fix(packaging): use conditional type exports for dual packages

[hassiebbot]

Problem

TypeScript nodenext CommonJS consumers could resolve @langfuse/* packages through their ESM declaration entrypoints because each package exported sibling types / import / require conditions. That caused mixed ESM/CJS type graphs and errors like CallbackHandler not being assignable to BaseCallbackHandler.

Changes

• nest types under import and require in all dual-format package export maps
• point require types at ./dist/index.d.cts
• add scripts/check-package-exports.mjs
• run the new check from precommit:check and ci

Release info Sub-libraries affected

Bump level

• Major
• Minor
• Patch

Libraries affected

• All of them
• langfuse
• langfuse-node

Changelog notes

• Fixed dual-package type resolution for CommonJS nodenext consumers by using conditional declaration exports.

Verification

• pnpm check:exports
• prettier --check package.json packages/*/package.json scripts/check-package-exports.mjs
• git diff --check

Disclaimer: Experimental PR review

Greptile Summary

Fixes dual-package TypeScript type resolution for CommonJS nodenext consumers by nesting types conditions under import and require in all 6 package export maps. Previously, a top-level types condition caused CJS consumers to resolve ESM declaration files, leading to mixed type graphs and assignability errors. The CJS require.types now correctly points to ./dist/index.d.cts (generated by tsup's dts: true for type: "module" packages).

• All 6 sub-packages (client, core, langchain, openai, otel, tracing) updated with identical conditional export structure
• New scripts/check-package-exports.mjs validation script enforces the export map structure
• Validation integrated into both precommit:check and ci pipelines

Confidence Score: 5/5

• This PR is safe to merge — it correctly fixes a well-known dual-package TypeScript resolution issue with a standard pattern.
• The changes are mechanical and consistent across all 6 packages. The conditional export structure is the recommended pattern for type: "module" packages with CJS support. tsup v8 with dts: true and format: ["cjs", "esm"] generates both .d.ts and .d.cts files for type: "module" packages, so the referenced declaration files will exist at build time. A new validation script enforces the structure going forward, and it's integrated into both pre-commit and CI.
• No files require special attention. All changes follow a consistent, well-understood pattern.

Important Files Changed

Filename	Overview
package.json	Adds check:exports script and integrates it into precommit:check and ci pipelines.
scripts/check-package-exports.mjs	New validation script that asserts all 6 packages use the correct conditional type exports structure. Hardcodes the package list which could drift if new packages are added.
packages/client/package.json	Nests types under import/require conditions, pointing CJS types to .d.cts. Correct for type: "module" + tsup dts: true.
packages/core/package.json	Same conditional type exports restructuring as other packages. Consistent and correct.
packages/langchain/package.json	Same conditional type exports restructuring. Consistent with all other packages.
packages/openai/package.json	Same conditional type exports restructuring. Consistent with all other packages.
packages/otel/package.json	Same conditional type exports restructuring. Consistent with all other packages.
packages/tracing/package.json	Same conditional type exports restructuring. Consistent with all other packages.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["TypeScript consumer<br/>moduleResolution: nodenext"] --> B{Module system?}
    B -->|"import"| C["exports['.'].import"]
    B -->|"require"| D["exports['.'].require"]
    C --> E["types → ./dist/index.d.ts<br/>(ESM declarations)"]
    C --> F["default → ./dist/index.mjs"]
    D --> G["types → ./dist/index.d.cts<br/>(CJS declarations)"]
    D --> H["default → ./dist/index.cjs"]
    E --> I["✅ Correct ESM type graph"]
    G --> J["✅ Correct CJS type graph"]

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_{Last reviewed commit: 8d5ec5e}

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Project	Deployment	Actions	Updated (UTC)
langfuse-js	Ready	Preview	Mar 16, 2026 6:16pm