Suppress verbose tracebacks by default, show only with -vv

docs/tools.rst

@@ -20,6 +20,7 @@ arguments
 * (optional) ``-v[v]``, verbosity flag, up to two
 
   - increments ``fre``'s verbosity from the default ``logging.WARNING`` to ``logging.INFO`` with one ``-v``, and again to ``logging.DEBUG`` with ``-vv``
+  - at default verbosity or ``-v``, unhandled exceptions print only the error message; use ``-vv`` to show the full traceback
 
 * (optional) ``-q``, quiet flag, up to one
 

fre/fre.py

@@ -5,6 +5,7 @@
 """
 
 import logging
+import sys
 
 import click
 
@@ -38,7 +39,8 @@
 )
 @click.option( '-v', '--verbose', default = 0, required = False, count = True, type = int,
                help = "Increment logging verbosity from default (logging.WARNING) to logging.INFO. " + \
-                      "use -vv for logging.DEBUG. will be overridden by -q/--quiet" )
+                      "use -vv for logging.DEBUG and to show full tracebacks on errors. " + \
+                      "will be overridden by -q/--quiet" )
 @click.option( '-q', '--quiet', default = False, required = False, is_flag = True, type = bool,
                help = "Set logging verbosity from default (logging.WARNING) to logging.ERROR, printing " + \
                       "less output to screen. overrides -v[v]/--verbose" )
@@ -79,3 +81,10 @@ def fre(verbose = 0, quiet = False, log_file = None):
         fre_logger.info('fre_file_handler added to base_fre_logger')
 
     fre_logger.debug('click entry-point function call done.')
+
+    # install custom exception hook to suppress tracebacks unless -vv is used
+    if log_level > logging.DEBUG:
+        def _brief_excepthook(exc_type, exc_value, exc_tb):
+            click.echo(f"{exc_type.__name__}: {exc_value}", err=True)
+            click.echo("(use 'fre -vv ...' for the full traceback)", err=True)
+        sys.excepthook = _brief_excepthook

fre/tests/test_fre_cli.py

@@ -10,6 +10,7 @@
   right and thinks the tool has a --optionDNE option)
 - fre --version, checking for version GTE current version (fails if version isn't defined)
 """
+import sys
 import subprocess
 from click.testing import CliRunner
 
@@ -50,3 +51,45 @@ def test_cli_fre_version():
 #    latest_testing_tag = result.stdout.split('\n')[0]
 #
 #    assert '2026.01.alpha2' == latest_testing_tag
+
+# ---- traceback suppression tests ----
+# These tests verify that unhandled exceptions print a clean error message
+# at default verbosity, and the full traceback only at -vv.
+
+_CLI_SCRIPT = """\
+import sys
+sys.argv = {argv!r}
+from fre.fre import fre
+fre(standalone_mode=True)
+"""
+
+def _run_fre_subprocess(argv):
+    """Helper: run fre via subprocess so sys.excepthook is exercised."""
+    return subprocess.run(
+        [sys.executable, "-c", _CLI_SCRIPT.format(argv=argv)],
+        capture_output=True, text=True
+    )
+
+def test_traceback_suppressed_by_default():
+    '''fre run function - default verbosity should suppress traceback'''
+    result = _run_fre_subprocess(["fre", "run", "function"])
+    assert result.returncode != 0
+    assert "NotImplementedError" in result.stderr
+    assert "Traceback" not in result.stderr
+    assert "fre -vv" in result.stderr
+
+def test_traceback_suppressed_with_single_v():
+    '''fre -v run function - single -v should still suppress traceback'''
+    result = _run_fre_subprocess(["fre", "-v", "run", "function"])
+    assert result.returncode != 0
+    assert "NotImplementedError" in result.stderr
+    assert "Traceback" not in result.stderr
+    assert "fre -vv" in result.stderr
+
+def test_traceback_shown_with_vv():
+    '''fre -vv run function - double -v should show full traceback'''
+    result = _run_fre_subprocess(["fre", "-vv", "run", "function"])
+    assert result.returncode != 0
+    assert "NotImplementedError" in result.stderr
+    assert "Traceback" in result.stderr
+    assert "fre -vv" not in result.stderr