feature: telemetry building blocks

- added: New flow-php/telemetry library for metrics and tracing (core
foundation)
- added: TraceId - OpenTelemetry-compatible 16-byte trace identifier
with hex/bytes conversion
- added: SpanId - OpenTelemetry-compatible 8-byte span identifier with
hex/bytes conversion
- added: Baggage - immutable key-value store for context propagation
across process boundaries
- added: Context - main telemetry context carrier with TraceId, Baggage,
and active span tracking
- added: Resource - immutable entity metadata (service.name, version,
host) attached to all telemetry signals
- added: DSL functions: trace_id(), span_id(), baggage(), context(),
resource()
- added: Serialization support via normalize()/fromArray() on all
context classes

feature: building blocks for tracer

- added: SpanStatus - status code with optional description
- added: SpanContext - immutable span identification (traceId, spanId,
parentSpanId)
- added: SpanEvent interface and GenericEvent implementation for span
events
- added: SpanLink - links between spans with attributes
- added: Span - mutable span with lifecycle management, attributes,
events, and links
- added: DSL functions: trace_id(), span_id(), baggage(), context(),
resource(), span_context(), span_event(), span_link()

feature: initial version of tracer

- added: SpanExporter interface - export spans to external systems
- added: TracerProvider interface with withContextStorage() for shared
context propagation
- added: Tracer - creates and manages spans with automatic parent-child
relationships
- added: ContextStorage interface and LocalContextStorage for shared
context access across providers
- added: InMemoryTracerProvider - caches tracers by name/version, stores
spans in memory for testing
- added: InMemorySpanProcessor - stores spans in memory grouped by trace
ID for testing
- added: VoidSpanProcessor, VoidSpanExporter, VoidTracerProvider - no-op
implementations for disabled tracing
- added: DSL functions: trace_id(), span_id(), baggage(), context(),
resource(), span_context(), span_event(), span_link()
- added: DSL functions: telemetry_provider_memory(),
telemetry_provider_void()
- added: psr/clock dependency for clock abstraction

feature: logger contract

- added: Severity enum - OpenTelemetry-aligned log levels (TRACE, DEBUG,
INFO, WARN, ERROR, FATAL)
- added: LogRecord - immutable value object for structured log data with
fluent API
- added: Logger interface - convenience methods (trace, debug, info,
warn, error, fatal) and emit(LogRecord)
- added: LogProcessor interface - log record processing with SpanContext
correlation
- added: LogExporter interface - export logs to external systems
- added: LoggerProvider interface - factory for creating Logger
instances

feature: logger implementations

- added: VoidLogger, VoidLogProcessor, VoidLogExporter,
VoidLoggerProvider - no-op implementations for disabled logging
- added: InMemoryLogger, InMemoryLogProcessor, InMemoryLoggerProvider -
in-memory implementations for testing
- added: DSL functions: void_logger_provider(), logger_provider_memory()

feature: meter provider

- added: VoidMetricProcessor, VoidMetricExporter, VoidMeterProvider -
no-op implementations for disabled metrics collection
- added: InMemoryMetricProcessor, InMemoryMeterProvider - in-memory
implementations for testing with query helpers
- added: void_meter_provider() and in_memory_meter_provider() DSL
factory functions
- added: comprehensive unit tests for all Void and InMemory meter
implementations
- added: MetricsIntegrationTest for complete metrics workflow testing
- changed: Updated VoidMeterProviderTest, InMemoryMeterProviderTest, and
MetricsIntegrationTest to use DSL factory functions
- changed: Added PHPDoc type annotations to ExemplarTest and MetricTest
for PHPStan compliance

feature: telemetry entry point

- added: Telemetry main entry point class providing unified access to
tracing, metrics, and logging
- added: Provider namespace structure
(Flow\Telemetry\Provider\{Memory,Void}) for consistent provider
organization
- added: DSL function telemetry() for creating Telemetry instances
- changed: Renamed InMemory* classes to Memory* (MemoryTracerProvider,
MemoryMeterProvider, MemoryLoggerProvider, etc.)
- changed: Moved all provider implementations from component-specific
namespaces to Flow\Telemetry\Provider\{Memory,Void}
- changed: Renamed DSL functions for consistency:
telemetry_provider_memory() → tracer_memory_provider(),
void_logger_provider() → logger_void_provider(), etc.

feature: missing building blocks

- added: Carrier interface and ArrayCarrier for type-safe context
propagation
- added: W3CTraceContext and W3CBaggage propagators for distributed
tracing
- added: CompositePropagator and BaggagePropagator interfaces
- added: Telemetry::extract() and Telemetry::inject() methods for
context propagation
- added: Sampler system (AlwaysOnSampler, AlwaysOffSampler,
ParentBasedSampler, TraceIdRatioBasedSampler)
- added: InstrumentationScope for tracking instrumentation library
metadata
- added: SpanLimits for configuring span attribute/event/link limits
- added: TraceFlags and TraceState for W3C trace context support
- added: normalize()/fromArray() serialization methods on telemetry
value objects
- changed: Span now requires InstrumentationScope in constructor
- changed: SpanContext now includes TraceFlags and TraceState
- changed: TextMapPropagator interface uses typed Carrier instead of
mixed

