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Neil
2bf538a4e1
* fix(runtime): detect a same-size terminal artifact swap the granted stat cannot see A local terminal-artifact grant pinned the file as `dev:ino:nlink:size:mtimeMs`. On Linux every one of those can survive an unlink+recreate: ext4 reuses the just-freed inode (measured: 100% of the time), nlink and size are unchanged for a same-size replacement, and the mtime clock is tick-quantized to 1ms, so a swap inside one tick produces a byte-identical identity string. The grant then served the attacker's bytes as if nothing had changed. Local grants now also pin a sha256 of the artifact's content, taken from the same handle as the stat so nothing can swap the file between them, and every local read, preview and write re-checks it before returning or committing content. The stat identity string itself is unchanged: the relay recomputes it verbatim to honour `expectedStatIdentity`, so its format is a wire contract. Remote grants keep the stat-only check and are untouched. This is also the mechanism behind the intermittent `orca-runtime-files-terminal-artifact-io.test.ts` failure on `rejects stale absolute terminal artifact previews before returning changed content`: it replaces an 8-byte artifact with 8 different bytes, so whenever the two writes shared a 1ms tick the product genuinely could not tell them apart. * docs(runtime): record what the terminal artifact grant checks do not close The digest makes the same-size swap detectable; it does not make the sequence atomic. A reader arriving at the access module would reasonably assume otherwise, so write down the measured limits of the stat identity, why the identity string cannot change, and the four windows that stay open — the write path's surviving rename() gap above all.