feat(pi): add subagent config and agents

modules/agents/pi/extensions/subagents/agents.ts

@@ -0,0 +1,141 @@
+import { existsSync, readdirSync, readFileSync } from "node:fs";
+import { homedir } from "node:os";
+import { basename, join } from "node:path";
+import type { ContextMode } from "./types.ts";
+import type { Diagnostics } from "./config.ts";
+
+export interface AgentDefinition {
+  name: string;
+  description: string;
+  body: string;
+  context?: ContextMode;
+  model?: string;
+  thinking?: string;
+  tools?: string;
+  allowedContexts?: ContextMode[];
+  hidden?: boolean;
+  source: string;
+}
+
+export function loadAgents(cwd: string, projectTrusted: boolean, diagnostics: Diagnostics, agentDir = defaultAgentDir()): Map<string, AgentDefinition> {
+  const user = loadTier(join(agentDir, "agents"), "user", diagnostics);
+  const project = projectTrusted ? loadTier(join(cwd, ".pi", "agents"), "project", diagnostics) : new Map<string, AgentDefinition>();
+  return new Map([...user, ...project]);
+}
+
+function loadTier(dir: string, tier: string, diagnostics: Diagnostics): Map<string, AgentDefinition> {
+  const agents = new Map<string, AgentDefinition>();
+  if (!existsSync(dir)) return agents;
+  for (const entry of readdirSync(dir, { withFileTypes: true })) {
+    if (!entry.isFile() || !entry.name.endsWith(".md")) continue;
+    const path = join(dir, entry.name);
+    const parsed = parseAgent(path, diagnostics);
+    if (!parsed) continue;
+    if (agents.has(parsed.name)) {
+      diagnostics.warnings.push(`Duplicate ${tier} agent '${parsed.name}' ignored at ${path}`);
+      continue;
+    }
+    const stem = basename(entry.name, ".md");
+    if (stem !== parsed.name) diagnostics.warnings.push(`${tier} agent file '${entry.name}' name '${parsed.name}' does not match filename`);
+    agents.set(parsed.name, parsed);
+  }
+  return agents;
+}
+
+export function parseAgent(path: string, diagnostics: Diagnostics): AgentDefinition | undefined {
+  try {
+    const text = readFileSync(path, "utf8");
+    const match = /^---\n([\s\S]*?)\n---\n?([\s\S]*)$/u.exec(text);
+    if (!match) {
+      diagnostics.warnings.push(`Agent ${path} missing YAML frontmatter`);
+      return undefined;
+    }
+    const frontmatter = parseFrontmatter(match[1]);
+    const name = stringField(frontmatter, "name");
+    const description = stringField(frontmatter, "description");
+    if (!name || !/^[a-z0-9-]+$/.test(name)) {
+      diagnostics.warnings.push(`Agent ${path} has invalid name`);
+      return undefined;
+    }
+    if (!description) {
+      diagnostics.warnings.push(`Agent ${path} has invalid description`);
+      return undefined;
+    }
+    const context = contextField(frontmatter.context);
+    const allowedContexts = contextsField(frontmatter.allowedContexts);
+    if (frontmatter.context !== undefined && !context) diagnostics.warnings.push(`Agent ${path} has invalid context`);
+    if (frontmatter.allowedContexts !== undefined && !allowedContexts) diagnostics.warnings.push(`Agent ${path} has invalid allowedContexts`);
+    if (context && allowedContexts && !allowedContexts.includes(context)) diagnostics.warnings.push(`Agent ${path} context is outside allowedContexts`);
+    return {
+      name,
+      description,
+      body: match[2].trim(),
+      context,
+      model: stringField(frontmatter, "model"),
+      thinking: stringField(frontmatter, "thinking"),
+      tools: stringField(frontmatter, "tools"),
+      allowedContexts,
+      hidden: booleanField(frontmatter, "hidden"),
+      source: path,
+    };
+  } catch (error) {
+    diagnostics.warnings.push(`Failed to load agent ${path}: ${error instanceof Error ? error.message : String(error)}`);
+    return undefined;
+  }
+}
+
+function parseFrontmatter(text: string): Record<string, unknown> {
+  const result: Record<string, unknown> = {};
+  const lines = text.split(/\r?\n/u);
+  for (let i = 0; i < lines.length; i += 1) {
+    const line = lines[i];
+    if (!line.trim() || line.trimStart().startsWith("#")) continue;
+    const scalar = /^(\w+):\s*(.*?)\s*$/u.exec(line);
+    if (!scalar) continue;
+    const [, key, raw] = scalar;
+    if (raw !== "") {
+      result[key] = parseScalar(raw);
+      continue;
+    }
+    const values: string[] = [];
+    while (i + 1 < lines.length) {
+      const item = /^\s+-\s*(.*?)\s*$/u.exec(lines[i + 1]);
+      if (!item) break;
+      values.push(String(parseScalar(item[1])));
+      i += 1;
+    }
+    result[key] = values;
+  }
+  return result;
+}
+
+function parseScalar(raw: string): string | boolean {
+  const unquoted = raw.replace(/^['"]|['"]$/gu, "");
+  if (unquoted === "true") return true;
+  if (unquoted === "false") return false;
+  return unquoted;
+}
+
+function stringField(record: Record<string, unknown>, key: string): string | undefined {
+  const value = record[key];
+  return typeof value === "string" && value.trim() ? value.trim() : undefined;
+}
+
+function booleanField(record: Record<string, unknown>, key: string): boolean | undefined {
+  const value = record[key];
+  return typeof value === "boolean" ? value : undefined;
+}
+
+function contextField(value: unknown): ContextMode | undefined {
+  return value === "independent" || value === "fork" ? value : undefined;
+}
+
+function contextsField(value: unknown): ContextMode[] | undefined {
+  if (!Array.isArray(value)) return undefined;
+  const contexts = value.map(contextField);
+  return contexts.every(Boolean) ? (contexts as ContextMode[]) : undefined;
+}
+
+function defaultAgentDir(): string {
+  return process.env.PI_CODING_AGENT_DIR ?? join(homedir(), ".pi", "agent");
+}

