diff --git a/.changeset/yellow-guests-double.md b/.changeset/yellow-guests-double.md
new file mode 100644
index 000000000000..454caacdba22
--- /dev/null
+++ b/.changeset/yellow-guests-double.md
@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+chore: backwards compat for dash-case warnings
diff --git a/packages/svelte/scripts/process-messages/templates/compile-warnings.js b/packages/svelte/scripts/process-messages/templates/compile-warnings.js
index cac547de6049..97e0d860dcfe 100644
--- a/packages/svelte/scripts/process-messages/templates/compile-warnings.js
+++ b/packages/svelte/scripts/process-messages/templates/compile-warnings.js
@@ -2,9 +2,12 @@ import { getLocator } from 'locate-character';
 
 /** @typedef {{ start?: number, end?: number }} NodeLike */
 
-/** @type {import('#compiler').Warning[]} */
+/** @type {Array<{ warning: import('#compiler').Warning; legacy_code: string | null }>} */
 let warnings = [];
 
+/** @type {Set<string>[]} */
+let ignore_stack = [];
+
 /** @type {string | undefined} */
 let filename;
 
@@ -15,13 +18,61 @@ let locator = getLocator('', { offsetLine: 1 });
  *   source: string;
  *   filename: string | undefined;
  * }} options
- * @returns {import('#compiler').Warning[]}
  */
 export function reset_warnings(options) {
 	filename = options.filename;
+	ignore_stack = [];
+	warnings = [];
 	locator = getLocator(options.source, { offsetLine: 1 });
+}
+
+/**
+ * @param {boolean} is_runes
+ */
+export function get_warnings(is_runes) {
+	/** @type {import('#compiler').Warning[]} */
+	const final = [];
+	for (const { warning, legacy_code } of warnings) {
+		if (legacy_code) {
+			if (is_runes) {
+				final.push({
+					...warning,
+					message:
+						(warning.message += ` (this warning was tried to silence using code ${legacy_code}. In runes mode, use the new code ${warning.code} instead)`)
+				});
+			}
+		} else {
+			final.push(warning);
+		}
+	}
+
+	return final;
+}
+
+/**
+ * @param {string[]} ignores
+ */
+export function push_ignore(ignores) {
+	const next = new Set([...(ignore_stack.at(-1) || []), ...ignores]);
+	ignore_stack.push(next);
+}
 
-	return (warnings = []);
+export function pop_ignore() {
+	ignore_stack.pop();
+}
+
+// TODO add more mappings for prominent codes that have been renamed
+const legacy_codes = new Map([
+	['reactive_declaration_invalid_placement', 'non-top-level-reactive-declaration']
+]);
+
+const new_codes = new Map([...legacy_codes.entries()].map(([key, value]) => [value, key]));
+
+/**
+ * @param {string} legacy_code
+ */
+export function legacy_to_new_code(legacy_code) {
+	return new_codes.get(legacy_code) || legacy_code.replaceAll('-', '_');
 }
 
 /**
@@ -30,15 +81,25 @@ export function reset_warnings(options) {
  * @param {string} message
  */
 function w(node, code, message) {
-	// @ts-expect-error
-	if (node?.ignores?.has(code)) return;
+	const ignores = ignore_stack.at(-1);
+	if (ignores?.has(code)) return;
+
+	// backwards compat: Svelte 5 changed all warnings from dash to underscore
+	/** @type {string | null} */
+	let legacy_code = legacy_codes.get(code) || code.replaceAll('_', '-');
+	if (!ignores?.has(legacy_code)) {
+		legacy_code = null;
+	}
 
 	warnings.push({
-		code,
-		message,
-		filename,
-		start: node?.start !== undefined ? locator(node.start) : undefined,
-		end: node?.end !== undefined ? locator(node.end) : undefined
+		legacy_code,
+		warning: {
+			code,
+			message,
+			filename,
+			start: node?.start !== undefined ? locator(node.start) : undefined,
+			end: node?.end !== undefined ? locator(node.end) : undefined
+		}
 	});
 }
 
