From bf71cacb9ab7aeb60bddf9ce36715fa67c5f6667 Mon Sep 17 00:00:00 2001
From: Ivan FB <ivansete@status.im>
Date: Thu, 11 Jun 2026 23:31:43 +0200
Subject: [PATCH] fix: pass a non-empty participantId to enable SDS-R

The pre-nim-ffi binding had no participantId concept; mirroring that
with an empty id disables SDS-R, but the new libsds unwrap path
SIGSEGVs on real received messages in that configuration. Generate a
random per-manager participantId so SDS-R is enabled, matching the
nim-ffi 0.2.0 SDS-R/retrieval-hint design intent.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 sds/sds.go | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/sds/sds.go b/sds/sds.go
index 13e7b09..d646b9c 100644
--- a/sds/sds.go
+++ b/sds/sds.go
@@ -110,6 +110,8 @@ package sds
 */
 import "C"
 import (
+	"crypto/rand"
+	"encoding/hex"
 	"errors"
 	"sync"
 	"unsafe"
@@ -132,6 +134,15 @@ var eventNames = []string{
 	eventPeriodicSync,
 }
 
+// randomParticipantID returns a random hex-encoded SDS-R participant identity.
+func randomParticipantID() (string, error) {
+	var b [16]byte
+	if _, err := rand.Read(b[:]); err != nil {
+		return "", err
+	}
+	return hex.EncodeToString(b[:]), nil
+}
+
 //export SdsGoCallback
 func SdsGoCallback(ret C.int, msg *C.char, len C.size_t, resp unsafe.Pointer) {
 	if resp != nil {
@@ -199,12 +210,17 @@ func NewReliabilityManager(logger *zap.Logger) (*ReliabilityManager, error) {
 
 	rm.logger.Info("creating new reliability manager")
 
-	// Empty participantId keeps plain SDS (causal history, acks, missing-deps)
-	// and disables SDS-R repair — matching the pre-nim-ffi binding's behavior.
-	createReq := sdsCreateReq{Config: sdsConfig{ParticipantID: ""}}
+	// participantId is the per-manager SDS-R identity. A non-empty id enables
+	// SDS-R (repair/retrieval); we generate a random one so each manager has a
+	// distinct identity.
+	participantID, err := randomParticipantID()
+	if err != nil {
+		return nil, errorspkg.Wrap(err, "failed to generate participant id")
+	}
+	createReq := sdsCreateReq{Config: sdsConfig{ParticipantID: participantID}}
 
 	var ret int
-	err := withReqCbor(createReq, func(ptr unsafe.Pointer, length C.size_t) {
+	err = withReqCbor(createReq, func(ptr unsafe.Pointer, length C.size_t) {
 		var data []byte
 		ret, data = sdsCall(func(resp unsafe.Pointer) {
 			rm.rmCtx = C.cGoSdsCreate(ptr, length, resp)