harness

Category: Tools & Productivity | Uploader: makoMakoGo | Downloads: 0 | Version: v1.0（Latest）
This skill should be used for multi-session autonomous agent work requiring progress checkpointing, failure recovery, and task dependency management. Triggers on '/harness' command, or when a task involves many subtasks needing progress persistence, sleep/resume cycles across context windows, recovery from mid-task failures with partial state, or distributed work across multiple agent sessions. Synthesized from Anthropic and OpenAI engineering practices for long-running agents.
Changelog: Source: GitHub https://github.com/makoMakoGo/fish-claude
Directory Structure

Current level: tree/main/packs/harness/
📁 hooks/
- 📄 _harness_common.py 12.3 KB
- 📄 harness-claim.py 9.1 KB
- 📄 harness-renew.py 6.7 KB
- 📄 harness-sessionstart.py 5.4 KB
- 📄 harness-stop.py 10.5 KB
- 📄 harness-subagentstop.py 4.3 KB
- 📄 harness-teammateidle.py 4.9 KB
- 📄 self-reflect-stop.py 6.9 KB
📁 tests/
- 📄 e2e-100tasks.sh 5.3 KB
- 📄 test_hooks.py 33.0 KB
📄 README.md 2.3 KB
📄 settings.json 1.3 KB
📄 SKILL.md 20.1 KB
SKILL.md

---
name: harness
description: "This skill should be used for multi-session autonomous agent work requiring progress checkpointing, failure recovery, and task dependency management. Triggers on '/harness' command, or when a task involves many subtasks needing progress persistence, sleep/resume cycles across context windows, recovery from mid-task failures with partial state, or distributed work across multiple agent sessions. Synthesized from Anthropic and OpenAI engineering practices for long-running agents."
---

# Harness — Long-Running Agent Framework

Executable protocol enabling any agent task to run continuously across multiple sessions with automatic progress recovery, task dependency resolution, failure rollback, and standardized error handling.

This port keeps the original harness skill semantics. The only intentional structural change is that runtime state lives under `.harness/` in the project root instead of scattering files at the repository root.

## Design Principles

1. **Design for the agent, not the human** — Test output, docs, and task structure are the agent's primary interface
2. **Progress files ARE the context** — When context window resets, progress files + git history = full recovery
3. **Premature completion is the #1 failure mode** — Structured task lists with explicit completion criteria prevent declaring victory early
4. **Standardize everything grep-able** — ERROR on same line, structured timestamps, consistent prefixes
5. **Fast feedback loops** — Pre-compute stats, run smoke tests before full validation
6. **Idempotent everything** — Init scripts, task execution, environment setup must all be safe to re-run
7. **Fail safe, not fail silent** — Every failure must have an explicit recovery strategy

## Commands

```
/harness init <project-path>     # Initialize harness files in project
/harness run                     # Start/resume the infinite loop
/harness status                  # Show current progress and stats
/harness add "task description"  # Add a task to the list
```

## Activation Marker

Hooks only take effect when `.harness/active` marker file exists in the harness state directory.

- `/harness init` and `/harness run` MUST create this marker: `touch <project-path>/.harness/active`
- When all tasks complete (no pending/in_progress/retryable left), remove it: `rm <project-path>/.harness/active`
- Without this marker, all hooks are no-ops — they exit 0 immediately

## Progress Persistence (Dual-File System)

Maintain two primary files inside the project's `.harness/` directory:

### .harness/progress.txt (Append-Only Log)

Free-text log of all agent actions across sessions. Never truncate.

```
[2025-07-01T10:00:00Z] [SESSION-1] INIT Harness initialized for project /path/to/project
[2025-07-01T10:00:05Z] [SESSION-1] INIT Environment health check: PASS
[2025-07-01T10:00:10Z] [SESSION-1] LOCK acquired (pid=12345)
[2025-07-01T10:00:11Z] [SESSION-1] Starting [task-001] Implement user authentication (base=def5678)
[2025-07-01T10:05:00Z] [SESSION-1] CHECKPOINT [task-001] step=2/4 "auth routes created, tests pending"
[2025-07-01T10:15:30Z] [SESSION-1] Completed [task-001] (commit abc1234)
[2025-07-01T10:15:31Z] [SESSION-1] Starting [task-002] Add rate limiting (base=abc1234)
[2025-07-01T10:20:00Z] [SESSION-1] ERROR [task-002] [TASK_EXEC] Redis connection refused
[2025-07-01T10:20:01Z] [SESSION-1] ROLLBACK [task-002] git reset --hard abc1234
[2025-07-01T10:20:02Z] [SESSION-1] STATS tasks_total=5 completed=1 failed=1 pending=3 blocked=0 attempts_total=2 checkpoints=1
```

