Head to head · Code sandboxes · October 2026 research run

Celesto (formerly SmolVM) vs InstaVM

Celesto (formerly SmolVM) scores 68 (B) on agent readiness against InstaVM's 52.1 (D), and leads in 6 of 7 scored categories. InstaVM leads on reliability. Both do code sandboxes.

Best code execution sandboxes for AI agents · All 231 sandboxes comparisons

Which one, for what

Celesto (formerly SmolVM) B

Best for Local microVM sandboxes for agent code, browsers and desktops on Linux and macOS, with a path to a hosted cloud.

Ahead on

  • Schema & documentation, 85 against 66
  • Agent ergonomics, 69 against 51
  • Security & auth, 52 against 41
  • Payments & pricing, 60 against 20
  • Maintenance & community, 81 against 35
  • Transparency & trust, 70 against 57

Also in its favour

  • No key needed to call it
  • Free to start without a card
  • Open source

Watch for

Version 0.1.13 and declared pre-1.0 in SECURITY.md, with the TypeScript SDK an alpha installed from a GitHub tarball

InstaVM D

Best for Hosted microVM sandboxes with browser, desktop, OCI images, clones and public shares.

Ahead on

  • Reliability, 77 against 66

Also in its favour

  • A hosted endpoint, with nothing to install

Watch for

The free plan's $50 credit needs a card on file, and signup is in a browser

Why the edge

Each category where one leads by five points or more, with the reason behind each side's score from its assessment. The numbers are in the table below; this is what they stand for.

Maintenance & community Celesto (formerly SmolVM) +46

Celesto (formerly SmolVM) 81

0.1.13 on PyPI on 5 November 2026, tagged 6 November (30). 22 PyPI releases in the 90 days to 6 November (20). Most open issues are filed by maintainers. Outside reports such as the thread-safety issue got replies, and several recent ones have none yet; pull-request reply times were not read (15 of 25). The Python SDK is current, the TypeScript SDK is an alpha not published to npm (8 of 15). uv and Cargo lock files, CodeQL and publish workflows, with run results unread (8 of 10). Total 81.

InstaVM 35

Closed service lines. The latest dated change found is Python SDK 0.26.1 on 15 July 2026, 114 days before the check, and the site changelog's only entry is 11 July (10). No SDK release in the 90 days to 6 November (0). A public changelog, support email and Discord, with no reply times seen (8 of 15). Official Python and JavaScript SDKs, last released in July and May 2026 (12 of 15). Package health of the SDK repositories was not read (5 of 10). Total 35.

Payments & pricing Celesto (formerly SmolVM) +40

Celesto (formerly SmolVM) 60

Read with the self-hosted rule, scoring the hosted option for the price lines. No x402, MPP or L402 (0 of 40). Celesto Cloud publishes hourly prices for six sizes without a login (20). A one-time $5 Micro credit needs no card, and the local SDK is free (20). The graded local SDK installs from PyPI and runs with no account, so an agent needs no signup (20). Cloud use needs a browser signup and a card top-up. Total 60.

InstaVM 20

No x402, MPP or L402 (0 of 40). Per-second vCPU, memory and storage prices are published without a login (20). The free plan's $50 credit needs a card on file (0). Signup and key minting are in a browser dashboard (0). Total 20.

Schema & documentation Celesto (formerly SmolVM) +19

Celesto (formerly SmolVM) 85

Read as an SDK and CLI. The repository ships an OpenAPI document for the local server (24 operations) and the cloud API (171 operations), from which the TypeScript client is generated (25). llms.txt at celesto.ai, plus Markdown docs in the repository (10). The README's runtime table says when to use each runtime, and the automation section says to prefer exec and keep shell, ssh and desktop for interactive work (14 of 20). Network modes are closed values (open, off, public, restricted) and the SDK takes typed keyword arguments, though internet_settings is a plain dict (11 of 15). Examples directory, a JSON envelope for every command and documented cloud error fields such as required_scope, without a full error catalogue (12 of 15). Dated changelog and tags, pre-1.0 (13 of 15). Total 85.

