diff --git a/scripts/lib/orchestrator-gateway.mjs b/scripts/lib/orchestrator-gateway.mjs
index 2204fef41..4b8ced9de 100644
--- a/scripts/lib/orchestrator-gateway.mjs
+++ b/scripts/lib/orchestrator-gateway.mjs
@@ -274,9 +274,10 @@ export function requireOrchestratorApiKey(rawKey) {
 /**
  * Fetch `/healthz` without a bearer token and require the orchestrator identity.
  *
- * The response body is always bounded by byte count. When the caller supplies
- * `timeoutMs`, that explicit deadline also covers request and body reads. Noema
- * does not invent a default availability deadline for contextual-orchestrator.
+ * The successful response must identify itself as `application/json`; its body
+ * is always bounded by byte count. When the caller supplies `timeoutMs`, that
+ * explicit deadline also covers request and body reads. Noema does not invent
+ * a default availability deadline for contextual-orchestrator.
  *
  * @param {string} healthzUrl Absolute health URL derived from the `/v1` base.
  * @param {{ fetchImpl?: typeof fetch, timeoutMs?: number }} [options]
@@ -334,6 +335,20 @@ export async function verifyOrchestratorHealthz(healthzUrl, options = {}) {
         `contextual-orchestrator health response status is ${response.status}`,
       );
     }
+    const mediaType = String(response.headers?.get?.("content-type") ?? "")
+      .split(";", 1)[0]
+      .trim()
+      .toLowerCase();
+    if (mediaType !== "application/json") {
+      try {
+        void response.body?.cancel?.().catch(() => undefined);
+      } catch {
+        // Cancellation is cleanup only after the media-type decision is final.
+      }
+      throw new Error(
+        "contextual-orchestrator health response content-type is not application/json",
+      );
+    }
     const advertisedLength = response.headers?.get?.("content-length");
     if (
       typeof advertisedLength === "string" &&
diff --git a/test/orchestrator-gateway-body-timeout.test.ts b/test/orchestrator-gateway-body-timeout.test.ts
index ad699be6c..da6ad7dd6 100644
--- a/test/orchestrator-gateway-body-timeout.test.ts
+++ b/test/orchestrator-gateway-body-timeout.test.ts
@@ -6,6 +6,14 @@ afterEach(() => {
   vi.useRealTimers();
 });
 
+function jsonHeaders() {
+  return {
+    get(name: string) {
+      return name.toLowerCase() === "content-type" ? "application/json" : null;
+    },
+  };
+}
+
 describe("contextual-orchestrator health body timeout", () => {
   it("keeps an explicit caller timeout active while reading a stalled response body", async () => {
     let cancelled = false;
@@ -24,7 +32,7 @@ describe("contextual-orchestrator health body timeout", () => {
     const response = {
       ok: true,
       status: 200,
-      headers: { get: () => null },
+      headers: jsonHeaders(),
       body: { getReader: () => reader },
     } as unknown as Response;
 
@@ -66,7 +74,7 @@ describe("contextual-orchestrator health body timeout", () => {
     resolveFetch({
       ok: true,
       status: 200,
-      headers: { get: () => null },
+      headers: jsonHeaders(),
       body: null,
       arrayBuffer: async () => encoded.buffer,
     } as unknown as Response);
diff --git a/test/orchestrator-gateway-bounded-healthz.test.ts b/test/orchestrator-gateway-bounded-healthz.test.ts
index 519e41dcc..3f021c62e 100644
--- a/test/orchestrator-gateway-bounded-healthz.test.ts
+++ b/test/orchestrator-gateway-bounded-healthz.test.ts
@@ -2,17 +2,23 @@ import { describe, expect, it } from "vitest";
 
 import { verifyOrchestratorHealthz } from "../scripts/lib/orchestrator-gateway.mjs";
 
