diff --git a/.github/workflows/energy-hardware.yml b/.github/workflows/energy-hardware.yml
index 97efed37e..3d8e891c4 100644
--- a/.github/workflows/energy-hardware.yml
+++ b/.github/workflows/energy-hardware.yml
@@ -21,6 +21,12 @@ name: energy meters on real hardware
 # The host has no Node, so there are no JavaScript actions: the source is
 # fetched with plain git, and each workspace keeps its target directory in the
 # runner's home between runs.
+#
+# The source is the run's own commit, fetched by its hash, not the branch it was
+# pushed to. On a busy main the branch moves on while this run waits for the one
+# linux-hw runner, and the push that moved it rarely touches the paths below, so
+# no newer run of this workflow follows: a run that refused a moved branch tested
+# nothing, and none after it did either.
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -75,16 +81,15 @@ jobs:
         shell: bash
         run: |
           set -euo pipefail
-          ref="${{ github.event_name == 'pull_request' && format('refs/pull/{0}/head', github.event.pull_request.number) || github.ref }}"
           want="${{ github.event.pull_request.head.sha || github.sha }}"
           rm -rf src && mkdir src && cd src
           git init -q
-          git fetch -q --depth 1 http://100.64.224.0:3400/Transaction-Science/open-standards.git "$ref"
+          git fetch -q --depth 1 http://100.64.224.0:3400/Transaction-Science/open-standards.git "$want"
           git checkout -q FETCH_HEAD
           got="$(git rev-parse HEAD)"
-          echo "fetched $ref at $got"
+          echo "fetched ${{ github.ref }} at $got"
           if [ "$got" != "$want" ]; then
-            echo "::error::$ref is at $got, not $want: it moved after this run started, and a newer run tests it"
+            echo "::error::asked the forge for $want and was given $got"
             exit 1
           fi
 
@@ -166,16 +171,15 @@ jobs:
         shell: bash
         run: |
           set -euo pipefail
-          ref="${{ github.event_name == 'pull_request' && format('refs/pull/{0}/head', github.event.pull_request.number) || github.ref }}"
           want="${{ github.event.pull_request.head.sha || github.sha }}"
           rm -rf src && mkdir src && cd src
           git init -q
-          git fetch -q --depth 1 http://100.64.224.0:3400/Transaction-Science/open-standards.git "$ref"
+          git fetch -q --depth 1 http://100.64.224.0:3400/Transaction-Science/open-standards.git "$want"
           git checkout -q FETCH_HEAD
           got="$(git rev-parse HEAD)"
-          echo "fetched $ref at $got"
+          echo "fetched ${{ github.ref }} at $got"
           if [ "$got" != "$want" ]; then
-            echo "::error::$ref is at $got, not $want: it moved after this run started, and a newer run tests it"
+            echo "::error::asked the forge for $want and was given $got"
             exit 1
           fi