Updated docs.

Author: uhop

AGENTS.md

@@ -40,7 +40,7 @@ stream-chain/
 │   ├── defs.d.ts         # TypeScript definitions for defs
 │   ├── gen.js            # Creates async generator pipeline from functions
 │   ├── gen.d.ts          # TypeScript definitions for gen
-│   ├── fun.js            # Creates async function pipeline from functions
+│   ├── fun.js            # Creates function pipeline from functions (sync-first)
 │   ├── fun.d.ts          # TypeScript definitions for fun
 │   ├── asStream.js       # Converts a function into a Duplex stream
 │   ├── asStream.d.ts     # TypeScript definitions for asStream
@@ -95,7 +95,7 @@ stream-chain/
 - `chain(fns, options)` is the main entry point. It accepts an array of functions, streams, or arrays (which are flattened). Returns a `Duplex` stream with `.streams`, `.input`, `.output` properties.
 - Functions in the chain are grouped together using `gen()` for efficiency (unless `noGrouping: true`).
 - `gen(...fns)` creates an async generator pipeline from a list of functions. It handles all special return values (`none`, `stop`, `many()`, `finalValue()`, flushable functions).
-- `fun(...fns)` is like `gen()` but returns an async function instead of a generator.
+- `fun(...fns)` is like `gen()` but returns a function instead of a generator. Returns sync results for sync pipelines, `Promise` for async.
 - `asStream(fn)` wraps any function as a `Duplex` stream.
 - Special return values are defined in `defs.js`: `none` (skip), `stop` (terminate), `many(values)` (emit multiple), `finalValue(value)` (skip rest of chain), `flushable(fn)` (called at stream end).
 - Web streams (`ReadableStream`, `WritableStream`, duplex `{readable, writable}`) are automatically adapted to Node streams.

ARCHITECTURE.md

@@ -13,7 +13,7 @@ src/                      # Source code
 ├── defs.d.ts             # TypeScript declarations for defs
 ├── gen.js                # Async generator pipeline from a list of functions
 ├── gen.d.ts              # TypeScript declarations for gen
-├── fun.js                # Async function pipeline from a list of functions
+├── fun.js                # Function pipeline from a list of functions (sync-first)
 ├── fun.d.ts              # TypeScript declarations for fun
 ├── asStream.js           # Wraps any function as a Duplex stream
 ├── asStream.d.ts         # TypeScript declarations for asStream
@@ -84,9 +84,9 @@ Functions in a chain can return special values to control flow:
 4. Calls flushable functions with `none` when the input is exhausted.
 5. Tags the result with a function list (`fListSymbol`) so `chain()` can inline it.
 
-### fun() — async function pipeline
+### fun() — function pipeline (sync-first)
 
-`fun(...fns)` is like `gen()` but returns an async function instead of a generator. Generator results are collected into `many()` arrays.
+`fun(...fns)` is like `gen()` but returns a function instead of a generator. Generator results are collected into `many()` arrays. For purely synchronous pipelines it returns a synchronous result; for asynchronous pipelines it returns a `Promise`.
 
 ### asStream() — function to Duplex
 

dev-docs/underlying-ideas.md

@@ -80,7 +80,7 @@ Core ideas:
 - A pipeline is an array of processing units applied sequentially.
 - Each unit can be a function (sync/async), a generator (sync/async), a stream (Node or Web), or another pipeline.
 - Functional sub-pipelines group consecutive functions without stream overhead:
-  - `fun()` — takes a list of functions, returns an async function. Handles `none`, `stop`, `many()`, and `finalValue()` returns.
+  - `fun()` — takes a list of functions, returns a function (sync-first: returns sync results for sync pipelines, `Promise` for async). Handles `none`, `stop`, `many()`, and `finalValue()` returns.
   - `gen()` — takes a list of functions, returns an async generator. It handles `none`, `many()`, and other special values internally, but never produces them — a generator naturally yields zero, one, or many values.
 - `asStream()` wraps any function as a Duplex stream.
 

llms-full.txt

@@ -261,7 +261,7 @@ for await (const v of pipeline(3)) {
 
 ## fun(...fns)
 
-Like `gen()` but returns an async function. Values from generators are collected into `many()` arrays. Like `gen()`, passes `null`/`undefined` through the pipeline (unlike `asStream()`/`chain()`).
+Like `gen()` but returns a function instead of a generator. Values from generators are collected into `many()` arrays. For purely synchronous pipelines it returns a synchronous result; for asynchronous pipelines it returns a `Promise`. Like `gen()`, passes `null`/`undefined` through the pipeline (unlike `asStream()`/`chain()`).
 
 ```js
 import fun from 'stream-chain/fun.js';

src/fun.d.ts

@@ -9,10 +9,9 @@ export = fun;
 declare function fun(): (arg: unknown) => Many<unknown> | Promise<Many<unknown>>;
 
 /**
- * Returns a function that applies the given functions in sequence wrapping them as
- * an asynchronous function.
+ * Returns a function that applies the given functions in sequence.
  * @param fns functions to be wrapped
- * @returns an asynchronous function
+ * @returns a function that returns a synchronous result or a `Promise`
  * @remarks It collects values and returns them as a {@link Many}.
  */
 declare function fun<L extends unknown[]>(