+function jsonHeaders(contentLength: string | null = null) {
+  return {
+    get(name: string) {
+      if (name.toLowerCase() === "content-type") return "application/json";
+      if (name.toLowerCase() === "content-length") return contentLength;
+      return null;
+    },
+  };
+}
+
 describe("contextual-orchestrator bounded health response", () => {
   it("rejects an advertised oversized body before materializing it", async () => {
     let materialized = false;
     const response = {
       ok: true,
       status: 200,
-      headers: {
-        get(name: string) {
-          return name.toLowerCase() === "content-length" ? "65537" : null;
-        },
-      },
+      headers: jsonHeaders("65537"),
       async arrayBuffer() {
         materialized = true;
         return new Uint8Array(65_537).buffer;
@@ -32,11 +38,7 @@ describe("contextual-orchestrator bounded health response", () => {
     const response = {
       ok: true,
       status: 200,
-      headers: {
-        get() {
-          return null;
-        },
-      },
+      headers: jsonHeaders(),
       async arrayBuffer() {
         materialized += 1;
         return new Uint8Array(65_537).buffer;
diff --git a/test/orchestrator-gateway-contract.test.ts b/test/orchestrator-gateway-contract.test.ts
index ead582091..582f1b3dc 100644
--- a/test/orchestrator-gateway-contract.test.ts
+++ b/test/orchestrator-gateway-contract.test.ts
@@ -52,6 +52,12 @@ function publicRepositoryEventFile(): string {
   return path;
 }
 
+function jsonResponse(body: BodyInit | null, init: ResponseInit = {}): Response {
+  const headers = new Headers(init.headers);
+  headers.set("content-type", "application/json");
+  return new Response(body, { ...init, headers });
+}
+
 describe("contextual-orchestrator gateway contract", () => {
   it("accepts an HTTPS /v1 URL and derives /healthz", () => {
     const parsed = parseOrchestratorGatewayUrl(
@@ -162,7 +168,7 @@ describe("contextual-orchestrator gateway contract", () => {
         NOEMA_LLM_API_URL: "https://orchestrator.example/v1",
         NOEMA_LLM_MODEL: "orchestrator/free",
       },
-      fetchImpl: async () => new Response(
+      fetchImpl: async () => jsonResponse(
         JSON.stringify({ status: "ok", service: "contextual-orchestrator" }),
         { status: 200 },
       ),
@@ -173,7 +179,7 @@ describe("contextual-orchestrator gateway contract", () => {
       env: {
         NOEMA_LLM_API_URL: "https://orchestrator.example/v1",
       },
-      fetchImpl: async () => new Response(
+      fetchImpl: async () => jsonResponse(
         JSON.stringify({ status: "ok", service: "openai" }),
         { status: 200 },
       ),
@@ -193,7 +199,7 @@ describe("contextual-orchestrator gateway contract", () => {
       env: {
         NOEMA_LLM_API_URL: "https://orchestrator.example/v1/",
       },
-      fetchImpl: async () => new Response(
+      fetchImpl: async () => jsonResponse(
         JSON.stringify({ status: "ok", service: "contextual-orchestrator" }),
         { status: 200 },
       ),
@@ -211,10 +217,10 @@ describe("contextual-orchestrator gateway contract", () => {
       fetchImpl: async () => new Response("nope", { status: 503 }),
     })).rejects.toThrow(/status is 503/);
     await expect(verifyOrchestratorHealthz("https://orchestrator.example/healthz", {
-      fetchImpl: async () => new Response("{", { status: 200 }),
+      fetchImpl: async () => jsonResponse("{", { status: 200 }),
     })).rejects.toThrow(/is not JSON/);
     await expect(verifyOrchestratorHealthz("https://orchestrator.example/healthz", {
-      fetchImpl: async () => new Response("x".repeat(65_537), { status: 200 }),
+      fetchImpl: async () => jsonResponse("x".repeat(65_537), { status: 200 }),
     })).rejects.toThrow(/too large/);
     await expect(verifyOrchestratorHealthz("https://orchestrator.example/healthz", {
       fetchImpl: "not-a-function" as unknown as typeof fetch,
@@ -229,7 +235,7 @@ describe("contextual-orchestrator gateway contract", () => {
     })).rejects.toThrow(/health request failed/);
 
     const previousFetch = globalThis.fetch;
-    globalThis.fetch = async () => new Response(
+    globalThis.fetch = async () => jsonResponse(
       JSON.stringify({ status: "ok", service: "contextual-orchestrator" }),
       { status: 200 },
     );
@@ -243,7 +249,7 @@ describe("contextual-orchestrator gateway contract", () => {
     }
 
