feat(ai): record usage after each OpenRouter extraction

Wire AiUsageRepository into AppState and add a fire-and-forget
record_ai_usage helper. All extraction route handlers now capture
the usage tuple and record it in the background.

src/application/routes/roasters.rs

@@ -118,15 +118,15 @@ define_delete_handler!(
     render_roaster_list_fragment
 );
 
-#[tracing::instrument(skip(state, _auth_user, headers, payload))]
+#[tracing::instrument(skip(state, auth_user, headers, payload))]
 pub(crate) async fn extract_roaster(
     State(state): State<AppState>,
-    _auth_user: AuthenticatedUser,
+    auth_user: AuthenticatedUser,
     headers: HeaderMap,
     payload: FlexiblePayload<ExtractionInput>,
 ) -> Result<Response, ApiError> {
     let (input, _) = payload.into_parts();
-    let result = ai::extract_roaster(
+    let (result, usage) = ai::extract_roaster(
         &state.http_client,
         &state.openrouter_api_key,
         &state.openrouter_model,
@@ -135,6 +135,14 @@ pub(crate) async fn extract_roaster(
     .await
     .map_err(ApiError::from)?;
 
+    super::support::record_ai_usage(
+        state.ai_usage_repo.clone(),
+        auth_user.0.id,
+        &state.openrouter_model,
+        "extract-roaster",
+        usage,
+    );
+
     if is_datastar_request(&headers) {
         use serde_json::Value;
         let signals = vec![

src/application/routes/roasts.rs

@@ -257,15 +257,15 @@ impl TastingNotesInput {
     }
 }
 
-#[tracing::instrument(skip(state, _auth_user, headers, payload))]
+#[tracing::instrument(skip(state, auth_user, headers, payload))]
 pub(crate) async fn extract_roast_info(
     State(state): State<AppState>,
-    _auth_user: AuthenticatedUser,
+    auth_user: AuthenticatedUser,
     headers: HeaderMap,
     payload: FlexiblePayload<ExtractionInput>,
 ) -> Result<Response, ApiError> {
     let (input, _) = payload.into_parts();
-    let result = ai::extract_roast(
+    let (result, usage) = ai::extract_roast(
         &state.http_client,
         &state.openrouter_api_key,
         &state.openrouter_model,
@@ -274,6 +274,14 @@ pub(crate) async fn extract_roast_info(
     .await
     .map_err(ApiError::from)?;
 
+    super::support::record_ai_usage(
+        state.ai_usage_repo.clone(),
+        auth_user.0.id,
+        &state.openrouter_model,
+        "extract-roast",
+        usage,
+    );
+
     if is_datastar_request(&headers) {
         use serde_json::Value;
 

src/application/routes/scan.rs

@@ -14,17 +14,17 @@ use crate::domain::errors::RepositoryError;
 use crate::domain::roasters::NewRoaster;
 use crate::domain::roasts::NewRoast;
 use crate::domain::timeline::{NewTimelineEvent, TimelineEventDetail};
-use crate::infrastructure::ai::{self, ExtractionInput};
+use crate::infrastructure::ai::{self, ExtractionInput, Usage};
 
-#[tracing::instrument(skip(state, _auth_user, headers, payload))]
+#[tracing::instrument(skip(state, auth_user, headers, payload))]
 pub(crate) async fn extract_bag_scan(
     State(state): State<AppState>,
-    _auth_user: AuthenticatedUser,
+    auth_user: AuthenticatedUser,
     headers: HeaderMap,
     payload: FlexiblePayload<ExtractionInput>,
 ) -> Result<Response, ApiError> {
     let (input, _) = payload.into_parts();
-    let result = ai::extract_bag_scan(
+    let (result, usage) = ai::extract_bag_scan(
         &state.http_client,
         &state.openrouter_api_key,
         &state.openrouter_model,
@@ -33,6 +33,14 @@ pub(crate) async fn extract_bag_scan(
     .await
     .map_err(ApiError::from)?;
 
+    super::support::record_ai_usage(
+        state.ai_usage_repo.clone(),
+        auth_user.0.id,
+        &state.openrouter_model,
+        "extract-bag-scan",
+        usage,
+    );
+
     if is_datastar_request(&headers) {
         use serde_json::Value;
 
@@ -130,15 +138,16 @@ struct ScanResult {
 }
 
 /// Populate a `BagScanSubmission` from AI extraction when image/prompt is provided.
+/// Returns the usage data so the caller can record it.
 async fn extract_into_submission(
     state: &AppState,
     submission: &mut BagScanSubmission,
-) -> Result<(), ApiError> {
+) -> Result<Option<Usage>, ApiError> {
     let input = ExtractionInput {
         image: submission.image.take(),
         prompt: submission.prompt.take(),
     };
-    let result = ai::extract_bag_scan(
+    let (result, usage) = ai::extract_bag_scan(
         &state.http_client,
         &state.openrouter_api_key,
         &state.openrouter_model,
@@ -178,14 +187,14 @@ async fn extract_into_submission(
         submission.tasting_notes = TastingNotesInput::Text(notes.join(", "));
     }
 