### .harness/tasks.json (Structured State)

```json
{
  "version": 2,
  "created": "2025-07-01T10:00:00Z",
  "session_config": {
    "concurrency_mode": "exclusive",
    "max_tasks_per_session": 20,
    "max_sessions": 50
  },
  "tasks": [
    {
      "id": "task-001",
      "title": "Implement user authentication",
      "status": "completed",
      "priority": "P0",
      "depends_on": [],
      "attempts": 1,
      "max_attempts": 3,
      "started_at_commit": "def5678",
      "validation": {
        "command": "npm test -- --testPathPattern=auth",
        "timeout_seconds": 300
      },
      "on_failure": {
        "cleanup": null
      },
      "error_log": [],
      "checkpoints": [],
      "completed_at": "2025-07-01T10:15:30Z"
    },
    {
      "id": "task-002",
      "title": "Add rate limiting",
      "status": "failed",
      "priority": "P1",
      "depends_on": [],
      "attempts": 1,
      "max_attempts": 3,
      "started_at_commit": "abc1234",
      "validation": {
        "command": "npm test -- --testPathPattern=rate-limit",
        "timeout_seconds": 120
      },
      "on_failure": {
        "cleanup": "docker compose down redis"
      },
      "error_log": ["[TASK_EXEC] Redis connection refused"],
      "checkpoints": [],
      "completed_at": null
    },
    {
      "id": "task-003",
      "title": "Add OAuth providers",
      "status": "pending",
      "priority": "P1",
      "depends_on": ["task-001"],
      "attempts": 0,
      "max_attempts": 3,
      "started_at_commit": null,
      "validation": {
        "command": "npm test -- --testPathPattern=oauth",
        "timeout_seconds": 180
      },
      "on_failure": {
        "cleanup": null
      },
      "error_log": [],
      "checkpoints": [],
      "completed_at": null
    }
  ],
  "session_count": 1,
  "last_session": "2025-07-01T10:20:02Z"
}
```

Task statuses: `pending` → `in_progress` (transient, set only during active execution) → `completed` or `failed`. A task found as `in_progress` at session start means the previous session was interrupted — handle via Context Window Recovery Protocol.

In concurrent mode (see Concurrency Control), tasks may also carry claim metadata: `claimed_by` and `lease_expires_at` (ISO timestamp).

**Session boundary**: A session starts when the agent begins executing the Session Start protocol and ends when a Stopping Condition is met or the context window resets. Each session gets a unique `SESSION-N` identifier (N = `session_count` after increment).

## Concurrency Control

Before modifying `.harness/tasks.json`, acquire an exclusive lock using portable `mkdir` (atomic on all POSIX systems, works on both macOS and Linux):

```bash
# Acquire lock (fail fast if another agent is running)
# Lock key must be stable even if invoked from a subdirectory.
ROOT="$PWD"
SEARCH="$PWD"
while [ "$SEARCH" != "/" ] && [ ! -f "$SEARCH/.harness/tasks.json" ]; do
  SEARCH="$(dirname "$SEARCH")"
done
if [ -f "$SEARCH/.harness/tasks.json" ]; then
  ROOT="$SEARCH"
fi

PWD_HASH="$(
  printf '%s' "$ROOT" |
    (shasum -a 256 2>/dev/null || sha256sum 2>/dev/null) |
    awk '{print $1}' |
    cut -c1-16
)"
LOCKDIR="/tmp/harness-${PWD_HASH:-unknown}.lock"
if ! mkdir "$LOCKDIR" 2>/dev/null; then
  # Check if lock holder is still alive
  LOCK_PID=$(cat "$LOCKDIR/pid" 2>/dev/null)
  if [ -n "$LOCK_PID" ] && kill -0 "$LOCK_PID" 2>/dev/null; then
    echo "ERROR: Another harness session is active (pid=$LOCK_PID)"; exit 1
  fi
  # Stale lock — atomically reclaim via mv to avoid TOCTOU race
  STALE="$LOCKDIR.stale.$$"
  if mv "$LOCKDIR" "$STALE" 2>/dev/null; then
    rm -rf "$STALE"
    mkdir "$LOCKDIR" || { echo "ERROR: Lock contention"; exit 1; }
    echo "WARN: Removed stale lock${LOCK_PID:+ from pid=$LOCK_PID}"
  else
    echo "ERROR: Another agent reclaimed the lock"; exit 1
  fi
fi
echo "$$" > "$LOCKDIR/pid"
trap 'rm -rf "$LOCKDIR"' EXIT
```

