diff --git a/.dockerignore b/.dockerignore
index e2a5e34..8db1dad 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -1,9 +1,12 @@
 # Mirrors .gitignore, with one deliberate exception: .gitignore itself stays
 # in the build context, because prettier 3 reads it as a default ignore file
 # and dropping it would change what the lint phase's prettier check sees.
-
-# VCS
-.git
+#
+# .git is deliberately NOT excluded: the build derives the version it stamps
+# from it (script/version). It is sent without its config, which holds the
+# clone's remote URL and any credential in it, and which the build stage, the
+# final image, would otherwise carry. git describe does not need it.
+.git/config
 
 # OS
 .DS_Store
diff --git a/Dockerfile b/Dockerfile
index 144308a..03a95a3 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -61,9 +61,12 @@ RUN script/bootstrap
 
 COPY . .
 
-# The version is computed on the host and passed in, because
-# .dockerignore excludes .git.
-ARG VERSION=dev
+# Version stamped into the build: the VERSION build arg when one is given,
+# otherwise what script/version derives from the .git the build context
+# carries (script/bootstrap installed git), so any `docker build .` of a
+# clone stamps its commit. The label can only carry the build arg, and is
+# empty without one.
+ARG VERSION
 LABEL org.opencontainers.image.version="${VERSION}"
 
 RUN make build
diff --git a/Makefile b/Makefile
index 80fb8c1..a71e286 100644
--- a/Makefile
+++ b/Makefile
@@ -26,8 +26,10 @@ check:
 build:
 	@script/build
 
-build-bin:
-	nix-shell -p bun --run "bun build bin/quak.ts --compile --outfile bin/quak"
+# Bundles the built dist/, so the binary reports the version script/build
+# stamped.
+build-bin: build
+	nix-shell -p bun --run "bun build dist/bin/quak.js --compile --outfile bin/quak"
 
 install: build-bin
 	mkdir -p ~/bin
diff --git a/README.md b/README.md
index 97b703e..984fc0f 100644
--- a/README.md
+++ b/README.md
@@ -126,9 +126,12 @@ alpine. We provide:
   `script/bootstrap`, then `script/install-precommit`
 - `script/projectname` — output the project name (our own extension); used by
   `script/docker` for the image tag
-- `script/build` — compile the TypeScript sources into `dist/`, then verify that
-  the entrypoints `package.json` declares (`main`, `types`, `bin`) are among the
-  files the compiler wrote, and make the CLI executable (our own extension)
+- `script/build` — compile the TypeScript sources into `dist/`, stamp the
+  version into `dist/package.json`, then verify that the entrypoints
+  `package.json` declares (`main`, `types`, `bin`) are among the files the
+  compiler wrote, and make the CLI executable (our own extension)
+- `script/version` — print the version `script/build` stamps (our own
+  extension); see Version below
 - `script/test` — run the test suite, by building the `test` phase of the
   `Dockerfile` (vitest, 90s timeout, verbose rerun on failure); requires docker
 - `script/lint` — run eslint and a prettier check, by building the `lint` phase
@@ -176,6 +179,34 @@ an exact version, installed from `yarn.lock` under `--frozen-lockfile` in both
 places, and reads `.gitignore` as its default ignore file — which is why
 `.dockerignore` keeps `.gitignore` in the build context.
 
+### Version
+
+`quak --version` reports the `version` of `dist/package.json`, which
+`script/build` writes after compiling; the repo's own `package.json` keeps
+`0.0.0`, and that is what the tests, which run from source, report.
+`script/version` decides what is written:
+
+- the `VERSION` environment variable, or the `Dockerfile`'s `VERSION` build arg
+  (`--build-arg VERSION=...`), when one is given and not empty;
+- otherwise, in a checkout with `.git`, `git describe --tags --always`: the tag
+  on a tagged commit; the tag, the commits since it and the short commit on a
+  later commit (`v1.2.3-4-gabc1234`); the short commit when no tag is reachable;
+- otherwise, as in a source tarball, the version `package.json` declares.
+
+The build fails if the checkout has `.git` and the version still comes out
+empty, `dev` or `unknown`: such a build could not be traced back to its commit.
+
+`.dockerignore` therefore does not leave out `.git`, so any `docker build .` of
+a clone stamps the commit it was built from; a shallow clone stamps a tag only
+when the cloned commit itself carries one, and otherwise the short commit. It
+leaves out `.git/config`, which holds the clone's remote URL and any credential
+in it, so the image carries `.git` without its config; `git describe` does not
+need that file. `script/docker` (and so `make docker`) and `script/cibuild` pass
+the version they resolve on the host, with `--dirty`, as the build arg, which
+takes precedence. The image's `org.opencontainers.image.version` label carries
+that build arg only, so a build given none leaves it empty. `make build-bin`
+bundles the built `dist/`, so the single binary reports the stamped version too.
+
 ## Rationale
 
 Ente is one of very few photo services with a credible end-to-end encryption
diff --git a/TODO.md b/TODO.md
index d6972af..2907015 100644
--- a/TODO.md
+++ b/TODO.md
@@ -25,6 +25,15 @@ declares one.
 
