diff --git a/ts/packages/cli-keyring/tsdown.config.ts b/ts/packages/cli-keyring/tsdown.config.ts
index 42109e2433..bfbbdca738 100644
--- a/ts/packages/cli-keyring/tsdown.config.ts
+++ b/ts/packages/cli-keyring/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../tsdown.config.base';
+import { baseConfig } from '../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/cli/tsdown.config.ts b/ts/packages/cli/tsdown.config.ts
index b3114cc2d4..87339978c9 100644
--- a/ts/packages/cli/tsdown.config.ts
+++ b/ts/packages/cli/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../tsdown.config.base';
+import { baseConfig } from '../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/core/package.json b/ts/packages/core/package.json
index b890abbad0..22eef077b2 100644
--- a/ts/packages/core/package.json
+++ b/ts/packages/core/package.json
@@ -131,7 +131,7 @@
   ],
   "scripts": {
     "clean": "git clean -xdf node_modules",
-    "build": "pnpm exec tsdown",
+    "build": "pnpm exec tsdown --config-loader unrun",
     "test": "vitest run",
     "typecheck": "pnpm exec tsgo --noEmit --skipLibCheck && pnpm exec tsgo --noEmit --skipLibCheck -p tsconfig.type-tests.json",
     "typecheck:tsc": "tsc --noEmit --skipLibCheck && tsc --noEmit --skipLibCheck -p tsconfig.type-tests.json",
diff --git a/ts/packages/core/tsdown.config.ts b/ts/packages/core/tsdown.config.ts
index 4721e6e890..97ca9b0057 100644
--- a/ts/packages/core/tsdown.config.ts
+++ b/ts/packages/core/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig, UserConfig } from 'tsdown';
-import { baseConfig } from '../../../tsdown.config.base';
+import { baseConfig } from '../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/json-schema-to-zod/tsdown.config.ts b/ts/packages/json-schema-to-zod/tsdown.config.ts
index b1be8d9fc1..c7792da3b6 100644
--- a/ts/packages/json-schema-to-zod/tsdown.config.ts
+++ b/ts/packages/json-schema-to-zod/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../tsdown.config.base';
+import { baseConfig } from '../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/providers/anthropic/tsdown.config.ts b/ts/packages/providers/anthropic/tsdown.config.ts
index fa478cbd3c..a1602691fa 100644
--- a/ts/packages/providers/anthropic/tsdown.config.ts
+++ b/ts/packages/providers/anthropic/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../../tsdown.config.base';
+import { baseConfig } from '../../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/providers/claude-agent-sdk/tsdown.config.ts b/ts/packages/providers/claude-agent-sdk/tsdown.config.ts
index fa478cbd3c..a1602691fa 100644
--- a/ts/packages/providers/claude-agent-sdk/tsdown.config.ts
+++ b/ts/packages/providers/claude-agent-sdk/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../../tsdown.config.base';
+import { baseConfig } from '../../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/providers/cloudflare/tsdown.config.ts b/ts/packages/providers/cloudflare/tsdown.config.ts
index fa478cbd3c..a1602691fa 100644
--- a/ts/packages/providers/cloudflare/tsdown.config.ts
+++ b/ts/packages/providers/cloudflare/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../../tsdown.config.base';
+import { baseConfig } from '../../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/providers/google/tsdown.config.ts b/ts/packages/providers/google/tsdown.config.ts
index fa478cbd3c..a1602691fa 100644
--- a/ts/packages/providers/google/tsdown.config.ts
+++ b/ts/packages/providers/google/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../../tsdown.config.base';
+import { baseConfig } from '../../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/providers/langchain/tsdown.config.ts b/ts/packages/providers/langchain/tsdown.config.ts
index 4bb27177e6..c242a227cc 100644
--- a/ts/packages/providers/langchain/tsdown.config.ts
+++ b/ts/packages/providers/langchain/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../../tsdown.config.base';
+import { baseConfig } from '../../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/providers/llamaindex/tsdown.config.ts b/ts/packages/providers/llamaindex/tsdown.config.ts
index fa478cbd3c..a1602691fa 100644
--- a/ts/packages/providers/llamaindex/tsdown.config.ts
+++ b/ts/packages/providers/llamaindex/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../../tsdown.config.base';
+import { baseConfig } from '../../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/providers/mastra/tsdown.config.ts b/ts/packages/providers/mastra/tsdown.config.ts
index fa478cbd3c..a1602691fa 100644
--- a/ts/packages/providers/mastra/tsdown.config.ts
+++ b/ts/packages/providers/mastra/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../../tsdown.config.base';
+import { baseConfig } from '../../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/providers/openai-agents/tsdown.config.ts b/ts/packages/providers/openai-agents/tsdown.config.ts
index fa478cbd3c..a1602691fa 100644
--- a/ts/packages/providers/openai-agents/tsdown.config.ts
+++ b/ts/packages/providers/openai-agents/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../../tsdown.config.base';
+import { baseConfig } from '../../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/providers/openai/tsdown.config.ts b/ts/packages/providers/openai/tsdown.config.ts
index fa478cbd3c..a1602691fa 100644
--- a/ts/packages/providers/openai/tsdown.config.ts
+++ b/ts/packages/providers/openai/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../../tsdown.config.base';
+import { baseConfig } from '../../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/providers/vercel/tsdown.config.ts b/ts/packages/providers/vercel/tsdown.config.ts
index fa478cbd3c..a1602691fa 100644
--- a/ts/packages/providers/vercel/tsdown.config.ts
+++ b/ts/packages/providers/vercel/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../../tsdown.config.base';
+import { baseConfig } from '../../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,
diff --git a/ts/packages/ts-builders/tsdown.config.ts b/ts/packages/ts-builders/tsdown.config.ts
index b1be8d9fc1..c7792da3b6 100644
--- a/ts/packages/ts-builders/tsdown.config.ts
+++ b/ts/packages/ts-builders/tsdown.config.ts
@@ -1,5 +1,5 @@
 import { defineConfig } from 'tsdown';
-import { baseConfig } from '../../../tsdown.config.base';
+import { baseConfig } from '../../../tsdown.config.base.ts';
 
 export default defineConfig({
   ...baseConfig,