fix

codex-rs/MODELS_STARTUP_PLAN.md

@@ -29,16 +29,17 @@ Acceptance:
 
 ---
 
-## Step 2 - Core: Provide a placeholder `ModelFamily` for UI startup
+## Step 2 - Protocol: SessionConfigured includes the selected model family metadata
 
-- [x] Add a public placeholder constructor in `core/src/models_manager/model_family.rs`
-      (e.g. `ModelFamily::placeholder(&Config) -> ModelFamily`).
-  - Must not claim a real model slug; it is only used for pre-session rendering.
-  - Uses safe defaults (no reasoning summaries, no parallel tool calls, etc),
-    then applies config overrides.
+- [x] Change `SessionConfiguredEvent` to carry `model_family` metadata (not a plain model string).
+  - Implemented as `codex_protocol::openai_models::ModelFamily` (a type alias of `ModelInfo`,
+    matching the `/models` payload shape).
+  - Consumers derive the model slug from `event.model_family.slug`.
 
 Acceptance:
-- TUI can construct a `ModelFamily` without resolving a real model slug.
+- UIs can render the selected model name (and gate features) without making additional `/models`
+  calls after startup completes.
+  - No placeholder model family exists or is required.
 
 ---
 
@@ -52,7 +53,7 @@ Files:
   - Do not call `ModelsManager::get_model(...).await` during startup.
   - Do not call `ModelsManager::list_models(...).await` during startup.
   - Do not run the existing model migration prompt at startup.
-- [x] Construct `ChatWidget` immediately using the placeholder `ModelFamily`.
+- [x] Construct `ChatWidget` immediately with `model_family: None` (no placeholder).
 
 Acceptance:
 - The TUI event loop begins immediately (frame scheduled before any `/models` IO).
@@ -70,11 +71,9 @@ Files:
 - `tui/src/chatwidget.rs`
 - `tui2/src/chatwidget.rs`
 
-- [x] Stop mutating `config.model` in `ChatWidget::new` based on the
-      (placeholder) `ModelFamily`.
-  - Start session header with a non-model value like `"Starting..."`.
-  - Once `SessionConfigured` arrives, update header from `event.model` (already
-    happens in `on_session_configured`).
+- [x] Keep any model-family-dependent behavior gated until `SessionConfigured`.
+  - No placeholder: `ChatWidget` stores `model_family: Option<ModelFamily>`.
+  - Once `SessionConfigured` arrives, hydrate `model_family` from `event.model_family`.
 - [x] Gate turn submission:
   - While not configured, pressing Enter enqueues into the existing
     `queued_user_messages` queue and updates the queued display.
@@ -89,6 +88,8 @@ Files:
 - [x] Gate `/model`:
   - While not configured, show an info message explaining `/model` is disabled
     until startup completes.
+- [x] Gate other model-family-dependent flows (e.g. popups/status helpers) so they
+      early-return instead of assuming a model family exists.
 
 Acceptance:
 - Users can type immediately.
@@ -120,10 +121,7 @@ Acceptance:
 ## Step 6 - Formatting, lint, and tests
 
 - [x] Run `just fmt` (required after Rust changes).
-- [x] Run `just fix -p codex-core` (core changes).
-  - Note: in this environment, `just fix` needs to run outside the sandbox
-    (`clippy --fix` uses a TCP listener to manage locking).
-- [x] Run `just fix -p codex-tui` / `just fix -p codex-tui2` (if those crates changed).
+- [ ] Ask before running `just fix -p codex-core` / `just fix -p codex-tui` / `just fix -p codex-tui2`.
 - [x] Run targeted tests:
   - `cargo test -p codex-core`
   - `cargo test -p codex-tui`

codex-rs/app-server/src/codex_message_processor.rs

@@ -1300,7 +1300,7 @@ impl CodexMessageProcessor {
                 } = conversation_id;
                 let response = NewConversationResponse {
                     conversation_id,
-                    model: session_configured.model,
+                    model: session_configured.model_family.slug,
                     reasoning_effort: session_configured.reasoning_effort,
                     rollout_path: session_configured.rollout_path,
                 };
@@ -1374,7 +1374,7 @@ impl CodexMessageProcessor {
                 };
 
                 let SessionConfiguredEvent {
-                    model,
+                    model_family,
                     model_provider_id,
                     cwd,
                     approval_policy,
@@ -1383,7 +1383,7 @@ impl CodexMessageProcessor {
                 } = session_configured;
                 let response = ThreadStartResponse {
                     thread: thread.clone(),
-                    model,
+                    model: model_family.slug,
                     model_provider: model_provider_id,
                     cwd,
                     approval_policy: approval_policy.into(),
@@ -1717,7 +1717,7 @@ impl CodexMessageProcessor {
 
                 let response = ThreadResumeResponse {
                     thread,
-                    model: session_configured.model,
+                    model: session_configured.model_family.slug,
                     model_provider: session_configured.model_provider_id,
                     cwd: session_configured.cwd,
                     approval_policy: session_configured.approval_policy.into(),
@@ -2330,7 +2330,7 @@ impl CodexMessageProcessor {
                     .send_server_notification(ServerNotification::SessionConfigured(
                         SessionConfiguredNotification {
                             session_id: session_configured.session_id,
-                            model: session_configured.model.clone(),
+                            model: session_configured.model_family.slug.clone(),
                             reasoning_effort: session_configured.reasoning_effort,
                             history_log_id: session_configured.history_log_id,
                             history_entry_count: session_configured.history_entry_count,
@@ -2346,7 +2346,7 @@ impl CodexMessageProcessor {
                 // Reply with conversation id + model and initial messages (when present)
                 let response = ResumeConversationResponse {
                     conversation_id,
-                    model: session_configured.model.clone(),
+                    model: session_configured.model_family.slug.clone(),
                     initial_messages,
                     rollout_path: session_configured.rollout_path.clone(),
                 };

codex-rs/core/src/client.rs

@@ -49,7 +49,7 @@ use crate::features::FEATURES;
 use crate::flags::CODEX_RS_SSE_FIXTURE;
 use crate::model_provider_info::ModelProviderInfo;
 use crate::model_provider_info::WireApi;
-use crate::models_manager::model_family::ModelFamily;
+use codex_protocol::openai_models::ModelFamily;
 use crate::tools::spec::create_tools_json_for_chat_completions_api;
 use crate::tools::spec::create_tools_json_for_responses_api;
 

codex-rs/core/src/client_common.rs

@@ -1,9 +1,9 @@
 use crate::client_common::tools::ToolSpec;
 use crate::error::Result;
-use crate::models_manager::model_family::ModelFamily;
 pub use codex_api::common::ResponseEvent;
 use codex_apply_patch::APPLY_PATCH_TOOL_INSTRUCTIONS;
 use codex_protocol::models::ResponseItem;
+use codex_protocol::openai_models::ModelFamily;
 use futures::Stream;
 use serde::Deserialize;
 use serde_json::Value;

codex-rs/core/src/codex.rs

@@ -17,14 +17,12 @@ use crate::exec_policy::ExecPolicyManager;
 use crate::features::Feature;
 use crate::features::Features;
 use crate::models_manager::manager::ModelsManager;
-use crate::models_manager::model_family::ModelFamily;
 use crate::parse_command::parse_command;
 use crate::parse_turn_item;
 use crate::stream_events_utils::HandleOutputCtx;
 use crate::stream_events_utils::handle_non_tool_response_item;
 use crate::stream_events_utils::handle_output_item_done;
 use crate::terminal;
-use crate::truncate::TruncationPolicy;
 use crate::user_notification::UserNotifier;
 use crate::util::error_or_panic;
 use async_channel::Receiver;
@@ -32,6 +30,8 @@ use async_channel::Sender;
 use codex_protocol::ConversationId;
 use codex_protocol::approvals::ExecPolicyAmendment;
 use codex_protocol::items::TurnItem;
+use codex_protocol::openai_models::ModelFamily;
+use codex_protocol::openai_models::TruncationPolicy;
 use codex_protocol::protocol::FileChange;
 use codex_protocol::protocol::HasLegacyEvent;
 use codex_protocol::protocol::ItemCompletedEvent;
@@ -527,7 +527,7 @@ impl Session {
             final_output_json_schema: None,
             codex_linux_sandbox_exe: per_turn_config.codex_linux_sandbox_exe.clone(),
             tool_call_gate: Arc::new(ReadinessFlag::new()),
-            truncation_policy: TruncationPolicy::new(
+            truncation_policy: crate::truncate::new_truncation_policy(
                 per_turn_config.as_ref(),
                 model_family.truncation_policy,
             ),
@@ -681,11 +681,14 @@ impl Session {
         // Dispatch the SessionConfiguredEvent first and then report any errors.
         // If resuming, include converted initial messages in the payload so UIs can render them immediately.
         let initial_messages = initial_history.get_event_msgs();
+        let session_model_family = models_manager
+            .construct_model_family(session_configuration.model.as_str(), config.as_ref())
+            .await;
         let events = std::iter::once(Event {
             id: INITIAL_SUBMIT_ID.to_owned(),
             msg: EventMsg::SessionConfigured(SessionConfiguredEvent {
                 session_id: conversation_id,
-                model: session_configuration.model.clone(),
+                model_family: session_model_family,
                 model_provider_id: config.model_provider_id.clone(),
                 approval_policy: session_configuration.approval_policy.value(),
                 sandbox_policy: session_configuration.sandbox_policy.get().clone(),
@@ -2144,7 +2147,10 @@ async fn spawn_review_thread(
         final_output_json_schema: None,
         codex_linux_sandbox_exe: parent_turn_context.codex_linux_sandbox_exe.clone(),
         tool_call_gate: Arc::new(ReadinessFlag::new()),
-        truncation_policy: TruncationPolicy::new(&per_turn_config, model_family.truncation_policy),
+        truncation_policy: crate::truncate::new_truncation_policy(
+            &per_turn_config,
+            model_family.truncation_policy,
+        ),
     };
 
     // Seed the child task with the review prompt as the initial user message.

codex-rs/core/src/compact.rs

@@ -15,7 +15,7 @@ use crate::protocol::EventMsg;
 use crate::protocol::TaskStartedEvent;
 use crate::protocol::TurnContextItem;
 use crate::protocol::WarningEvent;
-use crate::truncate::TruncationPolicy;
+use codex_protocol::openai_models::TruncationPolicy;
 use crate::truncate::approx_token_count;
 use crate::truncate::truncate_text;
 use crate::util::backoff;

codex-rs/core/src/context_manager/history.rs

@@ -1,6 +1,6 @@
 use crate::codex::TurnContext;
 use crate::context_manager::normalize;
-use crate::truncate::TruncationPolicy;
+use codex_protocol::openai_models::TruncationPolicy;
 use crate::truncate::approx_token_count;
 use crate::truncate::approx_tokens_from_byte_count;
 use crate::truncate::truncate_function_output_items_with_policy;
@@ -225,7 +225,7 @@ impl ContextManager {
     }
 
     fn process_item(&self, item: &ResponseItem, policy: TruncationPolicy) -> ResponseItem {
-        let policy_with_serialization_budget = policy.mul(1.2);
+        let policy_with_serialization_budget = policy * 1.2;
         match item {
             ResponseItem::FunctionCallOutput { call_id, output } => {
                 let truncated =

codex-rs/core/src/context_manager/history_tests.rs

@@ -1,6 +1,5 @@
 use super::*;
 use crate::truncate;
-use crate::truncate::TruncationPolicy;
 use codex_git::GhostCommit;
 use codex_protocol::models::ContentItem;
 use codex_protocol::models::FunctionCallOutputPayload;
@@ -9,6 +8,7 @@ use codex_protocol::models::LocalShellExecAction;
 use codex_protocol::models::LocalShellStatus;
 use codex_protocol::models::ReasoningItemContent;
 use codex_protocol::models::ReasoningItemReasoningSummary;
+use codex_protocol::openai_models::TruncationPolicy;
 use pretty_assertions::assert_eq;
 use regex_lite::Regex;
 

codex-rs/core/src/error.rs

@@ -1,7 +1,7 @@
 use crate::exec::ExecToolCallOutput;
 use crate::token_data::KnownPlan;
 use crate::token_data::PlanType;
-use crate::truncate::TruncationPolicy;
+use codex_protocol::openai_models::TruncationPolicy;
 use crate::truncate::truncate_text;
 use chrono::DateTime;
 use chrono::Datelike;

codex-rs/core/src/models_manager/manager.rs

@@ -25,7 +25,7 @@ use crate::default_client::build_reqwest_client;
 use crate::error::Result as CoreResult;
 use crate::features::Feature;
 use crate::model_provider_info::ModelProviderInfo;
-use crate::models_manager::model_family::ModelFamily;
+use codex_protocol::openai_models::ModelFamily;
 use crate::models_manager::model_presets::builtin_model_presets;
 
 const MODEL_CACHE_FILE: &str = "models_cache.json";
@@ -149,9 +149,11 @@ impl ModelsManager {
 
     /// Look up the requested model family while applying remote metadata overrides.
     pub async fn construct_model_family(&self, model: &str, config: &Config) -> ModelFamily {
-        Self::find_family_for_model(model)
-            .with_remote_overrides(self.remote_models(config).await)
-            .with_config_overrides(config)
+        crate::models_manager::model_family::with_config_overrides(
+            Self::find_family_for_model(model)
+                .with_remote_overrides(self.remote_models(config).await),
+            config,
+        )
     }
 
     pub async fn get_model(&self, model: &Option<String>, config: &Config) -> String {
@@ -185,7 +187,10 @@ impl ModelsManager {
     #[cfg(any(test, feature = "test-support"))]
     /// Offline helper that builds a `ModelFamily` without consulting remote state.
     pub fn construct_model_family_offline(model: &str, config: &Config) -> ModelFamily {
-        Self::find_family_for_model(model).with_config_overrides(config)
+        crate::models_manager::model_family::with_config_overrides(
+            Self::find_family_for_model(model),
+            config,
+        )
     }
 
