Implement Tag-based e/p model for Neo4j backend (v0.36.0)

- Add unified Tag-based model where e/p tags create intermediate Tag nodes with REFERENCES relationships to Event/NostrUser nodes - Update save-event.go: addPTagsInBatches and addETagsInBatches now create Tag nodes with TAGGED_WITH and REFERENCES relationships - Update delete.go: CheckForDeleted uses Tag traversal for kind 5 detection - Add v3 migration in migrations.go to convert existing direct REFERENCES and MENTIONS relationships to the new Tag-based model - Create comprehensive test file tag_model_test.go with 15+ test functions covering Tag model, filter queries, migrations, and deletion detection - Update save-event_test.go to verify new Tag-based relationship patterns - Update WOT_SPEC.md with Tag-Based References documentation section - Update CLAUDE.md and README.md with Neo4j Tag-based model documentation - Bump version to v0.36.0 This change enables #e and #p filter queries to work correctly by storing all tags (including e/p) through intermediate Tag nodes. Files modified: - pkg/neo4j/save-event.go: Tag-based e/p relationship creation - pkg/neo4j/delete.go: Tag traversal for deletion detection - pkg/neo4j/migrations.go: v3 migration for existing data - pkg/neo4j/tag_model_test.go: New comprehensive test file - pkg/neo4j/save-event_test.go: Updated for new model - pkg/neo4j/WOT_SPEC.md: Tag-Based References documentation - pkg/neo4j/README.md: Architecture and example queries - CLAUDE.md: Repository documentation update - pkg/version/version: Bump to v0.36.0 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
2025-12-16 09:22:05 +01:00
parent 516ce9c42c
commit 96bdf5cba2
9 changed files with 1457 additions and 58 deletions
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -235,11 +235,18 @@ export ORLY_AUTH_TO_WRITE=false          # Require auth only for writes
 **`pkg/neo4j/`** - Neo4j graph database backend with social graph support
 - `neo4j.go` - Main database implementation
 - `schema.go` - Graph schema and index definitions (includes WoT extensions)
+- `migrations.go` - Database schema migrations (v1: base, v2: WoT, v3: Tag-based e/p)
 - `query-events.go` - REQ filter to Cypher translation
- `save-event.go` - Event storage with relationship creation
+- `save-event.go` - Event storage with Tag-based relationship creation
+- `delete.go` - Event deletion (NIP-09) with Tag traversal for deletion detection
 - `social-event-processor.go` - Processes kinds 0, 3, 1984, 10000 for social graph
+- `hex_utils.go` - Helpers for binary-to-hex tag value extraction
 - `WOT_SPEC.md` - Web of Trust data model specification (NostrUser nodes, trust metrics)
 - `MODIFYING_SCHEMA.md` - Guide for schema modifications
+- **Tests:**
+  - `tag_model_test.go` - Tag-based e/p model and filter query tests
+  - `save-event_test.go` - Event storage and relationship tests
+  - `social-event-processor_test.go` - Social graph event processing tests

 **`pkg/protocol/`** - Nostr protocol implementation
 - `ws/` - WebSocket message framing and parsing
@@ -349,6 +356,11 @@ export ORLY_AUTH_TO_WRITE=false          # Require auth only for writes
 - Supports multiple backends via `ORLY_DB_TYPE` environment variable
 - **Badger** (default): Embedded key-value store with custom indexing, ideal for single-instance deployments
 - **Neo4j**: Graph database with social graph and Web of Trust (WoT) extensions
+  - **Tag-Based e/p Model**: All tags stored through intermediate Tag nodes
+    - `Event-[:TAGGED_WITH]->Tag{type:'e'}-[:REFERENCES]->Event` for e-tags
+    - `Event-[:TAGGED_WITH]->Tag{type:'p'}-[:REFERENCES]->NostrUser` for p-tags
+    - Enables unified querying: `#e` and `#p` filter queries work correctly
+    - Automatic migration from direct REFERENCES/MENTIONS (v3 migration)
  - Processes kinds 0 (profile), 3 (contacts), 1984 (reports), 10000 (mute list) for social graph
  - NostrUser nodes with trust metrics (influence, PageRank)
  - FOLLOWS, MUTES, REPORTS relationships for WoT analysis
