diff --git a/.gitea/infra-pin b/.gitea/infra-pin
new file mode 100644
index 0000000..97dc92a
--- /dev/null
+++ b/.gitea/infra-pin
@@ -0,0 +1,2 @@
+# The admin/goodwe commit CI tests against. Bump: set to the full SHA of admin/goodwe master HEAD (README.md, "CI and the infra pin").
+a783602ea131d49bc0c904333c1ccb101aac02d0
diff --git a/.gitea/workflows/checks.yml b/.gitea/workflows/checks.yml
index 44709c0..56427fd 100644
--- a/.gitea/workflows/checks.yml
+++ b/.gitea/workflows/checks.yml
@@ -488,6 +488,26 @@ jobs:
           fi
           echo "OK: the \`on:\` block of the merged checks.yml carries no event filter."
 
+      # CI-12: the infra repo at the ONE pinned commit in .gitea/infra-pin (read
+      # from the merged tree), as the sibling test_freeze.py looks for. Any
+      # failure here fails the job; the tests step below refuses the stub.
+      - name: check out admin/goodwe at the pin in .gitea/infra-pin
+        env:
+          URL: ${{ github.server_url }}/admin/goodwe.git
+          TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          set -eu
+          PIN=$(grep -v '^#' "$WS/goodwe-addon/.gitea/infra-pin" | tr -d '[:space:]')
+          echo "$PIN" | grep -Eq '^[0-9a-f]{40}$' || { echo "FAIL: .gitea/infra-pin holds '$PIN', not a full 40-hex SHA."; exit 1; }
+          rm -rf "$WS/goodwe" && mkdir -p "$WS/goodwe" && cd "$WS/goodwe"
+          git init -q .
+          git remote add origin "$(echo "$URL" | sed "s#://#://x-access-token:${TOKEN}@#")"
+          git fetch -q origin "$PIN" || { echo "FAIL: could not fetch admin/goodwe at $PIN."; exit 1; }
+          git -c advice.detachedHead=false checkout -qf FETCH_HEAD
+          test "$(git rev-parse HEAD)" = "$PIN"
+          test -f sim/hwsim.py || { echo "FAIL: admin/goodwe@$PIN has no sim/hwsim.py."; exit 1; }
+          echo "infra: admin/goodwe @ $(git log --oneline -1)"
+
       - name: build the test image (shipped deps, from apk - see .gitea/ci/Dockerfile)
         run: |
           set -eu
@@ -508,16 +528,9 @@ jobs:
       # shorter timeout - a 60 s limit was tried during CI-01 and reported
       # exactly the false hang the docstring predicts.
       #
-      # ⚠️ WHAT THIS RUN DOES NOT COVER, stated because a pass here would
-      # otherwise over-claim. test_freeze.py's third section wants the infra
-      # repo's `sim/hwsim.py` to drive a real HTTP meter through the real
-      # transport. admin/goodwe is PRIVATE (checked via the API) and this
-      # workflow's GITHUB_TOKEN is minted for THIS repository only, so hwsim is
-      # absent here and `find_hwsim()` returns None. The rest of the file runs
-      # and passes. It does so SILENTLY - the file prints nothing to say the
-      # hwsim section was skipped - so "test_freeze.py: PASS" below is a weaker
-      # claim than it looks. That belongs to whoever owns test_freeze.py next;
-      # naming it here is the least this gate can do about it.
+      # test_freeze.py part 3 runs against the real `sim/hwsim.py` from the
+      # checkout above; GOODWE_REQUIRE_HWSIM=1 makes it fail rather than use its
+      # stub (CI-12). Lines a test prints with a `CI: ` prefix are echoed on PASS.
       # ⚠️ PYTHONDONTWRITEBYTECODE=1 IS BELT AND BRACES, NOT A FIX FOR A LIVE
       # HOLE. TEST-15 measured this runner's actual exposure and found none: the
       # checkout below is bind mounted `:ro`, so the interpreter physically
@@ -533,7 +546,7 @@ jobs:
       - name: the add-on's own tests
         run: |
           set -eu
-          docker run --rm -e PYTHONDONTWRITEBYTECODE=1 -v "$WS:/w:ro" goodwe-addon-checks:1 sh -eu -c '
+          docker run --rm -e PYTHONDONTWRITEBYTECODE=1 -e GOODWE_REQUIRE_HWSIM=1 -v "$WS:/w:ro" goodwe-addon-checks:1 sh -eu -c '
             cd /w/goodwe-addon/goodwe_controller
             set -- test_*.py
             if [ "$1" = "test_*.py" ]; then
@@ -546,6 +559,7 @@ jobs:
               start=$(date +%s)
               if python3 "$f" > /tmp/out 2>&1; then
                 echo "PASS  $f  ($(( $(date +%s) - start ))s)"
+                grep "^CI: " /tmp/out || true
               else
                 echo "FAIL  $f  ($(( $(date +%s) - start ))s)"
                 tail -40 /tmp/out
diff --git a/.gitea/workflows/infra-pin.yml b/.gitea/workflows/infra-pin.yml
new file mode 100644
index 0000000..5d4e4e9
--- /dev/null
+++ b/.gitea/workflows/infra-pin.yml
@@ -0,0 +1,38 @@
+# CI-12: goes red when admin/goodwe master has moved past .gitea/infra-pin, so
+# the pin cannot go stale silently. Deliberately NOT a required check: it
+# reports; `checks / unit` stays the only gate. How to bump: README.md,
+# "CI and the infra pin".
+name: infra-pin
+
+on:
+  pull_request:
+  push:
+    branches: [release/1.0]
+
+jobs:
+  fresh:
+    runs-on: [self-hosted, goodwe-rig]
+    timeout-minutes: 30   # seconds of work; the rest is queueing for the shared slot
+    steps:
+      - name: compare .gitea/infra-pin with admin/goodwe master
+        env:
+          SELF: ${{ github.server_url }}/${{ github.repository }}.git
+          INFRA: ${{ github.server_url }}/admin/goodwe.git
+          TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          set -eu
+          auth() { echo "$1" | sed "s#://#://x-access-token:${TOKEN}@#"; }
+          D=$(mktemp -d) && cd "$D"
+          git init -q . && git remote add origin "$(auth "$SELF")"
+          # The pin of the commit this event is about (the PR head, or the push).
+          git fetch -q --depth 1 origin "$GITHUB_SHA"
+          PIN=$(git show FETCH_HEAD:.gitea/infra-pin | grep -v '^#' | tr -d '[:space:]')
+          HEAD=$(git ls-remote "$(auth "$INFRA")" refs/heads/master | cut -f1)
+          cd / && rm -rf "$D"
+          test -n "$HEAD" || { echo "FAIL: could not read admin/goodwe master."; exit 1; }
+          if [ "$PIN" != "$HEAD" ]; then
+            echo "STALE: .gitea/infra-pin is $PIN but admin/goodwe master is $HEAD."
+            echo "       Test against $HEAD and bump the pin (README.md, \"CI and the infra pin\")."
+            exit 1
+          fi
+          echo "OK: .gitea/infra-pin $PIN is admin/goodwe master HEAD."
diff --git a/README.md b/README.md
index c341fb3..d2a9799 100644
--- a/README.md
+++ b/README.md
@@ -105,6 +105,11 @@ has the mechanism, the measurement, and what the flags do not do. They are not u
 each assertion corresponds to a rule whose absence produced an observed failure
 on real hardware, and the comments in `control.py` say which.
 
