Compaction fails with: Error running remote compact task: Request blocked.

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• #30596

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Experienced the same problem ( in CLI ) today with all the 5.6 models, only affecting one of my sessions.
Temporarily switching to a 5.5 model and compacting there worked fine.
Compacting with a 5.6 model afterwards also worked fine.
Edit: Until normal prompts also started getting blocked. Guess it's back to 5.5.

Cross-referencing related gpt-5.6 Request blocked reports that may share the same root cause.

• #32177 — compacted thread state / text-log attachment triggers Request blocked on gpt-5.6-sol.
• #32533 — changing reasoning effort → full-history request → Request blocked on gpt-5.6.
• oh-my-pi#5184 — performed marker minimization: the specific input text <|channel|>analysis is sufficient to trigger Request blocked / invalid_request_body on all gpt-5.6-* models (luna/sol/terra). Earlier models (gpt-5-mini through gpt-5.5) all accept the same payload.

Since your issue is compaction itself being blocked: compaction serializes conversation history into a text summary and sends it as input to the model. If that serialized text contains Harmony control-token markers (e.g. <|channel|>analysis from assistant reasoning/thinking), the gpt-5.6 input-side safety classifier may reject it — which would explain why compaction fails on 5.6 but works on 5.5.

Your workaround (switch to 5.5, compact, switch back) is consistent with this: the 5.5 compaction produces a summary that strips or doesn't trigger the control-token pattern, after which 5.6 can process the cleaned summary. However, your edit noting that "normal prompts also started getting blocked" suggests the trigger text may persist in the thread's context even after compaction, eventually poisoning subsequent requests as well.

Related: #32177, #32533.

i see this error still having 21% context left

no change on restart with codex resume

I also received this error when working with codex on modifications to a llama.cpp jinja template for an open weights model, that channel marker was definitely in my context, as we'd been discussing the template logic. I asked for a change to the template at some point later and then the session died with every request blocked. I tried to compact, the compact operation was also blocked.

I also received this error when working with codex on modifications to a llama.cpp jinja template for an open weights model, that channel marker was definitely in my context, as we'd been discussing the template logic. I asked for a change to the template at some point later and then the session died with every request blocked. I tried to compact, the compact operation was also blocked.

I second this. My requests consistently get blocked when I'm using codex to help me with a jinja template