diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 344899f..442548f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,7 +19,7 @@ jobs:
             launch.sh dashboard.sh harvest.sh \
             costs.sh progress.sh \
             lib/*.sh lib/drivers/*.sh \
-            tests/test_*.sh tests/test.sh
+            tests/*.sh
 
   unit-tests:
     strategy:
diff --git a/tests/_test_env.sh b/tests/_test_env.sh
new file mode 100644
index 0000000..246a228
--- /dev/null
+++ b/tests/_test_env.sh
@@ -0,0 +1,7 @@
+#!/bin/bash
+
+# Keep test behavior independent of host Git settings.
+export GIT_CONFIG_GLOBAL=/dev/null
+export GIT_CONFIG_SYSTEM=/dev/null
+export GIT_CONFIG_COUNT=0
+unset GIT_CONFIG GIT_CONFIG_PARAMETERS
diff --git a/tests/manual_interactive_e2e.sh b/tests/manual_interactive_e2e.sh
index a4cb317..57916b9 100755
--- a/tests/manual_interactive_e2e.sh
+++ b/tests/manual_interactive_e2e.sh
@@ -1,6 +1,9 @@
 #!/bin/bash
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Manual interactive E2E fixture generator.
 #
 # This is intentionally not named test_*.sh, so tests/test.sh --unit
diff --git a/tests/runtime_signal_trap.sh b/tests/runtime_signal_trap.sh
index f0e3fec..3730fe4 100755
--- a/tests/runtime_signal_trap.sh
+++ b/tests/runtime_signal_trap.sh
@@ -2,6 +2,9 @@
 # shellcheck disable=SC2034
 set -uo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # tests/runtime_signal_trap.sh
 #
 # Drive the harness's emergency-push paths under real Docker.
@@ -180,6 +183,22 @@ wait_for_session() {
     return 1
 }
 
+wait_for_test_commit() {
+    local name="$1" tag="$2" timeout="${3:-30}"
+    local i subject
+    for i in $(seq 1 "$timeout"); do
+        subject=$(docker exec "$name" \
+            git -C /workspace log -1 --format='%s' 2>/dev/null || true)
+        if [ "$subject" = "test commit [${tag}]" ]; then
+            return 0
+        fi
+        sleep 1
+    done
+    echo "    timed out waiting for test commit [${tag}] in ${name}"
+    docker logs "$name" 2>&1 | tail -15 | sed 's/^/      /'
+    return 1
+}
+
 await_exit() {
     local name="$1" timeout="${2:-90}"
     local i status
@@ -205,8 +224,7 @@ count_landed() {
 echo
 echo "=== Item 3: SIGTERM mid-session ==="
 start_container "${NAMES[0]}" -e TC_TAG=sigterm-tag
-wait_for_session "${NAMES[0]}" || exit 1
-sleep 2
+wait_for_test_commit "${NAMES[0]}" sigterm-tag || exit 1
 echo "  sending docker stop -t 60..."
 docker stop -t 60 "${NAMES[0]}" >/dev/null
 EXIT_3=$(await_exit "${NAMES[0]}")
@@ -221,8 +239,7 @@ echo
 
 echo "=== Item 4: SIGINT mid-session ==="
 start_container "${NAMES[1]}" -e TC_TAG=sigint-tag
-wait_for_session "${NAMES[1]}" || exit 1
-sleep 2
+wait_for_test_commit "${NAMES[1]}" sigint-tag || exit 1
 echo "  sending docker kill --signal=SIGINT..."
 docker kill --signal=SIGINT "${NAMES[1]}" >/dev/null
 EXIT_4=$(await_exit "${NAMES[1]}")
diff --git a/tests/test.sh b/tests/test.sh
index 0ae7c89..19406c0 100755
--- a/tests/test.sh
+++ b/tests/test.sh
@@ -1,6 +1,9 @@
 #!/bin/bash
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Smoke test: launch agents with a counting prompt, verify results.
 # Each agent N writes test-results/agent-N.txt with N*100..N*100+99.
 #
diff --git a/tests/test_activity_filter.sh b/tests/test_activity_filter.sh
index b3a5517..2ae9324 100755
--- a/tests/test_activity_filter.sh
+++ b/tests/test_activity_filter.sh
@@ -2,6 +2,9 @@
 # shellcheck disable=SC2034
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Unit tests for lib/activity-filter.sh.
 # No Docker or API key required.
 
diff --git a/tests/test_ci_workflows.sh b/tests/test_ci_workflows.sh
index d5b123d..5d107a5 100755
--- a/tests/test_ci_workflows.sh
+++ b/tests/test_ci_workflows.sh
@@ -1,11 +1,16 @@
 #!/bin/bash
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Unit tests for GitHub Actions workflow shape.
 
