DeepSeek Harness v0.1.3-alpha.1: Session v2 & File Uploads

DeepSeek published the dsh-v0.1.3-alpha.1 GitHub pre-release on September 4, 2026. Built on the newly default 0.1.2-rc.1 line, it advances general file uploads, proxy environment support, model discovery, Session v2, and cross-Agent messaging semantics.

Release channels matter here. The version has an official tag, release notes, and source archives, but as of September 5 it has not been published as an npm package. npm's latest and next remain on 0.1.2-rc.1, while alpha remains on 0.1.2-alpha.5.

The short version

Alpha.1 shows the next direction for 0.1.3, but it is not a default or installable npm upgrade. SessionHandle, the v2 Session format, and an acknowledged historical-Session performance regression make it more appropriate for source evaluation and plugin compatibility work than for replacing a daily environment.

Release status

Do not put this command in installation instructions because the npm version does not currently exist:

# Not available from npm as of 2026-09-05
npx @deepseek-ai/[email protected] web

General file uploads in Web

Web can now mix files and images in one preview area. Background uploads expose progress and cancellation and remain visible across conversation switches; after saving, the model can use existing file tools to read the stored paths.

This does not mean every model understands every file format natively. Harness stores the file and exposes a path, while actual processing still depends on the tool composition, parser support, and workspace permissions.

Outbound requests honor proxy variables

Outbound network requests now follow HTTP_PROXY, HTTPS_PROXY, ALL_PROXY, and NO_PROXY from the startup environment. That makes enterprise networks, local proxies, and restricted development setups easier to configure, but it also makes the proxy a trust boundary that may observe request metadata or forwarded content.

Tests should cover proxy routing, NO_PROXY exclusions, and whether credentials are sent only to intended hosts.

Model and image-tool improvements

Model discovery supports models objects from custom providers and native Anthropic model lists, and can fill model names, context windows, and maximum output tokens. Top-level and PTC-nested read_image calls now render images directly in Web tool cards.

The Python SDK source line adds a macOS x64 runtime wheel, but the matching 0.1.3 packages are not yet available through PyPI or npm. Intel Mac users should follow actual package files rather than installing from the release-note claim alone.

SessionHandle and Session v2

The largest developer change moves Session persistence ownership into lifecycle-scoped SessionHandles. agentLoop.create() becomes asynchronous, and a Session lock ensures that at most one process owns a Session.

The Session format moves to v2. Immutable adjacent-generation migrations convert older v0/v1 logs, Assistant streams are aggregated by attempt into durable settlements, and Web retains real-time incremental display.

These changes improve concurrency ownership and recovery semantics, but they are explicitly breaking. Plugins that depend on Session creation timing, direct log access, or custom locking need to recompile and test migration behavior.

Fixes and interaction changes

The release notes also cover:

• Manually pausing a Goal immediately aborts the current model turn.
• DeepSeek streaming continuation preserves tool-call IDs and names.
• Windows drive-root Workspaces are fixed.
• Session cache reads and navigation from conversation search are corrected.
• The Skill picker supports fuzzy search.
• Agent Team send_message consistently uses steer semantics while preserving sender attribution and ordering.

Known performance regression

The official notes acknowledge a performance regression that may slow some historical Session loads and say it will be fixed in a later release. Evaluation with large histories should measure load time, memory, and post-migration recovery rather than testing only new conversations.

Who should pay attention

Related reading

• DeepSeek Harness v0.1.2-rc.1: default npm upgrade and migration notes
• DeepSeek Harness v0.1.2-alpha.5: release notes and npm status
• DeepSeek Harness Python SDK guide
• DeepSeek Harness remote development comparison

Frequently asked questions

Can v0.1.3-alpha.1 be installed from npm?

No. As of September 5, 2026, npm does not contain that exact version. The official publication is a GitHub pre-release with a tag and source archives.

Does Session v2 delete older conversations?

The release notes describe generation-based migration from v0/v1 rather than deletion. Back up important data and validate migration plus recovery against a copy.

Should regular users move from rc.1 to this release?

Not as a routine upgrade. It is not published on npm, includes breaking Session API changes, and carries an officially acknowledged historical-Session performance regression.