needle2

Needle 2 is an open 45M-parameter model for tool calling, device use and structured extraction. The whole model is a single 14MB binary that runs a full session in 28MB of RAM. It is built on our Simple Attention Network findings, compressed to CQ2-bit with Cactus Quants, and baked into its own engine. On the benchmarks below, Needle 2 trades wins with other small models like FunctionGemma 270M, LFM2.5 230M and Apple FM, at 5x to 70x smaller, and 2 bits against their f16. Needle hits 500 tokens/sec decode speed on a Raspberry Pi 5, between 400-1,500 tokens/sec on VR devices like Meta Quest 3S and Apple Vision Pro, and ranges 300-700 on sub-$200 phones such as the Samsung A-Series. With a peak session RAM around 28MB, Needle reaches microcontrollers like the ESP32-P4; others have reported running it on an ESP32-S3 in about 11MB.

• Self-contained: model baked into the binary, no runtime, no downloads, no network.
• Runs everywhere: ARM64, x86-64, ARMv7, RISC-V, and WebAssembly, on Apple, Windows, Linux, Android, Raspberry Pi.
• Simple contract: tool calls come back as structured data, text in, JSON out; a byte-level grammar compiled from your schemas constrains every token.
• Confidence-gated: every response carries a calibrated confidence score from a learned head; set a threshold, act above it, escalate below it.
• Tool retrieval: declare a large catalogue and a built-in retrieval head renders only the top five tools per turn, with the grammar constrained to that subset.
• Bounded memory: a 256-token sliding window with the tools pinned as KV sinks, so total memory stays near 28MB no matter how long the conversation runs.

Source, engine, and training code: github.com/cactus-compute/needle.

Simple Attention Network

Needle 2 is a Simple Attention Network, our dense small-model recipe: a Hadamard MLP in place of the FFN, GQA attention, engram key-value memory, and multi-lane hyper-connections. See the paper for the design and ablations: arXiv:2607.18363.

Each block carries its update rule. Here x̂ is the RMS-normalised flattening of the four residual streams, H the orthonormal Walsh-Hadamard transform (a fixed matrix, applied in n log n time with no weights to read), (kₜ, vₜ) rows gathered from hashed n-gram tables, and P the doubly-stochastic normalisation of the routing logits A, computed by Sinkhorn iteration; a, b, g and all σ-gates are learned and input-dependent. Both attention and MLP residuals are sandwich-normed and gated, the engram sites fire at two layers, and decoding is constrained by a byte-level grammar compiled from the declared schemas.

Quickstart with Python

pip install cactus-needle

Needle reads your tool descriptions to decide what to call and how to fill arguments, so describing them well is the whole game. You can do it three ways, from least to most control.

Simple: decorate a function. The signature gives the argument types, the docstring is the tool description, and run() completes the loop: model picks the call, Needle executes your function, feeds the result back, and returns the model's final answer.

import needle

@needle.tool
def get_weather(city: str):
    "Get the current weather for a city."
    return {"city": city, "temp_c": 27, "sky": "clear"}

agent = needle.Needle(tools=[get_weather])
print(agent.run("what's it like in Lagos right now?")["reasoning"])

Medium: describe each argument and offer choices. Needle reads a Google-style Args: block for per-parameter descriptions; a default makes an argument optional; a Literal becomes a fixed set the model must choose from (it cannot emit anything else).

from typing import Literal

@needle.tool
def set_thermostat(temperature: int, mode: Literal["heat", "cool", "auto"] = "auto"):
    """Set the thermostat.

    Args:
        temperature: target temperature in Celsius
        mode: heating strategy to use
    """
    return {"temperature": temperature, "mode": mode}

agent = needle.Needle(tools=[set_thermostat])
agent.run("make it 21 and cool the room")

Advanced: constrain the values with needle.Field, attached inline via Annotated. Ranges, patterns, lengths, and item counts are compiled into the decode grammar, so the model can only ever emit values that satisfy them.

from typing import Annotated

@needle.tool
def send_money(
    amount: Annotated[float, needle.Field(gt=0, le=10000, description="USD, up to 10,000")],
    to:     Annotated[str,   needle.Field(pattern=r"^@[a-z0-9_]+$", description="recipient handle")],
    memo:   Annotated[str,   needle.Field(max_length=80)] = "",
):
    "Send money to a handle."
    return {"sent": amount, "to": to}

Field supports description, enum, const, ge/le/gt/lt, multiple_of, min_length/max_length, pattern, format, min_items/max_items, and unique_items.

Extraction: to pull structured data out of text, declare the shape and call extract(). Pass a Pydantic model and you get a typed object back.

from pydantic import BaseModel

class Invoice(BaseModel):
    vendor: str
    total: float
    due_date: str

invoice = needle.extract("Invoice from Acme Corp, $1,200.00, due 2026-09-01", Invoice)
print(invoice.vendor, invoice.total)   # -> Acme Corp 1200.0

By hand - the decorator just builds a JSON schema; you can pass that schema directly, which is exactly what Needle consumes. This is how you set descriptions and constraints without the decorator (and tools.json for the CLI is the same shape):

tools = [{
    "name": "set_lights",
    "description": "Turn a room's lights on or off and set brightness",
    "parameters": {
        "type": "object",
        "properties": {
            "room": {"type": "string", "description": "which room to control"},
            "on": {"type": "boolean"},
            "brightness": {"ty