diff --git a/app/api/graph/coverage/extract/route.ts b/app/api/graph/coverage/extract/route.ts
new file mode 100644
index 0000000..2687f67
--- /dev/null
+++ b/app/api/graph/coverage/extract/route.ts
@@ -0,0 +1,36 @@
+/**
+ * POST /api/graph/coverage/extract — the manual extraction affordance
+ * (vision-extraction-coverage.md): run the pipeline over ONE session's
+ * uncovered content, whatever its size — the user's answer to an aborted
+ * run, a pipeline error, or a session that went dormant under the chunk
+ * budget. The pipeline itself batches under EXTRACTION.chunkTokens and
+ * checkpoints coverage per merged batch, so this is the same run the
+ * trigger fires, just user-initiated. 409 while a run is already in
+ * flight (the dock is the source of truth for that); failures are logged
+ * by the pipeline and leave coverage untouched — the button stays honest.
+ */
+import { extraction, extractionStatuses } from "@/src/server";
+
+export const dynamic = "force-dynamic";
+
+export async function POST(request: Request) {
+	let body: unknown;
+	try {
+		body = await request.json();
+	} catch {
+		return Response.json({ error: "Invalid JSON body" }, { status: 400 });
+	}
+	const chatId = (body as { chatId?: unknown }).chatId;
+	if (typeof chatId !== "string" || chatId === "") {
+		return Response.json({ error: 'Body must be {chatId: string}' }, { status: 400 });
+	}
+	if (extractionStatuses().some((run) => run.kind === "chat" && run.chatId === chatId)) {
+		return Response.json({ error: "An extraction run is already in flight for this session" }, { status: 409 });
+	}
+	// Fire-and-forget, like the trigger: the dock + the coverage panel's
+	// running flags track progress; the promise never blocks the response.
+	void extraction.runExtraction(chatId).catch((err: unknown) => {
+		console.error(`[chat ${chatId}] manual extraction failed:`, err);
+	});
+	return Response.json({ started: true }, { status: 202 });
+}
\ No newline at end of file
diff --git a/app/api/graph/coverage/route.ts b/app/api/graph/coverage/route.ts
new file mode 100644
index 0000000..8ebecfe
--- /dev/null
+++ b/app/api/graph/coverage/route.ts
@@ -0,0 +1,40 @@
+/**
+ * GET /api/graph/coverage — the exact extraction coverage of every session
+ * (vision-extraction-coverage.md, settled 2026-09-15): which sessions have
+ * unextracted content, how much (tokens + message counts), and which runs
+ * are in flight. "Uncovered" is DERIVED here per request — fingerprint the
+ * current transcript, diff against the coverage ledger — never tracked as
+ * a second ledger. This is the data behind the graph view's coverage panel
+ * and its per-session "extract what's missing" buttons.
+ */
+import type { UIMessage } from "ai";
+import { chatStore, extractionStatuses, stores } from "@/src/server";
+import { coverageOf } from "@/src/core";
+
+export const dynamic = "force-dynamic";
+
+export async function GET() {
+	const running = new Set(
+		extractionStatuses().filter((run) => run.kind === "chat").map((run) => run.chatId),
+	);
+	const entries = stores.graphStore.readCoverage();
+	const chats = chatStore.listChats().map((summary) => {
+		const record = chatStore.getChat(summary.id);
+		const messages = (record?.messages ?? []) as UIMessage[];
+		const cov = coverageOf(messages, entries, summary.id);
+		return {
+			chatId: summary.id,
+			title: summary.title,
+			updatedAt: summary.updatedAt,
+			totalMessages: cov.slots.length,
+			coveredMessages: cov.coveredCount,
+			uncoveredMessages: cov.uncoveredCount,
+			coveredTokens: cov.coveredTokens,
+			uncoveredTokens: cov.uncoveredTokens,
+			running: running.has(summary.id),
+		};
+	});
+	// Most uncovered first — the actionable sessions lead the panel.
+	chats.sort((a, b) => b.uncoveredTokens - a.uncoveredTokens || (a.updatedAt < b.updatedAt ? 1 : -1));
+	return Response.json({ chats });
+}
\ No newline at end of file
diff --git a/components/graph-coverage.tsx b/components/graph-coverage.tsx
new file mode 100644
index 0000000..aec46c1
--- /dev/null
+++ b/components/graph-coverage.tsx
@@ -0,0 +1,190 @@
+"use client";
+
+import { useCallback, useEffect, useState } from "react";
+import { ListChecksIcon, Loader2Icon } from "lucide-react";
+import { formatTokens } from "@/components/usage-format";
+
+/**
+ * The extraction-coverage control (vision-extraction-coverage.md, settled
+ * 2026-09-15): the graph view's window into WHAT THE PIPELINE HAS COVERED.
+ * One button in the top-right chrome opens a panel with the exact coverage
+ * of every session — covered/uncovered tokens and message counts — and a
+ * per-session "Extract" button: the manual answer to an aborted run, a
+ * pipeline error, or a session that went dormant under the chunk budget.
+ *
+ * Data: GET /api/graph/coverage (uncovered is DERIVED server-side —
+ * fingerprint the transcript, diff the ledger — never dual-tracked).
+ * Manual runs: POST /api/graph/coverage/extract; the run then surfaces in
+ * the status chips + this panel's running row, and the graph refetches when
+ * it finishes (the parent's runs-empty transition). The panel polls only
+ * while open — no new standing poll.
+ */
+
+interface CoverageChat {
+	chatId: string;
+	title: string;
+	updatedAt: string;
+	totalMessages: number;
+	coveredMessages: number;
+	uncoveredMessages: number;
+	coveredTokens: number;
+	uncoveredTokens: number;
+	running: boolean;
+}
+
+export function GraphCoverageControl({ refreshKey = 0 }: { refreshKey?: number }) {
+	const [open, setOpen] = useState(false);
+	const [chats, setChats] = useState<CoverageChat[]>([]);
+	const [loaded, setLoaded] = useState(false);
+	const [extracting, setExtracting] = useState<string[]>([]); // click-pending ids (optimistic until the poll says running)
+
+	const load = useCallback(async () => {
+		try {
+			const res = await fetch("/api/graph/coverage");
+			if (!res.ok) return;
+			const data = (await res.json()) as { chats: CoverageChat[] };
+			setChats(data.chats);
+			setLoaded(true);
+			// Drop click-pending ids the server now reports as running (or
+			// that have finished — coverage moved, so the row settled).
+			setExtracting((ids) => ids.filter((id) => data.chats.find((c) => c.chatId === id)?.running === true));
+		} catch {
+			/* transient — the next tick retries */
+		}
+	}, []);
+
+	useEffect(() => {
+		if (!open) return;
+		void load();
+		const timer = setInterval(load, 2000);
+		return () => clearInterval(timer);
+	}, [open, load, refreshKey]);
+
+	const onExtract = async (chatId: string) => {
+		setExtracting((ids) => [...ids, chatId]);
+		try {
+			const res = await fetch("/api/graph/coverage/extract", {
+				method: "POST",
+				headers: { "content-type": "application/json" },
+				body: JSON.stringify({ chatId }),
+			});
+			if (!res.ok && res.status !== 409) {
+				console.error("manual extraction failed:", res.status);
+				setExtracting((ids) => ids.filter((id) => id !== chatId));
+				return;
+			}
+			// 409 = already running (e.g. the trigger raced us): the row's
+			// running flag takes over on the next poll.
+			void load();
+		} catch {
+			setExtracting((ids) => ids.filter((id) => id !== chatId));
+		}
+	};
+
+	const pending = (chat: CoverageChat) => chat.running || extracting.includes(chat.chatId);
+	return (
+		<div className="relative">
+			<button
+				type="button"
+				title="Extraction coverage — what the knowledge graph has covered"
+				aria-expanded={open}
+				onClick={() => setOpen((o) => !o)}
+				className={`flex size-11 items-center justify-center rounded-xl border bg-card/85 shadow-lg backdrop-blur transition-colors hover:bg-accent ${
+					open ? "text-foreground" : "text-muted-foreground hover:text-foreground"
+				}`}
+			>
+				<ListChecksIcon className="size-4" />
+			</button>
+			{open && (
+				<div className="absolute right-0 top-full mt-2">
+					<CoveragePanel
+						chats={chats}
+						loaded={loaded}
+						isBusy={(c) => pending(c)}
+						onExtract={(c) => void onExtract(c.chatId)}
+					/>
+				</div>
+			)}
+		</div>
+	);
+}
+
+/**
+ * The panel body — exported for static-render tests. Rows: exact coverage
+ * numbers per session, "Extract" for the uncovered ones, "Running" while a
+ * run is in flight.
+ */
+export function CoveragePanel({
+	chats,
+	loaded,
+	isBusy,
+	onExtract,
+}: {
+	chats: CoverageChat[];
+	loaded: boolean;
+	isBusy: (chat: CoverageChat) => boolean;
+	onExtract: (chat: CoverageChat) => void;
+}) {
+	const anyUncovered = chats.some((c) => c.uncoveredTokens > 0 || c.uncoveredMessages > 0);
+	return (
+		<div
+			data-testid="coverage-panel"
+			className="flex max-h-[60vh] w-[24rem] flex-col rounded-xl border bg-card/85 p-2.5 shadow-lg backdrop-blur"
+		>
+			<div className="mb-1.5 flex items-baseline justify-between px-1">
+				<span className="text-xs font-medium uppercase tracking-widest text-muted-foreground/70">
+					Extraction coverage
+				</span>
+				<span className="text-xxs text-muted-foreground">uncovered first</span>
+			</div>
+			{!anyUncovered && (
+				<p className="px-1 py-2 text-xs text-muted-foreground">
+					{loaded ? "Every session is fully extracted — nothing pending." : "…"}
+				</p>
+			)}
+			<div className="flex flex-col gap-1 overflow-y-auto">
+				{chats.map((c) => (
+					<CoverageRow key={c.chatId} chat={c} busy={isBusy(c)} onExtract={() => onExtract(c)} />
+				))}
+			</div>
+		</div>
+	);
+}
+
+function CoverageRow({ chat, busy, onExtract }: { chat: CoverageChat; busy: boolean; onExtract: () => void }) {
+	return (
+		<div className="flex items-center gap-2 rounded-lg px-1 py-1.5 hover:bg-accent/50" data-testid="coverage-row">
+			<div className="min-w-0 flex-1">
+				<div className="truncate text-xs text-foreground">{chat.title}</div>
+				<div className="flex items-baseline gap-1.5 text-xxs text-muted-foreground">
+					{busy ? (
+						<span className="flex items-center gap-1">
+							<Loader2Icon className="size-3 animate-spin" /> extracting…
+						</span>
+					) : (
+						<>
+							<span className="tabular-nums">{formatTokens(chat.coveredTokens)} covered</span>
+							{chat.uncoveredTokens > 0 && (
+								<span className="tabular-nums text-foreground">
+									{formatTokens(chat.uncoveredTokens)} uncovered
+								</span>
+							)}
+							{chat.uncoveredTokens === 0 && <span>· complete</span>}
+							{chat.uncoveredMessages > 0 && (
+								<span className="tabular-nums">({chat.uncoveredMessages} msgs)</span>
+							)}
+						</>
+					)}
+				</div>
+			</div>
+			<button
+				type="button"
+				disabled={busy || chat.uncoveredTokens === 0}
+				onClick={onExtract}
+				className="shrink-0 rounded-lg border px-2 py-1 text-xxs text-muted-foreground transition-colors hover:bg-accent hover:text-foreground disabled:opacity-40 disabled:hover:bg-transparent"
+			>
+				{busy ? "Running" : "Extract"}
+			</button>
+		</div>
+	);
+}
\ No newline at end of file
diff --git a/components/graph-view.tsx b/components/graph-view.tsx
index 21dc619..1725e0b 100644
--- a/components/graph-view.tsx
+++ b/components/graph-view.tsx
@@ -66,6 +66,7 @@ import Link from "next/link";
 import { FileTextIcon, Loader2Icon, SearchIcon, SettingsIcon, UploadIcon, WaypointsIcon } from "lucide-react";
 import { incrementalLayout, type GraphNode, type GraphSnapshot } from "@/src/core";
 import { GraphCanvasRenderer, type GraphRenderSettings } from "./graph-canvas.ts";
+import { GraphCoverageControl } from "./graph-coverage.tsx";
 import {
 	ARROW_LENGTH_RANGE,
 	CHARGE_RANGE,
@@ -843,11 +844,15 @@ export function GraphView() {
 			)}
 
