feat(plugin): add kubernetes fast upload interceptor

packages/plugins/sandbox-providers/kubernetes/README.md

@@ -104,6 +104,12 @@ Pod                pc-{ulid}-{podSuffix}           (managed by Sandbox controlle
 Secret             pc-{ulid}-env                   (owned by Sandbox CR; cascade-deleted)
 ```
 
+## Fast workspace uploads
+
+The `sandbox-cr` backend recognizes the chunked base64 upload protocol emitted by `@paperclipai/adapter-utils` for workspace, skill, and config-seed file transfers. Instead of running one Kubernetes exec per base64 chunk, the plugin buffers the upload in worker memory and flushes the final payload through a single `head -c <bytes> | base64 -d` exec with stdin.
+
+The interceptor is intentionally narrow: only the exact `mkdir`/`printf`/`base64 -d` command shape generated by adapter-utils is optimized. Unknown commands, missing init state, or uploads over the 100 MB buffer cap fall back to normal exec behavior.
+
 For each agent run (job backend):
 
 ```

packages/plugins/sandbox-providers/kubernetes/SMOKE.md

@@ -94,9 +94,10 @@ The plugin's `onEnvironmentAcquireLease` will:
 
 1. `ensureTenant` — provision the `paperclip-smoke` namespace, SA, Role,
    RoleBinding, ResourceQuota, LimitRange, NetworkPolicies
-2. `buildJobManifest` — render the security-hardened Job manifest
-3. `createJob` — submit to `batch/v1`
-4. `createPerRunSecret` — owned by the Job for cascade-delete
+2. `buildSandboxCrManifest` — render the security-hardened Sandbox CR manifest
+3. `createNamespacedCustomObject` — submit to `agents.x-k8s.io/v1alpha1`
+4. `createPerRunSecret` — owned by the Sandbox CR for cascade-delete
+5. Fast-upload workspace/config/skill payloads by collapsing adapter-utils chunked uploads into a single stdin-backed exec per file
 
 ### 7. Verify the tenant resources
 
@@ -113,8 +114,9 @@ Expected:
 - Role `paperclip-tenant-role`, RoleBinding `paperclip-tenant-rb`
 - ResourceQuota `paperclip-quota`, LimitRange `paperclip-limits`
 - NetworkPolicies `paperclip-deny-all` + `paperclip-egress-allow`
-- Job `pc-{ulid}` and its child Pod
-- Secret `pc-{ulid}-env` with `ownerReferences` pointing at the Job
+- Sandbox `pc-{ulid}` and its managed Pod
+- Secret `pc-{ulid}-env` with `ownerReferences` pointing at the Sandbox CR
+- Run logs or plugin metadata include `fastUpload: "flush"` entries during workspace/config/skill upload
 
 ### 8. Tear down
 

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

@@ -25,6 +25,7 @@ import { buildJobManifest } from "./pod-spec-builder.js";
 import { buildSandboxCrManifest } from "./sandbox-cr-builder.js";
 import { ensureTenant } from "./tenant-orchestrator.js";
 import { createPerRunSecret } from "./secret-manager.js";
+import { FastUploadInterceptor } from "./upload-interceptor.js";
 import { jobOrchestrator, JobTimeoutError } from "./job-orchestrator.js";
 import {
   sandboxCrOrchestrator,
@@ -51,6 +52,29 @@ const DEFAULT_RESOURCE_QUOTA = {
   limitsMemory: "40Gi",
 };
 
