v0.1.9 kv flag added, unix and nofs build tags, heartbeat and rotation filename and test update

builder.go

@@ -7,8 +7,10 @@ import (
 // Builder provides a fluent API for building logger configurations
 // It wraps a Config instance and provides chainable methods for setting values
 type Builder struct {
-	cfg *Config
+	err     error // Accumulate errors for deferred handling
-	err error // Accumulate errors for deferred handling
+	cfg     *Config
+	ctxTag  string
+	ctxVals []string
 }
 
 // NewBuilder creates a new configuration builder with default values
@@ -18,6 +20,13 @@ func NewBuilder() *Builder {
 	}
 }
 
+// ContextKeys names the record keys for Context values
+func (b *Builder) ContextKeys(tag string, vals ...string) *Builder {
+	b.ctxTag = tag
+	b.ctxVals = vals
+	return b
+}
+
 // Build creates a new Logger instance with the specified configuration
 func (b *Builder) Build() (*Logger, error) {
 	if b.err != nil {
@@ -31,6 +40,9 @@ func (b *Builder) Build() (*Logger, error) {
 	if err := logger.ApplyConfig(b.cfg); err != nil {
 		return nil, err
 	}
+	if b.ctxTag != "" || len(b.ctxVals) > 0 {
+		logger.SetContextKeys(b.ctxTag, b.ctxVals...)
+	}
 
 	return logger, nil
 }

constant.go

@@ -28,6 +28,7 @@ const (
 	FlagShowTimestamp  = formatter.FlagShowTimestamp
 	FlagShowLevel      = formatter.FlagShowLevel
 	FlagStructuredJSON = formatter.FlagStructuredJSON
+	FlagKV             = formatter.FlagKV
 	FlagNoTimestamp    = formatter.FlagNoTimestamp
 	FlagNoLevel        = formatter.FlagNoLevel
 	FlagDefault        = formatter.FlagDefault
@@ -57,4 +58,3 @@ const (
 	adaptiveIntervalFactor float64 = 1.5 // Slow down
 	adaptiveSpeedUpFactor  float64 = 0.8 // Speed up
 )
-

formatter/formatter.go

@@ -34,6 +34,7 @@ const (
 	FlagStructuredJSON int64 = 0b1000
 	FlagNoTimestamp    int64 = 0b010000
 	FlagNoLevel        int64 = 0b100000
+	FlagKV             int64 = 0b1000000 // args are alternating string keys and values
 	FlagDefault              = FlagShowTimestamp | FlagShowLevel
 )
 
@@ -44,7 +45,31 @@ type Formatter struct {
 	timestampFormat string
 	showTimestamp   bool
 	showLevel       bool
+	ctxKeys         ContextKeys
 	buf             []byte
+
+	// Serializers are stateless and format-fixed; built once to keep the
+	// per-record path allocation-free
+	serTxt  *sanitizer.Serializer
+	serJSON *sanitizer.Serializer
+	serRaw  *sanitizer.Serializer
+}
+
+// ContextSlots is the number of correlation values a Context carries
+const ContextSlots = 3
+
+// Context carries caller-stamped values emitted with a record.
+// Tag names the source; Vals are correlation counters keyed by ContextKeys.
+type Context struct {
+	Tag  string
+	Vals [ContextSlots]uint64
+}
+
+// ContextKeys names the record keys for Context fields; empty names are omitted.
+// Names are emitted verbatim and must be plain identifiers.
+type ContextKeys struct {
+	Tag  string
+	Vals [ContextSlots]string
 }
 
 // New creates a formatter with the provided sanitizer
@@ -62,6 +87,30 @@ func New(s ...*sanitizer.Sanitizer) *Formatter {
 		showTimestamp:   true,
 		showLevel:       true,
 		buf:             make([]byte, 0, 1024),
+		serTxt:          sanitizer.NewSerializer("txt", san),
+		serJSON:         sanitizer.NewSerializer("json", san),
+		serRaw:          sanitizer.NewSerializer("raw", san),
+	}
+}
+
+// ContextKeys sets the record keys used for Context values
+func (f *Formatter) ContextKeys(tag string, vals ...string) *Formatter {
+	f.ctxKeys = ContextKeys{Tag: tag}
+	for i := 0; i < len(vals) && i < ContextSlots; i++ {
+		f.ctxKeys.Vals[i] = vals[i]
+	}
+	return f
+}
+
+// serializerFor returns the cached serializer for a normalized format name
+func (f *Formatter) serializerFor(format string) *sanitizer.Serializer {
+	switch format {
+	case "json":
+		return f.serJSON
+	case "raw":
+		return f.serRaw
+	default:
+		return f.serTxt
 	}
 }
 
@@ -94,14 +143,24 @@ func (f *Formatter) ShowTimestamp(show bool) *Formatter {
 // Format formats using configured options resolved against explicit flags.
 // Returned slice aliases the internal buffer.
 func (f *Formatter) Format(flags int64, timestamp time.Time, level int64, trace string, args []any) []byte {
-	f.buf = f.AppendFormat(f.buf[:0], flags, timestamp, level, trace, args)
+	return f.FormatCtx(Context{}, flags, timestamp, level, trace, args)
+}
+
+// FormatCtx is Format with caller-stamped context.
+// Returned slice aliases the internal buffer.
+func (f *Formatter) FormatCtx(ctx Context, flags int64, timestamp time.Time, level int64, trace string, args []any) []byte {
+	f.buf = f.AppendFormatCtx(f.buf[:0], ctx, flags, timestamp, level, trace, args)
 	return f.buf
 }
 
 // AppendFormat appends a formatted entry to dst using configured options
 // resolved against explicit flags. Safe for concurrent use.
 func (f *Formatter) AppendFormat(dst []byte, flags int64, timestamp time.Time, level int64, trace string, args []any) []byte {
-	// CHANGED: D3 — additive resolution replaces `flags == 0` guard
+	return f.AppendFormatCtx(dst, Context{}, flags, timestamp, level, trace, args)
+}
+
+// AppendFormatCtx is AppendFormat with caller-stamped context
+func (f *Formatter) AppendFormatCtx(dst []byte, ctx Context, flags int64, timestamp time.Time, level int64, trace string, args []any) []byte {
 	eff := flags &^ (FlagShowTimestamp | FlagShowLevel)
 	if resolveShow(flags, FlagShowTimestamp, FlagNoTimestamp, f.showTimestamp) {
 		eff |= FlagShowTimestamp
@@ -109,31 +168,25 @@ func (f *Formatter) AppendFormat(dst []byte, flags int64, timestamp time.Time, l
 	if resolveShow(flags, FlagShowLevel, FlagNoLevel, f.showLevel) {
 		eff |= FlagShowLevel
 	}
-	return f.AppendFormatWithOptions(dst, f.format, eff, timestamp, level, trace, args)
+	return f.AppendFormatWithOptionsCtx(dst, f.format, ctx, eff, timestamp, level, trace, args)
-}
-
-func resolveShow(flags, show, no int64, configured bool) bool {
-	switch {
-	case flags&no != 0:
-		return false
-	case flags&show != 0:
-		return true
-	default:
-		return configured
-	}
 }
 
 // FormatWithOptions formats with explicit format and flags, ignoring
 // configured display defaults. Returned slice aliases the internal buffer.
 func (f *Formatter) FormatWithOptions(format string, flags int64, timestamp time.Time, level int64, trace string, args []any) []byte {
-	f.buf = f.AppendFormatWithOptions(f.buf[:0], format, flags, timestamp, level, trace, args)
+	f.buf = f.AppendFormatWithOptionsCtx(f.buf[:0], format, Context{}, flags, timestamp, level, trace, args)
 	return f.buf
 }
 
-// AppendFormatWithOptions is the allocation-explicit core. Safe for
+// AppendFormatWithOptions is the compatibility wrapper over the context core
-// concurrent use. Unknown formats fall back to "txt".
 func (f *Formatter) AppendFormatWithOptions(dst []byte, format string, flags int64, timestamp time.Time, level int64, trace string, args []any) []byte {
-	// FlagRaw completely bypasses formatting and sanitization
+	return f.AppendFormatWithOptionsCtx(dst, format, Context{}, flags, timestamp, level, trace, args)
+}
+
+// AppendFormatWithOptionsCtx is the allocation-explicit core. Safe for
+// concurrent use. Unknown formats fall back to "txt".
+func (f *Formatter) AppendFormatWithOptionsCtx(dst []byte, format string, ctx Context, flags int64, timestamp time.Time, level int64, trace string, args []any) []byte {
+	// FlagRaw completely bypasses formatting, context, and sanitization
 	if flags&FlagRaw != 0 {
 		for i, arg := range args {
 			if i > 0 {
@@ -155,9 +208,8 @@ func (f *Formatter) AppendFormatWithOptions(dst []byte, format string, flags int
 		return dst
 	}
 
