diff --git a/.release-please-manifest.json b/.release-please-manifest.json
index da59f99..2aca35a 100644
--- a/.release-please-manifest.json
+++ b/.release-please-manifest.json
@@ -1,3 +1,3 @@
 {
-  ".": "0.4.0"
+  ".": "0.5.0"
 }
\ No newline at end of file
diff --git a/.stats.yml b/.stats.yml
index be606c6..d654666 100644
--- a/.stats.yml
+++ b/.stats.yml
@@ -1,4 +1,4 @@
 configured_endpoints: 11
-openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/kernel%2Fkernel-64ccdff4ca5d73d79d89e817fe83ccfd3d529696df3e6818c3c75e586ae00801.yml
-openapi_spec_hash: 21c7b8757fc0cc9415cda1bc06251de6
-config_hash: b3fcacd707da56b21d31ce0baf4fb87d
+openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/kernel%2Fkernel-4502c65bef0843a6ae96d23bba075433af6bab49b55b544b1522f63e7881c00c.yml
+openapi_spec_hash: 3e67b77bbc8cd6155b8f66f3271f2643
+config_hash: c6bab7ac8da570a5abbcfb19db119b6b
diff --git a/CHANGELOG.md b/CHANGELOG.md
index fd5ee11..ce46874 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,26 @@
 # Changelog
 
+## 0.5.0 (2025-06-04)
+
+Full Changelog: [v0.4.0...v0.5.0](https://github.com/onkernel/kernel-go-sdk/compare/v0.4.0...v0.5.0)
+
+### Features
+
+* **api:** update via SDK Studio ([f0b66f8](https://github.com/onkernel/kernel-go-sdk/commit/f0b66f87541f4bc109f479906c3554bffb38c26f))
+* **api:** update via SDK Studio ([d60d333](https://github.com/onkernel/kernel-go-sdk/commit/d60d3337306d90c8c51a54c6abeece2731dd4834))
+* **client:** allow overriding unions ([51d877d](https://github.com/onkernel/kernel-go-sdk/commit/51d877d1ae7584b237fdb9238e97949b832c3cc8))
+
+
+### Bug Fixes
+
+* **client:** cast to raw message when converting to params ([de14358](https://github.com/onkernel/kernel-go-sdk/commit/de14358a78248e642c03bd669f9c361bf6b3c8ba))
+* fix error ([7d27985](https://github.com/onkernel/kernel-go-sdk/commit/7d2798511671e285d41943c51c3ac8ebc6a7d6d6))
+
+
+### Chores
+
+* make go mod tidy continue on error ([91b5021](https://github.com/onkernel/kernel-go-sdk/commit/91b50217a8a08dd06ba64e05d025386d91d586c8))
+
 ## 0.4.0 (2025-05-28)
 
 Full Changelog: [v0.3.0...v0.4.0](https://github.com/onkernel/kernel-go-sdk/compare/v0.3.0...v0.4.0)
diff --git a/README.md b/README.md
index 2221887..0e2dd3d 100644
--- a/README.md
+++ b/README.md
@@ -24,7 +24,7 @@ Or to pin the version:
 <!-- x-release-please-start-version -->
 
 ```sh
-go get -u 'github.com/onkernel/kernel-go-sdk@v0.4.0'
+go get -u 'github.com/onkernel/kernel-go-sdk@v0.5.0'
 ```
 
 <!-- x-release-please-end -->
diff --git a/app.go b/app.go
index c3d26dc..6e6f185 100644
--- a/app.go
+++ b/app.go
@@ -38,8 +38,7 @@ func NewAppService(opts ...option.RequestOption) (r AppService) {
 	return
 }
 
-// List application versions for the authenticated user. Optionally filter by app
-// name and/or version label.
+// List applications. Optionally filter by app name and/or version label.
 func (r *AppService) List(ctx context.Context, query AppListParams, opts ...option.RequestOption) (res *[]AppListResponse, err error) {
 	opts = append(r.Options[:], opts...)
 	path := "apps"
diff --git a/appdeployment.go b/appdeployment.go
index c565687..373e942 100644
--- a/appdeployment.go
+++ b/appdeployment.go
@@ -42,7 +42,7 @@ func NewAppDeploymentService(opts ...option.RequestOption) (r AppDeploymentServi
 	return
 }
 
-// Deploy a new application
+// Deploy a new application and associated actions to Kernel.
 func (r *AppDeploymentService) New(ctx context.Context, body AppDeploymentNewParams, opts ...option.RequestOption) (res *AppDeploymentNewResponse, err error) {
 	opts = append(r.Options[:], opts...)
 	path := "deploy"
diff --git a/appinvocation.go b/appinvocation.go
index 48e4c44..18663be 100644
--- a/appinvocation.go
+++ b/appinvocation.go
@@ -35,7 +35,7 @@ func NewAppInvocationService(opts ...option.RequestOption) (r AppInvocationServi
 	return
 }
 
