Andersonlimahw OpenCode — Cross-Harness Subagent Skill
Teach Claude Code, Codex, and Antigravity (Agy) to delegate work to OpenCode efficiently. OpenCode is a standalone AI coding harness with its own provider system, plugin architecture, and MCP/ACP support. Use it as a specialist subagent for tasks your current harness handles poorly.
Why OpenCode as Subagent
OpenCode excels where other harnesses fall short:
| Capability | OpenCode | Notes |
|---|---|---|
| Any provider/model | Yes | Opus, Sonnet, Haiku, GLM, GPT, Claude, Gemini, Ollama |
| ACP (Agent Client Protocol) | Native | Run headless servers, attach remotely |
| Plugin system | Yes | Install any plugin from npm or local |
| Autonomous mode | --auto |
Complete approval-free execution |
| Session management | --continue, --fork, --session |
Resume/interrupt workflows |
| Remote attach | opencode attach <url> |
Connect to headless opencode servers |
| MCP servers | Native | Full Model Context Protocol support |
| Mini mode | --mini |
Lightweight TUI for constrained envs |
| Token tracking | opencode stats |
Per-session cost analytics |
| Export/Import | opencode export/import |
Share sessions across machines |
When to Delegate
Use opencode subagent when:
- Provider flexibility: Task needs a specific model (GLM, GPT, Opus) not available on your current harness
- Parallel execution: Fan out multiple independent tasks to separate opencode instances
- Specialized plugins: Task needs an opencode plugin not available in your ecosystem
- Remote execution: Task must run on a remote machine or CI/CD via ACP
- Session isolation: Task should not pollute your current session context
- Cost tracking: Need per-task token/cost accounting via
opencode stats
How to Invoke
From Claude Code
# Simple task
opencode run "refactor src/utils.ts to use async/await"
# Autonomous (no prompts)
opencode run "fix all TypeScript errors in src/" --auto
# With specific model
opencode run "audit bundle size" -m anthropic:claude-opus-4
# Continue previous session
opencode run "now optimize further" --continue
# Run headless server + attach
opencode serve --port 3001 &
opencode attach http://localhost:3001
From Codex (OpenAI CLI)
# Basic delegation
opencode run "add unit tests for the auth module" --auto
# With session tracking
SESSION=$(opencode run "migrate database schema" --auto --print-logs 2>&1 | grep session.id | grep -oP 'ses_\w+')
echo "Task running in session: $SESSION"
# Export results
opencode export $SESSION > migration-results.json
From Antigravity (Agy CLI)
# Drop-in delegation
agy exec -- opencode run "deploy to staging" --auto
# Or direct
opencode run "run performance benchmarks" -m openai:gpt-4o --auto
Task Formatting Best Practices
1. Self-Contained Prompts
Include all context — OpenCode has no access to your current session:
# BAD — lacks context
opencode run "fix the bug in auth.ts" --auto
# GOOD — self-contained
opencode run "
File: src/auth.ts (lines 42-67)
Bug: JWT token refresh throws 'invalid signature'
when the token has < 5min expiry.
Expected: Token should refresh silently.
Fix the validateToken function to check expiry before signature.
" --auto
2. Use --continue for Multi-Step
opencode run "step 1: scaffold the component" --auto
STATUS=$?
if [ $STATUS -eq 0 ]; then
opencode run "step 2: add styles and tests" --auto --continue
fi
3. Fan-Out Pattern (Parallel)
# Launch parallel tasks
opencode run "task A: API docs" --auto &
PID1=$!
opencode run "task B: client SDK" --auto &
PID2=$!
opencode run "task C: examples" --auto &
PID3=$!
# Wait for all
wait $PID1 $PID2 $PID3
echo "All parallel tasks complete"
4. Remote ACP Pattern
# On remote server
opencode serve --port 3001 --hostname 0.0.0.0 &
# On local machine
opencode attach http://remote-server:3001
5. Provider Routing via Models
Use OpenCode's multi-provider to route each task to the best model:
# Budget work → cheap model
opencode run "format all files" -m openai:gpt-4o-mini --auto
# Complex reasoning → quality model
opencode run "design auth architecture" -m anthropic:claude-opus-4 --auto
# Balanced → mid-tier
opencode run "implement CRUD endpoints" -m openai:gpt-4o --auto
Result Handling
Capture Output
# Capture to variable
RESULT=$(opencode run "analyze package.json dependencies" --auto --print-logs 2>&1)
echo "$RESULT" | grep -v "^timestamp=" # Strip logs, show AI output only
# Capture to file
opencode run "generate migration SQL" --auto > migration-output.txt
Check Exit Code
opencode run "validate all schemas" --auto
if [ $? -eq 0 ]; then
echo "Validation passed"
else
echo "Validation failed — check session output"
fi
Export Session for Review
# After task completes
opencode export <session-id> > task-report.json
# Parse results
cat task-report.json | jq '.messages[-1].content'
Agent Definitions for Each Harness
Claude Code Agent
Place in ~/.claude/agents/opencode-subagent.md:
---
name: opencode-subagent
description: >
Delegates work to OpenCode CLI. Use when a task needs a specific provider,
plugin, or autonomous execution that Claude Code doesn't handle well.
Triggers on "delegate to opencode", "opencode run", "open code subagent".
color: "#F97316"
mode: subagent
permission:
bash: allow
read: allow
---
Codex Plugin
Place in .codex-plugin/agents/opencode-subagent.json:
{
"name": "opencode-subagent",
"description": "Delegates work to OpenCode CLI from Codex. Use for autonomous task execution, multi-provider routing, or headless ACP operations.",
"triggers": ["delegate to opencode", "opencode run"]
}
Agy Agent
Place in ~/.agy/agents/opencode-subagent.yaml:
name: opencode-subagent
description: |
Delegates work to OpenCode CLI from Antigravity.
Use for parallel task execution, remote ACP, or provider-specific work.
Protocol Summary
┌──────────────┐ opencode run "<task>" ┌──────────────┐
│ │ ──────────────────────────────> │ │
│ Claude / │ │ OpenCode │
│ Codex / │ <────────────────────────────── │ │
│ Agy │ session output + exit code │ │
└──────────────┘ └──────────────┘
│ │
│ 3. Process Results 2. Execute Task
│ - Parse output │
│ - Check exit code - Auto mode
│ - Export if needed - Any provider
│ - Log metrics - Isolated session
│ - MCP/ACP if needed
Testing the Setup
# Quick smoke test
opencode run "respond only with 'opencode subagent OK'" --auto
# Full delegation test
opencode run "
Create a hello.txt file with content 'Hello from OpenCode subagent'
Then read it back to confirm.
" --auto --print-logs 2>&1 | tail -5
# Provider routing test
opencode run "echo 'model test'" -m openai:gpt-4o-mini --auto
# Session persistence test
opencode run "create a note" --auto
opencode run "now read the note back" --auto --continue
Requirements
- OpenCode CLI installed and in
$PATH - At least one provider configured (
opencode providers) - For remote ACP: network access to target server