diff --git a/packages/svelte/src/compiler/index.js b/packages/svelte/src/compiler/index.js
index ba312a1a639e..4a10b84d055a 100644
--- a/packages/svelte/src/compiler/index.js
+++ b/packages/svelte/src/compiler/index.js
@@ -8,7 +8,7 @@ import { remove_typescript_nodes } from './phases/1-parse/remove_typescript_node
 import { analyze_component, analyze_module } from './phases/2-analyze/index.js';
 import { transform_component, transform_module } from './phases/3-transform/index.js';
 import { validate_component_options, validate_module_options } from './validate-options.js';
-import { reset_warnings } from './warnings.js';
+import { get_warnings, reset_warnings } from './warnings.js';
 export { default as preprocess } from './preprocess/index.js';
 
 /**
@@ -21,7 +21,7 @@ export { default as preprocess } from './preprocess/index.js';
  */
 export function compile(source, options) {
 	try {
-		const warnings = reset_warnings({ source, filename: options.filename });
+		reset_warnings({ source, filename: options.filename });
 		const validated = validate_component_options(options, '');
 		let parsed = _parse(source);
 
@@ -46,7 +46,7 @@ export function compile(source, options) {
 		const analysis = analyze_component(parsed, source, combined_options);
 
 		const result = transform_component(analysis, source, combined_options);
-		result.warnings = warnings;
+		result.warnings = get_warnings(analysis.runes);
 		result.ast = to_public_ast(source, parsed, options.modernAst);
 		return result;
 	} catch (e) {
@@ -68,11 +68,11 @@ export function compile(source, options) {
  */
 export function compileModule(source, options) {
 	try {
-		const warnings = reset_warnings({ source, filename: options.filename });
+		reset_warnings({ source, filename: options.filename });
 		const validated = validate_module_options(options, '');
 		const analysis = analyze_module(parse_acorn(source, false), validated);
 		const result = transform_module(analysis, source, validated);
-		result.warnings = warnings;
+		result.warnings = get_warnings(true);
 		return result;
 	} catch (e) {
 		if (e instanceof CompileError) {
diff --git a/packages/svelte/src/compiler/migrate/index.js b/packages/svelte/src/compiler/migrate/index.js
index e6328c70baff..b00a9b8343b6 100644
--- a/packages/svelte/src/compiler/migrate/index.js
+++ b/packages/svelte/src/compiler/migrate/index.js
@@ -4,9 +4,10 @@ import { parse } from '../phases/1-parse/index.js';
 import { analyze_component } from '../phases/2-analyze/index.js';
 import { validate_component_options } from '../validate-options.js';
 import { get_rune } from '../phases/scope.js';
-import { reset_warnings } from '../warnings.js';
+import { legacy_to_new_code, reset_warnings } from '../warnings.js';
 import { extract_identifiers } from '../utils/ast.js';
 import { regex_is_valid_identifier } from '../phases/patterns.js';
+import { extract_svelte_ignore } from '../utils/extract_svelte_ignore.js';
 
 /**
  * Does a best-effort migration of Svelte code towards using runes, event attributes and render tags.
@@ -174,6 +175,30 @@ export function migrate(source) {
 
