isError results replace thrown ToolInputError (pi 1.0 convention)

Authoring refinements (quizInputProblems, nodeId checks, ask/explain
refinements, submit-agent pipeline laws) now return invalidInputResult —
same model-facing failure and retry semantics pi minted from the throw,
but details keeps {tool, problems} as data instead of the throw path's
empty {}. ToolInputError deleted; wire shape unchanged (verified against
pi's own thrown-error conversion in agent-loop).

src/agent/subagents/practice.ts

@@ -4,7 +4,7 @@
  * Three single-submit workers on the shared runSubmitAgent seam (one
  * TypeBox-validated submit call each; a pi agent purely so the model can
  * retry a schema-invalid or LAW-violating call — the validate hook throws
- * ToolInputError at the execute seam and pi turns it into an error tool
+ * an invalidInputResult isError result at the execute seam (pi 1.0 convention)
  * result the model sees).
  *
  * Roles: partitioner | problemGenerator | grader — all strong-tier

src/agent/subagents/submit-agent.ts

@@ -10,7 +10,7 @@
 import type { Usage } from "@earendil-works/pi-ai";
 import type { AgentTool } from "@earendil-works/pi-agent-core";
 import type { TSchema } from "typebox";
-import { toToolResult, ToolInputError } from "../tool-execute.ts";
+import { invalidInputResult, toToolResult } from "../tool-execute.ts";
 import type { ModelRole } from "../../../config.ts";
 import type { PiEngine } from "../models.ts";
 import { runSubagent } from "./pi-run.ts";
@@ -63,14 +63,16 @@ export async function runSubmitAgent<T>(opts: {
 	/** Turn budget for the loop (default 4 = retry-only; the auditor runs
 	 *  an exploration loop instead — 16). */
 	maxTurns?: number;
+	/** Debug: raw provider-event recording key (LH_PROVIDER_EVENTS=1). */
+	chatId?: string;
 	/** Weak-model argument heal at pi's prepareArguments seam (runs BEFORE
 	 *  TypeBox validation — the sanctioned shim point). Identity by
 	 *  default; extraction wires healStringifiedArrays here. */
 	prepareArguments?: (args: unknown) => unknown;
 	/** Semantic validation at the submit seam: the value is schema-valid
 	 *  but may violate a PIPELINE law (coverage, echo-equality). Returning
-	 *  a problem string throws ToolInputError → pi turns it into an error
-	 *  tool result → the model retries within maxTurns. null = accept. */
+	 *  a problem string yields an isError result (invalidInputResult) →
+	 *  the model retries within maxTurns. null = accept. */
 	validate?: (value: T) => string | null;
 }): Promise<T> {
 	let submitted: T | undefined;
@@ -87,7 +89,7 @@ export async function runSubmitAgent<T>(opts: {
 				execute: async (_toolCallId, input) => {
 					const value = opts.fill(input);
 					const problem = opts.validate?.(value) ?? null;
-					if (problem) throw new ToolInputError(opts.toolName, [problem]);
+					if (problem) return invalidInputResult(opts.toolName, [problem]);
 					submitted = value;
 					return toToolResult(submitted);
 				},
@@ -100,6 +102,7 @@ export async function runSubmitAgent<T>(opts: {
 			prompt: opts.prompt,
 			maxTurns: opts.maxTurns ?? 4,
 			abortSignal: opts.signal,
+			chatId: opts.chatId,
 			onAssistantMessage: (message, step) =>
 				opts.onStep(
 					message.usage,

src/agent/tool-execute.ts

@@ -9,10 +9,10 @@ import type { Static, TSchema } from "typebox";
  * (lh-tool.ts, deleted) used to add around every execute:
  *
  * - the system-level per-call timeout + abort cascade (runWithAbortGuard),
- * - the authoring-refinement failure shape (ToolInputError — thrown from
- *   execute; pi's loop converts the throw into an error tool result the
- *   model sees and retries on, exactly the old InvalidToolInputError
- *   semantics),
+ * - the authoring-refinement failure shape (invalidInputResult —
+ *   returned from execute as an isError result; pi 1.0's convention, the
+ *   model sees the same retryable problem list it always did, and
+ *   `details` keeps the problems as data),
  * - the result mapping (string verbatim / object JSON / image results to
  *   native content parts; details carries the record-facing value),
  * - the question-tool placeholder (quiz / ask_user_question): a synthetic
@@ -107,17 +107,26 @@ function runWithAbortGuard<T>(
 		.finally(cleanup);
 }
 
