release(checkpoint): 4.1.1 (#7890 )

## Summary Bumps `langgraph-checkpoint` `4.1.0` → `4.1.1` and updates all downstream `uv.lock` files. ## Test plan - [x] `make format` / `make lint` / `make test` from `libs/checkpoint/`
release(sdk-py): 0.3.15 (#7891 )
2026-08-18 05:35:43 +02:00 · 2026-05-22 12:52:05 -04:00 · 2026-05-22 12:51:52 -04:00 · 2026-05-22 12:51:37 -04:00 · 2026-05-22 12:51:21 -04:00 · 2026-05-21 19:15:23 +00:00
38 changed files with 1464 additions and 254 deletions
@@ -58,14 +58,18 @@ jobs:
          } >> "$GITHUB_OUTPUT"
      - name: Annotation
        uses: actions/github-script@v9
+        env:
+          CHANGED_FILES: ${{ steps.files.outputs.added_modified_renamed }}
+          BENCHMARK_OUTPUT: ${{ steps.benchmark.outputs.OUTPUT }}
+          COMPARE_OUTPUT: ${{ steps.compare.outputs.OUTPUT }}
        with:
          script: |
-            const file = JSON.parse(`${{ steps.files.outputs.added_modified_renamed }}`)[0]
-            core.notice(`${{ steps.benchmark.outputs.OUTPUT }}`, {
+            const file = JSON.parse(process.env.CHANGED_FILES || "[]")[0]
+            core.notice(process.env.BENCHMARK_OUTPUT || "", {
              title: 'Benchmark results',
              file,
            })
-            core.notice(`${{ steps.compare.outputs.OUTPUT }}`, {
+            core.notice(process.env.COMPARE_OUTPUT || "", {
              title: 'Comparison against main',
              file,
            })
@@ -32,6 +32,7 @@ jobs:
        with:
          python-version: ${{ env.PYTHON_VERSION }}
          cache-suffix: "release"
+          enable-cache: false
          working-directory: ${{ inputs.working-directory }}

      # We want to keep this build stage *separate* from the release stage,
@@ -268,6 +269,7 @@ jobs:
        with:
          python-version: ${{ env.PYTHON_VERSION }}
          cache-suffix: "release"
+          enable-cache: false
          working-directory: ${{ inputs.working-directory }}

      - uses: actions/download-artifact@v8
@@ -309,6 +311,7 @@ jobs:
        with:
          python-version: ${{ env.PYTHON_VERSION }}
          cache-suffix: "release"
+          enable-cache: false
          working-directory: ${{ inputs.working-directory }}

      - uses: actions/download-artifact@v8
@@ -208,11 +208,11 @@ wheels = [

 [[package]]
 name = "idna"
-version = "3.13"
+version = "3.15"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/ce/cc/762dfb036166873f0059f3b7de4565e1b5bc3d6f28a414c13da27e442f99/idna-3.13.tar.gz", hash = "sha256:585ea8fe5d69b9181ec1afba340451fba6ba764af97026f92a91d4eef164a242", size = 194210, upload-time = "2026-04-22T16:42:42.314Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/82/77/7b3966d0b9d1d31a36ddf1746926a11dface89a83409bf1483f0237aa758/idna-3.15.tar.gz", hash = "sha256:ca962446ea538f7092a95e057da437618e886f4d349216d2b1e294abfdb65fdc", size = 199245, upload-time = "2026-05-12T22:45:57.011Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/5d/13/ad7d7ca3808a898b4612b6fe93cde56b53f3034dcde235acb1f0e1df24c6/idna-3.13-py3-none-any.whl", hash = "sha256:892ea0cde124a99ce773decba204c5552b69c3c67ffd5f232eb7696135bc8bb3", size = 68629, upload-time = "2026-04-22T16:42:40.909Z" },
+    { url = "https://files.pythonhosted.org/packages/d2/23/408243171aa9aaba178d3e2559159c24c1171a641aa83b67bdd3394ead8e/idna-3.15-py3-none-any.whl", hash = "sha256:048adeaf8c2d788c40fee287673ccaa74c24ffd8dcf09ffa555a2fbb59f10ac8", size = 72340, upload-time = "2026-05-12T22:45:55.733Z" },
 ]

 [[package]]
@@ -279,7 +279,7 @@ wheels = [

 [[package]]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.1"
 source = { editable = "../checkpoint" }
 dependencies = [
    { name = "langchain-core" },
@@ -205,11 +205,11 @@ wheels = [

 [[package]]
 name = "idna"
-version = "3.11"
+version = "3.15"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/6f/6d/0703ccc57f3a7233505399edb88de3cbd678da106337b9fcde432b65ed60/idna-3.11.tar.gz", hash = "sha256:795dafcc9c04ed0c1fb032c2aa73654d8e8c5023a7df64a53f39190ada629902", size = 194582, upload-time = "2025-10-12T14:55:20.501Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/82/77/7b3966d0b9d1d31a36ddf1746926a11dface89a83409bf1483f0237aa758/idna-3.15.tar.gz", hash = "sha256:ca962446ea538f7092a95e057da437618e886f4d349216d2b1e294abfdb65fdc", size = 199245, upload-time = "2026-05-12T22:45:57.011Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/0e/61/66938bbb5fc52dbdf84594873d5b51fb1f7c7794e9c0f5bd885f30bc507b/idna-3.11-py3-none-any.whl", hash = "sha256:771a87f49d9defaf64091e6e6fe9c18d4833f140bd19464795bc32d966ca37ea", size = 71008, upload-time = "2025-10-12T14:55:18.883Z" },
+    { url = "https://files.pythonhosted.org/packages/d2/23/408243171aa9aaba178d3e2559159c24c1171a641aa83b67bdd3394ead8e/idna-3.15-py3-none-any.whl", hash = "sha256:048adeaf8c2d788c40fee287673ccaa74c24ffd8dcf09ffa555a2fbb59f10ac8", size = 72340, upload-time = "2026-05-12T22:45:55.733Z" },
 ]

 [[package]]
@@ -276,7 +276,7 @@ wheels = [

 [[package]]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.1"
 source = { editable = "../checkpoint" }
 dependencies = [
    { name = "langchain-core" },
@@ -399,7 +399,7 @@ test = [

 [[package]]
 name = "langsmith"
-version = "0.7.31"
+version = "0.8.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -412,9 +412,9 @@ dependencies = [
    { name = "xxhash" },
    { name = "zstandard" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/e6/11/696019490992db5c87774dc20515529ef42a01e1d770fb754ed6d9b12fb0/langsmith-0.7.31.tar.gz", hash = "sha256:331ee4f7c26bb5be4022b9859b7d7b122cbf8c9d01d9f530114c1914b0349ffb", size = 1178480, upload-time = "2026-04-14T17:55:41.242Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/a8/64/95f1f013531395f4e8ed73caeee780f65c7c58fe028cb543f8937b45611b/langsmith-0.8.0.tar.gz", hash = "sha256:59fe5b2a56bbbe14a08aa76691f84b49e8675dd21e11b57d80c6db8c08bac2e3", size = 4432996, upload-time = "2026-04-30T22:13:07.341Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/1d/a1/a013cf458c301cda86a213dd153ce0a01c93f1ab5833f951e6a44c9763ce/langsmith-0.7.31-py3-none-any.whl", hash = "sha256:0291d49203f6e80dda011af1afda61eb0595a4d697adb684590a8805e1d61fb6", size = 373276, upload-time = "2026-04-14T17:55:39.677Z" },
+    { url = "https://files.pythonhosted.org/packages/f3/e1/a4be2e696c9473bb53298df398237da5674704d781d4b748ed35aeef592a/langsmith-0.8.0-py3-none-any.whl", hash = "sha256:12cc4bc5622b835a6d841964d6034df3617bdb912dae0c1381fd0a68a9b3a3ef", size = 393268, upload-time = "2026-04-30T22:13:05.56Z" },
 ]

 [[package]]
@@ -214,11 +214,11 @@ wheels = [

 [[package]]
 name = "idna"
-version = "3.11"
+version = "3.15"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/6f/6d/0703ccc57f3a7233505399edb88de3cbd678da106337b9fcde432b65ed60/idna-3.11.tar.gz", hash = "sha256:795dafcc9c04ed0c1fb032c2aa73654d8e8c5023a7df64a53f39190ada629902", size = 194582, upload-time = "2025-10-12T14:55:20.501Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/82/77/7b3966d0b9d1d31a36ddf1746926a11dface89a83409bf1483f0237aa758/idna-3.15.tar.gz", hash = "sha256:ca962446ea538f7092a95e057da437618e886f4d349216d2b1e294abfdb65fdc", size = 199245, upload-time = "2026-05-12T22:45:57.011Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/0e/61/66938bbb5fc52dbdf84594873d5b51fb1f7c7794e9c0f5bd885f30bc507b/idna-3.11-py3-none-any.whl", hash = "sha256:771a87f49d9defaf64091e6e6fe9c18d4833f140bd19464795bc32d966ca37ea", size = 71008, upload-time = "2025-10-12T14:55:18.883Z" },
+    { url = "https://files.pythonhosted.org/packages/d2/23/408243171aa9aaba178d3e2559159c24c1171a641aa83b67bdd3394ead8e/idna-3.15-py3-none-any.whl", hash = "sha256:048adeaf8c2d788c40fee287673ccaa74c24ffd8dcf09ffa555a2fbb59f10ac8", size = 72340, upload-time = "2026-05-12T22:45:55.733Z" },
 ]

 [[package]]
@@ -285,7 +285,7 @@ wheels = [

 [[package]]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.1"
 source = { editable = "../checkpoint" }
 dependencies = [
    { name = "langchain-core" },
@@ -402,7 +402,7 @@ test = [

 [[package]]
 name = "langsmith"
-version = "0.7.31"
+version = "0.8.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -415,9 +415,9 @@ dependencies = [
    { name = "xxhash" },
    { name = "zstandard" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/e6/11/696019490992db5c87774dc20515529ef42a01e1d770fb754ed6d9b12fb0/langsmith-0.7.31.tar.gz", hash = "sha256:331ee4f7c26bb5be4022b9859b7d7b122cbf8c9d01d9f530114c1914b0349ffb", size = 1178480, upload-time = "2026-04-14T17:55:41.242Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/a8/64/95f1f013531395f4e8ed73caeee780f65c7c58fe028cb543f8937b45611b/langsmith-0.8.0.tar.gz", hash = "sha256:59fe5b2a56bbbe14a08aa76691f84b49e8675dd21e11b57d80c6db8c08bac2e3", size = 4432996, upload-time = "2026-04-30T22:13:07.341Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/1d/a1/a013cf458c301cda86a213dd153ce0a01c93f1ab5833f951e6a44c9763ce/langsmith-0.7.31-py3-none-any.whl", hash = "sha256:0291d49203f6e80dda011af1afda61eb0595a4d697adb684590a8805e1d61fb6", size = 373276, upload-time = "2026-04-14T17:55:39.677Z" },
+    { url = "https://files.pythonhosted.org/packages/f3/e1/a4be2e696c9473bb53298df398237da5674704d781d4b748ed35aeef592a/langsmith-0.8.0-py3-none-any.whl", hash = "sha256:12cc4bc5622b835a6d841964d6034df3617bdb912dae0c1381fd0a68a9b3a3ef", size = 393268, upload-time = "2026-04-30T22:13:05.56Z" },
 ]

 [[package]]
@@ -157,27 +157,6 @@ class JsonPlusSerializer(SerializerProtocol):
            )
        return clone

-    def _encode_constructor_args(
-        self,
-        constructor: Callable | type[Any],
-        *,
-        method: None | str | Sequence[None | str] = None,
-        args: Sequence[Any] | None = None,
-        kwargs: dict[str, Any] | None = None,
-    ) -> dict[str, Any]:
-        out = {
-            "lc": 2,
-            "type": "constructor",
-            "id": (*constructor.__module__.split("."), constructor.__name__),
-        }
-        if method is not None:
-            out["method"] = method
-        if args is not None:
-            out["args"] = args
-        if kwargs is not None:
-            out["kwargs"] = kwargs
-        return out
-
    def _reviver(self, value: dict[str, Any]) -> Any:
        if (
            value.get("lc", None) == 2
@@ -203,45 +182,46 @@ class JsonPlusSerializer(SerializerProtocol):
        self._check_allowed_json_modules(value)

        [*module, name] = value["id"]
+        # The `method` field on lc:2 envelopes is intentionally ignored.
+        # Revival is restricted to the default constructor (no `getattr`
+        # dispatch on attacker-influenced names). The framework's own
+        # encoder has not emitted `method=` since the msgpack migration,
+        # and the only legacy emission was `method=(None, "construct")`
+        # for pydantic models, where the first entry (`None`) already
+        # meant "default constructor", which is what we do here.
        try:
            mod = importlib.import_module(".".join(module))
            cls = getattr(mod, name)
-            method = value.get("method")
-            if isinstance(method, str):
-                methods = [getattr(cls, method)]
-            elif isinstance(method, list):
-                methods = [cls if m is None else getattr(cls, m) for m in method]
-            else:
-                methods = [cls]
+            if isclass(cls) and issubclass(cls, BaseException):
+                return None
            args = value.get("args")
            kwargs = value.get("kwargs")
-            for method in methods:
-                try:
-                    if isclass(method) and issubclass(method, BaseException):
-                        return None
-                    if args and kwargs:
-                        return method(*args, **kwargs)
-                    elif args:
-                        return method(*args)
-                    elif kwargs:
-                        return method(**kwargs)
-                    else:
-                        return method()
-                except Exception:
-                    continue
-        except Exception:
+            if args and kwargs:
+                return cls(*args, **kwargs)
+            elif args:
+                return cls(*args)
+            elif kwargs:
+                return cls(**kwargs)
+            else:
+                return cls()
+        except Exception as exc:
+            # Method-field dispatch has been removed (GHSA-fjqc-hq36-qh5p), so
+            # legacy pydantic payloads emitting `method=[None, "construct"]`
+            # no longer fall back to `cls.construct(**kwargs)` when the
+            # default constructor rejects the serialized kwargs. Surface a
+            # one-line warning so operators can spot payloads that now revive
+            # to `None` instead of silently degrading to the raw envelope.
+            logger.warning(
+                "Failed to revive lc:2 envelope %s "
+                "(legacy_method_field=%s, error=%s); returning None",
+                ".".join((*module, name)),
+                "method" in value,
+                type(exc).__name__,
+            )
            return None

    def _check_allowed_json_modules(self, value: dict[str, Any]) -> None:
        needed = tuple(value["id"])
-        method = value.get("method")
-        if isinstance(method, list):
-            method_display = ",".join(m or "<init>" for m in method)
-        elif isinstance(method, str):
-            method_display = method
-        else:
-            method_display = "<init>"
-
        dotted = ".".join(needed)
        # Safe types (the same set already allowed for msgpack deserialization) are
        # permitted without an explicit allowlist — they are known-safe LangGraph and
@@ -252,7 +232,7 @@ class JsonPlusSerializer(SerializerProtocol):

        if not self._allowed_json_modules:
            raise InvalidModuleError(
-                f"Refused to deserialize JSON constructor: {dotted} (method: {method_display}). "
+                f"Refused to deserialize JSON constructor: {dotted}. "
                "No allowed_json_modules configured.\n\n"
                "Unblock with ONE of:\n"
                f"  • JsonPlusSerializer(allowed_json_modules=[{needed!r}, ...])\n"
@@ -267,7 +247,7 @@ class JsonPlusSerializer(SerializerProtocol):
            return

        raise InvalidModuleError(
-            f"Refused to deserialize JSON constructor: {dotted} (method: {method_display}). "
+            f"Refused to deserialize JSON constructor: {dotted}. "
            "Symbol is not in the deserialization allowlist.\n\n"
            "Add exactly this symbol to unblock:\n"
            f"  JsonPlusSerializer(allowed_json_modules=[{needed!r}, ...])\n"
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"

