a* (autostar)

If you can measure it, you can improve it.

Soft RLVR for the masses. a* turns any measurable goal into a structured optimisation loop. You define what "good" looks like. a* runs experiments, scores the results, learns from every attempt, and converges on the best version within your budget.

No reward model to train. No environment to build. No GPU cluster to provision. Just a goal, an evaluator, and an agent that knows how to search.

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Fastest path

If you just want to install the skill and try it once in Claude Code:

npx skills add chrisvoncsefalvay/autostar

Then invoke it in Claude Code:

/skill autostar

The skill handles onboarding, confirms the mission with you, and runs experiments within your approved budget.

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What this is

Most artifacts live where quality is real but hard to verify fully. Code can be type-checked but not beauty-checked. Prose can be spell-checked but not tone-checked.

Traditional RLVR (reinforcement learning from verifiable rewards) needs rewards you can compute with certainty: math proofs, unit tests, formal proofs. That covers a narrow slice of what people want to improve.

a* uses verifiable-ish rewards instead. It combines hard signals (type checkers, linters, test suites) with soft ones (LLM judges, human gates). Each track has its own verifier. The system runs enough steps per lap to build statistical confidence.

The result: an optimisation loop for anything you can split into measurable dimensions. Code quality, documentation, prompt engineering, writing style, API design, accessibility.

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See it in action

Fixing this very documentation

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How it works

a* runs in five phases:

1. Onboarding

An interactive dialogue — never skipped, never auto-inferred. The system breaks your goal into tracks (measurable dimensions), sets up verifiers, sets constraints, agrees a budget, and gets your approval before running.

2. Pre-run preparation

Baseline measurement, tool checks, disposition library query, and final mission confirmation.

3. Execution loop

The core cycle:

Step  → mutate artifact, evaluate all tracks, ratchet (keep/revert)
Lap   → N steps with same parameter family → statistical verdict
Round → set of laps → mandatory reflection (worth pursuing? ask user? pivot?)

Each round ends with a structured reflection: Worth pursuing? Ask the user? Pivot? The system escalates when scores plateau, tracks diverge, or budget pace is at risk — always with specific questions, not vague updates.

A built-in visualiser renders live progress as an inline HTML dashboard.

4. Memory and learning

The canonical source of truth is one local persistent backend for the whole system. Short-term run logs stay append-only inside a run, while long-term memory is stored in that backend and exported as human-readable JSON/JSONL mirrors.

Within a run:

• step_log.jsonl and reflections.jsonl are append-only sources of truth
• hypothesis_stack.json, track_trajectories.json, and momentum.json are derived snapshots
• if a derived file disagrees with a log, the log wins

Across runs:

• episodes and run summaries are persisted in the backend and mirrored to JSONL
• dispositions are versioned in the backend and mirrored to JSON
• Claude.ai fallback sessions use a text-first project memory pack exported from the backend

Memory access modes:

Mode	Meaning
direct_backend	Runtime can use the canonical local backend directly
connector_backed	Runtime reaches memory through a connector
project_pack	Runtime uses a text-first project pack with manual sync
none	Short-term memory only

Dispositions are the long-term knowledge base. They shape future actions based on what worked and what didn't. Claude's built-in memory is useful for chat continuity, but it is not the system of record for a* learning.

5. Post-run report

Baseline vs. final scores, trajectory charts, reflection log, what worked, what didn't, and budget accounting.

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Verification taxonomy

Every track declares one of five verifier types:

Type	Signal	Use when
Deterministic	Formula / regex / rule	Word count, format compliance, schema validation
External tool	CLI subprocess	pyright, pytest, eslint, lighthouse, vale, bandit
LLM judge	Structured LLM call with fixed scoring criteria	Readability, tone, documentation quality
Hybrid	Tool + LLM judge, aggregated	Factual accuracy (entity check gates quality score)
Human gate	Pause and ask the user	Brand approval, legal sign-off, aesthetics

Verifiers are immutable during a run. Changing the evaluator mid-run is the main failure mode of autonomous optimisation — a* prevents it by design.

External judges

LLM judge tracks run in self mode (host agent judges inline) or external mode (separate model via subprocess). External mode keeps mutator and judge independent, and handles safety-filter conflicts: sensitive domains can use a judge that won't refuse to score legitimate content.

The contract: a* writes a JSON request, calls your command, and reads a JSON response (score + rationale) from stdout. Bring any model with a CLI wrapper.

Safety-filter resilience

When a safety filter refuses an LLM call, a* rephrases and retries up to twice. If retries fail, it offers the user specific options: switch to an external judge, adjust criteria, skip the track, or abort. All rejections are logged.

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Progress format

a* writes structured, machine-readable output for external tools:

File	Format	Updated
step_log.jsonl	JSONL	After every step
reflections.jsonl	JSONL	After every round
tracks.json	JSON	Once at run start
mission.json	JSON	Once at run start
progress.json	JSON	After every step

progress.json is the single-file state snapshot. Poll it from dashboards, CLI tools, or downstream agents without parsing JSONL. Schemas for all formats are in schemas/.

