SpacetimeDB TypeScript SDK

Build real-time TypeScript clients that connect directly to SpacetimeDB modules. The SDK provides type-safe database access, automatic synchronization, and reactive updates for web apps, Node.js, Deno, Bun, and other JavaScript runtimes.

---

HALLUCINATED APIs — DO NOT USE

These APIs DO NOT EXIST. LLMs frequently hallucinate them.

// WRONG PACKAGE — does not exist
import { SpacetimeDBClient } from "@clockworklabs/spacetimedb-sdk";

// WRONG — these methods don't exist
SpacetimeDBClient.connect(...);
SpacetimeDBClient.call("reducer_name", [...]);
connection.call("reducer_name", [arg1, arg2]);

// WRONG — positional reducer arguments
conn.reducers.doSomething("value");  // WRONG!

// WRONG — old 1.0 patterns
spacetimedb.reducer('reducer_name', params, fn);  // Use export const name = spacetimedb.reducer(params, fn)
schema(myTable);          // Use schema({ myTable })
schema(t1, t2, t3);      // Use schema({ t1, t2, t3 })
scheduled: 'run_cleanup'  // Use scheduled: () => run_cleanup
.withModuleName('db')     // Use .withDatabaseName('db') (2.0)
setReducerFlags.x('NoSuccessNotify')  // Removed in 2.0

CORRECT PATTERNS:

// CORRECT IMPORTS
import { DbConnection, tables } from './module_bindings';  // Generated!
import { SpacetimeDBProvider, useTable } from 'spacetimedb/react';
import { Identity } from 'spacetimedb';

// CORRECT REDUCER CALLS — object syntax, not positional!
conn.reducers.doSomething({ value: 'test' });
conn.reducers.updateItem({ itemId: 1n, newValue: 42 });

// CORRECT DATA ACCESS — useTable returns [rows, isReady]
const [items, isReady] = useTable(tables.item);

DO NOT:

• Invent hooks like useItems(), useData() — use useTable(tables.tableName)
• Import from fake packages — only spacetimedb, spacetimedb/react, ./module_bindings

---

Common Mistakes Table

Server-side errors

Wrong	Right	Error
Missing package.json	Create package.json	"could not detect language"
Missing tsconfig.json	Create tsconfig.json	"TsconfigNotFound"
Entrypoint not at src/index.ts	Use src/index.ts	Module won't bundle
indexes in COLUMNS (2nd arg)	indexes in OPTIONS (1st arg) of table()	"reading 'tag'" error
Index without algorithm	algorithm: 'btree'	"reading 'tag'" error
filter({ ownerId })	filter(ownerId)	"does not exist in type 'Range'"
.filter() on unique column	.find() on unique column	TypeError
insert({ ...without id })	insert({ id: 0n, ... })	"Property 'id' is missing"
const id = table.insert(...)	const row = table.insert(...)	.insert() returns ROW, not ID
.unique() + explicit index	Just use .unique()	"name is used for multiple entities"
Import spacetimedb from index.ts	Import from schema.ts	"Cannot access before initialization"
Incorrect multi-column .filter() range shape	Match index prefix/tuple shape	Empty results or range/type errors
.iter() in views	Use index lookups only	Views can't scan tables
ctx.db in procedures	ctx.withTx(tx => tx.db...)	Procedures need explicit transactions

Client-side errors

Wrong	Right	Error
Inline connectionBuilder	useMemo(() => ..., [])	Reconnects every render
const rows = useTable(table)	const [rows, isReady] = useTable(table)	Tuple destructuring
Optimistic UI updates	Let subscriptions drive state	Desync issues
<SpacetimeDBProvider builder={...}>	connectionBuilder={...}	Wrong prop name

---

Hard Requirements

1. schema({ table }) — use a single tables object; optional module settings are allowed as a second argument
2. Reducer/procedure names from exports — export const name = spacetimedb.reducer(params, fn); never reducer('name', ...)
3. Reducer calls use object syntax — { param: 'value' } not positional args
4. Import DbConnection from ./module_bindings — not from spacetimedb
5. DO NOT edit generated bindings — regenerate with spacetime generate
6. Indexes go in OPTIONS (1st arg) — not in COLUMNS (2nd arg) of table()
7. Use BigInt for u64/i64 fields — 0n, 1n, not 0, 1
8. Reducers are transactional — they do not return data
9. Reducers must be deterministic — no filesystem, network, timers, random
10. Views should use index lookups — .iter() causes severe performance issues
11. Procedures need ctx.withTx() — ctx.db doesn't exist in procedures
12. Sum type values — use { tag: 'variant', value: payload } not { variant: payload }
13. Use .withDatabaseName() — not .withModuleName() (2.0)

---

Installation

npm install spacetimedb

For Node.js environments without native fetch/WebSocket support, install undici.

