diff --git a/runtime/reference/cli/eval.md b/runtime/reference/cli/eval.md
index 8fc21a087..df2a55d04 100644
--- a/runtime/reference/cli/eval.md
+++ b/runtime/reference/cli/eval.md
@@ -24,14 +24,25 @@ TypeScript works out of the box:
 deno eval "const greeting: string = 'Hello'; console.log(greeting)"
 ```
 
-## CommonJS support
+## CommonJS and ESM auto-detection
 
-CommonJS modules are automatically recognized and supported:
+Starting in Deno 2.8, `deno eval` inspects the snippet for `import` /
+`export` declarations and treats it as ESM if it finds any. Otherwise the
+snippet runs as CommonJS — meaning `require`, `module.exports`, and friends
+work without any flag.
 
 ```sh
+# Detected as CommonJS — no --ext=cjs needed
 deno eval "const path = require('path'); console.log(path.join('a', 'b'))"
+
+# Detected as ESM because of the static import
+deno eval "import { ok } from 'node:assert'; ok(true); console.log('ok')"
 ```
 
+If you need to override the heuristic — for example when a snippet has no
+imports but you still want it parsed as ESM — pass `--ext=mjs` (or
+`--ext=cjs` to force CommonJS).
+
 ## Printing expression results
 
 Use `--print` (or `-p`) to evaluate an expression and print its result, similar