Move skill catalog rendering out of core (#36364)

## What changed

- Make the skills extension own the catalog prompt templates and rendering path.
- Remove the duplicate core fallback that injected available skills into initial context.
- Update core integration tests to install the skills extension explicitly when they expect model-visible skill context.

GitOrigin-RevId: bbe6b15c4e776a09c98b7f4166426fe4e58434ba

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

@@ -18,20 +18,17 @@ use crate::agent_communication::AgentCommunicationContext;
 use crate::agent_communication::AgentCommunicationKind;
 use crate::attestation::AttestationProvider;
 use crate::audio_preparation::prepare_response_items as prepare_audio_response_items;
-use crate::build_available_skills;
 use crate::compact;
 use crate::compact::CompactedHistoryMetadata;
 use crate::config::ManagedFeatures;
 use crate::config::resolve_tool_suggest_config_from_layer_stack;
 use crate::context::ApprovedCommandPrefixSaved;
-use crate::context::AvailableSkillsInstructions;
 use crate::context::ContextualUserFragment;
 use crate::context::ModelSwitchInstructions;
 use crate::context::NetworkRuleSaved;
 use crate::context::RecommendedPluginsInstructions;
 use crate::context::world_state::WorldState;
 use crate::current_time::TimeProvider;
-use crate::default_skill_metadata_budget;
 use crate::environment_selection::TurnEnvironmentSnapshot;
 use crate::exec_policy::BANNED_PREFIX_SUGGESTIONS;
 use crate::exec_policy::ExecPolicyManager;
@@ -42,7 +39,6 @@ use crate::realtime_conversation::RealtimeConversationManager;
 use crate::session::step_context::StepContext;
 use crate::session::turn_context::TurnEnvironment;
 use crate::session_prefix::format_inter_agent_completion_message;
-use crate::skills::SkillRenderSideEffects;
 use crate::skills_load_input_from_config;
 use crate::turn_metadata::TurnMetadataState;
 use crate::turn_timing::now_unix_timestamp_ms;
@@ -55,7 +51,6 @@ use codex_analytics::SubAgentThreadStartedInput;
 use codex_analytics::TurnCodexErrorFact;
 use codex_async_utils::OrCancelExt;
 use codex_connectors::connector_runtime_context_key;
-use codex_core_skills::injection::HostSkillsCatalogInWorldState;
 use codex_exec_server::Environment;
 use codex_exec_server::EnvironmentManager;
 use codex_execpolicy::prefix_rule_migration;
@@ -304,8 +299,6 @@ pub(crate) struct PreviousTurnSettings {
     pub(crate) realtime_active: Option<bool>,
 }
 
-#[cfg(test)]
-use crate::SkillMetadata;
 use crate::SkillsService;
 use crate::exec_policy::ExecPolicyUpdateError;
 use crate::guardian::GuardianReviewOptions;
@@ -315,8 +308,6 @@ use crate::network_policy_decision::execpolicy_network_rule_amendment;
 use crate::rollout::map_session_init_error;
 use crate::session_startup_prewarm::SessionStartupPrewarmHandle;
 use crate::shell;
-#[cfg(test)]
-use crate::skills::SkillLoadOutcome;
 use crate::state::AutoCompactWindowIds;
 use crate::state::AutoCompactWindowSnapshot;
 use crate::state::PendingRequestPermissions;
@@ -3410,37 +3401,6 @@ impl Session {
         {
             developer_sections.push(developer_instructions.to_string());
         }
-        if turn_context.config.include_skill_instructions
-            && turn_context
-                .extension_data
-                .get::<HostSkillsCatalogInWorldState>()
-                .is_none()
-        {
-            let available_skills = build_available_skills(
-                turn_context.turn_skills.snapshot.outcome(),
-                default_skill_metadata_budget(turn_context.model_info.context_window),
-                SkillRenderSideEffects::ThreadStart {
-                    session_telemetry: &self.services.session_telemetry,
-                },
-            );
-            if let Some(available_skills) = available_skills {
-                let warning_message = available_skills.warning_message.clone();
-                let skills_instructions = AvailableSkillsInstructions::from_available_skills(
-                    &available_skills,
-                    turn_context.model_info.include_skills_usage_instructions,
-                );
-                if let Some(warning_message) = warning_message {
-                    self.send_event_raw(Event {
-                        id: String::new(),
-                        msg: EventMsg::Warning(WarningEvent {
-                            message: warning_message,
-                        }),
-                    })
-                    .await;
-                }
-                developer_sections.push(skills_instructions.render());
-            }
-        }
         let loaded_plugins = self
             .services
             .plugins_manager

