diff --git a/src/__tests__/workout-sport-provenance-guard.test.ts b/src/__tests__/workout-sport-provenance-guard.test.ts
new file mode 100644
index 000000000..ea9eca33f
--- /dev/null
+++ b/src/__tests__/workout-sport-provenance-guard.test.ts
@@ -0,0 +1,252 @@
+/**
+ * Structural guards on workout sport provenance.
+ *
+ * Every provider labels a workout in its own vocabulary, and every ingest
+ * collapses that label onto the canonical `WorkoutSportType` set. The
+ * collapse is lossy at both ends: an unmapped label lands on `"other"`, and
+ * `"other"` read back cannot be told apart from a label that genuinely meant
+ * "other". The rule that keeps it recoverable is one line long — a
+ * server-side ingest that maps a raw sport label writes that label verbatim
+ * to `Workout.metadata`.
+ *
+ * Google Health broke that rule silently for three releases while the
+ * comment above its type map asserted the opposite, and a user's workout
+ * showed as "Other" with the original nowhere in the database. Three sibling
+ * providers had carried the provenance write the whole time. Nothing
+ * connected them, so nothing noticed.
+ *
+ * These are tripwires, not proofs. A grep cannot show that a metadata key
+ * holds the right value — only that a registered ingest still writes one, and
+ * that a new ingest cannot appear without someone editing this file.
+ */
+import { describe, it, expect } from "vitest";
+import { readFileSync } from "node:fs";
+import { join, sep } from "node:path";
+import { globSync } from "node:fs";
+
+const SRC = join(process.cwd(), "src");
+
+/** Every non-test `.ts` / `.tsx` under `src/`, minus the generated client. */
+function sourceFiles(): string[] {
+  return globSync("**/*.{ts,tsx}", { cwd: SRC })
+    .filter(
+      (p) => !p.startsWith(`generated${sep}`) && !p.startsWith("generated/"),
+    )
+    .filter((p) => !p.includes("__tests__"))
+    .filter((p) => !p.endsWith(".test.ts") && !p.endsWith(".test.tsx"))
+    .map((p) => p.split(sep).join("/"))
+    .sort();
+}
+
+function read(rel: string): string {
+  return readFileSync(join(SRC, rel), "utf8");
+}
+
+interface ProviderIngest {
+  /** Human name, for the failure message. */
+  provider: string;
+  /** The exported function that resolves the upstream label. */
+  mapper: string;
+  /** File declaring the mapper. */
+  mapperFile: string;
+  /** File where the raw label is captured alongside the mapped one. */
+  captureFile: string;
+  /** Identifier or literal that carries the raw label out of the capture. */
+  captureField: string;
+  /** File that builds the `Workout` row written to Postgres. */
+  writeFile: string;
+  /** The `metadata` key the raw label is stored under. */
+  metadataKey: string;
+}
+
+/**
+ * Every server-side workout ingest that maps a raw sport label onto the
+ * canonical enum, with the provenance write that makes the mapping
+ * reversible. Adding a provider means adding a row here.
+ */
+const PROVIDER_INGESTS: ProviderIngest[] = [
+  {
+    provider: "Google Health",
+    mapper: "mapGoogleHealthSportType",
+    mapperFile: "lib/google-health/mappers.ts",
+    captureFile: "lib/google-health/mappers.ts",
+    captureField: "sportTypeRaw",
+    writeFile: "lib/google-health/sync-workout.ts",
+    metadataKey: "googleExerciseType",
+  },
+  {
+    provider: "WHOOP",
+    mapper: "mapWhoopSportType",
+    mapperFile: "lib/whoop/sport-map.ts",
+    captureFile: "lib/whoop/sync-workout.ts",
+    captureField: "sport_name",
+    writeFile: "lib/whoop/sync-workout.ts",
+    metadataKey: "whoopSportName",
+  },
+  {
+    provider: "Polar",
+    mapper: "mapPolarSportType",
+    mapperFile: "lib/polar/sport-map.ts",
+    captureFile: "lib/polar/client.ts",
+    captureField: "detailed_sport_info",
+    writeFile: "lib/polar/sync-workouts.ts",
+    metadataKey: "polarSport",
+  },
+  {
+    provider: "Strava",
+    mapper: "mapStravaSportType",
+    mapperFile: "lib/strava/sport-map.ts",
+    captureFile: "lib/strava/client.ts",
+    captureField: "rawSportType",
+    writeFile: "lib/strava/sync.ts",
+    metadataKey: "stravaType",
+  },
+  {
+    provider: "Apple Health export",
+    mapper: "resolveHkWorkoutSportType",
+    mapperFile: "lib/measurements/hk-workout-activity-type-map.ts",
+    captureFile: "lib/measurements/import-apple-health-export.ts",
+    captureField: "workoutActivityType",
+    writeFile: "lib/measurements/import-apple-health-export.ts",
+    metadataKey: "activityType",
+  },
+];
+
+/**
+ * Fitbit carries the identical defect Google Health just had: an unmapped
+ * `activityName` collapses to `"other"` and the original is discarded. It is
+ * excluded here deliberately, not overlooked. The standing rule for this
+ * repository is that Fitbit changes ship as small isolated releases with
+ * parity tests against a provider that already works, so it follows this one
+ * rather than riding along inside it — the two providers share no code, so
+ * deferring leaves nothing half-wired.