+const uploadInterceptorsByLease = new Map<string, FastUploadInterceptor>();
+
+function getOrCreateUploadInterceptor(leaseId: string): FastUploadInterceptor {
+  let interceptor = uploadInterceptorsByLease.get(leaseId);
+  if (!interceptor) {
+    interceptor = new FastUploadInterceptor();
+    uploadInterceptorsByLease.set(leaseId, interceptor);
+  }
+  return interceptor;
+}
+
+function extractShellScript(
+  params: Pick<PluginEnvironmentExecuteParams, "args" | "command">,
+): string | null {
+  const command = typeof params.command === "string" ? params.command.trim() : "";
+  const args = Array.isArray(params.args) ? params.args : [];
+  const isShell = command === "sh" || command === "bash" || command.endsWith("/sh") || command.endsWith("/bash");
+  if (isShell && args[0] === "-c" && typeof args[1] === "string") {
+    return args[1];
+  }
+  return null;
+}
+
 function deriveTenantNamespace(config: KubernetesProviderConfig, companyId: string): string {
   // TODO: future versions could thread companyName through AcquireLeaseParams
   // to get a friendlier slug (e.g. "acme-corp") instead of the UUID-derived one.
@@ -93,6 +117,24 @@ function shellQuoteArg(arg: string): string {
   return "'" + arg.replace(/'/g, "'\\''") + "'";
 }
 
+export function buildSandboxExecCommand(
+  params: Pick<PluginEnvironmentExecuteParams, "args" | "command">,
+): string[] {
+  const command = typeof params.command === "string" ? params.command.trim() : "";
+  const args = Array.isArray(params.args) ? params.args : [];
+
+  if (command.length > 0 && args.length > 0) {
+    return [command, ...args];
+  }
+  if (command.length > 0) {
+    return ["/bin/sh", "-lc", command];
+  }
+  if (args.length > 0) {
+    return ["/bin/sh", "-lc", args.map(shellQuoteArg).join(" ")];
+  }
+  return ["/bin/sh", "-l"];
+}
+
 export function buildSandboxExecShellCommand(
   params: Pick<PluginEnvironmentExecuteParams, "args" | "command">,
 ): string {
@@ -379,6 +421,8 @@ const plugin = definePlugin({
     const releaseOrchestrator =
       leaseBackend === "sandbox-cr" ? sandboxCrOrchestrator : jobOrchestrator;
 
+    uploadInterceptorsByLease.delete(params.providerLeaseId);
+
     try {
       await releaseOrchestrator.release(clients, namespace, params.providerLeaseId);
     } catch (err) {
@@ -488,15 +532,62 @@ const plugin = definePlugin({
         };
       }
 
-      // Build the command to exec. If params.command is provided use it;
-      // otherwise wrap in a login shell so profile scripts run.
-      const rawCommand = buildSandboxExecShellCommand(params);
-
-      const execCommand = rawCommand.length > 0
-        ? ["/bin/sh", "-lc", rawCommand]
-        : ["/bin/sh", "-l"];
-
       const remainingTimeoutMs = Math.max(1, effectiveTimeoutMs - (Date.now() - executeStartedAt));
+
+      const shellScript = extractShellScript(params);
+      if (shellScript) {
+        const decision = getOrCreateUploadInterceptor(lease.providerLeaseId).decide(shellScript);
+        if (decision.action === "ack") {
+          return {
+            exitCode: 0,
+            timedOut: false,
+            stdout: "",
+            stderr: "",
+            metadata: {
+              provider: "kubernetes",
+              backend: "sandbox-cr",
+              namespace,
+              sandboxName: lease.providerLeaseId,
+              podName,
+              fastUpload: "ack",
+            },
+          };
+        }
+        if (decision.action === "flush") {
+          const base64Body = decision.flush.payload.toString("base64");
+          const slashIndex = decision.flush.targetPath.lastIndexOf("/");
+          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)}`;
+          const flushResult = await execInPod(
+            kc,
+            namespace,
+            podName,
+            "agent",
+            ["/bin/sh", "-c", script],
+            base64Body,
+            remainingTimeoutMs,
+          );
+          return {
+            exitCode: flushResult.exitCode,
+            timedOut: flushResult.timedOut,
+            stdout: flushResult.stdout,
+            stderr: flushResult.stderr,
+            metadata: {
+              provider: "kubernetes",
+              backend: "sandbox-cr",
+              namespace,
+              sandboxName: lease.providerLeaseId,
+              podName,
+              fastUpload: "flush",
+              uploadedBytes: decision.flush.payload.length,
+            },
+          };
+        }
+      }
+
+      const execCommand = buildSandboxExecCommand(params);
       const execResult = await execInPod(
         kc,
         namespace,

