diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index 495fdeff..b3d96d7a 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -7,6 +7,7 @@
 - Fixed offline startup hangs by adding offline startup behavior and network timeouts during managed tool setup ([#1631](https://github.com/badlogic/pi-mono/pull/1631) by [@mcollina](https://github.com/mcollina))
 - Fixed Windows VT input initialization in ESM by loading koffi via createRequire, avoiding runtime and bundling issues in end-user environments ([#1627](https://github.com/badlogic/pi-mono/pull/1627) by [@kaste](https://github.com/kaste))
 - Fixed managed `fd`/`rg` bootstrap on Windows in Git Bash by using `extract-zip` for `.zip` archives, searching extracted layouts more robustly, and isolating extraction temp directories to avoid concurrent download races ([#1348](https://github.com/badlogic/pi-mono/issues/1348))
+- Fixed extension loading on Windows when resolving `@sinclair/typebox` aliases so subpath imports like `@sinclair/typebox/compiler` resolve correctly.
 
 ## [0.55.0] - 2026-02-24
 
diff --git a/packages/coding-agent/src/core/extensions/loader.ts b/packages/coding-agent/src/core/extensions/loader.ts
index cec13e61..b18d6252 100644
--- a/packages/coding-agent/src/core/extensions/loader.ts
+++ b/packages/coding-agent/src/core/extensions/loader.ts
@@ -60,7 +60,7 @@ function getAliases(): Record<string, string> {
 	const packageIndex = path.resolve(__dirname, "../..", "index.js");
 
 	const typeboxEntry = require.resolve("@sinclair/typebox");
-	const typeboxRoot = typeboxEntry.replace(/\/build\/cjs\/index\.js$/, "");
+	const typeboxRoot = typeboxEntry.replace(/[\\/]build[\\/]cjs[\\/]index\.js$/, "");
 
 	_aliases = {
 		"@mariozechner/pi-coding-agent": packageIndex,