OpenCode

OpenCode integration ships out of the box. Like Claude Code, OpenCode supports user-typed slash commands; unlike Claude, OpenCode injects context via a TypeScript plugin rather than a JSON hook.

What gets installed

.opencode/
├── commands/ark/
│   ├── quick.md          # /ark:quick $ARGUMENTS
│   ├── design.md         # /ark:design [--deep] $ARGUMENTS
│   └── commit.md         # /ark:commit
└── plugins/
    └── ark-context.ts    # injects `ark context` output as additionalContext

AGENTS.md                 # managed block (shared with Codex if both are installed)

Slash commands

OpenCode commands look very similar to Claude's, but with OpenCode-specific frontmatter:

---
description: Run a quick-tier Ark task — reversible, no new abstractions.
---

# `/ark:quick $ARGUMENTS`

... body identical to Claude's, with the same flow ...

Two structural invariants are tested:

every_claude_command_has_an_opencode_command_sibling — adding a Claude command without an OpenCode twin fails the build.
opencode_command_bodies_have_opencode_frontmatter_and_arguments_token — each OpenCode command body must open with ---\ndescription: (no argument-hint: line — that's Claude-specific) and contain the verbatim heading # `/ark:<name> $ARGUMENTS` matching the Claude templates exactly.

Plugin-based context injection

OpenCode doesn't have a JSON hook schema like Claude or Codex. Instead, Ark ships a TypeScript plugin at .opencode/plugins/ark-context.ts that runs on session start, calls ark context --scope session --format json, and injects the output as additionalContext for the conversation.

The plugin is shipped via a separate mechanism (extra_files in the platform registry) rather than the embedded template tree, because:

The plugin is a real TypeScript file with imports, not a markdown command body.
The path is .opencode/plugins/, parallel to but distinct from .opencode/commands/.

The plugin file is never hash-tracked — it's re-applied unconditionally on every ark init / ark load / ark upgrade. User edits to the plugin will be overwritten on the next upgrade.

Plugin internals

The plugin defines two pure helpers — buildEnvelopePrefix and shouldInject — as plain function declarations, not export function. OpenCode's plugin runtime treats every named export as a plugin factory and invokes it at load time with no arguments; exporting a parameterized helper crashes plugin loading. This invariant is locked down in templates.rs tests:

#![allow(unused)]
fn main() {
assert!(
    !body.contains("export function buildEnvelopePrefix("),
    "`buildEnvelopePrefix` must NOT be exported — opencode invokes every named export at \
     load time and the helper takes parameters"
);
}

If you're modifying the plugin, keep helpers internal and only export the actual plugin factory.

AGENTS.md managed block

OpenCode reads AGENTS.md (same file Codex uses). When both platforms are installed, the managed block is recorded once in the manifest ((file, marker) dedupe), and the on-disk file contains exactly one  marker.

What `unload` / `remove` do

ark unload captures .opencode/commands/, .opencode/plugins/, and the AGENTS.md managed block. There's no hook file to capture (OpenCode's plugin isn't hook-shaped). The whole .opencode/ tree is deleted from disk.
ark remove removes the entire .opencode/ directory (including any sibling subdirs the user added — there's no surgical hook removal because there's no hook).

OpenCode's removal_root is .opencode/ itself, not just .opencode/commands/. This is intentional: the .opencode/plugins/ subtree is also Ark-managed (the plugin file is the only thing in it), so removing the whole .opencode/ keeps the cleanup honest.

If you want to keep .opencode/ for some other purpose (e.g. you have non-Ark plugins or commands there), use ark unload to snapshot, then manually edit before load. Or don't install OpenCode integration in the first place: ark init --no-opencode.

Ark