 			{/* Legend + filters: search box and per-state toggle rows. */}
-			{/* Top-right controls — three separate floating containers (owner,
+			{/* Top-right controls — separate floating containers (owner,
 			    graph-view round 2): the search box, the settings gear (its own
-			    collapsible component), and the import button. */}
-			{!isEmpty && (
-				<div className="absolute right-3 top-3 z-10 flex items-center gap-2">
+			    collapsible component), the import button, and the coverage
+			    control. Coverage renders even when the graph is EMPTY — an
+			    empty graph with unextracted sessions is exactly when it
+			    matters (extract → the graph gains nodes). */}
+			<div className="absolute right-3 top-3 z-10 flex items-center gap-2">
+				{!isEmpty && (
+					<>
 					{/* Search — its own container (icon + input + no-match note). */}
 					<div className="w-56 rounded-xl border bg-card/85 p-1.5 shadow-lg backdrop-blur">
 						<div className="relative">
@@ -893,8 +898,12 @@ export function GraphView() {
 					    gear sits at the far right (owner, round 3) so its panel
 					    drops at the very right edge, over less of the graph. */}
 					<GraphSettingsControl settings={settings} changeSettings={changeSettings} />
-				</div>
-			)}
+					</>
+				)}
+				{/* Extraction coverage — own container, always present; the
+				    panel re-reads when background runs settle (refreshTick). */}
+				<GraphCoverageControl refreshKey={refreshTick} />
+			</div>
 
 			{/* Background pipeline status: what is currently running. */}
 			{pipelineRuns.length > 0 && (
diff --git a/config.ts b/config.ts
index 8162991..f01349c 100644
--- a/config.ts
+++ b/config.ts
@@ -62,7 +62,16 @@ export type ModelRole = keyof typeof MODELS;
  * (server/turn-service.ts) so it can be swapped without touching the
  * pipeline.
  */
-export const EXTRACTION = { everyNQuizAnswers: 3 } as const;
+/**
+ * The extraction trigger (vision-extraction-coverage.md, 2026-09-15): a run
+ * fires when a chat's UNCOVERED transcript tokens reach the chunk budget.
+ * Runs are token-budgeted batches of the oldest uncovered messages — this
+ * knob is the transcript share of the extractor's context (it also carries
+ * the whole graph + instructions), so it bounds both cost and chunk size.
+ * Replaces the old every-3-quiz-answers trigger, which never fired for
+ * quiz-less sessions.
+ */
+export const EXTRACTION = { chunkTokens: 4096 } as const;
 
 /**
  * The LIVE graph store (src/store/graph.ts) — owned by the app's extraction
@@ -74,6 +83,10 @@ export const LEDGER_FILES = {
 	events: path.join(PATHS.graph, "events.jsonl"),
 	mappings: path.join(PATHS.graph, "mappings.jsonl"),
 	sessions: path.join(PATHS.graph, "sessions.jsonl"),
+	/** Per-message extraction coverage (contracts/graph.ts CoverageEntry;
+	 *  the checkpoint's replacement for chat extractions — notes keep
+	 *  sessions.jsonl, whole-file as they are). */
+	coverage: path.join(PATHS.graph, "coverage.jsonl"),
 	/** LLM-named community records (contracts/graph.ts ClusterLabeling). */
 	clusterLabels: path.join(PATHS.graph, "cluster-labels.jsonl"),
 } as const;
diff --git a/src/agent/subagents/extraction.ts b/src/agent/subagents/extraction.ts
index 67157f6..119652b 100644
--- a/src/agent/subagents/extraction.ts
+++ b/src/agent/subagents/extraction.ts
@@ -18,6 +18,8 @@ import type {
 import { getGraph, mergeFindings, type EmissionStats, type GraphDeps } from "../../core/graph.ts";
 import type { GraphStore } from "../../core/ports.ts";
 import { settleGraphLayout } from "../../core/layout-settle.ts";
+import { batchRuns, batchTag, coverageOf, messageViewLines } from "../../core/coverage.ts";
+import { EXTRACTION } from "../../../config.ts";
 import { refreshClusterLabels } from "./cluster-namer.ts";
 
 /**
@@ -71,15 +73,6 @@ import { refreshClusterLabels } from "./cluster-namer.ts";
  * (question text + what the learner did — kind/correct are rebuilt by the
  * merger; the extractor only needs enough to attribute.)
  */
-function quizLine(part: { toolCallId: string; input: unknown; output: unknown }): string {
-	const input = part.input as { question?: unknown } | undefined;
-	const out = part.output as Partial<{ questionText: string; correct: boolean; dontKnow: boolean; note: string }> | undefined;
-	const question = typeof input?.question === "string" ? input.question : out?.questionText ?? "(no question)";
-	const outcome = out?.dontKnow === true ? "did not know" : out?.correct === true ? "answered correctly" : "answered incorrectly";
-	const note = typeof out?.note === "string" && out.note ? ` (note: ${out.note})` : "";
-	return `QUIZ [${part.toolCallId}] ${question} — the learner ${outcome}${note}`;
-}
-
 /**
  * The compact transcript both LLM stages see: user/teacher text VERBATIM,
  * each tagged with its message id (provenance anchors — the extractor
@@ -90,25 +83,12 @@ function quizLine(part: { toolCallId: string; input: unknown; output: unknown })
  * are summarized as one line each.
  */
 export function transcriptView(record: ChatRecord): string {
-	const lines: string[] = [];
-	lines.push(`SESSION: ${record.title}`);
-
+	// The shared seam (core/coverage.ts messageViewLines): the LLM's prompt
+	// view and the coverage fingerprint use ONE line builder, so "covered"
+	// means — exactly — what the extractor saw.
+	const lines = [`SESSION: ${record.title}`];
 	record.messages.forEach((message, index) => {
-		const who = message.role === "user" ? "LEARNER" : "TEACHER";
-		const mid = (message as UIMessage).id || `m${index}`;
-		for (const part of (message as UIMessage).parts) {
-			if (part.type === "text" && part.text.trim()) {
-				lines.push(`${who} [${mid}] ${part.text.trim()}`);
-			} else if (part.type.startsWith("tool-")) {
-				const name = part.type.slice("tool-".length);
-				const p = part as unknown as { toolCallId: string; state: string; input: unknown; output: unknown };
-				if (name === "quiz" && p.state === "output-available") {
-					lines.push(quizLine(p));
-				} else if (p.state === "output-available") {
-					lines.push(`(${name} tool result delivered)`);
-				}
-			}
-		}
+		lines.push(...messageViewLines(message as UIMessage, (message as UIMessage).id || `m${index}`));
 	});
 	return lines.join("\n");
 }
@@ -623,12 +603,9 @@ export function createExtractionPipeline(deps: ExtractionPipelineDeps): Extracti
 		};
 	}
 
-	async function extract(chatId: string): Promise<SessionFindings> {
-		const record = chatStore.getChat(chatId);
-		if (!record) throw new Error(`Chat not found: ${chatId}`);
+	async function extract(chatId: string, view: string): Promise<SessionFindings> {
 		const signal = runningExtractions.get(chatId)?.controller.signal;
 		signal?.throwIfAborted(); // an abort during a sync gap ends the run here
-		const view = transcriptView(record);
 		console.info(`[extraction ${chatId}] extractor starting (${view.split("\n").length} transcript lines)`);
 		const t0 = performance.now();
 
