Electric Transport

Durable stream transport, proxy and AI SDK adapters.

Packages

Durable transport

• proxy -- node service that proxies backend API requests via Electric shape streams

• transport -- protocol agnostic transport library with proxy-aware fetch client and storage utilities

• ai-transport -- Vercel AI SDK adapter

• tanstack-ai-transport -- TanStack AI adapter

Durable sessions

Durable sessions use a TanStack DB collection as the data model. The durable stream is the source of truth, with messages materialized via a dervied live query pipeline.

• ai-db -- framework-agnostic client, collections, and materialization

• react-ai-db -- React bindings (useDurableChat hook)

• ai-db-proxy -- HTTP proxy for session management and agent invocation

Seperation of concerns

The proxy, transport and ai-db packages should be protocol and reactivity framework agnostic.

How it works

Transport

Resilient transport

1. SDK adapters

• configure the chat UIs to use the durable fetchClient

2. fetchClient

• routes the API request via the proxy

3. the proxy

• proxies the request to the backend API
• writes the response to a shape/stream
• sends back stream urls to the fetchClient

4. fetchClient

• consumes data and control streams
• emits the data stream as a standard response

Persistence

Currently message persistence is all handled by the SDK adapters and localStorage.

There's no server-side persistence or specific protocol-aware proxy services.

Resumability

1. SDK adapters

• configure the chat UIs to reconnect with specific headers

2. fetchClient

• records active generations in localStorage by default
• looks for headers like X-Resume-Active-Generation
• if present, resumes the active generation when requested

Stream protocol

Currently implemented on-top of Postgres using Electric shapes.

Designed to be easily swappable to the new durable streams protocol via a dual data and control stream pattern, aligned with a lastReceivedRowId value that can be swapped for the Stream-Next-Offset when we have that returned from writes to the new dirable streams.

This allows the data stream to be a pure binary stream, with a control stream of transport specific messages handling done and errors. When the client recieves a done or error message, it waits to make sure it's recieves all the preceding data before closing the data stream. Thus preventing race conditions across the two streams.

Note on IDS

We currently use sessionId and requestId identifiers in the database tables. We can move to just a streamId when we have this.

Durable Sessions

See docs/DurableSessions.md for details.

Demos

Standard AI SDK demos adapted to use the Electric Durable transport:

• vercel-ai-sdk-durable-transport -- Vercel AI SDK + Durable Transport
• tanstack-ai-durable-transport -- TanStack AI + Durable Transport

Standard TanStack AI demo adapted to use TanStack DB and Durable Session:

• tanstack-ai-durable-session -- TanStack AI + DB + Durable Session

Usage

Transport Demos (Vercel AI SDK, TanStack AI)

These demos use Electric as the durable stream backend:

pnpm i
pnpm build
pnpm transport-backend:up  # Starts Postgres + Electric on port 3000

# In one terminal
pnpm dev:transport-proxy

# In another terminal, run the default demo (vercel-ai-sdk-durable-transport)
pnpm dev:demo

# Or specify a demo by name
pnpm dev:demo tanstack-ai-durable-transport

Durable Sessions Demo (TanStack AI + TanStack DB)

This demo uses the Durable Streams server:

pnpm i
pnpm build
pnpm session-backend:up  # Starts Durable Streams server on port 3001

# In one terminal
pnpm dev:session-proxy

# In another terminal
pnpm dev:demo tanstack-ai-durable-session

Backend Services

Script	Services	Port
pnpm transport-backend:up	Postgres + Electric	3000
pnpm session-backend:up	Durable Streams	3001
pnpm backend:up	All services	3000, 3001

Demo Ports

• vercel-ai-sdk-durable-transport: http://localhost:5173
• tanstack-ai-durable-transport: http://localhost:5174
• tanstack-ai-durable-session: http://localhost:5175

Demo

Start long generations. Disconnect, reconnect, refresh the page, etc.

With Durable Sessions, you can extend to show multi-user, multi-agent, multi-tab, multi-device etc.