Krish Chainani cb66dbecf2 Replace unavailable image references in model requests (#57585) ...

## Why

Image files can become unavailable between turns. Model requests should reflect their current availability while preserving the original references in saved history.

## What changed

- Add opt-in availability checks through `AttachmentStore::is_resolvable`, retaining references by default and on backend or access errors.
- Check distinct file IDs concurrently for each prepared request and replace confirmed-missing images with `[image unavailable]` in messages and tool outputs.
- Apply the same handling to compaction requests, with background image checks running outside the session lock without delaying foreground turn completion.

## Testing

Add unit tests and multi-turn scenarios covering placeholders, preserved history and annotations, concurrent deduplicated checks, backend errors, and nonblocking background compaction.

GitOrigin-RevId: ec98c7014c6e6b5063d87b943d2cd66a9ce7c1e3

2026-10-27 22:59:22 +00:00

..

src

Replace unavailable image references in model requests (#57585)

2026-10-27 22:59:22 +00:00

BUILD.bazel

Add an injectable attachment store to ThreadManager (#42634)

2026-09-03 23:20:54 +00:00

Cargo.toml

Route prepared images through the attachment store (#46065)

2026-09-17 00:49:12 +00:00