Share the skills budget across host and executor catalogs (#35769)

## Why

Rendering host and executor skill catalogs independently allows their combined
metadata to exceed the skills context budget.

## What changed

- Allocate one budget across both catalogs when both contain model-visible
  skills.
- Prefer retaining executor skills when budget pressure requires omissions,
  while preserving an executor omission marker and reporting when all host
  skills were omitted.
- Evaluate absolute and aliased host paths under the shared budget and select
  the rendering that best preserves executor entries, total entries, and
  descriptions, in that order.

## Testing

Added renderer and production-turn coverage for shared-budget description
shortening, host-first omission, executor omission markers, and alias selection.

GitOrigin-RevId: 30041736a76aa173cb641aa98a876a306cb437d2

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

@@ -127,6 +127,8 @@ const FULL_CATALOG_CONTEXT_WINDOW: i64 = 40_000;
 const SHORTENING_CONTEXT_WINDOW: i64 = 12_000;
 const EXECUTOR_OMITTING_CONTEXT_WINDOW: i64 = 2_000;
 const HOST_OMITTING_CONTEXT_WINDOW: i64 = 2_000;
+const MIXED_EXECUTOR_OMITTING_CONTEXT_WINDOW: i64 = 2_000;
+const MIXED_HOST_OMITTING_CONTEXT_WINDOW: i64 = 6_000;
 const HOST_CATALOG: [(&str, &str); 4] = [
     (
         "host-alpha",
@@ -550,6 +552,25 @@ async fn production_turn_shortens_executor_only_catalog_with_the_full_budget() -
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn production_turn_shares_catalog_budget_across_host_and_executor_sections() -> Result<()> {
+    let (developer_texts, _) =
+        rendered_catalogs(&HOST_CATALOG, &EXECUTOR_CATALOG, SHORTENING_CONTEXT_WINDOW).await?;
+    let host_lines = skill_lines(catalog_text(&developer_texts, "host"), "host");
+    let executor_lines = skill_lines(catalog_text(&developer_texts, "exec"), "exec");
+    let combined_lines = host_lines
+        .iter()
+        .chain(executor_lines.iter())
+        .copied()
+        .collect::<Vec<_>>();
+
+    assert_shortened_descriptions(&host_lines, &HOST_CATALOG);
+    assert_shortened_descriptions(&executor_lines, &EXECUTOR_CATALOG);
+    assert!(metadata_cost(&combined_lines) <= 240);
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn production_turn_keeps_full_host_only_catalog_when_it_fits() -> Result<()> {
     let (developer_texts, _) =
@@ -647,6 +668,60 @@ async fn production_turn_omits_executor_skills_under_extreme_executor_only_press
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn production_turn_omits_executor_skills_after_host_skills_under_extreme_pressure()
+-> Result<()> {
+    let (developer_texts, _) = rendered_catalogs(
+        &HOST_CATALOG,
+        &EXECUTOR_CATALOG,
+        MIXED_EXECUTOR_OMITTING_CONTEXT_WINDOW,
+    )
+    .await?;
+    let host_lines = developer_texts
+        .iter()
+        .flat_map(|text| skill_lines(text, "host"))
+        .collect::<Vec<_>>();
+    let executor_text = executor_omission_text(&developer_texts);
+    let executor_lines = skill_lines(executor_text, "exec");
+
+    assert_eq!(skill_names(&host_lines), Vec::<&str>::new());
+    assert_eq!(skill_names(&executor_lines), vec!["exec-alpha"]);
+    assert!(executor_text.contains("- 5 additional skills omitted from this bounded skills list."));
+    assert!(developer_texts.iter().any(|text| text.contains(
+        "Host skills are available but omitted from the model-visible skills list because the skills context budget was exceeded."
+    )));
+
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn production_turn_omits_host_skills_before_executor_skills_under_extreme_mixed_pressure()
+-> Result<()> {
+    let (developer_texts, warning_messages) = rendered_catalogs(
+        &HOST_CATALOG,
+        &EXECUTOR_CATALOG,
+        MIXED_HOST_OMITTING_CONTEXT_WINDOW,
+    )
+    .await?;
+    let host_lines = skill_lines(catalog_text(&developer_texts, "host"), "host");
+    let executor_lines = skill_lines(catalog_text(&developer_texts, "exec"), "exec");
+
+    assert_eq!(skill_names(&host_lines), vec!["host-beta"]);
+    assert_eq!(
+        skill_names(&executor_lines),
+        EXECUTOR_CATALOG
+            .iter()
+            .map(|(name, _)| *name)
+            .collect::<Vec<_>>()
+    );
+    assert!(warning_messages.contains(
+        &"Exceeded skills context budget. All skill descriptions were removed and 3 additional skills were not included in the model-visible skills list."
+            .to_string()
+    ));
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn production_turn_fairly_shortens_extension_catalog_descriptions() -> Result<()> {
     let server = responses::start_mock_server().await;

