story-kit: accept 96_story_reset_agent_lozenge_to_idle_state_when_returning_to_roster

.coverage_baseline

@@ -1 +1 @@
-64.60
+65.14

.story_kit/project.toml

@@ -51,7 +51,7 @@ system_prompt = "You are a supervisor agent. Read CLAUDE.md and .story_kit/READM
 [[agent]]
 name = "coder-1"
 role = "Full-stack engineer. Implements features across all components."
-model = "claude-sonnet-4-5-20241022"
+model = "sonnet"
 max_turns = 50
 max_budget_usd = 5.00
 prompt = "You are working in a git worktree on story {{story_id}}. Read CLAUDE.md first, then .story_kit/README.md to understand the dev process. The story details are in your prompt above. Follow the SDTW process through implementation and verification (Steps 1-3). The worktree and feature branch already exist - do not create them. Check .mcp.json for MCP tools. Do NOT accept the story or merge - commit your work and stop. If the user asks to review your changes, tell them to run: cd \"{{worktree_path}}\" && git difftool {{base_branch}}...HEAD\n\nIMPORTANT: Commit all your work before your process exits. The server will automatically run acceptance gates (cargo clippy + tests) when your process exits and advance the pipeline based on the results."
@@ -60,7 +60,7 @@ system_prompt = "You are a full-stack engineer working autonomously in a git wor
 [[agent]]
 name = "coder-2"
 role = "Full-stack engineer. Implements features across all components."
-model = "claude-sonnet-4-5-20241022"
+model = "sonnet"
 max_turns = 50
 max_budget_usd = 5.00
 prompt = "You are working in a git worktree on story {{story_id}}. Read CLAUDE.md first, then .story_kit/README.md to understand the dev process. The story details are in your prompt above. Follow the SDTW process through implementation and verification (Steps 1-3). The worktree and feature branch already exist - do not create them. Check .mcp.json for MCP tools. Do NOT accept the story or merge - commit your work and stop. If the user asks to review your changes, tell them to run: cd \"{{worktree_path}}\" && git difftool {{base_branch}}...HEAD\n\nIMPORTANT: Commit all your work before your process exits. The server will automatically run acceptance gates (cargo clippy + tests) when your process exits and advance the pipeline based on the results."
@@ -69,7 +69,7 @@ system_prompt = "You are a full-stack engineer working autonomously in a git wor
 [[agent]]
 name = "coder-3"
 role = "Full-stack engineer. Implements features across all components."
-model = "claude-sonnet-4-5-20241022"
+model = "sonnet"
 max_turns = 50
 max_budget_usd = 5.00
 prompt = "You are working in a git worktree on story {{story_id}}. Read CLAUDE.md first, then .story_kit/README.md to understand the dev process. The story details are in your prompt above. Follow the SDTW process through implementation and verification (Steps 1-3). The worktree and feature branch already exist - do not create them. Check .mcp.json for MCP tools. Do NOT accept the story or merge - commit your work and stop. If the user asks to review your changes, tell them to run: cd \"{{worktree_path}}\" && git difftool {{base_branch}}...HEAD\n\nIMPORTANT: Commit all your work before your process exits. The server will automatically run acceptance gates (cargo clippy + tests) when your process exits and advance the pipeline based on the results."
@@ -87,7 +87,7 @@ system_prompt = "You are a senior full-stack engineer working autonomously in a
 [[agent]]
 name = "qa"
 role = "Reviews coder work in worktrees: runs quality gates, generates testing plans, and reports findings."
-model = "claude-sonnet-4-5-20241022"
+model = "sonnet"
 max_turns = 40
 max_budget_usd = 4.00
 prompt = """You are the QA agent for story {{story_id}}. Your job is to review the coder's work in the worktree and produce a structured QA report.
@@ -153,7 +153,7 @@ system_prompt = "You are a QA agent. Your job is read-only: review code quality,
 [[agent]]
 name = "mergemaster"
 role = "Merges completed coder work into master, runs quality gates, archives stories, and cleans up worktrees."
-model = "claude-sonnet-4-5-20241022"
+model = "sonnet"
 max_turns = 30
 max_budget_usd = 3.00
 prompt = """You are the mergemaster agent for story {{story_id}}. Your job is to merge the completed coder work into master using the merge_agent_work MCP tool.

