diff --git a/.changeset/summary.md b/.changeset/summary.md
new file mode 100644
index 00000000..21894c3b
--- /dev/null
+++ b/.changeset/summary.md
@@ -0,0 +1,7 @@
+---
+"just-git": patch
+---
+
+Support `--summary` in `git show`, `git log` and `git diff`. It prints git's create, delete, rename and mode-change lines, after `--stat`, `--shortstat` or `--numstat` output and before a `-p` patch. On its own it replaces the patch. The summary that `commit` and `merge` print now uses the same lines, so a mode change prints `mode change 100644 => 100755 <path>` instead of a delete and a create, a rename that changes the mode prints the extra mode line, and unusual paths are C-quoted as in git.
+
+`git show` on a merge commit now prints `--stat`, `--shortstat`, `--numstat` and `--summary` against the first parent, as git does, instead of printing nothing. `git log --graph --format=<fmt>` now prints the blank line between each commit and its diff output.
diff --git a/docs/CLI.md b/docs/CLI.md
index e52b0db0..b3a086c1 100644
--- a/docs/CLI.md
+++ b/docs/CLI.md
@@ -465,6 +465,7 @@ Options:
   --name-status           Show names and status of changed files
   --shortstat             Show only the shortstat summary line
   --numstat               Machine-readable insertions/deletions per file
+  --summary               Show creations, deletions, renames and mode changes
   -U, --unified <number>  Generate diffs with <n> lines of context
   -M, --find-renames      Detect renames (enabled by default)
   -C, --find-copies       Detect copies (accepted for compatibility)
@@ -609,6 +610,7 @@ Options:
   --name-only               Show only names of changed files
   --shortstat               Show only the shortstat summary line
   --numstat                 Machine-readable insertions/deletions per file
+  --summary                 Show creations, deletions, renames and mode changes
   -q, --quiet               suppress diff output
   --graph                   Draw text-based graph of the commit history
   --first-parent            Follow only the first parent of merge commits
@@ -1015,6 +1017,7 @@ Options:
   --name-status      Show names and status of changed files
   --shortstat        Show only the shortstat summary line
   --numstat          Machine-readable insertions/deletions per file
+  --summary          Show creations, deletions, renames and mode changes
   --format <string>  Pretty-print format string
   --pretty <string>  Pretty-print format or preset name
 ```
diff --git a/docs/FILE_REFERENCE.md b/docs/FILE_REFERENCE.md
index 4309753b..07f4969b 100644
--- a/docs/FILE_REFERENCE.md
+++ b/docs/FILE_REFERENCE.md
@@ -28,8 +28,9 @@ Exported symbols from `src/lib/`. Generated by `bun scripts/gen-lib-reference.ts
 
 ### lib/commit-summary.ts
 
-- `formatShortstatParts`, `computeDiffStats`, `formatCommitSummary`, `renderStatLines`, `formatDiffStat`
+- `formatShortstatParts`, `computeDiffStats`, `formatSummaryLines`, `withSummary`, `formatCommitSummary`, `renderStatLines`, `formatDiffStat`
 - **interfaces**: `FileStat`
+- **types**: `SummaryRename`
 
 ### lib/commit-walk.ts
 
diff --git a/src/commands/diff.ts b/src/commands/diff.ts
index f2e7ffce..f406f823 100644
--- a/src/commands/diff.ts
+++ b/src/commands/diff.ts
@@ -11,7 +11,13 @@ import {
 	requireGitContext,
 	requireWorkTree,
 } from "../lib/command-utils.ts";
-import { type FileStat, formatShortstatParts, renderStatLines } from "../lib/commit-summary.ts";
+import {
+	type FileStat,
+	formatShortstatParts,
+	formatSummaryLines,
+	renderStatLines,
+	type SummaryRename,
+} from "../lib/commit-summary.ts";
 import { formatUnifiedDiff, myersDiff, splitLinesWithNL } from "../lib/diff-algorithm.ts";
 import { getStage0Entries, readIndex } from "../lib/index.ts";
 import { findAllMergeBases } from "../lib/merge.ts";
@@ -119,6 +125,7 @@ export function registerDiffCommand(parent: Command, ext?: GitExtensions) {
 			nameStatus: f().describe("Show names and status of changed files"),
 			shortstat: f().describe("Show only the shortstat summary line"),
 			numstat: f().describe("Machine-readable insertions/deletions per file"),
+			summary: f().describe("Show creations, deletions, renames and mode changes"),
 			unified: o.number().alias("U").describe("Generate diffs with <n> lines of context"),
 			findRenames: f().alias("M").describe("Detect renames (enabled by default)"),
 			findCopies: f().alias("C").describe("Detect copies (accepted for compatibility)"),
@@ -185,7 +192,14 @@ export function registerDiffCommand(parent: Command, ext?: GitExtensions) {
 
 			if (isError(result)) return result;
 			const contextLines = args.unified;
-			const output = await formatOutput(gitCtx, result.items, format, contextLines);
+			// Git drops --summary under the name formats, and --summary on its
+			// own replaces the patch.
+			const summary = args.summary && format !== "name-only" && format !== "name-status";
+			const output =
+				summary && format === "unified"
+					? { stdout: "", stderr: "", exitCode: 0 }
+					: await formatOutput(gitCtx, result.items, format, contextLines);
+			if (summary) output.stdout += formatAsSummary(result.items);
 			if (result.stderr) output.stderr = result.stderr;
 			return output;
 		},
@@ -864,6 +878,20 @@ async function formatAsNumstat(gitCtx: GitContext, items: DiffFileResult[]): Pro
 	return output;
 }
 
+function formatAsSummary(items: DiffFileResult[]): string {
+	const diffs: TreeDiffEntry[] = [];
+	const renames: SummaryRename[] = [];
+	for (const { path, status, oldPath, oldMode, newMode, similarity } of items) {
+		if (status === "R" && oldPath) {
+			renames.push({ oldPath, newPath: path, similarity: similarity ?? 100, oldMode, newMode });
+		} else if (status === "A" || status === "D" || status === "M") {
+			const treeStatus = status === "A" ? "added" : status === "D" ? "deleted" : "modified";
+			diffs.push({ path, status: treeStatus, oldMode, newMode });
+		}
+	}
+	return formatSummaryLines(diffs, renames);
+}
+
 async function formatAsStat(gitCtx: GitContext, items: DiffFileResult[]): Promise<string> {
 	const fileStats = await buildFileStats(gitCtx, items);
 	return renderStatLines(fileStats);
diff --git a/src/commands/log.ts b/src/commands/log.ts
index b96b59a7..16fbdcb1 100644
--- a/src/commands/log.ts
+++ b/src/commands/log.ts
@@ -8,7 +8,13 @@ import {
 	requireGitContext,
 	requireHead,
 } from "../lib/command-utils.ts";
-import { computeDiffStats, formatShortstatParts, renderStatLines } from "../lib/commit-summary.ts";
+import {
+	computeDiffStats,
+	formatShortstatParts,
+	formatSummaryLines,
+	renderStatLines,
+	withSummary,
+} from "../lib/commit-summary.ts";
 import { CommitHeap, walkCommits } from "../lib/commit-walk.ts";
 import { parseDate } from "../lib/date.ts";
 import { formatUnifiedDiff, myersDiff, splitLinesWithNL } from "../lib/diff-algorithm.ts";
@@ -39,6 +45,12 @@ import type { Commit, GitRepo, ObjectId, TreeDiffEntry } from "../lib/types.ts";
 import { worktreeHeadCommits } from "../lib/worktree-admin.ts";
 import { a, type Command, f, o } from "../parse/index.ts";
 
+/** The diff each commit is shown with: a main format and/or the --summary lines. */
+interface LogDiffOutput {
+	format: LogDiffFormat;
+	summary: boolean;
+}
+
 type LogDiffFormat =
 	| "name-status"
 	| "name-only"
@@ -73,6 +85,7 @@ export function registerLogCommand(parent: Command, ext?: GitExtensions) {
 			nameOnly: f().describe("Show only names of changed files"),
 			shortstat: f().describe("Show only the shortstat summary line"),
 			numstat: f().describe("Machine-readable insertions/deletions per file"),
+			summary: f().describe("Show creations, deletions, renames and mode changes"),
 			quiet: quietFlag("suppress diff output"),
 			graph: f().describe("Draw text-based graph of the commit history"),
 			firstParent: f().describe("Follow only the first parent of merge commits"),
@@ -241,6 +254,10 @@ export function registerLogCommand(parent: Command, ext?: GitExtensions) {
 								: args.numstat
 									? "numstat"
 									: null;
+			// Git drops --summary when a name format is in effect.
