v0.4.13: fix delete-while-playing race, /videoCache, config additions, name resolution

Crash fix (4K delete EXCEPTION_ACCESS_VIOLATION):
- JavaCvBackend.stopWorker() no longer calls grabber.close() from caller thread.
  Only flips running=false, stops/flushes audio line, then interrupt+join(2s). The
  worker's own finally still closes grabber from the decoder thread, so the av_frame
  native plane is never freed mid-memCopy.
- Validate memCopy length against ByteBuffer.capacity() AND width*height*4 before
  copying, and re-check running/closed inside the frameLock.

Config:
- max_preload_mb (default 1024) — replaces the hard-coded 512 MB cap in VideoCache.
  Pushed to clients at join via CachePolicyPayload.
- render_distance_blocks (default 128) — replaces the hard-coded 128 in
  VideoAnchorRenderer.getViewDistance(). Mirrored client-side via ClientPolicy.

Command rename: /videopreload → /videoCache add|list|remove
- Persistent named index in cache_entries (server config).
- /videoCache list prints clickable URLs (ClickEvent.OpenUrl).
- /videoCache remove broadcasts DeleteCachePayload so each client purges its disk
  cache file.

Name resolution:
- /videoPlace ... <urlOrName> and the GUI save path both accept a /videoCache name
  in place of an http(s) URL; VideoPlayerConfig.resolveUrlOrName() does the lookup
  server-side before persisting to the anchor BE.

Cleanup:
- Drop the lowercase Brigadier aliases (videoplace, videostick, videodelete,
  videomute) — keep camelCase only.

README.md

@@ -3,7 +3,7 @@
 마인크래프트 안에서 임의의 동영상 URL을 벽·바닥·천장에 평면으로 재생하는 Fabric 모드.
 
 - 모드 ID: `video_player`
-- 현재 버전: **0.4.10**
+- 현재 버전: **0.4.12**
 - 마인크래프트 버전: **26.1.2**
 - 필요 Java: **25** (마인크래프트 26.x 가 요구함)
 
@@ -51,23 +51,23 @@ Fabric은 마인크래프트에 모드 기능을 추가해 주는 로더입니
      https://cdn.modrinth.com/data/P7dR8mSH/versions/Sy2Bq7Xc/fabric-api-0.149.0%2B26.1.2.jar
    - 더 최신 빌드를 찾을 땐: https://modrinth.com/mod/fabric-api/versions → 페이지에서 게임 버전 필터 `26.1.2` 를 직접 선택. (URL 파라미터 필터가 듣지 않는 경우가 있어서 페이지 안에서 한 번 더 확인하는 게 안전합니다.)
    - 받은 `fabric-api-0.149.0+26.1.2.jar` 를 `mods` 폴더에 넣습니다.
-2. **video_player** (이 모드, 0.4.10 부터 JavaCV 가 jar 안에 포함됨)
+2. **video_player** (이 모드, 0.4.12 부터 JavaCV 가 jar 안에 포함됨)
    - 다운로드: https://git.tkrmagid.kr/tkrmagid/mc_video_player_mod/releases
    - 자신의 OS·CPU 에 맞는 jar **한 개** 만 받아서 `mods` 폴더에 넣으면 됩니다 (별도 JavaCV 설치 불필요):
-     - Windows 64bit: `video_player-windows-x86_64-0.4.10.jar` (~32MB)
-     - macOS Intel: `video_player-macosx-x86_64-0.4.10.jar` (~24MB)
-     - macOS Apple Silicon (M1/M2/M3/M4): `video_player-macosx-arm64-0.4.10.jar` (~21MB)
-     - Linux 64bit: `video_player-linux-x86_64-0.4.10.jar` (~27MB)
+     - Windows 64bit: `video_player-windows-x86_64-0.4.12.jar` (~32MB)
+     - macOS Intel: `video_player-macosx-x86_64-0.4.12.jar` (~24MB)
+     - macOS Apple Silicon (M1/M2/M3/M4): `video_player-macosx-arm64-0.4.12.jar` (~21MB)
+     - Linux 64bit: `video_player-linux-x86_64-0.4.12.jar` (~27MB)
    - 자기 OS 가 헷갈리면: Windows 는 거의 다 `windows-x86_64`, 인텔맥은 `macosx-x86_64`, 애플 실리콘 맥은 `macosx-arm64`, 리눅스는 `linux-x86_64`.
 
-이전 버전(`video_player-0.4.0.jar`, `0.4.2.jar`, `0.4.3.jar`, `0.3.x.jar` 등)이 mods 폴더에 남아있다면 **반드시 삭제**하세요. 두 개가 같이 있으면 마인크래프트가 충돌로 켜지지 않습니다. 0.4.7 이하에서 쓰던 JVM 인수(`-Xbootclasspath/a:...javacv...`) 도 0.4.10 부터는 **빼주세요** — 모드 jar 안에 같은 JavaCV 가 들어있어서 부트클래스패스의 것과 충돌해 검은 화면이 날 수 있습니다.
+이전 버전(`video_player-0.4.0.jar`, `0.4.2.jar`, `0.4.3.jar`, `0.3.x.jar` 등)이 mods 폴더에 남아있다면 **반드시 삭제**하세요. 두 개가 같이 있으면 마인크래프트가 충돌로 켜지지 않습니다. 0.4.7 이하에서 쓰던 JVM 인수(`-Xbootclasspath/a:...javacv...`) 도 0.4.12 부터는 **빼주세요** — 모드 jar 안에 같은 JavaCV 가 들어있어서 부트클래스패스의 것과 충돌해 검은 화면이 날 수 있습니다.
 
 ### STEP 5. 잘 설치됐는지 확인
 
 게임 안에서 채팅창에 `/videostick` 을 입력하세요. 정상이라면:
 
 - 인벤토리에 **비디오 스틱** 아이템이 들어옵니다 (보라/검정 missing-texture 가 아니라 작대기 모양 아이콘).
-- 보라/검정 missing texture 가 나오면 **STEP 4** 에서 이전 버전 jar(`video_player-0.4.0.jar` / `0.4.1.jar` 등)가 mods 폴더에 같이 남아있는 경우입니다. 다 지우고 `0.4.10` 만 남기고 다시 시작하세요. (0.4.1 이하는 Fabric 26.1.2 model 로더가 unprefixed `item/generated` parent 를 거부해서 스틱 아이콘이 missing-model 큐브로 보입니다 — 0.4.2 에서 수정됨.)
+- 보라/검정 missing texture 가 나오면 **STEP 4** 에서 이전 버전 jar(`video_player-0.4.0.jar` / `0.4.1.jar` 등)가 mods 폴더에 같이 남아있는 경우입니다. 다 지우고 `0.4.12` 만 남기고 다시 시작하세요. (0.4.1 이하는 Fabric 26.1.2 model 로더가 unprefixed `item/generated` parent 를 거부해서 스틱 아이콘이 missing-model 큐브로 보입니다 — 0.4.2 에서 수정됨.)
 
 ---
 
@@ -172,7 +172,7 @@ Fabric은 마인크래프트에 모드 기능을 추가해 주는 로더입니
 ```sh
 JAVA_HOME=/usr/lib/jvm/java-25-openjdk-amd64 ./gradlew build
 ```
-산출물: `build/libs/video_player-0.4.10.jar` (~85KB)
+산출물: `build/libs/video_player-0.4.12.jar` (~85KB)
 
 플랫폼별 fat jar (JavaCV 1.5.13 + ffmpeg 8.0.1 네이티브 nested):
 ```sh
@@ -181,7 +181,7 @@ JAVA_HOME=/usr/lib/jvm/java-25-openjdk-amd64 ./gradlew clean build -Pplatform=li
 JAVA_HOME=/usr/lib/jvm/java-25-openjdk-amd64 ./gradlew clean build -Pplatform=macosx-x86_64
 JAVA_HOME=/usr/lib/jvm/java-25-openjdk-amd64 ./gradlew clean build -Pplatform=macosx-arm64
 ```
-산출물: `build/libs/video_player-<platform>-0.4.10.jar` (~21-32MB, jar 내부에 nested 로 javacv/javacpp/ffmpeg jar 5개 포함, Fabric loader 가 런타임에 classpath 로 풀어서 로딩)
+산출물: `build/libs/video_player-<platform>-0.4.12.jar` (~21-32MB, jar 내부에 nested 로 javacv/javacpp/ffmpeg jar 5개 포함, Fabric loader 가 런타임에 classpath 로 풀어서 로딩)
 
