diff --git a/test/fixtures/sources/README.md b/test/fixtures/sources/README.md
new file mode 100644
index 0000000..afd835b
--- /dev/null
+++ b/test/fixtures/sources/README.md
@@ -0,0 +1,3 @@
+# Source fixtures
+
+This file is intentionally not a review target.
diff --git a/test/fixtures/sources/example.go b/test/fixtures/sources/example.go
new file mode 100644
index 0000000..38dd16d
--- /dev/null
+++ b/test/fixtures/sources/example.go
@@ -0,0 +1,3 @@
+package main
+
+func main() {}
diff --git a/test/fixtures/sources/example.py b/test/fixtures/sources/example.py
new file mode 100644
index 0000000..e3010cc
--- /dev/null
+++ b/test/fixtures/sources/example.py
@@ -0,0 +1,2 @@
+def greet(name: str) -> str:
+    return f"Hello, {name}"
diff --git a/test/sources.test.mjs b/test/sources.test.mjs
index 287ebe9..36689d4 100644
--- a/test/sources.test.mjs
+++ b/test/sources.test.mjs
@@ -2,6 +2,41 @@ import assert from 'node:assert/strict'
 import test from 'node:test'
 import { loadTargets } from '../dist/agents/code-review/sources.js'
 
+test('local source directories normalize supported files and ignore Markdown', async () => {
+  const targets = await loadTargets({ kind: 'paths', paths: ['test/fixtures/sources'] })
+  const byFile = new Map(targets.map((target) => [target.file, target]))
+
+  assert.deepEqual([...byFile.keys()].sort(), [
+    'test/fixtures/sources/example.go',
+    'test/fixtures/sources/example.py',
+  ])
+  assert.equal(byFile.get('test/fixtures/sources/example.go')?.language, 'go')
+  assert.equal(byFile.get('test/fixtures/sources/example.py')?.language, 'py')
+  assert.equal(byFile.get('test/fixtures/sources/example.go')?.isChanged, false)
+  assert.equal(byFile.get('test/fixtures/sources/example.py')?.isChanged, false)
+  assert.equal(
+    byFile.get('test/fixtures/sources/example.go')?.fullContent,
+    'package main\n\nfunc main() {}\n',
+  )
+  assert.equal(
+    byFile.get('test/fixtures/sources/example.py')?.fullContent,
+    'def greet(name: str) -> str:\n    return f"Hello, {name}"\n',
+  )
+})
+
+test('stdin source normalization derives Python language and marks the target changed', async () => {
+  const [target] = await loadTargets({
+    kind: 'stdin',
+    filename: 'example.py',
+    content: 'print("hello")\n',
+  })
+
+  assert.equal(target?.language, 'py')
+  assert.equal(target?.isChanged, true)
+  assert.equal(target?.file, 'example.py')
+  assert.equal(target?.fullContent, 'print("hello")\n')
+})
+
 test('GitHub PR ingestion fails when a reviewable file cannot be loaded', async () => {
   const originalFetch = globalThis.fetch
   globalThis.fetch = async (url) => {