diff --git a/CHANGELOG.md b/CHANGELOG.md
index a528383bcd..d87daffd9e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,14 @@ file is the human-readable summary of what changed and why.
 
 ### Desktop / Web UI
 
+- **Named egress rules for sandboxes** — administrators can grant sandboxes
+  extra brokered destinations beyond the model gateway by creating
+  `sandbox-egress.json` in the app's data directory: an object of name →
+  upstream URL (for example `{"npm": "https://registry.npmjs.org"}`), each
+  reachable inside every sandbox at `http://127.0.0.1:8788/<name>/...`. It
+  is an allowlist of named upstreams — there is deliberately no general
+  proxy mode — and a malformed file fails the sandbox start with the parse
+  error rather than silently granting less than intended.
 - **Reset now upgrades a sandbox to the current image** — each sandbox
   records which image it was provisioned from. When a new image is
   published, Reset re-provisions from it (previously the only way to pick
diff --git a/packages/codev-sandbox/src/broker.test.ts b/packages/codev-sandbox/src/broker.test.ts
index 43ce9088c4..f1ef99fb13 100644
--- a/packages/codev-sandbox/src/broker.test.ts
+++ b/packages/codev-sandbox/src/broker.test.ts
@@ -2,7 +2,7 @@ import { expect, test } from "bun:test"
 import { mkdtemp, rm } from "node:fs/promises"
 import { tmpdir } from "node:os"
 import { dirname, join } from "node:path"
-import { createBrokerServer, forwardableRequestHeaders, resolveBrokerTarget } from "./broker"
+import { createBrokerServer, forwardableRequestHeaders, parseBrokerRules, resolveBrokerTarget } from "./broker"
 
 const routes = [{ prefix: "/llm", upstream: "https://gateway.test/api/" }]
 
@@ -91,6 +91,19 @@ test("serves the same routes over a unix socket for netns-isolated guests", asyn
   await rm(dirname(socketPath), { recursive: true, force: true })
 })
 
+test("parses named egress rules and rejects malformed ones", () => {
+  expect(parseBrokerRules({ npm: "https://registry.npmjs.org", pypi: "http://mirror.corp/simple" })).toEqual([
+    { prefix: "/npm", upstream: "https://registry.npmjs.org/" },
+    { prefix: "/pypi", upstream: "http://mirror.corp/simple" },
+  ])
+  expect(parseBrokerRules({})).toEqual([])
+  expect(() => parseBrokerRules(["npm"])).toThrow("object of name")
+  expect(() => parseBrokerRules({ "Bad Name": "https://x.test" })).toThrow("invalid sandbox egress rule name")
+  expect(() => parseBrokerRules({ llm: "https://x.test" })).toThrow("reserved")
+  expect(() => parseBrokerRules({ npm: "ftp://x.test" })).toThrow("http(s) upstream")
+  expect(() => parseBrokerRules({ npm: 5 })).toThrow("http(s) upstream")
+})
+
 test("route headers replace the guest's placeholder credential", async () => {
   const upstream = Bun.serve({
     port: 0,
diff --git a/packages/codev-sandbox/src/broker.ts b/packages/codev-sandbox/src/broker.ts
index df4963dd0e..84986e41b8 100644
--- a/packages/codev-sandbox/src/broker.ts
+++ b/packages/codev-sandbox/src/broker.ts
@@ -24,6 +24,26 @@ export type SandboxEgress = {
   fetchImpl?: typeof fetch
 }
 