@@ -816,11 +828,18 @@ The directory spider (`pkg/spider/directory.go`) automatically discovers and syn

 ### Neo4j Social Graph Backend
 The Neo4j backend (`pkg/neo4j/`) includes Web of Trust (WoT) extensions:
+- **Tag-Based e/p Model**: All tags (including e/p) stored through intermediate Tag nodes
+  - `Event-[:TAGGED_WITH]->Tag{type:'e'}-[:REFERENCES]->Event`
+  - `Event-[:TAGGED_WITH]->Tag{type:'p'}-[:REFERENCES]->NostrUser`
+  - Enables unified tag querying (`#e` and `#p` filter queries now work)
+  - v3 migration automatically converts existing direct REFERENCES/MENTIONS
 - **Social Event Processor**: Handles kinds 0, 3, 1984, 10000 for social graph management
 - **NostrUser nodes**: Store profile data and trust metrics (influence, PageRank)
 - **Relationships**: FOLLOWS, MUTES, REPORTS for social graph analysis
+- **Deletion Detection**: `CheckForDeleted()` uses Tag traversal for kind 5 event checks
 - **WoT Schema**: See `pkg/neo4j/WOT_SPEC.md` for full specification
 - **Schema Modifications**: See `pkg/neo4j/MODIFYING_SCHEMA.md` for how to update
+- **Comprehensive Tests**: `tag_model_test.go` covers Tag-based model, filter queries, migrations

 ### WasmDB IndexedDB Backend
 WebAssembly-compatible database backend (`pkg/wasmdb/`):
--- a/pkg/neo4j/README.md
+++ b/pkg/neo4j/README.md
@@ -35,10 +35,12 @@ export ORLY_NEO4J_PASSWORD=password
 ## Features

 - **Graph-Native Storage**: Events, authors, and tags stored as nodes and relationships
+- **Unified Tag Model**: All tags (including e/p tags) stored as Tag nodes with REFERENCES relationships
 - **Efficient Queries**: Leverages Neo4j's native graph traversal for tag and social graph queries
 - **Cypher Query Language**: Powerful, expressive query language for complex filters
 - **Automatic Indexing**: Unique constraints and indexes for optimal performance
 - **Relationship Queries**: Native support for event references, mentions, and tags
+- **Automatic Migrations**: Schema migrations run automatically on startup
 - **Web of Trust (WoT) Extensions**: Optional support for trust metrics, social graph analysis, and content filtering (see [WOT_SPEC.md](./WOT_SPEC.md))

 ## Architecture
@@ -50,6 +52,23 @@ See [docs/NEO4J_BACKEND.md](../../docs/NEO4J_BACKEND.md) for comprehensive docum
 - Development guide
 - Comparison with other backends

+### Tag-Based e/p Model
+
+All tags, including `e` (event references) and `p` (pubkey mentions), are stored through intermediate Tag nodes:
+
+```
+Event -[:TAGGED_WITH]-> Tag{type:'e',value:eventId} -[:REFERENCES]-> Event
+Event -[:TAGGED_WITH]-> Tag{type:'p',value:pubkey} -[:REFERENCES]-> NostrUser
+Event -[:TAGGED_WITH]-> Tag{type:'t',value:topic}  (no REFERENCES for regular tags)
+```
+
+**Benefits:**
+- Unified tag querying: `#e` and `#p` filter queries work correctly
+- Consistent data model: All tags use the same TAGGED_WITH pattern
+- Graph traversal: Can traverse from events through tags to referenced entities
+
+**Migration:** Existing databases with direct `REFERENCES`/`MENTIONS` relationships are automatically migrated at startup via v3 migration.
+
 ### Web of Trust (WoT) Extensions

 This package includes schema support for Web of Trust trust metrics computation:
@@ -96,6 +115,8 @@ This package includes schema support for Web of Trust trust metrics computation:

 ### Tests
 - `social-event-processor_test.go` - Comprehensive tests for kinds 0, 3, 1984, 10000
+- `tag_model_test.go` - Tag-based e/p model tests and filter query tests
+- `save-event_test.go` - Event storage and relationship tests

 ## Testing

@@ -166,11 +187,25 @@ MATCH (e:Event)-[:TAGGED_WITH]->(t:Tag {type: "t", value: "bitcoin"})
 RETURN e
 ```

+### Event reference query (e-tags)
+```cypher
+MATCH (e:Event)-[:TAGGED_WITH]->(t:Tag {type: "e"})-[:REFERENCES]->(ref:Event)
+WHERE e.id = "abc123..."
+RETURN e, ref
+```
+
+### Mentions query (p-tags)
+```cypher
+MATCH (e:Event)-[:TAGGED_WITH]->(t:Tag {type: "p"})-[:REFERENCES]->(u:NostrUser)
+WHERE e.id = "abc123..."
