diff --git tree/agents/rocko/work/queue-56/delta-check.sh r2/agents/rocko/work/queue-56/delta-check.sh
index 69224ea..a502d1d 100755
--- tree/agents/rocko/work/queue-56/delta-check.sh
+++ r2/agents/rocko/work/queue-56/delta-check.sh
@@ -59,4 +59,7 @@ if [ "$(id -u)" != 0 ]; then
   hdr "runs directory unreadable: list"; run_case unreadable list
   hdr "runs directory unreadable: show"; run_case unreadable show "$A"
   chmod 755 "$D/runs"
+  D="$(root run-unreadable)"; mkdir -p "$D/runs/$A"; printf '%s\n' "$RESULT" > "$D/runs/$A/result.json"; chmod 000 "$D/runs/$A"
+  hdr "run directory unreadable: show"; run_case run-unreadable show "$A"
+  chmod 755 "$D/runs/$A"
 fi
diff --git tree/packages/runs/README.md r2/packages/runs/README.md
index 84230a1..8fd7808 100644
--- tree/packages/runs/README.md
+++ r2/packages/runs/README.md
@@ -40,7 +40,11 @@ printed them.
   - a run document resolving outside reads as `null`;
   - `active.json` or `activation-log.jsonl` resolving outside refuses.
 
-  A link that stays inside the data root is followed.
+  Only a path that exists can resolve. A link with nothing behind it reads
+  as missing wherever it points. A `state/` link out of the data root to a
+  path that doesn't exist reads as no release and an empty log, and a
+  `runs/` link like that lists nothing. A link that stays inside the data
+  root is followed.
 - **Run documents are JSON objects or `null`.** A document that is
   missing, unreadable, not JSON, or JSON but not an object (`null`, `5`,
   `[]`) reads as `null`. Run records are never validated beyond that,
@@ -49,11 +53,14 @@ printed them.
   shape `scripts/release.sh` writes: exactly `pointerVersion` 1 and
   non-empty strings `release`, `imageTag` and `activatedAt`. Anything else
   refuses with exit code 2 rather than being guessed at.
-- **The activation log is lenient per line.** An entry needs string `at`,
-  `event`, `release` and `imageTag`, an optional string `note`, and no
-  other keys. Other lines are counted in `malformed` and skipped, the way
-  `release.sh rollback` skips them. Blank lines aren't counted. `last`
-  must be a positive integer and keeps the newest entries.
+- **The activation log is read per line.** One bad line never refuses
+  the log. An entry needs string `at`, `event`, `release` and `imageTag`,
+  an optional string `note`, and no other keys. A line that isn't JSON,
+  or is JSON with another shape, is counted in `malformed` and skipped.
+  That is stricter than `release.sh rollback`, which skips only lines that
+  aren't JSON and would act on an entry with an extra key or a non-string
+  field. Blank lines aren't counted. `last` must be a positive integer and
+  keeps the newest entries.
 - **Errors.** Every refusal is a `RunsError` with `exitCode` 2 (invalid
   data) or 4 (a file or environment problem), matching
   `mosaic-task.mjs`. A missing data root, `runs/` or `state/` file is not
@@ -78,6 +85,7 @@ output changes on purpose:
 | `task.json` or `mission.json` is JSON but not an object | `show` printed its snapshot line | snapshot line omitted |
 | run is a regular file | `show` crashed | `run not found`, exit 4 |
 | `runs/` unreadable | `list` printed nothing | refuses, exit 4 |
+| run directory unreadable (mode 000) | `show` printed two lines, then crashed, exit 1 | refuses with EACCES, exit 4 |
 | link loop or a permission error resolving a run | `run not found` | refuses with the error code, exit 4 |
 
 `agents/rocko/work/queue-56/delta-check.sh` prints the before and after
diff --git tree/packages/runs/src/state.mjs r2/packages/runs/src/state.mjs
index a92c871..af5cc92 100644
--- tree/packages/runs/src/state.mjs
+++ r2/packages/runs/src/state.mjs
@@ -60,10 +60,11 @@ function logEntry(line) {
   return entry;
 }
 
-// The activation log as { entries, malformed }, oldest first. Lines that
-// aren't a well-formed entry are counted in malformed and skipped, the way
-// release.sh rollback skips them. A missing log is empty. With last, only
-// the newest last well-formed entries are returned.
+// The activation log as { entries, malformed }, oldest first. A line that
+// isn't JSON, or is JSON but not the entry shape release.sh writes, is
+// counted in malformed and skipped. This is stricter than release.sh
+// rollback, which skips only lines that aren't JSON. A missing log is empty.
+// With last, only the newest last well-formed entries are returned.
 export function readActivationLog(dataRoot, { last } = {}) {
   if (last !== undefined && (!Number.isInteger(last) || last < 1)) {
     throw new RunsError(`last must be a positive integer (got ${JSON.stringify(last)})`);
diff --git tree/packages/runs/tests/runs.test.mjs r2/packages/runs/tests/runs.test.mjs
index 85838e5..a652f62 100644
--- tree/packages/runs/tests/runs.test.mjs
+++ r2/packages/runs/tests/runs.test.mjs
@@ -216,6 +216,15 @@ test("listRunIds sorts whatever order the directory returns", (t) => {
   assert.deepEqual(listRunIds(dataRoot), [A, B]);
 });
 
