diff --git a/crates/goose/src/agents/extension_manager.rs b/crates/goose/src/agents/extension_manager.rs
index bc48d0e30..27522adc1 100644
--- a/crates/goose/src/agents/extension_manager.rs
+++ b/crates/goose/src/agents/extension_manager.rs
@@ -309,10 +309,15 @@ pub(crate) fn recover_mangled_tool_name<'a>(
         let owner_mangled = owner.map(|o| format!("{o}.{name}"));
         let owner_prefixed = owner.map(|o| format!("{o}__{name}"));
 
+        // Models prompted with bare tool names ("write_file") drop the extension
+        // prefix entirely; recover only when exactly one extension owns that tool.
+        let bare_tool = name.split_once("__").map(|(_, tool)| tool);
+
         let matches = stripped == name
             || separator_mangled.as_deref() == Some(stripped)
             || owner_mangled.as_deref() == Some(stripped)
-            || owner_prefixed.as_deref() == Some(stripped);
+            || owner_prefixed.as_deref() == Some(stripped)
+            || bare_tool == Some(stripped);
         if name == emitted || !matches {
             continue;
         }
@@ -3805,6 +3810,36 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_recover_mangled_tool_name_bare_tool_without_extension_prefix() {
+        let tools = [
+            ("sandbox-fs__write_file", None),
+            ("sandbox-fs__read_file", None),
+            ("developer__shell", None),
+        ];
+        assert_eq!(
+            recover_mangled_tool_name("write_file", tools.iter().copied()).as_deref(),
+            Some("sandbox-fs__write_file")
+        );
+        assert_eq!(
+            recover_mangled_tool_name("functions.read_file", tools.iter().copied()).as_deref(),
+            Some("sandbox-fs__read_file")
+        );
+        assert_eq!(
+            recover_mangled_tool_name("edit_file", tools.iter().copied()),
+            None
+        );
+
+        let ambiguous = [
+            ("sandbox-fs__write_file", None),
+            ("other__write_file", None),
+        ];
+        assert_eq!(
+            recover_mangled_tool_name("write_file", ambiguous.iter().copied()),
+            None
+        );
+    }
+
     #[test]
     fn test_recover_mangled_tool_name_non_extension_manager_tools() {
         // recipe__final_output and platform__manage_schedule are appended by