diff --git a/.changeset/runtime-fixture-shape.md b/.changeset/runtime-fixture-shape.md
new file mode 100644
index 00000000..9dc53de7
--- /dev/null
+++ b/.changeset/runtime-fixture-shape.md
@@ -0,0 +1,17 @@
+---
+"@taskless/cli": patch
+---
+
+Document where a runtime rule's test fixtures go.
+
+`create-runtime-rule` described a rule directory as `captures/*.yml` plus
+`check.ts` and said nothing about `.tests/`, so an agent authoring a runtime
+rule had no statement of the fixture layout at all. `verify-rule` reported
+runtime tests as "not run" without saying what was not being run.
+
+Both now state it: cases live in `.tests/pass/` and `.tests/fail/`, and a
+case is a **directory** whose path is the `root` the harness hands the
+check, so it may hold as many files as the case needs. That last part is
+load-bearing rather than incidental — a runtime rule exists because its
+evidence spans more than one file, so a layout allowing one file per case
+could not express the rules the tier is for.
diff --git a/packages/cli/src/agent/create-runtime-rule.txt b/packages/cli/src/agent/create-runtime-rule.txt
index 821a87ed..c0b66ccd 100644
--- a/packages/cli/src/agent/create-runtime-rule.txt
+++ b/packages/cli/src/agent/create-runtime-rule.txt
@@ -1,4 +1,4 @@
-# Topic: create-runtime-rule     (CLI v%(CLI_VERSION)s / topic v1)
+# Topic: create-runtime-rule     (CLI v%(CLI_VERSION)s / topic v2)
 
 ## You are here
 This is `create-runtime-rule`. It helps you write a runtime rule: a
@@ -31,6 +31,22 @@ kinds of file:
 |------------------|---------------------------------------------------------------------------|
 | `captures/*.yml` | ast-grep capture rules that narrow which files the check looks at         |
 | `check.ts`       | a module whose default export receives those matches and returns findings |
+| `.tests/`        | fixtures, in `pass/` and `fail/` buckets                                  |
+
+A fixture case is a DIRECTORY, not a file: `.tests/pass/case-1/`, and its
+path is the `root` the harness hands the check, with every `match.file`
+relative to it. So a case may hold as many files as the case needs.
+
+That is not a detail. A runtime rule exists because its evidence spans
+more than one file, so a layout allowing one file per case could not
+express the rules the tier is for. `pass/case-1/src/a.ts` alongside
+`pass/case-1/src/b.ts` is the ordinary shape, not the exotic one.
+
+`pass`/`fail` rather than `valid`/`invalid`, matching Vale's buckets.
+`valid`/`invalid` are key names inside an ast-grep test YAML and are
+right for `sg` for one reason only: that file is handed to `sg test`
+verbatim. Nothing hands a runtime fixture to ast-grep, so borrowing the
+word here would make it mean two things.
 
 `verify` fails a runtime rule with no capture rule in `captures/`,
 because `check.ts` would then never be invoked.
diff --git a/packages/cli/src/agent/verify-rule.txt b/packages/cli/src/agent/verify-rule.txt
index 4cc03b4b..b9d511ce 100644
--- a/packages/cli/src/agent/verify-rule.txt
+++ b/packages/cli/src/agent/verify-rule.txt
@@ -35,7 +35,7 @@ What each engine is checked for:
 |-----------|--------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------|
 | `sg`      | ast-grep schema, plus `id`/`language`/`severity`/`message`/`rule`, and `regex` accompanied by `kind`                                 | the `valid`/`invalid` cases in `.tests/`                   |
 | `vale`    | style parses, `extends` and `message` present, `level` in vocabulary, and the rule's `.vale.ini` enables `<id>.<id>` under a matcher | the `.tests/pass/` and `.tests/fail/` buckets              |
-| `runtime` | `check.ts` present, at least one capture rule in `captures/`                                                                         | reported as not run: runtime tests need the server harness |
+| `runtime` | `check.ts` present, at least one capture rule in `captures/`                                                                         | reported as not run: the `.tests/pass/` and `.tests/fail/` cases need the server harness |
 
 ## What a path means