diff --git a/libs/sdk-py/langgraph_sdk/_sync/stream.py b/libs/sdk-py/langgraph_sdk/_sync/stream.py
index 8e4415258..3b338d99d 100644
--- a/libs/sdk-py/langgraph_sdk/_sync/stream.py
+++ b/libs/sdk-py/langgraph_sdk/_sync/stream.py
@@ -12,11 +12,13 @@ Sync mirror of `libs/sdk-py/langgraph_sdk/_async/stream.py`.
 from __future__ import annotations
 
 import contextlib
+import queue
 import threading
 from collections.abc import Iterator, Mapping
 from dataclasses import dataclass
 from typing import Any, Literal, TypedDict
 
+from langchain_core.language_models.chat_model_stream import ChatModelStream
 from langchain_protocol import Event, SubscribeParams
 
 from langgraph_sdk._sync.http import SyncHttpClient
@@ -56,6 +58,42 @@ _ALL_CHANNELS: list[str] = [
 ]
 
 
+def _exact_namespace_params(
+    channels: list[str],
+    namespace: list[str],
+) -> SubscribeParams:
+    return {
+        "channels": channels,
+        "namespaces": [list(namespace)],
+        "depth": 0,
+    }
+
+
+def _event_namespace(params_field: Any) -> list[str]:
+    if not isinstance(params_field, dict):
+        return []
+    namespace = params_field.get("namespace") or []
+    return list(namespace) if isinstance(namespace, list) else []
+
+
+def _message_event_id(data: dict[str, Any]) -> str | None:
+    message_id = data.get("id") or data.get("message_id")
+    return str(message_id) if message_id is not None else None
+
+
+def _message_route_key(data: dict[str, Any], fallback: str | None = None) -> str:
+    metadata = data.get("metadata") if isinstance(data.get("metadata"), dict) else {}
+    run_id = metadata.get("run_id") if metadata else None
+    message_id = _message_event_id(data)
+    if run_id is not None:
+        return f"run:{run_id}"
+    if message_id is not None:
+        return f"message:{message_id}"
+    if fallback is not None:
+        return f"message:{fallback}"
+    return "__single__"
+
+
 class _BlockingResult:
     def __init__(self) -> None:
         self._event = threading.Event()
@@ -209,6 +247,398 @@ class _SyncValuesProjection:
             self._thread._unregister_subscription(sub.id)
 