+### CI and the infra pin
+
+CI (`.gitea/workflows/checks.yml`) runs every `test_*.py`, with `admin/goodwe` checked out next to this repo at the commit in `.gitea/infra-pin`, so `test_freeze.py` grades against the real `sim/hwsim.py`. If that checkout fails, the job fails. The local stub is used only in local runs, and it prints `STUB USED` when it is.
+**Bump the pin** whenever `infra-pin / fresh` is red, which happens once `admin/goodwe` master has moved past the pin. Set `.gitea/infra-pin` to the new master SHA (`git ls-remote <gitea>/admin/goodwe.git refs/heads/master`) in a PR, and let `checks / unit` grade the tests against it.
+
 ## Compatibility
 
 **Check the serial number, not the model name.** Characters 6-8 of the serial are
diff --git a/goodwe_controller/test_freeze.py b/goodwe_controller/test_freeze.py
index 63f30e3..a5e0f00 100644
--- a/goodwe_controller/test_freeze.py
+++ b/goodwe_controller/test_freeze.py
@@ -19,7 +19,8 @@ shipped `meter_freeze_s` itself:
      a check that calls the predicate directly would not be testing the thing
      that ships. Uses the rig's own `sim/hwsim.py --fault freeze` when the infra
      repo is next to this one (or `$GOODWE_SIM`), and an equivalent local stub
-     otherwise. Both are exercised; the run says which one it used.
+     otherwise. Both are exercised; the run says which one it used. CI sets
+     `GOODWE_REQUIRE_HWSIM=1`, which refuses the stub (CI-12).
 
   4. THE WIRING: the real `Controller.cycle()`, asserted on the service call
      that leaves the process;
@@ -600,6 +601,15 @@ hw = find_hwsim()
 # that cannot fail, from the other end.
 PART3_TRANSPORT = f"the rig hwsim at {hw}" if hw else "the local stub"
 print(f"frozen meter over HTTP - using {PART3_TRANSPORT}")
+# CI-12: CI sets GOODWE_REQUIRE_HWSIM=1, so a missing infra checkout fails here
+# instead of passing on the stub. Local runs may still use the stub, and say so.
+if not hw:
+    if os.environ.get("GOODWE_REQUIRE_HWSIM"):
+        print("FAIL: GOODWE_REQUIRE_HWSIM is set but sim/hwsim.py was not found "
+              "(sibling ../goodwe or $GOODWE_SIM) - refusing to fall back to the stub")
+        sys.exit(1)
+    print("STUB USED: part 3 ran against the local stub, NOT the infra repo's "
+          "sim/hwsim.py - not a CI-grade result")
 if hw:
     def argv_for(mode):
         return [HWSIM_DRIVER, "8791" if mode == "freeze" else "8792", mode,
@@ -1263,7 +1273,8 @@ check("a Controller built with the key absent lands on the SHIPPED hold, so "
       _ctl_c.freeze_wd.cfg.hold_s == SHIPPED_HOLD_S)
 
 print()
-print(f"part 3 (the live HTTP transport) ran against: {PART3_TRANSPORT}")
+# `CI: ` lines are echoed into the CI log even on a pass (checks.yml).
+print(f"CI: test_freeze part 3 (the live HTTP transport) ran against: {PART3_TRANSPORT}")
 if fails:
     print(f"{len(fails)} FAILED: {', '.join(fails)}")
     sys.exit(1)