diff --git a/src/server/workspace-metadata-monitor.ts b/src/server/workspace-metadata-monitor.ts
index aa2c24cd7..ddfdf2066 100644
--- a/src/server/workspace-metadata-monitor.ts
+++ b/src/server/workspace-metadata-monitor.ts
@@ -7,7 +7,12 @@ import type {
 import { getGitSyncSummary, probeGitWorkspaceState } from "../workspace/git-sync";
 import { getTaskWorkspacePathInfo } from "../workspace/task-worktree";
 
-const WORKSPACE_METADATA_POLL_INTERVAL_MS = 1_000;
+// The UI refreshes imperatively via updateWorkspaceState whenever the board
+// changes, so this timer only needs to catch external edits (out-of-band
+// commits, agent file writes). Polling more aggressively just spawns a
+// continuous stream of git subprocesses (~3·(N+1) per tick) even when no
+// task is running, which shows up as sustained energy impact at idle.
+const WORKSPACE_METADATA_POLL_INTERVAL_MS = 10_000;
 
 interface TrackedTaskWorkspace {
 	taskId: string;
@@ -18,11 +23,13 @@ interface CachedHomeGitMetadata {
 	summary: RuntimeGitSyncSummary | null;
 	stateToken: string | null;
 	stateVersion: number;
+	repoRoot: string | null;
 }
 
 interface CachedTaskWorkspaceMetadata {
 	data: RuntimeTaskWorkspaceMetadata;
 	stateToken: string | null;
+	repoRoot: string | null;
 }
 
 interface WorkspaceMetadataEntry {
@@ -147,6 +154,7 @@ function createWorkspaceEntry(workspacePath: string): WorkspaceMetadataEntry {
 			summary: null,
 			stateToken: null,
 			stateVersion: 0,
+			repoRoot: null,
 		},
 		taskMetadataByTaskId: new Map<string, CachedTaskWorkspaceMetadata>(),
 	};
@@ -164,18 +172,21 @@ function buildWorkspaceMetadataSnapshot(entry: WorkspaceMetadataEntry): RuntimeW
 
 async function loadHomeGitMetadata(entry: WorkspaceMetadataEntry): Promise<CachedHomeGitMetadata> {
 	try {
-		const probe = await probeGitWorkspaceState(entry.workspacePath);
+		const probe = await probeGitWorkspaceState(entry.workspacePath, {
+			repoRoot: entry.homeGit.repoRoot ?? undefined,
+		});
 		if (entry.homeGit.stateToken === probe.stateToken) {
-			return entry.homeGit;
+			return { ...entry.homeGit, repoRoot: probe.repoRoot };
 		}
 		const summary = await getGitSyncSummary(entry.workspacePath, { probe });
 		return {
 			summary,
 			stateToken: probe.stateToken,
 			stateVersion: Date.now(),
+			repoRoot: probe.repoRoot,
 		};
 	} catch {
-		return entry.homeGit;
+		return { ...entry.homeGit, repoRoot: null };
 	}
 }
 
@@ -214,11 +225,14 @@ async function loadTaskWorkspaceMetadata(
 				stateVersion: Date.now(),
 			},
 			stateToken: null,
+			repoRoot: null,
 		};
 	}
 
 	try {
-		const probe = await probeGitWorkspaceState(pathInfo.path);
+		const probe = await probeGitWorkspaceState(pathInfo.path, {
+			repoRoot: current && current.data.path === pathInfo.path && current.repoRoot ? current.repoRoot : undefined,
+		});
 		if (
 			current &&
 			current.stateToken === probe.stateToken &&
@@ -243,6 +257,7 @@ async function loadTaskWorkspaceMetadata(
 				stateVersion: Date.now(),
 			},
 			stateToken: probe.stateToken,
+			repoRoot: probe.repoRoot,
 		};
 	} catch {
 		if (current) {
@@ -263,6 +278,7 @@ async function loadTaskWorkspaceMetadata(
 				stateVersion: Date.now(),
 			},
 			stateToken: null,
+			repoRoot: null,
 		};
 	}
 }
diff --git a/src/workspace/git-sync.ts b/src/workspace/git-sync.ts
index 6de0a6dfe..ca42e69e8 100644
--- a/src/workspace/git-sync.ts
+++ b/src/workspace/git-sync.ts
@@ -110,12 +110,9 @@ function parseStatusPath(line: string): string | null {
 	return tokens[tokens.length - 1] ?? null;
 }
 
-export async function probeGitWorkspaceState(cwd: string): Promise<GitWorkspaceProbe> {
-	const repoRoot = await resolveRepoRoot(cwd);
-	const [statusResult, headCommitResult] = await Promise.all([
-		runGit(repoRoot, ["status", "--porcelain=v2", "--branch", "--untracked-files=all"]),
-		runGit(repoRoot, ["rev-parse", "--verify", "HEAD"]),
-	]);
+export async function probeGitWorkspaceState(cwd: string, options?: { repoRoot?: string }): Promise<GitWorkspaceProbe> {
+	const repoRoot = options?.repoRoot ?? (await resolveRepoRoot(cwd));
+	const statusResult = await runGit(repoRoot, ["status", "--porcelain=v2", "--branch", "--untracked-files=all"]);
 
