diff --git a/scripts/dev/peer-stamp.mjs b/scripts/dev/peer-stamp.mjs
new file mode 100644
index 0000000000..b4e18d213a
--- /dev/null
+++ b/scripts/dev/peer-stamp.mjs
@@ -0,0 +1,53 @@
+import { randomUUID } from "node:crypto";
+
+/**
+ * Trusted peer-IP stamping for the custom Node HTTP servers.
+ *
+ * The Next.js middleware runtime (proxy.ts → runAuthzPipeline) exposes NO socket
+ * or peer IP — only request headers, ALL of which are client-controlled. The
+ * LOCAL_ONLY route guard (spawn-capable routes) must decide locality from the
+ * real TCP peer, never from the spoofable Host header.
+ *
+ * Our custom servers DO have the real `req.socket.remoteAddress`. They stamp it
+ * into PEER_IP_HEADER as `<token>|<ip>`, where <token> is a per-process secret
+ * (OMNIROUTE_PEER_STAMP_TOKEN). Any client-supplied value of PEER_IP_HEADER is
+ * deleted first, so a remote caller cannot pre-populate it. The middleware
+ * (src/server/authz/policies/management.ts → resolveStampedPeer) trusts the IP
+ * ONLY when the token matches this process's secret; otherwise it fails closed.
+ *
+ * Keep PEER_IP_HEADER in sync with PEER_IP_HEADER in
+ * src/server/authz/headers.ts (the TS side cannot import this .mjs).
+ */
+export const PEER_IP_HEADER = "x-omniroute-peer-ip";
+
+/** Generate (once) and return the per-process stamp token, persisting it in env
+ *  so the middleware running in the same process reads the identical value. */
+export function ensurePeerStampToken() {
+  process.env.OMNIROUTE_PEER_STAMP_TOKEN ||= randomUUID();
+  return process.env.OMNIROUTE_PEER_STAMP_TOKEN;
+}
+
+/** Strip any client-supplied PEER_IP_HEADER and stamp the real TCP peer IP,
+ *  token-prefixed. Never throws — a stamping failure must not block a request
+ *  (it degrades to "locality unknown" → fail closed in the middleware). */
+export function stampPeerIp(req) {
+  try {
+    if (!req || !req.headers) return;
+    // Node lowercases incoming header names; delete kills any client value.
+    delete req.headers[PEER_IP_HEADER];
+    const ip = req.socket && req.socket.remoteAddress;
+    if (ip) {
+      req.headers[PEER_IP_HEADER] = `${ensurePeerStampToken()}|${ip}`;
+    }
+  } catch {
+    /* never block a request on peer stamping */
+  }
+}
+
+/** Wrap a Node request listener so every request is peer-stamped first. */
+export function wrapRequestListenerWithPeerStamp(listener) {
+  return function peerStampingRequestHandler(req, res) {
+    stampPeerIp(req);
+    return listener.call(this, req, res);
+  };
+}
diff --git a/scripts/dev/run-next.mjs b/scripts/dev/run-next.mjs
index 61e490311a..7a956d93a9 100644
--- a/scripts/dev/run-next.mjs
+++ b/scripts/dev/run-next.mjs
@@ -8,6 +8,7 @@ import { bootstrapEnv } from "../build/bootstrap-env.mjs";
 import { resolveRuntimePorts, withRuntimePortEnv } from "../build/runtime-env.mjs";
 import { createOmnirouteWsBridge } from "./v1-ws-bridge.mjs";
 import { createResponsesWsProxy } from "./responses-ws-proxy.mjs";
+import { ensurePeerStampToken, stampPeerIp } from "./peer-stamp.mjs";
 import { randomUUID } from "node:crypto";
 
 // Pre-read DATA_DIR from local .env before bootstrap resolves paths
@@ -49,6 +50,9 @@ const { dashboardPort } = runtimePorts;
 const hostname = process.env.HOST || "0.0.0.0";
 const useTurbopack = dev && mergedEnv.OMNIROUTE_USE_TURBOPACK === "1";
 process.env.OMNIROUTE_WS_BRIDGE_SECRET ||= randomUUID();
+// Per-process secret used to prove the trusted peer-IP stamp came from this
+// server (read by the authz middleware in the same process). See peer-stamp.mjs.
+ensurePeerStampToken();
 
 const nextApp = next({
   dev,
@@ -71,7 +75,12 @@ async function start() {
     baseUrl: `http://127.0.0.1:${dashboardPort}`,
   });
 
