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opencode

o2b install --target opencode --apply performs a native integration in one pass:

  1. MCP servers - merges the two Open Second Brain servers (open-second-brain, open-second-brain-writer) into ${XDG_CONFIG_HOME:-$HOME/.config}/opencode/opencode.json under the mcp key, using opencode's entry schema ({"type": "local", "command": [...], "environment": {...}, "enabled": true}). User-authored entries are preserved.
  2. Plugin - copies the bundled Open Second Brain plugin into ${XDG_CONFIG_HOME:-$HOME/.config}/opencode/plugins/open-second-brain.ts. opencode auto-loads it at startup.
  3. Legacy cleanup - releases before v1.4.0 wrote ~/.config/opencode/mcp.json, a file opencode never reads. Apply removes the two Open Second Brain keys from it (and deletes the file when nothing else remains).

Install

o2b install --target opencode --apply

Restart opencode to load the MCP servers and the plugin.

opencode's Brain writes attribute to an opencode-specific identity derived from your configured agent_name: the host segment is kept and the vendor token is swapped to opencode (claude-vps-agent -> opencode-vps-agent; a name that does not fit the <vendor>-<host>-agent shape is prefixed with opencode-). So opencode activity is distinguishable per runtime - and, in a shared multi-device vault, per device - rather than logged under the shared identity. apply stamps this on VAULT_AGENT_NAME in opencode.json; no manual step is needed.

What the plugin does

  • Active context inject - appends the rendered Brain/active.md digest to the system prompt of each chat request (cached, 5 minute TTL), so the agent sees live preferences without calling brain_query first. Uses the same o2b-hook active-inject shim as the Claude Code and Codex hook layers; if the shim or the vault is missing the inject silently skips.

  • Session capture - on session.idle / session.compacted / session.deleted the plugin snapshots the session as a JSONL spool under ${XDG_DATA_HOME:-$HOME/.local/share}/open-second-brain/opencode/. Import captured sessions with:

    o2b brain import-session ~/.local/share/open-second-brain/opencode/ \
  --vault /path/to/vault

  • Post-write reminder - after file-mutating tools (write, edit, multiedit, patch, apply_patch) the standard logging nudge is appended to the tool output so the agent considers brain_feedback / brain_apply_evidence / brain_note before its final reply.

Every plugin hook is fail-soft: a missing vault, missing o2b-hook binary, or SDK error never breaks the opencode session.

Verify

o2b install --check --target opencode

Reports drift when the MCP entries differ from canonical or the installed plugin copy differs from the bundled version (for example after an Open Second Brain upgrade - re-run apply to refresh it).

Uninstall

o2b uninstall --target opencode --apply

Removes the two mcp keys from opencode.json and deletes the installed plugin file. User-authored config is untouched.

Known gaps relative to Claude Code / Codex

  • No stop-log guardrail. opencode exposes no blocking stop hook, so the guardrail that vetoes an unlogged artifact turn cannot be reproduced; the post-write reminder still fires.
  • Context inject rides an experimental hook (experimental.chat.system.transform). If a future opencode release changes it, the inject degrades to no-op while capture and the MCP servers keep working.

Notes

  • Upstream is anomalyco/opencode (formerly hosted under sst/opencode); config schema verified against https://opencode.ai/docs 2026-06-10.
  • Rules: opencode reads AGENTS.md natively, so vault-level rules can also travel as project instructions without any Open Second Brain involvement.