 PASS=0
 FAIL=0
-REPO_ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+TESTS_DIR="$(cd "$(dirname "$0")" && pwd)"
+REPO_ROOT="$(cd "$TESTS_DIR/.." && pwd)"
+CI_YML="$REPO_ROOT/.github/workflows/ci.yml"
 INTEGRATION_YML="$REPO_ROOT/.github/workflows/integration.yml"
 
 assert_eq() {
@@ -32,6 +37,23 @@ assert_eq "workflow has no full-matrix job" "0" \
 assert_eq "workflow does not run --all" "0" \
     "$(grep -cF './tests/test.sh --all' "$INTEGRATION_YML" || true)"
 
+echo ""
+echo "=== 2. Shared test environment ==="
+
+missing_env=""
+for test_file in "$TESTS_DIR"/*.sh; do
+    [ "$test_file" = "$TESTS_DIR/_test_env.sh" ] && continue
+    if ! grep -qF \
+            'source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"' \
+            "$test_file"; then
+        missing_env="${missing_env} $(basename "$test_file")"
+    fi
+done
+
+assert_eq "all test scripts source the shared environment" "" "$missing_env"
+assert_eq "CI checks every test script" "1" \
+    "$(grep -cF 'tests/*.sh' "$CI_YML")"
+
 echo ""
 echo "==============================="
 echo "  ${PASS} passed, ${FAIL} failed"
diff --git a/tests/test_config.sh b/tests/test_config.sh
index 33c3df7..812630a 100755
--- a/tests/test_config.sh
+++ b/tests/test_config.sh
@@ -2,6 +2,9 @@
 # shellcheck disable=SC2034
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Unit tests for swarm.json config parsing.
 # No Docker or API key required -- validates jq expressions only.
 
diff --git a/tests/test_costs.sh b/tests/test_costs.sh
index 3c00ea8..ffc1dbc 100755
--- a/tests/test_costs.sh
+++ b/tests/test_costs.sh
@@ -1,6 +1,9 @@
 #!/bin/bash
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Unit tests for costs.sh aggregation and formatting logic.
 # No Docker or API key required.
 
diff --git a/tests/test_dashboard.sh b/tests/test_dashboard.sh
index af75a8b..6b8f557 100755
--- a/tests/test_dashboard.sh
+++ b/tests/test_dashboard.sh
@@ -2,6 +2,9 @@
 # shellcheck disable=SC2034,SC2016
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Unit tests for dashboard.sh helper functions:
 #   format_model, truncate_str, and column layout (with optional Tag).
 # No Docker or API key required.
diff --git a/tests/test_drivers.sh b/tests/test_drivers.sh
index a0a88ac..2a2947f 100755
--- a/tests/test_drivers.sh
+++ b/tests/test_drivers.sh
@@ -2,6 +2,9 @@
 # shellcheck disable=SC2034
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Unit tests for the driver role interface.
 # No Docker or API key required.
 
@@ -1323,14 +1326,15 @@ for _drv in claude-code codex-cli gemini-cli; do
         "$(grep -cE 'stdbuf -oL tee "\$logfile"' "$DRIVERS_DIR/$_drv.sh" || true)"
 done
 
-# --- Behavioral tests below require `setsid` and `stdbuf` on the
-# host (both GNU utilities).  Stock macOS ships neither, so skip
-# these assertions when they're missing -- the structural pins
-# above are what prevent the bug from silently regressing; the
-# behavioural tests just provide end-to-end confidence on Linux CI.
+# --- Behavioral tests below require `setsid`, `stdbuf`, and `timeout`
+# on the host (all GNU utilities). Stock macOS ships none of them, so
+# skip these assertions when they're missing. The structural pins above
+# prevent silent regressions; the behavioural tests provide end-to-end
+# confidence on Linux CI.
 if ! command -v setsid >/dev/null 2>&1 \
-        || ! command -v stdbuf >/dev/null 2>&1; then
-    echo "  SKIP: reaper behavioural tests (setsid/stdbuf unavailable)"
+        || ! command -v stdbuf >/dev/null 2>&1 \
+        || ! command -v timeout >/dev/null 2>&1; then
+    echo "  SKIP: reaper behavioural tests (setsid/stdbuf/timeout unavailable)"
 else
     # --- Behavioral: fake CLI that forks a surviving child and exits.
     # Without reaping, the child's stdout FD would keep the pipeline
@@ -1346,23 +1350,25 @@ CLI
     chmod +x "$TMPDIR/reap_cli.sh"
 
