Exception thrown when using /rebase in description of conflict-free MR

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Summary

When opening an MR which doesn't contain merge conflicts, and using the /rebase in the MR description, an exception is thrown.

Steps to reproduce

Create a project
Introduce a change, and commit into a new branch
Create an MR from new branch into default branch
Use /rebase anywhere in the Description

Example Project

https://gitlab.com/customer-issue-reproduction/zd-622067

What is the current bug behavior?

A user facing exception is thrown:

01JSHNQ4PJEF2TQNZ4FKK3V0ND

What is the expected correct behavior?

Either:

/rebase is ignored or,
a user-friendly error is thrown.

Workaround

Don't use /rebase in MR descriptions.

Relevant logs and/or screenshots

Log event

{
  "correlation_id": "01JSHNQ4PJEF2TQNZ4FKK3V0ND",
  "username": "niklasjanz",
  "meta.caller_id": "Projects::MergeRequests::CreationsController#create",
  "user_id": 7538998,
  "meta.feature_category": "code_review_workflow",
  "meta.user": "niklasjanz",
  "meta.project": "customer-issue-reproduction/zd-622067",
  "cf_ray": "934e8a2420a18fe8-IAD",
  "status": 500,
  "cf_ipcountry": "DE",
  "exception.backtrace": [
    "app/services/issuable_base_service.rb:201:in `create'",
    "app/services/merge_requests/base_service.rb:149:in `create'",
    "app/services/merge_requests/create_service.rb:16:in `execute'",
    "app/controllers/projects/merge_requests/creations_controller.rb:38:in `create'",
    "lib/gitlab/ip_address_state.rb:11:in `with'",
    "ee/app/controllers/ee/application_controller.rb:45:in `set_current_ip_address'",
    "app/controllers/application_controller.rb:487:in `set_current_admin'",
    "lib/gitlab/session.rb:11:in `with_session'",
    "app/controllers/application_controller.rb:478:in `set_session_storage'",
    "lib/gitlab/i18n.rb:114:in `with_locale'",
    "lib/gitlab/i18n.rb:120:in `with_user_locale'",
    "app/controllers/application_controller.rb:469:in `set_locale'",
    "app/controllers/application_controller.rb:462:in `set_current_context'",
    "lib/gitlab/middleware/action_controller_static_context.rb:23:in `call'",
    "ee/lib/omni_auth/strategies/group_saml.rb:41:in `other_phase'",
    "lib/gitlab/metrics/elasticsearch_rack_middleware.rb:16:in `call'",
    "lib/gitlab/middleware/sidekiq_shard_awareness_validation.rb:20:in `block in call'",
    "lib/gitlab/sidekiq_sharding/validator.rb:42:in `enabled'",
    "lib/gitlab/middleware/sidekiq_shard_awareness_validation.rb:20:in `call'",
    "lib/gitlab/middleware/memory_report.rb:13:in `call'",
    "lib/gitlab/middleware/speedscope.rb:13:in `call'",
    "lib/gitlab/database/load_balancing/rack_middleware.rb:23:in `call'",
    "lib/gitlab/middleware/rails_queue_duration.rb:33:in `call'",
    "lib/gitlab/etag_caching/middleware.rb:21:in `call'",
    "lib/gitlab/metrics/rack_middleware.rb:16:in `block in call'",
    "lib/gitlab/metrics/web_transaction.rb:46:in `run'",
    "lib/gitlab/metrics/rack_middleware.rb:16:in `call'",
    "lib/gitlab/middleware/go.rb:21:in `call'",
    "lib/gitlab/middleware/query_analyzer.rb:11:in `block in call'",
    "lib/gitlab/database/query_analyzer.rb:83:in `within'",
    "lib/gitlab/middleware/query_analyzer.rb:11:in `call'",
    "lib/ci/job_token/middleware.rb:11:in `call'",
    "lib/gitlab/middleware/multipart.rb:173:in `call'",
    "lib/gitlab/middleware/read_only/controller.rb:50:in `call'",
    "lib/gitlab/middleware/read_only.rb:18:in `call'",
    "lib/gitlab/middleware/unauthenticated_session_expiry.rb:18:in `call'",
    "lib/gitlab/middleware/secure_headers.rb:11:in `call'",
    "lib/gitlab/middleware/same_site_cookies.rb:27:in `call'",
    "lib/gitlab/middleware/path_traversal_check.rb:40:in `call'",
    "lib/gitlab/middleware/handle_malformed_strings.rb:21:in `call'",
    "lib/gitlab/middleware/basic_health_check.rb:25:in `call'",
    "lib/gitlab/middleware/handle_ip_spoof_attack_error.rb:25:in `call'",
    "lib/gitlab/middleware/request_context.rb:15:in `call'",
    "lib/gitlab/middleware/webhook_recursion_detection.rb:15:in `call'",
    "config/initializers/fix_local_cache_middleware.rb:11:in `call'",
    "lib/gitlab/middleware/compressed_json.rb:44:in `call'",
    "lib/gitlab/middleware/rack_multipart_tempfile_factory.rb:19:in `call'",
    "lib/gitlab/middleware/sidekiq_web_static.rb:20:in `call'",
    "lib/gitlab/metrics/requests_rack_middleware.rb:83:in `call'",
    "lib/gitlab/middleware/release_env.rb:12:in `call'"
  ],
  "format": "html",
  "method": "POST",
  "shard": "default",
  "meta.root_namespace": "customer-issue-reproduction",
  "params": [
    {
      "key": "authenticity_token",
      "value": "[FILTERED]"
    },
    {
      "key": "merge_request",
      "value": "{\"title\"=>\"[FILTERED]\", \"description\"=>\"[FILTERED]\", \"assignee_ids\"=>[\"0\"], \"reviewer_ids\"=>[\"0\"], \"milestone_id\"=>\"\", \"merge_after\"=>\"\", \"force_remove_source_branch\"=>\"1\", \"squash\"=>\"0\", \"lock_version\"=>\"0\", \"source_project_id\"=>\"69227657\", \"source_branch\"=>\"niklasjanz-main-patch-81781\", \"target_project_id\"=>\"69227657\", \"target_branch\"=>\"main\"}"
    },
    {
      "value": "acf5066599cce24771381e80e828331024296ec8",
      "key": "merge_request_diff_head_sha"
    },
    {
      "key": "namespace_id",
      "value": "customer-issue-reproduction"
    },
    {
      "key": "project_id",
      "value": "zd-622067"
    }
  ],
  "redis_shared_state_calls": 4,
  "exception.class": "ActiveModel::UnknownAttributeError",
  "controller": "Projects::MergeRequests::CreationsController",
  "type": "web",
  "meta.http_router_rule_action": "proxy",
  "subcomponent": "production_json",
  "exception.message": "unknown attribute 'rebase' for MergeRequest.",
  "path": "/customer-issue-reproduction/zd-622067/-/merge_requests",
  "action": "create",
  "time": "2025-04-23T15:54:28.100Z",
  "meta.user_id": 7538998,
  "stage": "cny",
  "tier": "sv"
}

Output of checks

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Results of GitLab environment info

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(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes

Edited Jul 15, 2025 by 🤖 GitLab Bot 🤖