 JavaCV를 직접 의존성으로 가져오는 경우의 Maven 좌표:
 ```

gradle.properties

@@ -5,7 +5,7 @@ org.gradle.configuration-cache=false
 
 # Mod
 mod_id=video_player
-mod_version=0.4.10
+mod_version=0.4.13
 maven_group=com.ejclaw.videoplayer
 archives_base_name=video_player
 

src/main/java/com/ejclaw/videoplayer/VideoPlayerConfig.java

@@ -2,6 +2,8 @@ package com.ejclaw.videoplayer;
 
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonParser;
 import net.fabricmc.loader.api.FabricLoader;
@@ -12,88 +14,249 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Map;
 
 /**
  * Server-side mod config, stored at {@code <gameDir>/config/video_player.json}.
  *
- * <p>Format (auto-generated on first start):
+ * <p>Schema (auto-generated on first start):
  * <pre>{@code
  * {
- *   // List of HTTP(S) video URLs that the server will tell every player to preload
- *   // into their local video_player_cache/ folder when they join. Identical to running
- *   // /videopreload <url> for each joining player.
+ *   "max_preload_mb": 1024,
  *   "preload_urls": [
  *     "https://example.com/intro.mp4"
+ *   ],
+ *   "cache_entries": [
+ *     { "name": "intro", "url": "https://example.com/intro.mp4" }
  *   ]
  * }
  * }</pre>
  *
- * <p>Why a list and not a dedicated tool: the same {@link
- * com.ejclaw.videoplayer.net.PreloadPayload} that powers {@code /videopreload} is reused, so the
- * client-side cache, chat feedback, and {@code /videoplace} → cache lookup paths all behave
- * identically for config-driven and command-driven preloads.
+ * <p>{@code max_preload_mb} is the hard ceiling each client enforces on a single video download
+ * (default 1024 MB ≈ 1 GB; enough headroom for ~50 short FHD clips). Pushed to every client on
+ * join via {@link com.ejclaw.videoplayer.net.CachePolicyPayload}.
+ *
+ * <p>{@code cache_entries} is the named cache index managed by {@code /videocache add|list|remove}.
+ * Each entry's URL is pushed to clients on join (and immediately on {@code add}). Names are unique.
+ *
+ * <p>{@code preload_urls} is the legacy un-named auto-preload list — same behavior as
+ * {@code cache_entries} but without a removable handle. Kept for backward-compat.
  */
 public final class VideoPlayerConfig {
     private VideoPlayerConfig() {}
 
     private static final String FILE_NAME = "video_player.json";
-    private static volatile List<String> PRELOAD_URLS = Collections.emptyList();
+
+    private static final int DEFAULT_MAX_PRELOAD_MB = 1024;
+    /** Default render-distance cap for video anchors, in blocks. 128 = the legacy hard-coded value. */
+    private static final int DEFAULT_RENDER_DISTANCE = 128;
+
+    private static volatile int    maxPreloadMb = DEFAULT_MAX_PRELOAD_MB;
+    private static volatile int    renderDistanceBlocks = DEFAULT_RENDER_DISTANCE;
+    private static volatile List<String> preloadUrls = Collections.emptyList();
+    /** Insertion-ordered name → url. Mutated only under the class monitor. */
+    private static final Map<String, String> CACHE_ENTRIES = new LinkedHashMap<>();
 
     /** Load (or create) the config file. Called once during mod initialization. */
-    public static void load() {
-        Path path = FabricLoader.getInstance().getConfigDir().resolve(FILE_NAME);
+    public static synchronized void load() {
+        Path path = configPath();
         try {
             if (!Files.exists(path)) {
                 writeDefault(path);
                 VideoPlayerMod.LOG.info("[{}] created default config at {}",
                     VideoPlayerMod.MOD_ID, path);
-                PRELOAD_URLS = Collections.emptyList();
+                maxPreloadMb = DEFAULT_MAX_PRELOAD_MB;
+                preloadUrls = Collections.emptyList();
+                CACHE_ENTRIES.clear();
                 return;
             }
             String raw = Files.readString(path, StandardCharsets.UTF_8);
             JsonObject json = JsonParser.parseString(raw).getAsJsonObject();
+
+            // max_preload_mb (sanity-clamped to [16, 16384] so a typo can't brick a client)
+            int cap = DEFAULT_MAX_PRELOAD_MB;
+            if (json.has("max_preload_mb") && json.get("max_preload_mb").isJsonPrimitive()
+                    && json.get("max_preload_mb").getAsJsonPrimitive().isNumber()) {
+                cap = json.get("max_preload_mb").getAsInt();
+            }
+            if (cap < 16) cap = 16;
+            if (cap > 16384) cap = 16384;
+            maxPreloadMb = cap;
+
+            // render_distance_blocks (sanity-clamped to [16, 2048])
+            int rd = DEFAULT_RENDER_DISTANCE;
+            if (json.has("render_distance_blocks") && json.get("render_distance_blocks").isJsonPrimitive()
+                    && json.get("render_distance_blocks").getAsJsonPrimitive().isNumber()) {
+                rd = json.get("render_distance_blocks").getAsInt();
+            }
+            if (rd < 16)   rd = 16;
+            if (rd > 2048) rd = 2048;
+            renderDistanceBlocks = rd;
+
+            // preload_urls (legacy)
             List<String> urls = new ArrayList<>();
             if (json.has("preload_urls") && json.get("preload_urls").isJsonArray()) {
                 json.getAsJsonArray("preload_urls").forEach(el -> {
                     if (el.isJsonPrimitive() && el.getAsJsonPrimitive().isString()) {
-                        String u = el.getAsString().trim();
-                        if (!u.isEmpty() && (u.startsWith("http://") || u.startsWith("https://"))
-                            && u.length() <= 256) {
-                            urls.add(u);
-                        } else if (!u.isEmpty()) {
-                            VideoPlayerMod.LOG.warn(
-                                "[{}] config: ignoring invalid preload url '{}' (must be http/https, ≤256 chars)",
-                                VideoPlayerMod.MOD_ID, u);
-                        }
+                        String u = sanitizeUrl(el.getAsString());
+                        if (u != null) urls.add(u);
                     }
                 });
             }
-            PRELOAD_URLS = Collections.unmodifiableList(urls);
-            VideoPlayerMod.LOG.info("[{}] config loaded: {} preload url(s)",
-                VideoPlayerMod.MOD_ID, urls.size());
-        } catch (Throwable t) {
-            VideoPlayerMod.LOG.warn("[{}] failed to read config {}: {} — using empty list",
-                VideoPlayerMod.MOD_ID, path, t.toString());
-            PRELOAD_URLS = Collections.emptyList();
+            preloadUrls = Collections.unmodifiableList(urls);
+
+            // cache_entries (named)
+            CACHE_ENTRIES.clear();
+            if (json.has("cache_entries") && json.get("cache_entries").isJsonArray()) {
+                for (JsonElement el : json.getAsJsonArray("cache_entries")) {
+                    if (!el.isJsonObject()) continue;
+                    JsonObject o = el.getAsJsonObject();
+                    String name = o.has("name") && o.get("name").isJsonPrimitive()
+                        ? o.get("name").getAsString().trim() : null;
+                    String url  = o.has("url")  && o.get("url").isJsonPrimitive()
+                        ? sanitizeUrl(o.get("url").getAsString()) : null;
+                    if (name == null || name.isEmpty() || url == null) continue;
+                    if (CACHE_ENTRIES.containsKey(name)) {
+                        VideoPlayerMod.LOG.warn(
+                            "[{}] config: duplicate cache entry name '{}' — keeping first",
+                            VideoPlayerMod.MOD_ID, name);
+                        continue;
+                    }
+                    CACHE_ENTRIES.put(name, url);
                 }
             }
 
-    /** URLs to push to each joining player. Never null; possibly empty. */
-    public static List<String> preloadUrls() {
-        return PRELOAD_URLS;
+            VideoPlayerMod.LOG.info(
+                "[{}] config loaded: cap={} MB, render={} blocks, preload_urls={}, cache_entries={}",
+                VideoPlayerMod.MOD_ID, maxPreloadMb, renderDistanceBlocks, urls.size(), CACHE_ENTRIES.size());
+        } catch (Throwable t) {
+            VideoPlayerMod.LOG.warn("[{}] failed to read config {}: {} — using defaults",
+                VideoPlayerMod.MOD_ID, path, t.toString());
+            maxPreloadMb = DEFAULT_MAX_PRELOAD_MB;
+            renderDistanceBlocks = DEFAULT_RENDER_DISTANCE;
+            preloadUrls = Collections.emptyList();
+            CACHE_ENTRIES.clear();
+        }
+    }
+
+    // -- accessors ---------------------------------------------------------------------------
+
+    /** Hard cap on a single client-side video download, in MB. */
+    public static int maxPreloadMb() { return maxPreloadMb; }
+
+    /** Same value in bytes. */
+    public static long maxPreloadBytes() { return (long) maxPreloadMb * 1024L * 1024L; }
+
+    /** Anchor BE view-distance cap, in blocks. */
+    public static int renderDistanceBlocks() { return renderDistanceBlocks; }
