diff --git a/biome.json b/biome.json
index 0d93874..5436c99 100644
--- a/biome.json
+++ b/biome.json
@@ -22,6 +22,7 @@
   "javascript": {
     "formatter": {
       "quoteStyle": "double"
-    }
+    },
+    "globals": ["__HTTP_LOGGING_ENABLED__"]
   }
 }
diff --git a/docs/CONTRIBUTING.md b/docs/CONTRIBUTING.md
index 3957c61..9435370 100644
--- a/docs/CONTRIBUTING.md
+++ b/docs/CONTRIBUTING.md
@@ -43,6 +43,23 @@ Please ensure that the dev-production separation still works when adding new fun
 In particular, when adding new top-level buttons, make them distinguishable for dev and production versions
 (see [webpack-config](../webpack.config.js) to see how this is currently handled for the manifest.json).
 
+### Log request-response pairs
+
+For tests it might be useful to have the full request-response interaction with an LLM.
+For this we added an extra development mode which can be enabled by runing
+```shell
+npm run with-http-logging
+```
+instead of `npm start`.
+
+With this, each request that is made to an LLM will open a download modal in Thunderbird where you download a json
+file which contains the request you made (minus the Authorization header) and the response by the backend.
+
+This request-response json can be reused in tests to mock the backend.
+See also [mockResponses](../src/__tests__/mockResponses).
+
+Make sure that the content of these examples is save for publication (See also: Test mails down below).
+
 ### Build the plugin locally
 
 - Build the addon package:
diff --git a/manifest.json b/manifest.json
index e69ff92..0112acd 100644
--- a/manifest.json
+++ b/manifest.json
@@ -11,7 +11,7 @@
       "update_url": "https://raw.githubusercontent.com/TNG/tb-llm-composer/refs/heads/main/updates.json"
     }
   },
-  "permissions": ["menus", "compose", "storage", "notifications", "messagesRead", "accountsRead"],
+  "permissions": ["menus", "compose", "storage", "notifications", "messagesRead", "accountsRead", "downloads"],
   "icons": {
     "64": "icons/icon-64px.png",
     "32": "icons/icon-32px.png",
diff --git a/package.json b/package.json
index 0e0f8c0..dedac91 100644
--- a/package.json
+++ b/package.json
@@ -5,6 +5,7 @@
   "main": "background.js",
   "scripts": {
     "start": "webpack --watch",
+    "with-http-logging": "webpack --env HTTP_LOGGING=true --watch",
     "build": "webpack --mode production",
     "zip": "run-script-os",
     "zip:darwin:linux": "cd build && zip -r ../llm-thunderbird.xpi ./*",
diff --git a/src/__tests__/mockResponses/README.md b/src/__tests__/mockResponses/README.md
new file mode 100644
index 0000000..24d01b4
--- /dev/null
+++ b/src/__tests__/mockResponses/README.md
@@ -0,0 +1,32 @@
+# Mock LLM responses
+
+Real-world mock request-response pairs of interactions with the LLM.
+
+The format is inspired by [mock-server](https://www.mock-server.com/mock_server/creating_expectations.html), however,
+the request matching should mostly be done based on the request body since the path is configurable for example.
+This enables easy copy-pasting examples from wherever you get your examples from.
+
+A very basic example of a json in this folder looks like this:
+```json
+{
+    "httpRequest": {
+        "method": "POST",
+        "path": "/login",
+        "body": {
+            "username": "foo",
+            "password": "bar"
+        }
+    },
+    "httpResponse": {
+        "statusCode": 302,
+        "headers": {
+            "Location": [
+                "https://www.mock-server.com"
+            ]
+        },
+        "cookies": {
+            "sessionId": "2By8LOhBmaW5nZXJwcmludCIlMDAzMW"
+        }
+    }
+}
+```
diff --git a/src/llmConnection.ts b/src/llmConnection.ts
index 32a8ec1..b70b96c 100644
--- a/src/llmConnection.ts
+++ b/src/llmConnection.ts
@@ -1,3 +1,4 @@
+import { logRequestResponseToFile } from "./logRequestResponseToFile";
 import { getPluginOptions, type LlmParameters } from "./optionsParams";
 
 export enum LlmRoles {
@@ -84,6 +85,8 @@ export async function sendContentToLlm(
   return callLlmApi(options.model, requestBody, abortSignal, options.api_token);
 }
 
