diff --git a/tests/bun/tests/event-source.test.ts b/tests/bun/tests/event-source.test.ts
new file mode 100644
index 00000000..b31fa67c
--- /dev/null
+++ b/tests/bun/tests/event-source.test.ts
@@ -0,0 +1,67 @@
+import { ErrorEvent } from '@standard-server/core'
+import { toFetchResponse } from '@standard-server/fetch'
+import { afterAll, describe, expect, it } from 'bun:test'
+
+let createBody: () => AsyncGenerator
+
+const server = Bun.serve({
+  port: 0,
+  fetch: () => toFetchResponse({
+    status: 200,
+    headers: {},
+    body: createBody(),
+  }),
+})
+
+afterAll(() => server.stop(true))
+
+/**
+ * Listens with EventSource until a close or error event arrives.
+ */
+function receive(): Promise<{ event: string, data: string }[]> {
+  const source = new EventSource(server.url)
+  const received: { event: string, data: string }[] = []
+
+  return new Promise((resolve) => {
+    for (const event of ['message', 'close', 'error']) {
+      source.addEventListener(event, ({ data }: any) => {
+        received.push({ event, data })
+
+        if (event !== 'message') {
+          source.close()
+          resolve(received)
+        }
+      })
+    }
+  })
+}
+
+// bun-types declares EventSource, but Bun doesn't implement it yet
+describe.skipIf(typeof EventSource === 'undefined')('eventSource', () => {
+  it('receives message and close events', async () => {
+    createBody = async function* () {
+      yield 'hello'
+      yield { order: 2 }
+      // must return a value: a close event without data is dropped by EventSource, which reconnects
+      return 'bye'
+    }
+
+    expect(await receive()).toEqual([
+      { event: 'message', data: '"hello"' },
+      { event: 'message', data: '{"order":2}' },
+      { event: 'close', data: '"bye"' },
+    ])
+  })
+
+  it('receives message and error events', async () => {
+    createBody = async function* () {
+      yield 'hello'
+      throw new ErrorEvent({ code: 'BOOM' })
+    }
+
+    expect(await receive()).toEqual([
+      { event: 'message', data: '"hello"' },
+      { event: 'error', data: '{"code":"BOOM"}' },
+    ])
+  })
+})
diff --git a/tests/deno/tests/event-source.test.ts b/tests/deno/tests/event-source.test.ts
new file mode 100644
index 00000000..b40f51c0
--- /dev/null
+++ b/tests/deno/tests/event-source.test.ts
@@ -0,0 +1,64 @@
+import { ErrorEvent } from '@standard-server/core'
+import { toFetchResponse } from '@standard-server/fetch'
+import { expect } from '@std/expect'
+import { afterAll, describe, it } from '@std/testing/bdd'
+
+let createBody: () => AsyncGenerator
+
+const server = Deno.serve({ port: 0, onListen: () => {} }, () => toFetchResponse({
+  status: 200,
+  headers: {},
+  body: createBody(),
+}))
+
+afterAll(() => server.shutdown())
+
+/**
+ * Listens with Deno's native EventSource until a close or error event arrives.
+ */
+function receive(): Promise<{ event: string, data: string }[]> {
+  const source = new EventSource(`http://localhost:${server.addr.port}`)
+  const received: { event: string, data: string }[] = []
+
+  return new Promise((resolve) => {
+    for (const event of ['message', 'close', 'error']) {
+      source.addEventListener(event, ({ data }: any) => {
+        received.push({ event, data })
+
+        if (event !== 'message') {
+          source.close()
+          resolve(received)
+        }
+      })
+    }
+  })
+}
+
+describe('eventSource', () => {
+  it('receives message and close events', async () => {
+    createBody = async function* () {
+      yield 'hello'
+      yield { order: 2 }
+      // must return a value: a close event without data is dropped by EventSource, which reconnects
+      return 'bye'
+    }
+
+    expect(await receive()).toEqual([
+      { event: 'message', data: '"hello"' },
+      { event: 'message', data: '{"order":2}' },
+      { event: 'close', data: '"bye"' },
+    ])
+  })
+
+  it('receives message and error events', async () => {
+    createBody = async function* () {
+      yield 'hello'
+      throw new ErrorEvent({ code: 'BOOM' })
+    }
+
+    expect(await receive()).toEqual([
+      { event: 'message', data: '"hello"' },
+      { event: 'error', data: '{"code":"BOOM"}' },
+    ])
+  })
+})
diff --git a/tests/event-source.test.ts b/tests/event-source.test.ts
new file mode 100644
index 00000000..7838adfa
--- /dev/null
+++ b/tests/event-source.test.ts
@@ -0,0 +1,68 @@
+import type { AddressInfo } from 'node:net'
+import * as http from 'node:http'
+import { ErrorEvent } from '@standard-server/core'
+import { sendStandardResponse } from '@standard-server/node'
+
+let createBody: () => AsyncGenerator
+
+const server = http.createServer((_req, res) => sendStandardResponse(res, {
+  status: 200,
+  headers: {},
+  body: createBody(),
+}))
+
+server.listen(0)
+
+afterAll(() => {
+  server.close()
+})
+
+/**
+ * Listens with EventSource until a close or error event arrives.
+ */
+function receive(): Promise<{ event: string, data: string }[]> {
+  const source = new EventSource(`http://localhost:${(server.address() as AddressInfo).port}`)
+  const received: { event: string, data: string }[] = []
+
+  return new Promise((resolve) => {
+    for (const event of ['message', 'close', 'error']) {
+      source.addEventListener(event, ({ data }: any) => {
+        received.push({ event, data })
+
+        if (event !== 'message') {
+          source.close()
+          resolve(received)
+        }
+      })
+    }
+  })
+}
+
+describe.skipIf(typeof EventSource === 'undefined')('eventSource', () => {
+  it('receives message and close events', async () => {
+    createBody = async function* () {
+      yield 'hello'
+      yield { order: 2 }
+      // must return a value: a close event without data is dropped by EventSource, which reconnects
+      return 'bye'
+    }
+
+    expect(await receive()).toEqual([
+      { event: 'message', data: '"hello"' },
+      { event: 'message', data: '{"order":2}' },
+      { event: 'close', data: '"bye"' },
+    ])
+  })
+
+  it('receives message and error events', async () => {
+    createBody = async function* () {
+      yield 'hello'
+      throw new ErrorEvent({ code: 'BOOM' })
+    }
+
+    expect(await receive()).toEqual([
+      { event: 'message', data: '"hello"' },
+      { event: 'error', data: '{"code":"BOOM"}' },
+    ])
+  })
+})
diff --git a/vitest.config.ts b/vitest.config.ts
index f5567ec0..a01eaf16 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -7,6 +7,8 @@ export default defineConfig(() => ({
     globals: true,
     include: ['**/*.test.ts'],
     exclude: [...defaultExclude, '**/.claude/**', './tests/bun/**', './tests/deno/**'],
+    // exposes Node's EventSource global, which is still behind a flag (Node 20 - 26)
+    execArgv: ['--experimental-eventsource'],
     coverage: {
       include: ['packages/*/src/**'],
       exclude: ['**.test-d.*', '**.test.*', '**/*.bench.ts', './tests/bun/**', './tests/deno/**'],