diff --git a/.release-please-manifest.json b/.release-please-manifest.json
index f80372ae..a397c094 100644
--- a/.release-please-manifest.json
+++ b/.release-please-manifest.json
@@ -1,3 +1,3 @@
 {
-  ".": "3.20.0"
+  ".": "3.21.0"
 }
diff --git a/.stats.yml b/.stats.yml
index 391cde37..0339c57c 100644
--- a/.stats.yml
+++ b/.stats.yml
@@ -1,4 +1,4 @@
 configured_endpoints: 8
-openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/browserbase/stagehand-6f6bfb81d092f30a5e2005328c97d61b9ea36132bb19e9e79e55294b9534ce20.yml
-openapi_spec_hash: f3fc1e3688a38dc2c28f7178f7d534e5
+openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/browserbase/stagehand-eae8400fade7b2c8329c4148f56de92e147c34c0feecb420c015aab6544a9acc.yml
+openapi_spec_hash: 0a9eff1ac1d464e89cbd9db64709b08a
 config_hash: 1fb12ae9b478488bc1e56bfbdc210b01
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c5ab97a1..b28f0bd6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,18 @@
 # Changelog
 
+## 3.21.0 (2026-05-09)
+
+Full Changelog: [v3.20.0...v3.21.0](https://github.com/browserbase/stagehand-python/compare/v3.20.0...v3.21.0)
+
+### Features
+
+* [feat]: add `ignoreSelectors` to `observe()` ([77be2c2](https://github.com/browserbase/stagehand-python/commit/77be2c2463c7b1d0ce6768eecf130adc3ef91149))
+
+
+### Bug Fixes
+
+* **client:** add missing f-string prefix in file type error message ([fb40f50](https://github.com/browserbase/stagehand-python/commit/fb40f50c2fb3337be84a3f973b8a27a8f53fbfae))
+
 ## 3.20.0 (2026-05-06)
 
 Full Changelog: [v3.19.5...v3.20.0](https://github.com/browserbase/stagehand-python/compare/v3.19.5...v3.20.0)
diff --git a/pyproject.toml b/pyproject.toml
index d3411cde..7a595051 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "stagehand"
-version = "3.20.0"
+version = "3.21.0"
 description = "The official Python library for the stagehand API"
 dynamic = ["readme"]
 license = "MIT"
diff --git a/src/stagehand/_files.py b/src/stagehand/_files.py
index 0fdce17b..76da9e08 100644
--- a/src/stagehand/_files.py
+++ b/src/stagehand/_files.py
@@ -99,7 +99,7 @@ async def async_to_httpx_files(files: RequestFiles | None) -> HttpxRequestFiles
     elif is_sequence_t(files):
         files = [(key, await _async_transform_file(file)) for key, file in files]
     else:
-        raise TypeError("Unexpected file type input {type(files)}, expected mapping or sequence")
+        raise TypeError(f"Unexpected file type input {type(files)}, expected mapping or sequence")
 
     return files
 
diff --git a/src/stagehand/_version.py b/src/stagehand/_version.py
index b5e0b8a6..6dcaaca6 100644
--- a/src/stagehand/_version.py
+++ b/src/stagehand/_version.py
@@ -1,4 +1,4 @@
 # File generated from our OpenAPI spec by Stainless. See CONTRIBUTING.md for details.
 
 __title__ = "stagehand"
-__version__ = "3.20.0"  # x-release-please-version
+__version__ = "3.21.0"  # x-release-please-version
diff --git a/src/stagehand/types/session_observe_params.py b/src/stagehand/types/session_observe_params.py
index 6c08105a..246bf367 100644
--- a/src/stagehand/types/session_observe_params.py
+++ b/src/stagehand/types/session_observe_params.py
@@ -5,6 +5,7 @@
 from typing import Dict, Union, Optional
 from typing_extensions import Literal, Required, Annotated, TypeAlias, TypedDict
 
+from .._types import SequenceNotStr
 from .._utils import PropertyInfo
 from .model_config_param import ModelConfigParam
 
@@ -45,6 +46,9 @@ class OptionsVariablesUnionMember3(TypedDict, total=False):
 
 
 class Options(TypedDict, total=False):
+    ignore_selectors: Annotated[SequenceNotStr[str], PropertyInfo(alias="ignoreSelectors")]
+    """Selectors for elements and subtrees that should be excluded from observation"""
+
     model: OptionsModel
     """Model configuration object or model name string (e.g., 'openai/gpt-5-nano')"""
 
diff --git a/tests/api_resources/test_sessions.py b/tests/api_resources/test_sessions.py
index 1929c8f5..6742ce4f 100644
--- a/tests/api_resources/test_sessions.py
+++ b/tests/api_resources/test_sessions.py
@@ -645,6 +645,7 @@ def test_method_observe_with_all_params_overload_1(self, client: Stagehand) -> N
             frame_id="frameId",
             instruction="Find all clickable navigation links",
             options={
+                "ignore_selectors": ["nav", ".cookie-banner", "#sidebar-ads"],
                 "model": {
                     "model_name": "openai/gpt-5.4-mini",
                     "api_key": "sk-some-openai-api-key",
@@ -719,6 +720,7 @@ def test_method_observe_with_all_params_overload_2(self, client: Stagehand) -> N
             frame_id="frameId",
             instruction="Find all clickable navigation links",
             options={
+                "ignore_selectors": ["nav", ".cookie-banner", "#sidebar-ads"],
                 "model": {
                     "model_name": "openai/gpt-5.4-mini",
                     "api_key": "sk-some-openai-api-key",
@@ -1579,6 +1581,7 @@ async def test_method_observe_with_all_params_overload_1(self, async_client: Asy
             frame_id="frameId",
             instruction="Find all clickable navigation links",
             options={
+                "ignore_selectors": ["nav", ".cookie-banner", "#sidebar-ads"],
                 "model": {
                     "model_name": "openai/gpt-5.4-mini",
                     "api_key": "sk-some-openai-api-key",
@@ -1653,6 +1656,7 @@ async def test_method_observe_with_all_params_overload_2(self, async_client: Asy
             frame_id="frameId",
             instruction="Find all clickable navigation links",
             options={
+                "ignore_selectors": ["nav", ".cookie-banner", "#sidebar-ads"],
                 "model": {
                     "model_name": "openai/gpt-5.4-mini",
                     "api_key": "sk-some-openai-api-key",