fix(connection): fence every /api request behind one browser-trust check

The only browser-trust guard covered host.pickDirectory, while the
consequential methods (session.prompt drives bash) accepted any Host —
open to DNS rebinding, where a rebound page reads and writes the API as
if same-origin and only the Host header betrays the attacker's domain.

The pickDirectory-specific loopback guard becomes a prefix-wide fence:
Host must be loopback or an exact host[:port] from the new trustedHosts
config, an attached Origin must equal that authority, and explicit
cross-site markers are refused; requests without browser markers (curl,
tests, native clients) pass, because without a browser there is no
confused deputy. The loopback-socket check is dropped — binding policy
expresses reachability, and the fence is not an auth layer. The Agent
Note records the full threat model and the alternatives.

packages/client/connection/README.i18n.yaml

@@ -1,6 +1,6 @@
 # Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
-#   pnpm run verify-translation-pairing --write
-README.md: 80228a180faba0c556ff720e999b29b5bb1635b6
-README.zh.md: f4b857886bfafa891ceb1bd6b79b27e1fb725819
+#   pnpm run verify-translation-pairing --write packages/client/connection/README.md
+README.md: a301b85d707d17d1e8159655b540556eee5c9d83
+README.zh.md: 88d7aa806167033308a9913053f621ecea07c3d8

packages/client/connection/README.md

@@ -4,6 +4,10 @@ English | [中文](README.zh.md)
 
 Wire consumer layer: the client plugin's apply mounts `ctx.connection` (shared api client + single-consumer stream-loop starter); the export face carries the wire contract types, the `AbstractApiClient` seam, and the loop's sink/config types. The platform subclasses (WebApiClient/FixtureApiClient), the ConnectionController loop, and the fixture data source are package-internal — apply selects and drives them; tests reach them via src. Contract: api-contracts v3 §3.
 
+## /api browser-trust fence
+
+The node half guards every request under `/api` before bridging (`src/api-request-trust.ts`): the `Host` header must be a loopback authority or an exact `host[:port]` entry from the plugin's `trustedHosts` config (DNS-rebinding defense), an attached `Origin` must equal that authority, and an explicit `sec-fetch-site: cross-site` marker is refused. Requests without browser markers (curl, tests, native clients) pass — without a browser there is no confused deputy. Failures answer plain 403 before any RPC dispatch. A non-loopback (`--host 0.0.0.0`) deployment must therefore list the authorities it is reached by in `trustedHosts`; the fence is deliberately not an authentication layer — reachability policy stays with the webserver binding, and auth remains deferred work. Decision record: [the api browser-trust boundary Agent Note](../../../.agents/notes/implemented/architecture/2026-07-28-api-browser-trust-boundary.md).
+
 ## Keyless fixture
 
 Any `fixture` query parameter selects the in-memory carrier. `fixture=empty` starts with no Workspace or Session; `fixturePrompt=reject` rejects prompts before acceptance; `fixtureAttach=fail` publishes a Session but rejects its Workspace attachment; `fixtureSessionCreate=drop-response` publishes and frames a Session before dropping the create response; and `fixtureFrames=workspace-first` reverses the default session-first create-frame order. Workspace creation by name/path and caller-preallocated SessionIds remain deterministic enough for assembled Web tests to reconcile list and frame arrival.

packages/client/connection/README.zh.md

@@ -4,6 +4,10 @@
 
 协议消费层：客户端插件的 apply 会挂载 `ctx.connection`（共享 API 客户端 + 单消费方流循环启动器）；导出表层携带协议契约类型、`AbstractApiClient` seam，以及循环的 sink／配置类型。平台子类（WebApiClient/FixtureApiClient）、ConnectionController 循环和 fixture 数据源都属于包内部：apply 负责选择并驱动它们，测试则通过 src 访问。契约：api-contracts v3 §3。
 
+## /api 浏览器信任栅栏
+
+node 半侧在桥接前守卫 `/api` 下的每个请求（`src/api-request-trust.ts`）：`Host` 头必须是回环地址权威，或与插件 `trustedHosts` 配置中的某个 `host[:port]` 精确匹配（DNS rebinding 防御）；若带有 `Origin` 则必须与该权威完全一致；显式的 `sec-fetch-site: cross-site` 标记一律拒绝。不带浏览器标头的请求（curl、测试、原生客户端）直接放行——没有浏览器就不存在"混淆代理人"。失败在任何 RPC 分发之前以纯 403 应答。因此非回环（`--host 0.0.0.0`）部署必须在 `trustedHosts` 中列出自己被访问时使用的权威；这道栅栏刻意不承担认证职责——可达性策略归 webserver 绑定配置，认证仍是延期工作。决策记录：[api 浏览器信任边界 Agent Note](../../../.agents/notes/implemented/architecture/2026-07-28-api-browser-trust-boundary.md)。
+
 ## 无密钥 fixture
 
