diff --git a/lang/releases/v1.0.0-20260501/el_runtime.c b/lang/releases/v1.0.0-20260501/el_runtime.c
index 35b006f..129986c 100644
--- a/lang/releases/v1.0.0-20260501/el_runtime.c
+++ b/lang/releases/v1.0.0-20260501/el_runtime.c
@@ -7077,16 +7077,33 @@ el_val_t engram_activate(el_val_t query, el_val_t depth) {
     }
 
     /* Persist working_memory_weight (post Pass 3) to node store.
-     * Also emit ISE when a node transitions into working memory (was 0, now > 0.5),
+     *
+     * ACT-R semantics: spreading activation is additive. An absent spreading
+     * source contributes zero to the spread term but does NOT override existing
+     * base-level / WM state. Nodes not reached by this activation pass therefore
+     * retain their current working_memory_weight, decayed by ENGRAM_WM_DECAY
+     * (the per-turn attenuation factor). This replaces the prior behaviour of
+     * zeroing every non-reached node on each call, which destroyed WM state
+     * accumulated by MCP-layer activations within one tick of idle operation.
+     *
+     * Hard floor: weights decayed below 0.005 are cleared to 0.0 to avoid
+     * an infinite tail of near-zero values accumulating.
+     *
+     * Also emit ISE when a node transitions into working memory (was 0, now > 0.1),
      * excluding InternalStateEvent nodes to prevent ISEs about ISEs. */
     for (int64_t i = 0; i < g->node_count; i++) {
         EngramNode* wn = &g->nodes[i];
         double prev_wm = wn->working_memory_weight;
+        /* Nodes not participating in this pass: decay rather than zero. */
+        if (!reached[i] || best_bg[i] <= 0.0) {
+            if (prev_wm > 0.0) {
+                double decayed = prev_wm * ENGRAM_WM_DECAY;
+                wn->working_memory_weight = (decayed < 0.005) ? 0.0 : decayed;
+            }
+            continue;
+        }
         wn->working_memory_weight = wm_weights[i];
-        /* ISE: working memory promotion — on 0→>0.1 transition, non-ISE nodes.
-         * Threshold lowered from 0.5 to 0.1 so quieter promotions are observable.
-         * Previously only very strong promotions (wm_weight>0.5) fired an ISE,
-         * leaving most activations invisible in the state-event log. */
+        /* ISE: working memory promotion — on 0→>0.1 transition, non-ISE nodes. */
         if (prev_wm <= 0.0 && wm_weights[i] > 0.1 &&
             wn->node_type && strcmp(wn->node_type, "InternalStateEvent") != 0) {
             char ise_buf[512];