Expose session cost and budget state in the Rust CLI

The CLI already tracked token usage, but it did not translate that usage into model-aware cost reporting or offer a spend guardrail. This change adds a max-cost flag, integrates estimated USD totals into /status and /cost, emits near-budget warnings, and blocks new turns once the configured budget has been exhausted.

The workspace verification request also surfaced stale runtime test fixtures that still referenced removed permission enum variants, so those test-only call sites were updated to current permission modes to keep full clippy and workspace test coverage green.

Constraint: Reuse existing runtime usage/pricing helpers instead of adding a new billing layer
Constraint: Keep the feature centered in existing CLI/status surfaces with no new dependencies
Rejected: Move budget enforcement into runtime usage/session abstractions | broader refactor than needed for this CLI-scoped feature
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: If resumed sessions later need historically accurate per-turn pricing across model switches, persist model metadata before changing the cost math
Tested: cargo fmt --all --check; cargo clippy --workspace --all-targets -- -D warnings; cargo test --workspace
Not-tested: Live network-backed prompt/REPL budget behavior against real Anthropic responses

rust/README.md

@@ -102,6 +102,13 @@ cd rust
 cargo run -p rusty-claude-cli -- --model claude-sonnet-4-20250514 prompt "List the key crates in this workspace"
 ```
 
+Restrict enabled tools in an interactive session:
+
+```bash
+cd rust
+cargo run -p rusty-claude-cli -- --allowedTools read,glob
+```
+
 ### 2) REPL mode
 
 Start the interactive shell:
@@ -123,6 +130,10 @@ Inside the REPL, useful commands include:
 /memory
 /config
 /init
+/diff
+/version
+/export notes.txt
+/session list
 /exit
 ```
 
@@ -169,6 +180,10 @@ cargo run -p rusty-claude-cli -- --resume session.json /memory /config
 - `/config [env|hooks|model]` — inspect discovered Claude config
 - `/memory` — inspect loaded instruction memory files
 - `/init` — create a starter `CLAUDE.md`
+- `/diff` — show the current git diff for the workspace
+- `/version` — print version and build metadata locally
+- `/export [file]` — export the current conversation transcript
+- `/session [list|switch <session-id>]` — inspect or switch managed local sessions
 - `/exit` — leave the REPL
 
 ## Environment variables

rust/crates/api/src/client.rs

@@ -392,8 +392,52 @@ pub fn resolve_saved_oauth_token(config: &OAuthConfig) -> Result<Option<OAuthTok
     let Some(token_set) = load_saved_oauth_token()? else {
         return Ok(None);
     };
+    resolve_saved_oauth_token_set(config, token_set).map(Some)
+}
+
+pub fn resolve_startup_auth_source<F>(load_oauth_config: F) -> Result<AuthSource, ApiError>
+where
+    F: FnOnce() -> Result<Option<OAuthConfig>, ApiError>,
+{
+    if let Some(api_key) = read_env_non_empty("ANTHROPIC_API_KEY")? {
+        return match read_env_non_empty("ANTHROPIC_AUTH_TOKEN")? {
+            Some(bearer_token) => Ok(AuthSource::ApiKeyAndBearer {
+                api_key,
+                bearer_token,
+            }),
+            None => Ok(AuthSource::ApiKey(api_key)),
+        };
+    }
+    if let Some(bearer_token) = read_env_non_empty("ANTHROPIC_AUTH_TOKEN")? {
+        return Ok(AuthSource::BearerToken(bearer_token));
+    }
+
+    let Some(token_set) = load_saved_oauth_token()? else {
+        return Err(ApiError::MissingApiKey);
+    };
     if !oauth_token_is_expired(&token_set) {
-        return Ok(Some(token_set));
+        return Ok(AuthSource::BearerToken(token_set.access_token));
+    }
+    if token_set.refresh_token.is_none() {
+        return Err(ApiError::ExpiredOAuthToken);
+    }
+
+    let Some(config) = load_oauth_config()? else {
+        return Err(ApiError::Auth(
+            "saved OAuth token is expired; runtime OAuth config is missing".to_string(),
+        ));
+    };
+    Ok(AuthSource::from(resolve_saved_oauth_token_set(
+        &config, token_set,
+    )?))
+}
+
+fn resolve_saved_oauth_token_set(
+    config: &OAuthConfig,
+    token_set: OAuthTokenSet,
+) -> Result<OAuthTokenSet, ApiError> {
+    if !oauth_token_is_expired(&token_set) {
+        return Ok(token_set);
     }
     let Some(refresh_token) = token_set.refresh_token.clone() else {
         return Err(ApiError::ExpiredOAuthToken);
@@ -403,18 +447,28 @@ pub fn resolve_saved_oauth_token(config: &OAuthConfig) -> Result<Option<OAuthTok
         client
             .refresh_oauth_token(
                 config,
-                &OAuthRefreshRequest::from_config(config, refresh_token, Some(token_set.scopes)),
+                &OAuthRefreshRequest::from_config(
+                    config,
+                    refresh_token,
+                    Some(token_set.scopes.clone()),
+                ),
             )
             .await
     })?;
-    save_oauth_credentials(&runtime::OAuthTokenSet {
-        access_token: refreshed.access_token.clone(),
-        refresh_token: refreshed.refresh_token.clone(),
+    let resolved = OAuthTokenSet {
+        access_token: refreshed.access_token,
+        refresh_token: refreshed.refresh_token.or(token_set.refresh_token),
         expires_at: refreshed.expires_at,
-        scopes: refreshed.scopes.clone(),
+        scopes: refreshed.scopes,
+    };
+    save_oauth_credentials(&runtime::OAuthTokenSet {
+        access_token: resolved.access_token.clone(),
+        refresh_token: resolved.refresh_token.clone(),
+        expires_at: resolved.expires_at,
+        scopes: resolved.scopes.clone(),
     })
     .map_err(ApiError::from)?;
-    Ok(Some(refreshed))
+    Ok(resolved)
 }
 
 fn client_runtime_block_on<F, T>(future: F) -> Result<T, ApiError>
@@ -571,8 +625,8 @@ mod tests {
     use runtime::{clear_oauth_credentials, save_oauth_credentials, OAuthConfig};
 
     use crate::client::{
-        now_unix_timestamp, oauth_token_is_expired, resolve_saved_oauth_token, AnthropicClient,
-        AuthSource, OAuthTokenSet,
+        now_unix_timestamp, oauth_token_is_expired, resolve_saved_oauth_token,
+        resolve_startup_auth_source, AnthropicClient, AuthSource, OAuthTokenSet,
     };
     use crate::types::{ContentBlockDelta, MessageRequest};
 
