diff --git a/tests/04_brief_extraction.bats b/tests/04_brief_extraction.bats
index fe4c43f..fd51574 100644
--- a/tests/04_brief_extraction.bats
+++ b/tests/04_brief_extraction.bats
@@ -53,7 +53,7 @@ teardown() {
   local brief
   brief=$(git config --file "$proj/.repos/.orbit" --get repos.myrepo.brief)
   [ "${#brief}" -le 120 ]
-  [[ "$brief" != *" "* ]] || [[ "$brief" =~ [a-z]$ ]]
+  refute_contains "$brief" " " || assert_matches "$brief" '[a-z]$'
 }
 
 @test "brief: skips HTML block elements and their plain-text contents" {
diff --git a/tests/05_workspace_lifecycle.bats b/tests/05_workspace_lifecycle.bats
index bc84e4b..de5f810 100644
--- a/tests/05_workspace_lifecycle.bats
+++ b/tests/05_workspace_lifecycle.bats
@@ -45,7 +45,7 @@ teardown() {
   cd "$proj" && orbit new "first task" >/dev/null 2>&1
   local created
   created=$(git config --file "$proj/task-01/.orbit" --get workspace.created)
-  [[ "$created" =~ ^[0-9]+$ ]]
+  assert_matches "$created" '^[0-9]+$'
 }
 
 @test "new: --name creates custom-named workspace directory" {
@@ -126,7 +126,7 @@ teardown() {
   cd "$proj/dev" && orbit done >/dev/null 2>&1
   local done_at
   done_at=$(git config --file "$proj/dev/.orbit" --get workspace.done-at)
-  [[ "$done_at" =~ ^[0-9]+$ ]]
+  assert_matches "$done_at" '^[0-9]+$'
 }
 
 @test "done: writes done-date in ISO format" {
@@ -139,7 +139,7 @@ teardown() {
   cd "$proj/dev" && orbit done >/dev/null 2>&1
   local done_date
   done_date=$(git config --file "$proj/dev/.orbit" --get workspace.done-date)
-  [[ "$done_date" =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}$ ]]
+  assert_matches "$done_date" '^[0-9]{4}-[0-9]{2}-[0-9]{2}$'
 }
 
 @test "done: --pr writes PR URL to [pr] section" {
diff --git a/tests/06_worktree_integration.bats b/tests/06_worktree_integration.bats
index 86ddd19..290c65e 100644
--- a/tests/06_worktree_integration.bats
+++ b/tests/06_worktree_integration.bats
@@ -397,7 +397,7 @@ teardown() {
   # scoped branch prints without the ws/<ws>/ prefix; clean repo folds to 'clean'
   assert_contains "$output" "myrepo"
   assert_contains "$output" "clean"
-  [[ "$output" != *"ws/dev/main"* ]]
+  refute_contains "$output" "ws/dev/main"
 }
 
 @test "status: raw mode branch gets the conversion steering line (parity with context/done)" {
diff --git a/tests/07_metadata.bats b/tests/07_metadata.bats
index 39027c7..b599796 100644
--- a/tests/07_metadata.bats
+++ b/tests/07_metadata.bats
@@ -33,5 +33,5 @@ teardown() {
   cd "$proj/manual-ws" && orbit goal "set from nothing" >/dev/null 2>&1
   local created
   created=$(git config --file "$proj/manual-ws/.orbit" --get workspace.created)
-  [[ "$created" =~ ^[0-9]+$ ]]
+  assert_matches "$created" '^[0-9]+$'
 }
diff --git a/tests/09_prune.bats b/tests/09_prune.bats
index 5d4241f..9329a85 100644
--- a/tests/09_prune.bats
+++ b/tests/09_prune.bats
@@ -699,8 +699,8 @@ setup_project_with_done_workspace() {
   run bash -c "cd '$proj/dev' && PATH='$stubs':\$PATH ORBIT_ROOT='$proj' bash '$ORBIT_CMD' prune --dry-run 2>&1"
   [ "$status" -ne 0 ]
   assert_contains "$output" "prune must be run from the project root"
-  [[ "$output" != *"&&"* ]]
-  [[ "$output" != *"cd $proj"* ]]
+  refute_contains "$output" "&&"
+  refute_contains "$output" "cd $proj"
   assert_dir_exists "$proj/dev"
 }
 
