fix(agents): prioritize per-model thinking defaults (#30439)

* fix(agents): honor per-model thinking defaults

* fix(agents): preserve thinking fallback with model defaults

---------

Co-authored-by: Mark L <73659136+markliuyuxiang@users.noreply.github.com>
Co-authored-by: Peter Steinberger <steipete@gmail.com>

src/agents/model-selection.test.ts

@@ -11,6 +11,7 @@ import {
   modelKey,
   resolveAllowedModelRef,
   resolveConfiguredModelRef,
+  resolveThinkingDefault,
   resolveModelRefFromString,
 } from "./model-selection.js";
 
@@ -470,6 +471,39 @@ describe("model-selection", () => {
       expect(result).toEqual({ provider: "openai", model: "gpt-4" });
     });
   });
+
+  describe("resolveThinkingDefault", () => {
+    it("prefers per-model params.thinking over global thinkingDefault", () => {
+      const cfg = {
+        agents: {
+          defaults: {
+            thinkingDefault: "low",
+            models: {
+              "anthropic/claude-opus-4-6": {
+                params: { thinking: "high" },
+              },
+            },
+          },
+        },
+      } as OpenClawConfig;
+
+      expect(
+        resolveThinkingDefault({
+          cfg,
+          provider: "anthropic",
+          model: "claude-opus-4-6",
+          catalog: [
+            {
+              provider: "anthropic",
+              id: "claude-opus-4-6",
+              name: "Claude Opus 4.6",
+              reasoning: true,
+            },
+          ],
+        }),
+      ).toBe("high");
+    });
+  });
 });
 
 describe("normalizeModelSelection", () => {