From 376234539ee6dc7502d5e547e2881494d01caf8f Mon Sep 17 00:00:00 2001
From: Lucio Lelii <lucio.lelii@isti.cnr.it>
Date: Mon, 9 Mar 2026 14:39:58 +0100
Subject: [PATCH] Add block example caching and structural refresh UX

---
 src/app/models/flow.ts                        |   2 +
 .../main/editor-sidebar/editor-sidebar.html   |   8 +-
 src/app/services/blocks/blocks-call.ts        |  39 ++++-
 src/app/services/blocks/blocks.ts             | 139 ++++++------------
 .../flows-list/flow-item/flow-item.html       |   6 +-
 src/app/shared/group-holder/group-holder.html |   8 +-
 .../nodes/generic-node/generic-node.css       |  41 ++++++
 .../nodes/generic-node/generic-node.html      |  20 +++
 .../shared/nodes/generic-node/generic-node.ts |  22 ++-
 src/app/shared/rete-editor/rete-editor.css    |  53 +++++++
 src/app/shared/rete-editor/rete-editor.html   |  13 +-
 src/app/shared/rete-editor/rete-editor.ts     |   7 +
 .../shared/title-toolbar/title-toolbar.css    |   4 +
 .../shared/title-toolbar/title-toolbar.html   |  18 +--
 14 files changed, 262 insertions(+), 118 deletions(-)

diff --git a/src/app/models/flow.ts b/src/app/models/flow.ts
index 1f5e3bd..e2994c5 100644
--- a/src/app/models/flow.ts
+++ b/src/app/models/flow.ts
@@ -28,6 +28,8 @@ export type BlockType = {
   type: BlockTypeName;
   description: string;
   userInteractive: boolean;
+  hasExampleBlock?: boolean;
+  exampleBlockEndpoint?: string | null;
   configurationType: string | null;
   configurationClass: string | null;
   schema: BlockTypeSchema;
diff --git a/src/app/pages/main/editor-sidebar/editor-sidebar.html b/src/app/pages/main/editor-sidebar/editor-sidebar.html
index 97a5450..e16fafb 100644
--- a/src/app/pages/main/editor-sidebar/editor-sidebar.html
+++ b/src/app/pages/main/editor-sidebar/editor-sidebar.html
@@ -3,8 +3,8 @@
     [class.w-14]="collapsed()"
     [class.w-72]="!collapsed()"
   >
-<aside class="h-full w-72 bg-white border-r border-gray-200 flex">
-  <div class="flex flex-col h-full">
+<aside class="h-full w-full min-w-0 bg-white border-r border-gray-200 flex overflow-hidden">
+  <div class="flex flex-col h-full shrink-0">
 
     <button (click)="collapse()" class="relative
              w-6 h-6 rounded-full
@@ -28,9 +28,9 @@
 
   @if (!collapsed()) {
   <!-- CONTENT -->
-  <div class="h-full bg-white flex-1">
+  <div class="h-full min-w-0 bg-white flex-1 overflow-hidden">
 
-    <div class="space-y-6 h-full">
+    <div class="space-y-6 h-full min-w-0 overflow-hidden">
       @switch (open) {
       @case ('flows') {
       <app-group-holder title="Flows" icon="bi-lightning-charge-fill">
diff --git a/src/app/services/blocks/blocks-call.ts b/src/app/services/blocks/blocks-call.ts
index 34a4ee1..ea7c5aa 100644
--- a/src/app/services/blocks/blocks-call.ts
+++ b/src/app/services/blocks/blocks-call.ts
@@ -2,7 +2,7 @@ import { BlockType, FlowBlock } from "@models/flow";
 import { HttpClient } from "@angular/common/http";
 import { inject } from "@angular/core";
 import { environment } from "@environment";
-import { map, Observable, of, switchMap, take } from "rxjs";
+import { catchError, map, Observable, of, switchMap, take, throwError } from "rxjs";
 import { BlocksCallServiceBase } from "./block-call.base";
 
