fix(flow): free only the exact port on Windows, not every port it prefixes

openflow.ts

@@ -18,7 +18,7 @@
  * `packages/flow/lib/launch.ts` (unit-tested); this file only spawns, streams,
  * waits, and tears down.
  */
-import { launchPlan } from "./packages/flow/lib/launch"
+import { launchPlan, listeningPids } from "./packages/flow/lib/launch"
 import { healthy } from "./packages/flow/lib/opencode-process"
 
 const repo = import.meta.dir
@@ -56,15 +56,7 @@ async function pipe(stream: ReadableStream<Uint8Array> | number | undefined, pre
 function freePort(port: string) {
   if (process.platform === "win32") {
     const { stdout } = Bun.spawnSync(["netstat", "-ano"], { stdout: "pipe" })
-    const pids = new Set(
-      stdout
-        .toString()
-        .split(/\r?\n/)
-        .filter((line) => line.includes(`:${port}`) && line.includes("LISTENING"))
-        .map((line) => line.trim().split(/\s+/).pop())
-        .filter((pid): pid is string => !!pid && pid !== "0"),
-    )
-    for (const pid of pids) Bun.spawnSync(["taskkill", "/pid", pid, "/T", "/F"], { stdout: "ignore", stderr: "ignore" })
+    for (const pid of listeningPids(stdout.toString(), port)) Bun.spawnSync(["taskkill", "/pid", pid, "/T", "/F"], { stdout: "ignore", stderr: "ignore" })
     return
   }
   const { stdout } = Bun.spawnSync(["lsof", "-ti", `tcp:${port}`], { stdout: "pipe" })

packages/flow/lib/launch.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, test } from "bun:test"
-import { launchPlan } from "./launch"
+import { launchPlan, listeningPids } from "./launch"
 
 const repo = "/repo"
 
@@ -103,3 +103,30 @@ describe("launchPlan", () => {
     expect(plan.engine.skip).toBe(false)
   })
 })
+
+describe("listeningPids", () => {
+  const netstat = [
+    "Active Connections",
+    "",
+    "  Proto  Local Address          Foreign Address        State           PID",
+    "  TCP    0.0.0.0:4096           0.0.0.0:0              LISTENING       100",
+    "  TCP    [::]:4096              [::]:0                 LISTENING       100",
+    "  TCP    0.0.0.0:40961          0.0.0.0:0              LISTENING       200",
+    "  TCP    127.0.0.1:51234        127.0.0.1:4096         ESTABLISHED     300",
+    "  TCP    0.0.0.0:5174           0.0.0.0:0              ABHÖREN         400",
+    "  UDP    0.0.0.0:4096           *:*                                    500",
+  ].join("\r\n")
+
+  test("matches the port exactly, not as a prefix of a longer one", () => {
+    expect(listeningPids(netstat, "4096")).toEqual(["100"])
+    expect(listeningPids(netstat, "409")).toEqual([])
+  })
+
+  test("ignores a connection whose remote end is the port", () => {
+    expect(listeningPids(netstat, "51234")).toEqual([])
+  })
+
+  test("finds a listener whatever language the state column is in", () => {
+    expect(listeningPids(netstat, "5174")).toEqual(["400"])
+  })
+})

packages/flow/lib/launch.ts

@@ -92,3 +92,28 @@ export async function launchPlan(input: {
     built,
   }
 }
+
+/**
+ * PIDs listening on exactly `port`, read from Windows `netstat -ano` output.
+ *
+ * The port is compared against the local-address column rather than searched
+ * for in the line: `:4096` is a substring of `:40961`, so a substring test hands
+ * an unrelated process to `taskkill /T /F`. A listening socket is told by its
+ * foreign address (`0.0.0.0:0` or `[::]:0`), not by the state column, because
+ * that column is translated on non-English Windows.
+ */
+export function listeningPids(netstat: string, port: string) {
+  return [
+    ...new Set(
+      netstat
+        .split(/\r?\n/)
+        .map((line) => line.trim().split(/\s+/))
+        .filter(
+          ([proto, local, foreign]) =>
+            proto === "TCP" && local?.endsWith(`:${port}`) && (foreign === "0.0.0.0:0" || foreign === "[::]:0"),
+        )
+        .map((columns) => columns.at(-1))
+        .filter((pid): pid is string => !!pid && pid !== "0"),
+    ),
+  ]
+}