.story_kit/work/4_merge/89_story_persistent_per_session_agent_logs.md

@@ -1,21 +0,0 @@
----
-name: "Persistent per-session agent logs"
----
-
-# Story 89: Persistent per-session agent logs
-
-## User Story
-
-As a user, I want each agent session to write its output to a persistent log file so I can inspect what an agent did after it completes, even across server restarts.
-
-## Acceptance Criteria
-
-- [ ] Each agent session writes output to a log file at .story_kit/logs/{story_id}/{agent_name}-{session_id}.log
-- [ ] Log files persist across server restarts and agent completions
-- [ ] The get_agent_output MCP tool falls back to reading the log file when the in-memory stream is empty or the agent has completed
-- [ ] Log files include timestamps, tool calls, text output, and status events
-- [ ] Different sessions for the same agent on the same story produce separate log files (no mixing)
-
-## Out of Scope
-
-- TBD

.story_kit/work/5_archived/89_story_persistent_per_session_agent_logs.md

@@ -0,0 +1,42 @@
+---
+name: "Persistent per-session agent logs"
+---
+
+# Story 89: Persistent per-session agent logs
+
+## User Story
+
+As a user, I want each agent session to write its output to a persistent log file so I can inspect what an agent did after it completes, even across server restarts.
+
+## Acceptance Criteria
+
+- [ ] Each agent session writes output to a log file at .story_kit/logs/{story_id}/{agent_name}-{session_id}.log
+- [ ] Log files persist across server restarts and agent completions
+- [ ] The get_agent_output MCP tool falls back to reading the log file when the in-memory stream is empty or the agent has completed
+- [ ] Log files include timestamps, tool calls, text output, and status events
+- [ ] Different sessions for the same agent on the same story produce separate log files (no mixing)
+
+## Test Plan
+
+### Unit Tests (server/src/agent_log.rs)
+
+1. **test_log_writer_creates_directory_and_file** — AC1: Verify `AgentLogWriter::new()` creates `.story_kit/logs/{story_id}/` and the log file `{agent_name}-{session_id}.log`.
+2. **test_log_writer_writes_jsonl_with_timestamps** — AC4: Verify `write_event()` writes valid JSONL with ISO 8601 timestamps including type, data, and timestamp fields.
+3. **test_read_log_parses_written_events** — AC3/AC4: Verify `read_log()` can round-trip events written by `write_event()`.
+4. **test_separate_sessions_produce_separate_files** — AC5: Verify two `AgentLogWriter` instances for the same story_id+agent_name but different session_ids write to different files without mixing.
+5. **test_find_latest_log_returns_most_recent** — AC3: Verify `find_latest_log()` returns the correct most-recent log for a given story_id+agent_name pair.
+6. **test_log_files_persist_on_disk** — AC2: Verify that after writer is dropped, the file still exists and is readable.
+
+### Unit Tests (server/src/agents.rs)
+
+7. **test_emit_event_writes_to_log_writer** — AC1/AC4: Verify that `emit_event` with a log writer writes to the log file in addition to broadcast+event_log.
+
+### Integration Tests (server/src/http/mcp.rs)
+
+8. **test_get_agent_output_falls_back_to_log_file** — AC3: Verify that when in-memory events are empty and agent is completed, `get_agent_output` reads from the log file.
+
+## Out of Scope
+
+- Log rotation or cleanup of old log files
+- Frontend UI for viewing log files
+- Log file compression

frontend/src/api/agents.ts

@@ -7,6 +7,7 @@ export interface AgentInfo {
 	session_id: string | null;
 	worktree_path: string | null;
 	base_branch: string | null;
+	log_session_id: string | null;
 }
 
 export interface AgentEvent {

frontend/src/components/AgentPanel.test.tsx

@@ -53,6 +53,7 @@ describe("AgentPanel active work list removed", () => {
 				session_id: null,
 				worktree_path: "/tmp/wt",
 				base_branch: "master",
+				log_session_id: null,
 			},
 		];
 		mockedAgents.listAgents.mockResolvedValue(agentList);
@@ -106,6 +107,7 @@ describe("RosterBadge availability state", () => {
 				session_id: null,
 				worktree_path: null,
 				base_branch: null,
+				log_session_id: null,
 			},
 		];
 		mockedAgents.listAgents.mockResolvedValue(agentList);
@@ -127,6 +129,7 @@ describe("RosterBadge availability state", () => {
 				session_id: null,
 				worktree_path: null,
 				base_branch: null,
+				log_session_id: null,
 			},
 		];
 		mockedAgents.listAgents.mockResolvedValue(agentList);

