fix: harden GIF support — ref-counted sources, defensive detection, play budget

1. Move GIF loading behind TextureManager.loadGif/releaseGif with
   ref-counting (fixes shared-source invalidation on duplicate GIFs)
2. Strip query strings/fragments before .gif extension check
3. GIFs now load paused — separate MAX_PLAYING_GIFS=8 budget in
   culling system, only nearest N animate (others show static frame)

frontend/src/canvas/PixiCanvas.tsx

@@ -176,6 +176,7 @@ const PixiCanvas = forwardRef<PixiCanvasHandle, PixiCanvasProps>(
         // Distance-based priority: nearest to viewport center get resources first.
 
         const MAX_LOADED_TEXTURES = 60;   // max image textures in GPU
+        const MAX_PLAYING_GIFS = 8;      // max GIFs actively animating
         const MAX_INITIALIZED_VIDEOS = 6; // max <video> elements (tier 1+)
         const MAX_POSTER_VIDEOS = 4;      // max poster textures in GPU (tier 2)
 
@@ -215,12 +216,20 @@ const PixiCanvas = forwardRef<PixiCanvasHandle, PixiCanvasProps>(
             }
           }
 
-          // ---- Image budget management ----
+          // ---- Image + GIF texture budget management ----
+          // Both static images and GIFs share the texture load budget.
+          // GIFs additionally have a separate play budget (only nearest N animate).
           imageItems.sort((a, b) => a.dist - b.dist);
           const shouldLoadImage = new Set(
             imageItems.slice(0, MAX_LOADED_TEXTURES).map(i => i.item.id)
           );
 
+          // Build GIF play budget: only nearest loaded GIFs should animate
+          const gifItems = imageItems.filter(i => i.sprite instanceof AnimatedGifSprite);
+          const shouldPlayGif = new Set(
+            gifItems.slice(0, MAX_PLAYING_GIFS).map(i => i.item.id)
+          );
+
           let imgLoadsThisTick = 0;
           for (const { item, sprite } of imageItems) {
             if (shouldLoadImage.has(item.id) && !sprite.loaded && imgLoadsThisTick < 3) {
@@ -228,6 +237,14 @@ const PixiCanvas = forwardRef<PixiCanvasHandle, PixiCanvasProps>(
               loadedImages.add(item.id);
               imgLoadsThisTick++;
             }
+            // Manage GIF play/stop based on play budget
+            if (sprite instanceof AnimatedGifSprite && sprite.loaded) {
+              if (shouldPlayGif.has(item.id)) {
+                sprite.play();
+              } else {
+                sprite.stop();
+              }
+            }
           }
 
           // Unload images that left the viewport (check tracked set, not all items)

frontend/src/canvas/SceneManager.ts

@@ -27,6 +27,18 @@ import type {
   SceneObject,
 } from './scene-format';
 
+// ---------------------------------------------------------------------------
+// GIF detection
+// ---------------------------------------------------------------------------
+
+/** Check if an asset key points to a GIF file.
+ *  Strips query strings and fragments before checking extension. */
+function isGifAsset(asset: string): boolean {
+  // Strip query string and fragment
+  const clean = asset.split('?')[0].split('#')[0];
+  return clean.toLowerCase().endsWith('.gif');
+}
+
 // ---------------------------------------------------------------------------
 // SceneItem
 // ---------------------------------------------------------------------------
@@ -276,7 +288,7 @@ export class SceneManager {
     switch (data.type) {
       case 'image': {
         const imgData = data as ImageObject;
-        if (imgData.asset.toLowerCase().endsWith('.gif')) {
+        if (isGifAsset(imgData.asset)) {
           displayObject = new AnimatedGifSprite(imgData.asset, imgData.w, imgData.h, this.textures);
         } else {
           displayObject = new ImageSprite(imgData.asset, imgData.w, imgData.h, this.textures);

frontend/src/canvas/TextureManager.ts

@@ -1,4 +1,5 @@
 import { Texture, Assets } from "pixi.js";
+import type { GifSource } from "pixi.js/gif";
 
 interface TextureEntry {
   texture: Texture;
@@ -6,6 +7,12 @@ interface TextureEntry {
   refCount: number;
 }
 
+interface GifEntry {
+  source: GifSource;
+  url: string;
+  refCount: number;
+}
+
 /**
  * TextureManager — GPU texture cache with reference counting.
  *
@@ -19,6 +26,7 @@ interface TextureEntry {
  */
 export class TextureManager {
   private cache = new Map<string, TextureEntry>();
+  private gifCache = new Map<string, GifEntry>();
 
   /** Build the URL for a given asset. */
   urlForAsset(assetKey: string): string {
@@ -84,11 +92,54 @@ export class TextureManager {
     }
   }
 