 
+class _SyncMessagesProjection:
+    """Typed projection for root-scope `thread.messages`.
+
+    Iterating yields one `ChatModelStream` per message-start event. Each
+    stream is fully dispatched before being yielded so that `str(message.text)`
+    works immediately inside a `for` loop.
+    """
+
+    def __init__(
+        self, thread: SyncThreadStream, namespace: list[str] | None = None
+    ) -> None:
+        self._thread = thread
+        self._namespace = list(namespace or [])
+
+    def __iter__(self) -> Iterator[ChatModelStream]:
+        return self._messages_iter()
+
+    def _messages_iter(self) -> Iterator[ChatModelStream]:
+        if self._thread._transport is None:
+            raise RuntimeError("SyncThreadStream not entered — use `with`.")
+        root_inbox = self._thread._root_messages_inbox if not self._namespace else None
+        if root_inbox is not None:
+            yield from _drain_messages_inbox(root_inbox, self._namespace, self._thread)
+            return
+        params = _exact_namespace_params(["messages"], self._namespace)
+        sub = self._thread._register_subscription(params)
+        active: dict[str, ChatModelStream] = {}
+        try:
+            self._thread._reconcile_stream(params)
+            self._thread._ensure_fanout_running()
+            while True:
+                item = sub.queue.get()
+                if item is None:
+                    return
+                params_field = item.get("params") or {}
+                if _event_namespace(params_field) != self._namespace:
+                    continue
+                data = (
+                    params_field.get("data") if isinstance(params_field, dict) else None
+                )
+                if not isinstance(data, dict):
+                    continue
+                event_type = data.get("event")
+                if event_type == "message-start":
+                    message_id = _message_event_id(data)
+                    key = _message_route_key(data, fallback=message_id)
+                    metadata = (
+                        data.get("metadata")
+                        if isinstance(data.get("metadata"), dict)
+                        else {}
+                    )
+                    stream = ChatModelStream(
+                        namespace=list(self._namespace),
+                        node=metadata.get("langgraph_node") if metadata else None,
+                        message_id=message_id,
+                    )
+                    active[key] = stream
+                    self._thread._register_active_message_stream(stream)
+                    stream.dispatch(data)
+                    # Pre-dispatch all remaining events for this message so the
+                    # caller can access str(message.text) inside a for loop.
+                    while not stream._done:
+                        next_item = sub.queue.get()
+                        if next_item is None:
+                            sub.queue.put(None)
+                            break
+                        next_params = next_item.get("params") or {}
+                        next_data = (
+                            next_params.get("data")
+                            if isinstance(next_params, dict)
+                            else None
+                        )
+                        if not isinstance(next_data, dict):
+                            continue
+                        next_event_type = next_data.get("event")
+                        next_key = _message_route_key(next_data)
+                        target = active.get(next_key)
+                        if target is not None:
+                            target.dispatch(next_data)
+                            if next_event_type in ("message-finish", "error"):
+                                self._thread._unregister_active_message_stream(target)
+                                for rk, cand in list(active.items()):
+                                    if cand is target:
+                                        del active[rk]
+                    yield stream
+                else:
+                    key = _message_route_key(data)
+                    stream = active.get(key)
+                    if stream is None:
+                        # No active stream matches this event's key. Drop rather
+                        # than silently misroute to the only remaining stream.
+                        continue
+                    stream.dispatch(data)
+                    if event_type in ("message-finish", "error"):
+                        self._thread._unregister_active_message_stream(stream)
+                        for route_key, candidate in list(active.items()):
+                            if candidate is stream:
+                                del active[route_key]
+        finally:
+            for s in active.values():
+                self._thread._unregister_active_message_stream(s)
+            self._thread._unregister_subscription(sub.id)
+
+
+def _drain_messages_inbox(
+    inbox: queue.Queue[Event | None],
+    namespace: list[str],
+    thread: SyncThreadStream,
+) -> Iterator[ChatModelStream]:
+    """Drain a pre-filled inbox of messages events, yielding one stream per message.
+
+    Mirrors the pre-dispatch pattern in `_SyncMessagesProjection._messages_iter`:
+    each `message-start` triggers an inner loop that reads ahead until the stream
+    is `_done` before yielding, so callers can do `str(stream.text)` immediately.
+    """
+    active: dict[str, ChatModelStream] = {}
+    try:
+        while True:
+            item = inbox.get()
+            if item is None:
+                return
+            params_field = item.get("params") or {}
+            data = params_field.get("data") if isinstance(params_field, dict) else None
+            if not isinstance(data, dict):
+                continue
+            event_type = data.get("event")
+            if event_type == "message-start":
+                message_id = _message_event_id(data)
+                key = _message_route_key(data, fallback=message_id)
+                metadata = (
+                    data.get("metadata")
+                    if isinstance(data.get("metadata"), dict)
+                    else {}
+                )
+                stream = ChatModelStream(
+                    namespace=list(namespace),
+                    node=metadata.get("langgraph_node") if metadata else None,
+                    message_id=message_id,
+                )
+                active[key] = stream
+                thread._register_active_message_stream(stream)
+                stream.dispatch(data)
+                # Pre-dispatch all remaining events for this message so the
+                # caller can access str(stream.text) immediately inside a for loop.
+                while not stream._done:
+                    next_item = inbox.get()
+                    if next_item is None:
+                        inbox.put(None)
+                        break
+                    next_params = next_item.get("params") or {}
+                    next_data = (
+                        next_params.get("data")
+                        if isinstance(next_params, dict)
+                        else None
+                    )
+                    if not isinstance(next_data, dict):
+                        continue
+                    next_event_type = next_data.get("event")
+                    next_key = _message_route_key(next_data)
+                    target = active.get(next_key)
+                    if target is not None:
+                        target.dispatch(next_data)
+                        if next_event_type in ("message-finish", "error"):
+                            thread._unregister_active_message_stream(target)
+                            for rk, cand in list(active.items()):
+                                if cand is target:
+                                    del active[rk]
+                yield stream
+            else:
+                key = _message_route_key(data)
+                stream = active.get(key)
+                if stream is None:
+                    # No active stream matches this event's key. Drop rather
+                    # than silently misroute to the only remaining stream.
+                    continue
+                stream.dispatch(data)
+                if event_type in ("message-finish", "error"):
+                    thread._unregister_active_message_stream(stream)
+                    for route_key, candidate in list(active.items()):
+                        if candidate is stream:
+                            del active[route_key]
+    finally:
+        for s in active.values():
+            thread._unregister_active_message_stream(s)
+
+
+class SyncToolCallHandle:
+    """Sync handle for one root-scope tool call."""
+