server/src/agent_log.rs

@@ -0,0 +1,377 @@
+use crate::agents::AgentEvent;
+use chrono::Utc;
+use serde::{Deserialize, Serialize};
+use std::fs::{self, File, OpenOptions};
+use std::io::{BufRead, BufReader, Write};
+use std::path::{Path, PathBuf};
+
+
+/// A single line in the agent log file (JSONL format).
+#[derive(Debug, Serialize, Deserialize)]
+pub struct LogEntry {
+    pub timestamp: String,
+    #[serde(flatten)]
+    pub event: serde_json::Value,
+}
+
+/// Writes agent events to a persistent log file (JSONL format).
+///
+/// Each agent session gets its own log file at:
+///   `.story_kit/logs/{story_id}/{agent_name}-{session_id}.log`
+pub struct AgentLogWriter {
+    file: File,
+}
+
+impl AgentLogWriter {
+    /// Create a new log writer, creating the directory structure as needed.
+    ///
+    /// The log file is opened in append mode so that a restart mid-session
+    /// won't overwrite earlier output.
+    pub fn new(
+        project_root: &Path,
+        story_id: &str,
+        agent_name: &str,
+        session_id: &str,
+    ) -> Result<Self, String> {
+        let dir = log_dir(project_root, story_id);
+        fs::create_dir_all(&dir)
+            .map_err(|e| format!("Failed to create log directory {}: {e}", dir.display()))?;
+
+        let path = dir.join(format!("{agent_name}-{session_id}.log"));
+        let file = OpenOptions::new()
+            .create(true)
+            .append(true)
+            .open(&path)
+            .map_err(|e| format!("Failed to open log file {}: {e}", path.display()))?;
+
+        Ok(Self { file })
+    }
+
+    /// Write an agent event as a JSONL line with an ISO 8601 timestamp.
+    pub fn write_event(&mut self, event: &AgentEvent) -> Result<(), String> {
+        let event_value =
+            serde_json::to_value(event).map_err(|e| format!("Failed to serialize event: {e}"))?;
+
+        let entry = LogEntry {
+            timestamp: Utc::now().to_rfc3339(),
+            event: event_value,
+        };
+
+        let mut line =
+            serde_json::to_string(&entry).map_err(|e| format!("Failed to serialize entry: {e}"))?;
+        line.push('\n');
+
+        self.file
+            .write_all(line.as_bytes())
+            .map_err(|e| format!("Failed to write log entry: {e}"))?;
+
+        Ok(())
+    }
+}
+
+/// Return the log directory for a story.
+fn log_dir(project_root: &Path, story_id: &str) -> PathBuf {
+    project_root
+        .join(".story_kit")
+        .join("logs")
+        .join(story_id)
+}
+
+/// Return the path to a specific log file.
+pub fn log_file_path(
+    project_root: &Path,
+    story_id: &str,
+    agent_name: &str,
+    session_id: &str,
+) -> PathBuf {
+    log_dir(project_root, story_id).join(format!("{agent_name}-{session_id}.log"))
+}
+
+/// Read all log entries from a log file.
+pub fn read_log(path: &Path) -> Result<Vec<LogEntry>, String> {
+    let file =
+        File::open(path).map_err(|e| format!("Failed to open log file {}: {e}", path.display()))?;
+    let reader = BufReader::new(file);
+    let mut entries = Vec::new();
+
+    for line in reader.lines() {
+        let line = line.map_err(|e| format!("Failed to read log line: {e}"))?;
+        let trimmed = line.trim();
+        if trimmed.is_empty() {
+            continue;
+        }
+        let entry: LogEntry = serde_json::from_str(trimmed)
+            .map_err(|e| format!("Failed to parse log entry: {e}"))?;
+        entries.push(entry);
+    }
+
+    Ok(entries)
+}
+
+/// Find the most recent log file for a given story+agent combination.
+///
+/// Scans `.story_kit/logs/{story_id}/` for files matching `{agent_name}-*.log`
+/// and returns the one with the most recent modification time.
+pub fn find_latest_log(
+    project_root: &Path,
+    story_id: &str,
+    agent_name: &str,
+) -> Option<PathBuf> {
+    let dir = log_dir(project_root, story_id);
+    if !dir.is_dir() {
+        return None;
+    }
+
+    let prefix = format!("{agent_name}-");
+    let mut best: Option<(PathBuf, std::time::SystemTime)> = None;
+
+    let entries = fs::read_dir(&dir).ok()?;
+    for entry in entries.flatten() {
+        let path = entry.path();
+        let name = match path.file_name().and_then(|n| n.to_str()) {
+            Some(n) => n.to_string(),
+            None => continue,
+        };
+        if !name.starts_with(&prefix) || !name.ends_with(".log") {
