diff --git a/skills/README.md b/skills/README.md
index d287f6762..091e3d3b1 100644
--- a/skills/README.md
+++ b/skills/README.md
@@ -48,6 +48,7 @@ bin/lbs env show     # inspect resolved env defaults (redacted)
 bin/lbs env doctor   # diagnose local environment readiness
 bin/lbs case list --ready
 bin/lbs test plan <case-id>
+bin/lbs suite plan langbot-debug-chat-load-gate
 ```
 
 ## Maintenance rule
diff --git a/skills/docs/user-guide.md b/skills/docs/user-guide.md
index d52a77247..846b7f5c4 100644
--- a/skills/docs/user-guide.md
+++ b/skills/docs/user-guide.md
@@ -117,6 +117,21 @@ bin/lbs suite plan langbot-user-path-performance-gate
 bin/lbs suite run langbot-user-path-performance-gate --run-id langbot-user-path-local --include-manual-check
 ```
 
+Controlled Debug Chat message-path load gate:
+
+```bash
+bin/lbs suite plan langbot-debug-chat-load-gate
+bin/lbs test run langbot-fake-provider-debug-chat-load --run-id langbot-fake-load-local
+bin/lbs test run langbot-space-debug-chat-concurrency-smoke --run-id langbot-space-smoke-local
+```
+
+Start with `langbot-fake-provider-debug-chat-load`. It launches a local
+OpenAI-compatible fake provider, creates the matching provider/model/pipeline,
+then sends concurrent WebSocket Debug Chat messages through the real backend.
+Use `langbot-space-debug-chat-concurrency-smoke` only as a low-volume live
+provider smoke; it includes Space/model/network latency and should be compared
+against the fake-provider baseline before attributing failures to LangBot.
+
 `manual_check` means the agent must confirm the declared preconditions for that
 run window. When setup automation is declared, run output may stop early with
 `env_issue`; fix that environment input before treating the product path as
diff --git a/skills/schemas/case.schema.json b/skills/schemas/case.schema.json
index 0d63d8dec..9f4da284a 100644
--- a/skills/schemas/case.schema.json
+++ b/skills/schemas/case.schema.json
@@ -209,6 +209,38 @@
     "automation_debug_chat_max_error_rate": {
       "type": "string"
     },
+    "automation_debug_chat_load_requests": {
+      "type": "string"
+    },
+    "automation_debug_chat_load_concurrency": {
+      "type": "string"
+    },
+    "automation_debug_chat_load_timeout_ms": {
+      "type": "string"
+    },
+    "automation_debug_chat_load_response_p95_ms": {
+      "type": "string"
+    },
+    "automation_debug_chat_load_first_response_p95_ms": {
+      "type": "string"
+    },
+    "automation_debug_chat_load_max_error_rate": {
+      "type": "string"
+    },
+    "automation_debug_chat_load_expected_prefix": {
+      "type": "string"
+    },
+    "automation_debug_chat_load_prompt_template": {
+      "type": "string"
+    },
+    "automation_debug_chat_load_stream": {
+      "type": "string",
+      "enum": ["0", "1", "false", "true"]
+    },
+    "automation_debug_chat_load_reset": {
+      "type": "string",
+      "enum": ["0", "1", "false", "true"]
+    },
     "automation_filesystem_checks_json": {
       "type": "string"
     },
diff --git a/skills/scripts/e2e/ensure-fake-provider-pipeline.mjs b/skills/scripts/e2e/ensure-fake-provider-pipeline.mjs
new file mode 100644
index 000000000..94a17c08a
--- /dev/null
+++ b/skills/scripts/e2e/ensure-fake-provider-pipeline.mjs
@@ -0,0 +1,539 @@
+#!/usr/bin/env node
+
+import { spawn } from "node:child_process";
+import { open, readFile, mkdir, writeFile } from "node:fs/promises";
+import { dirname, resolve } from "node:path";
+import { env } from "node:process";
+import {
+  apiJson,
+  ensureEvidence,
+  evidencePaths,
+  loadEnvFiles,
+  redact,
+  resetAndAuthLocalUser,
+  writeResult,
+} from "./lib/langbot-e2e.mjs";
+
+const RUNNER_ID = "local-agent";
+const DEFAULT_LOCAL_PASSWORD = "LangBotE2ELocalPass!2026";
+const DEFAULT_PIPELINE_NAME = "Agent QA Fake Provider Debug Chat";
+const DEFAULT_PROVIDER_NAME = "LangBot QA Fake OpenAI Provider";
+const DEFAULT_MODEL_NAME = "gpt-4o-mini";
+const DEFAULT_REQUESTER = "openai-chat-completions";
+
+const caseId = "ensure-fake-provider-pipeline";
+
+await loadEnvFiles();
+const paths = evidencePaths(caseId);
+await ensureEvidence(paths);
+
+const writeEnv = process.argv.includes("--write-env");
+const frontendUrl = env.LANGBOT_FRONTEND_URL || "";
+const backendUrl = env.LANGBOT_BACKEND_URL || "";
+const envLocalPath = resolve("skills/.env.local");
+const repoRoot = resolve(env.LANGBOT_REPO || "..");
+const fakeStateDir = resolve(env.LANGBOT_FAKE_PROVIDER_STATE_DIR || resolve(repoRoot, ".qa/fake-provider"));
+const fakeStatePath = resolve(fakeStateDir, "state.json");
+const fakeStdoutPath = resolve(fakeStateDir, "fake-provider.stdout.log");
+const fakeStderrPath = resolve(fakeStateDir, "fake-provider.stderr.log");
+const pipelineName = env.LANGBOT_FAKE_PROVIDER_PIPELINE_NAME || DEFAULT_PIPELINE_NAME;
+const providerName = env.LANGBOT_FAKE_PROVIDER_NAME || DEFAULT_PROVIDER_NAME;
+const requester = env.LANGBOT_FAKE_PROVIDER_REQUESTER || DEFAULT_REQUESTER;
+const modelName = env.LANGBOT_FAKE_PROVIDER_MODEL_NAME || DEFAULT_MODEL_NAME;
+
+const result = {
+  source: "automation",
+  case_id: caseId,
+  run_id: paths.runId,
+  status: "fail",
+  reason: "",
+  frontend_url: frontendUrl,
+  backend_url: backendUrl,
+  fake_provider: {
+    url: "",
+    base_url: "",
+    pid: null,
+    reused: false,
+    state_file: fakeStatePath,
+    stdout_log: fakeStdoutPath,
+    stderr_log: fakeStderrPath,
+  },
+  provider: {
+    uuid: "",
+    name: providerName,
+    requester,
+    created: false,
+    updated: false,
+  },
+  model: {
+    uuid: "",
+    name: modelName,
+    created: false,
+    updated: false,
+    test_status: "not_run",
+    test_reason: "",
+  },
+  pipeline_id: "",
+  pipeline_name: pipelineName,
+  pipeline_url: "",
+  created: false,
+  updated: false,
+  wrote_env: false,
+  evidence: {
+    console_log: paths.consoleLog,
+    network_log: paths.networkLog,
+    automation_result_json: paths.automationResultJson,
+    result_json: paths.resultJson,
+  },
+  evidence_collected: ["api_diagnostic", "network", "filesystem"],
+};
+
+try {
+  if (!backendUrl) {
+    result.status = "env_issue";
+    throw new Error("LANGBOT_BACKEND_URL is not configured.");
+  }
+  if (!frontendUrl) {
+    result.status = "env_issue";
+    throw new Error("LANGBOT_FRONTEND_URL is not configured.");
+  }
+
+  const fakeProvider = await ensureFakeProvider();
+  result.fake_provider = {
+    ...result.fake_provider,
+    ...fakeProvider,
+  };
+
+  const user = env.LANGBOT_E2E_LOGIN_USER || "";
+  const password = env.LANGBOT_E2E_LOGIN_PASSWORD || DEFAULT_LOCAL_PASSWORD;
+  if (!user) {
+    result.status = "env_issue";
+    throw new Error("LANGBOT_E2E_LOGIN_USER is required so this setup can create/update the fake provider pipeline.");
+  }
+
+  const auth = await resetAndAuthLocalUser({ backendUrl, user, password });
+  const wizard = await skipWizard({ backendUrl, token: auth.token });
+  if (wizard.status !== "pass") {
+    result.status = "fail";
+    throw new Error(wizard.reason || "Failed to mark the local QA wizard as skipped.");
+  }
+
+  const provider = await ensureProvider({
+    backendUrl,
+    token: auth.token,
+    name: providerName,
+    requester,
+    baseUrl: fakeProvider.base_url,
+  });
+  result.provider = provider;
+
+  const model = await ensureModel({
+    backendUrl,
+    token: auth.token,
+    providerUuid: provider.uuid,
+    name: modelName,
+  });
+  result.model = model;
+
+  const pipeline = await ensurePipeline({
+    backendUrl,
+    token: auth.token,
+    name: pipelineName,
+    modelUuid: model.uuid,
+  });
+  Object.assign(result, pipeline);
+  result.pipeline_url = `${frontendUrl.replace(/\/$/, "")}/home/pipelines?id=${encodeURIComponent(pipeline.pipeline_id)}`;
+
+  if (writeEnv) {
+    await upsertEnvLocal(envLocalPath, {
+      LANGBOT_E2E_LOGIN_USER: user,
+      LANGBOT_FAKE_PROVIDER_URL: fakeProvider.url,
+      LANGBOT_FAKE_PROVIDER_BASE_URL: fakeProvider.base_url,
+      LANGBOT_FAKE_PROVIDER_PID: fakeProvider.pid ? String(fakeProvider.pid) : "",
+      LANGBOT_FAKE_PROVIDER_PROVIDER_UUID: provider.uuid,
+      LANGBOT_FAKE_PROVIDER_MODEL_UUID: model.uuid,
+      LANGBOT_FAKE_PROVIDER_PIPELINE_URL: result.pipeline_url,
+      LANGBOT_FAKE_PROVIDER_PIPELINE_NAME: pipelineName,
+    });
+    result.wrote_env = true;
+  }
+
+  result.status = "pass";
+  result.reason = `Fake provider pipeline is configured with ${requester}/${modelName}.`;
+} catch (error) {
+  result.status = result.status === "env_issue" ? "env_issue" : "fail";
+  result.reason = result.reason || safeReason(error.message);
+} finally {
+  await writeResult(paths, result);
+  console.log(JSON.stringify(result, null, 2));
+}
+
+process.exit(result.status === "pass" ? 0 : result.status === "env_issue" ? 2 : 1);
+
+async function ensureFakeProvider() {
+  const envUrl = normalizeProviderRootUrl(env.LANGBOT_FAKE_PROVIDER_URL || "");
+  if (envUrl && await fakeProviderHealthy(envUrl)) {
+    return {
+      url: envUrl,
+      base_url: `${envUrl}/v1`,
