Images exceeding 2000px are rejected by Anthropic API

Bug

When pasting or reading images that exceed 2000 pixels in either dimension, Anthropic's API rejects the request with:

At least one of the image dimensions exceed max allowed size for many-image requests: 2000 pixels

This happens in two paths:

Clipboard paste (clipboard.ts) — images pasted from clipboard are sent raw without any size check
File read tool (read.ts) — images read via the Read tool are base64-encoded and sent as-is

Reproduction

Copy a large screenshot (e.g. 2560x1440) to clipboard
Paste it into OpenCode while using an Anthropic model
API returns dimension error

Expected Behavior

Images should be automatically resized to fit within Anthropic's limits before being sent to the API. A progressive resize strategy works well: attempt compression first, then resize to fit within 2000px, then reduce JPEG quality, and finally aggressive downscale to 1000px as a last resort.

Environment

OpenCode latest on dev
Any Anthropic model (Claude Sonnet, Opus, etc.)
Any OS (macOS, Linux, Windows)

This issue might be a duplicate of existing issues. Please check:

413 Payload Too Large when reading local image (gpt-5.2-codex + opus-4.5) #12060: 413 Payload Too Large when reading local image (gpt-5.2-codex + opus-4.5)

Feel free to ignore if this doesn't address your specific case.

this happens too much

Still hitting this on OpenCode 1.2.10 (macOS 15.7.4, ARM64).

Error:

Error: messages.5.content.297.image.source.base64.data: At least one of the image dimensions exceed max allowed size for many-image requests: 2000 pixels

When a conversation accumulates multiple images (screenshots, diagrams, etc.), OpenCode doesn't downscale them to fit Anthropic's multi-image limit (2000px per dimension). The API rejects the entire request.

OpenCode should auto-resize images to ≤2000px when the message contains multiple images before sending to the Anthropic API.

I built a plugin that solves this — opencode-image-compact.

It hooks into experimental.chat.messages.transform and automatically compresses oversized images (resize + recompress via Sharp) before the request reaches the API. Handles both paste/drag-drop and read-tool images.

bun add opencode-image-compact

{ "plugin": ["opencode-image-compact"] }

Zero-config, MIT licensed. Feedback welcome.

I tried above opencode-image-compact but it doesn't work with my claude auth.
So I made by myself:

https://github.com/kargnas/opencode-large-image-optimizer

opencode.json

  "plugin": [
    "opencode-large-image-optimizer@latest"
  ]

feat: add image optimizer plugin to prevent oversized image API errors

Once a session breaks, you can export it to a .md file, fork to the last sent message, repeat it with an addendum like "EDIT: Here's what happened last time, carry on - <path>", and recover quickly
I adopted kargnas/opencode-large-image-optimizer for now, but I think a general error recovery mechanism for "bricked" chats would be really nice. This isn't the only time messages gets polluted with something illegal and forces a recovery like 1, and opencode should be able to handle this elegantly (or at least make the recovery more ergonomic)

shouldnt happen anymore: 981e009

feat: add image optimizer plugin to prevent oversized image API errors

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Images exceeding 2000px are rejected by Anthropic API #12068

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Images exceeding 2000px are rejected by Anthropic API #12068

Description

Bug

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Expected Behavior

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github-actions commented on Feb 4, 2026

lucasrueda commented on Feb 6, 2026

neocody commented on Mar 5, 2026

JlMoreno00 commented on Mar 18, 2026

kargnas commented on Mar 28, 2026

fadedlamp42 commented on Apr 16, 2026

rekram1-node commented on May 22, 2026

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