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

@@ -14,8 +14,6 @@ use crate::function_tool::FunctionCallError;
 use crate::session::step_context::StepContext;
 use crate::shell::default_user_shell;
 use crate::shell_snapshot::ShellSnapshot;
-use crate::skills::SkillRenderSideEffects;
-use crate::skills::render::SkillMetadataBudget;
 use crate::test_support::models_manager_with_provider;
 use crate::tools::format_exec_output_str;
 use crate::tools::registry::CoreToolRuntime;
@@ -33,7 +31,6 @@ use codex_config::loader::project_trust_key;
 use codex_config::types::McpServerConfig;
 use codex_config::types::McpServerTransportConfig;
 use codex_config::types::ToolSuggestDisabledTool;
-use codex_core_skills::HostSkillsSnapshot;
 use core_test_support::test_codex::local_selections;
 
 use codex_features::Feature;
@@ -109,10 +106,6 @@ use codex_execpolicy::Policy;
 use codex_network_proxy::NetworkProxyConfig;
 use codex_otel::MetricsClient;
 use codex_otel::MetricsConfig;
-use codex_otel::THREAD_SKILLS_DESCRIPTION_TRUNCATED_CHARS_METRIC;
-use codex_otel::THREAD_SKILLS_ENABLED_TOTAL_METRIC;
-use codex_otel::THREAD_SKILLS_KEPT_TOTAL_METRIC;
-use codex_otel::THREAD_SKILLS_TRUNCATED_METRIC;
 use codex_otel::TelemetryAuthMode;
 use codex_protocol::config_types::CollaborationMode;
 use codex_protocol::config_types::ModeKind;
@@ -143,7 +136,6 @@ use codex_protocol::protocol::ResumedHistory;
 use codex_protocol::protocol::RolloutItem;
 use codex_protocol::protocol::SessionMeta;
 use codex_protocol::protocol::SessionMetaLine;
-use codex_protocol::protocol::SkillScope;
 use codex_protocol::protocol::Submission;
 use codex_protocol::protocol::ThreadRolledBackEvent;
 use codex_protocol::protocol::ThreadSettingsOverrides;
@@ -318,28 +310,6 @@ fn assistant_message(text: &str) -> ResponseItem {
     }
 }
 
-fn test_session_telemetry_without_metadata() -> SessionTelemetry {
-    let exporter = InMemoryMetricExporter::default();
-    let metrics = MetricsClient::new(
-        MetricsConfig::in_memory("test", "codex-core", env!("CARGO_PKG_VERSION"), exporter)
-            .with_runtime_reader(),
-    )
-    .expect("in-memory metrics client");
-    SessionTelemetry::new(
-        ThreadId::new(),
-        "gpt-5.4",
-        "gpt-5.4",
-        /*account_id*/ None,
-        /*account_email*/ None,
-        /*auth_mode*/ None,
-        "test_originator".to_string(),
-        /*log_user_prompts*/ false,
-        "tty".to_string(),
-        SessionSource::Cli,
-    )
-    .with_metrics_without_metadata_tags(metrics)
-}
-
 fn find_metric<'a>(resource_metrics: &'a ResourceMetrics, name: &str) -> &'a Metric {
     for scope_metrics in resource_metrics.scope_metrics() {
         for metric in scope_metrics.metrics() {
@@ -351,21 +321,6 @@ fn find_metric<'a>(resource_metrics: &'a ResourceMetrics, name: &str) -> &'a Met
     panic!("metric {name} missing");
 }
 
-fn histogram_sum(resource_metrics: &ResourceMetrics, name: &str) -> u64 {
-    let metric = find_metric(resource_metrics, name);
-    match metric.data() {
-        AggregatedMetrics::F64(data) => match data {
-            MetricData::Histogram(histogram) => {
-                let points: Vec<_> = histogram.data_points().collect();
-                assert_eq!(points.len(), 1);
-                points[0].sum().round() as u64
-            }
-            _ => panic!("unexpected histogram aggregation"),
-        },
-        _ => panic!("unexpected metric data type"),
-    }
-}
-
 fn single_histogram_attributes(
     resource_metrics: &ResourceMetrics,
     name: &str,
@@ -9168,220 +9123,6 @@ async fn build_initial_context_omits_multi_agent_v2_usage_hints_when_hint_is_emp
     );
 }
 
