diff --git a/config/unidesk-cli.yaml b/config/unidesk-cli.yaml
index 8b3aefe0..5393e50e 100644
--- a/config/unidesk-cli.yaml
+++ b/config/unidesk-cli.yaml
@@ -193,8 +193,9 @@ gc:
             enabled: false
             reason: NC01 主机 Docker 承载主服务运行面，通用远端 GC 不得截断活跃服务日志。
           buildCachePrune:
-            enabled: false
-            reason: NC01 不是通用构建主机，通用远端 GC 不得清理其活跃 Docker 状态。
+            enabled: true
+            until: 24h
+            reason: 仅回收超过 YAML 年龄阈值且 Docker 判定可回收的 BuildKit cache；不清理 images、containers 或 volumes。
         memoryPressure:
           planPreviewLimit: 6
           processPatterns:
diff --git a/docs/reference/gc.md b/docs/reference/gc.md
index 801286b4..27a533f2 100644
--- a/docs/reference/gc.md
+++ b/docs/reference/gc.md
@@ -137,7 +137,7 @@ Worktree 清理由 `--include-merged-worktrees` 显式启用，只扫描 `config
 
 - systemd journal vacuum 到目标上限。
 - Docker `json-file` 日志截断。
-- Docker BuildKit cache prune，默认只清理超过 `--build-cache-until` 的 cache。
+- Docker BuildKit cache prune 只清理 owning YAML `hostDockerGc.buildCachePrune.until` 声明年龄之外的 cache；显式 `--build-cache-until` 可覆盖本次计划，不清理 images、containers 或 volumes。
 - apt archive clean。
 - allowlisted `/tmp` 诊断目录删除。
 - 受限 core dump 删除。
diff --git a/scripts/src/gc-remote-runner.py b/scripts/src/gc-remote-runner.py
index eaf12c45..297e1bc0 100644
--- a/scripts/src/gc-remote-runner.py
+++ b/scripts/src/gc-remote-runner.py
@@ -1192,7 +1192,7 @@ def collect_candidates(observed_at):
         if system_df["exitCode"] == 0:
             cache = parse_docker_build_cache(system_df["stdout"])
             if cache is not None and cache["reclaimableBytes"] > 0:
-                until = str(OPTIONS.get("buildCacheUntil") or "24h")
+                until = str(OPTIONS.get("buildCacheUntil") or host_docker_gc_section("buildCachePrune").get("until") or "24h")
                 candidates.append({
                     "id": "docker-builder:prune",
                     "kind": "docker-build-cache-prune",
@@ -1588,7 +1588,7 @@ def execute(candidate):
     if kind == "docker-build-cache-prune":
         if not host_docker_gc_enabled("buildCachePrune"):
             raise RuntimeError(host_docker_gc_reason("buildCachePrune", "refusing Docker builder prune on this provider"))
-        until = str(OPTIONS.get("buildCacheUntil") or "24h")
+        until = str(OPTIONS.get("buildCacheUntil") or host_docker_gc_section("buildCachePrune").get("until") or "24h")
         result = command(["docker", "builder", "prune", "--all", "--force", "--filter", "until=%s" % until], 45)
         if result["exitCode"] != 0:
             raise RuntimeError((result["stderr"] or "docker builder prune failed").strip())
diff --git a/scripts/src/gc-remote.ts b/scripts/src/gc-remote.ts
index 3390a16f..b9b52586 100644
--- a/scripts/src/gc-remote.ts
+++ b/scripts/src/gc-remote.ts
@@ -47,7 +47,7 @@ const DEFAULT_REMOTE_OPTIONS: RemoteGcOptions = {
   dockerLogs: true,
   dockerLogMaxBytes: 50 * 1024 * 1024,
   buildCache: true,
-  buildCacheUntil: "24h",
+  buildCacheUntil: "",
   tmp: true,
   tmpMinAgeHours: 24,
   toolCaches: false,