@@ -26,6 +26,7 @@
 # Optional env:
 #   FARM_REPO             default "hyperpolymath/.git-private-farm"
 #   DRY_RUN               "true" prints the payload without dispatching
+#   GH_BIN                GitHub CLI command (test seam; default "gh")
 set -euo pipefail
 
 usage() {
@@ -40,6 +41,7 @@ FINDING_FILE="$2"
 
 FARM_REPO="${FARM_REPO:-hyperpolymath/.git-private-farm}"
 DRY_RUN="${DRY_RUN:-false}"
+GH_BIN="${GH_BIN:-gh}"
 
 # Title-keyword exclusion regex. Keep in sync with:
 #   feedback_pr_sweep_title_keyword_exclusion
@@ -88,6 +90,45 @@ case "$source_workflow" in
     *) echo "ERROR: source_workflow not in expected shape: '$source_workflow'" >&2; exit 1 ;;
 esac
 
+# A SHA can exist in GitHub's object database yet be unusable as a cross-repo
+# reusable workflow. Feature-branch commits that are later squash-merged have
+# exactly that shape: Contents/Commits APIs resolve them, but Actions rejects
+# `uses: ...@sha` at startup with `workflow was not found`. Prove the proposed
+# target is on the source repository's default-branch history before searching
+# consumers or dispatching a mutation.
+default_branch=$($GH_BIN api "repos/${source_repo}" --jq '.default_branch') || {
+    echo "ERROR: could not resolve ${source_repo}'s default branch" >&2
+    exit 1
+}
+
+compare_status=$($GH_BIN api \
+    "repos/${source_repo}/compare/${new_sha}...${default_branch}" \
+    --jq '.status') || {
+    echo "ERROR: could not verify ${new_sha} against ${source_repo}:${default_branch}" >&2
+    exit 1
+}
+
+case "$compare_status" in
+    identical|ahead) ;;
+    *)
+        echo "ERROR: new_sha ${new_sha} exists but is not reachable from ${source_repo}:${default_branch} (compare status: ${compare_status:-unknown})" >&2
+        exit 1
+        ;;
+esac
+
+if [[ "$source_workflow" == .github/workflows/* ]]; then
+    source_type=$($GH_BIN api \
+        "repos/${source_repo}/contents/${source_workflow}?ref=${new_sha}" \
+        --jq '.type') || {
+        echo "ERROR: ${source_workflow} does not resolve at ${source_repo}@${new_sha}" >&2
+        exit 1
+    }
+    [[ "$source_type" == "file" ]] || {
+        echo "ERROR: ${source_workflow} at ${source_repo}@${new_sha} is not a file" >&2
+        exit 1
+    }
+fi
+
 # --- 3. Title-keyword pre-filter (HARD) ---------------------------------------
 
 # Per feedback_no_automated_licence_edits: licence/SPDX changes are MANUAL,
@@ -119,41 +160,102 @@ CONSUMERS_TSV="$TMPDIR_RUN/consumers.tsv"
 
 echo "Enumerating consumers pinning: $needle" >&2
 
-# gh code-search has a 100-result cap per query. For larger sweeps the
-# operator should pre-build a TSV manually and supply it via a CONSUMERS_TSV
-# env override. Tracked here for posterity.
+# Search both named estates, page to the authoritative `total_count`, and fail
+# rather than silently truncate if GitHub's 1,000-result search horizon is ever
+# reached. The old `gh search code --limit 100 --owner hyperpolymath` path both
+# capped its answer and omitted metadatastician entirely.
 if [[ -n "${CONSUMERS_TSV_OVERRIDE:-}" && -f "$CONSUMERS_TSV_OVERRIDE" ]]; then
     cp "$CONSUMERS_TSV_OVERRIDE" "$CONSUMERS_TSV"
     echo "Using override consumers TSV: $CONSUMERS_TSV_OVERRIDE" >&2
 else
-    gh search code "$needle" --owner hyperpolymath --limit 100 \
-        --json repository,path \
-        --jq '.[] | select(.path | startswith(".github/workflows/")) | "\(.repository.nameWithOwner)\t\(.path)"' \
-        > "$CONSUMERS_TSV" || true
+    : > "$CONSUMERS_TSV"
+
+    # Paginate GitHub code-search for a given scope (user:… or org:…), validate
+    # result integrity, and append workflow YAML paths to CONSUMERS_TSV. Fails
+    # if total_count exceeds GitHub's 1,000-result horizon or if the API returns
+    # incomplete_results=true.
+    #
+    # Args:
+    #   $1  scope qualifier (e.g. "user:hyperpolymath" or "org:metadatastician")
+    # Env:
+    #   needle          search pattern (reusable path + old SHA)
+    #   GH_BIN          GitHub CLI command
+    #   CONSUMERS_TSV   output file (appended)
+    # Returns:
+    #   0 on success, 1 on search failure or integrity violation
+    search_scope() {
+        local scope="$1" page=1 body total incomplete count
+        while :; do
+            body=$($GH_BIN api -X GET search/code \
+                -f "q=${needle} ${scope}" \
+                -F per_page=100 \
+                -F "page=${page}") || {
+                echo "ERROR: code search failed for scope '${scope}' page ${page}" >&2
+                return 1
+            }
+
+            total=$(jq -r '.total_count' <<<"$body")
+            incomplete=$(jq -r '.incomplete_results' <<<"$body")
+            [[ "$total" =~ ^[0-9]+$ && "$incomplete" == false ]] || {
+                echo "ERROR: invalid/incomplete code-search result for '${scope}'" >&2
+                return 1
+            }
+            (( total <= 1000 )) || {
+                echo "ERROR: '${scope}' has ${total} matches, beyond GitHub's 1,000-result search horizon; split the query before propagating" >&2
+                return 1
+            }
+
+            jq -r '.items[]
+                | select(.path | startswith(".github/workflows/"))
+                | select(.path | test("\\.ya?ml$"))
+                | "\(.repository.full_name)\t\(.path)"' <<<"$body" >> "$CONSUMERS_TSV"
+
+            count=$(jq '.items | length' <<<"$body")
+            (( count == 100 && page * 100 < total )) || break
+            page=$((page + 1))
+        done
+    }
+
+    search_scope "user:hyperpolymath"
+    search_scope "org:metadatastician"
+    sort -u -o "$CONSUMERS_TSV" "$CONSUMERS_TSV"
 fi
 
