feat: jsonl-session progress

rust/crates/commands/src/lib.rs

@@ -125,8 +125,8 @@ const SLASH_COMMAND_SPECS: &[SlashCommandSpec] = &[
     },
     SlashCommandSpec {
         name: "session",
-        summary: "List or switch managed local sessions",
-        argument_hint: Some("[list|switch <session-id>]"),
+        summary: "List, switch, or fork managed local sessions",
+        argument_hint: Some("[list|switch <session-id>|fork [branch-name]]"),
         resume_supported: false,
     },
 ];
@@ -229,7 +229,7 @@ pub fn resume_supported_slash_commands() -> Vec<&'static SlashCommandSpec> {
 pub fn render_slash_command_help() -> String {
     let mut lines = vec![
         "Slash commands".to_string(),
-        "  [resume] means the command also works with --resume SESSION.json".to_string(),
+        "  [resume] means the command also works with --resume SESSION.jsonl".to_string(),
     ];
     for spec in slash_command_specs() {
         let name = match spec.argument_hint {
@@ -365,12 +365,19 @@ mod tests {
                 target: Some("abc123".to_string())
             })
         );
+        assert_eq!(
+            SlashCommand::parse("/session fork incident-review"),
+            Some(SlashCommand::Session {
+                action: Some("fork".to_string()),
+                target: Some("incident-review".to_string())
+            })
+        );
     }
 
     #[test]
     fn renders_help_from_shared_specs() {
         let help = render_slash_command_help();
-        assert!(help.contains("works with --resume SESSION.json"));
+        assert!(help.contains("works with --resume SESSION.jsonl"));
         assert!(help.contains("/help"));
         assert!(help.contains("/status"));
         assert!(help.contains("/compact"));
@@ -385,7 +392,7 @@ mod tests {
         assert!(help.contains("/diff"));
         assert!(help.contains("/version"));
         assert!(help.contains("/export [file]"));
-        assert!(help.contains("/session [list|switch <session-id>]"));
+        assert!(help.contains("/session [list|switch <session-id>|fork [branch-name]]"));
         assert_eq!(slash_command_specs().len(), 15);
         assert_eq!(resume_supported_slash_commands().len(), 11);
     }
@@ -453,6 +460,12 @@ mod tests {
             CompactionConfig::default()
         )
         .is_none());
+        assert!(handle_slash_command(
+            "/resume session.jsonl",
+            &session,
+            CompactionConfig::default()
+        )
+        .is_none());
         assert!(handle_slash_command("/config", &session, CompactionConfig::default()).is_none());
         assert!(
             handle_slash_command("/config env", &session, CompactionConfig::default()).is_none()

rust/crates/runtime/src/conversation.rs

@@ -286,6 +286,11 @@ where
         &self.session
     }
 
+    #[must_use]
+    pub fn fork_session(&self, branch_name: Option<String>) -> Session {
+        self.session.fork(branch_name)
+    }
+
     #[must_use]
     pub fn into_session(self) -> Session {
         self.session
@@ -838,6 +843,35 @@ mod tests {
         assert_eq!(restored.session_id, runtime.session().session_id);
     }
 
+    #[test]
+    fn forks_runtime_session_without_mutating_original() {
+        let mut session = Session::new();
+        session
+            .push_user_text("branch me")
+            .expect("message should append");
+
+        let runtime = ConversationRuntime::new(
+            session.clone(),
+            ScriptedApiClient { call_count: 0 },
+            StaticToolExecutor::new(),
+            PermissionPolicy::new(PermissionMode::DangerFullAccess),
+            vec!["system".to_string()],
+        );
+
+        let forked = runtime.fork_session(Some("alt-path".to_string()));
+
+        assert_eq!(forked.messages, session.messages);
+        assert_ne!(forked.session_id, session.session_id);
+        assert_eq!(
+            forked
+                .fork
+                .as_ref()
+                .map(|fork| (fork.parent_session_id.as_str(), fork.branch_name.as_deref())),
+            Some((session.session_id.as_str(), Some("alt-path")))
+        );
+        assert!(runtime.session().fork.is_none());
+    }
+
     fn temp_session_path(label: &str) -> PathBuf {
         let nanos = SystemTime::now()
             .duration_since(UNIX_EPOCH)