 # Completed Steps
 
+- 2026-10-02: `docker build .` stamps the commit's tag or short commit, not
+  `dev` (issue 154). `script/build` writes the version `script/version` prints
+  into `dist/package.json`: the `VERSION` environment variable or build arg when
+  one is given, otherwise `git describe --tags --always`, otherwise the version
+  `package.json` declares. `.dockerignore` sends `.git`, and a checkout with
+  `.git` whose version comes out empty, `dev` or `unknown` fails the build.
+  `make build-bin` bundles the built `dist/`, so the single binary reports the
+  same version.
+
 - 2026-10-02: `photo.exif()` returns every EXIF tag in the file as `ExifTags`,
   keyed by tag name, each as exifreader decodes it, not only the thirteen common
   fields (issue 156). The embedded thumbnail's tags are under `Thumbnail`,
diff --git a/script/build b/script/build
index 0a074b7..81df6ba 100755
--- a/script/build
+++ b/script/build
@@ -1,7 +1,7 @@
 #!/bin/sh
-# script/build: compile the TypeScript sources into dist/, then verify that
-# the artifacts package.json advertises are among the files the compiler
-# actually wrote. tsc reports success by exit status alone and knows nothing
+# script/build: compile the TypeScript sources into dist/, stamp the version
+# script/version prints into it, then verify that the artifacts package.json
+# advertises are among the files the compiler actually wrote. tsc reports success by exit status alone and knows nothing
 # about the manifest, so without this step a green build can still ship a
 # package whose main, types or bin resolve to nothing. Our own extension to
 # scripts-to-rule-them-all.
@@ -46,13 +46,24 @@ for (const bin of bins) {
 }
 
 # src/index.ts imports ../package.json for the version, which tsc copies to
-# dist/package.json. Running the built CLI proves that import resolves from
-# dist/ and reports the version package.json declares.
+# dist/package.json. The version script/version prints is written into that
+# copy only; the repo's own package.json is left as it is.
+stamp_version() {
+    node -e '
+const { readFileSync, writeFileSync } = require("node:fs");
+
+const pkg = JSON.parse(readFileSync("dist/package.json", "utf-8"));
+pkg.version = process.argv[1];
+writeFileSync("dist/package.json", JSON.stringify(pkg, null, 4) + "\n");
+' "$1"
+}
+
+# Running the built CLI proves the import resolves from dist/ and reports
+# the stamped version.
 verify_version() {
     built="$(node dist/bin/quak.js --version)"
-    declared="$(node -p 'require("./package.json").version')"
-    if [ "$built" != "$declared" ]; then
-        echo "build: dist/bin/quak.js reports $built, package.json declares $declared" >&2
+    if [ "$built" != "$1" ]; then
+        echo "build: dist/bin/quak.js reports $built, the build stamped $1" >&2
         exit 1
     fi
     echo "build: dist/bin/quak.js reports version $built"
@@ -60,9 +71,12 @@ verify_version() {
 
 main() {
     cd "$ROOT"
+    # Own line, so that a failing script/version stops the build.
+    version="$("$ROOT/script/version")"
     yarn run tsc
+    stamp_version "$version"
     verify_entrypoints
-    verify_version
+    verify_version "$version"
 }
 
