From 90a392e5e29c595b2536d26513914ffcc2b34547 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Mon, 20 Jul 2026 18:16:09 +0000
Subject: [PATCH 1/2] Initial plan


From e9991dbb53b98d6f26b28dffc779922318c740bc Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Mon, 20 Jul 2026 18:23:08 +0000
Subject: [PATCH 2/2] fix(spec-api): ignore XML declaration in
 validateXmlBodyEquals

Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>
---
 .chronus/changes/spec-api-xml-declaration-fix-2026-7-20.md | 7 +++++++
 packages/spec-api/src/request-validations.ts               | 2 +-
 packages/spector/test/xml-validation.test.ts               | 6 ++++++
 3 files changed, 14 insertions(+), 1 deletion(-)
 create mode 100644 .chronus/changes/spec-api-xml-declaration-fix-2026-7-20.md

diff --git a/.chronus/changes/spec-api-xml-declaration-fix-2026-7-20.md b/.chronus/changes/spec-api-xml-declaration-fix-2026-7-20.md
new file mode 100644
index 00000000000..96ecd21c04f
--- /dev/null
+++ b/.chronus/changes/spec-api-xml-declaration-fix-2026-7-20.md
@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/spec-api"
+---
+
+XML declarations no longer affect semantic body equality in `validateXmlBodyEquals`; both actual and expected XML declarations are ignored during comparison.
diff --git a/packages/spec-api/src/request-validations.ts b/packages/spec-api/src/request-validations.ts
index da170b07aed..1b18b9a65e8 100644
--- a/packages/spec-api/src/request-validations.ts
+++ b/packages/spec-api/src/request-validations.ts
@@ -64,7 +64,7 @@ export const validateXmlBodyEquals = (
     throw new ValidationError(BODY_EMPTY_ERROR_MESSAGE, expectedXml, request.rawBody);
   }
 
-  const parser = new XMLParser({ parseTagValue: false });
+  const parser = new XMLParser({ parseTagValue: false, ignoreDeclaration: true });
   const actualParsed: unknown = parser.parse(request.rawBody);
   let expectedParsed: unknown = parser.parse(expectedXml);
 
diff --git a/packages/spector/test/xml-validation.test.ts b/packages/spector/test/xml-validation.test.ts
index 93e3579506f..a990772368f 100644
--- a/packages/spector/test/xml-validation.test.ts
+++ b/packages/spector/test/xml-validation.test.ts
@@ -35,6 +35,12 @@ describe("with plain string (no matchers)", () => {
     ).toThrow("Body provided doesn't match expected body");
   });
 
+  it("should accept matching XML when actual has no declaration", () => {
+    expect(() =>
+      validateXmlBodyEquals(makeRequest("<Root><a>1</a></Root>"), "<Root><a>1</a></Root>"),
+    ).not.toThrow();
+  });
+
   it("should reject empty body", () => {
     expect(() => validateXmlBodyEquals(makeRequest(""), "<Root/>")).toThrow("Body should exists");
   });