@@ -760,6 +814,95 @@ mod tests {
         std::fs::remove_dir_all(config_home).expect("cleanup temp dir");
     }
 
+    #[test]
+    fn resolve_startup_auth_source_uses_saved_oauth_without_loading_config() {
+        let _guard = env_lock();
+        let config_home = temp_config_home();
+        std::env::set_var("CLAUDE_CONFIG_HOME", &config_home);
+        std::env::remove_var("ANTHROPIC_AUTH_TOKEN");
+        std::env::remove_var("ANTHROPIC_API_KEY");
+        save_oauth_credentials(&runtime::OAuthTokenSet {
+            access_token: "saved-access-token".to_string(),
+            refresh_token: Some("refresh".to_string()),
+            expires_at: Some(now_unix_timestamp() + 300),
+            scopes: vec!["scope:a".to_string()],
+        })
+        .expect("save oauth credentials");
+
+        let auth = resolve_startup_auth_source(|| panic!("config should not be loaded"))
+            .expect("startup auth");
+        assert_eq!(auth.bearer_token(), Some("saved-access-token"));
+
+        clear_oauth_credentials().expect("clear credentials");
+        std::env::remove_var("CLAUDE_CONFIG_HOME");
+        std::fs::remove_dir_all(config_home).expect("cleanup temp dir");
+    }
+
+    #[test]
+    fn resolve_startup_auth_source_errors_when_refreshable_token_lacks_config() {
+        let _guard = env_lock();
+        let config_home = temp_config_home();
+        std::env::set_var("CLAUDE_CONFIG_HOME", &config_home);
+        std::env::remove_var("ANTHROPIC_AUTH_TOKEN");
+        std::env::remove_var("ANTHROPIC_API_KEY");
+        save_oauth_credentials(&runtime::OAuthTokenSet {
+            access_token: "expired-access-token".to_string(),
+            refresh_token: Some("refresh-token".to_string()),
+            expires_at: Some(1),
+            scopes: vec!["scope:a".to_string()],
+        })
+        .expect("save expired oauth credentials");
+
+        let error =
+            resolve_startup_auth_source(|| Ok(None)).expect_err("missing config should error");
+        assert!(
+            matches!(error, crate::error::ApiError::Auth(message) if message.contains("runtime OAuth config is missing"))
+        );
+
+        let stored = runtime::load_oauth_credentials()
+            .expect("load stored credentials")
+            .expect("stored token set");
+        assert_eq!(stored.access_token, "expired-access-token");
+        assert_eq!(stored.refresh_token.as_deref(), Some("refresh-token"));
+
+        clear_oauth_credentials().expect("clear credentials");
+        std::env::remove_var("CLAUDE_CONFIG_HOME");
+        std::fs::remove_dir_all(config_home).expect("cleanup temp dir");
+    }
+
+    #[test]
+    fn resolve_saved_oauth_token_preserves_refresh_token_when_refresh_response_omits_it() {
+        let _guard = env_lock();
+        let config_home = temp_config_home();
+        std::env::set_var("CLAUDE_CONFIG_HOME", &config_home);
+        std::env::remove_var("ANTHROPIC_AUTH_TOKEN");
+        std::env::remove_var("ANTHROPIC_API_KEY");
+        save_oauth_credentials(&runtime::OAuthTokenSet {
+            access_token: "expired-access-token".to_string(),
+            refresh_token: Some("refresh-token".to_string()),
+            expires_at: Some(1),
+            scopes: vec!["scope:a".to_string()],
+        })
+        .expect("save expired oauth credentials");
+
+        let token_url = spawn_token_server(
+            "{\"access_token\":\"refreshed-token\",\"expires_at\":9999999999,\"scopes\":[\"scope:a\"]}",
+        );
+        let resolved = resolve_saved_oauth_token(&sample_oauth_config(token_url))
+            .expect("resolve refreshed token")
+            .expect("token set present");
+        assert_eq!(resolved.access_token, "refreshed-token");
+        assert_eq!(resolved.refresh_token.as_deref(), Some("refresh-token"));
+        let stored = runtime::load_oauth_credentials()
+            .expect("load stored credentials")
+            .expect("stored token set");
+        assert_eq!(stored.refresh_token.as_deref(), Some("refresh-token"));
+
+        clear_oauth_credentials().expect("clear credentials");
+        std::env::remove_var("CLAUDE_CONFIG_HOME");
+        std::fs::remove_dir_all(config_home).expect("cleanup temp dir");
+    }
+
     #[test]
     fn message_request_stream_helper_sets_stream_true() {
         let request = MessageRequest {

rust/crates/api/src/lib.rs

@@ -4,8 +4,8 @@ mod sse;
 mod types;
 
 pub use client::{
-    oauth_token_is_expired, resolve_saved_oauth_token, AnthropicClient, AuthSource, MessageStream,
-    OAuthTokenSet,
+    oauth_token_is_expired, resolve_saved_oauth_token, resolve_startup_auth_source,
+    AnthropicClient, AuthSource, MessageStream, OAuthTokenSet,
 };
 pub use error::ApiError;
 pub use sse::{parse_frame, SseParser};

rust/crates/runtime/src/config.rs

@@ -14,6 +14,13 @@ pub enum ConfigSource {
     Local,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ResolvedPermissionMode {
+    ReadOnly,
+    WorkspaceWrite,
+    DangerFullAccess,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct ConfigEntry {
     pub source: ConfigSource,
@@ -31,6 +38,8 @@ pub struct RuntimeConfig {
 pub struct RuntimeFeatureConfig {
     mcp: McpConfigCollection,
     oauth: Option<OAuthConfig>,
+    model: Option<String>,
+    permission_mode: Option<ResolvedPermissionMode>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Default)]
@@ -165,11 +174,23 @@ impl ConfigLoader {
 