Generating Type Bindings

spacetime generate --lang typescript --out-dir ./src/module_bindings --module-path ./server

Client Connection

import { DbConnection } from './module_bindings';

const connection = DbConnection.builder()
  .withUri('ws://localhost:3000')
  .withDatabaseName('my_database')
  .withToken(localStorage.getItem('spacetimedb_token') ?? undefined)
  .onConnect((conn, identity, token) => {
    // identity: your unique Identity for this database
    console.log('Connected as:', identity.toHexString());

    // Save token for reconnection (preserves identity across sessions)
    localStorage.setItem('spacetimedb_token', token);

    conn.subscriptionBuilder()
      .onApplied(() => console.log('Cache ready'))
      .subscribe('SELECT * FROM player');
  })
  .onDisconnect((ctx) => console.log('Disconnected'))
  .onConnectError((ctx, error) => console.error('Connection failed:', error))
  .build();

Subscribing to Tables

// Basic subscription
connection.subscriptionBuilder()
  .onApplied((ctx) => console.log('Cache ready'))
  .subscribe('SELECT * FROM player');

// Multiple queries
connection.subscriptionBuilder()
  .subscribe(['SELECT * FROM player', 'SELECT * FROM game_state']);

// Subscribe to all tables (development only — cannot mix with Subscribe)
connection.subscriptionBuilder().subscribeToAllTables();

// Subscription handle for later unsubscribe
const handle = connection.subscriptionBuilder()
  .onApplied(() => console.log('Subscribed'))
  .subscribe('SELECT * FROM player');

handle.unsubscribeThen(() => console.log('Unsubscribed'));

Accessing Table Data

for (const player of connection.db.player.iter()) { console.log(player.name); }
const players = Array.from(connection.db.player.iter());
const count = connection.db.player.count();
const player = connection.db.player.id.find(42n);

Table Event Callbacks

connection.db.player.onInsert((ctx, player) => console.log('New:', player.name));
connection.db.player.onDelete((ctx, player) => console.log('Left:', player.name));
connection.db.player.onUpdate((ctx, old, new_) => console.log(`${old.score} -> ${new_.score}`));

Calling Reducers

CRITICAL: Use object syntax, not positional arguments.

connection.reducers.createPlayer({ name: 'Alice', location: { x: 0, y: 0 } });

Snake_case to camelCase conversion

• Server: export const do_something = spacetimedb.reducer(...)
• Client: conn.reducers.doSomething({ ... })

---

Identity and Authentication

• identity and token are provided in the onConnect callback (see Client Connection above)
• identity.toHexString() for display or logging
• Omit .withToken() for anonymous connection — server assigns a new identity
• Pass a stale/invalid token: server issues a new identity and token in onConnect

---

Error Handling

Connection-level errors (.onConnectError, .onDisconnect) are shown in the Client Connection example above.

// Subscription error
connection.subscriptionBuilder()
  .onApplied(() => console.log('Subscribed'))
  .onError((ctx) => console.error('Subscription error:', ctx.event))
  .subscribe('SELECT * FROM player');

---

Server-Side Module Development

Table Definition

import { schema, table, t } from 'spacetimedb/server';

export const Task = table({
  name: 'task',
  public: true,
  indexes: [{ name: 'task_owner_id', algorithm: 'btree', columns: ['ownerId'] }]
}, {
  id: t.u64().primaryKey().autoInc(),
  ownerId: t.identity(),
  title: t.string(),
  createdAt: t.timestamp(),
});

Column types

t.identity()           // User identity
t.u64()                // Unsigned 64-bit integer (use for IDs)
t.string()             // Text
t.bool()               // Boolean
t.timestamp()          // Timestamp
t.scheduleAt()         // For scheduled tables only
t.object('Name', {})   // Product types (nested objects)
t.enum('Name', {})     // Sum types (tagged unions)
t.string().optional()  // Nullable

BigInt syntax: All u64/i64 fields use 0n, 1n, not 0, 1.

Schema export

const spacetimedb = schema({ Task, Player });
export default spacetimedb;

Reducer Definition (2.0)

Name comes from the export — NOT from a string argument.

import spacetimedb from './schema';
import { t, SenderError } from 'spacetimedb/server';

export const create_task = spacetimedb.reducer(
  { title: t.string() },
  (ctx, { title }) => {
    if (!title) throw new SenderError('title required');
    ctx.db.task.insert({ id: 0n, ownerId: ctx.sender, title, createdAt: ctx.timestamp });
  }
);

Update Pattern

const existing = ctx.db.task.id.find(taskId);
if (!existing) throw new SenderError('Task not found');
ctx.db.task.id.update({ ...existing, title: newTitle, updatedAt: ctx.timestamp });

Lifecycle Hooks

spacetimedb.clientConnected((ctx) => { /* ctx.sender is the connecting identity */ });
spacetimedb.clientDisconnected((ctx) => { /* clean up */ });

---

Event Tables (2.0)

Reducer callbacks are removed in 2.0. Use event tables + onInsert instead.

export const DamageEvent = table(
  { name: 'damage_event', public: true, event: true },
  { target: t.identity(), amount: t.u32() }
);

export const deal_damage = spacetimedb.reducer(
  { target: t.identity(), amount: t.u32() },
  (ctx, { target, amount }) => {
    ctx.db.damageEvent.insert({ target, amount });
  }
);

Client subscribes and uses onInsert:

conn.db.damageEvent.onInsert((ctx, evt) => {
  playDamageAnimation(evt.target, evt.amount);
});

Event tables must be subscribed explicitly — they are excluded from subscribeToAllTables().