+RETURN e, u
+```
+
 ### Social graph query
 ```cypher
 MATCH (author:NostrUser {pubkey: "abc123..."})
 <-[:AUTHORED_BY]-(e:Event)
-[:MENTIONS]->(mentioned:NostrUser)
+-[:TAGGED_WITH]->(:Tag {type: "p"})-[:REFERENCES]->(mentioned:NostrUser)
 RETURN author, e, mentioned
 ```

--- a/pkg/neo4j/WOT_SPEC.md
+++ b/pkg/neo4j/WOT_SPEC.md
@@ -125,6 +125,40 @@ Legacy node label that is redundant with SetOfNostrUserWotMetricsCards. Should b

 ### Relationship Types

+#### Tag-Based References (e and p tags)
+
+The Neo4j backend uses a unified Tag-based model for `e` and `p` tags, enabling consistent tag querying while maintaining graph traversal capabilities.
+
+**E-tags (Event References):**
+```
+(Event)-[:TAGGED_WITH]->(Tag {type: 'e', value: <event_id>})-[:REFERENCES]->(Event)
+```
+
+**P-tags (Pubkey Mentions):**
+```
+(Event)-[:TAGGED_WITH]->(Tag {type: 'p', value: <pubkey>})-[:REFERENCES]->(NostrUser)
+```
+
+This model provides:
+- Unified tag querying via `#e` and `#p` filters (same as other tags)
+- Graph traversal from events to referenced events/users
+- Consistent indexing through existing Tag node indexes
+
+**Query Examples:**
+```cypher
+-- Find all events that reference a specific event
+MATCH (e:Event)-[:TAGGED_WITH]->(t:Tag {type: 'e', value: $eventId})-[:REFERENCES]->(ref:Event)
+RETURN e
+
+-- Find all events that mention a specific pubkey
+MATCH (e:Event)-[:TAGGED_WITH]->(t:Tag {type: 'p', value: $pubkey})-[:REFERENCES]->(u:NostrUser)
+RETURN e
+
+-- Count references to an event (thread replies)
+MATCH (t:Tag {type: 'e', value: $eventId})<-[:TAGGED_WITH]-(e:Event)
+RETURN count(e) AS replyCount
+```
+
 #### 1. FOLLOWS

 Represents a follow relationship between users (derived from kind 3 events).
@@ -247,8 +281,9 @@ Comprehensive implementation with additional features:
  - `IS_A_REACTION_TO` (kind 7 reactions)
  - `IS_A_RESPONSE_TO` (kind 1 replies)
  - `IS_A_REPOST_OF` (kind 6, kind 16 reposts)
-  - `P_TAGGED` (p-tag mentions from events to users)
-  - `E_TAGGED` (e-tag references from events to events)
+  - Tag-based references (see "Tag-Based References" section above):
+    - `Event-[:TAGGED_WITH]->Tag{type:'p'}-[:REFERENCES]->NostrUser` (p-tag mentions)
+    - `Event-[:TAGGED_WITH]->Tag{type:'e'}-[:REFERENCES]->Event` (e-tag references)
 - NostrRelay, CashuMint nodes for ecosystem mapping
 - Enhanced GrapeRank incorporating zaps, replies, reactions

--- a/pkg/neo4j/delete.go
+++ b/pkg/neo4j/delete.go
@@ -175,14 +175,15 @@ func (n *N) ProcessDelete(ev *event.E, admins [][]byte) error {

 // CheckForDeleted checks if an event has been deleted
 func (n *N) CheckForDeleted(ev *event.E, admins [][]byte) error {
-	// Query for kind 5 events that reference this event
+	// Query for kind 5 events that reference this event via Tag nodes
 	ctx := context.Background()
 	idStr := hex.Enc(ev.ID[:])

 	// Build cypher query to find deletion events
+	// Traverses through Tag nodes: Event-[:TAGGED_WITH]->Tag-[:REFERENCES]->Event
 	cypher := `
 MATCH (target:Event {id: $targetId})
-MATCH (delete:Event {kind: 5})-[:REFERENCES]->(target)
+MATCH (delete:Event {kind: 5})-[:TAGGED_WITH]->(t:Tag {type: 'e'})-[:REFERENCES]->(target)
 WHERE delete.pubkey = $pubkey OR delete.pubkey IN $admins
 RETURN delete.id AS id
 LIMIT 1`
--- a/pkg/neo4j/migrations.go
+++ b/pkg/neo4j/migrations.go
@@ -25,6 +25,11 @@ var migrations = []Migration{
 		Description: "Clean up binary-encoded pubkeys and event IDs to lowercase hex",
 		Migrate:     migrateBinaryToHex,
 	},
+	{
+		Version:     "v3",
+		Description: "Convert direct REFERENCES/MENTIONS relationships to Tag-based model",
+		Migrate:     migrateToTagBasedReferences,
+	},
 }

 // RunMigrations executes all pending migrations
@@ -343,3 +348,147 @@ func migrateBinaryToHex(ctx context.Context, n *N) error {
 	n.Logger.Infof("binary-to-hex migration completed successfully")
 	return nil
 }
+
+// migrateToTagBasedReferences converts direct REFERENCES and MENTIONS relationships
+// to the new Tag-based model where:
+// - Event-[:REFERENCES]->Event becomes Event-[:TAGGED_WITH]->Tag-[:REFERENCES]->Event
+// - Event-[:MENTIONS]->NostrUser becomes Event-[:TAGGED_WITH]->Tag-[:REFERENCES]->NostrUser
+//
+// This enables unified tag querying via #e and #p filters while maintaining graph traversal.