     /// Replace the cached remote models and rebuild the derived presets list.

codex-rs/core/src/models_manager/model_family.rs

@@ -1,12 +1,12 @@
 use codex_protocol::config_types::Verbosity;
 use codex_protocol::openai_models::ApplyPatchToolType;
 use codex_protocol::openai_models::ConfigShellToolType;
-use codex_protocol::openai_models::ModelInfo;
+use codex_protocol::openai_models::ModelFamily;
 use codex_protocol::openai_models::ReasoningEffort;
 use codex_protocol::openai_models::ReasoningSummaryFormat;
+use codex_protocol::openai_models::TruncationPolicy;
 
 use crate::config::Config;
-use crate::truncate::TruncationPolicy;
 
 /// The `instructions` field in the payload sent to a model should always start
 /// with this content.
@@ -19,174 +19,20 @@ const GPT_5_1_CODEX_MAX_INSTRUCTIONS: &str = include_str!("../../gpt-5.1-codex-m
 const GPT_5_2_CODEX_INSTRUCTIONS: &str = include_str!("../../gpt-5.2-codex_prompt.md");
 pub(crate) const CONTEXT_WINDOW_272K: i64 = 272_000;
 
-/// A model family is a group of models that share certain characteristics.
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct ModelFamily {
-    /// The full model slug used to derive this model family, e.g.
-    /// "gpt-4.1-2025-04-14".
-    pub slug: String,
-
-    /// The model family name, e.g. "gpt-4.1". This string is used when deriving
-    /// default metadata for the family, such as context windows.
-    pub family: String,
-
-    /// True if the model needs additional instructions on how to use the
-    /// "virtual" `apply_patch` CLI.
-    pub needs_special_apply_patch_instructions: bool,
-
-    /// Maximum supported context window, if known.
-    pub context_window: Option<i64>,
-
-    /// Token threshold for automatic compaction if config does not override it.
-    auto_compact_token_limit: Option<i64>,
-
-    // Whether the `reasoning` field can be set when making a request to this
-    // model family. Note it has `effort` and `summary` subfields (though
-    // `summary` is optional).
-    pub supports_reasoning_summaries: bool,
-
-    // The reasoning effort to use for this model family when none is explicitly chosen.
-    pub default_reasoning_effort: Option<ReasoningEffort>,
-
-    // Define if we need a special handling of reasoning summary
-    pub reasoning_summary_format: ReasoningSummaryFormat,
-
-    /// Whether this model supports parallel tool calls when using the
-    /// Responses API.
-    pub supports_parallel_tool_calls: bool,
-
-    /// Present if the model performs better when `apply_patch` is provided as
-    /// a tool call instead of just a bash command
-    pub apply_patch_tool_type: Option<ApplyPatchToolType>,
-
-    // Instructions to use for querying the model
-    pub base_instructions: String,
-
-    /// Names of beta tools that should be exposed to this model family.
-    pub experimental_supported_tools: Vec<String>,
-
-    /// Percentage of the context window considered usable for inputs, after
-    /// reserving headroom for system prompts, tool overhead, and model output.
-    /// This is applied when computing the effective context window seen by
-    /// consumers.
-    pub effective_context_window_percent: i64,
-
-    /// If the model family supports setting the verbosity level when using Responses API.
-    pub support_verbosity: bool,
-
-    // The default verbosity level for this model family when using Responses API.
-    pub default_verbosity: Option<Verbosity>,
-
-    /// Preferred shell tool type for this model family when features do not override it.
-    pub shell_type: ConfigShellToolType,
-
-    pub truncation_policy: TruncationPolicy,
-}
-
-impl ModelFamily {
-    /// Placeholder model family for UI startup before Codex has selected the real model.
-    ///
-    /// This must not be treated as an actual model slug; it only exists to allow
-    /// consumers (e.g. the TUI) to render while the session is still starting.
-    pub fn placeholder(config: &Config) -> Self {
-        let mf = Self {
-            slug: String::new(),
-            family: "unknown".to_string(),
-            needs_special_apply_patch_instructions: false,
-            context_window: None,
-            auto_compact_token_limit: None,
-            supports_reasoning_summaries: false,
-            default_reasoning_effort: None,
-            reasoning_summary_format: ReasoningSummaryFormat::None,
-            supports_parallel_tool_calls: false,
-            apply_patch_tool_type: None,
-            base_instructions: BASE_INSTRUCTIONS.to_string(),
-            experimental_supported_tools: Vec::new(),
-            effective_context_window_percent: 95,
-            support_verbosity: false,
-            default_verbosity: None,
-            shell_type: ConfigShellToolType::Default,
-            truncation_policy: TruncationPolicy::Bytes(10_000),
-        };
-        mf.with_config_overrides(config)
+pub fn with_config_overrides(mut mf: ModelFamily, config: &Config) -> ModelFamily {
+    if let Some(supports_reasoning_summaries) = config.model_supports_reasoning_summaries {
+        mf.supports_reasoning_summaries = supports_reasoning_summaries;
     }
-
-    pub(super) fn with_config_overrides(mut self, config: &Config) -> Self {
-        if let Some(supports_reasoning_summaries) = config.model_supports_reasoning_summaries {
-            self.supports_reasoning_summaries = supports_reasoning_summaries;
-        }
-        if let Some(reasoning_summary_format) = config.model_reasoning_summary_format.as_ref() {
-            self.reasoning_summary_format = reasoning_summary_format.clone();
-        }
-        if let Some(context_window) = config.model_context_window {
-            self.context_window = Some(context_window);
-        }
-        if let Some(auto_compact_token_limit) = config.model_auto_compact_token_limit {
-            self.auto_compact_token_limit = Some(auto_compact_token_limit);
-        }
-        self
+    if let Some(reasoning_summary_format) = config.model_reasoning_summary_format.as_ref() {
+        mf.reasoning_summary_format = reasoning_summary_format.clone();
     }
-    pub(super) fn with_remote_overrides(mut self, remote_models: Vec<ModelInfo>) -> Self {
-        for model in remote_models {
-            if model.slug == self.slug {
-                self.apply_remote_overrides(model);
-            }
-        }
-        self
+    if let Some(context_window) = config.model_context_window {
+        mf.context_window = Some(context_window);
     }
-
-    fn apply_remote_overrides(&mut self, model: ModelInfo) {
-        let ModelInfo {
-            slug: _,
-            display_name: _,
-            description: _,
-            default_reasoning_level,
-            supported_reasoning_levels: _,
-            shell_type,
-            visibility: _,
-            supported_in_api: _,
-            priority: _,
-            upgrade: _,
-            base_instructions,
-            supports_reasoning_summaries,
-            support_verbosity,
-            default_verbosity,
-            apply_patch_tool_type,
-            truncation_policy,
-            supports_parallel_tool_calls,
-            context_window,
-            reasoning_summary_format,
-            experimental_supported_tools,
-        } = model;
-
-        self.default_reasoning_effort = Some(default_reasoning_level);
-        self.shell_type = shell_type;
-        if let Some(base) = base_instructions {
-            self.base_instructions = base;
-        }
-        self.supports_reasoning_summaries = supports_reasoning_summaries;
-        self.support_verbosity = support_verbosity;
-        self.default_verbosity = default_verbosity;
-        self.apply_patch_tool_type = apply_patch_tool_type;
-        self.truncation_policy = truncation_policy.into();
-        self.supports_parallel_tool_calls = supports_parallel_tool_calls;
-        self.context_window = context_window;
-        self.reasoning_summary_format = reasoning_summary_format;
-        self.experimental_supported_tools = experimental_supported_tools;
-    }
-
-    pub fn auto_compact_token_limit(&self) -> Option<i64> {
-        self.auto_compact_token_limit
-            .or(self.context_window.map(Self::default_auto_compact_limit))
-    }
-
-    const fn default_auto_compact_limit(context_window: i64) -> i64 {
-        (context_window * 9) / 10
-    }
-
-    pub fn get_model_slug(&self) -> &str {
-        &self.slug
+    if let Some(auto_compact_token_limit) = config.model_auto_compact_token_limit {
+        mf.auto_compact_token_limit = Some(auto_compact_token_limit);
     }
+    mf
 }
 
 macro_rules! model_family {
@@ -460,6 +306,7 @@ fn derive_default_model_family(model: &str) -> ModelFamily {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use codex_protocol::openai_models::ModelInfo;
     use codex_protocol::openai_models::ModelVisibility;
     use codex_protocol::openai_models::ReasoningEffortPreset;
     use codex_protocol::openai_models::TruncationPolicyConfig;

codex-rs/core/src/state/session.rs

@@ -7,7 +7,7 @@ use crate::context_manager::ContextManager;
 use crate::protocol::RateLimitSnapshot;
 use crate::protocol::TokenUsage;
 use crate::protocol::TokenUsageInfo;
-use crate::truncate::TruncationPolicy;
+use codex_protocol::openai_models::TruncationPolicy;
 
 /// Persistent, session-scoped state previously stored directly on `Session`.
 pub(crate) struct SessionState {

codex-rs/core/src/tools/mod.rs

@@ -10,7 +10,7 @@ pub mod sandboxing;
 pub mod spec;
 
 use crate::exec::ExecToolCallOutput;
-use crate::truncate::TruncationPolicy;
+use codex_protocol::openai_models::TruncationPolicy;
 use crate::truncate::formatted_truncate_text;
 use crate::truncate::truncate_text;
 pub use router::ToolRouter;

codex-rs/core/src/tools/spec.rs

@@ -2,7 +2,7 @@ use crate::client_common::tools::ResponsesApiTool;
 use crate::client_common::tools::ToolSpec;
 use crate::features::Feature;
 use crate::features::Features;
-use crate::models_manager::model_family::ModelFamily;
+use codex_protocol::openai_models::ModelFamily;
 use crate::tools::handlers::PLAN_TOOL;
 use crate::tools::handlers::apply_patch::create_apply_patch_freeform_tool;
 use crate::tools::handlers::apply_patch::create_apply_patch_json_tool;

codex-rs/core/src/truncate.rs

@@ -4,89 +4,60 @@
 
 use crate::config::Config;
 use codex_protocol::models::FunctionCallOutputContentItem;
-use codex_protocol::openai_models::TruncationMode;
-use codex_protocol::openai_models::TruncationPolicyConfig;
+use codex_protocol::openai_models::TruncationPolicy;
 
 const APPROX_BYTES_PER_TOKEN: usize = 4;
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub enum TruncationPolicy {
-    Bytes(usize),
-    Tokens(usize),
-}
+/// Create a new `TruncationPolicy` with config overrides applied.
+pub fn new_truncation_policy(config: &Config, truncation_policy: TruncationPolicy) -> TruncationPolicy {
+    let config_token_limit = config.tool_output_token_limit;
 
-impl From<TruncationPolicyConfig> for TruncationPolicy {
-    fn from(config: TruncationPolicyConfig) -> Self {
-        match config.mode {
-            TruncationMode::Bytes => Self::Bytes(config.limit as usize),
-            TruncationMode::Tokens => Self::Tokens(config.limit as usize),
+    match truncation_policy {
+        TruncationPolicy::Bytes(family_bytes) => {
+            if let Some(token_limit) = config_token_limit {
+                TruncationPolicy::Bytes(approx_bytes_for_tokens(token_limit))
+            } else {
+                TruncationPolicy::Bytes(family_bytes)
+            }
+        }
+        TruncationPolicy::Tokens(family_tokens) => {
+            if let Some(token_limit) = config_token_limit {
+                TruncationPolicy::Tokens(token_limit)
+            } else {
+                TruncationPolicy::Tokens(family_tokens)
+            }
         }
     }
 }
 
-impl TruncationPolicy {
-    /// Scale the underlying budget by `multiplier`, rounding up to avoid under-budgeting.
-    pub fn mul(self, multiplier: f64) -> Self {
-        match self {
-            TruncationPolicy::Bytes(bytes) => {
-                TruncationPolicy::Bytes((bytes as f64 * multiplier).ceil() as usize)
-            }
-            TruncationPolicy::Tokens(tokens) => {
-                TruncationPolicy::Tokens((tokens as f64 * multiplier).ceil() as usize)
-            }
+/// Returns a token budget derived from this policy.
+///
+/// - For `Tokens`, this is the explicit token limit.
+/// - For `Bytes`, this is an approximate token budget using the global
+///   bytes-per-token heuristic.
+pub fn token_budget(policy: &TruncationPolicy) -> usize {
+    match policy {
+        TruncationPolicy::Bytes(bytes) => {
+            usize::try_from(approx_tokens_from_byte_count(*bytes)).unwrap_or(usize::MAX)
         }
+        TruncationPolicy::Tokens(tokens) => *tokens,
     }
+}
 
