From a01f4bfc02ff75236948e3006781fb53c8cd26e4 Mon Sep 17 00:00:00 2001
From: Arash Deshmeh <adshmh@gmail.com>
Date: Thu, 14 Aug 2025 14:22:02 -0400
Subject: [PATCH 1/6] QoS Solana: disqualify endpoints with recent non-JSONRPC
 response

---
 .../qos/jsonrpc_validation_error.pb.go        | 194 ++++++++++++++++++
 observation/qos/solana.pb.go                  |  49 +++--
 proto/path/qos/jsonrpc_validation_error.proto |  24 +++
 proto/path/qos/solana.proto                   |   6 +-
 qos/solana/endpoint.go                        |  61 ++++--
 qos/solana/response_generic.go                |  54 +++--
 6 files changed, 335 insertions(+), 53 deletions(-)
 create mode 100644 observation/qos/jsonrpc_validation_error.pb.go
 create mode 100644 proto/path/qos/jsonrpc_validation_error.proto

diff --git a/observation/qos/jsonrpc_validation_error.pb.go b/observation/qos/jsonrpc_validation_error.pb.go
new file mode 100644
index 000000000..f0cfc7350
--- /dev/null
+++ b/observation/qos/jsonrpc_validation_error.pb.go
@@ -0,0 +1,194 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// versions:
+// 	protoc-gen-go v1.36.6
+// 	protoc        v5.29.3
+// source: path/qos/jsonrpc_validation_error.proto
+
+package qos
+
+import (
+	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
+	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
+	timestamppb "google.golang.org/protobuf/types/known/timestamppb"
+	reflect "reflect"
+	sync "sync"
+	unsafe "unsafe"
+)
+
+const (
+	// Verify that this generated code is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
+	// Verify that runtime/protoimpl is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
+)
+
+// Enum for different types of JSON-RPC validation errors
+type JsonRpcValidationErrorType int32
+
+const (
+	// Default/unspecified validation error
+	JsonRpcValidationErrorType_JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED JsonRpcValidationErrorType = 0
+	// Response is not a valid JSON-RPC response
+	JsonRpcValidationErrorType_NON_JSONRPC_RESPONSE JsonRpcValidationErrorType = 1
+)
+
+// Enum value maps for JsonRpcValidationErrorType.
+var (
+	JsonRpcValidationErrorType_name = map[int32]string{
+		0: "JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED",
+		1: "NON_JSONRPC_RESPONSE",
+	}
+	JsonRpcValidationErrorType_value = map[string]int32{
+		"JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED": 0,
+		"NON_JSONRPC_RESPONSE":                       1,
+	}
+)
+
+func (x JsonRpcValidationErrorType) Enum() *JsonRpcValidationErrorType {
+	p := new(JsonRpcValidationErrorType)
+	*p = x
+	return p
+}
+
+func (x JsonRpcValidationErrorType) String() string {
+	return protoimpl.X.EnumStringOf(x.Descriptor(), protoreflect.EnumNumber(x))
+}
+
+func (JsonRpcValidationErrorType) Descriptor() protoreflect.EnumDescriptor {
+	return file_path_qos_jsonrpc_validation_error_proto_enumTypes[0].Descriptor()
+}
+
+func (JsonRpcValidationErrorType) Type() protoreflect.EnumType {
+	return &file_path_qos_jsonrpc_validation_error_proto_enumTypes[0]
+}
+
+func (x JsonRpcValidationErrorType) Number() protoreflect.EnumNumber {
+	return protoreflect.EnumNumber(x)
+}
+
+// Deprecated: Use JsonRpcValidationErrorType.Descriptor instead.
+func (JsonRpcValidationErrorType) EnumDescriptor() ([]byte, []int) {
+	return file_path_qos_jsonrpc_validation_error_proto_rawDescGZIP(), []int{0}
+}
+
+// JsonRpcResponseValidationError captures validation errors for JSON-RPC responses
+type JsonRpcResponseValidationError struct {
+	state protoimpl.MessageState `protogen:"open.v1"`
+	// Type of validation error
+	ErrorType JsonRpcValidationErrorType `protobuf:"varint,1,opt,name=error_type,json=errorType,proto3,enum=path.qos.JsonRpcValidationErrorType" json:"error_type,omitempty"`
+	// Timestamp when the validation error occurred
+	Timestamp     *timestamppb.Timestamp `protobuf:"bytes,2,opt,name=timestamp,proto3" json:"timestamp,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *JsonRpcResponseValidationError) Reset() {
+	*x = JsonRpcResponseValidationError{}
+	mi := &file_path_qos_jsonrpc_validation_error_proto_msgTypes[0]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *JsonRpcResponseValidationError) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*JsonRpcResponseValidationError) ProtoMessage() {}
+
+func (x *JsonRpcResponseValidationError) ProtoReflect() protoreflect.Message {
+	mi := &file_path_qos_jsonrpc_validation_error_proto_msgTypes[0]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use JsonRpcResponseValidationError.ProtoReflect.Descriptor instead.
+func (*JsonRpcResponseValidationError) Descriptor() ([]byte, []int) {
+	return file_path_qos_jsonrpc_validation_error_proto_rawDescGZIP(), []int{0}
+}
+
+func (x *JsonRpcResponseValidationError) GetErrorType() JsonRpcValidationErrorType {
+	if x != nil {
+		return x.ErrorType
+	}
+	return JsonRpcValidationErrorType_JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED
+}
+
+func (x *JsonRpcResponseValidationError) GetTimestamp() *timestamppb.Timestamp {
+	if x != nil {
+		return x.Timestamp
+	}
+	return nil
+}
+
+var File_path_qos_jsonrpc_validation_error_proto protoreflect.FileDescriptor
+
+const file_path_qos_jsonrpc_validation_error_proto_rawDesc = "" +
+	"\n" +
+	"'path/qos/jsonrpc_validation_error.proto\x12\bpath.qos\x1a\x1fgoogle/protobuf/timestamp.proto\"\x9f\x01\n" +
+	"\x1eJsonRpcResponseValidationError\x12C\n" +
+	"\n" +
+	"error_type\x18\x01 \x01(\x0e2$.path.qos.JsonRpcValidationErrorTypeR\terrorType\x128\n" +
+	"\ttimestamp\x18\x02 \x01(\v2\x1a.google.protobuf.TimestampR\ttimestamp*f\n" +
+	"\x1aJsonRpcValidationErrorType\x12.\n" +
+	"*JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED\x10\x00\x12\x18\n" +
+	"\x14NON_JSONRPC_RESPONSE\x10\x01B0Z.github.com/buildwithgrove/path/observation/qosb\x06proto3"
+
+var (
+	file_path_qos_jsonrpc_validation_error_proto_rawDescOnce sync.Once
+	file_path_qos_jsonrpc_validation_error_proto_rawDescData []byte
+)
+
+func file_path_qos_jsonrpc_validation_error_proto_rawDescGZIP() []byte {
+	file_path_qos_jsonrpc_validation_error_proto_rawDescOnce.Do(func() {
+		file_path_qos_jsonrpc_validation_error_proto_rawDescData = protoimpl.X.CompressGZIP(unsafe.Slice(unsafe.StringData(file_path_qos_jsonrpc_validation_error_proto_rawDesc), len(file_path_qos_jsonrpc_validation_error_proto_rawDesc)))
+	})
+	return file_path_qos_jsonrpc_validation_error_proto_rawDescData
+}
+
+var file_path_qos_jsonrpc_validation_error_proto_enumTypes = make([]protoimpl.EnumInfo, 1)
+var file_path_qos_jsonrpc_validation_error_proto_msgTypes = make([]protoimpl.MessageInfo, 1)
+var file_path_qos_jsonrpc_validation_error_proto_goTypes = []any{
+	(JsonRpcValidationErrorType)(0),        // 0: path.qos.JsonRpcValidationErrorType
+	(*JsonRpcResponseValidationError)(nil), // 1: path.qos.JsonRpcResponseValidationError
+	(*timestamppb.Timestamp)(nil),          // 2: google.protobuf.Timestamp
+}
+var file_path_qos_jsonrpc_validation_error_proto_depIdxs = []int32{
+	0, // 0: path.qos.JsonRpcResponseValidationError.error_type:type_name -> path.qos.JsonRpcValidationErrorType
+	2, // 1: path.qos.JsonRpcResponseValidationError.timestamp:type_name -> google.protobuf.Timestamp
+	2, // [2:2] is the sub-list for method output_type
+	2, // [2:2] is the sub-list for method input_type
+	2, // [2:2] is the sub-list for extension type_name
+	2, // [2:2] is the sub-list for extension extendee
+	0, // [0:2] is the sub-list for field type_name
+}
+
+func init() { file_path_qos_jsonrpc_validation_error_proto_init() }
+func file_path_qos_jsonrpc_validation_error_proto_init() {
+	if File_path_qos_jsonrpc_validation_error_proto != nil {
+		return
+	}
+	type x struct{}
+	out := protoimpl.TypeBuilder{
+		File: protoimpl.DescBuilder{
+			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
+			RawDescriptor: unsafe.Slice(unsafe.StringData(file_path_qos_jsonrpc_validation_error_proto_rawDesc), len(file_path_qos_jsonrpc_validation_error_proto_rawDesc)),
+			NumEnums:      1,
+			NumMessages:   1,
+			NumExtensions: 0,
+			NumServices:   0,
+		},
+		GoTypes:           file_path_qos_jsonrpc_validation_error_proto_goTypes,
+		DependencyIndexes: file_path_qos_jsonrpc_validation_error_proto_depIdxs,
+		EnumInfos:         file_path_qos_jsonrpc_validation_error_proto_enumTypes,
+		MessageInfos:      file_path_qos_jsonrpc_validation_error_proto_msgTypes,
+	}.Build()
+	File_path_qos_jsonrpc_validation_error_proto = out.File
+	file_path_qos_jsonrpc_validation_error_proto_goTypes = nil
+	file_path_qos_jsonrpc_validation_error_proto_depIdxs = nil
+}
diff --git a/observation/qos/solana.pb.go b/observation/qos/solana.pb.go
index 478bdb87a..faa7a7d70 100644
--- a/observation/qos/solana.pb.go
+++ b/observation/qos/solana.pb.go
@@ -354,6 +354,8 @@ func (x *SolanaGetHealthResponse) GetResult() string {
 type SolanaUnrecognizedResponse struct {
 	state           protoimpl.MessageState `protogen:"open.v1"`
 	JsonrpcResponse *JsonRpcResponse       `protobuf:"bytes,1,opt,name=jsonrpc_response,json=jsonrpcResponse,proto3" json:"jsonrpc_response,omitempty"`
+	// Optional validation error information
+	ValidationError *JsonRpcResponseValidationError `protobuf:"bytes,2,opt,name=validation_error,json=validationError,proto3,oneof" json:"validation_error,omitempty"`
 	unknownFields   protoimpl.UnknownFields
 	sizeCache       protoimpl.SizeCache
 }
@@ -395,11 +397,18 @@ func (x *SolanaUnrecognizedResponse) GetJsonrpcResponse() *JsonRpcResponse {
 	return nil
 }
 