     # Exit-0 path: pipeline drains, stdout tee'd, exit code preserved.
-    _reap_start=$(date +%s)
-    _run_reaped "$TMPDIR/reap_zero.log" "$TMPDIR/reap_cli.sh" 0 "hello from CLI"
-    _reap_ec=$?
-    _reap_elapsed=$(($(date +%s) - _reap_start))
+    # The timeout bounds a process-group regression without making
+    # normal elapsed time part of the assertion.
+    _reap_ec=0
+    timeout --kill-after=5 30 bash -c \
+        'source "$1"; shift; _run_reaped "$@"' \
+        _ "$DRIVERS_DIR/_common.sh" "$TMPDIR/reap_zero.log" \
+        "$TMPDIR/reap_cli.sh" 0 "hello from CLI" || _reap_ec=$?
 
     assert_eq "reaped run: exit code preserved (0)" "0" "$_reap_ec"
     assert_eq "reaped run: stdout captured in logfile" "hello from CLI" \
         "$(cat "$TMPDIR/reap_zero.log")"
-    # Generous bound for slow CI; actual drain is ~10-50ms.
-    assert_eq "reaped run: drains despite surviving child" "true" \
-        "$([ "$_reap_elapsed" -lt 5 ] && echo true || echo false)"
 
     # Non-zero exit path: exit code is likewise propagated.
     # `|| _reap_ec=$?` keeps set -e from aborting the test script.
     _reap_ec=0
-    _run_reaped "$TMPDIR/reap_nz.log" "$TMPDIR/reap_cli.sh" 42 "boom" \
-        || _reap_ec=$?
+    timeout --kill-after=5 30 bash -c \
+        'source "$1"; shift; _run_reaped "$@"' \
+        _ "$DRIVERS_DIR/_common.sh" "$TMPDIR/reap_nz.log" \
+        "$TMPDIR/reap_cli.sh" 42 "boom" || _reap_ec=$?
     assert_eq "reaped run: non-zero exit preserved (42)" "42" "$_reap_ec"
 
     # --- Defensive cleanup: if the kill-group regressed, sweep any
@@ -1460,13 +1466,12 @@ assert_eq "_run_reaped reaps watchdog after kill" "1" \
     "$(grep -cE 'wait "\$_wd_pid" 2>/dev/null' "$COMMON_FILE")"
 
 # --- §40b. Behavioral: a deadlocked CLI is force-killed by the
-# watchdog within the configured timeout window.
+# watchdog.
 #
-# Skips on hosts without setsid/stdbuf -- the structural pins
-# above are the main regression guard; the behavioural test just
-# provides live coverage on Linux CI.  We drive the watchdog at
-# SWARM_ACTIVITY_POLL=1, SWARM_WATCHDOG_GRACE=1 so the full
-# escalation completes in ~3s and the test adds ~5s to the suite.
+# Skips on hosts without setsid/stdbuf/timeout -- the structural
+# pins above are the main regression guard; the behavioural test
+# provides live coverage on Linux CI. We use the shortest supported
+# polling and grace intervals to keep the suite quick.
 
 # Small helper to count matches without tripping assert_eq with
 # grep's noisy `0 + exit 1 + || echo 0` behaviour (which was
@@ -1478,8 +1483,9 @@ _wd_count() {
 }
 
