diff --git a/src/app/api/v1/responses/route.ts b/src/app/api/v1/responses/route.ts
index 6d6d5ad60f..66270896e5 100644
--- a/src/app/api/v1/responses/route.ts
+++ b/src/app/api/v1/responses/route.ts
@@ -6,8 +6,7 @@ import {
 } from "@omniroute/open-sse/utils/earlyStreamKeepalive";
 import { withInjectionGuard } from "@/middleware/promptInjectionGuard";
 import { resolveResponsesApiModel } from "@/app/api/internal/codex-responses-ws/modelResolution";
-import { getModelInfo } from "@/sse/services/model";
-import { getComboByName } from "@/lib/db/combos";
+import { getModelInfo, getComboForModel } from "@/sse/services/model";
 import { resolveKeepaliveThreshold } from "@omniroute/open-sse/utils/keepaliveThreshold";
 import { resolveStreamFlag } from "@omniroute/open-sse/utils/aiSdkCompat";
 
@@ -58,7 +57,7 @@ export async function withCodexPreferredModel(
     const { model, changed } = await resolveResponsesApiModel(
       body.model,
       getModelInfo,
-      async (name) => !!(await getComboByName(name))
+      async (name) => !!(await getComboForModel(name))
     );
     if (!changed) return { request, body };
 
diff --git a/tests/unit/responses-case-insensitive-combo-guard.test.ts b/tests/unit/responses-case-insensitive-combo-guard.test.ts
new file mode 100644
index 0000000000..532e1e1a15
--- /dev/null
+++ b/tests/unit/responses-case-insensitive-combo-guard.test.ts
@@ -0,0 +1,100 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import { readFileSync } from "node:fs";
+
+import { resolveResponsesApiModel } from "../../src/app/api/internal/codex-responses-ws/modelResolution.ts";
+
+const resolver = async (modelStr: string) => {
+  if (modelStr.startsWith("codex/")) {
+    return { provider: "codex", model: modelStr.slice("codex/".length) };
+  }
+  return { provider: "openrouter", model: modelStr };
+};
+
+test("case-insensitive combo match prevents Codex rewrite on /v1/responses", async () => {
+  const storedComboName = "GPT-5.6-SOL";
+  const isCombo = async (name: string) => name.toLowerCase() === storedComboName.toLowerCase();
+
+  const result = await resolveResponsesApiModel("gpt-5.6-sol", resolver, isCombo);
+
+  assert.equal(result.changed, false);
+  assert.equal(result.model, "gpt-5.6-sol");
+});
+
+test("bare codex model is still rewritten when not a combo (Codex preference preserved)", async () => {
+  const isCombo = async () => false;
+
+  const result = await resolveResponsesApiModel("gpt-5.5", resolver, isCombo);
+
+  assert.equal(result.changed, true);
+  assert.equal(result.model, "codex/gpt-5.5");
+});
+
+test("provider-prefixed models pass through unchanged", async () => {
+  const isCombo = async () => false;
+
+  for (const model of ["anthropic/claude-opus-4-8", "codex/gpt-5.5", "combo/my-combo"]) {
+    const result = await resolveResponsesApiModel(model, resolver, isCombo);
+    assert.equal(result.changed, false, `${model} must not be marked as changed`);
+    assert.equal(result.model, model, `${model} must pass through unchanged`);
+  }
+});
+
+test("Responses route uses the downstream combo resolver for the Codex rewrite guard", () => {
+  const source = readFileSync(
+    new URL("../../src/app/api/v1/responses/route.ts", import.meta.url),
+    "utf8"
+  );
+
+  assert.match(
+    source,
+    /import \{ getModelInfo, getComboForModel \} from "@\/sse\/services\/model"/
+  );
+  assert.match(source, /async \(name\) => !!\(await getComboForModel\(name\)\)/);
+  assert.doesNotMatch(source, /getComboByName\(name\)/);
+});
+
+const TEST_DATA_DIR = fs.mkdtempSync(
+  path.join(os.tmpdir(), "omniroute-responses-ci-" + Date.now())
+);
+process.env.DATA_DIR = TEST_DATA_DIR;
+
+const core = await import("../../src/lib/db/core.ts");
+const combosDb = await import("../../src/lib/db/combos.ts");
+const sseModelService = await import("../../src/sse/services/model.ts");
+
+test.after(() => {
+  core.resetDbInstance();
+  fs.rmSync(TEST_DATA_DIR, { recursive: true, force: true });
+});
+
+test("getComboForModel resolves a stored combo by a case-insensitive request name", async () => {
+  core.resetDbInstance();
+
+  await combosDb.createCombo({
+    name: "GPT-5.6-SOL",
+    models: [{ provider: "openrouter", model: "gpt-5.6" }],
+  });
+
+  const resolved = await sseModelService.getComboForModel("gpt-5.6-sol");
+  assert.ok(resolved, "expected lowercased request to resolve to the stored GPT-5.6-SOL combo");
+  assert.equal((resolved as { name: string }).name, "GPT-5.6-SOL");
+});
+
+test("real getComboForModel predicate prevents the Codex rewrite on /v1/responses", async () => {
+  core.resetDbInstance();
+
+  await combosDb.createCombo({
+    name: "Archon-Gate-9",
+    models: [{ provider: "openrouter", model: "gpt-5.6" }],
+  });
+
+  const isCombo = async (name: string) => !!(await sseModelService.getComboForModel(name));
+
+  const result = await resolveResponsesApiModel("archon-gate-9", resolver, isCombo);
+  assert.equal(result.changed, false);
+  assert.equal(result.model, "archon-gate-9");
+});