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max_completion_tokens needs to be <= max_tokens - prompt_len #9611
Description
Description
With local models, opencode often reports errors like this one:
'max_tokens' or 'max_completion_tokens' is too large: 65536. This model's maximum context length is 65536 tokens and your request has 10969 input tokens (65536 > 65536 - 10969). (parameter=max_tokens, value=65536)
There SHOULDN'T be a problem here: the prompt is only 10k, and we have 64k available.
I believe this is happening because opencode is not actually respecting the model's max tokens in its requests to the llm -- in max_completion_tokens.
For example, if max_tokens is 10, and the prompt is 9, then max_completion_tokens should be no more than 1 (min(max_completion_tokens, max_tokens - prompt_len)).
Plugins
Just some skills
OpenCode version
1.1.26
Steps to reproduce
See session transcript. vllm; glm-4.7-flash, 64k context, launching with OPENCODE_EXPERIMENTAL_OUTPUT_TOKEN_MAX=65536 opencode.
Operating System
Linux mint
Terminal
konsole
Activity
hsn8888866666-blip commentedon Jan 22, 2026
Is this also related to the automatic context compression mechanism? Logically, when the condition "x > z−y" occurs, it indicates that OpenCode failed to perform compression in a timely manner. Claude Code has the same issue, which seems to be a problem with model support.
hsn8888866666-blip commentedon Jan 22, 2026
like:
RNGMARTIN commentedon Feb 4, 2026
me too. Do you solve this problem?
khli-001 commentedon Feb 5, 2026
easy,
you should set max output tokenm in linux you can export OPENCODE_EXPERIMENTAL_OUTPUT_TOKEN_MAX=32000;
But there is another bug, only "finish-step" case (opencode/packages/opencode/src/session/processor.ts), it will compact context. If read tool return too many content, it also will trigger this error. I think this is a bug, need being fixed.
ZeusJupiter commentedon Mar 9, 2026
My config:
{
"$schema": "https://opencode.ai/config.json",
"disabled_providers": [],
"provider": {
"myprovider": {
"name": "MyProvider",
"npm": "@ai-sdk/openai-compatible",
"models": {
"glm-4.7-flash": {
"id": "glm-4.7-flash",
"name": "GLM-4.7-Flash",
"family": "glm-flash",
"attachment": false,
"reasoning": true,
"tool_call": true,
"temperature": true,
"knowledge": "2025-04",
"release_date": "2026-01-19",
"last_updated": "2026-01-19",
"modalities": { "input": ["text"], "output": ["text"] },
"open_weights": true,
"cost": { "input": 0, "output": 0, "cache_read": 0, "cache_write": 0 },
"limit": { "context": 200000, "output": 131072 }
}
},
"options": {
"baseURL": "http://127.0.0.1:8000/v1"
}
}
}
}
opencode web rebport: max_tokens=32000cannot be greater than max_model_len=max_total_tokens=28000. Please request fewer output tokens. (parameter=max_tokens, value=32000)
github-actions commentedon Jul 6, 2026
To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.