 if ! command -v setsid >/dev/null 2>&1 \
-        || ! command -v stdbuf >/dev/null 2>&1; then
-    echo "  SKIP: watchdog behavioural test (setsid/stdbuf unavailable)"
+        || ! command -v stdbuf >/dev/null 2>&1 \
+        || ! command -v timeout >/dev/null 2>&1; then
+    echo "  SKIP: watchdog behavioural test (setsid/stdbuf/timeout unavailable)"
 else
     # Synthetic CLI: emits one line, then sleeps indefinitely.
     # The log mtime will freeze after the initial write and the
@@ -1497,17 +1503,18 @@ CLI
     #   "alive" write advances _last_mtime), second poll at t=2s
     #   (mtime stale for ≥2s → SIGTERM → the bash default handler
     #   exits → the grace loop returns early).  End-to-end ~2-3s.
-    _wd_start=$(date +%s)
+    # The outer timeout bounds a regression without making normal
+    # elapsed time an assertion.
+    _wd_ec=0
     SWARM_ACTIVITY_TIMEOUT=2 \
     SWARM_ACTIVITY_POLL=1 \
     SWARM_WATCHDOG_GRACE=1 \
-        _run_reaped "$TMPDIR/wd_run.log" "$TMPDIR/wd_cli.sh" \
-        >/dev/null 2>&1 || true
-    _wd_elapsed=$(($(date +%s) - _wd_start))
+        timeout --kill-after=5 30 bash -c \
+        'source "$1"; shift; _run_reaped "$@"' \
+        _ "$COMMON_FILE" "$TMPDIR/wd_run.log" "$TMPDIR/wd_cli.sh" \
+        >/dev/null 2>&1 || _wd_ec=$?
 
-    assert_eq "watchdog terminates deadlocked CLI within budget" \
-        "true" \
-        "$([ "$_wd_elapsed" -lt 10 ] && echo true || echo false)"
+    assert_eq "watchdog propagates SIGTERM exit (143)" "143" "$_wd_ec"
 
     # The watchdog's diagnostic line lands on stderr, which
     # _run_reaped redirects to <logfile>.err.  Its presence is
@@ -1523,9 +1530,8 @@ CLI
         "$(head -1 "$TMPDIR/wd_run.log" 2>/dev/null)"
 
     # --- Watchdog must stay dormant when the knob is unset or
-    # non-numeric.  Run a short well-behaved CLI and verify no
-    # watchdog diagnostics leak and elapsed stays near the CLI's
-    # own runtime rather than inflating to the grace window.
+    # non-numeric. Run a short well-behaved CLI and verify the
+    # watchdog does not alter its observable behavior.
     cat > "$TMPDIR/wd_quick.sh" <<'CLI'
 #!/bin/bash
 echo "done"
@@ -1534,19 +1540,21 @@ CLI
     chmod +x "$TMPDIR/wd_quick.sh"
 
     unset SWARM_ACTIVITY_TIMEOUT SWARM_ACTIVITY_POLL SWARM_WATCHDOG_GRACE
-    _wd_start=$(date +%s)
+    _wd_ec=0
     _run_reaped "$TMPDIR/wd_quick.log" "$TMPDIR/wd_quick.sh" \
-        >/dev/null 2>&1 || true
-    _wd_elapsed=$(($(date +%s) - _wd_start))
-    assert_eq "unset timeout: watchdog stays dormant" "true" \
-        "$([ "$_wd_elapsed" -lt 3 ] && echo true || echo false)"
+        >/dev/null 2>&1 || _wd_ec=$?
+    assert_eq "unset timeout: exit code preserved (0)" "0" "$_wd_ec"
+    assert_eq "unset timeout: stdout captured" "done" \
+        "$(cat "$TMPDIR/wd_quick.log")"
     assert_eq "unset timeout: no watchdog diagnostics" "0" \
         "$(_wd_count 'swarm watchdog' "$TMPDIR/wd_quick.log.err")"
 
     # Non-integer value must degrade to disabled, not crash.
+    _wd_ec=0
     SWARM_ACTIVITY_TIMEOUT="nonsense" \
         _run_reaped "$TMPDIR/wd_bad.log" "$TMPDIR/wd_quick.sh" \
-        >/dev/null 2>&1 || true
+        >/dev/null 2>&1 || _wd_ec=$?
+    assert_eq "non-integer timeout: run succeeds" "0" "$_wd_ec"
     assert_eq "non-integer timeout: no watchdog diagnostics" "0" \
         "$(_wd_count 'swarm watchdog' "$TMPDIR/wd_bad.log.err")"
 
diff --git a/tests/test_format.sh b/tests/test_format.sh
index ba784cb..c323316 100755
--- a/tests/test_format.sh
+++ b/tests/test_format.sh
@@ -1,6 +1,9 @@
 #!/bin/bash
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Unit tests for formatting functions used by dashboard.sh and costs.sh.
 # No Docker or API key required.
 
diff --git a/tests/test_harness.sh b/tests/test_harness.sh
index d3f8b82..4919309 100755
--- a/tests/test_harness.sh
+++ b/tests/test_harness.sh
@@ -2,6 +2,9 @@
 # shellcheck disable=SC2034
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Unit tests for harness.sh stat extraction and logic.
 # No Docker or API key required.
 