     await expect(verifyOrchestratorGatewayContract({
-      fetchImpl: async () => new Response(
+      fetchImpl: async () => jsonResponse(
         JSON.stringify({ status: "ok", service: "contextual-orchestrator" }),
         { status: 200 },
       ),
@@ -366,7 +372,7 @@ describe("contextual-orchestrator gateway contract", () => {
         NOEMA_LLM_API_URL: "https://orchestrator.example/v1",
         NOEMA_LLM_MODEL: "orchestrator/free",
       },
-      fetchImpl: async () => new Response(
+      fetchImpl: async () => jsonResponse(
         JSON.stringify({ status: "ok", service: "contextual-orchestrator" }),
         { status: 200 },
       ),
@@ -398,7 +404,7 @@ describe("contextual-orchestrator gateway contract", () => {
       env: {
         NOEMA_LLM_API_URL: "https://orchestrator.example/v1",
       },
-      fetchImpl: async () => new Response(
+      fetchImpl: async () => jsonResponse(
         JSON.stringify({ status: "ok", service: "contextual-orchestrator" }),
         { status: 200 },
       ),
@@ -449,7 +455,7 @@ describe("contextual-orchestrator gateway contract", () => {
       env: {
         NOEMA_LLM_API_URL: "https://orchestrator.example/v1",
       },
-      fetchImpl: async () => new Response(
+      fetchImpl: async () => jsonResponse(
         JSON.stringify({ status: "ok", service: "contextual-orchestrator" }),
         { status: 200 },
       ),
@@ -467,4 +473,4 @@ describe("contextual-orchestrator gateway contract", () => {
     expect(emptyProcessStderr.join("")).toMatch(/absolute HTTPS URL/);
     process.exitCode = previousProcessExit;
   });
-});
+});
\ No newline at end of file
diff --git a/test/orchestrator-gateway-json-integrity.test.ts b/test/orchestrator-gateway-json-integrity.test.ts
index 090c7c278..b9d77dec9 100644
--- a/test/orchestrator-gateway-json-integrity.test.ts
+++ b/test/orchestrator-gateway-json-integrity.test.ts
@@ -34,4 +34,89 @@ describe("contextual-orchestrator health JSON integrity", () => {
       }),
     ).rejects.toThrow(/duplicate decoded JSON keys/);
   });
+
+  it("rejects a valid identity document served under a non-JSON media type", async () => {
+    const response = new Response(
+      JSON.stringify({ status: "ok", service: "contextual-orchestrator" }),
+      {
+        status: 200,
+        headers: { "content-type": "text/plain; charset=utf-8" },
+      },
+    );
+
+    await expect(
+      verifyOrchestratorHealthz("https://orchestrator.example/healthz", {
+        fetchImpl: (async () => response) as typeof fetch,
+      }),
+    ).rejects.toThrow(
+      "contextual-orchestrator health response content-type is not application/json",
+    );
+  });
+
+  it("keeps the media-type rejection when response cancellation rejects asynchronously", async () => {
+    let cancelCalled = false;
+    const response = {
+      ok: true,
+      status: 200,
+      headers: {
+        get(name: string) {
+          return name.toLowerCase() === "content-type" ? "text/plain" : null;
+        },
+      },
+      body: {
+        cancel() {
+          cancelCalled = true;
+          return Promise.reject(new Error("cleanup transport failed"));
+        },
+      },
+    } as unknown as Response;
+
+    await expect(
+      verifyOrchestratorHealthz("https://orchestrator.example/healthz", {
+        fetchImpl: (async () => response) as typeof fetch,
+      }),
+    ).rejects.toThrow(
+      "contextual-orchestrator health response content-type is not application/json",
+    );
+    await Promise.resolve();
+    expect(cancelCalled).toBe(true);
+  });
+
+  it("rejects a health identity when the media type is missing", async () => {
+    const body = JSON.stringify({
+      status: "ok",
+      service: "contextual-orchestrator",
+    });
+    const response = {
+      ok: true,
+      status: 200,
+      headers: { get: () => null },
+      body: null,
+      arrayBuffer: async () => new TextEncoder().encode(body).buffer,
+    } as unknown as Response;
+
+    await expect(
+      verifyOrchestratorHealthz("https://orchestrator.example/healthz", {
+        fetchImpl: (async () => response) as typeof fetch,
+      }),
+    ).rejects.toThrow(
+      "contextual-orchestrator health response content-type is not application/json",
+    );
+  });
+
+  it("accepts application/json with media-type parameters", async () => {
+    const response = new Response(
+      JSON.stringify({ status: "ok", service: "contextual-orchestrator" }),
+      {
+        status: 200,
+        headers: { "content-type": "application/json; charset=utf-8" },
+      },
+    );
+
+    await expect(
+      verifyOrchestratorHealthz("https://orchestrator.example/healthz", {
+        fetchImpl: (async () => response) as typeof fetch,
+      }),
+    ).resolves.toEqual({ status: "ok", service: "contextual-orchestrator" });
+  });
 });
diff --git a/test/orchestrator-gateway-residual-coverage.test.ts b/test/orchestrator-gateway-residual-coverage.test.ts
index cf53602d9..0ada45f3a 100644
--- a/test/orchestrator-gateway-residual-coverage.test.ts
+++ b/test/orchestrator-gateway-residual-coverage.test.ts
@@ -18,7 +18,11 @@ function responseLike(input: {
     ok: true,
     status: 200,
     headers: {
-      get: () => input.contentLength ?? null,
+      get(name: string) {
+        if (name.toLowerCase() === "content-type") return "application/json";
+        if (name.toLowerCase() === "content-length") return input.contentLength ?? null;
+        return null;
+      },
     },
     body: input.body ?? null,
     arrayBuffer: input.arrayBuffer ?? (async () => new TextEncoder().encode(healthyPayload).buffer),
@@ -34,6 +38,7 @@ describe("contextual-orchestrator residual health coverage", () => {
     const response = new Response(healthyPayload, {
       status: 200,
       headers: {
+        "content-type": "application/json",
         "content-length": "not-a-decimal-length",
       },
     });
diff --git a/test/orchestrator-gateway-secret-source.test.ts b/test/orchestrator-gateway-secret-source.test.ts
index 2e1ffb23f..524dfa097 100644
--- a/test/orchestrator-gateway-secret-source.test.ts
+++ b/test/orchestrator-gateway-secret-source.test.ts
@@ -13,7 +13,7 @@ import {
 function healthyResponse(): Response {
   return new Response(
     JSON.stringify({ status: "ok", service: "contextual-orchestrator" }),
-    { status: 200 },
+    { status: 200, headers: { "content-type": "application/json" } },
   );
 }
 
