Bug: Memory search fails to match words with punctuation in extractWords

Bug: Memory search fails to match words with punctuation

Summary

The extractWords function in memory/inmemory.go uses space-only splitting and doesn't strip punctuation, causing memory search to miss relevant results when text contains punctuation or non-space whitespace.

Reproduction

Scenario: Add a session with content containing punctuation, then search for a word without punctuation.

// Add session with punctuation
session := makeSession("app1", "user1", "sess1", []*session.Event{
    {
        LLMResponse: model.LLMResponse{
            Content: genai.NewContentFromText("The agent works great!", genai.RoleModel),
        },
    },
})
memSvc.AddSession(ctx, session)

// Search for "great" (without punctuation)
resp, _ := memSvc.Search(ctx, &memory.SearchRequest{
    AppName: "app1",
    UserID:  "user1",
    Query:   "great",
})

// Expected: 1 memory found
// Actual: 0 memories (because stored token is "great!" not "great")

Root Cause

File: memory/inmemory.go, line ~155

func extractWords(text string) map[string]struct{} {
	res := make(map[string]struct{})

	for s := range strings.SplitSeq(text, " ") {  // ← Only splits on space
		if s == "" {
			continue
		}
		res[strings.ToLower(s)] = struct{}{}  // ← Doesn't strip punctuation
	}

	return res
}

Issues:

1. Space-only splitting: strings.SplitSeq(text, " ") doesn't handle tabs, newlines, or multiple spaces
2. No punctuation normalization: "great!" is stored as-is, won't match "great"
3. Case sensitivity handled but not enough: Lowercasing happens after punctuation is included

Impact

• Search accuracy degraded: Users searching for "error" won't find memories containing "error." or "error," or "error!"
• Common patterns affected:
  • Sentences ending with punctuation (., !, ?)
  • Comma-separated lists
  • Quoted text
  • Multi-line responses with \n or \t

Proposed Fix

Replace space-only splitting with proper whitespace tokenization and strip punctuation:

func extractWords(text string) map[string]struct{} {
	res := make(map[string]struct{})

	for _, word := range strings.Fields(text) {  // Splits on all whitespace
		// Strip punctuation
		cleaned := strings.TrimFunc(word, func(r rune) bool {
			return !unicode.IsLetter(r) && !unicode.IsNumber(r)
		})
		if cleaned == "" {
			continue
		}
		res[strings.ToLower(cleaned)] = struct{}{}
	}

	return res
}

Alternative: Use a proper tokenizer/stemmer for production-grade search, but the above fix would resolve the immediate issue.

Test Case to Add

{
    name: "match words with punctuation",
    initSessions: []session.Session{
        makeSession(t, "app1", "user1", "sess1", []*session.Event{
            {
                LLMResponse: model.LLMResponse{
                    Content: genai.NewContentFromText("Error: connection timeout! Please retry.", genai.RoleModel),
                },
            },
        }),
    },
    req: &memory.SearchRequest{
        AppName: "app1",
        UserID:  "user1",
        Query:   "error timeout retry",  // No punctuation
    },
    wantResp: &memory.SearchResponse{
        Memories: []memory.Entry{/* should find the memory */},
    },
},

Environment

• Version: main branch (commit: latest as of 2026-02-16)
• Go version: 1.22+

Additional Context

This is particularly problematic for AI agent memory since LLM responses naturally contain punctuation. The current implementation significantly reduces search recall in real-world usage.