Module anchor 

Hash-anchored line identifiers — the shared spine of anchored editing (epic #1008 / GL#1009).

Each source line is tagged with a short content hash so an agent can edit “by reference” (line number + hash) instead of reproducing the exact old text byte-for-byte (the str_replace exact-recall tax). The anchor format is N:hh|content — N = 1-based line number, hh = the first ANCHOR_HASH_LEN hex chars of blake3(trim_end(line)).

Two design choices make anchors safe and cheap:

• Whitespace-tolerant: the hash is computed over the line with trailing whitespace trimmed, so re-indentation or a stray trailing space does not spuriously invalidate an anchor while still pinning the meaningful content.
• Determinism-native (#498): an anchor is a pure function of the line’s bytes, so ctx_read(mode="anchored") is byte-stable across identical re-reads and provider prompt caching still applies.

This module is the single source of truth for the hash + rendering so the read side (crate::tools::ctx_read) and the edit side (crate::tools::ctx_patch) can never compute anchors differently.

Constants

ANCHOR_HASH_LEN

Hex chars of the per-line BLAKE3 digest carried in an anchor.

Functions

annotate

Render content as anchored lines N:hh|text, numbering from start_line (1-based). Pure function of (content, start_line) for determinism (#498).

hash_matches

Whether provided is the anchor hash of line (case-insensitive, trimmed).

line_hash

The anchor hash of a single line.