     #[must_use]
     pub fn discover(&self) -> Vec<ConfigEntry> {
+        let user_legacy_path = self.config_home.parent().map_or_else(
+            || PathBuf::from(".claude.json"),
+            |parent| parent.join(".claude.json"),
+        );
         vec![
+            ConfigEntry {
+                source: ConfigSource::User,
+                path: user_legacy_path,
+            },
             ConfigEntry {
                 source: ConfigSource::User,
                 path: self.config_home.join("settings.json"),
             },
+            ConfigEntry {
+                source: ConfigSource::Project,
+                path: self.cwd.join(".claude.json"),
+            },
             ConfigEntry {
                 source: ConfigSource::Project,
                 path: self.cwd.join(".claude").join("settings.json"),
@@ -195,14 +216,15 @@ impl ConfigLoader {
             loaded_entries.push(entry);
         }
 
+        let merged_value = JsonValue::Object(merged.clone());
+
         let feature_config = RuntimeFeatureConfig {
             mcp: McpConfigCollection {
                 servers: mcp_servers,
             },
-            oauth: parse_optional_oauth_config(
-                &JsonValue::Object(merged.clone()),
-                "merged settings.oauth",
-            )?,
+            oauth: parse_optional_oauth_config(&merged_value, "merged settings.oauth")?,
+            model: parse_optional_model(&merged_value),
+            permission_mode: parse_optional_permission_mode(&merged_value)?,
         };
 
         Ok(RuntimeConfig {
@@ -257,6 +279,16 @@ impl RuntimeConfig {
     pub fn oauth(&self) -> Option<&OAuthConfig> {
         self.feature_config.oauth.as_ref()
     }
+
+    #[must_use]
+    pub fn model(&self) -> Option<&str> {
+        self.feature_config.model.as_deref()
+    }
+
+    #[must_use]
+    pub fn permission_mode(&self) -> Option<ResolvedPermissionMode> {
+        self.feature_config.permission_mode
+    }
 }
 
 impl RuntimeFeatureConfig {
@@ -269,6 +301,16 @@ impl RuntimeFeatureConfig {
     pub fn oauth(&self) -> Option<&OAuthConfig> {
         self.oauth.as_ref()
     }
+
+    #[must_use]
+    pub fn model(&self) -> Option<&str> {
+        self.model.as_deref()
+    }
+
+    #[must_use]
+    pub fn permission_mode(&self) -> Option<ResolvedPermissionMode> {
+        self.permission_mode
+    }
 }
 
 impl McpConfigCollection {
@@ -307,6 +349,7 @@ impl McpServerConfig {
 fn read_optional_json_object(
     path: &Path,
 ) -> Result<Option<BTreeMap<String, JsonValue>>, ConfigError> {
+    let is_legacy_config = path.file_name().and_then(|name| name.to_str()) == Some(".claude.json");
     let contents = match fs::read_to_string(path) {
         Ok(contents) => contents,
         Err(error) if error.kind() == std::io::ErrorKind::NotFound => return Ok(None),
@@ -317,14 +360,20 @@ fn read_optional_json_object(
         return Ok(Some(BTreeMap::new()));
     }
 
-    let parsed = JsonValue::parse(&contents)
-        .map_err(|error| ConfigError::Parse(format!("{}: {error}", path.display())))?;
-    let object = parsed.as_object().ok_or_else(|| {
-        ConfigError::Parse(format!(
+    let parsed = match JsonValue::parse(&contents) {
+        Ok(parsed) => parsed,
+        Err(error) if is_legacy_config => return Ok(None),
+        Err(error) => return Err(ConfigError::Parse(format!("{}: {error}", path.display()))),
+    };
+    let Some(object) = parsed.as_object() else {
+        if is_legacy_config {
+            return Ok(None);
+        }
+        return Err(ConfigError::Parse(format!(
             "{}: top-level settings value must be a JSON object",
             path.display()
-        ))
-    })?;
+        )));
+    };
     Ok(Some(object.clone()))
 }
 
@@ -355,6 +404,47 @@ fn merge_mcp_servers(
     Ok(())
 }
 
+fn parse_optional_model(root: &JsonValue) -> Option<String> {
+    root.as_object()
+        .and_then(|object| object.get("model"))
+        .and_then(JsonValue::as_str)
+        .map(ToOwned::to_owned)
+}
+
+fn parse_optional_permission_mode(
+    root: &JsonValue,
+) -> Result<Option<ResolvedPermissionMode>, ConfigError> {
+    let Some(object) = root.as_object() else {
+        return Ok(None);
+    };
+    if let Some(mode) = object.get("permissionMode").and_then(JsonValue::as_str) {
+        return parse_permission_mode_label(mode, "merged settings.permissionMode").map(Some);
+    }
+    let Some(mode) = object
+        .get("permissions")
+        .and_then(JsonValue::as_object)
+        .and_then(|permissions| permissions.get("defaultMode"))
+        .and_then(JsonValue::as_str)
+    else {
+        return Ok(None);
+    };
+    parse_permission_mode_label(mode, "merged settings.permissions.defaultMode").map(Some)
+}
+
+fn parse_permission_mode_label(
+    mode: &str,
+    context: &str,
+) -> Result<ResolvedPermissionMode, ConfigError> {
+    match mode {
+        "default" | "plan" | "read-only" => Ok(ResolvedPermissionMode::ReadOnly),
+        "acceptEdits" | "auto" | "workspace-write" => Ok(ResolvedPermissionMode::WorkspaceWrite),
+        "dontAsk" | "danger-full-access" => Ok(ResolvedPermissionMode::DangerFullAccess),
+        other => Err(ConfigError::Parse(format!(
+            "{context}: unsupported permission mode {other}"
+        ))),
+    }
+}
+
 fn parse_optional_oauth_config(
     root: &JsonValue,
     context: &str,
@@ -594,7 +684,8 @@ fn deep_merge_objects(
 #[cfg(test)]
 mod tests {
     use super::{
-        ConfigLoader, ConfigSource, McpServerConfig, McpTransport, CLAUDE_CODE_SETTINGS_SCHEMA_NAME,
+        ConfigLoader, ConfigSource, McpServerConfig, McpTransport, ResolvedPermissionMode,
+        CLAUDE_CODE_SETTINGS_SCHEMA_NAME,
     };
     use crate::json::JsonValue;
     use std::fs;
@@ -635,14 +726,24 @@ mod tests {
         fs::create_dir_all(cwd.join(".claude")).expect("project config dir");
         fs::create_dir_all(&home).expect("home config dir");
 
