diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..9282590
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,43 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+defaults:
+  run:
+    shell: bash
+
+env:
+  DEBIAN_FRONTEND: noninteractive
+
+jobs:
+  build:
+    name: Ubuntu ${{ matrix.ubuntu }} (${{ matrix.arch }})
+    runs-on: ${{ matrix.runner }}
+    container: ubuntu:${{ matrix.ubuntu }}
+    strategy:
+      fail-fast: false
+      matrix:
+        ubuntu: ["24.04", "26.04"]
+        arch: [amd64, arm64]
+        include:
+          - arch: amd64
+            runner: ubuntu-24.04
+          - arch: arm64
+            runner: ubuntu-24.04-arm
+    steps:
+      # Without git, actions/checkout downloads an archive, and init.sh can't check out the submodules
+      - name: Install git
+        run: apt-get update && apt-get install -y --no-install-recommends ca-certificates git
+      - uses: actions/checkout@v5
+      - name: Install dependencies
+        run: |
+          git config --global --add safe.directory '*'
+          ./init.sh
+      - name: Build
+        run: ./build.sh
+      - name: Test
+        run: ctest --test-dir build --output-on-failure --no-tests=error
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..82f6e36
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,7 @@
+[submodule "external/openocean-messages"]
+	path = external/openocean-messages
+	url = https://github.com/openocean-software/openocean-messages.git
+[submodule "external/moos-ivp"]
+	path = external/moos-ivp
+	url = https://github.com/GobySoft/moos-ivp.git
+	shallow = true
diff --git a/CMakeLists.txt b/CMakeLists.txt
index b847828..78324dd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,4 +9,9 @@ endif()
 
 set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/")
 
+# MOOS-IvP's helm libraries (IVP_BUILD_HELM_LIBS_ONLY)
+find_package(IVP CONFIG REQUIRED)
+
+include(CTest)
+
 add_subdirectory(src)
diff --git a/README.md b/README.md
index 2f1ac14..9421a49 100644
--- a/README.md
+++ b/README.md
@@ -15,14 +15,26 @@ One way to think of this project is as a generator for the equivalent of the MOO
   - bin: Binary source
     - goby: Goby middleware app
     - ros: ROS middleware node
+- external: Submodules
+  - openocean-messages: [openocean-messages](https://github.com/openocean-software/openocean-messages), for the `Navigation` and `ControlSetpoint` messages
+  - moos-ivp: [MOOS-IvP](https://github.com/GobySoft/moos-ivp), for the IvP solver and behaviors
 
