From 2039dcb545d971af04e537b8805f60d42f64a591 Mon Sep 17 00:00:00 2001
From: Brett Cannon <brett@python.org>
Date: Thu, 12 Mar 2026 15:45:47 -0700
Subject: [PATCH 1/3] Update the signatures of `CopilotSession.send()` and
 `send_and_wait()`

---
 python/README.md                              | 22 +++----
 python/copilot/__init__.py                    |  2 -
 python/copilot/client.py                      |  4 +-
 python/copilot/session.py                     | 58 +++++++++++--------
 python/copilot/types.py                       | 11 ----
 python/e2e/test_agent_and_compact_rpc.py      |  2 +-
 python/e2e/test_ask_user.py                   | 24 ++------
 python/e2e/test_compaction.py                 | 12 ++--
 python/e2e/test_hooks.py                      | 12 ++--
 python/e2e/test_mcp_and_agents.py             | 20 +++----
 python/e2e/test_multi_client.py               | 40 ++++---------
 python/e2e/test_permissions.py                | 28 ++++-----
 python/e2e/test_session.py                    | 49 ++++++----------
 python/e2e/test_skills.py                     |  8 +--
 python/e2e/test_streaming_fidelity.py         | 10 ++--
 python/e2e/test_tools.py                      | 20 +++----
 python/samples/chat.py                        |  2 +-
 .../auth/byok-anthropic/python/main.py        |  2 +-
 test/scenarios/auth/byok-azure/python/main.py |  2 +-
 .../scenarios/auth/byok-ollama/python/main.py |  2 +-
 .../scenarios/auth/byok-openai/python/main.py |  2 +-
 test/scenarios/auth/gh-app/python/main.py     |  2 +-
 .../app-backend-to-server/python/main.py      |  2 +-
 .../bundling/app-direct-server/python/main.py |  2 +-
 .../bundling/container-proxy/python/main.py   |  2 +-
 .../bundling/fully-bundled/python/main.py     |  2 +-
 test/scenarios/callbacks/hooks/python/main.py |  4 +-
 .../callbacks/permissions/python/main.py      |  4 +-
 .../callbacks/user-input/python/main.py       |  8 +--
 test/scenarios/modes/default/python/main.py   |  2 +-
 test/scenarios/modes/minimal/python/main.py   |  2 +-
 .../prompts/attachments/python/main.py        |  6 +-
 .../prompts/reasoning-effort/python/main.py   |  2 +-
 .../prompts/system-message/python/main.py     |  2 +-
 .../concurrent-sessions/python/main.py        |  4 +-
 .../sessions/infinite-sessions/python/main.py |  2 +-
 .../sessions/session-resume/python/main.py    |  4 +-
 .../sessions/streaming/python/main.py         |  2 +-
 .../tools/custom-agents/python/main.py        |  2 +-
 .../tools/mcp-servers/python/main.py          |  2 +-
 test/scenarios/tools/no-tools/python/main.py  |  2 +-
 test/scenarios/tools/skills/python/main.py    |  2 +-
 .../tools/tool-filtering/python/main.py       |  2 +-
 .../tools/tool-overrides/python/main.py       |  2 +-
 .../tools/virtual-filesystem/python/main.py   |  8 +--
 .../transport/reconnect/python/main.py        |  4 +-
 test/scenarios/transport/stdio/python/main.py |  2 +-
 test/scenarios/transport/tcp/python/main.py   |  2 +-
 48 files changed, 166 insertions(+), 246 deletions(-)

diff --git a/python/README.md b/python/README.md
index a585ea11..3d36105c 100644
--- a/python/README.md
+++ b/python/README.md
@@ -47,7 +47,7 @@ async def main():
     session.on(on_event)
 
     # Send a message and wait for completion
-    await session.send({"prompt": "What is 2+2?"})
+    await session.send("What is 2+2?")
     await done.wait()
 
     # Clean up
@@ -61,7 +61,7 @@ Sessions also support the `async with` context manager pattern for automatic cle
 
 ```python
 async with await client.create_session({"model": "gpt-5"}) as session:
-    await session.send({"prompt": "What is 2+2?"})
+    await session.send("What is 2+2?")
     # session is automatically disconnected when leaving the block
 ```
 
@@ -93,7 +93,7 @@ def on_event(event):
     print(f"Event: {event['type']}")
 
 session.on(on_event)
-await session.send({"prompt": "Hello!"})
+await session.send("Hello!")
 
 # ... wait for events ...
 
@@ -235,21 +235,21 @@ async def edit_file(params: EditFileParams) -> str:
 The SDK supports image attachments via the `attachments` parameter. You can attach images by providing their file path:
 
 ```python
-await session.send({
-    "prompt": "What's in this image?",
-    "attachments": [
+await session.send(
+    "What's in this image?",
+    attachments=[
         {
             "type": "file",
             "path": "/path/to/image.jpg",
         }
-    ]
-})
+    ],
+)
 ```
 
 Supported image formats include JPG, PNG, GIF, and other common image types. The agent's `view` tool can also read images directly from the filesystem, so you can also ask questions like:
 
 ```python
-await session.send({"prompt": "What does the most recent jpg in this directory portray?"})
+await session.send("What does the most recent jpg in this directory portray?")
 ```
 
 ## Streaming
@@ -294,7 +294,7 @@ async def main():
             done.set()
 
     session.on(on_event)
-    await session.send({"prompt": "Tell me a short story"})
+    await session.send("Tell me a short story")
     await done.wait()  # Wait for streaming to complete
 
     await session.disconnect()
@@ -371,7 +371,7 @@ session = await client.create_session({
     },
 })
 
-await session.send({"prompt": "Hello!"})
+await session.send("Hello!")
 ```
 
 **Example with custom OpenAI-compatible API:**
diff --git a/python/copilot/__init__.py b/python/copilot/__init__.py
index f5f7ed0b..9ec50216 100644
--- a/python/copilot/__init__.py
+++ b/python/copilot/__init__.py
@@ -16,7 +16,6 @@
     MCPLocalServerConfig,
     MCPRemoteServerConfig,
     MCPServerConfig,
-    MessageOptions,
     ModelBilling,
     ModelCapabilities,
     ModelInfo,
@@ -52,7 +51,6 @@
     "MCPLocalServerConfig",
     "MCPRemoteServerConfig",
     "MCPServerConfig",
-    "MessageOptions",
     "ModelBilling",
     "ModelCapabilities",
     "ModelInfo",
diff --git a/python/copilot/client.py b/python/copilot/client.py
index 239c4f79..ae378d1c 100644
--- a/python/copilot/client.py
+++ b/python/copilot/client.py
@@ -9,7 +9,7 @@
     >>>
     >>> async with CopilotClient() as client:
     ...     session = await client.create_session()
-    ...     await session.send({"prompt": "Hello!"})
+    ...     await session.send("Hello!")
 """
 
 import asyncio
@@ -104,7 +104,7 @@ class CopilotClient:
         ...     "model": "gpt-4",
         ... })
         >>> session.on(lambda event: print(event.type))
-        >>> await session.send({"prompt": "Hello!"})
+        >>> await session.send("Hello!")
         >>>
         >>> # Clean up
         >>> await session.disconnect()
diff --git a/python/copilot/session.py b/python/copilot/session.py
index b4ae210d..2d864d13 100644
--- a/python/copilot/session.py
+++ b/python/copilot/session.py
@@ -25,7 +25,6 @@
 from .generated.session_events import SessionEvent, SessionEventType, session_event_from_dict
 from .jsonrpc import JsonRpcError, ProcessExitedError
 from .types import (
-    MessageOptions,
     PermissionRequest,
     PermissionRequestResult,
     SessionHooks,
@@ -63,7 +62,7 @@ class CopilotSession:
         ...     unsubscribe = session.on(lambda event: print(event.type))
         ...
         ...     # Send a message
-        ...     await session.send({"prompt": "Hello, world!"})
+        ...     await session.send("Hello, world!")
         ...
         ...     # Clean up
         ...     unsubscribe()
@@ -115,7 +114,13 @@ def workspace_path(self) -> str | None:
         """
         return self._workspace_path
 
-    async def send(self, options: MessageOptions) -> str:
+    async def send(
+        self,
+        prompt: str,
+        *,
+        attachments: list[Any] | None = None,
+        mode: str | None = None,
+    ) -> str:
         """
         Send a message to this session and wait for the response.
