diff --git a/src/agents/model-fallback.test.ts b/src/agents/model-fallback.test.ts
index 53990e9fdc2..d5b3b780358 100644
--- a/src/agents/model-fallback.test.ts
+++ b/src/agents/model-fallback.test.ts
@@ -907,7 +907,7 @@ describe("runWithModelFallback", () => {
     });
   });
 
-  it("falls back directly to configured primary when an override model fails", async () => {
+  it("puts configured primary next when an override model is requested", () => {
     const cfg = makeCfg({
       agents: {
         defaults: {
@@ -919,31 +919,19 @@ describe("runWithModelFallback", () => {
       },
     });
 
-    const run = createOverrideFailureRun({
-      overrideProvider: "anthropic",
-      overrideModel: "claude-opus-4-5",
-      fallbackProvider: "openai",
-      fallbackModel: "gpt-4.1-mini",
-      firstError: Object.assign(new Error("unauthorized"), { status: 401 }),
-    });
-
-    const result = await runWithModelFallback({
-      cfg,
-      provider: "anthropic",
-      model: "claude-opus-4-5",
-      run,
-    });
-
-    expect(result.result).toBe("ok");
-    expect(result.provider).toBe("openai");
-    expect(result.model).toBe("gpt-4.1-mini");
-    expect(run.mock.calls).toEqual([
-      ["anthropic", "claude-opus-4-5"],
-      ["openai", "gpt-4.1-mini"],
+    expect(
+      __testing.resolveFallbackCandidates({
+        cfg,
+        provider: "anthropic",
+        model: "claude-opus-4-5",
+      }),
+    ).toEqual([
+      { provider: "anthropic", model: "claude-opus-4-5" },
+      { provider: "openai", model: "gpt-4.1-mini" },
     ]);
   });
 
-  it("keeps configured fallback chain when current model is a configured fallback", async () => {
+  it("keeps configured fallback chain when current model is a configured fallback", () => {
     const cfg = makeCfg({
       agents: {
         defaults: {
@@ -955,33 +943,20 @@ describe("runWithModelFallback", () => {
       },
     });
 
-    const run = vi.fn().mockImplementation(async (provider: string, model: string) => {
-      if (provider === "anthropic" && model === "claude-haiku-3-5") {
-        throw Object.assign(new Error("rate-limited"), { status: 429 });
-      }
-      if (provider === "openrouter" && model === "openrouter/deepseek-chat") {
-        return "ok";
-      }
-      throw new Error(`unexpected fallback candidate: ${provider}/${model}`);
-    });
-
-    const result = await runWithModelFallback({
-      cfg,
-      provider: "anthropic",
-      model: "claude-haiku-3-5",
-      run,
-    });
-
-    expect(result.result).toBe("ok");
-    expect(result.provider).toBe("openrouter");
-    expect(result.model).toBe("openrouter/deepseek-chat");
-    expect(run.mock.calls).toEqual([
-      ["anthropic", "claude-haiku-3-5"],
-      ["openrouter", "openrouter/deepseek-chat"],
+    expect(
+      __testing.resolveFallbackCandidates({
+        cfg,
+        provider: "anthropic",
+        model: "claude-haiku-3-5",
+      }),
+    ).toEqual([
+      { provider: "anthropic", model: "claude-haiku-3-5" },
+      { provider: "openrouter", model: "openrouter/deepseek-chat" },
+      { provider: "openai", model: "gpt-4.1-mini" },
     ]);
   });
 
-  it("treats normalized default refs as primary and keeps configured fallback chain", async () => {
+  it("treats normalized default refs as primary and keeps configured fallback chain", () => {
     const cfg = makeCfg({
       agents: {
         defaults: {
@@ -993,44 +968,18 @@ describe("runWithModelFallback", () => {
       },
     });
 
-    const run = vi
-      .fn()
-      .mockRejectedValueOnce(Object.assign(new Error("nope"), { status: 401 }))
-      .mockResolvedValueOnce("ok");
-
-    const result = await runWithModelFallback({
-      cfg,
-      provider: " OpenAI ",
-      model: "gpt-4.1-mini",
-      run,
-    });
-
-    expect(result.result).toBe("ok");
-    expect(run.mock.calls).toEqual([
-      ["openai", "gpt-4.1-mini"],
-      ["anthropic", "claude-haiku-3-5"],
+    expect(
+      __testing.resolveFallbackCandidates({
+        cfg,
+        provider: " OpenAI ",
+        model: "gpt-4.1-mini",
+      }),
+    ).toEqual([
+      { provider: "openai", model: "gpt-4.1-mini" },
+      { provider: "anthropic", model: "claude-haiku-3-5" },
     ]);
   });
 
-  it("records 400 insufficient_quota payloads as billing during fallback", async () => {
-    const cfg = makeCfg();
-    const run = vi
-      .fn()
-      .mockRejectedValueOnce(Object.assign(new Error(INSUFFICIENT_QUOTA_PAYLOAD), { status: 400 }))
-      .mockResolvedValueOnce("ok");
-
-    const result = await runWithModelFallback({
-      cfg,
-      provider: "openai",
-      model: "gpt-4.1-mini",
-      run,
-    });
-
-    expect(result.result).toBe("ok");
-    expect(result.attempts).toHaveLength(1);
-    expect(result.attempts[0]?.reason).toBe("billing");
-  });
-
   it("falls back to configured primary for override credential validation errors", async () => {
     const cfg = makeCfg();
     const run = createOverrideFailureRun({
@@ -1055,6 +1004,25 @@ describe("runWithModelFallback", () => {
     ]);
   });
 
+  it("records 400 insufficient_quota payloads as billing during fallback", async () => {
+    const cfg = makeCfg();
+    const run = vi
+      .fn()
+      .mockRejectedValueOnce(Object.assign(new Error(INSUFFICIENT_QUOTA_PAYLOAD), { status: 400 }))
+      .mockResolvedValueOnce("ok");
+
+    const result = await runWithModelFallback({
+      cfg,
+      provider: "openai",
+      model: "gpt-4.1-mini",
+      run,
+    });
+
+    expect(result.result).toBe("ok");
+    expect(result.attempts).toHaveLength(1);
+    expect(result.attempts[0]?.reason).toBe("billing");
+  });
+
   it("falls back on model-not-found error shapes", async () => {
     const cases: Array<{
       name: string;
@@ -1257,7 +1225,7 @@ describe("runWithModelFallback", () => {
     expect(result.attempts).toEqual([]);
   });
 
-  it("does not append configured primary when fallbacksOverride is set", async () => {
+  it("does not append configured primary when fallbacksOverride is set", () => {
     const cfg = makeCfg({
       agents: {
         defaults: {
@@ -1267,23 +1235,17 @@ describe("runWithModelFallback", () => {
         },
       },
     });
-    const run = vi
-      .fn()
-      .mockImplementation(() => Promise.reject(Object.assign(new Error("nope"), { status: 401 })));
 
-    await expect(
-      runWithModelFallback({
+    expect(
+      __testing.resolveFallbackCandidates({
         cfg,
         provider: "anthropic",
         model: "claude-opus-4-5",
         fallbacksOverride: ["anthropic/claude-haiku-3-5"],
-        run,
       }),
-    ).rejects.toThrow("All models failed");
-
-    expect(run.mock.calls).toEqual([
-      ["anthropic", "claude-opus-4-5"],
-      ["anthropic", "claude-haiku-3-5"],
+    ).toEqual([
+      { provider: "anthropic", model: "claude-opus-4-5" },
+      { provider: "anthropic", model: "claude-haiku-3-5" },
     ]);
   });