feat: write truncated tool outputs to files (#7239)

packages/opencode/src/tool/truncation.ts

@@ -0,0 +1,98 @@
+import fs from "fs/promises"
+import path from "path"
+import { Global } from "../global"
+import { Identifier } from "../id/id"
+import { lazy } from "../util/lazy"
+import { PermissionNext } from "../permission/next"
+import type { Agent } from "../agent/agent"
+
+export namespace Truncate {
+  export const MAX_LINES = 2000
+  export const MAX_BYTES = 50 * 1024
+  export const DIR = path.join(Global.Path.data, "tool-output")
+  const RETENTION_MS = 7 * 24 * 60 * 60 * 1000 // 7 days
+
+  export type Result = { content: string; truncated: false } | { content: string; truncated: true; outputPath: string }
+
+  export interface Options {
+    maxLines?: number
+    maxBytes?: number
+    direction?: "head" | "tail"
+  }
+
+  export async function cleanup() {
+    const cutoff = Identifier.timestamp(Identifier.create("tool", false, Date.now() - RETENTION_MS))
+    const glob = new Bun.Glob("tool_*")
+    const entries = await Array.fromAsync(glob.scan({ cwd: DIR, onlyFiles: true })).catch(() => [] as string[])
+    for (const entry of entries) {
+      if (Identifier.timestamp(entry) >= cutoff) continue
+      await fs.unlink(path.join(DIR, entry)).catch(() => {})
+    }
+  }
+
+  const init = lazy(cleanup)
+
+  function hasTaskTool(agent?: Agent.Info): boolean {
+    if (!agent?.permission) return false
+    const rule = PermissionNext.evaluate("task", "*", agent.permission)
+    return rule.action !== "deny"
+  }
+
+  export async function output(text: string, options: Options = {}, agent?: Agent.Info): Promise<Result> {
+    const maxLines = options.maxLines ?? MAX_LINES
+    const maxBytes = options.maxBytes ?? MAX_BYTES
+    const direction = options.direction ?? "head"
+    const lines = text.split("\n")
+    const totalBytes = Buffer.byteLength(text, "utf-8")
+
+    if (lines.length <= maxLines && totalBytes <= maxBytes) {
+      return { content: text, truncated: false }
+    }
+
+    const out: string[] = []
+    let i = 0
+    let bytes = 0
+    let hitBytes = false
+
+    if (direction === "head") {
+      for (i = 0; i < lines.length && i < maxLines; i++) {
+        const size = Buffer.byteLength(lines[i], "utf-8") + (i > 0 ? 1 : 0)
+        if (bytes + size > maxBytes) {
+          hitBytes = true
+          break
+        }
+        out.push(lines[i])
+        bytes += size
+      }
+    } else {
+      for (i = lines.length - 1; i >= 0 && out.length < maxLines; i--) {
+        const size = Buffer.byteLength(lines[i], "utf-8") + (out.length > 0 ? 1 : 0)
+        if (bytes + size > maxBytes) {
+          hitBytes = true
+          break
+        }
+        out.unshift(lines[i])
+        bytes += size
+      }
+    }
+
+    const removed = hitBytes ? totalBytes - bytes : lines.length - out.length
+    const unit = hitBytes ? "bytes" : "lines"
+    const preview = out.join("\n")
+
+    await init()
+    const id = Identifier.ascending("tool")
+    const filepath = path.join(DIR, id)
+    await Bun.write(Bun.file(filepath), text)
+
+    const hint = hasTaskTool(agent)
+      ? `The tool call succeeded but the output was truncated. Full output saved to: ${filepath}\nUse the Task tool to have a subagent process this file with Grep and Read (with offset/limit). Do NOT read the full file yourself - delegate to save context.`
+      : `The tool call succeeded but the output was truncated. Full output saved to: ${filepath}\nUse Grep to search the full content or Read with offset/limit to view specific sections.`
+    const message =
+      direction === "head"
+        ? `${preview}\n\n...${removed} ${unit} truncated...\n\n${hint}`
+        : `...${removed} ${unit} truncated...\n\n${hint}\n\n${preview}`
+
+    return { content: message, truncated: true, outputPath: filepath }
+  }
+}