modules/agents/pi/extensions/subagents/config.test.ts

@@ -0,0 +1,117 @@
+import assert from "node:assert/strict";
+import { mkdtempSync, mkdirSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import test from "node:test";
+import { loadAgents } from "./agents.ts";
+import { BUILT_IN_TOOL_PROFILES, loadConfig, resolveSpawn, type Diagnostics } from "./config.ts";
+
+function fixture() {
+  const root = mkdtempSync(join(tmpdir(), "subagents-config-"));
+  const agentDir = join(root, "agent");
+  const cwd = join(root, "project");
+  mkdirSync(agentDir, { recursive: true });
+  mkdirSync(cwd, { recursive: true });
+  return { root, agentDir, cwd };
+}
+
+function diagnostics(): Diagnostics {
+  return { warnings: [] };
+}
+
+test("missing config files and agent directories are normal", () => {
+  const { cwd, agentDir } = fixture();
+  const diag = diagnostics();
+
+  const config = loadConfig(cwd, true, diag, agentDir);
+  const agents = loadAgents(cwd, true, diag, agentDir);
+
+  assert.equal(config.defaultContext, "independent");
+  assert.equal(config.defaultTools, "read-only");
+  assert.equal(agents.size, 0);
+  assert.deepEqual(diag.warnings, []);
+});
+
+test("global and trusted project config merge in order", () => {
+  const { cwd, agentDir } = fixture();
+  mkdirSync(join(cwd, ".pi"), { recursive: true });
+  writeFileSync(join(agentDir, "subagents.json"), JSON.stringify({ defaultTools: "global-profile", toolProfiles: { "global-profile": { activeTools: ["read"] } } }));
+  writeFileSync(join(cwd, ".pi", "subagents.json"), JSON.stringify({ defaultTools: "project-profile", toolProfiles: { "project-profile": { activeTools: ["ls"] } } }));
+
+  const config = loadConfig(cwd, true, diagnostics(), agentDir);
+
+  assert.equal(config.defaultTools, "project-profile");
+  assert.deepEqual(config.toolProfiles["global-profile"].activeTools, ["read"]);
+  assert.deepEqual(config.toolProfiles["project-profile"].activeTools, ["ls"]);
+});
+
+test("project config is ignored when project is untrusted", () => {
+  const { cwd, agentDir } = fixture();
+  mkdirSync(join(cwd, ".pi"), { recursive: true });
+  writeFileSync(join(cwd, ".pi", "subagents.json"), JSON.stringify({ defaultTools: "project-profile", toolProfiles: { "project-profile": { activeTools: ["ls"] } } }));
+
+  const config = loadConfig(cwd, false, diagnostics(), agentDir);
+
+  assert.equal(config.defaultTools, "read-only");
+  assert.equal(config.toolProfiles["project-profile"], undefined);
+});
+
+test("agents load with project precedence over user", () => {
+  const { cwd, agentDir } = fixture();
+  mkdirSync(join(agentDir, "agents"), { recursive: true });
+  mkdirSync(join(cwd, ".pi", "agents"), { recursive: true });
+  writeFileSync(join(agentDir, "agents", "review.md"), "---\nname: review\ndescription: User review\ntools: read-only\n---\nuser body\n");
