From f654caec507ebb6199f054e9f855ed987741d15a Mon Sep 17 00:00:00 2001
From: Peter Wielander <mittgfu@gmail.com>
Date: Thu, 2 Apr 2026 17:23:30 -0700
Subject: [PATCH 1/2] accept Web WritableStream in runCommand stdout/stderr

runCommand now accepts both Node.js Writable and Web WritableStream
for stdout/stderr options. The conversion happens inside the step
(where Node.js APIs are available), so workflow code can pass
Web streams from getWritable() directly.
---
 packages/vercel-sandbox/src/sandbox.ts | 29 ++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/packages/vercel-sandbox/src/sandbox.ts b/packages/vercel-sandbox/src/sandbox.ts
index 2a895c5..cdff14a 100644
--- a/packages/vercel-sandbox/src/sandbox.ts
+++ b/packages/vercel-sandbox/src/sandbox.ts
@@ -154,13 +154,15 @@ interface RunCommandParams {
    */
   detached?: boolean;
   /**
-   * A `Writable` stream where `stdout` from the command will be piped
+   * A stream where `stdout` from the command will be piped.
+   * Accepts a Node.js `Writable` or a Web `WritableStream`.
    */
-  stdout?: Writable;
+  stdout?: Writable | WritableStream;
   /**
-   * A `Writable` stream where `stderr` from the command will be piped
+   * A stream where `stderr` from the command will be piped.
+   * Accepts a Node.js `Writable` or a Web `WritableStream`.
    */
-  stderr?: Writable;
+  stderr?: Writable | WritableStream;
   /**
    * An AbortSignal to cancel the command execution
    */
@@ -501,12 +503,27 @@ export class Sandbox {
         return;
       }
 
+      // Resolve writers: support both Node.js Writable and Web WritableStream
+      const getWriter = (
+        stream: Writable | WritableStream | undefined,
+      ): { write: (data: string) => void } | undefined => {
+        if (!stream) return undefined;
+        if ("getWriter" in stream) {
+          const writer = stream.getWriter();
+          return { write: (data: string) => writer.write(data) };
+        }
+        return stream;
+      };
+
+      const stdoutWriter = getWriter(params.stdout);
+      const stderrWriter = getWriter(params.stderr);
+
       try {
         for await (const log of command.logs({ signal: params.signal })) {
           if (log.stream === "stdout") {
-            params.stdout?.write(log.data);
+            stdoutWriter?.write(log.data);
           } else if (log.stream === "stderr") {
-            params.stderr?.write(log.data);
+            stderrWriter?.write(log.data);
           }
         }
       } catch (err) {

From e004eeb26bc7c407b8ceca049abce71c1702c1ed Mon Sep 17 00:00:00 2001
From: Pranay Prakash <pranay.gp@gmail.com>
Date: Fri, 27 Mar 2026 16:07:31 -0700
Subject: [PATCH 2/2] fix typecheck: guard .emit() call for WritableStream
 compatibility

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 packages/vercel-sandbox/src/sandbox.ts | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/packages/vercel-sandbox/src/sandbox.ts b/packages/vercel-sandbox/src/sandbox.ts
index cdff14a..cfdf14c 100644
--- a/packages/vercel-sandbox/src/sandbox.ts
+++ b/packages/vercel-sandbox/src/sandbox.ts
@@ -584,7 +584,10 @@ export class Sandbox {
       if (params.signal?.aborted) {
         return;
       }
-      (params.stderr ?? params.stdout)?.emit("error", err);
+      const errStream = params.stderr ?? params.stdout;
+      if (errStream && "emit" in errStream) {
+        errStream.emit("error", err);
+      }
     });
 
     return command;