migrations/2026-04-02-000000_photo_insights_history/down.sql

@@ -0,0 +1,19 @@
+-- Restore original schema, retaining only the current insight per file.
+CREATE TABLE photo_insights_old (
+    id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
+    file_path TEXT NOT NULL UNIQUE,
+    title TEXT NOT NULL,
+    summary TEXT NOT NULL,
+    generated_at BIGINT NOT NULL,
+    model_version TEXT NOT NULL
+);
+
+INSERT INTO photo_insights_old (id, file_path, title, summary, generated_at, model_version)
+    SELECT id, file_path, title, summary, generated_at, model_version
+    FROM photo_insights
+    WHERE is_current = 1;
+
+DROP TABLE photo_insights;
+ALTER TABLE photo_insights_old RENAME TO photo_insights;
+
+CREATE INDEX IF NOT EXISTS idx_photo_insights_path ON photo_insights(file_path);

migrations/2026-04-02-000000_photo_insights_history/up.sql

@@ -0,0 +1,25 @@
+-- Convert photo_insights to an append-only history table.
+-- SQLite cannot drop a UNIQUE constraint via ALTER TABLE, so we recreate the table.
+-- This preserves existing insight IDs so that future entity_facts.source_insight_id
+-- FK references remain valid.
+
+CREATE TABLE photo_insights_new (
+    id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
+    file_path TEXT NOT NULL,
+    title TEXT NOT NULL,
+    summary TEXT NOT NULL,
+    generated_at BIGINT NOT NULL,
+    model_version TEXT NOT NULL,
+    is_current BOOLEAN NOT NULL DEFAULT 0
+);
+
+-- Migrate existing rows; mark them all as current (one row per path currently).
+INSERT INTO photo_insights_new (id, file_path, title, summary, generated_at, model_version, is_current)
+    SELECT id, file_path, title, summary, generated_at, model_version, 1
+    FROM photo_insights;
+
+DROP TABLE photo_insights;
+ALTER TABLE photo_insights_new RENAME TO photo_insights;
+
+CREATE INDEX idx_photo_insights_file_path ON photo_insights(file_path);
+CREATE INDEX idx_photo_insights_current ON photo_insights(file_path, is_current);

migrations/2026-04-02-000100_add_knowledge_memory/down.sql

@@ -0,0 +1,3 @@
+DROP TABLE IF EXISTS entity_photo_links;
+DROP TABLE IF EXISTS entity_facts;
+DROP TABLE IF EXISTS entities;

migrations/2026-04-02-000100_add_knowledge_memory/up.sql

@@ -0,0 +1,55 @@
+-- Entity-relationship knowledge memory tables.
+-- Entities are the nodes (people, places, events, things).
+-- entity_facts are typed claims about or between entities.
+-- entity_photo_links connect entities to specific photos.
+
+CREATE TABLE entities (
+    id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
+    name TEXT NOT NULL,
+    entity_type TEXT NOT NULL,          -- 'person' | 'place' | 'event' | 'thing'
+    description TEXT NOT NULL DEFAULT '',
+    embedding BLOB,                     -- 768-dim f32 vector; nullable if embedding service was unavailable
+    confidence REAL NOT NULL DEFAULT 0.5,
+    status TEXT NOT NULL DEFAULT 'active',  -- 'active' | 'reviewed' | 'rejected'
+    created_at BIGINT NOT NULL,
+    updated_at BIGINT NOT NULL,
+    UNIQUE(name, entity_type)
+);
+
+CREATE INDEX idx_entities_type ON entities(entity_type);
+CREATE INDEX idx_entities_status ON entities(status);
+CREATE INDEX idx_entities_name ON entities(name);
+
+CREATE TABLE entity_facts (
+    id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
+    subject_entity_id INTEGER NOT NULL,
+    predicate TEXT NOT NULL,
+    object_entity_id INTEGER,           -- nullable: entity-to-entity relationship target
+    object_value TEXT,                  -- nullable: free-text attribute value
+    source_photo TEXT,                  -- photo path that prompted extraction (injected server-side)
+    source_insight_id INTEGER,          -- backfilled after insight is stored
+    confidence REAL NOT NULL DEFAULT 0.6,
+    status TEXT NOT NULL DEFAULT 'active',  -- 'active' | 'reviewed' | 'rejected'
+    created_at BIGINT NOT NULL,
+    CONSTRAINT fk_ef_subject FOREIGN KEY (subject_entity_id) REFERENCES entities(id) ON DELETE CASCADE,
+    CONSTRAINT fk_ef_object  FOREIGN KEY (object_entity_id)  REFERENCES entities(id) ON DELETE SET NULL,
+    CONSTRAINT fk_ef_insight FOREIGN KEY (source_insight_id) REFERENCES photo_insights(id) ON DELETE SET NULL,
+    CHECK (object_entity_id IS NOT NULL OR object_value IS NOT NULL)
+);
+
+CREATE INDEX idx_entity_facts_subject ON entity_facts(subject_entity_id);
+CREATE INDEX idx_entity_facts_predicate ON entity_facts(predicate);
+CREATE INDEX idx_entity_facts_status ON entity_facts(status);
+CREATE INDEX idx_entity_facts_source_photo ON entity_facts(source_photo);
+
+CREATE TABLE entity_photo_links (
+    id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
+    entity_id INTEGER NOT NULL,
+    file_path TEXT NOT NULL,
+    role TEXT NOT NULL,                 -- 'subject' | 'location' | 'event' | 'thing'
+    CONSTRAINT fk_epl_entity FOREIGN KEY (entity_id) REFERENCES entities(id) ON DELETE CASCADE,
+    UNIQUE(entity_id, file_path, role)
+);
+
+CREATE INDEX idx_entity_photo_links_entity ON entity_photo_links(entity_id);
+CREATE INDEX idx_entity_photo_links_photo ON entity_photo_links(file_path);

src/database/insights_dao.rs

@@ -21,6 +21,12 @@ pub trait InsightDao: Sync + Send {
         file_path: &str,
     ) -> Result<Option<PhotoInsight>, DbError>;
 
+    fn get_insight_history(
+        &mut self,
+        context: &opentelemetry::Context,
+        file_path: &str,
+    ) -> Result<Vec<PhotoInsight>, DbError>;
+
     fn delete_insight(
         &mut self,
         context: &opentelemetry::Context,
@@ -49,6 +55,11 @@ impl SqliteInsightDao {
             connection: Arc::new(Mutex::new(connect())),
         }
     }
+
+    #[cfg(test)]
+    pub fn from_connection(conn: Arc<Mutex<SqliteConnection>>) -> Self {
+        SqliteInsightDao { connection: conn }
+    }
 }
 
 impl InsightDao for SqliteInsightDao {
@@ -62,15 +73,22 @@ impl InsightDao for SqliteInsightDao {
 
             let mut connection = self.connection.lock().expect("Unable to get InsightDao");
 
-            // Insert or replace on conflict (UNIQUE constraint on file_path)
+            // Mark all existing insights for this file as no longer current
-            diesel::replace_into(photo_insights)
+            diesel::update(photo_insights.filter(file_path.eq(&insight.file_path)))
+                .set(is_current.eq(false))
+                .execute(connection.deref_mut())
+                .map_err(|_| anyhow::anyhow!("Update is_current error"))?;
+
+            // Insert the new insight as current
+            diesel::insert_into(photo_insights)
                 .values(&insight)
                 .execute(connection.deref_mut())
                 .map_err(|_| anyhow::anyhow!("Insert error"))?;
 
-            // Retrieve the inserted record
+            // Retrieve the inserted record (is_current = true)
             photo_insights
                 .filter(file_path.eq(&insight.file_path))
+                .filter(is_current.eq(true))
                 .first::<PhotoInsight>(connection.deref_mut())
                 .map_err(|_| anyhow::anyhow!("Query error"))
         })
@@ -89,6 +107,7 @@ impl InsightDao for SqliteInsightDao {
 
             photo_insights
                 .filter(file_path.eq(path))
+                .filter(is_current.eq(true))
                 .first::<PhotoInsight>(connection.deref_mut())
                 .optional()
                 .map_err(|_| anyhow::anyhow!("Query error"))
@@ -96,6 +115,25 @@ impl InsightDao for SqliteInsightDao {
         .map_err(|_| DbError::new(DbErrorKind::QueryError))
     }
 
