feat: add git history visualization frontend

- Add API client functions for commit history and detail endpoints
- Create GitHistoryPage with commit list, graph visualization, and detail panel
- Add branch selector for viewing different branches
- Integrate history view into repository list with History button
- Add comprehensive CSS styles for history page layout

Quality gates: typecheck ✓, lint ✓, build ✓

apps/web/src/api/git_repositories.ts

@@ -49,3 +49,61 @@ export async function createRepository(
 export async function deleteRepository(projectId: string, repoId: string): Promise<void> {
   await apiClient.delete(`/projects/${projectId}/repositories/${repoId}`);
 }
+
+export interface CommitHistoryEntry {
+  hash: string;
+  short_hash: string;
+  message: string;
+  author_name: string;
+  author_email: string;
+  author_date: string;
+  refs: string[];
+  graph_symbol: string;
+  graph_depth: number;
+}
+
+export interface CommitHistoryResponse {
+  commits: CommitHistoryEntry[];
+  branches: string[];
+  tags: string[];
+}
+
+export async function getRepositoryHistory(
+  projectId: string,
+  repoId: string,
+  branch?: string
+): Promise<CommitHistoryResponse> {
+  const params = branch ? `?branch=${encodeURIComponent(branch)}` : "";
+  const response = await apiClient.get(`/projects/${projectId}/repositories/${repoId}/history${params}`);
+  return response.data;
+}
+
+export interface CommitDetail {
+  hash: string;
+  short_hash: string;
+  message: string;
+  author_name: string;
+  author_email: string;
+  author_date: string;
+  committer_name: string;
+  committer_email: string;
+  committer_date: string;
+  stats: {
+    additions: number;
+    deletions: number;
+    files_changed: number;
+  };
+  diff: string;
+  parents: string[];
+}
+
+export async function getCommitDetail(
+  projectId: string,
+  repoId: string,
+  commitHash: string
+): Promise<CommitDetail> {
+  const response = await apiClient.get(
+    `/projects/${projectId}/repositories/${repoId}/commits/${commitHash}`
+  );
+  return response.data;
+}