 /** @type {import('zimmerframe').Visitors<import('../types/template.js').SvelteNode, State>} */
 const instance_script = {
+	_(node, { state, next }) {
+		// @ts-expect-error
+		const comments = node.leadingComments;
+		if (comments) {
+			for (const comment of comments) {
+				if (comment.type === 'Line') {
+					/** @type {string} */
+					const text = comment.value;
+					const ignores = extract_svelte_ignore(text);
+					if (ignores.length > 0) {
+						const svelte_ignore = text.indexOf('svelte-ignore');
+						state.str.overwrite(
+							comment.start + svelte_ignore + 13 + '//'.length,
+							comment.end,
+							text
+								.substring(svelte_ignore + 13)
+								.replace(new RegExp(ignores.join('|'), 'g'), (match) => legacy_to_new_code(match))
+						);
+					}
+				}
+			}
+		}
+		next();
+	},
 	Identifier(node, { state }) {
 		handle_identifier(node, state);
 	},
@@ -474,6 +499,19 @@ const template = {
 		} else {
 			state.str.update(node.start, node.end, `{@render ${name}?.(${slot_props})}`);
 		}
+	},
+	Comment(node, { state }) {
+		const ignores = extract_svelte_ignore(node.data);
+		if (ignores.length > 0) {
+			const svelte_ignore = node.data.indexOf('svelte-ignore');
+			state.str.overwrite(
+				node.start + svelte_ignore + 13 + '<!--'.length,
+				node.end - '-->'.length,
+				node.data
+					.substring(svelte_ignore + 13)
+					.replace(new RegExp(ignores.join('|'), 'g'), (match) => legacy_to_new_code(match))
+			);
+		}
 	}
 };
 
diff --git a/packages/svelte/src/compiler/phases/2-analyze/index.js b/packages/svelte/src/compiler/phases/2-analyze/index.js
index e4d6f6a4db9c..306c740f7b19 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/index.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/index.js
@@ -439,8 +439,7 @@ export function analyze_component(root, source, options) {
 				component_slots: new Set(),
 				expression: null,
 				private_derived_state: [],
-				function_depth: scope.function_depth,
-				ignores: new Set()
+				function_depth: scope.function_depth
 			};
 
 			walk(
@@ -511,8 +510,7 @@ export function analyze_component(root, source, options) {
 				component_slots: new Set(),
 				expression: null,
 				private_derived_state: [],
-				function_depth: scope.function_depth,
-				ignores: new Set()
+				function_depth: scope.function_depth
 			};
 
 			walk(
@@ -1093,62 +1091,44 @@ function is_safe_identifier(expression, scope) {
 
 /** @type {import('./types').Visitors} */
 const common_visitors = {
-	_(node, context) {
-		// @ts-expect-error
-		const comments = /** @type {import('estree').Comment[]} */ (node.leadingComments);
-
-		if (comments) {
+	_(node, { next, path }) {
+		const parent = path.at(-1);
+		if (parent?.type === 'Fragment') {
+			const idx = parent.nodes.indexOf(/** @type {any} */ (node));
 			/** @type {string[]} */
 			const ignores = [];
 
-			for (const comment of comments) {
-				ignores.push(...extract_svelte_ignore(comment.value));
+			for (let i = idx - 1; i >= 0; i--) {
+				const prev = parent.nodes[i];
+				if (prev.type === 'Comment') {
+					ignores.push(...extract_svelte_ignore(prev.data));
+				} else if (prev.type !== 'Text') {
+					break;
+				}
 			}
 
 			if (ignores.length > 0) {
-				// @ts-expect-error see below
-				node.ignores = new Set([...context.state.ignores, ...ignores]);
+				w.push_ignore(ignores);
+				next();
+				w.pop_ignore();
 			}
-		}
-
-		// @ts-expect-error
-		if (node.ignores) {
-			context.next({
-				...context.state,
-				// @ts-expect-error see below
-				ignores: node.ignores
-			});
-		} else if (context.state.ignores.size > 0) {
+		} else {
 			// @ts-expect-error
-			node.ignores = context.state.ignores;
-		}
-	},
-	Fragment(node, context) {
-		/** @type {string[]} */
-		let ignores = [];
+			const comments = /** @type {import('estree').Comment[]} */ (node.leadingComments);
 
-		for (const child of node.nodes) {
-			if (child.type === 'Text' && child.data.trim() === '') {
-				continue;
-			}
+			if (comments) {
+				/** @type {string[]} */
+				const ignores = [];
 
