diff --git a/sdk/go/agent/control_plane_memory_backend.go b/sdk/go/agent/control_plane_memory_backend.go
index 776e3d72..4cc20e61 100644
--- a/sdk/go/agent/control_plane_memory_backend.go
+++ b/sdk/go/agent/control_plane_memory_backend.go
@@ -56,7 +56,11 @@ func (b *ControlPlaneMemoryBackend) Set(scope MemoryScope, scopeID, key string,
 		"data":  value,
 		"scope": b.apiScope(scope),
 	}
-	req, err := http.NewRequest(http.MethodPost, endpoint, mustJSONReader(body))
+	reader, err := jsonReader(body)
+	if err != nil {
+		return err
+	}
+	req, err := http.NewRequest(http.MethodPost, endpoint, reader)
 	if err != nil {
 		return err
 	}
@@ -81,11 +85,7 @@ func (b *ControlPlaneMemoryBackend) Get(scope MemoryScope, scopeID, key string)
 		return nil, false, err
 	}
 
-	body := map[string]any{
-		"key":   key,
-		"scope": b.apiScope(scope),
-	}
-	req, err := http.NewRequest(http.MethodPost, endpoint, mustJSONReader(body))
+	req, err := http.NewRequest(http.MethodPost, endpoint, keyScopeReader(key, b.apiScope(scope)))
 	if err != nil {
 		return nil, false, err
 	}
@@ -118,11 +118,7 @@ func (b *ControlPlaneMemoryBackend) Delete(scope MemoryScope, scopeID, key strin
 		return err
 	}
 
-	body := map[string]any{
-		"key":   key,
-		"scope": b.apiScope(scope),
-	}
-	req, err := http.NewRequest(http.MethodPost, endpoint, mustJSONReader(body))
+	req, err := http.NewRequest(http.MethodPost, endpoint, keyScopeReader(key, b.apiScope(scope)))
 	if err != nil {
 		return err
 	}
@@ -200,7 +196,11 @@ func (b *ControlPlaneMemoryBackend) SetVector(scope MemoryScope, scopeID, key st
 		"metadata":  metadata,
 		"scope":     b.apiScope(scope),
 	}
-	req, err := http.NewRequest(http.MethodPost, endpoint, mustJSONReader(body))
+	reader, err := jsonReader(body)
+	if err != nil {
+		return err
+	}
+	req, err := http.NewRequest(http.MethodPost, endpoint, reader)
 	if err != nil {
 		return err
 	}
@@ -285,7 +285,11 @@ func (b *ControlPlaneMemoryBackend) SearchVector(scope MemoryScope, scopeID stri
 		body["scope"] = b.apiScope(opts.Scope)
 	}
 
-	req, err := http.NewRequest(http.MethodPost, endpoint, mustJSONReader(body))
+	reader, err := jsonReader(body)
+	if err != nil {
+		return nil, err
+	}
+	req, err := http.NewRequest(http.MethodPost, endpoint, reader)
 	if err != nil {
 		return nil, err
 	}
@@ -399,7 +403,22 @@ func (b *ControlPlaneMemoryBackend) apiScope(scope MemoryScope) string {
 	}
 }
 
-func mustJSONReader(v any) io.Reader {
-	data, _ := json.Marshal(v)
-	return bytes.NewReader(data)
+func jsonReader(v any) (io.Reader, error) {
+	data, err := json.Marshal(v)
+	if err != nil {
+		return nil, err
+	}
+	return bytes.NewReader(data), nil
+}
+
+func keyScopeReader(key, scope string) io.Reader {
+	var body bytes.Buffer
+	_ = json.NewEncoder(&body).Encode(struct {
+		Key   string `json:"key"`
+		Scope string `json:"scope"`
+	}{
+		Key:   key,
+		Scope: scope,
+	})
+	return &body
 }
diff --git a/sdk/go/agent/control_plane_memory_backend_test.go b/sdk/go/agent/control_plane_memory_backend_test.go
index c2d61766..1fa4ee82 100644
--- a/sdk/go/agent/control_plane_memory_backend_test.go
+++ b/sdk/go/agent/control_plane_memory_backend_test.go
@@ -201,7 +201,7 @@ func TestControlPlaneMemoryBackend_ErrorPathsAndHelpers(t *testing.T) {
 		assert.Contains(t, err.Error(), "vector memory search failed")
 	})
 
-	t.Run("scope helpers and mustJSONReader", func(t *testing.T) {
+	t.Run("scope helpers and jsonReader", func(t *testing.T) {
 		b := NewControlPlaneMemoryBackend("http://example.com///", "token-123", "agent-1")
 		assert.Equal(t, "http://example.com", b.baseURL)
 		assert.Equal(t, "workflow", b.apiScope(ScopeWorkflow))
@@ -210,8 +210,18 @@ func TestControlPlaneMemoryBackend_ErrorPathsAndHelpers(t *testing.T) {
 		assert.Equal(t, "global", b.apiScope(ScopeGlobal))
 		assert.Equal(t, "global", b.apiScope(MemoryScope("unexpected")))
 
-		body, err := io.ReadAll(mustJSONReader(map[string]any{"ok": true}))
+		reader, err := jsonReader(map[string]any{"ok": true})
+		require.NoError(t, err)
+		body, err := io.ReadAll(reader)
 		require.NoError(t, err)
 		assert.JSONEq(t, `{"ok":true}`, string(body))
 	})
+
+	t.Run("jsonReader surfaces marshal errors", func(t *testing.T) {
+		// Values that cannot be serialized (e.g. a channel) must return an
+		// error instead of silently yielding an empty reader. See issue #434.
+		reader, err := jsonReader(map[string]any{"bad": make(chan int)})
+		require.Error(t, err)
+		assert.Nil(t, reader)
+	})
 }