Add random pattern selection (-r / --pattern random)

Pick a different movement pattern every time a sweep is triggered, so the
motion varies across the day instead of repeating one shape.

- strategies.ts: add the `random` sentinel, `SELECTABLE_PATTERN_NAMES`,
  `isSelectablePattern`, and `createRandomPicker`. `random` is deliberately
  NOT a registry entry: it has no path of its own, so `STRATEGIES` stays a
  total lookup and `PATTERN_NAMES` keeps listing only real generators. The
  picker is a closure over `last`, giving a uniform draw that never returns
  the same pattern twice in a row. Building CANONICAL_PATTERNS from the
  selectable list makes both validation boundaries accept `random` (and
  loose spellings) for free, and extends the normalization-collision
  assertion to cover the sentinel.
- cli.ts: add `-r`/`--random` plus an exported `selectPattern` holding the
  conflict rule. `-r` is sugar for `--pattern random`, so the two agreeing
  is a no-op while `-r -p arc` is rejected as contradictory. The flag folds
  into `pattern`, so ConfigOverrides, resolveConfig, and move.ts are
  untouched. `parseCliArgs` now takes its argv as an optional parameter so
  the flag surface is testable without process.argv.
- keeper.ts: resolve `random` via the picker once per trigger, before the
  loop-mode branch, so a pick holds for a whole loop run rather than
  changing mid-run. runKeeper builds one picker for the process, so the
  no-repeat memory spans sweeps minutes apart. Because the pick is a real
  strategy, --verbose logs the concrete pattern name and a pick with an
  infinite loopPath still bounces edge-to-edge under --loop.
- config.ts / configFile.ts: accept the sentinel where a pattern is valid,
  and quote the selectable list in errors. No `random` boolean config key —
  the file spells it "pattern": "random".

executor.ts and move.ts needed no changes.

Tests: new tests/cli.test.ts (the file had no coverage before) covering the
flag surface and the conflict rule; picker tests pinning the no-repeat and
full-registry-coverage properties; keeper tests pinning once-per-trigger and
once-per-loop-run.

CHANGELOG.md

@@ -5,6 +5,35 @@ All notable changes to `move` are documented here.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+- Random pattern selection: `-r` / `--random`, and `random` as a value for
+  `--pattern` and the `pattern` config key. Every time a sweep is triggered,
+  a different movement pattern is chosen, so the motion varies across the day
+  instead of repeating one shape. Two rules keep it predictable: the same
+  pattern is never chosen twice in a row, and the pick happens once per
+  trigger — in loop mode it holds for the whole loop run rather than changing
+  mid-run. The pick is a real strategy, so `--verbose` logs the concrete
+  pattern name and a pick with an infinite loop path (`line`, `diagonal`)
+  still bounces edge-to-edge under `--loop`.
+
+  `-r` is defined as sugar for `--pattern random`, so passing both is
+  rejected (exit `2`) unless they agree: `move -r -p arc` is an error, while
+  `move -r -p random` is a no-op. There is no `random` boolean config key —
+  the file spells it `"pattern": "random"`.
+
+  `random` is deliberately not a registry entry: it has no path of its own,
+  and the keeper resolves it to a real strategy per sweep. `PATTERN_NAMES`
+  therefore still lists only real generators, with the new
+  `SELECTABLE_PATTERN_NAMES` covering what a user may select.
+
+### Changed
+- `parseCliArgs` now takes its argument list as an optional parameter
+  (defaulting to the real command line), so the flag surface is unit-testable
+  without touching `process.argv`. Adds `tests/cli.test.ts`, which previously
+  had no coverage.
+
 ## [1.4.0] - 2026-08-17
 
 ### Added

README.md

@@ -119,8 +119,12 @@ Options:
   -d, --step-delay <ms>           Pause between synthetic steps. Default: 50.
   -p, --pattern <name>            Movement strategy. Default: line.
                                   One of: line, diagonal, jitter, walk, arc,
-                                  figureEight. Each pattern defines its own
+                                  figureEight, random. Each pattern defines
-                                  size and speed.
+                                  its own size and speed.
+  -r, --random                    Shorthand for --pattern random. Picks a
+                                  different pattern for each sweep, never the
+                                  same one twice in a row. In loop mode the
+                                  pick holds for the whole loop run.
   -V, --verbose                   Log every sweep and interrupt
                                   (default prints only the startup banner).
   -l, --loop                      Loop mode: once a sweep is triggered,
@@ -191,7 +195,7 @@ doesn't set.
 All keys are optional; supply only the ones you want to override. Keys
 and units mirror the CLI flags exactly: `moveInterval` and
 `checkInterval` are seconds, `stepDelay` is milliseconds, `pattern` is a
-movement strategy name, `verbose` and `loop` are booleans.
+movement strategy name (or `"random"`), `verbose` and `loop` are booleans.
 
 > The obsolete `stepCount` / `stepSize` keys (removed in 1.3.0) are
 > tolerated for backward compatibility: they're ignored with a one-line
@@ -223,9 +227,11 @@ The loader is strict:
 - Root must be a JSON object.
 - Unknown keys are rejected (catches typos like `"movInterval"`).
 - Numeric values must be finite and strictly positive.
-- `pattern` must resolve to a registered strategy name. Matching ignores
+- `pattern` must resolve to a registered strategy name, or to `random`.
-  case and separators (`-`, `_`, spaces), so `figure-eight` and `figureEight`
+  Matching ignores case and separators (`-`, `_`, spaces), so `figure-eight`
-  are equivalent.
+  and `figureEight` are equivalent. There is no `random` boolean key — the
+  CLI's `-r` is sugar for `--pattern random`, and the file spells it the
+  same way.
 - `verbose` must be a boolean.
 - `loop` must be a boolean.
 
