diff --git a/autoassistant/audit_skill_apis.py b/autoassistant/audit_skill_apis.py
index ce02f78..1233ac7 100644
--- a/autoassistant/audit_skill_apis.py
+++ b/autoassistant/audit_skill_apis.py
@@ -774,7 +774,26 @@ def compute_baseline() -> dict:
     }
 
 
-def write_baseline(root: Path) -> Path:
+def write_baseline(root: Path, *, allow_dev_stack: bool = False) -> Path:
+    # The committed baseline is the contract "these docs were validated against this
+    # released stack". Nightly releases are wheels/tags-only, so a source checkout /
+    # PYTHONPATH / editable stack reports the *last-committed* version string, not the
+    # latest release — a baseline snapshotted from one silently pins a version PyPI has
+    # moved past (this exact incident shipped once and was caught by the wiki-currency
+    # CI). Refuse unless the caller explicitly owns the risk.
+    if not allow_dev_stack:
+        check = inspect_installation()
+        if check.install_kind not in (
+            "packaged install (pip/conda provenance not distinguishable)",
+        ):
+            sys.exit(
+                f"[baseline] refusing to write: the active stack is a dev install "
+                f"({check.install_kind}), whose version string can trail the latest "
+                f"release (wheels/tags-only nightlies never bump source `main`). "
+                f"Write the baseline from a clean venv with the released wheel "
+                f"(`env -u PYTHONPATH <venv>/bin/python ... --write-baseline`), or "
+                f"pass --allow-dev-stack to snapshot this stack deliberately."
+            )
     baseline = compute_baseline()
     path = root / BASELINE_REL_PATH
     path.parent.mkdir(parents=True, exist_ok=True)
@@ -1378,7 +1397,14 @@ def main() -> int:
         "--write-baseline",
         action="store_true",
         help="Snapshot the installed stack (versions + API-surface hash) to "
-        "wiki/core/api_audit_baseline.json and exit. Re-pin after a deliberate upgrade.",
+        "wiki/core/api_audit_baseline.json and exit. Re-pin after a deliberate upgrade. "
+        "Refuses a dev-source stack unless --allow-dev-stack is passed.",
+    )
+    parser.add_argument(
+        "--allow-dev-stack",
+        action="store_true",
+        help="Permit --write-baseline against a source-checkout/PYTHONPATH/editable "
+        "stack, whose version string can trail the latest PyPI release.",
     )
     parser.add_argument(
         "--check-version",
@@ -1472,7 +1498,7 @@ def main() -> int:
             return install_status
         return check_version(root)
     if args.write_baseline:
-        path = write_baseline(root)
+        path = write_baseline(root, allow_dev_stack=args.allow_dev_stack)
         print(f"[baseline] wrote {path}", file=sys.stderr)
         return 0
 
diff --git a/autoassistant/tests/test_install_preflight.py b/autoassistant/tests/test_install_preflight.py
index e6c4d7e..4611ed1 100644
--- a/autoassistant/tests/test_install_preflight.py
+++ b/autoassistant/tests/test_install_preflight.py
@@ -75,3 +75,35 @@ def test_version_check_routes_absent_stack_to_install_preflight():
     assert process.returncode == 2
     assert "[install] NOT INSTALLED" in process.stderr
     assert "API DRIFT" not in process.stderr
+
+
+def test_write_baseline_refuses_dev_stack(tmp_path, monkeypatch):
+    """The baseline contract is 'validated against this RELEASED stack'; a dev-source
+    stack's version string can trail PyPI (wheels/tags-only nightlies), so snapshotting
+    one without --allow-dev-stack must refuse."""
+    import importlib.util
+    import sys as _sys
+
+    spec = importlib.util.spec_from_file_location(
+        "audit_under_test_baseline", ROOT / "autoassistant" / "audit_skill_apis.py"
+    )
+    mod = importlib.util.module_from_spec(spec)
+    _sys.modules[spec.name] = mod
+    spec.loader.exec_module(mod)
+
+    dev_check = mod.InstallationCheck(
+        status="ready", python="py", prefix="env", versions={}, locations={},
+        missing=[], errors={}, install_kind="source checkout or PYTHONPATH install",
+        cache_defaults={},
+    )
+    monkeypatch.setattr(mod, "inspect_installation", lambda: dev_check)
+
+    import pytest as _pytest
+
+    with _pytest.raises(SystemExit) as exc:
+        mod.write_baseline(tmp_path)
+    assert "refusing to write" in str(exc.value)
+
+    # With the explicit flag the same stack is snapshotted deliberately.
+    path = mod.write_baseline(tmp_path, allow_dev_stack=True)
+    assert path.exists()
diff --git a/skills/af_audit_skill_apis.md b/skills/af_audit_skill_apis.md
index 0b235bd..323160a 100644
--- a/skills/af_audit_skill_apis.md
+++ b/skills/af_audit_skill_apis.md
@@ -92,6 +92,13 @@ python autoassistant/audit_skill_apis.py --check-version
 python autoassistant/audit_skill_apis.py --write-baseline
 ```
 
+`--write-baseline` **refuses a dev-source stack** (source checkout / PYTHONPATH /
+editable): nightly releases are wheels/tags-only, so a dev stack's version string can
+trail the latest PyPI release and would bake a stale pin into the baseline. Write the
+baseline from a clean venv holding the released wheel
+(`env -u PYTHONPATH <venv>/bin/python autoassistant/audit_skill_apis.py --write-baseline`);
+`--allow-dev-stack` overrides deliberately.
+
 The workflow is: `--check-version` flags that the installed autofit moved → run the full
 `--scope all` audit to find what broke → fix the references (per the Branch section below)
 → `--write-baseline` to re-pin once the audit is clean. **Only re-pin after fixing**, never