diff --git a/packages/mosaic/framework/tools/git/test-issue-close-fail-closed.sh b/packages/mosaic/framework/tools/git/test-issue-close-fail-closed.sh
index 44f190f0..fdc774dd 100755
--- a/packages/mosaic/framework/tools/git/test-issue-close-fail-closed.sh
+++ b/packages/mosaic/framework/tools/git/test-issue-close-fail-closed.sh
@@ -1,17 +1,26 @@
 #!/usr/bin/env bash
-# Regression: issue-close.sh must NOT close an issue when the closing comment
-# could not be posted, and comment+close must be made by ONE principal.
+# Regression: issue-close.sh must NOT close an issue when the closing comment could not
+# be posted, and comment+close must be made by ONE principal.
 #
 # Guards two defects fixed together (see #1081):
-#   1. `tea issue comment` is not a subcommand -- tea exposes comments as the
-#      TOP-LEVEL `tea comment`. The old call always failed, was unchecked, and
-#      the issue closed anyway, losing the record of WHY it was closed.
-#   2. Routing the comment through the token-authenticated API helper while the
-#      close used --login would attribute one operation to two principals.
+#   1. `tea issue comment` is not a subcommand -- tea exposes comments as the TOP-LEVEL
+#      `tea comment`. The old call always failed, was unchecked, and the issue closed
+#      anyway, losing the record of WHY it was closed.
+#   2. Routing the comment through the token-authenticated API helper while the close
+#      used --login would attribute one operation to two principals.
 #
-# Fully offline: `tea` and `curl` are mocked onto PATH, the repo is a throwaway
-# `git init`, everything lives under $SANDBOX, removed on EXIT.
-set -uo pipefail
+# SAFETY (rev-974, #1085 review 130): this test previously ran under `set -uo pipefail`
+# with unchecked mkdir/redirect/cd, then prepended a possibly-nonexistent $MOCK_BIN to
+# PATH -- while `git remote add origin` names the REAL repository. Forcing setup failure
+# with an unwritable AGENT_WORK_ROOT made it `git init` in its CALLER's directory and
+# invoke the real, provider-mutating issue-close.sh. Setup now fails closed, and both
+# `tea` and `curl` are asserted to resolve INSIDE $MOCK_BIN before any target run.
+set -euo pipefail
+# NOTE: with `set -e`, `grep -q X && fail "..."` is a trap -- the ABSENT case (grep rc=1,
+# which is the PASSING case for a must-not-appear assertion) is the last command of an &&
+# list and silently terminates the script with no message. Every must-not-appear check
+# below is therefore an if-block. This is the same set -e + &&-list defect be-coder-08
+# found in #1086, reintroduced here by adding `set -e` for the sandbox-safety fix.
 
 WORK_ROOT="${AGENT_WORK_ROOT:-${TMPDIR:-/tmp}}"
 SANDBOX="$WORK_ROOT/issue-close-fail-closed-test-$$"
@@ -24,56 +33,118 @@ TARGET="$SCRIPT_DIR/issue-close.sh"
 [ -f "$TARGET" ] || { echo "FAIL: issue-close.sh not found beside this test"; exit 1; }
 fail() { echo "FAIL: $*"; exit 1; }
 
-mkdir -p "$MOCK_BIN" "$REPO_DIR"; : > "$CALLS"
-cd "$REPO_DIR"; git init -q
-git remote add origin https://git.mosaicstack.dev/mosaicstack/stack.git
+# Every setup step is checked. Under `set -e` these abort; the explicit || fail keeps the
+# reason legible instead of a bare non-zero exit.
+mkdir -p "$MOCK_BIN" "$REPO_DIR" || fail "setup: cannot create sandbox under $WORK_ROOT"
+: > "$CALLS"                     || fail "setup: cannot write calls log at $CALLS"
+cd "$REPO_DIR"                   || fail "setup: cannot cd into $REPO_DIR"
+git init -q                      || fail "setup: git init failed"
+git remote add origin https://git.mosaicstack.dev/mosaicstack/stack.git || fail "setup: git remote add failed"
 export PATH="$MOCK_BIN:$PATH" CALLS
-export GITEA_LOGIN="git.mosaicstack.dev"
 export GITEA_URL="https://git.mosaicstack.dev"
 export GITEA_TOKEN="redacted-test-token"
 
