diff --git a/changelog.d/features/6666-felo-chat-aggregator-provider.md b/changelog.d/features/6666-felo-chat-aggregator-provider.md
new file mode 100644
index 0000000000..bea5f71f5a
--- /dev/null
+++ b/changelog.d/features/6666-felo-chat-aggregator-provider.md
@@ -0,0 +1 @@
+- **feat(providers):** add Felo (felo.ai) as a free, no-signup, no-API-key chat/search-agent aggregator provider (`felo-web`) — joins the existing `-web` family (DuckDuckGo AI Chat, Blackbox, etc). Five models (`felo-chat`, `felo-search`, `felo-scholar`, `felo-social`, `felo-document`) map to Felo's search categories; the executor opens a search thread then translates Felo's bespoke SSE stream into OpenAI-compatible chunks (#6666).
diff --git a/open-sse/config/freeModelCatalog.data.ts b/open-sse/config/freeModelCatalog.data.ts
index a9accafb60..6b807affb1 100644
--- a/open-sse/config/freeModelCatalog.data.ts
+++ b/open-sse/config/freeModelCatalog.data.ts
@@ -148,6 +148,11 @@ export const FREE_MODEL_BUDGETS: FreeModelBudget[] = [
   { provider: "duckduckgo-web", modelId: "llama-4-scout", displayName: "Llama 4 Scout", monthlyTokens: 0, creditTokens: 0, freeType: "keyless", poolKey: "duckduckgo-web", tos: "avoid" },
   { provider: "duckduckgo-web", modelId: "mistral-small-2501", displayName: "Mistral Small", monthlyTokens: 0, creditTokens: 0, freeType: "keyless", poolKey: "duckduckgo-web", tos: "avoid" },
   { provider: "duckduckgo-web", modelId: "o3-mini", displayName: "O3 Mini", monthlyTokens: 0, creditTokens: 0, freeType: "keyless", poolKey: "duckduckgo-web", tos: "avoid" },
+  { provider: "felo-web", modelId: "felo-chat", displayName: "Felo Chat", monthlyTokens: 0, creditTokens: 0, freeType: "keyless", poolKey: "felo-web", tos: "avoid" },
+  { provider: "felo-web", modelId: "felo-search", displayName: "Felo Search", monthlyTokens: 0, creditTokens: 0, freeType: "keyless", poolKey: "felo-web", tos: "avoid" },
+  { provider: "felo-web", modelId: "felo-scholar", displayName: "Felo Scholar", monthlyTokens: 0, creditTokens: 0, freeType: "keyless", poolKey: "felo-web", tos: "avoid" },
+  { provider: "felo-web", modelId: "felo-social", displayName: "Felo Social", monthlyTokens: 0, creditTokens: 0, freeType: "keyless", poolKey: "felo-web", tos: "avoid" },
+  { provider: "felo-web", modelId: "felo-document", displayName: "Felo Document", monthlyTokens: 0, creditTokens: 0, freeType: "keyless", poolKey: "felo-web", tos: "avoid" },
   { provider: "fireworks", modelId: "deepseek-v4-flash", displayName: "DeepSeek V4 Flash", monthlyTokens: 0, creditTokens: 1000000, freeType: "one-time-initial", poolKey: "fireworks", tos: "avoid" },
   { provider: "fireworks", modelId: "deepseek-v4-pro", displayName: "DeepSeek V4 Pro", monthlyTokens: 0, creditTokens: 1000000, freeType: "one-time-initial", poolKey: "fireworks", tos: "avoid" },
   { provider: "fireworks", modelId: "glm-5p1", displayName: "GLM 5.1", monthlyTokens: 0, creditTokens: 1000000, freeType: "one-time-initial", poolKey: "fireworks", tos: "avoid" },
diff --git a/open-sse/config/freeTierCatalog.ts b/open-sse/config/freeTierCatalog.ts
index 5262697625..c6e17698e1 100644
--- a/open-sse/config/freeTierCatalog.ts
+++ b/open-sse/config/freeTierCatalog.ts
@@ -41,6 +41,7 @@ export const FREE_TIER_BUDGETS: Record<string, number> = {
 export const FREE_TIER_TOS: Record<string, TosVerdict> = {
   opencode: "avoid",
   "duckduckgo-web": "avoid",
+  "felo-web": "avoid",
   agy: "avoid",
   kiro: "avoid",
   "amazon-q": "avoid",
diff --git a/open-sse/config/providers/index.ts b/open-sse/config/providers/index.ts
index 8763f6326f..848ce8bfb7 100644
--- a/open-sse/config/providers/index.ts
+++ b/open-sse/config/providers/index.ts
@@ -121,6 +121,7 @@ import { longcatProvider } from "./registry/longcat/index.ts";
 import { vertex_partnerProvider } from "./registry/vertex/partner/index.ts";
 import { vertexProvider } from "./registry/vertex/index.ts";
