diff --git a/crates/prometeu-bytecode/src/abi.rs b/crates/prometeu-bytecode/src/abi.rs
index d16c1a85..6feb351a 100644
--- a/crates/prometeu-bytecode/src/abi.rs
+++ b/crates/prometeu-bytecode/src/abi.rs
@@ -45,6 +45,10 @@ pub const TRAP_STACK_UNDERFLOW: u32 = 0x0000_0008;
 pub const TRAP_INVALID_LOCAL: u32 = 0x0000_0009;
 /// Division or modulo by zero.
 pub const TRAP_DIV_ZERO: u32 = 0x0000_000A;
+/// Attempted to call a function that does not exist in the function table.
+pub const TRAP_INVALID_FUNC: u32 = 0x0000_000B;
+/// Executed RET with an incorrect stack height (mismatch with function metadata).
+pub const TRAP_BAD_RET_SLOTS: u32 = 0x0000_000C;
 
 /// Detailed information about a runtime trap.
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -87,6 +91,8 @@ mod tests {
         assert_eq!(TRAP_STACK_UNDERFLOW, 0x08);
         assert_eq!(TRAP_INVALID_LOCAL, 0x09);
         assert_eq!(TRAP_DIV_ZERO, 0x0A);
+        assert_eq!(TRAP_INVALID_FUNC, 0x0B);
+        assert_eq!(TRAP_BAD_RET_SLOTS, 0x0C);
     }
 
     #[test]
@@ -104,6 +110,8 @@ System Traps:
 - STACK_UNDERFLOW (0x08): Missing syscall arguments.
 - INVALID_LOCAL (0x09): Local slot out of bounds.
 - DIV_ZERO (0x0A): Division by zero.
+- INVALID_FUNC (0x0B): Function table index out of bounds.
+- BAD_RET_SLOTS (0x0C): Stack height mismatch at RET.
 