 export class BlocksCallService extends BlocksCallServiceBase {
@@ -26,6 +26,14 @@ export class BlocksCallService extends BlocksCallServiceBase {
       take(1),
       switchMap((types) => {
         const descriptor = types.find((type) => type.type === blockType);
+        const exampleEndpoint = this.resolveExampleBlockEndpoint(descriptor);
+
+        if (exampleEndpoint) {
+          return this.http
+            .get<unknown>(exampleEndpoint)
+            .pipe(map((raw) => this.flowBlockFromApi(raw, descriptor?.type ?? blockType)));
+        }
+
         const configuration = descriptor
           ? this.buildObjectFromSchema(descriptor.schema, descriptor.schema)
           : {};
@@ -48,6 +56,12 @@ export class BlocksCallService extends BlocksCallServiceBase {
     return this.http
       .post<unknown>(`${environment.apiUrl}/blocks`, payload)
       .pipe(
+        map((raw) => {
+          if (!raw || typeof raw !== "object") {
+            throw new Error(`Invalid updateBlock response for ${blockType}`);
+          }
+          return raw;
+        }),
         map((raw) =>
           this.flowBlockFromApi(
             {
@@ -57,7 +71,8 @@ export class BlocksCallService extends BlocksCallServiceBase {
             blockType,
             payload
           )
-        )
+        ),
+        catchError((error) => throwError(() => this.toUpdateBlockError(error, blockType)))
       );
   }
 
@@ -74,6 +89,8 @@ export class BlocksCallService extends BlocksCallServiceBase {
       type: String(value["type"] ?? value["blockType"] ?? value["name"] ?? "LLMBlock"),
       description: String(value["description"] ?? ""),
       userInteractive: Boolean(value["userInteractive"] ?? value["interactive"] ?? false),
+      hasExampleBlock: Boolean(value["hasExampleBlock"] ?? false),
+      exampleBlockEndpoint: this.toApiPath(value["exampleBlockEndpoint"]),
       configurationType: this.toNullableString(value["configurationType"]),
       configurationClass: this.toNullableString(value["configurationClass"]),
       schema: this.toSchema(value["schema"] ?? value["configurationSchema"] ?? null)
@@ -134,6 +151,12 @@ export class BlocksCallService extends BlocksCallServiceBase {
     return typeof value === "string" && value.length > 0 ? value : null;
   }
 
+  private toApiPath(value: unknown): string | null {
+    if (typeof value !== "string" || value.length === 0) return null;
+    if (/^https?:\/\//.test(value)) return value;
+    return `${environment.apiUrl}${value.startsWith("/") ? value : `/${value}`}`;
+  }
+
   private buildBlockConfigurationPayload(blockType: string, configuration: Record<string, unknown>) {
     const { typeName: _ignoreTypeName, ...sanitized } = configuration;
     return {
@@ -144,6 +167,18 @@ export class BlocksCallService extends BlocksCallServiceBase {
     };
   }
 
+  private resolveExampleBlockEndpoint(descriptor?: BlockType): string | null {
+    if (!descriptor?.hasExampleBlock) return null;
+    return descriptor.exampleBlockEndpoint ?? null;
+  }
+
+  private toUpdateBlockError(error: unknown, blockType: string): Error {
+    if (error instanceof Error) {
+      return new Error(`updateBlock failed for ${blockType}: ${error.message}`);
+    }
+    return new Error(`updateBlock failed for ${blockType}`);
+  }
+
   private defaultIOForBlockType(typeName: string) {
     if (typeName === "SourceBlock") {
       return {
diff --git a/src/app/services/blocks/blocks.ts b/src/app/services/blocks/blocks.ts
index 978d875..aae3e16 100644
--- a/src/app/services/blocks/blocks.ts
+++ b/src/app/services/blocks/blocks.ts
@@ -2,7 +2,7 @@ import { Injectable, signal } from '@angular/core';
 import { environment } from '@environment';
 import { BlockType, BlockTypeName, FlowBlock } from '@models/flow';
 import { BlocksCallServiceBase } from './block-call.base';
-import { catchError, firstValueFrom, of, throwError } from 'rxjs';
+import { catchError, finalize, firstValueFrom, map, Observable, of, shareReplay, throwError } from 'rxjs';
 
 @Injectable({
   providedIn: 'root',
@@ -12,6 +12,8 @@ export class BlocksService {
 
   toInit: boolean = true;
   private loadingPromise: Promise<void> | null = null;
+  private readonly emptyBlockCache = new Map<string, FlowBlock>();
+  private readonly pendingEmptyBlockRequests = new Map<string, Observable<FlowBlock>>();
 
   private _blockTypes = signal<BlockType[]>([]);
 
