diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..29d39ae
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+tests/coverage/
diff --git a/tests/README.md b/tests/README.md
index d96bba2..b0a901e 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -37,3 +37,25 @@ under test. Since every script here resolves its config from
 
 There's no CI wiring for this suite yet — run it manually before/after
 touching anything under `skills/` or `vendor/claude-code/plugins/`.
+
+## Coverage
+
+```bash
+sudo apt install kcov   # or a user-local install, as done for bats
+kcov --include-pattern=/repo/skills/,/repo/vendor/claude-code/plugins/,force-ask-on-chaining.sh,force-ask-on-raw-git.sh \
+     tests/coverage bats -r tests/
+```
+
+Opens as `tests/coverage/bats.<hash>/index.html` (not committed — see
+`.gitignore`). `kcov` follows every bash subprocess `bats` forks, so this
+covers the actual wrapper/setup/hook scripts, not just `bats` itself.
+
+The `--include-pattern` needs three things, not just the two source
+directories: `git_cmd.sh`/`vault_*.sh`/`setup.sh` run straight from this
+checkout, so `/repo/skills/` and `/repo/vendor/claude-code/plugins/` catch
+them (the leading `/repo/` matters — a plain `skills/` would also match this
+repo's own outer directory name and pull in unrelated files). The two
+`PreToolUse` hooks are different: `tests/git-manager/hooks.bats` exercises
+the *deployed* copies under `~/.agent-skills/git-manager/bin/` (matching how
+Claude Code actually invokes them), which live outside both of those
+directories — hence matching them by filename instead.
diff --git a/tests/git-manager/git_cmd.bats b/tests/git-manager/git_cmd.bats
index 4411aa9..71cf848 100644
--- a/tests/git-manager/git_cmd.bats
+++ b/tests/git-manager/git_cmd.bats
@@ -123,3 +123,9 @@ setup() {
   commit_lines=$(printf '%s\n' "$output" | grep -c '^[0-9a-f]\{7,\} ')
   [ "$commit_lines" -eq 2 ]
 }
+
+@test "an argument outside --repo/-- is rejected" {
+  run "$SCRIPT" status extra
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"unexpected argument 'extra'"* ]]
+}
diff --git a/tests/git-manager/hooks.bats b/tests/git-manager/hooks.bats
index 7b43178..0a3de9c 100644
--- a/tests/git-manager/hooks.bats
+++ b/tests/git-manager/hooks.bats
@@ -4,15 +4,26 @@
 # repo source under hooks/ directly, because force-ask-on-raw-git.sh only
 # gets its companion _lib.sh (for the "already supports" wording) once
 # deployed alongside it — exactly like real usage.
+#
+# Deployed once in setup_file() (bats-core: runs once per file, not per
+# test) into $BATS_FILE_TMPDIR rather than a fresh $BATS_TEST_TMPDIR/home
+# per test: besides being faster (one setup.sh run instead of one per
+# test), it gives every test in this file the *same* absolute script path,
+# which matters for coverage tooling (kcov) to aggregate hits against one
+# file instead of splintering across a differently-pathed copy per test.
 
 load '../helpers/common'
 
+setup_file() {
+  FILE_HOME="$BATS_FILE_TMPDIR/home"
+  mkdir -p "$FILE_HOME"
+  HOME="$FILE_HOME" "$REPO_ROOT/vendor/claude-code/plugins/git-manager/scripts/setup.sh" \
+    --settings-scope user --install-hook --install-raw-git-hook > /dev/null
+}
+
 setup() {
-  sandbox_home
-  SETUP="$REPO_ROOT/vendor/claude-code/plugins/git-manager/scripts/setup.sh"
-  "$SETUP" --settings-scope user --install-hook --install-raw-git-hook > /dev/null
-  CHAIN_HOOK="$HOME/.agent-skills/git-manager/bin/force-ask-on-chaining.sh"
-  RAWGIT_HOOK="$HOME/.agent-skills/git-manager/bin/force-ask-on-raw-git.sh"
+  CHAIN_HOOK="$BATS_FILE_TMPDIR/home/.agent-skills/git-manager/bin/force-ask-on-chaining.sh"
+  RAWGIT_HOOK="$BATS_FILE_TMPDIR/home/.agent-skills/git-manager/bin/force-ask-on-raw-git.sh"
 }
 
 # --- force-ask-on-chaining.sh ---
@@ -38,6 +49,14 @@ setup() {
   [ -z "$output" ]
 }
 
+@test "chaining hook: missing jq fails open instead of blocking every Bash call" {
+  input='{"tool_name":"Bash","tool_input":{"command":"a && b"}}'
+  hide_command jq
+  run "$CHAIN_HOOK" <<< "$input"
+  [ "$status" -eq 0 ]
+  [ -z "$output" ]
+}
+
 # --- force-ask-on-raw-git.sh ---
 