-// Invoke an application
+// Invoke an action.
 func (r *AppInvocationService) New(ctx context.Context, body AppInvocationNewParams, opts ...option.RequestOption) (res *AppInvocationNewResponse, err error) {
 	opts = append(r.Options[:], opts...)
 	path := "invocations"
@@ -43,7 +43,7 @@ func (r *AppInvocationService) New(ctx context.Context, body AppInvocationNewPar
 	return
 }
 
-// Get an app invocation by id
+// Get details about an invocation's status and output.
 func (r *AppInvocationService) Get(ctx context.Context, id string, opts ...option.RequestOption) (res *AppInvocationGetResponse, err error) {
 	opts = append(r.Options[:], opts...)
 	if id == "" {
@@ -55,7 +55,7 @@ func (r *AppInvocationService) Get(ctx context.Context, id string, opts ...optio
 	return
 }
 
-// Update invocation status or output
+// Update an invocation's status or output.
 func (r *AppInvocationService) Update(ctx context.Context, id string, body AppInvocationUpdateParams, opts ...option.RequestOption) (res *AppInvocationUpdateResponse, err error) {
 	opts = append(r.Options[:], opts...)
 	if id == "" {
diff --git a/browser.go b/browser.go
index c0254da..bbcc1f5 100644
--- a/browser.go
+++ b/browser.go
@@ -4,6 +4,7 @@ package kernel
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"net/http"
@@ -36,7 +37,7 @@ func NewBrowserService(opts ...option.RequestOption) (r BrowserService) {
 	return
 }
 
-// Create Browser Session
+// Create a new browser session from within an action.
 func (r *BrowserService) New(ctx context.Context, body BrowserNewParams, opts ...option.RequestOption) (res *BrowserNewResponse, err error) {
 	opts = append(r.Options[:], opts...)
 	path := "browsers"
@@ -44,7 +45,7 @@ func (r *BrowserService) New(ctx context.Context, body BrowserNewParams, opts ..
 	return
 }
 
-// Get Browser Session by ID
+// Get information about a browser session.
 func (r *BrowserService) Get(ctx context.Context, id string, opts ...option.RequestOption) (res *BrowserGetResponse, err error) {
 	opts = append(r.Options[:], opts...)
 	if id == "" {
@@ -56,7 +57,7 @@ func (r *BrowserService) Get(ctx context.Context, id string, opts ...option.Requ
 	return
 }
 
-// List active browser sessions for the authenticated user
+// List active browser sessions
 func (r *BrowserService) List(ctx context.Context, opts ...option.RequestOption) (res *[]BrowserListResponse, err error) {
 	opts = append(r.Options[:], opts...)
 	path := "browsers"
@@ -64,7 +65,7 @@ func (r *BrowserService) List(ctx context.Context, opts ...option.RequestOption)
 	return
 }
 
-// Delete a persistent browser session by persistent_id query parameter.
+// Delete a persistent browser session by its persistent_id.
 func (r *BrowserService) Delete(ctx context.Context, body BrowserDeleteParams, opts ...option.RequestOption) (err error) {
 	opts = append(r.Options[:], opts...)
 	opts = append([]option.RequestOption{option.WithHeader("Accept", "")}, opts...)
@@ -73,7 +74,7 @@ func (r *BrowserService) Delete(ctx context.Context, body BrowserDeleteParams, o
 	return
 }
 
-// Delete Browser Session by ID
+// Delete a browser session by ID
 func (r *BrowserService) DeleteByID(ctx context.Context, id string, opts ...option.RequestOption) (err error) {
 	opts = append(r.Options[:], opts...)
 	opts = append([]option.RequestOption{option.WithHeader("Accept", "")}, opts...)
@@ -110,7 +111,7 @@ func (r *BrowserPersistence) UnmarshalJSON(data []byte) error {
 // be used at the last possible moment before sending a request. Test for this with
 // BrowserPersistenceParam.Overrides()
 func (r BrowserPersistence) ToParam() BrowserPersistenceParam {
-	return param.Override[BrowserPersistenceParam](r.RawJSON())
+	return param.Override[BrowserPersistenceParam](json.RawMessage(r.RawJSON()))
 }
 
 // Optional persistence configuration for the browser session.
@@ -211,6 +212,9 @@ func (r *BrowserListResponse) UnmarshalJSON(data []byte) error {
 type BrowserNewParams struct {
 	// action invocation ID
 	InvocationID string `json:"invocation_id,required"`
+	// If true, launches the browser in stealth mode to reduce detection by anti-bot
+	// mechanisms.
+	Stealth param.Opt[bool] `json:"stealth,omitzero"`
 	// Optional persistence configuration for the browser session.
 	Persistence BrowserPersistenceParam `json:"persistence,omitzero"`
 	paramObj
diff --git a/browser_test.go b/browser_test.go
index 8646234..91c6038 100644
--- a/browser_test.go
+++ b/browser_test.go
@@ -31,6 +31,7 @@ func TestBrowserNewWithOptionalParams(t *testing.T) {
 		Persistence: kernel.BrowserPersistenceParam{
 			ID: "my-awesome-browser-for-user-1234",
 		},
+		Stealth: kernel.Bool(true),
 	})
 	if err != nil {
 		var apierr *kernel.Error
diff --git a/internal/version.go b/internal/version.go
index 5c62cac..67c4d40 100644
--- a/internal/version.go
+++ b/internal/version.go
@@ -2,4 +2,4 @@
 
