The Wizards of Odd

A live AI app where renaming one YAML field fails the database schema, the API types, and the LLM prompts — in CI.

Play it live → wizardsofodd.com · a "council" of ten eccentric wizard personas answers your question via Anthropic tool-calls, argues, and a Clerk delivers a verdict — streamed over SSE. ("Wizards of Odd" = weird, not gambling odds.)

It's also a reference implementation of MetaObjects — a real, deployed adopter, open so you can see the pattern used in anger instead of a quickstart. One typed-metadata spine drives every generated surface, and a drift gate keeps them from silently diverging.

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Why this repo exists

MetaObjects treats typed metadata as the durable spine and generated code as the disposable artifact. This app is a working proof: one spine → many outputs, one gate.

Metadata (metaobjects/, data/)	Generator	Generated artifact	Consumed by
object.entity (Council, CouncilTurn) — source.rdb, identity, field.enum, field.object	entityFile / queriesFile	Drizzle D1 tables + Zod + typed finders (src/db/generated/)	src/db/queries.ts
object.value payloads + template.prompt	promptRender	typed render handles (src/render/generated/prompts.ts)	src/council/prompts.ts
Mustache text (data/templates/)	mustacheTemplates (custom)	inlined template map (.../templates.ts)	the render provider
template.toolcall	structuredCompletion (custom)	Anthropic tool_use wrappers + retry/fallback ladder (src/llm/generated/toolcalls.ts)	orchestrator
template.streamFrame (a project-local subtype)	sseFrames (custom)	CouncilFrame discriminated union + typed sse() (src/web/generated/council-frames.ts)	Worker and React reducer
Wizard instance data (data/wizards/)	wizardData + wizardRegistry (custom)	typed roster + render registry (src/personas/generated/)	orchestrator + gallery

The wiring is one file: metaobjects.config.ts. Every generator writes to a named target so meta verify --codegen diffs the entire generated surface — nothing escapes the gate.

The money shot — rename a field, watch it fail

The whole point of a metadata spine is that the model and everything generated from it cannot silently drift apart. Prove it in ~10 seconds, offline:

Rename question in metaobjects/meta-wizard-user-payload.yaml to anything else, then run npm run demo:drift:

meta: [brikUser]   (prompt) ERR_VAR_NOT_ON_PAYLOAD: question
meta: [dominoUser] (prompt) ERR_VAR_NOT_ON_PAYLOAD: question
…  (all 10 wizard prompts)
meta: meta verify — 10 drift error(s) across 29 template(s).
meta: meta verify — codegen drift (2 file(s) differ from a fresh regen):
meta:   ~ src/db/generated/WizardUserPayload.ts (committed content differs from a fresh regen)
meta:   ~ src/render/generated/prompts.ts (committed content differs from a fresh regen)

One field. Ten prompt templates and two generated artifacts fail at once — every Mustache prompt that binds {{question}}, the Zod/DB payload schema (WizardUserPayload.ts), and the typed render handle (prompts.ts). That's a guarantee a single-language ORM structurally can't give you, and the CI workflow (.github/workflows/meta-verify.yml) runs exactly this gate on every PR.

This repo is the demo, so the drift gate is held to its own standard: an earlier version routed four generated files outside the checked directories via ../../ path escapes, so a breaking wire-format change passed the gate clean. Fixed by putting every generator on a named target — see the git history and docs/how-metaobjects-is-used.md.

The four MetaObjects pillars, as exercised here

• Codegen — Drizzle/D1 + Zod + typed finders, typed prompt payloads + render handles, Anthropic tool-call wrappers, and the SSE frame union, all from the spine.
• Runtime metadata — the wizard roster is generated from data/wizards/ data and drives the council loop + the "Meet the Guild" gallery; add a persona, no orchestrator edit.
• Drift detection — meta verify (templates and codegen) on every PR + npm run demo:drift.
• Prompt construction — typed payload value-objects, external Mustache text resolved by a provider, a byte-equivalence snapshot test, and tool_use output parsed with a retry/fallback ladder.

This is the TypeScript port used end-to-end; MetaObjects' cross-language conformance (the "one model, many languages" claim) lives upstream at metaobjects.dev. Here the story is one model, many outputs: a single YAML spine → a database, an API's types, LLM prompts, and an SSE protocol.

It's a standard, not a framework — extend the metamodel

src/codegen/wizardsofodd-provider.ts is a consumer registering its own vocabulary, strict-provenance-clean (ADR-0023):

• a project-local template.streamFrame subtype (the SSE envelope — MetaObjects core has no such concept), and
• an Anthropic @retryReminder attr added to the core template.toolcall subtype, with the structured fallback payload riding the registered attr.properties bag.

Three small custom generators (sseFrames, structuredCompletion, wizardRegistry) implement the same Generator interface as the built-ins.

Add a wizard — data files, zero TypeScript

A persona is instance data + prompt text, not code: drop data/wizards/<id>.yaml, two data/templates/wizards/<id>-{system,user}.mustache files, add the two template.prompt nodes, and a portrait — then npm run gen:db. The roster, the gallery, the council loop, and the drift gate all pick it up. (10 personas ship; 5 run by default, the visitor can enable any subset.)

Run it yourself

npm install
echo 'ANTHROPIC_API_KEY = "sk-ant-..."' > .dev.vars   # local only; gitignored
npm run check        # gen → verify (the drift gate) → typecheck → tests
npm run dev          # wrangler dev

Fork & deploy: create your own Cloudflare KV + D1 and swap their ids in wrangler.jsonc (they're non-secret account resources); set a SEARCH_URL Worker secret if you want the optional SearXNG-backed search (it degrades gracefully without one). Portraits/background are AI-generated (local SDXL) and covered by the repo license.

Repo map

metaobjects/      the metadata spine (entities, value-objects, prompts, toolcalls, sse-frames)
data/             instance data OUTSIDE the metadata: wizard YAML + Mustache prompt text
codegen/          owned generators (entity/queries/barrel — ADR-0034 scaffold-and-own)
src/codegen/      custom generators + the project provider
src/**/generated/ generated code (drift-gated; never hand-edited)
src/             the Worker: council orchestrator, D1 layer, LLM calls, React SPA, SSR share pages
docs/             architecture.md, adr/, how-metaobjects-is-used.md
.claude/, .metaobjects/  the shipped agent-context (skills + AGENTS.md) for coding agents

More: docs/architecture.md · docs/how-metaobjects-is-used.md · docs/adr/ · docs/runbook.md.

Scope & status

Live and deployed on Cloudflare Workers. This is a reference project: the app's feature set is intentionally frozen; bug reports and doc PRs are welcome, and questions about MetaObjects itself go to metaobjects.dev. Licensed under Apache-2.0.