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WIP: feat(native): introduce WER mode for better WER interop #1833

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feat(native): introduce WER mode for better WER interop
jpnurmi Jun 30, 2026
02732a8
Update CHANGELOG.md
jpnurmi Jun 30, 2026
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -5,6 +5,7 @@
**Features**

- Android: Expose app-hang detection through the NDK bindings via `NdkOptions.setEnableAppHangTracking()` and `NdkOptions.setAppHangTimeoutMillis()`. ([#1823](https://github.com/getsentry/sentry-native/pull/1823))
- Native/Windows: Allow configuring whether SEH and fast-fail crashes propagate to WER via `sentry_options_set_wer_mode`. ([#1833](https://github.com/getsentry/sentry-native/pull/1833))

## 0.15.2

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45 changes: 45 additions & 0 deletions include/sentry.h
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Expand Up @@ -1116,6 +1116,36 @@ typedef enum {
SENTRY_CACHE_KEEP_ALWAYS = 2,
} sentry_cache_keep_t;

/**
* Windows Error Reporting (WER) mode.
*/
typedef enum {
/**
* SEH crashes: the SDK's unhandled exception filter returns
* `EXCEPTION_EXECUTE_HANDLER`, the process is terminated, and the crash is
* not propagated to WER.
* Fast-fail crashes: no WER module is registered, so fast-fail crashes are
* not captured by Sentry, and are handled by WER instead.
*/
SENTRY_WER_MODE_NONE = 0,
/**
* SEH crashes: the SDK's unhandled exception filter returns
* `EXCEPTION_EXECUTE_HANDLER`, the process is terminated, and the crash is
* not propagated to WER.
* Fast-fail crashes: the WER module claims ownership and terminates the
* process, preventing WER to also process them.
*/
SENTRY_WER_MODE_EXCLUSIVE = 1,
/**
* SEH crashes: the SDK's unhandled exception filter returns
* `EXCEPTION_CONTINUE_SEARCH`, which proceeds with normal exception
* handling and lets WER also process the crash.
* Fast-fail crashes: the WER module does not claim ownership, allowing WER
* to also process them.
*/
SENTRY_WER_MODE_SHARED = 2,
Comment on lines +1140 to +1146

@sentry sentry Bot Jun 30, 2026

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Bug: The SEH crash handler crash_exception_filter unconditionally returns EXCEPTION_CONTINUE_SEARCH, ignoring the wer_mode for SENTRY_WER_MODE_EXCLUSIVE and SENTRY_WER_MODE_NONE.
Severity: HIGH

Suggested Fix

Add logic to the crash_exception_filter function to check ctx->wer_mode. It should return EXCEPTION_EXECUTE_HANDLER for SENTRY_WER_MODE_EXCLUSIVE and SENTRY_WER_MODE_NONE, and EXCEPTION_CONTINUE_SEARCH for SENTRY_WER_MODE_SHARED.

Prompt for AI Agent 
Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: include/sentry.h#L1140-L1146

Potential issue: The SEH crash handler in `src/backends/native/sentry_crash_handler.c`,
specifically the function `crash_exception_filter`, unconditionally returns
`EXCEPTION_CONTINUE_SEARCH`. This contradicts the documented behavior for
`SENTRY_WER_MODE_EXCLUSIVE` and `SENTRY_WER_MODE_NONE`, which require the function to
return `EXCEPTION_EXECUTE_HANDLER` to prevent Windows Error Reporting (WER) from
processing the crash. The implementation fails to check the `ctx->wer_mode`, thus
violating the API contract and causing incorrect WER interop behavior for SEH crashes on
Windows.

Did we get this right? 👍 / 👎 to inform future reviews.

} sentry_wer_mode_t;

/**
* Creates a new options struct.
* Can be freed with `sentry_options_free`.
Expand Down Expand Up @@ -1924,6 +1954,21 @@ SENTRY_API void sentry_options_set_crash_upload_mode(
SENTRY_API sentry_crash_upload_mode_t sentry_options_get_crash_upload_mode(
const sentry_options_t *opts);

/**
* Sets the WER (Windows Error Reporting) mode for the native backend.
*
* This setting only has an effect when using the `native` backend.
* Default is `SENTRY_WER_MODE_SHARED`.
*/
SENTRY_EXPERIMENTAL_API void sentry_options_set_wer_mode(
sentry_options_t *opts, sentry_wer_mode_t mode);

/**
* Gets the WER (Windows Error Reporting) mode.
*/
SENTRY_EXPERIMENTAL_API sentry_wer_mode_t sentry_options_get_wer_mode(
const sentry_options_t *opts);

