Document esmOnly option for the TypeScript SDK generator

[devin-ai-integration]

Summary

The TypeScript SDK generator gained an opt-in esmOnly config option that makes the generated package ship only an ESM build instead of the default dual CommonJS + ESM output. This matters for customers whose consumers are ESM-only: it avoids the dual package hazard (two copies of the same module loaded via require and import) and yields a smaller, single-format package. Default behavior is unchanged when the flag is omitted.

Implements docs for: feat(typescript): add opt-in esmOnly flag for ESM-only SDK output (fern-api/fern#17503) — fern-api/fern#17503

Details

• fern/products/sdks/generators/typescript/configuration.mdx: new <ParamField path="esmOnly" type="boolean" default="false"> entry, placed alphabetically between enableInlineTypes and extraDependencies. Covers the package.json / exports / build-script effects, the dual package hazard motivation, the incompatibility with useLegacyExports: true and bundle: true, and a generators.yml example. The page has no outputEsm entry, so no contrast was added.
• No changelog entry (SDK changelogs are auto-generated).

Vale: the only remaining findings in the new block are FernStyles.Acronyms suggestions for ESM, which is defined on first use. fern check --warnings passes with 0 errors.

Link to Devin session: https://app.devin.ai/sessions/9854c806214d470da26ea53336829309
Open in Devin Desktop: https://app.devin.ai/desktop/session/9854c806214d470da26ea53336829309?variant=devin

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🌿 Preview your docs: https://fern-preview-devin-1789319077-ts-esm-only.docs.buildwithfern.com/learn

Here are the markdown pages you've updated:

• learn/sdks/generators/typescript/configuration

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✅ Devin Review: No Issues Found

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