diff --git a/go.mod b/go.mod
index 4964786..72545cf 100644
--- a/go.mod
+++ b/go.mod
@@ -3,22 +3,20 @@ module forge.lthn.ai/core/go-ratelimit
 go 1.26.0
 
 require (
-	dappco.re/go/core/io v0.2.0
-	dappco.re/go/core/log v0.1.0
+	dappco.re/go/core v0.8.0-alpha.1
 	gopkg.in/yaml.v3 v3.0.1
 	modernc.org/sqlite v1.47.0
 )
 
 require (
-	forge.lthn.ai/core/go-log v0.0.4 // indirect
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/google/uuid v1.6.0 // indirect
+	github.com/kr/text v0.2.0 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/ncruces/go-strftime v1.0.0 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
-	golang.org/x/mod v0.34.0 // indirect
-	golang.org/x/sync v0.20.0 // indirect
 	golang.org/x/sys v0.42.0 // indirect
+	golang.org/x/tools v0.43.0 // indirect
 	modernc.org/libc v1.70.0 // indirect
 	modernc.org/mathutil v1.7.1 // indirect
 	modernc.org/memory v1.11.0 // indirect
diff --git a/go.sum b/go.sum
index 19c63b0..adafd38 100644
--- a/go.sum
+++ b/go.sum
@@ -1,9 +1,6 @@
-dappco.re/go/core/io v0.2.0 h1:zuudgIiTsQQ5ipVt97saWdGLROovbEB/zdVyy9/l+I4=
-dappco.re/go/core/io v0.2.0/go.mod h1:1QnQV6X9LNgFKfm8SkOtR9LLaj3bDcsOIeJOOyjbL5E=
-dappco.re/go/core/log v0.1.0 h1:pa71Vq2TD2aoEUQWFKwNcaJ3GBY8HbaNGqtE688Unyc=
-dappco.re/go/core/log v0.1.0/go.mod h1:Nkqb8gsXhZAO8VLpx7B8i1iAmohhzqA20b9Zr8VUcJs=
-forge.lthn.ai/core/go-log v0.0.4 h1:KTuCEPgFmuM8KJfnyQ8vPOU1Jg654W74h8IJvfQMfv0=
-forge.lthn.ai/core/go-log v0.0.4/go.mod h1:r14MXKOD3LF/sI8XUJQhRk/SZHBE7jAFVuCfgkXoZPw=
+dappco.re/go/core v0.8.0-alpha.1 h1:gj7+Scv+L63Z7wMxbJYHhaRFkHJo2u4MMPuUSv/Dhtk=
+dappco.re/go/core v0.8.0-alpha.1/go.mod h1:f2/tBZ3+3IqDrg2F5F598llv0nmb/4gJVCFzM5geE4A=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
 github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dustin/go-humanize v1.0.1 h1:GzkhY7T5VNhEkwH0PVJgjz+fX1rhBrR7pRT3mDkpeCY=
diff --git a/ratelimit.go b/ratelimit.go
index 0e34709..35d4c3b 100644
--- a/ratelimit.go
+++ b/ratelimit.go
@@ -1,24 +1,18 @@
 package ratelimit
 
 import (
-	"bytes"
 	"context"
-	"encoding/json"
-	"fmt"
 	"io"
 	"iter"
 	"maps"
 	"net/http"
 	"net/url"
 	"os"
-	"path/filepath"
 	"slices"
-	"strings"
 	"sync"
 	"time"
 
-	coreio "dappco.re/go/core/io"
-	coreerr "dappco.re/go/core/log"
+	core "dappco.re/go/core"
 	"gopkg.in/yaml.v3"
 )
 
