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fix(agent): return collected output when exec auto-backgrounds

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Previously, when a command exceeded yieldMs (default 5s) and was
auto-backgrounded, exec returned an empty output string. This caused
agents to misinterpret slow commands (like curl) as failed, leading
to infinite retry loops.

Changes:
- Implement three-layer buffer system (pending 30KB + aggregated 200KB + tail 1KB)
- Return collected output snapshot when backgrounding instead of empty string
- Increase default yieldMs from 5s to 10s for better coverage
- Add auto sweeper for terminated process cleanup (30min TTL)
- Register process immediately on spawn to capture all output

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Jiayuan 2026-01-31 18:12:00 +08:00
parent a5f979fceb
commit cbb13b26d1
3 changed files with 172 additions and 56 deletions
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64
src/agent/tools/exec.ts
View file

@ -1,7 +1,12 @@
import { spawn } from "child_process";
import { Type } from "@sinclair/typebox";
import type { AgentTool } from "@mariozechner/pi-agent-core";
import { registerProcess } from "./process-registry.js";
import {
registerProcess,
getOutputSnapshot,
getFullOutput,
PROCESS_REGISTRY,
} from "./process-registry.js";
const ExecSchema = Type.Object({
command: Type.String({ description: "Shell command to execute." }),
@ -12,7 +17,7 @@ const ExecSchema = Type.Object({
yieldMs: Type.Optional(
Type.Number({
description:
"Auto-background threshold in milliseconds. If command doesn't complete within this time, it runs in background. Default 5000ms. Set to 0 to disable auto-backgrounding.",
"Auto-background threshold in milliseconds. If command doesn't complete within this time, it runs in background. Default 10000ms. Set to 0 to disable auto-backgrounding.",
minimum: 0,
}),
),
@ -33,15 +38,14 @@ export type ExecResult = {
processId?: string;
};
const MAX_OUTPUT_BYTES = 64 * 1024;
const DEFAULT_YIELD_MS = 5000;
const DEFAULT_YIELD_MS = 10000; // Changed from 5000 to 10000
export function createExecTool(defaultCwd?: string): AgentTool<typeof ExecSchema, ExecResult> {
return {
name: "exec",
label: "Exec",
description:
"Execute a shell command. If the command doesn't complete within yieldMs (default 5s), it automatically runs in background and returns a process ID. Use 'process output <id>' to check output, 'process status <id>' to check status, 'process stop <id>' to terminate.",
"Execute a shell command. If the command doesn't complete within yieldMs (default 10s), it automatically runs in background and returns a process ID with any output collected so far. Use 'process output <id>' to check output, 'process status <id>' to check status, 'process stop <id>' to terminate.",
parameters: ExecSchema,
execute: async (_toolCallId, args, signal) => {
const { command, cwd, timeoutMs, yieldMs = DEFAULT_YIELD_MS } = args as ExecArgs;
@ -59,6 +63,10 @@ export function createExecTool(defaultCwd?: string): AgentTool<typeof ExecSchema
let timeout: NodeJS.Timeout | undefined;
let yieldTimer: NodeJS.Timeout | undefined;
// Register process immediately to start buffering output
// This ensures output is captured even before yield timeout
const processId = registerProcess(child, command, effectiveCwd, "exec");
// Timeout handling (hard kill)
if (timeoutMs && timeoutMs > 0) {
timeout = setTimeout(() => {
@ -76,20 +84,27 @@ export function createExecTool(defaultCwd?: string): AgentTool<typeof ExecSchema
// Clear timeout since we're backgrounding
if (timeout) clearTimeout(timeout);
// Register to shared process registry
const processId = registerProcess(child, command, effectiveCwd, "exec");
// Get output collected so far (THE KEY FIX)
const entry = PROCESS_REGISTRY.get(processId);
const snapshot = entry
? getOutputSnapshot(entry)
: { output: "", truncated: false };
const outputPreview = snapshot.output
? `\n\nOutput so far:\n${snapshot.output}${snapshot.truncated ? "\n[truncated]" : ""}`
: "";
resolve({
content: [
{
type: "text",
text: `Command running in background. Process ID: ${processId}\nUse 'process output ${processId}' to check output.`,
text: `Command running in background. Process ID: ${processId}${outputPreview}\n\nUse 'process output ${processId}' to check more output.`,
},
],
details: {
output: "",
output: snapshot.output,
exitCode: null,
truncated: false,
truncated: snapshot.truncated,
backgrounded: true,
processId,
},
@ -97,24 +112,7 @@ export function createExecTool(defaultCwd?: string): AgentTool<typeof ExecSchema
}, yieldMs);
}
const chunks: Buffer[] = [];
let size = 0;
let truncated = false;
const handleData = (data: Buffer) => {
if (truncated) return;
size += data.length;
if (size > MAX_OUTPUT_BYTES) {
truncated = true;
const remaining = MAX_OUTPUT_BYTES - (size - data.length);
if (remaining > 0) chunks.push(data.subarray(0, remaining));
return;
}
chunks.push(data);
};
child.stdout?.on("data", handleData);
child.stderr?.on("data", handleData);
// Note: Output is now collected by process-registry, no local chunk collection needed
let spawnError: Error | null = null;
child.on("error", (err) => {
@ -131,6 +129,15 @@ export function createExecTool(defaultCwd?: string): AgentTool<typeof ExecSchema
// If already backgrounded, don't resolve again
if (yielded) return;
// Get output from registry buffer
const entry = PROCESS_REGISTRY.get(processId);
const { output, truncated } = entry
? getFullOutput(entry)
: { output: "", truncated: false };
// Remove from registry since we're returning synchronously
PROCESS_REGISTRY.delete(processId);
// If there's a spawn error, return error message
if (spawnError) {
resolve({
@ -144,7 +151,6 @@ export function createExecTool(defaultCwd?: string): AgentTool<typeof ExecSchema
return;
}
const output = Buffer.concat(chunks).toString("utf8");
resolve({
content: [{ type: "text", text: output || (timedOut ? "Process timed out." : "") }],
details: {