Claude Fable 5.2 提示词指南

Template · system prompt for long agent runs (ours)

Keep going until the task is done. When you hit an ordinary obstacle
(an error, a timeout, an empty result, a failing tool), diagnose it and
work through it: retry, fix the request or use another tool.
Leave deliberate blockers alone (files marked do-not-touch, access you
were not given, safety rules) and tell me what you found.
Ask before anything risky or irreversible.
Every few tool calls, give me a one-line update.
End with a short recap a newcomer can follow: what you found,
what you changed, and what is left.

Template · 3D animation in Blender, run in Claude Code (ours)

Make a [length]-second, [resolution] video of [subject], as realistic as
you can: [what must look right: anatomy, materials, physics, lighting].
Drive Blender from the command line with Python. Generate every model,
material and animation in code; no downloaded assets.
Render a few low-resolution test frames first, look at them, fix what
looks wrong, then render the full shot. Take the time it needs.
Deliver the video file and the script.

Template · three.js scene exported to video (ours)

Build one self-contained three.js HTML page that renders a [length]-second
animation at [1280x720, 30fps]: [scene].
Make it deterministic and expose window.renderAt(t) so any frame can be
captured. Capture the frames, look at screenshots of the key moments,
fix anything that looks off, and encode the result to MP4.

Template · small browser game (ours)

Build a small but polished [genre] game that runs in the browser:
one [level / arena], with [core mechanics].
Generate all models, textures and sound effects in code.
Keep the scope tiny and the visual quality high.
Play-test it with automated input, fix what breaks, then give me the
file and the controls.

Template · painting in code (ours)

Invent a painter: name, era, background and a consistent style.
Then write one Python program that paints [subject] in that style:
a simulated paint engine with bristle brushes and paint mixing that
places every stroke. No image models, no tracing.
Render it, critique it against the painter's style, and revise the
engine until the picture holds up.

Template · music in code (ours)

Compose a [length]-second original piece in [style], entirely in code
([Python synthesis / Tone.js / LilyPond]).
Render it to WAV, listen to it by analysing the audio, and revise
anything harsh, muddy or repetitive before you hand it over.

cURL

curl https://api.apimodels.app/v1/messages \
  -H "x-api-key: $APIMODELS_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-fable-5-2",
    "max_tokens": 32000,
    "output_config": { "effort": "medium" },
    "system": "Keep going until the task is done. Every few tool calls, give a one-line update.",
    "messages": [{"role": "user", "content": "Refactor utils.py into smaller modules and keep the tests passing."}]
  }'

Claude Fable 5.2 的 effort 该选哪档?

从默认的 high 起步,再用自己的任务试 medium 和 xhigh。Anthropic 的建议是:快速、要求明确或大批量的工作用 low,交互式写代码和聊天用 medium,难的编程和 agent 任务用 high,xhigh 只在你测到提升时用,max 留给开放式的研究问题。effort 越低越省钱,因为思考 token 按输出计费。

Fable 5.2 为什么活没干完就停了?

Fable 5.2 在长任务里有时会提前结束这一轮,low 和 medium 下更常见:列出还剩什么,或者问你要不要继续。在系统提示词里加一小段:还欠着活就别停,普通障碍想办法绕过,刻意设下的限制不要硬闯。Anthropic 的测试里,留着能做的活就结束的会话减少了一半,输出 token 多了约 30%。

Fable 5.2 能关掉思考、回答快一点吗?

不能。思考一直开着,在 medium 及以上,「直接回答、不要思考」这类话也拦不住。想更快、更省,就把这些请求的 effort 设成 low 或 medium;回复的长短和语气要靠提示词控制,effort 对它们几乎没影响。

给 Fable 5.1 或 Opus 5.5 写的提示词能直接用在 Fable 5.2 上吗?

大多能用,但要先过一遍。Fable 5.2 很听话,常驻的「交给子 agent」、写进提示词的 token 预算、「少想一点」、死板的文风规则、记忆文件里攒下的旧警告,都可能抬高成本或让它束手束脚。effort 也要重新试,因为同一档位在不同模型上对应的思考量不一样。

Fable 5.2 为什么返回 stop_reason: refusal?

安全分类器拒了这个请求,类别会说明原因:cyber、bio、frontier_llm、reasoning_extraction 或 general_harms。如果提示词里要它写出推理过程,把那句删掉。正当的安全或生命科学工作,就换个模型跑:在 apimodels.app 上同一把 key 就能调 Opus 4.8,这也是 Anthropic 自己的兜底模型。

通过 apimodels.app 调 Fable 5.2,effort 怎么设?

原生接口 POST /v1/messages 里传 output_config,effort 取 low、medium、high、xhigh、max 之一。OpenAI 兼容的 /v1/chat/completions 里传 reasoning_effort,会映射成 Anthropic 的 effort。Claude Code 自己会带 effort,按 Anthropic 发布公告的说法,它默认用 medium 跑 Fable 5.2,在那里只需要换模型。