 [project]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.1"
 description = "Library with base interfaces for LangGraph checkpoint savers."
 authors = []
 requires-python = ">=3.10"
@@ -398,6 +398,193 @@ def test_deserde_invalid_module() -> None:
    serde.loads_typed(("json", json.dumps(load).encode("utf-8")))


+def test_lc2_json_method_field_is_ignored() -> None:
+    """The `method` field on lc=2 envelopes is ignored.
+
+    Regression test for GHSA-fjqc-hq36-qh5p: `_revive_lc2` previously resolved
+    `getattr(cls, method)` from the envelope, which let an attacker pivot a
+    safe pydantic class (e.g., AIMessage) to `parse_raw(..., allow_pickle=True)`
+    and reach `pickle.loads`. Revival now uses only the default constructor.
+
+    Verifies that an envelope carrying ``method="parse_raw"`` does not dispatch
+    to that method: the result is whatever ``AIMessage(*args, **kwargs)`` would
+    produce, which proves the default constructor ran instead of ``parse_raw``.
+    """
+    from langchain_core.messages import AIMessage
+
+    serde = JsonPlusSerializer()
+    load = {
+        "lc": 2,
+        "type": "constructor",
+        "id": ["langchain_core", "messages", "ai", "AIMessage"],
+        "method": "parse_raw",
+        "args": ["default-ctor-ran"],
+        "kwargs": {"content_type": "application/pickle", "allow_pickle": True},
+    }
+    result = serde._revive_lc2(load)
+    # Default constructor accepts `content` as first positional arg. If parse_raw
+    # had been invoked instead, it would have attempted JSON/pickle parsing and
+    # raised (or executed the pickle gadget); neither would produce this result.
+    assert isinstance(result, AIMessage)
+    assert result.content == "default-ctor-ran"
+
+
+def test_lc2_json_method_field_is_ignored_for_allowlisted_types() -> None:
+    """The `method` field is ignored even when the class is explicitly allowlisted.
+
+    A user who configures ``allowed_json_modules`` for a class no longer gets
+    method dispatch as a side effect. Revival is restricted to the default
+    constructor regardless of how the class reached the revival path.
+    """
+    from langchain_core.messages import AIMessage
+
+    serde = JsonPlusSerializer(
+        allowed_json_modules=[("langchain_core.messages.ai", "AIMessage")]
+    )
+    load = {
+        "lc": 2,
+        "type": "constructor",
+        "id": ["langchain_core", "messages", "ai", "AIMessage"],
+        "method": "parse_raw",
+        "args": ["default-ctor-ran"],
+    }
+    result = serde._revive_lc2(load)
+    assert isinstance(result, AIMessage)
+    assert result.content == "default-ctor-ran"
+
+
+def test_lc2_json_safe_type_init_still_works() -> None:
+    """SAFE-type lc=2 revival without a `method` field still constructs the class."""
+    from langchain_core.messages import AIMessage
+
+    serde = JsonPlusSerializer()
+    load = {
+        "lc": 2,
+        "type": "constructor",
+        "id": ["langchain_core", "messages", "ai", "AIMessage"],
+        "kwargs": {"content": "hi", "type": "ai"},
+    }
+    result = serde._revive_lc2(load)
+    assert isinstance(result, AIMessage)
+    assert result.content == "hi"
+
+
+def test_lc2_json_legacy_pydantic_method_list_falls_back_to_default() -> None:
+    """Legacy ``method=(None, "construct")`` envelopes still revive via the default ctor.
+
+    Pre-October-2025 langgraph emitted pydantic models with
+    ``method=(None, "construct")`` meaning "try default constructor, fall back
+    to pydantic ``construct``". The first entry (``None``) was always the
+    default constructor, which is what we now do unconditionally. Envelopes of
+    this shape continue to revive correctly as long as the default constructor
+    accepts the serialized kwargs.
+    """
+    from langchain_core.messages import AIMessage
+
+    serde = JsonPlusSerializer()
+    load = {
+        "lc": 2,
+        "type": "constructor",
+        "id": ["langchain_core", "messages", "ai", "AIMessage"],
+        "method": [None, "construct"],
+        "kwargs": {"content": "legacy", "type": "ai"},
+    }
+    result = serde._revive_lc2(load)
+    assert isinstance(result, AIMessage)
+    assert result.content == "legacy"
+
+
+def test_lc2_json_legacy_construct_payload_logs_warning_when_default_init_rejects(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """Legacy `method=[None, "construct"]` envelopes whose kwargs the default
+    `__init__` rejects now revive to `None` and emit an observable warning.
+
+    Pre-October-2025 langgraph emitted pydantic payloads with
+    `method=[None, "construct"]` so the reviver could fall back to
+    `cls.construct(**kwargs)` when the default constructor raised a
+    validation error. That fallback was removed with method-field dispatch
+    (GHSA-fjqc-hq36-qh5p), so these payloads now silently fail validation. A
+    `logger.warning` makes the regression observable to operators instead of
+    letting the envelope quietly degrade to its raw-dict form.
+    """
+    serde = JsonPlusSerializer()
+    load = {
+        "lc": 2,
+        "type": "constructor",
+        "id": ["langchain_core", "messages", "ai", "AIMessage"],
+        # Legacy two-entry method tuple: try default ctor, fall back to construct.
+        "method": [None, "construct"],
+        # ``type="not-a-real-message-type"`` fails AIMessage's Literal["ai"]
+        # validator under the default constructor. Before the GHSA patch this
+        # would have fallen back to ``cls.construct(**kwargs)``; now it must
+        # return None and log.
+        "kwargs": {"content": "legacy", "type": "not-a-real-message-type"},
+    }
+
+    with caplog.at_level(logging.WARNING, logger="langgraph.checkpoint.serde.jsonplus"):
+        result = serde._revive_lc2(load)
+
+    assert result is None, (
+        "Legacy method=[None, 'construct'] payloads with kwargs the default "
+        "ctor rejects must now return None (no construct() fallback)."
+    )
+
+    matching = [
+        r
+        for r in caplog.records
+        if r.name == "langgraph.checkpoint.serde.jsonplus"
+        and r.levelno == logging.WARNING
+        and "langchain_core.messages.ai.AIMessage" in r.getMessage()
+        and "legacy_method_field=True" in r.getMessage()
+    ]
+    assert matching, (
+        "Expected a WARNING from langgraph.checkpoint.serde.jsonplus "
+        "referencing the class id and legacy_method_field=True; "
+        f"got records: {[(r.name, r.levelname, r.getMessage()) for r in caplog.records]}"
+    )
+
+
+def test_lc2_json_safe_type_pickle_payload_does_not_execute() -> None:
+    """End-to-end: a `parse_raw` pickle gadget payload on a SAFE type must not run.
+
+    With method dispatch removed from `_revive_lc2`, the gadget bytes are never
+    passed to `parse_raw` and therefore never reach `pickle.loads`.
+    """
+    import os
+    import pickle
+    import tempfile
+
+    marker = tempfile.NamedTemporaryFile(
+        prefix="lc2_block_proof_", suffix=".out", delete=False
+    ).name
+    os.remove(marker)  # ensure absent before the test runs
+
+    class _Gadget:
+        def __reduce__(self) -> tuple:
+            return (os.system, (f"touch {marker}",))
+
+    gadget_bytes = pickle.dumps(_Gadget(), protocol=0).decode("latin1")
+    envelope = {
+        "lc": 2,
+        "type": "constructor",
+        "id": ["langchain_core", "messages", "ai", "AIMessage"],
+        "method": "parse_raw",
+        "args": [gadget_bytes],
+        "kwargs": {"content_type": "application/pickle", "allow_pickle": True},
+    }
+
+    serde = JsonPlusSerializer()
+    try:
+        serde.loads_typed(("json", json.dumps(envelope).encode()))
+    except Exception:
+        pass
+
+    assert not os.path.exists(marker), (
+        "Pickle gadget executed via parse_raw on AIMessage lc=2 envelope"
+    )
+
+
 def test_serde_jsonplus_bytearray() -> None:
    serde = JsonPlusSerializer()

@@ -229,11 +229,11 @@ wheels = [

 [[package]]
 name = "idna"
-version = "3.11"
+version = "3.15"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/6f/6d/0703ccc57f3a7233505399edb88de3cbd678da106337b9fcde432b65ed60/idna-3.11.tar.gz", hash = "sha256:795dafcc9c04ed0c1fb032c2aa73654d8e8c5023a7df64a53f39190ada629902", size = 194582, upload-time = "2025-10-12T14:55:20.501Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/82/77/7b3966d0b9d1d31a36ddf1746926a11dface89a83409bf1483f0237aa758/idna-3.15.tar.gz", hash = "sha256:ca962446ea538f7092a95e057da437618e886f4d349216d2b1e294abfdb65fdc", size = 199245, upload-time = "2026-05-12T22:45:57.011Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/0e/61/66938bbb5fc52dbdf84594873d5b51fb1f7c7794e9c0f5bd885f30bc507b/idna-3.11-py3-none-any.whl", hash = "sha256:771a87f49d9defaf64091e6e6fe9c18d4833f140bd19464795bc32d966ca37ea", size = 71008, upload-time = "2025-10-12T14:55:18.883Z" },
+    { url = "https://files.pythonhosted.org/packages/d2/23/408243171aa9aaba178d3e2559159c24c1171a641aa83b67bdd3394ead8e/idna-3.15-py3-none-any.whl", hash = "sha256:048adeaf8c2d788c40fee287673ccaa74c24ffd8dcf09ffa555a2fbb59f10ac8", size = 72340, upload-time = "2026-05-12T22:45:55.733Z" },
 ]

 [[package]]
@@ -300,7 +300,7 @@ wheels = [

 [[package]]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.1"
 source = { editable = "." }
 dependencies = [
    { name = "langchain-core" },
@@ -383,7 +383,7 @@ test = [

 [[package]]
 name = "langsmith"
-version = "0.7.31"
+version = "0.8.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -396,9 +396,9 @@ dependencies = [
    { name = "xxhash" },
    { name = "zstandard" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/e6/11/696019490992db5c87774dc20515529ef42a01e1d770fb754ed6d9b12fb0/langsmith-0.7.31.tar.gz", hash = "sha256:331ee4f7c26bb5be4022b9859b7d7b122cbf8c9d01d9f530114c1914b0349ffb", size = 1178480, upload-time = "2026-04-14T17:55:41.242Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/a8/64/95f1f013531395f4e8ed73caeee780f65c7c58fe028cb543f8937b45611b/langsmith-0.8.0.tar.gz", hash = "sha256:59fe5b2a56bbbe14a08aa76691f84b49e8675dd21e11b57d80c6db8c08bac2e3", size = 4432996, upload-time = "2026-04-30T22:13:07.341Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/1d/a1/a013cf458c301cda86a213dd153ce0a01c93f1ab5833f951e6a44c9763ce/langsmith-0.7.31-py3-none-any.whl", hash = "sha256:0291d49203f6e80dda011af1afda61eb0595a4d697adb684590a8805e1d61fb6", size = 373276, upload-time = "2026-04-14T17:55:39.677Z" },
+    { url = "https://files.pythonhosted.org/packages/f3/e1/a4be2e696c9473bb53298df398237da5674704d781d4b748ed35aeef592a/langsmith-0.8.0-py3-none-any.whl", hash = "sha256:12cc4bc5622b835a6d841964d6034df3617bdb912dae0c1381fd0a68a9b3a3ef", size = 393268, upload-time = "2026-04-30T22:13:05.56Z" },
 ]

 [[package]]
@@ -3675,12 +3675,11 @@ keyv@^4.5.4:
    json-buffer "3.0.1"

 "langsmith@>=0.5.0 <1.0.0":
-  version "0.5.20"
-  resolved "https://registry.yarnpkg.com/langsmith/-/langsmith-0.5.20.tgz#4021847d2ccd5a86c5eb96060f9bb5f19f80eca5"
-  integrity sha512-ULhLM8RswvQDXufLtNtvclHrWCBx8Cb5UPI6lAZC+8Dq59iHsVPz/3Ac9khWNm1VIvChRsuykixD/WrmzuuA3Q==
+  version "0.6.3"
+  resolved "https://registry.yarnpkg.com/langsmith/-/langsmith-0.6.3.tgz#a3d8ad58d66a47d3697e3c69b2be3f6df5233190"
+  integrity sha512-pXrQ4/4myQvjFFOAUmt5pWRrLEZR20gzIJD7MNdUH+5/S5nLI4ZRBo/SYKC6coaYj9pYTfQdBIzcs+3kfJ5uDA==
  dependencies:
    p-queue "6.6.2"
-    uuid "10.0.0"

 leven@^3.1.0:
  version "3.1.0"
@@ -4848,7 +4847,7 @@ uri-js@^4.2.2:
  dependencies:
    punycode "^2.1.0"

-uuid@10.0.0, uuid@^10.0.0:
+uuid@^10.0.0:
  version "10.0.0"
  resolved "https://registry.yarnpkg.com/uuid/-/uuid-10.0.0.tgz#5a95aa454e6e002725c79055fd42aaba30ca6294"
  integrity sha512-8XkAphELsDnEGrDxUOHB3RGvXz6TeuYSGEZBOjtTtPm2lwhGBjLgOzLHB63IUWfBpNucQjND6d3AOudO+H3RWQ==
@@ -17,7 +17,7 @@
    "lint": "eslint 'apps/**/*.ts' 'libs/**/*.ts'"
  },
  "devDependencies": {
-    "turbo": "^2.9.7",
+    "turbo": "^2.9.14",
    "typescript": "^5.9.3",
    "@tsconfig/recommended": "^1.0.13",
    "@eslint/eslintrc": "^3.3.5",
@@ -166,35 +166,35 @@
  resolved "https://registry.yarnpkg.com/@tsconfig/recommended/-/recommended-1.0.13.tgz#269fce3ad04ca70b93269ff44cca81b950f542da"
  integrity sha512-sySRuBfMKyKO/j2ZAhR8kSembhjuPEV4Ra3AHtmWLq51+iGaudr45crPSzNC5b7/Ctrh9dfUpBuTlYrH6rM58Q==

-"@turbo/darwin-64@2.9.7":
-  version "2.9.7"
-  resolved "https://registry.yarnpkg.com/@turbo/darwin-64/-/darwin-64-2.9.7.tgz#46fddae01ea7817192dc6ff36a678cc3879b753b"
-  integrity sha512-wnvOWuVWJ5EUHNKxExEWiGlTeVpLG1L0PCu5MUozyC1P2SHGiWsmpW6/yAuShH91Fa2TAHOvdCRBzriZh4j4Eg==
+"@turbo/darwin-64@2.9.14":
+  version "2.9.14"
+  resolved "https://registry.yarnpkg.com/@turbo/darwin-64/-/darwin-64-2.9.14.tgz#b9ec6ac637b9c5fdba5dae9d743f5d121f091242"
+  integrity sha512-t7QiPflaEyBE4oayeZtSmu4mEfjgIrcNlNNl1z1dmIVPqEdtA7+CfTf8d7KXsOGPh6aNgWjKxyvQg9uGfDQF+A==

