diff --git a/toolchain/check/check.cpp b/toolchain/check/check.cpp
index 14728ebb9a22..1fb42f89e5ae 100644
--- a/toolchain/check/check.cpp
+++ b/toolchain/check/check.cpp
@@ -706,12 +706,24 @@ auto NodeIdTraversal::Next() -> std::optional<Parse::NodeId> {
 // for example if an unrecoverable state is encountered.
 // NOLINTNEXTLINE(readability-function-size)
 static auto ProcessNodeIds(Context& context, llvm::raw_ostream* vlog_stream,
-                           ErrorTrackingDiagnosticConsumer& err_tracker)
-    -> bool {
+                           ErrorTrackingDiagnosticConsumer& err_tracker,
+                           Parse::NodeLocConverter* converter) -> bool {
   NodeIdTraversal traversal(context, vlog_stream);
 
+  Parse::NodeId node_id = Parse::NodeId::Invalid;
+
+  // On crash, report which token we were handling.
+  PrettyStackTraceFunction node_dumper([&](llvm::raw_ostream& output) {
+    auto loc = converter->ConvertLoc(
+        node_id, [](DiagnosticLoc, const Internal::DiagnosticBase<>&) {});
+    loc.FormatLocation(output);
+    output << ": Check::Handle" << context.parse_tree().node_kind(node_id)
+           << "\n";
+    loc.FormatSnippet(output);
+  });
+
   while (auto maybe_node_id = traversal.Next()) {
-    auto node_id = *maybe_node_id;
+    node_id = *maybe_node_id;
     auto parse_kind = context.parse_tree().node_kind(node_id);
 
     switch (parse_kind) {
@@ -762,7 +774,8 @@ static auto CheckParseTree(
   // TODO: Do this selectively when we see an impl query.
   ImportImpls(context);
 
-  if (!ProcessNodeIds(context, vlog_stream, unit_info.err_tracker)) {
+  if (!ProcessNodeIds(context, vlog_stream, unit_info.err_tracker,
+                      &unit_info.converter)) {
     context.sem_ir().set_has_errors(true);
     return;
   }
diff --git a/toolchain/diagnostics/BUILD b/toolchain/diagnostics/BUILD
index 08e2e94d15a8..32ee2f31ea58 100644
--- a/toolchain/diagnostics/BUILD
+++ b/toolchain/diagnostics/BUILD
@@ -13,7 +13,10 @@ filegroup(
 
 cc_library(
     name = "diagnostic_emitter",
-    srcs = ["diagnostic_consumer.cpp"],
+    srcs = [
+        "diagnostic.cpp",
+        "diagnostic_consumer.cpp",
+    ],
     hdrs = [
         "diagnostic.h",
         "diagnostic_consumer.h",
diff --git a/toolchain/diagnostics/diagnostic.cpp b/toolchain/diagnostics/diagnostic.cpp
new file mode 100644
index 000000000000..1eaadc5e3a9e
--- /dev/null
+++ b/toolchain/diagnostics/diagnostic.cpp
@@ -0,0 +1,45 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include "toolchain/diagnostics/diagnostic.h"
+
+#include <algorithm>
+#include <cstdint>
+
+namespace Carbon {
+
+auto DiagnosticLoc::FormatLocation(llvm::raw_ostream& out) const -> void {
+  out << filename;
+  if (line_number > 0) {
+    out << ":" << line_number;
+    if (column_number > 0) {
+      out << ":" << column_number;
+    }
+  }
+}
+
+auto DiagnosticLoc::FormatSnippet(llvm::raw_ostream& out) const -> void {
+  if (column_number <= 0) {
+    return;
+  }
+
+  // column_number is 1-based.
+  int32_t column = column_number - 1;
+
+  out << line << "\n";
+  out.indent(column);
+  out << "^";
+  // We want to ensure that we don't underline past the end of the line in
+  // case of a multiline token.
+  // TODO: revisit this once we can reference multiple ranges on multiple
+  // lines in a single diagnostic message.
+  int underline_length =
+      std::min(length, static_cast<int32_t>(line.size()) - column);
+  for (int i = 1; i < underline_length; ++i) {
+    out << '~';
+  }
+  out << '\n';
+}
+
+}  // namespace Carbon
diff --git a/toolchain/diagnostics/diagnostic.h b/toolchain/diagnostics/diagnostic.h
index 11d35adf462c..8f06a0a3a657 100644
--- a/toolchain/diagnostics/diagnostic.h
+++ b/toolchain/diagnostics/diagnostic.h
@@ -46,6 +46,14 @@ enum class DiagnosticLevel : int8_t {
 // is required to be less than SourceBuffer that it refers to due to the
 // contained filename and line references.
 struct DiagnosticLoc {
+  // Write the filename, line number, and column number corresponding to this
+  // location to the given stream.
+  auto FormatLocation(llvm::raw_ostream& out) const -> void;
+
+  // Write the source snippet corresponding to this location to the given
+  // stream.
+  auto FormatSnippet(llvm::raw_ostream& out) const -> void;
+
   // Name of the file or buffer that this diagnostic refers to.
   llvm::StringRef filename;
   // A reference to the line of the error.
diff --git a/toolchain/diagnostics/diagnostic_consumer.cpp b/toolchain/diagnostics/diagnostic_consumer.cpp
index c8bed5136eaf..26e94af01967 100644
--- a/toolchain/diagnostics/diagnostic_consumer.cpp
+++ b/toolchain/diagnostics/diagnostic_consumer.cpp
@@ -17,35 +17,13 @@ auto StreamDiagnosticConsumer::HandleDiagnostic(Diagnostic diagnostic) -> void {
   }
 
   for (const auto& message : diagnostic.messages) {
-    *stream_ << message.loc.filename;
-    if (message.loc.line_number > 0) {
-      *stream_ << ":" << message.loc.line_number;
-      if (message.loc.column_number > 0) {
-        *stream_ << ":" << message.loc.column_number;
-      }
-    }
+    message.loc.FormatLocation(*stream_);
     *stream_ << ": ";
     if (message.level == DiagnosticLevel::Error) {
       *stream_ << "ERROR: ";
     }
     *stream_ << message.format_fn(message) << "\n";
-    if (message.loc.column_number > 0) {
-      *stream_ << message.loc.line << "\n";
-      stream_->indent(message.loc.column_number - 1);
-      *stream_ << "^";
-      int underline_length = std::max(0, message.loc.length - 1);
-      // We want to ensure that we don't underline past the end of the line in
-      // case of a multiline token.
-      // TODO: revisit this once we can reference multiple ranges on multiple
-      // lines in a single diagnostic message.
-      underline_length = std::min(
-          underline_length, static_cast<int32_t>(message.loc.line.size()) -
-                                message.loc.column_number);
-      for (int i = 0; i < underline_length; ++i) {
-        *stream_ << "~";
-      }
-      *stream_ << "\n";
-    }
+    message.loc.FormatSnippet(*stream_);
   }
 }