[CahidArda]

Stack: #100 → #102 → #103 → #104 → #106. Merge in order.

Adds Upstash Redis stores for TanStack AI's sandbox and MCP packages, under two new entry points.

Sandbox snapshots (@upstash/agentkit-tanstack-ai/sandbox)

Sandbox files survive after the provider sandbox is gone, any server can resume a thread's sandbox, and you can fork a conversation (files included) from an earlier checkpoint.

import { createSandboxSnapshots, withSandbox } from "@tanstack/ai-sandbox";
import { upstashLocks } from "@upstash/agentkit-tanstack-ai";
import { upstashPersistence } from "@upstash/agentkit-tanstack-ai/persistence";
import {
  upstashSandboxCheckpointStore,
  upstashSandboxInstanceStore,
} from "@upstash/agentkit-tanstack-ai/sandbox";

const persistence = upstashPersistence({ bucket: Bucket.fromEnv() });
const instances = upstashSandboxInstanceStore();
const snapshots = createSandboxSnapshots({
  persistence,
  checkpoints: upstashSandboxCheckpointStore(), // same Redis + prefix as `persistence`
  instances,
  locks: upstashLocks(),
});

chat({
  adapter,
  messages,
  threadId,
  middleware: [withPersistence(snapshots.persistence), withSandbox(sandbox, { instances, snapshots })],
});

await snapshots.fork({ threadId, checkpointId, destinationThreadId: "thread-2" });

MCP stores (@upstash/agentkit-tanstack-ai/mcp)

MCP tasks, event subscriptions and MCP Apps sessions are shared across instances and survive restarts.

import { upstashMcpEventStore, upstashMcpTaskStore } from "@upstash/agentkit-tanstack-ai/mcp";

const server = createMCPServer({ name: "tools", version: "1.0.0", tools, taskStore: upstashMcpTaskStore() });

const mcp = await createMCPClient({
  transport: { type: "http", url: "https://mcp.example.com/mcp" },
  experimental_events: { store: upstashMcpEventStore() },
});

upstashMcpSessionStore() stores MCP Apps server descriptors. Transport headers can be encrypted with encryptionKey, and code-only fields like needsApproval come back through a resolve callback. If one is missing, get returns null, so a widget never reaches a server without its approval gate.

Also

• upstashPersistence({ bucket }) is now typed with a required blobs store, so it can be passed straight to createSandboxSnapshots().
• New optional peers: @tanstack/ai-sandbox >=1.0.0, @tanstack/ai-mcp >=1.0.0. The root entry doesn't import them.

Tested against TanStack's own sandbox conformance suites on live Redis, plus MCP store tests. Changeset: minor for @upstash/agentkit-tanstack-ai.

[linear-code]

DX-3285