Tell agents to shorten a merge title over 72 characters

internal/agents/guidance.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"regexp"
+	"unicode/utf8"
 
 	"g.fc.run/misc/byre/internal/api"
 	"g.fc.run/misc/byre/internal/claude"
@@ -92,6 +93,15 @@ func (m *Manager) taskGuidance(ctx context.Context, task api.Task) (string, erro
 	return g + forkGuidance(task, src), nil
 }
 
+func longTitleGuidance(task api.Task) string {
+	n := utf8.RuneCountInString(task.MergeTitle)
+	if n <= maxMergeTitle {
+		return ""
+	}
+	return fmt.Sprintf("\n- This task's merge commit title, %q, is %d characters, over the %d allowed, so Merge will refuse it. Early in your first turn, call set_merge_title with a one-line title of at most %d characters that describes the work.",
+		task.MergeTitle, n, maxMergeTitle, maxMergeTitle)
+}
+
 func subtaskGuidance(parent api.Task) string {
 	return fmt.Sprintf("\n- This task is a subtask of byre task %q (%s), whose agent created it and manages it. Your final message at the end of each turn is sent to that agent, which may answer with more instructions. "+
 		"Your work reaches %s's branch or the default branch when the subtask is merged.",

internal/agents/manager.go

@@ -680,6 +680,9 @@ func (m *Manager) startLive(ctx context.Context, sess api.AgentSession, task api
 		return nil, err
 	}
 	tools := append([]mcp.Tool{m.askTool(l), m.cancelQuestionTool(l), m.setMergeTitleTool(l), m.stopMergeTool(l), m.setTaskSummaryTool(l), m.searchClosedTool(l), m.exposePortTool(l)}, m.subtaskTools(l)...)
+	if sess.Role == api.Implementer {
+		g += longTitleGuidance(task)
+	}
 	if sess.Role == api.Implementer && task.WorkflowStage != nil {
 		frozen, err := m.store.TaskWorkflow(ctx, task.Id)
 		if err != nil {