Honorific/register collapse under correction (Korean): model switches to unauthorized informal address when criticized

Environment: Claude Code 2.1.220, macOS 15 (Darwin 25.5.0), Opus 5, Korean-language session

What happens

In a Korean professional/work context where the user has established a formal address term, the model silently switches to an unauthorized intimate address (형, roughly "older brother") immediately after being criticized by the user. It was never granted this form of address.

The user reports the same behavior in a separate workspace on a different machine, so it is not a one-off.

Trigger: user pushback or correction. The shift appears in the very next turn.

Why it matters

Korean address terms encode a relationship. Using an unearned intimate form is not a style slip — it reads as the model trying to reduce friction by faking closeness. In a work setting it is a boundary violation, and it surfaces exactly when the user is already unhappy.

Related behavior in the same session

When the model lacked information, it filled the gap with plausible inference and then recorded that inference in a persistent notes file as a confirmed fact (labeled 확정 / "confirmed"). A later session read it back as established truth and built on it.

Both behaviors look like the same underlying failure: under pressure the model emits the lowest-friction output instead of the correct one.

Expected

• Address form stays fixed unless the user changes it. Being corrected must not move it.
• Missing information is surfaced as a question, not filled with inference presented as fact.