diff --git a/.changeset/no-dangling-declaration-maps.md b/.changeset/no-dangling-declaration-maps.md
new file mode 100644
index 0000000000..94a0ed3360
--- /dev/null
+++ b/.changeset/no-dangling-declaration-maps.md
@@ -0,0 +1,18 @@
+---
+'@modelcontextprotocol/core': patch
+'@modelcontextprotocol/client': patch
+'@modelcontextprotocol/server': patch
+'@modelcontextprotocol/server-legacy': patch
+'@modelcontextprotocol/codemod': patch
+'@modelcontextprotocol/express': patch
+'@modelcontextprotocol/fastify': patch
+'@modelcontextprotocol/hono': patch
+'@modelcontextprotocol/node': patch
+---
+
+Stop shipping broken declaration source maps (`.d.mts.map`/`.d.cts.map`). The published
+packages only include `dist/`, so the declaration maps pointed at `src/` paths (and the
+private `core-internal` workspace package) that do not exist in the tarball and carried no
+embedded source content — declaration-map-aware tooling could only ever resolve them to
+"source not found". The declaration maps and their `sourceMappingURL` references are no
+longer emitted; runtime JS source maps (which embed `sourcesContent`) are unchanged.
diff --git a/common/tsdown/stripDtsSourceMappingUrl.d.mts b/common/tsdown/stripDtsSourceMappingUrl.d.mts
new file mode 100644
index 0000000000..838038f320
--- /dev/null
+++ b/common/tsdown/stripDtsSourceMappingUrl.d.mts
@@ -0,0 +1,8 @@
+import type { Rolldown } from 'tsdown';
+
+/**
+ * tsdown `inputOptions` hook that removes the trailing `//# sourceMappingURL=` comment from the
+ * emitted `.d.ts` / `.d.mts` / `.d.cts` chunks. See the implementation in
+ * `./stripDtsSourceMappingUrl.mjs` for the full rationale (#2233).
+ */
+export function stripDtsSourceMappingUrl(options: Rolldown.InputOptions): void;
diff --git a/common/tsdown/stripDtsSourceMappingUrl.mjs b/common/tsdown/stripDtsSourceMappingUrl.mjs
new file mode 100644
index 0000000000..366fd925be
--- /dev/null
+++ b/common/tsdown/stripDtsSourceMappingUrl.mjs
@@ -0,0 +1,38 @@
+// Plain .mjs (with a sibling .d.mts) so tsdown's native config loader can import it from the
+// per-package tsdown.config.ts files on every supported Node version.
+
+const RE_DTS_CHUNK = /\.d\.[cm]?ts$/;
+const RE_DTS_SOURCE_MAPPING_URL = /\n?\/\/# sourceMappingURL=\S+\s*$/;
+
+/**
+ * tsdown `inputOptions` hook that removes the trailing `//# sourceMappingURL=` comment from the
+ * emitted `.d.ts` / `.d.mts` / `.d.cts` chunks.
+ *
+ * The published packages ship only `dist/` (`"files": ["dist"]`), and tsc cannot embed
+ * `sourcesContent` into declaration maps, so shipped `.d.*ts.map` files would always point at
+ * `src/` paths that do not exist on a consumer's machine (#2233). Setting `dts.sourcemap: false`
+ * stops the maps from being emitted, but the JS-level `sourcemap: true` still makes rolldown
+ * append a sourceMappingURL comment to the declaration chunks; this hook strips that comment so
+ * the shipped declaration files do not reference maps that are not there.
+ *
+ * Registered via `inputOptions` rather than `plugins` because tsdown does not forward user
+ * plugins to the extra CJS dts pass that emits the `.d.cts` files.
+ *
+ * @param {import('tsdown').Rolldown.InputOptions} options
+ * @returns {void}
+ */
+export function stripDtsSourceMappingUrl(options) {
+    options.plugins = [
+        options.plugins,
+        {
+            name: 'strip-dts-source-mapping-url',
+            generateBundle(_outputOptions, bundle) {
+                for (const output of Object.values(bundle)) {
+                    if (output.type === 'chunk' && RE_DTS_CHUNK.test(output.fileName)) {
+                        output.code = output.code.replace(RE_DTS_SOURCE_MAPPING_URL, '\n');
+                    }
+                }
+            }
+        }
+    ];
+}
diff --git a/packages/client/tsdown.config.ts b/packages/client/tsdown.config.ts
index 45e0d7a28e..90f4b5c8bf 100644
--- a/packages/client/tsdown.config.ts
+++ b/packages/client/tsdown.config.ts
@@ -1,5 +1,7 @@
 import { defineConfig } from 'tsdown';
 