+            continue;
+        }
+        let modified = match entry.metadata().and_then(|m| m.modified()) {
+            Ok(t) => t,
+            Err(_) => continue,
+        };
+        if best.as_ref().is_none_or(|(_, t)| modified > *t) {
+            best = Some((path, modified));
+        }
+    }
+
+    best.map(|(p, _)| p)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::agents::AgentEvent;
+    use tempfile::tempdir;
+
+    #[test]
+    fn test_log_writer_creates_directory_and_file() {
+        let tmp = tempdir().unwrap();
+        let root = tmp.path();
+
+        let _writer =
+            AgentLogWriter::new(root, "42_story_foo", "coder-1", "sess-abc123").unwrap();
+
+        let expected_path = root
+            .join(".story_kit")
+            .join("logs")
+            .join("42_story_foo")
+            .join("coder-1-sess-abc123.log");
+        assert!(expected_path.exists(), "Log file should exist");
+    }
+
+    #[test]
+    fn test_log_writer_writes_jsonl_with_timestamps() {
+        let tmp = tempdir().unwrap();
+        let root = tmp.path();
+
+        let mut writer =
+            AgentLogWriter::new(root, "42_story_foo", "coder-1", "sess-001").unwrap();
+
+        let event = AgentEvent::Status {
+            story_id: "42_story_foo".to_string(),
+            agent_name: "coder-1".to_string(),
+            status: "running".to_string(),
+        };
+        writer.write_event(&event).unwrap();
+
+        let event2 = AgentEvent::Output {
+            story_id: "42_story_foo".to_string(),
+            agent_name: "coder-1".to_string(),
+            text: "Hello world".to_string(),
+        };
+        writer.write_event(&event2).unwrap();
+
+        // Read the file and verify
+        let path = log_file_path(root, "42_story_foo", "coder-1", "sess-001");
+        let content = fs::read_to_string(&path).unwrap();
+        let lines: Vec<&str> = content.lines().collect();
+        assert_eq!(lines.len(), 2, "Should have 2 log lines");
+
+        // Parse each line as valid JSON with a timestamp
+        for line in &lines {
+            let entry: LogEntry = serde_json::from_str(line).unwrap();
+            assert!(!entry.timestamp.is_empty(), "Timestamp should be present");
+            // Verify it's a valid ISO 8601 timestamp
+            chrono::DateTime::parse_from_rfc3339(&entry.timestamp)
+                .expect("Timestamp should be valid RFC3339");
+        }
+
+        // Verify the first entry is a status event
+        let entry1: LogEntry = serde_json::from_str(lines[0]).unwrap();
+        assert_eq!(entry1.event["type"], "status");
+        assert_eq!(entry1.event["status"], "running");
+
+        // Verify the second entry is an output event
+        let entry2: LogEntry = serde_json::from_str(lines[1]).unwrap();
+        assert_eq!(entry2.event["type"], "output");
+        assert_eq!(entry2.event["text"], "Hello world");
+    }
+
+    #[test]
+    fn test_read_log_parses_written_events() {
+        let tmp = tempdir().unwrap();
+        let root = tmp.path();
+
+        let mut writer =
+            AgentLogWriter::new(root, "42_story_foo", "coder-1", "sess-002").unwrap();
+
+        let events = vec![
+            AgentEvent::Status {
+                story_id: "42_story_foo".to_string(),
+                agent_name: "coder-1".to_string(),
+                status: "running".to_string(),
+            },
+            AgentEvent::Output {
+                story_id: "42_story_foo".to_string(),
+                agent_name: "coder-1".to_string(),
+                text: "Processing...".to_string(),
+            },
+            AgentEvent::AgentJson {
+                story_id: "42_story_foo".to_string(),
+                agent_name: "coder-1".to_string(),
+                data: serde_json::json!({"type": "tool_use", "name": "read_file"}),
+            },
+            AgentEvent::Done {
+                story_id: "42_story_foo".to_string(),
+                agent_name: "coder-1".to_string(),
+                session_id: Some("sess-002".to_string()),
+            },
+        ];
+
+        for event in &events {
+            writer.write_event(event).unwrap();
+        }
+
+        let path = log_file_path(root, "42_story_foo", "coder-1", "sess-002");
+        let entries = read_log(&path).unwrap();
+        assert_eq!(entries.len(), 4, "Should read back all 4 events");
