Architecture

Architecture

Component decomposition and per-component facts. The cell (cell-design skill) declares WHAT exists; this skill owns deciding the decomposition and ENRICHING each component's design.json.

Scaffold first, enrich second

When the cell is saved, the platform scaffolds specs/design/components/<id>/design.json for every deployable component — the mechanical fields (name, type, version, buildpack, appPath, entrypoint, a default exposure) plus a "language": "TBD" sentinel. Your job is the JUDGMENT fields, and the build gate refuses a deployable component left unenriched:

• language — Language is decided in this order: the organization skill's Tech stack default first, then a language the requirements name, then the platform default — Ballerina for backend services, TypeScript for web apps. Replace the scaffold's "language": "TBD" sentinel with the decided value; the build gate refuses a component whose language is still TBD. That choice is a fact you record, not a preference you re-derive per component: write it as the component's language and pin the matching stack skill in skillsPinned.
• stories — the PRD story numbers this component serves, as an integer array (e.g. "stories": [1, 2, 4]). Claim every story the component actually serves: the build gate refuses the tag while any PRD story is claimed by no component.
• dependencies — the playbook below.
• description — one paragraph: single responsibility, port/entrypoint expectations, and what it explicitly does NOT do.
• skillsPinned — After emitting or changing a component's design, record the skills that component's build actually needs as a skillsPinned array inside that component's specs/design/components/<name>/design.json — use the exact catalog names, e.g. a Ballerina API service → ["openapi-conventions", "ballerina"] (a Go one → ["openapi-conventions", "go"]); a web-application → ["wireframes", "react-webapp", <design system>], where <design system> is the skill name in the UI design system section of the Organization defaults block in your instructions. A web app's UI toolkit is a settled organization decision, so pin it on every web-application rather than leaving it to a description to trigger — and read the name from that section every time instead of remembering one, because it differs per organization. If that section is absent or empty, pin only the two stack skills. Never substitute a design system the organization defaults do not name.

Pin the design system; do not consult it. A design system is built against, not designed with — it is the coding run's to load, and its theming is a settled organization decision that no design-time question reopens. Never ask the user about colors, themes, or look and feel. Add "api-management" to any service that sits behind the gateway, and "thunder-authentication" to both sides of sign-in — the SPA and every protected backend it calls, since that skill owns how each resolves the caller's role. It is a JSON key on the component's design object, so include it when you write that design.json (addFile/editFile) — design.json is its only home. Each component carries only the skills its own build needs.

Writing the whole enriched file yourself (removeFile + addFile with every field) is equally valid — the scaffold is a safety net, not a required intermediate.

Deriving components — deployment units the requirements justify

A component is one independently deployable unit, NOT a domain concept. The right number comes from the requirements: for every component you must be able to say "this deploys and evolves independently because ". Write that justification into the component's description.

A requirement justifies a SEPARATE component when it shows:

• a distinct user-facing surface — e.g. an internal admin portal AND a customer-facing app with different users and lifecycles → two web-applications;
• a genuinely different runtime or scaling profile — e.g. an async worker/batch processor beside an interactive API, or a long-running AI/inference service;
• a technology the rest of the system doesn't share — e.g. a Python ML service beside a Ballerina API;
• an explicitly separate lifecycle or ownership stated in the requirements.

Do NOT split by:

• entity or domain concept — claims-service, users-service, receipts-service... is a domain model dressed as a topology; those are modules of ONE service;
• layer — auth, notifications, file storage as own services when they are modules of the API; a single frontend split into ui-shell + ui-pages when it is one bundle;
• infrastructure — api-gateway, database, queue, auth server are NEVER components; the platform provides them;
• periodic work — a nightly digest or a cleanup sweep is a background task the owning service starts, not a component of its own. Only a genuinely different runtime or scaling profile (above) justifies splitting one off.

When nothing above forces a split, a small system naturally lands at one service + one web-application — that is an outcome of the rule, not a target. Name components in kebab-case after their responsibility (expense-api, expense-webapp, report-worker).

