From dca14900c4746153555d4c1b805324b1397a452a Mon Sep 17 00:00:00 2001
From: Honey Tyagi <78690656+HoneyTyagii@users.noreply.github.com>
Date: Wed, 7 Oct 2026 21:16:44 +0530
Subject: [PATCH] perf(domain): batch canonical digest writes with bounded
 buffer

---
 src/domain/canonicalDigest.test.ts |  7 +++++++
 src/domain/canonicalDigest.ts      | 13 ++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/domain/canonicalDigest.test.ts b/src/domain/canonicalDigest.test.ts
index 02a641905..51df94619 100644
--- a/src/domain/canonicalDigest.test.ts
+++ b/src/domain/canonicalDigest.test.ts
@@ -62,6 +62,13 @@ describe("incremental canonical digest", () => {
     expect(digestCanonicalValue(value)).toBe(legacyDigest(value));
   });
 
+  it("keeps digests identical when buffered parts cross flush boundaries", () => {
+    const manyKeys: Record<string, unknown> = {};
+    for (let i = 0; i < 2000; i += 1) manyKeys[`k${i}`] = i;
+    const value = { keys: manyKeys, tail: ["€", "😀", "x".repeat(9000)] };
+    expect(digestCanonicalValue(value)).toBe(legacyDigest(value));
+  });
+
   it("preserves canonicalize property access and toJSON cycle behavior", () => {
     const createAccessor = () => {
       let reads = 0;
diff --git a/src/domain/canonicalDigest.ts b/src/domain/canonicalDigest.ts
index c9f1c6260..3c4f9e3c6 100644
--- a/src/domain/canonicalDigest.ts
+++ b/src/domain/canonicalDigest.ts
@@ -6,8 +6,19 @@ export const digestCanonicalValue = (
   context = "Comparison",
 ): string => {
   const hash = createHash("sha256");
-  const encoded = emitCanonical(value, (part) => hash.update(part), new Set());
+  // Batch small emitted parts to cut hash.update crossings.
+  // Flush cuts only at part boundaries, so the hashed byte stream is unchanged.
+  let buffered = "";
+  const emit = (part: string): void => {
+    buffered += part;
+    if (buffered.length >= 8192) {
+      hash.update(buffered);
+      buffered = "";
+    }
+  };
+  const encoded = emitCanonical(value, emit, new Set());
   if (!encoded) throw new TypeError(`${context} could not canonicalize data`);
+  if (buffered) hash.update(buffered);
   return hash.digest("hex");
 };