apps/web/src/pages/git-history.tsx

@@ -0,0 +1,231 @@
+import { useCallback, useEffect, useState } from "react";
+import { useNavigate, useParams } from "react-router-dom";
+
+import { getCommitDetail, getRepositoryHistory, type CommitDetail, type CommitHistoryEntry } from "../api/git_repositories";
+
+export const GitHistoryPage = () => {
+  const { projectId, repoId } = useParams<{ projectId: string; repoId: string }>();
+  const navigate = useNavigate();
+  const [commits, setCommits] = useState<CommitHistoryEntry[]>([]);
+  const [selectedCommit, setSelectedCommit] = useState<string | null>(null);
+  const [commitDetail, setCommitDetail] = useState<CommitDetail | null>(null);
+  const [branches, setBranches] = useState<string[]>([]);
+  const [selectedBranch, setSelectedBranch] = useState<string>("");
+  const [status, setStatus] = useState<"loading" | "ready" | "error">("loading");
+  const [detailStatus, setDetailStatus] = useState<"idle" | "loading" | "ready" | "error">("idle");
+
+  const loadHistory = useCallback(async () => {
+    if (!projectId || !repoId) return;
+    setStatus("loading");
+    try {
+      const data = await getRepositoryHistory(projectId, repoId, selectedBranch || undefined);
+      setCommits(data.commits);
+      setBranches(data.branches);
+      if (data.branches.length > 0 && !selectedBranch) {
+        setSelectedBranch(data.branches[0]);
+      }
+      setStatus("ready");
+    } catch {
+      setStatus("error");
+    }
+  }, [projectId, repoId, selectedBranch]);
+
+  useEffect(() => {
+    void loadHistory();
+  }, [loadHistory]);
+
+  const handleCommitClick = async (hash: string) => {
+    if (!projectId || !repoId) return;
+    setSelectedCommit(hash);
+    setDetailStatus("loading");
+    try {
+      const detail = await getCommitDetail(projectId, repoId, hash);
+      setCommitDetail(detail);
+      setDetailStatus("ready");
+    } catch {
+      setDetailStatus("error");
+    }
+  };
+
+  const handleCloseDetail = () => {
+    setSelectedCommit(null);
+    setCommitDetail(null);
+    setDetailStatus("idle");
+  };
+
+  const formatDate = (dateStr: string) => {
+    return new Date(dateStr).toLocaleString();
+  };
+
+  if (status === "loading") {
+    return (
+      <section className="stack">
+        <p className="muted">Loading commit history...</p>
+      </section>
+    );
+  }
+
+  if (status === "error") {
+    return (
+      <section className="stack">
+        <p>Failed to load commit history</p>
+        <button className="secondary-button" onClick={() => void loadHistory()} type="button">
+          Retry
+        </button>
+      </section>
+    );
+  }
+
+  return (
+    <section className="stack">
+      <div className="page-header">
+        <div>
+          <h1>Commit History</h1>
+          <p className="muted">{commits.length} commits</p>
+        </div>
+        <div className="history-actions">
+          {branches.length > 0 && (
+            <select
+              value={selectedBranch}
+              onChange={(e) => setSelectedBranch(e.target.value)}
+              className="branch-selector"
+            >
+              {branches.map((branch) => (
+                <option key={branch} value={branch}>
+                  {branch}
+                </option>
+              ))}
+            </select>
+          )}
+          <button
+            className="secondary-button"
+            onClick={() => navigate(`/projects/${projectId}/repositories`)}
+            type="button"
+          >
+            Back to Repositories
+          </button>
+        </div>
+      </div>
+
+      <div className="history-container">
+        <div className={`commit-list ${selectedCommit ? "with-detail" : ""}`}>
+          {commits.map((commit) => (
+            <div
+              key={commit.hash}
+              className={`commit-item ${selectedCommit === commit.hash ? "selected" : ""}`}
+              onClick={() => void handleCommitClick(commit.hash)}
+              role="button"
+              tabIndex={0}
+              onKeyDown={(e) => {
+                if (e.key === "Enter" || e.key === " ") {
+                  void handleCommitClick(commit.hash);
+                }
+              }}
+            >
+              <div className="commit-graph">
+                <span className="graph-line" style={{ marginLeft: `${commit.graph_depth * 12}px` }}>
+                  {commit.graph_symbol}
+                </span>
+              </div>
+              <div className="commit-content">
+                <div className="commit-header">
+                  <span className="commit-hash">{commit.short_hash}</span>
+                  {commit.refs.length > 0 && (
+                    <span className="commit-refs">
+                      {commit.refs.map((ref) => (
+                        <span key={ref} className="ref-tag">
+                          {ref}
+                        </span>
+                      ))}
+                    </span>
+                  )}
+                </div>
+                <p className="commit-message">{commit.message.split("\n")[0]}</p>
+                <div className="commit-meta">
+                  <span>{commit.author_name}</span>
+                  <span className="muted">{formatDate(commit.author_date)}</span>
+                </div>
+              </div>
+            </div>
+          ))}
+        </div>
+
+        {selectedCommit && (
+          <div className="commit-detail-panel">
+            <div className="detail-header">
+              <h3>Commit Details</h3>
+              <button className="ghost-button" onClick={handleCloseDetail} type="button">
+                ×
+              </button>
+            </div>
+
+            {detailStatus === "loading" && <p className="muted">Loading details...</p>}
+            
+            {detailStatus === "error" && (
+              <p>Failed to load commit details</p>
+            )}
+
+            {detailStatus === "ready" && commitDetail && (
+              <div className="detail-content">
+                <div className="detail-section">
+                  <p className="commit-hash-full">{commitDetail.hash}</p>
+                  <p className="commit-message-full">{commitDetail.message}</p>
+                </div>
+
+                <div className="detail-section">
+                  <h4>Author</h4>
+                  <p>{commitDetail.author_name} &lt;{commitDetail.author_email}&gt;</p>
+                  <p className="muted">{formatDate(commitDetail.author_date)}</p>
+                </div>
+
+                <div className="detail-section">
+                  <h4>Committer</h4>
+                  <p>{commitDetail.committer_name} &lt;{commitDetail.committer_email}&gt;</p>
+                  <p className="muted">{formatDate(commitDetail.committer_date)}</p>
+                </div>
+
+                <div className="detail-section">
+                  <h4>Stats</h4>
+                  <div className="stats-grid">
+                    <div className="stat">
+                      <span className="stat-value">{commitDetail.stats.files_changed}</span>
+                      <span className="stat-label">Files</span>
+                    </div>
+                    <div className="stat additions">
+                      <span className="stat-value">+{commitDetail.stats.additions}</span>
+                      <span className="stat-label">Additions</span>
+                    </div>
+                    <div className="stat deletions">
+                      <span className="stat-value">-{commitDetail.stats.deletions}</span>
+                      <span className="stat-label">Deletions</span>
+                    </div>
+                  </div>
+                </div>
+
+                {commitDetail.parents.length > 0 && (
+                  <div className="detail-section">
+                    <h4>Parents</h4>
+                    <div className="parent-list">
+                      {commitDetail.parents.map((parent) => (
+                        <span key={parent} className="parent-hash">
+                          {parent.substring(0, 8)}
+                        </span>
+                      ))}
+                    </div>
+                  </div>
+                )}
+
+                {commitDetail.diff && (
+                  <div className="detail-section">
+                    <h4>Diff</h4>
+                    <pre className="diff-content">{commitDetail.diff}</pre>
+                  </div>
+                )}
+              </div>
+            )}
+          </div>
+        )}
+      </div>
+    </section>
+  );
+};

