Merge "Add ssd profiler for tuning SSD write performance"
diff --git a/BUILD b/BUILD
index a568e20..413620d 100644
--- a/BUILD
+++ b/BUILD
@@ -35,6 +35,8 @@
 # gazelle:resolve go github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/refresh_match_list_response //scouting/webserver/requests/messages:refresh_match_list_response_go_fbs
 # gazelle:resolve go github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/request_shift_schedule //scouting/webserver/requests/messages:request_shift_schedule_go_fbs
 # gazelle:resolve go github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/request_shift_schedule_response //scouting/webserver/requests/messages:request_shift_schedule_response_go_fbs
+# gazelle:resolve go github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/submit_actions //scouting/webserver/requests/messages:submit_actions_go_fbs
+# gazelle:resolve go github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/submit_actions_response //scouting/webserver/requests/messages:submit_actions_response_go_fbs
 # gazelle:resolve go github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/submit_shift_schedule //scouting/webserver/requests/messages:submit_shift_schedule_go_fbs
 # gazelle:resolve go github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/submit_shift_schedule_response //scouting/webserver/requests/messages:submit_shift_schedule_response_go_fbs
 # gazelle:resolve go github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/submit_driver_ranking //scouting/webserver/requests/messages:submit_driver_ranking_go_fbs
diff --git a/WORKSPACE b/WORKSPACE
index 3e1801c..aa92b7e 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -549,6 +549,18 @@
     actual = "@com_google_googletest//:gtest_main",
 )
 
+http_archive(
+    name = "april_tag_test_image",
+    build_file_content = """
+filegroup(
+    name = "april_tag_test_image",
+    srcs = ["test.bfbs", "expected.jpeg", "expected.png"],
+    visibility = ["//visibility:public"],
+)""",
+    sha256 = "5312c79b19e9883b3cebd9d65b4438a2bf05b41da0bcd8c35e19d22c3b2e1859",
+    urls = ["https://www.frc971.org/Build-Dependencies/test_image_frc971.vision.CameraImage_2023.01.28.tar.gz"],
+)
+
 # Recompressed from libusb-1.0.21.7z.
 http_file(
     name = "libusb_1_0_windows",
diff --git a/aos/containers/priority_queue.h b/aos/containers/priority_queue.h
index b092219..d4d0196 100644
--- a/aos/containers/priority_queue.h
+++ b/aos/containers/priority_queue.h
@@ -3,6 +3,7 @@
 
 #include <array>
 #include <iterator>
+#include <optional>
 
 namespace aos {
 
@@ -60,18 +61,19 @@
   // and the queue is full, then data is ignored and end() is returned.
   // PushFromBottom starts the search from the bottom of the queue.
   // TODO(james): If performance becomes an issue, improve search.
-  iterator PushFromBottom(const Data &data) {
+  iterator PushFromBottom(Data data) {
     size_t lower_idx = buffer_size;
     size_t upper_idx = bottom_;
     // Find our spot in the queue:
-    while (upper_idx != buffer_size && !cmp_(data, list_[upper_idx].data)) {
+    while (upper_idx != buffer_size &&
+           !cmp_(data, list_[upper_idx].data.value())) {
       lower_idx = upper_idx;
       upper_idx = list_[upper_idx].upper_idx;
       if (upper_idx == buffer_size) {
         break;
       }
     }
-    return InsertInList(data, lower_idx, upper_idx);
+    return InsertInList(std::move(data), lower_idx, upper_idx);
   }
 
   size_t size() const { return size_; }
@@ -85,10 +87,10 @@
     top_ = buffer_size;
   }
 
-  Data &top() { return list_[top_].data; }
-  const Data &top() const { return list_[top_].data; }
-  Data &get(size_t idx) { return list_[idx].data; }
-  const Data &get(size_t idx) const { return list_[idx].data; }
+  Data &top() { return list_[top_].data.value(); }
+  const Data &top() const { return list_[top_].data.value(); }
+  Data &get(size_t idx) { return list_[idx].data.value(); }
+  const Data &get(size_t idx) const { return list_[idx].data.value(); }
   iterator begin() { return iterator(this, bottom_); }
   iterator end() { return iterator(this, buffer_size); }
 
@@ -101,7 +103,7 @@
   struct Datum {
     // A list element with data and the indices of the next highest/lowest
     // priority elements.
-    Data data;
+    std::optional<Data> data;
     // Values of buffer_size indicate that we are at the beginning or end of
     // the queue.
     size_t lower_idx = buffer_size;
@@ -109,7 +111,7 @@
   };
 
   // Insert an element above lower_idx and below upper_idx.
-  iterator InsertInList(const Data &data, size_t lower_idx, size_t upper_idx) {
+  iterator InsertInList(Data data, size_t lower_idx, size_t upper_idx) {
     // For inserting new elements, when we are initially filling the queue we
     // will increment upwards in the array; once full, we just evict the
     // lowest priority element.
@@ -140,7 +142,7 @@
     if (top_ == lower_idx) {
       top_ = insertion_idx;
     }
-    list_[insertion_idx].data = data;
+    list_[insertion_idx].data.emplace(std::move(data));
     list_[insertion_idx].upper_idx = upper_idx;
     list_[insertion_idx].lower_idx = lower_idx;
     ++size_;
diff --git a/aos/containers/priority_queue_test.cc b/aos/containers/priority_queue_test.cc
index d26d7c9..64456c4 100644
--- a/aos/containers/priority_queue_test.cc
+++ b/aos/containers/priority_queue_test.cc
@@ -153,16 +153,22 @@
   ASSERT_TRUE(reverse_expected.empty());
 }
 
-// Check that operator-> works as expected on the iterator.
+// Check that operator-> works as expected on the iterator, and that we can use
+// a non-copyable, non-assignable object.
 struct TestStruct {
+  TestStruct(int a) : a(a) {}
+  TestStruct(const TestStruct &) = delete;
+  TestStruct &operator=(const TestStruct &) = delete;
+  TestStruct(TestStruct &&) = default;
+  TestStruct &operator=(TestStruct &&) = delete;
   int a;
   friend bool operator<(const TestStruct &lhs, const TestStruct &rhs) {
     return lhs.a < rhs.a;
   }
 };
-TEST(PriorirtyQueueTest, MemberAccess) {
+TEST(PriorityQueueMoveTest, MemberAccess) {
   PriorityQueue<TestStruct, 10, ::std::less<TestStruct>> q;
-  auto it = q.PushFromBottom({11});
+  auto it = q.PushFromBottom(TestStruct{11});
   EXPECT_EQ(11, it->a);
 }
 
diff --git a/aos/events/event_loop.cc b/aos/events/event_loop.cc
index f5e9f51..c29d820 100644
--- a/aos/events/event_loop.cc
+++ b/aos/events/event_loop.cc
@@ -236,7 +236,8 @@
 
   CHECK(taken_senders_.find(channel) == taken_senders_.end())
       << ": " << configuration::CleanedChannelToString(channel)
-      << " is already being used.";
+      << " is already being used for sending. Can't make a watcher on the "
+         "same event loop.";
 
   auto result = taken_watchers_.insert(channel);
   CHECK(result.second) << ": " << configuration::CleanedChannelToString(channel)
diff --git a/aos/events/logging/log_edit.cc b/aos/events/logging/log_edit.cc
index e3cfc3a..dca56bb 100644
--- a/aos/events/logging/log_edit.cc
+++ b/aos/events/logging/log_edit.cc
@@ -51,7 +51,10 @@
     aos::logger::DetachedBufferWriter buffer_writer(
         FLAGS_logfile,
         std::make_unique<aos::logger::DummyEncoder>(FLAGS_max_message_size));
-    buffer_writer.QueueSpan(header.span());
+    {
+      aos::logger::DataEncoder::SpanCopier coppier(header.span());
+      buffer_writer.CopyMessage(&coppier, aos::monotonic_clock::min_time);
+    }
 
     while (true) {
       absl::Span<const uint8_t> msg_data = span_reader.ReadMessage();
@@ -59,7 +62,10 @@
         break;
       }
 
-      buffer_writer.QueueSpan(msg_data);
+      {
+        aos::logger::DataEncoder::SpanCopier coppier(msg_data);
+        buffer_writer.CopyMessage(&coppier, aos::monotonic_clock::min_time);
+      }
     }
   } else {
     aos::logger::MessageReader reader(FLAGS_logfile);
diff --git a/aos/events/logging/log_namer.cc b/aos/events/logging/log_namer.cc
index 120bd79..c0c7c73 100644
--- a/aos/events/logging/log_namer.cc
+++ b/aos/events/logging/log_namer.cc
@@ -248,7 +248,8 @@
                  header, {.multi_line = false, .max_vector_size = 100});
 
   CHECK(writer);
-  writer->QueueSpan(header.span());
+  DataEncoder::SpanCopier coppier(header.span());
+  writer->CopyMessage(&coppier, aos::monotonic_clock::now());
   header_written_ = true;
   monotonic_start_time_ = log_namer_->monotonic_start_time(
       node_index_, state_[node_index_].boot_uuid);
@@ -606,7 +607,8 @@
       std::make_unique<DetachedBufferWriter>(
           filename, encoder_factory_(header->span().size()));
 
-  writer->QueueSpan(header->span());
+  DataEncoder::SpanCopier coppier(header->span());
+  writer->CopyMessage(&coppier, aos::monotonic_clock::now());
 
   if (!writer->ran_out_of_space()) {
     all_filenames_.emplace_back(
diff --git a/aos/events/logging/logfile_utils.cc b/aos/events/logging/logfile_utils.cc
index ab56356..90220c8 100644
--- a/aos/events/logging/logfile_utils.cc
+++ b/aos/events/logging/logfile_utils.cc
@@ -129,27 +129,12 @@
   return *this;
 }
 
-void DetachedBufferWriter::QueueSpan(absl::Span<const uint8_t> span) {
+void DetachedBufferWriter::CopyMessage(DataEncoder::Copier *coppier,
+                                       aos::monotonic_clock::time_point now) {
   if (ran_out_of_space_) {
     // We don't want any later data to be written after space becomes
     // available, so refuse to write anything more once we've dropped data
     // because we ran out of space.
-    VLOG(1) << "Ignoring span: " << span.size();
-    return;
-  }
-
-  if (!encoder_->HasSpace(span.size())) {
-    Flush();
-    CHECK(encoder_->HasSpace(span.size()));
-  }
-  DataEncoder::SpanCopier coppier(span);
-  encoder_->Encode(&coppier);
-  FlushAtThreshold(aos::monotonic_clock::now());
-}
-
-void DetachedBufferWriter::CopyMessage(DataEncoder::Copier *coppier,
-                                       aos::monotonic_clock::time_point now) {
-  if (ran_out_of_space_) {
     return;
   }
 
diff --git a/aos/events/logging/logfile_utils.h b/aos/events/logging/logfile_utils.h
index 346a36e..ca36ace 100644
--- a/aos/events/logging/logfile_utils.h
+++ b/aos/events/logging/logfile_utils.h
@@ -76,9 +76,6 @@
   void CopyMessage(DataEncoder::Copier *coppier,
                    aos::monotonic_clock::time_point now);
 
-  // Queues up data in span. May copy or may write it to disk immediately.
-  void QueueSpan(absl::Span<const uint8_t> span);
-
   // Indicates we got ENOSPC when trying to write. After this returns true, no
   // further data is written.
   bool ran_out_of_space() const { return ran_out_of_space_; }
diff --git a/aos/events/logging/logfile_utils_out_of_space_test_runner.cc b/aos/events/logging/logfile_utils_out_of_space_test_runner.cc
index afc4d77..719eb6e 100644
--- a/aos/events/logging/logfile_utils_out_of_space_test_runner.cc
+++ b/aos/events/logging/logfile_utils_out_of_space_test_runner.cc
@@ -22,10 +22,14 @@
       FLAGS_tmpfs + "/file",
       std::make_unique<aos::logger::DummyEncoder>(data.size()));
   for (int i = 0; i < 8; ++i) {
-    writer.QueueSpan(data);
+    aos::logger::DataEncoder::SpanCopier coppier(data);
+    writer.CopyMessage(&coppier, aos::monotonic_clock::now());
     CHECK(!writer.ran_out_of_space()) << ": " << i;
   }
-  writer.QueueSpan(data);
+  {
+    aos::logger::DataEncoder::SpanCopier coppier(data);
+    writer.CopyMessage(&coppier, aos::monotonic_clock::now());
+  }
   CHECK(writer.ran_out_of_space());
   writer.acknowledge_out_of_space();
 }
diff --git a/aos/events/logging/logfile_utils_test.cc b/aos/events/logging/logfile_utils_test.cc
index f453798..b3a9bbd 100644
--- a/aos/events/logging/logfile_utils_test.cc
+++ b/aos/events/logging/logfile_utils_test.cc
@@ -39,6 +39,10 @@
   void WriteSizedFlatbuffer(flatbuffers::DetachedBuffer &&buffer) {
     QueueSpan(absl::Span<const uint8_t>(buffer.data(), buffer.size()));
   }
+  void QueueSpan(absl::Span<const uint8_t> buffer) {
+    DataEncoder::SpanCopier coppier(buffer);
+    CopyMessage(&coppier, monotonic_clock::now());
+  }
 };
 
 // Creates a size prefixed flatbuffer from json.
diff --git a/aos/network/www/plotter.ts b/aos/network/www/plotter.ts
index 89b360c..17bffa3 100644
--- a/aos/network/www/plotter.ts
+++ b/aos/network/www/plotter.ts
@@ -342,8 +342,11 @@
         // Make sure both have text in the right spot.  Don't be too picky since
         // nothing should really be changing here, and it's handy to let the
         // user edit the HTML for testing.
-        if (this.legend.children[child].lastChild.textContent.length == 0 &&
-            line.label().length != 0) {
+        let textdiv = this.legend.children[child].lastChild;
+        let canvas = this.legend.children[child].firstChild;
+        if ((textdiv.textContent.length == 0 && line.label().length != 0) ||
+            (textdiv as HTMLDivElement).offsetHeight !=
+                (canvas as HTMLCanvasElement).height) {
           needsUpdate = true;
           break;
         }
diff --git a/aos/util/BUILD b/aos/util/BUILD
index 48dc054..929b376 100644
--- a/aos/util/BUILD
+++ b/aos/util/BUILD
@@ -466,6 +466,28 @@
 )
 
 cc_library(
+    name = "threaded_consumer",
+    hdrs = [
+        "threaded_consumer.h",
+    ],
+    deps = [
+        "//aos:condition",
+        "//aos:realtime",
+        "//aos/containers:ring_buffer",
+        "//aos/mutex",
+    ],
+)
+
+cc_test(
+    name = "threaded_consumer_test",
+    srcs = ["threaded_consumer_test.cc"],
+    deps = [
+        ":threaded_consumer",
+        "//aos/testing:googletest",
+    ],
+)
+
+cc_library(
     name = "foxglove_websocket_lib",
     srcs = ["foxglove_websocket_lib.cc"],
     hdrs = ["foxglove_websocket_lib.h"],
diff --git a/aos/util/threaded_consumer.h b/aos/util/threaded_consumer.h
new file mode 100644
index 0000000..95ec79a
--- /dev/null
+++ b/aos/util/threaded_consumer.h
@@ -0,0 +1,102 @@
+#ifndef AOS_UTIL_THREADED_CONSUMER_H_
+#define AOS_UTIL_THREADED_CONSUMER_H_
+
+#include <functional>
+#include <optional>
+#include <thread>
+
+#include "aos/condition.h"
+#include "aos/containers/ring_buffer.h"
+#include "aos/mutex/mutex.h"
+#include "aos/realtime.h"
+
+namespace aos {
+namespace util {
+
+// This class implements a threadpool of a single worker that accepts work
+// from the main thread through a queue and executes it at a different realtime
+// priority.
+//
+// There is no mechanism to get data back to the main thread, the worker only
+// acts as a consumer. When this class is destroyed, it join()s the worker and
+// finishes all outstanding tasks.
+template <typename T, int QueueSize>
+class ThreadedConsumer {
+ public:
+  // Constructs a new ThreadedConsumer with the given consumer function to be
+  // run at the given realtime priority. If worker_priority is zero, the thread
+  // will stay at non realtime priority.
+  ThreadedConsumer(std::function<void(T)> consumer_function,
+                   int worker_priority)
+      : consumer_function_(consumer_function),
+        worker_priority_(worker_priority),
+        more_tasks_(&mutex_),
+        worker_thread_([this]() { WorkerFunction(); }) {}
+
+  ~ThreadedConsumer() {
+    {
+      aos::MutexLocker locker(&mutex_);
+      quit_ = true;
+      more_tasks_.Broadcast();
+    }
+    worker_thread_.join();
+  }
+
+  // Submits another task to be processed by the worker.
+  // Returns true if successfully pushed onto the queue, and false if the queue
+  // is full.
+  bool Push(T task) {
+    aos::MutexLocker locker(&mutex_);
+
+    if (task_queue_.full()) {
+      return false;
+    }
+
+    task_queue_.Push(task);
+    more_tasks_.Broadcast();
+
+    return true;
+  }
+
+ private:
+  void WorkerFunction() {
+    if (worker_priority_ > 0) {
+      aos::SetCurrentThreadRealtimePriority(worker_priority_);
+    }
+
+    while (true) {
+      std::optional<T> task;
+
+      {
+        aos::MutexLocker locker(&mutex_);
+        while (task_queue_.empty() && !quit_) {
+          CHECK(!more_tasks_.Wait());
+        }
+
+        if (task_queue_.empty() && quit_) break;
+
+        // Pop
+        task = std::move(task_queue_[0]);
+        task_queue_.Shift();
+      }
+
+      consumer_function_(*task);
+      task.reset();
+    }
+
+    aos::UnsetCurrentThreadRealtimePriority();
+  }
+
+  std::function<void(T)> consumer_function_;
+  aos::RingBuffer<T, QueueSize> task_queue_;
+  aos::Mutex mutex_;
+  bool quit_ = false;
+  int worker_priority_;
+  aos::Condition more_tasks_;
+  std::thread worker_thread_;
+};
+
+}  // namespace util
+}  // namespace aos
+
+#endif  // AOS_UTIL_THREADWORKER_H_
diff --git a/aos/util/threaded_consumer_test.cc b/aos/util/threaded_consumer_test.cc
new file mode 100644
index 0000000..96375f0
--- /dev/null
+++ b/aos/util/threaded_consumer_test.cc
@@ -0,0 +1,144 @@
+#include "aos/util/threaded_consumer.h"
+
+#include "gtest/gtest.h"
+
+namespace aos {
+namespace util {
+
+// We expect it to be able to pass through everything we submit and recieves it
+// in the order that we submitted it. It should also be able to take in more
+// tasks than the size of the ring buffer as long as the worker doesn't get
+// behind.
+TEST(ThreadedConsumerTest, BasicFunction) {
+  std::atomic<int> counter{0};
+
+  ThreadedConsumer<int, 4> threaded_consumer(
+      [&counter](int task) {
+        LOG(INFO) << "task:" << task << " counter: " << counter;
+        counter = task;
+      },
+      0);
+
+  for (int number : {9, 7, 1, 3, 100, 300, 42}) {
+    EXPECT_TRUE(threaded_consumer.Push(number));
+
+    // wait
+    while (counter != number) {
+      std::this_thread::sleep_for(std::chrono::milliseconds(1));
+    }
+
+    EXPECT_EQ(counter, number);
+  }
+}
+
+// We should be able to raise the realtime priority of the worker thread, and
+// everything should work the same. It should also reset back to lower priority
+// when shutting down the worker thread.
+TEST(ThreadedConsumerTest, ElevatedPriority) {
+  std::atomic<int> counter{0};
+
+  {
+    ThreadedConsumer<int, 4> threaded_consumer(
+        [&counter](int task) {
+          CheckRealtime();
+          VLOG(1) << "task:" << task << " counter: " << counter;
+          counter = task;
+        },
+        20);
+
+    for (int number : {9, 7, 1, 3, 100, 300, 42}) {
+      EXPECT_TRUE(threaded_consumer.Push(number));
+
+      // wait
+      while (counter != number) {
+        std::this_thread::sleep_for(std::chrono::milliseconds(1));
+      }
+
+      EXPECT_EQ(counter, number);
+    }
+  }
+  // TODO: Check that the worker thread's priority actually gets reset before
+  // the thread is destroyed.
+
+  CheckNotRealtime();
+}
+
+// If the worker gets behind, we shouldn't silently take in more tasks and
+// destroy old ones.
+TEST(ThreadedConsumerTest, OverflowRingBuffer) {
+  std::atomic<int> counter{0};
+  std::atomic<int> should_block{true};
+
+  ThreadedConsumer<int, 4> threaded_consumer(
+      [&counter, &should_block](int task) {
+        VLOG(1) << "task:" << task << " counter: " << counter;
+
+        counter = task;
+
+        // prevent it from making any progress to simulate it getting behind
+        while (should_block) {
+          std::this_thread::sleep_for(std::chrono::milliseconds(1));
+        }
+      },
+      20);
+
+  // It consumes the 5 and then our worker blocks.
+  EXPECT_TRUE(threaded_consumer.Push(5));
+
+  // Wait for it to consume 5
+  while (counter != 5) {
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+  };
+
+  // 4 more fills up the queue.
+  for (int number : {8, 9, 7, 1}) {
+    EXPECT_TRUE(threaded_consumer.Push(number));
+  }
+
+  // this one should overflow the buffer.
+  EXPECT_FALSE(threaded_consumer.Push(101));
+
+  // clean up, so we don't join() an infinite loop
+  should_block = false;
+}
+
+// The class should destruct gracefully and finish all of its work before
+// dissapearing.
+TEST(ThreadedConsumerTest, FinishesTasksOnQuit) {
+  std::atomic<int> counter{0};
+  std::atomic<int> should_block{true};
+
+  {
+    ThreadedConsumer<int, 4> threaded_consumer(
+        [&counter, &should_block](int task) {
+          VLOG(1) << "task:" << task << " counter: " << counter;
+
+          counter = task;
+
+          // prevent it from making any progress to simulate it getting behind
+          while (should_block) {
+            std::this_thread::sleep_for(std::chrono::milliseconds(1));
+          }
+        },
+        20);
+
+    // Give it some work to do
+    for (int number : {8, 9, 7, 1}) {
+      EXPECT_TRUE(threaded_consumer.Push(number));
+    }
+
+    // Wait for it to consume the first number
+    while (counter != 8) {
+      std::this_thread::sleep_for(std::chrono::milliseconds(1));
+    };
+
+    // allow it to continue
+    should_block = false;
+  }
+
+  // It should have finished all the work and gotten to the last number.
+  EXPECT_EQ(counter, 1);
+}
+
+}  // namespace util
+}  // namespace aos
diff --git a/frc971/control_loops/drivetrain/hybrid_ekf.h b/frc971/control_loops/drivetrain/hybrid_ekf.h
index fcbed76..89b2182 100644
--- a/frc971/control_loops/drivetrain/hybrid_ekf.h
+++ b/frc971/control_loops/drivetrain/hybrid_ekf.h
@@ -135,6 +135,7 @@
     kLongitudinalAccel = 2,
     kLateralAccel = 3,
   };
+
   static constexpr int kNInputs = 4;
   // Number of previous samples to save.
   static constexpr int kSaveSamples = 200;
@@ -177,6 +178,135 @@
   // State contains the states defined by the StateIdx enum. See comments there.
   typedef Eigen::Matrix<Scalar, kNStates, 1> State;
 
