diff --git a/.claude/hooks/post-edit-lint.sh b/.claude/hooks/post-edit-lint.sh
new file mode 100755
index 0000000..b1a972a
--- /dev/null
+++ b/.claude/hooks/post-edit-lint.sh
@@ -0,0 +1,17 @@
+#!/bin/bash
+# PostToolUse (Edit|Write|MultiEdit): record touched file for batch processing in Stop.
+# Must be <50ms. No linting, no formatting, no git calls.
+cd "$CLAUDE_PROJECT_DIR" || exit 0
+
+INPUT=$(cat)
+FILE=$(echo "$INPUT" | jq -r '.tool_input.file_path // empty')
+
+# Only track .py files, skip vendored/generated paths
+if [[ "$FILE" == *.py ]] && [[ "$FILE" != *__pycache__* ]] && [[ "$FILE" != *.egg-info* ]] && [[ "$FILE" != */dist/* ]] && [[ "$FILE" != */build/* ]]; then
+  TRACKER="$CLAUDE_PROJECT_DIR/.claude/tmp/edited-py-files-${CLAUDE_HOOK_SESSION_ID:-default}"
+  mkdir -p "$CLAUDE_PROJECT_DIR/.claude/tmp"
+  echo "$FILE" >> "$TRACKER"
+  sort -u "$TRACKER" -o "$TRACKER"
+fi
+
+exit 0
diff --git a/.claude/hooks/post-stop-validate.sh b/.claude/hooks/post-stop-validate.sh
new file mode 100755
index 0000000..59648b5
--- /dev/null
+++ b/.claude/hooks/post-stop-validate.sh
@@ -0,0 +1,42 @@
+#!/bin/bash
+# Stop: batch-lint touched files, run test suite (~0.13s).
+# Python has no autoformatter configured, so lint + tests only.
+cd "$CLAUDE_PROJECT_DIR" || exit 0
+
+TRACKER="$CLAUDE_PROJECT_DIR/.claude/tmp/edited-py-files-${CLAUDE_HOOK_SESSION_ID:-default}"
+
+ctx=""
+
+# Batch flake8 on tracked files (if any were edited)
+if [[ -f "$TRACKER" ]]; then
+  files=$(cat "$TRACKER")
+  rm -f "$TRACKER"
+
+  if [[ -n "$files" ]]; then
+    lint_out=$(echo "$files" | xargs python3 -m flake8 2>&1) || true
+    offenses=$(echo "$lint_out" | grep -E "^.+:[0-9]+:[0-9]+:" | head -20)
+    if [[ -n "$offenses" ]]; then
+      ctx+="flake8 offenses:\n$offenses\n"
+    fi
+  fi
+fi
+
+# Always run tests - edits to tests or source both matter (~0.13s)
+test_out=$(python3 -m unittest 2>&1)
+test_exit=$?
+if [[ $test_exit -ne 0 ]]; then
+  summary=$(echo "$test_out" | grep -E "^(FAILED|ERROR)" | tail -1)
+  failures=$(echo "$test_out" | grep -E "^(FAIL|ERROR):" | head -10)
+  ctx+="tests failed ($summary):\n$failures\n"
+fi
+
+if [[ -n "$ctx" ]]; then
+  jq -n --arg ctx "$ctx" '{
+    "hookSpecificOutput": {
+      "hookEventName": "Stop",
+      "additionalContext": $ctx
+    }
+  }'
+fi
+
+exit 0
diff --git a/.claude/hooks/session-start-setup.sh b/.claude/hooks/session-start-setup.sh
new file mode 100755
index 0000000..c2e9e9e
--- /dev/null
+++ b/.claude/hooks/session-start-setup.sh
@@ -0,0 +1,42 @@
+#!/bin/bash
+# SessionStart: persist session ID, detect repo state. Must be <1s, no network.
+cd "$CLAUDE_PROJECT_DIR" || exit 0
+
+INPUT=$(cat)
+SESSION_ID=$(echo "$INPUT" | jq -r '.session_id // empty')
+
+# Persist session ID via CLAUDE_ENV_FILE so the edit tracker
+# and stop hook share the same file path
+if [[ -n "$CLAUDE_ENV_FILE" ]] && [[ -n "$SESSION_ID" ]]; then
+  echo "export CLAUDE_HOOK_SESSION_ID='$SESSION_ID'" >> "$CLAUDE_ENV_FILE"
+fi
+
+ctx=""
+
+# Warn about uncommitted changes
+dirty=$(git diff --name-only 2>/dev/null | head -5)
+if [[ -n "$dirty" ]]; then
+  ctx+="Uncommitted changes:\n$dirty\n"
+fi
+
+# Report current branch
+branch=$(git branch --show-current 2>/dev/null)
+if [[ -n "$branch" ]]; then
+  ctx+="Branch: $branch\n"
+fi
+
+# Check if deps are installed
+if ! python3 -c "import chartmogul" 2>/dev/null; then
+  ctx+="WARNING: chartmogul package not installed. Run: pip install -e .[testing]\n"
+fi
+
+if [[ -n "$ctx" ]]; then
+  jq -n --arg ctx "$ctx" '{
+    "hookSpecificOutput": {
+      "hookEventName": "SessionStart",
+      "additionalContext": $ctx
+    }
+  }'
+fi
+
+exit 0
diff --git a/.claude/settings.json b/.claude/settings.json
new file mode 100644
index 0000000..cd37dbd
--- /dev/null
+++ b/.claude/settings.json
@@ -0,0 +1,76 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(pip install:*)",
+      "Bash(python -m unittest:*)",
+      "Bash(python -m pytest:*)",
+      "Bash(flake8:*)",
+      "Bash(coverage:*)",
+      "Bash(python setup.py sdist:*)",
+      "Bash(python --version)",
+      "Bash(git status:*)",
+      "Bash(git log:*)",
+      "Bash(git diff:*)",
+      "Bash(git branch:*)",
+      "Bash(git fetch:*)",
+      "Bash(git stash:*)",
+      "Bash(git checkout:*)",
+      "Bash(git add:*)",
+      "Bash(git commit:*)",
+      "Bash(git push:*)",
+      "Bash(git pull:*)",
+      "Bash(git cherry-pick:*)",
+      "Bash(git reset:*)",
+      "Bash(gh pr view:*)",