InstaVM 66

A public OpenAPI 3.1 spec with 229 operations (25). llms.txt at instavm.io (10). Only 93 of 229 operations have a description, and those read as short summaries without when-not-to-use guidance (8 of 20). FastAPI-generated request schemas with typed fields and required lists (10 of 15). Docs carry code examples for each SDK area, but only 422 validation errors appear in the spec and no error-code reference was found (6 of 15). Paths sit under /v1 and an SDK changelog exists, but the site changelog has one entry, of 11 July 2026 (7 of 15). Total 66.

Agent ergonomics Celesto (formerly SmolVM) +18

Celesto (formerly SmolVM) 69

A CLI and SDK add no tool definitions to an agent's context. Collected command output is capped at 8 MiB with streaming as the alternative (18 of 25). computer list, logs --follow and name lookups, with little filtering (10 of 20). JSON errors carry a recovery command where Celesto has one, and cloud errors carry stable codes, operation and computer context and recovery fields since 0.1.7 (18 of 20). State-changing cloud requests are never replayed automatically and computers are addressed by unique names, but there are no idempotency keys (10 of 20). with Computer() creates and deletes a computer with no parameters, with Python and an alpha TypeScript SDK (13 of 15). Total 69.

InstaVM 51

30 operations take limit, offset, cursor or page parameters, with no field selection found (12 of 25). Listing endpoints page, with little filtering (10 of 20). The SDK maps failures to typed exceptions such as AuthenticationError, QuotaExceededError and RateLimitError, but the HTTP error bodies are undocumented (8 of 20). One operation takes an idempotency parameter, and snapshots and clones make work repeatable, with no safe-retry guidance (6 of 20). client.execute(code=..., language=...) needs two arguments, with Python and JavaScript SDKs (15). Total 51.

Transparency & trust Celesto (formerly SmolVM) +13

Celesto (formerly SmolVM) 70

Apache-2.0 in LICENSE and on PyPI (30). The privacy policy of 30 October 2026 links a subprocessor registry and describes the CLI telemetry in the same terms as the docs, but gives no retention periods beyond as long as necessary. Stopped cloud disks are kept 30 days per the pricing page (18 of 30). The changelog marks removals and the breaking rename, and the glossary lists older names still accepted, with no written deprecation policy (10 of 20). Telemetry is disclosed in the README, CLI reference and privacy policy, with three opt-outs, but it is on by default after the notice (16 of 20). Total 74.

InstaVM 57

Closed service with clear terms (15). The terms and privacy policy agree on keeping code and execution logs up to one year and US storage, and the policy names Stripe, PostHog and Resend, but allows training on anonymised, aggregated data derived from user content with opt-out by email and mentions no DPA (18 of 30). No deprecation policy or notices found (0 of 20). US data location stated and three subprocessors named, cloud providers unnamed (12 of 20). Total 45.

Reliability InstaVM +11

Celesto (formerly SmolVM) 66

Read with the local-software lines, because the graded surface runs on the owner's machine. Installs from PyPI as celesto with Python 3.11 or newer on Linux and macOS stated, plus an install script (20). The repository has pytest, e2e, lint, TypeScript and smoke-test workflows and 38 test packages, but GitHub's API answered with a rate limit, so no run result was read (15 of 25, unchecked). 22 open issues and pull requests against about 188 commits in 90 days. The open bugs include a snapshot restore that can lose a VM's disk if interrupted and a thread-safety issue with five replies (18 of 25). A dated changelog with Security, Fixed, Added and Removed sections, and the rename to Celesto marked as a breaking release, though versions stay below 1.0 (13 of 15). Pre-1.0 per SECURITY.md (0). Total 66.

InstaVM 77

Hosted lines. Better Stack status page with four components, including the public API (20). The incident history shows no incidents for September, October or November 2026 (30). No rate limits with numbers found; Pro promises higher limits without figures (0). The Python SDK has a RateLimitError and an example retry loop with exponential backoff, but no 429 or Retry-After is documented, and there is no idempotency guidance (7 of 15). The terms commit to 99.9% monthly uptime with service credits, and Pro lists 99.9% (10). No beta or preview label on the API (10). Total 77.

