diff --git a/codex-rs/tui/src/app/tests/session_lifecycle_requests.rs b/codex-rs/tui/src/app/tests/session_lifecycle_requests.rs
index 9103a17412..4d45285e80 100644
--- a/codex-rs/tui/src/app/tests/session_lifecycle_requests.rs
+++ b/codex-rs/tui/src/app/tests/session_lifecycle_requests.rs
@@ -1097,9 +1097,6 @@ async fn local_daemon_registers_approval_gated_mcp_tools_for_both_start_paths()
     let codex_home = tempdir()?;
     app.config.codex_home = codex_home.path().to_path_buf().abs();
     app.config.sqlite = SqliteConfig::new_for_testing(codex_home.path().abs());
-    app.config
-        .web_search_mode
-        .set(codex_protocol::config_types::WebSearchMode::Live)?;
     std::fs::write(
         codex_home.path().join("config.toml"),
         "web_search = \"disabled\"\n",
@@ -1169,7 +1166,7 @@ async fn local_daemon_registers_approval_gated_mcp_tools_for_both_start_paths()
     assert_eq!(starts.len(), 2);
     for params in &starts {
         assert_eq!(params["dynamicTools"], serde_json::Value::Null);
-        assert_eq!(params["config"]["web_search"], "live");
+        assert_eq!(params["config"].get("web_search"), None);
         let server = &params["config"]["mcp_servers.codex_tui"];
         assert!(
             server["url"]
diff --git a/codex-rs/tui/src/app_server_session.rs b/codex-rs/tui/src/app_server_session.rs
index fac4b63702..dceab5c168 100644
--- a/codex-rs/tui/src/app_server_session.rs
+++ b/codex-rs/tui/src/app_server_session.rs
@@ -14,6 +14,7 @@ mod provider_selection_tests;
 mod realtime;
 mod rollout_history;
 mod thread_list;
+mod web_search;
 
 #[cfg(test)]
 #[path = "app_server_session/collaboration_catalog_tests.rs"]
@@ -1831,6 +1832,7 @@ pub(crate) fn personality_opt_out_only(personality: Option<Personality>) -> Opti
 
 fn config_request_overrides_from_config(
     config: &Config,
+    thread_params_mode: ThreadParamsMode,
 ) -> Option<HashMap<String, serde_json::Value>> {
     let mut session_config = toml::Value::Table(toml::Table::new());
     for layer in config.config_layer_stack.layers_low_to_high() {
@@ -1877,13 +1879,16 @@ fn config_request_overrides_from_config(
         "personality",
         personality_opt_out_only(config.personality).map(|personality| personality.to_string()),
     );
-    insert(
-        "web_search",
-        Some(config.web_search_mode.value().to_string()),
-    );
     // Only winning launch choices may replace server defaults or saved thread settings.
     let origins = config.config_layer_stack.origins();
     let effective = config.config_layer_stack.effective_config();
+    web_search::apply_launch_override(
+        config,
+        thread_params_mode,
+        &effective,
+        &origins,
+        &mut overrides,
+    );
     for key in ["model_reasoning_summary", "model_verbosity"] {
         if origins.get(key).is_some_and(|origin| {
             matches!(
@@ -1921,7 +1926,8 @@ fn remove_permission_config_overrides(config: &mut Option<HashMap<String, serde_
 }
 
 fn new_thread_reasoning_overrides(config: &Config) -> Option<HashMap<String, serde_json::Value>> {
-    let mut overrides = config_request_overrides_from_config(config).unwrap_or_default();
+    let mut overrides = config_request_overrides_from_config(config, ThreadParamsMode::Embedded)
+        .unwrap_or_default();
     let summary = config
         .model_reasoning_summary
         .unwrap_or(codex_protocol::config_types::ReasoningSummary::None);
@@ -2084,7 +2090,9 @@ pub(crate) fn thread_start_params_from_config(
         permissions,
         config: match thread_params_mode {
             ThreadParamsMode::Embedded => new_thread_reasoning_overrides(config),
-            ThreadParamsMode::Remote => config_request_overrides_from_config(config),
+            ThreadParamsMode::Remote => {
+                config_request_overrides_from_config(config, thread_params_mode)
+            }
         },
         ephemeral: Some(config.ephemeral),
         history_mode: (!config.ephemeral).then_some(ThreadHistoryMode::Paginated),
@@ -2121,7 +2129,7 @@ fn thread_resume_params_from_config(
             )
         })
         .flatten();
-    let mut config_overrides = config_request_overrides_from_config(&config);
+    let mut config_overrides = config_request_overrides_from_config(&config, thread_params_mode);
     if model_settings == ResumeModelSettings::RestoreFromThread
         && let Some(overrides) = config_overrides.as_mut()
     {
@@ -2200,7 +2208,7 @@ fn thread_fork_params_from_config(
         approvals_reviewer: approvals_reviewer_override_from_config(&config),
         sandbox,
         permissions,
-        config: config_request_overrides_from_config(&config),
+        config: config_request_overrides_from_config(&config, thread_params_mode),
         base_instructions: config.base_instructions.clone().filter(|_| {
             !matches!(
                 config.base_instructions_provenance,
@@ -3425,7 +3433,6 @@ mod tests {
         let string = |value: &str| serde_json::Value::String(value.to_string());
         let expected_config = HashMap::from([
             ("model_reasoning_effort".to_string(), string("high")),
-            ("web_search".to_string(), string("disabled")),
             ("bypass_hook_trust".to_string(), true.into()),
         ]);
         let mut expected_start_config = expected_config.clone();
@@ -3440,34 +3447,54 @@ mod tests {
     }
 