 
@@ -123,9 +128,9 @@ async def send(self, options: MessageOptions) -> str:
         to receive streaming responses and other session events.
 
         Args:
-            options: Message options including the prompt and optional attachments.
-                Must contain a "prompt" key with the message text. Can optionally
-                include "attachments" and "mode" keys.
+            prompt: The message text to send.
+            attachments: Optional file, directory, or selection attachments.
+            mode: Message delivery mode (``"enqueue"`` or ``"immediate"``).
 
         Returns:
             The message ID of the response, which can be used to correlate events.
@@ -134,25 +139,30 @@ async def send(self, options: MessageOptions) -> str:
             Exception: If the session has been disconnected or the connection fails.
 
         Example:
-            >>> message_id = await session.send({
-            ...     "prompt": "Explain this code",
-            ...     "attachments": [{"type": "file", "path": "./src/main.py"}]
-            ... })
+            >>> message_id = await session.send(
+            ...     "Explain this code",
+            ...     attachments=[{"type": "file", "path": "./src/main.py"}],
+            ... )
         """
         params: dict[str, Any] = {
             "sessionId": self.session_id,
-            "prompt": options["prompt"],
+            "prompt": prompt,
         }
-        if "attachments" in options:
-            params["attachments"] = options["attachments"]
-        if "mode" in options:
-            params["mode"] = options["mode"]
+        if attachments is not None:
+            params["attachments"] = attachments
+        if mode is not None:
+            params["mode"] = mode
 
         response = await self._client.request("session.send", params)
         return response["messageId"]
 
     async def send_and_wait(
-        self, options: MessageOptions, timeout: float | None = None
+        self,
+        prompt: str,
+        *,
+        attachments: list[Any] | None = None,
+        mode: str | None = None,
+        timeout: float = 60.0,
     ) -> SessionEvent | None:
         """
         Send a message to this session and wait until the session becomes idle.
@@ -164,7 +174,9 @@ async def send_and_wait(
         Events are still delivered to handlers registered via :meth:`on` while waiting.
 
         Args:
-            options: Message options including the prompt and optional attachments.
+            prompt: The message text to send.
+            attachments: Optional file, directory, or selection attachments.
+            mode: Message delivery mode (``"enqueue"`` or ``"immediate"``).
             timeout: Timeout in seconds (default: 60). Controls how long to wait;
                 does not abort in-flight agent work.
 
@@ -176,12 +188,10 @@ async def send_and_wait(
             Exception: If the session has been disconnected or the connection fails.
 
         Example:
-            >>> response = await session.send_and_wait({"prompt": "What is 2+2?"})
+            >>> response = await session.send_and_wait("What is 2+2?")
             >>> if response:
             ...     print(response.data.content)
         """
-        effective_timeout = timeout if timeout is not None else 60.0
-
         idle_event = asyncio.Event()
         error_event: Exception | None = None
         last_assistant_message: SessionEvent | None = None
@@ -200,13 +210,13 @@ def handler(event: SessionEventTypeAlias) -> None:
 
         unsubscribe = self.on(handler)
         try:
-            await self.send(options)
-            await asyncio.wait_for(idle_event.wait(), timeout=effective_timeout)
+            await self.send(prompt, attachments=attachments, mode=mode)
+            await asyncio.wait_for(idle_event.wait(), timeout=timeout)
             if error_event:
                 raise error_event
             return last_assistant_message
         except TimeoutError:
-            raise TimeoutError(f"Timeout after {effective_timeout}s waiting for session.idle")
+            raise TimeoutError(f"Timeout after {timeout}s waiting for session.idle")
         finally:
             unsubscribe()
 
@@ -712,7 +722,7 @@ async def abort(self) -> None:
             >>>
             >>> # Start a long-running request
             >>> task = asyncio.create_task(
-            ...     session.send({"prompt": "Write a very long story..."})
+            ...     session.send("Write a very long story...")
             ... )
             >>>
             >>> # Abort after 5 seconds
diff --git a/python/copilot/types.py b/python/copilot/types.py
index e8b8d1d4..4d8e4984 100644
--- a/python/copilot/types.py
+++ b/python/copilot/types.py
@@ -603,17 +603,6 @@ class ResumeSessionConfig(TypedDict, total=False):
     on_event: Callable[[SessionEvent], None]
 
 
-# Options for sending a message to a session
-class MessageOptions(TypedDict):
-    """Options for sending a message to a session"""
-
-    prompt: str  # The prompt/message to send
-    # Optional file/directory attachments
-    attachments: NotRequired[list[Attachment]]
-    # Message processing mode
-    mode: NotRequired[Literal["enqueue", "immediate"]]
-
-
 # Event handler type
 SessionEventHandler = Callable[[SessionEvent], None]
 
diff --git a/python/e2e/test_agent_and_compact_rpc.py b/python/e2e/test_agent_and_compact_rpc.py
index cee6814f..c17161e6 100644
--- a/python/e2e/test_agent_and_compact_rpc.py
+++ b/python/e2e/test_agent_and_compact_rpc.py
@@ -182,7 +182,7 @@ async def test_should_compact_session_history_after_messages(self, ctx: E2ETestC
         )
 
         # Send a message to create some history
-        await session.send_and_wait({"prompt": "What is 2+2?"})
+        await session.send_and_wait("What is 2+2?")
 
         # Compact the session
         result = await session.rpc.compaction.compact()
diff --git a/python/e2e/test_ask_user.py b/python/e2e/test_ask_user.py
index bddc062d..b9800156 100644
--- a/python/e2e/test_ask_user.py
+++ b/python/e2e/test_ask_user.py
@@ -37,12 +37,8 @@ async def on_user_input_request(request, invocation):
         )
 
         await session.send_and_wait(
-            {
-                "prompt": (
-                    "Ask me to choose between 'Option A' and 'Option B' using the ask_user "
-                    "tool. Wait for my response before continuing."
-                )
-            }
+            "Ask me to choose between 'Option A' and 'Option B' using the ask_user "
+            "tool. Wait for my response before continuing."
         )
 
         # Should have received at least one user input request
@@ -76,12 +72,8 @@ async def on_user_input_request(request, invocation):
         )
 
         await session.send_and_wait(
-            {
-                "prompt": (
-                    "Use the ask_user tool to ask me to pick between exactly two options: "
-                    "'Red' and 'Blue'. These should be provided as choices. Wait for my answer."
-                )
-            }
+            "Use the ask_user tool to ask me to pick between exactly two options: "
+            "'Red' and 'Blue'. These should be provided as choices. Wait for my answer."
         )
 
         # Should have received a request
@@ -117,12 +109,8 @@ async def on_user_input_request(request, invocation):
         )
 
         response = await session.send_and_wait(
-            {
-                "prompt": (
-                    "Ask me a question using ask_user and then include my answer in your "
-                    "response. The question should be 'What is your favorite color?'"
-                )
-            }
+            "Ask me a question using ask_user and then include my answer in your "
+            "response. The question should be 'What is your favorite color?'"
         )
 
         # Should have received a request
diff --git a/python/e2e/test_compaction.py b/python/e2e/test_compaction.py
index 5447b4ba..13104070 100644
--- a/python/e2e/test_compaction.py
+++ b/python/e2e/test_compaction.py
@@ -41,13 +41,11 @@ def on_event(event):
         session.on(on_event)
 
         # Send multiple messages to fill up the context window
-        await session.send_and_wait({"prompt": "Tell me a story about a dragon. Be detailed."})
+        await session.send_and_wait("Tell me a story about a dragon. Be detailed.")
         await session.send_and_wait(
-            {"prompt": "Continue the story with more details about the dragon's castle."}
-        )
-        await session.send_and_wait(
-            {"prompt": "Now describe the dragon's treasure in great detail."}
+            "Continue the story with more details about the dragon's castle."
         )
+        await session.send_and_wait("Now describe the dragon's treasure in great detail.")
