Undisk vs E2B for Agent File Access

Undisk and E2B solve different problems for AI agents, but they appear side-by-side in platform engineering evaluations. This article provides an honest, data-backed comparison so you can decide which to use — or whether to use both.

The short answer: E2B gives your agents a place to run code. Undisk gives your agents a place to store files safely. If you need both, they work well together.

What E2B Does

E2B provides cloud-based sandboxes for AI agent code execution. Built on Firecracker microVMs, each E2B sandbox is an isolated Linux environment where agents can run Python, JavaScript, shell commands, and other code. Perplexity, Hugging Face, Vercel, and Cursor all use E2B for their AI-powered code execution features.

E2B’s strengths are clear: fast sandbox provisioning, strong isolation via microVMs, and excellent SDKs for Python and TypeScript. If your agent needs to execute code in a safe, isolated environment, E2B is a strong choice.

E2B sandboxes are ephemeral by default. When a sandbox is destroyed, its filesystem is gone. There is no built-in file versioning, no undo for file operations, and no audit trail of what the agent wrote or modified.

What Undisk Does

Undisk is a file workspace built specifically for MCP-compatible AI agents. Every file operation — write, create, delete, move — creates an immutable, content-addressed version. Any file can be restored to any prior state in under 50ms. Every mutation is logged with timestamps, agent identity, and content hashes.

Undisk does not execute code. It does not manage containers or VMs. It is purpose-built for one thing: making AI agent file operations safe, reversible, and auditable.

Feature Comparison

Where Undisk Leads

Per-File Versioning with Undo

Undisk versions every file mutation automatically. Every write_file, create_file, or delete_file call through MCP creates an immutable version with a SHA-256 content hash. Restoring a single file to any prior state takes under 50ms and leaves every other file in the workspace untouched.

E2B has no file versioning at all. If an agent overwrites a file in an E2B sandbox, the previous content is gone. The only recovery option is to destroy the sandbox entirely and start over — losing all progress on every other file.

This difference matters because AI agents make mistakes frequently. When 66% of developers say AI output is “almost right but not quite,” surgical undo becomes essential. Rolling back one bad file should not destroy twenty good ones.

Structured Audit Trails

Undisk records every file operation with timestamps, agent identity, operation type, file path, content hash before and after, and policy evaluation results. These logs are append-only, content-addressed, and retained per configurable policy (default 180 days).

E2B provides no audit trail for file operations. There is no log of which files were written, what they contained, or when operations occurred. For teams that need to review, audit, or comply with regulatory requirements, this is a significant gap.

Scoped File Permissions

Undisk supports path-level access control lists. You can grant an agent read-write access to /output/ while restricting /config/ to read-only and blocking /secrets/ entirely. Policies are versioned, auditable, and support glob patterns.

E2B’s isolation is at the sandbox level. Within a sandbox, the agent has full filesystem access. There is no mechanism to restrict access to specific paths or files within the sandbox environment.

EU AI Act Compliance Primitives

Undisk’s tamper-evident audit logs, configurable retention, and content-addressed versioning directly enable EU AI Act Article 12 record-keeping requirements. The compliance deadline for deployers of high-risk AI systems is December 2, 2027.

E2B has no compliance-specific features. No audit trails, no retention policies, no tamper-evident logging.

Where E2B Leads

Code Execution

E2B’s primary feature is sandboxed code execution. Agents can run Python, JavaScript, shell scripts, and other languages in isolated Firecracker microVMs. This is E2B’s core value proposition, and it does it well.

Undisk does not execute code. It is a file workspace, not a sandbox. If your agents need to run code, E2B (or Fly.io Sprites, Daytona, or Blaxel) is the right tool.

Sandbox Isolation

E2B provides full operating system-level isolation via Firecracker microVMs. Each sandbox has its own kernel, filesystem, network stack, and process space. This isolation model is ideal for running untrusted or agent-generated code.

Undisk isolates at the workspace level using Cloudflare Durable Objects. This provides strong data isolation but does not include process isolation since there are no processes to isolate — Undisk does not execute code.

Ecosystem Integrations

E2B has mature integrations with LangChain, OpenAI Agents SDK, CrewAI, and other agent frameworks. It is used by Perplexity, Hugging Face, Vercel, and Cursor in production. The SDK ergonomics are excellent — typically 3–5 lines to integrate.

Undisk is newer and has a smaller integration ecosystem. It speaks standard MCP, so any MCP-compatible client can use it, but framework-specific integrations are still developing.

When to Use Both

The strongest architecture for production AI agents combines E2B for compute with Undisk for persistent file storage:

1. Agent code runs in E2B — isolated execution with full Linux capabilities
2. Agent file outputs persist in Undisk — versioned, auditable, restorable
3. If the agent makes a bad write — restore the file in Undisk without destroying the E2B sandbox
4. When compliance reviews happen — export the audit trail from Undisk showing every file mutation

This is not a theoretical pattern. Any team running AI agents in production faces both problems: “where does the code run safely?” (E2B’s answer) and “where do the files live safely?” (Undisk’s answer).

The Bottom Line

E2B and Undisk are complementary tools solving different problems. E2B gives agents a safe place to execute code. Undisk gives agents a safe place to store files with full versioning, undo, and audit trails.

If you need code execution, choose E2B. If you need reversible file operations with compliance-grade audit trails, choose Undisk. If you need both — and most production AI platforms do — use them together.

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Frequently Asked Questions

Frequently Asked Questions

Can I use Undisk and E2B together?

Yes. Undisk and E2B are complementary, not competing. E2B provides sandboxed code execution environments — it runs your agent's code. Undisk provides versioned, persistent file storage — it manages your agent's files. A common pattern is to use E2B for compute and Undisk for durable file operations that need undo, audit trails, and compliance logging.

Does E2B support file versioning?

No. E2B provides basic file read and write operations within its sandbox, but does not version file mutations. If an agent overwrites a file in E2B, the previous content is gone. When the sandbox is destroyed, all files are lost unless explicitly exported. Undisk versions every write automatically and retains all prior versions.

Which is better for EU AI Act compliance?

Undisk. E2B does not provide audit trails, tamper-evident logs, or configurable retention policies. Undisk records every file operation with timestamps, agent identity, content hashes, and operation metadata — the primitives needed for EU AI Act Article 12 record-keeping. E2B has no compliance-specific features.

Can E2B undo a single file change?

No. E2B sandboxes are ephemeral by default. There is no undo, no rollback, and no version history for individual files. The only recovery option is to destroy the sandbox and create a new one. Undisk supports per-file, per-operation undo with sub-50ms restore latency.

Is E2B or Undisk faster for file operations?

For file read/write latency, Undisk targets under 10ms at the edge via Cloudflare's global network. E2B file operations run inside a remote Firecracker microVM, typically adding 50–100ms of network latency. For code execution (which Undisk does not do), E2B is the clear choice.

Does Undisk support code execution like E2B?

No. Undisk is a file workspace, not a sandbox. It does not execute code, manage containers, or provide GPU access. If you need code execution, use E2B (or Fly.io Sprites, Daytona, or Blaxel) and connect Undisk as the persistent file layer.