diff --git a/src/execution-world/README.md b/src/execution-world/README.md
index eabbe35..d65ec12 100644
--- a/src/execution-world/README.md
+++ b/src/execution-world/README.md
@@ -44,8 +44,12 @@ Its digest excludes its own digest field. Paths must be normalized and relative.
 `checkExecutionWorld` verifies plan identity, supported codecs, exact source and
 binding schema, service fallback, promised targets, declared exports, and all
 supplied file bytes. The reader must confine paths/symlinks to the checked output
-and honor its byte limit before allocation. LF-05 supplies that filesystem adapter,
-checks actual module registries/imports, and verifies build receipts; a manifest
+and honor its byte limit before allocation. `artifactFileReader` supplies that
+adapter for trusted immutable output roots. `loadArtifactWorld` checks candidate
+outputs without importing package code. `BrowserArtifactGateway` registers only
+declared browser assets and verifies bytes before serving; Web Studio places it
+behind workspace authentication. LF-05 still checks actual module
+registries/imports and verifies build receipts; a manifest
 claim alone does not establish the JavaScript exports or an isolated process.
 
 The returned `camino-world-v1` descriptor includes every declared implementation
@@ -75,8 +79,9 @@ from an asynchronous completion order or the transport sequence number.
 
 The coordinator resolves each port through the installed operation binding,
 checks effects/selected methods, validates typed arguments/references, and joins
-nested calls to the outer logical transaction. A nested failure rolls back to its
-frame boundary; process completion cannot independently commit. The coordinator
+nested calls to the outer logical transaction. A nested failure poisons the outer domain
+transaction even if application code catches it; frame cleanup cannot turn it into
+a partial success. Process completion cannot independently commit. The coordinator
 owns savepoints, cancellation, frame expiry, and rejection. These enforcement
 mechanisms are LF-06/LF-08, not guarantees provided by TypeScript frame types.
 
diff --git a/src/execution-world/files.ts b/src/execution-world/files.ts
new file mode 100644
index 0000000..765a590
--- /dev/null
+++ b/src/execution-world/files.ts
@@ -0,0 +1,155 @@
+import { constants } from "node:fs";
+import { lstat, open, realpath } from "node:fs/promises";
+import path from "node:path";
+import { createHash } from "node:crypto";
+import {
+  artifactPath,
+  parsePackageArtifacts,
+  checkExecutionWorld,
+  checkedWorldDigest,
+  type ArtifactReader,
+  type ArtifactFile,
+  type PackageArtifacts,
+  type CheckedWorld,
+} from "./artifacts.js";
+import { type ExecutionPlan, ExecutionPlanError } from "./plan.js";
+
+const maxFileBytes = 256 * 1024 * 1024;
+const metadataLimit = 16 * 1024 * 1024;
+const fail = (where: string, message: string): never => {
+  throw new ExecutionPlanError("ARTIFACT_FILE_INVALID", where, message);
+};
+/** Roots must be trusted immutable output directories. Refuse symlinks, including
+ * interior directory links. Hash verification is still required before serving bytes. */
+export async function artifactFileReader(roots: Readonly<Record<string, string>>): Promise<ArtifactReader> {
+  const directories = new Map<string, string>();
+  for (const [revision, root] of Object.entries(roots)) {
+    if (!path.isAbsolute(root) || path.normalize(root) !== root || (await realpath(root)) !== root)
+      fail(revision, "Output root must be a canonical absolute directory");
+    const stat = await lstat(root);
+    if (!stat.isDirectory() || stat.isSymbolicLink()) fail(root, "Output root is not a directory");
+    directories.set(revision, root);
+  }
+  return async (revision, relative, limit) => {
+    const root = directories.get(revision);
+    if (!root) fail(revision, "Unknown package output");
+    artifactPath(relative);
+    if (!Number.isSafeInteger(limit) || limit < 0 || limit > maxFileBytes) fail(relative, "Invalid file byte limit");
+    const components = relative.split("/");
+    let resolved = root!;
+    for (let index = 0; index < components.length; index++) {
+      resolved = path.join(resolved, components[index]!);
+      const stat = await lstat(resolved);
+      if (stat.isSymbolicLink() || (index < components.length - 1 ? !stat.isDirectory() : !stat.isFile()))
+        fail(relative, "Only real directories and regular files are allowed");
+    }
+    const handle = await open(resolved, constants.O_RDONLY | constants.O_NOFOLLOW | constants.O_NONBLOCK);
+    try {
+      const stat = await handle.stat();
+      if (!stat.isFile() || stat.size > limit) fail(relative, "File exceeds its declared bound");
+      // A fixed allocation and one extra byte detect growth without readFile's unbounded allocation.