 import { duckduckgo_webProvider } from "./registry/duckduckgo-web/index.ts";
+import { felo_webProvider } from "./registry/felo-web/index.ts";
 import { xaiProvider } from "./registry/xai/index.ts";
 import { morphProvider } from "./registry/morph/index.ts";
 import { siliconflowProvider } from "./registry/siliconflow/index.ts";
@@ -308,6 +309,7 @@ export const REGISTRY: Record<string, RegistryEntry> = {
   "vertex-partner": vertex_partnerProvider,
   vertex: vertexProvider,
   "duckduckgo-web": duckduckgo_webProvider,
+  "felo-web": felo_webProvider,
   xai: xaiProvider,
   morph: morphProvider,
   siliconflow: siliconflowProvider,
diff --git a/open-sse/config/providers/registry/felo-web/index.ts b/open-sse/config/providers/registry/felo-web/index.ts
new file mode 100644
index 0000000000..4cf8fcae25
--- /dev/null
+++ b/open-sse/config/providers/registry/felo-web/index.ts
@@ -0,0 +1,18 @@
+import type { RegistryEntry } from "../../shared.ts";
+
+export const felo_webProvider: RegistryEntry = {
+  id: "felo-web",
+  alias: "felo",
+  format: "openai",
+  executor: "felo-web",
+  baseUrl: "https://felo.ai/api-proxy/main/search/threads",
+  authType: "none",
+  authHeader: "none",
+  models: [
+    { id: "felo-chat", name: "Felo Chat" },
+    { id: "felo-search", name: "Felo Search" },
+    { id: "felo-scholar", name: "Felo Scholar" },
+    { id: "felo-social", name: "Felo Social" },
+    { id: "felo-document", name: "Felo Document" },
+  ],
+};
diff --git a/open-sse/executors/felo-web.ts b/open-sse/executors/felo-web.ts
new file mode 100644
index 0000000000..847b8d3f77
--- /dev/null
+++ b/open-sse/executors/felo-web.ts
@@ -0,0 +1,362 @@
+import { randomUUID } from "node:crypto";
+import { BaseExecutor, type ExecuteInput } from "./base.ts";
+import { sanitizeErrorMessage } from "../utils/error.ts";
+
+/**
+ * FeloWebExecutor — anonymous, free access to Felo (felo.ai), a chat/search-agent
+ * aggregator. No API key or session cookie required (`needs_auth = False` in the
+ * g4f reference implementation, `g4f/Provider/Felo.py`, fetched 2026-07-17).
+ *
+ * Flow:
+ * 1. POST /api-proxy/main/search/threads — opens a search thread, returns `stream_key`.
+ * 2. GET /api/message/v1/stream/{stream_key}?offset=0 — SSE-shaped stream. Each line is
+ *    `data:{...}` (no space after the colon, unlike most SSE producers). The JSON payload
+ *    carries a double-encoded `content` string; parsing that yields `{ data: { type, data } }`
+ *    where `type` is `"answer"` (incremental/snapshot text) or `"final_contexts"` (sources,
+ *    dropped here — no OpenAI-compatible slot for citations on this translation path).
+ *
+ * Felo has no published API; this is a reverse-engineered, scrape-style integration in the
+ * same family as `duckduckgo-web.ts` / `blackbox-web.ts` (see #6666 plan). It may break
+ * without notice if Felo changes its frontend contract.
+ */
+
+export const FELO_BASE = "https://felo.ai";
+export const FELO_THREADS_URL = `${FELO_BASE}/api-proxy/main/search/threads`;
+export const FELO_PROVIDER_PREFIX = "felo-web/";
+
+export function feloStreamUrl(streamKey: string): string {
+  return `${FELO_BASE}/api/message/v1/stream/${encodeURIComponent(streamKey)}?offset=0`;
+}
+
+const FELO_USER_AGENT =
+  "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 " +
+  "(KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36";
+
+export const FELO_HEADERS: Record<string, string> = {
+  Accept: "*/*",
+  "Content-Type": "application/json",
+  Origin: FELO_BASE,
+  Referer: `${FELO_BASE}/search?q=hello`,
+  "User-Agent": FELO_USER_AGENT,
+};
+
+const FELO_STREAM_REQUEST_HEADERS: Record<string, string> = {
+  Accept: "*/*",
+  Origin: FELO_BASE,
+  Referer: FELO_HEADERS.Referer,
+  "User-Agent": FELO_USER_AGENT,
+};
+
+// Mirrors g4f's `Felo.model_aliases` — Felo has no published model list; this
+// reverse-engineered mapping is the only reference (category drives which
+// search/answer pipeline Felo routes the query through).
