M7.1: extract nisse-core

What isn't the dev agent's moves to nisse-core, unchanged in behaviour,
with its tests: canonical, render, render_anthropic, llm, catalog, probe,
context, views, state, reconcile, worker, cancel, dump, transport, matrix,
execution, testing, vault, memory, oplog, envfile and gitea (whole).

- nisse_core.state.StateStore holds the tables every agent has; an
  agent's subclass adds its tables (version, migrations), roles and
  views. nisse_dev.state.StateStore adds the build VM blocks (v5).
- views.project takes what each role is shown, rather than a fixed table.
- Vault takes the agent's name (agent=), for provenance.
- A test that nisse_core never imports an agent.
- The loop, config, git, delegation, expert, tools and evals stay in
  nisse-dev until nisse-ops has a loop to share.

Docs: the Development Plan marks M7.1 done and notes that Phase 6 waits on
the agent host and Terraform; Architecture Part L names the package.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01J5Utyfzw7gF7UhjRDEtjTk

nisse-core/tests/test_context.py

@@ -0,0 +1,300 @@
+"""The context budget (architecture L6)."""
+
+import io
+from pathlib import Path
+from typing import Any
+
+import pytest
+
+from nisse_core.canonical import (
+    AssistantText,
+    CanonicalEvent,
+    StoredEvent,
+    ToolCall,
+    ToolResult,
+    UserMessage,
+)
+from nisse_core.catalog import ModelCatalog, UnknownLimits
+from nisse_core.context import (
+    Budget,
+    BudgetedClient,
+    ContextOverflow,
+    estimate_tokens,
+    fit,
+    head_and_tail,
+)
+from nisse_core.oplog import OpLog
+from nisse_core.state import StateStore
+from nisse_dev.loop.driver import Driver
+
+
+def stored(events: list[CanonicalEvent]) -> list[StoredEvent]:
+    return [StoredEvent(id=i + 1, ts="t", event=e) for i, e in enumerate(events)]
+
+
+def turn(n: int, output: str) -> list[CanonicalEvent]:
+    """One executor turn: a command and its (possibly long) output."""
+    return [
+        ToolCall(call_id=f"c{n}", tool="run_command", arguments={"command": "make"}),
+        ToolResult(call_id=f"c{n}", result=output, success=True),
+    ]
+
+
+def transcript(turns: int, output_chars: int) -> list[StoredEvent]:
+    events: list[CanonicalEvent] = [UserMessage(text="start milestone 1", source="t")]
+    for n in range(turns):
+        events += turn(n, f"output {n} " + "x" * output_chars)
+    return stored(events)
+
+
+def budget(window: int, keep: int = 2) -> Budget:
+    return Budget(
+        window=window, max_output=500, keep_recent_turns=keep, safety_margin=0.1
+    )
+
+
+def results(events: list[StoredEvent]) -> dict[str, str]:
+    return {
+        e.event.call_id: e.event.result
+        for e in events
+        if isinstance(e.event, ToolResult)
+    }
+
+
+# --- keeping the end of long output ---------------------------------------
+
+
+def test_head_and_tail_keeps_the_failure_summary_at_the_end() -> None:
+    output = (
+        "exit code: 1\nstdout:\n"
+        + "collected 400 items\n" * 500
+        + "FAILED tests/test_app.py::test_greet - AssertionError\n"
+        + "==== 1 failed, 399 passed ====\n"
+    )
+    kept = head_and_tail(output, 1000)
+    assert len(kept) < 1100
+    assert kept.startswith("exit code: 1")  # the head keeps the exit code
+    assert "FAILED tests/test_app.py::test_greet" in kept
+    assert "1 failed, 399 passed" in kept
+    assert "characters omitted" in kept
+
+
+def test_short_text_is_untouched() -> None:
+    assert head_and_tail("fine", 1000) == "fine"
+
+
+# --- fitting, step by step -------------------------------------------------
+
+
+def test_a_transcript_that_fits_is_sent_unchanged() -> None:
+    events = transcript(turns=3, output_chars=100)
+    assert fit(events, "system", None, budget(100_000)) == events
+
+
+def test_step_one_cuts_older_tool_results_and_keeps_recent_ones_whole() -> None:
+    events = transcript(turns=6, output_chars=3000)
+    fitted = fit(events, "system", None, budget(4000, keep=2))
+
+    kept = results(fitted)
+    assert len(kept) == 6  # nothing dropped yet
