Task 2: Implement preset-driven subagent tool, update schema and tests

src/tool-parallel.test.ts

@@ -2,16 +2,23 @@ import test from "node:test";
 import assert from "node:assert/strict";
 import { createSubagentTool } from "./tool.ts";
 
-test("parallel mode runs each task and uses the top-level model unless a task overrides it", async () => {
+test("parallel mode runs each task and resolves model from preset unless a task overrides it", async () => {
   const requestedModels: Array<string | undefined> = [];
 
   const tool = createSubagentTool({
+    discoverSubagentPresets: () => ({
+      presets: [
+        { name: "openai-preset", description: "openai", model: "openai/gpt-5", systemPrompt: "", source: "project", filePath: "/repo/.pi/subagents/openai.md" },
+        { name: "anthropic-preset", description: "anthropic", model: "anthropic/claude-opus-4-5", systemPrompt: "", source: "project", filePath: "/repo/.pi/subagents/anthropic.md" },
+      ],
+      projectPresetsDir: "/repo/.pi/subagents",
+    }),
     resolveChildModel: ({ taskModel, topLevelModel }: any) => ({
       requestedModel: taskModel ?? topLevelModel,
       resolvedModel: taskModel ?? topLevelModel,
     }),
     runSingleTask: async ({ meta }: any) => {
-      requestedModels.push(meta.requestedModel);
+      requestedModels.push(meta.requestedModel as string | undefined);
       return {
         runId: `run-${requestedModels.length}`,
         task: meta.task,
@@ -26,10 +33,9 @@ test("parallel mode runs each task and uses the top-level model unless a task ov
   const result = await tool.execute(
     "tool-1",
     {
-      model: "openai/gpt-5",
       tasks: [
-        { task: "find auth code" },
+        { preset: "openai-preset", task: "find auth code" },
-        { task: "review auth code", model: "anthropic/claude-opus-4-5" },
+        { preset: "anthropic-preset", task: "review auth code", model: "anthropic/claude-opus-4-5" },
       ],
     },
     undefined,
@@ -57,6 +63,12 @@ test("parallel mode rejects per-task model overrides that are not currently avai
   let didRun = false;
 
   const tool = createSubagentTool({
+    discoverSubagentPresets: () => ({
+      presets: [
+        { name: "auth-preset", description: "auth", model: "anthropic/claude-sonnet-4-5", systemPrompt: "", source: "project", filePath: "/repo/.pi/subagents/auth.md" },
+      ],
+      projectPresetsDir: "/repo/.pi/subagents",
+    }),
     runSingleTask: async () => {
       didRun = true;
       throw new Error("should not run");
@@ -66,8 +78,7 @@ test("parallel mode rejects per-task model overrides that are not currently avai
   const result = await tool.execute(
     "tool-1",
     {
-      model: "anthropic/claude-sonnet-4-5",
+      tasks: [{ preset: "auth-preset", task: "find auth code", model: "openai/gpt-5" }],
-      tasks: [{ task: "find auth code", model: "openai/gpt-5" }],
     },
     undefined,
     undefined,

src/tool.test.ts

@@ -2,10 +2,24 @@ import test from "node:test";
 import assert from "node:assert/strict";
 import { createSubagentTool } from "./tool.ts";
 
-test("single-mode subagent uses the required top-level model and emits humanized live progress", async () => {
+test("single-mode subagent uses preset default model and emits humanized live progress", async () => {
   const updates: string[] = [];
 
   const tool = createSubagentTool({
+    discoverSubagentPresets: () => ({
+      presets: [
+        {
+          name: "auth-inspector",
+          description: "inspect auth",
+          model: "anthropic/claude-sonnet-4-5",
+          tools: ["read"],
+          systemPrompt: "",
+          source: "project",
+          filePath: "/repo/.pi/subagents/auth.md",
+        },
+      ],
+      projectPresetsDir: "/repo/.pi/subagents",
+    }),
     runSingleTask: async ({ onEvent, meta }: any) => {
       onEvent?.({ type: "assistant_text", text: "Inspecting auth flow" });
       onEvent?.({ type: "tool_call", toolName: "read", args: { path: "src/auth.ts" } });
@@ -27,8 +41,8 @@ test("single-mode subagent uses the required top-level model and emits humanized
   const result = await tool.execute(
     "tool-1",
     {
+      preset: "auth-inspector",
       task: "inspect auth",
-      model: "anthropic/claude-sonnet-4-5",
     },
     undefined,
     (partial: any) => {
@@ -50,7 +64,6 @@ test("single-mode subagent uses the required top-level model and emits humanized
   assert.equal(result.details.results[0]?.task, "inspect auth");
   assert.equal(result.details.results[0]?.paneId, "%3");
   assert.equal(result.details.results[0]?.requestedModel, "anthropic/claude-sonnet-4-5");
-  assert.equal("agent" in (result.details.results[0] ?? {}), false);
   assert.deepEqual(updates, ["Inspecting auth flow", "Reading src/auth.ts", "Finished reading src/auth.ts"]);
   assert.doesNotMatch(updates.join("\n"), /tool_call|tool_result/);
 });
@@ -59,6 +72,20 @@ test("single-mode subagent ignores blank assistant text and falls back to tool a
   const updates: string[] = [];
 