+    def __init__(
+        self,
+        *,
+        tool_call_id: str,
+        name: str,
+        input: Any = None,
+        namespace: list[str] | None = None,
+        max_queue_size: int = 1024,
+    ) -> None:
+        self.tool_call_id = tool_call_id
+        self.name = name
+        self.input = input
+        self.namespace = list(namespace or [])
+        self.done = False
+        self.error: BaseException | None = None
+        self._result: _BlockingResult = _BlockingResult()
+        self._deltas: queue.Queue[str | None] = queue.Queue(maxsize=max_queue_size)
+        self._deltas_consumed: bool = False
+
+    @property
+    def output(self) -> Any:
+        """Block until the tool call completes and return its output."""
+        return self._result.result()
+
+    @property
+    def deltas(self) -> Iterator[str]:
+        """Iterate over tool output deltas emitted before the terminal event.
+
+        Raises:
+            RuntimeError: if called more than once — the underlying queue is
+                single-consumer and cannot be fanned out safely.
+        """
+        if self._deltas_consumed:
+            raise RuntimeError(
+                "SyncToolCallHandle.deltas can only be iterated by a single consumer."
+            )
+        self._deltas_consumed = True
+        return self._delta_iter()
+
+    def _delta_iter(self) -> Iterator[str]:
+        while True:
+            item = self._deltas.get()
+            if item is None:
+                return
+            yield item
+
+    def _push_delta(self, delta: str) -> None:
+        if self.done:
+            return
+        self._deltas.put_nowait(delta)
+
+    def _finish(self, output: Any) -> None:
+        if self.done:
+            return
+        self.done = True
+        self._result.set_result(output)
+        self._deltas.put_nowait(None)
+
+    def _fail(self, err: BaseException) -> None:
+        if self.done:
+            return
+        self.done = True
+        self.error = err
+        self._result.set_exception(err)
+        self._deltas.put_nowait(None)
+
+
+class _SyncToolCallsProjection:
+    """Typed projection for root-scope `thread.tool_calls`."""
+
+    def __init__(
+        self, thread: SyncThreadStream, namespace: list[str] | None = None
+    ) -> None:
+        self._thread = thread
+        self._namespace = list(namespace or [])
+
+    def __iter__(self) -> Iterator[SyncToolCallHandle]:
+        return self._tool_calls_iter()
+
+    def _tool_calls_iter(self) -> Iterator[SyncToolCallHandle]:
+        if self._thread._transport is None:
+            raise RuntimeError("SyncThreadStream not entered — use `with`.")
+        params = _exact_namespace_params(["tools"], self._namespace)
+        sub = self._thread._register_subscription(params)
+        active: dict[str, SyncToolCallHandle] = {}
+        try:
+            self._thread._reconcile_stream(params)
+            self._thread._ensure_fanout_running()
+            while True:
+                item = sub.queue.get()
+                if item is None:
+                    return
+                params_field = item.get("params") or {}
+                if _event_namespace(params_field) != self._namespace:
+                    continue
+                data = (
+                    params_field.get("data") if isinstance(params_field, dict) else None
+                )
+                if not isinstance(data, dict):
+                    continue
+                event_type = data.get("event")
+                tool_call_id = data.get("tool_call_id")
+                if not isinstance(tool_call_id, str):
+                    continue
+                if event_type == "tool-started":
+                    tool_name = data.get("tool_name")
+                    if not isinstance(tool_name, str):
+                        tool_name = ""
+                    handle = SyncToolCallHandle(
+                        tool_call_id=tool_call_id,
+                        name=tool_name,
+                        input=data.get("input"),
+                        namespace=list(self._namespace),
+                    )
+                    active[tool_call_id] = handle
+                    self._thread._register_active_tool_call(handle)
+                    # Pre-dispatch events until this tool call completes so that
+                    # `call.output` is resolved when the caller receives the handle.
+                    while not handle.done:
+                        next_item = sub.queue.get()
+                        if next_item is None:
+                            sub.queue.put(None)
+                            break
+                        next_params = next_item.get("params") or {}
+                        if _event_namespace(next_params) != self._namespace:
+                            continue
+                        next_data = (
+                            next_params.get("data")
+                            if isinstance(next_params, dict)
+                            else None
+                        )
+                        if not isinstance(next_data, dict):
+                            continue
+                        next_event_type = next_data.get("event")
+                        next_tcid = next_data.get("tool_call_id")
+                        if not isinstance(next_tcid, str):
+                            continue
+                        if next_event_type == "tool-output-delta":
+                            h = active.get(next_tcid)
+                            delta = next_data.get("delta")
+                            if h is not None and isinstance(delta, str):
+                                h._push_delta(delta)
+                        elif next_event_type == "tool-finished":
+                            h = active.pop(next_tcid, None)
+                            if h is not None:
+                                self._thread._unregister_active_tool_call(h)
+                                h._finish(next_data.get("output"))
+                        elif next_event_type == "tool-error":
+                            h = active.pop(next_tcid, None)
+                            if h is not None:
+                                self._thread._unregister_active_tool_call(h)
+                                message = next_data.get("message")
+                                h._fail(
+                                    RuntimeError(
+                                        str(message) if message else "Tool call errored"
+                                    )
+                                )
+                    yield handle
+                elif event_type == "tool-output-delta":
+                    h = active.get(tool_call_id)
+                    delta = data.get("delta")
+                    if h is not None and isinstance(delta, str):
+                        h._push_delta(delta)
+                elif event_type == "tool-finished":
+                    h = active.pop(tool_call_id, None)
+                    if h is not None:
+                        self._thread._unregister_active_tool_call(h)
+                        h._finish(data.get("output"))
+                elif event_type == "tool-error":
+                    h = active.pop(tool_call_id, None)
+                    if h is not None:
+                        self._thread._unregister_active_tool_call(h)
+                        message = data.get("message")
+                        h._fail(
+                            RuntimeError(
+                                str(message) if message else "Tool call errored"
+                            )
+                        )
+        finally:
+            # Read terminal error from _run_done if it is already resolved.
+            # We do NOT block here: callers who need a terminal observation
+            # should access `thread.output` directly. Blocking in iterator
+            # teardown would stall every early break or exception exit for
+            # up to the full wait timeout (previously 1 s).
+            run_done = self._thread._run_done
+            terminal_err: BaseException | None = None
+            if run_done is not None and run_done.done():
+                try:
+                    terminal = run_done.result()
+                    terminal_err = terminal.error
+                except Exception:
+                    pass
+            err: BaseException = (
+                terminal_err
+                if terminal_err is not None
+                else RuntimeError("Tool call stream closed before terminal tool event.")
+            )
+            for h in active.values():
+                self._thread._unregister_active_tool_call(h)
+                h._fail(err)
+            self._thread._unregister_subscription(sub.id)
+
+
 class SyncThreadStream:
     """Synchronous context manager for one thread's v3 streaming session.
 