 任何 `fixture` 查询参数都会选择内存载体。`fixture=empty` 启动时不含 Workspace 或 Session；`fixturePrompt=reject` 在接受前拒绝提示词；`fixtureAttach=fail` 发布 Session 但拒绝将其附加到 Workspace；`fixtureSessionCreate=drop-response` 在丢弃创建响应前发布 Session 并为其发出帧；`fixtureFrames=workspace-first` 则反转默认的 Session 优先创建帧顺序。按名称／路径创建 Workspace 以及由调用方预先分配 SessionId，均具有足够的确定性，组装后的 Web 测试可以据此协调列表与帧的到达。

packages/client/connection/package.json

@@ -32,7 +32,8 @@
     "@deepseek-ai/dsh-host-apiproxy": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
-    "@deepseek-ai/dsh-tools": "workspace:^"
+    "@deepseek-ai/dsh-tools": "workspace:^",
+    "schemastery": "^3.18.0"
   },
   "files": [
     "lib/index.js",

packages/client/connection/src/api-request-trust.ts

@@ -0,0 +1,71 @@
+/**
+ * Browser-trust fence for every /api request. Defends the two confused-deputy
+ * paths a browser opens against a local HTTP API — DNS rebinding (Host names
+ * the attacker's domain while the socket reaches this server) and cross-site
+ * requests fired from a malicious page — without blocking non-browser clients
+ * (no browser markers → no deputy to confuse) or legitimately remote browsers
+ * (their authority is declared via `trustedHosts`). Network reachability and
+ * authentication stay out of scope: binding policy belongs to the webserver
+ * config, and this fence is not an auth layer.
+ */
+
+import type { IncomingHttpHeaders } from 'node:http'
+
+/** The request facts the fence reads (structural subset of IncomingMessage). */
+interface ApiTrustRequest {
+  headers: IncomingHttpHeaders
+}
+
+function header(headers: IncomingHttpHeaders, name: string): string | undefined {
+  const value = headers[name]
+  return typeof value === 'string' ? value : undefined
+}
+
+function isLoopbackHostname(hostname: string): boolean {
+  if (hostname === 'localhost' || hostname === '[::1]') return true
+  const parts = hostname.split('.')
+  return parts.length === 4
+    && parts[0] === '127'
+    && parts.every(part => /^\d{1,3}$/.test(part) && Number(part) <= 255)
+}
+
+/** Hostname of a Host-header authority (port stripped, lowercased, IPv6 bracketed), or undefined when unparsable. */
+function authorityHostname(authority: string): string | undefined {
+  try {
+    // http: is a WHATWG "special scheme": parsing yields a non-empty hostname or throws.
+    return new URL(`http://${authority}`).hostname
+  } catch {
+    return undefined
+  }
+}
+
+/**
+ * Decide whether one /api request may reach the RPC bridge.
+ * @param request - node HTTP request facts (headers).
+ * @param trustedHosts - exact non-loopback `host[:port]` authorities this deployment serves.
+ * @returns true when the Host is ours and any browser markers are same-origin.
+ */
+export function isTrustedApiRequest(request: ApiTrustRequest, trustedHosts: readonly string[]): boolean {
+  // Host fence (DNS-rebinding defense): the browser fills Host from the URL it
+  // believes it is talking to, so a rebound page carries the attacker's domain
+  // here even though the socket lands on this server.
+  const host = header(request.headers, 'host')
+  if (host === undefined) return false
+  const hostname = authorityHostname(host)
+  if (hostname === undefined) return false
+  if (!isLoopbackHostname(hostname) && !trustedHosts.includes(host)) return false
+  // Cross-site fence: modern browsers label the initiator relationship on
+  // every fetch; an explicit cross-site marker is refused regardless of Origin.
+  if (header(request.headers, 'sec-fetch-site') === 'cross-site') return false
+  // Origin fence: when a browser attaches an Origin it must be exactly this
+  // authority. Absent Origin = non-browser client (curl, tests, native shells)
+  // — allowed, because without a browser there is no confused deputy. The
+  // literal "null" (sandboxed iframes, file: pages) is an opaque origin, refused.
+  const origin = header(request.headers, 'origin')
+  if (origin === undefined) return true
+  try {
+    return new URL(origin).host === host
+  } catch {
+    return false
+  }
+}

