refactor(agents): centralize model fallback resolution

src/agents/agent-scope.test.ts

@@ -2,13 +2,16 @@ import path from "node:path";
 import { afterEach, describe, expect, it, vi } from "vitest";
 import type { OpenClawConfig } from "../config/config.js";
 import {
+  hasConfiguredModelFallbacks,
   resolveAgentConfig,
   resolveAgentDir,
   resolveAgentEffectiveModelPrimary,
   resolveAgentExplicitModelPrimary,
+  resolveFallbackAgentId,
   resolveEffectiveModelFallbacks,
   resolveAgentModelFallbacksOverride,
   resolveAgentModelPrimary,
+  resolveRunModelFallbacksOverride,
   resolveAgentWorkspaceDir,
 } from "./agent-scope.js";
 
@@ -210,6 +213,109 @@ describe("resolveAgentConfig", () => {
     ).toEqual([]);
   });
 
+  it("resolves fallback agent id from explicit agent id first", () => {
+    expect(
+      resolveFallbackAgentId({
+        agentId: "Support",
+        sessionKey: "agent:main:session",
+      }),
+    ).toBe("support");
+  });
+
+  it("resolves fallback agent id from session key when explicit id is missing", () => {
+    expect(
+      resolveFallbackAgentId({
+        sessionKey: "agent:worker:session",
+      }),
+    ).toBe("worker");
+  });
+
+  it("resolves run fallback overrides via shared helper", () => {
+    const cfg: OpenClawConfig = {
+      agents: {
+        defaults: {
+          model: {
+            fallbacks: ["openai/gpt-4.1"],
+          },
+        },
+        list: [
+          {
+            id: "support",
+            model: {
+              fallbacks: ["openai/gpt-5.2"],
+            },
+          },
+        ],
+      },
+    };
+
+    expect(
+      resolveRunModelFallbacksOverride({
+        cfg,
+        agentId: "support",
+        sessionKey: "agent:main:session",
+      }),
+    ).toEqual(["openai/gpt-5.2"]);
+    expect(
+      resolveRunModelFallbacksOverride({
+        cfg,
+        agentId: undefined,
+        sessionKey: "agent:support:session",
+      }),
+    ).toEqual(["openai/gpt-5.2"]);
+  });
+
+  it("computes whether any model fallbacks are configured via shared helper", () => {
+    const cfgDefaultsOnly: OpenClawConfig = {
+      agents: {
+        defaults: {
+          model: {
+            fallbacks: ["openai/gpt-4.1"],
+          },
+        },
+        list: [{ id: "main" }],
+      },
+    };
+    expect(
+      hasConfiguredModelFallbacks({
+        cfg: cfgDefaultsOnly,
+        sessionKey: "agent:main:session",
+      }),
+    ).toBe(true);
+
+    const cfgAgentOverrideOnly: OpenClawConfig = {
+      agents: {
+        defaults: {
+          model: {
+            fallbacks: [],
+          },
+        },
+        list: [
+          {
+            id: "support",
+            model: {
+              fallbacks: ["openai/gpt-5.2"],
+            },
+          },
+        ],
+      },
+    };
+    expect(
+      hasConfiguredModelFallbacks({
+        cfg: cfgAgentOverrideOnly,
+        agentId: "support",
+        sessionKey: "agent:support:session",
+      }),
+    ).toBe(true);
+    expect(
+      hasConfiguredModelFallbacks({
+        cfg: cfgAgentOverrideOnly,
+        agentId: "main",
+        sessionKey: "agent:main:session",
+      }),
+    ).toBe(false);
+  });
+
   it("should return agent-specific sandbox config", () => {
     const cfg: OpenClawConfig = {
       agents: {