diff --git a/.env.example b/.env.example
index 25009dd..ed80997 100644
--- a/.env.example
+++ b/.env.example
@@ -27,7 +27,10 @@ LLM_FALLBACK_MODEL=
 # LOCAL_BASE_URL=
 # LOCAL_API_KEY=
 
-# Commit bundle changes to git after each mutation
+# Commit bundle changes to git after each mutation. Requires git in PATH
+# (the official Docker image ships it); a bundle that is not yet a repo is
+# initialized automatically, and the server refuses to start if autocommit
+# is requested but cannot work.
 GIT_AUTOCOMMIT=false
 
 PORT=3800
diff --git a/Dockerfile b/Dockerfile
index 68e44e6..1acab4a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -10,6 +10,15 @@ COPY packages packages
 RUN pnpm -r build && pnpm prune --prod
 
 FROM node:22-alpine
+# GIT_AUTOCOMMIT shells out to git (issue #21). Alpine ships none, and a bare
+# container also lacks a committer identity and trips git's dubious-ownership
+# check on bind-mounted bundles — cover all three here. The wildcard
+# safe.directory is acceptable in a single-purpose container whose only
+# writable tree is the bundle.
+RUN apk add --no-cache git \
+ && git config --system --add safe.directory '*' \
+ && git config --system user.name "understory" \
+ && git config --system user.email "understory@localhost"
 WORKDIR /app
 COPY --from=build /app/node_modules node_modules
 COPY --from=build /app/packages/core/dist packages/core/dist
diff --git a/packages/core/src/okf/knowledge-base.ts b/packages/core/src/okf/knowledge-base.ts
index ce923c5..4a3b283 100644
--- a/packages/core/src/okf/knowledge-base.ts
+++ b/packages/core/src/okf/knowledge-base.ts
@@ -37,6 +37,47 @@ export class KnowledgeBase {
     this.git = options.gitAutocommit ? simpleGit(this.bundle.root) : null;
   }
 
+  /**
+   * Verify autocommit can actually work (issue #21: a missing git binary made
+   * GIT_AUTOCOMMIT=true silently commit nothing). Call at startup and fail
+   * loudly on the result. A bundle that isn't a repo yet is initialized with
+   * a first commit of the current state — that's what the operator asked for.
+   */
+  async ensureGitReady(): Promise<{ ok: boolean; reason?: string }> {
+    if (!this.git) return { ok: true }; // autocommit not requested
+    const version = await this.git.version().catch(() => ({ installed: false }));
+    if (!version.installed) {
+      return {
+        ok: false,
+        reason:
+          "git binary not found in PATH — autocommit cannot work (the official Docker image ships git as of this fix; rebuild/re-pull, or install git)",
+      };
+    }
+    try {
+      const isRepo = await this.git.checkIsRepo();
+      if (!isRepo) await this.git.init();
+      // Environments without a global committer identity (fresh containers,
+      // CI) get a repo-local fallback — same identity the Docker image sets
+      // at system scope.
+      const email = await this.git.raw(["config", "--get", "user.email"]).catch(() => "");
+      if (!email.trim()) {
+        await this.git.addConfig("user.name", "understory");
+        await this.git.addConfig("user.email", "understory@localhost");
+      }
+      if (!isRepo) {
+        // --allow-empty: always produces the commit and proves committing
+        // works, independent of staging quirks; the first real mutation's
+        // add+commit captures the existing content.
+        await this.git.raw(["commit", "--allow-empty", "-m", "chore: initialize memory history"]);
+      }
+      // Surface identity/ownership problems now, not on the first mutation.
+      await this.git.raw(["rev-parse", "--git-dir"]);
+      return { ok: true };
+    } catch (err) {
+      return { ok: false, reason: (err as Error).message };
+    }
+  }
+
   // ── Reads (no queue) ────────────────────────────────────────────────
 
   readConcept(conceptPath: string): Promise<Concept> {
diff --git a/packages/core/test/okf.test.ts b/packages/core/test/okf.test.ts
index 670c90d..2b9bd77 100644
--- a/packages/core/test/okf.test.ts
+++ b/packages/core/test/okf.test.ts
@@ -312,3 +312,26 @@ describe("empty directory pruning (#10)", () => {
     await expect(fs.access(path.join(root, ".traces/t.json"))).resolves.toBeUndefined();
   });
 });
+
+describe("git autocommit readiness (#21)", () => {
+  it("initializes a non-repo bundle with a first commit, then commits mutations", async () => {
+    const gkb = new KnowledgeBase(root, { gitAutocommit: true });
+    const ready = await gkb.ensureGitReady();
+    expect(ready.ok).toBe(true);
+
+    await gkb.writeConcept("/facts/one.md", { type: "Fact", title: "One" }, "x", "Added one.");
+    const { execSync } = await import("node:child_process");
+    const log = execSync("git log --oneline", { cwd: root }).toString().trim().split("\n");
+    // init commit + mutation commit
+    expect(log.length).toBeGreaterThanOrEqual(2);
+    expect(log[0]).toContain("creation");
+    expect(log[log.length - 1]).toContain("initialize memory history");
+  });
+
+  it("is a no-op when autocommit is not requested", async () => {
+    const ready = await kb.ensureGitReady();
+    expect(ready.ok).toBe(true);
+    const { existsSync } = await import("node:fs");
+    expect(existsSync(path.join(root, ".git"))).toBe(false);
+  });
+});
diff --git a/packages/server/src/index.ts b/packages/server/src/index.ts
index 75451f1..0faadd3 100644
--- a/packages/server/src/index.ts
+++ b/packages/server/src/index.ts
@@ -22,6 +22,16 @@ const kb = new KnowledgeBase(bundleRoot, {
 
 startDreamer(kb);
 
+if (process.env.GIT_AUTOCOMMIT === "true") {
+  const gitReady = await kb.ensureGitReady();
+  if (!gitReady.ok) {
+    console.error(`[understory] GIT_AUTOCOMMIT=true but autocommit cannot work: ${gitReady.reason}`);
+    process.exit(1);
+  }
+  console.log("[understory] git autocommit: enabled (bundle history is being recorded)");
+}
+
+
 const app = express();
 
 // Validate LLM config at startup — fail fast with a clear error.
diff --git a/packages/server/src/mcp/stdio.ts b/packages/server/src/mcp/stdio.ts
index 2829892..8888eac 100644
--- a/packages/server/src/mcp/stdio.ts
+++ b/packages/server/src/mcp/stdio.ts
@@ -37,6 +37,16 @@ try {
 const kb = new KnowledgeBase(bundleRoot, {
   gitAutocommit: process.env.GIT_AUTOCOMMIT === "true",
 });
+
+if (process.env.GIT_AUTOCOMMIT === "true") {
+  const gitReady = await kb.ensureGitReady();
+  if (!gitReady.ok) {
+    console.error(`[understory] GIT_AUTOCOMMIT=true but autocommit cannot work: ${gitReady.reason}`);
+    process.exit(1);
+  }
+  console.log("[understory] git autocommit: enabled (bundle history is being recorded)");
+}
+
 const server = await buildMcpServer(kb);
 await server.connect(new StdioServerTransport());
 // stdio transport keeps the process alive; logs must go to stderr only.