Persist CLI conversation history across sessions

The Rust CLI now stores managed sessions under ~/.claude/sessions,
records additive session metadata in the canonical JSON transcript,
and exposes a /sessions listing alias alongside ID-or-path resume.
Inactive oversized sessions are compacted automatically so old
transcripts remain resumable without growing unchecked.

Constraint: Session JSON must stay backward-compatible with legacy files that lack metadata
Constraint: Managed sessions must use a single canonical JSON file per session without new dependencies
Rejected: Sidecar metadata/index files | duplicated state and diverged from the requested single-file persistence model
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Keep CLI policy in the CLI; only add transcript-adjacent metadata to runtime::Session unless another consumer truly needs more
Tested: cargo fmt; cargo clippy --workspace --all-targets -- -D warnings; cargo test --workspace
Not-tested: Manual interactive REPL smoke test against the live Anthropic API

rust/crates/runtime/src/compact.rs

@@ -105,6 +105,7 @@ pub fn compact_session(session: &Session, config: CompactionConfig) -> Compactio
         compacted_session: Session {
             version: session.version,
             messages: compacted_messages,
+            metadata: session.metadata.clone(),
         },
         removed_message_count: removed.len(),
     }
@@ -393,6 +394,7 @@ mod tests {
         let session = Session {
             version: 1,
             messages: vec![ConversationMessage::user_text("hello")],
+            metadata: None,
         };
 
         let result = compact_session(&session, CompactionConfig::default());
@@ -420,6 +422,7 @@ mod tests {
                     usage: None,
                 },
             ],
+            metadata: None,
         };
 
         let result = compact_session(

rust/crates/runtime/src/conversation.rs

@@ -408,7 +408,7 @@ mod tests {
                 .sum::<i32>();
             Ok(total.to_string())
         });
-        let permission_policy = PermissionPolicy::new(PermissionMode::Prompt);
+        let permission_policy = PermissionPolicy::new(PermissionMode::WorkspaceWrite);
         let system_prompt = SystemPromptBuilder::new()
             .with_project_context(ProjectContext {
                 cwd: PathBuf::from("/tmp/project"),
@@ -487,7 +487,7 @@ mod tests {
             Session::new(),
             SingleCallApiClient,
             StaticToolExecutor::new(),
-            PermissionPolicy::new(PermissionMode::Prompt),
+            PermissionPolicy::new(PermissionMode::WorkspaceWrite),
             vec!["system".to_string()],
         );
 
@@ -536,7 +536,7 @@ mod tests {
             session,
             SimpleApi,
             StaticToolExecutor::new(),
-            PermissionPolicy::new(PermissionMode::Allow),
+            PermissionPolicy::new(PermissionMode::DangerFullAccess),
             vec!["system".to_string()],
         );
 
@@ -563,7 +563,7 @@ mod tests {
             Session::new(),
             SimpleApi,
             StaticToolExecutor::new(),
-            PermissionPolicy::new(PermissionMode::Allow),
+            PermissionPolicy::new(PermissionMode::DangerFullAccess),
             vec!["system".to_string()],
         );
         runtime.run_turn("a", None).expect("turn a");

rust/crates/runtime/src/lib.rs

@@ -73,7 +73,9 @@ 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, SessionError, SessionMetadata,
+};
 pub use usage::{
     format_usd, pricing_for_model, ModelPricing, TokenUsage, UsageCostEstimate, UsageTracker,
 };

rust/crates/runtime/src/session.rs

@@ -39,10 +39,19 @@ pub struct ConversationMessage {
     pub usage: Option<TokenUsage>,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct SessionMetadata {
+    pub started_at: String,
+    pub model: String,
+    pub message_count: u32,
+    pub last_prompt: Option<String>,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Session {
     pub version: u32,
     pub messages: Vec<ConversationMessage>,
+    pub metadata: Option<SessionMetadata>,
 }
 
 #[derive(Debug)]
@@ -82,6 +91,7 @@ impl Session {
         Self {
             version: 1,
             messages: Vec::new(),
+            metadata: None,
         }
     }
 
@@ -111,6 +121,9 @@ impl Session {
                     .collect(),
             ),
         );
+        if let Some(metadata) = &self.metadata {
+            object.insert("metadata".to_string(), metadata.to_json());
+        }
         JsonValue::Object(object)
     }
 
