feat: add disable_1m_context toggle to settings UI

Adds a new config option to expose the CLAUDE_CODE_DISABLE_1M_CONTEXT
environment variable through the settings sidebar, allowing users to
opt out of the extended 1M context window without manually setting
environment variables.

Closes #154

src-tauri/src/config.rs

@@ -28,6 +28,9 @@ pub struct ClaudeStartOptions {
 
     #[serde(default)]
     pub use_worktree: bool,
+
+    #[serde(default)]
+    pub disable_1m_context: bool,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -119,6 +122,9 @@ pub struct HikariConfig {
 
     #[serde(default)]
     pub use_worktree: bool,
+
+    #[serde(default)]
+    pub disable_1m_context: bool,
 }
 
 impl Default for HikariConfig {
@@ -152,6 +158,7 @@ impl Default for HikariConfig {
             budget_warning_threshold: 0.8,
             discord_rpc_enabled: true,
             use_worktree: false,
+            disable_1m_context: false,
         }
     }
 }
@@ -259,6 +266,8 @@ mod tests {
         assert_eq!(config.budget_action, BudgetAction::Warn);
         assert!((config.budget_warning_threshold - 0.8).abs() < f32::EPSILON);
         assert!(config.discord_rpc_enabled);
+        assert!(!config.use_worktree);
+        assert!(!config.disable_1m_context);
     }
 
     #[test]
@@ -292,6 +301,7 @@ mod tests {
             budget_warning_threshold: 0.75,
             discord_rpc_enabled: true,
             use_worktree: true,
+            disable_1m_context: false,
         };
 
         let json = serde_json::to_string(&config).unwrap();

src-tauri/src/types.rs

@@ -305,6 +305,8 @@ pub struct AgentEndEvent {
     pub duration_ms: Option<u64>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub num_turns: Option<u32>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub last_assistant_message: Option<String>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]

src-tauri/src/wsl_bridge.rs

@@ -279,6 +279,11 @@ impl WslBridge {
                 }
             }
 
+            // Disable 1M context window if requested
+            if options.disable_1m_context {
+                cmd.env("CLAUDE_CODE_DISABLE_1M_CONTEXT", "1");
+            }
+
             cmd
         } else {
             // Running on Windows - use wsl with bash login shell to ensure PATH is loaded
@@ -319,6 +324,11 @@ impl WslBridge {
                 }
             }
 
+            // Disable 1M context window if requested
+            if options.disable_1m_context {
+                claude_cmd.push_str("CLAUDE_CODE_DISABLE_1M_CONTEXT=1 ");
+            }
+
             claude_cmd.push_str(
                 "claude --output-format stream-json --input-format stream-json --verbose",
             );
@@ -755,6 +765,7 @@ fn handle_stderr(
                                     conversation_id: conversation_id.clone(),
                                     duration_ms: None,
                                     num_turns: None,
+                                    last_assistant_message: stop_data.last_assistant_message,
                                 },
                             );
                         }
@@ -828,27 +839,78 @@ fn parse_subagent_start_hook(line: &str) -> Option<SubagentStartData> {
 #[derive(Debug)]
 struct SubagentStopData {
     parent_tool_use_id: Option<String>,
+    last_assistant_message: Option<String>,
+}
+
+/// Extracts the content of a Rust Debug-formatted `Some("...")` field from a hook line.
+/// Handles escaped characters (e.g. `\"` → `"`, `\\` → `\`, `\n` → newline).
+/// Returns `None` if the field is absent or formatted as `None`.
+fn extract_debug_string_value(line: &str, key: &str) -> Option<String> {
+    let prefix = format!("{}=Some(\"", key);
+    let start_idx = line.find(&prefix)? + prefix.len();
+    let rest = &line[start_idx..];
+
+    let mut result = String::new();
+    let mut chars = rest.chars();
+    loop {
+        match chars.next() {
+            Some('"') => return Some(result),
+            Some('\\') => match chars.next() {
+                Some('n') => result.push('\n'),
+                Some('t') => result.push('\t'),
+                Some('"') => result.push('"'),
+                Some('\\') => result.push('\\'),
+                Some(c) => {
+                    result.push('\\');
+                    result.push(c);
+                }
+                None => break,
+            },
+            Some(c) => result.push(c),
+            None => break,
+        }
+    }
+    None
 }
 
 fn parse_subagent_stop_hook(line: &str) -> Option<SubagentStopData> {
-    // Parse: [SubagentStop Hook] ... parent_tool_use_id=Some("toolu_xxx"), ...
+    // Parse: [SubagentStop Hook] ... parent_tool_use_id=Some("toolu_xxx"), last_assistant_message=Some("..."), ...
 