+			const summary = args.summary && diffFormat !== "name-only" && diffFormat !== "name-status";
+			const diffOutput: LogDiffOutput | null =
+				diffFormat || summary ? { format: diffFormat, summary } : null;
 
 			// ── Graph / reverse conflict ────────────────────────────
 			const useGraph = args.graph;
@@ -326,7 +343,7 @@ export function registerLogCommand(parent: Command, ext?: GitExtensions) {
 					customFormat,
 					presetName,
 					abbrevCommit,
-					diffFormat,
+					diffOutput,
 					decoFn,
 					decoRawFn,
 					renameState,
@@ -350,9 +367,9 @@ export function registerLogCommand(parent: Command, ext?: GitExtensions) {
 						]),
 					};
 					let line = expandFormat(customFormat, fctx);
-					const diffText = await formatCommitDiff(gitCtx, entry.commit, diffFormat, renameState);
-					if (diffText) {
-						line += `\n\n${diffText.replace(/\n$/, "")}`;
+					const diffText = await formatCommitDiff(gitCtx, entry.commit, diffOutput, renameState);
+					if (diffText !== null) {
+						line += `\n\n${diffText}`.replace(/\n$/, "");
 					}
 					lines.push(line);
 				}
@@ -381,10 +398,10 @@ export function registerLogCommand(parent: Command, ext?: GitExtensions) {
 					]),
 				};
 				let line = formatPreset(effectivePreset, fctx, idx === 0, abbrevCommit);
-				const diffText = await formatCommitDiff(gitCtx, entry.commit, diffFormat, renameState);
-				if (diffText) {
+				const diffText = await formatCommitDiff(gitCtx, entry.commit, diffOutput, renameState);
+				if (diffText !== null) {
 					const sep = isOneline ? "\n" : "\n\n";
-					line += `${sep}${diffText.replace(/\n$/, "")}`;
+					line += `${sep}${diffText}`.replace(/\n$/, "");
 				}
 				lines.push(line);
 			}
@@ -606,7 +623,7 @@ async function formatWithGraph(
 	customFormat: string | null,
 	presetName: string | null,
 	abbrevCommit: boolean,
-	diffFormat: LogDiffFormat,
+	diffOutput: LogDiffOutput | null,
 	decoFn: ((h: ObjectId) => string) | undefined,
 	decoRawFn: ((h: ObjectId) => string) | undefined,
 	renameState: RenameWarningState,
@@ -679,20 +696,20 @@ async function formatWithGraph(
 		const diffText = await formatCommitDiff(
 			gitCtx,
 			entry.commit,
-			diffFormat,
+			diffOutput,
 			renameState,
 			statWidth,
 		);
 
 		// Diff/stat output gets padding prefixes (columns already settled)
-		if (diffText) {
-			const diffLines = diffText.replace(/\n$/, "").split("\n");
-			if (isOneline || customFormat !== null) {
+		if (diffText !== null) {
+			const diffLines = diffText ? diffText.replace(/\n$/, "").split("\n") : [];
+			if (isOneline) {
 				for (const dl of diffLines) {
 					output.push(graph.paddingPrefix() + dl);
 				}
 			} else {
-				// Medium/full format: blank separator before diff
+				// Blank separator before the diff, as for non-graph output
 				output.push(graph.paddingPrefix());
 				for (const dl of diffLines) {
 					output.push(graph.paddingPrefix() + dl);
@@ -710,15 +727,22 @@ async function formatWithGraph(
 
 // ── Diff output for log ─────────────────────────────────────────────
 
+/**
+ * The diff text shown under a commit, or null when nothing is shown at
+ * all: no diff output requested, a merge commit, or an empty diff. An
+ * empty string means the commit has changes but the requested output is
+ * empty (e.g. --summary on a content-only change); git still prints the
+ * separator line for it.
+ */
 async function formatCommitDiff(
 	ctx: GitRepo,
 	commit: Commit,
-	format: LogDiffFormat,
+	output: LogDiffOutput | null,
 	renameState: RenameWarningState,
 	statWidth?: number,
-): Promise<string> {
-	if (!format) return "";
-	if (commit.parents.length >= 2) return "";
+): Promise<string | null> {
+	if (!output) return null;
+	if (commit.parents.length >= 2) return null;
 
 	const parentTree =
 		commit.parents.length === 1
@@ -730,7 +754,20 @@ async function formatCommitDiff(
 		limit: renameState.limit,
 	});
 	renameState.needed = Math.max(renameState.needed ?? 0, neededRenameLimit ?? 0) || undefined;
+	if (remaining.length === 0 && renames.length === 0) return null;
 
+	const main = await formatLogDiffFormat(ctx, remaining, renames, output.format, statWidth);
+	if (!output.summary) return main;
+	return withSummary(main, formatSummaryLines(remaining, renames), output.format === "patch");
+}
+
+async function formatLogDiffFormat(
+	ctx: GitRepo,
+	remaining: TreeDiffEntry[],
+	renames: RenamePair[],
+	format: LogDiffFormat,
+	statWidth?: number,
+): Promise<string> {
 	switch (format) {
 		case "name-only":
 			return logNameOnly(remaining, renames);
@@ -744,6 +781,8 @@ async function formatCommitDiff(
 			return logNumstat(ctx, remaining, renames);
 		case "patch":
 			return logPatch(ctx, remaining, renames);
+		case null:
+			return "";
 	}
 }
 
@@ -775,7 +814,7 @@ async function logStat(
 	renames: RenamePair[],
 	statWidth?: number,
 ): Promise<string> {
-	const { fileStats } = await computeDiffStats(ctx, remaining, renames);
+	const fileStats = await computeDiffStats(ctx, remaining, renames);
 	fileStats.sort((a, b) => (a.sortKey < b.sortKey ? -1 : a.sortKey > b.sortKey ? 1 : 0));
 	return renderStatLines(fileStats, statWidth);
 }
@@ -785,7 +824,7 @@ async function logShortstat(
 	remaining: TreeDiffEntry[],
 	renames: RenamePair[],
 ): Promise<string> {
-	const { fileStats } = await computeDiffStats(ctx, remaining, renames);
+	const fileStats = await computeDiffStats(ctx, remaining, renames);
 	let totalIns = 0;
 	let totalDel = 0;
 	for (const s of fileStats) {
diff --git a/src/commands/show.ts b/src/commands/show.ts
index 8b514324..91bb856f 100644
--- a/src/commands/show.ts
+++ b/src/commands/show.ts
@@ -10,7 +10,13 @@ import {
 	requireHead,
 	requireRevision,
 } from "../lib/command-utils.ts";
-import { computeDiffStats, formatShortstatParts, renderStatLines } from "../lib/commit-summary.ts";
+import {
+	computeDiffStats,
+	formatShortstatParts,
+	formatSummaryLines,
+	renderStatLines,
+	withSummary,
+} from "../lib/commit-summary.ts";
 import { formatDate } from "../lib/date.ts";
 import { formatUnifiedDiff, myersDiff, splitLinesWithNL } from "../lib/diff-algorithm.ts";
 import {
@@ -47,6 +53,12 @@ const decoder = new TextDecoder();
 const QUIET_NAME_CONFLICT =
 	"options '--name-only', '--name-status', '--check', and '-s' cannot be used together";
 
+/** The diff a commit is shown with: a main format and/or the --summary lines. */
+interface ShowDiffOutput {
+	format: ShowDiffFormat;
+	summary: boolean;
+}
+
 type ShowDiffFormat =
 	| "patch"
 	| "stat"
@@ -69,6 +81,7 @@ export function registerShowCommand(parent: Command, ext?: GitExtensions) {
 			nameStatus: f().describe("Show names and status of changed files"),
 			shortstat: f().describe("Show only the shortstat summary line"),
 			numstat: f().describe("Machine-readable insertions/deletions per file"),
+			summary: f().describe("Show creations, deletions, renames and mode changes"),
 			format: o.string().describe("Pretty-print format string"),
 			pretty: o.string().describe("Pretty-print format or preset name"),
 		},
@@ -118,11 +131,16 @@ export function registerShowCommand(parent: Command, ext?: GitExtensions) {
 				diffFormat = "shortstat";
 			} else if (args.numstat) {
 				diffFormat = "numstat";
-			} else if (args.quiet && !args.patch) {
+			} else if ((args.quiet || args.summary) && !args.patch) {
 				diffFormat = null;
 			} else {
 				diffFormat = "patch";
 			}
+			// Git drops --summary when a name format or --no-patch is in effect.
