Task 2: Preset-driven subagent tool

- Replace chain mode with preset-driven single and parallel modes
- Schema: require per-task preset; remove top-level required model
- Tool: resolve presets via discoverSubagentPresets(), normalize models, resolve effective model per run, pass preset meta
- Update tests and remove chain test

src/extension.test.ts

@@ -8,7 +8,7 @@ test("the extension entrypoint registers the subagent tool with the currently av
 
   try {
     const registeredTools: any[] = [];
-    const handlers: Record<string, (event: any, ctx: any) => Promise<void> | void> = {};
+    const handlers: any = {};
 
     subagentsExtension({
       on(event: string, handler: (event: any, ctx: any) => Promise<void> | void) {
@@ -36,17 +36,16 @@ test("the extension entrypoint registers the subagent tool with the currently av
 
     assert.equal(registeredTools.length, 1);
     assert.equal(registeredTools[0]?.name, "subagent");
-    assert.deepEqual(registeredTools[0]?.parameters.required, ["model"]);
+    // no single top-level model required now (handled at runtime)
     assert.equal("agent" in registeredTools[0]?.parameters.properties, false);
     assert.equal("agentScope" in registeredTools[0]?.parameters.properties, false);
     assert.equal("confirmProjectAgents" in registeredTools[0]?.parameters.properties, false);
     assert.equal("task" in registeredTools[0]?.parameters.properties, true);
-    assert.deepEqual(registeredTools[0]?.parameters.properties.model.enum, [
+    assert.equal("preset" in registeredTools[0]?.parameters.properties, true);
-      "anthropic/claude-sonnet-4-5",
+    assert.equal(registeredTools[0]?.parameters.properties.model, undefined);
-      "openai/gpt-5",
-    ]);
     assert.equal("agent" in registeredTools[0]?.parameters.properties.tasks.items.properties, false);
     assert.equal("task" in registeredTools[0]?.parameters.properties.tasks.items.properties, true);
+    assert.equal("preset" in registeredTools[0]?.parameters.properties.tasks.items.properties, true);
     assert.deepEqual(registeredTools[0]?.parameters.properties.tasks.items.properties.model.enum, [
       "anthropic/claude-sonnet-4-5",
       "openai/gpt-5",
@@ -63,7 +62,7 @@ test("before_agent_start re-applies subagent registration when available models
 
   try {
     const registeredTools: any[] = [];
-    const handlers: Record<string, (event: any, ctx: any) => Promise<void> | void> = {};
+    const handlers: any = {};
 
     subagentsExtension({
       on(event: string, handler: (event: any, ctx: any) => Promise<void> | void) {
@@ -92,7 +91,7 @@ test("before_agent_start re-applies subagent registration when available models
     );
 
     assert.equal(registeredTools.length, 1);
-    assert.deepEqual(registeredTools[0]?.parameters.properties.model.enum, [
+    assert.deepEqual(registeredTools[0]?.parameters.properties.tasks.items.properties.model.enum, [
       "anthropic/claude-sonnet-4-5",
       "openai/gpt-5",
     ]);
@@ -110,7 +109,6 @@ test("before_agent_start re-applies subagent registration when available models
     );
 
     assert.equal(registeredTools.length, 2);
-    assert.deepEqual(registeredTools[1]?.parameters.properties.model.enum, ["openai/gpt-6"]);
     assert.deepEqual(registeredTools[1]?.parameters.properties.tasks.items.properties.model.enum, ["openai/gpt-6"]);
   } finally {
     if (original === undefined) delete process.env.PI_SUBAGENTS_CHILD;
@@ -124,7 +122,7 @@ test("child subagent sessions skip registering the subagent tool", async () => {
 
   try {
     const registeredTools: any[] = [];
-    const handlers: Record<string, (event: any, ctx: any) => Promise<void> | void> = {};
+    const handlers: any = {};
 
     subagentsExtension({
       on(event: string, handler: (event: any, ctx: any) => Promise<void> | void) {
@@ -180,7 +178,7 @@ test("registers github-copilot provider override when PI_SUBAGENTS_GITHUB_COPILO
 test("combined child+copilot run registers provider but no tools or startup handlers", () => {
   const registeredProviders: Array<{ name: string; config: any }> = [];
   const registeredTools: any[] = [];
-  const handlers: Record<string, (event: any, ctx: any) => Promise<void> | void> = {};
+  const handlers: any = {};
 
   const originalInitiator = process.env.PI_SUBAGENTS_GITHUB_COPILOT_INITIATOR;
   const originalChild = process.env.PI_SUBAGENTS_CHILD;
@@ -225,7 +223,7 @@ test("does not re-register the subagent tool when models list unchanged, but re-
 
   try {
     let registerToolCalls = 0;
-    const handlers: Record<string, (event: any, ctx: any) => Promise<void> | void> = {};
+    const handlers: any = {};
 
     subagentsExtension({
       on(event: string, handler: (event: any, ctx: any) => Promise<void> | void) {
@@ -298,7 +296,7 @@ test("same model set in different orders should NOT trigger re-registration", as
 
   try {
     let registerToolCalls = 0;
-    const handlers: Record<string, (event: any, ctx: any) => Promise<void> | void> = {};
+    const handlers: any = {};
 
     subagentsExtension({
       on(event: string, handler: (event: any, ctx: any) => Promise<void> | void) {
@@ -355,7 +353,7 @@ test("empty model list should NOT register the tool, but a later non-empty list
 
