fix(plugin): harden kubernetes fast upload edges

packages/plugins/sandbox-providers/kubernetes/src/pod-exec.ts

@@ -102,6 +102,10 @@ export async function execInPod(
           stderr: stderrData,
         });
       };
+      const endOutputStreams = () => {
+        if (!stdoutStream.writableEnded) stdoutStream.end();
+        if (!stderrStream.writableEnded) stderrStream.end();
+      };
 
       stdoutStream.on("end", () => {
         stdoutEnded = true;
@@ -126,6 +130,7 @@ export async function execInPod(
             // status.status is "Success" | "Failure"
             if (status.status === "Success") {
               pendingResult = { exitCode: 0, timedOut: false };
+              endOutputStreams();
               tryFinish();
               return;
             }
@@ -140,6 +145,7 @@ export async function execInPod(
               ? Number(exitCodeCause.message)
               : 1;
             pendingResult = { exitCode, timedOut: false };
+            endOutputStreams();
             tryFinish();
           },
         );

packages/plugins/sandbox-providers/kubernetes/src/upload-interceptor.ts

@@ -54,7 +54,16 @@ export class FastUploadInterceptor {
         return { action: "passthrough", reason: "init dir/target mismatch" };
       }
 
-      this.buffers.set(`${targetPath}.paperclip-upload.b64`, {
+      const tempPath = `${targetPath}.paperclip-upload.b64`;
+      if (this.buffers.has(tempPath)) {
+        this.buffers.delete(tempPath);
+        return {
+          action: "error",
+          message: `Fast upload already in progress for ${targetPath}; retry the upload from the beginning.`,
+        };
+      }
+
+      this.buffers.set(tempPath, {
         targetPath,
         chunks: [],
         totalBase64Chars: 0,