 main "$@"
diff --git a/script/cibuild b/script/cibuild
index 38f5706..38fecf3 100755
--- a/script/cibuild
+++ b/script/cibuild
@@ -15,9 +15,9 @@ main() {
     cd "$ROOT"
     # Own line: a failing command substitution inside an argument does
     # not trip `set -e`, so the inline form degrades silently to an
-    # empty constant. VERSION is computed here because .dockerignore
-    # excludes .git, so `git describe` in a build stage yields an empty
-    # version without failing.
+    # empty constant. The version resolved here goes in as the VERSION
+    # build arg, which takes precedence over what the build would derive
+    # from the .git in its context.
     version="$(git describe --tags --always --dirty 2>/dev/null || true)"
     [ -n "$version" ] || version="unknown"
     docker build --no-cache \
diff --git a/script/docker b/script/docker
index c4688e8..940f456 100755
--- a/script/docker
+++ b/script/docker
@@ -12,9 +12,9 @@ main() {
     cd "$ROOT"
     # Own line: a failing command substitution inside an argument does
     # not trip `set -e`, so the inline form degrades silently to an
-    # empty constant. VERSION is computed here because .dockerignore
-    # excludes .git, so `git describe` in a build stage yields an empty
-    # version without failing.
+    # empty constant. The version resolved here goes in as the VERSION
+    # build arg, which takes precedence over what the build would derive
+    # from the .git in its context.
     version="$(git describe --tags --always --dirty 2>/dev/null || true)"
     [ -n "$version" ] || version="unknown"
     docker build --no-cache \
diff --git a/script/version b/script/version
new file mode 100755
index 0000000..2af8a6a
--- /dev/null
+++ b/script/version
@@ -0,0 +1,41 @@
+#!/bin/sh
+# script/version: print the version script/build stamps into the built
+# package. Our own extension to scripts-to-rule-them-all.
+#
+# Order of precedence:
+#
+#   1. $VERSION, if set and not empty: an explicit value, such as the
+#      Dockerfile's VERSION build arg.
+#   2. If this checkout has .git, `git describe --tags --always`: the tag
+#      on a tagged commit; the tag, the commits since it and the short
+#      commit on a later commit (v1.2.3-4-gabc1234); the short commit when
+#      no tag is reachable.
+#   3. Otherwise, as in a source tarball, the version package.json declares.
+#
+# A checkout with .git whose version still comes out empty, dev or unknown
+# fails: git is missing or could not read the checkout, and the build could
+# not be traced back to its commit.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    version="${VERSION:-}"
+    if [ -e .git ]; then
+        if [ -z "$version" ]; then
+            version="$(git describe --tags --always || true)"
+        fi
+        case "$version" in
+            "" | dev | unknown)
+                echo "version: $ROOT has .git, but the version came out '$version'" >&2
+                exit 1
+                ;;
+        esac
+    elif [ -z "$version" ]; then
+        version="$(node -p 'require("./package.json").version')"
+    fi
+    echo "$version"
+}
+
+main "$@"
diff --git a/src/index.ts b/src/index.ts
index 1e8b631..60d90ee 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,5 +1,7 @@
-// package.json is the one place the version is written. tsc copies it to
-// dist/package.json, so this path resolves from source and from dist/src/.
+// A build reports the version script/build stamps into dist/package.json;
+// package.json's own version is reported only when running from source. tsc
+// copies package.json to dist/package.json, so this path resolves from source
+// and from dist/src/.
 import pkg from "../package.json" with { type: "json" };
 
 export const VERSION: string = pkg.version;
diff --git a/test/packaging/build-context.test.ts b/test/packaging/build-context.test.ts
index d6c24e4..ea52581 100644
--- a/test/packaging/build-context.test.ts
+++ b/test/packaging/build-context.test.ts
@@ -9,8 +9,10 @@
 // Excluding too much: Prettier 3 reads `.gitignore` as a default ignore file,
 // so dropping it from the context silently changes which files the lint
 // phase's prettier check looks at compared to `make fmt-check` on the host.
+// And without `.git`, a `docker build .` given no `VERSION` build arg cannot
+// derive the version (`script/version`) and stamps `package.json`'s instead.
 //
-// Neither shows up as a build failure, so they are asserted here.
+// None of these shows up as a build failure, so they are asserted here.
 import { describe, expect, it } from "vitest";
 import { existsSync, readFileSync } from "node:fs";
 import { fileURLToPath } from "node:url";
@@ -47,6 +49,17 @@ describe(".dockerignore", () => {
         expect(dockerignore).not.toContain(".gitignore");
     });
 
