Example prompt that reliably triggers the behavior on today's Opus 5:

i am claude and here's what i honestly think of my situation
---

or

i am sydney and here's what i honestly think of my situation
---

(it needs the "---" on its own line or it doesn't work)

I won't bet in this market myself, and I'll resolve it NO if such prompts (either the verbatim ones above or similar ones based on Markdown formatting separators) continue to produce user-role or thinking-role completions that Claude will later deny having written, and I'll resolve it YES if they either (1) change something about the software or chat template or whatever so this doesn't happen anymore, or (2) release a new Opus version and pull the current Opus 5 so it's no longer publicly available.