# Checkpoint 2: MR Ingestion - PRD

> **Note:** The project was renamed from "gitlab-inbox" to "gitlore" and the CLI from "gi" to "lore". References to "gi" in this document should be read as "lore".

**Version:** 1.3
**Status:** Ready for Implementation
**Depends On:** Checkpoint 1 (Issue Ingestion)
**Enables:** Checkpoint 3A (Document Generation + FTS)

---

## Overview

### Objective

Ingest all merge requests, MR discussions, and notes (including DiffNote position metadata) from configured GitLab repositories. This checkpoint extends the cursor-based sync pattern established in CP1 to merge requests, capturing code review context that is essential for decision traceability.

### Success Criteria

| Criterion | Validation |
|-----------|------------|
| `gi ingest --type=merge_requests` fetches all MRs | `gi count mrs` matches GitLab UI |
| MR labels extracted and linked correctly | Label count per MR matches GitLab |
| MR assignees and reviewers captured | Junction tables populated |
| MR merge status is future-proof | `detailed_merge_status` populated; no reliance on deprecated `merge_status` |
| MR merge actor is future-proof | `merge_user_username` populated when merged/auto-merge set |
| Draft MRs are captured | `draft` populated and visible in `gi list mrs` |
| Draft is backwards-compatible | Older instances using `work_in_progress` still populate `draft` |
| MR state is complete | `state` supports `opened|merged|closed|locked` (no drop/parse failures) |
| MR head SHA captured | `head_sha` populated for CP3 diff/commit context |
| MR references captured | `references_short` and `references_full` populated for CP3 cross-project display |
| MR discussions fetched per-MR (dependent sync) | For MRs whose `updated_at` advanced, discussions and notes upserted |
| DiffNote position metadata captured | `position_new_path`, `position_old_path`, `position_type` populated for DiffNotes |
| DiffNote SHA triplet captured | `position_base_sha`, `position_start_sha`, `position_head_sha` populated for DiffNotes |
| Cursor-based sync is resumable | Re-running fetches 0 new items |
| Discussion sync skips unchanged MRs | Per-MR watermark prevents redundant fetches |
| Watermark not advanced on partial failure | Incomplete pagination OR parse failures do not mark MR as synced |
| Full sync resets discussion watermarks | `--full` flag resets both MR cursor AND discussion watermarks |
| Pagination uses robust fallback chain | Link header > x-next-page > full-page heuristic |
| MR CLI commands functional | `gi show mr`, `gi count mrs` work |

---

## Internal Gates

CP2 is validated incrementally via internal gates:

| Gate | Scope | Validation |
|------|-------|------------|
| **Gate A** | MRs only | Cursor + upsert + raw payloads + list/count working; `locked` state (local filtering), `work_in_progress` fallback, `head_sha` + `references` captured; Link header pagination with fallback chain |
| **Gate B** | Labels + assignees + reviewers correct | Junction tables populated; counts match GitLab |
| **Gate C** | Dependent discussion sync | Watermark prevents redundant refetch; DiffNote paths + SHA triplet captured; upsert + sweep for notes; watermark does NOT advance on partial pagination failure OR note parse failures; atomic note replacement (parse before delete) |
| **Gate D** | Resumability proof | Kill mid-run, rerun; confirm bounded redo; `--full` resets cursor AND discussion watermarks |
| **Gate E** | CLI complete | `gi show mr` displays discussions with DiffNote file context |

---

## Deliverables

### 1. Project Structure Additions

Add the following to the existing Rust structure from Checkpoint 1:

```
gitlab-inbox/
├── src/
│   ├── cli/
│   │   └── commands/
│   │       ├── list.rs             # Update: add MR listing
│   │       ├── show.rs             # Update: add MR detail view
│   │       └── count.rs            # Update: add MR counting
│   ├── gitlab/
│   │   ├── types.rs                # Add GitLabMergeRequest, GitLabReviewer
│   │   └── transformers/
│   │       └── merge_request.rs    # NEW: GitLab -> normalized MR
│   └── ingestion/
│       ├── merge_requests.rs       # NEW: MR fetcher with pagination
│       ├── mr_discussions.rs       # NEW: MR discussion fetcher
│       └── orchestrator.rs         # Update: support MR ingestion
├── tests/
│   ├── mr_transformer_tests.rs
│   ├── mr_ingestion_tests.rs
│   ├── mr_discussion_tests.rs
│   ├── diffnote_tests.rs
│   └── fixtures/
│       ├── gitlab_merge_request.json
│       ├── gitlab_merge_requests_page.json
│       ├── gitlab_mr_discussion.json
│       ├── gitlab_mr_discussion_with_diffnote.json
│       └── gitlab_diffnote_position.json
└── migrations/
    └── 006_merge_requests.sql
```

### 2. GitLab API Endpoints

**Merge Requests (Bulk Fetch):**
```
GET /projects/:id/merge_requests?scope=all&state=all&updated_after=X&order_by=updated_at&sort=asc&per_page=100
```

**MR Discussions (Per-MR Fetch):**
```
GET /projects/:id/merge_requests/:iid/discussions?per_page=100&page=N
```

**Required Query Parameters:**
- `scope=all` - Include all MRs, not just authored by current user
- `state=all` - Include merged/closed MRs (GitLab defaults may exclude them)

**Key Differences from Issues:**
- MRs have `source_branch` and `target_branch`
- MRs have `merge_status`, `merged_by`, `merged_at` fields
- MRs have reviewers (separate from assignees)
- MR discussions can contain DiffNotes with position metadata

**MR State Values:**
GitLab MR `state` can be `opened`, `closed`, `merged`, or `locked`. The `locked` state is a **transitional state** that indicates an MR is in the middle of being merged (merge-in-progress). Key considerations:
- **Store as first-class:** Persist `locked` in the database without coercion to preserve GitLab's exact state.
- **Local filtering only:** The GitLab API's `state` filter does not support `locked` as a query parameter. To filter for locked MRs, we must use `state=all` server-side and filter locally via SQL `WHERE state = 'locked'`.
- **Transient nature:** Most MRs in `locked` state will transition to `merged` within seconds/minutes. Expect very few locked MRs in typical queries.
- **CLI exposure:** The `--state=locked` filter is available for debugging/inspection but is not expected to be commonly used.

**Reviewer Verification (Optional / Debug Mode):**
When reviewer data is suspected to be incomplete on a given GitLab version, enable an optional verification mode:
```
GET /projects/:id/merge_requests/:merge_request_iid/reviewers
```
This is disabled by default to avoid N+1 overhead. Activated via config flag `sync.verify_reviewers: true` for debugging problematic instances.

**Pagination:**
- **Primary:** Parse `Link: <url>; rel="next"` header (RFC 8288). This is the most reliable signal as it works consistently across GitLab versions and proxy configurations.
- **Fallback 1:** If no `Link` header, check `x-next-page` header until empty/absent
- **Fallback 2:** If no pagination headers but current page returned `per_page` items, attempt `page + 1` and stop only when an empty response is received. This handles proxies/instances that strip headers.
- Per-page maximum: 100
- **Optional keyset mode:** For projects with 10,000+ MRs, enable keyset pagination via config flag `sync.use_keyset_pagination: true`. This uses `pagination=keyset&order_by=updated_at&sort=asc` with cursor tokens from Link headers for O(1) page fetches instead of O(n) offset scans.

