feat(host-wasm): add @parity/truapi-host-wasm runtime

.gitignore

@@ -11,6 +11,12 @@ lerna-debug.log*
 node_modules
 target
 
+# Gradle (Android workspace at repo root)
+/.gradle/
+/build/
+/android/*/build/
+local.properties
+
 # Environment / secrets (never commit real env files; keep example templates)
 .env
 .env.*
@@ -39,3 +45,16 @@ playground/public/static.files
 
 # Auto-generated by truapi-codegen (typecheck fixtures for rustdoc ts blocks)
 playground/test/generated/
+
+# Auto-generated FFI / WASM binding outputs
+android/truapi-host/src/main/kotlin/generated/
+ios/truapi-host/Sources/TrUAPIHost/truapi_server.swift
+ios/truapi-host/Sources/truapi_serverFFI/
+rust/crates/truapi-server/pkg/
+js/packages/truapi/src/generated/
+js/packages/truapi/dist/generated/
+js/packages/truapi-host/src/generated/
+js/packages/truapi-host/dist/generated/
+js/packages/truapi-host-wasm/src/generated/
+js/packages/truapi-host-wasm/dist/generated/
+js/packages/truapi-host-wasm/dist/wasm/

.prettierrc

@@ -10,7 +10,10 @@
   "endOfLine": "lf",
   "overrides": [
     {
-      "files": "js/packages/truapi/src/**/*.test.ts",
+      "files": [
+        "js/packages/truapi/src/**/*.test.ts",
+        "js/packages/truapi-host-wasm/src/**/*.test.ts"
+      ],
       "options": {
         "tabWidth": 4,
         "printWidth": 100

js/packages/truapi-host/.gitignore

@@ -0,0 +1,11 @@
+node_modules/
+*.tsbuildinfo
+# Ignore compiled TS output (top-level + the web/ and electron/ entry subdirs)
+# Generated WASM artifacts under dist/wasm/ are ignored by the repo root.
+dist/**/*.js
+dist/**/*.d.ts
+dist/**/*.js.map
+dist/**/*.d.ts.map
+dist/generated/
+# Codegen output from truapi-codegen --platform-ts-output.
+src/generated/

js/packages/truapi-host/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Parity Technologies
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

js/packages/truapi-host/README.md

@@ -0,0 +1,79 @@
+# @parity/truapi-host
+
+WASM-backed TrUAPI host runtime. It embeds the `truapi-server` Rust core (compiled to WASM)
+behind a Web Worker provider, plus per-environment integration entry points. It is the
+counterpart to the native Android/iOS host shells.
+
+## Entry points
+
+The package exposes tree-shakeable subpath exports — import only what your environment needs:
+
+| Import                               | Provides                                                                                                            |
+| ------------------------------------ | ------------------------------------------------------------------------------------------------------------------- |
+| `@parity/truapi-host`                | Shared runtime types plus generated typed host callback contracts.                                                  |
+| `@parity/truapi-host/web`            | Browser pairing host: `createIframeHost` (iframe MessageChannel handshake) and `createWebWorkerPairingHostRuntime`. |
+| `@parity/truapi-host/worker-runtime` | Web Worker entrypoint (import with your bundler's `?worker` suffix) so the WASM core runs off the page main thread. |
+| `@parity/truapi-host/wasm/web`       | The raw browser `wasm-bindgen` glue, if you need to instantiate the core yourself.                                  |
+
+## Generated WASM artefacts
+
+The ignored bundle under `dist/wasm/web/` is built with host-owned chain access.
+Hosts wire their JSON-RPC provider through `chainConnect`; if they omit it,
+chain calls fail with the core's standard unavailable error. The bundled WASM is
+about 1 MB (release build with `wasm-opt`).
+
+Build them after editing `rust/crates/truapi-server` and before packaging, publishing, or running
+tests that load the raw WASM bundle (requires `wasm-pack` on PATH):
+
+```bash
+npm run build:wasm   # or `make wasm` from the repo root
+```
+
+## Example — browser (Web Worker)
+
+```ts
+import HostWorker from "@parity/truapi-host/worker-runtime?worker";
+import { createWebWorkerPairingHostRuntime } from "@parity/truapi-host/web";
+
+const runtime = await createWebWorkerPairingHostRuntime(
+  new HostWorker(),
+  callbacks,
+  {
+    hostConfig,
+  },
+);
+
+const firstProvider = await runtime.createProvider({ productId: "first.dot" });
+const secondProvider = await runtime.createProvider({
+  productId: "second.dot",
+});
+```
+
+`@parity/truapi-host/web` also exports `createIframeHost` for the
+protocol-iframe MessageChannel handshake. Host code creates one worker runtime
+and then opens one provider per product id.
+
+## Publishing
+
+This package is published by the root `Release` workflow through
+`paritytech/npm_publish_automation`. Do not run `npm publish` locally. Cut a
+`release:` PR with a changeset for `@parity/truapi-host`; the workflow builds
+the generated host bindings, the browser WASM bundle, packs the tarball, and
+publishes it when the `@parity/truapi-host@<version>` tag does not already
+exist.
+
+## Architecture
+
+```text
+JS host code
+  protocol handlers / typed callbacks
+  (types from @parity/truapi-host)
+       |
+       v
+createWebWorkerPairingHostRuntime
+  shared worker runtime: pairing session, chain runtime, WASM instance
+       |
+       +-- createProvider({ productId }) -> product core / WireProvider
+       |
+       +-- createProvider({ productId }) -> product core / WireProvider
+```

