fluxRun
Open app

For AI-native Next.js backend teams

Production failure
replay for
AI-native backends.

AI wrote the route. Production found the bug. FluxRun captures the exact failed backend path, replays it safely with recorded IO, and turns the fix into regression protection.

Start free See demo Founding teams
Failures / highest priority execution live incident

Timeline

orders.getById started

+0ms

request id logged

+40ms

api.example.com/orders requested

+80ms

api.example.com/orders responded

+260ms

inventory.example.com requested

+285ms

inventory.example.com responded

+955ms

fallback path logged

+980ms

Issue focus / root cause / recorded IO / failed after 955ms

inventory.checkStock returned 503

The captured run keeps the request path, failing network response, logs, and replay controls together.

Status

failed (503)

Network calls

3

Events

9

Network evidence

GET /inventory/check-stock - 503 after 670ms

Open Failures Save regression test
Works alongside Sentry · Datadog · Vercel Next.js-first · Recorded IO replay · 0 production writes

Best first wedge

Built for the backend paths AI-assisted teams break first

Start with one money path: a Next.js route, webhook, external API call, or AI tool boundary that fails only after real users hit it.

Proof path

Next.js + Stripe webhook

Webhook failed after a duplicate delivery

Capture the raw request, verify the signature path, replay the duplicate delivery safely, and save the fixed idempotency branch.

Open Next.js guide
Proof path

External API failure

Checkout fallback missed a 503 branch

Replay the same upstream timeout or malformed response with recorded IO while payment, email, queue, and database writes stay blocked.

Watch replay demo
Proof path

AI-agent backend

Tool call looked valid but broke the server path

Trace generated backend code, inspect the exact tool input/output boundary, and keep the repaired behavior as a regression guard.

Read SDK reference

How it works

From failure to fix in three steps

Step 1

Capture

Wrap your route with FluxRun. It records request/response, network calls, console logs, database queries, timers, random values, and execution state — everything needed for a deterministic replay.

Step 2

Replay

When a failure occurs, replay the exact execution path with recorded IO. No live side effects.

Step 3

Test

Save the fixed path as a regression test. Run it on every deploy to prevent regressions.

Interactive demo

See how real failures are replayed

SEV-1 Live demo failure

18.4% checkout impact

Payment provider timeout during checkout

Root cause

Payment provider returned 503 after retry exhaustion. The fallback branch was not handled, so checkout failed instead of degrading safely.

Impact

18.4% checkout impact

Evidence

recorded IO

Side effects

0

Replay this failure safely →

Features

Everything you need to debug with confidence

Safe Replay

Reproduce production failures with recorded IO, fixed clocks, and no live side effects.

Zero Side Effects

Replay runs in isolation. Your database and APIs are never touched during debugging.

Protected Payloads

Sensitive data stays encrypted. Unlock via secure agent route only when needed.

Team Workflow

Shared orgs, projects, and incident response. Everyone sees the same failure context.

Regression Tests

Save fixed paths as tests. Prevent the same failure from shipping twice.

Framework Agnostic

Next.js, Express, Fastify, Hono, Koa, and Lambda. One SDK, any backend.

ROI calculator

Make production-only debugging cost visible

Estimate how many engineering hours disappear into reproducing failed webhooks, payment branches, malformed API responses, and AI-generated backend bugs.

Calculate debugging cost

Founding Teams

White-glove setup for 5-10 backend teams

Bring one real Next.js endpoint, webhook, or AI-tool boundary. We help you capture the first failure, replay it safely, and turn the fix into a regression guard.

Apply for founding access

Start with one endpoint

First replay value from one real backend path

Install the SDK, connect a project token and replay keys, expose your agent route, then wrap the route that hurts most. Keep the promise concrete: capture, replay, protect.

Start free Read docs
npm install fluxrun

# app/api/orders/route.ts
import { withFluxNextJs, fluxHost } from 'fluxrun';

const db = fluxHost.auto('db', prisma);

export const POST = withFluxNextJs(
  'orders.create',
  async (flux) => {
    const order = await flux.db.createOrder(flux.request.body);
    return { status: 201, body: order };
  },
  { host: { db } },
);

FAQ

Questions? Answered.

Still have questions? Contact us.

Ready to replay your
first backend failure?

Start free, or apply for guided founding-team setup.

Start free Founding teams