Merge PR #154 short opening URLs and recoverable prompt handoff

components/chat.tsx

@@ -26,6 +26,7 @@ import { Composer } from "@/components/composer";
 import { useEnterSubmits } from "@/components/enter-submits";
 import { blurAfterPointerClick } from "@/components/focus-hygiene";
 import { dockStateKey } from "@/components/dock-state-key";
+import { clearOpeningPrompt, readOpeningPromptEntry, stashOpeningPrompt, OPENING_PROMPT_FAILURE } from "@/components/opening-prompt";
 import { forwardDockWheel, useDockHeight } from "@/components/dock-height";
 import { QueuedSteersBody, type QueuedSteerLine } from "@/components/queued-steers";
 import { DictationBar, finishDictation, joinDictation, useDictation } from "@/components/dictation";
@@ -251,7 +252,7 @@ export function Chat({
 	// (core/view.ts projectView); sends are ONE explicit input event each
 	// ({chatId, input} — the stash indirection died with the SDK), and the
 	// turn stream is the VERBATIM AgentEvent passthrough the server emits.
-	const { messages, nativeMessages, contextTokens, send, continueIfOwed, steer, steerQueue, submitAnswer, dismissQuestion, dismissProblem, questionDraft, saveQuestionDraft, setMessages, adoptRecord, status, error, stop, clearError, resumeStream, setReattachSettled } =
+	const { messages, nativeMessages, hasConfirmedConversation, contextTokens, send, continueIfOwed, steer, steerQueue, submitAnswer, dismissQuestion, dismissProblem, questionDraft, saveQuestionDraft, setMessages, adoptRecord, status, error, stop, clearError, resumeStream, setReattachSettled } =
 		useChatSession({ chatId, initialMessages, initialError, initiallyInFlight });
 
 	const sessionFindScopeRef = useRef<HTMLDivElement | null>(null);
@@ -261,16 +262,6 @@ export function Chat({
 	// The reattach settled terminal → the sync-and-continue seam (below).
 	setReattachSettled(() => reattachSettledRef.current());
 
-	// New chat with a topic: send the first message exactly once
-	// (initialPromptOwed — the pure gate, pinned in the test suite).
-	const sentInitial = useRef(false);
-	useEffect(() => {
-		if (!sentInitial.current && initialPromptOwed(initialMessages, initialPrompt)) {
-			sentInitial.current = true;
-			void send({ type: "text", text: initialPrompt! });
-		}
-	}, [initialPrompt, initialMessages, send]);
-
 	// A turn running server-side, attached to no live view of ours (navigate
 	// away mid-turn, or a wake turn discovered mid-session): the reattach
 	// stream is the primary channel (resumeStream — the same rendering path
@@ -579,6 +570,66 @@ export function Chat({
 	 *  Auto-continuations (probe answers) never set it — their refusal
 	 *  opens recovery with no replay. */
 	const draftRef = useRef<string | null>(null);
+	const openingDraftRef = useRef<string | null>(null);
+	const [openingError, setOpeningError] = useState(false);
+	const openingMountedRef = useRef(false);
+	useEffect(() => {
+		openingMountedRef.current = true;
+		return () => { openingMountedRef.current = false; };
+	}, []);
+
+	const deliverOpeningPrompt = useCallback((prompt: string) => {
+		openingDraftRef.current = prompt;
+		// Persist uncertainty BEFORE the POST: another mount must restore,
+		// not race the still-arriving request. No storage means no auto-send.
+		if (!stashOpeningPrompt(chatId, prompt, true)) {
+			applyText(prompt);
+			setOpeningError(true);
+			return;
+		}
+		setOpeningError(false);
+		draftRef.current = prompt; // The existing 503 flow must restore it too.
+		applyText("");
+		void send({ type: "text", text: prompt }, () => {
+			clearOpeningPrompt(chatId);
+			openingDraftRef.current = null;
+			if (draftRef.current === prompt) draftRef.current = null;
+		}).then(accepted => {
+			if (!accepted && openingMountedRef.current && openingDraftRef.current === prompt && !textRef.current) {
+				applyText(prompt);
+			}
+		});
+	}, [chatId, send, applyText]);
+
+	const sentInitial = useRef(false);
+	useEffect(() => {
+		if (sentInitial.current) return;
+		sentInitial.current = true;
+		const entry = readOpeningPromptEntry(chatId);
+		const prompt = initialPrompt || entry?.text; // Legacy links still work.
+		if (!initialPromptOwed(initialMessages, prompt)) {
+			if (initialMessages.some(m => m.role === "user" || m.role === "assistant")) clearOpeningPrompt(chatId);
+			return;
+		}
+		openingDraftRef.current = prompt!;
+		if (entry?.attempted || initiallyInFlight) {
+			applyText(prompt!); // Interrupted start: the learner explicitly resends.
+			return;
+		}
+		deliverOpeningPrompt(prompt!);
+	}, [chatId, initialPrompt, initialMessages, initiallyInFlight, deliverOpeningPrompt, applyText]);
+
+	useEffect(() => {
+		if (!hasConfirmedConversation) return;
+		clearOpeningPrompt(chatId);
+		// A later canonical read may confirm a lost acknowledgment. Clear
+		// only the unchanged recovered draft, never the learner's newer work.
+		const opening = openingDraftRef.current;
+		if (opening !== null && textRef.current === opening) applyText("");
+		if (draftRef.current === opening) draftRef.current = null;
+		openingDraftRef.current = null;
+		setOpeningError(false);
+	}, [chatId, hasConfirmedConversation, applyText]);
 
 	// THE BYOK REFUSAL (owner, 2026-09-22): a send that lands the server's
 	// 503 models_not_configured envelope renders as the SETUP FLOW, never
@@ -1161,6 +1212,10 @@ export function Chat({
 			openModelPicker();
 			return; // No optimistic send and no change to the learner's draft.
 		}
+		if (openingDraftRef.current !== null) {
+			deliverOpeningPrompt(t);
+			return;
+		}
 		draftRef.current = t; // the refusal flow's preserve-and-replay seam
 		applyText("");
 		void send({ type: "text", text: t });
@@ -1592,6 +1647,7 @@ export function Chat({
 									</Shimmer>
 								</span>
 							)}
+							{openingError && <p role="alert" className="text-sm text-destructive">{OPENING_PROMPT_FAILURE}</p>}
 							{error && (
 								<div className="flex items-center justify-between gap-3 rounded-lg border border-destructive/50 bg-destructive/10 px-3 py-2 text-sm">
 									<span>Something went wrong: {error.message}</span>
@@ -1779,7 +1835,8 @@ export function Chat({
  *  2026-10-02 abort chain proper (question before turn). */
 export type EscAbortTarget = "mermaid" | "plan" | "setup" | "question" | "problem" | "turn" | null;
 	/**
- * Does the ?prompt topic still owe its first send? The gate is "no real
+ * Does the opening topic still owe its first send? The topic is the
+ * server's ?prompt= or the sessionStorage stash. The gate is "no real
  * conversation yet" (no user/assistant message) — NOT emptiness: a
  * session started with map picks carries a graph-context MARKER as
  * message[0], and that scaffolding must never swallow the first send

components/home.tsx

@@ -12,6 +12,8 @@ import { DictationBar, joinDictation, useDictation } from "@/components/dictatio
 import { useFieldCycle } from "@/components/field-cycle";
 import { SidebarToggle } from "@/components/sidebar";
 import { StatsBar } from "@/components/stats-bar";
+import { OPENING_PROMPT_FAILURE } from "@/components/opening-prompt";
+import { SessionStarter } from "@/components/start-session";
 import type { TurnUsage } from "@/src/core";
 