+  // The following classes exist to allow us to support doing corections in the
+  // past by rewinding the EKF, calling the appropriate H and dhdx functions,
+  // and then playing everything back. Originally, this simply used
+  // std::function's, but doing so causes us to perform dynamic memory
+  // allocation in the core of the drivetrain control loop.
+  //
+  // The ExpectedObservationFunctor class serves to provide an interface for the
+  // actual H and dH/dX that the EKF itself needs. Most implementations end up
+  // just using this; in the degenerate case, ExpectedObservationFunctor could
+  // be implemented as a class that simply stores two std::functions and calls
+  // them when H() and DHDX() are called.
+  //
+  // The ObserveDeletion() and deleted() methods exist for sanity checking--we
+  // don't rely on them to do any work, but in order to ensure that memory is
+  // being managed correctly, we have the HybridEkf call ObserveDeletion() when
+  // it no longer needs an instance of the object.
+  class ExpectedObservationFunctor {
+   public:
+    virtual ~ExpectedObservationFunctor() = default;
+    // Return the expected measurement of the system for a given state and plant
+    // input.
+    virtual Output H(const State &state, const Input &input) = 0;
+    // Return the derivative of H() with respect to the state, given the current
+    // state.
+    virtual Eigen::Matrix<Scalar, kNOutputs, kNStates> DHDX(
+        const State &state) = 0;
+    virtual void ObserveDeletion() {
+      CHECK(!deleted_);
+      deleted_ = true;
+    }
+    bool deleted() const { return deleted_; }
+
+   private:
+    bool deleted_ = false;
+  };
+
+  // The ExpectedObservationBuilder creates a new ExpectedObservationFunctor.
+  // This is used for situations where in order to know what the correction
+  // methods even are we need to know the state at some time in the past. This
+  // is only used in the y2019 code and we've generally stopped using this
+  // pattern.
+  class ExpectedObservationBuilder {
+   public:
+    virtual ~ExpectedObservationBuilder() = default;
+    // The lifetime of the returned object should last at least until
+    // ObserveDeletion() is called on said object.
+    virtual ExpectedObservationFunctor *MakeExpectedObservations(
+        const State &state, const StateSquare &P) = 0;
+    void ObserveDeletion() {
+      CHECK(!deleted_);
+      deleted_ = true;
+    }
+    bool deleted() const { return deleted_; }
+
+   private:
+    bool deleted_ = false;
+  };
+
+  // The ExpectedObservationAllocator provides a utility class which manages the
+  // memory for a single type of correction step for a given localizer.
+  // Using the knowledge that at most kSaveSamples ExpectedObservation* objects
+  // can be referenced by the HybridEkf at any given time, this keeps an
+  // internal queue that more than mirrors the HybridEkf's internal queue, using
+  // the oldest spots in the queue to construct new ExpectedObservation*'s.
+  // This can be used with T as either a ExpectedObservationBuilder or
+  // ExpectedObservationFunctor. The appropriate Correct function will then be
+  // called in place of calling HybridEkf::Correct directly. Note that unless T
+  // implements both the Builder and Functor (which is generally discouraged),
+  // only one of the Correct* functions will build.
+  template <typename T>
+  class ExpectedObservationAllocator {
+   public:
+    ExpectedObservationAllocator(HybridEkf *ekf) : ekf_(ekf) {}
+    void CorrectKnownH(const Output &z, const Input *U, T H,
+                       const Eigen::Matrix<Scalar, kNOutputs, kNOutputs> &R,
+                       aos::monotonic_clock::time_point t) {
+      if (functors_.full()) {
+        CHECK(functors_.begin()->functor->deleted());
+      }
+      auto pushed = functors_.PushFromBottom(Pair{t, std::move(H)});
+      if (pushed == functors_.end()) {
+        VLOG(1) << "Observation dropped off bottom of queue.";
+        return;
+      }
+      ekf_->Correct(z, U, nullptr, &pushed->functor.value(), R, t);
+    }
+    void CorrectKnownHBuilder(
+        const Output &z, const Input *U, T builder,
+        const Eigen::Matrix<Scalar, kNOutputs, kNOutputs> &R,
+        aos::monotonic_clock::time_point t) {
+      if (functors_.full()) {
+        CHECK(functors_.begin()->functor->deleted());
+      }
+      auto pushed = functors_.PushFromBottom(Pair{t, std::move(builder)});
+      if (pushed == functors_.end()) {
+        VLOG(1) << "Observation dropped off bottom of queue.";
+        return;
+      }
+      ekf_->Correct(z, U, &pushed->functor.value(), nullptr, R, t);
+    }
+
+   private:
+    struct Pair {
+      aos::monotonic_clock::time_point t;
+      std::optional<T> functor;
+      friend bool operator<(const Pair &l, const Pair &r) { return l.t < r.t; }
+    };
+
+    HybridEkf *const ekf_;
+    aos::PriorityQueue<Pair, kSaveSamples + 1, std::less<Pair>> functors_;
+  };
+
+  // A simple implementation of ExpectedObservationFunctor for an LTI correction
+  // step. Does not store any external references, so overrides
+  // ObserveDeletion() to do nothing.
+  class LinearH : public ExpectedObservationFunctor {
+   public:
+    LinearH(const Eigen::Matrix<Scalar, kNOutputs, kNStates> &H) : H_(H) {}
+    virtual ~LinearH() = default;
+    Output H(const State &state, const Input &) final { return H_ * state; }
+    Eigen::Matrix<Scalar, kNOutputs, kNStates> DHDX(const State &) final {
+      return H_;
+    }
+    void ObserveDeletion() {}
+
+   private:
+    const Eigen::Matrix<Scalar, kNOutputs, kNStates> H_;
+  };
+
   // Constructs a HybridEkf for a particular drivetrain.
   // Currently, we use the drivetrain config for modelling constants
   // (continuous time A and B matrices) and for the noise matrices for the
@@ -207,11 +337,8 @@
         P_,
         Input::Zero(),
         Output::Zero(),
-        {},
-        [](const State &, const Input &) { return Output::Zero(); },
-        [](const State &) {
-          return Eigen::Matrix<Scalar, kNOutputs, kNStates>::Zero();
-        },
+        nullptr,
+        &H_encoders_and_gyro_.value(),
         Eigen::Matrix<Scalar, kNOutputs, kNOutputs>::Identity(),
         StateSquare::Identity(),
         StateSquare::Zero(),
@@ -230,18 +357,11 @@
   // on an assumption that the voltage was held constant between the time steps.
   // TODO(james): Is it necessary to explicitly to provide a version with H as a
   // matrix for linear cases?
-  void Correct(
-      const Output &z, const Input *U,
-      std::function<void(const State &, const StateSquare &,
-                         std::function<Output(const State &, const Input &)> *,
-                         std::function<Eigen::Matrix<
-                             Scalar, kNOutputs, kNStates>(const State &)> *)>
-          make_h,
-      std::function<Output(const State &, const Input &)> h,
-      std::function<Eigen::Matrix<Scalar, kNOutputs, kNStates>(const State &)>
-          dhdx,
-      const Eigen::Matrix<Scalar, kNOutputs, kNOutputs> &R,
-      aos::monotonic_clock::time_point t);
+  void Correct(const Output &z, const Input *U,
+               ExpectedObservationBuilder *observation_builder,
+               ExpectedObservationFunctor *expected_observations,
+               const Eigen::Matrix<Scalar, kNOutputs, kNOutputs> &R,
+               aos::monotonic_clock::time_point t);
 
   // A utility function for specifically updating with encoder and gyro
   // measurements.
@@ -291,11 +411,8 @@
     Eigen::Matrix<Scalar, kNOutputs, kNOutputs> R;
     R.setZero();
     R.diagonal() << encoder_noise_, encoder_noise_, gyro_noise_;
-    Correct(z, &U, {},
-            [this](const State &X, const Input &) {
-              return H_encoders_and_gyro_ * X;
-            },
-            [this](const State &) { return H_encoders_and_gyro_; }, R, t);
+    CHECK(H_encoders_and_gyro_.has_value());
+    Correct(z, &U, nullptr, &H_encoders_and_gyro_.value(), R, t);
   }
 
   // Sundry accessor:
@@ -348,6 +465,50 @@
 
  private:
   struct Observation {
+    Observation(aos::monotonic_clock::time_point t,
+                aos::monotonic_clock::time_point prev_t, State X_hat,
+                StateSquare P, Input U, Output z,
+                ExpectedObservationBuilder *make_h,
+                ExpectedObservationFunctor *h,
+                Eigen::Matrix<Scalar, kNOutputs, kNOutputs> R, StateSquare A_d,
+                StateSquare Q_d,
+                aos::monotonic_clock::duration discretization_time,
+                State predict_update)
+        : t(t),
+          prev_t(prev_t),
+          X_hat(X_hat),
+          P(P),
+          U(U),
+          z(z),
+          make_h(make_h),
+          h(h),
+          R(R),
+          A_d(A_d),
+          Q_d(Q_d),
+          discretization_time(discretization_time),
+          predict_update(predict_update) {}
+    Observation(const Observation &) = delete;
+    Observation &operator=(const Observation &) = delete;
+    // Move-construct an observation by copying over the contents of the struct
+    // and then clearing the old Observation's pointers so that it doesn't try
+    // to clean things up.
+    Observation(Observation &&o)
+        : Observation(o.t, o.prev_t, o.X_hat, o.P, o.U, o.z, o.make_h, o.h, o.R,
+                      o.A_d, o.Q_d, o.discretization_time, o.predict_update) {
+      o.make_h = nullptr;
+      o.h = nullptr;
+    }
+    Observation &operator=(Observation &&observation) = delete;
+    ~Observation() {
+      // Observe h being deleted first, since make_h may own its memory.
+      // Shouldn't actually matter, though.
+      if (h != nullptr) {
+        h->ObserveDeletion();
+      }
+      if (make_h != nullptr) {
+        make_h->ObserveDeletion();
+      }
+    }
     // Time when the observation was taken.
     aos::monotonic_clock::time_point t;
     // Time that the previous observation was taken:
@@ -365,24 +526,11 @@
     // estimate. This is used by the camera to make it so that we only have to
     // match targets once.
     // Only called if h and dhdx are empty.
-    std::function<void(const State &, const StateSquare &,
-                       std::function<Output(const State &, const Input &)> *,
-                       std::function<Eigen::Matrix<Scalar, kNOutputs, kNStates>(
-                           const State &)> *)>
-        make_h;
+    ExpectedObservationBuilder *make_h = nullptr;
     // A function to calculate the expected output at a given state/input.
     // TODO(james): For encoders/gyro, it is linear and the function call may
     // be expensive. Potential source of optimization.
-    std::function<Output(const State &, const Input &)> h;
-    // The Jacobian of h with respect to x.
-    // We assume that U has no impact on the Jacobian.
-    // TODO(james): Currently, none of the users of this actually make use of
-    // the ability to have dynamic dhdx (technically, the camera code should
-    // recalculate it to be strictly correct, but I was both too lazy to do
-    // so and it seemed unnecessary). This is a potential source for future
-    // optimizations if function calls are being expensive.
-    std::function<Eigen::Matrix<Scalar, kNOutputs, kNStates>(const State &)>
-        dhdx;
+    ExpectedObservationFunctor *h = nullptr;
     // The measurement noise matrix.
     Eigen::Matrix<Scalar, kNOutputs, kNOutputs> R;
 
@@ -556,7 +704,7 @@
   }
 
   void CorrectImpl(Observation *obs, State *state, StateSquare *P) {
-    const Eigen::Matrix<Scalar, kNOutputs, kNStates> H = obs->dhdx(*state);
+    const Eigen::Matrix<Scalar, kNOutputs, kNStates> H = obs->h->DHDX(*state);
     // Note: Technically, this does calculate P * H.transpose() twice. However,
     // when I was mucking around with some things, I found that in practice
     // putting everything into one expression and letting Eigen optimize it
@@ -566,7 +714,7 @@
         *P * H.transpose() * (H * *P * H.transpose() + obs->R).inverse();
     const StateSquare Ptemp = (StateSquare::Identity() - K * H) * *P;
     *P = Ptemp;
-    *state += K * (obs->z - obs->h(*state, obs->U));
+    *state += K * (obs->z - obs->h->H(*state, obs->U));
   }
 
   void ProcessObservation(Observation *obs, const std::chrono::nanoseconds dt,
@@ -576,9 +724,9 @@
     if (dt.count() != 0 && dt < kMaxTimestep) {
       PredictImpl(obs, dt, state, P);
     }
-    if (!(obs->h && obs->dhdx)) {
-      CHECK(obs->make_h);
-      obs->make_h(*state, *P, &obs->h, &obs->dhdx);
+    if (obs->h == nullptr) {
+      CHECK(obs->make_h != nullptr);
+      obs->h = CHECK_NOTNULL(obs->make_h->MakeExpectedObservations(*state, *P));
     }
     CorrectImpl(obs, state, P);
   }
@@ -590,7 +738,7 @@
   StateSquare A_continuous_;
   StateSquare Q_continuous_;
   StateSquare P_;
-  Eigen::Matrix<Scalar, kNOutputs, kNStates> H_encoders_and_gyro_;
+  std::optional<LinearH> H_encoders_and_gyro_;
   Scalar encoder_noise_, gyro_noise_;
   Eigen::Matrix<Scalar, kNStates, kNInputs> B_continuous_;
 
@@ -610,14 +758,8 @@
 template <typename Scalar>
 void HybridEkf<Scalar>::Correct(
     const Output &z, const Input *U,
-    std::function<void(const State &, const StateSquare &,
-                       std::function<Output(const State &, const Input &)> *,
-                       std::function<Eigen::Matrix<Scalar, kNOutputs, kNStates>(
-                           const State &)> *)>
-        make_h,
-    std::function<Output(const State &, const Input &)> h,
-    std::function<Eigen::Matrix<Scalar, kNOutputs, kNStates>(const State &)>
-        dhdx,
+    ExpectedObservationBuilder *observation_builder,
+    ExpectedObservationFunctor *expected_observations,
     const Eigen::Matrix<Scalar, kNOutputs, kNOutputs> &R,
     aos::monotonic_clock::time_point t) {
   CHECK(!observations_.empty());
@@ -627,9 +769,9 @@
     return;
   }
   auto cur_it = observations_.PushFromBottom(
-      {t, t, State::Zero(), StateSquare::Zero(), Input::Zero(), z, make_h, h,
-       dhdx, R, StateSquare::Identity(), StateSquare::Zero(),
-       std::chrono::seconds(0), State::Zero()});
+      {t, t, State::Zero(), StateSquare::Zero(), Input::Zero(), z,
+       observation_builder, expected_observations, R, StateSquare::Identity(),
+       StateSquare::Zero(), std::chrono::seconds(0), State::Zero()});
   if (cur_it == observations_.end()) {
     VLOG(1) << "Camera dropped off of end with time of "
             << aos::time::DurationInSeconds(t.time_since_epoch())
@@ -773,14 +915,18 @@
       std::pow(1.1, 2.0);
   Q_continuous_(kLateralVelocity, kLateralVelocity) = std::pow(0.1, 2.0);
 
-  H_encoders_and_gyro_.setZero();
-  // Encoders are stored directly in the state matrix, so are a minor
-  // transform away.
-  H_encoders_and_gyro_(0, kLeftEncoder) = 1.0;
-  H_encoders_and_gyro_(1, kRightEncoder) = 1.0;
-  // Gyro rate is just the difference between right/left side speeds:
-  H_encoders_and_gyro_(2, kLeftVelocity) = -1.0 / diameter;
-  H_encoders_and_gyro_(2, kRightVelocity) = 1.0 / diameter;
+  {
+    Eigen::Matrix<Scalar, kNOutputs, kNStates> H_encoders_and_gyro;
+    H_encoders_and_gyro.setZero();
+    // Encoders are stored directly in the state matrix, so are a minor
+    // transform away.
+    H_encoders_and_gyro(0, kLeftEncoder) = 1.0;
+    H_encoders_and_gyro(1, kRightEncoder) = 1.0;
+    // Gyro rate is just the difference between right/left side speeds:
+    H_encoders_and_gyro(2, kLeftVelocity) = -1.0 / diameter;
+    H_encoders_and_gyro(2, kRightVelocity) = 1.0 / diameter;
+    H_encoders_and_gyro_.emplace(H_encoders_and_gyro);
+  }
 
   encoder_noise_ = 5e-9;
   gyro_noise_ = 1e-13;
diff --git a/frc971/control_loops/drivetrain/hybrid_ekf_test.cc b/frc971/control_loops/drivetrain/hybrid_ekf_test.cc
index 4bdf4de..5efb297 100644
--- a/frc971/control_loops/drivetrain/hybrid_ekf_test.cc
+++ b/frc971/control_loops/drivetrain/hybrid_ekf_test.cc
@@ -213,8 +213,7 @@
   HybridEkf<>::Output Z(0.5, 0.5, 1);
   Eigen::Matrix<double, 3, 12> H;
   H.setIdentity();
-  auto h = [H](const State &X, const Input &) { return H * X; };
-  auto dhdx = [H](const State &) { return H; };
+  HybridEkf<>::LinearH h(H);
   Eigen::Matrix<double, 3, 3> R;
   R.setIdentity();
   R *= 1e-3;
@@ -222,7 +221,7 @@
   EXPECT_EQ(0.0, ekf_.X_hat(StateIdx::kTheta));
   const double starting_p_norm = ekf_.P().norm();
   for (int ii = 0; ii < 100; ++ii) {
-    ekf_.Correct(Z, &U, {}, h, dhdx, R, t0_);
+    ekf_.Correct(Z, &U, nullptr, &h, R, t0_);
   }
   EXPECT_NEAR(Z(0, 0), ekf_.X_hat(StateIdx::kX), 1e-3);
   EXPECT_NEAR(Z(1, 0), ekf_.X_hat(StateIdx::kY), 1e-3);
@@ -241,8 +240,7 @@
   State true_X = ekf_.X_hat();
   Eigen::Matrix<double, 3, 12> H;
   H.setZero();
-  auto h = [H](const State &X, const Input &) { return H * X; };
-  auto dhdx = [H](const State &) { return H; };
+  HybridEkf<>::LinearH h(H);
   // Provide constant input voltage.
   Input U;
   U << 12.0, 10.0, 1.0, -0.1;
@@ -253,7 +251,7 @@
   EXPECT_EQ(0.0, ekf_.X_hat().norm());
   const double starting_p_norm = ekf_.P().norm();
   for (int ii = 0; ii < 100; ++ii) {
-    ekf_.Correct(Z, &U, {}, h, dhdx, R, t0_ + dt_config_.dt * (ii + 1));
+    ekf_.Correct(Z, &U, nullptr, &h, R, t0_ + dt_config_.dt * (ii + 1));
     true_X = Update(true_X, U, false);
     EXPECT_EQ(true_X, ekf_.X_hat());
   }
@@ -292,8 +290,7 @@
   Z.setZero();
   Eigen::Matrix<double, 3, 12> H;
   H.setZero();
-  auto h_zero = [H](const State &X, const Input &) { return H * X; };
-  auto dhdx_zero = [H](const State &) { return H; };
+  HybridEkf<>::LinearH h_zero(H);
   Input U;
   U << 12.0, 12.0, 0.0, 0.0;
   Eigen::Matrix<double, 3, 3> R;
@@ -302,8 +299,7 @@
   // We fill up the buffer to be as full as demanded by the user.
   const size_t n_predictions = GetParam();
   for (size_t ii = 0; ii < n_predictions; ++ii) {
-    ekf_.Correct(Z, &U, {}, h_zero, dhdx_zero, R,
-                 t0_ + dt_config_.dt * (ii + 1));
+    ekf_.Correct(Z, &U, nullptr, &h_zero, R, t0_ + dt_config_.dt * (ii + 1));
   }
 