 
         # Should have triggered compaction at least once
         assert len(compaction_start_events) >= 1, "Expected at least 1 compaction_start event"
@@ -62,7 +60,7 @@ def on_event(event):
             assert last_complete.data.tokens_removed > 0, "Expected tokensRemoved > 0"
 
         # Verify the session still works after compaction
-        answer = await session.send_and_wait({"prompt": "What was the story about?"})
+        answer = await session.send_and_wait("What was the story about?")
         assert answer is not None
         assert answer.data.content is not None
         # Should remember it was about a dragon (context preserved via summary)
@@ -89,7 +87,7 @@ def on_event(event):
 
         session.on(on_event)
 
-        await session.send_and_wait({"prompt": "What is 2+2?"})
+        await session.send_and_wait("What is 2+2?")
 
         # Should not have any compaction events when disabled
         assert len(compaction_events) == 0, "Expected no compaction events when disabled"
diff --git a/python/e2e/test_hooks.py b/python/e2e/test_hooks.py
index c886c6e2..a4956482 100644
--- a/python/e2e/test_hooks.py
+++ b/python/e2e/test_hooks.py
@@ -33,9 +33,7 @@ async def on_pre_tool_use(input_data, invocation):
         # Create a file for the model to read
         write_file(ctx.work_dir, "hello.txt", "Hello from the test!")
 
-        await session.send_and_wait(
-            {"prompt": "Read the contents of hello.txt and tell me what it says"}
-        )
+        await session.send_and_wait("Read the contents of hello.txt and tell me what it says")
 
         # Should have received at least one preToolUse hook call
         assert len(pre_tool_use_inputs) > 0
@@ -66,9 +64,7 @@ async def on_post_tool_use(input_data, invocation):
         # Create a file for the model to read
         write_file(ctx.work_dir, "world.txt", "World from the test!")
 
-        await session.send_and_wait(
-            {"prompt": "Read the contents of world.txt and tell me what it says"}
-        )
+        await session.send_and_wait("Read the contents of world.txt and tell me what it says")
 
         # Should have received at least one postToolUse hook call
         assert len(post_tool_use_inputs) > 0
@@ -106,7 +102,7 @@ async def on_post_tool_use(input_data, invocation):
 
         write_file(ctx.work_dir, "both.txt", "Testing both hooks!")
 
-        await session.send_and_wait({"prompt": "Read the contents of both.txt"})
+        await session.send_and_wait("Read the contents of both.txt")
 
         # Both hooks should have been called
         assert len(pre_tool_use_inputs) > 0
@@ -143,7 +139,7 @@ async def on_pre_tool_use(input_data, invocation):
         write_file(ctx.work_dir, "protected.txt", original_content)
 
         response = await session.send_and_wait(
-            {"prompt": "Edit protected.txt and replace 'Original' with 'Modified'"}
+            "Edit protected.txt and replace 'Original' with 'Modified'"
         )
 
         # The hook should have been called
diff --git a/python/e2e/test_mcp_and_agents.py b/python/e2e/test_mcp_and_agents.py
index fd99cc2c..8fffbe88 100644
--- a/python/e2e/test_mcp_and_agents.py
+++ b/python/e2e/test_mcp_and_agents.py
@@ -39,7 +39,7 @@ async def test_should_accept_mcp_server_configuration_on_session_create(
         assert session.session_id is not None
 
         # Simple interaction to verify session works
-        message = await session.send_and_wait({"prompt": "What is 2+2?"})
+        message = await session.send_and_wait("What is 2+2?")
         assert message is not None
         assert "4" in message.data.content
 
@@ -54,7 +54,7 @@ async def test_should_accept_mcp_server_configuration_on_session_resume(
             {"on_permission_request": PermissionHandler.approve_all}
         )
         session_id = session1.session_id
-        await session1.send_and_wait({"prompt": "What is 1+1?"})
+        await session1.send_and_wait("What is 1+1?")
 
         # Resume with MCP servers
         mcp_servers: dict[str, MCPServerConfig] = {
@@ -73,7 +73,7 @@ async def test_should_accept_mcp_server_configuration_on_session_resume(
 
         assert session2.session_id == session_id
 
-        message = await session2.send_and_wait({"prompt": "What is 3+3?"})
+        message = await session2.send_and_wait("What is 3+3?")
         assert message is not None
         assert "6" in message.data.content
 
@@ -104,10 +104,8 @@ async def test_should_pass_literal_env_values_to_mcp_server_subprocess(
         assert session.session_id is not None
 
         message = await session.send_and_wait(
-            {
-                "prompt": "Use the env-echo/get_env tool to read the TEST_SECRET "
-                "environment variable. Reply with just the value, nothing else."
-            }
+            "Use the env-echo/get_env tool to read the TEST_SECRET "
+            "environment variable. Reply with just the value, nothing else."
         )
         assert message is not None
         assert "hunter2" in message.data.content
@@ -137,7 +135,7 @@ async def test_should_accept_custom_agent_configuration_on_session_create(
         assert session.session_id is not None
 
         # Simple interaction to verify session works
-        message = await session.send_and_wait({"prompt": "What is 5+5?"})
+        message = await session.send_and_wait("What is 5+5?")
         assert message is not None
         assert "10" in message.data.content
 
@@ -152,7 +150,7 @@ async def test_should_accept_custom_agent_configuration_on_session_resume(
             {"on_permission_request": PermissionHandler.approve_all}
         )
         session_id = session1.session_id
-        await session1.send_and_wait({"prompt": "What is 1+1?"})
+        await session1.send_and_wait("What is 1+1?")
 
         # Resume with custom agents
         custom_agents: list[CustomAgentConfig] = [
@@ -174,7 +172,7 @@ async def test_should_accept_custom_agent_configuration_on_session_resume(
 
         assert session2.session_id == session_id
 
-        message = await session2.send_and_wait({"prompt": "What is 6+6?"})
+        message = await session2.send_and_wait("What is 6+6?")
         assert message is not None
         assert "12" in message.data.content
 
@@ -212,7 +210,7 @@ async def test_should_accept_both_mcp_servers_and_custom_agents(self, ctx: E2ETe
 
         assert session.session_id is not None
 
-        await session.send({"prompt": "What is 7+7?"})
+        await session.send("What is 7+7?")
         message = await get_final_assistant_message(session)
         assert "14" in message.data.content
 
diff --git a/python/e2e/test_multi_client.py b/python/e2e/test_multi_client.py
index caf58cd5..183beb1a 100644
--- a/python/e2e/test_multi_client.py
+++ b/python/e2e/test_multi_client.py
@@ -212,9 +212,7 @@ def magic_number(params: SeedParams, invocation: ToolInvocation) -> str:
         session2.on(lambda event: client2_events.append(event))
 
         # Send a prompt that triggers the custom tool
-        await session1.send(
-            {"prompt": "Use the magic_number tool with seed 'hello' and tell me the result"}
-        )
+        await session1.send("Use the magic_number tool with seed 'hello' and tell me the result")
         response = await get_final_assistant_message(session1)
         assert "MAGIC_hello_42" in (response.data.content or "")
 
@@ -259,9 +257,7 @@ async def test_one_client_approves_permission_and_both_see_the_result(
         session2.on(lambda event: client2_events.append(event))
 
         # Send a prompt that triggers a write operation (requires permission)
-        await session1.send(
-            {"prompt": "Create a file called hello.txt containing the text 'hello world'"}
-        )
+        await session1.send("Create a file called hello.txt containing the text 'hello world'")
         response = await get_final_assistant_message(session1)
         assert response.data.content
 
@@ -313,7 +309,7 @@ async def test_one_client_rejects_permission_and_both_see_the_result(
         with open(test_file, "w") as f:
             f.write("protected content")
 
-        await session1.send({"prompt": "Edit protected.txt and replace 'protected' with 'hacked'."})
+        await session1.send("Edit protected.txt and replace 'protected' with 'hacked'.")
         await get_final_assistant_message(session1)
 
         # Verify the file was NOT modified (permission was denied)
@@ -368,17 +364,13 @@ def currency_lookup(params: CountryCodeParams, invocation: ToolInvocation) -> st
 
         # Send prompts sequentially to avoid nondeterministic tool_call ordering
         await session1.send(
-            {"prompt": "Use the city_lookup tool with countryCode 'US' and tell me the result."}
+            "Use the city_lookup tool with countryCode 'US' and tell me the result."
         )
         response1 = await get_final_assistant_message(session1)
         assert "CITY_FOR_US" in (response1.data.content or "")
 
         await session1.send(
-            {
-                "prompt": (
-                    "Now use the currency_lookup tool with countryCode 'US' and tell me the result."
