@wsz987/channel-files

Generic Attachment Compatibility Backend for DeepSeek Harness Channels.

Stores session-scoped non-image attachments and preserves legacy readable extraction while Harness does not yet provide a native generic attachment contract. Inbound PDF / DOCX / XLSX / text files are stored and exposed to the model through the read_channel_attachment tool — without routing raw platform payloads through the prompt.

Legacy extraction (PDF / DOCX / XLSX / TXT) is compatibility behavior: it keeps working for existing users via read_channel_attachment, and no new "understanding" features (ASR, video analysis, OCR, PPTX parsing) are added here — those belong to Harness skills, plugins or MCP.

Install

pnpm add @wsz987/channel-files

It is included in the @wsz987/dsh-channels bundle by default. To disable the extension, remove the channels-files plugin from the bundle patch; Harness native images and plain text messages keep working.

Features

| Area | Detail | | --- | --- | | Storage | Private, session-scoped asset store under the channel data directory; reads enforce the channel Session ACL | | Extraction (compatibility) | Legacy PDF (unpdf), DOCX (mammoth), XLSX (xlsx), plain text — compatibility behavior, no new understanding features | | Tool | read_channel_attachment (compatibility tool) installs on the agent so models can read stored files | | Limits | 100 MiB inbound per file · 32 MiB parser input · 5 MiB extracted text output |

How it works

ChannelFileService implements the ChannelAttachmentProvider port from @wsz987/channel-harness (the former ChannelFileProvider name is kept as a deprecated alias):

ctx.channelFiles.store(channelAttachmentContext, binaryPart); // store + extract
ctx.channelFiles.resolveAttachment(attachmentId, sessionId);  // Session ACL enforced
await ctx.channelFiles.installCompatibilityTools(agentContext); // add the read tool

Roadmap

Harness currently has no native generic attachment surface. Until it ships one, this package remains the generic attachment backend. Ahead of that, the following infrastructure exists default-off and activates only via public capability detection once the official API appears:

• Attachment Catalog v2 (attachments/catalog/v2) — logical att-* id → backend locator index, kept separate from the legacy v1 tree;
• native capability seam (src/backends/harness-native.ts) — interface + fake only, never fooled by the image-only ctx.attachments service;
• lazy copy + verify migration (src/migration/) — a failed migration keeps the legacy backend authoritative.

Legacy attachments/v1 data remains permanently readable and is never rewritten or deleted on upgrade.

Development

pnpm --filter @wsz987/channel-files build
pnpm --filter @wsz987/channel-files typecheck
pnpm --filter @wsz987/channel-files test

Related

• Repository root
• Architecture design

License

MIT