diff --git a/.claude/rules/testing.md b/.claude/rules/testing.md
index cad4d713..b9c617b5 100644
--- a/.claude/rules/testing.md
+++ b/.claude/rules/testing.md
@@ -49,6 +49,7 @@ assert_have_been_called_times 2 function_name          # count first, then spy
 assert_have_been_called_with function_name "arg"       # spy first, then expected
 assert_have_been_called_with function_name "arg" 1     # ...of call #1
 assert_have_been_called_nth_with 1 function_name "arg"
+assert_have_been_called_with_args function_name "a b"  # boundary-exact, no call index
 
 # Mocks - replace behavior
 bashunit::mock date echo "2024-05-01"
diff --git a/CHANGELOG.md b/CHANGELOG.md
index be76c83e..9ae0196a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## Unreleased
 
 ### Added
+- `assert_have_been_called_with_args <spy> <arg>...`: compares the recorded arguments one by one, so `cmd "a b"` no longer matches `cmd a b` (#894)
 - `BASHUNIT_COVERAGE_ENGINE=auto|xtrace|trap`: a new `xtrace` coverage engine, ~4x cheaper per captured line. Needs Bash 4.1+, so `auto` (the default) falls back to `trap` below that (#860)
 - `BASHUNIT_COVERAGE_SHOW_LINE_HITS=true` prints per-line execution counts in the text coverage report (#856)
 - An [Agentic coding](https://bashunit.com/ai-agents) docs page, and `llms.txt` / `llms-full.txt` are now linked
@@ -18,6 +19,7 @@
 - The `--parallel` unsupported-OS warning no longer claims Alpine is excluded
 
 ### Fixed
+- The per-argument form a spy records was written with a literal `$'\x1f'` separator instead of the byte, so it could not be compared against (#894)
 - `--parallel` no longer discards worker stderr written outside a test body; it renders as a `Stderr from <file>` block (#864)
 - The minimum-bash gate compares the minor version and parses suffixed versions; the floor is unchanged at **Bash 3.0+**
 - An empty entry in `.env` no longer blanks a value the caller exported or passed on the command line (#865)
diff --git a/docs/ai-agents.md b/docs/ai-agents.md
index bb303dd3..1567d19b 100644
--- a/docs/ai-agents.md
+++ b/docs/ai-agents.md
@@ -114,6 +114,10 @@ actually make against this API:
 - Spy assertion argument order is inconsistent — check, don't guess:
   `assert_have_been_called_times <count> <spy>` but
   `assert_have_been_called_with <spy> <expected> [call_index]`.
+- `assert_have_been_called_with` joins the expected arguments with spaces, so it cannot
+  tell `cmd "a b"` from `cmd a b` — a quoting bug passes it. Use
+  `assert_have_been_called_with_args <spy> <arg>...` (no `call_index`) to compare
+  argument by argument whenever an argument may contain a space.
 - Do not delete a shared fixture in `tear_down_after_script`: under `--parallel` the
   file's tests may still be running, and they will vanish from the totals silently.
 - There is no `--update-snapshots` flag. Re-record a snapshot by deleting the file and
diff --git a/docs/assertions.md b/docs/assertions.md
index b5713375..6b6e010e 100644
--- a/docs/assertions.md
+++ b/docs/assertions.md
@@ -29,7 +29,7 @@ to narrow it (`bashunit doc json`).