 Operand Sizes:
 - Alloc: 8 bytes (u32 type_id, u32 slots)
@@ -114,9 +122,9 @@ Operand Sizes:
         // This test serves as a "doc-lock". 
         // If you change the ABI, you must update this string.
         let current_info = format!(
-            "\nHIP Traps:\n- INVALID_GATE (0x{:02X}): Non-existent gate handle.\n- DEAD_GATE (0x{:02X}): Gate handle with RC=0.\n- OOB (0x{:02X}): Access beyond allocated slots.\n- TYPE (0x{:02X}): Type mismatch during heap access.\n\nSystem Traps:\n- INVALID_SYSCALL (0x{:02X}): Unknown syscall ID.\n- STACK_UNDERFLOW (0x{:02X}): Missing syscall arguments.\n- INVALID_LOCAL (0x{:02X}): Local slot out of bounds.\n- DIV_ZERO (0x{:02X}): Division by zero.\n\nOperand Sizes:\n- Alloc: {} bytes (u32 type_id, u32 slots)\n- GateLoad: {} bytes (u32 offset)\n- GateStore: {} bytes (u32 offset)\n- PopN: {} bytes (u32 count)\n",
+            "\nHIP Traps:\n- INVALID_GATE (0x{:02X}): Non-existent gate handle.\n- DEAD_GATE (0x{:02X}): Gate handle with RC=0.\n- OOB (0x{:02X}): Access beyond allocated slots.\n- TYPE (0x{:02X}): Type mismatch during heap access.\n\nSystem Traps:\n- INVALID_SYSCALL (0x{:02X}): Unknown syscall ID.\n- STACK_UNDERFLOW (0x{:02X}): Missing syscall arguments.\n- INVALID_LOCAL (0x{:02X}): Local slot out of bounds.\n- DIV_ZERO (0x{:02X}): Division by zero.\n- INVALID_FUNC (0x{:02X}): Function table index out of bounds.\n- BAD_RET_SLOTS (0x{:02X}): Stack height mismatch at RET.\n\nOperand Sizes:\n- Alloc: {} bytes (u32 type_id, u32 slots)\n- GateLoad: {} bytes (u32 offset)\n- GateStore: {} bytes (u32 offset)\n- PopN: {} bytes (u32 count)\n",
             TRAP_INVALID_GATE, TRAP_DEAD_GATE, TRAP_OOB, TRAP_TYPE,
-            TRAP_INVALID_SYSCALL, TRAP_STACK_UNDERFLOW, TRAP_INVALID_LOCAL, TRAP_DIV_ZERO,
+            TRAP_INVALID_SYSCALL, TRAP_STACK_UNDERFLOW, TRAP_INVALID_LOCAL, TRAP_DIV_ZERO, TRAP_INVALID_FUNC, TRAP_BAD_RET_SLOTS,
             operand_size(OpCode::Alloc),
             operand_size(OpCode::GateLoad),
             operand_size(OpCode::GateStore),
diff --git a/crates/prometeu-core/src/prometeu_os/prometeu_os.rs b/crates/prometeu-core/src/prometeu_os/prometeu_os.rs
index b6c74cb3..e2712238 100644
--- a/crates/prometeu-core/src/prometeu_os/prometeu_os.rs
+++ b/crates/prometeu-core/src/prometeu_os/prometeu_os.rs
@@ -686,6 +686,7 @@ mod tests {
             rom: vec![
                 0x17, 0x00, // PushI32
                 0x00, 0x00, 0x00, 0x00, // value 0
+                0x11, 0x00, // Pop
                 0x51, 0x00  // Ret
             ],
         }).unwrap();
diff --git a/crates/prometeu-core/src/virtual_machine/virtual_machine.rs b/crates/prometeu-core/src/virtual_machine/virtual_machine.rs
index 7717c3fa..a4535152 100644
--- a/crates/prometeu-core/src/virtual_machine/virtual_machine.rs
+++ b/crates/prometeu-core/src/virtual_machine/virtual_machine.rs
@@ -5,7 +5,7 @@ use crate::virtual_machine::value::Value;
 use crate::virtual_machine::{NativeInterface, Program, VmInitError};
 use prometeu_bytecode::opcode::OpCode;
 use prometeu_bytecode::pbc::{self, ConstantPoolEntry};
-use prometeu_bytecode::abi::{TrapInfo, TRAP_OOB, TRAP_DIV_ZERO, TRAP_TYPE};
+use prometeu_bytecode::abi::{TrapInfo, TRAP_OOB, TRAP_DIV_ZERO, TRAP_TYPE, TRAP_INVALID_FUNC, TRAP_BAD_RET_SLOTS};
 
 /// Reason why the Virtual Machine stopped execution during a specific run.
 /// This allows the system to decide if it should continue execution in the next tick
@@ -835,10 +835,20 @@ impl VirtualMachine {
             }
             OpCode::Call => {
                 let func_id = u32::from_le_bytes(instr.imm[0..4].try_into().unwrap()) as usize;
-                let callee = self.program.functions.get(func_id).ok_or_else(|| LogicalFrameEndingReason::Panic(format!("Invalid func_id {}", func_id)))?;
+                let callee = self.program.functions.get(func_id).ok_or_else(|| {
+                    LogicalFrameEndingReason::Trap(TrapInfo {
+                        code: TRAP_INVALID_FUNC,
+                        opcode: opcode as u16,
+                        message: format!("Invalid func_id {}", func_id),
+                        pc: start_pc as u32,
+                    })
+                })?;
                 
                 if self.operand_stack.len() < callee.param_slots as usize {
-                    return Err(LogicalFrameEndingReason::Panic("Stack underflow during CALL: not enough arguments".into()));
+                    return Err(LogicalFrameEndingReason::Panic(format!(
+                        "Stack underflow during CALL to func {}: expected at least {} arguments, got {}",
+                        func_id, callee.param_slots, self.operand_stack.len()
+                    )));
                 }
 
                 let stack_base = self.operand_stack.len() - callee.param_slots as usize;
@@ -860,7 +870,22 @@ impl VirtualMachine {
                 let func = &self.program.functions[frame.func_idx];
                 let return_slots = func.return_slots as usize;
                 
