fix(compaction): configurable summarizer tool_choice; wider overflow detection

Port of upstream grok-build 0.2.105 + 0.2.118.

- CompactionToolChoice (auto default | none), resolved env
  KIGI_COMPACTION_TOOL_CHOICE > [features].compaction_tool_choice >
  remote settings. Some OpenAI-compatible servers reject
  tool_choice:"none" with tools attached, failing every long-session
  compaction; auto keeps them working (the summarization prompt already
  forbids tool use). Threaded from agent + subagent spawn through
  CompactionConfig into generate_session_compact; the Responses gate
  counts hosted tools too, so a hosted-only request still carries the
  configured choice.
- is_context_length_error recognizes the "current message ... exceeds
  budget" phrasing, so that overflow is Fatal instead of burning the
  retry budget on a deterministic failure.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KSy9S31pZNWXtRZNVJ1sDf

crates/codegen/kigi-shell/src/session/acp_session_impl/spawn.rs

@@ -112,6 +112,7 @@ pub(crate) async fn spawn_session_actor(
     system_prompt_label: String,
     compaction_mode: kigi_chat_state::CompactionMode,
     compaction_verbatim_input: bool,
+    compaction_tool_choice: crate::util::config::CompactionToolChoice,
     two_pass_enabled: bool,
     buffering_settings: Option<BufferingSettings>,
     origin_client: Option<crate::http::OriginClientInfo>,
@@ -1032,6 +1033,7 @@ pub(crate) async fn spawn_session_actor(
             previous_model: std::cell::Cell::new(None),
             compaction_mode,
             verbatim_input: compaction_verbatim_input,
+            tool_choice: compaction_tool_choice,
             prefire: crate::session::compaction_config::PrefireState::default(),
             prefix_released: std::sync::atomic::AtomicBool::new(false),
         },
@@ -1535,6 +1537,7 @@ pub(crate) async fn spawn_session_on_thread(
     system_prompt_label: String,
     compaction_mode: kigi_chat_state::CompactionMode,
     compaction_verbatim_input: bool,
+    compaction_tool_choice: crate::util::config::CompactionToolChoice,
     two_pass_enabled: bool,
     buffering_settings: Option<BufferingSettings>,
     origin_client: Option<crate::http::OriginClientInfo>,
@@ -1679,6 +1682,7 @@ pub(crate) async fn spawn_session_on_thread(
                     system_prompt_label,
                     compaction_mode,
                     compaction_verbatim_input,
+                    compaction_tool_choice,
                     two_pass_enabled,
                     buffering_settings,
                     origin_client,

crates/codegen/kigi-shell/src/session/acp_session_tests/cancel_running_task_tests.rs

@@ -157,6 +157,7 @@ async fn persist_ack_waits_for_disk_flush_before_success() {
                     previous_model: std::cell::Cell::new(None),
                     compaction_mode: kigi_chat_state::CompactionMode::Transcript,
                     verbatim_input: true,
+                    tool_choice: Default::default(),
                     prefire: crate::session::compaction_config::PrefireState::default(),
                     prefix_released: std::sync::atomic::AtomicBool::new(false),
                 },
@@ -611,6 +612,7 @@ async fn first_turn_memory_injection_disabled_does_not_persist_to_chat_history()
                     previous_model: std::cell::Cell::new(None),
                     compaction_mode: kigi_chat_state::CompactionMode::Transcript,
                     verbatim_input: true,
+                    tool_choice: Default::default(),
                     prefire: crate::session::compaction_config::PrefireState::default(),
                     prefix_released: std::sync::atomic::AtomicBool::new(false),
                 },
@@ -871,6 +873,7 @@ async fn cancel_running_task_teardown_clears_running_and_pending_work() {
                     previous_model: std::cell::Cell::new(None),
                     compaction_mode: kigi_chat_state::CompactionMode::Transcript,
                     verbatim_input: true,
+                    tool_choice: Default::default(),
                     prefire: crate::session::compaction_config::PrefireState::default(),
                     prefix_released: std::sync::atomic::AtomicBool::new(false),
                 },
@@ -1865,6 +1868,7 @@ async fn cancel_propagates_to_sampler_handle_so_no_further_emission() {
                     previous_model: std::cell::Cell::new(None),
                     compaction_mode: kigi_chat_state::CompactionMode::Transcript,
                     verbatim_input: true,
+                    tool_choice: Default::default(),
                     prefire: crate::session::compaction_config::PrefireState::default(),
                     prefix_released: std::sync::atomic::AtomicBool::new(false),
                 },

crates/codegen/kigi-shell/src/session/acp_session_tests/idle_resume_tests.rs

@@ -176,6 +176,7 @@ async fn test_e2e_idle_resume_refreshes_model_metadata() {
                     previous_model: std::cell::Cell::new(None),
                     compaction_mode: kigi_chat_state::CompactionMode::Transcript,
                     verbatim_input: true,
+                    tool_choice: Default::default(),
                     prefire: crate::session::compaction_config::PrefireState::default(),
                     prefix_released: std::sync::atomic::AtomicBool::new(false),
                 },

crates/codegen/kigi-shell/src/session/acp_session_tests/inline_auto_compact_flow_tests.rs

