diff --git a/README.md b/README.md
index 18cc75f..7efbb02 100644
--- a/README.md
+++ b/README.md
@@ -151,10 +151,13 @@ This file will then be passed to the underlying Ruby interpreter with
 You can find several test harnesses in this repository:
 
 * harness - the normal default harness, with duration controlled by warmup iterations and time/count limits
-* harness-perf - a simplified harness that runs for exactly the hinted number of iterations
 * harness-bips - a harness that measures iterations/second until stable
 * harness-continuous - a harness that adjusts the batch sizes of iterations to run in stable iteration size batches
+* harness-once - a simplified harness that simply runs once
+* harness-perf - a simplified harness that runs for exactly the hinted number of iterations
+* harness-stackprof - a harness to profile the benchmark with stackprof
 * harness-stats - count method calls and loop iterations
+* harness-vernier - a harness to profile the benchmark with vernier
 * harness-warmup - a harness which runs as long as needed to find warmed up (peak) performance
 
 To use it, run a benchmark script directly, specifying a harness directory with `-I`:
diff --git a/harness-stackprof/harness.rb b/harness-stackprof/harness.rb
new file mode 100644
index 0000000..ef01342
--- /dev/null
+++ b/harness-stackprof/harness.rb
@@ -0,0 +1,84 @@
+# frozen_string_literal: true
+
+# Profile the benchmark (ignoring initialization code) with stackprof.
+# Customize stackprof options with an env var of STACKPROF_OPTS='key:value,...'.
+# Usage:
+# STACKPROF_OPTS='mode:object' MIN_BENCH_TIME=0 MIN_BENCH_ITRS=1 ruby -v -I harness-stackprof benchmarks/.../benchmark.rb
+# STACKPROF_OPTS='mode:cpu,interval:10' MIN_BENCH_TIME=1 MIN_BENCH_ITRS=10 ruby -v -I harness-stackprof benchmarks/.../benchmark.rb
+
+require_relative "../harness/harness-common"
+require_relative "../harness/harness-extra"
+
+ensure_global_gem("stackprof")
+
+# Default to collecting more information so that more post-processing options are
+# available (like generating a flamegraph).
+DEFAULTS = {
+  aggregate: true,
+  raw: true,
+}.freeze
+
+# Convert strings of "true" or "false" to their actual boolean values (or raise).
+BOOLS = {"true" => true, "false" => false}
+def bool!(val)
+  case val
+  when TrueClass, FalseClass
+    # Respect values that are already booleans so that we can specify defaults intuitively.
+    val
+  else
+    BOOLS.fetch(val) { raise ArgumentError, "must be 'true' or 'false'" }
+  end
+end
+
+# Parse the string of "key:value,..." into a hash that we can pass to stackprof.
+def parse_opts_string(str)
+  return {} unless str
+
+  str.split(/,/).map { |x| x.strip.split(/[=:]/, 2) }.to_h.transform_keys(&:to_sym)
+end
+
+# Get options for stackprof from env var and convert strings to the types stackprof expects.
+def stackprof_opts
+  opts = DEFAULTS.merge(parse_opts_string(ENV['STACKPROF_OPTS']))
+
+  bool = method(:bool!)
+
+  # Use {key: conversion_proc_or_sym} to convert present options to their necessary types.
+  {
+    aggregate: bool,
+    raw: bool,
+    mode: :to_sym,
+    interval: :to_i,
+  }.each do |key, method|
+    next unless opts.key?(key)
+
+    method = proc(&method) if method.is_a?(Symbol)
+    opts[key] = method.call(opts[key])
+  rescue => error
+    raise ArgumentError, "Option '#{key}' failed to convert: #{error}"
+  end
+
+  opts
+end
+
+def run_benchmark(n, &block)
+  require "stackprof"
+
+  opts = stackprof_opts
+  prefix = "stackprof"
+  prefix = "#{prefix}-#{opts[:mode]}" if opts[:mode]
+
+  out = output_file_path(prefix: prefix, ext: "dump")
+  StackProf.run(out: out, **opts) do
+    run_enough_to_profile(n, &block)
+  end
+
+  # Show the basic textual report.
+  gem_exe("stackprof", "--text", out)
+  # Print the file path at the end to make it easy to copy the file name
+  # and use it for further analysis.
+  puts "Stackprof dump file:\n#{out}"
+
+  # Dummy results to satisfy ./run_benchmarks.rb
+  return_results([0], [1.0]) if ENV['RESULT_JSON_PATH']
+end
diff --git a/harness-vernier/harness.rb b/harness-vernier/harness.rb
new file mode 100644
index 0000000..fb7fa24
--- /dev/null
+++ b/harness-vernier/harness.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+# Profile the benchmark (ignoring initialization code) using vernier and display the profile.
