sveltejs/svelte · error · Error

invariant_violation

invariant_violation

Error message

invariant_violation
An invariant violation occurred, meaning Svelte's internal assumptions were flawed. This is a bug in Svelte, not your app — please open an issue at https://github.com/sveltejs/svelte, citing the following message: "${message}"
https://svelte.dev/e/invariant_violation

What it means

This is Svelte asserting its own internal invariants — conditions the framework considers always true. A violation is a bug in Svelte, not in your app. The error asks you to file an issue citing the `%message%`. It is thrown in both DEV (detailed) and production (URL-only) builds.

Source

Thrown at packages/svelte/src/internal/shared/errors.js:67

	} else {
		throw new Error(`https://svelte.dev/e/invalid_snippet_arguments`);
	}
}

/**
 * An invariant violation occurred, meaning Svelte's internal assumptions were flawed. This is a bug in Svelte, not your app — please open an issue at https://github.com/sveltejs/svelte, citing the following message: "%message%"
 * @param {string} message
 * @returns {never}
 */
export function invariant_violation(message) {
	if (DEV) {
		const error = new Error(`invariant_violation\nAn invariant violation occurred, meaning Svelte's internal assumptions were flawed. This is a bug in Svelte, not your app — please open an issue at https://github.com/sveltejs/svelte, citing the following message: "${message}"\nhttps://svelte.dev/e/invariant_violation`);

		error.name = 'Svelte error';

		throw error;
	} else {
		throw new Error(`https://svelte.dev/e/invariant_violation`);
	}
}

/**
 * `%name%(...)` can only be used during component initialisation
 * @param {string} name
 * @returns {never}
 */
export function lifecycle_outside_component(name) {
	if (DEV) {
		const error = new Error(`lifecycle_outside_component\n\`${name}(...)\` can only be used during component initialisation\nhttps://svelte.dev/e/lifecycle_outside_component`);

		error.name = 'Svelte error';

		throw error;
	} else {
		throw new Error(`https://svelte.dev/e/lifecycle_outside_component`);
	}

View on GitHub (pinned to 20b341f100)

Solutions

Read the `%message%` and search https://github.com/sveltejs/svelte/issues for it.
Minimize the reproduction and file an issue with the Svelte version and a minimal repro.
Try the latest Svelte patch — it may already be fixed.
Work around it by simplifying reactivity (avoid mixing runes and legacy stores in one component).

Defensive patterns

Strategy: try-catch

Try / catch

try {
	// risky Svelte render/mount/teardown path
} catch (e) {
	if (String(e).includes('invariant_violation')) {
		// report to bug tracker; show fallback UI
		handleError(e);
	} else {
		throw e;
	}
}

Prevention

Pin a stable, tested Svelte version.
Avoid mixing runes ($state/$derived) with legacy stores in one component.
Ensure SSR and client render identical markup to avoid hydration mismatches.
Report violations with a minimal repro to sveltejs/svelte.

When it happens

Trigger: Reaching an internal code path Svelte considered unreachable: a corrupted effect/state graph, an unexpected null internal handle, state used after teardown, or a double-activated effect. Often surfaces after unusual reactivity patterns, SSR/hydration mismatches, or rapid mount/unmount cycles.

Common situations: Hitting an edge case in Svelte's reactivity engine; SSR hydration mismatches; rapid concurrent mounting; upgrading to a Svelte version with a regression; combining runes with legacy stores in unsupported ways.

Related errors

AI-assisted analysis of sveltejs/svelte@20b341f100 (2026-08-12). Data as JSON: /api/errors/27d066f592b94cbf. Report an issue: GitHub.