@@ -344,11 +344,14 @@ impl WastRunner {
                         );
                         continue;
                     };
-                    if !message.starts_with(trap.message()) && !trap.message().starts_with(message) {
+                    // The core test suite's "call stack exhausted" text denotes stack exhaustion,
+                    // not which internal stack reaches its configured limit first. Function-entry
+                    // operand reservation can exhaust a value lane before the call-frame stack.
+                    if !matches!(trap, tinywasm::Trap::CallStackOverflow | tinywasm::Trap::ValueStackOverflow) {
                         test_group.add_result(
                             &format!("AssertExhaustion({i})"),
                             span.linecol_in(wast_raw),
-                            Err(anyhow!("expected trap: {}, got: {}", message, trap.message())),
+                            Err(anyhow!("expected stack exhaustion ({message}), got: {}", trap.message())),
                         );
                         continue;
                     }
 
@@ -197,34 +197,35 @@ pub(crate) fn convert_module_code(
     }
 
     #[cfg(feature = "validate")]
-    let (body, data, uses_local_memory, validator_allocs, reader_allocs) = match validator {
+    let (body, data, uses_local_memory, max_stack, validator_allocs, reader_allocs) = match validator {
         Some(validator) => {
-            let (body, data, uses_local_memory, validator_allocs, reader_allocs) = process_operators_and_validate(
-                validator,
-                func,
-                (local_types, local_addr_map),
-                metadata,
-                context,
-                reader_allocs,
-                options,
-            )?;
-            (body, data, uses_local_memory, Some(validator_allocs), reader_allocs)
+            let (body, data, uses_local_memory, max_stack, validator_allocs, reader_allocs) =
+                process_operators_and_validate(
+                    validator,
+                    func,
+                    (local_types, local_addr_map),
+                    metadata,
+                    context,
+                    reader_allocs,
+                    options,
+                )?;
+            (body, data, uses_local_memory, max_stack, Some(validator_allocs), reader_allocs)
         }
         None => {
-            let (body, data, uses_local_memory, reader_allocs) =
+            let (body, data, uses_local_memory, max_stack, reader_allocs) =
                 process_operators(func, (local_types, local_addr_map), metadata, context, reader_allocs, options)?;
-            (body, data, uses_local_memory, None, reader_allocs)
+            (body, data, uses_local_memory, max_stack, None, reader_allocs)
         }
     };
     #[cfg(not(feature = "validate"))]
-    let (body, data, uses_local_memory, validator_allocs, reader_allocs) = {
+    let (body, data, uses_local_memory, max_stack, validator_allocs, reader_allocs) = {
         let _ = validator;
-        let (body, data, uses_local_memory, reader_allocs) =
+        let (body, data, uses_local_memory, max_stack, reader_allocs) =
             process_operators(func, (local_types, local_addr_map), metadata, context, reader_allocs, options)?;
-        (body, data, uses_local_memory, None, reader_allocs)
+        (body, data, uses_local_memory, max_stack, None, reader_allocs)
     };
     Ok((
-        FunctionCode { instructions: body, data: data.finish(), locals: local_counts, uses_local_memory },
+        FunctionCode { instructions: body, data: data.finish(), locals: local_counts, max_stack, uses_local_memory },
         validator_allocs,
         reader_allocs,
     ))
 
@@ -14,6 +14,7 @@ pub(crate) struct FunctionCode {
     pub instructions: Vec<Instruction>,
     pub data: WasmFunctionData,
     pub locals: ValueCounts,
+    pub max_stack: ValueCounts,
     pub uses_local_memory: bool,
 }
 
@@ -553,6 +554,7 @@ impl<'a> ModuleReader<'a> {
                     locals: code.locals,
                     params,
                     results,
+                    max_stack: code.max_stack,
                 }))
             })
             .collect::<Result<_>>()?;
 
