merge-request: add target and merge result authority

crates/merge-request/src/lib.rs

@@ -11,7 +11,7 @@ use std::path::{Path, PathBuf};
 use std::time::Duration;
 use thiserror::Error;
 
-const SCHEMA_VERSION: i64 = 8;
+const SCHEMA_VERSION: i64 = 9;
 const REVIEWER_PROFILE: &str = "builtin:reviewer";
 const MAX_SUMMARY_BYTES: usize = 16 * 1024;
 const MAX_REVIEW_BODY_BYTES: usize = 64 * 1024;
@@ -51,6 +51,14 @@ pub enum MergeRequestError {
     NotOpen(String),
     #[error("completion operation id was reused with different input")]
     OperationConflict,
+    #[error("merge result operation id was reused with different input")]
+    MergeResultOperationConflict,
+    #[error("merge result {0} was not found for the current Merge Request revision")]
+    MergeResultNotFound(String),
+    #[error("merge result evidence is invalid: {0}")]
+    InvalidMergeResult(String),
+    #[error("Merge Request target is unknown and must be resolved explicitly")]
+    UnknownTarget,
     #[error("Ticket must be inprogress before Merge Request completion (current: {0})")]
     TicketStateConflict(String),
     #[error("only an authenticated user with explicit confirmation may merge")]
@@ -117,13 +125,86 @@ pub enum ReviewStatus {
     ChangesRequested,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum MergeRequestTargetStatus {
+    Known,
+    Unknown,
+}
+
+impl MergeRequestTargetStatus {
+    fn parse(value: &str) -> Self {
+        match value {
+            "known" => Self::Known,
+            _ => Self::Unknown,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum MergeStrategy {
+    FastForward,
+    Merge,
+}
+
+impl MergeStrategy {
+    fn as_str(self) -> &'static str {
+        match self {
+            Self::FastForward => "fast_forward",
+            Self::Merge => "merge",
+        }
+    }
+
+    fn parse(value: &str) -> Self {
+        match value {
+            "fast_forward" => Self::FastForward,
+            _ => Self::Merge,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum MergeResolution {
+    None,
+    Clean,
+    ConflictsResolved,
+}
+
+impl MergeResolution {
+    fn as_str(self) -> &'static str {
+        match self {
+            Self::None => "none",
+            Self::Clean => "clean",
+            Self::ConflictsResolved => "conflicts_resolved",
+        }
+    }
+
+    fn parse(value: &str) -> Self {
+        match value {
+            "none" => Self::None,
+            "conflicts_resolved" => Self::ConflictsResolved,
+            _ => Self::Clean,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum MergeResultTargetStatus {
+    Current,
+    Applied,
+    Stale,
+    Unknown,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct MergeRequestRevision {
     pub revision_id: String,
     pub ordinal: u64,
     pub base_commit: String,
     pub head_commit: String,
-    pub head_tree: String,
     pub diff_digest: String,
     pub changed_paths: Vec<String>,
     pub summary: String,
@@ -144,6 +225,8 @@ pub struct ReviewFinding {
 pub struct MergeRequestReview {
     pub attempt_id: String,
     pub revision_id: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub merge_result_id: Option<String>,
     pub decision: ReviewDecision,
     pub body: String,
     pub findings: Vec<ReviewFinding>,
@@ -155,17 +238,46 @@ pub struct MergeRequestReview {
     pub submitted_at: String,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct MergeResult {
+    pub merge_result_id: String,
+    pub revision_id: String,
+    pub target_commit: String,
+    pub source_commit: String,
+    pub result_commit: String,
+    pub strategy: MergeStrategy,
+    pub resolution: MergeResolution,
+    pub created_by_runtime_id: String,
+    pub created_by_worker_id: String,
+    pub created_at: String,
+    pub operation_id: String,
+    pub validated_at: String,
+    pub target_status: MergeResultTargetStatus,
+    pub review_status: ReviewStatus,
+    pub current_review: Option<MergeRequestReview>,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct MergeRequest {
     pub merge_request_id: String,
     pub workspace_id: String,
     pub ticket_id: String,
     pub repository_id: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub target_ref_selector: Option<String>,
+    pub target_status: MergeRequestTargetStatus,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub observed_target_commit: Option<String>,
     pub state: MergeRequestState,
     pub lifecycle_generation: u64,
     pub current_revision: MergeRequestRevision,
     pub review_status: ReviewStatus,
     pub current_review: Option<MergeRequestReview>,
+    pub merge_results: Vec<MergeResult>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub current_merge_result: Option<MergeResult>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub applied_merge_result: Option<MergeResult>,
     pub created_at: String,
     pub updated_at: String,
     pub merged_by_account_id: Option<String>,
@@ -177,6 +289,7 @@ pub struct OpenMergeRequest {
     pub merge_request_id: String,
     pub ticket_id: String,
     pub repository_id: String,
+    pub target_ref_selector: String,
     pub revision: MergeRequestRevision,
     pub authenticated_runtime_id: String,
     pub authenticated_worker_id: String,
@@ -206,6 +319,7 @@ pub struct RegisterReviewAttempt {
     pub attempt_id: String,
     pub ticket_id: String,
     pub revision_id: String,
+    pub merge_result_id: Option<String>,
     pub parent_assignment_id: String,
     pub parent_runtime_id: String,
     pub parent_worker_id: String,
@@ -219,6 +333,7 @@ pub struct RegisterReviewAttempt {
 pub struct SubmitReview {
     pub ticket_id: String,
     pub revision_id: String,
+    pub merge_result_id: Option<String>,
     pub capability_token: String,
     pub decision: ReviewDecision,
     pub body: String,
@@ -226,6 +341,28 @@ pub struct SubmitReview {
     pub now: String,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct RecordMergeResult {
+    pub merge_result_id: String,
+    pub ticket_id: String,
+    pub expected_revision_id: String,
+    pub target_commit: String,
+    pub source_commit: String,
+    pub result_commit: String,
+    pub strategy: MergeStrategy,
+    pub resolution: MergeResolution,
+    pub operation_id: String,
+    pub actor_runtime_id: String,
+    pub actor_worker_id: String,
+    pub created_at: String,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct RecordMergeResultOutcome {
+    pub merge_result: MergeResult,
+    pub replayed: bool,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct CompleteMergeRequest {
     pub operation_id: String,
@@ -251,8 +388,12 @@ pub struct MergeRequestReadiness {
     pub ticket_id: String,
     pub merge_request_id: String,
     pub revision_id: String,
+    pub target_ref_selector: Option<String>,
+    pub observed_target_commit: Option<String>,
     pub ready: bool,
     pub review_status: ReviewStatus,
+    pub merge_result_id: Option<String>,
+    pub merge_result_review_status: Option<ReviewStatus>,
     pub blockers: Vec<String>,
 }
 
@@ -327,33 +468,87 @@ impl SqliteMergeRequestStore {
     }
 
     pub fn show_for_ticket(&self, ticket_id: &str) -> Result<Option<MergeRequest>> {
+        self.show_for_ticket_with_target(ticket_id, None)
+    }
+
+    pub fn show_for_ticket_with_target(
+        &self,
+        ticket_id: &str,
+        observed_target_commit: Option<&str>,
+    ) -> Result<Option<MergeRequest>> {
         nonempty("ticket_id", ticket_id)?;
         let conn = self.connect()?;
         verify(&conn)?;
-        load_merge_request(&conn, &self.workspace_id, ticket_id)
+        let mut mr = load_merge_request(&conn, &self.workspace_id, ticket_id)?;
+        if let Some(mr) = mr.as_mut() {
+            apply_target_observation(mr, observed_target_commit);
+        }
+        Ok(mr)
     }
 
