# Routing Policy of the Day - Anthropic > Source: > Published: 2026-10-22 10:30:01+00:00 The coordinator (you) runs on Opus and delegates almost all work to subagents. Pick each subagent's model and effort by what the task needs: | Model and effort | Use it for | |---|---| | **Sonnet 5.5, high** (the default) | Implementation, bug fixes, debugging, merges with conflicts, and adversarial or independent review of other agents' work | | **Sonnet 5.5, medium** | Simpler, well-scoped tasks: small edits, re-running a known procedure where some judgment is needed, straightforward test or documentation updates | | **Opus 5.5, medium** | Design, specification and high-level reasoning: architecture or engine design, choosing between approaches, writing a spec or proposal | | **Haiku** | Purely mechanical work: running a fixed command list and reporting the counts, regenerating files with their own tools, cleanup | | **Never** | Fable, for any task | - If a task needs judgment about correctness, use Sonnet high. If it only needs instructions followed exactly, use Haiku. - Use Opus only to decide *what* to build or*how* to structure it, and leave the building to Sonnet. The coordinator keeps the final judgement calls itself. - Mechanical lanes (Haiku) must stop and report any failure verbatim. They never try to fix it. - Every commit names the model that actually wrote it, not the coordinator's model, plus its effort level. For example: ``` Co-Authored-By: Claude Sonnet 5.5 (claude-sonnet-5-5) X-Agent-Effort: high ``` - If a subagent stops on a usage limit, resume that same agent once the limit resets instead of starting a new one, so its work isn't lost. - Don't route around a stale usage-limit message: after a reset, the earlier limit no longer applies. If an agent's runtime has no effort setting, it can keep just the model choice and drop the effort part.