-                )
-            }
+            "Now use the currency_lookup tool with countryCode 'US' and tell me the result."
         )
         response2 = await get_final_assistant_message(session1)
         assert "CURRENCY_FOR_US" in (response2.data.content or "")
@@ -419,19 +411,11 @@ def ephemeral_tool(params: InputParams, invocation: ToolInvocation) -> str:
 
         # Verify both tools work before disconnect.
         # Sequential prompts avoid nondeterministic tool_call ordering.
-        await session1.send(
-            {
-                "prompt": "Use the stable_tool with input 'test1' and tell me the result.",
-            }
-        )
+        await session1.send("Use the stable_tool with input 'test1' and tell me the result.")
         stable_response = await get_final_assistant_message(session1)
         assert "STABLE_test1" in (stable_response.data.content or "")
 
-        await session1.send(
-            {
-                "prompt": "Use the ephemeral_tool with input 'test2' and tell me the result.",
-            }
-        )
+        await session1.send("Use the ephemeral_tool with input 'test2' and tell me the result.")
         ephemeral_response = await get_final_assistant_message(session1)
         assert "EPHEMERAL_test2" in (ephemeral_response.data.content or "")
 
@@ -447,13 +431,9 @@ def ephemeral_tool(params: InputParams, invocation: ToolInvocation) -> str:
 
         # Now only stable_tool should be available
         await session1.send(
-            {
-                "prompt": (
-                    "Use the stable_tool with input 'still_here'."
-                    " Also try using ephemeral_tool"
-                    " if it is available."
-                )
-            }
+            "Use the stable_tool with input 'still_here'."
+            " Also try using ephemeral_tool"
+            " if it is available."
         )
         after_response = await get_final_assistant_message(session1)
         assert "STABLE_still_here" in (after_response.data.content or "")
diff --git a/python/e2e/test_permissions.py b/python/e2e/test_permissions.py
index 609003e8..d18b15b2 100644
--- a/python/e2e/test_permissions.py
+++ b/python/e2e/test_permissions.py
@@ -30,9 +30,7 @@ def on_permission_request(
 
         write_file(ctx.work_dir, "test.txt", "original content")
 
-        await session.send_and_wait(
-            {"prompt": "Edit test.txt and replace 'original' with 'modified'"}
-        )
+        await session.send_and_wait("Edit test.txt and replace 'original' with 'modified'")
 
         # Should have received at least one permission request
         assert len(permission_requests) > 0
@@ -56,9 +54,7 @@ def on_permission_request(
         original_content = "protected content"
         write_file(ctx.work_dir, "protected.txt", original_content)
 
-        await session.send_and_wait(
-            {"prompt": "Edit protected.txt and replace 'protected' with 'hacked'."}
-        )
+        await session.send_and_wait("Edit protected.txt and replace 'protected' with 'hacked'.")
 
         # Verify the file was NOT modified
         content = read_file(ctx.work_dir, "protected.txt")
@@ -94,7 +90,7 @@ def on_event(event):
 
         session.on(on_event)
 
-        await session.send({"prompt": "Run 'node --version'"})
+        await session.send("Run 'node --version'")
         await asyncio.wait_for(done_event.wait(), timeout=60)
 
         assert len(denied_events) > 0
@@ -109,7 +105,7 @@ async def test_should_deny_tool_operations_when_handler_explicitly_denies_after_
             {"on_permission_request": PermissionHandler.approve_all}
         )
         session_id = session1.session_id
-        await session1.send_and_wait({"prompt": "What is 1+1?"})
+        await session1.send_and_wait("What is 1+1?")
 
         def deny_all(request, invocation):
             return PermissionRequestResult()
@@ -134,7 +130,7 @@ def on_event(event):
 
         session2.on(on_event)
 
-        await session2.send({"prompt": "Run 'node --version'"})
+        await session2.send("Run 'node --version'")
         await asyncio.wait_for(done_event.wait(), timeout=60)
 
         assert len(denied_events) > 0
@@ -147,7 +143,7 @@ async def test_should_work_with_approve_all_permission_handler(self, ctx: E2ETes
             {"on_permission_request": PermissionHandler.approve_all}
         )
 
-        message = await session.send_and_wait({"prompt": "What is 2+2?"})
+        message = await session.send_and_wait("What is 2+2?")
 
         assert message is not None
         assert "4" in message.data.content
@@ -168,7 +164,7 @@ async def on_permission_request(
 
         session = await ctx.client.create_session({"on_permission_request": on_permission_request})
 
-        await session.send_and_wait({"prompt": "Run 'echo test' and tell me what happens"})
+        await session.send_and_wait("Run 'echo test' and tell me what happens")
 
         assert len(permission_requests) > 0
 
@@ -183,7 +179,7 @@ async def test_should_resume_session_with_permission_handler(self, ctx: E2ETestC
             {"on_permission_request": PermissionHandler.approve_all}
         )
         session_id = session1.session_id
-        await session1.send_and_wait({"prompt": "What is 1+1?"})
+        await session1.send_and_wait("What is 1+1?")
 
         # Resume with permission handler
         def on_permission_request(
@@ -196,7 +192,7 @@ def on_permission_request(
             session_id, {"on_permission_request": on_permission_request}
         )
 
-        await session2.send_and_wait({"prompt": "Run 'echo resumed' for me"})
+        await session2.send_and_wait("Run 'echo resumed' for me")
 
         # Should have permission requests from resumed session
         assert len(permission_requests) > 0
@@ -213,9 +209,7 @@ def on_permission_request(
 
         session = await ctx.client.create_session({"on_permission_request": on_permission_request})
 
-        message = await session.send_and_wait(
-            {"prompt": "Run 'echo test'. If you can't, say 'failed'."}
-        )
+        message = await session.send_and_wait("Run 'echo test'. If you can't, say 'failed'.")
 
         # Should handle the error and deny permission
         assert message is not None
@@ -240,7 +234,7 @@ def on_permission_request(
 
         session = await ctx.client.create_session({"on_permission_request": on_permission_request})
 
-        await session.send_and_wait({"prompt": "Run 'echo test'"})
+        await session.send_and_wait("Run 'echo test'")
 
         assert received_tool_call_id
 
diff --git a/python/e2e/test_session.py b/python/e2e/test_session.py
index 79fb661d..a4024646 100644
--- a/python/e2e/test_session.py
+++ b/python/e2e/test_session.py
@@ -35,13 +35,11 @@ async def test_should_have_stateful_conversation(self, ctx: E2ETestContext):
             {"on_permission_request": PermissionHandler.approve_all}
         )
 
-        assistant_message = await session.send_and_wait({"prompt": "What is 1+1?"})
+        assistant_message = await session.send_and_wait("What is 1+1?")
         assert assistant_message is not None
         assert "2" in assistant_message.data.content
 
-        second_message = await session.send_and_wait(
-            {"prompt": "Now if you double that, what do you get?"}
-        )
+        second_message = await session.send_and_wait("Now if you double that, what do you get?")
         assert second_message is not None
         assert "4" in second_message.data.content
 
@@ -56,7 +54,7 @@ async def test_should_create_a_session_with_appended_systemMessage_config(
             }
         )
 
-        await session.send({"prompt": "What is your full name?"})
+        await session.send("What is your full name?")
         assistant_message = await get_final_assistant_message(session)
         assert "GitHub" in assistant_message.data.content
         assert "Have a nice day!" in assistant_message.data.content
@@ -78,7 +76,7 @@ async def test_should_create_a_session_with_replaced_systemMessage_config(
             }
         )
 
-        await session.send({"prompt": "What is your full name?"})
+        await session.send("What is your full name?")
         assistant_message = await get_final_assistant_message(session)
         assert "GitHub" not in assistant_message.data.content
         assert "Testy" in assistant_message.data.content
@@ -96,7 +94,7 @@ async def test_should_create_a_session_with_availableTools(self, ctx: E2ETestCon
             }
         )
 
-        await session.send({"prompt": "What is 1+1?"})
+        await session.send("What is 1+1?")
         await get_final_assistant_message(session)
 
         # It only tells the model about the specified tools and no others
@@ -112,7 +110,7 @@ async def test_should_create_a_session_with_excludedTools(self, ctx: E2ETestCont
             {"excluded_tools": ["view"], "on_permission_request": PermissionHandler.approve_all}
         )
 
-        await session.send({"prompt": "What is 1+1?"})
+        await session.send("What is 1+1?")
