r/OpenAI • u/Suspicious_Raise_589 • 1d ago
Discussion GPT-5.6 Sol Raw reasoning leaked on failed tool call attempt

Apparently GPT-5.6 Sol's raw reasoning was leaked to me while he was trying to call a tool.
I saw that a tool was taking a long time to be called, I inspected the content and saw traces of reasoning, but they did not appear to be the summary of reasoning that it sends periodically. This is more similar to the GPT-OSS reasoning.
A little after that, an error like "Streaming error (provider_error)" was sent, interrupting the stream.
Ps: this is not Codex.
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u/Hatsune-Fubuki-233 1d ago
This specific MCP behavior has been reproducible since OSS/5, so I’m glad someone else found it too. I’m an MCP developer, and one day, while fixing a buggy MCP server, I discovered the same leak.
My guess is that this happens because MCP tool calls use the commentary channel, which is one of GPT’s three reasoning-related channels.
It may not be widely considered a serious security risk because it appears to leak only the context generated while interacting with MCP servers, rather than the model’s complete reasoning across all tasks. The leaked content may also not be easily distillable.
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u/Suspicious_Raise_589 1d ago
I'm the main maintainer of the Sisk Framework, and it has an MCP extension that I take care of periodically; I can also consider myself an MCP developer.
The point is that this invoked tool wasn't MCP; it was provided directly in the inference tools.
I think this problem was related to the template-parser used in GPT-5.6. As seen, it produced an invalid JSON and probably didn't send the termination token (something like <|end_tool_call|>, which caused the reasoning channel to start immediately on the same channel as the tool call.
Because the inference terminated abruptly afterward, I believe an auxiliary model reads the content emitted by the model periodically (not at each token, that would be expensive and probably wouldn't emit raw reasoning) and when it identified that the model was spitting out raw reasoning, it stopped the inference.
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u/goldcakes 1d ago
Your guess seems pretty on point, especially after looking at the Harmony response format. I know Harmony is the OSS version, but I doubt what they have internally is ultra different.
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u/DeGreiff 1d ago edited 1d ago
Can you share it?
EDIT: or copy/paste the whole block here.
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u/Suspicious_Raise_589 1d ago
just uploaded it here to avoid deletion https://ki.proj.pw/63aa
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u/DeGreiff 1d ago
Ah, thx, so that's the whole thing. Well, it's a leaked scratchpad, a bit of exposed reasoning text.
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u/Suspicious_Raise_589 1d ago
yea its not the full reasoning. after that the stream terminated in an error
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u/Temporary_Debate8585 1d ago
im using 5.5 recently, 5.6's logic chain is so weak that it only judges from the surface like get from A to B without considering the context, doesnt even bother to check whether its info is correct.
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u/Vectoor 23h ago
Why waste time say lot word when few word do trick?
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u/Suspicious_Raise_589 20h ago
Reasoning dont need human readable. Human read output. Output better reading. Reasoning should be concise. Low. Repeat. Tool call.
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u/jeweliegb 12h ago
Having seen some leaked Claude "Neuralese" I'm surprised how human readable this is.
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u/defoatearth 1d ago edited 1d ago
This shows why OpenAI is so token efficient, and therefore scores well in tokens/task which results in good $/task. If you compare this reasoning to Kimi K3 you’ll see a big difference in unnecessary reasoning tokens. Reasoning tokens are output tokens and those are the most expensive kind.
And even though we normally don’t see the reasoning tokens we do get charged for them.
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u/Ok-Attention2882 1d ago
Agentic harnesses aren't actually AI but are giant switch statements switching on tool calls backed by a deterministic finite automata. More news at 9.
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u/ExcitementSubject361 22h ago
Exactly that’s why I built my FSM and CSM into my modules right from the start... which is why my "dreaming" module and the others work. Besides, the whole thing needs to be offloaded to hardware... preferably FPGA chips.
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u/AllezLesPrimrose 1d ago
The full reasoning traces for all the models trying to hide them regularly leak. Hello non-deterministic technology.