checkpoint

name	checkpoint
description	Persist bounded mid-task progress as a kernel.checkpoint/v1 JSON manifest so a fresh session or context reset can resume at the exact position without a full handoff. Triggers: checkpoint, save progress, context reset, compact soon, long task.
user-invocable	true
allowed-tools	Read, Bash, Grep, Glob, Write
kernel	{"kind":"state_transition","version":1,"side_effects":"writes_meta","confirmation":"none","produces":["kernel.checkpoint/v1"]}

The small resumable manifest. A handoff transfers a whole session; a checkpoint records bounded progress INSIDE a long-running task so work can continue after a context reset with a fresh, minimal context instead of an inherited transcript.

When to fire (EXP-L21: attention efficiency decays to ~11% late-session; a reset from a checkpoint restores the flat ~50-70k load-bearing line):

• a long task crosses a natural boundary (a commit lands, a phase completes)
• context is about to compact, or the session is degrading (anchor-drift, I0.13)
• the manifest's execution.checkpoints list says so

Checkpoint vs handoff: same task + same session continuation → checkpoint. Ending the session / transferring to a future session with decisions and policy → handoff.

1. Gather provenance: ```bash git branch --show-current && git rev-parse HEAD && git status --short ```