Log lock acquisition: `[timestamp] [SESSION-N] LOCK acquired (pid=<PID>)`
Log lock release: `[timestamp] [SESSION-N] LOCK released`

Modes:

- **Exclusive (default)**: hold the lock for the entire session (the `trap EXIT` handler releases it automatically). Any second session in the same state root fails fast.
- **Concurrent (opt-in via `session_config.concurrency_mode: "concurrent"`)**: treat this as a **state transaction lock**. Hold it only while reading/modifying/writing `.harness/tasks.json` (including `.bak`/`.tmp`) and appending to `.harness/progress.txt`. Release it immediately before doing real work.

Concurrent mode invariants:

- All workers MUST point at the same project root (the directory that contains `.harness/`). If you are using separate worktrees/clones, pin it explicitly (e.g., `HARNESS_STATE_ROOT=/abs/path/to/project-root`).
- Task selection is advisory; the real gate is **atomic claim** under the lock: set `status="in_progress"`, set `claimed_by` (stable worker id, e.g., `HARNESS_WORKER_ID`), set `lease_expires_at`. If claim fails (already `in_progress` with a valid lease), pick another eligible task and retry.
- Never run two workers in the same git working directory. Use separate worktrees/clones. Otherwise rollback (`git reset --hard` / `git clean -fd`) will destroy other workers.

## Infinite Loop Protocol

### Session Start (Execute Every Time)

1. **Read state**: Read last 200 lines of `.harness/progress.txt` + full `.harness/tasks.json`. If JSON is unparseable, see JSON corruption recovery in Error Handling.
2. **Read git**: Run `git log --oneline -20` and `git diff --stat` to detect uncommitted work
3. **Acquire lock** (mode-dependent): Exclusive mode fails if another session is active. Concurrent mode uses the lock only for state transactions.
4. **Recover interrupted tasks** (see Context Window Recovery below)
5. **Health check**: Run `.harness/init.sh` if it exists
6. **Track session**: Increment `session_count` in JSON. Check `session_count` against `max_sessions` — if reached, log STATS and STOP. Initialize per-session task counter to 0.
7. **Pick next task** using Task Selection Algorithm below

### Task Selection Algorithm

Before selecting, run dependency validation:

1. **Cycle detection**: For each non-completed task, walk `depends_on` transitively. If any task appears in its own chain, mark it `failed` with `[DEPENDENCY] Circular dependency detected: task-A -> task-B -> task-A`. Self-references (`depends_on` includes own id) are also cycles.
2. **Blocked propagation**: If a task's `depends_on` includes a task that is `failed` and will never be retried (either `attempts >= max_attempts` OR its `error_log` contains a `[DEPENDENCY]` entry), mark the blocked task as `failed` with `[DEPENDENCY] Blocked by failed task-XXX`. Repeat until no more tasks can be propagated.

Then pick the next task in this priority order:

1. Tasks with `status: "pending"` where ALL `depends_on` tasks are `completed` — sorted by `priority` (P0 > P1 > P2), then by `id` (lowest first)
2. Tasks with `status: "failed"` where `attempts < max_attempts` and ALL `depends_on` are `completed` — sorted by priority, then oldest failure first
3. If no eligible tasks remain → log final STATS → STOP

### Task Execution Cycle

For each task, execute this exact sequence:

1. **Claim** (atomic, under lock): Record `started_at_commit` = current HEAD hash. Set status to `in_progress`, set `claimed_by`, set `lease_expires_at`, log `Starting [<task-id>] <title> (base=<hash>)`. If the task is already claimed (`in_progress` with a valid lease), pick another eligible task and retry.
2. **Execute with checkpoints**: Perform the work. After each significant step, log:
   ```
   [timestamp] [SESSION-N] CHECKPOINT [task-id] step=M/N "description of what was done"
   ```
   Also append to the task's `checkpoints` array: `{ "step": M, "total": N, "description": "...", "timestamp": "ISO" }`. In concurrent mode, renew the lease at each checkpoint (push `lease_expires_at` forward).
3. **Validate**: Run the task's `validation.command` with a timeout wrapper (prefer `timeout`; on macOS use `gtimeout` from coreutils). If `validation.command` is empty/null, log `ERROR [<task-id>] [CONFIG] Missing validation.command` and STOP — do not declare completion without an objective check. Before running, verify the command exists (e.g., `command -v <binary>`) — if missing, treat as `ENV_SETUP` error.
   - Command exits 0 → PASS
   - Command exits non-zero → FAIL
   - Command exceeds timeout → TIMEOUT
4. **Record outcome**:
   - **Success**: status=`completed`, set `completed_at`, log `Completed [<task-id>] (commit <hash>)`, git commit
   - **Failure**: increment `attempts`, append error to `error_log`. Verify `started_at_commit` exists via `git cat-file -t <hash>` — if missing, mark failed at max_attempts. Otherwise execute `git reset --hard <started_at_commit>` and `git clean -fd` to rollback ALL commits and remove untracked files. Execute `on_failure.cleanup` if defined. Log `ERROR [<task-id>] [<category>] <message>`. Set status=`failed` (Task Selection Algorithm pass 2 handles retries when attempts < max_attempts)
5. **Track**: Increment per-session task counter. If `max_tasks_per_session` reached, log STATS and STOP.
6. **Continue**: Immediately pick next task (zero idle time)

### Stopping Conditions

- All tasks `completed`
- All remaining tasks `failed` at max_attempts or blocked by failed dependencies
- `session_config.max_tasks_per_session` reached for this session
- `session_config.max_sessions` reached across all sessions
- User interrupts

## Context Window Recovery Protocol

When a new session starts and finds a task with `status: "in_progress"`:

- Exclusive mode: treat this as an interrupted previous session and run the Recovery Protocol below.
- Concurrent mode: only recover a task if either (a) `claimed_by` matches this worker, or (b) `lease_expires_at` is in the past (stale lease). Otherwise, treat it as owned by another worker and do not modify it.

1. **Check git state**:
   ```bash
   git diff --stat          # Uncommitted changes?
   git log --oneline -5     # Recent commits since task started?
   git stash list           # Any stashed work?
   ```
2. **Check checkpoints**: Read the task's `checkpoints` array to determine last completed step
3. **Decision matrix** (verify recent commits belong to this task by checking commit messages for the task-id):

| Uncommitted? | Recent task commits? | Checkpoints? | Action |
|---|---|---|---|
| No | No | None | Mark `failed` with `[SESSION_TIMEOUT] No progress detected`, increment attempts |
| No | No | Some | Verify file state matches checkpoint claims. If files reflect checkpoint progress, resume from last step. If not, mark `failed` — work was lost |
| No | Yes | Any | Run `validation.command`. If passes → mark `completed`. If fails → `git reset --hard <started_at_commit>`, mark `failed` |
| Yes | No | Any | Run validation WITH uncommitted changes present. If passes → commit, mark `completed`. If fails → `git reset --hard <started_at_commit>` + `git clean -fd`, mark `failed` |
| Yes | Yes | Any | Commit uncommitted changes, run `validation.command`. If passes → mark `completed`. If fails → `git reset --hard <started_at_commit>` + `git clean -fd`, mark `failed` |

4. **Log recovery**: `[timestamp] [SESSION-N] RECOVERY [task-id] action="<action taken>" reason="<reason>"`

## Error Handling & Recovery Strategies

Each error category has a default recovery strategy:

| Category | Default Recovery | Agent Action |
|----------|-----------------|--------------|
| `ENV_SETUP` | Re-run init, then STOP if still failing | Run `.harness/init.sh` again immediately. If fails twice, log and stop — environment is broken |
| `CONFIG` | STOP (requires human fix) | Log the config error precisely (file + field), then STOP. Do not guess or auto-mutate task metadata |
| `TASK_EXEC` | Rollback via `git reset --hard <started_at_commit>`, retry | Verify `started_at_commit` exists (`git cat-file -t <hash>`). If missing, mark failed at max_attempts. Otherwise reset, run `on_failure.cleanup` if defined, retry if attempts < max_attempts |
| `TEST_FAIL` | Rollback via `git reset --hard <started_at_commit>`, retry | Reset to `started_at_commit`, analyze test output to identify fix, retry with targeted changes |
| `TIMEOUT` | Kill process, execute cleanup, retry | Wrap validation with `timeout <seconds> <command>`. On timeout, run `on_failure.cleanup`, retry (consider splitting task if repeated) |
| `DEPENDENCY` | Skip task, mark blocked | Log which dependency failed, mark task as `failed` with dependency reason |
| `SESSION_TIMEOUT` | Use Context Window Recovery Protocol | New session assesses partial progress via Recovery Protocol — may result in completion or failure depending on validation |

**JSON corruption**: If `.harness/tasks.json` cannot be parsed, check for `.harness/tasks.json.bak` (written before each modification). If backup exists and is valid, restore from it. If no valid backup, log `ERROR [ENV_SETUP] .harness/tasks.json corrupted and unrecoverable` and STOP — task metadata (validation commands, dependencies, cleanup) cannot be reconstructed from logs alone.