@@ -170,8 +164,8 @@ func NewWithConfig(cfg Config) (*RateLimiter, error) {
 
 	if backend == backendSQLite {
 		if cfg.FilePath == "" {
-			if err := os.MkdirAll(filepath.Dir(filePath), 0o755); err != nil {
-				return nil, coreerr.E("ratelimit.NewWithConfig", "mkdir", err)
+			if err := ensureDir(core.PathDir(filePath)); err != nil {
+				return nil, core.E("ratelimit.NewWithConfig", "mkdir", err)
 			}
 		}
 		return NewWithSQLiteConfig(filePath, cfg)
@@ -210,7 +204,7 @@ func (rl *RateLimiter) Load() error {
 		return rl.loadSQLite()
 	}
 
-	content, err := coreio.Local.Read(rl.filePath)
+	content, err := readLocalFile(rl.filePath)
 	if os.IsNotExist(err) {
 		return nil
 	}
@@ -265,7 +259,7 @@ func (rl *RateLimiter) Persist() error {
 
 	if sqlite != nil {
 		if err := sqlite.saveSnapshot(quotas, state); err != nil {
-			return coreerr.E("ratelimit.Persist", "sqlite snapshot", err)
+			return core.E("ratelimit.Persist", "sqlite snapshot", err)
 		}
 		return nil
 	}
@@ -280,11 +274,11 @@ func (rl *RateLimiter) Persist() error {
 		State:  state,
 	})
 	if err != nil {
-		return coreerr.E("ratelimit.Persist", "marshal", err)
+		return core.E("ratelimit.Persist", "marshal", err)
 	}
 
-	if err := coreio.Local.Write(filePath, string(data)); err != nil {
-		return coreerr.E("ratelimit.Persist", "write", err)
+	if err := writeLocalFile(filePath, string(data)); err != nil {
+		return core.E("ratelimit.Persist", "write", err)
 	}
 	return nil
 }
@@ -428,7 +422,7 @@ func (rl *RateLimiter) RecordUsage(model string, promptTokens, outputTokens int)
 // WaitForCapacity blocks until capacity is available or context is cancelled.
 func (rl *RateLimiter) WaitForCapacity(ctx context.Context, model string, tokens int) error {
 	if tokens < 0 {
-		return coreerr.E("ratelimit.WaitForCapacity", "negative tokens", nil)
+		return core.E("ratelimit.WaitForCapacity", "negative tokens", nil)
 	}
 
 	ticker := time.NewTicker(1 * time.Second)
@@ -600,14 +594,14 @@ func (rl *RateLimiter) Close() error {
 // database is created if it does not exist.
 func MigrateYAMLToSQLite(yamlPath, sqlitePath string) error {
 	// Load from YAML.
-	content, err := coreio.Local.Read(yamlPath)
+	content, err := readLocalFile(yamlPath)
 	if err != nil {
-		return coreerr.E("ratelimit.MigrateYAMLToSQLite", "read", err)
+		return core.E("ratelimit.MigrateYAMLToSQLite", "read", err)
 	}
 
 	var rl RateLimiter
 	if err := yaml.Unmarshal([]byte(content), &rl); err != nil {
-		return coreerr.E("ratelimit.MigrateYAMLToSQLite", "unmarshal", err)
+		return core.E("ratelimit.MigrateYAMLToSQLite", "unmarshal", err)
 	}
 
 	// Write to SQLite.
@@ -631,7 +625,7 @@ func CountTokens(ctx context.Context, apiKey, model, text string) (int, error) {
 func countTokensWithClient(ctx context.Context, client *http.Client, baseURL, apiKey, model, text string) (int, error) {
 	requestURL, err := countTokensURL(baseURL, model)
 	if err != nil {
-		return 0, coreerr.E("ratelimit.CountTokens", "build url", err)
+		return 0, core.E("ratelimit.CountTokens", "build url", err)
 	}
 
 	reqBody := map[string]any{
@@ -644,14 +638,14 @@ func countTokensWithClient(ctx context.Context, client *http.Client, baseURL, ap
 		},
 	}
 