 /**
@@ -56,6 +58,9 @@ export function Home({
 		},
 	});
 	const [busy, setBusy] = useState(false);
+	const startingRef = useRef(false);
+	const starterRef = useRef(new SessionStarter());
+	const [startError, setStartError] = useState(false);
 	/* Run end focuses the topic input (owner, 2026-10-01): the hands are on
 	 * the keyboard from the stop. Falling edge only; this surface's only
 	 * dictation target IS this textarea, so no case-split is needed. */
@@ -105,7 +110,7 @@ export function Home({
 	};
 	const begin = async () => {
 		const t = topicRef.current.trim();
-		if (!t || busy) return;
+		if (!t || startingRef.current) return;
 		// Unconfigured: the send INTERCEPTS into the setup flow (the draft
 		// stays in the textarea; the learner sends it after Save).
 		if (!configured) {
@@ -128,29 +133,25 @@ export function Home({
 			openModelPicker();
 			return; // Preserve the draft and never create an orphan session.
 		}
+		startingRef.current = true;
 		setBusy(true);
+		setStartError(false);
 		try {
 			// The map context (owner, 2026-10-04): picks in EITHER mode ride
 			// the CREATION as graphContext — the server writes a
 			// graph-context marker as message[0] (a separate custom message
 			// before the learner's first user message, propositions + the
 			// chains among them); the prompt stays the learner's own words.
-			const res = await fetch("/api/chats", {
-				method: "POST",
-				headers: { "Content-Type": "application/json" },
-				body: JSON.stringify({
-					title: t,
-					...(mode === "practice" ? { kind: "practice" } : {}),
-					...(practiceProps.length > 0 ? { graphContext: { propositions: practiceProps } } : {}),
-				}),
-			});
-			const { id } = (await res.json()) as { id: string };
-			// No settings PUT on create (per-session models, owner
-			// 2026-09-28): the SERVER stamps the newborn from the strong
-			// slot — the same default this surface's model control edits.
-			router.push(`/chat/${id}?prompt=${encodeURIComponent(t)}`);
+			const target = await starterRef.current.start({
+				title: t,
+				...(mode === "practice" ? { kind: "practice" } : {}),
+				...(practiceProps.length > 0 ? { graphContext: { propositions: practiceProps } } : {}),
+			}, fetch, JSON.stringify(catalog?.slots.strong));
+			router.push(target);
 		} catch {
+			startingRef.current = false;
 			setBusy(false);
+			setStartError(true);
 		}
 	};
 
@@ -239,6 +240,7 @@ export function Home({
 							)
 						)}
 					/>
+					{startError && <p role="alert" className="mb-2 text-sm text-destructive">{OPENING_PROMPT_FAILURE}</p>}
 					<form
 						className="flex items-end gap-1.5 rounded-2xl border bg-card p-1.5 shadow-lg"
 					onSubmit={(e) => {

components/new-session.tsx

@@ -12,6 +12,8 @@ import { useModelSetup, selectedModelUnavailable, openModelPicker, ZeroKeysPill
 import { StatsBar } from "@/components/stats-bar";
 import { ChainTableOverlay } from "@/components/chain-table.tsx";
 import { ComposerActions, NodePickerControl } from "@/components/composer-actions";
+import { OPENING_PROMPT_FAILURE } from "@/components/opening-prompt";
+import { SessionStarter } from "@/components/start-session";
 import type { ChatSettings, GraphSnapshot } from "@/src/core";
 
 /** The draft's pick set (owner round 10): the SAME shape the home pick
@@ -33,18 +35,18 @@ export type DraftPick = { id: string; name: string; statement: string };
 const DOCK = "mx-auto w-full max-w-[46rem] px-4";
 
 /**
- * The draft's whole behavior as one pure seam: create the session (title =
- * the first message), persist the lifted pre-chat settings, return the push
- * target — /chat/<id>?prompt=<msg> — whose initialPrompt path delivers the
- * message as turn 1. Injected fetch/router so tests pin the contract.
- * Returns null on empty text; rethrows on transport failure (the caller's
- * busy flag resets).
+ * Create, safely hand over the full opening text, then return a short
+ * /chat/<id> target. Storage/creation failures leave the caller's draft
+ * intact. A per-composer starter reuses an already-created session on an
+ * unchanged retry. The server stamps settings at birth; no settings PUT.
  */
 export async function startDraftSession(
 	text: string,
 	fetchLike: typeof fetch,
 	mode?: "practice",
 	picks?: readonly DraftPick[],
+	starter = new SessionStarter(),
+	settingsIdentity?: string,
 ): Promise<string | null> {
 	const t = text.trim();
 	if (!t) return null;
@@ -52,19 +54,13 @@ export async function startDraftSession(
 	// from the pick bar creates its session WITH the graph context — the
 	// same contract as the home screen's practice send (the marker with
 	// [id] name: statement lines, target validation's truth set).
-	const res = await fetchLike("/api/chats", {
-		method: "POST",
-		headers: { "Content-Type": "application/json" },
-		body: JSON.stringify(
-			mode === "practice"
-				? { title: t, kind: "practice", ...(picks && picks.length > 0 ? { graphContext: { propositions: picks } } : {}) }
-				: { title: t },
-		),
-	});
-	const { id } = (await res.json()) as { id: string };
-	// No settings PUT on create (per-session models, owner 2026-09-28):
-	// the SERVER stamps the newborn from the strong slot.
-	return `/chat/${id}?prompt=${encodeURIComponent(t)}`;
+	return starter.start(
+		mode === "practice"
+			? { title: t, kind: "practice", ...(picks && picks.length > 0 ? { graphContext: { propositions: picks } } : {}) }
+			: { title: t },
+		fetchLike,
+		settingsIdentity,
+	);
 }
 
 /** The pure shell (no router) — the render-test seam: the draft view's
@@ -77,6 +73,7 @@ export function DraftShell({
 	text,
 	onChange,
 	onSend,
+	startError = false,
 	setupCta,
 	mode = "teach",
 	picks = [],
@@ -88,6 +85,7 @@ export function DraftShell({
 	text: string;
 	onChange: (v: string) => void;
 	onSend: () => void;
+	startError?: boolean;
 	/** The practice draft (owner, 2026-10-04): ?mode=practice — the
 	 *  created session carries kind:"practice" and the copy changes
 	 *  (the practice agent opens; no probing). */
@@ -190,6 +188,7 @@ export function DraftShell({
 									)}
 									setup={setupCta}
 								/>
+								{startError && <p role="alert" className="pointer-events-auto mb-2 text-sm text-destructive">{OPENING_PROMPT_FAILURE}</p>}
 								<div className="pointer-events-auto overflow-hidden rounded-2xl border bg-card shadow-lg">
 									<Composer
 										busy={busy}
@@ -243,6 +242,9 @@ export function NewSession({ initialConfigured, mode = "teach" }: { initialConfi
 		setText(v);
 	};
 	const [busy, setBusy] = useState(false);
+	const startingRef = useRef(false);
+	const starterRef = useRef(new SessionStarter());
+	const [startError, setStartError] = useState(false);
 	// THE PICK BAR (owner round 10): the draft's lifted pick set + the
 	// snapshot the standalone chain-table picker reads. Lazy — the graph
 	// is fetched on FIRST open only, then reused.
@@ -280,7 +282,7 @@ export function NewSession({ initialConfigured, mode = "teach" }: { initialConfi
 
 	const send = useCallback(() => {
 		const draft = textRef.current.trim();
-		if (!draft || busy) return;
+		if (!draft || startingRef.current) return;
 		if (!configured) {
 			setSetupOpen(true);
 			return;
@@ -300,19 +302,27 @@ export function NewSession({ initialConfigured, mode = "teach" }: { initialConfi
 			openModelPicker();
 			return; // The learner replaces it explicitly, then sends again.
 		}
+		startingRef.current = true;
 		setBusy(true);
-		void startDraftSession(draft, fetch, mode === "practice" ? "practice" : undefined, mode === "practice" ? picksRef.current : undefined)
+		setStartError(false);
+		void startDraftSession(draft, fetch, mode === "practice" ? "practice" : undefined, mode === "practice" ? picksRef.current : undefined,
+			starterRef.current, JSON.stringify(catalog?.slots.strong))
 			.then((target) => {
 				if (target) router.push(target);
-				else setBusy(false);
+				else { startingRef.current = false; setBusy(false); }
 			})
-			.catch(() => setBusy(false));
-	}, [busy, router, configured, zeroKeys, catalog]);
+			.catch(() => {
+				startingRef.current = false;
+				setBusy(false);
+				setStartError(true);
+			});
+	}, [router, configured, zeroKeys, catalog, mode]);
 
 	return (
 		<>
 			<DraftShell
 				busy={busy}
+				startError={startError}
 				text={text}
 				onChange={applyText}
 				onSend={send}