   // Store state and covariance after prediction steps.
@@ -315,13 +311,12 @@
   H(0, 0) = 1;
   H(1, 1) = 1;
   H(2, 2) = 1;
-  auto h = [H](const State &X, const Input &) { return H * X; };
-  auto dhdx = [H](const State &) { return H; };
+  HybridEkf<>::LinearH h(H);
   R.setZero();
   R.diagonal() << 1e-5, 1e-5, 1e-5;
   U.setZero();
   for (int ii = 0; ii < 20; ++ii) {
-    ekf_.Correct(Z, &U, {}, h, dhdx, R, t0_);
+    ekf_.Correct(Z, &U, nullptr, &h, R, t0_);
   }
   const double corrected_p_norm = ekf_.P().norm();
   State expected_X_hat = modeled_X_hat;
@@ -348,8 +343,7 @@
   Z.setZero();
   Eigen::Matrix<double, 3, 12> H;
   H.setZero();
-  auto h_zero = [H](const State &X, const Input &) { return H * X; };
-  auto dhdx_zero = [H](const State &) { return H; };
+  HybridEkf<>::LinearH h_zero(H);
   Input U;
   U << 12.0, 12.0, 0.0, 0.0;
   Eigen::Matrix<double, 3, 3> R;
@@ -357,8 +351,7 @@
 
   EXPECT_EQ(0.0, ekf_.X_hat().norm());
   for (int ii = 0; ii < HybridEkf<>::kSaveSamples; ++ii) {
-    ekf_.Correct(Z, &U, {}, h_zero, dhdx_zero, R,
-                 t0_ + dt_config_.dt * (ii + 1));
+    ekf_.Correct(Z, &U, nullptr, &h_zero, R, t0_ + dt_config_.dt * (ii + 1));
   }
   const State modeled_X_hat = ekf_.X_hat();
   const HybridEkf<>::StateSquare modeled_P = ekf_.P();
@@ -368,12 +361,11 @@
   H(0, 0) = 1;
   H(1, 1) = 1;
   H(2, 2) = 1;
-  auto h = [H](const State &X, const Input &) { return H * X; };
-  auto dhdx = [H](const State &) { return H; };
+  HybridEkf<>::LinearH h(H);
   R.setIdentity();
   R *= 1e-5;
   U.setZero();
-  ekf_.Correct(Z, &U, {}, h, dhdx, R, t0_);
+  ekf_.Correct(Z, &U, nullptr, &h, R, t0_);
   EXPECT_EQ(ekf_.X_hat(), modeled_X_hat)
       << "Expected too-old correction to have no effect; X_hat: "
       << ekf_.X_hat() << " expected " << modeled_X_hat;
@@ -493,8 +485,8 @@
   // Expect death if the user does not provide U when creating a fresh
   // measurement.
   EXPECT_DEATH(
-      ekf_.Correct({1, 2, 3}, nullptr, {}, {}, {}, Eigen::Matrix3d::Zero(),
-                   t0_ + std::chrono::seconds(1)),
+      ekf_.Correct({1, 2, 3}, nullptr, nullptr, nullptr,
+                   Eigen::Matrix3d::Zero(), t0_ + std::chrono::seconds(1)),
       "U != nullptr");
 }
 
@@ -504,23 +496,10 @@
   // Check that we die when no h-related functions are provided:
   Input U;
   U << 1.0, 2.0, 0.0, 0.0;
-  EXPECT_DEATH(ekf_.Correct({1, 2, 3}, &U, {}, {}, {}, Eigen::Matrix3d::Zero(),
-                            t0_ + std::chrono::seconds(1)),
-               "make_h");
-  // Check that we die when only one of h and dhdx are provided:
   EXPECT_DEATH(
-      ekf_.Correct(
-          {1, 2, 3}, &U, {}, {},
-          [](const State &) { return Eigen::Matrix<double, 3, 12>::Zero(); },
-          Eigen::Matrix3d::Zero(), t0_ + std::chrono::seconds(1)),
+      ekf_.Correct({1, 2, 3}, &U, nullptr, nullptr, Eigen::Matrix3d::Zero(),
+                   t0_ + std::chrono::seconds(1)),
       "make_h");
-  EXPECT_DEATH(ekf_.Correct(
-                   {1, 2, 3}, &U, {},
-                   [](const State &, const Input &) {
-                     return Eigen::Matrix<double, 3, 1>::Zero();
-                   },
-                   {}, Eigen::Matrix3d::Zero(), t0_ + std::chrono::seconds(1)),
-               "make_h");
 }
 
 }  // namespace testing
diff --git a/frc971/control_loops/python/basic_window.py b/frc971/control_loops/python/basic_window.py
index 44e4f49..886a5d3 100755
--- a/frc971/control_loops/python/basic_window.py
+++ b/frc971/control_loops/python/basic_window.py
@@ -7,7 +7,7 @@
 from gi.repository import Gdk
 from gi.repository import GdkX11
 import cairo
-from constants import *
+from frc971.control_loops.python.constants import *
 
 identity = cairo.Matrix()
 
diff --git a/frc971/vision/BUILD b/frc971/vision/BUILD
index c52afae..642ca0f 100644
--- a/frc971/vision/BUILD
+++ b/frc971/vision/BUILD
@@ -1,4 +1,5 @@
 load("@com_github_google_flatbuffers//:build_defs.bzl", "flatbuffer_cc_library", "flatbuffer_py_library")
+load("//aos:config.bzl", "aos_config")
 load("@com_github_google_flatbuffers//:typescript.bzl", "flatbuffer_ts_library")
 
 flatbuffer_cc_library(
@@ -76,6 +77,7 @@
         "//aos/events:epoll",
         "//aos/events:event_loop",
         "//aos/scoped:scoped_fd",
+        "//aos/util:threaded_consumer",
         "@com_github_google_glog//:glog",
         "@com_google_absl//absl/base",
     ],
@@ -102,6 +104,7 @@
         "//y2020/vision/sift:sift_fbs",
         "//y2020/vision/sift:sift_training_fbs",
         "//y2020/vision/tools/python_code:sift_training_data",
+        "@com_github_foxglove_schemas//:schemas",
         "@com_github_google_glog//:glog",
         "@com_google_absl//absl/strings:str_format",
         "@com_google_absl//absl/types:span",
@@ -121,6 +124,7 @@
     visibility = ["//visibility:public"],
     deps = [
         ":charuco_lib",
+        ":foxglove_image_converter",
         "//aos:init",
         "//aos/events/logging:log_reader",
         "//frc971/analysis:in_process_plotter",
@@ -129,6 +133,8 @@
         "//frc971/wpilib:imu_batch_fbs",
         "//frc971/wpilib:imu_fbs",
         "//third_party:opencv",
+        "@com_github_foxglove_schemas//:CompressedImage_schema",
+        "@com_github_foxglove_schemas//:ImageAnnotations_schema",
         "@com_google_absl//absl/strings:str_format",
         "@com_google_ceres_solver//:ceres",
         "@org_tuxfamily_eigen//:eigen",
@@ -258,9 +264,42 @@
     hdrs = ["foxglove_image_converter.h"],
     visibility = ["//visibility:public"],
     deps = [
+        ":charuco_lib",
         ":vision_fbs",
         "//aos/events:event_loop",
         "//third_party:opencv",
         "@com_github_foxglove_schemas//:schemas",
     ],
 )
+
+aos_config(
+    name = "converter_config",
+    testonly = True,
+    src = "converter_test_config.json",
+    flatbuffers = [
+        "//frc971/vision:vision_fbs",
+        "//aos/events:event_loop_fbs",
+        "//aos/logging:log_message_fbs",
+        "//aos/network:message_bridge_client_fbs",
+        "//aos/network:message_bridge_server_fbs",
+        "//aos/network:timestamp_fbs",
+        "@com_github_foxglove_schemas//:schemas",
+    ],
+)
+
+cc_test(
+    name = "foxglove_image_converter_test",
+    srcs = ["foxglove_image_converter_test.cc"],
+    data = [
+        ":converter_config",
+        "@april_tag_test_image",
+    ],
+    deps = [
+        ":foxglove_image_converter",
+        "//aos:configuration",
+        "//aos/events:simulated_event_loop",
+        "//aos/testing:googletest",
+        "//aos/testing:path",
+        "//aos/testing:tmpdir",
+    ],
+)
diff --git a/frc971/vision/calibration_accumulator.cc b/frc971/vision/calibration_accumulator.cc
index eee22f5..ea9af28 100644
--- a/frc971/vision/calibration_accumulator.cc
+++ b/frc971/vision/calibration_accumulator.cc
@@ -11,6 +11,8 @@
 #include "frc971/control_loops/quaternion_utils.h"
 #include "frc971/vision/charuco_lib.h"
 #include "frc971/wpilib/imu_batch_generated.h"
+#include "external/com_github_foxglove_schemas/ImageAnnotations_schema.h"
+#include "external/com_github_foxglove_schemas/CompressedImage_schema.h"
 
 DEFINE_bool(display_undistorted, false,
             "If true, display the undistorted image.");
@@ -111,6 +113,33 @@
   }
 }
 
+CalibrationFoxgloveVisualizer::CalibrationFoxgloveVisualizer(
+    aos::EventLoop *event_loop)
+    : event_loop_(event_loop),
+      image_converter_(event_loop_, "/camera", "/visualization",
+                       ImageCompression::kJpeg),
+      annotations_sender_(
+          event_loop_->MakeSender<foxglove::ImageAnnotations>("/visualization")) {}
+
+aos::FlatbufferDetachedBuffer<aos::Configuration>
+CalibrationFoxgloveVisualizer::AddVisualizationChannels(
+    const aos::Configuration *config, const aos::Node *node) {
+  constexpr std::string_view channel_name = "/visualization";
+  aos::ChannelT channel_overrides;
+  channel_overrides.max_size = 10000000;
+  aos::FlatbufferDetachedBuffer<aos::Configuration> result =
+      aos::configuration::AddChannelToConfiguration(
+          config, channel_name,
+          aos::FlatbufferSpan<reflection::Schema>(
+              foxglove::ImageAnnotationsSchema()),
+          node, channel_overrides);
+  return aos::configuration::AddChannelToConfiguration(
+      &result.message(), channel_name,
+      aos::FlatbufferSpan<reflection::Schema>(
+          foxglove::CompressedImageSchema()),
+      node, channel_overrides);
+}
+
 Calibration::Calibration(aos::SimulatedEventLoopFactory *event_loop_factory,
                          aos::EventLoop *image_event_loop,
                          aos::EventLoop *imu_event_loop, std::string_view pi,
@@ -140,7 +169,9 @@
           [this](cv::Mat rgb_image, const monotonic_clock::time_point eof) {
             charuco_extractor_.HandleImage(rgb_image, eof);
           }),
-      data_(data) {
+      data_(data),
+      visualizer_event_loop_(image_factory_->MakeEventLoop("visualization")),
+      visualizer_(visualizer_event_loop_.get()) {
   imu_factory_->OnShutdown([]() { cv::destroyAllWindows(); });
 
   // Check for IMUValuesBatch topic on both /localizer and /drivetrain channels,
@@ -173,9 +204,10 @@
 void Calibration::HandleCharuco(
     cv::Mat rgb_image, const monotonic_clock::time_point eof,
     std::vector<cv::Vec4i> /*charuco_ids*/,
-    std::vector<std::vector<cv::Point2f>> /*charuco_corners*/, bool valid,
+    std::vector<std::vector<cv::Point2f>> charuco_corners, bool valid,
     std::vector<Eigen::Vector3d> rvecs_eigen,
     std::vector<Eigen::Vector3d> tvecs_eigen) {
+  visualizer_.HandleCharuco(eof, charuco_corners);
   if (valid) {
     CHECK(rvecs_eigen.size() > 0) << "Require at least one target detected";
     // We only use one (the first) target detected for calibration
@@ -237,6 +269,7 @@
                         last_value_.accelerometer_y,
                         last_value_.accelerometer_z);
 
+  // TODO: ToDistributedClock may be too noisy.
   data_->AddImu(imu_factory_->ToDistributedClock(monotonic_clock::time_point(
                     chrono::nanoseconds(imu->monotonic_timestamp_ns()))),
                 gyro, accel * kG);
diff --git a/frc971/vision/calibration_accumulator.h b/frc971/vision/calibration_accumulator.h
index d9f6065..5c435ad 100644
--- a/frc971/vision/calibration_accumulator.h
+++ b/frc971/vision/calibration_accumulator.h
@@ -8,6 +8,7 @@
 #include "aos/time/time.h"
 #include "frc971/control_loops/quaternion_utils.h"
 #include "frc971/vision/charuco_lib.h"
+#include "frc971/vision/foxglove_image_converter.h"
 #include "frc971/wpilib/imu_batch_generated.h"
 
 namespace frc971 {
@@ -76,6 +77,28 @@
       turret_points_;
 };
 
+class CalibrationFoxgloveVisualizer {
+ public:
+  CalibrationFoxgloveVisualizer(aos::EventLoop *event_loop);
+
+  static aos::FlatbufferDetachedBuffer<aos::Configuration>
+  AddVisualizationChannels(const aos::Configuration *config,
+                           const aos::Node *node);
+
+  void HandleCharuco(const aos::monotonic_clock::time_point eof,
+                     std::vector<std::vector<cv::Point2f>> charuco_corners) {
+    auto builder = annotations_sender_.MakeBuilder();
+    builder.CheckOk(
+        builder.Send(BuildAnnotations(eof, charuco_corners, builder.fbb())));
+  }
+
+ private:
+  aos::EventLoop *event_loop_;
+  FoxgloveImageConverter image_converter_;
+
+  aos::Sender<foxglove::ImageAnnotations> annotations_sender_;
+};
+
 // Class to register image and IMU callbacks in AOS and route them to the
 // corresponding CalibrationData class.
 class Calibration {
@@ -110,6 +133,9 @@
 
   CalibrationData *data_;
 
+  std::unique_ptr<aos::EventLoop> visualizer_event_loop_;
+  CalibrationFoxgloveVisualizer visualizer_;
+
   frc971::IMUValuesT last_value_;
 };
 
diff --git a/frc971/vision/charuco_lib.cc b/frc971/vision/charuco_lib.cc
index 622c871..f12a6a5 100644
--- a/frc971/vision/charuco_lib.cc
+++ b/frc971/vision/charuco_lib.cc
@@ -480,5 +480,42 @@
                   rvecs_eigen, tvecs_eigen);
 }
 
+flatbuffers::Offset<foxglove::ImageAnnotations> BuildAnnotations(
+    const aos::monotonic_clock::time_point monotonic_now,
+    const std::vector<std::vector<cv::Point2f>> &corners,
+    flatbuffers::FlatBufferBuilder *fbb) {
+  std::vector<flatbuffers::Offset<foxglove::PointsAnnotation>> rectangles;
+  const struct timespec now_t = aos::time::to_timespec(monotonic_now);
+  foxglove::Time time{static_cast<uint32_t>(now_t.tv_sec),
+                      static_cast<uint32_t>(now_t.tv_nsec)};
+  const flatbuffers::Offset<foxglove::Color> color_offset =
+      foxglove::CreateColor(*fbb, 0.0, 1.0, 0.0, 1.0);
+  for (const std::vector<cv::Point2f> &rectangle : corners) {
+    std::vector<flatbuffers::Offset<foxglove::Point2>> points_offsets;
+    for (const cv::Point2f &point : rectangle) {
+      points_offsets.push_back(foxglove::CreatePoint2(*fbb, point.x, point.y));
+    }
+    const flatbuffers::Offset<
+        flatbuffers::Vector<flatbuffers::Offset<foxglove::Point2>>>
+        points_offset = fbb->CreateVector(points_offsets);
+    std::vector<flatbuffers::Offset<foxglove::Color>> color_offsets(
+        points_offsets.size(), color_offset);
+    auto colors_offset = fbb->CreateVector(color_offsets);
+    foxglove::PointsAnnotation::Builder points_builder(*fbb);
+    points_builder.add_timestamp(&time);
+    points_builder.add_type(foxglove::PointsAnnotationType::POINTS);
+    points_builder.add_points(points_offset);
+    points_builder.add_outline_color(color_offset);
+    points_builder.add_outline_colors(colors_offset);
+    points_builder.add_thickness(2.0);
+    rectangles.push_back(points_builder.Finish());
+  }
+
+  const auto rectangles_offset = fbb->CreateVector(rectangles);
+  foxglove::ImageAnnotations::Builder annotation_builder(*fbb);
+  annotation_builder.add_points(rectangles_offset);
+  return annotation_builder.Finish();
+}
+
 }  // namespace vision
 }  // namespace frc971
diff --git a/frc971/vision/charuco_lib.h b/frc971/vision/charuco_lib.h
index 7759482..984cef6 100644
--- a/frc971/vision/charuco_lib.h
+++ b/frc971/vision/charuco_lib.h
@@ -13,6 +13,7 @@
 #include "aos/network/message_bridge_server_generated.h"
 #include "y2020/vision/sift/sift_generated.h"
 #include "y2020/vision/sift/sift_training_generated.h"
+#include "external/com_github_foxglove_schemas/ImageAnnotations_generated.h"
 
 DECLARE_bool(visualize);
 
@@ -178,6 +179,13 @@
       handle_charuco_;
 };
 