-	jsonBody, err := json.Marshal(reqBody)
-	if err != nil {
-		return 0, coreerr.E("ratelimit.CountTokens", "marshal request", err)
+	jsonBody := core.JSONMarshal(reqBody)
+	if !jsonBody.OK {
+		return 0, core.E("ratelimit.CountTokens", "marshal request", resultError(jsonBody))
 	}
 
-	req, err := http.NewRequestWithContext(ctx, http.MethodPost, requestURL, bytes.NewReader(jsonBody))
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, requestURL, core.NewReader(string(jsonBody.Value.([]byte))))
 	if err != nil {
-		return 0, coreerr.E("ratelimit.CountTokens", "new request", err)
+		return 0, core.E("ratelimit.CountTokens", "new request", err)
 	}
 	req.Header.Set("Content-Type", "application/json")
 	req.Header.Set("x-goog-api-key", apiKey)
@@ -662,23 +656,29 @@ func countTokensWithClient(ctx context.Context, client *http.Client, baseURL, ap
 
 	resp, err := client.Do(req)
 	if err != nil {
-		return 0, coreerr.E("ratelimit.CountTokens", "do request", err)
+		return 0, core.E("ratelimit.CountTokens", "do request", err)
 	}
 	defer resp.Body.Close()
 
 	if resp.StatusCode != http.StatusOK {
 		body, err := readLimitedBody(resp.Body, countTokensErrorBodyLimit)
 		if err != nil {
-			return 0, coreerr.E("ratelimit.CountTokens", "read error body", err)
+			return 0, core.E("ratelimit.CountTokens", "read error body", err)
 		}
-		return 0, coreerr.E("ratelimit.CountTokens", fmt.Sprintf("api error status %d: %s", resp.StatusCode, body), nil)
+		return 0, core.E("ratelimit.CountTokens", core.Sprintf("api error status %d: %s", resp.StatusCode, body), nil)
+	}
+
+	body, err := readLimitedBody(resp.Body, countTokensSuccessBodyLimit)
+	if err != nil {
+		return 0, core.E("ratelimit.CountTokens", "decode response", err)
 	}
 
 	var result struct {
 		TotalTokens int `json:"totalTokens"`
 	}
-	if err := json.NewDecoder(io.LimitReader(resp.Body, countTokensSuccessBodyLimit)).Decode(&result); err != nil {
-		return 0, coreerr.E("ratelimit.CountTokens", "decode response", err)
+	decode := core.JSONUnmarshalString(body, &result)
+	if !decode.OK {
+		return 0, core.E("ratelimit.CountTokens", "decode response", resultError(decode))
 	}
 
 	return result.TotalTokens, nil
@@ -711,13 +711,13 @@ func applyConfig(rl *RateLimiter, cfg Config) {
 }
 
 func normaliseBackend(backend string) (string, error) {
-	switch strings.ToLower(strings.TrimSpace(backend)) {
+	switch core.Lower(core.Trim(backend)) {
 	case "", backendYAML:
 		return backendYAML, nil
 	case backendSQLite:
 		return backendSQLite, nil
 	default:
-		return "", coreerr.E("ratelimit.NewWithConfig", fmt.Sprintf("unknown backend %q", backend), nil)
+		return "", core.E("ratelimit.NewWithConfig", core.Sprintf("unknown backend %q", backend), nil)
 	}
 }
 
@@ -732,7 +732,7 @@ func defaultStatePath(backend string) (string, error) {
 		fileName = defaultSQLiteStateFile
 	}
 
-	return filepath.Join(home, defaultStateDirName, fileName), nil
+	return core.Path(home, defaultStateDirName, fileName), nil
 }
 
 func safeTokenSum(a, b int) int {
@@ -761,8 +761,8 @@ func safeTokenTotal(tokens []TokenEntry) int {
 }
 
 func countTokensURL(baseURL, model string) (string, error) {
-	if strings.TrimSpace(model) == "" {
-		return "", fmt.Errorf("empty model")
+	if core.Trim(model) == "" {
+		return "", core.NewError("empty model")
 	}
 
 	parsed, err := url.Parse(baseURL)
@@ -770,10 +770,10 @@ func countTokensURL(baseURL, model string) (string, error) {
 		return "", err
 	}
 	if parsed.Scheme == "" || parsed.Host == "" {
-		return "", fmt.Errorf("invalid base url")
+		return "", core.NewError("invalid base url")
 	}
 
