Tinker API - LLM Fine-Tuning Skill

Tinker API - LLM Fine-Tuning

Overview

Tinker is a training API for large language models from Thinking Machines Lab. It provides:

Supervised Fine-Tuning (SFT): Train models on instruction/completion pairs
Reinforcement Learning (RL): PPO and policy gradient losses; cookbook patterns include GRPO-like group rollouts/advantage centering
Multimodal Models: vision via Qwen3.5/3.6 and Kimi K2.x; vision + audio via Inkling
Inkling: Thinking Machines' own open-weights MoE model (975B/41B active, released July 2026) with text/image/audio inputs and tunable thinking effort
LoRA Training: Efficient parameter-efficient fine-tuning

Two abstraction levels:

Tinker Cookbook: High-level patterns with automatic training loops
Low-Level API: Manual control for custom training logic

Quick Reference

| Topic | Reference | |-------|-----------| | Setup & Core Concepts | Getting Started | | API Classes & Types | API Reference | | Supervised Learning | Supervised Learning | | RL Training | Reinforcement Learning | | Loss Functions | Loss Functions | | Chat Templates | Rendering | | Models & LoRA | Models & LoRA | | Inkling (multimodal, thinking effort) | Inkling | | Example Scripts | Recipes |

Installation

pip install tinker tinker-cookbook
export TINKER_API_KEY=your_api_key_here

Minimal Example

import numpy as np
import tinker
from tinker import types

# Create clients
service_client = tinker.ServiceClient()
training_client = service_client.create_lora_training_client(
    base_model="Qwen/Qwen3.6-35B-A3B", rank=32
)
tokenizer = training_client.get_tokenizer()

# Prepare data
prompt = "English: hello\nPig Latin:"
completion = " ello-hay\n"
prompt_tokens = tokenizer.encode(prompt, add_special_tokens=True)
completion_tokens = tokenizer.encode(completion, add_special_tokens=False)
tokens = prompt_tokens + completion_tokens
weights = np.array(([0] * len(prompt_tokens)) + ([1] * len(completion_tokens)), dtype=np.float32)
target_tokens = np.array(tokens[1:], dtype=np.int64)

datum = types.Datum(
    model_input=types.ModelInput.from_ints(tokens=tokens[:-1]),
    loss_fn_inputs={
        "target_tokens": target_tokens,
        "weights": weights[1:]
    }
)

# Train
fwdbwd = training_client.forward_backward([datum], "cross_entropy")
optim = training_client.optim_step(types.AdamParams(learning_rate=1e-4))
fwdbwd.result(); optim.result()

# Sample
sampling_client = training_client.save_weights_and_get_sampling_client(name="v1")
result = sampling_client.sample(
    prompt=types.ModelInput.from_ints(tokens=tokenizer.encode("English: world\nPig Latin:", add_special_tokens=True)),
    sampling_params=types.SamplingParams(max_tokens=20),
    num_samples=1
).result()
print(tokenizer.decode(result.sequences[0].tokens))

Common Imports

# Low-level API
import tinker
from tinker import types
from tinker.types import Datum, ModelInput, TensorData, AdamParams, SamplingParams

# Cookbook (high-level)
import chz
import asyncio
from tinker_cookbook.supervised import train
from tinker_cookbook.supervised.types import ChatDatasetBuilder, ChatDatasetBuilderCommonConfig
from tinker_cookbook.supervised.data import (
    SupervisedDatasetFromHFDataset,
    StreamingSupervisedDatasetFromHFDataset,
    FromConversationFileBuilder,
    conversation_to_datum,
)
from tinker_cookbook.renderers import get_renderer, TrainOnWhat
from tinker_cookbook.model_info import get_recommended_renderer_name
from tinker_cookbook.tokenizer_utils import get_tokenizer

When to Use What

| Scenario | Approach | |----------|----------| | Standard SFT with HF/JSONL data | Cookbook ChatDatasetBuilder + tinker_cookbook.supervised.train.main() | | Custom preprocessing | Custom SupervisedDataset class | | Large datasets (>1M) | StreamingSupervisedDatasetFromHFDataset | | RL / GRPO | Cookbook RL patterns | | Research / custom loops | Low-level forward_backward() + optim_step() | | Vision-language | Inkling or Qwen3.5/3.6 vision models | | Audio / thinking-effort control | Inkling + tml-renderers (Inkling) |

External Resources

Documentation: https://tinker-docs.thinkingmachines.ai/
Cookbook Repo: https://github.com/thinking-machines-lab/tinker-cookbook
Console: https://tinker-console.thinkingmachines.ai

Agent Skills: Tinker API - LLM Fine-Tuning

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