diff --git a/toolchain/check/BUILD b/toolchain/check/BUILD
index abf01dad08bf..b77dc369a4bc 100644
--- a/toolchain/check/BUILD
+++ b/toolchain/check/BUILD
@@ -241,6 +241,7 @@ cc_library(
         "//common:vlog",
         "//toolchain/parse:node_kind",
         "//toolchain/parse:tree",
+        "//toolchain/sem_ir:formatter",
         "//toolchain/sem_ir:ids",
         "@llvm-project//llvm:Support",
     ],
diff --git a/toolchain/check/context.cpp b/toolchain/check/context.cpp
index b158b323d0ce..d3edcd199eee 100644
--- a/toolchain/check/context.cpp
+++ b/toolchain/check/context.cpp
@@ -1193,14 +1193,22 @@ auto Context::GetUnqualifiedType(SemIR::TypeId type_id) -> SemIR::TypeId {
 }
 
 auto Context::PrintForStackDump(llvm::raw_ostream& output) const -> void {
-  node_stack_.PrintForStackDump(output);
-  inst_block_stack_.PrintForStackDump(output);
-  param_and_arg_refs_stack_.PrintForStackDump(output);
-  args_type_info_stack_.PrintForStackDump(output);
+  output << "Check::Context\n";
+
+  // In a stack dump, this is probably indented by a tab. We treat that as 8
+  // spaces then add a couple to indent past the Context label.
+  constexpr int Indent = 10;
+
+  SemIR::Formatter formatter(*tokens_, *parse_tree_, *sem_ir_);
+  node_stack_.PrintForStackDump(formatter, Indent, output);
+  inst_block_stack_.PrintForStackDump(formatter, Indent, output);
+  param_and_arg_refs_stack_.PrintForStackDump(formatter, Indent, output);
+  args_type_info_stack_.PrintForStackDump(formatter, Indent, output);
 }
 
 auto Context::DumpFormattedFile() const -> void {
-  FormatFile(*tokens_, *parse_tree_, *sem_ir_, llvm::errs());
+  SemIR::Formatter formatter(*tokens_, *parse_tree_, *sem_ir_);
+  formatter.Print(llvm::errs());
 }
 
 }  // namespace Carbon::Check
diff --git a/toolchain/check/inst_block_stack.cpp b/toolchain/check/inst_block_stack.cpp
index 7220e49af1d5..9ffcc3540b51 100644
--- a/toolchain/check/inst_block_stack.cpp
+++ b/toolchain/check/inst_block_stack.cpp
@@ -61,16 +61,17 @@ auto InstBlockStack::PopAndDiscard() -> void {
   CARBON_VLOG() << name_ << " PopAndDiscard " << id_stack_.size() << "\n";
 }
 
-auto InstBlockStack::PrintForStackDump(llvm::raw_ostream& output) const
+auto InstBlockStack::PrintForStackDump(SemIR::Formatter& formatter, int indent,
+                                       llvm::raw_ostream& output) const
     -> void {
+  output.indent(indent);
   output << name_ << ":\n";
   for (const auto& [i, id] : llvm::enumerate(id_stack_)) {
-    output << "\t" << i << ".\t" << id << "\t{";
-    llvm::ListSeparator sep;
-    for (auto id : insts_stack_.PeekArrayAt(i)) {
-      output << sep << id;
-    }
-    output << "}\n";
+    output.indent(indent + 2);
+    output << i << ". " << id;
+    formatter.PrintPartialTrailingCodeBlock(insts_stack_.PeekArrayAt(i),
+                                            indent + 4, output);
+    output << "\n";
   }
 }
 
diff --git a/toolchain/check/inst_block_stack.h b/toolchain/check/inst_block_stack.h
index 159cf3ccb340..0115861d4bcf 100644
--- a/toolchain/check/inst_block_stack.h
+++ b/toolchain/check/inst_block_stack.h
@@ -8,6 +8,7 @@
 #include "common/array_stack.h"
 #include "llvm/ADT/SmallVector.h"
 #include "toolchain/sem_ir/file.h"
+#include "toolchain/sem_ir/formatter.h"
 
 namespace Carbon::Check {
 
@@ -69,7 +70,8 @@ class InstBlockStack {
   }
 
   // Prints the stack for a stack dump.
-  auto PrintForStackDump(llvm::raw_ostream& output) const -> void;
+  auto PrintForStackDump(SemIR::Formatter& formatter, int indent,
+                         llvm::raw_ostream& output) const -> void;
 
   // Runs verification that the processing cleanly finished.
   auto VerifyOnFinish() const -> void {
diff --git a/toolchain/check/node_stack.cpp b/toolchain/check/node_stack.cpp
index 13cb9f432e97..8b28e0707d78 100644
--- a/toolchain/check/node_stack.cpp
+++ b/toolchain/check/node_stack.cpp
@@ -8,21 +8,28 @@
 
 namespace Carbon::Check {
 
-auto NodeStack::PrintForStackDump(llvm::raw_ostream& output) const -> void {
+auto NodeStack::PrintForStackDump(SemIR::Formatter& formatter, int indent,
+                                  llvm::raw_ostream& output) const -> void {
   auto print_id = [&]<Id::Kind Kind>(Id id) {
     if constexpr (Kind == Id::Kind::None) {
-      output << " -> no value";
+      output << "no value\n";
     } else if constexpr (Kind == Id::Kind::Invalid) {
       CARBON_FATAL() << "Should not be in node stack";
+    } else if constexpr (Kind == Id::KindFor<SemIR::InstId>()) {
+      output << "\n";
+      formatter.PrintInst(id.As<Id::KindFor<SemIR::InstId>()>(), indent + 4,
+                          output);
     } else {
-      output << " -> " << id.As<Kind>();
+      output << id.As<Kind>() << "\n";
     }
   };
 
+  output.indent(indent);
   output << "NodeStack:\n";
   for (auto [i, entry] : llvm::enumerate(stack_)) {
     auto node_kind = parse_tree_->node_kind(entry.node_id);
-    output << "\t" << i << ".\t" << node_kind;
+    output.indent(indent + 2);
+    output << i << ". " << node_kind << ": ";
     switch (node_kind) {
 #define CARBON_PARSE_NODE_KIND(Kind)                                        \
   case Parse::NodeKind::Kind:                                               \
@@ -30,7 +37,6 @@ auto NodeStack::PrintForStackDump(llvm::raw_ostream& output) const -> void {
     break;
 #include "toolchain/parse/node_kind.def"
     }
-    output << "\n";
   }
 }
 
diff --git a/toolchain/check/node_stack.h b/toolchain/check/node_stack.h
index 989f964c4c06..463979cb8105 100644
--- a/toolchain/check/node_stack.h
+++ b/toolchain/check/node_stack.h
@@ -11,6 +11,7 @@
 #include "toolchain/parse/node_kind.h"
 #include "toolchain/parse/tree.h"
 #include "toolchain/parse/typed_nodes.h"
+#include "toolchain/sem_ir/formatter.h"
 #include "toolchain/sem_ir/id_kind.h"
 #include "toolchain/sem_ir/ids.h"
 
@@ -325,7 +326,8 @@ class NodeStack {
   }
 
   // Prints the stack for a stack dump.
-  auto PrintForStackDump(llvm::raw_ostream& output) const -> void;
+  auto PrintForStackDump(SemIR::Formatter& formatter, int indent,
+                         llvm::raw_ostream& output) const -> void;
 
   auto empty() const -> bool { return stack_.empty(); }
   auto size() const -> size_t { return stack_.size(); }
diff --git a/toolchain/check/param_and_arg_refs_stack.h b/toolchain/check/param_and_arg_refs_stack.h
index aa91838f5b7b..dbdfa516fedd 100644
--- a/toolchain/check/param_and_arg_refs_stack.h
+++ b/toolchain/check/param_and_arg_refs_stack.h
@@ -72,8 +72,9 @@ class ParamAndArgRefsStack {
   auto VerifyOnFinish() -> void { stack_.VerifyOnFinish(); }
 
   // Prints the stack for a stack dump.
-  auto PrintForStackDump(llvm::raw_ostream& output) const -> void {
-    return stack_.PrintForStackDump(output);
+  auto PrintForStackDump(SemIR::Formatter& formatter, int indent,
+                         llvm::raw_ostream& output) const -> void {
+    return stack_.PrintForStackDump(formatter, indent, output);
   }
 
