diff --git a/packages/middleware/express/tsdown.config.ts b/packages/middleware/express/tsdown.config.ts
index 64ed143a86..c67ee585cd 100644
--- a/packages/middleware/express/tsdown.config.ts
+++ b/packages/middleware/express/tsdown.config.ts
@@ -12,11 +12,11 @@ export default defineConfig({
     shims: true,
     dts: {
         resolver: 'tsc',
+        // Keep workspace deps as external imports in the bundled .d.ts instead of
+        // inlining their type graph — see ../node/tsdown.config.ts for the rationale.
         compilerOptions: {
-            baseUrl: '.',
-            paths: {
-                '@modelcontextprotocol/server': ['../server/src/index.ts']
-            }
+            paths: {},
+            preserveSymlinks: true
         }
     }
 });
diff --git a/packages/middleware/fastify/tsdown.config.ts b/packages/middleware/fastify/tsdown.config.ts
index 64ed143a86..c67ee585cd 100644
--- a/packages/middleware/fastify/tsdown.config.ts
+++ b/packages/middleware/fastify/tsdown.config.ts
@@ -12,11 +12,11 @@ export default defineConfig({
     shims: true,
     dts: {
         resolver: 'tsc',
+        // Keep workspace deps as external imports in the bundled .d.ts instead of
+        // inlining their type graph — see ../node/tsdown.config.ts for the rationale.
         compilerOptions: {
-            baseUrl: '.',
-            paths: {
-                '@modelcontextprotocol/server': ['../server/src/index.ts']
-            }
+            paths: {},
+            preserveSymlinks: true
         }
     }
 });
diff --git a/packages/middleware/hono/tsdown.config.ts b/packages/middleware/hono/tsdown.config.ts
index 64ed143a86..c67ee585cd 100644
--- a/packages/middleware/hono/tsdown.config.ts
+++ b/packages/middleware/hono/tsdown.config.ts
@@ -12,11 +12,11 @@ export default defineConfig({
     shims: true,
     dts: {
         resolver: 'tsc',
+        // Keep workspace deps as external imports in the bundled .d.ts instead of
+        // inlining their type graph — see ../node/tsdown.config.ts for the rationale.
         compilerOptions: {
-            baseUrl: '.',
-            paths: {
-                '@modelcontextprotocol/server': ['../server/src/index.ts']
-            }
+            paths: {},
+            preserveSymlinks: true
         }
     }
 });
diff --git a/packages/middleware/node/src/streamableHttp.ts b/packages/middleware/node/src/streamableHttp.ts
index 68a0c224f0..c101fcd0af 100644
--- a/packages/middleware/node/src/streamableHttp.ts
+++ b/packages/middleware/node/src/streamableHttp.ts
@@ -10,8 +10,14 @@
 import type { IncomingMessage, ServerResponse } from 'node:http';
 
 import { getRequestListener } from '@hono/node-server';
-import type { AuthInfo, JSONRPCMessage, MessageExtraInfo, RequestId, Transport } from '@modelcontextprotocol/core';
-import type { WebStandardStreamableHTTPServerTransportOptions } from '@modelcontextprotocol/server';
+import type {
+    AuthInfo,
+    JSONRPCMessage,
+    MessageExtraInfo,
+    RequestId,
+    Transport,
+    WebStandardStreamableHTTPServerTransportOptions
+} from '@modelcontextprotocol/server';
 import { WebStandardStreamableHTTPServerTransport } from '@modelcontextprotocol/server';
 
 /**
diff --git a/packages/middleware/node/tsdown.config.ts b/packages/middleware/node/tsdown.config.ts
index 7d90f6517f..f953bc65de 100644
--- a/packages/middleware/node/tsdown.config.ts
+++ b/packages/middleware/node/tsdown.config.ts
@@ -21,12 +21,23 @@ export default defineConfig({
     //    Bundles d.ts files into a single output
     dts: {
         resolver: 'tsc',
-        // override just for DTS generation:
+        // The dev tsconfig.json maps @modelcontextprotocol/* to workspace source via
+        // `paths` so typecheck/IDE work without a prior build. For declaration emit we
+        // need the opposite: resolve workspace deps through node_modules and keep them
+        // as *external* imports in the bundled .d.ts (server is a peerDependency, so
+        // consumers already have its types). `paths: {}` disables the dev source
+        // mappings; `preserveSymlinks` keeps `node_modules` in the resolved path so
+        // rolldown-plugin-dts recognises the dep as external instead of inlining the
+        // whole upstream type graph (which OOMs once core's surface gets large enough).
+        //
+        // TODO: drop this override once tsdown pulls rolldown-plugin-dts >=0.21.0
+        // (sxzz/rolldown-plugin-dts@03998d41 honours rolldown `external` before the
+        // node_modules path test). Bumping also requires reworking the `dts.resolve`
+        // usage in packages/{server,client}/tsdown.config.ts — that option was removed
+        // in the same release.
         compilerOptions: {
-            baseUrl: '.',
-            paths: {
-                '@modelcontextprotocol/core': ['../core/src/index.ts']
-            }
+            paths: {},
+            preserveSymlinks: true
         }
     }
 });