Atto (Claude Code plugin)
Hooks-based capture of Claude Code session context for downstream systems (e.g. Testsigma): prompts, tool inputs/outputs (including large reads), subagent boundaries, stop/summary signals, and transcript paths.
Install
This repo is also a marketplace (.claude-plugin/marketplace.json lists atto).
From GitHub (no clone):
claude plugin marketplace add testsigmahq/atto-claude-plugin
claude plugin install atto@Testsigma
From a local clone (for development):
git clone [email protected]:testsigmahq/atto-claude-plugin.git
cd atto-claude-plugin
claude plugin marketplace add ./
claude plugin install atto@Testsigma
claude plugin list should then show atto@Testsigma as enabled.
To update after a code change, bump version in plugins/atto/.claude-plugin/plugin.json and run claude plugin update atto@Testsigma. To remove: claude plugin uninstall atto@Testsigma && claude plugin marketplace remove Testsigma.
Requirements: Python 3.9+ on PATH as python3 (standard on macOS/Linux).
Authenticate
Capture only ships data once you log in:
/atto:login # SSO; stores refresh token in OS keychain. Run once per machine.
Until then hooks run as a no-op — nothing is sent remotely.
Commands
| Command | Purpose |
|---|
/atto:login | Authenticate via SSO. Stores refresh token in OS keychain. |
/atto:logout | Clear local credentials (server-side revoke not yet supported). |
/atto:project list [search] | List accessible Testsigma projects (optional substring filter). |
/atto:project use <project_id> | Pin a project; future events carry it. |
/atto:project current | Show the pinned project. |
/atto:map ticket <KEY> | Link a ticket (Jira / ADO / Linear / ClickUp / GitHub) to the session's workflow. |
/atto:help | Show commands and typical flow. |
Typical flow: /atto:login → /atto:project list then /atto:project use <id> → work on a branch (each session auto-resolves to a workflow) → /atto:map ticket <KEY>.
What gets captured
| Hook | Captured |
|---|
| SessionStart | session_id, cwd, transcript_path, start reason |
| UserPromptSubmit | Raw user prompt |
| Pre/PostToolUse | Tool name, input, and tool_response (e.g. full Read content) |
| PostToolUseFailure | Tool errors |
| Subagent Start/Stop | Subagent id/type; agent transcript path |
| Stop / StopFailure | Last assistant message or API error |
| SessionEnd | Exit reason |
Each hook POSTs to {host}/api/v1/plugin/events (host from /atto:login). Read/Write/Edit file snapshots and large binaries (base64 images, long strings) are also captured and sent as attachments. Nothing is written to a local event log.
Per-session state lives under $CLAUDE_PLUGIN_DATA/sessions/<session_id>/ (override with TESTSIGMA_CONTEXT_DIR) — a session_manifest.json (cwd, transcript, git/ticket grouping signals, Testsigma link) plus attachments/ and context_files/.
Privacy & data controls
Sensitive files are always blocked regardless of settings — .env*, private keys (*.pem/*.key/*.p12/*.jks), credentials*, service-account*.json, .netrc, .pgpass, and anything under ~/.ssh, ~/.gnupg, ~/.aws/credentials, ~/.gcloud/legacy_credentials. Blocked files are sent as {skipped: true, reason: 'sensitive_path'}.
Noise dirs are excluded from capture — files under dependency, build, and VCS directories are never snapshotted or sent. Built-in list:
node_modules bower_components jspm_packages .pnp .yarn
.next .nuxt .svelte-kit .angular .astro .expo .docusaurus
.cache .parcel-cache .turbo .vite .webpack
dist build out .output coverage .nyc_output
.venv venv __pycache__ .mypy_cache .pytest_cache .ruff_cache .tox .eggs *.egg-info
target vendor .gradle .mvn
.terraform .serverless
Pods Carthage DerivedData
.git .hg .svn .idea .vscode
Env-var toggles (accept true/false/yes/no/1/0):
| Variable | Default | Effect |
|---|
TESTSIGMA_CONTEXT_INCLUDE_FILES | true | Send attachment bytes; false = manifest metadata only |
TESTSIGMA_DISABLE_CONTEXT_FILE_SNAPSHOTS | unset | true skips local context_files/ snapshots |
TESTSIGMA_SENSITIVE_PATTERNS | unset | Comma-separated globs added to the sensitive denylist |
TESTSIGMA_EXCLUDE_PATTERNS | unset | Comma-separated globs added to the noise-exclusion list |
Additional tuning knobs (attachment size caps, webhook retries/timeout, blob externalization threshold) are documented inline in scripts/capture_hook.py and scripts/capture_sinks.py.
How it works