@@ -243,8 +673,13 @@ class SyncThreadStream:
         self._lifecycle_watcher_handle: SyncEventStreamHandle | None = None
         self._run_seen: bool = False
         self._run_done: _BlockingResult | None = None
+        self._active_message_streams: set[ChatModelStream] = set()
+        self._active_tool_calls: set[SyncToolCallHandle] = set()
+        self._root_messages_inbox: queue.Queue[Event | None] | None = None
         self.run = SyncRunModule(self)
         self.values = _SyncValuesProjection(self)
+        self.messages = _SyncMessagesProjection(self, namespace=[])
+        self.tool_calls = _SyncToolCallsProjection(self, namespace=[])
 
     def __enter__(self) -> SyncThreadStream:
         if self._closed:
@@ -314,6 +749,8 @@ class SyncThreadStream:
         if thread is not None and thread.is_alive():
             with contextlib.suppress(RuntimeError):
                 thread.join(timeout=1.0)
+        self._fail_active_message_streams(RuntimeError("SyncThreadStream closed"))
+        self._fail_active_tool_calls(RuntimeError("SyncThreadStream closed"))
         if self._transport is not None:
             self._transport.close()
 
@@ -339,6 +776,33 @@ class SyncThreadStream:
             raise RuntimeError("SyncThreadStream not entered — use `with`.")
         self._controller.reconcile_stream(candidate_filter)
 
+    def _activate_root_messages_inbox(self) -> queue.Queue[Event | None]:
+        if self._root_messages_inbox is None:
+            self._root_messages_inbox = queue.Queue()
+        return self._root_messages_inbox
+
+    def _register_active_message_stream(self, stream: ChatModelStream) -> None:
+        self._active_message_streams.add(stream)
+
+    def _unregister_active_message_stream(self, stream: ChatModelStream) -> None:
+        self._active_message_streams.discard(stream)
+
+    def _fail_active_message_streams(self, err: BaseException) -> None:
+        for stream in list(self._active_message_streams):
+            stream.fail(err)
+        self._active_message_streams.clear()
+
+    def _register_active_tool_call(self, handle: SyncToolCallHandle) -> None:
+        self._active_tool_calls.add(handle)
+
+    def _unregister_active_tool_call(self, handle: SyncToolCallHandle) -> None:
+        self._active_tool_calls.discard(handle)
+
+    def _fail_active_tool_calls(self, err: BaseException) -> None:
+        for handle in list(self._active_tool_calls):
+            handle._fail(err)
+        self._active_tool_calls.clear()
+
     def subscribe(
         self,
         channels: list[str],
@@ -498,6 +962,8 @@ class SyncThreadStream:
                         error = RuntimeError(
                             f"Run errored: {error_msg}" if error_msg else "Run errored"
                         )
+                        self._fail_active_message_streams(error)
+                        self._fail_active_tool_calls(error)
                         run_done.set_result(_RunTerminal(status="errored", error=error))
                     else:
                         run_done.set_result(_RunTerminal(status="completed"))
diff --git a/libs/sdk-py/tests/streaming/_events.py b/libs/sdk-py/tests/streaming/_events.py
index 1ef35f7c4..201dda5db 100644
--- a/libs/sdk-py/tests/streaming/_events.py
+++ b/libs/sdk-py/tests/streaming/_events.py
@@ -77,9 +77,12 @@ def message_start_event(
     *,
     message_id: str = "msg-1",
     role: str = "ai",
-    run_id: str = "run-1",
+    run_id: str | None = None,
     node: str = "agent",
 ) -> dict[str, Any]:
+    metadata: dict[str, Any] = {"langgraph_node": node}
+    if run_id is not None:
+        metadata["run_id"] = run_id
     return _base(
         seq,
         "messages",
@@ -88,7 +91,7 @@ def message_start_event(
             "event": "message-start",
             "id": message_id,
             "role": role,
-            "metadata": {"run_id": run_id, "langgraph_node": node},
+            "metadata": metadata,
         },
     )
 
