cell-sim: Instructions file for Claude Code

CLAUDE.md

cell-sim CLAUDE.md is an instructions file for Claude Code from atopile/cell-sim. It costs 5,132 tokens per session, scanned A, a copy of atopile ato.instructions.md, MIT.

Project instructions for cell-sim that explain Ato, a declarative language for designing electronics and printed circuit boards. They document its syntax, imports, and unsupported features.

In plain words
What is it for?
Use them when editing the cell-sim project's Ato files or understanding how its build process works.
Why use it?
They give an agent the project-specific rules needed to work with Ato code correctly.

Instructions file for Claude Code

Written for Claude Code: the file is CLAUDE.md. Also seen: mentions CLAUDE.md.

This is atopile/cell-sim's own configuration. It tells Claude Code how to work on cell-sim itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything cell-sim configures →

Reuse

Borrowing it

Nothing to install: this file belongs to atopile/cell-sim. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/atopile/cell-sim/main/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/atopile/cell-sim

Made for: Claude Code.

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Per session 5,132 This file is loaded in full into every session.
When invoked 5,132 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 98% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

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ModelPer sessionOnce invoked
Fable 5.1 $0.05132 $0.05132
Opus 5.5 $0.02053 $0.02053
Sonnet 5.5 $0.01026 $0.01026
Haiku 4.5 $0.00513 $0.00513

Measured 1mo ago against content hash 481cc9234a8c, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

cell-sim CLAUDE.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 1mo 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.

Origin

This is a copy

98% identical to atopile ato.instructions.md — 7 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

CLAUDE.md · 711 lines

How it starts

The opening of the file, as written. The whole thing — 711 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md

ato is a declarative DSL to design electronics (PCBs) with. It is part of the atopile project. Atopile is run by the vscode/cursor/windsurf extension. The CLI (which is invoked by the extension) actually builds the project.

Not available in ato

  • if statements
  • while loops
  • functions (calls or definitions)
  • classes
  • objects
  • exceptions
  • generators

Ato Syntax

ato sytax is heavily inspired by Python, but fully declarative. ato thus has no procedural code, and no side effects.

Examples of syntax

#pragma text
#pragma func("X")
# enable for loop syntax feature:
#pragma experiment("FOR_LOOP)

# --- Imports ---
# Standard import (newline terminated)
import ModuleName

# Import with multiple modules (newline terminated)
import Module1, Module2.Submodule

# Import from a specific file/source (newline terminated)
from "path/to/source.ato" import SpecificModule

# Multiple imports on one line (semicolon separated)
import AnotherModule; from "another/source.ato" import AnotherSpecific

# Deprecated import form (newline terminated)
# TODO: remove when unsupported
import DeprecatedModule from "other/source.ato"

# --- Top-level Definitions and Statements ---

pass
pass;

"docstring-like statement"
"docstring-like statement";

top_level_var = 123

# Compound statement
pass; another_var = 456; "another docstring"

# Block definitions
component MyComponent:
    # Simple statement inside block (newline terminated)
    pass

    # Multiple simple statements on one line (semicolon separated)
    pass; internal_flag = True

module AnotherBaseModule:
    pin base_pin
    base_param = 10

interface MyInterface:
    pin io

module DemoModule from AnotherBaseModule:
    # --- Declarations ---
    pin p1              # Pin declaration with name
    pin 1               # Pin declaration with number
    pin "GND"           # Pin declaration with string
    signal my_signal    # Signal definition
    a_field: AnotherBaseModule      # Field declaration with type hint

    # --- Assignments ---
    # Newline terminated:
    internal_variable = 123

    # Semicolon separated on one line:
    var_a = 1; var_b = "string"

    # Cumulative assignment (+=, -=) - Newline terminated
    value = 1
    value += 1; value -= 1

    # Set assignment (|=, &=) - Newline terminated
    flags |= 1; flags &= 2

    # --- Connections ---
    p1 ~ base_pin
    mif ~> bridge
    mif ~> bridge ~> bridge
    mif ~> bridge ~> bridge ~> mif
    bridge ~> mif
    mif <~ bridge
    mif <~ bridge <~ bridge
    mif <~ bridge <~ bridge <~ mif
    bridge <~ mif