+func (x *SolanaUnrecognizedResponse) GetValidationError() *JsonRpcResponseValidationError {
+	if x != nil {
+		return x.ValidationError
+	}
+	return nil
+}
+
 var File_path_qos_solana_proto protoreflect.FileDescriptor
 
 const file_path_qos_solana_proto_rawDesc = "" +
 	"\n" +
-	"\x15path/qos/solana.proto\x12\bpath.qos\x1a\x16path/qos/jsonrpc.proto\x1a\x1dpath/qos/request_origin.proto\x1a\x1cpath/qos/request_error.proto\"\xd5\x03\n" +
+	"\x15path/qos/solana.proto\x12\bpath.qos\x1a\x16path/qos/jsonrpc.proto\x1a\x1dpath/qos/request_origin.proto\x1a\x1cpath/qos/request_error.proto\x1a'path/qos/jsonrpc_validation_error.proto\"\xd5\x03\n" +
 	"\x19SolanaRequestObservations\x12\x19\n" +
 	"\bchain_id\x18\x01 \x01(\tR\achainId\x12\x1d\n" +
 	"\n" +
@@ -421,9 +430,11 @@ const file_path_qos_solana_proto_rawDesc = "" +
 	"\fblock_height\x18\x01 \x01(\x04R\vblockHeight\x12\x14\n" +
 	"\x05epoch\x18\x02 \x01(\x04R\x05epoch\"1\n" +
 	"\x17SolanaGetHealthResponse\x12\x16\n" +
-	"\x06result\x18\x01 \x01(\tR\x06result\"b\n" +
+	"\x06result\x18\x01 \x01(\tR\x06result\"\xd1\x01\n" +
 	"\x1aSolanaUnrecognizedResponse\x12D\n" +
-	"\x10jsonrpc_response\x18\x01 \x01(\v2\x19.path.qos.JsonRpcResponseR\x0fjsonrpcResponseB0Z.github.com/buildwithgrove/path/observation/qosb\x06proto3"
+	"\x10jsonrpc_response\x18\x01 \x01(\v2\x19.path.qos.JsonRpcResponseR\x0fjsonrpcResponse\x12X\n" +
+	"\x10validation_error\x18\x02 \x01(\v2(.path.qos.JsonRpcResponseValidationErrorH\x00R\x0fvalidationError\x88\x01\x01B\x13\n" +
+	"\x11_validation_errorB0Z.github.com/buildwithgrove/path/observation/qosb\x06proto3"
 
 var (
 	file_path_qos_solana_proto_rawDescOnce sync.Once
@@ -439,15 +450,16 @@ func file_path_qos_solana_proto_rawDescGZIP() []byte {
 
 var file_path_qos_solana_proto_msgTypes = make([]protoimpl.MessageInfo, 5)
 var file_path_qos_solana_proto_goTypes = []any{
-	(*SolanaRequestObservations)(nil),  // 0: path.qos.SolanaRequestObservations
-	(*SolanaEndpointObservation)(nil),  // 1: path.qos.SolanaEndpointObservation
-	(*SolanaGetEpochInfoResponse)(nil), // 2: path.qos.SolanaGetEpochInfoResponse
-	(*SolanaGetHealthResponse)(nil),    // 3: path.qos.SolanaGetHealthResponse
-	(*SolanaUnrecognizedResponse)(nil), // 4: path.qos.SolanaUnrecognizedResponse
-	(RequestOrigin)(0),                 // 5: path.qos.RequestOrigin
-	(*RequestError)(nil),               // 6: path.qos.RequestError
-	(*JsonRpcRequest)(nil),             // 7: path.qos.JsonRpcRequest
-	(*JsonRpcResponse)(nil),            // 8: path.qos.JsonRpcResponse
+	(*SolanaRequestObservations)(nil),      // 0: path.qos.SolanaRequestObservations
+	(*SolanaEndpointObservation)(nil),      // 1: path.qos.SolanaEndpointObservation
+	(*SolanaGetEpochInfoResponse)(nil),     // 2: path.qos.SolanaGetEpochInfoResponse
+	(*SolanaGetHealthResponse)(nil),        // 3: path.qos.SolanaGetHealthResponse
+	(*SolanaUnrecognizedResponse)(nil),     // 4: path.qos.SolanaUnrecognizedResponse
+	(RequestOrigin)(0),                     // 5: path.qos.RequestOrigin
+	(*RequestError)(nil),                   // 6: path.qos.RequestError
+	(*JsonRpcRequest)(nil),                 // 7: path.qos.JsonRpcRequest
+	(*JsonRpcResponse)(nil),                // 8: path.qos.JsonRpcResponse
+	(*JsonRpcResponseValidationError)(nil), // 9: path.qos.JsonRpcResponseValidationError
 }
 var file_path_qos_solana_proto_depIdxs = []int32{
 	5, // 0: path.qos.SolanaRequestObservations.request_origin:type_name -> path.qos.RequestOrigin
@@ -458,11 +470,12 @@ var file_path_qos_solana_proto_depIdxs = []int32{
 	3, // 5: path.qos.SolanaEndpointObservation.get_health_response:type_name -> path.qos.SolanaGetHealthResponse
 	4, // 6: path.qos.SolanaEndpointObservation.unrecognized_response:type_name -> path.qos.SolanaUnrecognizedResponse
 	8, // 7: path.qos.SolanaUnrecognizedResponse.jsonrpc_response:type_name -> path.qos.JsonRpcResponse
-	8, // [8:8] is the sub-list for method output_type
-	8, // [8:8] is the sub-list for method input_type
-	8, // [8:8] is the sub-list for extension type_name
-	8, // [8:8] is the sub-list for extension extendee
-	0, // [0:8] is the sub-list for field type_name
+	9, // 8: path.qos.SolanaUnrecognizedResponse.validation_error:type_name -> path.qos.JsonRpcResponseValidationError
+	9, // [9:9] is the sub-list for method output_type
+	9, // [9:9] is the sub-list for method input_type
+	9, // [9:9] is the sub-list for extension type_name
+	9, // [9:9] is the sub-list for extension extendee
+	0, // [0:9] is the sub-list for field type_name
 }
 
