fix(mcp): give 'mcp add --command' a distinct argparse dest

The --command flag of `hermes mcp add` shared its argparse dest with the
top-level subparser (`dest="command"` in `hermes_cli/_parser.py`). When
the flag was omitted, argparse still wrote `args.command = None`,
clobbering the top-level value of `"mcp"`. The dispatcher then saw
`args.command is None` and fell through to interactive chat, so
`hermes mcp add ...` silently launched chat instead of registering the
server. `cmd_mcp_add` was never reached.

Use `dest="mcp_command"` on the flag and read it from `cmd_mcp_add`.
The user-facing CLI flag `--command` is unchanged; only the in-memory
namespace attribute moves. Also updates the `_make_args` helper in
`tests/hermes_cli/test_mcp_config.py` to populate the new dest, and
adds `tests/hermes_cli/test_mcp_add_command_dest.py` with a parser-
level regression test.

Closes #19785.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

hermes_cli/main.py

@@ -10007,7 +10007,15 @@ Examples:
     )
     mcp_add_p.add_argument("name", help="Server name (used as config key)")
     mcp_add_p.add_argument("--url", help="HTTP/SSE endpoint URL")
-    mcp_add_p.add_argument("--command", help="Stdio command (e.g. npx)")
+    # dest="mcp_command" so this flag does not clobber the top-level
+    # subparser's args.command attribute, which the dispatcher reads to
+    # route to cmd_mcp.  Without an explicit dest, argparse derives
+    # dest="command" from the flag name and sets it to None when the
+    # flag is omitted, causing `hermes mcp add ...` to fall through to
+    # interactive chat.
+    mcp_add_p.add_argument(
+        "--command", dest="mcp_command", help="Stdio command (e.g. npx)"
+    )
     mcp_add_p.add_argument(
         "--args", nargs="*", default=[], help="Arguments for stdio command"
     )

hermes_cli/mcp_config.py

@@ -221,7 +221,10 @@ def cmd_mcp_add(args):
     """Add a new MCP server with discovery-first tool selection."""
     name = args.name
     url = getattr(args, "url", None)
-    command = getattr(args, "command", None)
+    # Read from `mcp_command` (set by --command via explicit dest) — see
+    # mcp_add_p.add_argument("--command", dest="mcp_command", ...) in
+    # hermes_cli/main.py for why the dest is renamed.
+    command = getattr(args, "mcp_command", None)
     cmd_args = getattr(args, "args", None) or []
     auth_type = getattr(args, "auth", None)
     preset_name = getattr(args, "preset", None)

tests/hermes_cli/test_mcp_add_command_dest.py

@@ -0,0 +1,87 @@
+"""Regression test: ``hermes mcp add --command`` must not clobber the
+top-level ``args.command`` subparser dest.
+
+The top-level argparse parser uses ``dest="command"`` for its subparsers
+(``hermes_cli/_parser.py``).  The dispatcher in ``hermes_cli/main.py``
+reads ``args.command`` to decide which command to run; if it is ``None``
+it falls through to interactive chat.
+
+The ``mcp add`` subparser exposes a ``--command`` flag (the stdio command
+for an MCP server, e.g. ``npx``).  Without an explicit ``dest=``, argparse
+derives the dest from the flag name and writes ``args.command = None``
+when the flag is omitted, overwriting the top-level ``"mcp"`` value.  As a
+result, ``hermes mcp add foo --url ...`` silently launches chat instead
+of registering an MCP server.
+
+The fix: declare the flag with ``dest="mcp_command"``.  The CLI flag name
+is unchanged; only the in-memory attribute moves.
+
+We replicate the relevant parser shape here rather than importing the
+real builder, mirroring ``test_argparse_flag_propagation.py`` and
+``test_subparser_routing_fallback.py``.
+"""
+
+import argparse
+
+
+def _build_parser():
+    """Minimal replica of the slice of the hermes parser that exhibits
+    the bug: top-level subparsers (dest="command") and ``mcp add`` with
+    its ``--command`` flag.
+    """
+    parser = argparse.ArgumentParser(prog="hermes")
+    subparsers = parser.add_subparsers(dest="command")
+
+    subparsers.add_parser("chat")
+
+    mcp_p = subparsers.add_parser("mcp")
+    mcp_sub = mcp_p.add_subparsers(dest="mcp_action")
+
+    mcp_add = mcp_sub.add_parser("add")
+    mcp_add.add_argument("name")
+    mcp_add.add_argument("--url")
+    mcp_add.add_argument("--command", dest="mcp_command")
+
+    return parser
+
+
+class TestMcpAddCommandDest:
+    def test_url_invocation_preserves_top_level_command(self):
+        """`hermes mcp add foo --url ...` must keep args.command == "mcp".
+
+        Before the dest fix this was clobbered to None, sending the
+        dispatcher into the chat fallback.
+        """
+        parser = _build_parser()
+        args = parser.parse_args(
+            ["mcp", "add", "foo", "--url", "https://example.com/mcp"]
+        )
+
+        assert args.command == "mcp"
+        assert args.mcp_action == "add"
+        assert args.name == "foo"
+        assert args.url == "https://example.com/mcp"
+        assert args.mcp_command is None
+
+    def test_command_flag_writes_to_mcp_command_dest(self):
+        """`--command npx` must populate args.mcp_command, not args.command."""
+        parser = _build_parser()
+        args = parser.parse_args(
+            ["mcp", "add", "github", "--command", "npx"]
+        )
+
+        assert args.command == "mcp"
+        assert args.mcp_command == "npx"
+
+    def test_bare_mcp_add_does_not_clobber_command(self):
+        """Even without --url or --command, args.command stays "mcp".
+
+        Catches the regression at the parser layer regardless of which
+        transport flag the user passes.
+        """
+        parser = _build_parser()
+        args = parser.parse_args(["mcp", "add", "foo"])
+
+        assert args.command == "mcp"
+        assert args.mcp_command is None
+        assert args.url is None

tests/hermes_cli/test_mcp_config.py

@@ -43,7 +43,7 @@ def _make_args(**kwargs):
     defaults = {
         "name": "test-server",
         "url": None,
-        "command": None,
+        "mcp_command": None,
         "args": None,
         "auth": None,
         "preset": None,
@@ -233,7 +233,7 @@ class TestMcpAdd:
 
         cmd_mcp_add(_make_args(
             name="github",
-            command="npx",
+            mcp_command="npx",
             args=["@mcp/github"],
         ))
         out = capsys.readouterr().out
@@ -291,7 +291,7 @@ class TestMcpAdd:
 
         cmd_mcp_add(_make_args(
             name="github",
-            command="npx",
+            mcp_command="npx",
             args=["@mcp/github"],
             env=["MY_API_KEY=secret123", "DEBUG=true"],
         ))
@@ -313,7 +313,7 @@ class TestMcpAdd:
 
         cmd_mcp_add(_make_args(
             name="github",
-            command="npx",
+            mcp_command="npx",
             args=["@mcp/github"],
             env=["BAD-NAME=value"],
         ))
@@ -390,7 +390,7 @@ class TestMcpAdd:
         cmd_mcp_add(_make_args(
             name="custom",
             preset="testmcp",
-            command="uvx",
+            mcp_command="uvx",
             args=["custom-server"],
         ))
         out = capsys.readouterr().out