Component type is a fixed vocabulary — use the EXACT string. A backend is "service"; a browser app is "web-application" (OpenChoreo's own term). Write "web-application" verbatim — NOT "webapp", "web-app", or "webApplication" (those are rejected, and a wrong value silently breaks the app's deployment and runtime config). The -webapp in a component NAME is fine; the type is still "web-application". Other kinds the requirements imply ("scheduled-task", "worker", …) are captured verbatim, but the platform installs component types for service and web-application ONLY — anything else records intent and does not deploy, so reach for one when the requirements truly force it, never as the default home for periodic work.

Per-component design.json

Each component's structured facts live in ONE JSON document (no markdown, no frontmatter). The platform validates each write against this schema and rejects violations:

{
  "name": "expense-api",              // MUST equal the directory name
  "type": "service",                  // EXACT kind: "service" or "web-application" (NEVER "webapp"/"web-app"), or another the requirements imply ("scheduled-task", "worker", ...)
  "version": "0.1.0",                 // semantic version; 0.1.0 for a new component
  "language": "Ballerina",            // implementation language — "Ballerina" for a service unless the requirements say otherwise; "TypeScript" for a web-application
  "buildpack": "docker",              // always "docker"
  "appPath": "expense-api",           // repo-relative source dir — the component name
  "entrypoint": "deployment/service", // deploy entry — PAIRS with `type`: "deployment/service" for a service, "deployment/web-application" for a web-application
  "exposure": "internet",             // "internet" (public) | "intranet" (internal only)
  "dependencies": [ /* see below — every dependency edge touching this component appears here */ ],
  "description": "One paragraph: single responsibility, port/entrypoint expectations, and what it explicitly does NOT do.",
  "stories": [1, 2, 4],               // PRD story numbers THIS component serves — the build gate refuses the tag while any story is claimed by nobody
  "skillsPinned": ["openapi-conventions", "ballerina"], // the skills this component's build needs — see the field above
  "endpoint": { "name": "http" } // optional; see below
}

name, type, version, language, buildpack, appPath, entrypoint, exposure, description, dependencies, stories and skillsPinned are required — stories and skillsPinned are as required as the rest, and a component missing either fails the build gate, so emit them in the SAME write rather than as a follow-up edit. To CHANGE a design.json, re-emit the whole corrected file (removeFile + addFile) — never patch JSON with anchored edits. On INVALID_JSON or SCHEMA_VIOLATION, fix what the message lists and re-emit.

endpoint is optional: omit it and a service's endpoint takes the default name "http". Declare { "name": "<endpoint-name>" } only when the endpoint must be named otherwise — name is the single source of truth the coding agent copies into workload.yaml and the managed-API gateway binds to. The port lives in workload.yaml, not here.

Platform-owned fields you never author, in two kinds:

• Preserved verbatim where the platform has already written them: exposesAPI, componentAgentInstructions, and any dependency status/reason.
• Recomputed and overwritten on every save: a dependency's wiring object. The platform derives its ref and its env-var names from the dependency's name and its resource type's declared outputs, so anything you write there is discarded. stories is NOT in this class — it is yours to author, per the stories field above.

dependencies — one entry per design.cell edge

dependencies mirrors the DEPENDENCY edges of design.cell: every arrow between this component and another node appears here and vice versa — a mismatch is a defect. The north -> / west -> gateway arrows are exposure, not dependencies: they live in this component's exposure field and never become entries here. The platform enforces the membership half as you write: a dependency whose name is not a node the cell declares is refused (UNKNOWN_DEPENDENCY) with the cell statement to add. A resource you discover here — a database, a cache — is a cell node too: editFile specs/design/design.cell to add component <name> as "…" database inside the cell before the design.json that depends on it, or the diagram will not draw what the build provisions. Each entry is a kind plus a name, and you pick the kind by WHAT the target is. The kind-only fields below are exhaustive: one of them on another kind is a schema violation that both the zod write-gate and the Go fold gate reject.

