self-review 2026-07-22: persist canonical snapshot on write routes; newest-first tie-break in node listings

Durability: the 2026-07-21 fix stopped read routes writing the canonical
snapshot but left no save on ANY write path — every mutation lived in RAM
until a manual POST /api/save. Observed live: two restarts reverted the
store to a 17h-old snapshot, destroying same-day writes. persist_canonical()
now runs after node/edge create, knowledge capture, forget, strengthen, and
load-merge. ISE telemetry excluded deliberately (48h-pruned, loss-tolerant,
~2/min; snapshotting 28MB per heartbeat is waste).

Listing order: scan routes sort by salience with store-order ties, so
equal-salience telemetry (all ISEs are 0.3) returned OLDEST first — a
limited /api/nodes query silently returned a stale window, and a 41h-old
heartbeat series read as a live outage during this review. Ties now break
newest-first by created_at.

engram/src/server.el

@@ -85,6 +85,26 @@ fn route_stats(method: String, path: String, body: String) -> String {
 // save/load with no "path" hit engram_save(""). Rewritten to the
 // `let x = if cond { a } else { b }` expression form (the pattern the newer
 // routes route_emit_ise/route_capture_knowledge already use correctly).
+// persist_canonical — save the canonical snapshot after a durable write.
+//
+// WHY (2026-07-22 self-review): the 2026-07-21 fix correctly stopped READ
+// routes from writing the canonical snapshot.json — but nothing was left
+// that saved it on WRITE. Every mutation (node create, edge create,
+// knowledge capture, forget, merge) lived only in RAM until someone POSTed
+// /api/save manually; a process restart silently discarded everything since
+// the last manual save. Observed live: two engram restarts during the
+// 2026-07-22 review reverted the store to a ~17h-old snapshot, destroying
+// same-day writes. Reads must never write the canonical; writes must always
+// persist it. ISE telemetry is deliberately excluded (48h-pruned, loss-
+// tolerant, ~2/min — snapshotting the whole store per heartbeat is waste;
+// any durable write that follows persists the pruning too).
+fn persist_canonical() -> Int {
+    let dir_raw: String = env("ENGRAM_DATA_DIR")
+    let dir: String = if str_eq(dir_raw, "") { "/tmp/engram" } else { dir_raw }
+    engram_save(dir + "/snapshot.json")
+    return 1
+}
+
 fn route_create_node(method: String, path: String, body: String) -> String {
     let content: String = json_get_string(body, "content")
     let nt_raw: String = json_get_string(body, "node_type")
@@ -92,6 +112,7 @@ fn route_create_node(method: String, path: String, body: String) -> String {
     let sal_raw: Float = json_get_float(body, "salience")
     let salience: Float = if sal_raw == 0.0 { 0.5 } else { sal_raw }
     let id: String = engram_node(content, node_type, salience)
+    let saved: Int = persist_canonical()
     "{\"id\":\"" + id + "\",\"content\":\"" + content + "\",\"node_type\":\"" + node_type + "\"}"
 }
 
@@ -159,6 +180,7 @@ fn route_create_edge(method: String, path: String, body: String) -> String {
     let w_raw: Float = json_get_float(body, "weight")
     let weight: Float = if w_raw == 0.0 { 0.5 } else { w_raw }
     engram_connect(from_id, to_id, weight, relation)
+    let saved: Int = persist_canonical()
     "{\"ok\":true,\"from_id\":\"" + from_id + "\",\"to_id\":\"" + to_id + "\",\"relation\":\"" + relation + "\"}"
 }
 
@@ -173,6 +195,7 @@ fn route_strengthen(method: String, path: String, body: String) -> String {
     let id: String = json_get_string(body, "node_id")
     if str_eq(id, "") { return err_json("missing node_id") }
     engram_strengthen(id)
+    let saved: Int = persist_canonical()
     ok_json()
 }
 
@@ -180,6 +203,7 @@ fn route_forget(method: String, path: String, body: String) -> String {
     let id: String = extract_id(path, "/api/nodes/")
     if str_eq(id, "") { return err_json("missing id") }
     engram_forget(id)
+    let saved: Int = persist_canonical()
     ok_json()
 }
 
@@ -244,6 +268,7 @@ fn route_load_merge(method: String, path: String, body: String) -> String {
     engram_load_merge(p)
     let added_n: Int = engram_node_count() - before_n
     let added_e: Int = engram_edge_count() - before_e
+    let saved: Int = persist_canonical()
     "{\"ok\":true,\"nodes_added\":" + int_to_str(added_n) + ",\"edges_added\":" + int_to_str(added_e) + ",\"node_count\":" + int_to_str(engram_node_count()) + "}"
 }
 
@@ -342,6 +367,7 @@ fn route_capture_knowledge(method: String, path: String, body: String) -> String
         sal, imp, conf,
         "Semantic", tags
     )
+    let saved: Int = persist_canonical()
     "{\"ok\":true,\"id\":\"" + id + "\"}"
 }