-	// unknown formats normalize to txt instead of returning nil
 	format = normalizeFormat(format)
-	serializer := sanitizer.NewSerializer(format, f.sanitizer)
+	serializer := f.serializerFor(format)
 
 	switch format {
 	case "raw":
@@ -166,9 +218,20 @@ func (f *Formatter) AppendFormatWithOptions(dst []byte, format string, flags int
 		}
 		return dst
 	case "json":
-		return f.appendJSON(dst, flags, timestamp, level, trace, args, serializer)
+		return f.appendJSON(dst, ctx, flags, timestamp, level, trace, args, serializer)
 	default: // "txt"
-		return f.appendTxt(dst, flags, timestamp, level, trace, args, serializer)
+		return f.appendTxt(dst, ctx, flags, timestamp, level, trace, args, serializer)
+	}
+}
+
+func resolveShow(flags, show, no int64, configured bool) bool {
+	switch {
+	case flags&no != 0:
+		return false
+	case flags&show != 0:
+		return true
+	default:
+		return configured
 	}
 }
 
@@ -188,10 +251,8 @@ func (f *Formatter) FormatValue(v any) []byte {
 }
 
 // AppendValue appends a single formatted value to dst. Safe for concurrent use.
-// ADDED: R1
 func (f *Formatter) AppendValue(dst []byte, v any) []byte {
-	serializer := sanitizer.NewSerializer(normalizeFormat(f.format), f.sanitizer)
+	return f.appendValue(dst, v, f.serializerFor(normalizeFormat(f.format)), false)
-	return f.appendValue(dst, v, serializer, false)
 }
 
 // FormatArgs formats multiple arguments. Returned slice aliases the internal buffer.
@@ -202,9 +263,8 @@ func (f *Formatter) FormatArgs(args ...any) []byte {
 
 // AppendArgs appends multiple space-separated values to dst. Safe for
 // concurrent use.
-// ADDED: R1
 func (f *Formatter) AppendArgs(dst []byte, args ...any) []byte {
-	serializer := sanitizer.NewSerializer(normalizeFormat(f.format), f.sanitizer)
+	serializer := f.serializerFor(normalizeFormat(f.format))
 	for i, arg := range args {
 		dst = f.appendValue(dst, arg, serializer, i > 0)
 	}
@@ -278,8 +338,29 @@ func LevelToString(level int64) string {
 	}
 }
 
+// appendJSONKey writes a quoted literal key followed by ':'
+func appendJSONKey(dst []byte, key string) []byte {
+	dst = append(dst, '"')
+	dst = append(dst, key...)
+	dst = append(dst, '"', ':')
+	return dst
+}
+
+// isKV reports whether args form an even-length list with string keys
+func isKV(args []any) bool {
+	if len(args) == 0 || len(args)%2 != 0 {
+		return false
+	}
+	for i := 0; i < len(args); i += 2 {
+		if _, ok := args[i].(string); !ok {
+			return false
+		}
+	}
+	return true
+}
+
 // appendJSON unifies JSON output over a caller-provided buffer
-func (f *Formatter) appendJSON(dst []byte, flags int64, timestamp time.Time, level int64, trace string, args []any, serializer *sanitizer.Serializer) []byte {
+func (f *Formatter) appendJSON(dst []byte, ctx Context, flags int64, timestamp time.Time, level int64, trace string, args []any, serializer *sanitizer.Serializer) []byte {
 	dst = append(dst, '{')
 	needsComma := false
 
@@ -300,6 +381,27 @@ func (f *Formatter) appendJSON(dst []byte, flags int64, timestamp time.Time, lev
 		needsComma = true
 	}
 
+	// Caller-stamped context, emitted as top-level keys
+	if ctx.Tag != "" && f.ctxKeys.Tag != "" {
+		if needsComma {
+			dst = append(dst, ',')
+		}
+		dst = appendJSONKey(dst, f.ctxKeys.Tag)
+		serializer.WriteString(&dst, ctx.Tag)
+		needsComma = true
+	}
+	for i, key := range f.ctxKeys.Vals {
+		if key == "" {
+			continue
+		}
+		if needsComma {
+			dst = append(dst, ',')
+		}
+		dst = appendJSONKey(dst, key)
+		dst = strconv.AppendUint(dst, ctx.Vals[i], 10)
+		needsComma = true
+	}
+
 	if trace != "" {
 		if needsComma {
 			dst = append(dst, ',')
@@ -336,19 +438,32 @@ func (f *Formatter) appendJSON(dst []byte, flags int64, timestamp time.Time, lev
 		}
 	}
 
-	// Regular JSON with fields array
 	if len(args) > 0 {
 		if needsComma {
 			dst = append(dst, ',')
 		}
-		dst = append(dst, `"fields":[`...)
+		// Keyed object when the caller declares k/v args, positional array otherwise
-		for i, arg := range args {
+		if flags&FlagKV != 0 && isKV(args) {
-			if i > 0 {
+			dst = append(dst, `"fields":{`...)
-				dst = append(dst, ',')
+			for i := 0; i < len(args); i += 2 {
+				if i > 0 {
+					dst = append(dst, ',')
+				}
+				serializer.WriteString(&dst, args[i].(string))
+				dst = append(dst, ':')
+				dst = f.appendValue(dst, args[i+1], serializer, false)
 			}
-			dst = f.appendValue(dst, arg, serializer, false)
+			dst = append(dst, '}')
+		} else {
+			dst = append(dst, `"fields":[`...)
+			for i, arg := range args {
+				if i > 0 {
+					dst = append(dst, ',')
+				}
+				dst = f.appendValue(dst, arg, serializer, false)
+			}
+			dst = append(dst, ']')
 		}
-		dst = append(dst, ']')
 	}
 
 	dst = append(dst, '}', '\n')
@@ -356,7 +471,7 @@ func (f *Formatter) appendJSON(dst []byte, flags int64, timestamp time.Time, lev
 }
 
 // appendTxt handles txt format output over a caller-provided buffer
-func (f *Formatter) appendTxt(dst []byte, flags int64, timestamp time.Time, level int64, trace string, args []any, serializer *sanitizer.Serializer) []byte {
+func (f *Formatter) appendTxt(dst []byte, ctx Context, flags int64, timestamp time.Time, level int64, trace string, args []any, serializer *sanitizer.Serializer) []byte {
 	needsSpace := false
 
 	if flags&FlagShowTimestamp != 0 {
@@ -372,14 +487,35 @@ func (f *Formatter) appendTxt(dst []byte, flags int64, timestamp time.Time, leve
 		needsSpace = true
 	}
 
+	if ctx.Tag != "" && f.ctxKeys.Tag != "" {
+		if needsSpace {
+			dst = append(dst, ' ')
+		}
+		dst = append(dst, f.ctxKeys.Tag...)
+		dst = append(dst, '=')
+		dst = f.appendValue(dst, ctx.Tag, serializer, false)
+		needsSpace = true
+	}
+	for i, key := range f.ctxKeys.Vals {
+		if key == "" {
+			continue
+		}
+		if needsSpace {
+			dst = append(dst, ' ')
+		}
+		dst = append(dst, key...)
+		dst = append(dst, '=')
+		dst = strconv.AppendUint(dst, ctx.Vals[i], 10)
+		needsSpace = true
+	}
+
 	if trace != "" {
 		if needsSpace {
 			dst = append(dst, ' ')
 		}
 		// Sanitize trace to prevent terminal control sequence injection
-		traceHandler := sanitizer.NewSerializer("txt", f.sanitizer)
 		tempBuf := make([]byte, 0, len(trace)*2)
-		traceHandler.WriteString(&tempBuf, trace)
+		f.serTxt.WriteString(&tempBuf, trace)
 		// Extract content without quotes if added by txt serializer
 		if len(tempBuf) > 2 && tempBuf[0] == '"' && tempBuf[len(tempBuf)-1] == '"' {
 			dst = append(dst, tempBuf[1:len(tempBuf)-1]...)
@@ -389,9 +525,21 @@ func (f *Formatter) appendTxt(dst []byte, flags int64, timestamp time.Time, leve
 		needsSpace = true
 	}
 
-	for _, arg := range args {
+	if flags&FlagKV != 0 && isKV(args) {
-		dst = f.appendValue(dst, arg, serializer, needsSpace)
+		for i := 0; i < len(args); i += 2 {
-		needsSpace = true
+			if needsSpace {
+				dst = append(dst, ' ')
+			}
+			dst = append(dst, args[i].(string)...)
+			dst = append(dst, '=')
+			dst = f.appendValue(dst, args[i+1], serializer, false)
+			needsSpace = true
+		}
+	} else {
+		for _, arg := range args {
+			dst = f.appendValue(dst, arg, serializer, needsSpace)
+			needsSpace = true
+		}
 	}
 
 	dst = append(dst, '\n')
@@ -402,4 +550,3 @@ func (f *Formatter) appendTxt(dst []byte, flags int64, timestamp time.Time, leve
 func (f *Formatter) Reset() {
 	f.buf = f.buf[:0]
 }
-

heartbeat.go

@@ -128,18 +128,16 @@ func (l *Logger) logSysHeartbeat() {
 	l.writeHeartbeatRecord(LevelSys, sysArgs)
 }
 
