diff --git a/backend/src/pi/management.ts b/backend/src/pi/management.ts
index 8b7eb58d..38030b02 100644
--- a/backend/src/pi/management.ts
+++ b/backend/src/pi/management.ts
@@ -7,6 +7,7 @@ import {
   type Settings,
 } from "../settings/settings-store.js";
 import type { PiModel } from "./list-models.js";
+import { createPiProviderSmoke, type PiProviderSmoke } from "./provider-smoke.js";
 
 const execFile = promisify(nodeExecFile);
 const REASONING_CHOICES = ["low", "medium", "high"] as const;
@@ -80,6 +81,7 @@ export class PiManagementError extends Error {
 interface PiManagementDeps {
   execute?: PiExecFile;
   listModels: () => Promise<PiModel[]>;
+  smokeProvider?: PiProviderSmoke;
   readSettings?: () => Settings;
   saveSettings?: (settings: Settings) => Settings;
   readLogs?: () => string | Promise<string>;
@@ -97,6 +99,7 @@ export function createPiManagement(config: AppConfig, deps: PiManagementDeps): P
   const readSettings = deps.readSettings ?? (() => loadSettings(config));
   const persistSettings = deps.saveSettings ?? ((settings) => saveSettings(config, settings));
   const readLogs = deps.readLogs ?? (() => diagnostics.join("\n"));
+  const smokeProvider = deps.smokeProvider ?? createPiProviderSmoke(config);
 
   const closedOptions = async (): Promise<Omit<PiOptions, "checkedAt">> => {
     let listed: PiModel[];
@@ -123,12 +126,12 @@ export function createPiManagement(config: AppConfig, deps: PiManagementDeps): P
     return { providers, models, reasoning: [...REASONING_CHOICES] };
   };
 
-  const version = async (): Promise<string> => {
+  const version = async (timeoutMs = config.piManagementTimeoutMs): Promise<string> => {
     let output: { stdout: string; stderr: string };
     try {
       // The Pi executable and every argument are installation-owned constants. Do not add a shell.
       output = await execute(config.piBin, ["--version"], {
-        timeout: config.piManagementTimeoutMs,
+        timeout: timeoutMs,
         maxBuffer: MAX_EXEC_OUTPUT_BYTES,
       });
     } catch (error) {
@@ -193,20 +196,40 @@ export function createPiManagement(config: AppConfig, deps: PiManagementDeps): P
 
     async test(): Promise<PiTestResult> {
       const checkedAt = now().toISOString();
+      const deadline = Date.now() + config.piManagementTimeoutMs;
+      let timer: NodeJS.Timeout | undefined;
       try {
-        await version();
-        const current = installationConfig();
-        if (!current.provider || !current.model || !current.reasoning) {
-          return smokeFailure("Pi installation configuration is incomplete", checkedAt, addDiagnostic);
-        }
-        const choices = await closedOptions();
-        if (!choices.models.some((model) => model.provider === current.provider && model.id === current.model)) {
-          return smokeFailure("Configured Pi provider and model are unavailable", checkedAt, addDiagnostic);
-        }
+        const check = async (): Promise<void> => {
+          await version(remainingBudget(deadline));
+          const current = installationConfig();
+          if (!current.provider || !current.model || !current.reasoning) {
+            throw new PiManagementError(
+              "pi_management_unavailable",
+              "Pi installation configuration is incomplete",
+            );
+          }
+          await smokeProvider({
+            provider: current.provider,
+            model: current.model,
+            reasoning: current.reasoning,
+            timeoutMs: remainingBudget(deadline),
+          });
+        };
+        await Promise.race([
+          check(),
+          new Promise<never>((_resolve, reject) => {
+            timer = setTimeout(
+              () => reject(new PiManagementError("pi_management_unavailable", "Pi smoke check timed out")),
+              config.piManagementTimeoutMs,
+            );
+          }),
+        ]);
         addDiagnostic("Pi smoke check succeeded");
         return { ready: true, checkedAt };
       } catch (error) {
-        return smokeFailure(stableMessage(error, "Pi smoke check failed"), checkedAt, addDiagnostic);