codex-rs/ext/skills/src/extension.rs

@@ -42,6 +42,7 @@ use crate::fragments::SkillInstructions;
 use crate::provider::HostSkillProvider;
 use crate::provider::SkillListQuery;
 use crate::provider::SkillReadRequest;
+use crate::render::AvailableSkillsRender;
 use crate::render::MAX_SKILL_NAME_BYTES;
 use crate::render::MAX_SKILL_PATH_BYTES;
 use crate::render::SkillCatalogRenderPolicy;
@@ -49,10 +50,12 @@ use crate::render::SkillMetadataBudget;
 use crate::render::SkillRenderReport;
 use crate::render::capped_skill_metadata_budget;
 use crate::render::render_available_skills;
+use crate::render::render_combined_available_skills;
 use crate::render::truncate_main_prompt_contents;
 use crate::render::truncate_utf8_to_bytes;
 use crate::render_observability::CatalogSurface;
 use crate::render_observability::record_catalog_render;
+use crate::render_observability::trace_catalog_budget_pressure;
 use crate::selection::collect_explicit_skill_mentions;
 use crate::shadow_selection_experiment::ShadowSelectionExperiment;
 use crate::sources::SkillProviders;
@@ -66,6 +69,7 @@ use crate::warnings::bounded_warnings;
 use crate::world_state::HostSkillsWarningEmitter;
 use crate::world_state::executor_skills_world_state_section;
 use crate::world_state::host_skills_world_state_section;
+use crate::world_state::rendered_host_skills_world_state_section;
 
