From 52109674ddb52c7b9db214ee7b735d343fb9f4c2 Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 13 Jul 2026 19:26:41 -0400
Subject: [PATCH] =?UTF-8?q?Revert=20"breaking:=20replace=20`EnvVarConfig.s?=
 =?UTF-8?q?tatic`=20with=20`EnvVarConfig.availabili=E2=80=A6"?=
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Content-Transfer-Encoding: 8bit

This reverts commit d5ffa2d16bae492c49cef826caf24da5c62b17a4.
---
 .changeset/env-availability.md                |  5 --
 .../70-environment-variables.md               | 20 +++----
 .../25-build-and-deploy/90-adapter-vercel.md  |  2 +-
 .../test/apps/prerendered/src/env.ts          |  2 +-
 .../adapter-static/test/apps/spa/src/env.ts   |  2 +-
 packages/kit/src/core/adapt/builder.js        |  5 +-
 packages/kit/src/core/env.js                  | 53 ++++++-------------
 packages/kit/src/exports/public.d.ts          | 11 ++--
 packages/kit/src/exports/vite/index.js        |  4 +-
 packages/kit/test/apps/async/src/env.ts       |  8 +--
 packages/kit/test/apps/basics/src/env.ts      | 14 ++---
 packages/kit/test/apps/options-2/src/env.ts   |  8 +--
 packages/kit/test/apps/options/source/env.ts  |  2 +-
 .../kit/test/prerendering/basics/src/env.ts   |  4 +-
 packages/kit/types/index.d.ts                 | 11 ++--
 15 files changed, 57 insertions(+), 94 deletions(-)
 delete mode 100644 .changeset/env-availability.md

diff --git a/.changeset/env-availability.md b/.changeset/env-availability.md
deleted file mode 100644
index 0ac9bfbdf485..000000000000
--- a/.changeset/env-availability.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'@sveltejs/kit': major
----
-
-breaking: replace `EnvVarConfig.static` with `EnvVarConfig.availability`
diff --git a/documentation/docs/20-core-concepts/70-environment-variables.md b/documentation/docs/20-core-concepts/70-environment-variables.md
index 8e73d34e7606..d785468585c0 100644
--- a/documentation/docs/20-core-concepts/70-environment-variables.md
+++ b/documentation/docs/20-core-concepts/70-environment-variables.md
@@ -121,31 +121,27 @@ export const variables = defineEnvVars({
 });
 ```
 
-If a value is invalid, the app will fail to start (or build). If the variable is only available at run time (for example a secret that isn't set during the build), use `availability: 'runtime'` so that it is only validated when the app starts:
+If a value is invalid, the app will fail to start (or build). To opt out of one or the other, use [`building`]($app-env#building) from `$app/env` along with a validator that accepts an optional value:
 
 ```ts
 /// file: src/env.ts
 import { defineEnvVars } from '@sveltejs/kit/hooks';
++++import { building } from '$app/env'+++
 import * as v from 'valibot';
 
 export const variables = defineEnvVars({
 	SECRET: {
-		// required when the app starts, but not validated during the build
-		+++availability: 'runtime',+++
-		schema: v.string()
+		// optional when building but required when starting the app
+		+++schema: building ? v.optional(v.string()) : v.string()+++
 	}
 });
 ```
 
 You can use validators to make values optional, or transform them (such as turning a string into a boolean, or parsing JSON) — see your validation library's documentation to learn how.
 
-### Availability
+### Static variables
 
-The `availability` property controls when a variable's value is available, and therefore when it is validated. It has three possible values:
-
-- `'dynamic'` (default) — the value is validated and used during runtime and build time.
-- `'inline'` — the value is inlined into your application code at build time, enabling optimisations like dead-code elimination. It is validated at build time.
-- `'runtime'` — the value is validated and used during runtime only. The value is `undefined` during the build, so the variable is typed as `T | undefined`.
