diff --git a/README.md b/README.md
index 986a977..d182c99 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,7 @@ If you're looking for a friendlier GUI-based controller remapper, search "Game C
 - **Button combos** — hold a modifier button to change what other buttons do (e.g., X+dpad_up)
 - **Per-app profiles** — automatic profile switching based on the frontmost application
 - **Modes** — multiple binding sets per profile, switchable via picker, cycling, or direct jump
+- **Automatic modes** — let an external program pick the mode, e.g. the app in your terminal's focused pane ([herdr](https://herdr.dev/) plugin [available](https://github.com/vgreg/herdr-padio))
 - **Custom menus** — define popup menus with labeled items that trigger any action
 - **Haptic feedback** — rumble on system beep, notifications, or on-demand from any binding
 - **Media keys** — play/pause, track skip, volume, brightness (no Accessibility permission needed)
diff --git a/config.json b/config.json
index 8108e7e..53c8170 100644
--- a/config.json
+++ b/config.json
@@ -44,7 +44,21 @@
         "LB":      { "type": "prev_mode" },
         "RB":      { "type": "next_mode" }
       },
+      "context_modes": {
+        "claude": "agent",
+        "nvim":   "nvim",
+        "zsh":    "shell",
+        "ssh":    "shell"
+      },
+      "hidden_modes": ["agent"],
       "modes": {
+        "agent": {
+          "A":          { "type": "keystroke", "key": "return" },
+          "B":          { "type": "keystroke", "key": "escape" },
+          "X":          { "type": "keystroke", "key": "`continue`" },
+          "dpad_up":    { "type": "keystroke", "key": "up" },
+          "dpad_down":  { "type": "keystroke", "key": "down" }
+        },
         "shell": {
           "A":          { "type": "keystroke", "key": "return" },
           "B":          { "type": "keystroke", "key": "c", "modifiers": ["ctrl"] },
diff --git a/docs/configuration/automatic-modes.md b/docs/configuration/automatic-modes.md
new file mode 100644
index 0000000..8fddbdc
--- /dev/null
+++ b/docs/configuration/automatic-modes.md
@@ -0,0 +1,130 @@
+# Automatic Modes
+
+PadIO can switch mode by itself based on what you are actually doing, instead of you picking a mode by hand every time. An external program reports a short **context token** (usually the name of the app you are working in), and each profile maps tokens to modes.
+
+The motivating case is a terminal multiplexer: focus a Claude Code pane and the controller is in agent mode, move to a shell pane and it is in shell mode, launch `nvim` and it becomes vim mode. But nothing about the mechanism is terminal-specific. Any program that can write a file can drive it.
+
+## How it works
+
+PadIO watches `~/.config/padio/context`, a plain text file holding one token:
+
+```
+claude
+```
+
+When the token **changes**, PadIO looks it up in the active profile's `context_modes` and switches mode if there is a match.
+
+```
+producer                        PadIO
+────────                        ─────
+write ~/.config/padio/context ──> file watch → context_modes → mode
+```
+
+## Configuration
+
+Add `context_modes` to a profile. Keep bindings that should always be available in the profile's `global`, so they survive every mode change:
+
+```json
+"profiles": {
+  "terminal": {
+    "apps": ["com.mitchellh.ghostty"],
+    "default_mode": "shell",
+    "global": {
+      "options": { "type": "mode_select" }
+    },
+    "context_modes": {
+      "claude": "agent",
+      "nvim": "nvim",
+      "zsh": "shell",
+      "ssh": "shell"
+    },
+    "hidden_modes": ["agent", "nvim"],
+    "modes": {
+      "shell": { },
+      "agent": { },
+      "nvim": { }
+    }
+  }
+}
+```
+
+| Field           | Type   | Description |
+|-----------------|--------|-------------|
+| `context_modes` | object | Maps a context token to a mode name. Matching is exact. |
+
+## Resolution rules
+
+Four rules govern automatic switching. They exist to keep it from fighting you.
+
+**1. It fires only when the token changes.** A producer rewriting the same token repeatedly does nothing.