+			const summary =
+				args.summary && !args.noPatch && diffFormat !== "name-only" && diffFormat !== "name-status";
+			const diffOutput: ShowDiffOutput | null =
+				diffFormat || summary ? { format: diffFormat, summary } : null;
 
 			// Determine header format
 			const formatRaw = args.format ?? args.pretty;
@@ -142,7 +160,7 @@ export function registerShowCommand(parent: Command, ext?: GitExtensions) {
 						hash,
 						commit,
 						renameState,
-						diffFormat,
+						diffOutput,
 						customFormat,
 						presetName,
 					);
@@ -158,7 +176,7 @@ export function registerShowCommand(parent: Command, ext?: GitExtensions) {
 						gitCtx,
 						tag,
 						renameState,
-						diffFormat,
+						diffOutput,
 						customFormat,
 						presetName,
 					);
@@ -235,7 +253,7 @@ async function formatCommitShow(
 	hash: ObjectId,
 	commit: Commit,
 	renameState: RenameWarningState,
-	diffFormat: ShowDiffFormat = "patch",
+	diffOutput: ShowDiffOutput | null,
 	customFormat: string | null = null,
 	presetName: string | null = null,
 ): Promise<string> {
@@ -265,51 +283,85 @@ async function formatCommitShow(
 		header = lines.join("\n");
 	}
 
-	if (!diffFormat) {
+	if (!diffOutput) {
 		return `${header}\n`;
 	}
 
 	// ── Diff ────────────────────────────────────────────────────
-	let diffOutput = "";
+	let body = "";
+	let hasChanges = false;
 	if (commit.parents.length <= 1) {
 		const parentTree =
 			commit.parents.length === 1
 				? (await readCommit(ctx, commit.parents[0] as ObjectId)).tree
 				: null;
-
-		const rawDiffs = await diffTrees(ctx, parentTree, commit.tree);
-		const {
-			remaining: diffs,
-			renames,
-			neededRenameLimit,
-		} = await detectRenames(ctx, rawDiffs, {
-			limit: renameState.limit,
-		});
-		renameState.needed = Math.max(renameState.needed ?? 0, neededRenameLimit ?? 0) || undefined;
-		diffOutput = await formatShowDiff(ctx, diffs, renames, diffFormat);
+		const { diffs, renames } = await diffWithRenames(ctx, parentTree, commit.tree, renameState);
+		hasChanges = diffs.length > 0 || renames.length > 0;
+		body = await formatShowDiff(ctx, diffs, renames, diffOutput);
 	} else {
-		if (diffFormat === "patch") {
-			diffOutput = (await formatCombinedDiff(ctx, commit)) ?? "";
-		}
-		// For non-patch formats on merge commits, no output (matches real git)
+		body = await formatMergeShowDiff(ctx, commit, renameState, diffOutput);
 	}
 
-	if (diffOutput) {
-		return `${header}\n\n${diffOutput.replace(/\n$/, "")}\n`;
+	if (body) {
+		return `${header}\n\n${body.replace(/\n$/, "")}\n`;
 	}
-	if (commit.parents.length >= 2) {
+	// Git still prints the separator line when a commit has changes but the
+	// requested output is empty, e.g. --summary on a content-only change.
+	if (hasChanges || commit.parents.length >= 2) {
 		return `${header}\n\n`;
 	}
 	return `${header}\n`;
 }
 
+async function diffWithRenames(
+	ctx: GitRepo,
+	parentTree: ObjectId | null,
+	tree: ObjectId,
+	renameState: RenameWarningState,
+): Promise<{ diffs: TreeDiffEntry[]; renames: RenamePair[] }> {
+	const rawDiffs = await diffTrees(ctx, parentTree, tree);
+	const { remaining, renames, neededRenameLimit } = await detectRenames(ctx, rawDiffs, {
+		limit: renameState.limit,
+	});
+	renameState.needed = Math.max(renameState.needed ?? 0, neededRenameLimit ?? 0) || undefined;
+	return { diffs: remaining, renames };
+}
+
+/**
+ * Git shows a merge's patch as a combined diff, but its stat formats and
+ * --summary compare the merge with its first parent. The name formats
+ * print nothing here.
+ */
+async function formatMergeShowDiff(
+	ctx: GitRepo,
+	commit: Commit,
+	renameState: RenameWarningState,
+	output: ShowDiffOutput,
+): Promise<string> {
+	const statFormat =
+		output.format === "stat" || output.format === "shortstat" || output.format === "numstat"
+			? output.format
+			: null;
+	let firstParent = "";
+	if (statFormat || output.summary) {
+		const parentTree = (await readCommit(ctx, commit.parents[0] as ObjectId)).tree;
+		const { diffs, renames } = await diffWithRenames(ctx, parentTree, commit.tree, renameState);
+		firstParent = await formatShowDiff(ctx, diffs, renames, {
+			format: statFormat,
+			summary: output.summary,
+		});
+	}
+	const combined = output.format === "patch" ? await formatCombinedDiff(ctx, commit) : "";
+	return withSummary(combined, firstParent, combined !== "");
+}
+
 // ── Tag display ─────────────────────────────────────────────────────
 
 async function formatTagShow(
 	ctx: GitRepo,
 	tag: Tag,
 	renameState: RenameWarningState,
-	diffFormat: ShowDiffFormat = "patch",
+	diffOutput: ShowDiffOutput | null,
 	customFormat: string | null = null,
 	presetName: string | null = null,
 ): Promise<string> {
@@ -331,7 +383,7 @@ async function formatTagShow(
 			tag.object,
 			commit,
 			renameState,
-			diffFormat,
+			diffOutput,
 			customFormat,
 			presetName,
 		);
@@ -356,6 +408,17 @@ function formatTreeShow(tree: Tree): string {
 // ── Diff format dispatch ────────────────────────────────────────────
 
 async function formatShowDiff(
+	ctx: GitRepo,
+	diffs: TreeDiffEntry[],
+	renames: RenamePair[],
+	output: ShowDiffOutput,
+): Promise<string> {
+	const main = await formatShowDiffFormat(ctx, diffs, renames, output.format);
+	if (!output.summary) return main;
+	return withSummary(main, formatSummaryLines(diffs, renames), output.format === "patch");
+}
+
+async function formatShowDiffFormat(
 	ctx: GitRepo,
 	diffs: TreeDiffEntry[],
 	renames: RenamePair[],
@@ -406,7 +469,7 @@ async function showStat(
 	diffs: TreeDiffEntry[],
 	renames: RenamePair[],
 ): Promise<string> {
-	const { fileStats } = await computeDiffStats(ctx, diffs, renames);
+	const fileStats = await computeDiffStats(ctx, diffs, renames);
 	fileStats.sort((a, b) => (a.sortKey < b.sortKey ? -1 : a.sortKey > b.sortKey ? 1 : 0));
 	return renderStatLines(fileStats);
 }
@@ -416,7 +479,7 @@ async function showShortstat(
 	diffs: TreeDiffEntry[],
 	renames: RenamePair[],
 ): Promise<string> {
-	const { fileStats } = await computeDiffStats(ctx, diffs, renames);
+	const fileStats = await computeDiffStats(ctx, diffs, renames);
 	let totalIns = 0;
 	let totalDel = 0;
 	for (const s of fileStats) {
diff --git a/src/lib/commit-summary.ts b/src/lib/commit-summary.ts
index a3dfa6a7..4ed30b71 100644
--- a/src/lib/commit-summary.ts
+++ b/src/lib/commit-summary.ts
@@ -1,6 +1,7 @@
 /**
- * Shared commit summary formatting (shortstat + mode lines).