-// writeHeartbeatRecord creates and sends a heartbeat log record through the main processing channel
+// writeHeartbeatRecord creates and sends a heartbeat record, bypassing the level gate
 func (l *Logger) writeHeartbeatRecord(level int64, args []any) {
 	if l.state.LoggerDisabled.Load() || l.state.ShutdownCalled.Load() {
 		return
 	}
 
-	// Create heartbeat record with appropriate flags
 	record := logRecord{
-		Flags:     FlagDefault | FlagShowLevel,
+		Flags:     FlagDefault | FlagKV,
 		TimeStamp: time.Now(),
 		Level:     level,
-		Trace:     "",
 		Args:      args,
 	}
 

integration_test.go

@@ -53,7 +53,7 @@ func TestFullLifecycle(t *testing.T) {
 
 	// MaxSizeKB=1 forces rotation, so assertions span every file in the directory
 	mustEventually(t, 3*time.Second, "proc heartbeat emitted", func() bool {
-		return strings.Contains(readAllLogs(t, tmpDir), `"type","proc"`)
+		return strings.Contains(readAllLogs(t, tmpDir), `"type":"proc"`)
 	})
 	mustNoErr(t, logger.Flush(time.Second), "Flush")
 
@@ -63,8 +63,8 @@ func TestFullLifecycle(t *testing.T) {
 	contains(t, content, `"user_id":123`, "structured field")
 	contains(t, content, "raw data write", "raw write")
 	contains(t, content, "after reconfiguration", "post-reconfiguration record")
-	contains(t, content, `"type","disk"`, "disk heartbeat")
+	contains(t, content, `"type":"disk"`, "disk heartbeat")
-	contains(t, content, `"type","sys"`, "sys heartbeat")
+	contains(t, content, `"type":"sys"`, "sys heartbeat")
 
 	files, err := os.ReadDir(tmpDir)
 	mustNoErr(t, err, "ReadDir")
@@ -162,4 +162,3 @@ func TestErrorRecovery(t *testing.T) {
 		isTrue(t, logger.state.DiskStatusOK.Load(), "DiskStatusOK after recovery")
 	})
 }
-

logger.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"math"
 	"os"
 	"sync"
 	"sync/atomic"
@@ -17,10 +18,16 @@ import (
 type Logger struct {
 	currentConfig atomic.Value // stores *Config
 	formatter     atomic.Value // stores *formatter.Formatter
+	ctxKeys       atomic.Pointer[formatter.ContextKeys]
+	spawner       atomic.Pointer[func(func())]
+	errHandler    atomic.Pointer[func(string)]
 	state         State
 	initMu        sync.Mutex
 }
 
+// levelOff closes the emit gate without touching configuration
+const levelOff int64 = math.MaxInt64
+
 // NewLogger creates a new Logger instance with default settings
 func NewLogger() *Logger {
 	l := &Logger{}
@@ -28,14 +35,20 @@ func NewLogger() *Logger {
 	// Set default configuration
 	defaultCfg := DefaultConfig()
 	l.currentConfig.Store(defaultCfg)
+	l.rebuildFormatter(defaultCfg)
 
-	// Initialize default formatter to prevent nil access
+	// Emission stays closed until ApplyConfig and Start succeed
-	defaultFormatter := formatter.New(sanitizer.New()).
+	l.state.Level.Store(levelOff)
-		Type(defaultCfg.Format).
+	l.state.Flags.Store(flagsFromConfig(defaultCfg))
-		TimestampFormat(defaultCfg.TimestampFormat).
+	l.state.TraceDepth.Store(defaultCfg.TraceDepth)
-		ShowLevel(defaultCfg.ShowLevel).
+
-		ShowTimestamp(defaultCfg.ShowTimestamp)
+	// // Initialize default formatter to prevent nil access
-	l.formatter.Store(defaultFormatter)
+	// defaultFormatter := formatter.New(sanitizer.New()).
+	// 	Type(defaultCfg.Format).
+	// 	TimestampFormat(defaultCfg.TimestampFormat).
+	// 	ShowLevel(defaultCfg.ShowLevel).
+	// 	ShowTimestamp(defaultCfg.ShowTimestamp)
+	// l.formatter.Store(defaultFormatter)
 
 	// Initialize the state
 	l.state.IsInitialized.Store(false)
@@ -54,13 +67,17 @@ func NewLogger() *Logger {
 	l.state.TotalRotations.Store(0)
 	l.state.TotalDeletions.Store(0)
 
-	// Create a closed channel initially to prevent nil pointer issues
+	// Typed nil: a non-blocking send on a nil channel always takes default
-	initialChan := make(chan logRecord)
+	l.state.ActiveLogChannel.Store((chan logRecord)(nil))
-	close(initialChan)
-	l.state.ActiveLogChannel.Store(initialChan)
-
 	l.state.flushRequestChan = make(chan chan struct{}, 1)
 
+	// // Create a closed channel initially to prevent nil pointer issues
+	// initialChan := make(chan logRecord)
+	// close(initialChan)
+	// l.state.ActiveLogChannel.Store(initialChan)
+	//
+	// l.state.flushRequestChan = make(chan chan struct{}, 1)
+
 	return l
 }
 
@@ -112,237 +129,6 @@ func (l *Logger) GetConfig() *Config {
 	return l.getConfig().Clone()
 }
 
