<p align="center">
  <strong>Tarn</strong><br>
  <em>API testing that AI agents can write, run, and debug</em>
</p>

<p align="center">
  <a href="https://github.com/NazarKalytiuk/hive/actions/workflows/ci.yml"><img src="https://github.com/NazarKalytiuk/hive/actions/workflows/ci.yml/badge.svg" alt="CI"></a>
  <a href="https://github.com/NazarKalytiuk/hive/blob/main/docs/CONFORMANCE.md"><img src="https://img.shields.io/github/actions/workflow/status/NazarKalytiuk/hive/ci.yml?branch=main&label=conformance" alt="Conformance"></a>
  <a href="https://github.com/NazarKalytiuk/hive/releases/latest"><img src="https://img.shields.io/github/v/release/NazarKalytiuk/hive" alt="Release"></a>
  <a href="https://github.com/NazarKalytiuk/hive/blob/main/LICENSE"><img src="https://img.shields.io/badge/license-MIT-blue" alt="License"></a>
</p>

---

Tests are `.tarn.yaml` files &mdash; YAML in, structured JSON out. Single binary, zero dependencies. Designed for the AI coding workflow: an LLM writes tests, runs `tarn run --format json`, parses results, iterates.

```yaml
name: Health check
steps:
  - name: GET /health
    request:
      method: GET
      url: "{{ env.base_url }}/health"
    assert:
      status: 200
```

```
$ tarn run
 TARN  Running tests/health.tarn.yaml

 ● Health check

   ✓ GET /health (4ms)

 Results: 1 passed (15ms)
```

## Why Tarn?

- **50% fewer tokens** than equivalent TypeScript/Python tests &mdash; faster LLM generation, lower cost
- **Structured JSON output** with request/response on failures &mdash; machines parse it, not regex
- **Single binary** &mdash; `curl | sh` install, runs in any CI, no runtime needed
- **MCP server** &mdash; direct integration with Claude Code, opencode, Cursor, Windsurf
- **Everything you need** &mdash; REST, GraphQL, captures, cookies, multipart, includes, polling, Lua scripting, parallel execution, 7 output formats

## Install

```bash
# One-liner (macOS / Linux)
curl -fsSL https://raw.githubusercontent.com/NazarKalytiuk/hive/main/install.sh | sh

# Install to a custom directory
TARN_INSTALL_DIR="$HOME/.local/bin" curl -fsSL https://raw.githubusercontent.com/NazarKalytiuk/hive/main/install.sh | sh

# Or build/install from source
cargo install --git https://github.com/NazarKalytiuk/hive.git --bin tarn
```

Binaries for **macOS** (Intel & Apple Silicon), **Linux** (amd64 & arm64), and **Windows** (amd64 zip) are published on the [releases page](https://github.com/NazarKalytiuk/hive/releases).
Each release also includes `hive-checksums.txt` for SHA256 verification and a generated `tarn.rb` Homebrew formula artifact.

Container path:
- `ghcr.io/<owner>/tarn:<tag>` from the release workflow

Installer notes:
- `install.sh` verifies the downloaded archive against `hive-checksums.txt`
- `TARN_INSTALL_DIR` controls the install destination
- `HIVE_INSTALL_DIR` is still accepted as a backward-compatible alias during the rename transition
- Manual verification also works with `shasum -a 256 -c hive-checksums.txt`

## Quick Start

```bash
tarn init                              # scaffold tests/health + advanced examples/ templates
# Edit tarn.env.yaml to point at your API, or start one on http://localhost:3000
tarn run                               # run all tests
tarn run tests/health.tarn.yaml        # run the scaffolded test directly
tarn fmt --check                       # verify canonical YAML formatting
tarn run --env staging                 # use staging environment
tarn run --format json                 # structured output for LLM/CI
tarn run --only-failed                 # show only failing tests in the output
tarn run --no-progress                 # disable streaming progress (batch dump at end)
tarn run --watch                       # re-run on file changes
tarn run --parallel                    # run files in parallel
tarn list --tag smoke                  # inspect matching tests without running them
```

## Hello World

Want a fully local demo path from this repo?

```bash
PORT=3000 cargo run -p demo-server &
cargo run -p tarn -- run examples/demo-server/hello-world.tarn.yaml
```

This exercises a local API with no external network dependency.
There are more local scenarios in `examples/demo-server/` for redirects, cookies, forms, error responses, and authenticated CRUD flows.

## Table of Contents

- [Docs Index](#docs-index)
- [Test File Format](#test-file-format)
- [Assertions](#assertions)
- [Variables](#variables)
- [Cookies](#cookies)
- [Form URL-Encoding](#form-url-encoding)
- [Multipart / File Upload](#multipart--file-upload)
- [Includes](#includes)
- [GraphQL](#graphql)
- [Polling](#polling)
- [Lua Scripting](#lua-scripting)
- [CLI Reference](#cli-reference)
- [Output Formats](#output-formats)
- [Performance Testing](#performance-testing)
- [MCP Server](#mcp-server)
- [Claude Code Plugin](#claude-code-plugin)
- [Claude Code Skill](#claude-code-skill)
- [Troubleshooting](#troubleshooting)
- [GitHub Action](#github-action)
- [Configuration](#configuration)
- [Step Options](#step-options)
- [JSON Schema](#json-schema)
- [VS Code Extension](#vs-code-extension)
- [Zed Extension](#zed-extension)
- [Shell Completions](#shell-completions)
- [Development](#development)

## Docs Index

Canonical project docs live in [`docs/INDEX.md`](./docs/INDEX.md).

If you are looking for product direction or comparisons, start with:

- [`docs/TARN_PRODUCT_STRATEGY.md`](./docs/TARN_PRODUCT_STRATEGY.md)
- [`docs/TARN_VS_HURL_COMPARISON.md`](./docs/TARN_VS_HURL_COMPARISON.md)
- [`docs/HURL_MIGRATION.md`](./docs/HURL_MIGRATION.md)
- [`docs/TARN_COMPETITIVENESS_ROADMAP.md`](./docs/TARN_COMPETITIVENESS_ROADMAP.md)

For AI-assisted workflows, see also:
- [Claude Code Plugin](#claude-code-plugin) &mdash; install Tarn as a Claude Code plugin
- [Claude Code Skill](#claude-code-skill) &mdash; structured knowledge for AI agents
- [`docs/MCP_WORKFLOW.md`](./docs/MCP_WORKFLOW.md) &mdash; MCP server usage patterns

For editor integrations:
- [`docs/TARN_LSP.md`](./docs/TARN_LSP.md) &mdash; `tarn-lsp` Language Server (LSP 3.17) for Claude Code, Neovim, Helix, Zed, and other compatible clients. Ships diagnostics, hover, nested schema-aware completion, document symbols, go-to-definition, references, rename, code lens (run test / run step), formatting, code actions (extract env var, capture this field, scaffold assert from last response), quick fix via `tarn::fix_plan`, and a JSONPath evaluator (`tarn.evaluateJsonpath` executeCommand).
- [`docs/VSCODE_EXTENSION.md`](./docs/VSCODE_EXTENSION.md) &mdash; the VS Code extension in [`editors/vscode`](./editors/vscode).
- [`editors/zed/README.md`](./editors/zed/README.md) &mdash; the Zed extension in [`editors/zed`](./editors/zed), published via the [zed-industries/extensions](https://github.com/zed-industries/extensions) registry.