+    for older in ("c0", "c1", "c2", "c3"):
+        assert "characters omitted" in kept[older]
+    for recent in ("c4", "c5"):
+        assert "characters omitted" not in kept[recent]
+
+
+def test_step_two_drops_the_oldest_turns_and_says_so() -> None:
+    events = transcript(turns=20, output_chars=3000)
+    fitted = fit(events, "system", None, budget(4000, keep=2))
+
+    first = fitted[0].event
+    assert isinstance(first, UserMessage)
+    assert "omitted to fit the context window" in first.text
+    kept = results(fitted)
+    assert "c0" not in kept  # the oldest went
+    assert {"c18", "c19"} <= kept.keys()  # the recent turns stayed
+    assert "characters omitted" not in kept["c19"]
+    # Every surviving result still has its call: a provider rejects an
+    # answer to a call it never saw.
+    calls = {e.event.call_id for e in fitted if isinstance(e.event, ToolCall)}
+    assert kept.keys() <= calls
+    assert estimate_tokens(fitted, "system", None) <= budget(4000).for_prompt
+
+
+def test_step_three_refuses_what_cannot_fit() -> None:
+    # Even the two most recent turns are bigger than the whole window.
+    events = transcript(turns=3, output_chars=20_000)
+    with pytest.raises(ContextOverflow, match="last 2 turns"):
+        fit(events, "system", None, budget(2000, keep=2))
+
+
+def test_a_huge_system_prompt_alone_overflows() -> None:
+    events = transcript(turns=1, output_chars=10)
+    with pytest.raises(ContextOverflow):
+        fit(events, "s" * 50_000, None, budget(4096))
+
+
+def test_the_output_ceiling_and_margin_come_out_of_the_window() -> None:
+    b = Budget(window=4096, max_output=1024, keep_recent_turns=6, safety_margin=0.1)
+    assert b.for_prompt == int(4096 * 0.9) - 1024
+
+
+# --- the client wrapper ----------------------------------------------------
+
+
+class RecordingClient:
+    def __init__(self, reported_input: int = 0) -> None:
+        self.calls: list[dict[str, Any]] = []
+        self.last_usage = {"input": reported_input, "output": 5}
+
+    def complete(self, events, tools, model, system=None, *, max_tokens=None, **kwargs):
+        self.calls.append({"events": events, "max_tokens": max_tokens, **kwargs})
+        return [AssistantText(text="ok", model=model)]
+
+
+def test_the_ceiling_is_the_smaller_of_config_and_model() -> None:
+    inner = RecordingClient()
+    client = BudgetedClient(inner, lambda m: (4096, 1024), max_output_tokens=16384)
+    client.complete(transcript(1, 10), None, "llama3.2")
+    assert inner.calls[0]["max_tokens"] == 1024
+
+    client = BudgetedClient(inner, lambda m: (200_000, 64_000), max_output_tokens=16384)
+    client.complete(transcript(1, 10), None, "claude-haiku-4-5")
+    assert inner.calls[1]["max_tokens"] == 16384
+
+
+def test_the_wrapper_sends_the_fitted_events() -> None:
+    inner = RecordingClient()
+    client = BudgetedClient(
+        inner, lambda m: (4000, 500), keep_recent_turns=2, safety_margin=0.1
+    )
+    client.complete(transcript(20, 3000), None, "m", system="system")
+    sent = inner.calls[0]["events"]
+    assert "omitted to fit" in sent[0].event.text
+
+
+def test_reported_usage_only_ever_raises_the_estimate() -> None:
+    events = transcript(1, 10)
+    estimate = estimate_tokens(events, None, None)
+
+    under = RecordingClient(reported_input=estimate * 2)  # we undercounted
+    client = BudgetedClient(under, lambda m: (100_000, None))
+    client.complete(events, None, "m")
+    assert client._factors["m"] == pytest.approx(2.0, rel=0.05)
+
+    over = RecordingClient(reported_input=estimate // 2)  # we overcounted
+    under_then_over = BudgetedClient(over, lambda m: (100_000, None))
+    under_then_over._factors["m"] = 2.0
+    under_then_over.complete(events, None, "m")
+    assert under_then_over._factors["m"] == 2.0  # never loosened
+
+
+def test_last_usage_passes_through() -> None:
+    client = BudgetedClient(RecordingClient(reported_input=7), lambda m: (100, None))
+    assert client.last_usage["input"] == 7
+
+
+# --- the limits come from LiteLLM's catalog --------------------------------