+    fn get_insight_history(
+        &mut self,
+        context: &opentelemetry::Context,
+        path: &str,
+    ) -> Result<Vec<PhotoInsight>, DbError> {
+        trace_db_call(context, "query", "get_insight_history", |_span| {
+            use schema::photo_insights::dsl::*;
+
+            let mut connection = self.connection.lock().expect("Unable to get InsightDao");
+
+            photo_insights
+                .filter(file_path.eq(path))
+                .order(generated_at.desc())
+                .load::<PhotoInsight>(connection.deref_mut())
+                .map_err(|_| anyhow::anyhow!("Query error"))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
     fn delete_insight(
         &mut self,
         context: &opentelemetry::Context,
@@ -124,6 +162,7 @@ impl InsightDao for SqliteInsightDao {
             let mut connection = self.connection.lock().expect("Unable to get InsightDao");
 
             photo_insights
+                .filter(is_current.eq(true))
                 .order(generated_at.desc())
                 .load::<PhotoInsight>(connection.deref_mut())
                 .map_err(|_| anyhow::anyhow!("Query error"))

src/database/knowledge_dao.rs

@@ -0,0 +1,854 @@
+use diesel::prelude::*;
+use diesel::sqlite::SqliteConnection;
+use std::ops::DerefMut;
+use std::sync::{Arc, Mutex};
+
+use crate::database::models::{
+    Entity, EntityFact, EntityPhotoLink, InsertEntity, InsertEntityFact, InsertEntityPhotoLink,
+};
+use crate::database::schema;
+use crate::database::{DbError, DbErrorKind, connect};
+use crate::otel::trace_db_call;
+
+// ---------------------------------------------------------------------------
+// Filter / patch types
+// ---------------------------------------------------------------------------
+
+pub struct EntityFilter {
+    pub entity_type: Option<String>,
+    /// "active" | "reviewed" | "rejected" | "all"
+    pub status: Option<String>,
+    /// LIKE match on name and description
+    pub search: Option<String>,
+    pub limit: i64,
+    pub offset: i64,
+}
+
+pub struct FactFilter {
+    pub entity_id: Option<i32>,
+    /// "active" | "reviewed" | "rejected" | "all"
+    pub status: Option<String>,
+    pub predicate: Option<String>,
+    pub limit: i64,
+    pub offset: i64,
+}
+
+pub struct EntityPatch {
+    pub name: Option<String>,
+    pub description: Option<String>,
+    pub status: Option<String>,
+    pub confidence: Option<f32>,
+}
+
+pub struct FactPatch {
+    pub predicate: Option<String>,
+    pub object_value: Option<String>,
+    pub status: Option<String>,
+    pub confidence: Option<f32>,
+}
+
+pub struct RecentActivity {
+    pub entities: Vec<Entity>,
+    pub facts: Vec<EntityFact>,
+}
+
+// ---------------------------------------------------------------------------
+// Trait
+// ---------------------------------------------------------------------------
+
+pub trait KnowledgeDao: Sync + Send {
+    // --- Entity ---
+    fn upsert_entity(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity: InsertEntity,
+    ) -> Result<Entity, DbError>;
+
+    fn get_entity_by_id(
+        &mut self,
+        cx: &opentelemetry::Context,
+        id: i32,
+    ) -> Result<Option<Entity>, DbError>;
+
+    fn get_entity_by_name(
+        &mut self,
+        cx: &opentelemetry::Context,
+        name: &str,
+        entity_type: Option<&str>,
+    ) -> Result<Vec<Entity>, DbError>;
+
+    fn get_entities_with_embeddings(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity_type: Option<&str>,
+    ) -> Result<Vec<Entity>, DbError>;
+
+    fn list_entities(
+        &mut self,
+        cx: &opentelemetry::Context,
+        filter: EntityFilter,
+    ) -> Result<(Vec<Entity>, i64), DbError>;
+
+    fn update_entity_status(
+        &mut self,
+        cx: &opentelemetry::Context,
+        id: i32,
+        status: &str,
+    ) -> Result<(), DbError>;
+
+    fn update_entity(
+        &mut self,
+        cx: &opentelemetry::Context,
+        id: i32,
+        patch: EntityPatch,
+    ) -> Result<Option<Entity>, DbError>;
+
+    fn delete_entity(&mut self, cx: &opentelemetry::Context, id: i32) -> Result<(), DbError>;
+
+    fn merge_entities(
+        &mut self,
+        cx: &opentelemetry::Context,
+        source_id: i32,
+        target_id: i32,
+    ) -> Result<(i64, i64), DbError>;
+
+    // --- Facts ---
+    fn upsert_fact(
+        &mut self,
+        cx: &opentelemetry::Context,
+        fact: InsertEntityFact,
+    ) -> Result<(EntityFact, bool), DbError>;
+
+    fn get_facts_for_entity(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity_id: i32,
+    ) -> Result<Vec<EntityFact>, DbError>;
+
+    fn list_facts(
+        &mut self,
+        cx: &opentelemetry::Context,
+        filter: FactFilter,
+    ) -> Result<(Vec<EntityFact>, i64), DbError>;
+
+    fn update_fact(
+        &mut self,
+        cx: &opentelemetry::Context,
+        id: i32,
+        patch: FactPatch,
+    ) -> Result<Option<EntityFact>, DbError>;
+
+    fn update_facts_insight_id(
+        &mut self,
+        cx: &opentelemetry::Context,
+        source_photo: &str,
+        insight_id: i32,
+    ) -> Result<(), DbError>;
+
+    fn delete_fact(&mut self, cx: &opentelemetry::Context, id: i32) -> Result<(), DbError>;
+
+    // --- Photo links ---
+    fn upsert_photo_link(
+        &mut self,
+        cx: &opentelemetry::Context,
+        link: InsertEntityPhotoLink,
+    ) -> Result<(), DbError>;
+
+    fn delete_photo_links_for_file(
+        &mut self,
+        cx: &opentelemetry::Context,
+        file_path: &str,
+    ) -> Result<(), DbError>;
+
+    fn get_links_for_photo(
+        &mut self,
+        cx: &opentelemetry::Context,
+        file_path: &str,
+    ) -> Result<Vec<EntityPhotoLink>, DbError>;
+
+    fn get_links_for_entity(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity_id: i32,
+    ) -> Result<Vec<EntityPhotoLink>, DbError>;
+
+    // --- Audit ---
+    fn get_recent_activity(
+        &mut self,
+        cx: &opentelemetry::Context,
+        since: i64,
+        limit: i64,
+    ) -> Result<RecentActivity, DbError>;
+}
+
+// ---------------------------------------------------------------------------
+// SQLite implementation
+// ---------------------------------------------------------------------------
+
+pub struct SqliteKnowledgeDao {
+    connection: Arc<Mutex<SqliteConnection>>,
+}
+
+impl Default for SqliteKnowledgeDao {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl SqliteKnowledgeDao {
+    pub fn new() -> Self {
+        SqliteKnowledgeDao {
+            connection: Arc::new(Mutex::new(connect())),
+        }
+    }
+
+    pub fn from_connection(conn: Arc<Mutex<SqliteConnection>>) -> Self {
+        SqliteKnowledgeDao { connection: conn }
+    }
+
+    fn serialize_embedding(vec: &[f32]) -> Vec<u8> {
+        vec.iter().flat_map(|f| f.to_le_bytes()).collect()
+    }
+
+    fn deserialize_embedding(bytes: &[u8]) -> Result<Vec<f32>, DbError> {
+        if bytes.len() % 4 != 0 {
+            return Err(DbError::new(DbErrorKind::QueryError));
+        }
+        Ok(bytes
+            .chunks_exact(4)
+            .map(|c| f32::from_le_bytes([c[0], c[1], c[2], c[3]]))
+            .collect())
+    }
+
+    pub fn cosine_similarity(a: &[f32], b: &[f32]) -> f32 {
+        if a.len() != b.len() || a.is_empty() {
+            return 0.0;
+        }
+        let dot: f32 = a.iter().zip(b.iter()).map(|(x, y)| x * y).sum();
+        let mag_a: f32 = a.iter().map(|x| x * x).sum::<f32>().sqrt();
+        let mag_b: f32 = b.iter().map(|x| x * x).sum::<f32>().sqrt();
+        if mag_a == 0.0 || mag_b == 0.0 {
+            0.0
+        } else {
+            dot / (mag_a * mag_b)
+        }
+    }
+}
+
+impl KnowledgeDao for SqliteKnowledgeDao {
+    // -----------------------------------------------------------------------
+    // Entity operations
+    // -----------------------------------------------------------------------
+
+    fn upsert_entity(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity: InsertEntity,
+    ) -> Result<Entity, DbError> {
+        trace_db_call(cx, "insert", "upsert_entity", |_span| {
+            use schema::entities::dsl::*;
+
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+
+            // Case-insensitive lookup by name + entity_type
+            let name_lower = entity.name.to_lowercase();
+            let existing: Option<Entity> = entities
+                .filter(diesel::dsl::sql::<diesel::sql_types::Bool>(&format!(
+                    "lower(name) = '{}' AND entity_type = '{}'",
+                    name_lower.replace('\'', "''"),
+                    entity.entity_type.replace('\'', "''")
+                )))
+                .first::<Entity>(conn.deref_mut())
+                .optional()
+                .map_err(|e| anyhow::anyhow!("Query error: {}", e))?;
+
+            if let Some(existing_entity) = existing {
+                // Update description, embedding, updated_at
+                diesel::update(entities.filter(id.eq(existing_entity.id)))
+                    .set((
+                        description.eq(&entity.description),
+                        embedding.eq(&entity.embedding),
+                        updated_at.eq(entity.updated_at),
+                    ))
+                    .execute(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Update error: {}", e))?;
+
+                entities
+                    .filter(id.eq(existing_entity.id))
+                    .first::<Entity>(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Query error: {}", e))
+            } else {
+                diesel::insert_into(entities)
+                    .values(&entity)
+                    .execute(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Insert error: {}", e))?;
+
+                entities
+                    .order(id.desc())
+                    .first::<Entity>(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Query error: {}", e))
+            }
+        })
+        .map_err(|_| DbError::new(DbErrorKind::InsertError))
+    }
+
+    fn get_entity_by_id(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity_id: i32,
+    ) -> Result<Option<Entity>, DbError> {
+        trace_db_call(cx, "query", "get_entity_by_id", |_span| {
+            use schema::entities::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+            entities
+                .filter(id.eq(entity_id))
+                .first::<Entity>(conn.deref_mut())
+                .optional()
+                .map_err(|e| anyhow::anyhow!("Query error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
+    fn get_entity_by_name(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity_name: &str,
