PR #64514: fix(agents): add resize cache to avoid redundant image reprocessing

• Repository: openclaw/openclaw
• Author: EronFan
• State: closed | merged: False
• Link: https://github.com/openclaw/openclaw/pull/64514

Description (problem / solution / changelog)

Summary

Images in session history were being re-processed through resizeImageBase64IfNeeded on every message turn via sanitizeSessionMessagesImages. This caused:

1. Duplicate Image resized to fit limits log entries on every message
2. Wasted CPU on redundant getImageMetadata header reads and resize evaluations
3. Token waste from re-processing already-resized images

Root Cause

sanitizeSessionMessagesImages processes ALL historical messages on every turn. For images, this calls sanitizeContentBlocksImages → resizeImageBase64IfNeeded each time. Even though there is an early-return when an image is already within limits, the expensive getImageMetadata call still happens every turn.

Fix

Added a resize cache (RESIZE_CACHE) in resizeImageBase64IfNeeded:

• Key: SHA-256 hash of (maxDimensionPx:maxBytes:base64.slice(0,1000))
• Value: The full result { base64, mimeType, resized, width?, height? }
• Eviction: Simple LRU at 200 entries (first key in insertion order)

Cache entries are stored after both:

1. The no-op early return (when image is already within limits)
2. The successful resize return (when image was resized)

On subsequent turns, identical inputs hit the cache and return instantly without any image processing.

Test

pnpm test -- --run src/agents/tool-images.test.ts passes all 5 tests.

Fixes #64418

Changed files

• src/agents/tool-images.ts (modified, +54/-3)
• src/commands/doctor-gateway-health.ts (modified, +2/-4)