fix(stt): pass speaker count hints

apps/desktop/src/stt/useRunBatch.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, test } from "vitest";
 
-import { getBatchProvider } from "./useRunBatch";
+import { getBatchProvider, getSessionSpeakerCount } from "./useRunBatch";
 
 describe("getBatchProvider", () => {
   test("maps pyannote to the batch transcription provider", () => {
@@ -19,3 +19,40 @@ describe("getBatchProvider", () => {
     );
   });
 });
+
+describe("getSessionSpeakerCount", () => {
+  test("counts distinct session participants plus the current user", () => {
+    const rows = new Map([
+      ["mapping-1", { session_id: "session-1", human_id: "human-a" }],
+      ["mapping-2", { session_id: "session-1", human_id: "human-a" }],
+      ["mapping-3", { session_id: "session-1", human_id: "human-b" }],
+      ["mapping-4", { session_id: "other-session", human_id: "human-c" }],
+    ]);
+    const store = {
+      forEachRow: (_table: string, callback: (rowId: string) => void) => {
+        for (const rowId of rows.keys()) callback(rowId);
+      },
+      getCell: (_table: string, rowId: string, cellId: string) =>
+        rows.get(rowId)?.[cellId as "session_id" | "human_id"],
+    };
+
+    expect(getSessionSpeakerCount(store as any, "session-1", "self")).toBe(3);
+  });
+
+  test("returns undefined until at least two speakers are known", () => {
+    const rows = new Map([
+      ["mapping-1", { session_id: "session-1", human_id: "human-a" }],
+    ]);
+    const store = {
+      forEachRow: (_table: string, callback: (rowId: string) => void) => {
+        for (const rowId of rows.keys()) callback(rowId);
+      },
+      getCell: (_table: string, rowId: string, cellId: string) =>
+        rows.get(rowId)?.[cellId as "session_id" | "human_id"],
+    };
+
+    expect(getSessionSpeakerCount(store as any, "session-1", null)).toBe(
+      undefined,
+    );
+  });
+});

apps/desktop/src/stt/useRunBatch.ts

@@ -32,6 +32,8 @@ type RunOptions = {
   maxSpeakers?: number;
 };
 
+type Store = NonNullable<ReturnType<typeof main.UI.useStore>>;
+
 const DIRECT_BATCH_PROVIDERS: Set<TranscriptionParams["provider"]> = new Set([
   "deepgram",
   "soniox",
@@ -81,6 +83,38 @@ export function isStoppedTranscriptionError(error: unknown) {
   );
 }
 
+export function getSessionSpeakerCount(
+  store: Store,
+  sessionId: string,
+  selfHumanId?: string | null,
+): number | undefined {
+  const humanIds = new Set<string>();
+
+  store.forEachRow("mapping_session_participant", (mappingId, _forEachCell) => {
+    const sid = store.getCell(
+      "mapping_session_participant",
+      mappingId,
+      "session_id",
+    );
+    if (sid !== sessionId) return;
+
+    const humanId = store.getCell(
+      "mapping_session_participant",
+      mappingId,
+      "human_id",
+    );
+    if (typeof humanId === "string" && humanId) {
+      humanIds.add(humanId);
+    }
+  });
+
+  if (typeof selfHumanId === "string" && selfHumanId) {
+    humanIds.add(selfHumanId);
+  }
+
+  return humanIds.size > 1 ? humanIds.size : undefined;
+}
+
 export const useRunBatch = (sessionId: string) => {
   const store = main.UI.useStore(main.STORE_ID);
   const indexes = main.UI.useIndexes(main.STORE_ID);
@@ -114,6 +148,12 @@ export const useRunBatch = (sessionId: string) => {
       const createdAt = new Date().toISOString();
       const memoMd = store.getCell("sessions", sessionId, "raw_md");
       let transcriptId: string | null = null;
+      const inferredNumSpeakers =
+        options?.numSpeakers === undefined &&
+        options?.minSpeakers === undefined &&
+        options?.maxSpeakers === undefined
+          ? getSessionSpeakerCount(store, sessionId, user_id)
+          : undefined;
 
       const handlePersist: BatchPersistCallback | undefined =
         options?.handlePersist;
@@ -232,7 +272,7 @@ export const useRunBatch = (sessionId: string) => {
         languages:
           options?.languages ??
           getTranscriptionLanguages(aiLanguage, spokenLanguages),
-        num_speakers: options?.numSpeakers,
+        num_speakers: options?.numSpeakers ?? inferredNumSpeakers,
         min_speakers: options?.minSpeakers,
         max_speakers: options?.maxSpeakers,
       };