@@ -32,6 +34,7 @@ export class BlocksService {
     this.loadingPromise = firstValueFrom(this.blocksCallService.retrieveAllBlocksTypes())
       .then((blockTypes) => {
         this._blockTypes.set(blockTypes);
+        this.clearEmptyBlockCache();
       })
       .catch((err) => {
         console.error('Retrieve blocks types failed', err);
@@ -50,30 +53,42 @@ export class BlocksService {
 
     const blockTypes = await firstValueFrom(this.blocksCallService.retrieveAllBlocksTypes());
     this._blockTypes.set(blockTypes);
+    this.clearEmptyBlockCache();
     return blockTypes.find((blockType) => blockType.type === typeName);
   }
 
   createEmptyBlock(blockType: BlockTypeName) {
-    const descriptor = this._blockTypes().find((type) => type.type === blockType);
-    const schema = (descriptor?.schema ?? null) as Record<string, unknown> | null;
-    const specificConfiguration = this.buildObjectFromSchema(schema, schema);
-    const io = this.defaultIOForBlockType(String(blockType));
+    const cacheKey = String(blockType);
+    const cached = this.emptyBlockCache.get(cacheKey);
+    if (cached) {
+      return of(this.cloneEmptyBlock(cached));
+    }
 
-    const block: FlowBlock = {
-      id: globalThis.crypto?.randomUUID?.() ?? `${Date.now()}`,
-      sink: String(blockType) === 'HumanInteractionBlock',
-      name: String(blockType),
-      position: undefined,
-      inputs: io.inputs,
-      outputs: io.outputs,
-      specificConfiguration: this.ensureBlockName(specificConfiguration, String(blockType)),
-      typeName: String(blockType)
-    };
+    const pending = this.pendingEmptyBlockRequests.get(cacheKey);
+    if (pending) {
+      return pending.pipe(map((block) => this.cloneEmptyBlock(block)));
+    }
 
-    return of({
-      ...block,
-      __needsServerCreate: true
-    } as FlowBlock);
+    const request = this.blocksCallService.createEmptyBlock(blockType).pipe(
+      map((block) => {
+        this.emptyBlockCache.set(cacheKey, this.cloneEmptyBlock(block));
+        return block;
+      }),
+      finalize(() => {
+        this.pendingEmptyBlockRequests.delete(cacheKey);
+      }),
+      shareReplay(1)
+    );
+
+    this.pendingEmptyBlockRequests.set(cacheKey, request);
+
+    return request.pipe(
+      map((block) => this.cloneEmptyBlock(block)),
+      catchError((err) => {
+        console.error('Create empty block failed', err);
+        return throwError(() => err);
+      })
+    );
   }
 
   updateBlock(blockId: string, configuration: any) {
@@ -85,86 +100,24 @@ export class BlocksService {
     );
   }
 
-  private ensureBlockName(configuration: Record<string, unknown>, blockType: string) {
-    const next = { ...configuration };
-    if (typeof next['name'] !== 'string' || next['name'].length === 0) {
-      next['name'] = blockType;
-    }
-    return next;
+  private clearEmptyBlockCache() {
+    this.emptyBlockCache.clear();
+    this.pendingEmptyBlockRequests.clear();
   }
 
-  private defaultIOForBlockType(typeName: string) {
-    void typeName;
+  private cloneEmptyBlock(block: FlowBlock): FlowBlock {
+    const clone = this.deepClone(block);
     return {
-      inputs: [],
-      outputs: []
+      ...clone,
+      id: globalThis.crypto?.randomUUID?.() ?? `${Date.now()}`,
+      position: undefined
     };
   }
 
