## Debugging tools

When a user sees an unexpected value, start with the tooling built into the Statsig console and SDKs.

### Diagnostics & log stream

Every gate, config, experiment, and layer has both a **Setup** and **Diagnostics** tab. The diagnostics view highlights pass/fail rates and bucketing counts so you can spot anomalies over time.

{% figure %}
![Diagnostics tab showing pass and fail counts](/images/sdks/debugging/diagnostics-overview.png)
{% /figure %}

Scroll to the log stream to inspect individual evaluations. Entries arrive within seconds for both production and non-production environments.

{% figure %}
![Log stream showing recent exposures](/images/sdks/debugging/log-stream.png)
{% /figure %}

{% callout type="note" %}
Enable **Show non-production logs** in the diagnostics view to surface checks coming from test keys and development builds.
{% /callout %}

### Logging levels and expected information

Statsig SDKs emit runtime logs across four verbosity levels:

* `Debug` – deep tracing meant for onboarding or issue triage.
  * Missing gate/config warnings when a definition is unavailable.
  * Step-by-step messages that follow SDK initialization and evaluations.
* `Info` – healthy lifecycle events for day-to-day operation.
  * Initialization summaries with source and SDK version details.
  * Notifications when the configuration store is populated.
* `Warning` – recoverable issues that might affect functionality.
  * Non-critical errors automatically handled by the SDK.
  * gRPC reconnection attempts or similar transient network events.
* `Error` – critical failures that block expected behavior.
  * Initialization timeouts or outright failures.
  * Fallback notices that indicate gRPC is unavailable or misconfigured.

## Evaluation details

Click any exposure in the log stream to drill into the precise rule, user attributes, evaluation reason, SDK metadata, and server timestamps. That detail is often enough to pinpoint why a user received a specific value.

{% figure %}
![Evaluation details modal with rule match information](/images/sdks/debugging/evaluation-details.png)
{% /figure %}

### Evaluation reasons

Evaluation reasons answer two questions: where the SDK sourced its definitions and why a particular value was returned. Use them to distinguish between healthy results, overrides, and error states.

{% figure %}
![Evaluation reason popover showing source and reason](/images/sdks/debugging/evaluation-reason.png)
{% /figure %}

{% tabs %}
{% tab title="Client SDKs" %}
#### Data source

| Source | Description | Type | Debugging Suggestions |
| --- | --- | --- | --- |
| `Network` | Values fetched during initialization from Statsig servers. | Normal | None |
| `Bootstrap` | Supplied during bootstrap (often from a server SDK). | Normal | None |
| `Prefetch` | Loaded via the `prefetchUsers` API (JS only). | Normal | None |
| `NetworkNotModified` | Network request succeeded but cached values were already current. | Normal | None |
| `Sticky` (legacy) | Persisted from a sticky evaluation. | Normal | None |
| `LocalOverride` (legacy) | Set locally via override APIs. | Normal | None |
| `Cache` | Served from local cache because network values were unavailable. | Warning | Ensure `initialize()` has completed before checks run. |
| `InvalidBootstrap` / `BootstrapPartialUserMatch` | Bootstrap values were generated for a different user profile. | Error | Refer to [Fixing InvalidBootstrap](#invalid-bootstrap). |
| `BootstrapStableIDMismatch` | StableID differed between bootstrap and runtime user. | Error | Refer to [BootstrapStableIDMismatch](#bootstrapstableidmismatch). |
| `Error` | A generic evaluation failure that was logged to Statsig. | Error | Ask for help in [Slack](https://statsig.com/slack). |
| `Error:NoClient` (JS) | No Statsig client was found in context. | Error | Wrap checks in `<StatsigProvider>` or equivalent. |
| `Unrecognized` (legacy) | The definition was missing from the initialize payload. | Error | Confirm the config exists and the correct API key is used. |
| `NoValues` | Initialization ran but failed to retrieve values. | Error | Verify client key and network connectivity. |
| `Loading` | Initialization is still in progress. | Error | Await `initializeAsync()` or guard checks until ready. |
| `Uninitialized` | Initialization never started. | Error | Call `initializeAsync()`/`initializeSync()` explicitly. |
| `UAParserNotLoaded` | UA parsing was disabled while targeting relies on it. | Error | Remove UA-based targeting or re-enable parsing. |
| `CountryLookupNotLoaded` | Country lookups were disabled while targeting relies on them. | Error | Avoid IP-based targeting or re-enable lookups. |

