diff --git a/packages/svelte/src/compiler/errors.js b/packages/svelte/src/compiler/errors.js
index a4000fb111..7c46bd1b4d 100644
--- a/packages/svelte/src/compiler/errors.js
+++ b/packages/svelte/src/compiler/errors.js
@@ -24,7 +24,7 @@ const internal = {
 const parse = {
 	/** @param {string} name */
 	'unclosed-element': (name) => `<${name}> was left open`,
-	'unclosed-block': () => `block was left open`,
+	'unclosed-block': () => `Block was left open`,
 	'unexpected-block-close': () => `Unexpected block closing tag`,
 	'unexpected-eof': () => `Unexpected end of input`,
 	/** @param {string} message */
diff --git a/packages/svelte/src/compiler/phases/1-parse/index.js b/packages/svelte/src/compiler/phases/1-parse/index.js
index 5199ad5960..d74c776efc 100644
--- a/packages/svelte/src/compiler/phases/1-parse/index.js
+++ b/packages/svelte/src/compiler/phases/1-parse/index.js
@@ -77,8 +77,10 @@ export class Parser {
 			const current = this.current();
 
 			if (current.type === 'RegularElement') {
+				current.end = current.start + 1;
 				error(current, 'unclosed-element', current.name);
 			} else {
+				current.end = current.start + 1;
 				error(current, 'unclosed-block');
 			}
 		}
diff --git a/packages/svelte/src/compiler/phases/1-parse/state/element.js b/packages/svelte/src/compiler/phases/1-parse/state/element.js
index a5e2a2a82a..31a3b2fe42 100644
--- a/packages/svelte/src/compiler/phases/1-parse/state/element.js
+++ b/packages/svelte/src/compiler/phases/1-parse/state/element.js
@@ -202,11 +202,12 @@ export default function tag(parser) {
 
 	let attribute;
 	while ((attribute = read(parser))) {
-		if (
-			(attribute.type === 'Attribute' || attribute.type === 'BindDirective') &&
-			unique_names.includes(attribute.name)
-		) {
-			error(attribute.start, 'duplicate-attribute');
+		if (attribute.type === 'Attribute' || attribute.type === 'BindDirective') {
+			if (unique_names.includes(attribute.name)) {
+				error(attribute.start, 'duplicate-attribute');
+			} else {
+				unique_names.push(attribute.name);
+			}
 		}
 
 		element.attributes.push(attribute);
@@ -635,13 +636,14 @@ function read_attribute_value(parser) {
 			'in attribute value'
 		);
 	} catch (/** @type {any} e */ e) {
-		if (e.code === 'parse-error') {
+		if (e.code === 'js-parse-error') {
 			// if the attribute value didn't close + self-closing tag
 			// eg: `<Component test={{a:1} />`
 			// acorn may throw a `Unterminated regular expression` because of `/>`
-			if (parser.template.slice(e.pos - 1, e.pos + 1) === '/>') {
-				parser.index = e.pos;
-				error(e.pos, 'unclosed-attribute-value', quote_mark || '}');
+			const pos = e.position?.[0];
+			if (pos !== undefined && parser.template.slice(pos - 1, pos + 1) === '/>') {
+				parser.index = pos;
+				error(pos, 'unclosed-attribute-value', quote_mark || '}');
 			}
 		}
 		throw e;
diff --git a/packages/svelte/tests/compiler-errors/samples/class-state-field-static/_config.js b/packages/svelte/tests/compiler-errors/samples/class-state-field-static/_config.js
index b6dca4e40d..27991ba427 100644
--- a/packages/svelte/tests/compiler-errors/samples/class-state-field-static/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/class-state-field-static/_config.js
@@ -4,6 +4,6 @@ export default test({
 	error: {
 		code: 'invalid-state-location',
 		message: '$state() can only be used as a variable declaration initializer or a class field',
-		position: process.platform === 'win32' ? [35, 43] : [33, 41]
+		position: [33, 41]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/css-global-without-selector/_config.js b/packages/svelte/tests/compiler-errors/samples/css-global-without-selector/_config.js
index c8e598d4a8..fc5349f233 100644
--- a/packages/svelte/tests/compiler-errors/samples/css-global-without-selector/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/css-global-without-selector/_config.js
@@ -2,7 +2,7 @@ import { test } from '../../test';
 