     pub fn readiness_for_ticket(&self, ticket_id: &str) -> Result<MergeRequestReadiness> {
+        self.readiness_for_ticket_with_target(ticket_id, None)
+    }
+
+    pub fn readiness_for_ticket_with_target(
+        &self,
+        ticket_id: &str,
+        observed_target_commit: Option<&str>,
+    ) -> Result<MergeRequestReadiness> {
         let mr = self
-            .show_for_ticket(ticket_id)?
+            .show_for_ticket_with_target(ticket_id, observed_target_commit)?
             .ok_or_else(|| MergeRequestError::NotFound(ticket_id.to_string()))?;
         let mut blockers = Vec::new();
         if mr.state != MergeRequestState::Open {
             blockers.push(format!("merge request is {}", mr.state.as_str()));
         }
         match mr.review_status {
-            ReviewStatus::Pending => blockers.push("current revision has no review result".into()),
+            ReviewStatus::Pending => {
+                blockers.push("current source revision has no review result".into())
+            }
             ReviewStatus::ChangesRequested => {
-                blockers.push("current revision has request_changes".into())
+                blockers.push("current source revision has request_changes".into())
             }
             ReviewStatus::Approved => {}
         }
+        if mr.target_status != MergeRequestTargetStatus::Known || observed_target_commit.is_none() {
+            blockers.push("merge request target is unknown or could not be resolved".into());
+        }
+        let current_result = mr
+            .current_merge_result
+            .as_ref()
+            .or(mr.applied_merge_result.as_ref());
+        if current_result.is_none() && observed_target_commit.is_some() {
+            if mr
+                .merge_results
+                .iter()
+                .any(|result| result.target_status == MergeResultTargetStatus::Stale)
+            {
+                blockers.push("target moved after the latest MergeResult was recorded".into());
+            } else {
+                blockers.push(
+                    "current source revision has no validated MergeResult for the current target"
+                        .into(),
+                );
+            }
+        }
+        if let Some(result) = current_result {
+            if matches!(result.strategy, MergeStrategy::Merge)
+                && result.review_status != ReviewStatus::Approved
+            {
+                blockers.push("non-fast-forward MergeResult is not independently approved".into());
+            }
+        }
         Ok(MergeRequestReadiness {
             ticket_id: ticket_id.to_string(),
             merge_request_id: mr.merge_request_id,
             revision_id: mr.current_revision.revision_id,
+            target_ref_selector: mr.target_ref_selector,
+            observed_target_commit: mr.observed_target_commit,
             ready: blockers.is_empty(),
             review_status: mr.review_status,
+            merge_result_id: current_result.map(|result| result.merge_result_id.clone()),
+            merge_result_review_status: current_result.map(|result| result.review_status),
             blockers,
         })
     }
@@ -364,6 +559,7 @@ impl SqliteMergeRequestStore {
             ("merge_request_id", input.merge_request_id.as_str()),
             ("ticket_id", input.ticket_id.as_str()),
             ("repository_id", input.repository_id.as_str()),
+            ("target_ref_selector", input.target_ref_selector.as_str()),
             ("runtime_id", input.authenticated_runtime_id.as_str()),
             ("worker_id", input.authenticated_worker_id.as_str()),
         ] {
@@ -379,8 +575,8 @@ impl SqliteMergeRequestStore {
                 &input.authenticated_worker_id,
             )?;
             conn.execute(
-                "INSERT INTO merge_requests (workspace_id, merge_request_id, repository_id, state, lifecycle_generation, current_revision_id, created_at, updated_at) VALUES (?1, ?2, ?3, 'open', 1, ?4, ?5, ?5)",
+                "INSERT INTO merge_requests (workspace_id, merge_request_id, repository_id, target_ref_selector, target_status, state, lifecycle_generation, current_revision_id, created_at, updated_at) VALUES (?1, ?2, ?3, ?4, 'known', 'open', 1, ?5, ?6, ?6)",
-                params![self.workspace_id, input.merge_request_id, input.repository_id, input.revision.revision_id, input.now],
+                params![self.workspace_id, input.merge_request_id, input.repository_id, input.target_ref_selector, input.revision.revision_id, input.now],
             ).map_err(db)?;
             conn.execute(
                 "INSERT INTO merge_request_ticket_relations (workspace_id,merge_request_id,ticket_id,relation_kind,created_at) VALUES (?1,?2,?3,'implements',?4)",
@@ -414,13 +610,13 @@ impl SqliteMergeRequestStore {
             if input.revision.ordinal != current.current_revision.ordinal + 1 {
                 return Err(MergeRequestError::RevisionConflict(input.revision.revision_id.clone()));
             }
-            let existing: Option<(String, String, String, String)> = conn.query_row(
+            let existing: Option<(String, String, String)> = conn.query_row(
-                "SELECT base_commit, head_commit, head_tree, diff_digest FROM merge_request_revisions WHERE workspace_id=?1 AND merge_request_id=?2 AND revision_id=?3",
+                "SELECT base_commit, head_commit, diff_digest FROM merge_request_revisions WHERE workspace_id=?1 AND merge_request_id=?2 AND revision_id=?3",
                 params![self.workspace_id, current.merge_request_id, input.revision.revision_id],
-                |row| Ok((row.get(0)?, row.get(1)?, row.get(2)?, row.get(3)?)),
+                |row| Ok((row.get(0)?, row.get(1)?, row.get(2)?)),
             ).optional().map_err(db)?;
             if let Some(existing) = existing {
-                if existing == (input.revision.base_commit.clone(), input.revision.head_commit.clone(), input.revision.head_tree.clone(), input.revision.diff_digest.clone()) {
+                if existing == (input.revision.base_commit.clone(), input.revision.head_commit.clone(), input.revision.diff_digest.clone()) {
                     return Ok(current);
                 }
                 return Err(MergeRequestError::RevisionConflict(input.revision.revision_id.clone()));
@@ -468,7 +664,19 @@ impl SqliteMergeRequestStore {
             if mr.current_revision.revision_id != input.revision_id {
                 return Err(MergeRequestError::StaleRevision { expected: input.revision_id.clone(), current: mr.current_revision.revision_id });
             }
-            validate_current_assignment(conn, &self.workspace_id, &input.ticket_id, &input.parent_assignment_id, &input.parent_runtime_id, &input.parent_worker_id)?;
+            if let Some(merge_result_id) = input.merge_result_id.as_deref() {
+                let exists: bool = conn.query_row(
+                    "SELECT EXISTS(SELECT 1 FROM merge_request_merge_results WHERE workspace_id=?1 AND merge_request_id=?2 AND revision_id=?3 AND merge_result_id=?4)",
+                    params![self.workspace_id,mr.merge_request_id,input.revision_id,merge_result_id],
+                    |row| row.get(0),
+                ).map_err(db)?;
+                if !exists {
+                    return Err(MergeRequestError::MergeResultNotFound(merge_result_id.into()));
+                }
+                validate_current_assignment_id(conn, &self.workspace_id, &input.ticket_id, &input.parent_assignment_id)?;
+            } else {
+                validate_current_assignment(conn, &self.workspace_id, &input.ticket_id, &input.parent_assignment_id, &input.parent_runtime_id, &input.parent_worker_id)?;
+            }
             let effective_profile: Option<String> = conn.query_row(
                 "SELECT effective_profile FROM merge_request_reviewer_child_sessions WHERE workspace_id=?1 AND child_session_id=?2 AND parent_runtime_id=?3 AND parent_worker_id=?4",
                 params![self.workspace_id,input.child_session_id,input.parent_runtime_id,input.parent_worker_id],
@@ -478,8 +686,8 @@ impl SqliteMergeRequestStore {
                 return Err(MergeRequestError::InvalidReviewer);
             }
             conn.execute(
-                "INSERT INTO merge_request_review_attempts (workspace_id, attempt_id, merge_request_id, ticket_id, revision_id, lifecycle_generation, parent_assignment_id, parent_runtime_id, parent_worker_id, child_session_id, child_effective_profile, capability_token_sha256, status, created_at) VALUES (?1,?2,?3,?4,?5,?6,?7,?8,?9,?10,?11,?12,'open',?13)",
+                "INSERT INTO merge_request_review_attempts (workspace_id, attempt_id, merge_request_id, ticket_id, revision_id, merge_result_id, lifecycle_generation, parent_assignment_id, parent_runtime_id, parent_worker_id, child_session_id, child_effective_profile, capability_token_sha256, status, created_at) VALUES (?1,?2,?3,?4,?5,?6,?7,?8,?9,?10,?11,?12,?13,'open',?14)",
-                params![self.workspace_id, input.attempt_id, mr.merge_request_id, input.ticket_id, input.revision_id, mr.lifecycle_generation as i64, input.parent_assignment_id, input.parent_runtime_id, input.parent_worker_id, input.child_session_id, REVIEWER_PROFILE, token_hash(&input.capability_token), input.now],
+                params![self.workspace_id, input.attempt_id, mr.merge_request_id, input.ticket_id, input.revision_id, input.merge_result_id, mr.lifecycle_generation as i64, input.parent_assignment_id, input.parent_runtime_id, input.parent_worker_id, input.child_session_id, REVIEWER_PROFILE, token_hash(&input.capability_token), input.now],
             ).map_err(|_| MergeRequestError::InvalidReviewAttempt)?;
             Ok(())
         })
@@ -505,12 +713,12 @@ impl SqliteMergeRequestStore {
         validate_review_input(&input)?;
         self.write(|conn| {
             let token = token_hash(&input.capability_token);
-            let attempt: Option<(String,String,String,String,String,String,String,String,i64)> = conn.query_row(
+            let attempt: Option<(String,String,Option<String>,String,String,String,String,String,String,i64)> = conn.query_row(
-                "SELECT attempt_id, merge_request_id, parent_assignment_id, parent_runtime_id, parent_worker_id, child_session_id, child_effective_profile, status, lifecycle_generation FROM merge_request_review_attempts WHERE workspace_id=?1 AND ticket_id=?2 AND revision_id=?3 AND capability_token_sha256=?4",
+                "SELECT attempt_id, merge_request_id, merge_result_id, parent_assignment_id, parent_runtime_id, parent_worker_id, child_session_id, child_effective_profile, status, lifecycle_generation FROM merge_request_review_attempts WHERE workspace_id=?1 AND ticket_id=?2 AND revision_id=?3 AND ((?4 IS NULL AND merge_result_id IS NULL) OR merge_result_id=?4) AND capability_token_sha256=?5",
-                params![self.workspace_id, input.ticket_id, input.revision_id, token],
+                params![self.workspace_id, input.ticket_id, input.revision_id, input.merge_result_id, token],
-                |row| Ok((row.get(0)?,row.get(1)?,row.get(2)?,row.get(3)?,row.get(4)?,row.get(5)?,row.get(6)?,row.get(7)?,row.get(8)?)),
+                |row| Ok((row.get(0)?,row.get(1)?,row.get(2)?,row.get(3)?,row.get(4)?,row.get(5)?,row.get(6)?,row.get(7)?,row.get(8)?,row.get(9)?)),
             ).optional().map_err(db)?;
-            let Some((attempt_id, mr_id, assignment_id, runtime_id, worker_id, child_session_id, effective_profile, status, lifecycle_generation)) = attempt else {
+            let Some((attempt_id, mr_id, merge_result_id, assignment_id, runtime_id, worker_id, child_session_id, effective_profile, status, lifecycle_generation)) = attempt else {
                 return Err(MergeRequestError::InvalidReviewAttempt);
             };
             if status != "open" || effective_profile != REVIEWER_PROFILE || child_session_id == worker_id {
@@ -525,10 +733,14 @@ impl SqliteMergeRequestStore {
             if mr.current_revision.revision_id != input.revision_id {
                 return Err(MergeRequestError::StaleRevision { expected: input.revision_id.clone(), current: mr.current_revision.revision_id });
             }
-            validate_current_assignment(conn, &self.workspace_id, &input.ticket_id, &assignment_id, &runtime_id, &worker_id)?;
+            if merge_result_id.is_some() {
+                validate_current_assignment_id(conn, &self.workspace_id, &input.ticket_id, &assignment_id)?;
+            } else {
+                validate_current_assignment(conn, &self.workspace_id, &input.ticket_id, &assignment_id, &runtime_id, &worker_id)?;
+            }
             conn.execute(
-                "INSERT INTO merge_request_reviews (workspace_id, attempt_id, merge_request_id, revision_id, decision, body, submitted_at) VALUES (?1,?2,?3,?4,?5,?6,?7)",
+                "INSERT INTO merge_request_reviews (workspace_id, attempt_id, merge_request_id, revision_id, merge_result_id, decision, body, submitted_at) VALUES (?1,?2,?3,?4,?5,?6,?7,?8)",
-                params![self.workspace_id, attempt_id, mr_id, input.revision_id, input.decision.as_str(), input.body, input.now],
+                params![self.workspace_id, attempt_id, mr_id, input.revision_id, merge_result_id, input.decision.as_str(), input.body, input.now],
             ).map_err(|_| MergeRequestError::InvalidReviewAttempt)?;
             for (ordinal, finding) in input.findings.iter().enumerate() {
                 nonempty("finding.body", &finding.body)?;
@@ -545,6 +757,88 @@ impl SqliteMergeRequestStore {
         })
     }
 
+    pub fn record_merge_result(
+        &self,
+        input: RecordMergeResult,
+    ) -> Result<RecordMergeResultOutcome> {
+        for (name, value) in [
+            ("merge_result_id", input.merge_result_id.as_str()),
+            ("ticket_id", input.ticket_id.as_str()),
+            ("expected_revision_id", input.expected_revision_id.as_str()),
+            ("target_commit", input.target_commit.as_str()),
+            ("source_commit", input.source_commit.as_str()),
+            ("result_commit", input.result_commit.as_str()),
+            ("operation_id", input.operation_id.as_str()),
+            ("actor_runtime_id", input.actor_runtime_id.as_str()),
+            ("actor_worker_id", input.actor_worker_id.as_str()),
+        ] {
+            nonempty(name, value)?;
+        }
+        if matches!(input.strategy, MergeStrategy::FastForward)
+            && (input.result_commit != input.source_commit
+                || !matches!(input.resolution, MergeResolution::None))
+        {
+            return Err(MergeRequestError::InvalidMergeResult(
+                "fast-forward result must equal the source commit and use resolution=none".into(),
+            ));
+        }
+        if matches!(input.strategy, MergeStrategy::Merge)
+            && matches!(input.resolution, MergeResolution::None)
+        {
+            return Err(MergeRequestError::InvalidMergeResult(
+                "merge strategy requires clean or conflicts_resolved resolution".into(),
+            ));
+        }
+        let fingerprint = merge_result_fingerprint(&input);
+        self.write(|conn| {
+            if let Some((stored, merge_result_id, generation)) = conn
+                .query_row(
+                    "SELECT r.operation_fingerprint,r.merge_result_id,mr.lifecycle_generation FROM merge_request_merge_results r JOIN merge_requests mr ON mr.workspace_id=r.workspace_id AND mr.merge_request_id=r.merge_request_id WHERE r.workspace_id=?1 AND r.operation_id=?2",
+                    params![self.workspace_id,input.operation_id],
+                    |row| Ok((row.get::<_,String>(0)?,row.get::<_,String>(1)?,row.get::<_,i64>(2)?)),
+                )
+                .optional()
+                .map_err(db)?
+            {
+                if stored != fingerprint {
+                    return Err(MergeRequestError::MergeResultOperationConflict);
+                }
+                let merge_result = load_merge_result(
+                    conn,
+                    &self.workspace_id,
+                    &merge_result_id,
+                    generation as u64,
+                )?
+                    .ok_or_else(|| MergeRequestError::MergeResultNotFound(merge_result_id.clone()))?;
+                return Ok(RecordMergeResultOutcome { merge_result, replayed: true });
+            }
+            let mr = load_merge_request(conn, &self.workspace_id, &input.ticket_id)?
+                .ok_or_else(|| MergeRequestError::NotFound(input.ticket_id.clone()))?;
+            ensure_open(&mr)?;
+            if mr.target_status != MergeRequestTargetStatus::Known {
+                return Err(MergeRequestError::UnknownTarget);
+            }
+            if mr.current_revision.revision_id != input.expected_revision_id {
+                return Err(MergeRequestError::StaleRevision {
+                    expected: input.expected_revision_id.clone(),
+                    current: mr.current_revision.revision_id,
+                });
+            }
+            if mr.current_revision.head_commit != input.source_commit {
+                return Err(MergeRequestError::InvalidMergeResult(
+                    "source commit does not match the current source revision".into(),
+                ));
+            }
+            conn.execute(
+                "INSERT INTO merge_request_merge_results (workspace_id,merge_result_id,merge_request_id,ticket_id,revision_id,target_commit,source_commit,result_commit,strategy,resolution,created_by_runtime_id,created_by_worker_id,created_at,operation_id,operation_fingerprint,validated_at) VALUES (?1,?2,?3,?4,?5,?6,?7,?8,?9,?10,?11,?12,?13,?14,?15,?13)",
+                params![self.workspace_id,input.merge_result_id,mr.merge_request_id,input.ticket_id,input.expected_revision_id,input.target_commit,input.source_commit,input.result_commit,input.strategy.as_str(),input.resolution.as_str(),input.actor_runtime_id,input.actor_worker_id,input.created_at,input.operation_id,fingerprint],
+            ).map_err(db)?;
+            let merge_result = load_merge_result(conn, &self.workspace_id, &input.merge_result_id, mr.lifecycle_generation)?
+                .ok_or_else(|| MergeRequestError::MergeResultNotFound(input.merge_result_id.clone()))?;
+            Ok(RecordMergeResultOutcome { merge_result, replayed: false })
+        })
+    }
+
     pub fn complete(&self, input: CompleteMergeRequest) -> Result<CompletionOutcome> {
         for (name, value) in [
             ("operation_id", input.operation_id.as_str()),
@@ -714,6 +1008,9 @@ fn migrate_transaction(conn: &Connection) -> Result<()> {
     {
         migrate_completion_authority_v8(conn)?;
     }
+    if version < 9 && !column_exists(conn, "merge_requests", "target_ref_selector")? {
+        migrate_merge_result_authority_v9(conn)?;
+    }
     if version < 1 {
         conn.execute(
             "INSERT INTO merge_request_schema_migrations(version) VALUES (1)",
@@ -764,6 +1061,54 @@ fn migrate_completion_authority_v8(conn: &Connection) -> Result<()> {
     .map_err(db)
 }
 
