diff --git a/pyproject.toml b/pyproject.toml
index be21077..a8e6676 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -88,6 +88,20 @@ include = ["src/bmad_loop"]
 # part of the package's import graph); type-checking them is noise.
 exclude = ["src/bmad_loop/data"]
 typeCheckingMode = "basic"
+# Stage 2 of #245: the pure/leaf modules (no live process, git, or mux I/O) are
+# held to strict analysis while the rest stays basic. `strict` overrides
+# typeCheckingMode for these paths only — the same effect as a per-file
+# `# pyright: strict` comment — so annotation drift in the domain core is caught
+# without forcing the I/O-heavy modules over the strict bar. No runtime changes.
+strict = [
+  "src/bmad_loop/model.py",
+  "src/bmad_loop/statemachine.py",
+  "src/bmad_loop/policy.py",
+  "src/bmad_loop/documents.py",
+  "src/bmad_loop/machine.py",
+  "src/bmad_loop/checks.py",
+  "src/bmad_loop/sanitize.py",
+]
 # Check against the floor of requires-python so we never lean on 3.12+ typing.
 pythonVersion = "3.11"
 # Resolve third-party imports from the uv-managed project venv (created by
diff --git a/src/bmad_loop/checks.py b/src/bmad_loop/checks.py
index 739841b..8460ae1 100644
--- a/src/bmad_loop/checks.py
+++ b/src/bmad_loop/checks.py
@@ -21,9 +21,17 @@
 on runtime data, so it is a lint with a stack trace rather than a validation.
 """
 
+# Strict-checked under #245 Stage 2, with one rule relaxed for this file only:
+# `ValidationReport.findings` uses the idiomatic `field(default_factory=list)`,
+# which pyright can only infer as `list[Unknown]` (it does not fold the declared
+# `list[Finding]` annotation back into the bare `list` factory) though the field
+# is correctly typed. Every other strict rule stays on.
+# pyright: reportUnknownVariableType=false
+
 from __future__ import annotations
 
 import sys
+from collections.abc import Mapping
 from dataclasses import dataclass, field
 from typing import Literal
 
@@ -80,7 +88,7 @@ class Finding:
     check: str
     severity: Severity
     message: str
-    detail: dict | None = None
+    detail: Mapping[str, object] | None = None
 
 
 @dataclass
@@ -95,17 +103,23 @@ class ValidationReport:
 
     findings: list[Finding] = field(default_factory=list)
 
-    def add(self, check: str, severity: Severity, message: str, detail: dict | None = None) -> None:
+    def add(
+        self,
+        check: str,
+        severity: Severity,
+        message: str,
+        detail: Mapping[str, object] | None = None,
+    ) -> None:
         assert check in VALIDATE_CHECKS, f"unregistered check id: {check!r}"
         self.findings.append(Finding(check, severity, message, detail))
 
-    def ok(self, check: str, message: str, detail: dict | None = None) -> None:
+    def ok(self, check: str, message: str, detail: Mapping[str, object] | None = None) -> None:
         self.add(check, "ok", message, detail)
 
-    def warn(self, check: str, message: str, detail: dict | None = None) -> None:
+    def warn(self, check: str, message: str, detail: Mapping[str, object] | None = None) -> None:
         self.add(check, "warning", message, detail)
 
-    def fail(self, check: str, message: str, detail: dict | None = None) -> None:
+    def fail(self, check: str, message: str, detail: Mapping[str, object] | None = None) -> None:
         self.add(check, "problem", message, detail)
 
     def extend(self, findings: list[Finding]) -> None:
diff --git a/src/bmad_loop/documents.py b/src/bmad_loop/documents.py
index ccbe43f..7c335ef 100644
--- a/src/bmad_loop/documents.py
+++ b/src/bmad_loop/documents.py
@@ -52,7 +52,9 @@
 VALIDATE_SCHEMA_VERSION = 1
 
 
-def validate_document(report: ValidationReport, stories_on: bool, spec_folder: str) -> dict:
+def validate_document(
+    report: ValidationReport, stories_on: bool, spec_folder: str
+) -> dict[str, object]:
     """The `validate --json` document: the verdict plus every check that produced it.
 
     Obeys the pure-document contract in machine.py (additive-only evolution;
@@ -211,7 +213,7 @@ def status_document(state: RunState, *, graceful_stop_pending: bool = False) ->
         status = "stopped"
     else:
         status = "in-progress"
-    tasks = []
+    tasks: list[dict[str, object]] = []
     for key, task in state.tasks.items():
         tokens = task.tokens.to_dict()
         tokens["raw"] = task.tokens.total
diff --git a/src/bmad_loop/machine.py b/src/bmad_loop/machine.py
index 5e5cab7..0270b97 100644
--- a/src/bmad_loop/machine.py
+++ b/src/bmad_loop/machine.py
@@ -118,7 +118,9 @@ def emit_document(rendered: str) -> None:
     # is a crash with stdout still empty — permitted by the contract above.
     if hasattr(sys.stdout, "reconfigure"):
         # hasattr-guarded: reconfigure exists on TextIOWrapper, not the TextIO base.
-        sys.stdout.reconfigure(encoding="utf-8")  # pyright: ignore[reportAttributeAccessIssue]
+        sys.stdout.reconfigure(  # pyright: ignore[reportAttributeAccessIssue, reportUnknownMemberType]
+            encoding="utf-8"
+        )
     print(document)
 
 
diff --git a/src/bmad_loop/model.py b/src/bmad_loop/model.py
index 3dc3ac6..8e8c6ea 100644
--- a/src/bmad_loop/model.py
+++ b/src/bmad_loop/model.py
@@ -1,5 +1,16 @@
 """Core data model: story lifecycle phases, per-task records, run state."""
 
