From 433960a43e296c124acfb843f7f75d9eb8bbbfbd Mon Sep 17 00:00:00 2001
From: galuis116 <galuis116@gmail.com>
Date: Wed, 15 Jul 2026 20:30:29 -0700
Subject: [PATCH] fix(compile): drop same-batch duplicate page titles before
 approval

compile_kb() computed taken_names once before validating drafts and
never folded accepted survivors back in, so two drafts in one llm
response with the same (or same-slugifying) title both passed the
collision guard. proposals.approve() exempts PAGE proposals from the
generic existing-artifact guard to support the vault-edit flow, so
approving the second duplicate silently routed through update_page and
overwrote the first-approved page with no error and no reviewer signal.

fold each survivor's title/slug into taken_names as soon as it's
accepted, mirroring what phase 2 already does for wikilink resolution.

new regression files two same-titled drafts in one batch, approves the
surviving proposal, and asserts the first page's body is untouched.

Fixes #439
---
 CHANGELOG.md          |  6 ++++++
 src/vouch/compile.py  |  6 ++++++
 tests/test_compile.py | 20 ++++++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 986dcb0e..ce8eae51 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,12 @@ All notable changes to vouch are documented here. Format follows
 
 ## [Unreleased]
 
+### Fixed
+- `compile_kb()` no longer lets two same-titled drafts in one LLM response
+  both survive the collision guard — the second draft is now dropped instead
+  of silently overwriting the first-approved page via the PAGE `update_page`
+  fallback in `approve()`. (#439)
+
 ## [1.2.2] — 2026-07-07
 
 ### Packaging
diff --git a/src/vouch/compile.py b/src/vouch/compile.py
index 8dbf4a86..a898cb99 100644
--- a/src/vouch/compile.py
+++ b/src/vouch/compile.py
@@ -343,6 +343,12 @@ def compile_kb(
             report.dropped.append({"title": title, "reason": problem})
             continue
         survivors.append((draft, title))
+        # fold the accepted title into taken_names immediately — otherwise a
+        # second draft later in the same batch with a colliding title passes
+        # the collision guard too, and approving both silently overwrites the
+        # first-approved page via the PAGE update_page fallback in approve().
+        taken_names.add(title.lower())
+        taken_names.add(_slugify(title))
 
     # phase 2: wikilinks resolve against existing pages + the *surviving*
     # batch, to a fixpoint — dropping a draft may dangle a link in another,
diff --git a/tests/test_compile.py b/tests/test_compile.py
index 64137a0d..92829a05 100644
--- a/tests/test_compile.py
+++ b/tests/test_compile.py
@@ -317,6 +317,26 @@ def test_collision_with_pending_proposal_dropped(
     assert "pending review" in second.dropped[0]["reason"]
 
 
+def test_collision_within_same_batch_second_draft_dropped(
+    store: KBStore, tmp_path: Path,
+) -> None:
+    """two drafts in one LLM response with the same title must not both
+    survive validation — approving both would silently overwrite the first
+    page via the PAGE update_page fallback in approve()."""
+    c1 = _approved_claim(store, "a fact")
+    report = compile_kb(store, config=_cfg(_stub_llm(tmp_path, [
+        {"title": "Deploy Workflow", "type": "workflow",
+         "body": f"first body [claim: {c1}]", "claims": [c1]},
+        {"title": "Deploy Workflow", "type": "workflow",
+         "body": f"SECOND BODY totally different [claim: {c1}]", "claims": [c1]},
+    ])))
+    assert len(report.proposed) == 1
+    assert "already exists" in report.dropped[0]["reason"]
+
+    approve(store, report.proposed[0]["proposal_id"], approved_by="human-B")
+    assert store.get_page("deploy-workflow").body == f"first body [claim: {c1}]"
+
+
 def test_dropped_sibling_dangles_wikilink_and_cascades(
     store: KBStore, tmp_path: Path,
 ) -> None: