fix: the knowledge-context slider is a discrete 6-stop scale — off, then powers of four from 64

The continuous 0-4096 dial was precision theater (a 128-token budget is
~2 propositions; nobody wants that granularity). Decided stops (owner,
2026-09-15): 0 / 64 / 256 / 1024 / 4096 / 16384 — the native range walks
positions 0-5 and maps through GRAPH_CONTEXT_TOKENS_STOPS in contracts.
Max rises to 16384 (route range follows); the server still accepts any
integer in range so a stale client cannot brick settings; non-stop
legacy values snap to the nearest stop for the thumb, readout stays
honest.

components/graph-context-control.tsx

@@ -3,8 +3,8 @@
 import { BookOpenIcon } from "lucide-react";
 import {
 	GRAPH_CONTEXT_TOKENS_DEFAULT,
-	GRAPH_CONTEXT_TOKENS_MAX,
+	GRAPH_CONTEXT_TOKENS_STOPS,
-	GRAPH_CONTEXT_TOKENS_STEP,
+	type ChatSettings,
 } from "@/src/core";
 
 /**
@@ -17,13 +17,15 @@ import {
  * session contributed to the graph asks first what the graph will
  * contribute to the session.
  *
- * One quiet compact row sized to sit in the stats band beside the model +
+ * A DISCRETE 6-position slider (owner, 2026-09-15): off, then powers of four
- * thinking pills: short slider, "tok" readout, the FULL number (owner,
+ * from 64 — a continuous 0–4096 dial was precision theater (a 128-token
- * 2026-09-15: no k-rounding — 1024 reads as 1024). 0 = off; absent settings
+ * budget is ~2 propositions). The native range input walks positions 0–5
- * show the DEFAULT (1024 — on). The value rides ChatSettings (the same
+ * and maps through GRAPH_CONTEXT_TOKENS_STOPS; every stop is a real
- * lifted settings the model picker uses), so it persists pre-chat via the
+ * decision. Non-stop values from a stale client snap to the nearest stop
- * same deferred PUT. Sessions never show this control — the injection is
+ * for display. The readout shows the FULL number (no k-rounding). The
- * one-shot at session start, so mid-session there is nothing to decide.
+ * value rides ChatSettings (the same lifted settings the model picker
+ * uses), so it persists pre-chat via the same deferred PUT. Sessions
+ * never show this control — the injection is one-shot at session start.
  */
 export function GraphContextControl({
 	value,
@@ -34,6 +36,12 @@ export function GraphContextControl({
 	onChange: (tokens: number) => void;
 	testId?: string;
 }) {
+	// Snap for display only: a legacy non-stop value shows its nearest stop
+	// and the next drag lands on a real one.
+	const stop = nearestStop(value);
+	// indexOf on a readonly tuple rejects a plain number; the snap above
+	// always yields a member, so the cast is honest.
+	const index = (GRAPH_CONTEXT_TOKENS_STOPS as readonly number[]).indexOf(stop);
 	return (
 		<div data-testid={testId} className="flex items-center gap-2 text-xs text-muted-foreground">
 			<BookOpenIcon className="size-3 shrink-0" />
@@ -41,16 +49,19 @@ export function GraphContextControl({
 			<input
 				type="range"
 				min={0}
-				max={GRAPH_CONTEXT_TOKENS_MAX}
+				max={GRAPH_CONTEXT_TOKENS_STOPS.length - 1}
-				step={GRAPH_CONTEXT_TOKENS_STEP}
+				step={1}
-				value={value}
+				value={index}
-				onChange={(e) => onChange(Number(e.target.value))}
+				onChange={(e) => {
+					const next = (GRAPH_CONTEXT_TOKENS_STOPS as readonly number[])[Number(e.target.value)];
+					if (next !== undefined) onChange(next);
+				}}
 				aria-label="Prior-knowledge token budget"
 				className="h-1 w-24 shrink-0 accent-primary"
 				data-testid="graph-context-slider"
 			/>
 			<span
-				className="w-14 shrink-0 tabular-nums"
+				className="w-16 shrink-0 tabular-nums"
 				data-testid="graph-context-value"
 			>
 				{value === 0 ? "off" : `${value} tok`}
@@ -59,9 +70,20 @@ export function GraphContextControl({
 	);
 }
 
