Auto-detect local Chrome CDP on port 9222 before falling to Playwright Chromium

[iRonin]

Problem

When a user has Chrome running with --remote-debugging-port=9222, the agent's browser_navigate tool still falls through to launching a separate headless Chromium instance via Playwright (--session mode). This wastes time, resources, and ignores the user's live browser — which may have logged-in sessions, specific tabs open, etc.

The /browser connect command already knows how to detect and connect to Chrome on port 9222 (cli.py lines 5203-5213), but this logic lives exclusively in the CLI and is not available to the agent's browser tool.

Solution

Add _auto_detect_local_chrome() to tools/browser_tool.py that:

1. Probes localhost:9222 for a listening socket (1s timeout)
2. If open, fetches /json/version and resolves the WebSocket debugger URL
3. Returns the ws://... URL, or empty string if Chrome isn't running

Wire this into _get_session_info() as a step between 'no cloud provider configured' and 'launch headless Chromium via Playwright'.

Priority chain

1. BROWSER_CDP_URL env var (explicit, e.g. /browser connect)
2. config.yaml → browser.cdp_url (persistent fallback)
3. Auto-detect Chrome on port 9222 (NEW)
4. Cloud browser provider (Browserbase, Browser-Use)
5. Local headless Chromium launch (--session)

Testing

• Manual: python3 -c 'from tools.browser_tool import _auto_detect_local_chrome; print(_auto_detect_local_chrome())' returns ws://localhost:9222/devtools/browser/... when Chrome is running
• Unit tests: mock socket probe, test resolution path
• Integration: browser_navigate connects to live Chrome without needing /browser connect

Files changed

• tools/browser_tool.py: new _auto_detect_local_chrome(), updated _get_session_info()
• Also synced _get_cdp_override() config.yaml fallback (was in installed version, missing from upstream)

[GottZ]

This was generated by AI during triage.

Summary

Two PRs address #6780 with materially identical diffs: both probe localhost:9222, create a CDP session when detected, and suppress AGENT_BROWSER_SOCKET_DIR in CDP mode. The implementation directly targets the reported fallback behavior, but silent attachment to a live browser conflicts with the repository's documented opt-in CDP consent boundary.

Related pull requests

• feat(browser): auto-detect local Chrome CDP on port 9222 #6781 best fix — (+37/-2) — partial fix; keep open for rework, not merge as-is: the diff implements localhost:9222 detection and avoids the CDP socket-directory path, directly addressing the reported cause. The contributor keep_open review on feat(browser): auto-detect local Chrome CDP on port 9222 #6781 must govern the rework: silent attachment can expose authenticated tabs, so detection should provide a non-attaching hint or otherwise preserve explicit consent, and the socket-directory change needs focused reproduction and tests.
• feat(browser): auto-detect local Chrome CDP on port 9222 #8483 [closed] partial — (+37/-2) — partial fix; closed duplicate of feat(browser): auto-detect local Chrome CDP on port 9222 #6781: its diff is materially identical, including silent localhost:9222 attachment and the untested AGENT_BROWSER_SOCKET_DIR change. It remains relevant as confirmation of the duplicate implementation, but the contributor explicitly closed it to consolidate review on feat(browser): auto-detect local Chrome CDP on port 9222 #6781.

Duplicates

#8483 is a material duplicate of #6781; both contain the same 37-line addition and 2-line deletion implementing the same auto-detection and socket-directory behavior.

Suggested consolidation

Consolidate on #6781 as the verify-selected best-fix PR, but do not merge it as-is: retain explicit CDP opt-in by re-scoping automatic detection to a visible non-attaching hint, or explicitly resolve the contributor's consent-boundary objection, and add focused coverage for the socket-directory behavior. Keep #8483 closed as a duplicate of #6781.

Complex graph

flowchart LR
    classDef open fill:#dbeafe,stroke:#1d4ed8,color:#1e3a8a
    classDef merged fill:#dcfce7,stroke:#15803d,color:#14532d
    classDef closed fill:#e5e7eb,stroke:#6b7280,color:#1f2937
    classDef unverified fill:#f3f4f6,stroke:#9ca3af,color:#374151
    classDef best stroke-width:3px,stroke:#b45309
    classDef target stroke-width:3px,stroke:#4338ca
    I6780(["issue #6780 (open)"])
    subgraph Dup6781 ["PRs duplicating each other"]
        P6781["PR #6781 (open)"]
        P8483["PR #8483 (closed)"]
    end
    P6781 -->|best fix| I6780
    P8483 -.->|partial| I6780
    class I6780 open
    class I6780 target
    class P6781 open
    class P8483 closed
    class P6781 best
    click I6780 "https://github.com/NousResearch/hermes-agent/issues/6780"
    click P6781 "https://github.com/NousResearch/hermes-agent/pull/6781"
    click P8483 "https://github.com/NousResearch/hermes-agent/pull/8483"

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Graph: solid arrow = fixes / best fix, dashed arrow = partial or unverified (see edge label); boxed group = PRs duplicating each other; amber border = best fix; indigo border = target; gray node = closed or no verify verdict yet (state tag in the node label).

Cross-PR triage: Reviewed 2 pull requests and 1 issue in this complex. Each diff was read against this issue; Assessment working set: 6 kB of PR diffs, 4 kB of issue/PR text, 2 kB of discussion (3 comments), 4 verify verdicts. verdicts reflect diff content, not PR titles. Part of an automated triage batch.