diff --git a/hermes_cli/tools_config.py b/hermes_cli/tools_config.py
index 404796322..eba4e4c0b 100644
--- a/hermes_cli/tools_config.py
+++ b/hermes_cli/tools_config.py
@@ -1471,7 +1471,11 @@ def _get_platform_tools(
             for ts_key, _, _ in CONFIGURABLE_TOOLSETS:
                 if not _toolset_allowed_for_platform(ts_key, platform):
                     continue
-                ts_tools = set(resolve_toolset(ts_key))
+                # Compare the toolset's STATIC membership: a tool registered
+                # into a toolset (e.g. delegate_cli -> delegation, desktop-only
+                # read_terminal -> terminal) that the composite never listed must
+                # not drop the whole toolset. See issue #49622.
+                ts_tools = set(resolve_toolset(ts_key, include_registry=False))
                 if ts_tools and ts_tools.issubset(composite_tools):
                     expanded.add(ts_key)
 
@@ -1494,7 +1498,12 @@ def _get_platform_tools(
         for ts_key, _, _ in CONFIGURABLE_TOOLSETS:
             if not _toolset_allowed_for_platform(ts_key, platform):
                 continue
-            ts_tools = set(resolve_toolset(ts_key))
+            # Compare the toolset's STATIC membership against the composite (see
+            # issue #49622): get_toolset() merges registry-registered tools into
+            # a toolset, but platform composites enumerate static tool names, so
+            # an all-tools subset test against the merged set drops the whole
+            # toolset the moment a plugin/overlay/desktop tool joins it.
+            ts_tools = set(resolve_toolset(ts_key, include_registry=False))
             if ts_tools and ts_tools.issubset(all_tool_names):
                 enabled_toolsets.add(ts_key)
 
@@ -1566,7 +1575,10 @@ def _get_platform_tools(
         # by agent/coding_context.py — not per-platform capabilities to recover.
         if ts_def.get("posture"):
             continue
-        ts_tools = set(resolve_toolset(ts_key))
+        # Static membership (see #49622): a registry-added tool absent from the
+        # platform composite must not block recovery of a non-configurable
+        # toolset whose authored tools the composite does list.
+        ts_tools = set(resolve_toolset(ts_key, include_registry=False))
         if not ts_tools or not ts_tools.issubset(platform_tool_universe):
             continue
         if ts_tools.issubset(configurable_tool_universe):
diff --git a/tests/gateway/test_api_server_toolset.py b/tests/gateway/test_api_server_toolset.py
index add2ce273..5940ee8c2 100644
--- a/tests/gateway/test_api_server_toolset.py
+++ b/tests/gateway/test_api_server_toolset.py
@@ -63,6 +63,58 @@ class TestApiServerPlatformConfig:
         assert "api_server" in PLATFORMS
         assert PLATFORMS["api_server"]["default_toolset"] == "hermes-api-server"
 
+    def test_default_api_server_includes_terminal_toolset(self):
+        """Regression #49622: desktop-only read_terminal is registered into the
+        'terminal' toolset (ships in-repo), so resolve_toolset('terminal') grows
+        to include it after discovery. read_terminal is NOT in the
+        hermes-api-server composite, so the old all-tools subset test dropped
+        'terminal' entirely. Its static membership (terminal, process) IS in the
+        composite, so it must stay enabled."""
+        from tools.registry import discover_builtin_tools
+        from hermes_cli.tools_config import _get_platform_tools
+        discover_builtin_tools()
+        assert "terminal" in _get_platform_tools({}, "api_server")
+
+    def test_registering_tool_into_toolset_does_not_drop_toolset_from_inference(self):
+        """Class invariant (covers the delegate_cli overlay case): registering a
+        NEW tool into an existing configurable toolset must never remove that
+        toolset from a platform whose composite lists the toolset's static
+        tools. Synthetic registration keeps the test hermetic in CI."""
+        from tools.registry import registry
+        from hermes_cli.tools_config import _get_platform_tools
+
+        sentinel = "test_sentinel_delegation_tool"
+        registry.register(
+            name=sentinel,
+            toolset="delegation",
+            schema={"name": sentinel, "description": "test",
+                    "parameters": {"type": "object", "properties": {}}},
+            handler=lambda args, **kw: "{}",
+        )
+        try:
+            # delegation's static membership (delegate_task) is in the composite,
+            # so the toolset must survive inference despite the extra registry tool.
+            assert "delegation" in _get_platform_tools({}, "api_server"), (
+                "registering a tool into 'delegation' dropped it from api_server"
+            )
+        finally:
+            registry.deregister(sentinel)
+
+    def test_default_off_and_restricted_toolsets_stay_off_on_api_server(self):
+        """Negative contract: the static-membership comparison must NOT newly
+        enable default-off or platform-restricted toolsets."""
+        import os
+        from unittest.mock import patch
+        from hermes_cli.tools_config import _get_platform_tools
+        with patch.dict(os.environ, {}, clear=False):
+            os.environ.pop("HASS_TOKEN", None)
+            os.environ.pop("XAI_API_KEY", None)
+            enabled = _get_platform_tools({}, "api_server")
+        assert "homeassistant" not in enabled
+        assert "discord" not in enabled
+        assert "discord_admin" not in enabled
+        assert "x_search" not in enabled
+
 
 class TestApiServerAdapterToolset:
     @patch("gateway.platforms.api_server.AIOHTTP_AVAILABLE", True)