diff --git a/app/tools/ocr.py b/app/tools/ocr.py
index 74ce18f..b8dd0ac 100644
--- a/app/tools/ocr.py
+++ b/app/tools/ocr.py
@@ -49,29 +49,56 @@ def _find_tesseract() -> str | None:
 def _find_tessdata(tess_exe: str | None) -> str | None:
     """Locate the tessdata directory across platforms.
 
-    Windows / macOS Homebrew put tessdata next to the binary. Debian /
-    Ubuntu put it under /usr/share/tesseract-ocr/<version>/tessdata,
-    and the binary itself often has a default path baked in that
-    points at the wrong version (Ubuntu 24.04 ships v5 but the
-    default still points at .../4.00/tessdata, see issue #27).
-    Without TESSDATA_PREFIX set explicitly, OCR fails with
+    Precedence (first match wins):
+
+    1. ``<bindir>/tessdata`` adjacent to the binary — Windows and any
+       install that bundles the data next to the executable.
+    2. The versioned Linux layout
+       ``/usr/share/tesseract-ocr/<version>/tessdata``, reverse-sorted so
+       the newest version wins. Checked *before* the relative prefix
+       derivation (step 3) on purpose: the binary often has a stale
+       default baked in (Ubuntu 24.04 ships v5 but still points at
+       .../4.00/tessdata, see issue #27), and a flat ``/usr/share/tessdata``
+       — which step 3 would derive from ``/usr/bin/tesseract`` — must never
+       shadow a newer versioned directory.
+    3. ``<prefix>/share/tessdata`` derived relative to the binary
+       (``<prefix>/bin/tesseract`` -> ``<prefix>/share/tessdata``). This
+       covers Homebrew (Intel ``/usr/local``, Apple Silicon
+       ``/opt/homebrew``) and non-standard install prefixes; on those
+       systems the versioned glob in step 2 finds nothing so we land here.
+    4. Fixed fallbacks for older Debian, manual installs, Homebrew and
+       snap layouts.
+
+    Without TESSDATA_PREFIX set explicitly, OCR would otherwise fail with
     'Error opening data file .../4.00/tessdata/eng.traineddata'."""
     import sys
+    # 1. tessdata adjacent to the binary (Windows and bundled installs).
     if tess_exe:
         adjacent = os.path.join(os.path.dirname(tess_exe), "tessdata")
         if os.path.isdir(adjacent):
             return adjacent
+    # 2. Versioned Linux layout, newest first. Kept ahead of the relative
+    #    prefix derivation so a stale /usr/share/tessdata never shadows a
+    #    newer /usr/share/tesseract-ocr/<version>/tessdata (issue #27).
     if sys.platform.startswith(("linux", "darwin")):
         import glob
-        # Sort descending so the latest version wins (5 over 4.00 on
-        # Ubuntu 24.04 where both folders may coexist).
         for p in sorted(glob.glob("/usr/share/tesseract-ocr/*/tessdata"),
                         reverse=True):
             if os.path.isdir(p):
                 return p
-        # Older Debian, manual installs, snap fallbacks.
+    # 3. Homebrew (Intel /usr/local, Apple Silicon /opt/homebrew) and
+    #    custom prefixes: <prefix>/bin/tesseract -> <prefix>/share/tessdata.
+    if tess_exe:
+        prefixed = os.path.join(os.path.dirname(os.path.dirname(tess_exe)),
+                                "share", "tessdata")
+        if os.path.isdir(prefixed):
+            return prefixed
+    # 4. Older Debian, manual installs, Homebrew (Intel + Apple Silicon),
+    #    snap fallbacks.
+    if sys.platform.startswith(("linux", "darwin")):
         for p in ("/usr/share/tessdata",
                   "/usr/local/share/tessdata",
+                  "/opt/homebrew/share/tessdata",
                   "/snap/tesseract/current/usr/share/tesseract-ocr/tessdata"):
             if os.path.isdir(p):
                 return p
diff --git a/tests/test_ocr_tessdata.py b/tests/test_ocr_tessdata.py
new file mode 100644
index 0000000..8d7681f
--- /dev/null
+++ b/tests/test_ocr_tessdata.py
@@ -0,0 +1,247 @@
+"""Regression tests for ``app.tools.ocr._find_tessdata``.
+
+The bug: on macOS Homebrew the ``tesseract`` binary lives in
+``<prefix>/bin`` but the language data lives in
+``<prefix>/share/tessdata`` — ``/usr/local`` on Intel and
+``/opt/homebrew`` on Apple Silicon. The old ``_find_tessdata`` only
+looked for a ``tessdata`` folder *adjacent* to the binary and, as a
+fixed fallback, ``/usr/local/share/tessdata`` (Intel only). On an
+Apple Silicon Mac (e.g. a MacBook Air M5) it therefore returned
+``None`` and the app never set ``TESSDATA_PREFIX``, so extra language
+packs such as Hebrew were silently invisible.
+
+The fix is additive:
+
+1. Derive ``<prefix>/share/tessdata`` relative to the binary
+   (``<prefix>/bin/tesseract`` -> ``<prefix>/share/tessdata``). This
+   covers Intel, Apple Silicon *and* non-standard install prefixes in
+   one generic step.
