Ecko for VS Code

Language support for Ecko - the language where ai is a keyword, not an import.

Diagnostics, completion, hover, go-to-definition and formatting come from ecko lsp, which is the compiler itself, so your editor cannot disagree with a build. Syntax highlighting and 37 snippets work with no server at all.

What Ecko looks like

An LLM call is a language construct, not a client library. There is nothing to import and nothing to configure:

answer = ai "What is the capital of France?"
print(answer)

# Ask for a type and you get that type back, not a string to parse.
count = ai[Int] "How many moons does Mars have?"
print(count + 1)

Because calls are ordinary expressions, they compose the way everything else does:

notes = "Meet me on 12 March, and again on 4 April."

dates = notes
    |> ai "Extract every date"
    |> ai "Format as ISO 8601, one per line"

print(dates)

Ask for one of your own types and the answer arrives already checked against it, so match stays exhaustive. Mark a function @tool and the model can call it while it works:

type Sentiment = Positive | Negative | Neutral

## Look up which plan a customer is on. The model may call this itself.
@tool("look up which plan a customer is on")
fn plan_for(customer) = "enterprise"

fn triage(message) = ai[Sentiment] message using [plan_for]

mood = triage("The build has been broken for three days.")

print(match mood {
    Positive => "no action"
    Negative => "escalate"
    Neutral => "queue"
})

The parts that usually get bolted on afterwards are in the language. Untrusted text is fenced off inside a prompt rather than concatenated into it, secrets resist being printed by accident, and contracts are checked at the boundary:

key = secret("sk-live-abc123")

template ask(@untrusted question) = """
Answer only from company policy.

{input question}
"""

@requires(len(q) > 0)
@ensures(len(result) > 0)
fn helpdesk(q) = ai ask(q)

print(helpdesk("How do I reset my password?"))

There is more than the ai keyword: pattern matching over union types, pipelines, sql { ... } blocks with real bind holes, share-nothing concurrency, and a standard library that is already installed - import std.http is an HTTP server, import std.sql is SQLite.

It all runs offline

Every example above runs with no API key. Ecko has a deterministic mock mode: typed calls return schema-valid values, so pipelines, tools and contracts keep working before you have configured a provider. Paste any of them into a file and run it:

ecko example.ecko

Try the language in your browser first, if you would rather: the playground is the real compiler built to WebAssembly, running client-side with no backend.

What this extension gives you

From the language server (needs the ecko binary):

• Live diagnostics as you type - parse errors, undefined names with did-you-mean, arity mismatches, use before definition, non-exhaustive matches, unreachable code, unused imports and variables, shadowed builtins, and unwrapped credentials
• Completion for keywords, builtins, std modules, your own top-level functions, types and variables, and a module's members after a .
• Hover showing signatures for your functions and labels for builtins
• Go to definition, document symbols for the outline and breadcrumbs, and workspace symbol search
• Find All References and occurrence highlighting, scoped to the open file and scope-aware - a name shadowed in an inner block resolves to its own declaration, not to every occurrence of the spelling
• Quick fixes on four diagnostics: correct a misspelled name to the suggestion the compiler already computed, remove an unused import, prefix an unused binding with _, or fill in the missing arms of a non-exhaustive match
• Semantic highlighting, coloured by the compiler rather than the grammar, so std modules and types are told apart from ordinary names
• Format Document, the same result as ecko fmt

Always, with no server:

• Syntax highlighting for .ecko, covering string interpolation, raw and byte strings, decimal literals, the ai clauses (using, with, on, -> stream), sql { ... } blocks, contract and tool annotations, and ## documentation comments
• 37 snippets - ai, ai[T], ai ... using, template, @tool, @requires, match, sql, secret and the rest
• Auto-closing brackets and quotes, indentation rules, and folding via # region / # endregion

Requirements

The editing intelligence is served by ecko lsp, so you need the binary. It is a single file with nothing to configure:

curl -fsSL https://ecko.sh/install | sh

The extension looks for it in this order:

1. ecko.server.path in your settings
2. the ECKO_BINARY environment variable
3. ecko on your PATH
4. ~/.local/bin/ecko, then ~/.ecko/bin/ecko, then /usr/local/bin/ecko

Those fallbacks matter because VS Code and Cursor started from a desktop launcher often do not inherit a shell's PATH, and "the server won't start" is almost always that. Set ecko.server.path to an absolute path if so.

Without the binary you still get highlighting and snippets, and a notice explaining how to switch the rest on.

Learn more

Licence

Ecko is proprietary software. It is free for personal and educational use, and for evaluating it in a business for up to 30 days. Any other business use, including internal tooling, needs a commercial licence - see ecko.sh/enterprise.

The extension and the language share these terms; the full text is in LICENSE.