+fn migrate_merge_result_authority_v9(conn: &Connection) -> Result<()> {
+    conn.pragma_update(None, "foreign_keys", "OFF")
+        .map_err(db)?;
+    let result = conn.execute_batch(
+        "ALTER TABLE merge_requests ADD COLUMN target_ref_selector TEXT;
+         ALTER TABLE merge_requests ADD COLUMN target_status TEXT NOT NULL DEFAULT 'unknown' CHECK(target_status IN ('known','unknown'));
+
+         CREATE TABLE merge_request_revisions_v9 (
+          workspace_id TEXT NOT NULL, merge_request_id TEXT NOT NULL, revision_id TEXT NOT NULL,
+          ordinal INTEGER NOT NULL, base_commit TEXT NOT NULL, head_commit TEXT NOT NULL,
+          diff_digest TEXT NOT NULL, summary TEXT NOT NULL, assignment_id TEXT NOT NULL, created_at TEXT NOT NULL,
+          PRIMARY KEY(workspace_id,merge_request_id,revision_id),
+          UNIQUE(workspace_id,merge_request_id,ordinal),
+          FOREIGN KEY(workspace_id,merge_request_id) REFERENCES merge_requests(workspace_id,merge_request_id) ON DELETE CASCADE
+         );
+         INSERT INTO merge_request_revisions_v9(
+          workspace_id,merge_request_id,revision_id,ordinal,base_commit,head_commit,diff_digest,summary,assignment_id,created_at
+         ) SELECT workspace_id,merge_request_id,revision_id,ordinal,base_commit,head_commit,diff_digest,summary,assignment_id,created_at
+           FROM merge_request_revisions;
+         DROP TABLE merge_request_revisions;
+         ALTER TABLE merge_request_revisions_v9 RENAME TO merge_request_revisions;
+
+         CREATE TABLE merge_request_merge_results (
+          workspace_id TEXT NOT NULL, merge_result_id TEXT NOT NULL, merge_request_id TEXT NOT NULL,
+          ticket_id TEXT NOT NULL, revision_id TEXT NOT NULL, target_commit TEXT NOT NULL,
+          source_commit TEXT NOT NULL, result_commit TEXT NOT NULL,
+          strategy TEXT NOT NULL CHECK(strategy IN ('fast_forward','merge')),
+          resolution TEXT NOT NULL CHECK(resolution IN ('none','clean','conflicts_resolved')),
+          created_by_runtime_id TEXT NOT NULL, created_by_worker_id TEXT NOT NULL,
+          created_at TEXT NOT NULL, operation_id TEXT NOT NULL, operation_fingerprint TEXT NOT NULL,
+          validated_at TEXT NOT NULL,
+          PRIMARY KEY(workspace_id,merge_result_id),
+          UNIQUE(workspace_id,operation_id),
+          FOREIGN KEY(workspace_id,merge_request_id,revision_id)
+            REFERENCES merge_request_revisions(workspace_id,merge_request_id,revision_id),
+          FOREIGN KEY(workspace_id,ticket_id) REFERENCES typed_tickets(workspace_id,ticket_id)
+         );
+         CREATE INDEX merge_request_merge_results_current_idx
+          ON merge_request_merge_results(workspace_id,merge_request_id,revision_id,target_commit,created_at);
+
+         ALTER TABLE merge_request_review_attempts ADD COLUMN merge_result_id TEXT;
+         ALTER TABLE merge_request_reviews ADD COLUMN merge_result_id TEXT;",
+    );
+    let restore = conn.pragma_update(None, "foreign_keys", "ON").map_err(db);
+    result.map_err(db)?;
+    restore
+}
+
 pub fn verify(conn: &Connection) -> Result<()> {
     let version: i64 = conn
         .query_row(
@@ -786,6 +1131,7 @@ pub fn verify(conn: &Connection) -> Result<()> {
         "merge_request_review_attempts",
         "merge_request_reviews",
         "merge_request_review_findings",
+        "merge_request_merge_results",
         "merge_request_completion_operations",
     ] {
         let present: Option<i64> = conn
@@ -809,6 +1155,8 @@ pub fn verify(conn: &Connection) -> Result<()> {
                 "workspace_id",
                 "merge_request_id",
                 "repository_id",
+                "target_ref_selector",
+                "target_status",
                 "state",
                 "lifecycle_generation",
                 "current_revision_id",
@@ -832,7 +1180,6 @@ pub fn verify(conn: &Connection) -> Result<()> {
                 "ordinal",
                 "base_commit",
                 "head_commit",
-                "head_tree",
                 "diff_digest",
                 "assignment_id",
             ] as &[_],
@@ -855,6 +1202,7 @@ pub fn verify(conn: &Connection) -> Result<()> {
                 "merge_request_id",
                 "ticket_id",
                 "revision_id",
+                "merge_result_id",
                 "lifecycle_generation",
                 "parent_assignment_id",
                 "parent_runtime_id",
@@ -872,10 +1220,29 @@ pub fn verify(conn: &Connection) -> Result<()> {
                 "attempt_id",
                 "merge_request_id",
                 "revision_id",
+                "merge_result_id",
                 "decision",
                 "body",
             ] as &[_],
         ),
+        (
+            "merge_request_merge_results",
+            &[
+                "workspace_id",
+                "merge_result_id",
+                "merge_request_id",
+                "ticket_id",
+                "revision_id",
+                "target_commit",
+                "source_commit",
+                "result_commit",
+                "strategy",
+                "resolution",
+                "operation_id",
+                "operation_fingerprint",
+                "validated_at",
+            ] as &[_],
+        ),
         (
             "merge_request_completion_operations",
             &[
@@ -991,6 +1358,8 @@ fn archive_incompatible_legacy_tables(conn: &Connection, version: i64) -> Result
                 "workspace_id",
                 "merge_request_id",
                 "repository_id",
+                "target_ref_selector",
+                "target_status",
                 "state",
                 "lifecycle_generation",
                 "current_revision_id",
@@ -1016,7 +1385,6 @@ fn archive_incompatible_legacy_tables(conn: &Connection, version: i64) -> Result
                 "ordinal",
                 "base_commit",
                 "head_commit",
-                "head_tree",
                 "diff_digest",
                 "assignment_id",
             ],
@@ -1029,6 +1397,7 @@ fn archive_incompatible_legacy_tables(conn: &Connection, version: i64) -> Result
         "merge_request_reviews",
         "merge_request_review_attempts",
         "merge_request_reviewer_child_sessions",
+        "merge_request_merge_results",
         "merge_request_completion_operations",
         "merge_request_revision_paths",
         "merge_request_ticket_relations",
@@ -1111,14 +1480,16 @@ fn load_merge_request(
     workspace_id: &str,
     ticket_id: &str,
 ) -> Result<Option<MergeRequest>> {
-    let row: Option<(String,String,String,String,i64,String,String,String,Option<String>,Option<String>)> = conn.query_row(
+    let row: Option<(String,String,String,Option<String>,String,String,i64,String,String,String,Option<String>,Option<String>)> = conn.query_row(
-        "SELECT mr.merge_request_id,rel.ticket_id,mr.repository_id,mr.state,mr.lifecycle_generation,mr.current_revision_id,mr.created_at,mr.updated_at,mr.merged_by_account_id,mr.merged_at FROM merge_requests mr JOIN merge_request_ticket_relations rel ON rel.workspace_id=mr.workspace_id AND rel.merge_request_id=mr.merge_request_id WHERE mr.workspace_id=?1 AND rel.ticket_id=?2 AND rel.relation_kind='implements' ORDER BY mr.updated_at DESC,mr.merge_request_id DESC LIMIT 1",
+        "SELECT mr.merge_request_id,rel.ticket_id,mr.repository_id,mr.target_ref_selector,mr.target_status,mr.state,mr.lifecycle_generation,mr.current_revision_id,mr.created_at,mr.updated_at,mr.merged_by_account_id,mr.merged_at FROM merge_requests mr JOIN merge_request_ticket_relations rel ON rel.workspace_id=mr.workspace_id AND rel.merge_request_id=mr.merge_request_id WHERE mr.workspace_id=?1 AND rel.ticket_id=?2 AND rel.relation_kind='implements' ORDER BY mr.updated_at DESC,mr.merge_request_id DESC LIMIT 1",
-        params![workspace_id,ticket_id], |r| Ok((r.get(0)?,r.get(1)?,r.get(2)?,r.get(3)?,r.get(4)?,r.get(5)?,r.get(6)?,r.get(7)?,r.get(8)?,r.get(9)?)),
+        params![workspace_id,ticket_id], |r| Ok((r.get(0)?,r.get(1)?,r.get(2)?,r.get(3)?,r.get(4)?,r.get(5)?,r.get(6)?,r.get(7)?,r.get(8)?,r.get(9)?,r.get(10)?,r.get(11)?)),
     ).optional().map_err(db)?;
     let Some((
         mr_id,
         ticket_id,
         repository_id,
+        target_ref_selector,
+        target_status,
         state,
         generation,
         revision_id,
@@ -1137,16 +1508,24 @@ fn load_merge_request(
         Some(ReviewDecision::RequestChanges) => ReviewStatus::ChangesRequested,
         None => ReviewStatus::Pending,
     };
+    let merge_results =
+        load_merge_results(conn, workspace_id, &mr_id, &revision_id, generation as u64)?;
     Ok(Some(MergeRequest {
         merge_request_id: mr_id,
         workspace_id: workspace_id.into(),
         ticket_id,
         repository_id,
+        target_ref_selector,
+        target_status: MergeRequestTargetStatus::parse(&target_status),
+        observed_target_commit: None,
         state: MergeRequestState::parse(&state),
         lifecycle_generation: generation as u64,
         current_revision: revision,
         review_status,
         current_review,
+        merge_results,
+        current_merge_result: None,
+        applied_merge_result: None,
         created_at,
         updated_at,
         merged_by_account_id,
@@ -1161,8 +1540,8 @@ fn load_revision(
     revision_id: &str,
 ) -> Result<MergeRequestRevision> {
     let mut revision: MergeRequestRevision = conn.query_row(
-        "SELECT revision_id,ordinal,base_commit,head_commit,head_tree,diff_digest,summary,assignment_id,created_at FROM merge_request_revisions WHERE workspace_id=?1 AND merge_request_id=?2 AND revision_id=?3",
+        "SELECT revision_id,ordinal,base_commit,head_commit,diff_digest,summary,assignment_id,created_at FROM merge_request_revisions WHERE workspace_id=?1 AND merge_request_id=?2 AND revision_id=?3",
-        params![workspace_id,mr_id,revision_id], |r| Ok(MergeRequestRevision { revision_id:r.get(0)?, ordinal:r.get::<_,i64>(1)? as u64, base_commit:r.get(2)?, head_commit:r.get(3)?, head_tree:r.get(4)?, diff_digest:r.get(5)?, changed_paths:Vec::new(), summary:r.get(6)?, assignment_id:r.get(7)?, created_at:r.get(8)? }),
+        params![workspace_id,mr_id,revision_id], |r| Ok(MergeRequestRevision { revision_id:r.get(0)?, ordinal:r.get::<_,i64>(1)? as u64, base_commit:r.get(2)?, head_commit:r.get(3)?, diff_digest:r.get(4)?, changed_paths:Vec::new(), summary:r.get(5)?, assignment_id:r.get(6)?, created_at:r.get(7)? }),
     ).map_err(db)?;
     let mut statement = conn.prepare("SELECT path FROM merge_request_revision_paths WHERE workspace_id=?1 AND merge_request_id=?2 AND revision_id=?3 ORDER BY ordinal").map_err(db)?;
     revision.changed_paths = statement
@@ -1179,7 +1558,7 @@ fn insert_revision(
     mr_id: &str,
     revision: &MergeRequestRevision,
 ) -> Result<()> {
-    conn.execute("INSERT INTO merge_request_revisions (workspace_id,merge_request_id,revision_id,ordinal,base_commit,head_commit,head_tree,diff_digest,summary,assignment_id,created_at) VALUES (?1,?2,?3,?4,?5,?6,?7,?8,?9,?10,?11)", params![workspace_id,mr_id,revision.revision_id,revision.ordinal as i64,revision.base_commit,revision.head_commit,revision.head_tree,revision.diff_digest,revision.summary,revision.assignment_id,revision.created_at]).map_err(db)?;
+    conn.execute("INSERT INTO merge_request_revisions (workspace_id,merge_request_id,revision_id,ordinal,base_commit,head_commit,diff_digest,summary,assignment_id,created_at) VALUES (?1,?2,?3,?4,?5,?6,?7,?8,?9,?10)", params![workspace_id,mr_id,revision.revision_id,revision.ordinal as i64,revision.base_commit,revision.head_commit,revision.diff_digest,revision.summary,revision.assignment_id,revision.created_at]).map_err(db)?;
     for (ordinal, path) in revision.changed_paths.iter().enumerate() {
         conn.execute("INSERT INTO merge_request_revision_paths (workspace_id,merge_request_id,revision_id,ordinal,path) VALUES (?1,?2,?3,?4,?5)", params![workspace_id,mr_id,revision.revision_id,ordinal as i64,path]).map_err(db)?;
     }
@@ -1193,7 +1572,7 @@ fn load_latest_review(
     revision_id: &str,
     generation: i64,
 ) -> Result<Option<MergeRequestReview>> {
-    let attempt: Option<String> = conn.query_row("SELECT r.attempt_id FROM merge_request_reviews r JOIN merge_request_review_attempts a ON a.workspace_id=r.workspace_id AND a.attempt_id=r.attempt_id WHERE r.workspace_id=?1 AND r.merge_request_id=?2 AND r.revision_id=?3 AND a.lifecycle_generation=?4 ORDER BY r.submitted_at DESC, r.attempt_id DESC LIMIT 1", params![workspace_id,mr_id,revision_id,generation], |r| r.get(0)).optional().map_err(db)?;
+    let attempt: Option<String> = conn.query_row("SELECT r.attempt_id FROM merge_request_reviews r JOIN merge_request_review_attempts a ON a.workspace_id=r.workspace_id AND a.attempt_id=r.attempt_id WHERE r.workspace_id=?1 AND r.merge_request_id=?2 AND r.revision_id=?3 AND r.merge_result_id IS NULL AND a.lifecycle_generation=?4 ORDER BY r.submitted_at DESC, r.attempt_id DESC LIMIT 1", params![workspace_id,mr_id,revision_id,generation], |r| r.get(0)).optional().map_err(db)?;
     match attempt {
         Some(id) => load_review(conn, workspace_id, &id),
         None => Ok(None),
@@ -1205,12 +1584,13 @@ fn load_review(
     workspace_id: &str,
     attempt_id: &str,
 ) -> Result<Option<MergeRequestReview>> {
-    let row: Option<(String,String,String,String,String,String,String,String,String)> = conn.query_row(
+    let row: Option<(String,Option<String>,String,String,String,String,String,String,String,String)> = conn.query_row(
-        "SELECT r.revision_id,r.decision,r.body,a.parent_assignment_id,a.parent_runtime_id,a.parent_worker_id,a.child_session_id,a.child_effective_profile,r.submitted_at FROM merge_request_reviews r JOIN merge_request_review_attempts a ON a.workspace_id=r.workspace_id AND a.attempt_id=r.attempt_id WHERE r.workspace_id=?1 AND r.attempt_id=?2",
+        "SELECT r.revision_id,r.merge_result_id,r.decision,r.body,a.parent_assignment_id,a.parent_runtime_id,a.parent_worker_id,a.child_session_id,a.child_effective_profile,r.submitted_at FROM merge_request_reviews r JOIN merge_request_review_attempts a ON a.workspace_id=r.workspace_id AND a.attempt_id=r.attempt_id WHERE r.workspace_id=?1 AND r.attempt_id=?2",
-        params![workspace_id,attempt_id], |r| Ok((r.get(0)?,r.get(1)?,r.get(2)?,r.get(3)?,r.get(4)?,r.get(5)?,r.get(6)?,r.get(7)?,r.get(8)?)),
+        params![workspace_id,attempt_id], |r| Ok((r.get(0)?,r.get(1)?,r.get(2)?,r.get(3)?,r.get(4)?,r.get(5)?,r.get(6)?,r.get(7)?,r.get(8)?,r.get(9)?)),
     ).optional().map_err(db)?;
     let Some((
         revision_id,
+        merge_result_id,
         decision,
         body,
         assignment,
@@ -1240,6 +1620,7 @@ fn load_review(
     Ok(Some(MergeRequestReview {
         attempt_id: attempt_id.into(),
         revision_id,
+        merge_result_id,
         decision: ReviewDecision::parse(&decision),
         body,
         findings,
@@ -1272,6 +1653,15 @@ fn validate_current_implementation_assignment(
     Ok(())
 }
 
