diff --git a/AGENTS.md b/AGENTS.md
index a1fc90a..3fce067 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -90,7 +90,9 @@ src/devx/
 │   ├── create_pr.py         # Create PRs with auto-derived title from Vikunja
 │   ├── pr_status.py         # Check CI status for a PR/commit (--wait polls)
 │   ├── pr_logs.py           # Fetch logs for failed CI jobs
-│   └── pr_label.py          # Add labels to PRs (idempotent)
+│   ├── pr_label.py          # Add labels to PRs (idempotent)
+│   ├── rebase.py            # Rebase current branch onto origin/master + force-push
+│   └── pr_rebase.py         # Rebase a PR's head branch via Gitea API (server-side)
 ├── opentofu.py          # OpenTofu output helpers (get_tofu_output, get_tofu_vm_ip, get_tofu_vm_field)
 └── molecule/            # Optional molecule testing helpers (for Ansible projects)
     ├── discover_runners.py    # Dynamic Gitea runner discovery
@@ -181,6 +183,12 @@ the PR. Then add the `ready-to-merge` label. The auto-merge workflow will:
 5. The post-merge workflow marks the Vikunja task as done
 6. The release workflow automatically versions, tags, and publishes
 
+**If the branch is behind master** (another PR merged first), auto-merge
+automatically rebases the PR's head branch via the Gitea API
+(`POST /pulls/{index}/update?style=rebase`). This triggers a new CI run.
+The next auto-merge attempt will find the branch up-to-date and merge
+successfully. No manual intervention needed.
+
 > **IMPORTANT**: Never manually merge PRs via the API. Always use the auto-merge
 > workflow by adding the `ready-to-merge` label.
 
@@ -409,6 +417,8 @@ projects.
 | `devx-pr-logs` | Fetch logs for failed CI jobs (`PR=`, `JOB=`, `TAIL=`) |
 | `devx-pr-label` | Add a label to a PR (`PR=`, `LABEL=ready-to-merge`) |
 | `devx-pr-review` | Post a review on a PR (`PR=`, `EVENT=`, `BODY=`, `CHECKLIST=`) |
+| `devx-rebase` | Rebase current branch onto origin/master + force-push (`NO_PUSH=1` for local only) |
+| `devx-pr-rebase` | Rebase a PR's head branch via Gitea API — server-side, no local git needed (`PR=`) |
 | `devx-check-config` | Validate devx configuration |
 | `devx-configure-gitea-pypi` | Configure Gitea private PyPI registry |
 | `devx-env` | Create .env from .env.example |
diff --git a/Makefile b/Makefile
index 80f7b9f..027cb61 100644
--- a/Makefile
+++ b/Makefile
@@ -98,6 +98,8 @@ create-task: devx-create-task
 create-pr: devx-create-pr
 push-with-pr: devx-push-with-pr
 git-push: devx-push
+rebase: devx-rebase
+pr-rebase: devx-pr-rebase
 
 lint-all: lint workflow-lint lint-dockerfiles
 	@echo "[lint-all] All linting checks passed."
diff --git a/docs/index.md b/docs/index.md
index 7cbd6d4..0a15feb 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -131,7 +131,7 @@ wiki sync details.
 devx provides a `devx` CLI with three command groups:
 
 - `devx ci <command>` — CI/CD automation (17 commands)
-- `devx tools <command>` — Developer tools (7 commands)
+- `devx tools <command>` — Developer tools (9 commands)
 - `devx molecule <command>` — Molecule testing (4 commands, optional)
 
 See [CLI Commands](CLI-Commands) for full command documentation with examples.
diff --git a/docs/user/cli-commands.md b/docs/user/cli-commands.md
index 1df8ada..9f7463e 100644
--- a/docs/user/cli-commands.md
+++ b/docs/user/cli-commands.md
@@ -421,6 +421,35 @@ Options:
 - `--no-pre-commit` — skip pre-commit hook installation
 - `--no-tea-login` — skip tea CLI login configuration
 
+### `devx tools rebase`
+
+Rebase the current branch onto `origin/master` and force-push with
+`--force-with-lease`. Checks if the branch is behind master first —
+if up-to-date, exits without doing anything.
+
+```bash
+devx tools rebase                          # rebase + force-push
+devx tools rebase -- --no-push             # rebase locally only
+```
+
+Options (pass after `--`):
+- `--no-push` — rebase locally without pushing
+
+### `devx tools pr-rebase`
+
+Rebase a pull request's head branch onto master via the Gitea API
+(server-side). This triggers a new `pull_request synchronize` event,
+which starts a new CI run. Useful when you don't have the branch
+checked out locally.
+
+```bash
+devx tools pr-rebase -- --pr 42            # rebase PR #42
+devx tools pr-rebase                       # auto-detect PR from current branch
+```
+
+Options (pass after `--`):
+- `--pr <N>` — PR number (auto-detected from current branch if omitted)
+
 ## Molecule Commands
 
 Molecule commands require the `molecule` extra (`pip install devx[molecule]`).
diff --git a/src/devx/api_clients.py b/src/devx/api_clients.py
index 9781105..d921f93 100644
--- a/src/devx/api_clients.py
+++ b/src/devx/api_clients.py
@@ -194,6 +194,19 @@ class GiteaClient:
         payload = {"Do": "squash", "MergeTitleField": merge_title}
         self._request("POST", f"/pulls/{pr_number}/merge", json=payload)
 
+    def update_pr_branch(self, pr_number: str | int, style: str = "rebase") -> None:
+        """Update PR head branch by merging/rebasing the base branch into it.
+
+        Uses the Gitea API ``POST /pulls/{index}/update?style=rebase`` endpoint.
+        This rebases the PR's head branch onto the latest base branch server-side,
+        triggering a ``pull_request synchronize`` event that starts a new CI run.
+
+        Args:
+            pr_number: PR number.
+            style: Update method — ``"rebase"`` (default) or ``"merge"``.
+        """
+        self._request("POST", f"/pulls/{pr_number}/update", params={"style": style})
+
     def get_commit_status(self, sha: str) -> list[dict[str, Any]]:
         """Fetch all status check contexts reported for a commit.
 
