# How do you find the root cause of a customer-reported bug?

> Start from the customer's exact failing request and work backward: find it in logs and traces, identify the failing service and code path, then check what changed there recently. Evidence first, hypotheses second.

Canonical: https://www.decimal.app/glossary/engineering/how-to-find-the-root-cause-of-a-customer-bug · Last reviewed: 2026-09-23

Start from the customer's exact failing request and work backward: find it in logs and traces, identify the failing service and code path, then check what changed there recently. Evidence first, hypotheses second.

## A repeatable approach

- Pin down the time window and identifiers
- Find the failing requests in logs and traces
- Identify the code path and read it
- Check recent commits, deploys, and config changes in that area
- Compare the customer's config and data against a working account
- Confirm the cause explains every symptom, not just one

## When to stop

Stop when you reach a cause you can change and that would prevent the next occurrence. A cause that only explains this one ticket is usually a symptom.

Decimal produces a cited root cause for technical tickets. See [root cause analysis](https://www.decimal.app/glossary/root-cause-analysis) and [agentic investigation](https://www.decimal.app/glossary/agentic-investigation).

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