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Author an app

Write an app in plain TypeScript: a provider, some queries and mutations, the approvals that guard them, stored data, and the call that deploys it.

An app is TypeScript source with a default defineApp export from the apps package. A new app is two files: index.ts and a package.json that pins the exact apps version the host runs:

{ "name": "hello", "private": true, "type": "module", "dependencies": { "apps": "<version>" } }

Read that version from the host. Agents call the Executor app’s framework.release; the CLI prints it with executor apps framework. Create the app with both files; a deploy without the version fails and names it. To type-check outside Executor, install exactly that version with npm install --save-exact apps@<version>. Do not install apps@latest: that tag is separate from the Executor beta series.

Executor builds the app with the pinned package’s server and browser framework. It retains the compiled code with the deployment, so host updates do not replace it. The exact version also keeps rebuilds on that version; a version range or tag can select a newer version on the next build. Change it only to upgrade the app. An unavailable or unsupported package fails the build and leaves the active app unchanged. The host protocol is small and shared; early beta releases do not promise indefinite support for every past version.

defineApp declares behavior and does not take a name. Set the package name in package.json, such as "name": "@team/calendar" when publishing. The name you choose when creating or renaming an installed app is its editable display label.

Write ordinary async TypeScript. You do not import Effect and you do not import the Executor SDK. The framework validates input and supplies the selected accounts.

A first app

import { defineApp, object, query, router, string } from "apps";

const Greet = object({ name: string().default("world") });

export default defineApp(
  { accounts: {} },
  {
    tools: router({
      greet: query(
        { description: "Greet someone by name", input: Greet },
        async (_ctx, { name }) => ({ message: `Hello, ${name}!` }),
      ),
    }),
  },
);

defineApp(requirements, definition) takes what the app needs and what it offers. query(options, handler) and mutation(options, handler) declare the operations. Options are description, input, and optionally output and approval. The tools router names them: this app has one tool, greet. Nest routers to group tools; router({ issues: router({ list, close }) }) gives issues.list and issues.close.

The schema helpers are object, string, number, boolean, array, record, json and literal. Use .optional() for a field that may be absent and .default(value) for a default. object strips properties you did not declare. Infer<typeof Input> gives you the parsed input type.

Using an account

Declare a provider, require it, and read it off the context.

import {
  array,
  decodeJson,
  defineApp,
  defineProvider,
  object,
  query,
  type QueryContext,
  router,
  secrets,
  string,
} from "apps";

const vercel = defineProvider({
  name: "Vercel",
  auth: {
    apiKey: secrets({
      label: "API token",
      fields: object({ token: string({ minLength: 1 }) }),
    }),
  },
});

const requirements = { accounts: { vercel } };
type Context = QueryContext<typeof requirements>;

const Projects = object({ projects: array(object({ id: string(), name: string() })) });

const listProjects = query(
  { description: "List projects for the selected Vercel account", input: object({}) },
  async ({ accounts, fetch }: Context) => {
    const response = await fetch("https://api.vercel.com/v9/projects?limit=10", {
      headers: { Authorization: `Bearer ${accounts.vercel.fields.token}` },
    });
    return decodeJson(response, Projects);
  },
);

export default defineApp(requirements, { tools: router({ listProjects }) });

accounts.vercel.fields holds exactly the fields the method declared. The token arrives per call, from whichever account the app has selected. Nothing in the source names an account, so the same code serves a work app and a personal one.

decodeJson(response, schema) checks the HTTP status and parses the body. Use oauth2({ discover: "..." }) instead of secrets for a browser sign-in; the access token then arrives as accounts.<slot>.fields.access_token.

For a slot that takes several accounts, use provider.many(). The context gives you a list.

Queries and mutations

Both become tools. The difference is what they may do to the app’s own stored data.

  • A query gets a read-only view.
  • A mutation writes in a transaction that commits only after its output validates.

External calls are allowed from both, and external effects are never rolled back.

Approvals

Approval is declared on the operation.

import { mutation, object, string } from "apps";
import { always } from "apps/operations/approval";

const closeIssue = mutation(
  {
    description: "Close an issue",
    input: object({ id: string() }),
    approval: always(), // ask a person first; never() runs without asking
  },
  async (_ctx, { id }) => ({ closed: id }),
);

A function gets the real decision. It receives the tool name, the decoded input and an abort signal, and returns approved, denied or user-approval. Annotate a shared one with Approval<Input> to reuse it. For an operation declared elsewhere, wrap it: withApproval(operation, policy). For an imported router, withApprovals(router, (tool, name) => policy) picks each tool’s policy.

