diff --git a/packages/core/src/gateway/upstream/executor.ts b/packages/core/src/gateway/upstream/executor.ts
index fa5bd0cd..416c10ef 100644
--- a/packages/core/src/gateway/upstream/executor.ts
+++ b/packages/core/src/gateway/upstream/executor.ts
@@ -610,12 +610,19 @@ function prepareUpstreamCredentialAttempt(input: {
   const credentials = activeProviderCredentials(target.provider);
   if (credentials.length === 0) {
     const preserveModelSelector = shouldPreserveCapabilityModelSelector(input.attempt.body, target);
+    const targetHeaders = targetProviderFallbackHeaders(attemptHeaders, target.provider, target.protocol);
+    const targetBody = target.body ?? normalizedBody?.body ?? input.attempt.body;
+    const providerQualifiedTargetBody = providerQualifiedTargetModelBody(
+      targetBody,
+      target.model,
+      targetHeaders["x-target-provider"]
+    );
     return {
       ...input.attempt,
-      body: attemptBody(preserveModelSelector ? input.attempt.body : target.body ?? normalizedBody?.body ?? input.attempt.body),
+      body: attemptBody(preserveModelSelector ? input.attempt.body : providerQualifiedTargetBody ?? targetBody),
       headers: preserveModelSelector
         ? clearTargetProviderHeaders(attemptHeaders)
-        : targetProviderFallbackHeaders(attemptHeaders, target.provider, target.protocol)
+        : targetHeaders
     };
   }
 
@@ -732,6 +739,22 @@ function shouldPreserveCapabilityModelSelector(body: Buffer | undefined, target:
 }
 
 
+function providerQualifiedTargetModelBody(
+  body: Buffer | undefined,
+  model: string | undefined,
+  providerSelector: string | undefined
+): Buffer | undefined {
+  if (!model || !providerSelector || !parseProviderModelSelector(model)) {
+    return undefined;
+  }
+  const parsedBody = parseJsonObjectSafe(body);
+  if (!parsedBody) {
+    return undefined;
+  }
+  return serializeJsonBodyWithModel(parsedBody, `${providerSelector}/${model}`);
+}
+
+
 function resolvePlannedProviderCredentialRoutingTarget(
   attempt: UpstreamAttempt,
   path: string
diff --git a/packages/core/test/unit/gateway/upstream-executor.test.mjs b/packages/core/test/unit/gateway/upstream-executor.test.mjs
index a7e17807..ae8ab61f 100644
--- a/packages/core/test/unit/gateway/upstream-executor.test.mjs
+++ b/packages/core/test/unit/gateway/upstream-executor.test.mjs
@@ -1,5 +1,7 @@
 import assert from "node:assert/strict";
 import test from "node:test";
+import { buildClaudeAppGatewayModelRoutes } from "@ccr/core/agents/claude-app/gateway-routes.ts";
+import { prepareClaudeAppDiscoveredModelRequest } from "@ccr/core/gateway/features/model-discovery.ts";
 import { fetchUpstreamWithFallback, prepareGatewayUpstreamAttemptForTest } from "@ccr/core/gateway/upstream/executor.ts";
 import { RequestRouteTraceRecorder } from "@ccr/core/observability/route-trace.ts";
 
@@ -116,6 +118,63 @@ test("target-provider routing preserves slash-namespaced model ids", () => {
   }
 });
 
+test("Claude App OpenRouter routes do not send conflicting vendor-prefixed model selectors to the core gateway", () => {
+  const targetModel = "OpenRouter/google/gemini-3.7-flash";
+  const config = {
+    Providers: [
+      {
+        apiKey: "openrouter-key",
+        capabilities: [
+          { baseUrl: "https://openrouter.ai/api/v1", type: "openai_chat_completions" },
+          { baseUrl: "https://openrouter.ai/api/v1", type: "openai_responses" }
+        ],
+        id: "openrouter",
+        models: ["google/gemini-3.7-flash"],
+        name: "OpenRouter"
+      }
+    ],
+    Router: { fallback: { mode: "off", models: [], retryCount: 0 }, rules: [] },
+    profile: {
+      enabled: true,
+      profiles: [
+        {
+          agent: "claude-code",
+          enabled: true,
+          id: "claude-code-openrouter",
+          model: targetModel,
+          name: "Claude Code OpenRouter",
+          scope: "global"
+        }
+      ]
+    },
+    virtualModelProfiles: []
+  };
+  const route = buildClaudeAppGatewayModelRoutes(config).find((item) => item.targetModel === targetModel);
+  assert.ok(route);
+
+  const rewrite = prepareClaudeAppDiscoveredModelRequest(
+    config,
+    "POST",
+    "/v1/messages",
+    Buffer.from(JSON.stringify({ max_tokens: 8, messages: [{ role: "user", content: "hello" }], model: route.id }))
+  );
+  assert.equal(rewrite?.routedModel, targetModel);
+
+  const rewrittenBody = JSON.parse(rewrite.body.toString("utf8"));
+  const attempt = prepareGatewayUpstreamAttemptForTest({
+    body: rewrittenBody,
+    config,
+    headers: {},
+    method: "POST",
+    path: "/v1/messages",
+    routedModel: rewrite.routedModel
+  });
+
+  assert.equal(attempt.headers["x-target-provider"], "openrouter::openai_chat_completions");
+  assert.equal(coreGatewayTargetProviderConflict(attempt), false);
+  assert.equal(attempt.body.model, "openrouter::openai_chat_completions/google/gemini-3.7-flash");
+});
+
 test("target-provider routing keeps vendor-prefixed model ids even when the prefix names another provider", () => {
   const config = {
     Providers: [
@@ -156,6 +215,52 @@ test("target-provider routing keeps vendor-prefixed model ids even when the pref
   assert.equal(attempt.logicalProvider, "Groq");
 });
 
+function coreGatewayTargetProviderConflict(attempt) {
+  const bodyModel = typeof attempt.body?.model === "string" ? attempt.body.model : "";
+  const targetProvider = attempt.headers?.["x-target-provider"];
+  if (!bodyModel || !targetProvider) {
+    return false;
+  }
+  const slashIndex = bodyModel.indexOf("/");
+  if (slashIndex <= 0 || slashIndex >= bodyModel.length - 1) {
+    return false;
+  }
+  const providerHint = bodyModel.slice(0, slashIndex);
+  if (providerHint === targetProvider) {
+    return false;
+  }
+  const modelProvider = coreGatewayBuiltinProvider(providerHint);
+  const targetProviderType = coreGatewayProviderType(targetProvider);
+  return Boolean(modelProvider && targetProviderType && modelProvider !== targetProviderType);
+}
+
+function coreGatewayProviderType(providerSelector) {
+  if (providerSelector.includes("::openai_chat_completions") || providerSelector.includes("::openai_responses")) {
+    return "openai";
+  }
+  if (providerSelector.includes("::anthropic_messages")) {
+    return "anthropic";
+  }
+  if (providerSelector.includes("::gemini_generate_content") || providerSelector.includes("::gemini_interactions")) {
+    return "gemini";
+  }
+  return coreGatewayBuiltinProvider(providerSelector);
+}
+
+function coreGatewayBuiltinProvider(value) {
+  const normalized = value.trim().toLowerCase();
+  if (normalized === "openai") {
+    return "openai";
+  }
+  if (normalized === "anthropic" || normalized === "claude") {
+    return "anthropic";
+  }
+  if (normalized === "gemini" || normalized === "google") {
+    return "gemini";
+  }
+  return undefined;
+}
+
 test("target-provider routing preserves slash model ids for providers without explicit capabilities", () => {
   const config = {
     Providers: [