diff --git a/src/pkg_manager.ts b/src/pkg_manager.ts
index 7580ebf..df0d87c 100644
--- a/src/pkg_manager.ts
+++ b/src/pkg_manager.ts
@@ -29,7 +29,8 @@ function toPackageArgs(pkgs: JsrPackage[]): string[] {
 
 async function isYarnBerry(cwd: string) {
   // this command works for both yarn classic and berry
-  const version = await exec("yarn", ["--version"], cwd, undefined, true);
+  const output = await exec("yarn", ["--version"], cwd, undefined, true);
+  const version = output.stdout;
   if (!version) {
     logDebug("Unable to detect yarn version, assuming classic");
     return false;
diff --git a/src/utils.ts b/src/utils.ts
index 8c52283..a83fcb0 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -205,13 +205,19 @@ export class ExecError extends Error {
   }
 }
 
+export interface ExecOutput {
+  combined: string;
+  stdout: string;
+  stderr: string;
+}
+
 export async function exec(
   cmd: string,
   args: string[],
   cwd: string,
   env?: Record<string, string | undefined>,
   captureOutput?: boolean,
-) {
+): Promise<ExecOutput> {
   const cp = spawn(
     cmd,
     args.map((arg) => process.platform === "win32" ? `"${arg}"` : `'${arg}'`),
@@ -223,20 +229,24 @@ export async function exec(
     },
   );
 
-  let output = "";
+  let combined = "";
+  let stdout = "";
+  let stderr = "";
 
   if (captureOutput) {
     cp.stdout?.on("data", (data) => {
-      output += data;
+      combined += data;
+      stdout += data;
     });
     cp.stderr?.on("data", (data) => {
-      output += data;
+      combined += data;
+      stderr += data;
     });
   }
 
-  return new Promise<string>((resolve, reject) => {
+  return new Promise<ExecOutput>((resolve, reject) => {
     cp.on("exit", (code) => {
-      if (code === 0) resolve(output);
+      if (code === 0) resolve({ combined, stdout, stderr });
       else reject(new ExecError(code ?? 1));
     });
   });
diff --git a/test/commands.test.ts b/test/commands.test.ts
index 6c58702..dacdea4 100644
--- a/test/commands.test.ts
+++ b/test/commands.test.ts
@@ -196,7 +196,7 @@ describe("install", () => {
 
       assert.match(
         pkgJson.dependencies["@std/encoding"],
-        /^npm:@jsr\/std__encoding@\^\d+\.\d+\.\d+.*$/,
+        /^npm:@jsr\/std__encoding@\d+\.\d+\.\d+.*$/,
       );
 
       const npmRc = await readTextFile(path.join(dir, ".npmrc"));
@@ -770,7 +770,7 @@ describe("show", () => {
       undefined,
       true,
     );
-    const txt = kl.stripColors(output);
+    const txt = kl.stripColors(output.combined);
     assert.ok(txt.includes("latest:"));
     assert.ok(txt.includes("npm tarball:"));
   });
@@ -796,7 +796,7 @@ describe("show", () => {
       undefined,
       true,
     );
-    const txt = kl.stripColors(output);
+    const txt = kl.stripColors(output.combined);
     assert.ok(txt.includes("latest: -"));
     assert.ok(txt.includes("npm tarball:"));
   });