diff --git a/.github/workflows/cmake-workflow.yml b/.github/workflows/cmake-workflow.yml
index a86e183..e9a0787 100644
--- a/.github/workflows/cmake-workflow.yml
+++ b/.github/workflows/cmake-workflow.yml
@@ -188,3 +188,13 @@ jobs:
           EOF
           cmake -G Ninja -S . -B build -DCAMERAD_SOURCE_DIR="$GITHUB_WORKSPACE"
           cmake --build build -j"$(nproc)"
+
+      # The reference instrument built the way an instrument repository will,
+      # so a change that breaks a consumer fails here rather than downstream
+      - name: Build the reference instrument
+        shell: bash
+        run: |
+          cmake -G Ninja -S examples/reference_instrument -B "$RUNNER_TEMP/reference" \
+                -DFETCHCONTENT_SOURCE_DIR_CAMERA_INTERFACE="$GITHUB_WORKSPACE"
+          cmake --build "$RUNNER_TEMP/reference" -j"$(nproc)"
+          test -x "$RUNNER_TEMP/reference/camerad"
diff --git a/.github/workflows/instrument-ci.yml b/.github/workflows/instrument-ci.yml
new file mode 100644
index 0000000..2257db7
--- /dev/null
+++ b/.github/workflows/instrument-ci.yml
@@ -0,0 +1,56 @@
+name: Instrument CI
+
+# Called by an instrument repository, which owns its own build but should not
+# own a copy of this. Runs in the caller's context, so checkout takes the
+# instrument, and the core arrives through its CMake fetch.
+#
+#   jobs:
+#     build:
+#       uses: CaltechOpticalObservatories/camera-interface/.github/workflows/instrument-ci.yml@main
+
+on:
+  workflow_call:
+    inputs:
+      cmake-args:
+        description: "Extra arguments for the configure step"
+        required: false
+        type: string
+        default: ""
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+
+    steps:
+      - name: Checkout the instrument
+        uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y \
+            build-essential cmake ninja-build \
+            libccfits-dev libcfitsio-dev libcurl4-openssl-dev \
+            nlohmann-json3-dev libzmq3-dev \
+            libboost-thread-dev libboost-chrono-dev
+
+      # Not packaged for common distros, so every consumer builds it
+      - name: Build and install zmqpp
+        run: |
+          git clone --depth 1 https://github.com/zeromq/zmqpp.git /tmp/zmqpp
+          cmake -S /tmp/zmqpp -B /tmp/zmqpp/build
+          cmake --build /tmp/zmqpp/build -j"$(nproc)"
+          sudo cmake --install /tmp/zmqpp/build
+          sudo ldconfig
+
+      - name: Build
+        run: |
+          cmake -G Ninja -S . -B build ${{ inputs.cmake-args }}
+          cmake --build build -j"$(nproc)"
+
+      # camerad exits 0 with no config and prints nothing, so there is nothing
+      # here to assert beyond the daemon having been produced. An instrument
+      # wanting more adds its own job against the emulator.
+      - name: Check the daemon was built
+        run: test -x build/camerad
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 58d714e..8ab9da9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -93,6 +93,10 @@ endif()
 option(CAMERAD_BUILD_TOOLS "Build the emulator, listener, socksend and shm_reader" ${PROJECT_IS_TOP_LEVEL})
 option(CAMERAD_INSTALL "Generate install rules" ${PROJECT_IS_TOP_LEVEL})
 
+# An instrument builds its own daemon from camerad_server, so the core's would
+# only collide with it
+option(CAMERAD_BUILD_DAEMON "Build the camerad executable" ${PROJECT_IS_TOP_LEVEL})
+
 add_subdirectory(${PROJECT_BASE_DIR}/utils)
 add_subdirectory(${PROJECT_BASE_DIR}/common)
 add_subdirectory(${PROJECT_BASE_DIR}/camerad)
diff --git a/camerad/CMakeLists.txt b/camerad/CMakeLists.txt
index 2837294..a9deef0 100644
--- a/camerad/CMakeLists.txt
+++ b/camerad/CMakeLists.txt
@@ -194,17 +194,14 @@ find_package(Threads)
 # ----------------------------------------------------------------------------
 # build the camera daemon
 # ----------------------------------------------------------------------------
-add_executable(camerad
+# The server and its whole link interface, so a project consuming this one
+# builds its own daemon by linking this and supplying Camera::Interface::create()
+add_library(camerad_server STATIC
   ${CAMERAD_DIR}/camerad.cpp
   ${CAMERAD_DIR}/camera_server.cpp
-  ${INSTRUMENT_REGISTRATION}
-  ${INSTRUMENT_OBJECTS}
   )
 
-# ----------------------------------------------------------------------------
-# link everything
-# ----------------------------------------------------------------------------
-target_link_libraries(camerad
+target_link_libraries(camerad_server PUBLIC
   network
   utilities
   logentry
@@ -220,6 +217,15 @@ target_link_libraries(camerad
   ${ZMQ_LIB}
   )
 
