Remove the process-wide current-partner setting
The quote singleton stores currentPartner before resolving a contract. Two overlapping synthetic requests can change that value between validation and calculation, applying one tenant's negotiated rate to another.
- Focused work estimate
- 3h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Tenant isolation · Dependency injection · Concurrency
Estimated field mix
- Backend50%
- Security50%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
Pattern topics
- SingletonRemove
Remove a globally mutable partner context that leaks negotiated rules across overlapping requests, while allowing immutable shared definitions.
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Project context
A fictional equipment-rental service supports direct customers and two reseller contracts. Pricing now lives in a long conditional with subclasses left over from a discontinued campaign. Build a local TypeScript quoting module and synthetic fixtures; no starter repository, real charges, tax advice, or payment connection is supplied. Amounts use integer cents and the exercise supports USD only.
Setup prerequisites
- Pure functions
- Object composition
- Integer arithmetic
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- PPOLICY-101 · Capture the reseller examples before splitting the pricing branch
- PPOLICY-102 · Stop incomplete quote requests reaching the calculator
- PPOLICY-103 · Add a capped volume contract without editing the existing rules
- PPOLICY-104 · Share quote assembly between the portal and nightly import
- PPOLICY-107 · Keep a cloned contract draft from changing the live tier table
Acceptance criteria
- Tenant and contract identity travel explicitly through each quote operation.
- Remove mutable request state from the Singleton; shared immutable rule definitions may remain cached.
- Any remaining cache uses tenant, contract, and revision in its identity and cannot expose another tenant's rule configuration.
Implementation constraints
- Do not serialize all requests behind a global lock to hide the leak; preserve independent concurrent execution.
Verification to include
- Interleave requests for two tenants at a controlled barrier and assert both receive their own rate.
- Repeat the test after a failed request and a cache hit to detect stale tenant state.
Deliverables
- Explicit request context and tenant-isolation concurrency regression
Rollout and recovery
Switch the local composition root to stateless quotation; discard the old mutable cache on rollback or restart.
Value of the work
For the engineer: Practice choosing, testing, and removing object-design abstractions around versioned business rules and tenant isolation.
For the team: Review changes that let a team introduce a contract without silently changing existing quotes, together with the maintenance costs of the chosen design.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.