feat: jsonl-session progress

rust/Cargo.lock

@@ -25,7 +25,6 @@ dependencies = [
  "runtime",
  "serde",
  "serde_json",
- "telemetry",
  "tokio",
 ]
 
@@ -1097,7 +1096,6 @@ dependencies = [
  "serde",
  "serde_json",
  "sha2",
- "telemetry",
  "tokio",
  "walkdir",
 ]
@@ -1430,14 +1428,6 @@ dependencies = [
  "yaml-rust",
 ]
 
-[[package]]
-name = "telemetry"
-version = "0.1.0"
-dependencies = [
- "serde",
- "serde_json",
-]
-
 [[package]]
 name = "thiserror"
 version = "2.0.18"

rust/crates/api/Cargo.toml

@@ -10,7 +10,6 @@ reqwest = { version = "0.12", default-features = false, features = ["json", "rus
 runtime = { path = "../runtime" }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
-telemetry = { path = "../telemetry" }
 tokio = { version = "1", features = ["io-util", "macros", "net", "rt-multi-thread", "time"] }
 
 [lints]

rust/crates/api/src/client.rs

@@ -2,19 +2,17 @@ use std::collections::VecDeque;
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
 use runtime::{
-    format_usd, load_oauth_credentials, pricing_for_model, save_oauth_credentials, OAuthConfig,
-    OAuthRefreshRequest, OAuthTokenExchangeRequest,
+    load_oauth_credentials, save_oauth_credentials, OAuthConfig, OAuthRefreshRequest,
+    OAuthTokenExchangeRequest,
 };
 use serde::Deserialize;
-use serde_json::{Map, Value};
-use telemetry::{AnalyticsEvent, AnthropicRequestProfile, ClientIdentity, SessionTracer};
 
 use crate::error::ApiError;
 use crate::sse::SseParser;
 use crate::types::{MessageRequest, MessageResponse, StreamEvent};
 
 const DEFAULT_BASE_URL: &str = "https://api.anthropic.com";
-const MESSAGES_PATH: &str = "/v1/messages";
+const ANTHROPIC_VERSION: &str = "2023-06-01";
 const REQUEST_ID_HEADER: &str = "request-id";
 const ALT_REQUEST_ID_HEADER: &str = "x-request-id";
 const DEFAULT_INITIAL_BACKOFF: Duration = Duration::from_millis(200);
@@ -110,8 +108,6 @@ pub struct AnthropicClient {
     max_retries: u32,
     initial_backoff: Duration,
     max_backoff: Duration,
-    request_profile: AnthropicRequestProfile,
-    session_tracer: Option<SessionTracer>,
 }
 
 impl AnthropicClient {
@@ -124,8 +120,6 @@ impl AnthropicClient {
             max_retries: DEFAULT_MAX_RETRIES,
             initial_backoff: DEFAULT_INITIAL_BACKOFF,
             max_backoff: DEFAULT_MAX_BACKOFF,
-            request_profile: AnthropicRequestProfile::default(),
-            session_tracer: None,
         }
     }
 
@@ -138,8 +132,6 @@ impl AnthropicClient {
             max_retries: DEFAULT_MAX_RETRIES,
             initial_backoff: DEFAULT_INITIAL_BACKOFF,
             max_backoff: DEFAULT_MAX_BACKOFF,
-            request_profile: AnthropicRequestProfile::default(),
-            session_tracer: None,
         }
     }
 
@@ -184,39 +176,6 @@ impl AnthropicClient {
         self
     }
 
-    #[must_use]
-    pub fn with_request_profile(mut self, request_profile: AnthropicRequestProfile) -> Self {
-        self.request_profile = request_profile;
-        self
-    }
-
-    #[must_use]
-    pub fn with_client_identity(mut self, client_identity: ClientIdentity) -> Self {
-        self.request_profile.client_identity = client_identity;
-        self
-    }
-
-    #[must_use]
-    pub fn with_beta(mut self, beta: impl Into<String>) -> Self {
-        let beta = beta.into();
-        if !self.request_profile.betas.contains(&beta) {
-            self.request_profile.betas.push(beta);
-        }
-        self
-    }
-
-    #[must_use]
-    pub fn with_extra_body_param(mut self, key: impl Into<String>, value: Value) -> Self {
-        self.request_profile.extra_body.insert(key.into(), value);
-        self
-    }
-
-    #[must_use]
-    pub fn with_session_tracer(mut self, session_tracer: SessionTracer) -> Self {
-        self.session_tracer = Some(session_tracer);
-        self
-    }
-
     #[must_use]
     pub fn with_retry_policy(
         mut self,
@@ -252,7 +211,6 @@ impl AnthropicClient {
         if response.request_id.is_none() {
             response.request_id = request_id;
         }
-        self.record_response_usage(&response);
         Ok(response)
     }
 
@@ -321,30 +279,18 @@ impl AnthropicClient {
 
         loop {
             attempts += 1;
-            self.record_request_started(request, attempts);
             match self.send_raw_request(request).await {
                 Ok(response) => match expect_success(response).await {
-                    Ok(response) => {
-                        self.record_request_succeeded(request, attempts, &response);
-                        return Ok(response);
-                    }
+                    Ok(response) => return Ok(response),
                     Err(error) if error.is_retryable() && attempts <= self.max_retries + 1 => {
-                        self.record_request_failed(request, attempts, &error);
                         last_error = Some(error);
                     }
-                    Err(error) => {
-                        self.record_request_failed(request, attempts, &error);
-                        return Err(error);
-                    }
+                    Err(error) => return Err(error),
                 },
                 Err(error) if error.is_retryable() && attempts <= self.max_retries + 1 => {
-                    self.record_request_failed(request, attempts, &error);
                     last_error = Some(error);
                 }
-                Err(error) => {
-                    self.record_request_failed(request, attempts, &error);
-                    return Err(error);
-                }
+                Err(error) => return Err(error),
             }
 
             if attempts > self.max_retries {
@@ -364,213 +310,18 @@ impl AnthropicClient {
         &self,
         request: &MessageRequest,
     ) -> Result<reqwest::Response, ApiError> {
-        let request_url = format!("{}{}", self.base_url.trim_end_matches('/'), MESSAGES_PATH);
-        let mut request_builder = self
+        let request_url = format!("{}/v1/messages", self.base_url.trim_end_matches('/'));
+        let request_builder = self
             .http
             .post(&request_url)
+            .header("anthropic-version", ANTHROPIC_VERSION)
             .header("content-type", "application/json");
-        for (name, value) in self.request_profile.header_pairs() {
-            request_builder = request_builder.header(name, value);
-        }
         let mut request_builder = self.auth.apply(request_builder);
 
-        let request_body = self.request_profile.render_json_body(request)?;
-        request_builder = request_builder.json(&request_body);
+        request_builder = request_builder.json(request);
         request_builder.send().await.map_err(ApiError::from)
     }
 
-    fn record_request_started(&self, request: &MessageRequest, attempt: u32) {
-        if let Some(tracer) = &self.session_tracer {
-            tracer.record_http_request_started(
-                attempt,
-                "POST",
-                MESSAGES_PATH,
-                self.request_attributes(request),
-            );
-        }
-    }
-
-    fn record_request_succeeded(
-        &self,
-        request: &MessageRequest,
-        attempt: u32,
-        response: &reqwest::Response,
-    ) {
-        if let Some(tracer) = &self.session_tracer {
-            tracer.record_http_request_succeeded(
-                attempt,
-                "POST",
-                MESSAGES_PATH,
-                response.status().as_u16(),
-                request_id_from_headers(response.headers()),
-                self.request_attributes(request),
-            );
-        }
-    }
-
-    fn record_request_failed(&self, request: &MessageRequest, attempt: u32, error: &ApiError) {
-        if let Some(tracer) = &self.session_tracer {
-            tracer.record_http_request_failed(
-                attempt,
-                "POST",
-                MESSAGES_PATH,
-                error.to_string(),
-                error.is_retryable(),
-                self.error_attributes(request, error),
-            );
-        }
-    }
-
-    fn record_response_usage(&self, response: &MessageResponse) {
-        let Some(tracer) = &self.session_tracer else {
-            return;
-        };
-
-        let cost = response.usage.estimated_cost_usd(&response.model);
-        let pricing_source = if pricing_for_model(&response.model).is_some() {
-            "model-specific"
-        } else {
-            "default-sonnet"
-        };
-
-        let mut properties = Map::new();
-        properties.insert("model".to_string(), Value::String(response.model.clone()));
-        properties.insert(
-            "pricing_source".to_string(),
-            Value::String(pricing_source.to_string()),
-        );
-        properties.insert(
-            "input_tokens".to_string(),
-            Value::from(response.usage.input_tokens),
-        );
-        properties.insert(
-            "output_tokens".to_string(),
-            Value::from(response.usage.output_tokens),
-        );
-        properties.insert(
-            "cache_creation_input_tokens".to_string(),
-            Value::from(response.usage.cache_creation_input_tokens),
-        );
-        properties.insert(
-            "cache_read_input_tokens".to_string(),
-            Value::from(response.usage.cache_read_input_tokens),
-        );
-        properties.insert(
-            "total_tokens".to_string(),
-            Value::from(response.usage.total_tokens()),
-        );
-        properties.insert(
-            "estimated_cost_usd".to_string(),
-            Value::String(format_usd(cost.total_cost_usd())),
-        );
-        properties.insert(
-            "estimated_input_cost_usd".to_string(),
-            Value::String(format_usd(cost.input_cost_usd)),
-        );
-        properties.insert(
-            "estimated_output_cost_usd".to_string(),
-            Value::String(format_usd(cost.output_cost_usd)),
-        );
-        properties.insert(
-            "estimated_cache_creation_cost_usd".to_string(),
-            Value::String(format_usd(cost.cache_creation_cost_usd)),
-        );
-        properties.insert(
-            "estimated_cache_read_cost_usd".to_string(),
-            Value::String(format_usd(cost.cache_read_cost_usd)),
-        );
-        if let Some(request_id) = &response.request_id {
-            properties.insert("request_id".to_string(), Value::String(request_id.clone()));
-        }
-
-        tracer.record_analytics(AnalyticsEvent {
-            namespace: "api".to_string(),
-            action: "message_usage".to_string(),
-            properties,
-        });
-    }
-
-    fn request_attributes(&self, request: &MessageRequest) -> Map<String, Value> {
-        let mut attributes = Map::new();
-        attributes.insert("model".to_string(), Value::String(request.model.clone()));
-        attributes.insert("stream".to_string(), Value::Bool(request.stream));
-        attributes.insert("max_tokens".to_string(), Value::from(request.max_tokens));
-        attributes.insert(
-            "message_count".to_string(),
-            Value::from(u64::try_from(request.messages.len()).unwrap_or(u64::MAX)),
-        );
-        attributes.insert(
-            "tool_count".to_string(),
-            Value::from(
-                u64::try_from(request.tools.as_ref().map_or(0, Vec::len)).unwrap_or(u64::MAX),
-            ),
-        );
-        attributes.insert(
-            "beta_count".to_string(),
-            Value::from(u64::try_from(self.request_profile.betas.len()).unwrap_or(u64::MAX)),
-        );
-        if !self.request_profile.betas.is_empty() {
-            attributes.insert(
-                "betas".to_string(),
-                Value::Array(
-                    self.request_profile
-                        .betas
-                        .iter()
-                        .cloned()
-                        .map(Value::String)
-                        .collect(),
-                ),
-            );
-        }
-        if !self.request_profile.extra_body.is_empty() {
-            attributes.insert(
-                "extra_body_keys".to_string(),
-                Value::Array(
-                    self.request_profile
-                        .extra_body
-                        .keys()
-                        .cloned()
-                        .map(Value::String)
-                        .collect(),
-                ),
-            );
-        }
-        attributes
-    }
-
-    fn error_attributes(&self, request: &MessageRequest, error: &ApiError) -> Map<String, Value> {
-        let mut attributes = self.request_attributes(request);
-        match error {
-            ApiError::Api {
-                status,
-                error_type,
-                message,
-                ..
-            } => {
-                attributes.insert("status".to_string(), Value::from(status.as_u16()));
-                if let Some(error_type) = error_type {
-                    attributes.insert("error_type".to_string(), Value::String(error_type.clone()));
-                }
-                if let Some(message) = message {
-                    attributes.insert("api_message".to_string(), Value::String(message.clone()));
-                }
-            }
-            ApiError::Http(_) => {
-                attributes.insert("error_type".to_string(), Value::String("http".to_string()));
-            }
-            ApiError::Json(_) => {
-                attributes.insert("error_type".to_string(), Value::String("json".to_string()));
-            }
-            _ => {
-                attributes.insert(
-                    "error_type".to_string(),
-                    Value::String("client".to_string()),
-                );
-            }
-        }
-        attributes
-    }
-
     fn backoff_for_attempt(&self, attempt: u32) -> Result<Duration, ApiError> {
         let Some(multiplier) = 1_u32.checked_shl(attempt.saturating_sub(1)) else {
             return Err(ApiError::BackoffOverflow {

rust/crates/api/src/lib.rs

@@ -15,9 +15,3 @@ pub use types::{
     MessageResponse, MessageStartEvent, MessageStopEvent, OutputContentBlock, StreamEvent,
     ToolChoice, ToolDefinition, ToolResultContentBlock, Usage,
 };
-
-pub use telemetry::{
-    AnalyticsEvent, AnthropicRequestProfile, ClientIdentity, JsonlTelemetrySink,
-    MemoryTelemetrySink, SessionTraceRecord, SessionTracer, TelemetryEvent, TelemetrySink,
-    DEFAULT_ANTHROPIC_VERSION,
-};

rust/crates/api/src/types.rs

@@ -1,4 +1,3 @@
-use runtime::{pricing_for_model, TokenUsage, UsageCostEstimate};
 use serde::{Deserialize, Serialize};
 use serde_json::Value;
 