@@ -645,12 +622,9 @@ export function createExtractionPipeline(deps: ExtractionPipelineDeps): Extracti
 		return findings;
 	}
 
-	async function audit(chatId: string, findings: SessionFindings): Promise<AuditResult> {
-		const record = chatStore.getChat(chatId);
-		if (!record) throw new Error(`Chat not found: ${chatId}`);
+	async function audit(chatId: string, findings: SessionFindings, view: string): Promise<AuditResult> {
 		const signal = runningExtractions.get(chatId)?.controller.signal;
 		signal?.throwIfAborted(); // an abort during the extract→audit gap ends here
-		const view = transcriptView(record);
 		const graph = getGraph(graphStore);
 		console.info(
 			`[extraction ${chatId}] auditor starting (${findings.propositions.length} propositions, ${findings.edges.length} edges, ` +
@@ -708,21 +682,66 @@ export function createExtractionPipeline(deps: ExtractionPipelineDeps): Extracti
 		if (inFlight.has(chatId)) return { nodes: 0, edges: 0, events: 0 };
 		inFlight.add(chatId);
 		const t0 = performance.now();
+		// COVERAGE (vision-extraction-coverage.md, 2026-09-15): extract ONLY
+		// what the per-chat coverage ledger doesn't already hold — never the
+		// whole session. Batches are token-budgeted runs of the oldest
+		// uncovered messages; each merged batch checkpoints its messages'
+		// coverage ATOMICALLY (inside the merger's step 4), so an abort or
+		// error below loses at most the in-flight batch — every earlier
+		// batch stays covered, the rest stays visibly uncovered.
+		let batchesDone = 0;
+		const total: EmissionStats = { nodes: 0, edges: 0, events: 0 };
 		try {
-			console.info(`[extraction ${chatId}] pipeline start`);
-			setPhase(chatId, "extracting", "chat");
-			const findings = await extract(chatId);
-			setPhase(chatId, "auditing", "chat");
-			const auditResult = await audit(chatId, findings);
-			setPhase(chatId, "merging", "chat");
-			// The merger merges from the CURRENT record — events are rebuilt
-			// from the live transcript, never from stale copies.
 			const record = chatStore.getChat(chatId);
 			if (!record) throw new Error(`Chat not found: ${chatId}`);
-			const stats = mergeFindings(chatId, auditResult, { chatStore, graphStore }, {
-				messages: record.messages as UIMessage[],
-				foldedAt: record.updatedAt,
-			});
+			const covered = coverageOf(record.messages as UIMessage[], graphStore.readCoverage(), chatId);
+			if (covered.uncovered.length === 0) {
+				console.info(`[extraction ${chatId}] nothing uncovered — no-op`);
+				return { nodes: 0, edges: 0, events: 0 };
+			}
+			const batches = batchRuns(covered.uncovered, EXTRACTION.chunkTokens);
+			console.info(
+				`[extraction ${chatId}] pipeline start — ${covered.uncoveredTokens} uncovered tok, ` +
+					`${covered.uncoveredCount} messages, ${batches.length} batch(es) of ≤${EXTRACTION.chunkTokens} tok`,
+			);
+			for (const batch of batches) {
+				// The batch's prompt view: SESSION header + the batch's lines,
+				// same provenance [id] tags the fingerprints used (coverage
+				// and prompt share ONE line builder — core/coverage.ts).
+				const mids = record.messages.map((m, i) => ((m as UIMessage).id || `m${i}`) as string);
+				const view = [
+					`SESSION: ${record.title}`,
+					...batch.flatMap((slot) => {
+						const idx = record.messages.indexOf(slot.message);
+						return messageViewLines(slot.message, mids[idx] ?? slot.message.id);
+					}),
+				].join("\n");
+				setPhase(chatId, "extracting", "chat");
+				const findings = await extract(chatId, view);
+				setPhase(chatId, "auditing", "chat");
+				const auditResult = await audit(chatId, findings, view);
+				setPhase(chatId, "merging", "chat");
+				// The batch's messages, snapshotted when the run computed
+				// coverage — if a message mutates mid-run (a quiz answer
+				// merges in), the stored fingerprint won't match its new
+				// one and it re-opens: honest by construction.
+				const foldedAt = new Date().toISOString();
+				const stats = mergeFindings(chatId, auditResult, { chatStore, graphStore }, {
+					messages: batch.map((slot) => slot.message),
+					foldedAt,
+					coverage: batch.map((slot) => ({ chatId, fp: slot.fp, tokens: slot.tokens, foldedAt })),
+					batchTag: batchTag(batch),
+				});
+				total.nodes += stats.nodes;
+				total.edges += stats.edges;
+				total.events += stats.events;
+				batchesDone++;
+				console.info(
+					`[extraction ${chatId}] batch ${batchesDone}/${batches.length} merged: ` +
+						`${stats.nodes} nodes, ${stats.edges} edges, ${stats.events} events`,
+				);
+			}
+			const stats = total;
 			// Semantic embeddings (DECIDED 2026-09-13): topics come from
 			// MEANING, so embed the new propositions BEFORE the settle and
 			// the namer look at clusters. Failure is non-fatal — clustering
@@ -747,18 +766,23 @@ export function createExtractionPipeline(deps: ExtractionPipelineDeps): Extracti
 			}).catch(() => {});
 			return stats;
 		} catch (err) {
-			persistRunUsage(chatId, Math.round(performance.now() - t0), undefined);
+			persistRunUsage(chatId, Math.round(performance.now() - t0), batchesDone > 0 ? total : undefined);
 			// Aborted (the dock's abort button): a deliberate stop, not a
-			// failure — same ledger discipline as a failure (nothing merged,
-			// nothing checkpointed, partial usage persisted), but the run
-			// reports zero emissions instead of throwing.
+			// failure. Per-batch coverage (above) makes the stop CHEAP: every
+			// merged batch stays covered; only the in-flight one doesn't — it
+			// stays uncovered, and the next trigger or manual run picks it
+			// up. Partial usage is persisted either way.
 			if (err instanceof Error && err.name === "AbortError") {
-				console.info(`[extraction ${chatId}] aborted (${Math.round(performance.now() - t0)}ms) — nothing merged, nothing checkpointed`);
-				return { nodes: 0, edges: 0, events: 0 };
+				console.info(
+					`[extraction ${chatId}] aborted (${Math.round(performance.now() - t0)}ms) — ` +
+						`${batchesDone} merged batch(es) stay covered, the in-flight one does not`,
+				);
+				return total;
 			}
-			// The throw travels to the caller; this line is what makes the
-			// run's log legible end-to-end (no hanging "pipeline start").
-			console.error(`[extraction ${chatId}] pipeline failed (${Math.round(performance.now() - t0)}ms):`, err);
+			// A failure keeps the same discipline: merged batches stay
+			// covered, nothing else is checkpointed, and the throw travels
+			// to the caller (this line keeps the run's log legible).
+			console.error(`[extraction ${chatId}] pipeline failed (${Math.round(performance.now() - t0)}ms) after ${batchesDone} batch(es):`, err);
 			throw err;
 		} finally {
 			inFlight.delete(chatId);
diff --git a/src/core/contracts/graph.ts b/src/core/contracts/graph.ts
index 3a69258..1ca8a75 100644
--- a/src/core/contracts/graph.ts
+++ b/src/core/contracts/graph.ts
@@ -116,6 +116,24 @@ export interface SessionCheckpoint {
 	foldedAt: string;
 }
 
