Add a subagent roster command

packages/harness/README.md

@@ -70,6 +70,10 @@ provider registration defaults to `us` for model discovery, and `/login` prompts
 region to authenticate against — which then takes over routing via `modifyModels` above. The OAuth
 loopback callback port can be overridden with `HARNESS_OAUTH_PORT` (default `8237`).
 
+While an interactive session is running, `/subagents` shows the bundled agent roster with each
+agent's effective model, reasoning level, and purpose. Use `/subagents all` to include project-local
+`.pi/agents/*.md` definitions; project settings are applied only for trusted projects.
+
 ## Spawn the CLI as a subprocess
 
 ```ts

packages/harness/src/extensions/subagent/extension.ts

@@ -2,6 +2,7 @@ import { fileURLToPath } from "node:url";
 import { StringEnum } from "@earendil-works/pi-ai";
 import type {
   ExtensionAPI,
+  ExtensionCommandContext,
   ExtensionContext,
   ExtensionFactory,
   Theme,
@@ -28,7 +29,9 @@ import {
 } from "./format";
 import { runPool } from "./process/pool";
 import { renderSubagentCall, renderSubagentResult } from "./render";
+import { formatSubagentRoster } from "./roster";
 import { isFailedResult, runAgent, type SingleRunResult } from "./run-agent";
+import { loadSubagentSettings } from "./settings";
 import { SubagentStatusEditor } from "./status-editor";
 import { renderSubagentFooterLines } from "./status-footer";
 import { showSubagentStatusOverlay } from "./status-overlay";
@@ -179,6 +182,17 @@ export function createSubagentExtension(
       skillPaths: [fileURLToPath(new URL("./skills", import.meta.url))],
     }));
 
+    pi.registerCommand("subagents", {
+      description:
+        "Show the configured subagent roster. Usage: /subagents [all]",
+      handler: async (args: string, ctx: ExtensionCommandContext) => {
+        const scope = args.trim().toLowerCase() === "all" ? "both" : "bundled";
+        const discovery = discoverAgents(ctx.cwd, scope);
+        const settings = loadSubagentSettings(ctx.cwd, ctx.isProjectTrusted());
+        ctx.ui.notify(formatSubagentRoster(discovery.agents, settings), "info");
+      },
+    });
+
     pi.registerTool(
       defineTool({
         name: "subagent",

packages/harness/src/extensions/subagent/roster.test.ts

@@ -0,0 +1,42 @@
+import { describe, expect, it } from "vitest";
+import type { AgentConfig } from "./agents";
+import { formatSubagentRoster } from "./roster";
+
+const agent: AgentConfig = {
+  name: "code-reviewer",
+  description: "Review diffs for correctness and quality",
+  model: "gpt-5.6-sol",
+  systemPrompt: "",
+  source: "bundled",
+};
+
+describe("formatSubagentRoster", () => {
+  it("renders the effective model and reasoning settings", () => {
+    const roster = formatSubagentRoster([agent], {
+      agentOverrides: { "code-reviewer": { thinking: "low" } },
+    });
+
+    expect(roster).toContain("Subagent");
+    expect(roster).toContain("code-reviewer");
+    expect(roster).toContain("gpt-5.6-sol");
+    expect(roster).toContain("low");
+    expect(roster).toContain("Review diffs for correctness and quality");
+  });
+
+  it("marks project agents and truncates long purposes", () => {
+    const roster = formatSubagentRoster(
+      [
+        {
+          ...agent,
+          source: "project",
+          description: "a".repeat(100),
+        },
+      ],
+      {},
+    );
+
+    expect(roster).toContain("code-reviewer (project)");
+    expect(roster).toContain("a".repeat(71));
+    expect(roster).toContain("…");
+  });
+});

packages/harness/src/extensions/subagent/roster.ts

@@ -0,0 +1,51 @@
+import type { AgentConfig } from "./agents";
+import { applyAgentOverrides, type SubagentSettings } from "./settings";
+
+const COLUMNS = [
+  { title: "Subagent", width: 24 },
+  { title: "Model", width: 24 },
+  { title: "Reasoning", width: 10 },
+  { title: "Purpose", width: 72 },
+] as const;
+
+function truncate(value: string, width: number): string {
+  if (value.length <= width) return value;
+  return `${value.slice(0, Math.max(0, width - 1))}…`;
+}
+
+function cell(value: string, width: number): string {
+  return truncate(value, width).padEnd(width, " ");
+}
+
+function row(values: string[]): string {
+  return values
+    .map((value, index) => cell(value, COLUMNS[index].width))
+    .join("  ");
+}
+
+export function formatSubagentRoster(
+  agents: AgentConfig[],
+  settings: SubagentSettings,
+): string {
+  if (agents.length === 0) return "No subagents available.";
+
+  const separatorWidth =
+    COLUMNS.reduce((total, column) => total + column.width, 0) +
+    (COLUMNS.length - 1) * 2;
+  const lines = [
+    row(COLUMNS.map((column) => column.title)),
+    "-".repeat(separatorWidth),
+  ];
+  for (const agent of agents) {
+    const effective = applyAgentOverrides(agent, settings);
+    lines.push(
+      row([
+        agent.source === "project" ? `${agent.name} (project)` : agent.name,
+        effective.model ?? "inherit",
+        effective.thinking ?? "default",
+        effective.description,
+      ]),
+    );
+  }
+  return lines.join("\n");
+}