Harness Self-Evolution Plugin

September 23, 2026 · View on GitHub

A MoonBit-native plugin that scans, monitors, proposes, and rolls back evolutions for the DeepSeek Harness (DSH) plugin ecosystem. Version 3.1.0. MIT.

This plugin targets DeepSeek Harness. Deployment hinges on how DSH launches the binary, where data is read and written, and which files (patches, manifests, panels) sit alongside the binary.

Where your data lives

DSH resolves its home via $DSH_HOME (~/.dsh by default; a managed launcher may point it elsewhere). The plugin mirrors that: user-scope sub-agent definitions land under <DSH home>/skills/. Full install, verification, and rollback: docs/deploy/deepseek-harness.md.

Since v3.0.0 the plugin is DSH-only: the earlier claim of MiniMax Code compatibility was a over-declaration (DSH's own source has no such host concept) and has been removed.

If you are writing or debugging a DSH plugin rather than deploying this one, read docs/dsh-plugin-integration.md: the host-half / client-half contract, the Lazy-CJS client bundle rule (one stray top-level export breaks every plugin in the combo), DSH_HOME routing, and the diagnosis order for "Failed to load plugins".

What it does

  • Scan installed plugins across the configured scan roots for the active host
  • Monitor call latency, success rate, token usage, retry count, and user feedback
  • Identify strong signals (user override, three consecutive failures, > 20% latency regression) and medium signals (repeated parameter misuses, loop detection, repeated preferences)
  • Propose benchmark-driven evolutions bound to Matt Pocock engineering principles
  • Approve is always a human step. auto_approve is false by default and stays false — the only gate against "code changes itself into a wall"
  • Execute with state machine pending → approved → executing → completed, with deterministic rollback from a verified snapshot on validator failure
  • Sub-agent factory persists Markdown + YAML frontmatter definitions; scope plugin lives under the plugin's data root, scope user lives under <DSH home>/skills/ (see the deploy guide)

Architecture in one paragraph

The compiled binary (bin/harness-evolution.exe) is a stdio MCP server exposing fourteen tools. The DSH home resolves in src/store/paths.mbt::dsh_home: $DSH_HOME when set, else derived from the plugin's own install path (<X>/profiles/<name>/node_modules/...), else ~/.dsh. The user-scope directory is <DSH home>/skills (HARNESS_EVOLUTION_USER_DIR overrides it), and the default scan roots follow the same resolved home (src/scanner/scanner.mbt::default_scan_roots). Since v3.0.0 the multi-host abstraction is gone — DSH is the only target.

See docs/code-architecture.md for the path-resolution detail.

Build

.\build.ps1 -Task all    # check + test + build; one command rebuilds the binary

Build prerequisites: MoonBit >=0.1.20260904, MSVC or Clang on Linux/macOS. The current binary in bin/harness-evolution.exe is Windows-native; rebuilding on the target platform produces a native binary for that platform.

Data and configuration

The plugin stores proposals, metrics, signals, cache, and execution log under $HARNESS_EVOLUTION_HOME (default ~/.harness-evolution/v2/). Override with the env var to keep dev/test data separate.

Configuration is read in this order, first file that exists wins:

  1. $HARNESS_EVOLUTION_CONFIG (explicit override)
  2. <cwd>/.dsh-plugin/plugin.json (self-manifest)
  3. .dsh-plugin/plugin.json (relative to plugin root)

If none exist the plugin starts with built-in defaults — missing config is not a startup failure.

Breaking change (unreleased v2.7.0): the legacy <cwd>/.zcode-plugin/plugin.json fallback is no longer read. A deployed instance that still carries that file must rename it to .dsh-plugin/plugin.json — the contents need no change.

Installing into the right tree (DSH_HOME)

Installing is per DSH tree: dsh plugin add writes into $DSH_HOME/profiles/<name>, and $DSH_HOME decides which tree boots (~/.dsh by default — a managed launcher may point it somewhere else). Trees share nothing: bundles, node_modules, sessions, and skills are all per-tree, so an install verified in one tree stays invisible to a host booting another.

Since v3.1 the shipped mount row is disabled: true and carries no machine path — a literal path for one machine points at a missing file everywhere else, so the plugin would simply never mount (DSH reports one warning line and keeps booting: mcp-harness-evolution is not in the host's requiredStartupEntryIds, so its activation failure is optional). The row is written per tree at install time:

# resolves $DSH_HOME (or ~/.dsh), installs the bundle, and injects the mount row
# into that tree's profile patch layer; add -DryRun to inspect first
pwsh -File scripts/install-dsh.ps1 -Profile web

# then verify statically (no boot needed)
dsh --profile web --dump-config | Select-String 'mcp-harness-evolution'

dsh.profile.bundles and the patch layers are read at boot, so the host must be restarted before the fourteen mcp__harness-evolution__* tools appear in a session. The plugin additionally derives its own tree from the install path, so create_sub_agent scope=user lands in <DSH home>/skills/ even if env.DSH_HOME were left unset.

What is actually fatal, and what is not. failOnStartupError: true on the mount row does not abort the profile boot: it only rejects that one plugin's activation, and app-boot downgrades it to an optional entry warning (see the paragraph above). The genuinely fatal case is a patch layer DSH cannot parse — parsePatchList throws and the profile never boots. scripts/install-dsh.ps1 writes that file, so its output is pinned by a regression suite that parses it with the host's own js-yaml:

pwsh -File scripts/test-install-dsh.ps1     # 7 scenarios; writes only to a temp tree

Full install, verification, and rollback: docs/deploy/deepseek-harness.md; the live-install practice (multi-home reality, .dsh-module-fallback pitfalls): docs/dsh-compatibility.md.

License

MIT. See LICENSE.