+import { stripDtsSourceMappingUrl } from '../../common/tsdown/stripDtsSourceMappingUrl.mjs';
+
 export default defineConfig({
     failOnWarn: 'ci-only',
     entry: [
@@ -20,6 +22,11 @@ export default defineConfig({
     platform: 'node',
     shims: true,
     dts: {
+        // Declaration maps would reference src/ (and, where bundled, the private
+        // core-internal's src/), which is not shipped ("files": ["dist"]); tsc cannot
+        // embed sourcesContent into .d.ts maps, so the shipped maps could never resolve
+        // on a consumer's machine. Don't emit them (#2233).
+        sourcemap: false,
         resolver: 'tsc',
         resolve: ['ajv', 'ajv-formats', 'json-schema-typed'],
         compilerOptions: {
@@ -37,5 +44,7 @@ export default defineConfig({
     // The schema modules live in @modelcontextprotocol/core (a real runtime dependency); the
     // bundled core-internal shims import them via the './internal' subpath, which must stay an
     // external import (explicit entry — the tsconfig paths alias would otherwise inline it).
-    external: ['@modelcontextprotocol/client/_shims', '@modelcontextprotocol/core/internal']
+    external: ['@modelcontextprotocol/client/_shims', '@modelcontextprotocol/core/internal'],
+    // Drop the dangling sourceMappingURL comment rolldown leaves on the (map-less) declaration output.
+    inputOptions: stripDtsSourceMappingUrl
 });
diff --git a/packages/codemod/tsdown.config.ts b/packages/codemod/tsdown.config.ts
index 44976b8256..d20cb8640f 100644
--- a/packages/codemod/tsdown.config.ts
+++ b/packages/codemod/tsdown.config.ts
@@ -1,5 +1,7 @@
 import { defineConfig } from 'tsdown';
 
+import { stripDtsSourceMappingUrl } from '../../common/tsdown/stripDtsSourceMappingUrl.mjs';
+
 export default defineConfig({
     failOnWarn: 'ci-only',
     entry: ['src/cli.ts', 'src/index.ts'],
@@ -12,6 +14,13 @@ export default defineConfig({
     platform: 'node',
     shims: true,
     dts: {
+        // Declaration maps would reference src/ (and, where bundled, the private
+        // core-internal's src/), which is not shipped ("files": ["dist"]); tsc cannot
+        // embed sourcesContent into .d.ts maps, so the shipped maps could never resolve
+        // on a consumer's machine. Don't emit them (#2233).
+        sourcemap: false,
         resolver: 'tsc'
-    }
+    },
+    // Drop the dangling sourceMappingURL comment rolldown leaves on the (map-less) declaration output.
+    inputOptions: stripDtsSourceMappingUrl
 });
diff --git a/packages/core/tsdown.config.ts b/packages/core/tsdown.config.ts
index e947feab67..bbd5e74ab2 100644
--- a/packages/core/tsdown.config.ts
+++ b/packages/core/tsdown.config.ts
@@ -1,5 +1,7 @@
 import { defineConfig } from 'tsdown';
 
+import { stripDtsSourceMappingUrl } from '../../common/tsdown/stripDtsSourceMappingUrl.mjs';
+
 // core owns the schema source modules (src/schemas.ts, src/auth.ts, src/constants.ts) and builds
 // two entries from them:
 //   - src/index.ts    → the curated public surface (spec + OAuth `*Schema` constants only)
@@ -17,6 +19,13 @@ export default defineConfig({
     target: 'esnext',
     platform: 'neutral',
     dts: {
+        // Declaration maps would reference src/ (and, where bundled, the private
+        // core-internal's src/), which is not shipped ("files": ["dist"]); tsc cannot
+        // embed sourcesContent into .d.ts maps, so the shipped maps could never resolve
+        // on a consumer's machine. Don't emit them (#2233).
+        sourcemap: false,
         resolver: 'tsc'
-    }
+    },
+    // Drop the dangling sourceMappingURL comment rolldown leaves on the (map-less) declaration output.
+    inputOptions: stripDtsSourceMappingUrl
 });
diff --git a/packages/middleware/express/tsdown.config.ts b/packages/middleware/express/tsdown.config.ts
index 5fb5f7b39b..4a8b48d584 100644
--- a/packages/middleware/express/tsdown.config.ts
+++ b/packages/middleware/express/tsdown.config.ts
@@ -1,5 +1,7 @@
 import { defineConfig } from 'tsdown';
 
