practice slice 3A — runSubmitAgent extracted to shared module; practice model roles

runSubmitAgent moved verbatim from extraction.ts to src/agent/subagents/
submit-agent.ts (exported; extraction imports it — zero behavior change,
extraction suites green untouched). New optional prepareArguments seam:
extraction wires its healStringifiedArrays heal; default is identity
pass-through. ModelRole += partitioner | problemGenerator | grader;
ROLE_SLOT pins all three to strong (quality-critical trio, plan default).
Note: BACKGROUND_MODEL_ROLES (per-role settings overrides) deliberately
NOT extended — settings-surface decision, flagged for the planning
session.

config.ts

@@ -53,7 +53,10 @@ export type ModelRole =
 	| "visualMaker"
 	| "pdfReader"
 	| "extractor"
-	| "auditor";
+	| "auditor"
+	| "partitioner"
+	| "problemGenerator"
+	| "grader";
 
 /**
  * The LIVE graph store (src/store/graph.ts) — owned by the app's extraction

src/agent/subagents/extraction.ts

@@ -29,6 +29,7 @@ import { batchRuns, coverageOf, messageViewLines } from "../../core/coverage.ts"
 import { teacherProseBlocks } from "../../core/coverage.ts";
 import type { LhMessage } from "../../core/native-messages.ts";
 import { auditorGraphTools } from "../tools/graph.ts";
+import { runSubmitAgent } from "./submit-agent.ts";
 
 /**
  * The extraction pipeline (vision §1 construction, 2026-09-02 redesign;
@@ -344,75 +345,6 @@ field because it is empty.
 
 Your entire deliverable is ONE submit_findings call.`;
 
-/** One single-submit agent run — the shared shape of EVERY LLM stage
- *  here (session + notes): the whole deliverable is ONE TypeBox-validated
- *  submit call (a pi agent purely so the model can retry a schema-invalid
- *  call). The submitted value is captured from the execute seam, which
- *  only fires on a schema-valid call — the ??-fill (the old zod defaults)
- *  applies at the capture. */
-async function runSubmitAgent<T>(opts: {
-	role: ModelRole;
-	toolName: string;
-	toolDescription: string;
-	parameters: TSchema;
-	/** Weak-model tolerance: the old zod `.default()`s, applied to the
-	 *  schema-valid raw input at the submit seam. */
-	fill: (input: any) => T;
-	systemPrompt: string;
-	prompt: string;
-	engine: PiEngine | undefined;
-	signal: AbortSignal | undefined;
-	onStep: (usage: Usage, model: string, step: number, finishReason: string, tools: string) => void;
-	neverSubmitted: string;
-	/** Extra tools beside the submit call (the auditor's graph-exploration
-	 *  set, 2026-09-27): a small agentic loop instead of a bare retry. */
-	extraTools?: Record<string, AgentTool<any>>;
-	/** Turn budget for the loop (default 4 = retry-only; the auditor runs
-	 *  an exploration loop instead — 16). */
-	maxTurns?: number;
-}): Promise<T> {
-	let submitted: T | undefined;
-	const result = await runSubagent(
-		[
-			...(opts.extraTools ? Object.values(opts.extraTools) : []),
-			{
-				name: opts.toolName,
-				label: opts.toolName,
-				description: opts.toolDescription,
-				parameters: opts.parameters,
-				prepareArguments: (args) => healStringifiedArrays(args) as never,
-				execute: async (_toolCallId, input) => {
-					submitted = opts.fill(input);
-					return toToolResult(submitted);
-				},
-			} satisfies AgentTool<any>,
-		],
-		{
-			role: opts.role,
-			engine: opts.engine,
-			systemPrompt: opts.systemPrompt,
-			prompt: opts.prompt,
-			maxTurns: opts.maxTurns ?? 4,
-			abortSignal: opts.signal,
-			onAssistantMessage: (message, step) =>
-				opts.onStep(
-					message.usage,
-					// Provider-qualified stamp (model slots wave, 2026-09-20):
-					// pi reports the bare id; usage stamps carry provider:id to
-					// match the price table's uniform keys.
-					`${message.provider}:${message.model}`,
-					step,
-					message.stopReason,
-					message.content.filter((c) => c.type === "toolCall").map((c) => (c as { name: string }).name).join(", ") || "(none)",
-				),
-			shouldStop: (_message, toolResults) => toolResults.some((r) => r.toolName === opts.toolName && !r.isError),
-		},
-	);
-	void result;
-	if (!submitted) throw new Error(opts.neverSubmitted);
-	return submitted;
-}
-
 /** The extractor over ONE session transcript (the chat front door). */
 function runExtractor(
 	engine: PiEngine | undefined,
@@ -432,6 +364,7 @@ function runExtractor(
 		signal,
 		onStep,
 		neverSubmitted: "the extractor never submitted findings",
+		prepareArguments: healStringifiedArrays,
 	});
 }
 
