Serialize Gradle and test runs

.gitignore

@@ -3,3 +3,4 @@
 .intellijPlatform
 .kotlin
 build
+.gradle-test.lock

AGENTS.md

@@ -277,12 +277,13 @@ The fast loop for grammar work:
   `ls -l build/classes/java/main/dev/hgh/jai/parser/JaiParser.class
   src/main/gen/dev/hgh/jai/parser/JaiParser.java`. The build wiring in
   `build.gradle.kts` should prevent both, but `rm -rf build` settles it.
-- **Concurrent Gradle runs corrupt the test results.** If something else (an
-  IDE, an agent's background checker) runs `test` at the same time, one of the
-  two dies with `java.io.EOFException` or
-  `NoSuchFileException: .../in-progress-results-generic.bin`, and no XML is
-  written. It is infrastructure, not a test failure — `./jaitest` retries once
-  automatically. Do not go debugging the test that "failed".
+- **Concurrent Gradle runs corrupt the test results.** `./jaigradle` and
+  `./jaitest` serialize project Gradle work with the atomic `.gradle-test.lock`
+  lock, including test-result cleanup and retries. Never run `./gradlew`
+  directly: it bypasses both the JDK wrapper and this lock. If an interrupted
+  process leaves a lock behind, confirm no Gradle run is active, then remove
+  `.gradle-test.lock` and rerun. The JUnit wrapper still retries once for
+  unexpected no-XML failures; do not debug a test until the XML exists.
 - **A poisoned build cache can make tests silently vanish.** Symptom:
   `BUILD SUCCESSFUL`, `:compileTestKotlin FROM-CACHE`, `:test NO-SOURCE`, and
   `build/classes/kotlin/test` is empty. The cache stored an empty output
@@ -293,7 +294,7 @@ The fast loop for grammar work:
 
   ```bash
   ./jaigradle --stop
-  rm -rf build .gradle ~/.gradle/caches/build-cache-1
+  rm -rf .gradle-test.lock build .gradle ~/.gradle/caches/build-cache-1
   ./jaitest
   ```
 

gradle-lock.sh

@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+# Shared, process-safe lock for Gradle and IntelliJ platform test runs.
+# This file is sourced by jaigradle and jaitest; it is not a standalone command.
+
+JAI_GRADLE_LOCK_DIR="${JAI_GRADLE_LOCK_DIR:-.gradle-test.lock}"
+JAI_GRADLE_LOCK_PID_FILE="$JAI_GRADLE_LOCK_DIR/pid"
+
+jai_gradle_lock_acquire() {
+	if [[ "${JAI_GRADLE_LOCK_HELD:-0}" == "1" ]]; then
+		return 0
+	fi
+
+	local reported=0
+	while ! mkdir "$JAI_GRADLE_LOCK_DIR" 2>/dev/null; do
+		if [[ -f "$JAI_GRADLE_LOCK_PID_FILE" ]]; then
+			local owner
+			owner=$(<"$JAI_GRADLE_LOCK_PID_FILE")
+			if [[ "$owner" =~ ^[0-9]+$ ]] && ! kill -0 "$owner" 2>/dev/null; then
+				rm -rf "$JAI_GRADLE_LOCK_DIR"
+				continue
+			fi
+		else
+			# A process can be killed between mkdir and writing its PID. Give that
+			# tiny window a chance to finish, then reclaim the incomplete lock.
+			sleep 1
+			if [[ ! -f "$JAI_GRADLE_LOCK_PID_FILE" ]]; then
+				rm -rf "$JAI_GRADLE_LOCK_DIR"
+				continue
+			fi
+		fi
+
+		if ((reported == 0)); then
+			echo "Waiting for another Gradle/test run in this worktree..." >&2
+			reported=1
+		fi
+		sleep 1
+	done
+
+	printf '%s\n' "$$" >"$JAI_GRADLE_LOCK_PID_FILE"
+	JAI_GRADLE_LOCK_HELD=1
+	JAI_GRADLE_LOCK_OWNER_PID=$$
+	export JAI_GRADLE_LOCK_HELD JAI_GRADLE_LOCK_OWNER_PID
+}
+
+jai_gradle_lock_release() {
+	if [[ "${JAI_GRADLE_LOCK_OWNER_PID:-}" == "$$" ]]; then
+		rm -rf "$JAI_GRADLE_LOCK_DIR"
+		unset JAI_GRADLE_LOCK_OWNER_PID JAI_GRADLE_LOCK_HELD
+	fi
+}

jaigradle

@@ -13,11 +13,22 @@
 # and throw UnsupportedClassVersionError on 17.
 set -euo pipefail
 cd "$(dirname "$0")"
+source ./gradle-lock.sh
 
-if command -v mise >/dev/null 2>&1; then
-  exec mise exec -- ./gradlew "$@"
+# `--stop` is an explicit recovery operation; it must be able to stop a
+# daemon even when a stale lock was left by an interrupted run.
+if [[ "${1:-}" != "--stop" ]]; then
+  jai_gradle_lock_acquire
+  trap jai_gradle_lock_release EXIT
+  trap 'exit 130' INT
+  trap 'exit 143' TERM
 fi
 
+status=0
+if command -v mise >/dev/null 2>&1; then
+  mise exec -- ./gradlew "$@" || status=$?
+else
+
 # Fallback: mise is not installed. Try an already-set JAVA_HOME, then any
 # JDK 21 that Gradle has auto-provisioned.
 if [ ! -x "${JAVA_HOME:-}/bin/java" ]; then
@@ -35,4 +46,9 @@ if [ ! -x "${JAVA_HOME:-}/bin/java" ]; then
   exit 1
 fi
 
-exec ./gradlew "$@"
+  ./gradlew "$@" || status=$?
+fi
+
+jai_gradle_lock_release
+trap - EXIT INT TERM
+exit "$status"

jaitest

@@ -4,10 +4,9 @@
 # A green `test` task does not prove tests ran (see AGENTS.md), so this always
 # prints tests/failures/errors per suite and dumps failure messages.
 #
-# Two concurrent Gradle invocations (e.g. an editor/agent running tests in the
-# background at the same time) fight over build/test-results and the loser dies
-# with `java.io.EOFException` or a missing in-progress-results bin. That is an
-# infrastructure failure, not a test failure, so it is retried once.
+# A repository-wide lock serializes Gradle/test runs. Without it, an editor or
+# another agent can delete build/test-results while this process is writing JUnit
+# XML, producing EOFException or a missing in-progress-results bin.
 #
 # A `--tests` filter STICKS: Gradle reuses the configuration cache entry from the
 # previous run, so a later unfiltered `./jaitest` silently re-runs just that one
@@ -18,6 +17,11 @@
 set -uo pipefail
 
 cd "$(dirname "$0")" || exit 1
+source ./gradle-lock.sh
+jai_gradle_lock_acquire
+trap jai_gradle_lock_release EXIT
+trap 'exit 130' INT
+trap 'exit 143' TERM
 
 extra=()
 if [[ " $* " != *" --tests "* ]]; then