+ *
+ * The exception is written as an assertion rather than an omission: when
+ * Fitbit gains the provenance write, this test fails and forces the entry to
+ * move up into `PROVIDER_INGESTS`. An exception nobody has to retire is how
+ * the original gap survived.
+ */
+const FITBIT_EXCEPTION = {
+  provider: "Fitbit",
+  mapper: "mapFitbitSportType",
+  mapperFile: "lib/fitbit/client.ts",
+  writeFile: "lib/fitbit/sync-workout.ts",
+} as const;
+
+/**
+ * Exported helpers whose name ends in `SportType` but which never see an
+ * upstream label — they narrow a value that is already canonical, at read
+ * time, and have no provenance to preserve.
+ */
+const READ_TIME_NARROWERS = [
+  "closedSportType", // lib/ai/coach/workout-evidence.ts — evidence payload
+  "narrowSportType", // lib/workouts/insight-evidence.ts — insight claims
+];
+
+describe("T1 — the set of sport-label mappers is frozen", () => {
+  it("every exported sport-type resolver is registered", () => {
+    const found = new Set<string>();
+    for (const rel of sourceFiles()) {
+      for (const m of read(rel).matchAll(
+        /export function (\w*(?:SportType|WorkoutSportType))\s*\(/g,
+      )) {
+        found.add(m[1]);
+      }
+    }
+
+    const registered = [
+      ...PROVIDER_INGESTS.map((p) => p.mapper),
+      FITBIT_EXCEPTION.mapper,
+      ...READ_TIME_NARROWERS,
+    ].sort();
+
+    // A new name here means a new provider vocabulary, which means a new
+    // provenance obligation. It belongs in a reviewed diff.
+    expect([...found].sort()).toEqual(registered);
+  });
+
+  it("each registered mapper lives where the registry says it does", () => {
+    for (const p of [...PROVIDER_INGESTS, FITBIT_EXCEPTION]) {
+      expect(
+        read(p.mapperFile).includes(`export function ${p.mapper}`),
+        `${p.provider}: ${p.mapper} is no longer declared in ${p.mapperFile}`,
+      ).toBe(true);
+    }
+  });
+});
+
+describe("T2 — the set of files writing Workout rows is frozen", () => {
+  /**
+   * Non-mapping writers: they persist a `sportType` that some other layer
+   * already resolved, so the provenance rule does not reach them.
+   */
+  const NON_MAPPING_WRITERS: Record<string, string> = {
+    // The iOS / client batch endpoint. The client sends an enum value and MAY
+    // send its own `metadata`; no server-side label mapping happens here.
+    "app/api/workouts/batch/route.ts": "client-supplied enum",
+    // Backup restore replays rows this app previously wrote, provenance and
+    // all.
+    "app/api/admin/backups/[id]/restore/route.ts": "restore replay",
+  };
+
+  it("only the registered ingests and the declared non-mappers create Workout rows", () => {
+    const writers = sourceFiles().filter((rel) =>
+      /(?:prisma|tx)\.workout\.(?:create|createMany|createManyAndReturn|upsert)\(/.test(
+        read(rel),
+      ),
+    );
+
+    const expected = [
+      ...PROVIDER_INGESTS.map((p) => p.writeFile),
+      FITBIT_EXCEPTION.writeFile,
+      ...Object.keys(NON_MAPPING_WRITERS),
+    ].sort();
+
+    expect(writers.sort()).toEqual(expected);
+  });
+});
+
+describe("T3 — every mapping ingest preserves the raw label", () => {
+  it.each(PROVIDER_INGESTS)(
+    "$provider writes metadata.$metadataKey",
+    ({ provider, captureFile, captureField, writeFile, metadataKey }) => {
+      expect(
+        read(captureFile).includes(captureField),
+        `${provider}: the raw label (${captureField}) is no longer read in ${captureFile}`,
+      ).toBe(true);
+
+      const writer = read(writeFile);
+      expect(
+        /metadata[,:]/.test(writer),
+        `${provider}: ${writeFile} writes no metadata onto the Workout row`,
+      ).toBe(true);
+
+      // The key itself is declared where the metadata object is built, which
+      // for two providers is the capture file rather than the writer.