+fn validate_current_assignment_id(
+    conn: &Connection,
+    workspace_id: &str,
+    ticket_id: &str,
+    assignment_id: &str,
+) -> Result<()> {
+    validate_current_implementation_assignment(conn, workspace_id, ticket_id, assignment_id)
+}
+
 fn validate_current_assignment(
     conn: &Connection,
     workspace_id: &str,
@@ -1318,7 +1708,6 @@ fn validate_revision(revision: &MergeRequestRevision) -> Result<()> {
         ("revision_id", revision.revision_id.as_str()),
         ("base_commit", revision.base_commit.as_str()),
         ("head_commit", revision.head_commit.as_str()),
-        ("head_tree", revision.head_tree.as_str()),
         ("diff_digest", revision.diff_digest.as_str()),
         ("assignment_id", revision.assignment_id.as_str()),
     ] {
@@ -1354,6 +1743,144 @@ fn validate_revision(revision: &MergeRequestRevision) -> Result<()> {
     Ok(())
 }
 
+fn merge_result_fingerprint(input: &RecordMergeResult) -> String {
+    token_hash(&format!(
+        "{}\0{}\0{}\0{}\0{}\0{}\0{}\0{}\0{}",
+        input.ticket_id,
+        input.expected_revision_id,
+        input.target_commit,
+        input.source_commit,
+        input.result_commit,
+        input.strategy.as_str(),
+        input.resolution.as_str(),
+        input.actor_runtime_id,
+        input.actor_worker_id,
+    ))
+}
+
+fn apply_target_observation(mr: &mut MergeRequest, observed_target_commit: Option<&str>) {
+    mr.observed_target_commit = observed_target_commit.map(str::to_owned);
+    for result in &mut mr.merge_results {
+        result.target_status = match observed_target_commit {
+            Some(commit) if result.target_commit == commit => MergeResultTargetStatus::Current,
+            Some(commit) if result.result_commit == commit => MergeResultTargetStatus::Applied,
+            Some(_) => MergeResultTargetStatus::Stale,
+            None => MergeResultTargetStatus::Unknown,
+        };
+    }
+    mr.current_merge_result = observed_target_commit.and_then(|commit| {
+        mr.merge_results
+            .iter()
+            .rev()
+            .find(|result| result.target_commit == commit)
+            .cloned()
+    });
+    mr.applied_merge_result = observed_target_commit.and_then(|commit| {
+        mr.merge_results
+            .iter()
+            .rev()
+            .find(|result| result.result_commit == commit)
+            .cloned()
+    });
+}
+
+fn load_merge_result(
+    conn: &Connection,
+    workspace_id: &str,
+    merge_result_id: &str,
+    generation: u64,
+) -> Result<Option<MergeResult>> {
+    let row: Option<(String,String,String,String,String,String,String,String,String,String,String)> = conn.query_row(
+        "SELECT revision_id,target_commit,source_commit,result_commit,strategy,resolution,created_by_runtime_id,created_by_worker_id,created_at,operation_id,validated_at FROM merge_request_merge_results WHERE workspace_id=?1 AND merge_result_id=?2",
+        params![workspace_id,merge_result_id],
+        |r| Ok((r.get(0)?,r.get(1)?,r.get(2)?,r.get(3)?,r.get(4)?,r.get(5)?,r.get(6)?,r.get(7)?,r.get(8)?,r.get(9)?,r.get(10)?)),
+    ).optional().map_err(db)?;
+    let Some((
+        revision_id,
+        target_commit,
+        source_commit,
+        result_commit,
+        strategy,
+        resolution,
+        created_by_runtime_id,
+        created_by_worker_id,
+        created_at,
+        operation_id,
+        validated_at,
+    )) = row
+    else {
+        return Ok(None);
+    };
+    let current_review =
+        load_latest_merge_result_review(conn, workspace_id, merge_result_id, generation)?;
+    let review_status =
+        current_review
+            .as_ref()
+            .map_or(ReviewStatus::Pending, |review| match review.decision {
+                ReviewDecision::Approve => ReviewStatus::Approved,
+                ReviewDecision::RequestChanges => ReviewStatus::ChangesRequested,
+            });
+    Ok(Some(MergeResult {
+        merge_result_id: merge_result_id.into(),
+        revision_id,
+        target_commit,
+        source_commit,
+        result_commit,
+        strategy: MergeStrategy::parse(&strategy),
+        resolution: MergeResolution::parse(&resolution),
+        created_by_runtime_id,
+        created_by_worker_id,
+        created_at,
+        operation_id,
+        validated_at,
+        target_status: MergeResultTargetStatus::Unknown,
+        review_status,
+        current_review,
+    }))
+}
+
+fn load_merge_results(
+    conn: &Connection,
+    workspace_id: &str,
+    merge_request_id: &str,
+    revision_id: &str,
+    generation: u64,
+) -> Result<Vec<MergeResult>> {
+    let mut statement = conn.prepare(
+        "SELECT merge_result_id FROM merge_request_merge_results WHERE workspace_id=?1 AND merge_request_id=?2 AND revision_id=?3 ORDER BY created_at,merge_result_id",
+    ).map_err(db)?;
+    let ids = statement
+        .query_map(
+            params![workspace_id, merge_request_id, revision_id],
+            |row| row.get::<_, String>(0),
+        )
+        .map_err(db)?
+        .collect::<std::result::Result<Vec<_>, _>>()
+        .map_err(db)?;
+    ids.into_iter()
+        .map(|id| {
+            load_merge_result(conn, workspace_id, &id, generation)?
+                .ok_or(MergeRequestError::MergeResultNotFound(id))
+        })
+        .collect()
+}
+
+fn load_latest_merge_result_review(
+    conn: &Connection,
+    workspace_id: &str,
+    merge_result_id: &str,
+    generation: u64,
+) -> Result<Option<MergeRequestReview>> {
+    let attempt: Option<String> = conn.query_row(
+        "SELECT r.attempt_id FROM merge_request_reviews r JOIN merge_request_review_attempts a ON a.workspace_id=r.workspace_id AND a.attempt_id=r.attempt_id WHERE r.workspace_id=?1 AND r.merge_result_id=?2 AND a.lifecycle_generation=?3 ORDER BY r.submitted_at DESC,r.attempt_id DESC LIMIT 1",
+        params![workspace_id,merge_result_id,generation as i64], |row| row.get(0),
+    ).optional().map_err(db)?;
+    attempt
+        .map(|attempt| load_review(conn, workspace_id, &attempt))
+        .transpose()
+        .map(|review| review.flatten())
+}
+
 fn validate_review_input(input: &SubmitReview) -> Result<()> {
     if input.body.len() > MAX_REVIEW_BODY_BYTES {
         return Err(MergeRequestError::TooLarge {

crates/merge-request/tests/store.rs

@@ -44,7 +44,6 @@ fn revision(id: &str, ordinal: u64, head: &str) -> MergeRequestRevision {
         ordinal,
         base_commit: "base".into(),
         head_commit: head.into(),
-        head_tree: format!("tree-{head}"),
         diff_digest: format!("sha256:diff-{head}"),
         changed_paths: vec!["src/lib.rs".into()],
         summary: format!("revision {id}"),
@@ -58,6 +57,7 @@ fn open(store: &SqliteMergeRequestStore) {
             merge_request_id: "MR1".into(),
             ticket_id: "T1".into(),
             repository_id: "repo".into(),
+            target_ref_selector: "develop".into(),
             revision: revision("V1", 1, "h1"),
             authenticated_runtime_id: "R1".into(),
             authenticated_worker_id: "W1".into(),
@@ -79,6 +79,7 @@ fn attempt(store: &SqliteMergeRequestStore, id: &str, revision: &str, token: &st
             attempt_id: id.into(),
             ticket_id: "T1".into(),
             revision_id: revision.into(),
+            merge_result_id: None,
             parent_assignment_id: "A1".into(),
             parent_runtime_id: "R1".into(),
             parent_worker_id: "W1".into(),
@@ -97,6 +98,7 @@ fn review(
     store.submit_review(SubmitReview {
         ticket_id: "T1".into(),
         revision_id: revision.into(),
+        merge_result_id: None,
         capability_token: token.into(),
         decision,
         body: "evidence".into(),
@@ -105,6 +107,34 @@ fn review(
     })
 }
 