+
+    /** Legacy un-named preload list (still pushed at join). Never null. */
+    public static List<String> preloadUrls() { return preloadUrls; }
+
+    /** Snapshot of name → url, insertion-ordered. Never null. */
+    public static synchronized Map<String, String> cacheEntries() {
+        return new LinkedHashMap<>(CACHE_ENTRIES);
+    }
+
+    /** Lookup a single entry's URL by name. */
+    public static synchronized String cacheUrl(String name) {
+        return CACHE_ENTRIES.get(name);
+    }
+
+    /**
+     * Accept either a raw HTTP(S) URL or a previously-registered cache entry name and return
+     * the canonical URL to store on the anchor. Returns the trimmed input when it's already a
+     * URL, the looked-up URL when the input matches a cache entry name, or {@code null} if the
+     * input is neither (caller decides whether to fail or fall through).
+     */
+    public static synchronized String resolveUrlOrName(String input) {
+        if (input == null) return null;
+        String t = input.trim();
+        if (t.isEmpty()) return "";
+        if (t.startsWith("http://") || t.startsWith("https://")) return t;
+        return CACHE_ENTRIES.get(t);
+    }
+
+    // -- mutations (driven by /videocache add|remove) -----------------------------------------
+
+    /** Returns true if added; false if the name already exists. Persists on success. */
+    public static synchronized boolean addCacheEntry(String name, String url) {
+        if (name == null || name.isEmpty() || url == null) return false;
+        if (CACHE_ENTRIES.containsKey(name)) return false;
+        CACHE_ENTRIES.put(name, url);
+        save();
+        return true;
+    }
+
+    /** Returns the removed URL, or null if no entry by that name. Persists on success. */
+    public static synchronized String removeCacheEntry(String name) {
+        if (name == null) return null;
+        String removed = CACHE_ENTRIES.remove(name);
+        if (removed != null) save();
+        return removed;
+    }
+
+    // -- io ----------------------------------------------------------------------------------
+
+    private static Path configPath() {
+        return FabricLoader.getInstance().getConfigDir().resolve(FILE_NAME);
+    }
+
+    private static String sanitizeUrl(String s) {
+        if (s == null) return null;
+        String t = s.trim();
+        if (t.isEmpty() || t.length() > 256) return null;
+        if (!(t.startsWith("http://") || t.startsWith("https://"))) return null;
+        return t;
     }
 
     private static void writeDefault(Path path) throws IOException {
         Files.createDirectories(path.getParent());
-        // Hand-rolled rather than Gson-serialized so we can carry a `_comment` field that
-        // explains the format directly inside the file.
         JsonObject root = new JsonObject();
         root.addProperty("_comment",
-            "preload_urls: HTTP(S) video URLs broadcast to every player on join. "
-                + "Equivalent to running /videopreload <url> per joiner. Max 256 chars per url.");
-        root.add("preload_urls", new com.google.gson.JsonArray());
+            "max_preload_mb: per-video download cap (each client). "
+                + "render_distance_blocks: max distance at which a video anchor still renders. "
+                + "preload_urls: HTTP(S) videos auto-pushed to every player on join (no name). "
+                + "cache_entries: named entries managed by /videoCache add|list|remove.");
+        root.addProperty("max_preload_mb", DEFAULT_MAX_PRELOAD_MB);
+        root.addProperty("render_distance_blocks", DEFAULT_RENDER_DISTANCE);
+        root.add("preload_urls", new JsonArray());
+        root.add("cache_entries", new JsonArray());
         Gson gson = new GsonBuilder().setPrettyPrinting().disableHtmlEscaping().create();
         Files.writeString(path, gson.toJson(root), StandardCharsets.UTF_8);
     }
+
+    /** Persist current in-memory state. Best-effort; logs on failure. */
+    private static void save() {
+        Path path = configPath();
+        try {
+            Files.createDirectories(path.getParent());
+            JsonObject root = new JsonObject();
+            root.addProperty("_comment",
+                "max_preload_mb: per-video download cap (each client). "
+                    + "render_distance_blocks: max distance at which a video anchor still renders. "
+                    + "preload_urls: legacy un-named auto-preload list. "
+                    + "cache_entries: managed by /videoCache add|list|remove.");
+            root.addProperty("max_preload_mb", maxPreloadMb);
+            root.addProperty("render_distance_blocks", renderDistanceBlocks);
+            JsonArray legacyArr = new JsonArray();
+            for (String u : preloadUrls) legacyArr.add(u);
+            root.add("preload_urls", legacyArr);
+            JsonArray entriesArr = new JsonArray();
+            for (Map.Entry<String, String> e : CACHE_ENTRIES.entrySet()) {
+                JsonObject o = new JsonObject();
+                o.addProperty("name", e.getKey());
+                o.addProperty("url",  e.getValue());
+                entriesArr.add(o);
+            }
+            root.add("cache_entries", entriesArr);
+            Gson gson = new GsonBuilder().setPrettyPrinting().disableHtmlEscaping().create();
+            Files.writeString(path, gson.toJson(root), StandardCharsets.UTF_8);
+        } catch (Throwable t) {
+            VideoPlayerMod.LOG.warn("[{}] failed to save config: {}",
+                VideoPlayerMod.MOD_ID, t.toString());
+        }
+    }
 }

src/main/java/com/ejclaw/videoplayer/VideoPlayerMod.java

@@ -1,10 +1,11 @@
 package com.ejclaw.videoplayer;
 
+import com.ejclaw.videoplayer.command.VideoCacheCommand;
 import com.ejclaw.videoplayer.command.VideoDeleteCommand;
 import com.ejclaw.videoplayer.command.VideoMuteCommand;
 import com.ejclaw.videoplayer.command.VideoPlaceCommand;
-import com.ejclaw.videoplayer.command.VideoPreloadCommand;
 import com.ejclaw.videoplayer.command.VideoStickCommand;
+import com.ejclaw.videoplayer.net.CachePolicyPayload;
 import com.ejclaw.videoplayer.net.PreloadPayload;
 import com.ejclaw.videoplayer.net.VideoPlayerNetwork;
 import com.ejclaw.videoplayer.registry.VideoPlayerBlockEntities;
@@ -37,20 +38,33 @@ public class VideoPlayerMod implements ModInitializer {
             VideoPlaceCommand.register(dispatcher);
             VideoDeleteCommand.register(dispatcher);
             VideoMuteCommand.register(dispatcher);
-            VideoPreloadCommand.register(dispatcher);
+            VideoCacheCommand.register(dispatcher);
         });
 
-        // When a player finishes joining, push every preload URL from the config so their
-        // client kicks off the background download. Reuses the same PreloadPayload that
-        // /videopreload sends, so the client-side caching path is identical.
+        // On join: (1) push the per-video download cap so the client knows whether to abort
+        // an over-cap stream, (2) replay every legacy preload_urls entry, (3) replay every
+        // named /videocache entry. Policy must go first so caps are honored before downloads
+        // start. Each PreloadPayload is fire-and-forget; clients post their own "[videopreload]"
+        // status lines when downloads finish.
         ServerPlayConnectionEvents.JOIN.register((handler, sender, server) -> {
-            java.util.List<String> urls = VideoPlayerConfig.preloadUrls();
-            if (urls.isEmpty()) return;
-            for (String url : urls) {
-                ServerPlayNetworking.send(handler.getPlayer(), new PreloadPayload(url));
+            var player = handler.getPlayer();
+            ServerPlayNetworking.send(player, new CachePolicyPayload(
+                VideoPlayerConfig.maxPreloadBytes(),
+                VideoPlayerConfig.renderDistanceBlocks()));
+
+            int sent = 0;
+            for (String url : VideoPlayerConfig.preloadUrls()) {
+                ServerPlayNetworking.send(player, new PreloadPayload(url));
+                sent++;
+            }
+            for (var e : VideoPlayerConfig.cacheEntries().entrySet()) {
+                ServerPlayNetworking.send(player, new PreloadPayload(e.getValue()));
+                sent++;
+            }
+            if (sent > 0) {
+                LOG.info("[{}] sent policy + {} preload(s) to {}",
+                    MOD_ID, sent, player.getName().getString());
             }
-            LOG.info("[{}] sent {} config preload(s) to {}",
-                MOD_ID, urls.size(), handler.getPlayer().getName().getString());
         });
 
         LOG.info("[{}] initialized", MOD_ID);

src/main/java/com/ejclaw/videoplayer/client/ClientPolicy.java

@@ -0,0 +1,30 @@
+package com.ejclaw.videoplayer.client;
+
+import com.ejclaw.videoplayer.VideoPlayerMod;
+import net.fabricmc.api.EnvType;
+import net.fabricmc.api.Environment;
+
+/**
+ * Client-side mirror of the server's policy bundle (pushed via {@code CachePolicyPayload}
