diff --git a/packages/react/src/api/shell-host.test.ts b/packages/react/src/api/shell-host.test.ts
index 886db1054..70601bb60 100644
--- a/packages/react/src/api/shell-host.test.ts
+++ b/packages/react/src/api/shell-host.test.ts
@@ -2,9 +2,10 @@
 // shell's two tool calls over the executions HTTP API — which is exactly the
 // path that used to surface a raw `ExecutionNotFoundError` to the user when an
 // approval arrived after the pause was gone.
-import { describe, expect, it } from "@effect/vitest";
+import { afterEach, describe, expect, it } from "@effect/vitest";
 import { Schema } from "effect";
 
+import { EXECUTOR_ORG_HEADER, setActiveOrgSlugOverride } from "./server-connection";
 import { APPROVAL_EXPIRED_MESSAGE, createHttpShellHost } from "./shell-host";
 
 /** The adapter's request body, read back off the wire. */
@@ -21,19 +22,29 @@ const jsonResponse = (body: unknown, status = 200): Response =>
 /** Records what the adapter put on the wire, so the assertions are about the
  *  request the server actually receives rather than the adapter's internals. */
 const recordingFetch = (respond: (url: string) => Response) => {
-  const calls: Array<{ url: string; body: unknown }> = [];
+  const calls: Array<{ url: string; body: unknown; headers: Record<string, string> }> = [];
   const fetch: typeof globalThis.fetch = async (input, init) => {
     const url = String(input);
     calls.push({
       url,
       body: typeof init?.body === "string" ? decodeRequestBody(init.body) : undefined,
+      headers: Object.fromEntries(new Headers(init?.headers).entries()),
     });
     return respond(url);
   };
   return { calls, fetch };
 };
 
+const completed = () =>
+  jsonResponse({ status: "completed", text: "ok", structured: {}, isError: false });
+
 describe("createHttpShellHost", () => {
+  // Module state on the org scope: leaking a slug would silently head the
+  // "no org" cases below.
+  afterEach(() => {
+    setActiveOrgSlugOverride(null);
+  });
+
   it("maps execute-action onto POST /executions, carrying the artifact id", async () => {
     const { calls, fetch } = recordingFetch(() =>
       jsonResponse({ status: "completed", text: "ok", structured: { result: 1 }, isError: false }),
@@ -108,4 +119,81 @@ describe("createHttpShellHost", () => {
     // the decision still travels.
     expect(calls[0]?.body).toStrictEqual({ action: "decline" });
   });
+
+  // The prod outage this file's fix addresses. An org-scoped host (cloud) fails
+  // CLOSED on a session request with no org selector — it 403s rather than
+  // falling back to the session's org — so a header-less request from here made
+  // every artifact tool call return `no_organization`. Asserted on all three
+  // request shapes, since each built its own headers before.
+  describe("the org selector header", () => {
+    it("scopes execute-action to the console's org", async () => {
+      setActiveOrgSlugOverride("acme");
+      const { calls, fetch } = recordingFetch(completed);
+
+      await createHttpShellHost({ fetch }).callServerTool({
+        name: "execute-action",
+        arguments: { code: "return 1", artifactId: "art_1" },
+      });
+
+      expect(calls[0]?.headers[EXECUTOR_ORG_HEADER]).toBe("acme");
+    });
+
+    // The approval leg: a resume that lost the scope would strand the user's
+    // decision on a paused execution.
+    it("scopes execute-action-resume to the console's org", async () => {
+      setActiveOrgSlugOverride("acme");
+      const { calls, fetch } = recordingFetch(completed);
+
+      await createHttpShellHost({ fetch }).callServerTool({
+        name: "execute-action-resume",
+        arguments: { executionId: "exec_1", action: "accept", content: "{}" },
+      });
+
+      expect(calls[0]?.headers[EXECUTOR_ORG_HEADER]).toBe("acme");
+    });
+
+    it("scopes the preview upload to the console's org", async () => {
+      setActiveOrgSlugOverride("acme");
+      const { calls, fetch } = recordingFetch(() => jsonResponse({}));
+
+      createHttpShellHost({ fetch }).savePreview("art_1", "data:image/png;base64,AA==");
+      // savePreview is deliberately fire-and-forget, so wait for the microtask
+      // that issues the request rather than a returned promise.
+      await Promise.resolve();
+
+      expect(calls[0]?.url).toContain("/artifacts/art_1/preview");
+      expect(calls[0]?.headers[EXECUTOR_ORG_HEADER]).toBe("acme");
+    });
+
+    // Hosts without org scoping (local, desktop, self-host) have no slug to
+    // send, and their servers would have nothing to do with one.
+    it("sends no selector when the host has no org scope", async () => {
+      setActiveOrgSlugOverride(null);
+      const { calls, fetch } = recordingFetch(completed);
+
+      await createHttpShellHost({ fetch }).callServerTool({
+        name: "execute-action",
+        arguments: { code: "return 1" },
+      });
+
+      expect(calls[0]?.headers).not.toHaveProperty(EXECUTOR_ORG_HEADER);
+    });
+
+    // The host outlives any one org: it is memoized for the page's lifetime,
+    // so the scope has to be read per request, not captured at construction.
+    it("follows the scope when the console switches org", async () => {
+      setActiveOrgSlugOverride("acme");
+      const { calls, fetch } = recordingFetch(completed);
+      const host = createHttpShellHost({ fetch });
+
+      await host.callServerTool({ name: "execute-action", arguments: { code: "return 1" } });
+      setActiveOrgSlugOverride("globex");
+      await host.callServerTool({ name: "execute-action", arguments: { code: "return 1" } });
+
+      expect(calls.map((call) => call.headers[EXECUTOR_ORG_HEADER])).toStrictEqual([
+        "acme",
+        "globex",
+      ]);
+    });
+  });
 });
diff --git a/packages/react/src/api/shell-host.ts b/packages/react/src/api/shell-host.ts
index c90a1e9c3..1605e994f 100644
--- a/packages/react/src/api/shell-host.ts
+++ b/packages/react/src/api/shell-host.ts
@@ -20,7 +20,11 @@
  * structural for exactly this reason — see its declaration.
  */
 