+By default, variables are dynamic. If a variable is configured with `static: true`, it will be inlined into your application code, enabling optimisations like dead-code elimination:
 
 ```ts
 /// file: src/env.ts
@@ -155,7 +151,7 @@ import * as v from 'valibot';
 export const variables = defineEnvVars({
 	SHOW_DEBUG_OVERLAY: {
 		public: true,
-		+++availability: 'inline',+++
+		+++static: true,+++
 
 		// coerce to true/false
 		schema: v.pipe(
@@ -166,7 +162,7 @@ export const variables = defineEnvVars({
 });
 ```
 
-Because this variable is `inline`, the `<DebugOverlay>` component shown here will be excluded from the JavaScript bundle unless `SHOW_DEBUG_OVERLAY` is truthy:
+Because this variable is `static`, the `<DebugOverlay>` component shown here will be excluded from the JavaScript bundle unless `SHOW_DEBUG_OVERLAY` is truthy:
 
 ```svelte
 <script>
diff --git a/documentation/docs/25-build-and-deploy/90-adapter-vercel.md b/documentation/docs/25-build-and-deploy/90-adapter-vercel.md
index 12867a69c5a8..29ba141a2535 100644
--- a/documentation/docs/25-build-and-deploy/90-adapter-vercel.md
+++ b/documentation/docs/25-build-and-deploy/90-adapter-vercel.md
@@ -181,7 +181,7 @@ export function load() {
 <p>This staging environment was deployed from {data.deploymentGitBranch}.</p>
 ```
 
-Since all of these variables are unchanged between build time and run time when building on Vercel, we recommend configuring the variable with `availability: 'inline'` — which will statically replace the variables, enabling optimisations like dead code elimination.
+Since all of these variables are unchanged between build time and run time when building on Vercel, we recommend configuring the variable with `static: true` — which will statically replace the variables, enabling optimisations like dead code elimination.
 
 ## Skew protection
 
diff --git a/packages/adapter-static/test/apps/prerendered/src/env.ts b/packages/adapter-static/test/apps/prerendered/src/env.ts
index 9c0332ea4dcf..01d2ca41b971 100644
--- a/packages/adapter-static/test/apps/prerendered/src/env.ts
+++ b/packages/adapter-static/test/apps/prerendered/src/env.ts
@@ -3,6 +3,6 @@ import { defineEnvVars } from '@sveltejs/kit/hooks';
 export const variables = defineEnvVars({
 	PUBLIC_ANSWER: {
 		public: true,
-		availability: 'inline'
+		static: true
 	}
 });
diff --git a/packages/adapter-static/test/apps/spa/src/env.ts b/packages/adapter-static/test/apps/spa/src/env.ts
index 81a364cb9bc2..70bc639e00bd 100644
--- a/packages/adapter-static/test/apps/spa/src/env.ts
+++ b/packages/adapter-static/test/apps/spa/src/env.ts
@@ -3,6 +3,6 @@ import { defineEnvVars } from '@sveltejs/kit/hooks';
 export const variables = defineEnvVars({
 	PUBLIC_VALUE: {
 		public: true,
-		availability: 'inline'
+		static: true
 	}
 });
diff --git a/packages/kit/src/core/adapt/builder.js b/packages/kit/src/core/adapt/builder.js
index 6ae07d10b31d..57d10b1e15c2 100644
--- a/packages/kit/src/core/adapt/builder.js
+++ b/packages/kit/src/core/adapt/builder.js
@@ -167,10 +167,7 @@ export function create_builder({
 			const issues = {};
 
 			for (const [name, config] of Object.entries(variables)) {
-				const availability = config.availability ?? 'dynamic';
-				// only `dynamic` public vars are included in the prerendered env.js.
