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,

packages/plugins/sandbox-providers/kubernetes/test/unit/pod-exec.test.ts

@@ -27,6 +27,17 @@ describe("execInPod", () => {
     expect(result).toEqual({ exitCode: 0, timedOut: false, stdout: "ok\n", stderr: "" });
   });
 
+  it("finishes when Kubernetes reports status without ending output streams", async () => {
+    execMock.mockImplementation((_namespace, _pod, _container, _command, stdout, _stderr, _stdin, _tty, statusCallback) => {
+      stdout.write("ok\n");
+      statusCallback({ status: "Success" });
+      return Promise.resolve(new EventEmitter());
+    });
+
+    const result = await execInPod({} as never, "ns", "pod-1", "agent", ["echo", "ok"]);
+    expect(result).toEqual({ exitCode: 0, timedOut: false, stdout: "ok\n", stderr: "" });
+  });
+
   it("returns an execution failure if the websocket closes before a status frame", async () => {
     const ws = new EventEmitter();
     execMock.mockResolvedValue(ws);

packages/plugins/sandbox-providers/kubernetes/test/unit/upload-interceptor.test.ts

@@ -75,6 +75,25 @@ describe("FastUploadInterceptor", () => {
     expect(interceptor.pendingCount).toBe(0);
   });
 
+  it("fails fast when init repeats for an in-progress upload", () => {
+    const interceptor = new FastUploadInterceptor();
+    const target = "/workspace/file.bin";
+    const initCommand =
+      `mkdir -p '/workspace' && rm -f '${target}.paperclip-upload.b64' && : > '${target}.paperclip-upload.b64'`;
+
+    expect(interceptor.decide(initCommand)).toMatchObject({ action: "ack" });
+    expect(
+      interceptor.decide(`printf '%s' 'aGVsbG8=' >> '${target}.paperclip-upload.b64'`),
+    ).toMatchObject({ action: "ack" });
+
+    const decision = interceptor.decide(initCommand);
+    expect(decision).toMatchObject({
+      action: "error",
+      message: expect.stringContaining("Fast upload already in progress"),
+    });
+    expect(interceptor.pendingCount).toBe(0);
+  });
+
   it("clears buffered uploads on reset", () => {
     const interceptor = new FastUploadInterceptor();
     const target = "/workspace/file.bin";