@@ -151,29 +150,7 @@ pub struct Usage {
 impl Usage {
     #[must_use]
     pub const fn total_tokens(&self) -> u32 {
-        self.input_tokens
-            + self.output_tokens
-            + self.cache_creation_input_tokens
-            + self.cache_read_input_tokens
-    }
-
-    #[must_use]
-    pub const fn token_usage(&self) -> TokenUsage {
-        TokenUsage {
-            input_tokens: self.input_tokens,
-            output_tokens: self.output_tokens,
-            cache_creation_input_tokens: self.cache_creation_input_tokens,
-            cache_read_input_tokens: self.cache_read_input_tokens,
-        }
-    }
-
-    #[must_use]
-    pub fn estimated_cost_usd(&self, model: &str) -> UsageCostEstimate {
-        let usage = self.token_usage();
-        pricing_for_model(model).map_or_else(
-            || usage.estimate_cost_usd(),
-            |pricing| usage.estimate_cost_usd_with_pricing(pricing),
-        )
+        self.input_tokens + self.output_tokens
     }
 }
 
@@ -233,47 +210,3 @@ pub enum StreamEvent {
     ContentBlockStop(ContentBlockStopEvent),
     MessageStop(MessageStopEvent),
 }
-
-#[cfg(test)]
-mod tests {
-    use runtime::format_usd;
-
-    use super::{MessageResponse, Usage};
-
-    #[test]
-    fn usage_total_tokens_includes_cache_tokens() {
-        let usage = Usage {
-            input_tokens: 10,
-            cache_creation_input_tokens: 2,
-            cache_read_input_tokens: 3,
-            output_tokens: 4,
-        };
-
-        assert_eq!(usage.total_tokens(), 19);
-        assert_eq!(usage.token_usage().total_tokens(), 19);
-    }
-
-    #[test]
-    fn message_response_estimates_cost_from_model_usage() {
-        let response = MessageResponse {
-            id: "msg_cost".to_string(),
-            kind: "message".to_string(),
-            role: "assistant".to_string(),
-            content: Vec::new(),
-            model: "claude-sonnet-4-20250514".to_string(),
-            stop_reason: Some("end_turn".to_string()),
-            stop_sequence: None,
-            usage: Usage {
-                input_tokens: 1_000_000,
-                cache_creation_input_tokens: 100_000,
-                cache_read_input_tokens: 200_000,
-                output_tokens: 500_000,
-            },
-            request_id: None,
-        };
-
-        let cost = response.usage.estimated_cost_usd(&response.model);
-        assert_eq!(format_usd(cost.total_cost_usd()), "$54.6750");
-        assert_eq!(response.total_tokens(), 1_800_000);
-    }
-}

rust/crates/api/tests/client_integration.rs

@@ -8,7 +8,6 @@ use api::{
     StreamEvent, ToolChoice, ToolDefinition,
 };
 use serde_json::json;
-use telemetry::{ClientIdentity, MemoryTelemetrySink, SessionTracer, TelemetryEvent};
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tokio::net::TcpListener;
 use tokio::sync::Mutex;
@@ -65,18 +64,6 @@ async fn send_message_posts_json_and_parses_response() {
         request.headers.get("authorization").map(String::as_str),
         Some("Bearer proxy-token")
     );
-    assert_eq!(
-        request.headers.get("anthropic-version").map(String::as_str),
-        Some("2023-06-01")
-    );
-    assert_eq!(
-        request.headers.get("user-agent").map(String::as_str),
-        Some("claude-code/0.1.0")
-    );
-    assert_eq!(
-        request.headers.get("anthropic-beta").map(String::as_str),
-        Some("claude-code-20250219,prompt-caching-scope-2026-01-05")
-    );
     let body: serde_json::Value =
         serde_json::from_str(&request.body).expect("request body should be json");
     assert_eq!(
@@ -86,115 +73,6 @@ async fn send_message_posts_json_and_parses_response() {
     assert!(body.get("stream").is_none());
     assert_eq!(body["tools"][0]["name"], json!("get_weather"));
     assert_eq!(body["tool_choice"]["type"], json!("auto"));
-    assert_eq!(
-        body["betas"],
-        json!(["claude-code-20250219", "prompt-caching-scope-2026-01-05"])
-    );
-}
-
-#[tokio::test]
-async fn send_message_applies_request_profile_and_records_telemetry() {
-    let state = Arc::new(Mutex::new(Vec::<CapturedRequest>::new()));
-    let server = spawn_server(
-        state.clone(),
-        vec![http_response_with_headers(
-            "200 OK",
-            "application/json",
-            concat!(
-                "{",
-                "\"id\":\"msg_profile\",",
-                "\"type\":\"message\",",
-                "\"role\":\"assistant\",",
-                "\"content\":[{\"type\":\"text\",\"text\":\"ok\"}],",
-                "\"model\":\"claude-3-7-sonnet-latest\",",
-                "\"stop_reason\":\"end_turn\",",
-                "\"stop_sequence\":null,",
-                "\"usage\":{\"input_tokens\":1,\"cache_creation_input_tokens\":2,\"cache_read_input_tokens\":3,\"output_tokens\":1}",
-                "}"
-            ),
-            &[("request-id", "req_profile_123")],
-        )],
-    )
-    .await;
-    let sink = Arc::new(MemoryTelemetrySink::default());
-
-    let client = AnthropicClient::new("test-key")
-        .with_base_url(server.base_url())
-        .with_client_identity(ClientIdentity::new("claude-code", "9.9.9").with_runtime("rust-cli"))
-        .with_beta("tools-2026-04-01")
-        .with_extra_body_param("metadata", json!({"source": "clawd-code"}))
-        .with_session_tracer(SessionTracer::new("session-telemetry", sink.clone()));
-
-    let response = client
-        .send_message(&sample_request(false))
-        .await
-        .expect("request should succeed");
-
-    assert_eq!(response.request_id.as_deref(), Some("req_profile_123"));
-
-    let captured = state.lock().await;
-    let request = captured.first().expect("server should capture request");
-    assert_eq!(
-        request.headers.get("anthropic-beta").map(String::as_str),
-        Some("claude-code-20250219,prompt-caching-scope-2026-01-05,tools-2026-04-01")
-    );
-    assert_eq!(
-        request.headers.get("user-agent").map(String::as_str),
-        Some("claude-code/9.9.9")
-    );
-    let body: serde_json::Value =
-        serde_json::from_str(&request.body).expect("request body should be json");
-    assert_eq!(body["metadata"]["source"], json!("clawd-code"));
-    assert_eq!(
-        body["betas"],
-        json!([
-            "claude-code-20250219",
-            "prompt-caching-scope-2026-01-05",
-            "tools-2026-04-01"
-        ])
-    );
-
-    let events = sink.events();
-    assert_eq!(events.len(), 6);
-    assert!(matches!(
-        &events[0],
-        TelemetryEvent::HttpRequestStarted {
-            session_id,
-            attempt: 1,
-            method,
-            path,
-            ..
-        } if session_id == "session-telemetry" && method == "POST" && path == "/v1/messages"
-    ));
-    assert!(matches!(
-        &events[1],
-        TelemetryEvent::SessionTrace(trace) if trace.name == "http_request_started"
-    ));
-    assert!(matches!(
-        &events[2],
-        TelemetryEvent::HttpRequestSucceeded {
-            request_id,
-            status: 200,
-            ..
-        } if request_id.as_deref() == Some("req_profile_123")
-    ));
-    assert!(matches!(
-        &events[3],
-        TelemetryEvent::SessionTrace(trace) if trace.name == "http_request_succeeded"
-    ));
-    assert!(matches!(
-        &events[4],
-        TelemetryEvent::Analytics(event)
-            if event.namespace == "api"
-                && event.action == "message_usage"
-                && event.properties.get("request_id") == Some(&json!("req_profile_123"))
-                && event.properties.get("total_tokens") == Some(&json!(7))
-                && event.properties.get("estimated_cost_usd") == Some(&json!("$0.0001"))
-    ));
-    assert!(matches!(
-        &events[5],
-        TelemetryEvent::SessionTrace(trace) if trace.name == "analytics"
-    ));
 }
 
 #[tokio::test]

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"));
@@ -385,16 +392,15 @@ 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);
     }
 
     #[test]
     fn compacts_sessions_via_slash_command() {
-        let session = Session {
-            version: 1,
-            messages: vec![
+        let mut session = Session::new();
+        session.messages = vec![
             ConversationMessage::user_text("a ".repeat(200)),
             ConversationMessage::assistant(vec![ContentBlock::Text {
                 text: "b ".repeat(200),
@@ -403,8 +409,7 @@ mod tests {
             ConversationMessage::assistant(vec![ContentBlock::Text {
                 text: "recent".to_string(),
             }]),
-            ],
-        };
+        ];
 
         let result = handle_slash_command(
             "/compact",
@@ -455,6 +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/Cargo.toml

@@ -11,7 +11,6 @@ glob = "0.3"
 regex = "1"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
-telemetry = { path = "../telemetry" }
 tokio = { version = "1", features = ["io-util", "macros", "process", "rt", "rt-multi-thread", "time"] }
 walkdir = "2"
 

rust/crates/runtime/src/compact.rs

@@ -99,13 +99,14 @@ pub fn compact_session(session: &Session, config: CompactionConfig) -> Compactio
     }];
     compacted_messages.extend(preserved);
 
+    let mut compacted_session = session.clone();
+    compacted_session.messages = compacted_messages;
+    compacted_session.record_compaction(summary.clone(), removed.len());
+
     CompactionResult {
         summary,
         formatted_summary,
-        compacted_session: Session {
-            version: session.version,
-            messages: compacted_messages,
-        },
+        compacted_session,
         removed_message_count: removed.len(),
     }
 }
@@ -390,10 +391,8 @@ mod tests {
 
     #[test]
     fn leaves_small_sessions_unchanged() {
-        let session = Session {
-            version: 1,
-            messages: vec![ConversationMessage::user_text("hello")],
-        };
+        let mut session = Session::new();
+        session.messages = vec![ConversationMessage::user_text("hello")];
 
         let result = compact_session(&session, CompactionConfig::default());
         assert_eq!(result.removed_message_count, 0);
@@ -404,9 +403,8 @@ mod tests {
 
     #[test]
     fn compacts_older_messages_into_a_system_summary() {
-        let session = Session {
-            version: 1,
-            messages: vec![
+        let mut session = Session::new();
+        session.messages = vec![
             ConversationMessage::user_text("one ".repeat(200)),
             ConversationMessage::assistant(vec![ContentBlock::Text {
                 text: "two ".repeat(200),
@@ -419,8 +417,7 @@ mod tests {
                 }],
                 usage: None,
             },
-            ],
-        };
+        ];
 
         let result = compact_session(
             &session,

rust/crates/runtime/src/conversation.rs

@@ -1,9 +1,6 @@
 use std::collections::BTreeMap;
 use std::fmt::{Display, Formatter};
 
-use serde_json::{Map, Value};
-use telemetry::SessionTracer;
-
 use crate::compact::{
     compact_session, estimate_session_tokens, CompactionConfig, CompactionResult,
 };
@@ -100,7 +97,6 @@ pub struct ConversationRuntime<C, T> {
     max_iterations: usize,
     usage_tracker: UsageTracker,
     hook_runner: HookRunner,
-    session_tracer: Option<SessionTracer>,
 }
 
 impl<C, T> ConversationRuntime<C, T>
@@ -122,7 +118,7 @@ where
             tool_executor,
             permission_policy,
             system_prompt,
-            &RuntimeFeatureConfig::default(),
+            RuntimeFeatureConfig::default(),
         )
     }
 
