diff --git a/.github/workflows/abi-codegen-drift.yml b/.github/workflows/abi-codegen-drift.yml
index 505928b3..0fdcd6f4 100644
--- a/.github/workflows/abi-codegen-drift.yml
+++ b/.github/workflows/abi-codegen-drift.yml
@@ -76,6 +76,42 @@ jobs:
       - name: Verify Idris is on PATH
         run: idris2 --version
 
+      # Compiling an EXECUTABLE needs the Chez support tree
+      # (`<libdir>/support/chez/support.ss`); type-checking and building a
+      # LIBRARY does not. `verify-proofs.yml` only ever does the latter, so the
+      # cache this job deliberately shares with it was populated without that
+      # tree and this job died at
+      #   INTERNAL ERROR: Can't find data file chez/support.ss
+      # on its very first run. Measured, not supposed: PR #811's gate run.
+      #
+      # `support/` is plain data (Scheme and C sources shipped in the Idris2
+      # repo); it needs no build, so a shallow clone is enough to repair it.
+      - name: Ensure the Chez support tree is installed
+        run: |
+          set -euo pipefail
+          libdir="$(idris2 --libdir)"
+          support="${libdir}/support"
+          if [ -f "${support}/chez/support.ss" ]; then
+            echo "chez support present: ${support}/chez/support.ss"
+          else
+            echo "chez support absent under ${support} -- installing from the Idris2 source tree"
+            rm -rf "${RUNNER_TEMP}/idris2-support-src"
+            git clone --depth 1 --branch "${IDRIS2_VERSION}" \
+              https://github.com/idris-lang/Idris2 "${RUNNER_TEMP}/idris2-support-src"
+            mkdir -p "${support}"
+            cp -R "${RUNNER_TEMP}/idris2-support-src/support/." "${support}/"
+          fi
+          # Assert, do not assume. A missing support tree previously surfaced as
+          # an opaque INTERNAL ERROR three steps later; fail here, by name.
+          if [ ! -f "${support}/chez/support.ss" ]; then
+            echo "::error::chez/support.ss still missing under ${support}"
+            if [ -d "${libdir}" ]; then
+              find "${libdir}" -maxdepth 3 -name 'support*' -print
+            fi
+            exit 1
+          fi
+          echo "support tree: ${support}"
+
       - name: Build the generator
         run: |
           set -euo pipefail
diff --git a/.github/workflows/zig.yml b/.github/workflows/zig.yml
index 458dd8f4..a7d88b19 100644
--- a/.github/workflows/zig.yml
+++ b/.github/workflows/zig.yml
@@ -103,12 +103,26 @@ jobs:
           zig test ffi/zig/src/unified-api-adapter.zig 2>&1 | tee "${RUNNER_TEMP}/zig-test.log"
 
           # The denominator. `zig test` on a file containing no `test` blocks
-          # exits 0 -- a green tick that proves nothing. Insist that it says
-          # how many it ran, and that the number is not zero.
-          summary=$(grep -Eo '[0-9]+ of [0-9]+ test[s]? passed|All [0-9]+ tests passed' \
-            "${RUNNER_TEMP}/zig-test.log" | tail -1 || true)
-          count=$(printf '%s' "${summary}" | grep -Eo '[0-9]+' | tail -1 || true)
-          count=${count:-0}
+          # exits 0 and prints "All 0 tests passed." -- a green tick that proves
+          # nothing. Insist that it says how many it ran, and that it is not 0.
+          #
+          # awk, not `grep ... || true`: grep exits 1 when it matches nothing,
+          # which under `set -e` needs suppressing, and a suppressed exit code
+          # is indistinguishable from a masked failure to a reader or a
+          # scanner. awk exits 0 whether or not it matched, so the no-match
+          # case needs no suppression and the check below stays the only thing
+          # that can fail this step.
+          count=$(awk '
+            match($0, /All [0-9]+ tests passed/) ||
+            match($0, /[0-9]+ of [0-9]+ tests? passed/) { last = $0 }
+            END {
+              n = 0
+              while (match(last, /[0-9]+/)) {
+                n = substr(last, RSTART, RLENGTH)
+                last = substr(last, RSTART + RLENGTH)
+              }
+              print n + 0
+            }' "${RUNNER_TEMP}/zig-test.log")
 
           echo "zig tests run: ${count}"
           {