@@ -287,7 +293,8 @@ and everything but the raw nut.js call is unit-testable:
   injectable, so tests drive the loop and executor with a fake.
 - `src/strategies.ts` holds the pure movement patterns — each a generator
   of target points given a start, screen size, config, and RNG — plus the
-  registry and name validation. Adding a pattern is one pure function.
+  registry, name validation, and the `random` picker. Adding a pattern is
+  one pure function.
 - `src/executor.ts` is the single `executePath` driver: it rounds targets,
   reflects any off-screen coordinate back inside, paces steps, detects
   real-user interruption, and restores the cursor on a clean sweep.
@@ -299,7 +306,7 @@ Defaults live in `src/config.ts` as `DEFAULT_CONFIG`:
 | `moveInterval`  | `4 * 60_000` | `-m`, `--move-interval`   | Idle time (ms) required before a synthetic sweep fires.          |
 | `checkInterval` | `10_000`     | `-c`, `--check-interval`  | How often (ms) the main loop polls the cursor for real activity. |
 | `stepDelay`     | `50`         | `-d`, `--step-delay`      | Pause (ms) between individual synthetic steps in a sweep.        |
-| `pattern`       | `"line"`     | `-p`, `--pattern`         | Movement strategy name (see Movement strategies below).          |
+| `pattern`       | `"line"`     | `-p`, `--pattern`, `-r`   | Movement strategy name, or `random` (see Movement strategies below). |
 
 `-m` and `-c` are accepted in seconds at the CLI; `resolveConfig` converts
 to milliseconds before handing the resolved `Config` to `runKeeper`.
@@ -319,6 +326,8 @@ to milliseconds before handing the resolved `Config` to `runKeeper`.
 1. `simulateActivity` snapshots the starting position and current screen
    dimensions (re-read every sweep so monitor changes are handled), looks
    up `config.pattern` in the strategy registry, and builds a `MoveContext`.
+   When `config.pattern` is `random` — the one name the registry doesn't
+   contain — the strategy comes from the picker instead, once per trigger.
 2. It hands the strategy and context to `executePath`, which drives the
    sweep. For each target the strategy yields:
    - Round to whole pixels and reflect any off-screen coordinate back inside
@@ -346,7 +355,8 @@ or multi-monitor displays isn't misread as the user grabbing the mouse.
 
 ### Movement strategies
 
-`config.pattern` selects one of the generators in `src/strategies.ts`:
+`config.pattern` selects one of the generators in `src/strategies.ts` (or
+`random`, which picks one for you):
 
 | Name          | Motion                                                        | Steps | Size        |
 | ------------- | ------------------------------------------------------------- | ----- | ----------- |
@@ -356,6 +366,35 @@ or multi-monitor displays isn't misread as the user grabbing the mouse.
 | `walk`        | Cumulative random walk; bounces off the screen edges.         | 200   | ±4px/step   |
 | `arc`         | Smooth quadratic-Bézier curve to a random on-screen point.    | 120   | ~300px      |
 | `figureEight` | Traces a figure-eight (lemniscate) and returns to the start.  | 90    | ~250px wide |
+| `random`      | Meta-selection: a different one of the above per sweep.       | —     | —           |
+
+### Random (`-r` / `--pattern random`)
+
+`random` isn't a movement pattern of its own — it's a selection that resolves
+to one of the real patterns above each time a sweep fires:
+
+```sh
+move -r                    # a different pattern every sweep
+move --pattern random -V   # verbose names the pattern each sweep picked
+move -r --loop             # one random pick, looped until you move the mouse
+```
+
+Two rules make it predictable:
+
+- **Never twice in a row.** Consecutive sweeps always use different patterns,
+  so the motion visibly varies instead of occasionally repeating itself.
+- **One pick per trigger.** In loop mode a single trigger runs many cycles;
+  the pattern is chosen once and holds for that whole run rather than
+  changing mid-run.
+
+Because the pick is a real strategy, it behaves exactly as if you'd named it:
+`--verbose` logs the concrete pattern (`Simulating activity (arc)...`), and a
+pick with an infinite loop path (`line`, `diagonal`) bounces edge-to-edge
+under `--loop` just as selecting it directly would.
+
+`-r` and `--pattern` state the same setting two ways, so passing both is
+rejected (exit `2`) unless they agree — `move -r -p arc` is an error, while
+`move -r -p random` is a harmless no-op.
 
 Every pattern is kept on-screen the same way: the executor reflects any
 coordinate that would fall past a screen edge back inside, so motion bounces
@@ -423,7 +462,7 @@ move --help
 | `src/errors.ts`     | Shared error types (`CliError`).                                              |
 | `src/keeper.ts`     | Idle-watch loop + per-sweep glue (selects a strategy, calls the executor).    |
 | `src/device.ts`     | `Device` I/O seam over nut.js (`Point`, `createNutDevice`); the only nut.js importer. |
-| `src/strategies.ts` | Pure movement-pattern generators, the strategy registry, and name validation. |
+| `src/strategies.ts` | Pure movement-pattern generators, the strategy registry, name validation, and the `random` picker. |
 | `src/executor.ts`   | `executePath` driver: on-screen reflection, pacing, interrupt detection, restore. |
 | `docs/execution-happy-path.md` | Sequence diagram + invariants for a clean sweep.                  |
 | `package.json`      | Bun project manifest. Single runtime dep: `@nut-tree-fork/nut-js`.            |

docs/execution-happy-path.md

@@ -37,14 +37,14 @@ sequenceDiagram
         Note over Keeper: pos == lastPos (no user movement)<br/>now - lastActivity ≥ moveInterval → fire
     end
 
-    Keeper->>Sim: simulateActivity(config, log, dev)
+    Keeper->>Sim: simulateActivity(config, log, dev, pickRandom)
     Sim->>Dev: width()
     Dev-->>Sim: width
     Sim->>Dev: height()
     Dev-->>Sim: height
     Sim->>Dev: getPosition()
     Dev-->>Sim: start
-    Note over Sim: strategy = STRATEGIES[config.pattern]<br/>ctx = { start, width, height, rng }
+    Note over Sim: strategy = STRATEGIES[config.pattern]<br/>(or pickRandom() when pattern is "random")<br/>ctx = { start, width, height, rng }
     Sim->>Exec: executePath(strategy, ctx, dev, log, config)
 
