[dezren39]

Fixes #3265. Queue task 5693.

What

graphemeWidth in pkgs/id/web/src/world-surface.ts returned 2 for every cluster containing U+FE0F. It now widens only when the code point immediately before U+FE0F can start an emoji presentation sequence; otherwise U+FE0F measures 0 in the plain sum (letter+FE0F = 1, lone FE0F = 0).

The gate table (EMOJI_PRESENTATION_SEQ_RANGES, 183 ranges / 371 code points) was decoded verbatim from unicode-width 0.2.2's starts_emoji_presentation_seq bit table (EMOJI_PRESENTATION_LEAVES in the crate's tables.rs) — the exact set the Rust validator widens, not a hand-picked approximation.

Tests

• bunx vitest run src/world-surface.test.ts — 11/11 pass, including a new parity test: narrow cases (a/x/Z/é/Ω/→/!/?/%/space + FE0F and ©+U+0301+FE0F at columns 1; lone FE0F refused at both widths) and wide cases (⚠️ ☝️ ❤️ ©️ ®️ ™️ ♠♥♦ ▶◀ ↔↩⤴ 〰〽㊗㊙, digit/#/* + FE0F, keycap 9️⃣) still at columns 2.
• Differential probe (real TS width machinery extracted verbatim vs a Rust probe pinned to unicode-width = "=0.2.2"): 14,607 base+FE0F clusters (U+0020–U+32FF, U+1F000–U+1F64F) + 8 special sequences (keycaps, mark-interrupted, lone/double FE0F, ☝️, ❤️‍🔥) — zero FE0F-effect mismatches (cluster width minus base-alone width agrees on every case) and 8/8 specials exact. The 127 raw cluster mismatches are fully inherited from base-alone divergences (CJK radical/unassigned points, trigrams, Khmer, zero-width classes) — that is the single-code-point scope of id(web): world presenter residual width divergences vs unicode-width 0.2.2 — 2529 code points in classes #1581 never scoped (trigrams, CJK radicals, format chars) #2962, explicitly out of this packet.

Dispositions

• ZWJ-alone (Rust 0 vs TS 1, from id(web): world presenter widens every U+FE0F cluster to 2 — a letter+VS16 cell (a️) is Rust-valid at columns 1 but renderWorldSurface refuses the whole screen #3265's table): documented in the graphemeWidth comment as unreachable from valid wire data — the server never emits a width-0 grapheme as a cell; width-0 cells only ever appear as empty-symbol continuation cells. No behaviour change.
• ZWJ-branch and U+FE0E narrowing behaviour unchanged.

---

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-02T12:16:53.702358Z	382eb52	PR opened

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