fix(strategy): warn when ambiguous worktree sessions block commit linking

When the sibling/parent worktree fallback finds live sessions but they
span multiple worktrees, it refuses to guess and the commit silently
loses its Entire-Checkpoint linkage with only a DEBUG trace. Surface
that refusal at WARN with the candidate worktrees and a pointer to
'entire session adopt' as the explicit remedy.

Requested in #1852 alongside the matching fix that landed in #1440.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Entire-Checkpoint: 01KYAQV3Z2X1A2FTS5K5MXTT83

Author: peyton-alt

cmd/entire/cli/strategy/manual_commit_session.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -13,6 +14,7 @@ import (
 	"github.com/entireio/cli/cmd/entire/cli/agent/types"
 	"github.com/entireio/cli/cmd/entire/cli/checkpoint"
 	"github.com/entireio/cli/cmd/entire/cli/checkpoint/id"
+	"github.com/entireio/cli/cmd/entire/cli/logging"
 	"github.com/entireio/cli/cmd/entire/cli/paths"
 	"github.com/entireio/cli/cmd/entire/cli/session"
 	"github.com/entireio/cli/cmd/entire/cli/versioninfo"
@@ -221,9 +223,40 @@ func (s *ManualCommitStrategy) findSessionsForWorktree(ctx context.Context, work
 	}
 
 	if len(parentWorktreeMatches) > 0 {
-		return sessionsFromSingleWorktree(parentWorktreeMatches), nil
+		matches := sessionsFromSingleWorktree(parentWorktreeMatches)
+		if matches == nil {
+			warnAmbiguousWorktreeSessions(ctx, worktreePath, parentWorktreeMatches)
+		}
+		return matches, nil
+	}
+	matches := sessionsFromSingleWorktree(commonDirMatches)
+	if matches == nil && len(commonDirMatches) > 0 {
+		warnAmbiguousWorktreeSessions(ctx, worktreePath, commonDirMatches)
 	}
-	return sessionsFromSingleWorktree(commonDirMatches), nil
+	return matches, nil
+}
+
+// warnAmbiguousWorktreeSessions surfaces refused fallback matches: live
+// sessions exist in other worktrees of this repo, but they span multiple
+// worktrees so no automatic match is safe. Without this warning, commits made
+// here silently lose their Entire-Checkpoint linkage (#1852) with only a
+// DEBUG-level trace.
+func warnAmbiguousWorktreeSessions(ctx context.Context, worktreePath string, candidates []*SessionState) {
+	logCtx := logging.WithComponent(ctx, "checkpoint")
+	seen := make(map[string]struct{}, len(candidates))
+	worktrees := make([]string, 0, len(candidates))
+	for _, state := range candidates {
+		if _, ok := seen[state.WorktreePath]; ok {
+			continue
+		}
+		seen[state.WorktreePath] = struct{}{}
+		worktrees = append(worktrees, state.WorktreePath)
+	}
+	logging.Warn(logCtx, "session matching: live sessions in multiple worktrees of this repo match; refusing to guess, so commits here will not be linked — run 'entire session adopt --from <worktree>' to link one explicitly",
+		slog.String("commit_worktree", worktreePath),
+		slog.Int("candidate_sessions", len(candidates)),
+		slog.Any("candidate_worktrees", worktrees),
+	)
 }
 
 // sessionsFromSingleWorktree returns the candidates only when they were all

cmd/entire/cli/strategy/manual_commit_worktree_session_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/entireio/cli/cmd/entire/cli/logging"
 	"github.com/entireio/cli/cmd/entire/cli/paths"
 	"github.com/entireio/cli/cmd/entire/cli/session"
 	"github.com/entireio/cli/cmd/entire/cli/testutil"
@@ -323,6 +324,62 @@ func TestGitCommonDirForWorktree_IgnoresHookGitDirEnv(t *testing.T) {
 	require.Equal(t, filepath.Join(mainDir, ".git"), commonDir)
 }
 
+func TestManualCommitStrategy_FindSessionsForWorktree_WarnsOnAmbiguousSiblingSessions(t *testing.T) {
+	testutil.IsolateGitConfigEnv(t)
+	ctx := context.Background()
+	mainDir := setupSessionMatchRepo(t)
+	firstWorktree := resolvedRemovedTempDir(t)
+	secondWorktree := resolvedRemovedTempDir(t)
+	commitWorktree := resolvedRemovedTempDir(t)
+	createSessionMatchWorktree(t, mainDir, firstWorktree, "first")
+	t.Cleanup(func() { removeSessionMatchWorktree(mainDir, firstWorktree) })
+	createSessionMatchWorktree(t, mainDir, secondWorktree, "second")
+	t.Cleanup(func() { removeSessionMatchWorktree(mainDir, secondWorktree) })
+	createSessionMatchWorktree(t, mainDir, commitWorktree, "commit")
+	t.Cleanup(func() { removeSessionMatchWorktree(mainDir, commitWorktree) })
+
+	s := &ManualCommitStrategy{}
+	saveSessionMatchState(ctx, t, s, mainDir, &SessionState{
+		SessionID:    "first-session",
+		WorktreePath: firstWorktree,
+	})
+	saveSessionMatchState(ctx, t, s, mainDir, &SessionState{
+		SessionID:    "second-session",
+		WorktreePath: secondWorktree,
+	})
+
+	t.Chdir(commitWorktree)
+	clearSessionMatchCaches()
+	require.NoError(t, logging.Init(ctx, "warn-test-session"))
+	t.Cleanup(logging.Close)
+
+	finder := &ManualCommitStrategy{}
+	matching, err := finder.findSessionsForWorktree(ctx, commitWorktree)
+	require.NoError(t, err)
+	require.Empty(t, matching)
+
+	logging.Close()
+	logs := readSessionMatchLogs(t, commitWorktree)
+	require.Contains(t, logs, `"level":"WARN"`, "ambiguous sibling sessions must be surfaced at WARN, not DEBUG")
+	require.Contains(t, logs, "refusing to guess")
+	require.Contains(t, logs, "entire session adopt")
+}
+
+func readSessionMatchLogs(t *testing.T, repoDir string) string {
+	t.Helper()
+
+	entries, err := filepath.Glob(filepath.Join(repoDir, ".entire", "logs", "*"))
+	require.NoError(t, err)
+	require.NotEmpty(t, entries, "expected a log file under .entire/logs")
+	var combined []byte
+	for _, entry := range entries {
+		content, err := os.ReadFile(entry)
+		require.NoError(t, err)
+		combined = append(combined, content...)
+	}
+	return string(combined)
+}
+
 func setupSessionMatchRepo(t *testing.T) string {
 	t.Helper()