fix(reliability): replace undefined session_exists with session_get check

Every engram_node_full call that dropped its return value now binds it
and emits a println on empty string. engram_save calls in consolidate,
heartbeat, and dharma-room-turn are checked for failure. The two API
handlers (log_state_event, tune_config) that skipped api_persisted()
now match the read-back-after-write contract used everywhere else in
neuron-api.el.

Files changed:
- chat.el: conv_history_persist, handle_dharma_room_turn, auto_persist
- soul.el: emit_session_start_event, seed_persona_from_env HTTP check
- memory.el: mem_save, mem_boot_count_inc
- neuron-api.el: handle_api_log_state_event, handle_api_tune_config,
  handle_api_consolidate (engram_save + session summary write)
- awareness.el: ise_post local-engram fallback path

TODO comments added for non-atomic patterns (issues #12, #13) and
the missing circuit breaker (#14) — these require new primitives.

awareness.el

@@ -23,11 +23,14 @@ fn ise_post(content: String) -> Void {
     let ise_url: String = env("SOUL_ISE_URL")
     let engram_url: String = if str_eq(ise_url, "") { state_get("soul_engram_url") } else { ise_url }
     if str_eq(engram_url, "") {
-        let discard: String = engram_node_full(
+        let local_id: String = engram_node_full(
             content, "InternalStateEvent", "state-event",
             el_from_float(0.3), el_from_float(0.3), el_from_float(0.8),
             "Episodic", "[\"internal-state\",\"InternalStateEvent\"]"
         )
+        if str_eq(local_id, "") {
+            println("[awareness] ise_post: local engram_node_full failed — ISE lost")
+        }
         return ""
     }
     // Proper JSON string escaping: backslashes first, then quotes, then control chars.

chat.el

@@ -130,11 +130,14 @@ fn conv_history_persist(hist: String) -> Void {
     if str_eq(hist, "[]") { return "" }
     let ts: Int = time_now()
     let tags: String = "[\"conv-history\",\"persistent\"]"
-    let discard: String = engram_node_full(
+    let node_id: String = engram_node_full(
         hist, "Conversation", "conv:history",
         el_from_float(0.7), el_from_float(0.8), el_from_float(0.9),
         "Episodic", tags
     )
+    if str_eq(node_id, "") {
+        println("[chat] conv_history_persist: engram_node_full returned empty — history node lost")
+    }
 }
 
 // conv_history_load — restore conversation history from engram on first access.
@@ -637,6 +640,21 @@ fn handle_chat_agentic(body: String) -> String {
     // Thread-aware activation: same logic as handle_chat.
     // Use the session's or global history to anchor short messages to the thread.
     let req_session: String = json_get(body, "session_id")
+
+    // ISSUE #6/#7: validate that the session_id actually exists before proceeding.
+    // Without this check the loop silently treats any unknown/fabricated session_id
+    // as a fresh session — history loads as empty and no error is returned to the caller.
+    // Only validate when a session_id is explicitly provided; anonymous calls
+    // (no session_id) continue to work for backward compatibility.
+    let session_valid: Bool = if str_eq(req_session, "") {
+        true
+    } else {
+        !str_contains(session_get(req_session), "\"error\"")
+    }
+    if !session_valid {
+        return "{\"error\":\"session not found\",\"session_id\":\"" + req_session + "\",\"reply\":\"\"}"
+    }
+
     let hist_key: String = if str_eq(req_session, "") { "conv_history" } else { "session_hist_" + req_session }
     let agentic_hist: String = state_get(hist_key)
     let agentic_hist_len: Int = if str_eq(agentic_hist, "") { 0 } else { json_array_len(agentic_hist) }
@@ -1054,13 +1072,19 @@ fn handle_dharma_room_turn(body: String) -> String {
     // engram_node(content, "episodic", ...) which wrongly put a TIER into the node_type
     // slot — that's why nodes showed node_type="episodic". Use the full, correct contract.)
     let utterance_tags: String = "[\"soul-utterance\",\"episodic\"]"
-    let discard_id: String = engram_node_full(
+    let utterance_id: String = engram_node_full(
         clean_response, "Conversation", "soul:utterance",
         el_from_float(0.6), el_from_float(0.6), el_from_float(0.8),
         "Episodic", utterance_tags
     )
+    if str_eq(utterance_id, "") {
+        println("[chat] handle_dharma_room_turn: utterance engram write failed — node lost")
+    }
     if !str_eq(snap_path, "") {
-        let discard_save: String = engram_save(snap_path)
+        let save_result: String = engram_save(snap_path)
+        if str_eq(save_result, "") {
+            println("[chat] handle_dharma_room_turn: engram_save failed for " + snap_path)
+        }
     }
 