-			if (child.type === 'Comment') {
-				ignores.push(...extract_svelte_ignore(child.data));
-			} else {
-				const combined_ignores = new Set(context.state.ignores);
-				for (const ignore of ignores) combined_ignores.add(ignore);
-
-				if (combined_ignores.size > 0) {
-					// TODO this is a grotesque hack that's made necessary by the fact that
-					// we can't call `context.visit(...)` here, because we do the convoluted
-					// visitor merging thing. I'm increasingly of the view that we should
-					// rearchitect this stuff and have a single visitor per node. It'd be
-					// more efficient and much simpler.
-					// @ts-expect-error
-					child.ignores = combined_ignores;
+				for (const comment of comments) {
+					ignores.push(...extract_svelte_ignore(comment.value));
 				}
 
-				ignores = [];
+				if (ignores.length > 0) {
+					w.push_ignore(ignores);
+					next();
+					w.pop_ignore();
+				}
 			}
 		}
 	},
diff --git a/packages/svelte/src/compiler/phases/2-analyze/types.d.ts b/packages/svelte/src/compiler/phases/2-analyze/types.d.ts
index cc815fae7b7b..d2c503e8b108 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/types.d.ts
+++ b/packages/svelte/src/compiler/phases/2-analyze/types.d.ts
@@ -22,7 +22,6 @@ export interface AnalysisState {
 	expression: ExpressionTag | ClassDirective | SpreadAttribute | null;
 	private_derived_state: string[];
 	function_depth: number;
-	ignores: Set<string>;
 }
 
 export interface LegacyAnalysisState extends AnalysisState {
diff --git a/packages/svelte/src/compiler/warnings.js b/packages/svelte/src/compiler/warnings.js
index 39d9d9efb0b8..52e50833636b 100644
--- a/packages/svelte/src/compiler/warnings.js
+++ b/packages/svelte/src/compiler/warnings.js
@@ -3,8 +3,10 @@
 import { getLocator } from 'locate-character';
 
 /** @typedef {{ start?: number, end?: number }} NodeLike */
-/** @type {import('#compiler').Warning[]} */
+/** @type {Array<{ warning: import('#compiler').Warning; legacy_code: string | null }>} */
 let warnings = [];
+/** @type {Set<string>[]} */
+let ignore_stack = [];
 /** @type {string | undefined} */
 let filename;
 let locator = getLocator('', { offsetLine: 1 });
@@ -14,12 +16,65 @@ let locator = getLocator('', { offsetLine: 1 });
  *   source: string;
  *   filename: string | undefined;
  * }} options
- * @returns {import('#compiler').Warning[]}
  */
 export function reset_warnings(options) {
 	filename = options.filename;
+	ignore_stack = [];
+	warnings = [];
 	locator = getLocator(options.source, { offsetLine: 1 });
-	return warnings = [];
+}
+
+/**
+ * @param {boolean} is_runes
+ */
+export function get_warnings(is_runes) {
+	/** @type {import('#compiler').Warning[]} */
+	const final = [];
+
+	for (const { warning, legacy_code } of warnings) {
+		if (legacy_code) {
+			if (is_runes) {
+				final.push({
+					...warning,
+					message: warning.message += ` (this warning was tried to silence using code ${legacy_code}. In runes mode, use the new code ${warning.code} instead)`
+				});
+			}
+		} else {
+			final.push(warning);
+		}
+	}
+
+	return final;
+}
+
+/**
+ * @param {string[]} ignores
+ */
+export function push_ignore(ignores) {
+	const next = new Set([...ignore_stack.at(-1) || [], ...ignores]);
+
+	ignore_stack.push(next);
+}
+
+export function pop_ignore() {
+	ignore_stack.pop();
+}
+
+// TODO add more mappings for prominent codes that have been renamed
+const legacy_codes = new Map([
+	[
+		'reactive_declaration_invalid_placement',
+		'non-top-level-reactive-declaration'
+	]
+]);
+
+const new_codes = new Map([...legacy_codes.entries()].map(([key, value]) => [value, key]));
+
+/**
+ * @param {string} legacy_code
+ */
+export function legacy_to_new_code(legacy_code) {
+	return new_codes.get(legacy_code) || legacy_code.replaceAll('-', '_');
 }
 