+ * on join). Currently just the anchor render-distance cap; the per-video download cap lives
+ * directly on {@link com.ejclaw.videoplayer.client.playback.VideoCache}.
+ *
+ * <p>Default 128 matches the legacy hard-coded value, so unpaired clients (e.g. dev tests
+ * with no JOIN packet, or older servers without the payload) render identically to before.
+ */
+@Environment(EnvType.CLIENT)
+public final class ClientPolicy {
+    private ClientPolicy() {}
+
+    private static volatile int renderDistanceBlocks = 128;
+
+    public static int renderDistanceBlocks() { return renderDistanceBlocks; }
+
+    public static void setRenderDistanceBlocks(int blocks) {
+        if (blocks < 16)   blocks = 16;
+        if (blocks > 2048) blocks = 2048;
+        renderDistanceBlocks = blocks;
+        VideoPlayerMod.LOG.info("[{}] anchor render distance set to {} blocks",
+            VideoPlayerMod.MOD_ID, blocks);
+    }
+}

src/main/java/com/ejclaw/videoplayer/client/net/ClientNetworking.java

@@ -1,9 +1,12 @@
 package com.ejclaw.videoplayer.client.net;
 
 import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
+import com.ejclaw.videoplayer.client.ClientPolicy;
 import com.ejclaw.videoplayer.client.gui.VideoConfigScreen;
 import com.ejclaw.videoplayer.client.playback.VideoCache;
 import com.ejclaw.videoplayer.client.playback.VideoPlayback;
+import com.ejclaw.videoplayer.net.CachePolicyPayload;
+import com.ejclaw.videoplayer.net.DeleteCachePayload;
 import com.ejclaw.videoplayer.net.OpenScreenPayload;
 import com.ejclaw.videoplayer.net.PreloadPayload;
 import com.ejclaw.videoplayer.net.SyncAnchorPayload;
@@ -40,5 +43,17 @@ public final class ClientNetworking {
         ClientPlayNetworking.registerGlobalReceiver(PreloadPayload.TYPE, (payload, context) -> {
             VideoCache.preload(payload.url());
         });
+
+        // Server tells us the per-video download cap (bytes). Must arrive before PreloadPayload
+        // (the server sends policy first on JOIN), so we don't accidentally use the stale default.
+        ClientPlayNetworking.registerGlobalReceiver(CachePolicyPayload.TYPE, (payload, context) -> {
+            VideoCache.setMaxBytes(payload.maxBytes());
+            ClientPolicy.setRenderDistanceBlocks(payload.renderDistanceBlocks());
+        });
+
+        // /videocache remove — drop the URL from this client's disk cache.
+        ClientPlayNetworking.registerGlobalReceiver(DeleteCachePayload.TYPE, (payload, context) -> {
+            VideoCache.purge(payload.url());
+        });
     }
 }

src/main/java/com/ejclaw/videoplayer/client/playback/JavaCvBackend.java

@@ -15,6 +15,7 @@ import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.nio.ShortBuffer;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicLong;
 
 /**
  * SPEC §5.3 — fallback mp4/http(s) backend driven by JavaCV's FFmpegFrameGrabber.
@@ -40,16 +41,35 @@ public class JavaCvBackend implements VideoBackend {
     private final AtomicBoolean running = new AtomicBoolean(false);
     private final AtomicBoolean paused  = new AtomicBoolean(false);
     /**
-     * Single preallocated RGBA staging buffer. Decoder thread writes into it under
-     * {@link #frameLock}; render thread reads via {@link #consumeFrame(long, long)} under the
-     * same lock. One allocation for the lifetime of the backend instead of one per frame —
-     * see 0.4.10 changelog for the regression that motivated this. The lock is short-held
-     * (one 8MB memcpy ≈ 1ms at 1080p) so contention is negligible.
+     * Ring buffer of preallocated RGBA staging slots. Decoder thread writes to {@code ringTail}
+     * under {@link #frameLock}; render thread drains the oldest slot via
+     * {@link #consumeFrame(long, long)} under the same lock.
+     *
+     * <p>0.4.10 used a single staging slot and relied on {@link SourceDataLine#write}
+     * backpressure to pace the decoder. That paced only at audio-buffer granularity (~0.5 s):
+     * the decoder burst-produced ~12 video frames into the slot while the audio line drained,
+     * the consumer (60+ Hz polling) saw only the last frame of each burst, then the decoder
+     * stalled until audio drained again — net effect ~2 fps of visible video despite the
+     * decoder producing at the source's 24 fps. The ring absorbs the burst; combined with the
+     * smaller audio buffer (~0.1 s) below the burst collapses to 2–3 frames which fits in
+     * {@link #FRAME_RING_SLOTS}.
+     *
+     * <p>If the ring still fills, the decoder overwrites the oldest slot and increments
+     * {@link #droppedFrames}. Memory cost: {@code 4 × w × h × 4} bytes (32 MB at 1080p,
+     * ~130 MB at 4K).
      */
+    private static final int FRAME_RING_SLOTS = 4;
     private final Object frameLock = new Object();
-    private ByteBuffer frameBuf;
-    private int frameBufBytes = 0;
-    private boolean frameDirty = false;
+    private final ByteBuffer[] ringBufs = new ByteBuffer[FRAME_RING_SLOTS];
+    private final int[] ringBytes = new int[FRAME_RING_SLOTS];
+    private int ringHead = 0;  // next slot to consume
+    private int ringTail = 0;  // next slot to produce into
+    private int ringCount = 0;
+
+    /** Decoder telemetry (cumulative). Logged ~every 10 s from the decode thread. */
+    private final AtomicLong producedFrames = new AtomicLong();
+    private final AtomicLong consumedFrames = new AtomicLong();
+    private final AtomicLong droppedFrames  = new AtomicLong();
     private volatile int width = 0;
     private volatile int height = 0;
     private volatile float gain = 1.0F;
@@ -101,17 +121,22 @@ public class JavaCvBackend implements VideoBackend {
     @Override
     public boolean consumeFrame(long dstAddr, long maxBytes) {
         synchronized (frameLock) {
-            if (!frameDirty || frameBuf == null || frameBufBytes <= 0) return false;
-            if (frameBufBytes > maxBytes) {
-                // Texture not yet resized for this frame's dimensions — drop and wait for the
-                // caller to ensure capacity next tick. ensureTexture() runs in Entry.upload
-                // before consumeFrame, so this is only hit on the exact tick of a resolution
-                // change.
-                frameDirty = false;
+            if (ringCount <= 0) return false;
+            int idx = ringHead;
+            int n = ringBytes[idx];
+            ByteBuffer buf = ringBufs[idx];
+            // Always advance head regardless of memcpy outcome — otherwise a single oversize
+            // frame (e.g. mid-resize) would jam the ring forever.
+            ringHead = (idx + 1) % FRAME_RING_SLOTS;
+            ringCount--;
+            if (buf == null || n <= 0 || n > maxBytes) {
+                // Texture not yet sized for this frame, or empty slot — skip. ensureTexture()
+                // runs in Entry.tryUpload() before consumeFrame, so n > maxBytes only happens
+                // on the exact tick of a resolution change.
                 return false;
             }
-            MemoryUtil.memCopy(MemoryUtil.memAddress(frameBuf), dstAddr, frameBufBytes);
-            frameDirty = false;
+            MemoryUtil.memCopy(MemoryUtil.memAddress(buf), dstAddr, n);
+            consumedFrames.incrementAndGet();
             return true;
         }
     }
@@ -121,9 +146,11 @@ public class JavaCvBackend implements VideoBackend {
         closed = true;
         stopWorker();
         synchronized (frameLock) {
-            frameBuf = null;
-            frameBufBytes = 0;
-            frameDirty = false;
+            for (int i = 0; i < FRAME_RING_SLOTS; i++) {
+                ringBufs[i] = null;
+                ringBytes[i] = 0;
+            }
+            ringHead = ringTail = ringCount = 0;
         }
     }
 
@@ -137,16 +164,44 @@ public class JavaCvBackend implements VideoBackend {
             try { line.stop();  } catch (Throwable ignored) {}
             try { line.flush(); } catch (Throwable ignored) {}
         }
-        // Yank the grabber too so a blocked grab() inside an HTTP read returns promptly.
-        // JavaCV's close() is best-effort thread-safe — worst case we trip an AVERROR which
-        // the catch-all in runLoop swallows.
-        Object g = grabberHandle;
-        if (g != null) {
-            try { g.getClass().getMethod("close").invoke(g); } catch (Throwable ignored) {}
-        }
+        // CRITICAL: we do NOT call grabber.close() from this (caller) thread. The decoder's
+        // per-frame path is:
+        //
+        //     frame = grab(grabber);                  // grabber-owned native memory
+        //     src = frame.image[0];                   // DirectByteBuffer over that memory
+        //     need = src.remaining();                 // (lock-free)
+        //     srcAddr = MemoryUtil.memAddress(src);   // (lock-free)
+        //     synchronized (frameLock) {
+        //         MemoryUtil.memCopy(srcAddr, ...);   // reads from grabber-owned memory
