`@cloudflare/vite-plugin`: AWS SDK v3 (≥ @aws-sdk/core 3.974) crashes in dev — subpath-barrel re-exports resolve to `undefined`

[feliperohdee]

Which Cloudflare product(s)?

@cloudflare/vite-plugin

Summary

On a fresh install, any Worker that constructs an AWS SDK v3 client (e.g. new DynamoDBClient({})) throws at runtime in vite dev:

[vite] Internal server error: (0 , __vite_ssr_import_5__.emitWarningIfUnsupportedVersion) is not a function
    at getRuntimeConfig (node_modules/@aws-sdk/client-dynamodb/dist-es/runtimeConfig.js:18:5)
    at new DynamoDBClient (node_modules/@aws-sdk/client-dynamodb/dist-es/DynamoDBClient.js:20:27)
    at Object.fetch (worker/index.ts)

The Worker's Vite environment runs @aws-sdk/* / @smithy/* through the SSR module runner, and it cannot resolve named re-exports that pass through the subpath-barrel entrypoints (@aws-sdk/core/client, @smithy/core/client) introduced in the current AWS SDK generation — the binding comes back undefined.

Reproduction

Worker entry:

import { DynamoDBClient } from '@aws-sdk/client-dynamodb';

export default {
  async fetch() {
    new DynamoDBClient({ region: 'us-east-1' }); // throws during construction
    return new Response('ok');
  },
};

package.json (fresh install today resolves the broken generation):

"@aws-sdk/client-dynamodb": "^3.983.0"   // → resolves 3.1081.0
// transitively: @aws-sdk/core 3.974.29, @smithy/smithy-client 4.14.6, @smithy/core 3.29.1

wrangler.jsonc: "compatibility_flags": ["nodejs_compat"], "compatibility_date": "2026-03-10".

Hit the Worker once → 500 with the error above.

Environment

• @cloudflare/vite-plugin: 1.43.2 (also repro on 1.41.0)
• vite: 6.4.3
• wrangler: 4.108.0
• node: v22.17.0
• OS: macOS (darwin 25.5.0)

Root cause

AWS reorganized the SDK internals so that top-level entrypoints re-export through subpath barrels. Example — installed @aws-sdk/core@3.974.29:

// @aws-sdk/core/dist-es/index.js
export { emitWarningIfUnsupportedVersion, ... } from "@aws-sdk/core/client";

@smithy/smithy-client@4.14.6 does the same via @smithy/core/client. The Worker environment's SSR runner resolves emitWarningIfUnsupportedVersion off that re-export chain as undefined, so calling it throws.

This is the downstream effect of an intentional AWS change — aws/aws-sdk-js-v3#7686 (v3.974.0, "Changes to AWS SDK internal package dependency version pinning"), which AWS closed as working-as-intended ("No changes are needed by AWS SDK users"). Because AWS declares every internal dep with ^caret ranges, a fresh install always floats the entire @aws-sdk/* + @smithy/* tree into this generation.

The previous generation resolves fine (@aws-sdk/core@3.973.27, @smithy/smithy-client@4.12.9), because those define the exports locally / via relative paths rather than through the subpath barrel.

What I tried (workarounds that do NOT work)

1. environments.<worker>.optimizeDeps.include: ['@aws-sdk/client-dynamodb', '@aws-sdk/lib-dynamodb']
   → pre-bundles a standalone @aws-sdk_client-dynamodb.js (esbuild does resolve the barrel there), but the actual importer keeps its own copy and still throws.
2. Nested syntax include: ['use-dynamodb > @aws-sdk/client-dynamodb']
   → no effect (looks like ssr.optimizeDeps.include with dep1 > dep2 syntax not working vitejs/vite#16405 — dep1 > dep2 not honored in the SSR/Worker environment).
3. optimizeDeps.exclude / resolve.external → rejected as incompatible with @cloudflare/vite-plugin (@cloudflare/vite-plugin doesn't allow optimizeDeps.exclude for framework packages to avoid being optimized #9538).

Current workaround

Pin the whole @aws-sdk/* + @smithy/* tree back to the last pre-3.974 generation via resolutions (yarn) / overrides (npm/pnpm). Pinning a single package skews (the newer middleware re-export from the newer @aws-sdk/core/client), so the entire generation must be pinned together.

Expected

The Worker environment's dep optimizer / SSR runner should resolve named re-exports through AWS SDK v3's subpath-barrel entrypoints, so the current (default-installed) AWS SDK works in vite dev without version pinning.

Related

• v3.974.0 - Changes to AWS SDK internal package dependency version pinning aws/aws-sdk-js-v3#7686 (the intentional v3.974.0 change)
• ssr.optimizeDeps.include with dep1 > dep2 syntax not working vitejs/vite#16405 (dep1 > dep2 include not working)
• @cloudflare/vite-plugin doesn't allow optimizeDeps.exclude for framework packages to avoid being optimized #9538 (optimizeDeps.exclude incompatible with the plugin)