feat: make headless terminal size configurable (#2829)

refs #2828

3 files changed, 31 insertions, 0 deletions

diff --git a/docs/next/CHANGELOG.md b/docs/next/CHANGELOG.md
index b2e5ec58..582830e5 100644
--- a/docs/next/CHANGELOG.md
+++ b/docs/next/CHANGELOG.md
@@ -16,6 +16,7 @@
 - The plugin marketplace now discovers valid manifests at repository roots and subdirectories, groups multiple plugins under each repository, and publishes their versions and exact default-branch commits.
 
 ### Changed
+- Headless servers now use a configurable 120×40 virtual terminal instead of 80×24 when no client is attached, giving newly created panes a practical default size. (#2828)
 - Desktop tab labels are now centered in their tabs, so the active-tab highlight has symmetric padding.
 - Bumped the client/server protocol version to 20 for pane terminal bell forwarding.
 - Experimental pane graphics now support bounded named layers, acknowledged full-RGBA primary-layer direct file frames on audited local terminals, owned BGRA fallback, exact pixel mouse input, and placement-only resize replay.
diff --git a/docs/next/website/src/content/docs/configuration.mdx b/docs/next/website/src/content/docs/configuration.mdx
index 4ba3a07a..9f6a96f3 100644
--- a/docs/next/website/src/content/docs/configuration.mdx
+++ b/docs/next/website/src/content/docs/configuration.mdx
@@ -50,6 +50,18 @@ You can also open the global menu in Herdr and choose `reload config`.
 
 Reload applies most UI settings without restarting panes. Startup-only settings still need a restart.
 
+## Headless terminal size
+
+When no client is attached, the server uses a 120×40 virtual terminal for layout and newly created panes. Change that fallback for headless orchestration with:
+
+```toml
+[server]
+headless_cols = 160
+headless_rows = 50
+```
+
+An attached client remains authoritative for the shared runtime size. After it detaches, existing pane PTYs retain their last attached size while new headless layout uses the configured fallback.
+
 ## Terminal defaults
 
 Set the executable Herdr uses for newly created interactive panes:
diff --git a/docs/next/website/src/data/config-reference.json b/docs/next/website/src/data/config-reference.json
index c16db7a1..a2f8d7a1 100644
--- a/docs/next/website/src/data/config-reference.json
+++ b/docs/next/website/src/data/config-reference.json
@@ -13,6 +13,24 @@
       ]
     },
     {
+      "id": "server",
+      "title": "Server",
+      "keys": [
+        {
+          "key": "server.headless_cols",
+          "type": "integer",
+          "default": "120",
+          "description": "Virtual terminal width used for layout and newly created panes when no client is attached. Must be greater than zero."
+        },
+        {
+          "key": "server.headless_rows",
+          "type": "integer",
+          "default": "40",
+          "description": "Virtual terminal height used for layout and newly created panes when no client is attached. Must be greater than zero."
+        }
+      ]
+    },
+    {
       "id": "theme",
       "title": "Theme",
       "keys": [