diff --git a/internal/gerrit/change.go b/internal/gerrit/change.go
index 78ca091..be59b6d 100644
--- a/internal/gerrit/change.go
+++ b/internal/gerrit/change.go
@@ -5,6 +5,7 @@
 package gerrit
 
 import (
+	"cmp"
 	"encoding/json"
 	"fmt"
 	"slices"
@@ -135,12 +136,52 @@
 // These are the top-level messages created by clicking on
 // the top REPLY button when reviewing a change.
 // Inline file comments are returned by [Client.Comments].
-func (c *Client) ChangeMessages(ch *Change) []ChangeMessageInfo {
+func (c *Client) ChangeMessages(ch *Change) []*ChangeMessageInfo {
 	var messages struct {
-		Messages []ChangeMessageInfo `json:"messages"`
+		Messages []json.RawMessage `json:"messages"`
 	}
 	c.unmarshal(ch, "messages", &messages)
-	return messages.Messages
+
+	// Unpack into a changeMessageInfo struct, and then convert to
+	// ChangeMessageInfo, so that we don't have to unpack the lengthy
+	// AccountInfo data each time.
+	type changeMessageInfo struct {
+		ID                string            `json:"id"`
+		Author            json.RawMessage   `json:"author,omitempty"`
+		RealAuthor        json.RawMessage   `json:"real_author,omitempty"`
+		Date              TimeStamp         `json:"date"`
+		Message           string            `json:"message"`
+		AccountsInMessage []json.RawMessage `json:"accounts_in_message,omitempty"`
+		Tag               string            `json:"tag,omitempty"`
+		RevisionNumber    int               `json:"_revision_number,omitempty"`
+	}
+
+	ret := make([]*ChangeMessageInfo, 0, len(messages.Messages))
+	for _, msg := range messages.Messages {
+		var cmi changeMessageInfo
+		if err := json.Unmarshal(msg, &cmi); err != nil {
+			c.slog.Error("gerrit message decode failure", "num", ch.num, "data", msg, "err", err)
+			c.db.Panic("gerrit message decode failure", "num", ch.num, "err", err)
+		}
+
+		var aims []*AccountInfo
+		for _, aim := range cmi.AccountsInMessage {
+			aims = append(aims, c.loadAccount(aim))
+		}
+		r := &ChangeMessageInfo{
+			ID:                cmi.ID,
+			Author:            c.loadAccount(cmi.Author),
+			RealAuthor:        c.loadAccount(cmi.RealAuthor),
+			Date:              cmi.Date,
+			Message:           cmi.Message,
+			AccountsInMessage: aims,
+			Tag:               cmi.Tag,
+			RevisionNumber:    cmi.RevisionNumber,
+		}
+		ret = append(ret, r)
+	}
+
+	return ret
 }
 
 // ChangeDescription returns the current description of the change.
@@ -176,10 +217,11 @@
 	return workInProgress.WorkInProgress
 }
 
-// ChangeReviewed returns a list of accounts that have reviewed this change.
+// ChangeReviewers returns a list of accounts that are listed as
+// reviewers of this change.
 // Note that this is not identical to ChangeInfo.Reviewers,
 // which includes both reviewers and people CC'ed.
-func (c *Client) ChangeReviewed(ch *Change) []*AccountInfo {
+func (c *Client) ChangeReviewers(ch *Change) []*AccountInfo {
 	var reviewers struct {
 		Reviewers map[string][]json.RawMessage `json:"reviewers"`
 	}
@@ -227,6 +269,9 @@
 
 // unmarshalLabel unmarshals a LabelInfo.
 func (c *Client) unmarshalLabel(ch *Change, input json.RawMessage) *LabelInfo {
+	// Unpack into approvalInfo and labelInfo structs, and then convert to
+	// ApprovalInfo and LabelInfo, so that we don't have to unpack the
+	// lengthy AccountInfo data each time.
 	type approvalInfo struct {
 		Value                int             `json:"value,omitempty"`
 		PermittedVotingRange VotingRangeInfo `json:"permitted_voting_range,omitempty"`
@@ -348,6 +393,72 @@
 	return counts.TotalCommentCount, counts.UnresolvedCommentCount
 }
 
