TanStack Start — Skill Spec

TanStack Start is a full-stack React framework built on TanStack Router and Vite. It adds SSR, streaming, server functions (type-safe RPCs), middleware, server routes, and universal deployment. All code is isomorphic by default — it runs in both server and client environments unless explicitly constrained.

Domains

Domain	Description	Skills
Project Setup	Scaffolding, Vite plugin, router factory, root route, entries	start-setup
Server Functions	Type-safe RPCs with createServerFn, validation, streaming	server-functions
Middleware and Context	Request/function middleware, context, global middleware	middleware
Execution Model	Isomorphic defaults, environment boundaries, env vars	execution-model
Server Routes	API endpoints, HTTP handlers, handler middleware	server-routes
Deployment and Rendering	Hosting, selective SSR, prerendering, SEO	deployment

Skill Inventory

Skill	Type	Domain	What it covers	Failure modes
start-setup	core	project-setup	tanstackStart(), getRouter(), root route, entries	3
server-functions	core	server-functions	createServerFn, validation, useServerFn, streaming	4
middleware	core	middleware-and-context	createMiddleware, context, global middleware, factories	3
execution-model	core	execution-model	Isomorphic defaults, environment functions, env vars	4
server-routes	core	server-routes	server property, HTTP handlers, createHandlers	2
deployment	core	deployment-and-rendering	Hosting, SSR modes, prerendering, SEO	3
react-start	framework	project-setup	React bindings, useServerFn, full setup	3
migrate-from-nextjs	lifecycle	project-setup	Next.js App Router migration checklist	3

Failure Mode Inventory

start-setup (3 failure modes)

#	Mistake	Priority	Source
1	React plugin before Start plugin in Vite config	CRITICAL	docs/build-from-scratch
2	Enabling verbatimModuleSyntax in tsconfig	HIGH	docs/build-from-scratch
3	Missing Scripts component in root route	HIGH	docs/guide/routing

server-functions (4 failure modes)

#	Mistake	Priority	Source
1	Putting server-only code in loaders instead of server functions	CRITICAL	maintainer interview
2	Generating Next.js/Remix server patterns ("use server", getServerSideProps)	CRITICAL	maintainer interview
3	Using dynamic imports for server functions	HIGH	docs/guide/server-functions
4	Not using useServerFn for component calls	MEDIUM	docs/guide/server-functions

middleware (3 failure modes)

#	Mistake	Priority	Source
1	Trusting client sendContext without server validation	HIGH	docs/guide/middleware
2	Confusing request vs server function middleware	MEDIUM	docs/guide/middleware
3	Wrong middleware method order	MEDIUM	docs/guide/middleware

execution-model (4 failure modes)

#	Mistake	Priority	Source
1	Assuming loaders are server-only	CRITICAL	docs/guide/execution-model
2	Exposing secrets via module-level process.env	CRITICAL	docs/guide/execution-model
3	Using VITE_ prefix for server secrets	CRITICAL	docs/guide/environment-variables
4	Hydration mismatches from env-dependent rendering	HIGH	docs/guide/execution-model

server-routes (2 failure modes)

#	Mistake	Priority	Source
1	Duplicate route path resolution	MEDIUM	docs/guide/server-routes
2	Forgetting to await request body methods	MEDIUM	docs/guide/server-routes

deployment (3 failure modes)

#	Mistake	Priority	Source
1	Missing nodejs_compat flag for Cloudflare Workers	HIGH	docs/guide/hosting
2	Bun deployment with React 18	MEDIUM	docs/guide/hosting
3	Child route loosening parent SSR config	MEDIUM	docs/guide/selective-ssr

Tensions

Tension	Skills	Agent implication
Isomorphic defaults vs server-only expectations	execution-model ↔ server-functions	Agents put secrets/DB queries in loaders instead of server functions
Simplicity of isomorphic code vs security boundaries	execution-model ↔ middleware	Agents expose secrets via module-level process.env or skip context validation

Cross-References

From	To	Reason
server-functions	execution-model	Server functions ARE the isomorphic boundary
server-functions	middleware	Middleware chains compose with server functions
middleware	server-routes	Server routes use the same middleware system
deployment	execution-model	Deployment target affects where code runs