-  const server = http.createServer((req, res) => requestHandler(req, res));
+  const server = http.createServer((req, res) => {
+    // Stamp the real TCP peer IP before Next sees the request, so the authz
+    // middleware can decide LOCAL_ONLY locality without trusting the Host header.
+    stampPeerIp(req);
+    return requestHandler(req, res);
+  });
   server.on("upgrade", async (req, socket, head) => {
     try {
       const responsesWsHandled = await responsesWsProxy.handleUpgrade(req, socket, head);
diff --git a/scripts/dev/standalone-server-ws.mjs b/scripts/dev/standalone-server-ws.mjs
index 12a20bf9eb..e7d4fb7672 100644
--- a/scripts/dev/standalone-server-ws.mjs
+++ b/scripts/dev/standalone-server-ws.mjs
@@ -1,11 +1,14 @@
 import http from "node:http";
 import { randomUUID } from "node:crypto";
 import { createResponsesWsProxy } from "./responses-ws-proxy.mjs";
+import { ensurePeerStampToken, wrapRequestListenerWithPeerStamp } from "./peer-stamp.mjs";
 
 const originalCreateServer = http.createServer.bind(http);
 const proxiesByPort = new Map();
 
 process.env.OMNIROUTE_WS_BRIDGE_SECRET ||= randomUUID();
+// Per-process secret proving the trusted peer-IP stamp came from this server.
+ensurePeerStampToken();
 
 function getPort(server) {
   const address = server.address?.();
@@ -46,6 +49,13 @@ function wrapUpgradeListener(server, listener) {
 }
 
 http.createServer = function createServerWithResponsesWs(...args) {
+  // Next's standalone server.js may pass its request listener directly to
+  // createServer; wrap it so the real TCP peer IP is stamped before Next runs.
+  const lastFnIdx = args.map((a) => typeof a === "function").lastIndexOf(true);
+  if (lastFnIdx >= 0) {
+    args[lastFnIdx] = wrapRequestListenerWithPeerStamp(args[lastFnIdx]);
+  }
+
   const server = originalCreateServer(...args);
   const originalOn = server.on.bind(server);
   const originalAddListener = server.addListener.bind(server);
@@ -54,6 +64,10 @@ http.createServer = function createServerWithResponsesWs(...args) {
     if (eventName === "upgrade" && typeof listener === "function") {
       return originalOn(eventName, wrapUpgradeListener(server, listener));
     }
+    // …or it may attach the handler via server.on("request"): wrap that too.
+    if (eventName === "request" && typeof listener === "function") {
+      return originalOn(eventName, wrapRequestListenerWithPeerStamp(listener));
+    }
     return originalOn(eventName, listener);
   };
 
@@ -61,6 +75,9 @@ http.createServer = function createServerWithResponsesWs(...args) {
     if (eventName === "upgrade" && typeof listener === "function") {
       return originalAddListener(eventName, wrapUpgradeListener(server, listener));
     }
+    if (eventName === "request" && typeof listener === "function") {
+      return originalAddListener(eventName, wrapRequestListenerWithPeerStamp(listener));
+    }
     return originalAddListener(eventName, listener);
   };
 
diff --git a/src/server/authz/headers.ts b/src/server/authz/headers.ts
index 32d9cb3323..dc5f4f548d 100644
--- a/src/server/authz/headers.ts
+++ b/src/server/authz/headers.ts
@@ -24,6 +24,19 @@ export const AUTHZ_HEADER_AUTH_SCOPES = "x-omniroute-auth-scopes";
 /** CLI sends this header so the local process can call management APIs without login. */
 export const CLI_TOKEN_HEADER = "x-omniroute-cli-token";
 