+
+
+CATALOG = ModelCatalog.from_payload(
+    {
+        "data": [
+            {
+                "model_name": "claude-haiku-4-5",
+                "litellm_params": {"model": "anthropic/claude-haiku-4-5"},
+                "model_info": {"max_input_tokens": 200000, "max_output_tokens": 64000},
+            },
+            {
+                "model_name": "llama3.2",
+                "litellm_params": {"model": "ollama/llama3.2"},
+                "model_info": {"max_input_tokens": 4096, "max_output_tokens": 1024},
+            },
+            {
+                "model_name": "undeclared",
+                "litellm_params": {"model": "ollama/qwen3"},
+                "model_info": {"max_input_tokens": None},
+            },
+        ]
+    }
+)
+
+
+def test_the_catalog_reads_each_models_limits() -> None:
+    facts = CATALOG.facts("llama3.2")
+    assert (facts.max_input_tokens, facts.max_output_tokens) == (4096, 1024)
+    assert CATALOG.facts("undeclared").max_input_tokens is None
+
+
+def test_a_role_on_a_model_without_a_window_is_refused() -> None:
+    CATALOG.require_limits({"driver": "llama3.2", "helper": "claude-haiku-4-5"})
+    with pytest.raises(UnknownLimits, match="driver='undeclared'"):
+        CATALOG.require_limits({"driver": "undeclared", "helper": "llama3.2"})
+
+
+def test_a_request_that_cannot_fit_ends_the_run(tmp_path: Path) -> None:
+    # Never sent: the driver's run fails and the item waits on the operator,
+    # like any failed call, rather than a server getting a prompt it would
+    # silently cut.
+    store = StateStore(tmp_path / "state.db", oplog=OpLog("t", io.StringIO()))
+    store.transcript("t", "operator").append(UserMessage(text="go", source="t"))
+    inner = RecordingClient()
+    client = BudgetedClient(inner, lambda m: (4096, 1024))
+    outcome = Driver(client, "m").run(
+        store.transcript("t", "driver"),
+        system="s" * 20_000,  # a system prompt too big to fit
+        tools=[],
+        workspace=None,
+    )
+
+    assert outcome.kind == "failed"
+    assert "fit" in outcome.note
+    assert inner.calls == []
+
+
+# --- tool_choice is only asked of servers that enforce it -------------------
+
+FINISH = [{"type": "function", "function": {"name": "finish", "parameters": {}}}]
+
+
+def test_required_is_asked_only_of_models_declared_to_enforce_it() -> None:
+    # Measured: qwen3-14b under "required" cannot stop and rambles to the
+    # output ceiling, so a model that is not declared is never asked.
+    inner = RecordingClient()
+    client = BudgetedClient(
+        inner, lambda m: (32768, 8192), enforces_tool_choice=lambda m: m == "local-fast"
+    )
+    client.complete(transcript(1, 10), FINISH, "local-fast")
+    client.complete(transcript(1, 10), FINISH, "local-coder")
+    client.complete(transcript(1, 10), None, "local-fast")
+    assert [c["require_tool_call"] for c in inner.calls] == [True, False, False]
+
+
+def test_the_catalog_reads_supports_tool_choice() -> None:
+    catalog = ModelCatalog.from_payload(
+        {
+            "data": [
+                {"model_name": "a", "model_info": {"supports_tool_choice": True}},
+                {"model_name": "b", "model_info": {"supports_tool_choice": False}},
+                {"model_name": "c", "model_info": {}},
+            ]
+        }
+    )
+    assert [catalog.facts(m).supports_tool_choice for m in "abc"] == [True, False, None]
+
+
+def test_a_fallback_answer_is_recognised() -> None:
+    facts = ModelCatalog.from_payload(
+        {
+            "data": [
+                {
+                    "model_name": "claude-haiku-4-5",
+                    "litellm_params": {"model": "anthropic/claude-haiku-4-5"},
+                }
+            ]
+        }
+    ).facts("claude-haiku-4-5")
+    assert facts.answered("claude-haiku-4-5")  # LiteLLM's alias
+    assert facts.answered("claude-haiku-4-5-20251001")  # the provider's own name
+    assert facts.answered(None)  # nothing reported
+    assert not facts.answered("claude-sonnet-5")  # somebody else answered