 @test "raw-git hook: git_cmd.sh invocations are exempted" {
@@ -69,3 +88,18 @@ setup() {
   [ "$status" -eq 0 ]
   [ -z "$output" ]
 }
+
+@test "raw-git hook: non-Bash tool_name produces no output even for raw git" {
+  input='{"tool_name":"Read","tool_input":{"command":"git status"}}'
+  run "$RAWGIT_HOOK" <<< "$input"
+  [ "$status" -eq 0 ]
+  [ -z "$output" ]
+}
+
+@test "raw-git hook: missing jq fails open instead of blocking every Bash call" {
+  input='{"tool_name":"Bash","tool_input":{"command":"git status"}}'
+  hide_command jq
+  run "$RAWGIT_HOOK" <<< "$input"
+  [ "$status" -eq 0 ]
+  [ -z "$output" ]
+}
diff --git a/tests/git-manager/setup.bats b/tests/git-manager/setup.bats
index 51b7e56..9f752c0 100644
--- a/tests/git-manager/setup.bats
+++ b/tests/git-manager/setup.bats
@@ -104,3 +104,22 @@ print(any('force-ask-on-raw-git.sh' in c for c in cmds))
   [ -f "$PROJECT_DIR/.claude/settings.json" ]
   [ ! -e "$HOME/.claude/settings.json" ]
 }
+
+@test "an unknown flag errors" {
+  run "$SETUP" --settings-scope user --bogus-flag
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"unknown argument '--bogus-flag'"* ]]
+}
+
+@test "an invalid --settings-scope value errors" {
+  run "$SETUP" --settings-scope nonsense
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"--settings-scope must be 'project' or 'user'"* ]]
+}
+
+@test "missing python3 fails with a clear error instead of a silent crash" {
+  hide_command python3
+  run "$SETUP" --settings-scope user
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"python3 is required"* ]]
+}
diff --git a/tests/helpers/common.bash b/tests/helpers/common.bash
index 7cee19e..ca030db 100644
--- a/tests/helpers/common.bash
+++ b/tests/helpers/common.bash
@@ -87,6 +87,38 @@ with open(config_file, "w") as f:
 PYEOF
 }
 
