fix(plugin): address kubernetes fast upload review

packages/plugins/sandbox-providers/kubernetes/src/plugin.ts

@@ -559,7 +559,7 @@ const plugin = definePlugin({
           const dir = slashIndex > 0 ? decision.flush.targetPath.slice(0, slashIndex) : ".";
           const script =
             `mkdir -p ${shellQuoteArg(dir)} && ` +
-            `head -c ${base64Body.length} | base64 -d > ${shellQuoteArg(decision.flush.targetPath)}`;
+            `base64 -d > ${shellQuoteArg(decision.flush.targetPath)}`;
           const flushResult = await execInPod(
             kc,
             namespace,
@@ -585,6 +585,22 @@ const plugin = definePlugin({
             },
           };
         }
+        if (decision.action === "error") {
+          return {
+            exitCode: 1,
+            timedOut: false,
+            stdout: "",
+            stderr: decision.message,
+            metadata: {
+              provider: "kubernetes",
+              backend: "sandbox-cr",
+              namespace,
+              sandboxName: lease.providerLeaseId,
+              podName,
+              fastUpload: "error",
+            },
+          };
+        }
       }
 
       const execCommand = buildSandboxExecCommand(params);

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

@@ -151,7 +151,6 @@ export async function execInPod(
         .then((webSocket) => {
           ws = webSocket as WebSocketLike;
           if (stdinStream && stdinPayload) {
-            stdinStream.removeAllListeners("end");
             stdinStream.end(stdinPayload);
           }
           ws.on("close", (code: number, reason: Buffer) => {

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

@@ -31,6 +31,7 @@ export interface FastUploadFlush {
 export type FastUploadDecision =
   | { action: "ack"; reason: string }
   | { action: "flush"; flush: FastUploadFlush }
+  | { action: "error"; message: string }
   | { action: "passthrough"; reason: string };
 
 interface BufferedUpload {
@@ -42,6 +43,8 @@ interface BufferedUpload {
 export class FastUploadInterceptor {
   private readonly buffers = new Map<string, BufferedUpload>();
 
+  constructor(private readonly maxBufferBytes = MAX_BUFFER_BYTES) {}
+
   decide(command: string): FastUploadDecision {
     const initMatch = INIT_RE.exec(command);
     if (initMatch) {
@@ -69,9 +72,12 @@ export class FastUploadInterceptor {
         return { action: "passthrough", reason: "chunk without prior init" };
       }
 
-      if (upload.totalBase64Chars + base64Chunk.length > (MAX_BUFFER_BYTES * 4) / 3) {
+      if (upload.totalBase64Chars + base64Chunk.length > (this.maxBufferBytes * 4) / 3) {
         this.buffers.delete(tempPath);
-        return { action: "passthrough", reason: "buffer cap exceeded" };
+        return {
+          action: "error",
+          message: `Fast upload buffer cap exceeded for ${upload.targetPath}; retry the upload with a smaller payload.`,
+        };
       }
 
       upload.chunks.push(base64Chunk);