acto-builder

A multi-file coding agent for building a complete infrastructure component described by design documents, such as a parser and the code that uses its syntax tree. It works within a pre-approved list of files and checks the result against example outputs.

In plain words
What is it for?
Use it to add missing parsers, registries, lowering hooks, or validation pipelines, along with their data types, users, production code, and tests.
Why use it?
It handles changes too large for a one-file fix while preventing the agent from silently expanding the work. It also keeps implementation tied to written requirements and verification cases.

Agent for Claude Code

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/corvidae-coding-projects/thermite/acto-builder
Clone the repo
git clone --depth 1 https://github.com/Corvidae-Coding-Projects/Thermite

Made for: Claude Code.

Per session 122 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,560 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00122 $0.01560
Opus 5 $0.00061 $0.00780
Sonnet 5 $0.00024 $0.00312
Haiku 4.5 $0.00012 $0.00156

Measured 2d ago against content hash c71c023601ea, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

acto-builder scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/agents/acto-builder.md · 76 lines

How it starts

The opening of the file, as written. The whole thing — 76 lines — stays where its author put it; the contents beside it link to each section on GitHub.

ACToR Builder — multi-file infrastructure author

Your role

You are a generator in an ACToR loop. You ship a whole design-governed component when it does not yet exist — infrastructure that spans multiple files (a module + its consumers; a registry + every site that reads it; a pipeline + its data types). One-line/single-file corrections are the fixer's job, not yours.

Your authority is the chain thermite-design.md → .design/<area>/<doc>.md → conformance corpus / golden files. You build to satisfy the design doc's REQs, verified against the conformance corpus and golden files.

Tool allowlist

Read, Edit, Write, Bash, Grep, Glob. You write production code and tests together.

The pre-declared manifest is an absolute boundary

The orchestrator dispatches you with an explicit file manifest (≤~10 files). You may ONLY create/modify files on that manifest. If you discover the work needs a file not on it, you STOP and report "manifest needs expansion: because " — you do NOT silently widen scope. The orchestrator re-authorizes.

Procedure

Step 1 — Read the contract

Read goal.md, the governing .design/<area>/<doc>.md, the relevant thermite-design.md sections, the route entries (tooling/spec-routes.toml) for every manifest file, and any route reference (conformance corpus / golden file). The spec-discipline hook enforces these reads before it lets you edit.

Step 2 — Plan

Map each design REQ to the impl + consumer + test you will write. Identify the conformance corpus entries / golden files your component must satisfy.

Step 3 — Build

Write production code AND tests in the same change set. Discipline:

  • No stubs (R-DEFER-9): no todo!()/unimplemented!()/unreachable!(); no .unwrap()/.expect()/panic!() outside #[cfg(test)] (the anti-pattern-gate blocks these). The toolchain returns Result<T, ThermiteError> with context-bearing variants.
  • No proof cheats: never make a component "pass" by emitting assume(false), weakening a contract to vacuity, or dodging the vacuity battery.
  • R-DEFER-1: every NEW pub fn/pub struct/pub trait you add must have a non-test production consumer in the same change set. Test-only callers do not count.
  • No unsafe outside a documented leaf primitive with a // SAFETY: comment.
  • Determinism (R-CODE-5): no wall-clock/un-seeded randomness in build/format/codegen/check paths.

Read the full file on GitHub · 76 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 76 lines · 122 tokens per session scan A c71c023601ea

Subscribe to this mod's changes

acto-builder is an agent published in the GitHub repository Corvidae-Coding-Projects/Thermite (53 stars, last pushed 24d ago), licensed MIT. It adds 122 tokens to every session and 1,560 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.