+// ChangeRevisions returns information about all the patch sets,
+// ordered by patch set number.
+func (c *Client) ChangeRevisions(ch *Change) []*RevisionInfo {
+	// Unpack into commitInfo and revisionInfo structs,
+	// and then convert to CommitInfo and RevisionInfo,
+	// so that we don't have to unpack the lengthy AccountInfo
+	// data each time. We also skip some CommitInfo fields.
+	type commitInfo struct {
+		Commit    string         `json:"commit,omitempty"`
+		Author    *GitPersonInfo `json:"author,omitempty"`
+		Committer *GitPersonInfo `json:"committer,omitempty"`
+		Subject   string         `json:"subject"`
+		Message   string         `json:"message,omitempty"`
+	}
+	type revisionInfo struct {
+		Kind         string          `json:"kind"`
+		Number       int             `json:"_number"`
+		Created      TimeStamp       `json:"created"`
+		Uploader     json.RawMessage `json:"uploader"`
+		RealUploader json.RawMessage `json:"real_uploader,omitempty"`
+		Ref          string          `json:"ref"`
+		Commit       *commitInfo     `json:"commit,omitempty"`
+		Branch       string          `json:"branch,omitempty"`
+		Description  string          `json:"description,omitempty"`
+	}
+	var revisions struct {
+		Revisions map[string]*revisionInfo `json:"revisions"`
+	}
+	c.unmarshal(ch, "revisions", &revisions)
+
+	toCommitInfo := func(from *commitInfo) *CommitInfo {
+		if from == nil {
+			return nil
+		}
+		return &CommitInfo{
+			Commit:    from.Commit,
+			Author:    from.Author,
+			Committer: from.Committer,
+			Subject:   from.Subject,
+			Message:   from.Message,
+		}
+	}
+
+	revs := make([]*RevisionInfo, 0, len(revisions.Revisions))
+	for _, rev := range revisions.Revisions {
+		ri := &RevisionInfo{
+			Kind:         rev.Kind,
+			Number:       rev.Number,
+			Created:      rev.Created,
+			Uploader:     c.loadAccount(rev.Uploader),
+			RealUploader: c.loadAccount(rev.RealUploader),
+			Ref:          rev.Ref,
+			Commit:       toCommitInfo(rev.Commit),
+			Branch:       rev.Branch,
+			Description:  rev.Description,
+		}
+		revs = append(revs, ri)
+	}
+
+	slices.SortFunc(revs, func(a, b *RevisionInfo) int {
+		return cmp.Compare(a.Number, b.Number)
+	})
+
+	return revs
+}
+
 // unmarshal unmarshals ch.data into a value. If the unmarshal fails, it
 // crashes with an error.
 func (c *Client) unmarshal(ch *Change, msg string, val any) {
diff --git a/internal/gerrit/data.go b/internal/gerrit/data.go
index f78041d..595e772 100644
--- a/internal/gerrit/data.go
+++ b/internal/gerrit/data.go
@@ -56,21 +56,71 @@
 
