chore(metrics): drop_reason::LIQUIDATOR_NOT_DEPLOYED + Grafana panel (closes #402)

crates/charon-cli/src/main.rs

@@ -2349,6 +2349,44 @@ async fn process_opportunity(
         sim,
         provider: pipeline.provider.as_ref(),
     };
+
+    // Issue #402: probe `eth_getCode` at the liquidator address before
+    // the simulation gate. If empty, label the drop
+    // `liquidator_not_deployed` and return early; otherwise fall
+    // through to `encode_and_simulate` whose Err arm now genuinely
+    // means the liquidation logic reverted (`sim_revert`).
+    match pipeline
+        .provider
+        .as_ref()
+        .get_code_at(pipeline.liquidator)
+        .block_id(alloy::eips::BlockId::latest())
+        .await
+    {
+        Ok(code) if code.is_empty() => {
+            charon_metrics::record_opportunity_dropped(chain, drop_stage::SIMULATION);
+            charon_metrics::record_opportunity_dropped_reason(
+                chain,
+                drop_reason::LIQUIDATOR_NOT_DEPLOYED,
+            );
+            warn!(
+                chain,
+                liquidator = %pipeline.liquidator,
+                borrower = %pos.borrower,
+                "liquidator contract has empty bytecode at head — opportunity dropped"
+            );
+            return Ok(false);
+        }
+        Ok(_) => {}
+        Err(err) => {
+            debug!(
+                chain,
+                liquidator = %pipeline.liquidator,
+                error = ?err,
+                "liquidator bytecode probe failed; deferring to simulator"
+            );
+        }
+    }
+
     let sim_block = pipeline
         .replay_block
         .map(BlockNumberOrTag::Number)

crates/charon-metrics/src/lib.rs

@@ -270,6 +270,14 @@ pub mod drop_reason {
     /// opportunity passed every earlier gate but the broadcast
     /// stage rejected it.
     pub const SUBMIT_FAILED: &str = "submit_failed";
+    /// Simulation reverted with the well-known "no code at address"
+    /// payload — the configured CharonLiquidator address has empty
+    /// bytecode on the connected chain, distinct from the liquidation
+    /// logic itself reverting (#402). The startup gate added in
+    /// #399 catches this at boot for chains with a router config;
+    /// this counter covers the runtime self-destruct edge case and
+    /// any scan-only / replay path that bypasses the startup gate.
+    pub const LIQUIDATOR_NOT_DEPLOYED: &str = "liquidator_not_deployed";
 }
 
 /// Issue #397: outcome label on `EXECUTOR_BROADCASTS_TOTAL`. Mirrors
@@ -1034,6 +1042,10 @@ mod tests {
         assert_eq!(drop_reason::GAS_CEILING, "gas_ceiling");
         assert_eq!(drop_reason::TTL_EXPIRED, "ttl_expired");
         assert_eq!(drop_reason::SUBMIT_FAILED, "submit_failed");
+        assert_eq!(
+            drop_reason::LIQUIDATOR_NOT_DEPLOYED,
+            "liquidator_not_deployed"
+        );
     }
 
     /// Issue #397: pin the public surface of the broadcast / inclusion
@@ -1088,6 +1100,7 @@ mod tests {
         record_opportunity_dropped_reason("bnb", drop_reason::GAS_CEILING);
         record_opportunity_dropped_reason("bnb", drop_reason::TTL_EXPIRED);
         record_opportunity_dropped_reason("bnb", drop_reason::SUBMIT_FAILED);
+        record_opportunity_dropped_reason("bnb", drop_reason::LIQUIDATOR_NOT_DEPLOYED);
         // Issue #397: broadcast / inclusion / realised-profit
         record_broadcast("bnb", broadcast_result::SUBMITTED);
         record_broadcast("bnb", broadcast_result::TIMEOUT);

deploy/grafana/charon.json

@@ -395,7 +395,7 @@
         {
           "datasource": { "type": "prometheus", "uid": "${datasource}" },
           "editorMode": "code",
-          "expr": "sum by (stage) (rate(charon_executor_opportunities_dropped_total{instance=~\"$instance\",chain=~\"$chain\",job=~\"$job\"}[$__rate_interval])) * 60",
+          "expr": "sum by (stage) (rate(charon_executor_opportunities_dropped_total{instance=~\"$instance\",chain=~\"$chain\",job=~\"$job\",stage!=\"\"}[$__rate_interval])) * 60",
           "legendFormat": "{{stage}}",
           "range": true,
           "refId": "B"
@@ -404,6 +404,43 @@
       "title": "Executor — opportunities queued vs dropped",
       "type": "timeseries"
     },
+    {
+      "datasource": { "type": "prometheus", "uid": "${datasource}" },
+      "description": "Drops broken out by root-cause reason label (issue #368 + #402). Distinguishes 'sim_revert' (the liquidation logic reverted) from 'liquidator_not_deployed' (no code at the configured CharonLiquidator address) so a misconfigured fork or a runtime self-destruct surfaces as its own series rather than collapsing into a generic SIM_REVERT.",
+      "fieldConfig": {
+        "defaults": {
+          "color": { "mode": "palette-classic" },
+          "custom": {
+            "axisLabel": "opps / min",
+            "drawStyle": "bars",
+            "fillOpacity": 80,
+            "lineWidth": 1,
+            "showPoints": "never",
+            "stacking": { "group": "A", "mode": "normal" }
+          },
+          "unit": "short"
+        },
+        "overrides": []
+      },
+      "gridPos": { "h": 8, "w": 12, "x": 0, "y": 24 },
+      "id": 12,
+      "options": {
+        "legend": { "displayMode": "list", "placement": "bottom", "showLegend": true },
+        "tooltip": { "mode": "multi", "sort": "none" }
+      },
+      "targets": [
+        {
+          "datasource": { "type": "prometheus", "uid": "${datasource}" },
+          "editorMode": "code",
+          "expr": "sum by (reason) (rate(charon_opportunities_dropped_total{instance=~\"$instance\",chain=~\"$chain\",job=~\"$job\"}[$__rate_interval])) * 60",
+          "legendFormat": "{{reason}}",
+          "range": true,
+          "refId": "A"
+        }
+      ],
+      "title": "Executor — drops by reason",
+      "type": "timeseries"
+    },
     {
       "datasource": { "type": "prometheus", "uid": "${datasource}" },
       "description": "Distribution of per-opportunity net profit (USD cents). Heat-map uses the underlying histogram buckets.",