fix(sync): register inbound sources before evidence in gated apply

CHANGELOG.md

@@ -64,6 +64,17 @@ All notable changes to vouch are documented here. Format follows
   per-prompt block, the session banner, `vouch status` and the opt-in
   question all say so rather than calling it "this repo's" knowledge.
 
+### Fixed
+- `vouch sync --as-proposals` no longer crashes when the inbound KB
+  carries a receipt-backed claim whose evidence AND source are both new
+  here. the gated apply registered substrate in one sorted path walk, and
+  `evidence/...` sorts ahead of `sources/...`, so `put_evidence` raised
+  "cites unknown source" for evidence arriving alongside its own source —
+  aborting the whole sync partway with no audit event, on input
+  `sync check` had just called ok (and that `vouch import-proposals`
+  accepts for the identical bundle). sources are now registered before
+  evidence, the same pass-1 order `import_as_proposals` already uses.
+
 ## [1.5.0] — 2026-07-20
 
 ### Added

src/vouch/sync.py

@@ -329,12 +329,20 @@ def _sync_apply_as_proposals(
     }
 
     # Pass 1: substrate registered directly so claim proposals can cite it.
+    # Sources before evidence, in two sub-passes: put_evidence rejects an
+    # evidence record whose cited source is not yet on disk, and the sorted
+    # path walk visits "evidence/..." ahead of "sources/..." — so a single
+    # interleaved loop crashes on any inbound evidence whose source arrives
+    # in the same sync. Mirrors the pass-1 order import_as_proposals
+    # (bundle.py) already uses for the same reason.
     for path in new:
         kind, _ = _artifact_kind(path)
         if kind == "source" and path.endswith("/content"):
             store.put_source(_read_source_file(src, path))
             sources_registered += 1
-        elif kind == "evidence":
+    for path in new:
+        kind, _ = _artifact_kind(path)
+        if kind == "evidence":
             ev = Evidence.model_validate(yaml.safe_load(_read_source_file(src, path)))
             store.put_evidence(ev)
             evidence_registered += 1

tests/test_sync.py

@@ -96,6 +96,48 @@ def test_sync_apply_as_proposals_approves_into_a_claim_with_origin(tmp_path: Pat
     assert "origin:kb-remote" in dest.get_claim(approved.id).tags
 
 
+def test_sync_apply_as_proposals_registers_sources_before_evidence(tmp_path: Path) -> None:
+    """An inbound receipt-backed claim (source + evidence + claim, all new) syncs.
+
+    Regression: pass 1 walked a single sorted(new_files) list, and
+    "evidence/..." sorts ahead of "sources/..." -- put_evidence then raised
+    "cites unknown source" for any evidence whose source arrived in the same
+    sync, crashing the whole gated apply before anything was audited.
+    import_as_proposals (bundle.py) already registered sources before
+    evidence; the sync path must keep the same order.
+    """
+    from vouch.models import Evidence
+
+    incoming = _store(tmp_path / "incoming")
+    content = b"the deploy runs at 03:00 utc"
+    src = incoming.put_source(content, title="runbook")
+    ev = Evidence(
+        id="ev-deploy-span",
+        source_id=src.id,
+        locator="bytes=0-28",
+        quote="the deploy runs at 03:00 utc",
+        byte_start=0,
+        byte_end=28,
+    )
+    incoming.put_evidence(ev)
+    incoming.put_claim(
+        Claim(id="deploy-time", text="deploys run at 03:00 utc", evidence=[ev.id])
+    )
+    dest = _store(tmp_path / "dest")
+
+    result = sync.sync_apply(
+        dest.kb_dir, incoming.root, as_proposals=True, origin_kb="kb-remote"
+    )
+
+    assert result["sources_registered"] == 1
+    assert result["evidence_registered"] == 1
+    assert result["failed"] == []
+    assert len(result["proposed"]) == 1
+    # The substrate landed, so the pending claim proposal can cite it.
+    assert dest.get_evidence("ev-deploy-span").source_id == src.id
+    assert dest.get_source(src.id).id == src.id
+
+
 def test_cli_sync_apply_as_proposals(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
     incoming = _store(tmp_path / "incoming")
     _claim(incoming, "c1", "alpha from the other kb")