+      expect(
+        writer.includes(metadataKey) || read(captureFile).includes(metadataKey),
+        `${provider}: nothing writes the raw label under metadata.${metadataKey}`,
+      ).toBe(true);
+    },
+  );
+});
+
+describe("T4 — Fitbit is the one declared exception", () => {
+  it("still discards its raw activity name, and says so when it stops", () => {
+    const writer = read(FITBIT_EXCEPTION.writeFile);
+    expect(
+      /metadata[,:]/.test(writer),
+      "Fitbit now writes workout metadata — move it into PROVIDER_INGESTS " +
+        "with its provenance key and delete FITBIT_EXCEPTION.",
+    ).toBe(false);
+  });
+
+  it("is the only ingest allowed to be non-compliant", () => {
+    const nonCompliant = [
+      ...PROVIDER_INGESTS.map((p) => p.writeFile),
+      FITBIT_EXCEPTION.writeFile,
+    ].filter((rel) => !/metadata[,:]/.test(read(rel)));
+
+    expect(nonCompliant).toEqual([FITBIT_EXCEPTION.writeFile]);
+  });
+});
diff --git a/src/lib/google-health/__tests__/mappers.test.ts b/src/lib/google-health/__tests__/mappers.test.ts
index 252653e3b..2eacc6d0a 100644
--- a/src/lib/google-health/__tests__/mappers.test.ts
+++ b/src/lib/google-health/__tests__/mappers.test.ts
@@ -533,6 +533,8 @@ describe("mapWorkout — exercise session", () => {
     });
     expect(w!.startedAt.toISOString()).toBe("2026-06-03T07:00:00.000Z");
     expect(w!.endedAt.toISOString()).toBe("2026-06-03T07:45:00.000Z");
+    // Provenance rides along even when the mapping succeeded.
+    expect(w!.sportTypeRaw).toBe("RUNNING");
   });
 
   it("falls back to a start-anchored externalId when the resource name is absent", () => {
@@ -563,12 +565,56 @@ describe("mapWorkout — exercise session", () => {
     ).toBeNull();
   });
 
+  it("keeps the raw exerciseType when the sport falls back to 'other'", () => {
+    // The whole point of the provenance field: `sportType` alone cannot say
+    // whether Google reported a sport the map has never heard of or a genuine
+    // OTHER_WORKOUT, and the answer is not recoverable from anywhere else.
+    const w = mapWorkout({
+      name: "users/me/dataTypes/exercise/dataPoints/kite1",
+      exercise: {
+        exerciseType: " KITESURFING ",
+        interval: {
+          startTime: "2026-06-04T10:00:00.000Z",
+          endTime: "2026-06-04T11:00:00.000Z",
+        },
+      },
+    });
+    expect(w!.sportType).toBe("other");
+    expect(w!.sportTypeRaw).toBe("KITESURFING");
+  });
+
+  it("reports a missing or blank exerciseType as null, not an empty string", () => {
+    const noType = mapWorkout({
+      exercise: {
+        interval: {
+          startTime: "2026-06-04T12:00:00.000Z",
+          endTime: "2026-06-04T12:30:00.000Z",
+        },
+      },
+    });
+    expect(noType!.sportType).toBe("other");
+    expect(noType!.sportTypeRaw).toBeNull();
+
+    const blankType = mapWorkout({
+      exercise: {
+        exerciseType: "   ",
+        interval: {
+          startTime: "2026-06-04T13:00:00.000Z",
+          endTime: "2026-06-04T13:30:00.000Z",
+        },
+      },
+    });
+    expect(blankType!.sportTypeRaw).toBeNull();
+  });
+
   it("resolves the UPPERCASE ExerciseType enum, with a generic fallback", () => {
     expect(mapGoogleHealthSportType("STRENGTH_TRAINING")).toBe("strength");
     expect(mapGoogleHealthSportType("HIGH_INTENSITY_INTERVAL_TRAINING")).toBe(
       "hiit",
     );
     expect(mapGoogleHealthSportType("CYCLING")).toBe("cycling");
+    // Lossy by design — `Workout.metadata.googleExerciseType` is what carries
+    // the original (see the mapWorkout provenance cases above).
