[Vite plugin]: add programmatic worker config

src/content/changelog/workers/2025-12-02-vite-optional-config.mdx

@@ -0,0 +1,11 @@
+---
+title: Wrangler config is optional when using Vite plugin
+description: When using the Cloudflare Vite plugin in an assets-only (static) site, a Wrangler configuration file is now optional.
+products:
+  - workers
+date: 2025-12-02
+---
+
+When using the [Cloudflare Vite plugin](/workers/vite-plugin/) to build and deploy Workers, a Wrangler configuration file is now optional for assets-only (static) sites. If no `wrangler.toml`, `wrangler.json`, or `wrangler.jsonc` file is found, the plugin generates sensible defaults for an assets-only site. The `name` is based on the `package.json` or the project directory name, and the `compatibility_date` uses the latest date supported by your installed Miniflare version.
+
+This allows easier setup for static sites using Vite. Note that SPAs will still need to [set `assets.not_found_handling` to `single-page-application`](https://developers.cloudflare.com/workers/static-assets/routing/single-page-application/) in order to function correctly.

src/content/changelog/workers/2025-12-02-vite-programmatic-config.mdx

@@ -0,0 +1,106 @@
+---
+title: Configure Workers programmatically using the Vite plugin
+description: The Cloudflare Vite plugin can now programmatically configure Workers without a Wrangler config file, or modify existing configuration.
+products:
+  - workers
+date: 2025-12-02
+---
+
+The [Cloudflare Vite plugin](/workers/vite-plugin/) now supports programmatic configuration of Workers without a Wrangler configuration file. You can use the `config` option to define Worker settings directly in your Vite configuration, or to modify existing configuration loaded from a Wrangler config file. This is particularly useful when integrating with other build tools or frameworks, as it allows them to control Worker configuration without needing users to manage a separate config file.
+
+## The `config` option
+
+The Vite plugin's new `config` option accepts either a partial configuration object or a function that receives the current configuration and returns overrides. This option is applied after any config file is loaded, allowing the plugin to override specific values or define Worker configuration entirely in code.
+
+## Example usage
+
+Setting `config` to an object to provide configuration values that merge with defaults and config file settings:
+
+```ts title="vite.config.ts"
+import { defineConfig } from "vite";
+import { cloudflare } from "@cloudflare/vite-plugin";
+
+export default defineConfig({
+	plugins: [
+		cloudflare({
+			config: {
+				name: "my-worker",
+				compatibility_flags: ["nodejs_compat"],
+				send_email: [
+					{
+						name: "EMAIL",
+					},
+				],
+			},
+		}),
+	],
+});
+```
+
+Use a function to modify the existing configuration:
+
+```ts title="vite.config.ts"
+import { defineConfig } from "vite";
+import { cloudflare } from "@cloudflare/vite-plugin";
+export default defineConfig({
+	plugins: [
+		cloudflare({
+			config: (userConfig) => {
+				delete userConfig.compatibility_flags;
+			},
+		}),
+	],
+});
+```
+
+Return an object with values to merge:
+
+```ts title="vite.config.ts"
+import { defineConfig } from "vite";
+import { cloudflare } from "@cloudflare/vite-plugin";
+
+export default defineConfig({
+	plugins: [
+		cloudflare({
+			config: (userConfig) => {
+				if (!userConfig.compatibility_flags.includes("no_nodejs_compat")) {
+					return { compatibility_flags: ["nodejs_compat"] };
+				}
+			},
+		}),
+	],
+});
+```
+
+### Auxiliary Workers
+
+Auxiliary Workers also support the `config` option, enabling multi-Worker architectures without config files.
+
+Define auxiliary Workers without config files using `config` inside the `auxiliaryWorkers` array:
+
+```ts title="vite.config.ts"
+import { defineConfig } from "vite";
+import { cloudflare } from "@cloudflare/vite-plugin";
+
+export default defineConfig({
+	plugins: [
+		cloudflare({
+			config: {
+				name: "entry-worker",
+				main: "./src/entry.ts",
+				services: [{ binding: "API", service: "api-worker" }],
+			},
+			auxiliaryWorkers: [
+				{
+					config: {
+						name: "api-worker",
+						main: "./src/api.ts",
+					},
+				},
+			],
+		}),
+	],
+});
+```
+
+For more details and examples, see [Programmatic configuration](/workers/vite-plugin/reference/programmatic-configuration/).

src/content/docs/workers/vite-plugin/reference/api.mdx

@@ -32,6 +32,15 @@ It accepts an optional `PluginConfig` parameter.
 