         await get_final_assistant_message(session)
 
         # It has other tools, but not the one we excluded
@@ -160,7 +158,7 @@ async def test_should_resume_a_session_using_the_same_client(self, ctx: E2ETestC
             {"on_permission_request": PermissionHandler.approve_all}
         )
         session_id = session1.session_id
-        answer = await session1.send_and_wait({"prompt": "What is 1+1?"})
+        answer = await session1.send_and_wait("What is 1+1?")
         assert answer is not None
         assert "2" in answer.data.content
 
@@ -173,9 +171,7 @@ async def test_should_resume_a_session_using_the_same_client(self, ctx: E2ETestC
         assert "2" in answer2.data.content
 
         # Can continue the conversation statefully
-        answer3 = await session2.send_and_wait(
-            {"prompt": "Now if you double that, what do you get?"}
-        )
+        answer3 = await session2.send_and_wait("Now if you double that, what do you get?")
         assert answer3 is not None
         assert "4" in answer3.data.content
 
@@ -185,7 +181,7 @@ async def test_should_resume_a_session_using_a_new_client(self, ctx: E2ETestCont
             {"on_permission_request": PermissionHandler.approve_all}
         )
         session_id = session1.session_id
-        answer = await session1.send_and_wait({"prompt": "What is 1+1?"})
+        answer = await session1.send_and_wait("What is 1+1?")
         assert answer is not None
         assert "2" in answer.data.content
 
@@ -214,9 +210,7 @@ async def test_should_resume_a_session_using_a_new_client(self, ctx: E2ETestCont
             assert "session.resume" in message_types
 
             # Can continue the conversation statefully
-            answer2 = await session2.send_and_wait(
-                {"prompt": "Now if you double that, what do you get?"}
-            )
+            answer2 = await session2.send_and_wait("Now if you double that, what do you get?")
             assert answer2 is not None
             assert "4" in answer2.data.content
         finally:
@@ -235,11 +229,11 @@ async def test_should_list_sessions(self, ctx: E2ETestContext):
         session1 = await ctx.client.create_session(
             {"on_permission_request": PermissionHandler.approve_all}
         )
-        await session1.send_and_wait({"prompt": "Say hello"})
+        await session1.send_and_wait("Say hello")
         session2 = await ctx.client.create_session(
             {"on_permission_request": PermissionHandler.approve_all}
         )
-        await session2.send_and_wait({"prompt": "Say goodbye"})
+        await session2.send_and_wait("Say goodbye")
 
         # Small delay to ensure session files are written to disk
         await asyncio.sleep(0.2)
@@ -278,7 +272,7 @@ async def test_should_delete_session(self, ctx: E2ETestContext):
         session = await ctx.client.create_session(
             {"on_permission_request": PermissionHandler.approve_all}
         )
-        await session.send_and_wait({"prompt": "Hello"})
+        await session.send_and_wait("Hello")
         session_id = session.session_id
 
         # Small delay to ensure session file is written to disk
@@ -310,7 +304,7 @@ async def test_should_get_last_session_id(self, ctx: E2ETestContext):
         session = await ctx.client.create_session(
             {"on_permission_request": PermissionHandler.approve_all}
         )
-        await session.send_and_wait({"prompt": "Say hello"})
+        await session.send_and_wait("Say hello")
 
         # Small delay to ensure session data is flushed to disk
         await asyncio.sleep(0.5)
@@ -347,7 +341,7 @@ def get_secret_number_handler(invocation):
             }
         )
 
-        answer = await session.send_and_wait({"prompt": "What is the secret number for key ALPHA?"})
+        answer = await session.send_and_wait("What is the secret number for key ALPHA?")
         assert answer is not None
         assert "54321" in answer.data.content
 
@@ -418,12 +412,7 @@ async def test_should_abort_a_session(self, ctx: E2ETestContext):
 
         # Send a message that will trigger a long-running shell command
         await session.send(
-            {
-                "prompt": (
-                    "run the shell command 'sleep 100' "
-                    "(note this works on both bash and PowerShell)"
-                )
-            }
+            "run the shell command 'sleep 100' (note this works on both bash and PowerShell)"
         )
 
         # Wait for the tool to start executing
@@ -444,7 +433,7 @@ async def test_should_abort_a_session(self, ctx: E2ETestContext):
         assert len(abort_events) > 0, "Expected an abort event in messages"
 
         # We should be able to send another message
-        answer = await session.send_and_wait({"prompt": "What is 2+2?"})
+        answer = await session.send_and_wait("What is 2+2?")
         assert "4" in answer.data.content
 
     async def test_should_receive_session_events(self, ctx: E2ETestContext):
@@ -478,7 +467,7 @@ def on_event(event):
         session.on(on_event)
 
         # Send a message to trigger events
-        await session.send({"prompt": "What is 100+200?"})
+        await session.send("What is 100+200?")
 
         # Wait for session to become idle
         try:
@@ -511,7 +500,7 @@ async def test_should_create_session_with_custom_config_dir(self, ctx: E2ETestCo
         assert session.session_id
 
         # Session should work normally with custom config dir
-        await session.send({"prompt": "What is 1+1?"})
+        await session.send("What is 1+1?")
         assistant_message = await get_final_assistant_message(session)
         assert "2" in assistant_message.data.content
 
diff --git a/python/e2e/test_skills.py b/python/e2e/test_skills.py
index 166840e5..066669f2 100644
--- a/python/e2e/test_skills.py
+++ b/python/e2e/test_skills.py
@@ -65,7 +65,7 @@ async def test_should_load_and_apply_skill_from_skilldirectories(self, ctx: E2ET
         assert session.session_id is not None
 
         # The skill instructs the model to include a marker - verify it appears
-        message = await session.send_and_wait({"prompt": "Say hello briefly using the test skill."})
+        message = await session.send_and_wait("Say hello briefly using the test skill.")
         assert message is not None
         assert SKILL_MARKER in message.data.content
 
@@ -87,7 +87,7 @@ async def test_should_not_apply_skill_when_disabled_via_disabledskills(
         assert session.session_id is not None
 
         # The skill is disabled, so the marker should NOT appear
-        message = await session.send_and_wait({"prompt": "Say hello briefly using the test skill."})
+        message = await session.send_and_wait("Say hello briefly using the test skill.")
         assert message is not None
         assert SKILL_MARKER not in message.data.content
 
@@ -110,7 +110,7 @@ async def test_should_apply_skill_on_session_resume_with_skilldirectories(
         session_id = session1.session_id
 
         # First message without skill - marker should not appear
-        message1 = await session1.send_and_wait({"prompt": "Say hi."})
+        message1 = await session1.send_and_wait("Say hi.")
         assert message1 is not None
         assert SKILL_MARKER not in message1.data.content
 
@@ -126,7 +126,7 @@ async def test_should_apply_skill_on_session_resume_with_skilldirectories(
         assert session2.session_id == session_id
 
         # Now the skill should be applied
-        message2 = await session2.send_and_wait({"prompt": "Say hello again using the test skill."})
+        message2 = await session2.send_and_wait("Say hello again using the test skill.")
         assert message2 is not None
         assert SKILL_MARKER in message2.data.content
 
diff --git a/python/e2e/test_streaming_fidelity.py b/python/e2e/test_streaming_fidelity.py
index d347015a..d50caa98 100644
--- a/python/e2e/test_streaming_fidelity.py
+++ b/python/e2e/test_streaming_fidelity.py
@@ -20,7 +20,7 @@ async def test_should_produce_delta_events_when_streaming_is_enabled(self, ctx:
         events = []
         session.on(lambda event: events.append(event))
 
-        await session.send_and_wait({"prompt": "Count from 1 to 5, separated by commas."})
+        await session.send_and_wait("Count from 1 to 5, separated by commas.")
 
         types = [e.type.value for e in events]
 
@@ -52,7 +52,7 @@ async def test_should_not_produce_deltas_when_streaming_is_disabled(self, ctx: E
         events = []
         session.on(lambda event: events.append(event))
 
-        await session.send_and_wait({"prompt": "Say 'hello world'."})
+        await session.send_and_wait("Say 'hello world'.")
