Match WebFetch prompt plural variants

Author: SqlRush

docs/cc-100-roadmap.md

@@ -179,6 +179,8 @@ M5 补充：BashOutput/PowerShellOutput structured content 现在会回传实际
 
 M5 补充：Read/Edit 现在接受 `offset`/`limit` 和 `replace_all` 的 quoted semantic string 输入；whole-decimal 数字字符串如 `"2.0"` 会按官方 `semanticNumber(...int())` 语义归一为整数，fractional 数字仍会被拒绝。
 
+M5 补充：WebFetch prompt-focused excerpt 的 term scoring 现在会匹配常见单复数变体，例如 prompt `cost` 可命中正文 `costs`，同时仍保持词边界匹配避免子串误命中。
+
 M5 补充：`Grep` content 输出现在支持 `only_matching`/`onlyMatching`/`only-matching`/`-o`，只输出匹配片段而不是整行，并在 structured matches 中暴露片段 column；`-o` 同样接受 quoted boolean。
 
 M5 补充：`Grep` count 输出现在支持 `count_matches`/`countMatches`/`count-matches`/`--count-matches`，需要时按匹配片段次数计数；`--count-matches` 可直接选择 count 输出，默认 count 继续保持匹配行计数，`countMatches` 同样接受 quoted boolean。

docs/claude-code-go-rewrite-plan.md

@@ -198,6 +198,7 @@ test/parity/                 # golden tests against TS/official behavior
 - 本轮补充：WebFetch 现在按官方 cross-host redirect 语义处理跨 host 跳转，HEAD preflight 和 GET 都不会自动触达新 host，而是返回包含 original URL、redirect URL 和 status 的 redirect notice；同 host redirect 仍继续跟随并保留 `final_url`。
 - 本轮补充：WebFetch input schema 现在与官方对齐，`url` 和 `prompt` 都是必填字段；既有本地扩展 `timeout`、`max_bytes`/`maxBytes` 仍保持可选。
 - 本轮补充：WebFetch 文本 body 现在会按 BOM、`Content-Type` charset 或 HTML `<meta charset>`/`http-equiv` charset 解码常见网页编码，包括 UTF-8/UTF-16LE/UTF-16BE、Latin-1 和 Windows-1252，并在 structured content 暴露归一化 `charset`。
+- 本轮补充：WebFetch prompt-focused excerpt 的 term scoring 现在会匹配常见单复数变体，例如 prompt `cost` 可命中正文 `costs`，同时仍保持词边界匹配避免子串误命中。
 - 本轮补充：WebSearch HTML 结果解析现在会按搜索页首个有效 `<base href>` 解析相对结果 anchor，覆盖镜像/自定义搜索页中浏览器可见结果 URL 与请求路径不一致的情况。
 - 本轮补充：WebSearch HTML 结果解析现在会读取 `application/ld+json` JSON-LD 结果，递归抽取 `@graph`、`ItemList.itemListElement.item`，支持 JSON-LD `@id` URL alias，并与后续 anchor 结果按 URL 去重。
 - 本轮补充：WebSearch JSON parser 现在会递归解包 `web`、`response`、`search`、`hits`、`documents`、`records`、`entries` 等常见后端 wrapper，保留 URL 去重和 domain filter。

internal/tools/web/web_fetch.go

@@ -1163,7 +1163,7 @@ func webFetchPromptPhrases(prompt string) []string {
 
 func isWebFetchStopWord(word string) bool {
 	switch word {
-	case "the", "and", "for", "with", "from", "this", "that", "you", "your", "are", "was", "were", "what", "when", "where", "which", "who", "why", "how", "summarize", "summary", "about", "please":
+	case "the", "and", "for", "with", "from", "this", "that", "you", "your", "are", "was", "were", "what", "when", "where", "which", "who", "why", "how", "does", "did", "much", "summarize", "summary", "about", "please", "extract", "find", "show", "tell":
 		return true
 	default:
 		return false
@@ -1255,7 +1255,7 @@ func scoreWebFetchPassage(passage string, terms []string, phrases []string) int
 		}
 	}
 	for _, term := range terms {
-		count := termCounts[term]
+		count := webFetchTermMatchCount(termCounts, term)
 		if count > 0 {
 			score += 2 + count
 		}
@@ -1274,10 +1274,50 @@ func webFetchSearchWordCounts(normalized string) map[string]int {
 	counts := map[string]int{}
 	for _, word := range strings.Fields(normalized) {
 		counts[word]++
+		for _, variant := range webFetchWordVariants(word) {
+			if variant != word {
+				counts[variant]++
+			}
+		}
 	}
 	return counts
 }
 
