Attribute command and plugin analytics to the invoking model (#45445)

## Why

Command execution and plugin measurement events lack model and reasoning-effort labels. Attribution needs to reflect the step that invoked the command, even when model settings change before a background process finishes.

## What changed

- Add `model_slug` and `reasoning_effort` to command execution and plugin measurement analytics.
- Capture model context from resolved step settings and carry it through execution, approval, Guardian review, and plugin metrics collection.
- Preserve the first command-start model context when subsequent start notifications arrive.
- Keep the carried context out of serialized protocol items and generated schemas.

## Testing

Extend analytics tests to cover model switches before invocation and during background execution, default reasoning effort, Guardian-denied commands, and repeated start notifications retaining the original model context.

GitOrigin-RevId: af90e1c0d39bab625f2e89786085b61a9b96c0ce

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

@@ -52,6 +52,8 @@ async fn command_approval_holds_an_elicitation_until_response() {
                 .request_command_approval(
                     turn_context.as_ref(),
                     ExecApprovalKind::Command,
+                    crate::guardian::GuardianReviewContext::from(turn_context.clone())
+                        .model_context(),
                     "call-1".to_string(),
                     /*approval_id*/ None,
                     /*environment_id*/ None,

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

@@ -1,4 +1,3 @@
-use crate::context::GuardianContextMode;
 use std::borrow::Cow;
 use std::collections::HashMap;
 use std::collections::HashSet;
@@ -23,6 +22,7 @@ use crate::config::ManagedFeatures;
 use crate::config::resolve_tool_suggest_config_from_layer_stack;
 use crate::context::ContextualUserFragment;
 use crate::context::DeveloperInstructions;
+use crate::context::GuardianContextMode;
 use crate::context::GuardianPolicy;
 use crate::context::ManagedDeveloperInstructions;
 use crate::context::ModelSwitchInstructions;
@@ -107,6 +107,7 @@ use codex_protocol::config_types::WebSearchMode;
 use codex_protocol::dynamic_tools::DynamicToolResponse;
 use codex_protocol::dynamic_tools::DynamicToolSpec;
 use codex_protocol::items::EnteredReviewModeItem;
+use codex_protocol::items::ModelInvocationContext;
 use codex_protocol::items::SubAgentActivityItem;
 use codex_protocol::items::TurnItem;
 use codex_protocol::items::UserMessageItem;
@@ -2790,6 +2791,7 @@ impl Session {
         &self,
         turn_context: &TurnContext,
         kind: ExecApprovalKind,
+        model_context: ModelInvocationContext,
         call_id: String,
         approval_id: Option<String>,
         environment_id: Option<String>,
@@ -2853,6 +2855,7 @@ impl Session {
             .map(PluginCommandAttribution::serialized_fields)
             .unzip();
         let event = EventMsg::ExecApprovalRequest(ExecApprovalRequestEvent {
+            model_context: Some(model_context),
             kind,
             call_id,
             plugin_id,

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

@@ -12,6 +12,7 @@ use codex_exec_server::ExecutorCapabilityDiscoverySnapshot;
 use codex_exec_server::ResolvedSelectedCapabilityRoot;
 use codex_mcp::McpBinding;
 use codex_otel::SessionTelemetry;
+use codex_protocol::items::ModelInvocationContext;
 use codex_protocol::protocol::TurnContextItem;
 
 /// Request-scoped state that may change between model sampling requests.
@@ -43,4 +44,14 @@ impl StepContext {
         item.summary = self.settings.reasoning_summary;
         item
     }
+
+    pub(crate) fn model_context(&self) -> ModelInvocationContext {
+        ModelInvocationContext {
+            model_slug: self.settings.model_info.slug.clone(),
+            reasoning_effort: self
+                .settings
+                .effective_reasoning_effort()
+                .map(|effort| effort.to_string()),
+        }
+    }
 }