Emoji in model output floods the console with font warnings

Date: 2026-08-02 Status: fixed (v0.13.1) Reported: user, live panel (“エージェントを走らせるとフォント関連で警告が頻発する”)

1. Symptom and root cause (measured)

The live editor log fills with:

The character with Unicode value ❌ was not found in the [] font asset
or any potential fallbacks. It was replaced by Unicode character □.

Observed codepoints: U+274C (cross mark) and U+2705 (check mark button) — i.e. ordinary emoji the model writes in its markdown. They are NOT panel glyphs: IconLoader.SafeGlyphCodepoints was curated for exactly this reason and none of its entries warn.

Why a flood rather than one line: Unity’s text generator logs once per missing-character OCCURRENCE on EVERY text-generation pass, with no caching (probe P2b). Two panel paths reassign .text on a timer while a turn runs — StreamingLabelPump.OnUpdate (~80 ms) and SubagentCard’s progress line (500 ms) — so a single visible emoji re-emits its warning for as long as it stays on screen.

The pre-existing sanitizer (IconLoader.StripVariationSelectors) only removed U+FE0F/U+FE0E, which does nothing for the base emoji codepoint.

2. Chokepoint audit (probe P3)

The probe mapped every path where untrusted text reaches a Label. Besides the two flood sources it found genuine BYPASSES that never sanitized at all: PermissionCard.PlainLabel and its summary title (model-authored tool descriptions, AskUserQuestion option text), CodeBlockElement’s fence language tag, ToolActivityCard’s tool-name label, HeaderView’s session title, HistoryView’s preview row, and (found in review) MessageBlockFactory.CreateTextBlock’s non-pump fallback plus the AskUserQuestion option tooltip.

InlineMarkupConverter.Escape is the single chokepoint for all markdown-rendered rich text and had its own duplicate FE0F logic.

3. Decision

IconLoader.SanitizeForDisplay(string) supersedes StripVariationSelectors at every untrusted-text chokepoint:

1. strip variation selectors and zero-width joiners (no orphan ZWJ left);
2. map a short curated table to font-safe equivalents so meaning survives (U+2705/U+2714 -> the existing check glyph, U+274C/U+274E -> the existing cross glyph, U+2757 -> ”!”, U+2753 -> ”?”, U+2728 -> the spark glyph, directional emoji -> existing chevrons);
3. drop anything left in the known-uncoverable ranges (pictographs and Misc Symbols/Dingbats outside the curated/whitelisted set).

CJK, kana, accented Latin, box-drawing (markdown tables) and math symbols are preserved verbatim — the review lens specifically hunted for over-stripping.

Why range-dropping rather than querying the font

FontAsset.HasCharacter(uint, searchFallbacks, tryAddCharacter) does work (the 3-arg overload only — the 1-arg overloads returned false even for U+2713, which renders fine), but reaching the font UI Toolkit actually uses requires PanelTextSettings.defaultPanelTextSettings, which is INTERNAL to UnityEngine.UIElementsModule. Getting there needs reflection into a version-specific internal, to decide something a static table decides just as well. Rejected: reflection fragility on the streaming hot path buys nothing over the curated table plus range drop. Documented so a future Unity version exposing the API can revisit.

4. Regression guards

Pure-function tests: curated mappings, unknown emoji dropped, CJK/accents/ box-drawing preserved verbatim, ZWJ sequences fully removed, lone surrogate handling across streaming delta boundaries, idempotence — plus a source scan asserting each identified render path calls the sanitizer, so a new Label added to a render path fails the suite rather than quietly reintroducing the flood. All emoji in test sources are \uXXXX escapes (ASCII-only source rule).

5. Review catches worth recording

• The pictograph drop range started at U+1F300, leaving U+1F000-U+1F2FF (Mahjong/Domino/Playing Cards, Enclosed Alphanumerics) still able to warn.
• Two more raw assignments (the non-pump text fallback, the AskUserQuestion option tooltip) that the initial pass missed — the source-scan guard exists precisely because this class of miss is easy.