diff --git a/codex-rs/cli/tests/worktree.rs b/codex-rs/cli/tests/worktree.rs
index 664b2e1d65..f3c41547ec 100644
--- a/codex-rs/cli/tests/worktree.rs
+++ b/codex-rs/cli/tests/worktree.rs
@@ -9,6 +9,7 @@ use std::io::Write as _;
 use std::path::Path;
 use std::process::Command;
 use std::time::Duration;
+use std::time::Instant;
 #[cfg(not(unix))]
 use tempfile::TempDir;
 use wiremock::Mock;
@@ -252,6 +253,10 @@ trust_level = "trusted"
     env.insert("TERM".into(), "xterm-256color".into());
     env.insert("TERM_PROGRAM".into(), "unrecognized-terminal".into());
     env.insert("OTEL_METRIC_EXPORT_INTERVAL".into(), "100".into());
+    env.insert(
+        "OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE".into(),
+        "delta".into(),
+    );
     for key in [
         "CODEX_EXEC_SERVER_URL",
         "CODEX_ACCESS_TOKEN",
@@ -335,8 +340,8 @@ trust_level = "trusted"
         }
         let (metric_tx, mut metric_rx) = tokio::sync::mpsc::unbounded_channel();
         Mock::given(wiremock::matchers::path("/metrics"))
-            .respond_with(move |_: &wiremock::Request| {
-                let _ = metric_tx.send(());
+            .respond_with(move |request: &wiremock::Request| {
+                let _ = metric_tx.send(request.body.clone());
                 ResponseTemplate::new(200).set_body_json(serde_json::json!({}))
             })
             .mount(&server)
@@ -409,7 +414,8 @@ trust_level = "trusted"
         if analytics {
             args.extend([
                 "-c".into(),
-                "analytics.enabled=true".into(),
+                // An explicit collector is independent of built-in analytics consent.
+                "analytics.enabled=false".into(),
                 "-c".into(),
                 format!(
                     "otel.metrics_exporter={{otlp-http={{endpoint=\"{}/metrics\",protocol=\"json\"}}}}",
@@ -551,9 +557,44 @@ trust_level = "trusted"
             .with_context(|| format!("daemon status timed out: {output}"))??;
         }
         if analytics {
-            tokio::time::timeout(Duration::from_secs(/*secs*/ 10), metric_rx.recv())
-                .await?
-                .context("metrics export while the TUI is running")?;
+            for reason in ["turn_start", "resize"] {
+                let started = Instant::now();
+                let wait = if reason == "resize" {
+                    session.resize(codex_utils_pty::TerminalSize {
+                        rows: 80,
+                        cols: 240,
+                    })?;
+                    Duration::from_secs(/*secs*/ 30)
+                } else {
+                    Duration::from_secs(/*secs*/ 10)
+                };
+                tokio::time::timeout(wait, async {
+                    loop {
+                        tokio::select! {
+                            body = metric_rx.recv() => {
+                                let payload: Value = serde_json::from_slice(&body.context("metric body")?)?;
+                                let found = payload["resourceMetrics"].as_array().into_iter().flatten()
+                                    .flat_map(|resource| resource["scopeMetrics"].as_array().into_iter().flatten())
+                                    .flat_map(|scope| scope["metrics"].as_array().into_iter().flatten())
+                                    .filter(|metric| metric["name"] == "codex.tui.terminal_size")
+                                    .flat_map(|metric| metric["sum"]["dataPoints"].as_array().into_iter().flatten())
+                                    .any(|point| point["attributes"].as_array().into_iter().flatten().any(|attribute|
+                                        attribute["key"] == "observation_reason" && attribute["value"]["stringValue"] == reason));
+                                if found { return Ok::<_, anyhow::Error>(()); }
+                            }
+                            bytes = stdout.recv() => {
+                                let bytes = bytes.context("TUI exited before size observation")?;
+                                output.push_str(&String::from_utf8_lossy(&bytes));
+                                let replies = queries.feed(&bytes);
+                                if !replies.is_empty() { session.writer_sender().send(replies).await?; }
+                            }
+                        }
+                    }
+                }).await.with_context(|| format!("waiting for {reason} observation"))??;
+                if reason == "resize" {
+                    assert!(started.elapsed() >= Duration::from_secs(/*secs*/ 15));
+                }
+            }
         }
         let startup_result = observed.as_ref().map(|result| result.as_ref().map(|_| ()));
         assert!(
@@ -637,6 +678,7 @@ trust_level = "trusted"
                 .flat_map(|metric| metric["sum"]["dataPoints"].as_array().into_iter().flatten())
                 .next()
                 .context("codex.tui.start data point")?;
+            assert_eq!(point["asInt"], 1);
             let tags = point["attributes"]
                 .as_array()
                 .context("codex.tui.start attributes")?
