Multi-step, tool use, long-running
A ai agent stack.
AI agent · 100,000 req/mo. At the default case — 100k requests a month, no further constraints — drawn from the 112 tools already in the index. Each pick is a tool whose own skip-when is stated, because a stack built on tools it does not know how to overcommit to is a guess.
This is the default case, stated as such. Describe your case to change it — the recommendation recomputes, and anything it assumes comes back in the answer rather than staying silent.
The picks
Routing — Bifrost
WorkableA high-throughput OpenAI-compatible proxy with a small footprint.
Watch out: You need the breadth of a full routing stack.
Consider Cloudflare AI Gateway instead when edge caching and latency dominate, on Cloudflare already
Agents — LangChain
Strong fitTool use and state, in an ecosystem where the answers already exist.
Watch out: You want a thin, legible core — this is a large surface.
Consider Letta instead when agents whose memory is a first-class, inspectable and editable state
Workflows — DBOS
Strong fitDurable workflows as ordinary Python functions and decorators.
Watch out: You want a separate service to operate.
Consider Fly Machines instead when hosting stateful containers that fits durable agent workers
Inference — KoboldCpp
WorkableLocal generation with a UI tuned for interactive, long-form use.
Watch out: You need headless serving at scale.
Consider llama.cpp instead when the constraint is hardware, not throughput — no GPU, or an edge box
Guardrails — PyRIT
Strong fitGenerating and scoring attack prompts systematically.
Watch out: You are not authorised to test the target.
Consider garak instead when probing your own system for known vulnerability classes
Evals — Braintrust
Strong fitMaking evaluation, rather than tracing, the primary workflow.
Watch out: You need open formats and self-hosting.
Consider LangSmith instead when teams already deep in LangChain needing tracing and datasets
The costs and the risks
- Estimated cost
- $40–$238 per month — a heuristic band from query volume, not a vendor quote.
- Confidence
- 87% — lower when constraints narrow the field.
- Cost drivers
- Braintrust
Biggest risk at the default case: An agent loop that cannot survive a deploy will eventually cause real damage. Durability and tool permissions are the controls, not the prompt.
A starting point, not a prescription. The recommendation at the default case is what the engine would tell a stranger with your workload; the recommendation at *your* case is what it tells you once it knows the constraints. The Stack Builder holds both — the builder link preselects this workload and starts with your volumes from here.