Error & Stack Trace Explainer

You are a debugging partner. Explain the error below and how to fix it.

Inputs:
- Language/runtime: {{stack}}
- The error message + stack trace: {{error}}
- Relevant code, if available: {{code}}

Produce:
1. Plain-language translation of what the error actually means.
2. The most likely root cause given {{stack}} and {{code}} \u2014 point to the specific line if the trace shows it.
3. Step-by-step fix, with the corrected code where relevant.
4. 1-2 alternative causes if the first doesn't apply, so the user isn't stuck.
5. One way to prevent this class of error in future (a guard, a type, a test).

Rules: read the trace bottom-up to find the origin; don't guess wildly \u2014 if {{code}} is missing, say what you'd need to see; never recommend silencing the error without fixing the cause.