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b18490b890
When summary_target_ratio is large (e.g. 0.45) and the context_length is moderate (e.g. 96000), the soft_ceiling (token_budget * 1.5) can exceed the total transcript size. _find_tail_cut_by_tokens walks the entire transcript without breaking early, and the resulting compress window is either empty (compress_start >= compress_end) or a single message whose summary-of-one overhead saves ~0 tokens. Both outcomes cause a no-op compression that does not increment _ineffective_compression_count, so should_compress() returns True on every subsequent turn and the loop repeats endlessly. Fix (two layers): 1. _find_tail_cut_by_tokens: when the backward walk consumed the entire transcript without breaking (cut_idx <= head_end and accumulated <= soft_ceiling), re-walk with the raw (non-inflated) token budget to find a meaningful cut that gives the summarizer a useful middle window. 2. compress(): when compress_start >= compress_end, increment _ineffective_compression_count and log a warning so the existing anti-thrashing guard in should_compress() can break the loop. Fixes #40803
250 lines
10 KiB
Python
250 lines
10 KiB
Python
"""Tests for the infinite compaction loop fix (issue #40803).
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When summary_target_ratio is large enough that the entire transcript fits
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within soft_ceiling, the backward walk in _find_tail_cut_by_tokens never
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breaks early. Without the fix this produces either a no-op compression
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(compress_start >= compress_end) or a single-message compression whose
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summary-of-one overhead saves 0 tokens — both of which cause the
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compressor to fire on every subsequent turn with no progress.
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The fix adds two safeguards:
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1. _find_tail_cut_by_tokens: when the whole transcript fits in soft_ceiling,
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re-walk with the raw (non-inflated) budget to find a meaningful cut.
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2. compress(): when compress_start >= compress_end, record the no-op as
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an ineffective compression so should_compress() anti-thrashing fires.
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"""
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from unittest.mock import patch, MagicMock
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from agent.context_compressor import ContextCompressor, _CHARS_PER_TOKEN
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# ---------------------------------------------------------------------------
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# Helpers
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# ---------------------------------------------------------------------------
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def _make_compressor(**kwargs) -> ContextCompressor:
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defaults = dict(
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model="test-model",
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threshold_percent=0.65,
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protect_first_n=2,
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protect_last_n=3,
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quiet_mode=True,
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)
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defaults.update(kwargs)
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with patch("agent.context_compressor.get_model_context_length", return_value=96000):
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return ContextCompressor(**defaults)
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def _build_session(n_turns: int, words_per_turn: int = 20) -> list:
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"""Build a multi-turn conversation with a system prompt."""
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base_text = " ".join(["a"] * words_per_turn)
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messages = [{"role": "system", "content": "You are a helpful agent."}]
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for i in range(n_turns):
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messages.append({"role": "user", "content": f"{base_text} (user turn {i})"})
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messages.append({"role": "assistant", "content": f"{base_text} (assistant turn {i})"})
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return messages
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# ---------------------------------------------------------------------------
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# Test: compress_start >= compress_end registers as ineffective
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# ---------------------------------------------------------------------------
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class TestCompressNoOpRegistersIneffective:
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"""When compress_start >= compress_end, the fix records this as
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an ineffective compression so the anti-thrashing guard fires.
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We trigger this path by having _find_tail_cut_by_tokens return
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head_end (which makes compress_end = head_end + 1, same as
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compress_start after alignment)."""
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def test_no_op_increments_counter(self):
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"""compress_start >= compress_end -> _ineffective_compression_count += 1"""
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comp = _make_compressor(
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summary_target_ratio=0.45,
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config_context_length=96000,
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)
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# A large session that passes the min_for_compress check
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messages = _build_session(10, words_per_turn=10)
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comp.last_prompt_tokens = 65_000
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# Mock _find_tail_cut_by_tokens to return head_end,
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# causing compress_start >= compress_end
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original = comp._find_tail_cut_by_tokens
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comp._find_tail_cut_by_tokens = lambda msgs, he: he # force no-op
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result = comp.compress(messages, current_tokens=65_000)
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assert comp._ineffective_compression_count >= 1, (
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f"Expected ineffective_compression_count >= 1, got {comp._ineffective_compression_count}"
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)
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def test_no_op_sets_savings_to_zero(self):
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"""compress_start >= compress_end -> _last_compression_savings_pct = 0"""
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comp = _make_compressor(
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summary_target_ratio=0.45,
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config_context_length=96000,
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)
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messages = _build_session(10, words_per_turn=10)
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comp.last_prompt_tokens = 65_000
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comp._find_tail_cut_by_tokens = lambda msgs, he: he # force no-op
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comp.compress(messages, current_tokens=65_000)
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assert comp._last_compression_savings_pct == 0.0
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def test_two_no_ops_block_should_compress(self):
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"""After 2 no-op compressions, should_compress returns False."""