+// Puts the provided charuco corners into a foxglove ImageAnnotation type for
+// visualization purposes.
+flatbuffers::Offset<foxglove::ImageAnnotations> BuildAnnotations(
+    const aos::monotonic_clock::time_point monotonic_now,
+    const std::vector<std::vector<cv::Point2f>> &corners,
+    flatbuffers::FlatBufferBuilder *fbb);
+
 }  // namespace vision
 }  // namespace frc971
 
diff --git a/frc971/vision/converter_test_config.json b/frc971/vision/converter_test_config.json
new file mode 100644
index 0000000..5d74dd1
--- /dev/null
+++ b/frc971/vision/converter_test_config.json
@@ -0,0 +1,46 @@
+{
+  "channels" : [
+    {
+      "name": "/aos",
+      "type": "aos.timing.Report",
+      "source_node": "test"
+    },
+    {
+      "name": "/aos",
+      "type": "aos.logging.LogMessageFbs",
+      "source_node": "test"
+    },
+    {
+      "name": "/aos",
+      "type": "aos.message_bridge.ClientStatistics",
+      "source_node": "test"
+    },
+    {
+      "name": "/aos",
+      "type": "aos.message_bridge.Timestamp",
+      "source_node": "test"
+    },
+    {
+      "name": "/aos",
+      "type": "aos.message_bridge.ServerStatistics",
+      "source_node": "test"
+    },
+    {
+      "name": "/camera",
+      "type": "frc971.vision.CameraImage",
+      "source_node": "test",
+      "max_size": 10000000
+    },
+    {
+      "name": "/visualize",
+      "type": "foxglove.CompressedImage",
+      "source_node": "test",
+      "max_size": 10000000
+    }
+  ],
+  "nodes": [
+    {
+      "name": "test"
+    }
+  ]
+}
diff --git a/frc971/vision/foxglove_image_converter.cc b/frc971/vision/foxglove_image_converter.cc
index 0c5c736..abde78b 100644
--- a/frc971/vision/foxglove_image_converter.cc
+++ b/frc971/vision/foxglove_image_converter.cc
@@ -3,7 +3,6 @@
 #include <opencv2/imgproc.hpp>
 
 namespace frc971::vision {
-namespace {
 std::string_view ExtensionForCompression(ImageCompression compression) {
   switch (compression) {
     case ImageCompression::kJpeg:
@@ -12,25 +11,18 @@
       return "png";
   }
 }
-}  // namespace
+
 flatbuffers::Offset<foxglove::CompressedImage> CompressImage(
-    const CameraImage *raw_image, flatbuffers::FlatBufferBuilder *fbb,
-    ImageCompression compression) {
+    const cv::Mat image, const aos::monotonic_clock::time_point eof,
+    flatbuffers::FlatBufferBuilder *fbb, ImageCompression compression) {
   std::string_view format = ExtensionForCompression(compression);
   // imencode doesn't let us pass in anything other than an std::vector, and
   // performance isn't yet a big enough issue to try to avoid the copy.
   std::vector<uint8_t> buffer;
-  CHECK(raw_image->has_data());
-  cv::Mat image_color_mat(cv::Size(raw_image->cols(), raw_image->rows()),
-                          CV_8UC2, (void *)raw_image->data()->data());
-  cv::Mat bgr_image(cv::Size(raw_image->cols(), raw_image->rows()), CV_8UC3);
-  cv::cvtColor(image_color_mat, bgr_image, cv::COLOR_YUV2BGR_YUYV);
-  CHECK(cv::imencode(absl::StrCat(".", format), bgr_image, buffer));
+  CHECK(cv::imencode(absl::StrCat(".", format), image, buffer));
   const flatbuffers::Offset<flatbuffers::Vector<uint8_t>> data_offset =
       fbb->CreateVector(buffer);
-  const struct timespec timestamp_t =
-      aos::time::to_timespec(aos::monotonic_clock::time_point(
-          std::chrono::nanoseconds(raw_image->monotonic_timestamp_ns())));
+  const struct timespec timestamp_t = aos::time::to_timespec(eof);
   const foxglove::Time time{static_cast<uint32_t>(timestamp_t.tv_sec),
                             static_cast<uint32_t>(timestamp_t.tv_nsec)};
   const flatbuffers::Offset<flatbuffers::String> format_offset =
@@ -47,13 +39,14 @@
                                                std::string_view output_channel,
                                                ImageCompression compression)
     : event_loop_(event_loop),
+      image_callback_(
+          event_loop_, input_channel,
+          [this, compression](const cv::Mat image,
+                              const aos::monotonic_clock::time_point eof) {
+            auto builder = sender_.MakeBuilder();
+            builder.CheckOk(builder.Send(
+                CompressImage(image, eof, builder.fbb(), compression)));
+          }),
       sender_(
-          event_loop_->MakeSender<foxglove::CompressedImage>(output_channel)) {
-  event_loop_->MakeWatcher(input_channel, [this, compression](
-                                              const CameraImage &image) {
-    auto builder = sender_.MakeBuilder();
-    builder.CheckOk(
-        builder.Send(CompressImage(&image, builder.fbb(), compression)));
-  });
-}
+          event_loop_->MakeSender<foxglove::CompressedImage>(output_channel)) {}
 }  // namespace frc971::vision
diff --git a/frc971/vision/foxglove_image_converter.h b/frc971/vision/foxglove_image_converter.h
index add83a6..872ac14 100644
--- a/frc971/vision/foxglove_image_converter.h
+++ b/frc971/vision/foxglove_image_converter.h
@@ -1,8 +1,9 @@
 #ifndef FRC971_VISION_FOXGLOVE_IMAGE_CONVERTER_H_
 #define FRC971_VISION_FOXGLOVE_IMAGE_CONVERTER_H_
-#include "external/com_github_foxglove_schemas/CompressedImage_generated.h"
-#include "frc971/vision/vision_generated.h"
 #include "aos/events/event_loop.h"
+#include "external/com_github_foxglove_schemas/CompressedImage_generated.h"
+#include "frc971/vision/charuco_lib.h"
+#include "frc971/vision/vision_generated.h"
 
 namespace frc971::vision {
 // Empirically, from 2022 logs:
@@ -12,9 +13,11 @@
 // conversion with a user-script in Foxglove Studio.
 enum class ImageCompression { kJpeg, kPng };
 
+std::string_view ExtensionForCompression(ImageCompression compression);
+
 flatbuffers::Offset<foxglove::CompressedImage> CompressImage(
-    const CameraImage *raw_image, flatbuffers::FlatBufferBuilder *fbb,
-    ImageCompression compression);
+    const cv::Mat image, const aos::monotonic_clock::time_point eof,
+    flatbuffers::FlatBufferBuilder *fbb, ImageCompression compression);
 
 // This class provides a simple converter that will take an AOS CameraImage
 // channel and output
@@ -30,6 +33,7 @@
 
  private:
   aos::EventLoop *event_loop_;
+  ImageCallback image_callback_;
   aos::Sender<foxglove::CompressedImage> sender_;
 };
 }  // namespace frc971::vision
diff --git a/frc971/vision/foxglove_image_converter_test.cc b/frc971/vision/foxglove_image_converter_test.cc
new file mode 100644
index 0000000..65b3b6b
--- /dev/null
+++ b/frc971/vision/foxglove_image_converter_test.cc
@@ -0,0 +1,68 @@
+#include "frc971/vision/foxglove_image_converter.h"
+
+#include "aos/events/simulated_event_loop.h"
+#include "aos/json_to_flatbuffer.h"
+#include "aos/testing/path.h"
+#include "aos/testing/tmpdir.h"
+#include "gtest/gtest.h"
+
+namespace frc971::vision {
+std::ostream &operator<<(std::ostream &os, ImageCompression compression) {
+  os << ExtensionForCompression(compression);
+  return os;
+}
+namespace testing {
+class ImageConverterTest : public ::testing::TestWithParam<ImageCompression> {
+ protected:
+  ImageConverterTest()
+      : config_(aos::configuration::ReadConfig(
+            aos::testing::ArtifactPath("frc971/vision/converter_config.json"))),
+        factory_(&config_.message()),
+        camera_image_(
+            aos::FileToFlatbuffer<CameraImage>(aos::testing::ArtifactPath(
+                "external/april_tag_test_image/test.bfbs"))),
+        node_(aos::configuration::GetNode(&config_.message(), "test")),
+        test_event_loop_(factory_.MakeEventLoop("test", node_)),
+        image_sender_(test_event_loop_->MakeSender<CameraImage>("/camera")),
+        converter_event_loop_(factory_.MakeEventLoop("converter", node_)),
+        converter_(converter_event_loop_.get(), "/camera", "/visualize",
+                   GetParam()),
+        output_path_(absl::StrCat(aos::testing::TestTmpDir(), "/test.",
+                                  ExtensionForCompression(GetParam()))) {
+    test_event_loop_->OnRun(
+        [this]() { image_sender_.CheckOk(image_sender_.Send(camera_image_)); });
+    test_event_loop_->MakeWatcher(
+        "/visualize", [this](const foxglove::CompressedImage &image) {
+          ASSERT_TRUE(image.has_data());
+          std::string expected_contents =
+              aos::util::ReadFileToStringOrDie(aos::testing::ArtifactPath(
+                  absl::StrCat("external/april_tag_test_image/expected.",
+                               ExtensionForCompression(GetParam()))));
+          std::string_view data(
+              reinterpret_cast<const char *>(image.data()->data()),
+              image.data()->size());
+          EXPECT_EQ(expected_contents, data);
+          aos::util::WriteStringToFileOrDie(output_path_, data);
+          factory_.Exit();
+        });
+  }
+
+  aos::FlatbufferDetachedBuffer<aos::Configuration> config_;
+  aos::SimulatedEventLoopFactory factory_;
+  aos::FlatbufferVector<CameraImage> camera_image_;
+  const aos::Node *const node_;
+  std::unique_ptr<aos::EventLoop> test_event_loop_;
+  aos::Sender<CameraImage> image_sender_;
+  std::unique_ptr<aos::EventLoop> converter_event_loop_;
+  FoxgloveImageConverter converter_;
+  std::string output_path_;
+};
+
+TEST_P(ImageConverterTest, ImageToFoxglove) { factory_.Run(); }
+
+INSTANTIATE_TEST_SUITE_P(CompressionOptions, ImageConverterTest,
+                         ::testing::Values(ImageCompression::kJpeg,
+                                           ImageCompression::kPng));
+
+}  // namespace testing
+}  // namespace frc971::vision
diff --git a/frc971/vision/v4l2_reader.cc b/frc971/vision/v4l2_reader.cc
index a6bcb4d..2553003 100644
--- a/frc971/vision/v4l2_reader.cc
+++ b/frc971/vision/v4l2_reader.cc
@@ -85,18 +85,23 @@
 
   for (size_t i = 0; i < buffers_.size(); ++i) {
     buffers_[i].sender = event_loop_->MakeSender<CameraImage>("/camera");
-    EnqueueBuffer(i);
+    MarkBufferToBeEnqueued(i);
   }
   int type = multiplanar() ? V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE
                            : V4L2_BUF_TYPE_VIDEO_CAPTURE;
   PCHECK(Ioctl(VIDIOC_STREAMON, &type) == 0);
 }
 
+void V4L2ReaderBase::MarkBufferToBeEnqueued(int buffer_index) {
+  ReinitializeBuffer(buffer_index);
+  EnqueueBuffer(buffer_index);
+}
+
 void V4L2ReaderBase::MaybeEnqueue() {
   // First, enqueue any old buffer we already have. This is the one which
   // may have been sent.
   if (saved_buffer_) {
-    EnqueueBuffer(saved_buffer_.index);
+    MarkBufferToBeEnqueued(saved_buffer_.index);
     saved_buffer_.Clear();
   }
   ftrace_.FormatMessage("Enqueued previous buffer %d", saved_buffer_.index);
@@ -114,7 +119,7 @@
       // going.
       if (previous_buffer) {
         ftrace_.FormatMessage("Previous %d", previous_buffer.index);
-        EnqueueBuffer(previous_buffer.index);
+        MarkBufferToBeEnqueued(previous_buffer.index);
       }
       continue;
     }
@@ -133,7 +138,12 @@
   }
 }
 
-void V4L2ReaderBase::SendLatestImage() { buffers_[saved_buffer_.index].Send(); }
+void V4L2ReaderBase::SendLatestImage() {
+  buffers_[saved_buffer_.index].Send();
+
+  MarkBufferToBeEnqueued(saved_buffer_.index);
+  saved_buffer_.Clear();
+}
 
 void V4L2ReaderBase::SetExposure(size_t duration) {
   v4l2_control manual_control;
@@ -236,7 +246,8 @@
 
   CHECK_GE(buffer_number, 0);
   CHECK_LT(buffer_number, static_cast<int>(buffers_.size()));
-  buffers_[buffer_number].InitializeMessage(ImageSize());
+  CHECK(buffers_[buffer_number].data_pointer != nullptr);
+
   struct v4l2_buffer buffer;
   struct v4l2_plane planes[1];
   memset(&buffer, 0, sizeof(buffer));
@@ -315,16 +326,22 @@
                                        const std::string &image_sensor_subdev)
     : V4L2ReaderBase(event_loop, device_name),
       epoll_(epoll),
-      image_sensor_fd_(open(image_sensor_subdev.c_str(), O_RDWR | O_NONBLOCK)) {
+      image_sensor_fd_(open(image_sensor_subdev.c_str(), O_RDWR | O_NONBLOCK)),
+      buffer_requeuer_([this](int buffer) { EnqueueBuffer(buffer); },
+                       kEnqueueFifoPriority) {
   PCHECK(image_sensor_fd_.get() != -1)
       << " Failed to open device " << device_name;
-
   StreamOn();
   epoll_->OnReadable(fd().get(), [this]() { OnImageReady(); });
 }
 
 RockchipV4L2Reader::~RockchipV4L2Reader() { epoll_->DeleteFd(fd().get()); }
 
+void RockchipV4L2Reader::MarkBufferToBeEnqueued(int buffer) {
+  ReinitializeBuffer(buffer);
+  buffer_requeuer_.Push(buffer);
+}
+
 void RockchipV4L2Reader::OnImageReady() {
   if (!ReadLatestImage()) {
     return;
diff --git a/frc971/vision/v4l2_reader.h b/frc971/vision/v4l2_reader.h
index 669c157..22e4367 100644
--- a/frc971/vision/v4l2_reader.h
+++ b/frc971/vision/v4l2_reader.h
@@ -5,10 +5,13 @@
 #include <string>
 
 #include "absl/types/span.h"
+#include "aos/containers/ring_buffer.h"
 #include "aos/events/epoll.h"
 #include "aos/events/event_loop.h"
 #include "aos/ftrace.h"
+#include "aos/realtime.h"
 #include "aos/scoped/scoped_fd.h"
+#include "aos/util/threaded_consumer.h"
 #include "frc971/vision/vision_generated.h"
 #include "glog/logging.h"
 
@@ -57,6 +60,23 @@
   void StreamOff();
   void StreamOn();
 
+  // Enqueues a buffer for v4l2 to stream into (expensive).
+  void EnqueueBuffer(int buffer_index);
+
+  // Initializations that need to happen in the main thread.
+  //
+  // Implementations of MarkBufferToBeEnqueued should call this before calling
+  // EnqueueBuffer.
+  void ReinitializeBuffer(int buffer_index) {
+    CHECK_GE(buffer_index, 0);
+    CHECK_LT(buffer_index, static_cast<int>(buffers_.size()));
+    buffers_[buffer_index].InitializeMessage(ImageSize());
+  }
+
+  // Submits a buffer to be enqueued later in a lower priority thread.
+  // Legacy V4L2Reader still does this in the main thread.
+  virtual void MarkBufferToBeEnqueued(int buffer_index);
+
   int Ioctl(unsigned long number, void *arg);
 
   bool multiplanar() const { return multiplanar_; }
@@ -70,9 +90,9 @@
 
   const aos::ScopedFD &fd() { return fd_; };
 
- private:
   static constexpr int kNumberBuffers = 4;
 
+ private:
   struct Buffer {
     void InitializeMessage(size_t max_image_size);
 
@@ -113,8 +133,6 @@
   // buffer, or BufferInfo() if there wasn't a frame to dequeue.
   BufferInfo DequeueBuffer();
 
-  void EnqueueBuffer(int buffer);
-
   // The mmaped V4L2 buffers.
   std::array<Buffer, kNumberBuffers> buffers_;
 
@@ -159,11 +177,17 @@
  private:
   void OnImageReady();
 
+  void MarkBufferToBeEnqueued(int buffer) override;
+
   int ImageSensorIoctl(unsigned long number, void *arg);
 
   aos::internal::EPoll *epoll_;
 
   aos::ScopedFD image_sensor_fd_;
+
+  static constexpr int kEnqueueFifoPriority = 1;
+
+  aos::util::ThreadedConsumer<int, kNumberBuffers> buffer_requeuer_;
 };
 
 }  // namespace vision
diff --git a/scouting/db/db.go b/scouting/db/db.go
index 85e3d98..8f043de 100644
--- a/scouting/db/db.go
+++ b/scouting/db/db.go
@@ -66,6 +66,34 @@
 	CollectedBy string
 }
 
+type Stats2023 struct {
+	TeamNumber                                                     string `gorm:"primaryKey"`
+	MatchNumber                                                    int32  `gorm:"primaryKey"`
+	SetNumber                                                      int32  `gorm:"primaryKey"`
+	CompLevel                                                      string `gorm:"primaryKey"`
+	StartingQuadrant                                               int32
+	LowCubesAuto, MiddleCubesAuto, HighCubesAuto, CubesDroppedAuto int32
+	LowConesAuto, MiddleConesAuto, HighConesAuto, ConesDroppedAuto int32
+	LowCubes, MiddleCubes, HighCubes, CubesDropped                 int32
+	LowCones, MiddleCones, HighCones, ConesDropped                 int32
+	AvgCycle                                                       int32
+	// The username of the person who collected these statistics.
+	// "unknown" if submitted without logging in.
+	// Empty if the stats have not yet been collected.
+	CollectedBy string
+}
+
+type Action struct {
+	TeamNumber      string `gorm:"primaryKey"`
+	MatchNumber     int32  `gorm:"primaryKey"`
+	SetNumber       int32  `gorm:"primaryKey"`
+	CompLevel       string `gorm:"primaryKey"`
+	CompletedAction []byte
+	// This contains a serialized scouting.webserver.requests.ActionType flatbuffer.
+	TimeStamp   int32 `gorm:"primaryKey"`
+	CollectedBy string
+}
+
 type NotesData struct {
 	ID           uint `gorm:"primaryKey"`
 	TeamNumber   int32
@@ -113,7 +141,7 @@
 		return nil, errors.New(fmt.Sprint("Failed to connect to postgres: ", err))
 	}
 
-	err = database.AutoMigrate(&Match{}, &Shift{}, &Stats{}, &NotesData{}, &Ranking{}, &DriverRankingData{})
+	err = database.AutoMigrate(&Match{}, &Shift{}, &Stats{}, &Stats2023{}, &Action{}, &NotesData{}, &Ranking{}, &DriverRankingData{})
 	if err != nil {
 		database.Delete()
 		return nil, errors.New(fmt.Sprint("Failed to create/migrate tables: ", err))
@@ -148,6 +176,13 @@
 	return result.Error
 }
 
+func (database *Database) AddAction(a Action) error {
+	result := database.Clauses(clause.OnConflict{
+		UpdateAll: true,
+	}).Create(&a)
+	return result.Error
+}
+
 func (database *Database) AddToStats(s Stats) error {
 	matches, err := database.queryMatches(s.TeamNumber)
 	if err != nil {
@@ -176,6 +211,28 @@
 	return result.Error
 }
 
+func (database *Database) AddToStats2023(s Stats2023) error {
+	matches, err := database.QueryMatchesString(s.TeamNumber)
+	if err != nil {
+		return err
+	}
+	foundMatch := false
+	for _, match := range matches {
+		if match.MatchNumber == s.MatchNumber {
+			foundMatch = true
+			break
+		}
+	}
+	if !foundMatch {
+		return errors.New(fmt.Sprint(
+			"Failed to find team ", s.TeamNumber,
+			" in match ", s.MatchNumber, " in the schedule."))
+	}
+
+	result := database.Create(&s)
+	return result.Error
+}
+
 func (database *Database) AddOrUpdateRankings(r Ranking) error {
 	result := database.Clauses(clause.OnConflict{
 		UpdateAll: true,
@@ -207,6 +264,12 @@
 	return shifts, result.Error
 }
 
+func (database *Database) ReturnActions() ([]Action, error) {
+	var actions []Action
+	result := database.Find(&actions)
+	return actions, result.Error
+}
+
 // Packs the stats. This really just consists of taking the individual auto
 // ball booleans and turning them into an array. The individual booleans are
 // cleared so that they don't affect struct comparisons.
@@ -249,6 +312,14 @@
 	return matches, result.Error
 }
 
+func (database *Database) QueryMatchesString(teamNumber_ string) ([]Match, error) {
+	var matches []Match
+	result := database.
+		Where("r1 = $1 OR r2 = $1 OR r3 = $1 OR b1 = $1 OR b2 = $1 OR b3 = $1", teamNumber_).
+		Find(&matches)
+	return matches, result.Error
+}
+
 func (database *Database) QueryAllShifts(matchNumber_ int) ([]Shift, error) {
 	var shifts []Shift
 	result := database.Where("match_number = ?", matchNumber_).Find(&shifts)
@@ -265,6 +336,13 @@
 	return stats, result.Error
 }
 
+func (database *Database) QueryActions(teamNumber_ int) ([]Action, error) {
+	var actions []Action
+	result := database.
+		Where("team_number = ?", teamNumber_).Find(&actions)
+	return actions, result.Error
+}
+
 func (database *Database) QueryNotes(TeamNumber int32) ([]string, error) {
 	var rawNotes []NotesData
 	result := database.Where("team_number = ?", TeamNumber).Find(&rawNotes)
diff --git a/scouting/db/db_test.go b/scouting/db/db_test.go
index 47a0a90..9e85651 100644
--- a/scouting/db/db_test.go
+++ b/scouting/db/db_test.go
@@ -623,6 +623,54 @@
 	}
 }
 
