diff --git a/fec/src/lower.h b/fec/src/lower.h
new file mode 100644
index 0000000..bb2e544
--- /dev/null
+++ b/fec/src/lower.h
@@ -0,0 +1,61 @@
+#ifndef FE_LOWER_H
+#define FE_LOWER_H
+
+#include "types.h"
+
+#define FE_LOWER_NO_SCOPE ((unsigned)~0U)
+
+typedef enum FeLowerExitKind {
+    FE_LOWER_EXIT_FALLTHROUGH = 0,
+    FE_LOWER_EXIT_RETURN,
+    FE_LOWER_EXIT_ERROR_RETURN,
+    FE_LOWER_EXIT_BREAK,
+    FE_LOWER_EXIT_CONTINUE
+} FeLowerExitKind;
+
+typedef enum FeLowerCleanupKind {
+    FE_LOWER_CLEANUP_DROP = 0,
+    FE_LOWER_CLEANUP_DEFER
+} FeLowerCleanupKind;
+
+typedef struct FeLowerScope {
+    FeNode *block;
+    unsigned parent;
+    unsigned ordinal;
+} FeLowerScope;
+
+typedef struct FeLowerCleanup {
+    FeLowerCleanupKind kind;
+    unsigned scope;
+    unsigned ordinal;
+    FeNode *node;
+    FeNode *decl;
+    FeType *type;
+} FeLowerCleanup;
+
+typedef struct FeLowerPlan {
+    FeArena *arena;
+    FeNode *fn;
+    FeLowerScope *scopes;
+    unsigned scope_count;
+    unsigned scope_capacity;
+    FeLowerCleanup *cleanups;
+    unsigned cleanup_count;
+    unsigned cleanup_capacity;
+    unsigned next_ordinal;
+} FeLowerPlan;
+
+void fe_lower_plan_init(FeLowerPlan *plan, FeArena *arena);
+int fe_lower_plan_build(FeLowerPlan *plan, FeNode *fn);
+unsigned fe_lower_scope_for_block(const FeLowerPlan *plan,
+                                  const FeNode *block);
+unsigned fe_lower_collect_cleanups(const FeLowerPlan *plan,
+                                   const FeNode *from_block,
+                                   const FeNode *stop_block,
+                                   const FeLowerCleanup **out,
+                                   unsigned out_capacity);
+int fe_lower_type_needs_drop(const FeType *type);
+int fe_lower_exit_runs_cleanup(FeLowerExitKind kind);
+int fe_lower_exit_leaves_function(FeLowerExitKind kind);
+
+#endif