# GLM 5.1 — API pricing & integration guide | Y-API

> GLM 5.1 is the earlier entry in the GLM 5 line, positioned for long-horizon coding tasks that run without step-by-step supervision. It has a smaller context window than the 5.2 and 5.3 entries.

This is the markdown representation of https://y-api.bestvirtualgoods.com/models/z-ai/glm-5.1. Generated by `scripts/generate-seo-assets.mjs` from the same copy the page renders — do not edit by hand.

Model ID: `z-ai/glm-5.1`

Sources reviewed: 2026-10-11. Y-API catalog snapshot: 2026-10-11.

## Choosing this model

Selection advice by Y-API. The checks below are suggested evaluations, not published test results.

### Where to start

Consider it for batch code work where the model is expected to keep working through a task on its own — refactors, test backfills, or dependency upgrades with a clear definition of done.

### What to watch for

At 204,800 tokens the window is roughly a fifth of the newer GLM entries while the input price is the same, so long documents belong on 5.2 or 5.3. Being the oldest entry, it is also the most likely to be superseded.

## Model specifications

These are OpenRouter model-level specifications, not a Y-API compatibility test. A particular route may accept fewer input formats, parameters or tokens. Verify the features you need with a small request; a successful text response does not validate vision or tool calling.

| Field | Value |
| --- | --- |
| Context window | 204,800 tokens |
| Input | Text |
| Output | Text |
| Listed on OpenRouter | 2026-04-07 |
| Parameters listed by OpenRouter | `frequency_penalty`, `include_reasoning`, `logit_bias`, `logprobs`, `max_tokens`, `min_p`, `presence_penalty`, `reasoning`, `repetition_penalty`, `response_format`, `seed`, `stop`, `structured_outputs`, `temperature`, `tool_choice`, `tools`, `top_k`, `top_logprobs`, `top_p` |

## API pricing & cost estimate

| Price basis | Input / 1M tokens | Output / 1M tokens |
| --- | --- | --- |
| Account credit | $1.40 | $4.40 |
| Cash equivalent | $0.14 | $0.44 |

$1 paid adds $10 of credit. Cash equivalent = credit consumed ÷ 10; this is not the model publisher’s list price.

Input tokens / request: 1000. Output tokens / request: 500. Number of requests: 1000.

Estimated credit consumed: $3.60. Estimated cash equivalent: $0.36.

Illustrative token budget, not measured usage or a quote. Includes input and output; excludes separate media charges, cache discounts and retries. Include billed reasoning tokens in your output budget where applicable. Actual billing follows usage returned by the service.

### Same token budget, different models

| Model | Estimated credit consumed | Estimated cash equivalent |
| --- | --- | --- |
| [GLM 5.1](https://y-api.bestvirtualgoods.com/models/z-ai/glm-5.1) | $3.60 | $0.36 |
| [GLM 5.2](https://y-api.bestvirtualgoods.com/models/z-ai/glm-5.2) | $3.60 | $0.36 |
| [DeepSeek V4 Flash 0731](https://y-api.bestvirtualgoods.com/models/deepseek/deepseek-v4-flash-0731) | $0.30 | $0.03 |

[View LLM API pricing & billing](https://y-api.bestvirtualgoods.com/pricing)

## API integration examples

These minimal, text-only requests use the exact Y-API model ID. They do not demonstrate image, audio, video, file or tool support. The output limit also needs room for reasoning; an empty answer with finish_reason=length can mean the budget was exhausted.

Set the TOKEN environment variable to a key from your console. Run this on your server or locally; never expose a key in browser code or a public repository.

### A task to try

Add tests for the untested branches in this module without changing its public behavior. Report which branches you could not reach and why.

```bash
curl --fail-with-body --silent --show-error --max-time 120 \
  'https://api.y-api.bestvirtualgoods.com/v1/chat/completions' \
  -H "Authorization: Bearer ${TOKEN:?Set TOKEN first}" \
  -H 'Content-Type: application/json' \
  --data-binary @- <<'JSON'
{
  "model": "z-ai/glm-5.1",
  "messages": [
    {
      "role": "user",
      "content": "Add tests for the untested branches in this module without changing its public behavior. Report which branches you could not reach and why."
    }
  ],
  "max_tokens": 4096
}
JSON
```

```python
import json
import os
import sys
import urllib.error
import urllib.request

payload = {
  "model": "z-ai/glm-5.1",
  "messages": [
    {
      "role": "user",
      "content": "Add tests for the untested branches in this module without changing its public behavior. Report which branches you could not reach and why."
    }
  ],
  "max_tokens": 4096
}

request = urllib.request.Request(
    "https://api.y-api.bestvirtualgoods.com/v1/chat/completions",
    data=json.dumps(payload).encode("utf-8"),
    headers={
        "Authorization": "Bearer " + os.environ["TOKEN"],
        "Content-Type": "application/json",
    },
    method="POST",
)
try:
    with urllib.request.urlopen(request, timeout=120) as response:
        result = json.load(response)
    print(json.dumps(result, ensure_ascii=False, indent=2))
except urllib.error.HTTPError as error:
    print(error.read().decode("utf-8"), file=sys.stderr)
    raise SystemExit(1)
```

### How to evaluate the result

Confirm the public API is unchanged by diffing the exported surface, then check that each new test fails when the corresponding branch is deliberately broken.

## Before you choose

### Why pick GLM 5.1 over 5.2 or 5.3 at the same price?

Usually you would not. Pick it when a shorter window is acceptable and you specifically want the older behavior; otherwise the newer entries cost the same per input token and give you more room.

## Sources & scope

Technical facts come from the cited model page and, where available, its linked publisher card. A card describes that checkpoint; it is not proof of the weights a gateway serves. Prices come only from the Y-API catalog. We do not claim measured latency, uptime or benchmark scores for this endpoint.

- [OpenRouter model page & specifications](https://openrouter.ai/z-ai/glm-5.1)
- [Publisher model card linked by OpenRouter](https://huggingface.co/zai-org/GLM-5.1)
- [Y-API catalog & prices (JSON)](https://y-api.bestvirtualgoods.com/models.json)

## Models to compare

Compare these alternatives on the same inputs. Their descriptions explain different roles; a lower price does not establish equivalent quality.

### [GLM 5.2](https://y-api.bestvirtualgoods.com/models/z-ai/glm-5.2)

GLM 5.2 is Z.ai’s text-reasoning model for long-horizon engineering. Its publisher highlights a million-token context and IndexShare, which reuses sparse-attention indexing work for long inputs.

### [DeepSeek V4 Flash 0731](https://y-api.bestvirtualgoods.com/models/deepseek/deepseek-v4-flash-0731)

DeepSeek V4 Flash 0731 is the publisher’s official V4 Flash release, following the earlier preview. It remains a text-only model; its post-training revision focuses on coding, reasoning and agent tasks.

## Links

- HTML version of this page: https://y-api.bestvirtualgoods.com/models/z-ai/glm-5.1
- Site index for agents: https://y-api.bestvirtualgoods.com/llms.txt
- Full reference (single file): https://y-api.bestvirtualgoods.com/llms-full.txt
- OpenAPI 3.1 spec: https://y-api.bestvirtualgoods.com/openapi.json
- Model catalog (JSON, no key needed): https://y-api.bestvirtualgoods.com/models.json
- API base URL: `https://api.y-api.bestvirtualgoods.com/v1`
- Contact: support@bestvirtualgoods.com
- Model catalog: https://y-api.bestvirtualgoods.com/models
- Integration guide: https://y-api.bestvirtualgoods.com/docs