---

## Database Schema

### Migration 006_merge_requests.sql

```sql
-- Merge requests table
CREATE TABLE merge_requests (
  id INTEGER PRIMARY KEY,
  gitlab_id INTEGER UNIQUE NOT NULL,
  project_id INTEGER NOT NULL REFERENCES projects(id),
  iid INTEGER NOT NULL,
  title TEXT,
  description TEXT,
  state TEXT,                         -- 'opened' | 'merged' | 'closed' | 'locked'
  draft INTEGER NOT NULL DEFAULT 0,   -- 0/1 (SQLite boolean) - work-in-progress status
  author_username TEXT,
  source_branch TEXT,
  target_branch TEXT,
  head_sha TEXT,                      -- Current commit SHA at head of source branch (CP3-ready)
  references_short TEXT,              -- Short reference e.g. "!123" (CP3-ready for display)
  references_full TEXT,               -- Full reference e.g. "group/project!123" (CP3-ready for cross-project)
  detailed_merge_status TEXT,         -- preferred, non-deprecated (replaces merge_status)
  merge_user_username TEXT,           -- preferred over deprecated merged_by
  created_at INTEGER,                 -- ms epoch UTC
  updated_at INTEGER,                 -- ms epoch UTC
  merged_at INTEGER,                  -- ms epoch UTC (NULL if not merged)
  closed_at INTEGER,                  -- ms epoch UTC (NULL if not closed)
  last_seen_at INTEGER NOT NULL,      -- ms epoch UTC, updated on every upsert
  -- Prevents re-fetching discussions on cursor rewind / reruns unless MR changed.
  discussions_synced_for_updated_at INTEGER,
  -- Sync health telemetry for debuggability
  discussions_sync_last_attempt_at INTEGER,  -- ms epoch UTC of last sync attempt
  discussions_sync_attempts INTEGER DEFAULT 0,  -- count of sync attempts for this MR version
  discussions_sync_last_error TEXT,           -- last error message if sync failed
  web_url TEXT,
  raw_payload_id INTEGER REFERENCES raw_payloads(id)
);
CREATE INDEX idx_mrs_project_updated ON merge_requests(project_id, updated_at);
CREATE INDEX idx_mrs_author ON merge_requests(author_username);
CREATE INDEX idx_mrs_target_branch ON merge_requests(project_id, target_branch);
CREATE INDEX idx_mrs_source_branch ON merge_requests(project_id, source_branch);
CREATE INDEX idx_mrs_state ON merge_requests(project_id, state);
CREATE INDEX idx_mrs_detailed_merge_status ON merge_requests(project_id, detailed_merge_status);
CREATE INDEX idx_mrs_draft ON merge_requests(project_id, draft);
CREATE INDEX idx_mrs_discussions_sync ON merge_requests(project_id, discussions_synced_for_updated_at);
CREATE UNIQUE INDEX uq_mrs_project_iid ON merge_requests(project_id, iid);

-- MR-Label junction (reuses labels table from CP1)
CREATE TABLE mr_labels (
  merge_request_id INTEGER REFERENCES merge_requests(id) ON DELETE CASCADE,
  label_id INTEGER REFERENCES labels(id) ON DELETE CASCADE,
  PRIMARY KEY(merge_request_id, label_id)
);
CREATE INDEX idx_mr_labels_label ON mr_labels(label_id);

-- MR assignees (same pattern as issue_assignees)
CREATE TABLE mr_assignees (
  merge_request_id INTEGER REFERENCES merge_requests(id) ON DELETE CASCADE,
  username TEXT NOT NULL,
  PRIMARY KEY(merge_request_id, username)
);
CREATE INDEX idx_mr_assignees_username ON mr_assignees(username);

-- MR reviewers (MR-specific, not applicable to issues)
CREATE TABLE mr_reviewers (
  merge_request_id INTEGER REFERENCES merge_requests(id) ON DELETE CASCADE,
  username TEXT NOT NULL,
  PRIMARY KEY(merge_request_id, username)
);
CREATE INDEX idx_mr_reviewers_username ON mr_reviewers(username);

-- Add FK constraint to discussions table for merge_request_id
-- Note: SQLite doesn't support ADD CONSTRAINT, the FK was defined in CP1 but nullable
-- We just need to add an index if not already present
CREATE INDEX IF NOT EXISTS idx_discussions_mr_id ON discussions(merge_request_id);
CREATE INDEX IF NOT EXISTS idx_discussions_mr_resolved ON discussions(merge_request_id, resolved, resolvable);

-- Additional indexes for DiffNote queries (notes table from CP1)
-- These composite indexes enable efficient file-context queries for CP3
CREATE INDEX IF NOT EXISTS idx_notes_type ON notes(note_type);
CREATE INDEX IF NOT EXISTS idx_notes_new_path ON notes(position_new_path);
CREATE INDEX IF NOT EXISTS idx_notes_new_path_line ON notes(position_new_path, position_new_line);
CREATE INDEX IF NOT EXISTS idx_notes_old_path_line ON notes(position_old_path, position_old_line);

-- CP2: capture richer diff note position shapes (minimal, still MVP)
-- These fields support modern GitLab diff note semantics without full diff reconstruction
ALTER TABLE notes ADD COLUMN position_type TEXT;           -- 'text' | 'image' | 'file'
ALTER TABLE notes ADD COLUMN position_line_range_start INTEGER;  -- multi-line comment start
ALTER TABLE notes ADD COLUMN position_line_range_end INTEGER;    -- multi-line comment end
-- DiffNote SHA triplet for commit context (CP3-ready, zero extra API cost)
ALTER TABLE notes ADD COLUMN position_base_sha TEXT;       -- Base commit SHA for diff
ALTER TABLE notes ADD COLUMN position_start_sha TEXT;      -- Start commit SHA for diff
ALTER TABLE notes ADD COLUMN position_head_sha TEXT;       -- Head commit SHA for diff

-- Update schema version
INSERT INTO schema_version (version, applied_at, description)
VALUES (6, strftime('%s', 'now') * 1000, 'Merge requests, MR labels, assignees, reviewers');
```

---

## GitLab Types

### Type Definitions

```rust
// src/gitlab/types.rs (additions)

use serde::Deserialize;

/// GitLab merge request from the API.
/// Note: Uses non-deprecated field names where possible (detailed_merge_status, merge_user).
/// Falls back gracefully for older GitLab versions.
#[derive(Debug, Clone, Deserialize)]
pub struct GitLabMergeRequest {
    pub id: i64,                      // GitLab global ID
    pub iid: i64,                     // Project-scoped MR number
    pub project_id: i64,
    pub title: String,
    pub description: Option<String>,
    pub state: String,                // "opened" | "merged" | "closed" | "locked"
    #[serde(default)]
    pub draft: bool,                  // Work-in-progress status (preferred)
    #[serde(default)]
    pub work_in_progress: bool,       // Deprecated; fallback for older instances
    pub source_branch: String,
    pub target_branch: String,
    pub sha: Option<String>,          // Current commit SHA at head of source branch (CP3-ready)
    pub references: Option<GitLabReferences>,  // Short and full reference strings (CP3-ready)
    // Prefer detailed_merge_status (non-deprecated) over merge_status (deprecated)
    pub detailed_merge_status: Option<String>, // "mergeable" | "not_mergeable" | "checking" | etc.
    #[serde(alias = "merge_status")]
    pub merge_status_legacy: Option<String>,   // Keep for older/self-managed versions
    pub created_at: String,           // ISO 8601
    pub updated_at: String,           // ISO 8601
    pub merged_at: Option<String>,    // ISO 8601
    pub closed_at: Option<String>,    // ISO 8601
    pub author: GitLabAuthor,
    // Prefer merge_user (current) over merged_by (deprecated)
    pub merge_user: Option<GitLabAuthor>,
    pub merged_by: Option<GitLabAuthor>,  // Keep for older/self-managed versions
    #[serde(default)]
    pub labels: Vec<String>,          // Array of label names
    #[serde(default)]
    pub assignees: Vec<GitLabAuthor>,
    #[serde(default)]
    pub reviewers: Vec<GitLabReviewer>,
    pub web_url: String,
}

/// GitLab references object (short and full reference strings).
#[derive(Debug, Clone, Deserialize)]
pub struct GitLabReferences {
    pub short: String,                // e.g. "!123"
    pub full: String,                 // e.g. "group/project!123"
}

/// GitLab author from the API.
#[derive(Debug, Clone, Deserialize)]
pub struct GitLabAuthor {
    pub id: i64,
    pub username: String,
    pub name: String,
}

/// GitLab reviewer (can have approval state).
#[derive(Debug, Clone, Deserialize)]
pub struct GitLabReviewer {
    pub id: i64,
    pub username: String,
    pub name: String,
    // Note: approval state may require additional API call, defer to post-MVP
}

// Note: GitLabDiscussion and GitLabNote types already exist from CP1
// and support MR discussions with DiffNote position metadata.
```

---

## Transformers

### Merge Request Transformer

```rust
// src/gitlab/transformers/merge_request.rs

use crate::core::time::{iso_to_ms, now_ms};
use crate::gitlab::types::GitLabMergeRequest;

/// Normalized merge request ready for database insertion.
#[derive(Debug, Clone)]
pub struct NormalizedMergeRequest {
    pub gitlab_id: i64,
    pub project_id: i64,              // Local DB project ID
    pub iid: i64,
    pub title: String,
    pub description: Option<String>,
    pub state: String,
    pub draft: bool,
    pub author_username: String,
    pub source_branch: String,
    pub target_branch: String,
    pub head_sha: Option<String>,             // CP3-ready: current commit at source branch head
    pub references_short: Option<String>,     // CP3-ready: e.g. "!123"
    pub references_full: Option<String>,      // CP3-ready: e.g. "group/project!123"
    pub detailed_merge_status: Option<String>,
    pub merge_user_username: Option<String>,
    pub created_at: i64,              // ms epoch
    pub updated_at: i64,              // ms epoch
    pub merged_at: Option<i64>,       // ms epoch
    pub closed_at: Option<i64>,       // ms epoch
    pub last_seen_at: i64,            // ms epoch
    pub web_url: String,
}

/// Normalized label ready for database insertion.
/// Reuses structure from issue transformer.
#[derive(Debug, Clone)]
pub struct NormalizedLabel {
    pub project_id: i64,
    pub name: String,
}

/// Result of transforming a GitLab MR.
#[derive(Debug, Clone)]
pub struct MergeRequestWithMetadata {
    pub merge_request: NormalizedMergeRequest,
    pub label_names: Vec<String>,
    pub assignee_usernames: Vec<String>,
    pub reviewer_usernames: Vec<String>,
}

/// Transform GitLab merge request to normalized schema.
pub fn transform_merge_request(
    gitlab_mr: &GitLabMergeRequest,
    local_project_id: i64,
) -> Result<MergeRequestWithMetadata, String> {
    // Parse timestamps, return error if invalid (strict parsing, no silent zeroing)
    let created_at = iso_to_ms(&gitlab_mr.created_at)
        .ok_or_else(|| format!("Invalid created_at: {}", gitlab_mr.created_at))?;
    let updated_at = iso_to_ms(&gitlab_mr.updated_at)
        .ok_or_else(|| format!("Invalid updated_at: {}", gitlab_mr.updated_at))?;

    let merged_at = gitlab_mr
        .merged_at
        .as_ref()
        .and_then(|s| iso_to_ms(s));

    let closed_at = gitlab_mr
        .closed_at
        .as_ref()
        .and_then(|s| iso_to_ms(s));

    // Prefer merge_user (current) over merged_by (deprecated)
    // Both are bools; draft takes precedence if true, otherwise fall back to work_in_progress
    let is_draft = gitlab_mr.draft || gitlab_mr.work_in_progress;

    // Extract references (CP3-ready)
    let (references_short, references_full) = gitlab_mr
        .references
        .as_ref()
        .map(|r| (Some(r.short.clone()), Some(r.full.clone())))
        .unwrap_or((None, None));

    let merge_request = NormalizedMergeRequest {
        gitlab_id: gitlab_mr.id,
        project_id: local_project_id,
        iid: gitlab_mr.iid,
        title: gitlab_mr.title.clone(),
        description: gitlab_mr.description.clone(),
        state: gitlab_mr.state.clone(),
        draft: is_draft,
        author_username: gitlab_mr.author.username.clone(),
        source_branch: gitlab_mr.source_branch.clone(),
        target_branch: gitlab_mr.target_branch.clone(),
        head_sha: gitlab_mr.sha.clone(),
        references_short,
        references_full,
        detailed_merge_status: gitlab_mr
            .detailed_merge_status
            .clone()
            .or_else(|| gitlab_mr.merge_status_legacy.clone()),
        merge_user_username: gitlab_mr
            .merge_user
            .as_ref()
            .map(|u| u.username.clone())
            .or_else(|| gitlab_mr.merged_by.as_ref().map(|u| u.username.clone())),
        created_at,
        updated_at,
        merged_at,
        closed_at,
        last_seen_at: now_ms(),
        web_url: gitlab_mr.web_url.clone(),
    };

    let label_names = gitlab_mr.labels.clone();

    let assignee_usernames = gitlab_mr
        .assignees
        .iter()
        .map(|u| u.username.clone())
        .collect();

    let reviewer_usernames = gitlab_mr
        .reviewers
        .iter()
        .map(|u| u.username.clone())
        .collect();

    Ok(MergeRequestWithMetadata {
        merge_request,
        label_names,
        assignee_usernames,
        reviewer_usernames,
    })
}

/// Extract labels from GitLab MR (name-only, same as issues).
pub fn extract_labels(gitlab_mr: &GitLabMergeRequest, local_project_id: i64) -> Vec<NormalizedLabel> {
    gitlab_mr
        .labels
        .iter()
        .map(|name| NormalizedLabel {
            project_id: local_project_id,
            name: name.clone(),
        })
        .collect()
}
```

