#400: classify the blanking loop's result on the observed value, not eval's exit status

eval "export NAME=" can return success even when zsh coerces the bare
assignment on an integer special parameter (SECONDS, RANDOM, SHLVL,
HISTSIZE, COLUMNS, LINES, USERNAME) instead of failing, leaving the
value unchanged. The old exit-status check then reported the name as
blanked when it was not -- a false receipt.

Classify on the observed effect instead: attempt the export, then read
the name's value back with the (P) indirection flag and decide from
whether it is now empty. One check now covers all three shapes a name
can take here -- a genuine blank, a fatal read-only error eval merely
contains, and this silent no-op -- with the exit status playing no
part in the decision.

Adds a test driving all three shapes through the real scrubScript in
one run (a normal name, LINENO for the fatal case, SECONDS for the
silent no-op), with the parent environment explicitly carrying those
names since a cleared ProcessBuilder parent does not expose them on
its own. Also corrects the previously-merged
unblankableNameInTheMiddleDoesNotAbortNamesAfterIt test, whose "exactly
one failed name" assertion turned out to only pass by accident: zsh
itself auto-exports SHLVL on every shell start, and the old exit-status
bug was silently miscounting it as blanked. The fixed classification
now correctly reports it unblankable too, so the test asserts presence
rather than an exact count.

CLAUDE.md

@@ -137,7 +137,7 @@ the merge — and merging on a reviewer's word is delegating it by proxy.
 | Answer a member's `fleet_ask` | `fleet_send{turnId, content}` — **not** `sessionId` |
 | Message a **peer lead** on this host | `fleet_send{sessionId: <their terminal>, content}` — `fleet_list` → `leads` reports it. Coordination only, **never** a task |
 | Message a **peer lead** on another daemon or host | `fleet_send{coordId: <their coord-id>, content}` — needs a `coordinator:` block; your own coord-id is in `fleet_list`. Coordination only, **never** a task |
-| Answer a peer lead that messaged you | `fleet_reply{content}` — the one case a lead replies |
+| Answer a peer lead that messaged you | `fleet_send{coordId}` — or `{sessionId}` if they are on this host. **Not** `fleet_reply`: it has no peer route and the publish is refused |
 | Collect a held reply | `fleet_poll{target}` · then `fleet_ack{target, msgId}` |
 | Tear down a member | `fleet_stop{paneId}` |
 
@@ -163,15 +163,21 @@ The traffic between leads is coordination and nothing else:
 3. **Verify a peer exactly as you verify yourself.** Peer status buys nothing: check the claim
    against the code, and re-run the build. A peer's correction gets the same treatment — right or
    wrong on the evidence, not on who said it. Neither of you merges the other's work unreviewed.
+   **N observations are N data points only if they differ in the axis you are trusting.** This cuts
+   both ways. N *failures* blamed on one cause are one data point when the cases share what you are
+   not varying. N *agreeing measurements* are also one data point when they share an instrument —
+   two hosts, two operators and the same formula is one formula, not two confirmations.
 4. **Ask a peer to read your project addendum.** Your addendum is instruction surface: every future
    session on your host obeys it, and a wrong one is obeyed just as faithfully as a right one. The
    author is the worst reader of their own qualifier placement — measured here, one addendum carried
    two defects and a non-author found both. If you have no peer, at least re-read it asking "which
    sentence goes false first, and would a reader reach the caveat before acting?"
 
-Being messaged by a peer does not make you its worker: answer with `fleet_reply`, and push back on
-the substance if it is wrong. A peer that simply complies has thrown away the reason there are two of
-you.
+Being messaged by a peer does not make you its worker: answer the way you would open —
+`fleet_send{coordId}` for another daemon, `fleet_send{sessionId}` on this host — and push back on
+the substance if it is wrong. `fleet_reply` resolves a member's blocked `fleet_send`; a peer's
+coord-id message is durable and non-blocking, so there is nothing for it to resolve. A peer that
+simply complies has thrown away the reason there are two of you.
 