diff --git a/src/devx/ci/auto_merge.py b/src/devx/ci/auto_merge.py
index 7563cf3..7e700b5 100644
--- a/src/devx/ci/auto_merge.py
+++ b/src/devx/ci/auto_merge.py
@@ -231,17 +231,35 @@ def main(branch: str, pr_title: str, repo: str, pr_number: str) -> None:
         client.merge_pr(pr_num, merge_title)
     except APIError as e:
         if e.status == 405 and "behind" in e.message.lower():
-            # Head branch is behind master — do NOT auto-rebase.
-            # Auto-rebasing creates a feedback loop: the force-push triggers
-            # a new pull_request synchronize event, which starts a new CI run,
-            # which runs auto-merge again, which rebases again, etc.
-            raise click.ClickException(
+            # Head branch is behind master. Auto-rebase via Gitea API.
+            # This triggers a new pull_request synchronize event → new CI run.
+            # The next auto-merge attempt will find the branch up-to-date and
+            # merge successfully. This is NOT an infinite loop: the rebase
+            # resolves the "behind" condition, so the next run merges.
+            # If another PR merges in between, the branch may fall behind
+            # again, but the process converges as PRs stop merging.
+            click.echo(
                 _(
-                    "Branch is behind master. Rebase manually:\n"
-                    "  git fetch origin master && git rebase origin/master && git push --force-with-lease\n"
-                    "Then re-add the ready-to-merge label.",
+                    "Branch is behind master. Auto-rebasing via Gitea API...\n"
+                    "A new CI run will start automatically after the rebase.\n"
+                    "The next auto-merge attempt will merge this PR.",
                 )
-            ) from None
+            )
+            try:
+                client.update_pr_branch(pr_num, style="rebase")
+            except APIError as rebase_err:
+                raise click.ClickException(
+                    _(
+                        "Auto-rebase failed with HTTP {status}: {message}\n"
+                        "Rebase manually:\n"
+                        "  git fetch origin master && git rebase origin/master && git push --force-with-lease\n"
+                        "Then re-add the ready-to-merge label.",
+                        status=rebase_err.status,
+                        message=rebase_err.message,
+                    )
+                ) from None
+            # Exit cleanly — the rebase triggers a new CI run that will retry.
+            return
         else:
             raise click.ClickException(
                 _(
diff --git a/src/devx/cli.py b/src/devx/cli.py
index a428b97..1cb3e08 100644
--- a/src/devx/cli.py
+++ b/src/devx/cli.py
@@ -226,6 +226,20 @@ def tools_setup(args: tuple[str, ...]) -> None:
     _run_module("devx.tools.setup", list(args))
 
 
+@tools.command("rebase")
+@click.argument("args", nargs=-1)
+def tools_rebase(args: tuple[str, ...]) -> None:
+    """Rebase current branch onto origin/master and force-push."""
+    _run_module("devx.tools.rebase", list(args))
+
+
+@tools.command("pr-rebase")
+@click.argument("args", nargs=-1)
+def tools_pr_rebase(args: tuple[str, ...]) -> None:
+    """Rebase a PR's head branch onto master via Gitea API (server-side)."""
+    _run_module("devx.tools.pr_rebase", list(args))
+
+
 @cli.group()
 def molecule() -> None:
     """Molecule testing commands (requires devx[molecule])."""
diff --git a/src/devx/make/devx.mak b/src/devx/make/devx.mak
index 910b789..98fd987 100644
--- a/src/devx/make/devx.mak
+++ b/src/devx/make/devx.mak
@@ -63,7 +63,7 @@ DEVX_PIP_INSTALL := if [ -z "$$CI_GITEA_TOKEN" ]; then . ./.env 2>/dev/null; fi;
 	$(DEVX_BIN)/pip
 
 .PHONY: devx-create-task devx-create-pr devx-push devx-push-with-pr devx-check-config
-.PHONY: devx-pr-status devx-pr-logs devx-pr-label devx-pr-review
+.PHONY: devx-pr-status devx-pr-logs devx-pr-label devx-pr-review devx-rebase devx-pr-rebase
 .PHONY: devx-configure-gitea-pypi devx-install-tools devx-install-checkmake devx-checkmake
 .PHONY: devx-workflow-lint devx-workflow-dryrun devx-workflow-dryrun-safe devx-workflow-check
 .PHONY: devx-notify-failure devx-install-hooks devx-activate-scripts
@@ -134,6 +134,20 @@ devx-pr-review:
 		$(if $(BODY),--body "$(BODY)") \
 		$(if $(CHECKLIST),--checklist-confirmed --checklist-categories $(CHECKLIST))
 
+# Rebase current branch onto origin/master and force-push
+# Usage: make devx-rebase
+#        make devx-rebase NO_PUSH=1
+devx-rebase:
+	@$(DEVX_PYTHON) -m devx.tools.rebase \
+		$(if $(NO_PUSH),--no-push)
+
+# Rebase a PR's head branch via Gitea API (server-side, no local git needed)
+# Usage: make devx-pr-rebase
+#        make devx-pr-rebase PR=42
+devx-pr-rebase:
+	@$(DEVX_PYTHON) -m devx.tools.pr_rebase \
+		$(if $(PR),--pr $(PR))
+
 # ── Environment setup ─────────────────────────────────────────────────────────
 
 # Configure Gitea private PyPI registry so pip can find devx and other
diff --git a/src/devx/tools/_shared.py b/src/devx/tools/_shared.py
index e92edcc..0707ee3 100644
--- a/src/devx/tools/_shared.py
+++ b/src/devx/tools/_shared.py
@@ -2,7 +2,9 @@
 