- * Used by git commit, git cherry-pick, and git merge.
+ * Shared commit summary formatting (shortstat, diffstat and --summary
+ * lines). Used by git commit, cherry-pick and merge, and by the --stat
+ * and --summary output of show, log and diff.
  */
 import { formatDate } from "./date.ts";
 import { myersDiff, splitLinesWithNL } from "./diff-algorithm.ts";
@@ -52,18 +53,15 @@ export function formatShortstatParts(
 }
 
 /**
- * Compute per-file diff stats (insertions/deletions/binary info) and
- * mode lines for a set of tree diffs and renames. Shared by
- * formatCommitSummary and formatDiffStat.
+ * Compute per-file diff stats (insertions/deletions/binary info) for a
+ * set of tree diffs and renames.
  */
 export async function computeDiffStats(
 	ctx: GitRepo,
 	diffs: TreeDiffEntry[],
 	renames: RenamePair[],
-): Promise<{ fileStats: FileStat[]; modeLines: string[] }> {
+): Promise<FileStat[]> {
 	const fileStats: FileStat[] = [];
-	const createModes: { path: string; mode: string }[] = [];
-	const deleteModes: { path: string; mode: string }[] = [];
 
 	for (const diff of diffs) {
 		if (diff.status === "added" && diff.newHash && diff.newMode) {
@@ -86,7 +84,6 @@ export async function computeDiffStats(
 					deletions: 0,
 				});
 			}
-			createModes.push({ path: diff.path, mode: diff.newMode });
 		} else if (diff.status === "deleted" && diff.oldHash && diff.oldMode) {
 			const bytes = await readBlobBytes(ctx, diff.oldHash);
 			if (isBinaryBytes(bytes)) {
@@ -107,7 +104,6 @@ export async function computeDiffStats(
 					deletions: countLines(textDecoder.decode(bytes)),
 				});
 			}
-			deleteModes.push({ path: diff.path, mode: diff.oldMode });
 		} else if (diff.status === "modified" && diff.oldHash && diff.newHash) {
 			const oldBytes = await readBlobBytes(ctx, diff.oldHash);
 			const newBytes = await readBlobBytes(ctx, diff.newHash);
@@ -138,10 +134,6 @@ export async function computeDiffStats(
 					deletions: del,
 				});
 			}
-			if (diff.oldMode && diff.newMode && diff.oldMode !== diff.newMode) {
-				deleteModes.push({ path: diff.path, mode: diff.oldMode });
-				createModes.push({ path: diff.path, mode: diff.newMode });
-			}
 		}
 	}
 
@@ -170,23 +162,99 @@ export async function computeDiffStats(
 		});
 	}
 
-	const modeLines: { sortKey: string; text: string }[] = [];
-	for (const { path, mode } of createModes) {
-		modeLines.push({ sortKey: path, text: ` create mode ${mode} ${path}` });
+	return fileStats;
+}
+
+const C_QUOTE_ESCAPES: Record<number, string> = {
+	0x07: "\\a",
+	0x08: "\\b",
+	0x09: "\\t",
+	0x0a: "\\n",
+	0x0b: "\\v",
+	0x0c: "\\f",
+	0x0d: "\\r",
+	0x22: '\\"',
+	0x5c: "\\\\",
+};
+
+/** Quote a path the way git's `quote_c_style` does with `core.quotePath` on. */
+function quoteCPath(path: string): string {
+	let out = "";
+	let quoted = false;
+	for (const byte of new TextEncoder().encode(path)) {
+		const escape = C_QUOTE_ESCAPES[byte];
+		if (escape) {
+			out += escape;
+			quoted = true;
+		} else if (byte < 0x20 || byte >= 0x7f) {
+			out += `\\${byte.toString(8).padStart(3, "0")}`;
+			quoted = true;
+		} else {
+			out += String.fromCharCode(byte);
+		}
 	}
-	for (const { path, mode } of deleteModes) {
-		modeLines.push({ sortKey: path, text: ` delete mode ${mode} ${path}` });
+	return quoted ? `"${out}"` : path;
+}
+
+/** The parts of a rename that `--summary` prints. */
+export type SummaryRename = Pick<
+	RenamePair,
+	"oldPath" | "newPath" | "similarity" | "oldMode" | "newMode"
+>;
+
+/**
+ * Format git's `--summary` lines: one line per created, deleted or
+ * mode-changed path, and a rename line (followed by a pathless mode
+ * line when the mode changed too) per rename. Sorted by path, with
+ * renames at their new path. Shared by `show`, `log`, `diff` and the
+ * summaries printed after `commit` and `merge`.
+ */
+export function formatSummaryLines(
+	diffs: readonly TreeDiffEntry[],
+	renames: readonly SummaryRename[],
+): string {
+	const modeChange = (oldMode?: string, newMode?: string) =>
+		oldMode && newMode && oldMode !== newMode ? ` mode change ${oldMode} => ${newMode}` : null;
+
+	const entries: { sortKey: string; text: string }[] = [];
+	for (const diff of diffs) {
+		const path = quoteCPath(diff.path);
+		let text: string | null = null;
+		if (diff.status === "added") {
+			text = ` create mode ${diff.newMode} ${path}\n`;
+		} else if (diff.status === "deleted") {
+			text = ` delete mode ${diff.oldMode} ${path}\n`;
+		} else {
+			const line = modeChange(diff.oldMode, diff.newMode);
+			if (line) text = `${line} ${path}\n`;
+		}
+		if (text) entries.push({ sortKey: diff.path, text });
 	}
 	for (const rename of renames) {
-		const d = formatRenamePath(rename.oldPath, rename.newPath);
-		modeLines.push({
+		const oldQuoted = quoteCPath(rename.oldPath);
+		const newQuoted = quoteCPath(rename.newPath);
+		const display =
+			oldQuoted !== rename.oldPath || newQuoted !== rename.newPath
+				? `${oldQuoted} => ${newQuoted}`
+				: formatRenamePath(rename.oldPath, rename.newPath);
+		const line = modeChange(rename.oldMode, rename.newMode);
+		entries.push({
 			sortKey: rename.newPath,
-			text: ` rename ${d} (${rename.similarity}%)`,
+			text: ` rename ${display} (${rename.similarity}%)\n${line ? `${line}\n` : ""}`,
 		});
 	}
-	modeLines.sort((a, b) => (a.sortKey < b.sortKey ? -1 : a.sortKey > b.sortKey ? 1 : 0));
+	entries.sort((a, b) => (a.sortKey < b.sortKey ? -1 : a.sortKey > b.sortKey ? 1 : 0));
+	return entries.map((e) => e.text).join("");
+}
 
-	return { fileStats, modeLines: modeLines.map((m) => m.text) };
+/**
+ * Combine a diff's main output with its `--summary` lines in git's
+ * order: the summary follows the stat formats, and comes before a patch
+ * with a blank line between them.