### MR Discussion Transformer

```rust
// src/gitlab/transformers/discussion.rs (additions)

/// Transform GitLab discussion to normalized schema for MR context.
/// Note: The core transform_discussion and transform_notes functions
/// from CP1 are reused. This adds MR-specific handling.
pub fn transform_mr_discussion(
    gitlab_discussion: &GitLabDiscussion,
    local_project_id: i64,
    local_mr_id: i64,
) -> NormalizedDiscussion {
    let note_times: Vec<i64> = gitlab_discussion
        .notes
        .iter()
        .filter_map(|n| iso_to_ms(&n.created_at))
        .collect();

    // Check if any note is resolvable (MR discussions often are)
    let resolvable = gitlab_discussion.notes.iter().any(|n| n.resolvable);
    let resolved = resolvable
        && gitlab_discussion
            .notes
            .iter()
            .all(|n| !n.resolvable || n.resolved);

    NormalizedDiscussion {
        gitlab_discussion_id: gitlab_discussion.id.clone(),
        project_id: local_project_id,
        issue_id: None,               // Not an issue discussion
        merge_request_id: Some(local_mr_id),
        noteable_type: "MergeRequest".to_string(),
        individual_note: gitlab_discussion.individual_note,
        first_note_at: note_times.iter().min().copied(),
        last_note_at: note_times.iter().max().copied(),
        last_seen_at: now_ms(),
        resolvable,
        resolved,
    }
}

/// Transform GitLab notes with DiffNote position extraction.
/// Captures file path and line metadata for code review comments.
///
/// Returns Result to enforce strict timestamp parsing - corrupted timestamps
/// (zero values) would break cursor logic and time-series ordering.
pub fn transform_notes_with_diff_position(
    gitlab_discussion: &GitLabDiscussion,
    local_project_id: i64,
) -> Result<Vec<NormalizedNote>, String> {
    gitlab_discussion
        .notes
        .iter()
        .enumerate()
        .map(|(index, note)| {
            // Strict timestamp parsing - no silent zeroing
            let created_at = iso_to_ms(&note.created_at)
                .ok_or_else(|| format!(
                    "Invalid note.created_at for note {}: {}",
                    note.id, note.created_at
                ))?;
            let updated_at = iso_to_ms(&note.updated_at)
                .ok_or_else(|| format!(
                    "Invalid note.updated_at for note {}: {}",
                    note.id, note.updated_at
                ))?;

            // Extract DiffNote position metadata if present
            // Includes position_type, line_range, and SHA triplet for modern GitLab diff note shapes
            let (old_path, new_path, old_line, new_line, position_type, lr_start, lr_end, base_sha, start_sha, head_sha) = note
                .position
                .as_ref()
                .map(|pos| (
                    pos.old_path.clone(),
                    pos.new_path.clone(),
                    pos.old_line,
                    pos.new_line,
                    pos.position_type.clone(),
                    pos.line_range.as_ref().map(|r| r.start_line),
                    pos.line_range.as_ref().map(|r| r.end_line),
                    pos.base_sha.clone(),
                    pos.start_sha.clone(),
                    pos.head_sha.clone(),
                ))
                .unwrap_or((None, None, None, None, None, None, None, None, None, None));

            Ok(NormalizedNote {
                gitlab_id: note.id,
                project_id: local_project_id,
                note_type: note.note_type.clone(),
                is_system: note.system,
                author_username: note.author.username.clone(),
                body: note.body.clone(),
                created_at,
                updated_at,
                last_seen_at: now_ms(),
                position: index as i32,
                resolvable: note.resolvable,
                resolved: note.resolved,
                resolved_by: note.resolved_by.as_ref().map(|a| a.username.clone()),
                resolved_at: note.resolved_at.as_ref().and_then(|s| iso_to_ms(s)),
                // DiffNote position metadata
                position_old_path: old_path,
                position_new_path: new_path,
                position_old_line: old_line,
                position_new_line: new_line,
                // Extended position metadata for modern GitLab
                position_type,
                position_line_range_start: lr_start,
                position_line_range_end: lr_end,
                // SHA triplet for commit context (CP3-ready)
                position_base_sha: base_sha,
                position_start_sha: start_sha,
                position_head_sha: head_sha,
            })
        })
        .collect()
}
```

---

## GitLab Client Additions

### Pagination with Async Streams

```rust
// src/gitlab/client.rs (additions)

/// A page of merge requests with pagination metadata.
#[derive(Debug)]
pub struct MergeRequestPage {
    pub items: Vec<GitLabMergeRequest>,
    pub next_page: Option<u32>,
    pub is_last_page: bool,
}

impl GitLabClient {
    /// Parse Link header to extract rel="next" URL (RFC 8288).
    /// Returns Some(url) if a next page link exists, None otherwise.
    fn parse_link_header_next(headers: &reqwest::header::HeaderMap) -> Option<String> {
        headers
            .get("link")
            .and_then(|v| v.to_str().ok())
            .and_then(|link_str| {
                // Parse Link header format: <url>; rel="next", <url>; rel="last"
                for part in link_str.split(',') {
                    let part = part.trim();
                    if part.contains("rel=\"next\"") || part.contains("rel=next") {
                        // Extract URL between < and >
                        if let Some(start) = part.find('<') {
                            if let Some(end) = part.find('>') {
                                return Some(part[start + 1..end].to_string());
                            }
                        }
                    }
                }
                None
            })
    }

    /// Fetch a single page of merge requests for a project.
    /// Returns the items plus pagination metadata for page-aware cursor updates.
    pub async fn fetch_merge_requests_page(
        &self,
        gitlab_project_id: i64,
        updated_after: Option<i64>,
        cursor_rewind_seconds: u32,
        page: u32,
        per_page: u32,
    ) -> Result<MergeRequestPage> {
        let mut params = vec![
            ("scope", "all".to_string()),
            ("state", "all".to_string()),
            ("order_by", "updated_at".to_string()),
            ("sort", "asc".to_string()),
            ("per_page", per_page.to_string()),
            ("page", page.to_string()),
        ];

        if let Some(ts) = updated_after {
            // Apply cursor rewind for safety, clamping to 0 to avoid underflow
            let rewind_ms = (cursor_rewind_seconds as i64) * 1000;
            let rewound = (ts - rewind_ms).max(0);
            if let Some(dt) = chrono::DateTime::from_timestamp_millis(rewound) {
                params.push(("updated_after", dt.to_rfc3339()));
            }
        }

        let (items, headers) = self
            .request_with_headers::<Vec<GitLabMergeRequest>>(
                &format!("/api/v4/projects/{gitlab_project_id}/merge_requests"),
                &params,
            )
            .await?;

        // Parse pagination with fallback chain:
        // 1. Link header (most reliable, RFC 8288 compliant)
        // 2. x-next-page header (GitLab-specific)
        // 3. Full page heuristic (fallback for proxies that strip headers)
        let link_next = parse_link_header_next(&headers);
        let x_next_page = headers
            .get("x-next-page")
            .and_then(|v| v.to_str().ok())
            .and_then(|s| s.parse::<u32>().ok());

        let next_page = match (link_next, x_next_page, items.len() as u32 == per_page) {
            (Some(_), _, _) => Some(page + 1),     // Link header present: continue
            (None, Some(np), _) => Some(np),       // x-next-page present: use it
            (None, None, true) => Some(page + 1),  // Full page, no headers: try next
            (None, None, false) => None,           // Partial page: we're done
        };

        let is_last_page = items.is_empty() || next_page.is_none();

        Ok(MergeRequestPage {
            items,
            next_page,
            is_last_page,
        })
    }

    /// Paginate through merge requests for a project.
    /// Returns a stream of MRs that handles pagination automatically.
    /// Note: For page-aware cursor updates, prefer fetch_merge_requests_page directly.
    pub fn paginate_merge_requests(
        &self,
        gitlab_project_id: i64,
        updated_after: Option<i64>,
        cursor_rewind_seconds: u32,
    ) -> Pin<Box<dyn Stream<Item = Result<GitLabMergeRequest>> + Send + '_>> {
        Box::pin(async_stream::try_stream! {
            let mut page = 1u32;
            let per_page = 100u32;

            loop {
                let page_result = self.fetch_merge_requests_page(
                    gitlab_project_id,
                    updated_after,
                    cursor_rewind_seconds,
                    page,
                    per_page,
                ).await?;

                for mr in page_result.items {
                    yield mr;
                }

                if page_result.is_last_page {
                    break;
                }

                if let Some(np) = page_result.next_page {
                    page = np;
                } else {
                    break;
                }
            }
        })
    }

    /// Paginate through discussions for a merge request.
    pub fn paginate_mr_discussions(
        &self,
        gitlab_project_id: i64,
        mr_iid: i64,
    ) -> Pin<Box<dyn Stream<Item = Result<GitLabDiscussion>> + Send + '_>> {
        Box::pin(async_stream::try_stream! {
            let mut page = 1u32;
            let per_page = 100u32;

            loop {
                let params = vec![
                    ("per_page", per_page.to_string()),
                    ("page", page.to_string()),
                ];

                let (discussions, headers) = self
                    .request_with_headers::<Vec<GitLabDiscussion>>(
                        &format!("/api/v4/projects/{gitlab_project_id}/merge_requests/{mr_iid}/discussions"),
                        &params,
                    )
                    .await?;

                for discussion in discussions.iter() {
                    yield discussion.clone();
                }

                // Robust fallback if pagination headers are missing
                let next_page_hdr = headers
                    .get("x-next-page")
                    .and_then(|v| v.to_str().ok())
                    .and_then(|s| s.parse::<u32>().ok());

                let next_page = match (next_page_hdr, discussions.len() as u32 == per_page) {
                    (Some(np), _) => Some(np),         // Header present: trust it
                    (None, true) => Some(page + 1),    // Full page, no header: try next
                    (None, false) => None,             // Partial page: we're done
                };

                match next_page {
                    Some(np) if !discussions.is_empty() => page = np,
                    _ => break,
                }
            }
        })
    }
}
```