/**
* Enables a wait for the crash report upload to be finished before shutting
* down. This is disabled by default.
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1 change: 1 addition & 0 deletions src/backends/native/sentry_crash_context.h
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Expand Up @@ -290,6 +290,7 @@ typedef struct {
uint64_t shutdown_timeout;
uint64_t transfer_timeout;
bool system_crash_reporter_enabled;
int wer_mode; // 0=none, 1=exclusive, 2=shared (see sentry_wer_mode_t)
uint32_t max_breadcrumbs;

// Atomic user consent (sentry_user_consent_t), updated whenever user
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17 changes: 14 additions & 3 deletions src/backends/native/sentry_wer.c
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Expand Up @@ -148,7 +148,16 @@ process_wer_exception(

InterlockedExchange(&ctx->state, SENTRY_CRASH_STATE_CRASHED);
if (SetEvent(event)) {
claimed = TRUE;
BOOL shared = ctx->wer_mode == SENTRY_WER_MODE_SHARED;
if (shared) {
// SHARED: signal the daemon asynchronously, but don't claim
// ownership so WER can also process the crash.
claimed = FALSE;
} else {
// EXCLUSIVE: wait for daemon and terminate process, claiming
// exclusive ownership of the crash.
claimed = TRUE;
}
uint64_t timeout_ms = ctx->shutdown_timeout
? ctx->shutdown_timeout
: SENTRY_CRASH_HANDLER_WAIT_TIMEOUT_MS;
Expand All @@ -161,8 +170,10 @@ process_wer_exception(
}
Sleep(SENTRY_CRASH_HANDLER_POLL_INTERVAL_MS);
}
TerminateProcess(exception_info->hProcess,
exception_info->exceptionRecord.ExceptionCode);
if (!shared) {
TerminateProcess(exception_info->hProcess,
exception_info->exceptionRecord.ExceptionCode);
}
}
}

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5 changes: 4 additions & 1 deletion src/backends/sentry_backend_native.c
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Expand Up @@ -297,6 +297,7 @@ native_backend_startup(
ctx->crash_reporting_mode = options->crash_reporting_mode;
ctx->system_crash_reporter_enabled = options->system_crash_reporter_enabled;
ctx->crash_upload_mode = options->crash_upload_mode;
ctx->wer_mode = options->wer_mode;

// Pass debug logging setting to daemon
ctx->debug_enabled = options->debug;
Expand Down Expand Up @@ -527,7 +528,9 @@ native_backend_startup(
}

# if defined(SENTRY_PLATFORM_WINDOWS) && !defined(SENTRY_PLATFORM_XBOX)
wer_register_module(tid);
if (options->wer_mode != SENTRY_WER_MODE_NONE) {
wer_register_module(tid);
}
# endif

if (sentry__crash_handler_init(state->ipc) < 0) {
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19 changes: 19 additions & 0 deletions src/sentry_options.c
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Expand Up @@ -114,6 +114,7 @@ sentry_options_new(void)
= SENTRY_CRASH_REPORTING_MODE_NATIVE_WITH_MINIDUMP; // Default: best of
// both worlds
opts->crash_upload_mode = SENTRY_CRASH_UPLOAD_MODE_SYNC;
opts->wer_mode = SENTRY_WER_MODE_SHARED;
opts->enable_app_hang_tracking = false;
opts->app_hang_timeout = 5000;
opts->http_retry = false;
Expand Down Expand Up @@ -1038,6 +1039,24 @@ sentry_options_set_handler_strategy(

#endif // SENTRY_PLATFORM_LINUX

void
sentry_options_set_wer_mode(sentry_options_t *opts, sentry_wer_mode_t mode)
{
int imode = (int)mode;
if (imode < SENTRY_WER_MODE_NONE) {
imode = SENTRY_WER_MODE_NONE;
} else if (imode > SENTRY_WER_MODE_SHARED) {
imode = SENTRY_WER_MODE_SHARED;
}
opts->wer_mode = imode;
}

sentry_wer_mode_t
sentry_options_get_wer_mode(const sentry_options_t *opts)
{
return (sentry_wer_mode_t)opts->wer_mode;
}

void
sentry_options_set_http_retry(sentry_options_t *opts, int enabled)
{
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1 change: 1 addition & 0 deletions src/sentry_options.h
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Expand Up @@ -105,6 +105,7 @@ struct sentry_options_s {
int crash_reporting_mode; // 0=minidump, 1=native, 2=native_with_minidump
// (see sentry_crash_reporting_mode_t)
int crash_upload_mode; // 0=sync, 1=async (see sentry_crash_upload_mode_t)
int wer_mode; // 0=none, 1=exclusive, 2=shared (see sentry_wer_mode_t)

#ifdef SENTRY_PLATFORM_NX
void (*network_connect_func)(void);
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