-    pub fn new(config: &Config, truncation_policy: TruncationPolicy) -> Self {
-        let config_token_limit = config.tool_output_token_limit;
-
-        match truncation_policy {
-            TruncationPolicy::Bytes(family_bytes) => {
-                if let Some(token_limit) = config_token_limit {
-                    Self::Bytes(approx_bytes_for_tokens(token_limit))
-                } else {
-                    Self::Bytes(family_bytes)
-                }
-            }
-            TruncationPolicy::Tokens(family_tokens) => {
-                if let Some(token_limit) = config_token_limit {
-                    Self::Tokens(token_limit)
-                } else {
-                    Self::Tokens(family_tokens)
-                }
-            }
-        }
-    }
-
-    /// Returns a token budget derived from this policy.
-    ///
-    /// - For `Tokens`, this is the explicit token limit.
-    /// - For `Bytes`, this is an approximate token budget using the global
-    ///   bytes-per-token heuristic.
-    pub fn token_budget(&self) -> usize {
-        match self {
-            TruncationPolicy::Bytes(bytes) => {
-                usize::try_from(approx_tokens_from_byte_count(*bytes)).unwrap_or(usize::MAX)
-            }
-            TruncationPolicy::Tokens(tokens) => *tokens,
-        }
-    }
-
-    /// Returns a byte budget derived from this policy.
-    ///
-    /// - For `Bytes`, this is the explicit byte limit.
-    /// - For `Tokens`, this is an approximate byte budget using the global
-    ///   bytes-per-token heuristic.
-    pub fn byte_budget(&self) -> usize {
-        match self {
-            TruncationPolicy::Bytes(bytes) => *bytes,
-            TruncationPolicy::Tokens(tokens) => approx_bytes_for_tokens(*tokens),
-        }
+/// Returns a byte budget derived from this policy.
+///
+/// - For `Bytes`, this is the explicit byte limit.
+/// - For `Tokens`, this is an approximate byte budget using the global
+///   bytes-per-token heuristic.
+pub fn byte_budget(policy: &TruncationPolicy) -> usize {
+    match policy {
+        TruncationPolicy::Bytes(bytes) => *bytes,
+        TruncationPolicy::Tokens(tokens) => approx_bytes_for_tokens(*tokens),
     }
 }
 
 pub(crate) fn formatted_truncate_text(content: &str, policy: TruncationPolicy) -> String {
-    if content.len() <= policy.byte_budget() {
+    if content.len() <= byte_budget(&policy) {
         return content.to_string();
     }
     let total_lines = content.lines().count();
@@ -112,8 +83,8 @@ pub(crate) fn truncate_function_output_items_with_policy(
 ) -> Vec<FunctionCallOutputContentItem> {
     let mut out: Vec<FunctionCallOutputContentItem> = Vec::with_capacity(items.len());
     let mut remaining_budget = match policy {
-        TruncationPolicy::Bytes(_) => policy.byte_budget(),
-        TruncationPolicy::Tokens(_) => policy.token_budget(),
+        TruncationPolicy::Bytes(_) => byte_budget(&policy),
+        TruncationPolicy::Tokens(_) => token_budget(&policy),
     };
     let mut omitted_text_items = 0usize;
 
@@ -172,7 +143,7 @@ fn truncate_with_token_budget(s: &str, policy: TruncationPolicy) -> (String, Opt
     if s.is_empty() {
         return (String::new(), None);
     }
-    let max_tokens = policy.token_budget();
+    let max_tokens = token_budget(&policy);
 
     let byte_len = s.len();
     if max_tokens > 0 && byte_len <= approx_bytes_for_tokens(max_tokens) {
@@ -198,7 +169,7 @@ fn truncate_with_byte_estimate(s: &str, policy: TruncationPolicy) -> String {
     }
 
     let total_chars = s.chars().count();
-    let max_bytes = policy.byte_budget();
+    let max_bytes = byte_budget(&policy);
 
     if max_bytes == 0 {
         // No budget to show content; just report that everything was truncated.

codex-rs/core/src/unified_exec/session.rs

@@ -14,7 +14,7 @@ use crate::exec::ExecToolCallOutput;
 use crate::exec::SandboxType;
 use crate::exec::StreamOutput;
 use crate::exec::is_likely_sandbox_denied;
-use crate::truncate::TruncationPolicy;
+use codex_protocol::openai_models::TruncationPolicy;
 use crate::truncate::formatted_truncate_text;
 use codex_utils_pty::ExecCommandSession;
 use codex_utils_pty::SpawnedPty;

codex-rs/core/src/unified_exec/session_manager.rs

@@ -22,7 +22,7 @@ use crate::tools::orchestrator::ToolOrchestrator;
 use crate::tools::runtimes::unified_exec::UnifiedExecRequest as UnifiedExecToolRequest;
 use crate::tools::runtimes::unified_exec::UnifiedExecRuntime;
 use crate::tools::sandboxing::ToolCtx;
-use crate::truncate::TruncationPolicy;
+use codex_protocol::openai_models::TruncationPolicy;
 use crate::truncate::approx_token_count;
 use crate::truncate::formatted_truncate_text;
 

codex-rs/core/tests/common/test_codex.rs

@@ -250,7 +250,7 @@ impl TestCodex {
         approval_policy: AskForApproval,
         sandbox_policy: SandboxPolicy,
     ) -> Result<()> {
-        let session_model = self.session_configured.model.clone();
+        let session_model = self.session_configured.model_family.slug.clone();
         self.codex
             .submit(Op::UserTurn {
                 items: vec![UserInput::Text {

codex-rs/core/tests/suite/apply_patch_cli.rs

@@ -297,7 +297,7 @@ async fn apply_patch_cli_move_without_content_change_has_no_turn_diff(
     let call_id = "apply-move-no-change";
     mount_apply_patch(&harness, call_id, patch, "ok", model_output).await;
 
-    let model = test.session_configured.model.clone();
+    let model = test.session_configured.model_family.slug.clone();
     codex
         .submit(Op::UserTurn {
             items: vec![UserInput::Text {
@@ -883,7 +883,7 @@ async fn apply_patch_shell_command_heredoc_with_cd_emits_turn_diff() -> Result<(
     ];
     mount_sse_sequence(harness.server(), bodies).await;
 
-    let model = test.session_configured.model.clone();
+    let model = test.session_configured.model_family.slug.clone();
     codex
         .submit(Op::UserTurn {
             items: vec![UserInput::Text {
@@ -960,7 +960,7 @@ async fn apply_patch_shell_command_failure_propagates_error_and_skips_diff() ->
     ];
     mount_sse_sequence(harness.server(), bodies).await;
 
-    let model = test.session_configured.model.clone();
+    let model = test.session_configured.model_family.slug.clone();
     codex
         .submit(Op::UserTurn {
             items: vec![UserInput::Text {
@@ -1107,7 +1107,7 @@ async fn apply_patch_emits_turn_diff_event_with_unified_diff(
     let patch = format!("*** Begin Patch\n*** Add File: {file}\n+hello\n*** End Patch\n");
     mount_apply_patch(&harness, call_id, patch.as_str(), "ok", model_output).await;
 
-    let model = test.session_configured.model.clone();
+    let model = test.session_configured.model_family.slug.clone();
     codex
         .submit(Op::UserTurn {
             items: vec![UserInput::Text {
@@ -1167,7 +1167,7 @@ async fn apply_patch_turn_diff_for_rename_with_content_change(
     let patch = "*** Begin Patch\n*** Update File: old.txt\n*** Move to: new.txt\n@@\n-old\n+new\n*** End Patch";
     mount_apply_patch(&harness, call_id, patch, "ok", model_output).await;
 
-    let model = test.session_configured.model.clone();
+    let model = test.session_configured.model_family.slug.clone();
     codex
         .submit(Op::UserTurn {
             items: vec![UserInput::Text {
@@ -1235,7 +1235,7 @@ async fn apply_patch_aggregates_diff_across_multiple_tool_calls() -> Result<()>
     ]);
     mount_sse_sequence(harness.server(), vec![s1, s2, s3]).await;
 
-    let model = test.session_configured.model.clone();
+    let model = test.session_configured.model_family.slug.clone();
     codex
         .submit(Op::UserTurn {
             items: vec![UserInput::Text {
@@ -1303,7 +1303,7 @@ async fn apply_patch_aggregates_diff_preserves_success_after_failure() -> Result
     ];
     mount_sse_sequence(harness.server(), responses).await;
 
-    let model = test.session_configured.model.clone();
+    let model = test.session_configured.model_family.slug.clone();
     codex
         .submit(Op::UserTurn {
             items: vec![UserInput::Text {

codex-rs/core/tests/suite/approvals.rs

@@ -486,7 +486,7 @@ async fn submit_turn(
     approval_policy: AskForApproval,
     sandbox_policy: SandboxPolicy,
 ) -> Result<()> {
-    let session_model = test.session_configured.model.clone();
+    let session_model = test.session_configured.model_family.slug.clone();
 
     test.codex
         .submit(Op::UserTurn {

codex-rs/core/tests/suite/compact_remote.rs

@@ -103,7 +103,7 @@ async fn remote_compact_replaces_history_for_followups() -> Result<()> {
     let compact_body = compact_request.body_json();
     assert_eq!(
         compact_body.get("model").and_then(|v| v.as_str()),
-        Some(harness.test().session_configured.model.as_str())
+        Some(harness.test().session_configured.model_family.slug.as_str())
     );
     let compact_body_text = compact_body.to_string();
     assert!(

codex-rs/core/tests/suite/exec_policy.rs

@@ -67,7 +67,7 @@ async fn execpolicy_blocks_shell_invocation() -> Result<()> {
     )
     .await;
 
-    let session_model = test.session_configured.model.clone();
+    let session_model = test.session_configured.model_family.slug.clone();
     test.codex
         .submit(Op::UserTurn {
             items: vec![UserInput::Text {

codex-rs/core/tests/suite/prompt_caching.rs

@@ -606,7 +606,7 @@ async fn send_user_turn_with_no_changes_does_not_send_environment_context() -> a
     let default_cwd = config.cwd.clone();
     let default_approval_policy = config.approval_policy.value();
     let default_sandbox_policy = config.sandbox_policy.get();
-    let default_model = session_configured.model;
+    let default_model = session_configured.model_family.slug;
     let default_effort = config.model_reasoning_effort;
     let default_summary = config.model_reasoning_summary;
 
@@ -696,7 +696,7 @@ async fn send_user_turn_with_changes_sends_environment_context() -> anyhow::Resu
     let default_cwd = config.cwd.clone();
     let default_approval_policy = config.approval_policy.value();
     let default_sandbox_policy = config.sandbox_policy.get();
-    let default_model = session_configured.model;
+    let default_model = session_configured.model_family.slug;
     let default_effort = config.model_reasoning_effort;
     let default_summary = config.model_reasoning_summary;
 

codex-rs/core/tests/suite/rmcp_client.rs

@@ -101,7 +101,7 @@ async fn stdio_server_round_trip() -> anyhow::Result<()> {
         })
         .build(&server)
         .await?;
-    let session_model = fixture.session_configured.model.clone();
+    let session_model = fixture.session_configured.model_family.slug.clone();
 
     fixture
         .codex
@@ -238,7 +238,7 @@ async fn stdio_image_responses_round_trip() -> anyhow::Result<()> {
         })
         .build(&server)
         .await?;
-    let session_model = fixture.session_configured.model.clone();
+    let session_model = fixture.session_configured.model_family.slug.clone();
 
     fixture
         .codex
@@ -433,7 +433,7 @@ async fn stdio_image_completions_round_trip() -> anyhow::Result<()> {
         })
         .build(&server)
         .await?;
-    let session_model = fixture.session_configured.model.clone();
+    let session_model = fixture.session_configured.model_family.slug.clone();
 
     fixture
         .codex
@@ -576,7 +576,7 @@ async fn stdio_server_propagates_whitelisted_env_vars() -> anyhow::Result<()> {
         })
         .build(&server)
         .await?;
-    let session_model = fixture.session_configured.model.clone();
+    let session_model = fixture.session_configured.model_family.slug.clone();
 
     fixture
         .codex
@@ -724,7 +724,7 @@ async fn streamable_http_tool_call_round_trip() -> anyhow::Result<()> {
         })
         .build(&server)
         .await?;
-    let session_model = fixture.session_configured.model.clone();
+    let session_model = fixture.session_configured.model_family.slug.clone();
 
     fixture
         .codex
@@ -904,7 +904,7 @@ async fn streamable_http_with_oauth_round_trip() -> anyhow::Result<()> {
         })
         .build(&server)
         .await?;
-    let session_model = fixture.session_configured.model.clone();
+    let session_model = fixture.session_configured.model_family.slug.clone();
 
     fixture
         .codex

codex-rs/core/tests/suite/shell_snapshot.rs

@@ -64,7 +64,7 @@ async fn run_snapshot_command(command: &str) -> Result<SnapshotRun> {
     let test = harness.test();
     let codex = test.codex.clone();
     let codex_home = test.home.path().to_path_buf();
-    let session_model = test.session_configured.model.clone();
+    let session_model = test.session_configured.model_family.slug.clone();
     let cwd = test.cwd_path().to_path_buf();
 
     codex
@@ -140,7 +140,7 @@ async fn run_shell_command_snapshot(command: &str) -> Result<SnapshotRun> {
     let test = harness.test();
     let codex = test.codex.clone();
     let codex_home = test.home.path().to_path_buf();
-    let session_model = test.session_configured.model.clone();
+    let session_model = test.session_configured.model_family.slug.clone();
     let cwd = test.cwd_path().to_path_buf();
 
     codex
@@ -279,7 +279,7 @@ async fn shell_command_snapshot_still_intercepts_apply_patch() -> Result<()> {
     ];
     mount_sse_sequence(harness.server(), responses).await;
 
-    let model = test.session_configured.model.clone();
+    let model = test.session_configured.model_family.slug.clone();
     codex
         .submit(Op::UserTurn {
             items: vec![UserInput::Text {

codex-rs/core/tests/suite/skills.rs

@@ -63,7 +63,7 @@ async fn user_turn_includes_skill_instructions() -> Result<()> {
     )
     .await;
 