+const FELO_MODEL_CATEGORIES: Record<string, string> = {
+  "felo-chat": "chat",
+  "felo-search": "google",
+  "felo-scholar": "scholar",
+  "felo-social": "social",
+  "felo-document": "document",
+};
+
+export const FELO_DEFAULT_MODEL = "felo-chat";
+
+export function normalizeFeloModel(model: string | undefined | null): string {
+  if (!model) return FELO_DEFAULT_MODEL;
+  const clean = model.startsWith(FELO_PROVIDER_PREFIX)
+    ? model.slice(FELO_PROVIDER_PREFIX.length)
+    : model;
+  return Object.prototype.hasOwnProperty.call(FELO_MODEL_CATEGORIES, clean)
+    ? clean
+    : FELO_DEFAULT_MODEL;
+}
+
+export function resolveFeloCategory(model: string | undefined | null): string {
+  return FELO_MODEL_CATEGORIES[normalizeFeloModel(model)];
+}
+
+export function extractFeloLastUserPrompt(messages: Array<Record<string, unknown>>): string {
+  const lastUser = [...messages].reverse().find((m) => m.role === "user");
+  if (!lastUser) return "";
+  const content = lastUser.content;
+  if (typeof content === "string") return content;
+  if (!Array.isArray(content)) return "";
+  return content
+    .map((part) => {
+      if (part && typeof part === "object" && typeof (part as Record<string, unknown>).text === "string") {
+        return (part as Record<string, unknown>).text as string;
+      }
+      return "";
+    })
+    .filter(Boolean)
+    .join("\n");
+}
+
+export function buildFeloThreadPayload(
+  model: string | undefined | null,
+  prompt: string
+): Record<string, unknown> {
+  const searchUuid = randomUUID();
+  return {
+    query: prompt,
+    search_uuid: searchUuid,
+    lang: "",
+    agent_lang: "en",
+    search_options: { langcode: "en-US" },
+    search_video: true,
+    query_from: "default",
+    category: resolveFeloCategory(model),
+    model: "",
+    auto_routing: true,
+    mode: "concise",
+    device_id: randomUUID().replaceAll("-", ""),
+    source_message_rid: "",
+    documents: [],
+    document_action: "",
+    slides_source: { type: "ask_question", files: {} },
+    slide_template_uid: "",
+    selected_resource_ids: [],
+    process_id: searchUuid,
+    stream_protocol: "message_center_v1",
+    enable_task_state: true,
+  };
+}
+
+function extractFeloAnswerText(contentJson: unknown): string | null {
+  if (!contentJson || typeof contentJson !== "object") return null;
+  const data = (contentJson as Record<string, unknown>).data;
+  if (!data || typeof data !== "object") return null;
+  const dataRecord = data as Record<string, unknown>;
+  if (dataRecord.type !== "answer") return null;
+  const inner = dataRecord.data;
+  if (!inner || typeof inner !== "object") return null;
+  const text = (inner as Record<string, unknown>).text;
+  return typeof text === "string" ? text : null;
+}
+
+export interface FeloParsedLine {
+  /** New text to emit for this line, or null when the line carried nothing new. */
+  newText: string | null;
+  /** Running "previous text" snapshot to pass into the next call. */
+  nextPreviousText: string;
+}
+
+/**
+ * Parse a single line of Felo's SSE-shaped stream, diffing against the running
+ * snapshot the same way the g4f reference implementation does: each `answer`
+ * event carries the full text-so-far, and only the new suffix is new content.
+ */
+export function parseFeloStreamLine(line: string, previousText: string): FeloParsedLine {
+  const trimmed = line.trim();
+  if (!trimmed.startsWith("data:{")) {
+    return { newText: null, nextPreviousText: previousText };
+  }
+
+  let outer: unknown;
+  try {
+    outer = JSON.parse(trimmed.slice(5));
+  } catch {
+    return { newText: null, nextPreviousText: previousText };
+  }
+
+  const content = (outer as Record<string, unknown> | null)?.content;
+  if (typeof content !== "string") {
+    return { newText: null, nextPreviousText: previousText };
+  }
+
+  let contentJson: unknown;
+  try {
+    contentJson = JSON.parse(content);
+  } catch {
+    return { newText: null, nextPreviousText: previousText };
+  }
+
+  const text = extractFeloAnswerText(contentJson);
+  if (text === null) {
+    return { newText: null, nextPreviousText: previousText };
+  }
+
+  if (text.startsWith(previousText)) {
+    const newPart = text.slice(previousText.length);
+    return newPart
+      ? { newText: newPart, nextPreviousText: text }
+      : { newText: null, nextPreviousText: previousText };
+  }
+
+  return { newText: text, nextPreviousText: text };
+}
+
+/** Replay a full raw stream body through `parseFeloStreamLine`, returning the final text. */