 from __future__ import annotations
 
+import os
 import platform
+import subprocess  # nosec B404
 
 import click
 
@@ -22,3 +24,52 @@ def arch_string() -> str:
     if machine in {"aarch64", "arm64"}:
         return "arm64"
     raise click.ClickException(f"Unsupported architecture: {machine}")
+
+
+def detect_pr_number() -> int | None:
+    """Detect the PR number for the current git branch.
+
+    Returns the PR number if the current branch has an open PR, or None
+    if no PR is found. Does NOT raise — callers decide how to handle None.
+    Best-effort: returns None on any failure (no token, API down, etc.).
+    """
+    result = subprocess.run(  # nosec B603, B607
+        ["git", "rev-parse", "--abbrev-ref", "HEAD"],
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+    if result.returncode != 0:
+        return None
+    branch = result.stdout.strip()
+    if branch == "HEAD":
+        return None
+
+    token = os.environ.get("CI_GITEA_TOKEN", "")
+    if not token:
+        return None
+
+    owner = os.environ.get("DEVX_REPO_OWNER", "")
+    repo = os.environ.get("DEVX_REPO_NAME", "")
+    if not owner or not repo:
+        github_repo = os.environ.get("GITHUB_REPOSITORY", "")
+        if "/" in github_repo:
+            owner, repo = github_repo.split("/", 1)
+
+    if not owner or not repo:
+        return None
+
+    # Lazy import to avoid circular dependency
+    from devx.api_clients import APIError, GiteaClient  # noqa: PLC0415
+    from devx.config import GITEA_API_URL  # noqa: PLC0415
+
+    client = GiteaClient(GITEA_API_URL, token, owner, repo)
+    try:
+        prs = client.list_prs(state="open")
+    except APIError:
+        # Best-effort: API down or auth failure → no PR detected
+        return None
+    for pr in prs:
+        if pr.get("head", {}).get("ref") == branch:
+            return int(pr["number"])
+    return None
diff --git a/src/devx/tools/pr_rebase.py b/src/devx/tools/pr_rebase.py
new file mode 100644
index 0000000..adedebc
--- /dev/null
+++ b/src/devx/tools/pr_rebase.py
@@ -0,0 +1,97 @@
+#!/usr/bin/env python3
+"""Rebase a pull request's head branch onto master via Gitea API.
+
+Uses the Gitea ``POST /pulls/{index}/update?style=rebase`` endpoint to
+rebase the PR's head branch server-side. This triggers a new
+``pull_request synchronize`` event, which starts a new CI run.
+
+This is useful when:
+  - You don't have the branch checked out locally
+  - You want to rebase a PR from another machine
+  - You want to trigger the auto-merge retry without local git operations
+
+Usage::
+
+    # Rebase PR #42
+    python -m devx.tools.pr_rebase --pr 42
+
+    # Rebase current branch's PR (auto-detected)
+    python -m devx.tools.pr_rebase
+
+The repository is auto-detected from ``DEVX_REPO_OWNER`` /
+``DEVX_REPO_NAME`` or ``GITHUB_REPOSITORY`` environment variables.
+"""
+
+from __future__ import annotations
+
+import os
+
+import click
+from dotenv import load_dotenv  # pyright: ignore[reportMissingImports,reportUnknownVariableType]
+
+from devx.api_clients import APIError, GiteaClient
+from devx.config import GITEA_API_URL
+from devx.i18n import _
+from devx.tools._shared import detect_pr_number
+
+
+@click.command()
+@click.option("--pr", type=int, help="PR number (auto-detected if omitted).")
+def main(pr: int | None) -> None:
+    """Rebase a pull request's head branch onto master via Gitea API."""
+    load_dotenv()
+
+    token = os.environ.get("CI_GITEA_TOKEN", "")
+    if not token:
+        raise click.ClickException(_("CI_GITEA_TOKEN is not set. Add it to .env or export it."))
+
+    pr_num = pr or detect_pr_number()
+    if not pr_num:
+        raise click.ClickException(
+            _(
+                "Could not detect PR number. Use --pr to specify it explicitly,\n"
+                "or run this command from a branch with an open PR.",
+            )
+        )
+
+    owner = os.environ.get("DEVX_REPO_OWNER", "")
+    repo = os.environ.get("DEVX_REPO_NAME", "")
+    if not owner or not repo:
+        github_repo = os.environ.get("GITHUB_REPOSITORY", "")
+        if "/" in github_repo:
+            owner, repo = github_repo.split("/", 1)
+
+    if not owner or not repo:
+        raise click.ClickException(
+            _(
+                "Could not determine repository. Set DEVX_REPO_OWNER and DEVX_REPO_NAME\n"
+                "or GITHUB_REPOSITORY environment variables.",
+            )
+        )
+
+    client = GiteaClient(GITEA_API_URL, token, owner, repo)
+
+    click.echo(_("Rebasing PR #{pr} via Gitea API...", pr=pr_num))
+    try:
+        client.update_pr_branch(pr_num, style="rebase")
+    except APIError as e:
+        raise click.ClickException(
+            _(
+                "Rebase failed with HTTP {status}: {message}",
+                status=e.status,
+                message=e.message,
+            )
+        ) from None
+
+    click.echo(
+        _(
+            "PR #{pr} rebased successfully. A new CI run will start automatically.\n"
+            "If auto-merge is enabled (ready-to-merge label), the next CI run\n"
+            "will attempt to merge this PR.",
+            pr=pr_num,
+        )
+    )
+
+
+if __name__ == "__main__":  # pragma: no cover
+    main()
diff --git a/src/devx/tools/rebase.py b/src/devx/tools/rebase.py
new file mode 100644
index 0000000..e558b69
--- /dev/null
+++ b/src/devx/tools/rebase.py
@@ -0,0 +1,97 @@
+#!/usr/bin/env python3
+"""Rebase current branch onto origin/master and force-push.
+
+Fetches origin/master, rebases the current branch, and force-pushes with
+``--force-with-lease``. This is the manual equivalent of what
+``auto_merge.py`` does automatically via the Gitea API.
+
+Usage::
+
+    # Rebase current branch onto master and force-push
+    python -m devx.tools.rebase
+
+    # Rebase without pushing (local only)
+    python -m devx.tools.rebase --no-push
+
+The tool fails if:
+  - The rebase encounters conflicts (exits with rebase in progress)
+  - The force-push is rejected (remote has unexpected commits)
+  - Not on a branch (detached HEAD)
+"""
+
+from __future__ import annotations
+
+import subprocess  # nosec B404
+
+import click
+
+from devx.i18n import _
+
+
+def _run_git(args: list[str], check: bool = True) -> subprocess.CompletedProcess[str]:
+    """Run a git command and return the result."""
+    return subprocess.run(  # nosec B603, B607
+        ["git", *args],
+        capture_output=True,
+        text=True,
+        check=check,
+    )
+
+
+@click.command()
+@click.option("--no-push", is_flag=True, help="Rebase locally without pushing.")
+def main(no_push: bool) -> None:
+    """Rebase current branch onto origin/master and force-push."""
+    # Ensure we're on a branch (check=False — we handle errors ourselves)
+    branch_result = _run_git(["rev-parse", "--abbrev-ref", "HEAD"], check=False)
+    if branch_result.returncode != 0:
+        raise click.ClickException(_("Could not detect current branch: {error}", error=branch_result.stderr.strip()))
+    branch = branch_result.stdout.strip()
+    if branch == "HEAD":
+        raise click.ClickException(_("Cannot rebase: not on a branch (detached HEAD)."))
+
+    click.echo(_("Fetching origin/master..."))
+    fetch = _run_git(["fetch", "origin", "master"], check=False)
+    if fetch.returncode != 0:
+        raise click.ClickException(_("Fetch failed: {error}", error=fetch.stderr.strip()))
+
+    # Check if behind master
+    behind = _run_git(
+        ["rev-list", "--count", "HEAD..origin/master"],
+        check=False,
+    )
+    behind_count = int(behind.stdout.strip()) if behind.stdout.strip().isdigit() else 0
+
+    if behind_count == 0:
+        click.echo(_("Branch is already up-to-date with origin/master."))
+        if not no_push:
+            click.echo(_("Nothing to push."))
+        return
+
+    click.echo(_("Branch is {count} commit(s) behind master. Rebasing...", count=behind_count))
+    rebase = _run_git(["rebase", "origin/master"], check=False)
+    if rebase.returncode != 0:
+        raise click.ClickException(
+            _(
+                "Rebase failed (conflicts or other error):\n{error}\nResolve conflicts and run: git rebase --continue",
+                error=rebase.stderr.strip() or rebase.stdout.strip(),
+            )
+        )
+
+    click.echo(_("Rebase successful."))
+
+    if not no_push:
+        click.echo(_("Force-pushing..."))
+        push = _run_git(["push", "--force-with-lease", "origin", branch], check=False)
+        if push.returncode != 0:
+            raise click.ClickException(
+                _(
+                    "Force-push failed:\n{error}\nThe remote may have unexpected commits. Fetch and try again.",
+                    error=push.stderr.strip(),
+                )
+            )
+        click.echo(_("Pushed {branch} to origin.", branch=branch))
+
+
+if __name__ == "__main__":  # pragma: no cover
+    main()
diff --git a/src/devx/translations.json b/src/devx/translations.json
index c97ba4e..8b72e57 100644
--- a/src/devx/translations.json
+++ b/src/devx/translations.json
@@ -775,14 +775,6 @@
     "ru": "Ветка '{branch}' не содержит ID задачи.\n  Ожидаемый формат: {prefix}-N-краткое-описание\n  Пример: {prefix}-42-add-feature\n  Исправление: переименуйте ветку или создайте задачу Vikunja:\n    python -m devx.tools.create_task --title \"Заголовок задачи\"",
     "zh": "分支 '{branch}' 不包含任务 ID。\n  预期格式: {prefix}-N-简短描述\n  示例: {prefix}-42-add-feature\n  修复: 重命名分支或先创建 Vikunja 任务:\n    python -m devx.tools.create_task --title \"任务标题\""
   },
-  "Branch is behind master. Rebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label.": {
-    "bg": "Branch is behind master. Rebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label.",
-    "de": "Branch is behind master. Rebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label.",
-    "en": "Branch is behind master. Rebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label.",
-    "pl": "Gałąź jest w tyle za master. Wykonaj rebase ręcznie:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nNastępnie dodaj ponownie etykietę ready-to-merge.",
-    "ru": "Branch is behind master. Rebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label.",
-    "zh": "Branch is behind master. Rebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label."
-  },
   "Branch is behind origin/master. Rebase first: git fetch origin master && git rebase origin/master": {
     "bg": "Branch is behind origin/master. Rebase first: git fetch origin master && git rebase origin/master",
     "de": "Branch is behind origin/master. Rebase first: git fetch origin master && git rebase origin/master",
@@ -2926,5 +2918,157 @@
     "pl": "Rebase attempt {n}/3 failed: {err}",
     "ru": "Rebase attempt {n}/3 failed: {err}",
     "zh": "Rebase attempt {n}/3 failed: {err}"
+  },
+  "Auto-rebase failed with HTTP {status}: {message}\nRebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label.": {
