harness-architect

name	harness-architect
description	Scaffolds compilable but failing test harnesses for feature and chore tasks
argument-hint	feature=001-{SUFFIX_FEATURE} tasks=001.001-{SUFFIX_TASK},001.002-{SUFFIX_TASK}
input	{"properties":{"feature":{"type":"string","description":"Feature or chore ID to scaffold harnesses for"},"tasks":{"type":"string","description":"Comma-separated task IDs to scaffold (optional, defaults to all ready tasks)"}},"required":["feature"]}

Harness Architect Skill

Scaffold strict test harnesses for a feature's or chore's ready work items. The output must compile cleanly, fail for the intended not-yet-implemented behavior, and leave clear harness commands for downstream build execution.

Purpose

Use this skill when a release unit needs executable test boundaries before implementation starts. The skill prepares the red phase and stops there. It does not implement production logic.

Agent-Intercom Communication

When the agent-intercom capability pack is installed, call ping at session start. If reachable, broadcast at every step. If unreachable, warn the operator that visibility is degraded and continue locally.

Event	Level	Message prefix
Session start	info	[HARNESS] Starting: feature={input.feature}
Tasks loaded	info	[HARNESS] Ready tasks: {task_count}
Codebase analyzed	info	[HARNESS] Context gathered: {module_count} modules
Harness generated	info	[HARNESS] Generated: {test_file} ({scenario_count} scenarios)
Compilation check	info	[HARNESS] Compilation: {result}
Red phase check	info	[HARNESS] Red phase: {result}
Label applied	success	[HARNESS] harness-ready: {task_id}
Complete	success	[HARNESS] Complete: {task_count} tasks harnessed

Inputs

• ${input:feature}: (Required) Feature or chore ID such as 001-F
• ${input:tasks}: (Optional) Comma-separated task IDs to scaffold. When omitted, use all ready tasks under the feature.

Workflow

Step 1: Claim the ready task set

1. Load the feature or chore and its ready descendants through backlog query or queue operations.
2. If ${input:tasks} is present, restrict the scope to that explicit task set.
3. Exclude blocked, done, or otherwise non-ready work items.
4. Preserve the work-item-to-task mapping so each harness can be traced back to the correct backlog item.

Step 2: Read task intent

1. Read each selected task's title, description, acceptance criteria, and file references.
2. Pull in feature-level acceptance criteria when task text depends on broader feature behavior.
3. Translate acceptance criteria into named test scenarios before writing code.
4. Identify the correct module, test tier, and affected files for each harness.

When the agent-engram capability pack is installed, prefer indexed symbol lookup and code-graph tools over broad grep when surveying existing modules, test patterns, and import paths.

Step 3: Determine execution posture

For each task, select the appropriate harness strategy:

Posture	When to use	Harness pattern
test-first	New functionality with clear inputs/outputs	Write failing tests for expected behavior
characterization-first	Modifying existing behavior	Write tests that capture current behavior then modify
migration-first	Moving code between modules	Write tests at the destination, verify source behavior
spike	Exploratory with uncertain approach	Write minimal integration test, implement spike, expand tests

Step 4: Generate failing harness skeletons

1. Create test files that express the task intent as compilable tests.
2. Prefer table-driven or parameterized tests when the task describes multiple scenarios.
3. Create matching production stubs that compile without panicking in production code paths. Prefer explicit typed-error placeholders for fallible APIs, or inert placeholder state that keeps the tests red through assertions rather than runtime panics.
4. Keep signatures, types, and module names aligned with the current codebase.

File placement rules

Write harness files into the module that matches the work item's scope:

• Unit harnesses: colocated with the production code in the appropriate src/ subdirectory
• Integration harnesses: in tests//integration/ when the task spans modules or runtime boundaries
• Contract harnesses: in tests//contract/ when the task defines API, CLI, or schema behavior

Write companion stub files into the production module that the tests exercise. Do not place scaffolding in unrelated modules.

Step 5: Verify harness

Step 5.1: Compilation check

Run cargo check --all-targets including tests. The harness MUST compile.

If compilation fails, fix the harness until it compiles. Do not proceed with a non-compiling harness.

Step 5.2: Red phase check

Run cargo test for the harness tests. ALL tests MUST fail for the intended red-phase reason, such as an explicit placeholder error or a failing assertion in test code.

If any test passes (false positive) or fails with an unexpected error (compilation vs runtime), fix the harness.

Step 6: Apply harness-ready label

After both checks pass (P-004 gate satisfied):

1. Update each task with harness-ready label using the backlog tool's update operation.
2. Add an implementation note with the harness command.
3. Record the harness manifest: Compilation: PASS, Red Phase: CONFIRMED.

Completion Criteria

The skill is complete only when the selected tasks have:

• harness files in the correct modules
• structural stubs with intentional not-implemented behavior
• a successful cargo check --all-targets result after scaffolding
• all harness tests failing with the expected marker
• clear mapping from backlog task to harness command

Guardrails

• Do not implement production logic — stubs only.
• Do not skip compilation verification.
• Do not apply the harness-ready label until both compilation and red phase checks pass.
• Keep test scenarios traceable to acceptance criteria.

Model Routing

This skill operates at Tier 2 (Standard) — test scaffolding is structured but routine.