 cat > "$MOCK_BIN/curl" <<'EOF'
 #!/bin/bash
-printf 'curl %q ' "$@" >> "$CALLS"; printf '\n' >> "$CALLS"; exit 0
+method=GET; url=""
+while [ $# -gt 0 ]; do
+    case "$1" in
+        -X) method="$2"; shift 2 ;;
+        http*|https*) url="$1"; shift ;;
+        *) shift ;;
+    esac
+done
+printf 'curl %s %s\n' "$method" "$url" >> "$CALLS"
+[ "${MOCK_CURL_FAIL:-}" = "1" ] && [ "$method" = "POST" ] && exit 22
+exit 0
 EOF
 chmod +x "$MOCK_BIN/curl"
 
-mk_tea() {  # $1 = exit code for `tea comment`
-  cat > "$MOCK_BIN/tea" <<EOF
+mk_tea() {  # $1 = exit code for a comment attempt; $2 = login list (empty => no login)
+    local rc="$1" login="${2-}"
+    cat > "$MOCK_BIN/tea" <<EOF
 #!/bin/bash
 printf 'tea %s\n' "\$*" >> "$CALLS"
 if [[ "\$*" == *"login list"* ]]; then
-    echo '[{"name":"git.mosaicstack.dev","url":"https://git.mosaicstack.dev"}]'; exit 0
+    printf '%s\n' '${login}'; exit 0
 fi
-# Fail ANY comment attempt -- both the correct top-level \`tea comment\` and the
-# broken \`tea issue comment\` -- so the test exercises the DEFECT on an unfixed
-# script rather than failing on a setup assertion.
-if [[ "\$1" == "comment" || ( "\$1" == "issue" && "\$2" == "comment" ) ]]; then exit $1; fi
+# Fail ANY comment attempt -- both the correct top-level \`tea comment\` and the broken
+# \`tea issue comment\` -- so an unfixed script exercises the DEFECT rather than tripping
+# a setup assertion.
+if [[ "\$1" == "comment" || ( "\$1" == "issue" && "\$2" == "comment" ) ]]; then exit $rc; fi
 exit 0
 EOF
-  chmod +x "$MOCK_BIN/tea"
+    chmod +x "$MOCK_BIN/tea"
+}
+LOGIN_JSON='[{"name":"git.mosaicstack.dev","url":"https://git.mosaicstack.dev"}]'
+
+# The mocks must be the ones that run. Without this, a failed setup silently falls through
+# to the real tea/curl and the "test" mutates the real provider.
+assert_mocked() {
+    local w
+    for w in tea curl; do
+        p=$(command -v "$w" || true)
+        [ -n "$p" ] || fail "SAFETY: $w does not resolve at all"
+        case "$p" in
+            "$MOCK_BIN"/*) : ;;
+            *) fail "SAFETY: $w resolves to $p, OUTSIDE the sandbox -- refusing to invoke the target" ;;
+        esac
+    done
 }
 
-# ── 1. NEGATIVE (the regression): comment fails => must NOT close, must exit non-zero
-mk_tea 1; : > "$CALLS"
-bash "$TARGET" -i 42 -c "closing note" >/dev/null 2>&1; rc=$?
-grep -qE 'tea (issue )?comment' "$CALLS" || fail "no comment attempt at all -- setup did not reach the tea branch"
-grep -q 'tea issue close' "$CALLS" && fail "ISSUE CLOSED AFTER THE COMMENT FAILED -- the regression"
+run_target() {  # never let a target failure abort the test; we assert on rc
+    # Call sites MUST use `rc=0; run_target ... || rc=$?` -- a bare `run_target ...; rc=$?`
+    # lets the non-zero RETURN trip set -e in the CALLER before rc is ever read.
+    set +e; bash "$TARGET" "$@" >/dev/null 2>&1; local rc=$?; set -e; return $rc
+}
+
+# ── tea path ────────────────────────────────────────────────────────────────────────
+# 1. NEGATIVE (the regression): comment fails => must NOT close, must exit non-zero
+mk_tea 1 "$LOGIN_JSON"; : > "$CALLS"; assert_mocked
+rc=0; run_target -i 42 -c "closing note" || rc=$?
+grep -qE 'tea (issue )?comment' "$CALLS" || fail "no comment attempt -- setup did not reach the tea branch"
+if grep -q 'tea issue close' "$CALLS"; then fail "ISSUE CLOSED AFTER THE COMMENT FAILED -- the regression"; fi
 [ "$rc" -ne 0 ] || fail "comment failed but issue-close exited 0 -- FAIL-OPEN"
 