 export default test({
 	error: {
-		code: 'css-syntax-error',
+		code: 'invalid-css-identifier',
 		message: ':global() must contain a selector',
 		position: [9, 9]
 	}
diff --git a/packages/svelte/tests/compiler-errors/samples/css/_config.js b/packages/svelte/tests/compiler-errors/samples/css/_config.js
index d1a7e346f9..9e7cd16601 100644
--- a/packages/svelte/tests/compiler-errors/samples/css/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/css/_config.js
@@ -2,7 +2,7 @@ import { test } from '../../test';
 
 export default test({
 	error: {
-		code: 'css-syntax-error',
+		code: 'invalid-css-identifier',
 		message: '"{" is expected',
 		position: [24, 24]
 	}
diff --git a/packages/svelte/tests/compiler-errors/samples/empty-classname-binding/_config.js b/packages/svelte/tests/compiler-errors/samples/empty-classname-binding/_config.js
index 0051e827a5..bd1d1d7682 100644
--- a/packages/svelte/tests/compiler-errors/samples/empty-classname-binding/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/empty-classname-binding/_config.js
@@ -3,7 +3,7 @@ import { test } from '../../test';
 export default test({
 	error: {
 		code: 'empty-directive-name',
-		message: 'Class name cannot be empty',
+		message: 'ClassDirective name cannot be empty',
 		position: [10, 10]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/empty-directive-name/_config.js b/packages/svelte/tests/compiler-errors/samples/empty-directive-name/_config.js
index 7f6d0f1d0f..48a0eb32c4 100644
--- a/packages/svelte/tests/compiler-errors/samples/empty-directive-name/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/empty-directive-name/_config.js
@@ -3,7 +3,7 @@ import { test } from '../../test';
 export default test({
 	error: {
 		code: 'empty-directive-name',
-		message: 'Action name cannot be empty',
+		message: 'UseDirective name cannot be empty',
 		position: [8, 8]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/illegal-expression/_config.js b/packages/svelte/tests/compiler-errors/samples/illegal-expression/_config.js
index 659679c345..887f11e882 100644
--- a/packages/svelte/tests/compiler-errors/samples/illegal-expression/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/illegal-expression/_config.js
@@ -2,7 +2,7 @@ import { test } from '../../test';
 
 export default test({
 	error: {
-		code: 'parse-error',
+		code: 'js-parse-error',
 		message: 'Assigning to rvalue',
 		position: [1, 1]
 	}
diff --git a/packages/svelte/tests/compiler-errors/samples/multiple-styles/_config.js b/packages/svelte/tests/compiler-errors/samples/multiple-styles/_config.js
index da3e69fc1e..66cdcd9553 100644
--- a/packages/svelte/tests/compiler-errors/samples/multiple-styles/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/multiple-styles/_config.js
@@ -2,7 +2,7 @@ import { test } from '../../test';
 
 export default test({
 	error: {
-		code: 'duplicate-style',
+		code: 'duplicate-style-element',
 		message: 'You can only have one top-level <style> tag per component',
 		position: [58, 58]
 	}
diff --git a/packages/svelte/tests/compiler-errors/samples/self-reference/_config.js b/packages/svelte/tests/compiler-errors/samples/self-reference/_config.js
index 5f5980b7ed..8148e18332 100644
--- a/packages/svelte/tests/compiler-errors/samples/self-reference/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/self-reference/_config.js
@@ -4,7 +4,7 @@ export default test({
 	error: {
 		code: 'invalid-self-placement',
 		message:
-			'<svelte:self> components can only exist inside {#if} blocks, {#each} blocks,, {#snippet} blocks or slots passed to components',
+			'<svelte:self> components can only exist inside {#if} blocks, {#each} blocks, {#snippet} blocks or slots passed to components',
 		position: [1, 1]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/svelte-selfdestructive/_config.js b/packages/svelte/tests/compiler-errors/samples/svelte-selfdestructive/_config.js
index d102c9f4ac..2cdd3e16da 100644
--- a/packages/svelte/tests/compiler-errors/samples/svelte-selfdestructive/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/svelte-selfdestructive/_config.js
@@ -2,7 +2,7 @@ import { test } from '../../test';
 