  private:
diff --git a/toolchain/check/testdata/class/fail_generic_method.carbon b/toolchain/check/testdata/class/fail_generic_method.carbon
index 2de067d5cfbd..ae4646874cee 100644
--- a/toolchain/check/testdata/class/fail_generic_method.carbon
+++ b/toolchain/check/testdata/class/fail_generic_method.carbon
@@ -83,7 +83,7 @@ fn Class(N:! i32).F[self: Self](n: T) {}
 // CHECK:STDOUT: class @Class
 // CHECK:STDOUT:     generic [file.%T.loc11_13.2: type] {
 // CHECK:STDOUT:   %T.ref.loc12: type = name_ref T, file.%T.loc11_13.2 [symbolic = file.%T.loc11_13.2 (constants.%T)]
-// CHECK:STDOUT:   %.loc12: <unexpected instref inst+28> (%.2) = field_decl a, element0 [template]
+// CHECK:STDOUT:   %.loc12: <unexpected>.inst+28 (%.2) = field_decl a, element0 [template]
 // CHECK:STDOUT:   %F.decl: %F.type = fn_decl @F [template = constants.%F] {
 // CHECK:STDOUT:     %.loc13: type = specific_constant constants.%Class.2, file.%Class.decl(constants.%T) [symbolic = %.loc13 (constants.%Class.2)]
 // CHECK:STDOUT:     %Self.ref: type = name_ref Self, %.loc13 [symbolic = %.loc13 (constants.%Class.2)]
diff --git a/toolchain/check/testdata/class/generic/basic.carbon b/toolchain/check/testdata/class/generic/basic.carbon
index ba7e2326d20d..4128b3cd320d 100644
--- a/toolchain/check/testdata/class/generic/basic.carbon
+++ b/toolchain/check/testdata/class/generic/basic.carbon
@@ -76,7 +76,7 @@ class Class(T:! type) {
 // CHECK:STDOUT:     %return.var.loc17: ref %T = var <return slot>
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %T.ref.loc21: type = name_ref T, file.%T.loc11_13.2 [symbolic = file.%T.loc11_13.2 (constants.%T)]
-// CHECK:STDOUT:   %.loc21: <unexpected instref inst+41> (%.4) = field_decl k, element0 [template]
+// CHECK:STDOUT:   %.loc21: <unexpected>.inst+41 (%.4) = field_decl k, element0 [template]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
 // CHECK:STDOUT:   .Self = constants.%Class.2
@@ -90,7 +90,7 @@ class Class(T:! type) {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %self.ref: @Class.%.loc12_29 (%.2) = name_ref self, @Class.%self.loc12_19.3
 // CHECK:STDOUT:   %.loc13_17.1: ref @Class.%.loc12_25 (%Class.2) = deref %self.ref
-// CHECK:STDOUT:   %k.ref: <unexpected instref inst+49> (%.4) = name_ref k, @Class.%.loc21 [template = @Class.%.loc21]
+// CHECK:STDOUT:   %k.ref: <unexpected>.inst+49 (%.4) = name_ref k, @Class.%.loc21 [template = @Class.%.loc21]
 // CHECK:STDOUT:   %.loc13_17.2: ref @Class.%T.ref.loc12 (%T) = class_element_access %.loc13_17.1, element0
 // CHECK:STDOUT:   %.loc13_12: @Class.%.loc12_38 (%.3) = addr_of %.loc13_17.2
 // CHECK:STDOUT:   return %.loc13_12
@@ -100,7 +100,7 @@ class Class(T:! type) {
 // CHECK:STDOUT:     generic [file.%T.loc11_13.2: type] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %self.ref: @Class.%.loc17 (%Class.2) = name_ref self, @Class.%self.loc17_15.2
-// CHECK:STDOUT:   %k.ref: <unexpected instref inst+55> (%.4) = name_ref k, @Class.%.loc21 [template = @Class.%.loc21]
+// CHECK:STDOUT:   %k.ref: <unexpected>.inst+55 (%.4) = name_ref k, @Class.%.loc21 [template = @Class.%.loc21]
 // CHECK:STDOUT:   %.loc18_16.1: ref @Class.%T.ref.loc17 (%T) = class_element_access %self.ref, element0
 // CHECK:STDOUT:   %.loc18_16.2: @Class.%T.ref.loc17 (%T) = bind_value %.loc18_16.1
 // CHECK:STDOUT:   return %.loc18_16.2
@@ -111,9 +111,9 @@ class Class(T:! type) {
 // CHECK:STDOUT:   file.%T.loc11_13.2 => constants.%T
 // CHECK:STDOUT:
 // CHECK:STDOUT: definition:
-// CHECK:STDOUT:   <unexpected instref inst+40> => constants.%Class.2
-// CHECK:STDOUT:   <unexpected instref inst+41> => constants.%.4
-// CHECK:STDOUT:   <unexpected instref inst+37> => <unexpected instref inst+38>
+// CHECK:STDOUT:   <unexpected>.inst+40 => constants.%Class.2
+// CHECK:STDOUT:   <unexpected>.inst+41 => constants.%.4
+// CHECK:STDOUT:   <unexpected>.inst+37.loc21_8 => <unexpected>.inst+38
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @Class.%GetAddr.decl(constants.%T) {
diff --git a/toolchain/check/testdata/class/generic/fail_todo_use.carbon b/toolchain/check/testdata/class/generic/fail_todo_use.carbon
index 94e19241099b..8ab253edd1bd 100644
--- a/toolchain/check/testdata/class/generic/fail_todo_use.carbon
+++ b/toolchain/check/testdata/class/generic/fail_todo_use.carbon
@@ -101,7 +101,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT:     %return.var: ref %.3 = var <return slot>
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %T.ref.loc16: type = name_ref T, file.%T.loc11_13.2 [symbolic = file.%T.loc11_13.2 (constants.%T)]
-// CHECK:STDOUT:   %.loc16: <unexpected instref inst+32> (%.4) = field_decl k, element0 [template]
+// CHECK:STDOUT:   %.loc16: <unexpected>.inst+32 (%.4) = field_decl k, element0 [template]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
 // CHECK:STDOUT:   .Self = constants.%Class.2
@@ -114,7 +114,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %self.ref: @Class.%.loc12_25 (%.2) = name_ref self, @Class.%self.loc12_15.3
 // CHECK:STDOUT:   %.loc13_17.1: ref @Class.%.loc12_21 (%Class.2) = deref %self.ref
-// CHECK:STDOUT:   %k.ref: <unexpected instref inst+40> (%.4) = name_ref k, @Class.%.loc16 [template = @Class.%.loc16]
+// CHECK:STDOUT:   %k.ref: <unexpected>.inst+40 (%.4) = name_ref k, @Class.%.loc16 [template = @Class.%.loc16]
 // CHECK:STDOUT:   %.loc13_17.2: ref @Class.%T.ref.loc12 (%T) = class_element_access %.loc13_17.1, element0
 // CHECK:STDOUT:   %.loc13_12: @Class.%.loc12_34 (%.3) = addr_of %.loc13_17.2
 // CHECK:STDOUT:   return %.loc13_12
@@ -149,9 +149,9 @@ fn Run() -> i32 {
 // CHECK:STDOUT:   file.%T.loc11_13.2 => constants.%T
 // CHECK:STDOUT:
 // CHECK:STDOUT: definition:
-// CHECK:STDOUT:   <unexpected instref inst+31> => constants.%Class.2
-// CHECK:STDOUT:   <unexpected instref inst+32> => constants.%.4
-// CHECK:STDOUT:   <unexpected instref inst+28> => <unexpected instref inst+29>
+// CHECK:STDOUT:   <unexpected>.inst+31 => constants.%Class.2
+// CHECK:STDOUT:   <unexpected>.inst+32 => constants.%.4
+// CHECK:STDOUT:   <unexpected>.inst+28.loc16_8 => <unexpected>.inst+29
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @Class.%Get.decl(constants.%T) {
@@ -172,8 +172,8 @@ fn Run() -> i32 {
 // CHECK:STDOUT:   file.%T.loc11_13.2 => i32
 // CHECK:STDOUT:
 // CHECK:STDOUT: definition:
-// CHECK:STDOUT:   <unexpected instref inst+31> => constants.%Class.3
-// CHECK:STDOUT:   <unexpected instref inst+32> => constants.%.7
-// CHECK:STDOUT:   <unexpected instref inst+28> => <unexpected instref inst+29>
+// CHECK:STDOUT:   <unexpected>.inst+31 => constants.%Class.3
+// CHECK:STDOUT:   <unexpected>.inst+32 => constants.%.7
+// CHECK:STDOUT:   <unexpected>.inst+28.loc16_8 => <unexpected>.inst+29
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/check/testdata/class/generic/field.carbon b/toolchain/check/testdata/class/generic/field.carbon
index 6691820b430b..ec662761be67 100644
--- a/toolchain/check/testdata/class/generic/field.carbon
+++ b/toolchain/check/testdata/class/generic/field.carbon
@@ -115,7 +115,7 @@ fn H(U:! type, c: Class(U)) -> U {
 // CHECK:STDOUT: class @Class
 // CHECK:STDOUT:     generic [file.%T.loc11_13.2: type] {
 // CHECK:STDOUT:   %T.ref: type = name_ref T, file.%T.loc11_13.2 [symbolic = file.%T.loc11_13.2 (constants.%T)]
-// CHECK:STDOUT:   %.loc12: <unexpected instref inst+18> (%.2) = field_decl x, element0 [template]
+// CHECK:STDOUT:   %.loc12: <unexpected>.inst+18 (%.2) = field_decl x, element0 [template]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
 // CHECK:STDOUT:   .Self = constants.%Class.2
@@ -137,7 +137,7 @@ fn H(U:! type, c: Class(U)) -> U {
 // CHECK:STDOUT:     generic [%T: type] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %c.ref: file.%.loc19_24 (%Class.2) = name_ref c, %c
-// CHECK:STDOUT:   %x.ref: <unexpected instref inst+68> (%.2) = name_ref x, @Class.%.loc12 [template = @Class.%.loc12]
+// CHECK:STDOUT:   %x.ref: <unexpected>.inst+68 (%.2) = name_ref x, @Class.%.loc12 [template = @Class.%.loc12]
 // CHECK:STDOUT:   %.loc20_11.1: ref @G.%T (%T) = class_element_access %c.ref, element0
 // CHECK:STDOUT:   %.loc20_11.2: @G.%T (%T) = bind_value %.loc20_11.1
 // CHECK:STDOUT:   return %.loc20_11.2
@@ -147,7 +147,7 @@ fn H(U:! type, c: Class(U)) -> U {
 // CHECK:STDOUT:     generic [%U: type] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %c.ref: file.%.loc23_24 (%Class.4) = name_ref c, %c
-// CHECK:STDOUT:   %x.ref: <unexpected instref inst+91> (%.6) = name_ref x, @Class.%.loc12 [template = @Class.%.loc12]
+// CHECK:STDOUT:   %x.ref: <unexpected>.inst+91 (%.6) = name_ref x, @Class.%.loc12 [template = @Class.%.loc12]
 // CHECK:STDOUT:   %.loc24_11.1: ref @H.%U (%U) = class_element_access %c.ref, element0
 // CHECK:STDOUT:   %.loc24_11.2: @H.%U (%U) = bind_value %.loc24_11.1
 // CHECK:STDOUT:   return %.loc24_11.2
@@ -158,9 +158,9 @@ fn H(U:! type, c: Class(U)) -> U {
 // CHECK:STDOUT:   file.%T.loc11_13.2 => constants.%T
 // CHECK:STDOUT:
 // CHECK:STDOUT: definition:
-// CHECK:STDOUT:   <unexpected instref inst+17> => constants.%Class.2
-// CHECK:STDOUT:   <unexpected instref inst+18> => constants.%.2
-// CHECK:STDOUT:   <unexpected instref inst+14> => <unexpected instref inst+15>
+// CHECK:STDOUT:   <unexpected>.inst+17 => constants.%Class.2
+// CHECK:STDOUT:   <unexpected>.inst+18 => constants.%.2
+// CHECK:STDOUT:   <unexpected>.inst+14.loc12_8 => <unexpected>.inst+15
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific file.%Class.decl(file.%T.loc11_13.2) {
@@ -173,9 +173,9 @@ fn H(U:! type, c: Class(U)) -> U {
 // CHECK:STDOUT:   file.%T.loc11_13.2 => i32
 // CHECK:STDOUT:
 // CHECK:STDOUT: definition:
-// CHECK:STDOUT:   <unexpected instref inst+17> => constants.%Class.3
-// CHECK:STDOUT:   <unexpected instref inst+18> => constants.%.4
-// CHECK:STDOUT:   <unexpected instref inst+14> => <unexpected instref inst+15>
+// CHECK:STDOUT:   <unexpected>.inst+17 => constants.%Class.3
+// CHECK:STDOUT:   <unexpected>.inst+18 => constants.%.4
+// CHECK:STDOUT:   <unexpected>.inst+14.loc12_8 => <unexpected>.inst+15
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific file.%G.decl(constants.%T) {
@@ -189,9 +189,9 @@ fn H(U:! type, c: Class(U)) -> U {
 // CHECK:STDOUT:   file.%T.loc11_13.2 => constants.%U
 // CHECK:STDOUT:
 // CHECK:STDOUT: definition:
-// CHECK:STDOUT:   <unexpected instref inst+17> => constants.%Class.4
-// CHECK:STDOUT:   <unexpected instref inst+18> => constants.%.6
-// CHECK:STDOUT:   <unexpected instref inst+14> => <unexpected instref inst+15>
+// CHECK:STDOUT:   <unexpected>.inst+17 => constants.%Class.4
+// CHECK:STDOUT:   <unexpected>.inst+18 => constants.%.6
+// CHECK:STDOUT:   <unexpected>.inst+14.loc12_8 => <unexpected>.inst+15
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific file.%H.decl(constants.%U) {