 ### Member (worker or architect) — the turn contract
 

fleetd/src/main/java/dev/ltms/fleet/member/EnvAllowListScrub.java

@@ -75,9 +75,39 @@ import java.util.stream.Stream;
  * never to the control.
  *
  * <p>The scrub also writes {@code scrub-report.txt} into its own directory: one {@code allowed N of
- * M} line (N = exports left untouched, M = exports present when the scrub ran), then the blanked
- * NAMES — never values. The launcher reads this back at teardown and logs it, because a blocked
- * count next to an unknown denominator is not a finding.
+ * M failed F} line (N = exports left untouched, M = exports present when the scrub ran, F = names
+ * the scrub attempted to blank but could not), then the NAMES — blanked ones bare, unblankable ones
+ * {@code !}-prefixed — never values. The launcher reads this back at teardown and logs it, because a
+ * blocked count next to an unknown denominator is not a finding.
+ *
+ * <p><b>fleetd #394:</b> plain {@code export "$n="} is a FATAL error for a zsh read-only or special
+ * parameter (for example {@code UID}) — it aborts the whole sourced file, so every name still to
+ * come is never blanked and the report above is never written at all. The blanking loop instead
+ * routes each attempt through {@code eval}, which contains that error to the single iteration: the
+ * loop always finishes, and a name that could not be blanked is counted as {@code failed} and
+ * listed {@code !}-prefixed rather than silently disappearing. This is deliberately not a skip-list
+ * of known-bad names — every enumerated name is still attempted, so a name nobody has thought of
+ * yet still gets tried and, if it fails, still gets counted.
+ *
+ * <p>The blanking loop also re-asserts, on its own, the same {@code [A-Za-z_][A-Za-z0-9_]*} shape
+ * check the enumeration loop already applied. Before {@code eval} was introduced a non-conforming
+ * name reaching {@code export "$n="} was harmless either way — the quoting made it inert. With
+ * {@code eval}, the name is spliced into a string and interpreted as shell syntax, so the enumeration
+ * loop's check is no longer sufficient on its own to keep that call site safe — it is a guard on a
+ * different loop, and the two must not silently drift apart. Re-checking right before the
+ * {@code eval} keeps that call site safe by its own reading, independent of whatever the enumeration
+ * loop does or stops doing in a later change.
+ *
+ * <p><b>fleetd #400:</b> {@code eval}'s exit status is not proof that the blank actually happened.
+ * zsh coerces a bare {@code NAME=} assignment on an integer special parameter (measured on macOS zsh
+ * 5.9: {@code SECONDS}, {@code RANDOM}, {@code SHLVL}, {@code HISTSIZE}, {@code COLUMNS},
+ * {@code LINES}, {@code USERNAME}) to a number instead of failing — {@code eval} returns success,
+ * the value is untouched, and a status-based classification reports it as blanked when it was not.
+ * The fix classifies on the observed effect instead: after the attempt, the name's value is read
+ * back with the {@code (P)} indirection flag and the decision is made from whether that is now
+ * empty. This one check covers all three shapes a name can take at this point — a genuine blank, a
+ * fatal read-only error {@code eval} merely contained, and this silent no-op — and the exit status
+ * plays no part in the decision at all.
  */
 public final class EnvAllowListScrub {
 
@@ -132,10 +162,16 @@ public final class EnvAllowListScrub {
     }
 
     /**
-     * A parsed {@code scrub-report.txt}: how many exported variables existed when the scrub ran,
-     * how many were left untouched (allowed), and the NAMES that were blanked. Values never appear.
+     * A parsed {@code scrub-report.txt}: how many exported variables existed when the scrub ran
+     * ({@code total}), how many were left untouched ({@code allowed}), how many the scrub attempted
+     * to blank but could not ({@code failed} — fleetd #394: a zsh read-only/special parameter such
+     * as {@code UID} fatally errors on plain {@code export NAME=}, so those attempts go through
+     * {@code eval} instead so the loop keeps going and the failure is counted rather than left
+     * invisible), and the NAMES in each of the latter two categories. {@code allowed +
+     * blanked.size() + unblankable.size() == total}, and {@code unblankable.size() == failed}.
+     * Values never appear.
      */
-    record ScrubReport(int allowed, int total, List<String> blanked) {
+    record ScrubReport(int allowed, int total, int failed, List<String> blanked, List<String> unblankable) {
     }
 
     /**
@@ -334,15 +370,57 @@ public final class EnvAllowListScrub {
                   _cb633_blank+=("$_cb633_n")
                 done
 
