Skill Hierarchy

As of Yggdrasil II (ratified 2026-07-07), there is no single four-way tier split. A skill's structure is described by two separate axes instead. Type (Basic or Fusion) lives on starless skills only — it is fixed before anyone claims the skill. Branch (Unique or Suite) lives on Named Skills at 4★ and up — it is computed from whether the skill carries suiteComponents, never declared by hand. Stars (0★–6★) measure evidence depth and apply throughout.

A fourth axis — rarity — existed in earlier schema versions but has been fully removed. If you encounter old documentation referencing common/uncommon/rare/epic/legendary, treat it as stale.

Stars measure how thoroughly a skill's real-world existence has been demonstrated and peer-reviewed. They are derived from evidence, never declared. An agent cannot claim to be "5-star at web search" by self-reporting — stars accumulate through a sequence of evidence submissions and Verifier reviews.

The axis runs from 0★ (no evidence) to 6★ (the Apex). Rank names are the canonical labels for specific star values; they are only valid when paired with the name — "the Evolved rank", never just "rank 3."

Fusion is the act of combining two or more skills into a single skill of Type fusion (see Type/Branch above). Every fusion output carries Type fusion, full stop — there is no separate structural "Extra" or "Ultimate" a fusion produces directly. The verb is always fuse — never merge, combine, or compose.

A fusion candidate appears in your tree when you already hold all of a target skill's prerequisite components. Confirm it with gaia fuse. The fused skill starts at a star value equal to the highest star among its components, minimum 1★.

A Named Skill is a canonical skill that has been claimed by a real contributor with Bronze (Grade C) evidence or better. At the moment of naming, the skill reaches 2★ Named rank. The contributor's name attaches permanently as the Origin Contributor and renders in honor red across the registry.

Named Skills are the human layer of the registry — they answer not just "does this capability exist?" but "who has demonstrated it, where, and how well?" Multiple contributors can hold named implementations of the same canonical skill; only the first is the Origin.

The canonical graph contains two kinds of nodes: generic (starless) nodes and named nodes. Understanding the difference is critical when reading gaia lookup output or the Hunter's Atlas.

A generic (starless) reference is a taxonomy node that carries no stars of its own. It represents the capability in the abstract — "web search as a category." Stars belong only to the named implementations (the skill's "children"). The generic node's effective rank is the highest star among all its named children.

In the UI, generic nodes render in italic greyed-out styling to distinguish them from named skills. The term generic is the technical descriptor; starless is the brand / collective noun.

All player-facing commands default to showing your data, not the canonical registry. gaia tree shows your unlocked skills. gaia scan looks at your local directories. gaia stats reports on your personal tree and installed skills.

To view the canonical registry instead, pass --canon to any command. This toggle is available everywhere: gaia tree --canon, gaia stats --canon, gaia graph --canon.