fix(extensions): close ext.commands / ext.tools / lastFrameTime races

CI's `go test -race` flagged two races introduced over the recent
extension work:

1. ext.commands / ext.tools were appended to from the read-loop
   goroutine without a lock, while Commands() / Tools() / HasCommand
   read them under m.mu. Same for the toolIndex pre-check. Fix:
   take m.mu around the appends and the index dedup so writers and
   readers serialise on the same lock.

2. assumeReadyAfterIdle read ext.lastFrameTime once on entry without
   the per-extension lock (the read inside the loop already had it).
   Fix: take ext.mu for the initial snapshot too.

Verified locally with `go test -race ./...`; all packages pass.
The corresponding CI run for the scratchpad-persistence commit
failed for exactly these two races on linux + macos.

commit: 744685d68da4f7d535ea976391b4efa9db92a774
author: patriceckhart · 6mo ago · 2026-04-19 13:27 UTC
parent: 463c62d
signature: unsigned
refs: tag: v0.0.26

1 file · +8 -2

M internal/agent/extensions/manager.go +8 -2


@@ -448,7 +448,9 @@ func (m Manager) spawn(ctx context.Context, ext Extension) error {
448	448		const readyIdleWindow = 250 * time.Millisecond
449	449
450	450		func (m Manager) assumeReadyAfterIdle(ext Extension) {
	451	+	ext.mu.Lock()
451	452		last := ext.lastFrameTime
	453	+	ext.mu.Unlock()
452	454		for {
453	455		select {
454	456		case <-ext.readyCh:

@@ -507,8 +509,12 @@ func (m Manager) readLoop(ext Extension, scanner *bufio.Scanner) {
507	509		case "register_command":
508	510		var rc extproto.RegisterCommandFromExt
509	511		if err := json.Unmarshal(line, &rc); err == nil {
510		-	ext.commands = append(ext.commands, rc)
	512	+	// Both ext.commands and m.commandIndex are read by
	513	+	// the public Commands() / HasCommand() helpers under
	514	+	// m.mu, so the writes have to take the same lock to
	515	+	// keep the race detector happy.
511	516		m.mu.Lock()
	517	+	ext.commands = append(ext.commands, rc)
512	518		if _, exists := m.commandIndex[rc.Name]; !exists {
513	519		m.commandIndex[rc.Name] = ext
514	520		}

@@ -529,8 +535,8 @@ func (m Manager) readLoop(ext Extension, scanner *bufio.Scanner) {
529	535		continue
530	536		}
531	537		}
532		-	ext.tools = append(ext.tools, rt)
533	538		m.mu.Lock()
	539	+	ext.tools = append(ext.tools, rt)
534	540		if _, exists := m.toolIndex[rt.Name]; !exists {
535	541		m.toolIndex[rt.Name] = ext
536	542		}

 const readyIdleWindow = 250 * time.Millisecond
 func (m *Manager) assumeReadyAfterIdle(ext *Extension) {
+	ext.mu.Lock()
 	last := ext.lastFrameTime
+	ext.mu.Unlock()
 	for {
 		select {
 		case <-ext.readyCh:
 		case "register_command":
 			var rc extproto.RegisterCommandFromExt
 			if err := json.Unmarshal(line, &rc); err == nil {
-				ext.commands = append(ext.commands, rc)
+				// Both ext.commands and m.commandIndex are read by
+				// the public Commands() / HasCommand() helpers under
+				// m.mu, so the writes have to take the same lock to
+				// keep the race detector happy.
 				m.mu.Lock()
+				ext.commands = append(ext.commands, rc)
 				if _, exists := m.commandIndex[rc.Name]; !exists {
 					m.commandIndex[rc.Name] = ext
 				}
 					continue
 				}
 			}
-			ext.tools = append(ext.tools, rt)
 			m.mu.Lock()
+			ext.tools = append(ext.tools, rt)
 			if _, exists := m.toolIndex[rt.Name]; !exists {
 				m.toolIndex[rt.Name] = ext
 			}