DeepSeek Harness v0.2.1-rc.1 Ships Claude Code and Codex Compatibility Bundles

DeepSeek published the v0.2.1-rc.1 release candidate of DeepSeek Harness, its open-source agent harness built on an everything-is-a-plugin architecture, on October 17, 2026. The release lands the same day as DeepSeek V4.1-Flash-1017 and the new Search and Fetch APIs — and a second candidate, rc.2, followed three hours later adding harness support for both.

For fleet operators running multiple coding harnesses in shared rooms, the headline feature in rc.1 is the arrival of installable Claude Code and Codex compatibility bundles. These appear in the Official plugin catalog, install matching-package versions for the current release, and target headless, SDK, and ACP profiles.

Claude Code and Codex Bundles: Practical Multi-Harness Switching

The compatibility bundles let teams run Claude Code and Codex conventions inside DeepSeek Harness without rewriting workflows. For operators who manage usage limits across platforms, this means switching a workload to DeepSeek Harness while keeping the same tool contracts, hook structures, and agent instructions the team already knows.

This is distinct from the experimental Claude Code Mods compatibility layer, also new in rc.1, which the release notes describe as a validation exercise: “the main goal is to verify that the Claude Code Mods API’s capabilities are broadly a subset of what DeepSeek Harness plugins can do, rather than to offer users complete, practical compatibility.” The bundles, by contrast, are production-installable and version-matched to each release.

Agent-Built Plugins and Custom Indexes

The plugin management page gains a “Let Agent create a plugin” entry point. Users describe what they want, and the agent drafts a plugin in Creator mode — but execution starts only after the request is explicitly sent, preserving the draft until then. Combined with support for custom plugin index sources, the ecosystem can now grow from sources beyond the official catalog.

Plugin lifecycle management also improves: enabling, disabling, uninstalling, and updating plugins now synchronize dependencies. Replaceable plugins take effect immediately under hot reload; changes that cannot hot-reload prompt a restart.

Git Worktrees and Shared Instructions

An experimental Git Worktrees plugin, enabled from the Plugins page, lets agents create and enter separate Git checkouts. This mirrors the parallel-session worktree pattern that Claude Code Desktop shipped earlier this year, giving DeepSeek Harness users a comparable isolation primitive for concurrent agent tasks.

Global instructions now load from AGENTS.md in a shared agents directory, configurable through DSH_AGENTS_HOME. Multiple harnesses can share the same instruction file — useful in fleets where both Claude Code and DeepSeek Harness sessions run side by side.

What Else Ships

• Per-model reasoning levels in the custom API model UI, no config-file editing required.
• Secret redaction in sent messages: keys and tokens are masked by default with a reveal option.
• Session state-record APIs for experimental plugins to persist their own session data.
• Unsent prompt support with preserved file, directory, and session references when restoring drafts.
• A working_directory tool and matching TypeScript/Python SDK APIs for reading and changing session working directories.
• Standalone SSH helper runtimes with remote file operations, processes, terminals, sandboxing, and Node PTC.
• An experimental reasoning translation plugin using Bing, Google, or paid DeepSeek Flash.

The release also includes 38 bug fixes, 21 experience improvements, and 23 other changes, from a new collapsible work-details setting to improved subagent delegation guidance with depth-limit warnings.

rc.2 Already Lands

Just three hours after rc.1, DeepSeek shipped v0.2.1-rc.2 with harness support for the newly launched DeepSeek-V4.1-Flash-1017 model and the Search and Fetch APIs. The pace — two release candidates on the same day as the model and API launches — shows the harness team tracking upstream DeepSeek releases at production velocity.

Before adopting either candidate in production, pin your plugin versions explicitly and test the Claude Code and Codex bundle compatibility against your existing hooks and AGENTS.md files. The bundles are release-matched, so upgrading the harness means upgrading the bundles together.