diff --git a/internal/providers/claude_cli_session.go b/internal/providers/claude_cli_session.go
index 047e8718..c042d663 100644
--- a/internal/providers/claude_cli_session.go
+++ b/internal/providers/claude_cli_session.go
@@ -272,7 +272,8 @@ func ResetCLISession(baseWorkDir, sessionKey string) {
 	}
 }
 
-// filterCLIEnv removes CLAUDE* env vars to prevent nested session conflicts.
+// filterCLIEnv removes CLAUDE* env vars to prevent nested session conflicts,
+// but preserves CLAUDE_CODE_OAUTH_TOKEN for authentication.
 func filterCLIEnv(environ []string) []string {
 	var filtered []string
 	for _, e := range environ {
@@ -280,8 +281,9 @@ func filterCLIEnv(environ []string) []string {
 		if before, _, ok := strings.Cut(e, "="); ok {
 			key = before
 		}
-		// Filter out variables that could cause nested CLI conflicts
-		if strings.HasPrefix(key, "CLAUDE") {
+		// Filter out variables that could cause nested CLI conflicts,
+		// but preserve auth token needed by the subprocess.
+		if strings.HasPrefix(key, "CLAUDE") && key != "CLAUDE_CODE_OAUTH_TOKEN" {
 			continue
 		}
 		filtered = append(filtered, e)