Token-Budgeted Observation Delta (What Changed)

observation.serialize_observation renders one full frame of the UI — feeding it to a model every turn blows the very token budget that module was built to respect, and forces the model to re-read the whole screen just to spot the one new dialog. element_diff gives the stable-ID correspondence between two frames but stops at matched / added / removed element pairs — it does not render a compact, indexed, budget-capped delta the model can act on.

observation_delta is the missing serializer: it diffs the previous and current observation, classifies each matched element as changed (role / name / enabled / value / moved) or stable, and renders only the churn — + [i] role "name" (appeared) / - role "name" (vanished) / ~ [i] role "name" (fields) (changed) — added and changed first, stable dropped, capped at max_lines. The model sees what changed instead of the whole screen again.

Pure-stdlib over element dicts; reuses element_diff.match_elements for the overlap join and observation.observation_index for reading-order indexing. Imports no PySide6.

Headless API

from je_auto_control import delta_observation, delta_index, summarize_delta

summary = delta_observation(prev_elements, curr_elements, max_lines=40)
# + [12] dialog "Saved"
# ~ [4] button "Submit" (enabled)
# - button "Spinner"

delta = delta_index(prev_elements, curr_elements)   # {added, removed, changed, stable}
text = summarize_delta(delta, max_lines=20)

delta_index returns {added, removed, changed, stable} (changed items are {"after", "fields"}); summarize_delta renders a delta_index result as budget-capped + / ~ / - lines; delta_observation indexes both frames (reading order, viewport clip, interactive-only) then diffs and renders in one call.

Executor command

AC_delta_observation (prev / curr / viewport / max_elements / max_lines / interactive_only → {summary, added, removed, changed}) is exposed as the MCP tool ac_delta_observation (read-only) and as the Script Builder command Observation: Delta (what changed) under Native UI.