feat: add subagent preset discovery and resolveChildModel change

src/models.test.ts

@@ -7,16 +7,26 @@ import {
   resolveChildModel,
 } from "./models.ts";
 
-test("resolveChildModel prefers the per-task override over the required top-level model", () => {
+test("resolveChildModel prefers explicit call model over preset default model", () => {
   const selection = resolveChildModel({
-    taskModel: "openai/gpt-5",
-    topLevelModel: "anthropic/claude-sonnet-4-5",
+    callModel: "openai/gpt-5",
+    presetModel: "anthropic/claude-sonnet-4-5",
   });
 
   assert.equal(selection.requestedModel, "openai/gpt-5");
   assert.equal(selection.resolvedModel, "openai/gpt-5");
 });
 
+test("resolveChildModel falls back to preset default model", () => {
+  const selection = resolveChildModel({
+    callModel: undefined,
+    presetModel: "anthropic/claude-sonnet-4-5",
+  });
+
+  assert.equal(selection.requestedModel, "anthropic/claude-sonnet-4-5");
+  assert.equal(selection.resolvedModel, "anthropic/claude-sonnet-4-5");
+});
+
 test("formatModelReference returns provider/id", () => {
   const ref = formatModelReference({ provider: "anthropic", id: "claude-sonnet-4-5" });
 

src/models.ts

@@ -46,10 +46,10 @@ export function normalizeAvailableModelReference(
 }
 
 export function resolveChildModel(input: {
-  taskModel?: string;
-  topLevelModel: string;
+  callModel?: string;
+  presetModel?: string;
 }): ModelSelection {
-  const requestedModel = input.taskModel ?? input.topLevelModel;
+  const requestedModel = input.callModel ?? input.presetModel;
 
   return {
     requestedModel,

src/presets.test.ts

@@ -0,0 +1,53 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { mkdir, mkdtemp, writeFile } from "node:fs/promises";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+import { discoverSubagentPresets } from "./presets.ts";
+
+test("discoverSubagentPresets loads global presets and lets nearest project presets override by name", async () => {
+  const root = await mkdtemp(join(tmpdir(), "pi-subagents-presets-"));
+  const homeDir = join(root, "home");
+  const repo = join(root, "repo", "apps", "web");
+  const globalDir = join(homeDir, ".pi", "agent", "subagents");
+  const projectDir = join(root, "repo", ".pi", "subagents");
+
+  await mkdir(globalDir, { recursive: true });
+  await mkdir(projectDir, { recursive: true });
+  await mkdir(repo, { recursive: true });
+
+  await writeFile(
+    join(globalDir, "reviewer.md"),
+    `---\nname: reviewer\ndescription: Global reviewer\nmodel: openai/gpt-5\ntools: read,grep\n---\nGlobal prompt`,
+    "utf8",
+  );
+  await writeFile(
+    join(projectDir, "reviewer.md"),
+    `---\nname: reviewer\ndescription: Project reviewer\nmodel: anthropic/claude-sonnet-4-5\n---\nProject prompt`,
+    "utf8",
+  );
+
+  const result = discoverSubagentPresets(repo, { homeDir });
+  const reviewer = result.presets.find((preset) => preset.name === "reviewer");
+
+  assert.equal(reviewer?.source, "project");
+  assert.equal(reviewer?.description, "Project reviewer");
+  assert.equal(reviewer?.model, "anthropic/claude-sonnet-4-5");
+  assert.equal(reviewer?.tools, undefined);
+  assert.equal(reviewer?.systemPrompt, "Project prompt");
+  assert.match(result.projectPresetsDir ?? "", /\.pi\/subagents$/);
+});
+
+test("discoverSubagentPresets ignores markdown files without required frontmatter", async () => {
+  const root = await mkdtemp(join(tmpdir(), "pi-subagents-presets-"));
+  const homeDir = join(root, "home");
+  const repo = join(root, "repo");
+  const globalDir = join(homeDir, ".pi", "agent", "subagents");
+
+  await mkdir(globalDir, { recursive: true });
+  await mkdir(repo, { recursive: true });
+  await writeFile(join(globalDir, "broken.md"), `---\nname: broken\n---\nMissing description`, "utf8");
+
+  const result = discoverSubagentPresets(repo, { homeDir });
+  assert.deepEqual(result.presets, []);
+});

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 };
+}