-                { for _cb633_n in "${_cb633_blank[@]}"; do export "$_cb633_n="; done; } 2>/dev/null
+                # fleetd #394: plain `export "$n="` is FATAL for a zsh read-only/special parameter
+                # (e.g. UID) and aborts this whole sourced file — every name still to come is never
+                # blanked, and the report below is never written, silently. `eval` contains that
+                # error to the single iteration instead: it still fails for that one name, but the
+                # loop continues and we can tell allowed / blanked / unblankable apart afterwards.
+                # This is not a skip-list of known-bad names (that would miss the next one nobody
+                # thought of) — every name in _cb633_blank is still attempted, unconditionally.
+                # Every name reaching this loop already passed the identical identifier check in the
+                # enumeration loop above — but that guard is 20 lines away in a different loop, and
+                # this line is about to splice the name into a string handed to `eval`. Before this
+                # fix the name only ever reached `export` quoted ("$n="), which is inert on a
+                # non-identifier string either way; `eval` makes THIS line the only thing standing
+                # between such a string and code execution in the member's pane, so it re-asserts the
+                # same check on its own rather than trusting a guard it does not own. Under normal
+                # operation this can never fire (the enumeration guard already filtered everything
+                # reaching _cb633_blank), so a name caught here is counted as unblankable rather than
+                # silently dropped — it is real evidence that the upstream guard was bypassed.
+                #
+                # fleetd #400: the attempt's own exit status is NOT proof of its effect. zsh coerces
+                # a bare `NAME=` assignment on an integer special parameter (SECONDS, RANDOM, SHLVL,
+                # HISTSIZE, COLUMNS, LINES, USERNAME on this host) to a number instead of failing —
+                # `eval` returns 0, the value is untouched, and the old exit-status check reported it
+                # as blanked when it was not. Classify on the observed effect instead: attempt the
+                # export, then read the name's value back with the `(P)` indirection flag and decide
+                # from whether it is now empty. One check then covers all three shapes a name can
+                # take here — a genuine blank, a fatal read-only error `eval` merely contained, and
+                # this silent no-op — without the exit status entering the decision at all.
+                typeset -a _cb633_ok _cb633_unblankable
+                _cb633_ok=()
+                _cb633_unblankable=()
+                for _cb633_n in "${_cb633_blank[@]}"; do
+                  if [[ ! "$_cb633_n" =~ ^[A-Za-z_][A-Za-z0-9_]*$ ]]; then
+                    _cb633_unblankable+=("$_cb633_n")
+                    continue
+                  fi
+                  eval "export ${_cb633_n}=" 2>/dev/null
+                  if [[ -z "${(P)_cb633_n}" ]]; then
+                    _cb633_ok+=("$_cb633_n")
+                  else
+                    _cb633_unblankable+=("$_cb633_n")
+                  fi
+                done
 
                 integer _cb633_kept=$(( _cb633_total - ${#_cb633_blank} ))
                 {
-                  print -r -- "allowed $_cb633_kept of $_cb633_total"
-                  for _cb633_n in "${_cb633_blank[@]}"; do print -r -- "$_cb633_n"; done
+                  print -r -- "allowed $_cb633_kept of $_cb633_total failed ${#_cb633_unblankable}"
+                  for _cb633_n in "${_cb633_ok[@]}"; do print -r -- "$_cb633_n"; done
+                  for _cb633_n in "${_cb633_unblankable[@]}"; do print -r -- "!$_cb633_n"; done
                 } > "$ZDOTDIR/%s" 2>/dev/null
 
-                unset _cb633_allowed _cb633_names _cb633_blank _cb633_n _cb633_total _cb633_kept
+                unset _cb633_allowed _cb633_names _cb633_blank _cb633_ok _cb633_unblankable _cb633_n _cb633_total _cb633_kept
                 """.formatted(names, MemberEnvAllowList.zshCasePattern(), REPORT_FILE);
     }
 