+        entity_type_filter: Option<&str>,
+    ) -> Result<Vec<Entity>, DbError> {
+        trace_db_call(cx, "query", "get_entity_by_name", |_span| {
+            use schema::entities::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+
+            let name_lower = entity_name.to_lowercase().replace('\'', "''");
+            let mut sql = format!("lower(name) = '{}'", name_lower);
+            if let Some(et) = entity_type_filter {
+                sql.push_str(&format!(" AND entity_type = '{}'", et.replace('\'', "''")));
+            }
+            sql.push_str(" AND status != 'rejected'");
+
+            entities
+                .filter(diesel::dsl::sql::<diesel::sql_types::Bool>(&sql))
+                .load::<Entity>(conn.deref_mut())
+                .map_err(|e| anyhow::anyhow!("Query error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
+    fn get_entities_with_embeddings(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity_type_filter: Option<&str>,
+    ) -> Result<Vec<Entity>, DbError> {
+        trace_db_call(cx, "query", "get_entities_with_embeddings", |_span| {
+            use schema::entities::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+
+            let mut query = entities
+                .filter(embedding.is_not_null())
+                .filter(status.ne("rejected"))
+                .into_boxed();
+
+            if let Some(et) = entity_type_filter {
+                query = query.filter(entity_type.eq(et));
+            }
+
+            query
+                .load::<Entity>(conn.deref_mut())
+                .map_err(|e| anyhow::anyhow!("Query error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
+    fn list_entities(
+        &mut self,
+        cx: &opentelemetry::Context,
+        filter: EntityFilter,
+    ) -> Result<(Vec<Entity>, i64), DbError> {
+        trace_db_call(cx, "query", "list_entities", |_span| {
+            use diesel::dsl::count_star;
+            use schema::entities::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+
+            let mut query = entities.into_boxed();
+
+            if let Some(ref et) = filter.entity_type {
+                query = query.filter(entity_type.eq(et));
+            }
+
+            let status_val = filter.status.as_deref().unwrap_or("active");
+            if status_val != "all" {
+                query = query.filter(status.eq(status_val));
+            }
+
+            if let Some(ref search_term) = filter.search {
+                let pattern = format!("%{}%", search_term);
+                query = query.filter(name.like(pattern.clone()).or(description.like(pattern)));
+            }
+
+            // Count with same filters applied (build separately since boxed query is consumed)
+            let mut count_query = entities.into_boxed();
+            if let Some(ref et) = filter.entity_type {
+                count_query = count_query.filter(entity_type.eq(et));
+            }
+            let status_val2 = filter.status.as_deref().unwrap_or("active");
+            if status_val2 != "all" {
+                count_query = count_query.filter(status.eq(status_val2));
+            }
+            if let Some(ref search_term) = filter.search {
+                let pattern = format!("%{}%", search_term);
+                count_query =
+                    count_query.filter(name.like(pattern.clone()).or(description.like(pattern)));
+            }
+            let total: i64 = count_query
+                .select(count_star())
+                .first(conn.deref_mut())
+                .unwrap_or(0);
+
+            let results = query
+                .order(updated_at.desc())
+                .limit(filter.limit)
+                .offset(filter.offset)
+                .load::<Entity>(conn.deref_mut())
+                .map_err(|e| anyhow::anyhow!("Query error: {}", e))?;
+
+            Ok((results, total))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
+    fn update_entity_status(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity_id: i32,
+        new_status: &str,
+    ) -> Result<(), DbError> {
+        trace_db_call(cx, "update", "update_entity_status", |_span| {
+            use schema::entities::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+            diesel::update(entities.filter(id.eq(entity_id)))
+                .set(status.eq(new_status))
+                .execute(conn.deref_mut())
+                .map(|_| ())
+                .map_err(|e| anyhow::anyhow!("Update error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::UpdateError))
+    }
+
+    fn update_entity(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity_id: i32,
+        patch: EntityPatch,
+    ) -> Result<Option<Entity>, DbError> {
+        trace_db_call(cx, "update", "update_entity", |_span| {
+            use schema::entities::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+
+            let now = chrono::Utc::now().timestamp();
+
+            if let Some(ref new_name) = patch.name {
+                diesel::update(entities.filter(id.eq(entity_id)))
+                    .set((name.eq(new_name), updated_at.eq(now)))
+                    .execute(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Update name error: {}", e))?;
+            }
+            if let Some(ref new_desc) = patch.description {
+                diesel::update(entities.filter(id.eq(entity_id)))
+                    .set((description.eq(new_desc), updated_at.eq(now)))
+                    .execute(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Update description error: {}", e))?;
+            }
+            if let Some(ref new_status) = patch.status {
+                diesel::update(entities.filter(id.eq(entity_id)))
+                    .set((status.eq(new_status), updated_at.eq(now)))
+                    .execute(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Update status error: {}", e))?;
+            }
+            if let Some(new_confidence) = patch.confidence {
+                diesel::update(entities.filter(id.eq(entity_id)))
+                    .set((confidence.eq(new_confidence), updated_at.eq(now)))
+                    .execute(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Update confidence error: {}", e))?;
+            }
+
+            entities
+                .filter(id.eq(entity_id))
+                .first::<Entity>(conn.deref_mut())
+                .optional()
+                .map_err(|e| anyhow::anyhow!("Query error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::UpdateError))
+    }
+
+    fn delete_entity(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity_id: i32,
+    ) -> Result<(), DbError> {
+        trace_db_call(cx, "delete", "delete_entity", |_span| {
+            use schema::entities::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+            diesel::delete(entities.filter(id.eq(entity_id)))
+                .execute(conn.deref_mut())
+                .map(|_| ())
+                .map_err(|e| anyhow::anyhow!("Delete error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
+    fn merge_entities(
+        &mut self,
+        cx: &opentelemetry::Context,
+        source_id: i32,
+        target_id: i32,
+    ) -> Result<(i64, i64), DbError> {
+        trace_db_call(cx, "update", "merge_entities", |_span| {
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+
+            conn.transaction::<(i64, i64), diesel::result::Error, _>(|conn| {
+                use schema::entity_facts::dsl as ef;
+                use schema::entity_photo_links::dsl as epl;
+
+                // 1. Re-point facts where source is subject
+                let facts_updated =
+                    diesel::update(ef::entity_facts.filter(ef::subject_entity_id.eq(source_id)))
+                        .set(ef::subject_entity_id.eq(target_id))
+                        .execute(conn)? as i64;
+
+                // 2. Re-point facts where source is object
+                diesel::update(ef::entity_facts.filter(ef::object_entity_id.eq(source_id)))
+                    .set(ef::object_entity_id.eq(Some(target_id)))
+                    .execute(conn)?;
+
+                // 3. Copy photo links to target (INSERT OR IGNORE to skip duplicates)
+                let links_updated = diesel::sql_query(
+                    "INSERT OR IGNORE INTO entity_photo_links (entity_id, file_path, role) \
+                     SELECT ?, file_path, role FROM entity_photo_links WHERE entity_id = ?",
+                )
+                .bind::<diesel::sql_types::Integer, _>(target_id)
+                .bind::<diesel::sql_types::Integer, _>(source_id)
+                .execute(conn)? as i64;
+
+                // 4. Delete source entity (FK CASCADE removes remaining facts/links)
+                diesel::delete(
+                    schema::entities::dsl::entities.filter(schema::entities::dsl::id.eq(source_id)),
+                )
+                .execute(conn)?;
+
+                Ok((facts_updated, links_updated))
+            })
+            .map_err(|e| anyhow::anyhow!("Merge transaction error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::UpdateError))
+    }
+
+    // -----------------------------------------------------------------------
+    // Fact operations
+    // -----------------------------------------------------------------------
+
+    fn upsert_fact(
+        &mut self,
+        cx: &opentelemetry::Context,
+        fact: InsertEntityFact,
+    ) -> Result<(EntityFact, bool), DbError> {
+        trace_db_call(cx, "insert", "upsert_fact", |_span| {
+            use schema::entity_facts::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+
+            // Look for an identical active fact
+            let mut dup_query = entity_facts
+                .filter(subject_entity_id.eq(fact.subject_entity_id))
+                .filter(predicate.eq(&fact.predicate))
+                .filter(status.ne("rejected"))
+                .into_boxed();
+
+            match &fact.object_entity_id {
+                Some(oid) => dup_query = dup_query.filter(object_entity_id.eq(oid)),
+                None => dup_query = dup_query.filter(object_entity_id.is_null()),
+            }
+            match &fact.object_value {
+                Some(ov) => dup_query = dup_query.filter(object_value.eq(ov)),
+                None => dup_query = dup_query.filter(object_value.is_null()),
+            }
+
+            let existing: Option<EntityFact> = dup_query
+                .first::<EntityFact>(conn.deref_mut())
+                .optional()
+                .map_err(|e| anyhow::anyhow!("Query error: {}", e))?;
+
+            if let Some(existing_fact) = existing {
+                // Corroborate: bump confidence by 0.1 capped at 0.95
