diff --git a/internal/adapter/openai/tool_sieve_state.go b/internal/adapter/openai/tool_sieve_state.go
index f36560a..60370e9 100644
--- a/internal/adapter/openai/tool_sieve_state.go
+++ b/internal/adapter/openai/tool_sieve_state.go
@@ -34,7 +34,8 @@ type toolCallDelta struct {
 	Arguments string
 }
 
-const toolSieveContextTailLimit = 256
+// Keep in sync with JS TOOL_SIEVE_CONTEXT_TAIL_LIMIT.
+const toolSieveContextTailLimit = 2048
 
 func (s *toolStreamSieveState) resetIncrementalToolState() {
 	s.disableDeltas = false
diff --git a/internal/js/helpers/stream-tool-sieve/parse_payload.js b/internal/js/helpers/stream-tool-sieve/parse_payload.js
index e658be5..c480033 100644
--- a/internal/js/helpers/stream-tool-sieve/parse_payload.js
+++ b/internal/js/helpers/stream-tool-sieve/parse_payload.js
@@ -102,7 +102,10 @@ function extractToolCallObjects(text) {
       const obj = extractJSONObjectFrom(raw, start);
       if (obj.ok) {
         out.push(raw.slice(start, obj.end).trim());
-        offset = obj.end;
+        // Ensure forward progress even when the matched keyword is outside
+        // the extracted JSON object (e.g. closing XML wrapper tags containing
+        // "tool_calls" after an earlier JSON arguments object).
+        offset = Math.max(obj.end, idx + matched.length);
         idx = -1;
         break;
       }
diff --git a/internal/js/helpers/stream-tool-sieve/state.js b/internal/js/helpers/stream-tool-sieve/state.js
index 74d1904..9a5b1c3 100644
--- a/internal/js/helpers/stream-tool-sieve/state.js
+++ b/internal/js/helpers/stream-tool-sieve/state.js
@@ -1,6 +1,7 @@
 'use strict';
 
-const TOOL_SIEVE_CONTEXT_TAIL_LIMIT = 4096;
+// Keep in sync with Go toolSieveContextTailLimit.
+const TOOL_SIEVE_CONTEXT_TAIL_LIMIT = 2048;
 
 function createToolSieveState() {
   return {
diff --git a/tests/node/stream-tool-sieve.test.js b/tests/node/stream-tool-sieve.test.js
index 33b666e..e53086e 100644
--- a/tests/node/stream-tool-sieve.test.js
+++ b/tests/node/stream-tool-sieve.test.js
@@ -227,6 +227,24 @@ test('sieve flushes incomplete captured XML tool blocks without leaking raw tags
   assert.equal(leakedText.includes('<tool_call'), false);
 });
 
+test('sieve captures XML wrapper tags with attributes without leaking wrapper text', () => {
+  const events = runSieve(
+    [
+      '前置正文H。',
+      '<tool_calls id="x"><tool_call><tool_name>read_file</tool_name><parameters>{"path":"README.MD"}</parameters></tool_call></tool_calls>',
+      '后置正文I。',
+    ],
+    ['read_file'],
+  );
+  const leakedText = collectText(events);
+  const hasToolCall = events.some((evt) => evt.type === 'tool_calls' && evt.calls?.length > 0);
+  assert.equal(hasToolCall, true);
+  assert.equal(leakedText.includes('前置正文H。'), true);
+  assert.equal(leakedText.includes('后置正文I。'), true);
+  assert.equal(leakedText.includes('<tool_calls id=\"x\">'), false);
+  assert.equal(leakedText.includes('</tool_calls>'), false);
+});
+
 test('sieve still intercepts large tool json payloads over previous capture limit', () => {
   const large = 'a'.repeat(9000);
   const payload = `{"tool_calls":[{"name":"read_file","input":{"path":"${large}"}}]}`;
@@ -252,6 +270,46 @@ test('sieve keeps plain text intact in tool mode when no tool call appears', ()
   assert.equal(leakedText, '你好，这是普通文本回复。请继续。');
 });
 
+test('sieve keeps plain "tool_calls" prose as text when no valid payload follows', () => {
+  const events = runSieve(
+    ['前置。', '这里提到 tool_calls 只是解释，不是调用。', '后置。'],
+    ['read_file'],
+  );
+  const leakedText = collectText(events);
+  const hasToolCall = events.some((evt) => evt.type === 'tool_calls' && evt.calls?.length > 0);
+  assert.equal(hasToolCall, false);
+  assert.equal(leakedText.includes('tool_calls'), true);
+  assert.equal(leakedText, '前置。这里提到 tool_calls 只是解释，不是调用。后置。');
+});
+
+test('sieve keeps numbered planning prose before a real tool payload (mobile-chat style)', () => {
+  const events = runSieve(
+    [
+      '好的，我会依次测试每个工具，先把所有工具都调用一遍，然后汇总结果给你看。\n\n1. 获取当前时间\n',
+      '{"tool_calls":[{"name":"get_current_time","input":{}}]}',
+    ],
+    ['get_current_time'],
+  );
+  const leakedText = collectText(events);
+  const finalCalls = events.filter((evt) => evt.type === 'tool_calls').flatMap((evt) => evt.calls || []);
+  assert.equal(finalCalls.length, 1);
+  assert.equal(finalCalls[0].name, 'get_current_time');
+  assert.equal(leakedText.includes('先把所有工具都调用一遍'), true);
+  assert.equal(leakedText.includes('1. 获取当前时间'), true);
+  assert.equal(leakedText.toLowerCase().includes('tool_calls'), false);
+});
+
+test('sieve keeps numbered planning prose when no tool payload follows', () => {
+  const events = runSieve(
+    ['好的，我会依次测试每个工具。\n\n1. 获取当前时间'],
+    ['get_current_time'],
+  );
+  const leakedText = collectText(events);
+  const hasToolCall = events.some((evt) => evt.type === 'tool_calls' && evt.calls?.length > 0);
+  assert.equal(hasToolCall, false);
+  assert.equal(leakedText, '好的，我会依次测试每个工具。\n\n1. 获取当前时间');
+});
+
 test('sieve emits unknown tool payload (no args) as executable tool call', () => {
   const events = runSieve(
     ['{"tool_calls":[{"name":"not_in_schema"}]}', '后置正文G。'],