 package internal
 
-const PackageVersion = "0.4.0" // x-release-please-version
+const PackageVersion = "0.5.0" // x-release-please-version
diff --git a/packages/param/encoder.go b/packages/param/encoder.go
index ba1821c..4ecb57b 100644
--- a/packages/param/encoder.go
+++ b/packages/param/encoder.go
@@ -35,7 +35,7 @@ func MarshalObject[T ParamStruct](f T, underlying any) ([]byte, error) {
 // MarshalWithExtras is used to marshal a struct with additional properties.
 //
 // Stability for the API of MarshalWithExtras is not guaranteed.
-func MarshalWithExtras[T ParamStruct](f T, underlying any, extras map[string]any) ([]byte, error) {
+func MarshalWithExtras[T ParamStruct, R any](f T, underlying any, extras map[string]R) ([]byte, error) {
 	if f.null() {
 		return []byte("null"), nil
 	} else if len(extras) > 0 {
@@ -44,7 +44,8 @@ func MarshalWithExtras[T ParamStruct](f T, underlying any, extras map[string]any
 			return nil, err
 		}
 		for k, v := range extras {
-			if v == Omit {
+			var a any = v
+			if a == Omit {
 				// Errors when handling ForceOmitted are ignored.
 				if b, e := sjson.DeleteBytes(bytes, k); e == nil {
 					bytes = b
@@ -67,7 +68,7 @@ func MarshalWithExtras[T ParamStruct](f T, underlying any, extras map[string]any
 // MarshalUnion uses a shimmed 'encoding/json' from Go 1.24, to support the 'omitzero' tag
 //
 // Stability for the API of MarshalUnion is not guaranteed.
-func MarshalUnion[T any](variants ...any) ([]byte, error) {
+func MarshalUnion[T ParamStruct](metadata T, variants ...any) ([]byte, error) {
 	nPresent := 0
 	presentIdx := -1
 	for i, variant := range variants {
@@ -77,6 +78,9 @@ func MarshalUnion[T any](variants ...any) ([]byte, error) {
 		}
 	}
 	if nPresent == 0 || presentIdx == -1 {
+		if ovr, ok := metadata.Overrides(); ok {
+			return shimjson.Marshal(ovr)
+		}
 		return []byte(`null`), nil
 	} else if nPresent > 1 {
 		return nil, &json.MarshalerError{
diff --git a/packages/param/encoder_test.go b/packages/param/encoder_test.go
index ec87450..c94cfc6 100644
--- a/packages/param/encoder_test.go
+++ b/packages/param/encoder_test.go
@@ -218,10 +218,11 @@ func TestExtraFieldsForceOmitted(t *testing.T) {
 type UnionWithDates struct {
 	OfDate param.Opt[time.Time]
 	OfTime param.Opt[time.Time]
+	param.APIUnion
 }
 
 func (r UnionWithDates) MarshalJSON() (data []byte, err error) {
-	return param.MarshalUnion[UnionWithDates](param.EncodedAsDate(r.OfDate), r.OfTime)
+	return param.MarshalUnion(r, param.EncodedAsDate(r.OfDate), r.OfTime)
 }
 
 func TestUnionDateMarshal(t *testing.T) {
@@ -324,3 +325,41 @@ func TestOptionalInterfaceAssignability(t *testing.T) {
 
 	notOpt.implOpt() // silence the warning
 }
+
+type PrimitiveUnion struct {
+	OfString param.Opt[string]
+	OfInt    param.Opt[int]
+	param.APIUnion
+}
+
+func (p PrimitiveUnion) MarshalJSON() (data []byte, err error) {
+	return param.MarshalUnion(p, p.OfString, p.OfInt)
+}
+
+func TestOverriddenUnion(t *testing.T) {
+	tests := map[string]struct {
+		value    PrimitiveUnion
+		expected string
+	}{
+		"string": {
+			param.Override[PrimitiveUnion](json.RawMessage(`"hello"`)),
+			`"hello"`,
+		},
+		"int": {
+			param.Override[PrimitiveUnion](json.RawMessage(`42`)),
+			`42`,
+		},
+	}
+
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			b, err := json.Marshal(test.value)
+			if err != nil {
+				t.Fatalf("didn't expect error %v, expected %s", err, test.expected)
+			}
+			if string(b) != test.expected {
+				t.Fatalf("expected %s, received %s", test.expected, string(b))
+			}
+		})
+	}
+}
diff --git a/scripts/bootstrap b/scripts/bootstrap
index 99810d3..d6ac165 100755
--- a/scripts/bootstrap
+++ b/scripts/bootstrap
@@ -13,4 +13,4 @@ fi
 
 echo "==> Installing Go dependencies…"
 
-go mod tidy
+go mod tidy -e