From d1dd0e768b1767df7ce3a9fd3963682c62fbbf1b Mon Sep 17 00:00:00 2001
From: GroophyLifefor <groophylifefor@gmail.com>
Date: Sat, 17 Oct 2026 23:49:17 +0300
Subject: [PATCH 1/2] perf: skip unused transform options in strip-only mode

`transform` is only read by swc in "transform" mode, but it was sent on
every call and deserialized through serde's flatten path. Leaving it out
in "strip-only" mode cuts the JS/wasm boundary calls per transformSync
call from 389 to 214 with identical output.

Signed-off-by: Murat Kirazkaya <groophylifefor@gmail.com>
Assisted-by: Claude Opus 5.5
---
 src/internal.ts | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/internal.ts b/src/internal.ts
index c866253e8..4fda5c27e 100644
--- a/src/internal.ts
+++ b/src/internal.ts
@@ -17,14 +17,22 @@ const DEFAULT_OPTIONS = {
 	},
 } as Options;
 
+const STRIP_ONLY_DEFAULT_OPTIONS = {
+	mode: DEFAULT_OPTIONS.mode,
+	deprecatedTsModuleAsError: DEFAULT_OPTIONS.deprecatedTsModuleAsError,
+} as Options;
+
 export function transformSync(
 	source: string,
 	options?: Options,
 ): TransformOutput {
 	// Ensure that the source code is a string
 	const input = `${source ?? ""}`;
+	const mode = options?.mode ?? DEFAULT_OPTIONS.mode;
+	// `transform` is only read in "transform" mode; leaving it out in
+	// "strip-only" mode saves deserializing it on every call.
 	return swc.transformSync(input, {
-		...DEFAULT_OPTIONS,
+		...(mode === "strip-only" ? STRIP_ONLY_DEFAULT_OPTIONS : DEFAULT_OPTIONS),
 		...options,
 	});
 }

From 190305417a9b165cc68fb18fb60bf13eef38191b Mon Sep 17 00:00:00 2001
From: GroophyLifefor <groophylifefor@gmail.com>
Date: Sun, 18 Oct 2026 22:49:54 +0300
Subject: [PATCH 2/2] refactor: use separate default options per mode

Keep the default options for "strip-only" and "transform" mode in two separate objects and pick one based on the requested mode, as suggested in review. The options sent to swc are unchanged.

Signed-off-by: Murat Kirazkaya <groophylifefor@gmail.com>
Assisted-by: Claude Sonnet 5.5
---
 src/internal.ts | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/src/internal.ts b/src/internal.ts
index 4fda5c27e..ba1334864 100644
--- a/src/internal.ts
+++ b/src/internal.ts
@@ -8,19 +8,20 @@ import swc from "../lib/wasm.js";
 const DEFAULT_OPTIONS = {
 	mode: "strip-only",
 	deprecatedTsModuleAsError: true,
-	// default transform will only work when mode is "transform"
+} satisfies Options;
+
+// swc only reads `transform` in "transform" mode, so these defaults are kept
+// out of strip-only calls to avoid deserializing them on every call.
+const DEFAULT_TRANSFORM_OPTIONS = {
+	mode: "transform",
+	deprecatedTsModuleAsError: true,
 	transform: {
 		verbatimModuleSyntax: true,
 		nativeClassProperties: true,
 		noEmptyExport: true,
 		importNotUsedAsValues: "preserve",
 	},
-} as Options;
-
-const STRIP_ONLY_DEFAULT_OPTIONS = {
-	mode: DEFAULT_OPTIONS.mode,
-	deprecatedTsModuleAsError: DEFAULT_OPTIONS.deprecatedTsModuleAsError,
-} as Options;
+} satisfies Options;
 
 export function transformSync(
 	source: string,
@@ -28,13 +29,9 @@ export function transformSync(
 ): TransformOutput {
 	// Ensure that the source code is a string
 	const input = `${source ?? ""}`;
-	const mode = options?.mode ?? DEFAULT_OPTIONS.mode;
-	// `transform` is only read in "transform" mode; leaving it out in
-	// "strip-only" mode saves deserializing it on every call.
-	return swc.transformSync(input, {
-		...(mode === "strip-only" ? STRIP_ONLY_DEFAULT_OPTIONS : DEFAULT_OPTIONS),
-		...options,
-	});
+	const defaults =
+		options?.mode === "transform" ? DEFAULT_TRANSFORM_OPTIONS : DEFAULT_OPTIONS;
+	return swc.transformSync(input, { ...defaults, ...options });
 }
 
 export function transformModuleSyntax(