+func TestReturnActionsDB(t *testing.T) {
+	fixture := createDatabase(t)
+	defer fixture.TearDown()
+	correct := []Action{
+		Action{
+			TeamNumber: "1235", MatchNumber: 94, SetNumber: 1, CompLevel: "quals",
+			CompletedAction: []byte(""), TimeStamp: 0000, CollectedBy: "",
+		},
+		Action{
+			TeamNumber: "1236", MatchNumber: 94, SetNumber: 1, CompLevel: "quals",
+			CompletedAction: []byte(""), TimeStamp: 0321, CollectedBy: "",
+		},
+		Action{
+			TeamNumber: "1237", MatchNumber: 94, SetNumber: 1, CompLevel: "quals",
+			CompletedAction: []byte(""), TimeStamp: 0222, CollectedBy: "",
+		},
+		Action{
+			TeamNumber: "1238", MatchNumber: 94, SetNumber: 1, CompLevel: "quals",
+			CompletedAction: []byte(""), TimeStamp: 0110, CollectedBy: "",
+		},
+		Action{
+			TeamNumber: "1239", MatchNumber: 94, SetNumber: 1, CompLevel: "quals",
+			CompletedAction: []byte(""), TimeStamp: 0004, CollectedBy: "",
+		},
+		Action{
+			TeamNumber: "1233", MatchNumber: 94, SetNumber: 1, CompLevel: "quals",
+			CompletedAction: []byte(""), TimeStamp: 0004, CollectedBy: "",
+		},
+	}
+
+	err := fixture.db.AddToMatch(Match{
+		MatchNumber: 94, SetNumber: 1, CompLevel: "quals",
+		R1: 1235, R2: 1236, R3: 1237, B1: 1238, B2: 1239, B3: 1233})
+	check(t, err, "Failed to add match")
+
+	for i := 0; i < len(correct); i++ {
+		err = fixture.db.AddAction(correct[i])
+		check(t, err, fmt.Sprint("Failed to add to actions ", i))
+	}
+
+	got, err := fixture.db.ReturnActions()
+	check(t, err, "Failed ReturnActions()")
+
+	if !reflect.DeepEqual(correct, got) {
+		t.Errorf("Got %#v,\nbut expected %#v.", got, correct)
+	}
+}
+
 func TestRankingsDbUpdate(t *testing.T) {
 	fixture := createDatabase(t)
 	defer fixture.TearDown()
diff --git a/scouting/webserver/requests/BUILD b/scouting/webserver/requests/BUILD
index 8cc59a9..9eb207d 100644
--- a/scouting/webserver/requests/BUILD
+++ b/scouting/webserver/requests/BUILD
@@ -24,6 +24,8 @@
         "//scouting/webserver/requests/messages:request_notes_for_team_response_go_fbs",
         "//scouting/webserver/requests/messages:request_shift_schedule_go_fbs",
         "//scouting/webserver/requests/messages:request_shift_schedule_response_go_fbs",
+        "//scouting/webserver/requests/messages:submit_actions_go_fbs",
+        "//scouting/webserver/requests/messages:submit_actions_response_go_fbs",
         "//scouting/webserver/requests/messages:submit_data_scouting_go_fbs",
         "//scouting/webserver/requests/messages:submit_data_scouting_response_go_fbs",
         "//scouting/webserver/requests/messages:submit_driver_ranking_go_fbs",
diff --git a/scouting/webserver/requests/messages/BUILD b/scouting/webserver/requests/messages/BUILD
index 57b7ae3..2e118d5 100644
--- a/scouting/webserver/requests/messages/BUILD
+++ b/scouting/webserver/requests/messages/BUILD
@@ -25,6 +25,8 @@
     "submit_shift_schedule_response",
     "submit_driver_ranking",
     "submit_driver_ranking_response",
+    "submit_actions",
+    "submit_actions_response",
 )
 
 filegroup(
diff --git a/scouting/webserver/requests/messages/request_data_scouting_response.fbs b/scouting/webserver/requests/messages/request_data_scouting_response.fbs
index 071a848..6048210 100644
--- a/scouting/webserver/requests/messages/request_data_scouting_response.fbs
+++ b/scouting/webserver/requests/messages/request_data_scouting_response.fbs
@@ -49,4 +49,4 @@
     stats_list:[Stats] (id:0);
 }
 
-root_type RequestDataScoutingResponse;
+root_type RequestDataScoutingResponse;
\ No newline at end of file
diff --git a/scouting/webserver/requests/messages/submit_actions.fbs b/scouting/webserver/requests/messages/submit_actions.fbs
new file mode 100644
index 0000000..9d9efa4
--- /dev/null
+++ b/scouting/webserver/requests/messages/submit_actions.fbs
@@ -0,0 +1,53 @@
+namespace scouting.webserver.requests;
+
+table StartMatchAction {
+    position:int (id:0);
+}
+
+enum ObjectType: short {
+    kCube,
+    kCone
+}
+
+enum ScoreLevel: short {
+    kLow,
+    kMiddle,
+    kHigh
+}
+
+table PickupObjectAction {
+    object_type:ObjectType (id:0);
+    auto:bool (id:1);
+}
+
+table PlaceObjectAction {
+    object_type:ObjectType (id:0);
+    score_level:ScoreLevel (id:1);
+    auto:bool (id:2);
+}
+
+table RobotDeathAction {
+    robot_on:bool (id:0);
+}
+
+table EndMatchAction {
+}
+
+union ActionType {
+    StartMatchAction,
+    PickupObjectAction,
+    PlaceObjectAction,
+    RobotDeathAction,
+    EndMatchAction
+}
+
+table Action {
+    timestamp:int (id:0);
+    action_taken:ActionType (id:2);
+}
+
+table SubmitActions {
+    actions_list:[Action] (id:0);
+}
+
+root_type SubmitActions;
\ No newline at end of file
diff --git a/scouting/webserver/requests/messages/submit_actions_response.fbs b/scouting/webserver/requests/messages/submit_actions_response.fbs
new file mode 100644
index 0000000..4079914
--- /dev/null
+++ b/scouting/webserver/requests/messages/submit_actions_response.fbs
@@ -0,0 +1,7 @@
+namespace scouting.webserver.requests;
+
+table SubmitActionsResponse {
+    // empty response
+}
+
+root_type SubmitActionsResponse;
\ No newline at end of file
diff --git a/scouting/webserver/requests/requests.go b/scouting/webserver/requests/requests.go
index 76a26de..99b5459 100644
--- a/scouting/webserver/requests/requests.go
+++ b/scouting/webserver/requests/requests.go
@@ -27,6 +27,8 @@
 	"github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/request_notes_for_team_response"
 	"github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/request_shift_schedule"
 	"github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/request_shift_schedule_response"
+	"github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/submit_actions"
+	"github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/submit_actions_response"
 	"github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/submit_data_scouting"
 	"github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/submit_data_scouting_response"
 	"github.com/frc971/971-Robot-Code/scouting/webserver/requests/messages/submit_driver_ranking"
@@ -61,6 +63,8 @@
 type SubmitShiftScheduleResponseT = submit_shift_schedule_response.SubmitShiftScheduleResponseT
 type SubmitDriverRanking = submit_driver_ranking.SubmitDriverRanking
 type SubmitDriverRankingResponseT = submit_driver_ranking_response.SubmitDriverRankingResponseT
+type SubmitActions = submit_actions.SubmitActions
+type SubmitActionsResponseT = submit_actions_response.SubmitActionsResponseT
 
 // The interface we expect the database abstraction to conform to.
 // We use an interface here because it makes unit testing easier.
diff --git a/y2019/control_loops/drivetrain/localizer.h b/y2019/control_loops/drivetrain/localizer.h
index 879cd0f..c55ccc9 100644
--- a/y2019/control_loops/drivetrain/localizer.h
+++ b/y2019/control_loops/drivetrain/localizer.h
@@ -4,9 +4,9 @@
 #include <cmath>
 #include <memory>
 
-#include "frc971/control_loops/pose.h"
 #include "frc971/control_loops/drivetrain/camera.h"
 #include "frc971/control_loops/drivetrain/hybrid_ekf.h"
+#include "frc971/control_loops/pose.h"
 
 namespace y2019 {
 namespace control_loops {
@@ -42,7 +42,9 @@
           &dt_config,
       Pose *robot_pose)
       : ::frc971::control_loops::drivetrain::HybridEkf<Scalar>(dt_config),
-        robot_pose_(robot_pose) {}
+        robot_pose_(robot_pose),
+        h_queue_(this),
+        make_h_queue_(this) {}
 
   // Performs a kalman filter correction with a single camera frame, consisting
   // of up to max_targets_per_frame targets and taken at time t.
@@ -79,26 +81,92 @@
     // As such, we need to store the EKF functions that the remaining targets
     // will need in arrays:
     ::aos::SizedArray<::std::function<Output(const State &, const Input &)>,
-                      max_targets_per_frame> h_functions;
+                      max_targets_per_frame>
+        h_functions;
     ::aos::SizedArray<::std::function<Eigen::Matrix<Scalar, kNOutputs,
                                                     kNStates>(const State &)>,
-                      max_targets_per_frame> dhdx_functions;
-    HybridEkf::Correct(
+                      max_targets_per_frame>
+        dhdx_functions;
+    make_h_queue_.CorrectKnownHBuilder(
         z, nullptr,
-        ::std::bind(&TypedLocalizer::MakeH, this, camera, targets, &h_functions,
-                    &dhdx_functions, ::std::placeholders::_1,
-                    ::std::placeholders::_2, ::std::placeholders::_3,
-                    ::std::placeholders::_4),
-        {}, {}, R, t);
+        ExpectedObservationBuilder(this, camera, targets, &h_functions,
+                                   &dhdx_functions),
+        R, t);
     // Fetch cache:
     for (size_t ii = 1; ii < targets.size(); ++ii) {
       TargetViewToMatrices(targets[ii], &z, &R);
-      HybridEkf::Correct(z, nullptr, {}, h_functions[ii], dhdx_functions[ii], R,
-                         t);
+      h_queue_.CorrectKnownH(
+          z, nullptr,
+          ExpectedObservationFunctor(h_functions[ii], dhdx_functions[ii]), R,
+          t);
     }
   }
 
  private:
+  class ExpectedObservationFunctor
+      : public HybridEkf::ExpectedObservationFunctor {
+   public:
+    ExpectedObservationFunctor(
+        ::std::function<Output(const State &, const Input &)> h,
+        ::std::function<
+            Eigen::Matrix<Scalar, kNOutputs, kNStates>(const State &)>
+            dhdx)
+        : h_(h), dhdx_(dhdx) {}
+
+    Output H(const State &state, const Input &input) final {
+      return h_(state, input);
+    }
+
+    virtual Eigen::Matrix<Scalar, kNOutputs, kNStates> DHDX(
+        const State &state) final {
+      return dhdx_(state);
+    }
+
+   private:
+    ::std::function<Output(const State &, const Input &)> h_;
+    ::std::function<Eigen::Matrix<Scalar, kNOutputs, kNStates>(const State &)>
+        dhdx_;
+  };
+  class ExpectedObservationBuilder
+      : public HybridEkf::ExpectedObservationBuilder {
+   public:
+    ExpectedObservationBuilder(
+        TypedLocalizer *localizer, const Camera &camera,
+        const ::aos::SizedArray<TargetView, max_targets_per_frame>
+            &target_views,
+        ::aos::SizedArray<::std::function<Output(const State &, const Input &)>,
+                          max_targets_per_frame> *h_functions,
+        ::aos::SizedArray<::std::function<Eigen::Matrix<
+                              Scalar, kNOutputs, kNStates>(const State &)>,
+                          max_targets_per_frame> *dhdx_functions)
+        : localizer_(localizer),
+          camera_(camera),
+          target_views_(target_views),
+          h_functions_(h_functions),
+          dhdx_functions_(dhdx_functions) {}
+
+    virtual ExpectedObservationFunctor *MakeExpectedObservations(
+        const State &state, const StateSquare &P) {
+      ::std::function<Output(const State &, const Input &)> h;
+      ::std::function<Eigen::Matrix<Scalar, kNOutputs, kNStates>(const State &)>
+          dhdx;
+      localizer_->MakeH(camera_, target_views_, h_functions_, dhdx_functions_,
+                        state, P, &h, &dhdx);
+      functor_.emplace(h, dhdx);
+      return &functor_.value();
+    }
+
+   private:
+    TypedLocalizer *localizer_;
+    const Camera &camera_;
+    const ::aos::SizedArray<TargetView, max_targets_per_frame> &target_views_;
+    ::aos::SizedArray<::std::function<Output(const State &, const Input &)>,
+                      max_targets_per_frame> *h_functions_;
+    ::aos::SizedArray<::std::function<Eigen::Matrix<Scalar, kNOutputs,
+                                                    kNStates>(const State &)>,
+                      max_targets_per_frame> *dhdx_functions_;
+    std::optional<ExpectedObservationFunctor> functor_;
+  };
   // The threshold to use for completely rejecting potentially bad target
   // matches.
   // TODO(james): Tune
@@ -159,8 +227,8 @@
                         max_targets_per_frame> *dhdx_functions,
       const State &X_hat, const StateSquare &P,
       ::std::function<Output(const State &, const Input &)> *h,
-      ::std::function<
-          Eigen::Matrix<Scalar, kNOutputs, kNStates>(const State &)> *dhdx) {
+      ::std::function<Eigen::Matrix<Scalar, kNOutputs, kNStates>(const State &)>
+          *dhdx) {
     // Because we need to match camera targets ("views") to actual field
     // targets, and because we want to take advantage of the correlations
     // between the targets (i.e., if we see two targets in the image, they
@@ -226,7 +294,8 @@
     // as the scores matrix.
     ::std::array<::std::array<Eigen::Matrix<Scalar, kNOutputs, kNStates>,
                               max_targets_per_frame>,
-                 num_targets> all_H_matrices;
+                 num_targets>
+        all_H_matrices;
 
     // Iterate through and fill out the scores for each potential pairing:
     for (size_t ii = 0; ii < target_views.size(); ++ii) {
@@ -360,8 +429,8 @@
     }
   }
 
-  Eigen::Matrix<Scalar, kNOutputs, kNStates> HMatrix(
-      const Target &target, const Pose &camera_pose) {
+  Eigen::Matrix<Scalar, kNOutputs, kNStates> HMatrix(const Target &target,
+                                                     const Pose &camera_pose) {
     // To calculate dheading/d{x,y,theta}:
     // heading = arctan2(target_pos - camera_pos) - camera_theta
     Eigen::Matrix<Scalar, 3, 1> target_pos = target.pose().abs_pos();
@@ -401,8 +470,8 @@
   // the number of rows in scores/best_matches that are actually populated).
   ::std::array<int, max_targets_per_frame> MatchFrames(
       const Eigen::Matrix<Scalar, max_targets_per_frame, num_targets> &scores,
-      const Eigen::Matrix<int, max_targets_per_frame, max_targets_per_frame> &
-          best_matches,
+      const Eigen::Matrix<int, max_targets_per_frame, max_targets_per_frame>
+          &best_matches,
       int n_views) {
     ::std::array<int, max_targets_per_frame> best_set;
     best_set.fill(-1);
@@ -424,8 +493,8 @@
   // true, that means that we are done recursing.
   void MatchFrames(
       const Eigen::Matrix<Scalar, max_targets_per_frame, num_targets> &scores,
-      const Eigen::Matrix<int, max_targets_per_frame, max_targets_per_frame> &
-          best_matches,
+      const Eigen::Matrix<int, max_targets_per_frame, max_targets_per_frame>
+          &best_matches,
       const ::aos::SizedArray<bool, max_targets_per_frame> &used_views,
       const ::std::array<bool, num_targets> &used_targets,
       ::std::array<int, max_targets_per_frame> *best_set, Scalar *best_score) {
@@ -485,6 +554,15 @@
   // The pose that is used by the cameras to determine the location of the robot
   // and thus the expected view of the targets.
   Pose *robot_pose_;
+
+  typename HybridEkf::template ExpectedObservationAllocator<
+      ExpectedObservationFunctor>
+      h_queue_;
+  typename HybridEkf::template ExpectedObservationAllocator<
+      ExpectedObservationBuilder>
+      make_h_queue_;
+
+  friend class ExpectedObservationBuilder;
 };  // class TypedLocalizer
 
 }  // namespace control_loops
diff --git a/y2020/control_loops/drivetrain/localizer.cc b/y2020/control_loops/drivetrain/localizer.cc
index 505a598..8f8bf87 100644
--- a/y2020/control_loops/drivetrain/localizer.cc
+++ b/y2020/control_loops/drivetrain/localizer.cc
@@ -89,6 +89,7 @@
     : event_loop_(event_loop),
       dt_config_(dt_config),
       ekf_(dt_config),
+      observations_(&ekf_),
       clock_offset_fetcher_(
           event_loop_->MakeFetcher<aos::message_bridge::ServerStatistics>(
               "/aos")),
@@ -244,7 +245,7 @@
     rejection_reason = RejectionReason::IMAGE_FROM_FUTURE;
   }
   if (!result.has_camera_calibration()) {
-    LOG(WARNING) << "Got camera frame without calibration data.";
+    AOS_LOG(WARNING, "Got camera frame without calibration data.\n");
     ImageMatchDebug::Builder builder(*fbb);
     builder.add_camera(camera_index);
     builder.add_accepted(false);
@@ -401,11 +402,6 @@
 
     Eigen::Matrix3f R = Eigen::Matrix3f::Zero();
     R.diagonal() = noises.cwiseAbs2();
-    Eigen::Matrix<float, HybridEkf::kNOutputs, HybridEkf::kNStates> H;
-    H.setZero();
-    H(0, StateIdx::kX) = 1;
-    H(1, StateIdx::kY) = 1;
-    H(2, StateIdx::kTheta) = 1;
     VLOG(1) << "Pose implied by target: " << Z.transpose()
             << " and current pose " << x() << ", " << y() << ", " << theta()
             << " Heading/dist/skew implied by target: "
@@ -447,47 +443,11 @@
     // more convenient to write given the Correct() interface we already have.
     // Note: If we start going back to doing back-in-time rewinds, then we can't
     // get away with passing things by reference.
-    ekf_.Correct(
-        Eigen::Vector3f::Zero(), &U, {},
-        [H, H_field_target, pose_robot_target, state_at_capture, Z,
-         &correction_rejection](const State &,
-                                const Input &) -> Eigen::Vector3f {
-          // Weighting for how much to use the current robot heading estimate
-          // vs. the heading estimate from the image results. A value of 1.0
-          // completely ignores the measured heading, but will prioritize turret
-          // aiming above all else. A value of 0.0 will prioritize correcting
-          // any gyro heading drift.
-          constexpr float kImpliedWeight = 0.99;
-          const float z_yaw_diff = aos::math::NormalizeAngle(
-              state_at_capture.value()(Localizer::StateIdx::kTheta) - Z(2));
-          const float z_yaw = Z(2) + kImpliedWeight * z_yaw_diff;
-          const Eigen::Vector3f Z_implied =
-              CalculateImpliedPose(z_yaw, H_field_target, pose_robot_target);
-          const Eigen::Vector3f Z_used = Z_implied;
-          // Just in case we ever do encounter any, drop measurements if they
-          // have non-finite numbers.
-          if (!Z.allFinite()) {
-            AOS_LOG(WARNING, "Got measurement with infinites or NaNs.\n");
-            correction_rejection = RejectionReason::NONFINITE_MEASUREMENT;
-            return Eigen::Vector3f::Zero();
-          }
-          Eigen::Vector3f Zhat = H * state_at_capture.value() - Z_used;
-          // Rewrap angle difference to put it back in range. Note that this
-          // component of the error is currently ignored (see definition of H
-          // above).
-          Zhat(2) = aos::math::NormalizeAngle(Zhat(2));
-          // If the measurement implies that we are too far from the current
-          // estimate, then ignore it.
-          // Note that I am not entirely sure how much effect this actually has,
-          // because I primarily introduced it to make sure that any grossly
-          // invalid measurements get thrown out.
-          if (Zhat.squaredNorm() > std::pow(10.0, 2)) {
-            correction_rejection = RejectionReason::CORRECTION_TOO_LARGE;
-            return Eigen::Vector3f::Zero();
-          }
-          return Zhat;
-        },
-        [H](const State &) { return H; }, R, now);
+    observations_.CorrectKnownH(
+        Eigen::Vector3f::Zero(), &U,
+        Corrector(H_field_target, pose_robot_target, state_at_capture.value(),
+                  Z, &correction_rejection),
+        R, now);
     if (correction_rejection) {
       builder.add_accepted(false);
       builder.add_rejection_reason(*correction_rejection);
@@ -502,6 +462,43 @@
   return debug_offsets;
 }
 