   For more information about the Worker configuration, see [Configuration](/workers/wrangler/configuration/).
 
+- `config` <Type text='Partial<WorkerConfig> | ((config: WorkerConfig) => Partial<WorkerConfig> | void)' /> <MetaInfo text='optional' />
+
+  Customize or override Worker configuration programmatically.
+  Accepts a partial configuration object or a function that receives the current config.
+
+  Applied after any config file loads. Use it to override values, modify the existing config, or define Workers entirely in code.
+
+  See [Programmatic configuration](/workers/vite-plugin/reference/programmatic-configuration/) for details.
+
 - `viteEnvironment` <Type text='{ name?: string }' /> <MetaInfo text='optional' />
 
   Optional Vite environment options.
@@ -75,12 +84,22 @@ It accepts an optional `PluginConfig` parameter.
 
 ## `interface AuxiliaryWorkerConfig`
 
-- `configPath` <Type text='string' />
+Auxiliary Workers require a `configPath`, a `config` option, or both.
 
-  A required path to your Worker config file.
+- `configPath` <Type text='string' /> <MetaInfo text='optional' />
+
+  The path to your Worker config file.
+  This field is required unless `config` is provided.
 
   For more information about the Worker configuration, see [Configuration](/workers/wrangler/configuration/).
 
+- `config` <Type text='Partial<WorkerConfig> | ((config: WorkerConfig) => Partial<WorkerConfig> | void)' /> <MetaInfo text='optional' />
+
+  Customize or override Worker configuration programmatically.
+  When used without `configPath`, this allows defining auxiliary Workers entirely in code.
+
+  See [Programmatic configuration](/workers/vite-plugin/reference/programmatic-configuration/) for usage examples.
+
 - `viteEnvironment` <Type text='{ name?: string }' /> <MetaInfo text='optional' />
 
   Optional Vite environment options.

src/content/docs/workers/vite-plugin/reference/migrating-from-wrangler-dev.mdx

@@ -25,5 +25,32 @@ Running `wrangler deploy --env some-env` is therefore not applicable and the env
 
 There are various options in the [Worker config file](/workers/wrangler/configuration/) that are ignored when using Vite, as they are either no longer applicable or are replaced by Vite equivalents.
 If these options are provided, then warnings will be printed to the console with suggestions for how to proceed.
-Examples where the Vite configuration should be used instead include `alias` and `define`.
+
+### Not applicable
+
+The following build-related options are handled by Vite and are not applicable when using the Cloudflare Vite plugin:
+
+- `tsconfig`
+- `rules`
+- `build`
+- `no_bundle`
+- `find_additional_modules`
+- `base_dir`
+- `preserve_file_names`
+
+### Not supported
+
+- `site` — Use [Workers Assets](/workers/static-assets/) instead.
+
+### Replaced by Vite equivalents
+
+The following options have Vite equivalents that should be used instead:
+
+| Wrangler option | Vite equivalent |
+| --- | --- |
+| `define` | [`define`](https://vite.dev/config/shared-options.html#define) |
+| `alias` | [`resolve.alias`](https://vite.dev/config/shared-options.html#resolve-alias) |
+| `minify` | [`build.minify`](https://vite.dev/config/build-options.html#build-minify) |
+| Local dev settings (`ip`, `port`, `local_protocol`, etc.) | [Server options](https://vite.dev/config/server-options.html) |
+
 See [Vite Environments](/workers/vite-plugin/reference/vite-environments/) for more information about configuring your Worker environments in Vite.