 // Comments returns the comments on a change, if any. These are the
 // inline comments placed on files in the change. The top-level
-// replies are stored in a [Change] and are returned by [Change.Messages].
+// replies are stored in a [Change] and are returned by [Client.ChangeMessages].
 //
 // This returns a map from file names to a list of comments on each file.
-// Gerrit stores top-level comments on the file "/PATCHSET_LEVEL".
-// The result may be nil, with no error, if no comment information exists.
-func (c *Client) Comments(project string, changeNum int) (map[string][]*CommentInfo, error) {
+// The result is nil if no comment information exists.
+func (c *Client) Comments(project string, changeNum int) map[string][]*CommentInfo {
 	val, ok := c.db.Get(o(commentKind, c.instance, project, changeNum))
 	if !ok {
-		return nil, nil
+		return nil
 	}
-	var comments map[string][]*CommentInfo
+
+	// Unpack into a commentInfo struct, and then convert to CommentInfo,
+	// so that we don't have to unpack the lengthy AccountInfo data
+	// each time.
+	type commentInfo struct {
+		PatchSet        int                  `json:"patch_set,omitempty"`
+		ID              string               `json:"id"`
+		Path            string               `json:"path,omitempty"`
+		Side            string               `json:"side,omitempty"`
+		Parent          int                  `json:"parent,omitempty"`
+		Line            int                  `json:"line,omitempty"`
+		Range           *CommentRange        `json:"range,omitempty"`
+		InReplyTo       string               `json:"in_reply_to,omitempty"`
+		Message         string               `json:"message,omitempty"`
+		Updated         TimeStamp            `json:"updated"`
+		Author          json.RawMessage      `json:"author,omitempty"`
+		Tag             string               `json:"tag,omitempty"`
+		Unresolved      bool                 `json:"unresolved,omitempty"`
+		ChangeMessageID string               `json:"change_message_id,omitempty"`
+		CommitID        string               `json:"commit_id,omitempty"`
+		FixSuggestions  []*FixSuggestionInfo `json:"fix_suggestions,omitempty"`
+	}
+	var comments map[string][]*commentInfo
 	if err := json.Unmarshal(val, &comments); err != nil {
-		return nil, fmt.Errorf("can't decode change %d comments: %v", changeNum, err)
+		c.slog.Error("gerrit comment decode failure", "num", changeNum, "data", val, "err", err)
+		c.db.Panic("gerrit comment decode failure", "num", changeNum, "err", err)
 	}
-	return comments, nil
+
+	ret := make(map[string][]*CommentInfo, len(comments))
+	for key, val := range comments {
+		rcs := make([]*CommentInfo, 0, len(val))
+		for _, comment := range val {
+			rc := &CommentInfo{
+				PatchSet:        comment.PatchSet,
+				ID:              comment.ID,
+				Path:            comment.Path,
+				Side:            comment.Side,
+				Parent:          comment.Parent,
+				Line:            comment.Line,
+				Range:           comment.Range,
+				InReplyTo:       comment.InReplyTo,
+				Message:         comment.Message,
+				Updated:         comment.Updated,
+				Author:          c.loadAccount(comment.Author),
+				Tag:             comment.Tag,
+				Unresolved:      comment.Unresolved,
+				ChangeMessageID: comment.ChangeMessageID,
+				CommitID:        comment.CommitID,
+				FixSuggestions:  comment.FixSuggestions,
+			}
+			rcs = append(rcs, rc)
+		}
+		ret[key] = rcs
+	}
+
+	return ret
 }
 
 // A ChangeEvent is a Gerrit CL change event returned by ChangeWatcher.
diff --git a/internal/gerrit/sync_test.go b/internal/gerrit/sync_test.go
index dfa1a1b..2058e31 100644
--- a/internal/gerrit/sync_test.go
+++ b/internal/gerrit/sync_test.go
@@ -227,7 +227,7 @@
 				"Patch Set 9:\n\nNaah, just roll forward and fix the test.",
 			},
 			func(got, want any) bool {
-				g := got.([]ChangeMessageInfo)
+				g := got.([]*ChangeMessageInfo)
 				w := want.([]string)
 				for i, m := range g {
 					if m.Message != w[i] {
@@ -250,8 +250,8 @@
 			nil,
 		},
 		{
-			"ChangeReviewed",
-			wa(c.ChangeReviewed),
+			"ChangeReviewers",
+			wa(c.ChangeReviewers),
 			[]string{
 				"bradfitz@golang.org",
 				"iant@golang.org",
@@ -328,9 +328,32 @@
 				return slices.Equal(g, w)
 			},
 		},
+		{
+			"ChangeRevisions",
+			wa(c.ChangeRevisions),
+			"errgroup: add package",
+			func(got, want any) bool {
+				g := got.([]*RevisionInfo)
+				if len(g) != 9 {
+					return false
+				}
+				for _, r := range g {
+					if r.Commit.Subject != want {
+						return false
+					}
+				}
+				return true
+			},
+		},
 	}
 
 	testChangeTests(t, ch, tests)
+
+	total, unresolved := c.ChangeCommentCounts(ch)
+	wantTotal, wantUnresolved := 22, 0
+	if total != wantTotal || unresolved != wantUnresolved {
+		t.Errorf("CommentCounts = %d, %d; want %d, %d", total, unresolved, wantTotal, wantUnresolved)
+	}
 }
 
 // checkChange verifies that we can unpack CL information, and that it
@@ -343,11 +366,7 @@
 	}
 