+                let new_confidence = (existing_fact.confidence + 0.1).min(0.95);
+                diesel::update(entity_facts.filter(id.eq(existing_fact.id)))
+                    .set(confidence.eq(new_confidence))
+                    .execute(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Update confidence error: {}", e))?;
+
+                let updated = entity_facts
+                    .filter(id.eq(existing_fact.id))
+                    .first::<EntityFact>(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Query error: {}", e))?;
+
+                Ok((updated, false)) // false = corroborated, not newly created
+            } else {
+                diesel::insert_into(entity_facts)
+                    .values(&fact)
+                    .execute(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Insert error: {}", e))?;
+
+                let inserted = entity_facts
+                    .order(id.desc())
+                    .first::<EntityFact>(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Query error: {}", e))?;
+
+                Ok((inserted, true)) // true = newly created
+            }
+        })
+        .map_err(|_| DbError::new(DbErrorKind::InsertError))
+    }
+
+    fn get_facts_for_entity(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity_id: i32,
+    ) -> Result<Vec<EntityFact>, DbError> {
+        trace_db_call(cx, "query", "get_facts_for_entity", |_span| {
+            use schema::entity_facts::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+            entity_facts
+                .filter(subject_entity_id.eq(entity_id))
+                .filter(status.ne("rejected"))
+                .load::<EntityFact>(conn.deref_mut())
+                .map_err(|e| anyhow::anyhow!("Query error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
+    fn list_facts(
+        &mut self,
+        cx: &opentelemetry::Context,
+        filter: FactFilter,
+    ) -> Result<(Vec<EntityFact>, i64), DbError> {
+        trace_db_call(cx, "query", "list_facts", |_span| {
+            use diesel::dsl::count_star;
+            use schema::entity_facts::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+
+            let mut query = entity_facts.into_boxed();
+
+            if let Some(eid) = filter.entity_id {
+                query = query.filter(subject_entity_id.eq(eid));
+            }
+            let status_val = filter.status.as_deref().unwrap_or("active");
+            if status_val != "all" {
+                query = query.filter(status.eq(status_val));
+            }
+            if let Some(ref pred) = filter.predicate {
+                query = query.filter(predicate.eq(pred));
+            }
+
+            let total: i64 = entity_facts
+                .select(count_star())
+                .first(conn.deref_mut())
+                .unwrap_or(0);
+
+            let results = query
+                .order(created_at.desc())
+                .limit(filter.limit)
+                .offset(filter.offset)
+                .load::<EntityFact>(conn.deref_mut())
+                .map_err(|e| anyhow::anyhow!("Query error: {}", e))?;
+
+            Ok((results, total))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
+    fn update_fact(
+        &mut self,
+        cx: &opentelemetry::Context,
+        fact_id: i32,
+        patch: FactPatch,
+    ) -> Result<Option<EntityFact>, DbError> {
+        trace_db_call(cx, "update", "update_fact", |_span| {
+            use schema::entity_facts::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+
+            if let Some(ref new_predicate) = patch.predicate {
+                diesel::update(entity_facts.filter(id.eq(fact_id)))
+                    .set(predicate.eq(new_predicate))
+                    .execute(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Update error: {}", e))?;
+            }
+            if let Some(ref new_value) = patch.object_value {
+                diesel::update(entity_facts.filter(id.eq(fact_id)))
+                    .set(object_value.eq(new_value))
+                    .execute(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Update error: {}", e))?;
+            }
+            if let Some(ref new_status) = patch.status {
+                diesel::update(entity_facts.filter(id.eq(fact_id)))
+                    .set(status.eq(new_status))
+                    .execute(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Update error: {}", e))?;
+            }
+            if let Some(new_confidence) = patch.confidence {
+                diesel::update(entity_facts.filter(id.eq(fact_id)))
+                    .set(confidence.eq(new_confidence))
+                    .execute(conn.deref_mut())
+                    .map_err(|e| anyhow::anyhow!("Update error: {}", e))?;
+            }
+
+            entity_facts
+                .filter(id.eq(fact_id))
+                .first::<EntityFact>(conn.deref_mut())
+                .optional()
+                .map_err(|e| anyhow::anyhow!("Query error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::UpdateError))
+    }
+
+    fn update_facts_insight_id(
+        &mut self,
+        cx: &opentelemetry::Context,
+        photo_path: &str,
+        insight_id: i32,
+    ) -> Result<(), DbError> {
+        trace_db_call(cx, "update", "update_facts_insight_id", |_span| {
+            use schema::entity_facts::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+            diesel::update(
+                entity_facts
+                    .filter(source_photo.eq(photo_path))
+                    .filter(source_insight_id.is_null()),
+            )
+            .set(source_insight_id.eq(insight_id))
+            .execute(conn.deref_mut())
+            .map(|_| ())
+            .map_err(|e| anyhow::anyhow!("Update error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::UpdateError))
+    }
+
+    fn delete_fact(&mut self, cx: &opentelemetry::Context, fact_id: i32) -> Result<(), DbError> {
+        trace_db_call(cx, "delete", "delete_fact", |_span| {
+            use schema::entity_facts::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+            diesel::delete(entity_facts.filter(id.eq(fact_id)))
+                .execute(conn.deref_mut())
+                .map(|_| ())
+                .map_err(|e| anyhow::anyhow!("Delete error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
+    // -----------------------------------------------------------------------
+    // Photo link operations
+    // -----------------------------------------------------------------------
+
+    fn upsert_photo_link(
+        &mut self,
+        cx: &opentelemetry::Context,
+        link: InsertEntityPhotoLink,
+    ) -> Result<(), DbError> {
+        trace_db_call(cx, "insert", "upsert_photo_link", |_span| {
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+            // INSERT OR IGNORE respects the UNIQUE(entity_id, file_path, role) constraint
+            diesel::sql_query(
+                "INSERT OR IGNORE INTO entity_photo_links (entity_id, file_path, role) VALUES (?, ?, ?)"
+            )
+            .bind::<diesel::sql_types::Integer, _>(link.entity_id)
+            .bind::<diesel::sql_types::Text, _>(&link.file_path)
+            .bind::<diesel::sql_types::Text, _>(&link.role)
+            .execute(conn.deref_mut())
+            .map(|_| ())
+            .map_err(|e| anyhow::anyhow!("Insert error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::InsertError))
+    }
+
+    fn delete_photo_links_for_file(
+        &mut self,
+        cx: &opentelemetry::Context,
+        file_path_val: &str,
+    ) -> Result<(), DbError> {
+        trace_db_call(cx, "delete", "delete_photo_links_for_file", |_span| {
+            use schema::entity_photo_links::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+            diesel::delete(entity_photo_links.filter(file_path.eq(file_path_val)))
+                .execute(conn.deref_mut())
+                .map(|_| ())
+                .map_err(|e| anyhow::anyhow!("Delete error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
+    fn get_links_for_photo(
+        &mut self,
+        cx: &opentelemetry::Context,
+        file_path_val: &str,
+    ) -> Result<Vec<EntityPhotoLink>, DbError> {
+        trace_db_call(cx, "query", "get_links_for_photo", |_span| {
+            use schema::entity_photo_links::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+            entity_photo_links
+                .filter(file_path.eq(file_path_val))
+                .load::<EntityPhotoLink>(conn.deref_mut())
+                .map_err(|e| anyhow::anyhow!("Query error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
+    fn get_links_for_entity(
+        &mut self,
+        cx: &opentelemetry::Context,
+        entity_id_val: i32,
+    ) -> Result<Vec<EntityPhotoLink>, DbError> {
+        trace_db_call(cx, "query", "get_links_for_entity", |_span| {
+            use schema::entity_photo_links::dsl::*;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+            entity_photo_links
+                .filter(entity_id.eq(entity_id_val))
+                .load::<EntityPhotoLink>(conn.deref_mut())
+                .map_err(|e| anyhow::anyhow!("Query error: {}", e))
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+
+    // -----------------------------------------------------------------------
+    // Audit
+    // -----------------------------------------------------------------------
+
+    fn get_recent_activity(
+        &mut self,
+        cx: &opentelemetry::Context,
+        since: i64,
+        limit: i64,
+    ) -> Result<RecentActivity, DbError> {
+        trace_db_call(cx, "query", "get_recent_activity", |_span| {
+            use schema::entities::dsl as e;
+            use schema::entity_facts::dsl as ef;
+            let mut conn = self.connection.lock().expect("KnowledgeDao lock");
+
+            let recent_entities = e::entities
+                .filter(e::created_at.gt(since))
+                .order(e::created_at.desc())
+                .limit(limit)
+                .load::<Entity>(conn.deref_mut())
+                .map_err(|err| anyhow::anyhow!("Query error: {}", err))?;
+
+            let recent_facts = ef::entity_facts
+                .filter(ef::created_at.gt(since))
+                .order(ef::created_at.desc())
+                .limit(limit)
+                .load::<EntityFact>(conn.deref_mut())
+                .map_err(|err| anyhow::anyhow!("Query error: {}", err))?;
+
+            Ok(RecentActivity {
+                entities: recent_entities,
+                facts: recent_facts,
+            })
+        })
+        .map_err(|_| DbError::new(DbErrorKind::QueryError))
+    }
+}