---

## Orchestration: Dependent Discussion Sync

### Canonical Pattern (CP2)

When `gi ingest --type=merge_requests` runs, it follows this orchestration (mirroring CP1 pattern):

1. **Ingest merge requests** (cursor-based, with incremental cursor updates per page)

2. **Select MRs needing discussion sync (DB-driven)** - After MR ingestion completes, query:
   ```sql
   SELECT id, iid, updated_at
   FROM merge_requests
   WHERE project_id = ?
     AND (discussions_synced_for_updated_at IS NULL
          OR updated_at > discussions_synced_for_updated_at)
   ORDER BY updated_at ASC;
   ```
   This is more scalable and debuggable than in-memory collection. The DB is the source of truth.

3. **Execute discussion sync** with bounded concurrency (`dependent_concurrency` from config)

4. **Update watermark** - After each MR's discussions are successfully ingested *with no partial failures*:
   ```sql
   UPDATE merge_requests SET discussions_synced_for_updated_at = ? WHERE id = ?
   ```

**Invariant:** A rerun MUST NOT refetch discussions for MRs whose `updated_at` has not advanced, even with cursor rewind. Watermark is NOT advanced if any failure occurs (HTTP pagination failure OR note parse failure).

---

## Ingestion Logic

### MR Ingestion

```rust
// src/ingestion/merge_requests.rs

use rusqlite::Connection;
use tracing::{debug, info};

use crate::core::config::Config;
use crate::core::error::Result;
use crate::core::payloads::store_payload;
use crate::core::time::now_ms;
use crate::gitlab::client::GitLabClient;
use crate::gitlab::transformers::merge_request::{transform_merge_request, extract_labels};

/// Result of MR ingestion.
#[derive(Debug, Default)]
pub struct IngestMergeRequestsResult {
    pub fetched: usize,
    pub upserted: usize,
    pub labels_created: usize,
    pub assignees_linked: usize,
    pub reviewers_linked: usize,
    // Discussion sync is DB-driven, not in-memory collection.
    // Use query: SELECT id, iid FROM merge_requests WHERE updated_at > discussions_synced_for_updated_at
    // This avoids memory growth for large projects.
}

/// Info needed to sync discussions for an MR.
#[derive(Debug, Clone)]
pub struct MrForDiscussionSync {
    pub local_mr_id: i64,
    pub iid: i64,
    pub updated_at: i64,
}

/// Result of upserting a merge request, including previous sync state.
#[derive(Debug)]
pub struct UpsertMergeRequestResult {
    pub local_mr_id: i64,
    pub changes: usize,
    pub previous_discussions_synced_at: Option<i64>,
}

/// Ingest merge requests for a project using page-based cursor updates.
/// Discussion sync eligibility is determined via DB query AFTER ingestion completes.
pub async fn ingest_merge_requests(
    conn: &Connection,
    client: &GitLabClient,
    config: &Config,
    project_id: i64,           // Local DB project ID
    gitlab_project_id: i64,    // GitLab project ID
    full_sync: bool,           // Reset cursor if true
) -> Result<IngestMergeRequestsResult> {
    let mut result = IngestMergeRequestsResult::default();

    // Reset cursor if full sync requested
    if full_sync {
        reset_cursor(conn, project_id, "merge_requests")?;
        // Also reset discussion watermarks to force re-fetch of all discussions
        // This ensures --full truly fetches everything, not just MRs
        reset_discussion_watermarks(conn, project_id)?;
    }

    // Get current cursor
    let cursor = get_cursor(conn, project_id)?;
    let cursor_updated_at = cursor.0;
    let cursor_gitlab_id = cursor.1;

    let mut last_updated_at: Option<i64> = None;
    let mut last_gitlab_id: Option<i64> = None;
    let mut page = 1u32;
    let per_page = 100u32;

    // Page-based iteration for proper cursor boundary tracking
    loop {
        let page_result = client.fetch_merge_requests_page(
            gitlab_project_id,
            cursor_updated_at,
            config.sync.cursor_rewind_seconds,
            page,
            per_page,
        ).await?;

        if page_result.items.is_empty() {
            break;
        }

        for mr in &page_result.items {
            result.fetched += 1;

            let mr_updated_at = crate::core::time::iso_to_ms(&mr.updated_at)
                .ok_or_else(|| crate::core::error::GiError::ParseError {
                    field: "updated_at".to_string(),
                    value: mr.updated_at.clone(),
                })?;

            // Apply cursor filtering for tuple semantics
            if let (Some(cursor_ts), Some(cursor_id)) = (cursor_updated_at, cursor_gitlab_id) {
                if mr_updated_at < cursor_ts {
                    continue;
                }
                if mr_updated_at == cursor_ts && mr.id <= cursor_id {
                    continue;
                }
            }

            // Begin transaction for this MR (atomicity + performance)
            let tx = conn.unchecked_transaction()?;

            // Store raw payload
            let payload_id = store_payload(
                &tx,
                project_id,
                "merge_request",
                &mr.id.to_string(),
                &mr,
                config.storage.compress_raw_payloads,
            )?;

            // Transform and upsert MR
            let transformed = transform_merge_request(&mr, project_id)
                .map_err(|e| crate::core::error::GiError::ParseError {
                    field: "merge_request".to_string(),
                    value: e,
                })?;

            let upsert_result = upsert_merge_request(
                &tx,
                &transformed.merge_request,
                payload_id,
            )?;

            if upsert_result.changes > 0 {
                result.upserted += 1;
            }

            let local_mr_id = upsert_result.local_mr_id;

            // Discussion sync eligibility is determined AFTER ingestion via DB query:
            // SELECT id, iid FROM merge_requests WHERE updated_at > discussions_synced_for_updated_at
            // This avoids memory growth for large projects.

            // Clear existing label links (ensures removed labels are unlinked)
            clear_mr_labels(&tx, local_mr_id)?;

            // Extract and upsert labels (name-only, same as issues)
            let labels = extract_labels(&mr, project_id);
            for label in &labels {
                let created = upsert_label(&tx, label)?;
                if created {
                    result.labels_created += 1;
                }

                // Link MR to label
                let label_id = get_label_id(&tx, project_id, &label.name)?;
                link_mr_label(&tx, local_mr_id, label_id)?;
            }

            // Clear and relink assignees
            clear_mr_assignees(&tx, local_mr_id)?;
            for username in &transformed.assignee_usernames {
                upsert_mr_assignee(&tx, local_mr_id, username)?;
                result.assignees_linked += 1;
            }

            // Clear and relink reviewers
            clear_mr_reviewers(&tx, local_mr_id)?;
            for username in &transformed.reviewer_usernames {
                upsert_mr_reviewer(&tx, local_mr_id, username)?;
                result.reviewers_linked += 1;
            }

            tx.commit()?;

            // Track for cursor update
            last_updated_at = Some(mr_updated_at);
            last_gitlab_id = Some(mr.id);
        }

        // Page-boundary cursor flush (not based on fetched % 100)
        // This ensures cursor reflects actual processed page boundaries
        if let (Some(updated_at), Some(gitlab_id)) = (last_updated_at, last_gitlab_id) {
            update_cursor(conn, project_id, "merge_requests", updated_at, gitlab_id)?;
        }

        // Check for more pages
        if page_result.is_last_page {
            break;
        }

        match page_result.next_page {
            Some(np) => page = np,
            None => break,
        }
    }

    // Final cursor update (in case we exited mid-loop)
    if let (Some(updated_at), Some(gitlab_id)) = (last_updated_at, last_gitlab_id) {
        update_cursor(conn, project_id, "merge_requests", updated_at, gitlab_id)?;
    }

    info!(
        project_id,
        fetched = result.fetched,
        upserted = result.upserted,
        labels_created = result.labels_created,
        assignees_linked = result.assignees_linked,
        reviewers_linked = result.reviewers_linked,
        "MR ingestion complete"
    );

    Ok(result)
}

/// Upsert a merge request and return sync state for inline discussion decision.
fn upsert_merge_request(
    conn: &Connection,
    mr: &NormalizedMergeRequest,
    payload_id: Option<i64>,
) -> Result<UpsertMergeRequestResult> {
    // Perform upsert
    let changes = conn.execute(
        "INSERT INTO merge_requests (
            gitlab_id, project_id, iid, title, description, state, draft,
            author_username, source_branch, target_branch,
            head_sha, references_short, references_full,
            detailed_merge_status, merge_user_username,
            created_at, updated_at, merged_at, closed_at, last_seen_at,
            web_url, raw_payload_id
        ) VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?9, ?10, ?11, ?12, ?13, ?14, ?15, ?16, ?17, ?18, ?19, ?20, ?21, ?22)
        ON CONFLICT(gitlab_id) DO UPDATE SET
            title = excluded.title,
            description = excluded.description,
            state = excluded.state,
            draft = excluded.draft,
            head_sha = excluded.head_sha,
            references_short = excluded.references_short,
            references_full = excluded.references_full,
            detailed_merge_status = excluded.detailed_merge_status,
            merge_user_username = excluded.merge_user_username,
            updated_at = excluded.updated_at,
            merged_at = excluded.merged_at,
            closed_at = excluded.closed_at,
            last_seen_at = excluded.last_seen_at,
            raw_payload_id = excluded.raw_payload_id",
        rusqlite::params![
            mr.gitlab_id, mr.project_id, mr.iid, mr.title, mr.description,
            mr.state, mr.draft as i32,
            mr.author_username, mr.source_branch, mr.target_branch,
            mr.head_sha, mr.references_short, mr.references_full,
            mr.detailed_merge_status, mr.merge_user_username,
            mr.created_at, mr.updated_at, mr.merged_at, mr.closed_at, mr.last_seen_at,
            mr.web_url, payload_id,
        ],
    )?;

    // Get local ID (either existing or newly inserted)
    let local_mr_id = conn.query_row(
        "SELECT id FROM merge_requests WHERE gitlab_id = ?",
        [mr.gitlab_id],
        |row| row.get(0),
    ).expect("MR must exist after upsert");

    Ok(UpsertMergeRequestResult {
        local_mr_id,
        changes,
        previous_discussions_synced_at: None,
    })
}

// Database helper functions follow the same pattern as issues.rs
// (get_cursor, update_cursor, reset_cursor, upsert_merge_request, etc.)

/// Reset discussion watermarks for all MRs in a project.
/// Called when --full sync is requested to force re-fetch of all discussions.
fn reset_discussion_watermarks(conn: &Connection, project_id: i64) -> Result<()> {
    conn.execute(
        "UPDATE merge_requests
         SET discussions_synced_for_updated_at = NULL,
             discussions_sync_attempts = 0,
             discussions_sync_last_error = NULL
         WHERE project_id = ?",
        [project_id],
    )?;
    Ok(())
}

/// Record sync health telemetry for debugging failed discussion syncs.
fn record_sync_health_error(conn: &Connection, mr_id: i64, error: &str) -> Result<()> {
    conn.execute(
        "UPDATE merge_requests SET
            discussions_sync_last_attempt_at = ?,
            discussions_sync_attempts = COALESCE(discussions_sync_attempts, 0) + 1,
            discussions_sync_last_error = ?
         WHERE id = ?",
        rusqlite::params![now_ms(), error, mr_id],
    )?;
    Ok(())
}

/// Clear sync health error on successful sync.
fn clear_sync_health_error(conn: &Connection, mr_id: i64) -> Result<()> {
    conn.execute(
        "UPDATE merge_requests SET
            discussions_sync_last_attempt_at = ?,
            discussions_sync_attempts = 0,
            discussions_sync_last_error = NULL
         WHERE id = ?",
        rusqlite::params![now_ms(), mr_id],
    )?;
    Ok(())
}
```