components/opening-prompt.ts

@@ -0,0 +1,59 @@
+/**
+ * Same-tab handover of a new session's full opening text. Never put the
+ * message in the navigation URL: long query payloads can be rejected before
+ * the chat page loads. Storage is required for automatic delivery, not an
+ * optional best-effort side effect of navigating away from the source draft.
+ */
+export const OPENING_PROMPT_FAILURE = "Couldn’t open the session. Your message is still here. Try sending again.";
+
+export interface OpeningPrompt {
+	text: string;
+	/** Written BEFORE sending. A later mount restores a draft, never reposts. */
+	attempted: boolean;
+}
+
+const keyFor = (id: string) => `lh.openingPrompt.${id}`;
+
+export function stashOpeningPrompt(id: string, text: string, attempted = false): boolean {
+	try {
+		const value = JSON.stringify({ text, attempted } satisfies OpeningPrompt);
+		// Catch both the storage getter and its methods (quota/security errors).
+		const storage = globalThis.sessionStorage;
+		storage.setItem(keyFor(id), value);
+		return storage.getItem(keyFor(id)) === value;
+	} catch {
+		return false;
+	}
+}
+
+export function readOpeningPromptEntry(id: string): OpeningPrompt | undefined {
+	try {
+		const value = globalThis.sessionStorage.getItem(keyFor(id));
+		if (!value) return undefined;
+		try {
+			const entry: unknown = JSON.parse(value);
+			if (entry && typeof entry === "object" && "text" in entry && typeof entry.text === "string" &&
+				entry.text.length > 0 && "attempted" in entry && typeof entry.attempted === "boolean") {
+				return { text: entry.text, attempted: entry.attempted };
+			}
+		} catch { /* Old raw-text stashes have no proof that sending never began. */ }
+		return { text: value, attempted: true };
+	} catch {
+		return undefined;
+	}
+}
+
+export function readOpeningPrompt(id: string): string | undefined {
+	return readOpeningPromptEntry(id)?.text;
+}
+
+export function clearOpeningPrompt(id: string): boolean {
+	try {
+		globalThis.sessionStorage.removeItem(keyFor(id));
+		return true;
+	} catch {
+		// Canonical conversation/acknowledgment remains the truth. A later
+		// mount with real conversation can try cleanup again; never crash it.
+		return false;
+	}
+}

components/session-core.ts

@@ -180,6 +180,8 @@ function sameDetails(a: unknown, b: unknown): boolean {
 export interface SessionState {
 	messages: LhViewMessage[];
 	nativeMessages: LhMessage[];
+	/** Server-read history only; optimistic bubbles are not delivery proof. */
+	hasConfirmedConversation: boolean;
 	/** Completed conversation usage; null after compaction or before first usage. */
 	contextTokens: number | null;
 	status: SessionStatus;
@@ -257,6 +259,9 @@ export class SessionModel {
 	// The single live consume (POST response or reattach stream): a newer
 	// consume cancels the older — one reader at a time.
 	private consumeAbort: AbortController | null = null;
+	/** Retain the latest request across stop(): an opening POST still owns
+	 * its refusal after view detachment, but never after a newer request. */
+	private latestRequest: AbortController | null = null;
 	/** Synchronous ready check for the gate (send/read mount logic). */
 	readyRef = true;
 
@@ -299,6 +304,7 @@ export class SessionModel {
 		return {
 			messages: projectView(messages, live),
 			nativeMessages: messages,
+			hasConfirmedConversation: this.base.some(m => m.role === "user" || m.role === "assistant"),
 			contextTokens: measuredContextTokens(messages, this.incompleteUsageIds),
 			status: this.statusValue,
 			error: this.errorValue ?? providerError,
@@ -553,6 +559,7 @@ export class SessionModel {
 		this.consumeAbort?.abort();
 		const controller = new AbortController();
 		this.consumeAbort = controller;
+		this.latestRequest = controller;
 		// REPLAY ONTO A CLEAN SLATE (owner, optimistic round 3, 2026-10-02):
 		// the reattach stream replays the turn from its FIRST event — an
 		// aborted earlier attempt (React StrictMode's simulated remount)
@@ -637,40 +644,41 @@ export class SessionModel {
 	 * POST + consume. Ready-gated: one turn per client at a time (the
 	 * server's 409 + identity retry covers the wake-race window).
 	 */
-	async send(input: ChatInput): Promise<void> {
+	async send(input: ChatInput, onAccepted?: () => void): Promise<boolean> {
 		const recovering = this.statusValue === "error";
-		if (!this.readyRef && !recovering) return;
+		if (!this.readyRef && !recovering) return false;
 		this.consumeAbort?.abort();
 		const controller = new AbortController();
 		this.consumeAbort = controller;
+		this.latestRequest = controller;
 		this.setError(null);
 		this.setStatus("submitted");
 		if (recovering && input.type === "answer") {
 			try {
 				const res = await this.fetch(`/api/chats/${encodeURIComponent(this.chatId)}`, { signal: controller.signal });
-				if (this.consumeAbort !== controller) return;
+				if (this.consumeAbort !== controller) return false;
 				if (!res.ok) throw new Error((await res.text()) || "An error occurred.");
 				const record = await res.json() as { messages?: LhMessage[]; turnInFlight?: boolean; turnError?: string };
-				if (this.consumeAbort !== controller) return;
+				if (this.consumeAbort !== controller) return false;
 				// No verified record/liveness: retain the draft and never guess
 				// whether a lost acknowledgement meant the input was accepted.
 				if (!Array.isArray(record.messages) || typeof record.turnInFlight !== "boolean") throw new Error("An error occurred.");
 				this.setMessages(record.messages, record.turnError);
 				if (record.turnInFlight) {
 					await this.resumeStream(false);
-					return;
+					return false;
 				}
 				if (input.type === "answer" && (answeredCallIds(record.messages).has(input.toolCallId) || danglingQuestionOf(record.messages)?.toolCallId !== input.toolCallId)) {
 					// The call already resolved, or no longer owns the dock. Adopt
 					// truth, never POST that answer a second time.
 					this.setStatus("ready");
-					return;
+					return false;
 				}
 			} catch (err) {
-				if (this.consumeAbort !== controller || controller.signal.aborted) return;
+				if (this.consumeAbort !== controller || controller.signal.aborted) return false;
 				this.setError((err as Error).message);
 				this.setStatus("error");
-				return;
+				return false;
 			}
 		}
 		if (input.type !== "continue") this.automaticContinuationBlocked = false;
@@ -697,6 +705,7 @@ export class SessionModel {
 		if (optimistic.length > 0) this.mutate(() => {
 			this.tail = [...this.tail, ...optimistic];
 		});
+		let accepted = false;
 		try {
 			// SUBMITS ARE NOT ABORTABLE BY VIEW TEARDOWN (owner, 2026-10-10 —
 			// the dead-session-start postmortem): the POST must NOT ride
@@ -727,6 +736,9 @@ export class SessionModel {
 				}
 				throw new Error(message);
 			}
+			accepted = true;
+			// Opening-message handover ends at acceptance, not stream completion.
+			onAccepted?.();
 			// CONNECTION DIET B (owner, 2026-10-10 — parallel-session freeze
 			// postmortem): the POST acknowledges and closes; there is no stream
 			// on this response to consume. Attach through the SAME reattach wire
@@ -738,13 +750,24 @@ export class SessionModel {
 			// 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;
+			if (this.consumeAbort !== controller) return true;
 			await this.resumeStream(true);
+			return true;
 		} catch (err) {
-			if (this.consumeAbort !== controller || controller.signal.aborted) return;
-			// Restore the question when acceptance failed or is unknown. Remove
-			// only THIS optimistic answer, never saved copies/newer live content.
-			// Other input kinds retain their existing optimistic presentation.
+			const failedOpening = input.type === "text" && onAccepted !== undefined && !accepted;
+			if (failedOpening) {
+				// The POST outlives stop(), including StrictMode's cleanup. Remove
+				// only its own failed optimistic bubble even if a newer request
+				// won; never touch canonical messages or another attempt's tail.
+				const ids = new Set(optimistic.map(m => m.id));
+				this.mutate(() => { this.tail = this.tail.filter(m => !ids.has(m.id)); });
+			}
+			const detachedOpening = failedOpening && this.consumeAbort === null && this.latestRequest === controller;
+			if ((this.consumeAbort !== controller || controller.signal.aborted) && !detachedOpening) return accepted;
+			// A detached opening refusal must still reach the replayed mount's
+			// existing setup recovery. A newer send/reattach ALWAYS owns errors
+			// and status instead, even if that request has since been stopped.
+			// Ordinary text and answer teardown behavior stays unchanged.
 			if (input.type === "answer") {
 				const ids = new Set(optimistic.map(m => m.id));
 				this.mutate(() => {
@@ -754,6 +777,10 @@ export class SessionModel {
 			}
 			this.setError((err as Error).message);
 			this.setStatus("error");
+			// true means we observed this POST's acknowledgment. false does
+			// NOT prove non-delivery: a network failure may hide acceptance.
+			// Opening-message callers restore a draft, never automatically retry.
+			return accepted;
 		}
 	}
 