+// Named egress rules: the admin-editable shape for extra routes beyond the
+// LLM gateway — an object of name → upstream URL, e.g.
+// { "npm": "https://registry.npmjs.org" }. Each becomes /name on the guest
+// broker stub (http://127.0.0.1:8788/npm/...). Deliberately an allowlist of
+// named upstreams, never a general proxy. Throws on anything malformed so a
+// bad config file fails the sandbox start with a message instead of silently
+// granting nothing.
+export function parseBrokerRules(input: unknown): BrokerRoute[] {
+  if (!input || typeof input !== "object" || Array.isArray(input))
+    throw new Error("sandbox egress rules must be an object of name → upstream URL")
+  return Object.entries(input as Record<string, unknown>).map(([name, upstream]) => {
+    if (!/^[a-z0-9][a-z0-9-]*$/.test(name))
+      throw new Error(`invalid sandbox egress rule name: ${JSON.stringify(name)} (use lowercase letters, digits, dashes)`)
+    if (name === "llm") throw new Error(`sandbox egress rule name "llm" is reserved for the model gateway`)
+    if (typeof upstream !== "string" || !/^https?:\/\//.test(upstream))
+      throw new Error(`sandbox egress rule ${JSON.stringify(name)} needs an http(s) upstream URL`)
+    return { prefix: `/${name}`, upstream: new URL(upstream).toString() }
+  })
+}
+
 export function resolveBrokerRoute(routes: BrokerRoute[], requestUrl: string) {
   const url = new URL(requestUrl, "http://sandbox-broker.local")
   const route = routes.find(
diff --git a/packages/desktop/src/main/sandbox/egress.ts b/packages/desktop/src/main/sandbox/egress.ts
index e3a6c55568..59cad8035a 100644
--- a/packages/desktop/src/main/sandbox/egress.ts
+++ b/packages/desktop/src/main/sandbox/egress.ts
@@ -1,5 +1,8 @@
-import { net } from "electron"
+import { readFile } from "node:fs/promises"
+import { join } from "node:path"
+import { app, net } from "electron"
 import { buildGatewayConfig, loadApiKey, normalizeGatewayBaseUrl } from "@codev/gateway"
+import { parseBrokerRules } from "@codev/sandbox"
 import type { SandboxEgress } from "@codev/sandbox"
 
 // Guest-side view of the broker: every backend bridges guest 127.0.0.1:8788
@@ -16,18 +19,21 @@ export async function resolveSandboxEgress(): Promise<SandboxEgress> {
   const creds = loadApiKey()
   const gateway = creds?.baseUrl && creds.model ? creds : null
   return {
-    routes: gateway
-      ? [
-          {
-            prefix: "/llm/v1",
-            upstream: normalizeGatewayBaseUrl(gateway.baseUrl!),
-            // The guest config carries a placeholder key; the broker swaps in
-            // the real one, so the token never enters the guest and rotation
-            // stays host-side.
-            headers: { authorization: `Bearer ${gateway.apiKey}` },
-          },
-        ]
-      : [],
+    routes: [
+      ...(gateway
+        ? [
+            {
+              prefix: "/llm/v1",
+              upstream: normalizeGatewayBaseUrl(gateway.baseUrl!),
+              // The guest config carries a placeholder key; the broker swaps in
+              // the real one, so the token never enters the guest and rotation
+              // stays host-side.
+              headers: { authorization: `Bearer ${gateway.apiKey}` },
+            },
+          ]
+        : []),
+      ...(await namedEgressRules()),
+    ],
     guestConfig: JSON.stringify(
       {
         ...(gateway
@@ -51,3 +57,14 @@ export async function resolveSandboxEgress(): Promise<SandboxEgress> {
     fetchImpl: (input, init) => net.fetch(input instanceof URL ? input.toString() : input, init),
   }
 }
+
+// Optional admin-editable allowlist of extra egress routes (a mirror registry,
+// an internal API): userData/sandbox-egress.json, an object of name →
+// upstream URL. Reachable in the guest at http://127.0.0.1:8788/<name>/...
+// A malformed file throws, so the sandbox start fails with the parse message
+// instead of silently granting less than the admin intended.
+async function namedEgressRules() {
+  const raw = await readFile(join(app.getPath("userData"), "sandbox-egress.json"), "utf8").catch(() => null)
+  if (raw === null) return []
+  return parseBrokerRules(JSON.parse(raw))
+}