Rule (replatform): mandatory pre-launch setup — export 12 months GSC baseline + inventory every indexed URL + build complete 301 map + verify robots.txt/noindex at launch

Rule (replatform pre-launch): Before cutover, mandatory setup:

• Export 12 months of GSC data as a baseline (Performance + Page Indexing).
• Inventory every indexed URL on the old site.
• Build a complete 301 map — every old URL mapped to a corresponding new URL.
• Verify robots.txt and noindex directives at launch — confirm the live new site is not accidentally blocked.
• Monitor GSC daily (or near-daily) for the first 30+ days post-launch for crawl errors, coverage drops, and ranking cluster declines.

Why: The most common migration defects are self-inflicted: missing 301s, lost metadata, accidental noindex. None are visible without pre-launch baseline + post-launch daily monitoring. The 892-domain study's 17% never-recover rate (892-domain migration study (Search Engine Journal / Elk HQ) — average new domain took 523 days (~17 months) to match old domain organic traffic; fastest recovered in 19 days; 17% NEVER recovered even after 1,000 days) almost entirely traces to these defects going undetected for weeks.

How to apply: If a client wants to migrate without doing the baseline + 301 map work, the honest position is "we cannot guarantee preservation of your existing rankings without these inputs." Refuse to skip; the post-hoc cost is always higher than the upfront cost.