ChangedINVCALC.rpgle, the state rate
C EVAL TaxRate = 0.0725
C EVAL TaxRate = 0.0750
Changed because the notice raises the state rate.
For IBM i teams
The code survived. The reason didn't. Keep the why.
Whylode runs inside IBM Bob. When a rule changes, it traces every line that has to change, asks the one person who knows why, and keeps the answer.
INVCALC.rpgle, line 44
AskedKeptC EVAL TaxRate = 0.0525
“C2 is our contract group, the wholesale distributors on the 2021 supply agreement. Sales ops negotiated a flat 5.25% with them and it's written into the contract until it renews in 2029. It doesn't follow state tax changes, so leave 0.0525 alone.”
The problem
Nothing breaks until the rule changes.
- 69%
- of IBM i shops name skills as a top concern, ahead of cybersecurity for the first time in nine years.Fortra, 2026 IBM i Marketplace Survey, 315 respondents. Source
- Rules
- Tax rates, EDI formats, and month-end jobs keep changing. Every time, someone has to edit code that nobody ever explained.
- Why
- Documentation tools can say what the code does. Nobody wrote down why it does it, and the person who knows is about to retire.
How it works
Four steps, all inside IBM Bob.
Every example below comes from a real run: California sales tax rate change. Open the full record.
01
Trace
Bob reads the change notice and finds every line that implements it, with a confidence score for each.
INVCALC.rpgle, line 30
C EVAL TaxRate = 0.0725
Traced by Bob, confidence 1.00
02
Ask
Where the code can’t explain itself, Bob asks the person who knows. One plain question, on their phone.
INVCALC.rpgle, lines 39 to 45
What is customer type C2, and should its hardcoded 0.0525 rate change with the new California state rate or stay fixed?
03
Keep
The answer is pinned to the exact lines it explains, so the next change starts from what’s already known.
INVCALC.rpgle, lines 39 to 45
“C2 is our contract group, the wholesale distributors on the 2021 supply agreement. Sales ops negotiated a flat 5.25% with them and it's written into the contract until it renews in 2029. It doesn't follow state tax changes, so leave 0.0525 alone.”
MystiqueMide
04
Change
Bob drafts the edit with a reason on every changed and kept line. A person approves it.
C EVAL TaxRate = 0.0725
C EVAL TaxRate = 0.0750
Approved by Mysiquemide
The proof
The code had two rates. Only the owner knew which one was the state's.
Nothing in INVCALC.rpgle says what the second rate is for. Bob didn't guess. It asked, and the approved change edits one line and leaves the other alone, with the owner's reason attached.
KeptINVCALC.rpgle, line 44
C EVAL TaxRate = 0.0525
Kept because the owner said: “C2 is our contract group, the wholesale distributors on the 2021 supply agreement. Sales ops negotiated a flat 5.25% with them and it's written into the contract until it renews in 2029. It doesn't follow state tax changes, so leave 0.0525 alone.”
MystiqueMide
The next change
Nobody gets asked the same thing twice.
The second change touched the same tax code. Bob found 3 lines already explained in the memoir and only asked about what was new.
The memoir
Knowledge that outlives the handover.
Every answer is kept in plain language, pinned to the exact lines it explains. The next developer reads it next to the code, and Bob checks it before asking the same question twice.
IBM Bob
Built on IBM Bob 2.0. Bob does the work, people keep the say.
- Custom mode
- Whylode runs as its own Bob mode, with its role and rules.
- Skills
- Trace, ask, and draft skills tell Bob exactly how to handle a change.
- MCP tools
- Eight tools connect Bob to the change record, the questions, and the memoir.
- Document understanding
- Bob reads the change notice PDF directly and splits it into clauses.
Every Bob task behind this project is in the repository. Session reports
