fix(browser): set AGENT_BROWSER_ARGS for --no-sandbox bypass

[pasevin]

Problem

The existing AppArmor/root sandbox detection (commit 74c1b946e, issue #15765) sets AGENT_BROWSER_CHROME_FLAGS in the subprocess env when --no-sandbox is needed. AGENT_BROWSER_CHROME_FLAGS is not a variable that agent-browser reads — it is a Hermes-internal guard variable and is silently ignored by the binary.

agent-browser 0.26+ reads AGENT_BROWSER_ARGS (comma-separated) for Chrome launch flags. That variable was never being set by the auto-detection code.

Result: on Ubuntu 23.10+ and other AppArmor-restricted hosts (/proc/sys/kernel/apparmor_restrict_unprivileged_userns == 1), the detection fires correctly but Chrome still exits with:

FATAL: No usable sandbox! ... unprivileged user namespaces disabled

A secondary issue: _needs_sandbox_bypass was declared inside the AGENT_BROWSER_CHROME_FLAGS guard, leaving it uninitialized when that guard is skipped. cmd_parts was also constructed before browser_env existed.

Fix

• Set AGENT_BROWSER_ARGS=--no-sandbox,--disable-dev-shm-usage when sandbox bypass is detected (alongside AGENT_BROWSER_CHROME_FLAGS which is retained as a Hermes-internal skip guard for backward compat).
• Move _needs_sandbox_bypass = False outside the AGENT_BROWSER_CHROME_FLAGS guard.
• Move cmd_parts construction inside the try block where browser_env is available.

Verification

Tested on Ubuntu 24.04 with apparmor_restrict_unprivileged_userns = 1, no system Chrome, Playwright Chromium at ~/.cache/ms-playwright. After the fix, browser_navigate succeeds using the native agent-browser daemon path without any CDP workaround.

The agent-browser binary itself correctly inherits AGENT_BROWSER_ARGS from the caller's environment into the daemon child — confirmed via /proc/<pid>/environ on a clean reproduction. The entire issue was the wrong variable name on the Hermes side.

[pasevin]

Looks like the ruff + ty diff check failure is unrelated to the code changes — it's a GitHub Actions permissions issue where fork PRs can't post comments back to the upstream repo (Resource not accessible by integration). The actual lint step passed cleanly, as confirmed by ruff enforcement (blocking) being green. Happy to rebase or squash if that helps the merge.

[alt-glitch]

Competing with #20014, #21659, #23517 for the same fix (issue #23496). All address AGENT_BROWSER_CHROME_FLAGS → AGENT_BROWSER_ARGS env var rename.

[pasevin]

Sorry, should have looked more before submitting. Feel free to close if redundant!

[teknium1]

This looks implemented on current main by the later browser sandbox-bypass fix. This is an automated hermes-sweeper review.

Evidence:

• tools/browser_tool.py now injects AGENT_BROWSER_ARGS=--no-sandbox,--disable-dev-shm-usage when root/AppArmor sandbox bypass is needed, while respecting pre-set AGENT_BROWSER_ARGS or legacy AGENT_BROWSER_CHROME_FLAGS.
• Commit 8ed2ef6f46e9642acfba57b4b8da893a574ecfd0 changed the bypass from the unused AGENT_BROWSER_CHROME_FLAGS variable to the agent-browser-consumed AGENT_BROWSER_ARGS variable.
• Commit 4695d2716f60da89152bdc9dfa7d96e54ea7c22e added the pre-set AGENT_BROWSER_ARGS guard and documentation.
• The fix is contained in v2026.5.16 and later tags.

Thanks for the clean report and verification notes. The maintainer thread also called out that this PR was competing with the same AGENT_BROWSER_ARGS fix from other PRs, so closing this as redundant with main.