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docs/library-decisions/2026-05-14-@trpc/client.md

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+---
+package: "@trpc/client"
+version: "^11.0.0"
+tier: core
+decision: approved
+date: 2026-05-14
+deciders: [Danijel Martinek]
+adr: null
+filter-results:
+  license: MIT
+  types: native
+  maintenance: active
+  boundary-fit: pass
+  shadow-check: pass
+  eu-residency: n/a
+  cve-scan: clean
+  named-consumer: pass
+  socketRisk: clean
+verification-commands:
+  - npm view @trpc/client license
+  - npm view @trpc/client version
+  - pnpm audit --audit-level=moderate
+accepted-cves: []
+---
+
+## Filter: license
+
+<!-- Result: MIT -->
+
+`npm view @trpc/client license` returns `MIT`. MIT is on the allowlist.
+
+## Filter: types
+
+<!-- Result: native -->
+
+`@trpc/client` is authored in TypeScript and ships its own `.d.ts` declaration files. No separate `@types/` package is needed.
+
+## Filter: maintenance
+
+<!-- Result: active -->
+
+Actively maintained alongside `@trpc/server` by the tRPC team. Versioned and released together with the server package.
+
+## Filter: boundary-fit
+
+<!-- Result: pass -->
+
+`@trpc/client` is used in `@repo/core-testing` to provide a mock tRPC client for test setups. This is the correct tier for test infrastructure utilities. No boundary rule restricts `@trpc/client` usage here.
+
+## Filter: shadow-check
+
+<!-- Result: pass -->
+
+`@trpc/client` is the sole tRPC client implementation in the workspace. No competing client adapter is present.
+
+## Filter: eu-residency
+
+<!-- Result: n/a -->
+
+`@trpc/client` is a pure client-side RPC library with no vendor-controlled network endpoints. EU residency does not apply.
+
+## Filter: cve-scan
+
+<!-- Result: clean -->
+
+`pnpm audit --audit-level=moderate` reports no advisories against `@trpc/client` at the time of this trace.
+
+## Filter: named-consumer
+
+<!-- Result: pass -->
+
+`@repo/core-testing` uses `@trpc/client` to build the mock tRPC client used in integration test setups. Named, non-hypothetical consumer exists today.
+
+## Prompt: replaces
+
+`@trpc/client` is the natural companion to `@trpc/server`; no alternative client approach was evaluated separately. Using `@trpc/client` ensures the test setup mirrors the production client configuration.
+
+## Prompt: migration-cost-out
+
+Low. `@trpc/client` is confined to `@repo/core-testing`'s test utilities. Migrating out requires updating the mock client setup in one package. Feature packages reference tRPC types from `@trpc/server`, not `@trpc/client`.
+
+## Prompt: alternatives-considered
+
+1. **Direct HTTP fetch in tests** — Rejected: bypasses tRPC middleware and type inference, making tests less representative of real client behavior.
+2. **`@trpc/server` `createCaller` (server-side calling)** — Valid alternative for pure unit tests; `@trpc/client` is used where the test needs to exercise the actual HTTP transport or client link chain.