packages/client/connection/src/index.ts

@@ -1,11 +1,12 @@
 /** Host HTTP bridge for browser-client RPC. */
 import type { Context } from 'cordis'
+import z from 'schemastery'
 // Activates the httpServer Context merge used below.
 import type { WebRoute } from '@deepseek-ai/dsh-host-webserver'
 import { toFetchHandler } from '@deepseek-ai/dsh-host-apiproxy'
 import { API_PATH } from './api-path.ts'
 import { bridge } from './http-bridge.ts'
-import { isTrustedNativeDialogRequest } from './native-dialog-request.ts'
+import { isTrustedApiRequest } from './api-request-trust.ts'
 
 export { API_PATH } from './api-path.ts'
 
@@ -15,19 +16,37 @@ export const name = 'client-connection'
 /** Services required before mounting the route. */
 export const inject = ['httpServer', 'apiProxy']
 
+/** Plugin config: the deployment's non-loopback serving authorities. */
+export interface ConnectionConfig {
+  /**
+   * Exact `host[:port]` authorities this deployment serves beyond loopback.
+   * The /api trust fence refuses any request whose Host is neither loopback
+   * nor listed here, so a non-loopback (`0.0.0.0`) deployment must declare
+   * the names it is reached by.
+   */
+  trustedHosts?: string[]
+}
+
+export const Config: z<ConnectionConfig> = z.object({
+  trustedHosts: z.array(String).default([]),
+})
+
 /**
- * Mounts the API gateway under the browser transport prefix.
+ * Mounts the API gateway under the browser transport prefix. Every request on
+ * the prefix passes the browser-trust fence first (DNS-rebinding and
+ * cross-site defense — [api-request-trust](./api-request-trust.ts)).
  * @param ctx - Host plugin context.
+ * @param config - resolved plugin config (schema defaults applied).
  */
-export function apply(ctx: Context): void {
+export function apply(ctx: Context, config?: ConnectionConfig): void {
+  // The Loader resolves schema defaults; hand-built test contexts may pass none.
+  const trustedHosts = config?.trustedHosts ?? []
   const apiHandler = toFetchHandler(ctx.apiProxy)
   const route: WebRoute = {
     kind: 'prefix',
     path: API_PATH,
     handler: async (req, res) => {
-      const pathname = new URL(req.url ?? '/', 'http://dsh.internal').pathname
-      if (pathname === `${API_PATH}/host.pickDirectory`
-        && !isTrustedNativeDialogRequest(req)) {
+      if (!isTrustedApiRequest(req, trustedHosts)) {
         res.writeHead(403)
         res.end('forbidden')
         return

packages/client/connection/src/native-dialog-request.ts

@@ -1,52 +0,0 @@
-/** Trust check for browser requests that can open an operating-system dialog. */
-
-import type { IncomingHttpHeaders } from 'node:http'
-
-interface NativeDialogRequest {
-  headers: IncomingHttpHeaders
-  socket: { remoteAddress?: string | undefined }
-}
-
-function header(headers: IncomingHttpHeaders, name: string): string | undefined {
-  const value = headers[name]
-  return typeof value === 'string' ? value : undefined
-}
-
-function isLoopback(address: string | undefined): boolean {
-  if (address === undefined) return false
-  if (address === '::1') return true
-  const ipv4 = address.startsWith('::ffff:') ? address.slice('::ffff:'.length) : address
-  const first = ipv4.split('.')[0]
-  return first === '127'
-}
-
-function isLoopbackHostname(hostname: string): boolean {
-  if (hostname === 'localhost' || hostname === '[::1]' || hostname === '::1') return true
-  const parts = hostname.split('.')
-  return parts.length === 4
-    && parts[0] === '127'
-    && parts.every(part => /^\d{1,3}$/.test(part) && Number(part) <= 255)
-}
-
-/**
- * Require a local socket plus browser-controlled same-origin metadata.
- * @param request - the node HTTP request facts used by the carrier guard.
- * @returns true only for a same-origin browser request whose peer and URL are loopback.
- */
-export function isTrustedNativeDialogRequest(request: NativeDialogRequest): boolean {
-  if (!isLoopback(request.socket.remoteAddress)) return false
-  if (header(request.headers, 'sec-fetch-site') !== 'same-origin') return false
-  const origin = header(request.headers, 'origin')
-  const host = header(request.headers, 'host')
-  if (origin === undefined || host === undefined) return false
-  try {
-    const parsed = new URL(origin)
-    const hostUrl = new URL(`http://${host}`)
-    return (parsed.protocol === 'http:' || parsed.protocol === 'https:')
-      && parsed.host === host
-      && isLoopbackHostname(parsed.hostname)
-      && isLoopbackHostname(hostUrl.hostname)
-  } catch {
-    return false
-  }
-}

