diff --git a/AGENTS.md b/AGENTS.md
index 13983ff9..b96bcff2 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -266,9 +266,14 @@ v2/main/
 │                                       #   silently drove the previous fixture — reported not as
 │                                       #   staleness but as a product failure in whatever the
 │                                       #   smoke was checking. Unconditional emit is still not a
-│                                       #   clean: a DELETED src file leaves its stale `.js`
-│                                       #   behind, so `rm -rf test-servers/build` after one —
-│                                       #   #2111;
+│                                       #   clean, and that is the one hole it does NOT close: a
+│                                       #   DELETED src file leaves its stale `.js` behind, the
+│                                       #   existence checks pass against it, and anything still
+│                                       #   importing that module SILENTLY runs the old code — the
+│                                       #   same failure class. So `rm -rf test-servers/build`
+│                                       #   after deleting or renaming a source file; the
+│                                       #   `.tsbuildinfo` is pinned inside `build/` so that
+│                                       #   clean actually invalidates the cache — #2111;
 │                                       #   resolve-node-bin.mjs resolves a
 │                                       #   package's bin through its own package.json, so the
 │                                       #   verify/smoke scripts spawn it with `process.execPath`
diff --git a/scripts/lib/ensure-test-servers.mjs b/scripts/lib/ensure-test-servers.mjs
index a273c7e8..d2bec471 100644
--- a/scripts/lib/ensure-test-servers.mjs
+++ b/scripts/lib/ensure-test-servers.mjs
@@ -21,14 +21,17 @@
  * smokes that take tens of seconds and a `pack:verify` that does a real
  * `npm install` from the registry.
  *
- * ⚠️ Unconditional emit is not a clean: `--noCheck` emit leaves the stale `.js`
- * of a *deleted* `src` file behind, and no path here removes it. That is
- * unchanged from before (the old early-return only skipped the build; it never
- * cleaned either), and it is a loud failure rather than a silent one — an
- * import of a removed module fails at the consumer. Fixing it properly means
- * `tsc -b` with `composite`, which forces `declaration` on and drops
- * `--noCheck`; not worth it for this. `rm -rf test-servers/build` if you have
- * deleted a source file.
+ * ⚠️ Unconditional emit is not a clean, and this is the one hole it does NOT
+ * close. `--noCheck` emit leaves the stale `.js` of a *deleted* `src` file
+ * behind, and no path here removes it — the post-build existence checks pass
+ * against that stale file, so if anything still imports the deleted module it
+ * silently keeps running the old code. That is the same failure class as the
+ * one this helper fixes, so do not read the unconditional build as covering it.
+ * (It is unchanged from before: the old early return only skipped the build, it
+ * never cleaned either.) Fixing it properly means `tsc -b` with `composite`,
+ * which forces `declaration` on and drops `--noCheck`; not worth it for this.
+ * **`rm -rf test-servers/build` after deleting or renaming a source file** —
+ * the `.tsbuildinfo` lives inside `build/` precisely so that clean is real.
  *
  * The root-installed tsc is run via this Node — `npx` is a `.cmd` shim on
  * Windows that a shell-free spawnSync can't start (ENOENT — #1939). That is