@@ -112,6 +112,7 @@ async fn create_test_actor(
             previous_model: std::cell::Cell::new(None),
             compaction_mode: kigi_chat_state::CompactionMode::Transcript,
             verbatim_input: true,
+            tool_choice: Default::default(),
             prefire: crate::session::compaction_config::PrefireState::default(),
             prefix_released: std::sync::atomic::AtomicBool::new(false),
         },
@@ -539,6 +540,7 @@ async fn create_test_actor_with_memory(
             previous_model: std::cell::Cell::new(None),
             compaction_mode: kigi_chat_state::CompactionMode::Transcript,
             verbatim_input: true,
+            tool_choice: Default::default(),
             prefire: crate::session::compaction_config::PrefireState::default(),
             prefix_released: std::sync::atomic::AtomicBool::new(false),
         },
@@ -1298,6 +1300,7 @@ async fn test_e2e_idle_resume_refreshes_model_metadata() {
                     previous_model: std::cell::Cell::new(None),
                     compaction_mode: kigi_chat_state::CompactionMode::Transcript,
                     verbatim_input: true,
+                    tool_choice: Default::default(),
                     prefire: crate::session::compaction_config::PrefireState::default(),
                     prefix_released: std::sync::atomic::AtomicBool::new(false),
                 },

crates/codegen/kigi-shell/src/session/acp_session_tests/memory_config_tests.rs

@@ -163,6 +163,7 @@ async fn create_test_actor_with_memory(
             previous_model: std::cell::Cell::new(None),
             compaction_mode: kigi_chat_state::CompactionMode::Transcript,
             verbatim_input: true,
+            tool_choice: Default::default(),
             prefire: crate::session::compaction_config::PrefireState::default(),
             prefix_released: std::sync::atomic::AtomicBool::new(false),
         },

crates/codegen/kigi-shell/src/session/acp_session_tests/replay_buffer_send_update_tests.rs

@@ -116,6 +116,7 @@ pub(super) async fn make_replay_send_update_fixture() -> ReplaySendUpdateFixture
             previous_model: std::cell::Cell::new(None),
             compaction_mode: kigi_chat_state::CompactionMode::Transcript,
             verbatim_input: true,
+            tool_choice: Default::default(),
             prefire: crate::session::compaction_config::PrefireState::default(),
             prefix_released: std::sync::atomic::AtomicBool::new(false),
         },

crates/codegen/kigi-shell/src/session/acp_session_tests/support.rs

@@ -226,6 +226,7 @@ pub(crate) async fn create_test_actor_ex(
             previous_model: std::cell::Cell::new(None),
             compaction_mode: kigi_chat_state::CompactionMode::Transcript,
             verbatim_input: true,
+            tool_choice: Default::default(),
             prefire: crate::session::compaction_config::PrefireState::default(),
             prefix_released: std::sync::atomic::AtomicBool::new(false),
         },

crates/codegen/kigi-shell/src/session/compaction.rs

@@ -212,6 +212,7 @@ impl SessionActor {
             &sampling_config,
             self.inference_idle_timeout,
             wall_clock_budget_secs,
+            self.compaction.tool_choice,
         )
         .await
         {
@@ -983,6 +984,7 @@ impl SessionActor {
             sampling_config.clone(),
             self.inference_idle_timeout,
             wall_clock_budget_secs,
+            self.compaction.tool_choice,
         );
         let observer =
             crate::session::helpers::full_replace_compaction::ShellFullReplaceObserver::new(
@@ -2198,6 +2200,7 @@ mod inline_auto_compact_flow_tests {
                 previous_model: std::cell::Cell::new(None),
                 compaction_mode: kigi_chat_state::CompactionMode::Transcript,
                 verbatim_input: true,
+                tool_choice: Default::default(),
                 prefire: crate::session::compaction_config::PrefireState::default(),
                 prefix_released: std::sync::atomic::AtomicBool::new(false),
             },

crates/codegen/kigi-shell/src/session/compaction_config.rs

@@ -146,6 +146,9 @@ pub struct CompactionConfig {
     pub compaction_mode: kigi_chat_state::CompactionMode,
     /// When `true`, feed the summarizer the verbatim conversation instead of the lossy rewrite (the retry loop may still fall back).
     pub verbatim_input: bool,
+    /// `tool_choice` for summarizer requests with tools attached (`auto` |
+    /// `none`); some backends reject `"none"`.
+    pub tool_choice: crate::util::config::CompactionToolChoice,
     /// Prefire two-pass state (background NOTE₁ cache + in-flight guard).
     /// `Default` (empty cache, not in-flight).
     pub prefire: PrefireState,

