Day 57: Coding Agents That Only Emit Intents

LLMs that emit unified diffs against moving files will corrupt JSX “successfully.” Safer coding agents emit intents (AST operations, codemod names, parameter maps). A deterministic apply layer turns intents into patches.

⚡ TL;DR: Model outputs Intent JSON; apply layer runs jscodeshift/libcst/ts-morph. Reject freeform file bytes. Validate AST after apply.

Intent schema

# intents/schema.py
from pydantic import BaseModel, Field
from typing import Literal, Any

class Intent(BaseModel):
    kind: Literal["rename_symbol", "add_import", "wrap_call", "codemod"]
    path: str
    params: dict[str, Any] = Field(default_factory=dict)
    rationale: str

{
  "kind": "rename_symbol",
  "path": "src/billing/invoice.ts",
  "params": {"from": "calcTotal", "to": "calculateInvoiceTotal"},
  "rationale": "Match domain language in ADR-17"
}

Deterministic apply

// apply/rename.ts
import { Project } from "ts-morph";

export function applyRename(path: string, from: string, to: string) {
  const project = new Project();
  const sf = project.addSourceFileAtPath(path);
  sf.getDescendantsOfKind(/* Identifier */).forEach((id) => {
    if (id.getText() === from) id.replaceWithText(to); // ✅ AST-aware
  });
  sf.saveSync();
}

# apply/dispatch.py
HANDLERS = {
  "rename_symbol": apply_rename,
  "add_import": apply_add_import,
  "codemod": apply_named_codemod,
}

def apply_intent(intent: Intent):
    fn = HANDLERS.get(intent.kind)
    if not fn:
        raise ValueError(f"unknown_intent:{intent.kind}")
    return fn(intent.path, **intent.params)

❌ open(path,'w').write(model_bytes) — never let the model own the file body.

Closing checklist

• [ ] Typed intents only
• [ ] AST/codemod apply layer
• [ ] Parse/typecheck after apply
• [ ] Allowlist codemod names
• [ ] Keep a rollback snapshot per intent

Series navigation

Day 56: Supervisor Patterns on Bedrock Agents · Day 58: Spec-First: OpenAPI Remains Source of Truth

Last updated September 11, 2026