---
name: lane-diff-byte-identity-limit
description: "Rebase-fidelity by byte-identical lane diff only holds while main's delta misses every lane-touched file; else strip index/@@ lines and compare content blobs."
metadata: 
  node_type: memory
  type: project
  originSessionId: 00d52893-7427-4ec7-85be-eebb7e921b11
  modified: 2026-08-04T02:11:30.801Z
---

Byte-identity of a raw `git diff base..tip` across a rebase is a valid fidelity instrument ONLY while main's delta touches none of the lane's files. The moment an upstream commit lands in a shared file above the lane's anchor (todlando's #145: hertz's REQ additions landed 25 lines above the toml insertion), the `index` line and `@@` hunk headers move with ZERO content change — different blobs, same change.

**Why:** treating the hash mismatch as a discrepancy manufactures a false red; shrugging at it un-audited manufactures a false green. Both wrong.

**How to apply:** when the raw diffs differ, strip `index` and `@@` lines from BOTH sides and compare the remainder by blob (`git hash-object`). Content-identical stripped remainders = faithful rebase; any surviving delta is real and must be read. Diff-of-diffs first to bound what moved. Related: [[assemble-onto-the-repair-tip-not-a-sibling]].