diff --git a/amber/src/test/python/core/architecture/handlers/control/test_add_input_channel_handler.py b/amber/src/test/python/core/architecture/handlers/control/test_add_input_channel_handler.py
new file mode 100644
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+++ b/amber/src/test/python/core/architecture/handlers/control/test_add_input_channel_handler.py
@@ -0,0 +1,233 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+import asyncio
+from types import SimpleNamespace
+from typing import Optional
+from unittest.mock import MagicMock, call
+
+import pytest
+
+from core.architecture.handlers.control.add_input_channel_handler import (
+    AddInputChannelHandler,
+)
+from core.architecture.packaging.input_manager import InputManager
+from core.models import Schema
+from core.models.internal_queue import InternalQueue
+
+# Side-effect import: patches Message.__hash__ onto betterproto's base class.
+# Already pulled in transitively; explicit so a refactor of that chain fails
+# loudly here.
+import core.util.proto  # noqa: F401
+
+from proto.org.apache.texera.amber.core import (
+    ActorVirtualIdentity,
+    ChannelIdentity,
+    PortIdentity,
+)
+from proto.org.apache.texera.amber.engine.architecture.rpc import (
+    AddInputChannelRequest,
+    EmptyReturn,
+)
+
+# Why hash() instead of ==:
+# Message.__hash__ is patched to hash(repr()), and betterproto's repr omits
+# fields never assigned. proto3 omits false, so a wire-parsed ChannelIdentity
+# is == to its canonical form yet hashes differently -- and InputManager keys
+# its channel registry by that hash (input_manager.py:66). == cannot see the
+# difference this handler exists to remove; only hash() and dict lookups can.
+#
+# NOTE: merely READING is_control materializes the field and fixes the hash.
+# Assert on pre-handler state via hash()/repr() only.
+
+WORKER_ID = "worker-1"
+
+UPSTREAM_ID = ActorVirtualIdentity("upstream-worker")
+SELF_ID = ActorVirtualIdentity(WORKER_ID)
+
+# Port 1 so a hardcoded PortIdentity() cannot pass; port 0 is the degenerate
+# wire case with its own test below.
+PORT_ID = PortIdentity(id=1, internal=False)
+DEFAULT_PORT_ID = PortIdentity(id=0, internal=False)
+
+# Canonical forms: is_control explicitly set rather than left to default.
+DATA_CHANNEL = ChannelIdentity(UPSTREAM_ID, SELF_ID, False)
+CONTROL_CHANNEL = ChannelIdentity(UPSTREAM_ID, SELF_ID, True)
+
+RAW_SCHEMA = {"name": "STRING", "count": "INTEGER"}
+
+
+def _request_off_the_wire(
+    channel_id: ChannelIdentity, port_id: Optional[PortIdentity] = None
+) -> AddInputChannelRequest:
+    """Serialize and re-parse, like a real request from the Scala controller.
+
+    proto3 does not put false on the wire, so the data channel's is_control
+    comes back UNSET -- the exact input the handler's workaround exists for.
+    An in-process request would arrive already canonical and prove nothing.
+    """
+    # Resolved here, not as a default argument (evaluated once at import):
+    # sharing one identity instance across tests is a footgun in this file.
+    port_id = PORT_ID if port_id is None else port_id
+    return AddInputChannelRequest().parse(
+        bytes(AddInputChannelRequest(channel_id, port_id))
+    )
+
+
+def _build_real_handler(
+    port_id: Optional[PortIdentity] = None,
+) -> AddInputChannelHandler:
+    """Handler over a real InputManager with the port already added --
+    in production AssignPort always precedes AddInputChannel."""
+    port_id = PORT_ID if port_id is None else port_id
+    manager = InputManager(WORKER_ID, InternalQueue())
+    manager.add_input_port(port_id, Schema(raw_schema=RAW_SCHEMA), [], [])
+    return AddInputChannelHandler(SimpleNamespace(input_manager=manager))
+
+
+class TestAddInputChannelHandler:
+    @pytest.fixture
+    def handler(self):
+        return AddInputChannelHandler(SimpleNamespace(input_manager=MagicMock()))
+
+    @pytest.fixture
+    def real_handler(self):
+        return _build_real_handler()
+
+    # --- delegation -------------------------------------------------------
+
+    def test_registers_the_requested_channel_on_the_requested_port(self, handler):
+        # == is blind to the materialization, so this pins only delegation
+        # and argument order; the hash tests below pin the form.
+        asyncio.run(handler.add_input_channel(_request_off_the_wire(DATA_CHANNEL)))
+        handler.context.input_manager.register_input.assert_called_once_with(
+            DATA_CHANNEL, PORT_ID
+        )
+
+    def test_register_input_is_the_only_call_on_the_input_manager(self, handler):
+        asyncio.run(handler.add_input_channel(_request_off_the_wire(DATA_CHANNEL)))
+        assert handler.context.input_manager.mock_calls == [
+            call.register_input(DATA_CHANNEL, PORT_ID)
+        ]
+
+    def test_returns_empty_return(self, handler):
+        result = asyncio.run(
+            handler.add_input_channel(_request_off_the_wire(DATA_CHANNEL))
+        )
+        assert result == EmptyReturn()
+
+    # --- is_control materialization ---------------------------------------
+
+    def test_a_data_channel_loses_its_is_control_marker_on_the_wire(self):
+        # Premise check: a betterproto upgrade that materializes defaults on
+        # parse reports itself here, not as a silently meaningless suite.