#### Reason (new SDKs only)

| Reason | Description | Type | Debugging Suggestions |
| --- | --- | --- | --- |
| `Recognized` | The definition was present and matched the current values. | Normal | None |
| `Sticky` | Result persisted because `keepDeviceValue` was set. | Normal | None |
| `LocalOverride` | Value came from a developer override. | Normal | None |
| `Unrecognized` | Definition missing from the payload. | Error | Confirm targeting and [Target Apps](/sdks/target-apps). |
| `Filtered` | Definition filtered from `/initialize` because the default value was `false`. | Error | Check [client bootstrapping](/client/concepts/initialize#bootstrapping-overview) or targeting.
{% /tab %}

{% tab title="Server SDKs" %}
#### Data source

| Source | Description | Type | Debugging Suggestions |
| --- | --- | --- | --- |
| `Network` | Configurations loaded from Statsig servers at initialization. | Normal | None |
| `Bootstrap` | Server SDK bootstrapped with precomputed values. | Normal | None |
| `DataAdapter` | Values retrieved from a data adapter or external store. | Normal | Review your [data adapter setup](/server/concepts/data_store#dataadapter-or-datastore). |
| `LocalOverride` (legacy) | Value supplied via server-side override APIs. | Normal | None |
| `StatsigNetwork` | Proxy/streaming fell back to Statsig APIs directly. | Fallback | Revisit your [proxy configuration](/server/concepts/forward_proxy/). |
| `Uninitialized` | SDK has not completed initialization. | Error | Ensure initialization succeeds before evaluations. |
| `Unrecognized` (legacy) | Definition missing from the cached payload. | Error | Confirm configuration exists and the API key is correct. |

#### Reason (new SDKs only)

| Reason | Description | Type | Debugging Suggestions |
| --- | --- | --- | --- |
| `LocalOverride` | Result supplied by a developer override. | Normal | None |
| *None* | Successful evaluation with the expected payload. | Normal | None |
| `Unrecognized` | Definition missing from the payload. | Error | Confirm configuration exists and the API key is correct. |
| `Unsupported` | SDK lacks support for a condition/operator. | Error | Upgrade to the latest SDK version. |
| `Error` | Generic evaluation failure captured by the SDK. | Error | Ask for help in [Slack](https://statsig.com/slack). |
{% /tab %}
{% /tabs %}

### Evaluation times

Evaluation timestamps reveal whether an SDK is serving fresh definitions. An up-to-date LCUT (Last Config Updated Time) indicates the SDK has the latest changes. If LCUT lags behind, users may be seeing stale values. This can happen because a browser tab remained open or because a server integration cannot sync.

{% tabs %}
{% tab title="Client SDKs" %}
| Time Field | Description | SDKs |
| --- | --- | --- |
| `LCUT` | Time of the most recent config change reflected in the SDK. | JavaScript (incl. React & RN), iOS, Dart |
| `receivedAt` | Timestamp when the client obtained the current values. | JavaScript (incl. React & RN), iOS, Dart |
{% /tab %}

{% tab title="Server SDKs" %}
| Time Field | Description | SDKs |
| --- | --- | --- |
| `initTime` | LCUT captured when the server SDK initialized. | All server SDKs except Rust |
| `configSyncTime` | Latest LCUT received from the network or data adapter. | All server SDKs except Rust |
| `serverTime` | Current server clock time when the evaluation was made. | All server SDKs except Rust |
{% /tab %}
{% /tabs %}

### Mocking Statsig / local mode

Use the following tools to validate code paths without making network requests:

* **Local mode:** Set `localMode` to `true` so the SDK skips network calls and returns default values. This is useful for tests and offline environments.
* **Override APIs:** Call `overrideGate` and `overrideConfig` to force specific values for an individual user or globally.