   const tool = createSubagentTool({
+    discoverSubagentPresets: () => ({
+      presets: [
+        {
+          name: "auth-inspector",
+          description: "inspect auth",
+          model: "anthropic/claude-sonnet-4-5",
+          tools: ["grep"],
+          systemPrompt: "",
+          source: "project",
+          filePath: "/repo/.pi/subagents/auth.md",
+        },
+      ],
+      projectPresetsDir: "/repo/.pi/subagents",
+    }),
     runSingleTask: async ({ onEvent, meta }: any) => {
       onEvent?.({ type: "assistant_text", text: "   " });
       onEvent?.({ type: "tool_call", toolName: "grep", args: { pattern: "auth" } });
@@ -76,8 +103,8 @@ test("single-mode subagent ignores blank assistant text and falls back to tool a
   await tool.execute(
     "tool-1",
     {
+      preset: "auth-inspector",
       task: "inspect auth",
-      model: "anthropic/claude-sonnet-4-5",
     },
     undefined,
     (partial: any) => {
@@ -96,10 +123,22 @@ test("single-mode subagent ignores blank assistant text and falls back to tool a
   assert.deepEqual(updates, ["Searching code for auth"]);
 });
 
-test("single-mode subagent requires a top-level model even when execute is called directly", async () => {
+test("single-mode subagent requires a model (either explicit or preset default) when execute is called directly", async () => {
   let didRun = false;
 
   const tool = createSubagentTool({
+    discoverSubagentPresets: () => ({
+      presets: [
+        {
+          name: "bare-preset",
+          description: "no model",
+          systemPrompt: "",
+          source: "project",
+          filePath: "/repo/.pi/subagents/bare.md",
+        },
+      ],
+      projectPresetsDir: "/repo/.pi/subagents",
+    }),
     runSingleTask: async () => {
       didRun = true;
       throw new Error("should not run");
@@ -108,7 +147,7 @@ test("single-mode subagent requires a top-level model even when execute is calle
 
   const result = await tool.execute(
     "tool-1",
-    { task: "inspect auth" },
+    { preset: "bare-preset", task: "inspect auth" },
     undefined,
     undefined,
     {
@@ -122,13 +161,25 @@ test("single-mode subagent requires a top-level model even when execute is calle
 
   assert.equal(didRun, false);
   assert.equal(result.isError, true);
-  assert.match(result.content[0]?.type === "text" ? result.content[0].text : "", /top-level model/i);
+  assert.match(result.content[0]?.type === "text" ? result.content[0].text : "", /no model provided/i);
 });
 
 test("single-mode subagent rejects models that are not currently available", async () => {
   let didRun = false;
 
   const tool = createSubagentTool({
+    discoverSubagentPresets: () => ({
+      presets: [
+        {
+          name: "auth-inspector",
+          description: "inspect auth",
+          systemPrompt: "",
+          source: "project",
+          filePath: "/repo/.pi/subagents/auth.md",
+        },
+      ],
+      projectPresetsDir: "/repo/.pi/subagents",
+    }),
     runSingleTask: async () => {
       didRun = true;
       throw new Error("should not run");
@@ -138,6 +189,7 @@ test("single-mode subagent rejects models that are not currently available", asy
   const result = await tool.execute(
     "tool-1",
     {
+      preset: "auth-inspector",
       task: "inspect auth",
       model: "openai/gpt-5",
     },
@@ -163,9 +215,9 @@ test("subagent rejects requests that combine single and parallel modes", async (
   const result = await tool.execute(
     "tool-1",
     {
+      preset: "auth-inspector",
       task: "inspect auth",
-      model: "anthropic/claude-sonnet-4-5",
+      tasks: [{ preset: "auth-inspector", task: "review auth" }],
-      tasks: [{ task: "review auth" }],
     },
     undefined,
     undefined,