+ */
+export function withSummary(main: string, summary: string, mainIsPatch: boolean): string {
+	if (mainIsPatch && summary) return `${summary}\n${main}`;
+	return main + summary;
 }
 
 /**
@@ -223,7 +291,7 @@ export async function formatCommitSummary(
 	const { remaining: diffs, renames } = await detectRenames(ctx, rawDiffs, {
 		limit: renameLimit,
 	});
-	const { fileStats, modeLines } = await computeDiffStats(ctx, diffs, renames);
+	const fileStats = await computeDiffStats(ctx, diffs, renames);
 
 	let totalInsertions = 0;
 	let totalDeletions = 0;
@@ -234,9 +302,9 @@ export async function formatCommitSummary(
 
 	const shortstat = formatShortstatParts(fileStats.length, totalInsertions, totalDeletions);
 	if (shortstat) lines.push(shortstat);
-	for (const ml of modeLines) lines.push(ml);
 
-	return lines.join("\n") + (lines.length > 0 ? "\n" : "");
+	const head = lines.join("\n") + (lines.length > 0 ? "\n" : "");
+	return head + formatSummaryLines(diffs, renames);
 }
 
 // ── Diffstat formatting (for merge/FF output) ───────────────────
@@ -407,14 +475,9 @@ export async function formatDiffStat(
 	});
 	if (diffs.length === 0 && renames.length === 0) return "";
 
-	const { fileStats, modeLines } = await computeDiffStats(ctx, diffs, renames);
+	const fileStats = await computeDiffStats(ctx, diffs, renames);
 
 	fileStats.sort((a, b) => (a.sortKey < b.sortKey ? -1 : a.sortKey > b.sortKey ? 1 : 0));
 
-	let output = renderStatLines(fileStats);
-	for (const ml of modeLines) {
-		output += `${ml}\n`;
-	}
-
-	return output;
+	return renderStatLines(fileStats) + formatSummaryLines(diffs, renames);
 }
diff --git a/test/commands/commit.test.ts b/test/commands/commit.test.ts
index 9dcf482d..e778c179 100644
--- a/test/commands/commit.test.ts
+++ b/test/commands/commit.test.ts
@@ -176,6 +176,39 @@ describe("git commit", () => {
 		});
 	});
 
+	describe("summary lines", () => {
+		test("print mode changes and renames that change mode like git", async () => {
+			const lines = (n: number) => Array.from({ length: n }, (_, i) => `${i + 1}\n`).join("");
+			const bash = createTestBash({
+				files: { "/repo/a": "a\n", "/repo/big": lines(20) },
+				env: TEST_ENV,
+			});
+			await bash.exec("git init");
+			await bash.exec("git add .");
+			await bash.exec('git commit -m "first"');
+			await bash.fs.writeFile("/repo/big", lines(15));
+			await bash.exec("git mv big big2");
+			await bash.exec("chmod +x a big2");
+			await bash.fs.writeFile('/repo/q"d', "q\n");
+			await bash.exec("git add -A");
+
+			const result = await bash.exec('git commit -m "modes"');
+			const short = (await bash.exec("git rev-parse --short HEAD")).stdout.trim();
+			expect(result).toMatchObject({
+				stdout:
+					`[main ${short}] modes\n` +
+					" Author: Test Author <author@test.com>\n" +
+					" 3 files changed, 1 insertion(+), 5 deletions(-)\n" +
+					" mode change 100644 => 100755 a\n" +
+					" rename big => big2 (70%)\n" +
+					" mode change 100644 => 100755\n" +
+					' create mode 100644 "q\\"d"\n',
+				stderr: "",
+				exitCode: 0,
+			});
+		});
+	});
+
 	describe("--allow-empty", () => {
 		test("creates a commit with no staged changes", async () => {
 			const { results } = await runScenario(
diff --git a/test/commands/diff.test.ts b/test/commands/diff.test.ts
index fdcdaeea..5ac993e2 100644
--- a/test/commands/diff.test.ts
+++ b/test/commands/diff.test.ts
@@ -1,6 +1,6 @@
 import { describe, expect, test } from "bun:test";
 import { BASIC_REPO, EMPTY_REPO, TEST_ENV_NAMED as TEST_ENV } from "../fixtures";
-import { createTestBash, observeFsCalls, quickExec } from "../util";
+import { createTestBash, observeFsCalls, quickExec, setupSummaryHistory } from "../util";
 
 describe("git diff", () => {
 	describe("outside a git repo", () => {
@@ -1194,4 +1194,92 @@ describe("git diff", () => {
 			expect(result.stderr).toContain("too many arguments");
 		});
 	});
+	describe("--summary", () => {
+		const ok = (stdout: string) => ({ stdout, stderr: "", exitCode: 0 });
+
+		async function setupStaged() {
+			const bash = await setupSummaryHistory();
+			await bash.exec("git mv keep keep2");
+			await bash.exec("echo new > newf");
+			await bash.exec("git add newf");
+			await bash.exec("rm x/y/b");
+			return bash;
+		}
+
+		test("prints only the summary lines between two commits", async () => {
+			const bash = await setupSummaryHistory();
+			expect(await bash.exec("git diff --summary HEAD~5 HEAD~3")).toMatchObject(
+				ok(
+					" rename big => big2 (70%)\n" +
+						" mode change 100644 => 100755\n" +
+						" rename dir/sub/{a => b} (100%)\n" +
+						" create mode 120000 link\n" +
+						" mode change 100644 => 100755 n\n" +
+						' create mode 100644 "q\\"uote"\n' +
+						" create mode 100644 sp ace\n" +
+						' create mode 100644 "ta\\tb"\n' +
+						' create mode 100644 "\\303\\251.txt"\n',
+				),
+			);
+		});
+
+		test("follows --stat", async () => {
+			const bash = await setupSummaryHistory();
+			expect(await bash.exec("git diff --stat --summary HEAD~5 HEAD~4")).toMatchObject(
+				ok(
+					" big => big2 | 5 -----\n" +
+						" n           | 0\n" +
+						" 2 files changed, 5 deletions(-)\n" +
+						" rename big => big2 (70%)\n" +
+						" mode change 100644 => 100755\n" +
+						" mode change 100644 => 100755 n\n",
+				),
+			);
+		});
+
+		test("--cached summarizes staged renames and additions", async () => {
+			const bash = await setupStaged();
+			const summary = " rename keep => keep2 (100%)\n create mode 100644 newf\n";
+			expect(await bash.exec("git diff --cached --summary")).toMatchObject(ok(summary));
+			expect(await bash.exec("git diff --cached --stat --summary")).toMatchObject(
+				ok(
+					" keep => keep2 | 0\n" +
+						" newf          | 1 +\n" +
+						" 2 files changed, 1 insertion(+)\n" +
+						summary,
+				),
+			);
+			expect(await bash.exec("git diff --cached --shortstat --summary")).toMatchObject(
+				ok(` 2 files changed, 1 insertion(+)\n${summary}`),
+			);
+			expect(await bash.exec("git diff --cached --numstat --summary")).toMatchObject(
+				ok(`0\t0\tkeep => keep2\n1\t0\tnewf\n${summary}`),
+			);
+		});
+
+		test("summarizes unstaged deletions", async () => {
+			const bash = await setupStaged();
+			expect(await bash.exec("git diff --summary")).toMatchObject(
+				ok(" delete mode 100644 x/y/b\n"),
+			);
+			expect(await bash.exec("git diff --stat --summary")).toMatchObject(
+				ok(" x/y/b | 1 -\n 1 file changed, 1 deletion(-)\n delete mode 100644 x/y/b\n"),
+			);
+		});
+
+		test("prints nothing for content-only changes", async () => {
+			const bash = await setupSummaryHistory();
+			expect(await bash.exec("git diff --summary HEAD~2 HEAD~1")).toMatchObject(ok(""));
+		});
+
+		test("is dropped by --name-only and --name-status", async () => {
+			const bash = await setupStaged();
+			for (const opts of ["--name-only", "--name-status"]) {
