knocking4thcylinder · knocking4thcylinder · Sep 28, 2026 · Sep 27, 2026
diff --git a/apps/mobile/src/features/threads/git/GitOverviewSheet.tsx b/apps/mobile/src/features/threads/git/GitOverviewSheet.tsx
@@ -157,11 +157,7 @@ export function GitOverviewSheet(props: GitOverviewSheetProps) {
   const [configurationOpen, setConfigurationOpen] = useState(false);
   const [configurationSaving, setConfigurationSaving] = useState(false);
   const configuration = useEnvironmentQuery(
-    configurationOpen &&
-      selectedThread !== null &&
-      selectedThreadCwd !== null &&
-      gitStatus.data?.isRepo === true &&
-      gitStatus.data.vcs?.kind !== "jj"
+    configurationOpen && selectedThread !== null && selectedThreadCwd !== null
       ? vcsEnvironment.configuration({
           environmentId: selectedThread.environmentId,
           input: { cwd: selectedThreadCwd },
@@ -448,7 +444,7 @@ export function GitOverviewSheet(props: GitOverviewSheetProps) {
             })
           }
         />
-        {isRepo && gitStatus.data?.vcs?.kind !== "jj" ? (
+        {isRepo ? (
           <>
             {Platform.OS !== "android" ? <View className="ml-12 h-px bg-border" /> : null}
             <SheetListRow
@@ -482,8 +478,16 @@ export function GitOverviewSheet(props: GitOverviewSheetProps) {
                   />
                   <ConfigurationField
                     key={`${selectedThread?.environmentId}:${selectedThreadCwd}:large:${configuration.data.largeFile.repository}:${configuration.data.largeFile.effective}`}
-                    label="Large file diff threshold"
-                    detail="Git treats files above this size as binary in diffs. Enter MiB."
+                    label={
+                      configuration.data.kind === "jj"
+                        ? "New file snapshot limit"
+                        : "Large file diff threshold"
+                    }
+                    detail={
+                      configuration.data.kind === "jj"
+                        ? "Files above this size stay outside snapshots and checkpoints. Enter MiB, or 0 for no limit."
+                        : "Git treats files above this size as binary in diffs. Enter MiB."
+                    }
                     entry={configuration.data.largeFile}
                     setting="largeFile"
                     disabled={configurationSaving}

diff --git a/apps/server/src/vcs/VcsConfigurationService.test.ts b/apps/server/src/vcs/VcsConfigurationService.test.ts
@@ -7,7 +7,7 @@ import * as Layer from "effect/Layer";
 import * as VcsConfigurationService from "./VcsConfigurationService.ts";
 import * as VcsDriverRegistry from "./VcsDriverRegistry.ts";
 import * as VcsProcess from "./VcsProcess.ts";
-import { runGit } from "./testing/JjTestSupport.ts";
+import { createJjRepo, describeJj, runGit, runJj } from "./testing/JjTestSupport.ts";
 