+export function accumulateFeloStreamText(rawText: string): string {
+  let previousText = "";
+  for (const line of rawText.split("\n")) {
+    previousText = parseFeloStreamLine(line, previousText).nextPreviousText;
+  }
+  return previousText;
+}
+
+export class FeloWebExecutor extends BaseExecutor {
+  constructor() {
+    super("felo-web", { baseUrl: FELO_BASE });
+  }
+
+  async testConnection(
+    _credentials: Record<string, unknown>,
+    signal?: AbortSignal
+  ): Promise<boolean> {
+    const controller = new AbortController();
+    const timeout = setTimeout(() => controller.abort(), this.getTimeoutMs());
+    try {
+      const mergedSignal = signal
+        ? AbortSignal.any([signal, controller.signal])
+        : controller.signal;
+
+      const response = await fetch(FELO_THREADS_URL, {
+        method: "POST",
+        headers: FELO_HEADERS,
+        body: JSON.stringify(buildFeloThreadPayload(FELO_DEFAULT_MODEL, "hi")),
+        signal: mergedSignal,
+      });
+      if (!response.ok) return false;
+      const data = await response.json().catch(() => null);
+      return typeof (data as Record<string, unknown> | null)?.stream_key === "string";
+    } catch {
+      return false;
+    } finally {
+      clearTimeout(timeout);
+    }
+  }
+
+  async execute(input: ExecuteInput): Promise<Response> {
+    const { model, body, stream, signal } = input;
+    const bodyObj = (body || {}) as Record<string, unknown>;
+    const messages = Array.isArray(bodyObj.messages)
+      ? (bodyObj.messages as Array<Record<string, unknown>>)
+      : [];
+    const isStreaming = stream !== false;
+
+    if (messages.length === 0) {
+      return feloErrorResponse(400, "No messages provided");
+    }
+    const prompt = extractFeloLastUserPrompt(messages);
+    if (!prompt) {
+      return feloErrorResponse(400, "No user message content found");
+    }
+
+    const controller = new AbortController();
+    const timeout = setTimeout(() => controller.abort(), this.getTimeoutMs());
+    const mergedSignal = signal ? AbortSignal.any([signal, controller.signal]) : controller.signal;
+
+    try {
+      const streamKey = await this.createFeloThread(model, prompt, mergedSignal);
+      if (streamKey instanceof Response) {
+        clearTimeout(timeout);
+        return streamKey;
+      }
+
+      const streamResponse = await fetch(feloStreamUrl(streamKey), {
+        method: "GET",
+        headers: FELO_STREAM_REQUEST_HEADERS,
+        signal: mergedSignal,
+      });
+      clearTimeout(timeout);
+
+      if (!streamResponse.ok || !streamResponse.body) {
+        const status = !streamResponse.ok && streamResponse.status >= 500 ? 502 : streamResponse.status || 502;
+        return feloErrorResponse(status, `Felo stream request failed with HTTP ${streamResponse.status}`);
+      }
+
+      return await processFeloResponse(streamResponse, isStreaming);
+    } catch (error) {
+      clearTimeout(timeout);
+      if (error instanceof DOMException && error.name === "AbortError") {
+        return feloErrorResponse(499, "Request cancelled");
+      }
+      return feloErrorResponse(500, error instanceof Error ? error.message : "Unknown error");
+    }
+  }
+
+  /** Returns the resolved `stream_key`, or an error Response to propagate as-is. */
+  private async createFeloThread(
+    model: string | undefined,
+    prompt: string,
+    signal: AbortSignal
+  ): Promise<string | Response> {
+    const threadResponse = await fetch(FELO_THREADS_URL, {
+      method: "POST",
+      headers: FELO_HEADERS,
+      body: JSON.stringify(buildFeloThreadPayload(model, prompt)),
+      signal,
+    });
+
+    if (!threadResponse.ok) {
+      const status = threadResponse.status >= 500 ? 502 : threadResponse.status;
+      return feloErrorResponse(status, `Felo thread creation failed with HTTP ${threadResponse.status}`);
+    }
+
+    const threadJson = await threadResponse.json().catch(() => null);
+    const streamKey = (threadJson as Record<string, unknown> | null)?.stream_key;
+    if (typeof streamKey !== "string" || !streamKey) {
+      return feloErrorResponse(502, "Felo did not return a stream_key");
+    }
+    return streamKey;
+  }
+}
+
+function feloErrorResponse(status: number, message: string): Response {
+  return new Response(JSON.stringify({ error: { message: sanitizeErrorMessage(message) } }), {
+    status,
+    headers: { "Content-Type": "application/json" },
+  });
+}
+
+function buildFeloStreamTransform(): TransformStream<Uint8Array, Uint8Array> {
+  let previousText = "";