+        //     }
+        //
+        // Even if we held frameLock while closing the grabber, there's a window between
+        // grab() returning and entering the synchronized block where the decoder is holding a
+        // stale srcAddr — closing the grabber there frees the av_frame plane and the next
+        // memcpy crashes inside StubRoutines::jbyte_disjoint_arraycopy (exactly the 4K-delete
+        // crash dump we saw). So the safe rule is: only the decoder thread touches the
+        // grabber. External stop signals `running=false`, stops the audio line, interrupts the
+        // worker, and joins briefly; the worker's own `finally` calls grabber.close(). Inside
+        // the loop, grab() unblocks via the rw_timeout/timeout options (3 s, set in runLoop)
+        // even on a stuck HTTP read, so the join below normally returns within a frame.
         Thread t = worker;
         worker = null;
-        if (t != null) t.interrupt();
+        if (t != null) {
+            t.interrupt();
+            try {
+                t.join(2000);
+            } catch (InterruptedException ie) {
+                Thread.currentThread().interrupt();
+            }
+            if (t.isAlive()) {
+                // Worker still blocked in native grab() — let it finish on its own. Its
+                // finally still closes the grabber when grab() eventually returns / throws.
+                // No native pointers leak in the meantime because we don't touch them here.
+                VideoPlayerMod.LOG.warn(
+                    "[{}] decoder did not exit within 2 s of stop; orphaning until next grab() returns",
+                    VideoPlayerMod.MOD_ID);
+            }
+        }
         ready = false;
     }
 
@@ -209,6 +264,18 @@ public class JavaCvBackend implements VideoBackend {
             localAudioLine = openLine(sampleRate, audioChannels);
             this.audioLine = localAudioLine;
 
+            // Decoder spec — printed once per playback so the user log shows what the decoder
+            // actually sees (resolution / frame rate / sample rate). Used to verify our pacing
+            // assumptions (e.g. ring depth, audio buffer length) match the source.
+            double srcFrameRate = 0;
+            try { srcFrameRate = ((Number) grabberCls.getMethod("getFrameRate").invoke(grabber)).doubleValue(); }
+            catch (Throwable ignored) {}
+            VideoPlayerMod.LOG.info(
+                "[{}] decoder started: {}x{} @ {} fps, audio {} Hz x{}, ring={} slots",
+                VideoPlayerMod.MOD_ID, width, height,
+                String.format("%.2f", srcFrameRate),
+                sampleRate, audioChannels, FRAME_RING_SLOTS);
+
             Class<?> frameCls    = Class.forName(FRAME_CLASS);
             Field imageField     = frameCls.getField("image");
             Field samplesField   = frameCls.getField("samples");
@@ -216,6 +283,14 @@ public class JavaCvBackend implements VideoBackend {
             // but we still resolve its class so a future code path could fall back to it if a
             // grabber refuses setPixelFormat. Keep the lookup defensive.
 
+            // Stats sampling: every 10 s of wall-clock we log produced/consumed/dropped deltas
+            // and the implied fps. Lets us tell from the log whether the decoder is keeping
+            // real-time pace (produced≈source fps) and whether the ring is overflowing
+            // (dropped>0). All counters are cumulative; we keep the previous sample to compute
+            // deltas.
+            long statsLastNs = System.nanoTime();
+            long lastProd = 0, lastCons = 0, lastDrop = 0;
+
             while (running.get() && !closed) {
                 if (paused.get()) { Thread.sleep(20); continue; }
                 Object frame;
@@ -243,35 +318,82 @@ public class JavaCvBackend implements VideoBackend {
                 Object[] images = (Object[]) imageField.get(frame);
                 if (images != null && images.length > 0 && images[0] instanceof ByteBuffer src) {
                     // frame.image[0] is the swscale-converted RGBA plane, reused by the grabber
-                    // across grab() calls. Copy into our preallocated staging buffer under
-                    // frameLock so the render thread's consumeFrame() sees a coherent image.
+                    // across grab() calls. Copy into the next ring slot under frameLock so the
+                    // render thread's consumeFrame() sees coherent frames in FIFO order.
                     //
-                    // 0.4.9 used `ByteBuffer.allocateDirect(w*h*4)` on every grab — at 1080p ×
-                    // 24fps that's ~192 MB/s of direct memory churn (each allocation zero-fills
-                    // the page, plus the Cleaner enqueues the old buffer for finalization).
-                    // The decoder thread spent so much time on memory bookkeeping that grab()
-                    // fell behind real time, the single-slot `latest` AtomicReference was
-                    // refilled in bursts, and the user saw ~5fps playback even though the
-                    // game/render thread was fine.
-                    //
-                    // Preallocating once eliminates both the zero-fill cost and the Cleaner
-                    // pressure. The decoder thread now spends its budget on the actual decode +
-                    // swscale + a single 8MB memcpy — well within 42ms at 1080p × 24fps.
+                    // Allocation is one-time per slot, lazily on first use (or on a resolution
+                    // upgrade) — never per frame. 0.4.9's per-frame allocateDirect was the
+                    // primary memory-churn problem; 0.4.10 fixed that; 0.4.11 adds the ring on
+                    // top to absorb the burst-then-stall caused by SourceDataLine backpressure
+                    // pacing only at audio-buffer granularity.
                     int need = src.remaining();
+                    // Reviewer-mandated sanity bounds: memCopy is a raw native copy with no
+                    // fence against overrun. Validate against (a) the source buffer's own
+                    // capacity (so a corrupt plane can't read past it) and (b) the expected
+                    // RGBA frame size (width*height*4) (so an unexpectedly oversized plane
+                    // can't smash the dst slot we'll allocate). If either fails, skip this
+                    // frame and continue — the next grab() will give us a fresh one.
+                    int expected = width * height * 4;
+                    if (need > src.capacity()) {
+                        VideoPlayerMod.LOG.warn("[{}] frame overruns source capacity (need={}, cap={}); skipping",
+                            VideoPlayerMod.MOD_ID, need, src.capacity());
+                        need = 0;
+                    } else if (need > expected) {
+                        VideoPlayerMod.LOG.warn("[{}] frame larger than expected RGBA size (need={}, expected={}); skipping",
+                            VideoPlayerMod.MOD_ID, need, expected);
+                        need = 0;
+                    }
                     if (need > 0) {
-                        synchronized (frameLock) {
-                            if (frameBuf == null || frameBuf.capacity() < need) {
-                                frameBuf = ByteBuffer.allocateDirect(need).order(ByteOrder.nativeOrder());
-                            }
                         int srcPos = src.position();
-                            long dstAddr = MemoryUtil.memAddress(frameBuf);
                         long srcAddr = MemoryUtil.memAddress(src) + srcPos;
+                        synchronized (frameLock) {
+                            // Recheck shutdown inside the lock: stopWorker() flipped running=false
+                            // before signaling, so worker is the only writer here and grabber.close()
+                            // only runs from this thread's finally — but the explicit check keeps
+                            // the contract obvious to future readers.
+                            if (!running.get() || closed) break;
+                            int idx = ringTail;
+                            if (ringBufs[idx] == null || ringBufs[idx].capacity() < need) {
+                                ringBufs[idx] = ByteBuffer.allocateDirect(need).order(ByteOrder.nativeOrder());
+                            }
+                            long dstAddr = MemoryUtil.memAddress(ringBufs[idx]);
                             MemoryUtil.memCopy(srcAddr, dstAddr, need);
-                            src.position(srcPos); // unchanged, but explicit — JavaCV reads it too
-                            frameBufBytes = need;
-                            frameDirty = true;
+                            ringBytes[idx] = need;
+                            ringTail = (idx + 1) % FRAME_RING_SLOTS;
+                            if (ringCount < FRAME_RING_SLOTS) {