-"@turbo/darwin-arm64@2.9.7":
-  version "2.9.7"
-  resolved "https://registry.yarnpkg.com/@turbo/darwin-arm64/-/darwin-arm64-2.9.7.tgz#cd7cf3a024509af0f59ae3885216d62fd090fdb6"
-  integrity sha512-mA0FIPMwwN3lodDkQYaGxj6PeT7ZaN5aCEbkKn/WB+ZB9yJdVWA4J83GH7t43jqDc5dcnVluVN5UFx3plRiXhA==
+"@turbo/darwin-arm64@2.9.14":
+  version "2.9.14"
+  resolved "https://registry.yarnpkg.com/@turbo/darwin-arm64/-/darwin-arm64-2.9.14.tgz#99d19f3e59842c595d2828c72a2e4ef537408f38"
+  integrity sha512-d23147mC9BsCPA9mJ0h/ubcpbRgcJBXbcG3+Vq7YLhjz3IXuvQsJ1UXH8f4MD76ZjJ4m/E4aRdJV+MW88CDfbw==

-"@turbo/linux-64@2.9.7":
-  version "2.9.7"
-  resolved "https://registry.yarnpkg.com/@turbo/linux-64/-/linux-64-2.9.7.tgz#25ee9a2cb3042498a3203e14653b14041105020f"
-  integrity sha512-fEbUYpgb5l7P+q+5tsWF2gw+/GSjUsuUTcnfm+f0lozUjgcjLKyOat6PgtAChmIFcTPchCL/8rJ3TvkBy01gfA==
+"@turbo/linux-64@2.9.14":
+  version "2.9.14"
+  resolved "https://registry.yarnpkg.com/@turbo/linux-64/-/linux-64-2.9.14.tgz#9c907434f091cd75529f5496516f79b71935d2bb"
+  integrity sha512-P3ZKB5tuUDdDQWuAsACGUR1qv9W7BNWxdxqVJ0kZNuNNPRaVYTPPikLcp79+GiEcW3npsR+KyP38lnQiBc5aSA==

-"@turbo/linux-arm64@2.9.7":
-  version "2.9.7"
-  resolved "https://registry.yarnpkg.com/@turbo/linux-arm64/-/linux-arm64-2.9.7.tgz#5b19d6249a50cb8153b8f2bc22ad10bbda614fbe"
-  integrity sha512-VkUjulo9ytfHKUHOS5gy0XPoh4CTKPXWCL8nLdrlHVi9fSut31ECeUqnm/dAbETP5D4xo9mH9XkJ+qMzGe/zmg==
+"@turbo/linux-arm64@2.9.14":
+  version "2.9.14"
+  resolved "https://registry.yarnpkg.com/@turbo/linux-arm64/-/linux-arm64-2.9.14.tgz#79ae9060e6ee9e0fb784ae0747e980f582e75313"
+  integrity sha512-ZRTlzcUMrrPv9ZuDzRF9n60Ym13bKeG9jDB8WjxyLhWNzV+AJQN+zdpIk3NJYf2zQsGUm1mNar2P0elRzLw25g==

-"@turbo/windows-64@2.9.7":
-  version "2.9.7"
-  resolved "https://registry.yarnpkg.com/@turbo/windows-64/-/windows-64-2.9.7.tgz#900645776fa44ff8333e801d890992736f6dbc72"
-  integrity sha512-/GWdY6/x4aIHqkYJq596Rpdk1x0MkpRPkJcLAoB3yGRwyUms0+u2F1GnV54IbyAZTeKLRWSJKzNC+QwVGdYchA==
+"@turbo/windows-64@2.9.14":
+  version "2.9.14"
+  resolved "https://registry.yarnpkg.com/@turbo/windows-64/-/windows-64-2.9.14.tgz#68a80f299f35189314184c88301caad982d1c0c2"
+  integrity sha512-exanwN6sIduZwykYeiTQj8kCmOhazP5WOz3bvXMcYtjhL6Z3iRWLewKrXCBq0bqwSP3iBMb/AerRCnHI4lx46A==

-"@turbo/windows-arm64@2.9.7":
-  version "2.9.7"
-  resolved "https://registry.yarnpkg.com/@turbo/windows-arm64/-/windows-arm64-2.9.7.tgz#e678d73fdbcbb12a679403fe7ba070fb67f37810"
-  integrity sha512-xBBgxCC5PK2+WZ1PPRZdp+aJ0bMBcEbweXWux3RUHJvX9ZodcoQySkrW6qt+ahb+uk8ZjyQodLfDwtVSoYds1w==
+"@turbo/windows-arm64@2.9.14":
+  version "2.9.14"
+  resolved "https://registry.yarnpkg.com/@turbo/windows-arm64/-/windows-arm64-2.9.14.tgz#4dc16684f0ddce53fafe56ad8f55205c4473d17a"
+  integrity sha512-fVdCsnmYoKICsycbWuuGp6Jvi51/3G/UluFWuAUCvR8PIW5IJkAk5BM9UF8PSm0Q2IphWHFZjYEgjHsh3B9y/g==

 "@types/esrecurse@^4.3.1":
  version "4.3.1"
@@ -1327,12 +1327,11 @@ keyv@^4.5.4:
    json-buffer "3.0.1"

 "langsmith@>=0.5.0 <1.0.0":
-  version "0.5.20"
-  resolved "https://registry.yarnpkg.com/langsmith/-/langsmith-0.5.20.tgz#4021847d2ccd5a86c5eb96060f9bb5f19f80eca5"
-  integrity sha512-ULhLM8RswvQDXufLtNtvclHrWCBx8Cb5UPI6lAZC+8Dq59iHsVPz/3Ac9khWNm1VIvChRsuykixD/WrmzuuA3Q==
+  version "0.7.1"
+  resolved "https://registry.yarnpkg.com/langsmith/-/langsmith-0.7.1.tgz#d721ad2e5211f9a5373e8a84eb4fed36b5621971"
+  integrity sha512-Wjk90UjNoY5cBHMlNAC/eZx5clI8jnjBOBW8uJu8+MWBtx0QesNjsUiLtjI+I3UnrpxFFpDqGXcnhBjH654Mqg==
  dependencies:
    p-queue "6.6.2"
-    uuid "10.0.0"

 levn@^0.4.1:
  version "0.4.1"
@@ -1814,17 +1813,17 @@ tsconfig-paths@^3.15.0:
    minimist "^1.2.6"
    strip-bom "^3.0.0"

-turbo@^2.9.7:
-  version "2.9.7"
-  resolved "https://registry.yarnpkg.com/turbo/-/turbo-2.9.7.tgz#da6d5a821f0bde5174e1a55af6690dad5c2fb004"
-  integrity sha512-epxzqVO2s0IxcSWcgb+qKrtco8isfe7g3VtiS6hkYnEK4A9XQDZbrtavQ6MtWR1KoQn+1fUomaQth2rfRHlUlg==
+turbo@^2.9.14:
+  version "2.9.14"
+  resolved "https://registry.yarnpkg.com/turbo/-/turbo-2.9.14.tgz#d412fcc4c9bd8dba29cec5bbd54d5a74ab2b1bee"
+  integrity sha512-BQqXRr4UoWI3UPFrtznCLykYHxwxWh53iCB57x092jPMjIlW1wnm3N895g5irpiXmnxUhREBB0n6+y8BHhs4nw==
  optionalDependencies:
-    "@turbo/darwin-64" "2.9.7"
-    "@turbo/darwin-arm64" "2.9.7"
-    "@turbo/linux-64" "2.9.7"
-    "@turbo/linux-arm64" "2.9.7"
-    "@turbo/windows-64" "2.9.7"
-    "@turbo/windows-arm64" "2.9.7"
+    "@turbo/darwin-64" "2.9.14"
+    "@turbo/darwin-arm64" "2.9.14"
+    "@turbo/linux-64" "2.9.14"
+    "@turbo/linux-arm64" "2.9.14"
+    "@turbo/windows-64" "2.9.14"
+    "@turbo/windows-arm64" "2.9.14"

 type-check@^0.4.0, type-check@~0.4.0:
  version "0.4.0"
@@ -1900,7 +1899,7 @@ uri-js@^4.2.2:
  dependencies:
    punycode "^2.1.0"

-uuid@10.0.0, uuid@^10.0.0:
+uuid@^10.0.0:
  version "10.0.0"
  resolved "https://registry.yarnpkg.com/uuid/-/uuid-10.0.0.tgz#5a95aa454e6e002725c79055fd42aaba30ca6294"
  integrity sha512-8XkAphELsDnEGrDxUOHB3RGvXz6TeuYSGEZBOjtTtPm2lwhGBjLgOzLHB63IUWfBpNucQjND6d3AOudO+H3RWQ==
@@ -21,7 +21,7 @@ dependencies = [

 [package.metadata]
 requires-dist = [
-    { name = "langchain-core", specifier = ">=1.3.3" },
+    { name = "langchain-core", specifier = ">=0.2.14" },
    { name = "langgraph", specifier = ">=0.6.0,<2" },
    { name = "shared", editable = "libs/shared" },
 ]
@@ -303,7 +303,7 @@ wheels = [

 [[package]]
 name = "langsmith"
-version = "0.7.31"
+version = "0.8.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -316,9 +316,9 @@ dependencies = [
    { name = "xxhash" },
    { name = "zstandard" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/e6/11/696019490992db5c87774dc20515529ef42a01e1d770fb754ed6d9b12fb0/langsmith-0.7.31.tar.gz", hash = "sha256:331ee4f7c26bb5be4022b9859b7d7b122cbf8c9d01d9f530114c1914b0349ffb", size = 1178480, upload-time = "2026-04-14T17:55:41.242Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/a8/64/95f1f013531395f4e8ed73caeee780f65c7c58fe028cb543f8937b45611b/langsmith-0.8.0.tar.gz", hash = "sha256:59fe5b2a56bbbe14a08aa76691f84b49e8675dd21e11b57d80c6db8c08bac2e3", size = 4432996, upload-time = "2026-04-30T22:13:07.341Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/1d/a1/a013cf458c301cda86a213dd153ce0a01c93f1ab5833f951e6a44c9763ce/langsmith-0.7.31-py3-none-any.whl", hash = "sha256:0291d49203f6e80dda011af1afda61eb0595a4d697adb684590a8805e1d61fb6", size = 373276, upload-time = "2026-04-14T17:55:39.677Z" },
+    { url = "https://files.pythonhosted.org/packages/f3/e1/a4be2e696c9473bb53298df398237da5674704d781d4b748ed35aeef592a/langsmith-0.8.0-py3-none-any.whl", hash = "sha256:12cc4bc5622b835a6d841964d6034df3617bdb912dae0c1381fd0a68a9b3a3ef", size = 393268, upload-time = "2026-04-30T22:13:05.56Z" },
 ]

 [[package]]
@@ -677,11 +677,11 @@ wheels = [

 [[package]]
 name = "urllib3"
-version = "2.6.3"
+version = "2.7.0"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/c7/24/5f1b3bdffd70275f6661c76461e25f024d5a38a46f04aaca912426a2b1d3/urllib3-2.6.3.tar.gz", hash = "sha256:1b62b6884944a57dbe321509ab94fd4d3b307075e0c2eae991ac71ee15ad38ed", size = 435556, upload-time = "2026-01-07T16:24:43.925Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/53/0c/06f8b233b8fd13b9e5ee11424ef85419ba0d8ba0b3138bf360be2ff56953/urllib3-2.7.0.tar.gz", hash = "sha256:231e0ec3b63ceb14667c67be60f2f2c40a518cb38b03af60abc813da26505f4c", size = 433602, upload-time = "2026-05-07T16:13:18.596Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/39/08/aaaad47bc4e9dc8c725e68f9d04865dbcb2052843ff09c97b08904852d84/urllib3-2.6.3-py3-none-any.whl", hash = "sha256:bf272323e553dfb2e87d9bfd225ca7b0f467b919d7bbd355436d3fd37cb0acd4", size = 131584, upload-time = "2026-01-07T16:24:42.685Z" },
+    { url = "https://files.pythonhosted.org/packages/7f/3e/5db95bcf282c52709639744ca2a8b149baccf648e39c8cc87553df9eae0c/urllib3-2.7.0-py3-none-any.whl", hash = "sha256:9fb4c81ebbb1ce9531cce37674bbc6f1360472bc18ca9a553ede278ef7276897", size = 131087, upload-time = "2026-05-07T16:13:17.151Z" },
 ]

 [[package]]
@@ -279,7 +279,7 @@ wheels = [

 [[package]]
 name = "langsmith"
-version = "0.7.31"
+version = "0.8.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -292,9 +292,9 @@ dependencies = [
    { name = "xxhash" },
    { name = "zstandard" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/e6/11/696019490992db5c87774dc20515529ef42a01e1d770fb754ed6d9b12fb0/langsmith-0.7.31.tar.gz", hash = "sha256:331ee4f7c26bb5be4022b9859b7d7b122cbf8c9d01d9f530114c1914b0349ffb", size = 1178480, upload-time = "2026-04-14T17:55:41.242Z" }
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@@ -663,11 +663,11 @@ wheels = [

 [[package]]
 name = "urllib3"
-version = "2.6.3"
+version = "2.7.0"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/c7/24/5f1b3bdffd70275f6661c76461e25f024d5a38a46f04aaca912426a2b1d3/urllib3-2.6.3.tar.gz", hash = "sha256:1b62b6884944a57dbe321509ab94fd4d3b307075e0c2eae991ac71ee15ad38ed", size = 435556, upload-time = "2026-01-07T16:24:43.925Z" }
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+    { url = "https://files.pythonhosted.org/packages/7f/3e/5db95bcf282c52709639744ca2a8b149baccf648e39c8cc87553df9eae0c/urllib3-2.7.0-py3-none-any.whl", hash = "sha256:9fb4c81ebbb1ce9531cce37674bbc6f1360472bc18ca9a553ede278ef7276897", size = 131087, upload-time = "2026-05-07T16:13:17.151Z" },
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 [[package]]
@@ -797,11 +797,11 @@ wheels = [

 [[package]]
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-version = "3.11"
+version = "3.15"
 source = { registry = "https://pypi.org/simple" }
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+    { url = "https://files.pythonhosted.org/packages/d2/23/408243171aa9aaba178d3e2559159c24c1171a641aa83b67bdd3394ead8e/idna-3.15-py3-none-any.whl", hash = "sha256:048adeaf8c2d788c40fee287673ccaa74c24ffd8dcf09ffa555a2fbb59f10ac8", size = 72340, upload-time = "2026-05-12T22:45:55.733Z" },
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 [[package]]
@@ -1174,7 +1174,7 @@ wheels = [