diff --git a/toolchain/check/testdata/class/generic/import.carbon b/toolchain/check/testdata/class/generic/import.carbon
index 4644962104c7..8b1020665ad4 100644
--- a/toolchain/check/testdata/class/generic/import.carbon
+++ b/toolchain/check/testdata/class/generic/import.carbon
@@ -154,7 +154,7 @@ class Class(U:! type) {
 // CHECK:STDOUT:   %int.make_type_32.loc7: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:   %.loc7_10.1: type = value_of_initializer %int.make_type_32.loc7 [template = i32]
 // CHECK:STDOUT:   %.loc7_10.2: type = converted %int.make_type_32.loc7, %.loc7_10.1 [template = i32]
-// CHECK:STDOUT:   %.loc7_8: <unexpected instref inst+39> (%.2) = field_decl n, element0 [template]
+// CHECK:STDOUT:   %.loc7_8: <unexpected>.inst+39 (%.2) = field_decl n, element0 [template]
 // CHECK:STDOUT:   %F.decl: %F.type.1 = fn_decl @F.1 [template = constants.%F.1] {
 // CHECK:STDOUT:     %int.make_type_32.loc8: init type = call constants.%Int32() [template = i32]
 // CHECK:STDOUT:     %.loc8_13.1: type = value_of_initializer %int.make_type_32.loc8 [template = i32]
@@ -206,7 +206,7 @@ class Class(U:! type) {
 // CHECK:STDOUT: --- foo.impl.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
-// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected instref inst+31> [symbolic]
+// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected>.inst+31 [symbolic]
 // CHECK:STDOUT:   %Class.type: type = generic_class_type @Class [template]
 // CHECK:STDOUT:   %.1: type = tuple_type () [template]
 // CHECK:STDOUT:   %Class.1: %Class.type = struct_value () [template]
@@ -308,7 +308,7 @@ class Class(U:! type) {
 // CHECK:STDOUT:   %CompleteClass.type: type = generic_class_type @CompleteClass [template]
 // CHECK:STDOUT:   %CompleteClass.1: %CompleteClass.type = struct_value () [template]
 // CHECK:STDOUT:   %.2: type = struct_type {.n: i32} [template]
-// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected instref inst+28> [symbolic]
+// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected>.inst+28 [symbolic]
 // CHECK:STDOUT:   %CompleteClass.2: type = class_type @CompleteClass, <invalid>(%T) [symbolic]
 // CHECK:STDOUT:   %CompleteClass.3: type = class_type @CompleteClass, <invalid>(i32) [template]
 // CHECK:STDOUT:   %.3: type = ptr_type %.2 [template]
@@ -399,7 +399,7 @@ class Class(U:! type) {
 // CHECK:STDOUT:   %CompleteClass.type: type = generic_class_type @CompleteClass [template]
 // CHECK:STDOUT:   %CompleteClass.1: %CompleteClass.type = struct_value () [template]
 // CHECK:STDOUT:   %.2: type = struct_type {.n: i32} [template]
-// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected instref inst+28> [symbolic]
+// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected>.inst+28 [symbolic]
 // CHECK:STDOUT:   %CompleteClass.2: type = class_type @CompleteClass, <invalid>(%T) [symbolic]
 // CHECK:STDOUT:   %CompleteClass.3: type = class_type @CompleteClass, <invalid>(i32) [template]
 // CHECK:STDOUT:   %.3: type = ptr_type %.2 [template]
@@ -483,7 +483,7 @@ class Class(U:! type) {
 // CHECK:STDOUT:   %CompleteClass.type: type = generic_class_type @CompleteClass [template]
 // CHECK:STDOUT:   %CompleteClass.1: %CompleteClass.type = struct_value () [template]
 // CHECK:STDOUT:   %.2: type = struct_type {.n: i32} [template]
-// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected instref inst+19> [symbolic]
+// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected>.inst+19 [symbolic]
 // CHECK:STDOUT:   %CompleteClass.2: type = class_type @CompleteClass, <invalid>(%T) [symbolic]
 // CHECK:STDOUT:   %Int32.type: type = fn_type @Int32 [template]
 // CHECK:STDOUT:   %Int32: %Int32.type = struct_value () [template]
@@ -562,7 +562,7 @@ class Class(U:! type) {
 // CHECK:STDOUT:   %Class.type: type = generic_class_type @Class [template]
 // CHECK:STDOUT:   %.1: type = tuple_type () [template]
 // CHECK:STDOUT:   %Class.1: %Class.type = struct_value () [template]
-// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected instref inst+17> [symbolic]
+// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected>.inst+17 [symbolic]
 // CHECK:STDOUT:   %Class.2: type = class_type @Class, <invalid>(%T) [symbolic]
 // CHECK:STDOUT:   %.type: type = generic_class_type @.1 [template]
 // CHECK:STDOUT:   %.2: %.type = struct_value () [template]
diff --git a/toolchain/check/testdata/class/generic_method.carbon b/toolchain/check/testdata/class/generic_method.carbon
index cb8bc1faad41..90d85dd15c05 100644
--- a/toolchain/check/testdata/class/generic_method.carbon
+++ b/toolchain/check/testdata/class/generic_method.carbon
@@ -57,7 +57,7 @@ fn Class(T:! type).F[self: Self](n: T) {}
 // CHECK:STDOUT: class @Class
 // CHECK:STDOUT:     generic [file.%T.loc11_13.2: type] {
 // CHECK:STDOUT:   %T.ref.loc12: type = name_ref T, file.%T.loc11_13.2 [symbolic = file.%T.loc11_13.2 (constants.%T)]
-// CHECK:STDOUT:   %.loc12: <unexpected instref inst+28> (%.2) = field_decl a, element0 [template]
+// CHECK:STDOUT:   %.loc12: <unexpected>.inst+28 (%.2) = field_decl a, element0 [template]
 // CHECK:STDOUT:   %F.decl: %F.type = fn_decl @F [template = constants.%F] {
 // CHECK:STDOUT:     %.loc13: type = specific_constant constants.%Class.2, file.%Class.decl(constants.%T) [symbolic = %.loc13 (constants.%Class.2)]
 // CHECK:STDOUT:     %Self.ref: type = name_ref Self, %.loc13 [symbolic = %.loc13 (constants.%Class.2)]
@@ -85,9 +85,9 @@ fn Class(T:! type).F[self: Self](n: T) {}
 // CHECK:STDOUT:   file.%T.loc11_13.2 => constants.%T
 // CHECK:STDOUT:
 // CHECK:STDOUT: definition:
-// CHECK:STDOUT:   <unexpected instref inst+27> => constants.%Class.2
-// CHECK:STDOUT:   <unexpected instref inst+28> => constants.%.2
-// CHECK:STDOUT:   <unexpected instref inst+14> => <unexpected instref inst+15>
+// CHECK:STDOUT:   <unexpected>.inst+27 => constants.%Class.2
+// CHECK:STDOUT:   <unexpected>.inst+28 => constants.%.2
+// CHECK:STDOUT:   <unexpected>.inst+14.loc12_8 => <unexpected>.inst+15
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @Class.%F.decl(constants.%T) {
diff --git a/toolchain/check/testdata/function/generic/redeclare.carbon b/toolchain/check/testdata/function/generic/redeclare.carbon
index 255f8071dc2e..2e6ddd9f4bf2 100644
--- a/toolchain/check/testdata/function/generic/redeclare.carbon
+++ b/toolchain/check/testdata/function/generic/redeclare.carbon
@@ -200,7 +200,7 @@ fn F(U:! type, T:! type) -> U* {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %F.type = name_ref F, file.%F.decl [template = constants.%F]
 // CHECK:STDOUT:   %T.ref: type = name_ref T, %T [symbolic = %T (constants.%T)]
-// CHECK:STDOUT:   %F.call: init <unexpected instref inst+32> (%.1) = call %F.ref(<invalid>) [template = <error>]
+// CHECK:STDOUT:   %F.call: init <unexpected>.inst+32 (%.1) = call %F.ref(<invalid>) [template = <error>]
 // CHECK:STDOUT:   return <error>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/check/testdata/if_expr/fail_not_in_function.carbon b/toolchain/check/testdata/if_expr/fail_not_in_function.carbon
index 0653948d1eab..34417d30d2ee 100644
--- a/toolchain/check/testdata/if_expr/fail_not_in_function.carbon
+++ b/toolchain/check/testdata/if_expr/fail_not_in_function.carbon
@@ -63,7 +63,7 @@ class C {
 // CHECK:STDOUT: file {
 // CHECK:STDOUT:   package: <namespace> = namespace [template] {
 // CHECK:STDOUT:     .Core = %Core
-// CHECK:STDOUT:     .x = <unexpected instref inst+12>
+// CHECK:STDOUT:     .x = <unexpected>.inst+12.loc23_5
 // CHECK:STDOUT:     .C = %C.decl
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import = import Core
@@ -80,7 +80,7 @@ class C {
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
 // CHECK:STDOUT:   .Self = constants.%C
-// CHECK:STDOUT:   .n = <unexpected instref inst+49>
+// CHECK:STDOUT:   .n = <unexpected>.inst+49.loc37_8
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @Int32() -> type = "int.make_type_32";
diff --git a/toolchain/check/testdata/impl/fail_extend_impl_forall.carbon b/toolchain/check/testdata/impl/fail_extend_impl_forall.carbon
index d80a947b486e..f8d6c6e87ad3 100644
--- a/toolchain/check/testdata/impl/fail_extend_impl_forall.carbon
+++ b/toolchain/check/testdata/impl/fail_extend_impl_forall.carbon
@@ -58,7 +58,7 @@ class C {
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @GenericInterface
 // CHECK:STDOUT:     generic [file.%T.loc11_28.2: type] {
-// CHECK:STDOUT:   %Self: <unexpected instref inst+22> (%.2) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self)]
+// CHECK:STDOUT:   %Self: <unexpected>.inst+22 (%.2) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self)]
 // CHECK:STDOUT:   %F.decl: %F.type.1 = fn_decl @F.1 [template = constants.%F.1] {
 // CHECK:STDOUT:     %T.ref: type = name_ref T, file.%T.loc11_28.2 [symbolic = %T.ref (constants.%T)]
 // CHECK:STDOUT:     %x.loc12_8.1: @GenericInterface.%T.ref (%T) = param x
@@ -102,7 +102,7 @@ class C {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @F.1(@GenericInterface.%x.loc12_8.2: @GenericInterface.%T.ref (%T))
-// CHECK:STDOUT:     generic [file.%T.loc11_28.2: type, @GenericInterface.%Self: <unexpected instref inst+22> (%.2)];
+// CHECK:STDOUT:     generic [file.%T.loc11_28.2: type, @GenericInterface.%Self: <unexpected>.inst+22 (%.2)];
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @F.2(@impl.%x.loc20_10.2: @impl.%T.ref (%T))
 // CHECK:STDOUT:     generic [@C.%T.loc19_23.2: type] {
diff --git a/toolchain/check/testdata/impl/fail_impl_bad_assoc_fn.carbon b/toolchain/check/testdata/impl/fail_impl_bad_assoc_fn.carbon
index ca917fd270e6..04fabac611d4 100644
--- a/toolchain/check/testdata/impl/fail_impl_bad_assoc_fn.carbon
+++ b/toolchain/check/testdata/impl/fail_impl_bad_assoc_fn.carbon
@@ -899,7 +899,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT: declaration:
 // CHECK:STDOUT:   @SelfNested.%Self.ref.loc188_12 => constants.%Self.3
 // CHECK:STDOUT:   @SelfNested.%.loc188_16.3 => constants.%.10
-// CHECK:STDOUT:   <unexpected instref inst+267> => <unexpected instref inst+268>
+// CHECK:STDOUT:   <unexpected>.inst+267.loc188_21 => <unexpected>.inst+268
 // CHECK:STDOUT:   @SelfNested.%.loc188_37 => constants.%.11
 // CHECK:STDOUT:   @SelfNested.%.loc188_38.2 => constants.%.13
 // CHECK:STDOUT:   @SelfNested.%.loc188_52 => constants.%.15
diff --git a/toolchain/check/testdata/impl/fail_redefinition.carbon b/toolchain/check/testdata/impl/fail_redefinition.carbon
index c5b4564238b2..7a1646fe9e3a 100644
--- a/toolchain/check/testdata/impl/fail_redefinition.carbon
+++ b/toolchain/check/testdata/impl/fail_redefinition.carbon
@@ -68,7 +68,7 @@ impl i32 as I {}
 // CHECK:STDOUT:
 // CHECK:STDOUT: impl @impl: i32 as %.1 {
 // CHECK:STDOUT: !members:
-// CHECK:STDOUT:   witness = <unexpected instref inst+18>
+// CHECK:STDOUT:   witness = <unexpected>.inst+18