-                // Copy return values
+                let current_height = self.operand_stack.len();
+                let expected_height = frame.stack_base + func.param_slots as usize + func.local_slots as usize + return_slots;
+                
+                if current_height != expected_height {
+                    return Err(LogicalFrameEndingReason::Trap(TrapInfo {
+                        code: TRAP_BAD_RET_SLOTS,
+                        opcode: opcode as u16,
+                        message: format!(
+                            "Incorrect stack height at RET in func {}: expected {} slots (stack_base={} + params={} + locals={} + returns={}), got {}",
+                            frame.func_idx, expected_height, frame.stack_base, func.param_slots, func.local_slots, return_slots, current_height
+                        ),
+                        pc: start_pc as u32,
+                    }));
+                }
+
+                // Copy return values (preserving order: pop return_slots values, then reverse to push back)
                 let mut return_vals = Vec::with_capacity(return_slots);
                 for _ in 0..return_slots {
                     return_vals.push(self.pop().map_err(|e| LogicalFrameEndingReason::Panic(e))?);
@@ -1355,8 +1380,10 @@ mod tests {
         let res = vm.step(&mut native, &mut hw); // RET -> should fail
         assert!(res.is_err());
         match res.unwrap_err() {
-            LogicalFrameEndingReason::Panic(msg) => assert!(msg.contains("Stack underflow")),
-            _ => panic!("Expected Panic"),
+            LogicalFrameEndingReason::Trap(trap) => {
+                assert_eq!(trap.code, TRAP_BAD_RET_SLOTS);
+            }
+            _ => panic!("Expected Trap(TRAP_BAD_RET_SLOTS)"),
         }
 
         // Agora com valor de retorno
@@ -1475,6 +1502,7 @@ mod tests {
         rom.extend_from_slice(&(OpCode::PushScope as u16).to_le_bytes());
         rom.extend_from_slice(&(OpCode::PushI64 as u16).to_le_bytes());
         rom.extend_from_slice(&300i64.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::PopScope as u16).to_le_bytes());
         rom.extend_from_slice(&(OpCode::Ret as u16).to_le_bytes());
 
         let functions = vec![
@@ -1505,7 +1533,7 @@ mod tests {
         assert!(vm.halted);
         assert_eq!(vm.operand_stack.len(), 2);
         assert_eq!(vm.operand_stack[0], Value::Int64(100));
-        assert_eq!(vm.operand_stack[1], Value::Int64(300));
+        assert_eq!(vm.operand_stack[1], Value::Int64(200));
     }
 
     #[test]
@@ -1747,6 +1775,7 @@ mod tests {
         let rom = vec![
             0x17, 0x00, // PushI32
             0x00, 0x00, 0x00, 0x00, // value 0
+            0x11, 0x00, // Pop
             0x51, 0x00  // Ret
         ];
         let mut vm = VirtualMachine::new(rom, vec![]);
@@ -2027,6 +2056,240 @@ mod tests {
         assert!(res.is_ok(), "Should NOT fail if Call pattern is in immediate: {:?}", res);
     }
 
