setting-up-oh-my-opencode

Agent Building

Use when installing or configuring oh-my-opencode plugin for OpenCode, or when Vertex AI models need to be configured for Claude/Gemini access

QUICK START

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I want to install this Agent Skill for this project in Codex.

Source SKILL.md: https://github.com/majiayu000/claude-skill-registry/blob/HEAD/skills/data/setting-up-oh-my-opencode/SKILL.md

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Setting Up oh-my-opencode

Install and configure oh-my-opencode plugin with platform-appropriate model routing.

Prerequisites

OpenCode installed via home-manager (from llm-agents.nix)
Authentication configured:
- ChatGPT Plus: opencode auth login → OpenAI → headless
- Vertex AI (macOS): gcloud auth application-default login

Platform Subscription Summary

Platform	Claude	OpenAI	Gemini	Copilot
devbox	Max 20x (personal)	ChatGPT Plus	No	No
macOS	Vertex AI (work)	ChatGPT Plus	Vertex AI (work)	Yes (work)

Verify Vertex AI Access (macOS only)

Before installing, confirm Vertex AI credentials work:

# Check env vars
echo "GOOGLE_CLOUD_PROJECT: $GOOGLE_CLOUD_PROJECT"
echo "VERTEX_LOCATION: $VERTEX_LOCATION"

# Test model access
opencode models | grep google-vertex
opencode run --model google-vertex/gemini-2.5-flash "Say hello"
opencode run --model google-vertex-anthropic/claude-sonnet-4@20250514 "Say hello"

Installation

macOS (Vertex AI + ChatGPT + Copilot)

npx oh-my-opencode install --no-tui \
  --claude=yes \
  --openai=yes \
  --gemini=yes \
  --copilot=yes

Devbox (Max 20x + ChatGPT)

npx oh-my-opencode install --no-tui \
  --claude=max20 \
  --openai=yes

Post-Install: Configure Vertex AI Models (macOS)

The installer configures anthropic/ and google/ model names, but macOS should route through Vertex AI for work billing.

Edit ~/.config/opencode/oh-my-opencode.json:

Before	After
`anthropic/claude-opus-4-5`	`google-vertex-anthropic/claude-opus-4-5@20251101`
`anthropic/claude-sonnet-4-5`	`google-vertex-anthropic/claude-sonnet-4-5@20250929`
`anthropic/claude-haiku-4-5`	`google-vertex-anthropic/claude-haiku-4-5@20251001`
`google/gemini-3-flash`	`google-vertex/gemini-3-flash-preview`
`google/gemini-3-pro`	`google-vertex/gemini-3-pro-preview`

Replace all occurrences in both agents and categories sections.

Verification

# Check agent assignments
cat ~/.config/opencode/oh-my-opencode.json | jq '.agents.sisyphus, .agents.oracle'

# Test a Vertex AI model
opencode run --model google-vertex-anthropic/claude-opus-4-5@20251101 "Say 'Vertex AI working'"

Troubleshooting

Issue	Fix
`opencode: command not found`	Run `home-manager switch` to install opencode
Vertex AI models not listed	Check `GOOGLE_CLOUD_PROJECT` and `gcloud auth application-default login`
"Permission denied" on Vertex	Verify IAM permissions in GCP console