src/database/mod.rs

@@ -12,6 +12,7 @@ use crate::otel::trace_db_call;
 pub mod calendar_dao;
 pub mod daily_summary_dao;
 pub mod insights_dao;
+pub mod knowledge_dao;
 pub mod location_dao;
 pub mod models;
 pub mod preview_dao;
@@ -21,6 +22,10 @@ pub mod search_dao;
 pub use calendar_dao::{CalendarEventDao, SqliteCalendarEventDao};
 pub use daily_summary_dao::{DailySummaryDao, InsertDailySummary, SqliteDailySummaryDao};
 pub use insights_dao::{InsightDao, SqliteInsightDao};
+pub use knowledge_dao::{
+    EntityFilter, EntityPatch, FactFilter, FactPatch, KnowledgeDao, RecentActivity,
+    SqliteKnowledgeDao,
+};
 pub use location_dao::{LocationHistoryDao, SqliteLocationHistoryDao};
 pub use preview_dao::{PreviewDao, SqlitePreviewDao};
 pub use search_dao::{SearchHistoryDao, SqliteSearchHistoryDao};

src/database/models.rs

@@ -1,4 +1,7 @@
-use crate::database::schema::{favorites, image_exif, photo_insights, users, video_preview_clips};
+use crate::database::schema::{
+    entities, entity_facts, entity_photo_links, favorites, image_exif, photo_insights, users,
+    video_preview_clips,
+};
 use serde::Serialize;
 
 #[derive(Insertable)]
@@ -82,6 +85,7 @@ pub struct InsertPhotoInsight {
     pub summary: String,
     pub generated_at: i64,
     pub model_version: String,
+    pub is_current: bool,
 }
 
 #[derive(Serialize, Queryable, Clone, Debug)]
@@ -92,6 +96,79 @@ pub struct PhotoInsight {
     pub summary: String,
     pub generated_at: i64,
     pub model_version: String,
+    pub is_current: bool,
+}
+
+// --- Knowledge memory models ---
+
+#[derive(Insertable)]
+#[diesel(table_name = entities)]
+pub struct InsertEntity {
+    pub name: String,
+    pub entity_type: String,
+    pub description: String,
+    pub embedding: Option<Vec<u8>>,
+    pub confidence: f32,
+    pub status: String,
+    pub created_at: i64,
+    pub updated_at: i64,
+}
+
+#[derive(Serialize, Queryable, Clone, Debug)]
+pub struct Entity {
+    pub id: i32,
+    pub name: String,
+    pub entity_type: String,
+    pub description: String,
+    pub embedding: Option<Vec<u8>>,
+    pub confidence: f32,
+    pub status: String,
+    pub created_at: i64,
+    pub updated_at: i64,
+}
+
+#[derive(Insertable)]
+#[diesel(table_name = entity_facts)]
+pub struct InsertEntityFact {
+    pub subject_entity_id: i32,
+    pub predicate: String,
+    pub object_entity_id: Option<i32>,
+    pub object_value: Option<String>,
+    pub source_photo: Option<String>,
+    pub source_insight_id: Option<i32>,
+    pub confidence: f32,
+    pub status: String,
+    pub created_at: i64,
+}
+
+#[derive(Serialize, Queryable, Clone, Debug)]
+pub struct EntityFact {
+    pub id: i32,
+    pub subject_entity_id: i32,
+    pub predicate: String,
+    pub object_entity_id: Option<i32>,
+    pub object_value: Option<String>,
+    pub source_photo: Option<String>,
+    pub source_insight_id: Option<i32>,
+    pub confidence: f32,
+    pub status: String,
+    pub created_at: i64,
+}
+
+#[derive(Insertable)]
+#[diesel(table_name = entity_photo_links)]
+pub struct InsertEntityPhotoLink {
+    pub entity_id: i32,
+    pub file_path: String,
+    pub role: String,
+}
+
+#[derive(Serialize, Queryable, Clone, Debug)]
+pub struct EntityPhotoLink {
+    pub id: i32,
+    pub entity_id: i32,
+    pub file_path: String,
+    pub role: String,
 }
 