packages/client/connection/tests/api-request-trust.spec.ts

@@ -0,0 +1,60 @@
+/** Behavior of the /api browser-trust fence (rebinding + cross-site defense). */
+
+import { describe, expect, it } from 'vitest'
+import { isTrustedApiRequest } from '../src/api-request-trust.ts'
+
+function request(headers: Record<string, string | undefined>): { headers: Record<string, string | undefined> } {
+  return { headers }
+}
+
+describe('isTrustedApiRequest', () => {
+  it('accepts loopback Hosts in every spelling, with and without ports', () => {
+    for (const host of ['localhost', 'localhost:3080', '127.0.0.1', '127.0.0.1:3080', '127.8.9.10:80', '[::1]', '[::1]:3080', 'LOCALHOST:3080']) {
+      expect(isTrustedApiRequest(request({ host }), [])).toBe(true)
+    }
+  })
+
+  it('accepts non-browser requests (no Origin, no sec-fetch-site) — curl, tests, native clients', () => {
+    expect(isTrustedApiRequest(request({ host: '127.0.0.1:3080' }), [])).toBe(true)
+  })
+
+  it('refuses a rebound Host: the attacker domain names the socket it did not expect', () => {
+    expect(isTrustedApiRequest(request({
+      host: 'evil.example:3080',
+      origin: 'http://evil.example:3080',
+      'sec-fetch-site': 'same-origin',
+    }), [])).toBe(false)
+  })
+
+  it('accepts a declared public authority only on exact host[:port] match', () => {
+    const headers = { host: 'harness.internal:3080', origin: 'http://harness.internal:3080' }
+    expect(isTrustedApiRequest(request(headers), ['harness.internal:3080'])).toBe(true)
+    expect(isTrustedApiRequest(request(headers), ['harness.internal'])).toBe(false)
+    expect(isTrustedApiRequest(request(headers), [])).toBe(false)
+  })
+
+  it('refuses cross-origin browser markers even on a loopback Host', () => {
+    // Origin present and different → cross-site request that survived preflight rules.
+    expect(isTrustedApiRequest(request({ host: '127.0.0.1:3080', origin: 'http://evil.example' }), [])).toBe(false)
+    // Explicit cross-site label → refused regardless of Origin.
+    expect(isTrustedApiRequest(request({ host: '127.0.0.1:3080', 'sec-fetch-site': 'cross-site' }), [])).toBe(false)
+    // Opaque origin (sandboxed iframe, file: page) parses to no authority.
+    expect(isTrustedApiRequest(request({ host: '127.0.0.1:3080', origin: 'null' }), [])).toBe(false)
+  })
+
+  it('accepts a same-origin browser request', () => {
+    expect(isTrustedApiRequest(request({
+      host: 'localhost:3080',
+      origin: 'http://localhost:3080',
+      'sec-fetch-site': 'same-origin',
+    }), [])).toBe(true)
+  })
+
+  it('refuses malformed authorities', () => {
+    expect(isTrustedApiRequest(request({}), [])).toBe(false)
+    expect(isTrustedApiRequest(request({ host: '' }), [])).toBe(false)
+    expect(isTrustedApiRequest(request({ host: 'bad host' }), [])).toBe(false)
+    expect(isTrustedApiRequest(request({ host: '127.0.0.999' }), [])).toBe(false)
+    expect(isTrustedApiRequest(request({ host: '128.0.0.1' }), [])).toBe(false)
+  })
+})