+  writeFileSync(join(cwd, ".pi", "agents", "review.md"), "---\nname: review\ndescription: Project review\ntools: full-tools\n---\nproject body\n");
+
+  const agents = loadAgents(cwd, true, diagnostics(), agentDir);
+
+  assert.equal(agents.get("review")?.description, "Project review");
+  assert.equal(agents.get("review")?.body, "project body");
+});
+
+test("duplicate same-tier definitions and invalid frontmatter produce diagnostics", () => {
+  const { cwd, agentDir } = fixture();
+  const dir = join(agentDir, "agents");
+  mkdirSync(dir, { recursive: true });
+  writeFileSync(join(dir, "one.md"), "---\nname: same\ndescription: One\n---\none\n");
+  writeFileSync(join(dir, "two.md"), "---\nname: same\ndescription: Two\n---\ntwo\n");
+  writeFileSync(join(dir, "bad.md"), "---\nname: Bad Name\n---\nbad\n");
+  const diag = diagnostics();
+
+  const agents = loadAgents(cwd, true, diag, agentDir);
+
+  assert.equal(agents.size, 1);
+  assert.ok(diag.warnings.some((warning) => warning.includes("Duplicate user agent 'same'")));
+  assert.ok(diag.warnings.some((warning) => warning.includes("invalid name")));
+});
+
+test("named spawn resolves overrides, frontmatter, config, and defaults", () => {
+  const { cwd, agentDir } = fixture();
+  mkdirSync(join(agentDir, "agents"), { recursive: true });
+  writeFileSync(join(agentDir, "subagents.json"), JSON.stringify({ defaultTools: "local-review", toolProfiles: { "local-review": { activeTools: ["read"] } } }));
+  writeFileSync(join(agentDir, "agents", "review.md"), "---\nname: review\ndescription: Review\ncontext: independent\nmodel: inherit\nthinking: high\ntools: local-review\n---\nagent body\n");
+  const diag = diagnostics();
+  const config = loadConfig(cwd, true, diag, agentDir);
+  const agents = loadAgents(cwd, true, diag, agentDir);
+
+  const resolved = resolveSpawn({ agent: "review", prompt: "check this", thinking: "low" }, config, agents);
+
+  assert.equal(resolved.prompt, "check this");
+  assert.equal(resolved.context, "independent");
+  assert.equal(resolved.model, "inherit");
+  assert.equal(resolved.thinking, "low");
+  assert.equal(resolved.tools, "local-review");
+  assert.deepEqual(resolved.toolProfile.activeTools, ["read"]);
+  assert.equal(resolved.agentBody, "agent body");
+});
+
+test("built-in tool profile names cannot be overridden", () => {
+  const { cwd, agentDir } = fixture();
+  writeFileSync(join(agentDir, "subagents.json"), JSON.stringify({ toolProfiles: { "read-only": { activeTools: ["bash"] } } }));
+  const diag = diagnostics();
+
+  const config = loadConfig(cwd, true, diag, agentDir);
+
+  assert.deepEqual(config.toolProfiles["read-only"], BUILT_IN_TOOL_PROFILES["read-only"]);
+  assert.ok(diag.warnings.some((warning) => warning.includes("Ignoring global override for built-in tool profile 'read-only'")));
+});

