diff --git a/MIGRATION_A365.md b/MIGRATION_A365.md
index 9576283c..cb5dbc11 100644
--- a/MIGRATION_A365.md
+++ b/MIGRATION_A365.md
@@ -38,6 +38,12 @@ pip uninstall -y microsoft-agents-a365-observability-extensions-agent-framework
 pip install microsoft-opentelemetry
 ```
 
+> If you use the hosting middleware (`BaggageMiddleware`,
+> `ObservabilityHostingManager`, etc.), also install
+> `microsoft-agents-activity` and `microsoft-agents-hosting-core`. If
+> they are not installed, importing from
+> `microsoft.opentelemetry.a365.hosting` raises an `ImportError`.
+
 ## Step 2 — Rewrite Import Paths
 
 The old packages used `microsoft_agents_a365.*` namespace.
diff --git a/dev_requirements.txt b/dev_requirements.txt
index 37e0ebe1..09a15ff8 100644
--- a/dev_requirements.txt
+++ b/dev_requirements.txt
@@ -2,3 +2,5 @@ pytest>=8.0
 pytest-asyncio>=0.23.0
 pytest-cov>=5.0
 black>=24.0
+microsoft-agents-activity
+microsoft-agents-hosting-core
diff --git a/pyproject.toml b/pyproject.toml
index 77dcf390..1da9331e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -41,8 +41,6 @@ dependencies = [
     "opentelemetry-resource-detector-azure<1.0.0,>=0.1.5",
     "wrapt>=1.0",
     "opentelemetry-util-genai>=0.3b0",
-    "microsoft-agents-activity>=0.9.0",
-    "microsoft-agents-hosting-core>=0.9.0",
     "aiohttp>=3.8.0",
     "PyJWT",
     "requests"