@@ -653,6 +695,8 @@ trust_level = "trusted"
             let mut expected_tags = HashMap::from([
                 ("app_server_mode", "in_process"),
                 ("terminal_name", "unknown"),
+                ("terminal_columns", "120-239"),
+                ("terminal_rows", "40-79"),
                 ("multiplexer", "none"),
                 ("daemon_selection_reason", "incompatible_option"),
                 (
@@ -680,6 +724,40 @@ trust_level = "trusted"
                 ]);
             }
             assert_eq!(tags, expected_tags);
+            let observations = exported
+                .iter()
+                .filter(|metric| metric["name"] == "codex.tui.terminal_size")
+                .flat_map(|metric| metric["sum"]["dataPoints"].as_array().into_iter().flatten())
+                .collect::<Vec<_>>();
+            assert_eq!(observations.len(), 2);
+            for observation in observations {
+                assert_eq!(observation["asInt"], 1);
+                let observation_tags = observation["attributes"]
+                    .as_array()
+                    .context("observation attributes")?
+                    .iter()
+                    .map(|attribute| {
+                        Ok((
+                            attribute["key"].as_str().context("observation key")?,
+                            attribute["value"]["stringValue"]
+                                .as_str()
+                                .context("observation value")?,
+                        ))
+                    })
+                    .collect::<anyhow::Result<HashMap<_, _>>>()?;
+                let reason = observation_tags["observation_reason"];
+                let mut expected = expected_tags.clone();
+                expected.insert("observation_reason", reason);
+                match reason {
+                    "turn_start" => {}
+                    "resize" => {
+                        expected.insert("terminal_columns", "240-479");
+                        expected.insert("terminal_rows", "80-119");
+                    }
+                    other => anyhow::bail!("unexpected observation: {other}"),
+                }
+                assert_eq!(observation_tags, expected);
+            }
         } else {
             assert!(metrics.is_empty(), "metrics exporter disabled");
         }
diff --git a/codex-rs/otel/src/metrics/client.rs b/codex-rs/otel/src/metrics/client.rs
index 8bbb12cdc5..9564f1eef4 100644
--- a/codex-rs/otel/src/metrics/client.rs
+++ b/codex-rs/otel/src/metrics/client.rs
@@ -43,6 +43,10 @@ use std::sync::Weak;
 use std::time::Duration;
 use tracing::debug;
 
+#[cfg(test)]
+#[path = "client_tests.rs"]
+mod tests;
+
 const ENV_ATTRIBUTE: &str = "env";
 const METER_NAME: &str = "codex";
 const MILLISECOND_DURATION_UNIT: &str = "ms";
@@ -109,6 +113,7 @@ pub(super) struct MetricsClientInner {
     histograms: Mutex<HashMap<String, Histogram<f64>>>,
     duration_histograms: Mutex<HashMap<InstrumentKey, Histogram<f64>>>,
     runtime_reader: Option<Arc<ManualReader>>,
+    requires_analytics_consent: bool,
     statsig_disabled_metrics: &'static [&'static str],
     default_tags: BTreeMap<String, String>,
 }
@@ -358,6 +363,8 @@ impl MetricsClient {
             )
         });
 
+        let requires_analytics_consent =
+            matches!(exporter, MetricsExporter::Otlp(OtelExporter::Statsig));
         let (meter_provider, meter) = match exporter {
             MetricsExporter::InMemory(exporter) => {
                 build_provider(resource, exporter, export_interval, runtime_reader.clone())
@@ -391,6 +398,7 @@ impl MetricsClient {
                 histograms: Mutex::new(HashMap::new()),
                 duration_histograms: Mutex::new(HashMap::new()),
                 runtime_reader,
+                requires_analytics_consent,
                 statsig_disabled_metrics,
                 default_tags,
             }),
@@ -414,6 +422,22 @@ impl MetricsClient {
             .counter(name, /*description*/ None, inc, tags)
     }
 
+    /// Record a counter while applying analytics consent only to the built-in exporter.