 #[derive(Insertable)]

src/database/schema.rs

@@ -31,6 +31,44 @@ diesel::table! {
     }
 }
 
+diesel::table! {
+    entities (id) {
+        id -> Integer,
+        name -> Text,
+        entity_type -> Text,
+        description -> Text,
+        embedding -> Nullable<Binary>,
+        confidence -> Float,
+        status -> Text,
+        created_at -> BigInt,
+        updated_at -> BigInt,
+    }
+}
+
+diesel::table! {
+    entity_facts (id) {
+        id -> Integer,
+        subject_entity_id -> Integer,
+        predicate -> Text,
+        object_entity_id -> Nullable<Integer>,
+        object_value -> Nullable<Text>,
+        source_photo -> Nullable<Text>,
+        source_insight_id -> Nullable<Integer>,
+        confidence -> Float,
+        status -> Text,
+        created_at -> BigInt,
+    }
+}
+
+diesel::table! {
+    entity_photo_links (id) {
+        id -> Integer,
+        entity_id -> Integer,
+        file_path -> Text,
+        role -> Text,
+    }
+}
+
 diesel::table! {
     favorites (id) {
         id -> Integer,
@@ -112,6 +150,7 @@ diesel::table! {
         summary -> Text,
         generated_at -> BigInt,
         model_version -> Text,
+        is_current -> Bool,
     }
 }
 
@@ -165,11 +204,16 @@ diesel::table! {
     }
 }
 
+diesel::joinable!(entity_facts -> photo_insights (source_insight_id));
+diesel::joinable!(entity_photo_links -> entities (entity_id));
 diesel::joinable!(tagged_photo -> tags (tag_id));
 
 diesel::allow_tables_to_appear_in_same_query!(
     calendar_events,
     daily_conversation_summaries,
+    entities,
+    entity_facts,
+    entity_photo_links,
     favorites,
     image_exif,
     knowledge_embeddings,