+// list has always shown any r- name, including ones show refuses as ids.
+test("listRunRecords lists an r- name that isn't a valid run id, as before", (t) => {
+  const { dataRoot } = scratch(t);
+  write(path.join(dataRoot, "runs", "r-.bad", "result.json"), {});
+  assert.equal(isRunId("r-.bad"), false);
+  assert.deepEqual(listRunIds(dataRoot), ["r-.bad"]);
+  assert.deepEqual(listRunRecords(dataRoot), [{ runId: "r-.bad", result: {} }]);
+});
+
 test("the readers write nothing", (t) => {
   const { dataRoot } = scratch(t);
   const runs = path.join(dataRoot, "runs");
diff --git tree/packages/runs/tests/state.test.mjs r2/packages/runs/tests/state.test.mjs
index 80ab5ea..4b126f3 100644
--- tree/packages/runs/tests/state.test.mjs
+++ r2/packages/runs/tests/state.test.mjs
@@ -72,6 +72,13 @@ test("a state directory linked out of the data root refuses", (t) => {
   assert.throws(() => readActivePointer(dataRoot), /state\/active.json resolves outside the data root/);
 });
 
+test("a state directory linked out to nothing reads as no release and an empty log", (t) => {
+  const { dataRoot, outside } = scratch(t);
+  fs.symlinkSync(path.join(outside, "absent"), path.join(dataRoot, "state"));
+  assert.equal(readActivePointer(dataRoot), null);
+  assert.deepEqual(readActivationLog(dataRoot), { entries: [], malformed: 0 });
+});
+
 test("a missing log is empty", (t) => {
   const { dataRoot } = scratch(t);
   assert.deepEqual(readActivationLog(dataRoot), { entries: [], malformed: 0 });
@@ -95,11 +102,13 @@ test("the log reads oldest first and counts malformed lines", (t) => {
     { ...good[1], extra: true },
     { ...good[1], at: 5 },
     { ...good[1], note: null },
+    { at: good[1].at, event: good[1].event, release: good[1].release },
+    { ...good[1], release: 5 },
     good[2],
     good[3],
   ]);
-  assert.deepEqual(readActivationLog(dataRoot), { entries: good, malformed: 5 });
-  assert.deepEqual(readActivationLog(dataRoot, { last: 2 }), { entries: good.slice(2), malformed: 5 });
+  assert.deepEqual(readActivationLog(dataRoot), { entries: good, malformed: 7 });
+  assert.deepEqual(readActivationLog(dataRoot, { last: 2 }), { entries: good.slice(2), malformed: 7 });
   assert.deepEqual(readActivationLog(dataRoot, { last: 99 }).entries, good);
 });
 
diff --git tree/packages/runs/tests/task-cli.test.mjs r2/packages/runs/tests/task-cli.test.mjs
index b5fafd4..ed13ecd 100644
--- tree/packages/runs/tests/task-cli.test.mjs
+++ r2/packages/runs/tests/task-cli.test.mjs
@@ -92,3 +92,20 @@ test("show refuses a run linked out of the data root; list reports it unknown",
   assert.equal(list.status, 0, list.stderr);
   assert.equal(list.stdout, `${A}  unknown    task=-                  ws=-          session=-\n`);
 });
+
+test("list shows an r- name that isn't a valid run id, as before", (t) => {
+  const { dataRoot } = scratch(t);
+  write(path.join(dataRoot, "runs", "r-.bad", "result.json"), RESULT);
+  const out = task(t, dataRoot, "list");
+  assert.equal(out.status, 0, out.stderr);
+  assert.equal(out.stdout, "r-.bad  succeeded  task=t-one              ws=-          session=-\n");
+});
+
+test("show refuses an invalid id before reading the config", (t) => {
+  const { dir } = scratch(t);
+  const env = { ...process.env, MOSAIC_CONFIG: path.join(dir, "missing.json") };
+  delete env.NODE_TEST_CONTEXT;
+  const proc = spawnSync(process.execPath, [path.join(ROOT, "scripts", "mosaic-task.mjs"), "show", "../x"], { cwd: ROOT, env, encoding: "utf8" });
+  assert.equal(proc.status, 4, proc.stderr);
+  assert.equal(proc.stderr, 'mosaic-task: invalid run id: "../x" (expected r-<id>)\n');
+});