+/** coverage.jsonl line (vision-extraction-coverage.md, settled 2026-09-15):
+ *  ONE MESSAGE of one chat has been extracted — by content fingerprint over
+ *  exactly what the extraction view sees. The MESSAGE is the unit of
+ *  coverage; "uncovered" is derived (fingerprint the current transcript,
+ *  diff) — never dual-tracked. A quiz answer merging into the asking
+ *  message changes its fingerprint: the message re-opens itself, only
+ *  itself. Chat extractions write these instead of whole-chat checkpoints;
+ *  notes imports keep the checkpoint (a file is one shot). */
+export interface CoverageEntry {
+	chatId: string;
+	/** sha256 of the message's view lines — "covered" means exactly this. */
+	fp: string;
+	/** chars/4 estimate of the message's view — display + budgeting. */
+	tokens: number;
+	/** ISO — when this message's last extraction run merged. */
+	foldedAt: string;
+}
+
 /**
  * Event kinds (DECIDED 2026-09-02): quiz outcomes only — correct / miss /
  * dont-know — plus `observation`, the extractor's per-proposition
diff --git a/src/core/coverage.ts b/src/core/coverage.ts
new file mode 100644
index 0000000..2587ac0
--- /dev/null
+++ b/src/core/coverage.ts
@@ -0,0 +1,174 @@
+/**
+ * Extraction coverage (vision-extraction-coverage.md, settled 2026-09-15) —
+ * the pure core. THE MESSAGE IS THE UNIT OF COVERAGE: a per-chat append-only
+ * ledger records which messages have been extracted, by CONTENT FINGERPRINT
+ * over exactly what the extraction view sees; "uncovered" is DERIVED at
+ * read time (fingerprint the current transcript, diff against the ledger) —
+ * never dual-tracked. Runs are token-budgeted batches of the oldest
+ * uncovered messages, so a tool call and its result (which share a message)
+ * can never be separated.
+ *
+ * The fingerprint and the LLM prompt share ONE line builder —
+ * messageViewLines — so "covered" and "what the model saw" cannot drift
+ * apart. The line logic is tree-blind, identical to the extractor's view:
+ * user/teacher text verbatim, quiz outcomes as one-line summaries, other
+ * tool results as one generic line each, data parts invisible (plan-block
+ * attach does not re-open a covered message).
+ */
+
+import { createHash } from "node:crypto";
+import type { UIMessage } from "ai";
+import { isToolUIPart } from "ai";
+
+import type { CoverageEntry } from "./contracts/graph.ts";
+
+export type { CoverageEntry };
+
+/** The quiz outcome line — both the fingerprint and the LLM view see the
+ *  quiz answer, so an answered quiz re-opens the message that asked it. */
+function quizLine(part: { toolCallId: string; input: unknown; output: unknown }): string {
+	const input = part.input as { question?: unknown } | undefined;
+	const out = part.output as Partial<{ questionText: string; correct: boolean; dontKnow: boolean; note: string }> | undefined;
+	const question = typeof input?.question === "string" ? input.question : out?.questionText ?? "(no question)";
+	const outcome = out?.dontKnow === true ? "did not know" : out?.correct === true ? "answered correctly" : "answered incorrectly";
+	const note = typeof out?.note === "string" && out.note ? ` (note: ${out.note})` : "";
+	return `QUIZ [${part.toolCallId}] ${question} — the learner ${outcome}${note}`;
+}
+
+/**
+ * The extraction-relevant lines of ONE message — the shared seam between
+ * transcriptView (the LLM's prompt) and messageFingerprint (coverage). Same
+ * logic, same order, so a covered message is by construction exactly what
+ * the extractor saw. `mid` is the provenance tag (the message id; the
+ * transcript view passes an index fallback for legacy id-less messages,
+ * coverage passes the id — persisted messages always have ids).
+ */
+export function messageViewLines(message: UIMessage, mid: string): string[] {
+	const lines: string[] = [];
+	const who = message.role === "user" ? "LEARNER" : "TEACHER";
+	for (const part of message.parts) {
+		if (part.type === "text" && part.text.trim()) {
+			lines.push(`${who} [${mid}] ${part.text.trim()}`);
+		} else if (isToolUIPart(part)) {
+			const name = part.type.slice("tool-".length);
+			if (name === "quiz" && part.state === "output-available") {
+				lines.push(quizLine(part as unknown as { toolCallId: string; input: unknown; output: unknown }));
+			} else if (part.state === "output-available") {
+				lines.push(`(${name} tool result delivered)`);
+			}
+		}
+	}
+	return lines;
+}
+
+/** Tokens of a message's view — chars/4, ceil, the app-wide estimate. */
+export function viewTokens(lines: string[]): number {
+	return Math.ceil(lines.join("\n").length / 4);
+}
+
+/**
+ * A message's coverage fingerprint: sha256 of role + its view lines (with
+ * the message's real id as the provenance tag). Changes exactly when the
+ * extraction view of the message changes: an answered quiz merges into the
+ * asking message → new line → the message re-opens itself, and only itself.
+ * Plan-block part attach changes data parts (invisible to the view) → the
+ * fingerprint is stable → still covered.
+ */
+export function messageFingerprint(message: UIMessage): string {
+	const h = createHash("sha256");
+	h.update(JSON.stringify([message.role, messageViewLines(message, message.id)]));
+	return h.digest("hex");
+}
+
+/** One message's coverage-relevant projection. */
+export interface CoverageSlot {
+	message: UIMessage;
+	fp: string;
+	tokens: number;
+}
+
+/** Fingerprint a whole transcript, in order (used by the trigger, the run,
+ *  and the coverage view — one derivation everywhere). */
+export function coverageSlots(messages: ReadonlyArray<UIMessage>): CoverageSlot[] {
+	return messages.map((message) => {
+		const lines = messageViewLines(message, message.id);
+		const h = createHash("sha256");
+		h.update(JSON.stringify([message.role, lines]));
+		return { message, fp: h.digest("hex"), tokens: viewTokens(lines) };
+	});
+}
+
+/** The covered-fingerprint set for one chat, from the ledger. */
+export function coveredSet(entries: ReadonlyArray<CoverageEntry>, chatId: string): Set<string> {
+	const out = new Set<string>();
+	for (const e of entries) if (e.chatId === chatId) out.add(e.fp);
+	return out;
+}
+
+/** The derived state: which slots are uncovered, plus the token totals.
+ *  "Uncovered" needs no ledger of its own — this diff IS the coverage view. */
+export function coverageOf(
+	messages: ReadonlyArray<UIMessage>,
+	entries: ReadonlyArray<CoverageEntry>,
+	chatId: string,
+): {
+	slots: CoverageSlot[];
+	uncovered: CoverageSlot[];
+	coveredTokens: number;
+	uncoveredTokens: number;
+	coveredCount: number;
+	uncoveredCount: number;
+} {
+	const covered = coveredSet(entries, chatId);
+	const slots = coverageSlots(messages);
+	const uncovered = slots.filter((s) => !covered.has(s.fp));
+	const coveredCount = slots.length - uncovered.length;
+	let coveredTokens = 0;
+	let uncoveredTokens = 0;
+	for (const s of slots) {
+		if (covered.has(s.fp)) coveredTokens += s.tokens;
+		else uncoveredTokens += s.tokens;
+	}
+	return { slots, uncovered, coveredTokens, uncoveredTokens, coveredCount, uncoveredCount: uncovered.length };
+}
+
+/**
+ * Batch the uncovered messages into token-budgeted RUNS: consecutive slots,
+ * oldest first, greedy fill — a message is never split (it is the unit), so
+ * a tool call and its result always travel together. A single message larger
+ * than the budget becomes its own (over-budget) run rather than being
+ * dropped. Runs are ephemeral — the durable record is per-message coverage,
+ * checkpointed after each run merges.
+ */
+export function batchRuns(uncovered: ReadonlyArray<CoverageSlot>, budget: number): CoverageSlot[][] {
+	if (budget <= 0 || uncovered.length === 0) return [];
+	const runs: CoverageSlot[][] = [];
+	let current: CoverageSlot[] = [];
+	let currentTokens = 0;
+	for (const slot of uncovered) {
+		if (current.length > 0 && currentTokens + slot.tokens > budget) {
+			runs.push(current);
+			current = [];
+			currentTokens = 0;
+		}
+		current.push(slot);
+		currentTokens += slot.tokens;
+	}
+	if (current.length > 0) runs.push(current);
+	return runs;
+}
+
+/**
+ * A batch's deterministic tag: hash of its member fingerprints. This is the
+ * observation-ref prefix for the run (obs:<tag>:<sourceId> in the merger):
+ * re-running the SAME batch (crash recovery) produces the same refs and
+ * dedupes; a re-opened (mutated) message changes the tag, so its fresh
+ * understanding observations land as new events — the most-recent fold
+ * sees the update. Run-local source ids ("p1"…) alone could never do this:
+ * their positions shift between runs.
+ */
+export function batchTag(batch: ReadonlyArray<CoverageSlot>): string {
+	const h = createHash("sha256");
+	for (const slot of batch) h.update(slot.fp);
+	return h.digest("hex").slice(0, 12);
+}
\ No newline at end of file
diff --git a/src/core/graph.ts b/src/core/graph.ts
index 1c4863c..986c81b 100644
--- a/src/core/graph.ts
+++ b/src/core/graph.ts
@@ -40,6 +40,7 @@
 
 import { createHash, randomBytes } from "node:crypto";
 import { isToolUIPart, type UIMessage } from "ai";
+import type { CoverageEntry } from "./contracts/graph.ts";
 import type {
 	AuditResult,
 	Cluster,
@@ -67,14 +68,29 @@ function newGraphNodeId(): string {
 }
 
 /** What one merge run merges FROM (the caller supplies it — the merger never
- *  reads the chat store): a session's transcript + its `updatedAt`
- *  checkpoint, or — for the format-agnostic notes front door (2026-09-13) —
- *  `messages: null`: raw notes carry no tool parts, so no quiz events are
- *  rebuilt (quiz outcomes inside notes surface only through the extractor's
- *  understanding observations), and the checkpoint stamps the import. */
+ *  reads the chat store): a session's transcript + its coverage checkpoint,
+ *  or — for the format-agnostic notes front door (2026-09-13) — `messages:
+ *  null`: raw notes carry no tool parts, so no quiz events are rebuilt (quiz
+ *  outcomes inside notes surface only through the extractor's understanding
+ *  observations), and the whole-file checkpoint stamps the import.
+ *
+ *  Coverage (vision-extraction-coverage.md, settled 2026-09-15): a chat merge
+ *  passes the BATCH it extracted — the caller computed the fingerprints
+ *  before the run, from the same snapshot the merger sees — and step 4
+ *  appends one CoverageEntry per message on success ("covered" means
+ *  exactly this merge happened). `batchTag` prefixes the observation refs so
+ *  re-runs of the SAME batch dedupe while a re-opened (mutated) message's
+ *  fresh understanding observations land as new events; the notes path
+ *  passes neither and keeps the whole-file checkpoint. */
 export interface MergeSource {
 	messages: UIMessage[] | null;
 	foldedAt: string;
+	/** The batch being merged (chat path): one entry per message in
+	 *  `messages`, same order — undefined (notes path / coverage-less
+	 *  callers) → the legacy whole-chat checkpoint is written instead. */
+	coverage?: CoverageEntry[];
+	/** The batch's deterministic tag (core/coverage.ts batchTag) — obs refs. */
+	batchTag?: string;
 }
 
 // ─── transcript scanning (shared by the merger + trigger) ─────────────────────
@@ -241,10 +257,13 @@ export function mergeFindings(chatId: string, audit: AuditResult, deps: GraphDep
 		}
 	}
 	// Understanding observations: one per proposition carrying a note,
-	// resolved to the node the verdict mapped it to.
+	// resolved to the node the verdict mapped it to. Refs carry the batch
+	// tag when there is one: run-local source ids ("p1"…) shift position
+	// between runs, so a bare obs:p1 could never both dedupe a re-run of
+	// the same batch AND let a re-opened message's fresh level through.
 	for (const p of audit.propositions) {
 		if (p.understanding === undefined || p.understanding.length === 0) continue;
-		const ref = `obs:${p.id}`;
+		const ref = source.batchTag !== undefined ? `obs:${source.batchTag}:${p.id}` : `obs:${p.id}`;
 		if (seenRefs.has(ref)) continue;
 		ledgers.appendEvent({
 			nodeId: mapping.get(p.id) ?? null,
@@ -258,9 +277,17 @@ export function mergeFindings(chatId: string, audit: AuditResult, deps: GraphDep
 		stats.events++;
 	}
 
-	// 4. Checkpoint: this source is extracted through its foldedAt (the
-	//    chat's updatedAt, or the import time for notes).
-	ledgers.appendCheckpoint({ chatId, foldedAt: source.foldedAt });
+	// 4. Checkpoint — THE COVERAGE DISCIPLINE (vision-extraction-coverage.md):
+	//    only now, after every append succeeded, is the batch covered. The
+	//    chat path appends one CoverageEntry per message (per-batch atomic —
+	//    an abort or failure mid-run leaves earlier batches covered, this
+	//    batch's messages uncovered); the notes path keeps the whole-file
+	//    checkpoint (a file is one shot).
+	if (source.coverage !== undefined) {
+		for (const entry of source.coverage) ledgers.appendCoverage(entry);
+	} else {
+		ledgers.appendCheckpoint({ chatId, foldedAt: source.foldedAt });
+	}
 	return stats;
 }
 
@@ -302,34 +329,6 @@ function quizEvent(
 	return event;
 }
 
-// ─── the trigger helper (v1: every N quiz answers — swappable seam) ──────────
-
-/**
- * How many ANSWERED quiz parts in this chat are not yet in the ledger — i.e.
- * new evidence since the last extraction. The v1 trigger (turn-service)
- * fires the pipeline when this crosses EXTRACTION.everyNQuizAnswers. Every
- * answered quiz always becomes an event (attribution only decides nodeId),
- * so ref-not-in-ledger is a correct "not yet processed" marker.
- */
-export function pendingQuizAnswers(chatId: string, deps: GraphDeps): number {
-	const record = deps.chatStore.getChat(chatId);
-	if (!record) return 0;
-	const seenRefs = new Set<string>();
-	for (const event of deps.graphStore.readEvents()) {
-		if (event.chatId === chatId && event.ref) seenRefs.add(event.ref);
-	}
-	let count = 0;
-	for (const part of toolParts(record.messages)) {
-		if (part.name !== "quiz" || part.state !== "output-available") continue;
-		const out = part.output;
-		if (typeof out !== "object" || out === null) continue;
-		const answer = out as Partial<QuestionAnswerData>;
-		if (answer.kind !== "quiz" || answer.dismissed === true) continue; // dismissed = not answered
-		if (!seenRefs.has(part.toolCallId)) count++;
-	}
-	return count;
-}
-
 // ─── derivation (reads only — everything below is recomputable) ─────────────
 
 /** The content identity of a community: "clu_" + sha256 of the sorted
diff --git a/src/core/index.ts b/src/core/index.ts
index 753794b..2405463 100644
--- a/src/core/index.ts
+++ b/src/core/index.ts
@@ -34,4 +34,5 @@ export * from "./ui-message.ts";
 export * from "./tool-parts.ts";
 export * from "./prices.ts";
 export * from "./fuzzy.ts";
+export * from "./coverage.ts";
 export * from "./graph-context.ts";
diff --git a/src/core/ports.ts b/src/core/ports.ts
index 9f9d893..aa9e3d7 100644
--- a/src/core/ports.ts
+++ b/src/core/ports.ts
@@ -23,6 +23,7 @@ import type {
 	NodeMapping,
 	PlanTree,
 	Position,
+	CoverageEntry,
 	SessionCheckpoint,
 	TurnUsage,
 	NotesSource,
@@ -84,6 +85,11 @@ export interface GraphStore {
 	/** Append one emission checkpoint. */
 	appendCheckpoint(checkpoint: SessionCheckpoint): void;
 	readCheckpoints(): SessionCheckpoint[];
+	/** Message-granular extraction coverage (vision-extraction-coverage.md):
+	 *  append-only; one line per covered message. The chat-extraction
+	 *  checkpoint — "uncovered" is derived from these, never tracked. */
+	appendCoverage(entry: CoverageEntry): void;
+	readCoverage(): CoverageEntry[];
 
 	/** Append one cluster labeling — idempotent by id (the id hashes the
 	 *  sorted core, so identical member sets dedupe). */
diff --git a/src/server/turn-service.ts b/src/server/turn-service.ts
index ff120cb..62f265e 100644
--- a/src/server/turn-service.ts
+++ b/src/server/turn-service.ts
@@ -17,7 +17,7 @@
 
 import type { UIMessage } from "ai";
 import { withPlanBlocks } from "../core/plan-blocks.ts";
-import { pendingQuizAnswers } from "../core/graph.ts";
+import { coverageOf } from "../core/coverage.ts";
 import type { ChatStore, GraphStore } from "../core/ports.ts";
 import { EXTRACTION } from "../../config.ts";
 import type { ExtractionPipeline } from "../agent/subagents/extraction.ts";
@@ -74,15 +74,17 @@ export function persistTurn(chatStore: ChatStore, chatId: string, messages: UIMe
 /**
  * The graph write channel (vision §1 construction): the extraction pipeline
  * (extractor → auditor → merger — the sole graph writer) runs ASYNC once a
- * chat accumulates EXTRACTION.everyNQuizAnswers new answered quizzes since
- * its last checkpoint. Fire-and-forget — never blocks the turn; failures
- * are logged by the pipeline and leave the checkpoint untouched, so the
- * next trigger re-runs the whole thing.
+ * chat's UNCOVERED transcript tokens reach EXTRACTION.chunkTokens
+ * (vision-extraction-coverage.md, 2026-09-15 — replacing the old
+ * every-3-quiz-answers count: content size is the honest signal, and
+ * quiz-less sessions extract too). The pipeline itself extracts only the
+ * uncovered batches. Fire-and-forget — never blocks the turn; failures are
+ * logged by the pipeline and leave coverage untouched, so the next trigger
+ * (or the manual extract button) re-runs what's left.
  *
- * v1 placeholder trigger, deliberately isolated in this one seam: swap
- * here when a better mechanism lands — the pipeline is trigger-agnostic.
- * Skipped under tests: scripted chats are fixtures, not knowledge (the
- * pipeline itself is tested directly with mock models).
+ * Deliberately isolated in this one seam — the pipeline is
+ * trigger-agnostic. Skipped under tests: scripted chats are fixtures, not
+ * knowledge (the pipeline itself is tested directly with mock models).
  */
 export function triggerExtraction(
 	deps: { chatStore: ChatStore; graphStore: GraphStore },
@@ -91,7 +93,10 @@ export function triggerExtraction(
 ): void {
 	if (process.env.NODE_ENV === "test") return;
 	try {
-		if (pendingQuizAnswers(chatId, deps) < EXTRACTION.everyNQuizAnswers) return;
+		const record = deps.chatStore.getChat(chatId);
+		if (!record) return;
+		const covered = coverageOf(record.messages as UIMessage[], deps.graphStore.readCoverage(), chatId);
+		if (covered.uncoveredTokens < EXTRACTION.chunkTokens) return;
 		void extraction.runExtraction(chatId).catch((err) => {
 			console.error(`[chat ${chatId}] extraction pipeline failed:`, err);
 		});
diff --git a/src/store/graph.ts b/src/store/graph.ts
index 8c72007..b18e6de 100644
--- a/src/store/graph.ts
+++ b/src/store/graph.ts
@@ -42,6 +42,7 @@ import type {
 	NodeMapping,
 	Position,
 	ProvenancePoint,
+	CoverageEntry,
 	SessionCheckpoint,
 } from "../core/contracts.ts";
 import type { GraphStore } from "../core/ports.ts";
@@ -133,6 +134,9 @@ const isNodeMapping = (v: unknown): v is NodeMapping =>
 const isCheckpoint = (v: unknown): v is SessionCheckpoint =>
 	isRecord(v) && isString(v.chatId) && isString(v.foldedAt);
 
+const isCoverageEntry = (v: unknown): v is CoverageEntry =>
+	isRecord(v) && isString(v.chatId) && isString(v.fp) && typeof v.tokens === "number" && isString(v.foldedAt);
+
 // ─── the port implementation ────────────────────────────────────────────────
 
 export const graphStore: GraphStore = {
@@ -175,6 +179,13 @@ export const graphStore: GraphStore = {
 		return readValid(LEDGER_FILES.sessions, isCheckpoint);
 	},
 
+	appendCoverage(entry: CoverageEntry): void {
+		appendLine(LEDGER_FILES.coverage, entry);
+	},
+	readCoverage(): CoverageEntry[] {
+		return readValid(LEDGER_FILES.coverage, isCoverageEntry);
+	},
+
 	// ── cluster labelings (config.LEDGER_FILES.clusterLabels) ──
 
 	/** Idempotent by id: the id is a hash of the sorted core, so re-appending
diff --git a/tests/coverage.test.ts b/tests/coverage.test.ts
new file mode 100644
index 0000000..3b7fdb5
--- /dev/null
+++ b/tests/coverage.test.ts
@@ -0,0 +1,159 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import type { UIMessage } from "ai";
+
+import {
+	batchRuns,
+	batchTag,
+	coverageOf,
+	coverageSlots,
+	messageFingerprint,
+	messageViewLines,
+} from "../src/core/coverage.ts";
+import type { CoverageEntry } from "../src/core/contracts.ts";
+
+/**
+ * Extraction coverage — the pure core (vision-extraction-coverage.md,
+ * settled 2026-09-15). THE MESSAGE IS THE UNIT OF COVERAGE; the fingerprint
+ * and the LLM prompt share ONE line builder (messageViewLines), so "covered"
+ * is by construction exactly "what the extractor saw".
+ */
+
+function user(id: string, text: string): UIMessage {
+	return { id, role: "user", parts: [{ type: "text", text }] } as unknown as UIMessage;
+}
+
+function slot(messages: UIMessage[], id: string) {
+	const found = coverageSlots(messages).find((s) => s.message.id === id);
+	assert.ok(found, `slot ${id}`);
+	return found;
+}
+
+describe("messageFingerprint — what changes it, what never does", () => {
+	it("a text edit changes the fingerprint; role participates", () => {
+		const a = messageFingerprint(user("m1", "hello world"));
+		const b = messageFingerprint(user("m1", "hello worlds"));
+		const same = messageFingerprint(user("m1", "hello world"));
+		assert.notEqual(a, b);
+		assert.equal(a, same);
+		// Role is hashed too — a user and an assistant line never collide.
+		const teacher = { id: "m1", role: "assistant", parts: [{ type: "text", text: "hello world" }] } as unknown as UIMessage;
+		assert.notEqual(a, messageFingerprint(teacher));
+	});
+
+	it("the message id is the provenance tag — part of exactly what the extractor saw", () => {
+		// The view lines carry the [id] tag, so identical content under a
+		// different id is a DIFFERENT fingerprint: coverage matches the
+		// extraction view byte-for-byte. (Ids are stable in practice — the
+		// write-ahead persist owns them.)
+		assert.notEqual(messageFingerprint(user("m1", "same")), messageFingerprint(user("m2", "same")));
+		// The id is the ONLY tag: the same id + content re-fingerprints equal.
+		assert.equal(messageFingerprint(user("m1", "same")), messageFingerprint(user("m1", "same")));
+	});
+
+	it("data parts are invisible — plan-block attach never re-opens a covered message", () => {
+		const plain = user("m1", "teach me the chain rule");
+		const withData = {
+			...plain,
+			parts: [...plain.parts, { type: "data-plan-blocks", planBlocks: [] }],
+		} as unknown as UIMessage;
+		assert.equal(messageFingerprint(plain), messageFingerprint(withData));
+	});
+
+	it("a quiz answer merging in changes the fingerprint — and only that message's", () => {
+		const asking = {
+			id: "a1",
+			role: "assistant",
+			parts: [{ type: "tool-quiz", toolCallId: "q1", state: "input-available", input: { question: "Q?" } }],
+		} as unknown as UIMessage;
+		const answered = {
+			id: "a1",
+			role: "assistant",
+			parts: [
+				{ type: "tool-quiz", toolCallId: "q1", state: "output-available", input: { question: "Q?" }, output: { questionText: "Q?", correct: true } },
+			],
+		} as unknown as UIMessage;
+		const fpBefore = messageFingerprint(asking);
+		assert.notEqual(fpBefore, messageFingerprint(answered));
+		// An output-bearing line's mass counts toward coverage tokens.
+		assert.ok(
+			messageViewLines(answered, answered.id).join("").length >
+				messageViewLines(asking, asking.id).join("").length,
+		);
+	});
+});
+
+describe("coverageOf — uncovered is DERIVED, never dual-tracked", () => {
+	it("diffs fingerprints: covered stays, uncovered counts, tokens split", () => {
+		const messages = [user("m1", "aaaa"), user("m2", "bbbb"), user("m3", "cccc")];
+		const fp1 = slot(messages, "m1").fp;
+		const fp2 = slot(messages, "m2").fp;
+		const entries: CoverageEntry[] = [
+			{ chatId: "c1", fp: fp1, tokens: 1, foldedAt: "2026-09-15T00:00:00.000Z" },
+			{ chatId: "c1", fp: fp2, tokens: 1, foldedAt: "2026-09-15T00:00:00.000Z" },
+			// Another chat's entries are irrelevant to c1's coverage.
+			{ chatId: "c2", fp: slot(messages, "m3").fp, tokens: 1, foldedAt: "2026-09-15T00:00:00.000Z" },
+		];
+		const cov = coverageOf(messages, entries, "c1");
+		assert.deepEqual(cov.uncovered.map((s) => s.message.id), ["m3"]);
+		assert.equal(cov.coveredCount, 2);
+		assert.equal(cov.uncoveredCount, 1);
+		assert.equal(cov.uncoveredTokens, slot(messages, "m3").tokens);
+		assert.equal(cov.coveredTokens, slot(messages, "m1").tokens + slot(messages, "m2").tokens);
+	});
+
+	it("a mutated covered message re-opens itself, and only itself", () => {
+		const messages = [user("m1", "aaaa"), user("m2", "bbbb")];
+		const entries: CoverageEntry[] = coverageSlots(messages).map((s) => ({
+			chatId: "c1",
+			fp: s.fp,
+			tokens: s.tokens,
+			foldedAt: "2026-09-15T00:00:00.000Z",
+		}));
+		assert.equal(coverageOf(messages, entries, "c1").uncoveredCount, 0);
+		const mutated = [user("m1", "aaaa!"), messages[1]!];
+		const cov = coverageOf(mutated, entries, "c1");
+		assert.deepEqual(cov.uncovered.map((s) => s.message.id), ["m1"]);
+	});
+});
+
+describe("batchRuns — token-budgeted, consecutive, never splits a message", () => {
+	it("greedy oldest-first fill; the overflowing message starts the next run", () => {
+		// Each message's view line is ~14 tok (chars/4) → budget 45 fits
+		// three, the fourth overflows: [m1,m2,m3] + [m4].
+		const slots = coverageSlots([
+			user("m1", "a".repeat(40)),
+			user("m2", "b".repeat(40)),
+			user("m3", "c".repeat(40)),
+			user("m4", "d".repeat(40)),
+		]);
+		const runs = batchRuns(slots, 45);
+		assert.deepEqual(runs.map((r) => r.map((s) => s.message.id)), [["m1", "m2", "m3"], ["m4"]]);
+	});
+
+	it("a single message larger than the budget becomes its own over-budget run", () => {
+		const slots = coverageSlots([user("m1", "x".repeat(400)), user("m2", "y".repeat(20))]);
+		const runs = batchRuns(slots, 10);
+		assert.deepEqual(runs.map((r) => r.map((s) => s.message.id)), [["m1"], ["m2"]]);
+	});
+
+	it("an empty or non-positive budget never drops messages into a void", () => {
+		assert.deepEqual(batchRuns(coverageSlots([user("m1", "hi")]), 0), []);
+		assert.deepEqual(batchRuns([], 4096), []);
+	});
+});
+
+describe("batchTag — deterministic, ref-stable, mutation-sensitive", () => {
+	it("the same members in the same order → the same 12-hex tag; a different order is a different batch", () => {
+		const slots = coverageSlots([user("m1", "aaaa"), user("m2", "bbbb")]);
+		assert.equal(batchTag(slots), batchTag(coverageSlots([user("m1", "aaaa"), user("m2", "bbbb")])));
+		assert.notEqual(batchTag(slots), batchTag([...slots].reverse()), "batches are ordered runs");
+		assert.match(batchTag(slots), /^[0-9a-f]{12}$/);
+	});
+
+	it("a re-opened member changes the tag — its observations land as new events", () => {
+		const slots = coverageSlots([user("m1", "aaaa"), user("m2", "bbbb")]);
+		const mutated = coverageSlots([user("m1", "aaaa!"), user("m2", "bbbb")]);
+		assert.notEqual(batchTag(slots), batchTag(mutated));
+	});
+});
\ No newline at end of file
diff --git a/tests/extraction.test.ts b/tests/extraction.test.ts
index 24e90ca..f713fe9 100644
--- a/tests/extraction.test.ts
+++ b/tests/extraction.test.ts
@@ -28,6 +28,7 @@ import type { PiEngine } from "../src/agent/models.ts";
 import type {
 	AuditResult,
 	ClusterLabeling,
+	CoverageEntry,
 	ExtractionRunUsage,
 	GraphEdge,
 	GraphNode,
@@ -39,6 +40,7 @@ import type {
 } from "../src/core/contracts.ts";
 import type { GraphStore } from "../src/core/ports.ts";
 import { abortExtraction, createExtractionPipeline, extractionStatuses, transcriptView } from "../src/agent/subagents/extraction.ts";
+import { batchTag, coverageOf, coverageSlots } from "../src/core/coverage.ts";
 import { clusterNamingSettled, refreshClusterLabels } from "../src/agent/subagents/cluster-namer.ts";
 import { semanticClusters } from "../src/core/semantic-clusters.ts";
 import { chatStore } from "../src/store/chats.ts";
@@ -65,6 +67,7 @@ function memoryLedgers() {
 	const events: LedgerEvent[] = [];
 	const mappings: NodeMapping[] = [];
 	const checkpoints: SessionCheckpoint[] = [];
+	const coverage: CoverageEntry[] = [];
 	const sources = new Map<string, NotesSource>();
 	const clusterLabels: ClusterLabeling[] = [];
 	const positions = new Map<string, { x: number; y: number }>();
@@ -86,6 +89,10 @@ function memoryLedgers() {
 		readMappings: () => mappings.map((m) => ({ ...m })),
 		appendCheckpoint: (c: SessionCheckpoint) => void checkpoints.push(c),
 		readCheckpoints: () => checkpoints.map((c) => ({ ...c })),
+		// Extraction coverage (vision-extraction-coverage.md) — append-only;
+		// the chat pipeline checkpoints one entry per covered message.
+		appendCoverage: (e) => void coverage.push({ ...e }),
+		readCoverage: () => coverage.map((e) => ({ ...e })),
 		upsertSource: (s: NotesSource) => {
 			// Mirrors the real store: an upsert KEEPS the existing usage log.
 			const prev = sources.get(s.id);
@@ -356,20 +363,35 @@ describe("the extraction pipeline (extractor → auditor → merger)", () => {
 		// Events rebuilt deterministically: quizzes in transcript order, then
 		// the observation. check-1's attribution pointed at the DROPPED p2 →
 		// unresolvable → null (the question text is kept for later attribution).
+		// The observation ref is BATCH-TAGGED (obs:<tag>:p1) so a re-run of
+		// the same batch dedupes while a re-opened message's update lands as
+		// a new event (vision-extraction-coverage.md).
 		const events = ledgers.readEvents();
+		const record = chatStore.getChat(chatId)!;
+		const expectedTag = batchTag(coverageSlots(record.messages as UIMessage[]));
 		assert.deepEqual(
 			events.map((e) => [e.kind, e.ref, e.nodeId]),
 			[
 				["miss", "probe-1", existingId],
 				["correct", "check-1", null],
-				["observation", "obs:p1", existingId],
+				["observation", `obs:${expectedTag}:p1`, existingId],
 			],
 		);
 		assert.equal(events[0]!.nodeId, existingId, "probe attributed via the verdict's mapping");
 		assert.equal(events[2]!.note, "solid", "the understanding note joins the ledger");
 
-		// Checkpointed through the record's updatedAt — never the same turns twice.
-		assert.equal(ledgers.readCheckpoints().length, 1);
+		// COVERAGE checkpointed per message (not a whole-chat checkpoint):
+		// one entry per transcript message, fingerprinted content each —
+		// the same turns are never extracted twice.
+		const covered = ledgers.readCoverage();
+		assert.equal(covered.length, record.messages.length);
+		assert.ok(covered.every((c) => c.chatId === chatId && c.fp.length === 64 && c.tokens > 0));
+		assert.equal(ledgers.readCheckpoints().length, 0, "the chat path writes coverage, not the legacy checkpoint");
+		assert.equal(
+			coverageOf(record.messages as UIMessage[], covered, chatId).uncoveredCount,
+			0,
+			"every message is now covered",
+		);
 	});
 
 	it("checkpoints nothing when a stage fails", async () => {
@@ -791,3 +813,225 @@ describe("the notes front door (importNotes — format-agnostic)", () => {
 		assert.equal(ledgers.readSources()[0]!.extractions![0]!.stats, undefined, "never merged → no stats");
 	});
 });
+
+// ── the chunked pipeline (extraction coverage — vision-extraction-coverage.md) ──
+
+/** Pull the pipeline's prompt view out of a model call: the pipeline sends
+ *  `Transcript:\n\n<view>` as the user turn, so the LAST user message's
+ *  text IS what the extractor saw. */
+function capturedView(context: unknown): string {
+	const messages = (context as { messages?: { role: string; content: string }[] }).messages ?? [];
+	const last = [...messages].reverse().find((m) => m.role === "user");
+	return typeof last?.content === "string" ? last.content : "";
+}
+
+/** An extractor step that submits FINDINGS, optionally capturing its view. */
+function findingsStep(capture?: (view: string) => void): FauxResponseStep {
+	return (context) => {
+		capture?.(capturedView(context));
+		return fauxAssistantMessage(
+			[fauxToolCall("submit_findings", FINDINGS as unknown as Record<string, unknown>, { id: "findings-call" })],
+			{ stopReason: "toolUse" },
+		);
+	};
+}
+
+/** An auditor step that passes p1 through (no linkTo — a fresh node), drops p2. */
+function passThroughAuditStep(): FauxResponseStep {
+	return () =>
+		fauxAssistantMessage(
+			[
+				fauxToolCall(
+					"submit_review",
+					{
+						propositions: [{ ...FINDINGS.propositions[0]! }],
+						edges: [],
+						attribution: { quiz: {} },
+						dropped: [{ ref: "p2", reason: "evidence not found" }],
+					} as unknown as Record<string, unknown>,
+					{ id: "review-call" },
+				),
+			],
+			{ stopReason: "toolUse" },
+		);
+}
+
+/** A session with UNCOVERED-multiple-batch mass: five long distinct messages
+ *  (~1200 tok each — 3600+1200 > EXTRACTION.chunkTokens 4096 → batches of
+ *  [m1,m2,m3] and [m4,m5]). */
+function chunkyChat() {
+	const chat = chatStore.createChat("Chunky coverage fixture");
+	createdChats.push(chat.id);
+	// ~1230 tok per message (chars/4): three fill the 4096 budget, the
+	// fourth would overflow — deterministic batches [m1,m2,m3] + [m4,m5].
+	chatStore.saveMessages(
+		chat.id,
+		[1, 2, 3, 4, 5].map((n) => user(`u${n}`, `topic ${n}: ${"detail ".repeat(700)}${n}`)),
+	);
+	return { chatId: chat.id, record: chatStore.getChat(chat.id)! };
+}
+
+describe("the chunked pipeline (extraction coverage)", () => {
+	it("extracts uncovered messages in token-budgeted batches, checkpoints coverage per batch, and no-ops once covered", async () => {
+		const { chatId, record } = chunkyChat();
+		const ledgers = memoryLedgers();
+		const views: string[] = [];
+
+		const pipeline = createExtractionPipeline({
+			chatStore,
+			graphStore: ledgers,
+			embedder: fakeEmbedder,
+			extractor: fauxEngine([findingsStep((v) => views.push(v)), findingsStep((v) => views.push(v))]),
+			auditor: fauxEngine([passThroughAuditStep(), passThroughAuditStep()]),
+			labeler: submitModel("submit_labels", { labels: [] }),
+		});
+		const stats = await pipeline.runExtraction(chatId);
+
+		// Two batches: the first held messages 1-3, the second 4-5 — a
+		// message is never split, batches are consecutive oldest-first.
+		assert.equal(views.length, 2, "one extractor call per batch");
+		assert.ok(views[0]!.includes("LEARNER [u1]") && views[0]!.includes("LEARNER [u3]"));
+		assert.ok(!views[0]!.includes("LEARNER [u4]"), "the batch stops at the token budget");
+		assert.ok(views[1]!.includes("LEARNER [u4]") && views[1]!.includes("LEARNER [u5]"));
+		assert.ok(!views[1]!.includes("LEARNER [u3]"));
+
+		// p1 was a fresh node in batch 1; batch 2's p1 mapped to the same
+		// node (chat-scoped mapping) — but its understanding note is a NEW
+		// batch-tagged observation.
+		assert.deepEqual(stats, { nodes: 1, edges: 0, events: 2 });
+
+		// Per-batch coverage: every message checkpointed, nothing legacy.
+		const coverage = ledgers.readCoverage();
+		assert.equal(coverage.length, record.messages.length);
+		assert.equal(ledgers.readCheckpoints().length, 0);
+		assert.equal(coverageOf(record.messages as UIMessage[], coverage, chatId).uncoveredCount, 0);
+
+		// A second run is a NO-OP: nothing uncovered → no model calls, no
+		// new usage entry (no money spent on covered ground).
+		const before = views.length;
+		const again = await pipeline.runExtraction(chatId);
+		assert.deepEqual(again, { nodes: 0, edges: 0, events: 0 });
+		assert.equal(views.length, before);
+		assert.equal(chatStore.getChat(chatId)!.extractions?.length, 1, "the no-op run persists no usage");
+	});
+
+	it("aborting after a merged batch keeps it covered; the re-run extracts only the remainder", async () => {
+		const { chatId, record } = chunkyChat();
+		const ledgers = memoryLedgers();
+		const views: string[] = [];
+
+		const pipeline = createExtractionPipeline({
+			chatStore,
+			graphStore: ledgers,
+			embedder: fakeEmbedder,
+			// Batch 1 submits and merges; batch 2's extractor call HANGS
+			// until the abort fires — the dock's abort button, mid-run.
+			extractor: fauxEngine([
+				findingsStep((v) => views.push(v)),
+				(_context, options) =>
+					new Promise((resolve) => {
+						const sig = options?.signal;
+						if (sig?.aborted) {
+							resolve(fauxAssistantMessage("late"));
+							return;
+						}
+						sig?.addEventListener("abort", () => resolve(fauxAssistantMessage("late")), { once: true });
+					}),
+			]),
+			auditor: fauxEngine([passThroughAuditStep()]),
+			labeler: submitModel("submit_labels", { labels: [] }),
+		});
+		const runPromise = pipeline.runExtraction(chatId);
+		// The abort must land while batch 2's extractor hangs. The faux
+		// stream only resolves on abort, so wait for the batch-1 merge to
+		// show in coverage, then abort.
+		await new Promise<void>((resolve) => {
+			const check = setInterval(() => {
+				if (ledgers.readCoverage().length > 0) {
+					clearInterval(check);
+					resolve();
+				}
+			}, 5);
+		});
+		assert.equal(abortExtraction(chatId), true);
+		const stats = await runPromise;
+
+		// Batch 1's emissions are kept and its messages stay covered.
+		assert.deepEqual(stats, { nodes: 1, edges: 0, events: 1 });
+		assert.equal(ledgers.readCoverage().length, 3, "batch 1 checkpointed its three messages");
+		const cov = coverageOf(record.messages as UIMessage[], ledgers.readCoverage(), chatId);
+		assert.equal(cov.uncoveredCount, 2, "the in-flight batch's messages stay uncovered");
+
+		// The re-run — the manual extract button — picks up ONLY the
+		// remainder: one batch, messages 4-5 alone in the prompt.
+		const reRunViews: string[] = [];
+		const finisher = createExtractionPipeline({
+			chatStore,
+			graphStore: ledgers,
+			embedder: fakeEmbedder,
+			extractor: fauxEngine([findingsStep((v) => reRunViews.push(v))]),
+			auditor: fauxEngine([passThroughAuditStep()]),
+			labeler: submitModel("submit_labels", { labels: [] }),
+		});
+		await finisher.runExtraction(chatId);
+		assert.equal(reRunViews.length, 1);
+		assert.ok(reRunViews[0]!.includes("LEARNER [u4]") && reRunViews[0]!.includes("LEARNER [u5]"));
+		assert.ok(!reRunViews[0]!.includes("LEARNER [u1]"), "the covered remainder never re-enters the prompt");
+		assert.equal(ledgers.readCoverage().length, 5, "the re-run closed the gap");
+	});
+
+	it("a re-opened message re-extracts alone; a data-part attach never re-opens it", async () => {
+		// A small session: one batch covers everything, so re-openings are
+		// the ONLY thing later runs can see.
+		const chat = chatStore.createChat("Re-open fixture");
+		createdChats.push(chat.id);
+		chatStore.saveMessages(chat.id, [user("s1", "short topic one"), user("s2", "short topic two")]);
+		const chatId = chat.id;
+		const ledgers = memoryLedgers();
+		const pipeline = createExtractionPipeline({
+			chatStore,
+			graphStore: ledgers,
+			embedder: fakeEmbedder,
+			extractor: fauxEngine([findingsStep()]),
+			auditor: fauxEngine([passThroughAuditStep()]),
+			labeler: submitModel("submit_labels", { labels: [] }),
+		});
+		await pipeline.runExtraction(chatId);
+		const messages = () => chatStore.getChat(chatId)!.messages as UIMessage[];
+		assert.equal(coverageOf(messages(), ledgers.readCoverage(), chatId).uncoveredCount, 0);
+
+		// Data parts are invisible to the extraction view — plan-block
+		// attach does NOT re-open a covered message.
+		const withDataPart = messages().map((m) =>
+			m.id === "u2"
+				? { ...m, parts: [...m.parts, { type: "data-plan-blocks", planBlocks: [] } as unknown as UIMessage["parts"][number]] }
+				: m,
+		);
+		chatStore.saveMessages(chatId, withDataPart);
+		const afterAttach = coverageOf(messages(), ledgers.readCoverage(), chatId);
+		assert.equal(afterAttach.uncoveredCount, 0, "data parts don't change the fingerprint");
+
+		// A quiz answer merging into an ASKING message changes its view →
+		// exactly that message re-opens, and the next run extracts it alone.
+		const mutated = messages().map((m) =>
+			m.id === "s1" ? { ...m, parts: [...m.parts, { type: "text", text: "the answer merged in late" }] } : m,
+		) as unknown as UIMessage[];
+		chatStore.saveMessages(chatId, mutated);
+		const afterMerge = coverageOf(messages(), ledgers.readCoverage(), chatId);
+		assert.equal(afterMerge.uncoveredCount, 1, "only the mutated message re-opens");
+
+		const reRunViews: string[] = [];
+		const reOpener = createExtractionPipeline({
+			chatStore,
+			graphStore: ledgers,
+			embedder: fakeEmbedder,
+			extractor: fauxEngine([findingsStep((v) => reRunViews.push(v))]),
+			auditor: fauxEngine([passThroughAuditStep()]),
+			labeler: submitModel("submit_labels", { labels: [] }),
+		});
+		await reOpener.runExtraction(chatId);
+		assert.equal(reRunViews.length, 1, "one batch: the single re-opened message");
+		assert.ok(reRunViews[0]!.includes("LEARNER [s1]") && !reRunViews[0]!.includes("LEARNER [s2]"));
+		assert.equal(coverageOf(messages(), ledgers.readCoverage(), chatId).uncoveredCount, 0, "re-covered");
+	});
+});
diff --git a/tests/graph.test.ts b/tests/graph.test.ts
index 2bfc79c..7f7f908 100644
--- a/tests/graph.test.ts
+++ b/tests/graph.test.ts
@@ -20,7 +20,7 @@ import { after, describe, it } from "node:test";
 import type { UIMessage } from "ai";
 import type { AuditResult } from "../src/core/contracts.ts";
 import type { QuestionAnswerData } from "../src/core/question-core.ts";
-import { clusterContentId, getGraph, graphSnapshot, mergeFindings, pendingQuizAnswers, type GraphDeps } from "../src/core/graph.ts";
+import { clusterContentId, getGraph, graphSnapshot, mergeFindings, type GraphDeps } from "../src/core/graph.ts";
 import { graphStore } from "../src/store/graph.ts";
 import { chatStore } from "../src/store/chats.ts";
 import { LEDGER_FILES, PATHS, SOURCES_FILE, EMBEDDINGS_FILE } from "../config.ts";
@@ -564,55 +564,6 @@ describe("the merger (mergeFindings)", () => {
 	});
 });
 
-// ─── the trigger helper ──────────────────────────────────────────────────────
-
-describe("the trigger helper (pendingQuizAnswers)", () => {
-	it("counts answered quizzes not yet in the ledger — dismissed/ask never count", () => {
-		const chat = fixtureChat("Trigger fixture", [
-			user("u1", "go"),
-			assistant("a1", [
-				quizPart(
-					"call-s",
-					{ question: "QS", options: [{ label: "a" }, { label: "b" }], correctAnswer: "a", explanation: "e" },
-					answer({ questionId: "call-s", questionText: "QS text", correct: true, answeredAt: "2026-08-22T03:00:00.000Z" }),
-				),
-				quizPart(
-					"call-s2",
-					{ question: "QS2", options: [{ label: "a" }, { label: "b" }], correctAnswer: "a", explanation: "e" },
-					answer({ questionId: "call-s2", questionText: "QS2 text", dismissed: true }),
-				),
-				{
-					type: "tool-ask_user_question",
-					toolCallId: "call-s3",
-					state: "output-available",
-					input: { question: "free?" },
-					output: answer({ questionId: "call-s3", kind: "ask", questionText: "free?", text: "y" }),
-				},
-			]),
-		]);
-
-		assert.equal(pendingQuizAnswers(chat.id, graphDeps), 1, "one answered quiz pending");
-		assert.equal(pendingQuizAnswers("chat_does_not_exist", graphDeps), 0);
-
-		mergeFindings(chat.id, fixtureAudit(), graphDeps, sessionSource(chat.id));
-		// call-s is unattributed here (fixtureAudit has no call-s attribution)
-		// — but it still becomes an event, so nothing stays pending.
-		assert.equal(pendingQuizAnswers(chat.id, graphDeps), 0, "extracted → nothing pending");
-
-		// A NEW answered quiz raises the count again (the re-trigger path).
-		chatStore.saveMessages(chat.id, [
-			...chatStore.getChat(chat.id)!.messages,
-			assistant("a3", [
-				quizPart(
-					"call-s4",
-					{ question: "QS4", options: [{ label: "a" }, { label: "b" }], correctAnswer: "a", explanation: "e" },
-					answer({ questionId: "call-s4", questionText: "QS4 text", correct: false, answeredAt: "2026-08-22T03:01:00.000Z" }),
-				),
-			]),
-		]);
-		assert.equal(pendingQuizAnswers(chat.id, graphDeps), 1);
-	});
-});
 
 // ─── store primitives ────────────────────────────────────────────────────────
 
diff --git a/tests/render-graph-coverage.test.tsx b/tests/render-graph-coverage.test.tsx
new file mode 100644
index 0000000..a2b38d5
--- /dev/null
+++ b/tests/render-graph-coverage.test.tsx
@@ -0,0 +1,85 @@
+import { renderToStaticMarkup } from "react-dom/server";
+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+import { CoveragePanel, GraphCoverageControl } from "../components/graph-coverage.tsx";
+
+// The extraction-coverage panel (vision-extraction-coverage.md, settled
+// 2026-09-15): the graph view's window into WHAT the pipeline has covered,
+// with a per-session "Extract" button for the uncovered remainder. Static
+// markup can't click — the closed control and the panel body are pinned
+// separately. (Interaction — the fetch + POST flow — is covered by the live
+// smoke.)
+
+describe("GraphCoverageControl", () => {
+	it("renders the coverage button in the chrome, closed by default", () => {
+		const html = renderToStaticMarkup(<GraphCoverageControl />);
+		assert.ok(html.includes("<button"));
+		assert.ok(html.includes("Extraction coverage"));
+		assert.ok(!html.includes('data-testid="coverage-panel"'), "the panel starts closed");
+	});
+});
+
+describe("CoveragePanel — exact per-session coverage data", () => {
+	const base = {
+		chatId: "chat_a",
+		title: "Modal logic",
+		updatedAt: "2026-09-15T00:00:00.000Z",
+		totalMessages: 12,
+		coveredMessages: 10,
+		uncoveredMessages: 2,
+		coveredTokens: 1536,
+		uncoveredTokens: 384,
+		running: false,
+	};
+
+	it("shows each session's covered/uncovered tokens and the Extract button", () => {
+		const html = renderToStaticMarkup(
+			<CoveragePanel chats={[base]} loaded isBusy={() => false} onExtract={() => {}} />,
+		);
+		assert.ok(html.includes("Modal logic"));
+		assert.ok(html.includes("1.5k covered"));
+		assert.ok(html.includes("384 uncovered"));
+		assert.ok(html.includes("(2 msgs)"));
+		assert.ok(html.includes(">Extract<"), "the uncovered session offers a manual extract");
+	});
+
+	it("a fully covered session shows · complete with a disabled Extract button", () => {
+		const html = renderToStaticMarkup(
+			<CoveragePanel
+				chats={[{ ...base, uncoveredMessages: 0, uncoveredTokens: 0, coveredMessages: 12, coveredTokens: 1920 }]}
+				loaded
+				isBusy={() => false}
+				onExtract={() => {}}
+			/>,
+		);
+		assert.ok(html.includes("· complete"));
+		assert.ok(html.includes("disabled"), "nothing to extract — the button is honest");
+		assert.ok(!html.includes(">Extract<") || html.includes("disabled"));
+	});
+
+	it("a running session shows extracting… and no clickable duplicate start", () => {
+		const html = renderToStaticMarkup(
+			<CoveragePanel
+				chats={[{ ...base, running: true }]}
+				loaded
+				isBusy={(c) => c.running}
+				onExtract={() => {}}
+			/>,
+		);
+		assert.ok(html.includes("extracting…"));
+		assert.ok(html.includes(">Running<"));
+		assert.ok(html.includes("disabled"), "single-flight: the in-flight run can't be double-started");
+	});
+
+	it("all-covered panel: the nothing-pending line, not a row list", () => {
+		const html = renderToStaticMarkup(
+			<CoveragePanel
+				chats={[{ ...base, uncoveredMessages: 0, uncoveredTokens: 0 }]}
+				loaded
+				isBusy={() => false}
+				onExtract={() => {}}
+			/>,
+		);
+		assert.ok(html.includes("Every session is fully extracted — nothing pending."));
+	});
+});
\ No newline at end of file