+        return smokeFailure(stableMessage(error, "Pi provider smoke check failed"), checkedAt, addDiagnostic);
+      } finally {
+        if (timer) clearTimeout(timer);
       }
     },
 
@@ -279,7 +302,11 @@ function smokeFailure(
 export function redact(value: string): string {
   return value
     .replace(/(\bauthorization\b\s*:\s*Bearer\s+)[^\s,;]+/giu, "$1[REDACTED]")
-    .replace(/(\b(?:api[_-]?key|token|password|secret|authorization)\b\s*(?:=|:)\s*)(?:"[^"\r\n]*"|'[^'\r\n]*'|[^\s,;]+)/giu, "$1[REDACTED]")
+    .replace(/((?:["']?)[A-Za-z0-9_-]*(?:api[_-]?key|token|password|secret|authorization)[A-Za-z0-9_-]*(?:["']?)\s*(?:=|:)\s*)(?:"[^"\r\n]*"|'[^'\r\n]*'|[^\s,;}]+)/giu, "$1[REDACTED]")
     .replace(/(\bBearer\s+)[^\s,;]+/giu, "$1[REDACTED]")
     .replace(/(\w+:\/\/[^:/\s]+:)[^@/\s]+@/gu, "$1[REDACTED]@");
 }
+
+function remainingBudget(deadline: number): number {
+  return Math.max(1, deadline - Date.now());
+}
diff --git a/backend/src/pi/provider-smoke.ts b/backend/src/pi/provider-smoke.ts
new file mode 100644
index 00000000..6b321ef3
--- /dev/null
+++ b/backend/src/pi/provider-smoke.ts
@@ -0,0 +1,121 @@
+import { spawn as nodeSpawn, type ChildProcessWithoutNullStreams } from "node:child_process";
+import type { AppConfig } from "../config.js";
+import { secretValue } from "../config/secret-bundle.js";
+import { clearPrincipalEnvironment } from "../auth/principal.js";
+import { RpcClient } from "../rpc/rpc-client.js";
+import { loadPiAuthProviders } from "./auth-providers.js";
+import { buildPiChildEnv, canonicalPiProvider } from "./provider-credentials.js";
+import type { PiReasoning } from "./management.js";
+
+const SMOKE_PROMPT = "Provider health check only. Reply with exactly OK without using tools.";
+
+export interface PiProviderSmokeRequest {
+  provider: string;
+  model: string;
+  reasoning: PiReasoning;
+  timeoutMs: number;
+}
+
+export type PiProviderSmoke = (request: PiProviderSmokeRequest) => Promise<void>;
+
+interface ProviderSmokeOptions {
+  spawnFn?: (
+    command: string,
+    args: string[],
+    options: { cwd: string; env: NodeJS.ProcessEnv },
+  ) => ChildProcessWithoutNullStreams;
+  authProviders?: () => ReadonlySet<string>;
+}
+
+export function createPiProviderSmoke(
+  config: AppConfig,
+  options: ProviderSmokeOptions = {},
+): PiProviderSmoke {
+  const spawnFn = options.spawnFn ?? nodeSpawn;
+  const authProviders = options.authProviders ?? (() => loadPiAuthProviders());
+
+  return async ({ provider, model, reasoning, timeoutMs }): Promise<void> => {
+    let child: ChildProcessWithoutNullStreams | undefined;
+    let timer: NodeJS.Timeout | undefined;
+    try {
+      const canonicalProvider = canonicalPiProvider(provider);
+      if (!canonicalProvider || timeoutMs <= 0) throw providerFailure();
+      const env = buildPiChildEnv({
+        provider: canonicalProvider,
+        authProviders: authProviders(),
+        credentialValue: secretValue(config, "THT_MODEL_API_KEY"),
+        credentialFile: config.modelApiKeyFile,
+      });
+      clearPrincipalEnvironment(env);
+      delete env.THT_DATA_ROOT;
+      if (config.dataRoot !== undefined) env.THT_DATA_ROOT = config.dataRoot;
+
+      child = spawnFn(config.piBin, ["--mode", "rpc"], { cwd: config.harnessDir, env });
+      child.stderr.resume();
+      const rpc = new RpcClient(child);
+      const turn = async (): Promise<void> => {
+        requireSuccessfulResponse(await rpc.request({
+          type: "set_model", provider: canonicalProvider, modelId: model,
+        } as object & { type: string }));
+        requireSuccessfulResponse(await rpc.request({
+          type: "set_thinking_level", level: reasoning,
+        } as object & { type: string }));
+        await waitForProviderTurn(rpc, child!);
+      };
+      await Promise.race([
+        turn(),
+        new Promise<never>((_resolve, reject) => {
+          timer = setTimeout(() => reject(providerTimeout()), timeoutMs);
+        }),
+      ]);
+    } catch (error) {
+      if (isProviderTimeout(error)) throw providerTimeout();