+    /// The consent check and recording use the same exporter even during provider replacement.
+    pub fn counter_with_analytics_consent(
+        &self,
+        name: &str,
+        inc: i64,
+        tags: &[(&str, &str)],
+        analytics_enabled: bool,
+    ) -> Result<()> {
+        let inner = self.active_inner();
+        if inner.requires_analytics_consent && !analytics_enabled {
+            return Ok(());
+        }
+        inner.counter(name, /*description*/ None, inc, tags)
+    }
+
     /// Send a single counter increment with an instrument description.
     pub fn counter_with_description(
         &self,
diff --git a/codex-rs/otel/src/metrics/client_tests.rs b/codex-rs/otel/src/metrics/client_tests.rs
new file mode 100644
index 0000000000..5363a3f53e
--- /dev/null
+++ b/codex-rs/otel/src/metrics/client_tests.rs
@@ -0,0 +1,57 @@
+//! Consent follows the actual counter destination across exporter replacements.
+
+use super::*;
+use opentelemetry_sdk::metrics::data::AggregatedMetrics;
+use opentelemetry_sdk::metrics::data::MetricData;
+use opentelemetry_sdk::metrics::data::ScopeMetrics;
+use opentelemetry_sdk::metrics::data::SumDataPoint;
+use pretty_assertions::assert_eq;
+
+#[test]
+fn counter_consent_uses_the_active_exporter() -> Result<()> {
+    let mut builtin = MetricsClient::new(
+        MetricsConfig::in_memory("test", "test", "1", Default::default()).with_runtime_reader(),
+    )?;
+    // Use the existing in-memory exporter to observe the built-in consent policy without
+    // contacting Statsig (the real Statsig exporter is disabled in debug builds).
+    Arc::get_mut(&mut builtin.inner)
+        .expect("unique provider")
+        .requires_analytics_consent = true;
+    let custom = MetricsClient::new(
+        MetricsConfig::in_memory("test", "test", "1", Default::default()).with_runtime_reader(),
+    )?;
+    let active = Arc::new(RwLock::new(Arc::clone(&builtin.inner)));
+    let metrics = MetricsClient {
+        inner: Arc::clone(&builtin.inner),
+        active: Some(Arc::clone(&active)),
+    };
+
+    // A config reload alone does not replace the installed built-in exporter.