 export default test({
 	error: {
-		code: 'invalid-tag-name',
+		code: 'invalid-svelte-tag',
 		message:
 			'Valid <svelte:...> tag names are svelte:head, svelte:options, svelte:window, svelte:document, svelte:body, svelte:self, svelte:component, svelte:fragment or svelte:element',
 		position: [10, 10]
diff --git a/packages/svelte/tests/compiler-errors/samples/unclosed-attribute-self-close-tag/_config.js b/packages/svelte/tests/compiler-errors/samples/unclosed-attribute-self-close-tag/_config.js
index a11d5d3654..2f4ec8835f 100644
--- a/packages/svelte/tests/compiler-errors/samples/unclosed-attribute-self-close-tag/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/unclosed-attribute-self-close-tag/_config.js
@@ -3,7 +3,7 @@ import { test } from '../../test';
 export default test({
 	error: {
 		code: 'unclosed-attribute-value',
-		message: 'Expected to close the attribute value with }',
-		position: [25, 25]
+		message: 'Expected closing } character',
+		position: [19, 19]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/unclosed-attribute-self-close-tag/main.svelte b/packages/svelte/tests/compiler-errors/samples/unclosed-attribute-self-close-tag/main.svelte
index 609b5532f4..3166782f6f 100644
--- a/packages/svelte/tests/compiler-errors/samples/unclosed-attribute-self-close-tag/main.svelte
+++ b/packages/svelte/tests/compiler-errors/samples/unclosed-attribute-self-close-tag/main.svelte
@@ -1 +1 @@
-<Component test={{a: 1} />
\ No newline at end of file
+<Component test={ />
\ No newline at end of file
diff --git a/packages/svelte/tests/compiler-errors/samples/unexpected-end-of-input-d/_config.js b/packages/svelte/tests/compiler-errors/samples/unexpected-end-of-input-d/_config.js
index 44a3558a54..b10de772d3 100644
--- a/packages/svelte/tests/compiler-errors/samples/unexpected-end-of-input-d/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/unexpected-end-of-input-d/_config.js
@@ -4,6 +4,6 @@ export default test({
 	error: {
 		code: 'unclosed-block',
 		message: 'Block was left open',
-		position: [0, 0]
+		position: [0, 1]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/unexpected-end-of-input/_config.js b/packages/svelte/tests/compiler-errors/samples/unexpected-end-of-input/_config.js
index 3b7864cad5..8ff85b7243 100644
--- a/packages/svelte/tests/compiler-errors/samples/unexpected-end-of-input/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/unexpected-end-of-input/_config.js
@@ -4,6 +4,6 @@ export default test({
 	error: {
 		code: 'unclosed-element',
 		message: '<div> was left open',
-		position: [0, 0]
+		position: [0, 1]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/unmatched-closing-tag-autoclose/_config.js b/packages/svelte/tests/compiler-errors/samples/unmatched-closing-tag-autoclose/_config.js
index 341a468311..b485095bc0 100644
--- a/packages/svelte/tests/compiler-errors/samples/unmatched-closing-tag-autoclose/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/unmatched-closing-tag-autoclose/_config.js
@@ -2,8 +2,8 @@ import { test } from '../../test';
 
 export default test({
 	error: {
-		code: 'invalid-closing-tag',
-		message: '</p> attempted to close <p> that was already automatically closed by <pre>',
+		code: 'invalid-closing-tag-after-autoclose',
+		message: '</p> attempted to close element that was already automatically closed by <pre>',
 		position: [24, 24]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/void-closing/_config.js b/packages/svelte/tests/compiler-errors/samples/void-closing/_config.js
index 2c9f9fad2d..704d8c6029 100644
--- a/packages/svelte/tests/compiler-errors/samples/void-closing/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/void-closing/_config.js
@@ -3,7 +3,7 @@ import { test } from '../../test';
 export default test({
 	error: {
 		code: 'invalid-void-content',
-		message: '<input> is a void element and cannot have children, or a closing tag',
+		message: 'Void elements cannot have children or closing tags',
 		position: [23, 23]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/window-children/_config.js b/packages/svelte/tests/compiler-errors/samples/window-children/_config.js
index 794381c939..33b57bf5f6 100644
--- a/packages/svelte/tests/compiler-errors/samples/window-children/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/window-children/_config.js
@@ -2,7 +2,7 @@ import { test } from '../../test';
 