-// Start begins log processing. Safe to call multiple times
-// Returns error if logger is not initialized
-func (l *Logger) Start() error {
-	if !l.state.IsInitialized.Load() {
-		return fmtErrorf("logger not initialized, call ApplyConfig first")
-	}
-
-	// Check if processor didn't exit cleanly last time
-	if l.state.Started.Load() && !l.state.ProcessorExited.Load() {
-		// Force stop to clean up
-		l.internalLog("warning - processor still running from previous start, forcing stop\n")
-		if err := l.Stop(); err != nil {
-			return fmtErrorf("failed to stop hung processor: %w", err)
-		}
-	}
-
-	// Only start if not already started
-	if l.state.Started.CompareAndSwap(false, true) {
-		cfg := l.getConfig()
-
-		// Create log channel
-		logChannel := make(chan logRecord, cfg.BufferSize)
-		l.state.ActiveLogChannel.Store(logChannel)
-
-		// Start processor
-		l.state.ProcessorExited.Store(false)
-		go l.processLogs(logChannel)
-	}
-
-	return nil
-}
-
-// Stop halts log processing. Can be restarted with Start()
-// Returns nil if already stopped
-func (l *Logger) Stop(timeout ...time.Duration) error {
-	if !l.state.Started.CompareAndSwap(true, false) {
-		return nil // Already stopped
-	}
-
-	// Calculate effective timeout
-	var effectiveTimeout time.Duration
-	if len(timeout) > 0 {
-		effectiveTimeout = timeout[0]
-	} else {
-		cfg := l.getConfig()
-		effectiveTimeout = 2 * time.Duration(cfg.FlushIntervalMs) * time.Millisecond
-	}
-
-	// Get current channel and close it
-	ch := l.getCurrentLogChannel()
-	if ch != nil {
-		// Create closed channel for immediate replacement
-		closedChan := make(chan logRecord)
-		close(closedChan)
-		l.state.ActiveLogChannel.Store(closedChan)
-
-		// Close the actual channel to signal processor
-		close(ch)
-	}
-
-	// Wait for processor to exit (with timeout)
-	deadline := time.Now().Add(effectiveTimeout)
-	for time.Now().Before(deadline) {
-		if l.state.ProcessorExited.Load() {
-			break
-		}
-		time.Sleep(10 * time.Millisecond)
-	}
-
-	if !l.state.ProcessorExited.Load() {
-		return fmtErrorf("processor did not exit within timeout (%v)", effectiveTimeout)
-	}
-
-	return nil
-}
-
-// Shutdown gracefully closes the logger, attempting to flush pending records
-// If no timeout is provided, uses a default of 2x flush interval
-func (l *Logger) Shutdown(timeout ...time.Duration) error {
-	if !l.state.ShutdownCalled.CompareAndSwap(false, true) {
-		return nil
-	}
-
-	l.state.LoggerDisabled.Store(true)
-
-	if !l.state.IsInitialized.Load() {
-		l.state.ShutdownCalled.Store(false)
-		l.state.LoggerDisabled.Store(false)
-		l.state.ProcessorExited.Store(true)
-		return nil
-	}
-
-	var stopErr error
-	if l.state.Started.Load() {
-		stopErr = l.Stop(timeout...)
-	}
-
-	l.state.IsInitialized.Store(false)
-
-	var finalErr error
-	cfPtr := l.state.CurrentFile.Load()
-	if cfPtr != nil {
-		if currentLogFile, ok := cfPtr.(*os.File); ok && currentLogFile != nil {
-			if err := currentLogFile.Sync(); err != nil {
-				syncErr := fmtErrorf("failed to sync log file '%s' during shutdown: %w", currentLogFile.Name(), err)
-				finalErr = errors.Join(finalErr, syncErr)
-			}
-			if err := currentLogFile.Close(); err != nil {
-				closeErr := fmtErrorf("failed to close log file '%s' during shutdown: %w", currentLogFile.Name(), err)
-				finalErr = errors.Join(finalErr, closeErr)
-			}
-			l.state.CurrentFile.Store((*os.File)(nil))
-		}
-	}
-
-	if stopErr != nil {
-		finalErr = errors.Join(finalErr, stopErr)
-	}
-
-	return finalErr
-}
-
-// Flush explicitly triggers a sync of the current log file buffer to disk and waits for completion or timeout
-func (l *Logger) Flush(timeout time.Duration) error {
-	l.state.flushMutex.Lock()
-	defer l.state.flushMutex.Unlock()
-
-	// State checks
-	if !l.state.IsInitialized.Load() || l.state.ShutdownCalled.Load() {
-		return fmtErrorf("logger not initialized or already shut down")
-	}
-	if !l.state.Started.Load() {
-		return fmtErrorf("logger not started")
-	}
-
-	// Create a channel to wait for confirmation from the processor
-	confirmChan := make(chan struct{})
-
-	// Send the request with the confirmation channel
-	select {
-	case l.state.flushRequestChan <- confirmChan:
-		// Request sent
-	case <-time.After(minWaitTime): // Short timeout to prevent blocking if processor is stuck
-		return fmtErrorf("failed to send flush request to processor (possible deadlock or high load)")
-	}
-
-	select {
-	case <-confirmChan:
-		return nil
-	case <-time.After(timeout):
-		return fmtErrorf("timeout waiting for flush confirmation (%v)", timeout)
-	}
-}
-
-// Debug logs a message at debug level
-func (l *Logger) Debug(args ...any) {
-	flags := l.getFlags()
-	cfg := l.getConfig()
-	l.log(flags, LevelDebug, cfg.TraceDepth, args...)
-}
-
-// Info logs a message at info level
-func (l *Logger) Info(args ...any) {
-	flags := l.getFlags()
-	cfg := l.getConfig()
-	l.log(flags, LevelInfo, cfg.TraceDepth, args...)
-}
-
-// Warn logs a message at warning level
-func (l *Logger) Warn(args ...any) {
-	flags := l.getFlags()
-	cfg := l.getConfig()
-	l.log(flags, LevelWarn, cfg.TraceDepth, args...)
-}
-
-// Error logs a message at error level
-func (l *Logger) Error(args ...any) {
-	flags := l.getFlags()
-	cfg := l.getConfig()
-	l.log(flags, LevelError, cfg.TraceDepth, args...)
-}
-
-// DebugTrace logs a debug message with function call trace
-func (l *Logger) DebugTrace(depth int, args ...any) {
-	flags := l.getFlags()
-	l.log(flags, LevelDebug, int64(depth), args...)
-}
-
-// InfoTrace logs an info message with function call trace
-func (l *Logger) InfoTrace(depth int, args ...any) {
-	flags := l.getFlags()
-	l.log(flags, LevelInfo, int64(depth), args...)
-}
-
-// WarnTrace logs a warning message with function call trace
-func (l *Logger) WarnTrace(depth int, args ...any) {
-	flags := l.getFlags()
-	l.log(flags, LevelWarn, int64(depth), args...)
-}
-
-// ErrorTrace logs an error message with function call trace
-func (l *Logger) ErrorTrace(depth int, args ...any) {
-	flags := l.getFlags()
-	l.log(flags, LevelError, int64(depth), args...)
-}
-
-// Log writes a timestamp-only record without level information
-func (l *Logger) Log(args ...any) {
-	l.log(FlagShowTimestamp|FlagNoLevel, LevelInfo, 0, args...)
-}
-
-// Message writes a plain record without timestamp or level info
-func (l *Logger) Message(args ...any) {
-	l.log(FlagNoTimestamp|FlagNoLevel, LevelInfo, 0, args...)
-}
-
-// LogTrace writes a timestamp record with call trace but no level info
-func (l *Logger) LogTrace(depth int, args ...any) {
-	l.log(FlagShowTimestamp|FlagNoLevel, LevelInfo, int64(depth), args...)
-}
-
-// LogStructured logs a message with structured fields as proper JSON
-func (l *Logger) LogStructured(level int64, message string, fields map[string]any) {
-	l.log(l.getFlags()|FlagStructuredJSON, level, 0, message, fields)
-}
-
-// Write outputs raw, unformatted data ignoring configured format and sanitization without trailing new line
-func (l *Logger) Write(args ...any) {
-	l.log(FlagRaw, LevelInfo, 0, args...)
-}
-
 // getConfig returns the current configuration (thread-safe)
 func (l *Logger) getConfig() *Config {
 	return l.currentConfig.Load().(*Config)
@@ -353,20 +139,19 @@ func (l *Logger) applyConfig(cfg *Config) error {
 	oldCfg := l.getConfig()
 	l.currentConfig.Store(cfg)
 
-	// Create formatter with sanitizer
+	// Shared formatter and sanitizer constructor with SetContextKeys
-	s := sanitizer.New().Policy(cfg.Sanitization)
+	l.rebuildFormatter(cfg)
-	newFormatter := formatter.New(s).
+
-		Type(cfg.Format).
+	// Emit fast-path mirrors
-		TimestampFormat(cfg.TimestampFormat).
+	l.state.Flags.Store(flagsFromConfig(cfg))
-		ShowLevel(cfg.ShowLevel).
+	l.state.TraceDepth.Store(cfg.TraceDepth)
-		ShowTimestamp(cfg.ShowTimestamp)
-	l.formatter.Store(newFormatter)
 
 	// Ensure log directory exists if file output is enabled
 	if cfg.EnableFile {
 		if err := os.MkdirAll(cfg.Directory, 0755); err != nil {
 			l.state.LoggerDisabled.Store(true)
 			l.currentConfig.Store(oldCfg) // Rollback
+			l.refreshLevelGate()
 			return fmtErrorf("failed to create log directory '%s': %w", cfg.Directory, err)
 		}
 	}
@@ -453,6 +238,7 @@ func (l *Logger) applyConfig(cfg *Config) error {
 	l.state.ShutdownCalled.Store(false)
 	l.state.DiskFullLogged.Store(false)
 	l.state.DiskStatusOK.Store(true)
+	l.refreshLevelGate()
 
 	// Restart processor if it was running and needs restart
 	if needsRestart {
@@ -461,3 +247,354 @@ func (l *Logger) applyConfig(cfg *Config) error {
 
