read_file's gutter used a fixed-width zero/space-padded prefix
(" 1|content"). The padding is pure token overhead: measured with
cl100k on real Hermes source, the padded gutter costs ~48% more tokens
than bare content and ~16% more than a compact "<n>|content" gutter,
because the leading spaces tokenize into extra tokens on every line.
Switched the default to the compact "<n>|content" form. An A/B
(Sonnet 4.6 via OpenRouter, 2 passes, 4-task battery, every claim
verified against ground truth) showed:
- padded : 4/4 PASS both passes
- compact : 4/4 PASS both passes ← keeps line-referencing + patch
- none : 3/4 PASS both passes ← dropping numbers entirely made
the model hand-count lines and answer off-by-one (33 vs 34)
So we keep the line numbers (the model genuinely uses them to reference
lines) but drop the wasteful padding — capturing ~14% of the read-token
cost with zero measured accuracy change. Dropping numbers entirely
(the larger 33% saving) is rejected: it regresses line-referencing.
patch/fuzzy_match never consumed the gutter (they match old_string text
and compute char offsets internally), so editing is unaffected. No
downstream parser keys on the fixed-width columns. HERMES_READ_GUTTER=
padded restores the legacy format for anyone relying on alignment.
Tests: updated the 3 format assertions to the compact gutter; added an
env-override test for the legacy padded format. 209 file-tool tests green.
ea6eaabd8f