The skip_pre_tool_call_hook flag was added to prevent double-firing of
pre_tool_call when run_agent._invoke_tool pre-checks for a block
directive and then dispatches via handle_function_call. But the
implementation added an else: branch that fired invoke_hook again for
'observers', without noticing that get_pre_tool_call_block_message() in
hermes_cli.plugins already fires invoke_hook('pre_tool_call', ...) as
part of its block-directive poll.
Result: every tool call ran through the run_agent loop fired the hook
twice — reported by community users whose observer / audit plugins
logged each tool invocation twice with identical timestamps.
Fix: delete the else: branch. The single-fire contract is now:
- skip=False (direct handle_function_call): hook fires once inside
get_pre_tool_call_block_message().
- skip=True (run_agent._invoke_tool path): caller fires the hook
once via get_pre_tool_call_block_message(); handle_function_call
must not fire it again.
Tightened the existing skip-flag test (renamed to
test_skip_flag_prevents_double_fire) to assert pre_tool_call fires
zero times when skip=True, and added
test_run_agent_pattern_fires_pre_tool_call_exactly_once to lock in
end-to-end that the full block-check + dispatch sequence fires the
hook exactly once.
Plugin hooks fired after a tool dispatch now receive an integer
duration_ms kwarg measuring how long the tool's registry.dispatch()
call took (time.monotonic() before/after). Inspired by Claude Code
2.1.119 which added the same field to PostToolUse hook inputs.
Wire points:
- model_tools.py: measure dispatch latency, pass duration_ms to
invoke_hook("post_tool_call", ...) and invoke_hook("transform_tool_result", ...)
- hermes_cli/hooks.py: include duration_ms in the synthetic payload
used by 'hermes hooks test' and 'hermes hooks doctor' so shell-hook
authors see the same shape at development time as runtime
- shell hooks (agent/shell_hooks.py): no code change needed;
_serialize_payload already surfaces non-top-level kwargs under
payload['extra'], so duration_ms lands at extra.duration_ms for
shell-hook scripts
Plugin authors can now build latency dashboards, per-tool SLO alerts,
and regression canaries without having to wrap every tool manually.
Test: tests/test_model_tools.py::test_post_tool_call_receives_non_negative_integer_duration_ms
E2E: real PluginManager + dispatch monkey-patched with a 50ms sleep,
hook callback observes duration_ms=50 (int).
Refs: https://code.claude.com/docs/en/changelog (2.1.119, Apr 23 2026)
Covers the two bugs salvaged from PR #15161:
- test_batch_runner_checkpoint: TestFinalCheckpointNoDuplicates asserts
the final aggregated completed_prompts list has no duplicate indices,
and keeps a sanity anchor test documenting the pre-fix pattern so a
future refactor that re-introduces it is caught immediately.
- test_model_tools: TestCoerceNumberInfNan asserts _coerce_number
returns the original string for inf/-inf/nan/Infinity inputs and that
the result round-trips through strict (allow_nan=False) json.dumps.
Closes#8933 more fully, extending the per-tool transform_terminal_output
hook from #12929 to a generic seam that fires after every tool dispatch.
Plugins can rewrite any tool's result string (normalize formats, redact
fields, summarize verbose output) without wrapping individual tools.
Changes
- hermes_cli/plugins.py: add "transform_tool_result" to VALID_HOOKS
- model_tools.py: invoke the hook in handle_function_call after
post_tool_call (which remains observational); first valid str return
replaces the result; fail-open
- tests/test_transform_tool_result_hook.py: 9 new tests covering no-op,
None return, non-string return, first-match wins, kwargs, hook
exception fallback, post_tool_call observation invariant, ordering
vs post_tool_call, and an end-to-end real-plugin integration
- tests/hermes_cli/test_plugins.py: assert new hook in VALID_HOOKS
- tests/test_model_tools.py: extend the hook-call-sequence assertion
to include the new hook
Design
- transform_tool_result runs AFTER post_tool_call so observers always
see the original (untransformed) result. This keeps post_tool_call's
observational contract.
- transform_terminal_output (from #12929) still runs earlier, inside
terminal_tool, so plugins can canonicalize BEFORE the 50k truncation
drops middle content. Both hooks coexist; they target different layers.
Plugins can now return {"action": "block", "message": "reason"} from
their pre_tool_call hook to prevent a tool from executing. The error
message is returned to the model as a tool result so it can adjust.
Covers both execution paths: handle_function_call (model_tools.py) and
agent-level tools (run_agent.py _invoke_tool + sequential/concurrent).
Blocked tools skip all side effects (counter resets, checkpoints,
callbacks, read-loop tracker).
Adds skip_pre_tool_call_hook flag to avoid double-firing the hook when
run_agent.py already checked and then calls handle_function_call.
Salvaged from PR #5385 (gianfrancopiana) and PR #4610 (oredsecurity).
Cover model_tools, toolset_distributions, context_compressor,
prompt_caching, cronjob_tools, session_search, process_registry,
and cron/scheduler with 127 new test cases.
