diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9d77e8fe03..c83cfc6a36 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 * Rust
   * Add support for determining `client_info.os_version` for Android binaries ([#3434](https://github.com/mozilla/glean/pull/3434))
+  * `client_info.os_version` can now be set by the application. If unset Glean still uses the auto-detection ([#3419](https://github.com/mozilla/glean/pull/3419))
 
 # v67.2.0 (2026-04-06)
 
diff --git a/docs/user/reference/general/initializing.md b/docs/user/reference/general/initializing.md
index 6a2edd50f4..a552ea0897 100644
--- a/docs/user/reference/general/initializing.md
+++ b/docs/user/reference/general/initializing.md
@@ -251,6 +251,7 @@ let client_info = ClientInfoMetrics {
     app_display_version: env!("CARGO_PKG_VERSION").to_string(),
     channel: None,
     locale: None,
+    os_version: None, // auto-detected
 };
 
 glean::initialize(cfg, client_info);
diff --git a/glean-core/rlb-tests/src/bin/crashing-threads.rs b/glean-core/rlb-tests/src/bin/crashing-threads.rs
index 1840689c18..e76734d9b1 100644
--- a/glean-core/rlb-tests/src/bin/crashing-threads.rs
+++ b/glean-core/rlb-tests/src/bin/crashing-threads.rs
@@ -123,6 +123,7 @@ fn main() {
         app_display_version: env!("CARGO_PKG_VERSION").to_string(),
         channel: None,
         locale: None,
+        os_version: None,
     };
 
     glean::initialize(cfg, client_info);
diff --git a/glean-core/rlb-tests/src/bin/delayed-ping-data.rs b/glean-core/rlb-tests/src/bin/delayed-ping-data.rs
index 4be459dcb1..cfa5fcc94a 100644
--- a/glean-core/rlb-tests/src/bin/delayed-ping-data.rs
+++ b/glean-core/rlb-tests/src/bin/delayed-ping-data.rs
@@ -115,6 +115,7 @@ fn main() {
         app_display_version: env!("CARGO_PKG_VERSION").to_string(),
         channel: None,
         locale: None,
+        os_version: None,
     };
 
     glean::initialize(cfg, client_info);
diff --git a/glean-core/rlb-tests/src/bin/enabled-pings.rs b/glean-core/rlb-tests/src/bin/enabled-pings.rs
index d94ee87cda..aeb8134e37 100644
--- a/glean-core/rlb-tests/src/bin/enabled-pings.rs
+++ b/glean-core/rlb-tests/src/bin/enabled-pings.rs
@@ -160,6 +160,7 @@ fn main() {
         app_display_version: env!("CARGO_PKG_VERSION").to_string(),
         channel: None,
         locale: None,
+        os_version: None,
     };
 
     glean::initialize(cfg, client_info);
diff --git a/glean-core/rlb-tests/src/bin/long-running.rs b/glean-core/rlb-tests/src/bin/long-running.rs
index 6f0b8ae7ed..a9065e1815 100644
--- a/glean-core/rlb-tests/src/bin/long-running.rs
+++ b/glean-core/rlb-tests/src/bin/long-running.rs
@@ -74,6 +74,7 @@ fn main() {
         app_display_version: env!("CARGO_PKG_VERSION").to_string(),
         channel: None,
         locale: None,
+        os_version: None,
     };
 
     glean::initialize(cfg, client_info);
diff --git a/glean-core/rlb-tests/src/bin/mps-delay.rs b/glean-core/rlb-tests/src/bin/mps-delay.rs
index d4114fcef5..be034966be 100644
--- a/glean-core/rlb-tests/src/bin/mps-delay.rs
+++ b/glean-core/rlb-tests/src/bin/mps-delay.rs
@@ -126,6 +126,7 @@ fn main() {
         app_display_version: env!("CARGO_PKG_VERSION").to_string(),
         channel: None,
         locale: None,
+        os_version: None,
     };
 
     glean::initialize(cfg, client_info);
diff --git a/glean-core/rlb-tests/src/bin/pending-gets-removed.rs b/glean-core/rlb-tests/src/bin/pending-gets-removed.rs
index b802fe38d0..46c285b379 100644
--- a/glean-core/rlb-tests/src/bin/pending-gets-removed.rs
+++ b/glean-core/rlb-tests/src/bin/pending-gets-removed.rs
@@ -141,6 +141,7 @@ fn main() {
         app_display_version: env!("CARGO_PKG_VERSION").to_string(),
         channel: None,
         locale: None,
+        os_version: None,
     };
 
     // Ensure this ping is always registered early.
diff --git a/glean-core/rlb-tests/src/bin/ping-lifetime-flush.rs b/glean-core/rlb-tests/src/bin/ping-lifetime-flush.rs
index eeceaa8358..f1a79e373d 100644
--- a/glean-core/rlb-tests/src/bin/ping-lifetime-flush.rs
+++ b/glean-core/rlb-tests/src/bin/ping-lifetime-flush.rs
@@ -118,6 +118,7 @@ fn main() {
         app_display_version: env!("CARGO_PKG_VERSION").to_string(),
         channel: None,
         locale: None,
+        os_version: None,
     };
 
     glean::initialize(cfg, client_info);
diff --git a/glean-core/rlb/examples/frequent-events.rs b/glean-core/rlb/examples/frequent-events.rs
index 3fcd145c4e..8ba6d7110a 100644
--- a/glean-core/rlb/examples/frequent-events.rs
+++ b/glean-core/rlb/examples/frequent-events.rs
@@ -96,6 +96,7 @@ fn main() {
         app_display_version: env!("CARGO_PKG_VERSION").to_string(),
         channel: None,
         locale: None,
+        os_version: None,
     };
 