+      throw providerFailure();
+    } finally {
+      if (timer) clearTimeout(timer);
+      if (child) {
+        try { child.kill(); } catch { /* preserve the sanitized smoke outcome */ }
+      }
+    }
+  };
+}
+
+function waitForProviderTurn(rpc: RpcClient, child: ChildProcessWithoutNullStreams): Promise<void> {
+  return new Promise((resolve, reject) => {
+    let failed = false;
+    rpc.on("event", (event) => {
+      if (event?.type === "message_end" && event.message?.role === "assistant"
+        && event.message.stopReason === "error") {
+        failed = true;
+        reject(providerFailure());
+        return;
+      }
+      if (event?.type === "agent_end") {
+        const messages = Array.isArray(event.messages) ? event.messages : [];
+        const eventFailed = messages.some((message: any) => (
+          message?.role === "assistant" && message?.stopReason === "error"
+        ));
+        if (failed || eventFailed) reject(providerFailure());
+        else resolve();
+      }
+    });
+    child.once("exit", () => reject(providerFailure()));
+    rpc.send({ type: "prompt", message: SMOKE_PROMPT });
+  });
+}
+
+function requireSuccessfulResponse(response: any): void {
+  if (!response || response.success !== true) throw providerFailure();
+}
+
+function providerFailure(): Error {
+  return new Error("Pi provider smoke check failed");
+}
+
+function providerTimeout(): Error {
+  return Object.assign(new Error("Pi smoke check timed out"), { code: "ETIMEDOUT" });
+}
+
+function isProviderTimeout(error: unknown): boolean {
+  return Boolean(error && typeof error === "object" && (error as { code?: unknown }).code === "ETIMEDOUT");
+}
diff --git a/backend/src/routes/pi-management.ts b/backend/src/routes/pi-management.ts
index 6fba64fe..c1a26a3a 100644
--- a/backend/src/routes/pi-management.ts
+++ b/backend/src/routes/pi-management.ts
@@ -29,6 +29,10 @@ async function run<T>(
   if (!managementAllowed(deps.config, principal.isAdmin)) {
     return reply.code(403).send({ code: "pi_management_forbidden", error: "Pi management is not permitted" });
   }
+  if (deps.config.authMode === "none" && isManagementWrite(request.method)
+    && !sameOriginOrNonBrowser(request)) {
+    return reply.code(403).send({ code: "pi_management_forbidden", error: "Pi management is not permitted" });
+  }
   try {
     return await action();
   } catch (error) {
@@ -44,3 +48,20 @@ function managementAllowed(config: AppConfig, isAdmin: boolean): boolean {
   return (config.authMode === "none" && !config.publicExposure)
     || (config.authMode === "upstream" && isAdmin);
 }
+
+function isManagementWrite(method: string): boolean {
+  return method === "POST" || method === "PUT" || method === "PATCH" || method === "DELETE";
+}
+
+function sameOriginOrNonBrowser(request: FastifyRequest): boolean {
+  const origin = request.headers.origin;
+  if (origin === undefined) return true;
+  if (typeof origin !== "string" || typeof request.headers.host !== "string") return false;
+  try {
+    const supplied = new URL(origin);
+    const expected = new URL(`${request.protocol}://${request.headers.host}`);
+    return supplied.origin === expected.origin;
+  } catch {
+    return false;
+  }
+}
diff --git a/backend/test/pi-management.test.ts b/backend/test/pi-management.test.ts
index 8963f6e5..14d3e21a 100644
--- a/backend/test/pi-management.test.ts
+++ b/backend/test/pi-management.test.ts
@@ -1,7 +1,7 @@
 import { mkdtempSync, readFileSync, readdirSync, rmSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
-import { expect, test } from "vitest";
+import { expect, test, vi } from "vitest";
 import { loadConfig } from "../src/config.js";
 import {
   PiManagementError,
@@ -140,12 +140,95 @@ test("smoke uses the configured timeout and reports a sanitized timeout", async
   expect(calls).toEqual([{ command: "/usr/local/bin/pi", args: ["--version"], timeout: 750 }]);
 });
 
+// Catches a smoke endpoint that validates only the Pi binary/model catalogue and never makes a
+// request through the configured provider and model.