-				// `inline` is inlined, and `runtime` isn't available at build time
-				if (!config.public || availability !== 'dynamic') continue;
+				if (config.static || !config.public) continue;
 				values[name] = validate(variables, env[name], name, issues);
 			}
 
diff --git a/packages/kit/src/core/env.js b/packages/kit/src/core/env.js
index 04830db4dd3f..63c493e61875 100644
--- a/packages/kit/src/core/env.js
+++ b/packages/kit/src/core/env.js
@@ -99,46 +99,33 @@ export async function load_explicit_env(kit, file, root, mode) {
 export function create_sveltekit_env(variables, env, entry, is_dev) {
 	const imports = entry
 		? [
-				`import { building } from '$app/env/internal';`,
 				`import { variables } from ${JSON.stringify(entry)};`,
 				`import { validate, handle_issues } from '@sveltejs/kit/internal/env';`
 			]
 		: [`const variables = {};`, `const handle_issues = () => {};`];
 
-	/** @type {string[]} */
 	const declarations = [];
-	/** @type {string[]} */
 	const setters = [];
-	/** @type {string[]} */
-	const runtime_setters = [];
 
 	/** @type {Record<string, StandardSchemaV1.Issue[]>} */
 	const issues = {};
 
 	for (const [name, config] of Object.entries(variables ?? {})) {
-		if (/** @type {any} */ (config)?.static) {
-			throw new Error('`static: true` has been removed. Use `availability: "inline"` instead.');
-		}
-
-		const availability = config?.availability ?? 'dynamic';
-
-		if (availability === 'inline') {
-			if (config?.public) {
+		if (config?.static) {
+			if (config.public) {
 				const value = validate(variables ?? {}, env[name], name, issues);
 				declarations.push(`explicit_public_env.${name} = ${devalue.uneval(value)};`);
 			}
 		} else {
-			const target = availability === 'runtime' ? runtime_setters : setters;
-
-			target.push(
+			setters.push(
 				`const ${name} = validate(variables, env.${name}, ${JSON.stringify(name)}, issues);`
 			);
 
 			if (config?.public) {
-				target.push(`explicit_public_env.${name} = ${name};`);
-				target.push(`rendered_env.${name} = ${name};`);
+				setters.push(`explicit_public_env.${name} = ${name};`);
+				setters.push(`rendered_env.${name} = ${name};`);
 			} else {
-				target.push(`dynamic_private_env.${name} = ${name};`);
+				setters.push(`dynamic_private_env.${name} = ${name};`);
 			}
 		}
 	}
@@ -159,11 +146,6 @@ export function create_sveltekit_env(variables, env, entry, is_dev) {
 			export function set_env(env) {
 				const issues = {};
 				${setters.join('\n')}
-				${
-					runtime_setters.length > 0
-						? `if (!building) {\n\t\t\t\t\t${runtime_setters.join('\n')}\n\t\t\t\t}`
-						: ''
-				}
 				handle_issues(issues);
 			}`
 	];
@@ -205,10 +187,9 @@ export function create_sveltekit_env_private(variables, env) {
 	for (const [name, config] of Object.entries(variables)) {
 		if (config.public) continue;
 
-		const value =
-			config.availability === 'inline'
-				? devalue.uneval(validate(variables, env[name], name, issues))
-				: `env.${name}`;
+		const value = config.static
+			? devalue.uneval(validate(variables, env[name], name, issues))
+			: `env.${name}`;
 
 		exports.push(`export const ${name} = ${value};\n`);
 	}
@@ -238,10 +219,9 @@ export function create_sveltekit_env_public(variables, env, prelude) {
 	for (const [name, config] of Object.entries(variables)) {
 		if (!config.public) continue;
 
-		const value =
-			config.availability === 'inline'
-				? devalue.uneval(validate(variables, env[name], name, issues))
-				: `env.${name}`;
+		const value = config.static
+			? devalue.uneval(validate(variables, env[name], name, issues))
+			: `env.${name}`;
 
 		exports.push(`export const ${name} = ${value};\n`);
 	}
@@ -263,7 +243,7 @@ export function create_sveltekit_env_public(variables, env, prelude) {
  */
 export function create_sveltekit_env_service_worker(variables, env, global, base, app_dir) {
 	const has_dynamic_public_env = Object.values(variables ?? {}).some(
-		(config) => config.public && config.availability !== 'inline'
+		(config) => config.public && !config.static
 	);
 
 	if (!has_dynamic_public_env) {
@@ -330,12 +310,9 @@ export function create_explicit_env_types(variables, relative, type) {
 		.filter(([_, config]) => !!config.public === (type === 'public'))
 		.map(([name, config]) => {
 			const comment = config.description ? `${create_jsdoc(config.description)}\n` : '';
-			const maybe_undefined = config.availability === 'runtime';
 			const type = config.schema
-				? `import('@sveltejs/kit/internal/types').StandardSchemaV1.InferOutput<typeof import('${relative}').variables.${name}.schema>${maybe_undefined ? ' | undefined' : ''}`
-				: maybe_undefined
-					? 'string | undefined'
-					: 'string';
+				? `import('@sveltejs/kit/internal/types').StandardSchemaV1.InferOutput<typeof import('${relative}').variables.${name}.schema>`
+				: 'string';
 			return `${comment}export const ${name}: ${type};`;
 		});
 
diff --git a/packages/kit/src/exports/public.d.ts b/packages/kit/src/exports/public.d.ts
index 73e2b37c2193..cab6332bac14 100644
--- a/packages/kit/src/exports/public.d.ts
+++ b/packages/kit/src/exports/public.d.ts
@@ -2454,13 +2454,12 @@ export interface EnvVarConfig<T> {
 	 */
 	public?: boolean;
 	/**
-	 * When the variable's value is available, and therefore when it is validated.