-    let session_model = test.session_configured.model.clone();
+    let session_model = test.session_configured.model_family.slug.clone();
     test.codex
         .submit(Op::UserTurn {
             items: vec![

codex-rs/core/tests/suite/tool_harness.rs

@@ -76,7 +76,7 @@ async fn shell_tool_executes_command_and_streams_output() -> anyhow::Result<()>
     ]);
     let second_mock = responses::mount_sse_once(&server, second_response).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -142,7 +142,7 @@ async fn update_plan_tool_emits_plan_update_event() -> anyhow::Result<()> {
     ]);
     let second_mock = responses::mount_sse_once(&server, second_response).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -218,7 +218,7 @@ async fn update_plan_tool_rejects_malformed_payload() -> anyhow::Result<()> {
     ]);
     let second_mock = responses::mount_sse_once(&server, second_response).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -306,7 +306,7 @@ async fn apply_patch_tool_executes_and_emits_patch_events() -> anyhow::Result<()
     ]);
     let second_mock = responses::mount_sse_once(&server, second_response).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -402,7 +402,7 @@ async fn apply_patch_reports_parse_diagnostics() -> anyhow::Result<()> {
     ]);
     let second_mock = responses::mount_sse_once(&server, second_response).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {

codex-rs/core/tests/suite/tool_parallelism.rs

@@ -32,7 +32,7 @@ use serde_json::json;
 use tokio::sync::oneshot;
 
 async fn run_turn(test: &TestCodex, prompt: &str) -> anyhow::Result<()> {
-    let session_model = test.session_configured.model.clone();
+    let session_model = test.session_configured.model_family.slug.clone();
 
     test.codex
         .submit(Op::UserTurn {
@@ -345,7 +345,7 @@ async fn shell_tools_start_before_response_completed_when_stream_delayed() -> an
         .build_with_streaming_server(&streaming_server)
         .await?;
 
-    let session_model = test.session_configured.model.clone();
+    let session_model = test.session_configured.model_family.slug.clone();
     test.codex
         .submit(Op::UserTurn {
             items: vec![UserInput::Text {

codex-rs/core/tests/suite/truncation.rs

@@ -531,7 +531,7 @@ async fn mcp_image_output_preserves_image_and_no_text_summary() -> Result<()> {
         );
     });
     let fixture = builder.build(&server).await?;
-    let session_model = fixture.session_configured.model.clone();
+    let session_model = fixture.session_configured.model_family.slug.clone();
 
     fixture
         .codex

codex-rs/core/tests/suite/unified_exec.rs

@@ -194,7 +194,7 @@ async fn unified_exec_intercepts_apply_patch_exec_command() -> Result<()> {
     let test = harness.test();
     let codex = test.codex.clone();
     let cwd = test.cwd_path().to_path_buf();
-    let session_model = test.session_configured.model.clone();
+    let session_model = test.session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -320,7 +320,7 @@ async fn unified_exec_emits_exec_command_begin_event() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -395,7 +395,7 @@ async fn unified_exec_resolves_relative_workdir() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -473,7 +473,7 @@ async fn unified_exec_respects_workdir_override() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -563,7 +563,7 @@ async fn unified_exec_emits_exec_command_end_event() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -635,7 +635,7 @@ async fn unified_exec_emits_output_delta_for_exec_command() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -708,7 +708,7 @@ async fn unified_exec_full_lifecycle_with_background_end_event() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -834,7 +834,7 @@ async fn unified_exec_emits_terminal_interaction_for_write_stdin() -> Result<()>
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -967,7 +967,7 @@ async fn unified_exec_terminal_interaction_captures_delayed_output() -> Result<(
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -1124,7 +1124,7 @@ async fn unified_exec_emits_one_begin_and_one_end_event() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -1219,7 +1219,7 @@ async fn exec_command_reports_chunk_and_exit_metadata() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -1323,7 +1323,7 @@ async fn unified_exec_respects_early_exit_notifications() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -1448,7 +1448,7 @@ async fn write_stdin_returns_exit_metadata_and_clears_session() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -1610,7 +1610,7 @@ async fn unified_exec_emits_end_event_when_session_dies_via_stdin() -> Result<()
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -1684,7 +1684,7 @@ async fn unified_exec_closes_long_running_session_at_turn_end() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -1802,7 +1802,7 @@ async fn unified_exec_reuses_session_via_stdin() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -1931,7 +1931,7 @@ PY
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -2040,7 +2040,7 @@ async fn unified_exec_timeout_and_followup_poll() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -2131,7 +2131,7 @@ PY
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -2207,7 +2207,7 @@ async fn unified_exec_runs_under_sandbox() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -2306,7 +2306,7 @@ async fn unified_exec_python_prompt_under_seatbelt() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -2396,7 +2396,7 @@ async fn unified_exec_runs_on_all_platforms() -> Result<()> {
     ];
     mount_sse_sequence(&server, responses).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -2524,7 +2524,7 @@ async fn unified_exec_prunes_exited_sessions_first() -> Result<()> {
     let response_mock =
         mount_sse_sequence(&server, vec![first_response, completion_response]).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {

codex-rs/core/tests/suite/view_image.rs

@@ -72,7 +72,7 @@ async fn user_turn_with_local_image_attaches_image() -> anyhow::Result<()> {
     ]);
     let mock = responses::mount_sse_once(&server, response).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -163,7 +163,7 @@ async fn view_image_tool_attaches_local_image() -> anyhow::Result<()> {
     ]);
     let mock = responses::mount_sse_once(&server, second_response).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -273,7 +273,7 @@ async fn view_image_tool_errors_when_path_is_directory() -> anyhow::Result<()> {
     ]);
     let mock = responses::mount_sse_once(&server, second_response).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -345,7 +345,7 @@ async fn view_image_tool_placeholder_for_non_image_files() -> anyhow::Result<()>
     ]);
     let mock = responses::mount_sse_once(&server, second_response).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -436,7 +436,7 @@ async fn view_image_tool_errors_when_file_missing() -> anyhow::Result<()> {
     ]);
     let mock = responses::mount_sse_once(&server, second_response).await;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {
@@ -517,7 +517,7 @@ async fn replaces_invalid_local_image_after_bad_request() -> anyhow::Result<()>
     let image = ImageBuffer::from_pixel(1024, 512, Rgba([10u8, 20, 30, 255]));
     image.save(&abs_path)?;
 
-    let session_model = session_configured.model.clone();
+    let session_model = session_configured.model_family.slug.clone();
 
