diff --git a/apps/api/src/hackproof/github/dependencies.py b/apps/api/src/hackproof/github/dependencies.py
index 91ded2b..6b9c5ee 100644
--- a/apps/api/src/hackproof/github/dependencies.py
+++ b/apps/api/src/hackproof/github/dependencies.py
@@ -6,6 +6,7 @@
 from hackproof.github.models import DependencyFingerprint
 
 MANIFESTS = {"Cargo.toml", "package.json", "requirements.txt", "pyproject.toml", "go.mod"}
+SKIP_DIRECTORIES = {"node_modules", "dist", "target", ".git", "build", "vendor", ".next"}
 ECOSYSTEM = {
     "Cargo.toml": "rust",
     "package.json": "js",
diff --git a/apps/api/src/hackproof/github/history.py b/apps/api/src/hackproof/github/history.py
index 3dd70c4..55f857c 100644
--- a/apps/api/src/hackproof/github/history.py
+++ b/apps/api/src/hackproof/github/history.py
@@ -1,24 +1,47 @@
 import asyncio
+from datetime import datetime
 from pathlib import PurePosixPath
 
 from hackproof.github.client import GithubClient
-from hackproof.github.dependencies import MANIFESTS, fingerprint
+from hackproof.github.dependencies import MANIFESTS, SKIP_DIRECTORIES, fingerprint
+
+MAX_MANIFESTS = 60
+
+
+async def _stellar_packages_at(
+    github: GithubClient, full_name: str, sha: str, wanted: dict[str, list[str]]
+) -> dict[str, str | None]:
+    tree = await github.json(f"/repos/{full_name}/git/trees/{sha}", {"recursive": "1"})
+    paths = sorted(
+        (
+            entry["path"]
+            for entry in (tree or {}).get("tree", [])
+            if entry["type"] == "blob"
+            and PurePosixPath(entry["path"]).name in MANIFESTS
+            and not SKIP_DIRECTORIES & set(PurePosixPath(entry["path"]).parts[:-1])
+        ),
+        key=lambda path: (len(PurePosixPath(path).parts), path),
+    )[:MAX_MANIFESTS]
+    contents = await asyncio.gather(*(github.raw(full_name, sha, path) for path in paths))
+    manifests = {
+        path: content.decode(errors="ignore")
+        for path, content in zip(paths, contents, strict=True)
+        if content
+    }
+    return fingerprint(manifests, wanted).packages
 
 
 async def stellar_added_in_window(
     github: GithubClient,
     full_name: str,
-    files: dict[str, str],
     wanted: dict[str, list[str]],
     base_sha: str | None,
+    window_end: datetime,
 ) -> bool:
-    if base_sha is None:
-        return True
-    manifests = [path for path in files if PurePosixPath(path).name in MANIFESTS]
-    contents = await asyncio.gather(*(github.raw(full_name, base_sha, path) for path in manifests))
-    earlier = {
-        path: content.decode(errors="ignore")
-        for path, content in zip(manifests, contents, strict=True)
-        if content
-    }
-    return not fingerprint(earlier, wanted).packages
+    until = window_end.strftime("%Y-%m-%dT%H:%M:%SZ")
+    commits = await github.json(f"/repos/{full_name}/commits", {"until": until, "per_page": 1})
+    if not commits:
+        return False
+    before = await _stellar_packages_at(github, full_name, base_sha, wanted) if base_sha else {}
+    after = await _stellar_packages_at(github, full_name, commits[0]["sha"], wanted)
+    return not before and bool(after)
diff --git a/apps/api/src/hackproof/github/jobs.py b/apps/api/src/hackproof/github/jobs.py
index c1d5a36..27860ee 100644
--- a/apps/api/src/hackproof/github/jobs.py
+++ b/apps/api/src/hackproof/github/jobs.py
@@ -78,7 +78,7 @@ async def run_scan(force: bool, projects_only: bool = False) -> None:
         repos = [Candidate(**row) for row in rows]
         log.info("scanning %s repos", len(repos))
 
-        scanner = Scanner(github, http, hackathon.discovery)
+        scanner = Scanner(github, http, hackathon.discovery, hackathon.window)
         gate = asyncio.Semaphore(SCAN_CONCURRENCY)
         done = 0
 
diff --git a/apps/api/src/hackproof/github/scan.py b/apps/api/src/hackproof/github/scan.py
index 2256ecd..ed251ae 100644
--- a/apps/api/src/hackproof/github/scan.py
+++ b/apps/api/src/hackproof/github/scan.py
@@ -8,13 +8,13 @@
 
 from hackproof.github.client import GithubClient
 from hackproof.github.demo import scan_demo
-from hackproof.github.dependencies import MANIFESTS, fingerprint
+from hackproof.github.dependencies import MANIFESTS, SKIP_DIRECTORIES, fingerprint
 from hackproof.github.files import fetch_texts
 from hackproof.github.history import stellar_added_in_window
 from hackproof.github.models import Candidate, Contributor, Ref, RepoScan
 from hackproof.github.refs import extract_refs
 from hackproof.github.track import declared_track
-from hackproof.hackathon import Discovery
+from hackproof.hackathon import Discovery, Window
 from hackproof.integrations.catalog import Catalog, get_catalog
 from hackproof.integrations.detect import detect, detect_tools
 
