diff --git a/doc/src/api/c/backend-notes.md b/doc/src/api/c/backend-notes.md
index 25576c4..e80e684 100644
--- a/doc/src/api/c/backend-notes.md
+++ b/doc/src/api/c/backend-notes.md
@@ -110,7 +110,13 @@ The PC-Talker backend communicates with PC-Talker through a client library distr
 
 ### ZDSR
 
-The ZDSR backend communicates with ZDSR through a client library distributed with ZDSR. The host process MUST be running on Windows, and the library MUST be resolvable through the host process's library search order; if it is not, `prism_backend_initialize` returns `PRISM_ERROR_BACKEND_NOT_AVAILABLE`. The runtime-supported probe reflects only the presence of a running ZDSR process and does not load the library.
+The ZDSR backend communicates with ZDSR through ZDSRAPI. The host process MUST be running on Windows, and the API library MUST be loadable; otherwise, `prism_backend_initialize` returns `PRISM_ERROR_BACKEND_NOT_AVAILABLE`.
+
+The runtime-supported probe requires both `ZDSRMain.exe` and `ZDSRDaemon.exe` to be running. It only checks for those processes and does not load ZDSRAPI. The ZDSR service processes are not used as a proxy for the reader, because they can remain running when the reader is not.
+
+The parameters in `ZDSRAPI.ini` take precedence over the arguments Prism passes to `InitTTS`. If `type=1` selects an independent channel, that channel may still be starting when initialization queries the speech state. In that transient state, ZDSR reports status 9 (independent channel not ready); Prism treats it as not speaking, so `prism_backend_initialize` succeeds and `prism_backend_is_speaking` returns `false`. A `prism_backend_speak` call made before the channel is ready returns `PRISM_ERROR_BACKEND_NOT_AVAILABLE`; applications MAY retry after the channel becomes ready. Reinitialization is not required.
+
+Some ZDSR API versions do not export the `Braille` function. After initialization, the ZDSR backend advertises `PRISM_BACKEND_SUPPORTS_BRAILLE` only if the loaded API provides it. Otherwise `prism_backend_braille` returns `PRISM_ERROR_NOT_IMPLEMENTED`, and `prism_backend_output` outputs speech only. Before initialization, the ZDSR backend does not advertise Braille support.
 
 ### BoyPCReader
 
@@ -210,4 +216,4 @@ The application-context and Java VM attachment requirements of the Android Text
 
 ### Web Speech
 
-In browsing contexts that enforce an autoplay policy, the first call to an instance of the web speech backend to produce speech MUST originate from a user-initiated event handler such as a `click` or `keydown` listener. This is a property of the browsing context, not of Prism. The set of available voices is populated asynchronously by the browser. The voice list reported by the backend MAY be briefly empty after initialization on first page load. Applications SHOULD invoke `prism_backend_refresh_voices` if the voice list is unexpectedly empty, or arrange to do so in response to the browser's `voiceschanged` event.
\ No newline at end of file
+In browsing contexts that enforce an autoplay policy, the first call to an instance of the web speech backend to produce speech MUST originate from a user-initiated event handler such as a `click` or `keydown` listener. This is a property of the browsing context, not of Prism. The set of available voices is populated asynchronously by the browser. The voice list reported by the backend MAY be briefly empty after initialization on first page load. Applications SHOULD invoke `prism_backend_refresh_voices` if the voice list is unexpectedly empty, or arrange to do so in response to the browser's `voiceschanged` event.