-	return strings.TrimRight(parsed.String(), "/") + "/v1beta/models/" + url.PathEscape(model) + ":countTokens", nil
+	return core.Concat(core.TrimSuffix(parsed.String(), "/"), "/v1beta/models/", url.PathEscape(model), ":countTokens"), nil
 }
 
 func readLimitedBody(r io.Reader, limit int64) (string, error) {
@@ -793,3 +793,40 @@ func readLimitedBody(r io.Reader, limit int64) (string, error) {
 	}
 	return result, nil
 }
+
+func readLocalFile(path string) (string, error) {
+	var fs core.Fs
+	result := fs.Read(path)
+	if !result.OK {
+		return "", resultError(result)
+	}
+
+	content, ok := result.Value.(string)
+	if !ok {
+		return "", core.NewError("read returned non-string")
+	}
+	return content, nil
+}
+
+func writeLocalFile(path, content string) error {
+	var fs core.Fs
+	return resultError(fs.Write(path, content))
+}
+
+func ensureDir(path string) error {
+	var fs core.Fs
+	return resultError(fs.EnsureDir(path))
+}
+
+func resultError(result core.Result) error {
+	if result.OK {
+		return nil
+	}
+	if err, ok := result.Value.(error); ok {
+		return err
+	}
+	if result.Value == nil {
+		return nil
+	}
+	return core.NewError(core.Sprint(result.Value))
+}
diff --git a/sqlite.go b/sqlite.go
index 863ede4..f6ea6f0 100644
--- a/sqlite.go
+++ b/sqlite.go
@@ -2,10 +2,9 @@ package ratelimit
 
 import (
 	"database/sql"
-	"fmt"
 	"time"
 
-	coreerr "dappco.re/go/core/log"
+	core "dappco.re/go/core"
 	_ "modernc.org/sqlite"
 )
 
@@ -20,7 +19,7 @@ type sqliteStore struct {
 func newSQLiteStore(dbPath string) (*sqliteStore, error) {
 	db, err := sql.Open("sqlite", dbPath)
 	if err != nil {
-		return nil, coreerr.E("ratelimit.newSQLiteStore", "open", err)
+		return nil, core.E("ratelimit.newSQLiteStore", "open", err)
 	}
 
 	// Single connection for PRAGMA consistency.
@@ -28,11 +27,11 @@ func newSQLiteStore(dbPath string) (*sqliteStore, error) {
 
 	if _, err := db.Exec("PRAGMA journal_mode=WAL"); err != nil {
 		db.Close()
-		return nil, coreerr.E("ratelimit.newSQLiteStore", "WAL", err)
+		return nil, core.E("ratelimit.newSQLiteStore", "WAL", err)
 	}
 	if _, err := db.Exec("PRAGMA busy_timeout=5000"); err != nil {
 		db.Close()
-		return nil, coreerr.E("ratelimit.newSQLiteStore", "busy_timeout", err)
+		return nil, core.E("ratelimit.newSQLiteStore", "busy_timeout", err)
 	}
 
 	if err := createSchema(db); err != nil {
@@ -72,7 +71,7 @@ func createSchema(db *sql.DB) error {
 