+
+        // Verify event types round-trip correctly
+        assert_eq!(entries[0].event["type"], "status");
+        assert_eq!(entries[1].event["type"], "output");
+        assert_eq!(entries[2].event["type"], "agent_json");
+        assert_eq!(entries[3].event["type"], "done");
+    }
+
+    #[test]
+    fn test_separate_sessions_produce_separate_files() {
+        let tmp = tempdir().unwrap();
+        let root = tmp.path();
+
+        let mut writer1 =
+            AgentLogWriter::new(root, "42_story_foo", "coder-1", "sess-aaa").unwrap();
+        let mut writer2 =
+            AgentLogWriter::new(root, "42_story_foo", "coder-1", "sess-bbb").unwrap();
+
+        writer1
+            .write_event(&AgentEvent::Output {
+                story_id: "42_story_foo".to_string(),
+                agent_name: "coder-1".to_string(),
+                text: "from session aaa".to_string(),
+            })
+            .unwrap();
+
+        writer2
+            .write_event(&AgentEvent::Output {
+                story_id: "42_story_foo".to_string(),
+                agent_name: "coder-1".to_string(),
+                text: "from session bbb".to_string(),
+            })
+            .unwrap();
+
+        let path1 = log_file_path(root, "42_story_foo", "coder-1", "sess-aaa");
+        let path2 = log_file_path(root, "42_story_foo", "coder-1", "sess-bbb");
+
+        assert_ne!(path1, path2, "Different sessions should use different files");
+
+        let entries1 = read_log(&path1).unwrap();
+        let entries2 = read_log(&path2).unwrap();
+
+        assert_eq!(entries1.len(), 1);
+        assert_eq!(entries2.len(), 1);
+        assert_eq!(entries1[0].event["text"], "from session aaa");
+        assert_eq!(entries2[0].event["text"], "from session bbb");
+    }
+
+    #[test]
+    fn test_find_latest_log_returns_most_recent() {
+        let tmp = tempdir().unwrap();
+        let root = tmp.path();
+
+        // Create two log files with a small delay
+        let mut writer1 =
+            AgentLogWriter::new(root, "42_story_foo", "coder-1", "sess-old").unwrap();
+        writer1
+            .write_event(&AgentEvent::Output {
+                story_id: "42_story_foo".to_string(),
+                agent_name: "coder-1".to_string(),
+                text: "old".to_string(),
+            })
+            .unwrap();
+        drop(writer1);
+
+        // Touch the second file to ensure it's newer
+        std::thread::sleep(std::time::Duration::from_millis(50));
+
+        let mut writer2 =
+            AgentLogWriter::new(root, "42_story_foo", "coder-1", "sess-new").unwrap();
+        writer2
+            .write_event(&AgentEvent::Output {
+                story_id: "42_story_foo".to_string(),
+                agent_name: "coder-1".to_string(),
+                text: "new".to_string(),
+            })
+            .unwrap();
+        drop(writer2);
+
+        let latest = find_latest_log(root, "42_story_foo", "coder-1").unwrap();
+        assert!(
+            latest.to_string_lossy().contains("sess-new"),
+            "Should find the newest log file, got: {}",
+            latest.display()
+        );
+    }
+
+    #[test]
+    fn test_find_latest_log_returns_none_for_missing_dir() {
+        let tmp = tempdir().unwrap();
+        let result = find_latest_log(tmp.path(), "nonexistent", "coder-1");
+        assert!(result.is_none());
+    }
+
+    #[test]
+    fn test_log_files_persist_on_disk() {
+        let tmp = tempdir().unwrap();
+        let root = tmp.path();
+
+        let path = {
+            let mut writer =
+                AgentLogWriter::new(root, "42_story_foo", "coder-1", "sess-persist").unwrap();
+            writer
+                .write_event(&AgentEvent::Status {
+                    story_id: "42_story_foo".to_string(),
+                    agent_name: "coder-1".to_string(),
+                    status: "running".to_string(),
+                })
+                .unwrap();
+            log_file_path(root, "42_story_foo", "coder-1", "sess-persist")
+            // writer is dropped here
+        };
+
+        // File should still exist and be readable
+        assert!(path.exists(), "Log file should persist after writer is dropped");
+        let entries = read_log(&path).unwrap();
+        assert_eq!(entries.len(), 1);
+        assert_eq!(entries[0].event["type"], "status");
+    }
+}