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @Int32() -> type = "int.make_type_32";
diff --git a/toolchain/check/testdata/impl/no_prelude/self_in_signature.carbon b/toolchain/check/testdata/impl/no_prelude/self_in_signature.carbon
index f8e10275a85c..42b2e1567f1b 100644
--- a/toolchain/check/testdata/impl/no_prelude/self_in_signature.carbon
+++ b/toolchain/check/testdata/impl/no_prelude/self_in_signature.carbon
@@ -284,7 +284,7 @@ impl D as SelfNested {
 // CHECK:STDOUT: declaration:
 // CHECK:STDOUT:   @SelfNested.%Self.ref.loc28_12 => constants.%Self.2
 // CHECK:STDOUT:   @SelfNested.%.loc28_16.3 => constants.%.10
-// CHECK:STDOUT:   <unexpected instref inst+86> => <unexpected instref inst+87>
+// CHECK:STDOUT:   <unexpected>.inst+86.loc28_21 => <unexpected>.inst+87
 // CHECK:STDOUT:   @SelfNested.%.loc28_36 => constants.%.11
 // CHECK:STDOUT:   @SelfNested.%.loc28_37.2 => constants.%.13
 // CHECK:STDOUT: }
diff --git a/toolchain/check/testdata/interface/no_prelude/fail_assoc_const_not_binding.carbon b/toolchain/check/testdata/interface/no_prelude/fail_assoc_const_not_binding.carbon
index 7da0a1ced255..386e094720c7 100644
--- a/toolchain/check/testdata/interface/no_prelude/fail_assoc_const_not_binding.carbon
+++ b/toolchain/check/testdata/interface/no_prelude/fail_assoc_const_not_binding.carbon
@@ -28,7 +28,7 @@ interface I {
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @I {
 // CHECK:STDOUT: !members:
-// CHECK:STDOUT:   .Self = <unexpected instref inst+3>
+// CHECK:STDOUT:   .Self = <unexpected>.inst+3
 // CHECK:STDOUT:   witness = invalid
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/check/testdata/interface/no_prelude/fail_assoc_const_template.carbon b/toolchain/check/testdata/interface/no_prelude/fail_assoc_const_template.carbon
index 6168a278b042..497f29f65d53 100644
--- a/toolchain/check/testdata/interface/no_prelude/fail_assoc_const_template.carbon
+++ b/toolchain/check/testdata/interface/no_prelude/fail_assoc_const_template.carbon
@@ -26,7 +26,7 @@ interface I {
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @I {
 // CHECK:STDOUT: !members:
-// CHECK:STDOUT:   .Self = <unexpected instref inst+3>
+// CHECK:STDOUT:   .Self = <unexpected>.inst+3
 // CHECK:STDOUT:   witness = invalid
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/check/testdata/interface/no_prelude/fail_duplicate.carbon b/toolchain/check/testdata/interface/no_prelude/fail_duplicate.carbon
index 0e002468e456..355d6fc31ae5 100644
--- a/toolchain/check/testdata/interface/no_prelude/fail_duplicate.carbon
+++ b/toolchain/check/testdata/interface/no_prelude/fail_duplicate.carbon
@@ -76,7 +76,7 @@ interface Class { }
 // CHECK:STDOUT:   %F.decl: %F.type = fn_decl @F [template = constants.%F] {}
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
-// CHECK:STDOUT:   .Self = <unexpected instref inst+3>
+// CHECK:STDOUT:   .Self = <unexpected>.inst+3
 // CHECK:STDOUT:   .F = <error>
 // CHECK:STDOUT:   witness = ()
 // CHECK:STDOUT: }
diff --git a/toolchain/check/testdata/interface/no_prelude/fail_generic_redeclaration.carbon b/toolchain/check/testdata/interface/no_prelude/fail_generic_redeclaration.carbon
index e736aa31bf0e..636b57adcfe7 100644
--- a/toolchain/check/testdata/interface/no_prelude/fail_generic_redeclaration.carbon
+++ b/toolchain/check/testdata/interface/no_prelude/fail_generic_redeclaration.carbon
@@ -92,7 +92,7 @@ interface DifferentParams(T:! ()) {}
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @.1
 // CHECK:STDOUT:     generic [file.%T.loc19_22.2: type] {
-// CHECK:STDOUT:   %Self: <unexpected instref inst+13> (%.4) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self.1)]
+// CHECK:STDOUT:   %Self: <unexpected>.inst+13 (%.4) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self.1)]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
 // CHECK:STDOUT:   .Self = %Self
@@ -115,7 +115,7 @@ interface DifferentParams(T:! ()) {}
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @.3
 // CHECK:STDOUT:     generic [file.%T.loc38_27.2: %.2] {
-// CHECK:STDOUT:   %Self: <unexpected instref inst+39> (%.7) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self.3)]
+// CHECK:STDOUT:   %Self: <unexpected>.inst+39 (%.7) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self.3)]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
 // CHECK:STDOUT:   .Self = %Self
diff --git a/toolchain/check/testdata/interface/no_prelude/fail_todo_generic_default_fn.carbon b/toolchain/check/testdata/interface/no_prelude/fail_todo_generic_default_fn.carbon
index 40d8a0aff8a0..a7d37323b55c 100644
--- a/toolchain/check/testdata/interface/no_prelude/fail_todo_generic_default_fn.carbon
+++ b/toolchain/check/testdata/interface/no_prelude/fail_todo_generic_default_fn.carbon
@@ -34,7 +34,7 @@ fn I(T:! type).F[self: Self]() -> Self { return self; }
 // CHECK:STDOUT:   %F: %F.type = struct_value () [template]
 // CHECK:STDOUT:   %.3: type = assoc_entity_type @I, %F.type [template]
 // CHECK:STDOUT:   %.4: %.3 = assoc_entity element0, @I.%F.decl [template]
-// CHECK:STDOUT:   %Self.2: <unexpected instref inst+28> (%.2) = bind_symbolic_name Self 1 [symbolic]
+// CHECK:STDOUT:   %Self.2: <unexpected>.inst+28 (%.2) = bind_symbolic_name Self 1 [symbolic]
 // CHECK:STDOUT:   %.type: type = fn_type @.1 [template]
 // CHECK:STDOUT:   %.5: %.type = struct_value () [template]
 // CHECK:STDOUT: }
@@ -50,14 +50,14 @@ fn I(T:! type).F[self: Self]() -> Self { return self; }
 // CHECK:STDOUT:   %.decl: %.type = fn_decl @.1 [template = constants.%.5] {
 // CHECK:STDOUT:     %T.loc22_6.1: type = param T
 // CHECK:STDOUT:     %T.loc22_6.2: type = bind_symbolic_name T 0, %T.loc22_6.1 [symbolic = %T.loc22_6.2 (constants.%T)]
-// CHECK:STDOUT:     %.loc22_24.1: <unexpected instref inst+44> (%.2) = specific_constant @I.%Self, %I.decl(constants.%T) [symbolic = %.loc22_24.1 (constants.%Self.2)]
-// CHECK:STDOUT:     %Self.ref.loc22_24: <unexpected instref inst+44> (%.2) = name_ref Self, %.loc22_24.1 [symbolic = %.loc22_24.1 (constants.%Self.2)]
+// CHECK:STDOUT:     %.loc22_24.1: <unexpected>.inst+44 (%.2) = specific_constant @I.%Self, %I.decl(constants.%T) [symbolic = %.loc22_24.1 (constants.%Self.2)]
+// CHECK:STDOUT:     %Self.ref.loc22_24: <unexpected>.inst+44 (%.2) = name_ref Self, %.loc22_24.1 [symbolic = %.loc22_24.1 (constants.%Self.2)]
 // CHECK:STDOUT:     %.loc22_24.2: type = facet_type_access %Self.ref.loc22_24 [symbolic = %.loc22_24.1 (constants.%Self.2)]
 // CHECK:STDOUT:     %.loc22_24.3: type = converted %Self.ref.loc22_24, %.loc22_24.2 [symbolic = %.loc22_24.1 (constants.%Self.2)]
 // CHECK:STDOUT:     %self.loc22_18.1: file.%.loc22_24.1 (%Self.2) = param self
 // CHECK:STDOUT:     @.1.%self: file.%.loc22_24.1 (%Self.2) = bind_name self, %self.loc22_18.1
-// CHECK:STDOUT:     %.loc22_35.1: <unexpected instref inst+44> (%.2) = specific_constant @I.%Self, %I.decl(constants.%T) [symbolic = %.loc22_24.1 (constants.%Self.2)]
-// CHECK:STDOUT:     %Self.ref.loc22_35: <unexpected instref inst+44> (%.2) = name_ref Self, %.loc22_35.1 [symbolic = %.loc22_24.1 (constants.%Self.2)]
+// CHECK:STDOUT:     %.loc22_35.1: <unexpected>.inst+44 (%.2) = specific_constant @I.%Self, %I.decl(constants.%T) [symbolic = %.loc22_24.1 (constants.%Self.2)]
+// CHECK:STDOUT:     %Self.ref.loc22_35: <unexpected>.inst+44 (%.2) = name_ref Self, %.loc22_35.1 [symbolic = %.loc22_24.1 (constants.%Self.2)]
 // CHECK:STDOUT:     %.loc22_35.2: type = facet_type_access %Self.ref.loc22_35 [symbolic = %.loc22_24.1 (constants.%Self.2)]
 // CHECK:STDOUT:     %.loc22_35.3: type = converted %Self.ref.loc22_35, %.loc22_35.2 [symbolic = %.loc22_24.1 (constants.%Self.2)]
 // CHECK:STDOUT:     @.1.%return: ref %Self.2 = var <return slot>
@@ -66,7 +66,7 @@ fn I(T:! type).F[self: Self]() -> Self { return self; }
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @I
 // CHECK:STDOUT:     generic [file.%T.loc11_13.2: type] {
-// CHECK:STDOUT:   %Self: <unexpected instref inst+28> (%.2) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self.1)]
+// CHECK:STDOUT:   %Self: <unexpected>.inst+28 (%.2) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self.1)]
 // CHECK:STDOUT:   %F.decl: %F.type = fn_decl @F [template = constants.%F] {
 // CHECK:STDOUT:     %.loc13_14.1: %.2 = specific_constant %Self, file.%I.decl(constants.%T) [symbolic = %.loc13_14.1 (constants.%Self.1)]
 // CHECK:STDOUT:     %Self.ref.loc13_14: %.2 = name_ref Self, %.loc13_14.1 [symbolic = %.loc13_14.1 (constants.%Self.1)]
@@ -89,7 +89,7 @@ fn I(T:! type).F[self: Self]() -> Self { return self; }
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @F[@I.%self.loc13_8.2: @I.%.loc13_14.1 (%Self.1)]() -> %Self.1
-// CHECK:STDOUT:     generic [file.%T.loc11_13.2: type, @I.%Self: <unexpected instref inst+28> (%.2)];
+// CHECK:STDOUT:     generic [file.%T.loc11_13.2: type, @I.%Self: <unexpected>.inst+28 (%.2)];
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @.1[%self: file.%.loc22_24.1 (%Self.2)]() -> %Self.2
 // CHECK:STDOUT:     generic [file.%T.loc22_6.2: type] {
@@ -103,7 +103,7 @@ fn I(T:! type).F[self: Self]() -> Self { return self; }
 // CHECK:STDOUT:   file.%T.loc11_13.2 => constants.%T
 // CHECK:STDOUT:
 // CHECK:STDOUT: definition:
-// CHECK:STDOUT:   <unexpected instref inst+28> => constants.%.2
+// CHECK:STDOUT:   <unexpected>.inst+28 => constants.%.2
 // CHECK:STDOUT:   @I.%Self => constants.%Self.2
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -125,7 +125,7 @@ fn I(T:! type).F[self: Self]() -> Self { return self; }
 // CHECK:STDOUT: specific file.%.decl(constants.%T) {
 // CHECK:STDOUT: declaration:
 // CHECK:STDOUT:   file.%T.loc22_6.2 => constants.%T
-// CHECK:STDOUT:   <unexpected instref inst+44> => constants.%.2
+// CHECK:STDOUT:   <unexpected>.inst+44 => constants.%.2
 // CHECK:STDOUT:   file.%.loc22_24.1 => constants.%Self.2
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/check/testdata/interface/no_prelude/generic.carbon b/toolchain/check/testdata/interface/no_prelude/generic.carbon
index 00c9a2e40ac0..d43431f2a217 100644
--- a/toolchain/check/testdata/interface/no_prelude/generic.carbon
+++ b/toolchain/check/testdata/interface/no_prelude/generic.carbon
@@ -145,7 +145,7 @@ fn G(T:! Generic(B)) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @Simple
 // CHECK:STDOUT:     generic [file.%T.loc4_18.2: type] {
-// CHECK:STDOUT:   %Self: <unexpected instref inst+11> (%.2) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self.1)]
+// CHECK:STDOUT:   %Self: <unexpected>.inst+11 (%.2) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self.1)]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
 // CHECK:STDOUT:   .Self = %Self
@@ -154,7 +154,7 @@ fn G(T:! Generic(B)) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @WithAssocFn
 // CHECK:STDOUT:     generic [file.%T.loc8_23.2: type] {