@@ -1235,9 +1235,9 @@ setup_project_with_done_workspace() {
   assert_contains "$output" "  myrepo:"
   assert_contains "$output" "    raw-orphan (unmerged)"
   assert_contains "$output" 'git -C ".repos/myrepo" branch -D raw-orphan'
-  [[ "$output" != *"raw-pushed"* ]]
-  [[ "$output" != *"raw-active"* ]]
-  [[ "$output" != *"release-1.2"* ]]
+  refute_contains "$output" "raw-pushed"
+  refute_contains "$output" "raw-active"
+  refute_contains "$output" "release-1.2"
 }
 
 @test "prune: report does not leak git's native branch-deletion output" {
@@ -1251,7 +1251,7 @@ setup_project_with_done_workspace() {
   run bash -c "cd '$proj' && ORBIT_ROOT='$proj' bash '$ORBIT_CMD' prune 2>&1"
   [ "$status" -eq 0 ]
   assert_contains "$output" "deleted branch (merged): ws/dev/main"
-  [[ "$output" != *"Deleted branch"* ]]
+  refute_contains "$output" "Deleted branch"
 }
 
 @test "prune --dry-run: ghost residue reported with would-forms, nothing deleted" {
@@ -1300,7 +1300,7 @@ setup_project_with_done_workspace() {
   assert_contains "$output" "untraceable branches (raw, no remote, no workspace)"
   assert_contains "$output" "    ws/lonely (merged)"
   # raw arm of the three-condition: residue present ⇒ NOT "nothing to prune"
-  [[ "$output" != *"nothing to prune"* ]]
+  refute_contains "$output" "nothing to prune"
   run git -C "$proj/.repos/myrepo" rev-parse --verify --quiet refs/heads/ws/lonely
   [ "$status" -eq 0 ]
 
@@ -1331,7 +1331,7 @@ setup_project_with_done_workspace() {
   run bash -c "cd '$proj' && ORBIT_ROOT='$proj' bash '$ORBIT_CMD' prune 2>&1"
   [ "$status" -eq 0 ]
   assert_contains "$output" 'git -C ".repos/myrepo" branch -D evil\;name'
-  [[ "$output" != *'branch -D evil;name'* ]]
+  refute_contains "$output" 'branch -D evil;name'
 }
 
 @test "prune: raw current branch never enters the branch pipeline — raw report only" {
@@ -1463,7 +1463,7 @@ setup_project_with_done_workspace() {
   run cat "$SANDBOX/e.txt"
   assert_contains "$output" "untraceable branches (raw, no remote, no workspace)"
   run cat "$SANDBOX/o.txt"
-  [[ "$output" != *"untraceable branches"* ]]
+  refute_contains "$output" "untraceable branches"
 
   # dry-run: everything is report → stdout
   run bash -c "cd '$proj' && ORBIT_ROOT='$proj' bash '$ORBIT_CMD' prune --dry-run >'$SANDBOX/o2.txt' 2>'$SANDBOX/e2.txt'"
@@ -1471,7 +1471,7 @@ setup_project_with_done_workspace() {
   run cat "$SANDBOX/o2.txt"
   assert_contains "$output" "untraceable branches (raw, no remote, no workspace)"
   run cat "$SANDBOX/e2.txt"
-  [[ "$output" != *"untraceable branches"* ]]
+  refute_contains "$output" "untraceable branches"
 }
 
 @test "prune: closing block — single caveat, scoped suggestions before raw commands" {
@@ -1578,7 +1578,7 @@ setup_project_with_done_workspace() {
   run bash -c "cd '$proj' && ORBIT_ROOT='$proj' bash '$ORBIT_CMD' prune 2>&1"
   [ "$status" -eq 0 ]
   assert_contains "$output" "    raw-orphan (unknown)"
-  [[ "$output" != *"raw-orphan (unknown) — review"* ]]
+  refute_contains "$output" "raw-orphan (unknown) — review"
 }
 
