diff --git a/src/knowledge.rs b/src/knowledge.rs
index 91fbd13..3baa900 100644
--- a/src/knowledge.rs
+++ b/src/knowledge.rs
@@ -11,6 +11,7 @@ use crate::database::{
     RecentActivity,
 };
 use crate::personas::PersonaDaoData;
+use crate::state::AppState;
 
 /// Resolve the `X-Persona-Id` header into a `PersonaFilter`. Missing
 /// header → `'default'`. If the persona has `include_all_memories=true`,
@@ -248,6 +249,18 @@ pub struct SupersedeRequest {
     pub by_fact_id: i32,
 }
 
+#[derive(Deserialize)]
+pub struct SynthesizeMergeRequest {
+    pub source_id: i32,
+    pub target_id: i32,
+}
+
+#[derive(serde::Serialize)]
+pub struct SynthesizeMergeResponse {
+    pub proposed_description: String,
+    pub model_used: String,
+}
+
 #[derive(Deserialize)]
 pub struct FactCreateRequest {
     pub subject_entity_id: i32,
@@ -300,6 +313,10 @@ where
         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/synthesize-merge")
+                    .route(web::post().to(synthesize_merge::<D>)),
+            )
             .service(
                 web::resource("/entities/{id}")
                     .route(web::get().to(get_entity::<D>))
@@ -634,6 +651,110 @@ async fn merge_entities<D: KnowledgeDao + 'static>(
     }
 }
 
+/// Preview a merged-description before the actual merge fires. Calls
+/// the local Ollama with both entities' names + descriptions and
+/// returns a synthesized rewrite that combines them. The curator
+/// previews, edits, and either accepts (PATCH target's description
+/// then POST /merge) or skips (just /merge as-is).
+///
+/// Deliberately doesn't touch the database — read-only on entities,
+/// no LLM call gets to write anything. If the model is unavailable
+/// the handler returns 503 so the UI can degrade gracefully (skip
+/// the preview, fall back to the existing merge action).
+async fn synthesize_merge<D: KnowledgeDao + 'static>(
+    _claims: Claims,
+    body: web::Json<SynthesizeMergeRequest>,
+    dao: web::Data<Mutex<D>>,
+    app_state: web::Data<AppState>,
+) -> impl Responder {
+    if body.source_id == body.target_id {
+        return HttpResponse::BadRequest()
+            .json(serde_json::json!({"error": "source_id and target_id must differ"}));
+    }
+
+    let cx = opentelemetry::Context::current();
+    let mut dao = dao.lock().expect("Unable to lock KnowledgeDao");
+
+    let source = match dao.get_entity_by_id(&cx, body.source_id) {
+        Ok(Some(e)) => e,
+        Ok(None) => {
+            return HttpResponse::BadRequest()
+                .json(serde_json::json!({"error": "source entity not found"}));
+        }
+        Err(e) => {
+            log::error!("synthesize_merge source lookup: {:?}", e);
+            return HttpResponse::InternalServerError()
+                .json(serde_json::json!({"error": "Database error"}));
+        }
+    };
+    let target = match dao.get_entity_by_id(&cx, body.target_id) {
+        Ok(Some(e)) => e,
+        Ok(None) => {
+            return HttpResponse::BadRequest()
+                .json(serde_json::json!({"error": "target entity not found"}));
+        }
+        Err(e) => {
+            log::error!("synthesize_merge target lookup: {:?}", e);
+            return HttpResponse::InternalServerError()
+                .json(serde_json::json!({"error": "Database error"}));
+        }
+    };
+
+    // Drop the DAO lock before the LLM call — the generate request
+    // is the slow part (seconds) and we don't want to block other
+    // knowledge reads while it runs.
+    drop(dao);
+
+    let source_desc = if source.description.trim().is_empty() {
+        "(none)".to_string()
+    } else {
+        source.description.clone()
+    };
+    let target_desc = if target.description.trim().is_empty() {
+        "(none)".to_string()
+    } else {
+        target.description.clone()
+    };
+
+    let system = "You are condensing two stored entity descriptions into one. The two \
+        entities refer to the same real-world thing and are about to be merged. Write a \
+        single neutral third-person description (1-2 sentences, max 300 chars) that \
+        preserves any concrete facts in either source. Do not invent details. Do not \
+        editorialize. Return ONLY the merged description — no preamble, no quotes.";
+    let prompt = format!(
+        "Entity A: {} [{}]\nDescription: {}\n\nEntity B: {} [{}]\nDescription: {}\n\nMerged description:",
+        source.name, source.entity_type, source_desc,
+        target.name, target.entity_type, target_desc,
+    );
+
+    let ollama = app_state.ollama.clone();
+    let model_used = ollama.primary_model.clone();
+    let proposed = match ollama.generate(&prompt, Some(system)).await {
+        Ok(out) => {
+            // Some models open with their own framing — strip a
+            // leading quote or "Merged:" lead-in defensively.
+            let cleaned = out
+                .trim()
+                .trim_start_matches("Merged description:")
+                .trim()
+                .trim_matches(|c| c == '"' || c == '\'')
+                .to_string();
+            cleaned
+        }
+        Err(e) => {
+            log::warn!("synthesize_merge generate failed: {:?}", e);
+            return HttpResponse::ServiceUnavailable().json(serde_json::json!({
+                "error": "LLM unavailable; the merge picker should fall back to skip-synthesis."
+            }));
+        }
+    };
+
+    HttpResponse::Ok().json(SynthesizeMergeResponse {
+        proposed_description: proposed,
+        model_used,
+    })
+}
+
 async fn list_facts<D: KnowledgeDao + 'static>(
     req: HttpRequest,
     claims: Claims,