A lightweight static docs site now lives in [`docs/site/index.html`](./docs/site/index.html) and is deployable via GitHub Pages from `.github/workflows/docs-site.yml`.

## Test File Format

Test files use `.tarn.yaml` and can be organized in any directory structure.

### Minimal Test

```yaml
name: Health check
steps:
  - name: GET /health
    request:
      method: GET
      url: "http://localhost:3000/health"
    assert:
      status: 200
```

`request.method` accepts standard verbs and custom tokens such as `PURGE` or `PROPFIND`.

### Full Format

```yaml
version: "1"
name: "User CRUD Operations"
description: "Tests complete user lifecycle"
tags: [crud, users, smoke]

env:
  base_url: "http://localhost:3000/api/v1"

defaults:
  headers:
    Content-Type: "application/json"
  timeout: 5000
  retries: 1

tests:
  create_and_verify:
    description: "Create a user, then verify it exists"
    tags: [smoke]
    steps:
      - name: Create user
        request:
          method: POST
          url: "{{ env.base_url }}/users"
          body:
            name: "Jane Doe"
            email: "jane.{{ $random_hex(6) }}@example.com"
        capture:
          user_id: "$.id"
        assert:
          status: 201
          body:
            "$.name": "Jane Doe"
            "$.id": { type: string, not_empty: true }

      - name: Verify user
        request:
          method: GET
          url: "{{ env.base_url }}/users/{{ capture.user_id }}"
        assert:
          status: 200
          body:
            "$.id": "{{ capture.user_id }}"
```

### Setup and Teardown

`setup` runs once before all tests. `teardown` runs after all tests **even if tests fail**.

```yaml
name: "CRUD with auth"

setup:
  - name: Login
    request:
      method: POST
      url: "{{ env.base_url }}/auth/login"
      body:
        email: "{{ env.admin_email }}"
        password: "{{ env.admin_password }}"
    capture:
      auth_token: "$.token"

teardown:
  - name: Cleanup
    request:
      method: POST
      url: "{{ env.base_url }}/test/cleanup"

tests:
  my_test:
    steps:
      - name: Authenticated request
        request:
          method: GET
          url: "{{ env.base_url }}/users"
          headers:
            Authorization: "Bearer {{ capture.auth_token }}"
        assert:
          status: 200
```

## Assertions

### Status

```yaml
assert:
  status: 200              # exact match
  status: "2xx"            # any 2xx status
  status:                  # set of allowed codes
    in: [200, 201, 204]
  status:                  # range
    gte: 400
    lt: 500
```

### Body (JSONPath)

All body assertions use [JSONPath](https://www.rfc-editor.org/rfc/rfc9535) expressions.

**Equality:**

```yaml
body:
  "$.name": "Alice"              # string
  "$.age": 30                    # number
  "$.active": true               # boolean
  "$.deletedAt": null            # null
  "$.field": { eq: "value" }     # explicit
  "$.field": { not_eq: "bad" }   # inequality
```

**Numeric comparisons:**

```yaml
body:
  "$.age": { gt: 18, lt: 100 }
  "$.count": { gte: 1, lte: 50 }
```

**String assertions:**

```yaml
body:
  "$.email": { contains: "@example.com" }
  "$.id": { starts_with: "usr_", matches: "^usr_[a-z0-9]+$" }
  "$.name": { not_empty: true }
  "$.notes": { empty: true }
  "$.code": { length: 6 }
  "$.msg": { not_contains: "error" }
```

**Format assertions:**

```yaml
body:
  "$.request_id": { is_uuid: true }
  "$.created_at": { is_date: true }
  "$.client_ip": { is_ipv4: true }
  "$.server_ip": { is_ipv6: true }
```

**Integrity assertions:**

```yaml
body:
  "$": { bytes: 15 }                                # raw response body length
  "$.payload": { sha256: "2cf24dba5fb0a30e..." }    # matched value digest
  "$.legacy": { md5: "5d41402abc4b2a76..." }
```

**Type checks:**

```yaml
body:
  "$.name": { type: string }
  "$.tags": { type: array, length_gt: 0 }
  "$.meta": { type: object }
```

**Existence:**

```yaml
body:
  "$.id": { exists: true }
  "$.internal": { exists: false }
```

**Combined (AND logic):**

```yaml
body:
  "$.id": { type: string, not_empty: true, starts_with: "usr_" }
```

### Headers

```yaml
assert:
  headers:
    content-type: "application/json"                    # exact match
    content-type: contains "application/json"           # substring
    x-request-id: matches "^[a-f0-9-]{36}$"            # regex
```

Header names are case-insensitive.

### Duration

```yaml
assert:
  duration: "< 500ms"
  duration: "<= 1s"
```

### Redirects

```yaml
assert:
  redirect:
    url: "https://api.example.com/health"
    count: 2
```

`redirect.url` checks the final response URL after following redirects. `redirect.count` checks how many redirects were actually followed.

## Variables

### Environment Variables

| Priority | Source | Example |
|----------|--------|---------|
| 1 (highest) | CLI `--var` | `--var base_url=http://staging` |
| 2 | Shell env `${VAR}` | `password: "${ADMIN_PASSWORD}"` |
| 3 | `tarn.env.local.yaml` | (gitignored, for secrets) |
| 4 | `tarn.env.{name}.yaml` | `--env staging` loads this |
| 5 | `tarn.env.yaml` | default env file |
| 6 (lowest) | Inline `env:` block | in the test file itself |

### Captures (Chaining)

Capture values from responses to use in subsequent steps. Captured values preserve their original JSON types (numbers stay numbers, booleans stay booleans).

```yaml
steps:
  - name: Login
    request:
      method: POST
      url: "{{ env.base_url }}/auth/login"
      body:
        email: "admin@example.com"
        password: "password123"
    capture:
      token: "$.token"              # JSONPath capture from body
      user_id: "$.user.id"          # nested path

  - name: Use token
    request:
      method: GET
      url: "{{ env.base_url }}/users"
      headers:
        Authorization: "Bearer {{ capture.token }}"
```

**Header capture** &mdash; capture values from response headers with optional regex:

```yaml
capture:
  session_token:
    header: "set-cookie"
    regex: "session_token=([^;]+)"
  request_id:
    header: "x-request-id"
```

**Cookie capture** &mdash; capture a response cookie by name from `Set-Cookie`:

```yaml
capture:
  session_cookie:
    cookie: "session"
```

**Status capture** &mdash; capture the HTTP status code as a number:

```yaml
capture:
  status_code:
    status: true
```

**Final URL capture** &mdash; capture the final response URL after redirects:

```yaml
capture:
  final_url:
    url: true
```

**JSONPath with regex** &mdash; extract a sub-match from a body field:

```yaml
capture:
  user_id:
    jsonpath: "$.message"
    regex: "ID: (\\w+)"
```

**Whole-body regex** &mdash; extract from the full response body string:

```yaml
capture:
  body_word:
    body: true
    regex: "plain (text)"
```

**Transform-lite in interpolation** &mdash; reshape captured arrays and collections without dropping into Lua:

```yaml
request:
  form:
    first_tag: "{{ capture.tags | first }}"
    last_tag: "{{ capture.tags | last }}"
    tag_count: "{{ capture.tags | count }}"
    joined_tags: "{{ capture.tags | join('|') }}"
    words: "{{ capture.message | split(' ') | count }}"
    normalized: "{{ capture.message | replace(' response', '') }}"
    status_code: "{{ capture.status_text | to_int }}"
    payload: "{{ capture.user | to_string }}"
```

`first` and `last` expect arrays. `count` works on arrays, objects, and strings. `join(...)` joins array items after converting each item to its string form. `split(...)` and `replace(..., ...)` operate on strings. `to_int` parses integer strings, and `to_string` stringifies any captured value.