src/tool.ts

@@ -4,6 +4,7 @@ import {
   normalizeAvailableModelReference,
   resolveChildModel,
 } from "./models.ts";
+import { discoverSubagentPresets } from "./presets.ts";
 import {
   SubagentParamsSchema,
   type SubagentRunResult,
@@ -39,14 +40,11 @@ function isFailure(result: Pick<SubagentRunResult, "exitCode" | "stopReason">) {
   return result.exitCode !== 0 || result.stopReason === "error" || result.stopReason === "aborted";
 }
 
-function makeDetails(
+function makeDetails(mode: "single" | "parallel", results: SubagentRunResult[]): SubagentToolDetails {
-  mode: "single" | "parallel" | "chain",
-  results: SubagentRunResult[],
-): SubagentToolDetails {
   return { mode, results };
 }
 
-function makeErrorResult(text: string, mode: "single" | "parallel" | "chain") {
+function makeErrorResult(text: string, mode: "single" | "parallel") {
   return {
     content: [{ type: "text" as const, text }],
     details: makeDetails(mode, []),
@@ -69,6 +67,7 @@ export function createSubagentTool(deps: {
   resolveChildModel?:
     | ((input: { callModel?: string; presetModel?: string; taskModel?: string; topLevelModel?: string }) => ModelSelection)
     | typeof resolveChildModel;
+  discoverSubagentPresets?: typeof discoverSubagentPresets;
   runSingleTask?: (input: {
     cwd: string;
     meta: Record<string, unknown>;
@@ -83,12 +82,11 @@ export function createSubagentTool(deps: {
     async execute(_toolCallId: string, params: any, _signal: AbortSignal | undefined, onUpdate: any, ctx: any) {
       const hasSingle = Boolean(params.task);
       const hasParallel = Boolean(params.tasks?.length);
-      const hasChain = Boolean(params.chain?.length);
+      const modeCount = Number(hasSingle) + Number(hasParallel);
-      const modeCount = Number(hasSingle) + Number(hasParallel) + Number(hasChain);
+      const mode = hasParallel ? "parallel" : "single";
-      const mode = hasParallel ? "parallel" : hasChain ? "chain" : "single";
 
       if (modeCount !== 1) {
-        return makeErrorResult("Provide exactly one mode: single, parallel, or chain.", "single");
+        return makeErrorResult("Provide exactly one mode: single or parallel.", "single");
       }
 
       const availableModelReferences = (deps.listAvailableModelReferences ?? listAvailableModelReferences)(ctx.modelRegistry);
@@ -103,41 +101,8 @@ export function createSubagentTool(deps: {
         );
       }
 
-      const topLevelModel = normalizeModelReference(params.model);
+      const discovery = (deps.discoverSubagentPresets ?? discoverSubagentPresets)(ctx.cwd);
-      if (!topLevelModel) {
+      const presets = discovery.presets;
-        const message =
-          typeof params.model !== "string" || params.model.trim().length === 0
-            ? `Subagent requires a top-level model chosen from the available models: ${availableModelsText}`
-            : `Invalid top-level model "${params.model}". Choose one of the available models: ${availableModelsText}`;
-        return makeErrorResult(message, mode);
-      }
-      params.model = topLevelModel;
-
-      for (const [index, task] of (params.tasks ?? []).entries()) {
-        if (task.model === undefined) continue;
-
-        const normalizedTaskModel = normalizeModelReference(task.model);
-        if (!normalizedTaskModel) {
-          return makeErrorResult(
-            `Invalid model for parallel task ${index + 1}: "${task.model}". Choose one of the available models: ${availableModelsText}`,
-            mode,
-          );
-        }
-        task.model = normalizedTaskModel;
-      }
-
-      for (const [index, step] of (params.chain ?? []).entries()) {
-        if (step.model === undefined) continue;
-
-        const normalizedStepModel = normalizeModelReference(step.model);
-        if (!normalizedStepModel) {
-          return makeErrorResult(
-            `Invalid model for chain step ${index + 1}: "${step.model}". Choose one of the available models: ${availableModelsText}`,
-            mode,
-          );
-        }
-        step.model = normalizedStepModel;
-      }
 