 # Drop fork repos — per estate license policy, third-party / forked stuff is
 # off-limits. (gh search code does not filter forks; we look up each owner-repo
 # pair and skip forks.) For large sweeps this round-trips N times — cache as
 # needed.
+#
+# Filters a TSV of repo + workflow path pairs, removing forks, archived repos,
+# and inaccessible repositories. Overwrites the input file in-place with the
+# filtered result.
+#
+# Args:
+#   $1  path to TSV file (format: "owner/repo<TAB>workflow_path")
+# Env:
+#   GH_BIN  GitHub CLI command
+# Side effects:
+#   Overwrites the input TSV with filtered content (non-fork, non-archived,
+#   accessible repos only). Logs skipped repos to stderr.
 filter_forks() {
     local tsv="$1"
     local out="${tsv}.no-forks"
     : > "$out"
     while IFS=$'\t' read -r repo path; do
-        local is_fork
-        is_fork=$(gh repo view "$repo" --json isFork --jq '.isFork' 2>/dev/null || echo "true")
-        if [[ "$is_fork" == "false" ]]; then
+        local repo_state
+        repo_state=$($GH_BIN api "repos/${repo}" --jq '[.fork, .archived] | @tsv' 2>/dev/null || printf 'true\ttrue\n')
+        if [[ "$repo_state" == $'false\tfalse' ]]; then
             printf '%s\t%s\n' "$repo" "$path" >> "$out"
         else
-            echo "SKIP (fork): $repo" >&2
+            echo "SKIP (fork, archived, or inaccessible): $repo" >&2
         fi
     done < "$tsv"
     mv "$out" "$tsv"
 }
 
-# Skip fork-filter if the operator supplied an override TSV — they've already vetted it.
-if [[ -s "$CONSUMERS_TSV" && -z "${CONSUMERS_TSV_OVERRIDE:-}" ]]; then
+# Apply the same active-root eligibility check to searched and overridden
+# consumers so the test seam cannot bypass the production safety boundary.
+if [[ -s "$CONSUMERS_TSV" ]]; then
     filter_forks "$CONSUMERS_TSV"
 fi
 
@@ -221,6 +323,6 @@ fi
 echo "Firing repository_dispatch propagate-sha-bump → $FARM_REPO ($n_consumers consumers)" >&2
 
 printf '%s' "$payload" \
-    | gh api -X POST "repos/${FARM_REPO}/dispatches" --input -
+    | "$GH_BIN" api -X POST "repos/${FARM_REPO}/dispatches" --input -
 
 echo "OK: dispatch fired. Receiver workflow will run async on $FARM_REPO." >&2
@@ -15,6 +15,23 @@ SCRIPT="scripts/propagate-sha-bump.sh"
 tmp=$(mktemp -d)
 trap 'rm -rf "$tmp"' EXIT
 
+# Hermetic GitHub seam. The actuator must prove the target is reachable and
+# that the reusable exists before it considers consumers; these responses model
+# a mainline target without touching the network.
+cat > "$tmp/gh" <<'EOF'
+#!/usr/bin/env bash
+set -euo pipefail
+case "$*" in
+  *'/compare/'*) printf '%s\n' "${MOCK_COMPARE_STATUS:-ahead}" ;;
+  *'/contents/'*) printf '%s\n' file ;;
+  *'repos/hyperpolymath/standards --jq .default_branch'*) printf '%s\n' main ;;
+  *'--jq [.fork, .archived] | @tsv'*) printf 'false\tfalse\n' ;;
+  *) printf '%s\n' '{}' ;;
+esac
+EOF
+chmod +x "$tmp/gh"
+export GH_BIN="$tmp/gh"
+
 pass=0
 fail=0
 
@@ -147,6 +164,14 @@ rc=$?
 set -e
 assert_exit "DRY_RUN with valid finding → exit 0" 0 "$rc"
 
+if printf '%s' "$out" | grep -q 'hyperpolymath/repo-a'; then
+    echo "ok    active override consumer remains eligible"
+    ((pass++))
+else
+    echo "FAIL  active override consumers were filtered out"
+    ((fail++))
+fi
+
 if printf '%s' "$out" | grep -q '"event_type": "propagate-sha-bump"'; then
     echo "ok    payload contains event_type"
     ((pass++))
@@ -173,6 +198,21 @@ else
     ((fail++))
 fi
 
+# 7. Existing but non-mainline new_sha → hard refusal before fan-out.
+set +e
+out=$(MOCK_COMPARE_STATUS=diverged CONSUMERS_TSV_OVERRIDE="$tmp/consumers.tsv" \
+    DRY_RUN=true "$SCRIPT" /ignored "$tmp/good.json" 2>&1)
+rc=$?
+set -e
+assert_exit "diverged reusable target → exit 1" 1 "$rc"
+if printf '%s' "$out" | grep -q 'not reachable'; then
+    echo "ok    non-mainline refusal explains reachability"
+    ((pass++))
+else
+    echo "FAIL  non-mainline refusal message missing"
+    ((fail++))
+fi
+
 echo ""
 echo "passed: $pass  failed: $fail"
 [[ "$fail" -eq 0 ]]