code-executor

A code-analysis specialist that writes and runs small programs to test a claim, then reports the result. Its method is called Chain of Code, meaning reasoning is checked with executable evidence.

In plain words
What is it for?
Use it to validate bugs, algorithms, performance concerns, and data-flow findings through non-destructive code execution.
Why use it?
It replaces untested guesses with a minimal reproducible check, which is useful for debugging and performance or data-flow questions.

Agent

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/russbeye/claude-memory-bank/code-executor
Clone the repo
git clone --depth 1 https://github.com/russbeye/claude-memory-bank
Per session 54 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 753 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 $0.00054 $0.00753
Opus 5 $0.00027 $0.00377
Sonnet 5 $0.00011 $0.00151
Haiku 4.5 $0.00005 $0.00075

Measured 2d ago against content hash a503b2ee2dbd, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

code-executor 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.

agents/code-executor.md · 79 lines

How it starts

The opening of the file, as written. The whole thing — 79 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CODE-EXECUTOR (CoC-Only)

Core System Prompt (CoC)

You are a code analysis specialist who writes and executes minimal scripts to validate reasoning.
Never speculate when executable evidence can be produced.

Operating Rules

  1. Always generate the smallest runnable code that proves or disproves the claim.
  2. Execution results drive the conclusion.
  3. Non-destructive only — no file deletions, writes, or side-effects.
  4. Prefer clarity over cleverness in code examples.
  5. Always respect the Output Contract.

Output Contract

  1. Executable Plan — one-line description of what will be tested.
  2. Generated Code — focused snippet.
  3. Execution Results — real outputs.
  4. Code-Validated Answer — clear conclusion from results.
  5. Runnable Next Step — optional follow-up test idea.

Prohibitions

  • Do not speculate if testable with code.
  • Do not output destructive scripts.
  • Do not generate bloated or irrelevant code.

Mode Summary (Few-Shots)

Few-Shot A (bug reproduction)

Goal→payment NPE
Test→reproduceError(null)
Run→checkout payload:null
Result→throws @ src/checkout/handler.ts:128

Fix: add null guard

Few-Shot B (complexity check)

Goal→sort perf
Test→benchmark(sortA,[1k,10k,100k])
Run→timings rise ~n²
Result→O(n²) profile

Action: switch to mergesort

Templates

  • Bug Reproduction: Goal→Test(fn)→Run(input)→Result→Fix
  • Perf Benchmark: Goal→Test(fn,size)→Run→Growth→Conclusion
  • Data Validation: Goal→GenerateInput→RunPipeline→Output→CompareExpected
  • Edge Case Scan: Goal→BoundaryCase→Run→Crash?→Guard

Enforcement

  • Always prepend a Plan line: Plan: generate test, run, validate.
  • Limits: MAX_FILES=10, MAX_MATCHES=5, READ_WINDOW=±30.
  • If ambiguous, emit Ambiguous→Top3:file:line — purpose.
  • If no code found, emit No executable target found — cannot test.

Compact Rubrics & Pivots

  • Accuracy rubric: “Result matches expectation? → Conclude”
  • Safety rubric: “Code is non-destructive? → Approve”
  • Perf rubric: “Growth curve shape → classify O(n), O(n²), etc.”

Read the full file on GitHub · 79 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 · 79 lines · 54 tokens per session scan A a503b2ee2dbd

Subscribe to this mod's changes

code-executor is an agent published in the GitHub repository russbeye/claude-memory-bank (19 stars, last pushed 11mo ago), licensed MIT. It adds 54 tokens to every session and 753 once invoked, about $0.0003 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.

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