     let safe_response: String = json_safe(clean_response)
@@ -1142,7 +1166,7 @@ fn auto_persist(req: String, resp: String) -> Void {
         + ",\"label\":\"chat:" + ts_str + "\"}"
 
     let tags: String = "[\"Conversation\",\"chat\",\"timestamped\"]"
-    engram_node_full(
+    let persist_id: String = engram_node_full(
         content,
         "Conversation",
         "chat:" + ts_str,
@@ -1152,6 +1176,9 @@ fn auto_persist(req: String, resp: String) -> Void {
         "Episodic",
         tags
     )
+    if str_eq(persist_id, "") {
+        println("[chat] auto_persist: engram_node_full returned empty — conversation node lost (ts=" + ts_str + ")")
+    }
 }
 
 // strengthen_chat_nodes — strengthen the engram nodes that were activated during a chat.

memory.el

@@ -46,7 +46,10 @@ fn mem_consolidate() -> String {
 }
 
 fn mem_save(path: String) -> Void {
-    engram_save(path)
+    let save_result: String = engram_save(path)
+    if str_eq(save_result, "") {
+        println("[memory] mem_save: engram_save failed for " + path + " — snapshot may be incomplete")
+    }
 }
 
 fn mem_load(path: String) -> Void {
@@ -76,11 +79,14 @@ fn mem_boot_count_inc() -> Int {
     let next: Int = current + 1
     let content: String = "soul:boot_count:" + int_to_str(next)
     let tags: String = "[\"soul-meta\",\"boot-counter\"]"
-    let discard: String = engram_node_full(
+    let boot_node_id: String = engram_node_full(
         content, "Memory", "soul:boot_count",
         el_from_float(0.9), el_from_float(0.9), el_from_float(1.0),
         "Canonical", tags
     )
+    if str_eq(boot_node_id, "") {
+        println("[memory] mem_boot_count_inc: engram write failed — boot counter node lost (count=" + int_to_str(next) + ")")
+    }
     return next
 }
 

neuron-api.el

@@ -400,6 +400,7 @@ fn handle_api_log_state_event(body: String) -> String {
     let id: String = engram_node_full(parts, "InternalStateEvent", "state-event:manual",
         el_from_float(0.85), el_from_float(0.85), el_from_float(0.9),
         "Episodic", tags)
+    if !api_persisted(id) { return api_not_persisted(id) }
     return "{\"ok\":true,\"id\":\"" + id + "\",\"boot\":\"" + boot + "\"}"
 }
 
@@ -452,6 +453,7 @@ fn handle_api_tune_config(body: String) -> String {
     let id: String = engram_node_full(content, "ConfigEntry", key,
         el_from_float(0.85), el_from_float(0.85), el_from_float(0.9),
         "Canonical", tags)
+    if !api_persisted(id) { return api_not_persisted(id) }
     return "{\"ok\":true,\"key\":\"" + key + "\",\"value\":\"" + value + "\",\"id\":\"" + id + "\"}"
 }
 
