fix(model): infer provider from allowlist for bare model IDs to prevent prefix drift (#48369)

src/agents/model-selection.test.ts

@@ -569,6 +569,34 @@ describe("model-selection", () => {
         ref: { provider: "openai", model: "@cf/openai/gpt-oss-20b" },
       });
     });
+
+    it("infers provider from allowlist for bare model ids to prevent prefix drift (#48369)", () => {
+      const cfg = {
+        agents: {
+          defaults: {
+            models: {
+              "openai-codex/gpt-5.4": {},
+              "opencode-go/kimi-k2.5": {},
+              "opencode-go/glm-5": {},
+            },
+          },
+        },
+      } as OpenClawConfig;
+
+      // When session default is openai-codex, switching to a bare "kimi-k2.5"
+      // should resolve to opencode-go/kimi-k2.5, not openai-codex/kimi-k2.5
+      const result = resolveAllowedModelRef({
+        cfg,
+        catalog: [],
+        raw: "kimi-k2.5",
+        defaultProvider: "openai-codex", // session's current provider
+      });
+
+      expect(result).toEqual({
+        key: "opencode-go/kimi-k2.5",
+        ref: { provider: "opencode-go", model: "kimi-k2.5" },
+      });
+    });
   });
 
   describe("resolveModelRefFromString", () => {

src/agents/model-selection.ts

@@ -660,9 +660,19 @@ export function resolveAllowedModelRef(params: {
     cfg: params.cfg,
     defaultProvider: params.defaultProvider,
   });
+
+  // When the model string has no provider prefix ("/"), try to infer the
+  // correct provider from the configured allowlist before falling back to the
+  // session's current default provider. This prevents provider prefix drift
+  // when switching models across different providers (see #48369).
+  const effectiveDefaultProvider = !trimmed.includes("/")
+    ? (inferUniqueProviderFromConfiguredModels({ cfg: params.cfg, model: trimmed }) ??
+      params.defaultProvider)
+    : params.defaultProvider;
+
   const resolved = resolveModelRefFromString({
     raw: trimmed,
-    defaultProvider: params.defaultProvider,
+    defaultProvider: effectiveDefaultProvider,
     aliasIndex,
   });
   if (!resolved) {