+      const buffer = Buffer.alloc(stat.size + 1);
+      let offset = 0;
+      while (offset < buffer.length) {
+        const { bytesRead } = await handle.read(buffer, offset, buffer.length - offset, offset);
+        if (!bytesRead) break;
+        offset += bytesRead;
+      }
+      if (offset !== stat.size) fail(relative, "File changed while reading");
+      return buffer.subarray(0, offset);
+    } finally {
+      await handle.close();
+    }
+  };
+}
+export interface LoadedArtifactWorld {
+  world: CheckedWorld;
+  digest: string;
+  manifests: PackageArtifacts[];
+  read: ArtifactReader;
+}
+/** Immutable-output loader. No module code is imported into the coordinator. */
+export async function loadArtifactWorld(
+  plan: ExecutionPlan,
+  roots: Readonly<Record<string, string>>,
+): Promise<LoadedArtifactWorld> {
+  const read = await artifactFileReader(roots),
+    manifests: PackageArtifacts[] = [];
+  const expected = plan.definition.packages.map((p) => p.revision).sort();
+  if (JSON.stringify(Object.keys(roots).sort()) !== JSON.stringify(expected))
+    fail("world", "Output roots must exactly match the installed plan");
+  for (const revision of expected) {
+    const bytes = await read(revision, "share/quixos/package-artifacts.json", metadataLimit);
+    const manifest = parsePackageArtifacts(JSON.parse(new TextDecoder("utf-8", { fatal: true }).decode(bytes)));
+    if (manifest.packageRevisionId !== revision) fail(revision, "Output belongs to another package revision");
+    manifests.push(manifest);
+  }
+  const world = await checkExecutionWorld(plan, manifests, read);
+  return { world, digest: checkedWorldDigest(world), manifests, read };
+}
+export interface BrowserArtifact {
+  url: string;
+  implementation: string;
+  packageRevisionId: string;
+  registryExport: string;
+  exports: readonly string[];
+}
+export interface ArtifactResponse {
+  status: 200 | 304;
+  headers: Record<string, string>;
+  body: Uint8Array;
+}
+/** This registry is placed behind the workspace gateway's existing authentication.
