diff --git a/hermes_cli/main.py b/hermes_cli/main.py
index 5f76c1fc8d4f..e0a753c468bc 100644
--- a/hermes_cli/main.py
+++ b/hermes_cli/main.py
@@ -13623,7 +13623,20 @@ def cmd_sessions(args):
 
     # Execute the command
     if hasattr(args, "func"):
-        args.func(args)
+        # Propagate a subcommand's shell-style exit code. Handlers that return
+        # an int (e.g. cmd_kanban -> kanban_command, cmd_project) mean it as an
+        # exit code; discarding it made `hermes kanban comment -- t_bogus x`
+        # exit 0 on a handled failure, so the card-drop receiver's
+        # unknown-card -> 404 mapping (keyed on returncode != 0) never fired.
+        # Handlers returning None keep the implicit exit-0 behavior.
+        rc = args.func(args)
+        # `bool` is a subclass of `int`, so a handler returning a success/failure
+        # flag (e.g. plugin CLI commands registered via
+        # PluginContext.register_cli_command) would otherwise be treated as an
+        # exit code -- sys.exit(True) exits 1, inverting a success signal.
+        # Only propagate genuine int exit codes; bools and None keep exit-0.
+        if isinstance(rc, int) and not isinstance(rc, bool):
+            sys.exit(rc)
     else:
         parser.print_help()
 
diff --git a/tests/hermes_cli/test_kanban_cli_exit_code.py b/tests/hermes_cli/test_kanban_cli_exit_code.py
new file mode 100644
index 000000000000..3176c9f70f1b
--- /dev/null
+++ b/tests/hermes_cli/test_kanban_cli_exit_code.py
@@ -0,0 +1,98 @@
+"""Regression: `hermes kanban <subcommand>` must propagate its shell exit code.
+
+Root cause (main.py dispatch): `args.func(args)` discarded the handler's return
+value, so `cmd_kanban` -> `kanban_command` returning 1 on a handled failure (e.g.
+commenting on an unknown task) still exited the process 0. That broke the kanban
+card-drop receiver, which maps unknown-card -> 404 only when `proc.returncode != 0`.
+
+These run the REAL CLI as a subprocess against a throwaway HERMES_HOME so the actual
+`main()` exit path is exercised (an in-process handler call would bypass the bug).
+"""
+from __future__ import annotations
+
+import os
+import subprocess
+import sys
+import tempfile
+
+import pytest
+
+
+def _run_kanban(home: str, *argv: str) -> subprocess.CompletedProcess:
+    env = dict(os.environ)
+    env["HERMES_HOME"] = home
+    return subprocess.run(
+        [sys.executable, "-m", "hermes_cli.main", "kanban", *argv],
+        env=env,
+        capture_output=True,
+        text=True,
+    )
+
+
+@pytest.fixture()
+def isolated_home():
+    home = tempfile.mkdtemp(prefix="kanban_exit_code_")
+    os.makedirs(os.path.join(home, "profiles", "default"), exist_ok=True)
+    yield home
+
+
+def test_comment_unknown_task_exits_nonzero(isolated_home):
+    """The repro from the bug report: an unknown task id must exit non-zero."""
+    proc = _run_kanban(
+        isolated_home, "comment", "--author", "card-drop", "--", "t_nonexistent", "x"
+    )
+    assert proc.returncode != 0, (
+        f"expected non-zero exit for unknown task, got {proc.returncode}\n"
+        f"stdout={proc.stdout!r} stderr={proc.stderr!r}"
+    )
+    assert "unknown task" in proc.stderr.lower()
+
+
+def test_list_success_exits_zero(isolated_home):
+    """A successful subcommand still exits 0 (guards the isinstance fix)."""
+    proc = _run_kanban(isolated_home, "list")
+    assert proc.returncode == 0, (
+        f"expected 0 for successful list, got {proc.returncode}\n"
+        f"stderr={proc.stderr!r}"
+    )
+
+
+def test_unknown_board_exits_nonzero(isolated_home):
+    """`--board <typo>` on a non-existent board is a handled failure -> non-zero."""
+    proc = _run_kanban(isolated_home, "--board", "does-not-exist", "list")
+    assert proc.returncode != 0, (
+        f"expected non-zero exit for unknown board, got {proc.returncode}\n"
+        f"stderr={proc.stderr!r}"
+    )
+
+
+@pytest.mark.parametrize("retval", ["True", "False"])
+def test_bool_return_does_not_propagate_as_exit_code(isolated_home, retval):
+    """A handler returning a bool (success/failure flag) must NOT be treated as
+    an exit code. Since bool subclasses int, sys.exit(True) would exit 1 and
+    invert a success signal; the dispatch guard excludes bools so bool returns
+    fall through to the implicit exit-0 path.
+
+    Exercises the REAL main() dispatch: an inline script points an existing
+    subcommand's handler at one returning a bool, then runs main() and reports
+    the process exit code.
+    """
+    script = (
+        "import sys\n"
+        "from hermes_cli import main as m\n"
+        "_orig = m.cmd_kanban\n"
+        f"m.cmd_kanban = lambda args: {retval}\n"
+        "sys.argv = ['hermes', 'kanban', 'list']\n"
+        "m.main()\n"
+    )
+    env = dict(os.environ)
+    env["HERMES_HOME"] = isolated_home
+    proc = subprocess.run(
+        [sys.executable, "-c", script], env=env, capture_output=True, text=True
+    )
+    assert proc.returncode == 0, (
+        f"bool return {retval} must not propagate as a failing exit code, "
+        f"got {proc.returncode}\nstdout={proc.stdout!r} stderr={proc.stderr!r}"
+    )
+
+