+    #[test]
+    fn test_calling_convention_add() {
+        let mut native = MockNative;
+        let mut hw = MockHardware;
+
+        // F0 (entry):
+        //   PUSH_I32 10
+        //   PUSH_I32 20
+        //   CALL 1 (add)
+        //   HALT
+        // F1 (add):
+        //   GET_LOCAL 0 (a)
+        //   GET_LOCAL 1 (b)
+        //   ADD
+        //   RET (1 slot)
+
+        let mut rom = Vec::new();
+        // F0
+        let f0_start = 0;
+        rom.extend_from_slice(&(OpCode::PushI32 as u16).to_le_bytes());
+        rom.extend_from_slice(&10i32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::PushI32 as u16).to_le_bytes());
+        rom.extend_from_slice(&20i32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::Call as u16).to_le_bytes());
+        rom.extend_from_slice(&1u32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::Halt as u16).to_le_bytes());
+        let f0_len = rom.len() - f0_start;
+
+        // F1
+        let f1_start = rom.len() as u32;
+        rom.extend_from_slice(&(OpCode::GetLocal as u16).to_le_bytes());
+        rom.extend_from_slice(&0u32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::GetLocal as u16).to_le_bytes());
+        rom.extend_from_slice(&1u32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::Add as u16).to_le_bytes());
+        rom.extend_from_slice(&(OpCode::Ret as u16).to_le_bytes());
+        let f1_len = rom.len() as u32 - f1_start;
+
+        let mut vm = VirtualMachine::new(rom, vec![]);
+        vm.program.functions = std::sync::Arc::from(vec![
+            FunctionMeta {
+                code_offset: f0_start as u32,
+                code_len: f0_len as u32,
+                ..Default::default()
+            },
+            FunctionMeta {
+                code_offset: f1_start,
+                code_len: f1_len,
+                param_slots: 2,
+                return_slots: 1,
+                ..Default::default()
+            },
+        ]);
+
+        vm.prepare_call("0");
+        let report = vm.run_budget(100, &mut native, &mut hw).unwrap();
+        assert_eq!(report.reason, LogicalFrameEndingReason::Halted);
+        assert_eq!(vm.operand_stack.last().unwrap(), &Value::Int32(30));
+    }
+
+    #[test]
+    fn test_calling_convention_multi_slot_return() {
+        let mut native = MockNative;
+        let mut hw = MockHardware;
+
+        // F0:
+        //   CALL 1
+        //   HALT
+        // F1:
+        //   PUSH_I32 100
+        //   PUSH_I32 200
+        //   RET (2 slots)
+
+        let mut rom = Vec::new();
+        // F0
+        let f0_start = 0;
+        rom.extend_from_slice(&(OpCode::Call as u16).to_le_bytes());
+        rom.extend_from_slice(&1u32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::Halt as u16).to_le_bytes());
+        let f0_len = rom.len() - f0_start;
+
+        // F1
+        let f1_start = rom.len() as u32;
+        rom.extend_from_slice(&(OpCode::PushI32 as u16).to_le_bytes());
+        rom.extend_from_slice(&100i32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::PushI32 as u16).to_le_bytes());
+        rom.extend_from_slice(&200i32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::Ret as u16).to_le_bytes());
+        let f1_len = rom.len() as u32 - f1_start;
+
+        let mut vm = VirtualMachine::new(rom, vec![]);
+        vm.program.functions = std::sync::Arc::from(vec![
+            FunctionMeta {
+                code_offset: f0_start as u32,
+                code_len: f0_len as u32,
+                ..Default::default()
+            },
+            FunctionMeta {
+                code_offset: f1_start,
+                code_len: f1_len,
+                param_slots: 0,
+                return_slots: 2,
+                ..Default::default()
+            },
