phase29af(p4): layout consistency fail-fast

src/mir/builder/control_flow/joinir/merge/boundary_carrier_layout.rs

@@ -42,7 +42,4 @@ impl BoundaryCarrierLayout {
         self.ordered_names.iter().position(|n| n == name)
     }
 
-    pub fn len(&self) -> usize {
-        self.ordered_names.len()
-    }
 }

src/mir/builder/control_flow/joinir/merge/contract_checks/boundary_hygiene.rs

@@ -38,17 +38,19 @@ pub(in crate::mir::builder::control_flow::joinir::merge) fn verify_boundary_hygi
     }
 
     if let Some(carrier_info) = &boundary.carrier_info {
-        let expected_len =
-            carrier_info.carriers.len() + if boundary.loop_var_name.is_some() { 1 } else { 0 };
-        let layout_len = BoundaryCarrierLayout::from_boundary(boundary).len();
-        if expected_len != layout_len {
+        let expected_names: Vec<&str> = std::iter::once(carrier_info.loop_var_name.as_str())
+            .chain(carrier_info.carriers.iter().map(|c| c.name.as_str()))
+            .collect();
+        let layout = BoundaryCarrierLayout::from_boundary(boundary);
+        let layout_names = layout.ordered_names();
+        if expected_names != layout_names {
             return Err(error_tags::freeze_with_hint(
-                "phase29af/boundary_hygiene/layout_len",
+                "phase29af/boundary_hygiene/layout_order",
                 &format!(
-                    "boundary carrier layout len {} does not match carrier_info len {}",
-                    layout_len, expected_len
+                    "boundary carrier order {:?} does not match carrier_info order {:?}",
+                    layout_names, expected_names
                 ),
-                "ensure loop_var + carriers ordering is consistent with carrier_info",
+                "ensure boundary carrier order matches carrier_info",
             ));
         }
 

src/mir/builder/control_flow/joinir/merge/contract_checks/header_phi_layout.rs

@@ -0,0 +1,39 @@
+use crate::mir::builder::control_flow::joinir::merge::boundary_carrier_layout::BoundaryCarrierLayout;
+use crate::mir::builder::control_flow::joinir::merge::loop_header_phi_info::LoopHeaderPhiInfo;
+use crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary;
+
+/// Phase 29af P4: Verify boundary carrier order matches header PHI order.
+pub(in crate::mir::builder::control_flow::joinir::merge) fn verify_header_phi_layout(
+    boundary: &JoinInlineBoundary,
+    loop_header_phi_info: &LoopHeaderPhiInfo,
+) -> Result<(), String> {
+    use crate::mir::join_ir::lowering::error_tags;
+
+    let strict = crate::config::env::joinir_strict_enabled()
+        || crate::config::env::joinir_dev_enabled();
+    if !strict {
+        return Ok(());
+    }
+
+    let boundary_layout = BoundaryCarrierLayout::from_boundary(boundary);
+    let boundary_names = boundary_layout.ordered_names();
+
+    let header_names: Vec<&str> = loop_header_phi_info
+        .carrier_order
+        .iter()
+        .map(|name| name.as_str())
+        .collect();
+
+    if boundary_names != header_names {
+        return Err(error_tags::freeze_with_hint(
+            "phase29af/layout/header_phi_order",
+            &format!(
+                "boundary carrier order {:?} does not match header PHI order {:?}",
+                boundary_names, header_names
+            ),
+            "ensure boundary carrier layout matches header PHI construction order",
+        ));
+    }
+
+    Ok(())
+}

src/mir/builder/control_flow/joinir/merge/contract_checks/mod.rs

@@ -15,6 +15,7 @@ mod exit_bindings;
 mod carrier_inputs;
 mod boundary_creation;
 mod boundary_hygiene;
+mod header_phi_layout;
 mod entry_params;
 mod entry_like_policy;
 
@@ -23,6 +24,7 @@ pub(super) use terminator_targets::verify_all_terminator_targets_exist;
 pub(super) use exit_bindings::verify_exit_bindings_have_exit_phis;
 pub(super) use carrier_inputs::verify_carrier_inputs_complete;
 pub(super) use boundary_hygiene::verify_boundary_hygiene;
+pub(super) use header_phi_layout::verify_header_phi_layout;
 pub(super) use entry_like_policy::is_entry_like_source;
 pub(in crate::mir::builder::control_flow::joinir) use boundary_creation::verify_boundary_contract_at_creation;
 pub(in crate::mir::builder::control_flow::joinir) use entry_params::run_all_pipeline_checks;

src/mir/builder/control_flow/joinir/merge/coordinator.rs

@@ -224,6 +224,9 @@ pub(in crate::mir::builder) fn merge_joinir_mir_blocks(
             &function_params,
             debug,
         )?;
+    if let Some(boundary) = boundary {
+        contract_checks::verify_header_phi_layout(boundary, &loop_header_phi_info)?;
+    }
 
     // Phase 3: Remap ValueIds (with reserved PHI dsts protection)
     // Phase 287 P0.2: Delegated to value_remapper module