fix(chat): pin composer, set reply language, and track model loading

packages/harness/src/skills.ts

@@ -3,6 +3,14 @@ import path from "node:path";
 import { DefaultResourceLoader, SettingsManager, type InlineExtension, type ResourceDiagnostic, type Skill } from "@earendil-works/pi-coding-agent";
 import type { SkillCatalogItem } from "@agent-studio/shared";
 
+const languagePolicy = `会话回复语言规则：
+默认使用中文回复，包括中文请求。
+仅当首条用户输入中的自然语言请求明确为英文时，当前 Session 才使用英文回复。
+判断时忽略 Skill 名称、Skill XML/正文、命令、路径、代码和技术标识；这些内容不作为英文发起会话的依据。
+首条输入仅包含 Skill 内容或 Skill 名称，或自然语言无法明确判断时，选择中文；不要等待后续请求再选择语言。
+选定的回复语言在当前 Session 内保持一致；Reset 创建新 Session 后重新判断。
+保留代码、路径、命令和技术标识的原文。`;
+
 export interface SkillIndexEntry extends SkillCatalogItem { canonicalPath: string }
 
 export class SkillCatalog {
@@ -68,6 +76,7 @@ export class SkillCatalog {
       settingsManager: SettingsManager.inMemory(),
       additionalSkillPaths: this.canonicalDirectories,
       extensionFactories,
+      appendSystemPromptOverride: (base) => [...base, languagePolicy],
       noPromptTemplates: true,
       noThemes: true,
       noContextFiles: true,

packages/harness/tests/core.test.ts

@@ -103,6 +103,34 @@ describe("SkillCatalog", () => {
   it("discovers .agents and .pi skills without reading bodies into the catalog", async () => {
     const root = await mkdtemp(path.join(tmpdir(), "studio-skills-")); await createSkill(root, ".agents/skills/one", "one", "First skill"); await createSkill(root, ".pi/skills/two", "two", "Second skill"); const catalog = new SkillCatalog(root, path.join(root, "agent-dir")); await catalog.reload(); expect(catalog.list().filter((item) => ["one", "two"].includes(item.name))).toHaveLength(2); expect(JSON.stringify(catalog.list())).not.toContain("SECRET BODY");
   });
+  it("appends the Session language policy while preserving default prompts, skills and extensions", async () => {
+    const root = await mkdtemp(path.join(tmpdir(), "studio-language-"));
+    const agentDir = path.join(root, "agent-dir");
+    await createSkill(root, ".agents/skills/one", "one", "First skill");
+    await mkdir(path.join(root, ".pi/skills"), { recursive: true });
+    await writeFile(path.join(root, ".pi/APPEND_SYSTEM.md"), "Existing appended instruction");
+    const catalog = new SkillCatalog(root, agentDir);
+    await catalog.reload();
+    const extension = vi.fn();
+    const loader = await catalog.createSessionLoader(root, agentDir, [extension]);
+    expect(loader.getSystemPrompt()).toBeUndefined(); // Pi still builds its default Tool/Skill prompt.
+    expect(loader.getSystemPromptSource()).toBeUndefined();
+    const appended = loader.getAppendSystemPrompt();
+    expect(appended[0]).toBe("Existing appended instruction");
+    const policy = appended.at(-1)!;
+    expect(policy).toContain("默认使用中文回复，包括中文请求");
+    expect(policy).toContain("仅当首条用户输入中的自然语言请求明确为英文时");
+    expect(policy).toContain("Skill 名称、Skill XML/正文、命令、路径、代码和技术标识");
+    expect(policy).toContain("首条输入仅包含 Skill 内容或 Skill 名称，或自然语言无法明确判断时，选择中文");
+    expect(policy).toContain("当前 Session 内保持一致");
+    expect(policy).toContain("Reset 创建新 Session 后重新判断");
+    expect(loader.getSkills().skills.some((skill) => skill.name === "one")).toBe(true);
+    expect(extension).toHaveBeenCalledOnce();
+    await writeFile(path.join(root, ".pi/SYSTEM.md"), "Existing system prompt");
+    const next = await catalog.createSessionLoader(root, agentDir, []);
+    expect(next.getSystemPrompt()).toBe("Existing system prompt");
+    expect(next.getAppendSystemPrompt()).toEqual(appended);
+  });
   it("loads path-delimited AGENT_SKILLS_DIRS and de-duplicates canonical paths", async () => {
     const root = await mkdtemp(path.join(tmpdir(), "studio-skills-")); await mkdir(path.join(root, ".agents/skills"), { recursive: true }); await mkdir(path.join(root, ".pi/skills"), { recursive: true }); const extra = path.join(root, "extra"); await createSkill(root, "extra/custom", "custom", "Extra skill"); const catalog = new SkillCatalog(root, path.join(root, "agent-dir"), [extra, extra].join(path.delimiter)); await catalog.reload(); expect(catalog.list().filter((item) => item.name === "custom")).toHaveLength(1);
   });