+# Set NO_VIERWER=1 to disable automatically opening the profile in a browser.
+# Usage:
+# MIN_BENCH_TIME=1 MIN_BENCH_ITRS=1 ruby -v -I harness-vernier benchmarks/...
+# NO_VIEWER=1 MIN_BENCH_TIME=1 MIN_BENCH_ITRS=1 ruby -v -I harness-vernier benchmarks/...
+
+require_relative "../harness/harness-common"
+require_relative "../harness/harness-extra"
+
+ensure_global_gem("vernier")
+ensure_global_gem_exe("profile-viewer")
+
+def run_benchmark(n, &block)
+  require "vernier"
+
+  out = output_file_path(ext: "json")
+  Vernier.profile(out: out) do
+    run_enough_to_profile(n, &block)
+  end
+
+  puts "Vernier profile:\n#{out}"
+  gem_exe("profile-viewer", out) unless ENV['NO_VIEWER'] == '1'
+
+  # Dummy results to satisfy ./run_benchmarks.rb
+  return_results([0], [1.0])
+end
diff --git a/harness/harness-extra.rb b/harness/harness-extra.rb
new file mode 100644
index 0000000..ab2cebd
--- /dev/null
+++ b/harness/harness-extra.rb
@@ -0,0 +1,76 @@
+# frozen_string_literal: true
+
+# Ensure a gem is installed globally (and add it to the load path)
+# in a way that doesn't interfere with the benchmark's bundler setup.
+def ensure_global_gem(name)
+  found = Gem.find_latest_files(name).first
+  unless found
+    Gem.install(name)
+    found = Gem.find_latest_files(name).first
+  end
+  warn "Adding to load path: #{File.dirname(found)}"
+  $LOAD_PATH << File.dirname(found)
+end
+
+# Ensure an executable provided by the gem is present
+# (useful for profile-viewer which has no lib, only the exe).
+def ensure_global_gem_exe(name, exe = name)
+  Gem.bin_path(name, exe)
+rescue Gem::GemNotFoundException
+  Gem.install(name)
+end
+
+# Call a gem exe, removing any bundler env vars that might confuse it.
+def gem_exe(*args)
+  system({'RUBYOPT' => '', 'BUNDLER_SETUP' => nil}, *args)
+end
+
+# Get benchmark base name from the file path.
+def benchmark_name
+  $0.match(%r{([^/]+?)(?:(?:/benchmark)?\.rb)?$})[1]
+end
+
+# Get name of harness (stackprof, vernier, etc) from the file path of the loaded harness.
+def harness_name
+  $LOADED_FEATURES.reverse_each do |feat|
+    if m = feat.match(%r{/harness-([^/]+)/harness\.rb$})
+      return m[1]
+    end
+  end
+  raise "Unable to determine harness name"
+end
+
+# Share a single timestamp for everything from this execution.
+TIMESTAMP = Time.now.strftime('%F-%H%M%S')
+
+# Create a consistent file path in the data directory
+# so that the data can be further analyzed.
+def output_file_path(prefix: harness_name, suffix: benchmark_name, ruby_info: ruby_version_info, timestamp: TIMESTAMP, ext: "bin")
+  File.expand_path("../data/#{prefix}-#{timestamp}-#{ruby_info}-#{suffix}.#{ext}", __dir__)
+end
+
+# Can we get the benchmark config name from somewhere?
+def ruby_version_info
+  "#{RUBY_ENGINE}-#{RUBY_ENGINE_VERSION}"
+end
+
+def get_time
+  Process.clock_gettime(Process::CLOCK_MONOTONIC)
+end
+
+MIN_BENCH_TIME = Integer(ENV.fetch('MIN_BENCH_TIME', 10))
+
+# Ensure the benchmark runs enough times for profilers to get sufficient data when sampling.
+# Use the "n" hint (provided by the benchmarks themselves) as a starting point
+# but allow that to be overridden by MIN_BENCH_ITRS env var.
+# Also use MIN_BENCH_TIME to loop until the benchmark has run for a sufficient duration.
+def run_enough_to_profile(n, &block)
+  start = get_time
+  loop do
+    # Allow MIN_BENCH_ITRS to override the argument.
+    n = ENV.fetch('MIN_BENCH_ITRS', n).to_i
+    n.times(&block)
+
+    break if (get_time - start) >= MIN_BENCH_TIME
+  end
+end