CDP support matrix

The Frame Agent emulates a subset of the Chrome DevTools Protocol against the real DOM. It registers exactly the domains and methods below; every other command returns a CDP error. The lists here are the cdp.register(...) calls in src/frame/index.ts — not the wider CDP surface a real browser exposes.

Browser- and Target-level registry methods (Target.getTargets, Target.attachToTarget, Target.setAutoAttach, Browser.getVersion, …) are answered by the Relay, not the Frame Agent. They read the Relay's own session and Target state and never reach the iframe. See the Relay reference for that list and the flat-session protocol for how Clients address Targets.

Implemented domains

Accessibility

Method	Behavior
disable	No-op.
enable	No-op.
getFullAXTree	Full accessibility tree, honoring depth.
getPartialAXTree	Subtree at a node; fetchRelatives defaults to true.
getRootAXNode	The root AX node.
getChildAXNodes	Child AX nodes of a given AX node id.
getAXNodeAndAncestors	A node and its ancestor chain; requires a nodeId or backendNodeId.
queryAXTree	AX nodes under a target, filtered by accessibleName and role.

See Accessibility tree for how the tree is computed and where it diverges from Chromium.

Animation

Method	Behavior
enable	No-op.

Autofill

Method	Behavior
setAddresses	No-op.

CSS

Method	Behavior
disable	No-op.
enable	No-op.
getComputedStyleForNode	Computed style for a node as { name, value } pairs.

DOM

The DOM domain unifies nodeId with backendNodeId, so either resolves the same node.

Method	Behavior
describeNode	Describe a node by backendNodeId/nodeId (defaults to node 1).
discardSearchResults	Drop a stored search by searchId.
enable	No-op.
focus	Focus an HTMLElement by node id.
getAttributes	Flat [name, value, …] attribute list for an element.
getBoxModel	Box model from getBoundingClientRect (content/padding/border/margin share the rect).
getContentQuads	Single content quad derived from the box model.
getDocument	Document root, honoring depth (defaults to 1).
getOuterHTML	outerHTML of an element or document.
getSearchResults	Slice stored search node ids by fromIndex/toIndex.
performSearch	Match by CSS selector, falling back to case-insensitive text search; returns a searchId.
pushNodesByBackendIdsToFrontend	Echo the requested backendNodeIds as node ids.
querySelector	First match under a root node (or document); 0 when none.
querySelectorAll	All matches under a root node (or document).
requestChildNodes	Emit DOM.setChildNodes for a node's children at depth (defaults to 1).
resolveNode	Wrap a node id as a backend:<id> remote object.
scrollIntoViewIfNeeded	Scroll the element to block/inline center.

Input

Method	Behavior
dispatchKeyEvent	Dispatch keydown/keyup; Backspace deletes backward and text is inserted into the active element.
dispatchMouseEvent	Resolve the target via elementFromPoint, then dispatch move/over/enter, down, up + synthetic click/dblclick, or wheel + scroll.
insertText	Insert text into the active input, textarea, or contenteditable element.

WARNING

dispatchMouseEvent resolves the target with document.elementFromPoint. A below-the-fold element must be scrolled into view first, or the click silently misses. See Drive with agent-browser.

Network

Method	Behavior
emulateNetworkConditionsByRule	Returns synthetic ruleIds for the matched conditions; applies no real throttling.
overrideNetworkState	No-op.
setBlockedURLs	No-op.

Page

Method	Behavior
addScriptToEvaluateOnNewDocument	Returns a synthetic identifier; no script is installed.
getFrameTree	Single-frame tree for the embedded document.
getResourceTree	Frame tree with an empty resources list.
navigate	Same-origin only. Navigating outside the embedded app's origin throws.

INFO

navigate sets location.href for a same-origin URL. A cross-origin URL throws — the embedded app's origin is the navigation boundary. Reloads and same-origin navigations keep the same targetId; see Target lifecycle.

Runtime

Method	Behavior
addBinding	No-op.
callFunctionOn	Indirect-eval a function declaration against a backend:<id> object or window; supports awaitPromise.
enable	Emits Runtime.executionContextCreated (context id 1, name top) and flushes queued events.
evaluate	Indirect-eval an expression; supports awaitPromise.
runIfWaitingForDebugger	No-op.

Runtime events (including Runtime.consoleAPICalled from the console bridge) are queued until Runtime.enable, capped at ~200, then flushed. The single execution context has id 1 and name top.

Storage

Method	Behavior
getStorageKey	Returns the document origin as the storageKey.

No-op methods

These are registered so domain enables and setup calls succeed, but they have no effect:

• Animation.enable
• Autofill.setAddresses
• Network.overrideNetworkState
• Network.setBlockedURLs
• Runtime.addBinding
• Runtime.runIfWaitingForDebugger

The disable/enable handlers on Accessibility and CSS, and DOM.enable, are also no-ops; the Frame Agent holds no per-domain state to toggle. (DOM.disable is not registered.)

Unknown methods

A method the Frame Agent has not registered returns a CDP error with code -32000 (CDP_SERVER_ERROR) and message Method not found: <method>. Commands in flight when the document dies fail with the same code. See the Frame reference for the full request path and the protocol reference for the error constants.

Intentionally unsupported

Page JavaScript cannot provide these capabilities, so they are out of scope by design — not pending work:

• Screenshots
• PDF generation
• File uploads
• Drag-and-drop
• Dialogs
• Real network interception

The compatibility bar is agent-browser's support matrix: AX-tree snapshots, semantic locators, click/fill/type, eval, waits, console, and SPA history. Raw Playwright over connectOverCDP is best-effort, not promised — it exercises commands outside this matrix and will hit the unknown-method error above.