fix(proxy): reduce unnecessary Copilot premium interaction consumption

- Fix request classification: treat messages containing tool_result as
  agent continuation instead of user-initiated, preventing false premium
  charges on every tool call
- Add subagent detection via __SUBAGENT_MARKER__ and metadata._agent_
  fallback, setting x-interaction-type=conversation-subagent
- Add deterministic x-interaction-id derived from session ID to group
  requests into a single billing interaction
- Add orphan tool_result sanitization to prevent upstream API errors
  that could cause retries and duplicate billing
- Reorder pipeline: classify (on original body) → sanitize → merge →
  warmup, ensuring classification sees raw tool_result semantics
- Enable warmup downgrade by default with gpt-5-mini model
- Enhance session ID extraction priority chain for Copilot cache keys
- Detect infinite whitespace bug in streaming tool call arguments

src-tauri/src/proxy/providers/claude.rs

@@ -81,13 +81,50 @@ pub fn transform_claude_request_for_api_format(
     provider: &Provider,
     api_format: &str,
 ) -> Result<serde_json::Value, ProxyError> {
-    match api_format {
-        "openai_responses" => {
-            let cache_key = provider
+    // Copilot 场景：优先从 metadata.user_id 提取 session ID 作为 cache key
+    // 格式: "uuid_sessionId" → 提取 "_" 后面的部分作为 session 标识
+    // 同一会话的请求共享 cache key，提升 Copilot 缓存命中率
+    let is_copilot = provider
+        .meta
+        .as_ref()
+        .and_then(|m| m.provider_type.as_deref())
+        == Some("github_copilot")
+        || provider
+            .settings_config
+            .get("baseUrl")
+            .and_then(|v| v.as_str())
+            .is_some_and(|u| u.contains("githubcopilot.com"));
+    let session_cache_key: Option<String> = if is_copilot {
+        let metadata = body.get("metadata");
+        // Session 提取优先级（与 forwarder 和 session.rs 统一）：
+        //   1. metadata.user_id 中的 _session_ 后缀
+        //   2. metadata.session_id（直接字段）
+        metadata
+            .and_then(|m| m.get("user_id"))
+            .and_then(|v| v.as_str())
+            .and_then(super::super::session::parse_session_from_user_id)
+            .or_else(|| {
+                metadata
+                    .and_then(|m| m.get("session_id"))
+                    .and_then(|v| v.as_str())
+                    .filter(|s| !s.is_empty())
+                    .map(|s| s.to_string())
+            })
+    } else {
+        None
+    };
+
+    let cache_key = session_cache_key
+        .as_deref()
+        .or_else(|| {
+            provider
                 .meta
                 .as_ref()
                 .and_then(|m| m.prompt_cache_key.as_deref())
-                .unwrap_or(&provider.id);
+        })
+        .unwrap_or(&provider.id);
+    match api_format {
+        "openai_responses" => {
             // Codex OAuth (ChatGPT Plus/Pro 反代) 需要在请求体里强制 store: false
             // + include: ["reasoning.encrypted_content"]，由 transform 层统一处理。
             let is_codex_oauth = provider
@@ -455,6 +492,7 @@ impl ProviderAdapter for ClaudeAdapter {
                         HeaderName::from_static("x-interaction-type"),
                         HeaderValue::from_static("conversation-agent"),
                     ),
+                    // x-interaction-id 由 forwarder 按需注入（仅在有 session 时）
                     (
                         HeaderName::from_static("x-vscode-user-agent-library-version"),
                         HeaderValue::from_static("electron-fetch"),

src-tauri/src/proxy/providers/streaming.rs

@@ -85,8 +85,16 @@ struct ToolBlockState {
     name: String,
     started: bool,
     pending_args: String,
+    /// 连续空白字符计数 — 用于检测 Copilot 无限换行 bug
+    /// 当 function call 参数中出现连续 20+ 空白字符时，强制终止流
+    consecutive_whitespace: usize,
+    /// 是否已因无限空白 bug 被中止
+    aborted: bool,
 }
 
+/// 无限空白 bug 的连续空白字符阈值
+const INFINITE_WHITESPACE_THRESHOLD: usize = 20;
+
 /// 创建 Anthropic SSE 流
 pub fn create_anthropic_sse_stream<E: std::error::Error + Send + 'static>(
     stream: impl Stream<Item = Result<Bytes, E>> + Send + 'static,
@@ -297,9 +305,16 @@ pub fn create_anthropic_sse_stream<E: std::error::Error + Send + 'static>(
                                                                 name: String::new(),
                                                                 started: false,
                                                                 pending_args: String::new(),
+                                                                consecutive_whitespace: 0,
+                                                                aborted: false,
                                                             }
                                                         });
 
+                                                    // 如果此 tool call 已被中止（无限空白 bug），跳过后续处理
+                                                    if state.aborted {
+                                                        continue;
+                                                    }
+
                                                     if let Some(id) = &tool_call.id {
                                                         state.id = id.clone();
                                                     }
@@ -328,7 +343,22 @@ pub fn create_anthropic_sse_stream<E: std::error::Error + Send + 'static>(
                                                         .as_ref()
                                                         .and_then(|f| f.arguments.clone());
                                                     let immediate_delta = if let Some(args) = args_delta {
-                                                        if state.started {
+                                                        // 无限空白 bug 检测：跟踪连续空白字符
+                                                        for ch in args.chars() {
+                                                            if ch.is_whitespace() {
+                                                                state.consecutive_whitespace += 1;
+                                                            } else {
+                                                                state.consecutive_whitespace = 0;
+                                                            }
+                                                        }
+                                                        if state.consecutive_whitespace >= INFINITE_WHITESPACE_THRESHOLD {
+                                                            log::warn!(
+                                                                "[Copilot] 检测到无限空白 bug (tool: {}), 中止此 tool call 流",
+                                                                state.name
+                                                            );
+                                                            state.aborted = true;
+                                                            None
+                                                        } else if state.started {
                                                             Some(args)
                                                         } else {
                                                             state.pending_args.push_str(&args);