Runtime vs Blaxel

Runtime bills the CPU your agent uses and costs 77% less than Blaxel while running an agent that mostly waits on a model.

The saving: 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox cost $0.64 on Runtime and $2.76 on Blaxel. At 100,000 runs a month that is $63.89 against $276.00, $212 a month saved.

Where Runtime is better

• Lower cost while running. Blaxel bills $0.0000115 per GB of memory per second of active time, $0.0414 per GB-hour, and CPU comes with the memory. Runtime charges $0.0075 per GiB-hour of memory and measured CPU at $0.025 per vCPU-hour.
• Cheaper even when busy. With both CPUs working the whole time, the example job costs $1.33 on Runtime and $2.76 on Blaxel.
• CPU and memory chosen apart. Blaxel sets a sandbox's CPU from its memory: 8 GB gets 4 cores. On Runtime you choose vCPUs and memory separately, so a CPU-heavy job does not pay for memory it does not need.
• Cheaper to keep paused work. A paused Runtime sandbox keeps its files, memory and processes for $0.08 per GB a month, for 1 to 365 days. Blaxel's standby snapshots cost $0.20 per GB a month.
• Your agent sets itself up. It runs npx withruntime sandbox run --trial -- ..., shows you a link, and starts once you approve in the browser. No API key goes into a prompt or a config file, and the MCP server reuses the same connection.
• Guardrails for agents. Give an agent a read-only key or a daily spending limit per key, and cap any create with maxCostMicros. Every write takes an idempotency key, so a lost response never creates a second sandbox.

At a glance

Blaxel's figures come from its public pricing and documentation, checked 23 September 2026.

	Runtime	Blaxel
Isolation	Firecracker microVM, own kernel	Lightweight virtual machines
CPU billing	$0.025 per vCPU-hour of measured CPU, with a small floor	Included with memory; 8 GB gets 4 cores
Memory billing	$0.0075 per reserved GiB-hour	$0.0000115 per GB-second of active time
Paused storage	$0.08 per GB-month; files, memory and processes	$0.20 per GB-month snapshot; files and processes
Plan fee	None; prepaid credit from $10	None; tiers grow with credit added
Free start	50 sandbox hours, no card	Up to $200 of credit

Cost for the same job

Take 1,000 runs of a 2 vCPU, 4 GiB sandbox (4 GB on Blaxel). Each run lasts 60 seconds and keeps the CPU busy for 20 CPU-seconds: an agent that spends most of its time waiting for a model.

TextRuntime  CPU    1,000 × 20 s / 3,600 × $0.025      = $0.14         Memory 1,000 × 60 s / 3,600 × 4 × $0.0075 = $0.50         Total                                        $0.64Blaxel   Memory 1,000 × 60 s × 4 × $0.0000115      = $2.76

• Saving: 77%, or $2.12 per 1,000 runs.
• Per month: at 100,000 runs, $63.89 on Runtime against $276.00 on Blaxel.
• Busier work: with both CPUs busy for the whole minute, $1.33 on Runtime against $2.76 on Blaxel.

The Blaxel figure assumes each sandbox goes to standby the moment its run ends; Blaxel's docs say standby starts about 15 seconds after the last connection closes. Storage, network, taxes and free credit are left out of both. See pricing for Runtime's terms.

How to switch

Give your coding agent the one instruction in migration. It replaces the Blaxel calls on a branch, tests them on the free trial, and tells you what you save each month. Your old code stays on the main branch until you merge.

Runtime:

TypeScriptimport { Sandbox } from "withruntime";const box = await Sandbox.create({ funding: "trial" });try {  console.log((await box.exec("python3 -c 'print(6 * 7)'", { check: true })).stdout);} finally {  await box.stop();}

When Blaxel may fit better

• Idle for free, back in milliseconds. A Blaxel sandbox goes to standby by itself when connections close, costs nothing for compute there, and resumes in about 25 ms.
• Very large fleets. Blaxel's top tier runs over 100,000 sandboxes at once.

Sources

Checked 23 September 2026.

• Blaxel pricing
• Blaxel sandboxes
• Runtime pricing, security and products