New short_v2 mode for conversation summaries

What

When a conversation grows long, Claude Code can compact it, which means replacing earlier parts with a written summary. There are several summary modes, and this release adds a new one:

• short_v2: joins control, lean, short and capped. It has its own instructions and resumeGuidance.
• What it asks for: the summarizer copies any earlier summary's record of what the user asked for, adds new requests, and rewrites only the account of the work done.

What selects this mode was not found, and it looks like one arm of an experiment.

Why

With this mode, your earlier requests are carried forward word for word from one summary to the next instead of being rewritten each time. You may not see it unless your session is assigned to this variant.