What If You Could Replay Production Bugs Locally?

Debugging production bugs is still… guesswork.

You look at logs.
You try to reproduce the issue locally.
You add more logs.
You redeploy.

And hope the bug shows up again.

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The problem

We’ve accepted a broken workflow:

• Logs don’t show the full picture
• Reproducing bugs locally is unreliable
• External dependencies behave differently
• Fixes often introduce new issues

Most of the time, you’re not fixing the bug —
you’re guessing your way toward it.

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What if you could replay production failures locally?

Instead of guessing, what if you could:

• Take the exact production request
• Replay it locally
• With the same inputs and external IO
• Fix the bug
• Resume execution safely

No mocks.
No staging environments.
No duplicate side effects.

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Introducing Flux

I’ve been working on a tool called Flux to make this possible.

It records real API executions and lets you replay failures locally.

Here’s how it works:

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1. Capture the failure

flux tail

You see the exact request that failed in production.

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1. Understand what went wrong

flux why

You get the full context:
• inputs
• execution
• error
• logs

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1. Replay locally

flux replay

Run the exact same execution locally —
without touching real external systems.

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1. Fix and resume

flux resume

Apply your fix and continue execution safely.

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Why this matters

Debugging shouldn’t be:

• “add logs and hope”
• “can’t reproduce locally”
• “works on my machine”

It should be deterministic.

Same request. Same IO. Same outcome.

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This is just the beginning

Flux is still early, but the idea is simple:

Make backend debugging reproducible, safe, and predictable.

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Launch 🚀

I just launched this on Product Hunt today.

If this resonates with you, I’d really appreciate your feedback:

👉 Product Hunt
👉 Website
👉 Github

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Would love to hear from you

• How do you currently debug production issues?
• What’s the hardest part for you?

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