crates/codegen/kigi-shell/src/session/helpers/full_replace_compaction.rs

@@ -70,6 +70,8 @@ pub(crate) struct ShellCompactionSampler {
     /// Wall-clock budget (secs) forwarded to `generate_session_compact` as the
     /// reasoning-runaway backstop; `0` disables it.
     wall_clock_budget_secs: u64,
+    /// Summarizer `tool_choice` forwarded to `generate_session_compact`.
+    tool_choice: crate::util::config::CompactionToolChoice,
     /// Full output of the most recent successful sample (for L5 telemetry).
     last_success: Mutex<Option<CompactOutput>>,
 }
@@ -86,6 +88,7 @@ impl ShellCompactionSampler {
         sampling_config: SamplingConfig,
         idle_timeout: Duration,
         wall_clock_budget_secs: u64,
+        tool_choice: crate::util::config::CompactionToolChoice,
     ) -> Self {
         Self {
             use_short_prompt,
@@ -97,6 +100,7 @@ impl ShellCompactionSampler {
             sampling_config,
             idle_timeout,
             wall_clock_budget_secs,
+            tool_choice,
             last_success: Mutex::new(None),
         }
     }
@@ -135,6 +139,7 @@ impl CompactionSampler for ShellCompactionSampler {
             &self.sampling_config,
             self.idle_timeout,
             self.wall_clock_budget_secs,
+            self.tool_choice,
         )
         .await
         {