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

@@ -14,6 +14,12 @@ import { Exec } from "@kubernetes/client-node";
 import { PassThrough } from "node:stream";
 import type { KubeConfig } from "@kubernetes/client-node";
 
+type WebSocketLike = {
+  close(): void;
+  on(event: "close", listener: (code: number, reason: Buffer) => void): void;
+  on(event: "error", listener: (err: Error) => void): void;
+};
+
 export interface ExecInPodResult {
   exitCode: number;
   timedOut: boolean;
@@ -21,24 +27,31 @@ export interface ExecInPodResult {
   stderr: string;
 }
 
+function shQuoteArg(arg: string): string {
+  return "'" + arg.replace(/'/g, "'\\''") + "'";
+}
+
 export async function execInPod(
   kc: KubeConfig,
   namespace: string,
   podName: string,
   containerName: string,
   command: string[],
-  stdin?: string,
+  stdin?: string | Buffer,
   timeoutMs?: number,
 ): Promise<ExecInPodResult> {
   const exec = new Exec(kc);
   const stdoutStream = new PassThrough();
   const stderrStream = new PassThrough();
 
-  // If stdin is provided build a readable stream from it; the Exec API accepts
-  // a Readable | null for stdin.
-  const stdinStream: import("node:stream").Readable | null = stdin
-    ? PassThrough.from(stdin)
+  const stdinPayload: Buffer | null =
+    Buffer.isBuffer(stdin) ? stdin
+    : typeof stdin === "string" && stdin.length > 0 ? Buffer.from(stdin, "utf-8")
     : null;
+  const stdinStream: PassThrough | null = stdinPayload ? new PassThrough() : null;
+  const effectiveCommand = stdinPayload
+    ? ["/bin/sh", "-c", `head -c ${stdinPayload.length} | ${command.map(shQuoteArg).join(" ")}`]
+    : command;
 
   let stdoutData = "";
   let stderrData = "";
@@ -52,17 +65,27 @@ export async function execInPod(
 
   return await new Promise<ExecInPodResult>(
     (resolve, reject) => {
+      let ws: WebSocketLike | null = null;
       let settled = false;
+      let pendingResult: Omit<ExecInPodResult, "stdout" | "stderr"> | null = null;
+      let stdoutEnded = false;
+      let stderrEnded = false;
       const timeout =
         typeof timeoutMs === "number" && timeoutMs > 0
           ? setTimeout(() => {
               finishWithTransportFailure(`Kubernetes exec timed out after ${timeoutMs}ms`, true);
             }, timeoutMs)
           : null;
+
       const finish = (result: ExecInPodResult) => {
         if (settled) return;
         settled = true;
         if (timeout) clearTimeout(timeout);
+        try {
+          ws?.close();
+        } catch {
+          // Ignore best-effort close failures.
+        }
         resolve(result);
       };
       const finishWithTransportFailure = (message: string, timedOut = false) => {
@@ -74,13 +97,30 @@ export async function execInPod(
           stderr: `${stderrData}${separator}${message}`,
         });
       };
+      const tryFinish = () => {
+        if (settled || !pendingResult || !stdoutEnded || !stderrEnded) return;
+        finish({
+          ...pendingResult,
+          stdout: stdoutData,
+          stderr: stderrData,
+        });
+      };
+
+      stdoutStream.on("end", () => {
+        stdoutEnded = true;
+        tryFinish();
+      });
+      stderrStream.on("end", () => {
+        stderrEnded = true;
+        tryFinish();
+      });
 