+/**
+ * The real TCP peer IP, stamped by the custom Node server BEFORE Next runs
+ * (scripts/dev/peer-stamp.mjs), formatted as `<token>|<ip>`. The middleware has
+ * no socket, so this is the only trustworthy locality signal — but ONLY when the
+ * token matches this process's OMNIROUTE_PEER_STAMP_TOKEN (see
+ * policies/management.ts → resolveStampedPeer). Any client-supplied value is
+ * deleted by the server before stamping, and this header is stripped from the
+ * forwarded request in pipeline.ts so it never reaches route handlers/upstream.
+ * NEVER decide locality from the Host header — it is fully client-controlled.
+ * Keep in sync with PEER_IP_HEADER in scripts/dev/peer-stamp.mjs.
+ */
+export const PEER_IP_HEADER = "x-omniroute-peer-ip";
+
 /**
  * Headers the pipeline must NEVER trust on incoming requests. They are
  * stripped before route classification to prevent header-spoofing attacks.
diff --git a/src/server/authz/peerStamp.ts b/src/server/authz/peerStamp.ts
new file mode 100644
index 0000000000..df099aa94c
--- /dev/null
+++ b/src/server/authz/peerStamp.ts
@@ -0,0 +1,34 @@
+import { timingSafeEqual } from "node:crypto";
+
+/**
+ * Resolve the real peer IP from the trusted `<token>|<ip>` stamp that the custom
+ * Node server writes into PEER_IP_HEADER (see scripts/dev/peer-stamp.mjs). Returns
+ * the IP ONLY when the token constant-time-matches this process's stamp token;
+ * any other value (no stamp, wrong/forged token, missing separator, empty IP)
+ * returns null.
+ *
+ * Pure + dependency-free so the auth boundary is directly unit-testable.
+ *
+ * SECURITY: this is the ONLY trustworthy locality signal in the Next middleware
+ * runtime (which has no socket). Never derive locality from the Host header — it
+ * is fully client-controlled, so `Host: 127.0.0.1` from a remote attacker would
+ * otherwise bypass the LOCAL_ONLY gate guarding spawn-capable routes.
+ */
+export function resolveStampedPeer(
+  headerValue: string | null,
+  token: string | undefined
+): string | null {
+  if (!headerValue || !token) return null;
+  const sep = headerValue.indexOf("|");
+  if (sep <= 0) return null;
+  const provided = headerValue.slice(0, sep);
+  const ip = headerValue.slice(sep + 1);
+  if (!ip) return null;
+  if (provided.length !== token.length) return null;
+  try {
+    if (!timingSafeEqual(Buffer.from(provided), Buffer.from(token))) return null;
+  } catch {
+    return null;
+  }
+  return ip;
+}
diff --git a/src/server/authz/pipeline.ts b/src/server/authz/pipeline.ts
index 36f0a96759..4504c3db9e 100644
--- a/src/server/authz/pipeline.ts
+++ b/src/server/authz/pipeline.ts
@@ -17,6 +17,7 @@ import {
   AUTHZ_HEADER_REQUEST_ID,
   AUTHZ_HEADER_ROUTE_CLASS,
   AUTHZ_TRUSTED_HEADERS,
+  PEER_IP_HEADER,
 } from "./headers";
 import type { AuthSubject, RouteClass, RouteClassification } from "./types";
 import type { AuthOutcome, RoutePolicy } from "./context";
@@ -228,6 +229,10 @@ export async function runAuthzPipeline(
   for (const trusted of AUTHZ_TRUSTED_HEADERS) {
     requestHeaders.delete(trusted);
   }
+  // The trusted peer-IP stamp is read by the policy from the ORIGINAL request
+  // (above); strip it from the forwarded headers so the per-process token never
+  // reaches route handlers or upstream providers.
+  requestHeaders.delete(PEER_IP_HEADER);
 
   requestHeaders.set(AUTHZ_HEADER_ROUTE_CLASS, classification.routeClass);
   requestHeaders.set(AUTHZ_HEADER_REQUEST_ID, requestId);
diff --git a/src/server/authz/policies/management.ts b/src/server/authz/policies/management.ts
index e4832d078a..8fbc15d6b5 100644
--- a/src/server/authz/policies/management.ts
+++ b/src/server/authz/policies/management.ts
@@ -7,7 +7,8 @@ import { allow, reject } from "../context";
 import { extractApiKey, isValidApiKey } from "../../../sse/services/auth";
 import { getApiKeyMetadata } from "../../../lib/db/apiKeys";
 import { hasManageScope } from "../../../lib/api/requireManagementAuth";
-import { CLI_TOKEN_HEADER } from "../headers";
+import { CLI_TOKEN_HEADER, PEER_IP_HEADER } from "../headers";
+import { resolveStampedPeer } from "../peerStamp";
 import {
   isAlwaysProtectedPath,
   isLocalOnlyBypassableByManageScope,
@@ -19,16 +20,18 @@ import {
 const MODEL_SYNC_MANAGEMENT_PATH = /^\/api\/providers\/[^/]+\/(sync-models|models)$/;
 
 function requestPeerAddress(ctx: PolicyContext): string | null {
-  // In the Next middleware runtime (proxy.ts → runAuthzPipeline), ctx.request is
-  // a NextRequest with no socket/.ip, so the only locality signal is the Host
-  // header — which is exactly what isLoopbackHost/isPrivateLanHost parse (they
-  // strip :port). This both fixes the loopback gate (previously the null socket
-  // made every LOCAL_ONLY request 403, even from localhost) and enables the
-  // owner-authorized private-LAN carve-out. Fall back to .ip/.socket for any
-  // non-middleware caller that provides them. Spawn-capable endpoints still
-  // require manage-scope auth after this gate.
-  const hostHeader = ctx.request.headers?.get?.("host") ?? null;
-  return hostHeader || ctx.request.ip || ctx.request.socket?.remoteAddress || null;
+  // The Next middleware runtime exposes no socket/.ip, so the only trustworthy
+  // locality signal is the token-stamped PEER_IP_HEADER our custom server writes
+  // from the real TCP peer (scripts/dev/peer-stamp.mjs). We NEVER read the Host
+  // header here — it is client-controlled and spoofable. Absent/forged stamp →
+  // null → isLoopbackRequest/isPrivateLanRequest return false → fail closed.
+  const stamped = resolveStampedPeer(
+    ctx.request.headers?.get?.(PEER_IP_HEADER) ?? null,
+    process.env.OMNIROUTE_PEER_STAMP_TOKEN
+  );
+  if (stamped) return stamped;
+  // Non-middleware callers (tests / direct Node) may carry a real socket peer.
+  return ctx.request.ip ?? ctx.request.socket?.remoteAddress ?? null;
 }
 