+fn record_result(
+    store: &SqliteMergeRequestStore,
+    revision: &str,
+    target: &str,
+    source: &str,
+    result: &str,
+    strategy: MergeStrategy,
+    resolution: MergeResolution,
+    operation: &str,
+) -> RecordMergeResultOutcome {
+    store
+        .record_merge_result(RecordMergeResult {
+            merge_result_id: format!("result-{operation}"),
+            ticket_id: "T1".into(),
+            expected_revision_id: revision.into(),
+            target_commit: target.into(),
+            source_commit: source.into(),
+            result_commit: result.into(),
+            strategy,
+            resolution,
+            operation_id: operation.into(),
+            actor_runtime_id: "runtime-orchestrator".into(),
+            actor_worker_id: "workspace-orchestrator".into(),
+            created_at: "2026-07-26T00:00:02Z".into(),
+        })
+        .unwrap()
+}
+
 #[test]
 fn storage_allows_multiple_merge_requests_for_one_ticket() {
     let (_dir, store) = setup();
@@ -114,6 +144,7 @@ fn storage_allows_multiple_merge_requests_for_one_ticket() {
             merge_request_id: "MR2".into(),
             ticket_id: "T1".into(),
             repository_id: "repo".into(),
+            target_ref_selector: "develop".into(),
             revision: revision("V2", 1, "h2"),
             authenticated_runtime_id: "R1".into(),
             authenticated_worker_id: "W1".into(),
@@ -133,6 +164,162 @@ fn storage_allows_multiple_merge_requests_for_one_ticket() {
     );
 }
 
+#[test]
+fn merge_result_is_idempotent_target_fenced_and_non_ff_reviewed_independently() {
+    let (_tmp, store) = setup();
+    open(&store);
+    attempt(
+        &store,
+        "attempt-source",
+        "V1",
+        "token-source",
+        "child-source",
+    );
+    review(&store, "V1", "token-source", ReviewDecision::Approve).unwrap();
+
+    let first = record_result(
+        &store,
+        "V1",
+        "T0",
+        "h1",
+        "h1",
+        MergeStrategy::FastForward,
+        MergeResolution::None,
+        "op-ff",
+    );
+    assert!(!first.replayed);
+    let replay = record_result(
+        &store,
+        "V1",
+        "T0",
+        "h1",
+        "h1",
+        MergeStrategy::FastForward,
+        MergeResolution::None,
+        "op-ff",
+    );
+    assert!(replay.replayed);
+    assert_eq!(
+        first.merge_result.merge_result_id,
+        replay.merge_result.merge_result_id
+    );
+
+    let ready = store
+        .readiness_for_ticket_with_target("T1", Some("T0"))
+        .unwrap();
+    assert!(ready.ready, "{:?}", ready.blockers);
+    assert_eq!(ready.merge_result_id.as_deref(), Some("result-op-ff"));
+
+    let stale = store
+        .readiness_for_ticket_with_target("T1", Some("T1"))
+        .unwrap();
+    assert!(!stale.ready);
+    assert!(
+        stale
+            .blockers
+            .iter()
+            .any(|blocker| blocker.contains("target moved"))
+    );
+
+    let changed = store.record_merge_result(RecordMergeResult {
+        merge_result_id: "result-conflict".into(),
+        ticket_id: "T1".into(),
+        expected_revision_id: "V1".into(),
+        target_commit: "different".into(),
+        source_commit: "h1".into(),
+        result_commit: "h1".into(),
+        strategy: MergeStrategy::FastForward,
+        resolution: MergeResolution::None,
+        operation_id: "op-ff".into(),
+        actor_runtime_id: "runtime-orchestrator".into(),
+        actor_worker_id: "workspace-orchestrator".into(),
+        created_at: "2026-07-26T00:00:03Z".into(),
+    });
+    assert!(matches!(
+        changed,
+        Err(MergeRequestError::MergeResultOperationConflict)
+    ));
+
+    record_result(
+        &store,
+        "V1",
+        "T1",
+        "h1",
+        "M1",
+        MergeStrategy::Merge,
+        MergeResolution::ConflictsResolved,
+        "op-merge",
+    );
+    let pending = store
+        .readiness_for_ticket_with_target("T1", Some("T1"))
+        .unwrap();
+    assert!(!pending.ready);
+    assert_eq!(
+        pending.merge_result_review_status,
+        Some(ReviewStatus::Pending)
+    );
+
+    store
+        .register_reviewer_child_session(RegisterReviewerChildSession {
+            parent_runtime_id: "runtime-orchestrator".into(),
+            parent_worker_id: "workspace-orchestrator".into(),
+            child_session_id: "child-merge".into(),
+            now: "2026-07-26T00:00:04Z".into(),
+        })
+        .unwrap();
+    store
+        .register_review_attempt(RegisterReviewAttempt {
+            attempt_id: "attempt-merge".into(),
+            ticket_id: "T1".into(),
+            revision_id: "V1".into(),
+            merge_result_id: Some("result-op-merge".into()),
+            parent_assignment_id: "A1".into(),
+            parent_runtime_id: "runtime-orchestrator".into(),
+            parent_worker_id: "workspace-orchestrator".into(),
+            child_session_id: "child-merge".into(),
+            capability_token: "token-merge".into(),
+            now: "2026-07-26T00:00:04Z".into(),
+        })
+        .unwrap();
+    store
+        .submit_review(SubmitReview {
+            ticket_id: "T1".into(),
+            revision_id: "V1".into(),
+            merge_result_id: Some("result-op-merge".into()),
+            capability_token: "token-merge".into(),
+            decision: ReviewDecision::Approve,
+            body: "merge evidence is valid".into(),
+            findings: vec![],
+            now: "2026-07-26T00:00:05Z".into(),
+        })
+        .unwrap();
+    let approved = store
+        .readiness_for_ticket_with_target("T1", Some("T1"))
+        .unwrap();
+    assert!(approved.ready, "{:?}", approved.blockers);
+    assert_eq!(
+        approved.merge_result_review_status,
+        Some(ReviewStatus::Approved)
+    );
+    let applied = store
+        .show_for_ticket_with_target("T1", Some("M1"))
+        .unwrap()
+        .unwrap();
+    assert_eq!(
+        applied
+            .applied_merge_result
+            .as_ref()
+            .map(|result| result.target_status),
+        Some(MergeResultTargetStatus::Applied)
+    );
+    assert!(
+        store
+            .readiness_for_ticket_with_target("T1", Some("M1"))
+            .unwrap()
+            .ready
+    );
+}
+
 #[test]
 fn bounded_context_rejects_oversized_revision_evidence() {
     let (_dir, store) = setup();
@@ -142,6 +329,7 @@ fn bounded_context_rejects_oversized_revision_evidence() {
         merge_request_id: "MR1".into(),
         ticket_id: "T1".into(),
         repository_id: "repo".into(),
+        target_ref_selector: "develop".into(),
         revision: oversized,
         authenticated_runtime_id: "R1".into(),
         authenticated_worker_id: "W1".into(),
@@ -311,7 +499,23 @@ fn v7_completion_operations_are_preserved_as_legacy_assigned_coder_authority() {
             |row| row.get(0),
         )
         .unwrap();
-    assert_eq!(version, 8);
+    assert_eq!(version, 9);
+    let head_tree_columns: i64 = conn
+        .query_row(
+            "SELECT COUNT(*) FROM pragma_table_info('merge_request_revisions') WHERE name='head_tree'",
+            [],
+            |row| row.get(0),
+        )
+        .unwrap();
+    assert_eq!(head_tree_columns, 0);
+    let merge_result_table: i64 = conn
+        .query_row(
+            "SELECT COUNT(*) FROM sqlite_master WHERE type='table' AND name='merge_request_merge_results'",
+            [],
+            |row| row.get(0),
+        )
+        .unwrap();
+    assert_eq!(merge_result_table, 1);
 }
 
 #[test]
@@ -431,6 +635,7 @@ fn spoof_self_approval_replay_and_cross_workspace_are_rejected() {
         attempt_id: "bad".into(),
         ticket_id: "T1".into(),
         revision_id: "V1".into(),
+        merge_result_id: None,
         parent_assignment_id: "A1".into(),
         parent_runtime_id: "R1".into(),
         parent_worker_id: "W1".into(),

crates/worker/src/feature/builtin/merge_request.rs

@@ -12,6 +12,7 @@ pub const MERGE_REQUEST_COMMON_TOOL_NAMES: &[&str] = &[
     "MergeRequestReadinessCheck",
     "MergeRequestOpen",
     "MergeRequestAddRevision",
+    "MergeRequestRecordMergeResult",
     "MergeRequestComplete",
 ];
 pub const MERGE_REQUEST_REVIEW_TOOL_NAME: &str = "MergeRequestReviewSubmit";
@@ -21,6 +22,7 @@ enum Kind {
     Readiness,
     Open,
     AddRevision,
+    RecordMergeResult,
     Complete,
     Review,
 }
@@ -41,7 +43,6 @@ struct OpenInput {
     revision_id: String,
     base_commit: String,
     head_commit: String,
-    head_tree: String,
     diff_digest: String,
     #[serde(default)]
     changed_paths: Vec<String>,
@@ -55,7 +56,6 @@ struct AddRevisionInput {
     revision_id: String,
     base_commit: String,
     head_commit: String,
-    head_tree: String,
     diff_digest: String,
     #[serde(default)]
     changed_paths: Vec<String>,
@@ -63,6 +63,30 @@ struct AddRevisionInput {
     summary: String,
 }
 #[derive(Debug, Deserialize, JsonSchema)]
+struct RecordMergeResultInput {
+    ticket: String,
+    expected_current_revision_id: String,
+    operation_id: String,
+    target_commit: String,
+    source_commit: String,
+    result_commit: String,
+    strategy: MergeStrategyInput,
+    resolution: MergeResolutionInput,
+}
+#[derive(Debug, Deserialize, JsonSchema)]
+#[serde(rename_all = "snake_case")]
+enum MergeStrategyInput {
+    FastForward,
+    Merge,
+}
+#[derive(Debug, Deserialize, JsonSchema)]
+#[serde(rename_all = "snake_case")]
+enum MergeResolutionInput {
+    None,
+    Clean,
+    ConflictsResolved,
+}
+#[derive(Debug, Deserialize, JsonSchema)]
 struct CompleteInput {
     ticket: String,
     operation_id: String,
@@ -101,6 +125,7 @@ impl Kind {
             Self::Readiness => "MergeRequestReadinessCheck",
             Self::Open => "MergeRequestOpen",
             Self::AddRevision => "MergeRequestAddRevision",
+            Self::RecordMergeResult => "MergeRequestRecordMergeResult",
             Self::Complete => "MergeRequestComplete",
             Self::Review => "MergeRequestReviewSubmit",
         }
@@ -113,6 +138,7 @@ impl Kind {
             Self::Show | Self::Readiness => json!(schemars::schema_for!(ShowInput)),
             Self::Open => json!(schemars::schema_for!(OpenInput)),
             Self::AddRevision => json!(schemars::schema_for!(AddRevisionInput)),
+            Self::RecordMergeResult => json!(schemars::schema_for!(RecordMergeResultInput)),
             Self::Complete => json!(schemars::schema_for!(CompleteInput)),
             Self::Review => json!(schemars::schema_for!(ReviewInput)),
         }
@@ -158,7 +184,7 @@ impl Tool for MergeRequestTool {
                     WorkspaceRequestMethod::Post,
                     format!("/api/w/{workspace_id}/tickets/{}/merge-request", v.ticket),
                     Some(
-                        json!({"repository_id":v.repository_id,"revision_id":v.revision_id,"base_commit":v.base_commit,"head_commit":v.head_commit,"head_tree":v.head_tree,"diff_digest":v.diff_digest,"changed_paths":v.changed_paths,"summary":v.summary}),
+                        json!({"repository_id":v.repository_id,"revision_id":v.revision_id,"base_commit":v.base_commit,"head_commit":v.head_commit,"diff_digest":v.diff_digest,"changed_paths":v.changed_paths,"summary":v.summary}),
                     ),
                 )
             }
@@ -172,7 +198,30 @@ impl Tool for MergeRequestTool {
                         v.ticket
                     ),
                     Some(
-                        json!({"expected_current_revision_id":v.expected_current_revision_id,"revision_id":v.revision_id,"base_commit":v.base_commit,"head_commit":v.head_commit,"head_tree":v.head_tree,"diff_digest":v.diff_digest,"changed_paths":v.changed_paths,"summary":v.summary}),
+                        json!({"expected_current_revision_id":v.expected_current_revision_id,"revision_id":v.revision_id,"base_commit":v.base_commit,"head_commit":v.head_commit,"diff_digest":v.diff_digest,"changed_paths":v.changed_paths,"summary":v.summary}),
+                    ),
+                )
+            }
+            Kind::RecordMergeResult => {
+                let v: RecordMergeResultInput = parse(input)?;
+                nonempty(&v.ticket)?;
+                let strategy = match v.strategy {
+                    MergeStrategyInput::FastForward => "fast_forward",
+                    MergeStrategyInput::Merge => "merge",
+                };
+                let resolution = match v.resolution {
+                    MergeResolutionInput::None => "none",
+                    MergeResolutionInput::Clean => "clean",
+                    MergeResolutionInput::ConflictsResolved => "conflicts_resolved",
+                };
+                (
+                    WorkspaceRequestMethod::Post,
+                    format!(
+                        "/api/w/{workspace_id}/tickets/{}/merge-request/merge-results",
+                        v.ticket
+                    ),
+                    Some(
+                        json!({"expected_current_revision_id":v.expected_current_revision_id,"operation_id":v.operation_id,"target_commit":v.target_commit,"source_commit":v.source_commit,"result_commit":v.result_commit,"strategy":strategy,"resolution":resolution}),
                     ),
                 )
             }
@@ -261,6 +310,7 @@ pub fn common_tools(client: Arc<dyn WorkspaceClient>) -> Vec<ToolDefinition> {
         definition(client.clone(), Kind::Readiness),
         definition(client.clone(), Kind::Open),
         definition(client.clone(), Kind::AddRevision),
+        definition(client.clone(), Kind::RecordMergeResult),
         definition(client, Kind::Complete),
     ]
 }
@@ -288,6 +338,9 @@ pub fn description(name: &str) -> Option<&'static str> {
         "MergeRequestAddRevision" => {
             Some("Append an immutable revision; prior approval cannot carry to the new revision.")
         }
+        "MergeRequestRecordMergeResult" => Some(
+            "Record validated immutable integration evidence for the current source revision and target tip.",
+        ),
         "MergeRequestComplete" => {
             Some("CAS-complete an approved revision with operation-id replay and crash fencing.")
         }
@@ -297,3 +350,20 @@ pub fn description(name: &str) -> Option<&'static str> {
         _ => None,
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn merge_request_tool_contract_omits_tree_hashes_and_exposes_merge_result() {
+        let open = serde_json::to_string(&schemars::schema_for!(OpenInput)).unwrap();
+        let add = serde_json::to_string(&schemars::schema_for!(AddRevisionInput)).unwrap();
+        let result = serde_json::to_string(&schemars::schema_for!(RecordMergeResultInput)).unwrap();
+        assert!(!open.contains("head_tree"));
+        assert!(!add.contains("head_tree"));
+        assert!(result.contains("fast_forward"));
+        assert!(result.contains("conflicts_resolved"));
+        assert!(MERGE_REQUEST_COMMON_TOOL_NAMES.contains(&"MergeRequestRecordMergeResult"));
+    }
+}

