fix: Filter out http-bound members from schema passed to payload serializer

packages/core/src/submodules/protocols/HttpBindingProtocol.ts

@@ -20,6 +20,12 @@ import { collectBody } from "./collect-stream-body";
 import { extendedEncodeURIComponent } from "./extended-encode-uri-component";
 import { HttpProtocol } from "./HttpProtocol";
 
+/**
+ * Cache key for the body-only schema view that excludes HTTP-bound members.
+ * @internal
+ */
+const HTTP_BODY_MEMBERS = Symbol.for("@smithy/http-body-members");
+
 /**
  * Base for HTTP-binding protocols. Downstream examples
  * include AWS REST JSON and AWS REST XML.
@@ -152,7 +158,17 @@ export abstract class HttpBindingProtocol extends HttpProtocol {
     }
 
     if (hasNonHttpBindingMember && input) {
-      serializer.write(schema, input);
+      const bodyNs = ns.filterMembers(HTTP_BODY_MEMBERS, (_name, memberNs) => {
+        const traits = memberNs.getMergedTraits();
+        return !(
+          traits.httpHeader ||
+          traits.httpLabel ||
+          traits.httpQuery ||
+          traits.httpPayload ||
+          traits.httpPrefixHeaders
+        );
+      });
+      serializer.write(bodyNs, input);
       payload = serializer.flush() as Uint8Array;
 
       // Due to Smithy validation, we can assume that the members with no HTTP

packages/core/src/submodules/schema/schemas/NormalizedSchema.ts

@@ -413,6 +413,43 @@ export class NormalizedSchema implements INormalizedSchema {
     return "";
   }
 
+  /**
+   * Returns a view of this schema whose structIterator only yields members
+   * matching the given predicate.
+   *
+   * The returned object delegates all other NormalizedSchema methods to this instance.
+   * This is useful when a caller needs to pass a subset of struct members to a
+   * generic serializer without copying the underlying schema arrays.
+   *
+   * Results are cached on the underlying struct schema keyed by the provided symbol,
+   * so the predicate only runs once per schema regardless of how many requests use it.
+   */
+  public filterMembers(
+    cacheKey: symbol,
+    predicate: (name: string, memberNs: NormalizedSchema) => boolean
+  ): NormalizedSchema {
+    const struct = this.getSchema() as StaticStructureSchema & {
+      [key: symbol]: NormalizedSchema;
+    };
+    if (struct[cacheKey]) {
+      return struct[cacheKey];
+    }
+
+    const entries: Array<[string, NormalizedSchema]> = [];
+    for (const [name, memberNs] of this.structIterator()) {
+      if (predicate(name, memberNs)) {
+        entries.push([name, memberNs]);
+      }
+    }
+
+    const view = Object.create(this) as NormalizedSchema;
+    (view as any).structIterator = function* (): Generator<[string, NormalizedSchema], undefined, undefined> {
+      yield* entries;
+    };
+    struct[cacheKey] = view;
+    return view;
+  }
+
   /**
    * Allows iteration over members of a structure schema.
    * Each yield is a pair of the member name and member schema.

packages/types/src/schema/schema.ts

@@ -180,6 +180,7 @@ export interface NormalizedSchema {
    */
   getMemberSchema(member: string): NormalizedSchema | undefined;
   structIterator(): Generator<[string, NormalizedSchema], undefined, undefined>;
+  filterMembers(cacheKey: symbol, predicate: (name: string, memberNs: NormalizedSchema) => boolean): NormalizedSchema;
 }
 
 /**