diff --git a/docs/command-line.md b/docs/command-line.md
index d2c3d73c..a75c1c50 100644
--- a/docs/command-line.md
+++ b/docs/command-line.md
@@ -7,6 +7,8 @@
 ```bash
 bashunit test [path] [options]    # Run tests (default)
 bashunit bench [path] [options]   # Run benchmarks
+bashunit watch [path] [options]   # Watch files, re-run tests on change
+bashunit assert <fn> <args>       # Run standalone assertion
 bashunit doc [filter]             # Show assertion documentation
 bashunit init [dir]               # Initialize test directory
 bashunit learn                    # Interactive tutorial
@@ -55,6 +57,10 @@ bashunit test tests/ --parallel --simple
 | `-a, --assert <fn> <args>`     | Run a standalone assert function                 |
 | `-e, --env, --boot <file>`     | Load custom env/bootstrap file (supports args)   |
 | `-f, --filter <name>`          | Only run tests matching name                     |
+| `--tag <name>`                 | Only run tests with matching `@tag` (repeatable) |
+| `--exclude-tag <name>`         | Skip tests with matching `@tag` (repeatable)     |
+| `--output <format>`            | Output format (`tap` for TAP version 13)         |
+| `-w, --watch`                  | Watch files and re-run tests on change           |
 | `--log-junit <file>`           | Write JUnit XML report                           |
 | `-j, --jobs <N>`               | Run tests in parallel with max N concurrent jobs |
 | `-p, --parallel`               | Run tests in parallel                            |
@@ -114,6 +120,84 @@ bashunit test tests/ --filter "user_login"
 ```
 :::
 
+### Tags
+
+> `bashunit test --tag <name>`
+> `bashunit test --exclude-tag <name>`
+
+Filter tests by `# @tag` annotations. Both flags are repeatable. `--tag` uses OR
+logic across names; `--exclude-tag` wins when a test matches both.
+
+::: code-group
+```bash [Annotate tests]
+# @tag slow
+function test_heavy_computation() {
+  ...
+}
+
+# @tag integration
+function test_api_call() {
+  ...
+}
+```
+```bash [Run by tag]
+bashunit test tests/ --tag slow
+bashunit test tests/ --tag slow --tag integration
+bashunit test tests/ --exclude-tag integration
+```
+:::
+
+### Output format
+
+> `bashunit test --output <format>`
+
+Select an alternative output format. Currently supported:
+
+- `tap` — [TAP version 13](https://testanything.org/tap-version-13-specification.html) for CI/CD integrations.
+
+The `TAP version 13` header comes first, each test file is announced via a
+`# <path>` diagnostic line, each test emits an `ok <n> - <name>` or
+`not ok <n> - <name>` line (failures include a YAML `--- ... ...` block with
+expected/actual), and the `1..N` plan line closes the report.
+
+::: code-group
+```bash [Example]
+bashunit test tests/ --output tap
+```
+```[Output]
+TAP version 13
+# tests/example_test.sh
+ok 1 - Should validate input
+not ok 2 - Should handle errors
+  ---
+  Expected 'foo'
+  but got  'bar'
+  ...
+
+1..2
+```
+:::
+
+### Watch mode
+
+> `bashunit test -w|--watch`
+
+Watch the test path (plus `src/` if present) and re-run tests when files change.
+The `-w`/`--watch` flag uses a lightweight **checksum polling loop** that works
+on any system — no external tools required.
+
+::: code-group
+```bash [Example]
+bashunit test tests/ --watch
+```
+:::
+
+::: tip
+For file-event-driven watching (no polling), use the dedicated
+[`watch`](#watch) subcommand, which relies on `inotifywait` (Linux) or
+`fswatch` (macOS).
+:::
+
 ### Environment / Bootstrap
 
 > `bashunit test -e|--env|--boot <file>`
@@ -326,7 +410,7 @@ This is useful for:
 bashunit test tests/ --no-progress
 ```
 ```[Output]
-bashunit - 0.32.0 | Tests: 10
+bashunit - 0.34.1 | Tests: 10
 Tests:      10 passed, 10 total
 Assertions: 25 passed, 25 total
 
@@ -464,6 +548,43 @@ bashunit bench --filter "parse"
 | `--skip-env-file` | Skip `.env` loading, use shell environment only |
 | `-l, --login` | Run in login shell context |
 