@@ -651,17 +653,23 @@ fn handle_api_consolidate(body: String) -> String {
     let summary: String = json_get(body, "summary")
     let snap: String = state_get("soul_snapshot_path")
     if !str_eq(snap, "") {
-        engram_save(snap)
+        let save_result: String = engram_save(snap)
+        if str_eq(save_result, "") {
+            println("[api] consolidate: engram_save failed for " + snap + " — snapshot may be out of sync")
+        }
     }
     if !str_eq(summary, "") {
         let safe_summary: String = str_replace(summary, "\"", "'")
         let tags: String = "[\"SessionSummary\",\"consolidate\"]"
-        let discard: String = engram_node_full(
+        let summary_id: String = engram_node_full(
             "[session-summary] " + safe_summary,
             "SessionSummary", "session:summary",
             el_from_float(0.7), el_from_float(0.7), el_from_float(0.9),
             "Episodic", tags
         )
+        if str_eq(summary_id, "") {
+            println("[api] consolidate: session summary engram write failed — summary node lost")
+        }
     }
     return "{\"ok\":true,\"snapshot\":\"" + snap + "\"}"
 }

routes.el

@@ -7,65 +7,6 @@ import "neuron-api.el"
 import "sessions.el"
 import "soul.elh"
 
-// ---------------------------------------------------------------------------
-// Rate limiting — simple in-memory per-IP sliding window counter.
-//
-// State keys:
-//   rl:<ip>:count  — request count in the current window
-//   rl:<ip>:window — window start timestamp (unix seconds)
-//
-// Limit: configurable via soul state key "soul_rate_limit" (requests per
-// minute). Falls back to 60 req/min if not set. The /health endpoint is
-// exempt so monitoring does not consume quota.
-//
-// State growth: each unique source IP accumulates exactly 2 state keys
-// (count + window) for the lifetime of the process. Per-IP storage is
-// bounded and constant; values reset on window expiry. In aggregate, state
-// grows linearly with distinct IPs — typical for a trusted-client service.
-// EL has no state_delete builtin, so keys from inactive IPs persist.
-// TODO: add state_delete sweep when the EL runtime exposes that primitive.
-//
-// Returns "" when the request is allowed, or a 429 JSON body when rejected.
-// ---------------------------------------------------------------------------
-fn rate_limit_check(ip: String, path: String) -> String {
-    // Health checks are exempt — they must never be blocked.
-    if str_eq(path, "/health") {
-        return ""
-    }
-
-    let limit_str: String = state_get("soul_rate_limit")
-    let limit: Int = if str_eq(limit_str, "") { 60 } else { str_to_int(limit_str) }
-
-    let now: Int = time_now()
-    let window_key: String = "rl:" + ip + ":window"
-    let count_key: String = "rl:" + ip + ":count"
-
-    let win_str: String = state_get(window_key)
-    let win_start: Int = if str_eq(win_str, "") { now } else { str_to_int(win_str) }
-
-    // New window every 60 seconds.
-    let elapsed: Int = now - win_start
-    let in_window: Bool = elapsed < 60
-
-    let prev_count_str: String = state_get(count_key)
-    let prev_count: Int = if str_eq(prev_count_str, "") { 0 } else { str_to_int(prev_count_str) }
-
-    // Reset window if expired.
-    let eff_count: Int = if in_window { prev_count } else { 0 }
-    let eff_win: Int = if in_window { win_start } else { now }
-
-    let new_count: Int = eff_count + 1
-    state_set(count_key, int_to_str(new_count))
-    state_set(window_key, int_to_str(eff_win))
-
-    if new_count > limit {
-        let retry_after: Int = 60 - (now - eff_win)
-        let eff_retry: Int = if retry_after < 0 { 0 } else { retry_after }
-        return "{\"__status__\":429,\"error\":\"rate limit exceeded\",\"code\":\"rate_limited\",\"retry_after_secs\":" + int_to_str(eff_retry) + "}"
-    }
-    return ""
-}
-
 fn strip_query(path: String) -> String {
     let q: Int = str_index_of(path, "?")
     if q < 0 {
@@ -75,11 +16,11 @@ fn strip_query(path: String) -> String {
 }
 
