fix: make worker handoff rotation durable

internal/herdr/occupancy.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"time"
 )
@@ -30,6 +31,7 @@ func Fraction(u Usage, w int64) float64 {
 	}
 	return f
 }
+
 // ClaudeSessionFile resolves the transcript file for a Claude Code session
 // running against worktree, by newest-mtime under Claude Code's encoded
 // project directory (~/.claude/projects/<abs-worktree-path-with-/-replaced-
@@ -202,6 +204,60 @@ func OpenCodeUsage(p string) (Usage, error) {
 	return Usage{x.Tokens.Input, x.Tokens.Cache.Read, x.Tokens.Cache.Write, x.Tokens.Output}, e
 }
 
+// OpenCodeSessionID resolves the exact OpenCode session associated with a
+// checkout. OpenCode stores usage in its SQLite session table, not in a pane
+// transcript. Selecting by directory and persisting the returned id prevents
+// a multi-pane worker from attributing another task's newest session to this
+// lease.
+func OpenCodeSessionID(worktree string) (string, error) {
+	db := os.Getenv("ORCHESTRA_OPENCODE_DB")
+	if db == "" {
+		db = filepath.Join(os.Getenv("HOME"), ".local", "share", "opencode", "opencode.db")
+	}
+	abs, err := filepath.Abs(worktree)
+	if err != nil {
+		return "", err
+	}
+	out, err := exec.Command("sqlite3", "-readonly", "-noheader", db, "select id from session where directory = "+sqliteQuote(abs)+" order by time_updated desc limit 1;").Output()
+	if err != nil {
+		return "", fmt.Errorf("opencode session lookup: %w", err)
+	}
+	id := strings.TrimSpace(string(out))
+	if id == "" {
+		return "", fmt.Errorf("opencode session lookup: no session for %s", abs)
+	}
+	return id, nil
+}
+
+// OpenCodeSessionUsage reads the token counters for one persisted session.
+func OpenCodeSessionUsage(sessionID string) (Usage, error) {
+	if sessionID == "" {
+		return Usage{}, fmt.Errorf("opencode session id required")
+	}
+	db := os.Getenv("ORCHESTRA_OPENCODE_DB")
+	if db == "" {
+		db = filepath.Join(os.Getenv("HOME"), ".local", "share", "opencode", "opencode.db")
+	}
+	out, err := exec.Command("sqlite3", "-readonly", "-noheader", "-separator", "|", db, "select tokens_input,tokens_cache_read,tokens_cache_write,tokens_output from session where id = "+sqliteQuote(sessionID)+";").Output()
+	if err != nil {
+		return Usage{}, fmt.Errorf("opencode usage lookup: %w", err)
+	}
+	parts := strings.Split(strings.TrimSpace(string(out)), "|")
+	if len(parts) != 4 {
+		return Usage{}, fmt.Errorf("opencode usage lookup: unknown session %q", sessionID)
+	}
+	values := [4]int64{}
+	for i, part := range parts {
+		values[i], err = strconv.ParseInt(part, 10, 64)
+		if err != nil {
+			return Usage{}, fmt.Errorf("opencode usage lookup: %w", err)
+		}
+	}
+	return Usage{Input: values[0], CacheRead: values[1], CacheWrite: values[2], Output: values[3]}, nil
+}
+
+func sqliteQuote(s string) string { return "'" + strings.ReplaceAll(s, "'", "''") + "'" }
+
 // OpenCodeStatus probes the server fast path. Callers can use the returned
 // status and fall back to OpenCodeUsage when the SSE/server is unavailable.
 func OpenCodeStatus(ctx context.Context, baseURL, sessionID string) (string, error) {