@@ -803,7 +830,7 @@ export class SessionModel {
 	 *  result (fork 1), riding as its input event. */
 	submitAnswer(tool: string, toolCallId: string, output: QuestionAnswerData): Promise<void> {
 		void tool;
-		return this.send({ type: "answer", toolCallId, answer: output });
+		return this.send({ type: "answer", toolCallId, answer: output }).then(() => undefined);
 	}
 
 	/** The dismissal path (owner design 2026-10-03, "A2"): the skipped

components/session.ts

@@ -102,7 +102,7 @@ export function useChatSession({ chatId, initialMessages, initialError, initiall
 		[model],
 	);
 
-	const send = useCallback((input: ChatInput) => void model.send(input), [model]);
+	const send = useCallback((input: ChatInput, onAccepted?: () => void) => model.send(input, onAccepted), [model]);
 	const continueIfOwed = useCallback((record: readonly LhMessage[]) => void model.continueIfOwed(record), [model]);
 	const steer = useCallback((text: string) => void model.steer(text), [model]);
 	const submitAnswer = useCallback(
@@ -129,6 +129,7 @@ export function useChatSession({ chatId, initialMessages, initialError, initiall
 	return {
 		messages: state.messages,
 		nativeMessages: state.nativeMessages,
+		hasConfirmedConversation: state.hasConfirmedConversation,
 		contextTokens: state.contextTokens,
 		status: state.status,
 		error: state.error,

components/start-session.ts

@@ -0,0 +1,34 @@
+import { clearOpeningPrompt, OPENING_PROMPT_FAILURE, stashOpeningPrompt } from "./opening-prompt";
+
+interface SessionCreation {
+	title: string;
+	kind?: "practice";
+	graphContext?: { propositions: readonly { id: string; name: string; statement: string }[] };
+}
+
+/** Per source-composer instance. Retain a successful creation if storage
+ * fails, so an unchanged retry does not create another empty session.
+ * Changed text/context/settings is a different start, not a stale title.
+ */
+export class SessionStarter {
+	private created?: { identity: string; id: string };
+
+	async start(body: SessionCreation, fetchLike: typeof fetch, settingsIdentity?: string): Promise<string> {
+		const identity = JSON.stringify([body, settingsIdentity]);
+		if (this.created?.identity !== identity) {
+			if (this.created) clearOpeningPrompt(this.created.id);
+			this.created = undefined;
+			const res = await fetchLike("/api/chats", {
+				method: "POST",
+				headers: { "Content-Type": "application/json" },
+				body: JSON.stringify(body),
+			});
+			if (!res.ok) throw new Error(OPENING_PROMPT_FAILURE);
+			const result = await res.json() as { id?: unknown };
+			if (typeof result.id !== "string" || !/^[A-Za-z0-9_-]+$/.test(result.id)) throw new Error(OPENING_PROMPT_FAILURE);
+			this.created = { identity, id: result.id };
+		}
+		if (!stashOpeningPrompt(this.created.id, body.title)) throw new Error(OPENING_PROMPT_FAILURE);
+		return `/chat/${this.created.id}`;
+	}
+}