 @test "prune: branch checked out in another workspace is NOT deleted — failure surfaces, no false 'deleted'" {
@@ -1689,7 +1689,7 @@ setup_project_with_done_workspace() {
   [ "$status" -eq 0 ]
   assert_contains "$output" "pruned: dev (0 worktrees removed, 1 branch deleted)"
   # deletion lines carry the recovery handle
-  [[ "$output" =~ deleted\ branch\ \(merged\):\ ws/dev/main\ \(was\ [0-9a-f]+\) ]]
+  assert_matches "$output" 'deleted\ branch\ \(merged\):\ ws/dev/main\ \(was\ [0-9a-f]+\)'
   [ ! -d "$proj/dev" ]
   run git -C "$proj/.repos/myrepo" rev-parse --verify --quiet refs/heads/ws/dev/main
   [ "$status" -ne 0 ]
diff --git a/tests/12_context.bats b/tests/12_context.bats
index f57ceb4..902655c 100644
--- a/tests/12_context.bats
+++ b/tests/12_context.bats
@@ -44,7 +44,7 @@ teardown() {
   run bash -c "cd '$proj/ws1' && ORBIT_ROOT='$proj' bash '$ORBIT_CMD' context"
   [ "$status" -eq 0 ]
   assert_contains "$output" "state: active"
-  [[ "$output" != *"This is the memo for context test."* ]]
+  refute_contains "$output" "This is the memo for context test."
 }
 
 @test "context --json: bare form mirrors the cruise block (no memos)" {
@@ -199,10 +199,10 @@ teardown() {
   # authoritative identity hint
   assert_contains "$output" "A mock repository for testing. ("
   assert_contains "$output" "no memo (write the card via orbit memo <repo>"
-  [[ "$output" != *"has no memo, using README instead"* ]]
+  refute_contains "$output" "has no memo, using README instead"
   # no stale header from the old format
-  [[ "$output" != *"=== PRIME"* ]]
-  [[ "$output" != *"primed"* ]]
+  refute_contains "$output" "=== PRIME"
+  refute_contains "$output" "primed"
 }
 
 @test "context --startup: reignite shows memos + per-repo status when populated" {
@@ -218,7 +218,7 @@ teardown() {
   assert_contains "$output" "status: 1 jots | memo thin"
   assert_contains "$output" "residual finding"
   # roster is prime-only
-  [[ "$output" != *"available in pool"* ]]
+  refute_contains "$output" "available in pool"
 }
 
 @test "context: --startup and --prime are mutually exclusive" {
diff --git a/tests/14_config.bats b/tests/14_config.bats
index 9a3711a..7b96416 100644
--- a/tests/14_config.bats
+++ b/tests/14_config.bats
@@ -243,5 +243,5 @@ teardown() {
   # the index entry is untouched
   run git config --file "$proj/.repos/.orbit" --get repos.myrepo.url
   [ "$status" -eq 0 ]
-  [[ "$output" != "http://evil" ]]
+  [ "$output" != "http://evil" ]
 }
diff --git a/tests/18_sync.bats b/tests/18_sync.bats
index 7d609fd..948d69d 100644
--- a/tests/18_sync.bats
+++ b/tests/18_sync.bats
@@ -335,7 +335,7 @@ _push_update_to() {
   [ "$status" -eq 0 ]
   assert_contains "$output" "myrepo: already up to date"
   # no false fast-forward claim when HEAD did not move
-  [[ "$output" != *"fast-forwarded"* ]]
+  refute_contains "$output" "fast-forwarded"
 }
 
 @test "sync: batch mode distinguishes fast-forwarded vs up-to-date and tallies" {
@@ -721,8 +721,8 @@ _push_update_to() {
   run bash -c "cd '$proj/dev' && PATH='$stubs':\$PATH ORBIT_ROOT='$proj' bash '$ORBIT_CMD' sync myrepo --force 2>&1"
   [ "$status" -ne 0 ]
   assert_contains "$output" "sync --force must be run from the project root"
-  [[ "$output" != *"&&"* ]]
-  [[ "$output" != *"cd $proj"* ]]
+  refute_contains "$output" "&&"
+  refute_contains "$output" "cd $proj"
 }
 