+if (CAMERAD_BUILD_DAEMON)
+  add_executable(camerad
+    ${INSTRUMENT_REGISTRATION}
+    ${INSTRUMENT_OBJECTS}
+    )
+
+  target_link_libraries(camerad camerad_server)
+endif()
+
 if (CAMERAD_INSTALL)
   install(TARGETS camerad RUNTIME DESTINATION ${CAMERAD_INSTALL_BINDIR})
 endif()
diff --git a/examples/reference_instrument/CMakeLists.txt b/examples/reference_instrument/CMakeLists.txt
new file mode 100644
index 0000000..7141fd9
--- /dev/null
+++ b/examples/reference_instrument/CMakeLists.txt
@@ -0,0 +1,33 @@
+# ----------------------------------------------------------------------------
+# @file    examples/reference_instrument/CMakeLists.txt
+# @brief   how an instrument repository consumes camerad
+#
+# Copy this into a new instrument repository as its top-level CMakeLists.txt.
+# Nothing here reaches into the core: it fetches camerad, links camerad_server,
+# and supplies Camera::Interface::create().
+# ----------------------------------------------------------------------------
+
+cmake_minimum_required(VERSION 3.24)
+
+project(reference_instrument CXX)
+
+include(FetchContent)
+
+# A consumer pins a tag here. The core's own CI points this at its working tree
+# with -DFETCHCONTENT_SOURCE_DIR_CAMERA_INTERFACE, so a change that breaks a
+# consumer fails there rather than in every instrument later.
+FetchContent_Declare(camera_interface
+  GIT_REPOSITORY https://github.com/CaltechOpticalObservatories/camera-interface
+  GIT_TAG        main
+)
+
+set(CONTROLLER archon CACHE STRING "Controller this instrument uses")
+
+FetchContent_MakeAvailable(camera_interface)
+
+add_executable(camerad
+  reference_instrument.cpp
+  reference_interface_factory.cpp
+)
+
+target_link_libraries(camerad PRIVATE camerad_server)
diff --git a/examples/reference_instrument/README.md b/examples/reference_instrument/README.md
new file mode 100644
index 0000000..bcf968f
--- /dev/null
+++ b/examples/reference_instrument/README.md
@@ -0,0 +1,21 @@
+# Reference instrument
+
+The smallest thing that builds against camerad, and the starting point for a new
+instrument repository.
+
+An instrument owns its interface class, the translation unit defining
+`Camera::Interface::create()`, its ACF and cfg, and its own `CMakeLists.txt`. It
+fetches camerad and links `camerad_server`, which carries the daemon and its
+whole link interface, so the instrument supplies only what is specific to it.
+
+```bash
+cmake -S . -B build
+cmake --build build
+```
+
+That produces a `camerad` running this instrument. Copy the four files into a
+new repository and pin `GIT_TAG` to a release of the core.
+
+The core's own CI builds this with
+`-DFETCHCONTENT_SOURCE_DIR_CAMERA_INTERFACE` pointed at its working tree, so a
+change that breaks a consumer fails there rather than in every instrument later.
diff --git a/examples/reference_instrument/reference_instrument.cpp b/examples/reference_instrument/reference_instrument.cpp
new file mode 100644
index 0000000..ba11957
--- /dev/null
+++ b/examples/reference_instrument/reference_instrument.cpp
@@ -0,0 +1,14 @@
+/**
+ * @file    reference_instrument.cpp
+ * @brief   the smallest instrument that builds against camerad
+ */
+
+#include "reference_instrument.h"
+
+namespace Camera {
+
+  void ReferenceInstrument::configure_instrument() {
+    logwrite("Camera::ReferenceInstrument::configure_instrument", "");
+  }
+
+}
diff --git a/examples/reference_instrument/reference_instrument.h b/examples/reference_instrument/reference_instrument.h
new file mode 100644
index 0000000..6d280fc
--- /dev/null
+++ b/examples/reference_instrument/reference_instrument.h
@@ -0,0 +1,17 @@
+/**
+ * @file    reference_instrument.h
+ * @brief   the smallest instrument that builds against camerad
+ */
+#pragma once
+
+#include "archon_interface.h"
+
+namespace Camera {
+
+  /// Instrument adding nothing to the Archon interface, as a starting point
+  class ReferenceInstrument : public ArchonInterface {
+    public:
+      void configure_instrument() override;
+  };
+
+}
diff --git a/examples/reference_instrument/reference_interface_factory.cpp b/examples/reference_instrument/reference_interface_factory.cpp
new file mode 100644
index 0000000..9d2eb90
--- /dev/null
+++ b/examples/reference_instrument/reference_interface_factory.cpp
@@ -0,0 +1,18 @@
+/**
+ * @file    reference_interface_factory.cpp
+ * @brief   the seam between camerad and an instrument
+ *
+ * camerad calls this to obtain its interface, so every instrument supplies one
+ * translation unit defining it.
+ */
+
+#include "reference_instrument.h"
+#include "camera_interface.h"
+
+namespace Camera {
+
+  std::unique_ptr<Interface> Interface::create() {
+    return std::make_unique<ReferenceInstrument>();
+  }
+
+}