+      pid: null,
+      reused: true,
+    };
+  }
+
+  const state = await readState(fakeStatePath);
+  const stateUrl = normalizeProviderRootUrl(state.url || "");
+  if (stateUrl && await fakeProviderHealthy(stateUrl)) {
+    return {
+      url: stateUrl,
+      base_url: state.base_url || `${stateUrl}/v1`,
+      pid: Number.isInteger(state.pid) ? state.pid : null,
+      reused: true,
+    };
+  }
+
+  await mkdir(fakeStateDir, { recursive: true });
+  await writeFile(fakeStatePath, `${JSON.stringify({ status: "starting", started_at: new Date().toISOString() }, null, 2)}\n`, "utf8");
+  const stdout = await open(fakeStdoutPath, "a");
+  const stderr = await open(fakeStderrPath, "a");
+  const scriptPath = resolve("scripts/e2e/fake-openai-provider.mjs");
+  const host = env.LANGBOT_FAKE_PROVIDER_HOST || "127.0.0.1";
+  const port = env.LANGBOT_FAKE_PROVIDER_PORT || "0";
+  const child = spawn(process.execPath, [
+    scriptPath,
+    `--host=${host}`,
+    `--port=${port}`,
+    `--state-file=${fakeStatePath}`,
+  ], {
+    cwd: resolve("."),
+    detached: true,
+    env: {
+      ...env,
+      LANGBOT_FAKE_PROVIDER_MODEL_NAME: modelName,
+    },
+    stdio: ["ignore", stdout.fd, stderr.fd],
+  });
+  child.unref();
+  await stdout.close();
+  await stderr.close();
+
+  const started = await waitForFakeProviderState(fakeStatePath, child.pid, 10_000);
+  if (!started.url || !await fakeProviderHealthy(started.url)) {
+    throw new Error(`Fake provider did not become healthy. See ${fakeStderrPath}`);
+  }
+
+  return {
+    url: started.url,
+    base_url: started.base_url || `${started.url}/v1`,
+    pid: child.pid ?? started.pid ?? null,
+    reused: false,
+  };
+}
+
+async function fakeProviderHealthy(rootUrl) {
+  try {
+    const response = await fetch(`${rootUrl.replace(/\/$/, "")}/healthz`, {
+      signal: AbortSignal.timeout(2000),
+    });
+    if (!response.ok) return false;
+    const json = await response.json().catch(() => ({}));
+    return json.ok === true;
+  } catch {
+    return false;
+  }
+}
+
+async function waitForFakeProviderState(path, expectedPid, timeoutMs) {
+  const startedAt = Date.now();
+  let lastState = {};
+  while (Date.now() - startedAt < timeoutMs) {
+    const state = await readState(path);
+    if (state.url && (!expectedPid || state.pid === expectedPid)) return state;
+    lastState = state;
+    await sleep(150);
+  }
+  return lastState;
+}
+
+async function readState(path) {
+  try {
+    return JSON.parse(await readFile(path, "utf8"));
+  } catch {
+    return {};
+  }
+}
+
+function normalizeProviderRootUrl(value) {
+  const trimmed = String(value || "").trim().replace(/\/$/, "");
+  return trimmed.endsWith("/v1") ? trimmed.slice(0, -3) : trimmed;
+}
+
+async function skipWizard({ backendUrl, token }) {
+  const response = await apiJson(backendUrl, "/api/v1/system/wizard/completed", {
+    method: "POST",
+    token,
+    body: { status: "skipped" },
+  });
+  const ok = response.status < 400 && response.json.code === 0;
+  return {
+    status: ok ? "pass" : "fail",
+    http_status: response.status,
+    code: response.json.code ?? null,
+    reason: ok ? "Wizard marked skipped for local QA." : response.json.msg || "Wizard status update failed.",
+  };
+}
+
+async function ensureProvider({ backendUrl, token, name, requester, baseUrl }) {
+  const list = await apiJson(backendUrl, "/api/v1/provider/providers", { token });
+  if (isApiFailure(list)) {
+    throw new Error(list.json.msg || "Failed to list providers.");
+  }
+  const providers = list.json.data?.providers || [];
+  const existing = providers.find((provider) => (
+    provider.name === name
+      || (provider.requester === requester && String(provider.base_url || "").replace(/\/$/, "") === baseUrl.replace(/\/$/, ""))
+  ));
+  const body = {
+    name,
+    requester,
+    base_url: baseUrl,
+    api_keys: [env.LANGBOT_FAKE_PROVIDER_API_KEY || "langbot-fake-provider-key"],
+  };
+
+  if (existing?.uuid) {
+    const update = await apiJson(backendUrl, `/api/v1/provider/providers/${encodeURIComponent(existing.uuid)}`, {
+      method: "PUT",
+      token,
+      body,
+    });
+    if (isApiFailure(update)) {
+      throw new Error(update.json.msg || "Failed to update fake provider.");
+    }
+    return {
+      uuid: existing.uuid,
+      name,
+      requester,
+      created: false,
+      updated: true,
+    };
+  }
+
+  const create = await apiJson(backendUrl, "/api/v1/provider/providers", {
+    method: "POST",
+    token,
+    body,
+  });
+  const uuid = create.json.data?.uuid || "";
+  if (isApiFailure(create) || !uuid) {
+    throw new Error(create.json.msg || "Failed to create fake provider.");
+  }
+  return {
+    uuid,
+    name,
+    requester,
+    created: true,
+    updated: false,
+  };
+}
+
+async function ensureModel({ backendUrl, token, providerUuid, name }) {
+  const list = await apiJson(backendUrl, `/api/v1/provider/models/llm?provider_uuid=${encodeURIComponent(providerUuid)}`, { token });
+  if (isApiFailure(list)) {
+    throw new Error(list.json.msg || "Failed to list fake provider models.");
+  }
+  const models = list.json.data?.models || [];
+  const existing = models.find((model) => model.name === name);
+  const body = {
+    name,
+    provider_uuid: providerUuid,
+    abilities: [],
+    context_length: positiveInteger(env.LANGBOT_FAKE_PROVIDER_CONTEXT_LENGTH, 8192),
+    extra_args: {},
+    prefered_ranking: 0,
+  };
+  let modelUuid = existing?.uuid || "";
+  let created = false;
+  let updated = false;
+
+  if (modelUuid) {
+    const update = await apiJson(backendUrl, `/api/v1/provider/models/llm/${encodeURIComponent(modelUuid)}`, {
+      method: "PUT",
+      token,
+      body,
+    });
+    if (isApiFailure(update)) {
+      throw new Error(update.json.msg || "Failed to update fake provider model.");
+    }
+    updated = true;
+  } else {
+    const create = await apiJson(backendUrl, "/api/v1/provider/models/llm", {
+      method: "POST",
+      token,
+      body,
+    });
+    modelUuid = create.json.data?.uuid || "";
+    if (isApiFailure(create) || !modelUuid) {
+      throw new Error(create.json.msg || "Failed to create fake provider model.");
+    }
+    created = true;
+  }
+
+  const test = await apiJson(backendUrl, `/api/v1/provider/models/llm/${encodeURIComponent(modelUuid)}/test`, {
+    method: "POST",
+    token,
+    body: { extra_args: {} },
+  });
+  if (isApiFailure(test)) {
+    throw new Error(safeReason(test.json.msg || test.json.message || "Fake provider model test failed."));
+  }
+
+  return {
+    uuid: modelUuid,
+    name,
+    created,
+    updated,
+    test_status: "pass",
+    test_reason: "",
+  };
+}
+
+async function ensurePipeline({ backendUrl, token, name, modelUuid }) {
+  const list = await apiJson(backendUrl, "/api/v1/pipelines", { token });
+  if (isApiFailure(list)) {
+    throw new Error(list.json.msg || "Failed to list pipelines.");
+  }
+  const pipelines = list.json.data?.pipelines || [];
+  let pipeline = pipelines.find((item) => item.name === name) || null;
+  let created = false;
+
+  if (!pipeline) {
+    const create = await apiJson(backendUrl, "/api/v1/pipelines", {
+      method: "POST",
+      token,
+      body: {
+        name,
+        description: "Local QA pipeline for controlled fake-provider Debug Chat load tests.",
+        emoji: "QA",
+      },
+    });
+    const pipelineId = create.json.data?.uuid || "";
+    if (isApiFailure(create) || !pipelineId) {
+      throw new Error(create.json.msg || "Failed to create fake provider pipeline.");
+    }
+    created = true;
+    pipeline = { uuid: pipelineId };
+  }
+
+  const loaded = await apiJson(backendUrl, `/api/v1/pipelines/${encodeURIComponent(pipeline.uuid)}`, { token });
+  pipeline = loaded.json.data?.pipeline || null;
+  if (isApiFailure(loaded) || !pipeline?.uuid) {
+    throw new Error(loaded.json.msg || "Failed to load fake provider pipeline.");
+  }
+
+  const config = pipeline.config && typeof pipeline.config === "object" ? pipeline.config : {};
+  const ai = config.ai && typeof config.ai === "object" ? config.ai : {};
+  const existingLocalAgentConfig = ai["local-agent"] && typeof ai["local-agent"] === "object"
+    ? ai["local-agent"]
+    : {};
+  const localAgentConfig = {
+    timeout: 60,
+    prompt: [{ role: "system", content: "You are a deterministic QA assistant. Reply exactly as instructed." }],
+    "remove-think": false,
+    "knowledge-bases": [],
+    "box-session-id-template": "{launcher_type}_{launcher_id}",
+    "retrieval-top-k": 5,
+    "rerank-model": "",
+    "rerank-top-k": 5,
+    "max-tool-iterations": 20,
+    "tool-execution-mode": "parallel",
+    "max-tool-result-chars": 20000,
+    "context-history-fetch-limit": 20,
+    "context-window-tokens": 8192,
+    "context-reserve-tokens": 1024,
+    "context-keep-recent-tokens": 2048,
+    "context-summary-tokens": 1024,
+    ...existingLocalAgentConfig,
+    // Current backend truncation still reads this field directly.
