diff --git a/docs/dci-troubleshooting.md b/docs/dci-troubleshooting.md
index d47cb2b..90e2c46 100644
--- a/docs/dci-troubleshooting.md
+++ b/docs/dci-troubleshooting.md
@@ -140,4 +140,37 @@ Then recycle any existing compute sessions - hot sessions keep the old setting u
 
 The app version is bundled into the frontend during the release, and is visible by clicking your username in the top right.
 
-You can also determine the app version (and SASjs Version, and build time) by opening browser Development Tools and running `appinfo()` in the console.
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+You can also determine the app version (and SASjs Version, and build time) by opening browser Development Tools and running `appinfo()` in the console.
+
+## Support Diagnostics
+
+Every service call the frontend makes carries a single-row `browser_info` input table, available to the service (and to any [hook script](macros.md)) as `work.browser_info`. It records where the request came from, so a support ticket can be diagnosed from the job log without asking the user follow-up questions, and a hook can adapt to its context.
+
+The table has these columns:
+
+| Column | Description |
+|---|---|
+| `url` | The URL of the Data Controller page itself (the iframe), not the document embedding it. When the editor is embedded in a report, any parameters the report author added to the embed URL are visible here. |
+| `referrer` | The embedding document, from `document.referrer`. For an embedded report this is the report URL, so the embedding report can be told apart from the editor URL. |
+| `timezone` | The browser's IANA timezone name, e.g. `Europe/Berlin`. |
+| `tz_offset` | The browser's UTC offset in minutes, as `Date.getTimezoneOffset()` returns it (positive west of UTC, so `Europe/Berlin` in summer is -120). |
+| `locale` | The browser locale, e.g. `en-GB`. |
+| `dc_version` | The Data Controller build, as shown by `appinfo()`. |
+| `adapter_version` | The `@sasjs/adapter` version the client was built with. |
+| `browser` | The browser family, parsed from the user agent. |
+| `browser_version` | The browser version. |
+| `platform` | The operating system, parsed from the user agent. |
+| `user_agent` | The raw `navigator.userAgent` string. |
+
+The values are supplied by the client, so treat them as diagnostics hints rather than a security boundary.
+
+To see the table, run any request with debug on (for example add `&_debug=131` to the service URL). The session initialisation then writes the row to the job log:
+
+```
+NOTE: MPEINIT: work.browser_info:
+url=... referrer=... timezone=Europe/Berlin tz_offset=-120 locale=en-GB
+dc_version=7.15.0 adapter_version=4.19.0 browser=Chrome browser_version=120.0
+platform=Linux user_agent=...
+```
+
+The table is sent by newer clients only. A service called directly (for instance from a URL, or by a script), or by an older frontend, has no `work.browser_info` - the log then records that fact instead.
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