-/** lh's port of the SDK's invalid-input message: what the model retried on.
- *  Thrown from a tool's execute when the authoring refinements fail —
- *  pi's loop catches the throw and turns it into an error tool result. */
-export class ToolInputError extends Error {
-	constructor(
-		public readonly toolName: string,
-		public readonly problems: string[],
-	) {
-		super(`Invalid tool input for tool "${toolName}":\n${problems.map((p) => `- ${p}`).join("\n")}`);
-		this.name = "ToolInputError";
-	}
+/** The 1.0-native authoring-failure result (pi convention, agent-core
+ *  1.0): return an isError result instead of throwing — the model sees the
+ *  same retryable problem list it always did (pi minted exactly this shape
+ *  from a thrown ToolInputError), but `details` now keeps the problems as
+ *  DATA for the record and the UI instead of the throw path's empty {}.
+ *  Content text is byte-identical to the old thrown message. */
+export function invalidInputResult(
+	toolName: string,
+	problems: string[],
+): AgentToolResult<{ tool: string; problems: string[] }> {
+	return {
+		content: [
+			{
+				type: "text",
+				text: `Invalid tool input for tool "${toolName}":\n${problems.map((p) => `- ${p}`).join("\n")}`,
+			},
+		],
+		isError: true,
+		details: { tool: toolName, problems },
+	};
 }
 
 /**

src/agent/tools.ts

@@ -1,6 +1,6 @@
 import { Type } from "typebox";
 import type { AgentTool } from "@earendil-works/pi-agent-core";
-import { questionResult, serverExecute, ToolInputError } from "./tool-execute.ts";
+import { invalidInputResult, questionResult, serverExecute } from "./tool-execute.ts";
 import {
 	askInputSchema,
 	askOptionProblems,
@@ -88,7 +88,7 @@ export const askUserQuestionTool: AgentTool<typeof askInputSchema> = {
 	executionMode: "sequential",
 	execute: async (_toolCallId, input) => {
 		const problems = askOptionProblems(input.options ?? []);
-		if (problems.length > 0) throw new ToolInputError("ask_user_question", problems);
+		if (problems.length > 0) return invalidInputResult("ask_user_question", problems);
 		return questionResult();
 	},
 };
@@ -153,7 +153,7 @@ export const probeQuizTool: AgentTool<typeof probeQuizInputSchema> = {
 	executionMode: "sequential",
 	execute: async (_toolCallId, input) => {
 		const problems = quizInputProblems(input);
-		if (problems.length > 0) throw new ToolInputError("quiz", problems);
+		if (problems.length > 0) return invalidInputResult("quiz", problems);
 		return questionResult();
 	},
 };
@@ -174,7 +174,7 @@ export function teachExplainToolFor(
 			const problems = [...explainInputProblems(input)];
 			const nodeIdProblemText = nodeIdProblem(ctx, input.nodeId);
 			if (nodeIdProblemText) problems.push(nodeIdProblemText);
-			if (problems.length > 0) throw new ToolInputError("explain", problems);
+			if (problems.length > 0) return invalidInputResult("explain", problems);
 			return questionResult();
 		},
 	};
@@ -191,7 +191,7 @@ export const probeExplainTool: AgentTool<typeof explainInputBase> = {
 	executionMode: "sequential",
 	execute: async (_toolCallId, input) => {
 		const problems = explainInputProblems(input);
-		if (problems.length > 0) throw new ToolInputError("explain", problems);
+		if (problems.length > 0) return invalidInputResult("explain", problems);
 		return questionResult();
 	},
 };
@@ -317,7 +317,7 @@ export function teachQuizToolFor(ctx: Pick<PlanToolContext, "chatId" | "chatStor
 			const problems = [...quizInputProblems(input)];
 			const nodeIdProblemText = nodeIdProblem(ctx, input.nodeId);
 			if (nodeIdProblemText) problems.push(nodeIdProblemText);
-			if (problems.length > 0) throw new ToolInputError("quiz", problems);
+			if (problems.length > 0) return invalidInputResult("quiz", problems);
 			return questionResult();
 		},
 	};

tests/question-tools.test.ts

@@ -64,29 +64,29 @@ const validQuiz = {
 };
 
 import type { AgentTool } from "@earendil-works/pi-agent-core";
-import { ToolInputError } from "../src/agent/tool-execute.ts";
+import type { AgentToolResult } from "@earendil-works/pi-agent-core";
 
