GPT-5.5 Codex vs Claude Opus 4.7: Real-world coding agent benchmarks

A Reddit user tested GPT-5.5 Codex (via Cursor) against Claude Opus 4.7 (Claude Code) on two production-grade tasks. Both used the same prompts, MCPs (GitHub + Slack), and machine. Results highlight tradeoffs in cost, architecture, and reliability.

Test 1: PR triage bot

• GitHub MCP, scoring formula, Slack alerts, retries, strict TypeScript (no any).
• Claude Code: Verified MCP reachable before writing code. Built 36 files in 12 minutes. Wrote its own WebSocket smoke test (3ms broadcast). Zero errors on first run. Total cost: ~$2.50.
• Codex: Failed — GitHub MCP unreachable due to Cursor environment issue (not model error). Could not complete task.

Test 2: Real-time code review UI

• React, WebSockets, optimistic rollback, virtualized diff, WS reconnect.
• Claude Code: Same clean delivery, 36 files, no errors.
• Codex: Shipped in 28 files (more compact architecture). Required one manual patch for an infinite React loop. Total cost: ~$2.04 (18% cheaper than Claude).

Takeaways: For complex, architecture-heavy work, Opus 4.7 still leads — better tool handling, zero-rewrite output, and thorough MCP validation. Codex is leaner and cheaper, suitable for tight, self-contained tasks where fast shipping matters and you can tolerate a minor patch pass. The user isn't switching yet but now watches the pricing gap.