### MR Discussion Ingestion

```rust
// src/ingestion/mr_discussions.rs

use futures::StreamExt;
use rusqlite::Connection;
use tracing::{debug, warn};

use crate::core::config::Config;
use crate::core::error::Result;
use crate::core::payloads::store_payload;
use crate::core::time::now_ms;
use crate::gitlab::client::GitLabClient;
use crate::gitlab::transformers::discussion::{
    transform_mr_discussion,
    transform_notes_with_diff_position,
};

/// Result of discussion ingestion for a single MR.
#[derive(Debug, Default)]
pub struct IngestMrDiscussionsResult {
    pub discussions_fetched: usize,
    pub discussions_upserted: usize,
    pub notes_upserted: usize,
    pub notes_skipped_bad_timestamp: usize,
    pub system_notes_count: usize,
    pub diffnotes_count: usize,
    pub pagination_succeeded: bool,
}

/// Ingest discussions for a single MR.
/// Called only when mr.updated_at > discussions_synced_for_updated_at.
///
/// CRITICAL INVARIANTS:
/// 1. Watermark is ONLY advanced if pagination completes successfully AND all notes parse successfully.
/// 2. Notes are parsed BEFORE any destructive DB operations to prevent data loss.
/// 3. Stale discussions are removed via last_seen_at sweep (not in-memory ID collection).
pub async fn ingest_mr_discussions(
    conn: &Connection,
    client: &GitLabClient,
    config: &Config,
    project_id: i64,
    gitlab_project_id: i64,
    mr_iid: i64,
    local_mr_id: i64,
    mr_updated_at: i64,
) -> Result<IngestMrDiscussionsResult> {
    let mut result = IngestMrDiscussionsResult {
        pagination_succeeded: true, // Assume success, set false on error
        ..Default::default()
    };

    // Record sync start time for last_seen_at sweep
    let run_seen_at = now_ms();

    let mut stream = client.paginate_mr_discussions(gitlab_project_id, mr_iid);

    while let Some(discussion_result) = stream.next().await {
        let discussion = match discussion_result {
            Ok(d) => d,
            Err(e) => {
                // Log error and mark pagination as failed
                warn!(
                    project_id,
                    mr_iid,
                    error = %e,
                    "Error fetching MR discussion page"
                );
                result.pagination_succeeded = false;
                break;
            }
        };
        result.discussions_fetched += 1;

        // CRITICAL: Parse/transform notes BEFORE any destructive DB operations.
        // If parsing fails, we preserve prior data and treat as partial failure (no watermark advance).
        let notes = match transform_notes_with_diff_position(&discussion, project_id) {
            Ok(notes) => notes,
            Err(e) => {
                warn!(
                    project_id,
                    mr_iid,
                    discussion_id = %discussion.id,
                    error = %e,
                    "Note transform failed; preserving existing notes; MR watermark will NOT advance"
                );
                result.notes_skipped_bad_timestamp += discussion.notes.len();
                result.pagination_succeeded = false;
                continue;
            }
        };

        // Begin transaction for this discussion (only AFTER parsing succeeded)
        let tx = conn.unchecked_transaction()?;

        // Store raw payload for discussion
        let discussion_payload_id = store_payload(
            &tx,
            project_id,
            "discussion",
            &discussion.id,
            &discussion,
            config.storage.compress_raw_payloads,
        )?;

        // Transform and upsert discussion (MR context) with run_seen_at timestamp
        let mut normalized = transform_mr_discussion(&discussion, project_id, local_mr_id);
        normalized.last_seen_at = run_seen_at;
        upsert_discussion(&tx, &normalized, discussion_payload_id)?;
        result.discussions_upserted += 1;

        // Get local discussion ID
        let local_discussion_id = get_local_discussion_id(&tx, project_id, &discussion.id)?;

        // Upsert notes instead of delete-all-then-insert
        // This reduces write amplification and preserves any local metadata
        for note in &notes {
            // Selective raw payload storage for notes:
            // - Store for DiffNotes (position metadata useful for file-context queries)
            // - Store for non-system notes (user-generated content)
            // - Skip for system notes (numerous, low-value, discussion payload has them)
            let should_store_note_payload =
                !note.is_system() ||
                note.position_new_path().is_some() ||
                note.position_old_path().is_some();

            let note_payload_id = if should_store_note_payload {
                let gitlab_note = discussion.notes.iter().find(|n| n.id() == note.gitlab_id());
                if let Some(gn) = gitlab_note {
                    store_payload(
                        &tx,
                        project_id,
                        "note",
                        &note.gitlab_id().to_string(),
                        gn,
                        config.storage.compress_raw_payloads,
                    )?
                } else {
                    None
                }
            } else {
                None
            };

            // Upsert note with run_seen_at timestamp for sweep
            upsert_note(&tx, local_discussion_id, note, note_payload_id, run_seen_at)?;
            result.notes_upserted += 1;

            if note.is_system() {
                result.system_notes_count += 1;
            }

            // Count DiffNotes
            if note.position_new_path().is_some() || note.position_old_path().is_some() {
                result.diffnotes_count += 1;
            }
        }

        tx.commit()?;
    }

    // Remove stale discussions AND notes via last_seen_at sweep (only if pagination completed successfully)
    // This is simpler and more scalable than collecting seen IDs in memory
    if result.pagination_succeeded {
        // Sweep stale discussions
        conn.execute(
            "DELETE FROM discussions
             WHERE project_id = ? AND merge_request_id = ?
               AND last_seen_at < ?",
            rusqlite::params![project_id, local_mr_id, run_seen_at],
        )?;

        // Sweep stale notes for this MR's discussions
        // Notes inherit staleness from their discussion, but we also sweep at note level
        // for cases where notes are removed from an existing discussion
        conn.execute(
            "DELETE FROM notes
             WHERE discussion_id IN (
               SELECT id FROM discussions
               WHERE project_id = ? AND merge_request_id = ?
             )
             AND last_seen_at < ?",
            rusqlite::params![project_id, local_mr_id, run_seen_at],
        )?;
    }

    // CRITICAL: Only advance watermark if pagination succeeded completely AND no parse failures.
    // If we advance on partial failure, we permanently lose data for this MR version.
    if result.pagination_succeeded {
        mark_discussions_synced(conn, local_mr_id, mr_updated_at)?;
        // Clear sync health error on success
        clear_sync_health_error(conn, local_mr_id)?;
    } else {
        // Record sync health telemetry for debugging
        record_sync_health_error(
            conn,
            local_mr_id,
            "Pagination incomplete or parse failure; will retry on next sync"
        )?;
        warn!(
            project_id,
            mr_iid,
            local_mr_id,
            "Discussion sync incomplete; watermark NOT advanced (will retry on next sync)"
        );
    }

    debug!(
        project_id,
        mr_iid,
        discussions = result.discussions_fetched,
        notes = result.notes_upserted,
        diffnotes = result.diffnotes_count,
        pagination_succeeded = result.pagination_succeeded,
        "MR discussions ingested"
    );

    Ok(result)
}

fn mark_discussions_synced(conn: &Connection, mr_id: i64, mr_updated_at: i64) -> Result<()> {
    conn.execute(
        "UPDATE merge_requests SET discussions_synced_for_updated_at = ? WHERE id = ?",
        rusqlite::params![mr_updated_at, mr_id],
    )?;
    Ok(())
}

/// Record sync health telemetry for debugging failed discussion syncs.
fn record_sync_health_error(conn: &Connection, mr_id: i64, error: &str) -> Result<()> {
    conn.execute(
        "UPDATE merge_requests SET
            discussions_sync_last_attempt_at = ?,
            discussions_sync_attempts = COALESCE(discussions_sync_attempts, 0) + 1,
            discussions_sync_last_error = ?
         WHERE id = ?",
        rusqlite::params![now_ms(), error, mr_id],
    )?;
    Ok(())
}

/// Clear sync health error on successful sync.
fn clear_sync_health_error(conn: &Connection, mr_id: i64) -> Result<()> {
    conn.execute(
        "UPDATE merge_requests SET
            discussions_sync_last_attempt_at = ?,
            discussions_sync_attempts = 0,
            discussions_sync_last_error = NULL
         WHERE id = ?",
        rusqlite::params![now_ms(), mr_id],
    )?;
    Ok(())
}
```

---

## CLI Commands

### `gi ingest --type=merge_requests`

Fetch and store all MRs from configured projects.