+
+**2. No match leaves the mode alone.** A token with no `context_modes` entry keeps the current mode. It does *not* fall back to `default_mode`. This is what makes it practical to add entries only for the apps you care about, and to ignore everything else.
+
+**3. A mode you picked by hand sticks.** Because switching happens only on token *change*, a mode chosen from the picker survives until you move to a different app. Pick `media` by hand inside a Claude pane and it stays `media`; move to an `nvim` pane and it becomes `nvim`.
+
+**4. An unknown mode name is ignored.** If `context_modes` names a mode that exists in neither the profile's `modes` nor `shared_modes`, PadIO logs it and does nothing.
+
+Only the active profile is consulted, so a token means whatever that profile says it means, and nothing at all in a profile with no `context_modes`.
+
+Returning to a profile re-applies the current token rather than snapping back to `default_mode`, so switching away from your terminal and back keeps the app-driven mode.
+
+## Hidden modes
+
+Automatic switching tends to produce one mode per app, which makes the mode picker unwieldy when only a couple of modes are ever chosen by hand. `hidden_modes` keeps them out of the way:
+
+```json
+"hidden_modes": ["agent", "nvim"]
+```
+
+Hidden modes are excluded from the [`mode_select`](actions.md#mode_select) picker and from [`prev_mode` / `next_mode`](actions.md#prev_mode-next_mode) cycling. They remain fully reachable via `context_modes`, [`mode:<name>`](actions.md#modename), and `default_mode`.
+
+The key can go on a profile, or at the top level for modes shared across profiles. The two lists are combined.
+
+```json
+{
+  "hidden_modes": ["media"],
+  "profiles": {
+    "terminal": {
+      "hidden_modes": ["agent", "nvim"]
+    }
+  }
+}
+```
+
+If hiding would leave nothing to show, PadIO shows every mode instead, so the picker can never become an empty panel you cannot escape.
+
+!!! note
+    Cycling with `prev_mode` / `next_mode` while a hidden mode is active moves you into the visible set, since the current mode is not part of the cycle.
+
+## The context file
+
+The file is a general-purpose extension point. PadIO does not care what writes it.
+
+| Property | Behaviour |
+|----------|-----------|
+| Path     | `~/.config/padio/context` |
+| Content  | A single token. Surrounding whitespace and newlines are stripped. |
+| Empty or missing | Treated as no context. Not an error, and never a mode change. |
+| Updates  | Picked up immediately, whether written in place or replaced atomically. |
+
+Producers should write atomically, to a temp file in the same directory followed by a rename, so PadIO never reads a half-written token. PadIO ignores a rewrite of an unchanged token, so a producer that cannot easily detect changes may simply write every time.
+
+A minimal producer is a one-liner:
+
+```bash
+printf 'nvim' > ~/.config/padio/context.tmp && mv ~/.config/padio/context.tmp ~/.config/padio/context
+```
+
+Which means anything can drive it: a shell hook on directory change, a window manager, a build script that switches you into a "watching CI" mode, or your editor.
+
+## herdr integration
+
+[herdr](https://herdr.dev/) is a terminal multiplexer for running coding agents, with workspaces, tabs and panes. The [herdr-padio](https://github.com/vgreg/herdr-padio) plugin is a ready-made producer for it:
+
+```
+herdr plugin install vgreg/herdr-padio
+```
+
+It watches the focused pane and writes the app running in it. Tokens are herdr's own agent name when it has detected one (`claude`), and otherwise the program driving the pane (`zsh`, `nvim`, `ssh`). Wrapped programs that report an unhelpful name can be renamed with substring rules; see that project's README.