 func init() { file_path_qos_solana_proto_init() }
@@ -473,12 +486,14 @@ func file_path_qos_solana_proto_init() {
 	file_path_qos_jsonrpc_proto_init()
 	file_path_qos_request_origin_proto_init()
 	file_path_qos_request_error_proto_init()
+	file_path_qos_jsonrpc_validation_error_proto_init()
 	file_path_qos_solana_proto_msgTypes[0].OneofWrappers = []any{}
 	file_path_qos_solana_proto_msgTypes[1].OneofWrappers = []any{
 		(*SolanaEndpointObservation_GetEpochInfoResponse)(nil),
 		(*SolanaEndpointObservation_GetHealthResponse)(nil),
 		(*SolanaEndpointObservation_UnrecognizedResponse)(nil),
 	}
+	file_path_qos_solana_proto_msgTypes[4].OneofWrappers = []any{}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
 		File: protoimpl.DescBuilder{
diff --git a/proto/path/qos/jsonrpc_validation_error.proto b/proto/path/qos/jsonrpc_validation_error.proto
new file mode 100644
index 000000000..3ae9cc5e3
--- /dev/null
+++ b/proto/path/qos/jsonrpc_validation_error.proto
@@ -0,0 +1,24 @@
+syntax = "proto3";
+package path.qos;
+
+option go_package = "github.com/buildwithgrove/path/observation/qos";
+
+import "google/protobuf/timestamp.proto";
+
+// JsonRpcResponseValidationError captures validation errors for JSON-RPC responses
+message JsonRpcResponseValidationError {
+  // Type of validation error
+  JsonRpcValidationErrorType error_type = 1;
+  
+  // Timestamp when the validation error occurred
+  google.protobuf.Timestamp timestamp = 2;
+}
+
+// Enum for different types of JSON-RPC validation errors
+enum JsonRpcValidationErrorType {
+  // Default/unspecified validation error
+  JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED = 0;
+  
+  // Response is not a valid JSON-RPC response
+  NON_JSONRPC_RESPONSE = 1;
+}
\ No newline at end of file
diff --git a/proto/path/qos/solana.proto b/proto/path/qos/solana.proto
index bbcb4f08f..570922e98 100644
--- a/proto/path/qos/solana.proto
+++ b/proto/path/qos/solana.proto
@@ -6,6 +6,7 @@ option go_package = "github.com/buildwithgrove/path/observation/qos";
 import "path/qos/jsonrpc.proto";
 import "path/qos/request_origin.proto";
 import "path/qos/request_error.proto";
+import "path/qos/jsonrpc_validation_error.proto";
 
 // SolanaRequestObservations captures QoS data for a single Solana blockchain service request,
 // including all observations made during potential retries.
@@ -79,4 +80,7 @@ message SolanaGetHealthResponse {
 // Examples: getTokenSupply, getTransaction
 message SolanaUnrecognizedResponse {
   JsonRpcResponse jsonrpc_response = 1;
-}
+  
+  // Optional validation error information
+  optional JsonRpcResponseValidationError validation_error = 2;
+}
\ No newline at end of file
diff --git a/qos/solana/endpoint.go b/qos/solana/endpoint.go
index 4d76435e4..aaadf9fc5 100644
--- a/qos/solana/endpoint.go
+++ b/qos/solana/endpoint.go
@@ -2,6 +2,7 @@ package solana
 
 import (
 	"fmt"
+	"time"
 
 	qosobservations "github.com/buildwithgrove/path/observation/qos"
 )
@@ -9,6 +10,11 @@ import (
 // Expected value of the `result` field to a `getHealth` request.
 const resultGetHealthOK = "ok"
 
+const (
+	// TODO_TECHDEBT(@adshmh): Make this configurable.
+	validationErrorWindow = 30 * time.Minute
+)
+
 // The errors below list all the possible basic validation errors on an endpoint.
 var (
 	errNoGetHealthObs                   = fmt.Errorf("endpoint has not had an observation of its response to a %q request", methodGetHealth)
@@ -16,30 +22,36 @@ var (
 	errNoGetEpochInfoObs                = fmt.Errorf("endpoint has not had an observation of its response to a %q request", methodGetEpochInfo)
 	errInvalidGetEpochInfoHeightZeroObs = fmt.Errorf("endpoint responded with blockHeight of 0 to a %q request, expected a blockHeight of > 0", methodGetEpochInfo)
 	errInvalidGetEpochInfoEpochZeroObs  = fmt.Errorf("endpoint responded with epoch of 0 to a %q request, expected an epoch of > 0", methodGetEpochInfo)
+	errRecentValidationError            = fmt.Errorf("endpoint has recent JSON-RPC validation errors")
 )
 
-// endpoint captures the details required to validate a Solana endpoint.
+// TODO_TECHDEBT(@adshmh): Include a Sanctions mechanism to handle endpoints with dishonest behavior, e.g. using public RPCs.
+//
+// endpoint captures details required to validate a Solana endpoint.
 type endpoint struct {
-	// SolanaGetHealthResponse stores the result of processing the endpoint's response to a `getHealth` request.
-	// A pointer is used to distinguish between the following scenarios:
-	// 	1. There has NOT been an observation of the endpoint's response to a `getHealth` request, and
-	// 	2. There has been an observation of the endpoint's response to a `getHealth` request.
+	// SolanaGetHealthResponse stores result of processing endpoint's `getHealth` response.
+	// Pointer distinguishes between no observation vs. observed response scenarios.
 	*qosobservations.SolanaGetHealthResponse
 
-	// SolanaGetEpochInfoResponse stores the result of processing the endpoint's response to a `getEpochInfo` request.
-	// A pointer is used to distinguish between the following scenarios:
-	// 	1. There has NOT been an observation of the endpoint's response to a `getEpochInfo` request
-	// 	2. There has been an observation of the endpoint's response to a `getEpochInfo` request
+	// SolanaGetEpochInfoResponse stores result of processing endpoint's `getEpochInfo` response.
+	// Pointer distinguishes between no observation vs. observed response scenarios.
 	*qosobservations.SolanaGetEpochInfoResponse
 
+	// latestValidationError tracks most recent JSON-RPC response validation error
+	latestValidationError *qosobservations.JsonRpcResponseValidationError
+
 	// TODO_FUTURE: support archival endpoints.
 }
 
-// validateBasic checks if the endpoint has the required observations to be considered valid.
-// Returns an error if the necessary responses are either lacking or invalid.
+// validateBasic checks if endpoint has required observations to be valid.
+// Returns error if necessary responses are lacking, invalid, or have recent validation errors.
 func (e endpoint) validateBasic() error {
-	switch {
+	// Check for recent validation errors first
+	if e.hasRecentValidationErrors() {
+		return errRecentValidationError
+	}
 
+	switch {
 	case e.SolanaGetHealthResponse == nil:
 		return errNoGetHealthObs
 
@@ -60,8 +72,18 @@ func (e endpoint) validateBasic() error {
 	}
 }
 
-// applyObservation updates the endpoint data using the provided observation.
-// Returns true if the observation was recognized.
+// hasRecentValidationErrors checks if endpoint has validation error within the configured window.
+func (e endpoint) hasRecentValidationErrors() bool {
+	if e.latestValidationError == nil {
+		return false
+	}
+
+	cutoff := time.Now().Add(-validationErrorWindow)
+	return e.latestValidationError.Timestamp.AsTime().After(cutoff)
+}
+
+// applyObservation updates endpoint data using provided observation.
+// Returns true if observation was recognized.
 // IMPORTANT: This function mutates the endpoint.
 func (e *endpoint) applyObservation(obs *qosobservations.SolanaEndpointObservation) bool {
 	if epochInfoResponse := obs.GetGetEpochInfoResponse(); epochInfoResponse != nil {
@@ -74,5 +96,16 @@ func (e *endpoint) applyObservation(obs *qosobservations.SolanaEndpointObservati
 		return true
 	}
 
