Cairn
NousResearch/hermes-agent

Cap MCP tool result size to prevent unbounded allocation

Cluster 56059 · mcp. Data as of

Nothing open on GitHub. Fix merged in #90336. Check it covers your case.

The short answer

0open issues
0open PRs
5items grouped
Known?
Yes. 5 related items grouped here, 1 issue already closed.
Fix event
A fix was merged to main in PR #90336. Check it covers your case. No release data is tracked.
Tracker
The maintainers' tracker marks this unresolved. That is separate from the fix event.
Still open
Nothing open on GitHub.

These issues and pull requests address a risk where MCP tool results have no size limit, potentially causing unbounded memory allocation. The proposed fix involves truncating or capping oversized tool results.

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.

  • #90336 feat: MCP results spill at 50K and flag provider-side elision (Composio eval findings)

    merged to main

    files: agent/tool_dispatch_helpers.py, agent/tool_executor.py, cli-config.yaml.example, tests/agent/test_tool_dispatch_helpers.py, tests/tools/test_budget_config.py, tests/tools/test_mcp_result_size_limit.py, tests/tools/test_tool_result_storage.py, tools/budget_config.py, tools/mcp_tool.py, tools/tool_result_storage.py, website/docs/user-guide/configuration.md

3 PRs closed without merging

From the close comments: done elsewhere 2 · duplicate 1

  • #56060 fix: cap MCP tool result size to prevent unbounded allocation · done elsewhere → 4a83b03, #90336, #56059
  • #56068 fix(mcp): cap tool result size · duplicate → #56060, #56059, #44172, #24444
  • #56072 fix(tools): truncate oversized MCP tool results to prevent unbounded allocation (#56059) · done elsewhere → 4a83b03, #90336, #56059
Closed issues · 1
  • Closed#56059MCP tool results have no size limit — unbounded allocation risk
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(structural links throughout): every member is connected by structural evidence: shared changed files, or a closing/superseded reference.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 0.40: 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.

Pick up a Lab task

Check whether a fix covers the open issues here, with your own agent. Bring back evidence for maintainers.

Open the Lab

At a glance

Subsystem
mcp
Merged PRs
#90336
Closed issues
1
Attempts
3 PRs closed without merging
Fix link checked
19 Aug 2026

For your agent

The same facts, typed.

cluster/56059.json
cluster/56059.md