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Quick Start

This tutorial introduces the basic Devlish workflow: write a small text file, supply its inputs, and run it from a terminal. You will then add a calculation and return a structured result that another program could use.

Start after completing Installation. No model account or MCP client is needed for these examples. Ask names an input; the commands below provide that input with --input. Print displays a value, while Respond with returns a result to the caller.

1. Write a program

Section titled “1. Write a program”

Create a file called hello.dvl:

Ask "What is your name?" as user name
Print user_name

Ask declares an input parameter. Print outputs a value.

2. Run it

Section titled “2. Run it”
Terminal window
devlish --run hello.dvl --input '{"user_name": "World"}'

Output: World

3. Add logic

Section titled “3. Add logic”
Ask "Customer tier?" as customer tier
Ask "Deal size?" as deal size


discount_rate equals 0.05
If customer_tier is "enterprise"
  discount_rate equals 0.15


discount equals deal_size times discount_rate
Print discount
Terminal window
devlish --run pricing.dvl --input '{"customer_tier": "enterprise", "deal_size": 500000}'
# 75000

4. Validate syntax

Section titled “4. Validate syntax”
Terminal window
devlish validate pricing.dvl

Returns exit 0 if the file is valid, or diagnostic errors with line numbers.

5. Compile to bytecode

Section titled “5. Compile to bytecode”
Terminal window
devlish compile pricing.dvl --output pricing.dvlc.json
devlish disassemble pricing.dvlc.json
devlish --run pricing.dvlc.json --input '{"customer_tier": "enterprise", "deal_size": 500000}'

Bytecode is the portable format. It runs natively (CLI), in browsers (WASM), or via MCP.

6. Structured output

Section titled “6. Structured output”

Replace Print with Respond with to return JSON instead of text:

Ask "Customer tier?" as customer tier
Ask "Deal size?" as deal size


discount_rate equals 0.05
If customer_tier is "enterprise"
  discount_rate equals 0.15


discount equals deal_size times discount_rate
Respond with record with discount as amount and customer_tier as tier
Terminal window
devlish --run pricing.dvl --input '{"customer_tier": "enterprise", "deal_size": 500000}'
# {"amount":75000,"tier":"enterprise"}

Application modes

Section titled “Application modes”

Run devlish for the interactive model prompt, devlish --run workflow.dvl (or -r) for file execution, and devlish --server (or -s) for the foreground HTTP service at 127.0.0.1:7420. File mode compiles source in memory; a separate compile step is optional.

The prompt uses your configured provider and model. Project overrides live in .devlish/agent.dvl and .devlish/policy.dvl. See local tools and policy for authorization defaults and tool execution.

CLI commands

Section titled “CLI commands”
Command Description
devlish run <file> Run a .dvl source or .dvlc.json bytecode
devlish compile <file> Compile to bytecode
devlish validate <file> Check syntax
devlish lint <file> Style and correctness suggestions
devlish disassemble <file> Show bytecode instructions
devlish new <name> Scaffold a new project
devlish mcp Start the MCP server
devlish package Build a distributable artifact

What’s next

Section titled “What’s next”