Model tiers and agent tooling

The workflow talks about capability tiers, not vendor names. Map whatever stack is in use onto these four tiers. The model names below are a mid-2026 snapshot — they go stale; when a name no longer exists, map its replacement by tier, not by nostalgia.

The four tiers

Tier	Role	Anthropic	OpenAI	Google
Escalation	Judgment calls the coordinator flags	Fable 5, Opus 4.8	Sol, GPT-5 (high)	Gemini 2.5 Pro
Coordinator	Resident; owns every phase by default	Sonnet 5	GPT-5, GPT-4.1	Gemini 2.5 Flash
Implementer	Pinned-spec work, often same tier as coordinator	Sonnet 5	GPT-5, GPT-4.1	Gemini 2.5 Flash
Trivial	Mechanical edits	Haiku 4.5	GPT-4.1 mini	Gemini Flash-Lite

• Escalation — the strongest reasoning model available, called only when a trigger in escalate.md fires: unclear root cause, architectural risk, security sensitivity, an irreversible operation, repeated spec gaps, or low confidence in a review. Answers one specific question, then hands control back to the coordinator.
• Coordinator — a capable mid-tier model, resident for the whole task. Owns analysis, planning, supervision, and verification by default. It's capable enough for the large majority of work, and cheap enough relative to Escalation tier that most tasks never need to call up at all — that's the point of the split.
• Implementer — often literally the same model as the coordinator; the distinction is parallelism and workspace isolation, not capability. Falls back to a smaller model for batches of mechanical, unambiguous edits.
• Trivial — small, very fast models for mechanical, unambiguous edits: renames, config tweaks, typo fixes, doc touch-ups. Batch several to amortize the dispatch overhead. When in doubt between trivial and implementer, pick implementer — a wrong cheap edit costs more than the price difference.

Tooling mappings

How to run the coordinator/escalation/implementer split in common agent tooling:

• Claude Code — run the session itself on a coordinator-tier model (e.g. Sonnet 5). Call Agent with model: opus (or fable) only at an escalation checkpoint, scoped to the one question that triggered it. Use worktree isolation for parallel implementer-tier tasks, and model: haiku for batched trivial edits.
• GitHub Copilot — run Copilot Chat on a coordinator-tier model for the whole flow; switch the model picker to the strongest reasoning model only for the specific question an escalation trigger flagged, then switch back. Standalone, well-specified tasks can still be assigned to the Copilot coding agent (assign the issue or PR to Copilot), which works on its own branch — the pinned spec becomes the issue body.
• Codex — orchestrate locally (CLI or chat) on a coordinator-tier model; dispatch each pinned spec as a Codex cloud task, one task per independent unit, and review the resulting diffs yourself, escalating to the frontier model only when a trigger fires.
• Cursor and similar IDE agents — one composer/agent session per task on a coordinator-tier model; background agents for the parallel implementer-tier ones; switch to the strongest model in-session only for an escalation checkpoint, then switch back.

No subagent support at all? Keep the phases, drop the parallelism: run the whole flow on a coordinator-tier model, and switch the session model up to the strongest one only for the specific question an escalation trigger flagged, then switch back down. The discipline transfers even when the delegation mechanism does not.