+    for analytics_enabled in [false, true] {
+        metrics.counter_with_analytics_consent(
+            "test.observations",
+            /*inc*/ 1,
+            &[],
+            analytics_enabled,
+        )?;
+    }
+    *active.write().unwrap() = Arc::clone(&custom.inner);
+    metrics.counter_with_analytics_consent(
+        "test.observations",
+        /*inc*/ 1,
+        &[],
+        /*analytics_enabled*/ false,
+    )?;
+
+    let mut counts = Vec::new();
+    for destination in [&builtin, &custom] {
+        let snapshot = destination.snapshot()?;
+        for metric in snapshot.scope_metrics().flat_map(ScopeMetrics::metrics) {
+            if let AggregatedMetrics::U64(MetricData::Sum(sum)) = metric.data() {
+                counts.extend(sum.data_points().map(SumDataPoint::value));
+            }
+        }
+    }
+    assert_eq!(counts, vec![1, 1]);
+    Ok(())
+}
diff --git a/codex-rs/tui/src/app.rs b/codex-rs/tui/src/app.rs
index 1b07e9826d..9a324aa3bd 100644
--- a/codex-rs/tui/src/app.rs
+++ b/codex-rs/tui/src/app.rs
@@ -536,6 +536,7 @@ pub(crate) struct App {
     config_notification_test_pending: Option<u64>,
     model_catalog: Arc<ModelCatalog>,
     pub(crate) session_telemetry: SessionTelemetry,
+    terminal_size_tags: crate::terminal_size_telemetry::LaunchTags,
     pub(crate) app_event_tx: AppEventSender,
     pub(crate) chat_widget: ChatWidget,
     workspace_command_runner: Option<WorkspaceCommandRunner>,
diff --git a/codex-rs/tui/src/app/startup.rs b/codex-rs/tui/src/app/startup.rs
index 4c329f3787..c053d540f1 100644
--- a/codex-rs/tui/src/app/startup.rs
+++ b/codex-rs/tui/src/app/startup.rs
@@ -889,6 +889,7 @@ See the Codex keymap documentation for supported actions and examples."
             config_notification_test_pending: None,
             model_catalog,
             session_telemetry: session_telemetry.clone(),
+            terminal_size_tags: tui.terminal_size_tags.clone(),
             app_event_tx,
             chat_widget,
             workspace_command_runner: Some(workspace_command_runner),
@@ -1160,6 +1161,9 @@ See the Codex keymap documentation for supported actions and examples."
             );
         }
 
+        let mut last_screen_size = tui.terminal.last_known_screen_size;
+        let mut settled_size_tags = crate::terminal_size_telemetry::tags(last_screen_size);
+        let mut pending_resize: Option<(ratatui::layout::Size, Instant)> = None;
         let mut listen_for_app_server_events = true;
         let mut reconnect = None;
         let mut waiting_for_initial_session_configured = wait_for_initial_session_configured;
@@ -1263,6 +1267,19 @@ See the Codex keymap documentation for supported actions and examples."
                             && has_pending_app_events
                         || (!waiting_for_initial_session_configured
                             && app.has_queued_startup_protected_request());
+                // The screen cache is physical geometry, not the inline viewport. This also
+                // notices the final size after returning from a standalone nested screen.
+                let size = tui.terminal.last_known_screen_size;
+                if !crate::terminal_size_telemetry::enabled(&app.config)
+                    || app.terminal_size_tags.is_empty()
+                {
+                    pending_resize = None;
+                    settled_size_tags = crate::terminal_size_telemetry::tags(size);
+                } else if size != last_screen_size {
+                    pending_resize =
+                        Some((size, Instant::now() + Duration::from_secs(/*secs*/ 15)));
+                }
+                last_screen_size = size;
                 let rate_limit_poll_deadline = app
                     .chat_widget
                     .rate_limit_refresh_interval()
@@ -1390,6 +1407,28 @@ See the Codex keymap documentation for supported actions and examples."
                         }
                         AppRunControl::Continue
                     }
+                    () = async {
+                        match pending_resize {
+                            Some((_, deadline)) => tokio::time::sleep_until(tokio::time::Instant::from_std(deadline)).await,
+                            None => std::future::pending().await,
+                        }
+                    } => {
+                        if let Some((expected, _)) = pending_resize.take()
+                            && crate::terminal_size_telemetry::enabled(&app.config)
+                        {
+                            let actual = crate::terminal_size_telemetry::read_size();
+                            if actual != expected {
+                                pending_resize = Some((actual, Instant::now() + Duration::from_secs(/*secs*/ 15)));
+                            } else {
+                                let tags = crate::terminal_size_telemetry::tags(actual);
+                                if tags != settled_size_tags {
+                                    crate::terminal_size_telemetry::record(&app.terminal_size_tags, &app.config, "resize", actual);
+                                }
+                                settled_size_tags = tags;
+                            }
+                        }
+                        AppRunControl::Continue
+                    }
                     () = async {
                         match rate_limit_poll_deadline {
                             Some(deadline) => {
diff --git a/codex-rs/tui/src/app/test_support.rs b/codex-rs/tui/src/app/test_support.rs
index 9394604dd2..a0efb33101 100644
--- a/codex-rs/tui/src/app/test_support.rs
+++ b/codex-rs/tui/src/app/test_support.rs
@@ -26,6 +26,7 @@ pub(crate) async fn make_test_app() -> Box<App> {
         config_notification_test_pending: None,
         model_catalog: chat_widget.model_catalog(),
         session_telemetry,
+        terminal_size_tags: Vec::new(),
         app_event_tx,
         chat_widget,
         workspace_command_runner: None,
diff --git a/codex-rs/tui/src/app/tests.rs b/codex-rs/tui/src/app/tests.rs
index 40c30df923..4fb6b8ac08 100644
--- a/codex-rs/tui/src/app/tests.rs
+++ b/codex-rs/tui/src/app/tests.rs
@@ -1,5 +1,8 @@
 //! App-level orchestration tests for the TUI.