@@ -356,6 +434,11 @@ public final class EnvAllowListScrub {
      * Read and parse {@link #REPORT_FILE} out of a generated ZDOTDIR directory. Returns {@code null}
      * when absent or unreadable (the pane may have been torn down before its login shell ever got to
      * the scrub) — callers treat that as "no measurement available", never as success.
+     *
+     * <p>First line is {@code "allowed <N> of <M> failed <F>"} (fleetd #394 added the trailing
+     * {@code failed <F>} — a count of names the scrub attempted to blank but could not, e.g. a zsh
+     * read-only/special parameter). Every following non-blank line is a name: a bare name was
+     * blanked, a {@code !}-prefixed name was attempted and failed. Values never appear on either.
      */
     static ScrubReport readReport(Path zdotdir) {
         Path report = zdotdir.resolve(REPORT_FILE);
@@ -368,17 +451,24 @@ public final class EnvAllowListScrub {
                 return null;
             }
             String[] parts = lines.getFirst().substring("allowed ".length()).trim().split("\\s+");
-            if (parts.length != 3 || !"of".equals(parts[1])) {
+            if (parts.length != 5 || !"of".equals(parts[1]) || !"failed".equals(parts[3])) {
                 return null;
             }
             List<String> blanked = new ArrayList<>();
+            List<String> unblankable = new ArrayList<>();
             for (int i = 1; i < lines.size(); i++) {
-                if (!lines.get(i).isBlank()) {
-                    blanked.add(lines.get(i));
+                String line = lines.get(i);
+                if (line.isBlank()) {
+                    continue;
+                }
+                if (line.startsWith("!")) {
+                    unblankable.add(line.substring(1));
+                } else {
+                    blanked.add(line);
                 }
             }
             return new ScrubReport(Integer.parseInt(parts[0]), Integer.parseInt(parts[2]),
-                    List.copyOf(blanked));
+                    Integer.parseInt(parts[4]), List.copyOf(blanked), List.copyOf(unblankable));
         } catch (IOException | NumberFormatException e) {
             return null;
         }

fleetd/src/main/java/dev/ltms/fleet/member/HerdrPeerLauncher.java

@@ -1643,11 +1643,19 @@ public abstract class HerdrPeerLauncher implements PeerLauncher {
             log.warn("memberCredentials allow-list: pane {} left no scrub report in {} — the "
                     + "environment scrub cannot be confirmed to have run. Either the pane ended "
                     + "before its shell finished starting, or its shell never read our generated "
-                    + "startup files, in which case that member saw the full host environment.",
+                    + "startup files. Either way, we cannot tell from here whether the scrub ran, "
+                    + "so we do not know what that member's environment contained.",
                     paneId, dir);
         } else {
             log.info("memberCredentials allow-list: pane {} allowed {} of {} environment variables",
                     paneId, report.allowed(), report.total());
+            if (report.failed() > 0) {
+                log.warn("memberCredentials allow-list: pane {} could not blank {} environment "
+                        + "variable(s) — {} (likely a zsh read-only/special parameter) — those "
+                        + "names were left in the member's environment. Confirm none of them is a "
+                        + "credential.",
+                        paneId, report.failed(), report.unblankable());
+            }
             List<String> shaped = report.blanked().stream()
                     .filter(name -> CREDENTIAL_SHAPED_NAME.matcher(name).matches())
                     .toList();

fleetd/src/test/java/dev/ltms/fleet/member/EnvAllowListScrubTest.java

@@ -18,6 +18,7 @@ import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -118,6 +119,205 @@ class EnvAllowListScrubTest {
                 "allowed N of M with N <= M — the denominator is always reported");
     }
 