+    "max-round": positiveInteger(existingLocalAgentConfig["max-round"], 10),
+    model: {
+      primary: modelUuid,
+      fallbacks: [],
+    },
+  };
+  const updatedConfig = {
+    ...config,
+    ai: {
+      ...ai,
+      runner: {
+        ...(ai.runner && typeof ai.runner === "object" ? ai.runner : {}),
+        id: RUNNER_ID,
+        runner: RUNNER_ID,
+        "expire-time": 0,
+      },
+      "local-agent": localAgentConfig,
+    },
+  };
+
+  const update = await apiJson(backendUrl, `/api/v1/pipelines/${encodeURIComponent(pipeline.uuid)}`, {
+    method: "PUT",
+    token,
+    body: {
+      name,
+      description: "Local QA pipeline for controlled fake-provider Debug Chat load tests.",
+      emoji: "QA",
+      config: updatedConfig,
+    },
+  });
+  if (isApiFailure(update)) {
+    throw new Error(update.json.msg || "Failed to update fake provider pipeline.");
+  }
+
+  return {
+    pipeline_id: pipeline.uuid,
+    pipeline_name: name,
+    created,
+    updated: true,
+  };
+}
+
+function isApiFailure(response) {
+  return response.status >= 400 || (response.json.code !== undefined && response.json.code !== 0);
+}
+
+function positiveInteger(value, fallback) {
+  const parsed = Number(value);
+  return Number.isInteger(parsed) && parsed > 0 ? parsed : fallback;
+}
+
+function sleep(ms) {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
+function safeReason(value) {
+  return redact(String(value || "")).slice(0, 1000);
+}
+
+async function upsertEnvLocal(path, updates) {
+  await mkdir(dirname(path), { recursive: true });
+  let text = "";
+  try {
+    text = await readFile(path, "utf8");
+  } catch {
+    text = "";
+  }
+  const lines = text.split(/\r?\n/);
+  const seen = new Set();
+  const next = lines.map((line) => {
+    const trimmed = line.trim();
+    const equals = trimmed.indexOf("=");
+    if (equals <= 0 || trimmed.startsWith("#")) return line;
+    const key = trimmed.slice(0, equals).trim();
+    if (!(key in updates)) return line;
+    seen.add(key);
+    return `${key}=${updates[key]}`;
+  });
+  for (const [key, value] of Object.entries(updates)) {
+    if (!seen.has(key)) next.push(`${key}=${value}`);
+  }
+  await writeFile(path, `${next.filter((line, index) => line !== "" || index < next.length - 1).join("\n")}\n`, "utf8");
+}
diff --git a/skills/scripts/e2e/fake-openai-provider.mjs b/skills/scripts/e2e/fake-openai-provider.mjs
new file mode 100644
index 000000000..f75d86ffe
--- /dev/null
+++ b/skills/scripts/e2e/fake-openai-provider.mjs
@@ -0,0 +1,332 @@
+#!/usr/bin/env node
+
+import { createServer } from "node:http";
+import { mkdir, writeFile } from "node:fs/promises";
+import { dirname, resolve } from "node:path";
+import { env, exit } from "node:process";
+
+const args = parseArgs(process.argv.slice(2));
+const host = args.host || env.LANGBOT_FAKE_PROVIDER_HOST || "127.0.0.1";
+const port = integer(args.port ?? env.LANGBOT_FAKE_PROVIDER_PORT, 0);
+const stateFile = args["state-file"] || env.LANGBOT_FAKE_PROVIDER_STATE_FILE || "";
+const modelName = env.LANGBOT_FAKE_PROVIDER_MODEL_NAME || "gpt-4o-mini";
+const responseText = env.LANGBOT_FAKE_PROVIDER_RESPONSE_TEXT || "OK";
+const firstTokenDelayMs = integer(env.LANGBOT_FAKE_PROVIDER_FIRST_TOKEN_DELAY_MS, 25);
+const chunkDelayMs = integer(env.LANGBOT_FAKE_PROVIDER_CHUNK_DELAY_MS, 10);
+const faultStatus = integer(env.LANGBOT_FAKE_PROVIDER_FAULT_STATUS, 500);
+const failFirstN = integer(env.LANGBOT_FAKE_PROVIDER_FAIL_FIRST_N, 0);
+const failEveryN = integer(env.LANGBOT_FAKE_PROVIDER_FAIL_EVERY_N, 0);
+const failAfterFirstChunk = bool(env.LANGBOT_FAKE_PROVIDER_FAIL_AFTER_FIRST_CHUNK, false);
+const requestLogLimit = integer(env.LANGBOT_FAKE_PROVIDER_REQUEST_LOG_LIMIT, 500);
+
+let requestCount = 0;
+const recentRequests = [];
+
+const server = createServer(async (request, response) => {
+  const startedAt = Date.now();
+  const url = new URL(request.url || "/", `http://${request.headers.host || `${host}:${port}`}`);
+  try {
+    if (request.method === "GET" && url.pathname === "/healthz") {
+      sendJson(response, 200, {
+        ok: true,
+        model: modelName,
+        request_count: requestCount,
+        recent_request_count: recentRequests.length,
+      });
+      return;
+    }
+
+    if (request.method === "GET" && ["/models", "/v1/models"].includes(url.pathname)) {
+      sendJson(response, 200, {
+        object: "list",
+        data: [
+          {
+            id: modelName,
+            object: "model",
+            created: 1,
+            owned_by: "langbot-qa",
+            type: "llm",
+          },
+        ],
+      });
+      return;
+    }
+
+    if (request.method === "POST" && ["/chat/completions", "/v1/chat/completions"].includes(url.pathname)) {
+      requestCount += 1;
+      const body = await readJson(request);
+      const requestId = `chatcmpl-langbot-fake-${requestCount}`;
+      const shouldFail = requestCount <= failFirstN || (failEveryN > 0 && requestCount % failEveryN === 0);
+      recordRequest({
+        id: requestId,
+        path: url.pathname,
+        stream: Boolean(body.stream),
+        model: body.model || "",
+        message_count: Array.isArray(body.messages) ? body.messages.length : 0,
+        should_fail: shouldFail,
+      });
+
+      if (shouldFail) {
+        await sleep(firstTokenDelayMs);
+        sendJson(response, faultStatus, {
+          error: {
+            message: `LangBot fake provider injected HTTP ${faultStatus}`,
+            type: "fake_provider_fault",
+            code: "fake_provider_fault",
+          },
+        });
+        return;
+      }
+
+      const replyText = responseTextForBody(body);
+
+      if (body.stream) {
+        await streamCompletion(response, {
+          requestId,
+          model: body.model || modelName,
+          content: replyText,
+          failAfterFirstChunk,
+        });
+      } else {
+        await sleep(firstTokenDelayMs + chunkDelayMs);
+        sendJson(response, 200, completionPayload({
+          requestId,
+          model: body.model || modelName,
+          content: replyText,
+        }));
+      }
+      return;
+    }
+
+    sendJson(response, 404, {
+      error: {
+        message: `No fake provider route for ${request.method} ${url.pathname}`,
+        type: "not_found",
+      },
+    });
+  } catch (error) {
+    sendJson(response, 500, {
+      error: {
+        message: error instanceof Error ? error.message : String(error),
+        type: "fake_provider_error",
+      },
+    });
+  } finally {
+    const durationMs = Date.now() - startedAt;
+    if (url.pathname !== "/healthz") {
+      console.log(JSON.stringify({
+        at: new Date().toISOString(),
+        method: request.method,
+        path: url.pathname,
+        duration_ms: durationMs,
+      }));
+    }
+  }
+});
+
+server.listen(port, host, async () => {
+  const address = server.address();
+  const selectedPort = typeof address === "object" && address ? address.port : port;
+  const url = `http://${host}:${selectedPort}`;
+  const state = {
+    status: "ready",
+    pid: process.pid,
+    url,
+    base_url: `${url}/v1`,
+    model: modelName,
+    started_at: new Date().toISOString(),
+  };
+  if (stateFile) {
+    const path = resolve(stateFile);
+    await mkdir(dirname(path), { recursive: true });
+    await writeFile(path, `${JSON.stringify(state, null, 2)}\n`, "utf8");
+  }
+  console.log(JSON.stringify(state));
+});
+
+server.on("error", (error) => {
+  console.error(JSON.stringify({
+    status: "error",
+    reason: error instanceof Error ? error.message : String(error),
+  }));
+  exit(1);
+});
+
+process.on("SIGTERM", () => {
+  server.close(() => exit(0));
+});
+
+function parseArgs(argv) {
+  const result = {};
+  for (const item of argv) {
+    const match = item.match(/^--([^=]+)(?:=(.*))?$/);
+    if (!match) continue;
+    result[match[1]] = match[2] ?? "1";
+  }
+  return result;
+}
+
+function integer(value, fallback) {
+  const parsed = Number.parseInt(String(value ?? ""), 10);
+  return Number.isFinite(parsed) && parsed >= 0 ? parsed : fallback;
+}
+
+function bool(value, fallback) {
+  if (value === undefined || value === "") return fallback;
+  if (/^(1|true|yes|on)$/i.test(String(value))) return true;
+  if (/^(0|false|no|off)$/i.test(String(value))) return false;
+  return fallback;
+}
+
+function sleep(ms) {
+  return new Promise((resolve) => setTimeout(resolve, Math.max(0, ms)));
+}
+
+async function readJson(request) {
+  let text = "";
+  for await (const chunk of request) text += chunk.toString();
+  if (!text) return {};
+  return JSON.parse(text);
+}
+
+function sendJson(response, status, payload) {
+  const text = `${JSON.stringify(payload)}\n`;
+  response.writeHead(status, {
+    "content-type": "application/json",
+    "content-length": Buffer.byteLength(text),
+  });
+  response.end(text);
+}
+
+function completionPayload({ requestId, model, content }) {
+  const completionTokens = tokenEstimate(content);
+  return {
+    id: requestId,
+    object: "chat.completion",
+    created: Math.floor(Date.now() / 1000),
+    model,
+    choices: [
+      {
+        index: 0,
+        message: {
+          role: "assistant",
+          content,
+        },
+        finish_reason: "stop",
+      },
+    ],
+    usage: {
+      prompt_tokens: 8,
+      completion_tokens: completionTokens,
+      total_tokens: 8 + completionTokens,
+    },
+  };
+}
+
+async function streamCompletion(response, { requestId, model, content, failAfterFirstChunk: failMidStream }) {
+  response.writeHead(200, {
+    "content-type": "text/event-stream; charset=utf-8",
+    "cache-control": "no-cache",
+    "connection": "keep-alive",
+  });
+
+  await sleep(firstTokenDelayMs);
+  writeSse(response, {
+    id: requestId,
+    object: "chat.completion.chunk",
+    created: Math.floor(Date.now() / 1000),
+    model,
+    choices: [{ index: 0, delta: { role: "assistant" }, finish_reason: null }],
+  });
+
+  const chunks = splitContent(content);
+  for (let index = 0; index < chunks.length; index += 1) {
+    await sleep(chunkDelayMs);
+    writeSse(response, {
+      id: requestId,
+      object: "chat.completion.chunk",
+      created: Math.floor(Date.now() / 1000),
+      model,
+      choices: [{ index: 0, delta: { content: chunks[index] }, finish_reason: null }],
+    });
+    if (failMidStream && index === 0) {
+      response.destroy(new Error("LangBot fake provider injected mid-stream disconnect"));
+      return;
+    }
+  }
+
+  await sleep(chunkDelayMs);
+  const completionTokens = tokenEstimate(content);
+  writeSse(response, {
+    id: requestId,
+    object: "chat.completion.chunk",
+    created: Math.floor(Date.now() / 1000),
+    model,
+    choices: [{ index: 0, delta: {}, finish_reason: "stop" }],
+    usage: {
+      prompt_tokens: 8,
+      completion_tokens: completionTokens,
+      total_tokens: 8 + completionTokens,
+    },
+  });
+  response.write("data: [DONE]\n\n");
+  response.end();
+}
+
