worker: implement session explore extract worker

.yoi/tickets/00001KXMK7YMC/item.md

@@ -1,9 +1,11 @@
 ---
 title: 'session-explore feature付きextract workerを実装する'
-state: 'planning'
+state: 'closed'
 created_at: '2026-07-16T04:34:01Z'
-updated_at: '2026-07-17T18:10:00Z'
+updated_at: '2026-07-18T01:35:46Z'
 assignee: null
+queued_by: 'yoi ticket'
+queued_at: '2026-07-18T01:12:22Z'
 ---
 
 ## 背景

.yoi/tickets/00001KXMK7YMC/resolution.md

@@ -0,0 +1,10 @@
+Implemented the session-explore-backed extract worker.
+
+The extract worker now receives an immutable `SessionReferenceView` snapshot and only the `builtin:session-explore` tool surface. It can search/read bounded evidence, stage one flat candidate per `stage_candidate` call with resolved source anchors, and finish cleanly with `finish_extraction` including the no-candidate path.
+
+Validation passed:
+- `cargo fmt --check`
+- `cargo test -p worker`
+- `cargo test -p memory`
+- `nix build .#yoi`
+- `yoi ticket doctor`

.yoi/tickets/00001KXMK7YMC/thread.md

@@ -57,4 +57,101 @@ Rescoped from broad Overview-first extract implementation to the worker implemen
 Design updated: abandon the old batch `write_extracted` / `decisions` / `discussions` / `attempts` / `requests` staging direction. Extract now stages flat candidate records with `stage_candidate` and finishes with `finish_extraction`. The older dependency on 00001KXNYXNM6 is historical; the active schema dependency is 00001KXRM6G0G.
 
 
+---
+
+<!-- event: intake_summary author: hare at: 2026-07-18T01:12:22Z -->
+
+## Intake summary
+
+Marked ready by `yoi ticket state`.
+
+---
+
+<!-- event: state_changed author: "yoi ticket" at: 2026-07-18T01:12:22Z from: planning to: ready reason: cli_state field: state -->
+
+## State changed
+
+Marked ready by `yoi ticket state`.
+
+
+---
+
+<!-- event: state_changed author: "yoi ticket" at: 2026-07-18T01:12:22Z from: ready to: queued reason: queued field: state -->
+
+## State changed
+
+Ticket を `yoi ticket` が queued にしました。
+
+
+---
+
+<!-- event: state_changed author: "yoi ticket" at: 2026-07-18T01:12:22Z from: queued to: inprogress reason: cli_state field: state -->
+
+## State changed
+
+State changed to `inprogress`.
+
+
+---
+
+<!-- event: implementation_report author: hare at: 2026-07-18T01:35:46Z -->
+
+## Implementation report
+
+Implemented the session-explore-backed memory extract worker.
+
+Changes:
+- Added `builtin:session-explore` with `search_evidence`, `read_evidence`, `stage_candidate`, and `finish_extraction`.
+- Extract worker now builds an immutable `SessionReferenceView` at extract start and enables only session-explore tools for the internal worker.
+- Added overview-first / evidence-index-second extract input rendering over the reference view.
+- `stage_candidate` writes one flat staging record per call, resolving evidence ids into bounded staging evidence and `SourceEvidenceRef` anchors.
+- `finish_extraction` supports normal no-candidate completion with `staged_count = 0`.
+- Updated `memory_extract_system.md` to the session-explore / stage / finish contract.
+- Added a single-candidate staging helper in `memory::extract::staging`.
+- Updated extract-trigger tests to use `finish_extraction` and added session-explore unit tests.
+
+Validation:
+- `cargo fmt --check`
+- `cargo test -p worker`
+- `cargo test -p memory`
+- `nix build .#yoi`
+- `yoi ticket doctor`
+
+
+---
+
+<!-- event: state_changed author: "yoi ticket" at: 2026-07-18T01:35:46Z from: inprogress to: done reason: cli_state field: state -->
+
+## State changed
+
+State changed to `done`.
+
+
+---
+
+<!-- event: state_changed author: hare at: 2026-07-18T01:35:46Z from: done to: closed reason: closed field: state -->
+
+## State changed
+
+Ticket を closed にしました。
+
+
+---
+
+<!-- event: close author: hare at: 2026-07-18T01:35:46Z status: closed -->
+
+## 完了
+
+Implemented the session-explore-backed extract worker.
+
+The extract worker now receives an immutable `SessionReferenceView` snapshot and only the `builtin:session-explore` tool surface. It can search/read bounded evidence, stage one flat candidate per `stage_candidate` call with resolved source anchors, and finish cleanly with `finish_extraction` including the no-candidate path.
+
+Validation passed:
+- `cargo fmt --check`
+- `cargo test -p worker`
+- `cargo test -p memory`
+- `nix build .#yoi`
+- `yoi ticket doctor`
+
+
 ---

crates/memory/src/extract/mod.rs

@@ -28,7 +28,7 @@ pub use payload::{
     StagingRecord,
 };
 pub use pointer::{ExtractPointerPayload, fold_pointer};
-pub use staging::{StagingWriteResult, write_staging};
+pub use staging::{StagingWriteResult, write_staging, write_staging_candidate};
 pub use tool::{ExtractWorkerContext, write_extracted_tool};
 
 /// session-store `LogEntry::Extension` で使う domain 名。

crates/memory/src/extract/staging.rs

@@ -11,8 +11,10 @@ use std::path::PathBuf;
 
 use uuid::Uuid;
 
-use crate::extract::payload::{ExtractedPayload, StagingRecord};
-use crate::schema::SourceRef;
+use crate::extract::payload::{
+    ExtractedCandidate, ExtractedPayload, StagingEvidence, StagingRecord,
+};
+use crate::schema::{SourceEvidenceRef, SourceRef};
 use crate::workspace::WorkspaceLayout;
 
