How to switch from E2B to Runtime by changing one import

Code written for E2B's SDK runs on Runtime unchanged, apart from the import. The same job costs 77% less. 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox cost $0.64 on Runtime, against $2.76 at E2B's published rates, checked 25 October 2026 (Runtime vs E2B). Both run each sandbox in a Firecracker microVM with its own kernel. The isolation model is the same kind.

The change

Terminalnpm install withruntime      # 0.11.2 or later; or: pip install withruntime (0.11.1 or later)

TypeScriptimport { Sandbox } from "withruntime/e2b"; // was: from "e2b"

Pythonfrom withruntime.e2b import Sandbox  # was: from e2b import Sandbox

E2B's code interpreter package changes the same way: withruntime/e2b/code-interpreter in JavaScript and withruntime.e2b.code_interpreter in Python.

Then give the process a key. Locally, any npx withruntime command connects the machine with one browser approval, and the SDK finds that connection by itself. On a server or in CI, set RUNTIME_API_KEY from your secret manager. Create a key at API keys, or run npx withruntime keys create --name app.

Test it without credit first

While you test, run the work on free usage so that no paid credit is used:

TypeScriptimport { Sandbox } from "withruntime/e2b";const sbx = await Sandbox.create();const result = await sbx.commands.run("python3 -c 'print(sum([125, 250, 375]))'");console.log(result.stdout);await sbx.kill();

Pythonfrom withruntime.e2b import Sandboxsbx = Sandbox.create()print(sbx.commands.run("python3 -c 'print(sum([125, 250, 375]))'").stdout)sbx.kill()

What stays the same

One thing differs on purpose. With no timeout, E2B deletes a sandbox after 300 seconds. Runtime pauses it instead, and keeps its memory and files as paused storage until you call kill().

What throws, and why that is safe

A call that Runtime handles differently, such as workload identity, throws NotSupportedError before anything happens. The message names what to use instead, so nothing runs partway. E2B.md in the package lists every mapping.

Two common replacements:

• Templates become custom images of the same name. Build your e2b.Dockerfile once with npx withruntime images build --dockerfile e2b.Dockerfile --name <template>. Then Sandbox.create("<template>") (or team/<template>:tag) starts from it.
• Long sessions need no change. The server keeps a timeoutMs of up to 24 hours. On a paid account, persistent: true keeps a sandbox running until you end it, even while idle.

When to port to Runtime's own calls

The import keeps your code running today. Moving to withruntime itself gives you calls that E2B's API has no equivalent for: exec that returns exitCode instead of throwing, forks of a running sandbox with its memory, network allow lists set on the host, secrets the sandbox never sees, and idlePauseSeconds. The calls map one to one (migration):

TypeScriptimport { Sandbox } from "withruntime";const box = await Sandbox.create();try {  await box.files.write("/workspace/invoice.py", "print(sum([125, 250, 375]))\n");  console.log((await box.exec("python3 /workspace/invoice.py", { check: true })).stdout);} finally {  await box.stop();}

Mistakes and how Runtime handles them

• An SDK older than 0.4.0. The withruntime/e2b entry point arrived in 0.4.0. Upgrade the package.
• Keeping only the E2B key. Runtime needs its own key. Set RUNTIME_API_KEY, or use the machine's saved connection.
• Forgetting that paused sandboxes are kept. A paused Runtime sandbox is kept while your account has credit, and its storage is billed until you delete it. Without credit, it is kept for seven days.
• Forgetting the welcome match. Credit you add within 30 days of signing up is matched, up to $1,000 in total.

Then check the saving on your own runs with runtime compare --from e2b (how to compare your costs).

Related

• E2B alternatives and E2B vs Daytona
• E2B pricing calculator
• JavaScript SDK and Python SDK

Sources

• E2B pricing, checked 25 October 2026

Facts on this page were checked on 26 October 2026.