modules/agents/pi/extensions/subagents/config.ts

@@ -0,0 +1,152 @@
+import { existsSync, readFileSync } from "node:fs";
+import { homedir } from "node:os";
+import { join } from "node:path";
+import type { ContextMode, SpawnRequest, ToolProfile } from "./types.ts";
+import type { AgentDefinition } from "./agents.ts";
+
+export interface Diagnostics {
+  warnings: string[];
+}
+
+export interface SubagentsConfig {
+  defaultContext: ContextMode;
+  defaultTools: string;
+  toolProfiles: Record<string, ToolProfile>;
+}
+
+export interface ResolvedSpawnRequest extends SpawnRequest {
+  prompt: string;
+  context: ContextMode;
+  tools: string;
+  toolProfile: ToolProfile;
+  agentBody?: string;
+}
+
+export const BUILT_IN_TOOL_PROFILES: Record<string, ToolProfile> = {
+  none: { activeTools: [] },
+  "read-only": { activeTools: ["read", "grep", "find", "ls"] },
+  "read-only-with-safe-bash": { activeTools: ["read", "grep", "find", "ls", "bash"] },
+  "full-tools": { activeTools: null },
+};
+
+const DEFAULT_CONFIG: SubagentsConfig = {
+  defaultContext: "independent",
+  defaultTools: "read-only",
+  toolProfiles: { ...BUILT_IN_TOOL_PROFILES },
+};
+
+export function loadConfig(cwd: string, projectTrusted: boolean, diagnostics: Diagnostics, agentDir = defaultAgentDir()): SubagentsConfig {
+  let config = cloneConfig(DEFAULT_CONFIG);
+  config = mergeConfig(config, readConfig(join(agentDir, "subagents.json"), diagnostics, "global"), diagnostics, "global");
+  if (projectTrusted) {
+    config = mergeConfig(config, readConfig(join(cwd, ".pi", "subagents.json"), diagnostics, "project"), diagnostics, "project");
+  }
+  if (!config.toolProfiles[config.defaultTools]) {
+    diagnostics.warnings.push(`Unknown defaultTools profile '${config.defaultTools}', using read-only`);
+    config.defaultTools = "read-only";
+  }
+  return config;
+}
+
+export function resolveSpawn(request: SpawnRequest, config: SubagentsConfig, agents: Map<string, AgentDefinition>): ResolvedSpawnRequest {
+  const prompt = typeof request.prompt === "string" ? request.prompt.trim() : "";
+  if (!prompt) throw new Error("prompt is required");
+  const agent = request.agent ? agents.get(request.agent) : undefined;
+  if (request.agent && !agent) throw new Error(`unknown subagent agent: ${request.agent}`);
+
+  const context = request.context ?? agent?.context ?? config.defaultContext;
+  if (context !== "independent" && context !== "fork") throw new Error(`unsupported context: ${context}`);
+  if (agent?.allowedContexts && !agent.allowedContexts.includes(context)) {
+    throw new Error(`agent '${agent.name}' does not allow ${context} context`);
+  }
+
+  const tools = request.tools ?? agent?.tools ?? config.defaultTools;
+  const toolProfile = config.toolProfiles[tools];
+  if (!toolProfile) throw new Error(`unknown tool profile: ${tools}`);
+
+  return {
+    ...request,
+    prompt,
+    agent: agent?.name ?? request.agent,
+    context,
+    model: request.model ?? agent?.model,
+    thinking: request.thinking ?? agent?.thinking,
+    tools,
+    toolProfile,
+    agentBody: agent?.body,
+  };
+}
+
+function readConfig(path: string, diagnostics: Diagnostics, label: string): Partial<SubagentsConfig> | undefined {
+  if (!existsSync(path)) return undefined;
+  try {
+    const parsed = JSON.parse(readFileSync(path, "utf8"));