 struct SkillsExtension<C> {
     providers: SkillProviders,
@@ -88,7 +92,23 @@ fn render_catalog(
     policy: SkillCatalogRenderPolicy,
     budget: SkillMetadataBudget,
 ) -> RenderedCatalog {
-    let Some(rendered) = render_available_skills(catalog, policy, budget) else {
+    render_prepared_catalog(
+        extension_metrics,
+        catalog_surface,
+        include_skills_usage_instructions,
+        budget,
+        render_available_skills(catalog, policy, budget),
+    )
+}
+
+fn render_prepared_catalog(
+    extension_metrics: Option<&dyn ExtensionMetrics>,
+    catalog_surface: CatalogSurface,
+    include_skills_usage_instructions: bool,
+    budget: SkillMetadataBudget,
+    rendered: Option<AvailableSkillsRender>,
+) -> RenderedCatalog {
+    let Some(rendered) = rendered else {
         record_catalog_render(
             extension_metrics,
             catalog_surface,
@@ -259,7 +279,61 @@ where
                 .and_then(ModelInfo::resolved_context_window);
             let metadata_budget = capped_skill_metadata_budget(context_window);
             let extension_metrics = input.extension_metrics.clone();
-            let rendered = if config.include_instructions {
+            let host_snapshot = input.turn_store.get::<HostSkillsSnapshot>();
+            let shared_rendered = if config.include_instructions
+                && let Some(host_snapshot) = host_snapshot.as_ref()
+                && self.providers.has_host_provider()
+            {
+                let host_catalog = self
+                    .providers
+                    .list_host_for_turn(SkillListQuery {
+                        turn_id: input.turn_id.to_string(),
+                        executor_roots: Vec::new(),
+                        resolved_executor_roots: Vec::new(),
+                        host_snapshot: Some(Arc::clone(host_snapshot)),
+                        include_host_skills: true,
+                        include_bundled_skills: false,
+                        include_orchestrator_skills: false,
+                        mcp_resources: None,
+                        executor_capability_discovery: None,
+                    })
+                    .await;
+                let (host_rendered, executor_rendered) =
+                    render_combined_available_skills(&host_catalog, &catalog, metadata_budget);
+                if host_catalog
+                    .entries
+                    .iter()
+                    .any(SkillCatalogEntry::is_model_visible)
+                    && catalog
+                        .entries
+                        .iter()
+                        .any(SkillCatalogEntry::is_model_visible)
+                {
+                    Some((host_rendered, executor_rendered))
+                } else {
+                    None
+                }
+            } else {
+                None
+            };
+            let (rendered, rendered_host) =
+                if let Some((host_rendered, executor_rendered)) = shared_rendered {
+                    if let Some(host_rendered) = host_rendered.as_ref() {
+                        trace_catalog_budget_pressure(metadata_budget, &host_rendered.report);
+                    }
+                    (
+                        render_prepared_catalog(
+                            extension_metrics.as_deref(),
+                            CatalogSurface::ExecutorWorldState,
+                            include_usage,
+                            metadata_budget,
+                            executor_rendered,
+                        ),
+                        host_rendered,
+                    )
+                } else {
+                    (
+                        if config.include_instructions {
                             render_catalog(
                                 extension_metrics.as_deref(),
                                 CatalogSurface::ExecutorWorldState,
@@ -270,8 +344,13 @@ where
                             )
                         } else {
                             RenderedCatalog::default()
+                        },
+                        None,
+                    )
                 };
-            let warning_message = rendered.warning_message;
+            let host_warning_message = rendered_host
+                .as_ref()
+                .and_then(|rendered_host| rendered_host.report.warning_message());
             let executor_body = rendered.fragment.map(|fragment| fragment.body());
             let mut sections = vec![executor_skills_world_state_section(
                 executor_body,
@@ -280,7 +359,7 @@ where
             let emitted_warnings = input
                 .turn_store
                 .get_or_init(EmittedCatalogBudgetWarnings::default);
-            if let Some(host_snapshot) = input.turn_store.get::<HostSkillsSnapshot>()
+            if let Some(host_snapshot) = host_snapshot
                 && self.providers.has_host_provider()
             {
                 input.turn_store.insert(HostSkillsCatalogInWorldState);
@@ -297,6 +376,26 @@ where
                         });
                     }
                 });
+                if let Some(rendered_host) = rendered_host {
+                    let report = &rendered_host.report;
+                    let render_metrics = Some((
+                        report.total_count,
+                        report.included_count,
+                        report.omitted_count,
+                        report.truncated_description_chars,
+                    ));
+                    let body = rendered_host
+                        .into_fragment(include_usage)
+                        .map(|fragment| fragment.body());
+                    sections.push(rendered_host_skills_world_state_section(
+                        body,
+                        config.include_instructions,
+                        render_metrics,
+                        extension_metrics,
+                        host_warning_message,
+                        warning_emitter,
+                    ));
+                } else {
                     sections.push(host_skills_world_state_section(
                         &host_snapshot,
                         config.include_instructions,
@@ -306,7 +405,8 @@ where
                         warning_emitter,
                     ));
                 }
-            if let Some(message) = warning_message
+            }
+            if let Some(message) = rendered.warning_message
                 && emitted_warnings.insert(&message)
             {
                 self.emit_warning(input.thread_store.level_id(), Some(input.turn_id), message);

codex-rs/ext/skills/src/render.rs

@@ -31,13 +31,6 @@ pub(crate) const MAX_SKILL_PATH_BYTES: usize = 1_024;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub(crate) enum SkillCatalogRenderPolicy {
-    #[cfg_attr(
-        not(test),
-        expect(
-            dead_code,
-            reason = "used by the host renderer compatibility path in a follow-up"
-        )
-    )]
     CoreCompatible,
     ExtensionCompatible,
 }
@@ -256,7 +249,6 @@ impl<'a> SkillLine<'a> {
 
 struct RenderedSkillLine {
     line: String,
-    truncated_description_chars: usize,
 }
 
 struct RenderedSkillLines {
@@ -266,14 +258,13 @@ struct RenderedSkillLines {
     truncated_description_count: usize,
 }
 
-struct DescriptionBudgetLine<'a> {
+struct DescriptionBudgetLine {
-    line: &'a SkillLine<'a>,
     description_char_count: usize,
     extra_costs: Vec<usize>,
 }
 
-impl<'a> DescriptionBudgetLine<'a> {
+impl DescriptionBudgetLine {
-    fn new(line: &'a SkillLine<'a>, budget: SkillMetadataBudget) -> Self {
+    fn new(line: &SkillLine<'_>, budget: SkillMetadataBudget) -> Self {
         let minimum_line = line.render_minimum();
         let minimum_chars = minimum_line.chars().count().saturating_add(1);
         let minimum_bytes = minimum_line.len().saturating_add(1);
@@ -297,92 +288,114 @@ impl<'a> DescriptionBudgetLine<'a> {
         }
 
