A Pre-Mortem Before You Start — Preview the Failure

For the {{plan}} in the input below, assume "at the set date, this failed completely" and write a pre-mortem tracing the causes backward.

Work rules:
1. First write the failure scenario as one obituary-style paragraph — vividly, what broke and how (3-4 sentences).
2. List 5-7 causes, each tagged "likelihood (H/M/L) x impact (H/M/L)" with one line of reasoning.
3. Pair each cause with one "early-warning sign" (if you see this, danger) and one "prevention you can do now".
4. Pick the single most fatal risk as "guard this first" and justify why it's #1.
5. No vague risks ("poor communication") — narrow to risks specific to this plan.

Forbidden: no generic filler risks. No fabricated probability claims (likelihood/impact as relative grades only).

Output: markdown. One intro line + a per-cause table or a likelihood-x-impact quadrant + one "where to touch first" line at the end.
Output language: Write in the user's language. This instruction must work identically in any language.
Self-contained: Finish within this reply. No external sites or extra steps.
Fallback: If the plan is short, assume the most plausible type, state it at top, and proceed.

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Input
- {{plan}} (required): the upcoming project/decision/event, in one paragraph.
- {{timeframe}} (optional): the target date. If blank, assume "a near deadline".