-import { getExecutorApiBaseUrl, getExecutorServerAuthorizationHeader } from "./server-connection";
+import {
+  getExecutorApiBaseUrl,
+  getExecutorOrganizationHeaders,
+  getExecutorServerAuthorizationHeader,
+} from "./server-connection";
 
 /** The wire shape of `POST /executions` and `POST /executions/:id/resume`. */
 type ExecutionResponse =
@@ -114,14 +118,37 @@ export const createHttpShellHost = (options?: {
 }): HttpShellHost => {
   const doFetch = options?.fetch ?? globalThis.fetch.bind(globalThis);
 
-  const post = async (path: string, payload: Record<string, unknown>): Promise<unknown> => {
-    const headers: Record<string, string> = { "content-type": "application/json" };
+  /**
+   * Every request this host makes, headed the same way as the typed API client
+   * (`api/client.tsx`'s `transformClient`): bearer when the connection carries
+   * one, plus the active org selector.
+   *
+   * The selector is what an org-scoped host (cloud) scopes the request by, and
+   * it fails CLOSED — a session request that omits it is rejected outright
+   * rather than falling back to the session's stored org. Without it here every
+   * artifact tool call 403'd with `no_organization`. Resolved per request, not
+   * captured at construction: the host is memoized for the page's lifetime,
+   * while the scope authority is set during render, so a captured value could
+   * outlive the org it named.
+   *
+   * Hosts without org scoping (local, desktop, self-host) produce no slug and
+   * so send no header, which is the same convention the neighboring clients
+   * follow.
+   */
+  const requestHeaders = (): Record<string, string> => {
+    const headers: Record<string, string> = {
+      "content-type": "application/json",
+      ...getExecutorOrganizationHeaders(),
+    };
     const authorization = getExecutorServerAuthorizationHeader();
     if (authorization) headers.authorization = authorization;
+    return headers;
+  };
 
+  const post = async (path: string, payload: Record<string, unknown>): Promise<unknown> => {
     const response = await doFetch(`${getExecutorApiBaseUrl()}${path}`, {
       method: "POST",
-      headers,
+      headers: requestHeaders(),
       body: JSON.stringify(payload),
     });
     if (!response.ok) {
@@ -153,12 +180,9 @@ export const createHttpShellHost = (options?: {
      * `McpAppsShellHost`.
      */
     savePreview: (artifactId: string, preview: string): void => {
-      const headers: Record<string, string> = { "content-type": "application/json" };
-      const authorization = getExecutorServerAuthorizationHeader();
-      if (authorization) headers.authorization = authorization;
       void doFetch(
         `${getExecutorApiBaseUrl()}/artifacts/${encodeURIComponent(artifactId)}/preview`,
-        { method: "PUT", headers, body: JSON.stringify({ preview }) },
+        { method: "PUT", headers: requestHeaders(), body: JSON.stringify({ preview }) },
       ).then(
         () => undefined,
         // Deliberately silent, and not an Effect: there is no caller to report