Add hook system.

mise.toml

@@ -22,6 +22,101 @@ description = "Screenshot playpen in a throwaway headless compositor"
 depends = ["build-debug"]
 run = "nix develop --command ./shot.sh"
 
+[tasks.install-claude-hooks]
+description = "Teach Claude Code to report its state to the tab it runs in"
+run = '''
+#!/usr/bin/env bash
+set -euo pipefail
+
+command -v jq >/dev/null || { echo "install-claude-hooks needs jq" >&2; exit 1; }
+
+claude="${CLAUDE_CONFIG_DIR:-$HOME/.claude}"
+settings="$claude/settings.json"
+script="$claude/hooks/playpen-status.sh"
+
+mkdir -p "$claude/hooks"
+install -m755 hooks/playpen-status.sh "$script"
+
+# Copied rather than referenced in place: hooks configured to run out of a
+# checkout break the day the checkout moves, and they break silently, in
+# every Claude session at once.
+[ -f "$settings" ] || echo '{}' > "$settings"
+
+# Every entry carries a marker comment. It is what makes re-running this
+# replace the previous install instead of stacking a second copy, and it is
+# what `uninstall-claude-hooks` matches on. The shell ignores it.
+merged=$(jq --arg script "$script" '
+  def marker: "# playpen-status-hook";
+
+  # Drop what a previous run added, leaving every other tools hooks alone.
+  def clean:
+    map(.hooks |= map(select((.command // "") | contains(marker) | not)))
+    | map(select((.hooks | length) > 0));
+
+  def entry($state; $async):
+    { hooks: [
+        { type: "command",
+          command: ($script + " " + $state + "  " + marker),
+          timeout: 5 }
+        + (if $async then { async: true } else {} end)
+    ] };
+
+  .hooks //= {}
+  # UserPromptSubmit is the only one left synchronous: it reads the prompt off
+  # stdin to build the tab title. The rest are a single printf and need not
+  # hold the turn up at all.
+  | .hooks.UserPromptSubmit = ((.hooks.UserPromptSubmit // []) | clean) + [entry("busy";  false)]
+  | .hooks.Notification     = ((.hooks.Notification     // []) | clean) + [entry("input"; true)]
+  | .hooks.Stop             = ((.hooks.Stop             // []) | clean) + [entry("idle";  true)]
+  | .hooks.SessionStart     = ((.hooks.SessionStart     // []) | clean) + [entry("idle";  true)]
+  | .hooks.SessionEnd       = ((.hooks.SessionEnd       // []) | clean) + [entry("idle";  true)]
+' "$settings")
+
+# Keep a copy of what was there, and swap the new file in whole. Claude reads
+# this file constantly; a half-written one is a broken session.
+cp "$settings" "$settings.playpen-backup"
+printf '%s\n' "$merged" > "$settings.tmp"
+mv "$settings.tmp" "$settings"
+
+echo "installed $script"
+echo "hooked into $settings (previous version kept at $settings.playpen-backup)"
+echo
+echo "Open a new Claude session to pick them up — hooks are read at startup."
+'''
+
+[tasks.uninstall-claude-hooks]
+description = "Remove the Claude Code hooks, leaving any other tools' alone"
+run = '''
+#!/usr/bin/env bash
+set -euo pipefail
+
+command -v jq >/dev/null || { echo "uninstall-claude-hooks needs jq" >&2; exit 1; }
+
+claude="${CLAUDE_CONFIG_DIR:-$HOME/.claude}"
+settings="$claude/settings.json"
+[ -f "$settings" ] || { echo "no $settings; nothing to do"; exit 0; }
+
+stripped=$(jq '
+  def marker: "# playpen-status-hook";
+  def clean:
+    map(.hooks |= map(select((.command // "") | contains(marker) | not)))
+    | map(select((.hooks | length) > 0));
+
+  .hooks //= {}
+  | reduce ("UserPromptSubmit","Notification","Stop","SessionStart","SessionEnd") as $ev
+      (.; .hooks[$ev] = ((.hooks[$ev] // []) | clean))
+  # An event we emptied was ours alone; drop the key rather than leave "Stop": []
+  | .hooks |= with_entries(select((.value | type) != "array" or (.value | length) > 0))
+' "$settings")
+
+cp "$settings" "$settings.playpen-backup"
+printf '%s\n' "$stripped" > "$settings.tmp"
+mv "$settings.tmp" "$settings"
+
+rm -f "$claude/hooks/playpen-status.sh"
+echo "removed the hooks from $settings (previous version kept at $settings.playpen-backup)"
+'''
+
 [tasks.install]
 description = "Install playpen into ~/.local with a desktop entry and icon"
 depends = ["build"]