     #[tokio::test]
-    async fn config_overrides_forward_explicit_summary_and_verbosity() -> Result<()> {
+    async fn config_overrides_forward_explicit_summary_verbosity_and_web_search() -> Result<()> {
         let home = tempfile::tempdir()?;
         let workspace = home.path().join("workspace");
         std::fs::create_dir_all(workspace.join(".codex"))?;
         std::fs::write(
             home.path().join("config.toml"),
             format!(
-                "model_reasoning_summary = \"concise\"\nmodel_verbosity = \"low\"\n[projects.{}]\ntrust_level = \"trusted\"\n",
+                "model_reasoning_summary = \"concise\"\nmodel_verbosity = \"low\"\nweb_search = \"disabled\"\n[projects.{}]\ntrust_level = \"trusted\"\n",
                 toml::Value::String(workspace.to_string_lossy().into_owned()),
             ),
         )?;
         let profile = AbsolutePathBuf::from_absolute_path(home.path().join("work.config.toml"))?;
         std::fs::write(
             &profile,
-            "model_reasoning_summary = \"detailed\"\nmodel_verbosity = \"high\"\n",
+            "model_reasoning_summary = \"detailed\"\nmodel_verbosity = \"high\"\nweb_search = \"cached\"\n",
         )?;
         for (selected_profile, project, cli, expected) in [
-            (false, false, false, [None, None]),
-            (true, false, false, [Some("detailed"), Some("high")]),
-            (false, false, true, [Some("auto"), Some("medium")]),
-            (true, false, true, [Some("auto"), Some("medium")]),
-            (true, true, false, [None, None]),
-            (true, true, true, [Some("auto"), Some("medium")]),
+            (false, false, false, [None, None, None]),
+            (
+                true,
+                false,
+                false,
+                [Some("detailed"), Some("high"), Some("cached")],
+            ),
+            (
+                false,
+                false,
+                true,
+                [Some("auto"), Some("medium"), Some("live")],
+            ),
+            (
+                true,
+                false,
+                true,
+                [Some("auto"), Some("medium"), Some("live")],
+            ),
+            (true, true, false, [None, None, None]),
+            (
+                true,
+                true,
+                true,
+                [Some("auto"), Some("medium"), Some("live")],
+            ),
         ] {
             std::fs::write(
                 workspace.join(".codex/config.toml"),
                 if project {
-                    "model_reasoning_summary = \"concise\"\nmodel_verbosity = \"low\"\n"
+                    "model_reasoning_summary = \"concise\"\nmodel_verbosity = \"low\"\nweb_search = \"disabled\"\n"
                 } else {
                     ""
                 },
@@ -3487,16 +3514,17 @@ mod tests {
                     vec![
                         ("model_reasoning_summary".to_string(), "auto".into()),
                         ("model_verbosity".to_string(), "medium".into()),
+                        ("web_search".to_string(), "live".into()),
                     ]
                 } else {
                     Vec::new()
                 })
                 .build()
                 .await?;
-            let overrides =
-                config_request_overrides_from_config(&config).expect("config overrides");
+            let overrides = config_request_overrides_from_config(&config, ThreadParamsMode::Remote)
+                .expect("config overrides");
             assert_eq!(
-                ["model_reasoning_summary", "model_verbosity"]
+                ["model_reasoning_summary", "model_verbosity", "web_search"]
                     .map(|key| overrides.get(key).and_then(serde_json::Value::as_str)),
                 expected,
             );
@@ -3525,13 +3553,7 @@ mod tests {
 
         assert_eq!(params.model, None);
         assert_eq!(params.model_provider, None);
-        assert_eq!(
-            params.config,
-            Some(HashMap::from([(
-                "web_search".to_string(),
-                serde_json::Value::String("cached".to_string()),
-            )]))
-        );
+        assert_eq!(params.config, None);
     }
 