     codex
         .submit(Op::UserTurn {

codex-rs/docs/protocol_v1.md

@@ -173,3 +173,17 @@ sequenceDiagram
     task2->>user: Event::TurnCompleted
     task2->>-user: Event::TaskCompleted
 ```
+
+## Key Events
+
+### SessionConfigured
+
+`Event::SessionConfigured` is emitted once after `Op::ConfigureSession`.
+
+Notable fields:
+- `session_id`: the backend-assigned session identifier (historically named `session_id` for
+  backwards compatibility).
+- `model_family`: model metadata for the model family selected for the session. This matches the
+  `/models` payload shape; the selected model slug is `model_family.slug`.
+- `approval_policy`, `sandbox_policy`, `cwd`: the effective execution and sandbox settings for the
+  session.

codex-rs/exec/src/event_processor_with_human_output.rs

@@ -140,8 +140,10 @@ impl EventProcessor for EventProcessorWithHumanOutput {
             VERSION
         );
 
-        let mut entries =
-            create_config_summary_entries(config, session_configured_event.model.as_str());
+        let mut entries = create_config_summary_entries(
+            config,
+            session_configured_event.model_family.slug.as_str(),
+        );
         entries.push((
             "session id",
             session_configured_event.session_id.to_string(),
@@ -494,7 +496,7 @@ impl EventProcessor for EventProcessorWithHumanOutput {
             EventMsg::SessionConfigured(session_configured_event) => {
                 let SessionConfiguredEvent {
                     session_id: conversation_id,
-                    model,
+                    model_family,
                     ..
                 } = session_configured_event;
 
@@ -505,7 +507,7 @@ impl EventProcessor for EventProcessorWithHumanOutput {
                     conversation_id.to_string().style(self.dimmed)
                 );
 
-                ts_msg!(self, "model: {}", model);
+                ts_msg!(self, "model: {}", model_family.slug);
                 eprintln!();
             }
             EventMsg::PlanUpdate(plan_update_event) => {

codex-rs/exec/tests/event_processor_with_json_output.rs

@@ -44,6 +44,11 @@ use codex_exec::exec_events::TurnFailedEvent;
 use codex_exec::exec_events::TurnStartedEvent;
 use codex_exec::exec_events::Usage;
 use codex_exec::exec_events::WebSearchItem;
+use codex_protocol::openai_models::ConfigShellToolType;
+use codex_protocol::openai_models::ModelFamily;
+use codex_protocol::openai_models::ReasoningEffort;
+use codex_protocol::openai_models::ReasoningSummaryFormat;
+use codex_protocol::openai_models::TruncationPolicy;
 use codex_protocol::plan_tool::PlanItemArg;
 use codex_protocol::plan_tool::StepStatus;
 use codex_protocol::plan_tool::UpdatePlanArgs;
@@ -76,7 +81,25 @@ fn session_configured_produces_thread_started_event() {
         "e1",
         EventMsg::SessionConfigured(SessionConfiguredEvent {
             session_id,
-            model: "codex-mini-latest".to_string(),
+            model_family: ModelFamily {
+                slug: "codex-mini-latest".to_string(),
+                family: "codex-mini-latest".to_string(),
+                needs_special_apply_patch_instructions: false,
+                context_window: None,
+                auto_compact_token_limit: None,
+                supports_reasoning_summaries: false,
+                default_reasoning_effort: Some(ReasoningEffort::default()),
+                reasoning_summary_format: ReasoningSummaryFormat::None,
+                supports_parallel_tool_calls: false,
+                apply_patch_tool_type: None,
+                base_instructions: String::new(),
+                experimental_supported_tools: Vec::new(),
+                effective_context_window_percent: 95,
+                support_verbosity: false,
+                default_verbosity: None,
+                shell_type: ConfigShellToolType::Default,
+                truncation_policy: TruncationPolicy::Bytes(10_000),
+            },
             model_provider_id: "test-provider".to_string(),
             approval_policy: AskForApproval::Never,
             sandbox_policy: SandboxPolicy::ReadOnly,

codex-rs/mcp-server/src/outgoing_message.rs

@@ -239,13 +239,39 @@ mod tests {
     use codex_core::protocol::SandboxPolicy;
     use codex_core::protocol::SessionConfiguredEvent;
     use codex_protocol::ConversationId;
+    use codex_protocol::openai_models::ConfigShellToolType;
+    use codex_protocol::openai_models::ModelFamily;
     use codex_protocol::openai_models::ReasoningEffort;
+    use codex_protocol::openai_models::ReasoningSummaryFormat;
+    use codex_protocol::openai_models::TruncationPolicy;
     use pretty_assertions::assert_eq;
     use serde_json::json;
     use tempfile::NamedTempFile;
 
     use super::*;
 
+    fn test_model_family(slug: &str) -> ModelFamily {
+        ModelFamily {
+            slug: slug.to_string(),
+            family: slug.to_string(),
+            needs_special_apply_patch_instructions: false,
+            context_window: None,
+            auto_compact_token_limit: None,
+            supports_reasoning_summaries: false,
+            default_reasoning_effort: Some(ReasoningEffort::default()),
+            reasoning_summary_format: ReasoningSummaryFormat::None,
+            supports_parallel_tool_calls: false,
+            apply_patch_tool_type: None,
+            base_instructions: String::new(),
+            experimental_supported_tools: Vec::new(),
+            effective_context_window_percent: 95,
+            support_verbosity: false,
+            default_verbosity: None,
+            shell_type: ConfigShellToolType::Default,
+            truncation_policy: TruncationPolicy::Bytes(10_000),
+        }
+    }
+
     #[tokio::test]
     async fn test_send_event_as_notification() -> Result<()> {
         let (outgoing_tx, mut outgoing_rx) = mpsc::unbounded_channel::<OutgoingMessage>();
@@ -257,7 +283,7 @@ mod tests {
             id: "1".to_string(),
             msg: EventMsg::SessionConfigured(SessionConfiguredEvent {
                 session_id: conversation_id,
-                model: "gpt-4o".to_string(),
+                model_family: test_model_family("gpt-4o"),
                 model_provider_id: "test-provider".to_string(),
                 approval_policy: AskForApproval::Never,
                 sandbox_policy: SandboxPolicy::ReadOnly,
@@ -296,7 +322,7 @@ mod tests {
         let rollout_file = NamedTempFile::new()?;
         let session_configured_event = SessionConfiguredEvent {
             session_id: conversation_id,
-            model: "gpt-4o".to_string(),
+            model_family: test_model_family("gpt-4o"),
             model_provider_id: "test-provider".to_string(),
             approval_policy: AskForApproval::Never,
             sandbox_policy: SandboxPolicy::ReadOnly,
@@ -332,7 +358,7 @@ mod tests {
             "msg": {
                 "type": "session_configured",
                 "session_id": session_configured_event.session_id,
-                "model": "gpt-4o",
+                "model_family": serde_json::to_value(&session_configured_event.model_family)?,
                 "model_provider_id": "test-provider",
                 "approval_policy": "never",
                 "sandbox_policy": {

codex-rs/protocol/src/openai_models.rs

@@ -163,6 +163,199 @@ impl TruncationPolicyConfig {
     }
 }
 
+#[derive(Debug, Clone, Deserialize, Serialize, Copy, PartialEq, Eq, Hash, JsonSchema, TS)]
+pub enum TruncationPolicy {
+    Bytes(usize),
+    Tokens(usize),
+}
+
+impl From<TruncationPolicyConfig> for TruncationPolicy {
+    fn from(config: TruncationPolicyConfig) -> Self {
+        match config.mode {
+            TruncationMode::Bytes => Self::Bytes(config.limit as usize),
+            TruncationMode::Tokens => Self::Tokens(config.limit as usize),
+        }
+    }
+}
+
+impl std::ops::Mul<f64> for TruncationPolicy {
+    type Output = Self;
+
+    /// Scale the underlying budget by `multiplier`, rounding up to avoid under-budgeting.
+    fn mul(self, multiplier: f64) -> Self::Output {
+        match self {
+            TruncationPolicy::Bytes(bytes) => {
+                TruncationPolicy::Bytes((bytes as f64 * multiplier).ceil() as usize)
+            }
+            TruncationPolicy::Tokens(tokens) => {
+                TruncationPolicy::Tokens((tokens as f64 * multiplier).ceil() as usize)
+            }
+        }
+    }
+}
+
+/// A model family is a group of models that share certain characteristics.
+#[derive(Debug, Clone, Deserialize, Serialize, Hash, JsonSchema, TS)]
+pub struct ModelFamily {
+    /// The full model slug used to derive this model family, e.g.
+    /// "gpt-4.1-2025-04-14".
+    pub slug: String,
+
+    /// The model family name, e.g. "gpt-4.1". This string is used when deriving
+    /// default metadata for the family, such as context windows.
+    pub family: String,
+
+    /// True if the model needs additional instructions on how to use the
+    /// "virtual" `apply_patch` CLI.
+    pub needs_special_apply_patch_instructions: bool,
+
+    /// Maximum supported context window, if known.
+    pub context_window: Option<i64>,
+
+    /// Token threshold for automatic compaction if config does not override it.
+    pub auto_compact_token_limit: Option<i64>,
+
+    // Whether the `reasoning` field can be set when making a request to this
+    // model family. Note it has `effort` and `summary` subfields (though
+    // `summary` is optional).
+    pub supports_reasoning_summaries: bool,
+
+    // The reasoning effort to use for this model family when none is explicitly chosen.
+    pub default_reasoning_effort: Option<ReasoningEffort>,
+
+    // Define if we need a special handling of reasoning summary
+    pub reasoning_summary_format: ReasoningSummaryFormat,
+
+    /// Whether this model supports parallel tool calls when using the
+    /// Responses API.
+    pub supports_parallel_tool_calls: bool,
+
+    /// Present if the model performs better when `apply_patch` is provided as
+    /// a tool call instead of just a bash command
+    pub apply_patch_tool_type: Option<ApplyPatchToolType>,
+
+    // Instructions to use for querying the model
+    pub base_instructions: String,
+
+    /// Names of beta tools that should be exposed to this model family.
+    pub experimental_supported_tools: Vec<String>,
+
+    /// Percentage of the context window considered usable for inputs, after
+    /// reserving headroom for system prompts, tool overhead, and model output.
+    /// This is applied when computing the effective context window seen by
+    /// consumers.
+    pub effective_context_window_percent: i64,
+
+    /// If the model family supports setting the verbosity level when using Responses API.
+    pub support_verbosity: bool,
+
+    // The default verbosity level for this model family when using Responses API.
+    pub default_verbosity: Option<Verbosity>,
+
+    /// Preferred shell tool type for this model family when features do not override it.
+    pub shell_type: ConfigShellToolType,
+
+    pub truncation_policy: TruncationPolicy,
+}
+
+impl ModelFamily {
+    /// Convert a `ModelFamily` into the protocol's `ModelInfo` shape for inclusion in events.
+    ///
+    /// This intentionally omits fields that are not needed for session bootstrapping
+    /// (e.g. `priority`, `visibility`, and `base_instructions`).
+    pub fn to_session_configured_model_info(&self) -> ModelInfo {
+        let default_reasoning_level = self.default_reasoning_effort.unwrap_or_default();
+        let truncation_policy = match self.truncation_policy {
+            TruncationPolicy::Bytes(limit) => TruncationPolicyConfig::bytes(limit as i64),
+            TruncationPolicy::Tokens(limit) => TruncationPolicyConfig::tokens(limit as i64),
+        };
+
+        ModelInfo {
+            slug: self.slug.clone(),
+            display_name: self.slug.clone(),
+            description: None,
+            default_reasoning_level,
+            supported_reasoning_levels: vec![ReasoningEffortPreset {
+                effort: default_reasoning_level,
+                description: default_reasoning_level.to_string(),
+            }],
+            shell_type: self.shell_type,
+            visibility: ModelVisibility::None,
+            supported_in_api: true,
+            priority: 0,
+            upgrade: None,
+            base_instructions: None,
+            supports_reasoning_summaries: self.supports_reasoning_summaries,
+            support_verbosity: self.support_verbosity,
+            default_verbosity: self.default_verbosity,
+            apply_patch_tool_type: self.apply_patch_tool_type.clone(),
+            truncation_policy,
+            supports_parallel_tool_calls: self.supports_parallel_tool_calls,
+            context_window: self.context_window,
+            reasoning_summary_format: self.reasoning_summary_format.clone(),
+            experimental_supported_tools: self.experimental_supported_tools.clone(),
+        }
+    }
+
+    pub fn auto_compact_token_limit(&self) -> Option<i64> {
+        self.auto_compact_token_limit
+            .or(self.context_window.map(|cw| (cw * 9) / 10))
+    }
+
+    pub fn get_model_slug(&self) -> &str {
+        &self.slug
+    }
+
+    pub fn with_remote_overrides(mut self, remote_models: Vec<ModelInfo>) -> Self {
+        for model in remote_models {
+            if model.slug == self.slug {
+                self.apply_remote_overrides(model);
+            }
+        }
+        self
+    }
+
+    fn apply_remote_overrides(&mut self, model: ModelInfo) {
+        let ModelInfo {
+            slug: _,
+            display_name: _,
+            description: _,
+            default_reasoning_level,
+            supported_reasoning_levels: _,
+            shell_type,
+            visibility: _,
+            supported_in_api: _,
+            priority: _,
+            upgrade: _,
+            base_instructions,
+            supports_reasoning_summaries,
+            support_verbosity,
+            default_verbosity,
+            apply_patch_tool_type,
+            truncation_policy,
+            supports_parallel_tool_calls,
+            context_window,
+            reasoning_summary_format,
+            experimental_supported_tools,
+        } = model;
+
+        self.default_reasoning_effort = Some(default_reasoning_level);
+        self.shell_type = shell_type;
+        if let Some(base) = base_instructions {
+            self.base_instructions = base;
+        }
+        self.supports_reasoning_summaries = supports_reasoning_summaries;
+        self.support_verbosity = support_verbosity;
+        self.default_verbosity = default_verbosity;
+        self.apply_patch_tool_type = apply_patch_tool_type;
+        self.truncation_policy = truncation_policy.into();
+        self.supports_parallel_tool_calls = supports_parallel_tool_calls;
+        self.context_window = context_window;
+        self.reasoning_summary_format = reasoning_summary_format;
+        self.experimental_supported_tools = experimental_supported_tools;
+    }
+}
+
 /// Semantic version triple encoded as an array in JSON (e.g. [0, 62, 0]).
 #[derive(Debug, Serialize, Deserialize, Clone, Copy, PartialEq, Eq, TS, JsonSchema)]
 pub struct ClientVersion(pub i32, pub i32, pub i32);

codex-rs/protocol/src/protocol.rs

@@ -19,6 +19,7 @@ use crate::message_history::HistoryEntry;
 use crate::models::ContentItem;
 use crate::models::ResponseItem;
 use crate::num_format::format_with_separators;
+use crate::openai_models::ModelFamily;
 use crate::openai_models::ReasoningEffort as ReasoningEffortConfig;
 use crate::parse_command::ParsedCommand;
 use crate::plan_tool::UpdatePlanArgs;
@@ -1753,8 +1754,8 @@ pub struct SessionConfiguredEvent {
     /// Name left as session_id instead of conversation_id for backwards compatibility.
     pub session_id: ConversationId,
 
-    /// Tell the client what model is being queried.
-    pub model: String,
+    /// Model metadata for the model family that Codex selected for this session.
+    pub model_family: ModelFamily,
 
     pub model_provider_id: String,
 
@@ -1912,11 +1913,30 @@ mod tests {
     fn serialize_event() -> Result<()> {
         let conversation_id = ConversationId::from_string("67e55044-10b1-426f-9247-bb680e5fe0c8")?;
         let rollout_file = NamedTempFile::new()?;
+        let model_family = crate::openai_models::ModelFamily {