There is no app-level approval setting, and nothing is inferred from an operation looking read-only. See Tools and approvals.

Asking for input mid-tool

import { object, query } from "apps";

const nameResult = query(
  { description: "Ask for a name", input: object({}) },
  async (ctx) => {
    const answer = await ctx.elicit({
      mode: "form",
      message: "Name this result",
      requestedSchema: {
        type: "object",
        properties: { name: { type: "string" } },
        required: ["name"],
      },
    });
    return answer.action === "accept" ? { ...answer.content } : {};
  },
);

The question reaches the person the same way an approval does. The answer’s action is accept, decline or cancel; only an accepted answer carries content, the submitted fields.

Importing an existing service

You do not have to write handlers to wrap an API.

import { defineApp } from "apps";
import { mcpRouter } from "apps/mcp";

export default defineApp({ accounts: {} }, async ({ signal }) => ({
  tools: await mcpRouter({
    url: "https://mcp.deepwiki.com/mcp",
    ...(signal === undefined ? {} : { signal }),
  }),
}));

The helpers are mcpRouter from apps/mcp, stdioRouter from apps/mcp/stdio, graphqlRouter from apps/graphql and liveOpenapiRouter from apps/openapi. Each returns a router. Use it as tools, or mount several under keys, such as tools: router({ docs: await mcpRouter(...) }), which names their tools docs.<tool>. An operation that cannot be classified becomes a mutation. The MCP helpers need @modelcontextprotocol/sdk in the app’s package.json dependencies, and graphqlRouter needs graphql.

The dashboard’s Custom app form does the same thing from a URL, for MCP, GraphQL and OpenAPI, without writing any source.

Storing data

Declare a database and the app gets tables.

import {
  defineApp,
  defineDatabase,
  json,
  mutation,
  type MutationContext,
  object,
  query,
  type QueryContext,
  router,
  string,
  table,
} from "apps";

const database = defineDatabase({
  messages: table({ mailbox: string(), subject: string() }).index("by_mailbox", ["mailbox"]),
});

const requirements = { accounts: {}, database };

const list = query(
  { description: "Recent messages", input: object({ mailbox: string() }), output: json() },
  async ({ db }: QueryContext<typeof requirements>, { mailbox }) =>
    db.messages
      .withIndex("by_mailbox", (q) => q.eq("mailbox", mailbox))
      .order("desc")
      .take(50),
);

const add = mutation(
  {
    description: "Store a message",
    input: object({ mailbox: string(), subject: string() }),
    output: json(),
  },
  async ({ db }: MutationContext<typeof requirements>, message) => db.messages.insert(message),
);

export default defineApp(requirements, { tools: router({ list, add }) });

Query it through db on the context, with withIndex, order, and a terminal: first, take, collect, count or paginate({ cursor, numItems }). A by_creation index exists without being declared. A mutation’s db also has insert, update and delete. The host sets each row’s id, createdAt and updatedAt.

Reads are bounded: 5,000 rows scanned, 1,000 returned, 4 MiB per invocation. collect and count fail rather than truncate, so you notice. A mutation allows 1,000 writes.

Shipping instructions

An app can carry its own guidance for agents. Put it beside the source:

  • index.ts
  • skills/
    • triage/
      • SKILL.md
      • references/
        • examples.md
---
name: triage
description: Search cached messages before fetching more history.
---

Read [examples](references/examples.md), then discover this app's tools.

An agent reads it with the skills tool. Skill text never grants a permission; the approval still decides.

Deploying

Deployment is an operation, not a command. Have your agent call it through the MCP endpoint. Read the version with framework.release, create the app from index.ts and the package.json that pins it, then deploy the same files:

const executor = tools.executor.profiles["<management-profile-id>"];
const path = { organization: "<approved-organization-id>" };
const { version } = await executor.framework.release({ path });
const files = [
  { path: "index.ts", content: "<contents of index.ts>" },
  {
    path: "package.json",
    content: JSON.stringify({
      name: "hello",
      private: true,
      type: "module",
      dependencies: { apps: version },
    }),
  },
];
const app = await executor.appManagement.create({ path, body: { name: "Hello", files } });
return await executor.appManagement.deploy({ path: { ...path, app: app.id }, body: { files } });
const executor = tools.executor.profiles["<management-profile-id>"];
const { version } = await executor.framework.release({});
const files = [
  { path: "index.ts", content: "<contents of index.ts>" },
  {
    path: "package.json",
    content: JSON.stringify({
      name: "hello",
      private: true,
      type: "module",
      dependencies: { apps: version },
    }),
  },
];
const app = await executor.appManagement.create({ body: { name: "Hello", files } });
return await executor.appManagement.deploy({ path: { app: app.id }, body: { files } });

