fix(mcp): ensure MCP discovery completes before agent build in non-interactive sessions - #75933
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kshitijk4poor merged 1 commit intoAug 1, 2026
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…teractive sessions Non-interactive sessions (hermes chat -q, hermes -z) snapshot the tool registry at AIAgent construction time. If background MCP discovery hasn't finished, MCP tools are invisible for the entire session — and unlike interactive mode, there is no between-turns late-binding refresh to recover. Root cause: wait_for_mcp_discovery() only joins an already-created discovery thread, so it no-ops if a direct/single-query path reaches agent construction before MCP startup created that thread. Oneshot._run_agent() didn't call it at all. Fix: - Add ensure_mcp_discovery_before_agent_build() helper to mcp_startup.py: idempotently starts discovery if needed + bounded wait. Fail-open on errors. - Add single_query parameter to _resolve_discovery_timeout/wait_for_mcp_discovery: uses mcp_single_query_discovery_timeout (default 15s) instead of the interactive mcp_discovery_timeout (1.5s) because one-shot sessions have no second turn to recover. - Wire into CLI _init_agent (single_query from _single_query_mode flag set in cli.py's single-query path) and oneshot._run_agent (single_query=True). - Interactive sessions unchanged: keep 1.5s bound (between-turns refresh covers). Closes NousResearch#38448, NousResearch#51316, NousResearch#37013, NousResearch#68137 Composite salvage of NousResearch#60017 (chrishart0), NousResearch#51322 (Bartok9), NousResearch#38620 (buptwz), NousResearch#43544 (halonke), NousResearch#36882 (vanhoof).
kshitijk4poor
enabled auto-merge (rebase)
August 1, 2026 06:57
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Summary
Non-interactive sessions (
hermes chat -q,hermes -z) now wait for MCP discovery to complete before building the agent, so configured MCP tools are visible in the one and only model turn instead of silently dropped.Root cause:
wait_for_mcp_discovery()only joins an already-created discovery thread — it no-ops if a direct/single-query path reaches agent construction before MCP startup created that thread.oneshot._run_agent()didn't call it at all. Interactive sessions recovered via between-turns late-binding refresh, but one-shot sessions have no second turn.Changes
hermes_cli/mcp_startup.py: Newensure_mcp_discovery_before_agent_build()helper — idempotently starts discovery if needed + bounded wait. Addedsingle_queryparam to_resolve_discovery_timeout()andwait_for_mcp_discovery()to use the largermcp_single_query_discovery_timeoutbound (default 15s) for one-shot sessions.hermes_cli/config_defaults.py: Newmcp_single_query_discovery_timeoutconfig key (default 15.0s). Interactivemcp_discovery_timeoutunchanged at 1.5s.hermes_cli/cli_agent_setup_mixin.py:_init_agentcallsensure_mcp_discovery_before_agent_build()instead of barewait_for_mcp_discovery(), forwardingsingle_queryfrom_single_query_mode.cli.py: Setscli._single_query_mode = Truein the single-query (-q/-z) path.hermes_cli/oneshot.py:_run_agentcallsensure_mcp_discovery_before_agent_build(single_query=True)before AIAgent construction.tests/hermes_cli/test_mcp_discovery_timing.py: 12 regression tests covering timeout resolution, helper behavior, ordering, bounded wait, and single_query flag forwarding.Why two timeout bounds
Interactive sessions keep 1.5s because the between-turns late-binding refresh (
agent/turn_context.py) picks up late-arriving MCP tools on the next turn. Single-query sessions have ONE turn — no refresh — so 15s gives slow cold-start servers (npx, uvx, remote HTTP) a chance to land.thread.join(timeout)returns the instant discovery completes, so fast servers pay ~0s regardless.Validation
hermes -z "use mcp__server__tool"hermes chat -q "prompt"_single_query_modehermes chat12 new tests pass. 10 existing MCP startup/refresh tests pass. E2E verified with real imports.
Credits
Composite salvage of 5 community PRs, each of which identified the same bug class from a different entry point:
ensure_mcp_discovery_before_agent_build()helper concept_single_query_modeflagmcp_startupentirelyCloses #38448
Closes #51316
Closes #37013
Closes #68137