 	return nil
 }
+
+// Start begins log processing. Safe to call multiple times
+// Returns error if logger is not initialized
+func (l *Logger) Start() error {
+	if !l.state.IsInitialized.Load() {
+		return fmtErrorf("logger not initialized, call ApplyConfig first")
+	}
+
+	// Check if processor didn't exit cleanly last time
+	if l.state.Started.Load() && !l.state.ProcessorExited.Load() {
+		// Force stop to clean up
+		l.internalLog("warning - processor still running from previous start, forcing stop\n")
+		if err := l.Stop(); err != nil {
+			return fmtErrorf("failed to stop hung processor: %w", err)
+		}
+	}
+
+	// Only start if not already started
+	if l.state.Started.CompareAndSwap(false, true) {
+		cfg := l.getConfig()
+
+		// Create log channels
+		ch := make(chan logRecord, cfg.BufferSize)
+		stop := make(chan struct{})
+		done := make(chan struct{})
+
+		l.state.ActiveLogChannel.Store(ch)
+		l.state.ProcStop.Store(stop)
+		l.state.ProcDone.Store(done)
+		l.state.ProcessorExited.Store(false)
+
+		// Start processor
+		l.spawn(func() { l.processLogs(ch, stop, done) })
+	}
+
+	l.refreshLevelGate()
+	return nil
+}
+
+// Stop halts log processing. Can be restarted with Start()
+// The record channel is never closed: producers are detached to a nil channel
+// first, so a concurrent send falls through to the drop counter instead of
+// racing a close.
+func (l *Logger) Stop(timeout ...time.Duration) error {
+	if !l.state.Started.CompareAndSwap(true, false) {
+		return nil // Already stopped
+	}
+	l.refreshLevelGate()
+
+	// Calculate effective timeout
+	var effectiveTimeout time.Duration
+	if len(timeout) > 0 {
+		effectiveTimeout = timeout[0]
+	} else {
+		effectiveTimeout = 2 * time.Duration(l.getConfig().FlushIntervalMs) * time.Millisecond
+	}
+	if effectiveTimeout < minWaitTime {
+		effectiveTimeout = minWaitTime
+	}
+
+	// 1. Detach producers
+	l.state.ActiveLogChannel.Store((chan logRecord)(nil))
+
+	// 2. Signal the processor to drain and exit
+	if s, ok := l.state.ProcStop.Load().(chan struct{}); ok && s != nil {
+		close(s)
+	}
+
+	// 3. Join
+	d, _ := l.state.ProcDone.Load().(chan struct{})
+	if d == nil {
+		return nil
+	}
+	select {
+	case <-d:
+		return nil
+	case <-time.After(effectiveTimeout):
+		return fmtErrorf("processor did not exit within timeout (%v)", effectiveTimeout)
+	}
+}
+
+// Shutdown gracefully closes the logger, attempting to flush pending records
+// If no timeout is provided, uses a default of 2x flush interval
+func (l *Logger) Shutdown(timeout ...time.Duration) error {
+	if !l.state.ShutdownCalled.CompareAndSwap(false, true) {
+		return nil
+	}
+
+	l.state.LoggerDisabled.Store(true)
+	l.refreshLevelGate()
+
+	if !l.state.IsInitialized.Load() {
+		l.state.ShutdownCalled.Store(false)
+		l.state.LoggerDisabled.Store(false)
+		l.state.ProcessorExited.Store(true)
+		l.refreshLevelGate()
+		return nil
+	}
+
+	var stopErr error
+	if l.state.Started.Load() {
+		stopErr = l.Stop(timeout...)
+	}
+
+	l.state.IsInitialized.Store(false)
+
+	var finalErr error
+	cfPtr := l.state.CurrentFile.Load()
+	if cfPtr != nil {
+		if currentLogFile, ok := cfPtr.(*os.File); ok && currentLogFile != nil {
+			if err := currentLogFile.Sync(); err != nil {
+				syncErr := fmtErrorf("failed to sync log file '%s' during shutdown: %w", currentLogFile.Name(), err)
+				finalErr = errors.Join(finalErr, syncErr)
+			}
+			if err := currentLogFile.Close(); err != nil {
+				closeErr := fmtErrorf("failed to close log file '%s' during shutdown: %w", currentLogFile.Name(), err)
+				finalErr = errors.Join(finalErr, closeErr)
+			}
+			l.state.CurrentFile.Store((*os.File)(nil))
+		}
+	}
+
+	if stopErr != nil {
+		finalErr = errors.Join(finalErr, stopErr)
+	}
+
+	return finalErr
+}
+
+// Flush explicitly triggers a sync of the current log file buffer to disk and waits for completion or timeout
+func (l *Logger) Flush(timeout time.Duration) error {
+	l.state.flushMutex.Lock()
+	defer l.state.flushMutex.Unlock()
+
+	// State checks
+	if !l.state.IsInitialized.Load() || l.state.ShutdownCalled.Load() {
+		return fmtErrorf("logger not initialized or already shut down")
+	}
+	if !l.state.Started.Load() {
+		return fmtErrorf("logger not started")
+	}
+
+	// Create a channel to wait for confirmation from the processor
+	confirmChan := make(chan struct{})
+
+	// Send the request with the confirmation channel
+	select {
+	case l.state.flushRequestChan <- confirmChan:
+		// Request sent
+	case <-time.After(minWaitTime): // Short timeout to prevent blocking if processor is stuck
+		return fmtErrorf("failed to send flush request to processor (possible deadlock or high load)")
+	}
+
+	select {
+	case <-confirmChan:
+		return nil
+	case <-time.After(timeout):
+		return fmtErrorf("timeout waiting for flush confirmation (%v)", timeout)
+	}
+}
+
+// SetSpawn installs the goroutine launcher used by Start. Hosts that own
+// panic recovery and terminal teardown pass their own launcher here.
+// Call before Start; a nil fn restores the default.
+func (l *Logger) SetSpawn(fn func(func())) {
+	if fn == nil {
+		l.spawner.Store(nil)
+		return
+	}
+	l.spawner.Store(&fn)
+}
+
+// SetErrorHandler routes internal diagnostics to fn instead of stderr.
+// Required for TUI hosts, where stderr writes corrupt the display.
+func (l *Logger) SetErrorHandler(fn func(string)) {
+	if fn == nil {
+		l.errHandler.Store(nil)
+		return
+	}
+	l.errHandler.Store(&fn)
+}
+
+// SetContextKeys names the record keys for Context values; empty names are
+// omitted. Safe to call at any time; rebuilds the formatter.
+func (l *Logger) SetContextKeys(tag string, vals ...string) {
+	l.initMu.Lock()
+	defer l.initMu.Unlock()
+
+	k := formatter.ContextKeys{Tag: tag}
+	for i := 0; i < len(vals) && i < formatter.ContextSlots; i++ {
+		k.Vals[i] = vals[i]
+	}
+	l.ctxKeys.Store(&k)
+	l.rebuildFormatter(l.getConfig())
+}
+
+// SetLevel changes the emit threshold in place, leaving the formatter and the
+// processor untouched
+func (l *Logger) SetLevel(level int64) {
+	l.initMu.Lock()
+	cfg := l.getConfig().Clone()
+	cfg.Level = level
+	l.currentConfig.Store(cfg)
+	l.initMu.Unlock()
+	l.refreshLevelGate()
+}
+
+// Enabled reports whether a record at level would be emitted. Single atomic
+// load: the intended guard for hot call sites, where argument slices are
+// built before the call and would otherwise escape to the heap.
+func (l *Logger) Enabled(level int64) bool {
+	return level >= l.state.Level.Load()
+}
+
+// Flags returns the default record flags derived from display config
+func (l *Logger) Flags() int64 {
+	return l.state.Flags.Load()
+}
+
+// LogContext emits a record with caller-supplied context and explicit flags
+func (l *Logger) LogContext(ctx Context, flags, level, depth int64, args ...any) {
+	if level < l.state.Level.Load() {
+		return
+	}
+	l.emit(ctx, flags, level, depth, args)
+}
+
+// spawn runs fn via the configured launcher; the default is a bare goroutine
+func (l *Logger) spawn(fn func()) {
+	if p := l.spawner.Load(); p != nil {
+		(*p)(fn)
+		return
+	}
+	go fn()
+}
+
+// rebuildFormatter installs a formatter matching cfg and the current context keys
+func (l *Logger) rebuildFormatter(cfg *Config) {
+	f := formatter.New(sanitizer.New().Policy(cfg.Sanitization)).
+		Type(cfg.Format).
+		TimestampFormat(cfg.TimestampFormat).
+		ShowLevel(cfg.ShowLevel).
+		ShowTimestamp(cfg.ShowTimestamp)
+	if k := l.ctxKeys.Load(); k != nil {
+		f.ContextKeys(k.Tag, k.Vals[:]...)
+	}
+	l.formatter.Store(f)
+}
+
+// flagsFromConfig derives the default record flags from display settings
+func flagsFromConfig(cfg *Config) int64 {
+	var flags int64
+	if cfg.ShowLevel {
+		flags |= FlagShowLevel
+	}
+	if cfg.ShowTimestamp {
+		flags |= FlagShowTimestamp
+	}
+	return flags
+}
+
+// refreshLevelGate recomputes the emit gate from lifecycle state.
+// MUST be called after every transition of IsInitialized, Started,
+// LoggerDisabled, or ShutdownCalled.
+func (l *Logger) refreshLevelGate() {
+	if !l.state.IsInitialized.Load() || !l.state.Started.Load() ||
+		l.state.LoggerDisabled.Load() || l.state.ShutdownCalled.Load() {
+		l.state.Level.Store(levelOff)
+		return
+	}
+	l.state.Level.Store(l.getConfig().Level)
+}
+
+// === Logging methods ===
+
+// Debug logs a message at debug level
+func (l *Logger) Debug(args ...any) {
+	if LevelDebug < l.state.Level.Load() {
+		return
+	}
+	l.emit(Context{}, l.getFlags(), LevelDebug, l.state.TraceDepth.Load(), args)
+}
+
+// Info logs a message at info level
+func (l *Logger) Info(args ...any) {
+	if LevelInfo < l.state.Level.Load() {
+		return
+	}
+	l.emit(Context{}, l.getFlags(), LevelInfo, l.state.TraceDepth.Load(), args)
+}
+
+// Warn logs a message at warning level
+func (l *Logger) Warn(args ...any) {
+	if LevelWarn < l.state.Level.Load() {
+		return
+	}
+	l.emit(Context{}, l.getFlags(), LevelWarn, l.state.TraceDepth.Load(), args)
+}
+
+// Error logs a message at error level
+func (l *Logger) Error(args ...any) {
+	if LevelError < l.state.Level.Load() {
+		return
+	}
+	l.emit(Context{}, l.getFlags(), LevelError, l.state.TraceDepth.Load(), args)
+}
+
+// DebugTrace logs a debug message with function call trace
+func (l *Logger) DebugTrace(depth int, args ...any) {
+	l.LogContext(Context{}, l.getFlags(), LevelDebug, int64(depth), args...)
+}
+
+// InfoTrace logs an info message with function call trace
+func (l *Logger) InfoTrace(depth int, args ...any) {
+	l.LogContext(Context{}, l.getFlags(), LevelInfo, int64(depth), args...)
+}
+
+// WarnTrace logs a warning message with function call trace
+func (l *Logger) WarnTrace(depth int, args ...any) {
+	l.LogContext(Context{}, l.getFlags(), LevelWarn, int64(depth), args...)
+}
+
+// ErrorTrace logs an error message with function call trace
+func (l *Logger) ErrorTrace(depth int, args ...any) {
+	l.LogContext(Context{}, l.getFlags(), LevelError, int64(depth), args...)
+}
+
+// Log writes a timestamp-only record without level information
+func (l *Logger) Log(args ...any) {
+	l.LogContext(Context{}, FlagShowTimestamp|FlagNoLevel, LevelInfo, 0, args...)
+}
+
+// Message writes a plain record without timestamp or level info
+func (l *Logger) Message(args ...any) {
+	l.LogContext(Context{}, FlagNoTimestamp|FlagNoLevel, LevelInfo, 0, args...)
+}
+
+// LogTrace writes a timestamp record with call trace but no level info
+func (l *Logger) LogTrace(depth int, args ...any) {
+	l.LogContext(Context{}, FlagShowTimestamp|FlagNoLevel, LevelInfo, int64(depth), args...)
+}
+
+// LogStructured logs a message with structured fields as proper JSON
+func (l *Logger) LogStructured(level int64, message string, fields map[string]any) {
+	l.LogContext(Context{}, l.getFlags()|FlagStructuredJSON, level, 0, message, fields)
+}
+
+// Write outputs raw, unformatted data ignoring configured format and sanitization
+func (l *Logger) Write(args ...any) {
+	l.LogContext(Context{}, FlagRaw, LevelInfo, 0, args...)
+}