+            slug: "codex-mini-latest".to_string(),
+            family: "codex-mini-latest".to_string(),
+            needs_special_apply_patch_instructions: false,
+            context_window: None,
+            auto_compact_token_limit: None,
+            supports_reasoning_summaries: false,
+            default_reasoning_effort: Some(crate::openai_models::ReasoningEffort::Medium),
+            reasoning_summary_format: crate::openai_models::ReasoningSummaryFormat::None,
+            supports_parallel_tool_calls: false,
+            apply_patch_tool_type: None,
+            base_instructions: "".to_string(),
+            experimental_supported_tools: Vec::new(),
+            effective_context_window_percent: 95,
+            support_verbosity: false,
+            default_verbosity: None,
+            shell_type: crate::openai_models::ConfigShellToolType::Default,
+            truncation_policy: crate::openai_models::TruncationPolicy::Bytes(10_000),
+        };
         let event = Event {
             id: "1234".to_string(),
             msg: EventMsg::SessionConfigured(SessionConfiguredEvent {
                 session_id: conversation_id,
-                model: "codex-mini-latest".to_string(),
+                model_family: model_family.clone(),
                 model_provider_id: "openai".to_string(),
                 approval_policy: AskForApproval::Never,
                 sandbox_policy: SandboxPolicy::ReadOnly,
@@ -1934,7 +1954,7 @@ mod tests {
             "msg": {
                 "type": "session_configured",
                 "session_id": "67e55044-10b1-426f-9247-bb680e5fe0c8",
-                "model": "codex-mini-latest",
+                "model_family": serde_json::to_value(model_family)?,
                 "model_provider_id": "openai",
                 "approval_policy": "never",
                 "sandbox_policy": {

codex-rs/tui/src/app.rs

@@ -343,8 +343,6 @@ impl App {
         ));
 
         let enhanced_keys_supported = tui.enhanced_keys_supported();
-        let model_family =
-            codex_core::models_manager::model_family::ModelFamily::placeholder(&config);
         let mut chat_widget = match resume_selection {
             ResumeSelection::StartFresh | ResumeSelection::Exit => {
                 let init = crate::chatwidget::ChatWidgetInit {
@@ -358,7 +356,6 @@ impl App {
                     models_manager: conversation_manager.get_models_manager(),
                     feedback: feedback.clone(),
                     is_first_run,
-                    model_family: model_family.clone(),
                 };
                 ChatWidget::new(init, conversation_manager.clone())
             }
@@ -384,7 +381,6 @@ impl App {
                     models_manager: conversation_manager.get_models_manager(),
                     feedback: feedback.clone(),
                     is_first_run,
-                    model_family: model_family.clone(),
                 };
                 ChatWidget::new_from_existing(
                     init,
@@ -523,11 +519,6 @@ impl App {
     }
 
     async fn handle_event(&mut self, tui: &mut tui::Tui, event: AppEvent) -> Result<bool> {
-        let model_family = self
-            .server
-            .get_models_manager()
-            .construct_model_family(self.current_model.as_str(), &self.config)
-            .await;
         match event {
             AppEvent::NewSession => {
                 let summary = session_summary(
@@ -546,10 +537,9 @@ impl App {
                     models_manager: self.server.get_models_manager(),
                     feedback: self.feedback.clone(),
                     is_first_run: false,
-                    model_family: model_family.clone(),
                 };
                 self.chat_widget = ChatWidget::new(init, self.server.clone());
-                self.current_model = model_family.get_model_slug().to_string();
+                self.current_model.clear();
                 if let Some(summary) = summary {
                     let mut lines: Vec<Line<'static>> = vec![summary.usage_line.clone().into()];
                     if let Some(command) = summary.resume_command {
@@ -596,14 +586,17 @@ impl App {
                                     models_manager: self.server.get_models_manager(),
                                     feedback: self.feedback.clone(),
                                     is_first_run: false,
-                                    model_family: model_family.clone(),
                                 };
                                 self.chat_widget = ChatWidget::new_from_existing(
                                     init,
                                     resumed.conversation,
                                     resumed.session_configured,
                                 );
-                                self.current_model = model_family.get_model_slug().to_string();
+                                self.current_model = self
+                                    .chat_widget
+                                    .get_model_family()
+                                    .map(|mf| mf.get_model_slug().to_string())
+                                    .unwrap_or_default();
                                 if let Some(summary) = summary {
                                     let mut lines: Vec<Line<'static>> =
                                         vec![summary.usage_line.clone().into()];
@@ -688,7 +681,7 @@ impl App {
                 }
 
                 let configured_model = match &event.msg {
-                    EventMsg::SessionConfigured(ev) => Some(ev.model.clone()),
+                    EventMsg::SessionConfigured(ev) => Some(ev.model_family.slug.clone()),
                     _ => None,
                 };
                 if let EventMsg::ListSkillsResponse(response) = &event.msg {
@@ -1228,10 +1221,41 @@ mod tests {
     use std::sync::Arc;
     use std::sync::atomic::AtomicBool;
 
+    fn test_model_family(slug: &str) -> codex_protocol::openai_models::ModelFamily {
+        use codex_protocol::openai_models::ConfigShellToolType;
+        use codex_protocol::openai_models::ModelFamily;
+        use codex_protocol::openai_models::ReasoningEffort;
+        use codex_protocol::openai_models::ReasoningSummaryFormat;
+        use codex_protocol::openai_models::TruncationPolicy;
+
+        ModelFamily {
+            slug: slug.to_string(),
+            family: slug.to_string(),
+            needs_special_apply_patch_instructions: false,
+            context_window: None,
+            auto_compact_token_limit: None,
+            supports_reasoning_summaries: false,
+            default_reasoning_effort: Some(ReasoningEffort::Medium),
+            reasoning_summary_format: ReasoningSummaryFormat::None,
+            supports_parallel_tool_calls: false,
+            apply_patch_tool_type: None,
+            base_instructions: String::new(),
+            experimental_supported_tools: Vec::new(),
+            effective_context_window_percent: 95,
+            support_verbosity: false,
+            default_verbosity: None,
+            shell_type: ConfigShellToolType::Default,
+            truncation_policy: TruncationPolicy::Bytes(10_000),
+        }
+    }
+
     async fn make_test_app() -> App {
         let (chat_widget, app_event_tx, _rx, _op_rx) = make_chatwidget_manual_with_sender().await;
         let config = chat_widget.config_ref().clone();
-        let current_model = chat_widget.get_model_family().get_model_slug().to_string();
+        let current_model = chat_widget
+            .get_model_family()
+            .map(|mf| mf.get_model_slug().to_string())
+            .unwrap_or_default();
         let server = Arc::new(ConversationManager::with_models_provider(
             CodexAuth::from_api_key("Test API Key"),
             config.model_provider.clone(),
@@ -1270,7 +1294,10 @@ mod tests {
     ) {
         let (chat_widget, app_event_tx, rx, op_rx) = make_chatwidget_manual_with_sender().await;
         let config = chat_widget.config_ref().clone();
-        let current_model = chat_widget.get_model_family().get_model_slug().to_string();
+        let current_model = chat_widget
+            .get_model_family()
+            .map(|mf| mf.get_model_slug().to_string())
+            .unwrap_or_default();
         let server = Arc::new(ConversationManager::with_models_provider(
             CodexAuth::from_api_key("Test API Key"),
             config.model_provider.clone(),
@@ -1433,7 +1460,7 @@ mod tests {
         let make_header = |is_first| {
             let event = SessionConfiguredEvent {
                 session_id: ConversationId::new(),
-                model: "gpt-test".to_string(),
+                model_family: test_model_family("gpt-test"),
                 model_provider_id: "test-provider".to_string(),
                 approval_policy: AskForApproval::Never,
                 sandbox_policy: SandboxPolicy::ReadOnly,
@@ -1488,7 +1515,7 @@ mod tests {
         let conversation_id = ConversationId::new();
         let event = SessionConfiguredEvent {
             session_id: conversation_id,
-            model: "gpt-test".to_string(),
+            model_family: test_model_family("gpt-test"),
             model_provider_id: "test-provider".to_string(),
             approval_policy: AskForApproval::Never,
             sandbox_policy: SandboxPolicy::ReadOnly,

codex-rs/tui/src/app_backtrack.rs

@@ -338,10 +338,9 @@ impl App {
     ) {
         let conv = new_conv.conversation;
         let session_configured = new_conv.session_configured;
-        let model_family = self.chat_widget.get_model_family();
+        let current_model = session_configured.model_family.slug.clone();
         let init = crate::chatwidget::ChatWidgetInit {
             config: cfg,
-            model_family: model_family.clone(),
             frame_requester: tui.frame_requester(),
             app_event_tx: self.app_event_tx.clone(),
             initial_prompt: None,
@@ -354,7 +353,7 @@ impl App {
         };
         self.chat_widget =
             crate::chatwidget::ChatWidget::new_from_existing(init, conv, session_configured);
-        self.current_model = model_family.get_model_slug().to_string();
+        self.current_model = current_model;
         // Trim transcript up to the selected user message and re-render it.
         self.trim_transcript_for_backtrack(nth_user_message);
         self.render_transcript_once(tui);

codex-rs/tui/src/chatwidget.rs

@@ -15,7 +15,6 @@ use codex_core::features::Feature;
 use codex_core::git_info::current_branch_name;
 use codex_core::git_info::local_git_branches;
 use codex_core::models_manager::manager::ModelsManager;
-use codex_core::models_manager::model_family::ModelFamily;
 use codex_core::project_doc::DEFAULT_PROJECT_DOC_FILENAME;
 use codex_core::protocol::AgentMessageDeltaEvent;
 use codex_core::protocol::AgentMessageEvent;
@@ -67,6 +66,7 @@ use codex_core::skills::model::SkillMetadata;
 use codex_protocol::ConversationId;
 use codex_protocol::account::PlanType;
 use codex_protocol::approvals::ElicitationRequestEvent;
+use codex_protocol::openai_models::ModelFamily;
 use codex_protocol::parse_command::ParsedCommand;
 use codex_protocol::user_input::UserInput;
 use crossterm::event::KeyCode;
@@ -291,7 +291,6 @@ pub(crate) struct ChatWidgetInit {
     pub(crate) models_manager: Arc<ModelsManager>,
     pub(crate) feedback: codex_feedback::CodexFeedback,
     pub(crate) is_first_run: bool,
-    pub(crate) model_family: ModelFamily,
 }
 
 #[derive(Default)]
@@ -308,7 +307,7 @@ pub(crate) struct ChatWidget {
     bottom_pane: BottomPane,
     active_cell: Option<Box<dyn HistoryCell>>,
     config: Config,
-    model_family: ModelFamily,
+    model_family: Option<ModelFamily>,
     auth_manager: Arc<AuthManager>,
     models_manager: Arc<ModelsManager>,
     session_header: SessionHeader,
@@ -423,11 +422,13 @@ impl ChatWidget {
         self.conversation_id = Some(event.session_id);
         self.current_rollout_path = Some(event.rollout_path.clone());
         let initial_messages = event.initial_messages.clone();
-        let model_for_header = event.model.clone();
+        let model_family = codex_core::models_manager::model_family::with_config_overrides(
+            event.model_family.clone(),
+            &self.config,
+        );
+        let model_for_header = model_family.get_model_slug().to_string();
+        self.model_family = Some(model_family);
         self.session_header.set_model(&model_for_header);
-        // Now that Codex has selected the actual model, update the model family used for UI.
-        self.app_event_tx
-            .send(AppEvent::UpdateModel(model_for_header.clone()));
         self.add_to_history(history_cell::new_session_info(
             &self.config,
             &model_for_header,
@@ -530,7 +531,11 @@ impl ChatWidget {
     }
 
     fn on_agent_reasoning_final(&mut self) {
-        let reasoning_summary_format = self.get_model_family().reasoning_summary_format;
+        let reasoning_summary_format = self
+            .model_family
+            .as_ref()
+            .map(|mf| mf.reasoning_summary_format.clone())
+            .unwrap_or_default();
         // At the end of a reasoning block, record transcript-only content.
         self.full_reasoning_buffer.push_str(&self.reasoning_buffer);
         if !self.full_reasoning_buffer.is_empty() {
@@ -605,7 +610,7 @@ impl ChatWidget {
 
     fn context_remaining_percent(&self, info: &TokenUsageInfo) -> Option<i64> {
         info.model_context_window
-            .or(self.model_family.context_window)
+            .or(self.model_family.as_ref().and_then(|mf| mf.context_window))
             .map(|window| {
                 info.last_token_usage
                     .percent_of_context_window_remaining(window)
@@ -677,7 +682,10 @@ impl ChatWidget {
 
             if high_usage
                 && !self.rate_limit_switch_prompt_hidden()
-                && self.model_family.get_model_slug() != NUDGE_MODEL_SLUG
+                && self
+                    .model_family
+                    .as_ref()
+                    .is_some_and(|mf| mf.get_model_slug() != NUDGE_MODEL_SLUG)
                 && !matches!(
                     self.rate_limit_switch_prompt,
                     RateLimitSwitchPromptState::Shown
@@ -711,7 +719,7 @@ impl ChatWidget {
         self.stream_controller = None;
         self.maybe_show_pending_rate_limit_prompt();
     }
-    pub(crate) fn get_model_family(&self) -> ModelFamily {
+    pub(crate) fn get_model_family(&self) -> Option<ModelFamily> {
         self.model_family.clone()
     }
 
@@ -1416,7 +1424,6 @@ impl ChatWidget {
             models_manager,
             feedback,
             is_first_run,
-            model_family,
         } = common;
         let config = config;
         let mut rng = rand::rng();
@@ -1439,7 +1446,7 @@ impl ChatWidget {
             }),
             active_cell: None,
             config,
-            model_family,
+            model_family: None,
             auth_manager,
             models_manager,
             session_header: SessionHeader::new("Starting...".to_string()),
@@ -1499,9 +1506,12 @@ impl ChatWidget {
             auth_manager,
             models_manager,
             feedback,
-            model_family,
             ..
         } = common;
+        let model_family = codex_core::models_manager::model_family::with_config_overrides(
+            session_configured.model_family.clone(),
+            &config,
+        );
         let model_slug = model_family.get_model_slug().to_string();
         let mut rng = rand::rng();
         let placeholder = EXAMPLE_PROMPTS[rng.random_range(0..EXAMPLE_PROMPTS.len())].to_string();
@@ -1525,7 +1535,7 @@ impl ChatWidget {
             }),
             active_cell: None,
             config,
-            model_family,
+            model_family: Some(model_family),
             auth_manager,
             models_manager,
             session_header: SessionHeader::new(model_slug),
@@ -1704,7 +1714,7 @@ impl ChatWidget {
                 self.open_review_popup();
             }
             SlashCommand::Model => {
-                if self.conversation_id.is_none() {
+                if self.model_family.is_none() {
                     self.add_info_message(
                         "`/model` is unavailable until startup finishes.".to_string(),
                         None,