@@ -133,7 +129,7 @@ where
         tool_executor: T,
         permission_policy: PermissionPolicy,
         system_prompt: Vec<String>,
-        feature_config: &RuntimeFeatureConfig,
+        feature_config: RuntimeFeatureConfig,
     ) -> Self {
         let usage_tracker = UsageTracker::from_session(&session);
         Self {
@@ -144,8 +140,7 @@ where
             system_prompt,
             max_iterations: usize::MAX,
             usage_tracker,
-            hook_runner: HookRunner::from_feature_config(feature_config),
-            session_tracer: None,
+            hook_runner: HookRunner::from_feature_config(&feature_config),
         }
     }
 
@@ -155,23 +150,14 @@ where
         self
     }
 
-    #[must_use]
-    pub fn with_session_tracer(mut self, session_tracer: SessionTracer) -> Self {
-        self.session_tracer = Some(session_tracer);
-        self
-    }
-
-    #[allow(clippy::too_many_lines)]
     pub fn run_turn(
         &mut self,
         user_input: impl Into<String>,
         mut prompter: Option<&mut dyn PermissionPrompter>,
     ) -> Result<TurnSummary, RuntimeError> {
-        let user_input = user_input.into();
-        self.record_turn_started(&user_input);
         self.session
-            .messages
-            .push(ConversationMessage::user_text(user_input));
+            .push_user_text(user_input.into())
+            .map_err(|error| RuntimeError::new(error.to_string()))?;
 
         let mut assistant_messages = Vec::new();
         let mut tool_results = Vec::new();
@@ -180,31 +166,17 @@ where
         loop {
             iterations += 1;
             if iterations > self.max_iterations {
-                let error = RuntimeError::new(
+                return Err(RuntimeError::new(
                     "conversation loop exceeded the maximum number of iterations",
-                );
-                self.record_turn_failed(iterations, &error);
-                return Err(error);
+                ));
             }
 
             let request = ApiRequest {
                 system_prompt: self.system_prompt.clone(),
                 messages: self.session.messages.clone(),
             };
-            let events = match self.api_client.stream(request) {
-                Ok(events) => events,
-                Err(error) => {
-                    self.record_turn_failed(iterations, &error);
-                    return Err(error);
-                }
-            };
-            let (assistant_message, usage) = match build_assistant_message(events) {
-                Ok(result) => result,
-                Err(error) => {
-                    self.record_turn_failed(iterations, &error);
-                    return Err(error);
-                }
-            };
+            let events = self.api_client.stream(request)?;
+            let (assistant_message, usage) = build_assistant_message(events)?;
             if let Some(usage) = usage {
                 self.usage_tracker.record(usage);
             }
@@ -218,13 +190,10 @@ where
                     _ => None,
                 })
                 .collect::<Vec<_>>();
-            self.record_assistant_iteration(
-                iterations,
-                &assistant_message,
-                pending_tool_uses.len(),
-            );
 
-            self.session.messages.push(assistant_message.clone());
+            self.session
+                .push_message(assistant_message.clone())
+                .map_err(|error| RuntimeError::new(error.to_string()))?;
             assistant_messages.push(assistant_message);
 
             if pending_tool_uses.is_empty() {
@@ -232,7 +201,6 @@ where
             }
 
             for (tool_use_id, tool_name, input) in pending_tool_uses {
-                self.record_tool_started(iterations, &tool_name);
                 let permission_outcome = if let Some(prompt) = prompter.as_mut() {
                     self.permission_policy
                         .authorize(&tool_name, &input, Some(*prompt))
@@ -283,20 +251,19 @@ where
                         ConversationMessage::tool_result(tool_use_id, tool_name, reason, true)
                     }
                 };
-                self.record_tool_finished(iterations, &result_message);
-                self.session.messages.push(result_message.clone());
+                self.session
+                    .push_message(result_message.clone())
+                    .map_err(|error| RuntimeError::new(error.to_string()))?;
                 tool_results.push(result_message);
             }
         }
 
-        let summary = TurnSummary {
+        Ok(TurnSummary {
             assistant_messages,
             tool_results,
             iterations,
             usage: self.usage_tracker.cumulative_usage(),
-        };
-        self.record_turn_completed(&summary);
-        Ok(summary)
+        })
     }
 
     #[must_use]
@@ -319,130 +286,15 @@ 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
     }
-
-    fn record_turn_started(&self, user_input: &str) {
-        if let Some(tracer) = &self.session_tracer {
-            let mut attributes = Map::new();
-            attributes.insert(
-                "message_count_before".to_string(),
-                Value::from(u64::try_from(self.session.messages.len()).unwrap_or(u64::MAX)),
-            );
-            attributes.insert(
-                "input_chars".to_string(),
-                Value::from(u64::try_from(user_input.chars().count()).unwrap_or(u64::MAX)),
-            );
-            tracer.record("turn_started", attributes);
-        }
-    }
-
-    fn record_assistant_iteration(
-        &self,
-        iteration: usize,
-        assistant_message: &ConversationMessage,
-        pending_tool_count: usize,
-    ) {
-        if let Some(tracer) = &self.session_tracer {
-            let mut attributes = Map::new();
-            attributes.insert(
-                "iteration".to_string(),
-                Value::from(u64::try_from(iteration).unwrap_or(u64::MAX)),
-            );
-            attributes.insert(
-                "block_count".to_string(),
-                Value::from(u64::try_from(assistant_message.blocks.len()).unwrap_or(u64::MAX)),
-            );
-            attributes.insert(
-                "pending_tool_count".to_string(),
-                Value::from(u64::try_from(pending_tool_count).unwrap_or(u64::MAX)),
-            );
-            tracer.record("assistant_iteration_completed", attributes);
-        }
-    }
-
-    fn record_tool_started(&self, iteration: usize, tool_name: &str) {
-        if let Some(tracer) = &self.session_tracer {
-            let mut attributes = Map::new();
-            attributes.insert(
-                "iteration".to_string(),
-                Value::from(u64::try_from(iteration).unwrap_or(u64::MAX)),
-            );
-            attributes.insert(
-                "tool_name".to_string(),
-                Value::String(tool_name.to_string()),
-            );
-            tracer.record("tool_execution_started", attributes);
-        }
-    }
-
-    fn record_tool_finished(&self, iteration: usize, result_message: &ConversationMessage) {
-        let Some(tracer) = &self.session_tracer else {
-            return;
-        };
-        let Some(ContentBlock::ToolResult {
-            tool_name,
-            is_error,
-            output,
-            ..
-        }) = result_message.blocks.first()
-        else {
-            return;
-        };
-        let mut attributes = Map::new();
-        attributes.insert(
-            "iteration".to_string(),
-            Value::from(u64::try_from(iteration).unwrap_or(u64::MAX)),
-        );
-        attributes.insert("tool_name".to_string(), Value::String(tool_name.clone()));
-        attributes.insert("is_error".to_string(), Value::Bool(*is_error));
-        attributes.insert(
-            "output_chars".to_string(),
-            Value::from(u64::try_from(output.chars().count()).unwrap_or(u64::MAX)),
-        );
-        tracer.record("tool_execution_finished", attributes);
-    }
-
-    fn record_turn_completed(&self, summary: &TurnSummary) {
-        if let Some(tracer) = &self.session_tracer {
-            let mut attributes = Map::new();
-            attributes.insert(
-                "assistant_message_count".to_string(),
-                Value::from(u64::try_from(summary.assistant_messages.len()).unwrap_or(u64::MAX)),
-            );
-            attributes.insert(
-                "tool_result_count".to_string(),
-                Value::from(u64::try_from(summary.tool_results.len()).unwrap_or(u64::MAX)),
-            );
-            attributes.insert(
-                "iterations".to_string(),
-                Value::from(u64::try_from(summary.iterations).unwrap_or(u64::MAX)),
-            );
-            attributes.insert(
-                "total_input_tokens".to_string(),
-                Value::from(summary.usage.input_tokens),
-            );
-            attributes.insert(
-                "total_output_tokens".to_string(),
-                Value::from(summary.usage.output_tokens),
-            );
-            tracer.record("turn_completed", attributes);
-        }
-    }
-
-    fn record_turn_failed(&self, iteration: usize, error: &RuntimeError) {
-        if let Some(tracer) = &self.session_tracer {
-            let mut attributes = Map::new();
-            attributes.insert(
-                "iteration".to_string(),
-                Value::from(u64::try_from(iteration).unwrap_or(u64::MAX)),
-            );
-            attributes.insert("error".to_string(), Value::String(error.to_string()));
-            tracer.record("turn_failed", attributes);
-        }
-    }
 }
 
 fn build_assistant_message(
@@ -565,9 +417,9 @@ mod tests {
     use crate::prompt::{ProjectContext, SystemPromptBuilder};
     use crate::session::{ContentBlock, MessageRole, Session};
     use crate::usage::TokenUsage;
+    use std::fs;
     use std::path::PathBuf;
-    use std::sync::Arc;
-    use telemetry::{MemoryTelemetrySink, SessionTracer, TelemetryEvent};
+    use std::time::{SystemTime, UNIX_EPOCH};
 
     struct ScriptedApiClient {
         call_count: usize,
@@ -680,39 +532,6 @@ mod tests {
         ));
     }
 
-    #[test]
-    fn records_runtime_session_trace_events() {
-        let sink = Arc::new(MemoryTelemetrySink::default());
-        let tracer = SessionTracer::new("session-runtime", sink.clone());
-        let mut runtime = ConversationRuntime::new(
-            Session::new(),
-            ScriptedApiClient { call_count: 0 },
-            StaticToolExecutor::new().register("add", |_input| Ok("4".to_string())),
-            PermissionPolicy::new(PermissionMode::WorkspaceWrite),
-            vec!["system".to_string()],
-        )
-        .with_session_tracer(tracer);
-
-        runtime
-            .run_turn("what is 2 + 2?", Some(&mut PromptAllowOnce))
-            .expect("conversation loop should succeed");
-
-        let events = sink.events();
-        let trace_names = events
-            .iter()
-            .filter_map(|event| match event {
-                TelemetryEvent::SessionTrace(trace) => Some(trace.name.as_str()),
-                _ => None,
-            })
-            .collect::<Vec<_>>();
-
-        assert!(trace_names.contains(&"turn_started"));
-        assert!(trace_names.contains(&"assistant_iteration_completed"));
-        assert!(trace_names.contains(&"tool_execution_started"));
-        assert!(trace_names.contains(&"tool_execution_finished"));
-        assert!(trace_names.contains(&"turn_completed"));
-    }
-
     #[test]
     fn records_denied_tool_results_when_prompt_rejects() {
         struct RejectPrompter;
@@ -801,7 +620,7 @@ mod tests {
             }),
             PermissionPolicy::new(PermissionMode::DangerFullAccess),
             vec!["system".to_string()],
-            &RuntimeFeatureConfig::default().with_hooks(RuntimeHookConfig::new(
+            RuntimeFeatureConfig::default().with_hooks(RuntimeHookConfig::new(
                 vec![shell_snippet("printf 'blocked by hook'; exit 2")],
                 Vec::new(),
             )),
@@ -867,7 +686,7 @@ mod tests {
             StaticToolExecutor::new().register("add", |_input| Ok("4".to_string())),
             PermissionPolicy::new(PermissionMode::DangerFullAccess),
             vec!["system".to_string()],
-            &RuntimeFeatureConfig::default().with_hooks(RuntimeHookConfig::new(
+            RuntimeFeatureConfig::default().with_hooks(RuntimeHookConfig::new(
                 vec![shell_snippet("printf 'pre hook ran'")],
                 vec![shell_snippet("printf 'post hook ran'")],
             )),
@@ -889,7 +708,7 @@ mod tests {
             "post hook should preserve non-error result: {output:?}"
         );
         assert!(
-            output.contains('4'),
+            output.contains("4"),
             "tool output missing value: {output:?}"
         );
         assert!(
@@ -979,6 +798,86 @@ mod tests {
             result.compacted_session.messages[0].role,
             MessageRole::System
         );
+        assert_eq!(
+            result.compacted_session.session_id,
+            runtime.session().session_id
+        );
+        assert!(result.compacted_session.compaction.is_some());
+    }
+
+    #[test]
+    fn persists_conversation_turn_messages_to_jsonl_session() {
+        struct SimpleApi;
+        impl ApiClient for SimpleApi {
+            fn stream(
+                &mut self,
+                _request: ApiRequest,
+            ) -> Result<Vec<AssistantEvent>, RuntimeError> {
+                Ok(vec![
+                    AssistantEvent::TextDelta("done".to_string()),
+                    AssistantEvent::MessageStop,
+                ])
+            }
+        }
+
+        let path = temp_session_path("persisted-turn");
+        let session = Session::new().with_persistence_path(path.clone());
+        let mut runtime = ConversationRuntime::new(
+            session,
+            SimpleApi,
+            StaticToolExecutor::new(),
+            PermissionPolicy::new(PermissionMode::DangerFullAccess),
+            vec!["system".to_string()],
+        );
+
+        runtime
+            .run_turn("persist this turn", None)
+            .expect("turn should succeed");
+
+        let restored = Session::load_from_path(&path).expect("persisted session should reload");
+        fs::remove_file(&path).expect("temp session file should be removable");
+
+        assert_eq!(restored.messages.len(), 2);
+        assert_eq!(restored.messages[0].role, MessageRole::User);
+        assert_eq!(restored.messages[1].role, MessageRole::Assistant);
+        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)
+            .expect("system time should be after epoch")
+            .as_nanos();
+        std::env::temp_dir().join(format!("runtime-conversation-{label}-{nanos}.json"))
     }
 