+    "bg": "Auto-rebase failed with HTTP {status}: {message}\nRebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label.",
+    "de": "Auto-rebase failed with HTTP {status}: {message}\nRebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label.",
+    "en": "Auto-rebase failed with HTTP {status}: {message}\nRebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label.",
+    "pl": "Auto-rebase failed with HTTP {status}: {message}\nRebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label.",
+    "ru": "Auto-rebase failed with HTTP {status}: {message}\nRebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label.",
+    "zh": "Auto-rebase failed with HTTP {status}: {message}\nRebase manually:\n  git fetch origin master && git rebase origin/master && git push --force-with-lease\nThen re-add the ready-to-merge label."
+  },
+  "Branch is already up-to-date with origin/master.": {
+    "bg": "Branch is already up-to-date with origin/master.",
+    "de": "Branch is already up-to-date with origin/master.",
+    "en": "Branch is already up-to-date with origin/master.",
+    "pl": "Branch is already up-to-date with origin/master.",
+    "ru": "Branch is already up-to-date with origin/master.",
+    "zh": "Branch is already up-to-date with origin/master."
+  },
+  "Branch is behind master. Auto-rebasing via Gitea API...\nA new CI run will start automatically after the rebase.\nThe next auto-merge attempt will merge this PR.": {
+    "bg": "Branch is behind master. Auto-rebasing via Gitea API...\nA new CI run will start automatically after the rebase.\nThe next auto-merge attempt will merge this PR.",
+    "de": "Branch is behind master. Auto-rebasing via Gitea API...\nA new CI run will start automatically after the rebase.\nThe next auto-merge attempt will merge this PR.",
+    "en": "Branch is behind master. Auto-rebasing via Gitea API...\nA new CI run will start automatically after the rebase.\nThe next auto-merge attempt will merge this PR.",
+    "pl": "Branch is behind master. Auto-rebasing via Gitea API...\nA new CI run will start automatically after the rebase.\nThe next auto-merge attempt will merge this PR.",
+    "ru": "Branch is behind master. Auto-rebasing via Gitea API...\nA new CI run will start automatically after the rebase.\nThe next auto-merge attempt will merge this PR.",
+    "zh": "Branch is behind master. Auto-rebasing via Gitea API...\nA new CI run will start automatically after the rebase.\nThe next auto-merge attempt will merge this PR."
+  },
+  "Branch is {count} commit(s) behind master. Rebasing...": {
+    "bg": "Branch is {count} commit(s) behind master. Rebasing...",
+    "de": "Branch is {count} commit(s) behind master. Rebasing...",
+    "en": "Branch is {count} commit(s) behind master. Rebasing...",
+    "pl": "Branch is {count} commit(s) behind master. Rebasing...",
+    "ru": "Branch is {count} commit(s) behind master. Rebasing...",
+    "zh": "Branch is {count} commit(s) behind master. Rebasing..."
+  },
+  "CI_GITEA_TOKEN is not set. Add it to .env or export it.": {
+    "bg": "CI_GITEA_TOKEN is not set. Add it to .env or export it.",
+    "de": "CI_GITEA_TOKEN is not set. Add it to .env or export it.",
+    "en": "CI_GITEA_TOKEN is not set. Add it to .env or export it.",
+    "pl": "CI_GITEA_TOKEN is not set. Add it to .env or export it.",
+    "ru": "CI_GITEA_TOKEN is not set. Add it to .env or export it.",
+    "zh": "CI_GITEA_TOKEN is not set. Add it to .env or export it."
+  },
+  "Cannot rebase: not on a branch (detached HEAD).": {
+    "bg": "Cannot rebase: not on a branch (detached HEAD).",
+    "de": "Cannot rebase: not on a branch (detached HEAD).",
+    "en": "Cannot rebase: not on a branch (detached HEAD).",
+    "pl": "Cannot rebase: not on a branch (detached HEAD).",
+    "ru": "Cannot rebase: not on a branch (detached HEAD).",
+    "zh": "Cannot rebase: not on a branch (detached HEAD)."
+  },
+  "Could not detect PR number. Use --pr to specify it explicitly,\nor run this command from a branch with an open PR.": {
+    "bg": "Could not detect PR number. Use --pr to specify it explicitly,\nor run this command from a branch with an open PR.",
+    "de": "Could not detect PR number. Use --pr to specify it explicitly,\nor run this command from a branch with an open PR.",
+    "en": "Could not detect PR number. Use --pr to specify it explicitly,\nor run this command from a branch with an open PR.",
+    "pl": "Could not detect PR number. Use --pr to specify it explicitly,\nor run this command from a branch with an open PR.",
+    "ru": "Could not detect PR number. Use --pr to specify it explicitly,\nor run this command from a branch with an open PR.",
+    "zh": "Could not detect PR number. Use --pr to specify it explicitly,\nor run this command from a branch with an open PR."
+  },
+  "Could not determine repository. Set DEVX_REPO_OWNER and DEVX_REPO_NAME\nor GITHUB_REPOSITORY environment variables.": {
+    "bg": "Could not determine repository. Set DEVX_REPO_OWNER and DEVX_REPO_NAME\nor GITHUB_REPOSITORY environment variables.",
+    "de": "Could not determine repository. Set DEVX_REPO_OWNER and DEVX_REPO_NAME\nor GITHUB_REPOSITORY environment variables.",
+    "en": "Could not determine repository. Set DEVX_REPO_OWNER and DEVX_REPO_NAME\nor GITHUB_REPOSITORY environment variables.",
+    "pl": "Could not determine repository. Set DEVX_REPO_OWNER and DEVX_REPO_NAME\nor GITHUB_REPOSITORY environment variables.",
+    "ru": "Could not determine repository. Set DEVX_REPO_OWNER and DEVX_REPO_NAME\nor GITHUB_REPOSITORY environment variables.",
+    "zh": "Could not determine repository. Set DEVX_REPO_OWNER and DEVX_REPO_NAME\nor GITHUB_REPOSITORY environment variables."
+  },
+  "Fetch failed: {error}": {
+    "bg": "Fetch failed: {error}",
+    "de": "Fetch failed: {error}",
+    "en": "Fetch failed: {error}",
+    "pl": "Fetch failed: {error}",
+    "ru": "Fetch failed: {error}",
+    "zh": "Fetch failed: {error}"
+  },
+  "Fetching origin/master...": {
+    "bg": "Fetching origin/master...",
+    "de": "Fetching origin/master...",
+    "en": "Fetching origin/master...",
+    "pl": "Fetching origin/master...",
+    "ru": "Fetching origin/master...",
+    "zh": "Fetching origin/master..."
+  },
+  "Force-push failed:\n{error}\nThe remote may have unexpected commits. Fetch and try again.": {
+    "bg": "Force-push failed:\n{error}\nThe remote may have unexpected commits. Fetch and try again.",
+    "de": "Force-push failed:\n{error}\nThe remote may have unexpected commits. Fetch and try again.",
+    "en": "Force-push failed:\n{error}\nThe remote may have unexpected commits. Fetch and try again.",
+    "pl": "Force-push failed:\n{error}\nThe remote may have unexpected commits. Fetch and try again.",
+    "ru": "Force-push failed:\n{error}\nThe remote may have unexpected commits. Fetch and try again.",
+    "zh": "Force-push failed:\n{error}\nThe remote may have unexpected commits. Fetch and try again."
+  },
+  "Force-pushing...": {
+    "bg": "Force-pushing...",
+    "de": "Force-pushing...",
+    "en": "Force-pushing...",
+    "pl": "Force-pushing...",
+    "ru": "Force-pushing...",
+    "zh": "Force-pushing..."
+  },
+  "Nothing to push.": {
+    "bg": "Nothing to push.",
+    "de": "Nothing to push.",
+    "en": "Nothing to push.",
+    "pl": "Nothing to push.",
+    "ru": "Nothing to push.",
+    "zh": "Nothing to push."
+  },
+  "PR #{pr} rebased successfully. A new CI run will start automatically.\nIf auto-merge is enabled (ready-to-merge label), the next CI run\nwill attempt to merge this PR.": {
+    "bg": "PR #{pr} rebased successfully. A new CI run will start automatically.\nIf auto-merge is enabled (ready-to-merge label), the next CI run\nwill attempt to merge this PR.",
+    "de": "PR #{pr} rebased successfully. A new CI run will start automatically.\nIf auto-merge is enabled (ready-to-merge label), the next CI run\nwill attempt to merge this PR.",
+    "en": "PR #{pr} rebased successfully. A new CI run will start automatically.\nIf auto-merge is enabled (ready-to-merge label), the next CI run\nwill attempt to merge this PR.",
+    "pl": "PR #{pr} rebased successfully. A new CI run will start automatically.\nIf auto-merge is enabled (ready-to-merge label), the next CI run\nwill attempt to merge this PR.",
+    "ru": "PR #{pr} rebased successfully. A new CI run will start automatically.\nIf auto-merge is enabled (ready-to-merge label), the next CI run\nwill attempt to merge this PR.",
+    "zh": "PR #{pr} rebased successfully. A new CI run will start automatically.\nIf auto-merge is enabled (ready-to-merge label), the next CI run\nwill attempt to merge this PR."
+  },
+  "Pushed {branch} to origin.": {
+    "bg": "Pushed {branch} to origin.",
+    "de": "Pushed {branch} to origin.",
+    "en": "Pushed {branch} to origin.",
+    "pl": "Pushed {branch} to origin.",
+    "ru": "Pushed {branch} to origin.",
+    "zh": "Pushed {branch} to origin."
+  },
+  "Rebase failed (conflicts or other error):\n{error}\nResolve conflicts and run: git rebase --continue": {
+    "bg": "Rebase failed (conflicts or other error):\n{error}\nResolve conflicts and run: git rebase --continue",
+    "de": "Rebase failed (conflicts or other error):\n{error}\nResolve conflicts and run: git rebase --continue",
+    "en": "Rebase failed (conflicts or other error):\n{error}\nResolve conflicts and run: git rebase --continue",
+    "pl": "Rebase failed (conflicts or other error):\n{error}\nResolve conflicts and run: git rebase --continue",
+    "ru": "Rebase failed (conflicts or other error):\n{error}\nResolve conflicts and run: git rebase --continue",
+    "zh": "Rebase failed (conflicts or other error):\n{error}\nResolve conflicts and run: git rebase --continue"
+  },
+  "Rebase failed with HTTP {status}: {message}": {
+    "bg": "Rebase failed with HTTP {status}: {message}",
+    "de": "Rebase failed with HTTP {status}: {message}",
+    "en": "Rebase failed with HTTP {status}: {message}",
+    "pl": "Rebase failed with HTTP {status}: {message}",
+    "ru": "Rebase failed with HTTP {status}: {message}",
+    "zh": "Rebase failed with HTTP {status}: {message}"
+  },
+  "Rebase successful.": {
+    "bg": "Rebase successful.",
+    "de": "Rebase successful.",
+    "en": "Rebase successful.",
+    "pl": "Rebase successful.",
+    "ru": "Rebase successful.",
+    "zh": "Rebase successful."
+  },
+  "Rebasing PR #{pr} via Gitea API...": {
+    "bg": "Rebasing PR #{pr} via Gitea API...",
+    "de": "Rebasing PR #{pr} via Gitea API...",
+    "en": "Rebasing PR #{pr} via Gitea API...",
+    "pl": "Rebasing PR #{pr} via Gitea API...",
+    "ru": "Rebasing PR #{pr} via Gitea API...",
+    "zh": "Rebasing PR #{pr} via Gitea API..."
   }
 }
diff --git a/tests/unit/test_api_clients.py b/tests/unit/test_api_clients.py
index 09d7817..aeb8422 100644
--- a/tests/unit/test_api_clients.py
+++ b/tests/unit/test_api_clients.py
@@ -233,6 +233,18 @@ class TestGiteaClient:
             json={"Do": "squash", "MergeTitleField": "fix: bug"},
         )
 