**Backup protocol**: Before every write to `.harness/tasks.json`, copy the current file to `.harness/tasks.json.bak`. Write updates atomically: write JSON to `.harness/tasks.json.tmp` then `mv` it into place (readers should never see a partial file).

## Environment Initialization

If `.harness/init.sh` exists, run it at every session start. The script must be idempotent.

Example `.harness/init.sh`:
```bash
#!/bin/bash
set -e
npm install 2>/dev/null || pip install -r requirements.txt 2>/dev/null || true
curl -sf http://localhost:5432 >/dev/null 2>&1 || echo "WARN: DB not reachable"
npm test -- --bail --silent 2>/dev/null || echo "WARN: Smoke test failed"
echo "Environment health check complete"
```

## Standardized Log Format

All log entries use grep-friendly format on a single line:

```
[ISO-timestamp] [SESSION-N] <TYPE> [task-id]? [category]? message
```

`[task-id]` and `[category]` are included when applicable (task-scoped entries). Session-level entries (`INIT`, `LOCK`, `STATS`) omit them.

Types: `INIT`, `Starting`, `Completed`, `ERROR`, `CHECKPOINT`, `ROLLBACK`, `RECOVERY`, `STATS`, `LOCK`, `WARN`

Error categories: `ENV_SETUP`, `CONFIG`, `TASK_EXEC`, `TEST_FAIL`, `TIMEOUT`, `DEPENDENCY`, `SESSION_TIMEOUT`

Filtering:
```bash
grep "ERROR" .harness/progress.txt                    # All errors
grep "ERROR" .harness/progress.txt | grep "TASK_EXEC" # Execution errors only
grep "SESSION-3" .harness/progress.txt                # All session 3 activity
grep "STATS" .harness/progress.txt                    # All session summaries
grep "CHECKPOINT" .harness/progress.txt               # All checkpoints
grep "RECOVERY" .harness/progress.txt                 # All recovery actions
```

## Session Statistics

At session end, update `.harness/tasks.json`: set `last_session` to current timestamp. (Do NOT increment `session_count` here — it is incremented at Session Start.) Then append:

```
[timestamp] [SESSION-N] STATS tasks_total=10 completed=7 failed=1 pending=2 blocked=0 attempts_total=12 checkpoints=23
```

`blocked` is computed at stats time: count of pending tasks whose `depends_on` includes a permanently failed task. It is not a stored status value.

## Init Command (`/harness init`)

1. Create `.harness/progress.txt` with initialization entry
2. Create `.harness/tasks.json` with empty task list and default `session_config`
3. Optionally create `.harness/init.sh` template (chmod +x)
4. If this is a git repo and `.gitignore` exists, ensure `.harness/` is ignored

## Status Command (`/harness status`)

Read `.harness/tasks.json` and `.harness/progress.txt`, then display:

1. Task summary: count by status (completed, failed, pending, blocked). `blocked` = pending tasks whose `depends_on` includes a permanently failed task (computed, not a stored status).
2. Per-task one-liner: `[status] task-id: title (attempts/max_attempts)`
3. Last 5 lines from `.harness/progress.txt`
4. Session count and last session timestamp

Does NOT acquire the lock (read-only operation).

## Add Command (`/harness add`)

Append a new task to `.harness/tasks.json` with auto-incremented id (`task-NNN`), status `pending`, default `max_attempts: 3`, empty `depends_on`, and no validation command (required before the task can be completed). Prompt user for optional fields: `priority`, `depends_on`, `validation.command`, `timeout_seconds`. Requires lock acquisition (modifies JSON).

## Tool Dependencies

Requires: Bash, file read/write, git. All harness operations must be executed from the project root directory.
Does NOT require: specific MCP servers, programming languages, or test frameworks.

Concurrent mode requires isolated working directories (`git worktree` or separate clones). Do not run concurrent workers in the same working tree.
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