 @test "sync --force: replays the intended command when the session is clean" {
diff --git a/tests/21_version.bats b/tests/21_version.bats
index 6a25fec..2e7681f 100644
--- a/tests/21_version.bats
+++ b/tests/21_version.bats
@@ -14,7 +14,7 @@ teardown() {
 @test "version: prints a semver on stdout and exits 0" {
   run bash -c "bash '$ORBIT_CMD' version"
   [ "$status" -eq 0 ]
-  [[ "$output" =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]]
+  assert_matches "$output" '^[0-9]+\.[0-9]+\.[0-9]+$'
 }
 
 @test "version: --version and -v are aliases" {
diff --git a/tests/23_install_cli.bats b/tests/23_install_cli.bats
index 7dd4689..fc02e3e 100644
--- a/tests/23_install_cli.bats
+++ b/tests/23_install_cli.bats
@@ -61,39 +61,39 @@ EOF
 @test "help: --help exits 0 and prints usage" {
   run_install --help
   [ "$status" -eq 0 ]
-  [[ "$output" == *"usage:"* ]]
+  assert_contains "$output" "usage:"
 }
 
 @test "parse: unknown flag exits 1" {
   run_install --bogus
   [ "$status" -eq 1 ]
-  [[ "$output" == *"unknown option: --bogus"* ]]
+  assert_contains "$output" "unknown option: --bogus"
 }
 
 @test "uninstall: no target is rejected" {
   run_install --uninstall
   [ "$status" -eq 1 ]
-  [[ "$output" == *"--uninstall requires at least one target"* ]]
+  assert_contains "$output" "--uninstall requires at least one target"
 }
 
 @test "uninstall: a single plugin target no-ops when its CLI is absent" {
   run_install --uninstall --claude
   [ "$status" -eq 0 ]
-  [[ "$output" == *"claude CLI not found"* ]]
+  assert_contains "$output" "claude CLI not found"
 }
 
 @test "uninstall: --all runs every target and exits 0 when nothing is installed" {
   run_install --uninstall --all
   [ "$status" -eq 0 ]
   # --all expands to all plugin targets; missing CLIs are skipped, not fatal.
-  [[ "$output" == *"codex CLI not found"* ]] || [[ "$output" == *"Removed"* ]]
-  [[ "$output" == *"Done."* ]]
+  assert_contains "$output" "codex CLI not found" || assert_contains "$output" "Removed"
+  assert_contains "$output" "Done."
 }
 
 @test "uninstall: --cli reports nothing to remove when runtime is absent" {
   run_install --uninstall --cli
   [ "$status" -eq 0 ]
-  [[ "$output" == *"nothing to remove"* ]]
+  assert_contains "$output" "nothing to remove"
 }
 
 # --- network resilience (ORBIT_RETRY / ORBIT_RETRY_DELAY_SECONDS / ORBIT_TIMEOUT_SECONDS) ---
@@ -101,19 +101,19 @@ EOF
 @test "env: non-numeric ORBIT_RETRY is rejected" {
   run env HOME="$FAKE_HOME" PATH="/usr/bin:/bin" ORBIT_RETRY=abc bash "$INSTALL"
   [ "$status" -eq 1 ]
-  [[ "$output" == *"ORBIT_RETRY must be a positive integer"* ]]
+  assert_contains "$output" "ORBIT_RETRY must be a positive integer"
 }
 
 @test "env: ORBIT_RETRY=0 is rejected" {
   run env HOME="$FAKE_HOME" PATH="/usr/bin:/bin" ORBIT_RETRY=0 bash "$INSTALL"
   [ "$status" -eq 1 ]
-  [[ "$output" == *"ORBIT_RETRY must be >= 1"* ]]
+  assert_contains "$output" "ORBIT_RETRY must be >= 1"
 }
 
 @test "env: non-numeric ORBIT_TIMEOUT_SECONDS is rejected" {
   run env HOME="$FAKE_HOME" PATH="/usr/bin:/bin" ORBIT_TIMEOUT_SECONDS=soon bash "$INSTALL"
   [ "$status" -eq 1 ]
-  [[ "$output" == *"ORBIT_TIMEOUT_SECONDS must be a positive integer"* ]]
+  assert_contains "$output" "ORBIT_TIMEOUT_SECONDS must be a positive integer"
 }
 