 
+#[path = "tests/terminal_size_telemetry_tests.rs"]
+mod terminal_size_telemetry_tests;
+
 #[path = "tests/copy_mode_tests.rs"]
 mod copy_mode_tests;
 #[path = "tests/mcp_login_tests.rs"]
@@ -6264,6 +6267,7 @@ async fn make_test_app() -> Box<App> {
         config_notification_test_pending: None,
         model_catalog: chat_widget.model_catalog(),
         session_telemetry,
+        terminal_size_tags: Vec::new(),
         app_event_tx,
         chat_widget,
         workspace_command_runner: None,
@@ -6389,6 +6393,7 @@ pub(super) async fn make_test_app_with_channels() -> (
             config_notification_test_pending: None,
             model_catalog: chat_widget.model_catalog(),
             session_telemetry,
+            terminal_size_tags: Vec::new(),
             app_event_tx,
             chat_widget,
             workspace_command_runner: None,
diff --git a/codex-rs/tui/src/app/tests/terminal_size_telemetry_tests.rs b/codex-rs/tui/src/app/tests/terminal_size_telemetry_tests.rs
new file mode 100644
index 0000000000..9542f599f2
--- /dev/null
+++ b/codex-rs/tui/src/app/tests/terminal_size_telemetry_tests.rs
@@ -0,0 +1,26 @@
+//! Terminal-size observation eligibility follows the config reloaded for resume.
+
+use super::*;
+use pretty_assertions::assert_eq;
+
+#[tokio::test]
+async fn terminal_size_telemetry_respects_reloaded_exporter_and_consent() -> Result<()> {
+    let (mut app, _app_event_rx, _op_rx) = Box::pin(make_test_app_with_channels()).await;
+    let cwd = app.config.cwd.to_path_buf();
+    let mut enabled = Vec::new();
+    for config in [
+        "[otel]\nmetrics_exporter = \"statsig\"\n",
+        "[otel]\nmetrics_exporter = \"none\"\n",
+        "[otel]\nmetrics_exporter = \"statsig\"\n[analytics]\nenabled = false\n",
+        "analytics.enabled = false\n[otel.metrics_exporter.otlp-http]\nendpoint = \"http://127.0.0.1:4318/v1/metrics\"\nprotocol = \"json\"\n",
+    ] {
+        std::fs::write(app.config.codex_home.join("config.toml"), config)?;
+        let (config, local_settings) =
+            Box::pin(app.rebuild_config_for_resume_or_fallback(&cwd, cwd.clone())).await?;
+        app.config = config;
+        app.local_settings = local_settings;
+        enabled.push(crate::terminal_size_telemetry::enabled(&app.config));
+    }
+    assert_eq!(enabled, vec![true, false, false, true]);
+    Ok(())
+}
diff --git a/codex-rs/tui/src/app/thread_routing.rs b/codex-rs/tui/src/app/thread_routing.rs
index c8d16dc9c6..f73bca912a 100644
--- a/codex-rs/tui/src/app/thread_routing.rs
+++ b/codex-rs/tui/src/app/thread_routing.rs
@@ -2059,6 +2059,23 @@ impl App {
     }
 
     pub(super) fn handle_thread_event_now(&mut self, event: ThreadBufferedEvent) {
+        // Replay has its own handler; suppress repeated notifications for the current turn.