 	if (!statusResult.ok) {
 		throw new Error(statusResult.error ?? "Git status command failed.");
@@ -125,6 +122,7 @@ export async function probeGitWorkspaceState(cwd: string): Promise<GitWorkspaceP
 	let upstreamBranch: string | null = null;
 	let aheadCount = 0;
 	let behindCount = 0;
+	let headCommit: string | null = null;
 	const fingerprintPaths: string[] = [];
 	const untrackedPaths: string[] = [];
 	let changedFiles = 0;
@@ -134,6 +132,11 @@ export async function probeGitWorkspaceState(cwd: string): Promise<GitWorkspaceP
 		if (!line) {
 			continue;
 		}
+		if (line.startsWith("# branch.oid ")) {
+			const oid = line.slice("# branch.oid ".length).trim();
+			headCommit = oid && oid !== "(initial)" ? oid : null;
+			continue;
+		}
 		if (line.startsWith("# branch.head ")) {
 			const branchName = line.slice("# branch.head ".length).trim();
 			currentBranch = branchName && branchName !== "(detached)" ? branchName : null;
@@ -174,7 +177,6 @@ export async function probeGitWorkspaceState(cwd: string): Promise<GitWorkspaceP
 		}
 	}
 
-	const headCommit = headCommitResult.ok && headCommitResult.stdout ? headCommitResult.stdout : null;
 	const fingerprints = await buildPathFingerprints(repoRoot, fingerprintPaths);
 
 	return {
@@ -208,6 +210,9 @@ async function resolveRepoRoot(cwd: string): Promise<string> {
 }
 
 async function countUntrackedAdditions(repoRoot: string, untrackedPaths: string[]): Promise<number> {
+	if (untrackedPaths.length === 0) {
+		return 0;
+	}
 	const counts = await Promise.all(
 		untrackedPaths.map(async (relativePath) => {
 			try {
@@ -221,6 +226,19 @@ async function countUntrackedAdditions(repoRoot: string, untrackedPaths: string[
 	return counts.reduce((total, value) => total + value, 0);
 }
 
+async function getTrackedDiffTotals(probe: GitWorkspaceProbe): Promise<{ additions: number; deletions: number }> {
+	// `git diff --numstat HEAD` only has output when there are tracked changes.
+	// `probe.changedFiles` already counts both tracked and untracked entries, so
+	// when those are equal (or both zero) we can skip the subprocess entirely —
+	// the dominant case for an idle clean repo on the metadata-monitor poll.
+	const trackedChangeCount = probe.changedFiles - probe.untrackedPaths.length;
+	if (trackedChangeCount <= 0) {
+		return { additions: 0, deletions: 0 };
+	}
+	const diffResult = await runGit(probe.repoRoot, ["diff", "--numstat", "HEAD", "--"]);
+	return diffResult.ok ? parseNumstatTotals(diffResult.stdout) : { additions: 0, deletions: 0 };
+}
+
 async function hasGitRef(repoRoot: string, ref: string): Promise<boolean> {
 	const result = await runGit(repoRoot, ["show-ref", "--verify", "--quiet", ref]);
 	return result.ok;
@@ -231,9 +249,10 @@ export async function getGitSyncSummary(
 	options?: { probe?: GitWorkspaceProbe },
 ): Promise<RuntimeGitSyncSummary> {
 	const probe = options?.probe ?? (await probeGitWorkspaceState(cwd));
-	const diffResult = await runGit(probe.repoRoot, ["diff", "--numstat", "HEAD", "--"]);
-	const trackedTotals = diffResult.ok ? parseNumstatTotals(diffResult.stdout) : { additions: 0, deletions: 0 };
-	const untrackedAdditions = await countUntrackedAdditions(probe.repoRoot, probe.untrackedPaths);
+	const [trackedTotals, untrackedAdditions] = await Promise.all([
+		getTrackedDiffTotals(probe),
+		countUntrackedAdditions(probe.repoRoot, probe.untrackedPaths),
+	]);
 
 	return {
 		currentBranch: probe.currentBranch,
diff --git a/web-ui/src/components/card-detail-view.tsx b/web-ui/src/components/card-detail-view.tsx
index b3b8be454..d58b9c118 100644
--- a/web-ui/src/components/card-detail-view.tsx
+++ b/web-ui/src/components/card-detail-view.tsx
@@ -32,8 +32,9 @@ import { useTerminalThemeColors } from "@/terminal/theme-colors";
 import { type BoardCard, type CardSelection, getTaskAutoReviewCancelButtonLabel } from "@/types";
 import { useWindowEvent } from "@/utils/react-use";
 
-// We still poll the open detail diff because line content can change without changing
-// the overall file or line counts that drive the shared workspace metadata stream.
+// We poll the open detail diff while a task is running because in-place line
+// edits can change without bumping the file/additions/deletions counters that
+// drive the shared workspace metadata stream's `taskWorkspaceStateVersion`.
 const DETAIL_DIFF_POLL_INTERVAL_MS = 1_000;
 const DIFF_MODE_ACTIVE_BACKGROUND = "color-mix(in srgb, var(--color-surface-3) 80%, var(--color-text-primary))";
 
@@ -494,7 +495,9 @@ export function CardDetailView({
 		selection.card.baseRef,
 		diffMode,
 		taskWorkspaceStateVersion,
-		isDocumentVisible && !gitHistoryPanel && selection.column.id !== "trash" ? DETAIL_DIFF_POLL_INTERVAL_MS : null,
+		isDocumentVisible && !gitHistoryPanel && selection.column.id !== "trash" && sessionSummary?.state === "running"
+			? DETAIL_DIFF_POLL_INTERVAL_MS
+			: null,
 		lastTurnViewKey,
 		true,
 	);