[AetherAI3]

Summary

Addresses #269. write_file now creates missing paths exclusively. Replacing an existing small text file requires expected_revision and an executor-scoped replace_token from the same complete byte-mode read_file result. Partial reads, old path/content-only calls, stale or cross-session proofs, binary targets, and files beyond one complete read page are rejected before any old content is changed.

Writes are staged and synced in a sibling file. New files commit with an atomic create-only hard link; existing files are checked against the digest-backed revision immediately before same-directory rename. Success reports prior and new revisions. The local tool schema, hosted request flag, protocol type, diff preview, and documentation use the same contract. Large-file callers are directed to patch_file.

The documented concurrency limit is that a non-cooperating external writer can change a path between the final revision check and rename; strict serializability against such writers needs a workspace lock.

Verification

• npm run build
• Focused tests: 114 tests, 102 passed, 12 platform skips; after final additions, 48 tests, 47 passed, 1 platform skip.
• Independent Linux host (Node 24): fresh branch checkout, npm ci, build, and 93 focused tests: 92 passed, 1 expected permission-mode skip.
• Cases cover complete and empty reads, multibyte text, partial and line reads, stale same-size edits, atomic path swaps, a swap during staging, create races, binary and oversized targets, legacy async calls, symlinks, failed staging, and failed rename.
• git diff --check

GitHub Actions jobs on this PR did not start: GitHub annotated them "The job was not started because your account is locked due to a billing issue." This is an account gate, so the Windows and Linux results above provide the executable test evidence.

The companion AETHER-CLOUD PR advertises the new schema and rejects older coding hosts that request write_file without the capability flag.