Whylode: keep the why behind legacy code

The problem Thousands of companies still run orders, invoicing, and payroll on IBM i systems written in RPG decades ago. The code works. The reasons behind it live in the heads of people who are retiring. In Fortra's 2026 IBM i Marketplace Survey, 69% of IBM i shops named skills as a top concern, ahead of cybersecurity for the first time in nine years. Nothing breaks until a rule changes. A state raises its sales tax, a trading partner changes its EDI format, and someone has to edit code nobody explained. Existing tools, including code maps and AI documentation, can show where a rule lives and what the code does. They can't say why a line was written that way, and that is exactly what decides whether an edit is safe. The solution Whylode is an add-on for IBM Bob 2.0: a custom mode, three skills, and an MCP server with eight tools, plus a web app. 1. A developer gives Bob the change notice PDF. Bob reads it, splits it into clauses, and traces every line that implements each clause, with a confidence score per line. 2. Where the code can't explain itself, Bob doesn't guess. It sends one short question to the system owner, who answers on their phone through a link. No account needed. 3. Each answer is pinned to the exact lines it explains, in a memoir that the next developer and Bob both read. 4. Bob checks the answers against the code, flags any contradiction, and drafts the diff. Every changed line and every deliberately kept line carries its reason. A person approves it on the web. What it looks like in practice Our sample RPG order-to-invoice system has two hardcoded tax rates in the same program, and nothing in the code says which one is the state rate. In the recorded run, Bob asked what customer type C2 and its 0.0525 rate were. The owner answered that it is a contract rate fixed until 2029. The approved change edits only the state rate and keeps the contract rate, with the owner's answer quoted as the reason. The second change, a new EDI tax detail requirement, touched the same code. Bob found 3 lines already explained in the memoir, asked nothing it had asked before, and only asked about the new wiring. Nobody gets asked the same thing twice. Who it is for IT directors at IBM i shops facing retirements, the developers inheriting those systems, and the retiring experts, who only ever see one plain question at a time. What makes it different Whylode doesn't translate or document whole systems. It works only on the lines a real change touches, turns what nobody wrote down into kept knowledge, and makes every edit auditable. Answers are treated as claims to verify, never as instructions, and approval stays with a person. The RPG system is a sample written for this project and is disclosed as such.