rust/crates/runtime/src/lib.rs

@@ -78,6 +78,7 @@ pub use remote::{
 };
 pub use session::{
     ContentBlock, ConversationMessage, MessageRole, Session, SessionCompaction, SessionError,
+    SessionFork,
 };
 pub use usage::{
     format_usd, pricing_for_model, ModelPricing, TokenUsage, UsageCostEstimate, UsageTracker,

rust/crates/runtime/src/session.rs

@@ -54,6 +54,12 @@ pub struct SessionCompaction {
     pub summary: String,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct SessionFork {
+    pub parent_session_id: String,
+    pub branch_name: Option<String>,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 struct SessionPersistence {
     path: PathBuf,
@@ -67,6 +73,7 @@ pub struct Session {
     pub updated_at_ms: u64,
     pub messages: Vec<ConversationMessage>,
     pub compaction: Option<SessionCompaction>,
+    pub fork: Option<SessionFork>,
     persistence: Option<SessionPersistence>,
 }
 
@@ -78,6 +85,7 @@ impl PartialEq for Session {
             && self.updated_at_ms == other.updated_at_ms
             && self.messages == other.messages
             && self.compaction == other.compaction
+            && self.fork == other.fork
     }
 }
 
@@ -125,6 +133,7 @@ impl Session {
             updated_at_ms: now,
             messages: Vec::new(),
             compaction: None,
+            fork: None,
             persistence: None,
         }
     }
@@ -178,6 +187,24 @@ impl Session {
         });
     }
 
+    #[must_use]
+    pub fn fork(&self, branch_name: Option<String>) -> Self {
+        let now = current_time_millis();
+        Self {
+            version: self.version,
+            session_id: generate_session_id(),
+            created_at_ms: now,
+            updated_at_ms: now,
+            messages: self.messages.clone(),
+            compaction: self.compaction.clone(),
+            fork: Some(SessionFork {
+                parent_session_id: self.session_id.clone(),
+                branch_name: normalize_optional_string(branch_name),
+            }),
+            persistence: None,
+        }
+    }
+
     #[must_use]
     pub fn to_json(&self) -> JsonValue {
         let mut object = BTreeMap::new();
@@ -209,6 +236,9 @@ impl Session {
         if let Some(compaction) = &self.compaction {
             object.insert("compaction".to_string(), compaction.to_json());
         }
+        if let Some(fork) = &self.fork {
+            object.insert("fork".to_string(), fork.to_json());
+        }
         JsonValue::Object(object)
     }
 
@@ -249,6 +279,7 @@ impl Session {
             .get("compaction")
             .map(SessionCompaction::from_json)
             .transpose()?;
+        let fork = object.get("fork").map(SessionFork::from_json).transpose()?;
         Ok(Self {
             version,
             session_id,
@@ -256,6 +287,7 @@ impl Session {
             updated_at_ms,
             messages,
             compaction,
+            fork,
             persistence: None,
         })
     }
@@ -267,6 +299,7 @@ impl Session {
         let mut updated_at_ms = None;
         let mut messages = Vec::new();
         let mut compaction = None;
+        let mut fork = None;
 
         for (line_number, raw_line) in contents.lines().enumerate() {
             let line = raw_line.trim();
@@ -300,6 +333,7 @@ impl Session {
                     session_id = Some(required_string(object, "session_id")?);
                     created_at_ms = Some(required_u64(object, "created_at_ms")?);
                     updated_at_ms = Some(required_u64(object, "updated_at_ms")?);
+                    fork = object.get("fork").map(SessionFork::from_json).transpose()?;
                 }
                 "message" => {
                     let message_value = object.get("message").ok_or_else(|| {
@@ -332,6 +366,7 @@ impl Session {
             updated_at_ms: updated_at_ms.unwrap_or(created_at_ms.unwrap_or(now)),
             messages,
             compaction,
+            fork,
             persistence: None,
         })
     }
@@ -389,6 +424,9 @@ impl Session {
             "updated_at_ms".to_string(),
             JsonValue::Number(i64_from_u64(self.updated_at_ms, "updated_at_ms")),
         );
+        if let Some(fork) = &self.fork {
+            object.insert("fork".to_string(), fork.to_json());
+        }
         JsonValue::Object(object)
     }
 