+test("smoke exercises the configured provider and model", async () => {
+  const providerChecks: unknown[] = [];
+  const service = createPiManagement(configFor(), {
+    execute: successfulExec([]),
+    listModels: async () => supportedModels,
+    readSettings: () => ({ provider: "zai", model: "glm-5.2", thinking: "medium" }),
+    smokeProvider: async (request) => { providerChecks.push(request); },
+    now: () => new Date("2026-08-05T10:00:00.000Z"),
+  });
+
+  await expect(service.test()).resolves.toEqual({
+    ready: true,
+    checkedAt: "2026-08-05T10:00:00.000Z",
+  });
+  expect(providerChecks).toEqual([{
+    provider: "zai", model: "glm-5.2", reasoning: "medium", timeoutMs: expect.any(Number),
+  }]);
+});
+
+// Catches expired provider credentials being treated as ready or raw provider diagnostics being
+// reflected through the management API.
+test("smoke fails closed and sanitizes configured-provider authentication errors", async () => {
+  const service = createPiManagement(configFor(), {
+    execute: successfulExec([]),
+    listModels: async () => supportedModels,
+    readSettings: () => ({ provider: "zai", model: "glm-5.2", thinking: "medium" }),
+    smokeProvider: async () => {
+      throw new Error('401 {"token":"raw-expired-token","output":"raw-provider-output"}');
+    },
+    now: () => new Date("2026-08-05T10:00:00.000Z"),
+  });
+
+  const result = await service.test();
+  expect(result).toEqual({
+    ready: false,
+    message: "Pi provider smoke check failed",
+    checkedAt: "2026-08-05T10:00:00.000Z",
+  });
+  expect(JSON.stringify(result)).not.toMatch(/raw-expired-token|raw-provider-output/);
+});
+
+// Catches separate per-phase timeouts that allow a later provider turn to exceed the one
+// end-to-end Pi Management smoke budget.
+test("smoke applies one deadline across version and a hung provider turn", async () => {
+  vi.useFakeTimers();
+  vi.setSystemTime(new Date("2026-08-05T10:00:00.000Z"));
+  try {
+    const providerTimeouts: number[] = [];
+    const service = createPiManagement(configFor(), {
+      execute: async () => await new Promise((resolve) => setTimeout(
+        () => resolve({ stdout: "pi 0.80.3\n", stderr: "" }),
+        500,
+      )),
+      listModels: async () => supportedModels,
+      readSettings: () => ({ provider: "zai", model: "glm-5.2", thinking: "medium" }),
+      smokeProvider: async ({ timeoutMs }) => {
+        providerTimeouts.push(timeoutMs);
+        await new Promise(() => {});
+      },
+      now: () => new Date("2026-08-05T10:00:00.000Z"),
+    });
+
+    let settled = false;
+    const pending = service.test().finally(() => { settled = true; });
+    await vi.advanceTimersByTimeAsync(500);
+    expect(providerTimeouts).toEqual([250]);
+    await vi.advanceTimersByTimeAsync(249);
+    expect(settled).toBe(false);
+    await vi.advanceTimersByTimeAsync(1);
+    await expect(pending).resolves.toEqual({
+      ready: false,
+      message: "Pi smoke check timed out",
+      checkedAt: "2026-08-05T10:00:00.000Z",
+    });
+  } finally {
+    vi.useRealTimers();
+  }
+});
+
 // Catches an unbounded diagnostics endpoint or one that returns bearer tokens and connection
 // passwords captured in Pi output.
