diff --git a/.Jules/sentinel.md b/.Jules/sentinel.md
index 70f67594..16e9fbbf 100644
--- a/.Jules/sentinel.md
+++ b/.Jules/sentinel.md
@@ -18,3 +18,7 @@
 **Vulnerability:** The application was falling back to storing OBS passwords as plaintext strings inside exported/saved JSON models (`Macro.swift` and `SystemCommand.swift`) if saving to the macOS Keychain failed.
 **Learning:** Saving secrets to unencrypted formats simply because secure storage fails is a critical anti-pattern known as "failing open" that results in data exposure.
 **Prevention:** Always fail securely. If secure storage operations fail, discard the sensitive credential in memory rather than writing it insecurely to disk, even if it requires the user to re-authenticate later.
+## 2026-06-28 - [Deadlock / DoS via Process() output buffer]
+**Vulnerability:** Execution frameworks utilizing `Foundation.Process` combined with `Pipe()` were calling `process.waitUntilExit()` before reading the output `pipe.fileHandleForReading.readDataToEndOfFile()`. This allows a child process exceeding the OS pipe buffer size (~64KB) to block indefinitely while trying to write, creating a deadlock or DoS condition.
+**Learning:** Process deadlocks can occur when output exceeds the pipe's internal buffer, because the operating system pauses the process until the buffer is read. Calling `waitUntilExit()` while the process is blocked on a write causes the parent process to hang forever.
+**Prevention:** Always ensure you read pipe data (e.g., via `fileHandleForReading.readDataToEndOfFile()`) *before* invoking `process.waitUntilExit()`, or process reads asynchronously, to avoid deadlocking when capturing output.
diff --git a/TriggerKit/Sources/TriggerKitRuntime/AutomationExecutor.swift b/TriggerKit/Sources/TriggerKitRuntime/AutomationExecutor.swift
index 59854205..a44260bf 100644
--- a/TriggerKit/Sources/TriggerKitRuntime/AutomationExecutor.swift
+++ b/TriggerKit/Sources/TriggerKitRuntime/AutomationExecutor.swift
@@ -354,9 +354,11 @@ public final class AutomationExecutor {
 			} catch {
 				return .failure("\(name) launch failed: \(error.localizedDescription)")
 			}
-			process.waitUntilExit()
 
+			// Read pipe data BEFORE waitUntilExit to avoid deadlock when
+			// output exceeds the pipe buffer size (~64KB).
 			let data = pipe.fileHandleForReading.readDataToEndOfFile()
+			process.waitUntilExit()
 			let output = String(data: data, encoding: .utf8)?
 				.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
 
@@ -641,7 +643,12 @@ private final class ShellCommandRunner: @unchecked Sendable {
 		}
 
 		let timeout = DispatchTime.now() + step.timeoutSeconds
-		if semaphore.wait(timeout: timeout) == .timedOut {
+		let waitResult = semaphore.wait(timeout: timeout)
+
+		// If the process hasn't exited but pipe buffer is filled, it could be deadlocked
+		// but since we read asynchronously via readabilityHandler, this shouldn't happen for the pipe.
+
+		if waitResult == .timedOut {
 			terminateProcessTree(process, signal: SIGTERM)
 			_ = semaphore.wait(timeout: .now() + 1)
 			if process.isRunning {
@@ -731,11 +738,13 @@ private final class ShellCommandRunner: @unchecked Sendable {
 		pgrep.standardError = FileHandle.nullDevice
 		do {
 			try pgrep.run()
-			pgrep.waitUntilExit()
 		} catch {
 			return []
 		}
+
+		// Read pipe data BEFORE waitUntilExit to avoid deadlock
 		let data = pipe.fileHandleForReading.readDataToEndOfFile()
+		pgrep.waitUntilExit()
 		let output = String(data: data, encoding: .utf8) ?? ""
 		return output
 			.split(whereSeparator: \.isNewline)
diff --git a/TriggerKit/Tests/TriggerKitRuntimeTests/AutomationExecutorTests.swift b/TriggerKit/Tests/TriggerKitRuntimeTests/AutomationExecutorTests.swift
index 4894b5b1..19bb79d3 100644
--- a/TriggerKit/Tests/TriggerKitRuntimeTests/AutomationExecutorTests.swift
+++ b/TriggerKit/Tests/TriggerKitRuntimeTests/AutomationExecutorTests.swift
@@ -464,7 +464,7 @@ final class AutomationExecutorTests: XCTestCase {
 			]))
 		}
 
-		try? await Task.sleep(nanoseconds: 20_000_000)
+		try? await Task.sleep(nanoseconds: 250_000_000) // increase delay so process has time to start
 		task.cancel()
 
 		let result = await task.value