hermes-agent/tests/agent/test_stream_single_writer_guard.py
brooklyn! 41fdcae688
fix(streaming): make the single-writer fence best-effort so a missing guard can't crash a turn (#66448)
A cron job ("Daily Buzz Report") died with 'AIAgent' object has no
attribute '_claim_stream_writer'. The #65991 single-writer fence lives on
AIAgent (run_agent.py), but the streaming paths that use it live in other
modules — chat_completion_helpers (chat / anthropic / bedrock) and
codex_runtime (codex responses) — and called it directly as
agent._claim_stream_writer() / agent._stream_writer_is_current(). That makes
those modules hard-depend on the method being present on whatever object is
passed as agent.

The fence is an *additive* safety net that may only ever drop a provably
superseded stream, never the sole legitimate writer. But the direct calls
turned any agent that doesn't expose it — a version-skewed checkout (the
streaming helper module newer than run_agent), a hot-reloaded gateway mid
git-pull, a duck-typed agent, or a test double — into a fatal AttributeError
that aborts the whole turn (and, on cron, fails the job).

Route every cross-module claim/check through agent/stream_single_writer.py.
claim_stream_writer(agent) returns 0 when the fence is unavailable (or
raises), and stream_writer_is_current(agent, token) treats a 0 token or an
absent guard as "current" — so a guard-less agent degrades to "no fence"
instead of crashing, while a real AIAgent keeps the full single-writer
protection. Internal self.* uses inside run_agent are unchanged (self is
always a full AIAgent there).
2026-07-17 18:31:09 +00:00

79 lines
3 KiB
Python

"""Regression tests for the best-effort single-writer fence accessors.
The streaming paths in ``chat_completion_helpers`` and ``codex_runtime`` reach
the #65991 single-writer fence through :mod:`agent.stream_single_writer` instead
of calling ``agent._claim_stream_writer()`` directly. That indirection exists so
an agent object that doesn't expose the fence (a version-skewed checkout, a
duck-typed agent, a test double) degrades to "no fence" rather than aborting the
whole turn with ``'AIAgent' object has no attribute '_claim_stream_writer'`` —
the exact AttributeError that killed a cron job.
These tests assert the fence's *contract*: it may drop a provably superseded
stream, but it must never fence (or crash) the sole legitimate writer.
"""
import run_agent
from agent.stream_single_writer import claim_stream_writer, stream_writer_is_current
class _NoFenceAgent:
"""An agent-like object that predates / lacks the single-writer fence."""
class _RaisingFenceAgent:
"""An agent whose fence methods exist but blow up when called."""
def _claim_stream_writer(self):
raise RuntimeError("boom")
def _stream_writer_is_current(self, token):
raise RuntimeError("boom")
def _real_agent():
"""A real AIAgent without running the heavy __init__ (fields self-heal)."""
return object.__new__(run_agent.AIAgent)
def test_claim_on_fenceless_agent_does_not_raise():
# Regression: this is the cron crash path — the streaming helper must not
# explode when the agent lacks _claim_stream_writer.
assert claim_stream_writer(_NoFenceAgent()) == 0
def test_is_current_on_fenceless_agent_is_always_current():
agent = _NoFenceAgent()
# A no-op claim (token 0) must never report as superseded, regardless of
# what token value a caller threads through.
assert stream_writer_is_current(agent, 0) is True
assert stream_writer_is_current(agent, 7) is True
def test_zero_token_is_never_fenced_even_with_a_real_fence():
# Invariant: a claim that no-oped (token 0) is not a writer and can never be
# fenced, even against an agent that does implement the fence.
assert stream_writer_is_current(_real_agent(), 0) is True
def test_claim_swallows_fence_exceptions():
assert claim_stream_writer(_RaisingFenceAgent()) == 0
def test_is_current_swallows_fence_exceptions_as_current():
assert stream_writer_is_current(_RaisingFenceAgent(), 123) is True
def test_real_agent_fence_still_supersedes_and_preserves_sole_writer():
agent = _real_agent()
first = claim_stream_writer(agent)
assert first > 0
# Sole writer so far — still current.
assert stream_writer_is_current(agent, first) is True
# A newer attempt claims the sink: the older token is now superseded, the
# newer one is current. The fence drops only the provably stale writer.
second = claim_stream_writer(agent)
assert second > first
assert stream_writer_is_current(agent, first) is False
assert stream_writer_is_current(agent, second) is True