Block Kit

EmDash’s Block Kit lets sandboxed plugins describe their admin UI as JSON. The host renders the blocks — no plugin-supplied JavaScript ever runs in the browser.

How it works

1. The user navigates to a plugin’s admin page.
2. The admin sends a page_load interaction to the plugin’s admin route.
3. The plugin returns a BlockResponse containing an array of blocks.
4. The admin renders the blocks using the BlockRenderer component.
5. When the user interacts (clicks a button, submits a form), the admin sends the interaction back to the plugin.
6. The plugin returns new blocks, and the cycle repeats.

import { definePlugin } from "emdash";
import type { PluginContext } from "emdash";

interface BlockInteraction {
	type: "page_load" | "block_action" | "form_submit";
	page?: string;
	action_id?: string;
	values?: Record<string, unknown>;
}

export default definePlugin({
	routes: {
		admin: {
			handler: async (routeCtx, ctx: PluginContext) => {
				const interaction = routeCtx.input as BlockInteraction;

				if (interaction.type === "page_load") {
					return {
						blocks: [
							{ type: "header", text: "My Plugin Settings" },
							{
								type: "form",
								block_id: "settings",
								fields: [
									{ type: "text_input", action_id: "api_url", label: "API URL" },
									{ type: "toggle", action_id: "enabled", label: "Enabled", initial_value: true },
								],
								submit: { label: "Save", action_id: "save" },
							},
						],
					};
				}

				if (interaction.type === "form_submit" && interaction.action_id === "save") {
					await ctx.kv.set("settings", interaction.values);
					return {
						blocks: [/* ... updated blocks ... */],
						toast: { message: "Settings saved", type: "success" },
					};
				}

				return { blocks: [] };
			},
		},
	},
});

The standard-format route handler takes two arguments: routeCtx (with input, request, requestMeta) and ctx (the PluginContext).

Block types

Element types

Builder helpers

The @emdash-cms/blocks package exports builder helpers for cleaner code:

import { blocks, elements } from "@emdash-cms/blocks";

const { header, form, section, stats } = blocks;
const { textInput, toggle, select, button } = elements;

return {
	blocks: [
		header("SEO Settings"),
		form({
			blockId: "settings",
			fields: [
				textInput("site_title", "Site Title", { initialValue: "My Site" }),
				toggle("generate_sitemap", "Generate Sitemap", { initialValue: true }),
				select("robots", "Default Robots", [
					{ label: "Index, Follow", value: "index,follow" },
					{ label: "No Index", value: "noindex,follow" },
				]),
			],
			submit: { label: "Save", actionId: "save" },
		}),
	],
};

Conditional fields

Form fields can be conditionally shown based on other field values:

{
	"type": "toggle",
	"action_id": "auth_enabled",
	"label": "Enable Authentication"
}

{
	"type": "secret_input",
	"action_id": "api_key",
	"label": "API Key",
	"condition": { "field": "auth_enabled", "eq": true }
}

The api_key field only appears when auth_enabled is toggled on. Conditions are evaluated client-side with no round-trip.

Try it

Use the Block Playground to interactively build and test block layouts.