+# Strict-checked under #245 Stage 2, with the two rules below relaxed for this
+# file only. `reportUnknownVariableType`: the dataclass collection fields use the
+# idiomatic `field(default_factory=list|dict)`, which pyright can only infer as
+# `list[Unknown]` / `dict[Unknown, Unknown]` (it does not fold the declared
+# annotation back into the factory) though the fields are correctly typed.
+# `reportUnknownArgumentType`: `from_dict` / snapshot readers pull values out of
+# run-persisted `dict[str, Any]`, so isinstance-narrowing an `Any` value yields
+# Unknown at that boundary. Both are inherent to the persistence edge, not
+# annotation drift; every other strict rule stays on.
+# pyright: reportUnknownArgumentType=false, reportUnknownVariableType=false
+
 from __future__ import annotations
 
 from dataclasses import dataclass, field
diff --git a/src/bmad_loop/policy.py b/src/bmad_loop/policy.py
index 39726b5..c636671 100644
--- a/src/bmad_loop/policy.py
+++ b/src/bmad_loop/policy.py
@@ -1,5 +1,15 @@
 """Policy-as-data: .bmad-loop/policy.toml -> immutable Policy dataclasses."""
 
+# Strict-checked under #245 Stage 2, with the three "expression fully known"
+# rules below relaxed for this file only: the snapshot/TOML readers rebuild typed
+# Policy objects from loosely-typed persisted data — `tomllib.load` and a run's
+# json-round-tripped `asdict(Policy)` both hand back `dict[str, Any]`, and
+# isinstance-narrowing an `Any` yields `dict[Unknown, Unknown]` — so `.get(...)`
+# chains off those dicts read as Unknown. Clearing them would take a TypedDict
+# per persisted shape or runtime coercions (out of scope for a no-runtime-change
+# gate); every other strict rule stays on and still catches annotation drift.
+# pyright: reportUnknownArgumentType=false, reportUnknownMemberType=false, reportUnknownVariableType=false
+
 from __future__ import annotations
 
 import re
diff --git a/src/bmad_loop/sanitize.py b/src/bmad_loop/sanitize.py
index aceab0c..0beec54 100644
--- a/src/bmad_loop/sanitize.py
+++ b/src/bmad_loop/sanitize.py
@@ -35,6 +35,14 @@
 bug or a future field can therefore never silently ship a secret/PII/path.
 """
 
+# Strict-checked under #245 Stage 2, with the two "expression fully known" rules
+# below relaxed for this file only: `_scrub` walks arbitrary, foreign JSON whose
+# leaves are `Any` by design (it exists to redact unknown/future fields), so
+# isinstance-narrowing that `Any` yields dict/list `[Unknown, ...]` and every
+# key/value it iterates is Unknown. Typing it away would defeat the point of a
+# catch-all scrubber. Every other strict rule stays on.
+# pyright: reportUnknownArgumentType=false, reportUnknownVariableType=false
+
 from __future__ import annotations
 
 import getpass
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 317e331..46f255a 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -3483,6 +3483,50 @@ def test_validate_json_warning_message_carries_no_severity_prefix(project, capsy
         assert not finding["message"].startswith(" ")
 
 
+def test_validate_json_detail_round_trips_for_every_real_shape(capsys):
+    """Every `detail` shape the real gates attach must survive `validate --json`'s
+    `json.dumps` boundary.
+
+    #268 widened `Finding.detail` to `Mapping[str, object]` for strict-mode
+    covariance — so `install.py`'s `dict[str, str]` stays assignable — which leaves
+    implicit the invariant this pins: the production path
+    `machine.emit(validate_document(...))` still emits one whole, parseable document
+    for every detail a caller actually builds. Each case below mirrors a real call
+    site (str values, the nested `dict(role_names)` dict, str+int, install.py's
+    `{**detail, "marker": ...}`, and the `detail=None` leg). A future caller that
+    attaches a non-JSON-serializable detail fails here, by name, rather than at
+    runtime on stdout.
+    """
+    from bmad_loop import machine
+
+    report = cli.ValidationReport()
+    report.ok("adapter.binary", "codex found", {"binary": "codex"})  # str values (cli.py)
+    report.ok(  # nested plain dict — the `dict(role_names)` shape (cli.py)
+        "policy",
+        "policy OK",
+        {"gates_mode": "warn", "adapters": {"dev": "claude", "review": "claude"}},
+    )
+    report.ok(  # str + int (cli.py)
+        "queue.stories-manifest", "stories OK", {"spec_folder": "docs", "stories": 3}
+    )
+    report.fail(  # install.py's `{**detail, "marker": ...}` shape
+        "skills.stories-dispatch-stale",
+        "stale",
+        {"tree": ".claude", "skill": "s", "file": "f", "marker": "m"},
+    )
+    report.ok("git.worktree-clean", "clean")  # the detail=None leg
+
+    # the exact production path: cli.py does `machine.emit(validate_document(...))`.
+    machine.emit(cli.validate_document(report, stories_on=False, spec_folder=""))
+    parsed = json.loads(capsys.readouterr().out)  # whole stdout parses => a pure document
+
+    by_check = {f["check"]: f for f in parsed["findings"]}
+    assert by_check["policy"]["detail"]["adapters"]["dev"] == "claude"  # nested dict survives
+    assert by_check["queue.stories-manifest"]["detail"]["stories"] == 3  # int, not "3"
+    assert by_check["skills.stories-dispatch-stale"]["detail"]["marker"] == "m"
+    assert by_check["git.worktree-clean"]["detail"] is None  # None -> null round-trips
+
+
 @pytest.mark.parametrize(
     ("spec", "mode", "folder"),
     [(None, "sprint", ""), (STORIES_SPEC_FOLDER, "stories", STORIES_SPEC_FOLDER)],