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Ship breaking changes.Break nothing.

When an API or SDK changes, Releo writes the migration for every repository that calls it, replays real traffic to prove the behavior is identical, and blocks the merge if it isn't.

  • Free during beta
  • Works on the repos you already have
  • Proof attached to every PR
Or talk to the founders
BREAKINGstripe-like · v2024-06 → v2025-11 · major

Major version upgrade across your whole fleet

14 breaking changes · 212 endpoints · 6 teams · detected 4 minutes after release

Affected repos

38

Call sites patched

1,204

Requests replayed

0

Open divergences

0

billing-service
Queued
checkout-web
Queued
ledger-worker
Queued
partner-sdk-node
Queued
invoicing-cron
Queued

+ 33 more repositories in this rollout

envelope: status · headers · body · timingtolerance: p95 latency ±5%policy: block on divergence

Product preview · one upstream change, five repositories, every patch proven before merge

Every company runs on APIs. Every API changes.

API economy by 2030
$17.3T1
of organizations are API-first
82%2
a week per developer on maintenance
17.3h3
median time to adopt a breaking change
34 days
01The problem

The release took an hour. The fallout took 36 days.

Every API you depend on will change. Here is how one ordinary breaking change plays out at a company that does everything right.

  1. Day 0

    Your payments provider ships v2.

    A changelog email lands. customer is renamed to customer_id, amounts move to minor units, and succeeded becomes paid. Nobody owns it.

  2. Day 3

    It becomes a ticket.

    The migration is scoped at "a day or two" and parked behind roadmap work. The deprecation clock keeps running.

  3. Day 21

    Someone finally patches it.

    An engineer, or an AI agent, swaps the calls across four repositories. All 214 tests pass. It merges on a Friday.

  4. Day 34

    Production disagrees.

    Charges go out at 1/100th of the price. The success branch never runs, so the ledger stops recording. The tests never called the real API.

  5. Day 36

    The bill arrives.

    Refunds, a support queue, a postmortem and a week of senior engineers. A single breakage like this averages $84K to $228K.

With Releo, it ends on day 0: a verified pull request for every affected repository, the afternoon v2 ships.

02Why it keeps happening

Tests passed. Production didn't.

AI can already write the migration. That's the easy half. Your tests check what someone thought to test, not what the upstream API actually does now, and a model can't grade its own homework. Scroll to watch the same patch go through both.
billing.ts · patched by an AI agent UNVERIFIED
1// migrate billing v1 → v2 (auto-generated)
2const res = await client.charges.create({
3! amount: order.total,

↳ v2 expects minor units: this charges 1/100th

4 currency: 'usd',
5! customer: user.id,

↳ renamed to customer_id; silently ignored

6})
7!if (res.state === 'succeeded') {

↳ enum is now 'paid', so the branch never runs

8 await ledger.record(res.amount)
9}
tests 214/214 passedbehavior: unknown
billing.ts · patched by releoREPLAYING…✓ BEHAVIOR VERIFIED
1// migrate billing v1 → v2 (releo #4821)
2✓const res = await client.charges.create({
3✓ amount: toMinorUnits(order.total, 'usd'),
4✓ currency: 'usd',
5✓ customer_id: user.id,
6✓})
7✓if (res.state === 'paid') {
8✓ await ledger.record(fromMinorUnits(res.amount, 'usd'))
9✓}
replayed 0 requestsdivergences: pending
03How it works

From changelog to proven pull request. Without a sprint.

Four steps, run for every upstream change, in every repository that is affected.
releo · detect
specpayments-api 1.14.0 → 2.0.04 breaking
renamedcharges.create · customercustomer_id
retypedcharges.amountinteger, minor units
enumcharge.state · succeededpaid
removedGET /v1/charges/searchgone
04The math

Put a number on your next breaking change. Then make it zero.

Breaking changes are a line item nobody budgets for. Move the sliders to see what they cost a team like yours each year, and what Releo gives back.
Per breakage incident

$84K to
$228K

Average cost of a single API breakage incident.

Cost of one breaking change, by day

illustrative · from the ranges shown

$0$50K$100K$150K$200K$250Kshipd7d14d21d28d34median fix lands

02

15 to 20

hours

Engineering hours lost per mid-market SaaS team, per breaking change.

03

1,247

hours

Spent keeping backwards compatibility alive across legacy API versions.

04

60%

of providers

Rank breaking changes as their single biggest challenge.

What breaking changes cost you

Move the sliders. Every assumption is yours to change.

800
3
18h
$110

Default of 18h sits inside the 15 to 20 hour range per breaking change above. A working year is taken as 1,800 hours.

