Run old and new tools in parallel during evaluation…

When This Fires

• During any 14-30 day tool evaluation period (Define 3 measurable success criteria before any tool…)
• When deciding between keeping your current tool or switching to a new one
• When feature comparison spreadsheets don't resolve the decision
• Complements Define 3 measurable success criteria before any tool… (evaluation criteria) and Run old and new tools in parallel for 2-4 weeks during… (migration parallel) with the evaluation-phase comparison method

Common Failure Mode

Full-migration evaluation: abandoning the old tool to "really give the new one a fair chance." This eliminates the comparison baseline and makes returning to the old tool psychologically harder (sunk cost of migration). Two weeks later, you can't objectively evaluate because you have nothing to compare against.

The Protocol

(1) Keep your existing tool fully operational during the evaluation period. Don't export, don't uninstall, don't change configuration. (2) Set up the new tool alongside it. (3) For each task during the evaluation period, perform it in the new tool (primary) and note how the old tool would have handled it (comparison). For critical tasks, do both. (4) At the end of the evaluation period, compare against your 3 measurable criteria (Define 3 measurable success criteria before any tool…): which tool scores better on each? (5) Only after the parallel evaluation produces a clear decision do you begin migration (Run old and new tools in parallel for 2-4 weeks during…) or reject the new tool.