### Built-in Functions

```yaml
"{{ $uuid }}"                    # UUID v4
"{{ $random_hex(8) }}"           # 8-char hex string
"{{ $random_int(1, 100) }}"      # random integer in range
"{{ $timestamp }}"               # unix timestamp
"{{ $now_iso }}"                 # ISO 8601 datetime
```

## Cookies

Tarn automatically captures `Set-Cookie` headers and sends stored cookies on subsequent requests. This is enabled by default.

```yaml
name: Auth flow
steps:
  - name: Login
    request:
      method: POST
      url: "{{ env.base_url }}/auth/login"
      body:
        email: "admin@test.com"
        password: "secret"
    # Set-Cookie from response is automatically stored
    assert:
      status: 200

  - name: Access protected resource
    request:
      method: GET
      url: "{{ env.base_url }}/profile"
    # Cookie header is automatically sent
    assert:
      status: 200
```

Disable automatic cookies per file:

```yaml
cookies: "off"
```

Or reset the default jar between named tests in a file so IDE subset runs and flaky suites never see session state from a prior test. Setup and teardown still share the file-level jar. Named jars (multi-user scenarios) are untouched.

```yaml
cookies: "per-test"
```

The `--cookie-jar-per-test` CLI flag forces per-test isolation regardless of the file's declared mode (except when the file sets `cookies: "off"`, which always wins).

## Auth

Tarn supports first-class `bearer` and `basic` auth helpers, while keeping explicit `Authorization` headers as the escape hatch:

```yaml
request:
  auth:
    bearer: "{{ env.token }}"
  headers:
    X-API-Key: "{{ env.api_key }}"
```

Basic auth:

```yaml
request:
  auth:
    basic:
      username: "{{ env.username }}"
      password: "{{ env.password }}"
```

You can also set `defaults.auth` once per file. If `headers.Authorization` is already present, Tarn leaves it unchanged.

### Step-Level Cookie Control

Use `cookies: false` on a step to bypass the cookie jar entirely. No cookies are sent and no `Set-Cookie` headers are captured:

```yaml
steps:
  - name: Login
    request:
      method: POST
      url: "{{ env.base_url }}/auth/login"
      body:
        email: "admin@test.com"
        password: "secret"
    assert:
      status: 200

  - name: Test unauthenticated access
    cookies: false
    request:
      method: GET
      url: "{{ env.base_url }}/profile"
    assert:
      status: 401
```

### Named Cookie Jars

For multi-user scenarios, use named jars to maintain separate cookie sessions:

```yaml
steps:
  - name: Login as admin
    cookies: "admin"
    request:
      method: POST
      url: "{{ env.base_url }}/auth/login"
      body:
        email: "admin@test.com"
        password: "secret"

  - name: Login as viewer
    cookies: "viewer"
    request:
      method: POST
      url: "{{ env.base_url }}/auth/login"
      body:
        email: "viewer@test.com"
        password: "secret"

  - name: Admin can manage users
    cookies: "admin"
    request:
      method: GET
      url: "{{ env.base_url }}/admin/users"
    assert:
      status: 200

  - name: Viewer cannot manage users
    cookies: "viewer"
    request:
      method: GET
      url: "{{ env.base_url }}/admin/users"
    assert:
      status: 403
```

Each named jar is independent &mdash; cookies captured in `"admin"` are never sent with `"viewer"` requests. Steps without a `cookies:` field (or with `cookies: true`) use the default jar.

### Persist Cookie Jars

Use `tarn run --cookie-jar .tarn-cookies.json` to preload jars from disk and write back the updated state after the run. The file stores named jars too, so multi-user sessions can survive across runs.

`--cookie-jar` currently works only with sequential execution. Combine it with `--parallel` only after jar sharing becomes deterministic.

### CSRF Protection

When the cookie jar sends cookies automatically, frameworks with CSRF protection (e.g., Better Auth) may reject requests that lack an `Origin` header. Add it to `defaults` to fix:

```yaml
defaults:
  headers:
    Content-Type: "application/json"
    Origin: "http://localhost:3000"
```

If your app derives the expected origin from the request URL, set `Origin` to match `env.base_url`:

```yaml
defaults:
  headers:
    Origin: "{{ env.base_url }}"
```

## Form URL-Encoding

Send `application/x-www-form-urlencoded` payloads with `form:`:

```yaml
steps:
  - name: Login form
    request:
      method: POST
      url: "{{ env.base_url }}/auth/login"
      form:
        email: "user@example.com"
        password: "{{ env.password }}"
    assert:
      status: 200
```

Tarn URL-encodes the fields and auto-sets `Content-Type: application/x-www-form-urlencoded` unless you override it explicitly.

> Note: `form` cannot be combined with `body`, `graphql`, or `multipart` on the same step.

## Multipart / File Upload

Send multipart form data for file uploads using the `multipart:` field:

```yaml
steps:
  - name: Upload photo
    request:
      method: POST
      url: "{{ env.base_url }}/api/photos"
      headers:
        Authorization: "Bearer {{ capture.token }}"
      multipart:
        fields:
          - name: "title"
            value: "My Photo"
          - name: "description"
            value: "A test upload"
        files:
          - name: "photo"
            path: "./fixtures/test.jpg"
            content_type: "image/jpeg"
          - name: "thumbnail"
            path: "./fixtures/thumb.png"
            filename: "custom-name.png"
    assert:
      status: 201
```

> Note: `multipart` cannot be combined with `body`, `form`, or `graphql` on the same step.

## Includes

Reuse shared step sequences across test files with `include:` directives:

```yaml
name: User tests
setup:
  - include: ./shared/auth-setup.tarn.yaml
steps:
  - name: Get users
    request:
      method: GET
      url: "{{ env.base_url }}/users"
    assert:
      status: 200
```

The included file's `setup` and `steps` are inlined at the include point. Includes work in `setup`, `teardown`, `steps`, and `tests.*.steps`. Circular includes are detected and rejected.

Includes also support lightweight parametrization and deep overrides for reusable step packs:

```yaml
steps:
  - include: ./shared/user-pack.tarn.yaml
    with:
      tenant: "acme"
      user_id: 42
    override:
      request:
        headers:
          X-Tenant: "acme"
```

Inside the included file, use `{{ params.tenant }}` and `{{ params.user_id }}` placeholders.