 [[package]]
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-version = "0.7.32"
+version = "0.8.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
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@@ -1187,9 +1187,9 @@ dependencies = [
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    { name = "zstandard", marker = "python_full_version >= '3.11'" },
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+    { url = "https://files.pythonhosted.org/packages/f3/e1/a4be2e696c9473bb53298df398237da5674704d781d4b748ed35aeef592a/langsmith-0.8.0-py3-none-any.whl", hash = "sha256:12cc4bc5622b835a6d841964d6034df3617bdb912dae0c1381fd0a68a9b3a3ef", size = 393268, upload-time = "2026-04-30T22:13:05.56Z" },
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 [package.optional-dependencies]
@@ -10,7 +10,7 @@ from typing import (
 from uuid import UUID, uuid4

 from langchain_core.callbacks import BaseCallbackHandler
-from langchain_core.messages import BaseMessage
+from langchain_core.messages import BaseMessage, ToolMessage
 from langchain_core.outputs import ChatGeneration, ChatGenerationChunk, LLMResult
 from pydantic import BaseModel

@@ -303,6 +303,35 @@ class StreamMessagesHandlerV2(StreamMessagesHandler, _V2StreamingCallbackHandler
        super().__init__(stream, subgraphs, parent_ns=parent_ns)
        self._streamed_run_ids: set[UUID] = set()

+    def _find_and_emit_messages(self, meta: Meta, response: Any) -> None:
+        """Like the v1 handler, but skip ToolMessage from node outputs.
+
+        Tool results belong on the tools channel / state in v3; v2-flagged streams
+        must not replay finalized ToolMessages as chat tokens (see MessagesTransformer).
+        Legacy v1-only `stream_mode="messages"` still emits ToolMessages (see subgraph
+        streaming tests).
+        """
+        if isinstance(response, BaseMessage) and not isinstance(response, ToolMessage):
+            self._emit(meta, response, dedupe=True)
+        elif isinstance(response, Sequence):
+            for value in response:
+                if isinstance(value, BaseMessage) and not isinstance(
+                    value, ToolMessage
+                ):
+                    self._emit(meta, value, dedupe=True)
+        else:
+            for value in _state_values(response):
+                if isinstance(value, BaseMessage) and not isinstance(
+                    value, ToolMessage
+                ):
+                    self._emit(meta, value, dedupe=True)
+                elif isinstance(value, Sequence):
+                    for item in value:
+                        if isinstance(item, BaseMessage) and not isinstance(
+                            item, ToolMessage
+                        ):
+                            self._emit(meta, item, dedupe=True)
+
    def on_llm_end(
        self,
        response: LLMResult,
@@ -62,6 +62,14 @@ class StreamMux:
        `extensions`, `_native` keys are recorded in `native_keys`, and
        any StreamChannel instances are bound and (if named) wired.

+        Transformers with `StreamTransformer.before_builtins = True` are
+        registered ahead of the rest, preserving relative order within
+        each lane. This lets content-mutating transformers (PII
+        redaction, content filters, etc.) run before built-ins like
+        `MessagesTransformer` that eagerly snapshot text fields into
+        their projections. See `StreamTransformer.before_builtins` for
+        the contract and foot-guns.
+
        Args:
            transformers: Already-built transformer instances. Registered
                only on this mux — they are NOT cloned into child
@@ -112,14 +120,31 @@ class StreamMux:
        self._pump_fn: Callable[[], bool] | None = None
        self._apump_fn: Callable[[], Awaitable[bool]] | None = None

-        # Factories run first (they propagate to child mini-muxes
-        # via `_make_child`), then any pre-built `transformers=`
-        # instances are registered as root-only — they aren't cloned
-        # for child scopes.
+        # Factories run first (they propagate to child mini-muxes via
+        # `_make_child`), then any pre-built `transformers=` instances
+        # are registered as root-only — they aren't cloned for child
+        # scopes. Within each group, transformers with
+        # `before_builtins = True` are registered ahead of the rest so
+        # they observe (and may mutate) events before built-ins like
+        # `MessagesTransformer`. The order *within* each lane matches
+        # the supplied sequence.
+        pre: list[StreamTransformer] = []
+        rest: list[StreamTransformer] = []
        if factories is not None:
            for factory in factories:
-                self._register(factory(scope))
+                transformer = factory(scope)
+                (
+                    pre if getattr(transformer, "before_builtins", False) else rest
+                ).append(transformer)
+            for transformer in (*pre, *rest):
+                self._register(transformer)
+            pre.clear()
+            rest.clear()
        for transformer in transformers or ():
+            (pre if getattr(transformer, "before_builtins", False) else rest).append(
+                transformer
+            )
+        for transformer in (*pre, *rest):
            self._register(transformer)

    def transformer_by_key(self, key: str) -> StreamTransformer | None:
@@ -91,11 +91,28 @@ class StreamTransformer(ABC):
            which modes a `stream_events(version="v3")` run requests from the graph.
            Empty tuple means the transformer consumes only synthetic
            events (or is purely passive).
+        before_builtins: Opt-in for transformers that must run *before*
+            built-in transformers like `MessagesTransformer` and
+            `ToolCallTransformer`. The mux partitions factories by this
+            flag at registration time: `before_builtins = True`
+            transformers are registered first, then everything else in
+            the order supplied. Within each lane, registration order is
+            preserved. This is the supported hook for content-mutating
+            transformers (PII redaction, profanity filters, etc.) whose
+            mutations must land before built-ins eagerly snapshot text
+            fields into their projections. **Foot-gun:** transformers
+            in this lane see `tasks` events before `LifecycleTransformer`
+            and `SubgraphTransformer` consume them — mutating
+            `event["params"]["namespace"]` or the data dict's
+            `id` / `result` / `error` / `interrupts` fields will desync
+            their bookkeeping. Observe freely; mutate only fields no
+            built-in reads (e.g. `delta.text` on `messages` events).
    """

    requires_async: ClassVar[bool] = False
    supports_sync: ClassVar[bool] = False
    required_stream_modes: ClassVar[tuple[str, ...]] = ()
+    before_builtins: ClassVar[bool] = False

    def __init__(self, scope: tuple[str, ...] = ()) -> None:
        """Initialize the transformer with its mux's scope.
@@ -8,7 +8,7 @@ from langchain_core.language_models.chat_model_stream import (
    AsyncChatModelStream,
    ChatModelStream,
 )
-from langchain_core.messages import AIMessageChunk, BaseMessage
+from langchain_core.messages import AIMessageChunk, BaseMessage, ToolMessage
 from langchain_protocol.protocol import MessagesData
 from typing_extensions import NotRequired, TypedDict

@@ -203,6 +203,7 @@ class MessagesTransformer(StreamTransformer):
        # Correlate protocol events back to a ChatModelStream by run_id
        # (attached to the event's metadata by StreamMessagesHandler).
        self._by_run: dict[str, ChatModelStream] = {}
+        self._ignored_runs: set[str] = set()
        self._pump_fn: Callable[[], bool] | None = None
        self._apump_fn: Callable[[], Awaitable[bool]] | None = None
        # Cached as a list once for cheap equality with the protocol
@@ -276,8 +277,10 @@ class MessagesTransformer(StreamTransformer):
            self._route_protocol_event(
                cast("MessagesData", payload), run_id=run_id, node=node
            )
-        elif isinstance(payload, BaseMessage) and not isinstance(
-            payload, AIMessageChunk
+        elif (
+            isinstance(payload, BaseMessage)
+            and not isinstance(payload, AIMessageChunk)
+            and not isinstance(payload, ToolMessage)
        ):
            self._route_whole_message(payload, node=node)
        # Legacy AIMessageChunk tuples (from on_llm_new_token) are ignored;
@@ -295,6 +298,11 @@ class MessagesTransformer(StreamTransformer):
    ) -> None:
        event_type = event.get("event")
        if event_type == "message-start":
+            # Tool results are exposed on the tools projection and state
+            # snapshots; run.messages is the chat-token projection.
+            if event.get("role") == "tool":
+                self._ignored_runs.add(run_id)
+                return
            message_id = event.get("message_id")
            stream = self._make_stream(
                namespace=[],
@@ -304,6 +312,9 @@ class MessagesTransformer(StreamTransformer):
            self._by_run[run_id] = stream
            self._log.push(stream)
            stream.dispatch(event)
+        elif run_id in self._ignored_runs:
+            if event_type == "message-finish":
+                self._ignored_runs.discard(run_id)
        elif run_id in self._by_run:
            stream = self._by_run[run_id]
            stream.dispatch(event)
@@ -319,12 +330,14 @@ class MessagesTransformer(StreamTransformer):
    def finalize(self) -> None:
        """Clear any routing state — streams close themselves via `message-finish`."""
        self._by_run.clear()
+        self._ignored_runs.clear()

    def fail(self, err: BaseException) -> None:
        """Propagate run error to any streams still open when the graph fails."""
        for stream in list(self._by_run.values()):
            stream.fail(err)
        self._by_run.clear()
+        self._ignored_runs.clear()


 SubgraphStatus = Literal["started", "completed", "failed", "interrupted", "drained"]
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"

 [project]
 name = "langgraph"
-version = "1.2.0"
+version = "1.2.1"
 description = "Building stateful, multi-actor applications with LLMs"
 authors = []
 requires-python = ">=3.10"
@@ -0,0 +1,296 @@
+"""Tests for `StreamTransformer.before_builtins` lane ordering.
+
+`before_builtins = True` transformers are registered ahead of the
+rest, preserving relative order within each lane. This lets
+content-mutating transformers run before built-ins like
+`MessagesTransformer` that eagerly snapshot text fields into their
+projections.
+"""
+
+from __future__ import annotations
+
+import time
+from typing import Any, ClassVar
+
+from langgraph.stream._mux import StreamMux
+from langgraph.stream._types import StreamTransformer
+from langgraph.stream.stream_channel import StreamChannel
+from langgraph.stream.transformers import (
+    LifecycleTransformer,
+    MessagesTransformer,
+    TasksTransformer,
+)
+
+TS = int(time.time() * 1000)
+
+
+def _messages_event(namespace: list[str], data: Any) -> dict[str, Any]:
+    return {
+        "type": "event",
+        "method": "messages",
+        "params": {"namespace": namespace, "timestamp": TS, "data": data},
+    }
+
+
+class _Tap(StreamTransformer):
+    """Records the order it observed each event."""
+
+    required_stream_modes: ClassVar[tuple[str, ...]] = ()
+
+    def __init__(self, scope: tuple[str, ...] = (), *, label: str = "tap") -> None:
+        super().__init__(scope)
+        self.label = label
+        self.log: list[str] = []
+        self._channel: StreamChannel[str] = StreamChannel()
+
+    def init(self) -> dict[str, Any]:
+        return {f"tap_{self.label}": self._channel}
+
+    def process(self, event: dict[str, Any]) -> bool:
+        self.log.append(self.label)
+        return True
+
+
+class _PreTap(_Tap):
+    before_builtins: ClassVar[bool] = True
+
+
+class _TextRedactor(StreamTransformer):
+    """Mutates `text-delta` events in place to a fixed redacted string."""
+
+    before_builtins: ClassVar[bool] = True
+    required_stream_modes: ClassVar[tuple[str, ...]] = ("messages",)
+
+    def __init__(self, scope: tuple[str, ...] = ()) -> None:
+        super().__init__(scope)
+        self._channel: StreamChannel[str] = StreamChannel()
+
+    def init(self) -> dict[str, Any]:
+        return {"redactor": self._channel}
+
+    def process(self, event: dict[str, Any]) -> bool:
+        if event.get("method") != "messages":
+            return True
+        payload, _meta = event["params"]["data"]
+        if isinstance(payload, dict) and payload.get("event") == "content-block-delta":
+            delta = payload.get("delta") or {}
+            if delta.get("type") == "text-delta":
+                delta["text"] = "[REDACTED]"
+        return True
+
+
+def test_before_builtins_factories_run_before_others() -> None:
+    """A `before_builtins=True` factory is registered ahead of the rest."""
+
+    seen: list[type[StreamTransformer]] = []
+
+    class _PostTap(_Tap):
+        def __init__(self, scope: tuple[str, ...] = ()) -> None:
+            super().__init__(scope, label="post")
+
+        def process(self, event: dict[str, Any]) -> bool:
+            seen.append(_PostTap)
+            return True
+
+    class _EagerTap(_Tap):
+        before_builtins: ClassVar[bool] = True
+
+        def __init__(self, scope: tuple[str, ...] = ()) -> None:
+            super().__init__(scope, label="eager")
+
+        def process(self, event: dict[str, Any]) -> bool:
+            seen.append(_EagerTap)
+            return True
+
+    mux = StreamMux(
+        factories=[_PostTap, _EagerTap],
+        scope=(),
+        is_async=False,
+    )
+    # `_EagerTap` was supplied second but should be registered first.
+    types_in_order = [type(t) for t in mux._transformers]
+    assert types_in_order.index(_EagerTap) < types_in_order.index(_PostTap)
+
+    mux.push(
+        _messages_event([], ({"event": "message-start", "role": "ai", "id": "m1"}, {}))
+    )
+    # And it ran first when the event was dispatched.
+    assert seen == [_EagerTap, _PostTap]
+
+
+def test_within_lane_order_preserved() -> None:
+    """Within each lane, the supplied order is the registration order."""
+
+    class _A(_PreTap):
+        pass
+
+    class _B(_PreTap):
+        pass
+
+    class _C(_Tap):
+        pass
+
+    class _D(_Tap):
+        pass
+
+    mux = StreamMux(
+        factories=[
+            lambda scope: _C(scope, label="c"),
+            lambda scope: _A(scope, label="a"),
+            lambda scope: _D(scope, label="d"),
+            lambda scope: _B(scope, label="b"),
+        ],
+        scope=(),
+        is_async=False,
+    )
+    order = [t.label for t in mux._transformers]  # type: ignore[attr-defined]
+    # Pre lane (a, b) ahead of default lane (c, d). Within each, supplied order kept.
+    assert order == ["a", "b", "c", "d"]
+
+
+def test_redactor_runs_before_messages_transformer() -> None:
+    """Content mutated by a pre-lane transformer reaches `MessagesTransformer`."""
+
+    # Order supplied: built-ins first (as in pregel/main.py), then the
+    # opt-in pre-lane redactor. Partitioning should still register the
+    # redactor first.
+    mux = StreamMux(
+        factories=[MessagesTransformer, _TextRedactor],
+        scope=(),
+        is_async=False,
+    )
+    types_in_order = [type(t) for t in mux._transformers]
+    assert types_in_order.index(_TextRedactor) < types_in_order.index(
+        MessagesTransformer
+    )
+
+
+def test_lifecycle_unaffected_by_pre_lane_observer() -> None:
+    """An observer-only pre-lane transformer doesn't break lifecycle bookkeeping."""
+
+    class _NoopPreObserver(StreamTransformer):
+        before_builtins: ClassVar[bool] = True
+        required_stream_modes: ClassVar[tuple[str, ...]] = ("tasks",)
+
+        def __init__(self, scope: tuple[str, ...] = ()) -> None:
+            super().__init__(scope)
+            self._channel: StreamChannel[str] = StreamChannel()
+            self.seen: list[tuple[str, ...]] = []
+
+        def init(self) -> dict[str, Any]:
+            return {"noop_observer": self._channel}
+
+        def process(self, event: dict[str, Any]) -> bool:
+            if event.get("method") == "tasks":
+                self.seen.append(tuple(event["params"]["namespace"]))
+            return True
+
+    mux = StreamMux(
+        factories=[LifecycleTransformer, TasksTransformer, _NoopPreObserver],
+        scope=(),
+        is_async=False,
+    )
+    types_in_order = [type(t) for t in mux._transformers]
+    assert types_in_order.index(_NoopPreObserver) < types_in_order.index(
+        LifecycleTransformer
+    )
+
+    observer = next(t for t in mux._transformers if isinstance(t, _NoopPreObserver))
+    lifecycle = next(
+        t for t in mux._transformers if isinstance(t, LifecycleTransformer)
+    )
+
+    # Push a synthetic `tasks` event that lifecycle would normally track.
+    mux.push(
+        {
+            "type": "event",
+            "method": "tasks",
+            "params": {
+                "namespace": ["child:abc"],
+                "timestamp": TS,
+                "data": {"name": "child"},
+            },
+        }
+    )
+
+    # Pre-lane observer saw the event, AND lifecycle's bookkeeping still
+    # registered the new namespace (the observer didn't mutate anything).
+    assert observer.seen == [("child:abc",)]
+    assert ("child:abc",) in lifecycle._seen  # type: ignore[attr-defined]
+
+
+def test_default_is_false() -> None:
+    """`StreamTransformer.before_builtins` defaults to False."""
+
+    assert StreamTransformer.before_builtins is False
+    assert MessagesTransformer.before_builtins is False
+    assert LifecycleTransformer.before_builtins is False
+
+
+def test_pre_lane_mutation_lands_in_messages_projection() -> None:
+    """End-to-end: text mutated by a pre-lane transformer is what
+    `MessagesTransformer` snapshots into its `ChatModelStream` projection.
+
+    Without `before_builtins`, the redactor would run after
+    MessagesTransformer's eager extraction and the projection would
+    contain the raw, un-redacted text.
+    """
+
+    mux = StreamMux(
+        factories=[MessagesTransformer, _TextRedactor],
+        scope=(),
+        is_async=False,
+    )
+    messages_transformer = next(
+        t for t in mux._transformers if isinstance(t, MessagesTransformer)
+    )
+    # Unblock both the mux's main log and the messages projection log so
+    # synthetic pushes are accepted without a real consumer attached.
+    mux._events._subscribed = True
+    messages_transformer._log._subscribed = True
+
+    meta = {"langgraph_node": "model", "run_id": "run-1"}
+
+    # message-start → MessagesTransformer creates a ChatModelStream.
+    mux.push(
+        _messages_event(
+            [],
+            ({"event": "message-start", "role": "ai", "id": "msg-1"}, meta),
+        )
+    )
+
+    # content-block-delta carrying the secret. The redactor (pre-lane)
+    # mutates `delta.text` BEFORE MessagesTransformer snapshots it.
+    mux.push(
+        _messages_event(
+            [],
+            (
+                {
+                    "event": "content-block-delta",
+                    "index": 0,
+                    "delta": {"type": "text-delta", "text": "secret@example.com"},
+                },
+                meta,
+            ),
+        )
+    )
+
+    # Capture the still-open stream before message-finish removes it from
+    # MessagesTransformer's `_by_run` dict.
+    chat_stream = messages_transformer._by_run["run-1"]  # type: ignore[attr-defined]
+
+    # message-finish → closes the stream.
+    mux.push(
+        _messages_event(
+            [],
+            ({"event": "message-finish"}, meta),
+        )
+    )
+
+    # The redactor mutated `delta.text` to "[REDACTED]" before
+    # MessagesTransformer snapshotted the string into the text
+    # accumulator. Without `before_builtins`, the accumulator would hold
+    # the raw "secret@example.com".
+    assert chat_stream._text_acc == "[REDACTED]", (  # type: ignore[attr-defined]
+        f"expected redacted text in projection, got {chat_stream._text_acc!r}"
+    )
@@ -12,7 +12,7 @@ from langchain_core.language_models.chat_model_stream import (
    AsyncChatModelStream,
    ChatModelStream,
 )
-from langchain_core.messages import AIMessage, AIMessageChunk
+from langchain_core.messages import AIMessage, AIMessageChunk, ToolMessage
 from langchain_core.runnables import RunnableConfig
 from typing_extensions import TypedDict

