diff --git a/.github/scripts/package.json b/.github/scripts/package.json
index 161ba425a60..b3ef3607692 100644
--- a/.github/scripts/package.json
+++ b/.github/scripts/package.json
@@ -9,6 +9,7 @@
     "conventional-changelog": "7.2.0",
     "debug": "4.4.3",
     "glob": "13.0.6",
+    "minimatch": "10.2.4",
     "semver": "7.7.4",
     "tempfile": "6.0.1"
   },
diff --git a/.github/scripts/pnpm-lock.yaml b/.github/scripts/pnpm-lock.yaml
index b547faa90a8..ebb2db3ba38 100644
--- a/.github/scripts/pnpm-lock.yaml
+++ b/.github/scripts/pnpm-lock.yaml
@@ -23,6 +23,9 @@ importers:
       glob:
         specifier: 13.0.6
         version: 13.0.6
+      minimatch:
+        specifier: 10.2.4
+        version: 10.2.4
       semver:
         specifier: 7.7.4
         version: 7.7.4
diff --git a/.github/scripts/quality/check-pr-size.mjs b/.github/scripts/quality/check-pr-size.mjs
index 775e233853f..554b7214d5c 100644
--- a/.github/scripts/quality/check-pr-size.mjs
+++ b/.github/scripts/quality/check-pr-size.mjs
@@ -1,6 +1,9 @@
 /**
  * Checks that the PR does not exceed the line addition limit.
  *
+ * Files matching any pattern in EXCLUDE_PATTERNS are not counted toward the
+ * limit (e.g. test files, snapshots).
+ *
  * A maintainer (write access or above) can override by commenting `/size-limit-override`
  * on the PR. The override takes effect on the next pull_request event (push, reopen, etc.).
  *
@@ -9,18 +12,43 @@
  *   1 – PR exceeds the limit with no valid override
  */
 
+import { minimatch } from 'minimatch';
 import { initGithub, getEventFromGithubEventPath } from '../github-helpers.mjs';
 
 export const SIZE_LIMIT = 1000;
 export const OVERRIDE_COMMAND = '/size-limit-override';
 
+export const EXCLUDE_PATTERNS = [
+	// Test files (by extension)
+	'**/*.test.ts',
+	'**/*.test.js',
+	'**/*.test.mjs',
+	'**/*.spec.ts',
+	'**/*.spec.js',
+	'**/*.spec.mjs',
+	// Test directories
+	'**/test/**',
+	'**/tests/**',
+	'**/__tests__/**',
+	// Snapshots
+	'**/__snapshots__/**',
+	'**/*.snap',
+	// Fixtures and mocks
+	'**/fixtures/**',
+	'**/__mocks__/**',
+	// Dedicated testing package
+	'packages/testing/**',
+	// Lock file (can produce massive diffs on dependency changes)
+	'pnpm-lock.yaml',
+];
+
 const BOT_MARKER = '<!-- pr-size-check -->';
 
 /**
  * Returns true if any comment in the list is a valid `/size-limit-override` from a
  * user with write access or above.
  *
- * @param {Array<{ body?: string, user: { login: string } }>} comments
+ * @param {Array<{ body?: string, user: { login: string } | null }>} comments
  * @param {(username: string) => Promise<string>} getPermission - returns the permission level string
  * @returns {Promise<boolean>}
  */
@@ -30,6 +58,10 @@ export async function hasValidOverride(comments, getPermission) {
 			continue;
 		}
 
+		if (!comment.user) {
+			return false;
+		}
+
 		const perm = await getPermission(comment.user.login);
 		if (['admin', 'write', 'maintain'].includes(perm)) {
 			return true;
@@ -38,12 +70,32 @@ export async function hasValidOverride(comments, getPermission) {
 	return false;
 }
 
+/**
+ * Returns the total additions across all files, excluding those matching any exclude pattern.
+ *
+ * @param {Array<{ filename: string, additions: number }>} files
+ * @param {string[]} excludePatterns
+ * @returns {number}
+ */
+export function countFilteredAdditions(files, excludePatterns) {
+	return files
+		.filter((file) => !excludePatterns.some((pattern) => minimatch(file.filename, pattern)))
+		.reduce((sum, file) => sum + file.additions, 0);
+}
+
 async function main() {
 	const event = getEventFromGithubEventPath();
 	const pr = event.pull_request;
 	const { octokit, owner, repo } = initGithub();
 
