RouteHP — How it works

The routing flow

From query to response in 4 steps

RouteHP sits invisibly between your app and Anthropic. Your code doesn't change — we just intercept each request and make a smarter decision about which model handles it.

📨

Query received

Your app sends a query to RouteHP exactly as it would to Anthropic. Same format, same headers, same everything.

0ms

🧠

Complexity scored

Our classifier reads the query and scores its complexity from 0.0 (trivial) to 1.0 (highly complex) using multiple signals.

< 1ms

⚡

Model selected

Based on the score, the query is routed to the cheapest model that can handle it well — Haiku, Sonnet, or Opus.

< 1ms

✅

Response returned

The response comes back in the standard Anthropic format, plus a routehp block showing the model used and saving.

~300ms

The classifier

How we score query complexity

Our classifier analyses multiple signals in each query to produce a complexity score. The higher the score, the more powerful the model we route to.

📏 Length signals

Short queries (under 10 words) → lower score

Medium queries (10–100 words) → neutral

Long queries (100+ words) → higher score

Example: "What is 2+2?" scores low. "Analyse this 50-page contract for liability clauses" scores high.

🔑 Keyword signals

Complex: analyse, evaluate, implement, legal, medical, financial

Simple: summarise, define, translate, what is, hello

Code blocks in the query → higher score

Example: "Define REST API" scores low. "Implement a distributed rate limiter in Python" scores high.

🏗️ Structure signals

Multiple questions in one query → higher score

Long conversation history → higher score

Single short question → lower score

Example: A query with 3 sub-questions scores higher than a single direct question of the same length.

📊 Final score

0.0 – 0.35 → Fast tier (Haiku)

0.35 – 0.65 → Balanced tier (Sonnet)

0.65 – 1.0 → Powerful tier (Opus)

Key insight: Most real-world workloads are 60–70% simple queries. RouteHP captures that saving automatically.

The three tiers

Which model gets used for what

RouteHP routes across three Anthropic model tiers. Each tier is matched to the right type of query — so you never pay for more than you need.

Fast tier

Claude Haiku

Complexity score: 0.0 – 0.35

Simple questions and lookups
Greetings and conversational replies
Short summaries
Translations
Basic definitions

95% cheaper than Opus

Balanced tier

Claude Sonnet

Complexity score: 0.35 – 0.65

Drafting emails and documents
Explaining technical concepts
Moderate-length analysis
Product descriptions
Multi-step instructions

80% cheaper than Opus

Powerful tier

Claude Opus

Complexity score: 0.65 – 1.0

Legal and contract analysis
Complex code implementation
Financial modelling
Long-form research
Multi-document reasoning

Full Opus capability

The response

What you get back

Every response from RouteHP is a standard Anthropic response — your existing code works unchanged. We add a routehp block showing exactly what happened and what you saved.

Standard response (unchanged)

{

  "id": "msg_abc123",

  "type": "message",

  "role": "assistant",

  "content": [{

    "type": "text",

    "text": "2 + 2 = 4"

  }],

  "model": "claude-haiku-4-5",

  "usage": {

    "input_tokens": 14,

    "output_tokens": 13

  }

}

RouteHP block (added by us)

{

  "routehp": {

    "original_model": "claude-opus-4-6",

    "chosen_model": "claude-haiku-4-5",

    "tier": "fast",

    "complexity_score": 0.20,

    "complexity_reason": "short query; simple keywords",

    "cost_actual_usd": 0.000063,

    "cost_original_usd": 0.001185,

    "saving_pct": 94.7,

    "latency_ms": 1448

  }

}

Data and privacy

What we see and what we don't

We take data privacy seriously. Here's exactly what RouteHP does and doesn't access.

👁️

What we read

The first 80 characters of each query to score its complexity. This is the minimum needed for routing. We do not store full query content.

🔑

Your API keys

Your Anthropic key is passed through in your request headers and used to call the model. We never store it. Your billing relationship with Anthropic stays direct.

🌍

Data location

All data is stored in West Europe (London). RouteHP is UK/EU native and designed for GDPR compliance from day one. DPA available on request.

How RouteHP decides which model to use