apps/web/src/pages/git-repositories.tsx

@@ -1,5 +1,5 @@
 import { useCallback, useEffect, useRef, useState } from "react";
-import { useParams } from "react-router-dom";
+import { useNavigate, useParams } from "react-router-dom";
 
 import {
   createRepository,
@@ -16,6 +16,7 @@ type UrlValidationStatus = "idle" | "validating" | "valid" | "needs-parsing" | "
 
 export const GitRepositoriesPage = () => {
   const { projectId } = useParams<{ projectId: string }>();
+  const navigate = useNavigate();
   const [status, setStatus] = useState<RepoStatus>("loading");
   const [repositories, setRepositories] = useState<GitRepository[]>([]);
   const [showCreate, setShowCreate] = useState(false);
@@ -188,6 +189,13 @@ export const GitRepositoriesPage = () => {
                 <p className="muted">{repo.path}</p>
               </div>
               <div className="repository-actions">
+                <button
+                  className="secondary-button small"
+                  onClick={() => navigate(`/projects/${projectId}/repositories/${repo.id}/history`)}
+                  type="button"
+                >
+                  History
+                </button>
                 {deleteConfirmId === repo.id ? (
                   <div className="delete-confirm">
                     <span>Are you sure?</span>

apps/web/src/router.tsx

@@ -7,6 +7,7 @@ import { LoginRedirectPage, NotFoundPage } from "./pages/placeholder";
 import { ProfilePage } from "./pages/profile";
 import { ProjectsPage } from "./pages/projects";
 import { GitRepositoriesPage } from "./pages/git-repositories";
+import { GitHistoryPage } from "./pages/git-history";
 import { SSHKeysPage } from "./pages/ssh-keys";
 import { SettingsPage } from "./pages/settings";
 import { ToolTypesPage } from "./pages/tool-types";
@@ -26,6 +27,7 @@ export const AppRouter = () => {
         <Route index element={<DashboardPage />} />
         <Route path="projects" element={<ProjectsPage />} />
         <Route path="projects/:projectId/repositories" element={<GitRepositoriesPage />} />
+        <Route path="projects/:projectId/repositories/:repoId/history" element={<GitHistoryPage />} />
         <Route path="ssh-keys" element={<SSHKeysPage />} />
         <Route path="profile" element={<ProfilePage />} />
         <Route path="settings" element={<SettingsPage />} />

