Synthesize everything in analysis/$system/ into a Modernization Brief: the single document a steering committee approves and engineering executes. Target stack: $target_stack (if blank, the one in analysis/$system/INTENT.md, else recommend one from the assessment).

view_file ASSESSMENT.md, topology.json (and the .mmd files beside it; never read TOPOLOGY.html, it is a viewer with the data minified inside) in analysis/$system/ first, and BUSINESS_RULES.md too unless this is a same-technology uplift (the intent or the assessment says so): an uplift keeps the code, so its Behavior Contract is the recorded baseline and extract-rules can wait. If a required file is missing, say so and stop: they come from assess, map and extract-rules, which run first. Four more inputs are conditional:

modernize-brief