diff --git a/docs/usage.md b/docs/usage.md
index 3df6fa0a..dd9ff1ed 100644
--- a/docs/usage.md
+++ b/docs/usage.md
@@ -476,7 +476,7 @@ on subsequent fetches and SSE reconnects.
 **WARNING: This is a dangerous option that disables security protections. Use only if you understand the implications.**
 
 - **Purpose**: Controls whether Codex runs with sandbox protection
-- **Default**: Not set (uses `--full-auto` with sandbox protection)
+- **Default**: Not set (uses `--sandbox workspace-write` with sandbox protection)
 - **Values**:
   - `true` or `1`: Bypasses Codex sandbox and approvals (uses `--dangerously-bypass-approvals-and-sandbox`)
   - Any other value or unset: Uses safe mode with sandbox
diff --git a/hooks/loop-codex-stop-hook.sh b/hooks/loop-codex-stop-hook.sh
index d3051f9c..fed93095 100755
--- a/hooks/loop-codex-stop-hook.sh
+++ b/hooks/loop-codex-stop-hook.sh
@@ -1208,7 +1208,8 @@ if [[ -n "$CODEX_EXEC_EFFORT" ]]; then
     CODEX_EXEC_ARGS+=("-c" "model_reasoning_effort=${CODEX_EXEC_EFFORT}")
 fi
 
-CODEX_AUTO_FLAG="--full-auto"
+# Same sandbox the removed --full-auto flag selected (see scripts/ask-codex.sh)
+CODEX_AUTO_FLAG="--sandbox=workspace-write"
 if [[ "${HUMANIZE_CODEX_BYPASS_SANDBOX:-}" == "true" ]] || [[ "${HUMANIZE_CODEX_BYPASS_SANDBOX:-}" == "1" ]]; then
     CODEX_AUTO_FLAG="--dangerously-bypass-approvals-and-sandbox"
 fi
diff --git a/scripts/ask-codex.sh b/scripts/ask-codex.sh
index f16c6656..d12a136a 100755
--- a/scripts/ask-codex.sh
+++ b/scripts/ask-codex.sh
@@ -277,7 +277,9 @@ if [[ -n "$CODEX_EFFORT" ]]; then
 fi
 
 # Determine automation flag based on environment variable
-CODEX_AUTO_FLAG="--full-auto"
+# Newer Codex CLIs removed --full-auto. For `codex exec` it only selected the
+# workspace-write sandbox, which --sandbox provides on every supported version.
+CODEX_AUTO_FLAG="--sandbox=workspace-write"
 if [[ "${HUMANIZE_CODEX_BYPASS_SANDBOX:-}" == "true" ]] || [[ "${HUMANIZE_CODEX_BYPASS_SANDBOX:-}" == "1" ]]; then
     CODEX_AUTO_FLAG="--dangerously-bypass-approvals-and-sandbox"
 fi
diff --git a/tests/test-ask-codex.sh b/tests/test-ask-codex.sh
index a6c70215..0614eba5 100755
--- a/tests/test-ask-codex.sh
+++ b/tests/test-ask-codex.sh
@@ -325,6 +325,46 @@ else
 fi
 reset_mock
 
+# Test: default run selects the workspace-write sandbox without the removed --full-auto flag
+reset_mock
+export MOCK_CODEX_STDOUT="sandbox-flag-test"
+ASK_CODEX_ARGS_FILE="$TEST_DIR/ask-codex-sandbox-args.txt"
+export MOCK_CODEX_ARGS_FILE="$ASK_CODEX_ARGS_FILE"
+EXIT_CODE=0
+run_ask_codex "sandbox flag test" > /dev/null 2>&1 || EXIT_CODE=$?
+CAPTURED_ARGS="$(cat "$ASK_CODEX_ARGS_FILE" 2>/dev/null || true)"
+if [[ $EXIT_CODE -eq 0 ]] \
+    && echo "$CAPTURED_ARGS" | grep -qx -- '--sandbox=workspace-write' \
+    && ! echo "$CAPTURED_ARGS" | grep -qx -- '--full-auto'; then
+    pass "default run uses --sandbox=workspace-write instead of --full-auto"
+else
+    fail "default run uses --sandbox=workspace-write instead of --full-auto" \
+        "exec args include --sandbox=workspace-write and no --full-auto" \
+        "exit=$EXIT_CODE, args=$CAPTURED_ARGS"
+fi
+reset_mock
+
+# Test: HUMANIZE_CODEX_BYPASS_SANDBOX still replaces the sandbox flag
+reset_mock
+export MOCK_CODEX_STDOUT="bypass-flag-test"
+ASK_CODEX_ARGS_FILE="$TEST_DIR/ask-codex-bypass-args.txt"
+export MOCK_CODEX_ARGS_FILE="$ASK_CODEX_ARGS_FILE"
+export HUMANIZE_CODEX_BYPASS_SANDBOX="1"
+EXIT_CODE=0
+run_ask_codex "bypass flag test" > /dev/null 2>&1 || EXIT_CODE=$?
+unset HUMANIZE_CODEX_BYPASS_SANDBOX
+CAPTURED_ARGS="$(cat "$ASK_CODEX_ARGS_FILE" 2>/dev/null || true)"
+if [[ $EXIT_CODE -eq 0 ]] \
+    && echo "$CAPTURED_ARGS" | grep -qx -- '--dangerously-bypass-approvals-and-sandbox' \
+    && ! echo "$CAPTURED_ARGS" | grep -qx -- '--sandbox=workspace-write'; then
+    pass "HUMANIZE_CODEX_BYPASS_SANDBOX=1 replaces the sandbox flag"
+else
+    fail "HUMANIZE_CODEX_BYPASS_SANDBOX=1 replaces the sandbox flag" \
+        "exec args include --dangerously-bypass-approvals-and-sandbox only" \
+        "exit=$EXIT_CODE, args=$CAPTURED_ARGS"
+fi
+reset_mock
+
 # ========================================
 # Error Handling Tests
 # ========================================
diff --git a/tests/test-disable-nested-codex-hooks.sh b/tests/test-disable-nested-codex-hooks.sh
index a4f1388a..2b26322b 100755
--- a/tests/test-disable-nested-codex-hooks.sh
+++ b/tests/test-disable-nested-codex-hooks.sh
@@ -222,6 +222,14 @@ else
         "exec --disable hooks --disable plugin_hooks --disable codex_hooks" "$(cat "$TEST_DIR/impl.args" 2>/dev/null || echo missing)"
 fi
 
+if grep -q -- '--sandbox=workspace-write' "$TEST_DIR/impl.args" \
+    && ! grep -q -- '--full-auto' "$TEST_DIR/impl.args"; then
+    pass "implementation-phase stop hook uses --sandbox=workspace-write instead of --full-auto"
+else
+    fail "implementation-phase stop hook uses --sandbox=workspace-write instead of --full-auto" \
+        "--sandbox=workspace-write and no --full-auto" "$(cat "$TEST_DIR/impl.args" 2>/dev/null || echo missing)"
+fi
+
 REPO_REVIEW="$TEST_DIR/repo-review"
 setup_repo "$REPO_REVIEW"
 run_loop_hook "$REPO_REVIEW" "$TEST_DIR/review.args" "true"