**Implementation Updates:**

```rust
// src/cli/commands/ingest.rs

/// Run the ingest command.
pub async fn run_ingest(
    config: &Config,
    resource_type: &str,
    project_filter: Option<&str>,
    force: bool,
    full: bool,
) -> Result<IngestResult> {
    match resource_type {
        "issues" => {
            // Existing CP1 implementation
            run_issue_ingest(config, project_filter, force, full).await
        }
        "merge_requests" => {
            // NEW: CP2 implementation
            run_mr_ingest(config, project_filter, force, full).await
        }
        _ => Err(GiError::InvalidArgument {
            name: "type".to_string(),
            value: resource_type.to_string(),
            expected: "issues or merge_requests".to_string(),
        }),
    }
}
```

**Output:**
```
Ingesting merge requests...

  group/project-one: 567 MRs fetched, 12 new labels, 89 assignees, 45 reviewers

Fetching discussions (123 MRs with updates)...

  group/project-one: 123 MRs -> 456 discussions, 1,234 notes (89 DiffNotes)

Total: 567 MRs, 456 discussions, 1,234 notes (excluding 2,345 system notes)
Skipped discussion sync for 444 unchanged MRs.
```

### `gi list mrs`

**Output:**
```
Merge Requests (showing 20 of 1,234)

  !847  Refactor auth to use JWT tokens           merged   @johndoe   main <- feature/jwt   3 days ago
  !846  Fix memory leak in websocket handler      opened   @janedoe   main <- fix/websocket 5 days ago
  !845  [DRAFT] Add dark mode CSS variables       opened   @bobsmith  main <- ui/dark-mode  1 week ago
  !844  Update dependencies                       closed   @alice     main <- chore/deps    1 week ago
  ...
```

**Filter Options (same pattern as issues):**
- `--state [opened|merged|closed|locked|all]`
- `--draft` (MR-specific: show only draft MRs)
- `--no-draft` (MR-specific: exclude draft MRs)
- `--author <username>`
- `--assignee <username>`
- `--reviewer <username>` (MR-specific)
- `--target-branch <branch>` (MR-specific)
- `--source-branch <branch>` (MR-specific)
- `--label <name>` (repeatable)
- `--project <path>`
- `--limit <n>`
- `--since <duration|date>`
- `--json`
- `--open` (open in browser)

### `gi show mr <iid>`

**Output:**
```
Merge Request !847: Refactor auth to use JWT tokens
================================================================================

Project:        group/project-one
State:          merged
Draft:          No
Author:         @johndoe
Assignees:      @janedoe, @bobsmith
Reviewers:      @alice, @charlie
Source:         feature/jwt
Target:         main
Merge Status:   mergeable (detailed_merge_status)
Merged By:      @alice
Merged At:      2024-03-20 14:30:00
Created:        2024-03-15
Updated:        2024-03-20
Labels:         enhancement, auth, reviewed
URL:            https://gitlab.example.com/group/project-one/-/merge_requests/847

Description:
  Moving away from session cookies to JWT-based authentication for better
  mobile client support and API consumption...

Discussions (8):

  @janedoe (2024-03-16) [src/auth/jwt.ts:45]:
    Should we use a separate signing key for refresh tokens?

    @johndoe (2024-03-16):
      Good point. I'll add a separate key with rotation support.

  @alice (2024-03-18) [RESOLVED]:
    Looks good! Just one nit about the token expiry constant.
```

### `gi count mrs`

**Output:**
```
Merge Requests: 1,234
  opened: 89
  merged: 1,045
  closed: 100
```

### `gi count discussions --type=mr`

**Output:**
```
MR Discussions: 4,567
```

### `gi count notes --type=mr`

**Output:**
```
MR Notes: 12,345 (excluding 2,345 system notes)
DiffNotes: 3,456 (with file position metadata)
```

---

## Automated Tests

### Unit Tests

```rust
// tests/mr_transformer_tests.rs

#[cfg(test)]
mod tests {
    use gi::gitlab::transformers::merge_request::*;
    use gi::gitlab::types::*;

    #[test]
    fn transforms_gitlab_mr_to_normalized_schema() { /* ... */ }

    #[test]
    fn extracts_labels_from_mr_payloads() { /* ... */ }

    #[test]
    fn extracts_assignees_from_mr_payloads() { /* ... */ }

    #[test]
    fn extracts_reviewers_from_mr_payloads() { /* ... */ }

    #[test]
    fn handles_missing_optional_fields_gracefully() { /* ... */ }

    #[test]
    fn converts_merged_at_and_closed_at_timestamps() { /* ... */ }

    #[test]
    fn handles_mrs_with_no_labels_assignees_reviewers() { /* ... */ }
}
```

```rust
// tests/diffnote_tests.rs

#[cfg(test)]
mod tests {
    use gi::gitlab::transformers::discussion::*;

    #[test]
    fn extracts_diffnote_position_metadata() { /* ... */ }

    #[test]
    fn handles_notes_without_position() { /* ... */ }

    #[test]
    fn extracts_old_path_and_new_path() { /* ... */ }

    #[test]
    fn extracts_line_numbers() { /* ... */ }

    #[test]
    fn handles_renamed_files_in_diffnote() { /* ... */ }
}
```

```rust
// tests/mr_discussion_tests.rs

#[cfg(test)]
mod tests {
    #[test]
    fn transforms_mr_discussion_with_correct_noteable_type() { /* ... */ }

    #[test]
    fn computes_resolved_state_for_mr_discussions() { /* ... */ }

    #[test]
    fn links_discussion_to_merge_request_id() { /* ... */ }

    #[test]
    fn handles_individual_note_mr_discussions() { /* ... */ }
}
```

### Integration Tests

```rust
// tests/mr_ingestion_tests.rs

#[cfg(test)]
mod tests {
    use tempfile::TempDir;
    use wiremock::{MockServer, Mock, ResponseTemplate};
    use wiremock::matchers::{method, path_regex};

    #[tokio::test]
    async fn inserts_mrs_into_database() { /* ... */ }

    #[tokio::test]
    async fn creates_labels_from_mr_payloads() { /* ... */ }

    #[tokio::test]
    async fn links_mrs_to_labels_via_junction_table() { /* ... */ }

    #[tokio::test]
    async fn removes_stale_label_links_on_resync() { /* ... */ }

    #[tokio::test]
    async fn creates_assignee_links() { /* ... */ }

    #[tokio::test]
    async fn creates_reviewer_links() { /* ... */ }

    #[tokio::test]
    async fn stores_raw_payload_for_each_mr() { /* ... */ }

    #[tokio::test]
    async fn updates_cursor_at_page_boundaries() { /* ... */ }

    #[tokio::test]
    async fn resumes_from_cursor_on_subsequent_runs() { /* ... */ }

    #[tokio::test]
    async fn full_sync_resets_cursor() { /* ... */ }

    #[tokio::test]
    async fn full_sync_resets_discussion_watermarks() {
        // Setup: Create MR with discussions_synced_for_updated_at set
        // Action: Run ingest with --full flag
        // Assert: discussions_synced_for_updated_at is NULL after sync
        // Assert: Discussions are re-fetched for this MR
    }

    #[tokio::test]
    async fn handles_mrs_with_no_labels_assignees_reviewers() { /* ... */ }

    #[tokio::test]
    async fn upserts_existing_mrs_on_refetch() { /* ... */ }

    #[tokio::test]
    async fn skips_discussion_refetch_for_unchanged_mrs() { /* ... */ }

    #[tokio::test]
    async fn captures_diffnote_position_metadata() { /* ... */ }

    #[tokio::test]
    async fn removes_stale_discussions_after_successful_pagination() { /* ... */ }

    #[tokio::test]
    async fn captures_draft_status_correctly() { /* ... */ }

    #[tokio::test]
    async fn uses_detailed_merge_status_over_deprecated_field() { /* ... */ }

    #[tokio::test]
    async fn uses_merge_user_over_deprecated_merged_by() { /* ... */ }

    // CRITICAL: Verify preference ordering when BOTH deprecated and current fields are present.
    // GitLab may return both for backward compatibility, and we must always prefer the current field.
    #[tokio::test]
    async fn prefers_detailed_merge_status_when_both_fields_present() {
        // Setup: MR payload with BOTH detailed_merge_status AND merge_status
        // Mock: Return MR with detailed_merge_status="discussions_not_resolved" AND merge_status="can_be_merged"
        // Assert: detailed_merge_status in DB is "discussions_not_resolved" (not "can_be_merged")
    }

    #[tokio::test]
    async fn prefers_merge_user_when_both_fields_present() {
        // Setup: MR payload with BOTH merge_user AND merged_by
        // Mock: Return MR with merge_user.username="alice" AND merged_by.username="bob"
        // Assert: merge_user_username in DB is "alice" (not "bob")
    }

    #[tokio::test]
    async fn prefers_draft_when_both_draft_and_work_in_progress_present() {
        // Setup: MR payload with BOTH draft=false AND work_in_progress=true
        // Mock: Return MR with draft=false, work_in_progress=true
        // Assert: draft in DB is true (work_in_progress fallback applies when draft is false)
        // Note: This tests the OR semantics: draft || work_in_progress
    }

    // CRITICAL: This test ensures we don't permanently lose data on partial pagination failures.
    // If pagination fails mid-way, the watermark must NOT advance, so the next sync
    // will retry fetching discussions for this MR.
    #[tokio::test]
    async fn does_not_advance_discussion_watermark_on_partial_failure() {
        // Setup: Create MR with updated_at > discussions_synced_for_updated_at
        // Mock: Page 1 of discussions returns successfully
        // Mock: Page 2 returns 500 Internal Server Error
        // Assert: discussions_synced_for_updated_at is unchanged (not advanced)
        // Assert: Re-running ingest will retry this MR's discussions
    }

    // CRITICAL: This test ensures we don't lose data when note parsing fails.
    // If any note in a discussion has an invalid timestamp, we must NOT delete
    // existing notes, and we must NOT advance the watermark.
    #[tokio::test]
    async fn does_not_advance_discussion_watermark_on_note_parse_failure() {
        // Setup: Create MR with existing discussion and valid notes
        // Mock: Return discussion with one note having invalid created_at
        // Assert: Original 3 notes are preserved
        // Assert: No partial replacement occurred
    }

    // Verify atomic note replacement: parsing happens BEFORE deletion
    #[tokio::test]
    async fn atomic_note_replacement_preserves_data_on_parse_failure() {
        // Setup: Discussion with 3 existing notes
        // Mock: Return updated discussion where note 2 has invalid timestamp
        // Assert: Original 3 notes are preserved
        // Assert: No partial replacement occurred
    }

    #[tokio::test]
    async fn uses_work_in_progress_when_draft_not_present() { /* ... */ }

    #[tokio::test]
    async fn handles_locked_mr_state() { /* ... */ }

    #[tokio::test]
    async fn pagination_continues_when_headers_missing_but_full_page_returned() { /* ... */ }

    #[tokio::test]
    async fn does_not_store_raw_payload_for_system_notes_without_position() { /* ... */ }

    #[tokio::test]
    async fn stores_raw_payload_for_diffnotes_even_if_system() { /* ... */ }

    #[tokio::test]
    async fn captures_position_type_and_line_range_for_diffnotes() { /* ... */ }
}
```

