Pasting multiple images in one session overwrites each other (all saved as image.png)

Description

When pasting two or more images into the same opencode session, every image is saved to the same fixed path ~/.local/share/opencode/attachments/{session_id}/image.png. Later images overwrite earlier ones, so the model only ever has access to the last image — even if the model itself supports vision.

Steps to reproduce

1. Paste screenshot A into a session.
2. Paste screenshot B into the same session (same message or a follow-up).
3. Ask the model to describe both images.

Actual behavior
Only B is accessible. The system attachment notice is byte-identical for both pastes:

[图片附件] 用户粘贴的图片 "image.png" 已保存到本地文件：
~\.local\share\opencode\attachments\ses_xxx\image.png

Evidence
Each session directory contains exactly one file named image.png. After pasting two different images, only the last-written one exists (e.g. 33,707 bytes at the second paste time); the first image is gone. All historical session dirs show the same single-image.png pattern, confirming pasted images use a fixed filename instead of a unique/hashed name.

Expected behavior
Each pasted image should get a unique filename (e.g. image-<timestamp>.png or a content hash) so multiple images in one session coexist and are all passed to the model.

Workaround
Paste images one at a time, or save them with distinct filenames before attaching (dragging in a file preserves its original name).

Plugins

No response

OpenCode version

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Steps to reproduce

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Screenshot and/or share link

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Operating System

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Terminal

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