Error types (Russian)

49 handlers, 110 subtypes across four detection categories (SPELL, MORPH, PUNCT, OTHER). The full subtype lists are in Reference → Handlers and subtypes and the schema mappings in Reference → Schemas; uv run synterr list-errors -l ru is the live, authoritative listing. LoRuGEC rule coverage was verified sentence-by-sentence on 2026-06-13 in docs/research/LORUGEC_COVERAGE.md (then 37/48 FULL, 11/48 PARTIAL, 0/48 NONE; the audit predates the handlers and subtypes added since).

A 5-handler French proof-of-concept exists on the same architecture (src/synterr/languages/french/, stanza fr_sequoia backend) — see Extending synterr.

Spelling — SPELL

Handler	What it does	Example
spelling	Phonetic confusions, keyboard typos, alternating/unchecked roots (§2–3)	молоко → малако
function_spelling	не/ни attachment, conjunction split/merge, -таки, negative-pronoun не/ни	чтобы → что бы
orthographic_spelling	пре/при, ы/и after prefixes, suffixes, participles, vowels after ц/sibilants (incl. root §5 п.3, -ем/-им endings)	преинтересный → приинтересный
compound_spelling	Hyphen / solid / separate writing of compounds, numeral-dash, пол-	по-моему → по моему
adverb_spelling	Adverb writing variants (4 directional subtypes)	по-русски → по русски

Morphological — MORPH

Handler	What it does	Example
noun_case	Wrong case on a governed/subject/other noun (dep-arc gated: obl/nmod/iobj/obj, nsubj, appos/conj/…)	на столе → на стол
noun_case_prep	Second locative -у vs standard -е (§152)	в лесу → в лесе
noun_case_gen_partitive	Partitive genitive -а/-у (§150)	история народа → народу
noun_case_instr_pl	Instrumental plural -ями/-ьми (§155); lexicon holds only кость	лечь костьми → лечь костями
noun_number	Singular ↔ plural	книга → книги
noun_number_gen_pl	Nonstandard genitive plural (§154)	носков → носок
neg_genitive	Acc↔Gen under negation, dep-arc (§201)	не читал книгу ↔ книги
adj_case, adj_number, adj_gender	Adjective/participle agreement via amod arc	новая книга → новый книга
adj_form	Short↔full adjective form	готовы → готовые
adj_possessive_form	Possessive-adjective oblique variants (§162)	маминого → мамина
adj_short_en_enen	Short-form -ен/-енен (§160)	свойствен → свойственен
adj_double_comparative	Insert pleonastic «более» before a synthetic comparative (length-changing)	лучше → более лучше
verb_person_number	Verb conjugation against an overt nsubj	они читают → они читаем
verb_tense	Past / present / future swap (finite forms only)	читал → читает
verb_iterative_suffix	о/а iterative suffix (§172.2)	обусловливать → обуславливать
numeral_declension	Numeral declension, incl. полтора	полтора часа → полутора часа
agr_sv_collective, agr_sv_counting, agr_sv_approximate, agr_sv_compound, agr_sv_coordinated	Subject–verb agreement flips, dep-arc (§183–190)	collective/numeral/compound subjects
agr_mn_apposition, agr_mn_compound_term, agr_mn_numeral_adj	Modifier–noun agreement: toponyms, hyphen compounds, два/три/четыре + adjective (§148, §191–197)	—

Lexical — OTHER

Handler	What it does
paronym	Confusable word pairs (одеть / надеть)
preposition	Wrong preposition
conjunction	Wrong conjunction
pleonasm	Tautological phrases (главный приоритет)
collocation	Lexical compatibility violations
pronoun_svoy	свой → personal possessive, нашёл свою книгу → мою книгу (§168.2)
pronoun_sebya	себя → personal pronoun, купил себе → купил ему (§168.1)
pronoun_n_form	н-augment after prepositions, у него → у его (§167)

Structural — OTHER

Handler	What it does
word_omission	Drop a function word (preposition or conjunction)
word_insertion	Insert a filler word (discourse marker, particle)
prep_repeat	Drop an obligatory repeated preposition under repeating и/ни: и в машинах, и в сырье → и в машинах, и сырье (§207)
parallel_mix	Coordinate a participial phrase with a который-clause (§211–212)

Punctuation — PUNCT

Handler	What it does
comma_delete	Delete a comma at clause boundaries (10 dep-tree-classified subtypes: subordinate, compound, parenthetical, isolation, homogeneous, interjection, response, repeated, asyndetic, vocative)
comma_pair_delete	Delete both commas of an isolated phrase (5 subtypes: participle, relative, gerund, parenthetical, apposition)
comma_insert	Add a spurious comma (12 subtypes, incl. bidirectional: homogeneous_conj §86, subj_pred, pseudo_parenthetical §99, after_odnako §99, compound_conj_split §108, x_ne_x §90)
dash_delete	Delete a required dash (5 subtypes: subj_pred, asyndetic, apposition, ellipsis §80, other)
dash_to_comma	Substitute dash → comma at sentence-final appositions (§93, non-length-changing)
comma_to_dash	Replace an asyndetic-clause comma with a spurious dash (§116; insert-direction mirror of dash_delete:dash_asyndetic)

Schema mapping cheat sheet

# See current mappings
uv run synterr coverage --lang ru --schema rlc
uv run synterr coverage --lang ru --schema rozental
uv run synterr coverage --lang ru --schema errant