docs: refresh provider package barrel refs

docs/plugins/architecture.md

@@ -1072,6 +1072,15 @@ authoring plugins:
   `<plugin-package-root>/runtime-api.js` is the runtime-only barrel,
   `<plugin-package-root>/index.js` is the bundled plugin entry,
   and `<plugin-package-root>/setup-entry.js` is the setup plugin entry.
+- Current bundled provider examples:
+  - Anthropic uses `api.js` / `contract-api.js` for Claude stream helpers such
+    as `wrapAnthropicProviderStream`, beta-header helpers, and `service_tier`
+    parsing.
+  - OpenAI uses `api.js` for provider builders, default-model helpers, and
+    realtime provider builders.
+  - OpenRouter uses `api.js` for its provider builder plus onboarding/config
+    helpers, while `register.runtime.js` can still re-export generic
+    `plugin-sdk/provider-stream` helpers for repo-local use.
 - Facade-loaded public entry points prefer the active runtime config snapshot
   when one exists, then fall back to the resolved config file on disk when
   OpenClaw is not yet serving a runtime snapshot.

docs/plugins/building-plugins.md

@@ -238,6 +238,13 @@ For the full subpath reference, see [SDK Overview](/plugins/sdk-overview).
 Within your plugin, use local barrel files (`api.ts`, `runtime-api.ts`) for
 internal imports — never import your own plugin through its SDK path.
 
+For provider plugins, keep provider-specific helpers in those package-root
+barrels unless the seam is truly generic. Current bundled examples:
+
+- Anthropic: Claude stream wrappers and `service_tier` / beta helpers
+- OpenAI: provider builders, default-model helpers, realtime providers
+- OpenRouter: provider builder plus onboarding/config helpers
+
 ## Pre-submission checklist
 
 <Check>**package.json** has correct `openclaw` metadata</Check>

docs/plugins/sdk-migration.md

@@ -54,6 +54,15 @@ stable plugin contracts. Use narrow generic SDK subpaths instead. Inside the
 bundled plugin workspace, keep provider-owned helpers in that plugin's own
 `api.ts` or `runtime-api.ts`.
 
+Current bundled provider examples:
+
+- Anthropic keeps Claude-specific stream helpers in its own `api.ts` /
+  `contract-api.ts` seam
+- OpenAI keeps provider builders, default-model helpers, and realtime provider
+  builders in its own `api.ts`
+- OpenRouter keeps provider builder and onboarding/config helpers in its own
+  `api.ts`
+
 ## How to migrate
 
 <Steps>