+
+With herdr, put the workspace, tab and pane navigation bindings in the profile's `global` so they work in every mode, and let `context_modes` handle the app in the pane.
diff --git a/docs/configuration/profiles.md b/docs/configuration/profiles.md
index 4a74b13..76a0c97 100644
--- a/docs/configuration/profiles.md
+++ b/docs/configuration/profiles.md
@@ -28,12 +28,14 @@ A profile is a named set of bindings that applies when specific apps are in the
 }
 ```
 
-| Field          | Type     | Description |
-|----------------|----------|-------------|
-| `apps`         | string[] | Bundle IDs this profile applies to. Empty list = default catch-all profile. |
-| `default_mode` | string   | Mode to activate when the profile is first entered. |
-| `global`       | object   | Bindings that apply in all modes of this profile. Overridden by top-level `global`. |
-| `modes`        | object   | Named modes, each containing button bindings. |
+| Field           | Type     | Description |
+|-----------------|----------|-------------|
+| `apps`          | string[] | Bundle IDs this profile applies to. Empty list = default catch-all profile. |
+| `default_mode`  | string   | Mode to activate when the profile is first entered. |
+| `global`        | object   | Bindings that apply in all modes of this profile. Overridden by top-level `global`. |
+| `modes`         | object   | Named modes, each containing button bindings. |
+| `context_modes` | object   | Optional. Maps an external context token to a mode, for [automatic mode switching](automatic-modes.md). |
+| `hidden_modes`  | string[] | Optional. Modes to [hide from the picker](automatic-modes.md#hidden-modes) and from mode cycling. |
 
 ### Profile resolution order
 
@@ -78,6 +80,9 @@ Each profile can have multiple modes. Only one mode is active at a time. Switch
 - [`mode_select`](actions.md#mode_select) — opens a picker overlay
 - [`prev_mode` / `next_mode`](actions.md#prev_mode-next_mode) — cycle through modes
 - [`mode:<name>`](actions.md#modename) — jump directly to a named mode
+- [automatic switching](automatic-modes.md) — let an external program pick the mode from what you are working in
+
+Modes that are only ever selected automatically can be kept out of the picker and the cycle with [`hidden_modes`](automatic-modes.md#hidden-modes).
 
 ## Button combos
 
diff --git a/docs/example-config.md b/docs/example-config.md
index d8b878c..751932d 100644
--- a/docs/example-config.md
+++ b/docs/example-config.md
@@ -49,7 +49,21 @@ A complete annotated config demonstrating profiles, modes, sequences, custom men
         "LB":      { "type": "prev_mode" },
         "RB":      { "type": "next_mode" }
       },
+      "context_modes": {
+        "claude": "agent",
+        "nvim":   "nvim",
+        "zsh":    "shell",
+        "ssh":    "shell"
+      },
+      "hidden_modes": ["agent"],
       "modes": {
+        "agent": {
+          "A":          { "type": "keystroke", "key": "return" },
+          "B":          { "type": "keystroke", "key": "escape" },
+          "X":          { "type": "keystroke", "key": "`continue`" },
+          "dpad_up":    { "type": "keystroke", "key": "up" },
+          "dpad_down":  { "type": "keystroke", "key": "down" }
+        },
         "shell": {
           "A":          { "type": "keystroke", "key": "return" },
           "B":          { "type": "keystroke", "key": "c", "modifiers": ["ctrl"] },
@@ -140,4 +154,6 @@ This config:
     - **shell mode**: return, ctrl-c, ctrl-l, git menu on Y (using `"type": "menu", "name": "git"` syntax)
     - **nvim mode**: vim-style hjkl navigation, with X+dpad combos for ctrl-j/ctrl-k (half-page scroll)
     - **tmux mode**: prefix sequences (ctrl-a + key) for pane navigation
+    - **agent mode**: return, escape, and `continue` as injected text — reached only via `context_modes`
+- **Automatic modes**: `context_modes` switches mode from an external token (see [Automatic Modes](configuration/automatic-modes.md)), and `hidden_modes` keeps `agent` out of the picker since it is never chosen by hand
 - **Git menu**: quick terminal commands accessible via Y button in shell mode
diff --git a/mkdocs.yml b/mkdocs.yml
index 707900c..9b5fce1 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -46,6 +46,7 @@ nav:
   - Configuration:
     - Overview: configuration/index.md
     - Profiles & Modes: configuration/profiles.md
+    - Automatic Modes: configuration/automatic-modes.md
     - Actions: configuration/actions.md
     - Custom Menus: configuration/menus.md
     - Haptics: configuration/haptics.md