diff --git a/.changeset/spec-dts-heap-ceiling.md b/.changeset/spec-dts-heap-ceiling.md
new file mode 100644
index 0000000000..c7318d2629
--- /dev/null
+++ b/.changeset/spec-dts-heap-ceiling.md
@@ -0,0 +1,23 @@
+---
+---
+
+chore(spec): 把 DTS 构建的堆上限从 12288 降到 8192(#4845)
+
+发布面零变化 —— 改的是 `packages/spec` 的 `build` 脚本里 DTS 那一趟的
+`--max-old-space-size`,不影响任何产物内容,故为空 changeset。
+
+`--max-old-space-size` 是**允许 V8 涨到多少的上限,不是预留**。设成 12288 时,
+V8 在逼近 12 GB 之前都不积极 GC;而 `Test Core` 跑在 16 GB 的 `ubuntu-latest`
+上,叠加堆外内存与其它进程后总量越过物理内存,**内核 OOM-killer 先于 V8 的
+OOM 处理把进程杀掉,于是没有任何 Node 侧错误输出** —— 日志里只看到
+`DTS Build start` 紧接着 ` ELIFECYCLE  Command failed.`。
+
+也就是说这个数字不是防 OOM,而是 OOM 的成因之一。
+
+实测(15 GB / 可用 13 GB 的机器,与 CI runner 同量级):DTS 构建在 8192 上限下
+**成功完成,峰值 RSS 6.29 GB**。8 GB 上限相对真实需求留约 27% 余量,同时给
+runner 剩下约 8 GB 供堆外与系统使用。
+
+一个上午内四次命中,横跨内容毫不相干的 PR(纯删除 / wire 形状迁移 / 纯文案
+patch),第四次发生在**合并队列**里并把 PR 踢了出来 —— 说明命中取决于是否真的
+跑这一趟 DTS(turbo 缓存失效时),与改动内容无关。
diff --git a/packages/spec/package.json b/packages/spec/package.json
index 282f29ed32..723220a580 100644
--- a/packages/spec/package.json
+++ b/packages/spec/package.json
@@ -182,7 +182,7 @@
     "spec-changes.json"
   ],
   "scripts": {
-    "build": "pnpm gen:schema && pnpm gen:openapi && tsup && if [ -z \"$OS_SKIP_DTS\" ]; then NODE_OPTIONS=\"--max-old-space-size=12288\" BUILD_DTS=true tsup; fi",
+    "build": "pnpm gen:schema && pnpm gen:openapi && tsup && if [ -z \"$OS_SKIP_DTS\" ]; then NODE_OPTIONS=\"--max-old-space-size=8192\" BUILD_DTS=true tsup; fi",
     "dev": "tsc --watch",
     "clean": "rm -rf dist",
     "gen:schema": "OS_EAGER_SCHEMAS=1 tsx scripts/build-schemas.ts",
diff --git a/packages/spec/tsup.config.ts b/packages/spec/tsup.config.ts
index 4173792c90..81d81143cc 100644
--- a/packages/spec/tsup.config.ts
+++ b/packages/spec/tsup.config.ts
@@ -21,7 +21,18 @@ const entries = [
   'src/shared/index.ts'
 ];
 
-// Generate DTS separately to avoid memory issues
+// Generate DTS separately to avoid memory issues.
+//
+// [#4845] The DTS pass runs under an explicit `--max-old-space-size` (see the
+// `build` script in package.json). That number is a CEILING V8 is allowed to
+// grow to, NOT a reservation — set it above what the machine can actually give
+// and V8 simply stops collecting aggressively, grows past physical memory, and
+// the kernel OOM-killer takes the process with NO diagnostic output at all
+// (`DTS Build start` followed straight by `ELIFECYCLE`). It was 12288 on a
+// 16 GB `ubuntu-latest` runner, which is that failure, not a guard against it:
+// four CI hits in one morning across PRs that shared no content — including one
+// pure-prose patch — and the fourth ejected a PR from the merge queue.
+// Keep this comfortably under the runner's physical memory.
 const isDts = process.env.BUILD_DTS === 'true';
 
 export default defineConfig({