This skill builds on electric-shapes. Read it first for ShapeStream configuration.
Electric — Proxy and Auth
Setup
import { ELECTRIC_PROTOCOL_QUERY_PARAMS } from '@electric-sql/client'
// Server route (Next.js App Router example)
export async function GET(request: Request) {
const url = new URL(request.url)
const originUrl = new URL('/v1/shape', process.env.ELECTRIC_URL)
// Only forward Electric protocol params — never table/where from client
url.searchParams.forEach((value, key) => {
if (ELECTRIC_PROTOCOL_QUERY_PARAMS.includes(key)) {
originUrl.searchParams.set(key, value)
}
})
// Server decides shape definition
originUrl.searchParams.set('table', 'todos')
originUrl.searchParams.set('secret', process.env.ELECTRIC_SOURCE_SECRET!)
const response = await fetch(originUrl)
const headers = new Headers(response.headers)
headers.delete('content-encoding')
headers.delete('content-length')
return new Response(response.body, {
status: response.status,
statusText: response.statusText,
headers,
})
}Client usage:
import { ShapeStream } from '@electric-sql/client'
const stream = new ShapeStream({
url: '/api/todos', // Points to your proxy, not Electric directly
})Core Patterns
Tenant isolation with WHERE params
// In proxy route — inject user context server-side
const user = await getAuthUser(request)
originUrl.searchParams.set('table', 'todos')
originUrl.searchParams.set('where', 'org_id = $1')
originUrl.searchParams.set('params[1]', user.orgId)Auth token refresh on 401
const stream = new ShapeStream({
url: '/api/todos',
headers: {
Authorization: async () => `Bearer ${await getToken()}`,
},
onError: async (error) => {
if (error instanceof FetchError && error.status === 401) {
const newToken = await refreshToken()
return { headers: { Authorization: `Bearer ${newToken}` } }
}
return {}
},
})CORS configuration for cross-origin proxies
// In proxy response headers
headers.set(
'Access-Control-Expose-Headers',
'electric-offset, electric-handle, electric-schema, electric-cursor'
)Subset security (AND semantics)
Electric combines the main shape WHERE (set in proxy) with subset WHERE (from POST body) using AND. Subsets can only narrow results, never widen them:
-- Main shape: WHERE org_id = $1 (set by proxy)
-- Subset: WHERE status = 'active' (from client POST)
-- Effective: WHERE org_id = $1 AND status = 'active'Even WHERE 1=1 in the subset cannot bypass the main shape's WHERE.
Common Mistakes
CRITICAL Forwarding all client params to Electric
Wrong:
url.searchParams.forEach((value, key) => {
originUrl.searchParams.set(key, value)
})Correct:
import { ELECTRIC_PROTOCOL_QUERY_PARAMS } from '@electric-sql/client'
url.searchParams.forEach((value, key) => {
if (ELECTRIC_PROTOCOL_QUERY_PARAMS.includes(key)) {
originUrl.searchParams.set(key, value)
}
})
originUrl.searchParams.set('table', 'todos')Forwarding all params lets the client control table, where, and columns, accessing any Postgres table. Only forward ELECTRIC_PROTOCOL_QUERY_PARAMS.
Source: examples/proxy-auth/app/shape-proxy/route.ts
CRITICAL Not deleting content-encoding and content-length headers
Wrong:
return new Response(response.body, {
status: response.status,
headers: response.headers,
})Correct:
const headers = new Headers(response.headers)
headers.delete('content-encoding')
headers.delete('content-length')
return new Response(response.body, { status: response.status, headers })fetch() decompresses the response body but keeps the original content-encoding and content-length headers, causing browser decoding failures.
Source: examples/proxy-auth/app/shape-proxy/route.ts:49-56
CRITICAL Exposing ELECTRIC_SECRET or SOURCE_SECRET to browser
Wrong:
// Client-side code
const url = `/v1/shape?table=todos&secret=${import.meta.env.VITE_ELECTRIC_SOURCE_SECRET}`Correct:
// Server proxy only
originUrl.searchParams.set('secret', process.env.ELECTRIC_SOURCE_SECRET!)Bundlers like Vite expose VITE_* env vars to client code. The secret must only be injected server-side in the proxy.
Source: AGENTS.md:17-20
CRITICAL SQL injection in WHERE clause via string interpolation
Wrong:
originUrl.searchParams.set('where', `org_id = '${user.orgId}'`)Correct:
originUrl.searchParams.set('where', 'org_id = $1')
originUrl.searchParams.set('params[1]', user.orgId)String interpolation in WHERE clauses enables SQL injection. Use positional params ($1, $2).
Source: website/docs/guides/auth.md
HIGH Not exposing Electric response headers via CORS
Wrong:
// No CORS header configuration — browser strips custom headers
return new Response(response.body, { headers })Correct:
headers.set(
'Access-Control-Expose-Headers',
'electric-offset, electric-handle, electric-schema, electric-cursor'
)
return new Response(response.body, { headers })The client throws MissingHeadersError if Electric response headers are stripped by CORS. Expose electric-offset, electric-handle, electric-schema, and electric-cursor.
Source: packages/typescript-client/src/error.ts:109-118
CRITICAL Calling Electric directly from production client
Wrong:
new ShapeStream({
url: 'https://my-electric.example.com/v1/shape',
params: { table: 'todos' },
})Correct:
new ShapeStream({
url: '/api/todos', // Your proxy route
})Electric's HTTP API is public by default with no auth. Always proxy through your server so the server controls shape definitions and injects secrets.
Source: AGENTS.md:19-20
See also: electric-shapes/SKILL.md — Shape URLs must point to proxy routes, not directly to Electric. See also: electric-deployment/SKILL.md — Production requires ELECTRIC_SECRET and proxy; dev uses ELECTRIC_INSECURE=true. See also: electric-postgres-security/SKILL.md — Proxy injects secrets that Postgres security enforces.
Version
Targets @electric-sql/client v1.5.10.