feat(chat): add chat.get_user() for cross-platform user lookups (#90)

Ports vercel/chat#391 — adds chat.get_user(adapter, user_id) and per-adapter get_user implementations across all 8 platforms.

- Chat.get_user(adapter: str | Adapter, user_id: str) -> User | None resolves string adapter names through registered adapters
- Adapter Protocol gains async def get_user(user_id: str) -> User | None
- User extended with optional email, display_name, avatar_url
- Per-adapter implementations: Slack users.info, Discord GET /users/{id}, Google Chat users.get, GitHub GET /users/{login}, Linear GraphQL user(id:), Teams Graph /users/{aadObjectId} (uses #85's AAD cache), Telegram getChat (best-effort), WhatsApp (Cloud API has no separate lookup)
- Slack get_user awaits _resolve_token_async() so it works under callable bot_token resolvers (#87) when called from background contexts (cron, etc.)
- Lazy imports of platform SDKs inside each method (hazard #10)
- Resolved merge conflicts with #85/#86/#87/#88/#89 — all surface areas coexist

26 new tests in test_get_user_adapters.py + 3 in test_chat_faithful.py.

Author: patrick-chinchill

docs/UPSTREAM_SYNC.md

@@ -515,6 +515,8 @@ stay explicit instead of being rediscovered in code review.
 | Google Chat file uploads | Ignored in message parse | Supported | API complexity; can add later |
 | Discord Gateway WebSocket | HTTP interactions only | Both HTTP and Gateway | Gateway requires persistent connection |
 | Teams `User-Agent: Vercel.ChatSDK` outbound header | Not set on `aiohttp` calls | Propagated by `botbuilder` 2.0.8 | Python Teams adapter doesn't use `botbuilder` (raw `aiohttp`). Upstream's vercel/chat#415 was a JS-only `botbuilder` SDK bump that flipped `X-User-Agent` → `User-Agent`. No equivalent dependency to bump on the Python side. Setting a `User-Agent` on the ~9 outbound `aiohttp` call sites would be a defense-in-depth nice-to-have; deferred to a follow-up. |
+| Telegram `get_user().is_bot` | Always `False` (matches upstream — `getChat` does not expose `is_bot`) | Always `false` (same caveat documented in upstream code comment) | The Telegram Bot API's `getChat` endpoint does not surface the `is_bot` field that's available on the `User` object inside incoming `Message` updates. Callers needing bot detection must use `message.author.is_bot` from webhooks instead of `chat.get_user(...).is_bot`. |
+| WhatsApp `get_user` | Raises `ChatNotImplementedError` (`Chat.get_user` translates to "does not support get_user") | Not implemented upstream either (no `getUser` on the WhatsApp adapter) | WhatsApp Cloud API has no user lookup endpoint — phone numbers are the only stable identifier and there's no equivalent of `users.info` exposed to business apps. Documented explicitly so callers don't expect parity with Slack/Teams/Discord. |
 
 ### Serialization differences
 

src/chat_sdk/__init__.py

@@ -185,6 +185,7 @@
     Thread,
     ThreadInfo,
     ThreadSummary,
+    UserInfo,
     WebhookOptions,
     WellKnownEmoji,
 )
@@ -395,6 +396,7 @@
     "Thread",
     "ThreadInfo",
     "ThreadSummary",
+    "UserInfo",
     "WebhookOptions",
     "WellKnownEmoji",
 ]

src/chat_sdk/adapters/discord/adapter.py

@@ -61,6 +61,7 @@
     SlashCommandEvent,
     StreamOptions,
     ThreadInfo,
+    UserInfo,
     WebhookOptions,
     _parse_iso,
 )
@@ -174,6 +175,39 @@ async def initialize(self, chat: ChatInstance) -> None:
         self._chat = chat
         self._logger.info("Discord adapter initialized")
 
+    async def get_user(self, user_id: str) -> UserInfo | None:
+        """Look up a Discord user via ``GET /users/{user_id}``.
+
+        Returns ``None`` on any failure (network error, 4xx/5xx, missing
+        bot scope). Discord user IDs are 17-19 digit snowflakes — we
+        validate the shape here both as a lightweight typo guard and to
+        prevent path-segment injection (``/`` would escape the URL).
+
+        Mirrors upstream ``DiscordAdapter.getUser`` (vercel/chat#391).
+        """
+        # Hazard #12: never let user input reach a URL path unvalidated.
+        # Snowflakes are pure digits — anything else is rejected before
+        # the network call so a crafted "../foo" can't pivot the request.
+        if not user_id or not user_id.isdigit():
+            return None
+        try:
+            user = await self._discord_fetch(f"/users/{quote(user_id, safe='')}", "GET")
+        except Exception:
+            return None
+        if not isinstance(user, dict):
+            return None
+        avatar = user.get("avatar")
+        avatar_url = f"https://cdn.discordapp.com/avatars/{user.get('id')}/{avatar}.png" if avatar else None
+        username = user.get("username") or user_id
+        return UserInfo(
+            user_id=str(user.get("id") or user_id),
+            user_name=username,
+            full_name=user.get("global_name") or username,
+            is_bot=bool(user.get("bot", False)),
+            avatar_url=avatar_url,
+            email=None,
+        )
+
     async def handle_webhook(
         self,
         request: Any,

