practice round: dead session starts, prompt laws, preamble, label unify

THE START BUG (owner report, reproduced live both kinds): new sessions
(?prompt flow — practice and teach alike) sat dead until a second
message, which then persisted WITHOUT the first. Root cause, proven
both directions: the submit POST rode the view's consumeAbort
controller; React StrictMode's simulated remount fires Diet A's
unmount cleanup (model.stop()) ~8ms in and killed the POST mid-flight;
the page's sentInitial guard had already flipped, so it never retried.
Teach was equally broken — only unnoticed, because every teach chat in
use predates the diet and practice starts are always fresh. Fix: the
submit law — POSTs are not abortable by view teardown (they are ~100ms
acks since Diet B and cannot starve the pool); after the ack, a
consumeAbort identity check guards the stream attach. Pinned with the
stop-mid-submit regression test. Live: StrictMode on, practice draft
POST 200/67ms, stream attached, message persisted, problem posed.

PRACTICE PROMPT (00-base): the opening rule — material arrives two
ways, both first-class (picked propositions primary; free-form —
topics, course material, files/PDFs — fully supported, never refused);
as soon as material exists the reply poses, at most one short line
before the problem call, no warm-up interview. Plus the hard law: no
problem is ever conversation — every problem through the tool (no
thinking field/no reveal/no verdict attaches to prose).

GRAPH-CONTEXT PREAMBLE: custom markers flatten to user-role on the
wire, so the old "Contextualization — the learner picked…" read like a
system broadcast in the learner's voice channel. Now the bracket
convention: "[Session context] — picked from the learner's knowledge
map…".

SIDEBAR: busy rows unify to "Working…" for both kinds (the spinner's
default label included); "Practicing…"/"Teacher is working…" retired.

Gates: 1490/1490, typecheck, lint. doctrine's stale doc pointer fixed.

components/braille-spinner.tsx

@@ -36,7 +36,7 @@ export const SPINNER_FRAMES = FRAMES.length;
 
 export function BrailleSpinner({
 	className,
-	label = "Teacher is working",
+	label = "Working",
 }: {
 	/** Sizing/position classes; height drives the scale (width is the cell's 1:2 aspect). */
 	className?: string;

components/session-core.ts

@@ -561,8 +561,19 @@ export class SessionModel {
 			this.tail = [...this.tail, ...optimistic];
 		});
 		try {
-			const res = await this.postInputEvent(input, controller.signal);
-			if (controller.signal.aborted) return;
+			// SUBMITS ARE NOT ABORTABLE BY VIEW TEARDOWN (owner, 2026-10-10 —
+			// the dead-session-start postmortem): the POST must NOT ride
+			// consumeAbort. Diet A's abort-on-unmount (session.ts's stop())
+			// fires on React StrictMode's simulated remount in dev — it killed
+			// the ?prompt first send ~8ms in (POST aborted, never retried:
+			// the page's sentInitial guard had already flipped), leaving the
+			// session dead until a second message, which then persisted
+			// WITHOUT the first — the optimistic tail rode a record that never
+			// contained it. The POST is a ~100ms ack since Diet B; it cannot
+			// starve the connection pool, so it needs no teardown guard. The
+			// STREAM consume stays on the controller — releasing that held
+			// connection is Diet A's whole job.
+			const res = await this.postInputEvent(input);
 			if (res.status === 409) {
 				this.setError("A turn is already running — try again in a moment.");
 				this.setStatus("error");
@@ -582,6 +593,10 @@ export class SessionModel {
 			// replay lands on top). One live view connection per page, always —
 			// the browser's 6-per-origin pool is the scarce resource.
 			await res.text().catch(() => {}); // drain the tiny ack; release the socket
+			// A stop() or a newer send/consume won while the ack was in
+			// flight: the turn is live server-side either way — do not attach
+			// a stream from a view that is gone or superseded.
+			if (this.consumeAbort !== controller) return;
 			await this.resumeStream(true);
 		} catch (err) {
 			if ((err as Error).name === "AbortError") return; // stop() or a newer consume won

components/sidebar.tsx

@@ -248,7 +248,7 @@ function sessionMeta(chat: ChatListItem): string {
 	if ((chat.kind ?? "teach") === "practice" && chat.pendingProblem) {
 		return `Problem waiting · ${timeAgo(chat.updatedAt)}`;
 	}
-	if (chat.busy) return (chat.kind ?? "teach") === "practice" ? "Practicing…" : "Teacher is working…";
+	if (chat.busy) return "Working…";
 	return timeAgo(chat.updatedAt);
 }