feat(web): add branch changes and review actions

apps/web/src/components/ChatView.logic.test.ts

@@ -21,6 +21,7 @@ import {
   dismissBranchMismatchForSession,
   getStartedThreadModelChangeBlockReason,
   hasServerAcknowledgedLocalDispatch,
+  insertReviewPromptIntoDraft,
   isBranchMismatchDismissedForSession,
   reconcileMountedTerminalThreadIds,
   reconcileRetainedMountedThreadIds,
@@ -36,6 +37,20 @@ const projectId = ProjectId.make("project-1");
 const threadId = ThreadId.make("thread-1");
 const now = "2026-03-29T00:00:00.000Z";
 
+describe("insertReviewPromptIntoDraft", () => {
+  it("inserts into an empty composer", () => {
+    expect(insertReviewPromptIntoDraft("", "  Review these changes.  ")).toBe(
+      "Review these changes.",
+    );
+  });
+
+  it("appends without overwriting an existing draft", () => {
+    expect(insertReviewPromptIntoDraft("Keep this context.  \n", "Review these changes.")).toBe(
+      "Keep this context.\n\nReview these changes.",
+    );
+  });
+});
+
 function makeThread(overrides: Partial<Thread> = {}): Thread {
   return {
     id: threadId,

apps/web/src/components/ChatView.logic.ts

@@ -564,3 +564,9 @@ export function hasServerAcknowledgedLocalDispatch(input: {
     input.localDispatch.sessionUpdatedAt !== (session?.updatedAt ?? null)
   );
 }
+
+export function insertReviewPromptIntoDraft(currentPrompt: string, reviewPrompt: string): string {
+  const current = currentPrompt.trimEnd();
+  const review = reviewPrompt.trim();
+  return current.length > 0 ? `${current}\n\n${review}` : review;
+}

apps/web/src/components/ChatView.tsx

@@ -260,6 +260,7 @@ import {
   deriveComposerSendState,
   dismissBranchMismatchForSession,
   hasServerAcknowledgedLocalDispatch,
+  insertReviewPromptIntoDraft,
   isBranchMismatchDismissedForSession,
   shouldShowBranchMismatchBanner,
   getStartedThreadModelChangeBlockReason,
@@ -3068,6 +3069,25 @@ function ChatViewContent(props: ChatViewProps) {
     onDiffPanelOpen,
     planSidebarOpen,
   ]);
+  const openBranchChanges = useCallback(() => {
+    if (!activeThreadRef || !isServerThread || !isGitRepo) return;
+    useDiffPanelStore.getState().selectGitScope(activeThreadRef, "branch");
+    addDiffSurface();
+  }, [activeThreadRef, addDiffSurface, isGitRepo, isServerThread]);
+  const insertReviewPrompt = useCallback(() => {
+    const currentPrompt =
+      useComposerDraftStore.getState().getComposerDraft(composerDraftTarget)?.prompt ?? "";
+    setComposerDraftPrompt(
+      composerDraftTarget,
+      insertReviewPromptIntoDraft(currentPrompt, primaryServerSettings.reviewPrompt),
+    );
+    scheduleComposerFocus();
+  }, [
+    composerDraftTarget,
+    primaryServerSettings.reviewPrompt,
+    scheduleComposerFocus,
+    setComposerDraftPrompt,
+  ]);
   const addFilesSurface = useCallback(() => {
     if (!activeThreadRef || !activeProject) return;
     useRightPanelStore.getState().open(activeThreadRef, "files");
@@ -5716,6 +5736,9 @@ function ChatViewContent(props: ChatViewProps) {
             availableEditors={availableEditors}
             rightPanelOpen={rightPanelOpen}
             gitCwd={gitCwd}
+            canOpenChanges={isServerThread && isGitRepo}
+            onOpenChanges={openBranchChanges}
+            onReview={insertReviewPrompt}
             onNewThreadInProject={handleNewThreadInActiveProject}
             onRunProjectScript={runProjectScript}
             onAddProjectScript={saveProjectScript}

