The comment you can take back

Docs/Development.md

@@ -176,7 +176,7 @@ Sources/Workspace/
     NewRepository.swift       making one instead of finding one: `git init`, `git clone`
     Project.swift             one repository: remote, status, PRs, ports, tree
     PullRequest.swift         unified PR model + gh/bkt loaders
-    PullRequestComment.swift  reading and posting PR comments
+    PullRequestComment.swift  reading, posting and rewriting PR comments
     PullRequestCommit.swift   a PR's commits + the diff of one commit
     PullRequestActions.swift  merge, reject, and drift from the target branch
     PullRequestReviewer.swift  who is reviewing, their verdicts, and asking more people

README.md

@@ -91,6 +91,7 @@ missing ones, so you never have to work out which command it wanted.
 | Read it all | Details, Diff and Commits tabs. Markdown, images and mentions rendered properly. |
 | Threads | Replies nested under what they answer, every author in a colour of their own. A resolved one folds to a single row — author, file and first line, under a green **Resolved** chip — in the conversation and in the diff alike; click it to read the rest. |
 | Write back | Comment, reply, resolve a thread or open it again, edit the description, approve, request changes, merge, reject. |
+| Second thoughts | **Edit** on a comment of your own — in the conversation or on a line of the diff — reopens it in place, wherever the host lets you change it. |
 | Reviewers | See who approved, add more from a searchable list of the people who can be asked. |
 | `@` anyone | Type `@` in any comment box and pick a name from the repo. |
 | Builds beside you | CI runs for the head commit in a side panel, failures first, kept current on their own while the panel is in front of you. |

Sources/Workspace/Models/PullRequest.swift

@@ -149,6 +149,7 @@ enum PullRequestError: LocalizedError {
     case commandFailed(String)
     case unsupportedHost
     case replyUnsupported
+    case editUnsupported
 
     var errorDescription: String? {
         switch self {
@@ -160,6 +161,8 @@ enum PullRequestError: LocalizedError {
             "This repository's remote is neither GitHub nor Bitbucket."
         case .replyUnsupported:
             "This host cannot thread a reply onto that comment."
+        case .editUnsupported:
+            "That comment cannot be edited from here."
         }
     }
 }

Sources/Workspace/Models/WorkspaceStore.swift

@@ -1613,6 +1613,35 @@ final class WorkspaceStore {
         item.isPostingComment = false
     }
 
+    /// Replaces what an already-posted comment says.
+    ///
+    /// The conversation is read back for the same reason a resolve reads it
+    /// back: the host's copy is the one that counts, and it is what renders the
+    /// edited comment — including the "edited" mark a host may add.
+    func updateComment(
+        _ body: String,
+        of comment: PullRequestComment,
+        on item: ViewerItem,
+        project: Project,
+        pr: PullRequest
+    ) async {
+        item.isPostingComment = true
+        item.commentError = nil
+        do {
+            try await PullRequestService.updateComment(
+                mentioning(body, on: item, pr: pr),
+                of: comment,
+                on: pr,
+                in: project.url
+            )
+            showStatus("Comment updated on #\(pr.number)")
+            await loadComments(item, project: project, pr: pr)
+        } catch {
+            item.commentError = error.localizedDescription
+        }
+        item.isPostingComment = false
+    }
+
     /// Settles a comment thread, or opens it again. The conversation is read
     /// back afterwards rather than edited in place: resolution is the host's
     /// word, and a thread someone else has already touched should come back