     expect(mapGoogleHealthSportType("KITESURFING")).toBe("other");
     expect(mapGoogleHealthSportType("")).toBe("other");
   });
diff --git a/src/lib/google-health/__tests__/sync-workout-insert-identity.test.ts b/src/lib/google-health/__tests__/sync-workout-insert-identity.test.ts
index e09c5fdfe..a0a61a56c 100644
--- a/src/lib/google-health/__tests__/sync-workout-insert-identity.test.ts
+++ b/src/lib/google-health/__tests__/sync-workout-insert-identity.test.ts
@@ -47,6 +47,7 @@ const startedAt = new Date("2026-07-19T08:00:00.000Z");
 const mapped = {
   externalId: "google-1",
   sportType: "running",
+  sportTypeRaw: "RUNNING",
   startedAt,
   endedAt: new Date("2026-07-19T09:00:00.000Z"),
   durationSec: 3600,
@@ -124,3 +125,52 @@ describe("syncUserWorkout — exact inserted identity", () => {
     await expect(syncUserWorkout("user-1")).resolves.toBe(1);
   });
 });
+
+describe("syncUserWorkout — raw activity-type provenance", () => {
+  it("writes the raw exerciseType to metadata on insert", async () => {
+    createManyAndReturn.mockResolvedValue([{ id: "new-workout", startedAt }]);
+    mapWorkout.mockReturnValue({ ...mapped, sportTypeRaw: "KITESURFING" });
+
+    await expect(syncUserWorkout("user-1")).resolves.toBe(1);
+
+    expect(createManyAndReturn).toHaveBeenCalledWith(
+      expect.objectContaining({
+        data: expect.objectContaining({
+          metadata: { googleExerciseType: "KITESURFING" },
+        }),
+      }),
+    );
+  });
+
+  it("repairs an existing row in place, because the update reuses the payload", async () => {
+    // A row synced before the provenance write existed has no metadata; the
+    // update arm is what a full re-sync goes through, so it has to carry the
+    // key too or the repair path advertised to users does nothing.
+    createManyAndReturn.mockResolvedValue([]);
+    mapWorkout.mockReturnValue({ ...mapped, sportTypeRaw: "KITESURFING" });
+
+    await expect(syncUserWorkout("user-1")).resolves.toBe(1);
+
+    expect(update).toHaveBeenCalledWith(
+      expect.objectContaining({
+        data: expect.objectContaining({
+          metadata: { googleExerciseType: "KITESURFING" },
+        }),
+      }),
+    );
+  });
+
+  it("omits the key entirely when the session carried no type", async () => {
+    // Omitted, not null: an update writing `metadata: null` would wipe what an
+    // earlier sync recorded.
+    createManyAndReturn.mockResolvedValue([]);
+    mapWorkout.mockReturnValue({ ...mapped, sportTypeRaw: null });
+
+    await expect(syncUserWorkout("user-1")).resolves.toBe(1);
+
+    const insertData = createManyAndReturn.mock.calls[0][0].data;
+    const updateData = update.mock.calls[0][0].data;
+    expect("metadata" in insertData).toBe(false);
+    expect("metadata" in updateData).toBe(false);
+  });
+});
diff --git a/src/lib/google-health/mappers.ts b/src/lib/google-health/mappers.ts
index 28ec45e71..df5de3049 100644
--- a/src/lib/google-health/mappers.ts
+++ b/src/lib/google-health/mappers.ts
@@ -955,9 +955,13 @@ export function mapSleepSession(
  * Google Health `Exercise.exerciseType` → HealthLog `WorkoutSportType`. The
  * enum arrives UPPERCASE (`RUNNING`, `STRENGTH_TRAINING`, …); the resolver
  * lowercases + underscores before the lookup, so the keys here are the
- * normalised forms. Unknown types fall through to a generic label; the column
- * is free-text so an unmapped type still persists (just not under a canonical
- * sport bucket).
+ * normalised forms. An unmapped type resolves to the literal `"other"`: the
+ * upstream label does NOT survive in `sportType`, and the column read back
+ * cannot tell a genuine `OTHER_WORKOUT` from a sport this map has never heard
+ * of. What preserves it is `GoogleHealthMappedWorkout.sportTypeRaw`, which the
+ * ingest writes verbatim to `Workout.metadata.googleExerciseType`
+ * (`sync-workout.ts`) — so a session that shows as "other" can still be traced
+ * back to what Google sent, without re-fetching it.
  */
 const GOOGLE_HEALTH_EXERCISE_TYPE_MAP: Record<string, string> = {
   walk: "walking",
@@ -1055,6 +1059,12 @@ export function mapGoogleHealthSportType(raw: unknown): string {
 export interface GoogleHealthMappedWorkout {
   externalId: string;
   sportType: string;
+  /**
+   * The upstream `exercise.exerciseType` verbatim (trimmed), or null when the
+   * session carried none. Provenance only — never the canonical `sportType`,
+   * which `mapGoogleHealthSportType()` owns.