     #[cfg(windows)]

rust/crates/runtime/src/hooks.rs

@@ -64,7 +64,7 @@ impl HookRunner {
 
     #[must_use]
     pub fn run_pre_tool_use(&self, tool_name: &str, tool_input: &str) -> HookRunResult {
-        Self::run_commands(
+        self.run_commands(
             HookEvent::PreToolUse,
             self.config.pre_tool_use(),
             tool_name,
@@ -82,7 +82,7 @@ impl HookRunner {
         tool_output: &str,
         is_error: bool,
     ) -> HookRunResult {
-        Self::run_commands(
+        self.run_commands(
             HookEvent::PostToolUse,
             self.config.post_tool_use(),
             tool_name,
@@ -93,6 +93,7 @@ impl HookRunner {
     }
 
     fn run_commands(
+        &self,
         event: HookEvent,
         commands: &[String],
         tool_name: &str,
@@ -113,19 +114,19 @@ impl HookRunner {
             "tool_result_is_error": is_error,
         })
         .to_string();
-        let invocation = HookInvocation {
+
+        let mut messages = Vec::new();
+
+        for command in commands {
+            match self.run_command(
+                command,
                 event,
                 tool_name,
                 tool_input,
                 tool_output,
                 is_error,
-            payload: &payload,
-        };
-
-        let mut messages = Vec::new();
-
-        for command in commands {
-            match Self::run_command(command, &invocation) {
+                &payload,
+            ) {
                 HookCommandOutcome::Allow { message } => {
                     if let Some(message) = message {
                         messages.push(message);
@@ -148,23 +149,29 @@ impl HookRunner {
         HookRunResult::allow(messages)
     }
 
-    fn run_command(command: &str, invocation: &HookInvocation<'_>) -> HookCommandOutcome {
+    fn run_command(
+        &self,
+        command: &str,
+        event: HookEvent,
+        tool_name: &str,
+        tool_input: &str,
+        tool_output: Option<&str>,
+        is_error: bool,
+        payload: &str,
+    ) -> HookCommandOutcome {
         let mut child = shell_command(command);
         child.stdin(std::process::Stdio::piped());
         child.stdout(std::process::Stdio::piped());
         child.stderr(std::process::Stdio::piped());
-        child.env("HOOK_EVENT", invocation.event.as_str());
-        child.env("HOOK_TOOL_NAME", invocation.tool_name);
-        child.env("HOOK_TOOL_INPUT", invocation.tool_input);
-        child.env(
-            "HOOK_TOOL_IS_ERROR",
-            if invocation.is_error { "1" } else { "0" },
-        );
-        if let Some(tool_output) = invocation.tool_output {
+        child.env("HOOK_EVENT", event.as_str());
+        child.env("HOOK_TOOL_NAME", tool_name);
+        child.env("HOOK_TOOL_INPUT", tool_input);
+        child.env("HOOK_TOOL_IS_ERROR", if is_error { "1" } else { "0" });
+        if let Some(tool_output) = tool_output {
             child.env("HOOK_TOOL_OUTPUT", tool_output);
         }
 
-        match child.output_with_stdin(invocation.payload.as_bytes()) {
+        match child.output_with_stdin(payload.as_bytes()) {
             Ok(output) => {
                 let stdout = String::from_utf8_lossy(&output.stdout).trim().to_string();
                 let stderr = String::from_utf8_lossy(&output.stderr).trim().to_string();
@@ -182,9 +189,8 @@ impl HookRunner {
                     },
                     None => HookCommandOutcome::Warn {
                         message: format!(
-                            "{} hook `{command}` terminated by signal while handling `{}`",
-                            invocation.event.as_str(),
-                            invocation.tool_name
+                            "{} hook `{command}` terminated by signal while handling `{tool_name}`",
+                            event.as_str()
                         ),
                     },
                 }
@@ -192,23 +198,13 @@ impl HookRunner {
             Err(error) => HookCommandOutcome::Warn {
                 message: format!(
                     "{} hook `{command}` failed to start for `{tool_name}`: {error}",
-                    invocation.event.as_str(),
-                    tool_name = invocation.tool_name
+                    event.as_str()
                 ),
             },
         }
     }
 }
 
-struct HookInvocation<'a> {
-    event: HookEvent,
-    tool_name: &'a str,
-    tool_input: &'a str,
-    tool_output: Option<&'a str>,
-    is_error: bool,
-    payload: &'a str,
-}
-
 enum HookCommandOutcome {
     Allow { message: Option<String> },
     Deny { message: Option<String> },

rust/crates/runtime/src/lib.rs

@@ -76,7 +76,10 @@ pub use remote::{
     RemoteSessionContext, UpstreamProxyBootstrap, UpstreamProxyState, DEFAULT_REMOTE_BASE_URL,
     DEFAULT_SESSION_TOKEN_PATH, DEFAULT_SYSTEM_CA_BUNDLE, NO_PROXY_HOSTS, UPSTREAM_PROXY_ENV_KEYS,
 };
-pub use session::{ContentBlock, ConversationMessage, MessageRole, Session, SessionError};
+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/mcp_stdio.rs

@@ -1144,20 +1144,8 @@ mod tests {
     }
 
     fn cleanup_script(script_path: &Path) {
-        if let Err(error) = fs::remove_file(script_path) {
-            assert_eq!(
-                error.kind(),
-                std::io::ErrorKind::NotFound,
-                "cleanup script: {error}"
-            );
-        }
-        if let Err(error) = fs::remove_dir_all(script_path.parent().expect("script parent")) {
-            assert_eq!(
-                error.kind(),
-                std::io::ErrorKind::NotFound,
-                "cleanup dir: {error}"
-            );
-        }
+        fs::remove_file(script_path).expect("cleanup script");
+        fs::remove_dir_all(script_path.parent().expect("script parent")).expect("cleanup dir");
     }
 
     fn manager_server_config(

rust/crates/runtime/src/session.rs

@@ -1,11 +1,19 @@
 use std::collections::BTreeMap;
 use std::fmt::{Display, Formatter};
-use std::fs;
-use std::path::Path;
+use std::fs::{self, OpenOptions};
+use std::io::Write;
+use std::path::{Path, PathBuf};
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::time::{SystemTime, UNIX_EPOCH};
 
 use crate::json::{JsonError, JsonValue};
 use crate::usage::TokenUsage;
 
+const SESSION_VERSION: u32 = 1;
+const ROTATE_AFTER_BYTES: u64 = 256 * 1024;
+const MAX_ROTATED_FILES: usize = 3;
+static SESSION_ID_COUNTER: AtomicU64 = AtomicU64::new(0);
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum MessageRole {
     System,
@@ -40,11 +48,49 @@ pub struct ConversationMessage {
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
+pub struct SessionCompaction {
+    pub count: u32,
+    pub removed_message_count: usize,
+    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,
+}
+
+#[derive(Debug, Clone)]
 pub struct Session {
     pub version: u32,
+    pub session_id: String,
+    pub created_at_ms: u64,
+    pub updated_at_ms: u64,
     pub messages: Vec<ConversationMessage>,
+    pub compaction: Option<SessionCompaction>,
+    pub fork: Option<SessionFork>,
+    persistence: Option<SessionPersistence>,
 }
 
+impl PartialEq for Session {
+    fn eq(&self, other: &Self) -> bool {
+        self.version == other.version
+            && self.session_id == other.session_id
+            && self.created_at_ms == other.created_at_ms
+            && self.updated_at_ms == other.updated_at_ms
+            && self.messages == other.messages
+            && self.compaction == other.compaction
+            && self.fork == other.fork
+    }
+}
+
+impl Eq for Session {}
+
 #[derive(Debug)]
 pub enum SessionError {
     Io(std::io::Error),
@@ -79,20 +125,84 @@ impl From<JsonError> for SessionError {
 impl Session {
     #[must_use]
     pub fn new() -> Self {
+        let now = current_time_millis();
         Self {
-            version: 1,
+            version: SESSION_VERSION,
+            session_id: generate_session_id(),
+            created_at_ms: now,
+            updated_at_ms: now,
             messages: Vec::new(),
+            compaction: None,
+            fork: None,
+            persistence: None,
         }
     }
 
+    #[must_use]
+    pub fn with_persistence_path(mut self, path: impl Into<PathBuf>) -> Self {
+        self.persistence = Some(SessionPersistence { path: path.into() });
+        self
+    }
+
+    #[must_use]
+    pub fn persistence_path(&self) -> Option<&Path> {
+        self.persistence.as_ref().map(|value| value.path.as_path())
+    }
+
     pub fn save_to_path(&self, path: impl AsRef<Path>) -> Result<(), SessionError> {
-        fs::write(path, self.to_json().render())?;
+        let path = path.as_ref();
+        rotate_session_file_if_needed(path)?;
+        write_atomic(path, &self.render_jsonl_snapshot())?;
+        cleanup_rotated_logs(path)?;
         Ok(())
     }
 
     pub fn load_from_path(path: impl AsRef<Path>) -> Result<Self, SessionError> {
+        let path = path.as_ref();
         let contents = fs::read_to_string(path)?;
-        Self::from_json(&JsonValue::parse(&contents)?)
+        let session = match JsonValue::parse(&contents) {
+            Ok(value) => Self::from_json(&value)?,
+            Err(_) => Self::from_jsonl(&contents)?,
+        };
+        Ok(session.with_persistence_path(path.to_path_buf()))
+    }
+
+    pub fn push_message(&mut self, message: ConversationMessage) -> Result<(), SessionError> {
+        self.touch();
+        self.messages.push(message.clone());
+        self.append_persisted_message(&message)
+    }
+
+    pub fn push_user_text(&mut self, text: impl Into<String>) -> Result<(), SessionError> {
+        self.push_message(ConversationMessage::user_text(text))
+    }
+
+    pub fn record_compaction(&mut self, summary: impl Into<String>, removed_message_count: usize) {
+        self.touch();
+        let count = self.compaction.as_ref().map_or(1, |value| value.count + 1);
+        self.compaction = Some(SessionCompaction {
+            count,
+            removed_message_count,
+            summary: summary.into(),
+        });
+    }
+
+    #[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]
@@ -102,6 +212,18 @@ impl Session {
             "version".to_string(),
             JsonValue::Number(i64::from(self.version)),
         );
+        object.insert(
+            "session_id".to_string(),
+            JsonValue::String(self.session_id.clone()),
+        );
+        object.insert(
+            "created_at_ms".to_string(),
+            JsonValue::Number(i64_from_u64(self.created_at_ms, "created_at_ms")),
+        );
+        object.insert(
+            "updated_at_ms".to_string(),
+            JsonValue::Number(i64_from_u64(self.updated_at_ms, "updated_at_ms")),
+        );
         object.insert(
             "messages".to_string(),
             JsonValue::Array(
@@ -111,6 +233,12 @@ impl Session {
                     .collect(),
             ),
         );
+        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)
     }
 
