feat(integration): add rust as a full example-based variant

Add a Rust integration variant anchored on a real example app
(example-apps/rust): an Axum service that builds one posthog-rs client
per process, configures it from the environment, identifies users via a
$set property, captures events, evaluates feature flags with the current
evaluate_flags snapshot API, captures exceptions, and calls flush() +
shutdown() on graceful shutdown (capture is fire-and-forget).

Ships a full example rather than docs-only so the wizard has a concrete
shape to match. Adds rust commandments (including honest limitations: no
alias/surveys/session-replay) and skips the Rust target/ build dir when
flattening the example.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: sarahxsanders

context/commandments.yaml

@@ -90,6 +90,17 @@ commandments:
     - Avoid deprecated feature flag helpers such as `IsFeatureEnabled`, `GetFeatureFlag`, `GetFeatureFlagPayload`, and `Capture.SendFeatureFlags` in new code
     - For error tracking, use `posthog.NewDefaultException(...)` for direct captures or wrap `log/slog` with `posthog.NewSlogCaptureHandler(...)` for automatic warning-and-above exception capture
 
+  rust:
+    - posthog-rs is the Rust SDK crate; add it with `cargo add posthog-rs` and construct the client with `posthog_rs::client(options).await`
+    - Create one client per process and share it (for example an `Arc` in your app state or a `OnceCell`); do not build a new client per request or task
+    - Configure the project token and host from environment variables via `ClientOptions` (the `(api_key, host)` tuple); never hardcode PostHog secrets
+    - Because `capture` is fire-and-forget, always call `client.flush().await` and `client.shutdown().await` during graceful shutdown so queued events are delivered before exit
+    - Server-side captures must set a stable `distinct_id` on `Event::new(event, distinct_id)` that matches frontend identify calls; avoid anonymous or literal IDs for business events
+    - The SDK has no `identify` or `alias` helper; set person properties by inserting a `$set` property on an event
+    - For feature flags, call `client.evaluate_flags(distinct_id, EvaluateFlagsOptions::default()).await` once per user/request, then read values from the returned snapshot with `is_enabled(...)`
+    - For error tracking, use `client.capture_exception_with(&err, CaptureExceptionOptions::new()...)`; the `error-tracking` feature is enabled by default in recent versions
+    - The Rust SDK has no surveys or session replay support; do not promise or scaffold those features
+
   dotnet:
     - posthog-dotnet package names are `PostHog` for general .NET apps and `PostHog.AspNetCore` for ASP.NET Core apps
     - Use environment variables, user secrets, or configuration providers for `ProjectToken`, `HostUrl`, and `PersonalApiKey`; never hardcode PostHog secrets

context/skills/integration/config.yaml

@@ -244,6 +244,15 @@ variants:
     docs_urls:
       - https://posthog.com/docs/libraries/go.md
 
+  - id: rust
+    framework: rust
+    example_paths: example-apps/rust
+    display_name: Rust
+    description: PostHog integration for Rust applications using the posthog-rs SDK
+    tags: [rust]
+    docs_urls:
+      - https://posthog.com/docs/libraries/rust.md
+
   - id: swift
     framework: swift
     example_paths:

context/skip-patterns.yaml

@@ -131,6 +131,9 @@ global:
     - bin/
     - obj/
 
+    # Rust
+    - target/
+
     # PHP General
     - vendor
     - .phpunit.result.cache

example-apps/rust/.env.example

@@ -0,0 +1,8 @@
+# Copy this file to `.env` and fill in your values, then export them
+# (e.g. `export $(grep -v '^#' .env | xargs)`) before running the app.
+
+# Your PostHog project token (from Project settings).
+POSTHOG_PROJECT_TOKEN=your_posthog_project_token
+
+# PostHog host. Defaults to https://us.i.posthog.com when unset.
+POSTHOG_HOST=https://us.i.posthog.com

example-apps/rust/.gitignore

@@ -0,0 +1,2 @@
+/target
+.env