-// CHECK:STDOUT:   %Self: <unexpected instref inst+31> (%.4) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self.2)]
+// CHECK:STDOUT:   %Self: <unexpected>.inst+31 (%.4) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self.2)]
 // CHECK:STDOUT:   %F.decl: %F.type.1 = fn_decl @F.1 [template = constants.%F.1] {
 // CHECK:STDOUT:     %X.ref: type = name_ref X, file.%X.decl [template = constants.%X]
 // CHECK:STDOUT:     %return.var: ref %X = var <return slot>
@@ -215,7 +215,7 @@ fn G(T:! Generic(B)) {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @F.1() -> %X
-// CHECK:STDOUT:     generic [file.%T.loc8_23.2: type, @WithAssocFn.%Self: <unexpected instref inst+31> (%.4)];
+// CHECK:STDOUT:     generic [file.%T.loc8_23.2: type, @WithAssocFn.%Self: <unexpected>.inst+31 (%.4)];
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @F.2() -> @impl.2.%return.var: %X {
 // CHECK:STDOUT: !entry:
@@ -345,7 +345,7 @@ fn G(T:! Generic(B)) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @Generic
 // CHECK:STDOUT:     generic [file.%T.loc4_19.2: type] {
-// CHECK:STDOUT:   %Self: <unexpected instref inst+11> (%.2) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self)]
+// CHECK:STDOUT:   %Self: <unexpected>.inst+11 (%.2) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self)]
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
 // CHECK:STDOUT:   .Self = %Self
diff --git a/toolchain/check/testdata/interface/no_prelude/generic_import.carbon b/toolchain/check/testdata/interface/no_prelude/generic_import.carbon
index f6315d812c94..ad2171a80bea 100644
--- a/toolchain/check/testdata/interface/no_prelude/generic_import.carbon
+++ b/toolchain/check/testdata/interface/no_prelude/generic_import.carbon
@@ -54,7 +54,7 @@ impl C as AddWith(C) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @AddWith
 // CHECK:STDOUT:     generic [file.%T.loc4_19.2: type] {
-// CHECK:STDOUT:   %Self: <unexpected instref inst+17> (%.2) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self)]
+// CHECK:STDOUT:   %Self: <unexpected>.inst+17 (%.2) = bind_symbolic_name Self 1 [symbolic = %Self (constants.%Self)]
 // CHECK:STDOUT:   %F.decl: %F.type = fn_decl @F [template = constants.%F] {}
 // CHECK:STDOUT:   %.loc5: %.3 = assoc_entity element0, %F.decl [template = constants.%.4]
 // CHECK:STDOUT:
@@ -65,7 +65,7 @@ impl C as AddWith(C) {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @F()
-// CHECK:STDOUT:     generic [file.%T.loc4_19.2: type, @AddWith.%Self: <unexpected instref inst+17> (%.2)];
+// CHECK:STDOUT:     generic [file.%T.loc4_19.2: type, @AddWith.%Self: <unexpected>.inst+17 (%.2)];
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific file.%AddWith.decl(constants.%T) {
 // CHECK:STDOUT: declaration:
@@ -89,7 +89,7 @@ impl C as AddWith(C) {
 // CHECK:STDOUT:   %AddWith.type: type = generic_interface_type @AddWith [template]
 // CHECK:STDOUT:   %.2: type = tuple_type () [template]
 // CHECK:STDOUT:   %AddWith: %AddWith.type = struct_value () [template]
-// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected instref inst+14> [symbolic]
+// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected>.inst+14 [symbolic]
 // CHECK:STDOUT:   %.3: type = interface_type @AddWith, <invalid>(%T) [symbolic]
 // CHECK:STDOUT:   %Self: %.3 = bind_symbolic_name Self 1 [symbolic]
 // CHECK:STDOUT:   %.4: type = interface_type @AddWith, <invalid>(%C) [template]
diff --git a/toolchain/check/testdata/operators/builtin/fail_and_or_not_in_function.carbon b/toolchain/check/testdata/operators/builtin/fail_and_or_not_in_function.carbon
index 479e71b763d7..c698a982cc6f 100644
--- a/toolchain/check/testdata/operators/builtin/fail_and_or_not_in_function.carbon
+++ b/toolchain/check/testdata/operators/builtin/fail_and_or_not_in_function.carbon
@@ -66,7 +66,7 @@ var or_: F(true or true);
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
 // CHECK:STDOUT:   %.loc42_17: bool = block_arg <unexpected instblockref block21> [template = constants.%.3]
-// CHECK:STDOUT:   %F.call: init type = call <unexpected instref inst+60>(%.loc42_17)
+// CHECK:STDOUT:   %F.call: init type = call <unexpected>.inst+60.loc42_10(%.loc42_17)
 // CHECK:STDOUT:   %.loc42_24.1: type = value_of_initializer %F.call
 // CHECK:STDOUT:   %.loc42_24.2: type = converted %F.call, %.loc42_24.1
 // CHECK:STDOUT:   %or_.var: ref <error> = var or_
diff --git a/toolchain/check/testdata/packages/no_prelude/fail_export_name_params.carbon b/toolchain/check/testdata/packages/no_prelude/fail_export_name_params.carbon
index a89ec94087c8..0d3ca81b4930 100644
--- a/toolchain/check/testdata/packages/no_prelude/fail_export_name_params.carbon
+++ b/toolchain/check/testdata/packages/no_prelude/fail_export_name_params.carbon
@@ -78,7 +78,7 @@ export C2(T:! type);
 // CHECK:STDOUT:   %C1.type: type = generic_class_type @C1 [template]
 // CHECK:STDOUT:   %.1: type = tuple_type () [template]
 // CHECK:STDOUT:   %C1.1: %C1.type = struct_value () [template]
-// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected instref inst+18> [symbolic]
+// CHECK:STDOUT:   %T: type = bind_symbolic_name T 0, <unexpected>.inst+18 [symbolic]
 // CHECK:STDOUT:   %C1.2: type = class_type @C1, <invalid>(%T) [symbolic]
 // CHECK:STDOUT:   %C2.type: type = generic_class_type @C2 [template]
 // CHECK:STDOUT:   %C2.1: %C2.type = struct_value () [template]
diff --git a/toolchain/check/testdata/return/fail_let_in_type.carbon b/toolchain/check/testdata/return/fail_let_in_type.carbon
index afda030a1a4d..b3588312352b 100644
--- a/toolchain/check/testdata/return/fail_let_in_type.carbon
+++ b/toolchain/check/testdata/return/fail_let_in_type.carbon
@@ -55,14 +55,14 @@ fn FirstPerfectNumber() -> z { return 6; }
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @HalfDozen() -> %y
-// CHECK:STDOUT:     generic [<unexpected instref inst+21>: type] {
+// CHECK:STDOUT:     generic [<unexpected>.inst+21.loc19_5: type] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %.loc24: i32 = int_literal 6 [template = constants.%.2]
 // CHECK:STDOUT:   return <error>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: specific <unexpected instref inst+29>(constants.%y) {
+// CHECK:STDOUT: specific <unexpected>.inst+29.loc24_21(constants.%y) {
 // CHECK:STDOUT: declaration:
-// CHECK:STDOUT:   <unexpected instref inst+27> => constants.%y
+// CHECK:STDOUT:   <unexpected>.inst+27.loc24_19 => constants.%y
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/check/testdata/struct/import.carbon b/toolchain/check/testdata/struct/import.carbon
index 72f1147e2701..befabf76dd9e 100644
--- a/toolchain/check/testdata/struct/import.carbon
+++ b/toolchain/check/testdata/struct/import.carbon
@@ -217,7 +217,7 @@ var c_bad: C({.a = 3, .b = 4}) = F();
 // CHECK:STDOUT:   %C.1: %C.type = struct_value () [template]
 // CHECK:STDOUT:   %.10: type = struct_type {} [template]
 // CHECK:STDOUT:   %.11: type = struct_type {.a: i32, .b: i32} [template]
-// CHECK:STDOUT:   %S: %.11 = bind_symbolic_name S 0, <unexpected instref inst+103> [symbolic]
+// CHECK:STDOUT:   %S: %.11 = bind_symbolic_name S 0, <unexpected>.inst+103 [symbolic]
 // CHECK:STDOUT:   %C.2: type = class_type @C, <invalid>(%S) [symbolic]
 // CHECK:STDOUT:   %.12: i32 = int_literal 1 [template]
 // CHECK:STDOUT:   %.13: i32 = int_literal 2 [template]
@@ -349,7 +349,7 @@ var c_bad: C({.a = 3, .b = 4}) = F();
 // CHECK:STDOUT:   %C.1: %C.type = struct_value () [template]
 // CHECK:STDOUT:   %.2: type = struct_type {} [template]
 // CHECK:STDOUT:   %.3: type = struct_type {.a: i32, .b: i32} [template]
-// CHECK:STDOUT:   %S: %.3 = bind_symbolic_name S 0, <unexpected instref inst+21> [symbolic]
+// CHECK:STDOUT:   %S: %.3 = bind_symbolic_name S 0, <unexpected>.inst+21 [symbolic]
 // CHECK:STDOUT:   %C.2: type = class_type @C, <invalid>(%S) [symbolic]
 // CHECK:STDOUT:   %.4: i32 = int_literal 1 [template]
 // CHECK:STDOUT:   %.5: i32 = int_literal 2 [template]
@@ -422,7 +422,7 @@ var c_bad: C({.a = 3, .b = 4}) = F();
 // CHECK:STDOUT:   %C.1: %C.type = struct_value () [template]
 // CHECK:STDOUT:   %.2: type = struct_type {} [template]
 // CHECK:STDOUT:   %.3: type = struct_type {.a: i32, .b: i32} [template]
-// CHECK:STDOUT:   %S: %.3 = bind_symbolic_name S 0, <unexpected instref inst+21> [symbolic]
+// CHECK:STDOUT:   %S: %.3 = bind_symbolic_name S 0, <unexpected>.inst+21 [symbolic]
 // CHECK:STDOUT:   %C.2: type = class_type @C, <invalid>(%S) [symbolic]
 // CHECK:STDOUT:   %.4: i32 = int_literal 3 [template]
 // CHECK:STDOUT:   %.5: i32 = int_literal 4 [template]
diff --git a/toolchain/check/testdata/tuples/import.carbon b/toolchain/check/testdata/tuples/import.carbon
index 704ec1e388fb..ea669d5432a9 100644
--- a/toolchain/check/testdata/tuples/import.carbon
+++ b/toolchain/check/testdata/tuples/import.carbon
@@ -242,7 +242,7 @@ var c_bad: C((3, 4)) = F();
 // CHECK:STDOUT:   %C.type: type = generic_class_type @C [template]
 // CHECK:STDOUT:   %C.1: %C.type = struct_value () [template]
 // CHECK:STDOUT:   %.14: type = struct_type {} [template]
-// CHECK:STDOUT:   %X: %.8 = bind_symbolic_name X 0, <unexpected instref inst+105> [symbolic]
+// CHECK:STDOUT:   %X: %.8 = bind_symbolic_name X 0, <unexpected>.inst+105 [symbolic]
 // CHECK:STDOUT:   %C.2: type = class_type @C, <invalid>(%X) [symbolic]
 // CHECK:STDOUT:   %.15: i32 = int_literal 1 [template]
 // CHECK:STDOUT:   %.16: i32 = int_literal 2 [template]
@@ -390,7 +390,7 @@ var c_bad: C((3, 4)) = F();
 // CHECK:STDOUT:   %C.1: %C.type = struct_value () [template]
 // CHECK:STDOUT:   %.2: type = struct_type {} [template]
 // CHECK:STDOUT:   %.3: type = tuple_type (i32, i32) [template]
-// CHECK:STDOUT:   %X: %.3 = bind_symbolic_name X 0, <unexpected instref inst+17> [symbolic]
+// CHECK:STDOUT:   %X: %.3 = bind_symbolic_name X 0, <unexpected>.inst+17 [symbolic]
 // CHECK:STDOUT:   %C.2: type = class_type @C, <invalid>(%X) [symbolic]
 // CHECK:STDOUT:   %.4: i32 = int_literal 1 [template]
 // CHECK:STDOUT:   %.5: i32 = int_literal 2 [template]
@@ -465,7 +465,7 @@ var c_bad: C((3, 4)) = F();
 // CHECK:STDOUT:   %C.1: %C.type = struct_value () [template]
 // CHECK:STDOUT:   %.2: type = struct_type {} [template]
 // CHECK:STDOUT:   %.3: type = tuple_type (i32, i32) [template]
-// CHECK:STDOUT:   %X: %.3 = bind_symbolic_name X 0, <unexpected instref inst+17> [symbolic]
+// CHECK:STDOUT:   %X: %.3 = bind_symbolic_name X 0, <unexpected>.inst+17 [symbolic]
 // CHECK:STDOUT:   %C.2: type = class_type @C, <invalid>(%X) [symbolic]
 // CHECK:STDOUT:   %.4: i32 = int_literal 3 [template]
 // CHECK:STDOUT:   %.5: i32 = int_literal 4 [template]
diff --git a/toolchain/driver/driver.cpp b/toolchain/driver/driver.cpp
index 66a942fbca5f..26ff39cb8c31 100644
--- a/toolchain/driver/driver.cpp
+++ b/toolchain/driver/driver.cpp
@@ -641,13 +641,16 @@ class Driver::CompilationUnit {
       }
     }
 