+function writeSse(response, payload) {
+  response.write(`data: ${JSON.stringify(payload)}\n\n`);
+}
+
+function splitContent(content) {
+  const text = String(content);
+  const requested = integer(env.LANGBOT_FAKE_PROVIDER_CHUNK_COUNT, 0);
+  if (requested <= 1 || text.length <= 1) return [text];
+  const chunkSize = Math.max(1, Math.ceil(text.length / requested));
+  const chunks = [];
+  for (let index = 0; index < text.length; index += chunkSize) {
+    chunks.push(text.slice(index, index + chunkSize));
+  }
+  return chunks;
+}
+
+function tokenEstimate(content) {
+  return Math.max(1, Math.ceil(String(content || "").length / 4));
+}
+
+function responseTextForBody(body) {
+  if (/^(0|false|no|off)$/i.test(env.LANGBOT_FAKE_PROVIDER_DYNAMIC_RESPONSE || "")) {
+    return responseText;
+  }
+  const messages = Array.isArray(body.messages) ? body.messages : [];
+  const lastUser = [...messages].reverse().find((message) => message?.role === "user");
+  const text = flattenContent(lastUser?.content || "");
+  const quoted = text.match(/["'“”](.{1,80}?)["'“”]/);
+  if (quoted?.[1]) return quoted[1].trim();
+  const exact = text.match(/(?:reply|回复|输出|return)\s+(?:exactly\s+)?([A-Za-z0-9_.:@-]{1,80})/i);
+  if (exact?.[1]) return exact[1].trim().replace(/[。.!?]+$/, "");
+  const only = text.match(/只回复\s*([A-Za-z0-9_.:@-]{1,80})/);
+  if (only?.[1]) return only[1].trim().replace(/[。.!?]+$/, "");
+  return responseText;
+}
+
+function flattenContent(content) {
+  if (typeof content === "string") return content;
+  if (Array.isArray(content)) {
+    return content
+      .map((item) => {
+        if (typeof item === "string") return item;
+        if (item && typeof item === "object") return item.text || "";
+        return "";
+      })
+      .join("\n");
+  }
+  return "";
+}
+
+function recordRequest(entry) {
+  recentRequests.push({
+    ...entry,
+    at: new Date().toISOString(),
+  });
+  while (recentRequests.length > requestLogLimit) recentRequests.shift();
+}
diff --git a/skills/skills.index.json b/skills/skills.index.json
index 9a2cbd13d..5bc988ed6 100644
--- a/skills/skills.index.json
+++ b/skills/skills.index.json
@@ -151,11 +151,13 @@
         "agent-runner-release-preflight",
         "agent-runner-runtime-chaos",
         "dify-agent-debug-chat",
+        "langbot-fake-provider-debug-chat-load",
         "langbot-fault-taxonomy-contract",
         "langbot-live-backend-latency",
         "langbot-live-backend-log-health",
         "langbot-live-control-plane-api",
         "langbot-overhead-accounting-contract",
+        "langbot-space-debug-chat-concurrency-smoke",
         "langrag-kb-retrieve",
         "langrag-parser-golden-e2e",
         "langrag-sentinel-kb-discover",
@@ -493,6 +495,43 @@
             "backend_log"
           ]
         },
+        {
+          "id": "langbot-fake-provider-debug-chat-load",
+          "title": "LangBot Debug Chat controlled fake-provider load probe",
+          "mode": "probe",
+          "area": "performance",
+          "type": "performance",
+          "priority": "p1",
+          "risk": "medium",
+          "ci_eligible": false,
+          "tags": [
+            "performance",
+            "debug-chat",
+            "websocket",
+            "fake-provider",
+            "load",
+            "metrics"
+          ],
+          "automation": "skills/langbot-testing/probes/langbot-debug-chat-concurrency.mjs",
+          "setup_automation": [
+            "node:scripts/e2e/ensure-fake-provider-pipeline.mjs --write-env"
+          ],
+          "setup_provides_env": [
+            "LANGBOT_FAKE_PROVIDER_URL",
+            "LANGBOT_FAKE_PROVIDER_BASE_URL",
+            "LANGBOT_FAKE_PROVIDER_PID",
+            "LANGBOT_FAKE_PROVIDER_PROVIDER_UUID",
+            "LANGBOT_FAKE_PROVIDER_MODEL_UUID",
+            "LANGBOT_FAKE_PROVIDER_PIPELINE_URL",
+            "LANGBOT_FAKE_PROVIDER_PIPELINE_NAME"
+          ],
+          "evidence_required": [
+            "metrics",
+            "network",
+            "api_diagnostic",
+            "filesystem"
+          ]
+        },
         {
           "id": "langbot-fault-taxonomy-contract",
           "title": "LangBot fault taxonomy and cleanup contract",
@@ -615,6 +654,43 @@
             "filesystem"
           ]
         },
+        {
+          "id": "langbot-space-debug-chat-concurrency-smoke",
+          "title": "LangBot Debug Chat real Space-provider concurrency smoke",
+          "mode": "probe",
+          "area": "performance",
+          "type": "performance",
+          "priority": "p1",
+          "risk": "high",
+          "ci_eligible": false,
+          "tags": [
+            "performance",
+            "debug-chat",
+            "websocket",
+            "space",
+            "live-provider",
+            "smoke",
+            "metrics"
+          ],
+          "automation": "skills/langbot-testing/probes/langbot-debug-chat-concurrency.mjs",
+          "setup_automation": [
+            "node:scripts/e2e/ensure-local-agent-pipeline.mjs --write-env"
+          ],
+          "setup_provides_env": [
+            "LANGBOT_PIPELINE_URL",
+            "LANGBOT_PIPELINE_NAME",
+            "LANGBOT_LOCAL_AGENT_PIPELINE_URL",
+            "LANGBOT_LOCAL_AGENT_PIPELINE_NAME",
+            "LANGBOT_LOCAL_AGENT_MODEL_UUID",
+            "LANGBOT_E2E_MODEL_UUID"
+          ],
+          "evidence_required": [
+            "metrics",
+            "network",
+            "api_diagnostic",
+            "filesystem"
+          ]
+        },
         {
           "id": "langrag-kb-retrieve",
           "title": "LangRAG knowledge base ingests and retrieves a sentinel document",
@@ -1220,6 +1296,7 @@
       "suites": [
         "agent-runner-release-gate",
         "core-smoke",
+        "langbot-debug-chat-load-gate",
         "langbot-live-backend-gate",
         "langbot-performance-contract-gate",
         "langbot-performance-reliability-gate",
@@ -1286,6 +1363,23 @@
             "local-agent-basic-debug-chat"
           ]
         },
+        {
+          "id": "langbot-debug-chat-load-gate",
+          "title": "LangBot Debug Chat load gate",
+          "description": "Message-path load checks for Pipeline Debug Chat: controlled fake-provider baseline plus optional real Space-provider smoke.",
+          "type": "performance",
+          "priority": "p1",
+          "tags": [
+            "performance",
+            "debug-chat",
+            "websocket",
+            "load"
+          ],
+          "cases": [
+            "langbot-fake-provider-debug-chat-load",
+            "langbot-space-debug-chat-concurrency-smoke"
+          ]
+        },
         {
           "id": "langbot-live-backend-gate",
           "title": "LangBot live backend reliability gate",
@@ -1501,6 +1595,7 @@
         "sandbox-native-tools-unavailable",
         "socks-proxy-without-socksio",
         "survey-widget-blocks-debug-chat",
+        "telemetry-proxy-noise",
         "tool-name-collision-between-mcp-and-plugin",
         "uv-run-resyncs-local-sdk"
       ],
@@ -1685,6 +1780,14 @@
             "mcp-stdio-tool-call"
           ]
         },
+        {
+          "id": "telemetry-proxy-noise",
+          "title": "Telemetry posting fails through the proxy while the target flow succeeds",
+          "category": "env_issue",
+          "related_cases": [
+            "langbot-space-debug-chat-concurrency-smoke"
+          ]
+        },
         {
           "id": "tool-name-collision-between-mcp-and-plugin",
           "title": "MCP and plugin expose the same tool name",
diff --git a/skills/skills/.env.example b/skills/skills/.env.example
index a8f5ebf09..d236c199a 100644
--- a/skills/skills/.env.example
+++ b/skills/skills/.env.example
@@ -26,6 +26,20 @@ LANGBOT_NO_PROXY=localhost,127.0.0.1,::1
 LANGBOT_PIPELINE_URL=
 LANGBOT_PIPELINE_NAME=
 
+# Optional fake OpenAI-compatible provider controls for Debug Chat load tests.
+# Leave URL empty to let setup automation start a local provider and write the
+# selected URL to skills/.env.local.
+LANGBOT_FAKE_PROVIDER_URL=
+LANGBOT_FAKE_PROVIDER_HOST=127.0.0.1
+LANGBOT_FAKE_PROVIDER_PORT=
+LANGBOT_FAKE_PROVIDER_MODEL_NAME=gpt-4o-mini
+LANGBOT_FAKE_PROVIDER_RESPONSE_TEXT=OK
+LANGBOT_FAKE_PROVIDER_FIRST_TOKEN_DELAY_MS=25
+LANGBOT_FAKE_PROVIDER_CHUNK_DELAY_MS=10
+LANGBOT_FAKE_PROVIDER_FAIL_FIRST_N=0
+LANGBOT_FAKE_PROVIDER_FAIL_EVERY_N=0
+LANGBOT_FAKE_PROVIDER_FAULT_STATUS=500
+
 # Optional case-specific runner targets. Prefer these for runner-specific cases
 # so the automation cannot silently test the wrong runner.
 LANGBOT_LOCAL_AGENT_PIPELINE_URL=
diff --git a/skills/skills/langbot-testing/cases/langbot-fake-provider-debug-chat-load.yaml b/skills/skills/langbot-testing/cases/langbot-fake-provider-debug-chat-load.yaml
new file mode 100644
index 000000000..8a71c3558
--- /dev/null
+++ b/skills/skills/langbot-testing/cases/langbot-fake-provider-debug-chat-load.yaml
@@ -0,0 +1,81 @@
+id: langbot-fake-provider-debug-chat-load
+title: "LangBot Debug Chat controlled fake-provider load probe"
+mode: probe
+area: performance
+type: performance
+priority: p1
+risk: medium
+ci_eligible: false
+tags:
+  - performance
+  - debug-chat
+  - websocket
+  - fake-provider
+  - load
+  - metrics
+skills:
+  - langbot-env-setup
+  - langbot-testing
+env:
+  - LANGBOT_BACKEND_URL
+  - LANGBOT_FRONTEND_URL
+  - LANGBOT_E2E_LOGIN_USER
+automation: skills/langbot-testing/probes/langbot-debug-chat-concurrency.mjs
+automation_env:
+  - LANGBOT_BACKEND_URL
+  - LANGBOT_E2E_LOGIN_USER
+  - LANGBOT_FAKE_PROVIDER_PIPELINE_URL
+  - LANGBOT_FAKE_PROVIDER_PIPELINE_NAME
+automation_pipeline_url_env: LANGBOT_FAKE_PROVIDER_PIPELINE_URL
+automation_pipeline_name_env: LANGBOT_FAKE_PROVIDER_PIPELINE_NAME
+automation_debug_chat_load_requests: "12"
+automation_debug_chat_load_concurrency: "4"
+automation_debug_chat_load_timeout_ms: "30000"
+automation_debug_chat_load_response_p95_ms: "5000"
+automation_debug_chat_load_first_response_p95_ms: "3000"
+automation_debug_chat_load_max_error_rate: "0"
+automation_debug_chat_load_expected_prefix: "FAKEQA"
+automation_debug_chat_load_prompt_template: '请只回复 "{expected}"，不要解释，不要添加其他字符。'
+automation_debug_chat_load_stream: "true"
+automation_debug_chat_load_reset: "true"
+metrics_thresholds_json: '{"response_p95_ms":{"max":5000},"first_response_p95_ms":{"max":3000},"error_rate":{"max":0}}'
+load_profile_json: '{"requests":12,"concurrency":4,"path":"Pipeline Debug Chat WebSocket","provider":"controlled fake OpenAI-compatible provider","metric":"send-to-final-assistant-response"}'
+setup_automation:
+  - "node:scripts/e2e/ensure-fake-provider-pipeline.mjs --write-env"
+setup_provides_env:
+  - LANGBOT_FAKE_PROVIDER_URL
+  - LANGBOT_FAKE_PROVIDER_BASE_URL
+  - LANGBOT_FAKE_PROVIDER_PID
+  - LANGBOT_FAKE_PROVIDER_PROVIDER_UUID
+  - LANGBOT_FAKE_PROVIDER_MODEL_UUID
+  - LANGBOT_FAKE_PROVIDER_PIPELINE_URL
+  - LANGBOT_FAKE_PROVIDER_PIPELINE_NAME
+steps:
+  - "Start or reuse the local fake OpenAI-compatible provider."
