docs(typescript): document guardProcessEnvAccess

[devin-ai-integration]

The TypeScript SDK generator (3.89.0) gained an opt-in guardProcessEnvAccess config option. When enabled, the generated auth providers (API key/header, bearer, basic, OAuth) only read credential environment variables behind a typeof process !== "undefined" check. This matters for customers whose SDKs run in browsers, Cloudflare Workers, Deno, or other non-Node runtimes: today process.env?.[KEY] throws ReferenceError: process is not defined when a credential isn't passed to the client, and with the option enabled the client instead surfaces its normal "provide apiKey or set the X_API_KEY environment variable" error. Default false keeps generated output unchanged.

Implements docs for: feat(typescript): add opt-in guardProcessEnvAccess for auth provider env reads (fern-api/fern#17605)

Summary

• fern/products/sdks/generators/typescript/configuration.mdx (TypeScript configuration reference, https://buildwithfern.com/learn/sdks/generators/typescript/configuration): new <ParamField path="guardProcessEnvAccess"> entry, placed alphabetically between generateSubpackageExports and includeContentHeadersOnFileDownloadResponse, with a short generators.yml example.

No changelog changes (already covered by the 2026-09-02 TypeScript generator changelog entry). Vale and fern check --warnings pass on the added content; the remaining Vale findings in the file are pre-existing.

Link to Devin session: https://app.devin.ai/sessions/ea4d0d848e454e0189ddb0aef1ac603d
Open in Devin Desktop: https://app.devin.ai/desktop/session/ea4d0d848e454e0189ddb0aef1ac603d?variant=devin

[devin-ai-integration]

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[github-actions]

🌿 Preview your docs: https://fern-preview-devin-1788541534-ts-guard-process-env-access.docs.buildwithfern.com/learn

Here are the markdown pages you've updated:

• learn/sdks/generators/typescript/configuration