+    return normalizeConfig(parsed, diagnostics, label);
+  } catch (error) {
+    diagnostics.warnings.push(`Invalid ${label} subagents.json: ${error instanceof Error ? error.message : String(error)}`);
+    return undefined;
+  }
+}
+
+function normalizeConfig(raw: unknown, diagnostics: Diagnostics, label: string): Partial<SubagentsConfig> | undefined {
+  if (!raw || typeof raw !== "object" || Array.isArray(raw)) {
+    diagnostics.warnings.push(`Invalid ${label} subagents.json: root must be an object`);
+    return undefined;
+  }
+  const input = raw as Record<string, unknown>;
+  const config: Partial<SubagentsConfig> = {};
+  if (input.defaultContext === "independent" || input.defaultContext === "fork") config.defaultContext = input.defaultContext;
+  else if (input.defaultContext !== undefined) diagnostics.warnings.push(`Invalid ${label} defaultContext ignored`);
+  if (typeof input.defaultTools === "string") config.defaultTools = input.defaultTools;
+  else if (input.defaultTools !== undefined) diagnostics.warnings.push(`Invalid ${label} defaultTools ignored`);
+  if (input.toolProfiles !== undefined) config.toolProfiles = normalizeProfiles(input.toolProfiles, diagnostics, label);
+  return config;
+}
+
+function normalizeProfiles(raw: unknown, diagnostics: Diagnostics, label: string): Record<string, ToolProfile> {
+  const profiles: Record<string, ToolProfile> = {};
+  if (!raw || typeof raw !== "object" || Array.isArray(raw)) {
+    diagnostics.warnings.push(`Invalid ${label} toolProfiles ignored`);
+    return profiles;
+  }
+  for (const [name, value] of Object.entries(raw as Record<string, unknown>)) {
+    if (name in BUILT_IN_TOOL_PROFILES) {
+      diagnostics.warnings.push(`Ignoring ${label} override for built-in tool profile '${name}'`);
+      continue;
+    }
+    const profile = normalizeProfile(value);
+    if (!profile) {
+      diagnostics.warnings.push(`Invalid ${label} tool profile '${name}' ignored`);
+      continue;
+    }
+    profiles[name] = profile;
+  }
+  return profiles;
+}
+
+function normalizeProfile(raw: unknown): ToolProfile | undefined {
+  if (!raw || typeof raw !== "object" || Array.isArray(raw)) return undefined;
+  const activeTools = (raw as { activeTools?: unknown }).activeTools;
+  if (!Array.isArray(activeTools) || !activeTools.every((tool) => typeof tool === "string")) return undefined;
+  return { activeTools };
+}
+
+function mergeConfig(base: SubagentsConfig, override: Partial<SubagentsConfig> | undefined, diagnostics: Diagnostics, label: string): SubagentsConfig {
+  if (!override) return base;
+  const merged = cloneConfig(base);
+  if (override.defaultContext) merged.defaultContext = override.defaultContext;
+  if (override.defaultTools) merged.defaultTools = override.defaultTools;
+  if (override.toolProfiles) merged.toolProfiles = { ...merged.toolProfiles, ...override.toolProfiles };
+  for (const key of Object.keys(merged.toolProfiles)) {
+    if (key in BUILT_IN_TOOL_PROFILES) merged.toolProfiles[key] = BUILT_IN_TOOL_PROFILES[key];
+  }
+  return merged;
+}
+
+function cloneConfig(config: SubagentsConfig): SubagentsConfig {
+  return { ...config, toolProfiles: { ...config.toolProfiles } };
+}
+
+function defaultAgentDir(): string {
+  return process.env.PI_CODING_AGENT_DIR ?? join(homedir(), ".pi", "agent");
+}

