diff --git a/CLAUDE.md b/CLAUDE.md
index 65a3e10..97fef4e 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -12,6 +12,7 @@ maestro daemon            tmux wrapper + session API on 127.0.0.1:7070
   ├── GET/POST /api/sessions        list / spawn
   ├── DELETE   /api/sessions/:id    kill
   ├── POST     /api/sessions/:id/input  type text into a session
+  ├── POST     /api/sessions/:id/prompt an agent reports its first prompt (#131)
   ├── GET      /api/info            hostname, version, home dir, spawn presets
   ├── GET      /api/dirs            directory listing (spawn autocomplete)
   ├── GET      /api/recent-dirs     spawn history
diff --git a/docs/SIDEBAR.md b/docs/SIDEBAR.md
index f7d5a37..5200407 100644
--- a/docs/SIDEBAR.md
+++ b/docs/SIDEBAR.md
@@ -20,6 +20,25 @@ A card is always two lines: **line 1** and **line 2**.
 Line 1 carries no badges. The `⚠ blocked work` badge (#83) and the `exited`
 badge move off this row into line 2.
 
+### Where a name comes from (#131)
+
+`metadata.name_source` says whether the name is settled or provisional:
+
+| Source | Means | Rendered |
+|---|---|---|
+| `User` | Typed in the spawn form, or set by a rename. | Normal |
+| `Generated` | The daemon's own handle, assigned because the spawn carried no name. | Muted |
+| `Haiku` | Derived from the session's first prompt. | Normal |
+
+A missing or unrecognised source reads as `User`. That way a session named
+before the field existed is never dimmed, and never autonamed over.
+
+Only `Generated` renders muted, and it is the only source the daemon will
+replace: the first prompt an agent reports to `POST /api/sessions/:id/prompt`
+settles the session at `Haiku`. A session that never reports a prompt — a
+shell, or an agent with no hook installed — keeps its muted handle for as long
+as it lives. That is accurate, not a missing state: nothing has named it yet.
+
 The name is editable in place (#125). In the web client, right-clicking a card
 opens a context menu whose **rename** entry swaps the name for a text field —
 Enter commits, Escape cancels. The TUI opens the same edit as a prompt, bound