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Reference

Error reference

Errors are { ok: false, error: { code, message } } all the way through, surfaced to MCP clients as isError with CODE: message.

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They are recoverable signals, and each implies a different next move. Two design choices show up repeatedly: failures carry the fix in the message, and a failed tool call never crashes a run.

Connection

Code Origin Meaning and next move
EXTENSION_OFFLINE Daemon No live browser link. Open the browser, or pair. Retrying will not help
DAEMON_UNREACHABLE RemoteBridge The daemon died mid-call

Targeting a page

Code Origin Meaning and next move
TAB_UNREACHABLE Extension The page refuses content scripts, or one was just injected. Navigate to an http(s) page, or re-snapshot
NO_ACTIVE_TAB Extension No focused tab in the current window
TARGET_NOT_FOUND Content script Nothing matched. The page changed — take a fresh snapshot
INVALID_TARGET Content script A target with neither selector nor text. role/nth only narrow
DEBUGGER_UNAVAILABLE Extension Chrome's debugger could not attach — usually DevTools is open on that tab. Close it, or use page_clickElement
CAPTCHA_NOT_FOUND Extension No known captcha widget, so whatever is blocking the run is something else

Input and dispatch

Code Origin Meaning and next move
INVALID_INPUT Dispatch zod rejected the input; the message names the field
UNSUPPORTED Action e.g. a non-http(s) URL
TIMEOUT Link or action A wait expired, or the extension did not answer in the window for that action
ACTION_FAILED Action execute() threw — e.g. back with no history
PICK_CANCELLED Content script The user dismissed A-Eye without pointing at anything. Terminal — ask in words rather than asking them to point again
UNKNOWN_ACTION Registry / daemon Tool-registry skew, or a reserved action reached from outside

Runs and sessions

Code Origin Meaning and next move
RUN_IN_PROGRESS AgentSession One instruction at a time per tab session; other sessions are unaffected
RUN_LIMIT AgentSession Too many sessions running at once — maxConcurrentRuns, default 3, ceiling 8
SESSION_LIMIT Extension Eight tab sessions are already open
SESSION_TAB_CLOSED Extension Every tab this conversation was working in has been closed
TAB_IN_USE Extension That tab belongs to another Browsentic conversation
RUN_INACTIVE AgentSession The run was cancelled while a tool call was in flight
SKILL_UNKNOWN AgentSession The attached agent skill's id no longer resolves — the file moved, changed agents, or outgrew the size cap. Reopen the / picker and choose again

Agents

Code Origin Meaning and next move
AGENT_MISSING Runner The chosen agent's binary is not on the daemon's PATH. Set agents.<name>.bin to an absolute path
AGENT_NEEDS_PERMISSION Runner Antigravity has no rule allowing Browsentic's MCP tools. browsentic-mcp agent setup antigravity
AGENT_UNUSABLE Runner The CLI is present but cannot run — usually too old for the flags Browsentic passes

Guardrails

Code Origin Meaning and next move
DECLINED Approval gate The user said no. Final — do not seek another route to the same effect
BLOCKED Policy A deny rule matched, or a confirm with nobody to answer it. The message names why. Guide
SECRET_NOT_RELEASABLE Extension A sealed secret placeholder was passed somewhere it cannot be released. Only page_fillInput's value and page_typeText's text release one
SECRET_EXPIRED Extension That placeholder is no longer held — it aged out, or it was read in an earlier browser session. Read the value again
MAPPING_READ_ONLY Mapping gate A mapping run may only call the 14 read-only actions (plus page_clickElement when allowClicks is on)
MAPPING_OFF_SITE Mapping gate Navigation must be an absolute URL on the mapped origin — back and forward included
MAPPING_BUDGET Mapping gate The page or screenshot budget is spent
MAPPING_TAB_CHANGED Mapping gate The tab the run was pinned to is gone

See also