@@ -634,6 +672,37 @@ impl SessionCompaction {
     }
 }
 
+impl SessionFork {
+    #[must_use]
+    pub fn to_json(&self) -> JsonValue {
+        let mut object = BTreeMap::new();
+        object.insert(
+            "parent_session_id".to_string(),
+            JsonValue::String(self.parent_session_id.clone()),
+        );
+        if let Some(branch_name) = &self.branch_name {
+            object.insert(
+                "branch_name".to_string(),
+                JsonValue::String(branch_name.clone()),
+            );
+        }
+        JsonValue::Object(object)
+    }
+
+    fn from_json(value: &JsonValue) -> Result<Self, SessionError> {
+        let object = value
+            .as_object()
+            .ok_or_else(|| SessionError::Format("fork metadata must be an object".to_string()))?;
+        Ok(Self {
+            parent_session_id: required_string(object, "parent_session_id")?,
+            branch_name: object
+                .get("branch_name")
+                .and_then(JsonValue::as_str)
+                .map(ToOwned::to_owned),
+        })
+    }
+}
+
 fn message_record(message: &ConversationMessage) -> JsonValue {
     let mut object = BTreeMap::new();
     object.insert("type".to_string(), JsonValue::String("message".to_string()));
@@ -723,6 +792,17 @@ fn i64_from_usize(value: usize, key: &str) -> i64 {
     i64::try_from(value).unwrap_or_else(|_| panic!("{key} out of range for JSON number"))
 }
 
+fn normalize_optional_string(value: Option<String>) -> Option<String> {
+    value.and_then(|value| {
+        let trimmed = value.trim();
+        if trimmed.is_empty() {
+            None
+        } else {
+            Some(trimmed.to_string())
+        }
+    })
+}
+
 fn current_time_millis() -> u64 {
     SystemTime::now()
         .duration_since(UNIX_EPOCH)
@@ -815,7 +895,7 @@ fn cleanup_rotated_logs(path: &Path) -> Result<(), SessionError> {
 mod tests {
     use super::{
         cleanup_rotated_logs, rotate_session_file_if_needed, ContentBlock, ConversationMessage,
-        MessageRole, Session,
+        MessageRole, Session, SessionFork,
     };
     use crate::json::JsonValue;
     use crate::usage::TokenUsage;
@@ -938,6 +1018,35 @@ mod tests {
         assert!(compaction.summary.contains("summarized"));
     }
 
+    #[test]
+    fn forks_sessions_with_branch_metadata_and_persists_it() {
+        let path = temp_session_path("fork");
+        let mut session = Session::new();
+        session
+            .push_user_text("before fork")
+            .expect("message should append");
+
+        let forked = session
+            .fork(Some("investigation".to_string()))
+            .with_persistence_path(path.clone());
+        forked
+            .save_to_path(&path)
+            .expect("forked session should save");
+
+        let restored = Session::load_from_path(&path).expect("forked session should load");
+        fs::remove_file(&path).expect("temp file should be removable");
+
+        assert_ne!(restored.session_id, session.session_id);
+        assert_eq!(
+            restored.fork,
+            Some(SessionFork {
+                parent_session_id: session.session_id,
+                branch_name: Some("investigation".to_string()),
+            })
+        );
+        assert_eq!(restored.messages, forked.messages);
+    }
+
     #[test]
     fn rotates_and_cleans_up_large_session_logs() {
         let path = temp_session_path("rotation");

rust/crates/rusty-claude-cli/src/main.rs

@@ -47,6 +47,8 @@ const DEFAULT_OAUTH_CALLBACK_PORT: u16 = 4545;
 const VERSION: &str = env!("CARGO_PKG_VERSION");
 const BUILD_TARGET: Option<&str> = option_env!("TARGET");
 const GIT_SHA: Option<&str> = option_env!("GIT_SHA");
+const PRIMARY_SESSION_EXTENSION: &str = "jsonl";
+const LEGACY_SESSION_EXTENSION: &str = "json";
 
 type AllowedToolSet = BTreeSet<String>;
 
