> ## Documentation Index
> Fetch the complete documentation index at: https://docs.slomo.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Slomo CLI: doctor — Root-Cause Diagnosis for Issues

> Run slomo doctor to get a heuristic root-cause report: category, severity, likely cause, first bad function and variable, and a suggested fix.

`slomo doctor` walks the recorded timeline backwards from the crash and applies heuristics to produce a structured diagnosis. Pass the issue id to diagnose.

```
slomo doctor REF
```

<ParamField path="REF" type="string" required>
  Issue id, e.g. `SM-1a2b3c4d`.
</ParamField>

```console theme={null}
$ slomo doctor SM-8b6f710a
Category              Null Reference  (95% confidence)
Occurrences           5  (5 unhandled) across 5 session(s)
Likely root cause     TypeError raised in checkout() at app.py:14.
                      Variable 'inventory' was None at the crash site.
First bad function    checkout()
First bad variable    inventory
Suggested fix         Guard against None before the failing access at app.py:14
                      — trace where the value is produced and handle the missing case.
Context just before the crash:
  13:04:52.133 sql.query   SELECT sku, qty FROM inventory WHERE sku = ?
  13:04:52.133 sql.result  0 rows, 9µs
```

## Reading the report

| Field                  | Meaning                                                                                                           |
| ---------------------- | ----------------------------------------------------------------------------------------------------------------- |
| **Category**           | Automatic [classification](/concepts/issues#classification) with its confidence score                             |
| **Severity**           | Inferred severity level of the issue                                                                              |
| **Status**             | Current status and stability (e.g. `open / recurring`)                                                            |
| **Occurrences**        | Incident count, unhandled count, affected sessions                                                                |
| **First seen**         | Timestamp of the first recorded incident                                                                          |
| **Last seen**          | Timestamp of the most recent incident                                                                             |
| **Likely root cause**  | Where the exception was raised, and what the crash-site state implies                                             |
| **First bad function** | The earliest function in the trace where the failing value appeared                                               |
| **First bad variable** | The variable that was already wrong at the crash site                                                             |
| **Suggested fix**      | A heuristic suggestion — a starting point, not gospel                                                             |
| **Context**            | The SQL/HTTP/log events immediately before the crash — often the actual answer (above: the query returned 0 rows) |
| **Related issues**     | Other issues with similar fingerprints and their similarity scores                                                |

The diagnosis is built from the same captured data you can inspect yourself — crash-frame locals ([snapshots](/reference/cli/data-views)), spans, and the surrounding events. When the doctor's heuristic isn't enough, [replay](/reference/cli/replay) the same incident and rewind from the crash by hand.

## See also

* `slomo issue explain REF` — one-paragraph version of this report
* [The investigation workflow](/investigating/issues-workflow) — where `doctor` fits in