-	 * - `'dynamic'` — the value is validated and used during runtime and build time.
-	 * - `'inline'` — the value is inlined into your application code at build time, enabling optimisations like dead-code elimination. It is validated at build time.
-	 * - `'runtime'` — the value is validated and used during runtime only. The value is `undefined` during the build, so the variable is typed as `T | undefined`.
-	 * @default 'dynamic'
+	 * Whether the value is determined at build time or when the app runs.
+	 * - if `true`, the build time value is inlined into the bundle. This enables optimisations like dead-code elimination
+	 * - if `false`, the value is read from the environment when the app starts
+	 * @default false
 	 */
-	availability?: 'inline' | 'dynamic' | 'runtime';
+	static?: boolean;
 	/**
 	 * A [Standard Schema](https://standardschema.dev/) validator that is applied to the value when the app starts.
 	 * The validator can output any value — not necessarily a string — but public, non-static values must be
diff --git a/packages/kit/src/exports/vite/index.js b/packages/kit/src/exports/vite/index.js
index cfb6d5793521..56479d7ebe1d 100644
--- a/packages/kit/src/exports/vite/index.js
+++ b/packages/kit/src/exports/vite/index.js
@@ -1656,11 +1656,11 @@ function kit({ svelte_config }) {
 					find_deps(vite_manifest, posixify(path.relative(root, entry)), add_dynamic_css, root);
 
 				const has_explicit_dynamic_public_env = Object.values(explicit_env_config ?? {}).some(
-					(variable) => variable.public && variable.availability !== 'inline'
+					(variable) => variable.public && !variable.static
 				);
 
 				// the app only depends on runtime public env if it imports `$app/env/public`
-				// *and* at least one public env var is actually dynamic (not inlined at build time)
+				// *and* at least one public env var is actually dynamic (non-static)
 				const uses_env_dynamic_public =
 					has_explicit_dynamic_public_env &&
 					client_chunks.some(
diff --git a/packages/kit/test/apps/async/src/env.ts b/packages/kit/test/apps/async/src/env.ts
index e05b0bb80d96..3ebd2aecc14e 100644
--- a/packages/kit/test/apps/async/src/env.ts
+++ b/packages/kit/test/apps/async/src/env.ts
@@ -3,18 +3,18 @@ import { defineEnvVars } from '@sveltejs/kit/hooks';
 export const variables = defineEnvVars({
 	PRIVATE_STATIC: {
 		public: false,
-		availability: 'inline'
+		static: true
 	},
 	PRIVATE_DYNAMIC: {
 		public: false,
-		availability: 'dynamic'
+		static: false
 	},
 	PUBLIC_STATIC: {
 		public: true,
-		availability: 'inline'
+		static: true
 	},
 	PUBLIC_DYNAMIC: {
 		public: true,
-		availability: 'dynamic'
+		static: false
 	}
 });
diff --git a/packages/kit/test/apps/basics/src/env.ts b/packages/kit/test/apps/basics/src/env.ts
index d17ef59bad69..cdf5d6a8d72b 100644
--- a/packages/kit/test/apps/basics/src/env.ts
+++ b/packages/kit/test/apps/basics/src/env.ts
@@ -3,30 +3,30 @@ import { defineEnvVars } from '@sveltejs/kit/hooks';
 export const variables = defineEnvVars({
 	PRIVATE_STATIC: {
 		public: false,
-		availability: 'inline'
+		static: true
 	},
 	PRIVATE_DYNAMIC: {
 		public: false,
-		availability: 'dynamic'
+		static: false
 	},
 	PUBLIC_STATIC: {
 		public: true,
-		availability: 'inline'
+		static: true
 	},
 	PUBLIC_DYNAMIC: {
 		public: true,
-		availability: 'dynamic'
+		static: false
 	},
 	PUBLIC_THEME: {
 		public: true,
-		availability: 'dynamic'
+		static: false
 	},
 	PUBLIC_PRERENDERING: {