 @test "retry: a download that fails transiently succeeds within ORBIT_RETRY" {
@@ -121,8 +121,8 @@ EOF
   run_install_mocked CURL_FAILS=2 ORBIT_SOURCE=acme/widgets \
     ORBIT_RETRY=3 ORBIT_RETRY_DELAY_SECONDS=0 bash "$INSTALL"
   [ "$status" -eq 0 ]
-  [[ "$output" == *"attempt 1/3 failed"* ]]
-  [[ "$output" == *"Installed orbit command to:"* ]]
+  assert_contains "$output" "attempt 1/3 failed"
+  assert_contains "$output" "Installed orbit command to:"
   [ -x "$FAKE_HOME/.local/bin/orbit" ]
 }
 
@@ -131,10 +131,10 @@ EOF
   run_install_mocked CURL_FAILS=99 ORBIT_SOURCE=acme/widgets \
     ORBIT_RETRY=2 ORBIT_RETRY_DELAY_SECONDS=0 bash "$INSTALL"
   [ "$status" -eq 1 ]
-  [[ "$output" == *"giving up after 2 attempts"* ]]
-  [[ "$output" == *"Could not resolve host"* ]]                  # the real curl error
-  [[ "$output" == *"failed to fetch orbit.sh"* ]]
-  [[ "$output" == *"local path source needs no network"* ]]      # escape-hatch hint
+  assert_contains "$output" "giving up after 2 attempts"
+  assert_contains "$output" "Could not resolve host"                  # the real curl error
+  assert_contains "$output" "failed to fetch orbit.sh"
+  assert_contains "$output" "local path source needs no network"      # escape-hatch hint
 }
 
 @test "timeout: a hung download is killed at ORBIT_TIMEOUT_SECONDS, not waited out" {
@@ -143,8 +143,8 @@ EOF
   run_install_mocked ORBIT_SOURCE=acme/widgets \
     ORBIT_RETRY=2 ORBIT_RETRY_DELAY_SECONDS=0 ORBIT_TIMEOUT_SECONDS=1 bash "$INSTALL"
   [ "$status" -eq 1 ]
-  [[ "$output" == *"timed out (1s)"* ]]
-  [[ "$output" == *"failed to fetch orbit.sh"* ]]
+  assert_contains "$output" "timed out (1s)"
+  assert_contains "$output" "failed to fetch orbit.sh"
 }
 
 @test "timeout: a TERM-immune download is KILLed after the grace period" {
@@ -158,8 +158,8 @@ EOF
   run_install_mocked ORBIT_SOURCE=acme/widgets \
     ORBIT_RETRY=1 ORBIT_RETRY_DELAY_SECONDS=0 ORBIT_TIMEOUT_SECONDS=1 bash "$INSTALL"
   [ "$status" -eq 1 ]
-  [[ "$output" == *"timed out after 1s"* ]]   # giving-up message names the timeout
-  [[ "$output" == *"failed to fetch orbit.sh"* ]]
+  assert_contains "$output" "timed out after 1s"   # giving-up message names the timeout
+  assert_contains "$output" "failed to fetch orbit.sh"
 }
 
 # --- marketplace error surfacing (fake claude on PATH) ---------------------
@@ -193,10 +193,10 @@ EOF
   run_install_mocked ORBIT_SOURCE="${BATS_TEST_DIRNAME}/.." \
     ORBIT_RETRY=2 ORBIT_RETRY_DELAY_SECONDS=0 bash "$INSTALL" --claude
   [ "$status" -eq 1 ]
-  [[ "$output" == *"unable to connect to github.com (fake)"* ]]   # the real add error
-  [[ "$output" == *"marketplace add/update failed"* ]]            # the causal warning…
-  [[ "$output" == *"cause is the add error"* ]]                   # …naming the root cause
-  [[ "$output" == *"not found in marketplace"* ]]                 # the install error
+  assert_contains "$output" "unable to connect to github.com (fake)"   # the real add error
+  assert_contains "$output" "marketplace add/update failed"            # the causal warning…
+  assert_contains "$output" "cause is the add error"                   # …naming the root cause
+  assert_contains "$output" "not found in marketplace"                 # the install error
 }
 