+        ]);
+
+        vm.prepare_call("0");
+        let report = vm.run_budget(100, &mut native, &mut hw).unwrap();
+        assert_eq!(report.reason, LogicalFrameEndingReason::Halted);
+        // Stack should be [100, 200]
+        assert_eq!(vm.operand_stack.len(), 2);
+        assert_eq!(vm.operand_stack[0], Value::Int32(100));
+        assert_eq!(vm.operand_stack[1], Value::Int32(200));
+    }
+
+    #[test]
+    fn test_calling_convention_void_call() {
+        let mut native = MockNative;
+        let mut hw = MockHardware;
+
+        // F0:
+        //   PUSH_I32 42
+        //   CALL 1
+        //   HALT
+        // F1:
+        //   POP
+        //   RET (0 slots)
+
+        let mut rom = Vec::new();
+        let f0_start = 0;
+        rom.extend_from_slice(&(OpCode::PushI32 as u16).to_le_bytes());
+        rom.extend_from_slice(&42i32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::Call as u16).to_le_bytes());
+        rom.extend_from_slice(&1u32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::Halt as u16).to_le_bytes());
+        let f0_len = rom.len() - f0_start;
+
+        let f1_start = rom.len() as u32;
+        rom.extend_from_slice(&(OpCode::Ret as u16).to_le_bytes());
+        let f1_len = rom.len() as u32 - f1_start;
+
+        let mut vm = VirtualMachine::new(rom, vec![]);
+        vm.program.functions = std::sync::Arc::from(vec![
+            FunctionMeta {
+                code_offset: f0_start as u32,
+                code_len: f0_len as u32,
+                ..Default::default()
+            },
+            FunctionMeta {
+                code_offset: f1_start,
+                code_len: f1_len,
+                param_slots: 1,
+                return_slots: 0,
+                ..Default::default()
+            },
+        ]);
+
+        vm.prepare_call("0");
+        let report = vm.run_budget(100, &mut native, &mut hw).unwrap();
+        assert_eq!(report.reason, LogicalFrameEndingReason::Halted);
+        assert_eq!(vm.operand_stack.len(), 0);
+    }
+
+    #[test]
+    fn test_trap_invalid_func() {
+        let mut native = MockNative;
+        let mut hw = MockHardware;
+
+        // CALL 99 (invalid)
+        let mut rom = Vec::new();
+        rom.extend_from_slice(&(OpCode::Call as u16).to_le_bytes());
+        rom.extend_from_slice(&99u32.to_le_bytes());
+
+        let mut vm = VirtualMachine::new(rom, vec![]);
+        let report = vm.run_budget(100, &mut native, &mut hw).unwrap();
+        
+        match report.reason {
+            LogicalFrameEndingReason::Trap(trap) => {
+                assert_eq!(trap.code, TRAP_INVALID_FUNC);
+                assert_eq!(trap.opcode, OpCode::Call as u16);
+            }
+            _ => panic!("Expected Trap(TRAP_INVALID_FUNC), got {:?}", report.reason),
+        }
+    }
+
+    #[test]
+    fn test_trap_bad_ret_slots() {
+        let mut native = MockNative;
+        let mut hw = MockHardware;
+
+        // F0: CALL 1; HALT
+        // F1: PUSH_I32 42; RET (expected 0 slots)
+
+        let mut rom = Vec::new();
+        let f0_start = 0;
+        rom.extend_from_slice(&(OpCode::Call as u16).to_le_bytes());
+        rom.extend_from_slice(&1u32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::Halt as u16).to_le_bytes());
+        let f0_len = rom.len() - f0_start;
+
+        let f1_start = rom.len() as u32;
+        rom.extend_from_slice(&(OpCode::PushI32 as u16).to_le_bytes());
+        rom.extend_from_slice(&42i32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::Ret as u16).to_le_bytes());
+        let f1_len = rom.len() as u32 - f1_start;
+
+        let mut vm = VirtualMachine::new(rom, vec![]);
+        vm.program.functions = std::sync::Arc::from(vec![
+            FunctionMeta {
+                code_offset: f0_start as u32,