-    if (vlog_stream_) {
-      CARBON_VLOG() << "*** SemIR::File ***\n";
-      SemIR::FormatFile(*tokens_, *parse_tree_, *sem_ir_, *vlog_stream_);
-    }
-    if (options_.dump_sem_ir && IncludeInDumps()) {
-      SemIR::FormatFile(*tokens_, *parse_tree_, *sem_ir_,
-                        driver_->output_stream_);
+    bool print = options_.dump_sem_ir && IncludeInDumps();
+    if (vlog_stream_ || print) {
+      SemIR::Formatter formatter(*tokens_, *parse_tree_, *sem_ir_);
+      if (vlog_stream_) {
+        CARBON_VLOG() << "*** SemIR::File ***\n";
+        formatter.Print(*vlog_stream_);
+      }
+      if (print) {
+        formatter.Print(driver_->output_stream_);
+      }
     }
     if (sem_ir_->has_errors()) {
       success_ = false;
diff --git a/toolchain/sem_ir/formatter.cpp b/toolchain/sem_ir/formatter.cpp
index a630f10411e0..021b0b164a9d 100644
--- a/toolchain/sem_ir/formatter.cpp
+++ b/toolchain/sem_ir/formatter.cpp
@@ -22,16 +22,11 @@
 namespace Carbon::SemIR {
 
