diff --git a/src/verbose_air.zig b/src/verbose_air.zig
index 1210837cb8..9311556012 100644
--- a/src/verbose_air.zig
+++ b/src/verbose_air.zig
@@ -298,3 +298,10 @@ fn zigCompileAirImpl(
     }
     return .{ .items = allocated.ptr, .len = len, .callback_count = collector.callback_count };
 }
+
+/// Return the tag name for an AIR instruction tag (u8).
+/// Exported for use by stage0 sema tests.
+export fn air_tag_name(tag_val: u8) [*:0]const u8 {
+    const e: Air.Inst.Tag = @enumFromInt(tag_val);
+    return @tagName(e);
+}
diff --git a/stage0/sema.h b/stage0/sema.h
index d9d30d210b..7e6de8308c 100644
--- a/stage0/sema.h
+++ b/stage0/sema.h
@@ -110,7 +110,8 @@ typedef struct {
 
 typedef struct {
     char* name; // function FQN (owned, null-terminated)
-    InternPoolIndex func_ip; // IP index of function value (for name resolution)
+    InternPoolIndex
+        func_ip; // IP index of function value (for name resolution)
     Air air; // per-function Air (owns its arrays)
 } SemaFuncAir;
 
diff --git a/stage0/sema_test.zig b/stage0/sema_test.zig
index 3276dc5db0..deced33968 100644
--- a/stage0/sema_test.zig
+++ b/stage0/sema_test.zig
@@ -309,6 +309,17 @@ fn cToOpt(comptime T: type, ptr: [*c]T) ?[*]const T {
     return if (ptr == null) null else @ptrCast(ptr);
 }
 
+fn airTagNameSlice(tag_val: u8) []const u8 {
+    return std.mem.span(air_tag_name(tag_val));
+}
+extern fn air_tag_name(tag: u8) [*:0]const u8;
+
+fn refKindStr(ref: u32) []const u8 {
+    if (ref == 0xFFFFFFFF) return "none";
+    if ((ref >> 31) != 0) return "inst";
+    return "ip";
+}
+
 /// Canonicalize an AIR Ref for comparison.  Inst refs (bit 31 set)
 /// and the special NONE sentinel are returned as-is.  IP refs (bit 31
 /// clear) are assigned a sequential canonical ID via the map, in
@@ -535,12 +546,12 @@ fn airCompareOne(name: []const u8, zig_air: *const c.Air, c_air: *const c.Air) !
         std.debug.print("'{s}': inst_len mismatch: zig={d} c={d}\n", .{ name, zig_air.inst_len, c_air.inst_len });
         if (cToOpt(u8, zig_air.inst_tags)) |zt| {
             std.debug.print("  zig tags:", .{});
-            for (0..zig_air.inst_len) |j| std.debug.print(" {d}", .{zt[j]});
+            for (0..zig_air.inst_len) |j| std.debug.print(" {s}", .{airTagNameSlice(zt[j])});
             std.debug.print("\n", .{});
         }
         if (cToOpt(u8, c_air.inst_tags)) |ct| {
             std.debug.print("  c   tags:", .{});
-            for (0..c_air.inst_len) |j| std.debug.print(" {d}", .{ct[j]});
+            for (0..c_air.inst_len) |j| std.debug.print(" {s}", .{airTagNameSlice(ct[j])});
             std.debug.print("\n", .{});
         }
         return error.AirMismatch;
@@ -568,7 +579,7 @@ fn airCompareOne(name: []const u8, zig_air: *const c.Air, c_air: *const c.Air) !
         if (!std.mem.eql(u8, zig_tags[0..inst_len], c_tags[0..inst_len])) {
             std.debug.print("'{s}': tags mismatch (inst_len={d}):", .{ name, inst_len });
             for (0..inst_len) |j| {
-                std.debug.print(" zig[{d}]={d} c[{d}]={d}", .{ j, zig_tags[j], j, c_tags[j] });
+                std.debug.print(" zig[{d}]={d}({s}) c[{d}]={d}({s})", .{ j, zig_tags[j], airTagNameSlice(zig_tags[j]), j, c_tags[j], airTagNameSlice(c_tags[j]) });
             }
             std.debug.print("\n", .{});
             return error.AirMismatch;
@@ -615,13 +626,13 @@ fn airCompareOne(name: []const u8, zig_air: *const c.Air, c_air: *const c.Air) !
                     const zig_canon = canonicalizeRef(zig_word, &zig_ref_map, &next_zig_id);
                     const c_canon = canonicalizeRef(c_word, &c_ref_map, &next_c_id);
                     if (zig_canon != c_canon) {
-                        std.debug.print("'{s}': datas ref mismatch at inst[{d}] slot {d}: zig=0x{x} c=0x{x} (canon: zig={d} c={d}) (tag={d})\n", .{ name, j, slot, zig_word, c_word, zig_canon, c_canon, tag_val });
+                        std.debug.print("'{s}': datas ref mismatch at inst[{d}] slot {d}: zig=0x{x}[{s}] c=0x{x}[{s}] (canon: zig={d} c={d}) (tag={s})\n", .{ name, j, slot, zig_word, refKindStr(zig_word), c_word, refKindStr(c_word), zig_canon, c_canon, airTagNameSlice(tag_val) });
                         return error.AirMismatch;
                     }
                 } else {
                     // Non-ref field — compare directly.
                     if (zig_word != c_word) {
-                        std.debug.print("'{s}': datas mismatch at inst[{d}] slot {d}: zig=0x{x} c=0x{x} (tag={d})\n", .{ name, j, slot, zig_word, c_word, tag_val });
+                        std.debug.print("'{s}': datas mismatch at inst[{d}] slot {d}: zig=0x{x} c=0x{x} (tag={s})\n", .{ name, j, slot, zig_word, c_word, airTagNameSlice(tag_val) });
                         return error.AirMismatch;
                     }
                 }