 export default test({
 	error: {
-		code: 'invalid-window-content',
+		code: 'invalid-element-content',
 		message: '<svelte:window> cannot have children',
 		position: [15, 15]
 	}
diff --git a/packages/svelte/tests/compiler-errors/samples/window-duplicate/_config.js b/packages/svelte/tests/compiler-errors/samples/window-duplicate/_config.js
index 3eff2d3e9f..9c068c0297 100644
--- a/packages/svelte/tests/compiler-errors/samples/window-duplicate/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/window-duplicate/_config.js
@@ -2,8 +2,8 @@ import { test } from '../../test';
 
 export default test({
 	error: {
-		code: 'duplicate-window',
-		message: 'A component can only have one <svelte:window> tag',
+		code: 'duplicate-svelte-element',
+		message: 'A component can only have one <svelte:window> element',
 		position: [17, 17]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/window-inside-block/_config.js b/packages/svelte/tests/compiler-errors/samples/window-inside-block/_config.js
index f47b6be7eb..698c3813e6 100644
--- a/packages/svelte/tests/compiler-errors/samples/window-inside-block/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/window-inside-block/_config.js
@@ -2,7 +2,7 @@ import { test } from '../../test';
 
 export default test({
 	error: {
-		code: 'invalid-window-placement',
+		code: 'invalid-svelte-element-placement',
 		message: '<svelte:window> tags cannot be inside elements or blocks',
 		position: [11, 11]
 	}
diff --git a/packages/svelte/tests/compiler-errors/samples/window-inside-element/_config.js b/packages/svelte/tests/compiler-errors/samples/window-inside-element/_config.js
index e4411b8df0..04aba56e54 100644
--- a/packages/svelte/tests/compiler-errors/samples/window-inside-element/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/window-inside-element/_config.js
@@ -2,7 +2,7 @@ import { test } from '../../test';
 
 export default test({
 	error: {
-		code: 'invalid-window-placement',
+		code: 'invalid-svelte-element-placement',
 		message: '<svelte:window> tags cannot be inside elements or blocks',
 		position: [7, 7]
 	}
diff --git a/packages/svelte/tests/compiler-errors/test.ts b/packages/svelte/tests/compiler-errors/test.ts
index ee14125dc0..2ee64edbc2 100644
--- a/packages/svelte/tests/compiler-errors/test.ts
+++ b/packages/svelte/tests/compiler-errors/test.ts
@@ -2,6 +2,7 @@ import * as fs from 'node:fs';
 import { assert, expect } from 'vitest';
 import { compile, compileModule, type CompileError } from 'svelte/compiler';
 import { suite, type BaseTest } from '../suite';
+import { read_file } from '../helpers.js';
 
 interface CompilerErrorTest extends BaseTest {
 	error: {
@@ -20,7 +21,7 @@ const { test, run } = suite<CompilerErrorTest>((config, cwd) => {
 		let caught_error = false;
 
 		try {
-			compile(fs.readFileSync(`${cwd}/main.svelte`, 'utf-8'), {
+			compile(read_file(`${cwd}/main.svelte`), {
 				generate: 'client'
 			});
 		} catch (e) {
@@ -45,7 +46,7 @@ const { test, run } = suite<CompilerErrorTest>((config, cwd) => {
 		let caught_error = false;
 
 		try {
-			compileModule(fs.readFileSync(`${cwd}/main.svelte.js`, 'utf-8'), {
+			compileModule(read_file(`${cwd}/main.svelte.js`), {
 				generate: 'client'
 			});
 		} catch (e) {
diff --git a/packages/svelte/tests/helpers.js b/packages/svelte/tests/helpers.js
index 46f70b011b..a8e3d605d9 100644
--- a/packages/svelte/tests/helpers.js
+++ b/packages/svelte/tests/helpers.js
@@ -20,13 +20,20 @@ export function try_load_json(file) {
  */
 export function try_read_file(file) {
 	try {
-		return fs.readFileSync(file, 'utf-8').replace(/\r\n/g, '\n');
+		return read_file(file);
 	} catch (err) {
 		if (/** @type {any} */ (err).code !== 'ENOENT') throw err;
 		return null;
 	}
 }
 
+/**
+ * @param {string} file
+ */
+export function read_file(file) {
+	return fs.readFileSync(file, 'utf-8').replace(/\r\n/g, '\n');
+}
+
 export function create_deferred() {
 	/** @param {any} [value] */
 	let resolve = (value) => {};