+  let buffer = "";
+  const decoder = new TextDecoder();
+  const encoder = new TextEncoder();
+
+  return new TransformStream<Uint8Array, Uint8Array>({
+    transform(chunk, controller) {
+      buffer += decoder.decode(chunk, { stream: true });
+      const lines = buffer.split("\n");
+      buffer = lines.pop() ?? "";
+      for (const line of lines) {
+        const parsed = parseFeloStreamLine(line, previousText);
+        previousText = parsed.nextPreviousText;
+        if (!parsed.newText) continue;
+        const openaiChunk = { choices: [{ delta: { content: parsed.newText }, index: 0 }] };
+        controller.enqueue(encoder.encode(`data: ${JSON.stringify(openaiChunk)}\n\n`));
+      }
+    },
+    flush(controller) {
+      controller.enqueue(encoder.encode("data: [DONE]\n\n"));
+    },
+  });
+}
+
+async function processFeloResponse(response: Response, streaming: boolean): Promise<Response> {
+  if (streaming) {
+    if (!response.body) {
+      return feloErrorResponse(500, "No response body");
+    }
+    const transformed = response.body.pipeThrough(buildFeloStreamTransform());
+    return new Response(transformed, { headers: { "Content-Type": "text/event-stream" } });
+  }
+
+  const rawText = await response.text();
+  const fullText = accumulateFeloStreamText(rawText);
+  return new Response(
+    JSON.stringify({
+      choices: [
+        {
+          message: { role: "assistant", content: fullText },
+          index: 0,
+          finish_reason: "stop",
+        },
+      ],
+    }),
+    { headers: { "Content-Type": "application/json" } }
+  );
+}
+
+export const feloWebExecutor = new FeloWebExecutor();
diff --git a/open-sse/executors/index.ts b/open-sse/executors/index.ts
index 68168fd8cf..ca832b8a6d 100644
--- a/open-sse/executors/index.ts
+++ b/open-sse/executors/index.ts
@@ -38,6 +38,7 @@ import { CopilotWebExecutor } from "./copilot-web.ts";
 import { CopilotM365WebExecutor } from "./copilot-m365-web.ts";
 import { VeoAIFreeWebExecutor } from "./veoaifree-web.ts";
 import { DuckDuckGoWebExecutor } from "./duckduckgo-web.ts";
+import { FeloWebExecutor } from "./felo-web.ts";
 import { T3ChatWebExecutor } from "./t3-chat-web.ts";
 import { ClaudeWebExecutor } from "./claude-web.ts";
 import { InnerAiExecutor } from "./inner-ai.ts";
@@ -127,6 +128,8 @@ const executors = {
   "veo-free": new VeoAIFreeWebExecutor(), // Alias
   "duckduckgo-web": new DuckDuckGoWebExecutor(),
   ddgw: new DuckDuckGoWebExecutor(), // Alias
+  "felo-web": new FeloWebExecutor(),
+  felo: new FeloWebExecutor(), // Alias
   "t3-web": new T3ChatWebExecutor(),
   t3chat: new T3ChatWebExecutor(), // Alias
   "inner-ai": new InnerAiExecutor(),
@@ -235,6 +238,7 @@ export { CopilotWebExecutor } from "./copilot-web.ts";
 export { CopilotM365WebExecutor } from "./copilot-m365-web.ts";
 export { VeoAIFreeWebExecutor } from "./veoaifree-web.ts";
 export { DuckDuckGoWebExecutor } from "./duckduckgo-web.ts";
+export { FeloWebExecutor } from "./felo-web.ts";
 export { ClaudeWebExecutor } from "./claude-web.ts";
 export { DeepSeekWebExecutor } from "./deepseek-web.ts";
 export { DeepSeekWebWithAutoRefreshExecutor } from "./deepseek-web-with-auto-refresh.ts";
diff --git a/src/shared/constants/providers/noauth.ts b/src/shared/constants/providers/noauth.ts
index a33e0d08e4..864ee048f1 100644
--- a/src/shared/constants/providers/noauth.ts
+++ b/src/shared/constants/providers/noauth.ts
@@ -35,6 +35,23 @@ export const NOAUTH_PROVIDERS = {
     freeNote: "Free — anonymous access to multiple AI models via DuckDuckGo.",
     authHint: "No credentials required — DuckDuckGo AI Chat is anonymous and free.",
   },
+  "felo-web": {
+    id: "felo-web",
+    alias: "felo",
+    name: "Felo",
+    icon: "travel_explore",
+    color: "#5B7FFF",
+    textIcon: "FL",
+    website: "https://felo.ai",
+    noAuth: true,
+    hasFree: true,
+    serviceKinds: ["llm"],
+    freeNote: "Free — anonymous access to Felo's chat/search-agent aggregator. No API key.",
+    authHint: "No credentials required — Felo is a free, no-signup chat/search aggregator.",
+    notice: {
+      text: "Felo uses a reverse-engineered public endpoint (no official API). No signup or API key needed. Behavior may change without notice if Felo updates its frontend.",
+    },
+  },
   theoldllm: {
     id: "theoldllm",
     alias: "tllm",
diff --git a/tests/snapshots/provider/translate-path.json b/tests/snapshots/provider/translate-path.json
index d8fc6518c9..3cf5ae91fc 100644
--- a/tests/snapshots/provider/translate-path.json