+## watch
+
+> `bashunit watch [path] [test-options]`
+
+Dedicated watch subcommand that uses **OS file-event notifications** (no
+polling) to re-run tests as soon as a `.sh` file changes. Any option accepted
+by `bashunit test` is also accepted here.
+
+::: code-group
+```bash [Examples]
+# Watch current directory
+bashunit watch
+
+# Watch the tests/ directory
+bashunit watch tests/
+
+# Watch and filter by name
+bashunit watch tests/ --filter user
+
+# Watch with simple output
+bashunit watch tests/ --simple
+```
+:::
+
+::: warning Requirements
+- **Linux:** `inotifywait` (`sudo apt install inotify-tools`)
+- **macOS:** `fswatch` (`brew install fswatch`)
+
+If the required tool is not installed, bashunit prints a clear installation hint
+and exits with a non-zero code.
+:::
+
+::: tip
+If you cannot install `inotifywait` or `fswatch`, use the portable
+[`-w/--watch`](#watch-mode) flag on `bashunit test` instead (uses polling).
+:::
+
 ## doc
 
 > `bashunit doc [filter]`
@@ -567,7 +688,7 @@ bashunit upgrade
 ```
 ```[Output]
 > Upgrading bashunit to latest version
-> bashunit upgraded successfully to latest version 0.28.0
+> bashunit upgraded successfully to latest version 0.34.1
 ```
 :::
 
@@ -604,16 +725,18 @@ bashunit --help
 Usage: bashunit <command> [arguments] [options]
 
 Commands:
-  test [path]       Run tests (default command)
-  bench [path]      Run benchmarks
-  doc [filter]      Display assertion documentation
-  init [dir]        Initialize a new test directory
-  learn             Start interactive tutorial
-  upgrade           Upgrade bashunit to latest version
+  test [path]         Run tests (default command)
+  bench [path]        Run benchmarks
+  assert <fn> <args>  Run standalone assertion
+  doc [filter]        Display assertion documentation
+  init [dir]          Initialize a new test directory
+  learn               Start interactive tutorial
+  watch [path]        Watch files and re-run tests on change
+  upgrade             Upgrade bashunit to latest version
 
 Global Options:
-  -h, --help        Show this help message
-  -v, --version     Display the current version
+  -h, --help          Show this help message
+  -v, --version       Display the current version
 
 Run 'bashunit <command> --help' for command-specific options.
 ```
@@ -624,6 +747,7 @@ Each subcommand also supports `--help`:
 ```bash
 bashunit test --help
 bashunit bench --help
+bashunit watch --help
 bashunit doc --help
 ```
 