@@ -131,7 +259,179 @@ impl Session {
             .iter()
             .map(ConversationMessage::from_json)
             .collect::<Result<Vec<_>, _>>()?;
-        Ok(Self { version, messages })
+        let now = current_time_millis();
+        let session_id = object
+            .get("session_id")
+            .and_then(JsonValue::as_str)
+            .map(ToOwned::to_owned)
+            .unwrap_or_else(generate_session_id);
+        let created_at_ms = object
+            .get("created_at_ms")
+            .map(|value| required_u64_from_value(value, "created_at_ms"))
+            .transpose()?
+            .unwrap_or(now);
+        let updated_at_ms = object
+            .get("updated_at_ms")
+            .map(|value| required_u64_from_value(value, "updated_at_ms"))
+            .transpose()?
+            .unwrap_or(created_at_ms);
+        let compaction = object
+            .get("compaction")
+            .map(SessionCompaction::from_json)
+            .transpose()?;
+        let fork = object.get("fork").map(SessionFork::from_json).transpose()?;
+        Ok(Self {
+            version,
+            session_id,
+            created_at_ms,
+            updated_at_ms,
+            messages,
+            compaction,
+            fork,
+            persistence: None,
+        })
+    }
+
+    fn from_jsonl(contents: &str) -> Result<Self, SessionError> {
+        let mut version = SESSION_VERSION;
+        let mut session_id = None;
+        let mut created_at_ms = None;
+        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();
+            if line.is_empty() {
+                continue;
+            }
+            let value = JsonValue::parse(line).map_err(|error| {
+                SessionError::Format(format!(
+                    "invalid JSONL record at line {}: {}",
+                    line_number + 1,
+                    error
+                ))
+            })?;
+            let object = value.as_object().ok_or_else(|| {
+                SessionError::Format(format!(
+                    "JSONL record at line {} must be an object",
+                    line_number + 1
+                ))
+            })?;
+            match object
+                .get("type")
+                .and_then(JsonValue::as_str)
+                .ok_or_else(|| {
+                    SessionError::Format(format!(
+                        "JSONL record at line {} missing type",
+                        line_number + 1
+                    ))
+                })? {
+                "session_meta" => {
+                    version = required_u32(object, "version")?;
+                    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(|| {
+                        SessionError::Format(format!(
+                            "JSONL record at line {} missing message",
+                            line_number + 1
+                        ))
+                    })?;
+                    messages.push(ConversationMessage::from_json(message_value)?);
+                }
+                "compaction" => {
+                    compaction = Some(SessionCompaction::from_json(&JsonValue::Object(
+                        object.clone(),
+                    ))?);
+                }
+                other => {
+                    return Err(SessionError::Format(format!(
+                        "unsupported JSONL record type at line {}: {other}",
+                        line_number + 1
+                    )))
+                }
+            }
+        }
+
+        let now = current_time_millis();
+        Ok(Self {
+            version,
+            session_id: session_id.unwrap_or_else(generate_session_id),
+            created_at_ms: created_at_ms.unwrap_or(now),
+            updated_at_ms: updated_at_ms.unwrap_or(created_at_ms.unwrap_or(now)),
+            messages,
+            compaction,
+            fork,
+            persistence: None,
+        })
+    }
+
+    fn render_jsonl_snapshot(&self) -> String {
+        let mut lines = vec![self.meta_record().render()];
+        if let Some(compaction) = &self.compaction {
+            lines.push(compaction.to_jsonl_record().render());
+        }
+        lines.extend(
+            self.messages
+                .iter()
+                .map(|message| message_record(message).render()),
+        );
+        let mut rendered = lines.join("\n");
+        rendered.push('\n');
+        rendered
+    }
+
+    fn append_persisted_message(&self, message: &ConversationMessage) -> Result<(), SessionError> {
+        let Some(path) = self.persistence_path() else {
+            return Ok(());
+        };
+
+        let needs_bootstrap = !path.exists() || fs::metadata(path)?.len() == 0;
+        if needs_bootstrap {
+            self.save_to_path(path)?;
+            return Ok(());
+        }
+
+        let mut file = OpenOptions::new().append(true).open(path)?;
+        writeln!(file, "{}", message_record(message).render())?;
+        Ok(())
+    }
+
+    fn meta_record(&self) -> JsonValue {
+        let mut object = BTreeMap::new();
+        object.insert(
+            "type".to_string(),
+            JsonValue::String("session_meta".to_string()),
+        );
+        object.insert(
+            "version".to_string(),
+            JsonValue::Number(i64::from(self.version)),
+        );
+        object.insert(
+            "session_id".to_string(),
+            JsonValue::String(self.session_id.clone()),
+        );
+        object.insert(
+            "created_at_ms".to_string(),
+            JsonValue::Number(i64_from_u64(self.created_at_ms, "created_at_ms")),
+        );
+        object.insert(
+            "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)
+    }
+
+    fn touch(&mut self) {
+        self.updated_at_ms = current_time_millis();
     }
 }
 
@@ -324,6 +624,92 @@ impl ContentBlock {
     }
 }
 
+impl SessionCompaction {
+    #[must_use]
+    pub fn to_json(&self) -> JsonValue {
+        let mut object = BTreeMap::new();
+        object.insert(
+            "count".to_string(),
+            JsonValue::Number(i64::from(self.count)),
+        );
+        object.insert(
+            "removed_message_count".to_string(),
+            JsonValue::Number(i64_from_usize(
+                self.removed_message_count,
+                "removed_message_count",
+            )),
+        );
+        object.insert(
+            "summary".to_string(),
+            JsonValue::String(self.summary.clone()),
+        );
+        JsonValue::Object(object)
+    }
+
+    #[must_use]
+    pub fn to_jsonl_record(&self) -> JsonValue {
+        let mut object = self
+            .to_json()
+            .as_object()
+            .cloned()
+            .expect("compaction should render to object");
+        object.insert(
+            "type".to_string(),
+            JsonValue::String("compaction".to_string()),
+        );
+        JsonValue::Object(object)
+    }
+
+    fn from_json(value: &JsonValue) -> Result<Self, SessionError> {
+        let object = value
+            .as_object()
+            .ok_or_else(|| SessionError::Format("compaction must be an object".to_string()))?;
+        Ok(Self {
+            count: required_u32(object, "count")?,
+            removed_message_count: required_usize(object, "removed_message_count")?,
+            summary: required_string(object, "summary")?,
+        })
+    }
+}
+
+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()));
+    object.insert("message".to_string(), message.to_json());
+    JsonValue::Object(object)
+}
+
 fn usage_to_json(usage: TokenUsage) -> JsonValue {
     let mut object = BTreeMap::new();
     object.insert(
@@ -376,22 +762,155 @@ fn required_u32(object: &BTreeMap<String, JsonValue>, key: &str) -> Result<u32,
     u32::try_from(value).map_err(|_| SessionError::Format(format!("{key} out of range")))
 }
 
+fn required_u64(object: &BTreeMap<String, JsonValue>, key: &str) -> Result<u64, SessionError> {
+    let value = object
+        .get(key)
+        .ok_or_else(|| SessionError::Format(format!("missing {key}")))?;
+    required_u64_from_value(value, key)
+}
+
+fn required_u64_from_value(value: &JsonValue, key: &str) -> Result<u64, SessionError> {
+    let value = value
+        .as_i64()
+        .ok_or_else(|| SessionError::Format(format!("missing {key}")))?;
+    u64::try_from(value).map_err(|_| SessionError::Format(format!("{key} out of range")))
+}
+
+fn required_usize(object: &BTreeMap<String, JsonValue>, key: &str) -> Result<usize, SessionError> {
+    let value = object
+        .get(key)
+        .and_then(JsonValue::as_i64)
+        .ok_or_else(|| SessionError::Format(format!("missing {key}")))?;
+    usize::try_from(value).map_err(|_| SessionError::Format(format!("{key} out of range")))
+}
+
+fn i64_from_u64(value: u64, key: &str) -> i64 {
+    i64::try_from(value).unwrap_or_else(|_| panic!("{key} out of range for JSON number"))
+}
+
+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)
+        .map(|duration| duration.as_millis() as u64)
+        .unwrap_or_default()
+}
+
+fn generate_session_id() -> String {
+    let millis = current_time_millis();
+    let counter = SESSION_ID_COUNTER.fetch_add(1, Ordering::Relaxed);
+    format!("session-{millis}-{counter}")
+}
+
+fn write_atomic(path: &Path, contents: &str) -> Result<(), SessionError> {
+    if let Some(parent) = path.parent() {
+        fs::create_dir_all(parent)?;
+    }
+    let temp_path = temporary_path_for(path);
+    fs::write(&temp_path, contents)?;
+    fs::rename(temp_path, path)?;
+    Ok(())
+}
+
+fn temporary_path_for(path: &Path) -> PathBuf {
+    let file_name = path
+        .file_name()
+        .and_then(|value| value.to_str())
+        .unwrap_or("session");
+    path.with_file_name(format!(
+        "{file_name}.tmp-{}-{}",
+        current_time_millis(),
+        SESSION_ID_COUNTER.fetch_add(1, Ordering::Relaxed)
+    ))
+}
+
+fn rotate_session_file_if_needed(path: &Path) -> Result<(), SessionError> {
+    let Ok(metadata) = fs::metadata(path) else {
+        return Ok(());
+    };
+    if metadata.len() < ROTATE_AFTER_BYTES {
+        return Ok(());
+    }
+    let rotated_path = rotated_log_path(path);
+    fs::rename(path, rotated_path)?;
+    Ok(())
+}
+
+fn rotated_log_path(path: &Path) -> PathBuf {
+    let stem = path
+        .file_stem()
+        .and_then(|value| value.to_str())
+        .unwrap_or("session");
+    path.with_file_name(format!("{stem}.rot-{}.jsonl", current_time_millis()))
+}
+
+fn cleanup_rotated_logs(path: &Path) -> Result<(), SessionError> {
+    let Some(parent) = path.parent() else {
+        return Ok(());
+    };
+    let stem = path
+        .file_stem()
+        .and_then(|value| value.to_str())
+        .unwrap_or("session");
+    let prefix = format!("{stem}.rot-");
+    let mut rotated_paths = fs::read_dir(parent)?
+        .filter_map(Result::ok)
+        .map(|entry| entry.path())
+        .filter(|entry_path| {
+            entry_path
+                .file_name()
+                .and_then(|value| value.to_str())
+                .is_some_and(|name| name.starts_with(&prefix) && name.ends_with(".jsonl"))
+        })
+        .collect::<Vec<_>>();
+
+    rotated_paths.sort_by_key(|entry_path| {
+        fs::metadata(entry_path)
+            .and_then(|metadata| metadata.modified())
+            .unwrap_or(UNIX_EPOCH)
+    });
+
+    let remove_count = rotated_paths.len().saturating_sub(MAX_ROTATED_FILES);
+    for stale_path in rotated_paths.into_iter().take(remove_count) {
+        fs::remove_file(stale_path)?;
+    }
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
-    use super::{ContentBlock, ConversationMessage, MessageRole, Session};
+    use super::{
+        cleanup_rotated_logs, rotate_session_file_if_needed, ContentBlock, ConversationMessage,
+        MessageRole, Session, SessionFork,
+    };
+    use crate::json::JsonValue;
     use crate::usage::TokenUsage;
     use std::fs;
+    use std::path::PathBuf;
     use std::time::{SystemTime, UNIX_EPOCH};
 
     #[test]
-    fn persists_and_restores_session_json() {
+    fn persists_and_restores_session_jsonl() {
         let mut session = Session::new();
         session
-            .messages
-            .push(ConversationMessage::user_text("hello"));
+            .push_user_text("hello")
+            .expect("user message should append");
         session
-            .messages
-            .push(ConversationMessage::assistant_with_usage(
+            .push_message(ConversationMessage::assistant_with_usage(
                 vec![
                     ContentBlock::Text {
                         text: "thinking".to_string(),
@@ -408,16 +927,15 @@ mod tests {
                     cache_creation_input_tokens: 1,
                     cache_read_input_tokens: 2,
                 }),
-            ));
-        session.messages.push(ConversationMessage::tool_result(
+            ))
+            .expect("assistant message should append");
+        session
+            .push_message(ConversationMessage::tool_result(
                 "tool-1", "bash", "hi", false,
-        ));
+            ))
+            .expect("tool result should append");
 