     Exec->>Strat: path(ctx)

src/cli.ts

@@ -17,6 +17,10 @@
  *   -c, --check-interval    Cursor poll cadence (seconds).
  *   -d, --step-delay        Pause between synthetic steps (ms).
  *   -p, --pattern           Movement strategy name (see strategies.ts).
+ *   -r, --random            Sugar for `--pattern random`: pick a different
+ *                           pattern for each sweep. Folded into `pattern`
+ *                           here, so nothing downstream knows the flag
+ *                           exists. Conflicts with an explicit `--pattern`.
  *   -V, --verbose           Enable per-sweep / interrupt logging.
  *                           (`-V` capital because `-v` is `--version`.)
  *   -l, --loop              Loop mode: once triggered, keep moving
@@ -33,7 +37,7 @@ import { parseArgs } from "node:util";
 
 import { DEFAULT_CONFIG, defaultConfigPath } from "./config.ts";
 import { CliError } from "./errors.ts";
-import { PATTERN_NAMES, resolvePatternName } from "./strategies.ts";
+import { RANDOM_PATTERN, SELECTABLE_PATTERN_NAMES, resolvePatternName } from "./strategies.ts";
 
 /**
  * Result of `parseCliArgs`. Numeric fields are `undefined` when the user
@@ -48,7 +52,13 @@ export interface ParsedCliArgs {
     moveInterval: number | undefined;   // seconds
     checkInterval: number | undefined;  // seconds
     stepDelay: number | undefined;      // milliseconds
-    /** Movement strategy name, validated against the registry. */
+    /**
+     * Movement strategy name, validated against the registry — or the
+     * `random` sentinel, which `-r/--random` also folds into this field.
+     * There is deliberately no separate `random` boolean: the flag's entire
+     * effect is the value here, so downstream layering (`ConfigOverrides`,
+     * `resolveConfig`) needs no knowledge of it.
+     */
     pattern: string | undefined;
     /**
      * `true` when `-V`/`--verbose` was passed; `undefined` when it was not.
@@ -87,21 +97,48 @@ function parsePatternName(raw: string | undefined): string | undefined {
     if (raw === undefined) return undefined;
     const canonical: string | null = resolvePatternName(raw);
     if (canonical === null) {
-        throw new CliError(`invalid value for --pattern: '${raw}' (valid: ${PATTERN_NAMES.join(", ")})`);
+        throw new CliError(
+            `invalid value for --pattern: '${raw}' (valid: ${SELECTABLE_PATTERN_NAMES.join(", ")})`,
+        );
     }
     return canonical;
 }
 
 /**
- * Parse `process.argv` into a typed `ParsedCliArgs`. Uses Node's built-in
+ * Fold `-r/--random` and `--pattern` into the single pattern selection that
- * `parseArgs` in strict mode so unknown flags and missing values surface
+ * the rest of the program consumes.
- * as `CliError`s that the entry point can turn into exit code 2.
+ *
+ * `-r` is defined as sugar for `--pattern random`, so passing both spellings
+ * of the same request (`-r --pattern random`) is a harmless no-op. Any other
+ * pairing states two different intentions at once, and silently honoring one
+ * would hide the user's mistake — so it's rejected. The message quotes the
+ * user's own spelling rather than the canonical name, since that's what they
+ * need to find and fix on their command line.
+ *
+ * Exported so the conflict rule is testable without touching `process.argv`.
  */
-export function parseCliArgs(): ParsedCliArgs {
+export function selectPattern(rawPattern: string | undefined, random: boolean): string | undefined {
+    const canonical: string | undefined = parsePatternName(rawPattern);
+    if (!random) return canonical;
+    if (canonical !== undefined && canonical !== RANDOM_PATTERN) {
+        throw new CliError(`-r/--random conflicts with --pattern '${rawPattern}' (pick one)`);
+    }
+    return RANDOM_PATTERN;
+}
+
+/**
+ * Parse command-line arguments into a typed `ParsedCliArgs`. Uses Node's
+ * built-in `parseArgs` in strict mode so unknown flags and missing values
+ * surface as `CliError`s that the entry point can turn into exit code 2.
+ *
+ * @param argv - Argument list to parse, defaulting to the real command line.
+ *               Injectable so the flag surface can be unit-tested directly.
+ */
+export function parseCliArgs(argv: string[] = process.argv.slice(2)): ParsedCliArgs {
     let values: Record<string, string | boolean | undefined>;
     try {
         const result = parseArgs({
-            args: process.argv.slice(2),
+            args: argv,
             options: {
                 help:             { type: "boolean", short: "h" },
                 version:          { type: "boolean", short: "v" },
@@ -111,6 +148,7 @@ export function parseCliArgs(): ParsedCliArgs {
                 "check-interval": { type: "string",  short: "c" },
                 "step-delay":     { type: "string",  short: "d" },
                 pattern:          { type: "string",  short: "p" },
+                random:           { type: "boolean", short: "r" },
                 verbose:          { type: "boolean", short: "V" },
                 loop:             { type: "boolean", short: "l" },
             },
@@ -133,7 +171,7 @@ export function parseCliArgs(): ParsedCliArgs {
         moveInterval:  parsePositiveNumber("move-interval",  values["move-interval"]  as string | undefined),
         checkInterval: parsePositiveNumber("check-interval", values["check-interval"] as string | undefined),
         stepDelay:     parsePositiveNumber("step-delay",     values["step-delay"]     as string | undefined),
-        pattern:       parsePatternName(values.pattern as string | undefined),
+        pattern:       selectPattern(values.pattern as string | undefined, values.random === true),
         verbose:       values.verbose === true ? true : undefined,
         loop:          values.loop === true ? true : undefined,
     };
@@ -178,8 +216,12 @@ Options:
   -c, --check-interval <seconds>  Cursor poll cadence. Default: ${checkDefaultSec}.
   -d, --step-delay <ms>           Pause between synthetic steps. Default: ${DEFAULT_CONFIG.stepDelay}.
   -p, --pattern <name>            Movement strategy. Default: ${DEFAULT_CONFIG.pattern}.
-                                  One of: ${PATTERN_NAMES.join(", ")}.
+                                  One of: ${SELECTABLE_PATTERN_NAMES.join(", ")}.
                                   Each pattern defines its own size and speed.
+  -r, --random                    Shorthand for --pattern random. Picks a
+                                  different pattern for each sweep, never the
+                                  same one twice in a row. In loop mode the
+                                  pick holds for the whole loop run.
   -V, --verbose                   Log every sweep and interrupt
                                   (default prints only the startup banner).
   -l, --loop                      Loop mode: once a sweep is triggered,
@@ -194,6 +236,8 @@ Examples:
   move -m 300 -V
   move --pattern arc
   move --pattern diagonal --loop
+  move -r
+  move --pattern random --loop
   move --config ~/myprofile.json
 `);
 }

src/config.ts

@@ -22,7 +22,7 @@
 import { join } from "node:path";
 
 import { CliError } from "./errors.ts";
-import { isPatternName, type PatternName } from "./strategies.ts";
+import { isSelectablePattern, type PatternName } from "./strategies.ts";
 