@@ -185,6 +185,7 @@ pub(crate) struct FunctionBuilder<'a> {
     control_stack: Vec<ControlFrame<'a>>,
     operand_stack: Vec<ValueLane>,
     lane_counts: ValueCounts,
+    max_lane_counts: ValueCounts,
     metadata: &'a ModuleMetadata,
     local_types: Vec<ValueLane>,
     local_addr_map: Vec<u16>,
@@ -223,6 +224,7 @@ impl<'a> FunctionBuilder<'a> {
             }],
             operand_stack: Vec::new(),
             lane_counts: ValueCounts::default(),
+            max_lane_counts: ValueCounts::default(),
             uses_local_memory: false,
         }
     }
@@ -436,7 +438,7 @@ pub(crate) fn process_operators(
     context: FunctionLoweringContext,
     allocs: OperatorsReaderAllocations,
     options: &ParserOptions,
-) -> Result<(Vec<Instruction>, FunctionDataBuilder, bool, OperatorsReaderAllocations)> {
+) -> Result<(Vec<Instruction>, FunctionDataBuilder, bool, ValueCounts, OperatorsReaderAllocations)> {
     let (local_types, local_addr_map) = locals;
     let body_size = body.as_bytes().len();
     let reader = body.get_binary_reader_for_operators()?;
@@ -459,7 +461,7 @@ pub(crate) fn process_operators(
 
     reader.finish()?;
     let instructions = builder.emitter.finish(&mut builder.data)?;
-    Ok((instructions, builder.data, builder.uses_local_memory, reader.into_allocations()))
+    Ok((instructions, builder.data, builder.uses_local_memory, builder.max_lane_counts, reader.into_allocations()))
 }
 
 #[cfg(feature = "validate")]
@@ -471,7 +473,14 @@ pub(crate) fn process_operators_and_validate(
     context: FunctionLoweringContext,
     allocs: OperatorsReaderAllocations,
     options: &ParserOptions,
-) -> Result<(Vec<Instruction>, FunctionDataBuilder, bool, FuncValidatorAllocations, OperatorsReaderAllocations)> {
+) -> Result<(
+    Vec<Instruction>,
+    FunctionDataBuilder,
+    bool,
+    ValueCounts,
+    FuncValidatorAllocations,
+    OperatorsReaderAllocations,
+)> {
     let (local_types, local_addr_map) = locals;
     let body_size = body.as_bytes().len();
     let reader = body.get_binary_reader_for_operators()?;
@@ -494,7 +503,14 @@ pub(crate) fn process_operators_and_validate(
 
     reader.finish()?;
     let instructions = builder.emitter.finish(&mut builder.data)?;
-    Ok((instructions, builder.data, builder.uses_local_memory, validator.into_allocations(), reader.into_allocations()))
+    Ok((
+        instructions,
+        builder.data,
+        builder.uses_local_memory,
+        builder.max_lane_counts,
+        validator.into_allocations(),
+        reader.into_allocations(),
+    ))
 }
 
 impl<'a> wasmparser::VisitOperator<'a> for FunctionBuilder<'_> {
@@ -859,11 +875,23 @@ impl<'a> wasmparser::VisitOperator<'a> for FunctionBuilder<'_> {
                 wasmparser::Catch::All { label } => (None, label, false),
                 wasmparser::Catch::AllRef { label } => (None, label, true),
             };
-            if let Some(tag) = tag {
-                self.metadata.tag_signature(tag)?;
-            }
             let target_idx = self.get_ctx_idx(depth)?;
             let target_base = self.control_stack[target_idx].base;
+            // The runtime truncates to the target base, then injects the exception payload and
+            // optional reference before executing this landing pad. These pushes do not pass
+            // through the ordinary logical operand stack, but still need function-entry capacity.
+            let mut landing_counts = target_base;
+            if let Some(tag) = tag {
+                for &lane in &self.metadata.tag_signature(tag)?.params {
+                    Self::increment_lane(&mut landing_counts, lane)?;
+                }
+            }
+            if with_ref {
+                Self::increment_lane(&mut landing_counts, ValueLane::S32)?;
+            }
+            self.max_lane_counts.c32 = self.max_lane_counts.c32.max(landing_counts.c32);
+            self.max_lane_counts.c64 = self.max_lane_counts.c64.max(landing_counts.c64);
+            self.max_lane_counts.c128 = self.max_lane_counts.c128.max(landing_counts.c128);
             let landing_label = self.emitter.new_label();
             self.emitter.bind(landing_label)?;
             self.emit_branch_jump_or_return(depth)?;
@@ -1432,17 +1460,29 @@ impl<'a> FunctionBuilder<'a> {
         Ok((size, addr))
     }
 