       // Adapter: accept only the flattened shape { callModel?, presetModel? }
       // to keep the tool logic simple. If a resolver was injected with the
@@ -160,12 +125,35 @@ export function createSubagentTool(deps: {
       const runTask = async (input: {
         task: string;
         cwd?: string;
-        taskModel?: string;
+        taskModel?: string | undefined;
         taskIndex?: number;
-        step?: number;
+        preset: typeof presets[number];
-        mode: "single" | "parallel" | "chain";
+        mode: "single" | "parallel";
       }) => {
-        const model = callResolveChildModel({ callModel: input.taskModel, presetModel: params.model });
+        // Normalize explicit/task model and preset default model against available models
+        const normalizedCallModel = normalizeModelReference(input.taskModel);
+        const normalizedPresetModel = normalizeModelReference(input.preset.model);
+
+        // Use the resolver to allow custom selection logic, but fall back to
+        // explicit then preset default. We pass normalized values to the
+        // resolver so it always sees canonical available-model strings.
+        const selection = callResolveChildModel({ callModel: normalizedCallModel, presetModel: normalizedPresetModel });
+
+        const requestedModel = selection.requestedModel ?? normalizedCallModel ?? normalizedPresetModel;
+        const resolvedModel = selection.resolvedModel ?? requestedModel;
+
+        if (!requestedModel) {
+          return Promise.resolve({
+            runId: "",
+            task: input.task,
+            requestedModel: undefined,
+            resolvedModel: undefined,
+            exitCode: 1,
+            finalText: "",
+            stopReason: "error",
+            errorMessage: `No model provided for preset "${input.preset.name}". Choose one of the available models: ${availableModelsText}`,
+          } as SubagentRunResult);
+        }
 
         const progressFormatter = createProgressFormatter();
 
@@ -182,20 +170,72 @@ export function createSubagentTool(deps: {
           meta: {
             mode: input.mode,
             taskIndex: input.taskIndex,
-            step: input.step,
             task: input.task,
             cwd: input.cwd ?? ctx.cwd,
-            requestedModel: model.requestedModel,
+            preset: input.preset.name,
-            resolvedModel: model.resolvedModel,
+            presetSource: input.preset.source,
+            systemPrompt: input.preset.systemPrompt,
+            tools: input.preset.tools,
+            requestedModel,
+            resolvedModel,
           },
         }) as Promise<SubagentRunResult>;
       };
 
       if (hasSingle) {
+        if (typeof params.preset !== "string" || params.preset.trim() === "") {
+          return makeErrorResult("Single mode requires a 'preset' string and a 'task'.", "single");
+        }
+
+        const preset = presets.find((p) => p.name === params.preset);
+        if (!preset) {
+          const names = presets.map((p) => p.name).join(", ") || "(none)";
+          return makeErrorResult(`Unknown preset "${params.preset}". Available presets: ${names}`, "single");
+        }
+
+        // Validate explicit model if provided
+        if (params.model !== undefined) {
+          const normalized = normalizeModelReference(params.model);
+          if (!normalized) {
+            return makeErrorResult(
+              typeof params.model !== "string" || params.model.trim().length === 0
+                ? `Single-mode requires a model chosen from the available models: ${availableModelsText}`
+                : `Invalid model "${params.model}". Choose one of the available models: ${availableModelsText}`,
+              "single",
+            );
+          }
+          params.model = normalized;
+        }
+
+        // Validate preset default model if present
+        if (preset.model !== undefined) {
+          const normalizedPresetModel = normalizeModelReference(preset.model);
+          if (!normalizedPresetModel) {
+            return makeErrorResult(
+              `Preset "${preset.name}" specifies an invalid model "${preset.model}". Choose one of the available models: ${availableModelsText}`,
+              "single",
+            );
+          }
+          // Use canonical preset model
+          preset.model = normalizedPresetModel;
+        }
+
+        // Ensure an effective model exists for this run (explicit override wins)
+        const singleSelection = callResolveChildModel({ callModel: params.model, presetModel: preset.model });
+        const singleRequested = singleSelection.requestedModel ?? params.model ?? preset.model;
+        if (!singleRequested) {
+          return makeErrorResult(
+            `No model provided for preset "${preset.name}". Choose one of the available models: ${availableModelsText}`,
+            "single",
+          );
+        }
+
         try {
           const result = await runTask({
             task: params.task,
             cwd: params.cwd,
+            preset,
+            taskModel: params.model,
             mode: "single",
           });
 