-    // Extract parent_tool_use_id if present
+    let parent_tool_use_id = extract_debug_string_value(line, "parent_tool_use_id");
-    let parent_tool_use_id = if line.contains("parent_tool_use_id=Some") {
+    let last_assistant_message = extract_debug_string_value(line, "last_assistant_message");
-        line.split("parent_tool_use_id=Some(\"")
-            .nth(1)?
-            .split('"')
-            .next()
-            .map(|s| s.to_string())
-    } else {
-        None
-    };
 
     Some(SubagentStopData {
         parent_tool_use_id,
+        last_assistant_message,
     })
 }
 
+/// Extract text content from a ToolResult's `content` field.
+/// The content may be a JSON string or an array of typed content blocks.
+fn extract_tool_result_text(content: &serde_json::Value) -> Option<String> {
+    match content {
+        serde_json::Value::String(s) if !s.is_empty() => Some(s.clone()),
+        serde_json::Value::Array(blocks) => {
+            let texts: Vec<String> = blocks
+                .iter()
+                .filter_map(|block| {
+                    if block.get("type")?.as_str()? == "text" {
+                        block.get("text")?.as_str().map(String::from)
+                    } else {
+                        None
+                    }
+                })
+                .collect();
+            if texts.is_empty() {
+                None
+            } else {
+                Some(texts.join("\n"))
+            }
+        }
+        _ => None,
+    }
+}
+
 fn process_json_line(
     line: &str,
     app: &AppHandle,
@@ -1150,8 +1212,8 @@ fn process_json_line(
                     }
                     ContentBlock::ToolResult {
                         tool_use_id,
+                        content,
                         is_error,
-                        ..
                     } => {
                         // Emit agent-end for all tool results
                         // The frontend will ignore IDs that don't match known agents
@@ -1169,6 +1231,7 @@ fn process_json_line(
                                 conversation_id: conversation_id.clone(),
                                 duration_ms: None,
                                 num_turns: None,
+                                last_assistant_message: extract_tool_result_text(content),
                             },
                         );
                     }
@@ -1586,8 +1649,8 @@ fn process_json_line(
             for block in &message.content {
                 if let ContentBlock::ToolResult {
                     tool_use_id,
+                    content,
                     is_error,
-                    ..
                 } = block
                 {
                     let now = SystemTime::now()
@@ -1604,6 +1667,7 @@ fn process_json_line(
                             conversation_id: conversation_id.clone(),
                             duration_ms: None,
                             num_turns: None,
+                            last_assistant_message: extract_tool_result_text(content),
                         },
                     );
                 }
@@ -2155,5 +2219,140 @@ mod tests {
         assert!(result.is_some());
         let data = result.unwrap();
         assert_eq!(data.parent_tool_use_id, None);
+        assert_eq!(data.last_assistant_message, None);
+    }
+
+    #[test]
+    fn test_parse_subagent_stop_hook_with_last_message() {
+        let line = r#"[SubagentStop Hook] stop_hook_active=true, parent_tool_use_id=Some("toolu_01ABC123"), last_assistant_message=Some("Task completed successfully."), session_id=123"#;
+        let result = parse_subagent_stop_hook(line);
+
+        assert!(result.is_some());
+        let data = result.unwrap();
+        assert_eq!(data.parent_tool_use_id, Some("toolu_01ABC123".to_string()));
+        assert_eq!(
+            data.last_assistant_message,
+            Some("Task completed successfully.".to_string())
+        );
+    }
+
+    #[test]
+    fn test_parse_subagent_stop_hook_with_last_message_none() {
+        let line = r#"[SubagentStop Hook] stop_hook_active=true, parent_tool_use_id=Some("toolu_01ABC123"), last_assistant_message=None, session_id=123"#;