scripts/smoke-opening-prompt.mjs

@@ -0,0 +1,251 @@
+/** Focused synthetic live-UI check. No model/provider calls: /api/chat is
+ * intercepted, catalog is a fixture, app HOME/data/auth are throwaway, and
+ * the browser uses a fresh profile. Creates only synthetic session records.
+ * Run: node scripts/smoke-opening-prompt.mjs
+ */
+import assert from "node:assert/strict";
+import { spawn } from "node:child_process";
+import { once } from "node:events";
+import fs from "node:fs";
+import net from "node:net";
+import { createRequire } from "node:module";
+import os from "node:os";
+import path from "node:path";
+import puppeteer from "puppeteer-core";
+
+const root = path.resolve(import.meta.dirname, "..");
+const home = fs.mkdtempSync(path.join(os.tmpdir(), "lh154-ui-"));
+fs.mkdirSync(path.join(home, "data"));
+fs.writeFileSync(path.join(home, "auth.json"), "{}\n");
+// Next's supported font fixture avoids external font downloads in this check.
+const require = createRequire(import.meta.url);
+const { getFontAxes } = require("next/dist/compiled/@next/font/dist/google/get-font-axes.js");
+const { getGoogleFontsUrl } = require("next/dist/compiled/@next/font/dist/google/get-google-fonts-url.js");
+const fonts = Object.fromEntries(["JetBrains Mono", "Source Sans 3"].map(family => [
+	getGoogleFontsUrl(family, getFontAxes(family, ["variable"], ["normal"]), "swap"),
+	`@font-face { font-family: '${family}'; src: local('Arial'); font-weight: 100 900; }`,
+]));
+fs.writeFileSync(path.join(home, "fonts.cjs"), `module.exports = ${JSON.stringify(fonts)};\n`);
+const listener = net.createServer();
+listener.listen(0, "127.0.0.1");
+await once(listener, "listening");
+const port = listener.address().port;
+await new Promise(resolve => listener.close(resolve));
+const origin = `http://127.0.0.1:${port}`;
+const env = {
+	PATH: process.env.PATH, HOME: home, TMPDIR: home, NODE_ENV: "development",
+	LH_DATA_DIR: path.join(home, "data"), LH_AUTH_FILE: path.join(home, "auth.json"),
+	LH_IGNORE_ENV_KEYS: "1", NEXT_TELEMETRY_DISABLED: "1",
+	NEXT_FONT_GOOGLE_MOCKED_RESPONSES: path.join(home, "fonts.cjs"),
+};
+const server = spawn(process.execPath, ["node_modules/next/dist/bin/next", "dev", "--hostname", "127.0.0.1", "--port", String(port)], {
+	cwd: root, env, stdio: ["ignore", "pipe", "pipe"],
+});
+let logs = "";
+const capture = data => { logs = (logs + data).slice(-24000); };
+server.stdout.on("data", capture); server.stderr.on("data", capture);
+let browser;
+let page;
+const errors = [];
+const checks = [];
+try {
+	await new Promise((resolve, reject) => {
+		const deadline = setTimeout(() => reject(new Error("app startup timed out")), 60000);
+		const ready = () => { if (logs.includes("Ready in")) { clearTimeout(deadline); server.stdout.off("data", ready); resolve(); } };
+		server.stdout.on("data", ready);
+		server.once("exit", code => { clearTimeout(deadline); reject(new Error(`app exited ${code}`)); });
+		ready();
+	});
+	browser = await puppeteer.launch({
+		executablePath: process.env.LH_TEST_CHROME || "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome",
+		headless: true, userDataDir: path.join(home, "browser"), env,
+		args: ["--disable-background-networking", "--disable-sync", "--no-first-run", "--disable-default-apps"],
+	});
+	page = await browser.newPage();
+	page.setDefaultTimeout(45000);
+	page.on("pageerror", err => errors.push(err.message));
+	const model = { id: "synthetic", name: "Synthetic (no calls)", provider: "fixture", input: ["text"], reasoning: false, supportedLevels: ["off"], cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 }, contextWindow: 8192, maxTokens: 1024 };
+	const slot = { model: { provider: model.provider, id: model.id }, thinkingLevel: "off" };
+	const catalog = { models: [model], providers: [{ id: "fixture", label: "Fixture", keyPresent: true }], defaults: null,
+		slots: { strong: slot, cheap: slot, vision: slot }, rolePins: {} };
+	const posts = [];
+	const creates = [];
+	const accepted = new Map();
+	let mode = "accepted";
+	let held = [];
+	await page.setRequestInterception(true);
+	page.on("request", async request => {
+		try {
+			const url = new URL(request.url());
+			if (url.origin !== origin) { await request.abort(); return; }
+			const pathname = url.pathname;
+			const respond = body => request.respond({ status: 200, contentType: "application/json", body: JSON.stringify(body) });
+			if (pathname === "/api/models") return await respond(catalog);
+			// Notifications are outside this handover check. 204 tells native
+			// EventSource not to reconnect or hold a test connection open.
+			if (pathname === "/api/events") return await request.respond({ status: 204 });
+			if (pathname === "/api/chat") {
+				const body = JSON.parse(request.postData()); posts.push(body);
+				if (mode === "held-post") { held.push(request); return; }
+				if (mode === "lost-ack") return await request.abort("failed");
+				if (mode === "refused") return await request.respond({ status: 503, contentType: "application/json", body: JSON.stringify({ code: "models_not_configured", missing: ["strong"] }) });
+				accepted.set(body.chatId, [{ id: "saved_user", role: "user", content: body.input.text, timestamp: Date.now() }]);
+				return await respond({ ok: true });
+			}
+			if (/^\/api\/chats\/[^/]+\/stream$/.test(pathname)) {
+				// Keep teacher delivery unfinished: cleanup must NOT wait for it.
+				held.push(request); return;
+			}
+			const match = pathname.match(/^\/api\/chats\/([^/]+)$/);
+			if (match && request.method() === "GET" && accepted.has(match[1])) {
+				return await respond({ messages: accepted.get(match[1]), turns: [], turnInFlight: false });
+			}
+			if (pathname === "/api/chats" && request.method() === "POST") creates.push(JSON.parse(request.postData()));
+			await request.continue();
+		} catch (err) { if (!/Target closed|Session closed|Invalid InterceptionId/.test(String(err))) errors.push(String(err)); }
+	});
+	async function open(route) {
+		// CDP-intercepted requests do not settle themselves on navigation.
+		// Release synthetic streams from prior cases rather than pin slots.
+		await Promise.all(held.splice(0).map(request => request.abort("aborted").catch(() => {})));
+		await page.goto(origin + route, { waitUntil: "domcontentloaded", timeout: 120000 });
+		await page.waitForSelector(route === "/" ? "textarea" : '[data-testid="composer"] textarea');
+		await page.waitForFunction(() => !document.querySelector('[data-testid="setup-cta"]') && !document.querySelector('[data-testid="setup-cta-keys"]'));
+	}
+	async function fill(text) {
+		await page.evaluate(value => {
+			const textarea = document.querySelector('[data-testid="composer"] textarea') || document.querySelector("textarea");
+			Object.getOwnPropertyDescriptor(HTMLTextAreaElement.prototype, "value").set.call(textarea, value);
+			textarea.dispatchEvent(new Event("input", { bubbles: true }));
+		}, text);
+	}
+	async function submit() {
+		await page.waitForFunction(() => {
+			const button = document.querySelector('button[aria-label="Start session"], [data-testid="composer"] button[aria-label="Send"]');
+			return button && !button.disabled;
+		});
+		await page.locator('button[aria-label="Start session"], [data-testid="composer"] button[aria-label="Send"]').click();
+	}
+	async function stash(id) { return page.evaluate(chat => sessionStorage.getItem(`lh.openingPrompt.${chat}`), id); }
+	async function assertDraft(text) { await page.waitForFunction(value => document.querySelector('[data-testid="composer"] textarea')?.value === value, {}, text); }
+	const long = "A full synthetic syllabus — 世界 & ? #. ".repeat(1200).trim();