 // Single source of truth for default values. The same file ships in the
 // install tree and is copied to $XDG_CONFIG_HOME/move/config.json on a
@@ -44,7 +44,10 @@ import seedRaw from "../scripts/config.default.json" with { type: "json" };
  *                     "interrupt" by moving the cursor. Milliseconds.
  * - `pattern`       — name of the movement strategy to use (see
  *                     `strategies.ts`; e.g. `line`, `walk`, `arc`). Each
- *                     pattern owns its own size and step count.
+ *                     pattern owns its own size and step count. May also be
+ *                     the `random` sentinel, which is not a registry key:
+ *                     the keeper resolves it to a real strategy once per
+ *                     sweep rather than looking it up here.
  * - `verbose`       — whether per-sweep / interrupt events are logged. The
  *                     startup banner is always printed.
  * - `loop`          — loop mode: once a sweep is triggered, keep
@@ -71,7 +74,7 @@ interface SeedShape {
     moveInterval: number;   // seconds
     checkInterval: number;  // seconds
     stepDelay: number;      // milliseconds
-    pattern: string;        // strategy name
+    pattern: string;        // strategy name, or the `random` sentinel
     verbose: boolean;
     loop: boolean;
 }
@@ -87,7 +90,7 @@ function assertSeedShape(raw: unknown): asserts raw is SeedShape {
             throw new Error(`scripts/config.default.json: '${key}' must be a positive finite number (got ${JSON.stringify(v)})`);
         }
     }
-    if (typeof r.pattern !== "string" || !isPatternName(r.pattern)) {
+    if (typeof r.pattern !== "string" || !isSelectablePattern(r.pattern)) {
         throw new Error(`scripts/config.default.json: 'pattern' must be a known strategy name (got ${JSON.stringify(r.pattern)})`);
     }
     if (typeof r.verbose !== "boolean") {

src/configFile.ts

@@ -10,10 +10,14 @@
  *   moveInterval   number   seconds, positive
  *   checkInterval  number   seconds, positive
  *   stepDelay      number   milliseconds, positive
- *   pattern        string   a registered strategy name
+ *   pattern        string   a registered strategy name, or "random"
  *   verbose        boolean
  *   loop           boolean
  *
+ * There is no `random` boolean key: the CLI's `-r` is defined as sugar for
+ * `--pattern random`, so the file expresses the same request as
+ * `"pattern": "random"` rather than as a second, redundant switch.
+ *
  * Unknown keys, wrong types, and non-positive numerics are rejected with a
  * `CliError` so the entry point can exit 2 (user error) with a clear
  * message pointing at the offending file. The removed `stepCount` /
@@ -32,7 +36,7 @@ import { existsSync, readFileSync, statSync } from "node:fs";
 
 import { defaultConfigPath, type ConfigOverrides } from "./config.ts";
 import { CliError } from "./errors.ts";
-import { PATTERN_NAMES, resolvePatternName } from "./strategies.ts";
+import { SELECTABLE_PATTERN_NAMES, resolvePatternName } from "./strategies.ts";
 
 const ALLOWED_KEYS: ReadonlySet<string> = new Set<string>([
     "moveInterval",
@@ -82,7 +86,7 @@ function requirePatternName(name: string, raw: unknown, path: string): string {
     const canonical: string | null = typeof raw === "string" ? resolvePatternName(raw) : null;
     if (canonical === null) {
         throw new CliError(
-            `invalid value for '${name}' in ${path}: ${JSON.stringify(raw)} (valid: ${PATTERN_NAMES.join(", ")})`,
+            `invalid value for '${name}' in ${path}: ${JSON.stringify(raw)} (valid: ${SELECTABLE_PATTERN_NAMES.join(", ")})`,
         );
     }
     return canonical;

src/keeper.ts

@@ -25,7 +25,14 @@
 
 import { createNutDevice, type Device, type Point } from "./device.ts";
 import { executePath, type Logger, type SweepOutcome } from "./executor.ts";
-import { DEFAULT_PATTERN, STRATEGIES, type MoveContext } from "./strategies.ts";
+import {
+    createRandomPicker,
+    DEFAULT_PATTERN,
+    RANDOM_PATTERN,
+    STRATEGIES,
+    type MoveContext,
+    type MovementStrategy,
+} from "./strategies.ts";
 
 import type { Config } from "./config.ts";
 
@@ -54,6 +61,14 @@ function makeLogger(verbose: boolean): Logger {
  * `config.pattern` falls back to the default strategy defensively; validation
  * at the CLI / config-file boundary should prevent that from ever happening.
  *
+ * `pattern: "random"` isn't a registry key — it asks for a fresh pattern per
+ * sweep, so `pickRandom` supplies one here. The pick happens once, before the
+ * loop-mode branch below, which is what makes a random selection hold for an
+ * entire loop run rather than changing under the user mid-run; the picker's
+ * own no-repeat memory then spans sweeps, since the keeper holds one picker
+ * for the life of the process. Because the pick is a real strategy, the log
+ * lines below and in `executePath` name the concrete pattern, not "random".
+ *
  * Single-sweep mode (`config.loop === false`) runs exactly one sweep via
  * `executePath`, which owns on-screen reflection, pacing, interrupt
  * detection, and restore-on-clean — unchanged from before loop mode existed.
@@ -66,10 +81,18 @@ function makeLogger(verbose: boolean): Logger {
  * position each cycle. Per-cycle event logs are suppressed to avoid unbounded
  * output — one line brackets the run at each end.
  */
-async function simulateActivity(config: Config, log: Logger, device: Device): Promise<void> {
+async function simulateActivity(
+    config: Config,
+    log: Logger,
+    device: Device,
+    pickRandom: () => MovementStrategy,
+): Promise<void> {
     const width: number = await device.width();
     const height: number = await device.height();
-    const strategy = STRATEGIES[config.pattern] ?? STRATEGIES[DEFAULT_PATTERN]!;
+    const strategy: MovementStrategy =
+        config.pattern === RANDOM_PATTERN
+            ? pickRandom()
+            : (STRATEGIES[config.pattern] ?? STRATEGIES[DEFAULT_PATTERN]!);
 