+	if unrecognizedResponse := obs.GetUnrecognizedResponse(); unrecognizedResponse != nil {
+		// Update latest validation error if observation contains more recent error
+		if validationError := unrecognizedResponse.ValidationError; validationError != nil {
+			if e.latestValidationError == nil ||
+				validationError.Timestamp.AsTime().After(e.latestValidationError.Timestamp.AsTime()) {
+				e.latestValidationError = validationError
+			}
+		}
+		return true
+	}
+
 	return false
 }
diff --git a/qos/solana/response_generic.go b/qos/solana/response_generic.go
index 8da18e452..69a1d2408 100644
--- a/qos/solana/response_generic.go
+++ b/qos/solana/response_generic.go
@@ -2,8 +2,10 @@ package solana
 
 import (
 	"encoding/json"
+	"time"
 
 	"github.com/pokt-network/poktroll/pkg/polylog"
+	"google.golang.org/protobuf/types/known/timestamppb"
 
 	qosobservations "github.com/buildwithgrove/path/observation/qos"
 	"github.com/buildwithgrove/path/qos/jsonrpc"
@@ -45,43 +47,46 @@ func responseUnmarshallerGeneric(
 	}
 }
 
-// TODO_MVP(@adshmh): implement the generic jsonrpc response
-// (with the scope limited to the Solana blockchain)
-// responseGeneric captures the fields expected in response to any request on the Solana blockchain.
-// It is intended to be used when no validation/observation is applicable to the corresponding request's JSON-RPC method.
-// i.e. when there are no unmarshallers/structs matching the method specified by the request.
+// responseGeneric captures fields for any Solana blockchain response.
+// Used when no validation/observation applies to the request's JSON-RPC method.
 type responseGeneric struct {
 	Logger polylog.Logger
 	jsonrpc.Response
+	// validationError tracks JSON-RPC validation errors if response unmarshaling failed
+	validationError *qosobservations.JsonRpcResponseValidationError
 }
 
-// GetObservation returns an observation that is NOT used in validating endpoints.
-// This allows sharing data with other entities, e.g. a data pipeline.
-// Implements the response interface.
-// As of PR 372, this is a default catchall for any response to any requests other than `getHealth` and `getEpochInfo`.
+// GetObservation returns observation NOT used for endpoint validation.
+// Shares data with other entities (e.g., data pipeline).
+// As of PR 372, default catchall for responses other than `getHealth` and `getEpochInfo`.
 func (r responseGeneric) GetObservation() qosobservations.SolanaEndpointObservation {
-	return qosobservations.SolanaEndpointObservation{
+	unrecognizedResponse := &qosobservations.SolanaUnrecognizedResponse{
 		// TODO_TECHDEBT(@adshmh): set additional JSON-RPC response fields, specifically the `error` object, on the observation.
 		// This needs a utility function to convert a `qos.jsonrpc.Response` to an `observation.qos.JsonRpcResponse.
+		JsonrpcResponse: &qosobservations.JsonRpcResponse{
+			Id: r.ID.String(),
+		},
+	}
+
+	// Include validation error if present
+	if r.validationError != nil {
+		unrecognizedResponse.ValidationError = r.validationError
+	}
+
+	return qosobservations.SolanaEndpointObservation{
 		ResponseObservation: &qosobservations.SolanaEndpointObservation_UnrecognizedResponse{
-			UnrecognizedResponse: &qosobservations.SolanaUnrecognizedResponse{
-				JsonrpcResponse: &qosobservations.JsonRpcResponse{
-					Id: r.ID.String(),
-				},
-			},
+			UnrecognizedResponse: unrecognizedResponse,
 		},
 	}
 }
 
-// GetResponsePayload returns the payload for the response to a `/health` request.
-// Implements the response interface.
-//
-// TODO_MVP(@adshmh): handle any unmarshaling errors and build a method-specific payload generator.
+// GetJSONRPCResponse returns response payload.
 func (r responseGeneric) GetJSONRPCResponse() jsonrpc.Response {
 	return r.Response
 }
 
-// getGenericJSONRPCErrResponse returns a generic response wrapped around a JSON-RPC error response with the supplied ID, error, and the invalid payload in the "data" field.
+// getGenericJSONRPCErrResponse returns generic response with JSON-RPC error and validation error observation.
+// Includes supplied ID, error, and invalid payload in "data" field.
 func getGenericJSONRPCErrResponse(
 	logger polylog.Logger,
 	id jsonrpc.ID,
@@ -93,7 +98,14 @@ func getGenericJSONRPCErrResponse(
 		errDataFieldUnmarshalingErr: err.Error(),
 	}
 
+	// Create validation error observation
+	validationError := &qosobservations.JsonRpcResponseValidationError{
+		ErrorType: qosobservations.JsonRpcValidationErrorType_NON_JSONRPC_RESPONSE,
+		Timestamp: timestamppb.New(time.Now()),
+	}
+
 	return responseGeneric{
-		Response: jsonrpc.GetErrorResponse(id, errCodeUnmarshaling, errMsgUnmarshaling, errData),
+		Response:        jsonrpc.GetErrorResponse(id, errCodeUnmarshaling, errMsgUnmarshaling, errData),
+		validationError: validationError,
 	}
 }

From 282b28e4128a97813f352d6d4c3331d28a25c618 Mon Sep 17 00:00:00 2001
From: Daniel Olshansky <olshansky.daniel@gmail.com>
Date: Thu, 14 Aug 2025 13:25:36 -0700
Subject: [PATCH 2/6] WIP review

---
 observation/qos/jsonrpc_validation_error.pb.go | 14 +++++++-------
 proto/path/qos/jsonrpc_validation_error.proto  |  8 ++++----
 proto/path/qos/solana.proto                    |  4 ++--
 qos/solana/endpoint.go                         | 13 +++++++------
 qos/solana/response_generic.go                 |  8 ++++----
 5 files changed, 24 insertions(+), 23 deletions(-)

diff --git a/observation/qos/jsonrpc_validation_error.pb.go b/observation/qos/jsonrpc_validation_error.pb.go
index f0cfc7350..f3d2708d4 100644
--- a/observation/qos/jsonrpc_validation_error.pb.go
+++ b/observation/qos/jsonrpc_validation_error.pb.go
@@ -29,18 +29,18 @@ const (
 	// Default/unspecified validation error
 	JsonRpcValidationErrorType_JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED JsonRpcValidationErrorType = 0
 	// Response is not a valid JSON-RPC response
-	JsonRpcValidationErrorType_NON_JSONRPC_RESPONSE JsonRpcValidationErrorType = 1
+	JsonRpcValidationErrorType_JSON_RPC_VALIDATION_ERROR_TYPE_NON_JSONRPC_RESPONSE JsonRpcValidationErrorType = 1
 )
 
 // Enum value maps for JsonRpcValidationErrorType.
 var (
 	JsonRpcValidationErrorType_name = map[int32]string{
 		0: "JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED",
-		1: "NON_JSONRPC_RESPONSE",
+		1: "JSON_RPC_VALIDATION_ERROR_TYPE_NON_JSONRPC_RESPONSE",
 	}
 	JsonRpcValidationErrorType_value = map[string]int32{
-		"JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED": 0,
-		"NON_JSONRPC_RESPONSE":                       1,
+		"JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED":          0,
+		"JSON_RPC_VALIDATION_ERROR_TYPE_NON_JSONRPC_RESPONSE": 1,
 	}
 )
 
