fix(packaging): resolve correct .d.cts types for CJS consumers

[david-illing-ck]

Problem

Fixes #748.

Importing any @langfuse/* package from a CommonJS project using TypeScript moduleResolution: node16/nodenext fails to type-check. Each package ships a single top-level types in its exports map pointing at the ESM .d.ts, and because every package is "type": "module", node16/nodenext resolution interprets that declaration as ESM. A CommonJS consumer therefore resolves an ESM declaration for a require() and the compiler rejects it:

• TS1479 on value imports
• TS1541 on type-only imports

This blocks CJS consumers on modern module resolution even though a working .cjs runtime build already ships.

Changes

The matching .d.cts declarations are already emitted by tsup — they were just never referenced in the exports map. This PR nests the types condition under each import/require branch so CJS consumers resolve .d.cts and ESM consumers resolve .d.ts:

// before
"exports": { ".": {
  "types":   "./dist/index.d.ts",
  "import":  "./dist/index.mjs",
  "require": "./dist/index.cjs"
}}

// after
"exports": { ".": {
  "import":  { "types": "./dist/index.d.ts",  "default": "./dist/index.mjs" },
  "require": { "types": "./dist/index.d.cts", "default": "./dist/index.cjs" }
}}

Applied identically to all 7 packages: core, client, tracing, otel, openai, langchain, and browser.

This is purely additive to type resolution — ESM consumers still resolve import.types → .d.ts byte-for-byte, runtime default entries are unchanged, and node/classic-resolution and bundler consumers are unaffected. No build config changes (the .d.cts artifacts already exist).

Verification

• ✅ @arethetypeswrong/cli — "No problems found" for every package across node10, node16 (from CJS), node16 (from ESM), and bundler (previously failed node16 (from CJS)).
• ✅ Real consumer build — a CommonJS + moduleResolution: node16 project went from failing to a clean tsc with no consumer-side source changes.

It apears I'm missing credentials to run to some of the tests, but I've run what I can without them.

• pnpm lint
• pnpm typecheck
• pnpm test
• pnpm test:integration
• pnpm test:e2e
• pnpm format:check

Release info

Bump level

• Major
• Minor
• Patch

Libraries affected

• All of them
• @langfuse/core
• @langfuse/client
• @langfuse/tracing
• @langfuse/otel
• @langfuse/openai
• @langfuse/langchain

Greptile Summary

This PR fixes TypeScript TS1479/TS1541 errors for CommonJS consumers using moduleResolution: node16 or nodenext by restructuring the exports field in all 7 package.json files. Previously, a single top-level types condition pointed only at the ESM .d.ts declaration; CJS consumers resolved that ESM declaration for a require() call, which modern TypeScript rejects.

• Type declaration routing fixed: The exports map is restructured so require.types resolves .d.cts and import.types resolves .d.ts, using the runtime files already emitted by tsup (dts: true with a CJS .cjs extension produces .d.cts automatically).
• Zero runtime impact: All default entries point to the same .mjs/.cjs artifacts as before; the top-level "types" fallback for pre-exports tooling is preserved.

Confidence Score: 5/5

Safe to merge — changes are confined to exports metadata in package manifests with no modifications to build config or source code.

All 7 packages receive an identical, mechanical change that adds nested types resolution under each import/require branch. The .d.cts artifacts were already being emitted by tsup; this PR simply wires the exports map to reference them. Runtime entries (default) are byte-for-byte unchanged, the top-level types fallback is preserved, and the PR author verified correctness with @arethetypeswrong/cli across all four resolution modes.

No files require special attention — all changes are structurally identical across the 7 package manifests.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    Consumer([TypeScript Consumer])

    Consumer -->|ESM / import| ImportBranch["exports.import"]
    Consumer -->|CJS / require| RequireBranch["exports.require"]

    ImportBranch --> ImportTypes["types: ./dist/index.d.ts"]
    ImportBranch --> ImportDefault["default: ./dist/index.mjs"]

    RequireBranch --> RequireTypes["types: ./dist/index.d.cts"]
    RequireBranch --> RequireDefault["default: ./dist/index.cjs"]

    ImportTypes --> ESMDecl["ESM declaration (.d.ts)"]
    RequireTypes --> CJSDecl["CJS declaration (.d.cts) new"]

    ImportDefault --> ESMRuntime[".mjs runtime"]
    RequireDefault --> CJSRuntime[".cjs runtime"]

    style CJSDecl fill:#22c55e,color:#fff
    style RequireTypes fill:#22c55e,color:#fff

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flowchart TD
    Consumer([TypeScript Consumer])

    Consumer -->|ESM / import| ImportBranch["exports.import"]
    Consumer -->|CJS / require| RequireBranch["exports.require"]

    ImportBranch --> ImportTypes["types: ./dist/index.d.ts"]
    ImportBranch --> ImportDefault["default: ./dist/index.mjs"]

    RequireBranch --> RequireTypes["types: ./dist/index.d.cts"]
    RequireBranch --> RequireDefault["default: ./dist/index.cjs"]

    ImportTypes --> ESMDecl["ESM declaration (.d.ts)"]
    RequireTypes --> CJSDecl["CJS declaration (.d.cts) new"]

    ImportDefault --> ESMRuntime[".mjs runtime"]
    RequireDefault --> CJSRuntime[".cjs runtime"]

    style CJSDecl fill:#22c55e,color:#fff
    style RequireTypes fill:#22c55e,color:#fff

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