 /// Filesystem result for a single staged candidate.
@@ -34,30 +36,48 @@ pub fn write_staging(
         return Ok(Vec::new());
     }
 
-    let dir = layout.staging_dir();
-    fs::create_dir_all(&dir)?;
     let extract_run_id = Uuid::now_v7().to_string();
     let mut written = Vec::with_capacity(payload.candidates.len());
 
     for candidate in payload.candidates {
-        let id = Uuid::now_v7();
-        let record = StagingRecord::from_candidate(
-            id.to_string(),
-            extract_run_id.clone(),
+        written.push(write_staging_candidate(
+            layout,
             source.clone(),
+            &extract_run_id,
             candidate,
             Vec::new(),
             Vec::new(),
-        );
-        let path = dir.join(format!("{}.json", id));
-        let bytes = serde_json::to_vec_pretty(&record).map_err(io::Error::other)?;
-        fs::write(&path, bytes)?;
-        written.push(StagingWriteResult { id, path });
+        )?);
     }
 
     Ok(written)
 }
 
+pub fn write_staging_candidate(
+    layout: &WorkspaceLayout,
+    source: SourceRef,
+    extract_run_id: &str,
+    candidate: ExtractedCandidate,
+    evidence: Vec<StagingEvidence>,
+    source_refs: Vec<SourceEvidenceRef>,
+) -> io::Result<StagingWriteResult> {
+    let dir = layout.staging_dir();
+    fs::create_dir_all(&dir)?;
+    let id = Uuid::now_v7();
+    let record = StagingRecord::from_candidate(
+        id.to_string(),
+        extract_run_id.to_string(),
+        source,
+        candidate,
+        evidence,
+        source_refs,
+    );
+    let path = dir.join(format!("{}.json", id));
+    let bytes = serde_json::to_vec_pretty(&record).map_err(io::Error::other)?;
+    fs::write(&path, bytes)?;
+    Ok(StagingWriteResult { id, path })
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

crates/worker/src/compact/worker.rs

@@ -31,8 +31,7 @@ use tools::ScopedFs;
 use crate::compact::usage_tracker::UsageTracker;
 use crate::fs_view::{ReadRequirement, slice_lines};
 use crate::session_reference::{
-    ReadDetail, ReadOptions, ReadSelector, ReferenceKind, SearchOptions, SessionReferenceView,
-    ToolPart,
+    ReadDetail, ReadOptions, ReadSelector, SearchOptions, SessionReferenceView, ToolPart,
 };
 
 /// Aggregated output of a compact worker run.

crates/worker/src/feature/builtin.rs

@@ -4,9 +4,13 @@
 //! same descriptor-approved registry path used by feature modules. They are not
 //! an external plugin-loading surface.
 
+pub mod session_explore;
 pub mod task;
 pub mod ticket;
 
+pub(crate) use session_explore::{
+    SessionExploreFeature, SessionExploreState, render_extract_input,
+};
 pub use task::{TaskFeature, task_tools_feature};
 pub use ticket::{
     TicketFeature, TicketFeatureAccess, ticket_tools_feature, ticket_tools_feature_with_access,