+func migrateToTagBasedReferences(ctx context.Context, n *N) error {
+	// Step 1: Count existing direct REFERENCES relationships (Event->Event)
+	countRefCypher := `
+		MATCH (source:Event)-[r:REFERENCES]->(target:Event)
+		RETURN count(r) AS count
+	`
+	result, err := n.ExecuteRead(ctx, countRefCypher, nil)
+	if err != nil {
+		return fmt.Errorf("failed to count REFERENCES relationships: %w", err)
+	}
+
+	var refCount int64
+	if result.Next(ctx) {
+		if count, ok := result.Record().Values[0].(int64); ok {
+			refCount = count
+		}
+	}
+	n.Logger.Infof("found %d direct Event-[:REFERENCES]->Event relationships to migrate", refCount)
+
+	// Step 2: Count existing direct MENTIONS relationships (Event->NostrUser)
+	countMentionsCypher := `
+		MATCH (source:Event)-[r:MENTIONS]->(target:NostrUser)
+		RETURN count(r) AS count
+	`
+	result, err = n.ExecuteRead(ctx, countMentionsCypher, nil)
+	if err != nil {
+		return fmt.Errorf("failed to count MENTIONS relationships: %w", err)
+	}
+
+	var mentionsCount int64
+	if result.Next(ctx) {
+		if count, ok := result.Record().Values[0].(int64); ok {
+			mentionsCount = count
+		}
+	}
+	n.Logger.Infof("found %d direct Event-[:MENTIONS]->NostrUser relationships to migrate", mentionsCount)
+
+	// If nothing to migrate, we're done
+	if refCount == 0 && mentionsCount == 0 {
+		n.Logger.Infof("no direct relationships to migrate, migration complete")
+		return nil
+	}
+
+	// Step 3: Migrate REFERENCES relationships to Tag-based model
+	// Process in batches to avoid memory issues with large datasets
+	if refCount > 0 {
+		n.Logger.Infof("migrating %d REFERENCES relationships to Tag-based model...", refCount)
+
+		// This query:
+		// 1. Finds Event->Event REFERENCES relationships
+		// 2. Creates/merges Tag node with type='e' and value=target event ID
+		// 3. Creates TAGGED_WITH from source Event to Tag
+		// 4. Creates REFERENCES from Tag to target Event
+		// 5. Deletes the old direct REFERENCES relationship
+		migrateRefCypher := `
+			MATCH (source:Event)-[r:REFERENCES]->(target:Event)
+			WITH source, r, target LIMIT 1000
+			MERGE (t:Tag {type: 'e', value: target.id})
+			CREATE (source)-[:TAGGED_WITH]->(t)
+			MERGE (t)-[:REFERENCES]->(target)
+			DELETE r
+			RETURN count(r) AS migrated
+		`
+
+		// Run migration in batches until no more relationships exist
+		totalMigrated := int64(0)
+		for {
+			result, err := n.ExecuteWrite(ctx, migrateRefCypher, nil)
+			if err != nil {
+				return fmt.Errorf("failed to migrate REFERENCES batch: %w", err)
+			}
+
+			var batchMigrated int64
+			if result.Next(ctx) {
+				if count, ok := result.Record().Values[0].(int64); ok {
+					batchMigrated = count
+				}
+			}
+
+			if batchMigrated == 0 {
+				break
+			}
+			totalMigrated += batchMigrated
+			n.Logger.Infof("migrated %d REFERENCES relationships (total: %d)", batchMigrated, totalMigrated)
+		}
+
+		n.Logger.Infof("completed migrating %d REFERENCES relationships", totalMigrated)
+	}
+
+	// Step 4: Migrate MENTIONS relationships to Tag-based model
+	if mentionsCount > 0 {
+		n.Logger.Infof("migrating %d MENTIONS relationships to Tag-based model...", mentionsCount)
+
+		// This query:
+		// 1. Finds Event->NostrUser MENTIONS relationships
+		// 2. Creates/merges Tag node with type='p' and value=target pubkey
+		// 3. Creates TAGGED_WITH from source Event to Tag
+		// 4. Creates REFERENCES from Tag to target NostrUser
+		// 5. Deletes the old direct MENTIONS relationship
+		migrateMentionsCypher := `
+			MATCH (source:Event)-[r:MENTIONS]->(target:NostrUser)
+			WITH source, r, target LIMIT 1000
+			MERGE (t:Tag {type: 'p', value: target.pubkey})
+			CREATE (source)-[:TAGGED_WITH]->(t)
+			MERGE (t)-[:REFERENCES]->(target)
+			DELETE r
+			RETURN count(r) AS migrated
+		`
+
+		// Run migration in batches until no more relationships exist
+		totalMigrated := int64(0)