@@ -134,10 +134,10 @@ const file_path_qos_jsonrpc_validation_error_proto_rawDesc = "" +
 	"\x1eJsonRpcResponseValidationError\x12C\n" +
 	"\n" +
 	"error_type\x18\x01 \x01(\x0e2$.path.qos.JsonRpcValidationErrorTypeR\terrorType\x128\n" +
-	"\ttimestamp\x18\x02 \x01(\v2\x1a.google.protobuf.TimestampR\ttimestamp*f\n" +
+	"\ttimestamp\x18\x02 \x01(\v2\x1a.google.protobuf.TimestampR\ttimestamp*\x85\x01\n" +
 	"\x1aJsonRpcValidationErrorType\x12.\n" +
-	"*JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED\x10\x00\x12\x18\n" +
-	"\x14NON_JSONRPC_RESPONSE\x10\x01B0Z.github.com/buildwithgrove/path/observation/qosb\x06proto3"
+	"*JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED\x10\x00\x127\n" +
+	"3JSON_RPC_VALIDATION_ERROR_TYPE_NON_JSONRPC_RESPONSE\x10\x01B0Z.github.com/buildwithgrove/path/observation/qosb\x06proto3"
 
 var (
 	file_path_qos_jsonrpc_validation_error_proto_rawDescOnce sync.Once
diff --git a/proto/path/qos/jsonrpc_validation_error.proto b/proto/path/qos/jsonrpc_validation_error.proto
index 3ae9cc5e3..bdea68715 100644
--- a/proto/path/qos/jsonrpc_validation_error.proto
+++ b/proto/path/qos/jsonrpc_validation_error.proto
@@ -9,7 +9,7 @@ import "google/protobuf/timestamp.proto";
 message JsonRpcResponseValidationError {
   // Type of validation error
   JsonRpcValidationErrorType error_type = 1;
-  
+
   // Timestamp when the validation error occurred
   google.protobuf.Timestamp timestamp = 2;
 }
@@ -18,7 +18,7 @@ message JsonRpcResponseValidationError {
 enum JsonRpcValidationErrorType {
   // Default/unspecified validation error
   JSON_RPC_VALIDATION_ERROR_TYPE_UNSPECIFIED = 0;
-  
+
   // Response is not a valid JSON-RPC response
-  NON_JSONRPC_RESPONSE = 1;
-}
\ No newline at end of file
+  JSON_RPC_VALIDATION_ERROR_TYPE_NON_JSONRPC_RESPONSE = 1;
+}
diff --git a/proto/path/qos/solana.proto b/proto/path/qos/solana.proto
index 570922e98..b43a8b41d 100644
--- a/proto/path/qos/solana.proto
+++ b/proto/path/qos/solana.proto
@@ -80,7 +80,7 @@ message SolanaGetHealthResponse {
 // Examples: getTokenSupply, getTransaction
 message SolanaUnrecognizedResponse {
   JsonRpcResponse jsonrpc_response = 1;
-  
+
   // Optional validation error information
   optional JsonRpcResponseValidationError validation_error = 2;
-}
\ No newline at end of file
+}
diff --git a/qos/solana/endpoint.go b/qos/solana/endpoint.go
index aaadf9fc5..49d8fcc04 100644
--- a/qos/solana/endpoint.go
+++ b/qos/solana/endpoint.go
@@ -11,8 +11,10 @@ import (
 const resultGetHealthOK = "ok"
 
 const (
-	// TODO_TECHDEBT(@adshmh): Make this configurable.
-	validationErrorWindow = 30 * time.Minute
+	// TODO_TECHDEBT(@adshmh): Make configurable via service config.
+	// 30 minutes allows for temporary network issues while preventing
+	// persistently broken endpoints from being used.
+	validationErrorResponseWindow = 30 * time.Minute
 )
 
 // The errors below list all the possible basic validation errors on an endpoint.
@@ -25,9 +27,8 @@ var (
 	errRecentValidationError            = fmt.Errorf("endpoint has recent JSON-RPC validation errors")
 )
 
-// TODO_TECHDEBT(@adshmh): Include a Sanctions mechanism to handle endpoints with dishonest behavior, e.g. using public RPCs.
-//
 // endpoint captures details required to validate a Solana endpoint.
+// TODO_TECHDEBT(@adshmh): Add sanctions mechanism for dishonest endpoints (e.g., using public RPCs).
 type endpoint struct {
 	// SolanaGetHealthResponse stores result of processing endpoint's `getHealth` response.
 	// Pointer distinguishes between no observation vs. observed response scenarios.
@@ -78,8 +79,8 @@ func (e endpoint) hasRecentValidationErrors() bool {
 		return false
 	}
 
-	cutoff := time.Now().Add(-validationErrorWindow)
-	return e.latestValidationError.Timestamp.AsTime().After(cutoff)
+	lastValidationErrorTimestamp := time.Now().Add(-validationErrorResponseWindow)
+	return e.latestValidationError.Timestamp.AsTime().After(lastValidationErrorTimestamp)
 }
 
 // applyObservation updates endpoint data using provided observation.
diff --git a/qos/solana/response_generic.go b/qos/solana/response_generic.go
index 69a1d2408..b88bf1039 100644
--- a/qos/solana/response_generic.go
+++ b/qos/solana/response_generic.go
@@ -58,11 +58,11 @@ type responseGeneric struct {
 
 // GetObservation returns observation NOT used for endpoint validation.
 // Shares data with other entities (e.g., data pipeline).
-// As of PR 372, default catchall for responses other than `getHealth` and `getEpochInfo`.
+// Default catchall for responses other than `getHealth` and `getEpochInfo`.
 func (r responseGeneric) GetObservation() qosobservations.SolanaEndpointObservation {
 	unrecognizedResponse := &qosobservations.SolanaUnrecognizedResponse{
-		// TODO_TECHDEBT(@adshmh): set additional JSON-RPC response fields, specifically the `error` object, on the observation.
-		// This needs a utility function to convert a `qos.jsonrpc.Response` to an `observation.qos.JsonRpcResponse.
+		// TODO_TECHDEBT(@adshmh): Add utility to convert qos.jsonrpc.Response to observation.qos.JsonRpcResponse
+		// to include error object and other fields in observations.
 		JsonrpcResponse: &qosobservations.JsonRpcResponse{
 			Id: r.ID.String(),
 		},
@@ -100,7 +100,7 @@ func getGenericJSONRPCErrResponse(
 
 	// Create validation error observation
 	validationError := &qosobservations.JsonRpcResponseValidationError{
-		ErrorType: qosobservations.JsonRpcValidationErrorType_NON_JSONRPC_RESPONSE,
+		ErrorType: qosobservations.JsonRpcValidationErrorType_JSON_RPC_VALIDATION_ERROR_TYPE_NON_JSONRPC_RESPONSE,
 		Timestamp: timestamppb.New(time.Now()),
 	}
 

From a938d033e0758c14428c9e525692b93043d6e0ad Mon Sep 17 00:00:00 2001
From: Arash <23505281+adshmh@users.noreply.github.com>
Date: Thu, 14 Aug 2025 20:34:08 -0400
Subject: [PATCH 3/6] Update qos/solana/endpoint.go

Co-authored-by: Daniel Olshansky <olshansky.daniel@gmail.com>
---
 qos/solana/endpoint.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/qos/solana/endpoint.go b/qos/solana/endpoint.go
index 49d8fcc04..703307038 100644
--- a/qos/solana/endpoint.go
+++ b/qos/solana/endpoint.go
@@ -24,7 +24,7 @@ var (
 	errNoGetEpochInfoObs                = fmt.Errorf("endpoint has not had an observation of its response to a %q request", methodGetEpochInfo)
 	errInvalidGetEpochInfoHeightZeroObs = fmt.Errorf("endpoint responded with blockHeight of 0 to a %q request, expected a blockHeight of > 0", methodGetEpochInfo)
 	errInvalidGetEpochInfoEpochZeroObs  = fmt.Errorf("endpoint responded with epoch of 0 to a %q request, expected an epoch of > 0", methodGetEpochInfo)
-	errRecentValidationError            = fmt.Errorf("endpoint has recent JSON-RPC validation errors")
+	errRecentJSONRPCValidationError            = fmt.Errorf("endpoint has recent JSON-RPC validation errors")
 )
 
 // endpoint captures details required to validate a Solana endpoint.