@@ -589,7 +591,19 @@ fn print_version() {
 }
 
 fn resume_session(session_path: &Path, commands: &[String]) {
-    let session = match Session::load_from_path(session_path) {
+    let resolved_path = if session_path.exists() {
+        session_path.to_path_buf()
+    } else {
+        match resolve_session_reference(&session_path.display().to_string()) {
+            Ok(handle) => handle.path,
+            Err(error) => {
+                eprintln!("failed to restore session: {error}");
+                std::process::exit(1);
+            }
+        }
+    };
+
+    let session = match Session::load_from_path(&resolved_path) {
         Ok(session) => session,
         Err(error) => {
             eprintln!("failed to restore session: {error}");
@@ -600,7 +614,7 @@ fn resume_session(session_path: &Path, commands: &[String]) {
     if commands.is_empty() {
         println!(
             "Restored session from {} ({} messages).",
-            session_path.display(),
+            resolved_path.display(),
             session.messages.len()
         );
         return;
@@ -612,7 +626,7 @@ fn resume_session(session_path: &Path, commands: &[String]) {
             eprintln!("unsupported resumed command: {raw_command}");
             std::process::exit(2);
         };
-        match run_resume_command(session_path, &session, &command) {
+        match run_resume_command(&resolved_path, &session, &command) {
             Ok(ResumeCommandOutcome {
                 session: next_session,
                 message,
@@ -973,6 +987,8 @@ struct ManagedSessionSummary {
     path: PathBuf,
     modified_epoch_secs: u64,
     message_count: usize,
+    parent_session_id: Option<String>,
+    branch_name: Option<String>,
 }
 
 struct LiveCli {
@@ -1433,8 +1449,41 @@ impl LiveCli {
                 );
                 Ok(true)
             }
+            Some("fork") => {
+                let forked = self.runtime.fork_session(target.map(ToOwned::to_owned));
+                let parent_session_id = self.session.id.clone();
+                let handle = create_managed_session_handle(&forked.session_id)?;
+                let branch_name = forked
+                    .fork
+                    .as_ref()
+                    .and_then(|fork| fork.branch_name.clone());
+                let forked = forked.with_persistence_path(handle.path.clone());
+                let message_count = forked.messages.len();
+                forked.save_to_path(&handle.path)?;
+                self.runtime = build_runtime(
+                    forked,
+                    self.model.clone(),
+                    self.system_prompt.clone(),
+                    true,
+                    true,
+                    self.allowed_tools.clone(),
+                    self.permission_mode,
+                )?;
+                self.session = handle;
+                println!(
+                    "Session forked\n  Parent session   {}\n  Active session   {}\n  Branch           {}\n  File             {}\n  Messages         {}",
+                    parent_session_id,
+                    self.session.id,
+                    branch_name.as_deref().unwrap_or("(unnamed)"),
+                    self.session.path.display(),
+                    message_count,
+                );
+                Ok(true)
+            }
             Some(other) => {
-                println!("Unknown /session action '{other}'. Use /session list or /session switch <session-id>.");
+                println!(
+                    "Unknown /session action '{other}'. Use /session list, /session switch <session-id>, or /session fork [branch-name]."
+                );
                 Ok(false)
             }
         }
@@ -1471,34 +1520,57 @@ fn create_managed_session_handle(
     session_id: &str,
 ) -> Result<SessionHandle, Box<dyn std::error::Error>> {
     let id = session_id.to_string();
-    let path = sessions_dir()?.join(format!("{id}.json"));
+    let path = sessions_dir()?.join(format!("{id}.{PRIMARY_SESSION_EXTENSION}"));
     Ok(SessionHandle { id, path })
 }
 
 fn resolve_session_reference(reference: &str) -> Result<SessionHandle, Box<dyn std::error::Error>> {
     let direct = PathBuf::from(reference);
+    let looks_like_path = direct.extension().is_some() || direct.components().count() > 1;
     let path = if direct.exists() {
         direct
+    } else if looks_like_path {
+        return Err(format!("session not found: {reference}").into());
     } else {
-        sessions_dir()?.join(format!("{reference}.json"))
+        resolve_managed_session_path(reference)?
     };
-    if !path.exists() {
-        return Err(format!("session not found: {reference}").into());
-    }
     let id = path
-        .file_stem()
+        .file_name()
         .and_then(|value| value.to_str())
+        .and_then(|name| {
+            name.strip_suffix(&format!(".{PRIMARY_SESSION_EXTENSION}"))
+                .or_else(|| name.strip_suffix(&format!(".{LEGACY_SESSION_EXTENSION}")))
+        })
         .unwrap_or(reference)
         .to_string();
     Ok(SessionHandle { id, path })
 }
 
