multi-model

A routing system that lets each delegated AI session use a selected model, including fast or more capable model tiers. The choice follows defined settings such as the agent, prompt, session, and default configuration.

In plain words
What is it for?
Use it to assign models per agent or prompt, route tasks by complexity, and handle fallback when a selected model is unavailable.
Why use it?
It lets simple work use faster or cheaper models while reserving more capable models for difficult reasoning tasks.

Agent

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/dsswift/ion/multi-model
Clone the repo
git clone --depth 1 https://github.com/dsswift/ion
Per session 11 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 763 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00011 $0.00763
Opus 5 $0.00005 $0.00381
Sonnet 5 $0.00002 $0.00153
Haiku 4.5 $0.00001 $0.00076

Measured yesterday against content hash fdf2bcdd909a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

multi-model scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

docs/agents/multi-model.md · 119 lines

How it starts

The opening of the file, as written. The whole thing — 119 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Multi-Model Routing

Each agent can specify its own model, allowing you to route expensive reasoning tasks to capable models and simple tasks to fast, cheap ones.

How model selection works

Model resolution has two stages: first the engine decides which name to use, then it resolves that name to a concrete model.

Stage 1 -- precedence. The first of these that is set wins:

  1. Agent definition -- the model field in the agent's frontmatter
  2. Per-prompt override -- model specified in the send_prompt command
  3. Session config -- model set when the session was started
  4. Engine default -- defaultModel from engine runtime config

Stage 2 -- tier resolution. If the name that won stage 1 is a tier alias (e.g. fast), the model config resolves it to a concrete model. This is not a fifth precedence level: it applies to whichever name stage 1 selected, so a tier alias in an agent definition is resolved rather than being overridden by defaultModel.

If the resolved model maps to no configured provider, the run falls back to defaultModel and emits engine_model_fallback once per run.

Cost optimization patterns

Cheap triage, expensive execution

Use a fast model for initial analysis, then delegate complex work to a capable model:

# .ion/agents/triage.md
---
name: triage
model: claude-haiku-4-5-20251001
description: Quick analysis and task routing
---

Analyze the request and determine which specialist agent to invoke.
# .ion/agents/deep-analysis.md
---
name: deep-analysis
model: claude-sonnet-4-6
description: Thorough code analysis and refactoring
---

Perform detailed analysis of the codebase...

Read-only agents on cheap models

Agents that only need to read and summarize (no tool calls that modify files) can run on the cheapest available model:

---
name: summarizer
model: gpt-4.1-mini
tools: [Read, Grep, Glob]
description: Summarizes code and documentation
---

Cross-provider routing

Read the full file on GitHub · 119 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 119 lines · 11 tokens per session scan A fdf2bcdd909a

Subscribe to this mod's changes

multi-model is an agent published in the GitHub repository dsswift/ion (4 stars, last pushed yesterday), licensed MIT. It adds 11 tokens to every session and 763 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.