-#[tokio::test]
-async fn build_initial_context_trims_skill_metadata_from_context_window_budget() {
-    let (session, mut turn_context) = make_session_and_context().await;
-    let mut outcome = SkillLoadOutcome::default();
-    outcome.skills = vec![
-        SkillMetadata {
-            name: "admin-skill".to_string(),
-            description: "desc".to_string(),
-            short_description: None,
-            interface: None,
-            dependencies: None,
-            policy: None,
-            path_to_skills_md: test_path_buf("/tmp/admin-skill/SKILL.md").abs(),
-            scope: SkillScope::Admin,
-            plugin_id: None,
-            remote_plugin_id: None,
-        },
-        SkillMetadata {
-            name: "repo-skill".to_string(),
-            description: "desc".to_string(),
-            short_description: None,
-            interface: None,
-            dependencies: None,
-            policy: None,
-            path_to_skills_md: test_path_buf("/tmp/repo-skill/SKILL.md").abs(),
-            scope: SkillScope::Repo,
-            plugin_id: None,
-            remote_plugin_id: None,
-        },
-    ];
-    turn_context.model_info.context_window = Some(100);
-    turn_context.turn_skills = TurnSkillsContext::new(HostSkillsSnapshot::new(Arc::new(outcome)));
-    let turn_context = Arc::new(turn_context);
-
-    let initial_context = build_initial_context(&session, &turn_context).await;
-    let developer_texts = developer_input_texts(&initial_context);
-
-    assert!(
-        developer_texts
-            .iter()
-            .all(|text| !text.contains("Exceeded skills context budget")),
-        "expected skill budget warning to stay out of the initial context, got {developer_texts:?}"
-    );
-    assert!(
-        developer_texts
-            .iter()
-            .all(|text| !text.contains("- admin-skill:") && !text.contains("- repo-skill:")),
-        "expected no skill metadata entries to fit the tiny budget, got {developer_texts:?}"
-    );
-}
-
-#[test]
-fn emit_thread_start_skill_metrics_records_enabled_kept_and_truncated_values() {
-    let session_telemetry = test_session_telemetry_without_metadata();
-    let mut outcome = SkillLoadOutcome::default();
-    outcome.skills = vec![SkillMetadata {
-        name: "repo-skill".to_string(),
-        description: "desc".to_string(),
-        short_description: None,
-        interface: None,
-        dependencies: None,
-        policy: None,
-        path_to_skills_md: test_path_buf("/tmp/repo-skill/SKILL.md").abs(),
-        scope: SkillScope::Repo,
-        plugin_id: None,
-        remote_plugin_id: None,
-    }];
-    let rendered = build_available_skills(
-        &outcome,
-        SkillMetadataBudget::Characters(1),
-        SkillRenderSideEffects::ThreadStart {
-            session_telemetry: &session_telemetry,
-        },
-    )
-    .expect("skills should render");
-
-    assert_eq!(
-        rendered.warning_message,
-        Some(
-            "Exceeded skills context budget. All skill descriptions were removed and 1 additional skill was not included in the model-visible skills list."
-                .to_string()
-        )
-    );
-    let snapshot = session_telemetry
-        .snapshot_metrics()
-        .expect("runtime metrics snapshot");
-    assert_eq!(
-        histogram_sum(&snapshot, THREAD_SKILLS_ENABLED_TOTAL_METRIC),
-        1
-    );
-    assert_eq!(histogram_sum(&snapshot, THREAD_SKILLS_KEPT_TOTAL_METRIC), 0);
-    assert_eq!(histogram_sum(&snapshot, THREAD_SKILLS_TRUNCATED_METRIC), 1);
-    assert_eq!(
-        histogram_sum(&snapshot, THREAD_SKILLS_DESCRIPTION_TRUNCATED_CHARS_METRIC),
-        4
-    );
-}
-
-#[test]
-fn emit_thread_start_skill_metrics_records_description_truncated_chars_without_omitted_skills() {
-    let session_telemetry = test_session_telemetry_without_metadata();
-    let alpha = SkillMetadata {
-        name: "alpha-skill".to_string(),
-        description: "abcdef".to_string(),
-        short_description: None,
-        interface: None,
-        dependencies: None,
-        policy: None,
-        path_to_skills_md: test_path_buf("/tmp/alpha-skill/SKILL.md").abs(),
-        scope: SkillScope::Repo,
-        plugin_id: None,
-        remote_plugin_id: None,
-    };
-    let beta = SkillMetadata {
