chore(python): Bump the oldest supported Python version to 3.11 (#561)

* Set Python 3.11 as the minimum version

* Run pyupgrade

* More modernization

* Address review comments

* Update python/copilot/generated` via codegen instead of by pyupgrade

* Update Python version matrix to only include 3.11 for compatibility testing

* Regenerate codegen files

Update generated files for Python and Go SDKs to include new agent API
types, compaction result types, and new session event types
(assistant.streaming_delta, session.task_complete).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Fix formatting

* fix: gofmt Go generated files and fix Python test for fork PRs

- Run gofmt on go/rpc/generated_rpc.go and go/generated_session_events.go
  to fix spaces→tabs formatting that caused the Codegen Check to fail.
- Fix test_resume_session_forwards_client_name to return a mock response
  for session.resume instead of forwarding to the real CLI, which requires
  the COPILOT_HMAC_KEY secret unavailable to fork PRs.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Patrick Nikoletich <patniko@github.com>

Author: 3 people

.github/workflows/python-sdk-tests.yml

@@ -37,6 +37,8 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
+        # Test the oldest supported Python version to make sure compatibility is maintained.
+        python-version: ["3.11"]
     runs-on: ${{ matrix.os }}
     defaults:
       run:
@@ -46,7 +48,7 @@ jobs:
       - uses: actions/checkout@v6.0.2
       - uses: actions/setup-python@v6
         with:
-          python-version: "3.12"
+          python-version: ${{ matrix.python-version }}
       - uses: actions/setup-node@v6
         with:
           node-version: "22"

python/README.md

@@ -401,11 +401,11 @@ async def handle_user_input(request, invocation):
     # request["question"] - The question to ask
     # request.get("choices") - Optional list of choices for multiple choice
     # request.get("allowFreeform", True) - Whether freeform input is allowed
-    
+
     print(f"Agent asks: {request['question']}")
     if request.get("choices"):
         print(f"Choices: {', '.join(request['choices'])}")
-    
+
     # Return the user's response
     return {
         "answer": "User's answer here",
@@ -483,5 +483,5 @@ session = await client.create_session({
 
 ## Requirements
 
-- Python 3.9+
+- Python 3.11+
 - GitHub Copilot CLI installed and accessible

python/copilot/client.py

@@ -19,9 +19,10 @@
 import subprocess
 import sys
 import threading
+from collections.abc import Callable
 from dataclasses import asdict, is_dataclass
 from pathlib import Path
-from typing import Any, Callable, Optional, cast
+from typing import Any, cast
 
 from .generated.rpc import ServerRpc
 from .generated.session_events import session_event_from_dict
@@ -51,7 +52,7 @@
 )
 
 
-def _get_bundled_cli_path() -> Optional[str]:
+def _get_bundled_cli_path() -> str | None:
     """Get the path to the bundled CLI binary, if available."""
     # The binary is bundled in copilot/bin/ within the package
     bin_dir = Path(__file__).parent / "bin"
@@ -106,7 +107,7 @@ class CopilotClient:
         >>> client = CopilotClient({"cli_url": "localhost:3000"})
     """
 
-    def __init__(self, options: Optional[CopilotClientOptions] = None):
+    def __init__(self, options: CopilotClientOptions | None = None):
         """
         Initialize a new CopilotClient.
 
@@ -151,7 +152,7 @@ def __init__(self, options: Optional[CopilotClientOptions] = None):
         self._is_external_server: bool = False
         if opts.get("cli_url"):
             self._actual_host, actual_port = self._parse_cli_url(opts["cli_url"])
-            self._actual_port: Optional[int] = actual_port
+            self._actual_port: int | None = actual_port
             self._is_external_server = True
         else:
             self._actual_port = None
@@ -197,19 +198,19 @@ def __init__(self, options: Optional[CopilotClientOptions] = None):
         if github_token:
             self.options["github_token"] = github_token
 
-        self._process: Optional[subprocess.Popen] = None
-        self._client: Optional[JsonRpcClient] = None
+        self._process: subprocess.Popen | None = None
+        self._client: JsonRpcClient | None = None
         self._state: ConnectionState = "disconnected"
         self._sessions: dict[str, CopilotSession] = {}
         self._sessions_lock = threading.Lock()
-        self._models_cache: Optional[list[ModelInfo]] = None
+        self._models_cache: list[ModelInfo] | None = None
         self._models_cache_lock = asyncio.Lock()
         self._lifecycle_handlers: list[SessionLifecycleHandler] = []
         self._typed_lifecycle_handlers: dict[
             SessionLifecycleEventType, list[SessionLifecycleHandler]
         ] = {}
         self._lifecycle_handlers_lock = threading.Lock()
-        self._rpc: Optional[ServerRpc] = None
+        self._rpc: ServerRpc | None = None
 