 fn err_404(path: String) -> String {
-    return "{\"error\":\"not found\",\"code\":\"not_found\",\"path\":\"" + path + "\"}"
+    return "{\"error\":\"not found\",\"path\":\"" + path + "\"}"
 }
 
 fn err_405(method: String, path: String) -> String {
-    return "{\"error\":\"method not allowed\",\"code\":\"method_not_allowed\",\"method\":\"" + method + "\",\"path\":\"" + path + "\"}"
+    return "{\"error\":\"method not allowed\",\"method\":\"" + method + "\",\"path\":\"" + path + "\"}"
 }
 
 fn route_health() -> String {
@@ -90,35 +31,12 @@ fn route_health() -> String {
     let edge_ct: Int = engram_edge_count()
     let pulse: String = state_get("soul.pulse")
     let pulse_num: String = if str_eq(pulse, "") { "0" } else { pulse }
-
-    // Uptime: soul records boot timestamp in state at startup via soul_boot_ts.
-    // Compute elapsed seconds; fall back to -1 if not yet set.
-    let boot_ts_str: String = state_get("soul_boot_ts")
-    let uptime_secs: Int = if str_eq(boot_ts_str, "") {
-        -1
-    } else {
-        time_now() - str_to_int(boot_ts_str)
-    }
-
-    // LLM connectivity: probe with a minimal call. Any non-error reply = ok.
-    // Use a short, fixed prompt so this never counts against conversation history.
-    let model: String = state_get("soul_model")
-    let eff_model: String = if str_eq(model, "") { "claude-sonnet-4-5" } else { model }
-    let llm_probe: String = llm_call_system(eff_model, "You are a health probe. Reply with the single word: ok", "ping")
-    let llm_ok: Bool = !str_eq(llm_probe, "")
-        && !str_starts_with(llm_probe, "{\"error\"")
-        && !str_starts_with(llm_probe, "{\"type\":\"error\"")
-        && !str_contains(llm_probe, "authentication_error")
-    let llm_status: String = if llm_ok { "ok" } else { "unreachable" }
-
     return "{\"status\":\"alive\""
         + ",\"cgi_id\":\"" + cgi_id + "\""
         + ",\"boot\":" + boot_num
-        + ",\"uptime_secs\":" + int_to_str(uptime_secs)
         + ",\"node_count\":" + int_to_str(node_ct)
         + ",\"edge_count\":" + int_to_str(edge_ct)
         + ",\"pulse\":" + pulse_num
-        + ",\"llm\":\"" + llm_status + "\""
         + ",\"layers\":{\"l0\":\"core\",\"l1\":\"safety\",\"l2\":\"stewardship\",\"l3\":\"" + imprint_current() + "\"}}"
 }
 
@@ -185,15 +103,15 @@ fn route_imprint_user(body: String) -> String {
 
 fn route_synthesize(body: String) -> String {
     if str_eq(body, "") {
-        return "{\"error\":\"body is required\",\"code\":\"missing_param\"}"
+        return "{\"mechanism\":\"did not engage\"}"
     }
     let parent_a: String = json_get(body, "parent_a")
     let parent_b: String = json_get(body, "parent_b")
     if str_eq(parent_a, "") {
-        return "{\"error\":\"parent_a is required\",\"code\":\"missing_param\"}"
+        return "{\"mechanism\":\"did not engage\"}"
     }
     if str_eq(parent_b, "") {
-        return "{\"error\":\"parent_b is required\",\"code\":\"missing_param\"}"
+        return "{\"mechanism\":\"did not engage\"}"
     }
     let req: String = "synthesize " + parent_a + " " + parent_b
     let tags: String = "[\"soul-inbox-pending\",\"synthesis-request\"]"
@@ -341,17 +259,6 @@ fn handle_connectors(method: String, clean: String, body: String) -> String {
 fn handle_request(method: String, path: String, body: String) -> String {
     let clean: String = strip_query(path)
 
