diff --git a/scripts/layering/check.ts b/scripts/layering/check.ts
index 0adacb1bf..f2682152c 100644
--- a/scripts/layering/check.ts
+++ b/scripts/layering/check.ts
@@ -89,6 +89,14 @@ function isDaemonServer(rel: string): boolean {
   return rel.startsWith('src/daemon/') && !rel.startsWith('src/daemon/client/');
 }
 
+// sdk/ are the package's PUBLIC re-export barrels (§5.5 "sdk = re-export barrels
+// only"). They legitimately re-export platform symbols as part of the public API,
+// and are OFF the CLI cold path (not imported by bin.ts/cli), so exempting them
+// from R3 does not regress cold-start — they sit above the internal DAG R3 governs.
+function isSdkBarrel(rel: string): boolean {
+  return rel.startsWith('src/sdk/');
+}
+
 // ── Import extraction ───────────────────────────────────────────────────────
 
 function scanDynamicImports(line: string, lineNo: number): ImportEdge[] {
@@ -180,7 +188,7 @@ function ruleCommandsFloor(ctx: EdgeContext): Violation | null {
 // daemon server; everywhere else use a dynamic import() or a type-only import.
 function rulePlatformsSeam(ctx: EdgeContext): Violation | null {
   if (ctx.toTop !== 'platforms' || ctx.imp.dynamic || ctx.imp.typeOnly) return null;
-  if (isCoreInteractor(ctx.file) || isDaemonServer(ctx.file)) return null;
+  if (isCoreInteractor(ctx.file) || isDaemonServer(ctx.file) || isSdkBarrel(ctx.file)) return null;
   return {
     rule: 'R3 platforms-seam',
     file: ctx.file,