diff --git a/CHANGELOG.md b/CHANGELOG.md
index 74f7a997..18fc0a55 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@
 - Deprecated forms now warn at runtime on stderr; silence with `BASHUNIT_NO_DEPRECATION_WARNINGS=true` (#866)
 - `bashunit::state::print_line` / `print_tap_line` moved to `bashunit::console_results::*`; no alias kept (#868)
 - `bashunit doc` and the [Assertions](https://bashunit.com/assertions) page now cover all 71 assertions, with a quick-reference table
+- Docs: `bashunit::unmock` and the lifecycle of a double — automatic per-test cleanup, `set_up_before_script` doubles, and what `unmock` reaches (#899)
 - Docs: invalid-input handling, `BASHUNIT_REPORT_TAP`/`BASHUNIT_REPORT_JSON`, the standalone exit code, and the optional `["snapshot_file"]` argument
 - The docs sidebar outline now lists `h3` headings
 - The `--parallel` unsupported-OS warning no longer claims Alpine is excluded
diff --git a/docs/ai-agents.md b/docs/ai-agents.md
index 9e32b40c..3c89820c 100644
--- a/docs/ai-agents.md
+++ b/docs/ai-agents.md
@@ -111,6 +111,10 @@ actually make against this API:
 - Use `$(bashunit::temp_file)` / `$(bashunit::temp_dir)` for scratch files — they are
   cleaned up automatically and are safe under `--parallel`.
 - Never call the network in a test. Use `bashunit::mock` / `bashunit::spy` instead.
+- Doubles are torn down after every test — do not add `bashunit::unmock` to `tear_down`.
+  Use it inside a test to get the real command back, or to suspend a
+  `set_up_before_script` double for that one test (it cannot undo it for the others,
+  since each test runs in its own subshell).
 - 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]`.
diff --git a/docs/public/bashunit-skill.md b/docs/public/bashunit-skill.md
index 92da8e67..28abdb52 100644
--- a/docs/public/bashunit-skill.md
+++ b/docs/public/bashunit-skill.md
@@ -200,6 +200,7 @@ bashunit::mock date echo "2024-05-01"   # replace behaviour
 bashunit::mock uname <<< "Linux"        # heredoc form ignores the call's arguments
 bashunit::mock curl 1                   # all-digits arg = exit code, no output (as for spy)
 bashunit::spy send_email                # record calls, keep behaviour
+bashunit::unmock date                   # restore the real command for the rest of this test
 
 assert_have_been_called send_email
 assert_have_been_called_times 2 send_email               # count FIRST, then spy
@@ -214,6 +215,11 @@ The argument order is inconsistent between `_times` and `_with`. A swapped pair
 the assertion* rather than erroring, so it reads like a real defect — check this list
 rather than guessing.
 
+A double declared inside a test is removed when that test ends, so never unmock in
+`tear_down` — it is noise. One declared in `set_up_before_script` lives for the whole
+file; `bashunit::unmock` on it only suspends it for the current test, because each test
+runs in its own subshell.
+
 ## Data providers
 
 Each line of the provider becomes one run, split on whitespace into `$1`, `$2`, …:
diff --git a/docs/test-doubles.md b/docs/test-doubles.md
index e985ccaf..206a3fb2 100644
--- a/docs/test-doubles.md
+++ b/docs/test-doubles.md
@@ -126,6 +126,35 @@ test_example() {
 ```
 :::
 
+## bashunit::unmock
+> `bashunit::unmock "function"`
+
+Removes a double: it drops the function override — restoring the real command — and deletes the state files a spy recorded its calls in. It is a no-op for a name that was never mocked or spied.
+
+::: code-group
+```bash [Example]
+function test_example() {
+  bashunit::mock ls echo "mocked"
+  assert_same "mocked" "$(ls)"
+
+  bashunit::unmock ls
+
+  assert_not_same "mocked" "$(ls)"
+}
+```
+:::
+
+### Lifecycle of a double
+
+You rarely need to call it, because doubles are cleaned up for you:
+
+- A double created **inside a test** is removed after that test. There is no need to unmock in `tear_down`, and nothing leaks into the next test.
+- A double created in **`set_up_before_script`** stays in place for every test in the file — that is the point of declaring it there.
+
+Each test runs in its own subshell, so `bashunit::unmock` only affects the test that calls it. Calling it on a `set_up_before_script` double suspends that double for the current test; the following tests still see it.
+
+Reach for it when a single test needs the real command back after exercising the mocked path, or when it needs a spy's recorded calls to start over mid-test. Re-declaring a double does not require it: a second `bashunit::mock` or `bashunit::spy` on the same command replaces the first.
+
 ## bashunit::spy
 > `bashunit::spy "function"`
 
diff --git a/tests/functional/doubles_lifecycle_test.sh b/tests/functional/doubles_lifecycle_test.sh
new file mode 100644
index 00000000..d35a1891
--- /dev/null
+++ b/tests/functional/doubles_lifecycle_test.sh
@@ -0,0 +1,58 @@
+#!/bin/bash
+
+# Pins the lifecycle documented in docs/test-doubles.md: doubles declared in
+# set_up_before_script live for the whole file, doubles declared inside a test
+# die with it, and bashunit::unmock reaches no further than the current test.
+
+function set_up_before_script() {
+  bashunit::mock lifecycle_shared_double echo "from before script"
+}
+
+function test_a_before_script_double_is_visible_in_a_test() {
+  assert_same "from before script" "$(lifecycle_shared_double)"
+}
+
+function test_b_unmock_only_affects_the_current_test() {
+  bashunit::unmock lifecycle_shared_double
+
+  assert_empty "$(lifecycle_shared_double 2>/dev/null || true)"
+}
+
+function test_c_before_script_double_survives_the_unmock_of_another_test() {
+  assert_same "from before script" "$(lifecycle_shared_double)"
+}
+
+function test_d_a_double_declared_in_a_test_does_not_leak() {
+  bashunit::mock lifecycle_local_double echo "local"
+
+  assert_same "local" "$(lifecycle_local_double)"
+}
+
+function test_e_the_previous_test_double_is_gone() {
+  assert_empty "$(lifecycle_local_double 2>/dev/null || true)"
+}
+
+function test_unmock_restores_the_real_command() {
+  bashunit::mock ls echo "mocked"
+  assert_same "mocked" "$(ls)"
+
+  bashunit::unmock ls
+
+  assert_not_same "mocked" "$(ls)"
+}
+
+function test_unmock_forgets_the_calls_recorded_so_far() {
+  bashunit::spy lifecycle_spy
+  lifecycle_spy once
+  bashunit::unmock lifecycle_spy
+
+  bashunit::spy lifecycle_spy
+
+  assert_empty "$(assert_not_called lifecycle_spy 2>&1)"
+}
+
+function test_unmock_of_an_unknown_name_is_a_no_op() {
+  bashunit::unmock lifecycle_never_mocked
+
+  assert_successful_code "$?"
+}