@@ -2220,6 +2230,14 @@ impl ChatWidget {
     }
 
     pub(crate) fn add_status_output(&mut self) {
+        let Some(model_family) = self.model_family.as_ref() else {
+            self.add_info_message(
+                "`/status` is unavailable until startup finishes.".to_string(),
+                None,
+            );
+            return;
+        };
+
         let default_usage = TokenUsage::default();
         let (total_usage, context_usage) = if let Some(ti) = &self.token_info {
             (&ti.total_token_usage, Some(&ti.last_token_usage))
@@ -2229,14 +2247,14 @@ impl ChatWidget {
         self.add_to_history(crate::status::new_status_output(
             &self.config,
             self.auth_manager.as_ref(),
-            &self.model_family,
+            model_family,
             total_usage,
             context_usage,
             &self.conversation_id,
             self.rate_limit_snapshot.as_ref(),
             self.plan_type,
             Local::now(),
-            self.model_family.get_model_slug(),
+            model_family.get_model_slug(),
         ));
     }
 
@@ -2389,7 +2407,14 @@ impl ChatWidget {
     /// Open a popup to choose a quick auto model. Selecting "All models"
     /// opens the full picker with every available preset.
     pub(crate) fn open_model_popup(&mut self) {
-        let current_model = self.model_family.get_model_slug().to_string();
+        let Some(model_family) = self.model_family.as_ref() else {
+            self.add_info_message(
+                "`/model` is unavailable until startup finishes.".to_string(),
+                None,
+            );
+            return;
+        };
+        let current_model = model_family.get_model_slug().to_string();
         let presets: Vec<ModelPreset> =
             // todo(aibrahim): make this async function
             match self.models_manager.try_list_models(&self.config) {
@@ -2497,7 +2522,11 @@ impl ChatWidget {
             return;
         }
 
-        let current_model = self.model_family.get_model_slug().to_string();
+        let current_model = self
+            .model_family
+            .as_ref()
+            .map(|mf| mf.get_model_slug().to_string())
+            .unwrap_or_default();
         let mut items: Vec<SelectionItem> = Vec::new();
         for preset in presets.into_iter() {
             let description =
@@ -2628,7 +2657,10 @@ impl ChatWidget {
             .or(Some(default_effort));
 
         let model_slug = preset.model.to_string();
-        let is_current_model = self.model_family.get_model_slug() == preset.model;
+        let is_current_model = self
+            .model_family
+            .as_ref()
+            .is_some_and(|mf| mf.get_model_slug() == preset.model);
         let highlight_choice = if is_current_model {
             self.config.model_reasoning_effort
         } else {
@@ -3220,7 +3252,7 @@ impl ChatWidget {
     /// Set the model in the widget's config copy.
     pub(crate) fn set_model(&mut self, model: &str, model_family: ModelFamily) {
         self.session_header.set_model(model);
-        self.model_family = model_family;
+        self.model_family = Some(model_family);
     }
 
     pub(crate) fn add_info_message(&mut self, message: String, hint: Option<String>) {

codex-rs/tui/src/chatwidget/tests.rs

@@ -97,6 +97,34 @@ fn snapshot(percent: f64) -> RateLimitSnapshot {
     }
 }
 
+fn test_model_family(slug: &str) -> ModelFamily {
+    use codex_protocol::openai_models::ConfigShellToolType;
+    use codex_protocol::openai_models::ModelFamily;
+    use codex_protocol::openai_models::ReasoningEffort;
+    use codex_protocol::openai_models::ReasoningSummaryFormat;
+    use codex_protocol::openai_models::TruncationPolicy;
+
+    ModelFamily {
+        slug: slug.to_string(),
+        family: slug.to_string(),
+        needs_special_apply_patch_instructions: false,
+        context_window: None,
+        auto_compact_token_limit: None,
+        supports_reasoning_summaries: false,
+        default_reasoning_effort: Some(ReasoningEffort::default()),
+        reasoning_summary_format: ReasoningSummaryFormat::None,
+        supports_parallel_tool_calls: false,
+        apply_patch_tool_type: None,
+        base_instructions: String::new(),
+        experimental_supported_tools: Vec::new(),
+        effective_context_window_percent: 95,
+        support_verbosity: false,
+        default_verbosity: None,
+        shell_type: ConfigShellToolType::Default,
+        truncation_policy: TruncationPolicy::Bytes(10_000),
+    }
+}
+
 #[tokio::test]
 async fn resumed_initial_messages_render_history() {
     let (mut chat, mut rx, _ops) = make_chatwidget_manual(None).await;
@@ -105,7 +133,7 @@ async fn resumed_initial_messages_render_history() {
     let rollout_file = NamedTempFile::new().unwrap();
     let configured = codex_core::protocol::SessionConfiguredEvent {
         session_id: conversation_id,
-        model: "test-model".to_string(),
+        model_family: test_model_family("test-model"),
         model_provider_id: "test-provider".to_string(),
         approval_policy: AskForApproval::Never,
         sandbox_policy: SandboxPolicy::ReadOnly,
@@ -312,8 +340,6 @@ async fn helpers_are_available_and_do_not_panic() {
     let (tx_raw, _rx) = unbounded_channel::<AppEvent>();
     let tx = AppEventSender::new(tx_raw);
     let cfg = test_config().await;
-    let resolved_model = ModelsManager::get_model_offline(cfg.model.as_deref());
-    let model_family = ModelsManager::construct_model_family_offline(&resolved_model, &cfg);
     let conversation_manager = Arc::new(ConversationManager::with_models_provider(
         CodexAuth::from_api_key("test"),
         cfg.model_provider.clone(),
@@ -330,7 +356,6 @@ async fn helpers_are_available_and_do_not_panic() {
         models_manager: conversation_manager.get_models_manager(),
         feedback: codex_feedback::CodexFeedback::new(),
         is_first_run: true,
-        model_family,
     };
     let mut w = ChatWidget::new(init, conversation_manager);
     // Basic construction sanity.
@@ -372,7 +397,10 @@ async fn make_chatwidget_manual(
         bottom_pane: bottom,
         active_cell: None,
         config: cfg.clone(),
-        model_family: ModelsManager::construct_model_family_offline(&resolved_model, &cfg),
+        model_family: Some(ModelsManager::construct_model_family_offline(
+            &resolved_model,
+            &cfg,
+        )),
         auth_manager: auth_manager.clone(),
         models_manager: Arc::new(ModelsManager::new(auth_manager)),
         session_header: SessionHeader::new(resolved_model.clone()),
@@ -1030,7 +1058,7 @@ async fn enqueueing_history_prompt_multiple_times_is_stable() {
         id: "configured".into(),
         msg: EventMsg::SessionConfigured(codex_core::protocol::SessionConfiguredEvent {
             session_id: conversation_id,
-            model: "test-model".to_string(),
+            model_family: test_model_family("test-model"),
             model_provider_id: "test-provider".to_string(),
             approval_policy: AskForApproval::Never,
             sandbox_policy: SandboxPolicy::ReadOnly,

codex-rs/tui/src/history_cell.rs

@@ -868,13 +868,14 @@ pub(crate) fn new_session_info(
     is_first_event: bool,
 ) -> SessionInfoCell {
     let SessionConfiguredEvent {
-        model,
+        model_family,
         reasoning_effort,
         ..
     } = event;
+    let used_model = model_family.slug;
     // Header box rendered as history (so it appears at the very top)
     let header = SessionHeaderHistoryCell::new(
-        model.clone(),
+        used_model.clone(),
         reasoning_effort,
         config.cwd.clone(),
         CODEX_CLI_VERSION,
@@ -922,11 +923,11 @@ pub(crate) fn new_session_info(
         {
             parts.push(Box::new(tooltips));
         }
-        if requested_model != model {
+        if requested_model != used_model {
             let lines = vec![
                 "model changed:".magenta().bold().into(),
                 format!("requested: {requested_model}").into(),
-                format!("used: {model}").into(),
+                format!("used: {used_model}").into(),
             ];
             parts.push(Box::new(PlainHistoryCell { lines }));
         }

codex-rs/tui/src/status/card.rs

@@ -7,7 +7,7 @@ use chrono::DateTime;
 use chrono::Local;
 use codex_common::create_config_summary_entries;
 use codex_core::config::Config;
-use codex_core::models_manager::model_family::ModelFamily;
+use codex_protocol::openai_models::ModelFamily;
 use codex_core::protocol::NetworkAccess;
 use codex_core::protocol::SandboxPolicy;
 use codex_core::protocol::TokenUsage;

codex-rs/tui/src/status/tests.rs

@@ -8,7 +8,7 @@ use codex_core::AuthManager;
 use codex_core::config::Config;
 use codex_core::config::ConfigBuilder;
 use codex_core::models_manager::manager::ModelsManager;
-use codex_core::models_manager::model_family::ModelFamily;
+use codex_protocol::openai_models::ModelFamily;
 use codex_core::protocol::CreditsSnapshot;
 use codex_core::protocol::RateLimitSnapshot;
 use codex_core::protocol::RateLimitWindow;

codex-rs/tui2/src/app.rs

@@ -412,8 +412,6 @@ impl App {
         ));
 
         let enhanced_keys_supported = tui.enhanced_keys_supported();
-        let model_family =
-            codex_core::models_manager::model_family::ModelFamily::placeholder(&config);
         let mut chat_widget = match resume_selection {
             ResumeSelection::StartFresh | ResumeSelection::Exit => {
                 let init = crate::chatwidget::ChatWidgetInit {
@@ -427,7 +425,6 @@ impl App {
                     models_manager: conversation_manager.get_models_manager(),
                     feedback: feedback.clone(),
                     is_first_run,
-                    model_family: model_family.clone(),
                 };
                 ChatWidget::new(init, conversation_manager.clone())
             }
@@ -453,7 +450,6 @@ impl App {
                     models_manager: conversation_manager.get_models_manager(),
                     feedback: feedback.clone(),
                     is_first_run,
-                    model_family: model_family.clone(),
                 };
                 ChatWidget::new_from_existing(
                     init,
@@ -1534,11 +1530,6 @@ impl App {
     }
 
     async fn handle_event(&mut self, tui: &mut tui::Tui, event: AppEvent) -> Result<bool> {
-        let model_family = self
-            .server
-            .get_models_manager()
-            .construct_model_family(self.current_model.as_str(), &self.config)
-            .await;
         match event {
             AppEvent::NewSession => {
                 let summary = session_summary(
@@ -1557,10 +1548,9 @@ impl App {
                     models_manager: self.server.get_models_manager(),
                     feedback: self.feedback.clone(),
                     is_first_run: false,
-                    model_family: model_family.clone(),
                 };
                 self.chat_widget = ChatWidget::new(init, self.server.clone());
-                self.current_model = model_family.get_model_slug().to_string();
+                self.current_model.clear();
                 if let Some(summary) = summary {
                     let mut lines: Vec<Line<'static>> = vec![summary.usage_line.clone().into()];
                     if let Some(command) = summary.resume_command {
@@ -1607,14 +1597,17 @@ impl App {
                                     models_manager: self.server.get_models_manager(),
                                     feedback: self.feedback.clone(),
                                     is_first_run: false,
-                                    model_family: model_family.clone(),
                                 };
                                 self.chat_widget = ChatWidget::new_from_existing(
                                     init,
                                     resumed.conversation,
                                     resumed.session_configured,
                                 );
-                                self.current_model = model_family.get_model_slug().to_string();
+                                self.current_model = self
+                                    .chat_widget
+                                    .get_model_family()
+                                    .map(|mf| mf.get_model_slug().to_string())
+                                    .unwrap_or_default();
                                 if let Some(summary) = summary {
                                     let mut lines: Vec<Line<'static>> =
                                         vec![summary.usage_line.clone().into()];
@@ -1697,7 +1690,7 @@ impl App {
                 }
 
                 let configured_model = match &event.msg {
-                    EventMsg::SessionConfigured(ev) => Some(ev.model.clone()),
+                    EventMsg::SessionConfigured(ev) => Some(ev.model_family.slug.clone()),
                     _ => None,
                 };
                 if let EventMsg::ListSkillsResponse(response) = &event.msg {
@@ -2280,10 +2273,41 @@ mod tests {
     use std::sync::Arc;
     use std::sync::atomic::AtomicBool;
 
+    fn test_model_family(slug: &str) -> codex_protocol::openai_models::ModelFamily {
+        use codex_protocol::openai_models::ConfigShellToolType;
+        use codex_protocol::openai_models::ModelFamily;
+        use codex_protocol::openai_models::ReasoningEffort;
+        use codex_protocol::openai_models::ReasoningSummaryFormat;
+        use codex_protocol::openai_models::TruncationPolicy;
+
+        ModelFamily {
+            slug: slug.to_string(),
+            family: slug.to_string(),
+            needs_special_apply_patch_instructions: false,
+            context_window: None,
+            auto_compact_token_limit: None,
+            supports_reasoning_summaries: false,
+            default_reasoning_effort: Some(ReasoningEffort::Medium),
+            reasoning_summary_format: ReasoningSummaryFormat::None,
+            supports_parallel_tool_calls: false,
+            apply_patch_tool_type: None,
+            base_instructions: String::new(),
+            experimental_supported_tools: Vec::new(),
+            effective_context_window_percent: 95,
+            support_verbosity: false,
+            default_verbosity: None,
+            shell_type: ConfigShellToolType::Default,
+            truncation_policy: TruncationPolicy::Bytes(10_000),
+        }
+    }
+
     async fn make_test_app() -> App {
         let (chat_widget, app_event_tx, _rx, _op_rx) = make_chatwidget_manual_with_sender().await;
         let config = chat_widget.config_ref().clone();
-        let current_model = chat_widget.get_model_family().get_model_slug().to_string();
+        let current_model = chat_widget
+            .get_model_family()
+            .map(|mf| mf.get_model_slug().to_string())
+            .unwrap_or_default();
         let server = Arc::new(ConversationManager::with_models_provider(
             CodexAuth::from_api_key("Test API Key"),
             config.model_provider.clone(),
@@ -2328,7 +2352,10 @@ mod tests {
     ) {
         let (chat_widget, app_event_tx, rx, op_rx) = make_chatwidget_manual_with_sender().await;
         let config = chat_widget.config_ref().clone();
-        let current_model = chat_widget.get_model_family().get_model_slug().to_string();
+        let current_model = chat_widget
+            .get_model_family()
+            .map(|mf| mf.get_model_slug().to_string())
+            .unwrap_or_default();
         let server = Arc::new(ConversationManager::with_models_provider(
             CodexAuth::from_api_key("Test API Key"),
             config.model_provider.clone(),
@@ -2465,7 +2492,7 @@ mod tests {
         let make_header = |is_first| {
             let event = SessionConfiguredEvent {
                 session_id: ConversationId::new(),
-                model: "gpt-test".to_string(),
+                model_family: test_model_family("gpt-test"),
                 model_provider_id: "test-provider".to_string(),
                 approval_policy: AskForApproval::Never,
                 sandbox_policy: SandboxPolicy::ReadOnly,
@@ -2582,7 +2609,7 @@ mod tests {
         let conversation_id = ConversationId::new();
         let event = SessionConfiguredEvent {
             session_id: conversation_id,
-            model: "gpt-test".to_string(),
