fix(providers): use prefix regex for web search fallback detector to catch versioned tool types (#9279)

Co-authored-by: diegosouzapw <diegosouzapw@users.noreply.github.com>

changelog.d/fixes/9279-fix.plan.md

@@ -0,0 +1 @@
+- **fix(providers):** the web search fallback detector in `webSearchFallback.ts` used an exact `Set` (`web_search`, `web_search_preview`) that missed Anthropic's date-suffixed server-tool variant `web_search_20250305` (sent by Claude Code 2.1.220+). Changed to prefix regex `/^web_search/`, matching the two other detectors in the codebase, so the fallback intercepts versioned web search tools for OpenAI-compatible upstreams ([#9279](https://github.com/diegosouzapw/OmniRoute/pull/9279))

open-sse/services/webSearchFallback.ts

@@ -1,7 +1,10 @@
 import { FORMATS } from "../translator/formats.ts";
 
 export const OMNIROUTE_WEB_SEARCH_FALLBACK_TOOL_NAME = "omniroute_web_search";
-const WEB_SEARCH_TOOL_TYPES = new Set(["web_search", "web_search_preview"]);
+// Prefix match — Anthropic sends date-suffixed variants (web_search_20250305, …).
+// The other two detectors (openai-responses/helpers.ts, webSearchRouting.ts) already
+// use /^web_search/ prefix matching; this aligns the fallback detector with them.
+const WEB_SEARCH_TOOL_TYPES = /^web_search/;
 const SEARCH_CONTEXT_DEFAULTS: Record<string, number> = {
   low: 5,
   medium: 8,
@@ -27,13 +30,13 @@ function toRecord(value: unknown): JsonRecord {
 function isBuiltInWebSearchTool(tool: unknown): tool is JsonRecord {
   const toolRecord = toRecord(tool);
   const toolType = typeof toolRecord.type === "string" ? toolRecord.type : "";
-  return WEB_SEARCH_TOOL_TYPES.has(toolType) && !toolRecord.function;
+  return WEB_SEARCH_TOOL_TYPES.test(toolType) && !toolRecord.function;
 }
 
 function isBuiltInWebSearchToolChoice(toolChoice: unknown): boolean {
   const choice = toRecord(toolChoice);
   const toolType = typeof choice.type === "string" ? choice.type : "";
-  return WEB_SEARCH_TOOL_TYPES.has(toolType);
+  return WEB_SEARCH_TOOL_TYPES.test(toolType);
 }
 
 function buildFallbackDescription(tool: JsonRecord): string {

tests/unit/web-search-9279-repro.test.ts

@@ -0,0 +1,81 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+
+const { prepareWebSearchFallbackBody, OMNIROUTE_WEB_SEARCH_FALLBACK_TOOL_NAME } =
+  await import("../../open-sse/services/webSearchFallback.ts");
+
+// #9279 — Anthropic's date-suffixed server-tool variant web_search_20250305
+// (sent by Claude Code 2.1.220+) is not intercepted by the web search fallback
+// detector in webSearchFallback.ts:4, which uses an exact Set.
+// Clasue -> OpenAI-compatible provider requests carry the raw Claude tool shape
+// { type: "web_search_20250305", name: "web_search", max_uses: 8 }.
+// The fallback must detect and intercept these too.
+
+test("#9279 versioned web_search_20250305 IS intercepted with interceptSearchOverride=true", () => {
+  const { body, fallback } = prepareWebSearchFallbackBody(
+    {
+      tools: [{ type: "web_search_20250305", name: "web_search", max_uses: 8 }],
+    },
+    {
+      provider: "opencode-go",
+      sourceFormat: "claude",
+      targetFormat: "openai",
+      nativeCodexPassthrough: false,
+      interceptSearchOverride: true,
+    }
+  );
+
+  assert.equal(fallback.enabled, true);
+  assert.equal(
+    fallback.toolName,
+    OMNIROUTE_WEB_SEARCH_FALLBACK_TOOL_NAME
+  );
+  assert.equal(fallback.convertedToolCount, 1);
+});
+
+test("#9279 versioned web_search_20250305 intercepted even without per-model override (claude->openai is not a native-bypass path)", () => {
+  // sourceFormat=claude, targetFormat=openai is NOT a native bypass path
+  // (supportsNativeWebSearchFallbackBypass returns false), so the fallback
+  // MUST fire without any interceptSearchOverride.
+  const { body, fallback } = prepareWebSearchFallbackBody(
+    {
+      tools: [{ type: "web_search_20250305", name: "web_search", max_uses: 8 }],
+    },
+    {
+      provider: "opencode-go",
+      sourceFormat: "claude",
+      targetFormat: "openai",
+      nativeCodexPassthrough: false,
+      // no interceptSearchOverride — must still be detected by tool type matching
+    }
+  );
+
+  assert.equal(fallback.enabled, true);
+  assert.equal(
+    fallback.toolName,
+    OMNIROUTE_WEB_SEARCH_FALLBACK_TOOL_NAME
+  );
+  assert.equal(fallback.convertedToolCount, 1);
+});
+
+test("#9279 tool_choice with web_search_20250305 redirects to omniroute_web_search", () => {
+  const { body, fallback } = prepareWebSearchFallbackBody(
+    {
+      tools: [{ type: "web_search_20250305", name: "web_search", max_uses: 8 }],
+      tool_choice: { type: "web_search_20250305" },
+    },
+    {
+      provider: "opencode-go",
+      sourceFormat: "claude",
+      targetFormat: "openai",
+      nativeCodexPassthrough: false,
+      interceptSearchOverride: true,
+    }
+  );
+
+  assert.equal(fallback.enabled, true);
+  const choice = body.tool_choice as Record<string, unknown>;
+  const fn = choice.function as Record<string, unknown> | undefined;
+  assert.equal(fn?.name, OMNIROUTE_WEB_SEARCH_FALLBACK_TOOL_NAME);
+  assert.equal(choice.type, "function");
+});