fix(core): stop repository discovery at nearest marker (#39714)

packages/core/src/git.ts

@@ -201,7 +201,7 @@ const layer = Layer.effect(
       locks.withLock(repository.gitDirectory)(effect)
 
     const discover = Effect.fn("Git.repo.discover")(function* (input: AbsolutePath) {
-      const dotgit = yield* fs.up({ targets: [".git"], start: input }).pipe(
+      const dotgit = yield* fs.up({ targets: [".git"], start: input, mode: "first" }).pipe(
         Effect.map((matches) => matches[0]),
         Effect.catch(() => Effect.succeed(undefined)),
       )

packages/core/src/project.ts

@@ -49,7 +49,7 @@ export const root = Effect.fn("Project.root")(function* (
   fs: FSUtil.Interface,
   input: AbsolutePath,
 ) {
-  return yield* fs.up({ targets: [".git", ".hg"], start: input }).pipe(
+  return yield* fs.up({ targets: [".git", ".hg"], start: input, mode: "first" }).pipe(
     Effect.map((matches) => matches[0] ? AbsolutePath.make(path.dirname(matches[0])) : undefined),
     Effect.catch(() => Effect.succeed(undefined)),
   )
@@ -224,7 +224,7 @@ const layer = Layer.effect(
     })
 
     const hgDiscover = Effect.fnUntraced(function* (input: AbsolutePath) {
-      const dotHg = yield* fs.up({ targets: [".hg"], start: input }).pipe(
+      const dotHg = yield* fs.up({ targets: [".hg"], start: input, mode: "first" }).pipe(
         Effect.map((matches) => matches[0]),
         Effect.catch(() => Effect.succeed(undefined)),
       )

packages/core/test/filesystem/filesystem.test.ts

@@ -1,5 +1,5 @@
 import { describe, test, expect } from "bun:test"
-import { Effect, FileSystem } from "effect"
+import { Effect, FileSystem, Layer } from "effect"
 import { LayerNodePlatform } from "@opencode-ai/util/effect/app-node-platform"
 import { LayerNode } from "@opencode-ai/util/effect/layer-node"
 import { FSUtil } from "@opencode-ai/util/fs-util"
@@ -267,6 +267,33 @@ describe("FSUtil", () => {
         expect(result).toContain(path.join(tmp, "b.txt"))
       }),
     )
+
+    it(
+      "stops at the first match when requested",
+      Effect.gen(function* () {
+        const filesys = yield* FileSystem.FileSystem
+        const tmp = yield* filesys.makeTempDirectoryScoped()
+        yield* filesys.writeFileString(path.join(tmp, "marker"), "root")
+        const child = path.join(tmp, "sub")
+        yield* filesys.makeDirectory(child)
+        yield* filesys.writeFileString(path.join(child, "marker"), "child")
+        const checked: string[] = []
+        const instrumented = FileSystem.FileSystem.of({
+          ...filesys,
+          exists: (target) => Effect.sync(() => checked.push(target)).pipe(Effect.andThen(filesys.exists(target))),
+        })
+        const search = yield* FSUtil.Service.pipe(
+          Effect.provide(
+            FSUtil.layer.pipe(Layer.fresh, Layer.provide(Layer.succeed(FileSystem.FileSystem, instrumented))),
+          ),
+        )
+
+        expect(yield* search.up({ targets: ["marker", "other"], start: child, mode: "first" })).toEqual([
+          path.join(child, "marker"),
+        ])
+        expect(checked).toEqual([path.join(child, "marker")])
+      }),
+    )
   })
 
   describe("glob", () => {