     #[tokio::test]
@@ -3836,20 +3858,23 @@ mod tests {
         config.personality = None;
 
         let implicit_overrides =
-            config_request_overrides_from_config(&config).expect("config overrides");
+            config_request_overrides_from_config(&config, ThreadParamsMode::Remote)
+                .expect("config overrides");
 
         assert!(!implicit_overrides.contains_key("personality"));
 
         for personality in [Personality::Friendly, Personality::Pragmatic] {
             config.personality = Some(personality);
             let ordinary_overrides =
-                config_request_overrides_from_config(&config).expect("config overrides");
+                config_request_overrides_from_config(&config, ThreadParamsMode::Remote)
+                    .expect("config overrides");
             assert!(!ordinary_overrides.contains_key("personality"));
         }
 
         config.personality = Some(Personality::None);
         let explicit_overrides =
-            config_request_overrides_from_config(&config).expect("config overrides");
+            config_request_overrides_from_config(&config, ThreadParamsMode::Remote)
+                .expect("config overrides");
 
         assert_eq!(
             explicit_overrides.get("personality"),
diff --git a/codex-rs/tui/src/app_server_session/reasoning_defaults_tests.rs b/codex-rs/tui/src/app_server_session/reasoning_defaults_tests.rs
index 3cb3cbdfba..057a51da65 100644
--- a/codex-rs/tui/src/app_server_session/reasoning_defaults_tests.rs
+++ b/codex-rs/tui/src/app_server_session/reasoning_defaults_tests.rs
@@ -3,8 +3,6 @@
 use super::*;
 use crate::legacy_core::config::ConfigBuilder;
 use codex_app_server_protocol::ServerNotification;
-use codex_protocol::config_types::ReasoningSummary;
-use codex_protocol::config_types::Verbosity;
 use core_test_support::responses;
 use pretty_assertions::assert_eq;
 use serde_json::json;
@@ -44,7 +42,7 @@ async fn reasoning_defaults_reach_responses() -> Result<()> {
             ThreadParamsMode::Embedded,
         ),
         (
-            "model_reasoning_summary = 'detailed'\nmodel_verbosity = 'high'",
+            "model_reasoning_summary = 'detailed'\nmodel_verbosity = 'high'\nweb_search = 'live'",
             json!("detailed"),
             json!(null),
             ThreadParamsMode::Remote,
@@ -75,16 +73,25 @@ stream_max_retries = 0
             codex_protocol::config_types::TrustLevel::Trusted,
         )
         .map_err(|error| color_eyre::eyre::eyre!(error.to_string()))?;
-        let mut config = ConfigBuilder::default()
+        let server_config = ConfigBuilder::default()
             .codex_home(home.path().to_path_buf())
             .build()
             .await?;
-        let mut app_server = crate::start_embedded_app_server_for_picker(&config).await?;
+        let client_home = tempfile::tempdir()?;
+        let config = if mode == ThreadParamsMode::Remote {
+            std::fs::write(
+                client_home.path().join("config.toml"),
+                "model_reasoning_summary = 'concise'\nmodel_verbosity = 'low'\nweb_search = 'disabled'",
+            )?;
+            ConfigBuilder::default()
+                .codex_home(client_home.path().to_path_buf())
+                .build()
+                .await?
+        } else {
+            server_config.clone()
+        };
+        let mut app_server = crate::start_embedded_app_server_for_picker(&server_config).await?;
         app_server.thread_params_mode = mode;
-        if mode == ThreadParamsMode::Remote {
-            config.model_reasoning_summary = Some(ReasoningSummary::Concise);
-            config.model_verbosity = Some(Verbosity::Low);
-        }
         let started = app_server.start_thread(&config).await?;
         for resume in [false, true] {
             if resume {
@@ -92,7 +99,7 @@ stream_max_retries = 0
                     break;
                 }
                 app_server.shutdown().await?;
-                app_server = crate::start_embedded_app_server_for_picker(&config).await?;
+                app_server = crate::start_embedded_app_server_for_picker(&server_config).await?;
                 app_server.thread_params_mode = mode;
                 app_server
                     .resume_thread(
@@ -156,6 +163,13 @@ stream_max_retries = 0
             );
             if mode == ThreadParamsMode::Remote {
                 assert_eq!(body["text"]["verbosity"], json!("high"));
+                let web_search = body["tools"]
+                    .as_array()
+                    .expect("tools")
+                    .iter()
+                    .find(|tool| tool["type"] == "web_search")
+                    .expect("server's web search tool");
+                assert_eq!(web_search["external_web_access"], json!(true));
