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NousResearch/hermes-agent

Prompt caching cache_control on tool results causes 400 errors

Cluster 89886 · agent. Data as of

Nothing open on GitHub. Fix merged in #97710 on 29 Aug 2026. Check it covers your case.

The short answer

0open issues
0open PRs
3items grouped
Known?
Yes. 3 related items grouped here, 1 issue already closed.
Fix event
A fix was merged to main in PR #97710. Check it covers your case. No release data is tracked.
Tracker
The maintainers' tracker marks this resolved, deciding PR #97710. That is separate from the fix event.
Still open
Nothing open on GitHub.

These items concern a bug where cache_control fields on tool_result content arrays trigger non-retryable 400 errors from Anthropic-format APIs, breaking tool-using sessions. The members include a version report and two related fix attempts targeting LiteLLM Anthropic proxy configurations.

Open issues0

No open issues.

Open PRs0

No open pull requests.

Fixes on record

Merged to main. A stamp counts the issues a fix is linked to.

  • #97710 fix(prompt-caching): tool-using sessions no longer 400 behind LiteLLM Anthropic proxies (salvage of #89931)

    merged to main

    files: agent/agent_runtime_helpers.py, agent/conversation_loop.py, agent/moa_loop.py, agent/prompt_caching.py, tests/agent/test_litellm_tool_part_cache_markers.py

1 PR closed without merging

From the close comments: merged via another change 1

  • #89931 fix(prompt-caching): tool-using sessions no longer 400 behind LiteLLM Anthropic proxies (#89886) · merged via another change → 1d8946b, #97710, #90971
Closed issues · 1
  • Closed#89886v2026.8.18: cache_control on tool_result.content[] rejected by Anthropic-format API (non-retryable 400, kills any tool-using session)
How this cluster was grouped
  • Link evidence (structural links throughout): every member is connected by structural evidence: shared changed files, or a closing/superseded reference.
  • Pairwise link density 0.67: the share of item pairs that carry a link, counting a structural link in full and a relevance-only link at 0.36. 1.00 means every pair is linked.

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At a glance

Subsystem
agent
Merged PRs
#97710
Closed issues
1
Attempts
1 PR closed without merging
Fix link checked
29 Aug 2026

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