feat(tool): concise error output for failed shell commands

packages/opencode/src/tool/shell.ts

@@ -254,6 +254,9 @@ function tail(text: string, maxLines: number, maxBytes: number) {
   }
 }
 
+const FAIL_TAIL_LINES = 50
+const FAIL_TAIL_BYTES = 8 * 1024
+
 const parse = Effect.fn("ShellTool.parse")(function* (command: string, ps: boolean) {
   const tree = yield* Effect.promise(() => parser().then((p) => (ps ? p.ps : p.bash).parse(command)))
   if (!tree) throw new Error("Failed to parse command")
@@ -566,7 +569,10 @@ export const ShellTool = Tool.define(
       }
       if (aborted) meta.push("User aborted the command")
       const raw = list.map((item) => item.text).join("")
-      const end = tail(raw, limits.maxLines, limits.maxBytes)
+      const failed = typeof code === "number" && code !== 0
+      const end = failed
+        ? tail(raw, FAIL_TAIL_LINES, FAIL_TAIL_BYTES)
+        : tail(raw, limits.maxLines, limits.maxBytes)
       if (end.cut) cut = true
       if (!file && end.cut) {
         file = yield* trunc.write(raw)
@@ -575,8 +581,12 @@ export const ShellTool = Tool.define(
       let output = end.text
       if (!output) output = "(no output)"
 
+      const status = failed ? `Command failed with exit code ${code}.\n\n` : ""
       if (cut && file) {
-        output = `...output truncated...\n\nFull output saved to: ${file}\n\n` + output
+        output =
+          `...output truncated...\n\n${status}Full output saved to: ${file}\n\n` + output
+      } else if (status) {
+        output = status + output
       }
 
       if (meta.length > 0) {

packages/opencode/test/tool/shell.test.ts

@@ -122,6 +122,10 @@ const fill = (mode: "lines" | "bytes", n: number) => {
   if (PS.has(sh())) return `& ${text}`
   return text
 }
+const failFill = (mode: "lines" | "bytes", n: number) => {
+  const text = fill(mode, n)
+  return sh() === "cmd" ? `${text} & exit 1` : `${text}; exit 1`
+}
 const glob = (p: string) =>
   process.platform === "win32" ? Filesystem.normalizePathPattern(p) : p.replaceAll("\\", "/")
 
@@ -1196,4 +1200,44 @@ describe("tool.shell truncation", () => {
       }),
     ),
   )
+  it.live("truncates failed command output to a short tail and saves full output to file", () =>
+    runIn(
+      projectRoot,
+      Effect.gen(function* () {
+        const lineCount = Truncate.MAX_LINES + 500
+        const result = yield* run({
+          command: failFill("lines", lineCount),
+        })
+        expect(result.metadata.exit).not.toBe(0)
+        expect(result.metadata.truncated).toBe(true)
+        expect(result.output).toMatch(/\.\.\.output truncated\.\.\./)
+        expect(result.output).toMatch(/Command failed with exit code 1/)
+        expect(result.output).toMatch(/Full output saved to:\s+\S+/)
+        expect(result.output.split("\n").length).toBeLessThan(Truncate.MAX_LINES)
+
+        const filepath = (result.metadata as { outputPath?: string }).outputPath
+        expect(filepath).toBeTruthy()
+        const saved = yield* (yield* FSUtil.Service).readFileString(filepath!)
+        const lines = saved.trim().split(/\r?\n/)
+        expect(lines.length).toBe(lineCount)
+      }),
+    ),
+    30_000,
+  )
+
+  it.live("does not truncate failed command output when it is small", () =>
+    runIn(
+      projectRoot,
+      Effect.gen(function* () {
+        const result = yield* run({
+          command: `exit 3`,
+        })
+        expect(result.metadata.exit).toBe(3)
+        expect(result.metadata.truncated).toBe(false)
+        expect(result.output).toContain("Command failed with exit code 3")
+        expect(result.output).toContain("(no output)")
+      }),
+    ),
+    30_000,
+  )
 })