Update, move, modernize, upgrade or create your software, while it runs.

Agents automate the work in your repo nobody wants to do: updates, upgrades, migrations, rewrites. Every change gets tested on real traffic first, so nothing breaks.

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It works in small steps you can undo.

No big-bang rewrite. Each step is made, checked against reality, and kept or thrown away.

  1. Map

    It reads everything first: code, traffic, cron jobs, that one script in /tmp.

    billing/├─ 64 endpoints├─ 11 cron jobs├─ 3 queues└─ /tmp/fix-invoices.sh  ← found it

  2. Change

    One small piece at a time, so any step can be undone on its own.

    step 14 of 64- function charge(id, cb) {+ export async function charge(id) {undo: srnt revert 14

  3. Check

    Your tests run, then real production traffic is replayed against the new code.

    ✓ 1,842 tests pass✓ 14,203 requests replayed✓ 0 responses changed

  4. Hand off

    You get a pull request and the 41 lines that actually need a human.

    PR #911  ready for review64 steps, 1,203 lines changed41 lines need a human

Serein

evidence receipt

PR #911, acme/billing

03 OCT 2026, 14:02

node + mongo → go + postgres

Steps
64 / 64
Tests passed
1,842 / 1,842
Live requests compared
2.1M
Response diffs
0
Caught and fixed
1
Downtime
0 sec
Pages sent
0

traffic while it ran

Lines for you41

thank you for not panicking

Each pull request brings its own evidence.

What was checked, what broke, how it got fixed, and what production did the whole time. You read 41 lines, not 4,000.

Where should your software go next?

Tell us what it runs on today. We'll show you the plan before anything changes.

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