+        fs::write(
+            home.parent().expect("home parent").join(".claude.json"),
+            r#"{"model":"haiku","env":{"A":"1"},"mcpServers":{"home":{"command":"uvx","args":["home"]}}}"#,
+        )
+        .expect("write user compat config");
         fs::write(
             home.join("settings.json"),
-            r#"{"model":"sonnet","env":{"A":"1"},"hooks":{"PreToolUse":["base"]}}"#,
+            r#"{"model":"sonnet","env":{"A2":"1"},"hooks":{"PreToolUse":["base"]},"permissions":{"defaultMode":"plan"}}"#,
         )
         .expect("write user settings");
+        fs::write(
+            cwd.join(".claude.json"),
+            r#"{"model":"project-compat","env":{"B":"2"}}"#,
+        )
+        .expect("write project compat config");
         fs::write(
             cwd.join(".claude").join("settings.json"),
-            r#"{"env":{"B":"2"},"hooks":{"PostToolUse":["project"]}}"#,
+            r#"{"env":{"C":"3"},"hooks":{"PostToolUse":["project"]},"mcpServers":{"project":{"command":"uvx","args":["project"]}}}"#,
         )
         .expect("write project settings");
         fs::write(
@@ -656,25 +757,37 @@ mod tests {
             .expect("config should load");
 
         assert_eq!(CLAUDE_CODE_SETTINGS_SCHEMA_NAME, "SettingsSchema");
-        assert_eq!(loaded.loaded_entries().len(), 3);
+        assert_eq!(loaded.loaded_entries().len(), 5);
         assert_eq!(loaded.loaded_entries()[0].source, ConfigSource::User);
         assert_eq!(
             loaded.get("model"),
             Some(&JsonValue::String("opus".to_string()))
         );
+        assert_eq!(loaded.model(), Some("opus"));
+        assert_eq!(
+            loaded.permission_mode(),
+            Some(ResolvedPermissionMode::WorkspaceWrite)
+        );
         assert_eq!(
             loaded
                 .get("env")
                 .and_then(JsonValue::as_object)
                 .expect("env object")
                 .len(),
-            2
+            4
         );
         assert!(loaded
             .get("hooks")
             .and_then(JsonValue::as_object)
             .expect("hooks object")
             .contains_key("PreToolUse"));
+        assert!(loaded
+            .get("hooks")
+            .and_then(JsonValue::as_object)
+            .expect("hooks object")
+            .contains_key("PostToolUse"));
+        assert!(loaded.mcp().get("home").is_some());
+        assert!(loaded.mcp().get("project").is_some());
 
         fs::remove_dir_all(root).expect("cleanup temp dir");
     }

rust/crates/runtime/src/conversation.rs

@@ -408,8 +408,7 @@ mod tests {
                 .sum::<i32>();
             Ok(total.to_string())
         });
-        let permission_policy = PermissionPolicy::new(PermissionMode::WorkspaceWrite)
-            .with_tool_requirement("add", PermissionMode::DangerFullAccess);
+        let permission_policy = PermissionPolicy::new(PermissionMode::WorkspaceWrite);
         let system_prompt = SystemPromptBuilder::new()
             .with_project_context(ProjectContext {
                 cwd: PathBuf::from("/tmp/project"),
@@ -488,8 +487,7 @@ mod tests {
             Session::new(),
             SingleCallApiClient,
             StaticToolExecutor::new(),
-            PermissionPolicy::new(PermissionMode::WorkspaceWrite)
-                .with_tool_requirement("blocked", PermissionMode::DangerFullAccess),
+            PermissionPolicy::new(PermissionMode::WorkspaceWrite),
             vec!["system".to_string()],
         );
 
@@ -538,7 +536,7 @@ mod tests {
             session,
             SimpleApi,
             StaticToolExecutor::new(),
-            PermissionPolicy::new(PermissionMode::ReadOnly),
+            PermissionPolicy::new(PermissionMode::DangerFullAccess),
             vec!["system".to_string()],
         );
 
@@ -565,7 +563,7 @@ mod tests {
             Session::new(),
             SimpleApi,
             StaticToolExecutor::new(),
-            PermissionPolicy::new(PermissionMode::ReadOnly),
+            PermissionPolicy::new(PermissionMode::DangerFullAccess),
             vec!["system".to_string()],
         );
         runtime.run_turn("a", None).expect("turn a");

