ACI-061: One Checkout, One Index

Thesis

On a shared checkout git's index and working tree belong to every node, so a scoped commit protects the committer and never the stager: a pathspec scopes files, never authors or bytes. Git can neither enforce single-writer nor say which agent wrote what, so what survives is a named list of commit practices, authorship disclosed in the message, and a declared multi-node commit where correct gates leave no node able to commit alone.

Story

On 11 August 2026 Lamplight's validation node folded, and its commit message said the control node's two inboxes were left untouched. One was in the diff: the commit carried the control node's uncommitted clear of that inbox, made a minute earlier in the shared worktree where the whiteboard lived (Lamplight@af66f4108, 2026-08-11). "True about their intent, false about their commit." It recurred that day, after the rule was written and the first instance filed: "An instrument you have to reach for is not a control" (Lamplight@58c9fc36c, 2026-08-11). The guard that followed refuses a commit that both appends to and clears an inbox, and states its blind half: a commit that only clears is well formed, and "nothing in git distinguishes the recipient committing their own from a peer sweeping it, because every node commits under one git author" (Lamplight@a62329dc1, 2026-08-11). The first instance had that shape.