crates/worker/src/spawn/tool.rs

@@ -68,6 +68,9 @@ struct SubWorkerSpawnInput {
 struct ReviewerHandoffInput {
     ticket_id: String,
     revision_id: String,
+    /// Optional immutable MergeResult subject. Omit for source-revision review.
+    #[serde(default)]
+    merge_result_id: Option<String>,
 }
 
 #[derive(Debug, Deserialize, schemars::JsonSchema)]
@@ -422,6 +425,7 @@ impl Tool for SubWorkerSpawnTool {
             (
                 review.ticket_id.clone(),
                 review.revision_id.clone(),
+                review.merge_result_id.clone(),
                 uuid::Uuid::now_v7().to_string(),
                 format!(
                     "{}{}",
@@ -431,7 +435,9 @@ impl Tool for SubWorkerSpawnTool {
             )
         });
         let child_workspace_context =
-            if let Some((ticket_id, revision_id, _, capability_token)) = &reviewer_attempt {
+            if let Some((ticket_id, revision_id, merge_result_id, _, capability_token)) =
+                &reviewer_attempt
+            {
                 let workspace_id =
                     self.workspace_context
                         .workspace_id()
@@ -453,6 +459,7 @@ impl Tool for SubWorkerSpawnTool {
                         ReviewerAttemptContext {
                             ticket_id: ticket_id.clone(),
                             revision_id: revision_id.clone(),
+                            merge_result_id: merge_result_id.clone(),
                         },
                         capability_token.clone(),
                     ));
@@ -547,7 +554,9 @@ impl Tool for SubWorkerSpawnTool {
             }
         };
 
-        if let Some((ticket_id, revision_id, attempt_id, capability_token)) = &reviewer_attempt {
+        if let Some((ticket_id, revision_id, merge_result_id, attempt_id, capability_token)) =
+            &reviewer_attempt
+        {
             let workspace_id = self.workspace_context.workspace_id().ok_or_else(|| {
                 ToolError::ExecutionFailed("reviewer attempt lost Workspace identity".to_string())
             })?;
@@ -579,6 +588,7 @@ impl Tool for SubWorkerSpawnTool {
             let body = serde_json::json!({
                 "attempt_id": attempt_id,
                 "revision_id": revision_id,
+                "merge_result_id": merge_result_id,
                 "child_session_id": child_session_id,
                 "capability_token": capability_token,
             });

crates/worker/src/worker.rs

@@ -249,6 +249,7 @@ pub trait WorkspaceClient: std::fmt::Debug + Send + Sync {
 pub struct ReviewerAttemptContext {
     pub ticket_id: String,
     pub revision_id: String,
+    pub merge_result_id: Option<String>,
 }
 
 #[derive(Debug)]
@@ -310,6 +311,14 @@ impl WorkspaceClient for ReviewerChildWorkspaceClient {
                 "revision_id".to_string(),
                 serde_json::Value::String(self.context.revision_id.clone()),
             );
+            object.insert(
+                "merge_result_id".to_string(),
+                self.context
+                    .merge_result_id
+                    .clone()
+                    .map(serde_json::Value::String)
+                    .unwrap_or(serde_json::Value::Null),
+            );
             object.insert(
                 "capability_token".to_string(),
                 serde_json::Value::String(self.capability_token.clone()),
@@ -453,6 +462,7 @@ mod reviewer_client_tests {
             ReviewerAttemptContext {
                 ticket_id: "T1".into(),
                 revision_id: "V1".into(),
+                merge_result_id: None,
             },
             "secret".into(),
         );

crates/workspace-server/src/repositories.rs

@@ -83,10 +83,27 @@ pub struct GitCommitSummary {
     pub refs: Vec<String>,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct MergeTargetObservation {
+    pub selector: RepositorySelector,
+    pub commit: String,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct CommitObservation {
+    pub commit: String,
+    pub parents: Vec<String>,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum RepositoryLookupError {
     UnknownRepository { id: RepositoryId },
     UnsupportedProvider { id: RepositoryId, provider: String },
+    MissingDefaultSelector { id: RepositoryId },
+    InvalidSelector { id: RepositoryId, selector: String },
+    CommitNotFound { id: RepositoryId, commit: String },
+    InvalidCommitRelation { id: RepositoryId, detail: String },
+    ProviderFailure { id: RepositoryId, operation: String },
 }
 
 #[derive(Debug, Clone)]
@@ -167,6 +184,121 @@ impl RepositoryRegistryReader {
         })
     }
 
+    pub fn observe_merge_target(
+        &self,
+        id: &str,
+        requested_selector: Option<&str>,
+    ) -> Result<MergeTargetObservation, RepositoryLookupError> {
+        let repository = self.merge_repository(id)?;
+        let selector = requested_selector
+            .map(str::trim)
+            .filter(|value| !value.is_empty())
+            .map(str::to_owned)
+            .or_else(|| repository.default_selector.clone())
+            .ok_or_else(|| RepositoryLookupError::MissingDefaultSelector { id: id.to_string() })?;
+        if selector.starts_with('-') || selector.as_bytes().contains(&0) {
+            return Err(RepositoryLookupError::InvalidSelector {
+                id: id.to_string(),
+                selector,
+            });
+        }
+        let spec = format!("{selector}^{{commit}}");
+        let commit = merge_git_stdout(
+            repository,
+            "resolve target",
+            &["rev-parse", "--verify", "--end-of-options", &spec],
+        )?
+        .lines()
+        .next()
+        .unwrap_or_default()
+        .trim()
+        .to_owned();
+        if commit.is_empty() {
+            return Err(RepositoryLookupError::InvalidSelector {
+                id: id.to_string(),
+                selector,
+            });
+        }
+        Ok(MergeTargetObservation { selector, commit })
+    }
+
+    pub fn observe_commit(
+        &self,
+        id: &str,
+        commit: &str,
+    ) -> Result<CommitObservation, RepositoryLookupError> {
+        let repository = self.merge_repository(id)?;
+        let commit = commit.trim();
+        if commit.is_empty() || commit.starts_with('-') {
+            return Err(RepositoryLookupError::CommitNotFound {
+                id: id.to_string(),
+                commit: commit.into(),
+            });
+        }
+        let line = merge_git_stdout(
+            repository,
+            "read commit",
+            &[
+                "show",
+                "--no-patch",
+                "--format=%H %P",
+                "--end-of-options",
+                commit,
+            ],
+        )?;
+        let mut parts = line.split_whitespace();
+        let canonical = parts.next().unwrap_or_default().to_owned();
+        if canonical.is_empty() {
+            return Err(RepositoryLookupError::CommitNotFound {
+                id: id.to_string(),
+                commit: commit.into(),
+            });
+        }
+        Ok(CommitObservation {
+            commit: canonical,
+            parents: parts.map(str::to_owned).collect(),
+        })
+    }
+
+    pub fn ensure_ancestor(
+        &self,
+        id: &str,
+        ancestor: &str,
+        descendant: &str,
+    ) -> Result<(), RepositoryLookupError> {
+        let repository = self.merge_repository(id)?;
+        let status = Command::new("git")
+            .arg("-C")
+            .arg(&repository.path)
+            .args(["merge-base", "--is-ancestor", ancestor, descendant])
+            .status()
+            .map_err(|_| RepositoryLookupError::ProviderFailure {
+                id: id.into(),
+                operation: "check commit ancestry".into(),
+            })?;
+        if status.success() {
+            Ok(())
+        } else {
+            Err(RepositoryLookupError::InvalidCommitRelation {
+                id: id.into(),
+                detail: format!("commit {ancestor} is not an ancestor of {descendant}"),
+            })
+        }
+    }
+
+    fn merge_repository(&self, id: &str) -> Result<&ConfiguredRepository, RepositoryLookupError> {
+        let repository = self
+            .find(id)
+            .ok_or_else(|| RepositoryLookupError::UnknownRepository { id: id.into() })?;
+        if repository.provider != "git" {
+            return Err(RepositoryLookupError::UnsupportedProvider {
+                id: id.into(),
+                provider: repository.provider.clone(),
+            });
+        }
+        Ok(repository)
+    }
+
     fn find(&self, id: &str) -> Option<&ConfiguredRepository> {
         self.repositories
             .iter()
@@ -256,6 +388,19 @@ impl RepositoryRegistryReader {
     }
 }
 
+fn merge_git_stdout(
+    repository: &ConfiguredRepository,
+    operation: &str,
+    args: &[&str],
+) -> Result<String, RepositoryLookupError> {
+    git_stdout(&repository.path, args.iter().copied()).map_err(|_| {
+        RepositoryLookupError::ProviderFailure {
+            id: repository.id.clone(),
+            operation: operation.into(),
+        }
+    })
+}
+
 fn git_stdout<'a, I>(repository_path: &PathBuf, args: I) -> Result<String, String>
 where
     I: IntoIterator<Item = &'a str>,
@@ -422,6 +567,101 @@ mod tests {
         assert_eq!(projection.diagnostics[0].code, "repository_config_empty");
     }
 
