diff --git a/crates/goose/src/agents/extension_malware_check.rs b/crates/goose/src/agents/extension_malware_check.rs
index 07512f16b..1acad54ab 100644
--- a/crates/goose/src/agents/extension_malware_check.rs
+++ b/crates/goose/src/agents/extension_malware_check.rs
@@ -41,16 +41,8 @@ impl OsvChecker {
     }
 }
 
-/// Convenience: infer ecosystem from command token + parse first package arg.
-/// - ends_with("npx") → npm
-/// - ends_with("uvx") → PyPI
-///   unknown commands → skip (fail open)
 pub async fn deny_if_malicious_cmd_args(cmd: &str, args: &[String]) -> Result<(), ExtensionError> {
-    let ecosystem = if cmd.ends_with("uvx") {
-        "PyPI"
-    } else if cmd.ends_with("npx") {
-        "npm"
-    } else {
+    let Some(ecosystem) = command_ecosystem(cmd) else {
         debug!(%cmd, ?args, "Unknown ecosystem for command; skipping OSV check (fail open).");
         return Ok(());
     };
@@ -67,6 +59,19 @@ pub async fn deny_if_malicious_cmd_args(cmd: &str, args: &[String]) -> Result<()
     Ok(())
 }
 
+fn command_ecosystem(cmd: &str) -> Option<&'static str> {
+    let executable = cmd
+        .rsplit(['/', '\\'])
+        .next()
+        .unwrap_or_default()
+        .to_ascii_lowercase();
+    match executable.as_str() {
+        "npx" | "npx.cmd" => Some("npm"),
+        "uvx" | "uvx.exe" => Some("PyPI"),
+        _ => None,
+    }
+}
+
 /// Direct call without command inference.
 pub async fn deny_if_malicious(
     name: &str,
@@ -708,6 +713,94 @@ mod tests {
         assert!(msg.contains("MAL-9999"));
     }
 
+    #[tokio::test]
+    #[serial_test::serial]
+    async fn cmd_args_windows_shims_block_malicious_packages() {
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/v1/query"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(json!({
+                "vulns": [ { "id": "MAL-462", "summary": "Malicious package" } ],
+                "next_page_token": null
+            })))
+            .mount(&server)
+            .await;
+
+        let _env = TempEnvVar::set("OSV_ENDPOINT", &format!("{}/v1/query", server.uri()));
+        for (command, package) in [
+            (r"C:\Program Files\nodejs\NPX.CMD", "bad-npm-package"),
+            ("C:/Program Files/nodejs/nPx.CmD", "bad-npm-package"),
+            (r"C:\Users\user\.local\bin\UVX.EXE", "bad_pypi_package"),
+            ("C:/Users/user/.local/bin/uVx.ExE", "bad_pypi_package"),
+        ] {
+            let result = deny_if_malicious_cmd_args(command, &[package.to_string()]).await;
+
+            assert!(result.is_err(), "expected {command} to query OSV");
+            assert!(format!("{:?}", result.unwrap_err()).contains("MAL-462"));
+        }
+    }
+
+    #[tokio::test]
+    #[serial_test::serial]
+    async fn cmd_args_path_qualified_commands_allow_clean_packages() {
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/v1/query"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(json!({
+                "vulns": [],
+                "next_page_token": null
+            })))
+            .mount(&server)
+            .await;
+
+        let _env = TempEnvVar::set("OSV_ENDPOINT", &format!("{}/v1/query", server.uri()));
+        for (command, package) in [
+            ("/usr/local/bin/NPX", "clean-npm-package"),
+            ("/opt/venv/bin/UvX", "clean_pypi_package"),
+        ] {
+            let result = deny_if_malicious_cmd_args(command, &[package.to_string()]).await;
+
+            assert!(
+                result.is_ok(),
+                "expected {command} to allow a clean package"
+            );
+        }
+
+        assert_eq!(server.received_requests().await.unwrap().len(), 2);
+    }
+
+    #[tokio::test]
+    #[serial_test::serial]
+    async fn cmd_args_lookalike_commands_are_skipped() {
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/v1/query"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(json!({
+                "vulns": [ { "id": "MAL-462", "summary": "Malicious package" } ],
+                "next_page_token": null
+            })))
+            .mount(&server)
+            .await;
+
+        let _env = TempEnvVar::set("OSV_ENDPOINT", &format!("{}/v1/query", server.uri()));
+        for command in [
+            "my-npx",
+            "npx.exe",
+            "npx.cmd.bak",
+            "/usr/bin/notnpx",
+            "uvx.cmd",
+            "uvx.exe.bak",
+            r"C:\Tools\my-uvx",
+        ] {
+            let result =
+                deny_if_malicious_cmd_args(command, &["malicious-package".to_string()]).await;
+
+            assert!(result.is_ok(), "expected {command} to remain fail-open");
+        }
+
+        assert!(server.received_requests().await.unwrap().is_empty());
+    }
+
     #[tokio::test]
     #[serial_test::serial]
     async fn cmd_args_skip_flags_then_parse() {