diff --git a/packages/ai/CHANGELOG.md b/packages/ai/CHANGELOG.md
index d0f23fc2..a0d5d791 100644
--- a/packages/ai/CHANGELOG.md
+++ b/packages/ai/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed bug where `ANTHROPIC_API_KEY` environment variable was deleted globally after first OAuth token usage, causing subsequent prompts to fail
+
 ## [0.17.0] - 2025-12-09
 
 ### Added
diff --git a/packages/ai/src/providers/anthropic.ts b/packages/ai/src/providers/anthropic.ts
index ff6e60e2..a1791b8a 100644
--- a/packages/ai/src/providers/anthropic.ts
+++ b/packages/ai/src/providers/anthropic.ts
@@ -289,11 +289,6 @@ function createClient(
 			...(model.headers || {}),
 		};
 
-		// Clear the env var if we're in Node.js to prevent SDK from using it
-		if (typeof process !== "undefined" && process.env) {
-			delete process.env.ANTHROPIC_API_KEY;
-		}
-
 		const client = new Anthropic({
 			apiKey: null,
 			authToken: apiKey,