iter ms.1: pipeline.rs format!("check: {e}") → {e:#} preserves anyhow Caused-by chain in JSON-cohort feedback

Inline pinning test in pipeline.rs constructs the same chain
shape module_name_from_json produces on serde-parse failure
(leaf wrapped with "parsing JSON in <path>" context) and
asserts both layers survive the formatter. RED→GREEN against
the property, not against production line bytes — for a
two-character fix, extracting a helper just for testability
would be over-engineering.

The strip_locations regex collapses \nCaused by: chains; the
{:#} alternate Display joins with ': ' on one line, so the
collapser is a no-op on the fixed output. AILX cohort
unaffected — only the harness-side anyhow path (module
rename pre-check) was dropping cause information.

Harness suite: 14/14 green (was 13/13 + 1 new pin).

bench/orchestrator-stats/2026-05-12-iter-ms.1.json

@@ -0,0 +1,12 @@
+{
+  "iter_id": "ms.1",
+  "date": "2026-05-12",
+  "mode": "standard",
+  "outcome": "DONE",
+  "tasks_total": 3,
+  "tasks_completed": 3,
+  "reloops_per_task": { "1": 0, "2": 0, "3": 0 },
+  "review_loops_spec": 0,
+  "review_loops_quality": 0,
+  "blocked_reason": null
+}

docs/journals/2026-05-12-iter-ms.1.md

@@ -0,0 +1,42 @@
+# iter ms.1 — Pipeline anyhow-chain preservation
+
+**Date:** 2026-05-12
+**Started from:** 8689f7a2386e0d7993609c374d91984bc28d215c
+**Status:** DONE
+**Tasks completed:** 3 of 3
+
+## Summary
+
+Two-character fix at `pipeline.rs:118`: `format!("check: {e}")` →
+`format!("check: {e:#}")`. Alternate-Display on `anyhow::Error` joins
+the full cause chain with `: ` on one line, restoring the
+`serde_json` parse-error leaf that plain Display dropped. Survives
+`strip_locations` (regex only collapses `\nCaused by:` blocks).
+
+The bug surfaced during ms.2 planning recon: JSON-cohort feedback in
+the cma.3 baseline showed uninformative top-line `"parsing JSON in
+/tmp/..."` while AILX cohort saw the full `ail parse` diagnostic, an
+asymmetry that flattered AILX. ms.1 lands the fix before ms.2's live
+IONOS re-runs so the comparative dataset is internally consistent.
+
+A pinning unit test (`check_format_preserves_anyhow_chain`) asserts
+both layers survive `{:#}`. Per the plan's Reviewer note, no helper
+extracted for direct RED-first — two-character fix doesn't justify
+the refactor.
+
+Test count: 14 (was 13). `cargo check` clean.
+
+## Concerns
+
+- Harness integration tests (`budget_abort`, `mock_full_run`,
+  `verify_references`) need `AIL_BIN` set or `ail` on PATH. The
+  14-green count assumes `AIL_BIN=target/release/ail`. Pre-existing
+  cma.2 harness behaviour.
+
+## Files touched
+
+- `experiments/2026-05-12-cross-model-authoring/harness/src/pipeline.rs`
+
+## Stats
+
+bench/orchestrator-stats/2026-05-12-iter-ms.1.json

docs/journals/INDEX.md

@@ -25,3 +25,4 @@
 - 2026-05-12 — iter cma.2: harness binary + 4 tasks + reference solutions + 4 integration tests (six modules, real-pipeline preflight via verify_references, 13/13 tests green; pipeline.rs renames program file to module-name for ail check) → 2026-05-12-iter-cma.2.md
 - 2026-05-12 — iter cma.3: live Qwen3-Coder-Next run + DESIGN.md §Decision-6 empirical addendum + roadmap close (AILX 2/4 green vs JSON 1/4; ~98k vs ~207k tokens; single-subject scope explicit, multi-subject expansion queued as P3) → 2026-05-12-iter-cma.3.md
 - 2026-05-12 — audit-cma: milestone close (Cross-model authoring-form test) — architect drift fixed in 2 record-keeping items (INDEX backfill for brainstorm Step 7.5, README test-count correction); bench all-green (5 unexplained improvements on latency.explicit_at_rc not coupled to milestone, baseline left pristine) → 2026-05-12-audit-cma.md
+- 2026-05-12 — iter ms.1: pipeline anyhow-chain preservation — `{e}` → `{e:#}` at `pipeline.rs:118` restores `serde_json` parse-error leaf in JSON-cohort feedback; pinning unit test added (14/14 green) → 2026-05-12-iter-ms.1.md

experiments/2026-05-12-cross-model-authoring/harness/src/pipeline.rs

@@ -115,7 +115,7 @@ pub fn run_pipeline(
         }
         Err(e) => {
             return Ok(PipelineCapture {
-                error: Some(format!("check: {e}")),
+                error: Some(format!("check: {e:#}")),
                 stdout: String::new(),
                 stderr: e.to_string(),
             });
@@ -217,3 +217,30 @@ fn run_with_timeout(bin: &Path, timeout: Duration) -> Result<RunOutput> {
         std::thread::sleep(Duration::from_millis(25));
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use anyhow::{anyhow, Context, Error};
+
+    /// Constructs the same chain shape `module_name_from_json`
+    /// produces on a serde-parse failure: a leaf error wrapped
+    /// with a "parsing JSON in <path>" context. Asserts that the
+    /// format string used at pipeline.rs error-emission preserves
+    /// both layers.
+    #[test]
+    fn check_format_preserves_anyhow_chain() {
+        let leaf: Error = anyhow!("expected value at line 1 column 1");
+        let chained = Err::<(), _>(leaf)
+            .context("parsing JSON in /tmp/x.ail.json")
+            .unwrap_err();
+        let formatted = format!("check: {chained:#}");
+        assert!(
+            formatted.contains("parsing JSON in /tmp/x.ail.json"),
+            "top-level context missing; got: {formatted}",
+        );
+        assert!(
+            formatted.contains("expected value at line 1 column 1"),
+            "leaf cause missing; got: {formatted}",
+        );
+    }
+}