+2. Add ``/opt/homebrew/share/tessdata`` to the fixed
+   ``linux``/``darwin`` fallback list, for the case where the binary is
+   resolved via ``PATH`` and the derived prefix does not match.
+
+The precedence enforced by ``_find_tessdata`` (first match wins) is:
+
+1. ``<bindir>/tessdata`` adjacent to the binary (Windows / bundled).
+2. Versioned Linux ``/usr/share/tesseract-ocr/<version>/tessdata``,
+   reverse-sorted so the newest version wins.
+3. The relative ``<prefix>/share/tessdata`` derivation from step (1)
+   above — deliberately *after* the versioned lookup so a stale flat
+   ``/usr/share/tessdata`` (which is what the derivation yields for
+   ``/usr/bin/tesseract``) never shadows a newer versioned directory
+   (issue #27, PR #146 review).
+4. Fixed ``/usr/share``, ``/usr/local/share``, ``/opt/homebrew/share``
+   and snap fallbacks.
+
+Nothing about the existing Windows-adjacent or Linux versioned
+behaviour changes.
+
+These tests never touch the real filesystem or the real ``sys.platform``
+— everything is monkeypatched so they run identically on the Windows and
+Linux CI runners (there is no macOS runner).
+"""
+
+from __future__ import annotations
+
+import glob as _glob
+import os
+import sys
+from pathlib import Path
+
+# Make the project root importable so ``from app.tools...`` works.
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+# _find_tessdata is a plain function and needs no GUI, but importing the
+# module pulls in PySide6 widget classes; force the offscreen platform so
+# a headless runner never tries to open a display.
+os.environ.setdefault("QT_QPA_PLATFORM", "offscreen")
+
+from app.tools.ocr import _find_tessdata  # noqa: E402
+
+
+# ---------------------------------------------------------------------------
+# helpers
+# ---------------------------------------------------------------------------
+def _norm(path):
+    """Collapse ``os.sep`` differences so a test can be written with forward
+    slashes yet still match paths that ``os.path.join`` built with ``\\`` on
+    Windows. ``None`` passes through so a regression that returns ``None``
+    fails as a plain assertion rather than an ``AttributeError``."""
+    return None if path is None else path.replace("\\", "/")
+
+
+def _fake_isdir(existing):
+    """Return an ``os.path.isdir`` replacement that reports *only* the given
+    (separator-normalised) directories as existing."""
+    wanted = {_norm(p) for p in existing}
+
+    def _isdir(path):
+        return _norm(path) in wanted
+
+    return _isdir
+
+
+def _patch_fs(monkeypatch, existing, *, platform=None, glob_results=None):
+    """Install a fake ``os.path.isdir`` (and optionally ``glob.glob`` /
+    ``sys.platform``) covering exactly *existing*."""
+    monkeypatch.setattr(os.path, "isdir", _fake_isdir(existing))
+    if platform is not None:
+        monkeypatch.setattr(sys, "platform", platform)
+    if glob_results is not None:
+        monkeypatch.setattr(_glob, "glob", lambda pattern: list(glob_results))
+
+
+# ---------------------------------------------------------------------------
+# prefix-relative derivation (step 3: runs after the adjacent probe AND the
+# versioned Linux glob, so the versioned glob is patched empty to prove we
+# fall through to the derivation, not to a real CI-runner tessdata dir)
+# ---------------------------------------------------------------------------
+def test_apple_silicon_homebrew(monkeypatch):
+    # <prefix>/bin/tesseract -> <prefix>/share/tessdata on /opt/homebrew.
+    # Only the share/tessdata dir exists; the adjacent bin/tessdata does not
+    # and macOS has no versioned /usr/share/tesseract-ocr layout.
+    _patch_fs(
+        monkeypatch,
+        {"/opt/homebrew/share/tessdata"},
+        platform="darwin",
+        glob_results=[],
+    )
+    result = _find_tessdata("/opt/homebrew/bin/tesseract")
+    assert _norm(result) == "/opt/homebrew/share/tessdata"
+
+
+def test_intel_homebrew_regression(monkeypatch):
+    # /usr/local (Intel Homebrew) must keep working via the same derivation.
+    _patch_fs(
+        monkeypatch,
+        {"/usr/local/share/tessdata"},
+        platform="darwin",
+        glob_results=[],
+    )
+    result = _find_tessdata("/usr/local/bin/tesseract")
+    assert _norm(result) == "/usr/local/share/tessdata"
+
+
+def test_custom_prefix(monkeypatch):
+    # A non-standard prefix proves the derivation is generic, not hard-coded.
+    _patch_fs(
+        monkeypatch,
+        {"/opt/custom/share/tessdata"},
+        platform="linux",
+        glob_results=[],
+    )
+    result = _find_tessdata("/opt/custom/bin/tesseract")
+    assert _norm(result) == "/opt/custom/share/tessdata"
+
+
+# ---------------------------------------------------------------------------
+# adjacent tessdata (Windows-style install) still wins first
+# ---------------------------------------------------------------------------
+def test_adjacent_bin_tessdata_takes_precedence(monkeypatch):
+    # When BOTH the adjacent bin/tessdata and the derived share/tessdata
+    # exist, the adjacent one (Windows layout) must be returned first.