-  private buildObjectFromSchema(
-    node: Record<string, unknown> | null,
-    root: Record<string, unknown> | null
-  ): Record<string, unknown> {
-    if (!node || !root) return {};
-    const resolved = this.resolveRef(node, root);
-    const properties = this.toRecord(resolved['properties']);
-    const result: Record<string, unknown> = {};
-
-    for (const [key, propSchema] of Object.entries(properties)) {
-      result[key] = this.buildValueFromSchema(this.toRecord(propSchema), root);
+  private deepClone<T>(value: T): T {
+    if (typeof globalThis.structuredClone === 'function') {
+      return globalThis.structuredClone(value);
     }
-
-    return result;
-  }
-
-  private buildValueFromSchema(node: Record<string, unknown>, root: Record<string, unknown>): unknown {
-    const resolved = this.resolveRef(node, root);
-
-    if (Object.prototype.hasOwnProperty.call(resolved, 'default')) {
-      return resolved['default'];
-    }
-
-    const enumValues = resolved['enum'];
-    if (Array.isArray(enumValues) && enumValues.length > 0) {
-      return enumValues[0];
-    }
-
-    const type = resolved['type'];
-    if (type === 'string') return '';
-    if (type === 'boolean') return false;
-    if (type === 'number' || type === 'integer') return 0;
-    if (type === 'array') return [];
-    if (type === 'object' || Object.prototype.hasOwnProperty.call(resolved, 'properties')) {
-      return this.buildObjectFromSchema(resolved, root);
-    }
-
-    return null;
-  }
-
-  private resolveRef(node: Record<string, unknown>, root: Record<string, unknown>): Record<string, unknown> {
-    const ref = node['$ref'];
-    if (typeof ref !== 'string' || !ref.startsWith('#/')) {
-      return node;
-    }
-
-    const segments = ref.slice(2).split('/');
-    let current: unknown = root;
-
-    for (const segment of segments) {
-      const asRecord = this.toRecord(current);
-      current = asRecord[segment];
-      if (current == null) {
-        return node;
-      }
-    }
-
-    return this.toRecord(current);
-  }
-
-  private toRecord(value: unknown): Record<string, unknown> {
-    if (!value || typeof value !== 'object' || Array.isArray(value)) {
-      return {};
-    }
-    return value as Record<string, unknown>;
+    return JSON.parse(JSON.stringify(value)) as T;
   }
 }
diff --git a/src/app/shared/flows-list/flow-item/flow-item.html b/src/app/shared/flows-list/flow-item/flow-item.html
index 667309d..655876b 100644
--- a/src/app/shared/flows-list/flow-item/flow-item.html
+++ b/src/app/shared/flows-list/flow-item/flow-item.html
@@ -1,4 +1,4 @@
-<div class="w-full text-left p-3 rounded-md border transition-all duration-150 select-none hover:-translate-y-0.5 hover:border-blue-300 hover:bg-blue-100 hover:shadow-md"
+<div class="w-full overflow-hidden text-left p-3 rounded-md border transition-all duration-150 select-none hover:-translate-y-0.5 hover:border-blue-300 hover:bg-blue-100 hover:shadow-md"
     [class.cursor-pointer]="flow().id !== openedFlowId()"
     [class.cursor-default]="flow().id === openedFlowId()"
     [class.border-blue-300]="flow().id === openedFlowId()"
@@ -8,11 +8,11 @@
     (click)="flow().id !== openedFlowId() && open()">
 
     <div class="flex items-start justify-between gap-2">
-        <div class="min-w-0">
+        <div class="flex-1 min-w-0 overflow-hidden">
             <div class="text-sm font-medium text-slate-800 truncate">{{ flow().name }}</div>
             <div class="text-xs text-slate-500 truncate">{{ flow().author }}</div>
         </div>
-        <span class="text-[10px] px-2 py-0.5 rounded-full border font-semibold"
+        <span class="shrink-0 text-[10px] px-2 py-0.5 rounded-full border font-semibold"
               [class.bg-indigo-100]="flow().visibility === 'PUBLIC'"
               [class.text-indigo-700]="flow().visibility === 'PUBLIC'"
               [class.border-indigo-200]="flow().visibility === 'PUBLIC'"
diff --git a/src/app/shared/group-holder/group-holder.html b/src/app/shared/group-holder/group-holder.html
index 20741df..f0a6b70 100644
--- a/src/app/shared/group-holder/group-holder.html
+++ b/src/app/shared/group-holder/group-holder.html
@@ -1,7 +1,7 @@
 <div
   class=" border-gray-200
          bg-white shadow-sm
-         transition flex-1 h-full">
+         transition flex flex-col flex-1 h-full min-w-0 overflow-hidden">
 
   <!-- Header -->
   <div
@@ -11,9 +11,9 @@
         bg-gray-50 h-18"
     >
 
-    <div class="flex items-center gap-2">
+    <div class="flex items-center gap-2 min-w-0">
       <i class="bi {{ icon }} text-lg"></i>
-      <span>{{ title }}</span>
+      <span class="truncate">{{ title }}</span>
   </div>
   <span>
   <ng-content select="header-button"></ng-content>
@@ -21,7 +21,7 @@
 </div>
   <!-- Body -->
   <div
-    class="transition-all duration-300 px-2 pb-2 flex flex-col flex-1 overflow-hidden h-[calc(100%-72px)]">
+    class="transition-all duration-300 px-2 pb-2 flex flex-col flex-1 min-w-0 overflow-hidden">
       <ng-content></ng-content>
     