## GraphQL

Native GraphQL support with the `graphql:` block. Automatically sets `Content-Type: application/json` and constructs the standard GraphQL JSON body.

```yaml
steps:
  - name: Get user
    request:
      method: POST
      url: "{{ env.base_url }}/graphql"
      graphql:
        query: |
          query GetUser($id: ID!) {
            user(id: $id) {
              id
              name
              email
            }
          }
        variables:
          id: "{{ capture.user_id }}"
        operation_name: "GetUser"
    assert:
      status: 200
      body:
        "$.data.user.name": "Alice"
        "$.errors": { exists: false }
```

## Polling

Re-execute a step until a condition is met. Useful for async workflows where you need to wait for a state change.

```yaml
steps:
  - name: Create export
    request:
      method: POST
      url: "{{ env.base_url }}/exports"
    capture:
      export_id: "$.id"
    assert:
      status: 202

  - name: Wait for completion
    request:
      method: GET
      url: "{{ env.base_url }}/exports/{{ capture.export_id }}"
    poll:
      until:
        body:
          "$.status": "completed"
      interval: "2s"
      max_attempts: 15
    assert:
      status: 200
      body:
        "$.status": "completed"
```

`poll.until` uses the same assertion syntax. The step re-executes every `interval` until the `until` condition passes or `max_attempts` is reached.

## Lua Scripting

For logic that goes beyond declarative assertions, use inline Lua scripts. Scripts run after the HTTP response is received and have access to `response` and `captures`.

```yaml
steps:
  - name: Validate complex logic
    request:
      method: GET
      url: "{{ env.base_url }}/users"
    script: |
      -- Access response
      assert(response.status == 200, "Expected 200")

      -- Work with the response body (Lua table)
      local users = response.body.users
      assert(#users > 0, "Expected at least one user")

      -- Cross-field validation
      for _, user in ipairs(users) do
        assert(user.email:find("@"), "Invalid email for " .. user.name)
      end

      -- Set captures for subsequent steps
      captures.first_user_id = users[1].id
    assert:
      status: 200
```

**Available in Lua:**
- `response.status` &mdash; HTTP status code
- `response.headers` &mdash; response headers table
- `response.body` &mdash; response body as Lua table (auto-parsed from JSON)
- `captures` &mdash; read/write captures table
- `assert(condition, message)` &mdash; assertion (collected, not thrown)
- `json.decode(string)` &mdash; parse a JSON string into a Lua table
- `json.encode(value)` &mdash; serialize a Lua value to a JSON string

## CLI Reference

```
tarn run [PATH] [OPTIONS]          Run test files
tarn bench <PATH> [OPTIONS]        Benchmark a step
tarn validate [PATH] [--format]    Validate YAML (--format human|json)
tarn fmt [PATH] [--check]          Normalize Tarn YAML
tarn list                          List all tests
tarn summary <PATH|->              Re-render a prior JSON report (llm/compact)
tarn import-hurl <PATH>            Convert common-case Hurl files to Tarn
tarn init                          Scaffold a new project
tarn update                        Update to the latest version
tarn update --check                Check for updates without installing
tarn completions <SHELL>           Generate shell completions
```

### `tarn run` Options

| Flag | Description |
|------|-------------|
| `--format <FORMAT>` | Repeatable. Supports `human`, `json`, `junit`, `tap`, `html`, `curl`, `curl-all`, `compact`, `llm`, or `FORMAT=PATH`. When omitted, tarn picks `human` on a TTY and `llm` when stdout is piped. |
| `--json-mode <MODE>` | For JSON outputs: `verbose` (default) or `compact` |
| `--tag <TAGS>` | Filter by tag (comma-separated, AND logic) |
| `--select <FILE[::TEST[::STEP]]>` | Narrow execution to specific files, tests, or steps (repeatable; ANDs with `--tag`) |
| `--var <KEY=VALUE>` | Override env variables (repeatable) |
| `--env <NAME>` | Load `tarn.env.{name}.yaml` |
| `-v, --verbose` | Print full request/response for every step in the streaming progress |
| `--verbose-responses` | Include response body, headers, and captures in the report for every step (not just failed ones). Applies to `json`, `html`, `compact`, and `llm`. |
| `--max-body <BYTES>` | Cap the response body size embedded when `--verbose-responses` or step-level `debug: true` is active (default 8192). Larger bodies are truncated with a `"...<truncated: N bytes>"` marker. |
| `--only-failed` | Show only failed tests and steps (summary counts stay accurate). `--only-fails` is accepted as an alias. |
| `--no-progress` | Disable streaming progress output; print the final report in one batch |
| `--ndjson` | Stream machine-readable NDJSON events to stdout (for editor integrations, MCP, structured CI) |
| `--dry-run` | Show interpolated requests without sending |
| `-w, --watch` | Re-run on file changes |
| `--parallel` | Run test files in parallel (see [Parallel Execution](#parallel-execution)) |
| `-j, --jobs <N>` | Number of parallel workers (default: CPU count) |
| `--no-parallel-warning` | Suppress the `--parallel` isolation warning (use in CI after the suite is audited) |

### Examples

```bash
tarn run                                        # all tests
tarn run tests/auth.tarn.yaml                   # specific file
tarn run --tag smoke                            # filter by tag
tarn run --env staging                          # staging env
tarn run --var base_url=http://localhost:8080    # override var
tarn run --format json                          # JSON for LLM/CI
tarn run --format json --json-mode compact     # smaller JSON for automation loops
tarn run --format html                          # HTML dashboard
tarn run --format curl                          # failed requests as curl
tarn run --format curl-all=reports/replay.sh    # full suite replay script
tarn run --format human --format json=reports/run.json --format junit=reports/junit.xml
tarn run --format human,json=reports/run.json   # comma-separated also works
tarn run --watch                                # re-run on changes
tarn run --parallel --jobs 4                    # parallel execution
tarn run -v                                     # verbose
tarn run --dry-run                              # preview only
tarn run --only-failed                          # hide passing tests, show failures only
tarn run --no-progress                          # disable streaming, batch dump at end
tarn run --only-failed --format json            # CI-friendly: only failed items in JSON
tarn run --select tests/users.tarn.yaml::login   # run just the "login" test in one file
tarn run --select tests/users.tarn.yaml::login::2   # run just step index 2 of login
tarn run --select "a.tarn.yaml::login" --select "b.tarn.yaml::checkout"  # union across files
tarn fmt tests/                                  # rewrite a directory in place
tarn fmt tests/auth.tarn.yaml --check            # CI-style formatting check
```

### LLM-friendly output (`--format llm`)

`--format llm` emits a grep-friendly summary line followed by only the
failed steps, each expanded with request, response, and the assertion
that failed. It strips ANSI colors automatically when stdout is piped
and omits boxed/colored headers entirely.

```bash
tarn run tests/                    # emits llm format when piped (auto-selected)
tarn run tests/ --format llm       # force llm format explicitly
tarn summary .tarn/last-run.json   # re-summarize a prior run as llm
```

`tarn summary` reads a prior JSON report (`.tarn/last-run.json` is
written after every run, or whatever you produced with `tarn run
--format json`) and re-renders it as the llm format without re-running
the tests. Use `-` to stream from stdin:

```bash
tarn run tests/ --format json > run.json
tarn summary run.json              # render run.json as llm
cat run.json | tarn summary -      # same, piped
tarn summary run.json --format compact  # render as compact instead
```

The sibling `--format compact` format is a shorter human-ish variant
for quick console scanning — one line per file, inline expansion of
failed tests, and a trailing `HTTP 500: 3 | JSONPath mismatch: 18`
tally of failure categories. Both formats strip colors in non-TTY
output.

