From 9ac2e9e84447185846c1204025ef359253bd8f09 Mon Sep 17 00:00:00 2001
From: Storm Dragon <stormdragon2976@gmail.com>
Date: Sun, 26 Jul 2026 20:44:50 -0400
Subject: [PATCH] Found and hopefullyfixed a bug with fenrir watchdog.

---
 .../screenDriver/vcsaDriver.py                |  5 +--
 tests/unit/test_vcsa_driver.py                | 35 +++++++++++++++++++
 2 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 tests/unit/test_vcsa_driver.py

diff --git a/src/fenrirscreenreader/screenDriver/vcsaDriver.py b/src/fenrirscreenreader/screenDriver/vcsaDriver.py
index a71af4a6..fa3bd550 100644
--- a/src/fenrirscreenreader/screenDriver/vcsaDriver.py
+++ b/src/fenrirscreenreader/screenDriver/vcsaDriver.py
@@ -263,9 +263,10 @@ class driver(screenDriver):
             while True:
                 # Read from file
                 try:
-                    d += file.readline(1)
-                    if not d:
+                    chunk = file.readline(1)
+                    if not chunk:
                         break
+                    d += chunk
                 except Exception as e:
                     break
         return d
diff --git a/tests/unit/test_vcsa_driver.py b/tests/unit/test_vcsa_driver.py
new file mode 100644
index 00000000..24b075bb
--- /dev/null
+++ b/tests/unit/test_vcsa_driver.py
@@ -0,0 +1,35 @@
+from unittest.mock import Mock
+
+from fenrirscreenreader.screenDriver.vcsaDriver import driver as VcsaDriver
+
+
+class BulkReadFailure:
+    def __init__(self, chunks):
+        self.chunks = iter(chunks)
+        self.readline_calls = 0
+
+    def seek(self, offset):
+        assert offset == 0
+
+    def read(self):
+        raise OSError(22, "Invalid argument")
+
+    def readline(self, size):
+        assert size == 1
+        self.readline_calls += 1
+        if self.readline_calls > 3:
+            raise RuntimeError("read continued after EOF")
+        return next(self.chunks)
+
+
+def test_vcsa_read_fallback_stops_at_eof():
+    vcsa_driver = VcsaDriver.__new__(VcsaDriver)
+    vcsa_driver.env = {
+        "runtime": {
+            "DebugManager": Mock(),
+        }
+    }
+    screen_file = BulkReadFailure([b"a", b"b", b""])
+
+    assert vcsa_driver.read_file(screen_file) == b"ab"
+    assert screen_file.readline_calls == 3