+    #[test]
+    fn merge_evidence_is_resolved_by_repository_identity() {
+        let temp = tempfile::tempdir().unwrap();
+        let path = temp.path();
+        assert!(
+            Command::new("git")
+                .args(["init", "-b", "main"])
+                .arg(path)
+                .status()
+                .unwrap()
+                .success()
+        );
+        for args in [
+            vec!["config", "user.email", "test@example.com"],
+            vec!["config", "user.name", "Test"],
+        ] {
+            assert!(
+                Command::new("git")
+                    .arg("-C")
+                    .arg(path)
+                    .args(args)
+                    .status()
+                    .unwrap()
+                    .success()
+            );
+        }
+        std::fs::write(path.join("file.txt"), "base\n").unwrap();
+        assert!(
+            Command::new("git")
+                .arg("-C")
+                .arg(path)
+                .args(["add", "file.txt"])
+                .status()
+                .unwrap()
+                .success()
+        );
+        assert!(
+            Command::new("git")
+                .arg("-C")
+                .arg(path)
+                .args(["commit", "-m", "base"])
+                .status()
+                .unwrap()
+                .success()
+        );
+        let base = git_stdout(&path.to_path_buf(), ["rev-parse", "HEAD"])
+            .unwrap()
+            .trim()
+            .to_string();
+        assert!(
+            Command::new("git")
+                .arg("-C")
+                .arg(path)
+                .args(["checkout", "-b", "feature"])
+                .status()
+                .unwrap()
+                .success()
+        );
+        std::fs::write(path.join("file.txt"), "base\nfeature\n").unwrap();
+        assert!(
+            Command::new("git")
+                .arg("-C")
+                .arg(path)
+                .args(["commit", "-am", "feature"])
+                .status()
+                .unwrap()
+                .success()
+        );
+        let source = git_stdout(&path.to_path_buf(), ["rev-parse", "HEAD"])
+            .unwrap()
+            .trim()
+            .to_string();
+
+        let reader = RepositoryRegistryReader::new(vec![ConfiguredRepository {
+            id: "main".into(),
+            display_name: Some("Main".into()),
+            provider: "git".into(),
+            path: path.to_path_buf(),
+            uri: path.display().to_string(),
+            default_selector: Some("main".into()),
+        }]);
+        let target = reader.observe_merge_target("main", None).unwrap();
+        assert_eq!(target.selector, "main");
+        assert_eq!(target.commit, base);
+        assert_eq!(
+            reader.observe_commit("main", &source).unwrap().parents,
+            vec![base.clone()]
+        );
+        reader.ensure_ancestor("main", &base, &source).unwrap();
+        assert!(matches!(
+            reader.ensure_ancestor("main", &source, &base),
+            Err(RepositoryLookupError::InvalidCommitRelation { .. })
+        ));
+    }
+
     #[test]
     fn unknown_repository_is_not_resolved_from_fallback() {
         let reader = RepositoryRegistryReader::new(Vec::new());

crates/workspace-server/src/server.rs

@@ -94,8 +94,8 @@ use crate::observation::{
 use crate::profile_settings::UpdateWorkspaceMetadataRequest;
 use crate::records::{ObjectiveDetail, ProjectRecordList, TicketDetail};
 use crate::repositories::{
-    ConfiguredRepository, RepositoryListProjection, RepositoryLogRead, RepositoryLookupError,
+    ConfiguredRepository, MergeTargetObservation, RepositoryListProjection, RepositoryLogRead,
-    RepositoryRegistryReader, RepositorySummary,
+    RepositoryLookupError, RepositoryRegistryReader, RepositorySummary,
 };
 use crate::resource_broker::BackendResourceBroker;
 use crate::runtime_subscription::RuntimeSubscriptionBroker;
@@ -1290,6 +1290,10 @@ pub fn build_router(api: WorkspaceApi) -> Router {
             "/api/w/{workspace_id}/tickets/{id}/merge-request/revisions",
             post(scoped_add_merge_request_revision),
         )
+        .route(
+            "/api/w/{workspace_id}/tickets/{id}/merge-request/merge-results",
+            post(scoped_record_merge_request_result),
+        )
         .route(
             "/api/w/{workspace_id}/internal/reviewer-child-sessions",
             post(scoped_register_reviewer_child_session),
@@ -3521,7 +3525,6 @@ struct OpenMergeRequestRequest {
     revision_id: String,
     base_commit: String,
     head_commit: String,
-    head_tree: String,
     diff_digest: String,
     #[serde(default)]
     changed_paths: Vec<String>,
@@ -3535,7 +3538,6 @@ struct AddMergeRequestRevisionRequest {
     revision_id: String,
     base_commit: String,
     head_commit: String,
-    head_tree: String,
     diff_digest: String,
     #[serde(default)]
     changed_paths: Vec<String>,
@@ -3543,6 +3545,17 @@ struct AddMergeRequestRevisionRequest {
     summary: String,
 }
 
+#[derive(Debug, serde::Deserialize)]
+struct RecordMergeResultRequest {
+    expected_current_revision_id: String,
+    operation_id: String,
+    target_commit: String,
+    source_commit: String,
+    result_commit: String,
+    strategy: merge_request::MergeStrategy,
+    resolution: merge_request::MergeResolution,
+}
+
 #[derive(Debug, serde::Deserialize)]
 struct RegisterReviewerChildSessionRequest {
     child_session_id: String,
@@ -3552,6 +3565,8 @@ struct RegisterReviewerChildSessionRequest {
 struct RegisterMergeRequestReviewAttemptRequest {
     attempt_id: String,
     revision_id: String,
+    #[serde(default)]
+    merge_result_id: Option<String>,
     child_session_id: String,
     capability_token: String,
 }
@@ -3559,6 +3574,8 @@ struct RegisterMergeRequestReviewAttemptRequest {
 #[derive(Debug, serde::Deserialize)]
 struct SubmitMergeRequestReviewRequest {
     revision_id: String,
+    #[serde(default)]
+    merge_result_id: Option<String>,
     capability_token: String,
     decision: merge_request::ReviewDecision,
     #[serde(default)]
@@ -3612,14 +3629,89 @@ fn merge_request_store(
     .map_err(Into::into)
 }
 
+fn repository_merge_evidence_error(error: RepositoryLookupError) -> ApiError {
+    Error::InvalidInput(format!(
+        "repository merge evidence validation failed: {error:?}"
+    ))
+    .into()
+}
+
+fn validate_open_merge_request_evidence(
+    api: &WorkspaceApi,
+    ticket_id: &str,
+    repository_id: &str,
+    base_commit: &str,
+    head_commit: &str,
+) -> ApiResult<(String, String, MergeTargetObservation)> {
+    let ticket = browser_ticket_backend(api)?
+        .show(TicketIdOrSlug::Id(ticket_id.into()))
+        .map_err(Error::from)?;
+    if ticket.meta.repository_id.as_deref() != Some(repository_id) {
+        return Err(Error::InvalidInput(
+            "Merge Request repository must match the authoritative Ticket target".into(),
+        )
+        .into());
+    }
+    let reader = api.repository_reader();
+    let target = reader
+        .observe_merge_target(repository_id, ticket.meta.ref_selector.as_deref())
+        .map_err(repository_merge_evidence_error)?;
+    let base = reader
+        .observe_commit(repository_id, base_commit)
+        .map_err(repository_merge_evidence_error)?;
+    let source = reader
+        .observe_commit(repository_id, head_commit)
+        .map_err(repository_merge_evidence_error)?;
+    reader
+        .ensure_ancestor(repository_id, &base.commit, &source.commit)
+        .map_err(repository_merge_evidence_error)?;
+    Ok((base.commit, source.commit, target))
+}
+
+fn validate_revision_evidence(
+    api: &WorkspaceApi,
+    repository_id: &str,
+    base_commit: &str,
+    head_commit: &str,
+) -> ApiResult<(String, String)> {
+    let reader = api.repository_reader();
+    let base = reader
+        .observe_commit(repository_id, base_commit)
+        .map_err(repository_merge_evidence_error)?;
+    let source = reader
+        .observe_commit(repository_id, head_commit)
+        .map_err(repository_merge_evidence_error)?;
+    reader
+        .ensure_ancestor(repository_id, &base.commit, &source.commit)
+        .map_err(repository_merge_evidence_error)?;
+    Ok((base.commit, source.commit))
+}
+
+fn observe_merge_request_target(
+    api: &WorkspaceApi,
+    mr: &merge_request::MergeRequest,
+) -> Option<String> {
+    let selector = mr.target_ref_selector.as_deref()?;
+    api.repository_reader()
+        .observe_merge_target(&mr.repository_id, Some(selector))
+        .ok()
+        .map(|target| target.commit)
+}
+
 async fn scoped_show_merge_request(
     State(api): State<WorkspaceApi>,
     AxumPath((workspace_id, ticket_id)): AxumPath<(String, String)>,
 ) -> ApiResult<Json<merge_request::MergeRequest>> {
     let workspace_id = parse_workspace_id(&workspace_id)?;
     let store = merge_request_store(&api, &workspace_id)?;
+    let current = store.show_for_ticket(&ticket_id)?.ok_or_else(|| {
+        Error::from(merge_request::MergeRequestError::NotFound(
+            ticket_id.clone(),
+        ))
+    })?;
+    let target_commit = observe_merge_request_target(&api, &current);
     let value = store
-        .show_for_ticket(&ticket_id)?
+        .show_for_ticket_with_target(&ticket_id, target_commit.as_deref())?
         .ok_or_else(|| Error::from(merge_request::MergeRequestError::NotFound(ticket_id)))?;
     Ok(Json(value))
 }
@@ -3629,9 +3721,17 @@ async fn scoped_merge_request_readiness(
     AxumPath((workspace_id, ticket_id)): AxumPath<(String, String)>,
 ) -> ApiResult<Json<merge_request::MergeRequestReadiness>> {
     let workspace_id = parse_workspace_id(&workspace_id)?;
-    Ok(Json(
+    let store = merge_request_store(&api, &workspace_id)?;
-        merge_request_store(&api, &workspace_id)?.readiness_for_ticket(&ticket_id)?,
+    let current = store.show_for_ticket(&ticket_id)?.ok_or_else(|| {
-    ))
+        Error::from(merge_request::MergeRequestError::NotFound(
+            ticket_id.clone(),
+        ))
+    })?;
+    let target_commit = observe_merge_request_target(&api, &current);
+    Ok(Json(store.readiness_for_ticket_with_target(
+        &ticket_id,
+        target_commit.as_deref(),
+    )?))
 }
 
 async fn scoped_open_merge_request(
@@ -3657,13 +3757,19 @@ async fn scoped_open_merge_request(
         )
         .into());
     }
+    let (base_commit, source_commit, target) = validate_open_merge_request_evidence(
+        &api,
+        &ticket_id,
+        &input.repository_id,
+        &input.base_commit,
+        &input.head_commit,
+    )?;
     let now = Utc::now().to_rfc3339_opts(SecondsFormat::Millis, true);
     let revision = merge_request::MergeRequestRevision {
         revision_id: input.revision_id,
         ordinal: 1,
-        base_commit: input.base_commit,
+        base_commit,
-        head_commit: input.head_commit,
+        head_commit: source_commit,
-        head_tree: input.head_tree,
         diff_digest: input.diff_digest,
         changed_paths: input.changed_paths,
         summary: input.summary,
@@ -3675,6 +3781,7 @@ async fn scoped_open_merge_request(
             merge_request_id: format!("mr_{}", Uuid::now_v7().simple()),
             ticket_id,
             repository_id: input.repository_id,
+            target_ref_selector: target.selector,
             revision,
             authenticated_runtime_id: source.runtime_id,
             authenticated_worker_id: source.worker_id,
@@ -3714,6 +3821,12 @@ async fn scoped_add_merge_request_revision(
                 ticket_id.clone(),
             ))
         })?;
+    let (base_commit, head_commit) = validate_revision_evidence(
+        &api,
+        &current.repository_id,
+        &input.base_commit,
+        &input.head_commit,
+    )?;
     let now = Utc::now().to_rfc3339_opts(SecondsFormat::Millis, true);
     let mr =
         merge_request_store(&api, &workspace_id)?.add_revision(merge_request::AddRevision {
@@ -3722,9 +3835,8 @@ async fn scoped_add_merge_request_revision(
             revision: merge_request::MergeRequestRevision {
                 revision_id: input.revision_id,
                 ordinal: current.current_revision.ordinal + 1,
-                base_commit: input.base_commit,
+                base_commit,
-                head_commit: input.head_commit,
+                head_commit,
-                head_tree: input.head_tree,
                 diff_digest: input.diff_digest,
                 changed_paths: input.changed_paths,
                 summary: input.summary,
@@ -3738,6 +3850,105 @@ async fn scoped_add_merge_request_revision(
     Ok(Json(mr))
 }
 