+    def test_update_pr_branch(self) -> None:
+        client = GiteaClient("https://git.example.com", "tok", "owner", "repo")
+        client._session.request = MagicMock(return_value=_mock_response())
+
+        client.update_pr_branch(7, style="rebase")
+        client._session.request.assert_called_once_with(
+            "POST",
+            "https://git.example.com/repos/owner/repo/pulls/7/update",
+            timeout=DEFAULT_TIMEOUT,
+            params={"style": "rebase"},
+        )
+
     def test_get_pr_labels(self) -> None:
         client = GiteaClient("https://git.example.com", "tok", "owner", "repo")
         client._session.request = MagicMock(return_value=_mock_response([{"name": "ready-to-merge"}]))
diff --git a/tests/unit/test_auto_merge.py b/tests/unit/test_auto_merge.py
index 16a3f45..0e3352d 100644
--- a/tests/unit/test_auto_merge.py
+++ b/tests/unit/test_auto_merge.py
@@ -292,14 +292,13 @@ class TestMain:
     @patch.dict("os.environ", {"CI_GITEA_TOKEN": "tok", "VIKUNJA_TOKEN": "tok"}, clear=True)
     @patch("devx.ci.auto_merge.validate_pr_title_matches_vikunja")
     @patch("devx.ci.auto_merge.GiteaClient")
-    def test_merge_behind_master_raises_no_rebase(
+    def test_merge_behind_master_auto_rebases(
         self, mock_client_cls: MagicMock, _mock_validate: MagicMock, tmp_path, monkeypatch
     ) -> None:  # type: ignore[no-untyped-def]
-        """When branch is behind master, auto-merge should NOT rebase.
+        """When branch is behind master, auto-merge rebases via Gitea API.
 