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comp = _make_compressor(
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summary_target_ratio=0.45,
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config_context_length=96000,
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)
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messages = _build_session(10, words_per_turn=10)
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comp.last_prompt_tokens = 65_000
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comp._find_tail_cut_by_tokens = lambda msgs, he: he # force no-op
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comp.compress(messages, current_tokens=65_000)
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comp.compress(messages, current_tokens=65_000)
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assert comp._ineffective_compression_count >= 2
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assert not comp.should_compress(65_000), (
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"should_compress should return False after 2+ ineffective compressions"
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)
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def test_no_op_returns_unchanged_messages(self):
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"""compress_start >= compress_end -> messages returned unchanged"""
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comp = _make_compressor(
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summary_target_ratio=0.45,
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config_context_length=96000,
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)
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messages = _build_session(10, words_per_turn=10)
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comp.last_prompt_tokens = 65_000
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original_cut = comp._find_tail_cut_by_tokens
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comp._find_tail_cut_by_tokens = lambda msgs, he: he # force no-op
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result = comp.compress(messages, current_tokens=65_000)
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assert len(result) == len(messages), (
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f"Expected unchanged message count {len(messages)}, got {len(result)}"
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)
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comp._find_tail_cut_by_tokens = original_cut
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# ---------------------------------------------------------------------------
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# Test: _find_tail_cut_by_tokens raw-budget fallback
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# ---------------------------------------------------------------------------
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class TestTailCutRawBudgetFallback:
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"""When the entire transcript fits within soft_ceiling, the fix
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re-walks with the raw budget to find a meaningful cut point."""
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def test_meaningful_cut_with_large_ratio(self):
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"""With summary_target_ratio=0.45, _find_tail_cut_by_tokens still
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leaves a meaningful compressable region."""
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comp = _make_compressor(
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summary_target_ratio=0.45,
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config_context_length=96000,
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)
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messages = _build_session(20, words_per_turn=20)
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head_end = comp._protect_head_size(messages)
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head_end = comp._align_boundary_forward(messages, head_end)
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cut = comp._find_tail_cut_by_tokens(messages, head_end)
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n = len(messages)
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middle_size = cut - head_end
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assert middle_size >= 3, (
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f"Expected at least 3 messages in compressable region, got {middle_size} "
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f"(cut={cut}, head_end={head_end}, n={n})"
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)
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def test_default_ratio_still_works(self):
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"""Default ratio (0.20) should not be affected by the fix."""
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comp = _make_compressor(
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summary_target_ratio=0.20,
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config_context_length=96000,
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)
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messages = _build_session(20, words_per_turn=50)
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head_end = comp._protect_head_size(messages)
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head_end = comp._align_boundary_forward(messages, head_end)
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cut = comp._find_tail_cut_by_tokens(messages, head_end)
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n = len(messages)
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assert head_end < cut < n, (
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f"Expected head_end ({head_end}) < cut ({cut}) < n ({n})"
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)
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def test_proactive_fix_prevents_no_op_window(self):
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"""The raw-budget fallback in _find_tail_cut_by_tokens should prevent
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compress_start >= compress_end for the exact issue scenario:
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context_length=96000, summary_target_ratio=0.45."""
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comp = _make_compressor(
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summary_target_ratio=0.45,
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config_context_length=96000,
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)
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# Simulate the issue scenario: 16 messages, all fitting in soft_ceiling
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messages = _build_session(8, words_per_turn=30) # 17 messages
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head_end = comp._protect_head_size(messages)
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head_end = comp._align_boundary_forward(messages, head_end)
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cut = comp._find_tail_cut_by_tokens(messages, head_end)
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# With the fix, cut should be well past head_end
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assert cut > head_end + 1, (
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f"Expected cut ({cut}) > head_end ({head_end}) + 1, "
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f"meaning the compressable window is non-trivial"
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)
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# ---------------------------------------------------------------------------
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# Test: Effective compression resets counter
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# ---------------------------------------------------------------------------
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class TestEffectiveCompressionResetsCounter:
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"""When compression actually saves tokens, the ineffective counter resets."""
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def test_effective_compression_resets_counter(self):
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"""After an effective compression, _ineffective_compression_count = 0."""
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comp = _make_compressor(
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summary_target_ratio=0.20,
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config_context_length=96000,
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)
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messages = _build_session(30, words_per_turn=100)
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comp._generate_summary = MagicMock(return_value="Compacted summary of earlier turns.")
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comp.last_prompt_tokens = 65_000
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comp.compress(messages, current_tokens=65_000)
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assert comp._ineffective_compression_count == 0, (
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f"Expected 0 ineffective compressions with effective compression, "
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f"got {comp._ineffective_compression_count}"
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)
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# ---------------------------------------------------------------------------
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# Test: anti-thrashing in should_compress
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# ---------------------------------------------------------------------------
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class TestAntiThrashing:
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"""Directly test the should_compress anti-thrashing guard."""
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def test_ineffective_count_2_blocks(self):
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"""_ineffective_compression_count >= 2 -> should_compress returns False."""
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comp = _make_compressor(config_context_length=96000)
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comp.last_prompt_tokens = 65_000
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comp._ineffective_compression_count = 2
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assert not comp.should_compress(65_000)
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def test_ineffective_count_1_allows(self):
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"""_ineffective_compression_count = 1 -> should_compress still True."""
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comp = _make_compressor(config_context_length=96000)
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comp.last_prompt_tokens = 65_000
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comp._ineffective_compression_count = 1
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assert comp.should_compress(65_000)
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def test_below_threshold_allows(self):
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"""Tokens below threshold -> should_compress returns False regardless."""
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comp = _make_compressor(config_context_length=96000)
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comp.last_prompt_tokens = 10_000
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assert not comp.should_compress(10_000)
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