+	for (const route of ["/", "/chat/new"]) {
+		for (const text of ["a short synthetic topic", long]) {
+			await open(route);
+			const count = posts.length;
+			await fill(text); await submit();
+			await page.waitForFunction(() => /^\/chat\/chat_/.test(location.pathname) && !location.search);
+			await page.waitForFunction(() => document.querySelector('[data-testid="composer"]'));
+			await page.waitForFunction(() => !Object.keys(sessionStorage).some(k => k.startsWith("lh.openingPrompt.")));
+			assert.equal(posts.length, count + 1);
+			assert.equal(posts.at(-1).input.text, text);
+			assert.equal(new URL(page.url()).search, "");
+			assert.equal(await stash(posts.at(-1).chatId), null);
+			checks.push(`${route}: ${text.length > 1000 ? "long" : "short"} input delivered intact through short URL; stash removed while stream held`);
+		}
+	}
+	// The old long-query mechanism really is rejected by this isolated Node server.
+	const oldResponse = await fetch(`${origin}${new URL(page.url()).pathname}?prompt=${encodeURIComponent(long)}`);
+	assert.equal(oldResponse.status, 431); await oldResponse.text();
+	checks.push("old long-query request returned431 (browser-shell blank appearance not asserted)");
+
+	for (const route of ["/", "/chat/new"]) {
+		await open(route);
+		await page.evaluate(() => {
+			const setItem = Storage.prototype.setItem;
+			Storage.prototype.setItem = function(key, value) {
+				if (window.failOpeningStorage && key.startsWith("lh.openingPrompt.")) throw new DOMException("synthetic quota", "QuotaExceededError");
+				return setItem.call(this, key, value);
+			};
+			window.failOpeningStorage = true;
+		});
+		const createCount = creates.length; const sendCount = posts.length;
+		await fill(long); await submit();
+		await page.waitForSelector('[role="alert"]');
+		assert.equal(new URL(page.url()).pathname, route);
+		assert.equal(await page.$eval("textarea", element => element.value), long);
+		assert.equal(posts.length, sendCount);
+		assert.equal(creates.length, createCount + 1);
+		await page.evaluate(() => { window.failOpeningStorage = false; });
+		await submit();
+		await page.waitForFunction(() => /^\/chat\/chat_/.test(location.pathname));
+		await page.waitForFunction(() => !Object.keys(sessionStorage).some(k => k.startsWith("lh.openingPrompt.")));
+		assert.equal(creates.length, createCount + 1, "unchanged retry reuses creation");
+		assert.equal(posts.at(-1).input.text, long);
+		checks.push(`${route}: quota failure preserved visible draft/no navigation; retry reused creation`);
+	}
+
+	for (const failure of ["lost-ack", "refused", "held-post"]) {
+		mode = failure;
+		await open("/chat/new");
+		const text = `recover interrupted ${failure}`;
+		await fill(text); await submit();
+		await page.waitForFunction(() => /^\/chat\/chat_/.test(location.pathname));
+		await page.waitForFunction(() => Object.values(sessionStorage).some(v => v.includes('"attempted":true')));
+		if (failure !== "held-post") await assertDraft(text);
+		const count = posts.length;
+		await page.reload({ waitUntil: "domcontentloaded" });
+		await assertDraft(text);
+		assert.equal(posts.length, count, "interrupted start must not automatically repost");
+		checks.push(`${failure}: reload restored full draft, no automatic repost`);
+		if (failure === "lost-ack") {
+			mode = "accepted";
+			await submit();
+			const id = new URL(page.url()).pathname.split("/").at(-1);
+			await page.waitForFunction(chat => !sessionStorage.getItem(`lh.openingPrompt.${chat}`), {}, id);
+			assert.equal(posts.length, count + 1);
+			assert.equal(posts.at(-1).input.text, text);
+			checks.push("restored draft sent only after explicit click and cleaned up on acceptance");
+		}
+	}
+	mode = "accepted";
+	// Marker-only session must still automatically deliver a fresh opening.
+	await open("/chat/new");
+	const markerId = await page.evaluate(async () => {
+		const res = await fetch("/api/chats", { method: "POST", headers: { "Content-Type": "application/json" }, body: JSON.stringify({ title: "marker fixture", graphContext: { propositions: [{ id: "synthetic_node", name: "Fixture", statement: "Synthetic" }] } }) });
+		return (await res.json()).id;
+	});
+	await page.evaluate(id => sessionStorage.setItem(`lh.openingPrompt.${id}`, JSON.stringify({ text: "marker opening", attempted: false })), markerId);
+	const markerCount = posts.length;
+	await page.goto(`${origin}/chat/${markerId}`, { waitUntil: "domcontentloaded" });
+	await page.waitForFunction(id => !sessionStorage.getItem(`lh.openingPrompt.${id}`), {}, markerId);
+	assert.equal(posts.length, markerCount + 1);
+	assert.equal(posts.at(-1).input.text, "marker opening");
+	checks.push("graph-marker-only record still receives opening text");
+	// A real persisted user prevents delivery and cleans a stale copy on mount.
+	const chatFile = path.join(home, "data", "chats", `${markerId}.json`);
+	const record = JSON.parse(fs.readFileSync(chatFile, "utf8"));
+	record.messages.push({ id: "confirmed_fixture", role: "user", content: "already received", timestamp: Date.now() });
+	fs.writeFileSync(chatFile, JSON.stringify(record));
+	await page.evaluate(id => sessionStorage.setItem(`lh.openingPrompt.${id}`, JSON.stringify({ text: "stale opening", attempted: true })), markerId);
+	const completedCount = posts.length;
+	await page.reload({ waitUntil: "domcontentloaded" });
+	await page.waitForFunction(id => !sessionStorage.getItem(`lh.openingPrompt.${id}`), {}, markerId);
+	assert.equal(posts.length, completedCount);
+	checks.push("persisted real conversation removed stale stash without reposting");
+	await open("/chat/new");
+	const legacyId = await page.evaluate(async () => {
+		const response = await fetch("/api/chats", { method: "POST", headers: { "Content-Type": "application/json" }, body: JSON.stringify({ title: "legacy fixture" }) });
+		return (await response.json()).id;
+	});
+	const legacyCount = posts.length;
+	await page.goto(`${origin}/chat/${legacyId}?prompt=${encodeURIComponent("legacy opening")}`, { waitUntil: "domcontentloaded" });
+	await page.waitForFunction(() => document.body.innerText.includes("legacy opening"));
+	await page.waitForFunction(id => !sessionStorage.getItem(`lh.openingPrompt.${id}`), {}, legacyId);
+	assert.equal(posts.length, legacyCount + 1);
+	assert.equal(posts.at(-1).input.text, "legacy opening");
+	checks.push("legacy short ?prompt link still sends its complete opening message");
+	assert.deepEqual(errors, []);
+	console.log(JSON.stringify({ checks, pageErrors: errors, isolation: "synthetic catalog/POST+streams; empty auth; no providers", origin }, null, 2));
+} catch (err) {
+	console.error(err);
+	console.error(JSON.stringify({ checks, errors, url: page?.url(), dom: await page?.evaluate(() => ({ textareas: [...document.querySelectorAll('textarea')].map(e => ({ length: e.value.length, placeholder: e.placeholder })), buttons: [...document.querySelectorAll('button[aria-label="Send"], button[aria-label="Start session"]')].map(e => ({ disabled: e.disabled, label: e.getAttribute('aria-label') })), alerts: [...document.querySelectorAll('[role="alert"]')].map(e => e.textContent), failStorage: window.failOpeningStorage, text: document.body.innerText.slice(-1200) })).catch(() => null) }, null, 2));
+	console.error(logs); process.exitCode = 1;
+} finally {
+	await browser?.close();
+	const exited = once(server, "exit");
+	server.kill("SIGTERM");
+	const killTimer = setTimeout(() => server.kill("SIGKILL"), 5000); killTimer.unref();
+	await exited; clearTimeout(killTimer);
+	fs.rmSync(home, { recursive: true, force: true });
+}

