fix(scanner): per-feed Chainlink max_age overrides (closes #331)

config/default.toml

@@ -107,3 +107,13 @@ BTCB = "0x8ECF7dE377F788A813F5215668E282556b35f300" # BTC / USD — 18-dec Aggre
 ETH  = "0x9ef1B8c0E4F7dc8bF5719Ea496883DC6401d5b2e"
 USDT = "0xB97Ad0E74fa7d920791E90258A6E2085088b4320"
 USDC = "0x51597f405303C4377E36123cBc172b13269EA163"
+
+# Per-feed staleness windows (seconds). Stable-coin Chainlink feeds on
+# BSC update on deviation, not heartbeat — the global 600s default
+# routinely flags USDT / USDC / FDUSD as stale even when the price has
+# not moved, and the freshness gate then drops every position priced
+# against them. Volatile feeds (BNB / ETH / BTCB) keep the global
+# default; only stables override here. See #331.
+[chainlink_max_age_secs.bnb]
+USDT = 86400
+USDC = 86400

config/fork.toml

@@ -100,3 +100,11 @@ BTCB = "0x8ECF7dE377F788A813F5215668E282556b35f300" # BTC / USD — 18-dec Aggre
 ETH  = "0x9ef1B8c0E4F7dc8bF5719Ea496883DC6401d5b2e"
 USDT = "0xB97Ad0E74fa7d920791E90258A6E2085088b4320"
 USDC = "0x51597f405303C4377E36123cBc172b13269EA163"
+
+# Per-feed staleness windows (seconds). Stable feeds (USDT/USDC) on BSC
+# are deviation-triggered — heartbeat ~24h. The global 600s default
+# routinely flags them stale and silently drops every position priced
+# against them. Match `default.toml`. See #331.
+[chainlink_max_age_secs.bnb]
+USDT = 86400
+USDC = 86400

crates/charon-cli/src/main.rs

@@ -41,7 +41,7 @@
 //!   and a fresh scan is cheaper than reconciling retroactive bucket
 //!   transitions.
 
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 use std::path::PathBuf;
 use std::str::FromStr;
 use std::sync::Arc;
@@ -604,10 +604,24 @@ async fn run_listen(config: &Config, borrowers: Vec<Address>, execute: bool) ->
                 .get(chain_name)
                 .cloned()
                 .unwrap_or_default();
-            let prices = Arc::new(PriceCache::new(
+            // Per-symbol max_age overrides: stable feeds (USDT/USDC/FDUSD)
+            // update on deviation, not heartbeat, so the global 600s
+            // default flags them as stale even when the price has not
+            // moved. Operators set these in `[chainlink_max_age_secs.<chain>]`.
+            let per_symbol_max_age: HashMap<String, Duration> = config
+                .chainlink_max_age_secs
+                .get(chain_name)
+                .map(|m| {
+                    m.iter()
+                        .map(|(sym, secs)| (sym.clone(), Duration::from_secs(*secs)))
+                        .collect()
+                })
+                .unwrap_or_default();
+            let prices = Arc::new(PriceCache::with_per_symbol_max_age(
                 provider.clone(),
                 price_feeds,
                 DEFAULT_MAX_AGE,
+                per_symbol_max_age,
             ));
             prices.refresh_all().await;
             let fresh_feeds: Vec<String> = prices.symbols().map(str::to_string).collect();

crates/charon-core/src/config.rs

@@ -111,6 +111,20 @@ pub struct Config {
     /// configured, scanner falls back to protocol oracle.
     #[serde(default)]
     pub chainlink: HashMap<String, HashMap<String, Address>>,
+    /// Per-feed Chainlink staleness window overrides, keyed by chain
+    /// then asset symbol (`chainlink_max_age_secs.bnb.USDT = 86400`).
+    /// Stable feeds (USDC/USDT/FDUSD on BSC) update on deviation, not
+    /// heartbeat, so the global 600s default routinely flags them as
+    /// stale even though the price has not moved. Missing entry =
+    /// fall back to the global default (`DEFAULT_MAX_AGE` / the
+    /// `CHARON_PRICE_MAX_AGE_SECS` env override). See #331.
+    ///
+    /// Top-level section (not nested under `[chainlink.<chain>]`)
+    /// because the existing `chainlink.<chain>` table is symbol-keyed
+    /// and mixing a typed `max_age_secs` sub-table with raw symbol
+    /// entries breaks serde's `HashMap<String, Address>` parse.
+    #[serde(default)]
+    pub chainlink_max_age_secs: HashMap<String, HashMap<String, u64>>,
     /// Prometheus exporter configuration. Missing `[metrics]` block ⇒
     /// defaults from [`MetricsConfig::default`] (enabled, port 9091).
     #[serde(default)]
@@ -915,6 +929,7 @@ mod private_rpc_tests {
             flashloan: HashMap::new(),
             liquidator: HashMap::new(),
             chainlink: HashMap::new(),
+            chainlink_max_age_secs: HashMap::new(),
             metrics: MetricsConfig::default(),
         }
     }
@@ -1168,6 +1183,7 @@ mod fork_profile_tests {
             flashloan: HashMap::new(),
             liquidator: HashMap::new(),
             chainlink: HashMap::new(),
+            chainlink_max_age_secs: HashMap::new(),
             metrics: MetricsConfig::default(),
         }
     }
@@ -1268,4 +1284,43 @@ mod fork_profile_tests {
         assert!(!is_loopback_url("http://192.168.1.1"));
         assert!(!is_loopback_url("not-a-url"));
     }
+
+    #[test]
+    fn chainlink_max_age_secs_round_trips_through_toml() {
+        // Round-trip the per-feed override map through the same
+        // serde derive Config uses. A standalone wrapper keeps the
+        // test focused on the new field — the rest of Config has
+        // a dozen required sections that are out of scope here.
+        #[derive(Deserialize)]
+        struct Wrapper {
+            #[serde(default)]
+            chainlink_max_age_secs: HashMap<String, HashMap<String, u64>>,
+        }
+
+        let toml_src = r#"
+            [chainlink_max_age_secs.bnb]
+            USDT = 86400
+            USDC = 3600
+        "#;
+        let w: Wrapper = toml::from_str(toml_src).expect("parse");
+        let bnb = w
+            .chainlink_max_age_secs
+            .get("bnb")
+            .expect("bnb override section");
+        assert_eq!(bnb.get("USDT"), Some(&86400u64));
+        assert_eq!(bnb.get("USDC"), Some(&3600u64));
+        assert_eq!(bnb.get("BNB"), None, "unspecified feed must fall through");
+    }
+
+    #[test]
+    fn chainlink_max_age_secs_defaults_to_empty_when_missing() {
+        #[derive(Deserialize)]
+        struct Wrapper {
+            #[serde(default)]
+            chainlink_max_age_secs: HashMap<String, HashMap<String, u64>>,
+        }
+
+        let w: Wrapper = toml::from_str("").expect("parse empty");
+        assert!(w.chainlink_max_age_secs.is_empty());
+    }
 }