents/skills/charges/SKILL.md	Passes the credits flag into flat-fee, usage-based, and credit-purchase services, which initialize their internal custom-currency state; test helpers set the flag through service configuration.
Currency handler enforcement api/v3/handlers/currencies/*.go, api/v3/server/server.go, openmeter/server/router/router.go	Passes the credits flag into currency handlers and rejects currency and cost-basis creation with validation errors when disabled.
Mutation and constructor tests api/v3/handlers/currencies/handler_test.go, api/v3/handlers/currencies/list_test.go	Verifies disabled mutation endpoints return HTTP 400 and updates existing handler construction calls for the new flag.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Config
  participant NewServer
  participant CurrencyHandler
  participant Client
  Config->>NewServer: credits.customCurrenciesEnabled
  NewServer->>CurrencyHandler: initialize with feature flag
  Client->>CurrencyHandler: create currency or cost basis
  CurrencyHandler-->>Client: 400 validation error when disabled

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Possibly related PRs

• openmeterio/openmeter#4638: Touches the same currency creation handler paths.
• openmeterio/openmeter#4772: Uses the same custom-currency enablement path for cost-basis behavior.
• openmeterio/openmeter#4773: Aligns with custom-currency feature gating in charge services.

Suggested reviewers: mark-vass-konghq, chrisgacsal, tothandras

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 8.33% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title is concise and accurately captures the main change: adding a custom-currencies configuration flag.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/custom-currencies-config

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 Checkov (3.3.8)

config.example.yaml

Traceback (most recent call last):
File "/usr/local/bin/checkov", line 2, in
from checkov.main import Checkov
ModuleNotFoundError: No module named 'checkov'

e2e/config.yaml

Traceback (most recent call last):
File "/usr/local/bin/checkov", line 2, in
from checkov.main import Checkov
ModuleNotFoundError: No module named 'checkov'

quickstart/config.yaml

Traceback (most recent call last):
File "/usr/local/bin/checkov", line 2, in
from checkov.main import Checkov
ModuleNotFoundError: No module named 'checkov'

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