Running Claude Code, Codex and Gemini side by side
Why a single AI coding agent is rarely enough, and how a multi-terminal workspace with worktree isolation changes the way you ship.
Most teams reach for a single AI coding agent and stop there. But Claude Code, Codex CLI and Gemini each have different strengths — and the real unlock is running them together, on the same codebase, without stepping on each other.
One agent is a bottleneck
When you run a single agent, everything is serial: refactor, then tests, then docs, then review. Each step waits for the last. The agent is fast, but you are still the queue.
The multi-harness pattern
Run several agents in parallel, each scoped to one job:
- Claude on the refactor — strong at large, structured edits.
- Codex on the flaky test suite — tight, iterative fixes.
- Gemini on the docs — fast long-form rewrites.
The catch: three agents writing to the same checkout collide. That is what worktree isolation solves — each agent gets its own detached Git worktree, so they physically cannot overwrite each other.
Cost is the hidden variable
Parallel agents burn tokens in parallel. Without a live cost meter you find out at the invoice. A per-session burn-rate clock turns that from a surprise into a decision.
That combination — multiple agents, worktree isolation, live cost — is the workflow Quorum Terminal is built around.