 test("logs keep only the latest 200 redacted lines", async () => {
   const source = Array.from({ length: 205 }, (_, index) => `line-${index + 1}`);
   source[203] = "Authorization: Bearer raw-bearer-token";
   source[204] = "database_url=postgres://thoth:raw-db-password@example.invalid/db";
+  source[202] = '{"token":"raw-json-secret","password":"raw-json-password"}';
+  source[201] = "THT_MODEL_API_KEY=raw-env-secret";
   const service = createPiManagement(configFor(), {
     execute: successfulExec([]),
     listModels: async () => supportedModels,
@@ -159,5 +242,8 @@ test("logs keep only the latest 200 redacted lines", async () => {
   expect(logs.lines[0]).toBe("line-6");
   expect(logs.lines.join("\n")).not.toContain("raw-bearer-token");
   expect(logs.lines.join("\n")).not.toContain("raw-db-password");
+  expect(logs.lines.join("\n")).not.toContain("raw-json-secret");
+  expect(logs.lines.join("\n")).not.toContain("raw-json-password");
+  expect(logs.lines.join("\n")).not.toContain("raw-env-secret");
   expect(logs.lines.join("\n")).toContain("[REDACTED]");
 });
diff --git a/backend/test/pi-provider-smoke.test.ts b/backend/test/pi-provider-smoke.test.ts
new file mode 100644
index 00000000..e48d8718
--- /dev/null
+++ b/backend/test/pi-provider-smoke.test.ts
@@ -0,0 +1,94 @@
+import { EventEmitter } from "node:events";
+import { expect, test, vi } from "vitest";
+import { loadConfig } from "../src/config.js";
+import { createPiProviderSmoke } from "../src/pi/provider-smoke.js";
+
+function rpcChild(onCommand: (command: any, emit: (message: unknown) => void) => void) {
+  const child: any = new EventEmitter();
+  child.stdout = new EventEmitter();
+  child.stderr = { resume: vi.fn() };
+  child.kill = vi.fn();
+  const emit = (message: unknown) => queueMicrotask(() => {
+    child.stdout.emit("data", `${JSON.stringify(message)}\n`);
+  });
+  child.stdin = {
+    write: (data: unknown) => {
+      onCommand(JSON.parse(String(data)), emit);
+      return true;
+    },
+  };
+  return child;
+}
+
+// Catches a provider smoke implementation that merely selects a model, leaks generated output,
+// or fails to terminate its ephemeral Pi process after a real model turn.
+test("provider smoke selects the configured model and completes a fixed output-discarding turn", async () => {
+  const commands: any[] = [];
+  const child = rpcChild((command, emit) => {
+    commands.push(command);
+    if (command.type === "set_model" || command.type === "set_thinking_level") {
+      emit({ type: "response", id: command.id, success: true });
+    }
+    if (command.type === "prompt") {
+      emit({
+        type: "message_end",
+        message: { role: "assistant", stopReason: "stop", content: "raw-provider-output" },
+      });
+      emit({
+        type: "agent_end",
+        messages: [{ role: "assistant", stopReason: "stop", content: "raw-provider-output" }],
+      });
+    }
+  });
+  const smoke = createPiProviderSmoke(loadConfig({
+    THT_HARNESS_DIR: "/app/harness",
+    PI_BIN: "/usr/local/bin/pi",
+  }), {
+    spawnFn: () => child,
+    authProviders: () => new Set(["zai"]),
+  });
+
+  await expect(smoke({
+    provider: "zai", model: "glm-5.2", reasoning: "medium", timeoutMs: 750,
+  })).resolves.toBeUndefined();
+  expect(commands.map(({ id: _id, ...command }) => command)).toEqual([
+    { type: "set_model", provider: "zai", modelId: "glm-5.2" },
+    { type: "set_thinking_level", level: "medium" },
+    { type: "prompt", message: expect.stringMatching(/health check/i) },
+  ]);
+  expect(child.kill).toHaveBeenCalledOnce();
+});
+
+// Catches provider errors that are accepted as a successful health check or returned with raw
+// credential/output diagnostics.
+test("provider smoke rejects a failed model turn with a stable non-secret error", async () => {
+  const child = rpcChild((command, emit) => {
+    if (command.type === "set_model" || command.type === "set_thinking_level") {
+      emit({ type: "response", id: command.id, success: true });
+    }
+    if (command.type === "prompt") {
+      emit({
+        type: "message_end",
+        message: {
+          role: "assistant", stopReason: "error",
+          errorMessage: '401 {"token":"raw-provider-secret"}',
+        },
+      });
+      emit({ type: "agent_end", messages: [] });
+    }
+  });
+  const smoke = createPiProviderSmoke(loadConfig({}), {
+    spawnFn: () => child,
+    authProviders: () => new Set(["zai"]),
+  });
+
+  let caught: unknown;
+  try {
+    await smoke({ provider: "zai", model: "glm-5.2", reasoning: "medium", timeoutMs: 750 });
+  } catch (error) {
+    caught = error;
+  }
+  expect(caught).toBeInstanceOf(Error);
+  expect((caught as Error).message).toBe("Pi provider smoke check failed");
+  expect(String(caught)).not.toContain("raw-provider-secret");
+});
diff --git a/backend/test/routes-pi-management.test.ts b/backend/test/routes-pi-management.test.ts
index 35d52a26..4477d5b0 100644
--- a/backend/test/routes-pi-management.test.ts
+++ b/backend/test/routes-pi-management.test.ts
@@ -85,6 +85,51 @@ test("loopback-only AUTH_MODE=none may read the sanitized Pi status", async () =
   }
 });
 
+// Catches an arbitrary website using browser CORS to mutate a loopback-only installation's Pi
+// defaults or trigger provider work with the local user's authority.