+                code_len: f0_len as u32,
+                ..Default::default()
+            },
+            FunctionMeta {
+                code_offset: f1_start,
+                code_len: f1_len,
+                param_slots: 0,
+                return_slots: 0, // ERROR: function pushes 42 but returns 0
+                ..Default::default()
+            },
+        ]);
+
+        vm.prepare_call("0");
+        let report = vm.run_budget(100, &mut native, &mut hw).unwrap();
+        
+        match report.reason {
+            LogicalFrameEndingReason::Trap(trap) => {
+                assert_eq!(trap.code, TRAP_BAD_RET_SLOTS);
+                assert_eq!(trap.opcode, OpCode::Ret as u16);
+                assert!(trap.message.contains("Incorrect stack height"));
+            }
+            _ => panic!("Expected Trap(TRAP_BAD_RET_SLOTS), got {:?}", report.reason),
+        }
+    }
     #[test]
     fn test_locals_round_trip() {
         let mut native = MockNative;
@@ -2044,6 +2307,7 @@ mod tests {
         rom.extend_from_slice(&0u32.to_le_bytes());
         rom.extend_from_slice(&(OpCode::PushI32 as u16).to_le_bytes());
         rom.extend_from_slice(&0i32.to_le_bytes());
+        rom.extend_from_slice(&(OpCode::Pop as u16).to_le_bytes());
         rom.extend_from_slice(&(OpCode::GetLocal as u16).to_le_bytes());
         rom.extend_from_slice(&0u32.to_le_bytes());
         rom.extend_from_slice(&(OpCode::Ret as u16).to_le_bytes());
@@ -2051,7 +2315,7 @@ mod tests {
         let mut vm = VirtualMachine::new(rom, vec![]);
         vm.program.functions = std::sync::Arc::from(vec![FunctionMeta {
             code_offset: 0,
-            code_len: 18,
+            code_len: 20,
             local_slots: 1,
             return_slots: 1,
             ..Default::default()
diff --git a/docs/specs/pbs/files/PRs para Junie.md b/docs/specs/pbs/files/PRs para Junie.md
index f03c9726..c63d44aa 100644
--- a/docs/specs/pbs/files/PRs para Junie.md	
+++ b/docs/specs/pbs/files/PRs para Junie.md	
@@ -1,77 +1,3 @@
-## PR-07 — Calling convention v0: CALL / RET / multi-slot returns
-
-**Why:** Without a correct call model, PBS isn’t executable.
-
-### Scope
-
-* Introduce `CALL <u16 func_id>`
-
-    * caller pushes args (slots)
-    * callee frame allocates locals
-* Introduce `RET`
-
-    * callee must leave exactly `return_slots` on operand stack at `RET`
-    * VM pops frame and transfers return slots to caller
-* Define return mechanics for `void` (`return_slots=0`)
-
-### Deliverables
-
-* `FunctionTable` indexing and bounds checks
-* Deterministic traps:
-
-    * `TRAP_INVALID_FUNC`
-    * `TRAP_BAD_RET_SLOTS`
-
-### Tests
-
-* `fn add(a:int,b:int):int { return a+b; }`
-* multi-slot return (e.g., `Pad` flattened)
-* void call
-
-### Acceptance
-
-* Calls are stable and stack-clean.
-
----
-
-## PR-08 — Host syscalls v0: stable ABI, multi-slot args/returns
-
-**Why:** PBS relies on deterministic syscalls; ABI must be frozen and enforced.
-
-### Scope
-
-* Unify syscall invocation opcode:
-
-    * `SYSCALL <u16 id> <u8 arg_slots> <u8 ret_slots>`
-* Runtime validates:
-
-    * pops `arg_slots`
-    * pushes `ret_slots`
-* Implement/confirm:
-
-    * `GfxClear565 (0x1010)`
-    * `InputPadSnapshot (0x2010)`
-    * `InputTouchSnapshot (0x2011)`
-
-### Deliverables
-
-* A `SyscallRegistry` mapping id -> handler + signature
-* Deterministic traps:
-
-    * `TRAP_INVALID_SYSCALL`
-    * `TRAP_SYSCALL_SIG_MISMATCH`
-
-### Tests
-
-* syscall isolated tests
-* wrong signature traps
-
-### Acceptance
-
-* Syscalls are “industrial”: typed by signature, deterministic, no host surprises.
-
----
-
 ## PR-09 — Debug info v0: spans, symbols, and traceable traps
 
 **Why:** Industrial debugging requires actionable failures.