 // Formatter for printing textual Semantics IR.
-class Formatter {
+class FormatterImpl {
  public:
-  enum class AddSpace : bool { Before, After };
-
-  explicit Formatter(const Lex::TokenizedBuffer& tokenized_buffer,
-                     const Parse::Tree& parse_tree, const File& sem_ir,
-                     llvm::raw_ostream& out)
-      : sem_ir_(sem_ir),
-        out_(out),
-        inst_namer_(tokenized_buffer, parse_tree, sem_ir) {}
+  explicit FormatterImpl(const File& sem_ir, InstNamer* inst_namer,
+                         llvm::raw_ostream& out, int indent)
+      : sem_ir_(sem_ir), inst_namer_(inst_namer), out_(out), indent_(indent) {}
 
   // Prints the SemIR.
   //
@@ -44,7 +39,7 @@ class Formatter {
     FormatConstants();
     FormatImportRefs();
 
-    out_ << inst_namer_.GetScopeName(InstNamer::ScopeId::File) << " ";
+    out_ << inst_namer_->GetScopeName(InstNamer::ScopeId::File) << " ";
     OpenBrace();
 
     // TODO: Handle the case where there are multiple top-level instruction
@@ -82,6 +77,37 @@ class Formatter {
     out_ << "\n";
   }
 
+  // Prints a code block.
+  auto FormatPartialTrailingCodeBlock(llvm::ArrayRef<SemIR::InstId> block)
+      -> void {
+    out_ << ' ';
+    OpenBrace();
+    constexpr int NumPrintedOnSkip = 9;
+    // Avoid only skipping one item.
+    if (block.size() > NumPrintedOnSkip + 1) {
+      Indent();
+      out_ << "... skipping " << (block.size() - NumPrintedOnSkip)
+           << " insts ...\n";
+      block = block.take_back(NumPrintedOnSkip);
+    }
+    FormatCodeBlock(block);
+    CloseBrace();
+  }
+
+  // Prints a single instruction.
+  auto FormatInstruction(InstId inst_id) -> void {
+    if (!inst_id.is_valid()) {
+      Indent();
+      out_ << "invalid\n";
+      return;
+    }
+
+    FormatInstruction(inst_id, sem_ir_.insts().Get(inst_id));
+  }
+
+ private:
+  enum class AddSpace : bool { Before, After };
+
   // Begins a braced block. Writes an open brace, and prepares to insert a
   // newline after it if the braced block is non-empty.
   auto OpenBrace() -> void {
@@ -139,7 +165,7 @@ class Formatter {
     }
 
     llvm::SaveAndRestore constants_scope(scope_, InstNamer::ScopeId::Constants);
-    out_ << inst_namer_.GetScopeName(InstNamer::ScopeId::Constants) << " ";
+    out_ << inst_namer_->GetScopeName(InstNamer::ScopeId::Constants) << " ";
     OpenBrace();
     FormatCodeBlock(sem_ir_.constants().array_ref());
     CloseBrace();
@@ -153,7 +179,7 @@ class Formatter {
     }
 
     llvm::SaveAndRestore scope(scope_, InstNamer::ScopeId::ImportRefs);
-    out_ << inst_namer_.GetScopeName(InstNamer::ScopeId::ImportRefs) << " ";
+    out_ << inst_namer_->GetScopeName(InstNamer::ScopeId::ImportRefs) << " ";
     OpenBrace();
     FormatCodeBlock(import_refs);
     CloseBrace();
@@ -170,7 +196,7 @@ class Formatter {
       FormatGeneric(class_info.generic_id);
     }
 
