diff --git a/internal/fwserver/schema_validation.go b/internal/fwserver/schema_validation.go
index 41af356e0..2830d1196 100644
--- a/internal/fwserver/schema_validation.go
+++ b/internal/fwserver/schema_validation.go
@@ -41,13 +41,13 @@ func SchemaValidate(ctx context.Context, s fwschema.Schema, req ValidateSchemaRe
 			AttributePathExpression: path.MatchRoot(name),
 			Config:                  req.Config,
 		}
-		attributeResp := &ValidateAttributeResponse{
-			Diagnostics: resp.Diagnostics,
-		}
+		// Instantiate a new response for each request to prevent validators
+		// from modifying or removing diagnostics.
+		attributeResp := &ValidateAttributeResponse{}
 
 		AttributeValidate(ctx, attribute, attributeReq, attributeResp)
 
-		resp.Diagnostics = attributeResp.Diagnostics
+		resp.Diagnostics.Append(attributeResp.Diagnostics...)
 	}
 
 	for name, block := range s.GetBlocks() {
@@ -56,13 +56,13 @@ func SchemaValidate(ctx context.Context, s fwschema.Schema, req ValidateSchemaRe
 			AttributePathExpression: path.MatchRoot(name),
 			Config:                  req.Config,
 		}
-		attributeResp := &ValidateAttributeResponse{
-			Diagnostics: resp.Diagnostics,
-		}
+		// Instantiate a new response for each request to prevent validators
+		// from modifying or removing diagnostics.
+		attributeResp := &ValidateAttributeResponse{}
 
 		BlockValidate(ctx, block, attributeReq, attributeResp)
 
-		resp.Diagnostics = attributeResp.Diagnostics
+		resp.Diagnostics.Append(attributeResp.Diagnostics...)
 	}
 
 	if s.GetDeprecationMessage() != "" {
diff --git a/internal/fwserver/server_validatedatasourceconfig.go b/internal/fwserver/server_validatedatasourceconfig.go
index 03b496d1d..34b51d2d1 100644
--- a/internal/fwserver/server_validatedatasourceconfig.go
+++ b/internal/fwserver/server_validatedatasourceconfig.go
@@ -55,9 +55,9 @@ func (s *Server) ValidateDataSourceConfig(ctx context.Context, req *ValidateData
 		logging.FrameworkTrace(ctx, "DataSource implements DataSourceWithConfigValidators")
 
 		for _, configValidator := range dataSource.ConfigValidators(ctx) {
-			vdscResp := &datasource.ValidateConfigResponse{
-				Diagnostics: resp.Diagnostics,
-			}
+			// Instantiate a new response for each request to prevent validators
+			// from modifying or removing diagnostics.
+			vdscResp := &datasource.ValidateConfigResponse{}
 
 			logging.FrameworkDebug(
 				ctx,
@@ -75,32 +75,32 @@ func (s *Server) ValidateDataSourceConfig(ctx context.Context, req *ValidateData
 				},
 			)
 
-			resp.Diagnostics = vdscResp.Diagnostics
+			resp.Diagnostics.Append(vdscResp.Diagnostics...)
 		}
 	}
 
 	if dataSource, ok := req.DataSource.(datasource.DataSourceWithValidateConfig); ok {
 		logging.FrameworkTrace(ctx, "DataSource implements DataSourceWithValidateConfig")
 
-		vdscResp := &datasource.ValidateConfigResponse{
-			Diagnostics: resp.Diagnostics,
-		}
+		// Instantiate a new response for each request to prevent validators
+		// from modifying or removing diagnostics.
+		vdscResp := &datasource.ValidateConfigResponse{}
 
 		logging.FrameworkDebug(ctx, "Calling provider defined DataSource ValidateConfig")
 		dataSource.ValidateConfig(ctx, vdscReq, vdscResp)
 		logging.FrameworkDebug(ctx, "Called provider defined DataSource ValidateConfig")
 
-		resp.Diagnostics = vdscResp.Diagnostics
+		resp.Diagnostics.Append(vdscResp.Diagnostics...)
 	}
 
 	validateSchemaReq := ValidateSchemaRequest{
 		Config: *req.Config,
 	}
-	validateSchemaResp := ValidateSchemaResponse{
-		Diagnostics: resp.Diagnostics,
-	}
+	// Instantiate a new response for each request to prevent validators
+	// from modifying or removing diagnostics.
+	validateSchemaResp := ValidateSchemaResponse{}
 
 	SchemaValidate(ctx, req.Config.Schema, validateSchemaReq, &validateSchemaResp)
 
-	resp.Diagnostics = validateSchemaResp.Diagnostics
+	resp.Diagnostics.Append(validateSchemaResp.Diagnostics...)
 }
diff --git a/internal/fwserver/server_validateproviderconfig.go b/internal/fwserver/server_validateproviderconfig.go
index fb40f1e16..abc760252 100644
--- a/internal/fwserver/server_validateproviderconfig.go
+++ b/internal/fwserver/server_validateproviderconfig.go
@@ -36,9 +36,9 @@ func (s *Server) ValidateProviderConfig(ctx context.Context, req *ValidateProvid
 		logging.FrameworkTrace(ctx, "Provider implements ProviderWithConfigValidators")
 
 		for _, configValidator := range providerWithConfigValidators.ConfigValidators(ctx) {
-			vpcRes := &provider.ValidateConfigResponse{
-				Diagnostics: resp.Diagnostics,
-			}
+			// Instantiate a new response for each request to prevent validators
+			// from modifying or removing diagnostics.
+			vpcRes := &provider.ValidateConfigResponse{}
 
 			logging.FrameworkDebug(
 				ctx,
@@ -56,34 +56,34 @@ func (s *Server) ValidateProviderConfig(ctx context.Context, req *ValidateProvid
 				},
 			)
 
