From cde12790d721ab2a90471750fd75d9f5bf13f57d Mon Sep 17 00:00:00 2001
From: Jake Leventhal <jakeleventhal@me.com>
Date: Tue, 1 Sep 2026 21:15:07 -0700
Subject: [PATCH] fix(contracts): accept legacy pull request checkout results
 (#8238)

---
 packages/contracts/src/git.test.ts | 41 ++++++++++++++++++++++++++++++
 packages/contracts/src/git.ts      |  3 ++-
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/packages/contracts/src/git.test.ts b/packages/contracts/src/git.test.ts
index 4ea86670ff8f3142dce6fd60ac7d6ffec14fe119..5dda491b009b2d09f5b82c882876dd7e5ee0181e 100644
--- a/packages/contracts/src/git.test.ts
+++ b/packages/contracts/src/git.test.ts
@@ -4,6 +4,7 @@ import * as Schema from "effect/Schema";
 import {
   VcsCreateWorktreeInput,
   GitPreparePullRequestThreadInput,
+  GitPreparePullRequestThreadResult,
   GitRunStackedActionResult,
   GitRunStackedActionInput,
   GitResolvePullRequestResult,
@@ -13,6 +14,9 @@ const decodeCreateWorktreeInput = Schema.decodeUnknownSync(VcsCreateWorktreeInpu
 const decodePreparePullRequestThreadInput = Schema.decodeUnknownSync(
   GitPreparePullRequestThreadInput,
 );
+const decodePreparePullRequestThreadResult = Schema.decodeUnknownSync(
+  GitPreparePullRequestThreadResult,
+);
 const decodeRunStackedActionInput = Schema.decodeUnknownSync(GitRunStackedActionInput);
 const decodeRunStackedActionResult = Schema.decodeUnknownSync(GitRunStackedActionResult);
 const decodeResolvePullRequestResult = Schema.decodeUnknownSync(GitResolvePullRequestResult);
@@ -55,6 +59,43 @@ describe("GitPreparePullRequestThreadInput", () => {
   });
 });
 
+describe("GitPreparePullRequestThreadResult", () => {
+  it("defaults legacy responses to the pull request head", () => {
+    const parsed = decodePreparePullRequestThreadResult({
+      pullRequest: {
+        number: 42,
+        title: "PR threads",
+        url: "https://github.com/pingdotgg/codething-mvp/pull/42",
+        baseBranch: "main",
+        headBranch: "feature/pr-threads",
+        state: "open",
+      },
+      branch: "feature/pr-threads",
+      worktreePath: "/tmp/pr-threads",
+    });
+
+    expect(parsed.isOnPullRequestHead).toBe(true);
+  });
+
+  it("preserves an explicit stale pull request checkout result", () => {
+    const parsed = decodePreparePullRequestThreadResult({
+      pullRequest: {
+        number: 42,
+        title: "PR threads",
+        url: "https://github.com/pingdotgg/codething-mvp/pull/42",
+        baseBranch: "main",
+        headBranch: "feature/pr-threads",
+        state: "open",
+      },
+      branch: "feature/pr-threads",
+      worktreePath: "/tmp/pr-threads",
+      isOnPullRequestHead: false,
+    });
+
+    expect(parsed.isOnPullRequestHead).toBe(false);
+  });
+});
+
 describe("GitResolvePullRequestResult", () => {
   it("decodes resolved pull request metadata", () => {
     const parsed = decodeResolvePullRequestResult({
diff --git a/packages/contracts/src/git.ts b/packages/contracts/src/git.ts
index 915c3627c9b9a695f995d2934588ae904e80e12b..d39be34bf6e9cb654aeb7691c1ebebd87450b12e 100644
--- a/packages/contracts/src/git.ts
+++ b/packages/contracts/src/git.ts
@@ -1,3 +1,4 @@
+import * as Effect from "effect/Effect";
 import * as Schema from "effect/Schema";
 import { NonNegativeInt, PositiveInt, ThreadId, TrimmedNonEmptyString } from "./baseSchemas.ts";
 import { SourceControlProviderError, SourceControlProviderInfo } from "./sourceControl.ts";
@@ -289,7 +290,7 @@ export const GitPreparePullRequestThreadResult = Schema.Struct({
    * holding local commits or uncommitted changes keeps its own state, so the code being handed
    * over is older than the pull request.
    */
-  isOnPullRequestHead: Schema.Boolean,
+  isOnPullRequestHead: Schema.Boolean.pipe(Schema.withDecodingDefaultKey(Effect.succeed(true))),
 });
 export type GitPreparePullRequestThreadResult = typeof GitPreparePullRequestThreadResult.Type;
 
-- 
2.54.0