-    /// Pushes logical operands while maintaining the lane counts used by `DropKeep`.
+    /// Increments a physical lane count, rejecting functions too large for the encoded count.
+    fn increment_lane(counts: &mut ValueCounts, lane: ValueLane) -> Result<()> {
+        let count = match lane {
+            ValueLane::S32 => &mut counts.c32,
+            ValueLane::S64 => &mut counts.c64,
+            ValueLane::S128 => &mut counts.c128,
+        };
+        *count = count
+            .checked_add(1)
+            .ok_or_else(|| crate::ParseError::Other("logical operand lane count is too large".into()))?;
+        Ok(())
+    }
+
+    /// Pushes logical operands while maintaining the lane counts used by `DropKeep` and their
+    /// maximum, which the runtime reserves when it enters the function.
     fn push_sizes(&mut self, sizes: &[ValueLane]) -> Result<()> {
         for &size in sizes {
-            let count = match size {
-                ValueLane::S32 => &mut self.lane_counts.c32,
-                ValueLane::S64 => &mut self.lane_counts.c64,
-                ValueLane::S128 => &mut self.lane_counts.c128,
-            };
-            *count = count
-                .checked_add(1)
-                .ok_or_else(|| crate::ParseError::Other("logical operand lane count is too large".into()))?;
+            Self::increment_lane(&mut self.lane_counts, size)?;
+            match size {
+                ValueLane::S32 => self.max_lane_counts.c32 = self.max_lane_counts.c32.max(self.lane_counts.c32),
+                ValueLane::S64 => self.max_lane_counts.c64 = self.max_lane_counts.c64.max(self.lane_counts.c64),
+                ValueLane::S128 => self.max_lane_counts.c128 = self.max_lane_counts.c128.max(self.lane_counts.c128),
+            }
             self.operand_stack.push(size);
         }
         Ok(())
 
@@ -157,16 +157,14 @@ impl Function {
             let host = store.state.funcs.host(self.addr()).func.clone();
             host.call_values(store, self.module_id, type_addr, params, results)
         } else {
-            let (wasm_params, wasm_locals) = {
+            let (wasm_params, wasm_locals, wasm_max_stack) = {
                 let wasm = store.state.funcs.wasm(self.addr());
-                let wasm_params = wasm.func.params;
-                let wasm_locals = wasm.func.locals;
-                (wasm_params, wasm_locals)
+                (wasm.func.params, wasm.func.locals, wasm.func.max_stack)
             };
             store.push_wasm_values(params).inspect_err(|_| store.value_stack.truncate_to_base(value_stack_base))?;
             let locals_base = store
                 .value_stack
-                .enter_locals(&wasm_params, &wasm_locals)
+                .enter_locals(&wasm_params, &wasm_locals, &wasm_max_stack)
                 .inspect_err(|_| store.value_stack.truncate_to_base(value_stack_base))?;
             let callframe = CallFrame::new(self.addr(), locals_base, wasm_locals);
             InterpreterRuntime::exec(store, callframe, call_stack_base).inspect_err(|_| {
@@ -213,14 +211,14 @@ impl Function {
             };
         }
 
-        let (type_addr, wasm_params, wasm_locals) = {
+        let (type_addr, wasm_params, wasm_locals, wasm_max_stack) = {
             let wasm = store.state.funcs.wasm(self.addr());
-            (wasm.type_addr, wasm.func.params, wasm.func.locals)
+            (wasm.type_addr, wasm.func.params, wasm.func.locals, wasm.func.max_stack)
         };
         store.push_typed_values::<false>(type_addr, params, value_stack_base)?;
         let locals_base = store
             .value_stack
-            .enter_locals(&wasm_params, &wasm_locals)
+            .enter_locals(&wasm_params, &wasm_locals, &wasm_max_stack)
             .inspect_err(|_| store.value_stack.truncate_to_base(value_stack_base))?;
         let callframe = CallFrame::new(self.addr(), locals_base, wasm_locals);
         InterpreterRuntime::exec(store, callframe, call_stack_base).inspect_err(|_| {
 
@@ -79,15 +79,15 @@ impl Function {
                 return Ok(ExecState::Completed(Some(CallResult::Written)));
             }
 
-            let (wasm_params, wasm_locals) = {
+            let (wasm_params, wasm_locals, wasm_max_stack) = {
                 let wasm = store.state.funcs.wasm(self.addr());
-                (wasm.func.params, wasm.func.locals)
+                (wasm.func.params, wasm.func.locals, wasm.func.max_stack)
             };
 
             store.call_stack.clear();
             store.value_stack.clear();
             store.push_wasm_values(params)?;
-            let locals_base = store.value_stack.enter_locals(&wasm_params, &wasm_locals)?;
+            let locals_base = store.value_stack.enter_locals(&wasm_params, &wasm_locals, &wasm_max_stack)?;
             let callframe = CallFrame::new(self.addr(), locals_base, wasm_locals);
 
