Core concepts
Agent mode and Plan mode
Two ways to run the same request, and how to pick between them.
The same request can be run two ways. Agent mode works autonomously with tools until it is satisfied; Plan mode asks you questions first and then walks a fixed pipeline. Neither is better in general, and the toggle sits on the composer so you can switch per run.
Agent mode
An agent is given your request, a working directory, and a small set of tools: it can read and write files, compile and simulate with iverilog, run synthesis with Yosys, and search the knowledge base. It decides the order to use them in and keeps going until the work holds up or it runs out of budget.
- Strengths. Anything where the right next step depends on what the last one produced: debugging, iterating on a failing testbench, multi-file work.
- Cost. Variable. Typical runs land near $0.28 from scratch and $0.37 inside a project, with a hard ceiling per run so a bad run cannot spiral.
- Limits. Verilog and SystemVerilog only. Project mode requires it.
Plan mode
Plan mode reads your description, asks you a handful of clarifying questions, and only then generates. It then walks the staged pipeline: generate, optionally reflect, write a testbench, verify, refine.
- Strengths. A well-specified block where you would rather answer four questions up front than review a wrong module afterwards.
- Language. The only mode that produces VHDL.
- Predictability. The same request tends to take the same shape every time, because the stages are fixed.
The questions step is covered in Clarifying questions.
Choosing between them
| If you want to... | Use |
|---|---|
| Write a standalone module in Verilog | Either; Agent needs less input from you |
| Write a module in VHDL | Plan |
| Edit an existing project | Agent; it is the only option |
| Chase a bug through simulation | Agent |
| Be asked about the ambiguities before code is written | Plan |
| Keep the cost of a run tightly predictable | Plan |
Where the toggle is
Two places, both writing to the same setting: the Agent / Plan pair on the composer, and the Mode section at the top of the Run setup panel. To change the mode every new chat starts in, set it in Settings under Setup.