Why Silas

Build agents the way you build Rails apps

Silas is for the same things every modern agent framework is for: a support desk that actually resolves tickets, an analyst that posts the Monday digest, an ops copilot in Slack, a back-office agent that chases invoices. An agent is a directory of plain files — a persona, a data-only config, one file per tool — and the framework supplies the durable loop, the scheduling, the channels, the memory, and the operator surface. If you’ve looked at eve, the authoring model will feel immediately familiar; that shape is the category’s best idea, and Silas embraces it.

What’s different is where it runs. Silas isn’t a second runtime you stand beside your app — it’s a gem inside the Rails app you already deploy:

  • Your tools are your app. Order.find_by!, refunds.create!, your service objects, your validations — no RPC layer between the agent and the domain, because the agent lives where the domain lives.
  • Your auth is the agent’s auth. The operator inbox mounts as an engine and hides behind whatever current_user already means. No second dashboard, no second login, no second audit domain.
  • Your deploy is the agent’s deploy. One repo, one CI, one Kamal push. The durable substrate — a database, Solid Queue, Active Job Continuations — is already booted.

The guarantees go further

Every serious framework makes the loop durable. Silas draws the line a step past that, and verifies it with a chaos harness that kill -9s live agents hundreds of times per release (zero duplicate effects, byte-identical replay — guarantees):

  • Exactly-once tool effects. A transactional! tool’s database write and the ledger’s record of it commit in one transaction. A crash mid-refund leaves exactly one refund row — never two, never zero — with no idempotency key required. Only a framework inside your app can offer this: an external runtime’s ledger can never join your database transaction.
  • Ambiguity waits for a person. The default mode is at-most-once: a crash that makes “did it send?” unanswerable parks the call in doubt for a human verdict instead of re-firing blind. Never double-pay; sometimes ask.
  • Holds cost nothing. An approval, a question, or a budget breach parks the turn at zero compute — the job exits, and clearing it resumes from durable rows without re-calling the model.

If your agents only ever read, any durable loop will do. The moment one touches money, inventory, or anything you’d hate to see happen twice, this is the difference you’ll feel.

Batteries included

A production operator inbox (live traces, approval cards, audit trail, cost accounting), approval-gated memory with provenance, deterministic evals as a deploy gate, Slack and email channels plus a generator for any transport, a JSON API with SSE, per-turn budgets, replay-safe compaction — shipped in the gem, not assembled from templates. And one command builds a working agent app from nothing:

rails new desk -m https://raw.githubusercontent.com/danielstpaul/silas/main/templates/desk.rb

The honest notes

  • Silas is early — 0.5.x, and the guarantees are proven by a reproducible chaos harness rather than years of production traffic. The contract is measured on every release, and it’s stated precisely so you know exactly what’s promised.
  • Rails-only, on purpose. If your team lives in TypeScript, eve is excellent and closer to home — the comparison is honest about that in both directions.
  • Exactly-once applies to effects in your database. A raw external call with no idempotency key of its own gets at-most-once + in-doubt parking — strong, but not transactional. Model money as rows (your app probably already does) and you get the full guarantee.
  • Inference goes to your configured provider. Agent state stays in your database; prompts still travel to the model you choose.
  • Untrusted code needs a real sandbox. The built-in Docker seam is interim; configure hermetic for microVM-class isolation before running code you didn’t write.

Try the claim

Run the template, ask for the £64 refund, clear it from the inbox — and while the turn is resuming, kill -9 the worker. Restart it. The turn completes from its last checkpoint, and Refund.count is exactly 1. That’s the pitch, reproduced on your laptop in five minutes.

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