     @property
     def rpc(self) -> ServerRpc:
@@ -786,7 +787,7 @@ def get_state(self) -> ConnectionState:
         """
         return self._state
 
-    async def ping(self, message: Optional[str] = None) -> "PingResponse":
+    async def ping(self, message: str | None = None) -> "PingResponse":
         """
         Send a ping request to the server to verify connectivity.
 
@@ -956,7 +957,7 @@ async def delete_session(self, session_id: str) -> None:
             if session_id in self._sessions:
                 del self._sessions[session_id]
 
-    async def get_foreground_session_id(self) -> Optional[str]:
+    async def get_foreground_session_id(self) -> str | None:
         """
         Get the ID of the session currently displayed in the TUI.
 
@@ -1009,7 +1010,7 @@ async def set_foreground_session_id(self, session_id: str) -> None:
     def on(
         self,
         event_type_or_handler: SessionLifecycleEventType | SessionLifecycleHandler,
-        handler: Optional[SessionLifecycleHandler] = None,
+        handler: SessionLifecycleHandler | None = None,
     ) -> Callable[[], None]:
         """
         Subscribe to session lifecycle events.
@@ -1267,7 +1268,7 @@ async def read_port():
 
         try:
             await asyncio.wait_for(read_port(), timeout=10.0)
-        except asyncio.TimeoutError:
+        except TimeoutError:
             raise RuntimeError("Timeout waiting for CLI server to start")
 
     async def _connect_to_server(self) -> None:

python/copilot/generated/rpc.py

@@ -10,7 +10,8 @@
 
 
 from dataclasses import dataclass
-from typing import Any, Optional, List, Dict, TypeVar, Type, cast, Callable
+from typing import Any, TypeVar, cast
+from collections.abc import Callable
 from enum import Enum
 
 
@@ -52,22 +53,22 @@ def from_bool(x: Any) -> bool:
     return x
 
 
-def to_class(c: Type[T], x: Any) -> dict:
+def to_class(c: type[T], x: Any) -> dict:
     assert isinstance(x, c)
     return cast(Any, x).to_dict()
 
 
-def from_list(f: Callable[[Any], T], x: Any) -> List[T]:
+def from_list(f: Callable[[Any], T], x: Any) -> list[T]:
     assert isinstance(x, list)
     return [f(y) for y in x]
 
 
-def from_dict(f: Callable[[Any], T], x: Any) -> Dict[str, T]:
+def from_dict(f: Callable[[Any], T], x: Any) -> dict[str, T]:
     assert isinstance(x, dict)
     return { k: f(v) for (k, v) in x.items() }
 
 
-def to_enum(c: Type[EnumT], x: Any) -> EnumT:
+def to_enum(c: type[EnumT], x: Any) -> EnumT:
     assert isinstance(x, c)
     return x.value
 
@@ -101,7 +102,7 @@ def to_dict(self) -> dict:
 
 @dataclass
 class PingParams:
-    message: Optional[str] = None
+    message: str | None = None
     """Optional message to echo back"""
 
     @staticmethod
@@ -138,8 +139,8 @@ def to_dict(self) -> dict:
 @dataclass
 class Limits:
     max_context_window_tokens: float
-    max_output_tokens: Optional[float] = None
-    max_prompt_tokens: Optional[float] = None
+    max_output_tokens: float | None = None
+    max_prompt_tokens: float | None = None
 
     @staticmethod
     def from_dict(obj: Any) -> 'Limits':
@@ -233,16 +234,16 @@ class Model:
     name: str
     """Display name"""
 
-    billing: Optional[Billing] = None
+    billing: Billing | None = None
     """Billing information"""
 
-    default_reasoning_effort: Optional[str] = None
+    default_reasoning_effort: str | None = None
     """Default reasoning effort level (only present if model supports reasoning effort)"""
 
-    policy: Optional[Policy] = None
+    policy: Policy | None = None
     """Policy state (if applicable)"""
 