+  - "Create or update the LangBot provider, model, and local-agent pipeline that points at the fake provider."
+  - "Reset the target Debug Chat session."
+  - "Open concurrent WebSocket Debug Chat connections and send unique deterministic prompts through the real backend pipeline."
+checks:
+  - "automation-result.json status is pass when every request receives its own expected assistant response."
+  - "metrics_summary includes request count, concurrency, p50/p95 response latency, first response latency, throughput, and error rate."
+  - "thresholds_summary shows response_p95_ms, first_response_p95_ms, and error_rate pass."
+evidence_required:
+  - metrics
+  - network
+  - api_diagnostic
+  - filesystem
+diagnostics:
+  - "This probe removes external model latency from the measurement; it still exercises the live LangBot backend, provider requester, local-agent runner, pipeline, and Debug Chat WebSocket adapter."
+  - "Use this as the repeatable message-path baseline before comparing against Space or another real provider."
+success_patterns:
+  - "Debug Chat WebSocket concurrency probe passed"
+  - "Streaming completed"
+failure_patterns:
+  - "WebSocket connection error"
+  - "Timed out after"
+  - "Final assistant response did not include"
+  - "All models failed during streaming setup"
+troubleshooting:
+  - backend-not-listening
+  - debug-chat-history-contaminates-automation
+  - local-agent-model-route-unavailable
diff --git a/skills/skills/langbot-testing/cases/langbot-space-debug-chat-concurrency-smoke.yaml b/skills/skills/langbot-testing/cases/langbot-space-debug-chat-concurrency-smoke.yaml
new file mode 100644
index 000000000..4f9fc779b
--- /dev/null
+++ b/skills/skills/langbot-testing/cases/langbot-space-debug-chat-concurrency-smoke.yaml
@@ -0,0 +1,84 @@
+id: langbot-space-debug-chat-concurrency-smoke
+title: "LangBot Debug Chat real Space-provider concurrency smoke"
+mode: probe
+area: performance
+type: performance
+priority: p1
+risk: high
+ci_eligible: false
+tags:
+  - performance
+  - debug-chat
+  - websocket
+  - space
+  - live-provider
+  - smoke
+  - metrics
+skills:
+  - langbot-env-setup
+  - langbot-testing
+env:
+  - LANGBOT_BACKEND_URL
+  - LANGBOT_FRONTEND_URL
+  - LANGBOT_E2E_LOGIN_USER
+automation: skills/langbot-testing/probes/langbot-debug-chat-concurrency.mjs
+automation_env:
+  - LANGBOT_BACKEND_URL
+  - LANGBOT_E2E_LOGIN_USER
+  - LANGBOT_LOCAL_AGENT_PIPELINE_URL
+  - LANGBOT_LOCAL_AGENT_PIPELINE_NAME
+automation_pipeline_url_env: LANGBOT_LOCAL_AGENT_PIPELINE_URL
+automation_pipeline_name_env: LANGBOT_LOCAL_AGENT_PIPELINE_NAME
+automation_debug_chat_load_requests: "3"
+automation_debug_chat_load_concurrency: "2"
+automation_debug_chat_load_timeout_ms: "120000"
+automation_debug_chat_load_response_p95_ms: "120000"
+automation_debug_chat_load_max_error_rate: "0"
+automation_debug_chat_load_expected_prefix: "SPACEQA"
+automation_debug_chat_load_prompt_template: '请只回复 "{expected}"，不要解释，不要添加其他字符。'
+automation_debug_chat_load_stream: "true"
+automation_debug_chat_load_reset: "true"
+metrics_thresholds_json: '{"response_p95_ms":{"max":120000},"error_rate":{"max":0}}'
+load_profile_json: '{"requests":3,"concurrency":2,"path":"Pipeline Debug Chat WebSocket","provider":"LangBot Space model route","metric":"send-to-final-assistant-response","classification":"smoke-not-benchmark"}'
+setup_automation:
+  - "node:scripts/e2e/ensure-local-agent-pipeline.mjs --write-env"
+setup_provides_env:
+  - LANGBOT_PIPELINE_URL
+  - LANGBOT_PIPELINE_NAME
+  - LANGBOT_LOCAL_AGENT_PIPELINE_URL
+  - LANGBOT_LOCAL_AGENT_PIPELINE_NAME
+  - LANGBOT_LOCAL_AGENT_MODEL_UUID
+  - LANGBOT_E2E_MODEL_UUID
+preconditions:
+  - "The selected local LangBot instance is safe for a low-volume real Space model smoke run."
+  - "Treat Space/provider/network failures as environment or dependency findings until fake-provider baseline evidence separates LangBot overhead."
+steps:
+  - "Prepare a local-agent pipeline with a tested Space model and fallback models."
+  - "Reset the target Debug Chat session."
+  - "Open a small number of concurrent WebSocket Debug Chat connections and send unique deterministic prompts through the live Space provider path."
+checks:
+  - "automation-result.json status is pass when every request receives its own expected assistant response."
+  - "metrics_summary includes request count, concurrency, p95 response latency, throughput, and error rate."
+  - "The report classifies the result as a live-provider smoke, not a stable LangBot overhead benchmark."
+evidence_required:
+  - metrics
+  - network
+  - api_diagnostic
+  - filesystem
+diagnostics:
+  - "This probe measures real user-path latency through Space and includes provider latency, model behavior, and network effects."
+  - "Compare with langbot-fake-provider-debug-chat-load before attributing slow or failed runs to LangBot itself."
+success_patterns:
+  - "Debug Chat WebSocket concurrency probe passed"
+  - "Streaming completed"
+failure_patterns:
+  - "invalid api key"
+  - "WebSocket connection error"
+  - "Timed out after"
+  - "Final assistant response did not include"
+  - "All models failed during streaming setup"
+troubleshooting:
+  - local-agent-model-route-unavailable
+  - marketplace-network-flaky
+  - proxy-env-mismatch
+  - telemetry-proxy-noise
diff --git a/skills/skills/langbot-testing/probes/langbot-debug-chat-concurrency.mjs b/skills/skills/langbot-testing/probes/langbot-debug-chat-concurrency.mjs
new file mode 100644
index 000000000..af40698a1
--- /dev/null
+++ b/skills/skills/langbot-testing/probes/langbot-debug-chat-concurrency.mjs
@@ -0,0 +1,664 @@
+#!/usr/bin/env node
+
+import crypto from "node:crypto";
+import net from "node:net";
+import tls from "node:tls";
+import { mkdir, writeFile } from "node:fs/promises";
+import { join, resolve } from "node:path";
+import { env, exit } from "node:process";
+import {
+  apiJson,
+  appendLine,
+  ensureEvidence,
+  evidencePaths,
+  loadEnvFiles,
+  localIsoWithOffset,
+  redact,
+  resetAndAuthLocalUser,
+  writeResult,
+} from "../../../scripts/e2e/lib/langbot-e2e.mjs";
+
+const DEFAULT_LOCAL_PASSWORD = "LangBotE2ELocalPass!2026";
+
+await loadEnvFiles();
+const caseId = env.LBS_CASE_ID || "langbot-debug-chat-concurrency";
+const paths = evidencePaths(caseId);
+await ensureEvidence(paths);
+
+const startedAt = new Date();
+const metricsPath = resolve(paths.evidenceDir, "metrics.json");
+const samplesPath = resolve(paths.evidenceDir, "samples.json");
+const resetDiagnosticPath = resolve(paths.evidenceDir, "debug-chat-reset-diagnostic.json");
+const backendUrl = env.LANGBOT_BACKEND_URL || "";
+const pipelineUrl = env.LANGBOT_E2E_PIPELINE_URL || env.LANGBOT_PIPELINE_URL || "";
+const pipelineName = env.LANGBOT_E2E_PIPELINE_NAME || env.LANGBOT_PIPELINE_NAME || "";
+const sessionType = env.LANGBOT_DEBUG_CHAT_LOAD_SESSION_TYPE || env.LANGBOT_E2E_DEBUG_CHAT_SESSION_TYPE || "person";
+const totalRequests = positiveInteger(env.LANGBOT_DEBUG_CHAT_LOAD_REQUESTS, defaultRequests(caseId));
+const concurrency = Math.min(totalRequests, positiveInteger(env.LANGBOT_DEBUG_CHAT_LOAD_CONCURRENCY, defaultConcurrency(caseId)));
+const timeoutMs = positiveInteger(env.LANGBOT_DEBUG_CHAT_LOAD_TIMEOUT_MS, defaultTimeout(caseId));
+const expectedPrefix = env.LANGBOT_DEBUG_CHAT_LOAD_EXPECTED_PREFIX || "LBQA";
+const promptTemplate = env.LANGBOT_DEBUG_CHAT_LOAD_PROMPT_TEMPLATE
+  || "请只回复 \"{expected}\"，不要解释，不要添加其他字符。";
+const stream = bool(env.LANGBOT_DEBUG_CHAT_LOAD_STREAM, true);
+const resetBeforeRun = bool(env.LANGBOT_DEBUG_CHAT_LOAD_RESET, true);
+const responseP95BudgetMs = positiveNumber(env.LANGBOT_DEBUG_CHAT_LOAD_RESPONSE_P95_MS, defaultP95Budget(caseId));
+const firstResponseP95BudgetMs = positiveNumber(env.LANGBOT_DEBUG_CHAT_LOAD_FIRST_RESPONSE_P95_MS, 0);
+const maxErrorRate = positiveNumber(env.LANGBOT_DEBUG_CHAT_LOAD_MAX_ERROR_RATE, 0);
+
+const result = {
+  source: "automation",
+  case_id: caseId,
+  run_id: paths.runId,
+  status: "fail",
+  reason: "",
+  started_at: startedAt.toISOString(),
+  started_at_local: localIsoWithOffset(startedAt),
+  finished_at: "",
+  finished_at_local: "",
+  duration_ms: 0,
+  backend_url: backendUrl,
+  pipeline_url: pipelineUrl,
+  pipeline_name: pipelineName,
+  pipeline_id: "",
+  session_type: sessionType,
+  load_profile: {
+    requests: totalRequests,
+    concurrency,
+    timeout_ms: timeoutMs,
+    stream,
+    reset_before_run: resetBeforeRun,
+  },
+  evidence: {
+    network_log: paths.networkLog,
+    metrics_json: metricsPath,
+    samples_json: samplesPath,
+    debug_chat_reset_diagnostic_json: resetDiagnosticPath,
+    automation_result_json: paths.automationResultJson,
+    result_json: paths.resultJson,
+  },
+  evidence_collected: ["metrics", "network", "api_diagnostic", "filesystem"],
+};
+
+try {
+  if (!backendUrl) {
+    result.status = "env_issue";
+    throw new Error("LANGBOT_BACKEND_URL is not configured.");
+  }
+  if (!["person", "group"].includes(sessionType)) {
+    throw new Error(`LANGBOT_DEBUG_CHAT_LOAD_SESSION_TYPE must be person or group, got ${sessionType}.`);
+  }
+  const backendReady = await backendReachable(backendUrl);
+  if (!backendReady) {
+    result.status = "env_issue";
+    throw new Error(`Backend did not respond at ${backendUrl}.`);
+  }
+
+  const user = env.LANGBOT_E2E_LOGIN_USER || "";
+  const password = env.LANGBOT_E2E_LOGIN_PASSWORD || DEFAULT_LOCAL_PASSWORD;
+  if (!user) {
+    result.status = "env_issue";
+    throw new Error("LANGBOT_E2E_LOGIN_USER is required so this probe can resolve/reset the Debug Chat session.");
+  }
+  const auth = await resetAndAuthLocalUser({ backendUrl, user, password });
+
+  const pipeline = await resolvePipeline({ backendUrl, token: auth.token, pipelineUrl, pipelineName });
+  result.pipeline_id = pipeline.id;
+  result.pipeline_name = pipeline.name || pipelineName;
+  if (!result.pipeline_url && env.LANGBOT_FRONTEND_URL) {
+    result.pipeline_url = `${env.LANGBOT_FRONTEND_URL.replace(/\/$/, "")}/home/pipelines?id=${encodeURIComponent(pipeline.id)}`;
+  }
+
+  if (resetBeforeRun) {
+    const reset = await apiJson(backendUrl, `/api/v1/pipelines/${encodeURIComponent(pipeline.id)}/ws/reset/${encodeURIComponent(sessionType)}`, {
+      method: "POST",
+      token: auth.token,
+    });
+    const resetDiagnostic = {
+      status: isApiFailure(reset) ? "fail" : "ready",
+      http_status: reset.status,
+      code: reset.json.code ?? null,