 | **JSON** | [assert_json_equals](#assert-json-equals) · [assert_json_contains](#assert-json-contains) · [assert_json_key_exists](#assert-json-key-exists) |
 | **Duration** | [assert_duration](#assert-duration) · [assert_duration_less_than](#assert-duration-less-than) · [assert_duration_greater_than](#assert-duration-greater-than) |
 | **Snapshots** | [assert_match_snapshot](#assert-match-snapshot) · [assert_match_snapshot_ignore_colors](#assert-match-snapshot-ignore-colors) |
-| **Spies** | [assert_have_been_called](#assert-have-been-called) · [assert_not_called](#assert-not-called) · [assert_have_been_called_with](#assert-have-been-called-with) · [assert_have_been_called_nth_with](#assert-have-been-called-nth-with) · [assert_have_been_called_times](#assert-have-been-called-times) |
+| **Spies** | [assert_have_been_called](#assert-have-been-called) · [assert_not_called](#assert-not-called) · [assert_have_been_called_with](#assert-have-been-called-with) · [assert_have_been_called_with_args](#assert-have-been-called-with-args) · [assert_have_been_called_nth_with](#assert-have-been-called-nth-with) · [assert_have_been_called_times](#assert-have-been-called-times) |
 | **Manual failure** | [bashunit::fail](#bashunit-fail) |
 
 ## assert_true
@@ -1679,6 +1679,31 @@ function test_failure() {
 ```
 :::
 
+## assert_have_been_called_with_args
+> `assert_have_been_called_with_args "command" "expected_arg"...`
+
+Reports an error if the **last** call to the spied `command` did not receive exactly these arguments. Unlike [assert_have_been_called_with](#assert-have-been-called-with), the arguments are compared one by one, so `cmd "a b"` does not match `cmd a b`. Use it whenever an argument may contain spaces, such as a path.
+
+There is no `nth` parameter: a trailing number would be indistinguishable from a numeric argument.
+
+::: code-group
+```bash [Example]
+function test_success() {
+  bashunit::spy touch
+  create_report "/tmp/my reports"
+
+  assert_have_been_called_with_args touch "/tmp/my reports/out.txt"
+}
+
+function test_failure() {
+  bashunit::spy touch
+  create_report "/tmp/my reports"
+
+  assert_have_been_called_with_args touch "/tmp/my" "reports/out.txt"
+}
+```
+:::
+
 ## assert_have_been_called_times
 > `assert_have_been_called_times "expected_count" "command"`
 
diff --git a/docs/public/bashunit-skill.md b/docs/public/bashunit-skill.md
index 7747cefe..bce8ab90 100644
--- a/docs/public/bashunit-skill.md
+++ b/docs/public/bashunit-skill.md
@@ -134,7 +134,8 @@ filters it. The same list is at https://bashunit.com/assertions. **Do not invent
 - JSON: `assert_json_equals`, `assert_json_contains`, `assert_json_key_exists`
 - Snapshots: `assert_match_snapshot`, `assert_match_snapshot_ignore_colors`
 - Spies: `assert_have_been_called`, `assert_not_called`, `assert_have_been_called_with`,
-  `assert_have_been_called_times`, `assert_have_been_called_nth_with`
+  `assert_have_been_called_with_args`, `assert_have_been_called_times`,
+  `assert_have_been_called_nth_with`
 
 `assert_same` compares exactly. `assert_equals` first strips ANSI colour codes, tabs and
 newlines — useful for asserting on coloured CLI output, misleading everywhere else.
@@ -164,6 +165,11 @@ failing_command || ec=$?            # correct
 local out; out=$(failing_command)   # WRONG under set -e
 ```
 
+**`assert_have_been_called_with` joins arguments with spaces**, so it cannot see argument
+boundaries: `touch "a b"` also satisfies `assert_have_been_called_with touch "a" "b"`. When
+an argument may contain a space — any path — use `assert_have_been_called_with_args`, which
+compares argument by argument.
+
 **A test with no assertions passes.** Always assert something; `--fail-on-risky` turns
 that into a failure.