-# ── 2. POSITIVE (rule MET must pass): comment succeeds => close proceeds, exit 0
-mk_tea 0; : > "$CALLS"
-bash "$TARGET" -i 42 -c "closing note" >/dev/null 2>&1; rc=$?
+# 2. POSITIVE: comment succeeds => close proceeds, exit 0
+mk_tea 0 "$LOGIN_JSON"; : > "$CALLS"; assert_mocked
+rc=0; run_target -i 42 -c "closing note" || rc=$?
 [ "$rc" -eq 0 ] || fail "comment succeeded but issue-close exited $rc"
 grep -q 'tea issue close' "$CALLS" || fail "issue not closed even though the comment succeeded"
 
-# ── 3. must use top-level `tea comment`, never `tea issue comment`
-grep -q 'tea issue comment' "$CALLS" && fail "used 'tea issue comment' -- not a valid subcommand"
+# 3. must use top-level `tea comment`, never `tea issue comment`
+if grep -q 'tea issue comment' "$CALLS"; then fail "used 'tea issue comment' -- not a valid subcommand"; fi
 
-# ── 4. ONE PRINCIPAL: comment and close must carry the SAME --login
-c=$(grep -m1 '^tea comment'    "$CALLS" | grep -o -- '--login [^ ]*' | awk '{print $2}')
+# 4. ONE PRINCIPAL: comment and close must carry the SAME --login
+c=$(grep -m1 '^tea comment'     "$CALLS" | grep -o -- '--login [^ ]*' | awk '{print $2}')
 k=$(grep -m1 '^tea issue close' "$CALLS" | grep -o -- '--login [^ ]*' | awk '{print $2}')
 [ -n "$c" ] || fail "comment carried no --login"
 [ "$c" = "$k" ] || fail "MIXED PRINCIPALS: comment=$c close=$k"
 
+# ── no-login / API fallback path ────────────────────────────────────────────────────
+# rev-974: the delta also adds fail-closed behaviour to this branch, and the suite never
+# reached it -- replacing the whole fallback contract with an unconditional close still
+# passed. These assert the POSTCONDITION (which HTTP calls happened, in what order),
+# not merely that a command ran.
+# 5. no login + comment FAILS => POST attempted, NO PATCH, non-zero
+mk_tea 0 ""; : > "$CALLS"; assert_mocked
+rc=0; MOCK_CURL_FAIL=1 run_target -i 42 -c "closing note" || rc=$?
+grep -q 'curl POST' "$CALLS" || fail "API path: no comment POST attempted"
+if grep -q 'curl PATCH' "$CALLS"; then fail "API path: ISSUE CLOSED (PATCH) AFTER THE COMMENT POST FAILED"; fi
+[ "$rc" -ne 0 ] || fail "API path: comment failed but exited 0 -- FAIL-OPEN"
+
+# 6. no login + comment SUCCEEDS => POST strictly BEFORE PATCH, exit 0
+mk_tea 0 ""; : > "$CALLS"; assert_mocked
+rc=0; run_target -i 42 -c "closing note" || rc=$?
+[ "$rc" -eq 0 ] || fail "API path: comment succeeded but exited $rc"
+order=$(grep -oE 'curl (POST|PATCH)' "$CALLS" | awk '{print $2}' | paste -sd, -)
+[ "$order" = "POST,PATCH" ] || fail "API path: expected POST,PATCH -- got '${order:-<none>}'"
+
+# 7. no login + NO comment => PATCH only, never a POST
+mk_tea 0 ""; : > "$CALLS"; assert_mocked
+rc=0; run_target -i 42 || rc=$?
+[ "$rc" -eq 0 ] || fail "API path: no-comment close exited $rc"
+if grep -q 'curl POST' "$CALLS"; then fail "API path: posted a comment when none was requested"; fi
+grep -q 'curl PATCH' "$CALLS" || fail "API path: issue not closed when no comment was requested"
+
 echo "issue-close.sh fail-closed + single-principal regression passed"