rust/crates/runtime/src/lib.rs

@@ -25,7 +25,8 @@ pub use config::{
     ConfigEntry, ConfigError, ConfigLoader, ConfigSource, McpClaudeAiProxyServerConfig,
     McpConfigCollection, McpOAuthConfig, McpRemoteServerConfig, McpSdkServerConfig,
     McpServerConfig, McpStdioServerConfig, McpTransport, McpWebSocketServerConfig, OAuthConfig,
-    RuntimeConfig, RuntimeFeatureConfig, ScopedMcpServerConfig, CLAUDE_CODE_SETTINGS_SCHEMA_NAME,
+    ResolvedPermissionMode, RuntimeConfig, RuntimeFeatureConfig, ScopedMcpServerConfig,
+    CLAUDE_CODE_SETTINGS_SCHEMA_NAME,
 };
 pub use conversation::{
     ApiClient, ApiRequest, AssistantEvent, ConversationRuntime, RuntimeError, StaticToolExecutor,
@@ -76,3 +77,11 @@ pub use session::{ContentBlock, ConversationMessage, MessageRole, Session, Sessi
 pub use usage::{
     format_usd, pricing_for_model, ModelPricing, TokenUsage, UsageCostEstimate, UsageTracker,
 };
+
+#[cfg(test)]
+pub(crate) fn test_env_lock() -> std::sync::MutexGuard<'static, ()> {
+    static LOCK: std::sync::OnceLock<std::sync::Mutex<()>> = std::sync::OnceLock::new();
+    LOCK.get_or_init(|| std::sync::Mutex::new(()))
+        .lock()
+        .unwrap_or_else(std::sync::PoisonError::into_inner)
+}

rust/crates/runtime/src/oauth.rs

@@ -448,7 +448,6 @@ fn decode_hex(byte: u8) -> Result<u8, String> {
 
 #[cfg(test)]
 mod tests {
-    use std::sync::{Mutex, OnceLock};
     use std::time::{SystemTime, UNIX_EPOCH};
 
     use super::{
@@ -470,10 +469,7 @@ mod tests {
     }
 
     fn env_lock() -> std::sync::MutexGuard<'static, ()> {
-        static LOCK: OnceLock<Mutex<()>> = OnceLock::new();
-        LOCK.get_or_init(|| Mutex::new(()))
-            .lock()
-            .expect("env lock")
+        crate::test_env_lock()
     }
 
     fn temp_config_home() -> std::path::PathBuf {

rust/crates/runtime/src/prompt.rs

@@ -201,6 +201,7 @@ fn discover_instruction_files(cwd: &Path) -> std::io::Result<Vec<ContextFile>> {
             dir.join("CLAUDE.md"),
             dir.join("CLAUDE.local.md"),
             dir.join(".claude").join("CLAUDE.md"),
+            dir.join(".claude").join("instructions.md"),
         ] {
             push_context_file(&mut files, candidate)?;
         }
@@ -468,6 +469,10 @@ mod tests {
         std::env::temp_dir().join(format!("runtime-prompt-{nanos}"))
     }
 
+    fn env_lock() -> std::sync::MutexGuard<'static, ()> {
+        crate::test_env_lock()
+    }
+
     #[test]
     fn discovers_instruction_files_from_ancestor_chain() {
         let root = temp_dir();
@@ -477,10 +482,21 @@ mod tests {
         fs::write(root.join("CLAUDE.local.md"), "local instructions")
             .expect("write local instructions");
         fs::create_dir_all(root.join("apps")).expect("apps dir");
+        fs::create_dir_all(root.join("apps").join(".claude")).expect("apps claude dir");
         fs::write(root.join("apps").join("CLAUDE.md"), "apps instructions")
             .expect("write apps instructions");
+        fs::write(
+            root.join("apps").join(".claude").join("instructions.md"),
+            "apps dot claude instructions",
+        )
+        .expect("write apps dot claude instructions");
         fs::write(nested.join(".claude").join("CLAUDE.md"), "nested rules")
             .expect("write nested rules");
+        fs::write(
+            nested.join(".claude").join("instructions.md"),
+            "nested instructions",
+        )
+        .expect("write nested instructions");
 
         let context = ProjectContext::discover(&nested, "2026-03-31").expect("context should load");
         let contents = context
@@ -495,7 +511,9 @@ mod tests {
                 "root instructions",
                 "local instructions",
                 "apps instructions",
-                "nested rules"
+                "apps dot claude instructions",
+                "nested rules",
+                "nested instructions"
             ]
         );
         fs::remove_dir_all(root).expect("cleanup temp dir");
@@ -574,7 +592,12 @@ mod tests {
         )
         .expect("write settings");
 
+        let _guard = env_lock();
         let previous = std::env::current_dir().expect("cwd");
+        let original_home = std::env::var("HOME").ok();
+        let original_claude_home = std::env::var("CLAUDE_CONFIG_HOME").ok();
+        std::env::set_var("HOME", &root);
+        std::env::set_var("CLAUDE_CONFIG_HOME", root.join("missing-home"));
         std::env::set_current_dir(&root).expect("change cwd");
         let prompt = super::load_system_prompt(&root, "2026-03-31", "linux", "6.8")
             .expect("system prompt should load")
@@ -584,6 +607,16 @@ mod tests {
 ",
             );
         std::env::set_current_dir(previous).expect("restore cwd");
+        if let Some(value) = original_home {
+            std::env::set_var("HOME", value);
+        } else {
+            std::env::remove_var("HOME");
+        }
+        if let Some(value) = original_claude_home {
+            std::env::set_var("CLAUDE_CONFIG_HOME", value);
+        } else {
+            std::env::remove_var("CLAUDE_CONFIG_HOME");
+        }
 
         assert!(prompt.contains("Project rules"));
         assert!(prompt.contains("permissionMode"));
@@ -631,6 +664,29 @@ mod tests {
         assert!(rendered.chars().count() <= 4_000 + "\n\n[truncated]".chars().count());
     }
 
+    #[test]
+    fn discovers_dot_claude_instructions_markdown() {
+        let root = temp_dir();
+        let nested = root.join("apps").join("api");
+        fs::create_dir_all(nested.join(".claude")).expect("nested claude dir");
+        fs::write(
+            nested.join(".claude").join("instructions.md"),
+            "instruction markdown",
+        )
+        .expect("write instructions.md");
+
+        let context = ProjectContext::discover(&nested, "2026-03-31").expect("context should load");
+        assert!(context
+            .instruction_files
+            .iter()
+            .any(|file| file.path.ends_with(".claude/instructions.md")));
+        assert!(
+            render_instruction_files(&context.instruction_files).contains("instruction markdown")
+        );
+
+        fs::remove_dir_all(root).expect("cleanup temp dir");
+    }
+
     #[test]
     fn renders_instruction_file_metadata() {
         let rendered = render_instruction_files(&[ContextFile {

