diff --git a/src/lib/database.ts b/src/lib/database.ts
index b2faee3..0ff14ae 100644
--- a/src/lib/database.ts
+++ b/src/lib/database.ts
@@ -394,6 +394,33 @@ export async function initializeDatabase(options: DatabaseOptions = {}) {
       END $$;
     `);
 
+    // SDK identity columns (SIT-235) — name + version of the SDK that sent the
+    // install/event, for SDK version diagnostics. Persisted on BOTH tables:
+    // install_events (version at install time) and in_app_events because an app
+    // that updates keeps its original install row but sends events with the new
+    // version — so version-fragmentation / outdated-version checks must read from
+    // the event stream. Nullable + backward compatible (older SDKs omit them).
+    // NOTE: no index on sdk_name/sdk_version yet — deferred until a consumer
+    // aggregates them (e.g. "installs by version"), so the index can match the
+    // real query shape.
+    await client.query(`
+      DO $$
+      BEGIN
+        IF NOT EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name='install_events' AND column_name='sdk_name') THEN
+          ALTER TABLE install_events ADD COLUMN sdk_name VARCHAR(50);
+        END IF;
+        IF NOT EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name='install_events' AND column_name='sdk_version') THEN
+          ALTER TABLE install_events ADD COLUMN sdk_version VARCHAR(50);
+        END IF;
+        IF NOT EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name='in_app_events' AND column_name='sdk_name') THEN
+          ALTER TABLE in_app_events ADD COLUMN sdk_name VARCHAR(50);
+        END IF;
+        IF NOT EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name='in_app_events' AND column_name='sdk_version') THEN
+          ALTER TABLE in_app_events ADD COLUMN sdk_version VARCHAR(50);
+        END IF;
+      END $$;
+    `);
+
     // Create indexes for performance
     await client.query('CREATE UNIQUE INDEX IF NOT EXISTS idx_links_short_code ON links(short_code)');
     await client.query('CREATE INDEX IF NOT EXISTS idx_links_user_id ON links(user_id)');
diff --git a/src/lib/fingerprint.test.ts b/src/lib/fingerprint.test.ts
index aab7a0c..d2b3431 100644
--- a/src/lib/fingerprint.test.ts
+++ b/src/lib/fingerprint.test.ts
@@ -329,4 +329,34 @@ describe('recordInstallEvent', () => {
       expect.arrayContaining([null, null, expect.any(String), null, expect.any(String), expect.any(String), null, null, null, null, null, null, null, 'device-1', null])
     );
   });
+
+  it('forwards sdk name + version as the last two positional params of the install insert (guards column misalignment)', async () => {
+    mockDbQuery.mockResolvedValueOnce({ rows: [] }); // matchInstallToClick -> no match
+    mockDbQuery.mockResolvedValueOnce({ rows: [{ id: 'install-456', deep_link_data: {} }] });
+
+    await fingerprint.recordInstallEvent(baseFingerprint, 'device-1', undefined, {
+      name: 'react-native',
+      version: '1.4.0',
+    });
+
+    const [sql, params] = mockDbQuery.mock.calls[1];
+    expect(sql).toMatch(/INSERT INTO install_events/);
+    expect(sql).toMatch(/sdk_name/);
+    expect(sql).toMatch(/sdk_version/);
+    // sdk_name / sdk_version are the LAST two positional values ($16, $17)
+    expect(params).toHaveLength(17);
+    expect(params[params.length - 2]).toBe('react-native');
+    expect(params[params.length - 1]).toBe('1.4.0');
+  });
+
+  it('stores null sdk on the install row when the metadata is absent or empty', async () => {
+    mockDbQuery.mockResolvedValueOnce({ rows: [] });
+    mockDbQuery.mockResolvedValueOnce({ rows: [{ id: 'install-789', deep_link_data: {} }] });
+
+    await fingerprint.recordInstallEvent(baseFingerprint, 'device-1', undefined, { name: '', version: undefined });
+
+    const params = mockDbQuery.mock.calls[1][1];
+    expect(params[params.length - 2]).toBeNull(); // '' -> null
+    expect(params[params.length - 1]).toBeNull(); // undefined -> null
+  });
 });
diff --git a/src/lib/fingerprint.ts b/src/lib/fingerprint.ts
index 370b694..063e5f9 100644
--- a/src/lib/fingerprint.ts
+++ b/src/lib/fingerprint.ts
@@ -388,7 +388,8 @@ export async function storeFingerprintForClick(
 export async function recordInstallEvent(
   fingerprintData: FingerprintData,
   deviceId?: string,
-  attributionWindowHours: number = DEFAULT_ATTRIBUTION_WINDOW_HOURS
+  attributionWindowHours: number = DEFAULT_ATTRIBUTION_WINDOW_HOURS,
+  sdk?: { name?: string | null; version?: string | null }
 ): Promise<{
   installId: string;
   match: FingerprintMatch | null;
@@ -418,8 +419,10 @@ export async function recordInstallEvent(
       platform,
       platform_version,
       device_id,
-      deep_link_data
-    ) VALUES ($1, $2, $3, $4, NOW(), NOW(), $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15)
+      deep_link_data,
+      sdk_name,
+      sdk_version
+    ) VALUES ($1, $2, $3, $4, NOW(), NOW(), $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17)
     RETURNING id, deep_link_data`,
     [
       match?.linkId || null,
@@ -437,6 +440,8 @@ export async function recordInstallEvent(
       fingerprintData.platformVersion || null,
       deviceId || null,
       match ? JSON.stringify({}) : JSON.stringify({}), // Will be populated from link data
+      sdk?.name || null,
+      sdk?.version || null,
     ]
   );
 