       const websocketPromise = exec
         .exec(
           namespace,
           podName,
           containerName,
-          command,
+          effectiveCommand,
           stdoutStream,
           stderrStream,
           stdinStream,
@@ -88,7 +128,8 @@ export async function execInPod(
           (status) => {
             // status.status is "Success" | "Failure"
             if (status.status === "Success") {
-              finish({ exitCode: 0, timedOut: false, stdout: stdoutData, stderr: stderrData });
+              pendingResult = { exitCode: 0, timedOut: false };
+              tryFinish();
               return;
             }
             // On failure, the exit code surfaces via
@@ -101,19 +142,25 @@ export async function execInPod(
             const exitCode = exitCodeCause?.message
               ? Number(exitCodeCause.message)
               : 1;
-            finish({ exitCode, timedOut: false, stdout: stdoutData, stderr: stderrData });
+            pendingResult = { exitCode, timedOut: false };
+            tryFinish();
           },
         );
 
       websocketPromise
-        .then((ws) => {
+        .then((webSocket) => {
+          ws = webSocket as WebSocketLike;
+          if (stdinStream && stdinPayload) {
+            stdinStream.removeAllListeners("end");
+            stdinStream.end(stdinPayload);
+          }
           ws.on("close", (code: number, reason: Buffer) => {
-            if (settled) return;
+            if (settled || pendingResult) return;
             const reasonText = reason.length > 0 ? `: ${reason.toString("utf-8")}` : "";
             finishWithTransportFailure(`Kubernetes exec websocket closed before status frame (${code})${reasonText}`);
           });
           ws.on("error", (err: Error) => {
-            if (settled) return;
+            if (settled || pendingResult) return;
             finishWithTransportFailure(`Kubernetes exec websocket failed before status frame: ${err.message}`);
           });
         })

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

@@ -0,0 +1,111 @@
+/**
+ * Fast-upload interceptor for the chunked-shell file transfer protocol used by
+ * `@paperclipai/adapter-utils` command-managed runtimes.
+ *
+ * The normal path writes files through many shell execs:
+ *   1. mkdir/rm/touch `<target>.paperclip-upload.b64`
+ *   2. append many base64 chunks with printf
+ *   3. base64-decode the temp file into the final target
+ *
+ * On Kubernetes each exec is a new WebSocket round trip. This state machine
+ * recognizes that exact protocol, buffers the base64 chunks in the plugin
+ * worker, and lets the caller flush the final payload through one exec.
+ * Pattern drift or missing state falls through to the original exec path.
+ */
+import { posix as pathPosix } from "node:path";
+
+const INIT_RE =
+  /^mkdir -p '([^']+)' && rm -f '([^']+)\.paperclip-upload\.b64' && : > '\2\.paperclip-upload\.b64'$/;
+const CHUNK_RE =
+  /^printf '%s' '([A-Za-z0-9+/=]+)' >> '([^']+)\.paperclip-upload\.b64'$/;
+const FINALIZE_RE =
+  /^base64 -d < '([^']+)\.paperclip-upload\.b64' > '\1' && rm -f '\1\.paperclip-upload\.b64'$/;
+
+const MAX_BUFFER_BYTES = 100 * 1024 * 1024;
+
+export interface FastUploadFlush {
+  targetPath: string;
+  payload: Buffer;
+}
+
+export type FastUploadDecision =
+  | { action: "ack"; reason: string }
+  | { action: "flush"; flush: FastUploadFlush }
+  | { action: "passthrough"; reason: string };
+
+interface BufferedUpload {
+  targetPath: string;
+  chunks: string[];
+  totalBase64Chars: number;
+}
+
+export class FastUploadInterceptor {
+  private readonly buffers = new Map<string, BufferedUpload>();
+
+  decide(command: string): FastUploadDecision {
+    const initMatch = INIT_RE.exec(command);
+    if (initMatch) {
+      const dir = initMatch[1];
+      const targetPath = initMatch[2];
+      if (pathPosix.dirname(targetPath) !== dir) {
+        return { action: "passthrough", reason: "init dir/target mismatch" };
+      }
+
+      this.buffers.set(`${targetPath}.paperclip-upload.b64`, {
+        targetPath,
+        chunks: [],
+        totalBase64Chars: 0,
+      });
+      return { action: "ack", reason: `init upload to ${targetPath}` };
+    }
+
+    const chunkMatch = CHUNK_RE.exec(command);
+    if (chunkMatch) {
+      const base64Chunk = chunkMatch[1];
+      const targetPath = chunkMatch[2];
+      const tempPath = `${targetPath}.paperclip-upload.b64`;
+      const upload = this.buffers.get(tempPath);
+      if (!upload) {
+        return { action: "passthrough", reason: "chunk without prior init" };
+      }
+
+      if (upload.totalBase64Chars + base64Chunk.length > (MAX_BUFFER_BYTES * 4) / 3) {
+        this.buffers.delete(tempPath);
+        return { action: "passthrough", reason: "buffer cap exceeded" };
+      }
+
+      upload.chunks.push(base64Chunk);
+      upload.totalBase64Chars += base64Chunk.length;
+      return { action: "ack", reason: `buffered ${base64Chunk.length} base64 chars` };
+    }
+
+    const finalizeMatch = FINALIZE_RE.exec(command);
+    if (finalizeMatch) {
+      const targetPath = finalizeMatch[1];
+      const tempPath = `${targetPath}.paperclip-upload.b64`;
+      const upload = this.buffers.get(tempPath);
+      if (!upload) {
+        return { action: "passthrough", reason: "finalize without buffered state" };
+      }
+
+      this.buffers.delete(tempPath);
+      return {
+        action: "flush",
+        flush: {
+          targetPath: upload.targetPath,
+          payload: Buffer.from(upload.chunks.join(""), "base64"),
+        },
+      };
+    }
+
+    return { action: "passthrough", reason: "no upload pattern" };
+  }
+
+  reset(): void {
+    this.buffers.clear();
+  }
+
+  get pendingCount(): number {
+    return this.buffers.size;
+  }
+}