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

@@ -2,7 +2,7 @@ use std::io::{self, Write};
 use std::path::PathBuf;
 
 use crate::args::{OutputFormat, PermissionMode};
-use crate::input::LineEditor;
+use crate::input::{LineEditor, ReadOutcome};
 use crate::render::{Spinner, TerminalRenderer};
 use runtime::{ConversationClient, ConversationMessage, RuntimeError, StreamEvent, UsageSummary};
 
@@ -111,16 +111,21 @@ impl CliApp {
     }
 
     pub fn run_repl(&mut self) -> io::Result<()> {
-        let editor = LineEditor::new("› ");
+        let mut editor = LineEditor::new("› ", Vec::new());
         println!("Rusty Claude CLI interactive mode");
         println!("Type /help for commands. Shift+Enter or Ctrl+J inserts a newline.");
 
-        while let Some(input) = editor.read_line()? {
-            if input.trim().is_empty() {
-                continue;
+        loop {
+            match editor.read_line()? {
+                ReadOutcome::Submit(input) => {
+                    if input.trim().is_empty() {
+                        continue;
+                    }
+                    self.handle_submission(&input, &mut io::stdout())?;
+                }
+                ReadOutcome::Cancel => continue,
+                ReadOutcome::Exit => break,
             }
-
-            self.handle_submission(&input, &mut io::stdout())?;
         }
 
         Ok(())

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

@@ -1,9 +1,8 @@
 use std::io::{self, IsTerminal, Write};
 
-use crossterm::cursor::MoveToColumn;
+use crossterm::cursor::{MoveDown, MoveToColumn, MoveUp};
 use crossterm::event::{self, Event, KeyCode, KeyEvent, KeyModifiers};
 use crossterm::queue;
-use crossterm::style::Print;
 use crossterm::terminal::{disable_raw_mode, enable_raw_mode, Clear, ClearType};
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -85,21 +84,124 @@ impl InputBuffer {
         self.buffer.clear();
         self.cursor = 0;
     }
+
+    pub fn replace(&mut self, value: impl Into<String>) {
+        self.buffer = value.into();
+        self.cursor = self.buffer.len();
+    }
+
+    #[must_use]
+    fn current_command_prefix(&self) -> Option<&str> {
+        if self.cursor != self.buffer.len() {
+            return None;
+        }
+        let prefix = &self.buffer[..self.cursor];
+        if prefix.contains(char::is_whitespace) || !prefix.starts_with('/') {
+            return None;
+        }
+        Some(prefix)
+    }
+
+    pub fn complete_slash_command(&mut self, candidates: &[String]) -> bool {
+        let Some(prefix) = self.current_command_prefix() else {
+            return false;
+        };
+
+        let matches = candidates
+            .iter()
+            .filter(|candidate| candidate.starts_with(prefix))
+            .map(String::as_str)
+            .collect::<Vec<_>>();
+        if matches.is_empty() {
+            return false;
+        }
+
+        let replacement = longest_common_prefix(&matches);
+        if replacement == prefix {
+            return false;
+        }
+
+        self.replace(replacement);
+        true
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct RenderedBuffer {
+    lines: Vec<String>,
+    cursor_row: u16,
+    cursor_col: u16,
+}
+
+impl RenderedBuffer {
+    #[must_use]
+    pub fn line_count(&self) -> usize {
+        self.lines.len()
+    }
+
+    fn write(&self, out: &mut impl Write) -> io::Result<()> {
+        for (index, line) in self.lines.iter().enumerate() {
+            if index > 0 {
+                writeln!(out)?;
+            }
+            write!(out, "{line}")?;
+        }
+        Ok(())
+    }
+
+    #[cfg(test)]
+    #[must_use]
+    pub fn lines(&self) -> &[String] {
+        &self.lines
+    }
+
+    #[cfg(test)]
+    #[must_use]
+    pub fn cursor_position(&self) -> (u16, u16) {
+        (self.cursor_row, self.cursor_col)
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ReadOutcome {
+    Submit(String),
+    Cancel,
+    Exit,
 }
 
 pub struct LineEditor {
     prompt: String,
+    continuation_prompt: String,
+    history: Vec<String>,
+    history_index: Option<usize>,
+    draft: Option<String>,
+    completions: Vec<String>,
 }
 
 impl LineEditor {
     #[must_use]
-    pub fn new(prompt: impl Into<String>) -> Self {
+    pub fn new(prompt: impl Into<String>, completions: Vec<String>) -> Self {
         Self {
             prompt: prompt.into(),
+            continuation_prompt: String::from("> "),
+            history: Vec::new(),
+            history_index: None,
+            draft: None,
+            completions,
         }
     }
 
-    pub fn read_line(&self) -> io::Result<Option<String>> {
+    pub fn push_history(&mut self, entry: impl Into<String>) {
+        let entry = entry.into();
+        if entry.trim().is_empty() {
+            return;
+        }
+        self.history.push(entry);
+        self.history_index = None;
+        self.draft = None;
+    }
+
+    pub fn read_line(&mut self) -> io::Result<ReadOutcome> {
         if !io::stdin().is_terminal() || !io::stdout().is_terminal() {
             return self.read_line_fallback();
         }
@@ -107,29 +209,43 @@ impl LineEditor {
         enable_raw_mode()?;
         let mut stdout = io::stdout();
         let mut input = InputBuffer::new();
-        self.redraw(&mut stdout, &input)?;
+        let mut rendered_lines = 1usize;
+        self.redraw(&mut stdout, &input, rendered_lines)?;
 
         loop {
             let event = event::read()?;
             if let Event::Key(key) = event {
-                match Self::handle_key(key, &mut input) {
-                    EditorAction::Continue => self.redraw(&mut stdout, &input)?,
+                match self.handle_key(key, &mut input) {
+                    EditorAction::Continue => {
+                        rendered_lines = self.redraw(&mut stdout, &input, rendered_lines)?;
+                    }
                     EditorAction::Submit => {
                         disable_raw_mode()?;
                         writeln!(stdout)?;
-                        return Ok(Some(input.as_str().to_owned()));
+                        self.history_index = None;
+                        self.draft = None;
+                        return Ok(ReadOutcome::Submit(input.as_str().to_owned()));
                     }
                     EditorAction::Cancel => {
                         disable_raw_mode()?;
                         writeln!(stdout)?;
-                        return Ok(None);
+                        self.history_index = None;
+                        self.draft = None;
+                        return Ok(ReadOutcome::Cancel);
+                    }
+                    EditorAction::Exit => {
+                        disable_raw_mode()?;
+                        writeln!(stdout)?;
+                        self.history_index = None;
+                        self.draft = None;
+                        return Ok(ReadOutcome::Exit);
                     }
                 }
             }
         }
     }
 