+# hide_command <name> — makes <name> unresolvable for the rest of the test
+# by building a shim directory with symlinks to every executable currently
+# reachable via $PATH *except* <name>, then replacing $PATH with just that
+# directory. A plain "remove one directory from $PATH" doesn't work here:
+# python3/jq/rg all live in the same directory (/usr/bin) as git/sed/grep/
+# realpath/etc that the scripts under test also need, so excluding that one
+# directory would break everything, not just the target command. Callers
+# must do any setup that itself needs the now-hidden command (e.g. writing
+# a config file with write_git_manager_config/write_vault_config, both of
+# which shell out to python3) *before* calling hide_command.
+hide_command() {
+  local hidden="$1"
+  local shim="$BATS_TEST_TMPDIR/shim-no-$hidden"
+  mkdir -p "$shim"
+  local dir
+  local oldIFS="$IFS"
+  IFS=':'
+  local dirs=($PATH)
+  IFS="$oldIFS"
+  for dir in "${dirs[@]}"; do
+    [ -d "$dir" ] || continue
+    # One `ln` call per PATH directory (not per file) — forking `basename`
+    # and `ln` per file made this take minutes with a few thousand files
+    # spread across a dozen PATH dirs. `-n` skips a name already placed by
+    # an earlier (higher-priority) directory, matching normal PATH lookup
+    # order; unreadable dirs/empty globs are silenced.
+    ln -sn -t "$shim" "$dir"/* 2>/dev/null || true
+  done
+  rm -f "$shim/$hidden"
+  export PATH="$shim"
+}
+
 # json_get <file> <dotted.path> — small helper for assertions against JSON
 # written by setup.sh, without needing jq as a test dependency.
 json_get() {
diff --git a/tests/obsidian-vault-kb/setup.bats b/tests/obsidian-vault-kb/setup.bats
index c804a70..753459f 100644
--- a/tests/obsidian-vault-kb/setup.bats
+++ b/tests/obsidian-vault-kb/setup.bats
@@ -62,3 +62,31 @@ setup() {
   mode=$(json_get "$CONFIG_FILE" "mode")
   [ "$mode" = '"maintain"' ]
 }
+
+@test "an unknown flag errors" {
+  run "$SETUP" --settings-scope user --mode append --vault v="$VAULT" --bogus-flag
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"unknown argument '--bogus-flag'"* ]]
+}
+
+@test "an invalid --settings-scope value errors" {
+  run "$SETUP" --settings-scope nonsense --mode append --vault v="$VAULT"
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"--settings-scope must be 'project' or 'user'"* ]]
+}
+
+@test "--settings-scope project writes under <project-dir>/.claude/settings.json" {
+  PROJECT_DIR="$BATS_TEST_TMPDIR/someproject"
+  mkdir -p "$PROJECT_DIR"
+  run "$SETUP" --settings-scope project --project-dir "$PROJECT_DIR" --mode append --vault v="$VAULT"
+  [ "$status" -eq 0 ]
+  [ -f "$PROJECT_DIR/.claude/settings.json" ]
+  [ ! -e "$HOME/.claude/settings.json" ]
+}
+
+@test "missing python3 fails with a clear error instead of a silent crash" {
+  hide_command python3
+  run "$SETUP" --settings-scope user --mode append --vault v="$VAULT"
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"python3 is required"* ]]
+}
diff --git a/tests/obsidian-vault-kb/vault_backlinks.bats b/tests/obsidian-vault-kb/vault_backlinks.bats
index dda0196..03ce763 100644
--- a/tests/obsidian-vault-kb/vault_backlinks.bats
+++ b/tests/obsidian-vault-kb/vault_backlinks.bats
@@ -50,3 +50,10 @@ EOF
   [ "$status" -eq 0 ]
   [[ "$output" == *"no backlinks found"* ]]
 }
+
+@test "grep fallback still finds backlinks when rg is unavailable" {
+  hide_command rg
+  run "$SCRIPT" homelab-overview
+  [ "$status" -eq 0 ]
+  [[ "$output" == *"dns-setup.md"* ]]
+}
diff --git a/tests/obsidian-vault-kb/vault_index.bats b/tests/obsidian-vault-kb/vault_index.bats
index 163d4bd..5bb5ad4 100644
--- a/tests/obsidian-vault-kb/vault_index.bats
+++ b/tests/obsidian-vault-kb/vault_index.bats
@@ -45,3 +45,54 @@ setup() {
   [ "$status" -eq 1 ]
   [[ "$output" == *"no vault named"* ]]
 }
+
+# --- resolve_vault_path / canonicalize_and_check_dir edge cases ---
+# (exercised via vault_index.sh as a representative of the shared _lib.sh
+# logic used identically by vault_search.sh and vault_backlinks.sh)
+
+@test "no config file at all errors" {
+  rm -f "$CONFIG_FILE"
+  run "$SCRIPT"
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"no configuration found"* ]]
+}
+
+@test "an empty vaults array errors" {
+  write_vault_config "$CONFIG_FILE" "append"
+  run "$SCRIPT"
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"no vaults defined"* ]]
+}
+
+@test "multiple vaults registered without a name errors and lists names" {
+  VAULT2="$BATS_TEST_TMPDIR/vault2"
+  make_test_vault "$VAULT2"
+  write_vault_config "$CONFIG_FILE" "append" "v=$VAULT" "v2=$VAULT2"
+  run "$SCRIPT"
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"multiple vaults configured"* ]]
+  [[ "$output" == *"v2"* ]]
+}
+
+@test "a registered vault path that no longer exists errors" {
+  write_vault_config "$CONFIG_FILE" "append" "gone=$BATS_TEST_TMPDIR/does-not-exist"
+  run "$SCRIPT" gone
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"does not exist"* ]]
+}
+
+@test "a registered vault path that is a file, not a directory, errors" {
+  FILE_PATH="$BATS_TEST_TMPDIR/not-a-dir"
+  echo "just a file" > "$FILE_PATH"
+  write_vault_config "$CONFIG_FILE" "append" "plain=$FILE_PATH"
+  run "$SCRIPT" plain
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"is not a directory"* ]]
+}
+
+@test "missing python3 fails with a clear error instead of a silent crash" {
+  hide_command python3
+  run "$SCRIPT" v
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"python3 is required"* ]]
+}
diff --git a/tests/obsidian-vault-kb/vault_search.bats b/tests/obsidian-vault-kb/vault_search.bats
index 83a565e..fc6ac44 100644
--- a/tests/obsidian-vault-kb/vault_search.bats
+++ b/tests/obsidian-vault-kb/vault_search.bats
@@ -64,3 +64,16 @@ setup() {
   [ "$status" -eq 1 ]
   [[ "$output" == *"outside the vault"* ]]
 }
+
+@test "a subfolder that doesn't exist in the vault errors" {
+  run "$SCRIPT" pihole v NoSuchFolder
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"does not exist in the vault"* ]]
+}
+
+@test "grep fallback still finds matches when rg is unavailable" {
+  hide_command rg
+  run "$SCRIPT" pihole
+  [ "$status" -eq 0 ]
+  [[ "$output" == *"dns-setup.md"* ]]
+}