 const TestLayer = VcsConfigurationService.layer.pipe(
   Layer.provide(VcsDriverRegistry.layer),
@@ -41,3 +41,30 @@ it.effect("reads, writes, and resets guided Git repository configuration", () =>
     assert.equal(failure._tag, "VcsUnsupportedOperationError");
   }).pipe(Effect.provide(TestLayer)),
 );
+
+describeJj("Jujutsu repository configuration", () => {
+  it.effect("raises the new-file snapshot limit and restores inheritance", () =>
+    Effect.gen(function* () {
+      const fileSystem = yield* FileSystem.FileSystem;
+      const root = yield* fileSystem.makeTempDirectoryScoped({ prefix: "t3-jj-config-" });
+      yield* createJjRepo(root);
+      const largeFile = `${root}/large.txt`;
+      yield* fileSystem.writeFileString(largeFile, "x".repeat(2 * 1024 * 1024));
+      const before = yield* runJj(root, ["file", "list"]);
+      assert.isFalse(before.includes("large.txt"));
+
+      const configuration = yield* VcsConfigurationService.VcsConfigurationService;
+      yield* configuration.write({ cwd: root, setting: "largeFile", value: "4" });
+      const saved = yield* configuration.read({ cwd: root });
+      assert.equal(saved.kind, "jj");
+      assert.equal(saved.largeFile.repository, "4MiB");
+      assert.isTrue((yield* runJj(root, ["file", "list"])).includes("large.txt"));
+
+      yield* configuration.write({ cwd: root, setting: "largeFile", value: "0" });
+      assert.equal((yield* configuration.read({ cwd: root })).largeFile.repository, "0");
+
+      yield* configuration.write({ cwd: root, setting: "largeFile", value: null });
+      assert.equal((yield* configuration.read({ cwd: root })).largeFile.repository, null);
+    }).pipe(Effect.provide(TestLayer)),
+  );
+});
diff --git a/apps/server/src/vcs/VcsConfigurationService.ts b/apps/server/src/vcs/VcsConfigurationService.ts
@@ -15,28 +15,47 @@ import * as VcsDriverRegistry from "./VcsDriverRegistry.ts";
 type Setting = VcsConfigurationWriteInput["setting"];
 type Handle = VcsDriverRegistry.VcsDriverHandle;
 
-const CONFIG_KEYS: Record<Setting, string> = {
-  userName: "user.name",
-  userEmail: "user.email",
-  largeFile: "core.bigFileThreshold",
+const CONFIG_KEYS: Record<Setting, Record<"git" | "jj", string>> = {
+  userName: { git: "user.name", jj: "user.name" },
+  userEmail: { git: "user.email", jj: "user.email" },
+  largeFile: { git: "core.bigFileThreshold", jj: "snapshot.max-new-file-size" },
 };
 
+function keyFor(handle: Handle, setting: Setting): string {
+  return CONFIG_KEYS[setting][handle.kind === "jj" ? "jj" : "git"];
+}
+
+function parseRepositoryValue(value: string): string {
+  const trimmed = value.trim();
+  try {
+    const parsed: unknown = JSON.parse(trimmed);
+    return typeof parsed === "string" || typeof parsed === "number" ? String(parsed) : trimmed;
+  } catch {
+    return trimmed;
+  }
+}
+
 function validateValue(
   setting: Setting,
   value: string,
+  kind: "git" | "jj",
 ): Effect.Effect<string, VcsUnsupportedOperationError> {
   const trimmed = value.trim();
   if (setting === "largeFile") {
+    if (kind === "jj" && trimmed === "0") return Effect.succeed("0");
     const match = /^([1-9]\d{0,3})(?:\s*(?:m|mib))?$/i.exec(trimmed);
     const mebibytes = match ? Number(match[1]) : 0;
     if (mebibytes >= 1 && mebibytes <= 4096) {
-      return Effect.succeed(`${mebibytes}m`);
+      return Effect.succeed(kind === "jj" ? `${mebibytes}MiB` : `${mebibytes}m`);
     }
     return Effect.fail(
       new VcsUnsupportedOperationError({
         operation: "VcsConfigurationService.write",
-        kind: "git",
-        detail: "Enter a large-file threshold between 1 and 4096 MiB.",
+        kind,
+        detail:
+          kind === "jj"
+            ? "Enter a snapshot limit between 1 and 4096 MiB, or 0 for no limit."
+            : "Enter a large-file threshold between 1 and 4096 MiB.",
       }),
     );
   }
@@ -50,7 +69,7 @@ function validateValue(
   return Effect.fail(
     new VcsUnsupportedOperationError({
       operation: "VcsConfigurationService.write",
-      kind: "git",
+      kind,
       detail: "Enter a name or email without control characters (up to 256 characters).",
     }),
   );
@@ -75,38 +94,50 @@ export const make = Effect.gen(function* () {
     setting: Setting,
     repositoryOnly: boolean,
   ) {
-    const key = CONFIG_KEYS[setting];
-    const args = ["config", ...(repositoryOnly ? ["--local"] : []), "--get", key];
+    const key = keyFor(handle, setting);
+    const isJj = handle.kind === "jj";
+    const args = isJj
+      ? repositoryOnly
+        ? ["--ignore-working-copy", "config", "list", "--repo", key, "-T", "value"]
+        : ["--ignore-working-copy", "config", "get", key]
+      : ["config", ...(repositoryOnly ? ["--local"] : []), "--get", key];
     const result = yield* handle.driver.execute({
       operation: "VcsConfigurationService.read",
       cwd,
       args,
       allowNonZeroExit: true,
       maxOutputBytes: 4_096,
     });
-    if (result.exitCode === 1) return null;
+    if (
+      result.exitCode === 1 &&
+      (!isJj ||
+        (repositoryOnly
+          ? result.stdout.trim() === ""
+          : result.stderr.includes("Value not found for")))
+    )
+      return null;
     if (result.exitCode !== 0) {
       return yield* new VcsProcessExitError({
         operation: "VcsConfigurationService.read",
-        command: "git config",
+        command: isJj ? "jj config" : "git config",
         cwd,
         exitCode: result.exitCode,
         detail: result.stderr.trim() || "Could not read repository configuration.",
       });
     }
     if (result.stdout.trim() === "") return null;
-    return result.stdout.trim();
+    return repositoryOnly && isJj ? parseRepositoryValue(result.stdout) : result.stdout.trim();
   });
 