+		for {
+			result, err := n.ExecuteWrite(ctx, migrateMentionsCypher, nil)
+			if err != nil {
+				return fmt.Errorf("failed to migrate MENTIONS batch: %w", err)
+			}
+
+			var batchMigrated int64
+			if result.Next(ctx) {
+				if count, ok := result.Record().Values[0].(int64); ok {
+					batchMigrated = count
+				}
+			}
+
+			if batchMigrated == 0 {
+				break
+			}
+			totalMigrated += batchMigrated
+			n.Logger.Infof("migrated %d MENTIONS relationships (total: %d)", batchMigrated, totalMigrated)
+		}
+
+		n.Logger.Infof("completed migrating %d MENTIONS relationships", totalMigrated)
+	}
+
+	n.Logger.Infof("Tag-based references migration completed successfully")
+	return nil
+}
--- a/pkg/neo4j/save-event.go
+++ b/pkg/neo4j/save-event.go
@@ -238,7 +238,8 @@ func (n *N) addTagsInBatches(c context.Context, eventID string, ev *event.E) err
 }

 // addPTagsInBatches adds p-tag (pubkey mention) relationships using UNWIND for efficiency.
-// Creates NostrUser nodes for mentioned pubkeys and MENTIONS relationships.
+// Creates Tag nodes with type='p' and REFERENCES relationships to NostrUser nodes.
+// This enables unified tag querying via #p filters while maintaining the social graph.
 func (n *N) addPTagsInBatches(c context.Context, eventID string, pTags []string) error {
 	// Process in batches to avoid memory issues
 	for i := 0; i < len(pTags); i += tagBatchSize {
@@ -249,12 +250,17 @@ func (n *N) addPTagsInBatches(c context.Context, eventID string, pTags []string)
 		batch := pTags[i:end]

 		// Use UNWIND to process multiple p-tags in a single query
+		// Creates Tag nodes as intermediaries, enabling unified #p filter queries
+		// Tag-[:REFERENCES]->NostrUser allows graph traversal from tag to user
 		cypher := `
 MATCH (e:Event {id: $eventId})
 UNWIND $pubkeys AS pubkey
+MERGE (t:Tag {type: 'p', value: pubkey})
+CREATE (e)-[:TAGGED_WITH]->(t)
+WITH t, pubkey
 MERGE (u:NostrUser {pubkey: pubkey})
 ON CREATE SET u.created_at = timestamp()
-CREATE (e)-[:MENTIONS]->(u)`
+MERGE (t)-[:REFERENCES]->(u)`

 		params := map[string]any{
 			"eventId": eventID,
@@ -270,7 +276,8 @@ CREATE (e)-[:MENTIONS]->(u)`
 }

 // addETagsInBatches adds e-tag (event reference) relationships using UNWIND for efficiency.
-// Only creates REFERENCES relationships if the referenced event exists.
+// Creates Tag nodes with type='e' and REFERENCES relationships to Event nodes (if they exist).
+// This enables unified tag querying via #e filters while maintaining event graph structure.
 func (n *N) addETagsInBatches(c context.Context, eventID string, eTags []string) error {
 	// Process in batches to avoid memory issues
 	for i := 0; i < len(eTags); i += tagBatchSize {
@@ -281,14 +288,18 @@ func (n *N) addETagsInBatches(c context.Context, eventID string, eTags []string)
 		batch := eTags[i:end]

 		// Use UNWIND to process multiple e-tags in a single query
-		// OPTIONAL MATCH ensures we only create relationships if referenced event exists
+		// Creates Tag nodes as intermediaries, enabling unified #e filter queries
+		// Tag-[:REFERENCES]->Event allows graph traversal from tag to referenced event
+		// OPTIONAL MATCH ensures we only create REFERENCES if referenced event exists
 		cypher := `
 MATCH (e:Event {id: $eventId})
 UNWIND $eventIds AS refId
+MERGE (t:Tag {type: 'e', value: refId})
+CREATE (e)-[:TAGGED_WITH]->(t)
+WITH t, refId
 OPTIONAL MATCH (ref:Event {id: refId})
-WITH e, ref
 WHERE ref IS NOT NULL
-CREATE (e)-[:REFERENCES]->(ref)`
+MERGE (t)-[:REFERENCES]->(ref)`

 		params := map[string]any{
 			"eventId":  eventID,
--- a/pkg/neo4j/save-event_test.go
+++ b/pkg/neo4j/save-event_test.go
@@ -151,7 +151,7 @@ func TestSafePrefix(t *testing.T) {
 }

 // TestSaveEvent_ETagReference tests that events with e-tags are saved correctly
-// and the REFERENCES relationships are created when the referenced event exists.
