MCP tool results can include ImageContent blocks (screenshots from
Playwright/Blockbench/Puppeteer etc). The tool result handler only
extracted block.text, so image blocks were silently dropped and the
agent saw an empty or text-only response — losing the actual payload.
Add _cache_mcp_image_block() that base64-decodes the block, validates
the bytes via gateway.platforms.base.cache_image_from_bytes (which
sniffs for PNG/JPEG/WebP signatures and rejects non-images), writes to
the shared `~/.hermes/cache/images/` dir, and returns a MEDIA:<path>
tag. The handler appends that tag to the result parts so downstream
gateway adapters render the image inline.
Logs and drops on malformed base64 / non-image payload rather than
raising — a single bad block shouldn't kill the tool call.
Distilled from #17915 (c3115644151) and #10848 (gnanirahulnutakki), both
too stale to cherry-pick (branches diverged enough to revert dozens of
unrelated fixes). Went with #10848's approach of plumbing through
Hermes' existing MEDIA tag / cache_image_from_bytes infrastructure
rather than #17915's raw tempfile path, because it integrates with the
remote-backend mount system and messaging adapters that already handle
MEDIA tags natively.
Co-authored-by: c3115644151 <c3115644151@users.noreply.github.com>
Co-authored-by: gnanirahulnutakki <gnanirahulnutakki@users.noreply.github.com>
