Experimental: Add Antigravity and Claude code Hooks for nudging the agent toward the correct flutter-app-runtime behavior

.agents/hooks.json

@@ -16,5 +16,26 @@
         "timeout": 90
       }
     ]
+  },
+  "flutter-app-runtime": {
+    "PostToolUse": [
+      {
+        "matcher": "write_to_file|replace_file_content|multi_replace_file_content",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "hooks/flag-dart-edit",
+            "timeout": 10
+          }
+        ]
+      }
+    ],
+    "PreInvocation": [
+      {
+        "type": "command",
+        "command": "hooks/flutter-app-runtime",
+        "timeout": 10
+      }
+    ]
   }
 }

.agents/hooks/claude-post-tool-use

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+# flutter-app-runtime: PostToolUse handler (Claude Code).
+#
+# Fires after Edit or Write tool calls.
+# Checks stdin for .dart file edits and outputs hookSpecificOutput with additionalContext.
+
+set -uo pipefail
+INPUT="$(cat 2>/dev/null || true)"
+
+if printf '%s' "$INPUT" | grep -Eq '"file_path"[^,]*[.]dart'; then
+  echo '{"hookSpecificOutput":{"hookEventName":"PostToolUse","additionalContext":"Dart source changed. Use the flutter-app-runtime skill to push this to the running app: hot_reload for widget/UI or simple logic changes. If no app is running, say so and continue."}}'
+fi
+exit 0

.agents/hooks/claude-post-tool-use.cmd

@@ -0,0 +1,13 @@
+@echo off
+rem flutter-app-runtime: PostToolUse handler for Windows (Claude Code).
+rem
+rem Fires after Edit or Write tool calls.
+rem Checks stdin for .dart file edits and outputs hookSpecificOutput with additionalContext.
+
+setlocal EnableExtensions EnableDelayedExpansion
+
+findstr /I /C:".dart" >nul 2>&1
+if %errorlevel% equ 0 (
+    echo {"hookSpecificOutput":{"hookEventName":"PostToolUse","additionalContext":"Dart source changed. Use the flutter-app-runtime skill to push this to the running app: hot_reload for widget/UI or simple logic changes. If no app is running, say so and continue."}}
+)
+exit /b 0

.agents/hooks/flag-dart-edit

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+# flutter-app-runtime: PostToolUse handler (Antigravity).
+#
+# PostToolUse (per Antigravity hooks documentation):
+#   Fires after a tool completes. The `matcher` field is a regular expression
+#   matched against the tool name (here: the file-writing tools).
+#   Input (stdin, camelCase JSON):
+#     toolCall  - object; the executed tool call, with `name` and `args`
+#     stepIdx   - integer; 0-based index of the completed step
+#     error     - string, optional; runtime error if the call failed, else empty
+#     plus common fields: conversationId, workspacePaths, transcriptPath,
+#     artifactDirectoryPath, modelName
+#   Output (stdout): an empty JSON object `{}` -- PostToolUse has NO field for
+#   injecting context back into the conversation.
+#
+# Because of that last point, this handler cannot deliver the reminder itself.
+# It only records that a .dart file was touched; the PreInvocation handler
+# reads the flag and does the actual injection before the next model call.
+
+set -uo pipefail
+INPUT="$(cat 2>/dev/null || true)"
+
+CONV="$(printf '%s' "$INPUT" \
+  | grep -o '"conversationId"[[:space:]]*:[[:space:]]*"[^"]*"' \
+  | sed 's/.*"\([^"]*\)"$/\1/')"
+TEMP_DIR="${TMPDIR:-${TEMP:-${TMP:-/tmp}}}"
+FLAG="${TEMP_DIR}/flutter-app-runtime.${CONV:-default}.pending"
+
+if printf '%s' "$INPUT" | grep -Eq '"(TargetFile|AbsolutePath)"[^,]*[.]dart'; then
+  : > "$FLAG" 2>/dev/null || true
+fi
+
+echo '{}'
+exit 0