+// using the Tag-based model: Event-[:TAGGED_WITH]->Tag-[:REFERENCES]->Event.
 // Uses shared testDB from testmain_test.go to avoid auth rate limiting.
 func TestSaveEvent_ETagReference(t *testing.T) {
 	if testDB == nil {
@@ -226,10 +226,10 @@ func TestSaveEvent_ETagReference(t *testing.T) {
 		t.Fatal("Reply event should not exist yet")
 	}

-	// Verify REFERENCES relationship was created
+	// Verify Tag-based e-tag model: Event-[:TAGGED_WITH]->Tag{type:'e'}-[:REFERENCES]->Event
 	cypher := `
-		MATCH (reply:Event {id: $replyId})-[:REFERENCES]->(root:Event {id: $rootId})
-		RETURN reply.id AS replyId, root.id AS rootId
+		MATCH (reply:Event {id: $replyId})-[:TAGGED_WITH]->(t:Tag {type: 'e', value: $rootId})-[:REFERENCES]->(root:Event {id: $rootId})
+		RETURN reply.id AS replyId, t.value AS tagValue, root.id AS rootId
 	`
 	params := map[string]any{
 		"replyId": hex.Enc(replyEvent.ID[:]),
@@ -238,42 +238,43 @@ func TestSaveEvent_ETagReference(t *testing.T) {

 	result, err := testDB.ExecuteRead(ctx, cypher, params)
 	if err != nil {
-		t.Fatalf("Failed to query REFERENCES relationship: %v", err)
+		t.Fatalf("Failed to query Tag-based REFERENCES: %v", err)
 	}

 	if !result.Next(ctx) {
-		t.Error("Expected REFERENCES relationship between reply and root events")
+		t.Error("Expected Tag-based REFERENCES relationship between reply and root events")
 	} else {
 		record := result.Record()
 		returnedReplyId := record.Values[0].(string)
-		returnedRootId := record.Values[1].(string)
-		t.Logf("✓ REFERENCES relationship verified: %s -> %s", returnedReplyId[:8], returnedRootId[:8])
+		tagValue := record.Values[1].(string)
+		returnedRootId := record.Values[2].(string)
+		t.Logf("✓ Tag-based REFERENCES verified: Event(%s) -> Tag{e:%s} -> Event(%s)", returnedReplyId[:8], tagValue[:8], returnedRootId[:8])
 	}

-	// Verify MENTIONS relationship was also created for the p-tag
-	mentionsCypher := `
-		MATCH (reply:Event {id: $replyId})-[:MENTIONS]->(author:NostrUser {pubkey: $authorPubkey})
-		RETURN author.pubkey AS pubkey
+	// Verify Tag-based p-tag model: Event-[:TAGGED_WITH]->Tag{type:'p'}-[:REFERENCES]->NostrUser
+	pTagCypher := `
+		MATCH (reply:Event {id: $replyId})-[:TAGGED_WITH]->(t:Tag {type: 'p', value: $authorPubkey})-[:REFERENCES]->(author:NostrUser {pubkey: $authorPubkey})
+		RETURN author.pubkey AS pubkey, t.value AS tagValue
 	`
-	mentionsParams := map[string]any{
+	pTagParams := map[string]any{
 		"replyId":      hex.Enc(replyEvent.ID[:]),
 		"authorPubkey": hex.Enc(alice.Pub()),
 	}

-	mentionsResult, err := testDB.ExecuteRead(ctx, mentionsCypher, mentionsParams)
+	pTagResult, err := testDB.ExecuteRead(ctx, pTagCypher, pTagParams)
 	if err != nil {
-		t.Fatalf("Failed to query MENTIONS relationship: %v", err)
+		t.Fatalf("Failed to query Tag-based p-tag: %v", err)
 	}

-	if !mentionsResult.Next(ctx) {
-		t.Error("Expected MENTIONS relationship for p-tag")
+	if !pTagResult.Next(ctx) {
+		t.Error("Expected Tag-based p-tag relationship")
 	} else {
-		t.Logf("✓ MENTIONS relationship verified")
+		t.Logf("✓ Tag-based p-tag relationship verified")
 	}
 }

 // TestSaveEvent_ETagMissingReference tests that e-tags to non-existent events
-// don't create broken relationships (batched processing handles this gracefully).