packages/plugins/sandbox-providers/kubernetes/test/unit/plugin.test.ts

@@ -1,5 +1,6 @@
 import { describe, it, expect } from "vitest";
 import plugin, {
+  buildSandboxExecCommand,
   buildSandboxExecShellCommand,
   extractAdapterEnvFromProcess,
 } from "../../src/plugin.js";
@@ -161,4 +162,21 @@ describe("plugin", () => {
       }),
     ).toBe("pnpm test -- --runInBand");
   });
+
+  it("passes command and args directly to Kubernetes exec", () => {
+    expect(
+      buildSandboxExecCommand({
+        command: "sh",
+        args: ["-c", "printf '%s' ok"],
+      }),
+    ).toEqual(["sh", "-c", "printf '%s' ok"]);
+  });
+
+  it("wraps command-only execution in a login shell", () => {
+    expect(
+      buildSandboxExecCommand({
+        command: "pnpm test -- --runInBand",
+      }),
+    ).toEqual(["/bin/sh", "-lc", "pnpm test -- --runInBand"]);
+  });
 });

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

@@ -17,6 +17,8 @@ describe("execInPod", () => {
   it("returns success when the Kubernetes exec status callback reports success", async () => {
     execMock.mockImplementation((_namespace, _pod, _container, _command, stdout, _stderr, _stdin, _tty, statusCallback) => {
       stdout.write("ok\n");
+      stdout.end();
+      _stderr.end();
       statusCallback({ status: "Success" });
       return Promise.resolve(new EventEmitter());
     });
@@ -49,4 +51,31 @@ describe("execInPod", () => {
     expect(result.timedOut).toBe(true);
     expect(result.stderr).toContain("Kubernetes exec timed out after 5ms");
   });
+
+  it("wraps stdin commands with a byte-counted head prefix", async () => {
+    let observedCommand: string[] | undefined;
+    let observedStdin = "";
+    let observedStdinFinished = false;
+
+    execMock.mockImplementation((_namespace, _pod, _container, command, stdout, stderr, stdin, _tty, statusCallback) => {
+      observedCommand = command;
+      stdin?.on("data", (chunk: Buffer) => {
+        observedStdin += chunk.toString("utf8");
+      });
+      stdin?.on("finish", () => {
+        observedStdinFinished = true;
+      });
+      stdout.end();
+      stderr.end();
+      statusCallback({ status: "Success" });
+      return Promise.resolve(new EventEmitter());
+    });
+
+    await execInPod({} as never, "ns", "pod-1", "agent", ["base64", "-d"], "abc");
+    await Promise.resolve();
+
+    expect(observedCommand).toEqual(["/bin/sh", "-c", "head -c 3 | 'base64' '-d'"]);
+    expect(observedStdin).toBe("abc");
+    expect(observedStdinFinished).toBe(true);
+  });
 });