 @test "marketplace: refresh failure warns but does not block an offline install" {
@@ -204,8 +204,8 @@ EOF
   run_install_mocked ORBIT_SOURCE="${BATS_TEST_DIRNAME}/.." \
     ORBIT_RETRY=2 ORBIT_RETRY_DELAY_SECONDS=0 CLAUDE_INSTALL_OK=1 bash "$INSTALL" --claude
   [ "$status" -eq 0 ]
-  [[ "$output" == *"cause is the add error"* ]]
-  [[ "$output" == *"Installed Orbit plugin into Claude Code"* ]]
+  assert_contains "$output" "cause is the add error"
+  assert_contains "$output" "Installed Orbit plugin into Claude Code"
   [ -e "$MOCK_STATE/plugin-installed" ]
 }
 
@@ -278,7 +278,7 @@ run_install_chained() {
   [ "$(sed -n '1p' "$MOCK_STATE/calls")" = "curl https://raw.githubusercontent.com/orbcli/orbit/main/orbit.sh" ]
   [ "$(sed -n '2p' "$MOCK_STATE/calls")" = "git-clone https://github.com/orbcli/orbit.git" ]
   [ "$(wc -l < "$MOCK_STATE/calls" | tr -d ' ')" -eq 2 ]   # SSH never needed
-  [[ "$output" == *"attempt 1/3 via orbcli/orbit failed"* ]]
+  assert_contains "$output" "attempt 1/3 via orbcli/orbit failed"
   [ -x "$FAKE_HOME/.local/bin/orbit" ]
   # The clone saw the no-prompt env (installer must never ask interactively):
   [ "$(sed -n '1p' "$MOCK_STATE/gtp")" = "gtp=0" ]
diff --git a/tests/25_try_demo.bats b/tests/25_try_demo.bats
index f0a30f6..2977444 100644
--- a/tests/25_try_demo.bats
+++ b/tests/25_try_demo.bats
@@ -75,45 +75,45 @@ run_try() {
   # One curl fetch, one install run. try.sh supplies the demo chain via
   # ORBIT_SOURCES but never invents a pinned ORBIT_SOURCE.
   [ "$(grep -c 'curl call' "$MOCK_STATE/calls")" -eq 1 ]
-  [[ "$(grep 'ORBIT_SOURCE=' "$MOCK_STATE/calls")" == *"<unset>"* ]]
+  assert_contains "$(grep 'ORBIT_SOURCE=' "$MOCK_STATE/calls")" "<unset>"
   [ "$(grep 'ORBIT_SOURCES=' "$MOCK_STATE/calls")" = \
     "ORBIT_SOURCES=orbcli/orbit https://github.com/orbcli/orbit.git git@github.com:orbcli/orbit.git" ]
-  [[ "$output" == *"plugin installed."* ]]
-  [[ "$output" == *"✓ Ready."* ]]
+  assert_contains "$output" "plugin installed."
+  assert_contains "$output" "✓ Ready."
 }
 
 @test "try.sh: a user-set ORBIT_SOURCE passes through untouched (no chain added)" {
   run_try CURL_FAILS=0 INSTALL_FAILS=0 ORBIT_SOURCE="https://pinned.example/orbit.git"
   [ "$status" -eq 0 ]
   [ "$(grep 'ORBIT_SOURCE=' "$MOCK_STATE/calls")" = "ORBIT_SOURCE=https://pinned.example/orbit.git" ]
-  [[ "$(grep 'ORBIT_SOURCES=' "$MOCK_STATE/calls")" == *"<unset>"* ]]
-  [[ "$output" == *"plugin installed."* ]]
+  assert_contains "$(grep 'ORBIT_SOURCES=' "$MOCK_STATE/calls")" "<unset>"
+  assert_contains "$output" "plugin installed."
 }
 
 @test "try.sh: a user-set ORBIT_SOURCES passes through untouched" {
   run_try CURL_FAILS=0 INSTALL_FAILS=0 ORBIT_SOURCES="custom/chain only-one"
   [ "$status" -eq 0 ]
   [ "$(grep 'ORBIT_SOURCES=' "$MOCK_STATE/calls")" = "ORBIT_SOURCES=custom/chain only-one" ]
-  [[ "$output" == *"plugin installed."* ]]
+  assert_contains "$output" "plugin installed."
 }
 