 ## Building
 
 *This section was written by Claude.*
 
-The interface messages use `Navigation` and `ControlSetpoint` from [openocean-messages](https://github.com/openocean-software/openocean-messages), found with `find_package(openocean_messages)`: install it, or point CMake at its build directory:
+`init.sh` checks out the submodules and installs the Ubuntu packages needed to build them and IvPico. `build.sh` then builds, all in `build/`:
+
+- openocean-messages, into `build/external/openocean-messages`;
+- MOOS-IvP's helm libraries (`IVP_BUILD_HELM_LIBS_ONLY`, as shared libraries, without MOOS or its apps), into `build/external/moos-ivp`, installed into `build/external/install` for `find_package(IVP)`;
+- IvPico, against both.
 
 ```
-cmake -S . -B build -Dopenocean_messages_DIR=/path/to/openocean-messages/build
-cmake --build build
+./init.sh
+./build.sh
+ctest --test-dir build
 ```
+
+`build.sh` passes any arguments on to IvPico's CMake, and `BUILD_DIR` overrides the build directory.
+
+To update a submodule, check out the commit you want in it and commit the new pointer, e.g. `git -C external/openocean-messages pull origin main && git add external/openocean-messages`.
diff --git a/build.sh b/build.sh
new file mode 100755
index 0000000..bfbe048
--- /dev/null
+++ b/build.sh
@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+# Builds the dependencies from their submodules (openocean-messages, and MOOS-IvP's helm libraries),
+# then IvPico against them, all in BUILD_DIR (default build). Arguments are passed on to IvPico's
+# cmake.
+set -euo pipefail
+
+cd "$(dirname "$0")"
+for submodule in openocean-messages moos-ivp; do
+    if [ -z "$(ls -A "external/${submodule}")" ]; then
+        echo "external/${submodule} is empty: run ./init.sh first" >&2
+        exit 1
+    fi
+done
+BUILD_DIR=$(realpath -m "${BUILD_DIR:-build}")
+OPENOCEAN_BUILD_DIR=${BUILD_DIR}/external/openocean-messages
+IVP_BUILD_DIR=${BUILD_DIR}/external/moos-ivp
+# find_package(IVP) only works from an installation
+IVP_INSTALL_DIR=${BUILD_DIR}/external/install
+
+BUILD_DIR=${OPENOCEAN_BUILD_DIR} external/openocean-messages/build.sh -DBUILD_TESTING=OFF
+
+cmake -S external/moos-ivp/ivp/src -B "${IVP_BUILD_DIR}" -G Ninja \
+    -DIVP_BUILD_HELM_LIBS_ONLY=ON -DBUILD_SHARED_LIBS=ON \
+    -DIVP_LIB_DIRECTORY="${IVP_BUILD_DIR}/lib" \
+    -DIVP_INC_DIRECTORY="${IVP_BUILD_DIR}/include" \
+    -DIVP_BIN_DIRECTORY="${IVP_BUILD_DIR}/bin"
+ninja -C "${IVP_BUILD_DIR}"
+cmake --install "${IVP_BUILD_DIR}" --prefix "${IVP_INSTALL_DIR}" > /dev/null
+
+cmake -S . -B "${BUILD_DIR}" -G Ninja \
+    -Dopenocean_messages_DIR="${OPENOCEAN_BUILD_DIR}" \
+    -DIVP_DIR="${IVP_INSTALL_DIR}/lib/cmake/IVP" \
+    "$@"
+ninja -C "${BUILD_DIR}"
diff --git a/external/moos-ivp b/external/moos-ivp
new file mode 160000
index 0000000..be40e2c
--- /dev/null
+++ b/external/moos-ivp
@@ -0,0 +1 @@
+Subproject commit be40e2c7cef168be29f57a756df6a16a1c7882f1
diff --git a/external/openocean-messages b/external/openocean-messages
new file mode 160000
index 0000000..11a1328
--- /dev/null
+++ b/external/openocean-messages
@@ -0,0 +1 @@
+Subproject commit 11a132839af11befb3d858f4a4b3570d9dc013e5
diff --git a/init.sh b/init.sh
new file mode 100755
index 0000000..1821fc7
--- /dev/null
+++ b/init.sh
@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+# Checks out the submodules and installs the Ubuntu packages needed to build them and IvPico.
+#
+# Usage: init.sh
+set -euo pipefail
+
+cd "$(dirname "$0")"
+
+case "${1:-}" in
+    "") ;;
+    -h | --help)
+        sed -n '4p' "$0" | sed 's/^# //'
+        exit 0
+        ;;
+    *)
+        sed -n '4p' "$0" | sed 's/^# //' >&2
+        exit 1
+        ;;
+esac
+
+git submodule update --init --recommend-shallow
+
+SUDO=""
+if [ "$(id -u)" -ne 0 ]; then
+    SUDO=sudo
+fi
+
+# moos-ivp's helm libraries (IVP_BUILD_HELM_LIBS_ONLY) need only CMake and a compiler
+packages=(cmake ninja-build g++ git ca-certificates protobuf-compiler libprotobuf-dev)
+$SUDO apt-get update
+$SUDO env DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends "${packages[@]}"
+
+external/openocean-messages/init.sh --cxx
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 1d235e1..9489610 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,2 +1,6 @@
 add_subdirectory(lib)
 add_subdirectory(bin)
+
+if(BUILD_TESTING)
+  add_subdirectory(test)
+endif()
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
new file mode 100644
index 0000000..6631915
--- /dev/null
+++ b/src/test/CMakeLists.txt
@@ -0,0 +1,3 @@
+add_executable(check_helm_libs check_helm_libs.cpp)
+target_link_libraries(check_helm_libs PRIVATE IVP::helmivp IVP::ivpbuild IVP::ivpsolve IVP::ivpcore)
+add_test(NAME helm_libs COMMAND check_helm_libs)
diff --git a/src/test/check_helm_libs.cpp b/src/test/check_helm_libs.cpp
new file mode 100644
index 0000000..0168326
--- /dev/null
+++ b/src/test/check_helm_libs.cpp
@@ -0,0 +1,59 @@
+// Checks that IvPico can use MOOS-IvP's helm libraries (external/moos-ivp, built by build.sh):
+//
+//  1. The static behavior factory creates behaviors from lib_behaviors-marine
+//     and lib_behaviors-colregs, which loads every helm library.
+//  2. The IvP solver finds the peak of a one-function problem over course.
+//
+// Prints one line per problem and exits non-zero if there were any.
+
+#include <cmath>
+#include <iostream>
+#include <string>
+
+#include "BFactoryStatic.h"
+#include "IvPBehavior.h"
+#include "IvPDomain.h"
+#include "IvPProblem.h"
+#include "ZAIC_PEAK.h"
+
+int main()
+{
+    int errors = 0;
+
+    IvPDomain domain;
+    domain.addDomain("course", 0, 359, 360);
+    domain.addDomain("speed", 0, 4, 41);
+
+    BFactoryStatic factory;
+    factory.setDomain(domain);
+    for (const std::string type : {"BHV_Waypoint", "BHV_AvdColregsV22"})
+    {
+        IvPBehavior* behavior = factory.newBehavior(type);
+        if (!behavior)
+        {
+            std::cerr << "failed: no " << type << " from BFactoryStatic\n";
+            ++errors;
+        }
+        delete behavior;
+    }
+
+    IvPDomain course;
+    course.addDomain("course", 0, 359, 360);
+    ZAIC_PEAK zaic(course, "course");
+    zaic.setSummit(90);
+    zaic.setBaseWidth(90);
+    zaic.setValueWrap(true);
+
+    IvPProblem problem;
+    problem.setDomain(course);
+    problem.addOF(zaic.extractIvPFunction());
+    problem.solve();
+    const double result = problem.getResult("course");
+    if (std::fabs(result - 90) > 1)
+    {
+        std::cerr << "failed: solved course " << result << ", not 90\n";
+        ++errors;
+    }
+
+    return errors == 0 ? 0 : 1;
+}