modules/agents/pi/extensions/subagents/index.ts

@@ -1,10 +1,13 @@
 import type { ExtensionAPI, ExtensionContext } from "@earendil-works/pi-coding-agent";
 import { Type } from "typebox";
+import { loadAgents } from "./agents.ts";
+import { loadConfig, resolveSpawn, type Diagnostics } from "./config.ts";
 import { SubprocessRpcRunner } from "./runner.ts";
 import { Supervisor } from "./supervisor.ts";
 import type { SpawnRequest } from "./types.ts";
 
 let supervisor: Supervisor | undefined;
+let lastDiagnostics: Diagnostics = { warnings: [] };
 
 export default function subagents(pi: ExtensionAPI) {
   const getSupervisor = (ctx: ExtensionContext): Supervisor => {
@@ -12,18 +15,30 @@ export default function subagents(pi: ExtensionAPI) {
     return supervisor;
   };
 
+  const resolve = (ctx: ExtensionContext, request: SpawnRequest): SpawnRequest => {
+    const diagnostics: Diagnostics = { warnings: [] };
+    const cwd = cwdOf(ctx);
+    const trusted = isProjectTrusted(ctx);
+    const config = loadConfig(cwd, trusted, diagnostics);
+    const agents = loadAgents(cwd, trusted, diagnostics);
+    lastDiagnostics = diagnostics;
+    return resolveSpawn(request, config, agents);
+  };
+
   pi.registerTool({
     name: "subagent_spawn",
     label: "Spawn subagent",
     description: "Start one ad hoc independent subagent and return immediately with its child id",
     parameters: Type.Object({
       prompt: Type.String({ description: "Prompt for the delegated subagent" }),
+      agent: Type.Optional(Type.String({ description: "Named agent definition to use" })),
       context: Type.Optional(Type.Literal("independent")),
-      model: Type.Optional(Type.String({ description: "Optional model selector for status metadata" })),
+      model: Type.Optional(Type.String({ description: "Optional model selector for the child" })),
-      thinking: Type.Optional(Type.String({ description: "Optional thinking level for status metadata" })),
+      thinking: Type.Optional(Type.String({ description: "Optional thinking level for the child" })),
+      tools: Type.Optional(Type.String({ description: "Tool profile name" })),
     }),
     async execute(_toolCallId, params, _signal, _onUpdate, ctx) {
-      const accepted = getSupervisor(ctx).spawn(params as SpawnRequest);
+      const accepted = getSupervisor(ctx).spawn(resolve(ctx, params as SpawnRequest));
       ctx.ui?.notify?.(`Started subagent ${accepted.id}`, "info");
       return textResult(accepted);
     },
@@ -78,7 +93,7 @@ export default function subagents(pi: ExtensionAPI) {
   pi.registerCommand("subagent-spawn", {
     description: "Start an ad hoc independent subagent",
     handler: async (args, ctx) => {
-      const accepted = getSupervisor(ctx).spawn({ prompt: args });
+      const accepted = getSupervisor(ctx).spawn(resolve(ctx, parseSpawnArgs(args)));
       ctx.ui.notify(`Started subagent ${accepted.id}`, "info");
     },
   });
@@ -104,6 +119,13 @@ export default function subagents(pi: ExtensionAPI) {
     },
   });
 
+  pi.registerCommand("subagent-diagnostics", {
+    description: "Show subagent configuration diagnostics from the last load",
+    handler: async (_args, ctx) => {
+      ctx.ui.notify(JSON.stringify(lastDiagnostics, null, 2), "info");
+    },
+  });
+
   pi.registerCommand("subagent-cancel", {
     description: "Cancel a running subagent by id",
     handler: async (args, ctx) => {
@@ -117,6 +139,17 @@ export default function subagents(pi: ExtensionAPI) {
   });
 }
 