-  /** Unload all cached textures. */
+  // -- GIF source management (ref-counted, same pattern as textures) --
+
+  /**
+   * Load a GifSource for the given asset. Increments ref count.
+   * Returns cached source if available, otherwise fetches and caches.
+   */
+  async loadGif(assetKey: string): Promise<GifSource> {
+    const existing = this.gifCache.get(assetKey);
+    if (existing) {
+      existing.refCount++;
+      return existing.source;
+    }
+
+    const url = this.urlForAsset(assetKey);
+    const source: GifSource = await Assets.load(url);
+
+    this.gifCache.set(assetKey, { source, url, refCount: 1 });
+    return source;
+  }
+
+  /**
+   * Release a reference to a GifSource. Only actually unloads
+   * when the last reference is released.
+   */
+  releaseGif(assetKey: string): void {
+    const entry = this.gifCache.get(assetKey);
+    if (!entry) return;
+
+    entry.refCount--;
+    if (entry.refCount > 0) return;
+
+    this.gifCache.delete(assetKey);
+    try {
+      Assets.unload(entry.url);
+    } catch {
+      // ignore
+    }
+  }
+
+  /** Unload all cached textures and GIF sources. */
   clear(): void {
     for (const [, entry] of this.cache) {
       try { Assets.unload(entry.url); } catch { /* ignore */ }
     }
     this.cache.clear();
+    for (const [, entry] of this.gifCache) {
+      try { Assets.unload(entry.url); } catch { /* ignore */ }
+    }
+    this.gifCache.clear();
   }
 }

frontend/src/canvas/sprites/AnimatedGifSprite.ts

@@ -1,5 +1,5 @@
-import { Container, Graphics, Assets } from "pixi.js";
-import { GifSprite, GifSource } from "pixi.js/gif";
+import { Container, Graphics } from "pixi.js";
+import { GifSprite } from "pixi.js/gif";
 import { TextureManager } from "../TextureManager";
 
 /**
@@ -8,7 +8,8 @@ import { TextureManager } from "../TextureManager";
  * Follows the same pattern as ImageSprite:
  * - Shadow + placeholder shown immediately
  * - Texture loaded lazily by viewport culling system
- * - GIF plays automatically when loaded, pauses when unloaded
+ * - GIF loaded/unloaded via TextureManager's ref-counted gifCache
+ *   (safe for duplicated GIFs on the same board)
  *
  * Uses PixiJS v8's built-in GifSprite (backed by gifuct-js).
  */
@@ -26,6 +27,7 @@ export class AnimatedGifSprite extends Container {
   private _shadow: Graphics;
   private _naturalWidth: number;
   private _naturalHeight: number;
+  private _playing = false;
 
   constructor(
     assetKey: string,
@@ -71,20 +73,29 @@ export class AnimatedGifSprite extends Container {
     return this._gif?.texture ?? null;
   }
 
-  /** Load the GIF. Called by viewport culling when near viewport. */
+  /** Whether the GIF is currently animating. */
+  get playing(): boolean {
+    return this._playing;
+  }
+
+  /** Load the GIF source (ref-counted). Called by viewport culling. */
   async loadTexture(): Promise<void> {
     if (this.loaded || this.loading) return;
 
     this.loading = true;
     try {
-      const url = this.textures.urlForAsset(this.assetKey);
-      const source: GifSource = await Assets.load(url);
-      if (this.destroyed) return;
+      const source = await this.textures.loadGif(this.assetKey);
+      if (this.destroyed) {
+        this.textures.releaseGif(this.assetKey);
+        return;
+      }
 
-      const gif = new GifSprite({ source, loop: true, autoPlay: true });
+      // Create GifSprite paused — culling system decides whether to play
+      const gif = new GifSprite({ source, loop: true, autoPlay: false });
       gif.width = this._naturalWidth;
       gif.height = this._naturalHeight;
       this._gif = gif;
+      this._playing = false;
       this.addChild(gif);
       this.loaded = true;
 
@@ -101,20 +112,36 @@ export class AnimatedGifSprite extends Container {
     }
   }
 
-  /** Unload GIF to free memory. Called by viewport culling when far from viewport. */
+  /** Start GIF animation. Called by culling when within play budget. */
+  play(): void {
+    if (this._gif && !this._playing) {
+      this._gif.play();
+      this._playing = true;
+    }
+  }
+
+  /** Stop GIF animation (stays on current frame). Called by culling when outside budget. */
+  stop(): void {
+    if (this._gif && this._playing) {
+      this._gif.stop();
+      this._playing = false;
+    }
+  }
+
+  /** Unload GIF to free memory (ref-counted). Called by viewport culling. */
   unloadTexture(): void {
     if (!this.loaded) return;
 
     if (this._gif) {
       this._gif.stop();
+      this._playing = false;
       this.removeChild(this._gif);
       this._gif.destroy();
       this._gif = null;
     }
 
-    // Unload the GifSource from Assets cache
-    const url = this.textures.urlForAsset(this.assetKey);
-    try { Assets.unload(url); } catch { /* ignore */ }
+    // Release through ref-counted manager (safe for duplicates)
+    this.textures.releaseGif(this.assetKey);
 
     this.loaded = false;