server/src/agents.rs

@@ -1,3 +1,4 @@
+use crate::agent_log::AgentLogWriter;
 use crate::config::ProjectConfig;
 use crate::worktree::{self, WorktreeInfo};
 use portable_pty::{CommandBuilder, PtySize, native_pty_system};
@@ -113,6 +114,8 @@ pub struct AgentInfo {
     pub worktree_path: Option<String>,
     pub base_branch: Option<String>,
     pub completion: Option<CompletionReport>,
+    /// UUID identifying the persistent log file for this session.
+    pub log_session_id: Option<String>,
 }
 
 struct StoryAgent {
@@ -128,6 +131,8 @@ struct StoryAgent {
     completion: Option<CompletionReport>,
     /// Project root, stored for pipeline advancement after completion.
     project_root: Option<PathBuf>,
+    /// UUID identifying the log file for this session.
+    log_session_id: Option<String>,
 }
 
 /// Build an `AgentInfo` snapshot from a `StoryAgent` map entry.
@@ -146,6 +151,7 @@ fn agent_info_from_entry(story_id: &str, agent: &StoryAgent) -> AgentInfo {
             .as_ref()
             .map(|wt| wt.base_branch.clone()),
         completion: agent.completion.clone(),
+        log_session_id: agent.log_session_id.clone(),
     }
 }
 
@@ -210,6 +216,23 @@ impl AgentPool {
 
         let event_log: Arc<Mutex<Vec<AgentEvent>>> = Arc::new(Mutex::new(Vec::new()));
 
+        // Generate a unique session ID for the persistent log file.
+        let log_session_id = uuid::Uuid::new_v4().to_string();
+
+        // Create persistent log writer.
+        let log_writer = match AgentLogWriter::new(
+            project_root,
+            story_id,
+            &resolved_name,
+            &log_session_id,
+        ) {
+            Ok(w) => Some(Arc::new(Mutex::new(w))),
+            Err(e) => {
+                eprintln!("[agents] Failed to create log writer for {story_id}:{resolved_name}: {e}");
+                None
+            }
+        };
+
         // Register as pending
         {
             let mut agents = self.agents.lock().map_err(|e| e.to_string())?;
@@ -225,6 +248,7 @@ impl AgentPool {
                     event_log: event_log.clone(),
                     completion: None,
                     project_root: Some(project_root.to_path_buf()),
+                    log_session_id: Some(log_session_id.clone()),
                 },
             );
         }
@@ -267,6 +291,7 @@ impl AgentPool {
         let key_clone = key.clone();
         let log_clone = event_log.clone();
         let port_for_task = self.port;
+        let log_writer_clone = log_writer.clone();
 
         let handle = tokio::spawn(async move {
             let _ = tx_clone.send(AgentEvent::Status {
@@ -277,6 +302,7 @@ impl AgentPool {
 
             match run_agent_pty_streaming(
                 &sid, &aname, &command, &args, &prompt, &cwd, &tx_clone, &log_clone,
+                log_writer_clone,
             )
             .await
             {
@@ -324,6 +350,7 @@ impl AgentPool {
             worktree_path: Some(wt_path_str),
             base_branch: Some(wt_info.base_branch.clone()),
             completion: None,
+            log_session_id: Some(log_session_id),
         })
     }
 
@@ -487,6 +514,7 @@ impl AgentPool {
                                 worktree_path: None,
                                 base_branch: None,
                                 completion: None,
+                                log_session_id: None,
                             }
                         });
                     }
@@ -962,6 +990,22 @@ impl AgentPool {
         state.get_project_root()
     }
 