diff --git a/libs/sdk-py/tests/streaming/test_sync_projections.py b/libs/sdk-py/tests/streaming/test_sync_projections.py
index 0325ba793..09979bad2 100644
--- a/libs/sdk-py/tests/streaming/test_sync_projections.py
+++ b/libs/sdk-py/tests/streaming/test_sync_projections.py
@@ -2,11 +2,29 @@
 
 from __future__ import annotations
 
+from typing import cast
+
 import httpx
+import pytest
+from langchain_core.language_models.chat_model_stream import ChatModelStream
+from langchain_protocol import Event
 
 from langgraph_sdk._sync.http import SyncHttpClient
 from langgraph_sdk._sync.threads import SyncThreadsClient
-from streaming._events import lifecycle_completed_event
+from streaming._events import (
+    lifecycle_completed_event,
+    lifecycle_errored_event,
+    lifecycle_started_event,
+    message_error_event,
+    message_finish_event,
+    message_start_event,
+    message_text_delta_event,
+    message_text_finish_event,
+    tool_error_event,
+    tool_finished_event,
+    tool_output_delta_event,
+    tool_started_event,
+)
 from streaming._sync_fake_server import SyncFakeServer
 
 
@@ -23,3 +41,407 @@ def test_sync_values_first_yield_is_rest_state_and_output_returns_final_state():
 
