manual_slop/conductor/directives/cache_stable_to_volatile/v1.md

Context must be ordered stable-to-volatile — the stable prefix (layers 1-7) gets cached, the volatile suffix (layers 8-12) never does

1. The 12-layer model (the stable-to-volatile ordering)

#	Layer	Stable across turns?	Source	SSDL
1	Role instructions (model + provider)	yes	_get_combined_system_prompt	[I]
2	Function-calling schema	yes	per provider	[I]
3	Discovered tool descriptions	yes	mcp_client.get_tool_schemas()	[I]
4	System prompt preset	yes	app_state.ai_settings.system_prompt	[I]
5	Persona profile	yes	app_state.active_persona	[I]
6	Project context (per manual_slop.toml)	yes	NEW (Candidate 14)	[I]
7	Knowledge digest (per knowledge/digest.md)	yes (within a gc cycle)	NEW (Candidate 8)	[I]
8	Discussion metadata (name, role count)	no (per turn)	disc_entries[:1] or disc_meta	─── (data)
9	Active preset (FileItem set)	no (per turn)	self.context_files	─── (data)
10	Per-file details (history, slices, notes)	no (per file)	per FileItem	─── (data)
11	Tool-call results from prior turns	no (per turn)	per _reread_file_items	─── (data)
12	The user message	no (per turn)	the input	─── (data)

The cache boundary is at layer 7/8. Layers 1-7 are byte-identical across turns of the same discussion (and across discussions of the same mode). Layers 8-12 change per turn.

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2. The byte-comparison test (the design contract)

The design rule "stable prefix is byte-identical" must be testable. The test:

# In tests/test_aggregate_caching.py (NEW)
def test_aggregate_stable_to_volatile_ordering():
    """The first N characters of the context should be identical across turns
    of the same conversation, when no stable-layer inputs change."""
    ctrl = mock_app_controller()
    ctrl.ai_settings.system_prompt = "Test system prompt"
    ctrl.active_persona = mock_persona()

    # Turn 1
    turn1 = aggregate.build_initial_context(ctrl, user_message="first prompt")

    # Turn 2 (same stable inputs, different user message)
    turn2 = aggregate.build_initial_context(ctrl, user_message="second prompt")

    # The first N characters should be identical (N = where the volatile layers start)
    N = aggregate.stable_prefix_length(ctrl)
    assert turn1[:N] == turn2[:N], f"Stable prefix mismatch: {turn1[:N]!r} != {turn2[:N]!r}"

The test is the contract. If a new layer is added in the middle of the stack, this test fails; the agent must either move the layer to the stable position or update the test (with written justification).