diff --git a/.changeset/patch-reclaim-sandbox-rootless-eacces.md b/.changeset/patch-reclaim-sandbox-rootless-eacces.md
new file mode 100644
index 00000000000..960913d147a
--- /dev/null
+++ b/.changeset/patch-reclaim-sandbox-rootless-eacces.md
@@ -0,0 +1,5 @@
+---
+"gh-aw": patch
+---
+
+Reclaim root-owned `/tmp/gh-aw/sandbox` before AWF `writeConfigs()` to prevent `EACCES: mkdir /tmp/gh-aw/sandbox/firewall/logs` on runners with rootless-container residue.
diff --git a/actions/setup/sh/create_gh_aw_tmp_dir.sh b/actions/setup/sh/create_gh_aw_tmp_dir.sh
index bd7c0a92aeb..1b96db8fdfc 100755
--- a/actions/setup/sh/create_gh_aw_tmp_dir.sh
+++ b/actions/setup/sh/create_gh_aw_tmp_dir.sh
@@ -1,5 +1,24 @@
 #!/usr/bin/env bash
 set +o histexpand
+
+# Reclaim /tmp/gh-aw/sandbox if it is not writable by the current user (e.g. root-owned, left by
+# a prior rootless container run on the same runner).  A root-owned sandbox causes AWF's
+# writeConfigs() to fail with EACCES when it tries to mkdir /tmp/gh-aw/sandbox/firewall/logs —
+# killing the run before the agent is ever invoked.  The chmod-based fallback in AWF also fails
+# Permission denied for the same reason, so the only reliable fix is to remove and recreate the
+# tree here, before AWF starts.
+sandbox_dir="/tmp/gh-aw/sandbox"
+if [ -d "${sandbox_dir}" ] && ! [ -w "${sandbox_dir}" ]; then
+  echo "[WARN] ${sandbox_dir} is not writable by the current user (uid $(id -u)); reclaiming before AWF starts..."
+  if sudo rm -rf "${sandbox_dir}" 2>/dev/null; then
+    echo "Removed stale non-writable ${sandbox_dir} via sudo"
+  elif rm -rf "${sandbox_dir}" 2>/dev/null; then
+    echo "Removed stale ${sandbox_dir}"
+  else
+    echo "[WARN] Failed to remove ${sandbox_dir}; AWF writeConfigs() may fail with EACCES" >&2
+  fi
+fi
+
 mkdir -p /tmp/gh-aw/agent
 mkdir -p /tmp/gh-aw/sandbox/agent/logs
 echo "Created /tmp/gh-aw/agent directory for agentic workflow temporary files"
diff --git a/actions/setup/sh/create_gh_aw_tmp_dir_test.sh b/actions/setup/sh/create_gh_aw_tmp_dir_test.sh
new file mode 100644
index 00000000000..b4d2fb3fd0d
--- /dev/null
+++ b/actions/setup/sh/create_gh_aw_tmp_dir_test.sh
@@ -0,0 +1,115 @@
+#!/usr/bin/env bash
+set +o histexpand
+
+# Test script for create_gh_aw_tmp_dir.sh
+# Run: bash create_gh_aw_tmp_dir_test.sh
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+SCRIPT="${SCRIPT_DIR}/create_gh_aw_tmp_dir.sh"
+
+TESTS_PASSED=0
+TESTS_FAILED=0
+
+assert() {
+  local name="$1"
+  local condition="$2"
+  if eval "${condition}" 2>/dev/null; then
+    echo "  ✓ ${name}"
+    TESTS_PASSED=$((TESTS_PASSED + 1))
+  else
+    echo "  ✗ ${name}"
+    TESTS_FAILED=$((TESTS_FAILED + 1))
+  fi
+}
+
+echo "Testing create_gh_aw_tmp_dir.sh"
+echo ""
+
+# ── Test 1: Script syntax is valid ──────────────────────────────────────────
+echo "Test 1: Script syntax is valid"
+assert "script passes bash -n" "bash -n '${SCRIPT}'"
+echo ""
+
+# ── Test 2: Creates expected directories when they don't exist ───────────────
+echo "Test 2: Creates expected directories from scratch"
+set +e
+OUTPUT="$(bash "${SCRIPT}" 2>&1)"
+EXIT_CODE=$?
