diff --git a/pyproject.toml b/pyproject.toml
index 90c4fa5..e871aef 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -68,6 +68,14 @@ build-backend = "setuptools.build_meta"
 [tool.setuptools.packages.find]
 include = ["sentinel*"]
 
+[tool.setuptools.package-data]
+# The non-editable wheel (the Docker image) must ship the versioned diagnosis
+# prompt + its integrity baseline; setuptools includes only *.py by default, so
+# without this the image crashes at PromptBundle.load. The eval corpus/cassettes
+# are deliberately NOT packaged — they are dev/CI-only and run from the source
+# tree, never from the installed wheel.
+"sentinel.diagnosis" = ["prompts/*.md", "prompts/*.sha256"]
+
 [tool.ruff]
 line-length = 100
 target-version = "py312"
diff --git a/tests/unit/test_packaging.py b/tests/unit/test_packaging.py
new file mode 100644
index 0000000..359730f
--- /dev/null
+++ b/tests/unit/test_packaging.py
@@ -0,0 +1,49 @@
+"""Contract test for the wheel's non-Python data files.
+
+setuptools packages only ``*.py`` by default. The diagnosis prompt bundle
+(``sentinel/diagnosis/prompts/{version}.md`` + ``.sha256``) is read at runtime
+via a package-relative path, so a non-editable install (the Docker image) must
+ship those files — otherwise the app crashes at ``PromptBundle.load`` on boot.
+
+CI runs the app from a source checkout and never builds the wheel, so nothing
+else guards this. This test pins the ``package-data`` declaration to the files
+it must cover. (A build-and-boot smoke of the actual image would be stronger but
+needs a Docker build in CI; tracked separately.)
+"""
+
+from __future__ import annotations
+
+import tomllib
+from pathlib import Path
+from typing import cast
+
+_REPO_ROOT = Path(__file__).resolve().parents[2]
+_PROMPTS_DIR = _REPO_ROOT / "sentinel" / "diagnosis" / "prompts"
+
+
+def _package_data() -> dict[str, list[str]]:
+    cfg = tomllib.loads((_REPO_ROOT / "pyproject.toml").read_text(encoding="utf-8"))
+    return cast("dict[str, list[str]]", cfg["tool"]["setuptools"]["package-data"])
+
+
+def test_diagnosis_prompts_are_declared_package_data() -> None:
+    patterns = _package_data().get("sentinel.diagnosis", [])
+    # The versioned prompt markdown is the file whose absence crashes the image.
+    assert any(
+        p.startswith("prompts/") and p.endswith(".md") for p in patterns
+    ), f"diagnosis prompts not declared as package-data: {patterns}"
+
+
+def test_every_prompt_file_exists_to_be_packaged() -> None:
+    """A declared glob with no files would silently ship nothing."""
+    md_files = list(_PROMPTS_DIR.glob("*.md"))
+    assert md_files, f"no prompt .md files under {_PROMPTS_DIR}"
+    # The loader also reads a sibling .sha256 integrity baseline per version; if a
+    # version ships a baseline it must be packaged too (declared via *.sha256).
+    for md in md_files:
+        baseline = md.with_suffix(".sha256")
+        if baseline.exists():
+            patterns = _package_data().get("sentinel.diagnosis", [])
+            assert any(
+                p.endswith(".sha256") for p in patterns
+            ), f"{baseline.name} exists but *.sha256 is not declared package-data"