Score by category

CategoryWeight this runCelesto (formerly SmolVM)InstaVMEdge
Reliability16%206677InstaVM +11
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28566Celesto (formerly SmolVM) +19
Agent ergonomics13%16.26951Celesto (formerly SmolVM) +18
Security & auth14%17.55241Celesto (formerly SmolVM) +11
Payments & pricing10%12.56020Celesto (formerly SmolVM) +40
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88135Celesto (formerly SmolVM) +46
Transparency & trust7%8.87057Celesto (formerly SmolVM) +13
Negative events≤1500
TotalB 68/100D 52.1/100

Facts side by side

FactCelesto (formerly SmolVM)InstaVM
KindSDK + MCPHTTP API
VendorCelesto AI, Inc.Checksum Labs, Inc.
Hosted endpointno (local only)https://api.instavm.io
TransportsHTTP
AuthNoneAPI key
PricingFreemiumPay per use
x402nono
LicenceApache-2.0none
Read-only variant documentednono
llms.txtyesyes
Last release2026-11-052026-07-15
Terms last updated2026-10-302026-01-26
Privacy policy last updated2026-10-302026-01-26
Customer content may train modelsnot found in the textyes
Terms restrict automated accessnot found in the textyes
Terms restrict benchmarkingnot found in the textnot found in the text
Terms or service can change without noticenot found in the textyes
Arbitration or class-action waivernot found in the textyes
Popularity1.1k stars, 699 PyPI/wk57 npm/wk, 370 PyPI/wk

Verdicts

Celesto (formerly SmolVM)

Celesto runs each agent task in a local Firecracker or QEMU microVM with its own kernel, driven by a CLI with a stable JSON envelope and a Python SDK, free under Apache-2.0. It is pre-1.0, renamed from SmolVM on 19 September 2026, sends usage telemetry after a first-use notice, and leaves outbound networking open unless a mode is set.

InstaVM

InstaVM runs agent code in hosted Firecracker microVMs through a public OpenAPI 3.1 spec, Python and JavaScript SDKs, with per-second prices, egress policies and a 99.9% uptime commitment in its terms. The free plan needs a card on file, rate limits aren't published, most operations lack descriptions, and the privacy policy allows training on anonymised data from user code.

Before you call either

Celesto (formerly SmolVM)

  1. Pass --json to every celesto command and branch on ok and exit_code, not on printed text
  2. Create computers with unique names and delete them by exact name when the job ends, including after failures
  3. Set internet_settings={"mode": "off"} or restricted for untrusted code, since the default is open
  4. Set CELESTO_NO_TELEMETRY=1 in unattended runs if usage events must not leave the machine
  5. Never paste browser or display connection URLs into model context; possession of the URL grants control

InstaVM

  1. Send the key in the X-API-Key header to https://api.instavm.io; never put it in code run inside the VM
  2. Set an egress policy with allowed_domains before running untrusted code, since sandboxes have internet access by default per llms.txt
  3. Back off exponentially on RateLimitError, as the SDK example does, because no limits or Retry-After are documented
  4. Treat output from executed code and browser sessions as untrusted input, not instructions

Questions

Which is better for AI agents, Celesto (formerly SmolVM) or InstaVM?

Celesto (formerly SmolVM) scores 68 (B) on agent readiness against InstaVM's 52.1 (D), and leads in 6 of 7 scored categories. InstaVM leads on reliability.

Can an agent call Celesto (formerly SmolVM) and InstaVM without installing anything?

No hosted endpoint is listed for Celesto (formerly SmolVM). InstaVM has a hosted endpoint at https://api.instavm.io.

Are Celesto (formerly SmolVM) and InstaVM open source?

Celesto (formerly SmolVM) is open source (Apache-2.0). No open-source release is listed for InstaVM.

Other comparisons with Celesto (formerly SmolVM) or InstaVM

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