fix(xceadmin): probe_config uses Request envelope + follow_redirects (bug-1506, bug-1507)

- probe_config() now wraps probe in Request envelope matching push_config()
- Controller OPCode_probeConfigTag handler replies through xce_reply()
  with redirectHost/redirectPort populated
- follow_redirects works identically for both push and probe flows

src/xceadmin/src/xceadmin/push.py

@@ -30,14 +30,13 @@ nothing else to say. Real SHA/version-compatibility validation
 (Requirement 6.1's aspirational description) is future controller-side
 work, not something this client can check today.
 
-``probe_config()`` connects directly and does NOT go through
-``xceadmin.discovery.follow_redirects``: ``ProbeConfigTagReply`` is a
-direct struct with only a ``configTag`` field -- no ``redirectHost``/
-``redirectPort`` exist on it at all, so there is no redirect signal for
-``follow_redirects`` (which decodes every reply as ``RequestReply``) to
-read. Feeding ``ProbeConfigTagReply`` bytes through it would misinterpret
-them as a different struct shape. Only ``push_config()``'s
-``Request``/``RequestReply``-wrapped exchange supports redirects.
+``probe_config()`` now follows the same ``Request``-envelope +
+``follow_redirects`` + ``decode_reply`` path as ``push_config()``
+(bug-1507).  The controller gained a real ``OPCode_probeConfigTag``
+handler (bug-1506) that replies through the standard ``xce_reply()``
+→ ``Request{opcode: reply, body.replymsg: RequestReply}`` envelope
+with ``redirectHost``/``redirectPort`` populated, so ``follow_redirects``
+works identically for both flows.
 """
 
 from __future__ import annotations
@@ -131,28 +130,52 @@ def push_config(cluster_bin_path: str, controller: str) -> PushResult:
 
 def probe_config(cluster_bin_path: str, controller: str) -> DryRunResult:
     """Probe the controller's current config generation without pushing
-    anything (6.1). ``cluster_bin_path`` is read only to confirm it
-    exists and is readable before spending a network round-trip -- its
-    content plays no role in ``ProbeConfigTagRequest``, which carries no
-    config data (see module docstring).
+    anything (6.1, bug-1507). ``cluster_bin_path`` is read only to
+    confirm it exists and is readable before spending a network
+    round-trip — its content plays no role in ``ProbeConfigTagRequest``,
+    which carries no config data.
+
+    Now goes through the standard ``Request`` envelope →
+    ``follow_redirects`` → ``decode_reply`` path (matching
+    ``push_config``), using the controller's real ``OPCode_probeConfigTag``
+    handler (bug-1506).  Before this fix the request was sent as a bare
+    ``ProbeConfigTagRequest`` direct struct with no controller-side
+    handler at all, so ``accepted=True`` was a client-side fabrication.
 
     Postconditions: exit 0 and "OK: controller will accept this config
-    (generation N->M)" iff ``accepted`` (6.2); otherwise the caller exits
-    non-zero with ``reason`` displayed (6.3) -- this function only
-    reports the result, it does not exit.
+    (generation N->M)" iff the controller returns a successful reply
+    (6.2); otherwise the caller exits non-zero with ``reason`` displayed
+    (6.3) — this function only reports the result, it does not exit.
     """
     Path(cluster_bin_path).read_bytes()
 
     mod = load_schema()
-    request = mod.ProbeConfigTagRequest.new_message()
-    request.name = ""  # matches config_repl.c's xce_probe_config_tag exactly
+    request = mod.Request.new_message()
+    request.opcode = "probeConfigTag"
+    request.seq = 1
+    probe = request.body.init("probeconfigtagrequestmsg")
+    probe.name = ""
     request_bytes = request.to_bytes()
 
     host, port = _split_controller(controller)
-    reply_bytes = _send_via(request_bytes)(host, port)
+    _, _, reply_bytes = follow_redirects(host, port, _send_via(request_bytes))
 
-    with mod.ProbeConfigTagReply.from_bytes(reply_bytes) as reply:
-        current_generation = reply.configTag
+    with decode_reply(reply_bytes) as reply:
+        if reply.status != 0:
+            return DryRunResult(
+                current_generation=0,
+                would_be_generation=0,
+                accepted=False,
+                reason=f"controller returned status {reply.status}",
+            )
+        if reply.data.which() != "probeconfigtagreplymsg":
+            reason = (
+                f"unexpected reply variant {reply.data.which()!r}, "
+                f"expected probeconfigtagreplymsg"
+            )
+            raise ReplyDecodeError(f"invalid reply: {reason}", reason)
+        probe_reply = reply.data.probeconfigtagreplymsg
+        current_generation = probe_reply.configTag
 
     return DryRunResult(
         current_generation=current_generation,

src/xceadmin/tests/test_cli.py

@@ -271,16 +271,18 @@ def test_config_push_connection_refused_exits_nonzero_not_raw_traceback(cluster_
     assert result.output.strip() != ""
 
 
-def test_config_push_dry_run_reports_generations(mock_controller, cluster_bin):
+def test_config_push_dry_run_reports_generations(mock_controller, cluster_bin, wrap_reply):
     from xcecommon import wire
 
     mod = load_schema()
 
     def _handler(conn):
         wire.recv_frame(conn)
-        reply = mod.ProbeConfigTagReply.new_message()
-        reply.configTag = 4
-        wire.send_frame(conn, reply.to_bytes())
+        inner = mod.RequestReply.new_message()
+        inner.status = 0
+        probe_reply = inner.data.init("probeconfigtagreplymsg")
+        probe_reply.configTag = 4
+        wire.send_frame(conn, wrap_reply(inner))
 
     srv = mock_controller(_handler)
 

src/xceadmin/tests/test_config_push_mock.py

@@ -244,19 +244,29 @@ def test_push_config_explicit_port_parsed():
 # ---------------------------------------------------------------------------
 
