git:20260823.3699cb8 to git:20260913.8b79211

- name: "model-selection"

- description: "Determines which LLM model to use for each agent spawn"

- domain: "orchestration"

- confidence: "medium"

- source: "extracted"

- > 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 a curated model catalog 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/prompts → Terra, docs → Luna, visual → Sol | Computed per-spawn |

- | **4** | Default | `gpt-5.6-luna` | 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) → `gpt-5.6-terra`

- - Prompts, agent designs → `gpt-5.6-terra`

- - Visual/design with image analysis → `gpt-5.6-sol`

- - Non-code (docs, planning, triage, changelogs) → `gpt-5.6-luna`

- 6. FALLBACK Layer 4: `gpt-5.6-luna`

- 7. INCLUDE model in spawn acknowledgment: `🔧 {Name} ({resolved_model}) — {task}`

-

- ### When User Sets a Preference

-

- **Trigger phrases:** "always use X", "use X for everything", "switch to X", "default to X"

-

- 1. VALIDATE the model ID against the catalog

- 2. WRITE `defaultModel` to `.squad/config.json` (merge, don't overwrite)

- 3. ACKNOWLEDGE: `✅ Model preference saved: {model} — all future sessions will use this until changed.`

-

- **Per-agent trigger:** "use X for {agent}"

-

- 1. VALIDATE model ID

- 2. WRITE to `agentModelOverrides.{agent}` in `.squad/config.json`

- 3. ACKNOWLEDGE: `✅ {Agent} will always use {model} — saved to config.`

-

- ### When User Clears a Preference

-

- **Trigger phrases:** "switch back to automatic", "clear model preference", "use default models"

-

- 1. REMOVE `defaultModel` from `.squad/config.json`

- 2. ACKNOWLEDGE: `✅ Model preference cleared — returning to automatic selection.`

- ### STOP

- After resolving the model and including it in the spawn template, this skill is done. Do NOT:

- - Generate model comparison reports

- - Run benchmarks or speed tests

- - Create new config files (only modify existing `.squad/config.json`)

- - Change the model after spawn (fallback chains handle runtime failures)

- ## Config Schema

- `.squad/config.json` model-related fields:

- ```json

- {

- "version": 1,

- "defaultModel": "claude-opus-4.6",

- "agentModelOverrides": {

- "fenster": "claude-sonnet-4.6",

- "mcmanus": "claude-haiku-4.5"

- }

- }

- ```

- - `defaultModel` — applies to ALL agents unless overridden by `agentModelOverrides`

- - `agentModelOverrides` — per-agent overrides that take priority over `defaultModel`

- - Both fields are optional. When absent, Layers 1-4 apply normally.

- ## Fallback Chains

- If a model is unavailable (rate limit, plan restriction), retry within the same tier:

- ```

- Premium: gpt-5.6-sol → claude-opus-5 → claude-opus-4.8 → claude-opus-4.7 → claude-opus-4.6 → claude-sonnet-4.6 → (omit model param)

- Standard: gpt-5.6-terra → claude-sonnet-5 → claude-sonnet-4.6 → gpt-5.5 → gpt-5.4 → gpt-5.3-codex → claude-sonnet-4.5 → gemini-3.1-pro → (omit model param)

- Fast: gpt-5.6-luna → claude-haiku-4.5 → gpt-5.4-mini → gpt-5-mini → (omit model param)

- ```

- **Never fall UP in tier.** A fast task won't land on a premium model via fallback.