+ * Lookup uses an explicit URL table; request paths never become filesystem paths. */
+export class BrowserArtifactGateway {
+  readonly entries: readonly BrowserArtifact[];
+  private readonly routes = new Map<string, { revision: string; file: ArtifactFile }>();
+  private readonly read: ArtifactReader;
+  constructor(loaded: LoadedArtifactWorld) {
+    this.read = loaded.read;
+    const entries: BrowserArtifact[] = [];
+    for (const manifest of loaded.manifests)
+      for (const implementation of manifest.implementations) {
+        if (implementation.target !== "browser" || implementation.compatibility !== "quixos-js-module-v1") continue;
+        const prefix = `/__quixos/artifacts/${loaded.digest}/${implementation.contentDigest}/`;
+        for (const file of implementation.files) {
+          if (!/^[a-zA-Z0-9.+-]+\/[a-zA-Z0-9.+-]+$/.test(file.mediaType)) fail(file.path, "Invalid asset MIME type");
+          const url = prefix + file.path.split("/").map(encodeURIComponent).join("/");
+          const previous = this.routes.get(url);
+          if (
+            previous &&
+            (previous.file.digest !== file.digest ||
+              previous.file.bytes !== file.bytes ||
+              previous.file.mediaType !== file.mediaType)
+          )
+            fail(url, "Conflicting browser asset route");
+          this.routes.set(url, { revision: manifest.packageRevisionId, file: Object.freeze({ ...file }) });
+        }
+        entries.push({
+          url: prefix + implementation.path.split("/").map(encodeURIComponent).join("/"),
+          implementation: implementation.id,
+          packageRevisionId: manifest.packageRevisionId,
+          registryExport: implementation.registryExport!,
+          exports: Object.freeze([...implementation.exports]),
+        });
+      }
+    this.entries = Object.freeze(entries.map((entry) => Object.freeze(entry)));
+  }
+  async response(url: string, ifNoneMatch?: string): Promise<ArtifactResponse | undefined> {
+    const route = this.routes.get(url);
+    if (!route) return undefined;
+    const bytes = await this.read(route.revision, route.file.path, route.file.bytes);
+    if (bytes.length !== route.file.bytes || createHash("sha256").update(bytes).digest("hex") !== route.file.digest)
+      fail(url, "Browser asset changed after world validation");
+    const etag = `"sha256-${route.file.digest}"`;
+    const headers = {
+      "content-type": route.file.mediaType,
+      "cache-control": "private, max-age=31536000, immutable",
+      etag,
+      "x-content-type-options": "nosniff",
+    };
+    return ifNoneMatch === etag
+      ? { status: 304, headers, body: new Uint8Array() }
+      : { status: 200, headers, body: bytes };
+  }
+}
diff --git a/src/execution-world/index.ts b/src/execution-world/index.ts
index 110c772..efd6ed6 100644
--- a/src/execution-world/index.ts
+++ b/src/execution-world/index.ts
@@ -1,3 +1,4 @@
 export * from "./plan.js";
 export * from "./artifacts.js";
 export * from "./ports.js";
+export * from "./files.js";
diff --git a/test/artifact-files.test.ts b/test/artifact-files.test.ts
new file mode 100644
index 0000000..45796e1
--- /dev/null
+++ b/test/artifact-files.test.ts
@@ -0,0 +1,88 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+import { mkdtemp, mkdir, writeFile, symlink, rm } from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import { createHash } from "node:crypto";
+import {
+  compileExecutionPlan,
+  artifactFileReader,
+  loadArtifactWorld,
+  BrowserArtifactGateway,
+  implementationDigest,
+} from "../src/execution-world/index.js";
+import { loadReaderWorkspace } from "./reader-fixture.js";
+import { buildArtifactFixture } from "./artifact-fixture.js";
+
+test("immutable-output loading rejects traversal, links, and files larger than the declared bound", async () => {
+  const root = await mkdtemp(path.join(os.tmpdir(), "camino-artifact-read-"));
+  try {
+    await mkdir(path.join(root, "output"));
+    await writeFile(path.join(root, "outside"), "secret");
+    await writeFile(path.join(root, "output", "file"), "data");