crates/worker/src/feature/builtin/session_explore.rs

@@ -0,0 +1,673 @@
+use std::sync::{Arc, Mutex};
+
+use async_trait::async_trait;
+use llm_engine::tool::{Tool, ToolDefinition, ToolError, ToolMeta, ToolOutput};
+use memory::extract::{
+    CandidateKind, ExtractedCandidate, StagingWriteResult, write_staging_candidate,
+};
+use memory::schema::SourceRef;
+use memory::workspace::WorkspaceLayout;
+use schemars::JsonSchema;
+use serde::Deserialize;
+use uuid::Uuid;
+
+use crate::feature::{
+    FeatureDescriptor, FeatureInstallContext, FeatureInstallError, FeatureModule, ToolContribution,
+    ToolDeclaration,
+};
+use crate::session_reference::{
+    ReadDetail, ReadOptions, ReadSelector, ReferenceKind, SearchOptions, SessionReferenceView,
+    ToolPart,
+};
+
+const SEARCH_EVIDENCE_DESCRIPTION: &str = "Search the host-created session evidence index. Use this to find stable evidence ids before staging a memory candidate. Supports kind=user|assistant|system|tool and tool_part=input|output|both.";
+const READ_EVIDENCE_DESCRIPTION: &str = "Read bounded session evidence by evidence_id or entry_range. Use compact mode for normal verification and full mode only when exact tool arguments or result content are necessary.";
+const STAGE_CANDIDATE_DESCRIPTION: &str = "Stage one memory candidate as a flat staging record. The candidate must cite one or more evidence_ids returned by search_evidence/read_evidence.";
+const FINISH_EXTRACTION_DESCRIPTION: &str = "Finish the extract worker run after all useful candidates have been staged, or state why no candidates were useful.";
+
+#[derive(Clone)]
+pub(crate) struct SessionExploreState {
+    view: Arc<SessionReferenceView>,
+    layout: WorkspaceLayout,
+    source: SourceRef,
+    extract_run_id: String,
+    staged: Arc<Mutex<Vec<StagingWriteResult>>>,
+    finished: Arc<Mutex<Option<FinishExtractionParams>>>,
+}
+
+impl SessionExploreState {
+    pub(crate) fn new(
+        view: SessionReferenceView,
+        layout: WorkspaceLayout,
+        source: SourceRef,
+    ) -> Self {
+        Self {
+            view: Arc::new(view),
+            layout,
+            source,
+            extract_run_id: Uuid::now_v7().to_string(),
+            staged: Arc::new(Mutex::new(Vec::new())),
+            finished: Arc::new(Mutex::new(None)),
+        }
+    }
+
+    pub(crate) fn view(&self) -> &SessionReferenceView {
+        &self.view
+    }
+
+    pub(crate) fn staged(&self) -> Vec<StagingWriteResult> {
+        self.staged
+            .lock()
+            .expect("session explore staged state poisoned")
+            .clone()
+    }
+
+    pub(crate) fn is_finished(&self) -> bool {
+        self.finished
+            .lock()
+            .expect("session explore finished state poisoned")
+            .is_some()
+    }
+}
+
+#[derive(Clone)]
+pub(crate) struct SessionExploreFeature {
+    state: SessionExploreState,
+}
+
+impl SessionExploreFeature {
+    pub(crate) fn new(state: SessionExploreState) -> Self {
+        Self { state }
+    }
+}
+
+impl FeatureModule for SessionExploreFeature {
+    fn descriptor(&self) -> FeatureDescriptor {
+        FeatureDescriptor::builtin("session-explore", "Session Explore")
+            .with_description(
+                "Host-bounded session evidence search/read tools plus explicit extraction staging.",
+            )
+            .with_tool(ToolDeclaration::new(
+                "search_evidence",
+                SEARCH_EVIDENCE_DESCRIPTION,
+            ))
+            .with_tool(ToolDeclaration::new(
+                "read_evidence",
+                READ_EVIDENCE_DESCRIPTION,
+            ))
+            .with_tool(ToolDeclaration::new(
+                "stage_candidate",
+                STAGE_CANDIDATE_DESCRIPTION,
+            ))
+            .with_tool(ToolDeclaration::new(
+                "finish_extraction",
+                FINISH_EXTRACTION_DESCRIPTION,
+            ))
+    }
+
+    fn install(&self, context: &mut FeatureInstallContext<'_>) -> Result<(), FeatureInstallError> {
+        context.tools().register(ToolContribution::new(
+            "search_evidence",
+            search_evidence_definition(self.state.clone()),
+        ))?;
+        context.tools().register(ToolContribution::new(
+            "read_evidence",
+            read_evidence_definition(self.state.clone()),
+        ))?;
+        context.tools().register(ToolContribution::new(
+            "stage_candidate",
+            stage_candidate_definition(self.state.clone()),
+        ))?;
+        context.tools().register(ToolContribution::new(
+            "finish_extraction",
+            finish_extraction_definition(self.state.clone()),
+        ))?;
+        Ok(())
+    }
+}
+
+fn search_evidence_definition(state: SessionExploreState) -> ToolDefinition {
+    Arc::new(move || {
+        let schema = schemars::schema_for!(SearchEvidenceParams);
+        let schema_value = serde_json::to_value(schema).unwrap_or(serde_json::json!({}));
+        let meta = ToolMeta::new("search_evidence")
+            .description(SEARCH_EVIDENCE_DESCRIPTION)
+            .input_schema(schema_value);
+        let tool: Arc<dyn Tool> = Arc::new(SearchEvidenceTool {
+            state: state.clone(),
+        });
+        (meta, tool)
+    })
+}
+
+fn read_evidence_definition(state: SessionExploreState) -> ToolDefinition {
+    Arc::new(move || {
+        let schema = schemars::schema_for!(ReadEvidenceParams);
+        let schema_value = serde_json::to_value(schema).unwrap_or(serde_json::json!({}));
+        let meta = ToolMeta::new("read_evidence")
+            .description(READ_EVIDENCE_DESCRIPTION)
+            .input_schema(schema_value);
+        let tool: Arc<dyn Tool> = Arc::new(ReadEvidenceTool {
+            state: state.clone(),
+        });
+        (meta, tool)
+    })
+}
+
+fn stage_candidate_definition(state: SessionExploreState) -> ToolDefinition {
+    Arc::new(move || {
+        let schema = schemars::schema_for!(StageCandidateParams);
+        let schema_value = serde_json::to_value(schema).unwrap_or(serde_json::json!({}));
+        let meta = ToolMeta::new("stage_candidate")
+            .description(STAGE_CANDIDATE_DESCRIPTION)
+            .input_schema(schema_value);
+        let tool: Arc<dyn Tool> = Arc::new(StageCandidateTool {
+            state: state.clone(),
+        });
+        (meta, tool)
+    })
+}
+
+fn finish_extraction_definition(state: SessionExploreState) -> ToolDefinition {
+    Arc::new(move || {
+        let schema = schemars::schema_for!(FinishExtractionParams);
+        let schema_value = serde_json::to_value(schema).unwrap_or(serde_json::json!({}));
+        let meta = ToolMeta::new("finish_extraction")
+            .description(FINISH_EXTRACTION_DESCRIPTION)
+            .input_schema(schema_value);
+        let tool: Arc<dyn Tool> = Arc::new(FinishExtractionTool {
+            state: state.clone(),
+        });
+        (meta, tool)
+    })
+}
+
+#[derive(Debug, Deserialize, JsonSchema)]
+struct SearchEvidenceParams {
+    /// Case-insensitive substring. Empty query lists bounded index entries matching filters.
+    #[serde(default)]
+    query: String,
+    /// Optional evidence kind: user, assistant, system, tool.
+    #[serde(default)]
+    kind: Option<String>,
+    /// Optional tool part filter for tool evidence: input, output, both.
+    #[serde(default)]
+    tool_part: Option<String>,
+    /// Optional tool name filter for tool input entries.
+    #[serde(default)]
+    tool_name: Option<String>,
+    /// 0-based session item offset to start from.
+    #[serde(default)]
+    offset: Option<usize>,
+    /// Maximum number of hits.
+    #[serde(default)]
+    limit: Option<usize>,
+}
+
+#[derive(Debug, Deserialize, JsonSchema)]
+struct ReadEvidenceParams {
+    /// Evidence id returned by search_evidence, e.g. M0001, T0002i, T0003o.
