diff --git a/sigma/cli/convert.py b/sigma/cli/convert.py
index e4c41b0..e98f9bb 100644
--- a/sigma/cli/convert.py
+++ b/sigma/cli/convert.py
@@ -153,11 +153,21 @@ def write_separate_files(
     files_written = 0
     rule_results = {}  # Maps rule ID to list of (result, rule) tuples
 
-    # Convert the entire collection
-    try:
-        backend.convert(rule_collection, format, correlation_method)
-    except Exception as e:
-        click.echo(f"Warning: Failed to convert rules: {e}", err=True)
+    # Convert rule by rule (mirroring Backend.convert) so that one failing rule neither
+    # aborts the conversion of the remaining rules nor gets silently ignored. Each
+    # successful conversion stores the finalized result on the rule, collected below.
+    failed_rules = []
+    backend.init_processing_pipeline(format)
+    rule_collection.resolve_rule_references()
+    for rule in rule_collection.rules:
+        try:
+            if isinstance(rule, SigmaCorrelationRule):
+                backend.convert_correlation_rule(rule, format, correlation_method)
+            else:
+                backend.convert_rule(rule, format)
+        except (SigmaError, NotImplementedError) as e:
+            failed_rules.append((rule, e))
+            click.echo(f"Error: Failed to convert rule {rule.source or rule.title}: {e}", err=True)
 
     # Collect the finalized conversion results of all rules that are output
     for rule in rule_collection.get_output_rules():
@@ -240,6 +250,11 @@ def write_separate_files(
     
     click.echo(f"Wrote {files_written} file(s) to {output_dir}", err=True)
 
+    if failed_rules:
+        raise click.ClickException(
+            f"{len(failed_rules)} rule(s) failed to convert, see errors above."
+        )
+
 
 @click.command()
 @click.option(
diff --git a/tests/test_convert.py b/tests/test_convert.py
index b02d51f..0a3cdc6 100644
--- a/tests/test_convert.py
+++ b/tests/test_convert.py
@@ -1,3 +1,5 @@
+import pathlib
+
 from click.testing import CliRunner
 import pytest
 from sigma.cli.convert import convert
@@ -539,3 +541,53 @@ def test_convert_output_dir_skips_non_output_correlation_base_rules(tmp_path):
     # correlation rules are output (the same three queries that -o prints).
     assert "Wrote 3 file(s)" in result.stderr
 
+
+UNCONVERTIBLE_RULE = """title: Unconvertible
+id: 9f1b8f4a-0000-4000-8000-000000000001
+logsource:
+  category: test
+detection:
+  sel:
+    fieldA|expand: "%var%"
+  condition: sel
+"""
+
+
+def _write_rules_with_unconvertible(tmp_path):
+    input_dir = tmp_path / "rules"
+    input_dir.mkdir()
+    (input_dir / "a_unconvertible.yml").write_text(UNCONVERTIBLE_RULE)
+    (input_dir / "b_rule.yml").write_text(
+        pathlib.Path("tests/files/valid/sigma_rule.yml").read_text()
+    )
+    return input_dir
+
+
+def test_convert_output_dir_conversion_error_fails_and_continues(tmp_path):
+    """A rule that fails to convert makes --output-dir exit non-zero, but later rules are still written."""
+    input_dir = _write_rules_with_unconvertible(tmp_path)
+    output_dir = tmp_path / "output"
+    cli = CliRunner()
+    result = cli.invoke(
+        convert,
+        ["-t", "text_query_test", "--output-dir", str(output_dir), str(input_dir)],
+    )
+    assert result.exit_code == 1
+    assert "a_unconvertible.yml" in result.stderr
+    assert "1 rule(s) failed to convert" in result.stderr
+    assert not (output_dir / "a_unconvertible.txt").exists()
+    assert (output_dir / "b_rule.txt").exists()
+
+
+def test_convert_output_dir_conversion_error_skip_unsupported(tmp_path):
+    """With --skip-unsupported the failing rule is only reported as ignored error."""
+    input_dir = _write_rules_with_unconvertible(tmp_path)
+    output_dir = tmp_path / "output"
+    cli = CliRunner()
+    result = cli.invoke(
+        convert,
+        ["-t", "text_query_test", "-s", "--output-dir", str(output_dir), str(input_dir)],
+    )
+    assert result.exit_code == 0
+    assert "Ignored errors" in result.output
+    assert (output_dir / "b_rule.txt").exists()