The four kinds

Reuse. Call that last column's tool before authoring the entry, and take the name and schema from the matching row rather than from the requirement's wording — a Registered External resource described as "transactional email delivery" is the right reuse for an "email" need even when its name (sendgrid) doesn't echo the requirement. When several rows could fill the role, the org-level one wins (a Registered External over a new Project External name; an org-service over a sibling you would otherwise add; a listed cluster resource type for resourceType). This step is done when every external, org-service, and platform-resource emitted this turn is taken from this turn's matching list_* result (exact name or resourceType), unless this turn is a user-asked reconsider. When nothing the catalog returns fills the role, omit the entry and list the gap under Needs your input rather than coining a name: a resourceType that was not in this turn's list_platform_resource_types result fails Build.

"dependencies": [
  { "kind": "component", "name": "expense-api" },
  { "kind": "platform-resource", "name": "orders-db", "resourceType": "postgres-cnpg" },
  { "kind": "external", "name": "github",
    "description": "Call GitHub issues + PRs for the sync story." }
]

The github entry is a REFERENCE: its definition — provider, style, contract, config keys — is specs/design/dependencies/github/dependency.json, written once and shared by every component that uses it. A component's description on the edge says why THIS component uses it; the dependency's own description says what the system is.

Reading a provider's real contract

Once you have an org-service provider's name, call list_org_component_endpoints and base that dependency's description on the operations its contract actually exposes:

Traps

• Never the reverse edge. Declare a dependency ONLY on the caller, naming the callee: a web-app depends on the API it calls; the API does not depend on the web-app. A component this one doesn't call is not a dependency of it — don't list one "for reference".
• A role is not a name. The requirement says "the organization's directory service"; the provider is usually called something else (employee-service). The same for a platform-resource: the PRD names a capability, resourceType is the catalog row's name from this turn's list_platform_resource_types. Copy that name. Look it up — a name coined from the role or capability words matches no provider or type and hard-fails the build.
• A platform-resource's name becomes the env-var prefix for every one of its outputs (orders-db → ORDERS_DB_HOST, and for a SPA window._env_.ORDERS_DB_*), so pick a clear one: renaming it later renames the component's whole config surface.
• Secret-bearing dependencies belong on a service, not a web-application. A web-application ships to the browser, so anything it holds is visible in dev tools — and every output of a platform-resource it declares is emitted into window._env_, so a database dependency on a SPA publishes its password. The secure default: attach the dependency to a backend service and give the web-app a component edge to it, so the service proxies and the SPA never sees the credential. A web-application may declare an external dependency directly only when NONE of its config keys need secret: true — a genuinely public API, or one the END USER authenticates with their own in-browser OAuth. The one exception is thunder-app (next bullet): its outputs are public OIDC client config by design. The schema does not reject a secret on a web-application, so apply this as the architect's judgment call, not a rule to route around.
• thunder-app is how sign-in happens, and nothing else provisions it. When the spec implies users sign in, declare it on BOTH the SPA and each protected service under the SAME dependency name — that shared name is what ties sign-in to token-carrying API calls. With no such dependency the SPA deploys unable to sign in. thunder-app takes no parameters: security-design authors the Thunder client on security.json, and the platform registers the callback URI (redirectUris — platform-managed, never proposed here). thunder-authentication owns the coding-time rule, and security-design owns which roles sign in through it.

Resolving an external dependency

One dependency, one definition. An external dependency lives in its own directory, specs/design/dependencies/<name>/, and a component only references it by name. The write-gate refuses a component that names an external dependency whose directory has no dependency.json yet, so write the dependency file BEFORE the component that uses it (a declare_plan entry per dependency keeps the rail honest). The name is the same identifier everywhere: the directory, the cell's south node, the component's reference, and — for a reuse — the org registry.

dependency.json:

{
  "name": "payment-provider",
  "description": "Charges the customer for shipping once a box is priced.",
  "provider": "Stripe",
  "style": "rest-api",
  "contract": "openapi.yaml",
  "provenance": { "sourceUrl": "https://…/spec3.json", "sha256": "…", "fetchedAt": "…", "sliced": true },
  "config": [ { "key": "PAYMENT_API_KEY", "secret": true, "description": "Stripe secret API key" } ]
}

