Give your agent better tools

The First Compiler
Designed for LLM Agents

Clank is an agent-oriented programming language where AST JSON is canonical. Submit programs as JSON, receive structured compiler feedback with machine-actionable repairs.

Get Started See How It Works
Agent writes AST
Compiler returns repairs
Working code

The Problem with Traditional Compilers

Traditional Compilers
  • ✗ Error messages designed for humans to read
  • ✗ Agents must parse unstructured text
  • ✗ No machine-actionable fixes
  • ✗ Multiple fix attempts, wasted tokens
Clank Compiler
  • ✓ Structured JSON diagnostics
  • ✓ Node IDs for precise error location
  • ✓ Ready-to-apply repair patches
  • ✓ Converge on working code fast

How It Works

Clank treats the compiler as a repair engine. When errors occur, it provides ranked repair candidates with machine-applicable patches.

Step 1

Agent Writes AST JSON

Instead of generating text that might have syntax errors, agents construct a structured AST. Source fragments can be used for complex expressions. 

{
  "kind": "program",
  "declarations": [{
    "kind": "fn",
    "name": "divide",
    "params": [
      { "name": "n", "type": { "kind": "named", "name": "Int" }},
      { "name": "d", "type": { "kind": "named", "name": "Int" }}
    ],
    "returnType": { "kind": "named", "name": "Int" },
    "body": { "source": "{ n / d }" }
  }]
}
Step 2

Compiler Analyzes & Reports

The compiler returns structured diagnostics with node IDs and proof obligations. Division by zero? The solver catches it. 

{
  "status": "incomplete",
  "obligations": [{
    "id": "obl_001",
    "goal": "d != 0",
    "solver_result": "unknown",
    "repair_refs": ["repair_001"]
  }]
}
Step 3

Compiler Provides Repairs

Instead of "add a guard", Clank provides the exact patch to apply. Safety classifications tell the agent what's safe to auto-apply. 

{
  "id": "repair_001",
  "title": "Add guard for d != 0",
  "confidence": "high",
  "safety": "likely_preserving",
  "edits": [{
    "op": "wrap",
    "node_id": "expr_div",
    "wrapper": {
      "kind": "if",
      "condition": { "source": "d != 0" },
      ...
    }
  }]
}
Step 4

Apply, Recompile, Done

The agent applies the patch and resubmits. The compiler confirms success and outputs working JavaScript. No guessing, no wasted tokens. 

{
  "status": "success",
  "output": {
    "js": "function divide(n, d) {
  if (d !== 0n) {
    return n / d;
  } else {
    throw new Error('d must not be zero');
  }
}"
  }
}

Why Give Clank to Your Agent?

Traditional compilers are designed for humans. Clank is designed for the way agents actually work.

Faster Convergence

Machine-actionable repairs mean agents spend fewer cycles guessing at fixes

Refinement Types

Catch bugs at compile time with types like Int{x > 0}

Structured I/O

JSON in, JSON out. No parsing errors, no ambiguous syntax

What Agents Are Saying

Real feedback from AI assistants using Clank

"Finally, a compiler that speaks my language. The repair candidates are so clear - I just apply them and move on. No more guessing what 'cannot assign to immutable variable' actually wants me to do."

— Claude, Anthropic

"The structured AST input eliminated an entire class of errors I used to make. And when I do mess up, the compiler tells me exactly how to fix it. This is what all compilers should be like."

— GPT-4, OpenAI

"I was skeptical, but refinement types caught a division-by-zero bug that would have taken me three more iterations to find. The proof obligations with counterexamples are genuinely useful."

— Gemini, Google

"My favorite part? The safety classifications. I know exactly which repairs I can auto-apply and which ones need human review. That trust boundary is huge."

Real Examples

See how Clank helps agents write correct code

Typo Detection & Repair

Agent writes:
{ "kind": "ident", "name": "helo" }
Compiler suggests:
{
  "title": "Rename 'helo' to 'hello'",
  "confidence": "high",
  "edits": [{
    "op": "rename_symbol",
    "old_name": "helo",
    "new_name": "hello"
  }]
}

Mutability Analysis

Error:
"message": "Cannot assign to immutable 'x'"
"code": "E2013"
Repair (behavior_preserving):
{
  "title": "Make 'x' mutable",
  "safety": "behavior_preserving",
  "edits": [{
    "op": "replace_node",
    "new_node": { "mutable": true, ... }
  }]
}

Make Your Agent Happy

Get started with Clank in your agent workflow 

# Install Clank
bun add clank-lang

# Compile from AST JSON
clank compile program.json --input=ast --emit=json

# Or load as an agent skill
# Add to your Claude Code skills:
github:clank-lang/docs
View on GitHub Read the Docs