+++ b/tests/snapshots/provider/translate-path.json
@@ -1508,6 +1508,29 @@
       "stream": "https://api.featherless.ai/v1/chat/completions"
     }
   },
+  "felo-web": {
+    "format": "openai",
+    "headers": {
+      "apiKey": {
+        "Accept": "text/event-stream",
+        "Authorization": "Bearer <TOK>",
+        "Content-Type": "application/json"
+      },
+      "nonStream": {
+        "Authorization": "Bearer <TOK>",
+        "Content-Type": "application/json"
+      },
+      "oauth": {
+        "Accept": "text/event-stream",
+        "Authorization": "Bearer <TOK>",
+        "Content-Type": "application/json"
+      }
+    },
+    "url": {
+      "nonStream": "https://felo.ai/api-proxy/main/search/threads",
+      "stream": "https://felo.ai/api-proxy/main/search/threads"
+    }
+  },
   "fireworks": {
     "format": "openai",
     "headers": {
diff --git a/tests/unit/felo-web-executor.test.ts b/tests/unit/felo-web-executor.test.ts
new file mode 100644
index 0000000000..232ca72b55
--- /dev/null
+++ b/tests/unit/felo-web-executor.test.ts
@@ -0,0 +1,325 @@
+import { describe, it, beforeEach, afterEach } from "node:test";
+import assert from "node:assert/strict";
+import type { ExecuteInput } from "../../open-sse/executors/base.ts";
+
+const mod = await import("../../open-sse/executors/felo-web.ts");
+const { REGISTRY } = await import("../../open-sse/config/providerRegistry.ts");
+const { AI_PROVIDERS } = await import("../../src/shared/constants/providers.ts");
+
+const {
+  FeloWebExecutor,
+  FELO_THREADS_URL,
+  feloStreamUrl,
+  normalizeFeloModel,
+  resolveFeloCategory,
+  extractFeloLastUserPrompt,
+  buildFeloThreadPayload,
+  parseFeloStreamLine,
+  accumulateFeloStreamText,
+} = mod;
+
+type FetchCall = { url: string; init: RequestInit };
+
+const realFetch = globalThis.fetch;
+let calls: FetchCall[] = [];
+
+function threadsResponse(streamKey = "sk-123", status = 200): Response {
+  return new Response(JSON.stringify({ stream_key: streamKey }), {
+    status,
+    headers: { "content-type": "application/json" },
+  });
+}
+
+/** Build a Felo-shaped `data:{...}` stream body from a list of answer snapshots. */
+function feloStreamResponse(answerSnapshots: string[], includeSourcesEvent = false): Response {
+  const encoder = new TextEncoder();
+  const lines: string[] = [];
+  for (const text of answerSnapshots) {
+    const contentJson = { data: { type: "answer", data: { text } } };
+    lines.push(`data:${JSON.stringify({ content: JSON.stringify(contentJson) })}`);
+  }
+  if (includeSourcesEvent) {
+    const contentJson = {
+      data: {
+        type: "final_contexts",
+        data: { sources: [{ link: "https://example.com", title: "Example" }] },
+      },
+    };
+    lines.push(`data:${JSON.stringify({ content: JSON.stringify(contentJson) })}`);
+  }
+  const stream = new ReadableStream({
+    start(controller) {
+      controller.enqueue(encoder.encode(lines.join("\n") + "\n"));
+      controller.close();
+    },
+  });
+  return new Response(stream, { status: 200, headers: { "content-type": "text/event-stream" } });
+}
+
+function mockFetch(handler: (url: string, init: RequestInit) => Response | Promise<Response>): void {
+  globalThis.fetch = (async (input: RequestInfo | URL, init: RequestInit = {}) => {
+    const url = String(input);
+    calls.push({ url, init });
+    return handler(url, init);
+  }) as typeof fetch;
+}
+
+function jsonBody(init: RequestInit): Record<string, unknown> {
+  return JSON.parse(String(init.body)) as Record<string, unknown>;
+}
+
+function baseExecuteInput(overrides: Partial<ExecuteInput> = {}): ExecuteInput {
+  return {
+    model: "felo-chat",
+    body: { messages: [{ role: "user", content: "hi" }] },
+    stream: false,
+    credentials: {},
+    signal: null,
+    ...overrides,
+  };
+}
+
+beforeEach(() => {
+  calls = [];
+});
+
+afterEach(() => {
+  globalThis.fetch = realFetch;
+});
+
+describe("FeloWebExecutor — registry wiring", () => {
+  it("is registered as a canonical noAuth provider (providers.ts)", () => {
+    const provider = AI_PROVIDERS["felo-web"];
+    assert.ok(provider, "felo-web should be a canonical provider");
+    assert.equal(provider.noAuth, true);
+  });
+
+  it("is registered in the provider REGISTRY with the felo-web executor", () => {
+    const entry = REGISTRY["felo-web"];
+    assert.ok(entry, "felo-web should have a REGISTRY entry");
+    assert.equal(entry.executor, "felo-web");
+    assert.equal(entry.authType, "none");
