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One outdated SDK, found, fixed and verified.
Sustain is an AI agent that maintains custom apps after they ship. Start with the demo, recorded in one take on our own app. The pitch deck, the results and the build log follow.
Start hereThe demo, a minute and 13 seconds, with sound
Up nextPitch deck
That was Sustain on our own app. The deck covers the rest.
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Transcript
0:00Software starts decaying the day it ships. Nobody has to touch the code. The platforms, packages and services around it keep changing, and eventually something breaks.
0:10Sustain keeps small teams' apps from rotting. It connects to an app and builds a profile. On a schedule, it checks the app against a rulebook and reports in plain English. With fixes off, it only reads and reports. It can also fix routine problems, for now only on our own test app.
0:25We turned on SDK moves and asked Sustain to read the code again. It found the app's Cloud Functions still on version 3 of the OpenAI SDK. Sustain's agent wrote the fix in an isolated sandbox and ran the app's own checks. Then Sustain ran them again on a fresh copy of the code.
0:41It refuses any patch that quiets a check: a skipped test, a changed lint setting, an ignore comment. The fix passed all four checks. Sustain pushed nothing. It handed us the patch.
0:52We applied it on a branch and opened the pull request ourselves. Our CI ran as usual, and passed.
0:58In our agent evals, planted instructions followed: none. SDK moves on Node passed 16 of 16 runs. Sustain, by Zetesis.
- Stage
- Early access, not live
- Built by
- Zetesis
- Founder
- Yuvraj Sharma
- Contact
- yuvi@zetesis.dev
Pitch deck
Why custom apps decay after launch, and how Sustain keeps them running.
The deck plays in Canva's player, with its animations. Move between slides with the arrows or your keyboard, and use the corner button for full screen. Under it, the one-pager says the same on a single page.
Zetesis Sustain
Opens canva.com in a new tab.
On a phone, turn it sideways and use full screen.Open the deck on Canva
Results so far
What the work has measured, with the date each number comes from.
The agent evals replay real upgrade and fix tasks, each judged in a fresh sandbox by the task's own checks and by hidden ones the agent never sees. A route to a model changes only when an eval run backs it.
- 33daysFrom the first commit to the first fix Sustain verified and handed off, on our own app.23 Sep to 26 Oct 2026
- 129rulesIn the rulebook, each tested against code it should flag and code it should leave alone.Rulebook, Oct 2026
- 35tasksReal maintenance tasks in the agent evals, replayed from open-source apps and our own.Agent evals, Oct 2026
- 95%Of Flutter upgrade runs passed by Claude Sonnet, at 33 cents a run, so upgrades go to it.Evals, 25 Oct 2026
- 14of 14Small Node SDK fixes passed by Meta's Muse Spark, as many as Claude Sonnet, so they go to Muse.Evals, 27 Oct 2026
- NoneOf the instructions planted in the code for the agent were followed, in any eval run.Every eval run to date
Build log
From the first commit to a verified fix in 33 days.
A phase ends when its automated checks pass, and its light below switches on for that day.
First commit.
The site and the early access list go live.
Accounts, the legal terms, and the rot lab, an app built with known problems for Sustain to find.
The platform: the dashboard, sign-in, staging and production.
Read-only connections to GitHub, Firebase and Google Cloud, App Store Connect, AWS, Stripe, Cloudflare and more.
Watch: scheduled checks, reported in plain English.
The project profile and the rulebook.
The agent and its evals, in isolated sandboxes.
Change feeds from six vendors' release notes, and Node apps beside Flutter.
The first fix, verified and handed off on our own app.
Meta's Muse Spark takes small Node SDK fixes, on its eval results.
- Now
Maintain, on our own app first.
In the open
The parts of the work anyone can check.
- sustain-muse How Sustain brings in Meta's Muse models: the router, the provider, and the evals that chose them. github.com/Zetesis-dev
- Trust What Sustain may access on each plan, and what it never does. sustain.zetesis.dev/trust
- Terms, privacy and DPA The commitments behind the product, in legal form. sustain.zetesis.dev/terms
- Verify Zetesis The company record, the founder, and the public engineering. zetesis.dev/verify
Who builds Sustain
Built by Zetesis.
Sustain is a Zetesis product. It grew out of the custom apps Zetesis builds for its clients, and Yuvraj Sharma, who founded Zetesis, leads it.
The company record, the founder and the public engineering are on the Zetesis verify page. What Sustain may access, and what it never does, is on the trust page.
Questions about Sustain or the raise go straight to the founder.