From a104834c15bb20d1b48791b8f4d417e866907494 Mon Sep 17 00:00:00 2001
From: Arash Deshmeh <adshmh@gmail.com>
Date: Fri, 15 Aug 2025 10:29:10 -0400
Subject: [PATCH 4/6] Address review comments

---
 observation/qos/jsonrpc_validation_error.pb.go |  4 ++++
 proto/path/qos/jsonrpc_validation_error.proto  |  3 +++
 qos/solana/endpoint.go                         |  9 +++++++--
 qos/solana/response_generic.go                 | 14 +++++++-------
 4 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/observation/qos/jsonrpc_validation_error.pb.go b/observation/qos/jsonrpc_validation_error.pb.go
index f3d2708d4..9f43f43a9 100644
--- a/observation/qos/jsonrpc_validation_error.pb.go
+++ b/observation/qos/jsonrpc_validation_error.pb.go
@@ -1,3 +1,7 @@
+// TODO_TECHDEBT(@adshmh): Use the JsonRpcResponseValidationError in all JSONRPC QoS.
+// Include this refactor in PR #253 (JUDGE framework)
+//
+
 // Code generated by protoc-gen-go. DO NOT EDIT.
 // versions:
 // 	protoc-gen-go v1.36.6
diff --git a/proto/path/qos/jsonrpc_validation_error.proto b/proto/path/qos/jsonrpc_validation_error.proto
index bdea68715..8d9f5b43c 100644
--- a/proto/path/qos/jsonrpc_validation_error.proto
+++ b/proto/path/qos/jsonrpc_validation_error.proto
@@ -1,3 +1,6 @@
+// TODO_TECHDEBT(@adshmh): Use the JsonRpcResponseValidationError in all JSONRPC QoS.
+// Include this refactor in PR #253 (JUDGE framework)
+//
 syntax = "proto3";
 package path.qos;
 
diff --git a/qos/solana/endpoint.go b/qos/solana/endpoint.go
index 703307038..4fc20a75e 100644
--- a/qos/solana/endpoint.go
+++ b/qos/solana/endpoint.go
@@ -11,6 +11,12 @@ import (
 const resultGetHealthOK = "ok"
 
 const (
+	// TODO_TECHDEBT(@adshmh): Add sanctions mechanism for dishonest endpoints (e.g., using public RPCs).
+	// The sanctions store will apply to all QoS packages via PR #253 (JUDGE framework).
+	// It will replace:
+	// - The constant below with configurable sanction duration for different errors.
+	// - endpoint struct's basicValidation method.
+	//
 	// TODO_TECHDEBT(@adshmh): Make configurable via service config.
 	// 30 minutes allows for temporary network issues while preventing
 	// persistently broken endpoints from being used.
@@ -24,11 +30,10 @@ var (
 	errNoGetEpochInfoObs                = fmt.Errorf("endpoint has not had an observation of its response to a %q request", methodGetEpochInfo)
 	errInvalidGetEpochInfoHeightZeroObs = fmt.Errorf("endpoint responded with blockHeight of 0 to a %q request, expected a blockHeight of > 0", methodGetEpochInfo)
 	errInvalidGetEpochInfoEpochZeroObs  = fmt.Errorf("endpoint responded with epoch of 0 to a %q request, expected an epoch of > 0", methodGetEpochInfo)
-	errRecentJSONRPCValidationError            = fmt.Errorf("endpoint has recent JSON-RPC validation errors")
+	errRecentJSONRPCValidationError     = fmt.Errorf("endpoint has recent JSON-RPC validation errors")
 )
 
 // endpoint captures details required to validate a Solana endpoint.
-// TODO_TECHDEBT(@adshmh): Add sanctions mechanism for dishonest endpoints (e.g., using public RPCs).
 type endpoint struct {
 	// SolanaGetHealthResponse stores result of processing endpoint's `getHealth` response.
 	// Pointer distinguishes between no observation vs. observed response scenarios.
diff --git a/qos/solana/response_generic.go b/qos/solana/response_generic.go
index b88bf1039..2a226d9e4 100644
--- a/qos/solana/response_generic.go
+++ b/qos/solana/response_generic.go
@@ -52,8 +52,8 @@ func responseUnmarshallerGeneric(
 type responseGeneric struct {
 	Logger polylog.Logger
 	jsonrpc.Response
-	// validationError tracks JSON-RPC validation errors if response unmarshaling failed
-	validationError *qosobservations.JsonRpcResponseValidationError
+	// jsonrpcResponseValidationError tracks JSON-RPC validation errors if response unmarshaling failed
+	jsonrpcResponseValidationError *qosobservations.JsonRpcResponseValidationError
 }
 
 // GetObservation returns observation NOT used for endpoint validation.
@@ -69,8 +69,8 @@ func (r responseGeneric) GetObservation() qosobservations.SolanaEndpointObservat
 	}
 
 	// Include validation error if present
-	if r.validationError != nil {
-		unrecognizedResponse.ValidationError = r.validationError
+	if r.jsonrpcResponseValidationError != nil {
+		unrecognizedResponse.ValidationError = r.jsonrpcResponseValidationError
 	}
 
 	return qosobservations.SolanaEndpointObservation{
@@ -99,13 +99,13 @@ func getGenericJSONRPCErrResponse(
 	}
 
 	// Create validation error observation
-	validationError := &qosobservations.JsonRpcResponseValidationError{
+	jsonrpcResponseValidationError := &qosobservations.JsonRpcResponseValidationError{
 		ErrorType: qosobservations.JsonRpcValidationErrorType_JSON_RPC_VALIDATION_ERROR_TYPE_NON_JSONRPC_RESPONSE,
 		Timestamp: timestamppb.New(time.Now()),
 	}
 
 	return responseGeneric{
-		Response:        jsonrpc.GetErrorResponse(id, errCodeUnmarshaling, errMsgUnmarshaling, errData),
-		validationError: validationError,
+		Response:                       jsonrpc.GetErrorResponse(id, errCodeUnmarshaling, errMsgUnmarshaling, errData),
+		jsonrpcResponseValidationError: jsonrpcResponseValidationError,
 	}
 }

From ce56847faaac572a45fb9629864ff29b0bc6a134 Mon Sep 17 00:00:00 2001
From: Arash Deshmeh <adshmh@gmail.com>
Date: Fri, 15 Aug 2025 11:22:52 -0400
Subject: [PATCH 5/6] Add JSONRPC response observations to qos

---
 observation/qos/jsonrpc.pb.go                 | 27 ++++++------
 .../qos/jsonrpc_validation_error.pb.go        |  3 ++
 proto/path/qos/jsonrpc.proto                  |  9 ++--
 proto/path/qos/jsonrpc_validation_error.proto |  3 ++
 qos/cosmos/check_evm_chainid_test.go          |  2 +-
 qos/cosmos/response_jsonrpc_unrecognized.go   |  5 +--
 qos/evm/response_generic.go                   |  5 +--
 qos/jsonrpc/observation.go                    | 41 +++++++++++++++++++
 qos/jsonrpc/response.go                       |  5 +++
 qos/solana/endpoint.go                        | 16 ++++----
 qos/solana/response_generic.go                |  7 +---
 11 files changed, 85 insertions(+), 38 deletions(-)

diff --git a/observation/qos/jsonrpc.pb.go b/observation/qos/jsonrpc.pb.go
index 4569457bd..b8316fa98 100644
--- a/observation/qos/jsonrpc.pb.go
+++ b/observation/qos/jsonrpc.pb.go
@@ -83,10 +83,11 @@ type JsonRpcResponse struct {
 	state protoimpl.MessageState `protogen:"open.v1"`
 	// Must match the id value from the corresponding request
 	Id string `protobuf:"bytes,1,opt,name=id,proto3" json:"id,omitempty"`
-	// JSON-serializable response data
-	Result string `protobuf:"bytes,2,opt,name=result,proto3" json:"result,omitempty"`
+	// A preview of the JSONRPC response's `result` field.
+	// It may have been truncated to reduce message size.
+	ResultPreview string `protobuf:"bytes,2,opt,name=result_preview,json=resultPreview,proto3" json:"result_preview,omitempty"`
 	// Error details, if the request failed
-	Err           *JsonRpcResponseError `protobuf:"bytes,3,opt,name=err,proto3,oneof" json:"err,omitempty"`
+	Error         *JsonRpcResponseError `protobuf:"bytes,3,opt,name=error,proto3,oneof" json:"error,omitempty"`
 	unknownFields protoimpl.UnknownFields
 	sizeCache     protoimpl.SizeCache
 }
@@ -128,16 +129,16 @@ func (x *JsonRpcResponse) GetId() string {
 	return ""
 }
 