-    fn read_line_fallback(&self) -> io::Result<Option<String>> {
+    fn read_line_fallback(&self) -> io::Result<ReadOutcome> {
         let mut stdout = io::stdout();
         write!(stdout, "{}", self.prompt)?;
         stdout.flush()?;
@@ -137,22 +253,32 @@ impl LineEditor {
         let mut buffer = String::new();
         let bytes_read = io::stdin().read_line(&mut buffer)?;
         if bytes_read == 0 {
-            return Ok(None);
+            return Ok(ReadOutcome::Exit);
         }
 
         while matches!(buffer.chars().last(), Some('\n' | '\r')) {
             buffer.pop();
         }
-        Ok(Some(buffer))
+        Ok(ReadOutcome::Submit(buffer))
     }
 
-    fn handle_key(key: KeyEvent, input: &mut InputBuffer) -> EditorAction {
+    #[allow(clippy::too_many_lines)]
+    fn handle_key(&mut self, key: KeyEvent, input: &mut InputBuffer) -> EditorAction {
         match key {
             KeyEvent {
                 code: KeyCode::Char('c'),
                 modifiers,
                 ..
-            } if modifiers.contains(KeyModifiers::CONTROL) => EditorAction::Cancel,
+            } if modifiers.contains(KeyModifiers::CONTROL) => {
+                if input.as_str().is_empty() {
+                    EditorAction::Exit
+                } else {
+                    input.clear();
+                    self.history_index = None;
+                    self.draft = None;
+                    EditorAction::Cancel
+                }
+            }
             KeyEvent {
                 code: KeyCode::Char('j'),
                 modifiers,
@@ -194,6 +320,25 @@ impl LineEditor {
                 input.move_right();
                 EditorAction::Continue
             }
+            KeyEvent {
+                code: KeyCode::Up, ..
+            } => {
+                self.navigate_history_up(input);
+                EditorAction::Continue
+            }
+            KeyEvent {
+                code: KeyCode::Down,
+                ..
+            } => {
+                self.navigate_history_down(input);
+                EditorAction::Continue
+            }
+            KeyEvent {
+                code: KeyCode::Tab, ..
+            } => {
+                input.complete_slash_command(&self.completions);
+                EditorAction::Continue
+            }
             KeyEvent {
                 code: KeyCode::Home,
                 ..
@@ -211,6 +356,8 @@ impl LineEditor {
                 code: KeyCode::Esc, ..
             } => {
                 input.clear();
+                self.history_index = None;
+                self.draft = None;
                 EditorAction::Cancel
             }
             KeyEvent {
@@ -219,22 +366,74 @@ impl LineEditor {
                 ..
             } if modifiers.is_empty() || modifiers == KeyModifiers::SHIFT => {
                 input.insert(ch);
+                self.history_index = None;
+                self.draft = None;
                 EditorAction::Continue
             }
             _ => EditorAction::Continue,
         }
     }
 
-    fn redraw(&self, out: &mut impl Write, input: &InputBuffer) -> io::Result<()> {
-        let display = input.as_str().replace('\n', "\\n\n> ");
+    fn navigate_history_up(&mut self, input: &mut InputBuffer) {
+        if self.history.is_empty() {
+            return;
+        }
+
+        match self.history_index {
+            Some(0) => {}
+            Some(index) => {
+                let next_index = index - 1;
+                input.replace(self.history[next_index].clone());
+                self.history_index = Some(next_index);
+            }
+            None => {
+                self.draft = Some(input.as_str().to_owned());
+                let next_index = self.history.len() - 1;
+                input.replace(self.history[next_index].clone());
+                self.history_index = Some(next_index);
+            }
+        }
+    }
+
+    fn navigate_history_down(&mut self, input: &mut InputBuffer) {
+        let Some(index) = self.history_index else {
+            return;
+        };
+
+        if index + 1 < self.history.len() {
+            let next_index = index + 1;
+            input.replace(self.history[next_index].clone());
+            self.history_index = Some(next_index);
+            return;
+        }
+
+        input.replace(self.draft.take().unwrap_or_default());
+        self.history_index = None;
+    }
+
+    fn redraw(
+        &self,
+        out: &mut impl Write,
+        input: &InputBuffer,
+        previous_line_count: usize,
+    ) -> io::Result<usize> {
+        let rendered = render_buffer(&self.prompt, &self.continuation_prompt, input);
+        if previous_line_count > 1 {
+            queue!(out, MoveUp(saturating_u16(previous_line_count - 1)))?;
+        }
+        queue!(out, MoveToColumn(0), Clear(ClearType::FromCursorDown),)?;
+        rendered.write(out)?;
         queue!(
             out,
+            MoveUp(saturating_u16(rendered.line_count().saturating_sub(1))),
             MoveToColumn(0),
-            Clear(ClearType::CurrentLine),
-            Print(&self.prompt),
-            Print(display),
         )?;
-        out.flush()
+        if rendered.cursor_row > 0 {
+            queue!(out, MoveDown(rendered.cursor_row))?;
+        }
+        queue!(out, MoveToColumn(rendered.cursor_col))?;
+        out.flush()?;
+        Ok(rendered.line_count())
     }
 }
 