     assert first == {"answer": 42}
     assert output == {"answer": 42}
+
+
+def test_sync_messages_yield_chat_model_stream():
+    fake = SyncFakeServer()
+    fake.script(
+        [
+            lifecycle_started_event(seq=0),
+            message_start_event(seq=1, message_id="msg-1"),
+            message_text_delta_event(seq=2, text="hi", message_id="msg-1"),
+            message_text_finish_event(seq=3, text="hi", message_id="msg-1"),
+            message_finish_event(seq=4, message_id="msg-1"),
+            lifecycle_completed_event(seq=5),
+        ]
+    )
+    with httpx.Client(transport=fake.transport, base_url="http://test") as raw:
+        threads = SyncThreadsClient(SyncHttpClient(raw))
+        with threads.stream(thread_id="t-1", assistant_id="agent") as thread:
+            thread.run.start(input={})
+            messages = list(thread.messages)
+
+    assert len(messages) == 1
+    assert isinstance(messages[0], ChatModelStream)
+    assert messages[0].message_id == "msg-1"
+    assert str(messages[0].text) == "hi"
+    assert messages[0].output.id == "msg-1"
+
+
+def test_sync_tool_calls_yield_handle_deltas_and_output():
+    fake = SyncFakeServer()
+    fake.script(
+        [
+            lifecycle_started_event(seq=0),
+            tool_started_event(seq=1, tool_call_id="call-1", tool_name="search"),
+            tool_output_delta_event(seq=2, tool_call_id="call-1", delta="a"),
+            tool_output_delta_event(seq=3, tool_call_id="call-1", delta="b"),
+            tool_finished_event(seq=4, tool_call_id="call-1", output={"ok": True}),
+            lifecycle_completed_event(seq=5),
+        ]
+    )
+    with httpx.Client(transport=fake.transport, base_url="http://test") as raw:
+        threads = SyncThreadsClient(SyncHttpClient(raw))
+        with threads.stream(thread_id="t-1", assistant_id="agent") as thread:
+            thread.run.start(input={})
+            calls = list(thread.tool_calls)
+
+    assert [call.tool_call_id for call in calls] == ["call-1"]
+    assert list(calls[0].deltas) == ["a", "b"]
+    assert calls[0].output == {"ok": True}
+
+
+# ---------------------------------------------------------------------------
+# Task 10.6 — messages pre-dispatch inner loop must filter by namespace
+# ---------------------------------------------------------------------------
+
+
+def test_sync_messages_ignores_nested_namespace_for_root_projection():
+    """Root projection must not yield messages from child namespaces."""
+    fake = SyncFakeServer()
+    fake.script(
+        [
+            lifecycle_started_event(seq=0),
+            message_start_event(seq=1, namespace=["child:1"], message_id="nested"),
+            message_text_delta_event(seq=2, namespace=["child:1"], text="nested"),
+            message_finish_event(seq=3, namespace=["child:1"]),
+            lifecycle_completed_event(seq=4),
+        ]
+    )
+    with httpx.Client(transport=fake.transport, base_url="http://test") as raw:
+        threads = SyncThreadsClient(SyncHttpClient(raw))
+        with threads.stream(thread_id="t-1", assistant_id="agent") as thread:
+            thread.run.start(input={})
+            messages = list(thread.messages)
+
+    assert messages == []
+
+
+# ---------------------------------------------------------------------------
+# Task 10.7 — comprehensive sync messages projection tests
+# ---------------------------------------------------------------------------
+
+
+def test_sync_messages_multiple_messages_are_distinct_streams():
+    """Two sequential messages produce two separate ChatModelStream objects."""
+    fake = SyncFakeServer()
+    fake.script(
+        [
+            lifecycle_started_event(seq=0),
+            message_start_event(seq=1, message_id="msg-1"),
+            message_text_delta_event(seq=2, text="one", message_id="msg-1"),
+            message_text_finish_event(seq=3, text="one", message_id="msg-1"),
+            message_finish_event(seq=4, message_id="msg-1"),
+            message_start_event(seq=5, message_id="msg-2"),
+            message_text_delta_event(seq=6, text="two", message_id="msg-2"),
+            message_text_finish_event(seq=7, text="two", message_id="msg-2"),
+            message_finish_event(seq=8, message_id="msg-2"),
+            lifecycle_completed_event(seq=9),
+        ]
+    )
+    with httpx.Client(transport=fake.transport, base_url="http://test") as raw:
+        threads = SyncThreadsClient(SyncHttpClient(raw))
+        with threads.stream(thread_id="t-1", assistant_id="agent") as thread:
+            thread.run.start(input={})
+            streams = list(thread.messages)
+
+    assert [s.message_id for s in streams] == ["msg-1", "msg-2"]
+    assert [str(s.text) for s in streams] == ["one", "two"]
+
+
+def test_sync_messages_error_event_fails_active_stream():
+    """A messages `error` event marks the stream as failed."""
+    fake = SyncFakeServer()
+    fake.script(
+        [
+            lifecycle_started_event(seq=0),
+            message_start_event(seq=1, message_id="msg-1"),
+            message_error_event(seq=2, message="model failed", message_id="msg-1"),
+            lifecycle_completed_event(seq=3),
+        ]
+    )
+    with httpx.Client(transport=fake.transport, base_url="http://test") as raw:
+        threads = SyncThreadsClient(SyncHttpClient(raw))
+        with threads.stream(thread_id="t-1", assistant_id="agent") as thread:
+            thread.run.start(input={})
+            streams = list(thread.messages)
+
+    assert len(streams) == 1
+    with pytest.raises(RuntimeError, match="model failed"):
+        _ = streams[0].output
+
+
+# ---------------------------------------------------------------------------
+# Task 10.7 — comprehensive sync tool_calls projection tests
