diff --git a/server/shell.ts b/server/shell.ts
index 4c38a7c..d50b62f 100644
--- a/server/shell.ts
+++ b/server/shell.ts
@@ -844,10 +844,12 @@ export function renderShell(opts: ShellOptions): string {
 
       // Reconcile remote layer changes (shared by BroadcastChannel + Automerge)
       function reconcileRemoteLayers(remoteLayers) {
+        console.log('[shell] reconcileRemoteLayers: remote=' + remoteLayers.length + ', local=' + layers.length + ', current=' + currentModuleId);
         // Guard: never let remote sync wipe all tabs when we have an active module.
         // Empty remote layers indicate a CRDT initial state or sync race, not
         // an intentional "close everything" action.
         if (remoteLayers.length === 0 && currentModuleId) {
+          console.log('[shell] BLOCKED empty remote layers (keeping local)');
           // Keep local layers intact — remote has nothing useful
           tabBar.setLayers(layers);
           return;
@@ -936,6 +938,7 @@ export function renderShell(opts: ShellOptions): string {
       // This prevents the visual desync where the tab highlights before content loads.
       tabBar.addEventListener('layer-switch', (e) => {
         const { layerId, moduleId } = e.detail;
+        console.log('[shell] layer-switch:', moduleId, 'layerId:', layerId, 'tabCache:', !!tabCache, 'layers:', layers.length);
         currentModuleId = moduleId;
         saveTabs();
         // Update settings panel to show config for the newly active module
@@ -943,15 +946,20 @@ export function renderShell(opts: ShellOptions): string {
         if (sp) sp.setAttribute('module-id', moduleId);
         if (tabCache) {
           tabCache.switchTo(moduleId).then(ok => {
+            console.log('[shell] switchTo result:', ok, 'for', moduleId);
             if (ok) {
               tabBar.setAttribute('active', layerId);
             } else {
-              window.location.href = window.__rspaceNavUrl(spaceSlug, moduleId);
+              const url = window.__rspaceNavUrl(spaceSlug, moduleId);
+              console.log('[shell] switchTo failed, navigating to:', url);
+              window.location.href = url;
             }
-          }).catch(() => {
+          }).catch((err) => {
+            console.error('[shell] switchTo error:', err);
             window.location.href = window.__rspaceNavUrl(spaceSlug, moduleId);
           });
         } else {
+          console.log('[shell] no tabCache, navigating to:', window.__rspaceNavUrl(spaceSlug, moduleId));
           window.location.href = window.__rspaceNavUrl(spaceSlug, moduleId);
         }
       });
diff --git a/shared/tab-cache.ts b/shared/tab-cache.ts
index 71353e0..799073d 100644
--- a/shared/tab-cache.ts
+++ b/shared/tab-cache.ts
@@ -101,14 +101,19 @@ export class TabCache {
 	/** Switch to a module tab within the current space. Returns true if handled client-side. */
 	async switchTo(moduleId: string): Promise<boolean> {
 		const key = this.paneKey(this.spaceSlug, moduleId);
-		if (moduleId === this.currentModuleId && this.panes.has(key)) return true;
+		if (moduleId === this.currentModuleId && this.panes.has(key)) {
+			console.log("[TabCache] switchTo", moduleId, "→ already current + cached");
+			return true;
+		}
 
 		if (this.panes.has(key)) {
+			console.log("[TabCache] switchTo", moduleId, "→ cached, showing pane");
 			this.showPane(this.spaceSlug, moduleId);
 			this.updateUrl(this.spaceSlug, moduleId);
 			return true;
 		}
 
+		console.log("[TabCache] switchTo", moduleId, "→ NOT cached, fetching…");
 		return this.fetchAndInject(this.spaceSlug, moduleId);
 	}
 
@@ -165,7 +170,7 @@ export class TabCache {
 	/** Fetch a module page, extract content, and inject into a new pane */
 	private async fetchAndInject(space: string, moduleId: string): Promise<boolean> {
 		const navUrl = (window as any).__rspaceNavUrl;
-		if (!navUrl) return false;
+		if (!navUrl) { console.warn("[TabCache] fetchAndInject: no __rspaceNavUrl"); return false; }
 		const url: string = navUrl(space, moduleId);
 
 		// For cross-space fetches, use the path-based API to stay same-origin
@@ -177,11 +182,14 @@ export class TabCache {
 				fetchUrl = `/${space}/${moduleId}`;
 			}
 		} catch {
+			console.warn("[TabCache] fetchAndInject: URL resolve failed for", url);
 			return false;
 		}
 
 		const app = document.getElementById("app");
-		if (!app) return false;
+		if (!app) { console.warn("[TabCache] fetchAndInject: no #app"); return false; }
+
+		console.log("[TabCache] fetchAndInject:", fetchUrl, "for", moduleId);
 
 		// Show loading spinner
 		const loadingPane = document.createElement("div");
@@ -197,13 +205,16 @@ export class TabCache {
 				signal: AbortSignal.timeout(10_000),
 			});
 			if (!resp.ok) {
+				console.warn("[TabCache] fetchAndInject: HTTP", resp.status, "for", fetchUrl);
 				loadingPane.remove();
 				return false;
 			}
 
 			const html = await resp.text();
+			console.log("[TabCache] fetchAndInject: got", html.length, "bytes for", moduleId);
 			const content = this.extractContent(html);
 			if (!content) {
+				console.warn("[TabCache] fetchAndInject: extractContent returned null for", moduleId, "— HTML has #app:", html.includes('id="app"'));
 				loadingPane.remove();
 				return false;
 			}
@@ -233,8 +244,10 @@ export class TabCache {
 			this.updateUrl(space, moduleId);
 			this.updateCanvasLayout(moduleId);
 
+			console.log("[TabCache] fetchAndInject: SUCCESS for", moduleId);
 			return true;
-		} catch {
+		} catch (err) {
+			console.error("[TabCache] fetchAndInject: CATCH for", moduleId, err);
 			loadingPane.remove();
 			return false;
 		}