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fix(mcp): use idle timeout instead of fixed caps for read/send/send-image #26

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fix(mcp): use idle timeout instead of fixed caps for read/send/send-image #26

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294786a
fix(mcp): use idle timeout for kmsg_send instead of fixed cap
mortalist Nov 12, 2026
33d5ca3
fix(mcp): apply idle timeout to kmsg_read and kmsg_send_image
mortalist Nov 12, 2026
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91 changes: 77 additions & 14 deletions Sources/kmsg/Commands/MCPServerCommand.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -32,13 +32,27 @@ private enum MCPStdioTransport {
private final class MCPDataBuffer: @unchecked Sendable {
private let lock = NSLock()
private var data = Data()
private var lastWrite = Date()

func store(_ newData: Data) {
lock.lock()
data = newData
lock.unlock()
}

func append(_ chunk: Data) {
lock.lock()
data.append(chunk)
lastWrite = Date()
lock.unlock()
}

func lastWriteDate() -> Date {
lock.lock()
defer { lock.unlock() }
return lastWrite
}

func load() -> Data {
lock.lock()
defer { lock.unlock() }
Expand All @@ -47,6 +61,12 @@ private final class MCPDataBuffer: @unchecked Sendable {
}

private final class KmsgSubprocessRunner {
/// Limits for commands that drive the KakaoTalk UI (read/send/send-image).
/// Cold runs measured 10-18s with silent gaps up to ~8s, so they fail on
/// 12s without stderr output (the `--trace-ax` heartbeat) under a 30s ceiling.
static let uiIdleTimeoutSec: TimeInterval = 12.0
static let uiHardTimeoutSec: TimeInterval = 30.0

let executablePath: String

init() {
Expand All @@ -57,7 +77,12 @@ private final class KmsgSubprocessRunner {
}
}

func run(_ arguments: [String], timeoutSec: TimeInterval) -> MCPCommandResult {
/// - Parameters:
/// - timeoutSec: Hard ceiling for the whole run.
/// - idleTimeoutSec: When set, the run is also killed after this many seconds
/// without stderr output. `--trace-ax` lines are written to stderr unbuffered,
/// so they act as a progress heartbeat. When nil, behavior is unchanged.
func run(_ arguments: [String], timeoutSec: TimeInterval, idleTimeoutSec: TimeInterval? = nil) -> MCPCommandResult {
let start = Date()
let process = Process()
process.executableURL = URL(fileURLWithPath: executablePath)
Expand Down Expand Up @@ -90,7 +115,12 @@ private final class KmsgSubprocessRunner {
stdoutSemaphore.signal()
}
DispatchQueue.global().async {
stderrData.store(stderrPipe.fileHandleForReading.readDataToEndOfFile())
let handle = stderrPipe.fileHandleForReading
while true {
let chunk = handle.availableData
if chunk.isEmpty { break }
stderrData.append(chunk)
}
stderrSemaphore.signal()
}

Expand All @@ -100,7 +130,19 @@ private final class KmsgSubprocessRunner {
waitSemaphore.signal()
}

let timedOut = waitSemaphore.wait(timeout: .now() + timeoutSec) == .timedOut
var timedOut = false
if let idleTimeoutSec {
while waitSemaphore.wait(timeout: .now() + 0.25) == .timedOut {
let now = Date()
if now.timeIntervalSince(start) > timeoutSec
|| now.timeIntervalSince(stderrData.lastWriteDate()) > idleTimeoutSec {
timedOut = true
break
}
}
} else {
timedOut = waitSemaphore.wait(timeout: .now() + timeoutSec) == .timedOut
}
if timedOut {
process.terminate()

Expand Down Expand Up @@ -501,10 +543,15 @@ private final class KmsgMCPServer {
if deepRecovery { command.append("--deep-recovery") }
if backgroundSafe { command.append("--background-safe") }
if keepWindow { command.append("--keep-window") }
if traceAX { command.append("--trace-ax") }

let timeoutSec = deepRecovery ? 15.0 : 8.0
var first = runner.run(command, timeoutSec: timeoutSec)
// Always trace: stderr trace lines are the heartbeat for the idle timeout.
// stderr is still only surfaced in the response when traceAX was requested.
command.append("--trace-ax")

var first = runner.run(
command,
timeoutSec: KmsgSubprocessRunner.uiHardTimeoutSec,
idleTimeoutSec: KmsgSubprocessRunner.uiIdleTimeoutSec
)

if first.timedOut {
return errorPayload(
Expand All @@ -523,7 +570,11 @@ private final class KmsgMCPServer {
if code == "CHAT_NOT_FOUND" && !deepRecovery && !backgroundSafe {
var retryCommand = command
retryCommand.append("--deep-recovery")
let retry = runner.run(retryCommand, timeoutSec: 15.0)
let retry = runner.run(
retryCommand,
timeoutSec: KmsgSubprocessRunner.uiHardTimeoutSec,
idleTimeoutSec: KmsgSubprocessRunner.uiIdleTimeoutSec
)
if retry.returncode == 0 && !retry.timedOut {
first = retry
} else {
Expand Down Expand Up @@ -614,9 +665,15 @@ private final class KmsgMCPServer {
var command = ["send", chat, message]
if deepRecovery { command.append("--deep-recovery") }
if keepWindow { command.append("--keep-window") }
if traceAX { command.append("--trace-ax") }

let run = runner.run(command, timeoutSec: deepRecovery ? 18.0 : 10.0)
// Always trace: stderr trace lines are the heartbeat for the idle timeout.
// stderr is still only surfaced in the response when traceAX was requested.
command.append("--trace-ax")

let run = runner.run(
command,
timeoutSec: KmsgSubprocessRunner.uiHardTimeoutSec,
idleTimeoutSec: KmsgSubprocessRunner.uiIdleTimeoutSec
)
if run.timedOut {
return errorPayload(
code: "PROCESS_TIMEOUT",
Expand Down Expand Up @@ -701,9 +758,15 @@ private final class KmsgMCPServer {
var command = ["send-image", chat, imagePath]
if deepRecovery { command.append("--deep-recovery") }
if keepWindow { command.append("--keep-window") }
if traceAX { command.append("--trace-ax") }

let run = runner.run(command, timeoutSec: deepRecovery ? 20.0 : 12.0)
// Always trace: stderr trace lines are the heartbeat for the idle timeout.
// stderr is still only surfaced in the response when traceAX was requested.
command.append("--trace-ax")

let run = runner.run(
command,
timeoutSec: KmsgSubprocessRunner.uiHardTimeoutSec,
idleTimeoutSec: KmsgSubprocessRunner.uiIdleTimeoutSec
)
if run.timedOut {
return errorPayload(
code: "PROCESS_TIMEOUT",
Expand Down