What is jac copilot-instructions.md?

Project-specific instructions for AI coding assistants working on Jac, a programming language and its compiler, runtime, and tools. The repository is a monorepo, meaning one repository contains several related parts and packages.

Use them when changing the Jac compiler, runtime, language server, documentation, integrations, or related scripts, and when running the project's tests or checks.

They provide the repository layout and the approved commands for building, testing, formatting, and checking changes, so work follows the project's process.

jac copilot-instructions.md — Instructions file for GitHub Copilot by jaseci-labs: Project-specific instructions for AI coding assistants wo

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 instructions/jaseci-labs/jac/copilot-instructions

Clone the repo

git clone --depth 1 https://github.com/jaseci-labs/jac

Made for: GitHub Copilot.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/jaseci-labs/jac/copilot-instructions.svg)](https://agentmods.dev/instructions/jaseci-labs/jac/copilot-instructions)

Your own site

<a href="https://agentmods.dev/instructions/jaseci-labs/jac/copilot-instructions"><img src="https://agentmods.dev/badge/instructions/jaseci-labs/jac/copilot-instructions.svg" alt="Measured on agentmods" height="20"></a>

Per session 635 This file is loaded in full into every session.

When invoked 635 The same file — it is already loaded in full.

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.

Model	Per session	Once invoked
Fable 5	$0.00635	$0.00635
Opus 5	$0.00318	$0.00318
Sonnet 5	$0.00127	$0.00127
Haiku 4.5	$0.00064	$0.00064

Measured 5d ago against content hash 28b3757d98aa, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

jac copilot-instructions.md 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 5d 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.

.github/copilot-instructions.md · 78 lines

How it starts

The opening of the file, as written. The whole thing — 78 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Copilot Instructions

Repository Structure

This monorepo contains:

jac/: Jac language compiler, runtime, language server, and the client/desktop runtimes (jac/jaclang/client/)
jac-byllm/: LLM integration and model-driven features
docs/: Documentation site and reference materials
scripts/: Build, test, and maintenance scripts

Common Workflows

jaclang ships as the single jac binary (a Jac launcher + bundled CPython) -- there is no pip-installed jaclang. Build it and put it on PATH with ./scripts/fresh_env.sh (see CONTRIBUTING.md).

Run tests through the binary's bundled runner (JAC_TEST_JOBS=auto runs them in parallel):

cd jac && JAC_TEST_JOBS=auto jac test tests

Run the formatting/lint gate (same checks the git hook runs):

jac precommit

Package-Specific Notes

jac/ (Compiler & Runtime)

Grammar: jac/jaclang/compiler/jac.lark
IR: unitree.py (UniTree nodes)
Passes: jac/jaclang/compiler/passes/
Codegen: jcir_gen_pass.jac, jcir_bc_gen_pass.jac
Compiler passes subclass Transform/UniPass with enter_*/exit_* hooks
Test fixtures: jac/jaclang/compiler/**/tests/fixtures/
For type system work, see .github/agents/type-system-agent.md

jac-byllm/ (LLM Features)

Core logic: byllm/lib.py, llm_connector.py
Schema definitions: schema.py
Examples: examples/agentic_ai/

Client & Desktop Runtimes

Now part of jaclang core: jac/jaclang/client/

Jac Language Conventions

Import syntax:

import from module { symbol, another_symbol }
import module as alias;

Entry point:

with entry { /* ... */ }

PR Guidelines

Target repository: Always create PRs against https://github.com/jaseci-labs/jaseci (not forks). Use gh pr create --repo jaseci-labs/jaseci.
Release notes: If your PR affects Jac developer experience, add a release-note fragment at release_notes/unreleased/<package>/<PR#>.<category>.md.
Grouping: Organize related changes under sections like "Type Checking Enhancements" or "Cloud Platform Updates".
Testing: Ensure relevant tests pass before submitting.

Read the full file on GitHub · 78 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.

5d ago First seen · 78 lines · 635 tokens per session scan A 28b3757d98aa

Subscribe to this mod's changes

jac copilot-instructions.md is an instructions file published in the GitHub repository jaseci-labs/jac (697 stars, last pushed today), licensed MIT. It adds 635 tokens to every session, about $0.0032 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.

Productivity

vscode buildNext.instructions.md

Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).

microsoft/vscode · 6,785 tokens

jac copilot-instructions.md