+test("loopback-only management rejects cross-origin writes", async () => {
+  const service = fakeService();
+  const app = appWith(service);
+  try {
+    const configured = await app.inject({
+      method: "PUT", url: "/pi-management/config",
+      headers: { host: "127.0.0.1:8080", origin: "https://evil.example" },
+      payload: { provider: "zai", model: "glm-5.2", reasoning: "high" },
+    });
+    const smoke = await app.inject({
+      method: "POST", url: "/pi-management/test",
+      headers: { host: "127.0.0.1:8080", origin: "https://evil.example" },
+    });
+
+    expect(configured.statusCode).toBe(403);
+    expect(smoke.statusCode).toBe(403);
+    expect(service.configure).not.toHaveBeenCalled();
+    expect(service.test).not.toHaveBeenCalled();
+  } finally {
+    await app.close();
+  }
+});
+
+// Catches an origin guard that also blocks the same-origin Docker frontend or non-browser local
+// lifecycle clients that do not send Origin.
+test("loopback-only management preserves same-origin frontend and origin-less local writes", async () => {
+  const service = fakeService();
+  const app = appWith(service);
+  try {
+    const sameOrigin = await app.inject({
+      method: "PUT", url: "/pi-management/config",
+      headers: { host: "127.0.0.1:8080", origin: "http://127.0.0.1:8080" },
+      payload: { provider: "zai", model: "glm-5.2", reasoning: "high" },
+    });
+    const lifecycleClient = await app.inject({ method: "POST", url: "/pi-management/test" });
+
+    expect(sameOrigin.statusCode).toBe(200);
+    expect(lifecycleClient.statusCode).toBe(200);
+  } finally {
+    await app.close();
+  }
+});
+
 // Catches route wiring that bypasses closed service validation or gives the browser a Docker/image
 // lifecycle endpoint rather than only installation-default configuration and diagnostics.
 test("trusted admins receive only configuration, smoke, options, and log endpoints", async () => {
diff --git a/deploy/nginx-authenticated-proxy.conf.example b/deploy/nginx-authenticated-proxy.conf.example
index 86c9b502..cb48c0f2 100644
--- a/deploy/nginx-authenticated-proxy.conf.example
+++ b/deploy/nginx-authenticated-proxy.conf.example
@@ -1,5 +1,5 @@
-# Host nginx example. The auth service MUST authenticate every request and return a stable
-# identity in X-Authenticated-User. ThothII itself remains on 127.0.0.1:8080.
+# Host nginx example. The auth service MUST authenticate every request and return only the
+# normalized X-Thoth-* identity/admin claims below. ThothII remains on 127.0.0.1:8080.
 server {
     listen 443 ssl;
     server_name thoth.example.test;
@@ -13,12 +13,33 @@ server {
         proxy_pass_request_body off;
         proxy_set_header Content-Length "";
         proxy_set_header X-Original-URI $request_uri;
+        proxy_set_header X-Authenticated-User "";
+        proxy_set_header X-Thoth-Principal-Issuer "";
+        proxy_set_header X-Thoth-Principal-Subject "";
+        proxy_set_header X-Thoth-Principal-Display-Name "";
+        proxy_set_header X-Thoth-Is-Admin "";
+        proxy_set_header X-Thoth-Trusted-Principal-Issuer "";
+        proxy_set_header X-Thoth-Trusted-Principal-Subject "";
+        proxy_set_header X-Thoth-Trusted-Principal-Display-Name "";
+        proxy_set_header X-Thoth-Trusted-Is-Admin "";
     }
 
     location / {
         auth_request /_authenticate;
-        auth_request_set $authenticated_user $upstream_http_x_authenticated_user;
-        proxy_set_header X-Authenticated-User $authenticated_user;
+        auth_request_set $thoth_principal_issuer $upstream_http_x_thoth_principal_issuer;
+        auth_request_set $thoth_principal_subject $upstream_http_x_thoth_principal_subject;
+        auth_request_set $thoth_principal_display_name $upstream_http_x_thoth_principal_display_name;
+        auth_request_set $thoth_is_admin $upstream_http_x_thoth_is_admin;
+        # Clear public normalized claims and carry auth_request results over the private hop.
