feat(opencode): add automatic heap snapshots for high-memory cli processes (anomalyco#20788)

Cherry-picked from upstream sst/opencode aa2239d (Dax). Drops the
TUI worker.ts hunk (file structure differs in this fork); keeps the
self-contained Heap module + flag + bootstrap call.

When OPENCODE_AUTO_HEAP_SNAPSHOT=1 is set, every minute the bootstrap
samples process.memoryUsage().rss; once it exceeds 2GB the module
writes a single heap snapshot into Global.Path.log and re-arms only
after RSS drops below the limit. unref() ensures it never holds the
event loop open.

Useful for diagnosing sidecar memory regressions in the wild without
requiring a running TUI debug session.

Author: panyw5

packages/opencode/src/cli/heap.ts

@@ -0,0 +1,59 @@
+import path from "path"
+import { writeHeapSnapshot } from "node:v8"
+import { Flag } from "@/flag/flag"
+import { Global } from "@/global"
+import { Log } from "@/util/log"
+
+const log = Log.create({ service: "heap" })
+const MINUTE = 60_000
+const LIMIT = 2 * 1024 * 1024 * 1024
+
+export namespace Heap {
+  let timer: Timer | undefined
+  let lock = false
+  let armed = true
+
+  export function start() {
+    if (!Flag.OPENCODE_AUTO_HEAP_SNAPSHOT) return
+    if (timer) return
+
+    const run = async () => {
+      if (lock) return
+
+      const stat = process.memoryUsage()
+      if (stat.rss <= LIMIT) {
+        armed = true
+        return
+      }
+      if (!armed) return
+
+      lock = true
+      armed = false
+      const file = path.join(
+        Global.Path.log,
+        `heap-${process.pid}-${new Date().toISOString().replace(/[:.]/g, "")}.heapsnapshot`,
+      )
+      log.warn("heap usage exceeded limit", {
+        rss: stat.rss,
+        heap: stat.heapUsed,
+        file,
+      })
+
+      await Promise.resolve()
+        .then(() => writeHeapSnapshot(file))
+        .catch((err) => {
+          log.error("failed to write heap snapshot", {
+            error: err instanceof Error ? err.message : String(err),
+            file,
+          })
+        })
+
+      lock = false
+    }
+
+    timer = setInterval(() => {
+      void run()
+    }, MINUTE)
+    timer.unref?.()
+  }
+}

packages/opencode/src/flag/flag.ts

@@ -12,6 +12,7 @@ function falsy(key: string) {
 
 export namespace Flag {
   export const OPENCODE_AUTO_SHARE = truthy("OPENCODE_AUTO_SHARE")
+  export const OPENCODE_AUTO_HEAP_SNAPSHOT = truthy("OPENCODE_AUTO_HEAP_SNAPSHOT")
   export const OPENCODE_GIT_BASH_PATH = process.env["OPENCODE_GIT_BASH_PATH"]
   export const OPENCODE_CONFIG = process.env["OPENCODE_CONFIG"]
   export declare const OPENCODE_TUI_CONFIG: string | undefined

packages/opencode/src/index.ts

@@ -37,6 +37,7 @@ import path from "path"
 import { Global } from "./global"
 import { JsonMigration } from "./storage/json-migration"
 import { Database } from "./storage/db"
+import { Heap } from "./cli/heap"
 
 process.on("unhandledRejection", (e) => {
   Log.Default.error("rejection", {
@@ -83,6 +84,8 @@ let cli = yargs(hideBin(process.argv))
     process.env.OPENCODE = "1"
     process.env.OPENCODE_PID = String(process.pid)
 
+    Heap.start()
+
     Log.create({ service: "startup" }).info("cli.bootstrap", {
       duration: Date.now() - start,
       print_logs: process.argv.includes("--print-logs"),