Agent37 Hosts Your Agent Harness. Is Renting Infrastructure Better Than Running Your Own on Vercel or Modal?

Agent37 is a Y Combinator Fall 2026 startup that hosts agent harnesses for you, and its pricing page lists a 2 vCPU, 4 GB sandbox running all month at $4.76 (checked 1 October 2026). On Vercel Sandbox the same always-on shape works out to roughly $80 at 10% CPU use by our arithmetic, and on Modal to roughly $174. Those gaps are real, but they compare a hosting product with general-purpose compute, and Agent37's own page says it compares prices, not throughput.

Last checked: 13 October 2026.

What is Agent37 and what does it host?

Agent37 hosts "any agent harness": Hermes, OpenClaw, Claude Code, Codex, OpenCode, Grok, Pi, a custom harness or your own Docker image. Each of your customers gets one isolated sandbox with root on a Linux machine, a browser, a desktop and files that persist across sessions, sleep and restarts, according to the company.

Y Combinator's company page lists it in the Fall 2026 batch, founded in 2026 in New York City, with the one-liner "Persistent sandboxes for agents like hermes, openclaw, claude code". The launch post is titled "Agent37: Host any agent harness".

Extras the homepage lists: sleep when idle and wake on request, automatic backups with restore, spending limits, an authenticated web address per agent, cron-scheduled runs and 1,000+ app connections through Composio. For a deeper look at the open-source harnesses you might run there, see Hermes Agent vs OpenClaw vs Claude Code.

Who built Agent37?

The only active founder listed on YC is Vishnu Krishnaprasad, Founder/CEO. YC's profile lists earlier roles as Senior Software Engineer at Amazon and Engineering Manager at Quantcast, and a master's from Carnegie Mellon. The company site is agent37.com. No funding figure is published on YC's page or the company site.

Agent37 says it serves "over 100 companies". That is a company claim with no independent count.

How much does Agent37 cost compared with Vercel Sandbox and Modal?

Agent37 has no plans or subscription. You top up a prepaid balance that is spent per minute while a sandbox runs, at $0.80 per vCPU, $0.70 per GB of RAM and $0.09 per GB of disk per 730-hour month. A "Performance" tier costs 4x compute for higher CPU priority. New accounts get $5 of credit once a card is on file.

Vercel and Modal price differently, so the table below uses the units each vendor publishes (as of 13 October 2026).

Vercel's Active CPU excludes time spent waiting on I/O such as network requests, database queries or AI model calls. That matters for agents, which spend much of their time waiting on a model.

What does a month of an always-on agent actually cost?

For a 2 vCPU, 4 GB sandbox running 730 hours, Agent37 lists $4.76. The same shape costs roughly $80 on Vercel at 10% CPU use and about $174 on Modal. The Vercel and Modal figures are our own arithmetic from the published rates, before any plan credits.

Three caveats. Vercel Pro usage is charged against a $20 monthly credit, and Modal's Starter plan includes $30 a month of credits, which shrinks the gap for small workloads. Vercel's maximum session on Pro is 24 hours, so a persistent agent has to stop and resume. And Agent37's idle cost depends on sleep settings: an awake sandbox pays for compute even when idle, so you must enable auto-sleep or stop it. Idle, its 4 GB disk alone is $0.36 a month.

Model tokens, search and integrations are metered separately on Agent37 unless you bring your own keys.

Where does Agent37 beat Vercel and Modal?

Agent37 wins on price for the persistent, always-on pattern, and on fit: it is built around the idea that each customer gets their own agent. Its lifecycle controls (create, stop, restart, resize, update, delete), per-instance spend caps and cron runs come in the box, where on a general platform you assemble them yourself.

Isolation is a selling point as well. Agent37 says every sandbox runs under gVisor with its own filesystem and a hard disk quota, inbound traffic enters through Cloudflare's edge and needs your API key unless you make a port public, and outbound traffic is firewalled to the public internet. It lists SOC 2 Type I, with Type II in progress.

The company also reports that customer Boon cut its cost per agent from $85 a month to $4.94 a month, according to the YC launch post. That is a self-reported figure for one customer.

Where do Vercel Sandbox and Modal still win?

They win on scale, ecosystem and proven limits. Vercel documents 10,000 concurrent sandboxes on Pro, up to 32 vCPUs and 64 GB on Enterprise, and sits next to the hosting, functions and AI tooling many teams already use. If your agent is part of a Next.js product already on Vercel, keeping it there removes a vendor.

Modal offers GPU sandboxes (which require the gVisor runtime and are subject to preemption), region selection at 1.15 to 1.75x base prices and non-preemptible execution at 3x. Agent37's pages document no GPU support or region choice. If your harness needs a GPU or must run in a specific region, they do not currently say it can.

Standard compute on Agent37 also shares host resources, so performance is not guaranteed under contention. The Performance tier at 4x compute addresses that, which narrows the price gap for CPU-bound work.

Should you rent a harness host or run your own?

Rent if you run many small, mostly idle agents, one per customer or user, and you want persistence without writing the lifecycle layer. Build on Vercel or Modal if agents are short, bursty jobs, need GPUs, need large concurrency or must sit inside infrastructure you already pay for.

Related reading on this site: Hermes for Businesses vs Copilot Studio covers the enterprise side of running an open-source agent.

What's still unclear?

Performance is the biggest gap. Agent37's own pricing page says its comparison of 31 providers covers prices, not throughput, and no independent benchmarks of start-up time, CPU contention or reliability appear to be published. Its claims of "over 95% less than most sandbox providers" and of the lowest list rate among managed providers are the company's own.

Other open questions: the YC page carries no launch date, the company has one listed founder, and the pages do not describe region options, larger disks or GPU support. The cheap headline also depends on auto-sleep and on bringing your own model keys. And any hosted harness adds a vendor that holds your agent's files and connected accounts, so check what each integration can access.

Last checked: 13 October 2026. Prices change often, so confirm on the vendors' pages before you commit.