[Bug] Image attachments are lost on session resume: pasted images live only in an in-memory registry keyed by [image #N] markers

[stanleytejakusuma]

Summary

Pasted images in the interactive TUI are held only in an in-memory registry (pastedImages map) keyed by the [image #N] marker text. The bytes are never written to disk. When a session is resumed or restored (new process, e.g. after a kernel restart or resume), the registry is empty, so any submitted message containing [image #N] reaches the agent as literal text with no image payload. The agent receives the marker string and nothing else.

Repro

1. Start an interactive session, paste a screenshot into the prompt. The editor shows [image feat(kernel): add IPython kernel manager + ipython tool #1] and the bytes sit in the live process registry.
2. Submit a message that includes the marker and let the session end or be resumed (or restore from a saved session state).
3. Resume the session and submit the same message text (history recall, retry, or a continuation that echoes the marker).
4. The agent message contains the plain text [image feat(kernel): add IPython kernel manager + ipython tool #1] with no image content part.

Observed in a real session twice in one day: the user message arrived at the model containing only the literal text [image #1] with zero bytes.

A secondary gap: when the active model lane lacks vision (for example a text only model), images are stripped or never attached at all, so even a live registry does not help a non vision agent see the screenshot.

Root cause

dist/modes/interactive/image-markers.js and interactive-mode.js: pastedImages is a Map created at session start (bounded by MAX_PASTED_IMAGE_BYTES) and collectMarkedImages resolves markers from that in memory map at submission time. Nothing persists the bytes. On resume the map is empty by construction.

Suggested fix

1. On paste, persist the image bytes to a stable per session path, for example ~/.prime/agent/attachments//image-..
2. Make marker resolution fall back to that path when the in memory registry misses (registry miss should read the file, not drop the image).
3. Surface the resolved path in the message content so non vision agents can run a vision digest on it automatically instead of silently stripping, and vision agents can attach the file directly.
4. Keep the existing in memory registry as a fast path but treat disk as the source of truth for resume and history recall.

Environment

prime-agent installed from npm, interactive mode, macOS. Version where observed: the current npm release (kernel state restore reproduces it deterministically).