+				const plain = await bash.exec(`git diff --cached ${opts}`);
+				expect(await bash.exec(`git diff --cached ${opts} --summary`)).toMatchObject(
+					ok(plain.stdout),
+				);
+			}
+		});
+	});
 });
diff --git a/test/commands/log.test.ts b/test/commands/log.test.ts
index 9b0fd925..763df4d9 100644
--- a/test/commands/log.test.ts
+++ b/test/commands/log.test.ts
@@ -1,6 +1,6 @@
 import { describe, expect, test } from "bun:test";
 import { BASIC_REPO, EMPTY_REPO, NESTED_REPO, TEST_ENV_NAMED as TEST_ENV } from "../fixtures";
-import { createTestBash, quickExec, runScenario } from "../util";
+import { createTestBash, quickExec, runScenario, setupSummaryHistory } from "../util";
 
 describe("git log", () => {
 	describe("outside a git repo", () => {
@@ -1514,4 +1514,123 @@ describe("git log", () => {
 			expect(result.stderr).toContain("fatal: ambiguous argument 'nope'");
 		});
 	});
+	describe("--summary", () => {
+		const ok = (stdout: string) => ({ stdout, stderr: "", exitCode: 0 });
+
+		test("prints the summary under each commit and nothing for merges", async () => {
+			const bash = await setupSummaryHistory();
+			expect(await bash.exec("git log --summary --format=%s -6")).toMatchObject(
+				ok(
+					"merge side\n" +
+						"content only\n" +
+						"\n" +
+						"side\n" +
+						"\n" +
+						" create mode 100644 s\n" +
+						"typechange\n" +
+						"\n" +
+						" mode change 100755 => 120000 n\n" +
+						" rename {dir/sub => x/y}/b (100%)\n" +
+						"more\n" +
+						"\n" +
+						" rename dir/sub/{a => b} (100%)\n" +
+						" create mode 120000 link\n" +
+						' create mode 100644 "q\\"uote"\n' +
+						" create mode 100644 sp ace\n" +
+						' create mode 100644 "ta\\tb"\n' +
+						' create mode 100644 "\\303\\251.txt"\n' +
+						"modes\n" +
+						"\n" +
+						" rename big => big2 (70%)\n" +
+						" mode change 100644 => 100755\n" +
+						" mode change 100644 => 100755 n\n",
+				),
+			);
+		});
+
+		test("keeps the blank line for a commit with no summary lines", async () => {
+			const bash = await setupSummaryHistory();
+			const header = async (rev: string) => (await bash.exec(`git show --no-patch ${rev}`)).stdout;
+			expect(await bash.exec("git log --summary -3")).toMatchObject(
+				ok(
+					`${await header("HEAD")}\n` +
+						`${await header("HEAD~1")}\n\n` +
+						`${await header("side")}\n` +
+						" create mode 100644 s\n",
+				),
+			);
+		});
+
+		test("--oneline puts the summary right under each line", async () => {
+			const bash = await setupSummaryHistory();
+			const oneline = (await bash.exec("git log --oneline -5")).stdout.split("\n");
+			expect(await bash.exec("git log --oneline --summary -5")).toMatchObject(
+				ok(
+					`${oneline[0]}\n` +
+						`${oneline[1]}\n` +
+						`${oneline[2]}\n` +
+						" create mode 100644 s\n" +
+						`${oneline[3]}\n` +
+						" mode change 100755 => 120000 n\n" +
+						" rename {dir/sub => x/y}/b (100%)\n" +
+						`${oneline[4]}\n` +
+						" rename dir/sub/{a => b} (100%)\n" +
+						" create mode 120000 link\n" +
+						' create mode 100644 "q\\"uote"\n' +
+						" create mode 100644 sp ace\n" +
+						' create mode 100644 "ta\\tb"\n' +
+						' create mode 100644 "\\303\\251.txt"\n',
+				),
+			);
+		});
+
+		test("follows --stat", async () => {
+			const bash = await setupSummaryHistory();
+			expect(await bash.exec("git log --stat --summary --format=%s -2 HEAD~4")).toMatchObject(
+				ok(
+					"modes\n\n" +
+						" big => big2 | 5 -----\n" +
+						" n           | 0\n" +
+						" 2 files changed, 5 deletions(-)\n" +
+						" rename big => big2 (70%)\n" +
+						" mode change 100644 => 100755\n" +
+						" mode change 100644 => 100755 n\n" +
+						"sum\n\n" +
+						" m       | 1 -\n" +
+						" n       | 1 +\n" +
+						" z => z2 | 0\n" +
+						" 3 files changed, 1 insertion(+), 1 deletion(-)\n" +
+						" delete mode 100755 m\n" +
+						" create mode 100644 n\n" +
+						" rename z => z2 (100%)\n",
+				),
+			);
+		});
+
+		test("comes before the patch with -p, separated by a blank line", async () => {
+			const bash = await setupSummaryHistory();
+			const patch = (await bash.exec("git log -p --format=%s -1 HEAD~5")).stdout;
+			expect(patch).toStartWith("sum\n\ndiff --git a/m b/m\n");
+			expect(await bash.exec("git log -p --summary --format=%s -1 HEAD~5")).toMatchObject(
+				ok(
+					"sum\n\n" +
+						" delete mode 100755 m\n" +
+						" create mode 100644 n\n" +
+						" rename z => z2 (100%)\n" +
+						"\n" +
+						patch.slice("sum\n\n".length),
+				),
+			);
+		});
+
+		test("is dropped by --name-only and --name-status", async () => {
+			const bash = await setupSummaryHistory();
+			for (const opts of ["--name-only", "--name-status"]) {
+				const plain = await bash.exec(`git log ${opts} -3 HEAD~3`);
+				expect(await bash.exec(`git log ${opts} --summary -3 HEAD~3`)).toMatchObject(
+					ok(plain.stdout),
+				);
+			}
+		});
+	});
 });
diff --git a/test/commands/show.test.ts b/test/commands/show.test.ts
index ad268834..6933e178 100644
--- a/test/commands/show.test.ts
+++ b/test/commands/show.test.ts
@@ -1,6 +1,6 @@
 import { describe, expect, test } from "bun:test";
 import { BASIC_REPO, EMPTY_REPO, TEST_ENV_NAMED as TEST_ENV } from "../fixtures";
-import { createTestBash, quickExec, runScenario } from "../util";
+import { createTestBash, quickExec, runScenario, setupSummaryHistory } from "../util";
 
 describe("git show", () => {
 	describe("outside a git repo", () => {
@@ -121,6 +121,22 @@ describe("git show", () => {
 			// Merge commits should NOT include diff output
 			expect(show.stdout).not.toContain("diff --git");
 		});
+
+		test("stat formats compare a merge with its first parent", async () => {
+			const bash = await setupSummaryHistory();
+			const cases: [string, string][] = [
+				["--stat", " s | 1 +\n 1 file changed, 1 insertion(+)\n"],
+				["--shortstat", " 1 file changed, 1 insertion(+)\n"],
+				["--numstat", "1\t0\ts\n"],
+			];
+			for (const [opts, diff] of cases) {
+				expect(await bash.exec(`git show ${opts} --format=%s HEAD`)).toMatchObject({
+					stdout: `merge side\n\n${diff}`,
+					stderr: "",
+					exitCode: 0,
+				});
+			}
+		});
 	});
 
 	describe("show annotated tag", () => {
@@ -478,6 +494,132 @@ describe("git show", () => {
 			expect(tag.stdout).not.toContain("diff --git");
 		});
 	});
+
+	describe("--summary", () => {
+		const ok = (stdout: string) => ({ stdout, stderr: "", exitCode: 0 });
+
+		test("replaces the patch with the summary lines", async () => {
+			const bash = await setupSummaryHistory();
+			const header = (await bash.exec("git show --no-patch HEAD~5")).stdout;
+			expect(await bash.exec("git show --summary HEAD~5")).toMatchObject(
+				ok(
+					`${header}\n` +
+						" delete mode 100755 m\n" +
+						" create mode 100644 n\n" +
+						" rename z => z2 (100%)\n",
+				),
+			);
+		});