 function isLoopbackRequest(ctx: PolicyContext): boolean {
diff --git a/tests/unit/route-guard-private-lan.test.ts b/tests/unit/route-guard-private-lan.test.ts
index 9117af0b75..c8e7c9df06 100644
--- a/tests/unit/route-guard-private-lan.test.ts
+++ b/tests/unit/route-guard-private-lan.test.ts
@@ -3,6 +3,7 @@ import assert from "node:assert/strict";
 import { readFileSync } from "node:fs";
 import { join } from "node:path";
 import { isPrivateLanHost, isLoopbackHost, isLocalOnlyPath } from "../../src/server/authz/routeGuard.ts";
+import { resolveStampedPeer } from "../../src/server/authz/peerStamp.ts";
 
 test("isPrivateLanHost: accepts RFC1918 IPv4 (incl. :port and ::ffff: mapped)", () => {
   for (const h of [
@@ -48,10 +49,46 @@ test("services + traffic-inspector remain LOCAL_ONLY paths", () => {
   assert.equal(isLocalOnlyPath("/api/tools/traffic-inspector/sessions"), true);
 });
 
-test("management policy derives locality from the Host header (middleware socket is null)", () => {
+test("management policy must NOT derive locality from the spoofable Host header", () => {
   const src = readFileSync(
     join(import.meta.dirname, "../../src/server/authz/policies/management.ts"),
     "utf8"
   );
-  assert.ok(src.includes('headers?.get?.("host")'), "requestPeerAddress must read the Host header");
+  // Regression guard: a prior fix read the client-controlled Host header for the
+  // LOCAL_ONLY decision, letting `Host: 127.0.0.1` bypass the gate. Locality must
+  // come from the token-stamped peer IP instead.
+  assert.ok(
+    !src.includes('get?.("host")') && !src.includes('get("host")'),
+    "requestPeerAddress must NOT read the Host header"
+  );
+  assert.ok(
+    src.includes("resolveStampedPeer") && src.includes("PEER_IP_HEADER"),
+    "requestPeerAddress must resolve the trusted token-stamped peer IP"
+  );
+});
+
+// ── resolveStampedPeer: the auth boundary that replaces Host-header trust ──
+const TOK = "process-secret-token-abc";
+
+test("resolveStampedPeer: returns the IP only for a correctly-tokened stamp", () => {
+  assert.equal(resolveStampedPeer(`${TOK}|127.0.0.1`, TOK), "127.0.0.1");
+  assert.equal(resolveStampedPeer(`${TOK}|192.168.0.15`, TOK), "192.168.0.15");
+  assert.equal(resolveStampedPeer(`${TOK}|::1`, TOK), "::1");
+  assert.equal(resolveStampedPeer(`${TOK}|::ffff:192.168.1.20`, TOK), "::ffff:192.168.1.20");
+});
+
+test("resolveStampedPeer: rejects forged token, missing token, no separator, empty ip", () => {
+  assert.equal(resolveStampedPeer("wrong-token|127.0.0.1", TOK), null, "forged token");
+  assert.equal(resolveStampedPeer(`${TOK}|127.0.0.1`, undefined), null, "no process token");
+  assert.equal(resolveStampedPeer("127.0.0.1", TOK), null, "no separator (raw client value)");
+  assert.equal(resolveStampedPeer(`${TOK}|`, TOK), null, "empty ip");
+  assert.equal(resolveStampedPeer("|127.0.0.1", TOK), null, "empty token segment");
+  assert.equal(resolveStampedPeer(null, TOK), null, "absent header");
+  assert.equal(resolveStampedPeer("", TOK), null, "empty header");
+});
+
+test("resolveStampedPeer: a spoofed Host-style value cannot pass without the token", () => {
+  // Simulates a remote attacker who knows the header name but not the secret.
+  assert.equal(resolveStampedPeer("127.0.0.1|127.0.0.1", TOK), null);
+  assert.equal(resolveStampedPeer("anything|127.0.0.1", TOK), null);
 });