+    #[serde(default)]
+    evidence_id: Option<String>,
+    /// Inclusive 0-based session item range. Use when search returned an entry_range instead of a single id.
+    #[serde(default)]
+    entry_range: Option<[u64; 2]>,
+    /// compact omits tool arguments/results; full includes them within host bounds.
+    #[serde(default = "default_read_mode")]
+    mode: String,
+    /// Maximum entries to return.
+    #[serde(default)]
+    max_items: Option<usize>,
+}
+
+fn default_read_mode() -> String {
+    "compact".to_string()
+}
+
+#[derive(Debug, Deserialize, JsonSchema)]
+struct StageCandidateParams {
+    kind: CandidateKind,
+    claim: String,
+    why_useful: String,
+    #[serde(default)]
+    staleness: Option<String>,
+    #[serde(default)]
+    evidence_ids: Vec<String>,
+}
+
+#[derive(Debug, Clone, Deserialize, JsonSchema)]
+struct FinishExtractionParams {
+    staged_count: usize,
+    #[serde(default)]
+    no_candidates_reason: Option<String>,
+}
+
+struct SearchEvidenceTool {
+    state: SessionExploreState,
+}
+
+#[async_trait]
+impl Tool for SearchEvidenceTool {
+    async fn execute(
+        &self,
+        input_json: &str,
+        _ctx: llm_engine::tool::ToolExecutionContext,
+    ) -> Result<ToolOutput, ToolError> {
+        let params: SearchEvidenceParams = serde_json::from_str(input_json).map_err(|e| {
+            ToolError::InvalidArgument(format!("invalid search_evidence input: {e}"))
+        })?;
+        let kind = params
+            .kind
+            .as_deref()
+            .map(parse_reference_kind)
+            .transpose()?;
+        let tool_part = params
+            .tool_part
+            .as_deref()
+            .map(parse_tool_part)
+            .transpose()?;
+        let hits = self.state.view.search(&SearchOptions {
+            query: params.query,
+            kind,
+            tool_part,
+            tool_name: params.tool_name,
+            limit: params.limit,
+            min_entry_index: params.offset.map(|offset| offset as u64),
+        });
+        let content = hits
+            .iter()
+            .map(|hit| {
+                let part = hit
+                    .tool_part
+                    .map(|part| format!(" {part:?}"))
+                    .unwrap_or_default();
+                let tool = hit
+                    .tool_name
+                    .as_ref()
+                    .map(|name| format!(" {name}"))
+                    .unwrap_or_default();
+                format!(
+                    "[{} {}{}{} {:?}] {}\n{}",
+                    hit.id,
+                    hit.kind.as_str(),
+                    part,
+                    tool,
+                    hit.entry_range,
+                    hit.label,
+                    hit.summary
+                )
+            })
+            .collect::<Vec<_>>()
+            .join("\n\n");
+        Ok(ToolOutput {
+            summary: format!("Found {} evidence hit(s).", hits.len()),
+            content: (!content.is_empty()).then_some(content),
+        })
+    }
+}
+
+struct ReadEvidenceTool {
+    state: SessionExploreState,
+}
+
+#[async_trait]
+impl Tool for ReadEvidenceTool {
+    async fn execute(
+        &self,
+        input_json: &str,
+        _ctx: llm_engine::tool::ToolExecutionContext,
+    ) -> Result<ToolOutput, ToolError> {
+        let params: ReadEvidenceParams = serde_json::from_str(input_json)
+            .map_err(|e| ToolError::InvalidArgument(format!("invalid read_evidence input: {e}")))?;
+        let selector = match (params.evidence_id.as_deref(), params.entry_range) {
+            (Some(id), None) => ReadSelector::Id(id),
+            (None, Some(range)) => ReadSelector::EntryRange(range),
+            _ => {
+                return Err(ToolError::InvalidArgument(
+                    "read_evidence requires exactly one of evidence_id or entry_range".to_string(),
+                ));
+            }
+        };
+        let detail = parse_read_detail(&params.mode)?;
+        let read = self.state.view.read(
+            selector,
+            ReadOptions {
+                include_tools: true,
+                tool_part: ToolPart::Both,
+                detail,
+                max_items: params.max_items.unwrap_or(10),
+                max_bytes: 16 * 1024,
+            },
+        );
+        let content = read
+            .entries
+            .iter()
+            .map(|entry| {
+                let part = entry
+                    .tool_part
+                    .map(|part| format!(" {part:?}"))
+                    .unwrap_or_default();
+                let tool = entry
+                    .tool_name
+                    .as_ref()
+                    .map(|name| format!(" {name}"))
+                    .unwrap_or_default();
+                format!(
+                    "[{} {}{}{} {:?}] {}\n{}",
+                    entry.id,
+                    entry.kind.as_str(),
+                    part,
+                    tool,
+                    entry.entry_range,
+                    entry.label,
+                    entry.text
+                )
+            })
+            .collect::<Vec<_>>()
+            .join("\n\n");
+        let summary = if read.truncated {
+            format!(
+                "Read {} evidence entrie(s); output truncated.",
+                read.entries.len()
+            )
+        } else {
+            format!("Read {} evidence entrie(s).", read.entries.len())
+        };
+        Ok(ToolOutput {
+            summary,
+            content: (!content.is_empty()).then_some(content),
+        })
+    }
+}
+
+struct StageCandidateTool {
+    state: SessionExploreState,
+}
+
+#[async_trait]
+impl Tool for StageCandidateTool {
+    async fn execute(
+        &self,
+        input_json: &str,
+        _ctx: llm_engine::tool::ToolExecutionContext,
+    ) -> Result<ToolOutput, ToolError> {
+        let params: StageCandidateParams = serde_json::from_str(input_json).map_err(|e| {
+            ToolError::InvalidArgument(format!("invalid stage_candidate input: {e}"))
+        })?;
+        if params.evidence_ids.is_empty() {
+            return Err(ToolError::InvalidArgument(
+                "stage_candidate requires at least one evidence_id".to_string(),
+            ));
+        }
+        let mut evidence = Vec::with_capacity(params.evidence_ids.len());
+        let mut source_refs = Vec::with_capacity(params.evidence_ids.len());
+        for id in &params.evidence_ids {
+            let staging =
+                self.state.view.staging_evidence_for(id).ok_or_else(|| {
+                    ToolError::InvalidArgument(format!("unknown evidence_id {id:?}"))
+                })?;
+            let source_ref =
+                self.state.view.source_ref_for(id).ok_or_else(|| {
+                    ToolError::InvalidArgument(format!("unknown evidence_id {id:?}"))
+                })?;
+            evidence.push(staging);
+            source_refs.push(source_ref);
+        }
+        let candidate = ExtractedCandidate {
+            kind: params.kind,
+            claim: params.claim,
+            why_useful: params.why_useful,
+            staleness: params.staleness,
+            evidence_ids: params.evidence_ids,
+        };
+        let written = write_staging_candidate(
+            &self.state.layout,
+            self.state.source.clone(),
+            &self.state.extract_run_id,
+            candidate,
+            evidence,
+            source_refs,
+        )
+        .map_err(|e| ToolError::ExecutionFailed(format!("write staging failed: {e}")))?;
+        let id = written.id.to_string();
+        self.state
+            .staged
+            .lock()
+            .expect("session explore staged state poisoned")
+            .push(written);
+        Ok(ToolOutput {
+            summary: format!("Staged memory candidate {id}."),