-    Ok(())
+    Ok(usage)
 }
 
 #[allow(clippy::too_many_lines)]
-#[tracing::instrument(skip(state, _auth_user, headers, payload))]
+#[tracing::instrument(skip(state, auth_user, headers, payload))]
 pub(crate) async fn submit_scan(
     State(state): State<AppState>,
-    _auth_user: AuthenticatedUser,
+    auth_user: AuthenticatedUser,
     headers: HeaderMap,
     payload: FlexiblePayload<BagScanSubmission>,
 ) -> Result<Response, ApiError> {
@@ -196,7 +205,14 @@ pub(crate) async fn submit_scan(
         || submission.prompt.as_deref().is_some_and(|s| !s.is_empty());
 
     if has_raw_input {
-        extract_into_submission(&state, &mut submission).await?;
+        let usage = extract_into_submission(&state, &mut submission).await?;
+        super::support::record_ai_usage(
+            state.ai_usage_repo.clone(),
+            auth_user.0.id,
+            &state.openrouter_model,
+            "extract-bag-scan",
+            usage,
+        );
     }
 
     // Build and normalize the roaster

src/application/routes/support.rs

@@ -236,6 +236,31 @@ pub(super) async fn load_cafe_options(state: &AppState) -> Result<Vec<CafeOption
     Ok(cafes.into_iter().map(CafeOptionView::from).collect())
 }
 
+/// Record AI usage in the background. Failures are logged but do not affect the response.
+pub fn record_ai_usage(
+    repo: std::sync::Arc<dyn crate::domain::repositories::AiUsageRepository>,
+    user_id: crate::domain::ids::UserId,
+    model: &str,
+    endpoint: &str,
+    usage: Option<crate::infrastructure::ai::Usage>,
+) {
+    let Some(usage) = usage else { return };
+    let new_usage = crate::domain::ai_usage::NewAiUsage {
+        user_id,
+        model: model.to_string(),
+        endpoint: endpoint.to_string(),
+        prompt_tokens: usage.prompt_tokens,
+        completion_tokens: usage.completion_tokens,
+        total_tokens: usage.total_tokens,
+        cost: usage.cost,
+    };
+    tokio::spawn(async move {
+        if let Err(err) = repo.insert(new_usage).await {
+            tracing::warn!(error = %err, "failed to record AI usage");
+        }
+    });
+}
+
 pub fn is_datastar_request(headers: &HeaderMap) -> bool {
     headers
         .get("datastar-request")

src/application/server.rs

@@ -12,13 +12,14 @@ use webauthn_rs::prelude::*;
 use crate::application::routes::app_router;
 use crate::domain::registration_tokens::NewRegistrationToken;
 use crate::domain::repositories::{
-    BagRepository, BrewRepository, CafeRepository, CupRepository, GearRepository,
-    PasskeyCredentialRepository, RegistrationTokenRepository, RoastRepository, RoasterRepository,
-    SessionRepository, TimelineEventRepository, TokenRepository, UserRepository,
+    AiUsageRepository, BagRepository, BrewRepository, CafeRepository, CupRepository,
+    GearRepository, PasskeyCredentialRepository, RegistrationTokenRepository, RoastRepository,
+    RoasterRepository, SessionRepository, TimelineEventRepository, TokenRepository, UserRepository,
 };
 use crate::infrastructure::auth::{generate_session_token, hash_token};
 use crate::infrastructure::backup::BackupService;
 use crate::infrastructure::database::Database;
+use crate::infrastructure::repositories::ai_usage::SqlAiUsageRepository;
 use crate::infrastructure::repositories::bags::SqlBagRepository;
 use crate::infrastructure::repositories::brews::SqlBrewRepository;
 use crate::infrastructure::repositories::cafes::SqlCafeRepository;
@@ -59,6 +60,7 @@ pub struct AppState {
     pub session_repo: Arc<dyn SessionRepository>,
     pub passkey_repo: Arc<dyn PasskeyCredentialRepository>,
     pub registration_token_repo: Arc<dyn RegistrationTokenRepository>,
+    pub ai_usage_repo: Arc<dyn AiUsageRepository>,
     pub webauthn: Arc<Webauthn>,
     pub challenge_store: Arc<ChallengeStore>,
     pub http_client: reqwest::Client,
@@ -101,6 +103,8 @@ pub async fn serve(config: ServerConfig) -> anyhow::Result<()> {
         Arc::new(SqlPasskeyCredentialRepository::new(database.clone_pool()));
     let registration_token_repo: Arc<dyn RegistrationTokenRepository> =
         Arc::new(SqlRegistrationTokenRepository::new(database.clone_pool()));
+    let ai_usage_repo: Arc<dyn AiUsageRepository> =
+        Arc::new(SqlAiUsageRepository::new(database.clone_pool()));
 
     let backup_service = Arc::new(BackupService::new(database.clone_pool()));
     let challenge_store = Arc::new(ChallengeStore::new());
@@ -122,6 +126,7 @@ pub async fn serve(config: ServerConfig) -> anyhow::Result<()> {
         session_repo,
         passkey_repo,
         registration_token_repo,
+        ai_usage_repo,
         webauthn,
         challenge_store,
         http_client: reqwest::Client::new(),

tests/server/helpers.rs

@@ -164,6 +164,11 @@ async fn spawn_app_inner(
         session_repo,
         passkey_repo,
         registration_token_repo,
+        ai_usage_repo: Arc::new(
+            brewlog::infrastructure::repositories::ai_usage::SqlAiUsageRepository::new(
+                _database.clone_pool(),
+            ),
+        ),
         webauthn: test_webauthn(),
         challenge_store: Arc::new(ChallengeStore::new()),
         http_client: reqwest::Client::new(),