crates/listener-core/src/actors/listener/adapters.rs

@@ -410,32 +410,25 @@ fn i16_bytes_to_f32(bytes: &Bytes) -> Vec<f32> {
 }
 
 fn build_listen_params(args: &ListenerArgs) -> owhisper_interface::ListenParams {
-    let adapter_kind =
-        AdapterKind::from_url_and_languages(&args.base_url, &args.languages, Some(&args.model));
     let redemption_time_ms = if args.onboarding { "60" } else { "400" };
-    let mut custom_query = std::collections::HashMap::from([(
+    let custom_query = std::collections::HashMap::from([(
         "redemption_time_ms".to_string(),
         redemption_time_ms.to_string(),
     )]);
-
-    if adapter_kind == AdapterKind::AssemblyAI
-        && let Some(expected_speakers) = assemblyai_expected_speakers(args)
-    {
-        custom_query.insert("speaker_labels".to_string(), "true".to_string());
-        custom_query.insert("max_speakers".to_string(), expected_speakers.to_string());
-    }
+    let num_speakers = expected_speakers(args);
 
     owhisper_interface::ListenParams {
         model: Some(args.model.clone()),
         languages: args.languages.clone(),
         sample_rate: super::super::SAMPLE_RATE,
         keywords: args.keywords.clone(),
+        num_speakers,
         custom_query: Some(custom_query),
         ..Default::default()
     }
 }
 
-fn assemblyai_expected_speakers(args: &ListenerArgs) -> Option<u32> {
+fn expected_speakers(args: &ListenerArgs) -> Option<u32> {
     let mut participants = args.participant_human_ids.clone();
 
     if let Some(self_human_id) = &args.self_human_id
@@ -655,31 +648,26 @@ mod tests {
     }
 
     #[test]
-    fn assemblyai_expected_speakers_counts_distinct_participants() {
+    fn expected_speakers_counts_distinct_participants() {
         let mut args = listener_args("https://api.assemblyai.com", "u3-rt-pro");
         args.participant_human_ids = vec!["remote".to_string(), "self".to_string()];
         args.self_human_id = Some("self".to_string());
 
-        assert_eq!(assemblyai_expected_speakers(&args), Some(2));
+        assert_eq!(expected_speakers(&args), Some(2));
     }
 
     #[test]
-    fn build_listen_params_adds_assemblyai_diarization_hints() {
+    fn build_listen_params_sets_num_speakers_without_assemblyai_custom_query() {
         let mut args = listener_args("https://api.assemblyai.com", "u3-rt-pro");
         args.participant_human_ids = vec!["remote".to_string()];
         args.self_human_id = Some("self".to_string());
 
         let params = build_listen_params(&args);
         let custom_query = params.custom_query.expect("custom query");
 
-        assert_eq!(
-            custom_query.get("speaker_labels").map(String::as_str),
-            Some("true")
-        );
-        assert_eq!(
-            custom_query.get("max_speakers").map(String::as_str),
-            Some("2")
-        );
+        assert_eq!(params.num_speakers, Some(2));
+        assert!(!custom_query.contains_key("speaker_labels"));
+        assert!(!custom_query.contains_key("max_speakers"));
     }
 
     #[test]
@@ -691,6 +679,7 @@ mod tests {
         let params = build_listen_params(&args);
         let custom_query = params.custom_query.expect("custom query");
 
+        assert_eq!(params.num_speakers, Some(2));
         assert!(!custom_query.contains_key("speaker_labels"));
         assert!(!custom_query.contains_key("max_speakers"));
     }

crates/owhisper-client/src/adapter/assemblyai/live.rs

@@ -57,18 +57,13 @@ impl RealtimeSttAdapter for AssemblyAIAdapter {
                 query_pairs.append_pair("max_turn_silence", max_silence);
             }
 
-            if matches!(resolved_model, ResolvedLiveModel::U3RtPro)
-                && let Some(custom) = &params.custom_query
-            {
-                if custom
-                    .get("speaker_labels")
-                    .is_some_and(|value| value == "true")
-                {
+            if matches!(resolved_model, ResolvedLiveModel::U3RtPro) {
+                if Self::streaming_speaker_labels_enabled(params) {
                     query_pairs.append_pair("speaker_labels", "true");
                 }
 
-                if let Some(max_speakers) = custom.get("max_speakers") {
-                    query_pairs.append_pair("max_speakers", max_speakers);
+                if let Some(max_speakers) = Self::streaming_max_speakers(params) {
+                    query_pairs.append_pair("max_speakers", &max_speakers.to_string());
                 }
             }
 