feature: otlp bridge

- added: New telemetry library (flow-php/telemetry) with
OpenTelemetry-inspired API for traces, metrics, and logs
- added: OTLP bridge (flow-php/telemetry-otlp) for exporting telemetry
to OpenTelemetry Protocol collectors
- added: Tracer API with spans, events, links, and context propagation
- added: Meter API with Counter, UpDownCounter, Gauge, and Histogram
instruments
- added: Logger API with severity levels (TRACE, DEBUG, INFO, WARN,
ERROR, FATAL)
- added: Memory and Void provider implementations for testing and
disabled telemetry
- added: Batching processors for efficient OTLP export with configurable
batch sizes
- added: JSON and Protobuf serializers for OTLP wire format
- added: HTTP, gRPC, and async curl transports for OTLP endpoints
- added: DSL functions for easy telemetry setup (telemetry(),
tracer_provider(), meter_provider(), logger_provider())
- changed: Processor interfaces now expose exporter() method instead of
signal-specific names
- changed: Exporter interfaces now expose transports() method for
lifecycle management
- changed: Removed shutdown() from Exporter interfaces - only Transport
has shutdown responsibility

refactor: unified exporters and attributres

- added: LogEntry class to wrap LogRecord with contextual information
- added: Signal-specific exporters (MemoryLogExporter,
MemoryMetricExporter, MemorySpanExporter)
- added: Signal-specific void exporters (VoidLogExporter,
VoidMetricExporter, VoidSpanExporter)
- added: Support for DateTimeInterface and Throwable in Attributes
values
- changed: Transport interface now has signal-specific methods
(sendSpans, sendMetrics, sendLogs)
- changed: Renamed LocalContextStorage to MemoryContextStorage
- changed: LogProcessor and LogExporter now work with LogEntry instead
of arrays
- changed: AttributeSerializer now accepts Attributes objects instead of
arrays
- removed: Logs, Metrics, Spans wrapper classes
- removed: Generic MemoryExporter and VoidExporter
- removed: Duplicate batching processors from OTLP bridge
- removed: OTLP Serializer interface, Signal enum and Transport
interface

feature: exemplar's

- added: ExemplarFilter interface with AlwaysOn, AlwaysOff, and
TraceBased implementations
- added: ExemplarReservoir interface with SimpleFixedSize and
AlignedHistogramBucket implementations
- added: DSL functions for exemplar filters (always_on_exemplar_filter,
always_off_exemplar_filter, trace_based_exemplar_filter)
- added: ExemplarFilter parameter to meter_provider() DSL function
- added: Exemplar trace context display in ConsoleMetricExporter
- changed: Sampler interface simplified - shouldSample() now takes Span,
getDescription() renamed to __toString()
- changed: MeterProvider and Meter now accept ExemplarFilter parameter
- changed: Instrument classes now use ExemplarFilter and
ExemplarReservoir
- changed: Tracer span creation refactored to propagate trace flags from
parent context
- removed: Old stub ExemplarFilter and ExemplarReservoir interfaces
(moved to Meter/Exemplar/)

feature: context propagators

- added: Unified `Propagator` interface for context propagation
- added: `PropagationContext` value object containing both `SpanContext`
and `Baggage`
- added: `SuperglobalCarrier` for extracting context from PHP
superglobals
- added: DSL functions for propagation: propagation_context(),
array_carrier(), superglobal_carrier(), w3c_trace_context(),
w3c_baggage(), composite_propagator()
- added: Telemetry exception namespace with Exception and
RuntimeException
- changed: BREAKING - Renamed TextMapPropagator to Propagator
- changed: BREAKING - Propagator::extract() now returns
PropagationContext instead of ?SpanContext
- changed: BREAKING - Propagator::inject() now accepts
PropagationContext instead of SpanContext
- changed: CompositePropagator now merges contexts from all propagators
instead of returning first match
- removed: TextMapPropagator interface (replaced by Propagator)
- removed: BaggagePropagator interface (merged into unified Propagator)

feature: rename simple processors to pass through processors

- added: Telemetry library documentation with comprehensive guides for
traces, metrics, logs, processors, exporters, and propagators
- added: Telemetry OTLP Bridge documentation covering transports (Curl,
HTTP, gRPC), serializers (JSON, Protobuf), and APM integration examples
- added: Telemetry contracts documentation listing all interfaces and
their implementations
- added: Monorepo split configuration for telemetry-otlp-bridge package
- changed: Renamed Simple*Processor classes to PassThrough*Processor
(spans, metrics, logs) for clarity
- changed: Renamed DSL functions: simple_*_processor() →
pass_through_*_processor()

fix: remove ext-pg_query from monorepo composer.json

chore: updated dependencies

fix: telemetry collector on ci/cd

fix: otel collector service at gh actions

fix: run otel collector in background

fix: mutation tests configuration

fix: mutation tests

Improve mutation score

fix: otel collector port on gh actions

rm: debug otel collector

fix: exposing metrics from otel collector to tests