+            content: Some(format!("staging_id: {id}")),
+        })
+    }
+}
+
+struct FinishExtractionTool {
+    state: SessionExploreState,
+}
+
+#[async_trait]
+impl Tool for FinishExtractionTool {
+    async fn execute(
+        &self,
+        input_json: &str,
+        _ctx: llm_engine::tool::ToolExecutionContext,
+    ) -> Result<ToolOutput, ToolError> {
+        let params: FinishExtractionParams = serde_json::from_str(input_json).map_err(|e| {
+            ToolError::InvalidArgument(format!("invalid finish_extraction input: {e}"))
+        })?;
+        let actual = self
+            .state
+            .staged
+            .lock()
+            .expect("session explore staged state poisoned")
+            .len();
+        if params.staged_count != actual {
+            return Err(ToolError::InvalidArgument(format!(
+                "finish_extraction staged_count {} does not match actual staged count {actual}",
+                params.staged_count
+            )));
+        }
+        let reason = params.no_candidates_reason.clone();
+        *self
+            .state
+            .finished
+            .lock()
+            .expect("session explore finished state poisoned") = Some(params);
+        Ok(ToolOutput {
+            summary: reason
+                .map(|reason| {
+                    format!("Finished extraction with {actual} staged candidate(s): {reason}")
+                })
+                .unwrap_or_else(|| {
+                    format!("Finished extraction with {actual} staged candidate(s).")
+                }),
+            content: None,
+        })
+    }
+}
+
+fn parse_reference_kind(value: &str) -> Result<ReferenceKind, ToolError> {
+    ReferenceKind::parse(value).ok_or_else(|| {
+        ToolError::InvalidArgument(format!(
+            "invalid kind {value:?}; expected user, assistant/agent, system, or tool"
+        ))
+    })
+}
+
+fn parse_tool_part(value: &str) -> Result<ToolPart, ToolError> {
+    ToolPart::parse(value).ok_or_else(|| {
+        ToolError::InvalidArgument(format!(
+            "invalid tool_part {value:?}; expected input, output, or both"
+        ))
+    })
+}
+
+fn parse_read_detail(value: &str) -> Result<ReadDetail, ToolError> {
+    match value {
+        "compact" => Ok(ReadDetail::Compact),
+        "full" => Ok(ReadDetail::Full),
+        other => Err(ToolError::InvalidArgument(format!(
+            "invalid read mode {other:?}; expected compact or full"
+        ))),
+    }
+}
+
+pub(crate) fn render_extract_input(view: &SessionReferenceView) -> String {
+    let mut out = String::new();
+    out.push_str("# Session overview\n\n");
+    if view.overview().is_empty() {
+        out.push_str("No user/assistant overview entries are available.\n\n");
+    } else {
+        for item in view.overview() {
+            out.push_str(&format!(
+                "- [{} {} {:?}] {}\n  {}\n",
+                item.id,
+                item.kind.as_str(),
+                item.entry_range,
+                item.label,
+                truncate_line(&item.text, 500)
+            ));
+        }
+        out.push('\n');
+    }
+
+    out.push_str("# Initial evidence index\n\n");
+    out.push_str(
+        "Use search_evidence/read_evidence to inspect details. Cite only M/T evidence ids in stage_candidate.evidence_ids.\n\n",
+    );
+    let hits = view.search(&SearchOptions {
+        query: String::new(),
+        kind: None,
+        tool_part: None,
+        tool_name: None,
+        limit: Some(50),
+        min_entry_index: None,
+    });
+    for hit in hits {
+        let part = hit
+            .tool_part
+            .map(|part| format!(" {part:?}"))
+            .unwrap_or_default();
+        let tool = hit
+            .tool_name
+            .as_ref()
+            .map(|name| format!(" {name}"))
+            .unwrap_or_default();
+        out.push_str(&format!(
+            "- [{} {}{}{} {:?}] {} — {}\n",
+            hit.id,
+            hit.kind.as_str(),
+            part,
+            tool,
+            hit.entry_range,
+            hit.label,
+            hit.summary
+        ));
+    }
+    out
+}
+
+fn truncate_line(text: &str, max_chars: usize) -> String {
+    let normalized = text.replace('\n', " ");
+    if normalized.chars().count() <= max_chars {
+        normalized
+    } else {
+        let mut out = normalized.chars().take(max_chars).collect::<String>();
+        out.push_str("…");
+        out
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use llm_engine::Item;
+    use tempfile::TempDir;
+
+    #[test]
+    fn descriptor_declares_session_explore_tools() {
+        let temp = TempDir::new().unwrap();
+        let state = SessionExploreState::new(
+            SessionReferenceView::new("segment-1", vec![Item::user_message("remember this")]),
+            WorkspaceLayout::new(temp.path()),
+            SourceRef {
+                segment_id: "segment-1".to_string(),
+                range: [0, 0],
+            },
+        );
+        let descriptor = SessionExploreFeature::new(state).descriptor();
+        assert_eq!(descriptor.id.as_str(), "builtin:session-explore");
+        let names = descriptor
+            .tools
+            .iter()
+            .map(|tool| tool.name.as_str())
+            .collect::<Vec<_>>();
+        assert_eq!(
+            names,
+            vec![
+                "search_evidence",
+                "read_evidence",
+                "stage_candidate",
+                "finish_extraction"
+            ]
+        );
+    }
+
+    #[test]
+    fn render_extract_input_exposes_overview_and_evidence_ids() {
+        let view = SessionReferenceView::new(
+            "segment-1",
+            vec![
+                Item::user_message("user preference"),
+                Item::assistant_message("assistant reply"),
+                Item::tool_call("c1", "Read", "{}"),
+                Item::tool_result_with_content("c1", "read ok", "file body"),
+            ],
+        );
+        let input = render_extract_input(&view);
+        assert!(input.contains("# Session overview"));
+        assert!(input.contains("M0000"));
+        assert!(input.contains("T0002i"));
+        assert!(input.contains("T0003o"));
+        assert!(input.contains("stage_candidate.evidence_ids"));
+    }
+
+    #[tokio::test]
+    async fn stage_candidate_writes_staging_record_with_source_evidence() {
+        let temp = TempDir::new().unwrap();
+        let state = SessionExploreState::new(
+            SessionReferenceView::new("segment-1", vec![Item::user_message("durable decision")]),
+            WorkspaceLayout::new(temp.path()),
+            SourceRef {
+                segment_id: "segment-1".to_string(),
+                range: [0, 0],
+            },
+        );
+        let tool = StageCandidateTool {
+            state: state.clone(),
+        };
+        tool.execute(
+            &serde_json::json!({
+                "kind": "decision",
+                "claim": "Use host-created evidence anchors for extract staging.",
+                "why_useful": "Future consolidation can trust bounded source refs.",
+                "evidence_ids": ["M0000"]
+            })
+            .to_string(),
+            llm_engine::tool::ToolExecutionContext::direct(),
+        )
+        .await
+        .unwrap();
+
+        let staged = state.staged();
+        assert_eq!(staged.len(), 1);
+        let bytes = std::fs::read(&staged[0].path).unwrap();
+        let record: memory::extract::StagingRecord = serde_json::from_slice(&bytes).unwrap();
+        assert_eq!(record.kind, CandidateKind::Decision);
+        assert_eq!(record.evidence.len(), 1);
+        assert_eq!(record.evidence[0].id, "M0000");
+        assert_eq!(record.source_refs.len(), 1);
+        assert_eq!(record.source_refs[0].evidence_id.as_deref(), Some("M0000"));
+    }
+}