             }
             let metadata: serde_json::Value = serde_json::from_str(
                 body["client_metadata"]["x-codex-turn-metadata"]
diff --git a/codex-rs/tui/src/app_server_session/web_search.rs b/codex-rs/tui/src/app_server_session/web_search.rs
new file mode 100644
index 0000000000..8502790b1e
--- /dev/null
+++ b/codex-rs/tui/src/app_server_session/web_search.rs
@@ -0,0 +1,100 @@
+//! Forward only winning launch search choices, preserving legacy precedence and embedded pins.
+
+use super::ThreadParamsMode;
+use crate::legacy_core::config::Config;
+use codex_config::ConfigLayerMetadata;
+use codex_config::ConfigLayerSource;
+use codex_features::Feature;
+use std::collections::HashMap;
+
+pub(super) fn apply_launch_override(
+    config: &Config,
+    thread_params_mode: ThreadParamsMode,
+    effective: &toml::Value,
+    origins: &HashMap<String, ConfigLayerMetadata>,
+    overrides: &mut HashMap<String, serde_json::Value>,
+) {
+    // Losing legacy flags must not independently change the server's search mode.
+    if let Some(features) = overrides
+        .get_mut("features")
+        .and_then(serde_json::Value::as_object_mut)
+    {
+        for key in ["web_search", "web_search_cached", "web_search_request"] {
+            features.remove(key);
+        }
+        if features.is_empty() {
+            overrides.remove("features");
+        }
+    }
+    let is_launch = |key: &str| {
+        origins.get(key).is_some_and(|origin| {
+            matches!(
+                origin.name,
+                ConfigLayerSource::SessionFlags
+                    | ConfigLayerSource::User {
+                        profile: Some(_),
+                        ..
+                    }
+            )
+        })
+    };
+    // A canonical setting always takes precedence, even when its origin is implicit.
+    if let Some(value) = effective.get("web_search") {
+        if is_launch("web_search") {
+            overrides.insert("web_search".to_string(), serde_json::json!(value));
+        }
+        return;
+    }
+    let Some(features) = effective.get("features").and_then(toml::Value::as_table) else {
+        return;
+    };
+    let request_key = if features.contains_key("web_search_request") {
+        "web_search_request"
+    } else {
+        "web_search"
+    };
+    let cached = config.features.enabled(Feature::WebSearchCached);
+    let live = config.features.enabled(Feature::WebSearchRequest);
+    let active = [("web_search_cached", "cached"), (request_key, "live")]
+        .into_iter()
+        .find(|(key, mode)| {
+            features.get(*key).and_then(toml::Value::as_bool) == Some(true)
+                && (thread_params_mode == ThreadParamsMode::Remote
+                    || if *mode == "cached" {
+                        cached
+                    } else {
+                        live && !cached
+                    })
+        });
+    let (key, mode) = match active {
+        Some(choice) => choice,
+        None => {
+            if thread_params_mode == ThreadParamsMode::Embedded && (cached || live) {
+                return;
+            }
+            // Explicitly disabling all legacy search features falls back to cached search.
+            let Some(key) = ["web_search_cached", request_key].into_iter().find(|key| {
+                features.get(*key).and_then(toml::Value::as_bool) == Some(false)
+                    && is_launch(&format!("features.{key}"))
+            }) else {
+                return;
+            };
+            (key, "cached")
+        }
+    };
+    // Remote servers enforce their own search-mode requirements on this raw choice.
+    if is_launch(&format!("features.{key}"))
+        || (mode == "live"
+            && features
+                .get("web_search_cached")
+                .and_then(toml::Value::as_bool)
+                == Some(false)
+            && is_launch("features.web_search_cached"))
+    {
+        overrides.insert("web_search".to_string(), mode.into());
+    }
+}
+
+#[cfg(test)]
+#[path = "web_search_tests.rs"]
+mod tests;
diff --git a/codex-rs/tui/src/app_server_session/web_search_tests.rs b/codex-rs/tui/src/app_server_session/web_search_tests.rs
new file mode 100644
index 0000000000..805f6a7098
--- /dev/null
+++ b/codex-rs/tui/src/app_server_session/web_search_tests.rs
@@ -0,0 +1,150 @@
+use super::super::ThreadParamsMode;
+use super::super::config_request_overrides_from_config;
+use crate::legacy_core::config::ConfigBuilder;
+use color_eyre::Result;
+use pretty_assertions::assert_eq;
+
+#[tokio::test]
+async fn legacy_search_overrides_respect_launch_origins() -> Result<()> {
+    let home = tempfile::tempdir()?;
+    for (settings, flags, expected) in [
+        (
+            "web_search = 'disabled'",