   </div>
diff --git a/src/app/shared/nodes/generic-node/generic-node.css b/src/app/shared/nodes/generic-node/generic-node.css
index 35490f0..8004af3 100644
--- a/src/app/shared/nodes/generic-node/generic-node.css
+++ b/src/app/shared/nodes/generic-node/generic-node.css
@@ -11,6 +11,47 @@
   color: #0f172a;
 }
 
+.llm-loading-overlay {
+  position: absolute;
+  inset: 0;
+  z-index: 150;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background: rgba(248, 250, 252, 0.68);
+  backdrop-filter: blur(2px);
+  border-radius: 16px;
+}
+
+.llm-loading-chip {
+  display: inline-flex;
+  align-items: center;
+  gap: 8px;
+  padding: 8px 12px;
+  border: 1px solid #bfdbfe;
+  border-radius: 999px;
+  background: rgba(255, 255, 255, 0.96);
+  color: #1d4ed8;
+  font-size: 12px;
+  font-weight: 600;
+  box-shadow: 0 8px 20px rgba(37, 99, 235, 0.16);
+}
+
+.llm-spinner {
+  width: 14px;
+  height: 14px;
+  border-radius: 999px;
+  border: 2px solid rgba(37, 99, 235, 0.2);
+  border-top-color: #2563eb;
+  animation: llm-spin 0.75s linear infinite;
+}
+
+@keyframes llm-spin {
+  to {
+    transform: rotate(360deg);
+  }
+}
+
 .llm-node--human {
   border-color: #f7d7a7;
   background: linear-gradient(180deg, #fffdf9 0%, #fff7ed 100%);
diff --git a/src/app/shared/nodes/generic-node/generic-node.html b/src/app/shared/nodes/generic-node/generic-node.html
index ff30459..5c35f07 100644
--- a/src/app/shared/nodes/generic-node/generic-node.html
+++ b/src/app/shared/nodes/generic-node/generic-node.html
@@ -1,5 +1,14 @@
 <div class="llm-node"
+  [class.llm-node-error]="hasUpdateBlockError()"
   [class.llm-node--human]="isHumanNode()">
+  @if (isCreatingOnServer()) {
+  <div class="llm-loading-overlay">
+    <div class="llm-loading-chip">
+      <span class="llm-spinner" aria-hidden="true"></span>
+      <span>Updating block...</span>
+    </div>
+  </div>
+  }
   <div class="llm-header cursor-move">
     <div class="llm-icon">
       @if (isHumanNode()) {
@@ -18,6 +27,17 @@
       </div>
     </div>
     <div class="llm-header-actions">
+      @if (hasUpdateBlockError()) {
+      <div class="llm-error-alert-wrap">
+        <div class="llm-error-alert">
+          <i class="bi bi-exclamation-circle-fill"></i>
+        </div>
+        <div class="llm-error-tooltip">
+          <div class="llm-error-title">Block update failed</div>
+          <div class="llm-error-item">{{ updateBlockErrorMessage() }}</div>
+        </div>
+      </div>
+      }
       @if (missingRequiredParams.length) {
       <div class="llm-warning-wrap">
         <div class="llm-warning">
diff --git a/src/app/shared/nodes/generic-node/generic-node.ts b/src/app/shared/nodes/generic-node/generic-node.ts
index 0c786a7..c5307d2 100644
--- a/src/app/shared/nodes/generic-node/generic-node.ts
+++ b/src/app/shared/nodes/generic-node/generic-node.ts
@@ -308,6 +308,20 @@ export class GenericNodeComponent {
     return match ? match[1] : token;
   }
 
