From 6db4a6d02e737c7104cedd23efeb767defa07d61 Mon Sep 17 00:00:00 2001
From: "pullfrog[bot]" <226033991+pullfrog[bot]@users.noreply.github.com>
Date: Wed, 6 May 2026 20:54:34 +0000
Subject: [PATCH] fix(mcp): preserve coveragePreflightRan across checkout_pr
 refreshes (#576)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

checkout_pr unconditionally rebuilds ctx.toolState.diffCoverage via
createDiffCoverageState, which initialised coveragePreflightRan to false.
a second checkout_pr therefore reset the "one-time nudge per review
session" guarantee in runDiffCoveragePreflight, and the next
create_pull_request_review threw the diff-coverage pre-flight error
again — even after the agent had already gone through the
read-and-resubmit dance once.

createDiffCoverageState now accepts an optional previous state and
carries forward coveragePreflightRan. coveredRanges are intentionally
not carried because their line numbers are tied to the previous diff's
content (especially under incremental diffs).

closes #566

Co-authored-by: pullfrog[bot] <226033991+pullfrog[bot]@users.noreply.github.com>
Co-authored-by: David Blass <david@arktype.io>
---
 mcp/checkout.ts            |  1 +
 utils/diffCoverage.test.ts | 18 ++++++++++++++++++
 utils/diffCoverage.ts      |  6 +++++-
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/mcp/checkout.ts b/mcp/checkout.ts
index 0d0f9b4..1b3eb48 100644
--- a/mcp/checkout.ts
+++ b/mcp/checkout.ts
@@ -545,6 +545,7 @@ export function CheckoutPrTool(ctx: ToolContext) {
         diffPath,
         totalLines: countLines({ content: formatResult.content }),
         toc: formatResult.toc,
+        previous: ctx.toolState.diffCoverage,
       });
       log.debug(
         `» diff coverage initialized: diffPath=${diffPath}, totalLines=${ctx.toolState.diffCoverage.totalLines}, tocEntries=${ctx.toolState.diffCoverage.tocEntries.length}`
diff --git a/utils/diffCoverage.test.ts b/utils/diffCoverage.test.ts
index dfa96db..c4877f0 100644
--- a/utils/diffCoverage.test.ts
+++ b/utils/diffCoverage.test.ts
@@ -98,6 +98,24 @@ describe("diff coverage line checker", () => {
     ]);
   });
 
+  it("carries forward coveragePreflightRan from a previous state across checkout refreshes", () => {
+    const previous = createDiffCoverageState({ diffPath, totalLines: 30, toc });
+    previous.coveragePreflightRan = true;
+    previous.coveredRanges = [{ startLine: 5, endLine: 10 }];
+
+    const next = createDiffCoverageState({ diffPath, totalLines: 50, toc, previous });
+
+    expect(next.coveragePreflightRan).toBe(true);
+    // coveredRanges are tied to the previous diff content and must not leak forward
+    expect(next.coveredRanges).toEqual([]);
+    expect(next.totalLines).toBe(50);
+  });
+
+  it("defaults coveragePreflightRan to false when no previous state is provided", () => {
+    const state = createDiffCoverageState({ diffPath, totalLines: 30, toc });
+    expect(state.coveragePreflightRan).toBe(false);
+  });
+
   it("computes per-file unread ranges from tracked reads", () => {
     const state = createDiffCoverageState({
       diffPath,
diff --git a/utils/diffCoverage.ts b/utils/diffCoverage.ts
index 125360d..2ced6d9 100644
--- a/utils/diffCoverage.ts
+++ b/utils/diffCoverage.ts
@@ -78,13 +78,17 @@ export function createDiffCoverageState(params: {
   diffPath: string;
   totalLines: number;
   toc: string;
+  previous?: DiffCoverageState | undefined;
 }): DiffCoverageState {
   return {
     diffPath: params.diffPath,
     totalLines: params.totalLines,
     tocEntries: parseDiffTocEntries({ toc: params.toc }),
     coveredRanges: [],
-    coveragePreflightRan: false,
+    // carry forward across checkout_pr refreshes so the nudge stays "once per
+    // review session". coveredRanges are intentionally not carried because
+    // line numbers are tied to the previous diff's content.
+    coveragePreflightRan: params.previous?.coveragePreflightRan ?? false,
   };
 }