feat(server): accept PDF, ZIP, and other file uploads up to 50MB

[t3dotgg]

T3 Code currently accepts only image attachments. This PR adds the server contract, streaming
upload, storage, and download support for generic files up to 50 MiB. The web and mobile file
pickers remain separate in #8236 and
#8237.

Each provider adapter chooses which attachments it sends as native inputs. The prompt includes the
real path for every attachment, so unsupported native inputs still reach the agent as paths.

The takeover fixes interrupted upload cleanup, returns HTTP 400 for unfinished oversize uploads
instead of resetting the socket, encodes extended download filenames correctly, keeps mobile from
rendering files as images before its file UI ships, and corrects the rollback documentation.

Compatibility warning: the tolerant schema only helps updated clients. Older clients cannot decode
messages with file attachments. Older servers can also fail startup for the whole environment when
event replay reaches a file-bearing message. Do not treat rollback as a per-thread failure.

Theo Browne wrote the original implementation with Claude Fable 5 in Claude Code. The original
commit authorship and co-author trailers are preserved.

Built with GPT-5.6 Sol in the Codex harness.

---

Note

Medium Risk
Touches attachment auth tokens, streaming upload I/O, and download response headers (XSS via mime/disposition), plus persisted event schemas—version skew can break whole-environment replay on rollback.

Overview
Adds generic file attachments (PDF, ZIP, etc.) alongside images: contracts expose ChatFileAttachment, type: "file" upload URLs (50 MiB cap), and environment capability fileAttachments.maxUploadBytes. Upload and storage stream bodies to .part files with size enforcement and cleanup on failure or interrupt; attachment IDs can carry a sanitized extension suffix so paths resolve without directory scans. Downloads bake download, fileName, and mimeType into signed asset tokens and serve attachment disposition, sandbox CSP, and vetted Content-Type (HTML/XML/SVG forced to octet-stream).

Provider turns append an on-disk path line for every attachment; image-only adapters skip non-images for native input while OpenCode sends supported PDFs/text/images under a size cap. Projection and cleanup handle file attachments; mobile thread feed shows images only until file UI ships; web gains isImageAttachment so file members typecheck without image-only UI.

Compatibility: tolerant ChatUnknownAttachment decoding on messages; legacy upload tokens default to image; older clients/servers and file-bearing persisted events remain a documented skew risk.

^{Reviewed by Cursor Bugbot for commit 88b541d. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Add support for generic file uploads up to 50MB with streaming

• Adds schemas for ChatFileAttachment and FileAttachmentCreateUploadUrlInput in orchestration.ts and assets.ts to validate generic files up to 50 MiB (PROVIDER_SEND_TURN_MAX_FILE_BYTES)
• Modifies storeAttachmentUpload in AttachmentUpload.ts to stream uploads to a .part file and enforce size limits, rejecting oversized or mismatched uploads with a 400 status
• Extends attachment IDs in attachmentStore.ts with a validated file extension suffix (e.g., -pdf) to allow direct path resolution without scanning directories
• Implements download headers (Content-Disposition, sandbox CSP) and safe mime type validation in http.ts for serving generic files
• Updates provider adapters in apps/server/src/provider/Layers/ to filter non-image attachments from native image ingestion paths, relying on prompt path lines for generic file access
• Risk: attachmentRelativePath now returns null for unknown attachment types; ProviderService.sendTurn no longer sets input.attachments to an empty array when absent, so downstream adapters may receive undefined

^{Macroscope summarized 88b541d.}

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.3 KiB	13.3 KiB	+4 B (+0.0%)	15.1 KiB	✅
Codex	Thread snapshot wire	6.9 KiB	6.9 KiB	−13 B (−0.2%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.4 KiB	6.4 KiB	+17 B (+0.3%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	55.6 KiB	55.6 KiB	+44 B (+0.1%)	66.4 KiB	✅
Codex	Live turn messages	10	11	+1 (+10.0%)	21	✅
Claude	Total thread wire	13.3 KiB	13.4 KiB	+12 B (+0.1%)	15.1 KiB	✅
Claude	Thread snapshot wire	6.9 KiB	6.9 KiB	+7 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.5 KiB	6.5 KiB	+5 B (+0.1%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	56.4 KiB	56.4 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	11	11	0 (0.0%)	21	✅

Baseline: f276e63 · PR result: 88b541d · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 109.4 KiB
• Claude decoded thread snapshot: 110.1 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR introduces generic file uploads and downloads up to 50 MiB, including streaming filesystem I/O, signed download metadata, provider-specific attachment handling, and persisted schema changes. The broad runtime and compatibility impact, plus security-sensitive MIME and browser-disposition behavior, warrants human review.

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[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

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