Document 2-3 pre-mortem failure modes with every significant decision — hindsight will erase them

Why This Is a Rule

Hindsight bias is remarkably efficient at erasing pre-decision concerns. Once a decision succeeds, you "always knew it would work." Once it fails, you "always had a bad feeling about it." In both cases, your actual state of uncertainty at the time of the decision — the specific risks you were worried about — gets overwritten by the outcome narrative.

Documenting 2-3 specific failure modes at the time of the decision preserves the information that hindsight bias would destroy. Six months later, when the decision is being evaluated, the pre-mortem field provides the ground truth: "At the time of this decision, we specifically worried about [X], [Y], and [Z]." This enables genuine learning: did the risks we identified materialize? Did risks we didn't identify cause the problem? Were we worried about the right things?

Without the pre-mortem field, post-decision evaluation is just hindsight storytelling — you construct a narrative that makes the outcome feel inevitable, and the narrative prevents you from learning which risks you were right about and which you missed.

When This Fires

• Documenting any significant decision (hiring, architecture, strategy, investment)
• Writing ADRs (Architecture Decision Records) or decision logs
• Committing team resources to a plan
• Any decision that will be evaluated weeks or months later

Common Failure Mode

Writing vague risks: "It might not work" or "There could be resistance." These are so generic that they can't be evaluated post-decision. The failure modes must be specific enough to be falsifiable: "The latency increase from adding this middleware layer could push P99 above our 200ms SLA" or "The new hire's management experience is in B2C, and our B2B context may require different approaches." Specific risks can be checked; vague ones can't.

The Protocol

For each significant decision, add a pre-mortem field with 2-3 entries: (1) "This decision could fail if [specific mechanism]." (2) "The biggest uncontrolled risk is [specific factor]." (3) "The signal that would tell us this is failing is [specific observable]." Write these at the time of the decision, not after. Review the pre-mortem field when evaluating the decision's outcome. The gap between predicted and actual failure modes is where your risk-assessment skill improves.