    # Semicolon separated on one line:
    p_multi1 ~ my_signal; p_multi2 ~ sig_multi1

    # --- Retyping ---
    instance.x -> AnotherBaseModule

    # --- Instantiation ---
    instance = new MyComponent
    container = new MyComponent[10]
    templated_instance_a = new MyComponent
    templated_instance_b = new MyComponent<int_=1>
    templated_instance_c = new MyComponent<float_=2.5>
    templated_instance_d = new MyComponent<string_="hello">
    templated_instance_e = new MyComponent<int_=1, float_=2.5, string_="hello">
    templated_instance_f = new MyComponent<int_=1, float_=2.5, string_="hello", bool_=True>

    # Semicolon separated instantiations (via assignment):
    inst_a = new MyComponent; inst_b = new AnotherBaseModule

    # --- Traits ---
    trait trait_name
    trait trait_name<int_=1>
    trait trait_name<float_=2.5>
    trait trait_name<string_="hello">
    trait trait_name<bool_=True>
    trait trait_name::constructor
    trait trait_name::constructor<int_=1>

    # Semicolon separated on one line:
    trait TraitA; trait TraitB::constructor; trait TraitC<arg_=1>

    # --- Assertions ---
    assert x > 5V
    assert x < 10V
    assert 5V < x < 10V
    assert x >= 5V
    assert x <= 10V
    assert current within 1A +/- 10mA
    assert voltage within 1V +/- 10%
    assert resistance is 1kohm to 1.1kohm

    # Semicolon separated on one line:
    assert x is 1V; assert another_param is 2V

    # --- Loops ---
    for item in container:
        item ~ p1

    # For loop iterating over a slice
    for item in container[0:4]:
        pass
        item.value = 1; pass

    # For loop iterating over a list literal of field references
    for ref in [p1, x.1, x.GND]:
        pass

    # --- References and Indexing ---
    # Reference with array index assignment
    array_element = container[3]

    # --- Literals and Expressions ---
    # Integer
    int_val = 100
    neg_int_val = -50
    hex_val = 0xF1
    bin_val = 0b10
    oct_val = 0o10
    # Float
    float_val = 3.14
    # Physical quantities
    voltage: V = 5V
    resistance: ohm = 10kohm
    capacitance: F = 100nF
    # Bilateral tolerance
    tolerance_val = 1kohm +/- 10%
    tolerance_abs = 5V +/- 500mV
    tolerance_explicit_unit = 10A +/- 1A
    # Bounded quantity (range)
    voltage_range = 3V to 3.6V
    # Boolean
    is_enabled = True
    is_active = False
    # String
    message = "Hello inside module"

    # Arithmetic expressions
    sum_val = 1 + 2
    diff_val = 10 - 3ohm
    prod_val = 5 * 2mA
    div_val = 10V / 2kohm # Results in current
    power_val = 2**3
    complex_expr = (5 + 3) * 2 - 1
    flag_check = state | MASK_VALUE

    # Comparisons
    assert voltage within voltage_range
    assert length <= 5mm
    assert height >= 2mm



# --- Multi-line variations ---
pass; nested_var=1; another=2

complex_assignment = (
    voltage + resistance
    * capacitance
)


Read the full file on GitHub · 711 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. 1mo ago First seen · 711 lines · 5,132 tokens per session scan A 481cc9234a8c

Subscribe to this mod's changes

cell-sim CLAUDE.md is an instructions file published in the GitHub repository atopile/cell-sim (24 stars, last pushed 6mo ago), licensed MIT. It adds 5,132 tokens to every session, about $0.0205 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 98% identical to atopile ato.instructions.md, differing in 7 lines, and is treated as a copy.

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