Sources/Workspace/Views/DiffView.swift

@@ -29,6 +29,8 @@ struct DiffView: View {
     /// The comment whose reply box is open, shared by every thread on screen so
     /// that opening one closes the last.
     @State private var replyingTo: PullRequestComment?
+    /// The comment being rewritten, shared the same way for the same reason.
+    @State private var editing: PullRequestComment?
     /// The diff flattened to one entry per visible line — see `DiffElement`.
     /// Cached rather than recomputed in `body`, which also runs on every frame
     /// of a window resize.
@@ -349,11 +351,13 @@ struct DiffView: View {
                 threads: threads(file: file, row: row),
                 isPosting: comments?.isPosting ?? false,
                 replyingTo: $replyingTo,
+                editing: $editing,
                 mentions: comments?.mentions ?? .none,
                 onReply: { parent, body in await comments?.reply(parent, body) },
                 // Flattened: chaining through an optional bundle onto an
                 // optional closure would otherwise nest one inside the other.
-                onResolve: comments?.resolve ?? nil
+                onResolve: comments?.resolve ?? nil,
+                onEdit: comments?.edit ?? nil
             )
             .frame(width: width, alignment: .leading)
         case .composer:
@@ -383,6 +387,7 @@ struct DiffView: View {
             guard let anchor = row.anchor(in: file, side: side) else { return }
             composing = composing == anchor ? nil : anchor
             replyingTo = nil
+            editing = nil
         }
     }
 
@@ -410,6 +415,8 @@ struct DiffComments {
     /// Settles a thread, or opens it again. Nil for a diff that has no host
     /// behind it to be told.
     var resolve: ((PullRequestComment, Bool) async -> Void)?
+    /// Replaces what a comment says. Nil for the same reason.
+    var edit: ((PullRequestComment, String) async -> Void)?
 }
 
 extension DiffRow {

Sources/Workspace/Views/InlineCommentViews.swift

@@ -35,9 +35,12 @@ struct DiffCommentThreads: View {
     let threads: [PullRequestCommentNode]
     let isPosting: Bool
     @Binding var replyingTo: PullRequestComment?
+    /// The comment whose text is being rewritten, if any.
+    @Binding var editing: PullRequestComment?
     var mentions: MentionSource = .none
     let onReply: (PullRequestComment, String) async -> Void
     var onResolve: ((PullRequestComment, Bool) async -> Void)?
+    var onEdit: ((PullRequestComment, String) async -> Void)?
 
     var body: some View {
         VStack(alignment: .leading, spacing: 8) {
@@ -46,12 +49,14 @@ struct DiffCommentThreads: View {
                     node: thread,
                     depth: 0,
                     replyingTo: $replyingTo,
+                    editing: $editing,
                     isPosting: isPosting,
                     mentions: mentions,
                     // The line it hangs under already says which file this is.
                     isInline: true,
                     onReply: onReply,
-                    onResolve: onResolve
+                    onResolve: onResolve,
+                    onEdit: onEdit
                 )
             }
         }
@@ -202,18 +207,43 @@ struct DiffCommentComposer: View {
     }
 }
 
-/// A text box with Cancel and a send button. Used for replies in a thread and
-/// for new comments on a line, which differ only in their wording.
+/// A text box with Cancel and a send button. Used for replies in a thread, for
+/// new comments on a line, and for rewriting a comment already posted — which
+/// differ only in their wording and in what the box starts out holding.
 struct CommentComposer: View {
     let prompt: String
     let sendTitle: String
-    var sendSymbol = "arrowshape.turn.up.left"
+    let sendSymbol: String
     let isPosting: Bool
-    var mentions: MentionSource = .none
+    let mentions: MentionSource
     let onCancel: () -> Void
     let onSend: (String) async -> Void
 
-    @State private var draft = ""
+    @State private var draft: String
+
+    /// `text` is what the box opens with — empty for anything being written for
+    /// the first time, and the comment as the host stores it for an edit. It is
+    /// spelled out rather than left to the memberwise initialiser because a
+    /// `@State` needs its starting value here, before the view is on screen.
+    init(
+        prompt: String,
+        sendTitle: String,
+        sendSymbol: String = "arrowshape.turn.up.left",
+        isPosting: Bool,
+        mentions: MentionSource = .none,
+        startingFrom text: String = "",
+        onCancel: @escaping () -> Void,
+        onSend: @escaping (String) async -> Void
+    ) {
+        self.prompt = prompt
+        self.sendTitle = sendTitle
+        self.sendSymbol = sendSymbol
+        self.isPosting = isPosting
+        self.mentions = mentions
+        self.onCancel = onCancel
+        self.onSend = onSend
+        _draft = State(initialValue: text)
+    }
 
     private var isEmpty: Bool {
         draft.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty