feat(history): add "Revert to this point" button in Time Machine panel

Forward Automerge change that overwrites content fields with snapshot data,
preserving meta and full history. Also fixes pre-existing TS errors in
folk-flow-river (undefined exitX) and test-full-loop (StepResult type).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/community-sync.ts

@@ -1435,6 +1435,33 @@ export class CommunitySync extends EventTarget {
 		return Automerge.view(this.#doc, heads);
 	}
 
+	/**
+	 * Revert document content to the state at a given change hash.
+	 * Creates a forward change (preserving full history) and syncs to peers.
+	 * Meta (space name/slug/config) is preserved — only content is reverted.
+	 */
+	revertToHash(hash: string): void {
+		const snapshot = Automerge.view(this.#doc, [hash]);
+		const data = JSON.parse(JSON.stringify(snapshot)) as CommunityDoc;
+
+		const newDoc = Automerge.change(this.#doc, makeChangeMessage(`Revert to change ${hash.slice(0, 8)}`), (doc) => {
+			doc.shapes = data.shapes || {};
+			if (data.layers) doc.layers = data.layers;
+			if (data.flows) doc.flows = data.flows;
+			if (data.connections) doc.connections = data.connections;
+			if (data.groups) doc.groups = data.groups;
+			if (data.nestedSpaces) doc.nestedSpaces = data.nestedSpaces;
+			if (data.activeLayerId !== undefined) doc.activeLayerId = data.activeLayerId;
+			if (data.layerViewMode !== undefined) doc.layerViewMode = data.layerViewMode;
+			if (data.commentPins) doc.commentPins = data.commentPins;
+			// Preserve meta — don't revert space name/slug/config
+		});
+
+		this._applyDocChange(newDoc);
+		this.#undoStack.length = 0;
+		this.#redoStack.length = 0;
+	}
+
 	/**
 	 * Get parsed history entries for the activity feed.
 	 */

modules/rflows/components/folk-flow-river.ts

@@ -517,7 +517,7 @@ function renderBranch(b: BranchLayout): string {
 		<path d="${spinePath}" fill="none" stroke="white" stroke-width="1.5" opacity="0.2" stroke-dasharray="4 12" style="animation:riverCurrent 1s linear infinite;animation-delay:-0.3s"/>` : "";
 
 	// Midpoint for label
-	const midX = (b.x1 + exitX + b.x2) / 3;
+	const midX = (b.x1 + b.x2) / 2;
 	const midY = (b.y1 + b.y2) / 2 - 12;
 
 	return `${outerStroke}${innerStroke}${waterFlow}

scripts/test-full-loop.ts

@@ -30,7 +30,7 @@ async function step(name: string, fn: () => Promise<StepResult>) {
 		return result;
 	} catch (err: any) {
 		console.log("ERROR", err.message);
-		return { ok: false, error: err.message };
+		return { ok: false, error: err.message } as StepResult;
 	}
 }
 

shared/components/rstack-history-panel.ts

@@ -413,6 +413,7 @@ export class RStackHistoryPanel extends HTMLElement {
 				</div>
 				` : ""}
 			</div>
+			<button class="revert-btn" id="revert-btn">Revert to this point</button>
 		`;
 
 		// Update the label
@@ -446,6 +447,18 @@ export class RStackHistoryPanel extends HTMLElement {
 				this._onScrub(parseInt(scrubber.value, 10));
 			});
 		}
+
+		// Revert to history point
+		sr.getElementById("revert-btn")?.addEventListener("click", () => {
+			const entry = this._entries[this._timeMachineIndex];
+			if (!entry?.hash) return;
+			if (!confirm(`Revert to change from ${new Date(entry.time).toLocaleString()} by ${entry.username}?\n\nThis creates a new change that restores the document to that state.`)) return;
+			this.dispatchEvent(new CustomEvent("revert-requested", {
+				bubbles: true, composed: true,
+				detail: { hash: entry.hash, index: this._timeMachineIndex },
+			}));
+			this.close();
+		});
 	}
 
 	// ── Helpers ──
@@ -743,6 +756,21 @@ const PANEL_CSS = `
 	word-break: break-word;
 }
 
+.revert-btn {
+	width: 100%;
+	margin-top: 16px;
+	padding: 10px;
+	background: rgba(239, 68, 68, 0.1);
+	border: 1px solid rgba(239, 68, 68, 0.3);
+	color: #ef4444;
+	border-radius: 8px;
+	font-size: 0.8rem;
+	font-weight: 600;
+	cursor: pointer;
+	transition: background 0.15s;
+}
+.revert-btn:hover { background: rgba(239, 68, 68, 0.2); }
+
 /* Load more */
 .load-more {
 	padding: 12px 20px;

website/canvas.html

@@ -3065,6 +3065,12 @@
 			const historyPanel = document.querySelector('rstack-history-panel');
 			if (historyPanel) historyPanel.setDoc(sync.doc);
 
+			// Wire history revert
+			document.querySelector("rstack-history-panel")?.addEventListener("revert-requested", (e) => {
+				const { hash } = (e as CustomEvent).detail;
+				if (hash) sync.revertToHash(hash);
+			});
+
 			// Non-blocking: open IndexedDB + load cache in background
 			// UI handlers below register immediately regardless of this outcome
 			(async () => {