+        let result = parse_subagent_stop_hook(line);
+
+        assert!(result.is_some());
+        let data = result.unwrap();
+        assert_eq!(data.last_assistant_message, None);
+    }
+
+    #[test]
+    fn test_extract_debug_string_value_simple() {
+        let line = r#"key=Some("hello world")"#;
+        assert_eq!(
+            extract_debug_string_value(line, "key"),
+            Some("hello world".to_string())
+        );
+    }
+
+    #[test]
+    fn test_extract_debug_string_value_with_escaped_quotes() {
+        let line = r#"key=Some("say \"hi\" there")"#;
+        assert_eq!(
+            extract_debug_string_value(line, "key"),
+            Some(r#"say "hi" there"#.to_string())
+        );
+    }
+
+    #[test]
+    fn test_extract_debug_string_value_none_variant() {
+        let line = "key=None";
+        assert_eq!(extract_debug_string_value(line, "key"), None);
+    }
+
+    #[test]
+    fn test_extract_debug_string_value_missing_key() {
+        let line = "other=Some(\"value\")";
+        assert_eq!(extract_debug_string_value(line, "key"), None);
+    }
+
+    #[test]
+    fn test_parse_subagent_stop_hook_with_commas_in_message() {
+        let line = r#"[SubagentStop Hook] parent_tool_use_id=Some("toolu_01"), last_assistant_message=Some("Found 3 files, all passing.")"#;
+        let result = parse_subagent_stop_hook(line);
+
+        assert!(result.is_some());
+        let data = result.unwrap();
+        assert_eq!(
+            data.last_assistant_message,
+            Some("Found 3 files, all passing.".to_string())
+        );
+    }
+
+    // extract_tool_result_text tests
+    #[test]
+    fn test_extract_tool_result_text_plain_string() {
+        let content = serde_json::json!("Hello from agent");
+        assert_eq!(
+            extract_tool_result_text(&content),
+            Some("Hello from agent".to_string())
+        );
+    }
+
+    #[test]
+    fn test_extract_tool_result_text_empty_string() {
+        let content = serde_json::json!("");
+        assert_eq!(extract_tool_result_text(&content), None);
+    }
+
+    #[test]
+    fn test_extract_tool_result_text_array_single_text_block() {
+        let content = serde_json::json!([{"type": "text", "text": "Agent completed the task."}]);
+        assert_eq!(
+            extract_tool_result_text(&content),
+            Some("Agent completed the task.".to_string())
+        );
+    }
+
+    #[test]
+    fn test_extract_tool_result_text_array_multiple_text_blocks() {
+        let content = serde_json::json!([
+            {"type": "text", "text": "First part."},
+            {"type": "text", "text": "Second part."}
+        ]);
+        assert_eq!(
+            extract_tool_result_text(&content),
+            Some("First part.\nSecond part.".to_string())
+        );
+    }
+
+    #[test]
+    fn test_extract_tool_result_text_array_non_text_block() {
+        let content = serde_json::json!([{"type": "image", "source": {"type": "base64"}}]);
+        assert_eq!(extract_tool_result_text(&content), None);
+    }
+
+    #[test]
+    fn test_extract_tool_result_text_array_mixed_blocks() {
+        let content = serde_json::json!([
+            {"type": "image", "source": {}},
+            {"type": "text", "text": "Found results."}
+        ]);
+        assert_eq!(
+            extract_tool_result_text(&content),
+            Some("Found results.".to_string())
+        );
+    }
+
+    #[test]
+    fn test_extract_tool_result_text_null() {
+        let content = serde_json::Value::Null;
+        assert_eq!(extract_tool_result_text(&content), None);
+    }
+
+    #[test]
+    fn test_extract_tool_result_text_empty_array() {
+        let content = serde_json::json!([]);
+        assert_eq!(extract_tool_result_text(&content), None);
     }
 }

src/lib/commands/slashCommands.ts

@@ -62,6 +62,7 @@ async function changeDirectory(path: string): Promise<void> {
         mcp_servers_json: config.mcp_servers_json || null,
         allowed_tools: allAllowedTools,
         use_worktree: config.use_worktree ?? false,
+        disable_1m_context: config.disable_1m_context ?? false,
       },
     });
 
