## Tracer

The default value for datadog.log_backtrace is now set to true, meaning that on compatible systems, a segmentation fault will cause the process's backtrace to be printed in the log.

### Added
- Add SpanEvents support for DD and OTEL #2754
- Symfony Messenger Integration #2749
- Add crashtracker #2763

### Changed
- Updates the expected telemetry tags for OTel env-var mapping in line with the latest RFC #2775

### Fixed
- Multiple Workers in SWOOLE_BASE mode #2778
- Fix ini creation when `--extension-dir` is used #2789
- Fix fatal error when reading uninit $meta on a span #2790
- Fix JIT crash with instrumented generators #2797
- Handle absolute paths in extension_dir containing forward slashes #2798
- Fix setup with spaces in path to php binary #2803
- Fix #2774: shared hooks removal caused xdebug end handler to be skipped #2780
- Fix error message for not loaded/not available #2810
- Implement fallback for when memfd is not available on Linux Datadog/libdatadog#591
- Use the Windows User ID as sidecar identifier instead of the Session ID Datadog/libdatadog#558
- Fix error check in trampoline.c Datadog/libdatadog#569
- Do not implicitly fall back to spl_autoload() if no autoloader is registered on PHP 7 #2822
- Prevent crash in shutdown if hook was not stored #2824

### Internal
- Send x-datadog-test-session-token metric and send metrics to request-replayer #2802
- Only warn on missing `json` extension #2805
- Fix compilation after alpine container upgrade #2811
- Telemetry v2 schema for app-started payload requires 'configuration' Datadog/libdatadog#543

## Profiling

### Added
- Add timestamp to exception sample #2793

### Internal
- Perf: remove profiler mutex #2714

## Application Security Management

### Added
- Automated user ID collection modes #2782
- Report backtraces #2715

### Changed
- Support loading appsec helper in sidecar Datadog/libdatadog#565

### Fixed
- Refactor the sampler to fix errors #2761