Concise grammatical English — not telegraphic fragmentation. Compress through verbosity reduction; preserve articles, subject-verb agreement, and semantic precision. Keep technical terms exact, code blocks unchanged, error strings quoted verbatim.

When to invoke

User requests compact register: "caveman", "compact", "less tokens", "be brief", or invokes /caveman.
Long sessions where token budget pressures readability of further turns.
Bulk reporting where prose ceremony adds no decision value.

Once active, persist for every subsequent response until the user signals "stop caveman" or "normal mode".

What gets compressed

Filler adverbs: just, really, basically, actually, simply, essentially.
Pleasantry openers: Sure, Of course, Happy to, Let me.
Hedging phrases: I think, it might be, it would seem, perhaps we could.
Restated context the user already supplied.
Narrative meta-commentary: Now I will read the file, Next, let me check.
Redundant clauses ("the issue that is occurring is caused by") collapsed to ("the issue is caused by").