 	for _, stmt := range stmts {
 		if _, err := db.Exec(stmt); err != nil {
-			return coreerr.E("ratelimit.createSchema", "exec", err)
+			return core.E("ratelimit.createSchema", "exec", err)
 		}
 	}
 	return nil
@@ -82,12 +81,12 @@ func createSchema(db *sql.DB) error {
 func (s *sqliteStore) saveQuotas(quotas map[string]ModelQuota) error {
 	tx, err := s.db.Begin()
 	if err != nil {
-		return coreerr.E("ratelimit.saveQuotas", "begin", err)
+		return core.E("ratelimit.saveQuotas", "begin", err)
 	}
 	defer tx.Rollback()
 
 	if _, err := tx.Exec("DELETE FROM quotas"); err != nil {
-		return coreerr.E("ratelimit.saveQuotas", "clear", err)
+		return core.E("ratelimit.saveQuotas", "clear", err)
 	}
 
 	if err := insertQuotas(tx, quotas); err != nil {
@@ -101,7 +100,7 @@ func (s *sqliteStore) saveQuotas(quotas map[string]ModelQuota) error {
 func (s *sqliteStore) loadQuotas() (map[string]ModelQuota, error) {
 	rows, err := s.db.Query("SELECT model, max_rpm, max_tpm, max_rpd FROM quotas")
 	if err != nil {
-		return nil, coreerr.E("ratelimit.loadQuotas", "query", err)
+		return nil, core.E("ratelimit.loadQuotas", "query", err)
 	}
 	defer rows.Close()
 
@@ -110,12 +109,12 @@ func (s *sqliteStore) loadQuotas() (map[string]ModelQuota, error) {
 		var model string
 		var q ModelQuota
 		if err := rows.Scan(&model, &q.MaxRPM, &q.MaxTPM, &q.MaxRPD); err != nil {
-			return nil, coreerr.E("ratelimit.loadQuotas", "scan", err)
+			return nil, core.E("ratelimit.loadQuotas", "scan", err)
 		}
 		result[model] = q
 	}
 	if err := rows.Err(); err != nil {
-		return nil, coreerr.E("ratelimit.loadQuotas", "rows", err)
+		return nil, core.E("ratelimit.loadQuotas", "rows", err)
 	}
 	return result, nil
 }
@@ -124,7 +123,7 @@ func (s *sqliteStore) loadQuotas() (map[string]ModelQuota, error) {
 func (s *sqliteStore) saveSnapshot(quotas map[string]ModelQuota, state map[string]*UsageStats) error {
 	tx, err := s.db.Begin()
 	if err != nil {
-		return coreerr.E("ratelimit.saveSnapshot", "begin", err)
+		return core.E("ratelimit.saveSnapshot", "begin", err)
 	}
 	defer tx.Rollback()
 
@@ -148,7 +147,7 @@ func (s *sqliteStore) saveSnapshot(quotas map[string]ModelQuota, state map[strin
 func (s *sqliteStore) saveState(state map[string]*UsageStats) error {
 	tx, err := s.db.Begin()
 	if err != nil {
-		return coreerr.E("ratelimit.saveState", "begin", err)
+		return core.E("ratelimit.saveState", "begin", err)
 	}
 	defer tx.Rollback()
 
@@ -166,17 +165,17 @@ func (s *sqliteStore) saveState(state map[string]*UsageStats) error {
 func clearSnapshotTables(tx *sql.Tx, includeQuotas bool) error {
 	if includeQuotas {
 		if _, err := tx.Exec("DELETE FROM quotas"); err != nil {
-			return coreerr.E("ratelimit.saveSnapshot", "clear quotas", err)
+			return core.E("ratelimit.saveSnapshot", "clear quotas", err)
 		}
 	}
 	if _, err := tx.Exec("DELETE FROM requests"); err != nil {
-		return coreerr.E("ratelimit.saveState", "clear requests", err)
+		return core.E("ratelimit.saveState", "clear requests", err)
 	}
 	if _, err := tx.Exec("DELETE FROM tokens"); err != nil {
-		return coreerr.E("ratelimit.saveState", "clear tokens", err)
+		return core.E("ratelimit.saveState", "clear tokens", err)
 	}
 	if _, err := tx.Exec("DELETE FROM daily"); err != nil {
-		return coreerr.E("ratelimit.saveState", "clear daily", err)
+		return core.E("ratelimit.saveState", "clear daily", err)
 	}
 	return nil
 }
@@ -184,13 +183,13 @@ func clearSnapshotTables(tx *sql.Tx, includeQuotas bool) error {
 func insertQuotas(tx *sql.Tx, quotas map[string]ModelQuota) error {
 	stmt, err := tx.Prepare("INSERT INTO quotas (model, max_rpm, max_tpm, max_rpd) VALUES (?, ?, ?, ?)")
 	if err != nil {
-		return coreerr.E("ratelimit.saveQuotas", "prepare", err)
+		return core.E("ratelimit.saveQuotas", "prepare", err)
 	}
 	defer stmt.Close()
 