 
@@ -191,6 +197,7 @@ assert_have_been_called_times 2 send_email               # count FIRST, then spy
 assert_have_been_called_with send_email "--to a@b.c"     # spy FIRST, then expected
 assert_have_been_called_with send_email "--to a@b.c" 1   # ...of call #1
 assert_have_been_called_nth_with 1 send_email "--to a@b.c"
+assert_have_been_called_with_args send_email "--to" "a@b.c"  # boundary-exact, no index
 ```
 
 The argument order is inconsistent between `_times` and `_with`. A swapped pair *fails
diff --git a/docs/test-doubles.md b/docs/test-doubles.md
index be736dab..98bfae25 100644
--- a/docs/test-doubles.md
+++ b/docs/test-doubles.md
@@ -178,6 +178,34 @@ function test_failure() {
 :::
 
 
+## assert_have_been_called_with_args
+> `assert_have_been_called_with_args spy expected...`
+
+Reports an error if the last invocation of `spy` did not receive exactly these arguments. Arguments are compared one by one instead of being joined with spaces, so an argument containing a space cannot be confused with two arguments — the check `assert_have_been_called_with` cannot make.
+
+There is no `call_index` parameter: a trailing number could not be told apart from a numeric argument.
+
+::: code-group
+```bash [Example]
+function test_success() {
+  bashunit::spy touch
+
+  touch "a b"
+
+  assert_have_been_called_with_args touch "a b"
+}
+
+function test_failure() {
+  bashunit::spy touch
+
+  touch "a b"
+
+  # passes with assert_have_been_called_with, fails here
+  assert_have_been_called_with_args touch "a" "b"
+}
+```
+:::
+
 ## assert_have_been_called_nth_with
 > `assert_have_been_called_nth_with "nth" "spy" "expected"`
 
diff --git a/src/test_doubles.sh b/src/test_doubles.sh
index 5146363e..0cf23d5e 100644
--- a/src/test_doubles.sh
+++ b/src/test_doubles.sh
@@ -23,6 +23,21 @@ function bashunit::spy::times_to_slot() {
   fi
 }
 
+_BASHUNIT_SPY_SERIALIZED_OUT=""
+
+# Serializes the given arguments into _BASHUNIT_SPY_SERIALIZED_OUT exactly the
+# way bashunit::spy records a call: each argument through `printf '%q'`, joined
+# with \x1f. Unlike the space-joined `raw` field, this keeps the argument
+# boundaries, so `f "a b"` and `f a b` serialize differently.
+function bashunit::spy::serialize_args_to_slot() {
+  local serialized=""
+  local arg
+  for arg in "$@"; do
+    serialized="$serialized$(builtin printf '%q' "$arg")"$'\x1f'
+  done
+  _BASHUNIT_SPY_SERIALIZED_OUT=${serialized%$'\x1f'}
+}
+
 function bashunit::unmock() {
   local command=$1
 
@@ -100,7 +115,7 @@ function bashunit::spy() {
     local serialized=\"\"
     local arg
     for arg in \"\$@\"; do
-      serialized=\"\$serialized\$(builtin printf '%q' \"\$arg\")$'\\x1f'\"
+      serialized=\"\$serialized\$(builtin printf '%q' \"\$arg\")\"$'\\x1f'
     done
     serialized=\${serialized%$'\\x1f'}
     builtin printf '%s\x1e%s\\n' \"\$raw\" \"\$serialized\" >> '$params_file'
@@ -173,6 +188,34 @@ function assert_have_been_called_with() {
   bashunit::state::add_assertions_passed
 }
 
+function assert_have_been_called_with_args() {
+  local command=$1
+  shift
+
+  bashunit::spy::serialize_args_to_slot "$@"
+  local expected=$_BASHUNIT_SPY_SERIALIZED_OUT
+
+  local variable
+  variable="$(bashunit::helper::normalize_variable_name "$command")"
+  local file_var="_BASHUNIT_SPY_${variable}_PARAMS_FILE"
+  local line=""
+  if [ -f "${!file_var-}" ]; then
+    line=$(tail -n 1 "${!file_var}" 2>/dev/null || true)
+  fi
+