apps/web/src/styles.css

@@ -437,3 +437,260 @@ a {
   padding: 0.35rem 0.6rem;
   font-size: 0.85rem;
 }
+
+/* Git History Page Styles */
+.history-actions {
+  display: flex;
+  gap: 0.75rem;
+  align-items: center;
+}
+
+.branch-selector {
+  padding: 0.45rem 0.7rem;
+  border: 1px solid var(--border);
+  border-radius: 10px;
+  font: inherit;
+  background: var(--panel);
+  color: var(--ink);
+}
+
+.history-container {
+  display: grid;
+  grid-template-columns: 1fr;
+  gap: 1rem;
+  min-height: 60vh;
+}
+
+.commit-list {
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  overflow-y: auto;
+  max-height: 70vh;
+}
+
+.commit-list.with-detail {
+  grid-column: 1;
+}
+
+.commit-item {
+  display: flex;
+  gap: 0.75rem;
+  padding: 0.75rem;
+  background: var(--panel);
+  border: 1px solid var(--border);
+  border-radius: 10px;
+  cursor: pointer;
+  transition: background-color 0.15s ease;
+}
+
+.commit-item:hover {
+  background: #ece7df;
+}
+
+.commit-item.selected {
+  border-color: var(--brand);
+  background: #f0f7f4;
+}
+
+.commit-graph {
+  font-family: monospace;
+  font-size: 0.9rem;
+  color: var(--brand);
+  white-space: pre;
+  flex-shrink: 0;
+  min-width: 60px;
+}
+
+.graph-line {
+  display: inline-block;
+}
+
+.commit-content {
+  flex: 1;
+  min-width: 0;
+}
+
+.commit-header {
+  display: flex;
+  gap: 0.5rem;
+  align-items: center;
+  margin-bottom: 0.35rem;
+}
+
+.commit-hash {
+  font-family: monospace;
+  font-size: 0.85rem;
+  color: var(--brand);
+  background: #f0f7f4;
+  padding: 0.15rem 0.4rem;
+  border-radius: 6px;
+}
+
+.commit-refs {
+  display: flex;
+  gap: 0.35rem;
+  flex-wrap: wrap;
+}
+
+.ref-tag {
+  font-size: 0.75rem;
+  padding: 0.15rem 0.4rem;
+  background: var(--brand);
+  color: white;
+  border-radius: 999px;
+}
+
+.commit-message {
+  margin: 0 0 0.35rem;
+  font-weight: 500;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.commit-meta {
+  display: flex;
+  gap: 0.75rem;
+  font-size: 0.85rem;
+  color: var(--muted);
+}
+
+.commit-detail-panel {
+  background: var(--panel);
+  border: 1px solid var(--border);
+  border-radius: 14px;
+  padding: 1.25rem;
+  overflow-y: auto;
+  max-height: 70vh;
+}
+
+.detail-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-bottom: 1rem;
+  padding-bottom: 0.75rem;
+  border-bottom: 1px solid var(--border);
+}
+
+.detail-header h3 {
+  margin: 0;
+}
+
+.detail-content {
+  display: flex;
+  flex-direction: column;
+  gap: 1.25rem;
+}
+
+.detail-section {
+  display: flex;
+  flex-direction: column;
+  gap: 0.35rem;
+}
+
+.detail-section h4 {
+  margin: 0 0 0.5rem;
+  color: var(--muted);
+  font-size: 0.9rem;
+  text-transform: uppercase;
+  letter-spacing: 0.05em;
+}
+
+.commit-hash-full {
+  font-family: monospace;
+  font-size: 0.85rem;
+  color: var(--brand);
+  margin: 0;
+}
+
+.commit-message-full {
+  margin: 0.5rem 0 0;
+  line-height: 1.5;
+  white-space: pre-wrap;
+}
+
+.stats-grid {
+  display: grid;
+  grid-template-columns: repeat(3, 1fr);
+  gap: 0.75rem;
+}
+
+.stat {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  padding: 0.75rem;
+  background: #f5f3ee;
+  border-radius: 10px;
+}
+
+.stat.additions {
+  background: #f0fdf4;
+}
+
+.stat.deletions {
+  background: #fef2f2;
+}
+
+.stat-value {
+  font-size: 1.25rem;
+  font-weight: 700;
+  color: var(--ink);
+}
+
+.stat.additions .stat-value {
+  color: #16a34a;
+}
+
+.stat.deletions .stat-value {
+  color: #dc2626;
+}
+
+.stat-label {
+  font-size: 0.8rem;
+  color: var(--muted);
+}
+
+.parent-list {
+  display: flex;
+  gap: 0.5rem;
+  flex-wrap: wrap;
+}
+
+.parent-hash {
+  font-family: monospace;
+  font-size: 0.85rem;
+  padding: 0.2rem 0.5rem;
+  background: #f5f3ee;
+  border-radius: 6px;
+}
+
+.diff-content {
+  font-family: monospace;
+  font-size: 0.8rem;
+  line-height: 1.5;
+  background: #f5f3ee;
+  padding: 0.75rem;
+  border-radius: 10px;
+  overflow-x: auto;
+  white-space: pre-wrap;
+  word-break: break-all;
+}
+
+@media (min-width: 1024px) {
+  .history-container {
+    grid-template-columns: 1fr 400px;
+  }
+
+  .commit-list.with-detail {
+    grid-column: 1;
+  }
+
+  .commit-detail-panel {
+    grid-column: 2;
+    position: sticky;
+    top: 1rem;
+  }
+}