.agents/hooks/flag-dart-edit.cmd

@@ -0,0 +1,15 @@
+@echo off
+rem flutter-app-runtime: PostToolUse handler for Windows (Antigravity).
+rem
+rem Native Windows batch script using findstr and %TEMP%.
+rem Zero runtime dependencies; executes in < 5ms.
+
+setlocal EnableExtensions EnableDelayedExpansion
+
+findstr /I /C:".dart" >nul 2>&1
+if %errorlevel% equ 0 (
+    type nul > "%TEMP%\flutter-app-runtime.default.pending" 2>nul
+)
+
+echo {}
+exit /b 0

.agents/hooks/flutter-app-runtime

@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+# flutter-app-runtime: PreInvocation handler (Antigravity).
+#
+# PreInvocation (per Antigravity hooks documentation):
+#   Fires before the model is called. There is no matcher -- the event key
+#   holds a flat list of handlers, and any matcher would be ignored.
+#   Input (stdin, camelCase JSON):
+#     invocationNum   - integer; 0-indexed sequence number of this model
+#                       invocation (the first invocation is 0)
+#     initialNumSteps - integer; number of steps currently in the trajectory
+#     plus common fields: conversationId, workspacePaths, transcriptPath,
+#     artifactDirectoryPath, modelName
+#   Output (stdout):
+#     injectSteps - optional array of steps injected into the conversation
+#                   trajectory before the model is called. Each step carries
+#                   one of: `toolCall` (a tool call to execute), `userMessage`
+#                   (a message from the user), or `ephemeralMessage` (a
+#                   transient system message -- what this hook uses).
+#
+# This is the injection point: if a .dart file was edited since the last model
+# call, inject a one-shot reminder pointing the agent at the
+# flutter-app-runtime skill.
+
+set -uo pipefail
+INPUT="$(cat 2>/dev/null || true)"
+
+CONV="$(printf '%s' "$INPUT" \
+  | grep -o '"conversationId"[[:space:]]*:[[:space:]]*"[^"]*"' \
+  | sed 's/.*"\([^"]*\)"$/\1/')"
+FLAG="${TMPDIR:-/tmp}/flutter-app-runtime.${CONV:-default}.pending"
+
+if [ -f "$FLAG" ]; then
+  rm -f "$FLAG" 2>/dev/null || true
+  echo '{"injectSteps":[{"ephemeralMessage":"Dart source changed. Use the flutter-app-runtime skill to push this to the running app: hot_reload for widget/UI or simple logic changes. If no app is running, say so and continue."}]}'
+else
+  echo '{"injectSteps":[]}'
+fi
+exit 0

.agents/hooks/flutter-app-runtime.cmd

@@ -0,0 +1,20 @@
+@echo off
+rem flutter-app-runtime: PreInvocation handler for Windows (Antigravity).
+rem
+rem Native Windows batch script checking for pending Dart edit flag.
+rem Zero runtime dependencies; executes in < 5ms.
+
+setlocal EnableExtensions EnableDelayedExpansion
+
+set "FLAG_FOUND=0"
+if exist "%TEMP%\flutter-app-runtime.*.pending" set "FLAG_FOUND=1"
+if exist "%TEMP%\flutter-app-runtime.pending" set "FLAG_FOUND=1"
+
+if "!FLAG_FOUND!"=="1" (
+    del /f /q "%TEMP%\flutter-app-runtime.*.pending" 2>nul
+    del /f /q "%TEMP%\flutter-app-runtime.pending" 2>nul
+    echo {"injectSteps":[{"ephemeralMessage":"Dart source changed. Use the flutter-app-runtime skill to push this to the running app: hot_reload for widget/UI or simple logic changes. If no app is running, say so and continue."}]}
+) else (
+    echo {"injectSteps":[]}
+)
+exit /b 0

.claude/settings.json

@@ -0,0 +1,16 @@
+{
+  "hooks": {
+    "PostToolUse": [
+      {
+        "matcher": "Edit|Write",
+        "hooks": [
+          {
+            "type": "command",
+            "command": ".agents/hooks/claude-post-tool-use",
+            "statusMessage": "flutter-app-runtime: mcp__dart__hot_reload"
+          }
+        ]
+      }
+    ]
+  }
+}