tinker-ai-skill

Turn your own coding-agent sessions into a fine-tuned model you can run locally. This is the recipe behind Tess-4 and Tess-4.5.

Every session you run with a coding agent is a worked example of how you want a model to behave: your repositories, your conventions, your tools, your way of debugging. This skill hands your agent the complete, production-tested pipeline to turn those sessions into a supervised fine-tuning dataset, train a LoRA on Tinker, merge it, and ship a GGUF that runs in llama.cpp on your own machine. One afternoon, a few dollars to a few hundred, and a model that works the way you do.

Install it once and say: "fine-tune Qwen3.6-35B-A3B on my Claude Code sessions from the last three months." The agent takes it from there and stops before anything that costs money.

Proven on real releases

We built the Tess family of agentic coding models from our own Claude Code sessions with exactly this method, and shipped them as open weights on Hugging Face: Tess-4-27B (GGUF, EAGLE-3 draft) and Tess-4.5-27B (GGUF). Read about them at continuityresearch.ai/tess-4-5.

What is in this repository is the distilled, cleaned-up version of the pipeline that produced them, from raw transcripts to a quantized GGUF, including the mistakes we made so you do not have to.

What you get

• One SKILL.md your agent follows: a nine-step workflow with the decision points spelled out and the rules that cost us runs.
• Eleven small scripts, plain Python and shell on top of tinker-cookbook and llama.cpp, each with an offline default and a --help that explains every flag.
• Six reference notes: the transcript format, the anonymization policy, the chunking and compaction design, Tinker training settings with the learning-rate evidence, export and serving, and the lessons learned.
• A synthetic transcript generator so you can dry-run the whole pipeline in five minutes without touching real data or spending a cent.

The method, from transcripts to a local model

Why this and not a generic SFT tutorial

Agent transcripts are not chat data. The details below are the difference between a model that works and one that looks fine on the loss curve and falls apart in use.

• Per-session anonymization. A single constant fake world in every row was memorized and later asserted over the real environment. Randomize per session.
• Compaction context on continuation slices. Long sessions outlive the context window; the model must learn to continue from a summary, not from nothing.
• Tool definitions and the system prompt on every row. Rows without them regressed tool use even though NLL improved.
• Thinking kept in history. Hybrid renderers silently strip earlier reasoning and train empty think blocks; the scripts rebuild the renderer to keep it.
• Measure with the real tokenizer. A tokenizer change moved rows by 14% and overflowed the budget. Rebuild per model.
• Judge by behaviour. Two "collapses" had monotonically falling loss. Sample.
• Serve the way you trained. A chat template that strips earlier thinking, or llama.cpp's default min-p, turned a good checkpoint into garble. The serve script carries the right flags.

Quick start: five minutes on synthetic data

git clone https://github.com/drost-ai/tinker-ai-skill.git ~/.claude/skills/tinker-ai-skill
cd ~/.claude/skills/tinker-ai-skill
uv venv && source .venv/bin/activate && uv pip install -r requirements.txt

python scripts/make_sample_transcript.py --out ./demo-claude-projects --turns 14 --long-results
python scripts/collect_sessions.py   --claude-dir ./demo-claude-projects --data-dir ./demo-data --min-bytes 1000
python scripts/normalize_sessions.py --data-dir ./demo-data
python scripts/anonymize_sessions.py --data-dir ./demo-data --name "Taylor Quintrell"
python scripts/build_dataset.py      --data-dir ./demo-data --model Qwen/Qwen3.6-35B-A3B --max-len 8192 \
                                     --system-prompt-file assets/system-prompt.md
python scripts/train_tinker.py       --data-dir ./demo-data --name qwen3.6-35b-a3b-8k   # offline smoke test

The last command prints a decoded training row, the token count and the resolved configuration. Add --train to launch a real run; afterwards export_checkpoint.py and make_gguf.sh take it to a GGUF you can run.

Then on your own sessions

1. Raise Claude Code's transcript retention first: "cleanupPeriodDays": 3650 in ~/.claude/settings.json. The default deletes sessions after 30 days.
2. Copy .env.example to .env and add your TINKER_API_KEY and WANDB_API_KEY.
3. Write identity.json (see identity.example.json): your usernames, full name, emails, handles, company, domains.
4. Follow SKILL.md, or let your agent drive. The decisions that stay yours: which projects to exclude, which model and context length, the system prompt and tool definitions of the harness you will serve in, and the learning rate when Tinker has no calibrated default.

Install the skill

Clone into your agent's skills directory. The directory name must be tinker-ai-skill, which git clone gives you by default:

# Claude Code
git clone https://github.com/drost-ai/tinker-ai-skill.git ~/.claude/skills/tinker-ai-skill
# Codex
git clone https://github.com/drost-ai/tinker-ai-skill.git ~/.agents/skills/tinker-ai-skill
# OpenCode
git clone https://github.com/drost-ai/tinker-ai-skill.git ~/.config/opencode/skills/tinker-ai-skill

OpenCode also reads .claude/skills and .agents/skills, so one project copy serves all three. Any other agent that supports the Agent Skills standard works the same way. Invoke it directly with /tinker-ai-skill in Claude Code; Codex and OpenCode pick it up from its description.

What it costs

Tinker bills per token. Training cost is train tokens times the model's train price (see the price list); the smoke test prints the token count before you launch. Ballpark figures at November 2026 prices, one epoch of 64K rows:

Dense models cost more per token than MoE models of similar quality (Tinker prices by active parameters); Qwen3.8-27B is the base of Tess-4.5.

Sampling and periodic evaluation are extra and small. The dataset steps are free and run on your laptop.

Requirements

• Python 3.11+ and uv (or pip)
• tinker-cookbook>=0.6.0 (installs tinker, torch, tml-renderers) and wandb
• A Tinker API key; a Weights & Biases key is optional but recommended
• Claude Code transcripts under ~/.claude/projects/ (other agents: emit the message schema in references/claude-code-transcripts.md and continue from step 2)
• For steps 8-9: a built llama.cpp checkout, and disk for the base model plus the merged copy

Layout

SKILL.md                            instructions the agent follows
scripts/collect_sessions.py         step 1
scripts/normalize_sessions.py       step 2a
scripts/anonymize_sessions.py       step 2b
scripts/build_dataset.py            steps 3-5
scripts/train_tinker.py             step 6
scripts/sample_checkpoint.py        step 7
scripts/export_checkpoint.py        step 8: download the LoRA, merge, optional PEFT adapter
scripts/make_gguf.sh                step 9: BF16 GGUF, quantize, mmproj, MTP draft
scripts/serve_gguf.sh               step 9: llama-server with training-matched flags
scripts/make_sample_transcript.py   synthetic transcript for a dry run
scripts/common.py                   shared rendering (builder, trainer and sampler render identically)
references/                         format, anonymization, chunking, training, export and serving, lessons
assets/system-prompt.md             a generic agent system prompt to start from
identity.example.json, .env.example

Data safety

data/, demo-*/, runs/, export/, wandb/ and .env are git-ignored. The anonymizer fails rather than writing a file that still leaks. Review anonymized rows before training, and never publish a dataset built from transcripts that belong to someone else without their consent.

Author and license

Written by Migel Tissera, creator of the Tess models. MIT license. Tinker and tinker-cookbook are products of Thinking Machines Lab; this skill is an independent guide built on them.

If this saved you a failed training run, star the repository and share what you trained.