apps/web/src/components/chat/ChatHeader.tsx

@@ -6,6 +6,7 @@ import {
   type ThreadId,
 } from "@t3tools/contracts";
 import { scopeThreadRef } from "@t3tools/client-runtime/environment";
+import { FileDiffIcon, ScanSearchIcon } from "lucide-react";
 import { memo } from "react";
 import GitActionsControl from "../GitActionsControl";
 import { type DraftId } from "~/composerDraftStore";
@@ -19,6 +20,7 @@ import { usePrimaryEnvironmentId } from "../../state/environments";
 import { useT3ProjectFileScripts } from "~/hooks/useT3ProjectFileScripts";
 import { ProjectFavicon } from "../ProjectFavicon";
 import { cn } from "~/lib/utils";
+import { Button } from "../ui/button";
 
 interface ChatHeaderProps {
   activeThreadEnvironmentId: EnvironmentId;
@@ -34,6 +36,9 @@ interface ChatHeaderProps {
   availableEditors: ReadonlyArray<EditorId>;
   rightPanelOpen: boolean;
   gitCwd: string | null;
+  canOpenChanges: boolean;
+  onOpenChanges: () => void;
+  onReview: () => void;
   onNewThreadInProject: () => void;
   onRunProjectScript: (script: ProjectScript) => void;
   onAddProjectScript: (input: NewProjectScriptInput) => Promise<ProjectScriptActionResult>;
@@ -70,6 +75,9 @@ export const ChatHeader = memo(function ChatHeader({
   availableEditors,
   rightPanelOpen,
   gitCwd,
+  canOpenChanges,
+  onOpenChanges,
+  onReview,
   onNewThreadInProject,
   onRunProjectScript,
   onAddProjectScript,
@@ -163,6 +171,51 @@ export const ChatHeader = memo(function ChatHeader({
               : null
           }
         />
+        {activeProjectName ? (
+          <>
+            <Tooltip>
+              <TooltipTrigger
+                render={
+                  <Button
+                    type="button"
+                    size="xs"
+                    variant="outline"
+                    disabled={!canOpenChanges}
+                    onClick={onOpenChanges}
+                    aria-label="View branch changes"
+                  />
+                }
+              >
+                <FileDiffIcon className="size-3.5" aria-hidden />
+                <span className="sr-only @3xl/header-actions:not-sr-only @3xl/header-actions:ml-0.5">
+                  Changes
+                </span>
+              </TooltipTrigger>
+              <TooltipPopup side="top">
+                {canOpenChanges
+                  ? "View files changed on this branch"
+                  : "Changes are available after this thread starts"}
+              </TooltipPopup>
+            </Tooltip>
+            <Tooltip>
+              <TooltipTrigger
+                render={
+                  <Button
+                    type="button"
+                    size="xs"
+                    variant="outline"
+                    onClick={onReview}
+                    aria-label="Insert review prompt"
+                  />
+                }
+              >
+                <ScanSearchIcon className="size-3.5" aria-hidden />
+                <span className="ml-0.5">Review</span>
+              </TooltipTrigger>
+              <TooltipPopup side="top">Insert the configured review prompt</TooltipPopup>
+            </Tooltip>
+          </>
+        ) : null}
         {activeProjectName && (
           <GitActionsControl
             gitCwd={gitCwd}

apps/web/src/components/settings/SourceControlWritingSettings.tsx

@@ -208,6 +208,40 @@ export function SourceControlWritingSettingsSection() {
           </div>
         }
       />
+
+      <SettingsRow
+        title="Review prompt"
+        description="Text inserted into the composer when you choose Review beside the Git actions."
+        resetAction={
+          settings.reviewPrompt !== DEFAULT_UNIFIED_SETTINGS.reviewPrompt ? (
+            <SettingResetButton
+              label="review prompt"
+              onClick={() =>
+                updateSettings({ reviewPrompt: DEFAULT_UNIFIED_SETTINGS.reviewPrompt })
+              }
+            />
+          ) : null
+        }
+      >
+        <div className="mt-3 max-w-2xl pb-3.5">
+          <Textarea
+            key={settings.reviewPrompt}
+            defaultValue={settings.reviewPrompt}
+            onBlur={(event) => {
+              const reviewPrompt = event.target.value.trim();
+              if (reviewPrompt.length === 0) {
+                event.target.value = settings.reviewPrompt;
+                return;
+              }
+              if (reviewPrompt !== settings.reviewPrompt) {
+                updateSettings({ reviewPrompt });
+              }
+            }}
+            rows={4}
+            aria-label="Review prompt"
+          />
+        </div>
+      </SettingsRow>
     </SettingsSection>
   );
 }

