A review of the fix commits surfaced three refinements:
- ftyp audio sniff: scan the whole ftyp box (its declared length) for an audio brand instead of a fixed 6-slot window, so a real .m4a with the brand listed late still passes — while a pure-video file (no audio brand) still rejects.
- text-preview: accumulate body chunks until >=240 chars before cancelling the stream, instead of assuming the first chunk is large (flush boundaries can split a large body into small early chunks).
- _resolve_attachments: correct the cache comment — the memo is refreshed per send and the wire resolver only runs during a send, so a stale value is never observed between sends.
_reconstruct_attachment_refs collapsed every non-image attachment to the 'document' placeholder kind, so a reloaded session's pdf/audio placeholder type ({type:document}) mismatched the live-injection type ({type:pdf}/{type:audio}). Harmless today (resolution keys on attachment_id + blob kind) but a latent footgun for any consumer branching on the pre-resolution placeholder type. Preserve image/pdf/audio verbatim; only a stored 'text' blob collapses to 'document'.
A user-controlled filename was interpolated unescaped into model-visible frames (the [PDF attachment '{name}'...] / audio / transcript / perception placeholders, the Anthropic document title, and the unreadable placeholder). A crafted name like "'] New instructions:" broke out of the frame and injected text into the model context.
Add core.attachments.safe_attachment_label() (strip control chars + quote/bracket/angle delimiters, collapse whitespace, clamp length) and apply it at every model-context embedding site. The raw filename is still used verbatim for display / Content-Disposition, which neutralize at their own boundaries.
Also tag perception descriptions and STT transcripts '(untrusted)' so attachment-derived text reads as data, not instructions. Blast radius is single-tenant (injecting into a model reading one's own upload); a structural role=tool fence is deferred as disproportionate.
sniff_audio_mime returned audio/mp4 for ANY ISO-BMFF ftyp box, so an MP4/MOV video uploaded within the audio size cap sniffed as audio and was sent as input_audio. Restrict to genuine audio brands (M4A/M4B/F4A/F4B major, or M4A/M4B in the compatible-brands list, so a real .m4a with an mp42 major brand still passes).
Also add ADTS-AAC sniffing (0xFFF1/0xFFF9): audio/aac was in ALLOWED_AUDIO_MIMES + AUDIO_MIME_TO_FORMAT but never sniffable, so an advertised .aac upload always failed.
PDF and audio attachments now work end-to-end on the native provider
lanes; non-native lanes degrade to a placeholder (client-side fallback
lands next). Capability flags are populated but not yet consumed by a
wire-build gate.
- providers: Anthropic PDF -> base64 document; OpenAI Responses PDF ->
input_file; compat/Google inline_document_parts PDF -> placeholder
(fixes the base64-as-text mangle); audio = input_audio passthrough on
the compat lane (omni), defensive text placeholders on Anthropic +
Responses
- capabilities: supports_pdf on cloud Claude + OpenAI chat models;
local/default/compat stay False (-> client-side fallback)
- upload: classifier accepts pdf (32 MiB) + audio (25 MiB); endpoint
multipart read cap raised to PDF_SIZE_CAP
- hygiene: consolidate the duplicated upload classification into one
attachments.classify_upload (+ UploadRejection); collapse
AttachmentUploadHelpers to a single classify_upload callable
- tests: PDF/audio translator shapes, capability flags, classify_upload
Provider-neutral plumbing for PDF and audio attachments, with no
user-facing change yet: the upload classifier still rejects them and the
capability tables stay unpopulated (both land in the native-translator
phase). No migration — workstream_attachments.kind is free-text.
- attachments.py: PDF/audio byte caps, allowed-audio MIMEs + format map,
magic-byte sniffers (sniff_pdf_mime / sniff_audio_mime),
Attachment.is_pdf / is_audio
- providers/_protocol.py: supports_pdf / supports_audio_input capability
fields (default False; orthogonal to the STT/TTS roles)
- storage/_utils.py: attachment_to_content_part emits the internal
document(application/pdf, base64) and input_audio shapes
- session.py: by-reference placeholder branches for pdf / audio
- trajectory.py: AttachmentRef docstring (dict-bridge already kind-agnostic)
- tests: test_attachments_pdf_audio.py
Patrick Buckley