refactor(plugins): split before-agent hooks by model and prompt phases

src/plugins/hooks.phase-hooks.test.ts

@@ -0,0 +1,75 @@
+import { beforeEach, describe, expect, it } from "vitest";
+import type {
+  PluginHookBeforeModelResolveResult,
+  PluginHookBeforePromptBuildResult,
+  TypedPluginHookRegistration,
+} from "./types.js";
+import { createHookRunner } from "./hooks.js";
+import { createEmptyPluginRegistry, type PluginRegistry } from "./registry.js";
+
+function addTypedHook(
+  registry: PluginRegistry,
+  hookName: "before_model_resolve" | "before_prompt_build",
+  pluginId: string,
+  handler: () =>
+    | PluginHookBeforeModelResolveResult
+    | PluginHookBeforePromptBuildResult
+    | Promise<PluginHookBeforeModelResolveResult | PluginHookBeforePromptBuildResult>,
+  priority?: number,
+) {
+  registry.typedHooks.push({
+    pluginId,
+    hookName,
+    handler,
+    priority,
+    source: "test",
+  } as TypedPluginHookRegistration);
+}
+
+describe("phase hooks merger", () => {
+  let registry: PluginRegistry;
+
+  beforeEach(() => {
+    registry = createEmptyPluginRegistry();
+  });
+
+  it("before_model_resolve keeps higher-priority override values", async () => {
+    addTypedHook(registry, "before_model_resolve", "low", () => ({ modelOverride: "gpt-4o" }), 1);
+    addTypedHook(
+      registry,
+      "before_model_resolve",
+      "high",
+      () => ({ modelOverride: "llama3.3:8b", providerOverride: "ollama" }),
+      10,
+    );
+
+    const runner = createHookRunner(registry);
+    const result = await runner.runBeforeModelResolve({ prompt: "test" }, {});
+
+    expect(result?.modelOverride).toBe("llama3.3:8b");
+    expect(result?.providerOverride).toBe("ollama");
+  });
+
+  it("before_prompt_build concatenates prependContext and preserves systemPrompt precedence", async () => {
+    addTypedHook(
+      registry,
+      "before_prompt_build",
+      "high",
+      () => ({ prependContext: "context A", systemPrompt: "system A" }),
+      10,
+    );
+    addTypedHook(
+      registry,
+      "before_prompt_build",
+      "low",
+      () => ({ prependContext: "context B" }),
+      1,
+    );
+
+    const runner = createHookRunner(registry);
+    const result = await runner.runBeforePromptBuild({ prompt: "test", messages: [] }, {});
+
+    expect(result?.prependContext).toBe("context A\n\ncontext B");
+    expect(result?.systemPrompt).toBe("system A");
+  });
+});