fix: correct ephemeral open-tip height

stackslib/src/clarity_vm/database/marf.rs

@@ -1628,9 +1628,10 @@ impl ClarityBackingStore for EphemeralMarfStore<'_> {
     /// Otherwise, use the disk-backed one.
     fn get_open_chain_tip_height(&mut self) -> u32 {
         if let EphemeralTip::RAM(..) = &self.open_tip {
-            self.ephemeral_marf
+            return self.ephemeral_marf
                 .get_open_chain_tip_height()
-                .expect("Attempted to get the open chain tip from an unopened context.");
+                .expect("Attempted to get the open chain tip from an unopened context.")
+                + self.base_tip_height;
         }
 
         self.read_only_marf.get_open_chain_tip_height()

stackslib/src/clarity_vm/tests/ephemeral.rs

@@ -16,6 +16,7 @@
 use std::fs;
 
 use clarity::vm::ast::ASTRules;
+use proptest::prelude::*;
 use rand::seq::SliceRandom;
 use rand::thread_rng;
 use stacks_common::types::chainstate::StacksBlockId;
@@ -431,6 +432,50 @@ fn test_ephemeral_nakamoto_block_replay_simple() {
     }
 }
 
+#[test]
+fn prop_ephemeral_tip_height_matches_current() {
+    proptest!(|(n in 1usize..=12)| {
+        let path = format!("/tmp/{}.marf", function_name!());
+        if fs::metadata(&path).is_ok() {
+            fs::remove_dir_all(&path).unwrap();
+        }
+
+        let mut marfed_kv = MarfedKV::open(
+            &path,
+            None,
+            Some(MARFOpenOpts::new(
+                TrieHashCalculationMode::Deferred,
+                "noop",
+                false,
+            )),
+        )
+        .unwrap();
+
+        let target_block_id = StacksBlockId([0xf0; 32]);
+        let mut tip = StacksBlockId::sentinel();
+        for blk in 0..n {
+            let final_block_id = StacksBlockId([(blk as u8) + 1; 32]);
+            let mut marf = marfed_kv.begin(&tip, &target_block_id);
+            let keys_and_values = vec![(
+                format!("key-{}", blk),
+                format!("value-{}", blk)
+            )];
+            marf.put_all_data(keys_and_values).unwrap();
+            marf.commit_to(&final_block_id).unwrap();
+            tip = final_block_id;
+        }
+
+        let ephemeral_tip = StacksBlockId([0xee; 32]);
+        let mut marf_ephemeral =
+            marfed_kv.begin_ephemeral(&tip, &ephemeral_tip).unwrap();
+
+        // Invariant: ephemeral tip height equals current height.
+        let height = marf_ephemeral.get_current_block_height();
+        let open_height = marf_ephemeral.get_open_chain_tip_height();
+        prop_assert_eq!(height, open_height);
+    });
+}
+
 // Test TODO:
 // * nakamoto boot plan with Clarity smart contracts which exercise the Clarity DB thoroghly 
 // * stacks 2.x test