+import { stripDtsSourceMappingUrl } from '../../../common/tsdown/stripDtsSourceMappingUrl.mjs';
+
 export default defineConfig({
     failOnWarn: 'ci-only',
     entry: ['src/index.ts'],
@@ -12,6 +14,11 @@ export default defineConfig({
     platform: 'node',
     shims: true,
     dts: {
+        // Declaration maps would reference src/ (and, where bundled, the private
+        // core-internal's src/), which is not shipped ("files": ["dist"]); tsc cannot
+        // embed sourcesContent into .d.ts maps, so the shipped maps could never resolve
+        // on a consumer's machine. Don't emit them (#2233).
+        sourcemap: false,
         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.
@@ -19,5 +26,7 @@ export default defineConfig({
             paths: {},
             preserveSymlinks: true
         }
-    }
+    },
+    // Drop the dangling sourceMappingURL comment rolldown leaves on the (map-less) declaration output.
+    inputOptions: stripDtsSourceMappingUrl
 });
diff --git a/packages/middleware/fastify/tsdown.config.ts b/packages/middleware/fastify/tsdown.config.ts
index 5fb5f7b39b..4a8b48d584 100644
--- a/packages/middleware/fastify/tsdown.config.ts
+++ b/packages/middleware/fastify/tsdown.config.ts
@@ -1,5 +1,7 @@
 import { defineConfig } from 'tsdown';
 
+import { stripDtsSourceMappingUrl } from '../../../common/tsdown/stripDtsSourceMappingUrl.mjs';
+
 export default defineConfig({
     failOnWarn: 'ci-only',
     entry: ['src/index.ts'],
@@ -12,6 +14,11 @@ export default defineConfig({
     platform: 'node',
     shims: true,
     dts: {
+        // Declaration maps would reference src/ (and, where bundled, the private
+        // core-internal's src/), which is not shipped ("files": ["dist"]); tsc cannot
+        // embed sourcesContent into .d.ts maps, so the shipped maps could never resolve
+        // on a consumer's machine. Don't emit them (#2233).
+        sourcemap: false,
         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.
@@ -19,5 +26,7 @@ export default defineConfig({
             paths: {},
             preserveSymlinks: true
         }
-    }
+    },
+    // Drop the dangling sourceMappingURL comment rolldown leaves on the (map-less) declaration output.
+    inputOptions: stripDtsSourceMappingUrl
 });
diff --git a/packages/middleware/hono/tsdown.config.ts b/packages/middleware/hono/tsdown.config.ts
index 5fb5f7b39b..4a8b48d584 100644
--- a/packages/middleware/hono/tsdown.config.ts
+++ b/packages/middleware/hono/tsdown.config.ts
@@ -1,5 +1,7 @@
 import { defineConfig } from 'tsdown';
 
+import { stripDtsSourceMappingUrl } from '../../../common/tsdown/stripDtsSourceMappingUrl.mjs';
+
 export default defineConfig({
     failOnWarn: 'ci-only',
     entry: ['src/index.ts'],
@@ -12,6 +14,11 @@ export default defineConfig({
     platform: 'node',
     shims: true,
     dts: {
+        // Declaration maps would reference src/ (and, where bundled, the private
+        // core-internal's src/), which is not shipped ("files": ["dist"]); tsc cannot
+        // embed sourcesContent into .d.ts maps, so the shipped maps could never resolve
+        // on a consumer's machine. Don't emit them (#2233).
+        sourcemap: false,
         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.
@@ -19,5 +26,7 @@ export default defineConfig({
             paths: {},
             preserveSymlinks: true
         }
-    }
+    },
+    // Drop the dangling sourceMappingURL comment rolldown leaves on the (map-less) declaration output.
+    inputOptions: stripDtsSourceMappingUrl
 });
diff --git a/packages/middleware/node/tsdown.config.ts b/packages/middleware/node/tsdown.config.ts
index 2af784601f..8f68afe55d 100644
--- a/packages/middleware/node/tsdown.config.ts
+++ b/packages/middleware/node/tsdown.config.ts
@@ -1,5 +1,7 @@
 import { defineConfig } from 'tsdown';
 