+      reason: isApiFailure(reset) ? reset.json.msg || "Debug Chat reset failed." : "Debug Chat session reset.",
+    };
+    await writeFile(resetDiagnosticPath, `${JSON.stringify(resetDiagnostic, null, 2)}\n`, "utf8");
+    if (resetDiagnostic.status === "fail") {
+      throw new Error(resetDiagnostic.reason);
+    }
+  }
+
+  const wsUrl = websocketUrl(backendUrl, pipeline.id, sessionType);
+  const loadStartedAt = performance.now();
+  const samples = await runLoad({
+    wsUrl,
+    totalRequests,
+    concurrency,
+    timeoutMs,
+    promptTemplate,
+    expectedPrefix,
+    stream,
+  });
+  const loadDurationMs = performance.now() - loadStartedAt;
+  const metrics = buildMetrics({
+    samples,
+    totalRequests,
+    concurrency,
+    timeoutMs,
+    loadDurationMs,
+    backendUrl,
+    pipelineId: pipeline.id,
+    sessionType,
+  });
+  const thresholds = buildThresholds(metrics);
+  const passed = Object.values(thresholds).every((item) => item.pass);
+  result.status = passed ? "pass" : "fail";
+  result.reason = passed
+    ? "Debug Chat WebSocket concurrency probe passed all thresholds."
+    : "Debug Chat WebSocket concurrency probe breached latency or error-rate thresholds.";
+  result.metrics_summary = {
+    requests: metrics.total_requests,
+    concurrency: metrics.concurrency,
+    ok_count: metrics.ok_count,
+    error_count: metrics.error_count,
+    timeout_count: metrics.timeout_count,
+    error_rate: metrics.error_rate,
+    response_p50_ms: metrics.response_duration_ms.p50,
+    response_p95_ms: metrics.response_duration_ms.p95,
+    first_response_p95_ms: metrics.first_response_ms.p95,
+    throughput_rps: metrics.throughput_rps,
+    status_counts: metrics.status_counts,
+  };
+  result.thresholds_summary = thresholds;
+  result.artifacts = {
+    metrics_json: metricsPath,
+    samples_json: samplesPath,
+    network_log: paths.networkLog,
+    automation_result_json: paths.automationResultJson,
+    result_json: paths.resultJson,
+  };
+
+  await writeFile(metricsPath, `${JSON.stringify({ ...metrics, thresholds }, null, 2)}\n`, "utf8");
+  await writeFile(samplesPath, `${JSON.stringify(samples, null, 2)}\n`, "utf8");
+} catch (error) {
+  if (!["env_issue", "blocked"].includes(result.status)) {
+    result.status = looksLikeEnvIssue(error) ? "env_issue" : "fail";
+  }
+  result.reason = result.reason || safeReason(error.message);
+} finally {
+  const finishedAt = new Date();
+  result.finished_at = finishedAt.toISOString();
+  result.finished_at_local = localIsoWithOffset(finishedAt);
+  result.duration_ms = finishedAt.getTime() - startedAt.getTime();
+  await mkdir(paths.evidenceDir, { recursive: true });
+  await writeResult(paths, result);
+  console.log(JSON.stringify(result, null, 2));
+}
+
+exit(result.status === "pass" ? 0 : result.status === "env_issue" || result.status === "blocked" ? 2 : 1);
+
+function defaultRequests(id) {
+  return id.includes("space") ? 3 : 12;
+}
+
+function defaultConcurrency(id) {
+  return id.includes("space") ? 1 : 4;
+}
+
+function defaultTimeout(id) {
+  return id.includes("space") ? 120_000 : 30_000;
+}
+
+function defaultP95Budget(id) {
+  return id.includes("space") ? 120_000 : 5_000;
+}
+
+function positiveInteger(value, fallback) {
+  const parsed = Number.parseInt(String(value || ""), 10);
+  return Number.isInteger(parsed) && parsed > 0 ? parsed : fallback;
+}
+
+function positiveNumber(value, fallback) {
+  const parsed = Number(value || "");
+  return Number.isFinite(parsed) && parsed >= 0 ? parsed : fallback;
+}
+
+function bool(value, fallback) {
+  if (value === undefined || value === "") return fallback;
+  if (/^(1|true|yes|on)$/i.test(String(value))) return true;
+  if (/^(0|false|no|off)$/i.test(String(value))) return false;
+  return fallback;
+}
+
+async function backendReachable(baseUrl) {
+  try {
+    const response = await fetch(`${baseUrl.replace(/\/$/, "")}/healthz`, {
+      signal: AbortSignal.timeout(3000),
+    });
+    return response.status < 500;
+  } catch {
+    return false;
+  }
+}
+
+function pipelineIdFromUrl(url) {
+  if (!url) return "";
+  try {
+    const parsed = new URL(url);
+    return parsed.searchParams.get("id") || "";
+  } catch {
+    return "";
+  }
+}
+
+async function resolvePipeline({ backendUrl, token, pipelineUrl, pipelineName }) {
+  const idFromUrl = pipelineIdFromUrl(pipelineUrl);
+  if (idFromUrl) {
+    const response = await apiJson(backendUrl, `/api/v1/pipelines/${encodeURIComponent(idFromUrl)}`, { token });
+    const pipeline = response.json.data?.pipeline;
+    if (isApiFailure(response) || !pipeline?.uuid) {
+      throw new Error(response.json.msg || `Could not load pipeline ${idFromUrl}.`);
+    }
+    return { id: pipeline.uuid, name: pipeline.name || "" };
+  }
+  if (!pipelineName) {
+    throw new Error("Set LANGBOT_E2E_PIPELINE_URL or LANGBOT_E2E_PIPELINE_NAME before running this probe.");
+  }
+  const response = await apiJson(backendUrl, "/api/v1/pipelines", { token });
+  if (isApiFailure(response)) {
+    throw new Error(response.json.msg || "Failed to list pipelines.");
+  }
+  const pipeline = (response.json.data?.pipelines || []).find((item) => item.name === pipelineName);
+  if (!pipeline?.uuid) {
+    throw new Error(`Could not find pipeline named ${pipelineName}.`);
+  }
+  return { id: pipeline.uuid, name: pipeline.name || pipelineName };
+}
+
+function isApiFailure(response) {
+  return response.status >= 400 || (response.json.code !== undefined && response.json.code !== 0);
+}
+
+function websocketUrl(baseUrl, pipelineId, sessionType) {
+  const parsed = new URL(baseUrl);
+  parsed.protocol = parsed.protocol === "https:" ? "wss:" : "ws:";
+  parsed.pathname = `/api/v1/pipelines/${encodeURIComponent(pipelineId)}/ws/connect`;
+  parsed.search = `?session_type=${encodeURIComponent(sessionType)}`;
+  return parsed.toString();
+}
+
+async function runLoad(options) {
+  const samples = [];
+  let nextIndex = 0;
+  const workers = Array.from({ length: options.concurrency }, async () => {
+    while (nextIndex < options.totalRequests) {
+      const index = nextIndex;
+      nextIndex += 1;
+      const sample = await runSingleRequest({ ...options, index });
+      samples.push(sample);
+    }
+  });
+  await Promise.all(workers);
+  return samples.sort((left, right) => left.index - right.index);
+}
+
+function expectedForIndex(prefix, index) {
+  return `${prefix}-${String(index + 1).padStart(4, "0")}`;
+}
+
+function promptForIndex(template, expected) {
+  return template.replaceAll("{expected}", expected);
+}
+
+function runSingleRequest({
+  wsUrl,
+  index,
+  timeoutMs,
+  promptTemplate,
+  expectedPrefix,
+  stream,
+}) {
+  return new Promise((resolve) => {
+    const expected = expectedForIndex(expectedPrefix, index);
+    const prompt = promptForIndex(promptTemplate, expected);
+    const sample = {
+      index,
+      status: "running",
+      ok: false,
+      expected_text: expected,
+      prompt,
+      response_text: "",
+      connected_ms: null,
+      first_response_ms: null,
+      response_duration_ms: null,
+      event_count: 0,
+      foreign_response_count: 0,
+      last_foreign_response_text: "",
+      error: "",
+      close_code: null,
+      close_reason: "",
+    };
+    let closed = false;
+    let connectedAt = 0;
+    let sentAt = 0;
+    const startedAt = performance.now();
+    let client = null;
+    const timer = setTimeout(() => {
+      finish("timeout", `Timed out after ${timeoutMs} ms.`);
+    }, timeoutMs);
+
+    client = openRawWebSocket(wsUrl, {
+      onOpen() {
+        connectedAt = performance.now();
+        sample.connected_ms = rounded(connectedAt - startedAt);
+      },
+      onMessage(text) {
+        sample.event_count += 1;
+        let data;
+        try {
+          data = JSON.parse(String(text || ""));
+        } catch (error) {
+          finish("error", `Invalid WebSocket JSON: ${error.message}`);
+          return;
+        }
+        appendLine(paths.networkLog, JSON.stringify({
+          request_index: index,
+          type: data.type,
+          session_type: data.session_type || "",
+          role: data.data?.role || "",
+          is_final: data.data?.is_final ?? null,
+          content_preview: redact(String(data.data?.content || data.message || "").slice(0, 200)),
+        })).catch(() => {});
+
+        if (data.type === "connected") {
+          sentAt = performance.now();
+          client.send(JSON.stringify({
+            type: "message",
+            message: [{ type: "Plain", text: prompt }],
+            stream,
+          }));
+          return;
+        }
+        if (data.type === "error") {
+          finish("error", data.message || "WebSocket error message.");
+          return;
+        }
+        if (data.type !== "response" || data.data?.role !== "assistant") return;
+
+        const content = String(data.data.content || "");
+        if (content) sample.response_text = content;
+      if (data.data.is_final === true) {
+        const ok = sample.response_text.includes(expected);
+        if (ok) {
+          if (sample.first_response_ms === null && sentAt > 0) {
+            sample.first_response_ms = rounded(performance.now() - sentAt);
+          }
+          finish("pass", "");
+        } else {
+          sample.foreign_response_count += 1;
+          sample.last_foreign_response_text = sample.response_text;
+        }
+      }
+      },
+      onError(error) {
+        finish("connection_error", `WebSocket connection error: ${error.message}`);
+      },
+      onClose(event) {
+        sample.close_code = event.code;
+        sample.close_reason = event.reason || "";
+        if (!closed) finish("closed", `WebSocket closed before final assistant response: ${event.code}`);
+      },
+    });
+
+    function finish(status, reason) {
+      if (closed) return;
+      closed = true;
+      clearTimeout(timer);
+      sample.status = status;
+      sample.ok = status === "pass";
+      sample.error = status === "timeout" && sample.foreign_response_count > 0
+        ? `${reason || ""} Saw ${sample.foreign_response_count} foreign assistant response(s); last=${sample.last_foreign_response_text}`
+        : reason || "";
+      if (sentAt > 0) sample.response_duration_ms = rounded(performance.now() - sentAt);
+      else sample.response_duration_ms = rounded(performance.now() - startedAt);
+      try {
+        client?.close();
+      } catch {
+        // Closing a failed socket should not hide the sample result.
