Three coding harnesses. Three different shapes.

Claude Code: long-horizon coherence. Codex CLI: per-session productivity. OpenCode: substrate freedom.

Six weeks ago you could draw a clean architectural line between them. Today the line is smudged. Read only the changelogs and you’d conclude they’re turning into the same product. Use them for a week each and you’d conclude something else.

Two pieces today, same field, different lenses.

Personal version: rundatarun.io/p/three-h…

Technical deep-dive: ai.rundatarun.io/AI%20D…