diff --git a/docs/configuration.md b/docs/configuration.md
index 36b01ef7..8a1cdfd8 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -203,6 +203,22 @@ BASHUNIT_SHOW_EXECUTION_TIME=false
 ```
 :::
 
+## Output format
+
+> `BASHUNIT_OUTPUT_FORMAT=tap`
+
+Select an alternative output format. Currently supported: `tap` for
+[TAP version 13](https://testanything.org/tap-version-13-specification.html),
+useful for CI/CD integrations.
+
+Similar as using `--output` option on the [command line](/command-line#output-format).
+
+::: code-group
+```bash [.env]
+BASHUNIT_OUTPUT_FORMAT=tap
+```
+:::
+
 ## Log JUnit
 
 > `BASHUNIT_LOG_JUNIT=file`
diff --git a/docs/globals.md b/docs/globals.md
index d410d0d2..76fca3ff 100644
--- a/docs/globals.md
+++ b/docs/globals.md
@@ -32,6 +32,12 @@ Internal messages from bashunit include the `[INTERNAL]` prefix so you can easil
 
 > `bashunit::caller_filename`: Gets the caller filename.
 
+## bashunit::caller_line
+
+> `bashunit::caller_line`: Gets the line number of the caller.
+
+Useful inside custom assertions to report the line that triggered the failure.
+
 ## bashunit::current_timestamp
 
 > `bashunit::current_timestamp`: Gets the current timestamp.
@@ -54,4 +60,39 @@ The directory is automatically deleted when bashunit completes.
 
 ## bashunit::is_command_available
 
-> `bashunit::is_command_available`: Checks if command is available
+> `bashunit::is_command_available <command>`: Checks if a command is available in `PATH`.
+
+Returns `0` when the command is found, `1` otherwise.
+
+```bash
+if bashunit::is_command_available jq; then
+  # jq-based assertions
+fi
+```
+
+## bashunit::print_line
+
+> `bashunit::print_line <?length> <?char>`: Prints a horizontal separator.
+
+Defaults to 70 characters of `-`. Both arguments are optional.
+
+```bash
+bashunit::print_line          # 70 dashes
+bashunit::print_line 40 '='   # 40 equals signs
+```
+
+## Custom assertion helpers
+
+These helpers are intended for building [custom assertions](/custom-asserts).
+
+- `bashunit::assertion_passed` — Mark the current assertion as passed.
+- `bashunit::assertion_failed <expected> <actual> <?label>` — Mark the current
+  assertion as failed and print a failure report.
+- `bashunit::fail <?message>` — Fail the current test with an optional message.
+
+See [Custom asserts](/custom-asserts) for full examples.
+
+## Test doubles
+
+The `bashunit::spy`, `bashunit::mock`, and `bashunit::unmock` helpers are
+documented in [Test doubles](/test-doubles).
diff --git a/tests/acceptance/bashunit_tap_output_test.sh b/tests/acceptance/bashunit_tap_output_test.sh
new file mode 100644
index 00000000..c72ad33f
--- /dev/null
+++ b/tests/acceptance/bashunit_tap_output_test.sh
@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+function set_up_before_script() {
+  TEST_ENV_FILE="tests/acceptance/fixtures/.env.default"
+}
+
+function test_tap_output_passing_tests_matches_snapshot() {
+  local test_file=tests/acceptance/fixtures/test_bashunit_when_a_test_passes.sh
+
+  assert_match_snapshot "$(./bashunit --no-parallel --env "$TEST_ENV_FILE" --output tap "$test_file")"
+}
+
+function test_tap_output_failing_tests_matches_snapshot() {
+  local test_file=tests/acceptance/fixtures/test_bashunit_when_a_test_fail.sh
+
+  assert_match_snapshot "$(./bashunit --no-parallel --env "$TEST_ENV_FILE" --output tap "$test_file" 2>&1 || true)"
+}
+
+function test_tap_output_env_var_equivalent_to_flag() {
+  local test_file=tests/acceptance/fixtures/test_bashunit_when_a_test_passes.sh
+  local via_flag
+  local via_env
+
+  via_flag=$(./bashunit --no-parallel --env "$TEST_ENV_FILE" --output tap "$test_file")
+  via_env=$(BASHUNIT_OUTPUT_FORMAT=tap ./bashunit --no-parallel --env "$TEST_ENV_FILE" "$test_file")
+
+  assert_equals "$via_flag" "$via_env"
+}
+
+function test_tap_output_exits_non_zero_on_failure() {
+  local test_file=tests/acceptance/fixtures/test_bashunit_when_a_test_fail.sh
+
+  assert_general_error "$(./bashunit --no-parallel --env "$TEST_ENV_FILE" --output tap "$test_file" 2>&1)"
+}
diff --git a/tests/acceptance/snapshots/bashunit_tap_output_test_sh.test_tap_output_failing_tests_matches_snapshot.snapshot b/tests/acceptance/snapshots/bashunit_tap_output_test_sh.test_tap_output_failing_tests_matches_snapshot.snapshot
new file mode 100644
index 00000000..8ca07169
--- /dev/null
+++ b/tests/acceptance/snapshots/bashunit_tap_output_test_sh.test_tap_output_failing_tests_matches_snapshot.snapshot
@@ -0,0 +1,13 @@
+TAP version 13
+# tests/acceptance/fixtures/test_bashunit_when_a_test_fail.sh
+ok 1 - Assert same
+ok 2 - Assert contains
+not ok 3 - Assert failing
+  ---
+  Expected '1'
+  but got  '0'
+  ...
+ok 4 - Assert greater and less than
+ok 5 - Assert empty
+
+1..5
diff --git a/tests/acceptance/snapshots/bashunit_tap_output_test_sh.test_tap_output_passing_tests_matches_snapshot.snapshot b/tests/acceptance/snapshots/bashunit_tap_output_test_sh.test_tap_output_passing_tests_matches_snapshot.snapshot
new file mode 100644
index 00000000..0b1bbc90
--- /dev/null
+++ b/tests/acceptance/snapshots/bashunit_tap_output_test_sh.test_tap_output_passing_tests_matches_snapshot.snapshot
@@ -0,0 +1,8 @@
+TAP version 13
+# tests/acceptance/fixtures/test_bashunit_when_a_test_passes.sh
+ok 1 - Assert same
+ok 2 - Assert contains
+ok 3 - Assert greater and less than
+ok 4 - Assert empty
+
+1..4