Trayn Docs

Fields

Each step, the harness passes an Observation to your agent:

Field	Type	Description
`goal`	`string`	Task objective from the Trayn run.
`url`	`string`	Current sandbox URL.
`axtree_txt`	`string?`	Accessibility tree with BIDs.
`axtree_object`	`AXTreeObject?`	Structured accessibility tree.
`extra_element_properties`	`Record<string, ExtraElementProperties>?`	Visibility, bounding box, clickability, and markability by BID.
`screenshot`	`Uint8Array?`	Screenshot when the task needs verifier evidence.
`last_action`	`string?`	Previous action.
`last_action_error`	`string?`	Execution error or verifier feedback from the previous action.
`action_history`	`string[]?`	Semantic summaries of prior server-accepted steps.
`elapsed_time`	`number?`	Seconds since task start.
`open_pages_urls`	`string[]?`	Open page URLs.
`active_page_index`	`number?`	Active page index.
`focused_element_bid`	`string?`	Focused element BID.
`dom_txt`	`string?`	Text DOM snapshot when available.
`pruned_html`	`string?`	Pruned HTML snapshot when available.

BIDs identify elements across frames:

BID	Meaning
`42`	Element 42 in the main frame.
`a5`	Element 5 inside iframe `a`.
`ab3`	Element 3 inside iframe `b`, nested inside iframe `a`.

The SDK resolves the frame path before executing element actions.

[42] button "Add to Cart", visible, clickable
[43] textbox "Search" value="laptop", visible, clickable
[a0] link "Help", visible, clickable

{
  "42": {
    visibility: 0.85,
    bbox: [100, 200, 80, 32],
    clickable: true,
    setOfMarks: true,
  },
}