@@ -404,11 +407,16 @@ hlog_pipe() {
 }
 
 AGENT_ID=3
-OUT=$(hlog "test message")
+OUT=$(
+    date() {
+        printf '%s\n' "12:34:56"
+    }
+    hlog "test message"
+)
 PLAIN=$(echo "$OUT" | strip_ansi)
 
 assert_contains "hlog timestamp" \
-    "$(date +%H:%M:%S)" "$PLAIN"
+    "12:34:56 harness[3] test message" "$PLAIN"
 assert_contains "hlog prefix" "harness[3]" "$PLAIN"
 assert_contains "hlog body" "test message" "$PLAIN"
 
@@ -644,6 +652,12 @@ source "$TESTS_DIR/../lib/signing.sh"
 # Exercises configure_git_signing from lib/signing.sh against
 # a sandboxed $HOME so --global writes land in a scratch dir
 # instead of the tester's real ~/.gitconfig.
+with_sandboxed_git_config() {
+    local sandbox="$1"
+    shift
+    HOME="$sandbox" GIT_CONFIG_GLOBAL="$sandbox/.gitconfig" "$@"
+}
+
 run_signing_config() {
     local create_key="$1"
     local sandbox="$TMPDIR/sign-sandbox-$$-${RANDOM}"
@@ -655,12 +669,14 @@ run_signing_config() {
         touch "$key_path"
     fi
 
-    HOME="$sandbox" configure_git_signing "$key_path" "$dst_path"
+    with_sandboxed_git_config "$sandbox" \
+        configure_git_signing "$key_path" "$dst_path"
 
     local format gpgsign
-    format=$(HOME="$sandbox" git config --global --get gpg.format \
-        2>/dev/null || echo "none")
-    gpgsign=$(HOME="$sandbox" git config --global --get commit.gpgsign)
+    format=$(with_sandboxed_git_config "$sandbox" \
+        git config --global --get gpg.format 2>/dev/null || echo "none")
+    gpgsign=$(with_sandboxed_git_config "$sandbox" \
+        git config --global --get commit.gpgsign)
     echo "${format}|${gpgsign}"
     rm -rf "$sandbox"
 }
@@ -683,7 +699,8 @@ copy_src="$copy_sandbox/src_key"
 copy_dst="$copy_sandbox/dst_key"
 echo "fake-key-bytes" > "$copy_src"
 chmod 644 "$copy_src"
-HOME="$copy_sandbox" configure_git_signing "$copy_src" "$copy_dst"
+with_sandboxed_git_config "$copy_sandbox" \
+    configure_git_signing "$copy_src" "$copy_dst"
 assert_eq "key copied to scratch location" \
     "yes" \
     "$([ -f "$copy_dst" ] && echo yes || echo no)"
@@ -693,7 +710,8 @@ assert_eq "key copy has 0600 perms" \
         || stat -f '%Lp' "$copy_dst" 2>/dev/null)"
 assert_eq "user.signingkey points at copy" \
     "$copy_dst" \
-    "$(HOME="$copy_sandbox" git config --global --get user.signingkey)"
+    "$(with_sandboxed_git_config "$copy_sandbox" \
+        git config --global --get user.signingkey)"
 assert_eq "no swarm key written under \$HOME" \
     "no" \
     "$([ -e "$copy_sandbox/.ssh/swarm-signing-key" ] && echo yes || echo no)"
@@ -709,15 +727,16 @@ fail_src="$fail_sandbox/src_key"
 fail_dst="$fail_sandbox/no/such/dir/dst_key"
 touch "$fail_src"
 fail_rc=0
-HOME="$fail_sandbox" configure_git_signing "$fail_src" "$fail_dst" \
-    >/dev/null 2>&1 || fail_rc=$?
+with_sandboxed_git_config "$fail_sandbox" \
+    configure_git_signing "$fail_src" "$fail_dst" \
+        >/dev/null 2>&1 || fail_rc=$?
 assert_eq "install failure -> non-zero return" \
     "1" \
     "$fail_rc"
 assert_eq "install failure -> user.signingkey not set" \
     "" \
-    "$(HOME="$fail_sandbox" git config --global --get user.signingkey \
-        2>/dev/null)"
+    "$(with_sandboxed_git_config "$fail_sandbox" \
+        git config --global --get user.signingkey 2>/dev/null)"
 rm -rf "$fail_sandbox"
 