+fn resolve_managed_session_path(session_id: &str) -> Result<PathBuf, Box<dyn std::error::Error>> {
+    let directory = sessions_dir()?;
+    for extension in [PRIMARY_SESSION_EXTENSION, LEGACY_SESSION_EXTENSION] {
+        let path = directory.join(format!("{session_id}.{extension}"));
+        if path.exists() {
+            return Ok(path);
+        }
+    }
+    Err(format!("session not found: {session_id}").into())
+}
+
+fn is_managed_session_file(path: &Path) -> bool {
+    path.extension()
+        .and_then(|ext| ext.to_str())
+        .is_some_and(|extension| {
+            extension == PRIMARY_SESSION_EXTENSION || extension == LEGACY_SESSION_EXTENSION
+        })
+}
+
 fn list_managed_sessions() -> Result<Vec<ManagedSessionSummary>, Box<dyn std::error::Error>> {
     let mut sessions = Vec::new();
     for entry in fs::read_dir(sessions_dir()?)? {
         let entry = entry?;
         let path = entry.path();
-        if path.extension().and_then(|ext| ext.to_str()) != Some("json") {
+        if !is_managed_session_file(&path) {
             continue;
         }
         let metadata = entry.metadata()?;
@@ -1508,8 +1580,23 @@ fn list_managed_sessions() -> Result<Vec<ManagedSessionSummary>, Box<dyn std::er
             .and_then(|time| time.duration_since(UNIX_EPOCH).ok())
             .map(|duration| duration.as_secs())
             .unwrap_or_default();
-        let (id, message_count) = Session::load_from_path(&path)
-            .map(|session| (session.session_id, session.messages.len()))
+        let (id, message_count, parent_session_id, branch_name) = Session::load_from_path(&path)
+            .map(|session| {
+                let parent_session_id = session
+                    .fork
+                    .as_ref()
+                    .map(|fork| fork.parent_session_id.clone());
+                let branch_name = session
+                    .fork
+                    .as_ref()
+                    .and_then(|fork| fork.branch_name.clone());
+                (
+                    session.session_id,
+                    session.messages.len(),
+                    parent_session_id,
+                    branch_name,
+                )
+            })
             .unwrap_or_else(|_| {
                 (
                     path.file_stem()
@@ -1517,6 +1604,8 @@ fn list_managed_sessions() -> Result<Vec<ManagedSessionSummary>, Box<dyn std::er
                         .unwrap_or("unknown")
                         .to_string(),
                     0,
+                    None,
+                    None,
                 )
             });
         sessions.push(ManagedSessionSummary {
@@ -1524,6 +1613,8 @@ fn list_managed_sessions() -> Result<Vec<ManagedSessionSummary>, Box<dyn std::er
             path,
             modified_epoch_secs,
             message_count,
+            parent_session_id,
+            branch_name,
         });
     }
     sessions.sort_by(|left, right| right.modified_epoch_secs.cmp(&left.modified_epoch_secs));
@@ -1546,11 +1637,23 @@ fn render_session_list(active_session_id: &str) -> Result<String, Box<dyn std::e
         } else {
             "○ saved"
         };
+        let lineage = match (
+            session.branch_name.as_deref(),
+            session.parent_session_id.as_deref(),
+        ) {
+            (Some(branch_name), Some(parent_session_id)) => {
+                format!(" branch={branch_name} from={parent_session_id}")
+            }
+            (None, Some(parent_session_id)) => format!(" from={parent_session_id}"),
+            (Some(branch_name), None) => format!(" branch={branch_name}"),
+            (None, None) => String::new(),
+        };
         lines.push(format!(
-            "  {id:<20} {marker:<10} msgs={msgs:<4} modified={modified} path={path}",
+            "  {id:<20} {marker:<10} msgs={msgs:<4} modified={modified}{lineage} path={path}",
             id = session.id,
             msgs = session.message_count,
             modified = session.modified_epoch_secs,
+            lineage = lineage,
             path = session.path.display(),
         ));
     }
@@ -2754,7 +2857,7 @@ fn print_help_to(out: &mut impl Write) -> io::Result<()> {
     writeln!(out, "      Shorthand non-interactive prompt mode")?;
     writeln!(
         out,
-        "  claw --resume SESSION.json [/status] [/compact] [...]"
+        "  claw --resume SESSION.jsonl [/status] [/compact] [...]"
     )?;
     writeln!(
         out,
@@ -2814,7 +2917,7 @@ fn print_help_to(out: &mut impl Write) -> io::Result<()> {
     )?;
     writeln!(
         out,
-        "  claw --resume session.json /status /diff /export notes.txt"
+        "  claw --resume session.jsonl /status /diff /export notes.txt"
     )?;
     writeln!(out, "  claw login")?;
     writeln!(out, "  claw init")?;
@@ -2828,18 +2931,23 @@ fn print_help() {
 #[cfg(test)]
 mod tests {
     use super::{
-        filter_tool_specs, format_compact_report, format_cost_report, format_model_report,
-        format_model_switch_report, format_permissions_report, format_permissions_switch_report,
-        format_resume_report, format_status_report, format_tool_call_start, format_tool_result,
+        create_managed_session_handle, filter_tool_specs, format_compact_report,
+        format_cost_report, format_model_report, format_model_switch_report,
+        format_permissions_report, format_permissions_switch_report, format_resume_report,
+        format_status_report, format_tool_call_start, format_tool_result,
         normalize_permission_mode, parse_args, parse_git_status_metadata, print_help_to,
         push_output_block, render_config_report, render_memory_report, render_repl_help,
-        resolve_model_alias, response_to_events, resume_supported_slash_commands, status_context,
-        CliAction, CliOutputFormat, SlashCommand, StatusUsage, DEFAULT_MODEL,
+        resolve_model_alias, resolve_session_reference, response_to_events,
+        resume_supported_slash_commands, status_context, CliAction, CliOutputFormat, SlashCommand,
+        StatusUsage, DEFAULT_MODEL,
     };
     use api::{MessageResponse, OutputContentBlock, Usage};
-    use runtime::{AssistantEvent, ContentBlock, ConversationMessage, MessageRole, PermissionMode};
+    use runtime::{
+        AssistantEvent, ContentBlock, ConversationMessage, MessageRole, PermissionMode, Session,
+    };
     use serde_json::json;
     use std::path::PathBuf;
+    use std::sync::{Mutex, OnceLock};
 