### Structured Validation (`tarn validate --format json`)

`tarn validate --format json` emits a machine-readable report so editors and CI can surface parse errors inline. The schema:

```json
{
  "files": [
    {
      "file": "tests/users.tarn.yaml",
      "valid": false,
      "errors": [
        { "message": "found unexpected end of stream ...", "line": 14, "column": 7 }
      ]
    }
  ]
}
```

- `line` and `column` are populated for YAML syntax errors (derived from `serde_yaml`'s error location).
- Parser semantic errors (unknown fields, shape mismatches) surface `message` only when the underlying error does not carry a location.
- Exit code is `0` when every file is valid, `2` otherwise. The human format (`--format human`, the default) is unchanged.

### Environment Discovery (`tarn env --json`)

`tarn env --json` prints the project's named environments in a stable schema so editors can populate pickers and previews:

```json
{
  "project_root": "/path/to/project",
  "default_env_file": "tarn.env.yaml",
  "environments": [
    {
      "name": "staging",
      "source_file": "tarn.env.staging.yaml",
      "vars": {
        "base_url": "https://staging.example.com",
        "api_token": "***"
      }
    }
  ]
}
```

Inline `vars` from `tarn.config.yaml` are redacted when the key matches `redaction.env` (case-insensitive), so `tarn env --json` never prints literal secrets. Environments are sorted alphabetically by name.

### Parallel Execution

`tarn run --parallel` dispatches test files across multiple rayon workers. The parallelism unit is the **file**: all setup, teardown, captures, and cookie jars stay file-scoped, but files may execute concurrently. That's unsafe when tests share mutable state (DB rows, singletons, filesystem fixtures, rate-limited upstreams). Tarn ships three isolation primitives to close the gap:

- **`serial_only: true`** on a `TestFile` (top-level) or on an individual named test under `tests:` pins the file onto a single worker that runs sequentially after every parallel bucket completes. A single `serial_only` test escalates its whole file to the serial bucket so per-file isolation (setup/teardown, cookie jars) stays intact.
- **`group: "postgres"`** on a `TestFile` buckets files by resource name. Files sharing a group run on the same worker (serialized within the group), while different groups run in parallel. Use this to serialize "all the postgres tests" without giving up concurrency across unrelated resources.
- **`parallel_opt_in: true`** in `tarn.config.yaml` silences the startup warning once the suite has been audited. While this flag is absent (or set to `false`), running `tarn run --parallel` emits a one-line stderr warning: `warning: --parallel enabled without parallel_opt_in: true in tarn.config.yaml. Tests without serial_only may share state.` Pass `--no-parallel-warning` on the CLI to suppress it for one-off CI runs.

```yaml
# tarn.config.yaml
parallel: true
parallel_opt_in: true  # opts in once the suite has been audited

# any .tarn.yaml that shares DB state
name: Users CRUD
serial_only: true

# or bucket by resource so postgres tests serialize while S3 tests run in parallel
name: Postgres integration
group: postgres
```

### Streaming Progress

By default `tarn run` streams per-test output as each test finishes instead of dumping everything at the end. The behaviour adapts to how stdout is used:

- **Sequential (default)** &mdash; each test is printed the moment it completes. You see progress live as the suite runs.
- **Parallel (`--parallel`)** &mdash; each file is printed atomically when it completes, so output from concurrently running files never interleaves.
- **Stdout is `human`** &mdash; streaming writes directly to stdout and the final emit prints only the summary line (no duplication).
- **Stdout is a structured format** (`json`, `junit`, `tap`, `html`, `curl`) &mdash; progress streams to stderr so stdout stays pure and parseable.

Pass `--no-progress` to disable streaming entirely and restore the old "batch at end" behaviour (useful for CI logs that already capture per-line timestamps).

### NDJSON Streaming (`--ndjson`)

`tarn run --ndjson` streams machine-readable events to stdout, one JSON object per line. Designed for editor integrations (live Test Explorer updates), MCP clients, and CI pipelines that want structured progress without post-processing the final report.

Event types, in order:

- `file_started` &mdash; a test file has begun running
- `step_finished` &mdash; one step finished (with `phase: "setup" | "test" | "teardown"`). On failure, also carries `failure_category`, `error_code`, and `assertion_failures[]`
- `test_finished` &mdash; a named test finished, with per-step counts
- `file_finished` &mdash; a file finished, with its own summary
- `done` &mdash; emitted once at the very end, carrying the aggregated summary for the whole run

`--ndjson` composes with file-bound `--format` targets, so you can stream live progress **and** write a final report at the same time:

```bash
# Stream NDJSON to stdout, final JSON report to disk
tarn run --ndjson --format json=reports/run.json | jq '.event'

# Pure NDJSON (default human output is silently dropped on stdout)
tarn run --ndjson
```

`--ndjson` collides with any other structured format writing to stdout (e.g. `--format json`). Route the other format to a file, or pick one of the two streams.

In parallel mode (`--parallel`), each file's event stream is emitted atomically on `file_finished` so events from concurrently running files never interleave.

`--only-failed` works with both streaming and batch modes: passing tests and steps are omitted everywhere, but the final summary still reports total passed/failed counts.

### Exit Codes

| Code | Meaning |
|------|---------|
| `0` | All tests passed |
| `1` | One or more tests failed |
| `2` | Configuration/parse error |
| `3` | Runtime error (network, timeout, script) |

## Output Formats

You can emit multiple formats in one run. Keep at most one bare non-HTML format for stdout and send the rest to files:

```bash
tarn run \
  --format human \
  --format json=reports/run.json \
  --format junit=reports/junit.xml \
  --format html=reports/run.html \
  --format curl=reports/failures.sh \
  --format curl-all=reports/replay.sh
```

### JSON (`--format json`)

Structured JSON with versioned schema. Key design:
- `schema_version: 1` for forward compatibility
- Full request/response included **only for failed steps**
- `failure_category` on failures: `assertion_failed`, `connection_error`, `timeout`, `parse_error`, `capture_error`, `unresolved_template`
- Stable `error_code` and `remediation_hints` are included on failed steps for automation-friendly diagnostics
- `response_status` and `response_summary` on all executed steps (passed and failed) &mdash; AI agents can see what a passed step returned
- `captures_set` on steps listing which capture variables were set; `captures` map on test groups showing all resolved values
- `--json-mode compact` keeps the same top-level schema but drops passed assertion details and truncates response bodies to ~200 chars
- Sensitive headers are redacted by default and can be customized per file with top-level `redaction:`
- `request` is present for failed executed steps; `response` is omitted for connection/setup failures where no response exists

Schema files:
- test files: `schemas/v1/testfile.json`
- JSON report output: `schemas/v1/report.json`

```json
{
  "schema_version": 1,
  "summary": { "status": "FAILED", "steps": { "total": 5, "passed": 4, "failed": 1 } },
  "files": [{
    "tests": [{
      "captures": { "user_id": "usr_123", "token": "abc" },
      "steps": [{
        "name": "Create user",
        "status": "PASSED",
        "response_status": 201,
        "response_summary": "201 Created: Object{3 keys}",
        "captures_set": ["user_id"]
      }, {
        "name": "Update user",
        "status": "FAILED",
        "response_status": 400,
        "response_summary": "400 Bad Request: name required",
        "failure_category": "assertion_failed",
        "error_code": "assertion_mismatch",
        "remediation_hints": ["..."],
        "assertions": {
          "failures": [{ "assertion": "status", "expected": "201", "actual": "400", "message": "..." }]
        },
        "request": { "method": "POST", "url": "..." },
        "response": { "status": 400, "body": { "error": "name required" } }
      }]
    }]
  }]
}
```

### Curl (`--format curl`, `--format curl-all`)

`curl` exports only failed executed requests. `curl-all` exports every executed request in run order, including setup and teardown.

```bash
tarn run --format human --format curl=reports/failures.sh
tarn run --format curl-all=reports/replay.sh
```

Also supports: **Human** (colored terminal), **JUnit XML**, **TAP**, **HTML** (self-contained dashboard).