     glean::initialize(cfg, client_info);
diff --git a/glean-core/rlb/examples/prototype.rs b/glean-core/rlb/examples/prototype.rs
index a74a75ca50..424d05dc79 100644
--- a/glean-core/rlb/examples/prototype.rs
+++ b/glean-core/rlb/examples/prototype.rs
@@ -66,6 +66,7 @@ fn main() {
         app_display_version: env!("CARGO_PKG_VERSION").to_string(),
         channel: None,
         locale: None,
+        os_version: None,
     };
 
     glean::initialize(cfg, client_info);
diff --git a/glean-core/rlb/src/core_metrics.rs b/glean-core/rlb/src/core_metrics.rs
index 70c11fea87..e749745398 100644
--- a/glean-core/rlb/src/core_metrics.rs
+++ b/glean-core/rlb/src/core_metrics.rs
@@ -15,6 +15,8 @@ pub struct ClientInfoMetrics {
     pub channel: Option<String>,
     /// The locale of the application during initialization (e.g. "es-ES").
     pub locale: Option<String>,
+    /// The user-visible version of the operating system (e.g. "1.2.3").
+    pub os_version: Option<String>,
 }
 
 impl ClientInfoMetrics {
@@ -25,6 +27,7 @@ impl ClientInfoMetrics {
             app_display_version: "Unknown".to_string(),
             channel: None,
             locale: None,
+            os_version: None,
         }
     }
 }
@@ -36,7 +39,7 @@ impl From<ClientInfoMetrics> for glean_core::ClientInfoMetrics {
             app_display_version: metrics.app_display_version,
             channel: metrics.channel,
             locale: metrics.locale,
-            os_version: system::get_os_version(),
+            os_version: metrics.os_version.unwrap_or_else(system::get_os_version),
             windows_build_number: system::get_windows_build_number(),
             architecture: system::ARCH.to_string(),
             ..Default::default()
diff --git a/glean-core/rlb/tests/collection_enabled.rs b/glean-core/rlb/tests/collection_enabled.rs
index 7ecfe2bad0..f32a34fb9c 100644
--- a/glean-core/rlb/tests/collection_enabled.rs
+++ b/glean-core/rlb/tests/collection_enabled.rs
@@ -114,6 +114,7 @@ fn nofollows_contains_client_info_when_collection_disabled() {
         app_display_version: "1.0.0".to_string(),
         channel: Some("testing".to_string()),
         locale: Some("xx-XX".to_string()),
+        os_version: None,
     };
     glean::test_reset_glean(cfg, client_info, false);
 
diff --git a/glean-core/rlb/tests/collection_enabled_bin.rs b/glean-core/rlb/tests/collection_enabled_bin.rs
index 7d83ad11d7..ec59e701d9 100644
--- a/glean-core/rlb/tests/collection_enabled_bin.rs
+++ b/glean-core/rlb/tests/collection_enabled_bin.rs
@@ -112,6 +112,7 @@ fn nofollows_contains_client_info_when_collection_disabled() {
         app_display_version: "1.0.0".to_string(),
         channel: Some("testing".to_string()),
         locale: Some("xx-XX".to_string()),
+        os_version: None,
     };
     glean::test_reset_glean(cfg, client_info, false);
 
diff --git a/glean-core/rlb/tests/common/mod.rs b/glean-core/rlb/tests/common/mod.rs
index c261666e02..828b543072 100644
--- a/glean-core/rlb/tests/common/mod.rs
+++ b/glean-core/rlb/tests/common/mod.rs
@@ -46,6 +46,7 @@ pub fn initialize(cfg: Configuration) {
         app_display_version: "1.0.0".to_string(),
         channel: Some("testing".to_string()),
         locale: Some("xx-XX".to_string()),
+        os_version: None,
     };
 
     _ = PingBuilder::new("store1").with_send_if_empty(true).build();
diff --git a/glean-core/rlb/tests/schema.rs b/glean-core/rlb/tests/schema.rs
index 893fb7c4d5..abc2d6fdce 100644
--- a/glean-core/rlb/tests/schema.rs
+++ b/glean-core/rlb/tests/schema.rs
@@ -83,6 +83,7 @@ fn validate_against_schema() {
         app_display_version: env!("CARGO_PKG_VERSION").to_string(),
         channel: Some("testing".to_string()),
         locale: Some("xx-XX".to_string()),
+        os_version: None,
     };
 
     glean::initialize(cfg, client_info);
diff --git a/samples/rapid-metrics/src/main.rs b/samples/rapid-metrics/src/main.rs
index 430d05c2b1..ceaa80dacb 100644
--- a/samples/rapid-metrics/src/main.rs
+++ b/samples/rapid-metrics/src/main.rs
@@ -78,6 +78,7 @@ fn main() {
         app_display_version: env!("CARGO_PKG_VERSION").to_string(),
         channel: None,
         locale: None,
+        os_version: None,
     };
 
     _ = &*glean_metrics::prototype;
diff --git a/samples/rust/src/main.rs b/samples/rust/src/main.rs
index 8e08f1cdf5..b36a594f71 100644
--- a/samples/rust/src/main.rs
+++ b/samples/rust/src/main.rs
@@ -111,6 +111,7 @@ fn main() {
         app_display_version: env!("CARGO_PKG_VERSION").to_string(),
         channel: None,
         locale: None,
+        os_version: None,
     };
 
     _ = &*glean_metrics::prototype;