feat(auto-reply): add model fallback lifecycle visibility in status, verbose logs, and WebUI (#20704)

src/auto-reply/fallback-state.test.ts

@@ -0,0 +1,123 @@
+import { describe, expect, it } from "vitest";
+import {
+  resolveActiveFallbackState,
+  resolveFallbackTransition,
+  type FallbackNoticeState,
+} from "./fallback-state.js";
+
+const baseAttempt = {
+  provider: "fireworks",
+  model: "fireworks/minimax-m2p5",
+  error: "Provider fireworks is in cooldown (all profiles unavailable)",
+  reason: "rate_limit" as const,
+};
+
+describe("fallback-state", () => {
+  it("treats fallback as active only when state matches selected and active refs", () => {
+    const state: FallbackNoticeState = {
+      fallbackNoticeSelectedModel: "fireworks/minimax-m2p5",
+      fallbackNoticeActiveModel: "deepinfra/moonshotai/Kimi-K2.5",
+      fallbackNoticeReason: "rate limit",
+    };
+
+    const resolved = resolveActiveFallbackState({
+      selectedModelRef: "fireworks/minimax-m2p5",
+      activeModelRef: "deepinfra/moonshotai/Kimi-K2.5",
+      state,
+    });
+
+    expect(resolved.active).toBe(true);
+    expect(resolved.reason).toBe("rate limit");
+  });
+
+  it("does not treat runtime drift as fallback when persisted state does not match", () => {
+    const state: FallbackNoticeState = {
+      fallbackNoticeSelectedModel: "anthropic/claude",
+      fallbackNoticeActiveModel: "deepinfra/moonshotai/Kimi-K2.5",
+      fallbackNoticeReason: "rate limit",
+    };
+
+    const resolved = resolveActiveFallbackState({
+      selectedModelRef: "fireworks/minimax-m2p5",
+      activeModelRef: "deepinfra/moonshotai/Kimi-K2.5",
+      state,
+    });
+
+    expect(resolved.active).toBe(false);
+    expect(resolved.reason).toBeUndefined();
+  });
+
+  it("marks fallback transition when selected->active pair changes", () => {
+    const resolved = resolveFallbackTransition({
+      selectedProvider: "fireworks",
+      selectedModel: "fireworks/minimax-m2p5",
+      activeProvider: "deepinfra",
+      activeModel: "moonshotai/Kimi-K2.5",
+      attempts: [baseAttempt],
+      state: {},
+    });
+
+    expect(resolved.fallbackActive).toBe(true);
+    expect(resolved.fallbackTransitioned).toBe(true);
+    expect(resolved.fallbackCleared).toBe(false);
+    expect(resolved.stateChanged).toBe(true);
+    expect(resolved.reasonSummary).toBe("rate limit");
+    expect(resolved.nextState.selectedModel).toBe("fireworks/minimax-m2p5");
+    expect(resolved.nextState.activeModel).toBe("deepinfra/moonshotai/Kimi-K2.5");
+  });
+
+  it("normalizes fallback reason whitespace for summaries", () => {
+    const resolved = resolveFallbackTransition({
+      selectedProvider: "fireworks",
+      selectedModel: "fireworks/minimax-m2p5",
+      activeProvider: "deepinfra",
+      activeModel: "moonshotai/Kimi-K2.5",
+      attempts: [{ ...baseAttempt, reason: "rate_limit\n\tburst" }],
+      state: {},
+    });
+
+    expect(resolved.reasonSummary).toBe("rate limit burst");
+  });
+
+  it("refreshes reason when fallback remains active with same model pair", () => {
+    const resolved = resolveFallbackTransition({
+      selectedProvider: "fireworks",
+      selectedModel: "fireworks/minimax-m2p5",
+      activeProvider: "deepinfra",
+      activeModel: "moonshotai/Kimi-K2.5",
+      attempts: [{ ...baseAttempt, reason: "timeout" }],
+      state: {
+        fallbackNoticeSelectedModel: "fireworks/minimax-m2p5",
+        fallbackNoticeActiveModel: "deepinfra/moonshotai/Kimi-K2.5",
+        fallbackNoticeReason: "rate limit",
+      },
+    });
+
+    expect(resolved.fallbackTransitioned).toBe(false);
+    expect(resolved.stateChanged).toBe(true);
+    expect(resolved.nextState.reason).toBe("timeout");
+  });
+
+  it("marks fallback as cleared when runtime returns to selected model", () => {
+    const resolved = resolveFallbackTransition({
+      selectedProvider: "fireworks",
+      selectedModel: "fireworks/minimax-m2p5",
+      activeProvider: "fireworks",
+      activeModel: "fireworks/minimax-m2p5",
+      attempts: [],
+      state: {
+        fallbackNoticeSelectedModel: "fireworks/minimax-m2p5",
+        fallbackNoticeActiveModel: "deepinfra/moonshotai/Kimi-K2.5",
+        fallbackNoticeReason: "rate limit",
+      },
+    });
+
+    expect(resolved.fallbackActive).toBe(false);
+    expect(resolved.fallbackCleared).toBe(true);
+    expect(resolved.fallbackTransitioned).toBe(false);
+    expect(resolved.stateChanged).toBe(true);
+    expect(resolved.nextState.selectedModel).toBeUndefined();
+    expect(resolved.nextState.activeModel).toBeUndefined();
+    expect(resolved.nextState.reason).toBeUndefined();
+  });
+});