+function parseSpawnArgs(args: string): SpawnRequest {
+  const match = /^--agent\s+(\S+)\s+([\s\S]+)$/u.exec(args.trim());
+  if (!match) return { prompt: args };
+  return { agent: match[1], prompt: match[2] };
+}
+
+function isProjectTrusted(ctx: ExtensionContext): boolean {
+  const value = (ctx as unknown as { isProjectTrusted?: () => boolean }).isProjectTrusted?.();
+  return value === true;
+}
+
 function cwdOf(ctx: ExtensionContext): string {
   const sessionCwd = (ctx as unknown as { sessionManager?: { getCwd?: () => string }; cwd?: string }).sessionManager?.getCwd?.();
   return sessionCwd ?? (ctx as unknown as { cwd?: string }).cwd ?? process.cwd();

modules/agents/pi/extensions/subagents/runner.ts

@@ -156,7 +156,7 @@ class RpcChildHandle implements ChildHandle {
 
 export class SubprocessRpcRunner implements ChildRunner {
   async start(id: string, request: SpawnRequest, cwd: string, events: RunnerEvents): Promise<ChildHandle> {
-    const args = [process.argv[1], "--mode", "rpc", "--no-extensions", "--name", `subagent ${id}`];
+    const args = [process.argv[1], "--mode", "rpc", "--no-extensions", "--name", `subagent ${id}`, ...toolArgs(request), ...modelArgs(request)];
     const child = spawn(process.execPath, args, {
       cwd,
       env: childEnvironment(),
@@ -174,6 +174,20 @@ function delay(ms: number): Promise<void> {
   return new Promise((resolve) => setTimeout(resolve, ms));
 }
 
+function toolArgs(request: SpawnRequest): string[] {
+  const activeTools = request.toolProfile?.activeTools;
+  if (activeTools === undefined || activeTools === null) return [];
+  if (activeTools.length === 0) return ["--no-tools"];
+  return ["--tools", activeTools.join(",")];
+}
+
+function modelArgs(request: SpawnRequest): string[] {
+  const args: string[] = [];
+  if (request.model && request.model !== "inherit") args.push("--model", request.model);
+  if (request.thinking) args.push("--thinking", request.thinking);
+  return args;
+}
+
 function childEnvironment(): NodeJS.ProcessEnv {
   const env = { ...process.env };
   delete env.PI_SESSION_ID;
@@ -185,5 +199,6 @@ function childEnvironment(): NodeJS.ProcessEnv {
 }
 
 function independentPrompt(request: SpawnRequest): string {
-  return `You are running as a delegated subagent in independent context.\nDo not assume access to the parent conversation transcript.\nReturn a concise final answer for the parent agent.\n\nTask:\n${request.prompt}`;
+  const base = request.agentBody ? `${request.agentBody}\n\n` : "";
+  return `${base}You are running as a delegated subagent in independent context.\nDo not assume access to the parent conversation transcript.\nReturn a concise final answer for the parent agent.\n\nTask:\n${request.prompt}`;
 }

modules/agents/pi/extensions/subagents/supervisor.ts

@@ -46,7 +46,7 @@ export class Supervisor {
       cwd: this.cwd,
       model: request.model,
       thinking: request.thinking,
-      tools: "pi-default",
+      tools: request.tools ?? "read-only",
       startedAt: now,
       elapsedMs: 0,
       lastEvent: "queued",
@@ -216,7 +216,7 @@ export class Supervisor {
 
   private resolveContext(context: ContextMode | undefined): ContextMode {
     if (context === undefined) return "independent";
-    if (context !== "independent") throw new Error("only independent context is implemented in this tracer bullet");
+    if (context !== "independent") throw new Error("only independent context is implemented before fork mode lands");
     return context;
   }
 

modules/agents/pi/extensions/subagents/types.ts

@@ -11,6 +11,10 @@ export type SubagentState =
   | "timed_out"
   | "orphaned";
 
+export interface ToolProfile {
+  activeTools: string[] | null;
+}
+
 export interface SpawnRequest {
   prompt: string;
   context?: ContextMode;
@@ -18,6 +22,8 @@ export interface SpawnRequest {
   model?: string;
   thinking?: string;
   tools?: string;
+  toolProfile?: ToolProfile;
+  agentBody?: string;
 }
 
 export interface SpawnAccepted {