Module capture 

Passive console and network capture for the MCP server.

The MCP server keeps one CDP WebSocket open for its lifetime, and CDP pushes Runtime.* / Log.* / Network.* events to any attached session that has those domains enabled. This module keeps one long-lived flat session per touched tab (any tab a tool call has routed to), enables the domains once, and routes the pushed events into bounded per-tab ring buffers that browser_console_messages / browser_network_requests read on demand.

This is the sanctioned exception to the “no idle work” rule in docs/specs/boundaries.md: nothing here polls or wakes on a timer. The only background task blocks on the event channel and does a mutex push per event; when the browser is quiet, it is parked.

Lifecycle: state for a tab is dropped when the tab is closed through the MCP server (forget), when the browser detaches the session (Target.detachedFromTarget), when the renderer crashes (Inspector.targetCrashed), and wholesale on browser_select (reset) or when the socket closes. Nothing in here ever returns TabHung / TabCrashed: attach failures are swallowed and retried on the next touch, so the recover-once flows elsewhere are unaffected.

Firefox (WebDriver BiDi) uses the same hub with a different ingress: one global session.subscribe per backend for log.entryAdded, network.beforeRequestSent / responseCompleted / fetchError, and browsingContext.navigationStarted / contextDestroyed, routed by the browsing-context id, which is the target id. Response bodies are not available on BiDi (no getResponseBody equivalent without browser-side retention), so browser_network_body stays Chromium-only.

Opt-out: BROWSER_CONTROL_CAPTURE=0 (or false) disables attachment entirely on both engines. Runtime.enable is observable by some anti-bot scripts, and a user logging into such a site through browser_show may prefer the server not to touch their tabs.

Structs

BodyResult

Result of a body fetch.

CaptureHub

The capture hub. Cheap to clone via Arc on ServerState.

ConsoleEntry

One captured console line.

ConsoleQuery

Filters for read_console.

ConsoleReport

Result of a console read.

NetworkEntry

One captured network request.

NetworkQuery

Filters for read_network.

NetworkReport

Result of a network read.

Enums

Level

NetState

StatusFilter

Constants

BIDI_NO_BODIES_HINT

Agent-facing explanation for browser_network_body on Firefox.

BODY_DEFAULT_MAX

Default cap for browser_network_body.

BODY_HARD_MAX

Hard cap for browser_network_body, aligned with browser_curl.

CONSOLE_CAP

Console entries kept per tab.

CONSOLE_TEXT_CAP

Bytes of rendered text kept per console entry.

NETWORK_CAP

Network entries kept per tab.

TOUCH_WAIT

How long a reader (or browser_navigate) waits for an in-flight attach.

URL_CAP

Bytes of URL kept per entry.

Functions

fmt_iso_ms

Epoch milliseconds → YYYY-MM-DDTHH:MM:SS.mmmZ.

format_console_line

One console entry as a single text line (no page separator).

format_console_text

Render a console report as text with -- page: <url> -- separators.

format_network_line

One network entry as a single text line.

format_network_text

Render a network report as text.

render_bidi_remote_value

Render a BiDi script.RemoteValue for console output.

render_remote_object

Render a Runtime.RemoteObject the way DevTools’ console preview does, without any round trip: primitives verbatim, objects from their preview, everything else by description.