+                                ringCount++;
+                            } else {
+                                // Ring was full — we overwrote the oldest frame. Advance head
+                                // to point at the next-oldest so consume order stays FIFO.
+                                ringHead = (ringHead + 1) % FRAME_RING_SLOTS;
+                                droppedFrames.incrementAndGet();
+                            }
+                            producedFrames.incrementAndGet();
+                        }
+                        src.position(srcPos); // restore — JavaCV reads it on subsequent grabs
                     }
                 }
+
+                // Periodic stats — once per ~10 s of wall-clock. Includes ring depth so we can
+                // see whether the consumer is keeping up.
+                long now = System.nanoTime();
+                if (now - statsLastNs > 10_000_000_000L) {
+                    long prod = producedFrames.get();
+                    long cons = consumedFrames.get();
+                    long drop = droppedFrames.get();
+                    double elapsedS = (now - statsLastNs) / 1e9;
+                    int depth;
+                    synchronized (frameLock) { depth = ringCount; }
+                    VideoPlayerMod.LOG.info(
+                        "[{}] decoder stats: produced={} ({} fps), consumed={} ({} fps), dropped={} (+{}) over {}s, ring={}/{}",
+                        VideoPlayerMod.MOD_ID,
+                        prod, String.format("%.1f", (prod - lastProd) / elapsedS),
+                        cons, String.format("%.1f", (cons - lastCons) / elapsedS),
+                        drop, (drop - lastDrop),
+                        String.format("%.1f", elapsedS),
+                        depth, FRAME_RING_SLOTS);
+                    statsLastNs = now;
+                    lastProd = prod; lastCons = cons; lastDrop = drop;
                 }
 
                 // If we have an open audio line, SourceDataLine.write() blocks for backpressure
@@ -308,10 +430,17 @@ public class JavaCvBackend implements VideoBackend {
         try {
             AudioFormat fmt = new AudioFormat(sampleRate, 16, channels, true, false); // signed 16-bit LE
             SourceDataLine line = AudioSystem.getSourceDataLine(fmt);
-            // ~0.5 s of audio buffered in the driver. Smooths over upstream hiccups without
-            // delaying close() — stopWorker() calls line.stop() / line.flush() to dump it.
+            // ~0.1 s of audio buffered in the driver. 0.4.10 used 0.5 s, which let the decoder
+            // burst ~12 video frames between backpressure stalls — way past the video ring's
+            // capacity and the visible cause of the "2-5 fps" stutter the user saw. With 0.1 s
+            // the audio line refills more often, so the decoder is paced more tightly and
+            // bursts collapse to 2-3 frames (well inside FRAME_RING_SLOTS).
+            //
+            // Floor at frameSizeBytes * 256 keeps the buffer above the typical OS / driver
+            // minimum so we don't get UnsupportedOperationException at line.open() on
+            // exotic sample rates.
             int frameSizeBytes = 2 * channels;
-            int bufferBytes    = Math.max(sampleRate * frameSizeBytes / 2, frameSizeBytes * 1024);
+            int bufferBytes    = Math.max(sampleRate * frameSizeBytes / 10, frameSizeBytes * 256);
             line.open(fmt, bufferBytes);
             line.start();
             return line;

src/main/java/com/ejclaw/videoplayer/client/playback/VideoCache.java

@@ -41,8 +41,49 @@ public final class VideoCache {
     /** urls whose download is currently in flight. */
     private static final Set<String> IN_FLIGHT = ConcurrentHashMap.newKeySet();
 
-    /** Hard ceiling on a single preload — 512 MB. Keeps an accidental giant URL from filling disk. */
-    private static final long MAX_BYTES = 512L * 1024 * 1024;
+    /**
+     * Hard ceiling on a single preload, in bytes. Default 1 GB so a fresh client without a
+     * policy packet (e.g. integrated server, dev test) still has a sensible cap. Overridden by
+     * {@link com.ejclaw.videoplayer.net.CachePolicyPayload} on join.
+     */
+    private static volatile long MAX_BYTES = 1024L * 1024 * 1024;
+
+    /** Server-driven override of the per-video cap. */
+    public static void setMaxBytes(long bytes) {
+        if (bytes < 16L * 1024 * 1024)   bytes = 16L * 1024 * 1024;
+        if (bytes > 16L * 1024 * 1024 * 1024) bytes = 16L * 1024 * 1024 * 1024;
+        MAX_BYTES = bytes;
+        VideoPlayerMod.LOG.info("[{}] preload cap set to {} MB",
+            VideoPlayerMod.MOD_ID, bytes / (1024 * 1024));
+    }
+
+    /** Server-driven delete of a cached URL. Removes from READY and from disk. */
+    public static void purge(String url) {
+        if (url == null || url.isEmpty()) return;
+        Path p = READY.remove(url);
+        if (p == null) {
+            // Not in this session's index, but the file may still be on disk from a prior run.
+            // Reconstruct the path by hash + extension and try to delete it.
+            try {
+                Path dir = cacheDir();
+                if (dir != null) {
+                    Path guess = dir.resolve(sha256(url) + extensionFromUrl(url));
+                    if (Files.exists(guess)) p = guess;
+                }
+            } catch (Throwable ignored) {}
+        }
+        if (p != null) {
+            try {
+                boolean gone = Files.deleteIfExists(p);
+                VideoPlayerMod.LOG.info("[{}] purge: {} -> deleted={} ({})",
+                    VideoPlayerMod.MOD_ID, url, gone, p.getFileName());
+                if (gone) notifyChat("[videocache] 캐시 삭제: " + url, ChatFormatting.YELLOW);
+            } catch (Throwable t) {
+                VideoPlayerMod.LOG.warn("[{}] purge failed for {}: {}",
+                    VideoPlayerMod.MOD_ID, url, t.toString());
+            }
+        }
+    }
 
     /** Kick off a background download. No-op if already cached or in flight. */
     public static void preload(String url) {
@@ -133,11 +174,12 @@ public final class VideoCache {
                 while ((n = in.read(buf)) >= 0) {
                     total += n;
                     if (total > MAX_BYTES) {
+                        long capMb = MAX_BYTES / (1024 * 1024);
                         VideoPlayerMod.LOG.warn(
                             "[{}] preload: {} exceeded {} MB cap; aborting",
-                            VideoPlayerMod.MOD_ID, url, MAX_BYTES / (1024 * 1024));
+                            VideoPlayerMod.MOD_ID, url, capMb);
                         try { Files.deleteIfExists(partPath); } catch (Throwable ignored) {}
-                        notifyChat("[videopreload] 실패 (512MB 초과): " + url, ChatFormatting.RED);
+                        notifyChat("[videopreload] 실패 (" + capMb + "MB 초과): " + url, ChatFormatting.RED);
                         return;
                     }
                     out.write(buf, 0, n);

src/main/java/com/ejclaw/videoplayer/client/render/VideoAnchorRenderer.java

@@ -1,6 +1,7 @@
 package com.ejclaw.videoplayer.client.render;
 
 import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
+import com.ejclaw.videoplayer.client.ClientPolicy;
 import com.ejclaw.videoplayer.client.playback.VideoPlayback;
 import com.mojang.blaze3d.vertex.PoseStack;
 import com.mojang.math.Axis;
@@ -76,16 +77,14 @@ public class VideoAnchorRenderer implements BlockEntityRenderer<VideoAnchorBlock
         final Matrix4f mat = new Matrix4f(pose.last().pose());
         RenderType rt = RenderTypes.entityCutout(tex);
         collector.submitCustomGeometry(pose, rt, (poseUnused, vc) -> {
-            // Front face (visible from outside, looking back at the wall)
+            // Single-sided: the back of the anchor is by design pressed against the wall the
+            // player clicked, so a back face is pure GPU waste. Halves the fragment shader work
+            // per anchor and removes the mirrored-texture artifact a player would see if they
+            // somehow clipped behind the wall.
             emit(vc, mat, 0F, 0F, 0F, 0F, 1F, light);
             emit(vc, mat, w,  0F, 0F, 1F, 1F, light);
             emit(vc, mat, w,  h,  0F, 1F, 0F, light);
             emit(vc, mat, 0F, h,  0F, 0F, 0F, light);
-            // Back face (in case the player ends up on the other side, e.g. clipping into the wall)
-            emit(vc, mat, 0F, h,  0F, 0F, 0F, light);
-            emit(vc, mat, w,  h,  0F, 1F, 0F, light);
-            emit(vc, mat, w,  0F, 0F, 1F, 1F, light);
-            emit(vc, mat, 0F, 0F, 0F, 0F, 1F, light);
         });
 
         pose.popPose();
@@ -126,7 +125,9 @@ public class VideoAnchorRenderer implements BlockEntityRenderer<VideoAnchorBlock
 
     @Override
     public int getViewDistance() {
-        return 128;
+        // Driven by server config (video_player.json:render_distance_blocks), pushed to clients