processor.go

@@ -7,10 +7,14 @@ import (
 	"github.com/lixenwraith/log/formatter"
 )
 
-// processLogs is the main log processing loop running in a separate goroutine
+// processLogs is the main log processing loop running in a separate goroutine.
-func (l *Logger) processLogs(ch <-chan logRecord) {
+// Exits on stop, draining buffered records first. No panic recovery: a fault
-	l.state.ProcessorExited.Store(false)
+// here is fatal by design and is surfaced by the host's spawner.
-	defer l.state.ProcessorExited.Store(true)
+func (l *Logger) processLogs(ch <-chan logRecord, stop <-chan struct{}, done chan<- struct{}) {
+	defer func() {
+		l.state.ProcessorExited.Store(true)
+		close(done)
+	}()
 
 	// Set up timers and state variables
 	timers := l.setupProcessingTimers()
@@ -45,12 +49,12 @@ func (l *Logger) processLogs(ch <-chan logRecord) {
 	// --- Main Loop ---
 	for {
 		select {
-		case record, ok := <-ch:
+		case <-stop:
-			if !ok {
+			l.drain(ch)
-				l.performSync()
+			l.performSync()
-				return
+			return
-			}
 
+		case record := <-ch:
 			// Process the received log record
 			bytesWritten := l.processLogRecord(record)
 			if bytesWritten > 0 {
@@ -81,7 +85,7 @@ func (l *Logger) processLogs(ch <-chan logRecord) {
 			}
 
 		case confirmChan := <-l.state.flushRequestChan:
-			// Barrier semantics — drain queued records before sync
+			// Barrier: drain queued records before sync
 			l.handleFlushRequest(ch, confirmChan)
 
 		case <-timers.retentionChan:
@@ -93,6 +97,26 @@ func (l *Logger) processLogs(ch <-chan logRecord) {
 	}
 }
 
+// drain processes every buffered record without blocking
+func (l *Logger) drain(ch <-chan logRecord) {
+	for {
+		select {
+		case record := <-ch:
+			l.processLogRecord(record)
+		default:
+			return
+		}
+	}
+}
+
+// handleFlushRequest drains pending records, then syncs. Gives Flush barrier
+// semantics: records enqueued before the Flush call are processed first.
+func (l *Logger) handleFlushRequest(ch <-chan logRecord, confirmChan chan struct{}) {
+	l.drain(ch)
+	l.performSync()
+	close(confirmChan)
+}
+
 // processLogRecord handles individual log records and returns bytes written
 func (l *Logger) processLogRecord(record logRecord) int64 {
 	c := l.getConfig()
@@ -113,7 +137,8 @@ func (l *Logger) processLogRecord(record logRecord) int64 {
 	f := formatterPtr.(*formatter.Formatter)
 
 	// Format the log entry using atomically-loaded formatter
-	formattedData := f.Format(
+	formattedData := f.FormatCtx(
+		record.Ctx,
 		record.Flags,
 		record.TimeStamp,
 		record.Level,
@@ -193,27 +218,6 @@ func (l *Logger) handleFlushTick() {
 	}
 }
 
-// handleFlushRequest drains pending records, then syncs. Gives Flush barrier semantics:
-// Records enqueued before the Flush call are processed before confirmation.
-// Channel close is left to the main loop.
-func (l *Logger) handleFlushRequest(ch <-chan logRecord, confirmChan chan struct{}) {
-	for {
-		select {
-		case record, ok := <-ch:
-			if !ok {
-				l.performSync()
-				close(confirmChan)
-				return
-			}
-			l.processLogRecord(record)
-		default:
-			l.performSync()
-			close(confirmChan)
-			return
-		}
-	}
-}
-
 // handleRetentionCheck performs file retention check and cleanup
 func (l *Logger) handleRetentionCheck() {
 	c := l.getConfig()
@@ -244,10 +248,7 @@ func (l *Logger) adjustDiskCheckInterval(timers *TimerSet, lastCheckTime time.Ti
 		return
 	}
 
-	elapsed := time.Since(lastCheckTime)
+	elapsed := max(time.Since(lastCheckTime), minWaitTime) // Min arbitrary reasonable value
-	if elapsed < minWaitTime { // Min arbitrary reasonable value
-		elapsed = minWaitTime
-	}
 
 	logsPerSecond := float64(logsSinceLastCheck) / elapsed.Seconds()
 	targetLogsPerSecond := float64(100) // Baseline
@@ -281,4 +282,3 @@ func (l *Logger) adjustDiskCheckInterval(timers *TimerSet, lastCheckTime time.Ti
 
 	timers.diskCheckTicker.Reset(newInterval)
 }
-

processor_test.go

@@ -7,8 +7,37 @@ import (
 	"time"
 )
 
+// // procRecords parses PROC heartbeat records out of json-formatted content.
+// // Heartbeat arguments are emitted as a flat key/value array.
+// func procRecords(tb testing.TB, content string) []map[string]any {
+// 	tb.Helper()
+// 	var out []map[string]any
+// 	for _, line := range strings.Split(content, "\n") {
+// 		if !strings.Contains(line, `"level":"PROC"`) {
+// 			continue
+// 		}
+// 		var entry map[string]any
+// 		if json.Unmarshal([]byte(line), &entry) != nil {
+// 			continue
+// 		}
+// 		fields, ok := entry["fields"].([]any)
+// 		if !ok {
+// 			continue
+// 		}
+// 		rec := make(map[string]any, len(fields)/2)
+// 		for i := 0; i+1 < len(fields); i += 2 {
+// 			if key, ok := fields[i].(string); ok {
+// 				rec[key] = fields[i+1]
+// 			}
+// 		}
+// 		out = append(out, rec)
+// 	}
+// 	return out
+// }
+
 // procRecords parses PROC heartbeat records out of json-formatted content.
-// Heartbeat arguments are emitted as a flat key/value array.
+// Heartbeat arguments are emitted as a keyed object (FlagKV); the flat
+// key/value array is still accepted for records written without the flag.
 func procRecords(tb testing.TB, content string) []map[string]any {
 	tb.Helper()
 	var out []map[string]any
@@ -20,17 +49,18 @@ func procRecords(tb testing.TB, content string) []map[string]any {
 		if json.Unmarshal([]byte(line), &entry) != nil {
 			continue
 		}
-		fields, ok := entry["fields"].([]any)
+		switch fields := entry["fields"].(type) {
-		if !ok {
+		case map[string]any:
-			continue
+			out = append(out, fields)
-		}
+		case []any:
-		rec := make(map[string]any, len(fields)/2)
+			rec := make(map[string]any, len(fields)/2)
-		for i := 0; i+1 < len(fields); i += 2 {
+			for i := 0; i+1 < len(fields); i += 2 {
-			if key, ok := fields[i].(string); ok {
+				if key, ok := fields[i].(string); ok {
-				rec[key] = fields[i+1]
+					rec[key] = fields[i+1]
+				}
 			}
+			out = append(out, rec)
 		}
-		out = append(out, rec)
 	}
 	return out
 }

record.go

@@ -7,56 +7,27 @@ import (
 	"time"
 )
 
