[Streams][Streamlang][API] Fully use meta({id}) to reuse schema partials in OAS output

src/platform/packages/shared/kbn-router-to-openapispec/src/oas_converter/zod/lib.ts

@@ -937,6 +937,13 @@ export const convert = (schema: z.ZodTypeAny) => {
           return;
         }
 
+        // Zod v4's toJSONSchema() writes the .meta({ id }) value as a plain
+        // `id` property on the JSON schema node. OAS 3.0 Schema Objects do not
+        // allow `id`, so we strip it unconditionally here and track the
+        // component name via our own COMPONENT_ID_MARKER instead.
+        // See https://github.com/colinhacks/zod/issues/5731
+        delete (js as any).id;
+
         // Inject stable OAS component name and optional OAS extensions for
         // schemas that declare .meta({ id }) / .meta({ openapi: { ... } }).
         // Picked up by extractDefsToShared (for $defs entries) and

x-pack/platform/packages/shared/kbn-streamlang/src/oas_definitions.ts

@@ -41,11 +41,13 @@ import {
 
 export const streamlangOasDefinitions = {
   // Core condition — recursive schema referenced throughout routing and processing
-  Condition: conditionSchema.meta({ id: 'Condition' }),
+  // .meta({ id: 'Condition' }) is applied at definition time in types/conditions.ts
+  Condition: conditionSchema,
 
   // DSL root and step types
   StreamlangDSL: streamlangDSLSchema.meta({ id: 'StreamlangDSL' }),
-  StreamlangStep: streamlangStepSchema.meta({ id: 'StreamlangStep' }),
+  // .meta({ id: 'StreamlangStep' }) is applied at definition time in types/streamlang.ts
+  StreamlangStep: streamlangStepSchema,
 
   // Union of all processors (useful for $ref in generic processing endpoints)
   StreamlangProcessor: streamlangProcessorSchema.meta({ id: 'StreamlangProcessor' }),