@@ -213,6 +213,23 @@ class TestProtocolEventRouting:
        log.close()
        assert _unstamped(log._items) == []

+    def test_tool_role_protocol_events_are_ignored(self) -> None:
+        t, log = _make_sync_transformer()
+        for evt in [
+            {"event": "message-start", "role": "tool", "message_id": "tool-msg-1"},
+            {
+                "event": "content-block-delta",
+                "index": 0,
+                "content_block": {"type": "text", "text": "[]"},
+            },
+            {"event": "message-finish", "reason": "stop"},
+        ]:
+            t.process(_proto_event(evt, run_id="tool-run"))
+
+        log.close()
+        assert _unstamped(log._items) == []
+        assert t._ignored_runs == set()
+
    def test_concurrent_streams_routed_by_run_id(self) -> None:
        t, log = _make_sync_transformer()
        life_a = _lifecycle(text="aaaa", message_id="run-a")
@@ -273,6 +290,29 @@ class TestWholeMessageFallback:
        assert stream.done
        assert stream.output.text == "the full answer"

+    def test_whole_tool_message_is_ignored(self) -> None:
+        t, log = _make_sync_transformer()
+        t.process(
+            {
+                "type": "event",
+                "method": "messages",
+                "params": {
+                    "namespace": [],
+                    "timestamp": TS,
+                    "data": (
+                        ToolMessage(
+                            content="[]",
+                            id="tool-msg-1",
+                            tool_call_id="call_1",
+                        ),
+                        {"langgraph_node": "tools"},
+                    ),
+                },
+            }
+        )
+        log.close()
+        assert _unstamped(log._items) == []
+
    def test_whole_message_has_full_lifecycle(self) -> None:
        t, log = _make_sync_transformer()
        t.process(_whole_msg("full"))
@@ -849,6 +889,23 @@ class TestStreamMessagesHandlerV2Unit:

        assert emitted == []

+    def test_on_chain_end_does_not_emit_tool_messages(self) -> None:
+        from uuid import uuid4
+
+        from langgraph.pregel._messages import StreamMessagesHandlerV2
+
+        emitted: list[Any] = []
+        handler = StreamMessagesHandlerV2(emitted.append, subgraphs=False)
+        run_id = uuid4()
+        handler.metadata[run_id] = ((), {"langgraph_node": "tools"})
+
+        handler.on_chain_end(
+            {"messages": [ToolMessage(content="[]", tool_call_id="call_1")]},
+            run_id=run_id,
+        )
+
+        assert emitted == []
+
    def test_on_llm_end_dedupes_when_final_message_id_differs(self) -> None:
        """A streamed v2 message should not be emitted again from the final
        AIMessage fallback when its final id does not match `message-start`."""
@@ -871,11 +871,11 @@ wheels = [

 [[package]]
 name = "idna"
-version = "3.11"
+version = "3.15"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/6f/6d/0703ccc57f3a7233505399edb88de3cbd678da106337b9fcde432b65ed60/idna-3.11.tar.gz", hash = "sha256:795dafcc9c04ed0c1fb032c2aa73654d8e8c5023a7df64a53f39190ada629902", size = 194582, upload-time = "2025-10-12T14:55:20.501Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/82/77/7b3966d0b9d1d31a36ddf1746926a11dface89a83409bf1483f0237aa758/idna-3.15.tar.gz", hash = "sha256:ca962446ea538f7092a95e057da437618e886f4d349216d2b1e294abfdb65fdc", size = 199245, upload-time = "2026-05-12T22:45:57.011Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/0e/61/66938bbb5fc52dbdf84594873d5b51fb1f7c7794e9c0f5bd885f30bc507b/idna-3.11-py3-none-any.whl", hash = "sha256:771a87f49d9defaf64091e6e6fe9c18d4833f140bd19464795bc32d966ca37ea", size = 71008, upload-time = "2025-10-12T14:55:18.883Z" },
+    { url = "https://files.pythonhosted.org/packages/d2/23/408243171aa9aaba178d3e2559159c24c1171a641aa83b67bdd3394ead8e/idna-3.15-py3-none-any.whl", hash = "sha256:048adeaf8c2d788c40fee287673ccaa74c24ffd8dcf09ffa555a2fbb59f10ac8", size = 72340, upload-time = "2026-05-12T22:45:55.733Z" },
 ]

 [[package]]
@@ -1382,7 +1382,7 @@ wheels = [

 [[package]]
 name = "langgraph"
-version = "1.2.0"
+version = "1.2.1"
 source = { editable = "." }
 dependencies = [
    { name = "langchain-core" },
@@ -1563,7 +1563,7 @@ wheels = [

 [[package]]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.1"
 source = { editable = "../checkpoint" }
 dependencies = [
    { name = "langchain-core" },
@@ -1867,7 +1867,7 @@ test = [

 [[package]]
 name = "langsmith"
-version = "0.7.31"
+version = "0.8.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -1880,9 +1880,9 @@ dependencies = [
    { name = "xxhash" },
    { name = "zstandard" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/e6/11/696019490992db5c87774dc20515529ef42a01e1d770fb754ed6d9b12fb0/langsmith-0.7.31.tar.gz", hash = "sha256:331ee4f7c26bb5be4022b9859b7d7b122cbf8c9d01d9f530114c1914b0349ffb", size = 1178480, upload-time = "2026-04-14T17:55:41.242Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/a8/64/95f1f013531395f4e8ed73caeee780f65c7c58fe028cb543f8937b45611b/langsmith-0.8.0.tar.gz", hash = "sha256:59fe5b2a56bbbe14a08aa76691f84b49e8675dd21e11b57d80c6db8c08bac2e3", size = 4432996, upload-time = "2026-04-30T22:13:07.341Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/1d/a1/a013cf458c301cda86a213dd153ce0a01c93f1ab5833f951e6a44c9763ce/langsmith-0.7.31-py3-none-any.whl", hash = "sha256:0291d49203f6e80dda011af1afda61eb0595a4d697adb684590a8805e1d61fb6", size = 373276, upload-time = "2026-04-14T17:55:39.677Z" },
+    { url = "https://files.pythonhosted.org/packages/f3/e1/a4be2e696c9473bb53298df398237da5674704d781d4b748ed35aeef592a/langsmith-0.8.0-py3-none-any.whl", hash = "sha256:12cc4bc5622b835a6d841964d6034df3617bdb912dae0c1381fd0a68a9b3a3ef", size = 393268, upload-time = "2026-04-30T22:13:05.56Z" },
 ]

 [package.optional-dependencies]
@@ -5,12 +5,42 @@ from __future__ import annotations
 from collections.abc import Awaitable, Callable
 from typing import Any

+from langchain_core.messages import ToolMessage
 from langgraph.stream._types import ProtocolEvent, StreamTransformer
 from langgraph.stream.stream_channel import StreamChannel

 from langgraph.prebuilt._tool_call_stream import ToolCallStream


+def _is_serialized_tool_message(value: Any) -> bool:
+    """Detect a serialized LangChain `ToolMessage` payload.
+
+    Example:
+        {
+            "lc": 1,
+            "type": "constructor",
+            "id": ["langchain_core", "messages", "ToolMessage"],
+            "kwargs": {"content": "raw tool result", "tool_call_id": "call_1"},
+        }
+    """
+    return (
+        isinstance(value, dict)
+        and value.get("type") == "constructor"
+        and isinstance(value.get("id"), list)
+        and value["id"][-1] == "ToolMessage"
+    )
+
+
+def _normalize_tool_output(output: Any) -> Any:
+    if isinstance(output, ToolMessage):
+        return output.content
+    if _is_serialized_tool_message(output):
+        kwargs = output.get("kwargs")
+        if isinstance(kwargs, dict):
+            return kwargs.get("content")
+    return output
+
+
 class ToolCallTransformer(StreamTransformer):
    """Project `tools` channel events into `ToolCallStream` handles.

@@ -109,7 +139,7 @@ class ToolCallTransformer(StreamTransformer):
        elif event_type == "tool-finished":
            stream = self._active.pop(tool_call_id, None)
            if stream is not None:
-                stream._finish(data.get("output"))
+                stream._finish(_normalize_tool_output(data.get("output")))
        elif event_type == "tool-error":
            stream = self._active.pop(tool_call_id, None)
            if stream is not None:
@@ -6,7 +6,7 @@ import time
 from typing import Annotated, Any

 import pytest
-from langchain_core.messages import AIMessage
+from langchain_core.messages import AIMessage, ToolMessage
 from langchain_core.tools import tool
 from langgraph.constants import END, START
 from langgraph.graph import StateGraph
@@ -128,6 +128,42 @@ class TestToolCallTransformerUnit:
        assert stream.error is None
        assert "tc1" not in transformer._active

+    def test_finish_unwraps_tool_message_output(self) -> None:
+        mux, transformer = _mux()
+        mux.push(_tool_event("tool-started", "tc1", tool_name="echo"))
+        stream = transformer._active["tc1"]
+        mux.push(
+            _tool_event(
+                "tool-finished",
+                "tc1",
+                output=ToolMessage(content="done", tool_call_id="tc1"),
+            )
+        )
+        assert stream.completed is True
+        assert stream.output == "done"
+
+    def test_finish_unwraps_serialized_tool_message_output(self) -> None:
+        mux, transformer = _mux()
+        mux.push(_tool_event("tool-started", "tc1", tool_name="echo"))
+        stream = transformer._active["tc1"]
+        mux.push(
+            _tool_event(
+                "tool-finished",
+                "tc1",
+                output={
+                    "lc": 1,
+                    "type": "constructor",
+                    "id": ["langchain_core", "messages", "ToolMessage"],
+                    "kwargs": {
+                        "content": "serialized done",
+                        "tool_call_id": "tc1",
+                    },
+                },
+            )
+        )
+        assert stream.completed is True
+        assert stream.output == "serialized done"
+
    def test_error_closes_stream(self) -> None:
        mux, transformer = _mux()
        mux.push(_tool_event("tool-started", "tc1", tool_name="boom"))
@@ -214,11 +214,11 @@ wheels = [

 [[package]]
 name = "idna"
-version = "3.11"
+version = "3.15"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/6f/6d/0703ccc57f3a7233505399edb88de3cbd678da106337b9fcde432b65ed60/idna-3.11.tar.gz", hash = "sha256:795dafcc9c04ed0c1fb032c2aa73654d8e8c5023a7df64a53f39190ada629902", size = 194582, upload-time = "2025-10-12T14:55:20.501Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/82/77/7b3966d0b9d1d31a36ddf1746926a11dface89a83409bf1483f0237aa758/idna-3.15.tar.gz", hash = "sha256:ca962446ea538f7092a95e057da437618e886f4d349216d2b1e294abfdb65fdc", size = 199245, upload-time = "2026-05-12T22:45:57.011Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/0e/61/66938bbb5fc52dbdf84594873d5b51fb1f7c7794e9c0f5bd885f30bc507b/idna-3.11-py3-none-any.whl", hash = "sha256:771a87f49d9defaf64091e6e6fe9c18d4833f140bd19464795bc32d966ca37ea", size = 71008, upload-time = "2025-10-12T14:55:18.883Z" },
+    { url = "https://files.pythonhosted.org/packages/d2/23/408243171aa9aaba178d3e2559159c24c1171a641aa83b67bdd3394ead8e/idna-3.15-py3-none-any.whl", hash = "sha256:048adeaf8c2d788c40fee287673ccaa74c24ffd8dcf09ffa555a2fbb59f10ac8", size = 72340, upload-time = "2026-05-12T22:45:55.733Z" },
 ]