-// getCurrentLogChannel safely retrieves the current log channel
+// getCurrentLogChannel returns the active record channel, nil when detached
 func (l *Logger) getCurrentLogChannel() chan logRecord {
-	chVal := l.state.ActiveLogChannel.Load()
+	ch, _ := l.state.ActiveLogChannel.Load().(chan logRecord)
-	// No defensive nil check required in correct use of initialized logger
+	return ch
-	return chVal.(chan logRecord)
 }
 
-// getFlags from config
+// getFlags returns the cached default record flags
 func (l *Logger) getFlags() int64 {
-	var flags int64 = 0
+	return l.state.Flags.Load()
-	cfg := l.getConfig()
-
-	if cfg.ShowLevel {
-		flags |= FlagShowLevel
-	}
-	if cfg.ShowTimestamp {
-		flags |= FlagShowTimestamp
-	}
-	return flags
 }
 
-// sendLogRecord handles safe sending to the active channel
+// sendLogRecord queues a record without blocking. The channel is never closed,
+// so no recovery is needed: a detached (nil) channel takes the default branch.
 func (l *Logger) sendLogRecord(record logRecord) {
-	defer func() {
+	if l.state.LoggerDisabled.Load() {
-		if r := recover(); r != nil {
-			// A panic is only expected when a race condition occurs during shutdown
-			if err, ok := r.(error); ok && err.Error() == "send on closed channel" {
-				// Expected race condition between logging and shutdown
-				l.handleFailedSend()
-			} else {
-				// Unexpected panic, re-throw to surface
-				panic(r)
-			}
-		}
-	}()
-
-	if l.state.ShutdownCalled.Load() ||
-		l.state.LoggerDisabled.Load() ||
-		!l.state.Started.Load() {
-		// Process drops even if logger is disabled or shutting down
 		l.handleFailedSend()
 		return
 	}
-
 	ch := l.getCurrentLogChannel()
-
-	// Non-blocking send
 	select {
 	case ch <- record:
-		// Success
 	default:
 		l.handleFailedSend()
 	}
@@ -68,59 +39,79 @@ func (l *Logger) handleFailedSend() {
 	l.state.TotalDroppedLogs.Add(1) // Total counter
 }
 
-// log handles the core logging logic
+// emit builds and queues a record; the caller has already passed the level gate
-func (l *Logger) log(flags int64, level int64, depth int64, args ...any) {
+func (l *Logger) emit(ctx Context, flags, level, depth int64, args []any) {
-	// State checks
-	if !l.state.IsInitialized.Load() {
-		return
-	}
-
-	if !l.state.Started.Load() {
-		// Log to internal error channel if configured
-		cfg := l.getConfig()
-		if cfg.InternalErrorsToStderr {
-			l.internalLog("warning - logger not started, dropping log entry\n")
-		}
-		return
-	}
-
-	// Discard or proceed based on level
-	cfg := l.getConfig()
-	if level < cfg.Level {
-		return
-	}
-
-	// Get trace info from runtime
 	// Depth filter hard-coded based on call stack of current package design
 	var trace string
 	if depth > 0 {
-		const skipTrace = 3 // log.Info -> log -> getTrace (Adjust if call stack changes)
+		const skipTrace = 3 // Logger.Info -> emit -> getTrace
 		trace = getTrace(depth, skipTrace)
 	}
 
-	record := logRecord{
+	l.sendLogRecord(logRecord{
+		Ctx:       ctx,
 		Flags:     flags,
 		TimeStamp: time.Now(),
 		Level:     level,
 		Trace:     trace,
 		Args:      args,
-	}
+	})
-	l.sendLogRecord(record)
 }
 
-// internalLog handles writing internal logger diagnostics to stderr if enabled
+// internalLog reports logger diagnostics to the registered handler, or to
+// stderr when configured. Hosts owning a terminal must register a handler.
 func (l *Logger) internalLog(format string, args ...any) {
-	// Check if internal error reporting is enabled
-	cfg := l.getConfig()
-	if !cfg.InternalErrorsToStderr {
-		return
-	}
-
-	// Ensure consistent "log: " prefix
 	if !strings.HasPrefix(format, "log: ") {
 		format = "log: " + format
 	}
 
-	// Write to stderr
+	if h := l.errHandler.Load(); h != nil {
+		(*h)(strings.TrimRight(fmt.Sprintf(format, args...), "\n"))
+		return
+	}
+
+	if !l.getConfig().InternalErrorsToStderr {
+		return
+	}
 	fmt.Fprintf(os.Stderr, format, args...)
 }
+
+// // log handles the core logging logic
+// func (l *Logger) log(flags int64, level int64, depth int64, args ...any) {
+// 	// State checks
+// 	if !l.state.IsInitialized.Load() {
+// 		return
+// 	}
+//
+// 	if !l.state.Started.Load() {
+// 		// Log to internal error channel if configured
+// 		cfg := l.getConfig()
+// 		if cfg.InternalErrorsToStderr {
+// 			l.internalLog("warning - logger not started, dropping log entry\n")
+// 		}
+// 		return
+// 	}
+//
+// 	// Discard or proceed based on level
+// 	cfg := l.getConfig()
+// 	if level < cfg.Level {
+// 		return
+// 	}
+//
+// 	// Get trace info from runtime
+// 	// Depth filter hard-coded based on call stack of current package design
+// 	var trace string
+// 	if depth > 0 {
+// 		const skipTrace = 3 // log.Info -> log -> getTrace (Adjust if call stack changes)
+// 		trace = getTrace(depth, skipTrace)
+// 	}
+//
+// 	record := logRecord{
+// 		Flags:     flags,
+// 		TimeStamp: time.Now(),
+// 		Level:     level,
+// 		Trace:     trace,
+// 		Args:      args,
+// 	}
+// 	l.sendLogRecord(record)
+// }

state.go

@@ -16,6 +16,12 @@ type State struct {
 	Started         atomic.Bool // Tracks calls to Start() and Stop()
 	ProcessorExited atomic.Bool // Tracks if the processor goroutine is running or has exited
 
+	// Emit fast path: config mirrors refreshed by applyConfig and the
+	// lifecycle transitions. Level holds levelOff while emission is closed
+	Level      atomic.Int64
+	Flags      atomic.Int64
+	TraceDepth atomic.Int64
+
 	// Flushing state
 	flushRequestChan chan chan struct{} // Channel to request a flush
 	flushMutex       sync.Mutex         // Protect concurrent Flush calls
@@ -30,6 +36,8 @@ type State struct {
 
 	// Log state
 	ActiveLogChannel atomic.Value  // stores chan logRecord
+	ProcStop         atomic.Value  // stores chan struct{}, closed to signal exit
+	ProcDone         atomic.Value  // stores chan struct{}, closed by the processor
 	DroppedLogs      atomic.Uint64 // Counter for logs dropped since last heartbeat
 	TotalDroppedLogs atomic.Uint64 // Counter for total logs dropped since logger start
 

storage.go

@@ -5,8 +5,6 @@ import (
 	"os"
 	"path/filepath"
 	"sort"
-	"strings"
-	"syscall"
 	"time"
 )
 
@@ -25,10 +23,14 @@ func (l *Logger) performSync() {
 			if err := currentLogFile.Sync(); err != nil {
 				// Log sync error
 				syncErrRecord := logRecord{
-					Flags:     FlagDefault,
+					Flags:     FlagDefault | FlagKV,
 					TimeStamp: time.Now(),
 					Level:     LevelWarn,
-					Args:      []any{"Log file sync failed", "file", currentLogFile.Name(), "error", err.Error()},
+					Args: []any{
+						"msg", "log file sync failed",
+						"file", currentLogFile.Name(),
+						"error", err.Error(),
+					},
 				}
 				l.sendLogRecord(syncErrRecord)
 			}
@@ -106,8 +108,11 @@ func (l *Logger) performDiskCheck(forceCleanup bool) bool {
 		if err := l.cleanOldLogs(spaceToFree); err != nil {
 			if !l.state.DiskFullLogged.Swap(true) {
 				diskFullRecord := logRecord{
-					Flags: FlagDefault, TimeStamp: time.Now(), Level: LevelError,
+					Flags: FlagDefault | FlagKV, TimeStamp: time.Now(), Level: LevelError,
-					Args: []any{"Log directory full or disk space low, cleanup failed", "error", err.Error()},
+					Args: []any{
+						"msg", "log directory full or disk space low, cleanup failed",
+						"error", err.Error(),
+					},
 				}
 				l.sendLogRecord(diskFullRecord)
 			}
@@ -135,27 +140,27 @@ func (l *Logger) performDiskCheck(forceCleanup bool) bool {
 	}
 }
 