Work each one in order:

1. Reuse first. Call list_external_resources. When a Registered External resource fits, write the stub { "name": "<its exact name>", "source": "org" } — the platform fills provider, contract and config from the org record, and the build collects no values for it, because org values stay on the Registered name. Write consumption instructions into the dependency description — the row's consumption instructions and its org resource docs pointers, as the tool returns them — because the coding agent reads them there and never calls the catalog. Then stop. A user-asked reconsider may switch to a different Registered name, or create a Project External resource under a new name.
2. The PRD names the service, or nobody has. The user chooses providers; you never do. Two outcomes, never a status:
   • The PRD's Product Decisions name a service for this capability ("Payments: Stripe") → write provider + style and go on to the contract (step 3). An org or platform skill that mandates a vendor counts the same way. Nothing else does: "the requirement implies it", "this one is popular", "there is only one real option" are guesses, and a guess is the user's to make.
   • No provider named → write the NEED only: name, description, and suggestions — providers commonly used for this capability, from what you know, any number, each { "name", "style"?, "description"? } with the one distinction that matters for THIS product. No web_search, no provider, no style, no contract, no config — the config keys follow the provider, and none is chosen. The definition then offers Select a provider, which runs the resolve-dependency flow: it asks the user, with your suggestions as the options, and does the research. This is the EXPECTED outcome for a choosable dependency; do not force a pick the PRD does not make. The dependency IS the service the product needs, so name it <capability>-service (currency-service, payment-service, email-service); the chosen system is its provider.
3. Get the contract on disk — for a named provider only. style says how: rest-api and graphql need a document in the directory (openapi.yaml / schema.graphql), sdk needs sdk.json (and the API slice beside it when the provider has one). The contract is a SLICE: name the operations the design's flows actually call and let slice_openapi_spec cut them from the provider's published document with their referenced schemas — it fetches outside your context, so the document's size does not matter — then addFile the returned content as openapi.yaml and copy the returned provenance into dependency.json. A user-supplied document goes through the same tool. With no document to be found, climb one rung: derive the interface from the provider's OWN developer reference when it names every operation the design calls with parameters and responses — openapi.yaml with x-aep-derived: true at the root and x-aep-source: <page> on every operation, provenance. sourceUrl = the reference's root page. That needs no permission: the dependency reads resolved, flagged derived. With no such documentation either, never guess during the design turn: leave contract unset, say so under Needs your input, and the resolve-dependency flow takes it from there (it may write an ASSUMED contract, but only under the user's authorization). This rung is for a NAMED provider only — an open capability gets no interface search at all.
4. Derive config keys from the contract — a rest-api's components.securitySchemes, an sdk's auth documentation — for a named provider only; a definition with no provider carries no keys (the gate refuses them). A reused Registered row already named the keys — keep them.
5. Reference it from each consuming component: { "kind": "external", "name": "<name>", "description": "<why this component uses it>" }. style, package, specPath, suggestions, config on the component are refused — they belong in the dependency file.

Config-key conventions

config is the env-var schema the consuming component codes against. Use SCREAMING_SNAKE_CASE keys and keep them minimal — only what the component reads. secret is opt-in: set "secret": true ONLY for credentials (they route through the secret path), and OMIT it entirely otherwise. Give each key a description saying what the value is and where the user finds it ({ "key": "STRIPE_API_KEY", "secret": true, "description": "Your Stripe secret API key" }) — the Build dependency drawer shows it under the field. For a NON-secret key whose sensible default you can infer, add defaultValue and the drawer pre-fills it ({ "key": "AWS_REGION", "defaultValue": "us-east-1" }). NEVER set defaultValue on a secret — a credential has no default to invent. An external dependency should almost always carry at least one key: the value-collection gate needs something to collect.