src/chat_sdk/adapters/github/adapter.py

@@ -59,6 +59,7 @@
     StreamOptions,
     ThreadInfo,
     ThreadSummary,
+    UserInfo,
     WebhookOptions,
     _parse_iso,
 )
@@ -214,6 +215,40 @@ async def initialize(self, chat: ChatInstance) -> None:
             except Exception as error:
                 self._logger.warn("Could not fetch bot user ID", {"error": str(error)})
 
+    async def get_user(self, user_id: str) -> UserInfo | None:
+        """Look up a GitHub user by numeric account ID.
+
+        Uses the ``GET /user/{account_id}`` endpoint, mirroring the
+        upstream Octokit ``GET /user/{account_id}`` call.
+
+        ``user_id`` must be a numeric string — GitHub account IDs are
+        integers, so we reject anything else before issuing a request
+        (defense against URL injection and a guard for callers that pass
+        a login name by mistake).
+
+        Returns ``None`` when the user is not found, the API returns an
+        error, or authentication is unavailable. Mirrors upstream
+        ``GitHubAdapter.getUser`` (vercel/chat#391).
+        """
+        if not user_id or not user_id.isdigit():
+            return None
+        try:
+            user = await self._github_api_request("GET", f"/user/{user_id}")
+        except Exception as error:
+            self._logger.debug("Failed to fetch user", {"userId": user_id, "error": str(error)})
+            return None
+        if not isinstance(user, dict):
+            return None
+        login = user.get("login") or user_id
+        return UserInfo(
+            user_id=str(user.get("id") if user.get("id") is not None else user_id),
+            user_name=login,
+            full_name=user.get("name") or login,
+            is_bot=user.get("type") == "Bot",
+            avatar_url=user.get("avatar_url"),
+            email=user.get("email"),
+        )
+
     async def _get_http_session(self) -> Any:
         """Return the shared aiohttp session, creating it lazily if needed."""
         import aiohttp

src/chat_sdk/adapters/google_chat/adapter.py

@@ -81,6 +81,7 @@
     StreamOptions,
     ThreadInfo,
     ThreadSummary,
+    UserInfo,
     WebhookOptions,
     _parse_iso,
 )
@@ -728,6 +729,36 @@ async def _verify_bearer_token(
             self._logger.warn("JWT verification failed", {"error": error})
             return False
 
+    # =========================================================================
+    # Public user lookup (chat.get_user)
+    # =========================================================================
+
+    async def get_user(self, user_id: str) -> UserInfo | None:
+        """Look up a Google Chat user from the cached webhook sender info.
+
+        Google Chat does not expose a direct ``users.get`` API for chat
+        bots — display names, avatars, and emails are only available on
+        inbound message ``sender`` payloads. We surface what we've cached
+        from previous webhooks; callers see ``None`` until the user has
+        interacted with the bot at least once.
+
+        Mirrors upstream ``GoogleChatAdapter.getUser`` (vercel/chat#391).
+        """
+        try:
+            cached = await self._user_info_cache.get(user_id)
+        except Exception:
+            return None
+        if not cached:
+            return None
+        return UserInfo(
+            user_id=user_id,
+            user_name=cached.display_name,
+            full_name=cached.display_name,
+            is_bot=bool(cached.is_bot) if cached.is_bot is not None else False,
+            email=cached.email,
+            avatar_url=cached.avatar_url,
+        )
+
     # =========================================================================
     # Webhook handling
     # =========================================================================
@@ -1302,12 +1333,15 @@ def _parse_google_chat_message(
 
             try:
                 loop = asyncio.get_running_loop()
+                sender = message.get("sender") or {}
                 _pin_task(
                     loop.create_task(
                         self._user_info_cache.set(
                             user_id,
                             display_name,
-                            (message.get("sender") or {}).get("email"),
+                            sender.get("email"),
+                            sender.get("type") == "BOT",
+                            sender.get("avatarUrl"),
                         )
                     )
                 )

src/chat_sdk/adapters/google_chat/user_info.py

@@ -26,6 +26,8 @@ class CachedUserInfo:
 
     display_name: str
     email: str | None = None
+    is_bot: bool | None = None
+    avatar_url: str | None = None
 
 
 class UserInfoCache:
@@ -50,12 +52,19 @@ async def set(
         user_id: str,
         display_name: str,
         email: str | None = None,
+        is_bot: bool | None = None,
+        avatar_url: str | None = None,
     ) -> None:
         """Cache user info for later lookup."""
         if not display_name or display_name == "unknown":
             return
 