-// getDiskFreeSpace retrieves available disk space for the given path
+// // getDiskFreeSpace retrieves available disk space for the given path
-func (l *Logger) getDiskFreeSpace(path string) (int64, error) {
+// func (l *Logger) getDiskFreeSpace(path string) (int64, error) {
-	var stat syscall.Statfs_t
+// 	var stat syscall.Statfs_t
-	info, err := os.Stat(path)
+// 	info, err := os.Stat(path)
-	if err != nil {
+// 	if err != nil {
-		if os.IsNotExist(err) {
+// 		if os.IsNotExist(err) {
-			return 0, fmtErrorf("log directory '%s' does not exist for disk check: %w", path, err)
+// 			return 0, fmtErrorf("log directory '%s' does not exist for disk check: %w", path, err)
-		}
+// 		}
-		return 0, fmtErrorf("failed to stat log directory '%s': %w", path, err)
+// 		return 0, fmtErrorf("failed to stat log directory '%s': %w", path, err)
-	}
+// 	}
-	if !info.IsDir() {
+// 	if !info.IsDir() {
-		path = filepath.Dir(path)
+// 		path = filepath.Dir(path)
-	}
+// 	}
-
+//
-	if err := syscall.Statfs(path, &stat); err != nil {
+// 	if err := syscall.Statfs(path, &stat); err != nil {
-		return 0, fmtErrorf("failed to get disk stats for '%s': %w", path, err)
+// 		return 0, fmtErrorf("failed to get disk stats for '%s': %w", path, err)
-	}
+// 	}
-	// Explicit cast to int64 to satisfy both Linux and FreebSD
+// 	// Explicit cast to int64 to satisfy both Linux and FreebSD
-	availableBytes := int64(stat.Bavail) * int64(stat.Bsize)
+// 	availableBytes := int64(stat.Bavail) * int64(stat.Bsize)
-	return availableBytes, nil
+// 	return availableBytes, nil
-}
+// }
 
 // getLogDirSize calculates total size of log files matching the current extension
 func (l *Logger) getLogDirSize(dir, ext string) (int64, error) {
@@ -254,7 +259,9 @@ func (l *Logger) cleanOldLogs(required int64) error {
 	return nil
 }
 
-// updateEarliestFileTime scans the log directory for the oldest log file
+// updateEarliestFileTime scans the log directory for the oldest log file.
+// Matches by extension only: a name-prefix filter would hide files written by
+// earlier runs when the active name carries a per-run timestamp.
 func (l *Logger) updateEarliestFileTime() {
 	c := l.getConfig()
 	dir := c.Directory
@@ -275,17 +282,15 @@ func (l *Logger) updateEarliestFileTime() {
 	}
 
 	targetExt := "." + ext
-	prefix := name + "_"
 	for _, entry := range entries {
 		if entry.IsDir() {
 			continue
 		}
 		fname := entry.Name()
-		// Skip the active log file
 		if fname == staticLogName {
-			continue
+			continue // Skip the active log file
 		}
-		if !strings.HasPrefix(fname, prefix) || (ext != "" && filepath.Ext(fname) != targetExt) {
+		if ext != "" && filepath.Ext(fname) != targetExt {
 			continue
 		}
 		info, errInfo := entry.Info()
@@ -371,19 +376,28 @@ func (l *Logger) getStaticLogFilePath() string {
 	return filepath.Join(dir, filename)
 }
 
-// generateArchiveLogFileName creates a timestamped filename for archived logs during rotation
+// fileExists reports whether path names an existing regular file
+func fileExists(path string) bool {
+	info, err := os.Stat(path)
+	return err == nil && !info.IsDir()
+}
+
+// generateArchiveLogFileName creates a second-resolution name for a rotated
+// log, disambiguating with a counter when that name is already taken
 func (l *Logger) generateArchiveLogFileName(timestamp time.Time) string {
 	c := l.getConfig()
-	ext := c.Extension
-	name := c.Name
 
-	tsFormat := timestamp.Format("060102_150405")
+	suffix := ""
-	nano := timestamp.Nanosecond()
+	if c.Extension != "" {
-
+		suffix = "." + c.Extension
-	if ext != "" {
-		return fmt.Sprintf("%s_%s_%d.%s", name, tsFormat, nano, ext)
 	}
-	return fmt.Sprintf("%s_%s_%d", name, tsFormat, nano)
+	base := fmt.Sprintf("%s_%s", c.Name, timestamp.Format("060102_150405"))
+
+	name := base + suffix
+	for i := 1; i < 1000 && fileExists(filepath.Join(c.Directory, name)); i++ {
+		name = fmt.Sprintf("%s_%d%s", base, i, suffix)
+	}
+	return name
 }
 
 // createNewLogFile generates a unique name and opens a new log file
@@ -449,6 +463,7 @@ func (l *Logger) rotateLogFile() error {
 		l.internalLog("failed to rename log file from '%s' to '%s': %v. file logging disabled.",
 			currentPath, archivePath, err)
 		l.state.LoggerDisabled.Store(true)
+		l.refreshLevelGate()
 		return fmtErrorf("failed to rotate log file, logging is disabled: %w", err)
 	}
 
@@ -492,4 +507,3 @@ func (l *Logger) getLogFileCount(dir, ext string) (int, error) {
 	}
 	return count, nil
 }
-

storage_nofs.go

@@ -0,0 +1,11 @@
+//go:build !unix
+
+package log
+
+import "math"
+
+// getDiskFreeSpace reports unlimited space where statfs is unavailable.
+// Total-size limits still apply; only the free-space check is inert.
+func (l *Logger) getDiskFreeSpace(path string) (int64, error) {
+	return math.MaxInt64, nil
+}

storage_test.go

@@ -42,7 +42,7 @@ func TestLogRotation(t *testing.T) {
 		switch {
 		case name == "log.log":
 			hasActive = true
-		// Archive pattern: log_YYMMDD_HHMMSS_<nano>.log
+		// Archive pattern: log_YYMMDD_HHMMSS[_N].log
 		case strings.HasPrefix(name, "log_") && strings.HasSuffix(name, ".log"):
 			archives++
 		default:
@@ -195,7 +195,8 @@ func TestLogDirAccounting(t *testing.T) {
 	equal(t, count, 0, "count of missing dir")
 }
 
-// TestArchiveNaming verifies archive names are unique and carry the base name.
+// TestArchiveNaming verifies archive names carry the base name and never
+// collide with a file already present in the directory.
 func TestArchiveNaming(t *testing.T) {
 	logger, tmpDir := newTestLogger(t)
 
@@ -203,12 +204,17 @@ func TestArchiveNaming(t *testing.T) {
 
 	ts := time.Now()
 	first := logger.generateArchiveLogFileName(ts)
-	second := logger.generateArchiveLogFileName(ts.Add(time.Nanosecond))
-
 	isTrue(t, strings.HasPrefix(first, "log_"), "archive prefix")
 	isTrue(t, strings.HasSuffix(first, ".log"), "archive extension")
-	if first == second {
-		t.Errorf("archive names must be unique at nanosecond resolution: %s", first)
-	}
-}
 
+	// Names are second-resolution; the counter disambiguates against files
+	// already on disk, not against clock resolution
+	mustNoErr(t, os.WriteFile(filepath.Join(tmpDir, first), []byte("archived"), 0644), "WriteFile archive")
+
+	second := logger.generateArchiveLogFileName(ts)
+	if second == first {
+		t.Errorf("archive name collided with existing file: %s", second)
+	}
+	isTrue(t, strings.HasPrefix(second, "log_"), "archive prefix")
+	isTrue(t, strings.HasSuffix(second, ".log"), "archive extension")
+}

storage_unix.go

@@ -0,0 +1,30 @@
+//go:build unix
+
+package log
+
+import (
+	"os"
+	"path/filepath"
+	"syscall"
+)
+
+// getDiskFreeSpace retrieves available disk space for the given path
+func (l *Logger) getDiskFreeSpace(path string) (int64, error) {
+	var stat syscall.Statfs_t
+	info, err := os.Stat(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return 0, fmtErrorf("log directory '%s' does not exist for disk check: %w", path, err)
+		}
+		return 0, fmtErrorf("failed to stat log directory '%s': %w", path, err)
+	}
+	if !info.IsDir() {
+		path = filepath.Dir(path)
+	}
+
+	if err := syscall.Statfs(path, &stat); err != nil {
+		return 0, fmtErrorf("failed to get disk stats for '%s': %w", path, err)
+	}
+	// Explicit cast to int64 to satisfy both Linux and FreeBSD
+	return int64(stat.Bavail) * int64(stat.Bsize), nil
+}

type.go

@@ -3,15 +3,24 @@ package log
 import (
 	"io"
 	"time"
+
+	"github.com/lixenwraith/log/formatter"
 )
 
+// Context carries caller-stamped values emitted with a record
+type Context = formatter.Context
+
+// ContextSlots is the number of correlation values a Context carries
+const ContextSlots = formatter.ContextSlots
+
 // logRecord represents a single log entry
 type logRecord struct {
-	Flags     int64
 	TimeStamp time.Time
-	Level     int64
 	Trace     string
 	Args      []any
+	Ctx       Context
+	Flags     int64
+	Level     int64
 }
 
 // TimerSet holds all timers used in processLogs