GPT-5.5 Excels in Coding Execution with Opus 4.7 Plans
GPT-5.5 hits 62.5/100 on senior engineer benchmark (humans: 80-90, Opus 4.7: 33), but peaks using Opus 4.7's terse, contract-style plans for bold rewrites; strong in TypeScript/Swift, business writing, fast desktop agents.
Unlock GPT-5.5's Bold Coding with Precise Plans
GPT-5.5 delivers a step change in coding, scoring 62.5/100 on the Senior Engineer (SE) benchmark—rewriting a real codebase (Vibecoded Slap app, from speaker's "Proof" app) from first principles with conceptual clarity—versus Opus 4.7's consistent low-30s (33 average) and GPT-5.4's similar patching. Humans score 80-90/100, leaving room for improvement, but GPT-5.5 closes a 30-point gap over Opus 4.7. The key: pair it with Opus 4.7 plans. Opus 4.7 excels at terse, contract-driven plans specifying invariants, deletions, file counts (e.g., "big file only 100 lines"), and outcomes, enabling GPT-5.5's agency to delete files, avoid patches, and execute multi-hour rewrites assertively. Self-plans from GPT-5.5 reach low-50s/mid-50s, still beating others but lagging Opus-guided runs.
Real-world wins include building a native iOS/Mac to-do app (Dayline) turning through features on a solid plan, and shipping Monologue app features using 900M tokens pre-release—hitting deadlines an "incredible senior engineer" couldn't match alone. It shines in TypeScript and Swift but falters on Ruby (e.g., Rails). For product-forward tasks like LFG bench (feature building with frontend/design), Opus 4.7 has a higher ceiling, especially aesthetics; underspecified plans expose GPT-5.5's limits versus Opus 4.7's vibe-coding speed.
Pro Tip: Prompt GPT-5.5 with Opus 4.7's robotic terseness and specifics for maximum boldness—its tuning favors human-readable output, so override with exact contracts.
Business Writing and Fast Knowledge Agents
For writing, GPT-5.5 one-shots investor updates near-send-ready and replicates voices subtly without excess personality (less than Opus 4.6/4.7), making it ideal for restrained business prose. Staff writers prefer it over recent GPTs or Sonnet for the first time in years.
In knowledge work, Codex desktop app with GPT-5.5 offers best-in-class agentic speed—faster than sluggish Opus 4.7—handling computer apps, web browsing, dashboards, and data analysis. OpenAI's hardware edge is palpable. However, detail-oriented insights (e.g., grading code trajectories) favor Opus 4.7's sharper eye; GPT-5.5 sacrifices some precision for digestibility.
Trade-offs and Daily Driver Shift
GPT-5.5 isn't perfect: Opus 4.7 plans better, designs with more aesthetic sense, and suits sharp analysis. Yet its speed, usability, and frontier power in a collaborative package make it a top daily driver for desktop/agentic work (speaker switched from Claude). In OpenClaw (free under ChatGPT sub), it's stable despite Opus bias, worth retrying post-5.4. Use Opus for planning/mobile, GPT-5.5 for execution—team powers amplify with frequent releases.