+    /**
+     * fleetd #394: the actual defect. Plain {@code export "$n="} is FATAL for a zsh read-only or
+     * special parameter (e.g. {@code UID}) and aborts the whole sourced file — every name still to
+     * come is never blanked, and the {@code scrub-report.txt} below is never written at all,
+     * silently ({@code 2>/dev/null} swallows the error). This plants an unblankable, exported,
+     * read-only variable in the MIDDLE of the names the scrub attempts to blank, with two more
+     * names after it, and asserts that both of those later names are STILL blanked and the report
+     * is STILL written with the failure counted — a test that only checked names BEFORE the failure
+     * point would pass today and prove nothing.
+     *
+     * <p>The planted name is a made-up one ({@code FLEETD_TEST_UNBLANKABLE}), not {@code UID} or
+     * any other name a skip-list might already know about — invariant 1 is that the loop survives
+     * ANY unblankable name, not a known one, so the test must not lean on one either.
+     *
+     * <p>Exercises the real artefact: {@link EnvAllowListScrub#scrubScript} is run verbatim under a
+     * real {@code /bin/zsh}, not just asserted on as a Java string. The four planted names are
+     * exported one at a time via {@code typeset -x}/{@code typeset -rx} immediately before the
+     * script runs, in a fixed order — zsh's {@code export}/{@code typeset -x} appends to the
+     * process's environment table in call order (verified empirically: a freshly-exported name
+     * always sorts after every inherited one and after every earlier freshly-exported name in
+     * {@code command env}'s own output), which is what makes the "middle" position deterministic
+     * here, unlike relying on the OS's own inherited-environment order.
+     */
+    @Test
+    void unblankableNameInTheMiddleDoesNotAbortNamesAfterIt(@TempDir Path tmp) throws Exception {
+        assumeTrue(Files.isExecutable(ZSH), "/bin/zsh not present — nothing to prove here");
+
+        // Only ZDOTDIR is allowed — it must survive the scrub itself, since the report is written
+        // to "$ZDOTDIR/..." AFTER the blanking loop runs; if ZDOTDIR were blanked as a side effect,
+        // the report write would silently go to the wrong place instead of testing anything.
+        String script = EnvAllowListScrub.scrubScript(Set.of("ZDOTDIR"));
+        String setup = """
+                typeset -x FLEETD_TEST_BEFORE=1
+                typeset -rx FLEETD_TEST_UNBLANKABLE=1
+                typeset -x FLEETD_TEST_AFTER_A=1
+                typeset -x FLEETD_TEST_AFTER_B=1
+                """;
+
+        ProcessBuilder pb = new ProcessBuilder("/bin/zsh");
+        pb.environment().clear();
+        pb.environment().put("PATH", "/usr/bin:/bin");
+        pb.environment().put("ZDOTDIR", tmp.toAbsolutePath().toString());
+        pb.redirectError(ProcessBuilder.Redirect.DISCARD);
+        Process zsh = pb.start();
+        zsh.getOutputStream().write((setup + script).getBytes(StandardCharsets.UTF_8));
+        zsh.getOutputStream().flush();
+        zsh.getOutputStream().close();
+        assertTrue(zsh.waitFor(60, java.util.concurrent.TimeUnit.SECONDS),
+                "the scrub script did not exit within 60s");
+        assertEquals(0, zsh.exitValue(),
+                "the scrub script itself must never abort — an unblankable name must not kill the "
+                        + "sourced file");
+
+        EnvAllowListScrub.ScrubReport report = EnvAllowListScrub.readReport(tmp);
+        assertNotNull(report, "the report must still be written even though one name could not be "
+                + "blanked — a report that silently never appears is the #394 bug");
+        assertTrue(report.blanked().contains("FLEETD_TEST_BEFORE"),
+                "sanity: the name before the unblankable one must be blanked");
+        assertTrue(report.blanked().contains("FLEETD_TEST_AFTER_A"),
+                "the FIRST name AFTER the unblankable one must still be blanked — before the fix, "
+                        + "the whole loop aborted at the unblankable name and every later name was "
+                        + "silently left untouched");
+        assertTrue(report.blanked().contains("FLEETD_TEST_AFTER_B"),
+                "the SECOND name after the unblankable one must also still be blanked");
+        assertTrue(report.unblankable().contains("FLEETD_TEST_UNBLANKABLE"),
+                "the unblankable name is reported by name, not silently dropped");
+        // fleetd #400 note: zsh itself auto-exports SHLVL on every shell start (measured: it appears