             Ok(ExecState::Running { callframe, root_func_addr: self.addr() })
@@ -224,9 +224,9 @@ impl<P: IntoWasmValues, R: FromWasmValues> FunctionTyped<P, R> {
             let execution = ExecutionInner { store, state: ExecState::Completed(None) };
             return Ok(FuncExecutionTyped { execution, result: Some(result) });
         }
-        let (type_addr, wasm_params, wasm_locals) = {
+        let (type_addr, wasm_params, wasm_locals, wasm_max_stack) = {
             let wasm = store.state.funcs.wasm(self.func.addr());
-            (wasm.type_addr, wasm.func.params, wasm.func.locals)
+            (wasm.type_addr, wasm.func.params, wasm.func.locals, wasm.func.max_stack)
         };
 
         store.enter_execution()?;
@@ -236,7 +236,7 @@ impl<P: IntoWasmValues, R: FromWasmValues> FunctionTyped<P, R> {
             store.push_typed_values::<false>(type_addr, params.into_wasm_values(), StackBase::default())?;
             let locals_base = store
                 .value_stack
-                .enter_locals(&wasm_params, &wasm_locals)
+                .enter_locals(&wasm_params, &wasm_locals, &wasm_max_stack)
                 .inspect_err(|_| store.value_stack.clear())?;
             let callframe = CallFrame::new(self.func.addr(), locals_base, wasm_locals);
             Ok(ExecState::Running { callframe, root_func_addr: self.func.addr() })
 
@@ -620,7 +620,7 @@ impl<'store> Executor<'store> {
                     let Store { state, value_stack, .. } = self.store;
                     let object = state.gc.get(exception).ok_or(Trap::InvalidReference)?;
                     for value in object.values.iter().copied() {
-                        value_stack.push_dyn(value)?;
+                        value_stack.push_reserved(value)?;
                     }
                 }
                 if with_ref {
@@ -706,9 +706,8 @@ impl<'store> Executor<'store> {
 
     fn exec_call_self(&mut self, return_instr_ptr: usize) -> ExecResult<()> {
         self.charge_call_fuel(FUEL_COST_CALL_TOTAL);
-        let Ok(locals_base) = self.store.value_stack.enter_locals(&self.func.params, &self.func.locals) else {
-            return cold!(Err(Trap::CallStackOverflow.into()));
-        };
+        let locals_base =
+            self.store.value_stack.enter_locals(&self.func.params, &self.func.locals, &self.func.max_stack)?;
         let new = CallFrame::new(self.cf.func_addr, locals_base, self.func.locals);
         self.store.call_stack.push(core::mem::replace(&mut self.cf, new), return_instr_ptr)?;
         Ok(())
@@ -718,9 +717,8 @@ impl<'store> Executor<'store> {
         self.charge_call_fuel(FUEL_COST_CALL_TOTAL);
 
         self.store.value_stack.truncate_keep_counts(self.cf.locals_base, self.func.params);
-        let Ok(locals_base) = self.store.value_stack.enter_locals(&self.func.params, &self.func.locals) else {
-            return cold!(Err(Trap::CallStackOverflow.into()));
-        };
+        let locals_base =
+            self.store.value_stack.enter_locals(&self.func.params, &self.func.locals, &self.func.max_stack)?;
         self.cf = CallFrame::new(self.cf.func_addr, locals_base, self.func.locals);
         Ok(())
     }
@@ -780,14 +778,14 @@ impl<'store> Executor<'store> {
         return_instr_ptr: usize,
     ) -> ExecResult<ExecFlow> {
         let wasm_func = self.store.state.funcs.wasm(func_addr);
-        let (params, locals, owner, next_func) = {
+        let (params, locals, max_stack, owner, next_func) = {
             let next_func = (!Shared::ptr_eq(&self.func, &wasm_func.func)).then(|| wasm_func.func.clone());
-            (wasm_func.func.params, wasm_func.func.locals, wasm_func.owner, next_func)
+            (wasm_func.func.params, wasm_func.func.locals, wasm_func.func.max_stack, wasm_func.owner, next_func)
         };
         if TAIL {
             self.store.value_stack.truncate_keep_counts(self.cf.locals_base, params);
         }
-        let locals_base = self.store.value_stack.enter_locals(&params, &locals)?;
+        let locals_base = self.store.value_stack.enter_locals(&params, &locals, &max_stack)?;
         if TAIL {
             self.cf = CallFrame::new(func_addr, locals_base, locals);
         } else {