tests/opening-delivery.test.ts

@@ -0,0 +1,203 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import { SessionModel } from "../components/session-core.ts";
+import { newUserMessage } from "../src/core/native-messages.ts";
+
+function deferred<T>() {
+	let resolve!: (value: T) => void;
+	let reject!: (reason: unknown) => void;
+	const promise = new Promise<T>((done, fail) => { resolve = done; reject = fail; });
+	return { promise, resolve, reject };
+}
+
+describe("new-session opening delivery acceptance", () => {
+	it("notifies acceptance before the record read or teacher stream completes", async () => {
+		const record = deferred<Response>();
+		const accepted = deferred<void>();
+		const calls: string[] = [];
+		const m = new SessionModel({ chatId: "c1", initialMessages: [], fetch: async url => {
+			calls.push(String(url));
+			if (String(url) === "/api/chat") return Response.json({ ok: true });
+			if (String(url).endsWith("/stream")) return new Response("data: [DONE]\n\n");
+			return record.promise;
+		} });
+		let completed = false;
+		const sending = m.send({ type: "text", text: "my syllabus" }, () => accepted.resolve()).then(result => { completed = true; return result; });
+		await accepted.promise;
+		assert.equal(completed, false);
+		assert.equal(m.getState().hasConfirmedConversation, false, "optimistic user text is not canonical proof");
+		record.resolve(Response.json({ messages: [newUserMessage("my syllabus")] }));
+		assert.equal(await sending, true);
+		assert.equal(m.getState().hasConfirmedConversation, true);
+		assert.equal(calls.filter(url => url === "/api/chat").length, 1);
+	});
+
+	it("a teardown racing the POST still cleans up on acknowledgment without attaching", async () => {
+		const post = deferred<Response>();
+		let notified = 0;
+		const m = new SessionModel({ chatId: "c1", initialMessages: [], fetch: async url => {
+			assert.equal(String(url), "/api/chat");
+			return post.promise;
+		} });
+		const sending = m.send({ type: "text", text: "hello" }, () => { notified++; });
+		m.stop();
+		post.resolve(Response.json({ ok: true }));
+		assert.equal(await sending, true);
+		assert.equal(notified, 1);
+	});
+
+	for (const failure of ["refusal", "409", "lost acknowledgment"] as const) {
+		it(`${failure} does not notify acceptance or leave a false confirmed conversation`, async () => {
+			let notified = false;
+			const m = new SessionModel({ chatId: "c1", initialMessages: [], waitMaxMs: 0, fetch: async () => {
+				if (failure === "lost acknowledgment") throw new TypeError("connection lost");
+				return new Response("refused", { status: failure === "409" ? 409 : 503 });
+			} });
+			assert.equal(await m.send({ type: "text", text: "keep this" }, () => { notified = true; }), false);
+			assert.equal(notified, false);
+			assert.equal(m.getState().hasConfirmedConversation, false);
+			assert.equal(m.getState().nativeMessages.length, 0, "restore the opening draft, not a stranded optimistic bubble");
+			assert.equal(m.status, "error");
+		});
+	}
+
+	for (const failure of ["network", "503"] as const) {
+		it(`a teardown racing an opening ${failure} failure restores the bubble/error recovery state`, async () => {
+			const post = deferred<Response>();
+			let notified = 0;
+			const envelope = JSON.stringify({ code: "models_not_configured", missing: ["strong"] });
+			const m = new SessionModel({ chatId: "c1", initialMessages: [], fetch: async url => {
+				assert.equal(String(url), "/api/chat", "failure must not attach or resend");
+				return post.promise;
+			} });
+			const sending = m.send({ type: "text", text: "recover this opening" }, () => { notified++; });
+			m.stop(); // StrictMode's cleanup detaches the consume, NOT this POST.
+			if (failure === "network") post.reject(new TypeError("opening connection lost"));
+			else post.resolve(new Response(envelope, { status: 503 }));
+			assert.equal(await sending, false);
+			assert.equal(notified, 0);
+			assert.equal(m.getState().nativeMessages.length, 0, "no stranded optimistic opening bubble");
+			assert.equal(m.status, "error");
+			assert.equal(m.getState().error?.message, failure === "network" ? "opening connection lost" : envelope,
+				"the raw refusal must reach the existing setup-recovery effect");
+		});
+
+		it(`an older opening ${failure} failure removes only its own bubble while a newer send owns state`, async () => {
+			const first = deferred<Response>();
+			const second = deferred<Response>();
+			let posts = 0;
+			const m = new SessionModel({ chatId: "c1", initialMessages: [], fetch: async url => {
+				assert.equal(String(url), "/api/chat");
+				return ++posts === 1 ? first.promise : second.promise;
+			} });
+			const older = m.send({ type: "text", text: "older opening" }, () => assert.fail("not accepted"));
+			m.stop();
+			const newer = m.send({ type: "text", text: "newer text" });
+			if (failure === "network") first.reject(new TypeError("older lost acknowledgment"));
+			else first.resolve(new Response("older refusal", { status: 503 }));
+			assert.equal(await older, false);
+			assert.equal(m.status, "submitted", "older failure must not settle the newer send");
+			assert.equal(m.getState().error, null);
+			assert.deepEqual(m.getState().nativeMessages.map(message => message.content), ["newer text"]);
+			second.resolve(new Response("newer failure", { status: 503 }));
+			assert.equal(await newer, false);
+			assert.equal(m.getState().error?.message, "newer failure");
+			assert.deepEqual(m.getState().nativeMessages.map(message => message.content), ["newer text"],
+				"ordinary text retains its existing optimistic failure presentation");
+		});
+	}
+
+	it("a newer send remains the owner even after it fails and is stopped", async () => {
+		const first = deferred<Response>();
+		let posts = 0;
+		const m = new SessionModel({ chatId: "c1", initialMessages: [], fetch: async () => {
+			return ++posts === 1 ? first.promise : new Response("newer failure", { status: 503 });
+		} });
+		const older = m.send({ type: "text", text: "older opening" }, () => assert.fail("not accepted"));
+		m.stop();
+		await m.send({ type: "text", text: "newer text" });
+		m.stop();
+		first.reject(new TypeError("older failure"));
+		assert.equal(await older, false);
+		assert.equal(m.status, "ready");
+		assert.equal(m.getState().error?.message, "newer failure");
+		assert.deepEqual(m.getState().nativeMessages.map(message => message.content), ["newer text"]);
+	});
+
+	it("a replacement reattach owns state instead of the older stopped opening POST", async () => {
+		const post = deferred<Response>();
+		const record = deferred<Response>();
+		const saved = newUserMessage("server-owned text");
+		const m = new SessionModel({ chatId: "c1", initialMessages: [], fetch: async url => {
+			if (String(url) === "/api/chat") return post.promise;
+			if (String(url).endsWith("/stream")) return new Response("data: [DONE]\n\n");
+			return record.promise;
+		} });
+		const older = m.send({ type: "text", text: "older opening" }, () => assert.fail("not accepted"));
+		m.stop();
+		const replacement = m.resumeStream();
+		post.reject(new TypeError("older failure"));
+		assert.equal(await older, false);
+		assert.equal(m.status, "submitted");
+		assert.equal(m.getState().error, null);
+		record.resolve(Response.json({ messages: [saved] }));
+		await replacement;
+		assert.equal(m.status, "ready");
+		assert.deepEqual(m.getState().nativeMessages, [saved]);
+		assert.equal(m.getState().error, null);
+	});
+
+	it("a stopped replacement reattach still supersedes the older opening refusal", async () => {
+		const post = deferred<Response>();
+		const record = deferred<Response>();
+		const m = new SessionModel({ chatId: "c1", initialMessages: [], fetch: async url => {
+			return String(url) === "/api/chat" ? post.promise : record.promise;
+		} });
+		const older = m.send({ type: "text", text: "older opening" }, () => assert.fail("not accepted"));
+		m.stop();
+		const replacement = m.resumeStream();
+		m.stop();
+		post.resolve(new Response("older refusal", { status: 503 }));
+		assert.equal(await older, false);
+		assert.equal(m.status, "ready");
+		assert.equal(m.getState().error, null);
+		assert.equal(m.getState().nativeMessages.length, 0);
+		record.resolve(Response.json({ messages: [] }));
+		await replacement;
+		assert.equal(m.status, "ready");
+		assert.equal(m.getState().error, null);
+	});
+
+	it("a stopped ordinary text failure retains the pre-existing teardown behavior", async () => {
+		const post = deferred<Response>();
+		const m = new SessionModel({ chatId: "c1", initialMessages: [], fetch: async () => post.promise });
+		const sending = m.send({ type: "text", text: "ordinary text" });
+		m.stop();
+		post.reject(new TypeError("connection lost"));
+		assert.equal(await sending, false);
+		assert.equal(m.status, "ready");
+		assert.equal(m.getState().error, null);
+		assert.deepEqual(m.getState().nativeMessages.map(message => message.content), ["ordinary text"]);
+	});
+
+	it("post-acceptance attachment failure remains accepted and does not resend input", async () => {
+		let posts = 0;
+		let notified = 0;
+		const m = new SessionModel({ chatId: "c1", initialMessages: [], fetch: async url => {
+			if (String(url) === "/api/chat") { posts++; return Response.json({ ok: true }); }
+			throw new TypeError("record read failed");
+		} });
+		assert.equal(await m.send({ type: "text", text: "hello" }, () => { notified++; }), true);
+		assert.equal(notified, 1);
+		assert.equal(posts, 1);
+		assert.equal(m.status, "error");
+	});
+
+	it("a busy gate sends nothing, then canonical adoption can confirm an earlier lost acknowledgment", async () => {
+		const m = new SessionModel({ chatId: "c1", initialMessages: [], fetch: async () => { throw new Error("must not post"); } });
+		m.readyRef = false;
+		assert.equal(await m.send({ type: "text", text: "hello" }, () => assert.fail("must not acknowledge")), false);
+		m.setMessages([newUserMessage("hello")]);
+		assert.equal(m.getState().hasConfirmedConversation, true);
+	});
+});