+/** The nearest stop to any budget value (display snapping). */
+export function nearestStop(value: number): number {
+	let best: number = GRAPH_CONTEXT_TOKENS_STOPS[0] ?? 0;
+	for (const s of GRAPH_CONTEXT_TOKENS_STOPS) {
+		if (Math.abs(s - value) < Math.abs(best - value)) best = s;
+	}
+	return best;
+}
+
 /** The control's effective value for a chat's settings — absent = the
  *  default (on), never 0: the decided default is a modest slice of prior
  *  knowledge for every fresh session. */
-export function effectiveContextTokens(settings: { graphContextTokens?: number } | undefined): number {
+export function effectiveContextTokens(
+	settings: Pick<ChatSettings, "graphContextTokens"> | undefined,
+): number {
 	return settings?.graphContextTokens ?? GRAPH_CONTEXT_TOKENS_DEFAULT;
 }

src/core/contracts/chat.ts

@@ -68,12 +68,17 @@ export interface ChatSettings {
 	graphContextTokens?: number;
 }
 
-/** The injection budget's decided knobs (2026-09-14): default 1024 (a
+/** The injection budget's decided knobs (2026-09-14; scale revised
- *  meaningful, modest slice of prior knowledge), hard max 4096, slider
+ *  2026-09-15, owner): default 1024 (a meaningful, modest slice of prior
- *  step 128, 0 = off. */
+ *  knowledge), hard max 16384, 0 = off. The UI is a DISCRETE slider over
+ *  these stops — powers of four from 64 (the fine-grained low end was
+ *  theater: a 128-token budget is ~2 propositions, nobody wants that
+ *  dial); the server still accepts any integer in range (a stale client
+ *  can't brick settings), the stops only govern what the slider sends. */
 export const GRAPH_CONTEXT_TOKENS_DEFAULT = 1024;
-export const GRAPH_CONTEXT_TOKENS_MAX = 4096;
+export const GRAPH_CONTEXT_TOKENS_MAX = 16384;
-export const GRAPH_CONTEXT_TOKENS_STEP = 128;
+/** The slider's positions, left to right: off, then powers of four. */
+export const GRAPH_CONTEXT_TOKENS_STOPS = [0, 64, 256, 1024, 4096, 16384] as const;
 
 // ─── Background-extraction usage (the money channel, extraction side) ────────
 

tests/graph-context-core.test.ts

@@ -13,7 +13,7 @@ import {
 	steerDelivered,
 	GRAPH_CONTEXT_TOKENS_DEFAULT,
 	GRAPH_CONTEXT_TOKENS_MAX,
-	GRAPH_CONTEXT_TOKENS_STEP,
+	GRAPH_CONTEXT_TOKENS_STOPS,
 	graphContextText,
 	type GraphContextData,
 } from "../src/core/contracts.ts";
@@ -279,10 +279,12 @@ describe("the runner's pure gates", () => {
 		assert.equal(effectiveContextBudget({ graphContextTokens: 2048 }), 2048);
 	});
 
-	it("the decided knobs: default 1024, max 4096, step 128", () => {
+	it("the decided knobs: default 1024, max 16384, discrete powers-of-four stops from 64", () => {
 		assert.equal(GRAPH_CONTEXT_TOKENS_DEFAULT, 1024);
-		assert.equal(GRAPH_CONTEXT_TOKENS_MAX, 4096);
+		assert.equal(GRAPH_CONTEXT_TOKENS_MAX, 16384);
-		assert.equal(GRAPH_CONTEXT_TOKENS_STEP, 128);
+		// The scale revision (owner, 2026-09-15): off then powers of four —
+		// every stop a real decision, no fine-grained dial theater.
+		assert.deepEqual([...GRAPH_CONTEXT_TOKENS_STOPS], [0, 64, 256, 1024, 4096, 16384]);
 	});
 
 	it("contextToolCallId is deterministic per chat (the one-shot dedup key)", () => {

tests/render-new-session.test.tsx

@@ -102,8 +102,10 @@ describe("DraftShell — the sessionless surface", () => {
 			html.indexOf('data-testid="stats-bar"') < html.indexOf('data-testid="graph-context-control"'),
 			"the slider is the stats bar's left slot",
 		);
-		// The slider's default position: 1024 of 4096, step 128 (decided).
+		// The DISCRETE slider (owner, 2026-09-15): 6 positions (off + powers of
-		assert.ok(html.includes('min="0"') && html.includes('max="4096"') && html.includes('step="128"'));
+		// four from 64), not a continuous 0-4096 dial.
+		assert.ok(html.includes('min="0"') && html.includes('max="5"') && html.includes('step="1"'));
+		assert.ok(html.includes('value="3"'), "default 1024 = stop index 3");
 		// The readout: "tok" abbreviated, but the FULL number (owner, 2026-09-15:
 		// no k-rounding — 1024 reads as 1024).
 		assert.ok(html.includes("1024 tok"), "the readout shows the default budget, not 0 — default is ON");