+    _patch_fs(monkeypatch, {
+        "/opt/homebrew/bin/tessdata",
+        "/opt/homebrew/share/tessdata",
+    })
+    result = _find_tessdata("/opt/homebrew/bin/tesseract")
+    assert _norm(result) == "/opt/homebrew/bin/tessdata"
+
+
+def test_windows_adjacent(monkeypatch):
+    # A real Windows install path: tessdata sits next to tesseract.exe.
+    # Compute the adjacent path exactly as the function does so the test is
+    # OS-agnostic (ntpath vs posixpath split \\ differently).
+    tess_exe = r"C:\Program Files\Tesseract-OCR\tesseract.exe"
+    adjacent = os.path.join(os.path.dirname(tess_exe), "tessdata")
+    _patch_fs(monkeypatch, {adjacent})
+    result = _find_tessdata(tess_exe)
+    assert _norm(result) == _norm(adjacent)
+
+
+# ---------------------------------------------------------------------------
+# fixed macOS fallback (binary found via PATH, derived prefix does not match)
+# ---------------------------------------------------------------------------
+def test_apple_silicon_fixed_fallback(monkeypatch):
+    # tesseract resolved from an unrelated location -> derived
+    # /weird/share/tessdata is absent, so the explicit
+    # /opt/homebrew/share/tessdata fallback must catch it.
+    _patch_fs(
+        monkeypatch,
+        {"/opt/homebrew/share/tessdata"},
+        platform="darwin",
+        glob_results=[],
+    )
+    result = _find_tessdata("/weird/place/tesseract")
+    assert _norm(result) == "/opt/homebrew/share/tessdata"
+
+
+# ---------------------------------------------------------------------------
+# Linux regressions (unchanged behaviour)
+# ---------------------------------------------------------------------------
+def test_linux_versioned_tessdata(monkeypatch):
+    # Debian/Ubuntu layout: /usr/share/tesseract-ocr/<version>/tessdata.
+    _patch_fs(
+        monkeypatch,
+        {"/usr/share/tesseract-ocr/5/tessdata"},
+        platform="linux",
+        glob_results=["/usr/share/tesseract-ocr/5/tessdata"],
+    )
+    result = _find_tessdata("/usr/bin/tesseract")
+    assert _norm(result) == "/usr/share/tesseract-ocr/5/tessdata"
+
+
+def test_linux_reverse_sort_prefers_latest(monkeypatch):
+    # When 4.00 and 5 coexist (Ubuntu 24.04), the reverse sort must pick 5.
+    _patch_fs(
+        monkeypatch,
+        {
+            "/usr/share/tesseract-ocr/4.00/tessdata",
+            "/usr/share/tesseract-ocr/5/tessdata",
+        },
+        platform="linux",
+        # Deliberately unsorted to prove the function sorts, not glob.
+        glob_results=[
+            "/usr/share/tesseract-ocr/4.00/tessdata",
+            "/usr/share/tesseract-ocr/5/tessdata",
+        ],
+    )
+    result = _find_tessdata("/usr/bin/tesseract")
+    assert _norm(result) == "/usr/share/tesseract-ocr/5/tessdata"
+
+
+def test_linux_versioned_wins_over_flat_usr_share(monkeypatch):
+    # PR #146 review regression: for /usr/bin/tesseract the relative prefix
+    # derivation yields the flat /usr/share/tessdata. If that derivation ran
+    # before the versioned lookup (the bug), a stale /usr/share/tessdata
+    # would shadow a newer /usr/share/tesseract-ocr/5/tessdata. Both dirs
+    # exist here; the versioned lookup runs first, so 5 must win (issue #27).
+    #
+    # This test FAILS against the pre-fix ordering (which returned
+    # /usr/share/tessdata) and PASSES once the versioned glob is checked
+    # before the relative derivation.
+    _patch_fs(
+        monkeypatch,
+        {
+            "/usr/share/tessdata",
+            "/usr/share/tesseract-ocr/5/tessdata",
+        },
+        platform="linux",
+        glob_results=["/usr/share/tesseract-ocr/5/tessdata"],
+    )
+    result = _find_tessdata("/usr/bin/tesseract")
+    assert _norm(result) == "/usr/share/tesseract-ocr/5/tessdata"
+
+
+# ---------------------------------------------------------------------------
+# nothing found
+# ---------------------------------------------------------------------------
+def test_nothing_found_returns_none(monkeypatch):
+    _patch_fs(monkeypatch, set(), platform="darwin", glob_results=[])
+    assert _find_tessdata("/opt/homebrew/bin/tesseract") is None
+
+
+def test_none_binary_returns_none(monkeypatch):
+    # No binary and no system paths -> None (never raises on tess_exe=None).
+    _patch_fs(monkeypatch, set(), platform="linux", glob_results=[])
+    assert _find_tessdata(None) is None