+  local actual
+  IFS=$'\x1e' read -r _ actual <<<"$line" || true
+
+  if [ "$expected" != "$actual" ]; then
+    bashunit::state::add_assertions_failed
+    bashunit::console_results::print_failed_test "$(bashunit::helper::normalize_test_function_name \
+      "${FUNCNAME[1]}")" "${expected//$'\x1f'/ }" "but got " "${actual//$'\x1f'/ }"
+    return
+  fi
+
+  bashunit::state::add_assertions_passed
+}
+
 function assert_have_been_called_times() {
   local expected_count=$1
   local command=$2
diff --git a/tests/acceptance/snapshots/bashunit_test_sh.test_bashunit_should_display_all_assert_docs.snapshot b/tests/acceptance/snapshots/bashunit_test_sh.test_bashunit_should_display_all_assert_docs.snapshot
index 86287445..b6086a3c 100644
--- a/tests/acceptance/snapshots/bashunit_test_sh.test_bashunit_should_display_all_assert_docs.snapshot
+++ b/tests/acceptance/snapshots/bashunit_test_sh.test_bashunit_should_display_all_assert_docs.snapshot
@@ -651,6 +651,15 @@ Reports an error if the spied `command` was not called with `expected_args`. Che
 Note the argument order: the spy comes first here, but *second* in assert_have_been_called_times.
 
 
+## assert_have_been_called_with_args
+--------------
+> `assert_have_been_called_with_args "command" "expected_arg"...`
+
+Reports an error if the **last** call to the spied `command` did not receive exactly these arguments. Unlike assert_have_been_called_with, the arguments are compared one by one, so `cmd "a b"` does not match `cmd a b`. Use it whenever an argument may contain spaces, such as a path.
+
+There is no `nth` parameter: a trailing number would be indistinguishable from a numeric argument.
+
+
 ## assert_have_been_called_times
 --------------
 > `assert_have_been_called_times "expected_count" "command"`
diff --git a/tests/functional/doubles_test.sh b/tests/functional/doubles_test.sh
index cc0a01d1..4ba6b86a 100644
--- a/tests/functional/doubles_test.sh
+++ b/tests/functional/doubles_test.sh
@@ -107,6 +107,26 @@ function test_mock_mktemp_does_not_break_spy_creation() {
   assert_have_been_called_with rm "-f" "/tmp/mocked_temp_file"
 }
 
+function test_spy_call_with_args_matches_exact_argument_boundaries() {
+  bashunit::spy spy_boundary_command
+
+  spy_boundary_command "a b"
+
+  assert_empty "$(assert_have_been_called_with_args spy_boundary_command "a b")"
+}
+
+function test_spy_call_with_args_detects_wrong_argument_boundaries() {
+  bashunit::spy spy_boundary_command
+
+  spy_boundary_command "a b"
+
+  assert_same \
+    "$(bashunit::console_results::print_failed_test \
+      "Spy call with args detects wrong argument boundaries" \
+      "a b" "but got " "a\\ b")" \
+    "$(assert_have_been_called_with_args spy_boundary_command "a" "b")"
+}
+
 function test_spy_on_echo_does_not_hang() {
   source ./tests/functional/fixtures/echo_function.sh
   bashunit::spy echo
diff --git a/tests/unit/test_doubles_test.sh b/tests/unit/test_doubles_test.sh
index f8bdc686..f30521ad 100644
--- a/tests/unit/test_doubles_test.sh
+++ b/tests/unit/test_doubles_test.sh
@@ -135,6 +135,12 @@ function test_mock_called_in_subshell() {
   assert_same "2024-05-01" "$result"
 }
 
+function test_spy_serialize_args_joins_quoted_arguments_with_a_unit_separator() {
+  bashunit::spy::serialize_args_to_slot "a b" c
+
+  assert_same "a\\ b"$'\x1f'"c" "$_BASHUNIT_SPY_SERIALIZED_OUT"
+}
+
 function test_spy_called_with_different_arguments() {
   bashunit::spy ps