---
name: diagnose-crash
description: >
  Diagnose why a program crashed on this Panama machine, from a systemd-coredump core dump.
  Use when a process has segfaulted, aborted, or otherwise dumped core, when asked why an
  application crashed or disappeared, when launched by panama-agent-crash, or when a
  "stopped unexpectedly" desktop notification is acted on. Triggers: crash, segfault,
  SIGSEGV, SIGABRT, core dump, coredumpctl, "why did X crash", "X keeps crashing",
  backtrace symbolization.
---

<!--
  Adapted from Omarchy's diagnose-crash skill (default/agents/skills/diagnose-crash/SKILL.md).
  Copyright (c) David Heinemeier Hansson. MIT License: permission is hereby granted, free of
  charge, to any person obtaining a copy of this software and associated documentation files,
  to deal in the Software without restriction; the above copyright notice and this permission
  notice shall be included in all copies or substantial portions of the Software.
-->

# Diagnosing a Crash

Work from evidence. The goal is an honest account of what happened, not a
plausible-sounding story.

## Establish the facts

`coredumpctl info <pid>` is the starting point. Beyond the backtrace, note the
**command line** the process was started with — it usually reveals what the
program was working on when it died, which is often the whole answer.

`coredumpctl list` shows whether this crash is a one-off or a pattern. Repeated
crashes of the same program, or several programs dying together, point somewhere
different than a single failure does. On this machine, Panama's System Health
page keeps a crash count too — `panama doctor check desktop.portal-stability`
knows whether the portal backend has been dying, which it chronically does.

## Rule out the boring causes first

Check resource exhaustion before blaming the program: `free -h`, and the journal
for OOM kills. A process killed by the OOM killer is not a bug in that process.

## Correlate against the timeline

The crash timestamp is the most underused piece of evidence. Compare it against:

- **Filesystem mtimes.** A file whose mtime lands on the same second as the
  crash strongly suggests what triggered it.
- **The journal** around that moment, for related warnings from the same or
  neighbouring processes.
- **Recent package updates.** `rpm -qa --last | head` — a crash that starts
  right after an update points at the update. `dnf history` shows what a recent
  transaction actually changed.

## Read the whole core, not just frame 0

Thread stacks other than the crashing one show what work was **in flight**.
That context often explains the trigger even when the crashing frame itself
cannot be symbolized. Note any third-party code in the address space —
extensions, plugins, out-of-tree drivers — but do not pin blame on it without
evidence that it is actually implicated.

## Symbolize when you can

This is Fedora, which runs a public debuginfod server:

```bash
core=$(mktemp -t crash-XXXXXX.core)
trap 'rm -f "$core"' EXIT
coredumpctl dump <pid> --output="$core"
DEBUGINFOD_URLS="https://debuginfod.fedoraproject.org/" \
  gdb -q <executable> "$core" \
  -batch -ex 'set debuginfod enabled on' -ex 'bt'
```

A core is a verbatim copy of the process's memory and can hold passwords,
tokens, and private documents. Write it to a fresh `mktemp` path rather than a
predictable shared one, and delete it when you are done — never leave it in
`/tmp`.

Many packages publish no debug symbols. When frames stay unresolved, say so —
**never invent function names to fill the gap.** An unsymbolized stack still
has shape: which library each frame belongs to, and whether the crash came from
a signal handler, a main loop, or a worker thread.

## Report

1. What crashed, and what it was doing at the time.
2. The most likely mechanism — separating clearly what the evidence **proves**
   from what you are **inferring**.
3. Whether any user data was lost, and where it can be recovered from. Check
   the trash before concluding anything is gone.
4. Whether it is likely to recur, and what would avoid or fix it.

Be straight about the limits of the evidence. If the cause is genuinely
ambiguous, say so rather than assembling confidence out of guesswork.

**Leave the system as you found it.** Diagnosis reads; it does not fix, tidy,
or reconfigure. The one thing to clean up is your own: delete the core you
extracted above. If the user wants the fix applied, that is a second,
explicitly requested step — and anything needing root goes through
`panama-sudo --reason` (load the `panama-sudo` skill).

## If the crash is Panama's

The shell, the compositor config, and everything under `~/.local/share/Panama`
are the user's own repository — a crash there is fixable in place, not an
upstream report. Load the `panama` skill before touching the repo: it carries
the live-desktop rules that keep an investigation from becoming a second
outage.
