feat: add subagent preset discovery and resolveChildModel change

src/presets.ts

@@ -0,0 +1,95 @@
+import { existsSync, readdirSync, readFileSync, statSync } from "node:fs";
+import { dirname, join } from "node:path";
+import { getAgentDir, parseFrontmatter } from "@mariozechner/pi-coding-agent";
+
+export interface SubagentPreset {
+  name: string;
+  description: string;
+  model?: string;
+  tools?: string[];
+  systemPrompt: string;
+  source: "global" | "project";
+  filePath: string;
+}
+
+export interface SubagentPresetDiscoveryResult {
+  presets: SubagentPreset[];
+  projectPresetsDir: string | null;
+}
+
+function findNearestProjectPresetsDir(cwd: string): string | null {
+  let current = cwd;
+  while (true) {
+    const candidate = join(current, ".pi", "subagents");
+    try {
+      if (statSync(candidate).isDirectory()) return candidate;
+    } catch (_err) {
+      // ignore
+    }
+    const parent = dirname(current);
+    if (parent === current) return null;
+    current = parent;
+  }
+}
+
+function loadPresetDir(dir: string, source: "global" | "project"): SubagentPreset[] {
+  if (!existsSync(dir)) return [];
+  const entries = readdirSync(dir, { withFileTypes: true });
+  const presets: SubagentPreset[] = [];
+
+  for (const entry of entries) {
+    if (!entry.name.endsWith(".md")) continue;
+    if (!entry.isFile() && !entry.isSymbolicLink()) continue;
+    const filePath = join(dir, entry.name);
+    let content: string;
+    try {
+      content = readFileSync(filePath, "utf8");
+    } catch (_err) {
+      continue;
+    }
+
+    const parsed = parseFrontmatter<Record<string, unknown>>(content);
+    const frontmatter = parsed.frontmatter ?? {};
+    const body = parsed.body ?? "";
+
+    if (typeof frontmatter.name !== "string") continue;
+    if (typeof frontmatter.description !== "string") continue;
+
+    const tools = typeof frontmatter.tools === "string"
+      ? frontmatter.tools.split(",").map((t) => t.trim()).filter(Boolean)
+      : undefined;
+
+    presets.push({
+      name: frontmatter.name,
+      description: frontmatter.description,
+      model: typeof frontmatter.model === "string" ? frontmatter.model : undefined,
+      tools: tools && tools.length > 0 ? tools : undefined,
+      systemPrompt: body.trim(),
+      source,
+      filePath,
+    });
+  }
+
+  return presets;
+}
+
+export function discoverSubagentPresets(cwd: string, options: { homeDir?: string } = {}): SubagentPresetDiscoveryResult {
+  const globalAgentDir = options.homeDir ? join(options.homeDir, ".pi", "agent") : getAgentDir();
+  const globalDir = join(globalAgentDir, "subagents");
+  const projectPresetsDir = findNearestProjectPresetsDir(cwd);
+
+  const map = new Map<string, SubagentPreset>();
+
+  for (const preset of loadPresetDir(globalDir, "global")) {
+    map.set(preset.name, preset);
+  }
+
+  if (projectPresetsDir) {
+    for (const preset of loadPresetDir(projectPresetsDir, "project")) {
+      // project overrides global by name
+      map.set(preset.name, preset);
+    }
+  }
+
+  return { presets: Array.from(map.values()), projectPresetsDir };
+}