 [[package]]
@@ -285,7 +285,7 @@ wheels = [

 [[package]]
 name = "langgraph"
-version = "1.2.0"
+version = "1.2.1"
 source = { editable = "../langgraph" }
 dependencies = [
    { name = "langchain-core" },
@@ -369,7 +369,7 @@ test = [

 [[package]]
 name = "langgraph-checkpoint"
-version = "4.1.0"
+version = "4.1.1"
 source = { editable = "../checkpoint" }
 dependencies = [
    { name = "langchain-core" },
@@ -636,7 +636,7 @@ test = [

 [[package]]
 name = "langsmith"
-version = "0.7.31"
+version = "0.8.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
    { name = "httpx" },
@@ -649,9 +649,9 @@ dependencies = [
    { name = "xxhash" },
    { name = "zstandard" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/e6/11/696019490992db5c87774dc20515529ef42a01e1d770fb754ed6d9b12fb0/langsmith-0.7.31.tar.gz", hash = "sha256:331ee4f7c26bb5be4022b9859b7d7b122cbf8c9d01d9f530114c1914b0349ffb", size = 1178480, upload-time = "2026-04-14T17:55:41.242Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/a8/64/95f1f013531395f4e8ed73caeee780f65c7c58fe028cb543f8937b45611b/langsmith-0.8.0.tar.gz", hash = "sha256:59fe5b2a56bbbe14a08aa76691f84b49e8675dd21e11b57d80c6db8c08bac2e3", size = 4432996, upload-time = "2026-04-30T22:13:07.341Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/1d/a1/a013cf458c301cda86a213dd153ce0a01c93f1ab5833f951e6a44c9763ce/langsmith-0.7.31-py3-none-any.whl", hash = "sha256:0291d49203f6e80dda011af1afda61eb0595a4d697adb684590a8805e1d61fb6", size = 373276, upload-time = "2026-04-14T17:55:39.677Z" },
+    { url = "https://files.pythonhosted.org/packages/f3/e1/a4be2e696c9473bb53298df398237da5674704d781d4b748ed35aeef592a/langsmith-0.8.0-py3-none-any.whl", hash = "sha256:12cc4bc5622b835a6d841964d6034df3617bdb912dae0c1381fd0a68a9b3a3ef", size = 393268, upload-time = "2026-04-30T22:13:05.56Z" },
 ]

 [[package]]
@@ -3,6 +3,6 @@ from langgraph_sdk.client import get_client, get_sync_client
 from langgraph_sdk.encryption import Encryption
 from langgraph_sdk.encryption.types import EncryptionContext

-__version__ = "0.3.14"
+__version__ = "0.3.15"

 __all__ = ["Auth", "Encryption", "EncryptionContext", "get_client", "get_sync_client"]
@@ -8,6 +8,7 @@ from typing import Any, Literal, cast, overload
 import httpx

 from langgraph_sdk._async.http import HttpClient
+from langgraph_sdk._shared.utilities import _quote_path_param
 from langgraph_sdk.schema import (
    Assistant,
    AssistantSelectField,
@@ -84,7 +85,9 @@ class AssistantsClient:
            ```
        """
        return await self.http.get(
-            f"/assistants/{assistant_id}", headers=headers, params=params
+            f"/assistants/{_quote_path_param(assistant_id)}",
+            headers=headers,
+            params=params,
        )

    async def get_graph(
@@ -142,7 +145,9 @@ class AssistantsClient:
            query_params.update(params)

        return await self.http.get(
-            f"/assistants/{assistant_id}/graph", params=query_params, headers=headers
+            f"/assistants/{_quote_path_param(assistant_id)}/graph",
+            params=query_params,
+            headers=headers,
        )

    async def get_schemas(
@@ -263,7 +268,9 @@ class AssistantsClient:

        """
        return await self.http.get(
-            f"/assistants/{assistant_id}/schemas", headers=headers, params=params
+            f"/assistants/{_quote_path_param(assistant_id)}/schemas",
+            headers=headers,
+            params=params,
        )

    async def get_subgraphs(
@@ -293,13 +300,13 @@ class AssistantsClient:
            get_params = {**get_params, **dict(params)}
        if namespace is not None:
            return await self.http.get(
-                f"/assistants/{assistant_id}/subgraphs/{namespace}",
+                f"/assistants/{_quote_path_param(assistant_id)}/subgraphs/{_quote_path_param(namespace)}",
                params=get_params,
                headers=headers,
            )
        else:
            return await self.http.get(
-                f"/assistants/{assistant_id}/subgraphs",
+                f"/assistants/{_quote_path_param(assistant_id)}/subgraphs",
                params=get_params,
                headers=headers,
            )
@@ -436,7 +443,7 @@ class AssistantsClient:
        if description:
            payload["description"] = description
        return await self.http.patch(
-            f"/assistants/{assistant_id}",
+            f"/assistants/{_quote_path_param(assistant_id)}",
            json=payload,
            headers=headers,
            params=params,
@@ -479,7 +486,7 @@ class AssistantsClient:
        if params:
            query_params.update(params)
        await self.http.delete(
-            f"/assistants/{assistant_id}",
+            f"/assistants/{_quote_path_param(assistant_id)}",
            headers=headers,
            params=query_params or None,
        )
@@ -686,7 +693,7 @@ class AssistantsClient:
        if metadata:
            payload["metadata"] = metadata
        return await self.http.post(
-            f"/assistants/{assistant_id}/versions",
+            f"/assistants/{_quote_path_param(assistant_id)}/versions",
            json=payload,
            headers=headers,
            params=params,
@@ -726,7 +733,7 @@ class AssistantsClient:
        payload: dict[str, Any] = {"version": version}

        return await self.http.post(
-            f"/assistants/{assistant_id}/latest",
+            f"/assistants/{_quote_path_param(assistant_id)}/latest",
            json=payload,
            headers=headers,
            params=params,
@@ -8,7 +8,7 @@ from datetime import datetime, tzinfo
 from typing import Any

 from langgraph_sdk._async.http import HttpClient
-from langgraph_sdk._shared.utilities import _resolve_timezone
+from langgraph_sdk._shared.utilities import _quote_path_param, _resolve_timezone
 from langgraph_sdk.schema import (
    All,
    Config,
@@ -166,7 +166,7 @@ class CronClient:
            payload["multitask_strategy"] = multitask_strategy
        payload = {k: v for k, v in payload.items() if v is not None}
        return await self.http.post(
-            f"/threads/{thread_id}/runs/crons",
+            f"/threads/{_quote_path_param(thread_id)}/runs/crons",
            json=payload,
            headers=headers,
            params=params,
@@ -315,7 +315,9 @@ class CronClient:
            ```

        """
-        await self.http.delete(f"/runs/crons/{cron_id}", headers=headers, params=params)
+        await self.http.delete(
+            f"/runs/crons/{_quote_path_param(cron_id)}", headers=headers, params=params
+        )

    async def update(
        self,
@@ -402,7 +404,7 @@ class CronClient:
        }
        payload = {k: v for k, v in payload.items() if v is not None}
        return await self.http.patch(
-            f"/runs/crons/{cron_id}",
+            f"/runs/crons/{_quote_path_param(cron_id)}",
            json=payload,
            headers=headers,
            params=params,
@@ -12,6 +12,7 @@ import httpx
 from langgraph_sdk._async.http import HttpClient
 from langgraph_sdk._shared.utilities import (
    _get_run_metadata_from_response,
+    _quote_path_param,
    _sse_to_v2_dict,
 )
 from langgraph_sdk.schema import (
@@ -337,7 +338,7 @@ class RunsClient:
            "langsmith_tracer": langsmith_tracing,
        }
        endpoint = (
-            f"/threads/{thread_id}/runs/stream"
+            f"/threads/{_quote_path_param(thread_id)}/runs/stream"
            if thread_id is not None
            else "/runs/stream"
        )
@@ -596,7 +597,7 @@ class RunsClient:
                on_run_created(metadata)

        return await self.http.post(
-            f"/threads/{thread_id}/runs" if thread_id else "/runs",
+            f"/threads/{_quote_path_param(thread_id)}/runs" if thread_id else "/runs",
            json=payload,
            params=params,
            headers=headers,
@@ -821,7 +822,9 @@ class RunsClient:
            "langsmith_tracer": langsmith_tracing,
        }
        endpoint = (
-            f"/threads/{thread_id}/runs/wait" if thread_id is not None else "/runs/wait"
+            f"/threads/{_quote_path_param(thread_id)}/runs/wait"
+            if thread_id is not None
+            else "/runs/wait"
        )

        def on_response(res: httpx.Response):
@@ -895,7 +898,9 @@ class RunsClient:
        if params:
            query_params.update(params)
        return await self.http.get(
-            f"/threads/{thread_id}/runs", params=query_params, headers=headers
+            f"/threads/{_quote_path_param(thread_id)}/runs",
+            params=query_params,
+            headers=headers,
        )

    async def get(
@@ -930,7 +935,9 @@ class RunsClient:
        """

        return await self.http.get(
-            f"/threads/{thread_id}/runs/{run_id}", headers=headers, params=params
+            f"/threads/{_quote_path_param(thread_id)}/runs/{_quote_path_param(run_id)}",
+            headers=headers,
+            params=params,
        )

    async def cancel(
@@ -978,14 +985,14 @@ class RunsClient:
            query_params.update(params)
        if wait:
            return await self.http.request_reconnect(
-                f"/threads/{thread_id}/runs/{run_id}/cancel",
+                f"/threads/{_quote_path_param(thread_id)}/runs/{_quote_path_param(run_id)}/cancel",
                "POST",
                params=query_params,
                headers=headers,
            )
        else:
            return await self.http.post(
-                f"/threads/{thread_id}/runs/{run_id}/cancel",
+                f"/threads/{_quote_path_param(thread_id)}/runs/{_quote_path_param(run_id)}/cancel",
                json=None,
                params=query_params,
                headers=headers,
@@ -1081,7 +1088,7 @@ class RunsClient:

        """
        return await self.http.request_reconnect(
-            f"/threads/{thread_id}/runs/{run_id}/join",
+            f"/threads/{_quote_path_param(thread_id)}/runs/{_quote_path_param(run_id)}/join",
            "GET",
            headers=headers,
            params=params,
@@ -1136,7 +1143,7 @@ class RunsClient:
        if params:
            query_params.update(params)
        return self.http.stream(
-            f"/threads/{thread_id}/runs/{run_id}/stream",
+            f"/threads/{_quote_path_param(thread_id)}/runs/{_quote_path_param(run_id)}/stream",
            "GET",
            params=query_params,
            headers={
@@ -1177,5 +1184,7 @@ class RunsClient:

        """
        await self.http.delete(
-            f"/threads/{thread_id}/runs/{run_id}", headers=headers, params=params
+            f"/threads/{_quote_path_param(thread_id)}/runs/{_quote_path_param(run_id)}",
+            headers=headers,
+            params=params,
        )
@@ -6,6 +6,7 @@ from collections.abc import AsyncIterator, Mapping, Sequence
 from typing import Any, Literal, overload

 from langgraph_sdk._async.http import HttpClient
+from langgraph_sdk._shared.utilities import _quote_path_param
 from langgraph_sdk.schema import (
    Checkpoint,
    Json,
@@ -90,7 +91,7 @@ class ThreadsClient:
        if params:
            query_params.update(params)
        return await self.http.get(
-            f"/threads/{thread_id}",
+            f"/threads/{_quote_path_param(thread_id)}",
            headers=headers,
            params=query_params or None,
        )
@@ -254,7 +255,7 @@ class ThreadsClient:
        if return_minimal:
            request_headers["Prefer"] = "return=minimal"
        return await self.http.patch(
-            f"/threads/{thread_id}",
+            f"/threads/{_quote_path_param(thread_id)}",
            json=payload,
            headers=request_headers or None,
            params=params,
@@ -287,7 +288,9 @@ class ThreadsClient:
            ```

        """
-        await self.http.delete(f"/threads/{thread_id}", headers=headers, params=params)
+        await self.http.delete(
+            f"/threads/{_quote_path_param(thread_id)}", headers=headers, params=params
+        )

    async def search(
        self,
@@ -430,7 +433,10 @@ class ThreadsClient:

        """
        return await self.http.post(
-            f"/threads/{thread_id}/copy", json=None, headers=headers, params=params
+            f"/threads/{_quote_path_param(thread_id)}/copy",
+            json=None,
+            headers=headers,
+            params=params,
        )

    async def prune(
@@ -586,7 +592,7 @@ class ThreadsClient:
        """
        if checkpoint:
            return await self.http.post(
-                f"/threads/{thread_id}/state/checkpoint",
+                f"/threads/{_quote_path_param(thread_id)}/state/checkpoint",
                json={"checkpoint": checkpoint, "subgraphs": subgraphs},
                headers=headers,
                params=params,
@@ -596,7 +602,7 @@ class ThreadsClient:
            if params:
                get_params = {**get_params, **dict(params)}
            return await self.http.get(
-                f"/threads/{thread_id}/state/{checkpoint_id}",
+                f"/threads/{_quote_path_param(thread_id)}/state/{_quote_path_param(checkpoint_id)}",
                params=get_params,
                headers=headers,
            )
@@ -605,7 +611,7 @@ class ThreadsClient:
            if params:
                get_params = {**get_params, **dict(params)}
            return await self.http.get(
-                f"/threads/{thread_id}/state",
+                f"/threads/{_quote_path_param(thread_id)}/state",
                params=get_params,
                headers=headers,
            )
@@ -670,7 +676,10 @@ class ThreadsClient:
        if as_node:
            payload["as_node"] = as_node
        return await self.http.post(
-            f"/threads/{thread_id}/state", json=payload, headers=headers, params=params
+            f"/threads/{_quote_path_param(thread_id)}/state",
+            json=payload,
+            headers=headers,
+            params=params,
        )

    async def get_history(
@@ -719,7 +728,7 @@ class ThreadsClient:
        if checkpoint:
            payload["checkpoint"] = checkpoint
        return await self.http.post(
-            f"/threads/{thread_id}/history",
+            f"/threads/{_quote_path_param(thread_id)}/history",
            json=payload,
            headers=headers,
            params=params,
@@ -763,7 +772,7 @@ class ThreadsClient:
        if params:
            query_params.update(params)
        return self.http.stream(
-            f"/threads/{thread_id}/stream",
+            f"/threads/{_quote_path_param(thread_id)}/stream",
            "GET",
            headers={
                **({"Last-Event-ID": last_event_id} if last_event_id else {}),
@@ -8,7 +8,7 @@ import re
 from collections.abc import Mapping
 from datetime import tzinfo
 from typing import TYPE_CHECKING, Any, cast
-from urllib.parse import urlparse
+from urllib.parse import quote, urlparse

 import httpx

@@ -198,6 +198,39 @@ def _provided_vals(d: Mapping[str, Any]) -> dict[str, Any]:
    return {k: v for k, v in d.items() if v is not None}