Use both techniques together to exercise each branch of your application before shipping.

### Client SDK debugger

Inspect the exact values a client SDK is using by opening the Client SDK Debugger. It exposes the active user object and every gate/config tied to that client.

* **JavaScript / React:** Use the [Chrome extension](https://github.com/statsig-io/statsig-sdk-debugger-chrome-extension).
* **iOS:** Call `Statsig.openDebugView()` in [v1.26.0](https://github.com/statsig-io/statsig-kit/releases/tag/v1.26.0) or later.
* **Android:** Call `Statsig.openDebugView()` in [v4.29.0](https://github.com/statsig-io/android-sdk/releases/tag/4.29.0) or later.

{% callout type="note" %}
Accounts that sign in to the Statsig console through Google SSO aren't supported by the Chrome extension.
{% /callout %}

| Landing | Gates List | Gate Details | Experiment Details |
| --- | --- | --- | --- |
| ![Client debugger landing view](/images/sdks/debugging/client-debugger-landing.png) | ![Client debugger gates list](/images/sdks/debugging/client-debugger-gates.png) | ![Client debugger gate details](/images/sdks/debugging/client-debugger-gate-details.png) | ![Client debugger experiment details](/images/sdks/debugging/client-debugger-experiment.png) |

## FAQ

For SDK-specific edge cases, check each SDK’s FAQ or reach out to the Statsig team in the [Statsig Slack community](https://statsig.com/slack).

### Invalid bootstrap

`InvalidBootstrap` occurs when a client SDK is bootstrapped with values generated for a different user profile. The bootstrap user must exactly match the runtime user object.

```js
// Server side
const userA = { userID: 'user-a' };
const bootstrapValues = Statsig.getClientInitializeResponse(userA);

// Client side
const bootstrapValues = await fetchStatsigValuesFromMyServers();
const userB = { userID: 'user-b' }; // <-- Different from userA
await Statsig.initialize('client-key', userB, { initializeValues: bootstrapValues });
```

Even subtle differences count as a mismatch. Adding `customIDs` or other attributes results in a distinct user object.

```js
const userA = { userID: 'user-a' };
const userAExt = { userID: 'user-a', customIDs: { employeeID: 'employee-a' } };
```

### BootstrapStableIDMismatch

`BootstrapStableIDMismatch` is similar to `InvalidBootstrap` but focuses on `stableID`. Client SDKs generate a stable ID automatically when one is not provided, so mixing empty user objects between server and client code can cause drift.

```js
// Server side
const userA = {};
const bootstrapValues = Statsig.getClientInitializeResponse(userA);

// Client side
const bootstrapValues = await fetchStatsigValuesFromMyServers();
const userB = { stableID: '12345' }; // <-- Server user lacked a stableID
await Statsig.initialize('client-key', userB, { initializeValues: bootstrapValues });
```

Even if both sides start with `{}`, the client-generated stable ID may not match the server’s stable ID, which triggers the same mismatch warning.

```js
const userC = {}; // Client SDK auto-generates a stableID
await Statsig.initialize('client-key', userC, { initializeValues: bootstrapValues });
```

### Environments

SDKs inherit their environment from initialization options. If you don't provide an environment, the SDK defaults to production. To verify which environment a user evaluated under, open the diagnostics log stream and inspect the `statsigEnvironment` property on the exposure entry.

### Maximizing event throughput

{% callout type="info" %}
Python SDK v0.45.0+ introduces tunables that help handle high event volume without drops.
{% /callout %}

The SDK batches events and retries failures in the background. When throughput spikes, adjust these options to reduce dropped events:

* **`eventQueueSize`** – Number of events flushed per batch. Larger batches increase throughput but use more memory. Keep the value under approximately 3000 to avoid oversized payloads.
* **`retryQueueSize`** – Number of batches kept for retrying. The default is 10. Raise this value to retain more data at the cost of higher memory usage.

Tune both settings to match your traffic profile.