+  isCreatingOnServer(): boolean {
+    return this.data?.data?.['__isCreatingOnServer'] === true;
+  }
+
+  hasUpdateBlockError(): boolean {
+    return typeof this.data?.data?.['__updateBlockError'] === 'string'
+      && this.data.data['__updateBlockError'].length > 0;
+  }
+
+  updateBlockErrorMessage(): string | null {
+    const error = this.data?.data?.['__updateBlockError'];
+    return typeof error === 'string' && error.length > 0 ? error : null;
+  }
+
   private get blockConfiguration(): Record<string, any> | null {
     return this.data?.data?.specificConfiguration ?? null;
   }
@@ -799,12 +813,12 @@ export class GenericNodeComponent {
     const nodeData = this.data?.data as Record<string, unknown> | undefined;
     if (!nodeData?.['__needsServerCreate']) return;
     if (nodeData['__isCreatingOnServer'] === true) return;
-    if (this.missingRequiredPaths.length > 0) return;
 
     const blockType = this.blockType;
     if (!blockType) return;
 
     nodeData['__isCreatingOnServer'] = true;
+    nodeData['__updateBlockError'] = null;
     const configuration = this.ensureBlockConfiguration();
 
     this.blocksService.updateBlock(String(nodeData['id'] ?? ''), {
@@ -830,7 +844,8 @@ export class GenericNodeComponent {
           position: (current['position'] as { x: number; y: number } | undefined) ?? createdBlock.position,
           __needsServerCreate: false,
           __isCreatingOnServer: false,
-          __createdOnServer: true
+          __createdOnServer: true,
+          __updateBlockError: null
         };
         this.name = toStringOrNull(this.ensureBlockConfiguration()['name']) || createdBlock.name || this.name;
         this.refreshParameterFields();
@@ -839,6 +854,8 @@ export class GenericNodeComponent {
       },
       error: (err) => {
         nodeData['__isCreatingOnServer'] = false;
+        nodeData['__updateBlockError'] = err instanceof Error ? err.message : 'Block update failed';
+        this.refreshView();
         console.error('Create block failed', err);
       }
     });
@@ -849,5 +866,6 @@ export class GenericNodeComponent {
     if (!nodeData) return;
     nodeData['__needsServerCreate'] = true;
     nodeData['__createdOnServer'] = false;
+    nodeData['__updateBlockError'] = null;
   }
 }
diff --git a/src/app/shared/rete-editor/rete-editor.css b/src/app/shared/rete-editor/rete-editor.css
index 6e66f3a..695e5d4 100644
--- a/src/app/shared/rete-editor/rete-editor.css
+++ b/src/app/shared/rete-editor/rete-editor.css
@@ -1,3 +1,56 @@
+:host {
+  display: block;
+  position: relative;
+  width: 100%;
+  height: 100%;
+}
+
+.rete-editor-shell {
+  position: relative;
+  width: 100%;
+  height: 100%;
+}
+
+.rete-editor-loading {
+  position: absolute;
+  inset: 0;
+  z-index: 40;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background: rgba(248, 250, 252, 0.24);
+  pointer-events: none;
+}
+
+.rete-editor-loading-card {
+  display: inline-flex;
+  align-items: center;
+  gap: 10px;
+  padding: 10px 14px;
+  border: 1px solid #cbd5e1;
+  border-radius: 999px;
+  background: rgba(255, 255, 255, 0.96);
+  color: #0f172a;
+  box-shadow: 0 12px 28px rgba(15, 23, 42, 0.16);
+  font-size: 13px;
+  font-weight: 600;
+}
+
+.rete-editor-spinner {
+  width: 15px;
+  height: 15px;
+  border-radius: 999px;
+  border: 2px solid rgba(15, 23, 42, 0.18);
+  border-top-color: #2563eb;
+  animation: rete-editor-spin 0.75s linear infinite;
+}
+
+@keyframes rete-editor-spin {
+  to {
+    transform: rotate(360deg);
+  }
+}
+
 :host ::ng-deep [data-testid="node"] {
   user-select: none;
   -webkit-user-select: none;
diff --git a/src/app/shared/rete-editor/rete-editor.html b/src/app/shared/rete-editor/rete-editor.html
index 2a19579..953465f 100644
--- a/src/app/shared/rete-editor/rete-editor.html
+++ b/src/app/shared/rete-editor/rete-editor.html
@@ -1,2 +1,13 @@
-<div class="h-full w-full" #editor (dragover)="onDragOver($event)" (drop)="onDrop($event)">
+<div class="rete-editor-shell">
+  <div class="h-full w-full" #editor (dragover)="onDragOver($event)" (drop)="onDrop($event)">
+  </div>
+
+  @if (creatingEmptyBlock) {
+  <div class="rete-editor-loading">
+    <div class="rete-editor-loading-card">
+      <span class="rete-editor-spinner" aria-hidden="true"></span>
+      <span>Creating {{ creatingEmptyBlockType || 'block' }}...</span>
+    </div>
+  </div>
+  }
 </div>
diff --git a/src/app/shared/rete-editor/rete-editor.ts b/src/app/shared/rete-editor/rete-editor.ts
index a1e2f47..27909f9 100644
--- a/src/app/shared/rete-editor/rete-editor.ts
+++ b/src/app/shared/rete-editor/rete-editor.ts
@@ -29,6 +29,8 @@ export class ReteEditor implements OnChanges, OnDestroy {
   private rete?: ReteEditorInstance;
   private viewReady = false;
   private loadVersion = 0;
+  creatingEmptyBlock = false;
+  creatingEmptyBlockType = '';
   private readonly dirtyEventTypes = new Set([
     'nodecreated',
     'noderemoved',
@@ -72,11 +74,16 @@ export class ReteEditor implements OnChanges, OnDestroy {
     const blockType: BlockType = JSON.parse(payload);
     const position = this.getDropPosition(event);
     let newBlock: FlowBlock;
+    this.creatingEmptyBlock = true;
+    this.creatingEmptyBlockType = blockType.type;
     try {
       newBlock = await firstValueFrom(this.blocksService.createEmptyBlock(blockType.type));
     } catch (error) {
       console.error('Failed to create empty block', error);
       return;
+    } finally {
+      this.creatingEmptyBlock = false;
+      this.creatingEmptyBlockType = '';
     }
 