+# ---------------------------------------------------------------------------
+
+
+def test_sync_tool_calls_multiple_concurrent_calls_route_by_id():
+    """Two interleaved tool calls each resolve to the correct output."""
+    fake = SyncFakeServer()
+    fake.script(
+        [
+            lifecycle_started_event(seq=0),
+            tool_started_event(seq=1, tool_call_id="call-a", tool_name="alpha"),
+            tool_output_delta_event(seq=2, tool_call_id="call-a", delta="a1"),
+            tool_finished_event(seq=3, tool_call_id="call-a", output="A"),
+            tool_started_event(seq=4, tool_call_id="call-b", tool_name="beta"),
+            tool_output_delta_event(seq=5, tool_call_id="call-b", delta="b1"),
+            tool_finished_event(seq=6, tool_call_id="call-b", output="B"),
+            lifecycle_completed_event(seq=7),
+        ]
+    )
+    with httpx.Client(transport=fake.transport, base_url="http://test") as raw:
+        threads = SyncThreadsClient(SyncHttpClient(raw))
+        with threads.stream(thread_id="t-1", assistant_id="agent") as thread:
+            thread.run.start(input={})
+            calls = list(thread.tool_calls)
+
+    by_id = {call.tool_call_id: call for call in calls}
+    assert set(by_id) == {"call-a", "call-b"}
+    assert list(by_id["call-a"].deltas) == ["a1"]
+    assert list(by_id["call-b"].deltas) == ["b1"]
+    assert by_id["call-a"].output == "A"
+    assert by_id["call-b"].output == "B"
+
+
+def test_sync_tool_calls_ignores_nested_namespace_for_root_projection():
+    """Root tool_calls projection must not yield handles from child namespaces."""
+    fake = SyncFakeServer()
+    fake.script(
+        [
+            lifecycle_started_event(seq=0),
+            tool_started_event(seq=1, namespace=["child:1"], tool_call_id="nested"),
+            tool_finished_event(seq=2, namespace=["child:1"], tool_call_id="nested"),
+            lifecycle_completed_event(seq=3),
+        ]
+    )
+    with httpx.Client(transport=fake.transport, base_url="http://test") as raw:
+        threads = SyncThreadsClient(SyncHttpClient(raw))
+        with threads.stream(thread_id="t-1", assistant_id="agent") as thread:
+            thread.run.start(input={})
+            calls = list(thread.tool_calls)
+
+    assert calls == []
+
+
+def test_sync_tool_calls_error_event_fails_output():
+    """A `tool-error` event fails the handle's output property."""
+    fake = SyncFakeServer()
+    fake.script(
+        [
+            lifecycle_started_event(seq=0),
+            tool_started_event(seq=1, tool_call_id="call-1"),
+            tool_output_delta_event(seq=2, tool_call_id="call-1", delta="before"),
+            tool_error_event(seq=3, tool_call_id="call-1", message="boom"),
+            lifecycle_completed_event(seq=4),
+        ]
+    )
+    with httpx.Client(transport=fake.transport, base_url="http://test") as raw:
+        threads = SyncThreadsClient(SyncHttpClient(raw))
+        with threads.stream(thread_id="t-1", assistant_id="agent") as thread:
+            thread.run.start(input={})
+            calls = list(thread.tool_calls)
+
+    assert len(calls) == 1
+    assert list(calls[0].deltas) == ["before"]
+    with pytest.raises(RuntimeError, match="boom"):
+        _ = calls[0].output
+
+
+# ---------------------------------------------------------------------------
+# Task 10.10 — run-error propagates to active tool-call handle
+# ---------------------------------------------------------------------------
+
+
+def test_sync_tool_calls_run_error_fails_active_handle():
+    """A lifecycle errored event propagates its message to the active handle."""
+    fake = SyncFakeServer()
+    fake.script(
+        [
+            lifecycle_started_event(seq=0),
+            tool_started_event(seq=1, tool_call_id="call-1"),
+            tool_output_delta_event(seq=2, tool_call_id="call-1", delta="partial"),
+            lifecycle_errored_event(seq=3, error="run failed"),
+        ]
+    )
+    with httpx.Client(transport=fake.transport, base_url="http://test") as raw:
+        threads = SyncThreadsClient(SyncHttpClient(raw))
+        with threads.stream(thread_id="t-1", assistant_id="agent") as thread:
+            thread.run.start(input={})
+            calls = list(thread.tool_calls)
+
+    assert len(calls) == 1
+    with pytest.raises(RuntimeError, match="Run errored: run failed"):
+        _ = calls[0].output
+
+
+# ---------------------------------------------------------------------------
+# Task 10.9 — _drain_messages_inbox must pre-dispatch before yielding
+# ---------------------------------------------------------------------------
+
+
+def test_sync_drain_messages_inbox_pre_dispatches_before_yield():
+    """When draining the root inbox, str(message.text) must work immediately on yield."""
+    fake = SyncFakeServer()
+    fake.script([lifecycle_completed_event(seq=10)])
+    fake.set_state({})
+    collected_texts: list[str] = []
+    with httpx.Client(transport=fake.transport, base_url="http://test") as raw:
+        threads = SyncThreadsClient(SyncHttpClient(raw))
+        with threads.stream(thread_id="t-1", assistant_id="agent") as thread:
+            # Activate the root inbox and populate it directly (simulating what
+            # a sync _SubgraphsProjection would do).
+            inbox = thread._activate_root_messages_inbox()
+            inbox.put(
+                cast(
+                    Event,
+                    message_start_event(seq=1, message_id="msg-x"),
+                )
+            )
+            inbox.put(
+                cast(
+                    Event,
+                    message_text_delta_event(seq=2, text="hello", message_id="msg-x"),
+                )
+            )
+            inbox.put(
+                cast(
+                    Event,