-func (x *JsonRpcResponse) GetResult() string {
+func (x *JsonRpcResponse) GetResultPreview() string {
 	if x != nil {
-		return x.Result
+		return x.ResultPreview
 	}
 	return ""
 }
 
-func (x *JsonRpcResponse) GetErr() *JsonRpcResponseError {
+func (x *JsonRpcResponse) GetError() *JsonRpcResponseError {
 	if x != nil {
-		return x.Err
+		return x.Error
 	}
 	return nil
 }
@@ -207,12 +208,12 @@ const file_path_qos_jsonrpc_proto_rawDesc = "" +
 	"\x16path/qos/jsonrpc.proto\x12\bpath.qos\"8\n" +
 	"\x0eJsonRpcRequest\x12\x0e\n" +
 	"\x02id\x18\x01 \x01(\tR\x02id\x12\x16\n" +
-	"\x06method\x18\x02 \x01(\tR\x06method\"x\n" +
+	"\x06method\x18\x02 \x01(\tR\x06method\"\x8d\x01\n" +
 	"\x0fJsonRpcResponse\x12\x0e\n" +
-	"\x02id\x18\x01 \x01(\tR\x02id\x12\x16\n" +
-	"\x06result\x18\x02 \x01(\tR\x06result\x125\n" +
-	"\x03err\x18\x03 \x01(\v2\x1e.path.qos.JsonRpcResponseErrorH\x00R\x03err\x88\x01\x01B\x06\n" +
-	"\x04_err\"D\n" +
+	"\x02id\x18\x01 \x01(\tR\x02id\x12%\n" +
+	"\x0eresult_preview\x18\x02 \x01(\tR\rresultPreview\x129\n" +
+	"\x05error\x18\x03 \x01(\v2\x1e.path.qos.JsonRpcResponseErrorH\x00R\x05error\x88\x01\x01B\b\n" +
+	"\x06_error\"D\n" +
 	"\x14JsonRpcResponseError\x12\x12\n" +
 	"\x04code\x18\x01 \x01(\x03R\x04code\x12\x18\n" +
 	"\amessage\x18\x02 \x01(\tR\amessageB0Z.github.com/buildwithgrove/path/observation/qosb\x06proto3"
@@ -236,7 +237,7 @@ var file_path_qos_jsonrpc_proto_goTypes = []any{
 	(*JsonRpcResponseError)(nil), // 2: path.qos.JsonRpcResponseError
 }
 var file_path_qos_jsonrpc_proto_depIdxs = []int32{
-	2, // 0: path.qos.JsonRpcResponse.err:type_name -> path.qos.JsonRpcResponseError
+	2, // 0: path.qos.JsonRpcResponse.error:type_name -> path.qos.JsonRpcResponseError
 	1, // [1:1] is the sub-list for method output_type
 	1, // [1:1] is the sub-list for method input_type
 	1, // [1:1] is the sub-list for extension type_name
diff --git a/observation/qos/jsonrpc_validation_error.pb.go b/observation/qos/jsonrpc_validation_error.pb.go
index 9f43f43a9..118073793 100644
--- a/observation/qos/jsonrpc_validation_error.pb.go
+++ b/observation/qos/jsonrpc_validation_error.pb.go
@@ -1,6 +1,9 @@
 // TODO_TECHDEBT(@adshmh): Use the JsonRpcResponseValidationError in all JSONRPC QoS.
 // Include this refactor in PR #253 (JUDGE framework)
 //
+// TODO_TECHDEBT(@adshmh): The JsonRpcResponseValidationError should only be constructed by the qos/jsonrpc package.
+// See the comment in qos/jsonrpc/observation.go
+//
 
 // Code generated by protoc-gen-go. DO NOT EDIT.
 // versions:
diff --git a/proto/path/qos/jsonrpc.proto b/proto/path/qos/jsonrpc.proto
index 7645060d0..b5b01676b 100644
--- a/proto/path/qos/jsonrpc.proto
+++ b/proto/path/qos/jsonrpc.proto
@@ -22,11 +22,12 @@ message JsonRpcResponse {
   // Must match the id value from the corresponding request
   string id = 1;
 
-  // JSON-serializable response data
-  string result = 2;
+  // A preview of the JSONRPC response's `result` field.
+  // It may have been truncated to reduce message size.
+  string result_preview = 2;
 
   // Error details, if the request failed
-  optional JsonRpcResponseError err = 3;
+  optional JsonRpcResponseError error = 3;
 
   // Note: This message captures only essential JSON-RPC fields.
   // Add fields as needed.
@@ -42,4 +43,4 @@ message JsonRpcResponseError {
 
   // Human-readable error description
   string message = 2;
-}
\ No newline at end of file
+}
diff --git a/proto/path/qos/jsonrpc_validation_error.proto b/proto/path/qos/jsonrpc_validation_error.proto
index 8d9f5b43c..820f58025 100644
--- a/proto/path/qos/jsonrpc_validation_error.proto
+++ b/proto/path/qos/jsonrpc_validation_error.proto
@@ -1,6 +1,9 @@
 // TODO_TECHDEBT(@adshmh): Use the JsonRpcResponseValidationError in all JSONRPC QoS.
 // Include this refactor in PR #253 (JUDGE framework)
 //
+// TODO_TECHDEBT(@adshmh): The JsonRpcResponseValidationError should only be constructed by the qos/jsonrpc package.
+// See the comment in qos/jsonrpc/observation.go
+//
 syntax = "proto3";
 package path.qos;
 
diff --git a/qos/cosmos/check_evm_chainid_test.go b/qos/cosmos/check_evm_chainid_test.go
index b2ff9832b..a54822fa3 100644
--- a/qos/cosmos/check_evm_chainid_test.go
+++ b/qos/cosmos/check_evm_chainid_test.go
@@ -107,4 +107,4 @@ func TestEndpointCheckEVMChainID_GetChainID(t *testing.T) {
 // Helper function to create string pointers
 func stringPtr(s string) *string {
 	return &s
-}
\ No newline at end of file
+}
diff --git a/qos/cosmos/response_jsonrpc_unrecognized.go b/qos/cosmos/response_jsonrpc_unrecognized.go
index e0dc6a327..127df0302 100644
--- a/qos/cosmos/response_jsonrpc_unrecognized.go
+++ b/qos/cosmos/response_jsonrpc_unrecognized.go
@@ -31,10 +31,7 @@ func (r *jsonrpcUnrecognizedResponse) GetObservation() qosobservations.CosmosEnd
 			HttpStatusCode:         int32(r.jsonrpcResponse.GetRecommendedHTTPStatusCode()),
 			ValidationError:        &r.validationErr,
 			ParsedResponse: &qosobservations.CosmosEndpointResponseValidationResult_ResponseJsonrpc{
-				ResponseJsonrpc: &qosobservations.JsonRpcResponse{
-					Id: r.jsonrpcResponse.ID.String(),
-					// TODO_TECHDEBT(@adshmh): Store JSONRPC response's error code.
-				},
+				ResponseJsonrpc: r.jsonrpcResponse.GetObservation(),
 			},
 		},
 	}
diff --git a/qos/evm/response_generic.go b/qos/evm/response_generic.go
index 4db516a35..4270031e6 100644
--- a/qos/evm/response_generic.go
+++ b/qos/evm/response_generic.go
@@ -54,9 +54,8 @@ func (r responseGeneric) GetObservation() qosobservations.EVMEndpointObservation
 	return qosobservations.EVMEndpointObservation{
 		ResponseObservation: &qosobservations.EVMEndpointObservation_UnrecognizedResponse{
 			UnrecognizedResponse: &qosobservations.EVMUnrecognizedResponse{
-				JsonrpcResponse: &qosobservations.JsonRpcResponse{
-					Id: r.jsonRPCResponse.ID.String(),
-				},
+				// Include JSONRPC response's details in the observation.
+				JsonrpcResponse:         r.jsonRPCResponse.GetObservation(),
 				ResponseValidationError: r.validationError,
 				HttpStatusCode:          int32(r.getHTTPStatusCode()),
 			},
diff --git a/qos/jsonrpc/observation.go b/qos/jsonrpc/observation.go
index 8b35fb322..ab681809e 100644
--- a/qos/jsonrpc/observation.go
+++ b/qos/jsonrpc/observation.go
@@ -4,6 +4,13 @@ import (
 	"github.com/buildwithgrove/path/observation/qos"
 )
 
