practice — discretized parameter axes: named levels, never a number (owner-approved 2026-09-29)

Contracts: LadderRung 0-4, CueDistance 0-2, Presentation theory|
application; PracticeParams carries the three named levels. Doc
comments hold the three definition tables verbatim (rung names +
definitions from the ladder doctrine; cue levels; presentation
levels).

Core: LADDER_RUNGS/CUE_LEVELS/PRESENTATIONS tables in src/core/
practice.ts (definitions verbatim) — ONE source spoken by the agents'
prompts, the dialog's stepped controls, and the exam header; core
barrel re-exports practice.ts (pure domain, browser-safe).

Agents: Part I's ladder intro now 'five rungs, numbered; the request
arrives as a rung' with bullets numbered 0-4 (definitions untouched);
Part III's parameters block replaced with the named-level doctrine
(rung = exact class, no continuum; cue counts lesson examples AND
previous problems' situations; presentation dresses, never changes);
partitioner's RESPECT THE PARAMETERS replaced (low rungs = many small
assignments, high = larger; far cue makes confusables-together MORE
important; presentation does not shape the partition). renderParams
outputs the exact named-level block. Anchor/0..1 language swept dead.

Service + store: strict union validation — floats between levels,
out-of-range, wrong strings, legacy dial shapes all 400 at the API
and fail isProblemSet (legacy sets skipped from lists; no migration —
data/practice is disposable scratch, owner wipes before testing).

UI: dialog = 5-detent ladder slider + 3-detent cue slider (each shows
the level NAME + one-line definition) + Theory|Application segmented
toggle; defaults rung 2 / cue 1 / theory; Create posts the new shape.
Exam header gains the levels line ('Direct exercise · Adjacent
context · Theory').

Tests: renderParams exact-block pin; strict-validation pins (new
tests/practice-service.test.ts — bad unions 400, legacy shape 400);
store pins (legacy floats + 2.5 rung fail); render pins (detents +
names + definitions, defaults, detent-swap, toggle active segment,
levels line); every params fixture moved off floats. 1138/1138, tsc
0, lint 0, build 0.

Docs: architecture.md — discretization paragraph (compact tables,
named-level invocation, defaults, one-table source), UI mentions;
README axes sentence.

src/server/practice.ts

@@ -41,10 +41,13 @@ export function getPracticeSet(id: string): ProblemSet | null {
 function parseParams(raw: unknown): PracticeParams | null {
 	if (typeof raw !== "object" || raw === null) return null;
 	const p = raw as Record<string, unknown>;
-	const dial = (v: unknown): v is number => typeof v === "number" && Number.isFinite(v) && v >= 0 && v <= 1;
-	if (!dial(p.searchSolutionRatio) || !dial(p.cueDistance) || !dial(p.presentation)) return null;
+	// Named levels ONLY (owner, 2026-09-29): exact unions, nothing between —
+	// a rung is a rung; there is no float to interpolate.
+	if (p.ladderRung !== 0 && p.ladderRung !== 1 && p.ladderRung !== 2 && p.ladderRung !== 3 && p.ladderRung !== 4) return null;
+	if (p.cueDistance !== 0 && p.cueDistance !== 1 && p.cueDistance !== 2) return null;
+	if (p.presentation !== "theory" && p.presentation !== "application") return null;
 	return {
-		searchSolutionRatio: p.searchSolutionRatio,
+		ladderRung: p.ladderRung,
 		cueDistance: p.cueDistance,
 		presentation: p.presentation,
 	};
@@ -88,7 +91,7 @@ export async function createPracticeSetResponse(body: unknown): Promise<Response
 	const params = parseParams(b.params);
 	if (!params) {
 		return Response.json(
-			{ error: "params must carry searchSolutionRatio, cueDistance, presentation as numbers in [0,1]" },
+			{ error: "params must carry ladderRung (0-4), cueDistance (0-2), presentation (theory|application) as exact levels" },
 			{ status: 400 },
 		);
 	}