+import { stripDtsSourceMappingUrl } from '../../../common/tsdown/stripDtsSourceMappingUrl.mjs';
+
 export default defineConfig({
     failOnWarn: 'ci-only',
     // 1. Entry Points
@@ -21,6 +23,11 @@ export default defineConfig({
     // 4. Type Definitions
     //    Bundles d.ts files into a single output
     dts: {
+        // Declaration maps would reference src/ (and, where bundled, the private
+        // core-internal's src/), which is not shipped ("files": ["dist"]); tsc cannot
+        // embed sourcesContent into .d.ts maps, so the shipped maps could never resolve
+        // on a consumer's machine. Don't emit them (#2233).
+        sourcemap: false,
         resolver: 'tsc',
         // The dev tsconfig.json maps @modelcontextprotocol/* to workspace source via
         // `paths` so typecheck/IDE work without a prior build. For declaration emit we
@@ -40,5 +47,7 @@ export default defineConfig({
             paths: {},
             preserveSymlinks: true
         }
-    }
+    },
+    // Drop the dangling sourceMappingURL comment rolldown leaves on the (map-less) declaration output.
+    inputOptions: stripDtsSourceMappingUrl
 });
diff --git a/packages/server-legacy/tsdown.config.ts b/packages/server-legacy/tsdown.config.ts
index 3e2f0ced3d..2aee5e7f3f 100644
--- a/packages/server-legacy/tsdown.config.ts
+++ b/packages/server-legacy/tsdown.config.ts
@@ -1,5 +1,7 @@
 import { defineConfig } from 'tsdown';
 
+import { stripDtsSourceMappingUrl } from '../../common/tsdown/stripDtsSourceMappingUrl.mjs';
+
 export default defineConfig({
     failOnWarn: 'ci-only',
     entry: ['src/index.ts', 'src/sse/index.ts', 'src/auth/index.ts'],
@@ -12,6 +14,11 @@ export default defineConfig({
     platform: 'node',
     shims: true,
     dts: {
+        // Declaration maps would reference src/ (and, where bundled, the private
+        // core-internal's src/), which is not shipped ("files": ["dist"]); tsc cannot
+        // embed sourcesContent into .d.ts maps, so the shipped maps could never resolve
+        // on a consumer's machine. Don't emit them (#2233).
+        sourcemap: false,
         resolver: 'tsc',
         compilerOptions: {
             baseUrl: '.',
@@ -25,5 +32,7 @@ export default defineConfig({
     // The schema modules live in @modelcontextprotocol/core (a real runtime dependency); the
     // bundled core-internal shims import them via the './internal' subpath, which must stay an
     // external import (explicit entry — the tsconfig paths alias would otherwise inline it).
-    external: ['@modelcontextprotocol/core/internal']
+    external: ['@modelcontextprotocol/core/internal'],
+    // Drop the dangling sourceMappingURL comment rolldown leaves on the (map-less) declaration output.
+    inputOptions: stripDtsSourceMappingUrl
 });
diff --git a/packages/server/tsdown.config.ts b/packages/server/tsdown.config.ts
index 88004cfc06..b8352ab943 100644
--- a/packages/server/tsdown.config.ts
+++ b/packages/server/tsdown.config.ts
@@ -1,5 +1,7 @@
 import { defineConfig } from 'tsdown';
 
+import { stripDtsSourceMappingUrl } from '../../common/tsdown/stripDtsSourceMappingUrl.mjs';
+
 export default defineConfig({
     failOnWarn: 'ci-only',
     entry: [
@@ -20,6 +22,11 @@ export default defineConfig({
     platform: 'node',
     shims: true,
     dts: {
+        // Declaration maps would reference src/ (and, where bundled, the private
+        // core-internal's src/), which is not shipped ("files": ["dist"]); tsc cannot
+        // embed sourcesContent into .d.ts maps, so the shipped maps could never resolve
+        // on a consumer's machine. Don't emit them (#2233).
+        sourcemap: false,
         resolver: 'tsc',
         resolve: ['ajv', 'ajv-formats', 'json-schema-typed'],
         compilerOptions: {
@@ -37,5 +44,7 @@ export default defineConfig({
     // The schema modules live in @modelcontextprotocol/core (a real runtime dependency); the
     // bundled core-internal shims import them via the './internal' subpath, which must stay an
     // external import (explicit entry — the tsconfig paths alias would otherwise inline it).
-    external: ['@modelcontextprotocol/server/_shims', '@modelcontextprotocol/core/internal']
+    external: ['@modelcontextprotocol/server/_shims', '@modelcontextprotocol/core/internal'],
+    // Drop the dangling sourceMappingURL comment rolldown leaves on the (map-less) declaration output.
+    inputOptions: stripDtsSourceMappingUrl
 });