     #[test]
     fn defaults_to_repl_when_no_args() {
@@ -3013,13 +3121,13 @@ mod tests {
     fn parses_resume_flag_with_slash_command() {
         let args = vec![
             "--resume".to_string(),
-            "session.json".to_string(),
+            "session.jsonl".to_string(),
             "/compact".to_string(),
         ];
         assert_eq!(
             parse_args(&args).expect("args should parse"),
             CliAction::ResumeSession {
-                session_path: PathBuf::from("session.json"),
+                session_path: PathBuf::from("session.jsonl"),
                 commands: vec!["/compact".to_string()],
             }
         );
@@ -3029,7 +3137,7 @@ mod tests {
     fn parses_resume_flag_with_multiple_slash_commands() {
         let args = vec![
             "--resume".to_string(),
-            "session.json".to_string(),
+            "session.jsonl".to_string(),
             "/status".to_string(),
             "/compact".to_string(),
             "/cost".to_string(),
@@ -3037,7 +3145,7 @@ mod tests {
         assert_eq!(
             parse_args(&args).expect("args should parse"),
             CliAction::ResumeSession {
-                session_path: PathBuf::from("session.json"),
+                session_path: PathBuf::from("session.jsonl"),
                 commands: vec![
                     "/status".to_string(),
                     "/compact".to_string(),
@@ -3065,7 +3173,7 @@ mod tests {
     fn shared_help_uses_resume_annotation_copy() {
         let help = commands::render_slash_command_help();
         assert!(help.contains("Slash commands"));
-        assert!(help.contains("works with --resume SESSION.json"));
+        assert!(help.contains("works with --resume SESSION.jsonl"));
     }
 
     #[test]
@@ -3085,7 +3193,7 @@ mod tests {
         assert!(help.contains("/diff"));
         assert!(help.contains("/version"));
         assert!(help.contains("/export [file]"));
-        assert!(help.contains("/session [list|switch <session-id>]"));
+        assert!(help.contains("/session [list|switch <session-id>|fork [branch-name]]"));
         assert!(help.contains("/exit"));
     }
 