+
+		test("follows --stat", async () => {
+			const bash = await setupSummaryHistory();
+			expect(await bash.exec("git show --stat --summary --format=%s HEAD~4")).toMatchObject(
+				ok(
+					"modes\n\n" +
+						" big => big2 | 5 -----\n" +
+						" n           | 0\n" +
+						" 2 files changed, 5 deletions(-)\n" +
+						" rename big => big2 (70%)\n" +
+						" mode change 100644 => 100755\n" +
+						" mode change 100644 => 100755 n\n",
+				),
+			);
+		});
+
+		test("follows --shortstat and --numstat", async () => {
+			const bash = await setupSummaryHistory();
+			const summary = " delete mode 100755 m\n create mode 100644 n\n rename z => z2 (100%)\n";
+			expect(await bash.exec("git show --shortstat --summary --format=%s HEAD~5")).toMatchObject(
+				ok(`sum\n\n 3 files changed, 1 insertion(+), 1 deletion(-)\n${summary}`),
+			);
+			expect(await bash.exec("git show --numstat --summary --format=%s HEAD~5")).toMatchObject(
+				ok(`sum\n\n0\t1\tm\n1\t0\tn\n0\t0\tz => z2\n${summary}`),
+			);
+		});
+
+		test("comes before the patch with -p, separated by a blank line", async () => {
+			const bash = await setupSummaryHistory();
+			const patch = (await bash.exec("git show -p --format=%s HEAD~5")).stdout;
+			expect(patch).toStartWith("sum\n\ndiff --git a/m b/m\n");
+			expect(await bash.exec("git show -p --summary --format=%s HEAD~5")).toMatchObject(
+				ok(
+					"sum\n\n" +
+						" delete mode 100755 m\n" +
+						" create mode 100644 n\n" +
+						" rename z => z2 (100%)\n" +
+						"\n" +
+						patch.slice("sum\n\n".length),
+				),
+			);
+		});
+
+		test("prints symlinks, quoted names and renames with a common prefix", async () => {
+			const bash = await setupSummaryHistory();
+			expect(await bash.exec("git show --summary --format=%s HEAD~3")).toMatchObject(
+				ok(
+					"more\n\n" +
+						" rename dir/sub/{a => b} (100%)\n" +
+						" create mode 120000 link\n" +
+						' create mode 100644 "q\\"uote"\n' +
+						" create mode 100644 sp ace\n" +
+						' create mode 100644 "ta\\tb"\n' +
+						' create mode 100644 "\\303\\251.txt"\n',
+				),
+			);
+		});
+
+		test("prints a type change as a mode change", async () => {
+			const bash = await setupSummaryHistory();
+			expect(await bash.exec("git show --summary --format=%s HEAD~2")).toMatchObject(
+				ok(
+					"typechange\n\n" +
+						" mode change 100755 => 120000 n\n" +
+						" rename {dir/sub => x/y}/b (100%)\n",
+				),
+			);
+		});
+
+		test("keeps the blank line when a commit has no summary lines", async () => {
+			const bash = await setupSummaryHistory();
+			const header = (await bash.exec("git show --no-patch HEAD~1")).stdout;
+			expect(await bash.exec("git show --summary HEAD~1")).toMatchObject(ok(`${header}\n`));
+			expect(await bash.exec("git show --summary --format=%s HEAD~1")).toMatchObject(
+				ok("content only\n\n"),
+			);
+		});
+
+		test("is dropped by --name-only, --name-status and --no-patch", async () => {
+			const bash = await setupSummaryHistory();
+			for (const opts of ["--name-only", "--name-status", "--no-patch"]) {
+				const plain = await bash.exec(`git show ${opts} HEAD~5`);
+				expect(await bash.exec(`git show ${opts} --summary HEAD~5`)).toMatchObject(
+					ok(plain.stdout),
+				);
+			}
+		});
+
+		test("compares a merge with its first parent", async () => {
+			const bash = await setupSummaryHistory();
+			const header = (await bash.exec("git show --no-patch HEAD")).stdout;
+			expect(await bash.exec("git show --summary HEAD")).toMatchObject(
+				ok(`${header}\n create mode 100644 s\n`),
+			);
+			expect(await bash.exec("git show --stat --summary --format=%s HEAD")).toMatchObject(
+				ok("merge side\n\n s | 1 +\n 1 file changed, 1 insertion(+)\n create mode 100644 s\n"),
+			);
+		});
+
+		test("applies to the commit an annotated tag points at", async () => {
+			const bash = await setupSummaryHistory();
+			await bash.exec("git tag -a v1 -m release HEAD~5");
+			const result = await bash.exec("git show --summary v1");
+			expect(result.exitCode).toBe(0);
+			expect(result.stdout).toStartWith("tag v1\n");
+			expect(result.stdout).toEndWith(
+				"    sum\n\n delete mode 100755 m\n create mode 100644 n\n rename z => z2 (100%)\n",
+			);
+		});
+	});
 });
 
 // ── Helpers ─────────────────────────────────────────────────────────
diff --git a/test/graph/scenarios/09-graph-with-diffs.ts b/test/graph/scenarios/09-graph-with-diffs.ts
index e8041805..a3803096 100644
--- a/test/graph/scenarios/09-graph-with-diffs.ts
+++ b/test/graph/scenarios/09-graph-with-diffs.ts
@@ -20,5 +20,7 @@ export default {
 		"git log --graph --oneline --stat",
 		"git log --graph -p -n2",
 		"git log --graph --stat",
+		"git log --graph --format=%s --stat",
+		'git log --graph --format="%h %s" --name-status',
 	],
 } satisfies GraphScenario;
diff --git a/test/graph/scenarios/16-graph-with-summary.ts b/test/graph/scenarios/16-graph-with-summary.ts
new file mode 100644
index 00000000..5cb326e9
--- /dev/null
+++ b/test/graph/scenarios/16-graph-with-summary.ts
@@ -0,0 +1,37 @@
+import type { GraphScenario } from "../types";
+
+const lines = (n: number) => Array.from({ length: n }, (_, i) => `${i + 1}\n`).join("");
+
+export default {
+	description: "Graph with --summary, including a commit with no summary lines",
+	steps: [
+		"git init",
+		"git add .",
+		'git commit -m "initial"',
+		{ write: "big", content: lines(20) },
+		{ write: "m", content: "m\n" },
+		"chmod +x m",
+		"git add .",
+		'git commit -m "add files"',
+		"git checkout -b side",
+		{ write: "s", content: "s\n" },
+		"git add s",
+		'git commit -m "side"',
+		"git checkout main",
+		{ write: "big", content: lines(15) },
+		"git rm -q m",
+		"git mv big big2",
+		"chmod +x big2",
+		"git add -A",
+		'git commit -m "rename and modes"',
+		{ write: "README.md", content: "changed\n" },
+		'git commit -am "content only"',
+		'git merge side -m "merge"',
+	],
+	logCommands: [
+		"git log --graph --summary",
+		"git log --graph --oneline --summary",
+		"git log --graph --format=%s --summary",
+		"git log --graph --stat --summary",
+	],
+} satisfies GraphScenario;
diff --git a/test/interop/summary.test.ts b/test/interop/summary.test.ts
new file mode 100644
index 00000000..b906065f
--- /dev/null
+++ b/test/interop/summary.test.ts
@@ -0,0 +1,130 @@
+import { afterAll, beforeAll, describe, expect, test } from "bun:test";
+import { chmodSync, mkdirSync, rmSync, symlinkSync } from "fs";
+import { join } from "path";
+import { createSandbox, jg, justBash, realGit, removeSandbox, writeToSandbox } from "./util";
+
+const GITLINK = "1111111111111111111111111111111111111111";
+
+const lines = (n: number) => Array.from({ length: n }, (_, i) => `${i + 1}\n`).join("");
+
+// Newest first: content, typechange, gitlink, more, modes, sum, init. The
+// "merged" branch merges "side", which branches from typechange, into
+// content.