 	for model, q := range quotas {
 		if _, err := stmt.Exec(model, q.MaxRPM, q.MaxTPM, q.MaxRPD); err != nil {
-			return coreerr.E("ratelimit.saveQuotas", fmt.Sprintf("exec %s", model), err)
+			return core.E("ratelimit.saveQuotas", core.Concat("exec ", model), err)
 		}
 	}
 	return nil
@@ -199,19 +198,19 @@ func insertQuotas(tx *sql.Tx, quotas map[string]ModelQuota) error {
 func insertState(tx *sql.Tx, state map[string]*UsageStats) error {
 	reqStmt, err := tx.Prepare("INSERT INTO requests (model, ts) VALUES (?, ?)")
 	if err != nil {
-		return coreerr.E("ratelimit.saveState", "prepare requests", err)
+		return core.E("ratelimit.saveState", "prepare requests", err)
 	}
 	defer reqStmt.Close()
 
 	tokStmt, err := tx.Prepare("INSERT INTO tokens (model, ts, count) VALUES (?, ?, ?)")
 	if err != nil {
-		return coreerr.E("ratelimit.saveState", "prepare tokens", err)
+		return core.E("ratelimit.saveState", "prepare tokens", err)
 	}
 	defer tokStmt.Close()
 
 	dayStmt, err := tx.Prepare("INSERT INTO daily (model, day_start, day_count) VALUES (?, ?, ?)")
 	if err != nil {
-		return coreerr.E("ratelimit.saveState", "prepare daily", err)
+		return core.E("ratelimit.saveState", "prepare daily", err)
 	}
 	defer dayStmt.Close()
 
@@ -221,16 +220,16 @@ func insertState(tx *sql.Tx, state map[string]*UsageStats) error {
 		}
 		for _, t := range stats.Requests {
 			if _, err := reqStmt.Exec(model, t.UnixNano()); err != nil {
-				return coreerr.E("ratelimit.saveState", fmt.Sprintf("insert request %s", model), err)
+				return core.E("ratelimit.saveState", core.Concat("insert request ", model), err)
 			}
 		}
 		for _, te := range stats.Tokens {
 			if _, err := tokStmt.Exec(model, te.Time.UnixNano(), te.Count); err != nil {
-				return coreerr.E("ratelimit.saveState", fmt.Sprintf("insert token %s", model), err)
+				return core.E("ratelimit.saveState", core.Concat("insert token ", model), err)
 			}
 		}
 		if _, err := dayStmt.Exec(model, stats.DayStart.UnixNano(), stats.DayCount); err != nil {
-			return coreerr.E("ratelimit.saveState", fmt.Sprintf("insert daily %s", model), err)
+			return core.E("ratelimit.saveState", core.Concat("insert daily ", model), err)
 		}
 	}
 	return nil
@@ -238,7 +237,7 @@ func insertState(tx *sql.Tx, state map[string]*UsageStats) error {
 
 func commitTx(tx *sql.Tx, scope string) error {
 	if err := tx.Commit(); err != nil {
-		return coreerr.E(scope, "commit", err)
+		return core.E(scope, "commit", err)
 	}
 	return nil
 }
@@ -250,7 +249,7 @@ func (s *sqliteStore) loadState() (map[string]*UsageStats, error) {
 	// Load daily counters first (these define which models have state).
 	rows, err := s.db.Query("SELECT model, day_start, day_count FROM daily")
 	if err != nil {
-		return nil, coreerr.E("ratelimit.loadState", "query daily", err)
+		return nil, core.E("ratelimit.loadState", "query daily", err)
 	}
 	defer rows.Close()
 