+      "Bash(gh pr list:*)",
+      "Bash(gh pr diff:*)",
+      "Bash(gh pr checks:*)",
+      "Bash(gh pr status:*)",
+      "Bash(gh run view:*)",
+      "Bash(gh run list:*)",
+      "Bash(gh run watch:*)",
+      "Bash(gh issue view:*)",
+      "Bash(gh issue list:*)",
+      "Bash(gh release view:*)",
+      "Bash(gh release list:*)",
+      "Bash(gh repo view:*)",
+      "Bash(gh search:*)"
+    ],
+    "deny": [
+      "Read(./.env*)"
+    ]
+  },
+  "hooks": {
+    "SessionStart": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "./.claude/hooks/session-start-setup.sh"
+          }
+        ]
+      }
+    ],
+    "PostToolUse": [
+      {
+        "matcher": "Edit|Write|MultiEdit",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "./.claude/hooks/post-edit-lint.sh"
+          }
+        ]
+      }
+    ],
+    "Stop": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "./.claude/hooks/post-stop-validate.sh"
+          }
+        ]
+      }
+    ]
+  }
+}
diff --git a/.gitignore b/.gitignore
index 3b065ea..af46eb3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -90,4 +90,21 @@ ENV/
 # Rope project settings
 .ropeproject
 
-/.idea
\ No newline at end of file
+/.idea
+
+# AI agent local/ephemeral data (shared config is tracked via negation)
+.claude/*
+!.claude/hooks/
+!.claude/settings.json
+CLAUDE.local.md
+.cursor/chat/
+.cursor/composer/
+.cursor/mcp.json
+.windsurf/
+.cline/
+.continue/
+.junie/
+.aider*
+.codex/
+.codeium/
+.copilot/
\ No newline at end of file
diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 0000000..095f347
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,55 @@
+# ChartMogul Python SDK
+
+Python SDK wrapping the ChartMogul API. Requires Python >= 3.10. Uses `requests` for HTTP with automatic retry and exponential backoff.
+
+## Commands
+
+- `pip install -e .[testing]` - install with test dependencies
+- `python -m unittest` - run full test suite
+- `python -m unittest test.api.test_customer` - run single test module
+- `flake8 ./chartmogul` - lint source code
+- `coverage run -m unittest && coverage xml -i --include='chartmogul/*'` - run tests with coverage
+
+Version is in `chartmogul/version.py`.
+
+## Architecture
+
+The class hierarchy is: `DataObject` (base with dynamic attributes and `__repr__`) -> `Resource` (adds HTTP via `requests`, Promise-based responses, URI template expansion, retry logic) -> Concrete resources (Customer, Invoice, Plan, etc.).
+
+Resources use Marshmallow for serialization. Each resource defines an inner `_Schema(Schema)` class with `@post_load` returning a class instance. Fields use `data_key` to map between Python snake_case and API kebab-case (e.g. `data_key="customer-since"`).
+
+Class-level attributes configure behavior:
+- `_path`: URI template with `{/uuid}` syntax for optional path params
+- `_root_key`: key name for list results (e.g. `"entries"`)
+- `_many`: namedtuple for paginated list responses (entries + cursor + has_more)
+- `_schema`: instantiated Schema with `unknown=EXCLUDE`
+- `_bool_query_params`: list of query params to convert from Python bool to string
+
+HTTP methods are dynamically attached after class definition:
+```python
+Customer.all = Resource._method("all", "get")
+Customer.create = Resource._method("create", "post")
+```
+
+Verb mapping: create->POST, all->GET, retrieve->GET, update->PUT, modify->PATCH, destroy->DELETE.
+
+All API calls return `Promise` objects. Use `.get()` for synchronous access.
+
+Nested objects that don't have their own API endpoint extend `DataObject` instead of `Resource`.
+
+## Testing
+
+Stack: unittest + requests_mock. Tests live in `test/api/test_<resource>.py`.
+
+Test pattern:
+1. Define fixture dicts at module level matching API JSON responses
+2. Use `@requests_mock.mock()` decorator
+3. Register mock URI with expected headers, status, and JSON response
+4. Call the SDK method with `Config("token")` and `.get()` for sync result
+5. Assert call count, request body/params, and deserialized response types
+
+When adding a new resource, create a matching `test/api/test_<resource>.py` following this pattern.
+
+## Code style
+
+snake_case methods, PascalCase classes, UPPER_SNAKE_CASE constants. Leading underscore for internal attributes (`_path`, `_schema`). Linting via flake8 with max line length 100.
diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 100644
index 0000000..43c994c
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1 @@
+@AGENTS.md