┌─────────────┐      ┌───────────┐
│ diagnostics │ ──▶  │ arbiter  │ ─┐
│ (type check)│      │ (unit)    │  │
└─────────────┘      └───────────┘  │
                                    ├──▶ ┌─────────┐
                     ┌───────────┐  │    │  atlas  │
                     │  arbiter  │ ─┘    │ (e2e)   │
                     │ (integ)   │       └─────────┘
                     └───────────┘

  Pre-flight         Parallel              Sequential
  (~1 second)        fast tests            slow tests

tldr diagnostics . --project --format text 2>/dev/null | grep "^E " | head -10

tldr change-impact --session
# or for explicit files:
tldr change-impact src/changed_file.py

# Run both in parallel
Task(
  subagent_type="arbiter",
  prompt="""
  Run unit tests for: [SCOPE]

  Include:
  - Unit tests
  - Type checking
  - Linting

  Report: Pass/fail count, failures detail
  """,
  run_in_background=true
)

Task(
  subagent_type="arbiter",
  prompt="""
  Run integration tests for: [SCOPE]

  Include:
  - Integration tests
  - API tests
  - Database tests

  Report: Pass/fail count, failures detail
  """,
  run_in_background=true
)

# Wait for both
[Check TaskOutput for both]

Task(
  subagent_type="atlas",
  prompt="""
  Run E2E tests for: [SCOPE]

  Include:
  - End-to-end flows
  - Acceptance tests
  - UI tests if applicable

  Report: Pass/fail count, screenshots on failure
  """
)

User: /test
→ All unit + integration + E2E tests

User: /test authentication
→ Only auth-related tests

User: /test --quick
→ Only unit tests (skip integration and E2E)

User: /test the new payment feature

Claude: Starting /test workflow for payment feature...

Phase 0: Pre-flight diagnostics...
$ tldr diagnostics . --project --format text | grep "^E "
(no type errors found)

Phase 1: Running parallel tests...
┌─────────────────────────────────────────┐
│ arbiter: Running unit tests...          │
│ arbiter: Running integration tests...   │
└─────────────────────────────────────────┘

arbiter: ✅ 45/45 unit tests passing
arbiter: ✅ 12/12 integration tests passing

Phase 2: Running E2E tests...
atlas: ✅ 8/8 E2E tests passing

Test Summary:
┌─────────────┬─────────┬────────┐
│ Type        │ Passed  │ Failed │
├─────────────┼─────────┼────────┤
│ Unit        │ 45      │ 0      │
│ Integration │ 12      │ 0      │
│ E2E         │ 8       │ 0      │
├─────────────┼─────────┼────────┤
│ TOTAL       │ 65      │ 0      │
└─────────────┴─────────┴────────┘

All tests passing! ✅

User: /test

Claude: Starting /test workflow...

Phase 0: Pre-flight diagnostics...
$ tldr diagnostics . --project --format text | grep "^E "
E src/payment.py:45:12: Argument of type 'str' not assignable to 'int'
E src/refund.py:23:8: Return type 'None' not assignable to 'float'

Found 2 type errors. Fixing before running tests...

[Claude fixes the type errors]

Re-running diagnostics... clean.

Phase 1: Running parallel tests...

arbiter: ❌ 43/45 tests passing

2 failures:
- test_payment_validation: expected 'invalid' got 'valid'
- test_refund_calculation: off by $0.01

Stopping workflow. Fix failures before running E2E tests.