 /** The Wave A boundary predicate (2026-09-26): pi's loop structurally
  *  validates against the TypeBox parameters, then execute re-runs the
- *  authoring refinements (the old superRefine) and throws ToolInputError
- *  on problems — the model sees both as retryable input errors. This
- *  helper replicates the old safeParse seam end to end. */
+ *  authoring refinements (the old superRefine) and returns an isError
+ *  result on problems (pi 1.0 convention — invalidInputResult; the model
+ *  sees both as retryable input errors). This helper replicates the old
+ *  safeParse seam end to end. */
 async function boundaryParse(
 	// `input: never` param: contravariance lets any AgentTool's execute slot in.
 	tool: { parameters: any; execute: (id: string, input: never) => Promise<unknown> },
 	input: unknown,
-): Promise<{ success: boolean; error?: ToolInputError }> {
+): Promise<{ success: boolean; error?: AgentToolResult<{ tool: string; problems: string[] }> }> {
 	if (!Value.Check(tool.parameters, input)) return { success: false };
-	try {
-		await tool.execute("tc", input as never);
-		return { success: true };
-	} catch (e) {
-		assert.ok(e instanceof ToolInputError, `expected ToolInputError, got: ${e}`);
-		return { success: false, error: e };
-	}
+	const result = (await tool.execute("tc", input as never)) as AgentToolResult<{
+		tool: string;
+		problems: string[];
+	}>;
+	if (result.isError) return { success: false, error: result };
+	return { success: true };
 }
-const problemLines = (e?: ToolInputError): string[] =>
-	(e?.message.split("\n") ?? []).filter((l) => l.startsWith("- "));
+const problemLines = (r?: AgentToolResult<{ tool: string; problems: string[] }>): string[] =>
+	r?.details.problems ?? [];
 
 describe("teachQuizToolFor: the dynamic plan-nodeId validation (position signal)", () => {
 	it("accepts a nodeId that matches a node of the session's tree", async () => {

tests/tool-abort.test.ts

@@ -15,7 +15,6 @@ import {
 	questionResult,
 	serverExecute,
 	toolTimeoutMs,
-	ToolInputError,
 	toToolResult,
 	type ToolExecuteContext,
 } from "../src/agent/tool-execute.ts";
@@ -121,23 +120,18 @@ describe("serverExecute: cooperative settle, mapping parity, question bypass", (
 		assert.equal(result.terminate, true, "owner Option A: question results end the batch natively");
 	});
 
-	it("authoring failures throw ToolInputError with the retryable problem list", async () => {
-		await assert.rejects(
-			askUserQuestionTool.execute("c7", {
-				question: "q",
-				options: [
-					{ label: "A", value: "same" },
-					{ label: "B", value: "same" },
-				],
-			}),
-			(e: unknown) => {
-				assert.ok(e instanceof ToolInputError);
-				assert.equal(e.toolName, "ask_user_question");
-				assert.match(e.message, /Invalid tool input for tool "ask_user_question":/);
-				assert.match(e.message, /- .*same value/s);
-				return true;
-			},
-		);
+	it("authoring failures return an isError result with the retryable problem list", async () => {
+		const result = (await askUserQuestionTool.execute("c7", {
+			question: "q",
+			options: [
+				{ label: "A", value: "same" },
+			{ label: "B", value: "same" },
+			],
+		})) as { isError?: boolean; content: Array<{ text?: string }>; details?: { tool: string; problems: string[] } };
+		assert.equal(result.isError, true, "pi 1.0 convention: returned, not thrown");
+		assert.equal(result.details?.tool, "ask_user_question");
+		assert.match(result.content[0]!.text!, /Invalid tool input for tool "ask_user_question":/);
+		assert.match(result.details!.problems.map((p) => `- ${p}`).join("\n"), /- .*same value/s);
 	});
 
 	it("toToolResult parity: string verbatim, object as JSON, details rides the raw value", () => {