+// TODO_TECHDEBT(@adshmh): Add a method to response struct to build validation error observations.
+// - Prerequisite: updating of Response unmarshaling to define and use exported errors.
+// - Makes this file the single source of truth on observation.qos.JsonRpcResponseValidationError struct contents.
+//
+// Include only the first 100 characters of the JSONRPC response's result field in the observation.
+const maxResponseResultPreviewLength = 100
+
 // GetObservation returns a qos.JsonRpcRequest struct that can be used by QoS services
 // to populate observation fields.
 func (r Request) GetObservation() *qos.JsonRpcRequest {
@@ -12,3 +19,37 @@ func (r Request) GetObservation() *qos.JsonRpcRequest {
 		Method: string(r.Method),
 	}
 }
+
+// GetObservation builds and returns an observation.qos.JsonRpcResponse struct
+// Used to populate observation fields.
+// Truncates the result
+func (r Response) GetObservation() *qos.JsonRpcResponse {
+	// Build a preview string of the JSONRPC response's result field.
+	var resultPreview string
+	if err := r.UnmarshalResult(&resultPreview); err == nil {
+		// Pick a maximum of 100 characters to include in the observation
+		resultPreview = resultPreview[:max(len(resultPreview), maxResponseResultPreviewLength)]
+	}
+
+	// Build the JSONRPC response's observation.
+	responseObservation := &qos.JsonRpcResponse{
+		Id:            r.ID.String(),
+		ResultPreview: resultPreview,
+	}
+
+	// Update the observation with the JSONRPC response's error field, if present.
+	if r.Error != nil {
+		responseObservation.Error = r.Error.GetObservation()
+	}
+
+	return responseObservation
+}
+
+// GetObservation builds and returns an observation.qos.JsonRpcResponseError struct.
+// Used to populate observation fields.
+func (re ResponseError) GetObservation() *qos.JsonRpcResponseError {
+	return &qos.JsonRpcResponseError{
+		Code:    int64(re.Code),
+		Message: re.Message,
+	}
+}
diff --git a/qos/jsonrpc/response.go b/qos/jsonrpc/response.go
index dabef9999..3191b4ed9 100644
--- a/qos/jsonrpc/response.go
+++ b/qos/jsonrpc/response.go
@@ -77,6 +77,11 @@ func (r *Response) IsError() bool {
 	return r.Error != nil
 }
 
+// TODO_TECHDEBT(@adshmh): Validate the results JSONRPC result struct:
+// - Return an error if invalid: e.g. if missing both result and error fields.
+// - Define and use exported errors for each validation failure scenario.
+// - Add a method to construct an observation of type observation.qos.JsonRpcResponseValidationError from the above error.
+//
 // UnmarshalJSON implements custom unmarshaling to handle the result field presence detection
 func (r *Response) UnmarshalJSON(data []byte) error {
 	// Use a temporary struct to unmarshal into, avoiding infinite recursion
diff --git a/qos/solana/endpoint.go b/qos/solana/endpoint.go
index 4fc20a75e..800e31afe 100644
--- a/qos/solana/endpoint.go
+++ b/qos/solana/endpoint.go
@@ -43,8 +43,8 @@ type endpoint struct {
 	// Pointer distinguishes between no observation vs. observed response scenarios.
 	*qosobservations.SolanaGetEpochInfoResponse
 
-	// latestValidationError tracks most recent JSON-RPC response validation error
-	latestValidationError *qosobservations.JsonRpcResponseValidationError
+	// latestJSONRPCValidationError tracks most recent JSON-RPC response validation error
+	latestJSONRPCValidationError *qosobservations.JsonRpcResponseValidationError
 
 	// TODO_FUTURE: support archival endpoints.
 }
@@ -54,7 +54,7 @@ type endpoint struct {
 func (e endpoint) validateBasic() error {
 	// Check for recent validation errors first
 	if e.hasRecentValidationErrors() {
-		return errRecentValidationError
+		return errRecentJSONRPCValidationError
 	}
 
 	switch {
@@ -80,12 +80,12 @@ func (e endpoint) validateBasic() error {
 
 // hasRecentValidationErrors checks if endpoint has validation error within the configured window.
 func (e endpoint) hasRecentValidationErrors() bool {
-	if e.latestValidationError == nil {
+	if e.latestJSONRPCValidationError == nil {
 		return false
 	}
 
 	lastValidationErrorTimestamp := time.Now().Add(-validationErrorResponseWindow)
-	return e.latestValidationError.Timestamp.AsTime().After(lastValidationErrorTimestamp)
+	return e.latestJSONRPCValidationError.Timestamp.AsTime().After(lastValidationErrorTimestamp)
 }
 
 // applyObservation updates endpoint data using provided observation.
@@ -105,9 +105,9 @@ func (e *endpoint) applyObservation(obs *qosobservations.SolanaEndpointObservati
 	if unrecognizedResponse := obs.GetUnrecognizedResponse(); unrecognizedResponse != nil {
 		// Update latest validation error if observation contains more recent error
 		if validationError := unrecognizedResponse.ValidationError; validationError != nil {
-			if e.latestValidationError == nil ||
-				validationError.Timestamp.AsTime().After(e.latestValidationError.Timestamp.AsTime()) {
-				e.latestValidationError = validationError
+			if e.latestJSONRPCValidationError == nil ||
+				validationError.Timestamp.AsTime().After(e.latestJSONRPCValidationError.Timestamp.AsTime()) {
+				e.latestJSONRPCValidationError = validationError
 			}
 		}
 		return true
diff --git a/qos/solana/response_generic.go b/qos/solana/response_generic.go
index 2a226d9e4..76cedc05e 100644
--- a/qos/solana/response_generic.go
+++ b/qos/solana/response_generic.go
@@ -60,12 +60,9 @@ type responseGeneric struct {
 // Shares data with other entities (e.g., data pipeline).
 // Default catchall for responses other than `getHealth` and `getEpochInfo`.
 func (r responseGeneric) GetObservation() qosobservations.SolanaEndpointObservation {
+	// Build an observation from the stored JSONRPC response.
 	unrecognizedResponse := &qosobservations.SolanaUnrecognizedResponse{
-		// TODO_TECHDEBT(@adshmh): Add utility to convert qos.jsonrpc.Response to observation.qos.JsonRpcResponse
-		// to include error object and other fields in observations.
-		JsonrpcResponse: &qosobservations.JsonRpcResponse{
-			Id: r.ID.String(),
-		},
+		JsonrpcResponse: r.Response.GetObservation(),
 	}
 
 	// Include validation error if present

From 4d6f23083200e796cb91d74865e2cae359f22eba Mon Sep 17 00:00:00 2001
From: Arash Deshmeh <adshmh@gmail.com>
Date: Sun, 17 Aug 2025 13:59:39 -0400
Subject: [PATCH 6/6] Fix: use min length for JSONRPC result preview
 observation

---
 qos/jsonrpc/observation.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/qos/jsonrpc/observation.go b/qos/jsonrpc/observation.go
index ab681809e..5797b3e0a 100644
--- a/qos/jsonrpc/observation.go
+++ b/qos/jsonrpc/observation.go
@@ -28,7 +28,7 @@ func (r Response) GetObservation() *qos.JsonRpcResponse {
 	var resultPreview string
 	if err := r.UnmarshalResult(&resultPreview); err == nil {
 		// Pick a maximum of 100 characters to include in the observation
-		resultPreview = resultPreview[:max(len(resultPreview), maxResponseResultPreviewLength)]
+		resultPreview = resultPreview[:min(len(resultPreview), maxResponseResultPreviewLength)]
 	}
 
 	// Build the JSONRPC response's observation.