feat(security): Harden Docker browser container chromium flags (#23889) (#31504)

* Gateway: honor OPENCLAW_GATEWAY_URL override for remote/local calls

* Agents: fix sandbox sessionKey usage for PI embedded subagent calls

* Sandbox: tighten browser container Chromium runtime flags

* fix: add sandbox browser defaults for container hardening

* docs: expand sandbox browser default flags list

* fix: make sandbox browser flags optional and preserve gateway env auth overrides

* docs: scope PR 31504 changelog entry

* style: format gateway call override handling

* fix: dedupe sandbox browser chrome args

* fix: preserve remote tls fingerprint for env gateway override

* fix: enforce auth for env gateway URL override

* chore: document gateway override auth security expectations

docs/gateway/configuration-reference.md

@@ -1177,6 +1177,35 @@ noVNC observer access uses VNC auth by default and OpenClaw emits a short-lived
 - `network` defaults to `openclaw-sandbox-browser` (dedicated bridge network). Set to `bridge` only when you explicitly want global bridge connectivity.
 - `cdpSourceRange` optionally restricts CDP ingress at the container edge to a CIDR range (for example `172.21.0.1/32`).
 - `sandbox.browser.binds` mounts additional host directories into the sandbox browser container only. When set (including `[]`), it replaces `docker.binds` for the browser container.
+- Launch defaults are defined in `scripts/sandbox-browser-entrypoint.sh` and tuned for container hosts:
+  - `--remote-debugging-address=127.0.0.1`
+  - `--remote-debugging-port=<derived from OPENCLAW_BROWSER_CDP_PORT>`
+  - `--user-data-dir=${HOME}/.chrome`
+  - `--no-first-run`
+  - `--no-default-browser-check`
+  - `--disable-3d-apis`
+  - `--disable-gpu`
+  - `--disable-software-rasterizer`
+  - `--disable-dev-shm-usage`
+  - `--disable-background-networking`
+  - `--disable-features=TranslateUI`
+  - `--disable-breakpad`
+  - `--disable-crash-reporter`
+  - `--renderer-process-limit=2`
+  - `--no-zygote`
+  - `--metrics-recording-only`
+  - `--disable-extensions` (default enabled)
+  - `--disable-3d-apis`, `--disable-software-rasterizer`, and `--disable-gpu` are
+    enabled by default and can be disabled with
+    `OPENCLAW_BROWSER_DISABLE_GRAPHICS_FLAGS=0` if WebGL/3D usage requires it.
+  - `OPENCLAW_BROWSER_DISABLE_EXTENSIONS=0` re-enables extensions if your workflow
+    depends on them.
+  - `--renderer-process-limit=2` can be changed with
+    `OPENCLAW_BROWSER_RENDERER_PROCESS_LIMIT=<N>`; set `0` to use Chromium's
+    default process limit.
+  - plus `--no-sandbox` and `--disable-setuid-sandbox` when `noSandbox` is enabled.
+  - Defaults are the container image baseline; use a custom browser image with a custom
+    entrypoint to change container defaults.
 
 </Accordion>
 
@@ -2251,6 +2280,7 @@ See [Plugins](/tools/plugin).
     color: "#FF4500",
     // headless: false,
     // noSandbox: false,
+    // extraArgs: [],
     // executablePath: "/Applications/Brave Browser.app/Contents/MacOS/Brave Browser",
     // attachOnly: false,
   },
@@ -2265,6 +2295,8 @@ See [Plugins](/tools/plugin).
 - Remote profiles are attach-only (start/stop/reset disabled).
 - Auto-detect order: default browser if Chromium-based → Chrome → Brave → Edge → Chromium → Chrome Canary.
 - Control service: loopback only (port derived from `gateway.port`, default `18791`).
+- `extraArgs` appends extra launch flags to local Chromium startup (for example
+  `--disable-gpu`, window sizing, or debug flags).
 
 ---