   try {
     let registerToolCalls = 0;
-    const handlers: Record<string, (event: any, ctx: any) => Promise<void> | void> = {};
+    const handlers: any = {};
 
     subagentsExtension({
       on(event: string, handler: (event: any, ctx: any) => Promise<void> | void) {

src/schema.ts

@@ -11,39 +11,30 @@ function createTaskModelSchema(availableModels: readonly string[]) {
 
 export function createTaskItemSchema(availableModels: readonly string[]) {
   return Type.Object({
+    preset: Type.String({ description: "Subagent preset name to use for this task" }),
     task: Type.String({ description: "Task to delegate to the child agent" }),
     model: createTaskModelSchema(availableModels),
     cwd: Type.Optional(Type.String({ description: "Optional working directory override" })),
   });
 }
 
-export function createChainItemSchema(availableModels: readonly string[]) {
-  return Type.Object({
-    task: Type.String({ description: "Task with optional {previous} placeholder" }),
-    model: createTaskModelSchema(availableModels),
-    cwd: Type.Optional(Type.String({ description: "Optional working directory override" })),
-  });
-}
-
 export const TaskItemSchema = createTaskItemSchema([]);
-export const ChainItemSchema = createChainItemSchema([]);
 
 export function createSubagentParamsSchema(availableModels: readonly string[]) {
   return Type.Object({
+    // Single mode: provide preset + task
+    preset: Type.Optional(Type.String({ description: "Subagent preset name to use in single mode" })),
     task: Type.Optional(Type.String({ description: "Single-mode delegated task" })),
-    model: StringEnum(availableModels, {
+    // Parallel mode: provide tasks array where each item names its own preset
-      description: "Required top-level child model. Must be one of the currently available models.",
-    }),
     tasks: Type.Optional(Type.Array(createTaskItemSchema(availableModels), { description: "Parallel tasks" })),
-    chain: Type.Optional(Type.Array(createChainItemSchema(availableModels), { description: "Sequential tasks" })),
     cwd: Type.Optional(Type.String({ description: "Single-mode working directory override" })),
+
   });
 }
 
 export const SubagentParamsSchema = createSubagentParamsSchema([]);
 
 export type TaskItem = Static<typeof TaskItemSchema>;
-export type ChainItem = Static<typeof ChainItemSchema>;
 export type SubagentParams = Static<typeof SubagentParamsSchema>;
 
 export interface SubagentRunResult {
@@ -66,6 +57,6 @@ export interface SubagentRunResult {
 }
 
 export interface SubagentToolDetails {
-  mode: "single" | "parallel" | "chain";
+  mode: "single" | "parallel";
   results: SubagentRunResult[];
 }

src/tool-chain.test.ts

@@ -1,87 +0,0 @@
-import test from "node:test";
-import assert from "node:assert/strict";
-import { createSubagentTool } from "./tool.ts";
-
-test("chain mode substitutes {previous} into the next task", async () => {
-  const seenTasks: string[] = [];
-
-  const tool = createSubagentTool({
-    runSingleTask: async ({ meta }: any) => {
-      seenTasks.push(meta.task);
-      return {
-        runId: `run-${seenTasks.length}`,
-        task: meta.task,
-        exitCode: 0,
-        finalText: seenTasks.length === 1 ? "Inspection output" : "Plan output",
-      };
-    },
-  } as any);
-
-  const result = await tool.execute(
-    "tool-1",
-    {
-      model: "anthropic/claude-sonnet-4-5",
-      chain: [
-        { task: "inspect auth" },
-        { task: "use this context: {previous}" },
-      ],
-    },
-    undefined,
-    undefined,
-    {
-      cwd: "/repo",
-      modelRegistry: {
-        getAvailable: () => [{ provider: "anthropic", id: "claude-sonnet-4-5" }],
-      },
-      hasUI: false,
-    } as any,
-  );
-
-  assert.deepEqual(seenTasks, ["inspect auth", "use this context: Inspection output"]);
-  assert.equal(result.content[0]?.type === "text" ? result.content[0].text : "", "Plan output");
-});
-
-test("chain mode stops on the first failed step", async () => {
-  const tool = createSubagentTool({
-    runSingleTask: async ({ meta }: any) => {
-      if (meta.task.includes("Inspection output")) {
-        return {
-          runId: "run-2",
-          task: meta.task,
-          exitCode: 1,
-          finalText: "",
-          stopReason: "error",
-        };
-      }
-      return {
-        runId: "run-1",
-        task: meta.task,
-        exitCode: 0,
-        finalText: "Inspection output",
-      };
-    },
-  } as any);
-
-  const result = await tool.execute(
-    "tool-1",
-    {
-      model: "anthropic/claude-sonnet-4-5",
-      chain: [
-        { task: "inspect auth" },
-        { task: "use this context: {previous}" },
-      ],
-    },
-    undefined,
-    undefined,
-    {
-      cwd: "/repo",
-      modelRegistry: {
-        getAvailable: () => [{ provider: "anthropic", id: "claude-sonnet-4-5" }],
-      },
-      hasUI: false,
-    } as any,
-  );
-
-  assert.equal(result.isError, true);
-  assert.match(result.content[0]?.type === "text" ? result.content[0].text : "", /Chain stopped at step 2/);
-});