This project is maintained by kenakofer

Agent prompt — removing a \bar "" break workaround

The sweep this was written for is done — see the status section of removing-break-workarounds.md. In the end no agents were dispatched: the edit turned out to be a one-line deletion per occurrence, so a scripted pass over all 64 files plus one batch verification was faster and more consistent than 64 agent runs. Keep this as a template if a similar per-song sweep comes up.

If you do reuse it, fix the decision table first. The ink-delta thresholds below are not a sufficient gate: a real stem-direction flip measured 0.06% of page ink, which the table says to keep silently. Compare lyric/marker text separately and look at a render.

Hand one song per agent. The agent does the mechanical pass and reports numbers; it does not decide whether an output change is acceptable.

Read removing-break-workarounds.md first — it has the reasoning behind every step below.

Task

You are converting one song file to drop the obsolete \bar "" break workaround. LilyPond 2.24 made \break work mid-measure on its own, so the invisible barline is redundant.

File: <path> Baseline build: <scratch>/baseline64/<song>/ (out.midi, build.log, out-trad.pdf — already built, do not rebuild it)

Steps

  1. Remove every \bar "" (and \bar " ") in the file. Leave \bar "|." and \bar "||" untouched — those are real barlines. Do not move \bar "|." inside a \relative block; if it is already on its own line, keep it there.
  2. Remove the trailing | bar check at each block boundary you just changed — in all four voices (soprano, alto, tenor, bass) and in the chord line if it has one. Missing a voice is the single most common failure.
  3. Do not touch the \relative blocks at all — do not merge them, do not split them, do not add or remove octave marks (' / ,), do not change a block’s reference pitch. Leave the note content exactly as it is. Your edits are limited to removing \bar "" and the trailing bar checks. Any \relative edit risks silently transposing a phrase by an octave, and bar checks will still pass when it happens — only the MIDI comparison catches it.
  4. Do not remove \partial unless it is provably redundant. When in doubt, leave it.
  5. Delete any comment in the file that claims \bar "" is required for a mid-measure break — that is pre-2.24 advice.

Build

Build to a scratch directory. Never write into docs/local-lilypond-outputs/.

lilypond -o <scratch>/conv/<song>/out lilypond/songs/<song>/<song>.ly \
  > <scratch>/conv/<song>/build.log 2>&1

Report exactly these four numbers

# 1. bar checks, baseline vs yours
grep -icE 'barcheck' <baseline>/build.log
grep -icE 'barcheck' <conv>/build.log

# 2. MIDI equality
cmp -s <baseline>/out.midi <conv>/out.midi && echo SAME || echo DIFFERS

# 3+4. engraving bbox and ink delta
pdftoppm -r 100 -png <baseline>/out-trad.pdf <scratch>/b
pdftoppm -r 100 -png <conv>/out-trad.pdf     <scratch>/n
python3 -c "
from PIL import Image, ImageChops
import numpy as np, glob
a=Image.open(sorted(glob.glob('<scratch>/b-*.png'))[0]).convert('L')
b=Image.open(sorted(glob.glob('<scratch>/n-*.png'))[0]).convert('L')
A=np.array(a).astype(int); B=np.array(b).astype(int)
print('bbox:', ImageChops.difference(a,b).getbbox())
print('ink_delta:', int((B<128).sum()-(A<128).sum()))
print('ink_total:', int((A<128).sum()))"

Report as:

<song>: barchecks <base> -> <new> | MIDI <SAME|DIFFERS> | bbox <...> | ink <+N> of <total>

Decision rules — follow these exactly

Condition Action
MIDI DIFFERS Revert the file. Report it. This is always a bug, never a judgement call.
bar checks higher than baseline Revert. Report which lines fail (grep -iE barcheck). Usually a voice you missed in step 2.
bbox None Keep. Clean conversion.
bbox only a ~4x7 px box near the page bottom Keep. That is the footer date.
bbox large, abs(ink_delta) / ink_total < 0.001 Keep. Horizontal respacing, expected.
ink_delta positive by more than ~0.1% Stop and escalate. A symbol was added — usually an accidental the removed barline used to cancel.
ink_delta negative by more than ~0.1% Stop and escalate. Often the last system no longer justifying to the right margin. Check whether \bar "|." moved.

Do not “fix” an escalation case yourself. Report the numbers and stop.

Do not