diff --git a/.github/buildomat/build-and-test.sh b/.github/buildomat/build-and-test.sh
index 5cf086b1a3..30abd02f90 100755
--- a/.github/buildomat/build-and-test.sh
+++ b/.github/buildomat/build-and-test.sh
@@ -20,9 +20,13 @@ curl -sSfL --retry 10 https://get.nexte.st/"$NEXTEST_VERSION"/"$1" | gunzip | ta
 # we can check later whether we left detritus around.
 #
 TEST_TMPDIR='/var/tmp/omicron_tmp'
-echo "tests will store output in $TEST_TMPDIR" >&2
+echo "tests will store ephemeral output in $TEST_TMPDIR" >&2
 mkdir "$TEST_TMPDIR"
 
+OUTPUT_DIR='/work'
+echo "tests will store non-ephemeral output in $OUTPUT_DIR" >&2
+mkdir -p "$OUTPUT_DIR"
+
 #
 # Set up our PATH for the test suite.
 #
@@ -50,18 +54,27 @@ ptime -m bash ./tools/install_builder_prerequisites.sh -y
 #
 banner build
 export RUSTFLAGS="-D warnings"
+export RUSTDOCFLAGS="-D warnings"
 # When running on illumos we need to pass an additional runpath that is
 # usually configured via ".cargo/config" but the `RUSTFLAGS` env variable
 # takes precedence. This path contains oxide specific libraries such as
 # libipcc.
 if [[ $target_os == "illumos" ]]; then
-	RUSTFLAGS="-D warnings -C link-arg=-R/usr/platform/oxide/lib/amd64"
+    RUSTFLAGS="$RUSTFLAGS -C link-arg=-R/usr/platform/oxide/lib/amd64"
 fi
-export RUSTDOCFLAGS="-D warnings"
-export TMPDIR=$TEST_TMPDIR
+export TMPDIR="$TEST_TMPDIR"
 export RUST_BACKTRACE=1
+# We're building once, so there's no need to incur the overhead of an incremental build.
 export CARGO_INCREMENTAL=0
-ptime -m cargo test --locked --verbose --no-run
+# This allows us to build with unstable options, which gives us access to some
+# timing information.
+#
+# If we remove "--timings=json" below, this would no longer be needed.
+export RUSTC_BOOTSTRAP=1
+
+# Build all the packages and tests, and keep track of how long each took to build.
+# We report build progress to stderr, and the "--timings=json" output goes to stdout.
+ptime -m cargo build -Z unstable-options --timings=json --workspace --tests --locked --verbose 1> "$OUTPUT_DIR/crate-build-timings.json"
 
 #
 # We apply our own timeout to ensure that we get a normal failure on timeout
diff --git a/.github/buildomat/jobs/build-and-test-helios.sh b/.github/buildomat/jobs/build-and-test-helios.sh
index 2c7a1f884d..cfcbb61475 100755
--- a/.github/buildomat/jobs/build-and-test-helios.sh
+++ b/.github/buildomat/jobs/build-and-test-helios.sh
@@ -5,6 +5,7 @@
 #: target = "helios-2.0"
 #: rust_toolchain = "1.72.1"
 #: output_rules = [
+#:	"%/work/*",
 #:	"%/var/tmp/omicron_tmp/*",
 #:	"!/var/tmp/omicron_tmp/crdb-base*",
 #:	"!/var/tmp/omicron_tmp/rustc*",
diff --git a/.github/buildomat/jobs/build-and-test-linux.sh b/.github/buildomat/jobs/build-and-test-linux.sh
index 4f4ebc1d8a..22332ce65c 100755
--- a/.github/buildomat/jobs/build-and-test-linux.sh
+++ b/.github/buildomat/jobs/build-and-test-linux.sh
@@ -5,6 +5,7 @@
 #: target = "ubuntu-22.04"
 #: rust_toolchain = "1.72.1"
 #: output_rules = [
+#:	"%/work/*",
 #:	"%/var/tmp/omicron_tmp/*",
 #:	"!/var/tmp/omicron_tmp/crdb-base*",
 #:	"!/var/tmp/omicron_tmp/rustc*",