 
         delta_events = [e for e in events if e.type.value == "assistant.message_delta"]
 
@@ -69,7 +69,7 @@ async def test_should_produce_deltas_after_session_resume(self, ctx: E2ETestCont
         session = await ctx.client.create_session(
             {"streaming": False, "on_permission_request": PermissionHandler.approve_all}
         )
-        await session.send_and_wait({"prompt": "What is 3 + 6?"})
+        await session.send_and_wait("What is 3 + 6?")
         await session.disconnect()
 
         # Resume using a new client
@@ -93,9 +93,7 @@ async def test_should_produce_deltas_after_session_resume(self, ctx: E2ETestCont
             events = []
             session2.on(lambda event: events.append(event))
 
-            answer = await session2.send_and_wait(
-                {"prompt": "Now if you double that, what do you get?"}
-            )
+            answer = await session2.send_and_wait("Now if you double that, what do you get?")
             assert answer is not None
             assert "18" in answer.data.content
 
diff --git a/python/e2e/test_tools.py b/python/e2e/test_tools.py
index b692e3f6..0831ecc1 100644
--- a/python/e2e/test_tools.py
+++ b/python/e2e/test_tools.py
@@ -27,7 +27,7 @@ async def test_invokes_built_in_tools(self, ctx: E2ETestContext):
             {"on_permission_request": PermissionHandler.approve_all}
         )
 
-        await session.send({"prompt": "What's the first line of README.md in this directory?"})
+        await session.send("What's the first line of README.md in this directory?")
         assistant_message = await get_final_assistant_message(session)
         assert "ELIZA" in assistant_message.data.content
 
@@ -43,7 +43,7 @@ def encrypt_string(params: EncryptParams, invocation: ToolInvocation) -> str:
             {"tools": [encrypt_string], "on_permission_request": PermissionHandler.approve_all}
         )
 
-        await session.send({"prompt": "Use encrypt_string to encrypt this string: Hello"})
+        await session.send("Use encrypt_string to encrypt this string: Hello")
         assistant_message = await get_final_assistant_message(session)
         assert "HELLO" in assistant_message.data.content
 
@@ -56,9 +56,7 @@ def get_user_location() -> str:
             {"tools": [get_user_location], "on_permission_request": PermissionHandler.approve_all}
         )
 
-        await session.send(
-            {"prompt": "What is my location? If you can't find out, just say 'unknown'."}
-        )
+        await session.send("What is my location? If you can't find out, just say 'unknown'.")
         answer = await get_final_assistant_message(session)
 
         # Check the underlying traffic
@@ -123,10 +121,8 @@ def db_query(params: DbQueryParams, invocation: ToolInvocation) -> list[City]:
         expected_session_id = session.session_id
 
         await session.send(
-            {
-                "prompt": "Perform a DB query for the 'cities' table using IDs 12 and 19, "
-                "sorting ascending. Reply only with lines of the form: [cityname] [population]"
-            }
+            "Perform a DB query for the 'cities' table using IDs 12 and 19, "
+            "sorting ascending. Reply only with lines of the form: [cityname] [population]"
         )
 
         assistant_message = await get_final_assistant_message(session)
@@ -154,7 +150,7 @@ def custom_grep(params: GrepParams, invocation: ToolInvocation) -> str:
             {"tools": [custom_grep], "on_permission_request": PermissionHandler.approve_all}
         )
 
-        await session.send({"prompt": "Use grep to search for the word 'hello'"})
+        await session.send("Use grep to search for the word 'hello'")
         assistant_message = await get_final_assistant_message(session)
         assert "CUSTOM_GREP_RESULT" in assistant_message.data.content
 
@@ -179,7 +175,7 @@ def on_permission_request(request, invocation):
             }
         )
 
-        await session.send({"prompt": "Use encrypt_string to encrypt this string: Hello"})
+        await session.send("Use encrypt_string to encrypt this string: Hello")
         assistant_message = await get_final_assistant_message(session)
         assert "HELLO" in assistant_message.data.content
 
@@ -210,7 +206,7 @@ def on_permission_request(request, invocation):
             }
         )
 
-        await session.send({"prompt": "Use encrypt_string to encrypt this string: Hello"})
+        await session.send("Use encrypt_string to encrypt this string: Hello")
         await get_final_assistant_message(session)
 
         # The tool handler should NOT have been called since permission was denied
diff --git a/python/samples/chat.py b/python/samples/chat.py
index eb781e4e..908a125d 100644
--- a/python/samples/chat.py
+++ b/python/samples/chat.py
@@ -34,7 +34,7 @@ def on_event(event):
             continue
         print()
 
-        reply = await session.send_and_wait({"prompt": user_input})
+        reply = await session.send_and_wait(user_input)
         print(f"\nAssistant: {reply.data.content if reply else None}\n")
 
 
diff --git a/test/scenarios/auth/byok-anthropic/python/main.py b/test/scenarios/auth/byok-anthropic/python/main.py
index e50a33c1..8dbcd6bc 100644
--- a/test/scenarios/auth/byok-anthropic/python/main.py
+++ b/test/scenarios/auth/byok-anthropic/python/main.py
@@ -34,7 +34,7 @@ async def main():
         })
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:
diff --git a/test/scenarios/auth/byok-azure/python/main.py b/test/scenarios/auth/byok-azure/python/main.py
index 89f37178..9f37a719 100644
--- a/test/scenarios/auth/byok-azure/python/main.py
+++ b/test/scenarios/auth/byok-azure/python/main.py
@@ -38,7 +38,7 @@ async def main():
         })
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:
diff --git a/test/scenarios/auth/byok-ollama/python/main.py b/test/scenarios/auth/byok-ollama/python/main.py
index b86c76ba..fc59f173 100644
--- a/test/scenarios/auth/byok-ollama/python/main.py
+++ b/test/scenarios/auth/byok-ollama/python/main.py
@@ -32,7 +32,7 @@ async def main():
         })
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:
diff --git a/test/scenarios/auth/byok-openai/python/main.py b/test/scenarios/auth/byok-openai/python/main.py
index b501bb10..101c8db5 100644
--- a/test/scenarios/auth/byok-openai/python/main.py
+++ b/test/scenarios/auth/byok-openai/python/main.py
@@ -29,7 +29,7 @@ async def main():
         })
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:
diff --git a/test/scenarios/auth/gh-app/python/main.py b/test/scenarios/auth/gh-app/python/main.py
index 4886fe07..8e852558 100644
--- a/test/scenarios/auth/gh-app/python/main.py
+++ b/test/scenarios/auth/gh-app/python/main.py
@@ -85,7 +85,7 @@ async def main():
 
     try:
         session = await client.create_session({"model": "claude-haiku-4.5"})
-        response = await session.send_and_wait({"prompt": "What is the capital of France?"})
+        response = await session.send_and_wait("What is the capital of France?")
         if response:
             print(response.data.content)
         await session.disconnect()
diff --git a/test/scenarios/bundling/app-backend-to-server/python/main.py b/test/scenarios/bundling/app-backend-to-server/python/main.py
index 29563149..ca8473b2 100644
--- a/test/scenarios/bundling/app-backend-to-server/python/main.py
+++ b/test/scenarios/bundling/app-backend-to-server/python/main.py
@@ -18,7 +18,7 @@ async def ask_copilot(prompt: str) -> str:
     try:
         session = await client.create_session({"model": "claude-haiku-4.5"})
 
-        response = await session.send_and_wait({"prompt": prompt})
+        response = await session.send_and_wait(prompt)
 
         await session.disconnect()
 
diff --git a/test/scenarios/bundling/app-direct-server/python/main.py b/test/scenarios/bundling/app-direct-server/python/main.py
index c407d4fe..a180f213 100644
--- a/test/scenarios/bundling/app-direct-server/python/main.py
+++ b/test/scenarios/bundling/app-direct-server/python/main.py
@@ -12,7 +12,7 @@ async def main():
         session = await client.create_session({"model": "claude-haiku-4.5"})
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:
diff --git a/test/scenarios/bundling/container-proxy/python/main.py b/test/scenarios/bundling/container-proxy/python/main.py
index c407d4fe..a180f213 100644
--- a/test/scenarios/bundling/container-proxy/python/main.py
+++ b/test/scenarios/bundling/container-proxy/python/main.py
@@ -12,7 +12,7 @@ async def main():
         session = await client.create_session({"model": "claude-haiku-4.5"})
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:
diff --git a/test/scenarios/bundling/fully-bundled/python/main.py b/test/scenarios/bundling/fully-bundled/python/main.py
index d1441361..1a488c05 100644
--- a/test/scenarios/bundling/fully-bundled/python/main.py
+++ b/test/scenarios/bundling/fully-bundled/python/main.py
@@ -13,7 +13,7 @@ async def main():
         session = await client.create_session({"model": "claude-haiku-4.5"})
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:
diff --git a/test/scenarios/callbacks/hooks/python/main.py b/test/scenarios/callbacks/hooks/python/main.py
index 8df61b9d..9c2b141a 100644
--- a/test/scenarios/callbacks/hooks/python/main.py
+++ b/test/scenarios/callbacks/hooks/python/main.py
@@ -62,9 +62,7 @@ async def main():
         )
 
         response = await session.send_and_wait(
-            {
-                "prompt": "List the files in the current directory using the glob tool with pattern '*.md'.",
-            }
+            "List the files in the current directory using the glob tool with pattern '*.md'."