+    assert.ok(entry.models.some((m) => m.id === "felo-chat"));
+  });
+});
+
+describe("FeloWebExecutor — pure helpers", () => {
+  it("normalizeFeloModel: strips the felo-web/ prefix and falls back to felo-chat", () => {
+    assert.equal(normalizeFeloModel("felo-web/felo-search"), "felo-search");
+    assert.equal(normalizeFeloModel("felo-scholar"), "felo-scholar");
+    assert.equal(normalizeFeloModel("not-a-real-model"), "felo-chat");
+    assert.equal(normalizeFeloModel(undefined), "felo-chat");
+  });
+
+  it("resolveFeloCategory: maps each model alias to its g4f category", () => {
+    assert.equal(resolveFeloCategory("felo-chat"), "chat");
+    assert.equal(resolveFeloCategory("felo-search"), "google");
+    assert.equal(resolveFeloCategory("felo-scholar"), "scholar");
+    assert.equal(resolveFeloCategory("felo-social"), "social");
+    assert.equal(resolveFeloCategory("felo-document"), "document");
+  });
+
+  it("extractFeloLastUserPrompt: picks the last user message, string content", () => {
+    const prompt = extractFeloLastUserPrompt([
+      { role: "system", content: "be nice" },
+      { role: "user", content: "first" },
+      { role: "assistant", content: "reply" },
+      { role: "user", content: "second" },
+    ]);
+    assert.equal(prompt, "second");
+  });
+
+  it("extractFeloLastUserPrompt: joins array-of-parts content", () => {
+    const prompt = extractFeloLastUserPrompt([
+      {
+        role: "user",
+        content: [
+          { type: "text", text: "part one" },
+          { type: "text", text: "part two" },
+        ],
+      },
+    ]);
+    assert.equal(prompt, "part one\npart two");
+  });
+
+  it("buildFeloThreadPayload: carries the query and resolved category", () => {
+    const payload = buildFeloThreadPayload("felo-search", "hello world");
+    assert.equal(payload.query, "hello world");
+    assert.equal(payload.category, "google");
+    assert.equal(payload.stream_protocol, "message_center_v1");
+    assert.equal(typeof payload.search_uuid, "string");
+    assert.ok((payload.search_uuid as string).length > 0);
+  });
+
+  it("parseFeloStreamLine: ignores non-data lines and malformed JSON", () => {
+    assert.deepEqual(parseFeloStreamLine("", "prev"), { newText: null, nextPreviousText: "prev" });
+    assert.deepEqual(parseFeloStreamLine("not-a-data-line", "prev"), {
+      newText: null,
+      nextPreviousText: "prev",
+    });
+    assert.deepEqual(parseFeloStreamLine("data:{not json", "prev"), {
+      newText: null,
+      nextPreviousText: "prev",
+    });
+  });
+
+  it("parseFeloStreamLine: diffs incremental answer snapshots against the running text", () => {
+    const line1 = `data:${JSON.stringify({
+      content: JSON.stringify({ data: { type: "answer", data: { text: "Hel" } } }),
+    })}`;
+    const line2 = `data:${JSON.stringify({
+      content: JSON.stringify({ data: { type: "answer", data: { text: "Hello" } } }),
+    })}`;
+
+    const first = parseFeloStreamLine(line1, "");
+    assert.equal(first.newText, "Hel");
+    assert.equal(first.nextPreviousText, "Hel");
+
+    const second = parseFeloStreamLine(line2, first.nextPreviousText);
+    assert.equal(second.newText, "lo");
+    assert.equal(second.nextPreviousText, "Hello");
+  });
+
+  it("parseFeloStreamLine: ignores final_contexts events (no OpenAI-compatible slot)", () => {
+    const line = `data:${JSON.stringify({
+      content: JSON.stringify({
+        data: { type: "final_contexts", data: { sources: [{ link: "https://x", title: "X" }] } },
+      }),
+    })}`;
+    assert.deepEqual(parseFeloStreamLine(line, "prev"), { newText: null, nextPreviousText: "prev" });
+  });
+
+  it("accumulateFeloStreamText: replays a full stream body into the final text", () => {
+    const raw = [
+      `data:${JSON.stringify({ content: JSON.stringify({ data: { type: "answer", data: { text: "Hi" } } }) })}`,
+      `data:${JSON.stringify({
+        content: JSON.stringify({ data: { type: "answer", data: { text: "Hi there" } } }),
+      })}`,
+    ].join("\n");
+    assert.equal(accumulateFeloStreamText(raw), "Hi there");
+  });
+});
+
+describe("FeloWebExecutor — execute() input validation", () => {
+  it("rejects an empty messages array with 400", async () => {
+    const executor = new FeloWebExecutor();
+    const response = await executor.execute(baseExecuteInput({ body: { messages: [] } }));
+
+    assert.equal(response.status, 400);
+    const responseBody = (await response.json()) as { error?: { message?: string } };
+    assert.ok(responseBody.error?.message);
+  });