@@ -243,11 +442,76 @@ enum EditorAction {
     Continue,
     Submit,
     Cancel,
+    Exit,
+}
+
+#[must_use]
+pub fn render_buffer(
+    prompt: &str,
+    continuation_prompt: &str,
+    input: &InputBuffer,
+) -> RenderedBuffer {
+    let before_cursor = &input.as_str()[..input.cursor];
+    let cursor_row = saturating_u16(before_cursor.chars().filter(|ch| *ch == '\n').count());
+    let cursor_line = before_cursor.rsplit('\n').next().unwrap_or_default();
+    let cursor_prompt = if cursor_row == 0 {
+        prompt
+    } else {
+        continuation_prompt
+    };
+    let cursor_col = saturating_u16(cursor_prompt.chars().count() + cursor_line.chars().count());
+
+    let mut lines = Vec::new();
+    for (index, line) in input.as_str().split('\n').enumerate() {
+        let prefix = if index == 0 {
+            prompt
+        } else {
+            continuation_prompt
+        };
+        lines.push(format!("{prefix}{line}"));
+    }
+    if lines.is_empty() {
+        lines.push(prompt.to_string());
+    }
+
+    RenderedBuffer {
+        lines,
+        cursor_row,
+        cursor_col,
+    }
+}
+
+#[must_use]
+fn longest_common_prefix(values: &[&str]) -> String {
+    let Some(first) = values.first() else {
+        return String::new();
+    };
+
+    let mut prefix = (*first).to_string();
+    for value in values.iter().skip(1) {
+        while !value.starts_with(&prefix) {
+            prefix.pop();
+            if prefix.is_empty() {
+                break;
+            }
+        }
+    }
+    prefix
+}
+
+#[must_use]
+fn saturating_u16(value: usize) -> u16 {
+    u16::try_from(value).unwrap_or(u16::MAX)
 }
 
 #[cfg(test)]
 mod tests {
-    use super::InputBuffer;
+    use super::{render_buffer, InputBuffer, LineEditor};
+    use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
+
+    fn key(code: KeyCode) -> KeyEvent {
+        KeyEvent::new(code, KeyModifiers::NONE)
+    }
 
     #[test]
     fn supports_basic_line_editing() {
@@ -266,4 +530,119 @@ mod tests {
         assert_eq!(input.as_str(), "hix");
         assert_eq!(input.cursor(), 2);
     }
+
+    #[test]
+    fn completes_unique_slash_command() {
+        let mut input = InputBuffer::new();
+        for ch in "/he".chars() {
+            input.insert(ch);
+        }
+
+        assert!(input.complete_slash_command(&[
+            "/help".to_string(),
+            "/hello".to_string(),
+            "/status".to_string(),
+        ]));
+        assert_eq!(input.as_str(), "/hel");
+
+        assert!(input.complete_slash_command(&["/help".to_string(), "/status".to_string()]));
+        assert_eq!(input.as_str(), "/help");
+    }
+
+    #[test]
+    fn ignores_completion_when_prefix_is_not_a_slash_command() {
+        let mut input = InputBuffer::new();
+        for ch in "hello".chars() {
+            input.insert(ch);
+        }
+
+        assert!(!input.complete_slash_command(&["/help".to_string()]));
+        assert_eq!(input.as_str(), "hello");
+    }
+
+    #[test]
+    fn history_navigation_restores_current_draft() {
+        let mut editor = LineEditor::new("› ", vec![]);
+        editor.push_history("/help");
+        editor.push_history("status report");
+
+        let mut input = InputBuffer::new();
+        for ch in "draft".chars() {
+            input.insert(ch);
+        }
+
+        let _ = editor.handle_key(key(KeyCode::Up), &mut input);
+        assert_eq!(input.as_str(), "status report");
+
+        let _ = editor.handle_key(key(KeyCode::Up), &mut input);
+        assert_eq!(input.as_str(), "/help");
+
+        let _ = editor.handle_key(key(KeyCode::Down), &mut input);
+        assert_eq!(input.as_str(), "status report");
+
+        let _ = editor.handle_key(key(KeyCode::Down), &mut input);
+        assert_eq!(input.as_str(), "draft");
+    }
+
+    #[test]
+    fn tab_key_completes_from_editor_candidates() {
+        let mut editor = LineEditor::new(
+            "› ",
+            vec![
+                "/help".to_string(),
+                "/status".to_string(),
+                "/session".to_string(),
+            ],
+        );
+        let mut input = InputBuffer::new();
+        for ch in "/st".chars() {
+            input.insert(ch);
+        }
+
+        let _ = editor.handle_key(key(KeyCode::Tab), &mut input);
+        assert_eq!(input.as_str(), "/status");
+    }
+
+    #[test]
+    fn renders_multiline_buffers_with_continuation_prompt() {
+        let mut input = InputBuffer::new();
+        for ch in "hello\nworld".chars() {
+            if ch == '\n' {
+                input.insert_newline();
+            } else {
+                input.insert(ch);
+            }
+        }
+
+        let rendered = render_buffer("› ", "> ", &input);
+        assert_eq!(
+            rendered.lines(),
+            &["› hello".to_string(), "> world".to_string()]
+        );
+        assert_eq!(rendered.cursor_position(), (1, 7));
+    }
+
+    #[test]
+    fn ctrl_c_exits_only_when_buffer_is_empty() {
+        let mut editor = LineEditor::new("› ", vec![]);
+        let mut empty = InputBuffer::new();
+        assert!(matches!(
+            editor.handle_key(
+                KeyEvent::new(KeyCode::Char('c'), KeyModifiers::CONTROL),
+                &mut empty,
+            ),
+            super::EditorAction::Exit
+        ));
+
+        let mut filled = InputBuffer::new();
+        filled.insert('x');
+        assert!(matches!(
+            editor.handle_key(
+                KeyEvent::new(KeyCode::Char('c'), KeyModifiers::CONTROL),
+                &mut filled,
+            ),
+            super::EditorAction::Cancel
+        ));
+        assert!(filled.as_str().is_empty());
+    }
 }