# NousResearch/hermes-agent · Agent cache prefix stability and tool refresh fixes

## Open now

- Nothing open on GitHub.

These items address bugs where the cached system-prompt prefix or tool list was being invalidated or reset during a session—specifically across model switches, agent-cache evictions, and between-turn tool refreshes. The work focuses on preserving prefix-cache state to maintain high cache-hit rates.

## TL;DR

- 4 member(s): 0 open issue(s), 1 closed issue(s), 0 open PR(s), 1 merged PR(s), 2 PR(s) closed without merging.
- A fix was merged to main in PR #101367. Verify it addresses your case.
- **Recommended:** read PR #101367 (and any competing PRs below) before filing. Confirm the merged change covers your symptom.

## Maintainer resolution verdict

- Internal-tracker verdict over this cluster's issue members: `unresolved`. This is distinct from the fix status above. Weigh it yourself.

## How this cluster was grouped

- Link evidence (`STRUCTURAL_SPANNING`): every member is connected by structural evidence: shared changed files, or a closing/superseded reference.
- Pairwise link density `0.50`: the share of member 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.

## Closed / duplicate issues

- #100336: Prefix-cache invalidation on model switch: stored system prompt is nulled, forcing full re-prefill of entire history (2% -> 99% cache hit measured)

## Prior & competing PRs

- **#101367: fix(tools): tools\[\] stays frozen for the session — prefix preserved, survives agent-cache eviction, /reload-mcp re-probes (salvage #100638)**. merged to main · fix tier `verified`
  - maintainer direction: category `merged`
  - files: `agent/conversation_loop.py`, `agent/turn_context.py`, `cli.py`, `gateway/run.py`, `hermes_state.py`, `hermes_state_common.py`, `tests/tools/test_refresh_agent_mcp_tools.py`, `tools/mcp_tool.py`, `tui_gateway/methods_tools.py`, `website/docs/reference/slash-commands.md`, `website/docs/user-guide/features/mcp.md`
- **#100358: fix(agent): keep stored prompt prefix across a mid-session /model switch**. closed without merge
  - maintainer direction: category `uncategorized`; implication `needs_llm`; refs `#100336`, `#48173`, `#52666`
- **#100638: fix(agent): stop the between-turns tool refresh from forking the cached prefix (#100336 defect b)**. closed without merge
  - maintainer direction: category `merged_via`; implication `superseded`; refs `#101367`, `#100336`

## Fix status

- Merged to main in PR #101367 (cited above). No release data is tracked. Verify downstream.
- Fix last verified (merged) `2026-09-02`.