 @test "try.sh: the install.sh fetch retries through a transient failure" {
   run_try CURL_FAILS=1 INSTALL_FAILS=0
   [ "$status" -eq 0 ]
   [ "$(grep -c 'curl call' "$MOCK_STATE/calls")" -eq 2 ]   # one retry, still one fetch
-  [[ "$output" == *"plugin installed."* ]]
+  assert_contains "$output" "plugin installed."
 }
 
 @test "try.sh: a failing install shows its real error, never fails silently" {
   run_try CURL_FAILS=0 INSTALL_FAILS=1
   [ "$status" -eq 0 ]   # plugin step degrades to manual launch instructions
-  [[ "$output" == *"simulated install failure (fake)"* ]]
-  [[ "$output" == *"falling back to manual launch instructions"* ]]
+  assert_contains "$output" "simulated install failure (fake)"
+  assert_contains "$output" "falling back to manual launch instructions"
 }
 
 @test "try.sh: a non-numeric ORBIT_RETRY is rejected before any network use" {
   run_try ORBIT_RETRY=abc
   [ "$status" -eq 1 ]
-  [[ "$output" == *"ORBIT_RETRY must be a positive integer"* ]]
+  assert_contains "$output" "ORBIT_RETRY must be a positive integer"
   [ ! -e "$TRY_DIR/upstream" ]   # died in preflight, before any seeding/fetch
 }
diff --git a/tests/27_assertion_form.bats b/tests/27_assertion_form.bats
new file mode 100644
index 0000000..bdd1130
--- /dev/null
+++ b/tests/27_assertion_form.bats
@@ -0,0 +1,24 @@
+#!/usr/bin/env bats
+#
+# Assertion-form guard. On bash 3.2 (stock macOS /bin/bash, which the bats
+# shebang resolves to), a failing bare `[[ … ]]` statement does NOT trip
+# errexit — `[[ ]]`/`(( ))` only became subject to `set -e` in bash 4.1. Any
+# mid-test bare `[[ ]]` assertion therefore passes silently on stock macOS,
+# whatever it checks. Assertions must use the helpers in
+# test_helper/common.bash (assert_contains / refute_contains / assert_matches)
+# or plain `[ ]`, both of which fail through on every bash.
+#
+# This lint test greps the suite for the vacuous shape. The pattern is built
+# at runtime so this file's own text never self-matches.
+
+setup() {
+  load test_helper/common
+  common_setup
+}
+
+@test "lint: no bare [[ ]] assertions anywhere in tests/*.bats" {
+  pat='^[[:space:]]*\[\['   # bare-statement form; if/||/&& contexts are fine
+  run grep -rnE "$pat" "$BATS_TEST_DIRNAME"/*.bats
+  # grep exits 1 when nothing matches; 0 means a violation was found.
+  [ "$status" -eq 1 ]
+}
diff --git a/tests/test_helper/common.bash b/tests/test_helper/common.bash
index 955ee6c..0836493 100644
--- a/tests/test_helper/common.bash
+++ b/tests/test_helper/common.bash
@@ -53,6 +53,13 @@ orbit() {
 }
 
 # --- Assertion helpers ---
+#
+# IMPORTANT: always use these helpers (or plain `[ ]`) for assertions — never
+# a bare `[[ … ]]` statement. On bash 3.2 (stock macOS /bin/bash, which the
+# bats shebang resolves to), a failing `[[ ]]`/`(( ))` does NOT trip errexit
+# (they only became subject to `set -e` in bash 4.1), so a mid-test bare
+# `[[ ]]` assertion passes silently no matter what it checks. These helpers
+# fail through an external command (grep), which trips errexit on every bash.
 
 assert_contains() {
   local haystack="$1" needle="$2"
@@ -96,6 +103,18 @@ assert_dir_exists() {
   fi
 }
 
+assert_matches() {
+  local haystack="$1" regex="$2"
+  if printf '%s' "$haystack" | grep -qE -e "$regex"; then
+    return 0
+  else
+    echo "assert_matches failed"
+    echo "  expected to match: $regex"
+    echo "  actual: $haystack"
+    return 1
+  fi
+}
+
 # --- Mock repo utilities ---
 
 create_bare_repo() {