         Self {
-            line,
             description_char_count,
             extra_costs,
         }
     }
 }
 
+#[derive(Clone, Copy)]
+enum SkillLineAllocation {
+    Omitted,
+    DescriptionChars(usize),
+}
+
 fn render_skill_lines(
     skill_lines: Vec<SkillLine<'_>>,
     budget: SkillMetadataBudget,
 ) -> RenderedSkillLines {
+    let allocations = allocate_skill_lines(&skill_lines, budget);
+    render_allocated_skill_lines(&skill_lines, &allocations)
+}
+
+fn allocate_skill_lines(
+    skill_lines: &[SkillLine<'_>],
+    budget: SkillMetadataBudget,
+) -> Vec<SkillLineAllocation> {
     let full_cost = skill_lines.iter().fold(0usize, |used, line| {
         used.saturating_add(line.full_cost(budget))
     });
     if full_cost <= budget.limit() {
-        return RenderedSkillLines {
+        return skill_lines
-            lines: skill_lines
             .iter()
-                .map(|line| RenderedSkillLine {
+            .map(|line| SkillLineAllocation::DescriptionChars(line.description_char_count()))
-                    line: line.render_full(),
+            .collect();
-                    truncated_description_chars: 0,
-                })
-                .collect(),
-            omitted_count: 0,
-            truncated_description_chars: 0,
-            truncated_description_count: 0,
-        };
     }
 
     let minimum_cost = skill_lines.iter().fold(0usize, |used, line| {
         used.saturating_add(line.minimum_cost(budget))
     });
     if minimum_cost <= budget.limit() {
-        let lines = render_lines_with_description_budget(
+        return allocate_description_chars(
             budget,
-            &skill_lines,
+            skill_lines,
             budget.limit().saturating_sub(minimum_cost),
-        );
+        )
-        let (truncated_description_chars, truncated_description_count) =
+        .into_iter()
-            sum_description_truncation(&lines);
+        .map(SkillLineAllocation::DescriptionChars)
-        return RenderedSkillLines {
+        .collect();
-            lines,
-            omitted_count: 0,
-            truncated_description_chars,
-            truncated_description_count,
-        };
     }
 
-    let mut included = Vec::new();
     let mut used = 0usize;
-    let mut omitted = 0usize;
+    skill_lines
-    let mut truncated_description_chars = 0usize;
+        .iter()
-    let mut truncated_description_count = 0usize;
+        .map(|line| {
-    for line in skill_lines {
-        let description_char_count = line.description_char_count();
-        let rendered = line.render_minimum();
             let next_used = used.saturating_add(line.minimum_cost(budget));
             if next_used <= budget.limit() {
                 used = next_used;
-            included.push(RenderedSkillLine {
+                SkillLineAllocation::DescriptionChars(0)
-                line: rendered,
-                truncated_description_chars: description_char_count,
-            });
             } else {
-            omitted = omitted.saturating_add(1);
+                SkillLineAllocation::Omitted
+            }
+        })
+        .collect()
 }
 
+fn render_allocated_skill_lines(
+    skill_lines: &[SkillLine<'_>],
+    allocations: &[SkillLineAllocation],
+) -> RenderedSkillLines {
+    let mut lines = Vec::new();
+    let mut omitted_count = 0usize;
+    let mut truncated_description_chars = 0usize;
+    let mut truncated_description_count = 0usize;
+    for (line, allocation) in skill_lines.iter().zip(allocations) {
+        let description_char_count = line.description_char_count();
+        match allocation {
+            SkillLineAllocation::Omitted => {
+                omitted_count = omitted_count.saturating_add(1);
                 truncated_description_chars =
                     truncated_description_chars.saturating_add(description_char_count);
                 if description_char_count > 0 {
                     truncated_description_count = truncated_description_count.saturating_add(1);
                 }
             }
+            SkillLineAllocation::DescriptionChars(description_chars) => {
+                let truncated_chars = description_char_count.saturating_sub(*description_chars);
+                if truncated_chars > 0 {
+                    truncated_description_chars =
+                        truncated_description_chars.saturating_add(truncated_chars);
+                    truncated_description_count = truncated_description_count.saturating_add(1);
+                }
+                lines.push(RenderedSkillLine {
+                    line: line.render_with_description_chars(*description_chars),
+                });
+            }
+        }
+    }
     RenderedSkillLines {
-        lines: included,
+        lines,
-        omitted_count: omitted,
+        omitted_count,
         truncated_description_chars,
         truncated_description_count,
     }
 }
 