@@ -259,7 +258,7 @@ func (s *sqliteStore) loadState() (map[string]*UsageStats, error) {
 		var dayStartNano int64
 		var dayCount int
 		if err := rows.Scan(&model, &dayStartNano, &dayCount); err != nil {
-			return nil, coreerr.E("ratelimit.loadState", "scan daily", err)
+			return nil, core.E("ratelimit.loadState", "scan daily", err)
 		}
 		result[model] = &UsageStats{
 			DayStart: time.Unix(0, dayStartNano),
@@ -267,13 +266,13 @@ func (s *sqliteStore) loadState() (map[string]*UsageStats, error) {
 		}
 	}
 	if err := rows.Err(); err != nil {
-		return nil, coreerr.E("ratelimit.loadState", "daily rows", err)
+		return nil, core.E("ratelimit.loadState", "daily rows", err)
 	}
 
 	// Load requests.
 	reqRows, err := s.db.Query("SELECT model, ts FROM requests ORDER BY ts")
 	if err != nil {
-		return nil, coreerr.E("ratelimit.loadState", "query requests", err)
+		return nil, core.E("ratelimit.loadState", "query requests", err)
 	}
 	defer reqRows.Close()
 
@@ -281,7 +280,7 @@ func (s *sqliteStore) loadState() (map[string]*UsageStats, error) {
 		var model string
 		var tsNano int64
 		if err := reqRows.Scan(&model, &tsNano); err != nil {
-			return nil, coreerr.E("ratelimit.loadState", "scan requests", err)
+			return nil, core.E("ratelimit.loadState", "scan requests", err)
 		}
 		if _, ok := result[model]; !ok {
 			result[model] = &UsageStats{}
@@ -289,13 +288,13 @@ func (s *sqliteStore) loadState() (map[string]*UsageStats, error) {
 		result[model].Requests = append(result[model].Requests, time.Unix(0, tsNano))
 	}
 	if err := reqRows.Err(); err != nil {
-		return nil, coreerr.E("ratelimit.loadState", "request rows", err)
+		return nil, core.E("ratelimit.loadState", "request rows", err)
 	}
 
 	// Load tokens.
 	tokRows, err := s.db.Query("SELECT model, ts, count FROM tokens ORDER BY ts")
 	if err != nil {
-		return nil, coreerr.E("ratelimit.loadState", "query tokens", err)
+		return nil, core.E("ratelimit.loadState", "query tokens", err)
 	}
 	defer tokRows.Close()
 
@@ -304,7 +303,7 @@ func (s *sqliteStore) loadState() (map[string]*UsageStats, error) {
 		var tsNano int64
 		var count int
 		if err := tokRows.Scan(&model, &tsNano, &count); err != nil {
-			return nil, coreerr.E("ratelimit.loadState", "scan tokens", err)
+			return nil, core.E("ratelimit.loadState", "scan tokens", err)
 		}
 		if _, ok := result[model]; !ok {
 			result[model] = &UsageStats{}
@@ -315,7 +314,7 @@ func (s *sqliteStore) loadState() (map[string]*UsageStats, error) {
 		})
 	}
 	if err := tokRows.Err(); err != nil {
-		return nil, coreerr.E("ratelimit.loadState", "token rows", err)
+		return nil, core.E("ratelimit.loadState", "token rows", err)
 	}
 
 	return result, nil