packages/client/connection/tests/native-dialog-request.spec.ts

@@ -1,57 +0,0 @@
-import type { IncomingHttpHeaders } from 'node:http'
-import { describe, expect, it } from 'vitest'
-import { isTrustedNativeDialogRequest } from '../src/native-dialog-request.ts'
-
-function request(
-  remoteAddress: string | undefined,
-  headers: IncomingHttpHeaders = {
-    host: '127.0.0.1:3080',
-    origin: 'http://127.0.0.1:3080',
-    'sec-fetch-site': 'same-origin',
-  },
-) {
-  return { socket: { remoteAddress }, headers }
-}
-
-describe('native dialog request trust', () => {
-  it('accepts loopback same-origin browser requests', () => {
-    expect(isTrustedNativeDialogRequest(request('127.0.0.1'))).toBe(true)
-    expect(isTrustedNativeDialogRequest(request('::1', {
-      host: '[::1]:3080', origin: 'http://[::1]:3080', 'sec-fetch-site': 'same-origin',
-    }))).toBe(true)
-    expect(isTrustedNativeDialogRequest(request('::ffff:127.0.0.1'))).toBe(true)
-    expect(isTrustedNativeDialogRequest(request('127.0.0.1', {
-      host: 'localhost:3080', origin: 'http://localhost:3080', 'sec-fetch-site': 'same-origin',
-    }))).toBe(true)
-    expect(isTrustedNativeDialogRequest(request('127.0.0.2', {
-      host: '127.0.0.2:3080', origin: 'https://127.0.0.2:3080', 'sec-fetch-site': 'same-origin',
-    }))).toBe(true)
-  })
-
-  it('rejects remote sockets and requests without matching browser metadata', () => {
-    expect(isTrustedNativeDialogRequest(request('192.168.1.5'))).toBe(false)
-    expect(isTrustedNativeDialogRequest(request(undefined))).toBe(false)
-    expect(isTrustedNativeDialogRequest(request('127.0.0.1', {
-      host: '127.0.0.1:3080', origin: 'http://evil.example', 'sec-fetch-site': 'cross-site',
-    }))).toBe(false)
-    expect(isTrustedNativeDialogRequest(request('127.0.0.1', {
-      host: '127.0.0.1:3080', origin: 'http://localhost:3080', 'sec-fetch-site': 'same-origin',
-    }))).toBe(false)
-    expect(isTrustedNativeDialogRequest(request('127.0.0.1', { host: '127.0.0.1:3080' }))).toBe(false)
-    expect(isTrustedNativeDialogRequest(request('127.0.0.1', {
-      origin: 'http://127.0.0.1:3080', 'sec-fetch-site': 'same-origin',
-    }))).toBe(false)
-    expect(isTrustedNativeDialogRequest(request('127.0.0.1', {
-      host: 'attacker.example:3080', origin: 'http://attacker.example:3080', 'sec-fetch-site': 'same-origin',
-    }))).toBe(false)
-    expect(isTrustedNativeDialogRequest(request('127.0.0.1', {
-      host: '127.0.0.1:3080', origin: 'ftp://127.0.0.1:3080', 'sec-fetch-site': 'same-origin',
-    }))).toBe(false)
-    expect(isTrustedNativeDialogRequest(request('127.0.0.1', {
-      host: '127.999.0.1:3080', origin: 'http://127.999.0.1:3080', 'sec-fetch-site': 'same-origin',
-    }))).toBe(false)
-    expect(isTrustedNativeDialogRequest(request('127.0.0.1', {
-      host: '[invalid', origin: 'http://[invalid', 'sec-fetch-site': 'same-origin',
-    }))).toBe(false)
-  })
-})

packages/client/connection/tests/node-half.spec.ts

@@ -1,4 +1,6 @@
 /** Node half: registers the /api prefix route bridging to the api gateway. */
+import { EventEmitter } from 'node:events'
+import { Readable } from 'node:stream'
 import { Context } from 'cordis'
 import { describe, expect, it } from 'vitest'
 import type { IncomingMessage, ServerResponse } from 'node:http'
@@ -6,46 +8,84 @@ import type { ApiProxy } from '@deepseek-ai/dsh-host-apiproxy/api'
 import type { HttpServerService, WebRoute } from '@deepseek-ai/dsh-host-webserver'
 import { API_PATH, apply, inject } from '../src/index.ts'
 