-        let nanos = SystemTime::now()
-            .duration_since(UNIX_EPOCH)
-            .expect("system time should be after epoch")
-            .as_nanos();
-        let path = std::env::temp_dir().join(format!("runtime-session-{nanos}.json"));
+        let path = temp_session_path("jsonl");
         session.save_to_path(&path).expect("session should save");
         let restored = Session::load_from_path(&path).expect("session should load");
         fs::remove_file(&path).expect("temp file should be removable");
@@ -428,5 +946,157 @@ mod tests {
             restored.messages[1].usage.expect("usage").total_tokens(),
             17
         );
+        assert_eq!(restored.session_id, session.session_id);
+    }
+
+    #[test]
+    fn loads_legacy_session_json_object() {
+        let path = temp_session_path("legacy");
+        let legacy = JsonValue::Object(
+            [
+                ("version".to_string(), JsonValue::Number(1)),
+                (
+                    "messages".to_string(),
+                    JsonValue::Array(vec![ConversationMessage::user_text("legacy").to_json()]),
+                ),
+            ]
+            .into_iter()
+            .collect(),
+        );
+        fs::write(&path, legacy.render()).expect("legacy file should write");
+
+        let restored = Session::load_from_path(&path).expect("legacy session should load");
+        fs::remove_file(&path).expect("temp file should be removable");
+
+        assert_eq!(restored.messages.len(), 1);
+        assert_eq!(
+            restored.messages[0],
+            ConversationMessage::user_text("legacy")
+        );
+        assert!(!restored.session_id.is_empty());
+    }
+
+    #[test]
+    fn appends_messages_to_persisted_jsonl_session() {
+        let path = temp_session_path("append");
+        let mut session = Session::new().with_persistence_path(path.clone());
+        session
+            .save_to_path(&path)
+            .expect("initial save should succeed");
+        session
+            .push_user_text("hi")
+            .expect("user append should succeed");
+        session
+            .push_message(ConversationMessage::assistant(vec![ContentBlock::Text {
+                text: "hello".to_string(),
+            }]))
+            .expect("assistant append should succeed");
+
+        let restored = Session::load_from_path(&path).expect("session should replay from jsonl");
+        fs::remove_file(&path).expect("temp file should be removable");
+
+        assert_eq!(restored.messages.len(), 2);
+        assert_eq!(restored.messages[0], ConversationMessage::user_text("hi"));
+    }
+
+    #[test]
+    fn persists_compaction_metadata() {
+        let path = temp_session_path("compaction");
+        let mut session = Session::new();
+        session
+            .push_user_text("before")
+            .expect("message should append");
+        session.record_compaction("summarized earlier work", 4);
+        session.save_to_path(&path).expect("session should save");
+
+        let restored = Session::load_from_path(&path).expect("session should load");
+        fs::remove_file(&path).expect("temp file should be removable");
+
+        let compaction = restored.compaction.expect("compaction metadata");
+        assert_eq!(compaction.count, 1);
+        assert_eq!(compaction.removed_message_count, 4);
+        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");
+        fs::write(&path, "x".repeat((super::ROTATE_AFTER_BYTES + 10) as usize))
+            .expect("oversized file should write");
+        rotate_session_file_if_needed(&path).expect("rotation should succeed");
+        assert!(
+            !path.exists(),
+            "original path should be rotated away before rewrite"
+        );
+
+        for _ in 0..5 {
+            let rotated = super::rotated_log_path(&path);
+            fs::write(&rotated, "old").expect("rotated file should write");
+        }
+        cleanup_rotated_logs(&path).expect("cleanup should succeed");
+
+        let rotated_count = rotation_files(&path).len();
+        assert!(rotated_count <= super::MAX_ROTATED_FILES);
+        for rotated in rotation_files(&path) {
+            fs::remove_file(rotated).expect("rotated file should be removable");
+        }
+    }
+
+    fn temp_session_path(label: &str) -> PathBuf {
+        let nanos = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .expect("system time should be after epoch")
+            .as_nanos();
+        std::env::temp_dir().join(format!("runtime-session-{label}-{nanos}.json"))
+    }
+
+    fn rotation_files(path: &PathBuf) -> Vec<PathBuf> {
+        let stem = path
+            .file_stem()
+            .and_then(|value| value.to_str())
+            .expect("temp path should have file stem")
+            .to_string();
+        fs::read_dir(path.parent().expect("temp path should have parent"))
+            .expect("temp dir should read")
+            .filter_map(Result::ok)
+            .map(|entry| entry.path())
+            .filter(|entry_path| {
+                entry_path
+                    .file_name()
+                    .and_then(|value| value.to_str())
+                    .is_some_and(|name| {
+                        name.starts_with(&format!("{stem}.rot-")) && name.ends_with(".jsonl")
+                    })
+            })
+            .collect()
     }
 }

rust/crates/runtime/src/usage.rs

@@ -286,9 +286,8 @@ mod tests {
 
     #[test]
     fn reconstructs_usage_from_session_messages() {
-        let session = Session {
-            version: 1,
-            messages: vec![ConversationMessage {
+        let mut session = Session::new();
+        session.messages = vec![ConversationMessage {
             role: MessageRole::Assistant,
             blocks: vec![ContentBlock::Text {
                 text: "done".to_string(),
@@ -299,8 +298,7 @@ mod tests {
                 cache_creation_input_tokens: 1,
                 cache_read_input_tokens: 0,
             }),
-            }],
-        };
+        }];
 
         let tracker = UsageTracker::from_session(&session);
         assert_eq!(tracker.turns(), 1);

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

@@ -4,19 +4,17 @@ mod render;
 
 use std::collections::{BTreeMap, BTreeSet};
 use std::env;
-use std::fmt::Write as _;
 use std::fs;
 use std::io::{self, Read, Write};
 use std::net::TcpListener;
 use std::path::{Path, PathBuf};
 use std::process::Command;
-use std::time::{SystemTime, UNIX_EPOCH};
+use std::time::UNIX_EPOCH;
 
 use api::{
     resolve_startup_auth_source, AnthropicClient, AuthSource, ContentBlockDelta, InputContentBlock,
-    InputMessage, JsonlTelemetrySink, MessageRequest, MessageResponse, OutputContentBlock,
-    SessionTracer, StreamEvent as ApiStreamEvent, ToolChoice, ToolDefinition,
-    ToolResultContentBlock,
+    InputMessage, MessageRequest, MessageResponse, OutputContentBlock,
+    StreamEvent as ApiStreamEvent, ToolChoice, ToolDefinition, ToolResultContentBlock,
 };
 
 use commands::{
@@ -46,10 +44,11 @@ fn max_tokens_for_model(model: &str) -> u32 {
 }
 const DEFAULT_DATE: &str = "2026-03-31";
 const DEFAULT_OAUTH_CALLBACK_PORT: u16 = 4545;
-const TELEMETRY_LOG_PATH_ENV: &str = "CLAW_TELEMETRY_LOG_PATH";
 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>;
 
@@ -592,7 +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}");
@@ -603,7 +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;
@@ -615,7 +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,
@@ -976,6 +987,8 @@ struct ManagedSessionSummary {
     path: PathBuf,
     modified_epoch_secs: u64,
     message_count: usize,
+    parent_session_id: Option<String>,
+    branch_name: Option<String>,
 }
 
 struct LiveCli {
@@ -995,10 +1008,10 @@ impl LiveCli {
         permission_mode: PermissionMode,
     ) -> Result<Self, Box<dyn std::error::Error>> {
         let system_prompt = build_system_prompt()?;
-        let session = create_managed_session_handle()?;
+        let session_state = Session::new();
+        let session = create_managed_session_handle(&session_state.session_id)?;
         let runtime = build_runtime(
-            Session::new(),
-            &session.id,
+            session_state.with_persistence_path(session.path.clone()),
             model.clone(),
             system_prompt.clone(),
             enable_tools,
@@ -1090,7 +1103,6 @@ impl LiveCli {
         let session = self.runtime.session().clone();
         let mut runtime = build_runtime(
             session,
-            &self.session.id,
             self.model.clone(),
             self.system_prompt.clone(),
             true,
@@ -1237,7 +1249,6 @@ impl LiveCli {
         let message_count = session.messages.len();
         self.runtime = build_runtime(
             session,
-            &self.session.id,
             model.clone(),
             self.system_prompt.clone(),
             true,
@@ -1281,7 +1292,6 @@ impl LiveCli {
         self.permission_mode = permission_mode_from_label(normalized);
         self.runtime = build_runtime(
             session,
-            &self.session.id,
             self.model.clone(),
             self.system_prompt.clone(),
             true,
@@ -1304,10 +1314,10 @@ impl LiveCli {
             return Ok(false);
         }
 
-        self.session = create_managed_session_handle()?;
+        let session_state = Session::new();
+        self.session = create_managed_session_handle(&session_state.session_id)?;
         self.runtime = build_runtime(
-            Session::new(),
-            &self.session.id,
+            session_state.with_persistence_path(self.session.path.clone()),
             self.model.clone(),
             self.system_prompt.clone(),
             true,
@@ -1341,9 +1351,9 @@ impl LiveCli {
         let handle = resolve_session_reference(&session_ref)?;
         let session = Session::load_from_path(&handle.path)?;
         let message_count = session.messages.len();
+        let session_id = session.session_id.clone();
         self.runtime = build_runtime(
             session,
-            &handle.id,
             self.model.clone(),
             self.system_prompt.clone(),
             true,
@@ -1351,7 +1361,10 @@ impl LiveCli {
             self.allowed_tools.clone(),
             self.permission_mode,
         )?;
-        self.session = handle;
+        self.session = SessionHandle {
+            id: session_id,
+            path: handle.path,
+        };
         println!(
             "{}",
             format_resume_report(
@@ -1414,9 +1427,41 @@ impl LiveCli {
                 let handle = resolve_session_reference(target)?;
                 let session = Session::load_from_path(&handle.path)?;
                 let message_count = session.messages.len();
+                let session_id = session.session_id.clone();
                 self.runtime = build_runtime(
                     session,
-                    &handle.id,
+                    self.model.clone(),
+                    self.system_prompt.clone(),
+                    true,
+                    true,
+                    self.allowed_tools.clone(),
+                    self.permission_mode,
+                )?;
+                self.session = SessionHandle {
+                    id: session_id,
+                    path: handle.path,
+                };
+                println!(
+                    "Session switched\n  Active session   {}\n  File             {}\n  Messages         {}",
+                    self.session.id,
+                    self.session.path.display(),
+                    message_count,
+                );
+                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,
@@ -1426,15 +1471,19 @@ impl LiveCli {
                 )?;
                 self.session = handle;
                 println!(
-                    "Session switched\n  Active session   {}\n  File             {}\n  Messages         {}",
+                    "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)
             }
         }
@@ -1447,7 +1496,6 @@ impl LiveCli {
         let skipped = removed == 0;
         self.runtime = build_runtime(
             result.compacted_session,
-            &self.session.id,
             self.model.clone(),
             self.system_prompt.clone(),
             true,
@@ -1468,44 +1516,61 @@ fn sessions_dir() -> Result<PathBuf, Box<dyn std::error::Error>> {
     Ok(path)
 }
 
-fn create_managed_session_handle() -> Result<SessionHandle, Box<dyn std::error::Error>> {
-    let id = generate_session_id();
-    let path = sessions_dir()?.join(format!("{id}.json"));
+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}.{PRIMARY_SESSION_EXTENSION}"));
     Ok(SessionHandle { id, path })
 }
 
-fn generate_session_id() -> String {
-    let millis = SystemTime::now()
-        .duration_since(UNIX_EPOCH)
-        .map(|duration| duration.as_millis())
-        .unwrap_or_default();
-    format!("session-{millis}")
-}
-
 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 {
-        sessions_dir()?.join(format!("{reference}.json"))
-    };
-    if !path.exists() {
+    } else if looks_like_path {
         return Err(format!("session not found: {reference}").into());
-    }
+    } else {
+        resolve_managed_session_path(reference)?
+    };
     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()?;
@@ -1515,19 +1580,41 @@ 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 message_count = Session::load_from_path(&path)
-            .map(|session| session.messages.len())
-            .unwrap_or_default();
-        let id = path
-            .file_stem()
+        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()
                         .and_then(|value| value.to_str())
                         .unwrap_or("unknown")
-            .to_string();
+                        .to_string(),
+                    0,
+                    None,
+                    None,
+                )
+            });
         sessions.push(ManagedSessionSummary {
             id,
             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));
@@ -1550,11 +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(),
         ));
     }
@@ -1923,10 +2022,8 @@ fn build_runtime_feature_config(
         .clone())
 }
 
