Fix: web search query builder to use last user message

TEST_WEBSEARCH.md

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+# Web Search Fix - Test Guide
+
+## Summary
+
+Fixed the web search query builder to ensure it correctly picks the **last user message** from a conversation, preventing the "wrong query" bug.
+
+## Implementation Details
+
+### 1. Query Builder (`src/lib/tools/webSearch.ts`)
+
+- **Strategy**: Prefer the most recent (last) user message in the conversation
+- **Fallback**: If no user messages exist, use the most recent any message
+- **Sanitization**: Strips code fences, inline code, and citation markers `[1]`, `[12]`, etc.
+
+**Key Function**:
+
+```typescript
+export function buildWebSearchQuery(messages: Message[] = []): string {
+	// Loop from END of messages array backwards to find LAST user message
+	for (let i = messages.length - 1; i >= 0; i--) {
+		const m = messages[i];
+		if (m?.from === "user" && m.content && m.content.trim().length) {
+			return stripMarkdownAndCitations(m.content);
+		}
+	}
+	// ... fallback logic
+}
+```
+
+### 2. Unit Tests (`src/lib/tools/webSearch.test.ts`)
+
+Four test cases verify correctness:
+
+- ✅ Empty conversation returns empty string
+- ✅ **Picks the LAST user message** (not first)
+- ✅ Falls back to assistant message if no user messages
+- ✅ Strips markdown code fences, inline code, and citations
+
+### 3. Server Endpoint (`src/routes/api/tools/websearch/+server.ts`)
+
+- Accepts POST request with message history
+- Returns the correct query built from last user message
+- Prevents "wrong query" by using deterministic builder
+
+## How to Test
+
+### Test 1: Verify Query Builder Selects Correct Message
+
+```bash
+curl -X POST http://localhost:5173/api/tools/websearch \
+  -H "Content-Type: application/json" \
+  -d '{
+    "messages": [
+      {"from": "user", "content": "first question"},
+      {"from": "assistant", "content": "first answer"},
+      {"from": "user", "content": "second question - THIS SHOULD BE PICKED"}
+    ]
+  }'
+```
+
+**Expected Response**:
+
+```json
+{ "query": "second question - THIS SHOULD BE PICKED" }
+```
+
+### Test 2: Verify Markdown Sanitization
+
+```bash
+curl -X POST http://localhost:5173/api/tools/websearch \
+  -H "Content-Type: application/json" \
+  -d '{
+    "messages": [
+      {
+        "from": "user",
+        "content": "Show code:\n\`\`\`python\nprint(1)\n\`\`\`\n[1] See also `x=1`"
+      }
+    ]
+  }'
+```
+
+**Expected Response**:
+
+```json
+{ "query": "Show code: See also" }
+```
+
+(Code blocks, inline code, and citations removed)
+
+### Test 3: Run Unit Tests
+
+```bash
+npm test -- src/lib/tools/webSearch.test.ts --run
+```
+
+## Why This Fixes the Bug
+
+**Before**: If web search didn't explicitly select the last user message, it might:
+
+- Use the first message instead of the most recent question
+- Include assistant responses or system messages
+- Search for the wrong topic due to confusion in message order
+
+**After**: With our deterministic query builder:
+
+- Always searches for the **last user query** (most recent intent)
+- Strips formatting noise (code, citations)
+- Fully testable with unit tests
+- Consistent and predictable behavior
+
+## Files Modified/Created
+
+1. `src/lib/tools/webSearch.ts` - Query builder utility
+2. `src/lib/tools/webSearch.test.ts` - Unit tests (4 passing)
+3. `src/routes/api/tools/websearch/+server.ts` - Server endpoint

src/lib/tools/webSearch.test.ts

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+import { describe, it, expect } from "vitest";
+import buildWebSearchQuery from "./webSearch";
+
+describe("buildWebSearchQuery", () => {
+	it("returns empty string for empty conversation", () => {
+		expect(buildWebSearchQuery([])).toBe("");
+	});
+
+	it("prefers the most recent user message", () => {
+		const messages = [
+			{ from: "user", content: "first user message" },
+			{ from: "assistant", content: "assistant reply" },
+			{ from: "user", content: "second user message" },
+		];
+		expect(buildWebSearchQuery(messages)).toBe("second user message");
+	});
+
+	it("falls back to assistant message if no user messages", () => {
+		const messages = [{ from: "assistant", content: "assistant final thought" }];
+		expect(buildWebSearchQuery(messages)).toBe("assistant final thought");
+	});
+
+	it("strips code fences, inline code and citations", () => {
+		const messages = [
+			{
+				from: "user",
+				content: "Here is some code:\n```js\nconsole.log(1)\n```\nAlso see [1]. Inline `x = 1`.",
+			},
+		];
+		const q = buildWebSearchQuery(messages);
+		expect(q).toBe("Here is some code: Also see . Inline .");
+	});
+});

src/lib/tools/webSearch.ts

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+export type Message = {
+	from: string; // 'user' | 'assistant' | 'system' etc.
+	content?: string | null;
+};
+
+function stripMarkdownAndCitations(s: string): string {
+	// Remove fenced code blocks
+	let out = s.replace(/```[\s\S]*?```/g, "");
+	// Remove inline code
+	out = out.replace(/`[^`]*`/g, "");
+	// Remove citation-like [1], [12]
+	out = out.replace(/\[\d+\]/g, "");
+	// Collapse whitespace
+	out = out.replace(/[\r\n\t]+/g, " ");
+	out = out.replace(/\s+/g, " ").trim();
+	return out;
+}
+
+/**
+ * Build a web-search query from a list of conversation messages.
+ * Strategy:
+ * - prefer the most recent non-empty user message
+ * - if none, fallback to the most recent non-empty assistant or system message
+ * - sanitize by removing code fences, inline code and simple citation markers
+ */
+export function buildWebSearchQuery(messages: Message[] = []): string {
+	for (let i = messages.length - 1; i >= 0; i--) {
+		const m = messages[i];
+		if (m?.from === "user" && m.content && m.content.trim().length) {
+			return stripMarkdownAndCitations(m.content);
+		}
+	}
+
+	// fallback: any non-empty message from the end
+	for (let i = messages.length - 1; i >= 0; i--) {
+		const m = messages[i];
+		if (m?.content && m.content.trim().length) {
+			return stripMarkdownAndCitations(m.content);
+		}
+	}
+
+	return "";
+}
+
+export default buildWebSearchQuery;

src/routes/api/tools/websearch/+server.ts

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+import { json, type RequestEvent } from "@sveltejs/kit";
+import buildWebSearchQuery from "$lib/tools/webSearch";
+
+export async function POST({ request }: RequestEvent) {
+	const body = await request.json().catch(() => ({}));
+	const messages = Array.isArray(body?.messages) ? body.messages : [];
+	const q = buildWebSearchQuery(messages);
+	return json({ query: q });
+}