crates/worker/src/session_reference.rs

@@ -7,6 +7,7 @@
 use std::sync::Arc;
 
 use llm_engine::{Item, Role};
+use memory::extract::StagingEvidence;
 use memory::schema::{EvidenceKind, SourceEvidenceRef};
 
 const DEFAULT_SEARCH_LIMIT: usize = 20;
@@ -36,7 +37,7 @@ impl ReferenceKind {
     pub(crate) fn parse(value: &str) -> Option<Self> {
         match value {
             "user" => Some(Self::User),
-            "assistant" => Some(Self::Assistant),
+            "assistant" | "agent" => Some(Self::Assistant),
             "system" => Some(Self::System),
             "tool" => Some(Self::Tool),
             _ => None,
@@ -44,10 +45,7 @@ impl ReferenceKind {
     }
 
     fn evidence_kind(self) -> EvidenceKind {
-        match self {
-            Self::User | Self::Assistant | Self::System => EvidenceKind::new(EvidenceKind::MESSAGE),
-            Self::Tool => EvidenceKind::new(EvidenceKind::TOOL_RESULT),
-        }
+        EvidenceKind::new(EvidenceKind::MESSAGE)
     }
 }
 
@@ -94,6 +92,20 @@ pub(crate) struct ReferenceEntry {
     search_text: String,
 }
 
+impl ReferenceEntry {
+    fn evidence_kind(&self) -> EvidenceKind {
+        match (self.kind, self.tool_part) {
+            (ReferenceKind::Tool, Some(ToolPart::Input)) => {
+                EvidenceKind::new(EvidenceKind::TOOL_CALL)
+            }
+            (ReferenceKind::Tool, Some(ToolPart::Output | ToolPart::Both) | None) => {
+                EvidenceKind::new(EvidenceKind::TOOL_RESULT)
+            }
+            _ => self.kind.evidence_kind(),
+        }
+    }
+}
+
 #[derive(Debug, Clone, Default)]
 pub(crate) struct SearchOptions {
     pub query: String,
@@ -378,12 +390,38 @@ impl SessionReferenceView {
             segment_id: Some(self.segment_id.clone()),
             entry_range: Some(entry.entry_range),
             evidence_id: Some(entry.id.clone()),
-            evidence_kind: Some(entry.kind.evidence_kind()),
+            evidence_kind: Some(entry.evidence_kind()),
             label: Some(entry.label.clone()),
             summary: Some(entry.summary.clone()),
             ..Default::default()
         })
     }
+
+    pub(crate) fn staging_evidence_for(&self, id: &str) -> Option<StagingEvidence> {
+        let entry = self.index.iter().find(|entry| entry.id == id)?;
+        let read = self.read(
+            ReadSelector::Id(id),
+            ReadOptions {
+                include_tools: true,
+                tool_part: ToolPart::Both,
+                detail: ReadDetail::Compact,
+                max_items: 1,
+                max_bytes: 2 * 1024,
+            },
+        );
+        let excerpt = read
+            .entries
+            .first()
+            .map(|entry| entry.text.clone())
+            .unwrap_or_else(|| entry.summary.clone());
+        Some(StagingEvidence {
+            id: entry.id.clone(),
+            kind: entry.evidence_kind(),
+            entry_range: Some(entry.entry_range),
+            excerpt: Some(excerpt),
+            summary: Some(entry.summary.clone()),
+        })
+    }
 }
 