     if (!config.loop) {
         const start: Point = await device.getPosition();
@@ -121,8 +144,16 @@ async function simulateActivity(config: Config, log: Logger, device: Device): Pr
  *
  * @param config     - Resolved runtime config.
  * @param device     - I/O device; defaults to the production nut.js device.
+ * @param pickRandom - Supplies a strategy when `config.pattern` is `random`.
+ *                     Created once here (not per sweep) so its no-repeat
+ *                     memory spans the whole run; injectable so tests can
+ *                     drive a deterministic sequence.
  */
-export async function runKeeper(config: Config, device?: Device): Promise<void> {
+export async function runKeeper(
+    config: Config,
+    device?: Device,
+    pickRandom: () => MovementStrategy = createRandomPicker(),
+): Promise<void> {
     const dev: Device = device ?? (await createNutDevice());
 
     const log = makeLogger(config.verbose);
@@ -144,7 +175,7 @@ export async function runKeeper(config: Config, device?: Device): Promise<void>
         }
 
         if (now - lastActivity >= config.moveInterval) {
-            await simulateActivity(config, log, dev);
+            await simulateActivity(config, log, dev, pickRandom);
             // The sweep either restored the cursor to its start (clean) or
             // left it where the user moved it (interrupt). Either way, reset
             // the clock and require another full moveInterval of inactivity

src/strategies.ts

@@ -281,9 +281,28 @@ export const STRATEGIES: Readonly<Record<string, MovementStrategy>> = {
 /** Pattern used when neither the CLI nor the config file selects one. */
 export const DEFAULT_PATTERN = "line";
 
-/** All valid pattern names, for validation messages and help text. */
+/** All registered strategy names. Real generators only — see `RANDOM_PATTERN`. */
 export const PATTERN_NAMES: readonly string[] = Object.keys(STRATEGIES);
 
+/**
+ * The reserved name for "pick a different pattern each sweep".
+ *
+ * Deliberately NOT a registry entry: it has no path of its own, so there is
+ * nothing for `STRATEGIES` to hold and nothing for the executor to drive. It
+ * is a *selection* the user makes, resolved to a real strategy once per sweep
+ * by the keeper (see `createRandomPicker`). Keeping it out of the registry is
+ * what lets `STRATEGIES[name]` stay a total lookup for every key it contains.
+ */
+export const RANDOM_PATTERN = "random";
+
+/**
+ * Everything the user may pass to `--pattern` / the `pattern` config key:
+ * the registry names plus the `random` sentinel. This is the list to quote in
+ * help text and validation errors; `PATTERN_NAMES` is the narrower "real
+ * generators" list that the keeper and the strategy tests care about.
+ */
+export const SELECTABLE_PATTERN_NAMES: readonly string[] = [...PATTERN_NAMES, RANDOM_PATTERN];
+
 /**
  * The set of valid `--pattern` / `pattern` values as a string-literal-ish
  * type. Kept as `string` at the type level (the registry is the runtime
@@ -296,6 +315,16 @@ export function isPatternName(name: string): boolean {
     return Object.prototype.hasOwnProperty.call(STRATEGIES, name);
 }
 
+/**
+ * True when `name` is something the user may legitimately select: a registered
+ * strategy, or the `random` sentinel. This is the check for validating user
+ * input; `isPatternName` remains the narrower "is this a real generator the
+ * registry can hand back" question.
+ */
+export function isSelectablePattern(name: string): boolean {
+    return isPatternName(name) || name === RANDOM_PATTERN;
+}
+
 /**
  * Normalize a pattern name for lenient user-facing matching: lowercase and
  * strip separators (`-`, `_`, whitespace) so `figure-eight`, `figure_eight`,
@@ -304,16 +333,19 @@ export function isPatternName(name: string): boolean {
 const normalizePattern = (s: string): string => s.toLowerCase().replace(/[-_\s]/g, "");
 
 /**
- * Map of normalized name -> canonical registry key. Built once at module
+ * Map of normalized name -> canonical selectable name. Built once at module
- * load. The assertion below guards against two registered names collapsing
+ * load over `SELECTABLE_PATTERN_NAMES`, so the `random` sentinel normalizes
- * to the same normalized form (e.g. a future `"figure_eight"` alongside
+ * like any other name and both validation boundaries accept it without
- * `"figureEight"`), which would otherwise let one silently shadow the other.
+ * special-casing. The assertion below guards against two selectable names
+ * collapsing to the same normalized form (e.g. a future `"figure_eight"`
+ * alongside `"figureEight"`, or a strategy named `"Random"`), which would
+ * otherwise let one silently shadow the other.
  */
 const CANONICAL_PATTERNS: ReadonlyMap<string, string> = new Map(
-    PATTERN_NAMES.map((n) => [normalizePattern(n), n]),
+    SELECTABLE_PATTERN_NAMES.map((n) => [normalizePattern(n), n]),
 );
 
