From 83e19fb5568f2bf8eac6bd7ff47c88a6bd768711 Mon Sep 17 00:00:00 2001
From: Jens Verbeken <jens.verbeken@craftzing.com>
Date: Fri, 3 Apr 2026 23:01:10 +0200
Subject: [PATCH] fix(openapi3): missing discriminator mapping entry when first
 union variant causes circular emit

---
 packages/openapi3/src/schema-emitter.ts | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/packages/openapi3/src/schema-emitter.ts b/packages/openapi3/src/schema-emitter.ts
index a6970792702..520d8503af6 100644
--- a/packages/openapi3/src/schema-emitter.ts
+++ b/packages/openapi3/src/schema-emitter.ts
@@ -720,7 +720,13 @@ export class OpenAPI3SchemaEmitterBase<
     for (const [key, model] of variants.entries()) {
       const ref = this.emitter.emitTypeReference(model);
       compilerAssert(ref.kind === "code", "Unexpected ref schema. Should be kind: code");
-      mapping[key] = (ref.value as any).$ref;
+      if (ref.value instanceof Placeholder) {
+        ref.value.onValue((resolvedValue) => {
+          mapping[key] = (resolvedValue as any).$ref;
+        });
+      } else {
+        mapping[key] = (ref.value as any).$ref;
+      }
     }
     return mapping;
   }