-#[allow(clippy::too_many_arguments)]
 fn build_runtime(
     session: Session,
-    session_id: &str,
     model: String,
     system_prompt: Vec<String>,
     enable_tools: bool,
@@ -1935,41 +2032,14 @@ fn build_runtime(
     permission_mode: PermissionMode,
 ) -> Result<ConversationRuntime<AnthropicRuntimeClient, CliToolExecutor>, Box<dyn std::error::Error>>
 {
-    let session_tracer = build_session_tracer(session_id)?;
-    let api_client = match session_tracer.clone() {
-        Some(session_tracer) => {
-            AnthropicRuntimeClient::new(model, enable_tools, emit_output, allowed_tools.clone())?
-                .with_session_tracer(session_tracer)
-        }
-        None => {
-            AnthropicRuntimeClient::new(model, enable_tools, emit_output, allowed_tools.clone())?
-        }
-    };
-    let runtime = ConversationRuntime::new_with_features(
+    Ok(ConversationRuntime::new_with_features(
         session,
-        api_client,
+        AnthropicRuntimeClient::new(model, enable_tools, emit_output, allowed_tools.clone())?,
         CliToolExecutor::new(allowed_tools, emit_output),
         permission_policy(permission_mode),
         system_prompt,
-        &build_runtime_feature_config()?,
-    );
-    Ok(match session_tracer {
-        Some(session_tracer) => runtime.with_session_tracer(session_tracer),
-        None => runtime,
-    })
-}
-
-fn build_session_tracer(
-    session_id: &str,
-) -> Result<Option<SessionTracer>, Box<dyn std::error::Error>> {
-    let Some(path) = env::var_os(TELEMETRY_LOG_PATH_ENV) else {
-        return Ok(None);
-    };
-    let sink = JsonlTelemetrySink::new(PathBuf::from(path))?;
-    Ok(Some(SessionTracer::new(
-        session_id.to_string(),
-        std::sync::Arc::new(sink),
-    )))
+        build_runtime_feature_config()?,
+    ))
 }
 
 struct CliPermissionPrompter {
@@ -2044,11 +2114,6 @@ impl AnthropicRuntimeClient {
             allowed_tools,
         })
     }
-
-    fn with_session_tracer(mut self, session_tracer: SessionTracer) -> Self {
-        self.client = self.client.with_session_tracer(session_tracer);
-        self
-    }
 }
 
 fn resolve_cli_auth_source() -> Result<AuthSource, Box<dyn std::error::Error>> {
@@ -2154,7 +2219,12 @@ impl ApiClient for AnthropicRuntimeClient {
                         }
                     }
                     ApiStreamEvent::MessageDelta(delta) => {
-                        events.push(AssistantEvent::Usage(delta.usage.token_usage()));
+                        events.push(AssistantEvent::Usage(TokenUsage {
+                            input_tokens: delta.usage.input_tokens,
+                            output_tokens: delta.usage.output_tokens,
+                            cache_creation_input_tokens: 0,
+                            cache_read_input_tokens: 0,
+                        }));
                     }
                     ApiStreamEvent::MessageStop(_) => {
                         saw_stop = true;
@@ -2404,13 +2474,13 @@ fn format_bash_result(icon: &str, parsed: &serde_json::Value) -> String {
         .get("backgroundTaskId")
         .and_then(|value| value.as_str())
     {
-        write!(&mut lines[0], " backgrounded ({task_id})").expect("write to string");
+        lines[0].push_str(&format!(" backgrounded ({task_id})"));
     } else if let Some(status) = parsed
         .get("returnCodeInterpretation")
         .and_then(|value| value.as_str())
         .filter(|status| !status.is_empty())
     {
-        write!(&mut lines[0], " {status}").expect("write to string");
+        lines[0].push_str(&format!(" {status}"));
     }
 
     if let Some(stdout) = parsed.get("stdout").and_then(|value| value.as_str()) {
@@ -2432,15 +2502,15 @@ fn format_read_result(icon: &str, parsed: &serde_json::Value) -> String {
     let path = extract_tool_path(file);
     let start_line = file
         .get("startLine")
-        .and_then(serde_json::Value::as_u64)
+        .and_then(|value| value.as_u64())
         .unwrap_or(1);
     let num_lines = file
         .get("numLines")
-        .and_then(serde_json::Value::as_u64)
+        .and_then(|value| value.as_u64())
         .unwrap_or(0);
     let total_lines = file
         .get("totalLines")
-        .and_then(serde_json::Value::as_u64)
+        .and_then(|value| value.as_u64())
         .unwrap_or(num_lines);
     let content = file
         .get("content")
@@ -2466,7 +2536,8 @@ fn format_write_result(icon: &str, parsed: &serde_json::Value) -> String {
     let line_count = parsed
         .get("content")
         .and_then(|value| value.as_str())
-        .map_or(0, |content| content.lines().count());
+        .map(|content| content.lines().count())
+        .unwrap_or(0);
     format!(
         "{icon} \x1b[1;32m✏️ {} {path}\x1b[0m \x1b[2m({line_count} lines)\x1b[0m",
         if kind == "create" { "Wrote" } else { "Updated" },
@@ -2497,7 +2568,7 @@ fn format_edit_result(icon: &str, parsed: &serde_json::Value) -> String {
     let path = extract_tool_path(parsed);
     let suffix = if parsed
         .get("replaceAll")
-        .and_then(serde_json::Value::as_bool)
+        .and_then(|value| value.as_bool())
         .unwrap_or(false)
     {
         " (replace all)"
@@ -2525,7 +2596,7 @@ fn format_edit_result(icon: &str, parsed: &serde_json::Value) -> String {
 fn format_glob_result(icon: &str, parsed: &serde_json::Value) -> String {
     let num_files = parsed
         .get("numFiles")
-        .and_then(serde_json::Value::as_u64)
+        .and_then(|value| value.as_u64())
         .unwrap_or(0);
     let filenames = parsed
         .get("filenames")
@@ -2549,11 +2620,11 @@ fn format_glob_result(icon: &str, parsed: &serde_json::Value) -> String {
 fn format_grep_result(icon: &str, parsed: &serde_json::Value) -> String {
     let num_matches = parsed
         .get("numMatches")
-        .and_then(serde_json::Value::as_u64)
+        .and_then(|value| value.as_u64())
         .unwrap_or(0);
     let num_files = parsed
         .get("numFiles")
-        .and_then(serde_json::Value::as_u64)
+        .and_then(|value| value.as_u64())
         .unwrap_or(0);
     let content = parsed
         .get("content")
@@ -2650,7 +2721,12 @@ fn response_to_events(
         }
     }
 
-    events.push(AssistantEvent::Usage(response.usage.token_usage()));
+    events.push(AssistantEvent::Usage(TokenUsage {
+        input_tokens: response.usage.input_tokens,
+        output_tokens: response.usage.output_tokens,
+        cache_creation_input_tokens: response.usage.cache_creation_input_tokens,
+        cache_read_input_tokens: response.usage.cache_read_input_tokens,
+    }));
     events.push(AssistantEvent::MessageStop);
     Ok(events)
 }
@@ -2781,7 +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,
@@ -2841,7 +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")?;
@@ -2855,18 +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() {
@@ -3040,13 +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()],
             }
         );
@@ -3056,7 +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(),
@@ -3064,7 +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(),
@@ -3092,7 +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]
@@ -3112,7 +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"));
     }
 
@@ -3133,9 +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"));
     }
@@ -3237,7 +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,
@@ -3254,7 +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"));
     }
@@ -3329,9 +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!(
@@ -3350,6 +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]

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

@@ -286,7 +286,7 @@ impl TerminalRenderer {
     ) {
         match event {
             Event::Start(Tag::Heading { level, .. }) => {
-                Self::start_heading(state, level as u8, output);
+                self.start_heading(state, level as u8, output)
             }
             Event::End(TagEnd::Paragraph) => output.push_str("\n\n"),
             Event::Start(Tag::BlockQuote(..)) => self.start_quote(state, output),
@@ -426,7 +426,7 @@ impl TerminalRenderer {
         }
     }
 
-    fn start_heading(state: &mut RenderState, level: u8, output: &mut String) {
+    fn start_heading(&self, state: &mut RenderState, level: u8, output: &mut String) {
         state.heading_level = Some(level);
         if !output.is_empty() {
             output.push('\n');

rust/crates/telemetry/Cargo.toml

@@ -1,13 +0,0 @@
-[package]
-name = "telemetry"
-version.workspace = true
-edition.workspace = true
-license.workspace = true
-publish.workspace = true
-
-[dependencies]
-serde = { version = "1", features = ["derive"] }
-serde_json = "1"
-
-[lints]
-workspace = true