js/packages/truapi-host/package.json

@@ -0,0 +1,59 @@
+{
+  "name": "@parity/truapi-host",
+  "version": "0.1.0",
+  "description": "WASM-backed TrUAPI host runtime: embeds the Rust core, with web iframe and Web Worker entry points",
+  "license": "MIT",
+  "author": "Parity Technologies <admin@parity.io>",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/paritytech/truapi.git",
+    "directory": "js/packages/truapi-host"
+  },
+  "homepage": "https://github.com/paritytech/truapi#readme",
+  "bugs": {
+    "url": "https://github.com/paritytech/truapi/issues"
+  },
+  "type": "module",
+  "main": "dist/index.js",
+  "types": "dist/index.d.ts",
+  "sideEffects": [
+    "./dist/worker-runtime.js",
+    "./dist/wasm/**"
+  ],
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js"
+    },
+    "./web": {
+      "types": "./dist/web/index.d.ts",
+      "import": "./dist/web/index.js"
+    },
+    "./worker-runtime": {
+      "types": "./dist/worker-runtime.d.ts",
+      "import": "./dist/worker-runtime.js"
+    },
+    "./wasm/web": {
+      "types": "./dist/wasm/web/truapi_server.d.ts",
+      "import": "./dist/wasm/web/truapi_server.js"
+    }
+  },
+  "files": [
+    "dist",
+    "README.md",
+    "LICENSE"
+  ],
+  "scripts": {
+    "build": "tsc -b",
+    "build:wasm": "node scripts/build-wasm.mjs",
+    "test": "bun test"
+  },
+  "dependencies": {
+    "@parity/truapi": "file:../truapi"
+  },
+  "devDependencies": {
+    "@types/bun": "^1.3.0",
+    "neverthrow": "^8.2.0",
+    "typescript": "^5.7"
+  }
+}

js/packages/truapi-host/scripts/build-wasm.mjs

@@ -0,0 +1,63 @@
+#!/usr/bin/env node
+// Rebuild the browser truapi-server WASM artefacts generated under
+// `dist/wasm/web/`. wasm-pack is required.
+
+import { execFile } from "node:child_process";
+import { rm } from "node:fs/promises";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+import { promisify } from "node:util";
+
+const execFileAsync = promisify(execFile);
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const pkgRoot = resolve(__dirname, "..");
+const repoRoot = resolve(pkgRoot, "../../..");
+const rustCrate = resolve(repoRoot, "rust/crates/truapi-server");
+const wasmProfile = process.env.TRUAPI_WASM_PROFILE ?? "release";
+
+function args(target, outDir) {
+  const command = [
+    "build",
+    "--target",
+    target,
+    "--out-dir",
+    outDir,
+    "--out-name",
+    "truapi_server",
+  ];
+  if (wasmProfile === "dev") {
+    command.push("--dev");
+  } else if (wasmProfile === "profiling") {
+    command.push("--profiling");
+  } else if (wasmProfile !== "release") {
+    throw new Error(
+      `Unsupported TRUAPI_WASM_PROFILE=${wasmProfile}; expected release, dev, or profiling`,
+    );
+  }
+  command.push(rustCrate, "--no-default-features");
+  return command;
+}
+
+async function build(target, subdir) {
+  const outDir = resolve(pkgRoot, "dist/wasm", subdir);
+  process.stdout.write(
+    `wasm-pack build --target ${target} --${wasmProfile} → ${outDir}\n`,
+  );
+  try {
+    await execFileAsync("wasm-pack", args(target, outDir), { cwd: repoRoot });
+  } catch (err) {
+    if (err?.code === "ENOENT") {
+      console.error(
+        "wasm-pack is required. Install it with `cargo install wasm-pack` " +
+          "or see https://rustwasm.github.io/wasm-pack/installer/",
+      );
+      process.exit(1);
+    }
+    throw err;
+  }
+  // wasm-pack writes a nested `.gitignore: *`; the repo-level ignore already
+  // owns generated WASM outputs.
+  await rm(resolve(outDir, ".gitignore"), { force: true });
+}
+
+await build("web", "web");