@@ -3106,9 +3214,9 @@ mod tests {
 
     #[test]
     fn resume_report_uses_sectioned_layout() {
-        let report = format_resume_report("session.json", 14, 6);
+        let report = format_resume_report("session.jsonl", 14, 6);
         assert!(report.contains("Session resumed"));
-        assert!(report.contains("Session file     session.json"));
+        assert!(report.contains("Session file     session.jsonl"));
         assert!(report.contains("Messages         14"));
         assert!(report.contains("Turns            6"));
     }
@@ -3210,7 +3318,7 @@ mod tests {
             "workspace-write",
             &super::StatusContext {
                 cwd: PathBuf::from("/tmp/project"),
-                session_path: Some(PathBuf::from("session.json")),
+                session_path: Some(PathBuf::from("session.jsonl")),
                 loaded_config_files: 2,
                 discovered_config_files: 3,
                 memory_file_count: 4,
@@ -3227,7 +3335,7 @@ mod tests {
         assert!(status.contains("Cwd              /tmp/project"));
         assert!(status.contains("Project root     /tmp"));
         assert!(status.contains("Git branch       main"));
-        assert!(status.contains("Session          session.json"));
+        assert!(status.contains("Session          session.jsonl"));
         assert!(status.contains("Config files     loaded 2/3"));
         assert!(status.contains("Memory files     4"));
     }
@@ -3302,9 +3410,9 @@ mod tests {
     #[test]
     fn parses_resume_and_config_slash_commands() {
         assert_eq!(
-            SlashCommand::parse("/resume saved-session.json"),
+            SlashCommand::parse("/resume saved-session.jsonl"),
             Some(SlashCommand::Resume {
-                session_path: Some("saved-session.json".to_string())
+                session_path: Some("saved-session.jsonl".to_string())
             })
         );
         assert_eq!(
@@ -3323,6 +3431,65 @@ mod tests {
         );
         assert_eq!(SlashCommand::parse("/memory"), Some(SlashCommand::Memory));
         assert_eq!(SlashCommand::parse("/init"), Some(SlashCommand::Init));
+        assert_eq!(
+            SlashCommand::parse("/session fork incident-review"),
+            Some(SlashCommand::Session {
+                action: Some("fork".to_string()),
+                target: Some("incident-review".to_string())
+            })
+        );
+    }
+
+    #[test]
+    fn help_mentions_jsonl_resume_examples() {
+        let mut help = Vec::new();
+        print_help_to(&mut help).expect("help should render");
+        let help = String::from_utf8(help).expect("help should be utf8");
+        assert!(help.contains("claw --resume SESSION.jsonl"));
+        assert!(help.contains("claw --resume session.jsonl /status /diff /export notes.txt"));
+    }
+
+    #[test]
+    fn managed_sessions_default_to_jsonl_and_resolve_legacy_json() {
+        let _guard = cwd_lock().lock().expect("cwd lock");
+        let workspace = temp_workspace("session-resolution");
+        std::fs::create_dir_all(&workspace).expect("workspace should create");
+        let previous = std::env::current_dir().expect("cwd");
+        std::env::set_current_dir(&workspace).expect("switch cwd");
+
+        let handle = create_managed_session_handle("session-alpha").expect("jsonl handle");
+        assert!(handle.path.ends_with("session-alpha.jsonl"));
+
+        let legacy_path = workspace.join(".claude/sessions/legacy.json");
+        std::fs::create_dir_all(
+            legacy_path
+                .parent()
+                .expect("legacy path should have parent directory"),
+        )
+        .expect("session dir should exist");
+        Session::new()
+            .with_persistence_path(legacy_path.clone())
+            .save_to_path(&legacy_path)
+            .expect("legacy session should save");
+
+        let resolved = resolve_session_reference("legacy").expect("legacy session should resolve");
+        assert_eq!(resolved.path, legacy_path);
+
+        std::env::set_current_dir(previous).expect("restore cwd");
+        std::fs::remove_dir_all(workspace).expect("workspace should clean up");
+    }
+
+    fn cwd_lock() -> &'static Mutex<()> {
+        static LOCK: OnceLock<Mutex<()>> = OnceLock::new();
+        LOCK.get_or_init(|| Mutex::new(()))
+    }
+
+    fn temp_workspace(label: &str) -> PathBuf {
+        let nanos = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .expect("system time should be after epoch")
+            .as_nanos();
+        std::env::temp_dir().join(format!("claw-cli-{label}-{nanos}"))
     }
 
     #[test]