+export type LlmResponseBodyType = string | LlmTextCompletionResponse | TgiErrorResponse;
+
 async function callLlmApi(
   url: string,
   requestBody: LlmApiRequestBody,
@@ -98,20 +101,32 @@ async function callLlmApi(
   }
 
   console.log(`LLM-CONNECTION: Sending request to LLM: POST ${url} with body:\n`, JSON.stringify(requestBody));
-  const response = await fetch(url, {
+  const fetchOptions = {
     signal: signal,
     method: "POST",
     headers: headers,
     body: JSON.stringify(requestBody),
-  });
+  };
+  const response = await fetch(url, fetchOptions);
+  const responseBody = await safeParseBody(response);
+  if (process.env.NODE_ENV === "development" && __HTTP_LOGGING_ENABLED__) {
+    logRequestResponseToFile(url, fetchOptions, requestBody, response, responseBody);
+  }
   if (!response.ok) {
-    const errorResponseBody = await response.text();
-    throw Error(`LLM-CONNECTION: Error response from ${url}: ${errorResponseBody}`);
+    throw Error(`LLM-CONNECTION: Error response from ${url}: ${JSON.stringify(responseBody)}`);
   }
-  const responseBody = (await response.json()) as LlmTextCompletionResponse | TgiErrorResponse;
   console.log("LLM-CONNECTION: LLM responded with:", response.status, responseBody);
+  return responseBody as LlmTextCompletionResponse | TgiErrorResponse;
+}
 
-  return responseBody;
+async function safeParseBody(response: Response): Promise<LlmResponseBodyType> {
+  const responseBody = await response.text();
+  try {
+    return JSON.parse(responseBody);
+  } catch (e) {
+    console.warn("Could not parse response body", responseBody, e);
+    return responseBody;
+  }
 }
 
 export function isLlmTextCompletionResponse(response: LlmTextCompletionResponse | TgiErrorResponse) {
diff --git a/src/logRequestResponseToFile.ts b/src/logRequestResponseToFile.ts
new file mode 100644
index 0000000..bb1a585
--- /dev/null
+++ b/src/logRequestResponseToFile.ts
@@ -0,0 +1,42 @@
+import type { LlmResponseBodyType } from "./llmConnection";
+
+declare global {
+  const __HTTP_LOGGING_ENABLED__: boolean;
+}
+
+export function logRequestResponseToFile(
+  url: string,
+  requestOptions: RequestInit,
+  requestBody: object,
+  response: Response,
+  responseBody: LlmResponseBodyType,
+) {
+  const headers = { ...requestOptions.headers } as { [key: string]: string };
+  headers.Authorization = "***";
+  const json = {
+    request: {
+      url: new URL(url).pathname,
+      method: requestOptions.method,
+      headers: headers,
+      body: requestBody,
+    },
+    response: {
+      status: response.status,
+      statusText: response.statusText,
+      headers: response.headers,
+      body: responseBody,
+    },
+  };
+  const date = new Date();
+  const blob = new Blob([JSON.stringify(json, null, 2)], { type: "text/plain;charset=utf-8" });
+  browser.downloads
+    .download({
+      url: URL.createObjectURL(blob),
+      filename:
+        `request-response-${date.getFullYear()}${date.getMonth() + 1}${date.getDate()}-` +
+        `${date.getHours()}${date.getMinutes()}${date.getSeconds()}.json`,
+    })
+    .catch((e) => {
+      console.warn("Failed to trigger download of request-response", e);
+    });
+}
diff --git a/webpack.config.js b/webpack.config.js
index 924283c..bfd1984 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -1,3 +1,4 @@
+const { DefinePlugin } = require("webpack");
 const CopyWebpackPlugin = require("copy-webpack-plugin");
 const path = require("node:path");
 const TerserPlugin = require("terser-webpack-plugin");
@@ -62,6 +63,9 @@ module.exports = (_env, argv) => {
           },
         ],
       }),
+      new DefinePlugin({
+        __HTTP_LOGGING_ENABLED__: _env.HTTP_LOGGING === "true",
+      }),
     ],
     optimization: {
       minimize: isProductionMode,