[Amanbig]

Problem

An attached image lives in the conversation history and is re-sent in full on every model call for the rest of the session (and on every tool-loop iteration). Large screenshots are also sent at full resolution, although providers downscale anything beyond ~1568px, so the extra bytes and tokens are wasted.

Changes

• prune_old_images(): only the 2 most recent image-bearing messages keep their payload when building the request; older ones become a text note ([1 earlier image(s) omitted to save tokens: shot.png]) so the model knows and can ask for a re-attach. The stored history is not modified. Tunable via Agent.keep_recent_images
• downscale(): with Pillow, images over 1568px on the long side are resized (JPEG q85 / WebP q85 / optimized PNG), only if the result is actually smaller. Animated GIFs, small images and undecodable files are left untouched. Without Pillow it is a no-op
• Pillow is the optional extra devorch[images] and part of dev (CI installs .[dev])

Test plan

• Prune keeps only recent images, doesn't mutate history, no-op within the limit, agent sends pruned history while keeping stored originals
• Downscale: 4000x2000 -> 1568 long edge with aspect ratio kept and a smaller file; small images/GIFs untouched; garbage input survives
• Full suite passes (258), ruff check / ruff format clean
• Token numbers not measured against a live provider

Next

Anthropic prompt caching (system prompt + tools + history prefix) is the other big token lever; separate PR.