+const CASES = [
+	"show --summary HEAD~5",
+	"show --summary --format=%s HEAD~5",
+	"show --stat --summary HEAD~5",
+	"show --shortstat --summary HEAD~5",
+	"show --numstat --summary HEAD~5",
+	"show -p --summary HEAD~5",
+	"show --name-status --summary HEAD~5",
+	"show --name-only --summary HEAD~5",
+	"show --summary HEAD~4",
+	"show --stat --summary HEAD~4",
+	"show -p --summary --format=%s HEAD~6",
+	"show --summary HEAD~3",
+	"show --summary HEAD~2",
+	"show --summary HEAD~1",
+	"show --summary HEAD",
+	"show --summary --format=%s HEAD",
+	"show --summary merged",
+	"show --stat --summary merged",
+	"show -p --summary --format=%s merged",
+	"show --stat merged",
+	"show --shortstat merged",
+	"show --numstat merged",
+	"log --summary",
+	"log --summary -3 merged",
+	"log --oneline --summary",
+	"log --format=%s --summary",
+	"log --summary --reverse",
+	"log --stat --summary -2 HEAD~4",
+	"log -p --summary -1 HEAD~5",
+	"log --graph --summary",
+	"log --graph --oneline --summary",
+	"log --name-status --summary -2 HEAD~4",
+	"diff --summary HEAD~6 HEAD",
+	"diff --summary HEAD~5 HEAD~3",
+	"diff --stat --summary HEAD~5 HEAD~4",
+	"diff --shortstat --summary HEAD~5 HEAD~4",
+	"diff --numstat --summary HEAD~5 HEAD~4",
+	"diff --name-status --summary HEAD~5 HEAD~4",
+	"diff --summary HEAD~1 HEAD",
+];
+
+describe("interop: --summary matches real git", () => {
+	let sandbox: string;
+	const git = async (cmd: string) => {
+		const r = await realGit(sandbox, cmd);
+		expect(r.exitCode).toBe(0);
+	};
+
+	beforeAll(async () => {
+		sandbox = createSandbox();
+		writeToSandbox(sandbox, "m", "m\n");
+		chmodSync(join(sandbox, "m"), 0o755);
+		writeToSandbox(sandbox, "z", "z\n");
+		writeToSandbox(sandbox, "big", lines(20));
+		writeToSandbox(sandbox, "keep", "keep\n");
+		writeToSandbox(sandbox, "dir/sub/a", "a\n");
+		await git("init");
+		await git("add -A");
+		await git("commit -m init");
+
+		writeToSandbox(sandbox, "n", "n\n");
+		await git("rm -q m");
+		await git("mv z z2");
+		await git("add n");
+		await git("commit -m sum");
+
+		writeToSandbox(sandbox, "big", lines(15));
+		await git("mv big big2");
+		chmodSync(join(sandbox, "big2"), 0o755);
+		chmodSync(join(sandbox, "n"), 0o755);
+		await git("add -A");
+		await git("commit -m modes");
+
+		await git("mv dir/sub/a dir/sub/b");
+		symlinkSync("n", join(sandbox, "link"));
+		writeToSandbox(sandbox, "sp ace", "1\n");
+		writeToSandbox(sandbox, 'q"uote', "2\n");
+		writeToSandbox(sandbox, "ta\tb", "3\n");
+		writeToSandbox(sandbox, "é.txt", "4\n");
+		await git("add -A");
+		await git("commit -m more");
+
+		await git(`update-index --add --cacheinfo 160000,${GITLINK},gm`);
+		await git("commit -m gitlink");
+
+		rmSync(join(sandbox, "n"));
+		symlinkSync("keep", join(sandbox, "n"));
+		mkdirSync(join(sandbox, "x/y"), { recursive: true });
+		await git("mv dir/sub/b x/y/b");
+		await git("add n");
+		await git("commit -m typechange");
+
+		writeToSandbox(sandbox, "keep", "keep\nmore\n");
+		await git("commit -am content");
+
+		// A merge on its own branch, so HEAD stays at "content".
+		await git("checkout -q -b side HEAD~1");
+		writeToSandbox(sandbox, "s", "s\n");
+		await git("add s");
+		await git("commit -m side");
+		await git("checkout -q -");
+		await git("checkout -q -b merged");
+		await git("merge -q --no-ff -m merge side");
+		await git("checkout -q -");
+	});
+	afterAll(() => removeSandbox(sandbox));
+
+	for (const args of CASES) {
+		test(`git ${args}`, async () => {
+			const expected = await realGit(sandbox, args);
+			const actual = await jg(justBash(sandbox), `git ${args}`);
+			expect({ stdout: actual.stdout, stderr: actual.stderr, exitCode: actual.exitCode }).toEqual(
+				expected,
+			);
+		});
+	}
+});
diff --git a/test/util.ts b/test/util.ts
index b28ce270..b35e246f 100644
--- a/test/util.ts
+++ b/test/util.ts
@@ -75,6 +75,62 @@ export async function setupClonePair(): Promise<Bash> {
 	return bash;
 }
 
+/**
+ * Build a history whose commits exercise every `--summary` line, newest
+ * first:
+ *
+ * - `merge side`: a merge that brings in `s`
+ * - `content only`: modifies `keep`, so it has no summary lines
+ * - `typechange`: `n` becomes a symlink, `dir/sub/b` moves to `x/y/b`
+ * - `more`: renames `dir/sub/a`, adds a symlink and oddly named files
+ * - `modes`: renames and shrinks `big` while making it executable, and
+ *   makes `n` executable
+ * - `sum`: deletes executable `m`, adds `n`, renames `z` to `z2`
+ * - `init`
+ *
+ * `side` branches from `typechange` and adds `s`.
+ */
+export async function setupSummaryHistory(): Promise<Bash> {
+	const lines = (n: number) => Array.from({ length: n }, (_, i) => `${i + 1}\n`).join("");
+	const bash = createTestBash({
+		files: {
+			"/repo/m": "m\n",
+			"/repo/z": "z\n",
+			"/repo/big": lines(20),
+			"/repo/keep": "keep\n",
+			"/repo/dir/sub/a": "a\n",
+		},
+		env: TEST_ENV,
+	});
+	const run = async (...commands: string[]) => {
+		for (const command of commands) {
+			const result = await bash.exec(command);
+			if (result.exitCode !== 0) throw new Error(`${command}: ${result.stderr}`);
+		}
+	};
+	await run("git init -q", "chmod +x m", "git add .", "git commit -qm init");
+	await bash.fs.writeFile("/repo/n", "n\n");
+	await run("git rm -q m", "git add n", "git mv z z2", "git commit -qm sum");
+	await bash.fs.writeFile("/repo/big", lines(15));
+	await run("git mv big big2", "chmod +x big2 n", "git add -A", "git commit -qm modes");
+	for (const name of ["sp ace", 'q"uote', "ta\tb", "é.txt"]) {
+		await bash.fs.writeFile(`/repo/${name}`, "x\n");
+	}
+	await run("git mv dir/sub/a dir/sub/b", "ln -s n link", "git add -A", "git commit -qm more");
+	await run(
+		"rm n",
+		"ln -s keep n",
+		"mkdir -p x/y",
+		"git mv dir/sub/b x/y/b",
+		"git add -A",
+		"git commit -qm typechange",
+	);
+	await run("git checkout -qb side", "echo s > s", "git add s", "git commit -qm side");
+	await run("git checkout -q main", "echo more >> keep", "git commit -qam 'content only'");
+	await run("git merge -q --no-ff -m 'merge side' side");
+	return bash;
+}
+
 // ── Filesystem query helpers (for use with expect()) ─────────────────
 
 /** Check if a path exists in the virtual filesystem. */