 		public: true,
-		availability: 'dynamic'
+		static: false
 	},
 	SOME_JSON: {
 		public: false,
-		availability: 'inline'
+		static: true
 	}
 });
diff --git a/packages/kit/test/apps/options-2/src/env.ts b/packages/kit/test/apps/options-2/src/env.ts
index 916e4c0fe0ff..d61d03fddfec 100644
--- a/packages/kit/test/apps/options-2/src/env.ts
+++ b/packages/kit/test/apps/options-2/src/env.ts
@@ -1,21 +1,21 @@
 import process from 'node:process';
+import { building } from '$app/env';
 import * as v from 'valibot';
 
 export const variables = {
 	MESSAGE: {
 		public: true,
 		description: 'Public env var loaded from the shared test env directory',
-		availability: process.env.DYNAMIC_PUBLIC_ENV ? 'dynamic' : 'inline'
+		static: !process.env.DYNAMIC_PUBLIC_ENV
 	},
 	PRIVATE_EXPLICIT_ENV: {},
 	PRIVATE_STATIC_EXPLICIT_ENV: {
-		availability: 'inline'
+		static: true
 	},
 	PRIVATE_VALIDATED_DEFAULT_ENV: {
 		schema: v.optional(v.picklist(['foo', 'bar']), 'foo')
 	},
 	RUNTIME_ONLY: {
-		availability: 'runtime',
-		schema: v.string()
+		schema: building ? v.optional(v.string()) : v.string()
 	}
 };
diff --git a/packages/kit/test/apps/options/source/env.ts b/packages/kit/test/apps/options/source/env.ts
index c3a35d69181a..0b49d8f3845b 100644
--- a/packages/kit/test/apps/options/source/env.ts
+++ b/packages/kit/test/apps/options/source/env.ts
@@ -5,6 +5,6 @@ export const variables = defineEnvVars({
 		public: true
 	},
 	TOP_SECRET_SHH_PLS: {
-		availability: 'inline'
+		static: true
 	}
 });
diff --git a/packages/kit/test/prerendering/basics/src/env.ts b/packages/kit/test/prerendering/basics/src/env.ts
index 4bcce90f9dce..e5b56561f084 100644
--- a/packages/kit/test/prerendering/basics/src/env.ts
+++ b/packages/kit/test/prerendering/basics/src/env.ts
@@ -3,10 +3,10 @@ import { defineEnvVars } from '@sveltejs/kit/hooks';
 export const variables = defineEnvVars({
 	PUBLIC_STATIC: {
 		public: true,
-		availability: 'inline'
+		static: true
 	},
 	PRIVATE_STATIC: {
 		public: false,
-		availability: 'inline'
+		static: true
 	}
 });
diff --git a/packages/kit/types/index.d.ts b/packages/kit/types/index.d.ts
index bd90a4b62601..6f5d75500c29 100644
--- a/packages/kit/types/index.d.ts
+++ b/packages/kit/types/index.d.ts
@@ -2425,13 +2425,12 @@ declare module '@sveltejs/kit' {
 		 */
 		public?: boolean;
 		/**
-		 * When the variable's value is available, and therefore when it is validated.
-		 * - `'dynamic'` — the value is validated and used during runtime and build time.
-		 * - `'inline'` — the value is inlined into your application code at build time, enabling optimisations like dead-code elimination. It is validated at build time.
-		 * - `'runtime'` — the value is validated and used during runtime only. The value is `undefined` during the build, so the variable is typed as `T | undefined`.
-		 * @default 'dynamic'
+		 * Whether the value is determined at build time or when the app runs.
+		 * - if `true`, the build time value is inlined into the bundle. This enables optimisations like dead-code elimination
+		 * - if `false`, the value is read from the environment when the app starts
+		 * @default false
 		 */
-		availability?: 'inline' | 'dynamic' | 'runtime';
+		static?: boolean;
 		/**
 		 * A [Standard Schema](https://standardschema.dev/) validator that is applied to the value when the app starts.
 		 * The validator can output any value — not necessarily a string — but public, non-static values must be