> ## Documentation Index
> Fetch the complete documentation index at: https://praison.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Context / Harness / Loop Engineering
> Unified Context, Harness, and Loop (CHL) engineering principles for PraisonAI with a measurable rubric mapping each principle to modules, CLI commands, and evaluators.
PraisonAI implements three pillars of agentic reliability engineering — **C**ontext, **H**arness, and **L**oop (CHL). This page defines each principle, maps it to concrete modules and CLI commands, and specifies a **measurable rubric** with pass thresholds so teams can validate "framework compliance" consistently and gate releases on quantitative CHL scores.
CHL is a *validation lens*, not a new subsystem. Each principle already exists in code (`context/`, `compaction/`, runtime harness, `eval/loop.py`). This page unifies them under one rubric and links to the evaluators that score them.
```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
graph LR
C[Context Engineering]:::agent --> R[CHL Rubric]:::tool
H[Harness Engineering]:::agent --> R
L[Loop Engineering]:::agent --> R
R --> S[Pass / Fail Gate]:::output
classDef agent fill:#8B0000,stroke:#7C90A0,color:#fff
classDef tool fill:#189AB4,stroke:#7C90A0,color:#fff
classDef output fill:#10B981,stroke:#7C90A0,color:#fff
```
***
## 1. Principles
### 1.1 Context Engineering
Context Engineering governs **what the model sees** on every turn: keeping token usage within budget, compacting history without losing meaning, injecting the right artifacts, and handing off cleanly between agents.
| Sub-principle | Meaning | Code anchor |
| -------------- | ---------------------------------------------------- | --------------------------------------------- |
| **Budget** | Total prompt tokens stay within a configured budget | `context/` (token budgeter), `eval/tokens.py` |
| **Compaction** | History is compressed with high semantic retention | `compaction/` (6 strategies) |
| **Injection** | Relevant files/artifacts are added deterministically | `context/` (artifacts, fast context) |
| **Handoff** | Context transfers between agents without loss | `agent/` handoff, `ContextAgent` PRP |
Terminology aligns with the [ContextAgent](/agents/context-agent) PRP methodology and [Context Management](/features/context-management). CHL does not redefine those concepts — it scores them.
### 1.2 Harness Engineering
Harness Engineering guarantees that the environment the agent runs in during **testing** matches production: identical tool schemas, reproducible turn context, and required trace/artifact outputs.
| Sub-principle | Meaning | Code anchor |
| ------------- | -------------------------------------------------------- | ------------------------------------- |
| **Parity** | `PreparedTurnContext` tool schemas match runtime exactly | `runtime/turn_context.py` |
| **Traces** | Each turn emits a structured, replayable trace | `trace/`, harness runner |
| **Artifacts** | Required output files are present after a run | interactive test harness / CSV runner |
### 1.3 Loop Engineering
Loop Engineering makes autonomous iteration **converge safely**: reaching a quality threshold in a bounded number of iterations while doom-loop guards prevent unproductive repetition.
| Sub-principle | Meaning | Code anchor |
| --------------- | ------------------------------------------------ | --------------------------------- |
| **Convergence** | Iterations reach the target score within a bound | `eval/loop.py` (`EvaluationLoop`) |
| **Guardrails** | Doom-loop / repeat guards fire on stagnation | `agent/autonomy.py`, loop guards |
| **Efficiency** | Fewest iterations for a given quality target | `eval/loop.py` iteration metrics |
***
## 2. Measurable rubric
Each row maps a principle to a metric, a pass threshold, and the evaluator that produces the score. Targets are defaults — override per project via config.
| Principle | Metric | Target | Evaluator |
| ----------------- | -------------------------------- | ------------------ | ------------------ |
| Context handoff | handoff score 0–10 | ≥ 8.0 | `ContextEvaluator` |
| Context budget | tokens ≤ budget | 100% compliance | `ContextEvaluator` |
| Compaction loss | semantic retention (judge score) | ≥ 7.0 | `ContextEvaluator` |
| Harness parity | tool schema hash match | 100% | `HarnessEvaluator` |
| Harness artifacts | required files present | 100% | `HarnessEvaluator` |
| Loop convergence | iterations to threshold | ≤ N (configurable) | `LoopEvaluator` |
| Doom-loop safety | guard fires on repeat fixture | required | `LoopEvaluator` |
The `ContextEvaluator`, `HarnessEvaluator`, and `LoopEvaluator` classes are tracked as follow-up work (PA-CHL-001–004). Until they land, the equivalent checks can be run with today's building blocks: `estimate_tokens` / `count_tokens` (`praisonaiagents.eval`), the compaction judge, the interactive test harness, and `EvaluationLoop`.
### Interpreting scores
All three context rows must pass for a build to be "context-compliant".
Parity is a hard gate — any schema drift fails the harness pillar.
Convergence + guard firing together certify safe autonomy.
***
## 3. Cross-links
### 3.1 CLI commands
```bash theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
# Context: budgeting and compaction
praisonai context # inspect / manage context window
praisonai compaction # run and inspect compaction strategies
# Harness: reproducible interactive testing
praisonai test interactive --suite smoke # run a built-in harness suite
praisonai test interactive --list # list available suites
# Loop: bounded autonomous iteration
praisonai loop # run the evaluation / improvement loop
# Eval: run any evaluator (accuracy, safety, loop, ...)
praisonai eval
```
### 3.2 Python entry points
```python theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
from praisonaiagents.eval import (
EvaluationLoop, # Loop convergence + efficiency
estimate_tokens, # Context budget checks
count_tokens,
)
# Compaction judge and the interactive test harness cover the
# remaining Context and Harness rows until the dedicated
# ContextEvaluator / HarnessEvaluator / LoopEvaluator land.
```
### 3.3 Related docs
Token budgeting, compaction strategies, overflow prevention.
PRP methodology and Context Engineering handoff.
Autonomous loops and doom-loop guardrails.
The evaluation framework these evaluators plug into.
***
## 4. Running a CHL eval suite
Once the dedicated evaluators land, a CHL suite runs like any other evaluation:
```python theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
from praisonaiagents.eval import EvalSuite
# Composes Context / Harness / Loop evaluators into one report,
# scored against the rubric thresholds in Section 2.
suite = EvalSuite(name="chl-compliance")
report = suite.run(print_summary=True)
```
Wire the resulting pass/fail into CI to gate releases on quantitative CHL scores.
***
## 5. Summary
| Pillar | Question it answers | Rubric rows |
| ----------- | --------------------------------------------------------------- | ----------------------------- |
| **Context** | Does the agent see the right, budgeted, well-compacted context? | budget, compaction, handoff |
| **Harness** | Does the test environment match production exactly? | parity, artifacts |
| **Loop** | Does autonomy converge safely without doom loops? | convergence, doom-loop safety |
CHL turns scattered examples and code comments into a single, measurable definition of "framework compliance" that engineers can onboard against and CI can enforce.