+        // on join. Default 128 = legacy behavior, so an unpaired client behaves identically.
+        return ClientPolicy.renderDistanceBlocks();
     }
 
     /** Per-frame render data extracted from the BE. */

src/main/java/com/ejclaw/videoplayer/command/VideoCacheCommand.java

@@ -0,0 +1,147 @@
+package com.ejclaw.videoplayer.command;
+
+import com.ejclaw.videoplayer.VideoPlayerConfig;
+import com.ejclaw.videoplayer.net.DeleteCachePayload;
+import com.ejclaw.videoplayer.net.PreloadPayload;
+import com.mojang.brigadier.CommandDispatcher;
+import com.mojang.brigadier.arguments.StringArgumentType;
+import com.mojang.brigadier.builder.LiteralArgumentBuilder;
+import com.mojang.brigadier.context.CommandContext;
+import com.mojang.brigadier.exceptions.CommandSyntaxException;
+import net.fabricmc.fabric.api.networking.v1.PlayerLookup;
+import net.fabricmc.fabric.api.networking.v1.ServerPlayNetworking;
+import net.minecraft.ChatFormatting;
+import net.minecraft.commands.CommandSourceStack;
+import net.minecraft.commands.Commands;
+import net.minecraft.network.chat.ClickEvent;
+import net.minecraft.network.chat.Component;
+import net.minecraft.network.chat.MutableComponent;
+import net.minecraft.network.chat.Style;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.server.permissions.Permissions;
+
+import java.net.URI;
+import java.util.Map;
+
+/**
+ * {@code /videocache add <name> <url>} — name a URL, store it in server config, and broadcast a
+ * preload request to every client.
+ * <br>{@code /videocache list} — print the named index with clickable URLs.
+ * <br>{@code /videocache remove <name>} — drop the entry from server config and tell every client
+ * to delete the matching cache file.
+ *
+ * <p>Replaces the old {@code /videopreload}. Same permission gate
+ * ({@link Permissions#COMMANDS_GAMEMASTER}) so command blocks can drive it.
+ */
+public final class VideoCacheCommand {
+    private VideoCacheCommand() {}
+
+    public static void register(CommandDispatcher<CommandSourceStack> dispatcher) {
+        dispatcher.register(build("videoCache"));
+    }
+
+    private static LiteralArgumentBuilder<CommandSourceStack> build(String root) {
+        return Commands.literal(root)
+            .requires(s -> s.permissions().hasPermission(Permissions.COMMANDS_GAMEMASTER))
+            .then(Commands.literal("add")
+                .then(Commands.argument("name", StringArgumentType.word())
+                    .then(Commands.argument("url", StringArgumentType.greedyString())
+                        .executes(VideoCacheCommand::runAdd))))
+            .then(Commands.literal("list")
+                .executes(VideoCacheCommand::runList))
+            .then(Commands.literal("remove")
+                .then(Commands.argument("name", StringArgumentType.word())
+                    .executes(VideoCacheCommand::runRemove)));
+    }
+
+    private static int runAdd(CommandContext<CommandSourceStack> ctx) throws CommandSyntaxException {
+        CommandSourceStack src = ctx.getSource();
+        String name = StringArgumentType.getString(ctx, "name").trim();
+        String url  = StringArgumentType.getString(ctx, "url").trim();
+
+        if (name.isEmpty() || name.length() > 64) {
+            src.sendFailure(Component.literal("이름은 1~64자여야 합니다"));
+            return 0;
+        }
+        if (url.isEmpty() || !(url.startsWith("http://") || url.startsWith("https://"))) {
+            src.sendFailure(Component.literal("url 은 http:// 또는 https:// 로 시작해야 합니다"));
+            return 0;
+        }
+        if (url.length() > 256) {
+            src.sendFailure(Component.literal("url 이 너무 깁니다 (최대 256자)"));
+            return 0;
+        }
+        if (VideoPlayerConfig.cacheUrl(name) != null) {
+            src.sendFailure(Component.literal("이미 사용 중인 이름입니다: " + name));
+            return 0;
+        }
+        if (!VideoPlayerConfig.addCacheEntry(name, url)) {
+            src.sendFailure(Component.literal("저장 실패: 이름 중복 또는 IO 오류"));
+            return 0;
+        }
+
+        MinecraftServer server = src.getServer();
+        PreloadPayload payload = new PreloadPayload(url);
+        int sent = 0;
+        for (ServerPlayer p : PlayerLookup.all(server)) {
+            ServerPlayNetworking.send(p, payload);
+            sent++;
+        }
+        final int sentFinal = sent;
+        src.sendSuccess(() -> Component.literal(
+            "[videocache] 추가됨: " + name + " → " + url
+                + "  (" + sentFinal + " 클라이언트에 preload 전송)"), false);
+        return 1;
+    }
+
+    private static int runList(CommandContext<CommandSourceStack> ctx) {
+        CommandSourceStack src = ctx.getSource();
+        Map<String, String> entries = VideoPlayerConfig.cacheEntries();
+        if (entries.isEmpty()) {
+            src.sendSuccess(() -> Component.literal("[videocache] 저장된 항목이 없습니다")
+                .withStyle(ChatFormatting.GRAY), false);
+            return 0;
+        }
+        src.sendSuccess(() -> Component.literal("[videocache] 저장된 항목 " + entries.size() + "개:")
+            .withStyle(ChatFormatting.YELLOW), false);
+        for (Map.Entry<String, String> e : entries.entrySet()) {
+            String url = e.getValue();
+            ClickEvent click;
+            try {
+                click = new ClickEvent.OpenUrl(URI.create(url));
+            } catch (Throwable t) {
+                click = null; // bad URI — show without click action rather than failing the whole list
+            }
+            Style urlStyle = Style.EMPTY.withColor(ChatFormatting.AQUA).withUnderlined(true);
+            if (click != null) urlStyle = urlStyle.withClickEvent(click);
+            MutableComponent line = Component.literal(" • " + e.getKey() + " : ")
+                .withStyle(ChatFormatting.WHITE)
+                .append(Component.literal(url).withStyle(urlStyle));
+            src.sendSuccess(() -> line, false);
+        }
+        return entries.size();
+    }
+
+    private static int runRemove(CommandContext<CommandSourceStack> ctx) throws CommandSyntaxException {
+        CommandSourceStack src = ctx.getSource();
+        String name = StringArgumentType.getString(ctx, "name").trim();
+        String url = VideoPlayerConfig.removeCacheEntry(name);
+        if (url == null) {
+            src.sendFailure(Component.literal("해당 이름의 항목이 없습니다: " + name));
+            return 0;
+        }
+        MinecraftServer server = src.getServer();
+        DeleteCachePayload payload = new DeleteCachePayload(url);
+        int sent = 0;
+        for (ServerPlayer p : PlayerLookup.all(server)) {
+            ServerPlayNetworking.send(p, payload);
+            sent++;
+        }
+        final int sentFinal = sent;
+        src.sendSuccess(() -> Component.literal(
+            "[videocache] 삭제됨: " + name + " → " + url
+                + "  (" + sentFinal + " 클라이언트에 cache_delete 전송)"), false);
+        return 1;
+    }
+}

src/main/java/com/ejclaw/videoplayer/command/VideoDeleteCommand.java

@@ -19,7 +19,6 @@ public final class VideoDeleteCommand {
 
     public static void register(CommandDispatcher<CommandSourceStack> dispatcher) {
         dispatcher.register(build("videoDelete"));
-        dispatcher.register(build("videodelete"));
     }
 
     private static com.mojang.brigadier.builder.LiteralArgumentBuilder<CommandSourceStack>

src/main/java/com/ejclaw/videoplayer/command/VideoMuteCommand.java

@@ -22,7 +22,6 @@ public final class VideoMuteCommand {
 
     public static void register(CommandDispatcher<CommandSourceStack> dispatcher) {
         dispatcher.register(build("videoMute"));
-        dispatcher.register(build("videomute"));
     }
 
     private static com.mojang.brigadier.builder.LiteralArgumentBuilder<CommandSourceStack>

src/main/java/com/ejclaw/videoplayer/command/VideoPlaceCommand.java

@@ -1,5 +1,6 @@
 package com.ejclaw.videoplayer.command;
 
+import com.ejclaw.videoplayer.VideoPlayerConfig;
 import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
 import com.ejclaw.videoplayer.net.SyncAnchorPayload;
 import com.ejclaw.videoplayer.registry.VideoPlayerBlocks;
@@ -27,7 +28,6 @@ public final class VideoPlaceCommand {
 
     public static void register(CommandDispatcher<CommandSourceStack> dispatcher) {
         dispatcher.register(build("videoPlace"));
-        dispatcher.register(build("videoplace"));
     }
 
     private static com.mojang.brigadier.builder.LiteralArgumentBuilder<CommandSourceStack>
@@ -54,9 +54,14 @@ public final class VideoPlaceCommand {
         }
         int width  = IntegerArgumentType.getInteger(ctx, "width");
         int height = IntegerArgumentType.getInteger(ctx, "height");
-        String url = StringArgumentType.getString(ctx, "url").trim();
-        if (!url.isEmpty() && !(url.startsWith("http://") || url.startsWith("https://"))) {
-            src.sendFailure(Component.literal("url must be http:// or https:// (or empty)"));
+        String raw = StringArgumentType.getString(ctx, "url").trim();