+/** Structural httpServer fake: the plugin only touches register(). */
+function fakeHttpServer(routes: WebRoute[]): Pick<HttpServerService, 'register' | 'tapIndex' | 'port'> {
+  return {
+    register(route) {
+      routes.push(route)
+      return () => { routes.splice(routes.indexOf(route), 1) }
+    },
+    tapIndex: () => () => {},
+    port: 0,
+  }
+}
+
+/** Bodyless GET carrying the given headers (enough for the trust fence + bridge). */
+function fakeRequest(headers: Record<string, string>): IncomingMessage {
+  const request = Readable.from([]) as unknown as IncomingMessage
+  Object.assign(request, { url: `${API_PATH}/session.list`, method: 'GET', headers })
+  return request
+}
+
+/** Response recorder compatible with both the fence's short-circuit and the bridge. */
+function fakeResponse(): { response: ServerResponse; state: { status?: number; body?: unknown } } {
+  const state: { status?: number; body?: unknown } = {}
+  const response = Object.assign(new EventEmitter(), {
+    writableEnded: false,
+    writeHead(value: number) { state.status = value; return this },
+    write() { return true },
+    end(this: { writableEnded: boolean }, value?: unknown) {
+      if (value !== undefined) state.body = value
+      this.writableEnded = true
+      return this
+    },
+  }) as unknown as ServerResponse
+  return { response, state }
+}
+
+async function mounted(config?: { trustedHosts?: string[] }): Promise<{ routes: WebRoute[]; dispose: () => Promise<void> }> {
+  const ctx = new Context()
+  const routes: WebRoute[] = []
+  ctx.provide('httpServer', fakeHttpServer(routes) as HttpServerService)
+  ctx.provide('apiProxy', {} as unknown as ApiProxy)
+  const fiber = ctx.plugin({ inject: [...inject], apply }, config)
+  await fiber.await()
+  return { routes, dispose: () => fiber.dispose() }
+}
+
 describe('connection node half', () => {
   it('registers the /api prefix route and removes it with the fiber', async () => {
-    const ctx = new Context()
-    const routes: WebRoute[] = []
-    // Structural fake: the plugin only touches register(); the service class
-    // carries private state a literal cannot (and need not) reproduce.
-    const httpServer: Pick<HttpServerService, 'register' | 'tapIndex' | 'port'> = {
-      register(route) {
-        routes.push(route)
-        return () => { routes.splice(routes.indexOf(route), 1) }
-      },
-      tapIndex: () => () => {},
-      port: 0,
-    }
-    ctx.provide('httpServer', httpServer as HttpServerService)
-    ctx.provide('apiProxy', {} as unknown as ApiProxy)
-
-    const fiber = ctx.plugin({ inject: [...inject], apply })
-    await fiber.await()
+    const { routes, dispose } = await mounted()
     expect(routes).toHaveLength(1)
     expect(routes[0]).toMatchObject({ kind: 'prefix', path: API_PATH })
-
-    let status: number | undefined
-    let body: unknown
-    const deniedRequest = {
-      url: '/api/host.pickDirectory',
-      headers: {
-        host: 'harness.example', origin: 'http://harness.example', 'sec-fetch-site': 'same-origin',
-      },
-      socket: { remoteAddress: '192.168.1.8' },
-    } as unknown as IncomingMessage
-    const deniedResponse = {
-      writeHead(value: number) { status = value; return this },
-      end(value?: unknown) { body = value; return this },
-    } as unknown as ServerResponse
-    await routes[0]!.handler(deniedRequest, deniedResponse)
-    expect(status).toBe(403)
-    expect(body).toBe('forbidden')
-
-    await fiber.dispose()
+    await dispose()
     expect(routes).toHaveLength(0)
   })
+
+  it('refuses an untrusted Host on any /api path before the bridge runs', async () => {
+    const { routes, dispose } = await mounted()
+    const { response, state } = fakeResponse()
+    await routes[0]!.handler(fakeRequest({
+      host: 'harness.example', origin: 'http://harness.example', 'sec-fetch-site': 'same-origin',
+    }), response)
+    expect(state.status).toBe(403)
+    expect(state.body).toBe('forbidden')
+    await dispose()
+  })
+
+  it('passes loopback and declared-authority requests through to the bridge', async () => {
+    const { routes, dispose } = await mounted({ trustedHosts: ['harness.example:3080'] })
+    // Loopback, no browser markers (curl shape): the fence passes; the carrier
+    // answers 404 for a GET unary path — proof the bridge ran.
+    const loopback = fakeResponse()
+    await routes[0]!.handler(fakeRequest({ host: '127.0.0.1:3080' }), loopback.response)
+    expect(loopback.state.status).toBe(404)
+    // Declared public authority, same-origin browser shape.
+    const declared = fakeResponse()
+    await routes[0]!.handler(fakeRequest({
+      host: 'harness.example:3080', origin: 'http://harness.example:3080', 'sec-fetch-site': 'same-origin',
+    }), declared.response)
+    expect(declared.state.status).toBe(404)
+    await dispose()
+  })
 })