   const read: VcsConfigurationService["Service"]["read"] = Effect.fn(
     "VcsConfigurationService.read",
   )(function* (input) {
     const handle = yield* registry.resolve({ cwd: input.cwd });
-    if (handle.kind !== "git") {
+    if (handle.kind !== "git" && handle.kind !== "jj") {
       return yield* new VcsUnsupportedOperationError({
         operation: "VcsConfigurationService.read",
         kind: handle.kind,
-        detail: "Repository configuration is available for Git only.",
+        detail: "Repository configuration is available for Git and Jujutsu only.",
       });
     }
     const entry = (setting: Setting) =>
@@ -126,28 +157,39 @@ export const make = Effect.gen(function* () {
     "VcsConfigurationService.write",
   )(function* (input) {
     const handle = yield* registry.resolve({ cwd: input.cwd });
-    if (handle.kind !== "git") {
+    if (handle.kind !== "git" && handle.kind !== "jj") {
       return yield* new VcsUnsupportedOperationError({
         operation: "VcsConfigurationService.write",
         kind: handle.kind,
-        detail: "Repository configuration is available for Git only.",
+        detail: "Repository configuration is available for Git and Jujutsu only.",
       });
     }
-    const key = CONFIG_KEYS[input.setting];
+    const key = keyFor(handle, input.setting);
     if (
       input.value === null &&
       (yield* readValue(handle, input.cwd, input.setting, true)) === null
     ) {
       return;
     }
-    const value = input.value === null ? null : yield* validateValue(input.setting, input.value);
-    const args = [
-      "config",
-      "--local",
-      value === null ? "--unset-all" : "--replace-all",
-      key,
-      ...(value === null ? [] : [value]),
-    ];
+    const value =
+      input.value === null ? null : yield* validateValue(input.setting, input.value, handle.kind);
+    const args =
+      handle.kind === "jj"
+        ? [
+            "--ignore-working-copy",
+            "config",
+            value === null ? "unset" : "set",
+            "--repo",
+            key,
+            ...(value === null ? [] : [value]),
+          ]
+        : [
+            "config",
+            "--local",
+            value === null ? "--unset-all" : "--replace-all",
+            key,
+            ...(value === null ? [] : [value]),
+          ];
     yield* handle.driver.execute({
       operation: "VcsConfigurationService.write",
       cwd: input.cwd,

