sveltekit-adapters

SvelteKit Adapters

Specialization

Expert guidance for SvelteKit adapter selection, configuration, and deployment. Covers adapter-auto, adapter-node, adapter-static, adapter-vercel, adapter-cloudflare, platform-specific platform.env access, and the constraints each adapter places on rendering modes and runtime APIs.

Trigger Conditions

• Deploying a SvelteKit application to a specific hosting platform.
• Choosing the correct adapter for the target environment.
• Diagnosing runtime errors caused by adapter-incompatible APIs.
• Configuring environment variables and platform bindings for edge or serverless runtimes.
• Building a fully static site with adapter-static.

Scope Boundaries

In scope:

• @sveltejs/adapter-auto: zero-config detection for supported platforms.
• @sveltejs/adapter-node: self-hosted Node.js server output.
• @sveltejs/adapter-static: fully static HTML export.
• @sveltejs/adapter-vercel: Vercel Functions and Edge Functions.
• @sveltejs/adapter-cloudflare: Cloudflare Workers and Pages.
• svelte.config.js adapter configuration.
• platform.env and platform.context for platform-specific bindings.
• BODY_SIZE_LIMIT, ORIGIN, and ADDRESS_HEADER node adapter options.
• Adapter compatibility matrix: which adapters support SSR, edge, and static.

Out of scope:

• Page rendering mode decisions (covered by sveltekit-page-options).
• CI/CD pipeline setup (covered by ci-cd-workflows).
• Load function implementation (covered by sveltekit-load).
• Container packaging for Node adapter output (separate concern).

Inputs

• Target deployment platform.
• Rendering mode requirements (SSR, static, edge).
• Platform-specific bindings needed (KV, D1, R2, Vercel Blob, etc.).
• Environment variable strategy.
• Evaluation date in ISO format (YYYY-MM-DD).

Required Outputs

Depth Modes

Adapter Selection Guide

Workflow

1. Identify the target deployment platform and runtime (Node.js, edge, static CDN).
2. Select the adapter using the guide above; reject adapter-auto for production CI builds.
3. Install the adapter package and update svelte.config.js with adapter import and options.
4. Audit page options: adapter-static requires all routes to have prerender = true; SSR routes require a server-capable adapter.
5. Configure environment variable access: use $env/static/private for build-time secrets, $env/dynamic/private for runtime secrets.
6. For edge adapters, audit load functions and actions for incompatible Node.js APIs (fs, crypto, net); replace with Web API equivalents.
7. Access platform-specific bindings through event.platform.env in load functions and actions; type via App.Platform augmentation.
8. Test the production build locally (vite build + adapter output) before deploying.
9. Run the adapters quality checklist.

Adapters Quality Checklist

• Adapter matches the target deployment runtime; adapter-auto is not used in CI.
• svelte.config.js references the correct adapter with explicit options, not defaults.
• All routes rendered at runtime use a server-capable adapter; static-only routes use prerender = true.
• Secrets are accessed via $env/static/private or $env/dynamic/private; they are never exposed to the client.
• Edge adapter routes contain no Node.js-only APIs.
• platform.env is accessed through App.Platform typed interface augmentation.
• Production build output is tested locally before first deployment.

Security Notes

• Never access $env/static/public or $env/dynamic/public for secrets; these are exposed to the browser.
• $env/static/private values are inlined at build time; do not use for secrets that rotate.
• For rotating secrets use $env/dynamic/private or platform secret manager bindings.

L4 Coverage Matrix

References

See references/source-catalog.md for active source tracking.

Execution Context

Input Context

• Request objective and scope boundary.
• Applicable constraints and required outputs.

Process Context

• Follow this skill's deterministic workflow from intake to closure.
• Record ownership and decisions for required outputs.

Output Context

• Deliverables with explicit completion status.
• Residual risks and next actions.