docs(fumadocs): document SDK/CLI telemetry and opt-outs

[tembo]

Summary

PR #141 shipped PostHog telemetry, error tracking, and the new telemetry?: boolean client option, but the docs site had no telemetry page and the client reference did not list the option. This PR closes that gap with a dedicated, scannable Telemetry page verified against packages/email-sdk/src/telemetry.ts, core.ts, and cli.ts — no fabricated behavior.

Documentation-only change.

Docs added / updated

• New page apps/fumadocs/content/docs/telemetry.mdx — top-level page (parallel to Authentication), registered in content/docs/meta.json after authentication. Covers:
  • Intent and the opt-out, anonymous-by-default model, plus the first-run stderr notice.
  • Common properties and a table of all four events (client created, email sent, email batch sent, cli command run) with their exact property names.
  • delivery_path values (single / bulk_native / bulk_expanded) and the one-event-per-send() no-double-counting guarantee.
  • The error-reporting redaction pipeline (stack-frame path collapsing, message/name scrubbing, allowlisted error names, per-process dedupe/caps) and which errors are excluded.
  • Storage (~/.config/email-sdk/telemetry.json, XDG_CONFIG_HOME), write-only key, US PostHog host, fire-and-forget 3s timeout, read-only-FS behavior.
  • CI-vendor detection table, including why Vercel runtime is deliberately not treated as CI.
  • Every opt-out: EMAIL_SDK_TELEMETRY=0/false/off, DO_NOT_TRACK=1/true, telemetry: false, and NODE_ENV=test.
• apps/fumadocs/content/docs/reference/client.mdx — added the telemetry option to the createEmailClient options TypeTable and a cross-link to the new page.

Codepaths covered

• packages/email-sdk/src/telemetry.ts — createTelemetry, opt-out precedence (isTelemetryDisabled), CI detection (detectCiVendor), redaction (redactErrorMessage, sanitizeErrorName, sanitizeFrameFilename), dedupe/caps, state storage.
• packages/email-sdk/src/core.ts — client created, email sent (incl. delivery_path, used_recipient_variables, used_send_at), and email batch sent property shapes; telemetry: false handling.
• packages/email-sdk/src/cli.ts — cli command run properties, source: "cli" tagging, and flush-before-exit.

Key knowledge gaps addressed

• There was no discoverable place documenting what telemetry collects and how to turn it off beyond the README section — now surfaced in the docs nav.
• The public telemetry client option was undocumented in the client reference.
• The redaction guarantees for error reports (previously only implied by source comments) are now stated for users evaluating the SDK against privacy/compliance requirements.

Validation

• bun run types:check in apps/fumadocs (runs fumadocs-mdx && tsc --noEmit): passes — the new MDX compiles and frontmatter validates.
• Callout (from defaultMdxComponents) and TypeTable are globally registered in src/components/mdx.tsx; the Activity icon resolves via lucide-react.
• Full bun run build was not run (it fetches Notra blog posts over the network); the MDX compilation covered by types:check is the relevant check for this content change.

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🤖 Generated by the Tembo documentation agent, triggered by the merge of #141.

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Project	Deployment	Actions	Updated (UTC)
email-sdk-fumadocs	Ready	Preview, Comment	Jul 6, 2026 5:09pm

[tembo]

Requesting review from @leoisadev1 who has experience with the following files modified in this PR:

• apps/fumadocs/content/docs/meta.json

[leoisadev1]

Superseded by #147, which adds the /docs/telemetry page (plus the client-reference telemetry option and sidebar entry) rewritten in the post-#128 docs voice and re-verified against packages/email-sdk/src/telemetry.ts. Thanks — the docs site was indeed missing a telemetry disclosure page.