Example:

```yaml
redaction:
  headers:
    - authorization
    - x-session-token
  env:
    - api_token
  captures:
    - session_token
  replacement: "[redacted]"
```

## Performance Testing

Reuses your existing test files for benchmarking.

```bash
tarn bench tests/health.tarn.yaml -n 1000 -c 50
tarn bench tests/health.tarn.yaml -n 500 -c 25 --ramp-up 5s
tarn bench tests/health.tarn.yaml --format json     # for CI thresholds
tarn bench tests/health.tarn.yaml --format csv --export json=reports/bench.json
tarn bench tests/health.tarn.yaml --fail-under-rps 200 --fail-above-p95-ms 80
```

```
 TARN BENCH  GET http://localhost:3000/health — 200 requests, 20 concurrent

  Requests:      200 total, 200 ok, 0 failed (0.0%)
  Throughput:    3125.0 req/s

  Latency:
    min        1ms
    p50        2ms
    p95        43ms
    p99        45ms
    max        45ms
```

## MCP Server

Tarn includes an MCP (Model Context Protocol) server for direct integration with AI coding tools.

### Setup

The simplest approach is a project-level `.mcp.json` in the repo root (works with Claude Code and other MCP-compatible tools):

```json
{
  "mcpServers": {
    "tarn": {
      "command": "tarn-mcp",
      "args": []
    }
  }
}
```

Alternatively, add to your Claude Code project settings (`.claude/settings.json`):

```json
{
  "mcpServers": {
    "tarn": {
      "command": "tarn-mcp",
      "args": []
    }
  }
}
```

For Cursor, add to `.cursor/mcp.json`:

```json
{
  "mcpServers": {
    "tarn": {
      "command": "tarn-mcp"
    }
  }
}
```

### Available Tools

| Tool | Description |
|------|-------------|
| `tarn_run` | Run tests, returns structured JSON results |
| `tarn_validate` | Validate YAML syntax without executing |
| `tarn_list` | List all tests and their steps |
| `tarn_fix_plan` | Analyze a Tarn JSON report and return prioritized next actions |

The MCP server lets your AI agent write `.tarn.yaml` tests, execute them, parse structured results, and iterate &mdash; all without leaving the editor.

Typical agent loop:

1. `tarn_list` to discover tests and steps
2. `tarn_validate` after generating YAML
3. `tarn_run` to get structured failures
4. `tarn_fix_plan` to turn the latest report into machine-friendly next steps
5. inspect `failure_category`, `error_code`, `assertions.failures`, and optional `request`/`response`
6. patch the test or application code
7. rerun until summary status is `PASSED`

See [docs/MCP_WORKFLOW.md](./docs/MCP_WORKFLOW.md), [docs/AI_WORKFLOW_DEMO.md](./docs/AI_WORKFLOW_DEMO.md), and [docs/CONFORMANCE.md](./docs/CONFORMANCE.md).

## Claude Code Plugin

Tarn ships **two** Claude Code plugins from a single marketplace. They solve different problems and can be installed independently or together:

1. **`tarn`** (top-level `plugin/`) &mdash; bundles the `tarn-mcp` MCP server and the `tarn-api-testing` skill. Gives your agent structured API testing capabilities: `tarn_run`, `tarn_validate`, `tarn_list`, `tarn_fix_plan`.
2. **`tarn-lsp`** ([`editors/claude-code/tarn-lsp-plugin/`](./editors/claude-code/tarn-lsp-plugin/)) &mdash; registers the `tarn-lsp` language server with Claude Code's LSP plugin system so you get full `.tarn.yaml` language intelligence (diagnostics, hover, completion, code lens, code actions, quick fix, rename, go-to-definition, and the JSONPath evaluator) while editing in Claude Code.

Both plugins live in the same marketplace (the repo root `.claude-plugin/marketplace.json`). Register it once, then install either or both:

```bash
# 1. Register the marketplace (once)
claude plugin marketplace add NazarKalytiuk/hive

# 2a. Install the MCP + skill plugin
claude plugin install tarn@tarn

# 2b. Install the LSP plugin (project scope — see caveat below)
claude plugin install tarn-lsp@tarn --scope project
```

After installing `tarn`, Claude Code can write, run, and debug `.tarn.yaml` tests directly via the bundled MCP server and skill. See [MCP Server](#mcp-server) and [Claude Code Skill](#claude-code-skill) for what each component provides.

### `tarn` &mdash; MCP + skill plugin

#### Manual setup

If you prefer manual configuration, add the MCP server to a project-level `.mcp.json` in the repo root:

```json
{
  "mcpServers": {
    "tarn": {
      "command": "tarn-mcp",
      "args": []
    }
  }
}
```

This is equivalent to configuring the MCP server in `.claude/settings.json` but is portable across editors and tools that support MCP.

#### Plugin metadata

The `tarn` plugin configuration lives in `.claude-plugin/`:

- **`plugin.json`** &mdash; name, version, description, author, and repository URL
- **`marketplace.json`** &mdash; marketplace listing with owner info and the plugin registry (both `tarn` and `tarn-lsp`)

### `tarn-lsp` &mdash; language server plugin

Separate install from the MCP plugin above (same marketplace though). This one registers `tarn-lsp` for `.tarn.yaml` / `.yaml` / `.yml` via Claude Code's LSP plugin system so every feature documented in [`docs/TARN_LSP.md`](./docs/TARN_LSP.md) is available while you edit in Claude Code.

**Prerequisites:**

- Claude Code **2.0.74+**
- `tarn-lsp` binary available on `$PATH` &mdash; install with `cargo install --path tarn-lsp` from this repo, or symlink a workspace build (`ln -s $(pwd)/target/release/tarn-lsp /usr/local/bin/tarn-lsp`)

**Install** (from inside a Claude Code session):

```
/plugin marketplace add NazarKalytiuk/hive
/plugin install tarn-lsp@tarn --scope project
/reload-plugins
```

Already registered the marketplace for the `tarn` plugin? Skip the `add` line &mdash; both plugins share the same marketplace now. Substitute `/absolute/path/to/repo` for `NazarKalytiuk/hive` if you want to install from a local checkout instead.

**Compound-extension caveat:** Claude Code's LSP plugin system only supports simple file extensions, so the `tarn-lsp` plugin claims **all** `.yaml` and `.yml` files in any project it is installed in (not just `.tarn.yaml`). Always install with `--scope project` in Tarn-focused repos only &mdash; do not install it globally if you also edit unrelated YAML in Claude Code.