 /**
@@ -28,15 +83,27 @@ export function reset_warnings(options) {
  * @param {string} message
  */
 function w(node, code, message) {
-	// @ts-expect-error
-	if (node?.ignores?.has(code)) return;
+	const ignores = ignore_stack.at(-1);
+
+	if (ignores?.has(code)) return;
+
+	// backwards compat: Svelte 5 changed all warnings from dash to underscore
+	/** @type {string | null} */
+	let legacy_code = legacy_codes.get(code) || code.replaceAll('_', '-');
+
+	if (!ignores?.has(legacy_code)) {
+		legacy_code = null;
+	}
 
 	warnings.push({
-		code,
-		message,
-		filename,
-		start: node?.start !== undefined ? locator(node.start) : undefined,
-		end: node?.end !== undefined ? locator(node.end) : undefined
+		legacy_code,
+		warning: {
+			code,
+			message,
+			filename,
+			start: node?.start !== undefined ? locator(node.start) : undefined,
+			end: node?.end !== undefined ? locator(node.end) : undefined
+		}
 	});
 }
 
diff --git a/packages/svelte/tests/migrate/samples/svelte-ignore/input.svelte b/packages/svelte/tests/migrate/samples/svelte-ignore/input.svelte
new file mode 100644
index 000000000000..fa734942f9ff
--- /dev/null
+++ b/packages/svelte/tests/migrate/samples/svelte-ignore/input.svelte
@@ -0,0 +1,9 @@
+<script>
+	function foo() {
+		// svelte-ignore non-top-level-reactive-declaration
+		$: x = 1;
+	}
+</script>
+
+<!-- svelte-ignore a11y-something-something -->
+<div></div>
\ No newline at end of file
diff --git a/packages/svelte/tests/migrate/samples/svelte-ignore/output.svelte b/packages/svelte/tests/migrate/samples/svelte-ignore/output.svelte
new file mode 100644
index 000000000000..fa305cefb1fa
--- /dev/null
+++ b/packages/svelte/tests/migrate/samples/svelte-ignore/output.svelte
@@ -0,0 +1,9 @@
+<script>
+	function foo() {
+		// svelte-ignore reactive_declaration_invalid_placement
+		$: x = 1;
+	}
+</script>
+
+<!-- svelte-ignore a11y_something_something -->
+<div></div>
\ No newline at end of file
diff --git a/packages/svelte/tests/validator/samples/ignore-warning-dash-backwards-compat/input.svelte b/packages/svelte/tests/validator/samples/ignore-warning-dash-backwards-compat/input.svelte
new file mode 100644
index 000000000000..faae4636e5bf
--- /dev/null
+++ b/packages/svelte/tests/validator/samples/ignore-warning-dash-backwards-compat/input.svelte
@@ -0,0 +1,14 @@
+<script>
+	function foo() {
+		// svelte-ignore non-top-level-reactive-declaration
+		$: x = 1;
+	}
+</script>
+
+<!-- svelte-ignore a11y-missing-attribute -->
+<div>
+	<img src="this-is-fine.jpg">
+</div>
+
+<!-- svelte-ignore a11y-misplaced-scope -->
+<div scope></div>
diff --git a/packages/svelte/tests/validator/samples/ignore-warning-dash-backwards-compat/warnings.json b/packages/svelte/tests/validator/samples/ignore-warning-dash-backwards-compat/warnings.json
new file mode 100644
index 000000000000..fe51488c7066
--- /dev/null
+++ b/packages/svelte/tests/validator/samples/ignore-warning-dash-backwards-compat/warnings.json
@@ -0,0 +1 @@
+[]
diff --git a/packages/svelte/tests/validator/samples/ignore-warning-dash-runes/input.svelte b/packages/svelte/tests/validator/samples/ignore-warning-dash-runes/input.svelte
new file mode 100644
index 000000000000..268bb2e867f5
--- /dev/null
+++ b/packages/svelte/tests/validator/samples/ignore-warning-dash-runes/input.svelte
@@ -0,0 +1,9 @@
+<svelte:options runes={true} />
+
+<!-- svelte-ignore a11y-missing-attribute -->
+<div>
+	<img src="this-is-fine.jpg">
+</div>
+
+<!-- svelte-ignore a11y-misplaced-scope -->
+<div scope></div>
diff --git a/packages/svelte/tests/validator/samples/ignore-warning-dash-runes/warnings.json b/packages/svelte/tests/validator/samples/ignore-warning-dash-runes/warnings.json
new file mode 100644
index 000000000000..8bb98aff0eb9
--- /dev/null
+++ b/packages/svelte/tests/validator/samples/ignore-warning-dash-runes/warnings.json
@@ -0,0 +1,26 @@
+[
+	{
+		"code": "a11y_missing_attribute",
+		"end": {
+			"column": 29,
+			"line": 5
+		},
+		"message": "`<img>` element should have an alt attribute (this warning was tried to silence using code a11y-missing-attribute. In runes mode, use the new code a11y_missing_attribute instead)",
+		"start": {
+			"column": 1,
+			"line": 5
+		}
+	},
+	{
+		"code": "a11y_misplaced_scope",
+		"end": {
+			"column": 10,
+			"line": 9
+		},
+		"message": "The scope attribute should only be used with `<th>` elements (this warning was tried to silence using code a11y-misplaced-scope. In runes mode, use the new code a11y_misplaced_scope instead)",
+		"start": {
+			"column": 5,
+			"line": 9
+		}
+	}
+]
diff --git a/packages/svelte/tests/validator/samples/ignore-warning/input.svelte b/packages/svelte/tests/validator/samples/ignore-warning/input.svelte
index cfbe0e538daa..7a2328e57c43 100644
--- a/packages/svelte/tests/validator/samples/ignore-warning/input.svelte
+++ b/packages/svelte/tests/validator/samples/ignore-warning/input.svelte
@@ -4,4 +4,7 @@
 	<marquee>but this is still discouraged</marquee>
 </div>
 