+func webFetchTermMatchCount(counts map[string]int, term string) int {
+	best := 0
+	seen := map[string]bool{}
+	for _, variant := range webFetchWordVariants(term) {
+		if seen[variant] {
+			continue
+		}
+		seen[variant] = true
+		if counts[variant] > best {
+			best = counts[variant]
+		}
+	}
+	return best
+}
+
+func webFetchWordVariants(word string) []string {
+	word = strings.TrimSpace(strings.ToLower(word))
+	if word == "" {
+		return nil
+	}
+	variants := []string{word}
+	if utf8.RuneCountInString(word) <= 3 {
+		return variants
+	}
+	switch {
+	case strings.HasSuffix(word, "ies") && utf8.RuneCountInString(word) > 4:
+		variants = append(variants, strings.TrimSuffix(word, "ies")+"y")
+	case strings.HasSuffix(word, "es") && utf8.RuneCountInString(word) > 4:
+		variants = append(variants, strings.TrimSuffix(word, "es"))
+	case strings.HasSuffix(word, "s") && !strings.HasSuffix(word, "ss"):
+		variants = append(variants, strings.TrimSuffix(word, "s"))
+	}
+	return variants
+}
+
 func countWebFetchPhraseOccurrences(normalized string, phrase string) int {
 	phrase = strings.TrimSpace(strings.ToLower(phrase))
 	if normalized == "" || phrase == "" {

internal/tools/web/web_fetch_test.go

@@ -208,6 +208,39 @@ func TestWebFetchRendersHTMLAndPromptExcerpt(t *testing.T) {
 	}
 }
 
+func TestWebFetchPromptExcerptMatchesPluralVariants(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/html; charset=utf-8")
+		_, _ = w.Write([]byte(`<!doctype html>
+<html>
+<body>
+  <main>
+    <p>Overview page with general launch notes.</p>
+    <p>The beta plan costs $20 and includes priority support.</p>
+  </main>
+</body>
+</html>`))
+	}))
+	defer server.Close()
+	executor := webExecutor(t)
+	result, err := executor.Execute(tool.Context{Context: context.Background(), Metadata: map[string]any{}}, contracts.ToolUse{
+		ID:    "toolu_web_html_plural_excerpt",
+		Name:  "WebFetch",
+		Input: json.RawMessage(`{"url":` + strconvQuote(server.URL) + `,"prompt":"cost"}`),
+	}, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	content := result.Content.(string)
+	if !strings.Contains(content, "Relevant excerpt:") || !strings.Contains(content, "The beta plan costs $20") {
+		t.Fatalf("content = %#v", content)
+	}
+	excerpt, ok := result.StructuredContent["prompt_excerpt"].(string)
+	if !ok || !strings.Contains(excerpt, "The beta plan costs $20") || strings.Contains(excerpt, "Overview page") {
+		t.Fatalf("prompt excerpt = %#v", result.StructuredContent["prompt_excerpt"])
+	}
+}
+
 func TestWebFetchHTMLRenderingPreservesLinksAndImageText(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "text/html; charset=utf-8")
@@ -548,6 +581,12 @@ func TestWebFetchPromptPhraseScoring(t *testing.T) {
 	if score := scoreWebFetchPassage("Trust the process.", []string{"rust"}, nil); score != 0 {
 		t.Fatalf("substring term should not match word-boundary scoring: %d", score)
 	}
+	if score := scoreWebFetchPassage("The beta plan costs $20.", []string{"cost"}, nil); score == 0 {
+		t.Fatalf("singular prompt term should match plural passage word")
+	}
+	if score := scoreWebFetchPassage("The beta plan cost $20.", []string{"costs"}, nil); score == 0 {
+		t.Fatalf("plural prompt term should match singular passage word")
+	}
 }
 
 func TestWebFetchPreflightSkipsBinaryGet(t *testing.T) {