-	const additions = pr.additions;
+	const files = await octokit.paginate(octokit.rest.pulls.listFiles, {
+		owner,
+		repo,
+		pull_number: pr.number,
+		per_page: 100,
+	});
+
+	const additions = countFilteredAdditions(files, EXCLUDE_PATTERNS);
 
 	const { data: comments } = await octokit.rest.issues.listComments({
 		owner,
@@ -63,14 +115,14 @@ async function main() {
 		return perm.permission;
 	});
 
-	const botComment = comments.find((c) => c.body.includes(BOT_MARKER));
+	const botComment = comments.find((c) => c.body?.includes(BOT_MARKER));
 
 	if (additions > SIZE_LIMIT && !overrideFound) {
 		const message = [
 			BOT_MARKER,
-			`## ⚠️ PR exceeds size limit (${additions.toLocaleString()} lines added)`,
+			`## ! PR exceeds size limit (${additions.toLocaleString()} lines added)`,
 			'',
-			`This PR adds **${additions.toLocaleString()} lines**, exceeding the ${SIZE_LIMIT.toLocaleString()}-line limit.`,
+			`This PR adds **${additions.toLocaleString()} lines**, exceeding the ${SIZE_LIMIT.toLocaleString()}-line limit (test files excluded).`,
 			'',
 			'Large PRs are harder to review and increase the risk of bugs going unnoticed. Please consider:',
 			'- Breaking this into smaller, logically separate PRs',
@@ -96,7 +148,7 @@ async function main() {
 		}
 
 		console.log(
-			`::error::PR adds ${additions.toLocaleString()} lines, exceeding the ${SIZE_LIMIT.toLocaleString()}-line limit. Reduce PR size or ask a maintainer to comment \`${OVERRIDE_COMMAND}\`.`,
+			`::error::PR adds ${additions.toLocaleString()} lines (test files excluded), exceeding the ${SIZE_LIMIT.toLocaleString()}-line limit. Reduce PR size or ask a maintainer to comment \`${OVERRIDE_COMMAND}\`.`,
 		);
 		process.exit(1);
 	} else {
@@ -109,7 +161,7 @@ async function main() {
 		}
 		if (overrideFound && additions > SIZE_LIMIT) {
 			console.log(
-				`PR size limit overridden. ${additions.toLocaleString()} lines added (limit: ${SIZE_LIMIT.toLocaleString()}).`,
+				`PR size limit overridden. ${additions.toLocaleString()} lines added (limit: ${SIZE_LIMIT.toLocaleString()}, test files excluded).`,
 			);
 		}
 	}
diff --git a/.github/scripts/quality/check-pr-size.test.mjs b/.github/scripts/quality/check-pr-size.test.mjs
index f9cab62d30e..a52422808f6 100644
--- a/.github/scripts/quality/check-pr-size.test.mjs
+++ b/.github/scripts/quality/check-pr-size.test.mjs
@@ -13,9 +13,10 @@ mock.module('../github-helpers.mjs', {
 	},
 });
 
-let hasValidOverride, SIZE_LIMIT, OVERRIDE_COMMAND;
+let hasValidOverride, countFilteredAdditions, SIZE_LIMIT, OVERRIDE_COMMAND, EXCLUDE_PATTERNS;
 before(async () => {
-	({ hasValidOverride, SIZE_LIMIT, OVERRIDE_COMMAND } = await import('./check-pr-size.mjs'));
+	({ hasValidOverride, countFilteredAdditions, SIZE_LIMIT, OVERRIDE_COMMAND, EXCLUDE_PATTERNS } =
+		await import('./check-pr-size.mjs'));
 });
 