-if (CANONICAL_PATTERNS.size !== PATTERN_NAMES.length) {
+if (CANONICAL_PATTERNS.size !== SELECTABLE_PATTERN_NAMES.length) {
     throw new Error(
         "strategies.ts: two pattern names collide after normalization; rename one so they differ by more than case/separators",
     );
@@ -328,3 +360,33 @@ if (CANONICAL_PATTERNS.size !== PATTERN_NAMES.length) {
 export function resolvePatternName(name: string): string | null {
     return CANONICAL_PATTERNS.get(normalizePattern(name)) ?? null;
 }
+
+/**
+ * Build the picker that backs `--pattern random` / `-r`: a uniform draw over
+ * the registry that never returns the same pattern twice in a row.
+ *
+ * The `last` memory lives in the closure rather than in module scope so the
+ * lifetime is the caller's to choose — the keeper creates exactly one picker
+ * per process, which is what makes "never twice in a row" hold across sweeps
+ * that are minutes apart. `rng` is injected for the same reason it is on
+ * `MoveContext`: so tests can assert an exact sequence.
+ *
+ * Returns a `MovementStrategy`, not a name, because that's what the caller
+ * needs; the pick is a real registry entry, so it carries its own `loopPath`
+ * and drives through `executePath` exactly like an explicitly-chosen pattern.
+ */
+export function createRandomPicker(rng: () => number = Math.random): () => MovementStrategy {
+    let last: string | null = null;
+    return (): MovementStrategy => {
+        const pool: readonly string[] = PATTERN_NAMES.filter((n) => n !== last);
+        // A single-strategy registry leaves the filtered pool empty; fall back
+        // to the full list so the no-repeat rule degrades to "always repeat"
+        // instead of indexing off the end.
+        const names: readonly string[] = pool.length > 0 ? pool : PATTERN_NAMES;
+        // Math.min pins the index in range for an `rng` that returns exactly 1
+        // (outside the documented [0, 1) contract, but cheap to survive).
+        const name: string = names[Math.min(names.length - 1, Math.floor(rng() * names.length))]!;
+        last = name;
+        return STRATEGIES[name]!;
+    };
+}

tests/cli.test.ts

@@ -0,0 +1,131 @@
+/**
+ * cli.test.ts
+ * -----------
+ * Unit tests for CLI argument parsing. `parseCliArgs` takes its argv as a
+ * parameter (defaulting to the real command line), so the whole flag surface
+ * is exercised here without touching `process.argv`.
+ *
+ * The focus is the parts that make a decision: numeric validation, pattern
+ * validation/normalization, and the `-r`/`--pattern` conflict rule.
+ */
+
+import { describe, expect, test } from "bun:test";
+
+import { parseCliArgs, selectPattern } from "../src/cli.ts";
+import { CliError } from "../src/errors.ts";
+
+describe("parseCliArgs — general flags", () => {
+    test("returns all-undefined overrides for an empty argv", () => {
+        const args = parseCliArgs([]);
+        expect(args.moveInterval).toBeUndefined();
+        expect(args.checkInterval).toBeUndefined();
+        expect(args.stepDelay).toBeUndefined();
+        expect(args.pattern).toBeUndefined();
+        expect(args.verbose).toBeUndefined();
+        expect(args.loop).toBeUndefined();
+        expect(args.help).toBe(false);
+    });
+
+    test("parses numeric flags in both long and short form", () => {
+        const args = parseCliArgs(["-m", "300", "--check-interval", "5", "-d", "20"]);
+        expect(args.moveInterval).toBe(300);
+        expect(args.checkInterval).toBe(5);
+        expect(args.stepDelay).toBe(20);
+    });
+
+    test("boolean flags are true when present, undefined when absent", () => {
+        const args = parseCliArgs(["-V", "--loop"]);
+        expect(args.verbose).toBe(true);
+        expect(args.loop).toBe(true);
+        // `undefined` rather than `false` is what lets the resolver tell
+        // "not specified" from an explicit off-switch.
+        expect(parseCliArgs([]).verbose).toBeUndefined();
+    });
+
+    test("rejects non-positive and non-numeric values", () => {
+        expect(() => parseCliArgs(["-m", "0"])).toThrow(CliError);
+        // A bare `-m -5` is rejected earlier, by node:util, as an ambiguous
+        // dash argument; `=` is the form that actually reaches our validator.
+        expect(() => parseCliArgs(["--move-interval=-5"])).toThrow(/positive number/);
+        expect(() => parseCliArgs(["-c", "abc"])).toThrow(/positive number/);
+    });
+
+    test("surfaces node:util's own parse errors as CliError", () => {
+        // e.g. an ambiguous dash argument — the entry point turns any CliError
+        // into exit 2, so the message just needs to reach the user intact.
+        expect(() => parseCliArgs(["-m", "-5"])).toThrow(CliError);
+    });
+
+    test("rejects unknown flags", () => {
+        expect(() => parseCliArgs(["--nope"])).toThrow(CliError);
+    });
+});
+
+describe("parseCliArgs — pattern selection", () => {
+    test("accepts a registered pattern and normalizes loose spellings", () => {
+        expect(parseCliArgs(["-p", "arc"]).pattern).toBe("arc");
+        expect(parseCliArgs(["--pattern", "figure-eight"]).pattern).toBe("figureEight");
+        expect(parseCliArgs(["-p", "LINE"]).pattern).toBe("line");
+    });
+
+    test("rejects an unknown pattern, listing random among the valid names", () => {
+        expect(() => parseCliArgs(["-p", "zigzag"])).toThrow(CliError);
+        expect(() => parseCliArgs(["-p", "zigzag"])).toThrow(/valid:.*random/);
+    });
+
+    test("--pattern random is accepted like any other selection", () => {
+        expect(parseCliArgs(["--pattern", "random"]).pattern).toBe("random");
+        expect(parseCliArgs(["-p", "RANDOM"]).pattern).toBe("random");
+    });
+
+    test("-r/--random folds into pattern", () => {
+        // The flag has no field of its own: its entire effect is the pattern,
+        // so nothing downstream needs to know it exists.
+        expect(parseCliArgs(["-r"]).pattern).toBe("random");
+        expect(parseCliArgs(["--random"]).pattern).toBe("random");
+    });
+
+    test("-r combined with an explicit --pattern is rejected", () => {
+        expect(() => parseCliArgs(["-r", "-p", "arc"])).toThrow(CliError);
+        expect(() => parseCliArgs(["-r", "-p", "arc"])).toThrow(/conflicts with --pattern 'arc'/);
+        // Order on the command line doesn't change the verdict.
+        expect(() => parseCliArgs(["--pattern", "walk", "--random"])).toThrow(/conflicts/);
+    });
+
+    test("-r alongside --pattern random is a harmless no-op", () => {
+        // Both spellings request the same thing, so there's nothing to object to.
+        expect(parseCliArgs(["-r", "-p", "random"]).pattern).toBe("random");
+        expect(parseCliArgs(["-r", "-p", "Random"]).pattern).toBe("random");
+    });
+
+    test("-r still validates the pattern it is paired with", () => {
+        // An invalid --pattern is an error in its own right, reported as such
+        // rather than being masked by the conflict rule.
+        expect(() => parseCliArgs(["-r", "-p", "zigzag"])).toThrow(/invalid value for --pattern/);
+    });
+
+    test("-r composes with the other flags", () => {
+        const args = parseCliArgs(["-r", "--loop", "-m", "120", "-V"]);
+        expect(args.pattern).toBe("random");
+        expect(args.loop).toBe(true);
+        expect(args.moveInterval).toBe(120);
+        expect(args.verbose).toBe(true);
+    });
+});
+
+describe("selectPattern", () => {
+    test("passes the pattern through untouched when --random is absent", () => {
+        expect(selectPattern("arc", false)).toBe("arc");
+        expect(selectPattern(undefined, false)).toBeUndefined();
+    });
+
+    test("yields random when --random is present and no pattern was given", () => {
+        expect(selectPattern(undefined, true)).toBe("random");
+    });
+
+    test("quotes the user's own spelling in the conflict message", () => {
+        // Not the canonical name: the user needs to find the offending text on
+        // their command line.
+        expect(() => selectPattern("figure-eight", true)).toThrow(/--pattern 'figure-eight'/);
+    });
+});