+        arrived = _request_off_the_wire(DATA_CHANNEL).channel_id
+        assert arrived == DATA_CHANNEL
+        assert hash(arrived) != hash(DATA_CHANNEL)
+
+    def test_canonicalizes_the_channel_id_before_registering_it(self, handler):
+        # Snapshot the hash inside register_input: the mock keeps only a
+        # reference, so a post-hoc read cannot tell canonicalize-before from
+        # -after -- and "after" strands the key (see the scan test below).
+        seen = []
+        handler.context.input_manager.register_input.side_effect = (
+            lambda channel_id, port_id: seen.append(hash(channel_id))
+        )
+        asyncio.run(handler.add_input_channel(_request_off_the_wire(DATA_CHANNEL)))
+        assert seen == [hash(DATA_CHANNEL)]
+
+    def test_the_registered_channel_is_interchangeable_as_a_dict_key(self, handler):
+        # Equal-but-differently-hashed ids miss in BOTH directions, so both
+        # lookups are asserted.
+        asyncio.run(handler.add_input_channel(_request_off_the_wire(DATA_CHANNEL)))
+        registered = handler.context.input_manager.register_input.call_args.args[0]
+        assert {registered: "channel"}.get(DATA_CHANNEL) == "channel"
+        assert {DATA_CHANNEL: "channel"}.get(registered) == "channel"
+
+    def test_a_real_input_manager_resolves_the_registered_channel(self, real_handler):
+        # main_loop resolves every incoming batch through this lookup; without
+        # the handler's materialization it raises KeyError on the first tuple.
+        asyncio.run(real_handler.add_input_channel(_request_off_the_wire(DATA_CHANNEL)))
+        assert real_handler.context.input_manager.get_port_id(DATA_CHANNEL) == PORT_ID
+
+    def test_the_registered_channel_survives_a_data_channel_scan(self, real_handler):
+        # get_all_data_channel_ids() reads is_control on every key: on a
+        # non-canonical key that read changes the hash in place and strands
+        # the dict entry. ECM alignment runs this scan on every marker.
+        request = _request_off_the_wire(DATA_CHANNEL)
+        asyncio.run(real_handler.add_input_channel(request))
+        manager = real_handler.context.input_manager
+
+        assert manager.get_all_data_channel_ids() == {DATA_CHANNEL}
+        assert manager.get_port_id(request.channel_id) == PORT_ID
+
+    # --- port identities --------------------------------------------------
+
+    def test_registers_a_default_port_channel_in_a_real_input_manager(self):
+        # Port 0, the production default, is the worst wire shape: proto3
+        # omits id=0 AND internal=False, so the port arrives as a bare
+        # PortIdentity() -- non-canonical in both fields, on top of the unset
+        # is_control -- and _ports is keyed by PortIdentity. It registers
+        # correctly only because register_input's `is None` guards READ the
+        # fields; the branches never fire (betterproto yields 0/False, never
+        # None). TestPortIdentityDefaults in test_input_manager.py covers the
+        # hand-built None shape, which no production caller builds --
+        # complementary, not duplicates.
+        handler = _build_real_handler(DEFAULT_PORT_ID)
+
+        # Canary on a throwaway request: probing must not canonicalize the
+        # instance the handler receives.
+        arrived = _request_off_the_wire(DATA_CHANNEL, DEFAULT_PORT_ID).port_id
+        assert arrived == DEFAULT_PORT_ID
+        assert hash(arrived) != hash(DEFAULT_PORT_ID)
+
+        asyncio.run(
+            handler.add_input_channel(
+                _request_off_the_wire(DATA_CHANNEL, DEFAULT_PORT_ID)
+            )
+        )
+
+        # One assertion suffices: a non-canonical port strands the
+        # registration inside register_input itself.
+        manager = handler.context.input_manager
+        assert manager.get_port_id(DATA_CHANNEL) == DEFAULT_PORT_ID
+
+    # --- control channels -------------------------------------------------
+
+    def test_a_control_channel_keeps_its_marker_across_the_wire(self):
+        # True is serialized (not the default), so a control channel arrives
+        # already canonical and the guard has nothing to do.
+        arrived = _request_off_the_wire(CONTROL_CHANNEL).channel_id
+        assert hash(arrived) == hash(CONTROL_CHANNEL)
+
+    def test_registers_a_control_channel_without_clearing_its_marker(self, handler):
+        # Guards the `if not` condition: always assigning False would silently
+        # demote every control channel to a data channel.
+        asyncio.run(handler.add_input_channel(_request_off_the_wire(CONTROL_CHANNEL)))
+        registered = handler.context.input_manager.register_input.call_args.args[0]
+        assert registered.is_control is True
+        assert hash(registered) == hash(CONTROL_CHANNEL)
+
+    def test_a_real_input_manager_keeps_a_control_channel_out_of_the_data_set(
+        self, real_handler
+    ):
+        asyncio.run(
+            real_handler.add_input_channel(_request_off_the_wire(CONTROL_CHANNEL))
+        )
+        manager = real_handler.context.input_manager
+        assert manager.get_all_data_channel_ids() == set()
+        assert manager.get_port_id(CONTROL_CHANNEL) == PORT_ID