+<!-- svelte-ignore a11y_misplaced_scope -->
+<div scope></div>
+
 <img src="potato.jpg">
diff --git a/packages/svelte/tests/validator/samples/ignore-warning/warnings.json b/packages/svelte/tests/validator/samples/ignore-warning/warnings.json
index 926543bf3ff0..3997af9dbde7 100644
--- a/packages/svelte/tests/validator/samples/ignore-warning/warnings.json
+++ b/packages/svelte/tests/validator/samples/ignore-warning/warnings.json
@@ -15,12 +15,12 @@
 		"code": "a11y_missing_attribute",
 		"end": {
 			"column": 22,
-			"line": 7
+			"line": 10
 		},
 		"message": "`<img>` element should have an alt attribute",
 		"start": {
 			"column": 0,
-			"line": 7
+			"line": 10
 		}
 	}
 ]
diff --git a/sites/svelte-5-preview/src/routes/docs/content/03-appendix/02-breaking-changes.md b/sites/svelte-5-preview/src/routes/docs/content/03-appendix/02-breaking-changes.md
index 9cb885555b4b..d5883b06aeb5 100644
--- a/sites/svelte-5-preview/src/routes/docs/content/03-appendix/02-breaking-changes.md
+++ b/sites/svelte-5-preview/src/routes/docs/content/03-appendix/02-breaking-changes.md
@@ -158,9 +158,9 @@ In the event that you need to support ancient browsers that don't implement `:wh
 css = css.replace(/:where\((.+?)\)/, '$1');
 ```
 
-### Renames of various error/warning codes
+### Renames of error/warning codes
 
-Various error and warning codes have been renamed slightly.
+Error and warning codes have been renamed: Instead of using dashes they now use underscores as separators (e.g. `a11y_misplaced_scope` instead of `a11y-misplaced-scope`). Some codes have also been slightly reworded. For backwards compatibility, dash separators are still supported, but you should migrate towards underscores.
 
 ### Reduced number of namespaces