model-selection

Model Selection

Determines which LLM model to use for each agent spawn.

SCOPE

✅ THIS SKILL PRODUCES:

• A resolved model parameter for every task tool call
• Persistent model preferences in .squad/config.json
• Spawn acknowledgments that include the resolved model

❌ THIS SKILL DOES NOT PRODUCE:

• Code, tests, or documentation
• Model performance benchmarks
• Cost reports or billing artifacts

Context

Squad supports 18+ models across three tiers (premium, standard, fast). The coordinator must select the right model for each agent spawn. Users can set persistent preferences that survive across sessions.

5-Layer Model Resolution Hierarchy

Resolution is first-match-wins — the highest layer with a value wins.

Layer	Name	Source	Persistence
0a	Per-Agent Config	.squad/config.json → agentModelOverrides.{name}	Persistent (survives sessions)
0b	Global Config	.squad/config.json → defaultModel	Persistent (survives sessions)
1	Session Directive	User said "use X" in current session	Session-only
2	Charter Preference	Agent's charter.md → ## Model section	Persistent (in charter)
3	Task-Aware Auto	Code → sonnet, docs → haiku, visual → opus	Computed per-spawn
4	Default	claude-haiku-4.5	Hardcoded fallback

Key principle: Layer 0 (persistent config) beats everything. If the user said "always use opus" and it was saved to config.json, every agent gets opus regardless of role or task type. This is intentional — the user explicitly chose quality over cost.

AGENT WORKFLOW

On Session Start

1. READ .squad/config.json
2. CHECK for defaultModel field — if present, this is the Layer 0 override for all spawns
3. CHECK for agentModelOverrides field — if present, these are per-agent Layer 0a overrides
4. STORE both values in session context for the duration

On Every Agent Spawn

1. CHECK Layer 0a: Is there an agentModelOverrides.{agentName} in config.json? → Use it.
2. CHECK Layer 0b: Is there a defaultModel in config.json? → Use it.
3. CHECK Layer 1: Did the user give a session directive? → Use it.
4. CHECK Layer 2: Does the agent's charter have a ## Model section? → Use it.
5. CHECK Layer 3: Determine task type:
   • Code (implementation, tests, refactoring, bug fixes) → claude-sonnet-4.6
   • Prompts, agent designs → claude-sonnet-4.6
   • Visual/design with image analysis → claude-opus-4.8
   • Non-code (docs, planning, triage, changelogs) → claude-haiku-4.5
6. FALLBACK Layer 4: claude-haiku-4.5
7. INCLUDE model in spawn acknowledgment: 🔧 {Name} ({resolved_model}) — {task}