ADR 0149: The project mark is the Unicode glyph ◮

Terminal implementation amendment (2026-08-13; ADR 0279): The mark and discern's word mark, reveal, pyramid, and gasket compositions remain product authority. The published package now owns the reusable Unicode/ASCII triangle glyph set, weave and spinner orders, motifs, section rules, progress, and painting mechanics. Product compositions derive from those public constants instead of maintaining a second generic triangle vocabulary.

Status: accepted

discern lives in text: a CLI, generated Markdown, MCP output, and a docs site rendered from the same tree. Most surfaces where a mark could appear are plain text in someone else's font. An image-first logo would go missing from the places the project is most often seen. The docs site already uses ◮ as the ornament on rendered thematic breaks, and the map described it as "discern's intended mark" — an intent no record had fixed.

The project mark is the character ◮ — U+25EE, UP-POINTING TRIANGLE WITH RIGHT HALF BLACK.

The shape carries the name: one form split into two parts you can tell apart, which is the act of discerning. The triangle also reads as a delta, a change, which is what the gate judges.

The canonical reading is filled versus unfilled, never dark versus light. A glyph renders in the reader's foreground color, so on a dark theme the "black" half is the bright one; any reading that depends on which half is dark inverts when the theme does. For the same reason the mirror ◭ (U+25ED, left half black) carries no distinct meaning: the two are semantically equivalent, and ◮ wins on appearance.

Practical properties, checked against the Unicode character data for U+25EE:

• East Asian Width is Neutral, so terminals render it single-width even under CJK ambiguous-width settings; it cannot misalign columns.
• It has no emoji presentation, so no platform substitutes a colored pictograph.

Two rules bound its use:

• In CLI and machine-facing output the glyph is decorative, never load-bearing. Nothing parses it, no alignment depends on it, and output must read correctly in a font that lacks the codepoint.
• Drawn assets (favicon, social images) are bespoke SVGs derived from the shape, rendered theme-aware (currentColor or a light/dark pair), never a rasterized glyph. At favicon sizes the half-fill tends to collapse into a solid triangle, so drawn versions may exaggerate the split.

• One character serves every text surface (the README, CLI banners, the docs site, chat) with no asset pipeline, and theme adaptation costs nothing because the glyph rides the foreground color.
• Font coverage of U+25EE is wide but not universal; the decorative-only rule is what makes a missing-glyph box harmless.
• The site's thematic-break ornament (pinned by tests/site_docs_test.ts) is now the recorded mark rather than an unrecorded intention.

• ◭ (U+25ED), the mirror. A left-to-right dark-into-light reading was attractive, but it does not survive foreground-color inversion, so no stable meaning separates the mirrors. Appearance settled the choice.
• A solid ▲ (U+25B2). Loses the split that carries the meaning, and an up-pointing solid triangle is already Vercel's mark; wearing an adjacent shape in the same developer-tool space invites misreading.
• An image-first logo. Cannot travel through terminals, plain-text READMEs, or MCP output — the surfaces where discern is most read. Drawn assets remain, but as derivatives of the glyph rather than the primary mark.