diff --git a/apps/web/src/composerDraftStore.test.ts b/apps/web/src/composerDraftStore.test.ts
index d92417ba96d88..e79eb5c75e00d 100644
--- a/apps/web/src/composerDraftStore.test.ts
+++ b/apps/web/src/composerDraftStore.test.ts
@@ -1754,6 +1754,7 @@ describe("composerDraftStore modelSelection", () => {
     ).toEqual(
       expect.objectContaining({
         instanceId: CODEX_SECONDARY_INSTANCE,
+        model: "gpt-5-codex",
         options: [{ id: "reasoningEffort", value: "low" }],
       }),
     );
@@ -1770,6 +1771,19 @@ describe("composerDraftStore modelSelection", () => {
         options: [{ id: "reasoningEffort", value: "low" }],
       }),
     );
+    expect(
+      useComposerDraftStore.getState().stickyOptionsByModelByProvider[CODEX_SECONDARY_INSTANCE],
+    ).toEqual({ "gpt-5-codex": [{ id: "reasoningEffort", value: "low" }] });
+
+    // A custom slug that matches a Codex alias stays exact; the picker already resolved it.
+    store.setModelSelection(threadRef, createModelSelection(CODEX_SECONDARY_INSTANCE, "gpt-5.3"), {
+      explicit: true,
+      replaceOptions: true,
+    });
+    expect(
+      draftFor(threadId, TEST_ENVIRONMENT_ID)?.modelSelectionByProvider[CODEX_SECONDARY_INSTANCE]
+        ?.model,
+    ).toBe("gpt-5.3");
   });
 });
 
diff --git a/apps/web/src/composerDraftStore.ts b/apps/web/src/composerDraftStore.ts
index 4e6dfe04a7ebb..29a589cae66ff 100644
--- a/apps/web/src/composerDraftStore.ts
+++ b/apps/web/src/composerDraftStore.ts
@@ -42,6 +42,7 @@ import { DeepMutable } from "effect/Types";
 import {
   createModelSelection,
   draftModelPickMatchesThread,
+  normalizeCustomModelSlug,
   normalizeModelSlug,
 } from "@t3tools/shared/model";
 import { AsyncResult, Atom, type AtomRegistry } from "effect/reactivity";
@@ -990,7 +991,11 @@ function normalizeModelSelection(
   const driverKindHint =
     normalizeProviderDriverKind(candidate?.provider ?? legacy?.provider) ??
     ProviderDriverKind.make("codex");
-  const model = normalizeModelSlug(rawModel, driverKindHint);
+  // Instance-scoped picks are already resolved slugs; a custom slug can match a static alias.
+  const model =
+    candidate?.instanceId === undefined
+      ? normalizeModelSlug(rawModel, driverKindHint)
+      : normalizeCustomModelSlug(rawModel);
   if (!model) {
     return null;
   }
@@ -3051,7 +3056,7 @@ const composerDraftStore = create<ComposerDraftStoreState>()(
           }
           const instanceKey = options?.instanceId ?? defaultInstanceIdForDriver(normalizedProvider);
           const fallbackModel =
-            normalizeModelSlug(options?.model, normalizedProvider) ??
+            normalizeCustomModelSlug(options?.model) ??
             DEFAULT_MODEL_BY_PROVIDER[normalizedProvider] ??
             DEFAULT_MODEL;
           const providerOpts =
@@ -3083,8 +3088,7 @@ const composerDraftStore = create<ComposerDraftStoreState>()(
                 nextStickyMap[instanceKey] ??
                 base.modelSelectionByProvider[instanceKey] ??
                 createModelSelection(instanceKey, fallbackModel);
-              const rememberedModel =
-                normalizeModelSlug(options?.model, normalizedProvider) ?? stickyBase.model;
+              const rememberedModel = normalizeCustomModelSlug(options?.model) ?? stickyBase.model;
               if (providerOpts) {
                 nextStickyMap[instanceKey] = createModelSelection(
                   instanceKey,