@@ -232,6 +227,27 @@ impl AssemblyAIAdapter {
         }
     }
 
+    fn streaming_speaker_labels_enabled(params: &ListenParams) -> bool {
+        params.num_speakers.is_some()
+            || params.min_speakers.is_some()
+            || params.max_speakers.is_some()
+            || params
+                .custom_query
+                .as_ref()
+                .and_then(|custom| custom.get("speaker_labels"))
+                .is_some_and(|value| value == "true")
+    }
+
+    fn streaming_max_speakers(params: &ListenParams) -> Option<u32> {
+        params.max_speakers.or(params.num_speakers).or_else(|| {
+            params
+                .custom_query
+                .as_ref()
+                .and_then(|custom| custom.get("max_speakers"))
+                .and_then(|value| value.parse().ok())
+        })
+    }
+
     fn parse_speaker_label(label: Option<&str>) -> Option<i32> {
         let label = label?.trim();
         if label.is_empty() || label.eq_ignore_ascii_case("unknown") {
@@ -339,8 +355,6 @@ impl ResolvedLiveModel {
 
 #[cfg(test)]
 mod tests {
-    use std::collections::HashMap;
-
     use hypr_language::ISO639;
     use owhisper_interface::ListenParams;
     use owhisper_interface::stream::StreamResponse;
@@ -424,10 +438,7 @@ mod tests {
             API_BASE,
             &owhisper_interface::ListenParams {
                 model: Some("u3-rt-pro".to_string()),
-                custom_query: Some(HashMap::from([
-                    ("speaker_labels".to_string(), "true".to_string()),
-                    ("max_speakers".to_string(), "3".to_string()),
-                ])),
+                num_speakers: Some(3),
                 ..Default::default()
             },
             1,
@@ -439,14 +450,28 @@ mod tests {
     }
 
     #[test]
-    fn test_whisper_fallback_omits_streaming_diarization_hints() {
+    fn test_streaming_min_speakers_enables_diarization() {
+        let url = AssemblyAIAdapter.build_ws_url(
+            API_BASE,
+            &owhisper_interface::ListenParams {
+                model: Some("u3-rt-pro".to_string()),
+                min_speakers: Some(2),
+                ..Default::default()
+            },
+            1,
+        );
+
+        let query = url.query().expect("query string");
+        assert!(query.contains("speaker_labels=true"));
+        assert!(!query.contains("max_speakers"));
+    }
+
+    #[test]
+    fn test_streaming_diarization_hints_skip_whisper_fallback() {
         let url = AssemblyAIAdapter.build_ws_url(
             API_BASE,
             &owhisper_interface::ListenParams {
-                custom_query: Some(HashMap::from([
-                    ("speaker_labels".to_string(), "true".to_string()),
-                    ("max_speakers".to_string(), "3".to_string()),
-                ])),
+                num_speakers: Some(3),
                 languages: vec![ISO639::Ko.into()],
                 ..Default::default()
             },
@@ -455,8 +480,8 @@ mod tests {
 
         let query = url.query().expect("query string");
         assert!(query.contains("speech_model=whisper-rt"));
-        assert!(!query.contains("speaker_labels=true"));
-        assert!(!query.contains("max_speakers=3"));
+        assert!(!query.contains("speaker_labels"));
+        assert!(!query.contains("max_speakers"));
     }
 
     #[test]

crates/owhisper-client/src/adapter/elevenlabs/batch.rs

@@ -86,6 +86,10 @@ impl ElevenLabsAdapter {
             .text("diarize", "true")
             .text("timestamps_granularity", "word");
 
+        if let Some(num_speakers) = Self::num_speakers_hint(params) {
+            form = form.text("num_speakers", num_speakers.to_string());
+        }
+
         if let Some(lang) = params.languages.first() {
             form = form.text("language_code", lang.iso639().code().to_string());
         }
@@ -116,6 +120,10 @@ impl ElevenLabsAdapter {
         Ok(Self::convert_to_batch_response(transcript))
     }
 
+    fn num_speakers_hint(params: &ListenParams) -> Option<u32> {
+        params.num_speakers.or(params.max_speakers)
+    }
+
     fn convert_to_batch_response(response: TranscriptResponse) -> BatchResponse {
         let words: Vec<BatchWord> = response
             .words
@@ -164,6 +172,26 @@ mod tests {
     use super::*;
     use crate::http_client::create_client;
 
+    #[test]
+    fn num_speakers_hint_prefers_exact_count_then_max() {
+        let exact = ListenParams {
+            num_speakers: Some(3),
+            max_speakers: Some(5),
+            ..Default::default()
+        };
+        let ranged = ListenParams {
+            max_speakers: Some(5),
+            ..Default::default()
+        };
+
+        assert_eq!(ElevenLabsAdapter::num_speakers_hint(&exact), Some(3));
+        assert_eq!(ElevenLabsAdapter::num_speakers_hint(&ranged), Some(5));
+        assert_eq!(
+            ElevenLabsAdapter::num_speakers_hint(&ListenParams::default()),
+            None
+        );
+    }
+
     #[test]
     fn speaker_labeled_words_use_mixed_capture_channel() {
         let response = TranscriptResponse {