See [`editors/claude-code/tarn-lsp-plugin/README.md`](./editors/claude-code/tarn-lsp-plugin/README.md) for the full spec, troubleshooting, and the list of supported LSP features.

## opencode

[opencode](https://opencode.ai) supports Tarn through config only — there is no plugin installer or marketplace, so integration is three files checked into your repo:

```
your-repo/
├── opencode.jsonc                          # MCP + LSP registration
└── .opencode/skills/tarn-api-testing/      # agent-visible skill
    └── SKILL.md
```

This repo ships exactly this layout at [`opencode.jsonc`](./opencode.jsonc) and [`.opencode/skills/tarn-api-testing/`](./.opencode/skills/tarn-api-testing/) (the skill is a symlink to the canonical [`plugin/skills/tarn-api-testing/`](./plugin/skills/tarn-api-testing/)). Clone the repo, install `tarn-mcp` and `tarn-lsp` on `$PATH`, run `opencode` inside — MCP tools, `.tarn.yaml` diagnostics/hover/completion, and the `tarn-api-testing` skill light up immediately.

To mirror the setup in your own repo, copy the snippet from [`editors/opencode/opencode.example.jsonc`](./editors/opencode/opencode.example.jsonc) into your own `opencode.jsonc`:

```jsonc
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "tarn": { "type": "local", "command": ["tarn-mcp"], "enabled": true }
  },
  "lsp": {
    "tarn": { "command": ["tarn-lsp"], "extensions": [".yaml", ".yml"] }
  }
}
```

**Compound-extension caveat:** opencode's LSP matcher uses `path.parse(file).ext`, so the `tarn` LSP entry claims every `.yaml` / `.yml` file in the workspace (not just `.tarn.yaml`) — the same limitation as Claude Code. Keep this in project-level `opencode.jsonc`, not your global config.

See [`editors/opencode/README.md`](./editors/opencode/README.md) for prerequisites, troubleshooting, and the full skill-install flow.

## Claude Code Skill

The `skills/tarn-api-testing/` directory contains a Claude Code skill that teaches AI agents how to write, run, debug, and iterate on Tarn tests. The skill is automatically loaded when an agent encounters API testing tasks.

**What the skill provides:**

- Core workflow (write &rarr; validate &rarr; run &rarr; inspect &rarr; fix &rarr; rerun)
- Complete command reference with all CLI flags
- Test file format with minimal and full-featured examples
- Environment variable resolution chain
- Capture formats (JSONPath, headers, cookies, URL, status, body)
- Assertion operator quick reference
- JSON output schema and failure category taxonomy
- Diagnosis loop for structured failure triage
- MCP integration setup for Claude Code, opencode, Cursor, and Windsurf

**Reference docs** in `skills/tarn-api-testing/references/`:

| File | Contents |
|------|----------|
| `yaml-format.md` | Complete `.tarn.yaml` schema with all properties |
| `assertion-reference.md` | Every assertion operator with examples |
| `json-output.md` | Structured JSON report schema and diagnosis algorithm |
| `mcp-integration.md` | MCP server setup and tool reference |

The skill triggers on keywords like "API test", "tarn", ".tarn.yaml", "test this endpoint", "smoke test", and "integration test for API".

## Troubleshooting

See [`docs/TROUBLESHOOTING.md`](./docs/TROUBLESHOOTING.md) for the full
guide, including the NestJS-style [route ordering](./docs/TROUBLESHOOTING.md#route-ordering-nestjs-and-similar)
trap that Tarn flags automatically.

Common cases:

- `connection_error`: server is down, wrong host/port, DNS issue, TLS/connect failure
- `timeout`: step timed out before receiving a complete response
- `assertion_failed`: request succeeded, but status/header/body/duration check failed
- `capture_error`: the step passed assertions, but extraction failed afterward
- `parse_error`: invalid YAML, invalid JSONPath, or invalid config surface

Agent diagnosis loop:

1. run `tarn validate` first for syntax/config errors
2. run `tarn run --format json`
3. read `failure_category` before reading the message text
4. if a failed `status` assertion carries `hints`, follow the first hint before second-guessing the test
5. if `response` exists, inspect it before editing assertions
6. if `request.url` still contains `{{ ... }}`, fix env/capture interpolation before retrying

Non-JSON bodies:

- Tarn preserves plain text / HTML responses as JSON strings in the structured report
- use `body: { "$": "plain text response" }` to assert the whole root string when needed

## Intentional Gaps

Tarn does not aim for full Hurl parity. The main intentionally unclosed gaps are:

- XPath / HTML assertions and captures
- full Hurl-style filter DSL
- exotic auth and libcurl-specific transport features
- OpenAPI-first generation workflows

## GitHub Action

```yaml
- uses: NazarKalytiuk/hive@v1
  with:
    path: tests/
    format: junit
    env: staging
```

**Inputs:**

| Input | Default | Description |
|-------|---------|-------------|
| `path` | `tests` | Test file or directory |
| `format` | `human` | Output format |
| `env` | &mdash; | Environment name |
| `tag` | &mdash; | Tag filter |
| `version` | `latest` | Tarn version |
| `vars` | &mdash; | Variables (newline-separated `KEY=VALUE`) |

## Configuration

### `tarn.config.yaml` (optional)

```yaml
test_dir: "tests"
env_file: "tarn.env.yaml"
timeout: 10000
retries: 0
parallel: false
parallel_opt_in: false  # set to `true` once tests have been audited for cross-file state sharing; silences the --parallel warning
defaults:
  connect_timeout: 1000
  follow_redirects: true
redaction:
  headers: ["authorization", "cookie"]
environments:
  staging:
    env_file: "env/staging.yaml"
    vars:
      base_url: "https://staging.example.com"
```

Behavior:
- `test_dir` sets the default discovery directory for `tarn run`, `tarn validate`, and `tarn list`
- `env_file` changes the root env file name; Tarn also checks `.{name}` and `.local` variants
- `defaults` acts as project-wide request policy for headers/auth/timeouts/retries/redirects/delay
- `redaction` provides a project-wide default report sanitization policy
- `environments` makes named `--env` profiles first-class and powers `tarn env`
- `parallel: true` makes parallel file execution the default for `tarn run`
- `parallel_opt_in: true` acknowledges the isolation tradeoff (see [Parallel Execution](#parallel-execution)) and silences the `--parallel` warning; pair it with `serial_only:` and `group:` markers on files that share mutable state

### File-level defaults

```yaml
defaults:
  headers:
    Content-Type: "application/json"
  timeout: 5000
  retries: 1
  delay: "100ms"    # default delay before each request
```

## Step Options

### Retries

```yaml
retries: 3    # retry up to 3 times on failure (exponential backoff)
```

### Timeout

```yaml
timeout: 30000    # 30 seconds for this step
```

### Delay

```yaml
delay: "2s"    # wait before executing
```

### Debug

Mark an individual step so the report always records its response body,
response headers, and captures — even when the step passes. Equivalent
to running with `--verbose-responses` but scoped to a single step:

```yaml
- name: fetch user
  debug: true    # keep response in the report for this step
  request:
    method: GET
    url: "{{ env.base_url }}/users/42"
  assert:
    status: 200
```

The global `--verbose-responses` flag plus `--max-body <BYTES>` give
the same behavior for every step in the run; `debug: true` is a
targeted override for one-off debugging. Bodies exceeding the
`--max-body` cap (8 KiB by default) are truncated with a
`"...<truncated: N bytes>"` marker.

