test: enhance session source tests and add validation for chat types

- Renamed test method for clarity and added comprehensive tests for `SessionSource` including handling of numeric `chat_id`, missing optional fields, and invalid platforms.
- Introduced tests for session source descriptions based on chat types and names, ensuring accurate representation in prompts.
- Improved file tools tests by validating schema structures, ensuring no duplicate model IDs, and enhancing error handling in file operations.

tests/gateway/test_session.py

@@ -1,5 +1,6 @@
 """Tests for gateway session management."""
 
+import pytest
 from gateway.config import Platform, HomeChannel, GatewayConfig, PlatformConfig
 from gateway.session import (
     SessionSource,
@@ -9,7 +10,7 @@ from gateway.session import (
 
 
 class TestSessionSourceRoundtrip:
-    def test_to_dict_from_dict(self):
+    def test_full_roundtrip(self):
         source = SessionSource(
             platform=Platform.TELEGRAM,
             chat_id="12345",
@@ -36,22 +37,97 @@ class TestSessionSourceRoundtrip:
         restored = SessionSource.from_dict(d)
         assert restored.platform == Platform.LOCAL
         assert restored.chat_id == "cli"
+        assert restored.chat_type == "dm"  # default value preserved
+
+    def test_chat_id_coerced_to_string(self):
+        """from_dict should handle numeric chat_id (common from Telegram)."""
+        restored = SessionSource.from_dict({
+            "platform": "telegram",
+            "chat_id": 12345,
+        })
+        assert restored.chat_id == "12345"
+        assert isinstance(restored.chat_id, str)
+
+    def test_missing_optional_fields(self):
+        restored = SessionSource.from_dict({
+            "platform": "discord",
+            "chat_id": "abc",
+        })
+        assert restored.chat_name is None
+        assert restored.user_id is None
+        assert restored.user_name is None
+        assert restored.thread_id is None
+        assert restored.chat_type == "dm"
+
+    def test_invalid_platform_raises(self):
+        with pytest.raises((ValueError, KeyError)):
+            SessionSource.from_dict({"platform": "nonexistent", "chat_id": "1"})
 
 
-class TestLocalCliSource:
+class TestSessionSourceDescription:
     def test_local_cli(self):
+        source = SessionSource.local_cli()
+        assert source.description == "CLI terminal"
+
+    def test_dm_with_username(self):
+        source = SessionSource(
+            platform=Platform.TELEGRAM, chat_id="123",
+            chat_type="dm", user_name="bob",
+        )
+        assert "DM" in source.description
+        assert "bob" in source.description
+
+    def test_dm_without_username_falls_back_to_user_id(self):
+        source = SessionSource(
+            platform=Platform.TELEGRAM, chat_id="123",
+            chat_type="dm", user_id="456",
+        )
+        assert "456" in source.description
+
+    def test_group_shows_chat_name(self):
+        source = SessionSource(
+            platform=Platform.DISCORD, chat_id="789",
+            chat_type="group", chat_name="Dev Chat",
+        )
+        assert "group" in source.description
+        assert "Dev Chat" in source.description
+
+    def test_channel_type(self):
+        source = SessionSource(
+            platform=Platform.TELEGRAM, chat_id="100",
+            chat_type="channel", chat_name="Announcements",
+        )
+        assert "channel" in source.description
+        assert "Announcements" in source.description
+
+    def test_thread_id_appended(self):
+        source = SessionSource(
+            platform=Platform.DISCORD, chat_id="789",
+            chat_type="group", chat_name="General",
+            thread_id="thread-42",
+        )
+        assert "thread" in source.description
+        assert "thread-42" in source.description
+
+    def test_unknown_chat_type_uses_name(self):
+        source = SessionSource(
+            platform=Platform.SLACK, chat_id="C01",
+            chat_type="forum", chat_name="Questions",
+        )
+        assert "Questions" in source.description
+
+
+class TestLocalCliFactory:
+    def test_local_cli_defaults(self):
         source = SessionSource.local_cli()
         assert source.platform == Platform.LOCAL
         assert source.chat_id == "cli"
         assert source.chat_type == "dm"
-
-    def test_description_local(self):
-        source = SessionSource.local_cli()
-        assert source.description == "CLI terminal"
+        assert source.chat_name == "CLI terminal"
 
 
 class TestBuildSessionContextPrompt:
-    def test_contains_platform_info(self):
+    def test_telegram_prompt_contains_platform_and_chat(self):
         config = GatewayConfig(
             platforms={
                 Platform.TELEGRAM: PlatformConfig(
@@ -76,9 +152,29 @@ class TestBuildSessionContextPrompt:
 
         assert "Telegram" in prompt
         assert "Home Chat" in prompt
-        assert "Session Context" in prompt
 
-    def test_local_source_prompt(self):
+    def test_discord_prompt(self):
+        config = GatewayConfig(
+            platforms={
+                Platform.DISCORD: PlatformConfig(
+                    enabled=True,
+                    token="fake-discord-token",
+                ),
+            },
+        )
+        source = SessionSource(
+            platform=Platform.DISCORD,
+            chat_id="guild-123",
+            chat_name="Server",
+            chat_type="group",
+            user_name="alice",
+        )
+        ctx = build_session_context(source, config)
+        prompt = build_session_context_prompt(ctx)
+
+        assert "Discord" in prompt
+
+    def test_local_prompt_mentions_machine(self):
         config = GatewayConfig()
         source = SessionSource.local_cli()
         ctx = build_session_context(source, config)
@@ -86,3 +182,20 @@ class TestBuildSessionContextPrompt:
 
         assert "Local" in prompt
         assert "machine running this agent" in prompt
+
+    def test_whatsapp_prompt(self):
+        config = GatewayConfig(
+            platforms={
+                Platform.WHATSAPP: PlatformConfig(enabled=True, token=""),
+            },
+        )
+        source = SessionSource(
+            platform=Platform.WHATSAPP,
+            chat_id="15551234567@s.whatsapp.net",
+            chat_type="dm",
+            user_name="Phone User",
+        )
+        ctx = build_session_context(source, config)
+        prompt = build_session_context_prompt(ctx)
+
+        assert "WhatsApp" in prompt or "whatsapp" in prompt.lower()