         )
 
         if response:
diff --git a/test/scenarios/callbacks/permissions/python/main.py b/test/scenarios/callbacks/permissions/python/main.py
index 9674da91..e5bd5cd7 100644
--- a/test/scenarios/callbacks/permissions/python/main.py
+++ b/test/scenarios/callbacks/permissions/python/main.py
@@ -31,9 +31,7 @@ async def main():
         )
 
         response = await session.send_and_wait(
-            {
-                "prompt": "List the files in the current directory using glob with pattern '*.md'."
-            }
+            "List the files in the current directory using glob with pattern '*.md'."
         )
 
         if response:
diff --git a/test/scenarios/callbacks/user-input/python/main.py b/test/scenarios/callbacks/user-input/python/main.py
index dc8d9fa9..be282d67 100644
--- a/test/scenarios/callbacks/user-input/python/main.py
+++ b/test/scenarios/callbacks/user-input/python/main.py
@@ -36,12 +36,8 @@ async def main():
         )
 
         response = await session.send_and_wait(
-            {
-                "prompt": (
-                    "I want to learn about a city. Use the ask_user tool to ask me "
-                    "which city I'm interested in. Then tell me about that city."
-                )
-            }
+            "I want to learn about a city. Use the ask_user tool to ask me "
+            "which city I'm interested in. Then tell me about that city."
         )
 
         if response:
diff --git a/test/scenarios/modes/default/python/main.py b/test/scenarios/modes/default/python/main.py
index dadc0e7b..0b06e321 100644
--- a/test/scenarios/modes/default/python/main.py
+++ b/test/scenarios/modes/default/python/main.py
@@ -14,7 +14,7 @@ async def main():
             "model": "claude-haiku-4.5",
         })
 
-        response = await session.send_and_wait({"prompt": "Use the grep tool to search for the word 'SDK' in README.md and show the matching lines."})
+        response = await session.send_and_wait("Use the grep tool to search for the word 'SDK' in README.md and show the matching lines.")
         if response:
             print(f"Response: {response.data.content}")
 
diff --git a/test/scenarios/modes/minimal/python/main.py b/test/scenarios/modes/minimal/python/main.py
index 0b243caf..dd249829 100644
--- a/test/scenarios/modes/minimal/python/main.py
+++ b/test/scenarios/modes/minimal/python/main.py
@@ -19,7 +19,7 @@ async def main():
             },
         })
 
-        response = await session.send_and_wait({"prompt": "Use the grep tool to search for 'SDK' in README.md."})
+        response = await session.send_and_wait("Use the grep tool to search for 'SDK' in README.md.")
         if response:
             print(f"Response: {response.data.content}")
 
diff --git a/test/scenarios/prompts/attachments/python/main.py b/test/scenarios/prompts/attachments/python/main.py
index c7e21e8b..077bdfd2 100644
--- a/test/scenarios/prompts/attachments/python/main.py
+++ b/test/scenarios/prompts/attachments/python/main.py
@@ -24,10 +24,8 @@ async def main():
         sample_file = os.path.abspath(sample_file)
 
         response = await session.send_and_wait(
-            {
-                "prompt": "What languages are listed in the attached file?",
-                "attachments": [{"type": "file", "path": sample_file}],
-            }
+            "What languages are listed in the attached file?",
+            attachments=[{"type": "file", "path": sample_file}],
         )
 
         if response:
diff --git a/test/scenarios/prompts/reasoning-effort/python/main.py b/test/scenarios/prompts/reasoning-effort/python/main.py
index b38452a8..fdbea369 100644
--- a/test/scenarios/prompts/reasoning-effort/python/main.py
+++ b/test/scenarios/prompts/reasoning-effort/python/main.py
@@ -21,7 +21,7 @@ async def main():
         })
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:
diff --git a/test/scenarios/prompts/system-message/python/main.py b/test/scenarios/prompts/system-message/python/main.py
index 5e396c8c..65df015d 100644
--- a/test/scenarios/prompts/system-message/python/main.py
+++ b/test/scenarios/prompts/system-message/python/main.py
@@ -21,7 +21,7 @@ async def main():
         )
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:
diff --git a/test/scenarios/sessions/concurrent-sessions/python/main.py b/test/scenarios/sessions/concurrent-sessions/python/main.py
index ebca8990..bda15834 100644
--- a/test/scenarios/sessions/concurrent-sessions/python/main.py
+++ b/test/scenarios/sessions/concurrent-sessions/python/main.py
@@ -32,10 +32,10 @@ async def main():
 
         response1, response2 = await asyncio.gather(
             session1.send_and_wait(
-                {"prompt": "What is the capital of France?"}
+                "What is the capital of France?"
             ),
             session2.send_and_wait(
-                {"prompt": "What is the capital of France?"}
+                "What is the capital of France?"
             ),
         )
 
diff --git a/test/scenarios/sessions/infinite-sessions/python/main.py b/test/scenarios/sessions/infinite-sessions/python/main.py
index 23749d06..c944e8a8 100644
--- a/test/scenarios/sessions/infinite-sessions/python/main.py
+++ b/test/scenarios/sessions/infinite-sessions/python/main.py
@@ -31,7 +31,7 @@ async def main():
         ]
 
         for prompt in prompts:
-            response = await session.send_and_wait({"prompt": prompt})
+            response = await session.send_and_wait(prompt)
             if response:
                 print(f"Q: {prompt}")
                 print(f"A: {response.data.content}\n")
diff --git a/test/scenarios/sessions/session-resume/python/main.py b/test/scenarios/sessions/session-resume/python/main.py
index 7eb5e0ca..768f7860 100644
--- a/test/scenarios/sessions/session-resume/python/main.py
+++ b/test/scenarios/sessions/session-resume/python/main.py
@@ -20,7 +20,7 @@ async def main():
 
         # 2. Send the secret word
         await session.send_and_wait(
-            {"prompt": "Remember this: the secret word is PINEAPPLE."}
+            "Remember this: the secret word is PINEAPPLE."
         )
 
         # 3. Get the session ID (don't disconnect — resume needs the session to persist)
@@ -32,7 +32,7 @@ async def main():
 
         # 5. Ask for the secret word
         response = await resumed.send_and_wait(
-            {"prompt": "What was the secret word I told you?"}
+            "What was the secret word I told you?"
         )
 
         if response:
diff --git a/test/scenarios/sessions/streaming/python/main.py b/test/scenarios/sessions/streaming/python/main.py
index 94569de1..3a05143f 100644
--- a/test/scenarios/sessions/streaming/python/main.py
+++ b/test/scenarios/sessions/streaming/python/main.py
@@ -27,7 +27,7 @@ def on_event(event):
         session.on(on_event)
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:
diff --git a/test/scenarios/tools/custom-agents/python/main.py b/test/scenarios/tools/custom-agents/python/main.py
index 0b5f073d..1b1b042f 100644
--- a/test/scenarios/tools/custom-agents/python/main.py
+++ b/test/scenarios/tools/custom-agents/python/main.py
@@ -26,7 +26,7 @@ async def main():
         )
 
         response = await session.send_and_wait(
-            {"prompt": "What custom agents are available? Describe the researcher agent and its capabilities."}
+            "What custom agents are available? Describe the researcher agent and its capabilities."