-        name: "beta-skill".to_string(),
-        description: "uvwxyz".to_string(),
-        short_description: None,
-        interface: None,
-        dependencies: None,
-        policy: None,
-        path_to_skills_md: test_path_buf("/tmp/beta-skill/SKILL.md").abs(),
-        scope: SkillScope::Repo,
-        plugin_id: None,
-        remote_plugin_id: None,
-    };
-    let minimum_skill_line_cost = |skill: &SkillMetadata| {
-        let path = skill.path_to_skills_md.to_string_lossy().replace('\\', "/");
-        format!("- {}: (file: {})\n", skill.name, path)
-            .chars()
-            .count()
-    };
-    let minimum_budget = minimum_skill_line_cost(&alpha) + minimum_skill_line_cost(&beta);
-    let mut outcome = SkillLoadOutcome::default();
-    outcome.skills = vec![alpha, beta];
-
-    let rendered = build_available_skills(
-        &outcome,
-        SkillMetadataBudget::Characters(minimum_budget + 6),
-        SkillRenderSideEffects::ThreadStart {
-            session_telemetry: &session_telemetry,
-        },
-    )
-    .expect("skills should render");
-
-    assert_eq!(rendered.report.omitted_count, 0);
-    assert_eq!(rendered.report.truncated_description_chars, 8);
-    let snapshot = session_telemetry
-        .snapshot_metrics()
-        .expect("runtime metrics snapshot");
-    assert_eq!(histogram_sum(&snapshot, THREAD_SKILLS_TRUNCATED_METRIC), 0);
-    assert_eq!(
-        histogram_sum(&snapshot, THREAD_SKILLS_DESCRIPTION_TRUNCATED_CHARS_METRIC),
-        8
-    );
-}
-
-#[tokio::test]
-async fn build_initial_context_emits_thread_start_skill_warning_on_repeated_builds() {
-    let (session, turn_context, rx) = make_session_and_context_with_rx().await;
-    let mut turn_context = Arc::into_inner(turn_context).expect("sole thread settings owner");
-    let mut outcome = SkillLoadOutcome::default();
-    outcome.skills = vec![
-        SkillMetadata {
-            name: "admin-skill".to_string(),
-            description: "desc".to_string(),
-            short_description: None,
-            interface: None,
-            dependencies: None,
-            policy: None,
-            path_to_skills_md: test_path_buf("/tmp/admin-skill/SKILL.md").abs(),
-            scope: SkillScope::Admin,
-            plugin_id: None,
-            remote_plugin_id: None,
-        },
-        SkillMetadata {
-            name: "repo-skill".to_string(),
-            description: "desc".to_string(),
-            short_description: None,
-            interface: None,
-            dependencies: None,
-            policy: None,
-            path_to_skills_md: test_path_buf("/tmp/repo-skill/SKILL.md").abs(),
-            scope: SkillScope::Repo,
-            plugin_id: None,
-            remote_plugin_id: None,
-        },
-    ];
-    turn_context.model_info.context_window = Some(100);
-    turn_context.turn_skills = TurnSkillsContext::new(HostSkillsSnapshot::new(Arc::new(outcome)));
-    let turn_context = Arc::new(turn_context);
-
-    let _ = build_initial_context(&session, &turn_context).await;
-    let warning_event = timeout(Duration::from_secs(1), rx.recv())
-        .await
-        .expect("warning event should arrive")
-        .expect("warning event should be readable");
-    assert!(matches!(
-        warning_event.msg,
-        EventMsg::Warning(WarningEvent { message })
-            if message == "Exceeded skills context budget of 2%. All skill descriptions were removed and 2 additional skills were not included in the model-visible skills list."
-    ));
-
-    let _ = build_initial_context(&session, &turn_context).await;
-    let warning_event = timeout(Duration::from_secs(1), rx.recv())
-        .await
-        .expect("warning event should arrive on repeated build")
-        .expect("warning event should be readable");
-    assert!(matches!(
-        warning_event.msg,
-        EventMsg::Warning(WarningEvent { message })
-            if message == "Exceeded skills context budget of 2%. All skill descriptions were removed and 2 additional skills were not included in the model-visible skills list."
-    ));
-}
-
 #[tokio::test]
 async fn build_initial_context_restates_realtime_start_when_reference_context_is_missing() {
     let (session, mut turn_context) = make_session_and_context().await;