+        if crate::terminal_size_telemetry::enabled(&self.config)
+            && !self.terminal_size_tags.is_empty()
+            && let ThreadBufferedEvent::Notification(notification) = &event
+            && let ServerNotification::TurnStarted(started) = notification.as_ref()
+            && self
+                .active_thread_id
+                .is_some_and(|id| id.to_string() == started.thread_id)
+            && self.chat_widget.last_turn_id() != Some(started.turn.id.as_str())
+        {
+            crate::terminal_size_telemetry::record(
+                &self.terminal_size_tags,
+                &self.config,
+                "turn_start",
+                crate::terminal_size_telemetry::read_size(),
+            );
+        }
         let needs_refresh = matches!(
             &event,
             ThreadBufferedEvent::Notification(notification)
diff --git a/codex-rs/tui/src/chatwidget.rs b/codex-rs/tui/src/chatwidget.rs
index 2f74f843d5..fccd6e2c20 100644
--- a/codex-rs/tui/src/chatwidget.rs
+++ b/codex-rs/tui/src/chatwidget.rs
@@ -1950,6 +1950,10 @@ impl ChatWidget {
             .unwrap_or_default()
     }
 
+    pub(crate) fn last_turn_id(&self) -> Option<&str> {
+        self.turn_lifecycle.last_turn_id.as_deref()
+    }
+
     pub(crate) fn thread_id(&self) -> Option<ThreadId> {
         self.thread_id
     }
diff --git a/codex-rs/tui/src/daemon_startup_tests.rs b/codex-rs/tui/src/daemon_startup_tests.rs
index 2a6a2eaf1f..0d534c4a0c 100644
--- a/codex-rs/tui/src/daemon_startup_tests.rs
+++ b/codex-rs/tui/src/daemon_startup_tests.rs
@@ -125,6 +125,7 @@ fn daemon_launch_telemetry_records_once_on_connection_or_early_return() {
         let observations = std::cell::RefCell::new(Vec::new());
         let launch = daemon_telemetry::Launch(Some(|target: &AppServerTarget, actual: bool| {
             observations.borrow_mut().push((target.clone(), actual));
+            Vec::new()
         }));
         if connected {
             launch.record(&AppServerTarget::Embedded, connected);
diff --git a/codex-rs/tui/src/daemon_telemetry.rs b/codex-rs/tui/src/daemon_telemetry.rs
index 7f74003589..0c5a050791 100644
--- a/codex-rs/tui/src/daemon_telemetry.rs
+++ b/codex-rs/tui/src/daemon_telemetry.rs
@@ -1,19 +1,21 @@
 //! Records automatic daemon startup and ensures launch observations survive setup failures.
 
 use super::*;
+use crate::terminal_size_telemetry::LaunchTags;
 
 /// Emit once after connection, or as unconfirmed if startup returns early.