@@ -131,7 +144,15 @@ impl Session {
             .iter()
             .map(ConversationMessage::from_json)
             .collect::<Result<Vec<_>, _>>()?;
-        Ok(Self { version, messages })
+        let metadata = object
+            .get("metadata")
+            .map(SessionMetadata::from_json)
+            .transpose()?;
+        Ok(Self {
+            version,
+            messages,
+            metadata,
+        })
     }
 }
 
@@ -141,6 +162,41 @@ impl Default for Session {
     }
 }
 
+impl SessionMetadata {
+    #[must_use]
+    pub fn to_json(&self) -> JsonValue {
+        let mut object = BTreeMap::new();
+        object.insert(
+            "started_at".to_string(),
+            JsonValue::String(self.started_at.clone()),
+        );
+        object.insert("model".to_string(), JsonValue::String(self.model.clone()));
+        object.insert(
+            "message_count".to_string(),
+            JsonValue::Number(i64::from(self.message_count)),
+        );
+        if let Some(last_prompt) = &self.last_prompt {
+            object.insert(
+                "last_prompt".to_string(),
+                JsonValue::String(last_prompt.clone()),
+            );
+        }
+        JsonValue::Object(object)
+    }
+
+    fn from_json(value: &JsonValue) -> Result<Self, SessionError> {
+        let object = value.as_object().ok_or_else(|| {
+            SessionError::Format("session metadata must be an object".to_string())
+        })?;
+        Ok(Self {
+            started_at: required_string(object, "started_at")?,
+            model: required_string(object, "model")?,
+            message_count: required_u32(object, "message_count")?,
+            last_prompt: optional_string(object, "last_prompt"),
+        })
+    }
+}
+
 impl ConversationMessage {
     #[must_use]
     pub fn user_text(text: impl Into<String>) -> Self {
@@ -368,6 +424,13 @@ fn required_string(
         .ok_or_else(|| SessionError::Format(format!("missing {key}")))
 }
 
+fn optional_string(object: &BTreeMap<String, JsonValue>, key: &str) -> Option<String> {
+    object
+        .get(key)
+        .and_then(JsonValue::as_str)
+        .map(ToOwned::to_owned)
+}
+
 fn required_u32(object: &BTreeMap<String, JsonValue>, key: &str) -> Result<u32, SessionError> {
     let value = object
         .get(key)
@@ -378,7 +441,8 @@ fn required_u32(object: &BTreeMap<String, JsonValue>, key: &str) -> Result<u32,
 
 #[cfg(test)]
 mod tests {
-    use super::{ContentBlock, ConversationMessage, MessageRole, Session};
+    use super::{ContentBlock, ConversationMessage, MessageRole, Session, SessionMetadata};
+    use crate::json::JsonValue;
     use crate::usage::TokenUsage;
     use std::fs;
     use std::time::{SystemTime, UNIX_EPOCH};
@@ -386,6 +450,12 @@ mod tests {
     #[test]
     fn persists_and_restores_session_json() {
         let mut session = Session::new();
+        session.metadata = Some(SessionMetadata {
+            started_at: "2026-04-01T00:00:00Z".to_string(),
+            model: "claude-sonnet".to_string(),
+            message_count: 3,
+            last_prompt: Some("hello".to_string()),
+        });
         session
             .messages
             .push(ConversationMessage::user_text("hello"));
@@ -428,5 +498,23 @@ mod tests {
             restored.messages[1].usage.expect("usage").total_tokens(),
             17
         );
+        assert_eq!(restored.metadata, session.metadata);
+    }
+
+    #[test]
+    fn loads_legacy_session_without_metadata() {
+        let legacy = r#"{
+  "version": 1,
+  "messages": [
+    {
+      "role": "user",
+      "blocks": [{"type": "text", "text": "hello"}]
+    }
+  ]
+}"#;
+        let restored = Session::from_json(&JsonValue::parse(legacy).expect("legacy json"))
+            .expect("legacy session should parse");
+        assert_eq!(restored.messages.len(), 1);
+        assert!(restored.metadata.is_none());
     }
 }

rust/crates/runtime/src/usage.rs

@@ -300,6 +300,7 @@ mod tests {
                     cache_read_input_tokens: 0,
                 }),
             }],
+            metadata: None,
         };
 
         let tracker = UsageTracker::from_session(&session);