From a shell, write the same two files into a directory, using the version executor apps framework prints:

executor apps create --name "Hello" --files ./hello    # prints the app, including its id
executor apps source --app <app-id> | jq -r .revision.commit
executor apps deploy --app <app-id> --commit <first-commit>

The app activates only after the build succeeds, and earlier deployments are retained; see Apps and deployments. Then connect an account for each requirement and, in a new execute, call the path tools.search returns. An app without accounts is called by its slug:

return await tools.hello.greet({ name: "Ada" });

An app with accounts is called through a profile, such as tools.vercel.profiles["<profile-id>"].listProjects({}).

Updating an existing app

Create-by-name calls reject an existing name. Edit an existing app through the same source, commit and deploy operations on Local and Hosted. Read their current signatures first. Hosted paths include organization; Local paths contain only app.

const executor = tools.executor.profiles["<management-profile-id>"];
const path = { organization: "<approved-organization-id>", app: "<app-id>" };
const source = await executor.appManagement.source({ path });
const files = source.files.map((file) =>
  file.path === "index.ts" ? { ...file, content: "<complete updated source>" } : file,
);
const saved = await executor.appManagement.commit({
  path,
  body: { expected: source.revision.commit, message: "Update greeting", files },
});
return await executor.appManagement.deploy({
  path,
  body: { commit: saved.revision.commit },
});

The commit replaces the complete file list, so keep package.json in it. Saving source does not deploy it. Web pages show source; agents or ordinary Git clients edit it.

Discovery is not cached across a change, so run tools.search again after you deploy.

The CLI also provides executor apps source, executor apps commit, and executor apps deploy --commit <sha>. Deployment reads the chosen commit and leaves the Git branch unchanged. Ordinary Git pushes save source without deploying it.

Update a hosted app

Use appManagement.deploy with { files: [...] } to deploy a complete file set, or { commit: "<sha>" } to deploy an existing Git commit. File deployments do not save changes to Git. The app keeps its ID and stored data. The newest successful deployment becomes active. Use apps.activate to select a retained deployment; activation does not roll back stored data.

Open an app UI

React is the only supported app UI framework for now. Include ui/index.html, a React entry such as ui/main.tsx, and styles in the deployment. Declare react and react-dom in the app’s package dependencies. The host builds and activates the browser assets with the server code. No separate publish step is needed. SSR and React Server Components are not supported yet.

You can bring your own React components or browser-compatible npm component libraries. Declare their dependencies and include the required styles and assets. Libraries that need custom build plugins require additional build support.

Tailwind CSS v4 compilation is built in. Import a stylesheet from your React entry:

import "./style.css";

Start ui/style.css with:

@import "tailwindcss";

Write complete utility classes in your React components. No Tailwind dependency, config file or separate build command is needed. The build scans browser code, including imported components and lazy chunks. Ordinary CSS and component-library styles can share the same app.

Use CSS @theme for custom tokens. Use @source inline("...") to include classes that only arrive at runtime. Filesystem @source paths and JavaScript @config or @plugin files are not supported.

For hosted apps, discover appUi.location through tools.search and call it:

return await tools.executor.profiles["<management-profile-id>"].appUi.location({
  path: { organization: "<approved-organization-id>", app: "<app-id>" },
});

Open the returned url in a browser. Executor Cloud uses https://<app-slug>.<org-slug>.executor.website; self-host uses its configured app domain. Use the returned URL instead of guessing it. A null URL means the app has no UI or the host has no app domain configured.

App pages are private. Opening the link starts browser sign-in through Executor. A successful tool call or a 403 from a guessed address does not verify that the UI renders. Check the actual page before reporting it as working.

What is coming later

  • Scheduled and background work.
  • Calling one app from another.
  • Authoring general HTTP endpoints.
  • Stored-data schema migration between deployments.
  • A local executor dev loop.

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