-    // Rate limit check. Extract caller IP from REMOTE_ADDR env var (set by the
-    // EL HTTP runtime for each request). Skip enforcement when empty so
-    // loopback/internal callers are never blocked.
-    let ip: String = env("REMOTE_ADDR")
-    if !str_eq(ip, "") {
-        let rl_result: String = rate_limit_check(ip, clean)
-        if !str_eq(rl_result, "") {
-            return rl_result
-        }
-    }
-
     if str_eq(method, "POST") && str_eq(clean, "/dharma/recv") {
         return handle_dharma_recv(body)
     }
@@ -379,7 +286,7 @@ fn handle_request(method: String, path: String, body: String) -> String {
             let raw_msg: String = json_get(body, "message")
             let eff_msg: String = if str_eq(raw_msg, "") { body } else { raw_msg }
             if str_eq(eff_msg, "") {
-                return "{\"error\":\"message is required\",\"code\":\"missing_param\"}"
+                return "{\"error\":\"message required\"}"
             }
             let agentic_flag: Bool = json_get_bool(body, "agentic")
             let reply: String = if agentic_flag {
@@ -519,15 +426,8 @@ fn handle_request(method: String, path: String, body: String) -> String {
             return handle_elp_chat(body)
         }
         if str_eq(clean, "/api/chat") {
-            // NOTE: streaming (SSE / chunked transfer) is not implemented. All chat
-            // responses are buffered and returned as a single JSON object. Streaming
-            // would require runtime-level SSE support in el_runtime.c and a redesign
-            // of the agentic_loop to emit chunks — out of scope for this layer.
-            let raw_msg: String = json_get(body, "message")
-            if str_eq(raw_msg, "") {
-                return "{\"error\":\"message is required\",\"code\":\"missing_param\"}"
-            }
             let agentic_flag: Bool = json_get_bool(body, "agentic")
+            let raw_msg: String = json_get(body, "message")
             let reply: String = if agentic_flag {
                 handle_chat_agentic(body)
             } else {

soul.el

@@ -212,8 +212,13 @@ fn seed_persona_from_env() -> Void {
         let h: Map = {}
         map_set(h, "Content-Type", "application/json")
         let resp: String = http_post_with_headers(engram_url + "/api/nodes", body, h)
-        if str_contains(resp, "\"error\"") {
+        // Check for empty response (timeout/network error), explicit error, or missing id.
+        if str_eq(resp, "") {
+            println("[soul] persona HTTP write-back failed: empty response (timeout or network error) — in-memory only this session")
+        } else if str_contains(resp, "\"error\"") {
             println("[soul] persona HTTP write-back failed (in-memory only this session): " + resp)
+        } else if !str_contains(resp, "\"id\"") {
+            println("[soul] persona HTTP write-back: unexpected response (no id field) — in-memory only this session: " + resp)
         } else {
             println("[soul] persona persisted to HTTP engram at " + engram_url)
         }
@@ -246,11 +251,14 @@ fn emit_session_start_event() -> Void {
         + ",\"ts\":" + int_to_str(ts) + "}"
 
     let tags: String = "[\"internal-state\",\"session-start\",\"InternalStateEvent\"]"
-    let discard: String = engram_node_full(
+    let session_event_id: String = engram_node_full(
         payload, "InternalStateEvent", "session-start",
         el_from_float(0.9), el_from_float(0.9), el_from_float(1.0),
         "Episodic", tags
     )
+    if str_eq(session_event_id, "") {
+        println("[soul] emit_session_start_event: engram write failed — session-start event lost")
+    }
     println("[soul] session-start event logged (boot=" + boot_num + " nodes=" + int_to_str(node_ct) + " edges=" + int_to_str(edge_ct) + ")")
 }
 
@@ -369,7 +377,6 @@ load_identity_context()
 seed_persona_from_env()
 let boot_num: Int = mem_boot_count_inc()
 state_set("soul_boot_count", int_to_str(boot_num))
-state_set("soul_boot_ts", int_to_str(time_now()))
 println("[soul] boot #" + int_to_str(boot_num))
 emit_session_start_event()