-fn render_lines_with_description_budget(
+fn allocate_description_chars(
     budget: SkillMetadataBudget,
     skill_lines: &[SkillLine<'_>],
     limit: usize,
-) -> Vec<RenderedSkillLine> {
+) -> Vec<usize> {
     let budget_lines = skill_lines
         .iter()
         .map(|line| DescriptionBudgetLine::new(line, budget))
@@ -416,31 +429,7 @@ fn render_lines_with_description_budget(
         }
     }
 
-    budget_lines
+    char_allocations
-        .iter()
-        .zip(char_allocations)
-        .map(|(line, description_chars)| RenderedSkillLine {
-            line: line.line.render_with_description_chars(description_chars),
-            truncated_description_chars: line
-                .description_char_count
-                .saturating_sub(description_chars),
-        })
-        .collect()
-}
-
-fn sum_description_truncation(rendered: &[RenderedSkillLine]) -> (usize, usize) {
-    rendered
-        .iter()
-        .fold((0usize, 0usize), |(chars, count), line| {
-            if line.truncated_description_chars == 0 {
-                (chars, count)
-            } else {
-                (
-                    chars.saturating_add(line.truncated_description_chars),
-                    count.saturating_add(1),
-                )
-            }
-        })
 }
 
 struct RenderedCatalog {
@@ -517,6 +506,279 @@ pub(crate) fn render_available_skills(
     })
 }
 
