routing

A way to choose one agent to handle each request at runtime using an explicit routing function. An agent is a program or model configured to perform a particular task; routing decides which one receives the request.

In plain words
What is it for?
Use it to build fallback handling, A/B tests, planning modes, or automatic selection among agents, with one selected agent per invocation.
Why use it?
It lets an application select agents for different tasks, retry with a fallback after failure, run experiments between alternatives, or choose based on input complexity. The feature is experimental and may change.

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/google/adk-docs/routing
Clone the repo
git clone --depth 1 https://github.com/google/adk-docs
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,112 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 $0.00000 $0.01112
Opus 5 $0.00000 $0.00556
Sonnet 5 $0.00000 $0.00222
Haiku 4.5 $0.00000 $0.00111

Measured yesterday against content hash d8ca3c76bcf0, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

routing 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/routing.md · 127 lines

How it starts

The opening of the file, as written. The whole thing — 127 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Route between agents

!!! example "Experimental"

Agent routing is experimental and may change in future releases. We welcome
your
[feedback](https://github.com/google/adk-js/issues/new?template=feature_request.md)!

When building agents for different tasks, you can define a routing function that selects which one handles each invocation at runtime. RoutedAgent provides this capability, enabling agent fallback on error, A/B testing, planning modes, and auto-routing by input complexity. If the selected agent fails before producing any output, the routing function is called again with error context so it can select a fallback.

RoutedAgent is different from workflow agents like SequentialAgent or ParallelAgent, which orchestrate multiple agents in a fixed pattern, and from LLM-driven delegation, where the LLM decides which agent to hand off to. With RoutedAgent, you write an explicit routing function that selects one agent per invocation. For model-level routing, see Model routing.

How routing works

Both RoutedAgent and RoutedLlm are powered by a shared routing utility that handles selection and failover.

The router function receives the map of available agents and the current context, and returns the key of the agent to run. It can be synchronous or async:

=== "TypeScript"

```typescript
type AgentRouter = (
  agents: Readonly<Record<string, BaseAgent>>,
  context: InvocationContext,
  errorContext?: { failedKeys: ReadonlySet<string>; lastError: unknown },
) => Promise<string | undefined> | string | undefined;
```

The agents parameter accepts either a Record<string, BaseAgent> with explicit keys, or an array of agents. If an array is provided, each agent's name property is used as its key.

Read the full file on GitHub · 127 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 · 127 lines · 0 tokens per session scan A d8ca3c76bcf0

Subscribe to this mod's changes

routing is an agent published in the GitHub repository google/adk-docs (1,479 stars, last pushed 3d ago), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 1,112 tokens. 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 2026-08-30.

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