diff --git a/packages/adapter-utils/src/git-workspace-sync.test.ts b/packages/adapter-utils/src/git-workspace-sync.test.ts
index 1a233e4c5a..5bc79af33a 100644
--- a/packages/adapter-utils/src/git-workspace-sync.test.ts
+++ b/packages/adapter-utils/src/git-workspace-sync.test.ts
@@ -11,6 +11,7 @@ import {
   createRemoteGitExportRef,
   deleteLocalGitRef,
   fetchGitBundleIntoLocalRef,
+  integrateImportedGitHead,
   isMissingGitPrerequisiteError,
   readGitWorkspaceSnapshot,
   runLocalGit,
@@ -422,6 +423,60 @@ describe("git workspace sync", () => {
       await deleteLocalGitRef({ localDir: host, ref: importedRef });
     }
   });
+
+  it("creates the concurrent-history merge commit with a deterministic identity", async () => {
+    const rootDir = await mkdtemp(path.join(os.tmpdir(), "paperclip-git-merge-identity-"));
+    cleanupDirs.push(rootDir);
+    // No repo-local user.name/user.email on purpose: execution hosts are
+    // containers without git config, where commit-tree cannot auto-detect an
+    // identity. Setup commits pass their identity inline so only the merge
+    // commit under test depends on the sync-supplied identity.
+    const setupIdentity = ["-c", "user.name=Setup", "-c", "user.email=setup@paperclip.dev"];
+    const repo = path.join(rootDir, "repo");
+    await mkdir(repo, { recursive: true });
+    await git(repo, ["init"]);
+    await git(repo, ["checkout", "-b", "main"]);
+    await writeFile(path.join(repo, "tracked.txt"), "base\n", "utf8");
+    await git(repo, ["add", "tracked.txt"]);
+    await git(repo, [...setupIdentity, "commit", "-m", "base"]);
+    const baseHead = await git(repo, ["rev-parse", "HEAD"]);
+
+    await writeFile(path.join(repo, "local.txt"), "local\n", "utf8");
+    await git(repo, ["add", "local.txt"]);
+    await git(repo, [...setupIdentity, "commit", "-m", "local advance"]);
+    const currentHead = await git(repo, ["rev-parse", "HEAD"]);
+
+    await git(repo, ["checkout", "-b", "imported", baseHead]);
+    await writeFile(path.join(repo, "imported.txt"), "imported\n", "utf8");
+    await git(repo, ["add", "imported.txt"]);
+    await git(repo, [...setupIdentity, "commit", "-m", "sandbox change"]);
+    const importedHead = await git(repo, ["rev-parse", "HEAD"]);
+    await git(repo, ["checkout", "main"]);
+
+    // Ambient identity env vars would override the `-c` flags and make the
+    // assertion machine-dependent, so clear them for the call under test.
+    const identityEnvKeys = ["GIT_AUTHOR_NAME", "GIT_AUTHOR_EMAIL", "GIT_COMMITTER_NAME", "GIT_COMMITTER_EMAIL", "EMAIL"];
+    const savedEnv = new Map(identityEnvKeys.map((key) => [key, process.env[key]]));
+    for (const key of identityEnvKeys) delete process.env[key];
+    try {
+      await integrateImportedGitHead({ localDir: repo, importedHead });
+    } finally {
+      for (const [key, value] of savedEnv) {
+        if (value === undefined) delete process.env[key];
+        else process.env[key] = value;
+      }
+    }
+
+    const parents = (await git(repo, ["rev-list", "--parents", "-1", "HEAD"])).split(" ");
+    expect(parents.slice(1)).toEqual([currentHead, importedHead]);
+    expect(await git(repo, ["log", "-1", "--format=%an|%ae|%cn|%ce"]))
+      .toBe("Paperclip|noreply@paperclip.ing|Paperclip|noreply@paperclip.ing");
+    expect(await git(repo, ["log", "-1", "--format=%s"]))
+      .toBe(`Paperclip remote git sync merge ${importedHead.slice(0, 12)}`);
+    const mergedTree = await git(repo, ["ls-tree", "--name-only", "HEAD"]);
+    expect(mergedTree).toContain("local.txt");
+    expect(mergedTree).toContain("imported.txt");
+  });
 });
 
 describe("sanitizeGitRemoteUrl", () => {
diff --git a/packages/adapter-utils/src/git-workspace-sync.ts b/packages/adapter-utils/src/git-workspace-sync.ts
index fd3525ecc0..eb2973b116 100644
--- a/packages/adapter-utils/src/git-workspace-sync.ts
+++ b/packages/adapter-utils/src/git-workspace-sync.ts
@@ -42,6 +42,23 @@ export function setExpensiveWorkspaceGitExecutor(executor: ExpensiveWorkspaceGit
 
 export const GIT_ARCHIVE_EXCLUDES = [".git", ".git/*"] as const;
 
+/**
+ * Identity flags for commits the sync machinery itself creates (the merge
+ * commits that reconcile concurrent histories). Execution hosts are often
+ * containers with no git config and no resolvable hostname, so git cannot
+ * auto-detect an identity there and `commit-tree` hard-fails with "Author
+ * identity unknown" — which fails the whole run at finalize. Passing the
+ * identity per invocation keeps every deployment working without host
+ * configuration; `GIT_AUTHOR_*` / `GIT_COMMITTER_*` environment variables
+ * still take precedence over `-c` when an operator sets them.
+ */
+export const GIT_SYNC_COMMIT_IDENTITY_ARGS = [
+  "-c",
+  "user.name=Paperclip",
+  "-c",
+  "user.email=noreply@paperclip.ing",
+] as const;
+
 function shellQuote(value: string) {
   return `'${value.replace(/'/g, `'\"'\"'`)}'`;
 }
@@ -476,6 +493,7 @@ export async function integrateImportedGitHead(input: {
     const mergeCommit = await runLocalGit(
       input.localDir,
       [
+        ...GIT_SYNC_COMMIT_IDENTITY_ARGS,
         "commit-tree",
         mergedTreeId,
         "-p",
diff --git a/packages/adapter-utils/src/ssh.ts b/packages/adapter-utils/src/ssh.ts
index de86cdb678..5cda8c60eb 100644
--- a/packages/adapter-utils/src/ssh.ts
+++ b/packages/adapter-utils/src/ssh.ts
@@ -6,7 +6,7 @@ import os from "node:os";
 import path from "node:path";
 import { Transform } from "node:stream";
 import type { CommandManagedRuntimeRunner } from "./command-managed-runtime.js";
-import { readSanitizedOriginRemoteUrl } from "./git-workspace-sync.js";
+import { GIT_SYNC_COMMIT_IDENTITY_ARGS, readSanitizedOriginRemoteUrl } from "./git-workspace-sync.js";
 import type { RunProcessResult } from "./server-utils.js";
 import type { DirectorySnapshot } from "./workspace-restore-merge.js";
 import { mergeDirectoryWithBaseline } from "./workspace-restore-merge.js";
@@ -974,6 +974,7 @@ async function integrateImportedGitHead(input: {
     const mergeCommit = await runLocalGit(
       input.localDir,
       [
+        ...GIT_SYNC_COMMIT_IDENTITY_ARGS,
         "commit-tree",
         mergedTreeId,
         "-p",