---

Views

ViewContext vs AnonymousViewContext

// ViewContext — has ctx.sender, result varies per user
spacetimedb.view({ name: 'my_items', public: true }, t.array(Item.rowType), (ctx) => {
  return [...ctx.db.item.by_owner.filter(ctx.sender)];
});

// AnonymousViewContext — no ctx.sender, same result for everyone (better perf)
spacetimedb.anonymousView({ name: 'leaderboard', public: true }, t.array(Player.rowType), (ctx) => {
  return ctx.from.player.where(p => p.score.gt(1000));
});

Views can only use index lookups — .iter() is NOT allowed.

---

Scheduled Tables

export const CleanupJob = table({
  name: 'cleanup_job',
  scheduled: () => run_cleanup  // function returning the exported reducer
}, {
  scheduledId: t.u64().primaryKey().autoInc(),
  scheduledAt: t.scheduleAt(),
  targetId: t.u64(),
});

export const run_cleanup = spacetimedb.reducer(
  { arg: CleanupJob.rowType },
  (ctx, { arg }) => { /* arg.scheduledId, arg.targetId available */ }
);

// Schedule a job
import { ScheduleAt } from 'spacetimedb';
ctx.db.cleanupJob.insert({
  scheduledId: 0n,
  scheduledAt: ScheduleAt.time(ctx.timestamp.microsSinceUnixEpoch + 60_000_000n),
  targetId: someId
});

ScheduleAt on Client

// ScheduleAt is a tagged union on the client
// { tag: 'Time', value: Timestamp } or { tag: 'Interval', value: TimeDuration }
const schedule = row.scheduledAt;
if (schedule.tag === 'Time') {
  const date = new Date(Number(schedule.value.microsSinceUnixEpoch / 1000n));
}

---

Timestamps

Server-side

ctx.db.item.insert({ id: 0n, createdAt: ctx.timestamp });
const future = ctx.timestamp.microsSinceUnixEpoch + 300_000_000n;

Client-side

// Timestamps are objects with BigInt, not numbers
const date = new Date(Number(row.createdAt.microsSinceUnixEpoch / 1000n));

---

Procedures (Beta)

export const fetch_data = spacetimedb.procedure(
  { url: t.string() }, t.string(),
  (ctx, { url }) => {
    const response = ctx.http.fetch(url);
    ctx.withTx(tx => { tx.db.myTable.insert({ id: 0n, content: response.text() }); });
    return response.text();
  }
);

Procedures don't have ctx.db — use ctx.withTx(tx => tx.db...).

---

React Integration

import { useMemo } from 'react';
import { SpacetimeDBProvider, useTable } from 'spacetimedb/react';
import { DbConnection, tables } from './module_bindings';

function Root() {
  const connectionBuilder = useMemo(() =>
    DbConnection.builder()
      .withUri('ws://localhost:3000')
      .withDatabaseName('my_game')
      .withToken(localStorage.getItem('auth_token') || undefined)
      .onConnect((conn, identity, token) => {
        localStorage.setItem('auth_token', token);
        conn.subscriptionBuilder().subscribe(tables.player);
      }),
    []
  );

  return (
    <SpacetimeDBProvider connectionBuilder={connectionBuilder}>
      <App />
    </SpacetimeDBProvider>
  );
}

function PlayerList() {
  const [players, isReady] = useTable(tables.player);
  if (!isReady) return <div>Loading...</div>;
  return <ul>{players.map(p => <li key={p.id}>{p.name}</li>)}</ul>;
}

---

Project Structure

Server (backend/spacetimedb/)

src/schema.ts   -> Tables, export spacetimedb
src/index.ts    -> Reducers, lifecycle, import schema
package.json    -> { "type": "module", "dependencies": { "spacetimedb": "^2.0.0" } }
tsconfig.json   -> Standard config

Client (client/)

src/module_bindings/ -> Generated (spacetime generate)
src/main.tsx         -> Provider, connection setup
src/App.tsx          -> UI components

---

Commands

spacetime start
spacetime publish <module-name> --module-path <backend-dir>
spacetime publish <module-name> --clear-database -y --module-path <backend-dir>
spacetime generate --lang typescript --out-dir <client>/src/module_bindings --module-path <backend-dir>
spacetime logs <module-name>