Capability Matrix

Capability Matrix Maintenance

This repo is the canonical registry of features across Supabase's client SDKs (capabilities/*.yaml). The JSON Schema and npm run validate already catch everything mechanical: malformed IDs, area/filename mismatches, exact duplicate IDs, orphaned spec files. What they can't catch is judgment — whether a new feature is actually new, whether its name reads naturally next to its siblings, whether it's filed under the right group. That judgment is what this skill provides.

This is a local, advisory pass. There is no CI bot version of this — findings are suggestions for the person editing the file to accept, adjust, or ignore. Don't present anything as a hard requirement.

Step 0: run the mechanical checks first

Before spending any judgment calls, run the deterministic validator so you're not duplicating what it already guarantees:

cd packages/capability-matrix && npm run validate

This confirms schema conformance, area field matches the filename, IDs follow the <area>.<group_namespace>.<method_stem> pattern, no two features share an exact ID, and every spec file maps to a real feature. If this fails, fix that first — the checks below assume a structurally valid file.

Step 1: read for context, not just the diff

Read the whole target area file (capabilities/<area>.yaml), not just the new/changed entry — group names and sibling features are the only baseline for judging naming and grouping consistency. If the new feature could plausibly overlap another area (e.g. something touching both realtime and database, or client and auth session handling), skim that file too.

Step 2: semantic duplicates

npm run validate only catches identical IDs. Read every feature's name + description in the same area (and group, if cross-area overlap looks possible) and ask: does this describe behavior another entry already covers, just worded differently? Common patterns to watch for:

• Same underlying API call described from two angles (e.g. a "set" feature and a separate "update" feature that hit the same endpoint)
• A new entry that's actually a narrower case of an existing one (should it be a note on the existing feature instead of a new ID?)
• Copy-pasted description with only the verb changed

If you find a likely duplicate, name both IDs and describe the overlap — don't assume which one should win; that's the author's call.

Step 3: naming consistency

The schema enforces the <area>.<group>.<method> shape via regex, but not whether the words chosen fit. Compare the new feature's id/name against its siblings in the same group:

• Verb choice — if the group already uses create/delete/list for parallel operations, a new add_x or remove_x reads inconsistent. (See CONTRIBUTING.md's "Choosing a feature ID" section for the verb-object convention.)
• Admin/scoped variants should be namespaced the way existing ones are (auth.admin.delete_user, not auth.delete_user_admin).
• name (the human-readable title) should match the tone of sibling entries in the same group — not suddenly more/less verbose or technical.

Step 4: grouping

• Does the feature's group field point to a group that actually fits, or is it forcing a fit into the nearest existing one? If several recent features don't cleanly fit any group, say so and suggest a new group entry under groups: at the top of the file.
• Conversely, flag a group that's accumulated features with little in common — that's a sign it should split.
• A feature with no group at all is valid (it's optional) but worth a second look — is that intentional, or was a fitting group just missed?

Step 5: spec suggestion

Spec files (specs/<area>/<group_namespace>/<method_stem>.md) are optional, but valuable when a feature has real behavioral complexity: multiple named error conditions, branching behavior, side effects, or prerequisites. The directory always mirrors the feature id's own segments — e.g. auth.mfa.challenge lives at auth/mfa/challenge.md — regardless of what that feature's optional group field currently says; the two can diverge when a feature has been regrouped for display without renaming its id. If the new feature's description hints at real complexity and no spec exists, suggest creating one from specs/TEMPLATE.md. Don't suggest a spec for a simple getter/setter with an already-complete one-line description.

Step 6: platform-scope notes

There is no schema field for "this only applies to mobile/web SDKs" — that nuance (biometric auth, secure enclave storage, browser-only APIs like localStorage) is expected to live in prose, not structured data. If a feature's behavior is inherently platform-scoped, suggest a line either in the feature's description or, if it has a spec, in the spec's ## Notes section. Point out why it matters: SDKs that don't apply can declare not_applicable in their sdk-compliance.yaml, but only if the constraint is documented somewhere a maintainer would see it.

Presenting findings

Group findings by step, lead with the ones most likely to need a real change (duplicates, then naming, then grouping, then spec/platform notes). For each finding, name the specific IDs involved and explain the reasoning in one or two sentences — enough for the author to judge it themselves. Skip steps that have nothing to report; don't manufacture a finding to fill out every section. If everything looks clean, say so briefly and move on.