+    it("leaves .git in the build context for the version", () => {
+        expect(dockerignore).not.toContain(".git");
+        expect(dockerignore).not.toContain(".git/");
+    });
+
+    // The build stage is the final image, so a .git/config sent in would
+    // ship the clone's remote URL and any credential in it.
+    it("sends .git without its config", () => {
+        expect(dockerignore).toContain(".git/config");
+    });
+
     // BuildKit lets a `Dockerfile.dockerignore` shadow the root one; such a
     // file would silently give the build a different, unreviewed context —
     // and eslint's flat config does not ignore dot-directories, so a stray
diff --git a/test/packaging/version.test.ts b/test/packaging/version.test.ts
new file mode 100644
index 0000000..c1395fc
--- /dev/null
+++ b/test/packaging/version.test.ts
@@ -0,0 +1,137 @@
+// `script/version` prints the version `script/build` stamps into
+// `dist/package.json`, which is what `quak --version` reports from a build.
+// A `docker build .` of a clone is given no `VERSION` build arg, so the
+// version has to come from the `.git` in its context: the tag on a tagged
+// commit; the tag, the commits since it and the short commit on a later commit;
+// the short commit when no tag is reachable. A checkout with `.git` that still
+// yields no usable version must fail the build, not ship a version nobody can
+// trace back to its commit.
+//
+// Each test copies the script into a fresh directory, which the script then
+// treats as the checkout, and executes it there.
+import { afterEach, describe, expect, it } from "vitest";
+import { execFileSync, spawnSync } from "node:child_process";
+import {
+    chmodSync,
+    copyFileSync,
+    mkdirSync,
+    mkdtempSync,
+    rmSync,
+    writeFileSync,
+} from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const repoRoot = fileURLToPath(new URL("../../", import.meta.url));
+
+let checkout = "";
+
+afterEach(() => {
+    rmSync(checkout, { recursive: true, force: true });
+});
+
+// A checkout holding the script and a package.json that declares 0.0.0, with
+// no .git yet.
+const makeCheckout = (): void => {
+    checkout = mkdtempSync(join(tmpdir(), "quak-version-"));
+    mkdirSync(join(checkout, "script"));
+    copyFileSync(
+        join(repoRoot, "script/version"),
+        join(checkout, "script/version"),
+    );
+    chmodSync(join(checkout, "script/version"), 0o755);
+    writeFileSync(join(checkout, "package.json"), '{ "version": "0.0.0" }\n');
+};
+
+// git in the checkout, with an identity and no commit signing, whatever the
+// host's own git config says.
+const git = (...args: string[]): string =>
+    execFileSync(
+        "git",
+        [
+            "-c",
+            "user.name=quak",
+            "-c",
+            "user.email=quak@example.invalid",
+            "-c",
+            "commit.gpgsign=false",
+            ...args,
+        ],
+        { cwd: checkout, encoding: "utf-8", stdio: ["ignore", "pipe", "pipe"] },
+    ).trim();
+
+const makeCommittedCheckout = (): void => {
+    makeCheckout();
+    git("init", "-q");
+    git("add", "package.json");
+    git("commit", "-q", "-m", "first");
+};
+
+// Runs the script with nothing in its environment but PATH and, when given,
+// VERSION.
+const runVersion = (version?: string) =>
+    spawnSync(join(checkout, "script/version"), {
+        cwd: checkout,
+        encoding: "utf-8",
+        env: { PATH: process.env.PATH, VERSION: version },
+    });
+
+describe("script/version", () => {
+    it("prints the short commit of an untagged commit", () => {
+        makeCommittedCheckout();
+        expect(runVersion().stdout.trim()).toBe(
+            git("rev-parse", "--short", "HEAD"),
+        );
+    });
+
+    it("prints the tag of a tagged commit", () => {
+        makeCommittedCheckout();
+        git("tag", "v1.2.3");
+        expect(runVersion().stdout.trim()).toBe("v1.2.3");
+    });
+
+    // script/docker and script/cibuild pass the version they resolve on the
+    // host as the VERSION build arg.
+    it("prints the VERSION it is given over what git would derive", () => {
+        makeCommittedCheckout();
+        expect(runVersion("x").stdout.trim()).toBe("x");
+    });
+
+    // `--build-arg VERSION=` must not stamp an empty version.
+    it("treats an empty VERSION as unset", () => {
+        makeCommittedCheckout();
+        expect(runVersion("").stdout.trim()).toBe(
+            git("rev-parse", "--short", "HEAD"),
+        );
+    });
+
+    // A source tarball has no .git: it keeps the version package.json
+    // declares, and must still build.
+    it("prints package.json's version where there is no .git", () => {
+        makeCheckout();
+        const result = runVersion();
+        expect(result.status).toBe(0);
+        expect(result.stdout.trim()).toBe("0.0.0");
+    });
+
+    // A repository with no commits stands in for any .git that git cannot
+    // describe: git missing from the image, or refusing to read the checkout.
+    it("fails where .git yields no version", () => {
+        makeCheckout();
+        git("init", "-q");
+        const result = runVersion();
+        expect(result.status).not.toBe(0);
+        expect(result.stdout).toBe("");
+    });
+
+    it.each(["dev", "unknown"])(
+        "fails where there is .git and the version is %s",
+        (version) => {
+            makeCommittedCheckout();
+            const result = runVersion(version);
+            expect(result.status).not.toBe(0);
+            expect(result.stdout).toBe("");
+        },
+    );
+});