-			resp.Diagnostics = vpcRes.Diagnostics
+			resp.Diagnostics.Append(vpcRes.Diagnostics...)
 		}
 	}
 
 	if providerWithValidateConfig, ok := s.Provider.(provider.ProviderWithValidateConfig); ok {
 		logging.FrameworkTrace(ctx, "Provider implements ProviderWithValidateConfig")
 
-		vpcRes := &provider.ValidateConfigResponse{
-			Diagnostics: resp.Diagnostics,
-		}
+		// Instantiate a new response for each request to prevent validators
+		// from modifying or removing diagnostics.
+		vpcRes := &provider.ValidateConfigResponse{}
 
 		logging.FrameworkDebug(ctx, "Calling provider defined Provider ValidateConfig")
 		providerWithValidateConfig.ValidateConfig(ctx, vpcReq, vpcRes)
 		logging.FrameworkDebug(ctx, "Called provider defined Provider ValidateConfig")
 
-		resp.Diagnostics = vpcRes.Diagnostics
+		resp.Diagnostics.Append(vpcRes.Diagnostics...)
 	}
 
 	validateSchemaReq := ValidateSchemaRequest{
 		Config: *req.Config,
 	}
-	validateSchemaResp := ValidateSchemaResponse{
-		Diagnostics: resp.Diagnostics,
-	}
+	// Instantiate a new response for each request to prevent validators
+	// from modifying or removing diagnostics.
+	validateSchemaResp := ValidateSchemaResponse{}
 
 	SchemaValidate(ctx, req.Config.Schema, validateSchemaReq, &validateSchemaResp)
 
-	resp.Diagnostics = validateSchemaResp.Diagnostics
+	resp.Diagnostics.Append(validateSchemaResp.Diagnostics...)
 
 	// This RPC allows a modified configuration to be returned. This was
 	// previously used to allow a "required" provider attribute (as defined
diff --git a/internal/fwserver/server_validateresourceconfig.go b/internal/fwserver/server_validateresourceconfig.go
index 1c057f83a..0dfb28bf1 100644
--- a/internal/fwserver/server_validateresourceconfig.go
+++ b/internal/fwserver/server_validateresourceconfig.go
@@ -55,9 +55,9 @@ func (s *Server) ValidateResourceConfig(ctx context.Context, req *ValidateResour
 		logging.FrameworkTrace(ctx, "Resource implements ResourceWithConfigValidators")
 
 		for _, configValidator := range resourceWithConfigValidators.ConfigValidators(ctx) {
-			vdscResp := &resource.ValidateConfigResponse{
-				Diagnostics: resp.Diagnostics,
-			}
+			// Instantiate a new response for each request to prevent validators
+			// from modifying or removing diagnostics.
+			vdscResp := &resource.ValidateConfigResponse{}
 
 			logging.FrameworkDebug(
 				ctx,
@@ -75,32 +75,32 @@ func (s *Server) ValidateResourceConfig(ctx context.Context, req *ValidateResour
 				},
 			)
 
-			resp.Diagnostics = vdscResp.Diagnostics
+			resp.Diagnostics.Append(vdscResp.Diagnostics...)
 		}
 	}
 
 	if resourceWithValidateConfig, ok := req.Resource.(resource.ResourceWithValidateConfig); ok {
 		logging.FrameworkTrace(ctx, "Resource implements ResourceWithValidateConfig")
 
-		vdscResp := &resource.ValidateConfigResponse{
-			Diagnostics: resp.Diagnostics,
-		}
+		// Instantiate a new response for each request to prevent validators
+		// from modifying or removing diagnostics.
+		vdscResp := &resource.ValidateConfigResponse{}
 
 		logging.FrameworkDebug(ctx, "Calling provider defined Resource ValidateConfig")
 		resourceWithValidateConfig.ValidateConfig(ctx, vdscReq, vdscResp)
 		logging.FrameworkDebug(ctx, "Called provider defined Resource ValidateConfig")
 
-		resp.Diagnostics = vdscResp.Diagnostics
+		resp.Diagnostics.Append(vdscResp.Diagnostics...)
 	}
 
 	validateSchemaReq := ValidateSchemaRequest{
 		Config: *req.Config,
 	}
-	validateSchemaResp := ValidateSchemaResponse{
-		Diagnostics: resp.Diagnostics,
-	}
+	// Instantiate a new response for each request to prevent validators
+	// from modifying or removing diagnostics.
+	validateSchemaResp := ValidateSchemaResponse{}
 
 	SchemaValidate(ctx, req.Config.Schema, validateSchemaReq, &validateSchemaResp)
 
-	resp.Diagnostics = validateSchemaResp.Diagnostics
+	resp.Diagnostics.Append(validateSchemaResp.Diagnostics...)
 }