fix(browser-execute): resolve uv to absolute path before spawn

Windows users hit ENOENT when uv is installed but %USERPROFILE%\.local\bin
isn't on the bcode process PATH (User-PATH writes by the uv installer aren't
picked up until full re-login by GUI-launched processes).

Probe PATH then a per-platform allowlist; fall back to bare 'uv' so the
existing UV_MISSING_HINT path still fires when uv is genuinely absent.
Memoized via Effect.cached, bound once at make().

Author: Alezander9

packages/bcode-browser/src/browser-execute.ts

@@ -15,6 +15,7 @@ import { Effect, Stream } from "effect"
 import { ChildProcess, ChildProcessSpawner } from "effect/unstable/process"
 import z from "zod"
 import { resolveHarnessDir } from "./harness"
+import { uvLocate } from "./uv-locate"
 
 const DEFAULT_TIMEOUT_MS = 60 * 1000
 const MAX_TIMEOUT_MS = 10 * 60 * 1000
@@ -44,7 +45,9 @@ export interface ExecuteResult {
 }
 
 const UV_MISSING_HINT =
-  "uv is not installed or not on PATH. Install it once: curl -fsSL https://astral.sh/uv/install.sh | sh"
+  "uv is not installed or not on PATH. Install it once: curl -fsSL https://astral.sh/uv/install.sh | sh " +
+  "(Windows: irm https://astral.sh/uv/install.ps1 | iex). " +
+  "If you just installed uv, restart your terminal so PATH picks it up."
 
 // Spawn errors flow through effect's PlatformError; ENOENT lives on the wrapped
 // cause's `.code`. Walk the cause chain so we detect it regardless of nesting.
@@ -59,12 +62,14 @@ const isUvMissing = (err: unknown): boolean => {
 
 export const make = Effect.fn("BrowserExecute.make")(function* () {
   const spawner = yield* ChildProcessSpawner.ChildProcessSpawner
+  const locate = yield* uvLocate
 
   const execute = (args: Parameters, ctx: ExecuteContext) =>
     Effect.gen(function* () {
       const harnessDir = yield* Effect.promise(() => resolveHarnessDir())
+      const uv = yield* locate
       const proc = ChildProcess.make(
-        "uv",
+        uv,
         ["run", "--project", harnessDir, "python", "run.py", "-c", args.python],
         {
           cwd: harnessDir,

packages/bcode-browser/src/uv-locate.ts

@@ -0,0 +1,60 @@
+// Resolve the absolute path to the `uv` executable.
+//
+// Why: `ChildProcess.make("uv", ...)` resolves bare names against
+// `process.env.PATH` only. On Windows the official uv installer writes
+// `%USERPROFILE%\.local\bin` into the *User* PATH registry key, which
+// GUI-launched processes (Cursor / VSCode terminal, double-clicked bcode.exe)
+// don't pick up until a full re-login. Result: `uv --version` works in the
+// user's shell but the bcode child process gets ENOENT.
+//
+// Probe order:
+//   1. Walk `process.env.PATH` (with platform-correct extensions on Windows).
+//   2. Fall back to a per-platform allowlist of well-known install dirs.
+// On miss, return the bare name "uv" so the caller's existing ENOENT path
+// (UV_MISSING_HINT, exit 127) keeps working.
+//
+// Memoized per-process via `Effect.cached` — yield once at service
+// construction to bind the cached effect, then yield it on each call to get
+// the resolved path. First browser_execute call pays the fs probe; subsequent
+// calls are free.
+//
+// Pure addition. Level 1.
+import { Effect } from "effect"
+import fs from "fs/promises"
+import os from "os"
+import path from "path"
+
+const isWindows = process.platform === "win32"
+const EXTS = isWindows ? [".exe", ".cmd", ".bat", ""] : [""]
+
+const allowlist = (() => {
+  const home = os.homedir()
+  if (isWindows)
+    return [
+      path.join(home, ".local", "bin"),
+      path.join(process.env.LOCALAPPDATA ?? path.join(home, "AppData", "Local"), "uv", "bin"),
+      path.join(process.env.LOCALAPPDATA ?? path.join(home, "AppData", "Local"), "Programs", "uv"),
+    ]
+  return [path.join(home, ".local", "bin"), path.join(home, ".cargo", "bin"), "/opt/homebrew/bin", "/usr/local/bin"]
+})()
+
+const findIn = async (dir: string): Promise<string | null> => {
+  for (const ext of EXTS) {
+    const candidate = path.join(dir, `uv${ext}`)
+    if (await fs.access(candidate).then(() => true, () => false)) return candidate
+  }
+  return null
+}
+
+const probe = async (): Promise<string> => {
+  const pathDirs = (process.env.PATH ?? "").split(path.delimiter).filter(Boolean)
+  for (const dir of [...pathDirs, ...allowlist]) {
+    const hit = await findIn(dir)
+    if (hit) return hit
+  }
+  return "uv"
+}
+
+export const uvLocate = Effect.cached(Effect.promise(probe))
+
+export * as UvLocate from "./uv-locate"