+      }
+      resolve(sample);
+    }
+  });
+}
+
+function openRawWebSocket(wsUrl, handlers) {
+  const parsed = new URL(wsUrl);
+  const secure = parsed.protocol === "wss:";
+  const port = Number(parsed.port || (secure ? 443 : 80));
+  const host = parsed.hostname;
+  const path = `${parsed.pathname}${parsed.search}`;
+  const key = crypto.randomBytes(16).toString("base64");
+  const socket = secure
+    ? tls.connect({ host, port, servername: host })
+    : net.connect({ host, port });
+  let opened = false;
+  let closed = false;
+  let buffer = Buffer.alloc(0);
+
+  socket.setNoDelay(true);
+  socket.on("connect", () => {
+    const originProtocol = secure ? "https" : "http";
+    const request = [
+      `GET ${path} HTTP/1.1`,
+      `Host: ${parsed.host}`,
+      "Upgrade: websocket",
+      "Connection: Upgrade",
+      `Sec-WebSocket-Key: ${key}`,
+      "Sec-WebSocket-Version: 13",
+      `Origin: ${originProtocol}://${parsed.host}`,
+      "",
+      "",
+    ].join("\r\n");
+    socket.write(request);
+  });
+  socket.on("data", (chunk) => {
+    buffer = Buffer.concat([buffer, chunk]);
+    if (!opened) {
+      const headerEnd = buffer.indexOf("\r\n\r\n");
+      if (headerEnd === -1) return;
+      const headerText = buffer.slice(0, headerEnd).toString("utf8");
+      buffer = buffer.slice(headerEnd + 4);
+      if (!/^HTTP\/1\.1 101\b/i.test(headerText)) {
+        handlers.onError(new Error(`Handshake failed: ${headerText.split("\r\n")[0] || "missing status"}`));
+        socket.destroy();
+        return;
+      }
+      opened = true;
+      handlers.onOpen();
+    }
+    processFrames();
+  });
+  socket.on("error", (error) => {
+    if (!closed) handlers.onError(error);
+  });
+  socket.on("close", () => {
+    if (closed) return;
+    closed = true;
+    handlers.onClose({ code: null, reason: "" });
+  });
+
+  function processFrames() {
+    while (true) {
+      const frame = readFrame(buffer);
+      if (!frame) return;
+      buffer = buffer.slice(frame.consumed);
+      if (frame.opcode === 0x1) {
+        handlers.onMessage(frame.payload.toString("utf8"));
+      } else if (frame.opcode === 0x8) {
+        const code = frame.payload.length >= 2 ? frame.payload.readUInt16BE(0) : null;
+        const reason = frame.payload.length > 2 ? frame.payload.slice(2).toString("utf8") : "";
+        closed = true;
+        handlers.onClose({ code, reason });
+        socket.end();
+        return;
+      } else if (frame.opcode === 0x9) {
+        writeFrame(socket, 0xA, frame.payload);
+      }
+    }
+  }
+
+  return {
+    send(text) {
+      if (closed || !opened) return;
+      writeFrame(socket, 0x1, Buffer.from(text, "utf8"));
+    },
+    close() {
+      if (closed) return;
+      closed = true;
+      if (!socket.destroyed) {
+        if (opened) writeFrame(socket, 0x8, Buffer.alloc(0));
+        setTimeout(() => socket.end(), 50).unref();
+      }
+    },
+  };
+}
+
+function readFrame(buffer) {
+  if (buffer.length < 2) return null;
+  const first = buffer[0];
+  const second = buffer[1];
+  const opcode = first & 0x0f;
+  const masked = Boolean(second & 0x80);
+  let length = second & 0x7f;
+  let offset = 2;
+  if (length === 126) {
+    if (buffer.length < offset + 2) return null;
+    length = buffer.readUInt16BE(offset);
+    offset += 2;
+  } else if (length === 127) {
+    if (buffer.length < offset + 8) return null;
+    const high = buffer.readUInt32BE(offset);
+    const low = buffer.readUInt32BE(offset + 4);
+    length = high * 2 ** 32 + low;
+    offset += 8;
+  }
+  let mask = null;
+  if (masked) {
+    if (buffer.length < offset + 4) return null;
+    mask = buffer.slice(offset, offset + 4);
+    offset += 4;
+  }
+  if (buffer.length < offset + length) return null;
+  let payload = buffer.slice(offset, offset + length);
+  if (mask) {
+    payload = Buffer.from(payload);
+    for (let index = 0; index < payload.length; index += 1) {
+      payload[index] ^= mask[index % 4];
+    }
+  }
+  return {
+    opcode,
+    payload,
+    consumed: offset + length,
+  };
+}
+
+function writeFrame(socket, opcode, payload) {
+  const body = Buffer.isBuffer(payload) ? payload : Buffer.from(payload || "");
+  const mask = crypto.randomBytes(4);
+  const headerLength = body.length < 126 ? 2 : body.length <= 0xffff ? 4 : 10;
+  const header = Buffer.alloc(headerLength);
+  header[0] = 0x80 | opcode;
+  if (body.length < 126) {
+    header[1] = 0x80 | body.length;
+  } else if (body.length <= 0xffff) {
+    header[1] = 0x80 | 126;
+    header.writeUInt16BE(body.length, 2);
+  } else {
+    header[1] = 0x80 | 127;
+    header.writeUInt32BE(Math.floor(body.length / 2 ** 32), 2);
+    header.writeUInt32BE(body.length >>> 0, 6);
+  }
+  const masked = Buffer.from(body);
+  for (let index = 0; index < masked.length; index += 1) {
+    masked[index] ^= mask[index % 4];
+  }
+  socket.write(Buffer.concat([header, mask, masked]));
+}
+
+function rounded(value) {
+  return Number(value.toFixed(3));
+}
+
+function percentile(values, percentileValue) {
+  if (values.length === 0) return 0;
+  const sorted = [...values].sort((a, b) => a - b);
+  const index = Math.min(sorted.length - 1, Math.ceil((percentileValue / 100) * sorted.length) - 1);
+  return rounded(sorted[index]);
+}
+
+function stats(values) {
+  if (values.length === 0) return { min: 0, p50: 0, p95: 0, p99: 0, max: 0 };
+  return {
+    min: rounded(Math.min(...values)),
+    p50: percentile(values, 50),
+    p95: percentile(values, 95),
+    p99: percentile(values, 99),
+    max: rounded(Math.max(...values)),
+  };
+}
+
+function buildMetrics({ samples, totalRequests, concurrency, timeoutMs, loadDurationMs, backendUrl, pipelineId, sessionType }) {
+  const okSamples = samples.filter((sample) => sample.ok);
+  const statusCounts = {};
+  for (const sample of samples) {
+    statusCounts[sample.status] = (statusCounts[sample.status] || 0) + 1;
+  }
+  const errorCount = samples.length - okSamples.length;
+  return {
+    probe: caseId,
+    backend_url: backendUrl,
+    pipeline_id: pipelineId,
+    session_type: sessionType,
+    total_requests: totalRequests,
+    completed_requests: samples.length,
+    concurrency,
+    timeout_ms: timeoutMs,
+    ok_count: okSamples.length,
+    error_count: errorCount,
+    timeout_count: samples.filter((sample) => sample.status === "timeout").length,
+    error_rate: samples.length === 0 ? 1 : rounded(errorCount / samples.length),
+    load_duration_ms: rounded(loadDurationMs),
+    throughput_rps: loadDurationMs <= 0 ? 0 : rounded(okSamples.length / (loadDurationMs / 1000)),
+    status_counts: statusCounts,
+    connected_ms: stats(samples.map((sample) => sample.connected_ms).filter(Number.isFinite)),
+    first_response_ms: stats(okSamples.map((sample) => sample.first_response_ms).filter(Number.isFinite)),
+    response_duration_ms: stats(okSamples.map((sample) => sample.response_duration_ms).filter(Number.isFinite)),
+    samples,
+  };
+}
+
+function buildThresholds(metrics) {
+  const thresholds = {
+    error_rate: { actual: metrics.error_rate, max: maxErrorRate, pass: metrics.error_rate <= maxErrorRate },
+    response_p95_ms: {
+      actual: metrics.response_duration_ms.p95,
+      max: responseP95BudgetMs,
+      pass: metrics.ok_count > 0 && metrics.response_duration_ms.p95 <= responseP95BudgetMs,
+    },
+  };
+  if (firstResponseP95BudgetMs > 0) {
+    thresholds.first_response_p95_ms = {
+      actual: metrics.first_response_ms.p95,
+      max: firstResponseP95BudgetMs,
+      pass: metrics.ok_count > 0 && metrics.first_response_ms.p95 <= firstResponseP95BudgetMs,
+    };
+  }
+  return thresholds;
+}
+
+function looksLikeEnvIssue(error) {
+  const message = String(error?.message || error || "");
+  return /fetch failed|ECONNREFUSED|ENOTFOUND|LANGBOT_.*not configured|Could not read recovery_key|Backend did not respond/i.test(message);
+}
+
+function safeReason(value) {
+  return redact(String(value || "")).slice(0, 1000);
+}
diff --git a/skills/skills/langbot-testing/references/performance-reliability-testing.md b/skills/skills/langbot-testing/references/performance-reliability-testing.md
index db325318f..357cf0a74 100644
--- a/skills/skills/langbot-testing/references/performance-reliability-testing.md
+++ b/skills/skills/langbot-testing/references/performance-reliability-testing.md
@@ -121,6 +121,45 @@ Do not treat these starter live probes as Debug Chat or model-provider
 performance. They are control-plane readiness checks; user-facing performance
 needs browser/WebSocket/message-path measurements.