tests/opening-prompt.test.ts

@@ -0,0 +1,123 @@
+import assert from "node:assert/strict";
+import { afterEach, beforeEach, describe, it } from "node:test";
+import { clearOpeningPrompt, readOpeningPrompt, readOpeningPromptEntry, stashOpeningPrompt } from "../components/opening-prompt.ts";
+import { SessionStarter } from "../components/start-session.ts";
+
+const original = Object.getOwnPropertyDescriptor(globalThis, "sessionStorage");
+let data: Map<string, string>;
+let storage: Pick<Storage, "getItem" | "setItem" | "removeItem">;
+function install(value: unknown) {
+	Object.defineProperty(globalThis, "sessionStorage", { configurable: true, value });
+}
+beforeEach(() => {
+	data = new Map();
+	storage = {
+		getItem: key => data.get(key) ?? null,
+		setItem: (key, value) => { data.set(key, value); },
+		removeItem: key => { data.delete(key); },
+	};
+	install(storage);
+});
+afterEach(() => {
+	if (original) Object.defineProperty(globalThis, "sessionStorage", original);
+	else Reflect.deleteProperty(globalThis, "sessionStorage");
+});
+const fail = () => { throw new Error("synthetic storage failure"); };
+
+describe("opening message storage", () => {
+	it("keeps full text off the URL and records attempted delivery before send", () => {
+		const text = "a syllabus with Unicode 世界 & ? # ".repeat(1500);
+		assert.equal(stashOpeningPrompt("c1", text), true);
+		assert.deepEqual(readOpeningPromptEntry("c1"), { text, attempted: false });
+		assert.equal(stashOpeningPrompt("c1", text, true), true);
+		assert.deepEqual(readOpeningPromptEntry("c1"), { text, attempted: true });
+		assert.equal(clearOpeningPrompt("c1"), true);
+		assert.equal(readOpeningPrompt("c1"), undefined);
+	});
+
+	it("treats a legacy raw-text stash conservatively as a possibly attempted send", () => {
+		data.set("lh.openingPrompt.old", "teach me logic");
+		assert.deepEqual(readOpeningPromptEntry("old"), { text: "teach me logic", attempted: true });
+	});
+
+	for (const unavailable of [undefined, null]) {
+		it(`reports unavailable storage (${unavailable}) instead of claiming a safe handover`, () => {
+			install(unavailable);
+			assert.equal(stashOpeningPrompt("c1", "keep this"), false);
+			assert.equal(readOpeningPrompt("c1"), undefined);
+			assert.equal(clearOpeningPrompt("c1"), false);
+		});
+	}
+	it("catches a throwing storage getter", () => {
+		Object.defineProperty(globalThis, "sessionStorage", { configurable: true, get: fail });
+		assert.equal(stashOpeningPrompt("c1", "keep this"), false);
+		assert.equal(readOpeningPrompt("c1"), undefined);
+		assert.equal(clearOpeningPrompt("c1"), false);
+	});
+	for (const method of ["getItem", "setItem", "removeItem"] as const) {
+		it(`contains ${method} exceptions without crashing a source or chat page`, () => {
+			storage[method] = fail;
+			assert.doesNotThrow(() => stashOpeningPrompt("c1", "keep this"));
+			assert.doesNotThrow(() => readOpeningPrompt("c1"));
+			assert.doesNotThrow(() => clearOpeningPrompt("c1"));
+			if (method !== "removeItem") assert.equal(stashOpeningPrompt("c1", "keep this"), false);
+		});
+	}
+	it("does not accept a storage write that failed silently", () => {
+		storage.setItem = () => {};
+		assert.equal(stashOpeningPrompt("c1", "keep this"), false);
+	});
+});
+
+describe("new-session create and handover", () => {
+	function createFetch() {
+		const bodies: unknown[] = [];
+		const fetchLike = (async (_url, init) => {
+			bodies.push(JSON.parse(String(init?.body)));
+			return Response.json({ id: `chat_${bodies.length}` });
+		}) as typeof fetch;
+		return { bodies, fetchLike };
+	}
+	it("refuses navigation on quota failure, then reuses the created session for unchanged retry", async () => {
+		const starter = new SessionStarter();
+		const { bodies, fetchLike } = createFetch();
+		const text = "full text ".repeat(4000);
+		const setItem = storage.setItem;
+		storage.setItem = fail;
+		await assert.rejects(starter.start({ title: text }, fetchLike));
+		assert.equal(bodies.length, 1);
+		storage.setItem = setItem;
+		assert.equal(await starter.start({ title: text }, fetchLike), "/chat/chat_1");
+		assert.equal(bodies.length, 1);
+		assert.equal(readOpeningPrompt("chat_1"), text);
+	});
+	it("reuses creation even when verifying the first storage write failed", async () => {
+		const starter = new SessionStarter();
+		const { bodies, fetchLike } = createFetch();
+		const getItem = storage.getItem;
+		storage.getItem = fail;
+		await assert.rejects(starter.start({ title: "hello" }, fetchLike));
+		storage.getItem = getItem;
+		assert.equal(await starter.start({ title: "hello" }, fetchLike), "/chat/chat_1");
+		assert.equal(bodies.length, 1);
+	});
+	it("changed text, mode, picks or birth settings create a matching new session", async () => {
+		const starter = new SessionStarter();
+		const { bodies, fetchLike } = createFetch();
+		await starter.start({ title: "original" }, fetchLike, "model-a");
+		await starter.start({ title: "edited" }, fetchLike, "model-a");
+		await starter.start({ title: "edited", kind: "practice" }, fetchLike, "model-a");
+		const picked = { title: "edited", kind: "practice" as const, graphContext: { propositions: [{ id: "p1", name: "P", statement: "S" }] } };
+		await starter.start(picked, fetchLike, "model-a");
+		await starter.start(picked, fetchLike, "model-b");
+		assert.equal(bodies.length, 5);
+		assert.equal(readOpeningPrompt("chat_1"), undefined);
+	});
+	it("does not stash or navigate on a refused creation or invalid ID", async () => {
+		for (const response of [new Response("unavailable", { status: 503 }), Response.json({}), Response.json({ id: "../bad?prompt=leak" })]) {
+			const starter = new SessionStarter();
+			await assert.rejects(starter.start({ title: "hello" }, (async () => response) as typeof fetch));
+			assert.equal(data.size, 0);
+		}
+	});
+});

tests/render-new-session.test.tsx

@@ -2,9 +2,24 @@ import React from "react";
 (globalThis as Record<string, unknown>).React = React;
 
 import { renderToStaticMarkup } from "react-dom/server";
-import { describe, it } from "node:test";
+import { afterEach, beforeEach, describe, it } from "node:test";
 import assert from "node:assert/strict";
 import { DraftShell, startDraftSession } from "../components/new-session.tsx";
+import { clearOpeningPrompt, readOpeningPrompt, OPENING_PROMPT_FAILURE } from "../components/opening-prompt.ts";
+
+const originalStorage = Object.getOwnPropertyDescriptor(globalThis, "sessionStorage");
+beforeEach(() => {
+	const data = new Map<string, string>();
+	Object.defineProperty(globalThis, "sessionStorage", { configurable: true, value: {
+		getItem: (key: string) => data.get(key) ?? null,
+		setItem: (key: string, value: string) => { data.set(key, value); },
+		removeItem: (key: string) => { data.delete(key); },
+	} });
+});
+afterEach(() => {
+	if (originalStorage) Object.defineProperty(globalThis, "sessionStorage", originalStorage);
+	else Reflect.deleteProperty(globalThis, "sessionStorage");
+});
 
 /**
  * The sessionless draft view (/chat/new, owner 2026-09-13): "+ New session"
@@ -25,10 +40,10 @@ function fakeFetch(id: string) {
 }
 
 describe("startDraftSession — the create-on-send contract", () => {
-	it("creates the session titled with the first message, returns the prompt redirect", async () => {
+	it("creates the session titled with the first message and returns a short path", async () => {
 		const { f, calls } = fakeFetch("c_new");
 		const target = await startDraftSession("teach me orbital mechanics", f);
-		assert.equal(target, "/chat/c_new?prompt=teach%20me%20orbital%20mechanics");
+		assert.equal(target, "/chat/c_new");
 		assert.equal(calls.length, 1);
 		assert.equal(calls[0]!.url, "/api/chats");
 		assert.equal(calls[0]!.method, "POST");
@@ -41,6 +56,37 @@ describe("startDraftSession — the create-on-send contract", () => {
 		assert.equal(calls.length, 1, "a single create call — the birth stamp is server-side");
 	});
 
+	it("a long opening text stays out of the URL and is stashed for the chat page", async () => {
+		const mem = new Map<string, string>();
+		const fake = {
+			getItem: (k: string) => mem.get(k) ?? null,
+			setItem: (k: string, v: string) => {
+				mem.set(k, v);
+			},
+			removeItem: (k: string) => {
+				mem.delete(k);
+			},
+		};
+		const holder = globalThis as { sessionStorage?: Storage };
+		const prev = holder.sessionStorage;
+		Object.defineProperty(globalThis, "sessionStorage", { configurable: true, value: fake });
+		try {
+			const { f } = fakeFetch("c_long");
+			const text = `${"B2 First grammar item. ".repeat(1500)}end`;
+			const target = await startDraftSession(text, f);
+			assert.equal(target, "/chat/c_long");
+			assert.equal(target!.includes("?"), false);
+			const stashed = readOpeningPrompt("c_long");
+			assert.equal(stashed?.length, text.length);
+			assert.equal(stashed, text);
+			clearOpeningPrompt("c_long");
+			assert.equal(readOpeningPrompt("c_long"), undefined);
+		} finally {
+			if (prev === undefined) delete holder.sessionStorage;
+			else Object.defineProperty(globalThis, "sessionStorage", { configurable: true, value: prev });
+		}
+	});
+
 	it("empty or whitespace text never creates anything", async () => {
 		const { f, calls } = fakeFetch("never");
 		assert.equal(await startDraftSession("", f), null);
@@ -50,6 +96,12 @@ describe("startDraftSession — the create-on-send contract", () => {
 });
 
 describe("DraftShell — the sessionless surface", () => {
+	it("storage failure leaves the full draft editable beside the approved error", () => {
+		const html = renderToStaticMarkup(<DraftShell busy={false} text="keep all my text" onChange={() => {}} onSend={() => {}} startError />);
+		assert.ok(html.includes('role="alert"'));
+		assert.ok(html.includes(OPENING_PROMPT_FAILURE));
+		assert.match(html, /<textarea[^>]*>keep all my text<\/textarea>/);
+	});
 	it("renders the composer blob, the stats bar, and the fresh-chat empty state", () => {
 		const html = renderToStaticMarkup(
 			<DraftShell
@@ -188,7 +240,7 @@ describe("the practice draft (?mode=practice, 2026-10-04)", () => {
 			return new Response(JSON.stringify({ id: "c9" }), { status: 201 });
 		}) as unknown as typeof fetch;
 		const target = await startDraftSession("the parity chain", f, "practice");
-		assert.equal(target, "/chat/c9?prompt=the%20parity%20chain");
+		assert.equal(target, "/chat/c9");
 		assert.deepEqual(body, { title: "the parity chain", kind: "practice" });
 	});