src/content/docs/workers/vite-plugin/reference/programmatic-configuration.mdx

@@ -0,0 +1,168 @@
+---
+pcx_content_type: reference
+title: Programmatic configuration
+sidebar:
+  order: 10
+description: Configure Workers programmatically using the Vite plugin
+---
+
+import { WranglerConfig } from "~/components";
+
+The Wrangler configuration file is optional when using the Cloudflare Vite plugin. Without one, the plugin uses default values. You can customize Worker configuration programmatically with the `config` option. This is useful when the Cloudflare plugin runs inside another plugin or framework.
+
+:::note
+Programmatic configuration is primarily designed for use by frameworks and plugin developers. Users should normally use Wrangler config files instead. Configuration set via the `config` option will not be included when running `wrangler types` or resource based Wrangler CLI commands such as `wrangler kv` or `wrangler d1`.
+:::
+
+## Default configuration
+
+Without a configuration file, the plugin generates sensible defaults for an assets-only Worker. The `name` comes from `package.json` or the project directory name. The `compatibility_date` uses the latest date supported by your installed Miniflare version.
+
+## The `config` option
+
+The `config` option offers three ways to programmatically configure your Worker. You can set any property from the [Wrangler configuration file](/workers/wrangler/configuration/), though some options are [ignored or replaced by Vite equivalents](/workers/vite-plugin/reference/migrating-from-wrangler-dev/#redundant-fields-in-the-wrangler-config-file).
+
+:::note
+You cannot define [Cloudflare environments](/workers/vite-plugin/reference/cloudflare-environments/) via `config`, as they are resolved before this option is applied.
+:::
+
+### Configuration object
+
+Set `config` to an object to provide values that merge with defaults and Wrangler config file settings:
+
+```ts title="vite.config.ts"
+import { defineConfig } from "vite";
+import { cloudflare } from "@cloudflare/vite-plugin";
+
+export default defineConfig({
+	plugins: [
+		cloudflare({
+			config: {
+				compatibility_date: "2025-01-01",
+				vars: {
+					API_URL: "https://api.example.com",
+				},
+			},
+		}),
+	],
+});
+```
+
+These values merge with Wrangler config file values, with the `config` values taking precedence.
+
+### Dynamic configuration function
+
+Use a function when configuration depends on existing config values or external data, or if you need to compute or conditionally set values:
+
+```ts title="vite.config.ts"
+import { defineConfig } from "vite";
+import { cloudflare } from "@cloudflare/vite-plugin";
+
+export default defineConfig({
+	plugins: [
+		cloudflare({
+			config: (userConfig) => ({
+				vars: {
+					WORKER_NAME: userConfig.name,
+					BUILD_TIME: new Date().toISOString(),
+				},
+			}),
+		}),
+	],
+});
+```
+
+The function receives the current configuration (defaults or loaded config file). Return an object with values to merge.
+
+### In-place editing
+
+A `config` function can mutate the config object directly instead of returning overrides. This is useful for deleting properties or removing array items:
+
+```ts title="vite.config.ts"
+import { defineConfig } from "vite";
+import { cloudflare } from "@cloudflare/vite-plugin";
+
+export default defineConfig({
+	plugins: [
+		cloudflare({
+			config: (userConfig) => {
+				// Replace all existing compatibility flags
+				userConfig.compatibility_flags = ["nodejs_compat"];
+			},
+		}),
+	],
+});
+```
+
+:::note
+When editing in place, do not return a value from the function.
+:::
+
+## Auxiliary Workers
+
+Auxiliary Workers also support the `config` option, enabling multi-Worker architectures without config files.
+
+Define auxiliary Workers without config files using `config` inside the `auxiliaryWorkers` array:
+
+```ts title="vite.config.ts"
+import { defineConfig } from "vite";
+import { cloudflare } from "@cloudflare/vite-plugin";
+
+export default defineConfig({
+	plugins: [
+		cloudflare({
+			config: {
+				name: "entry-worker",
+				main: "./src/entry.ts",
+				compatibility_date: "2025-01-01",
+				services: [{ binding: "API", service: "api-worker" }],
+			},
+			auxiliaryWorkers: [
+				{
+					config: {
+						name: "api-worker",
+						main: "./src/api.ts",
+						compatibility_date: "2025-01-01",
+					},
+				},
+			],
+		}),
+	],
+});
+```
+
+### Configuration overrides
+
+Combine a config file with `config` to override specific values:
+
+```ts title="vite.config.ts"
+import { defineConfig } from "vite";
+import { cloudflare } from "@cloudflare/vite-plugin";
+
+export default defineConfig({
+	plugins: [
+		cloudflare({
+			configPath: "./wrangler.jsonc",
+			auxiliaryWorkers: [
+				{
+					configPath: "./workers/api/wrangler.jsonc",
+					config: {
+						vars: {
+							ENDPOINT: "https://api.example.com/v2",
+						},
+					},
+				},
+			],
+		}),
+	],
+});
+```
+
+## Configuration merging behavior
+
+The `config` option uses [defu](https://github.com/unjs/defu) for merging configuration objects.
+
+- Object properties are recursively merged
+- Arrays are concatenated (`config` values first, then existing values)
+- Primitive values from `config` override existing values
+- `undefined` values in `config` do not override existing values