docs/integrations/source-control-providers.md

@@ -35,6 +35,11 @@ T3 Code works with the platforms your team already uses:
 - T3 Code can suggest titles and descriptions based on your commits
 - Supports GitHub Pull Requests, GitLab Merge Requests, and Bitbucket Pull Requests
 
+**Review branch changes without leaving the thread**
+
+- **Changes** beside the Git actions opens the branch diff against its base, including after a pull request has been created
+- **Review** inserts a configurable review prompt into the composer; edit it under **Settings → Source Control → Text generation**
+
 **Stay on top of open reviews**
 
 - See if your current branch already has an open PR/MR

packages/contracts/src/settings.test.ts

@@ -5,6 +5,7 @@ import { ProviderInstanceId } from "./providerInstance.ts";
 import {
   ClientSettingsSchema,
   ClientSettingsPatch,
+  DEFAULT_REVIEW_PROMPT,
   DEFAULT_SERVER_SETTINGS,
   ServerSettings,
   ServerSettingsPatch,
@@ -206,6 +207,19 @@ describe("ServerSettings.sourceControlWritingStyle", () => {
   });
 });
 
+describe("ServerSettings.reviewPrompt", () => {
+  it("provides a useful default for legacy configs", () => {
+    expect(decodeServerSettings({}).reviewPrompt).toBe(DEFAULT_REVIEW_PROMPT);
+  });
+
+  it("trims review prompt updates and rejects empty prompts", () => {
+    expect(
+      decodeServerSettingsPatch({ reviewPrompt: "  Review this carefully.  " }).reviewPrompt,
+    ).toBe("Review this carefully.");
+    expect(() => decodeServerSettingsPatch({ reviewPrompt: "   " })).toThrow();
+  });
+});
+
 describe("ServerSettingsPatch.providerInstances", () => {
   it("treats providerInstances as an optional whole-map replacement", () => {
     const patch = decodeServerSettingsPatch({});

packages/contracts/src/settings.ts

@@ -85,6 +85,9 @@ export const DiffTheme = Schema.Literals([
 export type DiffTheme = typeof DiffTheme.Type;
 export const DEFAULT_DIFF_THEME: DiffTheme = "pierre-dark";
 
+export const DEFAULT_REVIEW_PROMPT =
+  "Review the current changes. Focus on correctness, regressions, security, performance, and missing tests. Report findings by severity with file and line references.";
+
 export const ClientSettingsSchema = Schema.Struct({
   autoOpenPlanSidebar: Schema.Boolean.pipe(Schema.withDecodingDefault(Effect.succeed(false))),
   confirmThreadArchive: Schema.Boolean.pipe(Schema.withDecodingDefault(Effect.succeed(false))),
@@ -538,6 +541,9 @@ export const ServerSettings = Schema.Struct({
   sourceControlWriterModelSelection: Schema.NullOr(ModelSelection).pipe(
     Schema.withDecodingDefault(Effect.succeed(null)),
   ),
+  reviewPrompt: TrimmedNonEmptyString.pipe(
+    Schema.withDecodingDefault(Effect.succeed(DEFAULT_REVIEW_PROMPT)),
+  ),
 
   // Legacy single-instance-per-driver settings. Continues to be the source
   // of truth until `providerInstances` (below) lands per-driver migration
@@ -682,6 +688,7 @@ export const ServerSettingsPatch = Schema.Struct({
     }),
   ),
   sourceControlWriterModelSelection: Schema.optionalKey(Schema.NullOr(ModelSelection)),
+  reviewPrompt: Schema.optionalKey(TrimmedNonEmptyString),
   observability: Schema.optionalKey(
     Schema.Struct({
       otlpTracesUrl: Schema.optionalKey(TrimmedString),