+set -e
+assert "script exits 0" "[ '${EXIT_CODE}' = '0' ]"
+assert "/tmp/gh-aw/agent directory created" "[ -d /tmp/gh-aw/agent ]"
+assert "/tmp/gh-aw/sandbox/agent/logs directory created" "[ -d /tmp/gh-aw/sandbox/agent/logs ]"
+assert "output mentions created directory" "echo '${OUTPUT}' | grep -q 'Created /tmp/gh-aw/agent directory'"
+echo ""
+
+# ── Test 3: Preserves sandbox owned by current user ──────────────────────────
+echo "Test 3: Preserves sandbox directory when owned by current user"
+mkdir -p /tmp/gh-aw/sandbox
+MARKER_FILE="/tmp/gh-aw/sandbox/.owner-check-marker"
+touch "${MARKER_FILE}"
+set +e
+OUTPUT="$(bash "${SCRIPT}" 2>&1)"
+EXIT_CODE=$?
+set -e
+assert "script exits 0 with existing user-owned sandbox" "[ '${EXIT_CODE}' = '0' ]"
+assert "/tmp/gh-aw/sandbox/agent/logs created" "[ -d /tmp/gh-aw/sandbox/agent/logs ]"
+# Marker should still be present — sandbox was NOT removed since we own it and it is writable
+assert "user-owned sandbox is preserved (marker still present)" "[ -f '${MARKER_FILE}' ]"
+assert "no WARN about reclaiming in output" "! echo '${OUTPUT}' | grep -q 'reclaiming'"
+rm -f "${MARKER_FILE}"
+echo ""
+
+# ── Test 4: Reclaims sandbox that is not writable by the current user ─────────
+# We simulate a non-writable sandbox by creating a read-only directory.  A fake sudo records
+# its arguments and performs the actual removal (rm -rf works here because the *parent*
+# /tmp/gh-aw is writable by the current user even when the child has mode 555).
+echo "Test 4: Reclaims sandbox that is not writable (simulated)"
+mkdir -p /tmp/gh-aw/sandbox
+MARKER_FILE="/tmp/gh-aw/sandbox/.non-writable-marker"
+touch "${MARKER_FILE}"
+# Make the sandbox not writable by the current user
+chmod 555 /tmp/gh-aw/sandbox
+
+FAKE_BIN="$(mktemp -d)"
+SUDO_ARGS_FILE="${FAKE_BIN}/sudo_args"
+
+# Fake sudo: record the full argument list, then execute the real command.
+# Before running rm -rf, fix permissions on mode-555 directories so the
+# removal succeeds (mimicking what root privilege provides in production).
+cat > "${FAKE_BIN}/sudo" <<EOF
+#!/usr/bin/env bash
+echo "\$*" >> "${SUDO_ARGS_FILE}"
+# Fix permissions on any non-writable subdirectories before removal
+# (root bypasses DAC checks; simulate that by chmod-ing first)
+for arg in "\$@"; do
+  if [ -d "\${arg}" ]; then
+    find "\${arg}" -type d -not -perm -u+w -exec chmod u+w {} + 2>/dev/null || true
+  fi
+done
+exec "\$@"
+EOF
+chmod +x "${FAKE_BIN}/sudo"
+
+set +e
+OUTPUT="$(PATH="${FAKE_BIN}:${PATH}" bash "${SCRIPT}" 2>&1)"
+EXIT_CODE=$?
+set -e
+
+assert "script exits 0 with non-writable sandbox" "[ '${EXIT_CODE}' = '0' ]"
+assert "sudo was invoked" "[ -f '${SUDO_ARGS_FILE}' ]"
+assert "sudo was called with rm -rf and the sandbox path" "grep -q 'rm -rf.*sandbox' '${SUDO_ARGS_FILE}'"
+assert "WARN about reclaiming appears in output" "echo '${OUTPUT}' | grep -q 'reclaiming'"
+assert "/tmp/gh-aw/sandbox/agent/logs recreated after removal" "[ -d /tmp/gh-aw/sandbox/agent/logs ]"
+assert "non-writable sandbox was removed (marker gone)" "[ ! -f '${MARKER_FILE}' ]"
+
+rm -rf "${FAKE_BIN}"
+echo ""
+
+# ── Summary ──────────────────────────────────────────────────────────────────
+echo "Results: ${TESTS_PASSED} passed, ${TESTS_FAILED} failed"
+if [ "${TESTS_FAILED}" -gt 0 ]; then
+  exit 1
+fi
+