-pub(super) struct Launch<F: FnOnce(&AppServerTarget, bool)>(pub(super) Option<F>);
+pub(super) struct Launch<F: FnOnce(&AppServerTarget, bool) -> LaunchTags>(pub(super) Option<F>);
 
-impl<F: FnOnce(&AppServerTarget, bool)> Launch<F> {
-    pub(super) fn record(mut self, target: &AppServerTarget, connected: bool) {
-        if let Some(record) = self.0.take() {
-            record(target, connected);
-        }
+impl<F: FnOnce(&AppServerTarget, bool) -> LaunchTags> Launch<F> {
+    pub(super) fn record(mut self, target: &AppServerTarget, connected: bool) -> LaunchTags {
+        self.0
+            .take()
+            .map(|record| record(target, connected))
+            .unwrap_or_default()
     }
 }
 
-impl<F: FnOnce(&AppServerTarget, bool)> Drop for Launch<F> {
+impl<F: FnOnce(&AppServerTarget, bool) -> LaunchTags> Drop for Launch<F> {
     fn drop(&mut self) {
         if let Some(record) = self.0.take() {
             record(&AppServerTarget::Embedded, /*connected*/ false);
diff --git a/codex-rs/tui/src/lib.rs b/codex-rs/tui/src/lib.rs
index 734c0f7f1b..545c0d48d3 100644
--- a/codex-rs/tui/src/lib.rs
+++ b/codex-rs/tui/src/lib.rs
@@ -230,6 +230,7 @@ mod temporary_structured_request;
 mod terminal_hyperlinks;
 mod terminal_palette;
 mod terminal_probe;
+mod terminal_size_telemetry;
 mod terminal_title;
 mod terminal_visualization_instructions;
 mod text_formatting;
@@ -1159,7 +1160,9 @@ async fn run_ratatui_app(
     managed_worktree: Option<ManagedTuiWorktree>,
     daemon_startup_warning: Option<String>,
     managed_daemon: bool,
-    launch_telemetry: daemon_telemetry::Launch<impl FnOnce(&AppServerTarget, bool)>,
+    launch_telemetry: daemon_telemetry::Launch<
+        impl FnOnce(&AppServerTarget, bool) -> terminal_size_telemetry::LaunchTags,
+    >,
     startup_draft: startup_draft::StartupDraft,
 ) -> color_eyre::Result<AppExitInfo> {
     let uses_remote_workspace = app_server_target.uses_remote_workspace();
@@ -1226,7 +1229,8 @@ async fn run_ratatui_app(
             ),
         )
         .await;
-    launch_telemetry.record(&app_server_target, matches!(&startup_app_server, Ok(Ok(_))));
+    tui.terminal_size_tags =
+        launch_telemetry.record(&app_server_target, matches!(&startup_app_server, Ok(Ok(_))));
     let mut app_server_session = match startup_app_server {
         Ok(Ok(app_server)) => {
             AppServerSession::new(app_server, app_server_target.thread_params_mode())
diff --git a/codex-rs/tui/src/startup_orchestration.rs b/codex-rs/tui/src/startup_orchestration.rs
index c29d464adc..a96e25bbfd 100644
--- a/codex-rs/tui/src/startup_orchestration.rs
+++ b/codex-rs/tui/src/startup_orchestration.rs
@@ -285,6 +285,9 @@ pub(super) async fn run_main_inner(
     })
     .await
     .map_err(std::io::Error::other)??;
+    // Snapshot the backend size sampled during init, before any viewport changes or resizes.
+    let initial_terminal_size = initialized_terminal.terminal.last_known_screen_size;
+    let terminal_size_tags = crate::terminal_size_telemetry::tags(initial_terminal_size);
     let startup_presentation::StartupPresentation {
         bootstrap_config,
         config_cwd,
@@ -684,6 +687,7 @@ pub(super) async fn run_main_inner(
         Vec::new()
     };
     let mut launch_tags = daemon_settings.to_vec();
+    launch_tags.extend(terminal_size_tags);
     launch_tags.extend([
         ("daemon_selection_reason", selection_reason),
         (
@@ -697,7 +701,9 @@ pub(super) async fn run_main_inner(
     ]);
     // Record the first connection attempt's actual mode, including embedded fallback; never reconnects.
     let launch_telemetry = move |target: &AppServerTarget, connected: bool| {
-        let Some(metrics) = metrics else { return };
+        let Some(metrics) = metrics else {
+            return Vec::new();
+        };
         let app_server_mode = match (connected, target) {
             (false, _) => "unconfirmed",
             (true, AppServerTarget::Embedded) => "in_process",
@@ -733,6 +739,8 @@ pub(super) async fn run_main_inner(
             ("multiplexer", multiplexer),
         ]);
         let _ = metrics.counter("codex.tui.start", /*inc*/ 1, &launch_tags);
+        launch_tags.retain(|(key, _)| !matches!(*key, "terminal_columns" | "terminal_rows"));
+        launch_tags
     };
     let launch_telemetry = daemon_telemetry::Launch(Some(launch_telemetry));
     let state_db = startup_draft
diff --git a/codex-rs/tui/src/terminal_size_telemetry.rs b/codex-rs/tui/src/terminal_size_telemetry.rs
new file mode 100644
index 0000000000..336a59a491
--- /dev/null
+++ b/codex-rs/tui/src/terminal_size_telemetry.rs
@@ -0,0 +1,64 @@
+//! Shared terminal-cell buckets and best-effort observations using the existing metrics provider.