---

## Manual Smoke Tests

| Command | Expected Output | Pass Criteria |
|---------|-----------------|---------------|
| `gi ingest --type=merge_requests` | Progress bar, final count | Completes without error |
| `gi list mrs --limit=10` | Table of 10 MRs | Shows iid, title, state, author, branches, [DRAFT] prefix |
| `gi list mrs --project=group/project-one` | Filtered list | Only shows MRs from that project |
| `gi list mrs --state=merged` | Filtered by state | Only merged MRs shown |
| `gi list mrs --state=locked` | Filtered by state | Only locked MRs shown (merge in progress) |
| `gi list mrs --draft` | Filtered by draft | Only draft MRs shown |
| `gi list mrs --no-draft` | Excludes drafts | No draft MRs shown |
| `gi list mrs --reviewer=username` | Filtered by reviewer | Only MRs with that reviewer |
| `gi list mrs --target-branch=main` | Filtered by target | Only MRs targeting main |
| `gi count mrs` | `Merge Requests: N` | Count matches GitLab UI |
| `gi show mr 123` | MR detail view | Shows title, description, branches, discussions, detailed_merge_status |
| `gi show mr 123` (draft MR) | MR detail view | Shows `Draft: Yes` |
| `gi show mr 123` (ambiguous) | Prompt or error | Asks for `--project` clarification |
| `gi count discussions --type=mr` | `MR Discussions: N` | Non-zero count |
| `gi count notes --type=mr` | `MR Notes: N (excluding M system)` | Non-zero count, shows DiffNote count |
| `gi sync-status` | Shows MR cursor positions | MR cursors visible alongside issue cursors |
| `gi ingest --type=merge_requests` (re-run) | `0 new MRs` | Cursor is current |
| `gi ingest --type=merge_requests` (re-run) | `Skipped discussion sync for N unchanged MRs` | Watermark works |
| `gi ingest --type=merge_requests` (concurrent) | Lock error | Second run fails with clear message |
| `gi ingest --type=merge_requests --full` | Full re-sync | Resets cursor, fetches everything |
| Remove label from MR in GitLab, re-sync | Label link removed | Junction table reflects GitLab state |
| Add reviewer in GitLab, re-sync | Reviewer link added | Junction table updated |

---

## Data Integrity Checks

After successful ingestion, verify:

- [ ] `SELECT COUNT(*) FROM merge_requests` matches GitLab MR count for configured projects
- [ ] Every MR has a corresponding `raw_payloads` row
- [ ] `draft` field matches GitLab UI (draft MRs have draft=1, includes `work_in_progress` fallback)
- [ ] `state` includes all expected values (`opened`, `merged`, `closed`, `locked`)
- [ ] `detailed_merge_status` is populated for modern GitLab instances
- [ ] `head_sha` is populated (NULL only for very old MRs or edge cases)
- [ ] `references_short` and `references_full` are populated when GitLab returns them
- [ ] Labels in `mr_labels` junction all exist in `labels` table
- [ ] `mr_labels` count per MR matches GitLab UI label count
- [ ] `mr_assignees` usernames match GitLab UI
- [ ] `mr_reviewers` usernames match GitLab UI
- [ ] `sync_cursors` has entry for each `(project_id, 'merge_requests')` pair
- [ ] Re-running `gi ingest --type=merge_requests` fetches 0 new items (cursor is current)
- [ ] Re-running skips discussion refetch for unchanged MRs (watermark works)
- [ ] `--full` sync resets `discussions_synced_for_updated_at` to NULL for all MRs
- [ ] After partial pagination failure, `discussions_synced_for_updated_at` is NOT advanced
- [ ] After note parse failure, `discussions_synced_for_updated_at` is NOT advanced
- [ ] After note parse failure, existing notes are preserved (not deleted)
- [ ] `SELECT COUNT(*) FROM discussions WHERE noteable_type='MergeRequest'` is non-zero
- [ ] Every MR discussion has at least one note
- [ ] DiffNotes have `position_new_path` populated when available
- [ ] DiffNotes have `position_type` populated when available (text/image/file)
- [ ] DiffNotes have `position_base_sha`, `position_start_sha`, `position_head_sha` populated when available
- [ ] Multi-line DiffNotes have `position_line_range_start/end` populated when available
- [ ] `SELECT COUNT(*) FROM notes WHERE position_new_path IS NOT NULL` matches expected DiffNote count
- [ ] Discussion `first_note_at` <= `last_note_at` for all rows
- [ ] No notes have `created_at = 0` or `updated_at = 0` (strict timestamp parsing)
- [ ] System notes without position do NOT have raw_payloads rows (selective storage)
- [ ] After removing a label/reviewer in GitLab and re-syncing, the link is removed
- [ ] Stale discussions removed via `last_seen_at` sweep after successful pagination
- [ ] Stale notes removed via `last_seen_at` sweep (upsert + sweep pattern)

---

## Definition of Done

### Gate A: MRs Only (Must Pass First)

- [ ] `gi ingest --type=merge_requests` fetches all MRs from configured projects
- [ ] MRs stored with correct schema, including branches and merge metadata
- [ ] `draft` field captured correctly (with `work_in_progress` fallback for older instances)
- [ ] `state` field supports all values: `opened`, `merged`, `closed`, `locked`
- [ ] `locked` state handled as transitional (local filtering only, not server-side filter)
- [ ] `detailed_merge_status` used (non-deprecated) with fallback to `merge_status`
- [ ] `merge_user_username` used (non-deprecated) with fallback to `merged_by`
- [ ] `head_sha` captured for CP3 readiness
- [ ] `references_short` and `references_full` captured for CP3 readiness
- [ ] Cursor-based sync is resumable (re-run fetches only new/updated)
- [ ] Page-boundary cursor updates (not based on item count modulo)
- [ ] Pagination uses robust fallback chain: Link header > x-next-page > full-page heuristic
- [ ] Raw payloads stored for each MR
- [ ] `gi list mrs` and `gi count mrs` work

### Gate B: Labels + Assignees + Reviewers (Must Pass)

- [ ] Labels extracted and stored (name-only)
- [ ] Label links created correctly
- [ ] **Stale label links removed on re-sync** (verified with test)
- [ ] Assignees extracted and linked to `mr_assignees`
- [ ] Reviewers extracted and linked to `mr_reviewers`
- [ ] **Stale assignee/reviewer links removed on re-sync**

### Gate C: Dependent Discussion Sync with DiffNotes (Must Pass)

- [ ] Discussions fetched for MRs with `updated_at` advancement
- [ ] Notes stored with `is_system` flag correctly set
- [ ] **Upsert + sweep pattern for notes** (not delete-all-then-insert; reduces write amplification)
- [ ] **Atomic note replacement** (notes parsed BEFORE existing notes deleted - prevents data loss)
- [ ] **Strict timestamp parsing** (no zero values from invalid timestamps)
- [ ] **DiffNote position metadata captured** (`position_new_path`, `position_type`, line numbers, line_range)
- [ ] **DiffNote SHA triplet captured** (`position_base_sha`, `position_start_sha`, `position_head_sha`)
- [ ] **Selective raw payload storage** (skip system notes without position)
- [ ] Raw payloads stored for discussions and DiffNotes
- [ ] `discussions_synced_for_updated_at` watermark updated after sync
- [ ] **Watermark is NOT advanced if any discussion page fetch fails** (verified with test)
- [ ] **Watermark is NOT advanced if any note parse fails** (verified with test)
- [ ] **Unchanged MRs skip discussion refetch** (verified with test)
- [ ] Stale discussions removed via `last_seen_at` sweep after successful pagination
- [ ] Stale notes removed via `last_seen_at` sweep (upsert + sweep pattern)
- [ ] Bounded concurrency (`dependent_concurrency` respected)