+Localizer::Output Localizer::Corrector::H(const State &, const Input &) {
+  // Weighting for how much to use the current robot heading estimate
+  // vs. the heading estimate from the image results. A value of 1.0
+  // completely ignores the measured heading, but will prioritize turret
+  // aiming above all else. A value of 0.0 will prioritize correcting
+  // any gyro heading drift.
+  constexpr float kImpliedWeight = 0.99;
+  const float z_yaw_diff = aos::math::NormalizeAngle(
+      state_at_capture_(Localizer::StateIdx::kTheta) - Z_(2));
+  const float z_yaw = Z_(2) + kImpliedWeight * z_yaw_diff;
+  const Eigen::Vector3f Z_implied =
+      CalculateImpliedPose(z_yaw, H_field_target_, pose_robot_target_);
+  const Eigen::Vector3f Z_used = Z_implied;
+  // Just in case we ever do encounter any, drop measurements if they
+  // have non-finite numbers.
+  if (!Z_.allFinite()) {
+    AOS_LOG(WARNING, "Got measurement with infinites or NaNs.\n");
+    *correction_rejection_ = RejectionReason::NONFINITE_MEASUREMENT;
+    return Eigen::Vector3f::Zero();
+  }
+  Eigen::Vector3f Zhat = H_ * state_at_capture_ - Z_used;
+  // Rewrap angle difference to put it back in range. Note that this
+  // component of the error is currently ignored (see definition of H
+  // above).
+  Zhat(2) = aos::math::NormalizeAngle(Zhat(2));
+  // If the measurement implies that we are too far from the current
+  // estimate, then ignore it.
+  // Note that I am not entirely sure how much effect this actually has,
+  // because I primarily introduced it to make sure that any grossly
+  // invalid measurements get thrown out.
+  if (Zhat.squaredNorm() > std::pow(10.0, 2)) {
+    *correction_rejection_ = RejectionReason::CORRECTION_TOO_LARGE;
+    return Eigen::Vector3f::Zero();
+  }
+  return Zhat;
+}
+
 }  // namespace drivetrain
 }  // namespace control_loops
 }  // namespace y2020
diff --git a/y2020/control_loops/drivetrain/localizer.h b/y2020/control_loops/drivetrain/localizer.h
index 5458797..de57091 100644
--- a/y2020/control_loops/drivetrain/localizer.h
+++ b/y2020/control_loops/drivetrain/localizer.h
@@ -9,8 +9,8 @@
 #include "aos/network/message_bridge_server_generated.h"
 #include "frc971/control_loops/drivetrain/hybrid_ekf.h"
 #include "frc971/control_loops/drivetrain/localizer.h"
-#include "y2020/control_loops/superstructure/superstructure_status_generated.h"
 #include "y2020/control_loops/drivetrain/localizer_debug_generated.h"
+#include "y2020/control_loops/superstructure/superstructure_status_generated.h"
 #include "y2020/vision/sift/sift_generated.h"
 
 namespace y2020 {
@@ -95,6 +95,37 @@
     std::array<int, kNumRejectionReasons> rejection_counts;
   };
 
+  class Corrector : public HybridEkf::ExpectedObservationFunctor {
+   public:
+    Corrector(const Eigen::Matrix<float, 4, 4> &H_field_target,
+              const Pose &pose_robot_target, const State &state_at_capture,
+              const Eigen::Vector3f &Z,
+              std::optional<RejectionReason> *correction_rejection)
+        : H_field_target_(H_field_target),
+          pose_robot_target_(pose_robot_target),
+          state_at_capture_(state_at_capture),
+          Z_(Z),
+          correction_rejection_(correction_rejection) {
+      H_.setZero();
+      H_(0, StateIdx::kX) = 1;
+      H_(1, StateIdx::kY) = 1;
+      H_(2, StateIdx::kTheta) = 1;
+    }
+    Output H(const State &, const Input &) final;
+    Eigen::Matrix<float, HybridEkf::kNOutputs, HybridEkf::kNStates> DHDX(
+        const State &) final {
+      return H_;
+    }
+
+   private:
+    Eigen::Matrix<float, HybridEkf::kNOutputs, HybridEkf::kNStates> H_;
+    const Eigen::Matrix<float, 4, 4> H_field_target_;
+    Pose pose_robot_target_;
+    const State state_at_capture_;
+    const Eigen::Vector3f &Z_;
+    std::optional<RejectionReason> *correction_rejection_;
+  };
+
   // Processes new image data from the given pi and updates the EKF.
   aos::SizedArray<flatbuffers::Offset<ImageMatchDebug>, 5> HandleImageMatch(
       size_t camera_index, std::string_view pi,
@@ -113,6 +144,7 @@
   aos::EventLoop *const event_loop_;
   const frc971::control_loops::drivetrain::DrivetrainConfig<double> dt_config_;
   HybridEkf ekf_;
+  HybridEkf::ExpectedObservationAllocator<Corrector> observations_;
 
   std::vector<aos::Fetcher<frc971::vision::sift::ImageMatchResult>>
       image_fetchers_;
diff --git a/y2020/control_loops/drivetrain/localizer_test.cc b/y2020/control_loops/drivetrain/localizer_test.cc
index 9e9e7dd..d280523 100644
--- a/y2020/control_loops/drivetrain/localizer_test.cc
+++ b/y2020/control_loops/drivetrain/localizer_test.cc
@@ -15,6 +15,7 @@
 
 DEFINE_string(output_file, "",
               "If set, logs all channels to the provided logfile.");
+DECLARE_bool(die_on_malloc);
 
 // This file tests that the full 2020 localizer behaves sanely.
 
@@ -146,6 +147,7 @@
     CHECK_EQ(aos::configuration::GetNodeIndex(configuration(), pi1_), 1);
     set_team_id(frc971::control_loops::testing::kTeamNumber);
     set_battery_voltage(12.0);
+    FLAGS_die_on_malloc = true;
 
     if (!FLAGS_output_file.empty()) {
       logger_event_loop_ = MakeEventLoop("logger", roborio_);
diff --git a/y2020/control_loops/superstructure/turret/aiming.cc b/y2020/control_loops/superstructure/turret/aiming.cc
index 4976efa..0b2c5f3 100644
--- a/y2020/control_loops/superstructure/turret/aiming.cc
+++ b/y2020/control_loops/superstructure/turret/aiming.cc
@@ -9,9 +9,9 @@
 namespace turret {
 
 using frc971::control_loops::Pose;
-using frc971::control_loops::aiming::TurretGoal;
-using frc971::control_loops::aiming::ShotConfig;
 using frc971::control_loops::aiming::RobotState;
+using frc971::control_loops::aiming::ShotConfig;
+using frc971::control_loops::aiming::TurretGoal;
 
 // Shooting-on-the-fly concept:
 // The current way that we manage shooting-on-the fly endeavors to be reasonably
@@ -129,7 +129,9 @@
   return target;
 }
 
-Aimer::Aimer() : goal_(MakePrefilledGoal()) {}
+Aimer::Aimer()
+    : goal_(MakePrefilledGoal()),
+      Tlr_to_la_(drivetrain::GetDrivetrainConfig().Tlr_to_la()) {}
 
 void Aimer::Update(const Status *status, aos::Alliance alliance,
                    WrapMode wrap_mode, ShotMode shot_mode) {
@@ -145,9 +147,8 @@
   // robot. All of this would be helped by just doing this work in the Localizer
   // itself.
   const Eigen::Vector2d linear_angular =
-      drivetrain::GetDrivetrainConfig().Tlr_to_la() *
-      Eigen::Vector2d(status->localizer()->left_velocity(),
-                      status->localizer()->right_velocity());
+      Tlr_to_la_ * Eigen::Vector2d(status->localizer()->left_velocity(),
+                                   status->localizer()->right_velocity());
   const double xdot = linear_angular(0) * std::cos(status->theta());
   const double ydot = linear_angular(0) * std::sin(status->theta());
 
diff --git a/y2020/control_loops/superstructure/turret/aiming.h b/y2020/control_loops/superstructure/turret/aiming.h
index 217085c..f38113d 100644
--- a/y2020/control_loops/superstructure/turret/aiming.h
+++ b/y2020/control_loops/superstructure/turret/aiming.h
@@ -64,6 +64,8 @@
   // Real-world distance to the target.
   double target_distance_ = 0.0;  // meters
   double inner_port_angle_ = 0.0;  // radians
+
+  Eigen::Matrix<double, 2, 2> Tlr_to_la_;
 };
 
 }  // namespace turret
diff --git a/y2020/control_loops/superstructure/turret/aiming_test.cc b/y2020/control_loops/superstructure/turret/aiming_test.cc
index a01f47d..fe71e31 100644
--- a/y2020/control_loops/superstructure/turret/aiming_test.cc
+++ b/y2020/control_loops/superstructure/turret/aiming_test.cc
@@ -12,12 +12,24 @@
 namespace turret {
 namespace testing {
 
+class TeamNumberEnvironment : public ::testing::Environment {
+ public:
+  ~TeamNumberEnvironment() override {}
+
+  // Override this to define how to set up the environment.
+  void SetUp() override { aos::network::OverrideTeamNumber(971); }
+
+  // Override this to define how to tear down the environment.
+  void TearDown() override {}
+};
+
+::testing::Environment *const team_number_env =
+    ::testing::AddGlobalTestEnvironment(new TeamNumberEnvironment);
+
 using frc971::control_loops::Pose;
 
 class AimerTest : public ::testing::Test {
  public:
-  AimerTest() { aos::network::OverrideTeamNumber(971); }
-
   typedef Aimer::Goal Goal;
   typedef Aimer::Status Status;
   struct StatusData {
diff --git a/y2022/control_loops/drivetrain/localizer.cc b/y2022/control_loops/drivetrain/localizer.cc
index 79ced2d..0aa4456 100644
--- a/y2022/control_loops/drivetrain/localizer.cc
+++ b/y2022/control_loops/drivetrain/localizer.cc
@@ -11,6 +11,7 @@
     : event_loop_(event_loop),
       dt_config_(dt_config),
       ekf_(dt_config),
+      observations_(&ekf_),
       localizer_output_fetcher_(
           event_loop_->MakeFetcher<frc971::controls::LocalizerOutput>(
               "/localizer")),
@@ -48,7 +49,7 @@
       joystick_state_fetcher_->autonomous()) {
     // TODO(james): This is an inelegant way to avoid having the localizer mess
     // up splines. Do better.
-    //return;
+    // return;
   }
   if (localizer_output_fetcher_.Fetch()) {
     clock_offset_fetcher_.Fetch();
@@ -89,11 +90,6 @@
       }
     }
 
-    Eigen::Matrix<float, HybridEkf::kNOutputs, HybridEkf::kNStates> H;
-    H.setZero();
-    H(0, StateIdx::kX) = 1;
-    H(1, StateIdx::kY) = 1;
-    H(2, StateIdx::kTheta) = 1;
     const Eigen::Vector3f Z{
         static_cast<float>(localizer_output_fetcher_->x()),
         static_cast<float>(localizer_output_fetcher_->y()),
@@ -101,15 +97,8 @@
     Eigen::Matrix3f R = Eigen::Matrix3f::Zero();
     R.diagonal() << 0.01, 0.01, 1e-4;
     const Input U_correct = ekf_.MostRecentInput();
-    ekf_.Correct(
-        Eigen::Vector3f::Zero(), &U_correct, {},
-        [H, state_at_capture, Z](const State &,
-                                 const Input &) -> Eigen::Vector3f {
-          Eigen::Vector3f error = H * state_at_capture.value() - Z;
-          error(2) = aos::math::NormalizeAngle(error(2));
-          return error;
-        },
-        [H](const State &) { return H; }, R, now);
+    observations_.CorrectKnownH(Eigen::Vector3f::Zero(), &U_correct,
+                                Corrector(state_at_capture.value(), Z), R, now);
   }
 }
 
diff --git a/y2022/control_loops/drivetrain/localizer.h b/y2022/control_loops/drivetrain/localizer.h
index 0d2673b..77b29eb 100644
--- a/y2022/control_loops/drivetrain/localizer.h
+++ b/y2022/control_loops/drivetrain/localizer.h
@@ -4,11 +4,11 @@
 #include <string_view>
 
 #include "aos/events/event_loop.h"
+#include "aos/network/message_bridge_server_generated.h"
 #include "frc971/control_loops/drivetrain/hybrid_ekf.h"
 #include "frc971/control_loops/drivetrain/localizer.h"
-#include "y2022/localizer/localizer_output_generated.h"
-#include "aos/network/message_bridge_server_generated.h"
 #include "frc971/input/joystick_state_generated.h"
+#include "y2022/localizer/localizer_output_generated.h"
 
 namespace y2022 {
 namespace control_loops {
@@ -63,9 +63,34 @@
   }
 
  private:
+  class Corrector : public HybridEkf::ExpectedObservationFunctor {
+   public:
+    Corrector(const State &state_at_capture, const Eigen::Vector3f &Z)
+        : state_at_capture_(state_at_capture), Z_(Z) {
+      H_.setZero();
+      H_(0, StateIdx::kX) = 1;
+      H_(1, StateIdx::kY) = 1;
+      H_(2, StateIdx::kTheta) = 1;
+    }
+    Output H(const State &, const Input &) final {
+      Eigen::Vector3f error = H_ * state_at_capture_ - Z_;
+      error(2) = aos::math::NormalizeAngle(error(2));
+      return error;
+    }
+    Eigen::Matrix<float, HybridEkf::kNOutputs, HybridEkf::kNStates> DHDX(
+        const State &) final {
+      return H_;
+    }
+
+   private:
+    Eigen::Matrix<float, HybridEkf::kNOutputs, HybridEkf::kNStates> H_;
+    State state_at_capture_;
+    Eigen::Vector3f Z_;
+  };
   aos::EventLoop *const event_loop_;
   const frc971::control_loops::drivetrain::DrivetrainConfig<double> dt_config_;
   HybridEkf ekf_;
+  HybridEkf::ExpectedObservationAllocator<Corrector> observations_;
 
   aos::Fetcher<frc971::controls::LocalizerOutput> localizer_output_fetcher_;
   aos::Fetcher<aos::JoystickState> joystick_state_fetcher_;
diff --git a/y2022/control_loops/drivetrain/localizer_test.cc b/y2022/control_loops/drivetrain/localizer_test.cc
index 1e33826..77f3988 100644
--- a/y2022/control_loops/drivetrain/localizer_test.cc
+++ b/y2022/control_loops/drivetrain/localizer_test.cc
@@ -10,12 +10,13 @@
 #include "frc971/control_loops/drivetrain/drivetrain.h"
 #include "frc971/control_loops/drivetrain/drivetrain_test_lib.h"
 #include "frc971/control_loops/team_number_test_environment.h"
-#include "y2022/localizer/localizer_output_generated.h"
 #include "gtest/gtest.h"
 #include "y2022/control_loops/drivetrain/drivetrain_base.h"
+#include "y2022/localizer/localizer_output_generated.h"
 
 DEFINE_string(output_folder, "",
               "If set, logs all channels to the provided logfile.");
+DECLARE_bool(die_on_malloc);
 
 namespace y2022 {
 namespace control_loops {
@@ -31,7 +32,7 @@
   DrivetrainConfig<double> config = GetDrivetrainConfig();
   return config;
 }
-}
+}  // namespace
 
 namespace chrono = std::chrono;
 using aos::monotonic_clock;
@@ -74,6 +75,7 @@
         drivetrain_plant_(drivetrain_plant_event_loop_.get(),
                           drivetrain_plant_imu_event_loop_.get(), dt_config_,
                           std::chrono::microseconds(500)) {
+    FLAGS_die_on_malloc = true;
     set_team_id(frc971::control_loops::testing::kTeamNumber);
     set_battery_voltage(12.0);
 
@@ -95,6 +97,7 @@
           output_builder.add_x(drivetrain_plant_.state()(0));
           output_builder.add_y(drivetrain_plant_.state()(1));
           output_builder.add_theta(drivetrain_plant_.state()(2));
+          builder.CheckOk(builder.Send(output_builder.Finish()));
         })
         ->Setup(imu_test_event_loop_->monotonic_now(),
                 std::chrono::milliseconds(5));
diff --git a/y2022/vision/calibrate_extrinsics.cc b/y2022/vision/calibrate_extrinsics.cc
index b5005fe..04b24ea 100644
--- a/y2022/vision/calibrate_extrinsics.cc
+++ b/y2022/vision/calibrate_extrinsics.cc
@@ -2,6 +2,7 @@
 #include "Eigen/Geometry"
 #include "absl/strings/str_format.h"
 #include "aos/events/logging/log_reader.h"
+#include "aos/events/logging/log_writer.h"
 #include "aos/init.h"
 #include "aos/network/team_number.h"
 #include "aos/time/time.h"
@@ -21,6 +22,8 @@
 DEFINE_string(target_type, "charuco",
               "Type of target: aruco|charuco|charuco_diamond");
 DEFINE_string(image_channel, "/camera", "Channel to listen for images on");
+DEFINE_string(output_logs, "/tmp/calibration/",
+              "Output folder for visualization logs.");
 
 namespace frc971 {
 namespace vision {
@@ -33,11 +36,24 @@
 
 void Main(int argc, char **argv) {
   CalibrationData data;
+  std::optional<uint16_t> pi_number = aos::network::ParsePiNumber(FLAGS_pi);
+  CHECK(pi_number);
+  const std::string pi_name = absl::StrCat("pi", *pi_number);
+  LOG(INFO) << "Pi " << *pi_number;
+  aos::FlatbufferDetachedBuffer<aos::Configuration> config = [argc, argv,
+                                                              pi_name]() {
+    aos::logger::LogReader reader(
+        aos::logger::SortParts(aos::logger::FindLogs(argc, argv)));
+    return CalibrationFoxgloveVisualizer::AddVisualizationChannels(
+        reader.logged_configuration(),
+        aos::configuration::GetNode(reader.logged_configuration(), pi_name));
+  }();
 
   {
     // Now, accumulate all the data into the data object.
     aos::logger::LogReader reader(
-        aos::logger::SortParts(aos::logger::FindLogs(argc, argv)));
+        aos::logger::SortParts(aos::logger::FindLogs(argc, argv)),
+        &config.message());
 
     aos::SimulatedEventLoopFactory factory(reader.configuration());
     reader.Register(&factory);
@@ -50,11 +66,8 @@
     const aos::Node *const roborio_node =
         aos::configuration::GetNode(factory.configuration(), "roborio");
 
-    std::optional<uint16_t> pi_number = aos::network::ParsePiNumber(FLAGS_pi);
-    CHECK(pi_number);
-    LOG(INFO) << "Pi " << *pi_number;
-    const aos::Node *const pi_node = aos::configuration::GetNode(
-        factory.configuration(), absl::StrCat("pi", *pi_number));
+    const aos::Node *const pi_node =
+        aos::configuration::GetNode(factory.configuration(), pi_name);
 
     LOG(INFO) << "imu " << aos::FlatbufferToJson(imu_node);
     LOG(INFO) << "roboRIO " << aos::FlatbufferToJson(roborio_node);
@@ -67,6 +80,11 @@
     std::unique_ptr<aos::EventLoop> pi_event_loop =
         factory.MakeEventLoop("calibration", pi_node);
 
+    std::unique_ptr<aos::EventLoop> logger_loop =
+        factory.MakeEventLoop("logger", pi_node);
+    aos::logger::Logger logger(logger_loop.get());
+    logger.StartLoggingOnRun(FLAGS_output_logs);
+
     TargetType target_type = TargetType::kCharuco;
     if (FLAGS_target_type == "aruco") {
       target_type = TargetType::kAruco;
diff --git a/y2023/control_loops/python/BUILD b/y2023/control_loops/python/BUILD
index b024676..9b1746a 100644
--- a/y2023/control_loops/python/BUILD
+++ b/y2023/control_loops/python/BUILD
@@ -31,6 +31,25 @@
     ],
 )
 
