Tutorial: Typed chain

Wires are not only “text.” A node can declare input / output as text, int, float, bool, or json. threadle checks that the payload parses before the next node runs, so a bad number fails loudly instead of poisoning the rest of the graph.

This tutorial builds two small demos from the repo examples.

Demo A. Text → json → float

Text stats emits a JSON object. Sum numbers walks that JSON and returns a float total.

char-stats

{
  "id": "char-stats",
  "label": "Text stats",
  "glyph": "∑",
  "description": "chars, words and lines of the input, as JSON",
  "entry": "node.ts",
  "input": "text",
  "output": "json"
}

export default class TextStats {
  async run(input: string): Promise<string> {
    return JSON.stringify(
      {
        chars: input.length,
        words: (input.trim().match(/\S+/g) ?? []).length,
        lines: input === "" ? 0 : input.split("\n").length,
      },
      null,
      2,
    );
  }
}

sum-numbers

{
  "id": "sum-numbers",
  "label": "Sum numbers",
  "glyph": "＋",
  "description": "sums every number found in a JSON value",
  "entry": "node.ts",
  "input": "json",
  "output": "float"
}

export default class SumNumbers {
  async run(input: string): Promise<string> {
    let total = 0;
    const walk = (v: unknown): void => {
      if (typeof v === "number") total += v;
      else if (Array.isArray(v)) v.forEach(walk);
      else if (v && typeof v === "object") Object.values(v).forEach(walk);
    };
    walk(JSON.parse(input));
    return String(total);
  }
}

Wire and run

prompt  →  Text stats  →  ◇ Data(json)  →  Sum numbers  →  output

(You can omit ◇ Data when Text stats already declares output: "json". The type gate accepts a direct wire. Data is useful when an upstream agent emits prose JSON you still want to coerce.)

Prompt:

one two
three

Expected JSON from Text stats (shape):

{ "chars": 14, "words": 3, "lines": 2 }

Sum numbers walks every number → output roughly 19 (exact chars depend on newlines).

If you wire a plain text prompt directly into Sum numbers, the run fails at the type gate. json expected. Instead of throwing inside JSON.parse mid-pipeline.

Demo B. Int prompt → Fibonacci

{
  "id": "fibonacci",
  "label": "Fibonacci",
  "glyph": "φ",
  "description": "first N Fibonacci numbers",
  "entry": "node.ts",
  "input": "int",
  "output": "text"
}

export default class Fibonacci {
  async run(input: string): Promise<string> {
    const n = Math.min(Number.parseInt(input.trim(), 10), 90);
    const seq: bigint[] = [];
    let [a, b] = [0n, 1n];
    for (let i = 0; i < n; i++) {
      seq.push(a);
      [a, b] = [b, a + b];
    }
    return seq.join(", ");
  }
}

Wire an int-typed prompt (inspector → value type int). Or ◇ Data(int). Into Fibonacci:

prompt(int: 8)  →  Fibonacci  →  output
◇ Data(int: 8)  →  Fibonacci  →  output

→ 0, 1, 1, 2, 3, 5, 8, 13

A text prompt containing eight will not satisfy int and the edge or run will refuse.

Compatibility cheat sheet

From → To	Allowed?
same type	yes
anything → `text`	yes
`int` → `float`	yes
`float` → `int`	no
`text` → `json`	only if the string parses as JSON

Named ports use the same types per port. See Params & named ports.

Install from the repo

If you have the threadle source tree:

Settings → custom nodes → ⇣ Import → pick examples/nodes/char-stats (and siblings), or copy the folders into ~/.config/threadle/nodes/.

Custom nodes
Stdlib pack. jq / extract-json after typed Data nodes
Params & named ports. Widgets + multi-lane I/O
Tutorial: Extract URLs
Tutorial: Command node
Lanes & value types