+        proxy_set_header X-Authenticated-User "";
+        proxy_set_header X-Thoth-Principal-Issuer "";
+        proxy_set_header X-Thoth-Principal-Subject "";
+        proxy_set_header X-Thoth-Principal-Display-Name "";
+        proxy_set_header X-Thoth-Is-Admin "";
+        proxy_set_header X-Thoth-Trusted-Principal-Issuer $thoth_principal_issuer;
+        proxy_set_header X-Thoth-Trusted-Principal-Subject $thoth_principal_subject;
+        proxy_set_header X-Thoth-Trusted-Principal-Display-Name $thoth_principal_display_name;
+        proxy_set_header X-Thoth-Trusted-Is-Admin $thoth_is_admin;
         proxy_set_header X-Forwarded-Proto https;
         proxy_set_header Host $host;
         proxy_pass http://127.0.0.1:8080;
diff --git a/docker/nginx.conf.template b/docker/nginx.conf.template
index 7668dbab..291b5c6c 100644
--- a/docker/nginx.conf.template
+++ b/docker/nginx.conf.template
@@ -6,7 +6,7 @@ server {
     location = /health {
         proxy_pass ${THT_FRONTEND_API_UPSTREAM}/health;
         proxy_http_version 1.1;
-        proxy_set_header Host $host;
+        proxy_set_header Host $http_host;
         proxy_cache off;
     }
 
@@ -14,13 +14,21 @@ server {
         # The trailing slash replaces the matched /api/ prefix before the private hop.
         proxy_pass ${THT_FRONTEND_API_UPSTREAM}/;
         proxy_http_version 1.1;
-        proxy_set_header Host $host;
+        proxy_set_header Host $http_host;
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Forwarded-Proto $scheme;
-        # Trusted only when AUTH_MODE=upstream and this frontend port is reachable solely
-        # from the authenticated host proxy documented in deploy/.
-        proxy_set_header X-Authenticated-User $http_x_authenticated_user;
+        # Public normalized claims are discarded by mapping only the private-hop values from the
+        # authenticated host proxy. Private-hop headers are then cleared before reaching core.
+        proxy_set_header X-Authenticated-User "";
+        proxy_set_header X-Thoth-Principal-Issuer $http_x_thoth_trusted_principal_issuer;
+        proxy_set_header X-Thoth-Principal-Subject $http_x_thoth_trusted_principal_subject;
+        proxy_set_header X-Thoth-Principal-Display-Name $http_x_thoth_trusted_principal_display_name;
+        proxy_set_header X-Thoth-Is-Admin $http_x_thoth_trusted_is_admin;
+        proxy_set_header X-Thoth-Trusted-Principal-Issuer "";
+        proxy_set_header X-Thoth-Trusted-Principal-Subject "";
+        proxy_set_header X-Thoth-Trusted-Principal-Display-Name "";
+        proxy_set_header X-Thoth-Trusted-Is-Admin "";
         proxy_buffering off;
         proxy_cache off;
         proxy_read_timeout 3600s;
diff --git a/docker/smoke/frontend-policy-smoke.sh b/docker/smoke/frontend-policy-smoke.sh
index ff8f6bae..2c3d5d1f 100755
--- a/docker/smoke/frontend-policy-smoke.sh
+++ b/docker/smoke/frontend-policy-smoke.sh
@@ -7,6 +7,7 @@ nginx_config=docker/nginx.conf.template
 for setting in \
   'proxy_pass ${THT_FRONTEND_API_UPSTREAM}/;' \
   'proxy_http_version 1.1;' \
+  'proxy_set_header Host $http_host;' \
   'proxy_buffering off;' \
   'proxy_read_timeout 3600s;'; do
   if ! grep -Fq "$setting" "$nginx_config"; then
diff --git a/docs/install/server-workspace-registry.md b/docs/install/server-workspace-registry.md
index b4b25611..22281a59 100644
--- a/docs/install/server-workspace-registry.md
+++ b/docs/install/server-workspace-registry.md
@@ -152,7 +152,11 @@ import it into the maintenance shell. Explicitly export the non-secret source an
 before running the commands below.
 
 Configure the portal proxy so the frontend and `/api` share one origin. It authenticates first and
-forwards the trusted identity expected by `AUTH_MODE=upstream`; it is the only public listener.