+        // in `command env` even from a fully cleared parent), and a bare assignment to it is coerced
+        // rather than failing — exactly the shape #400 fixes. Before that fix, eval's exit status
+        // alone silently misclassified SHLVL as blanked, so this test's old "exactly one" assertion
+        // passed by accident: it never actually proved SHLVL was absent from the candidates, only
+        // that the old bug hid it. Now that classification reads the value back, SHLVL and
+        // FLEETD_TEST_UNBLANKABLE both correctly land in unblankable() — real, unplanted evidence
+        // the #400 fix works, not just the synthetic case in the dedicated #400 test above.
+        assertTrue(report.unblankable().contains("SHLVL"),
+                "fleetd #400: zsh's own auto-exported SHLVL must also be reported unblankable, not "
+                        + "silently miscounted as blanked");
+        assertEquals(report.unblankable().size(), report.failed(),
+                "the failed count must equal the number of names actually reported unblankable");
+    }
+
+    /**
+     * fleetd #400: {@code eval}'s exit status is not proof that a name was actually blanked. zsh
+     * coerces a bare {@code NAME=} assignment on an integer special parameter to a number instead of
+     * failing, so {@code eval} reports success while the value stays non-empty — a status-based
+     * classification calls that "blanked" when it was not. This drives all three shapes a name can
+     * take through the real {@code scrubScript} in ONE run: a normal, genuinely blankable name; a
+     * fatal one ({@code LINENO} — deliberately not {@code UID}, so this test does not depend on the
+     * harness's uid); and the silent-no-op one the ticket is about ({@code SECONDS}, rc 0 but
+     * unchanged). Under the pre-#400 exit-status check, {@code SECONDS} would land in
+     * {@code blanked()} — that is the exact false receipt this fix removes.
+     *
+     * <p>Criterion 3: a cleared {@code ProcessBuilder} parent does not, by itself, give the child
+     * zsh any of these names — {@code SECONDS}/{@code LINENO} are zsh's own built-in parameters and
+     * only become CANDIDATES the enumeration loop can see (i.e. show up in {@code command env}) when
+     * they arrive via the process's own environment table, not merely by existing as zsh parameters
+     * inside the shell. So each is put into {@code pb.environment()} explicitly, after
+     * {@code clear()} — confirmed empirically first (a throwaway probe piping
+     * {@code env -i PATH=... SECONDS=999 LINENO=999 FLEETD_TEST_NORMAL=1 zsh -c 'command env | cut
+     * -d= -f1'}) that all three names really appear in {@code command env}'s output under exactly
+     * this construction, not relying on whatever the test-runner's own ambient environment happens
+     * to contain.
+     */
+    @Test
+    void classifiesByObservedValueNotExitStatusAcrossAllThreeShapes(@TempDir Path tmp) throws Exception {
+        assumeTrue(Files.isExecutable(ZSH), "/bin/zsh not present — nothing to prove here");
+
+        String script = EnvAllowListScrub.scrubScript(Set.of("ZDOTDIR"));
+
+        ProcessBuilder pb = new ProcessBuilder("/bin/zsh");
+        pb.environment().clear();
+        pb.environment().put("PATH", "/usr/bin:/bin");
+        pb.environment().put("ZDOTDIR", tmp.toAbsolutePath().toString());
+        // Explicitly placed in the child's environment table — see the javadoc above on why a
+        // cleared parent alone does not put these on the enumeration loop's candidate list.
+        pb.environment().put("SECONDS", "999");   // rc 0, value coerced/unchanged — the #400 bug
+        pb.environment().put("LINENO", "999");    // fatal on assignment, eval rc != 0, contained
+        pb.environment().put("FLEETD_TEST_NORMAL", "1"); // genuinely blankable, the control case
+        pb.redirectError(ProcessBuilder.Redirect.DISCARD);
+        Process zsh = pb.start();
+        zsh.getOutputStream().write(script.getBytes(StandardCharsets.UTF_8));
+        zsh.getOutputStream().flush();
+        zsh.getOutputStream().close();
+        assertTrue(zsh.waitFor(60, java.util.concurrent.TimeUnit.SECONDS),
+                "the scrub script did not exit within 60s");
+        assertEquals(0, zsh.exitValue(),
+                "the scrub script must still reach its end with both a fatal name and a silent "
+                        + "no-op name among the candidates");
+
+        EnvAllowListScrub.ScrubReport report = EnvAllowListScrub.readReport(tmp);
+        assertNotNull(report, "the report must still be written");
+        assertTrue(report.blanked().contains("FLEETD_TEST_NORMAL"),