     newBlock = {
diff --git a/src/app/shared/title-toolbar/title-toolbar.css b/src/app/shared/title-toolbar/title-toolbar.css
index 281738c..9d26ab7 100644
--- a/src/app/shared/title-toolbar/title-toolbar.css
+++ b/src/app/shared/title-toolbar/title-toolbar.css
@@ -1,3 +1,7 @@
+.title-toolbar-input {
+  width: min(100%, 48vw);
+}
+
 .save-snackbar {
   position: fixed;
   right: 24px;
diff --git a/src/app/shared/title-toolbar/title-toolbar.html b/src/app/shared/title-toolbar/title-toolbar.html
index 213d9aa..6ca1b0b 100644
--- a/src/app/shared/title-toolbar/title-toolbar.html
+++ b/src/app/shared/title-toolbar/title-toolbar.html
@@ -1,32 +1,32 @@
-<div class="flex items-center justify-between
+<div class="flex items-center justify-between gap-4
             px-4 py-2
             bg-white border-b border-gray-200
             shadow-sm">
 
   <!-- Title -->
-  <div class="flex items-center gap-2">
-    <i class="bi bi-pencil-square text-indigo-500"></i>
-    <h2 class="m-0 text-sm font-semibold text-gray-800">
-        <input type="text" class="border-0 text-sm font-semibold text-gray-800
+  <div class="flex min-w-0 flex-1 items-center gap-2">
+    <i class="bi bi-pencil-square shrink-0 text-indigo-500"></i>
+    <h2 class="m-0 min-w-0 flex-1 text-sm font-semibold text-gray-800">
+        <input type="text" class="title-toolbar-input border-0 text-sm font-semibold text-gray-800
        focus:ring-0 p-0 m-0 box-border
-       w-52 max-w-52
+       min-w-0
        bg-transparent"
                [value]="title()"
                (blur)="changeTitle(titleInput.value)"
                 (keydown.enter)="changeTitle(titleInput.value); $event.target.blur()"
                maxlength="20"
                size="20"
-               #titleInput
+                #titleInput
                 />
     </h2>
     @if (notSaved()) {
-    <span class="inline-flex items-center gap-x-1.5 py-1.5 px-3 rounded-full text-xs font-medium border border-yellow-500 text-yellow-500">not saved</span>
+    <span class="inline-flex shrink-0 items-center gap-x-1.5 rounded-full border border-yellow-500 px-3 py-1.5 text-xs font-medium text-yellow-500">not saved</span>
     }
   </div>
 
 
   <!-- Actions -->
-  <div class="flex items-center gap-2" >
+  <div class="flex shrink-0 items-center gap-2" >
     <button tabindex="-1"
       class="border-0
              flex items-center gap-1