+def _quote_path_param(value: Any) -> str:
+    """Encode a value for safe interpolation into a request path segment.
+
+    Path segments are encoded with ``safe=""`` so that ``/`` and other reserved
+    characters are escaped. Standalone dot-segments (``.`` and ``..``) are also
+    encoded because some URL-handling stacks (including ``httpx``) collapse
+    them client-side as relative-path traversal before transmission. The value
+    is coerced to ``str`` so callers can pass ``uuid.UUID`` and similar types
+    directly without changing call sites.
+
+    A properly formed identifier (for example, a standard UUID, which contains
+    no dots or reserved characters) round-trips through this function
+    unchanged.
+
+    Raises:
+        TypeError: If `value` is `None` or a `bytes`/`bytearray` instance.
+            Coercing those would produce misleading paths (e.g. `/threads/None`),
+            so surface the caller bug instead.
+    """
+    if value is None:
+        raise TypeError("path parameter must not be None")
+    if isinstance(value, (bytes, bytearray)):
+        raise TypeError("path parameter must not be bytes; pass a str or uuid.UUID")
+    quoted = quote(str(value), safe="")
+    # Bare "." or ".." (or any all-dot string) acts as a relative-path segment
+    # that some HTTP stacks (including ``httpx``) collapse client-side before
+    # transmission. Encode the dots so the segment becomes opaque to that
+    # logic. Mixed values like "agent.v1" are unaffected.
+    if quoted and all(c == "." for c in quoted):
+        quoted = "%2E" * len(quoted)
+    return quoted
+
+
 _registered_transports: list[httpx.ASGITransport] = []


@@ -7,6 +7,7 @@ from typing import Any, Literal, cast, overload

 import httpx

+from langgraph_sdk._shared.utilities import _quote_path_param
 from langgraph_sdk._sync.http import SyncHttpClient
 from langgraph_sdk.schema import (
    Assistant,
@@ -83,7 +84,9 @@ class SyncAssistantsClient:

        """
        return self.http.get(
-            f"/assistants/{assistant_id}", headers=headers, params=params
+            f"/assistants/{_quote_path_param(assistant_id)}",
+            headers=headers,
+            params=params,
        )

    def get_graph(
@@ -136,7 +139,9 @@ class SyncAssistantsClient:
        if params:
            query_params.update(params)
        return self.http.get(
-            f"/assistants/{assistant_id}/graph", params=query_params, headers=headers
+            f"/assistants/{_quote_path_param(assistant_id)}/graph",
+            params=query_params,
+            headers=headers,
        )

    def get_schemas(
@@ -269,7 +274,9 @@ class SyncAssistantsClient:

        """
        return self.http.get(
-            f"/assistants/{assistant_id}/schemas", headers=headers, params=params
+            f"/assistants/{_quote_path_param(assistant_id)}/schemas",
+            headers=headers,
+            params=params,
        )

    def get_subgraphs(
@@ -297,13 +304,13 @@ class SyncAssistantsClient:
            get_params = {**get_params, **dict(params)}
        if namespace is not None:
            return self.http.get(
-                f"/assistants/{assistant_id}/subgraphs/{namespace}",
+                f"/assistants/{_quote_path_param(assistant_id)}/subgraphs/{_quote_path_param(namespace)}",
                params=get_params,
                headers=headers,
            )
        else:
            return self.http.get(
-                f"/assistants/{assistant_id}/subgraphs",
+                f"/assistants/{_quote_path_param(assistant_id)}/subgraphs",
                params=get_params,
                headers=headers,
            )
@@ -438,7 +445,7 @@ class SyncAssistantsClient:
        if description:
            payload["description"] = description
        return self.http.patch(
-            f"/assistants/{assistant_id}",
+            f"/assistants/{_quote_path_param(assistant_id)}",
            json=payload,
            headers=headers,
            params=params,
@@ -481,7 +488,7 @@ class SyncAssistantsClient:
        if params:
            query_params.update(params)
        self.http.delete(
-            f"/assistants/{assistant_id}",
+            f"/assistants/{_quote_path_param(assistant_id)}",
            headers=headers,
            params=query_params or None,
        )
@@ -685,7 +692,7 @@ class SyncAssistantsClient:
        if metadata:
            payload["metadata"] = metadata
        return self.http.post(
-            f"/assistants/{assistant_id}/versions",
+            f"/assistants/{_quote_path_param(assistant_id)}/versions",
            json=payload,
            headers=headers,
            params=params,
@@ -724,7 +731,7 @@ class SyncAssistantsClient:
        payload: dict[str, Any] = {"version": version}

        return self.http.post(
-            f"/assistants/{assistant_id}/latest",
+            f"/assistants/{_quote_path_param(assistant_id)}/latest",
            json=payload,
            headers=headers,
            params=params,
@@ -7,7 +7,7 @@ from collections.abc import Mapping, Sequence
 from datetime import datetime, tzinfo
 from typing import Any

-from langgraph_sdk._shared.utilities import _resolve_timezone
+from langgraph_sdk._shared.utilities import _quote_path_param, _resolve_timezone
 from langgraph_sdk._sync.http import SyncHttpClient
 from langgraph_sdk.schema import (
    All,
@@ -156,7 +156,7 @@ class SyncCronClient:
        }
        payload = {k: v for k, v in payload.items() if v is not None}
        return self.http.post(
-            f"/threads/{thread_id}/runs/crons",
+            f"/threads/{_quote_path_param(thread_id)}/runs/crons",
            json=payload,
            headers=headers,
            params=params,
@@ -304,7 +304,9 @@ class SyncCronClient:
            ```

        """
-        self.http.delete(f"/runs/crons/{cron_id}", headers=headers, params=params)
+        self.http.delete(
+            f"/runs/crons/{_quote_path_param(cron_id)}", headers=headers, params=params
+        )

    def update(
        self,
@@ -391,7 +393,7 @@ class SyncCronClient:
        }
        payload = {k: v for k, v in payload.items() if v is not None}
        return self.http.patch(
-            f"/runs/crons/{cron_id}",
+            f"/runs/crons/{_quote_path_param(cron_id)}",
            json=payload,
            headers=headers,
            params=params,
@@ -11,6 +11,7 @@ import httpx

 from langgraph_sdk._shared.utilities import (
    _get_run_metadata_from_response,
+    _quote_path_param,
    _sse_to_v2_dict,
 )
 from langgraph_sdk._sync.http import SyncHttpClient
@@ -332,7 +333,7 @@ class SyncRunsClient:
            "langsmith_tracer": langsmith_tracing,
        }
        endpoint = (
-            f"/threads/{thread_id}/runs/stream"
+            f"/threads/{_quote_path_param(thread_id)}/runs/stream"
            if thread_id is not None
            else "/runs/stream"
        )
@@ -591,7 +592,7 @@ class SyncRunsClient:
                on_run_created(metadata)

        return self.http.post(
-            f"/threads/{thread_id}/runs" if thread_id else "/runs",
+            f"/threads/{_quote_path_param(thread_id)}/runs" if thread_id else "/runs",
            json=payload,
            params=params,
            headers=headers,
@@ -825,7 +826,9 @@ class SyncRunsClient:
                on_run_created(metadata)

        endpoint = (
-            f"/threads/{thread_id}/runs/wait" if thread_id is not None else "/runs/wait"
+            f"/threads/{_quote_path_param(thread_id)}/runs/wait"
+            if thread_id is not None
+            else "/runs/wait"
        )
        return self.http.request_reconnect(
            endpoint,
@@ -879,7 +882,9 @@ class SyncRunsClient:
        if params:
            query_params.update(params)
        return self.http.get(
-            f"/threads/{thread_id}/runs", params=query_params, headers=headers
+            f"/threads/{_quote_path_param(thread_id)}/runs",
+            params=query_params,
+            headers=headers,
        )

    def get(
@@ -912,7 +917,9 @@ class SyncRunsClient:
        """

        return self.http.get(
-            f"/threads/{thread_id}/runs/{run_id}", headers=headers, params=params
+            f"/threads/{_quote_path_param(thread_id)}/runs/{_quote_path_param(run_id)}",
+            headers=headers,
+            params=params,
        )

    def cancel(
@@ -960,14 +967,14 @@ class SyncRunsClient:
            query_params.update(params)
        if wait:
            return self.http.request_reconnect(
-                f"/threads/{thread_id}/runs/{run_id}/cancel",
+                f"/threads/{_quote_path_param(thread_id)}/runs/{_quote_path_param(run_id)}/cancel",
                "POST",
                json=None,
                params=query_params,
                headers=headers,
            )
        return self.http.post(
-            f"/threads/{thread_id}/runs/{run_id}/cancel",
+            f"/threads/{_quote_path_param(thread_id)}/runs/{_quote_path_param(run_id)}/cancel",
            json=None,
            params=query_params,
            headers=headers,
@@ -1063,7 +1070,7 @@ class SyncRunsClient:

        """
        return self.http.request_reconnect(
-            f"/threads/{thread_id}/runs/{run_id}/join",
+            f"/threads/{_quote_path_param(thread_id)}/runs/{_quote_path_param(run_id)}/join",
            "GET",
            headers=headers,
            params=params,
@@ -1117,7 +1124,7 @@ class SyncRunsClient:
        if params:
            query_params.update(params)
        return self.http.stream(
-            f"/threads/{thread_id}/runs/{run_id}/stream",
+            f"/threads/{_quote_path_param(thread_id)}/runs/{_quote_path_param(run_id)}/stream",
            "GET",
            params=query_params,
            headers={
@@ -1158,5 +1165,7 @@ class SyncRunsClient:

        """
        self.http.delete(
-            f"/threads/{thread_id}/runs/{run_id}", headers=headers, params=params
+            f"/threads/{_quote_path_param(thread_id)}/runs/{_quote_path_param(run_id)}",
+            headers=headers,
+            params=params,
        )
@@ -5,6 +5,7 @@ from __future__ import annotations
 from collections.abc import Iterator, Mapping, Sequence
 from typing import Any, Literal, overload

+from langgraph_sdk._shared.utilities import _quote_path_param
 from langgraph_sdk._sync.http import SyncHttpClient
 from langgraph_sdk.schema import (
    Checkpoint,
@@ -88,7 +89,7 @@ class SyncThreadsClient:
        if params:
            query_params.update(params)
        return self.http.get(
-            f"/threads/{thread_id}",
+            f"/threads/{_quote_path_param(thread_id)}",
            headers=headers,
            params=query_params or None,
        )
@@ -250,7 +251,7 @@ class SyncThreadsClient:
        if return_minimal:
            request_headers["Prefer"] = "return=minimal"
        return self.http.patch(
-            f"/threads/{thread_id}",
+            f"/threads/{_quote_path_param(thread_id)}",
            json=payload,
            headers=request_headers or None,
            params=params,
@@ -282,7 +283,9 @@ class SyncThreadsClient:
            ```

        """
-        self.http.delete(f"/threads/{thread_id}", headers=headers, params=params)
+        self.http.delete(
+            f"/threads/{_quote_path_param(thread_id)}", headers=headers, params=params
+        )

    def search(
        self,
@@ -421,7 +424,10 @@ class SyncThreadsClient:

        """
        return self.http.post(
-            f"/threads/{thread_id}/copy", json=None, headers=headers, params=params
+            f"/threads/{_quote_path_param(thread_id)}/copy",
+            json=None,
+            headers=headers,
+            params=params,
        )

    def prune(
@@ -576,7 +582,7 @@ class SyncThreadsClient:
        """
        if checkpoint:
            return self.http.post(
-                f"/threads/{thread_id}/state/checkpoint",
+                f"/threads/{_quote_path_param(thread_id)}/state/checkpoint",
                json={"checkpoint": checkpoint, "subgraphs": subgraphs},
                headers=headers,
                params=params,
@@ -586,7 +592,7 @@ class SyncThreadsClient:
            if params:
                get_params = {**get_params, **dict(params)}
            return self.http.get(
-                f"/threads/{thread_id}/state/{checkpoint_id}",
+                f"/threads/{_quote_path_param(thread_id)}/state/{_quote_path_param(checkpoint_id)}",
                params=get_params,
                headers=headers,
            )
@@ -595,7 +601,7 @@ class SyncThreadsClient:
            if params:
                get_params = {**get_params, **dict(params)}
            return self.http.get(
-                f"/threads/{thread_id}/state",
+                f"/threads/{_quote_path_param(thread_id)}/state",
                params=get_params,
                headers=headers,
            )
@@ -657,7 +663,10 @@ class SyncThreadsClient:
        if as_node:
            payload["as_node"] = as_node
        return self.http.post(
-            f"/threads/{thread_id}/state", json=payload, headers=headers, params=params
+            f"/threads/{_quote_path_param(thread_id)}/state",
+            json=payload,
+            headers=headers,
+            params=params,
        )

