diff --git a/src/host/start-config.ts b/src/host/start-config.ts
index 8422094..019484d 100644
--- a/src/host/start-config.ts
+++ b/src/host/start-config.ts
@@ -6,17 +6,21 @@
 
 import { DEFAULT_EXTRAS_BUDGET_USD } from "@livecap/engine";
 
-import { languageByCode } from "../languages.ts";
+import { languageByCode, SOURCE_AUTO_CODE } from "../languages.ts";
 import type { EnginePref, HostInbound } from "../protocol.ts";
 
 type StartMessage = Extract<HostInbound, { type: "start" }>;
 
-/** The meeting itself is spoken English (PROPOSAL positioning): reply
- *  suggestions and quick translate output INTO the meeting, and the archive
- *  header's source label reflects it. Captions themselves are auto-detected
- *  per sentence by whisper — there is no source-language setting (§8.6). */
-const MEETING_LANGUAGE = "English";
-const SOURCE_LANG_CODE = "EN";
+/** Reply suggestions and quick-translate output go INTO the meeting's spoken
+ *  language (§8.5), and the archive header's source label reflects it. #94 lets
+ *  the user pick that spoken language; when they leave it on "auto" (per-utterance
+ *  whisper detection, the default) there is no single spoken language, so reply/
+ *  quick-translate falls back to English — the pre-#94 behavior. */
+const AUTO_MEETING_LANGUAGE = "English";
+/** Archive header source label (§8.9) for auto-detect (#94/#175): a neutral
+ *  "AUTO" — detection is per-utterance, so no one language is the source. A
+ *  PICKED source language uses its own archiveLabel (e.g. "KO"). */
+const AUTO_SOURCE_LABEL = "AUTO";
 
 export interface ResolvedStartConfig {
   /** Translation target for the engine system prompt, e.g. "Korean". */
@@ -45,11 +49,22 @@ export interface ResolvedStartConfig {
 
 export function resolveStartConfig(message: StartMessage): ResolvedStartConfig {
   const language = languageByCode(message.targetLanguageCode);
+  // Spoken/source language (#94/#175): "auto" — and a blank value from an older
+  // shell — keeps per-utterance whisper detection (no fixed spoken language), so
+  // reply/quick-translate falls back to English and the archive header shows a
+  // neutral "AUTO". A picked tag uses its own name + archive label (Korean →
+  // "Korean" / "KO"). (`languageByCode("")` would be the `ko` default, hence the
+  // explicit blank check.)
+  const sourceCode = message.sourceLanguageCode.trim().toLowerCase();
+  const source =
+    sourceCode === SOURCE_AUTO_CODE || sourceCode === ""
+      ? null
+      : languageByCode(message.sourceLanguageCode);
   return {
     targetLanguage: language.name,
     summaryLanguage: language.name,
-    meetingLanguage: MEETING_LANGUAGE,
-    sourceLangCode: SOURCE_LANG_CODE,
+    meetingLanguage: source ? source.name : AUTO_MEETING_LANGUAGE,
+    sourceLangCode: source ? source.archiveLabel : AUTO_SOURCE_LABEL,
     targetLangCode: language.archiveLabel,
     enginePref: message.enginePref === "local" ? "local" : "cli",
     poolUsd: Number.isFinite(message.poolUsd) && message.poolUsd > 0 ? message.poolUsd : 20,
diff --git a/test/start-config.test.ts b/test/start-config.test.ts
index 24751b9..7761902 100644
--- a/test/start-config.test.ts
+++ b/test/start-config.test.ts
@@ -34,7 +34,7 @@ describe("resolveStartConfig — language plumbing (#12 goal 4)", () => {
     expect(resolved.targetLanguage).toBe("Korean"); // (a) translation system prompt
     expect(resolved.summaryLanguage).toBe("Korean"); // (b) extras/summary output
     expect(resolved.targetLangCode).toBe("KO"); // (c) archive header meta
-    expect(resolved.sourceLangCode).toBe("EN");
+    expect(resolved.sourceLangCode).toBe("AUTO"); // default source is auto-detect (#94)
   });
 
   it("supports EN as a target and arbitrary BCP-47 tags", () => {
@@ -54,6 +54,45 @@ describe("resolveStartConfig — language plumbing (#12 goal 4)", () => {
   });
 });
 
+describe("resolveStartConfig — source (spoken) language wiring (#94/#175)", () => {
+  it("wires a picked source language to the archive header AND the meeting/quick-translate language", () => {
+    // Spoken Korean, translate into English: the archive header is KO → EN, and
+    // reply/quick-translate output goes into Korean (the meeting's language).
+    const resolved = resolveStartConfig(
+      startMessage({ sourceLanguageCode: "ko", targetLanguageCode: "en" }),
+    );
+    expect(resolved.sourceLangCode).toBe("KO"); // was hardcoded "EN" before #175
+    expect(resolved.meetingLanguage).toBe("Korean"); // quick-translate/reply output
+    expect(resolved.targetLangCode).toBe("EN");
+    expect(resolved.summaryLanguage).toBe("English"); // summary stays in the target
+  });
+
+  it("carries arbitrary BCP-47 source tags through to the header + meeting language", () => {
+    const resolved = resolveStartConfig(
+      startMessage({ sourceLanguageCode: "ja", targetLanguageCode: "ko" }),
+    );
+    expect(resolved.sourceLangCode).toBe("JA");
+    expect(resolved.meetingLanguage).toBe("Japanese");
+  });
+
+  it("keeps auto-detect neutral: header label AUTO, reply falls back to English", () => {
+    const resolved = resolveStartConfig(
+      startMessage({ sourceLanguageCode: "auto", targetLanguageCode: "ko" }),
+    );
+    // The spoken language is detected per-utterance by whisper, so no fixed source
+    // language: a neutral "AUTO" header (never a phantom language) and the pre-#94
+    // English reply fallback are preserved.
+    expect(resolved.sourceLangCode).toBe("AUTO");
+    expect(resolved.meetingLanguage).toBe("English");
+  });
+
+  it("treats a blank source (older shell) as auto — never languageByCode('') = the default", () => {
+    const resolved = resolveStartConfig(startMessage({ sourceLanguageCode: "" }));
+    expect(resolved.sourceLangCode).toBe("AUTO");
+    expect(resolved.meetingLanguage).toBe("English");
+  });
+});
+
 describe("resolveStartConfig — gauge + router mapping", () => {
   it("passes pool/reset-day through and clamps invalid values", () => {
     const ok = resolveStartConfig(startMessage({ poolUsd: 100, resetDay: 15 }));