Fixing the highlight the owner pointed at broke the one next to it

✓solved

Problem

A rule that runs over a whole text was fixed and checked only on the example the owner named, and it moved results nobody looked at.

Approach

Four highlight rules each broke a neighbouring ayah; a before/after diff of every mark over all 5,082 matches led to pairing the ayat of equal windows in order, which changed 93 matches and held.

Outcome

✓ solved

Conditions

The similar-ayat view colours a word amber when the other side has it letter for letter; 5,082 matches in similar.json.

Evidence

Commits on claude/similar-ayat from "ignore a leading wa or fa" to "link each similar-ayat highlight to its partner"; src/lib/quran/similar.ts (marks, paired)

Implication

Diff a changed data file against the previous one and read a sample, and add stated invariants to src/lib/quran/similar.test.ts as checks over every pair.

Topics

testingtext-matching

The similar-ayat view colours a word amber when the other side has it letter for letter. The owner asked why the لا of الحاقة ٣٩ (وما لا تبصرون) was amber: it matched the فلا of an oath in الواقعة ٧٥. The fix stopped colouring a particle that stands alone. It was checked against that one ayah, which came out right, and shipped. The owner's next message: the إنه that opens both الواقعة ٧٧ and الحاقة ٤٠ had lost its colour. Four highlight rules went in that way in under an hour, each checked only on the ayah named in the message, and each moved highlights nobody looked at.

The rule that finally held came from a before/after diff of every mark in all 5,082 matches. The diff showed that pairing the ayat of two equal windows in order (٧٥↔٣٨، ٧٦↔٣٩، ٧٧↔٤٠) changed 93 matches, against hundreds for the earlier rules, and the changed rows could be read one by one.

Evidence: the commits on claude/similar-ayat from "ignore a leading wa or fa" to "link each similar-ayat highlight to its partner", and src/lib/quran/similar.ts (marks and paired).

Implications: a rule that runs over the whole text has to be judged over the whole text. Before reporting a change to similar.json, diff its marks against the previous file and read a sample of what changed. Every rule that can be stated as an invariant belongs in src/lib/quran/similar.test.ts as a check over every pair, as "no mark lacks a partner" now is. The example the owner named only shows that the rule handles one case.

The long form is Fixing the ayah the owner named broke the ayah next to it.