+clears client identity headers, carries auth-request claims over the private hop as
+`X-Thoth-Trusted-*`, and lets the frontend proxy inject only the normalized
+`X-Thoth-Principal-Issuer`, `X-Thoth-Principal-Subject`, `X-Thoth-Principal-Display-Name`, and
+`X-Thoth-Is-Admin` claims expected by `AUTH_MODE=upstream`; it is the only public listener. Use
+`deploy/nginx-authenticated-proxy.conf.example` as the forwarding contract.
 From a trusted maintenance shell:
 
 ```sh
diff --git a/docs/installazione-docker-4-contesti.md b/docs/installazione-docker-4-contesti.md
index b268bb4f..66018cc1 100644
--- a/docs/installazione-docker-4-contesti.md
+++ b/docs/installazione-docker-4-contesti.md
@@ -137,7 +137,11 @@ docker compose exec core /opt/venv/bin/tht doctor --json
 ```
 
 Se si abilita l'overlay production, il proxy autenticato TLS deve essere l'unico listener pubblico
-e deve iniettare `X-Authenticated-User`; non esporre direttamente la porta pubblicata da nginx.
+e deve sostituire gli header client con i claim restituiti dal proprio `auth_request`. L'esempio
+usa header `X-Thoth-Trusted-*` soltanto sul collegamento privato; nginx frontend li converte nei
+claim normalizzati `X-Thoth-Principal-Issuer`, `X-Thoth-Principal-Subject`,
+`X-Thoth-Principal-Display-Name` e `X-Thoth-Is-Admin` attesi dal core. Non esporre direttamente
+la porta pubblicata da nginx.
 
 Se il server deve essere raggiungibile da altri host, sostituire `COMPOSE_FILE` con
 `compose.yaml:deploy/compose.production.yaml`, configurare il proxy autenticato e impostare
diff --git a/scripts/test-authenticated-proxy-contract.sh b/scripts/test-authenticated-proxy-contract.sh
new file mode 100755
index 00000000..1fddaf00
--- /dev/null
+++ b/scripts/test-authenticated-proxy-contract.sh
@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+cd "$(dirname "$0")/.."
+
+outer=deploy/nginx-authenticated-proxy.conf.example
+inner=docker/nginx.conf.template
+
+# Catches a documented public proxy that forwards client-supplied normalized identity/admin
+# headers instead of replacing them with claims returned by auth_request.
+for suffix in Principal-Issuer Principal-Subject Principal-Display-Name Is-Admin; do
+  variable=$(printf '%s' "$suffix" | tr '[:upper:]-' '[:lower:]_')
+  grep -Fq "auth_request_set \$thoth_${variable} \$upstream_http_x_thoth_${variable};" "$outer"
+  if [[ $(grep -Fc "proxy_set_header X-Thoth-${suffix} \"\";" "$outer") -lt 2 ]]; then
+    echo "public proxy does not clear X-Thoth-${suffix} at both ingress hops" >&2
+    exit 1
+  fi
+  grep -Fq "proxy_set_header X-Thoth-Trusted-${suffix} \$thoth_${variable};" "$outer"
+done
+if rg -n 'proxy_set_header X-Thoth-[^;]+\$http_x_thoth_' "$outer"; then
+  echo "public proxy trusts client-supplied normalized Thoth claims" >&2
+  exit 1
+fi
+
+# Catches an included frontend hop that preserves a client normalized claim or drops the original
+# Host port needed for exact same-origin management checks.
+for suffix in Principal-Issuer Principal-Subject Principal-Display-Name Is-Admin; do
+  variable=$(printf '%s' "$suffix" | tr '[:upper:]-' '[:lower:]_')
+  grep -Fq "proxy_set_header X-Thoth-${suffix} \$http_x_thoth_trusted_${variable};" "$inner"
+  grep -Fq "proxy_set_header X-Thoth-Trusted-${suffix} \"\";" "$inner"
+done
+grep -Fq 'proxy_set_header Host $http_host;' "$inner"
+if rg -n 'proxy_set_header X-Thoth-(Principal|Is-Admin)[^;]+\$http_x_thoth_(principal|is_admin)' "$inner"; then
+  echo "frontend proxy trusts a client-supplied normalized Thoth claim" >&2
+  exit 1
+fi
+for config in "$outer" "$inner"; do
+  grep -Fq 'proxy_set_header X-Authenticated-User "";' "$config"
+done
+if rg --pcre2 -n 'proxy_set_header X-Authenticated-User\s+(?!"";)' "$outer" "$inner"; then
+  echo "legacy unnormalized identity is forwarded by the proxy chain" >&2
+  exit 1
+fi
+
+echo "authenticated proxy identity contract: ok"