-        user_info = CachedUserInfo(display_name=display_name, email=email)
+        user_info = CachedUserInfo(
+            display_name=display_name,
+            email=email,
+            is_bot=is_bot,
+            avatar_url=avatar_url,
+        )
 
         # Always update in-memory cache
         self._in_memory_cache[user_id] = user_info
@@ -73,7 +82,12 @@ async def set(
             cache_key = f"{USER_INFO_KEY_PREFIX}{user_id}"
             await self._state.set(
                 cache_key,
-                {"display_name": display_name, "email": email},
+                {
+                    "display_name": display_name,
+                    "email": email,
+                    "is_bot": is_bot,
+                    "avatar_url": avatar_url,
+                },
                 USER_INFO_CACHE_TTL_MS,
             )
 
@@ -96,12 +110,20 @@ async def get(self, user_id: str) -> CachedUserInfo | None:
 
         # Populate in-memory cache if found in state
         if from_state:
-            info = CachedUserInfo(
-                display_name=from_state.get("display_name", "unknown")
-                if isinstance(from_state, dict)
-                else getattr(from_state, "display_name", "unknown"),
-                email=from_state.get("email") if isinstance(from_state, dict) else getattr(from_state, "email", None),
-            )
+            if isinstance(from_state, dict):
+                info = CachedUserInfo(
+                    display_name=from_state.get("display_name", "unknown"),
+                    email=from_state.get("email"),
+                    is_bot=from_state.get("is_bot"),
+                    avatar_url=from_state.get("avatar_url"),
+                )
+            else:
+                info = CachedUserInfo(
+                    display_name=getattr(from_state, "display_name", "unknown"),
+                    email=getattr(from_state, "email", None),
+                    is_bot=getattr(from_state, "is_bot", None),
+                    avatar_url=getattr(from_state, "avatar_url", None),
+                )
             self._in_memory_cache[user_id] = info
             return info
 

src/chat_sdk/adapters/linear/adapter.py

@@ -55,6 +55,7 @@
     RawMessage,
     StreamOptions,
     ThreadInfo,
+    UserInfo,
     WebhookOptions,
     _parse_iso,
 )
@@ -258,6 +259,43 @@ async def _ensure_valid_token(self) -> None:
                 self._logger.info("Linear access token expired, refreshing...")
                 await self._refresh_client_credentials_token()
 
+    async def get_user(self, user_id: str) -> UserInfo | None:
+        """Look up a Linear user by UUID via the GraphQL ``user`` query.
+
+        Returns ``None`` on any failure (auth missing, user not found,
+        network error). Mirrors upstream ``LinearAdapter.getUser``
+        (vercel/chat#391), which uses the official Linear SDK; we issue
+        the equivalent GraphQL query directly so we don't take a runtime
+        dependency on the JS SDK.
+        """
+        try:
+            await self._ensure_valid_token()
+            data = await self._graphql_query(
+                "query GetUser($id: String!) {  user(id: $id) {    id displayName name email avatarUrl  }}",
+                {"id": user_id},
+            )
+        except Exception:
+            return None
+        user = (data.get("data") or {}).get("user") if isinstance(data, dict) else None
+        if not user or not isinstance(user, dict):
+            return None
+        # Match upstream literally (vercel/chat#391):
+        #   userName: user.displayName, fullName: user.name
+        # Fall back to `user_id` when either field is missing — matches
+        # the convention used by every other adapter's `get_user`
+        # (slack/discord/github/teams/telegram) and satisfies the
+        # non-Optional `str` typing of ``UserInfo.user_name`` /
+        # ``UserInfo.full_name`` that JS's ``undefined`` would otherwise
+        # violate.
+        return UserInfo(
+            user_id=user.get("id") or user_id,
+            user_name=user.get("displayName") or user_id,
+            full_name=user.get("name") or user_id,
+            is_bot=False,
+            avatar_url=user.get("avatarUrl"),
+            email=user.get("email"),
+        )
+
     async def handle_webhook(
         self,
         request: Any,