+            "web_search_request = true\nweb_search_cached = true\nweb_search = true",
+            None,
+        ),
+        ("[features]\nweb_search_request = true", "", None),
+        (
+            "[features]\nweb_search_cached = true\nweb_search_request = true",
+            "web_search_cached = false",
+            Some("live"),
+        ),
+    ] {
+        std::fs::write(home.path().join("config.toml"), settings)?;
+        let config = ConfigBuilder::default()
+            .codex_home(home.path().to_path_buf())
+            .cli_overrides(
+                toml::from_str::<toml::Table>(&format!("[features]\nmulti_agent = true\n{flags}"))?
+                    .into_iter()
+                    .collect(),
+            )
+            .loader_overrides(codex_config::LoaderOverrides::without_managed_config_for_tests())
+            .build()
+            .await?;
+        let overrides = config_request_overrides_from_config(&config, ThreadParamsMode::Remote)
+            .expect("config overrides");
+        assert_eq!(
+            overrides
+                .get("web_search")
+                .and_then(serde_json::Value::as_str),
+            expected,
+        );
+        assert_eq!(
+            overrides.get("features"),
+            Some(&serde_json::json!({"multi_agent": true})),
+        );
+    }
+    Ok(())
+}
+
+#[tokio::test]
+async fn web_search_overrides_preserve_explicit_legacy_choices() -> Result<()> {
+    let home = tempfile::tempdir()?;
+    for (settings, expected) in [
+        ("[features]\nweb_search_request = true", "live"),
+        (
+            "[features]\nweb_search_cached = true\nweb_search_request = true",
+            "cached",
+        ),
+        ("[features]\nweb_search = true", "live"),
+        (
+            "[features]\nweb_search = true\nweb_search_request = false",
+            "cached",
+        ),
+        (
+            "web_search = 'disabled'\n[features]\nweb_search_request = true",
+            "disabled",
+        ),
+    ] {
+        let config = ConfigBuilder::default()
+            .codex_home(home.path().to_path_buf())
+            .cli_overrides(
+                toml::from_str::<toml::Table>(settings)?
+                    .into_iter()
+                    .collect(),
+            )
+            .loader_overrides(codex_config::LoaderOverrides::without_managed_config_for_tests())
+            .build()
+            .await?;
+        assert_eq!(
+            config_request_overrides_from_config(&config, ThreadParamsMode::Remote),
+            Some(std::collections::HashMap::from([(
+                "web_search".to_string(),
+                serde_json::json!(expected),
+            )])),
+            "{settings}",
+        );
+    }
+    Ok(())
+}
+
+#[tokio::test]
+async fn embedded_legacy_search_honors_shared_feature_requirements() -> Result<()> {
+    let home = tempfile::tempdir()?;
+    let requirements_path = home.path().join("requirements.toml");
+    for (requirements, flags, embedded_mode, remote_mode) in [
+        (
+            "web_search_request = false",
+            "web_search_request = true",
+            None,
+            "live",
+        ),
+        (
+            "web_search_cached = true",
+            "web_search_request = true",
+            None,
+            "live",
+        ),
+        (
+            "web_search_request = true",
+            "web_search_request = false",
+            None,
+            "cached",
+        ),
+        (
+            "web_search_cached = false",
+            "web_search_cached = true\nweb_search_request = true",
+            Some("live"),
+            "cached",
+        ),
+    ] {
+        std::fs::write(&requirements_path, format!("[features]\n{requirements}"))?;
+        let config = ConfigBuilder::default()
+            .codex_home(home.path().to_path_buf())
+            .cli_overrides(
+                toml::from_str::<toml::Table>(&format!("[features]\n{flags}"))?
+                    .into_iter()
+                    .collect(),
+            )
+            .loader_overrides(codex_config::LoaderOverrides {
+                system_requirements_path: Some(requirements_path.clone()),
+                ..codex_config::LoaderOverrides::without_managed_config_for_tests()
+            })
+            .build()
+            .await?;
+        for (mode, expected) in [
+            (ThreadParamsMode::Embedded, embedded_mode),
+            (ThreadParamsMode::Remote, Some(remote_mode)),
+        ] {
+            let overrides =
+                config_request_overrides_from_config(&config, mode).expect("config overrides");
+            assert_eq!(
+                overrides
+                    .get("web_search")
+                    .and_then(serde_json::Value::as_str),
+                expected
+            );
+        }
+    }
+    Ok(())
+}