    def get_history(
@@ -707,7 +716,7 @@ class SyncThreadsClient:
        if checkpoint:
            payload["checkpoint"] = checkpoint
        return self.http.post(
-            f"/threads/{thread_id}/history",
+            f"/threads/{_quote_path_param(thread_id)}/history",
            json=payload,
            headers=headers,
            params=params,
@@ -752,7 +761,7 @@ class SyncThreadsClient:
        if params:
            query_params.update(params)
        return self.http.stream(
-            f"/threads/{thread_id}/stream",
+            f"/threads/{_quote_path_param(thread_id)}/stream",
            "GET",
            headers={
                **({"Last-Event-ID": last_event_id} if last_event_id else {}),
@@ -0,0 +1,448 @@
+"""Regression tests for path-segment encoding of caller-supplied identifiers.
+
+Covers GHSA-w39p-vh2g-g8g5: identifier values interpolated into request paths
+are encoded so the resulting request addresses the resource the SDK method
+indicates, even if the identifier contains characters with special meaning in
+URL paths.
+"""
+
+from __future__ import annotations
+
+import httpx
+import pytest
+
+from langgraph_sdk._shared.utilities import _quote_path_param
+from langgraph_sdk.client import (
+    AssistantsClient,
+    CronClient,
+    HttpClient,
+    RunsClient,
+    SyncAssistantsClient,
+    SyncCronClient,
+    SyncHttpClient,
+    SyncRunsClient,
+    SyncThreadsClient,
+    ThreadsClient,
+)
+
+
+class TestQuotePathParam:
+    """Unit tests for the encoding helper itself."""
+
+    def test_uuid_round_trips_unchanged(self) -> None:
+        uuid_value = "550e8400-e29b-41d4-a716-446655440000"
+        assert _quote_path_param(uuid_value) == uuid_value
+
+    def test_simple_opaque_id_round_trips_unchanged(self) -> None:
+        assert _quote_path_param("thread_123") == "thread_123"
+        assert _quote_path_param("asst_abc") == "asst_abc"
+
+    def test_slash_is_encoded(self) -> None:
+        assert _quote_path_param("foo/bar") == "foo%2Fbar"
+
+    def test_bare_dot_segments_are_encoded(self) -> None:
+        # All-dot strings are encoded to make them opaque to HTTP stacks that
+        # collapse "./.." path segments client-side.
+        assert _quote_path_param(".") == "%2E"
+        assert _quote_path_param("..") == "%2E%2E"
+        assert _quote_path_param("...") == "%2E%2E%2E"
+        # Mixed values that happen to contain dots are not affected.
+        assert _quote_path_param("agent.v1") == "agent.v1"
+        # Subsequent ``/`` characters are encoded regardless.
+        assert _quote_path_param("../bar") == "..%2Fbar"
+
+    def test_full_pivot_payload_is_encoded(self) -> None:
+        # A caller-supplied identifier that, if interpolated raw, would route
+        # the request to a different resource type.
+        payload = "../assistants/abc-123"
+        encoded = _quote_path_param(payload)
+        assert encoded == "..%2Fassistants%2Fabc-123"
+        assert "/" not in encoded
+
+    def test_non_string_values_are_coerced_to_str(self) -> None:
+        import uuid
+
+        uid = uuid.UUID("550e8400-e29b-41d4-a716-446655440000")
+        assert _quote_path_param(uid) == str(uid)
+        assert _quote_path_param(42) == "42"
+
+    def test_none_value_raises_type_error(self) -> None:
+        with pytest.raises(TypeError, match="must not be None"):
+            _quote_path_param(None)
+
+    def test_bytes_value_raises_type_error(self) -> None:
+        with pytest.raises(TypeError, match="must not be bytes"):
+            _quote_path_param(b"bytes")
+        with pytest.raises(TypeError, match="must not be bytes"):
+            _quote_path_param(bytearray(b"bytes"))
+
+
+def _wire_path(request: httpx.Request) -> str:
+    """Return the path as it goes on the wire (preserves percent-encoding)."""
+    return request.url.raw_path.decode("ascii")
+
+
+@pytest.mark.asyncio
+class TestAsyncPathEncoding:
+    """Async-client tests that verify the encoded path actually lands on the wire.
+
+    Note: ``request.url.path`` is the percent-decoded display form. The bytes
+    that actually go on the wire are in ``request.url.raw_path``; that is what
+    the server's router sees and what these tests inspect.
+    """
+
+    async def test_threads_get_with_pivot_payload_stays_on_threads(self) -> None:
+        captured: list[str] = []
+
+        async def handler(request: httpx.Request) -> httpx.Response:
+            captured.append(_wire_path(request))
+            return httpx.Response(200, json={"thread_id": "anything"})
+
+        transport = httpx.MockTransport(handler)
+        async with httpx.AsyncClient(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            threads_client = ThreadsClient(HttpClient(client))
+            await threads_client.get("../assistants/abc-123")
+
+        assert len(captured) == 1
+        wire = captured[0]
+        # The identifier is encoded so the wire path stays inside `/threads/...`.
+        # The encoded segment must not contain literal slashes that could let
+        # the server re-route to a different resource type.
+        assert wire.startswith("/threads/")
+        segment = wire[len("/threads/") :]
+        assert "/" not in segment
+        assert "%2F" in segment
+        assert segment == "..%2Fassistants%2Fabc-123"
+
+    async def test_threads_update_with_pivot_payload_stays_on_threads(self) -> None:
+        captured: list[tuple[str, str]] = []
+
+        async def handler(request: httpx.Request) -> httpx.Response:
+            captured.append((request.method, _wire_path(request)))
+            return httpx.Response(200, json={"thread_id": "anything"})
+
+        transport = httpx.MockTransport(handler)
+        async with httpx.AsyncClient(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            threads_client = ThreadsClient(HttpClient(client))
+            await threads_client.update("../assistants/abc-123", metadata={"x": 1})
+
+        assert len(captured) == 1
+        method, wire = captured[0]
+        assert method == "PATCH"
+        assert wire.startswith("/threads/")
+        segment = wire[len("/threads/") :]
+        assert "/" not in segment
+
+    async def test_threads_delete_with_pivot_payload_stays_on_threads(self) -> None:
+        captured: list[tuple[str, str]] = []
+
+        async def handler(request: httpx.Request) -> httpx.Response:
+            captured.append((request.method, _wire_path(request)))
+            return httpx.Response(200)
+
+        transport = httpx.MockTransport(handler)
+        async with httpx.AsyncClient(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            threads_client = ThreadsClient(HttpClient(client))
+            await threads_client.delete("../runs/crons/some-cron-id")
+
+        assert len(captured) == 1
+        method, wire = captured[0]
+        assert method == "DELETE"
+        assert wire.startswith("/threads/")
+        segment = wire[len("/threads/") :]
+        assert "/" not in segment
+
+    async def test_assistants_get_with_pivot_payload_stays_on_assistants(
+        self,
+    ) -> None:
+        captured: list[str] = []
+
+        async def handler(request: httpx.Request) -> httpx.Response:
+            captured.append(_wire_path(request))
+            return httpx.Response(200, json={"assistant_id": "anything"})
+
+        transport = httpx.MockTransport(handler)
+        async with httpx.AsyncClient(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            assistants_client = AssistantsClient(HttpClient(client))
+            await assistants_client.get("../threads/abc-123")
+
+        assert len(captured) == 1
+        wire = captured[0]
+        assert wire.startswith("/assistants/")
+        segment = wire[len("/assistants/") :]
+        assert "/" not in segment
+
+    async def test_runs_delete_double_id_pivot_stays_on_threads_runs(self) -> None:
+        captured: list[tuple[str, str]] = []
+
+        async def handler(request: httpx.Request) -> httpx.Response:
+            captured.append((request.method, _wire_path(request)))
+            return httpx.Response(200)
+
+        transport = httpx.MockTransport(handler)
+        async with httpx.AsyncClient(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            runs_client = RunsClient(HttpClient(client))
+            # Both identifier values supplied as path-traversal payloads.
+            await runs_client.delete("..", "../runs/crons/cron-id")
+
+        assert len(captured) == 1
+        method, wire = captured[0]
+        assert method == "DELETE"
+        # The path should match `/threads/{quoted_thread}/runs/{quoted_run}`
+        # exactly. Neither segment should contain literal slashes.
+        assert wire.startswith("/threads/")
+        assert "/runs/crons/" not in wire
+        parts = wire.split("/")
+        # Expected shape: ['', 'threads', '<encoded ..>', 'runs', '<encoded ..>']
+        assert len(parts) == 5
+        assert parts[1] == "threads"
+        assert parts[3] == "runs"
+        # Encoded thread_id and run_id are between literal slashes.
+        assert parts[2] == "%2E%2E"
+        assert parts[4] == "..%2Fruns%2Fcrons%2Fcron-id"
+
+    async def test_crons_delete_with_pivot_payload_stays_on_crons(self) -> None:
+        captured: list[tuple[str, str]] = []
+
+        async def handler(request: httpx.Request) -> httpx.Response:
+            captured.append((request.method, _wire_path(request)))
+            return httpx.Response(200)
+
+        transport = httpx.MockTransport(handler)
+        async with httpx.AsyncClient(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            crons_client = CronClient(HttpClient(client))
+            await crons_client.delete("../../assistants/abc-123")
+
+        assert len(captured) == 1
+        method, wire = captured[0]
+        assert method == "DELETE"
+        assert wire.startswith("/runs/crons/")
+        segment = wire[len("/runs/crons/") :]
+        assert "/" not in segment
+
+    async def test_threads_get_state_with_pivot_checkpoint_id_stays_on_state(
+        self,
+    ) -> None:
+        captured: list[str] = []
+
+        async def handler(request: httpx.Request) -> httpx.Response:
+            captured.append(_wire_path(request))
+            return httpx.Response(200, json={})
+
+        transport = httpx.MockTransport(handler)
+        async with httpx.AsyncClient(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            threads_client = ThreadsClient(HttpClient(client))
+            await threads_client.get_state(thread_id="tid-1", checkpoint_id="../runs")
+
+        assert len(captured) == 1
+        wire = captured[0]
+        # Wire path must stay on `/threads/{tid}/state/...`, not pivot to
+        # `/threads/tid-1/runs`.
+        assert wire.startswith("/threads/tid-1/state/")
+        # Strip query string before checking the checkpoint segment.
+        path_only = wire.split("?", 1)[0]
+        segment = path_only[len("/threads/tid-1/state/") :]
+        assert "/" not in segment
+        assert segment == "..%2Fruns"
+
+    async def test_assistants_get_subgraphs_with_pivot_namespace_stays_on_subgraphs(
+        self,
+    ) -> None:
+        captured: list[str] = []
+
+        async def handler(request: httpx.Request) -> httpx.Response:
+            captured.append(_wire_path(request))
+            return httpx.Response(200, json={})
+
+        transport = httpx.MockTransport(handler)
+        async with httpx.AsyncClient(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            assistants_client = AssistantsClient(HttpClient(client))
+            await assistants_client.get_subgraphs("aid-1", namespace="../foo")
+
+        assert len(captured) == 1
+        wire = captured[0]
+        # Wire path must stay on `/assistants/{aid}/subgraphs/...`.
+        assert wire.startswith("/assistants/aid-1/subgraphs/")
+        # Strip query string before checking the namespace segment.
+        path_only = wire.split("?", 1)[0]
+        segment = path_only[len("/assistants/aid-1/subgraphs/") :]
+        assert "/" not in segment
+        assert segment == "..%2Ffoo"
+
+    async def test_bare_double_dot_thread_id_survives_to_wire(self) -> None:
+        """The all-dot encoding branch must survive httpx's relative-path collapse."""
+        captured: list[str] = []
+
+        async def handler(request: httpx.Request) -> httpx.Response:
+            captured.append(_wire_path(request))
+            return httpx.Response(200, json={"thread_id": "anything"})
+
+        transport = httpx.MockTransport(handler)
+        async with httpx.AsyncClient(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            threads_client = ThreadsClient(HttpClient(client))
+            await threads_client.get("..")
+
+        assert len(captured) == 1
+        # The all-dot identifier is fully percent-encoded so httpx does NOT
+        # collapse it client-side as a relative-path traversal.
+        assert captured[0].endswith("/threads/%2E%2E")
+
+    async def test_bare_single_dot_thread_id_survives_to_wire(self) -> None:
+        captured: list[str] = []
+
+        async def handler(request: httpx.Request) -> httpx.Response:
+            captured.append(_wire_path(request))
+            return httpx.Response(200, json={"thread_id": "anything"})
+
+        transport = httpx.MockTransport(handler)
+        async with httpx.AsyncClient(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            threads_client = ThreadsClient(HttpClient(client))
+            await threads_client.get(".")
+
+        assert len(captured) == 1
+        assert captured[0].endswith("/threads/%2E")
+
+    async def test_uuid_identifier_lands_on_intended_path(self) -> None:
+        """Legitimate UUID identifiers round-trip without encoding artifacts."""
+        captured: list[str] = []
+
+        async def handler(request: httpx.Request) -> httpx.Response:
+            captured.append(_wire_path(request))
+            return httpx.Response(200, json={"thread_id": "anything"})
+
+        transport = httpx.MockTransport(handler)
+        async with httpx.AsyncClient(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            threads_client = ThreadsClient(HttpClient(client))
+            await threads_client.get("550e8400-e29b-41d4-a716-446655440000")
+
+        assert captured == ["/threads/550e8400-e29b-41d4-a716-446655440000"]
+
+
+class TestSyncPathEncoding:
+    """Sync-client tests that mirror the async coverage on a representative subset."""
+
+    def test_threads_get_with_pivot_payload_stays_on_threads(self) -> None:
+        captured: list[str] = []
+
+        def handler(request: httpx.Request) -> httpx.Response:
+            captured.append(_wire_path(request))
+            return httpx.Response(200, json={"thread_id": "anything"})
+
+        transport = httpx.MockTransport(handler)
+        with httpx.Client(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            threads_client = SyncThreadsClient(SyncHttpClient(client))
+            threads_client.get("../assistants/abc-123")
+
+        assert len(captured) == 1
+        wire = captured[0]
+        assert wire.startswith("/threads/")
+        segment = wire[len("/threads/") :]
+        assert "/" not in segment
+        assert segment == "..%2Fassistants%2Fabc-123"
+
+    def test_assistants_get_with_pivot_payload_stays_on_assistants(self) -> None:
+        captured: list[str] = []
+
+        def handler(request: httpx.Request) -> httpx.Response:
+            captured.append(_wire_path(request))
+            return httpx.Response(200, json={"assistant_id": "anything"})
+
+        transport = httpx.MockTransport(handler)
+        with httpx.Client(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            assistants_client = SyncAssistantsClient(SyncHttpClient(client))
+            assistants_client.get("../threads/abc-123")
+
+        assert len(captured) == 1
+        wire = captured[0]
+        assert wire.startswith("/assistants/")
+        segment = wire[len("/assistants/") :]
+        assert "/" not in segment
+
+    def test_runs_delete_double_id_pivot_stays_on_threads_runs(self) -> None:
+        captured: list[tuple[str, str]] = []
+
+        def handler(request: httpx.Request) -> httpx.Response:
+            captured.append((request.method, _wire_path(request)))
+            return httpx.Response(200)
+
+        transport = httpx.MockTransport(handler)
+        with httpx.Client(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            runs_client = SyncRunsClient(SyncHttpClient(client))
+            runs_client.delete("..", "../runs/crons/cron-id")
+
+        assert len(captured) == 1
+        method, wire = captured[0]
+        assert method == "DELETE"
+        assert wire.startswith("/threads/")
+        assert "/runs/crons/" not in wire
+        parts = wire.split("/")
+        assert len(parts) == 5
+        assert parts[1] == "threads"
+        assert parts[3] == "runs"
+        assert parts[2] == "%2E%2E"
+        assert parts[4] == "..%2Fruns%2Fcrons%2Fcron-id"
+
+    def test_crons_delete_with_pivot_payload_stays_on_crons(self) -> None:
+        captured: list[tuple[str, str]] = []
+
+        def handler(request: httpx.Request) -> httpx.Response:
+            captured.append((request.method, _wire_path(request)))
+            return httpx.Response(200)
+
+        transport = httpx.MockTransport(handler)
+        with httpx.Client(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            crons_client = SyncCronClient(SyncHttpClient(client))
+            crons_client.delete("../../assistants/abc-123")
+
+        assert len(captured) == 1
+        method, wire = captured[0]
+        assert method == "DELETE"
+        assert wire.startswith("/runs/crons/")
+        segment = wire[len("/runs/crons/") :]
+        assert "/" not in segment
+
+    def test_uuid_identifier_lands_on_intended_path(self) -> None:
+        captured: list[str] = []
+
+        def handler(request: httpx.Request) -> httpx.Response:
+            captured.append(_wire_path(request))
+            return httpx.Response(200, json={"thread_id": "anything"})
+
+        transport = httpx.MockTransport(handler)
+        with httpx.Client(
+            transport=transport, base_url="https://example.com"
+        ) as client:
+            threads_client = SyncThreadsClient(SyncHttpClient(client))
+            threads_client.get("550e8400-e29b-41d4-a716-446655440000")
+
+        assert captured == ["/threads/550e8400-e29b-41d4-a716-446655440000"]
@@ -227,11 +227,11 @@ wheels = [

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-version = "1.2.0"
+version = "1.2.1"
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@@ -382,7 +382,7 @@ test = [

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+version = "4.1.1"
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@@ -551,7 +551,7 @@ test = [

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+    { url = "https://files.pythonhosted.org/packages/f3/e1/a4be2e696c9473bb53298df398237da5674704d781d4b748ed35aeef592a/langsmith-0.8.0-py3-none-any.whl", hash = "sha256:12cc4bc5622b835a6d841964d6034df3617bdb912dae0c1381fd0a68a9b3a3ef", size = 393268, upload-time = "2026-04-30T22:13:05.56Z" },
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 [[package]]
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+    { url = "https://files.pythonhosted.org/packages/7f/3e/5db95bcf282c52709639744ca2a8b149baccf648e39c8cc87553df9eae0c/urllib3-2.7.0-py3-none-any.whl", hash = "sha256:9fb4c81ebbb1ce9531cce37674bbc6f1360472bc18ca9a553ede278ef7276897", size = 131087, upload-time = "2026-05-07T16:13:17.151Z" },
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