diff --git a/CHANGELOG.md b/CHANGELOG.md
index 905cde45..0c893f44 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@
 - Internal: `src/runner.sh` and `src/coverage.sh` are split into `src/runner/` and `src/coverage/` modules of single-responsibility files, each behind a `source`-only `index.sh` aggregator. A pure relocation, no behavior change; see [ADR-010](adrs/adr-010-src-module-directories.md) (#924, #925)
 
 ### Fixed
+- `assert_json_equals` no longer reports two invalid (unparseable) JSON strings as equal. It sorted both sides with `jq -S` but never checked jq's exit code, so two differently-invalid inputs both silently sorted to an empty string and compared equal instead of failing
 - Parallel runs no longer lose results when two test files in different directories share a filename. Per-test results were bucketed by basename, so the second file overwrote the first — silently, with the run still green. A tests/ tree mirroring a src/ tree makes that layout ordinary (#959)
 - Coverage no longer counts variable assignments as functions. A line like `URL="https://${host}/api"` was reported as a function, inflating `FNF`/`FNH` in the LCOV report (17 phantom entries in bashunit's own run); when the value also contained a `|`, the malformed record aborted the LCOV writer with a raw bash arithmetic error (#936)
 - `build.sh` dedupes embedded files by repo-relative path. The previous basename key compared the top-level loop's relative paths against the recursion's absolute ones, so a file reached from two places could be bundled twice in the released binary; it also collided for same-named files in different directories (#923)
diff --git a/src/assert/json.sh b/src/assert/json.sh
index 2fb7f419..0a0be553 100644
--- a/src/assert/json.sh
+++ b/src/assert/json.sh
@@ -53,12 +53,17 @@ function assert_json_equals() {
   local expected="$1"
   local actual="$2"
 
-  local expected_sorted
-  expected_sorted=$(printf '%s' "$expected" | jq -S '.' 2>/dev/null)
+  # jq -S prints nothing (not an error message) on invalid JSON, so its exit
+  # code -- not just its output -- has to gate the comparison: two inputs that
+  # both fail to parse would otherwise both sort to "" and compare equal,
+  # reporting unparseable input as matching JSON instead of failing.
+  local expected_sorted actual_valid=true expected_valid=true
+  expected_sorted=$(printf '%s' "$expected" | jq -S '.' 2>/dev/null) || expected_valid=false
   local actual_sorted
-  actual_sorted=$(printf '%s' "$actual" | jq -S '.' 2>/dev/null)
+  actual_sorted=$(printf '%s' "$actual" | jq -S '.' 2>/dev/null) || actual_valid=false
 
-  if [ "$expected_sorted" != "$actual_sorted" ]; then
+  if [ "$expected_valid" = false ] || [ "$actual_valid" = false ] ||
+    [ "$expected_sorted" != "$actual_sorted" ]; then
     bashunit::assert::fail_with "" "${expected}" "but got " "${actual}"
     return
   fi
diff --git a/tests/unit/assert/json_test.sh b/tests/unit/assert/json_test.sh
index 885a2016..0583cc8e 100644
--- a/tests/unit/assert/json_test.sh
+++ b/tests/unit/assert/json_test.sh
@@ -75,3 +75,31 @@ function test_unsuccessful_assert_json_equals() {
       "$expected" "but got " "$actual")" \
     "$(assert_json_equals "$expected" "$actual")"
 }
+
+# jq -S silently produces empty output (not a parse-error message) on invalid
+# JSON; without checking its exit code, two differently-invalid or identically
+# unparseable inputs both sort to "" and compare equal, turning "not JSON at
+# all" into a false pass.
+function test_unsuccessful_assert_json_equals_when_expected_is_invalid_json() {
+  if [ "$_JQ_AVAILABLE" = false ]; then bashunit::skip "jq required"; return; fi
+  local expected='not json'
+  local actual='{"a":1}'
+
+  assert_same \
+    "$(bashunit::console_results::print_failed_test \
+      "Unsuccessful assert json equals when expected is invalid json" \
+      "$expected" "but got " "$actual")" \
+    "$(assert_json_equals "$expected" "$actual")"
+}
+
+function test_unsuccessful_assert_json_equals_when_both_sides_are_invalid_json() {
+  if [ "$_JQ_AVAILABLE" = false ]; then bashunit::skip "jq required"; return; fi
+  local expected='not json'
+  local actual='also not json'
+
+  assert_same \
+    "$(bashunit::console_results::print_failed_test \
+      "Unsuccessful assert json equals when both sides are invalid json" \
+      "$expected" "but got " "$actual")" \
+    "$(assert_json_equals "$expected" "$actual")"
+}