@@ -137,6 +138,7 @@ async function startNewConversation(): Promise<void> {
         mcp_servers_json: config.mcp_servers_json || null,
         allowed_tools: allAllowedTools,
         use_worktree: config.use_worktree ?? false,
+        disable_1m_context: config.disable_1m_context ?? false,
       },
     });
 

src/lib/components/AgentMonitorPanel.svelte

@@ -318,6 +318,16 @@
                 <span class="text-[10px] text-red-400">Errored / Killed</span>
               {/if}
             </div>
+
+            <!-- Last assistant message snippet -->
+            {#if agent.lastAssistantMessage}
+              <p
+                class="mt-1 text-[10px] text-[var(--text-secondary)] italic truncate"
+                title={agent.lastAssistantMessage}
+              >
+                {agent.lastAssistantMessage}
+              </p>
+            {/if}
           </div>
         {/each}
       {/if}

src/lib/components/ConfigSidebar.svelte

@@ -54,6 +54,7 @@
     discord_rpc_enabled: true,
     show_thinking_blocks: true,
     use_worktree: false,
+    disable_1m_context: false,
   });
 
   let showCustomThemeEditor = $state(false);
@@ -489,6 +490,22 @@
           Launch sessions with <code class="font-mono">--worktree</code> for isolated git worktree environments
         </p>
       </div>
+
+      <!-- Disable 1M Context Window -->
+      <div class="mb-4">
+        <label class="flex items-center gap-3 cursor-pointer">
+          <input
+            type="checkbox"
+            bind:checked={config.disable_1m_context}
+            class="w-4 h-4 rounded border-[var(--border-color)] bg-[var(--bg-primary)] text-[var(--accent-primary)] focus:ring-[var(--accent-primary)]"
+          />
+          <span class="text-sm text-[var(--text-primary)]">Disable 1M context window</span>
+        </label>
+        <p class="text-xs text-[var(--text-tertiary)] mt-1 ml-7">
+          Sets <code class="font-mono">CLAUDE_CODE_DISABLE_1M_CONTEXT=1</code> to opt out of the extended
+          context window
+        </p>
+      </div>
     </section>
 
     <!-- Greeting Section -->

src/lib/components/InputBar.svelte

@@ -363,6 +363,7 @@ User: ${formattedMessage}`;
               mcp_servers_json: config.mcp_servers_json || null,
               allowed_tools: allAllowedTools,
               use_worktree: config.use_worktree ?? false,
+              disable_1m_context: config.disable_1m_context ?? false,
             },
           });
 

src/lib/components/PermissionModal.svelte

@@ -88,6 +88,7 @@
           mcp_servers_json: config.mcp_servers_json || null,
           allowed_tools: newGrantedTools,
           use_worktree: config.use_worktree ?? false,
+          disable_1m_context: config.disable_1m_context ?? false,
         },
       });
 

src/lib/components/StatusBar.svelte

@@ -102,6 +102,7 @@
     discord_rpc_enabled: true,
     show_thinking_blocks: true,
     use_worktree: false,
+    disable_1m_context: false,
   });
 
   let streamerModeActive = $state(false);
@@ -180,6 +181,7 @@
           mcp_servers_json: currentConfig.mcp_servers_json || null,
           allowed_tools: allAllowedTools,
           use_worktree: currentConfig.use_worktree ?? false,
+          disable_1m_context: currentConfig.disable_1m_context ?? false,
         },
       });
 
@@ -292,6 +294,7 @@
           mcp_servers_json: currentConfig.mcp_servers_json || null,
           allowed_tools: allAllowedTools,
           use_worktree: currentConfig.use_worktree ?? false,
+          disable_1m_context: currentConfig.disable_1m_context ?? false,
         },
       });
 

src/lib/components/UserQuestionModal.svelte

@@ -107,6 +107,7 @@
           mcp_servers_json: config.mcp_servers_json || null,
           allowed_tools: grantedToolsList,
           use_worktree: config.use_worktree ?? false,
+          disable_1m_context: config.disable_1m_context ?? false,
         },
       });
 