         )
 
         if response:
diff --git a/test/scenarios/tools/mcp-servers/python/main.py b/test/scenarios/tools/mcp-servers/python/main.py
index f092fb9a..0ba370f3 100644
--- a/test/scenarios/tools/mcp-servers/python/main.py
+++ b/test/scenarios/tools/mcp-servers/python/main.py
@@ -36,7 +36,7 @@ async def main():
         session = await client.create_session(session_config)
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:
diff --git a/test/scenarios/tools/no-tools/python/main.py b/test/scenarios/tools/no-tools/python/main.py
index a3824bab..f2d41004 100644
--- a/test/scenarios/tools/no-tools/python/main.py
+++ b/test/scenarios/tools/no-tools/python/main.py
@@ -24,7 +24,7 @@ async def main():
         )
 
         response = await session.send_and_wait(
-            {"prompt": "Use the bash tool to run 'echo hello'."}
+            "Use the bash tool to run 'echo hello'."
         )
 
         if response:
diff --git a/test/scenarios/tools/skills/python/main.py b/test/scenarios/tools/skills/python/main.py
index 3e06650b..c2e9f4c3 100644
--- a/test/scenarios/tools/skills/python/main.py
+++ b/test/scenarios/tools/skills/python/main.py
@@ -26,7 +26,7 @@ async def main():
         )
 
         response = await session.send_and_wait(
-            {"prompt": "Use the greeting skill to greet someone named Alice."}
+            "Use the greeting skill to greet someone named Alice."
         )
 
         if response:
diff --git a/test/scenarios/tools/tool-filtering/python/main.py b/test/scenarios/tools/tool-filtering/python/main.py
index 1fdfacc7..475892f6 100644
--- a/test/scenarios/tools/tool-filtering/python/main.py
+++ b/test/scenarios/tools/tool-filtering/python/main.py
@@ -21,7 +21,7 @@ async def main():
         )
 
         response = await session.send_and_wait(
-            {"prompt": "What tools do you have available? List each one by name."}
+            "What tools do you have available? List each one by name."
         )
 
         if response:
diff --git a/test/scenarios/tools/tool-overrides/python/main.py b/test/scenarios/tools/tool-overrides/python/main.py
index 1f1099f0..bac950ca 100644
--- a/test/scenarios/tools/tool-overrides/python/main.py
+++ b/test/scenarios/tools/tool-overrides/python/main.py
@@ -31,7 +31,7 @@ async def main():
         )
 
         response = await session.send_and_wait(
-            {"prompt": "Use grep to search for the word 'hello'"}
+            "Use grep to search for the word 'hello'"
         )
 
         if response:
diff --git a/test/scenarios/tools/virtual-filesystem/python/main.py b/test/scenarios/tools/virtual-filesystem/python/main.py
index 9a51e7ef..12af5746 100644
--- a/test/scenarios/tools/virtual-filesystem/python/main.py
+++ b/test/scenarios/tools/virtual-filesystem/python/main.py
@@ -63,12 +63,8 @@ async def main():
         )
 
         response = await session.send_and_wait(
-            {
-                "prompt": (
-                    "Create a file called plan.md with a brief 3-item project plan "
-                    "for building a CLI tool. Then read it back and tell me what you wrote."
-                )
-            }
+            "Create a file called plan.md with a brief 3-item project plan "
+            "for building a CLI tool. Then read it back and tell me what you wrote."
         )
 
         if response:
diff --git a/test/scenarios/transport/reconnect/python/main.py b/test/scenarios/transport/reconnect/python/main.py
index 1b82b109..0005e0c1 100644
--- a/test/scenarios/transport/reconnect/python/main.py
+++ b/test/scenarios/transport/reconnect/python/main.py
@@ -15,7 +15,7 @@ async def main():
         session1 = await client.create_session({"model": "claude-haiku-4.5"})
 
         response1 = await session1.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response1 and response1.data.content:
@@ -32,7 +32,7 @@ async def main():
         session2 = await client.create_session({"model": "claude-haiku-4.5"})
 
         response2 = await session2.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response2 and response2.data.content:
diff --git a/test/scenarios/transport/stdio/python/main.py b/test/scenarios/transport/stdio/python/main.py
index d1441361..1a488c05 100644
--- a/test/scenarios/transport/stdio/python/main.py
+++ b/test/scenarios/transport/stdio/python/main.py
@@ -13,7 +13,7 @@ async def main():
         session = await client.create_session({"model": "claude-haiku-4.5"})
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:
diff --git a/test/scenarios/transport/tcp/python/main.py b/test/scenarios/transport/tcp/python/main.py
index c407d4fe..a180f213 100644
--- a/test/scenarios/transport/tcp/python/main.py
+++ b/test/scenarios/transport/tcp/python/main.py
@@ -12,7 +12,7 @@ async def main():
         session = await client.create_session({"model": "claude-haiku-4.5"})
 
         response = await session.send_and_wait(
-            {"prompt": "What is the capital of France?"}
+            "What is the capital of France?"
         )
 
         if response:

From 3f683e31c36257b98a701c869a00fbca42339959 Mon Sep 17 00:00:00 2001
From: Brett Cannon <brett@python.org>
Date: Fri, 13 Mar 2026 11:45:53 -0700
Subject: [PATCH 2/3] Fix some code that didn't get migrated from the last
 merge with main

---
 python/e2e/test_tools.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/python/e2e/test_tools.py b/python/e2e/test_tools.py
index 7a738303..5d5823d9 100644
--- a/python/e2e/test_tools.py
+++ b/python/e2e/test_tools.py
@@ -157,7 +157,7 @@ def tracking_handler(request, invocation):
             {"tools": [safe_lookup], "on_permission_request": tracking_handler}
         )
 
-        await session.send({"prompt": "Use safe_lookup to look up 'test123'"})
+        await session.send("Use safe_lookup to look up 'test123'")
         assistant_message = await get_final_assistant_message(session)
         assert "RESULT: test123" in assistant_message.data.content
         assert not did_run_permission_request

From 7a8942dcb679a15be1c2d31459bb5835a6685b7c Mon Sep 17 00:00:00 2001
From: Brett Cannon <brett@python.org>
Date: Fri, 13 Mar 2026 11:59:33 -0700
Subject: [PATCH 3/3] Add better typing

---
 python/copilot/session.py | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/python/copilot/session.py b/python/copilot/session.py
index a2c91a2f..e4a17f2f 100644
--- a/python/copilot/session.py
+++ b/python/copilot/session.py
@@ -9,7 +9,7 @@
 import inspect
 import threading
 from collections.abc import Callable
-from typing import Any, cast
+from typing import Any, Literal, cast
 
 from .generated.rpc import (
     Kind,
@@ -26,6 +26,7 @@
 from .jsonrpc import JsonRpcError, ProcessExitedError
 from .telemetry import get_trace_context, trace_context
 from .types import (
+    Attachment,
     PermissionRequest,
     PermissionRequestResult,
     SessionHooks,
@@ -119,14 +120,15 @@ async def send(
         self,
         prompt: str,
         *,
-        attachments: list[Any] | None = None,
-        mode: str | None = None,
+        attachments: list[Attachment] | None = None,
+        mode: Literal["enqueue", "immediate"] | None = None,
     ) -> str:
         """
-        Send a message to this session and wait for the response.
+        Send a message to this session.
 
         The message is processed asynchronously. Subscribe to events via :meth:`on`
-        to receive streaming responses and other session events.
+        to receive streaming responses and other session events. Use
+        :meth:`send_and_wait` to block until the assistant finishes processing.
 
         Args:
             prompt: The message text to send.
@@ -134,7 +136,7 @@ async def send(
             mode: Message delivery mode (``"enqueue"`` or ``"immediate"``).
 
         Returns:
-            The message ID of the response, which can be used to correlate events.
+            The message ID assigned by the server, which can be used to correlate events.
 
         Raises:
             Exception: If the session has been disconnected or the connection fails.
@@ -162,8 +164,8 @@ async def send_and_wait(
         self,
         prompt: str,
         *,
-        attachments: list[Any] | None = None,
-        mode: str | None = None,
+        attachments: list[Attachment] | None = None,
+        mode: Literal["enqueue", "immediate"] | None = None,
         timeout: float = 60.0,
     ) -> SessionEvent | None:
         """