-        Auto-rebasing creates a feedback loop: the force-push triggers a new
-        pull_request synchronize event, which starts a new CI run, which runs
-        auto-merge again, which rebases again, etc.
+        The rebase triggers a new CI run. The next auto-merge attempt will
+        find the branch up-to-date and merge successfully.
         """
         monkeypatch.chdir(tmp_path)
 
@@ -315,12 +314,40 @@ class TestMain:
             main,
             ["DEVX-19-fix-bug", "DEVX-19: Fix timeout", "owner/repo", "7"],
         )
-        assert result.exit_code != 0
+        assert result.exit_code == 0
         assert "behind master" in result.output.lower()
-        assert "rebase manually" in result.output.lower()
-        # Must NOT have called merge_pr twice (no retry after rebase)
+        assert "auto-rebasing" in result.output.lower()
+        # Should have called update_pr_branch to trigger server-side rebase
+        mock_client.update_pr_branch.assert_called_once_with(7, style="rebase")
+        # Must NOT have called merge_pr twice (no immediate retry)
         assert mock_client.merge_pr.call_count == 1
 
+    @patch.dict("os.environ", {"CI_GITEA_TOKEN": "tok", "VIKUNJA_TOKEN": "tok"}, clear=True)
+    @patch("devx.ci.auto_merge.validate_pr_title_matches_vikunja")
+    @patch("devx.ci.auto_merge.GiteaClient")
+    def test_merge_behind_master_rebase_failure_raises(
+        self, mock_client_cls: MagicMock, _mock_validate: MagicMock, tmp_path, monkeypatch
+    ) -> None:  # type: ignore[no-untyped-def]
+        """When auto-rebase fails, raise with manual rebase instructions."""
+        monkeypatch.chdir(tmp_path)
+
+        mock_client = MagicMock()
+        mock_client.get_pr_commits.return_value = [
+            {"commit": {"message": "fix: resolve timeout"}},
+        ]
+        mock_client.merge_pr.side_effect = APIError(405, "HEAD branch is behind master")
+        mock_client.update_pr_branch.side_effect = APIError(409, "Conflict during rebase")
+        mock_client_cls.return_value = mock_client
+
+        runner = CliRunner()
+        result = runner.invoke(
+            main,
+            ["DEVX-19-fix-bug", "DEVX-19: Fix timeout", "owner/repo", "7"],
+        )
+        assert result.exit_code != 0
+        assert "auto-rebase failed" in result.output.lower()
+        assert "rebase manually" in result.output.lower()
+
     @patch.dict("os.environ", {"CI_GITEA_TOKEN": "tok", "VIKUNJA_TOKEN": "tok"}, clear=True)
     @patch("devx.ci.auto_merge.validate_pr_title_matches_vikunja")
     @patch("devx.ci.auto_merge.GiteaClient")
@@ -386,10 +413,10 @@ class TestMain:
     @patch.dict("os.environ", {"CI_GITEA_TOKEN": "tok", "VIKUNJA_TOKEN": "tok"}, clear=True)
     @patch("devx.ci.auto_merge.validate_pr_title_matches_vikunja")
     @patch("devx.ci.auto_merge.GiteaClient")
-    def test_merge_behind_master_does_not_force_push(
+    def test_merge_behind_master_does_not_run_git_commands(
         self, mock_client_cls: MagicMock, _mock_validate: MagicMock, tmp_path, monkeypatch
     ) -> None:  # type: ignore[no-untyped-def]
-        """Verify no git commands are run when branch is behind master."""
+        """When behind master, auto-merge uses API rebase — no local git commands."""
         monkeypatch.chdir(tmp_path)
 
         mock_client = MagicMock()
@@ -405,8 +432,8 @@ class TestMain:
                 main,
                 ["DEVX-19-fix-bug", "DEVX-19: Fix timeout", "owner/repo", "7"],
             )
-            assert result.exit_code != 0
-            # No git commands should be run (no rebase, no push)
+            assert result.exit_code == 0
+            # No local git commands should be run (rebase is via API)
             mock_run.assert_not_called()
 
 
diff --git a/tests/unit/test_cli.py b/tests/unit/test_cli.py
index 2d8c5b9..ab5de0a 100644
--- a/tests/unit/test_cli.py
+++ b/tests/unit/test_cli.py
@@ -201,6 +201,20 @@ class TestToolsCommands:
         assert result.exit_code == 0
         mock_run.assert_called_once_with("devx.tools.setup", [])
 
+    @patch("devx.cli._run_module")
+    def test_tools_rebase(self, mock_run: MagicMock) -> None:
+        runner = CliRunner()
+        result = runner.invoke(cli, ["tools", "rebase", "--", "--no-push"])
+        assert result.exit_code == 0
+        mock_run.assert_called_once_with("devx.tools.rebase", ["--no-push"])
+
+    @patch("devx.cli._run_module")
+    def test_tools_pr_rebase(self, mock_run: MagicMock) -> None:
+        runner = CliRunner()
+        result = runner.invoke(cli, ["tools", "pr-rebase", "--", "--pr", "42"])
+        assert result.exit_code == 0
+        mock_run.assert_called_once_with("devx.tools.pr_rebase", ["--pr", "42"])
+
 