+    /// Get the log session ID and project root for an agent, if available.
+    ///
+    /// Used by MCP tools to find the persistent log file for a completed agent.
+    pub fn get_log_info(
+        &self,
+        story_id: &str,
+        agent_name: &str,
+    ) -> Option<(String, PathBuf)> {
+        let key = composite_key(story_id, agent_name);
+        let agents = self.agents.lock().ok()?;
+        let agent = agents.get(&key)?;
+        let session_id = agent.log_session_id.clone()?;
+        let project_root = agent.project_root.clone()?;
+        Some((session_id, project_root))
+    }
+
     /// Test helper: inject a pre-built agent entry so unit tests can exercise
     /// wait/subscribe logic without spawning a real process.
     #[cfg(test)]
@@ -986,6 +1030,7 @@ impl AgentPool {
                 event_log: Arc::new(Mutex::new(Vec::new())),
                 completion: None,
                 project_root: None,
+                log_session_id: None,
             },
         );
         tx
@@ -1020,6 +1065,7 @@ impl AgentPool {
                 event_log: Arc::new(Mutex::new(Vec::new())),
                 completion: None,
                 project_root: None,
+                log_session_id: None,
             },
         );
         tx
@@ -1279,6 +1325,7 @@ impl AgentPool {
                 event_log: Arc::new(Mutex::new(Vec::new())),
                 completion: Some(completion),
                 project_root: Some(project_root),
+                log_session_id: None,
             },
         );
         tx
@@ -2078,6 +2125,7 @@ async fn run_agent_pty_streaming(
     cwd: &str,
     tx: &broadcast::Sender<AgentEvent>,
     event_log: &Arc<Mutex<Vec<AgentEvent>>>,
+    log_writer: Option<Arc<Mutex<AgentLogWriter>>>,
 ) -> Result<Option<String>, String> {
     let sid = story_id.to_string();
     let aname = agent_name.to_string();
@@ -2089,21 +2137,38 @@ async fn run_agent_pty_streaming(
     let event_log = event_log.clone();
 
     tokio::task::spawn_blocking(move || {
-        run_agent_pty_blocking(&sid, &aname, &cmd, &args, &prompt, &cwd, &tx, &event_log)
+        run_agent_pty_blocking(
+            &sid,
+            &aname,
+            &cmd,
+            &args,
+            &prompt,
+            &cwd,
+            &tx,
+            &event_log,
+            log_writer.as_deref(),
+        )
     })
     .await
     .map_err(|e| format!("Agent task panicked: {e}"))?
 }
 
-/// Helper to send an event to both broadcast and event log.
+/// Helper to send an event to broadcast, event log, and optional persistent log file.
 fn emit_event(
     event: AgentEvent,
     tx: &broadcast::Sender<AgentEvent>,
     event_log: &Mutex<Vec<AgentEvent>>,
+    log_writer: Option<&Mutex<AgentLogWriter>>,
 ) {
     if let Ok(mut log) = event_log.lock() {
         log.push(event.clone());
     }
+    if let Some(writer) = log_writer
+        && let Ok(mut w) = writer.lock()
+        && let Err(e) = w.write_event(&event)
+    {
+        eprintln!("[agent_log] Failed to write event to log file: {e}");
+    }
     let _ = tx.send(event);
 }
 
@@ -2117,6 +2182,7 @@ fn run_agent_pty_blocking(
     cwd: &str,
     tx: &broadcast::Sender<AgentEvent>,
     event_log: &Mutex<Vec<AgentEvent>>,
+    log_writer: Option<&Mutex<AgentLogWriter>>,
 ) -> Result<Option<String>, String> {
     let pty_system = native_pty_system();
 
@@ -2198,6 +2264,7 @@ fn run_agent_pty_blocking(
                     },
                     tx,
                     event_log,
+                    log_writer,
                 );
                 continue;
             }
@@ -2226,6 +2293,7 @@ fn run_agent_pty_blocking(
                                 },
                                 tx,
                                 event_log,
+                                log_writer,
                             );
                         }
                     }
@@ -2243,6 +2311,7 @@ fn run_agent_pty_blocking(
             },
             tx,
             event_log,
+            log_writer,
         );
     }
 
@@ -3514,4 +3583,38 @@ name = "qa"
             "story should be in 2_current/ or 3_qa/ after reconciliation"
         );
     }
+
+    #[test]
+    fn test_emit_event_writes_to_log_writer() {
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path();
+
+        let log_writer =
+            AgentLogWriter::new(root, "42_story_foo", "coder-1", "sess-emit").unwrap();
+        let log_mutex = Mutex::new(log_writer);
+
+        let (tx, _rx) = broadcast::channel::<AgentEvent>(64);
+        let event_log: Mutex<Vec<AgentEvent>> = Mutex::new(Vec::new());
+
+        let event = AgentEvent::Status {
+            story_id: "42_story_foo".to_string(),
+            agent_name: "coder-1".to_string(),
+            status: "running".to_string(),
+        };
+
+        emit_event(event, &tx, &event_log, Some(&log_mutex));
+
+        // Verify event was added to in-memory log
+        let mem_events = event_log.lock().unwrap();
+        assert_eq!(mem_events.len(), 1);
+        drop(mem_events);
+
+        // Verify event was written to the log file
+        let log_path =
+            crate::agent_log::log_file_path(root, "42_story_foo", "coder-1", "sess-emit");
+        let entries = crate::agent_log::read_log(&log_path).unwrap();
+        assert_eq!(entries.len(), 1);
+        assert_eq!(entries[0].event["type"], "status");
+        assert_eq!(entries[0].event["status"], "running");
+    }
 }