+    await symlink(path.join(root, "outside"), path.join(root, "output", "linked-file"));
+    await symlink(root, path.join(root, "output", "linked-dir"));
+    const read = await artifactFileReader({ package: path.join(root, "output") });
+    assert.equal(new TextDecoder().decode(await read("package", "file", 4)), "data");
+    await assert.rejects(read("package", "file", 3), /exceeds its declared bound/);
+    await assert.rejects(read("package", "linked-file", 100), /Only real directories/);
+    await assert.rejects(read("package", "linked-dir/outside", 100), /Only real directories/);
+    await assert.rejects(read("package", "../outside", 100), /normalized relative/);
+    await assert.rejects(read("unknown", "file", 100), /Unknown package output/);
+    await assert.rejects(read("package", "file", Infinity), /Invalid file byte limit/);
+    await assert.rejects(
+      artifactFileReader({ package: path.join(root, "output", "linked-dir") }),
+      /canonical absolute/,
+    );
+  } finally {
+    await rm(root, { recursive: true, force: true });
+  }
+});
+
+test("gateway serves only declared browser assets with correct Wasm MIME and content identity", async () => {
+  const root = await mkdtemp(path.join(os.tmpdir(), "camino-artifact-world-"));
+  try {
+    const plan = compileExecutionPlan(await loadReaderWorkspace()),
+      fixture = buildArtifactFixture(plan);
+    const wasm = new Uint8Array([0, 97, 115, 109, 1, 0, 0, 0]);
+    const browser = fixture.manifest.implementations.find((i) => i.target === "browser")!;
+    browser.files.push({
+      path: "portable/browser/assets/café.wasm",
+      bytes: wasm.length,
+      digest: createHash("sha256").update(wasm).digest("hex"),
+      mediaType: "application/wasm",
+    });
+    const { contentDigest, ...body } = browser;
+    browser.contentDigest = implementationDigest(body);
+    for (const implementation of fixture.manifest.implementations)
+      for (const file of implementation.files) {
+        const target = path.join(root, file.path);
+        await mkdir(path.dirname(target), { recursive: true });
+        await writeFile(target, file.mediaType === "application/wasm" ? wasm : fixture.bytes);
+      }
+    await mkdir(path.join(root, "share/quixos"), { recursive: true });
+    await writeFile(path.join(root, "share/quixos/package-artifacts.json"), JSON.stringify(fixture.manifest));
+    const loaded = await loadArtifactWorld(plan, { [fixture.manifest.packageRevisionId]: root });
+    const gateway = new BrowserArtifactGateway(loaded);
+    assert.equal(gateway.entries.length, 1);
+    const entry = gateway.entries[0]!;
+    const response = await gateway.response(entry.url);
+    assert.equal(response?.status, 200);
+    assert.equal(response?.headers["content-type"], "text/javascript");
+    assert.equal(response?.headers["cache-control"], "private, max-age=31536000, immutable");
+    assert.deepEqual(response?.body, Buffer.from(fixture.bytes));
+    assert.equal((await gateway.response(entry.url, response?.headers.etag))?.status, 304);
+    const wasmUrl = entry.url.replace("module.mjs", "assets/caf%C3%A9.wasm");
+    const wasmResponse = await gateway.response(wasmUrl);
+    assert.equal(wasmResponse?.headers["content-type"], "application/wasm");
+    assert.deepEqual(wasmResponse?.body, Buffer.from(wasm));
+    assert.equal(await gateway.response(entry.url.replace("portable/browser/module.mjs", "bin/service")), undefined);
+    assert.equal(await gateway.response("/nix/store/secret"), undefined);
+    assert.equal(await gateway.response(entry.url.replace(loaded.digest, "0".repeat(64))), undefined);
+    await writeFile(path.join(root, browser.path), "x".repeat(fixture.bytes.length));
+    await assert.rejects(gateway.response(entry.url), /changed after world validation/);
+    await assert.rejects(loadArtifactWorld(plan, { [fixture.manifest.packageRevisionId]: root }), /Artifact bytes/);
+  } finally {
+    await rm(root, { recursive: true, force: true });
+  }
+});
diff --git a/test/artifact-fixture.ts b/test/artifact-fixture.ts
