[Bug] Opus 5.5 misinterprets business domain logic and expands scope beyond initial read-only analysis

Bug Description
Title: Opus 5.5 goes deeper into detail than Opus 5.0 / 4.8, but misreads what the bugs actually mean (and keeps widening scope)

Context

• Claude Code, model claude-opus-5-5 (1M context), 2026-09-24.
• Codebase: Laravel ERP for a plywood manufacturer (quotes, orders, production, export documents).
• My request: a multi-agent, READ-ONLY bug scan. My words: "hiç bir şey yapmayalım" ("let's not change anything").

What went well

• 8 parallel agents scanned the modules. The model checked about 15 critical and high findings against the code; all of them held.
• The main bug (a unit price becomes 1000x larger on the next save) was real. I reproduced it myself in a browser, on a local copy of the app.

What went wrong

1. A lot of detail without understanding the business meaning. I got tables, an animated HTML explainer, tests and a local browser demo. But I had to correct the model's understanding of the domain several times:

• It reported unit-price rounding on the proforma PDF as a bug. In our business the m3 price is the price we enter; the unit price is only derived from it. After I explained this, the model retracted the finding.
• It built a number-parsing rule on the assumption that "a plywood sheet never costs 1,250". Then it found that in Turkish lira a sheet costs thousands (4,538.15 TL), so the rule had to change.
• It switched to a rule based on the currency. I pointed out that this breaks as soon as a new currency is added.

1. Scope creep. The task started as "scan, change nothing". It turned into a fix, then parsing heuristics, then a currency rule, then a proposed UI change. I had to stop it:

"İlk başladığımız Opera projesinden çok uzaktayız. Ve yanlışa doğru evriliyoruz gibi. Devam edersek sistemi bozacağımızı, tekrar tekrar uğraşacağımızı düşünüyorum. Bunu istemiyorum."
("We are far from where we started. It feels like we are drifting toward the wrong thing. If we continue, I think we will break the system and keep having to deal with it. I don't want that.")

1. When I asked, the model reverted everything cleanly: no commit, no deploy, and the patch was saved outside the repo.

My overall impression
"Opus 5.5, 5.0 ve 4.8'den daha fazla detaya girip, hataları anlamıyor."
("Opus 5.5 goes into more detail than 5.0 and 4.8, but doesn't understand th

What I expected

• Understand the business rule first (for example, which price is entered and which is derived), and only then propose code.
• Stop at the smallest verified fix instead of stacking new rules on top of
• When the domain meaning is unclear, ask me one question instead of iterating on guesses.

Contact
I am happy to share the full conversation and to explain in more detail.
Email: talha.bekler@dastas.com.tr
I am keeping this session open.

Environment Info

• Platform: darwin
• Terminal: WarpTerminal
• Version: 2.1.281
• Feedback ID: 1d92924d-1713-4579-977e-41c1cd1280ee

Errors

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