tests/configFile.test.ts

@@ -125,6 +125,23 @@ describe("loadConfigFile (explicit path)", () => {
         const path = writeFixture("badpattern.json", JSON.stringify({ pattern: "zigzag" }));
         expect(() => loadConfigFile(path)).toThrow(/'pattern'.*valid:/);
         expect(() => loadConfigFile(path)).toThrow(/line/);
+        expect(() => loadConfigFile(path)).toThrow(/random/);
+    });
+
+    test("accepts the random sentinel as a pattern", () => {
+        // `-r` is only CLI sugar for this, so the file has to express it too.
+        const path = writeFixture("randompattern.json", JSON.stringify({ pattern: "random" }));
+        expect(loadConfigFile(path)!.pattern).toBe("random");
+    });
+
+    test("normalizes a loosely-spelled random", () => {
+        const path = writeFixture("looserandom.json", JSON.stringify({ pattern: "RANDOM" }));
+        expect(loadConfigFile(path)!.pattern).toBe("random");
+    });
+
+    test("rejects a 'random' boolean key — the file spells it as a pattern", () => {
+        const path = writeFixture("randomkey.json", JSON.stringify({ random: true }));
+        expect(() => loadConfigFile(path)).toThrow(/unknown key 'random'/);
     });
 
     test("tolerates obsolete stepCount/stepSize keys, ignoring their values", () => {

tests/keeper.test.ts

@@ -16,6 +16,7 @@ import { DEFAULT_CONFIG } from "../src/config.ts";
 import type { Config } from "../src/config.ts";
 import type { Device, Point } from "../src/device.ts";
 import { runKeeper } from "../src/keeper.ts";
+import { diagonal, figureEight, type MovementStrategy } from "../src/strategies.ts";
 
 class StopError extends Error {}
 
@@ -60,9 +61,13 @@ const quietConfig = (overrides: Partial<Config>): Config => ({
     ...overrides,
 });
 
-async function runUntilStop(config: Config, device: Device): Promise<void> {
+async function runUntilStop(
+    config: Config,
+    device: Device,
+    pickRandom?: () => MovementStrategy,
+): Promise<void> {
     try {
-        await runKeeper(config, device);
+        await runKeeper(config, device, pickRandom);
     } catch (err) {
         if (!(err instanceof StopError)) throw err;
     }
@@ -90,9 +95,10 @@ describe("runKeeper", () => {
     });
 });
 
-describe("runKeeper — loop mode", () => {
+/** Furthest x any commanded point reached — the signal that a path ramped. */
-    const maxX = (pts: Point[]): number => pts.reduce((m, p) => Math.max(m, p.x), -Infinity);
+const maxX = (pts: Point[]): number => pts.reduce((m, p) => Math.max(m, p.x), -Infinity);
 
+describe("runKeeper — loop mode", () => {
     test("loop mode ramps far from the start via the infinite loopPath", async () => {
         // `line`'s loopPath ramps x by 4px/step from the start and never
         // restores, reflecting off the screen edge. From x=100 it climbs well
@@ -123,3 +129,81 @@ describe("runKeeper — loop mode", () => {
         expect(dev.commanded.length).toBeGreaterThan(180);
     });
 });
+
+describe("runKeeper — random pattern", () => {
+    /**
+     * A picker that always hands back `strategy` and counts how many times the
+     * keeper asked. The count is the observable that pins down *when* the pick
+     * happens, which is the whole contract for `random`.
+     */
+    function recordingPicker(strategy: MovementStrategy): {
+        pick: () => MovementStrategy;
+        calls: () => number;
+    } {
+        let calls = 0;
+        return {
+            pick: (): MovementStrategy => {
+                calls++;
+                return strategy;
+            },
+            calls: (): number => calls,
+        };
+    }
+
+    test("asks the picker again on every trigger", async () => {
+        // moveInterval 0 means each pass of the watch loop fires a sweep, so
+        // the budget covers several triggers. A pattern chosen once for the
+        // whole process would show exactly one call.
+        const picker = recordingPicker(figureEight);
+        const dev = new LoopDevice(400, { x: 800, y: 500 });
+        await runUntilStop(
+            quietConfig({ moveInterval: 0, pattern: "random", loop: false }),
+            dev,
+            picker.pick,
+        );
+        expect(picker.calls()).toBeGreaterThanOrEqual(2);
+    });
+
+    test("never consults the picker for a concrete pattern", async () => {
+        const picker = recordingPicker(figureEight);
+        const dev = new LoopDevice(400, { x: 800, y: 500 });
+        await runUntilStop(
+            quietConfig({ moveInterval: 0, pattern: "line", loop: false }),
+            dev,
+            picker.pick,
+        );
+        expect(picker.calls()).toBe(0);
+        expect(dev.commanded.length).toBeGreaterThan(0);
+    });
+
+    test("loop mode holds a single pick for the whole loop run", async () => {
+        // One trigger, many chained cycles: the pattern must not change under
+        // the user mid-run, so the picker is asked exactly once.
+        const picker = recordingPicker(figureEight);
+        const dev = new LoopDevice(400, { x: 800, y: 500 });
+        await runUntilStop(
+            quietConfig({ moveInterval: 0, pattern: "random", loop: true }),
+            dev,
+            picker.pick,
+        );
+        expect(picker.calls()).toBe(1);
+        // ...and those cycles really did run, so the single call isn't just
+        // the loop never getting started.
+        expect(dev.commanded.length).toBeGreaterThan(180);
+    });
+
+    test("a picked strategy keeps its own loopPath behavior", async () => {
+        // The picker returns real registry entries, so a pick with an infinite
+        // loopPath (`diagonal`) drives that path rather than a chained finite
+        // one — the same as selecting it explicitly. Mirrors the `line` loop
+        // test above: x ramps far past a single finite sweep's 250px reach.
+        const picker = recordingPicker(diagonal);
+        const dev = new LoopDevice(400, { x: 100, y: 100 });
+        await runUntilStop(
+            quietConfig({ moveInterval: 0, pattern: "random", loop: true }),
+            dev,
+            picker.pick,
+        );
+        expect(maxX(dev.commanded)).toBeGreaterThan(1000);
+    });
+});

