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3c4220cd9c
`apply_anthropic_cache_control` runs once per call block, before the retry
loop, and splits the system prompt into `[static prefix, volatile tail]` text
blocks carrying the cache_control breakpoints.
A failover fires *inside* that retry loop, and `_sync_failover_system_message`
assigns a bare string over `api_messages[0]["content"]` to refresh the
`Model:`/`Provider:` identity lines. That drops the block list and both
breakpoints. `convert_messages_to_anthropic` only emits system cache blocks for
list content (`isinstance(content, list)`), so the retried request ships
`system` as one plain string: zero breakpoints, nothing written to cache, and
the whole system prompt re-billed at full write price. The next call misses
too, so a failover costs two full-price prompts instead of one write + one
read.
Measured with the real functions, same history, native Anthropic layout:
normal turn system=BLOCK LIST(2) system breakpoints=2
after failover system=plain string system breakpoints=0
`_sync_failover_system_message`'s own docstring notes this fires on "every
gateway turn, since fallback re-activates per message while the primary is
down" -- so a gateway running on a degraded primary pays it on every message.
Fix: rewrite the decorated blocks in place instead of flattening them.
`rewrite_prompt_model_identity` only touches the LAST `Model:`/`Provider:`
lines, and those live in the volatile tail, so the static prefix stays
byte-identical and its cache entry keeps matching -- the failover retry keeps
both breakpoints AND the warm prefix. Shapes we cannot safely patch fall back
to the existing plain-string assignment.
This is the same class the retry loop already guards against eight lines below
the gap, for reasoning fields:
# api_messages is built once, before this retry loop, while the primary
# provider is active. [...] so the fallback request isn't sent with stale,
# primary-shaped reasoning fields.
agent._reapply_reasoning_echo_for_provider(api_messages)
There was no equivalent for cache decoration.
191 lines
8 KiB
Python
191 lines
8 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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from agent.prompt_caching import apply_anthropic_cache_control
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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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class TestSyncFailoverPreservesCacheDecoration:
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"""The sync must not flatten a cache-decorated system message.
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``apply_anthropic_cache_control`` runs once per call block, before the retry
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loop, splitting the system prompt into ``[static prefix, volatile tail]``
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blocks that carry the cache_control breakpoints. A failover fires *inside*
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that retry loop, so overwriting the list with a bare string drops both
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breakpoints and the retried request re-bills the whole system prompt.
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"""
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_STATIC = "You are a helpful assistant.\n\nStable brief.\n"
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def _decorated(self, prompt):
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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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return apply_anthropic_cache_control(
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messages,
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cache_ttl=None,
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native_anthropic=True,
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static_system_prefix=self._STATIC,
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)
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def test_keeps_breakpoints_and_static_prefix(self):
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prompt = self._STATIC + "Model: gpt-5.4-mini\nProvider: openai-codex"
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agent = _agent(prompt=prompt)
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api_messages = self._decorated(prompt)
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assert isinstance(api_messages[0]["content"], list)
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rewrite_prompt_model_identity(agent, "gemma4:e2b-mlx", "custom")
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_sync_failover_system_message(agent, api_messages, prompt)
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content = api_messages[0]["content"]
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assert isinstance(content, list), "cache decoration was flattened to a string"
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assert len(content) == 2
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assert all(part.get("cache_control") for part in content), (
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"the failover retry would ship zero system cache breakpoints"
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)
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# The static prefix must stay byte-identical or its cache entry misses.
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assert content[0]["text"] == self._STATIC
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# The identity refresh still lands, in the volatile tail.
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assert "Model: gemma4:e2b-mlx" in content[1]["text"]
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assert "Provider: custom" in content[1]["text"]
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def test_keeps_single_block_shape(self):
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prompt = "Model: gpt-5.4-mini\nProvider: openai-codex"
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agent = _agent(prompt=prompt)
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# No static prefix match -> the single-block fallback layout.
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api_messages = apply_anthropic_cache_control(
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[{"role": "system", "content": prompt}],
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cache_ttl=None,
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native_anthropic=True,
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static_system_prefix=None,
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)
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assert isinstance(api_messages[0]["content"], list)
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assert len(api_messages[0]["content"]) == 1
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rewrite_prompt_model_identity(agent, "gemma4:e2b-mlx", "custom")
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_sync_failover_system_message(agent, api_messages, prompt)
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content = api_messages[0]["content"]
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assert isinstance(content, list) and len(content) == 1
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assert content[0].get("cache_control")
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assert "Model: gemma4:e2b-mlx" in content[0]["text"]
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def test_ephemeral_prompt_lands_in_the_volatile_tail(self):
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prompt = self._STATIC + "Model: gpt-5.4-mini\nProvider: openai-codex"
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agent = _agent(prompt=prompt, ephemeral="Stay terse.")
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api_messages = self._decorated(prompt)
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_sync_failover_system_message(agent, api_messages, prompt)
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content = api_messages[0]["content"]
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assert content[0]["text"] == self._STATIC
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assert content[1]["text"].endswith("Stay terse.")
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def test_unknown_block_shape_falls_back_to_string(self):
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agent = _agent()
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api_messages = [
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{"role": "system", "content": [{"type": "image", "source": {}}]},
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]
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_sync_failover_system_message(agent, api_messages, _PROMPT)
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assert api_messages[0]["content"] == agent._cached_system_prompt
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