+
+use crate::legacy_core::config::Config;
+use codex_config::types::OtelExporterKind;
+use ratatui::layout::Size;
+
+pub(crate) type LaunchTags = Vec<(&'static str, &'static str)>;
+
+pub(crate) fn enabled(config: &Config) -> bool {
+    match config.otel.metrics_exporter {
+        OtelExporterKind::None => false,
+        OtelExporterKind::Statsig => config.analytics_enabled != Some(false),
+        OtelExporterKind::OtlpHttp { .. } | OtelExporterKind::OtlpGrpc { .. } => true,
+    }
+}
+
+pub(crate) fn tags(size: Size) -> [(&'static str, &'static str); 2] {
+    // Keep values compatible with metrics tag validation; `<` and `+` are rejected.
+    let columns = match size.width {
+        0 => "unknown",
+        1..40 => "under-40",
+        40..80 => "40-79",
+        80..120 => "80-119",
+        120..240 => "120-239",
+        240..480 => "240-479",
+        480.. => "480-and-up",
+    };
+    let rows = match size.height {
+        0 => "unknown",
+        1..15 => "under-15",
+        15..24 => "15-23",
+        24..40 => "24-39",
+        40..80 => "40-79",
+        80..120 => "80-119",
+        120.. => "120-and-up",
+    };
+    [("terminal_columns", columns), ("terminal_rows", rows)]
+}
+
+pub(crate) fn read_size() -> Size {
+    // On Unix, size() may synchronously spawn tput when the direct query fails.
+    #[cfg(unix)]
+    let size = crossterm::terminal::window_size().map(|size| Size::new(size.columns, size.rows));
+    // Windows size() queries the console directly; window_size() is unsupported there.
+    #[cfg(not(unix))]
+    let size = crossterm::terminal::size().map(|(width, height)| Size::new(width, height));
+    size.unwrap_or_default()
+}
+
+pub(crate) fn record(context: &LaunchTags, config: &Config, reason: &'static str, size: Size) {
+    if !context.is_empty()
+        && let Some(metrics) = codex_otel::global()
+    {
+        let mut labels = context.clone();
+        labels.extend(tags(size));
+        labels.push(("observation_reason", reason));
+        let _ = metrics.counter_with_analytics_consent(
+            "codex.tui.terminal_size",
+            /*inc*/ 1,
+            &labels,
+            config.analytics_enabled != Some(false),
+        );
+    }
+}
diff --git a/codex-rs/tui/src/tui.rs b/codex-rs/tui/src/tui.rs
index dd0fc95ccd..01201ec1a0 100644
--- a/codex-rs/tui/src/tui.rs
+++ b/codex-rs/tui/src/tui.rs
@@ -664,6 +664,7 @@ pub struct Tui {
     frame_requester: FrameRequester,
     draw_tx: broadcast::Sender<()>,
     event_broker: Arc<EventBroker>,
+    pub(crate) terminal_size_tags: crate::terminal_size_telemetry::LaunchTags,
     pub(crate) terminal: Terminal,
     pending_history_lines: Vec<PendingHistoryLines>,
     clear_thread_switch_on_draw: bool,
@@ -741,6 +742,7 @@ impl Tui {
             frame_requester,
             draw_tx,
             event_broker: Arc::new(event_broker),
+            terminal_size_tags: Vec::new(),
             terminal,
             pending_history_lines: vec![],
             clear_thread_switch_on_draw: false,