 /** @param {string} permission */
@@ -114,3 +115,92 @@ describe('hasValidOverride', () => {
 		assert.ok(result);
 	});
 });
+
+describe('countFilteredAdditions', () => {
+	it('sums additions across all files when no patterns are given', () => {
+		const files = [
+			{ filename: 'src/foo.ts', additions: 100 },
+			{ filename: 'src/bar.ts', additions: 200 },
+		];
+		assert.equal(countFilteredAdditions(files, []), 300);
+	});
+
+	it('excludes files matching a glob pattern', () => {
+		const files = [
+			{ filename: 'src/foo.ts', additions: 100 },
+			{ filename: 'src/foo.test.ts', additions: 500 },
+		];
+		assert.equal(countFilteredAdditions(files, ['**/*.test.ts']), 100);
+	});
+
+	it('excludes files matching any of multiple patterns', () => {
+		const files = [
+			{ filename: 'src/foo.ts', additions: 100 },
+			{ filename: 'src/foo.test.ts', additions: 200 },
+			{ filename: 'src/foo.spec.ts', additions: 300 },
+			{ filename: 'src/__tests__/bar.ts', additions: 400 },
+		];
+		assert.equal(
+			countFilteredAdditions(files, ['**/*.test.ts', '**/*.spec.ts', '**/__tests__/**']),
+			100,
+		);
+	});
+
+	it('returns 0 when all files are excluded', () => {
+		const files = [
+			{ filename: 'src/foo.test.ts', additions: 100 },
+			{ filename: 'src/bar.test.ts', additions: 200 },
+		];
+		assert.equal(countFilteredAdditions(files, ['**/*.test.ts']), 0);
+	});
+
+	it('returns 0 for an empty file list', () => {
+		assert.equal(countFilteredAdditions([], EXCLUDE_PATTERNS), 0);
+	});
+
+	it('applies EXCLUDE_PATTERNS to common test file extensions', () => {
+		const files = [
+			{ filename: 'src/service.ts', additions: 50 },
+			{ filename: 'src/service.test.ts', additions: 100 },
+			{ filename: 'src/service.spec.ts', additions: 100 },
+			{ filename: 'src/service.test.mjs', additions: 100 },
+			{ filename: 'src/service.spec.mjs', additions: 100 },
+			{ filename: 'src/service.test.js', additions: 100 },
+			{ filename: 'src/service.spec.js', additions: 100 },
+			{ filename: 'src/__tests__/helper.ts', additions: 100 },
+			{ filename: 'src/component.snap', additions: 100 },
+		];
+		assert.equal(countFilteredAdditions(files, EXCLUDE_PATTERNS), 50);
+	});
+
+	it('applies EXCLUDE_PATTERNS to test directories (test/, tests/, __tests__)', () => {
+		const files = [
+			{ filename: 'packages/cli/src/service.ts', additions: 50 },
+			{ filename: 'packages/cli/test/unit/service.test.ts', additions: 100 },
+			{ filename: 'packages/cli/test/integration/api.test.ts', additions: 100 },
+			{ filename: 'packages/nodes-base/nodes/Foo/tests/Foo.test.ts', additions: 100 },
+			{ filename: 'packages/core/src/__tests__/cipher.test.ts', additions: 100 },
+		];
+		assert.equal(countFilteredAdditions(files, EXCLUDE_PATTERNS), 50);
+	});
+
+	it('applies EXCLUDE_PATTERNS to snapshots, fixtures, and mocks', () => {
+		const files = [
+			{ filename: 'packages/cli/src/service.ts', additions: 50 },
+			{ filename: 'packages/editor-ui/src/__snapshots__/Canvas.test.ts.snap', additions: 100 },
+			{ filename: 'packages/workflow/test/fixtures/workflow.json', additions: 100 },
+			{ filename: 'packages/core/src/__mocks__/fs.ts', additions: 100 },
+		];
+		assert.equal(countFilteredAdditions(files, EXCLUDE_PATTERNS), 50);
+	});
+
+	it('applies EXCLUDE_PATTERNS to packages/testing and pnpm-lock.yaml', () => {
+		const files = [
+			{ filename: 'packages/cli/src/service.ts', additions: 50 },
+			{ filename: 'packages/testing/playwright/tests/workflow.spec.ts', additions: 100 },
+			{ filename: 'packages/testing/playwright/pages/CanvasPage.ts', additions: 100 },
+			{ filename: 'pnpm-lock.yaml', additions: 500 },
+		];
+		assert.equal(countFilteredAdditions(files, EXCLUDE_PATTERNS), 50);
+	});
+});