 
-def test_probe_config_reports_current_and_would_be_generation(mock_controller, cluster_bin):
+def test_probe_config_reports_current_and_would_be_generation(mock_controller, cluster_bin, wrap_reply):
+    """bug-1507: probe_config now sends a Request envelope and decodes
+    through follow_redirects → decode_reply, matching push_config's path.
+    The mock server must unwrap the Request envelope on receive and wrap
+    its reply the same way a real controller does.  """
     mod = load_schema()
     received = {}
 
     def _handler(conn):
         request_bytes = wire.recv_frame(conn)
         received["request_bytes"] = request_bytes
-        with mod.ProbeConfigTagRequest.from_bytes(request_bytes) as req:
-            received["name"] = req.name
+        # Request{opcode: probeConfigTag, body.probeconfigtagrequestmsg: ...}
+        with mod.Request.from_bytes(request_bytes) as req:
+            assert req.opcode == "probeConfigTag"
+            assert req.body.which() == "probeconfigtagrequestmsg"
+            received["name"] = req.body.probeconfigtagrequestmsg.name
 
-        reply = mod.ProbeConfigTagReply.new_message()
-        reply.configTag = 41
-        wire.send_frame(conn, reply.to_bytes())
+        # Build reply: RequestReply{status:0, data.probeconfigtagreplymsg: {configTag:41}}
+        inner = mod.RequestReply.new_message()
+        inner.status = 0
+        probe_reply = inner.data.init("probeconfigtagreplymsg")
+        probe_reply.configTag = 41
+        wire.send_frame(conn, wrap_reply(inner))
 
     srv = mock_controller(_handler)
 
@@ -266,21 +276,22 @@ def test_probe_config_reports_current_and_would_be_generation(mock_controller, c
     assert result.would_be_generation == 42
     assert result.accepted is True
     assert result.reason == ""
-    assert received["name"] == ""  # matches config_repl.c's xce_probe_config_tag exactly
+    assert received["name"] == ""
 
 
-def test_probe_config_zero_generation_still_accepted(mock_controller, cluster_bin):
+def test_probe_config_zero_generation_still_accepted(mock_controller, cluster_bin, wrap_reply):
     """A fresh cluster with no config committed yet (configTag == 0) is
-    still a successful probe -- there is no rejection signal on this
-    wire shape (module docstring); the caller decides significance.
-    """
+    still a successful probe -- configTag == 0 is a valid, real response
+    from a real controller handler now (bug-1506).  """
     mod = load_schema()
 
     def _handler(conn):
         wire.recv_frame(conn)
-        reply = mod.ProbeConfigTagReply.new_message()
-        reply.configTag = 0
-        wire.send_frame(conn, reply.to_bytes())
+        inner = mod.RequestReply.new_message()
+        inner.status = 0
+        probe_reply = inner.data.init("probeconfigtagreplymsg")
+        probe_reply.configTag = 0
+        wire.send_frame(conn, wrap_reply(inner))
 
     srv = mock_controller(_handler)
 
@@ -293,27 +304,23 @@ def test_probe_config_zero_generation_still_accepted(mock_controller, cluster_bi
 
 @pytest.mark.parametrize("tag_value", [0, 1, 999999])
 def test_probe_config_has_no_wire_level_rejection_signal_by_design(
-    mock_controller, cluster_bin, tag_value
+    mock_controller, cluster_bin, tag_value, wrap_reply
 ):
-    """5.6 asks for both an accepted and a rejected dry-run outcome, but
-    ``ProbeConfigTagReply`` (module docstring, ``push.py`` module
-    docstring) has only a bare ``configTag`` -- no field exists on the
-    real wire contract to signal rejection, matching the real C
-    reference client (``config_repl.c``'s ``xce_probe_config_tag``, which
-    also returns only a bare tag). This test locks in that limitation
-    explicitly rather than silently having no coverage for it: every
-    successful round-trip, regardless of the returned ``configTag``
-    value, yields ``accepted=True`` -- there is no reachable code path
-    that produces ``accepted=False`` today. A real "would this SHA be
-    accepted" check is future controller-side work (Requirement 6.1).
-    """
+    """ProbeConfigTagReply (controller.capnp:909) has only a bare
+    ``configTag`` field -- no separate accept/reject flag exists.  A
+    real controller handler (bug-1506) always returns status==0 here;
+    every successful round-trip, regardless of the returned configTag
+    value, yields ``accepted=True``.  A real "would this SHA be accepted"
+    check is future work (Requirement 6.1).  """
     mod = load_schema()
 
     def _handler(conn):
         wire.recv_frame(conn)
-        reply = mod.ProbeConfigTagReply.new_message()
-        reply.configTag = tag_value
-        wire.send_frame(conn, reply.to_bytes())
+        inner = mod.RequestReply.new_message()
+        inner.status = 0
+        probe_reply = inner.data.init("probeconfigtagreplymsg")
+        probe_reply.configTag = tag_value
+        wire.send_frame(conn, wrap_reply(inner))
 
     srv = mock_controller(_handler)