-    supported_reasoning_efforts: Optional[List[str]] = None
+    supported_reasoning_efforts: list[str] | None = None
     """Supported reasoning effort levels (only present if model supports reasoning effort)"""
 
     @staticmethod
@@ -275,7 +276,7 @@ def to_dict(self) -> dict:
 
 @dataclass
 class ModelsListResult:
-    models: List[Model]
+    models: list[Model]
     """List of available models with full metadata"""
 
     @staticmethod
@@ -298,14 +299,14 @@ class Tool:
     name: str
     """Tool identifier (e.g., "bash", "grep", "str_replace_editor")"""
 
-    instructions: Optional[str] = None
+    instructions: str | None = None
     """Optional instructions for how to use this tool effectively"""
 
-    namespaced_name: Optional[str] = None
+    namespaced_name: str | None = None
     """Optional namespaced name for declarative filtering (e.g., "playwright/navigate" for MCP
     tools)
     """
-    parameters: Optional[Dict[str, Any]] = None
+    parameters: dict[str, Any] | None = None
     """JSON Schema for the tool's input parameters"""
 
     @staticmethod
@@ -333,7 +334,7 @@ def to_dict(self) -> dict:
 
 @dataclass
 class ToolsListResult:
-    tools: List[Tool]
+    tools: list[Tool]
     """List of available built-in tools with metadata"""
 
     @staticmethod
@@ -350,7 +351,7 @@ def to_dict(self) -> dict:
 
 @dataclass
 class ToolsListParams:
-    model: Optional[str] = None
+    model: str | None = None
     """Optional model ID — when provided, the returned tool list reflects model-specific
     overrides
     """
@@ -385,7 +386,7 @@ class QuotaSnapshot:
     used_requests: float
     """Number of requests used so far this period"""
 
-    reset_date: Optional[str] = None
+    reset_date: str | None = None
     """Date when the quota resets (ISO 8601)"""
 
     @staticmethod
@@ -413,7 +414,7 @@ def to_dict(self) -> dict:
 
 @dataclass
 class AccountGetQuotaResult:
-    quota_snapshots: Dict[str, QuotaSnapshot]
+    quota_snapshots: dict[str, QuotaSnapshot]
     """Quota snapshots keyed by type (e.g., chat, completions, premium_interactions)"""
 
     @staticmethod
@@ -430,7 +431,7 @@ def to_dict(self) -> dict:
 
 @dataclass
 class SessionModelGetCurrentResult:
-    model_id: Optional[str] = None
+    model_id: str | None = None
 
     @staticmethod
     def from_dict(obj: Any) -> 'SessionModelGetCurrentResult':
@@ -447,7 +448,7 @@ def to_dict(self) -> dict:
 
 @dataclass
 class SessionModelSwitchToResult:
-    model_id: Optional[str] = None
+    model_id: str | None = None
 
     @staticmethod
     def from_dict(obj: Any) -> 'SessionModelSwitchToResult':
@@ -546,7 +547,7 @@ class SessionPlanReadResult:
     exists: bool
     """Whether plan.md exists in the workspace"""
 
-    content: Optional[str] = None
+    content: str | None = None
     """The content of plan.md, or null if it does not exist"""
 
     @staticmethod
@@ -606,7 +607,7 @@ def to_dict(self) -> dict:
 
 @dataclass
 class SessionWorkspaceListFilesResult:
-    files: List[str]
+    files: list[str]
     """Relative file paths in the workspace files directory"""
 
     @staticmethod
@@ -708,7 +709,7 @@ def to_dict(self) -> dict:
 
 @dataclass
 class SessionFleetStartParams:
-    prompt: Optional[str] = None
+    prompt: str | None = None
     """Optional user prompt to combine with fleet instructions"""
 
     @staticmethod
@@ -753,7 +754,7 @@ def to_dict(self) -> dict:
 
 @dataclass
 class SessionAgentListResult:
-    agents: List[AgentElement]
+    agents: list[AgentElement]
     """Available custom agents"""
 
     @staticmethod
@@ -797,7 +798,7 @@ def to_dict(self) -> dict:
 
 @dataclass
 class SessionAgentGetCurrentResult:
-    agent: Optional[SessionAgentGetCurrentResultAgent] = None
+    agent: SessionAgentGetCurrentResultAgent | None = None
     """Currently selected custom agent, or null if using the default agent"""
 
     @staticmethod