+pub(crate) fn render_combined_available_skills(
+    host_catalog: &SkillCatalog,
+    executor_catalog: &SkillCatalog,
+    budget: SkillMetadataBudget,
+) -> (Option<AvailableSkillsRender>, Option<AvailableSkillsRender>) {
+    let mut host_entries = host_catalog
+        .entries
+        .iter()
+        .filter(|entry| entry.is_model_visible())
+        .collect::<Vec<_>>();
+    let mut executor_entries = executor_catalog
+        .entries
+        .iter()
+        .filter(|entry| entry.is_model_visible())
+        .collect::<Vec<_>>();
+    SkillCatalogRenderPolicy::CoreCompatible.order_entries(&mut host_entries);
+    SkillCatalogRenderPolicy::ExtensionCompatible.order_entries(&mut executor_entries);
+    if host_entries.is_empty() || executor_entries.is_empty() {
+        return (
+            render_available_skills(
+                host_catalog,
+                SkillCatalogRenderPolicy::CoreCompatible,
+                budget,
+            ),
+            render_available_skills(
+                executor_catalog,
+                SkillCatalogRenderPolicy::ExtensionCompatible,
+                budget,
+            ),
+        );
+    }
+
+    let absolute = render_combined_lines(
+        host_entries
+            .iter()
+            .map(|entry| SkillLine::new(entry, SkillCatalogRenderPolicy::CoreCompatible))
+            .collect(),
+        executor_entries
+            .iter()
+            .map(|entry| SkillLine::new(entry, SkillCatalogRenderPolicy::ExtensionCompatible))
+            .collect(),
+        budget,
+        Vec::new(),
+    );
+    let selected = if combined_catalog_fully_rendered(&absolute) {
+        absolute
+    } else if let Some(aliased) =
+        build_aliased_combined_catalog(&host_entries, &executor_entries, budget)
+        && combined_render_is_better(&aliased, &absolute, budget)
+    {
+        aliased
+    } else {
+        absolute
+    };
+
+    (Some(selected.host), Some(selected.executor))
+}
+
+struct CombinedAvailableSkillsRender {
+    host: AvailableSkillsRender,
+    executor: AvailableSkillsRender,
+}
+
+fn render_combined_lines(
+    host_lines: Vec<SkillLine<'_>>,
+    executor_lines: Vec<SkillLine<'_>>,
+    budget: SkillMetadataBudget,
+    host_skill_root_lines: Vec<String>,
+) -> CombinedAvailableSkillsRender {
+    let executor_count = executor_lines.len();
+    let mut lines = executor_lines;
+    lines.extend(host_lines);
+    let mut allocations = allocate_skill_lines(&lines, budget);
+    let executor_omission_marker =
+        reserve_executor_omission_marker(&lines, executor_count, budget, &mut allocations);
+
+    CombinedAvailableSkillsRender {
+        executor: render_combined_group(
+            &lines[..executor_count],
+            &allocations[..executor_count],
+            Vec::new(),
+            executor_omission_marker,
+        ),
+        host: render_combined_group(
+            &lines[executor_count..],
+            &allocations[executor_count..],
+            host_skill_root_lines,
+            /*omission_marker*/ None,
+        ),
+    }
+}
+
+fn render_combined_group(
+    skill_lines: &[SkillLine<'_>],
+    allocations: &[SkillLineAllocation],
+    skill_root_lines: Vec<String>,
+    omission_marker: Option<String>,
+) -> AvailableSkillsRender {
+    let RenderedSkillLines {
+        mut lines,
+        omitted_count,
+        truncated_description_chars,
+        truncated_description_count,
+    } = render_allocated_skill_lines(skill_lines, allocations);
+    if let Some(marker) = omission_marker {
+        lines.push(RenderedSkillLine { line: marker });
+    }
+    AvailableSkillsRender {
+        skill_root_lines,
+        skill_lines: lines.into_iter().map(|rendered| rendered.line).collect(),
+        report: SkillRenderReport {
+            total_count: skill_lines.len(),
+            included_count: skill_lines.len().saturating_sub(omitted_count),
+            omitted_count,
+            truncated_description_chars,
+            truncated_description_count,
+        },
+    }
+}
+
+fn build_aliased_combined_catalog(
+    host_entries: &[&SkillCatalogEntry],
+    executor_entries: &[&SkillCatalogEntry],
+    budget: SkillMetadataBudget,
+) -> Option<CombinedAvailableSkillsRender> {
+    let plan = build_alias_plan(host_entries, budget)?;
+    if plan.table_cost >= budget.limit() {
+        return None;
+    }
+
+    let adjusted_limit = budget.limit().saturating_sub(plan.table_cost);
+    let adjusted_budget = match budget {
+        SkillMetadataBudget::Tokens(_) => SkillMetadataBudget::Tokens(adjusted_limit),
+        SkillMetadataBudget::Characters(_) => SkillMetadataBudget::Characters(adjusted_limit),
+    };
+    let host_lines = host_entries
+        .iter()
+        .map(|entry| {
+            SkillLine::with_locator(
+                entry,
+                SkillCatalogRenderPolicy::CoreCompatible,
+                render_skill_path_with_aliases(entry, &plan),
+            )
+        })
+        .collect();
+    let executor_lines = executor_entries
