What's New in DeepSeek Harness 0.1.5 RC

GitHub says RC; headlines say 0.1.5

DeepSeek Harness 0.1.5 is the search phrase people typed after 10 September 2026. On the GitHub Releases page the 0.1.5 tags are v0.1.5-rc.1 and v0.1.5-rc.2, both marked Pre-release. rc.1 is the notes dump since v0.1.2-rc.1; rc.2 is a small feedback-and-layout follow-up the same day.

Later candidates are a different query. Operator notes for DeepSeek Harness 0.1.7 are in What’s New in 0.1.7 RC.

This independent portal is not the vendor. We rewrite what operators should verify, then send you back to those notes when flags move. If the README disagrees with this page, the README wins. For product identity — why DSH is a harness, not a new LLM — stay on What is DeepSeek Harness.

Pulling the preview is still npx @deepseek-ai/dsh web from the install checklist or the npx quickstart. A cached older tarball is a common way to “upgrade” and see none of the items below.

Default model: V4.1 Flash (deepseek-flash)

The DeepSeek adapter in this RC adds DeepSeek-V41-Flash, exposed as deepseek-flash, with text, images, and in-history system-prompt updates. New sessions default to that model. If your config file already pins a model id, the pin wins.

That same calendar day DeepSeek also launched V4.1 Flash on the API. This article does not cover API price, routing of deepseek-v4-pro, or chat-product SKUs — those queries belong to the API docs, not this portal. Here the only question is: after you open a new DSH session, which model id actually loaded, and did an old profile silently keep the previous default?

If a run looks “dumber” or “faster” overnight, check the model field before you blame Standard vs PTC. Mode selection is still on modes.

File uploads and Sidebar preview

The Web UI now accepts arbitrary file uploads. Files and images share a preview area; background uploads show progress and can be cancelled; switching conversations should not hide an in-flight transfer. The model reads saved paths through the existing file tools when it needs them — uploading is not the same as stuffing the whole PDF into the next prompt.

The right Sidebar grows tabs, split panes, fullscreen, and previews for Markdown, code, HTML, PDF, and images, including files from subagents and inactive sessions. Models can deliver a file for preview, open-in-app, or reveal-in-folder. The former Detail panel is gone. If a teammate’s screenshot still shows Detail, they are not on this RC.

The header also adds Open in so the workspace can jump into an installed editor, IDE, terminal, or file manager. That is a local convenience, not a new cloud product.

Session log V3 does not downgrade

This is the change that bites people who treat Trajectory like a chat export. Session data moves to V3. Supported older logs are migrated; the original files are kept. Upgraded sessions cannot be read as the old format. Custom log readers have to follow V3.

If you pin plugins and DSH versions on one sticky note — as the Trajectory observability intro already asks — add the format generation. A replay from 0.1.2-era files is a poor bug template for 0.1.5-rc. Treat session files like core dumps: not in git, not in Slack.

Agent Teams stays off unless you opt in

An experimental Agent Teams package can be installed from npm. You must add a profile explicitly. It is not on by default. Subagent queuing, steer, and stop improved in this series; that is not a reason to point a team of agents at a payroll tree on day one. Permission review still lives in the plugin security checklist.

Other notes that matter in real rooms, not in a feature-list paste:

• Outbound HTTP now honors HTTP_PROXY, HTTPS_PROXY, ALL_PROXY, and NO_PROXY from the start environment.
• Models that declare support can update the system prompt without throwing away KV Cache.
• Windows non-terminal subprocesses should stop popping extra consoles — useful if you already read DSH on Windows.
• Plugin and session APIs moved (no ctx.agent grab-bag, Inbox is an interface, Web panel slots renamed). If you author plugins, read the release notes; this page will not re-host the whole changelog.

Operator checklist (ten minutes)

1. Confirm the running binary is actually 0.1.5-rc, not a leftover npx cache.
2. Open a new session and read the model id. Expect deepseek-flash unless config pinned something else.
3. Upload a small Markdown or image and find it in Sidebar, not Detail.
4. After one boring task, open the session inspector. If a custom reader breaks, assume session log V3.
5. Leave Agent Teams off unless you meant to add that profile.
6. If the office uses a proxy, confirm the four *_PROXY variables are in the same environment that launched npx.

None of this makes the preview “production-certified”. Upstream still warns that compatibility will break.

What this article is not

• Not a second architecture explainer — that remains What is DeepSeek Harness.
• Not a four-mode encyclopedia — four modes and when to use PTC.
• Not a how-to for reading Trajectory fields line by line — start from session logs and Trajectory.
• Not DeepSeek API pricing or V4.1 Flash SKU news.

Where to go next

1. Facts and flags: GitHub Releases and the official harness page.
2. Run it: install → npx quickstart.
3. After it runs: pick a mode, then inspect the log.