Summary

Convert AI SDK v6 file / image parts into the Anthropic image content block ({ type: "image", source: { type: "base64", media_type, data } }) expected by the Claude CLI on stream-json input. Without this change the plugin silently drops attachments and the model replies as if vision were unsupported.

Behavior

Accepts:

• Base64 data URIs (data:image/png;base64,...) — the format OpenCode stores on disk
• Raw base64 strings with mediaType / mime / mimeType
• Uint8Array buffers

Rejects with a warning (returns null, part is skipped):

• Remote http(s):// URLs — Claude API only accepts inline base64
• Media types outside image/png, image/jpeg, image/gif, image/webp
• Missing data / url / source.data

Config requirements

Models that should accept images must declare both in opencode.json:

{
  "attachment": true,
  "modalities": { "input": ["text", "image"], "output": ["text"] }
}

Without modalities.input including image, OpenCode filters file parts before they reach the plugin and replaces them with a [Image #N] text placeholder.

Test plan

• Roundtrip via Claude CLI stream-json: PNG inline base64 correctly described by Haiku 4.5
• End-to-end via OpenCode UI (with modalities set): image attached, Sonnet 4.6 and Opus 4.7 describe content correctly
• Unit checks for buildImageBlock: data URI, raw base64, Uint8Array, http(s) URL (rejected), unsupported media type (rejected), missing data (rejected)

Split from a previous combined PR per maintainer request. Depends on nothing; builds on top of current master.