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

Output	Description
Adapter selection decision	Chosen adapter with documented rationale
svelte.config.js configuration	Correct adapter import and options
Platform binding access	platform.env typed access for applicable adapters
Environment variable plan	$env/static/private, $env/dynamic/private, or platform env usage
Adapters quality checklist	Pass/fail against the checklist below

Depth Modes

Level	Intent	Exit Rule
L1 Orientation	Build output reaches the target platform	App deploys and responds to requests
L2 Practical Delivery	Correct adapter with platform bindings and env vars	SSR or static output verified; env vars accessible; platform bindings working
L3 Specialist Hardening	Optimise for cold start, edge latency, and bundle size	Bundle analysed; cold start measured; incompatible Node APIs removed
L4 Expert Standardisation	Adapter and deployment policy for a project	Adapter selection guide, platform env registry, and incompatibility matrix documented

Adapter Selection Guide

Target Platform	Recommended Adapter	Notes
Vercel	adapter-vercel	Auto-detects Edge vs. Serverless per route
Cloudflare Pages / Workers	adapter-cloudflare	Use platform.env for KV, D1, R2
Node.js server (self-hosted)	adapter-node	Produces build/ with index.js entry
Netlify	adapter-netlify (community)	Not in @sveltejs org; verify currency
Fully static site	adapter-static	Requires all routes to be prerenderable
Unknown / multi-platform	adapter-auto	Detects at build time; not for production use in CI

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

Requested Outcome	Skill Section
Adapter selection	Adapter Selection Guide
Configuration	Workflow steps 3–4
Environment variables	Workflow step 5 + Security Notes
Edge API compatibility	Workflow step 6
Platform bindings	Workflow step 7
Quality validation	Adapters Quality Checklist

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.