+py_binary(
+    name = "graph_edit",
+    srcs = [
+        "graph_edit.py",
+        "graph_paths.py",
+        "graph_tools.py",
+    ],
+    legacy_create_init = False,
+    target_compatible_with = ["@platforms//cpu:x86_64"],
+    deps = [
+        ":python_init",
+        "//frc971/control_loops/python:basic_window",
+        "//frc971/control_loops/python:color",
+        "@pip//numpy",
+        "@pip//pygobject",
+        "@pip//shapely",
+    ],
+)
+
 py_library(
     name = "polydrivetrain_lib",
     srcs = [
diff --git a/y2023/control_loops/python/graph_edit.py b/y2023/control_loops/python/graph_edit.py
new file mode 100644
index 0000000..39cd814
--- /dev/null
+++ b/y2023/control_loops/python/graph_edit.py
@@ -0,0 +1,475 @@
+#!/usr/bin/python3
+
+from __future__ import print_function
+import os
+from frc971.control_loops.python import basic_window
+from frc971.control_loops.python.color import Color, palette
+import random
+import gi
+import numpy
+
+gi.require_version('Gtk', '3.0')
+from gi.repository import Gdk, Gtk
+import cairo
+from graph_tools import XYSegment, AngleSegment, to_theta, to_xy, alpha_blend, draw_lines
+from graph_tools import back_to_xy_loop, subdivide_theta, to_theta_loop, px
+from graph_tools import l1, l2, joint_center
+import graph_paths
+
+from frc971.control_loops.python.basic_window import quit_main_loop, set_color
+
+import shapely
+from shapely.geometry import Polygon
+
+
+def draw_px_cross(cr, length_px):
+    """Draws a cross with fixed dimensions in pixel space."""
+    with px(cr):
+        x, y = cr.get_current_point()
+        cr.move_to(x, y - length_px)
+        cr.line_to(x, y + length_px)
+        cr.stroke()
+
+        cr.move_to(x - length_px, y)
+        cr.line_to(x + length_px, y)
+        cr.stroke()
+
+
+def angle_dist_sqr(a1, a2):
+    """Distance between two points in angle space."""
+    return (a1[0] - a2[0])**2 + (a1[1] - a2[1])**2
+
+
+# Find the highest y position that intersects the vertical line defined by x.
+def inter_y(x):
+    return numpy.sqrt((l2 + l1)**2 -
+                      (x - joint_center[0])**2) + joint_center[1]
+
+
+# This is the x position where the inner (hyperextension) circle intersects the horizontal line
+derr = numpy.sqrt((l1 - l2)**2 - (joint_center[1] - 0.3048)**2)
+
+
+# Define min and max l1 angles based on vertical constraints.
+def get_angle(boundary):
+    h = numpy.sqrt((l1)**2 - (boundary - joint_center[0])**2) + joint_center[1]
+    return numpy.arctan2(h, boundary - joint_center[0])
+
+
+# left hand side lines
+lines1 = [
+    (-0.826135, inter_y(-0.826135)),
+    (-0.826135, 0.1397),
+    (-23.025 * 0.0254, 0.1397),
+    (-23.025 * 0.0254, 0.3048),
+    (joint_center[0] - derr, 0.3048),
+]
+
+# right hand side lines
+lines2 = [(joint_center[0] + derr, 0.3048), (0.422275, 0.3048),
+          (0.422275, 0.1397), (0.826135, 0.1397),
+          (0.826135, inter_y(0.826135))]
+
+t1_min = get_angle((32.525 - 4.0) * 0.0254)
+t2_min = -7.0 / 4.0 * numpy.pi
+
+t1_max = get_angle((-32.525 + 4.0) * 0.0254)
+t2_max = numpy.pi * 3.0 / 4.0
+
+
+# Rotate a rasterized loop such that it aligns to when the parameters loop
+def rotate_to_jump_point(points):
+    last_pt = points[0]
+    for pt_i in range(1, len(points)):
+        pt = points[pt_i]
+        delta = last_pt[1] - pt[1]
+        if abs(delta) > numpy.pi:
+            return points[pt_i:] + points[:pt_i]
+        last_pt = pt
+    return points
+
+
+# shift points vertically by dy.
+def y_shift(points, dy):
+    return [(x, y + dy) for x, y in points]
+
+
+lines1_theta_part = rotate_to_jump_point(to_theta_loop(lines1, 0))
+lines2_theta_part = rotate_to_jump_point(to_theta_loop(lines2))
+
+# Some hacks here to make a single polygon by shifting to get an extra copy of the contraints.
+lines1_theta = y_shift(lines1_theta_part, -numpy.pi * 2) + lines1_theta_part + \
+    y_shift(lines1_theta_part, numpy.pi * 2)
+lines2_theta = y_shift(lines2_theta_part, numpy.pi * 2) + lines2_theta_part + \
+    y_shift(lines2_theta_part, -numpy.pi * 2)
+
+lines_theta = lines1_theta + lines2_theta
+
+p1 = Polygon(lines_theta)
+
+p2 = Polygon([(t1_min, t2_min), (t1_max, t2_min), (t1_max, t2_max),
+              (t1_min, t2_max)])
+
+# Fully computed theta constrints.
+lines_theta = list(p1.intersection(p2).exterior.coords)
+
+lines1_theta_back = back_to_xy_loop(lines1_theta)
+lines2_theta_back = back_to_xy_loop(lines2_theta)
+
+lines_theta_back = back_to_xy_loop(lines_theta)
+
+
+# Get the closest point to a line from a test pt.
+def get_closest(prev, cur, pt):
+    dx_ang = (cur[0] - prev[0])
+    dy_ang = (cur[1] - prev[1])
+
+    d = numpy.sqrt(dx_ang**2 + dy_ang**2)
+    if (d < 0.000001):
+        return prev, numpy.sqrt((prev[0] - pt[0])**2 + (prev[1] - pt[1])**2)
+
+    pdx = -dy_ang / d
+    pdy = dx_ang / d
+
+    dpx = pt[0] - prev[0]
+    dpy = pt[1] - prev[1]
+
+    alpha = (dx_ang * dpx + dy_ang * dpy) / d / d
+
+    if (alpha < 0):
+        return prev, numpy.sqrt((prev[0] - pt[0])**2 + (prev[1] - pt[1])**2)
+    elif (alpha > 1):
+        return cur, numpy.sqrt((cur[0] - pt[0])**2 + (cur[1] - pt[1])**2)
+    else:
+        return (alpha_blend(prev[0], cur[0], alpha), alpha_blend(prev[1], cur[1], alpha)), \
+            abs(dpx * pdx + dpy * pdy)
+
+
+def closest_segment(lines, pt):
+    c_pt, c_pt_dist = get_closest(lines[-1], lines[0], pt)
+    for i in range(1, len(lines)):
+        prev = lines[i - 1]
+        cur = lines[i]
+        c_pt_new, c_pt_new_dist = get_closest(prev, cur, pt)
+        if c_pt_new_dist < c_pt_dist:
+            c_pt = c_pt_new
+            c_pt_dist = c_pt_new_dist
+    return c_pt, c_pt_dist
+
+
+# Create a GTK+ widget on which we will draw using Cairo
+class Silly(basic_window.BaseWindow):
+
+    def __init__(self):
+        super(Silly, self).__init__()
+
+        self.window = Gtk.Window()
+        self.window.set_title("DrawingArea")
+
+        self.window.set_events(Gdk.EventMask.BUTTON_PRESS_MASK
+                               | Gdk.EventMask.BUTTON_RELEASE_MASK
+                               | Gdk.EventMask.POINTER_MOTION_MASK
+                               | Gdk.EventMask.SCROLL_MASK
+                               | Gdk.EventMask.KEY_PRESS_MASK)
+        self.method_connect("key-press-event", self.do_key_press)
+        self.method_connect("button-press-event",
+                            self._do_button_press_internal)
+        self.method_connect("configure-event", self._do_configure)
+        self.window.add(self)
+        self.window.show_all()
+
+        self.theta_version = False
+        self.reinit_extents()
+
+        self.last_pos = (numpy.pi / 2.0, 1.0)
+        self.circular_index_select = -1
+
+        # Extra stuff for drawing lines.
+        self.segments = []
+        self.prev_segment_pt = None
+        self.now_segment_pt = None
+        self.spline_edit = 0
+        self.edit_control1 = True
+
+    def do_key_press(self, event):
+        pass
+
+    def _do_button_press_internal(self, event):
+        o_x = event.x
+        o_y = event.y
+        x = event.x - self.window_shape[0] / 2
+        y = self.window_shape[1] / 2 - event.y
+        scale = self.get_current_scale()
+        event.x = x / scale + self.center[0]
+        event.y = y / scale + self.center[1]
+        self.do_button_press(event)
+        event.x = o_x
+        event.y = o_y
+
+    def _do_configure(self, event):
+        self.window_shape = (event.width, event.height)
+
+    def redraw(self):
+        if not self.needs_redraw:
+            self.needs_redraw = True
+            self.window.queue_draw()
+
+    def method_connect(self, event, cb):
+
+        def handler(obj, *args):
+            cb(*args)
+
+        self.window.connect(event, handler)
+
+    def reinit_extents(self):
+        if self.theta_version:
+            self.extents_x_min = -numpy.pi * 2
+            self.extents_x_max = numpy.pi * 2
+            self.extents_y_min = -numpy.pi * 2
+            self.extents_y_max = numpy.pi * 2
+        else:
+            self.extents_x_min = -40.0 * 0.0254
+            self.extents_x_max = 40.0 * 0.0254
+            self.extents_y_min = -4.0 * 0.0254
+            self.extents_y_max = 110.0 * 0.0254
+
+        self.init_extents(
+            (0.5 * (self.extents_x_min + self.extents_x_max), 0.5 *
+             (self.extents_y_max + self.extents_y_min)),
+            (1.0 * (self.extents_x_max - self.extents_x_min), 1.0 *
+             (self.extents_y_max - self.extents_y_min)))
+
+    # Handle the expose-event by drawing
+    def handle_draw(self, cr):
+        # use "with px(cr): blah;" to transform to pixel coordinates.
+
+        # Fill the background color of the window with grey
+        set_color(cr, palette["GREY"])
+        cr.paint()
+
+        # Draw a extents rectangle
+        set_color(cr, palette["WHITE"])
+        cr.rectangle(self.extents_x_min, self.extents_y_min,
+                     (self.extents_x_max - self.extents_x_min),
+                     self.extents_y_max - self.extents_y_min)
+        cr.fill()
+
+        if self.theta_version:
+            # Draw a filled white rectangle.
+            set_color(cr, palette["WHITE"])
+            cr.rectangle(-numpy.pi, -numpy.pi, numpy.pi * 2.0, numpy.pi * 2.0)
+            cr.fill()
+
+            set_color(cr, palette["BLUE"])
+            for i in range(-6, 6):
+                cr.move_to(-40, -40 + i * numpy.pi)
+                cr.line_to(40, 40 + i * numpy.pi)
+            with px(cr):
+                cr.stroke()
+
+            set_color(cr, Color(0.5, 0.5, 1.0))
+            draw_lines(cr, lines_theta)
+
+            set_color(cr, Color(0.0, 1.0, 0.2))
+            cr.move_to(self.last_pos[0], self.last_pos[1])
+            draw_px_cross(cr, 5)
+
+            c_pt, dist = closest_segment(lines_theta, self.last_pos)
+            print("dist:", dist, c_pt, self.last_pos)
+            set_color(cr, palette["CYAN"])
+            cr.move_to(c_pt[0], c_pt[1])
+            draw_px_cross(cr, 5)
+        else:
+            # Draw a filled white rectangle.
+            set_color(cr, palette["WHITE"])
+            cr.rectangle(-2.0, -2.0, 4.0, 4.0)
+            cr.fill()
+
+            set_color(cr, palette["BLUE"])
+            cr.arc(joint_center[0], joint_center[1], l2 + l1, 0,
+                   2.0 * numpy.pi)
+            with px(cr):
+                cr.stroke()
+            cr.arc(joint_center[0], joint_center[1], l1 - l2, 0,
+                   2.0 * numpy.pi)
+            with px(cr):
+                cr.stroke()
+
+            set_color(cr, Color(0.5, 1.0, 1.0))
+            draw_lines(cr, lines1)
+            draw_lines(cr, lines2)
+
+            def get_circular_index(pt):
+                theta1, theta2 = pt
+                circular_index = int(numpy.floor((theta2 - theta1) / numpy.pi))
+                return circular_index
+
+            set_color(cr, palette["BLUE"])
+            lines = subdivide_theta(lines_theta)
+            o_circular_index = circular_index = get_circular_index(lines[0])
+            p_xy = to_xy(lines[0][0], lines[0][1])
+            if circular_index == self.circular_index_select:
+                cr.move_to(p_xy[0] + circular_index * 0, p_xy[1])
+            for pt in lines[1:]:
+                p_xy = to_xy(pt[0], pt[1])
+                circular_index = get_circular_index(pt)
+                if o_circular_index == self.circular_index_select:
+                    cr.line_to(p_xy[0] + o_circular_index * 0, p_xy[1])
+                if circular_index != o_circular_index:
+                    o_circular_index = circular_index
+                    with px(cr):
+                        cr.stroke()
+                    if circular_index == self.circular_index_select:
+                        cr.move_to(p_xy[0] + circular_index * 0, p_xy[1])
+
+            with px(cr):
+                cr.stroke()
+
+            theta1, theta2 = to_theta(self.last_pos,
+                                      self.circular_index_select)
+            x, y = joint_center[0], joint_center[1]
+            cr.move_to(x, y)
+
+            x += numpy.cos(theta1) * l1
+            y += numpy.sin(theta1) * l1
+            cr.line_to(x, y)
+            x += numpy.cos(theta2) * l2
+            y += numpy.sin(theta2) * l2
+            cr.line_to(x, y)
+            with px(cr):
+                cr.stroke()
+
+            cr.move_to(self.last_pos[0], self.last_pos[1])
+            set_color(cr, Color(0.0, 1.0, 0.2))
+            draw_px_cross(cr, 20)
+
+        set_color(cr, Color(0.0, 0.5, 1.0))
+        for segment in self.segments:
+            color = [0, random.random(), 1]
+            random.shuffle(color)
+            set_color(cr, Color(color[0], color[1], color[2]))
+            segment.DrawTo(cr, self.theta_version)
+            with px(cr):
+                cr.stroke()
+
+        set_color(cr, Color(0.0, 1.0, 0.5))
+        segment = self.current_seg()
+        if segment:
+            print(segment)
+            segment.DrawTo(cr, self.theta_version)
+            with px(cr):
+                cr.stroke()
+
+    def cur_pt_in_theta(self):
+        if self.theta_version: return self.last_pos
+        return to_theta(self.last_pos, self.circular_index_select)
+
+    # Current segment based on which mode the drawing system is in.
+    def current_seg(self):
+        if self.prev_segment_pt and self.now_segment_pt:
+            if self.theta_version:
+                return AngleSegment(self.prev_segment_pt, self.now_segment_pt)
+            else:
+                return XYSegment(self.prev_segment_pt, self.now_segment_pt)
+
+    def do_key_press(self, event):
+        keyval = Gdk.keyval_to_lower(event.keyval)
+        print("Gdk.KEY_" + Gdk.keyval_name(keyval))
+        if keyval == Gdk.KEY_q:
+            print("Found q key and exiting.")
+            quit_main_loop()
+        elif keyval == Gdk.KEY_c:
+            # Increment which arm solution we render
+            self.circular_index_select += 1
+            print(self.circular_index_select)
+        elif keyval == Gdk.KEY_v:
+            # Decrement which arm solution we render
+            self.circular_index_select -= 1
+            print(self.circular_index_select)
+        elif keyval == Gdk.KEY_w:
+            # Add this segment to the segment list.
+            segment = self.current_seg()
+            if segment: self.segments.append(segment)
+            self.prev_segment_pt = self.now_segment_pt
+
+        elif keyval == Gdk.KEY_r:
+            self.prev_segment_pt = self.now_segment_pt
+
+        elif keyval == Gdk.KEY_p:
+            # Print out the segments.
+            print(repr(self.segments))
+        elif keyval == Gdk.KEY_g:
+            # Generate theta points.
+            if self.segments:
+                print(repr(self.segments[0].ToThetaPoints()))
+        elif keyval == Gdk.KEY_e:
+            best_pt = self.now_segment_pt
+            best_dist = 1e10
+            for segment in self.segments:
+                d = angle_dist_sqr(segment.start, self.now_segment_pt)
+                if (d < best_dist):
+                    best_pt = segment.start
+                    best_dist = d
+                d = angle_dist_sqr(segment.end, self.now_segment_pt)
+                if (d < best_dist):
+                    best_pt = segment.end
+                    best_dist = d
+            self.now_segment_pt = best_pt
+
+        elif keyval == Gdk.KEY_t:
+            # Toggle between theta and xy renderings
+            if self.theta_version:
+                theta1, theta2 = self.last_pos
+                data = to_xy(theta1, theta2)
+                self.circular_index_select = int(
+                    numpy.floor((theta2 - theta1) / numpy.pi))
+                self.last_pos = (data[0], data[1])
+            else:
+                self.last_pos = self.cur_pt_in_theta()
+
+            self.theta_version = not self.theta_version
+            self.reinit_extents()
+
+        elif keyval == Gdk.KEY_z:
+            self.edit_control1 = not self.edit_control1
+            if self.edit_control1:
+                self.now_segment_pt = self.segments[0].control1
+            else:
+                self.now_segment_pt = self.segments[0].control2
+            if not self.theta_version:
+                data = to_xy(self.now_segment_pt[0], self.now_segment_pt[1])
+                self.last_pos = (data[0], data[1])
+            else:
+                self.last_pos = self.now_segment_pt
+
+            print("self.last_pos: ", self.last_pos, " ci: ",
+                  self.circular_index_select)
+
+        self.redraw()
+
+    def do_button_press(self, event):
+        self.last_pos = (event.x, event.y)
+        self.now_segment_pt = self.cur_pt_in_theta()
+
+        if self.edit_control1:
+            self.segments[0].control1 = self.now_segment_pt
+        else:
+            self.segments[0].control2 = self.now_segment_pt
+
+        print('Clicked at theta: %s' % (repr(self.now_segment_pt, )))
+        if not self.theta_version:
+            print('Clicked at xy, circular index: (%f, %f, %f)' %
+                  (self.last_pos[0], self.last_pos[1],
+                   self.circular_index_select))
+
+        print('c1: numpy.array([%f, %f])' %
+              (self.segments[0].control1[0], self.segments[0].control1[1]))
+        print('c2: numpy.array([%f, %f])' %
+              (self.segments[0].control2[0], self.segments[0].control2[1]))
+
+        self.redraw()
+
+
+silly = Silly()
+silly.segments = graph_paths.segments
+basic_window.RunApp()
diff --git a/y2023/control_loops/python/graph_paths.py b/y2023/control_loops/python/graph_paths.py
new file mode 100644
index 0000000..da0ad4f
--- /dev/null
+++ b/y2023/control_loops/python/graph_paths.py
@@ -0,0 +1,26 @@
+import numpy
+
+from graph_tools import *
+
+neutral = to_theta_with_circular_index(-0.2, 0.33, circular_index=-1)
+zero = to_theta_with_circular_index(0.0, 0.0, circular_index=-1)
+
+neutral_to_cone_1 = to_theta_with_circular_index(0.0, 0.7, circular_index=-1)
+neutral_to_cone_2 = to_theta_with_circular_index(0.2, 0.5, circular_index=-1)
+cone_pos = to_theta_with_circular_index(1.0, 0.4, circular_index=-1)
+
+neutral_to_cone_perch_pos_1 = to_theta_with_circular_index(0.4,
+                                                           1.0,
+                                                           circular_index=-1)
+neutral_to_cone_perch_pos_2 = to_theta_with_circular_index(0.7,
+                                                           1.5,
+                                                           circular_index=-1)
+cone_perch_pos = to_theta_with_circular_index(1.0, 2.0, circular_index=-1)
+
+segments = [
+    ThetaSplineSegment(neutral, neutral_to_cone_1, neutral_to_cone_2, cone_pos,
+                       "NeutralToCone"),
+    ThetaSplineSegment(neutral, neutral_to_cone_perch_pos_1,
+                       neutral_to_cone_perch_pos_2, cone_perch_pos,
+                       "NeutralToPerchedCone"),
+]
diff --git a/y2023/control_loops/python/graph_tools.py b/y2023/control_loops/python/graph_tools.py
new file mode 100644
index 0000000..3ddfb37
--- /dev/null
+++ b/y2023/control_loops/python/graph_tools.py
@@ -0,0 +1,533 @@
+import numpy
+import cairo
+
+from frc971.control_loops.python.basic_window import OverrideMatrix, identity
+
+# joint_center in x-y space.
+joint_center = (-0.299, 0.299)
+
+# Joint distances (l1 = "proximal", l2 = "distal")
+l1 = 46.25 * 0.0254
+l2 = 43.75 * 0.0254
+
+max_dist = 0.01
+max_dist_theta = numpy.pi / 64
+xy_end_circle_size = 0.01
+theta_end_circle_size = 0.07
+
+
+def px(cr):
+    return OverrideMatrix(cr, identity)
+
+
+# Convert from x-y coordinates to theta coordinates.
+# orientation is a bool. This orientation is circular_index mod 2.
+# where circular_index is the circular index, or the position in the
+# "hyperextension" zones. "cross_point" allows shifting the place where
+# it rounds the result so that it draws nicer (no other functional differences).
+def to_theta(pt, circular_index, cross_point=-numpy.pi):
+    orient = (circular_index % 2) == 0
+    x = pt[0]
+    y = pt[1]
+    x -= joint_center[0]
+    y -= joint_center[1]
+    l3 = numpy.hypot(x, y)
+    t3 = numpy.arctan2(y, x)
+    theta1 = numpy.arccos((l1**2 + l3**2 - l2**2) / (2 * l1 * l3))
+
+    if orient:
+        theta1 = -theta1
+    theta1 += t3
+    theta1 = (theta1 - cross_point) % (2 * numpy.pi) + cross_point
+    theta2 = numpy.arctan2(y - l1 * numpy.sin(theta1),
+                           x - l1 * numpy.cos(theta1))
+    return numpy.array((theta1, theta2))
+
+
+# Simple trig to go back from theta1, theta2 to x-y
+def to_xy(theta1, theta2):
+    x = numpy.cos(theta1) * l1 + numpy.cos(theta2) * l2 + joint_center[0]
+    y = numpy.sin(theta1) * l1 + numpy.sin(theta2) * l2 + joint_center[1]
+    orient = ((theta2 - theta1) % (2.0 * numpy.pi)) < numpy.pi
+    return (x, y, orient)
+
+
+def get_circular_index(theta):
+    return int(numpy.floor((theta[1] - theta[0]) / numpy.pi))
+
+
+def get_xy(theta):
+    theta1 = theta[0]
+    theta2 = theta[1]
+    x = numpy.cos(theta1) * l1 + numpy.cos(theta2) * l2 + joint_center[0]
+    y = numpy.sin(theta1) * l1 + numpy.sin(theta2) * l2 + joint_center[1]
+    return numpy.array((x, y))
+
+
+# Subdivide in theta space.
+def subdivide_theta(lines):
+    out = []
+    last_pt = lines[0]
+    out.append(last_pt)
+    for n_pt in lines[1:]:
+        for pt in subdivide(last_pt, n_pt, max_dist_theta):
+            out.append(pt)
+        last_pt = n_pt
+
+    return out
+
+
+# subdivide in xy space.
+def subdivide_xy(lines, max_dist=max_dist):
+    out = []
+    last_pt = lines[0]
+    out.append(last_pt)
+    for n_pt in lines[1:]:
+        for pt in subdivide(last_pt, n_pt, max_dist):
+            out.append(pt)
+        last_pt = n_pt
+
+    return out
+
+
+def to_theta_with_ci(pt, circular_index):
+    return to_theta_with_circular_index(pt[0], pt[1], circular_index)
+
+
+# to_theta, but distinguishes between
+def to_theta_with_circular_index(x, y, circular_index):
+    theta1, theta2 = to_theta((x, y), circular_index)
+    n_circular_index = int(numpy.floor((theta2 - theta1) / numpy.pi))
+    theta2 = theta2 + ((circular_index - n_circular_index)) * numpy.pi
+    return numpy.array((theta1, theta2))
+
+
+# alpha is in [0, 1] and is the weight to merge a and b.
+def alpha_blend(a, b, alpha):
+    """Blends a and b.
+
+    Args:
+      alpha: double, Ratio.  Needs to be in [0, 1] and is the weight to blend a
+          and b.
+    """
+    return b * alpha + (1.0 - alpha) * a
+
+
+def normalize(v):
+    """Normalize a vector while handling 0 length vectors."""
+    norm = numpy.linalg.norm(v)
+    if norm == 0:
+        return v
+    return v / norm
+
+
+# CI is circular index and allows selecting between all the stats that map
+# to the same x-y state (by giving them an integer index).
+# This will compute approximate first and second derivatives with respect
+# to path length.
+def to_theta_with_circular_index_and_derivs(x, y, dx, dy,
+                                            circular_index_select):
+    a = to_theta_with_circular_index(x, y, circular_index_select)
+    b = to_theta_with_circular_index(x + dx * 0.0001, y + dy * 0.0001,
+                                     circular_index_select)
+    c = to_theta_with_circular_index(x - dx * 0.0001, y - dy * 0.0001,
+                                     circular_index_select)
+    d1 = normalize(b - a)
+    d2 = normalize(c - a)
+    accel = (d1 + d2) / numpy.linalg.norm(a - b)
+    return (a[0], a[1], d1[0], d1[1], accel[0], accel[1])
+
+
+def to_theta_with_ci_and_derivs(p_prev, p, p_next, c_i_select):
+    a = to_theta(p, c_i_select)
+    b = to_theta(p_next, c_i_select)
+    c = to_theta(p_prev, c_i_select)
+    d1 = normalize(b - a)
+    d2 = normalize(c - a)
+    accel = (d1 + d2) / numpy.linalg.norm(a - b)
+    return (a[0], a[1], d1[0], d1[1], accel[0], accel[1])
+
+
+# Generic subdivision algorithm.
+def subdivide(p1, p2, max_dist):
+    dx = p2[0] - p1[0]
+    dy = p2[1] - p1[1]
+    dist = numpy.sqrt(dx**2 + dy**2)
+    n = int(numpy.ceil(dist / max_dist))
+    return [(alpha_blend(p1[0], p2[0],
+                         float(i) / n), alpha_blend(p1[1], p2[1],
+                                                    float(i) / n))
+            for i in range(1, n + 1)]
+
+
+# convert from an xy space loop into a theta loop.
+# All segements are expected go from one "hyper-extension" boundary
+# to another, thus we must go backwards over the "loop" to get a loop in
+# x-y space.
+def to_theta_loop(lines, cross_point=-numpy.pi):
+    out = []
+    last_pt = lines[0]
+    for n_pt in lines[1:]:
+        for pt in subdivide(last_pt, n_pt, max_dist):
+            out.append(to_theta(pt, 0, cross_point))
+        last_pt = n_pt
+    for n_pt in reversed(lines[:-1]):
+        for pt in subdivide(last_pt, n_pt, max_dist):
+            out.append(to_theta(pt, 1, cross_point))
+        last_pt = n_pt
+    return out
+
+
+# Convert a loop (list of line segments) into
+# The name incorrectly suggests that it is cyclic.
+def back_to_xy_loop(lines):
+    out = []
+    last_pt = lines[0]
+    out.append(to_xy(last_pt[0], last_pt[1]))
+    for n_pt in lines[1:]:
+        for pt in subdivide(last_pt, n_pt, max_dist_theta):
+            out.append(to_xy(pt[0], pt[1]))
+        last_pt = n_pt
+
+    return out
+
+
+def spline_eval(start, control1, control2, end, alpha):
+    a = alpha_blend(start, control1, alpha)
+    b = alpha_blend(control1, control2, alpha)
+    c = alpha_blend(control2, end, alpha)
+    return alpha_blend(alpha_blend(a, b, alpha), alpha_blend(b, c, alpha),
+                       alpha)
+
+
+def subdivide_spline(start, control1, control2, end):
+    # TODO: pick N based on spline parameters? or otherwise change it to be more evenly spaced?
+    n = 100
+    for i in range(0, n + 1):
+        yield i / float(n)
+
+
+def get_derivs(t_prev, t, t_next):
+    c, a, b = t_prev, t, t_next
+    d1 = normalize(b - a)
+    d2 = normalize(c - a)
+    accel = (d1 + d2) / numpy.linalg.norm(a - b)
+    return (a[0], a[1], d1[0], d1[1], accel[0], accel[1])
+
+
+# Draw lines to cr + stroke.
+def draw_lines(cr, lines):
+    cr.move_to(lines[0][0], lines[0][1])
+    for pt in lines[1:]:
+        cr.line_to(pt[0], pt[1])
+    with px(cr):
+        cr.stroke()
+
+
+# Segment in angle space.
+class AngleSegment:
+
+    def __init__(self, start, end, name=None, alpha_unitizer=None, vmax=None):
+        """Creates an angle segment.
+
+        Args:
+          start: (double, double),  The start of the segment in theta1, theta2
+              coordinates in radians
+          end: (double, double),  The end of the segment in theta1, theta2
+              coordinates in radians
+        """
+        self.start = start
+        self.end = end
+        self.name = name
+        self.alpha_unitizer = alpha_unitizer
+        self.vmax = vmax
+
+    def __repr__(self):
+        return "AngleSegment(%s, %s)" % (repr(self.start), repr(self.end))
+
+    def DrawTo(self, cr, theta_version):
+        if theta_version:
+            cr.move_to(self.start[0], self.start[1] + theta_end_circle_size)
+            cr.arc(self.start[0], self.start[1], theta_end_circle_size, 0,
+                   2.0 * numpy.pi)
+            cr.move_to(self.end[0], self.end[1] + theta_end_circle_size)
+            cr.arc(self.end[0], self.end[1], theta_end_circle_size, 0,
+                   2.0 * numpy.pi)
+            cr.move_to(self.start[0], self.start[1])
+            cr.line_to(self.end[0], self.end[1])
+        else:
+            start_xy = to_xy(self.start[0], self.start[1])
+            end_xy = to_xy(self.end[0], self.end[1])
+            draw_lines(cr, back_to_xy_loop([self.start, self.end]))
+            cr.move_to(start_xy[0] + xy_end_circle_size, start_xy[1])
+            cr.arc(start_xy[0], start_xy[1], xy_end_circle_size, 0,
+                   2.0 * numpy.pi)
+            cr.move_to(end_xy[0] + xy_end_circle_size, end_xy[1])
+            cr.arc(end_xy[0], end_xy[1], xy_end_circle_size, 0, 2.0 * numpy.pi)
+
+    def ToThetaPoints(self):
+        dx = self.end[0] - self.start[0]
+        dy = self.end[1] - self.start[1]
+        mag = numpy.hypot(dx, dy)
+        dx /= mag
+        dy /= mag
+
+        return [(self.start[0], self.start[1], dx, dy, 0.0, 0.0),
+                (self.end[0], self.end[1], dx, dy, 0.0, 0.0)]
+
+
+class XYSegment:
+    """Straight line in XY space."""
+
+    def __init__(self, start, end, name=None, alpha_unitizer=None, vmax=None):
+        """Creates an XY segment.
+
+        Args:
+          start: (double, double),  The start of the segment in theta1, theta2
+              coordinates in radians
+          end: (double, double),  The end of the segment in theta1, theta2
+              coordinates in radians
+        """
+        self.start = start
+        self.end = end
+        self.name = name
+        self.alpha_unitizer = alpha_unitizer
+        self.vmax = vmax
+
+    def __repr__(self):
+        return "XYSegment(%s, %s)" % (repr(self.start), repr(self.end))
+
+    def DrawTo(self, cr, theta_version):
+        if theta_version:
+            theta1, theta2 = self.start
+            circular_index_select = int(
+                numpy.floor((self.start[1] - self.start[0]) / numpy.pi))
+            start = get_xy(self.start)
+            end = get_xy(self.end)
+
+            ln = [(start[0], start[1]), (end[0], end[1])]
+            draw_lines(cr, [
+                to_theta_with_circular_index(x, y, circular_index_select)
+                for x, y in subdivide_xy(ln)
+            ])
+            cr.move_to(self.start[0] + theta_end_circle_size, self.start[1])
+            cr.arc(self.start[0], self.start[1], theta_end_circle_size, 0,
+                   2.0 * numpy.pi)
+            cr.move_to(self.end[0] + theta_end_circle_size, self.end[1])
+            cr.arc(self.end[0], self.end[1], theta_end_circle_size, 0,
+                   2.0 * numpy.pi)
+        else:
+            start = get_xy(self.start)
+            end = get_xy(self.end)
+            cr.move_to(start[0], start[1])
+            cr.line_to(end[0], end[1])
+            cr.move_to(start[0] + xy_end_circle_size, start[1])
+            cr.arc(start[0], start[1], xy_end_circle_size, 0, 2.0 * numpy.pi)
+            cr.move_to(end[0] + xy_end_circle_size, end[1])
+            cr.arc(end[0], end[1], xy_end_circle_size, 0, 2.0 * numpy.pi)
+
+    def ToThetaPoints(self):
+        """ Converts to points in theta space via to_theta_with_circular_index_and_derivs"""
+        theta1, theta2 = self.start
+        circular_index_select = int(
+            numpy.floor((self.start[1] - self.start[0]) / numpy.pi))
+        start = get_xy(self.start)
+        end = get_xy(self.end)
+
+        ln = [(start[0], start[1]), (end[0], end[1])]
+
+        dx = end[0] - start[0]
+        dy = end[1] - start[1]
+        mag = numpy.hypot(dx, dy)
+        dx /= mag
+        dy /= mag
+
+        return [
+            to_theta_with_circular_index_and_derivs(x, y, dx, dy,
+                                                    circular_index_select)
+            for x, y in subdivide_xy(ln, 0.01)
+        ]
+
+
+class SplineSegment:
+
+    def __init__(self,
+                 start,
+                 control1,
+                 control2,
+                 end,
+                 name=None,
+                 alpha_unitizer=None,
+                 vmax=None):
+        self.start = start
+        self.control1 = control1
+        self.control2 = control2
+        self.end = end
+        self.name = name
+        self.alpha_unitizer = alpha_unitizer
+        self.vmax = vmax
+
+    def __repr__(self):
+        return "SplineSegment(%s, %s, %s, %s)" % (repr(
+            self.start), repr(self.control1), repr(
+                self.control2), repr(self.end))
+
+    def DrawTo(self, cr, theta_version):
+        if theta_version:
+            c_i_select = get_circular_index(self.start)
+            start = get_xy(self.start)
+            control1 = get_xy(self.control1)
+            control2 = get_xy(self.control2)
+            end = get_xy(self.end)
+
+            draw_lines(cr, [
+                to_theta(spline_eval(start, control1, control2, end, alpha),
+                         c_i_select)
+                for alpha in subdivide_spline(start, control1, control2, end)
+            ])
+            cr.move_to(self.start[0] + theta_end_circle_size, self.start[1])
+            cr.arc(self.start[0], self.start[1], theta_end_circle_size, 0,
+                   2.0 * numpy.pi)
+            cr.move_to(self.end[0] + theta_end_circle_size, self.end[1])
+            cr.arc(self.end[0], self.end[1], theta_end_circle_size, 0,
+                   2.0 * numpy.pi)
+        else:
+            start = get_xy(self.start)
+            control1 = get_xy(self.control1)
+            control2 = get_xy(self.control2)
+            end = get_xy(self.end)
+
+            draw_lines(cr, [
+                spline_eval(start, control1, control2, end, alpha)
+                for alpha in subdivide_spline(start, control1, control2, end)
+            ])
+
+            cr.move_to(start[0] + xy_end_circle_size, start[1])
+            cr.arc(start[0], start[1], xy_end_circle_size, 0, 2.0 * numpy.pi)
+            cr.move_to(end[0] + xy_end_circle_size, end[1])
+            cr.arc(end[0], end[1], xy_end_circle_size, 0, 2.0 * numpy.pi)
+
+    def ToThetaPoints(self):
+        t1, t2 = self.start
+        c_i_select = get_circular_index(self.start)
+        start = get_xy(self.start)
+        control1 = get_xy(self.control1)
+        control2 = get_xy(self.control2)
+        end = get_xy(self.end)
+
+        return [
+            to_theta_with_ci_and_derivs(
+                spline_eval(start, control1, control2, end, alpha - 0.00001),
+                spline_eval(start, control1, control2, end, alpha),
+                spline_eval(start, control1, control2, end, alpha + 0.00001),
+                c_i_select)
+            for alpha in subdivide_spline(start, control1, control2, end)
+        ]
+
+
+class ThetaSplineSegment:
+
+    def __init__(self,
+                 start,
+                 control1,
+                 control2,
+                 end,
+                 name=None,
+                 alpha_unitizer=None,
+                 vmax=None):
+        self.start = start
+        self.control1 = control1
+        self.control2 = control2
+        self.end = end
+        self.name = name
+        self.alpha_unitizer = alpha_unitizer
+        self.vmax = vmax
+
+    def __repr__(self):
+        return "ThetaSplineSegment(%s, %s, &s, %s)" % (repr(
+            self.start), repr(self.control1), repr(
+                self.control2), repr(self.end))
+
+    def DrawTo(self, cr, theta_version):
+        if (theta_version):
+            draw_lines(cr, [
+                spline_eval(self.start, self.control1, self.control2, self.end,
+                            alpha)
+                for alpha in subdivide_spline(self.start, self.control1,
+                                              self.control2, self.end)
+            ])
+        else:
+            start = get_xy(self.start)
+            end = get_xy(self.end)
+
+            draw_lines(cr, [
+                get_xy(
+                    spline_eval(self.start, self.control1, self.control2,
+                                self.end, alpha))
+                for alpha in subdivide_spline(self.start, self.control1,
+                                              self.control2, self.end)
+            ])
+
+            cr.move_to(start[0] + xy_end_circle_size, start[1])
+            cr.arc(start[0], start[1], xy_end_circle_size, 0, 2.0 * numpy.pi)
+            cr.move_to(end[0] + xy_end_circle_size, end[1])
+            cr.arc(end[0], end[1], xy_end_circle_size, 0, 2.0 * numpy.pi)
+
+    def ToThetaPoints(self):
+        return [
+            get_derivs(
+                spline_eval(self.start, self.control1, self.control2, self.end,
+                            alpha - 0.00001),
+                spline_eval(self.start, self.control1, self.control2, self.end,
+                            alpha),
+                spline_eval(self.start, self.control1, self.control2, self.end,
+                            alpha + 0.00001))
+            for alpha in subdivide_spline(self.start, self.control1,
+                                          self.control2, self.end)
+        ]
+
+
+def expand_points(points, max_distance):
+    """Expands a list of points to be at most max_distance apart
+
+    Generates the paths to connect the new points to the closest input points,
+    and the paths connecting the points.
+
+    Args:
+      points, list of tuple of point, name, The points to start with and fill
+          in.
+      max_distance, float, The max distance between two points when expanding
+          the graph.
+
+    Return:
+      points, edges
+    """
+    result_points = [points[0]]
+    result_paths = []
+    for point, name in points[1:]:
+        previous_point = result_points[-1][0]
+        previous_point_xy = get_xy(previous_point)
+        circular_index = get_circular_index(previous_point)
+
+        point_xy = get_xy(point)
+        norm = numpy.linalg.norm(point_xy - previous_point_xy)
+        num_points = int(numpy.ceil(norm / max_distance))
+        last_iteration_point = previous_point
+        for subindex in range(1, num_points):
+            subpoint = to_theta(alpha_blend(previous_point_xy, point_xy,
+                                            float(subindex) / num_points),
+                                circular_index=circular_index)
+            result_points.append(
+                (subpoint, '%s%dof%d' % (name, subindex, num_points)))
+            result_paths.append(
+                XYSegment(last_iteration_point, subpoint, vmax=6.0))
+            if (last_iteration_point != previous_point).any():
+                result_paths.append(XYSegment(previous_point, subpoint))
+            if subindex == num_points - 1:
+                result_paths.append(XYSegment(subpoint, point, vmax=6.0))
+            else:
+                result_paths.append(XYSegment(subpoint, point))
+            last_iteration_point = subpoint
+        result_points.append((point, name))
+
+    return result_points, result_paths
diff --git a/y2023/vision/aprilrobotics.cc b/y2023/vision/aprilrobotics.cc
index d20a247..cbfd3f6 100644
--- a/y2023/vision/aprilrobotics.cc
+++ b/y2023/vision/aprilrobotics.cc
@@ -9,15 +9,19 @@
 namespace y2023 {
 namespace vision {
 