 # Defaults to /etc/swarm/signing_key when called with no arg;
@@ -725,10 +744,11 @@ rm -rf "$fail_sandbox"
 # exist and expecting the "absent" branch.
 default_path_sandbox="$TMPDIR/sign-default-$$-${RANDOM}"
 mkdir -p "$default_path_sandbox"
-HOME="$default_path_sandbox" configure_git_signing
+with_sandboxed_git_config "$default_path_sandbox" configure_git_signing
 assert_eq "default key path absent -> gpgsign false" \
     "false" \
-    "$(HOME="$default_path_sandbox" git config --global --get commit.gpgsign)"
+    "$(with_sandboxed_git_config "$default_path_sandbox" \
+        git config --global --get commit.gpgsign)"
 rm -rf "$default_path_sandbox"
 
 # ============================================================
diff --git a/tests/test_harvest.sh b/tests/test_harvest.sh
index 73f4395..1c7dc39 100755
--- a/tests/test_harvest.sh
+++ b/tests/test_harvest.sh
@@ -1,6 +1,9 @@
 #!/bin/bash
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Unit tests for harvest.sh logic.
 # Uses local git repos (no Docker or API key required).
 
diff --git a/tests/test_launch.sh b/tests/test_launch.sh
index e0a52b6..d555293 100755
--- a/tests/test_launch.sh
+++ b/tests/test_launch.sh
@@ -2,15 +2,12 @@
 # shellcheck disable=SC2034
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Unit tests for launch.sh parsing logic.
 # No Docker or API key required.
 
-# Isolate from host gitconfig (signing keys, hooks, templates).
-# Several tests build scratch repos and run `git commit` /
-# `commit-tree`;
-export GIT_CONFIG_GLOBAL=/dev/null
-export GIT_CONFIG_SYSTEM=/dev/null
-
 PASS=0
 FAIL=0
 TMPDIR=$(mktemp -d)
diff --git a/tests/test_locale.sh b/tests/test_locale.sh
index 5987ba3..b966d65 100755
--- a/tests/test_locale.sh
+++ b/tests/test_locale.sh
@@ -1,6 +1,9 @@
 #!/bin/bash
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Guard against the regression reported in the bug:
 #   dashboard.sh: line 207: printf: 52.185737173...: invalid number
 # on systems using `,` as the decimal separator.  Pin the
diff --git a/tests/test_manual_interactive_e2e.sh b/tests/test_manual_interactive_e2e.sh
index 5fdbe66..dfb49b1 100755
--- a/tests/test_manual_interactive_e2e.sh
+++ b/tests/test_manual_interactive_e2e.sh
@@ -1,6 +1,9 @@
 #!/bin/bash
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Unit tests for the manual interactive E2E fixture generator.
 
 PASS=0
diff --git a/tests/test_session_end_push.sh b/tests/test_session_end_push.sh
index 73b7dd7..932900a 100755
--- a/tests/test_session_end_push.sh
+++ b/tests/test_session_end_push.sh
@@ -1,6 +1,9 @@
 #!/bin/bash
 set -euo pipefail
 
+# shellcheck source=_test_env.sh
+source "$(dirname "${BASH_SOURCE[0]}")/_test_env.sh"
+
 # Guard against the regression reported in issue #82:
 #   session-end `git pull --rebase && git push` at
 #   lib/harness.sh fails every retry when the target repo
@@ -11,11 +14,6 @@ set -euo pipefail
 #   the hook-suppression mechanism end-to-end, and pin the
 #   park-push retry loop both structurally and behaviorally.
 
-# Isolate from host gitconfig (signing keys, hooks, templates).
-# This test exercises rebase/push mechanics, not signing.
-export GIT_CONFIG_GLOBAL=/dev/null
-export GIT_CONFIG_SYSTEM=/dev/null
-
 PASS=0
 FAIL=0
 TMPDIR=$(mktemp -d)