fix: convert look back limit to actual epoch before searching for msg

src/rpc/methods/state.rs

@@ -1266,7 +1266,6 @@ impl RpcMethod<4> for StateSearchMsg {
     }
 }
 
-/// Looks back up to limit epochs in the chain for a message, and returns its receipt and the tipset where it was executed.
 /// See <https://github.com/filecoin-project/lotus/blob/master/documentation/en/api-methods-v0-deprecated.md#StateSearchMsgLimited>
 pub enum StateSearchMsgLimited {}
 
@@ -1275,7 +1274,9 @@ impl RpcMethod<2> for StateSearchMsgLimited {
     const PARAM_NAMES: [&'static str; 2] = ["message_cid", "look_back_limit"];
     const API_PATHS: BitFlags<ApiPaths> = make_bitflags!(ApiPaths::V0); // Not supported in V1
     const PERMISSION: Permission = Permission::Read;
-
+    const DESCRIPTION: Option<&'static str> = Some(
+        "Looks back up to limit epochs in the chain for a message, and returns its receipt and the tipset where it was executed.",
+    );
     type Params = (Cid, i64);
     type Ok = MessageLookup;
 

src/rpc/mod.rs

@@ -41,7 +41,8 @@ pub use methods::*;
 /// Protocol or transport-specific error
 pub use jsonrpsee::core::ClientError;
 
-const LOOKBACK_NO_LIMIT: ChainEpoch = -1;
+/// Sentinel value, indicating no limit on how far back to search in the chain (all the way to genesis epoch).
+pub const LOOKBACK_NO_LIMIT: ChainEpoch = -1;
 
 /// The macro `callback` will be passed in each type that implements
 /// [`RpcMethod`].

src/state_manager/mod.rs

@@ -1046,17 +1046,17 @@ where
         &self,
         mut current: Tipset,
         message: &ChainMessage,
-        look_back_limit: Option<i64>,
-        allow_replaced: Option<bool>,
+        lookback_max_epoch: ChainEpoch,
+        allow_replaced: bool,
     ) -> Result<Option<(Tipset, Receipt)>, Error> {
-        let allow_replaced = allow_replaced.unwrap_or(true);
         let message_from_address = message.from();
         let message_sequence = message.sequence();
         let mut current_actor_state = self
             .get_required_actor(&message_from_address, *current.parent_state())
             .map_err(Error::state)?;
         let message_from_id = self.lookup_required_id(&message_from_address, &current)?;
-        while current.epoch() > look_back_limit.unwrap_or_default() {
+
+        while current.epoch() >= lookback_max_epoch {
             let parent_tipset = self
                 .chain_index()
                 .load_required_tipset(current.parents())
@@ -1091,14 +1091,29 @@ where
         Ok(None)
     }
 
+    /// Searches backwards through the chain for a message receipt.
     fn search_back_for_message(
         &self,
         current: Tipset,
         message: &ChainMessage,
         look_back_limit: Option<i64>,
         allow_replaced: Option<bool>,
     ) -> Result<Option<(Tipset, Receipt)>, Error> {
-        self.check_search(current, message, look_back_limit, allow_replaced)
+        let current_epoch = current.epoch();
+        let allow_replaced = allow_replaced.unwrap_or(true);
+
+        // Calculate the max lookback epoch (inclusive lower bound) for the search.
+        let lookback_max_epoch = match look_back_limit {
+            // No search: limit = 0 means search 0 epochs
+            Some(0) => return Ok(None),
+            // Limited search: calculate the inclusive lower bound
+            // For ex: limit = 5 at epoch 1000: min_epoch = 996, searches [996, 1000] = 5 epochs
+            Some(limit) if limit > 0 && limit < current_epoch => current_epoch - limit + 1,
+            // Search all the way to genesis (epoch 0)
+            _ => 0,
+        };
+
+        self.check_search(current, message, lookback_max_epoch, allow_replaced)
     }
 
     /// Returns a message receipt from a given tipset and message CID.

src/tool/subcommands/api_cmd/test_snapshots.txt

@@ -286,8 +286,8 @@ filecoin_statereadstate_1748444218790447.rpcsnap.json.zst
 filecoin_statereadstate_1748444218790807.rpcsnap.json.zst
 filecoin_statereadstate_1749657617007020.rpcsnap.json.zst
 filecoin_statereplay_1743504051038215.rpcsnap.json.zst
-filecoin_statesearchmsg_1741784596636715.rpcsnap.json.zst
-filecoin_statesearchmsglimited_1741784596704877.rpcsnap.json.zst
+filecoin_statesearchmsg_1767947430707712.rpcsnap.json.zst
+filecoin_statesearchmsglimited_1767936905056090.rpcsnap.json.zst
 filecoin_statesectorexpiration_1741784727996672.rpcsnap.json.zst
 filecoin_statesectorgetinfo_1743098602783105.rpcsnap.json.zst
 filecoin_statesectorpartition_1737546933391247.rpcsnap.json.zst