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The session-stable system prompt embeds Model:/Provider: identity lines, but mid-turn failover (try_activate_fallback) swaps the runtime without touching them, so a fallback model misreports itself as the primary when asked "what model are you?". rewrite_prompt_model_identity() rewrites the last occurrence of each line on _cached_system_prompt when a fallback activates (and back on restore, byte-identical so the primary's prefix cache still hits). The rewrite is never persisted to the session DB. _sync_failover_system_message() patches the in-flight api_messages[0] at all 8 failover sites so the current turn ships the corrected identity. Cache-safe: the fallback's prefix cache is cold on a model switch anyway. Co-authored-by: Hermes Agent <noreply@nousresearch.com>
104 lines
4.3 KiB
Python
104 lines
4.3 KiB
Python
"""Tests for system-prompt model-identity sync across provider failover.
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The system prompt is session-stable and embeds ``Model:``/``Provider:``
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identity lines. When ``try_activate_fallback`` swaps the runtime, the
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prompt must be rewritten in place (and synced into the in-flight
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``api_messages``) or the agent reports the primary model's name while a
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fallback model is answering — e.g. a local gemma fallback claiming to be
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gpt-5.4-mini after a Codex usage-limit 429.
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"""
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from types import SimpleNamespace
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from agent.chat_completion_helpers import rewrite_prompt_model_identity
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from agent.conversation_loop import _sync_failover_system_message
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_PROMPT = (
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"You are a helpful assistant.\n"
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"\n"
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"Memory note at line start:\n"
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"Model: decoy-from-memory\n"
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"\n"
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"Conversation started: Wednesday, June 10, 2026\n"
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"Model: gpt-5.4-mini\n"
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"Provider: openai-codex"
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)
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def _agent(prompt=_PROMPT, ephemeral=None):
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return SimpleNamespace(
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_cached_system_prompt=prompt,
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ephemeral_system_prompt=ephemeral,
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)
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class TestRewritePromptModelIdentity:
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def test_swaps_identity_lines_to_fallback_runtime(self):
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agent = _agent()
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rewrite_prompt_model_identity(agent, "gemma4:e2b-mlx", "custom")
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assert "Model: gemma4:e2b-mlx" in agent._cached_system_prompt
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assert "Provider: custom" in agent._cached_system_prompt
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assert "Model: gpt-5.4-mini" not in agent._cached_system_prompt
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assert "Provider: openai-codex" not in agent._cached_system_prompt
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def test_only_last_occurrence_is_rewritten(self):
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agent = _agent()
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rewrite_prompt_model_identity(agent, "gemma4:e2b-mlx", "custom")
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# Earlier matching lines may be user content (memory snapshots,
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# context files) and must survive untouched.
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assert "Model: decoy-from-memory" in agent._cached_system_prompt
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def test_round_trip_restores_byte_identical_prompt(self):
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# restore_primary_runtime rewrites the lines back; the result must
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# match the stored prompt byte-for-byte so the primary's prefix
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# cache still hits after restoration.
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agent = _agent()
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rewrite_prompt_model_identity(agent, "gemma4:e2b-mlx", "custom")
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rewrite_prompt_model_identity(agent, "gpt-5.4-mini", "openai-codex")
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assert agent._cached_system_prompt == _PROMPT
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def test_noop_when_prompt_missing_or_empty(self):
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for prompt in (None, ""):
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agent = _agent(prompt=prompt)
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rewrite_prompt_model_identity(agent, "m", "p")
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assert agent._cached_system_prompt == prompt
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def test_empty_values_leave_lines_unchanged(self):
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agent = _agent()
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rewrite_prompt_model_identity(agent, "", "")
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assert agent._cached_system_prompt == _PROMPT
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class TestSyncFailoverSystemMessage:
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def test_patches_in_flight_system_message(self):
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agent = _agent()
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rewrite_prompt_model_identity(agent, "gemma4:e2b-mlx", "custom")
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api_messages = [
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{"role": "system", "content": _PROMPT},
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{"role": "user", "content": "what model are you?"},
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]
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result = _sync_failover_system_message(agent, api_messages, _PROMPT)
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assert "Model: gemma4:e2b-mlx" in api_messages[0]["content"]
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assert result == agent._cached_system_prompt
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def test_appends_ephemeral_system_prompt(self):
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agent = _agent(ephemeral="Stay terse.")
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api_messages = [{"role": "system", "content": _PROMPT}]
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_sync_failover_system_message(agent, api_messages, _PROMPT)
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assert api_messages[0]["content"].endswith("Stay terse.")
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def test_noop_without_cached_prompt(self):
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agent = _agent(prompt=None)
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api_messages = [{"role": "system", "content": "original"}]
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result = _sync_failover_system_message(agent, api_messages, "active")
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assert api_messages[0]["content"] == "original"
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assert result == "active"
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def test_noop_when_first_message_is_not_system(self):
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agent = _agent()
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api_messages = [{"role": "user", "content": "hi"}]
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result = _sync_failover_system_message(agent, api_messages, "active")
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assert api_messages == [{"role": "user", "content": "hi"}]
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# Still returns the cached prompt for subsequent call-block rebuilds.
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assert result == agent._cached_system_prompt
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