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.
npx agentmods add skills/samtalki/agentrepl.jl/run-agentreplnpx skills add samtalki/AgentREPL.jl --skill run-agentreplgit clone --depth 1 https://github.com/samtalki/AgentREPL.jlWhat 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 | $0.00061 | $0.01933 |
| Opus 5 | $0.00030 | $0.00966 |
| Sonnet 5 | $0.00012 | $0.00387 |
| Haiku 4.5 | $0.00006 | $0.00193 |
Grade A, and why
run-agentrepl scanned grade A with 1 finding 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
- **STDIO only, no port.** You cannot `curl` this server. The single local IPC channel is `session attach` (a chmod-600 Unix socket for an interactive human REPL), which needs `tmux` and is out of scope for headless driv How it starts
The opening of the file, as written. The whole thing — 116 lines — stays where its author put it; the contents beside it link to each section on GitHub.
AgentREPL.jl is an MCP server that exposes a persistent Julia REPL (eval, sessions, pkg, revise, plots) over JSON-RPC on STDIO. There is no GUI and no network port, so you drive it by being its MCP client: spawn the server, do the initialize handshake, call tools. The driver .claude/skills/run-agentrepl/driver.mjs does exactly that — use it for everything below.
All paths are relative to the repo root (/Users/sam/Research/AgentREPL.jl).
Prerequisites
Verified on macOS (darwin), Julia 1.12.6, Node v26. Linux is equivalent — there is nothing platform-specific in the launch path.
- Julia 1.12+ — the
juliabinary on PATH. Installed here via juliaup. - Node 18+ — only for
driver.mjs. Uses Node stdlib only, nonpm install.
Setup
Manifest.toml is gitignored, so resolve and precompile deps once after clone (~30s cold):
julia --project=. -e "using Pkg; Pkg.instantiate(); Pkg.precompile()"
Optional — enable Revise.jl hot-reload. Revise is only a test-extra of this package, not a runtime dep, and the worker inherits your global env on its load path. So hot-reload works only if Revise lives in your default environment:
julia -e 'using Pkg; Pkg.activate(); Pkg.add("Revise")'
Without this, info reports Revise.jl: not available and the server logs a Could not load Revise.jl on worker warning (and records a session note) per worker spawn. Eval is unaffected.
Run (agent path)
Drive the server with driver.mjs. It spawns julia --project=. bin/julia-repl-server, handles the handshake, and skips the non-JSON chatter the server interleaves on its streams.
Full smoke test — launches, exercises all 8 tools, prints PASS/FAIL, exits non-zero on any failure (~10s warm, after precompile):
node .claude/skills/run-agentrepl/driver.mjs
One-shot eval — spawn, eval, print the formatted result, exit:
node .claude/skills/run-agentrepl/driver.mjs eval 'using Statistics; mean([1,2,3,4,5])'
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 2d ago First seen · 116 lines · 61 tokens per session scan A 758dafdca036
run-agentrepl is a skill published in the GitHub repository samtalki/AgentREPL.jl (6 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 61 tokens to every session and 1,933 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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