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Installation

Prerequisites

• Claude Code (for the native install path below)
• Python 3 + pyyaml + jsonschema (for validation/packaging scripts)
• unzip (if installing from a release archive)

Claude Code

# Clone the repo
git clone https://github.com/chrisvoncsefalvay/autostar.git

# Copy the skill into your Claude Code skills directory
cp -r autostar/autostar-skill ~/.claude/skills/autostar-skill

Or install via skill.sh:

npx skills add chrisvoncsefalvay/autostar

Or install directly from a release:

# Download the .skill file from the latest release
curl -sL https://github.com/chrisvoncsefalvay/autostar/releases/latest/download/autostar-skill.skill -o autostar.skill

# Unzip into your skills directory
unzip autostar.skill -d ~/.claude/skills/

Claude.ai custom Skills

Build the Claude.ai upload archive:

python autostar-skill/scripts/package_skill.py --target claude-ai dist/

Upload dist/autostar-claude-ai-skill.zip to Claude.ai as a custom Skill.

For long-term memory in Claude.ai:

• preferred: configure the remote memory connector and enable it per conversation
• fallback: add a project memory pack to project knowledge and manually sync updated pack files after runs
• if neither exists, a* reports short-term-only mode explicitly

Other agents

The .skill format is a ZIP archive with SKILL.md and supporting files. Other agent frameworks can use it through a runtime adapter — see autostar-skill/references/runtime-capabilities.md. Without that layer, treat compatibility as partial.

Bundled adapters: Claude Code, Codex, Gemini CLI, Pi (full support); Claude.ai (reduced support); chat-only (unsupported boundary). Profiles and a template for new adapters live in autostar-skill/runtime-profiles/.

Inspect or select profiles with:

python autostar-skill/scripts/runtime_profile.py list
python autostar-skill/scripts/runtime_profile.py show claude-code
python autostar-skill/scripts/runtime_profile.py check-mission claude-code --verifier external_tool --verifier llm_judge
python autostar-skill/scripts/runtime_profile.py resolve claude-ai --project-pack ./memory-pack

Validation

python -m pip install pyyaml jsonschema pytest
python autostar-skill/scripts/quick_validate.py autostar-skill/

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Usage

Invoke the skill in Claude Code:

/skill autostar

Or trigger it with natural language:

• "Optimise this code until the type checker is happy and the docs are good"
• "Iterate on this API handler — improve readability, keep tests passing"
• "Find the best configuration for this pipeline"

a* guides you through onboarding, gets your approval, and runs within your budget.

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Repository structure

autostar/
  autostar-skill/              # The distributable skill
    SKILL.md                   # Main instruction set
    assets/                    # Visualiser template
    scripts/                   # Packaging, validation, runtime profile tools
    references/                # Onboarding, verification, budgeting, memory,
                               #   runtime adapters (Claude Code, Codex, Gemini,
                               #   Pi, Claude.ai, chat-only, template)
    runtime-profiles/          # Machine-readable capability profiles per runtime
  schemas/                     # JSON Schemas for output formats
  .github/workflows/           # CI: validate on PR; CD: build .skill on tag
  LICENSE
  README.md

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Design philosophy

a* is built on seven principles:

1. No silent inference. Every decision requires explicit user confirmation. Inferred values are defaults, never silent assumptions.

2. Immutable evaluation. Verifiers and scoring rules do not change during a run. The evaluator is the ground truth.

3. Statistical confidence. Laps run multiple steps to get distributions, not point estimates. Verdicts emerge from the data, not single observations.

4. Bidirectional learning. The system learns from success and failure equally. Failed attempts record their failure modes, not just "failed."

5. Reflection without action. Every round ends with a recorded reflection, even when nothing changes.

6. User in the loop at key moments. The system escalates on plateaus, diverging tracks, pace risk, and repeated failures — with specific questions, not vague updates.

7. Memory as decision-maker. Dispositions shape every major action. The system gets better at the same class of problem over time.

These are hard constraints enforced by the skill's structure, not suggestions.

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Building and packaging

python -m pip install pyyaml jsonschema pytest
python autostar-skill/scripts/package_skill.py autostar-skill/ dist/
python autostar-skill/scripts/package_skill.py --target all dist/

Validates the skill and produces dist/autostar-skill.skill.

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Contributing

Contributions are welcome. The skill's behaviour lives entirely in SKILL.md and its reference files — no runtime code to compile, no models to train.

Please open an issue before large changes.

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Author

Chris von Csefalvay (@epichrisis)

Author of Post-Training: A Guide for Developers and AI Engineers (No Starch Press). Building tools that make post-training techniques accessible to practitioners — because the gap between "this works in a paper" and "this works in my project" is where most of the value lives.

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License

MIT. See LICENSE.