Inner instruction lacks parent.

[spacecaterpillar]

If you parse this transaction: https://explorer.solana.com/tx/599kTg8k8Mz7QJnAimAUmiYXtbynx7oczqFCXXFGXF32Sb8MzKuX42EX2Lsj2PEdk2TDsZTMKqsBUqhxHnBSqJAD

The last inner instruction 3.10, will have:

StructuredInstruction { instruction: Inner(InnerInstruction { program_id_index: 22, accounts: [4, 5, 12], data: [3, 222, 65, 212, 19, 0, 0, 0, 0], stack_height: Some(2) }), accounts: [Pubkey("Aq28kYyDAHxxAk5RSbfogegBDnsCivRJA56Nj4et1vhG"), Pubkey("4w63iDuwHidFuXxUN7BDA3Gh8tSjZjU9eKeYMA9Vb6Kk"), Pubkey("2MFoS3MPtvyQ4Wh4M9pdfPjz6UhVoNbFbGJAskCPCj3h")], program_id: Pubkey("TokenkegQfeZyiNwAJbNbGKPFXCWuBvf9Ss623VQ5DA"), inner_instructions: RefCell { value: [] }, parent_instruction: RefCell { value: None }, logs: RefCell { value: Some([Invoke(InvokeLog { log: "Program TokenkegQfeZyiNwAJbNbGKPFXCWuBvf9Ss623VQ5DA invoke [2]" }), Program(ProgramLog { log: "Program log: Instruction: Transfer" }), Unknown(UnknownLog { log: "Program TokenkegQfeZyiNwAJbNbGKPFXCWuBvf9Ss623VQ5DA consumed 4645 of 1241316 compute units" }), Success(SuccessLog { log: "Program TokenkegQfeZyiNwAJbNbGKPFXCWuBvf9Ss623VQ5DA success" })]) } }

You can see that it has stack_height = 2, but parent_instruction = None, which shouldn't be possible.

I believe the issue occurs because you assign the parent on stack pop? That might not happen for the last instruction, so we should assign on stack push? Perhaps something like:

diff --git a/src/utils/instruction.rs b/src/utils/instruction.rs
index 3094d73..2530594 100644
--- a/src/utils/instruction.rs
+++ b/src/utils/instruction.rs
@@ -180,6 +180,7 @@ where
     for instruction in flattened_instructions {
         let structured_instruction = Rc::new(StructuredInstruction::new(instruction, Vec::new().into(), &accounts));
 
+        // Pop instructions off stack and establish parent relationships
         while !instruction_stack.is_empty() && instruction_stack.last().unwrap().stack_height() >= structured_instruction.stack_height() {
             let popped_instruction = instruction_stack.pop().unwrap();
             *popped_instruction.logs.borrow_mut() = log_stack.close(logs, popped_instruction.program_id());
@@ -192,6 +193,12 @@ where
             }
         }
 
+        // Set parent relationship for current instruction if there's a parent on stack
+        if !instruction_stack.is_empty() && structured_instruction.stack_height().unwrap_or(1) > 1 {
+            *structured_instruction.parent_instruction.borrow_mut() =
+                Some(Rc::downgrade(instruction_stack.last().unwrap()));
+        }
+
         log_stack.open(logs, structured_instruction.program_id());
         instruction_stack.push(structured_instruction);
     }
@@ -201,6 +208,7 @@ where
         *popped_instruction.logs.borrow_mut() = log_stack.close(logs, popped_instruction.program_id());
 
         if !instruction_stack.is_empty() {
+            *popped_instruction.parent_instruction.borrow_mut() = Some(Rc::downgrade(instruction_stack.last().unwrap()));
             instruction_stack.last_mut().unwrap().inner_instructions.borrow_mut().push(popped_instruction);
         } else {
             structured_instructions.push(popped_instruction)

[0xpcut]

Nice catch. I'll fix it.