+            model_family: test_model_family("gpt-test"),
             model_provider_id: "test-provider".to_string(),
             approval_policy: AskForApproval::Never,
             sandbox_policy: SandboxPolicy::ReadOnly,

codex-rs/tui2/src/app_backtrack.rs

@@ -338,10 +338,9 @@ impl App {
     ) {
         let conv = new_conv.conversation;
         let session_configured = new_conv.session_configured;
-        let model_family = self.chat_widget.get_model_family();
+        let current_model = session_configured.model_family.slug.clone();
         let init = crate::chatwidget::ChatWidgetInit {
             config: cfg,
-            model_family: model_family.clone(),
             frame_requester: tui.frame_requester(),
             app_event_tx: self.app_event_tx.clone(),
             initial_prompt: None,
@@ -354,7 +353,7 @@ impl App {
         };
         self.chat_widget =
             crate::chatwidget::ChatWidget::new_from_existing(init, conv, session_configured);
-        self.current_model = model_family.get_model_slug().to_string();
+        self.current_model = current_model;
         // Trim transcript up to the selected user message and re-render it.
         self.trim_transcript_for_backtrack(nth_user_message);
         self.render_transcript_once(tui);

codex-rs/tui2/src/chatwidget.rs

@@ -13,7 +13,7 @@ use codex_core::config::types::Notifications;
 use codex_core::git_info::current_branch_name;
 use codex_core::git_info::local_git_branches;
 use codex_core::models_manager::manager::ModelsManager;
-use codex_core::models_manager::model_family::ModelFamily;
+use codex_protocol::openai_models::ModelFamily;
 use codex_core::project_doc::DEFAULT_PROJECT_DOC_FILENAME;
 use codex_core::protocol::AgentMessageDeltaEvent;
 use codex_core::protocol::AgentMessageEvent;
@@ -267,7 +267,6 @@ pub(crate) struct ChatWidgetInit {
     pub(crate) models_manager: Arc<ModelsManager>,
     pub(crate) feedback: codex_feedback::CodexFeedback,
     pub(crate) is_first_run: bool,
-    pub(crate) model_family: ModelFamily,
 }
 
 #[derive(Default)]
@@ -284,7 +283,7 @@ pub(crate) struct ChatWidget {
     bottom_pane: BottomPane,
     active_cell: Option<Box<dyn HistoryCell>>,
     config: Config,
-    model_family: ModelFamily,
+    model_family: Option<ModelFamily>,
     auth_manager: Arc<AuthManager>,
     models_manager: Arc<ModelsManager>,
     session_header: SessionHeader,
@@ -398,11 +397,13 @@ impl ChatWidget {
         self.conversation_id = Some(event.session_id);
         self.current_rollout_path = Some(event.rollout_path.clone());
         let initial_messages = event.initial_messages.clone();
-        let model_for_header = event.model.clone();
+        let model_family = codex_core::models_manager::model_family::with_config_overrides(
+            event.model_family.clone(),
+            &self.config,
+        );
+        let model_for_header = model_family.get_model_slug().to_string();
+        self.model_family = Some(model_family);
         self.session_header.set_model(&model_for_header);
-        // Now that Codex has selected the actual model, update the model family used for UI.
-        self.app_event_tx
-            .send(AppEvent::UpdateModel(model_for_header.clone()));
         self.add_to_history(history_cell::new_session_info(
             &self.config,
             &model_for_header,
@@ -505,7 +506,11 @@ impl ChatWidget {
     }
 
     fn on_agent_reasoning_final(&mut self) {
-        let reasoning_summary_format = self.get_model_family().reasoning_summary_format;
+        let reasoning_summary_format = self
+            .model_family
+            .as_ref()
+            .map(|mf| mf.reasoning_summary_format.clone())
+            .unwrap_or_default();
         // At the end of a reasoning block, record transcript-only content.
         self.full_reasoning_buffer.push_str(&self.reasoning_buffer);
         if !self.full_reasoning_buffer.is_empty() {
@@ -579,7 +584,7 @@ impl ChatWidget {
 
     fn context_remaining_percent(&self, info: &TokenUsageInfo) -> Option<i64> {
         info.model_context_window
-            .or(self.model_family.context_window)
+            .or(self.model_family.as_ref().and_then(|mf| mf.context_window))
             .map(|window| {
                 info.last_token_usage
                     .percent_of_context_window_remaining(window)
@@ -651,7 +656,10 @@ impl ChatWidget {
 
             if high_usage
                 && !self.rate_limit_switch_prompt_hidden()
-                && self.model_family.get_model_slug() != NUDGE_MODEL_SLUG
+                && self
+                    .model_family
+                    .as_ref()
+                    .is_some_and(|mf| mf.get_model_slug() != NUDGE_MODEL_SLUG)
                 && !matches!(
                     self.rate_limit_switch_prompt,
                     RateLimitSwitchPromptState::Shown
@@ -685,7 +693,7 @@ impl ChatWidget {
         self.stream_controller = None;
         self.maybe_show_pending_rate_limit_prompt();
     }
-    pub(crate) fn get_model_family(&self) -> ModelFamily {
+    pub(crate) fn get_model_family(&self) -> Option<ModelFamily> {
         self.model_family.clone()
     }
 
@@ -1285,7 +1293,6 @@ impl ChatWidget {
             models_manager,
             feedback,
             is_first_run,
-            model_family,
         } = common;
         let config = config;
         let mut rng = rand::rng();
@@ -1308,7 +1315,7 @@ impl ChatWidget {
             }),
             active_cell: None,
             config,
-            model_family,
+            model_family: None,
             auth_manager,
             models_manager,
             session_header: SessionHeader::new("Starting...".to_string()),
@@ -1367,9 +1374,12 @@ impl ChatWidget {
             auth_manager,
             models_manager,
             feedback,
-            model_family,
             ..
         } = common;
+        let model_family = codex_core::models_manager::model_family::with_config_overrides(
+            session_configured.model_family.clone(),
+            &config,
+        );
         let model_slug = model_family.get_model_slug().to_string();
         let mut rng = rand::rng();
         let placeholder = EXAMPLE_PROMPTS[rng.random_range(0..EXAMPLE_PROMPTS.len())].to_string();
@@ -1393,7 +1403,7 @@ impl ChatWidget {
             }),
             active_cell: None,
             config,
-            model_family,
+            model_family: Some(model_family),
             auth_manager,
             models_manager,
             session_header: SessionHeader::new(model_slug),
@@ -1571,7 +1581,7 @@ impl ChatWidget {
                 self.open_review_popup();
             }
             SlashCommand::Model => {
-                if self.conversation_id.is_none() {
+                if self.model_family.is_none() {
                     self.add_info_message(
                         "`/model` is unavailable until startup finishes.".to_string(),
                         None,
@@ -2059,6 +2069,14 @@ impl ChatWidget {
     }
 
     pub(crate) fn add_status_output(&mut self) {
+        let Some(model_family) = self.model_family.as_ref() else {
+            self.add_info_message(
+                "`/status` is unavailable until startup finishes.".to_string(),
+                None,
+            );
+            return;
+        };
+
         let default_usage = TokenUsage::default();
         let (total_usage, context_usage) = if let Some(ti) = &self.token_info {
             (&ti.total_token_usage, Some(&ti.last_token_usage))
@@ -2068,14 +2086,14 @@ impl ChatWidget {
         self.add_to_history(crate::status::new_status_output(
             &self.config,
             self.auth_manager.as_ref(),
-            &self.model_family,
+            model_family,
             total_usage,
             context_usage,
             &self.conversation_id,
             self.rate_limit_snapshot.as_ref(),
             self.plan_type,
             Local::now(),
-            self.model_family.get_model_slug(),
+            model_family.get_model_slug(),
         ));
     }
     fn stop_rate_limit_poller(&mut self) {
@@ -2218,7 +2236,14 @@ impl ChatWidget {
     /// Open a popup to choose a quick auto model. Selecting "All models"
     /// opens the full picker with every available preset.
     pub(crate) fn open_model_popup(&mut self) {
-        let current_model = self.model_family.get_model_slug().to_string();
+        let Some(model_family) = self.model_family.as_ref() else {
+            self.add_info_message(
+                "`/model` is unavailable until startup finishes.".to_string(),
+                None,
+            );
+            return;
+        };
+        let current_model = model_family.get_model_slug().to_string();
         let presets: Vec<ModelPreset> =
             // todo(aibrahim): make this async function
             match self.models_manager.try_list_models(&self.config) {
@@ -2326,7 +2351,11 @@ impl ChatWidget {
             return;
         }
 
-        let current_model = self.model_family.get_model_slug().to_string();
+        let current_model = self
+            .model_family
+            .as_ref()
+            .map(|mf| mf.get_model_slug().to_string())
+            .unwrap_or_default();
         let mut items: Vec<SelectionItem> = Vec::new();
         for preset in presets.into_iter() {
             let description =
@@ -2457,7 +2486,10 @@ impl ChatWidget {
             .or(Some(default_effort));
 
         let model_slug = preset.model.to_string();
-        let is_current_model = self.model_family.get_model_slug() == preset.model;
+        let is_current_model = self
+            .model_family
+            .as_ref()
+            .is_some_and(|mf| mf.get_model_slug() == preset.model);
         let highlight_choice = if is_current_model {
             self.config.model_reasoning_effort
         } else {
@@ -3018,7 +3050,7 @@ impl ChatWidget {
     /// Set the model in the widget's config copy.
     pub(crate) fn set_model(&mut self, model: &str, model_family: ModelFamily) {
         self.session_header.set_model(model);
-        self.model_family = model_family;
+        self.model_family = Some(model_family);
     }
 
     pub(crate) fn add_info_message(&mut self, message: String, hint: Option<String>) {

codex-rs/tui2/src/chatwidget/tests.rs

@@ -95,6 +95,34 @@ fn snapshot(percent: f64) -> RateLimitSnapshot {
     }
 }
 
+fn test_model_family(slug: &str) -> ModelFamily {
+    use codex_protocol::openai_models::ConfigShellToolType;
+    use codex_protocol::openai_models::ModelFamily;
+    use codex_protocol::openai_models::ReasoningEffort;
+    use codex_protocol::openai_models::ReasoningSummaryFormat;
+    use codex_protocol::openai_models::TruncationPolicy;
+
+    ModelFamily {
+        slug: slug.to_string(),
+        family: slug.to_string(),
+        needs_special_apply_patch_instructions: false,
+        context_window: None,
+        auto_compact_token_limit: None,
+        supports_reasoning_summaries: false,
+        default_reasoning_effort: Some(ReasoningEffort::default()),
+        reasoning_summary_format: ReasoningSummaryFormat::None,
+        supports_parallel_tool_calls: false,
+        apply_patch_tool_type: None,
+        base_instructions: String::new(),
+        experimental_supported_tools: Vec::new(),
+        effective_context_window_percent: 95,
+        support_verbosity: false,
+        default_verbosity: None,
+        shell_type: ConfigShellToolType::Default,
+        truncation_policy: TruncationPolicy::Bytes(10_000),
+    }
+}
+
 #[tokio::test]
 async fn resumed_initial_messages_render_history() {
     let (mut chat, mut rx, _ops) = make_chatwidget_manual(None).await;
@@ -103,7 +131,7 @@ async fn resumed_initial_messages_render_history() {
     let rollout_file = NamedTempFile::new().unwrap();
     let configured = codex_core::protocol::SessionConfiguredEvent {
         session_id: conversation_id,
-        model: "test-model".to_string(),
+        model_family: test_model_family("test-model"),
         model_provider_id: "test-provider".to_string(),
         approval_policy: AskForApproval::Never,
         sandbox_policy: SandboxPolicy::ReadOnly,
@@ -310,8 +338,6 @@ async fn helpers_are_available_and_do_not_panic() {
     let (tx_raw, _rx) = unbounded_channel::<AppEvent>();
     let tx = AppEventSender::new(tx_raw);
     let cfg = test_config().await;
-    let resolved_model = ModelsManager::get_model_offline(cfg.model.as_deref());
-    let model_family = ModelsManager::construct_model_family_offline(&resolved_model, &cfg);
     let conversation_manager = Arc::new(ConversationManager::with_models_provider(
         CodexAuth::from_api_key("test"),
         cfg.model_provider.clone(),
@@ -328,7 +354,6 @@ async fn helpers_are_available_and_do_not_panic() {
         models_manager: conversation_manager.get_models_manager(),
         feedback: codex_feedback::CodexFeedback::new(),
         is_first_run: true,
-        model_family,
     };
     let mut w = ChatWidget::new(init, conversation_manager);
     // Basic construction sanity.
@@ -370,7 +395,10 @@ async fn make_chatwidget_manual(
         bottom_pane: bottom,
         active_cell: None,
         config: cfg.clone(),
-        model_family: ModelsManager::construct_model_family_offline(&resolved_model, &cfg),
+        model_family: Some(ModelsManager::construct_model_family_offline(
+            &resolved_model,
+            &cfg,
+        )),
         auth_manager: auth_manager.clone(),
         models_manager: Arc::new(ModelsManager::new(auth_manager)),
         session_header: SessionHeader::new(resolved_model.clone()),
@@ -991,7 +1019,7 @@ async fn enqueueing_history_prompt_multiple_times_is_stable() {
         id: "configured".into(),
         msg: EventMsg::SessionConfigured(codex_core::protocol::SessionConfiguredEvent {
             session_id: conversation_id,
-            model: "test-model".to_string(),
+            model_family: test_model_family("test-model"),
             model_provider_id: "test-provider".to_string(),
             approval_policy: AskForApproval::Never,
             sandbox_policy: SandboxPolicy::ReadOnly,

codex-rs/tui2/src/history_cell.rs

@@ -626,13 +626,14 @@ pub(crate) fn new_session_info(
     is_first_event: bool,
 ) -> SessionInfoCell {
     let SessionConfiguredEvent {
-        model,
+        model_family,
         reasoning_effort,
         ..
     } = event;
+    let used_model = model_family.slug;
     // Header box rendered as history (so it appears at the very top)
     let header = SessionHeaderHistoryCell::new(
-        model.clone(),
+        used_model.clone(),
         reasoning_effort,
         config.cwd.clone(),
         CODEX_CLI_VERSION,
@@ -680,11 +681,11 @@ pub(crate) fn new_session_info(
         {
             parts.push(Box::new(tooltips));
         }
-        if requested_model != model {
+        if requested_model != used_model {
             let lines = vec![
                 "model changed:".magenta().bold().into(),
                 format!("requested: {requested_model}").into(),
-                format!("used: {model}").into(),
+                format!("used: {used_model}").into(),
             ];
             parts.push(Box::new(PlainHistoryCell { lines }));
         }

codex-rs/tui2/src/status/card.rs

@@ -7,7 +7,7 @@ use chrono::DateTime;
 use chrono::Local;
 use codex_common::create_config_summary_entries;
 use codex_core::config::Config;
-use codex_core::models_manager::model_family::ModelFamily;
+use codex_protocol::openai_models::ModelFamily;
 use codex_core::protocol::NetworkAccess;
 use codex_core::protocol::SandboxPolicy;
 use codex_core::protocol::TokenUsage;

codex-rs/tui2/src/status/tests.rs

@@ -8,13 +8,13 @@ use codex_core::AuthManager;
 use codex_core::config::Config;
 use codex_core::config::ConfigBuilder;
 use codex_core::models_manager::manager::ModelsManager;
-use codex_core::models_manager::model_family::ModelFamily;
 use codex_core::protocol::CreditsSnapshot;
 use codex_core::protocol::RateLimitSnapshot;
 use codex_core::protocol::RateLimitWindow;
 use codex_core::protocol::SandboxPolicy;
 use codex_core::protocol::TokenUsage;
 use codex_protocol::config_types::ReasoningSummary;
+use codex_protocol::openai_models::ModelFamily;
 use codex_protocol::openai_models::ReasoningEffort;
 use insta::assert_snapshot;
 use ratatui::prelude::*;