src/knowledge.rs

@@ -0,0 +1,567 @@
+use actix_web::dev::{ServiceFactory, ServiceRequest};
+use actix_web::{App, HttpResponse, Responder, web};
+use chrono::Utc;
+use serde::{Deserialize, Serialize};
+use std::sync::Mutex;
+
+use crate::data::Claims;
+use crate::database::models::{Entity, EntityFact, EntityPhotoLink};
+use crate::database::{
+    EntityFilter, EntityPatch, FactFilter, FactPatch, KnowledgeDao, RecentActivity,
+};
+
+// ---------------------------------------------------------------------------
+// Request / Response types
+// ---------------------------------------------------------------------------
+
+#[derive(Serialize)]
+pub struct EntitySummary {
+    pub id: i32,
+    pub name: String,
+    pub entity_type: String,
+    pub description: String,
+    pub confidence: f32,
+    pub status: String,
+    pub created_at: i64,
+    pub updated_at: i64,
+}
+
+impl From<Entity> for EntitySummary {
+    fn from(e: Entity) -> Self {
+        EntitySummary {
+            id: e.id,
+            name: e.name,
+            entity_type: e.entity_type,
+            description: e.description,
+            confidence: e.confidence,
+            status: e.status,
+            created_at: e.created_at,
+            updated_at: e.updated_at,
+        }
+    }
+}
+
+#[derive(Serialize)]
+pub struct EntityListResponse {
+    pub entities: Vec<EntitySummary>,
+    pub total: i64,
+    pub limit: i64,
+    pub offset: i64,
+}
+
+#[derive(Serialize)]
+pub struct FactDetail {
+    pub id: i32,
+    pub predicate: String,
+    pub object_entity_id: Option<i32>,
+    pub object_entity_name: Option<String>,
+    pub object_value: Option<String>,
+    pub confidence: f32,
+    pub status: String,
+    pub source_photo: Option<String>,
+    pub source_insight_id: Option<i32>,
+    pub created_at: i64,
+}
+
+#[derive(Serialize)]
+pub struct PhotoLinkDetail {
+    pub file_path: String,
+    pub role: String,
+}
+
+impl From<EntityPhotoLink> for PhotoLinkDetail {
+    fn from(l: EntityPhotoLink) -> Self {
+        PhotoLinkDetail {
+            file_path: l.file_path,
+            role: l.role,
+        }
+    }
+}
+
+#[derive(Serialize)]
+pub struct EntityDetailResponse {
+    pub id: i32,
+    pub name: String,
+    pub entity_type: String,
+    pub description: String,
+    pub confidence: f32,
+    pub status: String,
+    pub created_at: i64,
+    pub updated_at: i64,
+    pub facts: Vec<FactDetail>,
+    pub photo_links: Vec<PhotoLinkDetail>,
+}
+
+#[derive(Serialize)]
+pub struct FactSummary {
+    pub id: i32,
+    pub subject_entity_id: i32,
+    pub subject_entity_name: Option<String>,
+    pub predicate: String,
+    pub object_entity_id: Option<i32>,
+    pub object_entity_name: Option<String>,
+    pub object_value: Option<String>,
+    pub confidence: f32,
+    pub status: String,
+    pub source_photo: Option<String>,
+    pub source_insight_id: Option<i32>,
+    pub created_at: i64,
+}
+
+#[derive(Serialize)]
+pub struct FactListResponse {
+    pub facts: Vec<FactSummary>,
+    pub total: i64,
+    pub limit: i64,
+    pub offset: i64,
+}
+
+#[derive(Deserialize)]
+pub struct MergeRequest {
+    pub source_id: i32,
+    pub target_id: i32,
+}
+
+#[derive(Serialize)]
+pub struct MergeResponse {
+    pub merged_entity_id: i32,
+    pub deleted_entity_id: i32,
+    pub facts_transferred: i64,
+    pub links_transferred: i64,
+}
+
+#[derive(Deserialize)]
+pub struct EntityPatchRequest {
+    pub name: Option<String>,
+    pub description: Option<String>,
+    pub status: Option<String>,
+    pub confidence: Option<f32>,
+}
+
+#[derive(Deserialize)]
+pub struct FactPatchRequest {
+    pub predicate: Option<String>,
+    pub object_value: Option<String>,
+    pub status: Option<String>,
+    pub confidence: Option<f32>,
+}
+
+#[derive(Deserialize)]
+pub struct EntityListQuery {
+    #[serde(rename = "type")]
+    pub entity_type: Option<String>,
+    pub status: Option<String>,
+    pub search: Option<String>,
+    pub limit: Option<i64>,
+    pub offset: Option<i64>,
+}
+
+#[derive(Deserialize)]
+pub struct FactListQuery {
+    pub entity_id: Option<i32>,
+    pub status: Option<String>,
+    pub predicate: Option<String>,
+    pub limit: Option<i64>,
+    pub offset: Option<i64>,
+}
+
+#[derive(Deserialize)]
+pub struct RecentQuery {
+    pub since: Option<i64>,
+    pub limit: Option<i64>,
+}
+
+// ---------------------------------------------------------------------------
+// Service registration
+// ---------------------------------------------------------------------------
+
+pub fn add_knowledge_services<T, D: KnowledgeDao + 'static>(app: App<T>) -> App<T>
+where
+    T: ServiceFactory<ServiceRequest, Config = (), Error = actix_web::Error, InitError = ()>,
+{
+    app.service(
+        web::scope("/knowledge")
+            .service(web::resource("/entities").route(web::get().to(list_entities::<D>)))
+            .service(web::resource("/entities/merge").route(web::post().to(merge_entities::<D>)))
+            .service(
+                web::resource("/entities/{id}")
+                    .route(web::get().to(get_entity::<D>))
+                    .route(web::patch().to(patch_entity::<D>))
+                    .route(web::delete().to(delete_entity::<D>)),
+            )
+            .service(web::resource("/facts").route(web::get().to(list_facts::<D>)))
+            .service(
+                web::resource("/facts/{id}")
+                    .route(web::patch().to(patch_fact::<D>))
+                    .route(web::delete().to(delete_fact::<D>)),
+            )
+            .service(web::resource("/recent").route(web::get().to(get_recent::<D>))),
+    )
+}
+
+// ---------------------------------------------------------------------------
+// Handlers
+// ---------------------------------------------------------------------------
+
+async fn list_entities<D: KnowledgeDao + 'static>(
+    _claims: Claims,
+    query: web::Query<EntityListQuery>,
+    dao: web::Data<Mutex<D>>,
+) -> impl Responder {
+    let limit = query.limit.unwrap_or(50).min(200);
+    let offset = query.offset.unwrap_or(0);
+
+    let status_filter = match query.status.as_deref() {
+        None | Some("active") => Some("active".to_string()),
+        Some("all") => None,
+        Some(s) => Some(s.to_string()),
+    };
+
+    let filter = EntityFilter {
+        entity_type: query.entity_type.clone(),
+        status: status_filter,
+        search: query.search.clone(),
+        limit,
+        offset,
+    };
+
+    let cx = opentelemetry::Context::current();
+    let mut dao = dao.lock().expect("Unable to lock KnowledgeDao");
+    match dao.list_entities(&cx, filter) {
+        Ok((entities, total)) => {
+            let summaries: Vec<EntitySummary> =
+                entities.into_iter().map(EntitySummary::from).collect();
+            HttpResponse::Ok().json(EntityListResponse {
+                entities: summaries,
+                total,
+                limit,
+                offset,
+            })
+        }
+        Err(e) => {
+            log::error!("list_entities error: {:?}", e);
+            HttpResponse::InternalServerError().json(serde_json::json!({"error": "Database error"}))
+        }
+    }
+}
+
+async fn get_entity<D: KnowledgeDao + 'static>(
+    _claims: Claims,
+    id: web::Path<i32>,
+    dao: web::Data<Mutex<D>>,
+) -> impl Responder {
+    let cx = opentelemetry::Context::current();
+    let entity_id = id.into_inner();
+    let mut dao = dao.lock().expect("Unable to lock KnowledgeDao");
+
+    let entity = match dao.get_entity_by_id(&cx, entity_id) {
+        Ok(Some(e)) => e,
+        Ok(None) => {
+            return HttpResponse::NotFound().json(serde_json::json!({"error": "Entity not found"}));
+        }
+        Err(e) => {
+            log::error!("get_entity error: {:?}", e);
+            return HttpResponse::InternalServerError()
+                .json(serde_json::json!({"error": "Database error"}));
+        }
+    };
+
+    // Fetch all facts (all statuses for audit)
+    let raw_facts: Vec<EntityFact> = match dao.get_facts_for_entity(&cx, entity_id) {
+        Ok(f) => f,
+        Err(e) => {
+            log::error!("get_facts_for_entity error: {:?}", e);
+            return HttpResponse::InternalServerError()
+                .json(serde_json::json!({"error": "Database error"}));
+        }
+    };
+
+    // Resolve object entity names
+    let mut facts = Vec::with_capacity(raw_facts.len());
+    for f in raw_facts {
+        let object_entity_name = if let Some(oid) = f.object_entity_id {
+            dao.get_entity_by_id(&cx, oid)
+                .ok()
+                .flatten()
+                .map(|e| e.name)
+        } else {
+            None
+        };
+        facts.push(FactDetail {
+            id: f.id,
+            predicate: f.predicate,
+            object_entity_id: f.object_entity_id,
+            object_entity_name,
+            object_value: f.object_value,
+            confidence: f.confidence,
+            status: f.status,
+            source_photo: f.source_photo,
+            source_insight_id: f.source_insight_id,
+            created_at: f.created_at,
+        });
+    }
+
+    // Fetch photo links
+    let photo_links: Vec<PhotoLinkDetail> = match dao.get_links_for_entity(&cx, entity_id) {
+        Ok(links) => links.into_iter().map(PhotoLinkDetail::from).collect(),
+        Err(e) => {
+            log::error!("get_links_for_entity error: {:?}", e);
+            return HttpResponse::InternalServerError()
+                .json(serde_json::json!({"error": "Database error"}));
+        }
+    };
+
+    HttpResponse::Ok().json(EntityDetailResponse {
+        id: entity.id,
+        name: entity.name,
+        entity_type: entity.entity_type,
+        description: entity.description,
+        confidence: entity.confidence,
+        status: entity.status,
+        created_at: entity.created_at,
+        updated_at: entity.updated_at,
+        facts,
+        photo_links,
+    })
+}
+
+async fn patch_entity<D: KnowledgeDao + 'static>(
+    _claims: Claims,
+    id: web::Path<i32>,
+    body: web::Json<EntityPatchRequest>,
+    dao: web::Data<Mutex<D>>,
+) -> impl Responder {
+    let cx = opentelemetry::Context::current();
+    let entity_id = id.into_inner();
+    let patch = EntityPatch {
+        name: body.name.clone(),
+        description: body.description.clone(),
+        status: body.status.clone(),
+        confidence: body.confidence,
+    };
+
+    let mut dao = dao.lock().expect("Unable to lock KnowledgeDao");
+    match dao.update_entity(&cx, entity_id, patch) {
+        Ok(Some(entity)) => HttpResponse::Ok().json(EntitySummary::from(entity)),
+        Ok(None) => HttpResponse::NotFound().json(serde_json::json!({"error": "Entity not found"})),
+        Err(e) => {
+            log::error!("patch_entity error: {:?}", e);
+            HttpResponse::InternalServerError().json(serde_json::json!({"error": "Database error"}))
+        }
+    }
+}
+
+async fn delete_entity<D: KnowledgeDao + 'static>(
+    _claims: Claims,
+    id: web::Path<i32>,
+    dao: web::Data<Mutex<D>>,
+) -> impl Responder {
+    let cx = opentelemetry::Context::current();
+    let entity_id = id.into_inner();
+    let mut dao = dao.lock().expect("Unable to lock KnowledgeDao");
+
+    // Verify entity exists before deleting
+    match dao.get_entity_by_id(&cx, entity_id) {
+        Ok(None) => {
+            return HttpResponse::NotFound().json(serde_json::json!({"error": "Entity not found"}));
+        }
+        Err(e) => {
+            log::error!("delete_entity lookup error: {:?}", e);
+            return HttpResponse::InternalServerError()
+                .json(serde_json::json!({"error": "Database error"}));
+        }
+        Ok(Some(_)) => {}
+    }
+
+    match dao.delete_entity(&cx, entity_id) {
+        Ok(()) => HttpResponse::NoContent().finish(),
+        Err(e) => {
+            log::error!("delete_entity error: {:?}", e);
+            HttpResponse::InternalServerError().json(serde_json::json!({"error": "Database error"}))
+        }
+    }
+}
+
+async fn merge_entities<D: KnowledgeDao + 'static>(
+    _claims: Claims,
+    body: web::Json<MergeRequest>,
+    dao: web::Data<Mutex<D>>,
+) -> impl Responder {
+    if body.source_id == body.target_id {
+        return HttpResponse::BadRequest()
+            .json(serde_json::json!({"error": "source_id and target_id must be different"}));
+    }
+
+    let cx = opentelemetry::Context::current();
+    let mut dao = dao.lock().expect("Unable to lock KnowledgeDao");
+
+    // Verify both entities exist
+    for id in [body.source_id, body.target_id] {
+        match dao.get_entity_by_id(&cx, id) {
+            Ok(None) => {
+                return HttpResponse::BadRequest()
+                    .json(serde_json::json!({"error": format!("Entity {} not found", id)}));
+            }
+            Err(e) => {
+                log::error!("merge_entities lookup error: {:?}", e);
+                return HttpResponse::InternalServerError()
+                    .json(serde_json::json!({"error": "Database error"}));
+            }
+            Ok(Some(_)) => {}
+        }
+    }
+
+    match dao.merge_entities(&cx, body.source_id, body.target_id) {
+        Ok((facts_transferred, links_transferred)) => HttpResponse::Ok().json(MergeResponse {
+            merged_entity_id: body.target_id,
+            deleted_entity_id: body.source_id,
+            facts_transferred,
+            links_transferred,
+        }),
+        Err(e) => {
+            log::error!("merge_entities error: {:?}", e);
+            HttpResponse::InternalServerError().json(serde_json::json!({"error": "Database error"}))
+        }
+    }
+}
+
+async fn list_facts<D: KnowledgeDao + 'static>(
+    _claims: Claims,
+    query: web::Query<FactListQuery>,
+    dao: web::Data<Mutex<D>>,
+) -> impl Responder {
+    let limit = query.limit.unwrap_or(50).min(200);
+    let offset = query.offset.unwrap_or(0);
+
+    let status_filter = match query.status.as_deref() {
+        None | Some("active") => Some("active".to_string()),
+        Some("all") => None,
+        Some(s) => Some(s.to_string()),
+    };
+
+    let filter = FactFilter {
+        entity_id: query.entity_id,
+        status: status_filter,
+        predicate: query.predicate.clone(),
+        limit,
+        offset,
+    };
+
+    let cx = opentelemetry::Context::current();
+    let mut dao = dao.lock().expect("Unable to lock KnowledgeDao");
+    match dao.list_facts(&cx, filter) {
+        Ok((facts, total)) => {
+            let mut summaries = Vec::with_capacity(facts.len());
+            for f in facts {
+                let subject_entity_name = dao
+                    .get_entity_by_id(&cx, f.subject_entity_id)
+                    .ok()
+                    .flatten()
+                    .map(|e| e.name);
+                let object_entity_name = if let Some(oid) = f.object_entity_id {
+                    dao.get_entity_by_id(&cx, oid)
+                        .ok()
+                        .flatten()
+                        .map(|e| e.name)
+                } else {
+                    None
+                };
+                summaries.push(FactSummary {
+                    id: f.id,
+                    subject_entity_id: f.subject_entity_id,
+                    subject_entity_name,
+                    predicate: f.predicate,
+                    object_entity_id: f.object_entity_id,
+                    object_entity_name,
+                    object_value: f.object_value,
+                    confidence: f.confidence,
+                    status: f.status,
+                    source_photo: f.source_photo,
+                    source_insight_id: f.source_insight_id,
+                    created_at: f.created_at,
+                });
+            }
+            HttpResponse::Ok().json(FactListResponse {
+                facts: summaries,
+                total,
+                limit,
+                offset,
+            })
+        }
+        Err(e) => {
+            log::error!("list_facts error: {:?}", e);
+            HttpResponse::InternalServerError().json(serde_json::json!({"error": "Database error"}))
+        }
+    }
+}
+
+async fn patch_fact<D: KnowledgeDao + 'static>(
+    _claims: Claims,
+    id: web::Path<i32>,
+    body: web::Json<FactPatchRequest>,
+    dao: web::Data<Mutex<D>>,
+) -> impl Responder {
+    let cx = opentelemetry::Context::current();
+    let fact_id = id.into_inner();
+    let patch = FactPatch {
+        predicate: body.predicate.clone(),
+        object_value: body.object_value.clone(),
+        status: body.status.clone(),
+        confidence: body.confidence,
+    };
+
+    let mut dao = dao.lock().expect("Unable to lock KnowledgeDao");
+    match dao.update_fact(&cx, fact_id, patch) {
+        Ok(Some(fact)) => HttpResponse::Ok().json(fact),
+        Ok(None) => HttpResponse::NotFound().json(serde_json::json!({"error": "Fact not found"})),
+        Err(e) => {
+            log::error!("patch_fact error: {:?}", e);
+            HttpResponse::InternalServerError().json(serde_json::json!({"error": "Database error"}))
+        }
+    }
+}
+
+async fn delete_fact<D: KnowledgeDao + 'static>(
+    _claims: Claims,
+    id: web::Path<i32>,
+    dao: web::Data<Mutex<D>>,
+) -> impl Responder {
+    let cx = opentelemetry::Context::current();
+    let fact_id = id.into_inner();
+    let mut dao = dao.lock().expect("Unable to lock KnowledgeDao");
+    match dao.delete_fact(&cx, fact_id) {
+        Ok(()) => HttpResponse::NoContent().finish(),
+        Err(e) => {
+            log::warn!("delete_fact({}) error: {:?}", fact_id, e);
+            HttpResponse::NotFound().json(serde_json::json!({"error": "Fact not found"}))
+        }
+    }
+}
+
+async fn get_recent<D: KnowledgeDao + 'static>(
+    _claims: Claims,
+    query: web::Query<RecentQuery>,
+    dao: web::Data<Mutex<D>>,
+) -> impl Responder {
+    let since = query
+        .since
+        .unwrap_or_else(|| Utc::now().timestamp() - 86400);
+    let limit = query.limit.unwrap_or(20).min(100);
+
+    let cx = opentelemetry::Context::current();
+    let mut dao = dao.lock().expect("Unable to lock KnowledgeDao");
+    match dao.get_recent_activity(&cx, since, limit) {
+        Ok(RecentActivity { entities, facts }) => {
+            let entity_summaries: Vec<EntitySummary> =
+                entities.into_iter().map(EntitySummary::from).collect();
+            HttpResponse::Ok().json(serde_json::json!({
+                "entities": entity_summaries,
+                "facts": facts
+            }))
+        }
+        Err(e) => {
+            log::error!("get_recent error: {:?}", e);
+            HttpResponse::InternalServerError().json(serde_json::json!({"error": "Database error"}))
+        }
+    }
+}