## JSON Schema

Add to the top of your `.tarn.yaml` files for IDE autocompletion:

```yaml
# yaml-language-server: $schema=https://raw.githubusercontent.com/NazarKalytiuk/hive/main/schemas/v1/testfile.json
name: My test
steps: ...
```

The schema is bundled at `schemas/v1/testfile.json` in the repository.
The structured report schema is bundled at `schemas/v1/report.json`.

## VS Code Extension

A full-featured Tarn extension lives in [`editors/vscode`](./editors/vscode) and is published from tagged releases to both the **VS Marketplace** (`nazarkalytiuk.tarn-vscode`) and **Open VSX** via [`.github/workflows/vscode-extension-release.yml`](./.github/workflows/vscode-extension-release.yml). Current version: **0.6.1**.

### Running tests from the editor

- **Test Explorer discovery** &mdash; `.tarn.yaml` files are indexed into a file &rarr; test &rarr; step tree. Run and Dry Run profiles, cancellable runs, and live streaming via `tarn run --ndjson` keep the UI in sync with long runs.
- **CodeLens** above every test and step for Run, Dry Run, and Run step &mdash; no Test Explorer navigation required.
- **Rich failure peek view** &mdash; on failure you get a unified diff of expected vs actual, plus the full request, response, remediation hints, `failure_category`, and `error_code` pulled straight from Tarn's JSON report.
- **Tag filter** command and an **"Install / Update Tarn"** helper command, both surfaced in the command palette.
- **Output channel** streams `tarn` stdout/stderr for each run.

### Environment management

- **Environment picker** with a status-bar entry, persisted per workspace.
- `tarn.defaultEnvironment` setting for the initial pick.
- Status bar entries summarize active environment, tag filter, and last-run status.

### Language features

- Tarn file association for `*.tarn.yaml` and `*.tarn.yml`.
- Full JSON schema validation for both test files and `tarn-report.json` via the [`redhat.vscode-yaml`](https://marketplace.visualstudio.com/items?itemName=redhat.vscode-yaml) extension dependency.
- Snippet library for test skeletons, polling, multipart, GraphQL, form requests, and includes. Prefix and coverage details live in [`editors/vscode/README.md`](./editors/vscode/README.md).
- **Experimental LSP client** (off by default) &mdash; the window-scoped `tarn.experimentalLspClient` setting spawns the `tarn-lsp` server alongside the extension's in-process providers. This is Phase V scaffolding; no feature has migrated to the LSP path yet, so leave it disabled unless you are testing the handoff.

### Workspace trust and remote development

- **Trusted / Untrusted workspace** aware. In untrusted workspaces, Tarn features run in a read-only mode &mdash; discovery and schema validation still work, but commands that would execute `tarn` are disabled.
- **Remote Development** audited end-to-end: Dev Container, GitHub Codespaces, WSL, and Remote SSH all work without additional configuration. See [`docs/VSCODE_REMOTE.md`](./docs/VSCODE_REMOTE.md).

### Public API

The extension exports a `TarnExtensionApi` for other extensions to consume:

```ts
const tarn = vscode.extensions
  .getExtension('nazarkalytiuk.tarn-vscode')
  ?.exports as TarnExtensionApi | undefined;
```

See [`editors/vscode/docs/API.md`](./editors/vscode/docs/API.md) for the surface and stability guarantees.

### Reference

- Canonical user docs: [`editors/vscode/README.md`](./editors/vscode/README.md)
- Design / internals: [`docs/VSCODE_EXTENSION.md`](./docs/VSCODE_EXTENSION.md)
- Changelog: [`editors/vscode/CHANGELOG.md`](./editors/vscode/CHANGELOG.md)

## Zed Extension

A Zed extension lives in [`editors/zed`](./editors/zed) and is published to the [zed-industries/extensions](https://github.com/zed-industries/extensions) registry under the id `tarn`. The extension wraps the same `tarn-lsp` binary used by the VS Code extension — installing from Zed's Extensions panel auto-downloads the matching `tarn-lsp` release on first activation.

Coverage:

- Syntax highlighting for `.tarn.yaml` / `.tarn.yml`, backed by `tree-sitter-yaml`.
- Full `tarn-lsp` language intelligence: diagnostics, completion, hover, code actions, code lens, formatting, symbols, rename, references.
- Snippet library ported from the VS Code extension (`tarn-test`, `tarn-step`, `tarn-capture`, `tarn-poll`, `tarn-form`, `tarn-graphql`, `tarn-multipart`, `tarn-lifecycle`, `tarn-include`).
- Runnable tasks: `tarn: run file`, `tarn: dry-run file`, `tarn: validate file`, plus whole-workspace variants. Accessible from the task picker or the gutter runnable at the top of each file.
- Settings passthrough via `lsp.tarn-lsp.settings` in Zed's `settings.json`, forwarded to `tarn-lsp` as `workspace/configuration`.

Zed has no custom UI surface for extensions, so the VS Code-only features (Test Explorer tree, environment picker, run-history panel, HTML report viewer, walkthrough) are not ported. Users who need them stay on VS Code; Zed users rely on LSP-driven feedback and the task runner.

See [`editors/zed/README.md`](./editors/zed/README.md) for install and configuration.

## Shell Completions

```bash
tarn completions bash > /etc/bash_completion.d/tarn
tarn completions zsh > ~/.zsh/completions/_tarn
tarn completions fish > ~/.config/fish/completions/tarn.fish
```

## Development

```bash
git clone https://github.com/NazarKalytiuk/hive.git
cd tarn

cargo build                    # build
cargo test --all               # test suite
cargo clippy                   # lint
cargo fmt                      # format
bash scripts/ci/smoke.sh       # release-path smoke test

# Run demo server + examples
PORT=3333 cargo run -p demo-server &
cargo run -p tarn -- run examples/ --var base_url=http://localhost:3333
```

See [docs/RELEASE_VERIFICATION.md](docs/RELEASE_VERIFICATION.md) for the broader release-candidate checklist, including watch-mode and installer verification.

### Architecture

Pipeline: **parse YAML &rarr; resolve env &rarr; interpolate &rarr; execute HTTP &rarr; assert &rarr; report**

| Module | Role |
|--------|------|
| `model.rs` | Serde structs for `.tarn.yaml` |
| `parser.rs` | YAML loading + validation |
| `env.rs` | 6-layer env resolution |
| `interpolation.rs` | `{{ }}` template engine |
| `runner.rs` | Orchestrator (setup &rarr; tests &rarr; teardown) |
| `http.rs` | HTTP client (reqwest) |
| `capture.rs` | JSONPath + header extraction |
| `cookie.rs` | Automatic cookie jar |
| `config.rs` | `tarn.config.yaml` parsing |
| `builtin.rs` | Built-in functions (`$uuid`, `$timestamp`, etc.) |
| `update.rs` | Self-update mechanism |
| `assert/` | Status, body, headers, duration |
| `report/` | Human, JSON, JUnit, TAP, HTML |
| `scripting.rs` | Lua scripting engine (mlua) |
| `watch.rs` | File watcher (notify) |
| `bench.rs` | Performance testing (async) |

## License

MIT