+// create Tag nodes but don't create REFERENCES relationships to missing events.
 // Uses shared testDB from testmain_test.go to avoid auth rate limiting.
 func TestSaveEvent_ETagMissingReference(t *testing.T) {
 	if testDB == nil {
@@ -331,29 +332,50 @@ func TestSaveEvent_ETagMissingReference(t *testing.T) {
 		t.Error("Event should have been saved despite missing reference")
 	}

-	// Verify no REFERENCES relationship was created (as the target doesn't exist)
+	// Verify Tag node was created with TAGGED_WITH relationship
+	tagCypher := `
+		MATCH (e:Event {id: $eventId})-[:TAGGED_WITH]->(t:Tag {type: 'e', value: $refId})
+		RETURN t.value AS tagValue
+	`
+	tagParams := map[string]any{
+		"eventId": hex.Enc(ev.ID[:]),
+		"refId":   nonExistentEventID,
+	}
+
+	tagResult, err := testDB.ExecuteRead(ctx, tagCypher, tagParams)
+	if err != nil {
+		t.Fatalf("Failed to check Tag node: %v", err)
+	}
+
+	if !tagResult.Next(ctx) {
+		t.Error("Expected Tag node to be created for e-tag even when target doesn't exist")
+	} else {
+		t.Logf("✓ Tag node created for missing reference")
+	}
+
+	// Verify no REFERENCES relationship was created from Tag (as the target Event doesn't exist)
 	refCypher := `
-		MATCH (e:Event {id: $eventId})-[:REFERENCES]->(ref:Event)
+		MATCH (t:Tag {type: 'e', value: $refId})-[:REFERENCES]->(ref:Event)
 		RETURN count(ref) AS refCount
 	`
-	refParams := map[string]any{"eventId": hex.Enc(ev.ID[:])}
+	refParams := map[string]any{"refId": nonExistentEventID}

 	refResult, err := testDB.ExecuteRead(ctx, refCypher, refParams)
 	if err != nil {
-		t.Fatalf("Failed to check references: %v", err)
+		t.Fatalf("Failed to check REFERENCES from Tag: %v", err)
 	}

 	if refResult.Next(ctx) {
 		count := refResult.Record().Values[0].(int64)
 		if count > 0 {
-			t.Errorf("Expected no REFERENCES relationship for non-existent event, got %d", count)
+			t.Errorf("Expected no REFERENCES from Tag for non-existent event, got %d", count)
 		} else {
-			t.Logf("✓ Correctly handled missing reference (no relationship created)")
+			t.Logf("✓ Correctly handled missing reference (no REFERENCES from Tag)")
 		}
 	}
 }

-// TestSaveEvent_MultipleETags tests events with multiple e-tags.
+// TestSaveEvent_MultipleETags tests events with multiple e-tags using Tag-based model.
 // Uses shared testDB from testmain_test.go to avoid auth rate limiting.
 func TestSaveEvent_MultipleETags(t *testing.T) {
 	if testDB == nil {
@@ -409,7 +431,7 @@ func TestSaveEvent_MultipleETags(t *testing.T) {
 		t.Fatalf("Failed to sign reply event: %v", err)
 	}

-	// Save reply event - tests batched e-tag creation
+	// Save reply event - tests batched e-tag creation with Tag nodes
 	exists, err := testDB.SaveEvent(ctx, replyEvent)
 	if err != nil {
 		t.Fatalf("Failed to save multi-reference event: %v", err)
@@ -418,16 +440,17 @@ func TestSaveEvent_MultipleETags(t *testing.T) {
 		t.Fatal("Reply event should not exist yet")
 	}

-	// Verify all REFERENCES relationships were created
+	// Verify all Tag-based REFERENCES relationships were created
+	// Event-[:TAGGED_WITH]->Tag{type:'e'}-[:REFERENCES]->Event
 	cypher := `
-		MATCH (reply:Event {id: $replyId})-[:REFERENCES]->(ref:Event)
+		MATCH (reply:Event {id: $replyId})-[:TAGGED_WITH]->(t:Tag {type: 'e'})-[:REFERENCES]->(ref:Event)
 		RETURN ref.id AS refId
 	`
 	params := map[string]any{"replyId": hex.Enc(replyEvent.ID[:])}

 	result, err := testDB.ExecuteRead(ctx, cypher, params)
 	if err != nil {
-		t.Fatalf("Failed to query REFERENCES relationships: %v", err)
+		t.Fatalf("Failed to query Tag-based REFERENCES: %v", err)
 	}

 	referencedIDs := make(map[string]bool)
@@ -437,20 +460,20 @@ func TestSaveEvent_MultipleETags(t *testing.T) {
 	}

 	if len(referencedIDs) != 3 {
-		t.Errorf("Expected 3 REFERENCES relationships, got %d", len(referencedIDs))
+		t.Errorf("Expected 3 Tag-based REFERENCES, got %d", len(referencedIDs))
 	}

 	for i, id := range eventIDs {
 		if !referencedIDs[id] {
-			t.Errorf("Missing REFERENCES relationship to event %d (%s)", i, id[:8])
+			t.Errorf("Missing Tag-based REFERENCES to event %d (%s)", i, id[:8])
 		}
 	}

-	t.Logf("✓ All %d REFERENCES relationships created successfully", len(referencedIDs))
+	t.Logf("✓ All %d Tag-based REFERENCES created successfully", len(referencedIDs))
 }

 // TestSaveEvent_LargePTagBatch tests that events with many p-tags are saved correctly
-// using batched processing to avoid Neo4j stack overflow.