src/main.rs

@@ -67,6 +67,7 @@ mod tags;
 mod utils;
 mod video;
 
+mod knowledge;
 mod memories;
 mod otel;
 mod service;
@@ -1186,6 +1187,7 @@ fn main() -> std::io::Result<()> {
                 .service(ai::get_all_insights_handler)
                 .service(ai::get_available_models_handler)
                 .add_feature(add_tag_services::<_, SqliteTagDao>)
+                .add_feature(knowledge::add_knowledge_services::<_, SqliteKnowledgeDao>)
                 .app_data(app_data.clone())
                 .app_data::<Data<RealFileSystem>>(Data::new(RealFileSystem::new(
                     app_data.base_path.clone(),
@@ -1204,6 +1206,9 @@ fn main() -> std::io::Result<()> {
                 .app_data::<Data<Mutex<Box<dyn PreviewDao>>>>(Data::new(Mutex::new(Box::new(
                     preview_dao,
                 ))))
+                .app_data::<Data<Mutex<SqliteKnowledgeDao>>>(Data::new(Mutex::new(
+                    SqliteKnowledgeDao::new(),
+                )))
                 .app_data(web::JsonConfig::default().error_handler(|err, req| {
                     let detail = err.to_string();
                     log::warn!(

src/state.rs

@@ -1,8 +1,8 @@
 use crate::ai::{InsightGenerator, OllamaClient, SmsApiClient};
 use crate::database::{
-    CalendarEventDao, DailySummaryDao, ExifDao, InsightDao, LocationHistoryDao, SearchHistoryDao,
+    CalendarEventDao, DailySummaryDao, ExifDao, InsightDao, KnowledgeDao, LocationHistoryDao,
-    SqliteCalendarEventDao, SqliteDailySummaryDao, SqliteExifDao, SqliteInsightDao,
+    SearchHistoryDao, SqliteCalendarEventDao, SqliteDailySummaryDao, SqliteExifDao,
-    SqliteLocationHistoryDao, SqliteSearchHistoryDao,
+    SqliteInsightDao, SqliteKnowledgeDao, SqliteLocationHistoryDao, SqliteSearchHistoryDao,
 };
 use crate::database::{PreviewDao, SqlitePreviewDao};
 use crate::tags::{SqliteTagDao, TagDao};
@@ -119,6 +119,8 @@ impl Default for AppState {
             Arc::new(Mutex::new(Box::new(SqliteSearchHistoryDao::new())));
         let tag_dao: Arc<Mutex<Box<dyn TagDao>>> =
             Arc::new(Mutex::new(Box::new(SqliteTagDao::default())));
+        let knowledge_dao: Arc<Mutex<Box<dyn KnowledgeDao>>> =
+            Arc::new(Mutex::new(Box::new(SqliteKnowledgeDao::new())));
 
         // Load base path
         let base_path = env::var("BASE_PATH").expect("BASE_PATH was not set in the env");
@@ -134,6 +136,7 @@ impl Default for AppState {
             location_dao.clone(),
             search_dao.clone(),
             tag_dao.clone(),
+            knowledge_dao,
             base_path.clone(),
         );
 
@@ -200,6 +203,8 @@ impl AppState {
             Arc::new(Mutex::new(Box::new(SqliteSearchHistoryDao::new())));
         let tag_dao: Arc<Mutex<Box<dyn TagDao>>> =
             Arc::new(Mutex::new(Box::new(SqliteTagDao::default())));
+        let knowledge_dao: Arc<Mutex<Box<dyn KnowledgeDao>>> =
+            Arc::new(Mutex::new(Box::new(SqliteKnowledgeDao::new())));
 
         // Initialize test InsightGenerator with all data sources
         let base_path_str = base_path.to_string_lossy().to_string();
@@ -213,6 +218,7 @@ impl AppState {
             location_dao.clone(),
             search_dao.clone(),
             tag_dao.clone(),
+            knowledge_dao,
             base_path_str.clone(),
         );