diff --git a/apps/web/src/components/settings/VcsConfigurationSettings.tsx b/apps/web/src/components/settings/VcsConfigurationSettings.tsx
@@ -85,16 +85,8 @@ export function VcsConfigurationSettingsSection() {
     (scope.kind === "project" || scope.kind === "checkout") && scope.members.length === 1
       ? scope.members[0]!
       : null;
-  const status = useEnvironmentQuery(
-    member === null
-      ? null
-      : vcsEnvironment.status({
-          environmentId: member.environmentId,
-          input: { cwd: member.workspaceRoot },
-        }),
-  );
   const configuration = useEnvironmentQuery(
-    member === null || status.data?.isRepo !== true || status.data.vcs?.kind === "jj"
+    member === null
       ? null
       : vcsEnvironment.configuration({
           environmentId: member.environmentId,
@@ -131,12 +123,12 @@ export function VcsConfigurationSettingsSection() {
   };
 
   const config = configuration.data;
-  if (status.data?.vcs?.kind === "jj") return null;
+  const kind = config?.kind;
   return (
     <SettingsSection title="Repository configuration">
       {member === null ? (
         <p className="px-4 py-3 text-sm text-muted-foreground">
-          Choose one Git checkout to edit its repository configuration.
+          Choose one checkout to edit its Git or Jujutsu configuration.
         </p>
       ) : configuration.error ? (
         <p className="px-4 py-3 text-sm text-destructive">{configuration.error}</p>
@@ -167,8 +159,12 @@ export function VcsConfigurationSettingsSection() {
           <ConfigurationRow
             key={`${member.environmentId}:${member.workspaceRoot}:large:${config.largeFile.repository}:${config.largeFile.effective}`}
             setting="largeFile"
-            title="Large file diff threshold"
-            description="Git treats files above this size as binary in diffs; checkpoints still include them. Enter a size in MiB."
+            title={kind === "jj" ? "New file snapshot limit" : "Large file diff threshold"}
+            description={
+              kind === "jj"
+                ? "Files above this size stay outside Jujutsu snapshots and T3 checkpoints. Enter MiB, or 0 for no limit."
+                : "Git treats files above this size as binary in diffs; checkpoints still include them. Enter a size in MiB."
+            }
             entry={config.largeFile}
             disabled={saving}
             onWrite={onWrite}

diff --git a/docs/user/source-control.md b/docs/user/source-control.md
@@ -164,11 +164,12 @@ For an existing Git repository, choose **Enable Jujutsu** from the repository ac
 desktop, or mobile. It keeps the Git history, remotes, and working files while adding a colocated
 Jujutsu workspace. Run it from the main checkout; Git worktrees continue to use Git.
 
-To configure a Git checkout on web or desktop, select it in **Settings → Source control → Repository
+To configure one checkout on web or desktop, select it in **Settings → Source control → Repository
 configuration**. On mobile, open **Repository configuration** from the repository sheet.
-The guided controls set its commit author, email, and large-file diff threshold. Git treats files
-above that threshold as binary in diffs; checkpoints still include them. Reset removes a repository
-override and returns to the user's Git configuration.
+The guided controls set its commit author and email. For Jujutsu, the new-file snapshot limit
+determines which files enter T3 checkpoints; for Git, the large-file threshold controls when Git
+treats a file as binary in diffs. Git checkpoints include large files regardless of that threshold.
+Reset removes a repository override and returns to the user's Git or Jujutsu configuration.
 
 ### What is different under Jujutsu
 
@@ -178,8 +179,8 @@ override and returns to the user's Git configuration.
 - A change with conflicts cannot be pushed until you resolve it, and its diff shows one side of each
   conflicted file rather than the markers on disk.
 - Jujutsu refuses to snapshot a new file above `snapshot.max-new-file-size`, 1 MiB by default. That
-  file is outside checkpoints, so reverting a turn leaves it on disk. Raise the limit in your own
-  Jujutsu config if you want those files tracked.
+  file is outside checkpoints, so reverting a turn leaves it on disk. Raise the limit in repository
+  configuration if you want those files tracked.
 - A repository that is not colocated, a missing `jj`, or a version below 0.42.0 leaves source control
   actions disabled with the reason, instead of silently falling back to Git. Install or upgrade
   Jujutsu, or run `jj git init --colocate` in the repository.