diff --git a/src/claude/desktop-3p.ts b/src/claude/desktop-3p.ts
index 5fce7b147e..bedc0ce5aa 100644
--- a/src/claude/desktop-3p.ts
+++ b/src/claude/desktop-3p.ts
@@ -312,6 +312,11 @@ export function generateDesktop3pModels(
   return models;
 }
 
+/** True while no Desktop registry has been generated in this process (fresh boot). */
+export function desktop3pRegistryIsEmpty(): boolean {
+  return desktop3pRegistry.size === 0;
+}
+
 /** Resolve an alias using the most recently generated Desktop model registry. */
 export function resolveDesktop3pAlias(alias: string): string | null {
   return desktop3pRegistry.get(alias) ?? null;
diff --git a/src/server/index.ts b/src/server/index.ts
index 70433d845c..519264d680 100644
--- a/src/server/index.ts
+++ b/src/server/index.ts
@@ -1283,6 +1283,25 @@ export function startServer(port?: number, deps: StartServerDeps = {}): Server<W
         });
       }
 
+      // Desktop-3P alias self-heal: the registry that decodes hashed discovery ids
+      // (claude-opus-4-8-<code>) is in-memory and only rebuilt by an anthropic-flavor
+      // GET /v1/models. A client that cached such an id from a previous process can
+      // replay it as the FIRST request after a restart; with an empty registry the
+      // alias cannot decode and the request misroutes (classifier affinity or raw
+      // passthrough → upstream "Invalid model name"). Warm the registry once via
+      // loopback discovery — semantically the same as the client refreshing models.
+      if ((url.pathname === "/v1/messages" || url.pathname === "/v1/messages/count_tokens") && req.method === "POST") {
+        const { desktop3pRegistryIsEmpty } = await import("../claude/desktop-3p");
+        if (desktop3pRegistryIsEmpty()) {
+          const warmHeaders = new Headers({ "anthropic-version": "2023-06-01" });
+          const warmAuth = req.headers.get("authorization");
+          const warmKey = req.headers.get("x-api-key");
+          if (warmAuth) warmHeaders.set("authorization", warmAuth);
+          if (warmKey) warmHeaders.set("x-api-key", warmKey);
+          try { await fetch(new URL("/v1/models", url.origin), { headers: warmHeaders }); } catch { /* fall through to existing resolution */ }
+        }
+      }
+
       // Anthropic Messages inbound (Claude Code). count_tokens FIRST (longer path).
       // Claude Code posts `/v1/messages?beta=true` — pathname match ignores the query (003 G9).
       if (url.pathname === "/v1/messages/count_tokens" && req.method === "POST") {
diff --git a/tests/claude-messages-endpoint.test.ts b/tests/claude-messages-endpoint.test.ts
index 03cacabe82..110912555f 100644
--- a/tests/claude-messages-endpoint.test.ts
+++ b/tests/claude-messages-endpoint.test.ts
@@ -1571,3 +1571,53 @@ test("count_tokens is CJK-aware: Korean body counts more tokens than equal-lengt
     await server.stop(true);
   }
 });
+
+test("first /v1/messages after a restart self-heals an empty Desktop-3P registry (cached hashed id)", async () => {
+  const { server: upstream, captured } = mockChatUpstreamCapturing();
+  const baseUrl = `${upstream.url.toString().replace(/\/$/, "")}/v1`;
+  saveConfig({
+    port: 0,
+    defaultProvider: "mock",
+    providers: {
+      mock: {
+        adapter: "openai-chat",
+        baseUrl,
+        apiKey: "k",
+        allowPrivateNetwork: true,
+        liveModels: false,
+        models: ["test-model"],
+      },
+    },
+  } as OcxConfig);
+  const server = startServer(0);
+  try {
+    const { buildDesktop3pRegistry, desktop3pAlias } = await import("../src/claude/desktop-3p");
+    // Post-restart state: no discovery GET has run in this process, so the
+    // in-memory registry is empty while the client replays the hashed id it
+    // cached from the previous process.
+    buildDesktop3pRegistry([], []);
+    const alias = desktop3pAlias("mock", "test-model");
+    const response = await fetch(new URL("/v1/messages?beta=true", server.url), {
+      method: "POST",
+      headers: {
+        "content-type": "application/json",
+        "x-api-key": "placeholder",
+        "anthropic-version": "2023-06-01",
+      },
+      body: JSON.stringify({
+        model: alias,
+        max_tokens: 128,
+        stream: true,
+        messages: [{ role: "user", content: "hi" }],
+      }),
+    });
+    expect(response.status).toBe(200);
+    const text = await response.text();
+    expect(text).toContain("Hello");
+    // The upstream must see the decoded route, not the raw hashed alias.
+    expect(captured[0]?.model).toBe("test-model");
+  } finally {
+    await server.stop(true);
+    upstream.stop(true);
+  }
+}, { timeout: SERVER_BUDGET_MS });