rust/crates/telemetry/src/lib.rs

@@ -1,526 +0,0 @@
-use std::fmt::{Debug, Formatter};
-use std::fs::{File, OpenOptions};
-use std::io::Write;
-use std::path::{Path, PathBuf};
-use std::sync::atomic::{AtomicU64, Ordering};
-use std::sync::{Arc, Mutex};
-use std::time::{SystemTime, UNIX_EPOCH};
-
-use serde::{Deserialize, Serialize};
-use serde_json::{Map, Value};
-
-pub const DEFAULT_ANTHROPIC_VERSION: &str = "2023-06-01";
-pub const DEFAULT_APP_NAME: &str = "claude-code";
-pub const DEFAULT_RUNTIME: &str = "rust";
-pub const DEFAULT_AGENTIC_BETA: &str = "claude-code-20250219";
-pub const DEFAULT_PROMPT_CACHING_SCOPE_BETA: &str = "prompt-caching-scope-2026-01-05";
-
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
-pub struct ClientIdentity {
-    pub app_name: String,
-    pub app_version: String,
-    pub runtime: String,
-}
-
-impl ClientIdentity {
-    #[must_use]
-    pub fn new(app_name: impl Into<String>, app_version: impl Into<String>) -> Self {
-        Self {
-            app_name: app_name.into(),
-            app_version: app_version.into(),
-            runtime: DEFAULT_RUNTIME.to_string(),
-        }
-    }
-
-    #[must_use]
-    pub fn with_runtime(mut self, runtime: impl Into<String>) -> Self {
-        self.runtime = runtime.into();
-        self
-    }
-
-    #[must_use]
-    pub fn user_agent(&self) -> String {
-        format!("{}/{}", self.app_name, self.app_version)
-    }
-}
-
-impl Default for ClientIdentity {
-    fn default() -> Self {
-        Self::new(DEFAULT_APP_NAME, env!("CARGO_PKG_VERSION"))
-    }
-}
-
-#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
-pub struct AnthropicRequestProfile {
-    pub anthropic_version: String,
-    pub client_identity: ClientIdentity,
-    #[serde(default, skip_serializing_if = "Vec::is_empty")]
-    pub betas: Vec<String>,
-    #[serde(default, skip_serializing_if = "Map::is_empty")]
-    pub extra_body: Map<String, Value>,
-}
-
-impl AnthropicRequestProfile {
-    #[must_use]
-    pub fn new(client_identity: ClientIdentity) -> Self {
-        Self {
-            anthropic_version: DEFAULT_ANTHROPIC_VERSION.to_string(),
-            client_identity,
-            betas: vec![
-                DEFAULT_AGENTIC_BETA.to_string(),
-                DEFAULT_PROMPT_CACHING_SCOPE_BETA.to_string(),
-            ],
-            extra_body: Map::new(),
-        }
-    }
-
-    #[must_use]
-    pub fn with_beta(mut self, beta: impl Into<String>) -> Self {
-        let beta = beta.into();
-        if !self.betas.contains(&beta) {
-            self.betas.push(beta);
-        }
-        self
-    }
-
-    #[must_use]
-    pub fn with_extra_body(mut self, key: impl Into<String>, value: Value) -> Self {
-        self.extra_body.insert(key.into(), value);
-        self
-    }
-
-    #[must_use]
-    pub fn header_pairs(&self) -> Vec<(String, String)> {
-        let mut headers = vec![
-            (
-                "anthropic-version".to_string(),
-                self.anthropic_version.clone(),
-            ),
-            ("user-agent".to_string(), self.client_identity.user_agent()),
-        ];
-        if !self.betas.is_empty() {
-            headers.push(("anthropic-beta".to_string(), self.betas.join(",")));
-        }
-        headers
-    }
-
-    pub fn render_json_body<T: Serialize>(&self, request: &T) -> Result<Value, serde_json::Error> {
-        let mut body = serde_json::to_value(request)?;
-        let object = body.as_object_mut().ok_or_else(|| {
-            serde_json::Error::io(std::io::Error::new(
-                std::io::ErrorKind::InvalidData,
-                "request body must serialize to a JSON object",
-            ))
-        })?;
-        for (key, value) in &self.extra_body {
-            object.insert(key.clone(), value.clone());
-        }
-        if !self.betas.is_empty() {
-            object.insert(
-                "betas".to_string(),
-                Value::Array(self.betas.iter().cloned().map(Value::String).collect()),
-            );
-        }
-        Ok(body)
-    }
-}
-
-impl Default for AnthropicRequestProfile {
-    fn default() -> Self {
-        Self::new(ClientIdentity::default())
-    }
-}
-
-#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
-pub struct AnalyticsEvent {
-    pub namespace: String,
-    pub action: String,
-    #[serde(default, skip_serializing_if = "Map::is_empty")]
-    pub properties: Map<String, Value>,
-}
-
-impl AnalyticsEvent {
-    #[must_use]
-    pub fn new(namespace: impl Into<String>, action: impl Into<String>) -> Self {
-        Self {
-            namespace: namespace.into(),
-            action: action.into(),
-            properties: Map::new(),
-        }
-    }
-
-    #[must_use]
-    pub fn with_property(mut self, key: impl Into<String>, value: Value) -> Self {
-        self.properties.insert(key.into(), value);
-        self
-    }
-}
-
-#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
-pub struct SessionTraceRecord {
-    pub session_id: String,
-    pub sequence: u64,
-    pub name: String,
-    pub timestamp_ms: u64,
-    #[serde(default, skip_serializing_if = "Map::is_empty")]
-    pub attributes: Map<String, Value>,
-}
-
-#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
-#[serde(tag = "type", rename_all = "snake_case")]
-pub enum TelemetryEvent {
-    HttpRequestStarted {
-        session_id: String,
-        attempt: u32,
-        method: String,
-        path: String,
-        #[serde(default, skip_serializing_if = "Map::is_empty")]
-        attributes: Map<String, Value>,
-    },
-    HttpRequestSucceeded {
-        session_id: String,
-        attempt: u32,
-        method: String,
-        path: String,
-        status: u16,
-        #[serde(default, skip_serializing_if = "Option::is_none")]
-        request_id: Option<String>,
-        #[serde(default, skip_serializing_if = "Map::is_empty")]
-        attributes: Map<String, Value>,
-    },
-    HttpRequestFailed {
-        session_id: String,
-        attempt: u32,
-        method: String,
-        path: String,
-        error: String,
-        retryable: bool,
-        #[serde(default, skip_serializing_if = "Map::is_empty")]
-        attributes: Map<String, Value>,
-    },
-    Analytics(AnalyticsEvent),
-    SessionTrace(SessionTraceRecord),
-}
-
-pub trait TelemetrySink: Send + Sync {
-    fn record(&self, event: TelemetryEvent);
-}
-
-#[derive(Default)]
-pub struct MemoryTelemetrySink {
-    events: Mutex<Vec<TelemetryEvent>>,
-}
-
-impl MemoryTelemetrySink {
-    #[must_use]
-    pub fn events(&self) -> Vec<TelemetryEvent> {
-        self.events
-            .lock()
-            .unwrap_or_else(std::sync::PoisonError::into_inner)
-            .clone()
-    }
-}
-
-impl TelemetrySink for MemoryTelemetrySink {
-    fn record(&self, event: TelemetryEvent) {
-        self.events
-            .lock()
-            .unwrap_or_else(std::sync::PoisonError::into_inner)
-            .push(event);
-    }
-}
-
-pub struct JsonlTelemetrySink {
-    path: PathBuf,
-    file: Mutex<File>,
-}
-
-impl Debug for JsonlTelemetrySink {
-    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        f.debug_struct("JsonlTelemetrySink")
-            .field("path", &self.path)
-            .finish_non_exhaustive()
-    }
-}
-
-impl JsonlTelemetrySink {
-    pub fn new(path: impl AsRef<Path>) -> Result<Self, std::io::Error> {
-        let path = path.as_ref().to_path_buf();
-        if let Some(parent) = path.parent() {
-            std::fs::create_dir_all(parent)?;
-        }
-        let file = OpenOptions::new().create(true).append(true).open(&path)?;
-        Ok(Self {
-            path,
-            file: Mutex::new(file),
-        })
-    }
-
-    #[must_use]
-    pub fn path(&self) -> &Path {
-        &self.path
-    }
-}
-
-impl TelemetrySink for JsonlTelemetrySink {
-    fn record(&self, event: TelemetryEvent) {
-        let Ok(line) = serde_json::to_string(&event) else {
-            return;
-        };
-        let mut file = self
-            .file
-            .lock()
-            .unwrap_or_else(std::sync::PoisonError::into_inner);
-        let _ = writeln!(file, "{line}");
-        let _ = file.flush();
-    }
-}
-
-#[derive(Clone)]
-pub struct SessionTracer {
-    session_id: String,
-    sequence: Arc<AtomicU64>,
-    sink: Arc<dyn TelemetrySink>,
-}
-
-impl Debug for SessionTracer {
-    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        f.debug_struct("SessionTracer")
-            .field("session_id", &self.session_id)
-            .finish_non_exhaustive()
-    }
-}
-
-impl SessionTracer {
-    #[must_use]
-    pub fn new(session_id: impl Into<String>, sink: Arc<dyn TelemetrySink>) -> Self {
-        Self {
-            session_id: session_id.into(),
-            sequence: Arc::new(AtomicU64::new(0)),
-            sink,
-        }
-    }
-
-    #[must_use]
-    pub fn session_id(&self) -> &str {
-        &self.session_id
-    }
-
-    pub fn record(&self, name: impl Into<String>, attributes: Map<String, Value>) {
-        let record = SessionTraceRecord {
-            session_id: self.session_id.clone(),
-            sequence: self.sequence.fetch_add(1, Ordering::Relaxed),
-            name: name.into(),
-            timestamp_ms: current_timestamp_ms(),
-            attributes,
-        };
-        self.sink.record(TelemetryEvent::SessionTrace(record));
-    }
-
-    pub fn record_http_request_started(
-        &self,
-        attempt: u32,
-        method: impl Into<String>,
-        path: impl Into<String>,
-        attributes: Map<String, Value>,
-    ) {
-        let method = method.into();
-        let path = path.into();
-        self.sink.record(TelemetryEvent::HttpRequestStarted {
-            session_id: self.session_id.clone(),
-            attempt,
-            method: method.clone(),
-            path: path.clone(),
-            attributes: attributes.clone(),
-        });
-        self.record(
-            "http_request_started",
-            merge_trace_fields(method, path, attempt, attributes),
-        );
-    }
-
-    pub fn record_http_request_succeeded(
-        &self,
-        attempt: u32,
-        method: impl Into<String>,
-        path: impl Into<String>,
-        status: u16,
-        request_id: Option<String>,
-        attributes: Map<String, Value>,
-    ) {
-        let method = method.into();
-        let path = path.into();
-        self.sink.record(TelemetryEvent::HttpRequestSucceeded {
-            session_id: self.session_id.clone(),
-            attempt,
-            method: method.clone(),
-            path: path.clone(),
-            status,
-            request_id: request_id.clone(),
-            attributes: attributes.clone(),
-        });
-        let mut trace_attributes = merge_trace_fields(method, path, attempt, attributes);
-        trace_attributes.insert("status".to_string(), Value::from(status));
-        if let Some(request_id) = request_id {
-            trace_attributes.insert("request_id".to_string(), Value::String(request_id));
-        }
-        self.record("http_request_succeeded", trace_attributes);
-    }
-
-    pub fn record_http_request_failed(
-        &self,
-        attempt: u32,
-        method: impl Into<String>,
-        path: impl Into<String>,
-        error: impl Into<String>,
-        retryable: bool,
-        attributes: Map<String, Value>,
-    ) {
-        let method = method.into();
-        let path = path.into();
-        let error = error.into();
-        self.sink.record(TelemetryEvent::HttpRequestFailed {
-            session_id: self.session_id.clone(),
-            attempt,
-            method: method.clone(),
-            path: path.clone(),
-            error: error.clone(),
-            retryable,
-            attributes: attributes.clone(),
-        });
-        let mut trace_attributes = merge_trace_fields(method, path, attempt, attributes);
-        trace_attributes.insert("error".to_string(), Value::String(error));
-        trace_attributes.insert("retryable".to_string(), Value::Bool(retryable));
-        self.record("http_request_failed", trace_attributes);
-    }
-
-    pub fn record_analytics(&self, event: AnalyticsEvent) {
-        let mut attributes = event.properties.clone();
-        attributes.insert(
-            "namespace".to_string(),
-            Value::String(event.namespace.clone()),
-        );
-        attributes.insert("action".to_string(), Value::String(event.action.clone()));
-        self.sink.record(TelemetryEvent::Analytics(event));
-        self.record("analytics", attributes);
-    }
-}
-
-fn merge_trace_fields(
-    method: String,
-    path: String,
-    attempt: u32,
-    mut attributes: Map<String, Value>,
-) -> Map<String, Value> {
-    attributes.insert("method".to_string(), Value::String(method));
-    attributes.insert("path".to_string(), Value::String(path));
-    attributes.insert("attempt".to_string(), Value::from(attempt));
-    attributes
-}
-
-fn current_timestamp_ms() -> u64 {
-    SystemTime::now()
-        .duration_since(UNIX_EPOCH)
-        .unwrap_or_default()
-        .as_millis()
-        .try_into()
-        .unwrap_or(u64::MAX)
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn request_profile_emits_headers_and_merges_body() {
-        let profile = AnthropicRequestProfile::new(
-            ClientIdentity::new("claude-code", "1.2.3").with_runtime("rust-cli"),
-        )
-        .with_beta("tools-2026-04-01")
-        .with_extra_body("metadata", serde_json::json!({"source": "test"}));
-
-        assert_eq!(
-            profile.header_pairs(),
-            vec![
-                (
-                    "anthropic-version".to_string(),
-                    DEFAULT_ANTHROPIC_VERSION.to_string()
-                ),
-                ("user-agent".to_string(), "claude-code/1.2.3".to_string()),
-                (
-                    "anthropic-beta".to_string(),
-                    "claude-code-20250219,prompt-caching-scope-2026-01-05,tools-2026-04-01"
-                        .to_string(),
-                ),
-            ]
-        );
-
-        let body = profile
-            .render_json_body(&serde_json::json!({"model": "claude-sonnet"}))
-            .expect("body should serialize");
-        assert_eq!(
-            body["metadata"]["source"],
-            Value::String("test".to_string())
-        );
-        assert_eq!(
-            body["betas"],
-            serde_json::json!([
-                "claude-code-20250219",
-                "prompt-caching-scope-2026-01-05",
-                "tools-2026-04-01"
-            ])
-        );
-    }
-
-    #[test]
-    fn session_tracer_records_structured_events_and_trace_sequence() {
-        let sink = Arc::new(MemoryTelemetrySink::default());
-        let tracer = SessionTracer::new("session-123", sink.clone());
-
-        tracer.record_http_request_started(1, "POST", "/v1/messages", Map::new());
-        tracer.record_analytics(
-            AnalyticsEvent::new("cli", "prompt_sent")
-                .with_property("model", Value::String("claude-opus".to_string())),
-        );
-
-        let events = sink.events();
-        assert!(matches!(
-            &events[0],
-            TelemetryEvent::HttpRequestStarted {
-                session_id,
-                attempt: 1,
-                method,
-                path,
-                ..
-            } if session_id == "session-123" && method == "POST" && path == "/v1/messages"
-        ));
-        assert!(matches!(
-            &events[1],
-            TelemetryEvent::SessionTrace(SessionTraceRecord { sequence: 0, name, .. })
-            if name == "http_request_started"
-        ));
-        assert!(matches!(&events[2], TelemetryEvent::Analytics(_)));
-        assert!(matches!(
-            &events[3],
-            TelemetryEvent::SessionTrace(SessionTraceRecord { sequence: 1, name, .. })
-            if name == "analytics"
-        ));
-    }
-
-    #[test]
-    fn jsonl_sink_persists_events() {
-        let path =
-            std::env::temp_dir().join(format!("telemetry-jsonl-{}.log", current_timestamp_ms()));
-        let sink = JsonlTelemetrySink::new(&path).expect("sink should create file");
-
-        sink.record(TelemetryEvent::Analytics(
-            AnalyticsEvent::new("cli", "turn_completed").with_property("ok", Value::Bool(true)),
-        ));
-
-        let contents = std::fs::read_to_string(&path).expect("telemetry log should be readable");
-        assert!(contents.contains("\"type\":\"analytics\""));
-        assert!(contents.contains("\"action\":\"turn_completed\""));
-
-        let _ = std::fs::remove_file(path);
-    }
-}

rust/crates/tools/src/lib.rs

@@ -13,7 +13,7 @@ use runtime::{
     edit_file, execute_bash, glob_search, grep_search, load_system_prompt, read_file, write_file,
     ApiClient, ApiRequest, AssistantEvent, BashCommandInput, ContentBlock, ConversationMessage,
     ConversationRuntime, GrepSearchInput, MessageRole, PermissionMode, PermissionPolicy,
-    RuntimeError, Session, ToolError, ToolExecutor,
+    RuntimeError, Session, TokenUsage, ToolError, ToolExecutor,
 };
 use serde::{Deserialize, Serialize};
 use serde_json::{json, Value};
@@ -1723,7 +1723,12 @@ impl ApiClient for AnthropicRuntimeClient {
                         }
                     }
                     ApiStreamEvent::MessageDelta(delta) => {
-                        events.push(AssistantEvent::Usage(delta.usage.token_usage()));
+                        events.push(AssistantEvent::Usage(TokenUsage {
+                            input_tokens: delta.usage.input_tokens,
+                            output_tokens: delta.usage.output_tokens,
+                            cache_creation_input_tokens: 0,
+                            cache_read_input_tokens: 0,
+                        }));
                     }
                     ApiStreamEvent::MessageStop(_) => {
                         saw_stop = true;
@@ -1869,7 +1874,12 @@ fn response_to_events(response: MessageResponse) -> Vec<AssistantEvent> {
         }
     }
 
-    events.push(AssistantEvent::Usage(response.usage.token_usage()));
+    events.push(AssistantEvent::Usage(TokenUsage {
+        input_tokens: response.usage.input_tokens,
+        output_tokens: response.usage.output_tokens,
+        cache_creation_input_tokens: response.usage.cache_creation_input_tokens,
+        cache_read_input_tokens: response.usage.cache_read_input_tokens,
+    }));
     events.push(AssistantEvent::MessageStop);
     events
 }