@@ -455,6 +388,7 @@ function runNotesExtractor(
 		signal,
 		onStep,
 		neverSubmitted: "the extractor never submitted findings",
+		prepareArguments: healStringifiedArrays,
 	});
 }
 
@@ -521,6 +455,7 @@ function runAuditor(
 		neverSubmitted: "the auditor never submitted a review",
 		extraTools: tools,
 		maxTurns: 16,
+		prepareArguments: healStringifiedArrays,
 	});
 }
 

src/agent/subagents/submit-agent.ts

@@ -0,0 +1,87 @@
+/**
+ * runSubmitAgent — the shared single-submit agent seam (moved verbatim from
+ * extraction.ts, practice slice 3, 2026-09-29): one TypeBox-validated submit
+ * call is the whole deliverable (a pi agent purely so the model can retry a
+ * schema-invalid call). The submitted value is captured from the execute
+ * seam, which only fires on a schema-valid call — the ??-fill (the old zod
+ * defaults) applies at the capture.
+ *
+ * Extraction passes its own weak-model argument heal (healStringifiedArrays)
+ * through `prepareArguments`; the default is identity pass-through.
+ */
+
+import type { Usage } from "@earendil-works/pi-ai";
+import type { AgentTool } from "@earendil-works/pi-agent-core";
+import type { TSchema } from "typebox";
+import { toToolResult } from "../tool-execute.ts";
+import type { ModelRole } from "../../../config.ts";
+import type { PiEngine } from "../models.ts";
+import { runSubagent } from "./pi-run.ts";
+
+export async function runSubmitAgent<T>(opts: {
+	role: ModelRole;
+	toolName: string;
+	toolDescription: string;
+	parameters: TSchema;
+	/** Weak-model tolerance: the old zod `.default()`s, applied to the
+	 *  schema-valid raw input at the submit seam. */
+	fill: (input: any) => T;
+	systemPrompt: string;
+	prompt: string;
+	engine: PiEngine | undefined;
+	signal: AbortSignal | undefined;
+	onStep: (usage: Usage, model: string, step: number, finishReason: string, tools: string) => void;
+	neverSubmitted: string;
+	/** Extra tools beside the submit call (the auditor's graph-exploration
+	 *  set, 2026-09-27): a small agentic loop instead of a bare retry. */
+	extraTools?: Record<string, AgentTool<any>>;
+	/** Turn budget for the loop (default 4 = retry-only; the auditor runs
+	 *  an exploration loop instead — 16). */
+	maxTurns?: number;
+	/** 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;
+}): Promise<T> {
+	let submitted: T | undefined;
+	const result = await runSubagent(
+		[
+			...(opts.extraTools ? Object.values(opts.extraTools) : []),
+			{
+				name: opts.toolName,
+				label: opts.toolName,
+				description: opts.toolDescription,
+				parameters: opts.parameters,
+				prepareArguments: (args) =>
+					(opts.prepareArguments ? opts.prepareArguments(args) : args) as never,
+				execute: async (_toolCallId, input) => {
+					submitted = opts.fill(input);
+					return toToolResult(submitted);
+				},
+			} satisfies AgentTool<any>,
+		],
+		{
+			role: opts.role,
+			engine: opts.engine,
+			systemPrompt: opts.systemPrompt,
+			prompt: opts.prompt,
+			maxTurns: opts.maxTurns ?? 4,
+			abortSignal: opts.signal,
+			onAssistantMessage: (message, step) =>
+				opts.onStep(
+					message.usage,
+					// Provider-qualified stamp (model slots wave, 2026-09-20):
+					// pi reports the bare id; usage stamps carry provider:id to
+					// match the price table's uniform keys.
+					`${message.provider}:${message.model}`,
+					step,
+					message.stopReason,
+					message.content.filter((c) => c.type === "toolCall").map((c) => (c as { name: string }).name).join(", ") || "(none)",
+				),
+			shouldStop: (_message, toolResults) => toolResults.some((r) => r.toolName === opts.toolName && !r.isError),
+		},
+	);
+	void result;
+	if (!submitted) throw new Error(opts.neverSubmitted);
+	return submitted;
+}

src/core/settings.ts

@@ -226,6 +226,12 @@ export const ROLE_SLOT: Readonly<Record<ModelRole, ModelSlotName>> = {
 	auditor: "cheap",
 	visualMaker: "vision",
 	pdfReader: "vision",
+	// The practice trio (2026-09-29): problem engineering is the product's
+	// quality-critical component — strong tier for partitioner/generator/
+	// grader alike (owner-approved plan default; one edit away from cheap).
+	partitioner: "strong",
+	problemGenerator: "strong",
+	grader: "strong",
 };
 
 /** General settings — app-level behavior. Version DISPLAY and plans login