diff --git a/test/orchestrator-gateway-stream-bound.test.ts b/test/orchestrator-gateway-stream-bound.test.ts
index ec968a7fb..902c8faff 100644
--- a/test/orchestrator-gateway-stream-bound.test.ts
+++ b/test/orchestrator-gateway-stream-bound.test.ts
@@ -18,6 +18,16 @@ async function settleWithin<T>(promise: Promise<T>, timeoutMs = 100): Promise<T
   ]);
 }
 
+function jsonHeaders(contentLength: string | null = null) {
+  return {
+    get(name: string) {
+      if (name.toLowerCase() === "content-type") return "application/json";
+      if (name.toLowerCase() === "content-length") return contentLength;
+      return null;
+    },
+  };
+}
+
 describe("contextual-orchestrator streamed health response", () => {
   it("stops a chunked response at the byte ceiling without arrayBuffer materialization", async () => {
     let readCount = 0;
@@ -45,7 +55,7 @@ describe("contextual-orchestrator streamed health response", () => {
     const response = {
       ok: true,
       status: 200,
-      headers: { get: () => null },
+      headers: jsonHeaders(),
       body: { getReader: () => reader },
       async arrayBuffer() {
         arrayBufferCalled = true;
@@ -83,7 +93,7 @@ describe("contextual-orchestrator streamed health response", () => {
     const response = {
       ok: true,
       status: 200,
-      headers: { get: () => null },
+      headers: jsonHeaders(),
       body: { getReader: () => reader },
     } as unknown as Response;
 
@@ -119,7 +129,7 @@ describe("contextual-orchestrator streamed health response", () => {
     const response = {
       ok: true,
       status: 200,
-      headers: { get: () => null },
+      headers: jsonHeaders(),
       body: { getReader: () => reader },
     } as unknown as Response;
 
@@ -156,7 +166,7 @@ describe("contextual-orchestrator streamed health response", () => {
     const response = {
       ok: true,
       status: 200,
-      headers: { get: () => "65537" },
+      headers: jsonHeaders("65537"),
       body: {
         cancel() {
           cancellationStarted = true;
@@ -184,7 +194,7 @@ describe("contextual-orchestrator streamed health response", () => {
     const response = {
       ok: true,
       status: 200,
-      headers: { get: () => "65537" },
+      headers: jsonHeaders("65537"),
       body: {
         cancel() {
           throw new Error("cleanup transport failed");
@@ -220,7 +230,7 @@ describe("contextual-orchestrator streamed health response", () => {
     const response = {
       ok: true,
       status: 200,
-      headers: { get: () => null },
+      headers: jsonHeaders(),
       body: { getReader: () => reader },
       async arrayBuffer() {
         throw new Error("streaming response must not fall back to arrayBuffer");