+                    message_text_finish_event(seq=3, text="hello", message_id="msg-x"),
+                )
+            )
+            inbox.put(cast(Event, message_finish_event(seq=4, message_id="msg-x")))
+            inbox.put(None)  # EOF sentinel
+
+            # Read text immediately inside the for loop — this requires pre-dispatch.
+            for stream in thread.messages:
+                collected_texts.append(str(stream.text))
+
+    assert collected_texts == ["hello"]
+
+
+# ---------------------------------------------------------------------------
+# Fix A — remove blocking 1s wait in tool_calls iterator finally
+# ---------------------------------------------------------------------------
+
+
+def test_sync_tool_calls_explicit_close_does_not_block_1s():
+    """Closing the tool_calls iterator must return in <200ms even without a terminal event.
+
+    The prior finally block called `run_done.result(timeout=1.0)` unconditionally,
+    causing a mandatory 1-second stall whenever the caller breaks out of the
+    iterator before a lifecycle terminal event arrives.
+    """
+    fake = SyncFakeServer()
+    # Script has a started lifecycle and one tool, but NO terminal lifecycle event.
+    # If the blocking wait is present, the iterator's finally will stall for 1s.
+    fake.script(
+        [
+            lifecycle_started_event(seq=0),
+            tool_started_event(seq=1, tool_call_id="call-1"),
+        ]
+    )
+    import time
+    from collections.abc import Generator
+    from typing import cast
+
+    from langgraph_sdk._sync.stream import SyncToolCallHandle
+
+    with httpx.Client(transport=fake.transport, base_url="http://test") as raw:
+        threads = SyncThreadsClient(SyncHttpClient(raw))
+        with threads.stream(thread_id="t-1", assistant_id="agent") as thread:
+            thread.run.start(input={})
+            gen = cast(
+                Generator[SyncToolCallHandle, None, None],
+                thread.tool_calls._tool_calls_iter(),
+            )
+            _handle = next(gen)  # receive the one tool-started handle
+            start = time.monotonic()
+            # Explicitly close the generator — must not stall 1s.
+            gen.close()
+            elapsed = time.monotonic() - start
+
+    assert elapsed < 0.2, f"tool_calls close() took {elapsed:.3f}s (expected <0.2s)"
+
+
+# ---------------------------------------------------------------------------
+# Fix B — drop len(active)==1 silent message routing fallback
+# ---------------------------------------------------------------------------
+
+
+def test_sync_messages_orphan_delta_without_matching_key_is_dropped():
+    """A delta whose message_id doesn't match any active stream must be dropped.
+
+    The old code fell back to routing the event to the only active stream when
+    `len(active) == 1`, causing orphan/mismatched deltas to silently corrupt
+    an unrelated stream's content.
+    """
+    fake = SyncFakeServer()
+    fake.script(
+        [
+            lifecycle_started_event(seq=0),
+            message_start_event(seq=1, message_id="msg-A"),
+            # Delta with a mismatched message_id — must be dropped, not routed to msg-A.
+            message_text_delta_event(seq=2, text="orphan", message_id="msg-UNKNOWN"),
+            message_text_delta_event(seq=3, text="real", message_id="msg-A"),
+            message_finish_event(seq=4, message_id="msg-A"),
+            lifecycle_completed_event(seq=5),
+        ]
+    )
+    with httpx.Client(transport=fake.transport, base_url="http://test") as raw:
+        threads = SyncThreadsClient(SyncHttpClient(raw))
+        with threads.stream(thread_id="t-1", assistant_id="agent") as thread:
+            thread.run.start(input={})
+            streams = list(thread.messages)
+
+    assert len(streams) == 1
+    # Only the correctly-keyed delta "real" must appear; "orphan" must be dropped.
+    assert str(streams[0].text) == "real"
+
+
+# ---------------------------------------------------------------------------
+# Fix C — bound SyncToolCallHandle._deltas via max_queue_size
+# ---------------------------------------------------------------------------
+
+
+def test_sync_tool_call_handle_deltas_queue_is_bounded():
+    """SyncToolCallHandle._deltas must be a bounded queue.
+
+    Unbounded queues allow producers to enqueue indefinitely, causing memory
+    growth when consumers are slow.
+    """
+    from langgraph_sdk._sync.stream import SyncToolCallHandle
+
+    handle_default = SyncToolCallHandle(tool_call_id="tc1", name="foo")
+    assert handle_default._deltas.maxsize > 0, (
+        "default maxsize must be positive (bounded)"
+    )
+
+    handle_custom = SyncToolCallHandle(tool_call_id="tc2", name="bar", max_queue_size=8)
+    assert handle_custom._deltas.maxsize == 8
+
+
+# ---------------------------------------------------------------------------
+# Fix D — enforce single consumer on SyncToolCallHandle.deltas
+# ---------------------------------------------------------------------------
+
+
+def test_sync_tool_call_handle_deltas_single_consumer_guard():
+    """Accessing `handle.deltas` a second time must raise immediately.
+
+    `_deltas` is a single-consumer queue; fanning out to multiple consumers
+    would cause each consumer to miss events already consumed by the other.
+    The property must raise before returning the iterator so the caller
+    sees the error even without iterating.
+    """
+    from langgraph_sdk._sync.stream import SyncToolCallHandle
+
+    handle = SyncToolCallHandle(tool_call_id="tc1", name="foo")
+
+    # First access: fine — returns the iterator.
+    _iter_1 = handle.deltas
+
+    # Second access: must raise immediately (before any iteration).
+    with pytest.raises(RuntimeError, match="single consumer"):
+        _ = handle.deltas