Cost your changes push onto customers each year

$4.8M

Customer migrations
2,400
Engineering hours
43,200
Engineer-years
24.0

That's engineering your customers spend standing still. It shows up as support tickets, delayed upgrades and churn.

05Who it's for

Everyone on either side of an API pays the migration tax.

Releo is SaaS for the teams that publish APIs, the teams that depend on them, and the firms that maintain integrations for others.

Ship v2 without a support-ticket wave.

Every breaking release means a migration guide, a deadline, and months of customers stuck on the old version you still have to run.

Faster adoption, fewer tickets, one less version to keep alive.

With Releo

  • ✓A verified migration PR delivered to each customer the day you release
  • ✓Replay evidence your customers can trust before they merge
  • ✓Retire old versions on schedule instead of supporting them for years
Get early access
06Why now

APIs are the economy now. Every change is a fleet-wide migration.

Software is assembled from other people's APIs, and AI agents are now calling them too. A single upstream release fans out into hundreds of repositories and thousands of call sites. Nobody proves those call sites still behave, until production does.

$17.3T1

Projected global economic impact of APIs by 2030.

82%2

Of organizations now call themselves API-first, up from 66% in 2023.

17.3h3

Per developer, per week, spent on maintenance and technical debt.

24%2

Of teams design APIs with AI agents in mind, while 89% of developers already build with AI.

A $20B+ toolchain4 manages APIs. None of it proves a change is safe.

Gateways, portals, monitors and tests each own a slice of the API lifecycle. The moment between "the provider shipped a change" and "every consumer is safely on it" belongs to no one. That gap is the category Releo is building: change verification.

Gateways & managementroute and meter traffic
Docs & developer portalsannounce the change
Monitoring & observabilitytell you after it broke
Contract & unit testscheck what you thought to test
Change verificationReleo · proves it before merge
  1. 1.Kong, 2024 API Impact Report (projection)
  2. 2.Postman, 2025 State of the API Report
  3. 3.Stripe, The Developer Coefficient (2018, self-reported)
  4. 4.Analyst forecasts for API management, 2030 (range $20B to $47B)
07Design partners

Build it with us. Ship your hardest migration first.

We are onboarding a small group of teams before launch. Partners shape the product and get their hardest upstream migrations done first.

01

Free for the whole beta

No invoice until general availability.

02

A direct line to the founders

A shared Slack channel. Questions answered by the people building it.

03

Your migrations first

We build for the upstream APIs and languages you depend on.

04

Founding-partner pricing

Partners keep a lower rate after launch.

What we ask in return

  • One upstream API you are already dreading
  • A 30-minute call every two weeks
  • Honest feedback, including the harsh kind
Apply as a design partnerTalk to the founders

Seats are limited so every partner gets real attention.

08Pricing

Pay for proof, not for seats.

Coming soon. Teams will pay per migration Releo verifies, so cost tracks the value delivered. Waitlist members hear about pricing first.

Developer

Free

during beta

For one engineer keeping a side project or service current.

  • 1 watched upstream API
  • Up to 3 repositories
  • Spec diffing and migration PRs
  • Community support
Join the waitlist
Most teams

Team

Usage-based

per verified migration

For SaaS teams and agencies that depend on many third-party APIs.

  • Unlimited repositories
  • Behavioral replay on every PR
  • Block-on-divergence policies
  • GitHub and Slack integrations
Join the waitlist

Enterprise

Custom

annual

For API providers migrating their customers, and regulated teams.

  • Customer-facing migration PRs
  • Self-hosted replay workers
  • SSO, audit log, data residency
  • Dedicated support and SLA
Join the waitlist
09FAQ

Questions, answered.

Something we didn't cover? Ask the founders directly.

An assistant writes the patch and runs the tests you already have. Releo writes the patch too, then proves behavior didn't change: it replays real traffic against the old and new endpoints and diffs the full response envelope. If anything diverges, the PR is blocked.

10Field notes

Writing on API change.

Blog All guides
Blog · 21 October 2026

Inside a behavioral diff: what to compare and what to ignore

A behavioral diff is only useful if it ignores noise and catches real changes. How to normalize IDs, timestamps, ordering, headers, latency and secrets.

Read →Blog · 7 October 2026

Deterministic verification vs LLM-as-judge for code changes

A model grading its own patch is not evidence. Why code changes need deterministic, reproducible verification, and where LLMs still earn their place.

Read →Guide · 7 min read

What is an API breaking change?

Twelve common examples, why tests miss them, and how to detect and verify breaking changes before they reach your customers.

Read →
11Early access

Your next breaking change is already on someone's roadmap.

Be ready for it. Join the waitlist, tell us which APIs keep you up at night, and we'll invite you as beta seats open.

What describes you best? (optional)

Free during beta · No credit card · Talk to the founders