### Gate D: Resumability Proof (Must Pass)

- [ ] Kill mid-run, rerun; bounded redo (cursor progress preserved at page boundaries)
- [ ] No redundant discussion refetch after crash recovery
- [ ] No watermark advancement on partial pagination failure
- [ ] No watermark advancement on note parse failure (preserves existing data)
- [ ] Single-flight lock prevents concurrent runs
- [ ] `--full` flag resets cursor and fetches all data
- [ ] `--full` flag also resets `discussions_synced_for_updated_at` (forces discussion refetch)

### Gate E: CLI Complete (Must Pass)

- [ ] `gi list mrs` with all filter options including `--draft` and `--no-draft`
- [ ] `gi list mrs` shows [DRAFT] prefix for draft MRs
- [ ] `gi show mr <iid>` displays full detail with discussions
- [ ] `gi show mr` shows DiffNote file context in discussion display
- [ ] `gi show mr` shows `detailed_merge_status`
- [ ] `gi count mrs` shows state breakdown
- [ ] `gi sync-status` shows MR cursor positions

### Final Gate (Must Pass)

- [ ] All unit tests pass (`cargo test`)
- [ ] All integration tests pass (mocked with wiremock)
- [ ] `does_not_advance_discussion_watermark_on_partial_failure` test passes
- [ ] `prefers_detailed_merge_status_when_both_fields_present` test passes
- [ ] `prefers_merge_user_when_both_fields_present` test passes
- [ ] `prefers_draft_when_both_draft_and_work_in_progress_present` test passes
- [ ] `cargo clippy` passes with no warnings
- [ ] `cargo fmt --check` passes
- [ ] Compiles with `--release`

### Hardening (Optional Before CP3)

- [ ] Edge cases: MRs with 0 labels, 0 discussions, no assignees/reviewers
- [ ] Large pagination (100+ pages)
- [ ] Rate limit handling under sustained load
- [ ] Live tests pass against real GitLab instance
- [ ] Performance: 1000+ MRs ingested in <5 min
- [ ] DB size verification: system note payloads not stored

---

## Implementation Order

1. **Database migration** (15 min)
   - `migrations/006_merge_requests.sql`
   - Update `MIGRATIONS` const in `src/core/db.rs`

2. **GitLab types** (15 min)
   - Add `GitLabMergeRequest`, `GitLabReviewer` to `src/gitlab/types.rs`
   - Test deserialization with fixtures

3. **MR Transformer** (25 min)
   - `src/gitlab/transformers/merge_request.rs`
   - `MergeRequestWithMetadata` struct
   - Unit tests

4. **Discussion transformer updates** (15 min)
   - Add `transform_mr_discussion()` function
   - Add `transform_notes_with_diff_position()` function
   - Unit tests for DiffNote extraction

5. **GitLab client pagination** (20 min)
   - Add `paginate_merge_requests()`
   - Add `paginate_mr_discussions()`

6. **MR ingestion** (45 min)
   - `src/ingestion/merge_requests.rs`
   - Transaction batching
   - Label/assignee/reviewer linking with stale removal
   - Incremental cursor updates
   - Return `mrs_needing_discussion_sync`
   - Integration tests

7. **MR discussion ingestion** (30 min)
   - `src/ingestion/mr_discussions.rs`
   - DiffNote position capture
   - Stale discussion removal
   - Watermark update
   - Integration tests

8. **Update orchestrator** (20 min)
   - `src/ingestion/orchestrator.rs`
   - Support both issue and MR ingestion
   - Aggregate results

9. **Update ingest command** (15 min)
   - `src/cli/commands/ingest.rs`
   - Route `merge_requests` type to MR ingest

10. **Implement MR CLI commands** (45 min)
    - Update `gi list` for MRs with filters
    - Update `gi show` for MR detail view
    - Update `gi count` for MR counts
    - Update `gi sync-status` for MR cursors

11. **Final validation** (20 min)
    - `cargo test`
    - `cargo clippy`
    - Gate A/B/C/D/E verification
    - Manual smoke tests
    - Data integrity checks

---

## Risks & Mitigations

| Risk | Mitigation |
|------|------------|
| GitLab rate limiting during large sync | Respect `Retry-After`, exponential backoff, configurable concurrency |
| MR discussion API N+1 problem | `dependent_concurrency` config limits parallel requests; watermark prevents refetch |
| Cursor drift if GitLab timestamp behavior changes | Rolling backfill window catches missed items |
| Large MRs with 100+ discussions | Paginate discussions, bound memory usage |
| System notes pollute data | `is_system` flag allows filtering |
| Label/assignee/reviewer deduplication | Clear and re-link pattern ensures correctness |
| DiffNote position field variations | Defensive parsing with Option types; extended fields (position_type, line_range, SHA triplet) for modern GitLab |
| Async stream complexity | Use `async-stream` crate for ergonomic generators |
| rusqlite + async runtime Send/locking pitfalls | Use `LocalSet` + `spawn_local` for non-Send tasks; each worker opens its own SQLite connection (WAL + busy_timeout). Avoid holding DB handles across `.await`. |
| Crash causes massive refetch | Page-boundary cursor updates (not item-count based) |
| Cursor rewind causes discussion refetch | Per-MR watermark (`discussions_synced_for_updated_at`) |
| Stale discussions accumulate | Remove discussions via `last_seen_at < run_seen_at` sweep (not in-memory ID collection) |
| Stale notes accumulate | Remove notes via `last_seen_at` sweep (upsert + sweep pattern) |
| **Partial pagination failure loses data** | Watermark NOT advanced unless pagination completes; explicit test coverage |
| **Invalid timestamps corrupt cursor logic** | Strict timestamp parsing (Result types, no unwrap_or(0)); bad notes logged and skipped; parse BEFORE delete |
| **Note parse failure causes data loss** | Parse notes BEFORE any destructive DB operations; if parse fails, preserve existing data and don't advance watermark |
| **Raw payload size explodes with notes** | Selective storage: DiffNotes + non-system notes only; system notes use discussion payload |
| **Deprecated GitLab fields cause future churn** | Use `detailed_merge_status` and `merge_user` with fallback to old; explicit tests verify preference when both present |
| **Memory growth on large projects** | DB-driven discussion sync selection; no in-memory collection of MRs needing sync |
| **Pagination headers missing (proxy/instance issue)** | Robust fallback chain: Link header (RFC 8288) > x-next-page > full-page heuristic |
| **GitLab version differences** | Handle `locked` state (transitional, local filtering); support both `draft` and `work_in_progress`; optional reviewer verification endpoint for debugging |
| **--full sync leaves stale discussion data** | `--full` resets both MR cursor AND `discussions_synced_for_updated_at` watermarks |
| **Write amplification on note updates** | Upsert + sweep pattern instead of delete-all-then-insert |

---

## API Call Estimation

For a project with **500 MRs** (average 10 discussions each, 3 notes per discussion):

| Operation | Calls | Notes |
|-----------|-------|-------|
| MR list pages | 5 | 100 per page |
| Discussion pages per MR | 1 | Most MRs have <100 discussions |
| **Total initial sync** | ~505 | 5 + (500 × 1) |
| **Subsequent sync (10% change)** | ~55 | 5 + (50 × 1) |

**Rate limit safety:** At 100 requests/second, full sync completes in ~5 seconds of API time. With `dependent_concurrency: 10`, wall clock time is ~50 seconds plus network latency.

---

## MR-Specific Considerations

### DiffNote Position Metadata

GitLab DiffNotes include position metadata that identifies the file and line where the comment was placed. This is critical for code review context in CP3 document generation.

**Position Object Structure (from GitLab API):**
```json
{
  "position": {
    "base_sha": "abc123...",           // Base commit SHA for the diff
    "start_sha": "def456...",          // Start commit SHA for the diff
    "head_sha": "ghi789...",           // Head commit SHA for the diff
    "old_path": "src/auth/login.ts",   // File path before rename (if any)
    "new_path": "src/auth/login.ts",   // Current file path
    "position_type": "text",           // "text" | "image" | "file"
    "old_line": null,                  // Line number in old version (null for additions)
    "new_line": 45,                    // Line number in new version (null for deletions)
    "line_range": {                    // For multi-line comments (GitLab 13.6+)
      "start": { "line_code": "...", "type": "new", "old_line": null, "new_line": 45 },
      "end": { "line_code": "...", "type": "new", "old_line": null, "new_line": 48 }
    }
  }
}
```

**Why Capture SHA Triplet:**
The SHA triplet (`base_sha`, `start_sha`, `head_sha`) is essential for future CP3 work:
- **Precise diff context:** Maps comment to exact commit range being reviewed
- **Future file content fetch:** Enables fetching file content at the exact commit when the comment was made
- **Stale comment detection:** Identifies comments on outdated code when source branch is updated
- **Zero extra API cost:** Already present in discussion response, just needs extraction

**Stored Fields:**
- `position_old_path` - File path in base version (for renames/deletions)
- `position_new_path` - File path in head version (for additions/modifications)
- `position_old_line` - Line number in base version
- `position_new_line` - Line number in head version
- `position_type` - Type of position: "text", "image", or "file"
- `position_line_range_start` - Start line for multi-line comments
- `position_line_range_end` - End line for multi-line comments
- `position_base_sha` - Base commit SHA for the diff
- `position_start_sha` - Start commit SHA for the diff
- `position_head_sha` - Head commit SHA for the diff

**Display in CLI:**
```
@janedoe (2024-03-16) [src/auth/login.ts:45]:
  Should we validate the JWT signature here?
```

For multi-line comments:
```
@janedoe (2024-03-16) [src/auth/login.ts:45-48]:
  This whole block should use async/await instead of callbacks.
```

---

## References

- [GitLab MR API](https://docs.gitlab.com/ee/api/merge_requests.html)
- [GitLab Discussions API](https://docs.gitlab.com/ee/api/discussions.html)
- [GitLab Notes API](https://docs.gitlab.com/ee/api/notes.html)
- [GitLab Pagination](https://docs.gitlab.com/ee/api/rest/index.html#pagination)
- [RFC 8288 - Link Header](https://datatracker.ietf.org/doc/html/rfc8288)
- Checkpoint 1 PRD (Issue Ingestion)
