OpenAI ships 467 versioned interface types inside Codex, and no door for anyone else

Two version fields per object is the tell. The recovered metadata carries both `server_learning_block_version` and `rendered_learning_block_version` ^[5], bookkeeping you only need when the two can disagree, and the client's named failure modes are precisely those disagreements: `missing_matched_type` and `unsupported_matched_type` when the server asks for a block the local bundle cannot draw, `external_egress_blocked` when the environment will not fetch what the block needs ^[6]. That is the operating shape of a renderer plus a spec, with the spec compiled into the download.

The registry arithmetic is worth doing, because 467 is not 467 ideas. 442 manifests resolving to 467 type-and-version pairs leaves 25 entries that are second versions of a type already present ^[17], so the catalog is a few hundred block types with a little version history behind it. Divide the runtime by the catalog and each versioned type costs roughly 2.3 KB ^[18]. Blocks are configuration. The weight sits in the shared rendering, control, caption, example, analytics and error-handling machinery the client ships once ^[4], and in the user-facing label the client already uses, "Interactive learning block" ^[3].

RuntimeWire's counting discipline is the most useful part of the write-up. It found 901 visualization-related JavaScript chunks and 552 example-related chunks, declined to treat compiled files as products, and held to 467 unique versioned types from the manifests as the defensible number ^[11]. Those 1,453 files work out to about three per versioned type ^[19], which is what a bundler emits, not a product line.

Then the naming. The math block's default render source is spelled `CHATGPT_MATH_BLOCK_RENDER_SOURCE_GENUI_LEARNING_BLOCK` ^[10], a ChatGPT-prefixed constant recovered from the Codex desktop client, and the surrounding code will reinterpret a generic GenUI payload as a `charts_widget_v2` ^[9]. Read together, that looks less like a Codex feature and more like a client-side asset with more than one consumer, which is also how RuntimeWire frames it: GenUI is the delivery architecture, Learning Blocks are one first-party family riding on it ^[9].

The evidence has stated limits. It is client-side, from one build: Windows package 26.820.7780.0, internal version 26.820.60940, build 7119 ^[16], parsed from a signed installation checked against a SHA-256 digest of the unmodified `app.asar` ^[20], with RuntimeWire saying it reproduced the core finding and kept confirmed client behavior apart from anything needing server-side proof ^[15]. What that is enough to establish is a contract, not a roadmap: a client that renders server-chosen, versioned interface types. The live question is who gets to define a type, and OpenAI's published material, which describes Visualize and nothing about GenUI, its refresh endpoint or the registry, does not answer it ^[12].