src/lib/stores/agents.test.ts

@@ -177,6 +177,32 @@ describe("agents store", () => {
       const agents = get(getAgentsForConversation(conversationId));
       expect(agents[0].status).toBe("running"); // Status unchanged
     });
+
+    it("stores lastAssistantMessage when provided", () => {
+      const agent = createMockAgent({ status: "running" });
+      agentStore.addAgent(conversationId, agent);
+
+      agentStore.endAgent(
+        conversationId,
+        agent.toolUseId,
+        Date.now(),
+        false,
+        "Task completed successfully."
+      );
+
+      const agents = get(getAgentsForConversation(conversationId));
+      expect(agents[0].lastAssistantMessage).toBe("Task completed successfully.");
+    });
+
+    it("leaves lastAssistantMessage undefined when not provided", () => {
+      const agent = createMockAgent({ status: "running" });
+      agentStore.addAgent(conversationId, agent);
+
+      agentStore.endAgent(conversationId, agent.toolUseId, Date.now(), false);
+
+      const agents = get(getAgentsForConversation(conversationId));
+      expect(agents[0].lastAssistantMessage).toBeUndefined();
+    });
   });
 
   describe("markAllErrored", () => {

src/lib/stores/agents.ts

@@ -45,7 +45,13 @@ function createAgentStore() {
       });
     },
 
-    endAgent(conversationId: string, toolUseId: string, endedAt: number, isError: boolean) {
+    endAgent(
+      conversationId: string,
+      toolUseId: string,
+      endedAt: number,
+      isError: boolean,
+      lastAssistantMessage?: string
+    ) {
       agentsByConversation.update((state) => {
         const agents = state[conversationId];
         if (!agents) return state;
@@ -62,6 +68,7 @@ function createAgentStore() {
           endedAt,
           status: isError ? "errored" : "completed",
           durationMs,
+          lastAssistantMessage,
         };
 
         return {

src/lib/stores/config.test.ts

@@ -195,6 +195,7 @@ describe("config store", () => {
         discord_rpc_enabled: true,
         show_thinking_blocks: true,
         use_worktree: false,
+        disable_1m_context: false,
       };
 
       expect(config.model).toBe("claude-sonnet-4");
@@ -242,6 +243,7 @@ describe("config store", () => {
         discord_rpc_enabled: true,
         show_thinking_blocks: true,
         use_worktree: false,
+        disable_1m_context: false,
       };
 
       expect(config.model).toBeNull();
@@ -788,6 +790,7 @@ describe("config store", () => {
         discord_rpc_enabled: false,
         show_thinking_blocks: true,
         use_worktree: false,
+        disable_1m_context: false,
       };
 
       const mockInvokeImpl = vi.mocked(invoke);

src/lib/stores/config.ts

@@ -49,6 +49,8 @@ export interface HikariConfig {
   show_thinking_blocks: boolean;
   // Worktree isolation
   use_worktree: boolean;
+  // Disable 1M context window
+  disable_1m_context: boolean;
 }
 
 const defaultConfig: HikariConfig = {
@@ -90,6 +92,7 @@ const defaultConfig: HikariConfig = {
   discord_rpc_enabled: true,
   show_thinking_blocks: true,
   use_worktree: false,
+  disable_1m_context: false,
 };
 
 function createConfigStore() {

src/lib/tauri.ts

@@ -474,10 +474,17 @@ export async function initializeTauriListeners() {
   unlisteners.push(agentUpdateUnlisten);
 
   const agentEndUnlisten = await listen<AgentEndPayload>("claude:agent-end", (event) => {
-    const { tool_use_id, ended_at, is_error, conversation_id } = event.payload;
+    const { tool_use_id, ended_at, is_error, conversation_id, last_assistant_message } =
+      event.payload;
     const targetConversationId = conversation_id || get(claudeStore.activeConversationId);
     if (targetConversationId) {
-      agentStore.endAgent(targetConversationId, tool_use_id, ended_at, is_error);
+      agentStore.endAgent(
+        targetConversationId,
+        tool_use_id,
+        ended_at,
+        is_error,
+        last_assistant_message
+      );
     }
   });
   unlisteners.push(agentEndUnlisten);

src/lib/types/agents.ts

@@ -12,6 +12,7 @@ export interface AgentInfo {
   durationMs?: number;
   characterName: string;
   characterAvatar: string;
+  lastAssistantMessage?: string;
 }
 
 export interface AgentStartPayload {
@@ -31,4 +32,5 @@ export interface AgentEndPayload {
   conversation_id?: string;
   duration_ms?: number;
   num_turns?: number;
+  last_assistant_message?: string;
 }