diff --git a/sdks/python/CHANGELOG.md b/sdks/python/CHANGELOG.md
index 46675e8a9..0c6ef7004 100644
--- a/sdks/python/CHANGELOG.md
+++ b/sdks/python/CHANGELOG.md
@@ -5,6 +5,23 @@ All notable changes to Hatchet's Python SDK will be documented in this changelog
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.21.4] - 2025-12-06
+
+### Added
+
+- Adds support for dynamic rate limits using CEL expressions (strings) for the `limit` parameter.
+
+### Changed
+
+- Fixes a serialization error caused by Pydantic sometimes being unable to encode bytes, reported here: https://github.com/hatchet-dev/hatchet/issues/2601
+- Fixes a bug where string-based CEL expressions for `limit` were rejected due to the validation logic.
+
+## [1.21.3] - 2025-11-26
+
+### Added
+
+- Adds GZIP compression for gRPC communication between the SDK and the Hatchet engine to reduce bandwidth usage.
+
 ## [1.21.2] - 2025-11-13
 
 ### Added
diff --git a/sdks/python/hatchet_sdk/rate_limit.py b/sdks/python/hatchet_sdk/rate_limit.py
index 8603d5f03..b20f25aff 100644
--- a/sdks/python/hatchet_sdk/rate_limit.py
+++ b/sdks/python/hatchet_sdk/rate_limit.py
@@ -62,8 +62,8 @@ class RateLimit(BaseModel):
         if self.dynamic_key and self.static_key:
             raise ValueError("Cannot have both static key and dynamic key set")
 
-        if self.limit and not isinstance(self.limit, int):
-            raise ValueError(f"Invalid CEL expression: {self.limit}")
+        if self.limit and not isinstance(self.limit, int | str):
+            raise ValueError(f"Invalid limit value: {self.limit}")
 
         if self.dynamic_key and not self.limit:
             raise ValueError("CEL based keys requires limit to be set")
diff --git a/sdks/python/hatchet_sdk/worker/runner/runner.py b/sdks/python/hatchet_sdk/worker/runner/runner.py
index e1aa4fd90..5f7229591 100644
--- a/sdks/python/hatchet_sdk/worker/runner/runner.py
+++ b/sdks/python/hatchet_sdk/worker/runner/runner.py
@@ -480,7 +480,14 @@ class Runner:
             return ""
 
         if isinstance(output, BaseModel):
-            output = output.model_dump(mode="json")
+            try:
+                output = output.model_dump(mode="json")
+            except Exception as e:
+                logger.exception("could not serialize pydantic model output")
+
+                raise IllegalTaskOutputError(
+                    f"could not serialize Pydantic BaseModel output: {e}"
+                ) from e
         elif is_dataclass(output):
             output = asdict(cast(DataclassInstance, output))
 
diff --git a/sdks/python/pyproject.toml b/sdks/python/pyproject.toml
index ec9e024cf..dc71b4e74 100644
--- a/sdks/python/pyproject.toml
+++ b/sdks/python/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "hatchet-sdk"
-version = "1.21.3"
+version = "1.21.4"
 description = "This is the official Python SDK for Hatchet, a distributed, fault-tolerant task queue. The SDK allows you to easily integrate Hatchet's task scheduling and workflow orchestration capabilities into your Python applications."
 authors = [
     "Alexander Belanger <alexander@hatchet.run>",