# I tested DeepSeek Harness for a week. I left with a shipped plugin and $0 in API costs > Source: > Published: 2026-09-10 18:57:25+00:00 I came to DeepSeek Harness as a reviewer and left as one of its plugin authors, which is a fair measure of how the week went. The hook is on the repo's first line: **"Everything is a plugin."** Not the usual marketing meaning — not a config file with a couple of third-party hooks. In DSH the agent hosts its own web UI as plugin packages; the settings screen where you pick and configure models is assembled from plugin contributions (this is the part I verified the hard way); even the optional subagents — Codex, Claude Code — ship as plugins you can add or drop. All of it loaded through manifests over a real extension API. I've poked at a lot of "extensible" tools. This one takes it literally, and poking at it turned into the most fun I've had with an agent harness in a while. The gap I kept feeling in Settings → Models was the two questions I ask before switching providers every time: **what does this model actually cost per million tokens, and is a cheaper route to the *same* model available?** DSH tells you which models exist. It doesn't tell you what they cost. `dsh-model-pricing` closes that, and it lives *inside the harness's own Settings page* — because that's the point of testing the plugin system: `cheapest` badge: GLM-5.2, say, runs from $3.08 to $4.84 per 1M output tokens depending on the gateway — the same model, 57% apart It installs through the harness's own plugin manager — I never forked anything: ``` npx -y @deepseek-ai/dsh plugin --profile web add dsh-model-pricing ``` Here's the part I didn't expect. I built the whole thing **using DeepSeek Harness, driven by Qwen3.8-Flash** through B.AI's current promotion — the one Eight records shipped on day one; one of them describes the free model that wrote this plugin's UI. | priced rows / providers | 7,178 / 213 | | harness-catalog overlaid rows | 788 (30 disagreements flagged, not averaged) | | plan rows grouped & excluded from ranking | 175 | | promo records at launch | 8 (each with source URL + verification date) | | commits / files / LOC | 28 / 18 / ~2,300 | | wall-clock | ~22h, incl. overnight autonomous rounds | | LLM cost | $0 — free API promotion, re-verify date 2026-10-10 | | UI languages | en + zh (platform), ru (plugin) | If you're curious about DeepSeek Harness the way I was: run it, then break into its settings page. The architecture is the product; the agent is very good at both jobs, even on a model that costs nothing. ``` npx -y @deepseek-ai/dsh plugin --profile web add dsh-model-pricing ``` Repo (docs, feature map, the promotion contribution rules — all public): [github.com/vitas/dsh-model-pricing](https://github.com/vitas/dsh-model-pricing) · npm: [dsh-model-pricing](https://www.npmjs.com/package/dsh-model-pricing) · Apache-2.0.