diff --git a/src/routes/sdk.event.test.ts b/src/routes/sdk.event.test.ts
index 962be12..125bd09 100644
--- a/src/routes/sdk.event.test.ts
+++ b/src/routes/sdk.event.test.ts
@@ -36,6 +36,8 @@ const stampedEvent = {
   attributedClickId: CLICK_ID,
   linkOpenedAt: LINK_OPENED_AT,
   sessionId: SESSION_ID,
+  sdkName: 'react-native',
+  sdkVersion: '1.4.0',
 };
 
 describe('POST /api/sdk/v1/event — last-click attribution stamp', () => {
@@ -68,6 +70,8 @@ describe('POST /api/sdk/v1/event — last-click attribution stamp', () => {
       CLICK_ID,
       LINK_OPENED_AT,
       SESSION_ID,
+      'react-native',
+      '1.4.0',
     ]);
 
     await app.close();
@@ -117,6 +121,8 @@ describe('POST /api/sdk/v1/event — last-click attribution stamp', () => {
       CLICK_ID,
       LINK_OPENED_AT,
       SESSION_ID,
+      'react-native',
+      '1.4.0',
     ]);
 
     await app.close();
diff --git a/src/routes/sdk.ts b/src/routes/sdk.ts
index e8552e4..51fc343 100644
--- a/src/routes/sdk.ts
+++ b/src/routes/sdk.ts
@@ -52,6 +52,11 @@ export async function sdkRoutes(fastify: FastifyInstance) {
       platformVersion: z.string().optional(),
       deviceId: z.string().optional(),
       attributionWindowHours: z.number().optional(),
+      // SDK identity for health/version diagnostics (SIT-235). Free-form by
+      // design: a consumer tolerates/normalizes non-semver versions — we never
+      // reject a request over this metadata. Empty → null.
+      sdkName: z.string().max(50).optional(),
+      sdkVersion: z.string().max(50).optional(),
       // Public app token shipped in SDK app bundles to scope organic
       // installs to the right org in multi-tenant deployments. Used by
       // Cloud's onSend hook (see cloud-event-hook.ts). Self-hosted
@@ -79,7 +84,8 @@ export async function sdkRoutes(fastify: FastifyInstance) {
       const result = await recordInstallEvent(
         fingerprintData,
         body.deviceId,
-        body.attributionWindowHours
+        body.attributionWindowHours,
+        { name: body.sdkName, version: body.sdkVersion }
       );
 
       return reply.status(200).send({
@@ -230,6 +236,11 @@ export async function sdkRoutes(fastify: FastifyInstance) {
       attributedClickId: z.string().uuid().optional(),
       linkOpenedAt: z.string().datetime().optional(),
       sessionId: z.string().uuid().optional(),
+      // SDK identity for version-health diagnostics (SIT-235). Free-form by
+      // design: a consumer tolerates/normalizes non-semver versions — we never
+      // reject a request over this metadata. Empty → null.
+      sdkName: z.string().max(50).optional(),
+      sdkVersion: z.string().max(50).optional(),
     });
 
     const body = schema.parse(request.body);
@@ -258,8 +269,9 @@ export async function sdkRoutes(fastify: FastifyInstance) {
         eventResult = await db.query(
           `INSERT INTO in_app_events
              (install_id, event_name, event_data, event_timestamp,
-              attributed_link_id, attributed_click_id, attributed_at, session_id)
-           VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
+              attributed_link_id, attributed_click_id, attributed_at, session_id,
+              sdk_name, sdk_version)
+           VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)
            RETURNING id`,
           [
             body.installId,
@@ -270,6 +282,8 @@ export async function sdkRoutes(fastify: FastifyInstance) {
             body.attributedClickId ?? null,
             body.linkOpenedAt ?? null,
             body.sessionId ?? null,
+            body.sdkName || null,
+            body.sdkVersion || null,
           ]
         );
       } catch (insertError: any) {
@@ -292,8 +306,9 @@ export async function sdkRoutes(fastify: FastifyInstance) {
           eventResult = await db.query(
             `INSERT INTO in_app_events
                (install_id, event_name, event_data, event_timestamp,
-                attributed_click_id, attributed_at, session_id)
-             VALUES ($1, $2, $3, $4, $5, $6, $7)
+                attributed_click_id, attributed_at, session_id,
+                sdk_name, sdk_version)
+             VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)
              RETURNING id`,
             [
               body.installId,
@@ -303,6 +318,8 @@ export async function sdkRoutes(fastify: FastifyInstance) {
               body.attributedClickId ?? null,
               body.linkOpenedAt ?? null,
               body.sessionId ?? null,
+              body.sdkName || null,
+              body.sdkVersion || null,
             ]
           );
         } else {