new file mode 100644
index 0000000..48144e8
--- /dev/null
+++ b/test/artifact-fixture.ts
@@ -0,0 +1,49 @@
+import { createHash } from "node:crypto";
+import {
+  implementationDigest,
+  type ExecutionPlan,
+  type PackageArtifacts,
+  type ArtifactImplementation,
+} from "../src/execution-world/index.js";
+export const buildArtifactFixture = (plan: ExecutionPlan) => {
+  const expected = plan.definition.packages[0]!;
+  const bytes = new TextEncoder().encode("export const handlers = Object.freeze({});\n");
+  const implementation = (
+    id: string,
+    target: string,
+    compatibility: ArtifactImplementation["compatibility"],
+  ): ArtifactImplementation => {
+    const path = compatibility === "quixos-service-v1" ? "bin/service" : `portable/${target}/module.mjs`;
+    const value = {
+      id,
+      target,
+      compatibility,
+      path,
+      ports: "quixos-transaction-ports-v1" as const,
+      ...(compatibility === "quixos-js-module-v1" ? { registryExport: "handlers" } : {}),
+      exports: expected.exports.map((e) => e.id),
+      files: [
+        {
+          path,
+          digest: createHash("sha256").update(bytes).digest("hex"),
+          bytes: bytes.length,
+          mediaType: compatibility === "quixos-service-v1" ? "application/octet-stream" : "text/javascript",
+        },
+      ],
+    };
+    return { ...value, contentDigest: implementationDigest(value) };
+  };
+  const manifest: PackageArtifacts = {
+    schemaVersion: 1,
+    packageRevisionId: expected.revision,
+    bindingDigest: expected.bindingDigest,
+    sourceDigest: expected.sourceDigest,
+    versions: plan.definition.versions,
+    implementations: [
+      implementation("service", "server", "quixos-service-v1"),
+      implementation("server", "server", "quixos-js-module-v1"),
+      implementation("browser", "browser", "quixos-js-module-v1"),
+    ],
+  };
+  return { manifest, bytes, read: async () => bytes };
+};
diff --git a/test/execution-world.test.ts b/test/execution-world.test.ts
index 2e2568d..3b3afe0 100644
--- a/test/execution-world.test.ts
+++ b/test/execution-world.test.ts
@@ -15,48 +15,7 @@ import {
   type ArtifactImplementation,
 } from "../src/execution-world/index.js";
 
-const buildFixture = (plan: ExecutionPlan) => {
-  const expected = plan.definition.packages[0]!;
-  const bytes = new TextEncoder().encode("export const handlers = Object.freeze({});\n");
-  const implementation = (
-    id: string,
-    target: string,
-    compatibility: ArtifactImplementation["compatibility"],
-  ): ArtifactImplementation => {
-    const path = compatibility === "quixos-service-v1" ? "bin/service" : `portable/${target}/module.mjs`;
-    const value = {
-      id,
-      target,
-      compatibility,
-      path,
-      ports: "quixos-transaction-ports-v1" as const,
-      ...(compatibility === "quixos-js-module-v1" ? { registryExport: "handlers" } : {}),
-      exports: expected.exports.map((e) => e.id),
-      files: [
-        {
-          path,
-          digest: createHash("sha256").update(bytes).digest("hex"),
-          bytes: bytes.length,
-          mediaType: compatibility === "quixos-service-v1" ? "application/octet-stream" : "text/javascript",
-        },
-      ],
-    };
-    return { ...value, contentDigest: implementationDigest(value) };
-  };
-  const manifest: PackageArtifacts = {
-    schemaVersion: 1,
-    packageRevisionId: expected.revision,
-    bindingDigest: expected.bindingDigest,
-    sourceDigest: expected.sourceDigest,
-    versions: plan.definition.versions,
-    implementations: [
-      implementation("service", "server", "quixos-service-v1"),
-      implementation("server", "server", "quixos-js-module-v1"),
-      implementation("browser", "browser", "quixos-js-module-v1"),
-    ],
-  };
-  return { manifest, bytes, read: async () => bytes };
-};
+import { buildArtifactFixture as buildFixture } from "./artifact-fixture.js";
 const resign = (implementation: ArtifactImplementation) => {
   const { contentDigest, ...body } = implementation;
   implementation.contentDigest = implementationDigest(body);