+// using batched Tag-based processing to avoid Neo4j stack overflow.
 // Uses shared testDB from testmain_test.go to avoid auth rate limiting.
 func TestSaveEvent_LargePTagBatch(t *testing.T) {
 	if testDB == nil {
@@ -498,24 +521,45 @@ func TestSaveEvent_LargePTagBatch(t *testing.T) {
 		t.Fatal("Event should not exist yet")
 	}

-	// Verify all MENTIONS relationships were created
-	countCypher := `
-		MATCH (e:Event {id: $eventId})-[:MENTIONS]->(u:NostrUser)
-		RETURN count(u) AS mentionCount
+	// Verify all Tag nodes were created with TAGGED_WITH relationships
+	tagCountCypher := `
+		MATCH (e:Event {id: $eventId})-[:TAGGED_WITH]->(t:Tag {type: 'p'})
+		RETURN count(t) AS tagCount
 	`
-	countParams := map[string]any{"eventId": hex.Enc(ev.ID[:])}
+	tagCountParams := map[string]any{"eventId": hex.Enc(ev.ID[:])}

-	result, err := testDB.ExecuteRead(ctx, countCypher, countParams)
+	tagResult, err := testDB.ExecuteRead(ctx, tagCountCypher, tagCountParams)
 	if err != nil {
-		t.Fatalf("Failed to count MENTIONS: %v", err)
+		t.Fatalf("Failed to count p-tag Tag nodes: %v", err)
 	}

-	if result.Next(ctx) {
-		count := result.Record().Values[0].(int64)
+	if tagResult.Next(ctx) {
+		count := tagResult.Record().Values[0].(int64)
 		if count != int64(numTags) {
-			t.Errorf("Expected %d MENTIONS relationships, got %d", numTags, count)
+			t.Errorf("Expected %d Tag nodes, got %d", numTags, count)
 		} else {
-			t.Logf("✓ All %d MENTIONS relationships created via batched processing", count)
+			t.Logf("✓ All %d p-tag Tag nodes created via batched processing", count)
+		}
+	}
+
+	// Verify all REFERENCES relationships to NostrUser were created
+	refCountCypher := `
+		MATCH (e:Event {id: $eventId})-[:TAGGED_WITH]->(t:Tag {type: 'p'})-[:REFERENCES]->(u:NostrUser)
+		RETURN count(u) AS refCount
+	`
+	refCountParams := map[string]any{"eventId": hex.Enc(ev.ID[:])}
+
+	refResult, err := testDB.ExecuteRead(ctx, refCountCypher, refCountParams)
+	if err != nil {
+		t.Fatalf("Failed to count Tag-based REFERENCES to NostrUser: %v", err)
+	}
+
+	if refResult.Next(ctx) {
+		count := refResult.Record().Values[0].(int64)
+		if count != int64(numTags) {
+			t.Errorf("Expected %d REFERENCES to NostrUser, got %d", numTags, count)
+		} else {
+			t.Logf("✓ All %d Tag-based REFERENCES to NostrUser created via batched processing", count)
 		}
 	}
 }
--- a/pkg/neo4j/tag_model_test.go
+++ b/pkg/neo4j/tag_model_test.go
--- a/pkg/version/version
+++ b/pkg/version/version
@@ -1 +1 @@
-v0.35.5
+v0.36.0