 
+## Debug Chat Load And Fake Provider Baseline
+
+Use `langbot-fake-provider-debug-chat-load` before real-provider load checks.
+The setup automation starts a local OpenAI-compatible fake provider, registers
+it as a normal LangBot provider/model, configures a local-agent pipeline, resets
+Debug Chat, and then drives concurrent WebSocket messages through the live
+backend.
+
+This is not a mocked backend test. It still exercises:
+
+- provider/model persistence and runtime reload;
+- LiteLLM OpenAI-compatible requester path;
+- local-agent runner selection and pipeline execution;
+- Debug Chat WebSocket adapter and broadcast behavior;
+- backend concurrency, timeout, and error-rate accounting.
+
+The fake provider is deterministic and can inject controlled latency or faults
+with `LANGBOT_FAKE_PROVIDER_*` variables, so it is the baseline for LangBot
+message-path overhead. The probe uses unique expected response tokens per
+request because Debug Chat broadcasts messages to every connection in the same
+session; unique tokens prevent one connection from counting another
+connection's response as its own.
+
+Use `langbot-space-debug-chat-concurrency-smoke` after the fake-provider
+baseline. It runs a deliberately small real Space-provider batch and reports
+user-visible latency, not pure LangBot overhead. Space/model/network failures
+are dependency findings until the fake baseline shows the same symptom.
+If a Space smoke passes but log guard finds telemetry posting Tracebacks,
+classify that separately as `telemetry-proxy-noise` instead of clearing the
+proxy or treating the Debug Chat path as failed.
+
+Useful commands:
+
+```bash
+rtk bin/lbs test run langbot-fake-provider-debug-chat-load --run-id langbot-fake-load-local
+rtk bin/lbs test run langbot-space-debug-chat-concurrency-smoke --run-id langbot-space-smoke-local
+rtk bin/lbs suite run langbot-debug-chat-load-gate --run-id langbot-debug-chat-load-local --include-manual-check
+```
+
 ## Gate Layers
 
 Use the smallest gate that answers the quality question:
@@ -134,6 +173,9 @@ Use the smallest gate that answers the quality question:
 - `langbot-user-path-performance-gate`: browser-visible user path performance,
   starting with Pipeline Debug Chat send-to-visible-completion latency. Run it
   only when the browser profile and target pipeline are ready.
+- `langbot-debug-chat-load-gate`: WebSocket Debug Chat load checks, starting
+  with a controlled fake-provider baseline and optionally a low-volume real
+  Space-provider smoke.
 - `langbot-performance-reliability-gate`: combined starter gate for synthetic
   contracts plus live backend checks.
 
diff --git a/skills/skills/langbot-testing/suites/langbot-debug-chat-load-gate.yaml b/skills/skills/langbot-testing/suites/langbot-debug-chat-load-gate.yaml
new file mode 100644
index 000000000..730e87583
--- /dev/null
+++ b/skills/skills/langbot-testing/suites/langbot-debug-chat-load-gate.yaml
@@ -0,0 +1,13 @@
+id: langbot-debug-chat-load-gate
+title: "LangBot Debug Chat load gate"
+description: "Message-path load checks for Pipeline Debug Chat: controlled fake-provider baseline plus optional real Space-provider smoke."
+type: performance
+priority: p1
+tags:
+  - performance
+  - debug-chat
+  - websocket
+  - load
+cases:
+  - langbot-fake-provider-debug-chat-load
+  - langbot-space-debug-chat-concurrency-smoke
diff --git a/skills/skills/langbot-testing/troubleshooting/telemetry-proxy-noise.yaml b/skills/skills/langbot-testing/troubleshooting/telemetry-proxy-noise.yaml
new file mode 100644
index 000000000..945109029
--- /dev/null
+++ b/skills/skills/langbot-testing/troubleshooting/telemetry-proxy-noise.yaml
@@ -0,0 +1,23 @@
+id: telemetry-proxy-noise
+title: "Telemetry posting fails through the proxy while the target flow succeeds"
+date: 2026-06-25
+category: env_issue
+symptoms:
+  - "The target Debug Chat or provider smoke request completes successfully."
+  - "The same log window contains a Traceback for telemetry posting."
+  - "The traceback references the Space telemetry endpoint."
+patterns:
+  - "Failed to post telemetry"
+  - "https://space.langbot.app/api/v1/telemetry"
+  - "httpx.ConnectError"
+likely_causes:
+  - "The backend process inherited proxy settings that are required for model/provider access but unreliable for telemetry posting."
+  - "The telemetry endpoint is temporarily unreachable through the local proxy route."
+  - "TLS or proxy negotiation failed for the non-critical telemetry request."
+fix_steps:
+  - "Keep the proxy configuration needed for model/provider access; do not clear it only to hide telemetry noise."
+  - "Check that uppercase and lowercase proxy variables are consistent before rerunning a live Space smoke."
+  - "Classify the target flow and log-health result separately: a successful Debug Chat run can still have an environment log-health finding."
+verification: "A rerun shows the target case success patterns and no telemetry Traceback in the scanned log window, or the report explicitly records the telemetry issue as environment noise."
+related_cases:
+  - langbot-space-debug-chat-concurrency-smoke
diff --git a/skills/src/commands/validate.ts b/skills/src/commands/validate.ts
index 1c0ef945d..9176b9f18 100644
--- a/skills/src/commands/validate.ts
+++ b/skills/src/commands/validate.ts
@@ -186,10 +186,32 @@ function validateCaseItem(root: string, item: StructuredItem, skillNames: Set<st
   if (timeout && (!/^\d+$/.test(timeout) || Number.parseInt(timeout, 10) <= 0)) {
     errors.push(`${item.path}: 'automation_response_timeout_ms' must be a positive integer string`);
   }
+  for (const key of [
+    "automation_debug_chat_load_requests",
+    "automation_debug_chat_load_concurrency",
+    "automation_debug_chat_load_timeout_ms",
+    "automation_debug_chat_load_response_p95_ms",
+    "automation_debug_chat_load_first_response_p95_ms",
+  ]) {
+    const value = scalar(item.fields, key);
+    if (value && (!/^\d+$/.test(value) || Number.parseInt(value, 10) <= 0)) {
+      errors.push(`${item.path}: '${key}' must be a positive integer string`);
+    }
+  }
+  const loadMaxErrorRate = scalar(item.fields, "automation_debug_chat_load_max_error_rate");
+  if (loadMaxErrorRate && (!/^(?:0(?:\.\d+)?|1(?:\.0+)?)$/.test(loadMaxErrorRate))) {
+    errors.push(`${item.path}: 'automation_debug_chat_load_max_error_rate' must be a number string between 0 and 1`);
+  }
   const streamOutput = scalar(item.fields, "automation_stream_output");
   if (streamOutput && !["0", "1", "false", "true"].includes(streamOutput)) {
     errors.push(`${item.path}: 'automation_stream_output' must be one of 0, 1, false, or true`);
   }
+  for (const key of ["automation_debug_chat_load_stream", "automation_debug_chat_load_reset"]) {
+    const value = scalar(item.fields, key);
+    if (value && !["0", "1", "false", "true"].includes(value)) {
+      errors.push(`${item.path}: '${key}' must be one of 0, 1, false, or true`);
+    }
+  }
   const imageBase64Fixture = scalar(item.fields, "automation_image_base64_fixture");
   if (imageBase64Fixture && !existsSync(join(root, imageBase64Fixture))) {
     errors.push(`${item.path}: automation image fixture does not exist: ${imageBase64Fixture}`);
diff --git a/skills/src/readiness.ts b/skills/src/readiness.ts
index e96f889b4..f4fc3fae0 100644
--- a/skills/src/readiness.ts
+++ b/skills/src/readiness.ts
@@ -116,6 +116,16 @@ export function automationEnvDefaults(item: StructuredItem, env: EnvSource = pro
     ["automation_debug_chat_session_type", "LANGBOT_E2E_DEBUG_CHAT_SESSION_TYPE"],
     ["automation_debug_chat_response_p95_ms", "LANGBOT_E2E_DEBUG_CHAT_RESPONSE_P95_MS"],
     ["automation_debug_chat_max_error_rate", "LANGBOT_E2E_DEBUG_CHAT_MAX_ERROR_RATE"],
+    ["automation_debug_chat_load_requests", "LANGBOT_DEBUG_CHAT_LOAD_REQUESTS"],
+    ["automation_debug_chat_load_concurrency", "LANGBOT_DEBUG_CHAT_LOAD_CONCURRENCY"],
+    ["automation_debug_chat_load_timeout_ms", "LANGBOT_DEBUG_CHAT_LOAD_TIMEOUT_MS"],
+    ["automation_debug_chat_load_response_p95_ms", "LANGBOT_DEBUG_CHAT_LOAD_RESPONSE_P95_MS"],
+    ["automation_debug_chat_load_first_response_p95_ms", "LANGBOT_DEBUG_CHAT_LOAD_FIRST_RESPONSE_P95_MS"],
+    ["automation_debug_chat_load_max_error_rate", "LANGBOT_DEBUG_CHAT_LOAD_MAX_ERROR_RATE"],
+    ["automation_debug_chat_load_expected_prefix", "LANGBOT_DEBUG_CHAT_LOAD_EXPECTED_PREFIX"],
+    ["automation_debug_chat_load_prompt_template", "LANGBOT_DEBUG_CHAT_LOAD_PROMPT_TEMPLATE"],
+    ["automation_debug_chat_load_stream", "LANGBOT_DEBUG_CHAT_LOAD_STREAM"],
+    ["automation_debug_chat_load_reset", "LANGBOT_DEBUG_CHAT_LOAD_RESET"],
     ["automation_filesystem_checks_json", "LANGBOT_E2E_FILESYSTEM_CHECKS_JSON"],
     ["automation_plugin_package", "LANGBOT_E2E_PLUGIN_PACKAGE"],
     ["automation_expected_plugin_id", "LANGBOT_E2E_EXPECTED_PLUGIN_ID"],