+        .iter()
+        .map(|entry| SkillLine::new(entry, SkillCatalogRenderPolicy::ExtensionCompatible))
+        .collect();
+    Some(render_combined_lines(
+        host_lines,
+        executor_lines,
+        adjusted_budget,
+        plan.skill_root_lines,
+    ))
+}
+
+fn combined_catalog_fully_rendered(rendered: &CombinedAvailableSkillsRender) -> bool {
+    rendered.host.report.omitted_count == 0
+        && rendered.host.report.truncated_description_chars == 0
+        && rendered.executor.report.omitted_count == 0
+        && rendered.executor.report.truncated_description_chars == 0
+}
+
+fn combined_render_is_better(
+    candidate: &CombinedAvailableSkillsRender,
+    current: &CombinedAvailableSkillsRender,
+    budget: SkillMetadataBudget,
+) -> bool {
+    if candidate.executor.report.included_count != current.executor.report.included_count {
+        return candidate.executor.report.included_count > current.executor.report.included_count;
+    }
+
+    let included_count = |rendered: &CombinedAvailableSkillsRender| {
+        rendered
+            .host
+            .report
+            .included_count
+            .saturating_add(rendered.executor.report.included_count)
+    };
+    if included_count(candidate) != included_count(current) {
+        return included_count(candidate) > included_count(current);
+    }
+
+    let truncated_chars = |rendered: &CombinedAvailableSkillsRender| {
+        rendered
+            .host
+            .report
+            .truncated_description_chars
+            .saturating_add(rendered.executor.report.truncated_description_chars)
+    };
+    if truncated_chars(candidate) != truncated_chars(current) {
+        return truncated_chars(candidate) < truncated_chars(current);
+    }
+
+    combined_available_skills_cost(budget, candidate)
+        < combined_available_skills_cost(budget, current)
+}
+
+fn combined_available_skills_cost(
+    budget: SkillMetadataBudget,
+    rendered: &CombinedAvailableSkillsRender,
+) -> usize {
+    [&rendered.host, &rendered.executor]
+        .into_iter()
+        .fold(0usize, |used, catalog| {
+            let root_cost = if !catalog.skill_root_lines.is_empty() {
+                aliased_metadata_overhead_cost(budget, &catalog.skill_root_lines)
+            } else {
+                Default::default()
+            };
+            catalog
+                .skill_lines
+                .iter()
+                .fold(used.saturating_add(root_cost), |used, line| {
+                    used.saturating_add(metadata_line_cost(budget, line))
+                })
+        })
+}
+
+fn reserve_executor_omission_marker(
+    skill_lines: &[SkillLine<'_>],
+    executor_count: usize,
+    budget: SkillMetadataBudget,
+    allocations: &mut [SkillLineAllocation],
+) -> Option<String> {
+    loop {
+        let omitted_count = allocations[..executor_count]
+            .iter()
+            .filter(|allocation| matches!(allocation, SkillLineAllocation::Omitted))
+            .count();
+        if omitted_count == 0 {
+            return None;
+        }
+
+        let marker = omission_marker(omitted_count);
+        let used = allocated_skill_lines_cost(skill_lines, allocations, budget);
+        if used.saturating_add(metadata_line_cost(budget, &marker)) <= budget.limit() {
+            return Some(marker);
+        }
+
+        let index = (executor_count..allocations.len())
+            .rev()
+            .chain((0..executor_count).rev())
+            .find(|index| {
+                matches!(
+                    allocations[*index],
+                    SkillLineAllocation::DescriptionChars(_)
+                )
+            })?;
+        allocations[index] = SkillLineAllocation::Omitted;
+    }
+}
+
+fn allocated_skill_lines_cost(
+    skill_lines: &[SkillLine<'_>],
+    allocations: &[SkillLineAllocation],
+    budget: SkillMetadataBudget,
+) -> usize {
+    skill_lines
+        .iter()
+        .zip(allocations)
+        .fold(0usize, |used, (line, allocation)| match allocation {
+            SkillLineAllocation::Omitted => used,
+            SkillLineAllocation::DescriptionChars(description_chars) => {
+                used.saturating_add(metadata_line_cost(
+                    budget,
+                    &line.render_with_description_chars(*description_chars),
+                ))
+            }
+        })
+}
+
 fn render_catalog(
     skill_lines: Vec<SkillLine<'_>>,
     budget: SkillMetadataBudget,
@@ -538,10 +800,7 @@ fn render_catalog(
         loop {
             let marker = omission_marker(omitted);
             if total_cost.saturating_add(metadata_line_cost(budget, &marker)) <= budget.limit() {
-                rendered_lines.push(RenderedSkillLine {
+                rendered_lines.push(RenderedSkillLine { line: marker });
-                    line: marker,
-                    truncated_description_chars: 0,
-                });
                 break;
             }
             let Some(rendered) = rendered_lines.pop() else {