@@ -22,7 +22,6 @@
     ".rs", ".ts", ".tsx", ".js", ".jsx", ".mjs", ".cjs", ".py", ".go", ".toml", ".json",
     ".md", ".yml", ".yaml", ".sh", ".txt", ".html", ".env", ".sol", ".vue", ".svelte",
 }  # fmt: skip
-SKIP_DIRECTORIES = {"node_modules", "dist", "target", ".git", "build", "vendor", ".next"}
 SKIP_FILES = {"package-lock.json", "pnpm-lock.yaml", "yarn.lock", "Cargo.lock", "poetry.lock"}
 FILE_CONCURRENCY = 100
 MAX_TEXT_FILES = 60
@@ -79,11 +78,13 @@ def __init__(
         github: GithubClient,
         http: httpx.AsyncClient,
         discovery: Discovery,
+        window: Window,
         catalog: Catalog | None = None,
     ) -> None:
         self._github = github
         self._http = http
         self._discovery = discovery
+        self._window = window
         self._catalog = catalog or get_catalog()
         self._files = asyncio.Semaphore(FILE_CONCURRENCY)
 
@@ -118,7 +119,7 @@ async def scan(self, repo: Candidate) -> RepoScan | None:
         dependencies = fingerprint(files, wanted)
         added = (
             await stellar_added_in_window(
-                self._github, repo.full_name, files, wanted, repo.base_sha
+                self._github, repo.full_name, wanted, repo.base_sha, self._window.end
             )
             if dependencies.packages
             else None
diff --git a/apps/api/tests/test_history.py b/apps/api/tests/test_history.py
index 4afd572..d8c689f 100644
--- a/apps/api/tests/test_history.py
+++ b/apps/api/tests/test_history.py
@@ -1,34 +1,50 @@
+from datetime import UTC, datetime
+
 from hackproof.github.history import stellar_added_in_window
 
 WANTED = {"js": ["@stellar/stellar-sdk"]}
-HEAD = {"package.json": '{"dependencies": {"@stellar/stellar-sdk": "14.0.0"}}'}
+END = datetime(2026, 10, 26, 12, tzinfo=UTC)
+WITH = b'{"dependencies": {"@stellar/stellar-sdk": "14.0.0"}}'
+WITHOUT = b'{"dependencies": {"react": "19"}}'
 
 
 class FakeGithub:
-    def __init__(self, earlier: dict[str, bytes]) -> None:
-        self._earlier = earlier
+    def __init__(self, commits: list[str], repo: dict[str, dict[str, bytes]]) -> None:
+        self._commits = commits
+        self._repo = repo
+
+    async def json(self, path: str, params: dict | None = None):
+        if path.endswith("/commits"):
+            return [{"sha": sha} for sha in self._commits]
+        sha = path.rsplit("/", 1)[-1]
+        return {"tree": [{"type": "blob", "path": name} for name in self._repo.get(sha, {})]}
 
     async def raw(self, full_name: str, ref: str, path: str) -> bytes | None:
-        return self._earlier.get(path)
+        return self._repo.get(ref, {}).get(path)
+
+
+async def added(base_sha: str | None, commits: list[str], repo: dict) -> bool:
+    return await stellar_added_in_window(FakeGithub(commits, repo), "a/b", WANTED, base_sha, END)
 
 
-async def added(base_sha: str | None, earlier: dict[str, bytes]) -> bool:
-    return await stellar_added_in_window(FakeGithub(earlier), "a/b", HEAD, WANTED, base_sha)
+async def test_stellar_missing_at_the_window_start_and_present_at_its_end_was_added_inside_it():
+    repo = {"start": {"package.json": WITHOUT}, "end": {"package.json": WITH}}
+    assert await added("start", ["end"], repo)
 
 
 async def test_a_repo_with_no_history_before_the_window_was_born_inside_it():
-    assert await added(None, {})
+    assert await added(None, ["end"], {"end": {"package.json": WITH}})
 
 
-async def test_a_dependency_missing_before_the_window_was_added_during_it():
-    before = {"package.json": b'{"dependencies": {"react": "19"}}'}
-    assert await added("abc", before)
+async def test_stellar_already_present_at_the_window_start_is_not_new():
+    repo = {"start": {"package.json": WITH}, "end": {"package.json": WITH}}
+    assert not await added("start", ["end"], repo)
 
 
-async def test_a_manifest_that_did_not_exist_before_counts_as_added():
-    assert await added("abc", {})
+async def test_stellar_added_only_after_the_window_ended_does_not_count():
+    repo = {"start": {"package.json": WITHOUT}, "end": {"package.json": WITHOUT}}
+    assert not await added("start", ["end"], repo)
 
 
-async def test_a_dependency_already_present_before_the_window_is_not_new():
-    before = {"package.json": b'{"dependencies": {"@stellar/stellar-sdk": "13.0.0"}}'}
-    assert not await added("abc", before)
+async def test_a_repo_with_no_commit_by_the_window_end_does_not_count():
+    assert not await added(None, [], {})