 class TestMoleculeCommands:
     @patch("devx.cli._run_module")
diff --git a/tests/unit/test_rebase.py b/tests/unit/test_rebase.py
new file mode 100644
index 0000000..af004b7
--- /dev/null
+++ b/tests/unit/test_rebase.py
@@ -0,0 +1,348 @@
+"""Tests for devx.tools.rebase, devx.tools.pr_rebase, and detect_pr_number."""
+
+from __future__ import annotations
+
+from unittest.mock import MagicMock, patch
+
+from click.testing import CliRunner
+
+from devx.tools.pr_rebase import main as pr_rebase_main
+from devx.tools.rebase import main as rebase_main
+
+_FULL_ENV = {
+    "CI_GITEA_TOKEN": "tok",
+    "DEVX_REPO_OWNER": "owner",
+    "DEVX_REPO_NAME": "repo",
+}
+
+
+class TestRunGitHelper:
+    """Tests for the _run_git helper function."""
+
+    @patch("devx.tools.rebase.subprocess.run")
+    def test_run_git_with_check(self, mock_run: MagicMock) -> None:
+        """_run_git passes check=True by default."""
+        from devx.tools.rebase import _run_git
+
+        mock_run.return_value = MagicMock(stdout="ok\n", returncode=0)
+        result = _run_git(["status"])
+        mock_run.assert_called_once_with(
+            ["git", "status"],
+            capture_output=True,
+            text=True,
+            check=True,
+        )
+        assert result.stdout == "ok\n"
+
+    @patch("devx.tools.rebase.subprocess.run")
+    def test_run_git_without_check(self, mock_run: MagicMock) -> None:
+        """_run_git passes check=False when specified."""
+        from devx.tools.rebase import _run_git
+
+        mock_run.return_value = MagicMock(stdout="", stderr="err", returncode=1)
+        result = _run_git(["rebase", "origin/master"], check=False)
+        mock_run.assert_called_once_with(
+            ["git", "rebase", "origin/master"],
+            capture_output=True,
+            text=True,
+            check=False,
+        )
+        assert result.returncode == 1
+
+
+class TestDetectPrNumber:
+    """Tests for the detect_pr_number helper in _shared."""
+
+    @patch("devx.tools._shared.subprocess.run")
+    @patch.dict("os.environ", _FULL_ENV, clear=True)
+    @patch("devx.api_clients.GiteaClient")
+    def test_detect_pr_found(self, mock_client_cls: MagicMock, mock_run: MagicMock) -> None:
+        """detect_pr_number returns PR number when branch has an open PR."""
+        from devx.tools._shared import detect_pr_number
+
+        mock_run.return_value = MagicMock(stdout="feature-branch\n", returncode=0)
+        mock_client = MagicMock()
+        mock_client.list_prs.return_value = [
+            {"number": 42, "head": {"ref": "feature-branch"}},
+            {"number": 99, "head": {"ref": "other-branch"}},
+        ]
+        mock_client_cls.return_value = mock_client
+
+        result = detect_pr_number()
+        assert result == 42
+
+    @patch("devx.tools._shared.subprocess.run")
+    @patch.dict("os.environ", _FULL_ENV, clear=True)
+    @patch("devx.api_clients.GiteaClient")
+    def test_detect_pr_not_found(self, mock_client_cls: MagicMock, mock_run: MagicMock) -> None:
+        """detect_pr_number returns None when no open PR matches branch."""
+        from devx.tools._shared import detect_pr_number
+
+        mock_run.return_value = MagicMock(stdout="no-pr-branch\n", returncode=0)
+        mock_client = MagicMock()
+        mock_client.list_prs.return_value = [
+            {"number": 42, "head": {"ref": "other-branch"}},
+        ]
+        mock_client_cls.return_value = mock_client
+
+        result = detect_pr_number()
+        assert result is None
+
+    @patch("devx.tools._shared.subprocess.run")
+    def test_detect_pr_detached_head(self, mock_run: MagicMock) -> None:
+        """detect_pr_number returns None on detached HEAD."""
+        from devx.tools._shared import detect_pr_number
+
+        mock_run.return_value = MagicMock(stdout="HEAD\n", returncode=0)
+        result = detect_pr_number()
+        assert result is None
+
+    @patch("devx.tools._shared.subprocess.run")
+    def test_detect_pr_git_failure(self, mock_run: MagicMock) -> None:
+        """detect_pr_number returns None when git command fails."""
+        from devx.tools._shared import detect_pr_number
+
+        mock_run.return_value = MagicMock(stdout="", stderr="error", returncode=1)
+        result = detect_pr_number()
+        assert result is None
+
+    @patch("devx.tools._shared.subprocess.run")
+    @patch.dict("os.environ", {}, clear=True)
+    def test_detect_pr_no_token(self, mock_run: MagicMock) -> None:
+        """detect_pr_number returns None when CI_GITEA_TOKEN is not set."""
+        from devx.tools._shared import detect_pr_number
+
+        mock_run.return_value = MagicMock(stdout="feature\n", returncode=0)
+        result = detect_pr_number()
+        assert result is None
+
+    @patch("devx.tools._shared.subprocess.run")
+    @patch.dict("os.environ", {"CI_GITEA_TOKEN": "tok", "GITHUB_REPOSITORY": "owner/repo"}, clear=True)
+    @patch("devx.api_clients.GiteaClient")
+    def test_detect_pr_github_repo_fallback(self, mock_client_cls: MagicMock, mock_run: MagicMock) -> None:
+        """detect_pr_number uses GITHUB_REPOSITORY as fallback for owner/repo."""
+        from devx.tools._shared import detect_pr_number
+
+        mock_run.return_value = MagicMock(stdout="feature\n", returncode=0)
+        mock_client = MagicMock()
+        mock_client.list_prs.return_value = [{"number": 7, "head": {"ref": "feature"}}]
+        mock_client_cls.return_value = mock_client
+
+        result = detect_pr_number()
+        assert result == 7
+
+    @patch("devx.tools._shared.subprocess.run")
+    @patch.dict("os.environ", {"CI_GITEA_TOKEN": "tok", "GITHUB_REPOSITORY": "invalid-no-slash"}, clear=True)
+    def test_detect_pr_github_repo_no_slash(self, mock_run: MagicMock) -> None:
+        """GITHUB_REPOSITORY without slash is ignored, returns None."""
+        from devx.tools._shared import detect_pr_number
+
+        mock_run.return_value = MagicMock(stdout="feature\n", returncode=0)
+        result = detect_pr_number()
+        assert result is None
+
+    @patch("devx.tools._shared.subprocess.run")
+    @patch.dict("os.environ", _FULL_ENV, clear=True)
+    @patch("devx.api_clients.GiteaClient")
+    def test_detect_pr_api_error_returns_none(self, mock_client_cls: MagicMock, mock_run: MagicMock) -> None:
+        """detect_pr_number returns None when API call fails (best-effort)."""
+        from devx.api_clients import APIError
+        from devx.tools._shared import detect_pr_number
+
+        mock_run.return_value = MagicMock(stdout="feature\n", returncode=0)
+        mock_client = MagicMock()
+        mock_client.list_prs.side_effect = APIError(401, "Unauthorized")
+        mock_client_cls.return_value = mock_client
+
+        result = detect_pr_number()
+        assert result is None
+
+
+class TestRebaseTool:
+    """Tests for the local rebase tool (devx.tools.rebase)."""
+
+    @patch("devx.tools.rebase._run_git")
+    def test_rebase_already_up_to_date(self, mock_run_git: MagicMock) -> None:
+        """When branch is up-to-date, no rebase or push happens."""
+        mock_run_git.side_effect = [
+            MagicMock(stdout="feature-branch\n", returncode=0),  # rev-parse
+            MagicMock(stdout="", returncode=0),  # fetch
+            MagicMock(stdout="0\n", returncode=0),  # rev-list --count
+        ]
+
+        runner = CliRunner()
+        result = runner.invoke(rebase_main, [])
+        assert result.exit_code == 0
+        assert "already up-to-date" in result.output.lower()
+
+    @patch("devx.tools.rebase._run_git")
+    def test_rebase_behind_master_success(self, mock_run_git: MagicMock) -> None:
+        """When behind master, rebase and force-push."""
+        mock_run_git.side_effect = [
+            MagicMock(stdout="feature-branch\n", returncode=0),  # rev-parse
+            MagicMock(stdout="", returncode=0),  # fetch
+            MagicMock(stdout="2\n", returncode=0),  # rev-list --count (behind by 2)
+            MagicMock(stdout="", stderr="", returncode=0),  # rebase
+            MagicMock(stdout="", stderr="", returncode=0),  # push
+        ]
+
+        runner = CliRunner()
+        result = runner.invoke(rebase_main, [])
+        assert result.exit_code == 0
+        assert "2 commit(s) behind" in result.output
+        assert "rebase successful" in result.output.lower()
+        assert "pushed" in result.output.lower()
+
+    @patch("devx.tools.rebase._run_git")
+    def test_rebase_no_push_flag(self, mock_run_git: MagicMock) -> None:
+        """With --no-push, rebase happens but no push."""
+        mock_run_git.side_effect = [
+            MagicMock(stdout="feature-branch\n", returncode=0),  # rev-parse
+            MagicMock(stdout="", returncode=0),  # fetch
+            MagicMock(stdout="1\n", returncode=0),  # rev-list --count
+            MagicMock(stdout="", stderr="", returncode=0),  # rebase
+        ]
+
+        runner = CliRunner()
+        result = runner.invoke(rebase_main, ["--no-push"])
+        assert result.exit_code == 0
+        assert "rebase successful" in result.output.lower()
+        # Only 4 git calls (no push)
+        assert mock_run_git.call_count == 4
+
+    @patch("devx.tools.rebase._run_git")
+    def test_rebase_detached_head_fails(self, mock_run_git: MagicMock) -> None:
+        """Detached HEAD should fail immediately."""
+        mock_run_git.return_value = MagicMock(stdout="HEAD\n", returncode=0)
+
+        runner = CliRunner()
+        result = runner.invoke(rebase_main, [])
+        assert result.exit_code != 0
+        assert "detached" in result.output.lower()
+
+    @patch("devx.tools.rebase._run_git")
+    def test_rebase_branch_detection_failure(self, mock_run_git: MagicMock) -> None:
+        """Git rev-parse failure should exit with error."""
+        mock_run_git.return_value = MagicMock(stdout="", stderr="fatal: not a repo", returncode=1)
+
+        runner = CliRunner()
+        result = runner.invoke(rebase_main, [])
+        assert result.exit_code != 0
+        assert "could not detect" in result.output.lower()
+
+    @patch("devx.tools.rebase._run_git")
+    def test_rebase_conflict_fails(self, mock_run_git: MagicMock) -> None:
+        """Rebase conflict should exit with error."""
+        mock_run_git.side_effect = [
+            MagicMock(stdout="feature-branch\n", returncode=0),  # rev-parse
+            MagicMock(stdout="", returncode=0),  # fetch
+            MagicMock(stdout="1\n", returncode=0),  # rev-list --count
+            MagicMock(stdout="", stderr="CONFLICT", returncode=1),  # rebase fails
+        ]
+
+        runner = CliRunner()
+        result = runner.invoke(rebase_main, [])
+        assert result.exit_code != 0
+        assert "rebase failed" in result.output.lower()
+
+    @patch("devx.tools.rebase._run_git")
+    def test_rebase_fetch_failure(self, mock_run_git: MagicMock) -> None:
+        """Fetch failure should exit with error."""
+        mock_run_git.side_effect = [
+            MagicMock(stdout="feature-branch\n", returncode=0),  # rev-parse
+            MagicMock(stdout="", stderr="network error", returncode=1),  # fetch fails
+        ]
+
+        runner = CliRunner()
+        result = runner.invoke(rebase_main, [])
+        assert result.exit_code != 0
+        assert "fetch failed" in result.output.lower()
+
+    @patch("devx.tools.rebase._run_git")
+    def test_rebase_push_failure(self, mock_run_git: MagicMock) -> None:
+        """Force-push rejection should exit with error."""
+        mock_run_git.side_effect = [
+            MagicMock(stdout="feature-branch\n", returncode=0),  # rev-parse
+            MagicMock(stdout="", returncode=0),  # fetch
+            MagicMock(stdout="1\n", returncode=0),  # rev-list --count
+            MagicMock(stdout="", stderr="", returncode=0),  # rebase
+            MagicMock(stdout="", stderr="rejected", returncode=1),  # push fails
+        ]
+
+        runner = CliRunner()
+        result = runner.invoke(rebase_main, [])
+        assert result.exit_code != 0
+        assert "force-push failed" in result.output.lower()
+
+
+class TestPrRebaseTool:
+    """Tests for the server-side PR rebase tool (devx.tools.pr_rebase)."""
+
+    @patch.dict("os.environ", _FULL_ENV, clear=True)
+    @patch("devx.tools.pr_rebase.GiteaClient")
+    def test_pr_rebase_success(self, mock_client_cls: MagicMock) -> None:
+        """Successful API rebase prints confirmation."""
+        mock_client = MagicMock()
+        mock_client_cls.return_value = mock_client
+
+        runner = CliRunner()
+        result = runner.invoke(pr_rebase_main, ["--pr", "42"])
+        assert result.exit_code == 0
+        assert "rebased successfully" in result.output.lower()
+        mock_client.update_pr_branch.assert_called_once_with(42, style="rebase")
+
+    @patch.dict("os.environ", _FULL_ENV, clear=True)
+    @patch("devx.tools.pr_rebase.GiteaClient")
+    def test_pr_rebase_api_error(self, mock_client_cls: MagicMock) -> None:
+        """API error during rebase exits with error."""
+        from devx.api_clients import APIError
+
+        mock_client = MagicMock()
+        mock_client.update_pr_branch.side_effect = APIError(409, "Conflict")
+        mock_client_cls.return_value = mock_client
+
+        runner = CliRunner()
+        result = runner.invoke(pr_rebase_main, ["--pr", "42"])
+        assert result.exit_code != 0
+        assert "rebase failed" in result.output.lower()
+
+    @patch("devx.tools.pr_rebase.load_dotenv")
+    @patch.dict("os.environ", {}, clear=True)
+    def test_pr_rebase_no_token(self, _mock_load: MagicMock) -> None:
+        """Missing CI_GITEA_TOKEN should fail."""
+        runner = CliRunner()
+        result = runner.invoke(pr_rebase_main, ["--pr", "42"])
+        assert result.exit_code != 0
+        assert "CI_GITEA_TOKEN" in result.output
+
+    @patch.dict("os.environ", _FULL_ENV, clear=True)
+    @patch("devx.tools.pr_rebase.detect_pr_number", return_value=None)
+    def test_pr_rebase_no_pr_detected(self, _mock_detect: MagicMock) -> None:
+        """When PR number can't be auto-detected, fail with instructions."""
+        runner = CliRunner()
+        result = runner.invoke(pr_rebase_main, [])
+        assert result.exit_code != 0
+        assert "could not detect" in result.output.lower()
+
+    @patch("devx.tools.pr_rebase.load_dotenv")
+    @patch.dict("os.environ", {"CI_GITEA_TOKEN": "tok"}, clear=True)
+    @patch("devx.tools.pr_rebase.GiteaClient")
+    def test_pr_rebase_no_repo_env(self, _mock_client: MagicMock, _mock_load: MagicMock) -> None:
+        """Missing repo env vars should fail."""
+        runner = CliRunner()
+        result = runner.invoke(pr_rebase_main, ["--pr", "42"])
+        assert result.exit_code != 0
+        assert "DEVX_REPO_OWNER" in result.output
+
+    @patch("devx.tools.pr_rebase.load_dotenv")
+    @patch.dict("os.environ", {"CI_GITEA_TOKEN": "tok", "GITHUB_REPOSITORY": "owner/repo"}, clear=True)
+    @patch("devx.tools.pr_rebase.GiteaClient")
+    def test_pr_rebase_github_repo_fallback(self, mock_client_cls: MagicMock, _mock_load: MagicMock) -> None:
+        """GITHUB_REPOSITORY env var is used as fallback for owner/repo."""
+        mock_client = MagicMock()
+        mock_client_cls.return_value = mock_client
+
+        runner = CliRunner()
+        result = runner.invoke(pr_rebase_main, ["--pr", "42"])
+        assert result.exit_code == 0
+        mock_client.update_pr_branch.assert_called_once_with(42, style="rebase")