+
+  it("rejects messages with no extractable user prompt with 400", async () => {
+    const executor = new FeloWebExecutor();
+    const response = await executor.execute(
+      baseExecuteInput({ body: { messages: [{ role: "system", content: "no user turn" }] } })
+    );
+
+    assert.equal(response.status, 400);
+  });
+});
+
+describe("FeloWebExecutor — execute() happy path (mocked fetch)", () => {
+  it("POSTs the thread payload, GETs the stream, and returns non-streaming OpenAI JSON", async () => {
+    mockFetch((url) => {
+      if (url === FELO_THREADS_URL) return threadsResponse("sk-abc");
+      if (url === feloStreamUrl("sk-abc")) return feloStreamResponse(["Hel", "Hello", "Hello there"], true);
+      throw new Error(`unexpected fetch: ${url}`);
+    });
+
+    const executor = new FeloWebExecutor();
+    const response = await executor.execute(baseExecuteInput());
+
+    assert.equal(calls.length, 2, "should call threads then stream exactly once each");
+    assert.equal(calls[0].init.method, "POST");
+    const threadPayload = jsonBody(calls[0].init);
+    assert.equal(threadPayload.query, "hi");
+    assert.equal(threadPayload.category, "chat");
+
+    assert.equal(response.status, 200);
+    const json = (await response.json()) as {
+      choices: Array<{ message: { role: string; content: string }; finish_reason: string }>;
+    };
+    assert.equal(json.choices[0].message.content, "Hello there");
+    assert.equal(json.choices[0].message.role, "assistant");
+    assert.equal(json.choices[0].finish_reason, "stop");
+  });
+
+  it("streams OpenAI-compatible SSE chunks ending with [DONE]", async () => {
+    mockFetch((url) => {
+      if (url === FELO_THREADS_URL) return threadsResponse("sk-stream");
+      if (url === feloStreamUrl("sk-stream")) return feloStreamResponse(["A", "AB", "ABC"]);
+      throw new Error(`unexpected fetch: ${url}`);
+    });
+
+    const executor = new FeloWebExecutor();
+    const response = await executor.execute(baseExecuteInput({ stream: true }));
+
+    assert.equal(response.status, 200);
+    assert.ok(response.body);
+    const text = await response.text();
+    assert.match(text, /"content":"A"/);
+    assert.match(text, /"content":"B"/);
+    assert.match(text, /"content":"C"/);
+    assert.match(text, /data: \[DONE\]/);
+  });
+});
+
+describe("FeloWebExecutor — error paths", () => {
+  it("propagates a 5xx from thread creation as a sanitized 502", async () => {
+    mockFetch((url) => {
+      if (url === FELO_THREADS_URL) return new Response("upstream on fire", { status: 503 });
+      throw new Error(`unexpected fetch: ${url}`);
+    });
+
+    const executor = new FeloWebExecutor();
+    const response = await executor.execute(baseExecuteInput());
+
+    assert.equal(response.status, 502);
+    const responseBody = (await response.json()) as { error: { message: string } };
+    assert.ok(responseBody.error.message.includes("HTTP 503"));
+    assert.ok(!responseBody.error.message.includes("at /"), "must not leak a stack trace");
+  });
+
+  it("returns 502 when the threads response omits stream_key", async () => {
+    mockFetch((url) => {
+      if (url === FELO_THREADS_URL) {
+        return new Response(JSON.stringify({}), {
+          status: 200,
+          headers: { "content-type": "application/json" },
+        });
+      }
+      throw new Error(`unexpected fetch: ${url}`);
+    });
+
+    const executor = new FeloWebExecutor();
+    const response = await executor.execute(baseExecuteInput());
+
+    assert.equal(response.status, 502);
+    const responseBody = (await response.json()) as { error: { message: string } };
+    assert.match(responseBody.error.message, /stream_key/);
+  });
+});
+
+describe("FeloWebExecutor — testConnection", () => {
+  it("returns true when threads endpoint responds with a stream_key", async () => {
+    mockFetch(() => threadsResponse("sk-health"));
+    const executor = new FeloWebExecutor();
+    assert.equal(await executor.testConnection({}), true);
+  });
+
+  it("returns false on a non-ok response", async () => {
+    mockFetch(() => new Response("nope", { status: 500 }));
+    const executor = new FeloWebExecutor();
+    assert.equal(await executor.testConnection({}), false);
+  });
+
+  it("returns false on a network error", async () => {
+    globalThis.fetch = (async () => {
+      throw new Error("network down");
+    }) as typeof fetch;
+    const executor = new FeloWebExecutor();
+    assert.equal(await executor.testConnection({}), false);
+  });
+});