Two Critical bugs caught in code review of the agent→user attachments PR:
1. **Empty-URI attachments slipped past validation.** Gin's
go-playground/validator does NOT iterate slice elements without
`dive` — verified zero `dive` usage anywhere in workspace-server —
so the inner `binding:"required"` tags on NotifyAttachment.URI/Name
were never enforced. `attachments: [{"uri":"","name":""}]` would
pass validation, broadcast empty-URI chips that render blank in
canvas, AND persist them in activity_logs for every page reload to
re-render. Added explicit per-element validation in Notify (returns
400 with `attachment[i]: uri and name are required`) plus
defence-in-depth in the canvas filter (rejects empty strings, not
just non-strings).
3-case regression test pins the rejection.
2. **Hardcoded application/octet-stream stripped real mime types.**
`_upload_chat_files` always passed octet-stream as the multipart
Content-Type. chat_files.go:Upload reads `fh.Header.Get("Content-Type")`
FIRST and only falls back to extension-sniffing when the header is
empty, so every agent-attached file lost its real type forever —
broke the canvas's MIME-based icon/preview logic. Now sniff via
`mimetypes.guess_type(path)` and only fall back to octet-stream
when sniffing returns None.
Plus three Required nits:
- `sqlmockArgMatcher` was misleading — the closure always returned
true after capture, identical to `sqlmock.AnyArg()` semantics, but
named like a custom matcher. Renamed to `sqlmockCaptureArg(*string)`
so the intent (capture for post-call inspection, not validate via
driver-callback) is unambiguous.
- Test asserted notify call by `await_args_list[1]` index — fragile
to any future _upload_chat_files refactor that adds a pre-flight
POST. Now filter call list by URL suffix `/notify` and assert
exactly one match.
- Added `TestNotify_RejectsAttachmentWithEmptyURIOrName` (3 cases)
covering empty-uri, empty-name, both-empty so the Critical fix
stays defended.
Deferred to follow-up:
- ORDER BY tiebreaker for same-millisecond notifies — pre-existing
risk, not regression.
- Streaming multipart upload — bounded by the platform's 50MB total
cap so RAM ceiling is fixed; switch to streaming if cap rises.
- Symlink rejection — agent UID can already read whatever its
filesystem perms allow via the shell tool; rejecting symlinks
doesn't materially shrink the attack surface.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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