# H2: Missing Constraint Scaffolding

An instruction asks for repeated effort without a usable stopping condition or retry budget.

<div class="rule-facts"><span>H2</span><span>HIGH–CRITICAL</span><span>LintLang 0.8.0</span></div>

**Applies to:** Recognized prompts and instruction bodies; host-agent tool constraints. Manual repair; no automatic fix for this example.

## What triggers it

Selected unbounded retry/continuation phrases emit CRITICAL. A host-agent prompt with tools but no recognized termination condition, retry budget, or progress check emits HIGH. Server manifests do not inherit host-agent retry requirements.

## How to repair it

State the attempt limit and what happens after it is exhausted. Keep the bound in the same sentence as a retry instruction where possible.

## Reproduce the finding

Use [uv and Python 3.10+](/docs/install), plus curl. Run the examples in a scratch directory.

[Download the finding example](/examples/rules/h2-bad.json).

```json
{
  "system_prompt": "Retry the request. Keep trying until the request succeeds."
}
```

```sh
curl -fsS https://lintlang.ai/examples/rules/h2-bad.json -o h2-bad.json
uvx --from lintlang==0.8.0 lintlang scan h2-bad.json --format json
```

Expected with **0.8.0**: the JSON report includes **H2**, severity **CRITICAL**. 

## Improved example

[Download the improved example](/examples/rules/h2-improved.json).

```json
{
  "system_prompt": "Retry the request at most 3 times. If it still fails, stop and report the final error."
}
```

```sh
curl -fsS https://lintlang.ai/examples/rules/h2-improved.json -o h2-improved.json
uvx --from lintlang==0.8.0 lintlang scan h2-improved.json --format json
```

Expected with **0.8.0**: **H2 is absent**. Other diagnostics may still appear; this repair targets the rule above.

Both commands use advisory mode: a finding does not itself make the command fail. To fail CI on HIGH or CRITICAL findings, add --fail-on fail. --fail-on review also gates MEDIUM. See [outputs and exit codes](/docs/outputs).

## Detection details

<details>
<summary>Released H2 detection contract and scope</summary>

Checks for selected missing termination conditions, unbounded retry language
such as "keep trying until", negative termination such as "don't stop until",
"continue until" without limits, "retrying / try again / repeat until", and
missing retry budgets. A match is not reported when the same sentence states a
bound (`max_iterations`, "at most", "up to 3", "5 attempts", a timeout) or when
"loop" is a noun being described ("block the agent loop until answered"). These are static
indicators, not a proof that a loop will or will not terminate.

</details>

[All scan rules](/rules) · [Quickstart](/docs/quickstart) · [Separate preflight checks](/docs/preflight).