-    llvm::SaveAndRestore class_scope(scope_, inst_namer_.GetScopeFor(id));
+    llvm::SaveAndRestore class_scope(scope_, inst_namer_->GetScopeFor(id));
 
     if (class_info.scope_id.is_valid()) {
       out_ << ' ';
@@ -194,7 +220,7 @@ class Formatter {
       FormatGeneric(interface_info.generic_id);
     }
 
-    llvm::SaveAndRestore interface_scope(scope_, inst_namer_.GetScopeFor(id));
+    llvm::SaveAndRestore interface_scope(scope_, inst_namer_->GetScopeFor(id));
 
     if (interface_info.scope_id.is_valid()) {
       out_ << ' ';
@@ -230,7 +256,7 @@ class Formatter {
     out_ << " as ";
     FormatType(impl_info.constraint_id);
 
-    llvm::SaveAndRestore impl_scope(scope_, inst_namer_.GetScopeFor(id));
+    llvm::SaveAndRestore impl_scope(scope_, inst_namer_->GetScopeFor(id));
 
     if (impl_info.scope_id.is_valid()) {
       out_ << ' ';
@@ -267,7 +293,7 @@ class Formatter {
     out_ << "fn ";
     FormatFunctionName(id);
 
-    llvm::SaveAndRestore function_scope(scope_, inst_namer_.GetScopeFor(id));
+    llvm::SaveAndRestore function_scope(scope_, inst_namer_->GetScopeFor(id));
 
     if (fn.implicit_param_refs_id.is_valid()) {
       out_ << "[";
@@ -462,16 +488,6 @@ class Formatter {
     }
   }
 
-  auto FormatInstruction(InstId inst_id) -> void {
-    if (!inst_id.is_valid()) {
-      Indent();
-      out_ << "invalid\n";
-      return;
-    }
-
-    FormatInstruction(inst_id, sem_ir_.insts().Get(inst_id));
-  }
-
   auto FormatInstruction(InstId inst_id, Inst inst) -> void {
     CARBON_KIND_SWITCH(inst) {
 #define CARBON_SEM_IR_INST_KIND(InstT)      \
@@ -909,26 +925,28 @@ class Formatter {
   }
 
   auto FormatInstName(InstId id) -> void {
-    out_ << inst_namer_.GetNameFor(scope_, id);
+    out_ << inst_namer_->GetNameFor(scope_, id);
   }
 
   auto FormatLabel(InstBlockId id) -> void {
-    out_ << inst_namer_.GetLabelFor(scope_, id);
+    out_ << inst_namer_->GetLabelFor(scope_, id);
   }
 
   auto FormatFunctionName(FunctionId id) -> void {
-    out_ << inst_namer_.GetNameFor(id);
+    out_ << inst_namer_->GetNameFor(id);
   }
 
   auto FormatClassName(ClassId id) -> void {
-    out_ << inst_namer_.GetNameFor(id);
+    out_ << inst_namer_->GetNameFor(id);
   }
 
   auto FormatInterfaceName(InterfaceId id) -> void {
-    out_ << inst_namer_.GetNameFor(id);
+    out_ << inst_namer_->GetNameFor(id);
   }
 
-  auto FormatImplName(ImplId id) -> void { out_ << inst_namer_.GetNameFor(id); }
+  auto FormatImplName(ImplId id) -> void {
+    out_ << inst_namer_->GetNameFor(id);
+  }
 
   auto FormatSpecificName(GenericInstanceId id) -> void {
     const auto& specific = sem_ir_.generic_instances().Get(id);
@@ -982,10 +1000,11 @@ class Formatter {
     }
   }
 
- private:
   const File& sem_ir_;
+  InstNamer* const inst_namer_;
+
+  // The output stream. Set while formatting instructions.
   llvm::raw_ostream& out_;
-  InstNamer inst_namer_;
 
   // The current scope that we are formatting within. References to names in
   // this scope will not have a `@scope.` prefix added.
@@ -997,7 +1016,7 @@ class Formatter {
   bool in_terminator_sequence_ = false;
 
   // The indent depth to use for new instructions.
-  int indent_ = 0;
+  int indent_;
 
   // Whether we are currently formatting immediately after an open brace. If so,
   // a newline will be inserted before the next line indent.
@@ -1014,10 +1033,28 @@ class Formatter {
   bool pending_constant_value_is_self_ = false;
 };
 
-auto FormatFile(const Lex::TokenizedBuffer& tokenized_buffer,
-                const Parse::Tree& parse_tree, const File& sem_ir,
-                llvm::raw_ostream& out) -> void {
-  Formatter(tokenized_buffer, parse_tree, sem_ir, out).Format();
+Formatter::Formatter(const Lex::TokenizedBuffer& tokenized_buffer,
+                     const Parse::Tree& parse_tree, const File& sem_ir)
+    : sem_ir_(sem_ir), inst_namer_(tokenized_buffer, parse_tree, sem_ir) {}
+
+Formatter::~Formatter() = default;
+
+auto Formatter::Print(llvm::raw_ostream& out) -> void {
+  FormatterImpl formatter(sem_ir_, &inst_namer_, out, /*indent=*/0);
+  formatter.Format();
+}
+
+auto Formatter::PrintPartialTrailingCodeBlock(
+    llvm::ArrayRef<SemIR::InstId> block, int indent, llvm::raw_ostream& out)
+    -> void {
+  FormatterImpl formatter(sem_ir_, &inst_namer_, out, indent);
+  formatter.FormatPartialTrailingCodeBlock(block);
+}
+
+auto Formatter::PrintInst(SemIR::InstId inst_id, int indent,
+                          llvm::raw_ostream& out) -> void {
+  FormatterImpl formatter(sem_ir_, &inst_namer_, out, indent);
+  formatter.FormatInstruction(inst_id);
 }
 
 }  // namespace Carbon::SemIR
diff --git a/toolchain/sem_ir/formatter.h b/toolchain/sem_ir/formatter.h
index c7d744afd0e9..7a2ff326159b 100644
--- a/toolchain/sem_ir/formatter.h
+++ b/toolchain/sem_ir/formatter.h
@@ -9,12 +9,33 @@
 #include "toolchain/lex/tokenized_buffer.h"
 #include "toolchain/parse/tree.h"
 #include "toolchain/sem_ir/file.h"
+#include "toolchain/sem_ir/inst_namer.h"
 
 namespace Carbon::SemIR {
 
-auto FormatFile(const Lex::TokenizedBuffer& tokenized_buffer,
-                const Parse::Tree& parse_tree, const File& sem_ir,
-                llvm::raw_ostream& out) -> void;
+// Formatter for printing textual Semantics IR.
+class Formatter {
+ public:
+  explicit Formatter(const Lex::TokenizedBuffer& tokenized_buffer,
+                     const Parse::Tree& parse_tree, const File& sem_ir);
+  ~Formatter();
+
+  // Prints the full IR.
+  auto Print(llvm::raw_ostream& out) -> void;
+  // Prints a single code block. Only prints the last several instructions of
+  // large blocks.
+  auto PrintPartialTrailingCodeBlock(llvm::ArrayRef<SemIR::InstId> block,
+                                     int indent, llvm::raw_ostream& out)
+      -> void;
+  // Prints a single instruction.
+  auto PrintInst(SemIR::InstId inst_id, int indent, llvm::raw_ostream& out)
+      -> void;
+
+ private:
+  const File& sem_ir_;
+  // Caches naming between Print calls.
+  InstNamer inst_namer_;
+};
 
 }  // namespace Carbon::SemIR
 
diff --git a/toolchain/sem_ir/inst_namer.cpp b/toolchain/sem_ir/inst_namer.cpp
index 4e6620fee653..470b6f156612 100644
--- a/toolchain/sem_ir/inst_namer.cpp
+++ b/toolchain/sem_ir/inst_namer.cpp
@@ -152,7 +152,15 @@ auto InstNamer::GetNameFor(ScopeId scope_id, InstId inst_id) const
   if (!inst_name) {
     // This should not happen in valid IR.
     std::string str;
-    llvm::raw_string_ostream(str) << "<unexpected instref " << inst_id << ">";
+    llvm::raw_string_ostream str_stream(str);
+    str_stream << "<unexpected>." << inst_id;
+    auto loc_id = sem_ir_.insts().GetLocId(inst_id);
+    // TODO: Consider handling inst_id cases.
+    if (loc_id.is_node_id()) {
+      auto token = parse_tree_.node_token(loc_id.node_id());
+      str_stream << ".loc" << tokenized_buffer_.GetLineNumber(token) << "_"
+                 << tokenized_buffer_.GetColumnNumber(token);
+    }
     return str;
   }
   if (inst_scope == scope_id) {