+                "the control case: an ordinary name is genuinely blankable and must be reported so");
+        assertTrue(report.unblankable().contains("LINENO"),
+                "a name fatal to assign to must be reported unblankable — sanity check that "
+                        + "containment still works under the new classification");
+        assertTrue(report.unblankable().contains("SECONDS"),
+                "the #400 defect: eval returns rc 0 for SECONDS (zsh coerces the assignment instead "
+                        + "of failing) but the value is left non-empty — classifying on the observed "
+                        + "value catches this; classifying on eval's exit status would have called "
+                        + "this \"blanked\" and produced a false receipt");
+        assertFalse(report.blanked().contains("SECONDS"),
+                "SECONDS must never appear as blanked — it was never actually emptied");
+    }
+
+    /**
+     * fleetd #394 follow-up: the blanking loop's {@code eval "export ${n}="} splices {@code n} into
+     * a string that zsh then interprets as shell syntax. That is only safe because every name
+     * reaching {@code _cb633_blank} already passed an identifier check in the ENUMERATION loop
+     * (20 lines away, in a different loop) — so the fix re-asserts the identical check immediately
+     * before the {@code eval} call, rather than trusting that distant guard to keep holding.
+     *
+     * <p>This test plants a value with an embedded newline, exploiting the exact "junk from
+     * multi-line values" gap the enumeration loop's own comment already documents: {@code command
+     * env}'s text output is read line-by-line, so a value's second line becomes a spurious extra
+     * "name" that was never a real exported variable. The fragment used here ({@code
+     * junk.fragment}) is merely non-conforming (it contains a dot) — never command-shaped; this
+     * test must never demonstrate command execution and plants no command-shaped payload.
+     *
+     * <p>Exercises the real artefact end-to-end: {@link EnvAllowListScrub#scrubScript} runs
+     * verbatim under a real {@code /bin/zsh}, exactly as {@code generate()} would produce it — this
+     * is not a synthetic call into just the blanking loop.
+     */
+    @Test
+    void nonIdentifierJunkFromAMultilineValueIsSkippedNotBlankedOrUnblankable(@TempDir Path tmp)
+            throws Exception {
+        assumeTrue(Files.isExecutable(ZSH), "/bin/zsh not present — nothing to prove here");
+
+        String script = EnvAllowListScrub.scrubScript(Set.of("ZDOTDIR"));
+
+        ProcessBuilder pb = new ProcessBuilder("/bin/zsh");
+        pb.environment().clear();
+        pb.environment().put("PATH", "/usr/bin:/bin");
+        pb.environment().put("ZDOTDIR", tmp.toAbsolutePath().toString());
+        // Embedded newline: `command env`'s own text output splits this into two lines, and the
+        // second ("junk.fragment") has no "=" at all, so `cut -d= -f1` returns it unchanged as a
+        // spurious candidate "name" — it was never an actual exported variable by that name.
+        pb.environment().put("FLEETD_TEST_MULTILINE", "keep\njunk.fragment");
+        pb.redirectError(ProcessBuilder.Redirect.DISCARD);
+        Process zsh = pb.start();
+        zsh.getOutputStream().write(script.getBytes(StandardCharsets.UTF_8));
+        zsh.getOutputStream().flush();
+        zsh.getOutputStream().close();
+        assertTrue(zsh.waitFor(60, java.util.concurrent.TimeUnit.SECONDS),
+                "the scrub script did not exit within 60s");
+        assertEquals(0, zsh.exitValue(), "the scrub script must reach its end");
+
+        EnvAllowListScrub.ScrubReport report = EnvAllowListScrub.readReport(tmp);
+        assertNotNull(report, "the report must still be written");
+        assertTrue(report.blanked().contains("FLEETD_TEST_MULTILINE"),
+                "sanity: the real, identifier-shaped variable must still be blanked normally");
+        assertFalse(report.blanked().contains("junk.fragment"),
+                "a non-identifier fragment is not a real variable and must never be blanked");
+        assertFalse(report.unblankable().contains("junk.fragment"),
+                "a non-identifier fragment must never even become a candidate the blanking loop "
+                        + "attempts — it must be filtered before either guard has to catch it, so "
+                        + "it is neither blanked nor counted as a failed attempt");
+    }
+
     /** A group-shared ZDOTDIR still lets the member truncate and write its pre-created receipt. */
     @Test
     void groupSharedScrubWritesAndReadsItsReport(@TempDir Path tmp) throws Exception {