+   */
+  sportTypeRaw: string | null;
   startedAt: Date;
   endedAt: Date;
   durationSec: number;
@@ -1113,6 +1123,9 @@ function readInstant(
  * the start instant is the fallback. metricsSummary carries no max/min HR →
  * null.
  *
+ * `exerciseType` leaves here twice: once mapped onto a canonical sport bucket,
+ * once verbatim as `sportTypeRaw` so the ingest can keep the provenance.
+ *
  * Session start/end can arrive OFFSET-LESS (local wall clock); `tz` anchors
  * them to the correct UTC instant rather than the process zone.
  */
@@ -1136,6 +1149,10 @@ export function mapWorkout(
       : `exercise:${startedAt.toISOString()}`;
 
   const sportRaw = readPath(point, `${k}.exerciseType`);
+  const sportTypeRaw =
+    typeof sportRaw === "string" && sportRaw.trim() !== ""
+      ? sportRaw.trim()
+      : null;
 
   const energyKcal = readNumber(point, [`${k}.metricsSummary.caloriesKcal`]);
   const distanceMm = readNumber(point, [
@@ -1148,6 +1165,7 @@ export function mapWorkout(
   return {
     externalId,
     sportType: mapGoogleHealthSportType(sportRaw),
+    sportTypeRaw,
     startedAt,
     endedAt,
     durationSec,
diff --git a/src/lib/google-health/mapping.md b/src/lib/google-health/mapping.md
index 1e8615101..48e46beb3 100644
--- a/src/lib/google-health/mapping.md
+++ b/src/lib/google-health/mapping.md
@@ -208,6 +208,18 @@ same run via Apple Health / WHOOP stay distinct rows; the read-time
 `pickCanonicalWorkoutRows` picker collapses the cross-source twin per the user's
 source ladder.
 
+**Sport provenance.** The `other` fallback is lossy: `sportType` alone cannot
+say whether Google reported `OTHER_WORKOUT` or a sport the map does not know.
+So the ingest also writes the label verbatim to
+`Workout.metadata.googleExerciseType` (`GoogleHealthMappedWorkout.sportTypeRaw`
+→ `sync-workout.ts`), matching Polar's `polarSport`, Strava's `stravaType` and
+WHOOP's `whoopSportName`. Provenance only — nothing reads it back as the
+canonical sport. The key is omitted, never nulled, when a session carries no
+type, so a re-sync cannot clear what an earlier run recorded. Rows written
+before this existed carry no key; a full sync (`{fullSync:true}`) re-fetches the
+session under the same externalId and fills it in, since insert and update share
+one payload.
+
 ## Idempotency
 
 `(userId, type, source: "GOOGLE_HEALTH", externalId)` unique. Spot/daily metric
diff --git a/src/lib/google-health/sync-workout.ts b/src/lib/google-health/sync-workout.ts
index c46b51616..80e1c252a 100644
--- a/src/lib/google-health/sync-workout.ts
+++ b/src/lib/google-health/sync-workout.ts
@@ -4,6 +4,9 @@
  * Reads exercise sessions from the `activity_and_fitness.readonly` Restricted
  * bundle and upserts each into the `Workout` table as `source = GOOGLE_HEALTH`,
  * keyed on `(userId, source, externalId)` so a re-fetch overwrites in place.
+ * Insert and update share one payload object, so a full sync repairs rows an
+ * older build wrote — including the raw activity type, which earlier releases
+ * discarded.
  *
  * A Google Health run and the same run via Apple Health (or WHOOP) stay distinct
  * `Workout` rows (different `source`); the read-time `pickCanonicalWorkoutRows`
@@ -76,6 +79,16 @@ export async function syncUserWorkout(
       avgHeartRate: w.avgHeartRate,
       maxHeartRate: w.maxHeartRate,
       minHeartRate: w.minHeartRate,
+      // Raw pre-mapping label, kept for provenance once
+      // `mapGoogleHealthSportType()` has resolved `sportType` to a canonical
+      // bucket — every unmapped `exerciseType` collapses to `"other"`, so
+      // without this the activity Google reported is gone after ingest. Never
+      // read back as the canonical `sportType`. Absent (rather than null) when
+      // the session carried no type, so a re-sync never clears metadata a
+      // previous run wrote.
+      ...(w.sportTypeRaw
+        ? { metadata: { googleExerciseType: w.sportTypeRaw } }
+        : {}),
     };
     try {
       const [inserted] = await prisma.workout.createManyAndReturn({