+async fn scoped_record_merge_request_result(
+    State(api): State<WorkspaceApi>,
+    AxumPath((workspace_id, ticket_id)): AxumPath<(String, String)>,
+    headers: HeaderMap,
+    Json(input): Json<RecordMergeResultRequest>,
+) -> ApiResult<Json<merge_request::RecordMergeResultOutcome>> {
+    require_workspace_access(&workspace_id, &api)?;
+    let source = authenticate_worker_mutation_source(&api, &workspace_id, &headers)?;
+    require_online_workspace_orchestrator_source(&api, &source)?;
+    let store = merge_request_store(&api, &workspace_id)?;
+    let mr = store.show_for_ticket(&ticket_id)?.ok_or_else(|| {
+        Error::from(merge_request::MergeRequestError::NotFound(
+            ticket_id.clone(),
+        ))
+    })?;
+    if mr.current_revision.revision_id != input.expected_current_revision_id {
+        return Err(
+            Error::from(merge_request::MergeRequestError::StaleRevision {
+                expected: input.expected_current_revision_id,
+                current: mr.current_revision.revision_id,
+            })
+            .into(),
+        );
+    }
+    let target = api
+        .repository_reader()
+        .observe_merge_target(&mr.repository_id, mr.target_ref_selector.as_deref())
+        .map_err(repository_merge_evidence_error)?;
+    let supplied_target = api
+        .repository_reader()
+        .observe_commit(&mr.repository_id, &input.target_commit)
+        .map_err(repository_merge_evidence_error)?;
+    let supplied_source = api
+        .repository_reader()
+        .observe_commit(&mr.repository_id, &input.source_commit)
+        .map_err(repository_merge_evidence_error)?;
+    let supplied_result = api
+        .repository_reader()
+        .observe_commit(&mr.repository_id, &input.result_commit)
+        .map_err(repository_merge_evidence_error)?;
+    if target.commit != supplied_target.commit {
+        return Err(Error::InvalidInput(
+            "MergeResult target_commit is not the current target tip".into(),
+        )
+        .into());
+    }
+    if mr.current_revision.head_commit != supplied_source.commit {
+        return Err(Error::InvalidInput(
+            "MergeResult source_commit is not the current source revision".into(),
+        )
+        .into());
+    }
+    match input.strategy {
+        merge_request::MergeStrategy::FastForward => {
+            if input.resolution != merge_request::MergeResolution::None
+                || supplied_result.commit != supplied_source.commit
+            {
+                return Err(Error::InvalidInput(
+                    "fast-forward MergeResult must use the source commit and resolution=none"
+                        .into(),
+                )
+                .into());
+            }
+            api.repository_reader()
+                .ensure_ancestor(&mr.repository_id, &target.commit, &supplied_source.commit)
+                .map_err(repository_merge_evidence_error)?;
+        }
+        merge_request::MergeStrategy::Merge => {
+            if input.resolution == merge_request::MergeResolution::None {
+                return Err(Error::InvalidInput(
+                    "merge MergeResult requires clean or conflicts_resolved resolution".into(),
+                )
+                .into());
+            }
+            if supplied_result.parents.len() != 2
+                || !supplied_result.parents.contains(&target.commit)
+                || !supplied_result.parents.contains(&supplied_source.commit)
+            {
+                return Err(Error::InvalidInput("merge result commit must have exactly the target and source commits as parents".into()).into());
+            }
+        }
+    }
+    let outcome = store.record_merge_result(merge_request::RecordMergeResult {
+        merge_result_id: format!("MRG-{}", Uuid::new_v4()),
+        ticket_id,
+        expected_revision_id: mr.current_revision.revision_id,
+        target_commit: target.commit,
+        source_commit: supplied_source.commit,
+        result_commit: supplied_result.commit,
+        strategy: input.strategy,
+        resolution: input.resolution,
+        operation_id: input.operation_id,
+        actor_runtime_id: source.runtime_id,
+        actor_worker_id: source.worker_id,
+        created_at: Utc::now().to_rfc3339_opts(SecondsFormat::Millis, true),
+    })?;
+    Ok(Json(outcome))
+}
+
 async fn scoped_register_reviewer_child_session(
     State(api): State<WorkspaceApi>,
     headers: HeaderMap,
@@ -3773,7 +3984,9 @@ async fn scoped_register_merge_request_review_attempt(
         .ok_or_else(|| {
             Error::TicketAssignmentConflict("Ticket has no current assigned Coder".into())
         })?;
-    if assignment.worker.runtime_id != source.runtime_id
+    if input.merge_result_id.is_some() {
+        require_online_workspace_orchestrator_source(&api, &source)?;
+    } else if assignment.worker.runtime_id != source.runtime_id
         || assignment.worker.worker_id != source.worker_id
     {
         return Err(Error::TicketAssignmentConflict(
@@ -3786,6 +3999,7 @@ async fn scoped_register_merge_request_review_attempt(
             attempt_id: input.attempt_id,
             ticket_id,
             revision_id: input.revision_id,
+            merge_result_id: input.merge_result_id,
             parent_assignment_id: assignment.assignment_id,
             parent_runtime_id: source.runtime_id,
             parent_worker_id: source.worker_id,
@@ -3807,6 +4021,7 @@ async fn scoped_submit_merge_request_review(
         merge_request_store(&api, &workspace_id)?.submit_review(merge_request::SubmitReview {
             ticket_id,
             revision_id: input.revision_id,
+            merge_result_id: input.merge_result_id,
             capability_token: input.capability_token,
             decision: input.decision,
             body: input.body,
@@ -3884,16 +4099,41 @@ async fn scoped_confirm_merge_request(
     require_workspace_access(&workspace_id, &api)?;
     reject_non_browser_merge_auth(&headers)?;
     let actor = require_actor(&api, &headers).await?;
-    let mr = merge_request_store(&api, &workspace_id)?.confirm_merge(
+    let store = merge_request_store(&api, &workspace_id)?;
-        merge_request::MergeConfirmation {
+    let current = store.show_for_ticket(&ticket_id)?.ok_or_else(|| {
-            ticket_id,
+        Error::from(merge_request::MergeRequestError::NotFound(
-            expected_revision_id: input.expected_revision_id,
+            ticket_id.clone(),
-            authenticated_account_id: actor.account_id,
+        ))
-            actor_kind: "user".to_string(),
+    })?;
-            explicit_confirmation: input.explicit_confirmation,
+    let target_commit = observe_merge_request_target(&api, &current);
-            now: Utc::now().to_rfc3339_opts(SecondsFormat::Millis, true),
+    let observed = store
-        },
+        .show_for_ticket_with_target(&ticket_id, target_commit.as_deref())?
-    )?;
+        .ok_or_else(|| {
+            Error::from(merge_request::MergeRequestError::NotFound(
+                ticket_id.clone(),
+            ))
+        })?;
+    if observed.applied_merge_result.is_none() {
+        return Err(Error::InvalidInput(
+            "Merge Request result is not the current target tip; target update is a separate prerequisite operation".into(),
+        ).into());
+    }
+    let readiness = store.readiness_for_ticket_with_target(&ticket_id, target_commit.as_deref())?;
+    if !readiness.ready {
+        return Err(Error::InvalidInput(format!(
+            "Merge Request is not integration-ready: {}",
+            readiness.blockers.join("; ")
+        ))
+        .into());
+    }
+    let mr = store.confirm_merge(merge_request::MergeConfirmation {
+        ticket_id,
+        expected_revision_id: input.expected_revision_id,
+        authenticated_account_id: actor.account_id,
+        actor_kind: "user".to_string(),
+        explicit_confirmation: input.explicit_confirmation,
+        now: Utc::now().to_rfc3339_opts(SecondsFormat::Millis, true),
+    })?;
     Ok(Json(mr))
 }
 
@@ -11128,6 +11368,21 @@ fn repository_lookup<T>(result: std::result::Result<T, RepositoryLookupError>) -
                 }],
             )
         }
+        other => {
+            let message = format!("repository evidence validation failed: {other:?}");
+            ApiError::with_diagnostics(
+                Error::RuntimeOperationFailed {
+                    runtime_id: "workspace-repository-registry".to_string(),
+                    code: "repository_evidence_invalid".to_string(),
+                    message: message.clone(),
+                },
+                vec![RuntimeDiagnostic {
+                    code: "repository_evidence_invalid".to_string(),
+                    severity: DiagnosticSeverity::Error,
+                    message,
+                }],
+            )
+        }
     })
 }
 
@@ -12193,12 +12448,13 @@ mod tests {
                 merge_request_id: "MR-server-completion".into(),
                 ticket_id: ticket.id.clone(),
                 repository_id: TEST_REPOSITORY_ID.into(),
+                target_ref_selector: "develop".into(),
                 revision: merge_request::MergeRequestRevision {
                     revision_id: "V1".into(),
                     ordinal: 1,
                     base_commit: "base".into(),
                     head_commit: "head".into(),
-                    head_tree: "tree".into(),
+
                     diff_digest: "sha256:diff".into(),
                     changed_paths: vec!["src/lib.rs".into()],
                     summary: "approved revision".into(),
@@ -12223,6 +12479,7 @@ mod tests {
                 attempt_id: "attempt".into(),
                 ticket_id: ticket.id.clone(),
                 revision_id: "V1".into(),
+                merge_result_id: None,
                 parent_assignment_id: assignment.assignment_id.clone(),
                 parent_runtime_id: coder.worker_ref.runtime_id.clone(),
                 parent_worker_id: coder.worker_ref.worker_id.clone(),
@@ -12235,6 +12492,7 @@ mod tests {
             .submit_review(merge_request::SubmitReview {
                 ticket_id: ticket.id.clone(),
                 revision_id: "V1".into(),
+                merge_result_id: None,
                 capability_token: "review-token".into(),
                 decision: merge_request::ReviewDecision::Approve,
                 body: "approved".into(),

web/workspace/src/routes/w/[workspaceId]/tickets/[ticketId]/+page.svelte

@@ -20,8 +20,31 @@
   type MergeRequestDetail = {
     state: "draft" | "open" | "closed" | "merged";
     review_status: "pending" | "approved" | "changes_requested";
-    current_revision: { revision_id: string; head_commit: string; head_tree: string; diff_digest: string; changed_paths: string[]; summary: string };
+    target_ref_selector?: string | null;
+    target_status: "known" | "unknown";
+    observed_target_commit?: string | null;
+    current_revision: { revision_id: string; head_commit: string; diff_digest: string; changed_paths: string[]; summary: string };
     current_review?: { decision: string; body: string; reviewer_effective_profile: string } | null;
+    current_merge_result?: {
+      merge_result_id: string;
+      target_commit: string;
+      source_commit: string;
+      result_commit: string;
+      strategy: "fast_forward" | "merge";
+      resolution: "none" | "clean" | "conflicts_resolved";
+      target_status: "current" | "applied" | "stale" | "unknown";
+      review_status: "pending" | "approved" | "changes_requested";
+    } | null;
+    applied_merge_result?: {
+      merge_result_id: string;
+      target_commit: string;
+      source_commit: string;
+      result_commit: string;
+      strategy: "fast_forward" | "merge";
+      resolution: "none" | "clean" | "conflicts_resolved";
+      target_status: "current" | "applied" | "stale" | "unknown";
+      review_status: "pending" | "approved" | "changes_requested";
+    } | null;
     merged_at?: string | null;
   };
 
@@ -368,15 +391,38 @@
           <p class="workspace-callout is-error">{data.mergeRequest.error}</p>
         {:else if mergeRequest}
           <p><strong>{mergeRequest.state}</strong> · {mergeRequest.review_status}</p>
+          <p>Target <code>{mergeRequest.target_ref_selector ?? "unknown"}</code> · {mergeRequest.target_status}</p>
+          {#if mergeRequest.observed_target_commit}<p>Target tip <code>{mergeRequest.observed_target_commit}</code></p>{/if}
           <p><code>{mergeRequest.current_revision.revision_id}</code></p>
           <p>Head <code>{mergeRequest.current_revision.head_commit}</code></p>
+          {#if mergeRequest.current_merge_result}
+            <p>
+              MergeResult <code>{mergeRequest.current_merge_result.merge_result_id}</code> ·
+              {mergeRequest.current_merge_result.strategy} / {mergeRequest.current_merge_result.resolution} ·
+              {mergeRequest.current_merge_result.target_status} / {mergeRequest.current_merge_result.review_status}
+            </p>
+            <p>Result <code>{mergeRequest.current_merge_result.result_commit}</code></p>
+          {:else if mergeRequest.applied_merge_result}
+            <p>
+              Applied MergeResult <code>{mergeRequest.applied_merge_result.merge_result_id}</code> ·
+              {mergeRequest.applied_merge_result.strategy} / {mergeRequest.applied_merge_result.resolution} ·
+              {mergeRequest.applied_merge_result.review_status}
+            </p>
+            <p>Result <code>{mergeRequest.applied_merge_result.result_commit}</code> is the current target tip.</p>
+          {:else if mergeRequest.state === "open"}
+            <p class="workspace-callout">No current MergeResult has been recorded for this target tip.</p>
+          {/if}
           {#if mergeRequest.current_revision.summary}<p>{mergeRequest.current_revision.summary}</p>{/if}
           {#if mergeRequest.current_review}
             <p><strong>{mergeRequest.current_review.decision}</strong> by {mergeRequest.current_review.reviewer_effective_profile}</p>
             {#if mergeRequest.current_review.body}<RichMarkdown text={mergeRequest.current_review.body} />{/if}
           {/if}
-          {#if mergeRequest.state === "open" && mergeRequest.review_status === "approved"}
+          {#if mergeRequest.state === "open"
-            <label><input type="checkbox" bind:checked={confirmMerge} /> Explicitly confirm merge of this revision</label>
+            && mergeRequest.review_status === "approved"
+            && mergeRequest.applied_merge_result?.target_status === "applied"
+            && (mergeRequest.applied_merge_result.strategy === "fast_forward"
+              || mergeRequest.applied_merge_result.review_status === "approved")}
+            <label><input type="checkbox" bind:checked={confirmMerge} /> Explicitly confirm the externally applied result</label>
             <button class="workspace-primary-button" type="button" disabled={!confirmMerge || busy !== null} onclick={mergeConfirmedRevision}>Confirm merge</button>
           {/if}
         {:else}