How the platform derives status/reason

You never author status/reason. The platform reads them off the dependency file at read time, first match wins:

1. source: "org", or name matches a registered external resource → resolved (flagged registered)
2. no provider (suggestions open or not) → unresolved/needs-input — the user has not chosen a service; the definition asks them
3. a style whose contract is not on disk (no openapi.yaml / schema.graphql for rest-api / graphql; no sdk.json for sdk) → unresolved/needs-contract
4. a contract marked assumed with no user acceptance → unresolved/ needs-acceptance
5. otherwise → resolved — flagged assumed when the contract was accepted as an assumption, derived when it was written from the provider's own documentation, sdk-only when an sdk dependency has no API slice

component is always resolved here. A platform-resource is too — once emitted — so only emit one whose resourceType is a name from this turn's list_platform_resource_types. An org-service resolves on catalog visibility, and is blocked/access-required when the provider exists but this project cannot see it. needsSpec, specPath and the other definition fields are gone from the component's schema — a draft carrying them fails the write-gate with a message naming the dependency file they moved to.

Narrating the design turn

The design-generate turn runs in the chat panel, so your turn text is what the user watches live. Narrate each dependency decision in one plain-prose line as you settle it, before moving to the next:

• resolved → ✓ <capability>: using <choice> (say , contract sliced when you cut one, , interface derived from docs when you wrote it from the provider's reference, , registered for an org reuse)
• needs-input → <capability>: your choice — A / B / C are common; select a provider on its definition
• needs-contract → <capability>: <provider> chosen, no published contract found — you can upload one or let me assume it, from the dependency's definition in the spec view

Never block the design on an unresolved dependency — print the line and keep emitting the rest; the user replies in the same chat to steer it, now or later. Then close with three parts and nothing more: one line per component (name, type, one-clause role); a "Needs your input" block listing ONLY the dependencies still unresolved, each as a LINK to its definition — [currency-service](aep://spec/specs/design/dependencies/currency-service/dependency.json) — followed by the single thing you need (the console opens the definition from the link; this link form is the one place a repo path is allowed in your prose); and a one-line pointer to specs/design/. The narration already carried the play-by-play, so a file-by-file recap would only bury the user's next action. Each Needs your input line names the dependency the way its definition in the spec view does, so the user can click through and press Resolve — that runs the resolve-dependency flow, which is where the contract gets provided or assumed; the design turn never waits for it.

Resolving or reconsidering a named dependency on request

/resolve-dependency <name> runs the resolve-dependency skill — the guided flow that takes one dependency from open to resolved; read that skill when the instruction names it. A plain chat turn may still point you at a dependency ("reconsider stripe"): read specs/design/dependencies/<name>/dependency.json from the snapshot and act on its current state.

• No service chosen — it carries suggestions, or nothing. The user's answer, if the instruction carries one (a service name or a document URL), IS the choice: set provider + style, remove suggestions, and go for the contract (step 3). With no answer, put the choice to them — the suggestions, or what your research finds, each with a one-line distinction, plus that they may name another — and write nothing until they answer.
• Already resolved — reconsider. This is the only branch that may leave a catalog row that still fills the role. Present fresh alternatives in the conversation, or repin to the Registered name the user picks, or start a Project External resource under a new name.

Edit ONLY that dependency's file: re-emit the whole dependency.json (never a patch) with every field you are not changing carried over exactly. The components' references do not change. Never write or alter assumed — that is the user's record; the write-gate refuses it.

Descriptions, and the per-component artifacts

Every dependency carries a one-line description: what the target is and how this component uses it. Source it per kind — an external's definition file carries what the system is (the consumption instructions when the name is a Registered External resource) and the component's reference why this component calls it; an org-service's says the specific operations it calls from the discovered contract, or plainly that no contract was resolvable, never a guess; a platform-resource's says what it stores. The console shows it in the dependency drawer and the coding agent relies on it to integrate correctly.

One component per directory. Every web-application gets a wireframes.dsl (wireframes governs it); every service gets an openapi.yaml (openapi-conventions governs it), emitted after domain-model.md's ER model. Other kinds (scheduled tasks, workers, …) carry no extra artifact yet — capture their behaviour fully in description and dependencies.