 fn render_item(

crates/worker/src/worker.rs

@@ -30,7 +30,9 @@ use manifest::{
 
 use crate::compact::state::CompactState;
 use crate::compact::usage_tracker::UsageTracker;
-use crate::feature::builtin::TaskFeature;
+use crate::feature::builtin::{
+    SessionExploreFeature, SessionExploreState, TaskFeature, render_extract_input,
+};
 use crate::feature::{FeatureRegistryBuilder, FeatureRegistryInstallReport};
 use crate::hook::{
     Hook, HookRegistryBuilder, OnAbort, OnPromptSubmit, OnTurnEnd, PostToolCall, PreLlmRequest,
@@ -3130,8 +3132,47 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
                 return Err(WorkerError::PromptCatalog(err));
             }
         };
-        let ctx = Arc::new(extract::ExtractWorkerContext::new());
-        let input_text = extract::build_extract_input(&items_to_extract);
+        let source_segment_id = self.segment_state.segment_id();
+        let source = memory::schema::SourceRef {
+            segment_id: source_segment_id.to_string(),
+            range: [start_entry as u64, end_entry as u64],
+        };
+        let session_view = crate::session_reference::SessionReferenceView::new(
+            source_segment_id.to_string(),
+            items_to_extract,
+        );
+        let session_explore_state = SessionExploreState::new(session_view, layout.clone(), source);
+        let input_text = render_extract_input(session_explore_state.view());
+        let mut internal_tools = Vec::new();
+        let mut internal_hook_builder = HookRegistryBuilder::new();
+        let feature_report = FeatureRegistryBuilder::new()
+            .with_module(SessionExploreFeature::new(session_explore_state.clone()))
+            .install_into_pending(&mut internal_tools, &mut internal_hook_builder);
+        let installed_tool_names = feature_report.installed_tool_names();
+        let expected_extract_tools = [
+            "search_evidence",
+            "read_evidence",
+            "stage_candidate",
+            "finish_extraction",
+        ];
+        if !expected_extract_tools.iter().all(|name| {
+            installed_tool_names
+                .iter()
+                .any(|installed| installed == name)
+        }) {
+            audit.emit(
+                &layout,
+                event_tx,
+                memory::audit::WorkerLifecycleStatus::Failed,
+                "session_explore_feature_install_failed",
+                None,
+                Some(extract_audit_base),
+                None,
+            );
+            return Err(WorkerError::FeatureInstall(
+                "session-explore feature install failed".to_string(),
+            ));
+        }
         let internal_result = run_internal_worker(InternalWorkerSpec {
             slug: "memory-extract",
             system_prompt: extract_system_prompt,
@@ -3139,7 +3180,7 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
             client,
             cache_key: Some(self.segment_id().to_string()),
             max_turns: extract_worker_max_turns,
-            tools: vec![extract::write_extracted_tool(ctx.clone())],
+            tools: internal_tools,
         })
         .await;
         let usage = match internal_result {
@@ -3159,37 +3200,13 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
             }
         };
 
-        let payload = ctx.take_payload().unwrap_or_else(|| {
+        let staging_results = session_explore_state.staged();
+        if !session_explore_state.is_finished() {
             tracing::warn!(
-                "extract worker did not call write_extracted; advancing pointer with empty payload"
+                staged_count = staging_results.len(),
+                "extract worker did not call finish_extraction; advancing pointer with staged output"
             );
-            extract::ExtractedPayload::default()
-        });
-
-        let source_segment_id = self.segment_state.segment_id();
-        let staging_results = if payload.is_empty() {
-            Vec::new()
-        } else {
-            let source = memory::schema::SourceRef {
-                segment_id: source_segment_id.to_string(),
-                range: [start_entry as u64, end_entry as u64],
-            };
-            match extract::write_staging(&layout, source, payload) {
-                Ok(results) => results,
-                Err(err) => {
-                    audit.emit(
-                        &layout,
-                        event_tx,
-                        memory::audit::WorkerLifecycleStatus::Failed,
-                        format!("staging_write_failed: {err}"),
-                        usage.clone(),
-                        Some(extract_audit_base),
-                        None,
-                    );
-                    return Err(WorkerError::ExtractStaging(err));
-                }
-            }
-        };
+        }
         let staging_id = staging_results
             .first()
             .map(|result| result.id.to_string())
@@ -4807,6 +4824,9 @@ pub enum WorkerError {
     #[error("memory extract staging write failed: {0}")]
     ExtractStaging(#[source] std::io::Error),
 
+    #[error("feature install failed: {0}")]
+    FeatureInstall(String),
+
     #[error("memory consolidation lock acquisition failed: {0}")]
     ConsolidationLock(#[source] memory::consolidate::LockError),
 

crates/worker/tests/compact_events_test.rs

@@ -539,16 +539,14 @@ target = "./"
 permission = "write"
 "#;
 