codex-rs/ext/skills/src/render_observability.rs

@@ -41,6 +41,13 @@ pub(crate) fn record_catalog_render(
         report.truncated_description_chars,
     );
 
+    trace_catalog_budget_pressure(budget, report);
+}
+
+pub(crate) fn trace_catalog_budget_pressure(
+    budget: SkillMetadataBudget,
+    report: &SkillRenderReport,
+) {
     if report.omitted_count > 0 || report.truncated_description_chars > 0 {
         tracing::info!(
             budget_limit = budget.limit(),

codex-rs/ext/skills/src/render_tests.rs

@@ -323,6 +323,135 @@ fn mixed_catalogs_keep_absolute_authority_aware_rendering_under_budget_pressure(
     assert!(!body.contains("additional skills omitted"));
 }
 
+#[test]
+fn mixed_catalog_reserves_executor_omission_marker_by_omitting_host_first() {
+    let host_catalog = SkillCatalog {
+        entries: vec![entry_with_path(
+            "h", "", /*short_description*/ None, "/h",
+        )],
+        warnings: Vec::new(),
+    };
+    let executor_entry = |name: &str, resource: &str| {
+        SkillCatalogEntry::new(
+            SkillPackageId(name.to_string()),
+            SkillAuthority::new(SkillSourceKind::Executor, "env-1"),
+            name,
+            "",
+            SkillResourceId::new(resource),
+        )
+        .with_display_path(resource)
+    };
+    let executor_catalog = SkillCatalog {
+        entries: vec![
+            executor_entry("e1", "skill://executor/one"),
+            executor_entry(
+                "e2",
+                "skill://executor/this-resource-is-intentionally-too-long",
+            ),
+        ],
+        warnings: Vec::new(),
+    };
+
+    let (host, executor) = render_combined_available_skills(
+        &host_catalog,
+        &executor_catalog,
+        SkillMetadataBudget::Tokens(28),
+    );
+    let host = host.expect("host catalog should render");
+    let executor = executor.expect("executor catalog should render");
+
+    assert_eq!(
+        host.report,
+        SkillRenderReport {
+            total_count: 1,
+            included_count: 0,
+            omitted_count: 1,
+            truncated_description_chars: 0,
+            truncated_description_count: 0,
+        }
+    );
+    assert_eq!(
+        executor.report,
+        SkillRenderReport {
+            total_count: 2,
+            included_count: 1,
+            omitted_count: 1,
+            truncated_description_chars: 0,
+            truncated_description_count: 0,
+        }
+    );
+    assert_eq!(
+        executor.skill_lines,
+        vec![
+            "- e1: (environment resource: skill://executor/one)".to_string(),
+            "- 1 additional skill omitted from this bounded skills list.".to_string(),
+        ]
+    );
+}
+
+#[test]
+fn mixed_catalog_prefers_executor_inclusion_over_total_aliased_inclusion() {
+    let root = format!("/{}", "r".repeat(219));
+    let host_catalog = SkillCatalog {
+        entries: ["h1", "h2"]
+            .into_iter()
+            .map(|name| {
+                entry(name, "", /*short_description*/ None)
+                    .with_display_path(format!("{root}/{name}/SKILL.md"))
+                    .with_display_path_root(root.as_str())
+            })
+            .collect(),
+        warnings: Vec::new(),
+    };
+    let executor_entry = |name: &str, resource: &str| {
+        SkillCatalogEntry::new(
+            SkillPackageId(name.to_string()),
+            SkillAuthority::new(SkillSourceKind::Executor, "env-1"),
+            name,
+            "",
+            SkillResourceId::new(resource),
+        )
+        .with_display_path(resource)
+    };
+    let executor_catalog = SkillCatalog {
+        entries: vec![
+            executor_entry("e1", "skill://executor/one"),
+            executor_entry("e2", &format!("skill://{}", "e".repeat(132))),
+        ],
+        warnings: Vec::new(),
+    };
+
+    let (host, executor) = render_combined_available_skills(
+        &host_catalog,
+        &executor_catalog,
+        SkillMetadataBudget::Tokens(74),
+    );
+    let host = host.expect("host catalog should render");
+    let executor = executor.expect("executor catalog should render");
+
+    assert_eq!(
+        executor.report,
+        SkillRenderReport {
+            total_count: 2,
+            included_count: 2,
+            omitted_count: 0,
+            truncated_description_chars: 0,
+            truncated_description_count: 0,
+        }
+    );
+    assert_eq!(
+        host.report,
+        SkillRenderReport {
+            total_count: 2,
+            included_count: 0,
+            omitted_count: 2,
+            truncated_description_chars: 0,
+            truncated_description_count: 0,
+        }
+    );
+    assert_eq!(host.skill_root_lines, Vec::<String>::new());
+}
+
 #[test]
 fn singleton_plugin_versions_share_the_marketplace_alias_root() {
     let github_root = "/Users/test/.codex/plugins/cache/openai-curated/github/hash123/skills";

codex-rs/ext/skills/src/world_state.rs

@@ -25,6 +25,7 @@ const HIDDEN_EXECUTOR_SKILLS_BODY: &str = "\n## Skills update\nSelected-environm
 const NO_HOST_SKILLS_BODY: &str =
     "\n## Host skills update\nNo host skills are currently available.\n";
 const HIDDEN_HOST_SKILLS_BODY: &str = "\n## Host skills update\nHost skills are not listed automatically. Explicit skill mentions can still be resolved when available.\n";
+const OMITTED_HOST_SKILLS_BODY: &str = "\n## Host skills update\nHost skills are available but omitted from the model-visible skills list because the skills context budget was exceeded.\n";
 
 pub(crate) type HostSkillsWarningEmitter = Arc<dyn Fn(String) + Send + Sync>;
 
@@ -142,6 +143,13 @@ pub(crate) fn rendered_host_skills_world_state_section(
     warning_message: Option<String>,
     warning_emitter: HostSkillsWarningEmitter,
 ) -> WorldStateSectionContribution {
+    let body = body.or_else(|| {
+        render_metrics
+            .is_some_and(|(total_count, included_count, omitted_count, _)| {
+                total_count > 0 && included_count == 0 && omitted_count > 0
+            })
+            .then(|| OMITTED_HOST_SKILLS_BODY.to_string())
+    });
     let snapshot = json!({
         "body": body,
         "includeInstructions": include_instructions,