diff --git a/backend/tests/test_compose_nginx_image_pin.py b/backend/tests/test_compose_nginx_image_pin.py
new file mode 100644
index 0000000000..f83388c5ec
--- /dev/null
+++ b/backend/tests/test_compose_nginx_image_pin.py
@@ -0,0 +1,48 @@
+"""Regression test pinning the nginx image tag in the shipped compose files.
+
+Both compose files deployed ``image: nginx:alpine`` — a floating tag. When the
+``nginx:alpine`` alias moved to the 1.31.3 alpine build (musl 1.2.6), nginx's
+pid-file ``pwrite()`` started issuing the ``pwritev2(RWF_NOAPPEND)`` syscall,
+which the default seccomp profile of older Docker releases (and EOL kernels
+such as CentOS 7) does not allowlist. The master then dies with ``pwrite()
+"/run/nginx.pid" failed (1: Operation not permitted)`` and the container
+restart-loops, so ``make docker-start`` / ``make up`` never become healthy
+(#7615; upstream nginx/docker-nginx#1059 — the image cannot fix this, only a
+pinned pre-musl-1.2.6 build or a host upgrade helps).
+
+This test pins the exact-tag policy so the alias (or any other floating tag)
+cannot silently return.
+"""
+
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+import yaml
+
+REPO_ROOT = Path(__file__).resolve().parents[2]
+COMPOSE_PATHS = {
+    "prod": REPO_ROOT / "docker" / "docker-compose.yaml",
+    "dev": REPO_ROOT / "docker" / "docker-compose-dev.yaml",
+}
+
+# An exact tag carries a full major.minor.patch; `alpine` / `latest` /
+# `1.31` style tags float and can re-resolve to a broken build overnight.
+EXACT_TAG = re.compile(r"^[^:]+:\d+\.\d+\.\d+(-[a-z]+)?$")
+
+
+def test_nginx_image_is_pinned_to_an_exact_tag() -> None:
+    for name, compose_path in COMPOSE_PATHS.items():
+        compose = yaml.safe_load(compose_path.read_text(encoding="utf-8"))
+        image = (compose.get("services") or {}).get("nginx", {}).get("image")
+        assert isinstance(image, str) and image, f"{name}: nginx service must declare an image"
+        assert EXACT_TAG.match(image), f"{name}: nginx image {image!r} must pin an exact tag — a floating tag resolved to the musl-1.2.6 alpine build whose pwritev2 syscall older Docker seccomp profiles reject (#7615)"
+
+
+def test_both_compose_files_pin_the_same_nginx_image() -> None:
+    images = set()
+    for compose_path in COMPOSE_PATHS.values():
+        compose = yaml.safe_load(compose_path.read_text(encoding="utf-8"))
+        images.add((compose.get("services") or {}).get("nginx", {}).get("image"))
+    assert len(images) == 1, "prod and dev compose files must pin the same nginx image"
diff --git a/docker/docker-compose-dev.yaml b/docker/docker-compose-dev.yaml
index 422009db05..b3c2fecbc0 100644
--- a/docker/docker-compose-dev.yaml
+++ b/docker/docker-compose-dev.yaml
@@ -123,7 +123,13 @@ services:
   # ── Reverse Proxy ──────────────────────────────────────────────────────
   # Routes API traffic to gateway and (optionally) provisioner.
   nginx:
-    image: nginx:alpine
+    # Pinned tag, not `nginx:alpine`: from 1.31.3 the alpine builds ship musl
+    # 1.2.6, whose pwrite() issues pwritev2(RWF_NOAPPEND) — seccomp profiles
+    # on older Docker/EOL kernels reject that syscall and the master dies in a
+    # restart loop with `pwrite() "/run/nginx.pid" failed (1: Operation not
+    # permitted)` (#7615, nginx/docker-nginx#1059). 1.31.2 is the last musl
+    # 1.2.5 (pwrite64) alpine build. Keep in lockstep with docker-compose.yaml.
+    image: nginx:1.31.2-alpine
     container_name: deer-flow-nginx
     # Loopback-only by default; see the note in docker-compose.yaml. Override
     # with BIND_HOST when you deliberately need the dev stack reachable from
diff --git a/docker/docker-compose.yaml b/docker/docker-compose.yaml
index a474bed90d..54b77050d7 100644
--- a/docker/docker-compose.yaml
+++ b/docker/docker-compose.yaml
@@ -50,7 +50,13 @@ services:
 
   # ── Reverse Proxy ──────────────────────────────────────────────────────────
   nginx:
-    image: nginx:alpine
+    # Pinned tag, not `nginx:alpine`: from 1.31.3 the alpine builds ship musl
+    # 1.2.6, whose pwrite() issues pwritev2(RWF_NOAPPEND) — seccomp profiles
+    # on older Docker/EOL kernels reject that syscall and the master dies in a
+    # restart loop with `pwrite() "/run/nginx.pid" failed (1: Operation not
+    # permitted)` (#7615, nginx/docker-nginx#1059). 1.31.2 is the last musl
+    # 1.2.5 (pwrite64) alpine build.
+    image: nginx:1.31.2-alpine
     container_name: deer-flow-nginx
     # Loopback-only by default: DeerFlow's agent can execute commands, so the
     # documented default deployment is a local trusted environment. A bare