OpenCode extends through two separate mechanisms: Agent Skills (SKILL.md folders surfaced to the model through a native skill tool, with per-skill permissions) and plugins (JavaScript or TypeScript modules that hook lifecycle events, loaded from local files or npm).
OpenCode splits extensibility cleanly where other harnesses blur it: declarative markdown for knowledge the model should follow, real code for behavior the harness must enforce, and that split is the pattern I would copy.
What it is #
Skills load from .opencode/skills, ~/.config/opencode/skills, and the Claude-compatible (.claude/skills) and agent-compatible (.agents/skills) paths, project and global, discovered by walking from the working directory up to the worktree root.
Frontmatter requires name and description, accepts license, compatibility, and metadata, and ignores unknown fields; as of 2026-11-07 the unified skills docs page no longer carries the OpenCode-1 disclaimer and documents the v2 surface directly: single-file skills, HTTP skill catalogs configured in opencode.json, ID-precedence discovery, explicit @skill-id prompt loads, and a metadata.opencode/autoinvoke: false (or disable-model-invocation) opt-out from the model-facing list.
The model loads a skill on demand by calling the skill tool, and permissions can allow, deny, or ask per pattern, be overridden per agent, or the tool can be disabled entirely.
Plugins are JS/TS modules from .opencode/plugins or npm (installed via Bun at startup) hooking events like tool.execute.before, session.idle, or experimental.session.compacting, and they can register custom tools.
Status #
Active; the skills and plugins docs are maintained closely, the skills page last updated 2026-10-30. The host project (anomalyco/opencode) shows about 213.3k stars under MIT as of 2026-10-13, and the v2 line is now the shipping release train: v2.2.0 through v2.2.5 published 2026-10-27 to 10-30, with the 1.x line still releasing beside it (v1.19.5 on 2026-10-28), after the v2 redesign had lived only in its own docs tree. The ecosystem page lists 31 community plugins, 10 projects, and 2 agent collections under separate section headers (counted 2026-10-31; the page states no count itself), the same 43 rows the 10-24 reading counted as “43 plugins” before the page was re-sectioned. There is no first-party skill marketplace; distribution rides plain git or third parties like skills.sh.
Strengths #
- It reads
.claude/skillsdirectly, so spec-subset Claude Code skills work unmodified. - The per-skill allow/deny/ask permission model is finer-grained than Claude Code’s, which gates tools but not skill loads.
- Plugins do what markdown cannot: rewrite tool arguments, inject environment variables, replace compaction prompts, add tools.
- npm distribution reuses the normal JS supply chain (registry, lockfiles, audits).
Cautions #
- Unknown frontmatter is ignored silently, so Claude Code extensions (
context: fork, hooks in skills,disable-model-invocation) do nothing here; the Vercel CLI’s compatibility matrix confirms OpenCode lacks bothcontext: forkand hooks. - Skills load by model judgment on the description; the slash-command mechanism this note recorded on 2026-10-16 is gone from the docs, the 10-30 “OpenCode 1 uses no metadata keys” line is gone too (the unified page now documents the v2 surface directly), and the surviving opt-outs are the
opencode/autoinvoke/disable-model-invocationkeys plus explicit@skill-idprompting, so there is still no skill versioning. - An npm plugin is arbitrary code executed at startup with your privileges; the docs’ own examples (an
.envread blocker) exist because that surface needs guarding. - The config surface moves fast and the project carries breaking-change warnings, so pin versions.
Pricing #
Free and MIT; you pay model providers, or OpenCode Zen, for tokens. Skills and plugins cost nothing to install, though some community plugins wrap paid services (Firecrawl, Tavily) with their own billing.
Compared to #
- Claude Code skills and plugins: richer skill frontmatter and bundled skills, but the extensions stay harness-locked.
- Codex skills and plugins: the same standard subset plus a universal plugin directory spanning ChatGPT and Codex.
- MCP servers (also supported here): choose plugins to change harness behavior, MCP to hand the model a new tool.
Bottom line #
Recommended for teams standardizing on SKILL.md that still need real hooks; write skills for procedure, plugins for policy. Not for teams that need stable extension APIs between releases; the surface moves fast enough to break you. My disagreeable claim: plugins, not skills, are OpenCode’s actual differentiator, because every harness now reads the same SKILL.md subset, so choosing a harness on skills support alone is a mistake.
Changes #
- 2026-08-24 - Created in the Skills category seed.
- 2026-08-26 - Restored the mandatory Not-for-Y bottom-line clauses in a review-driven maintenance pass.
- 2026-09-25 - Refreshed the volatile numbers (209,897 host stars; the ecosystem page, updated 2026-09-24, still lists roughly 40 plugins).
- 2026-10-16 - Rotation re-verification corrected the invocation claim: the skills docs now document
metadatakeys (opencode/slash,opencode/autoinvoke) that expose a skill as an explicit/<name>TUI command; every cited URL re-fetched live (39 plugins on the ecosystem page, docs pages updated 2026-10-15). - 2026-10-24 - Rotation re-verification reversed the 10-16 invocation reading: the rewritten skills docs (last updated 2026-10-23) state OpenCode 1 uses no metadata keys for slash commands or automatic skill selection, and the new v2 docs tree documents the replacement surface (
opencode/autoinvoke: falseanddisable-model-invocationopt-outs, explicit@skill-idprompt loads, HTTP skill catalogs, single-file skills); the ecosystem count moved to 43 plugins and the host release to v1.19.4 (2026-10-22). - 2026-10-31 - The v2 line became the shipping release train: v2.2.0 through v2.2.5 published 2026-10-27 to 10-30 (the 1.x line still releasing v1.19.5 on 10-28), so the v2 redesign is no longer docs-only; the same rotation pass corrected the 10-24 ecosystem reading, finding the page re-sectioned into Plugins, Projects, and Agents, with 31 plugin rows plus 10 project and 2 agent entries (the same 43 rows previously counted as “43 plugins”); every cited URL re-fetched live and all other claims held.
- 2026-11-07 - Out-of-rotation correction on a moving source: the unified skills docs page no longer carries the “OpenCode 1 uses no metadata keys” disclaimer and now documents the v2 catalog surface directly (HTTP catalogs in opencode.json,
opencode/autoinvokeanddisable-model-invocationopt-outs,@skill-idloads, ID precedence, “all frontmatter is optional at runtime”); the What-it-is and caution lines re-grounded on today’s fetch, conclusion unchanged, and every other cited URL re-fetched live with claims held.
See also #
- OpenCode - the harness this extends
- Agent Skills open standard - the spec OpenCode implements a subset of
- Anthropic Agent Skills - where most of the format’s richer features live
- skills.sh - the third-party distribution layer for these skills
- Crush - the sibling harness from the same 2025 split, also reading a skills directory
References #
https://opencode.ai/docs/skills/ - skill paths, frontmatter, permissions, the skill tool; the unified page as of 2026-11-07 documents the v2 catalog surface directly (HTTP catalogs, the autoinvoke and disable-model-invocation opt-outs,
@skill-idloads) and no longer carries the OpenCode-1 metadata disclaimer (re-fetched 2026-11-07, page moved since 10-31)@skill-idloading (fetched 2026-10-24, re-fetched 2026-10-31, claims unchanged)https://github.com/anomalyco/opencode - host project scale and MIT license as of 2026-10-24; release trains re-verified 2026-10-31 (v2.2.0-v2.2.5 published 2026-10-27 to 10-30, v1.19.5 on 2026-10-28)
https://agentskills.io/ - lists OpenCode among the standard’s clients
context: forkand hooks unsupported in OpenCode)