tests/strategies.test.ts

@@ -12,13 +12,17 @@ import { describe, expect, test } from "bun:test";
 import type { Point } from "../src/device.ts";
 import {
     arc,
+    createRandomPicker,
     diagonal,
     figureEight,
     isPatternName,
+    isSelectablePattern,
     jitter,
     line,
     PATTERN_NAMES,
+    RANDOM_PATTERN,
     resolvePatternName,
+    SELECTABLE_PATTERN_NAMES,
     STRATEGIES,
     walk,
     type MoveContext,
@@ -187,3 +191,102 @@ describe("registry", () => {
         expect(resolvePatternName("toString")).toBeNull();
     });
 });
+
+describe("random (the sentinel)", () => {
+    test("is selectable but is not a registry entry", () => {
+        // The whole design rests on this: `random` is a user-facing choice
+        // with no path of its own, so the registry must not contain it and
+        // `STRATEGIES[RANDOM_PATTERN]` must not resolve.
+        expect(PATTERN_NAMES).not.toContain(RANDOM_PATTERN);
+        expect(STRATEGIES[RANDOM_PATTERN]).toBeUndefined();
+        expect(isPatternName(RANDOM_PATTERN)).toBe(false);
+        expect(isSelectablePattern(RANDOM_PATTERN)).toBe(true);
+    });
+
+    test("SELECTABLE_PATTERN_NAMES is the registry plus the sentinel", () => {
+        expect(new Set(SELECTABLE_PATTERN_NAMES)).toEqual(
+            new Set([...PATTERN_NAMES, RANDOM_PATTERN]),
+        );
+        expect(SELECTABLE_PATTERN_NAMES.length).toBe(PATTERN_NAMES.length + 1);
+    });
+
+    test("isSelectablePattern still accepts every real strategy and rejects junk", () => {
+        for (const name of PATTERN_NAMES) expect(isSelectablePattern(name)).toBe(true);
+        expect(isSelectablePattern("zigzag")).toBe(false);
+        expect(isSelectablePattern("toString")).toBe(false);
+    });
+
+    test("resolvePatternName normalizes the sentinel like any other name", () => {
+        expect(resolvePatternName("random")).toBe(RANDOM_PATTERN);
+        expect(resolvePatternName("RANDOM")).toBe(RANDOM_PATTERN);
+        expect(resolvePatternName("  Random  ")).toBe(RANDOM_PATTERN);
+    });
+});
+
+describe("createRandomPicker", () => {
+    test("only ever returns registered strategies", () => {
+        const pick = createRandomPicker(mulberry32(7));
+        for (let i = 0; i < 100; i++) {
+            const s = pick();
+            expect(PATTERN_NAMES).toContain(s.name);
+            expect(STRATEGIES[s.name]).toBe(s);
+        }
+    });
+
+    test("never returns the same pattern twice in a row", () => {
+        const pick = createRandomPicker(mulberry32(1234));
+        let prev: string = pick().name;
+        for (let i = 0; i < 500; i++) {
+            const name: string = pick().name;
+            expect(name).not.toBe(prev);
+            prev = name;
+        }
+    });
+
+    test("alternates deterministically under a constant rng of 0", () => {
+        // rng()=0 always takes the first entry of the *remaining* pool, and
+        // the pool is the registry minus the previous pick — so this pins the
+        // exclusion logic exactly: first name, second name, first name, ...
+        const pick = createRandomPicker(() => 0);
+        const [first, second] = PATTERN_NAMES as [string, string];
+        expect(pick().name).toBe(first);
+        expect(pick().name).toBe(second);
+        expect(pick().name).toBe(first);
+        expect(pick().name).toBe(second);
+    });
+
+    test("stays in range for an rng that returns exactly 1", () => {
+        // Outside the documented [0, 1) contract; must clamp rather than
+        // index off the end and throw.
+        const pick = createRandomPicker(() => 1);
+        for (let i = 0; i < 10; i++) {
+            expect(PATTERN_NAMES).toContain(pick().name);
+        }
+    });
+
+    test("is reproducible for a given seed, and independent across pickers", () => {
+        const a = createRandomPicker(mulberry32(99));
+        const b = createRandomPicker(mulberry32(99));
+        const seqA = Array.from({ length: 20 }, () => a().name);
+        const seqB = Array.from({ length: 20 }, () => b().name);
+        expect(seqA).toEqual(seqB);
+    });
+
+    test("each picker carries its own no-repeat memory", () => {
+        // The memory is per-closure, not module state: a fresh picker has no
+        // notion of what a previous one returned, so it may open with the
+        // same pattern.
+        const a = createRandomPicker(() => 0);
+        const b = createRandomPicker(() => 0);
+        expect(a().name).toBe(b().name);
+    });
+
+    test("covers the whole registry over enough draws", () => {
+        // Guards against the exclusion logic accidentally pinning the pool to
+        // a subset (e.g. filtering by index rather than by name).
+        const pick = createRandomPicker(mulberry32(2024));
+        const seen = new Set<string>();
+        for (let i = 0; i < 400; i++) seen.add(pick().name);
+        expect(seen).toEqual(new Set(PATTERN_NAMES));
+    });
+});