@@ -213,7 +253,48 @@ export function createSubagentTool(deps: {
         }
       }
 
-      if (hasParallel) {
+      // Parallel
+      // Validate tasks and presets first
+      for (const [index, t] of (params.tasks ?? []).entries()) {
+        if (typeof t.preset !== "string" || t.preset.trim() === "") {
+          return makeErrorResult(`Parallel task ${index + 1} missing required 'preset'`, "parallel");
+        }
+        const preset = presets.find((p) => p.name === t.preset);
+        if (!preset) {
+          const names = presets.map((p) => p.name).join(", ") || "(none)";
+          return makeErrorResult(`Unknown preset "${t.preset}" for task ${index + 1}. Available presets: ${names}`, "parallel");
+        }
+
+        if (t.model !== undefined) {
+          const normalized = normalizeModelReference(t.model);
+          if (!normalized) {
+            return makeErrorResult(`Invalid model for parallel task ${index + 1}: "${t.model}". Choose one of the available models: ${availableModelsText}`, "parallel");
+          }
+          t.model = normalized;
+        }
+
+        if (preset.model !== undefined) {
+          const normalizedPresetModel = normalizeModelReference(preset.model);
+          if (!normalizedPresetModel) {
+            return makeErrorResult(
+              `Preset "${preset.name}" specifies an invalid model "${preset.model}". Choose one of the available models: ${availableModelsText}`,
+              "parallel",
+            );
+          }
+          preset.model = normalizedPresetModel;
+        }
+
+        // Ensure an effective model exists for this task
+        const sel = callResolveChildModel({ callModel: t.model, presetModel: preset.model });
+        const requested = sel.requestedModel ?? t.model ?? preset.model;
+        if (!requested) {
+          return makeErrorResult(
+            `Parallel task ${index + 1} has no model. Provide an explicit 'model' or set a default model on preset "${preset.name}". Available models: ${availableModelsText}`,
+            "parallel",
+          );
+        }
+      }
+
       if (params.tasks.length > MAX_PARALLEL_TASKS) {
         return {
           content: [
@@ -229,11 +310,13 @@ export function createSubagentTool(deps: {
 
       const liveResults: SubagentRunResult[] = [];
       const results = await mapWithConcurrencyLimit(params.tasks, MAX_CONCURRENCY, async (task: any, index) => {
+        const preset = presets.find((p) => p.name === task.preset)!;
         const result = await runTask({
           task: task.task,
           cwd: task.cwd,
           taskModel: task.model,
           taskIndex: index,
+          preset,
           mode: "parallel",
         });
         liveResults[index] = result;
@@ -254,49 +337,9 @@ export function createSubagentTool(deps: {
         details: makeDetails("parallel", results),
         isError: successCount !== results.length,
       };
-      }
-
-      const results: SubagentRunResult[] = [];
-      let previous = "";
-      for (let index = 0; index < params.chain.length; index += 1) {
-        const item = params.chain[index];
-        const task = item.task.replaceAll("{previous}", previous);
-        const result = await runTask({
-          task,
-          cwd: item.cwd,
-          taskModel: item.model,
-          step: index + 1,
-          mode: "chain",
-        });
-        onUpdate?.({
-          content: [{ type: "text", text: `Chain: completed step ${index + 1}/${params.chain.length}` }],
-          details: makeDetails("chain", [...results, result]),
-        });
-        results.push(result);
-        if (isFailure(result)) {
-          return {
-            content: [
-              {
-                type: "text" as const,
-                text: `Chain stopped at step ${index + 1}: ${result.finalText || result.stopReason || "failed"}`,
-              },
-            ],
-            details: makeDetails("chain", results),
-            isError: true,
-          };
-        }
-        previous = result.finalText;
-      }
-
-      const finalResult = results[results.length - 1];
-      return {
-        content: [{ type: "text" as const, text: finalResult?.finalText ?? "" }],
-        details: makeDetails("chain", results),
-      };
     },
     renderCall(args: any) {
       if (args.tasks?.length) return new Text(`subagent parallel (${args.tasks.length} tasks)`, 0, 0);
-      if (args.chain?.length) return new Text(`subagent chain (${args.chain.length} steps)`, 0, 0);
       return new Text("subagent", 0, 0);
     },
     renderResult(result: { content: Array<{ type: string; text?: string }> }) {