+        // Accept either an http(s) URL or a /videoCache add <name> entry: resolveUrlOrName()
+        // returns the canonical URL in both cases, or null when a non-URL string didn't match
+        // any named entry.
+        String url = VideoPlayerConfig.resolveUrlOrName(raw);
+        if (url == null) {
+            src.sendFailure(Component.literal(
+                "url 은 http(s):// 로 시작하거나 /videoCache add 로 등록된 이름이어야 합니다: " + raw));
             return 0;
         }
         if (url.length() > 256) url = url.substring(0, 256);

src/main/java/com/ejclaw/videoplayer/command/VideoPreloadCommand.java

@@ -1,74 +0,0 @@
-package com.ejclaw.videoplayer.command;
-
-import com.ejclaw.videoplayer.net.PreloadPayload;
-import com.mojang.brigadier.CommandDispatcher;
-import com.mojang.brigadier.arguments.StringArgumentType;
-import com.mojang.brigadier.exceptions.CommandSyntaxException;
-import net.fabricmc.fabric.api.networking.v1.PlayerLookup;
-import net.fabricmc.fabric.api.networking.v1.ServerPlayNetworking;
-import net.minecraft.commands.CommandSourceStack;
-import net.minecraft.commands.Commands;
-import net.minecraft.network.chat.Component;
-import net.minecraft.server.MinecraftServer;
-import net.minecraft.server.level.ServerPlayer;
-import net.minecraft.server.permissions.Permissions;
-
-/**
- * {@code /videoPreload <url>} — broadcast a preload request to every connected client so each
- * client fully downloads the URL into its local {@code video_player_cache/} folder. Subsequent
- * {@code /videoPlace} calls (or right-click placements) that use the same URL will then play
- * from the local file, eliminating mid-stream stutter.
- *
- * <p>Uses the same {@link Permissions#COMMANDS_GAMEMASTER} gate as {@code /videoPlace} et al.,
- * so command blocks (which run at op level 2 by default) can invoke it.
- */
-public final class VideoPreloadCommand {
-    private VideoPreloadCommand() {}
-
-    public static void register(CommandDispatcher<CommandSourceStack> dispatcher) {
-        dispatcher.register(build("videoPreload"));
-        dispatcher.register(build("videopreload"));
-    }
-
-    private static com.mojang.brigadier.builder.LiteralArgumentBuilder<CommandSourceStack>
-    build(String name) {
-        return Commands.literal(name)
-            .requires(s -> s.permissions().hasPermission(Permissions.COMMANDS_GAMEMASTER))
-            .then(Commands.argument("url", StringArgumentType.greedyString())
-                .executes(VideoPreloadCommand::run));
-    }
-
-    private static int run(com.mojang.brigadier.context.CommandContext<CommandSourceStack> ctx)
-            throws CommandSyntaxException {
-        CommandSourceStack src = ctx.getSource();
-        String url = StringArgumentType.getString(ctx, "url").trim();
-        if (url.isEmpty()) {
-            src.sendFailure(Component.literal("url is required"));
-            return 0;
-        }
-        if (!(url.startsWith("http://") || url.startsWith("https://"))) {
-            src.sendFailure(Component.literal("url must be http:// or https://"));
-            return 0;
-        }
-        if (url.length() > 256) {
-            src.sendFailure(Component.literal("url too long (max 256)"));
-            return 0;
-        }
-
-        MinecraftServer server = src.getServer();
-        PreloadPayload payload = new PreloadPayload(url);
-        int sent = 0;
-        for (ServerPlayer p : PlayerLookup.all(server)) {
-            ServerPlayNetworking.send(p, payload);
-            sent++;
-        }
-        final int sentFinal = sent;
-        // Use sendSuccess(..., false) so the chat noise is local-only and command blocks don't
-        // spam every operator on each tick. Be explicit that this is fire-and-forget: each
-        // client posts its own "[videopreload] 완료" chat line when the download finishes.
-        src.sendSuccess(() -> Component.literal(
-            "preload 요청을 " + sentFinal + " 클라이언트에 전송: " + payload.url()
-                + " (완료 알림 후 재생하세요)"), false);
-        return sent;
-    }
-}

src/main/java/com/ejclaw/videoplayer/command/VideoStickCommand.java

@@ -14,9 +14,6 @@ public final class VideoStickCommand {
     public static void register(CommandDispatcher<CommandSourceStack> dispatcher) {
         dispatcher.register(Commands.literal("videoStick")
             .executes(ctx -> run(ctx.getSource())));
-        // Lowercase alias — Brigadier is case-sensitive.
-        dispatcher.register(Commands.literal("videostick")
-            .executes(ctx -> run(ctx.getSource())));
     }
 
     private static int run(CommandSourceStack source) {

src/main/java/com/ejclaw/videoplayer/net/CachePolicyPayload.java

@@ -0,0 +1,29 @@
+package com.ejclaw.videoplayer.net;
+
+import com.ejclaw.videoplayer.VideoPlayerMod;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.minecraft.resources.Identifier;
+
+/**
+ * S2C — broadcasts the server-configured client-side policy bundle on join, before any
+ * {@link PreloadPayload}. Currently carries: {@code maxBytes} (per-video download cap) and
+ * {@code renderDistanceBlocks} (anchor BE view-distance cap).
+ */
+public record CachePolicyPayload(long maxBytes, int renderDistanceBlocks) implements CustomPacketPayload {
+    public static final CustomPacketPayload.Type<CachePolicyPayload> TYPE =
+        new CustomPacketPayload.Type<>(Identifier.fromNamespaceAndPath(VideoPlayerMod.MOD_ID, "cache_policy"));
+
+    public static final StreamCodec<RegistryFriendlyByteBuf, CachePolicyPayload> CODEC = StreamCodec.composite(
+        ByteBufCodecs.VAR_LONG, CachePolicyPayload::maxBytes,
+        ByteBufCodecs.VAR_INT,  CachePolicyPayload::renderDistanceBlocks,
+        CachePolicyPayload::new
+    );
+
+    @Override
+    public Type<? extends CustomPacketPayload> type() {
+        return TYPE;
+    }
+}

src/main/java/com/ejclaw/videoplayer/net/DeleteCachePayload.java

@@ -0,0 +1,28 @@
+package com.ejclaw.videoplayer.net;
+
+import com.ejclaw.videoplayer.VideoPlayerMod;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.minecraft.resources.Identifier;
+
+/**
+ * S2C — tell connected clients to drop a previously preloaded URL from their on-disk cache.
+ * Sent by {@code /videocache remove <name>}. Each client deletes the matching cache file and
+ * drops it from {@code VideoCache.READY}.
+ */
+public record DeleteCachePayload(String url) implements CustomPacketPayload {
+    public static final CustomPacketPayload.Type<DeleteCachePayload> TYPE =
+        new CustomPacketPayload.Type<>(Identifier.fromNamespaceAndPath(VideoPlayerMod.MOD_ID, "cache_delete"));
+
+    public static final StreamCodec<RegistryFriendlyByteBuf, DeleteCachePayload> CODEC = StreamCodec.composite(
+        ByteBufCodecs.STRING_UTF8, DeleteCachePayload::url,
+        DeleteCachePayload::new
+    );
+
+    @Override
+    public Type<? extends CustomPacketPayload> type() {
+        return TYPE;
+    }
+}

src/main/java/com/ejclaw/videoplayer/net/VideoPlayerNetwork.java

@@ -1,5 +1,6 @@
 package com.ejclaw.videoplayer.net;
 
+import com.ejclaw.videoplayer.VideoPlayerConfig;
 import com.ejclaw.videoplayer.VideoPlayerMod;
 import com.ejclaw.videoplayer.block.VideoAnchorBlockEntity;
 import net.fabricmc.fabric.api.networking.v1.PayloadTypeRegistry;
@@ -25,6 +26,8 @@ public final class VideoPlayerNetwork {
         PayloadTypeRegistry.clientboundPlay().register(OpenScreenPayload.TYPE, OpenScreenPayload.CODEC);
         PayloadTypeRegistry.clientboundPlay().register(SyncAnchorPayload.TYPE, SyncAnchorPayload.CODEC);
         PayloadTypeRegistry.clientboundPlay().register(PreloadPayload.TYPE, PreloadPayload.CODEC);
+        PayloadTypeRegistry.clientboundPlay().register(CachePolicyPayload.TYPE, CachePolicyPayload.CODEC);
+        PayloadTypeRegistry.clientboundPlay().register(DeleteCachePayload.TYPE, DeleteCachePayload.CODEC);
         // C2S
         PayloadTypeRegistry.serverboundPlay().register(SaveConfigPayload.TYPE, SaveConfigPayload.CODEC);
         PayloadTypeRegistry.serverboundPlay().register(DeleteAnchorPayload.TYPE, DeleteAnchorPayload.CODEC);
@@ -95,13 +98,13 @@ public final class VideoPlayerNetwork {
 
     private static String trimUrl(String s) {
         if (s == null) return "";
-        String t = s.trim();
-        if (t.length() > 256) t = t.substring(0, 256);
-        // SPEC §4.4: only https?:// or empty
-        if (!t.isEmpty() && !(t.startsWith("http://") || t.startsWith("https://"))) {
-            return "";
-        }
-        return t;
+        // GUI / C2S accepts either an http(s) URL or a /videoCache add <name>. Names resolve
+        // to their stored URL; URLs pass through verbatim. Anything else collapses to empty
+        // (SPEC §4.4: anchors with non-URL urls are no-ops).
+        String resolved = VideoPlayerConfig.resolveUrlOrName(s);
+        if (resolved == null) return "";
+        if (resolved.length() > 256) resolved = resolved.substring(0, 256);
+        return resolved;
     }
 
     private static int clamp(int v, int lo, int hi) {