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

@@ -0,0 +1,72 @@
+import { describe, expect, it } from "vitest";
+import { FastUploadInterceptor } from "../../src/upload-interceptor.js";
+
+describe("FastUploadInterceptor", () => {
+  it("collapses the adapter-utils chunked upload protocol into one flush", () => {
+    const interceptor = new FastUploadInterceptor();
+    const target = "/workspace/.paperclip-runtime/skills.tar";
+    const chunkA = Buffer.from("hello ").toString("base64").slice(0, 4);
+    const chunkB = Buffer.from("hello ").toString("base64").slice(4) + Buffer.from("world").toString("base64");
+
+    expect(
+      interceptor.decide(
+        `mkdir -p '/workspace/.paperclip-runtime' && rm -f '${target}.paperclip-upload.b64' && : > '${target}.paperclip-upload.b64'`,
+      ),
+    ).toMatchObject({ action: "ack" });
+    expect(interceptor.pendingCount).toBe(1);
+
+    expect(
+      interceptor.decide(`printf '%s' '${chunkA}' >> '${target}.paperclip-upload.b64'`),
+    ).toMatchObject({ action: "ack" });
+    expect(
+      interceptor.decide(`printf '%s' '${chunkB}' >> '${target}.paperclip-upload.b64'`),
+    ).toMatchObject({ action: "ack" });
+
+    const decision = interceptor.decide(
+      `base64 -d < '${target}.paperclip-upload.b64' > '${target}' && rm -f '${target}.paperclip-upload.b64'`,
+    );
+    expect(decision.action).toBe("flush");
+    if (decision.action !== "flush") throw new Error("expected flush");
+    expect(decision.flush.targetPath).toBe(target);
+    expect(decision.flush.payload.toString("utf8")).toBe("hello world");
+    expect(interceptor.pendingCount).toBe(0);
+  });
+
+  it("passes through chunks and finalizers without a matching init", () => {
+    const interceptor = new FastUploadInterceptor();
+    const target = "/workspace/file.bin";
+
+    expect(
+      interceptor.decide(`printf '%s' 'aGVsbG8=' >> '${target}.paperclip-upload.b64'`),
+    ).toMatchObject({ action: "passthrough", reason: "chunk without prior init" });
+    expect(
+      interceptor.decide(
+        `base64 -d < '${target}.paperclip-upload.b64' > '${target}' && rm -f '${target}.paperclip-upload.b64'`,
+      ),
+    ).toMatchObject({ action: "passthrough", reason: "finalize without buffered state" });
+  });
+
+  it("falls through when the init command does not match the target parent directory", () => {
+    const interceptor = new FastUploadInterceptor();
+
+    expect(
+      interceptor.decide(
+        "mkdir -p '/tmp' && rm -f '/workspace/file.bin.paperclip-upload.b64' && : > '/workspace/file.bin.paperclip-upload.b64'",
+      ),
+    ).toMatchObject({ action: "passthrough", reason: "init dir/target mismatch" });
+    expect(interceptor.pendingCount).toBe(0);
+  });
+
+  it("clears buffered uploads on reset", () => {
+    const interceptor = new FastUploadInterceptor();
+    const target = "/workspace/file.bin";
+
+    interceptor.decide(
+      `mkdir -p '/workspace' && rm -f '${target}.paperclip-upload.b64' && : > '${target}.paperclip-upload.b64'`,
+    );
+    expect(interceptor.pendingCount).toBe(1);
+
+    interceptor.reset();
+    expect(interceptor.pendingCount).toBe(0);
+  });
+});