crates/codegen/kigi-shell/src/session/helpers/session_compact.rs

@@ -339,9 +339,10 @@ where
 /// prefix and force a full prefill on the summarizer call — attaching them
 /// keeps the request prefix byte-identical to the turn requests so the
 /// engine reuses the session's KV cache (the whole point of the verbatim
-/// input path). Tool *use* is forbidden via `tool_choice: none` where the
-/// backend can express it (ChatCompletions, Responses); the Messages wire
-/// enum has no `none`, so that path relies on the prompt instruction alone.
+/// input path). Tool *use* is forbidden by the prompt instruction;
+/// `tool_choice` says what goes on the wire next to the attached tools
+/// (ChatCompletions, Responses — some servers reject `"none"`, hence the
+/// `auto` default). The Messages wire enum has no `none` either way.
 ///
 /// Errors carry a [`CompactFailure`] classification so the caller can
 /// short-circuit retries on deterministic failures (4xx schema violations,
@@ -356,8 +357,17 @@ pub(crate) async fn generate_session_compact(
     sampling_config: &SamplingConfig,
     idle_timeout: std::time::Duration,
     wall_clock_budget_secs: u64,
+    tool_choice: crate::util::config::CompactionToolChoice,
 ) -> Result<CompactOutput, CompactFailure> {
     let num_messages = chat_history.len();
+    let wire_tool_choice = match tool_choice {
+        crate::util::config::CompactionToolChoice::Auto => ToolChoice::auto(),
+        crate::util::config::CompactionToolChoice::None => ToolChoice::none(),
+    };
+    let conversation_tool_choice = match tool_choice {
+        crate::util::config::CompactionToolChoice::Auto => ConversationToolChoice::Auto,
+        crate::util::config::CompactionToolChoice::None => ConversationToolChoice::None,
+    };
     let output = match sampling_config.api_backend {
         ApiBackend::ChatCompletions => {
             let chat_messages: Vec<ChatRequestMessage> =
@@ -373,7 +383,7 @@ pub(crate) async fn generate_session_compact(
                             .map(|t| ToolDefinition::function(t.name, t.description, t.parameters))
                             .collect(),
                     )
-                    .with_tool_choice(ToolChoice::none());
+                    .with_tool_choice(wire_tool_choice);
             }
             let sid = session_id.to_string();
             message.x_kigi_conv_id = Some(sid.clone());
@@ -466,7 +476,10 @@ pub(crate) async fn generate_session_compact(
         ApiBackend::Responses => {
             let request = ConversationRequest {
                 items: chat_history,
-                tool_choice: (!tools.is_empty()).then_some(ConversationToolChoice::None),
+                // Hosted tools count: a hosted-only request with the choice
+                // omitted would leave the hosted tool callable mid-compact.
+                tool_choice: (!tools.is_empty() || !hosted_tools.is_empty())
+                    .then_some(conversation_tool_choice),
                 tools,
                 hosted_tools,
                 model: Some(sampling_config.model.to_owned()),
@@ -1573,6 +1586,7 @@ mod reasoning_compaction_regression_tests {
             &config,
             std::time::Duration::from_secs(30),
             0,
+            crate::util::config::CompactionToolChoice::Auto,
         )
         .await
         .unwrap_or_else(|_| panic!("compaction must succeed"));
@@ -1661,6 +1675,7 @@ mod reasoning_compaction_regression_tests {
             &config,
             std::time::Duration::from_secs(30),
             0,
+            crate::util::config::CompactionToolChoice::Auto,
         )
         .await;
         let output = result
@@ -1669,11 +1684,11 @@ mod reasoning_compaction_regression_tests {
         let _ = shutdown_tx.send(());
     }
     /// The compaction request must carry the turn loop's tool definitions
-    /// (prompt-prefix/KV-cache alignment) with `tool_choice: "none"`, and
-    /// must omit both keys when no tools are passed (Chat Completions rejects a bare
-    /// `tool_choice`).
+    /// (prompt-prefix/KV-cache alignment) with the configured `tool_choice`
+    /// (`auto` default; `none` when configured), and must omit both keys when
+    /// no tools are passed (Chat Completions rejects a bare `tool_choice`).
     #[tokio::test]
-    async fn chat_completions_compaction_attaches_tools_with_tool_choice_none() {
+    async fn chat_completions_compaction_attaches_tools_with_configured_tool_choice() {
         use std::sync::{Arc, Mutex};
         let captured: Arc<Mutex<Vec<serde_json::Value>>> = Arc::new(Mutex::new(Vec::new()));
         let cap = captured.clone();
@@ -1726,12 +1741,13 @@ mod reasoning_compaction_regression_tests {
             &config,
             std::time::Duration::from_secs(30),
             0,
+            crate::util::config::CompactionToolChoice::Auto,
         )
         .await
         .unwrap_or_else(|_| panic!("compaction with tools must succeed"));
         let client = Client::new(config.clone()).unwrap();
         generate_session_compact(
-            chat_history,
+            chat_history.clone(),
             vec![],
             vec![],
             client,
@@ -1739,16 +1755,36 @@ mod reasoning_compaction_regression_tests {
             &config,
             std::time::Duration::from_secs(30),
             0,
+            crate::util::config::CompactionToolChoice::Auto,
         )
         .await
         .unwrap_or_else(|_| panic!("compaction without tools must succeed"));
+        let tools = vec![ToolSpec {
+            name: "read_file".to_string(),
+            description: Some("Reads a file".to_string()),
+            parameters: json!({ "type" : "object", "properties" : {} }),
+        }];
+        let client = Client::new(config.clone()).unwrap();
+        generate_session_compact(
+            chat_history,
+            tools,
+            vec![],
+            client,
+            acp::SessionId::new("test-session"),
+            &config,
+            std::time::Duration::from_secs(30),
+            0,
+            crate::util::config::CompactionToolChoice::None,
+        )
+        .await
+        .unwrap_or_else(|_| panic!("compaction with tool_choice none must succeed"));
         let bodies = captured.lock().unwrap();
-        assert_eq!(bodies.len(), 2, "mock must have served both requests");
+        assert_eq!(bodies.len(), 3, "mock must have served all three requests");
         let with_tools = &bodies[0];
         assert_eq!(
             with_tools["tool_choice"],
-            json!("none"),
-            "tool use must be disabled at decode time"
+            json!("auto"),
+            "default tool_choice is auto — some backends reject none; the prompt forbids tool use"
         );
         let sent_tools = with_tools["tools"]
             .as_array()
@@ -1764,6 +1800,12 @@ mod reasoning_compaction_regression_tests {
             without_tools.get("tool_choice").is_none(),
             "tool_choice without tools is rejected by OpenAI-compat backends"
         );
+        let none_configured = &bodies[2];
+        assert_eq!(
+            none_configured["tool_choice"],
+            json!("none"),
+            "configured none must reach the wire"
+        );
         let _ = shutdown_tx.send(());
     }
     #[tokio::test]
@@ -1802,6 +1844,7 @@ mod reasoning_compaction_regression_tests {
             &config,
             std::time::Duration::from_millis(150),
             0,
+            crate::util::config::CompactionToolChoice::Auto,
         )
         .await;
         match result {
@@ -1869,6 +1912,7 @@ mod reasoning_compaction_regression_tests {
             &config,
             std::time::Duration::from_millis(150),
             0,
+            crate::util::config::CompactionToolChoice::Auto,
         )
         .await;
         match result {
@@ -1940,6 +1984,7 @@ mod reasoning_compaction_regression_tests {
             &config,
             std::time::Duration::from_millis(150),
             0,
+            crate::util::config::CompactionToolChoice::Auto,
         )
         .await;
         match result {
@@ -2008,6 +2053,7 @@ mod reasoning_compaction_regression_tests {
             &config,
             std::time::Duration::from_millis(150),
             0,
+            crate::util::config::CompactionToolChoice::Auto,
         )
         .await;
         match result {