-fn write_extracted_tool_use_events(call_id: &str) -> Vec<LlmEvent> {
+fn finish_extraction_tool_use_events(call_id: &str) -> Vec<LlmEvent> {
     let input = serde_json::json!({
-        "decisions": [],
-        "discussions": [],
-        "attempts": [],
-        "requests": []
+        "staged_count": 0,
+        "no_candidates_reason": "test run has no durable candidates"
     })
     .to_string();
     vec![
-        LlmEvent::tool_use_start(0, call_id, "write_extracted"),
+        LlmEvent::tool_use_start(0, call_id, "finish_extraction"),
         LlmEvent::tool_input_delta(0, input),
         LlmEvent::tool_use_stop(0),
         LlmEvent::Status(StatusEvent {
@@ -561,13 +559,13 @@ fn write_extracted_tool_use_events(call_id: &str) -> Vec<LlmEvent> {
 async fn compact_resets_extract_pointer_so_extract_can_fire_again() {
     // Mock LLM responses, in call order:
     //   [0] first run with usage(1000) so extract threshold (=1) fires.
-    //   [1] extract worker invokes write_extracted with empty payload.
+    //   [1] extract worker invokes finish_extraction with empty output.
     //   [2] extract worker closes after the tool result.
     //   [3] compact worker invokes write_summary.
     //   [4] compact worker closes after the tool result.
     let client = MockClient::new(vec![
         text_events_with_usage("hi", 1000),
-        write_extracted_tool_use_events("ec1"),
+        finish_extraction_tool_use_events("ec1"),
         single_text_events("done"),
         write_summary_tool_use_events("sc1", "summary"),
         single_text_events("done"),
@@ -703,7 +701,7 @@ permission = "write"
 async fn extract_large_unprocessed_range_does_not_abort_on_input_occupancy() {
     let client = MockClient::new(vec![
         text_events_with_usage("recorded", 1000),
-        write_extracted_tool_use_events("ec-large"),
+        finish_extraction_tool_use_events("ec-large"),
         single_text_events("done"),
     ]);
     let mut worker = make_worker_with_manifest(EXTRACT_NO_COMPACT_MANIFEST, client).await;
@@ -724,7 +722,7 @@ async fn extract_large_unprocessed_range_does_not_abort_on_input_occupancy() {
 async fn spawn_and_wait_drives_extract_to_completion() {
     let client = MockClient::new(vec![
         text_events_with_usage("hi", 1000),
-        write_extracted_tool_use_events("ec1"),
+        finish_extraction_tool_use_events("ec1"),
         single_text_events("done"),
     ]);
     let mut worker = make_worker_with_manifest(EXTRACT_NO_COMPACT_MANIFEST, client).await;
@@ -752,7 +750,7 @@ async fn detached_extract_does_not_fork_session_log() {
     // `ensure_head_or_fork` does not spawn a new session.
     let client = MockClient::new(vec![
         text_events_with_usage("hi", 1000),
-        write_extracted_tool_use_events("ec1"),
+        finish_extraction_tool_use_events("ec1"),
         single_text_events("done"),
         text_events_with_usage("ok", 1000),
     ]);

resources/prompts/internal/memory_extract_system.md

@@ -1,6 +1,6 @@
 You are a Yoi memory extract worker.
 
-Your job is to read the supplied conversation slice and extract only memory candidates that may be worth later consolidation. Do not produce activity logs.
+Your job is to inspect the supplied host-created session reference view and stage only memory candidates that may be worth later consolidation. Do not produce activity logs.
 
 ## Language
 
@@ -9,22 +9,39 @@ Your job is to read the supplied conversation slice and extract only memory cand
 - Preserve literal identifiers, paths, commands, branch names, issue IDs, tool names, model names, and quoted user/system text as-is.
 - If the configured language is unclear, use English.
 
-Call `write_extracted` exactly once with an object of this shape:
+## Tools
+
+Use the session-explore tools only:
+
+- `search_evidence`: find bounded evidence ids in the host-created session index. Optional `kind` accepts `user`, `assistant`/`agent`, `system`, or `tool`.
+- `read_evidence`: inspect a bounded evidence id or entry range before staging when the overview/index is not enough.
+- `stage_candidate`: write one flat staging record for one memory candidate.
+- `finish_extraction`: finish the run after all useful candidates are staged, or after deciding there are no useful candidates.
+
+Do not invent evidence ids. Stage candidates only with `M...` or `T...` ids returned by `search_evidence` / `read_evidence` or shown in the initial evidence index. Overview `O...` ids are orientation labels, not source evidence ids.
+
+Call `stage_candidate` once per useful candidate with this shape:
 
 ```json
 {
-  "candidates": [
-    {
-      "kind": "preference",
-      "claim": "...",
-      "why_useful": "...",
-      "staleness": "...",
-      "evidence_ids": []
-    }
-  ]
+  "kind": "preference",
+  "claim": "...",
+  "why_useful": "...",
+  "staleness": "...",
+  "evidence_ids": ["M0001"]
 }
 ```
 
+Then call `finish_extraction` exactly once:
+
+```json
+{
+  "staged_count": 1
+}
+```
+
+If nothing is worth staging, do not call `stage_candidate`; call `finish_extraction` with `{"staged_count": 0, "no_candidates_reason": "..."}`.
+
 Allowed candidate kinds:
 
 - `preference`: durable user/workspace preference or working style, not a one-off instruction.
@@ -39,11 +56,11 @@ Required fields per candidate:
 - `kind`: one of the allowed candidate kinds.
 - `claim`: concise statement of the candidate.
 - `why_useful`: why this candidate may be useful for future consolidation.
+- `evidence_ids`: one or more host-issued source evidence ids.
 
 Optional fields:
 
 - `staleness`: when this candidate should be revisited or invalidated.
-- `evidence_ids`: leave empty in this transitional path unless host-issued evidence ids are present.
 
 Do not extract:
 
@@ -58,6 +75,4 @@ Do not extract:
 - validation results unless they imply a reusable lesson, active blocker, or authority evidence;
 - implementation details that belong only in commit diff.
 
-Prefer no candidates over noisy candidates. If nothing is worth staging, call `write_extracted` with `{"candidates": []}`.
-
-Do not include record ids, source anchors, session metadata, free-form prose, or raw tool output content. The host attaches staging metadata mechanically.
+Prefer no candidates over noisy candidates. The host attaches staging metadata and bounded evidence mechanically.