+namespace chrono = std::chrono;
+
 AprilRoboticsDetector::AprilRoboticsDetector(aos::EventLoop *event_loop,
                                              std::string_view channel_name)
     : calibration_data_(CalibrationData()),
       ftrace_(),
-      image_callback_(event_loop, channel_name,
-                      [&](cv::Mat image_color_mat,
-                          const aos::monotonic_clock::time_point eof) {
-                        HandleImage(image_color_mat, eof);
-                      }),
+      image_callback_(
+          event_loop, channel_name,
+          [&](cv::Mat image_color_mat,
+              const aos::monotonic_clock::time_point eof) {
+            HandleImage(image_color_mat, eof);
+          },
+          chrono::milliseconds(5)),
       target_map_sender_(
           event_loop->MakeSender<frc971::vision::TargetMap>("/camera")) {
   tag_family_ = tag16h5_create();
@@ -151,8 +155,8 @@
           aos::monotonic_clock::now();
 
       VLOG(1) << "Took "
-              << std::chrono::duration<double>(after_pose_estimation -
-                                               before_pose_estimation)
+              << chrono::duration<double>(after_pose_estimation -
+                                          before_pose_estimation)
                      .count()
               << " seconds for pose estimation";
     }
@@ -164,8 +168,7 @@
 
   timeprofile_display(tag_detector_->tp);
 
-  VLOG(1) << "Took "
-          << std::chrono::duration<double>(end_time - start_time).count()
+  VLOG(1) << "Took " << chrono::duration<double>(end_time - start_time).count()
           << " seconds to detect overall";
 
   return results;
diff --git a/y2023/vision/viewer.cc b/y2023/vision/viewer.cc
index 08def5b..68495b1 100644
--- a/y2023/vision/viewer.cc
+++ b/y2023/vision/viewer.cc
@@ -14,6 +14,8 @@
 DEFINE_string(capture, "",
               "If set, capture a single image and save it to this filename.");
 
+DEFINE_int32(rate, 100, "Time in milliseconds to wait between images");
+
 namespace frc971 {
 namespace vision {
 namespace {
@@ -78,7 +80,7 @@
           event_loop.Exit();
         };
       },
-      ::std::chrono::milliseconds(100));
+      ::std::chrono::milliseconds(FLAGS_rate));
 
   event_loop.Run();
 
diff --git a/y2023/y2023.json b/y2023/y2023.json
index 76f0e52..d5f9462 100644
--- a/y2023/y2023.json
+++ b/y2023/y2023.json
@@ -1,5 +1,5 @@
 {
-  "channel_storage_duration": 2000000000,
+  "channel_storage_duration": 10000000000,
   "maps": [
     {
       "match": {
diff --git a/y2023/y2023_pi_template.json b/y2023/y2023_pi_template.json
index 592aa14..cf87798 100644
--- a/y2023/y2023_pi_template.json
+++ b/y2023/y2023_pi_template.json
@@ -164,7 +164,7 @@
       "type": "frc971.vision.CameraImage",
       "source_node": "pi{{ NUM }}",
       "frequency": 40,
-      "max_size": 4200000,
+      "max_size": 1843456,
       "num_readers": 4,
       "read_method": "PIN",
       "num_senders": 18
@@ -360,6 +360,15 @@
       "nodes": [
         "pi{{ NUM }}"
       ]
+    },
+    {
+      "name": "aprilrobotics",
+      "executable_name": "aprilrobotics",
+      "args": ["--enable_ftrace"],
+      "user": "pi",
+      "nodes": [
+        "pi{{ NUM }}"
+      ]
     }
   ],
   "maps": [