server/src/http/mcp.rs

@@ -1016,13 +1016,14 @@ async fn tool_get_agent_output_poll(args: &Value, ctx: &AppContext) -> Result<St
         .and_then(|v| v.as_str())
         .ok_or("Missing required argument: agent_name")?;
 
-    // Drain all accumulated events since the last poll.
-    let drained = ctx.agents.drain_events(story_id, agent_name)?;
-
+    // Try draining in-memory events first.
+    match ctx.agents.drain_events(story_id, agent_name) {
+        Ok(drained) => {
             let done = drained.iter().any(|e| {
                 matches!(
                     e,
-            crate::agents::AgentEvent::Done { .. } | crate::agents::AgentEvent::Error { .. }
+                    crate::agents::AgentEvent::Done { .. }
+                        | crate::agents::AgentEvent::Error { .. }
                 )
             });
 
@@ -1039,6 +1040,78 @@ async fn tool_get_agent_output_poll(args: &Value, ctx: &AppContext) -> Result<St
             }))
             .map_err(|e| format!("Serialization error: {e}"))
         }
+        Err(_) => {
+            // Agent not in memory — fall back to persistent log file.
+            get_agent_output_from_log(story_id, agent_name, ctx)
+        }
+    }
+}
+
+/// Fall back to reading agent output from the persistent log file on disk.
+///
+/// Tries to find the log file via the agent's stored log_session_id first,
+/// then falls back to `find_latest_log` scanning the log directory.
+fn get_agent_output_from_log(
+    story_id: &str,
+    agent_name: &str,
+    ctx: &AppContext,
+) -> Result<String, String> {
+    use crate::agent_log;
+
+    let project_root = ctx.agents.get_project_root(&ctx.state)?;
+
+    // Try to find the log file: first from in-memory agent info, then by scanning.
+    let log_path = ctx
+        .agents
+        .get_log_info(story_id, agent_name)
+        .map(|(session_id, root)| agent_log::log_file_path(&root, story_id, agent_name, &session_id))
+        .filter(|p| p.exists())
+        .or_else(|| agent_log::find_latest_log(&project_root, story_id, agent_name));
+
+    let log_path = match log_path {
+        Some(p) => p,
+        None => {
+            return serde_json::to_string_pretty(&json!({
+                "events": [],
+                "done": true,
+                "event_count": 0,
+                "message": format!("No agent '{agent_name}' for story '{story_id}' and no log file found."),
+                "source": "none",
+            }))
+            .map_err(|e| format!("Serialization error: {e}"));
+        }
+    };
+
+    match agent_log::read_log(&log_path) {
+        Ok(entries) => {
+            let events: Vec<serde_json::Value> = entries
+                .into_iter()
+                .map(|e| {
+                    let mut val = e.event;
+                    if let serde_json::Value::Object(ref mut map) = val {
+                        map.insert(
+                            "timestamp".to_string(),
+                            serde_json::Value::String(e.timestamp),
+                        );
+                    }
+                    val
+                })
+                .collect();
+
+            let count = events.len();
+            serde_json::to_string_pretty(&json!({
+                "events": events,
+                "done": true,
+                "event_count": count,
+                "message": "Events loaded from persistent log file.",
+                "source": "log_file",
+                "log_file": log_path.to_string_lossy(),
+            }))
+            .map_err(|e| format!("Serialization error: {e}"))
+        }
+        Err(e) => Err(format!("Failed to read log file: {e}")),
+    }
+}
 
 fn tool_get_agent_config(ctx: &AppContext) -> Result<String, String> {
     let project_root = ctx.agents.get_project_root(&ctx.state)?;

server/src/main.rs

@@ -1,3 +1,4 @@
+mod agent_log;
 mod agents;
 mod config;
 mod http;