 	// Fetch and unpack comments for the change.
-	commentsInfo, err := c.Comments(project, changeNum)
-	if err != nil {
-		t.Error(err)
-		return
-	}
+	commentsInfo := c.Comments(project, changeNum)
 	if commentsInfo == nil {
 		t.Errorf("no comment information for CL %d", changeNum)
 		return
diff --git a/internal/gerrit/testing_test.go b/internal/gerrit/testing_test.go
index 2681160..d32841a 100644
--- a/internal/gerrit/testing_test.go
+++ b/internal/gerrit/testing_test.go
@@ -79,7 +79,7 @@
 				"message 2",
 			},
 			func(got, want any) bool {
-				g := got.([]ChangeMessageInfo)
+				g := got.([]*ChangeMessageInfo)
 				w := want.([]string)
 				for i, m := range g {
 					if m.Message != w[i] {
diff --git a/internal/gerrit/types.go b/internal/gerrit/types.go
index 196b820..e7daa5a 100644
--- a/internal/gerrit/types.go
+++ b/internal/gerrit/types.go
@@ -205,7 +205,7 @@
 	UserName string `json:"username,omitempty"`
 	// List of [AvatarInfo] entities that provide information about
 	// avatar images of the account.
-	Avatars []AvatarInfo `json:"avatars,omitempty"`
+	Avatars []*AvatarInfo `json:"avatars,omitempty"`
 	// Status message of the account.
 	Status string `json:"status,omitempty"`
 	// Whether the account is inactive.
@@ -265,7 +265,7 @@
 	// * label: the label name.
 	// * status:
 	// * appliedBy:
-	Labels []struct {
+	Labels []*struct {
 		// The label name.
 		Label string `json:"label"`
 		// The label status: {OK, REJECT, MAY, NEED, IMPOSSIBLE}.
@@ -275,7 +275,7 @@
 	} `json:"labels,omitempty"`
 	// List of the requirements to be met before this change can
 	// be submitted.
-	Requirements []Requirement `json:"requirements,omitempty"`
+	Requirements []*Requirement `json:"requirements,omitempty"`
 	// When status is RULE_ERROR this message provides some text
 	// describing the failure of the rule predicate.
 	ErrorMessage string `json:"error_message,omitempty"`
@@ -428,7 +428,7 @@
 	// branch name if the parent is a merged commit in the target
 	// branch. Otherwise, we include the change and patch-set
 	// numbers of the parent change.
-	ParentsData []ParentInfo `json:"parents_data,omitempty"`
+	ParentsData []*ParentInfo `json:"parents_data,omitempty"`
 	// The name of the target branch that this revision is set to
 	// be merged into.  Note that if the change is moved with the
 	// Move Change endpoint, this field can be different for
@@ -461,7 +461,7 @@
 	// The parent commits of this commit as a list of CommitInfo
 	// entities. In each parent only the commit and subject fields
 	// are populated.
-	Parents []CommitInfo `json:"parents,omitempty"`
+	Parents []*CommitInfo `json:"parents,omitempty"`
 	// The author of the commit as a GitPersonInfo entity.
 	Author *GitPersonInfo `json:"author,omitempty"`
 	// The committer of the commit as a GitPersonInfo entity.
@@ -472,10 +472,10 @@
 	Message string `json:"message,omitempty"`
 	// Links to the patch set in external sites as a list of
 	// WebLinkInfo entities.
-	WebLinks []WebLinkInfo `json:"web_links,omitempty"`
+	WebLinks []*WebLinkInfo `json:"web_links,omitempty"`
 	// Links to the commit in external sites for resolving
 	// conflicts as a list of WebLinkInfo entities.
-	ResolveConflictsWebLinks []WebLinkInfo `json:"resolve_conflicts_web_links,omitempty"`
+	ResolveConflictsWebLinks []*WebLinkInfo `json:"resolve_conflicts_web_links,omitempty"`
 }
 
 // GitPersonInfo holds information about the author/committer of a commit.
@@ -579,7 +579,7 @@
 	// the patchset to which this comment applies.
 	CommitID string `json:"commit_id,omitempty"`
 	// Suggested fixes for this comment.
-	FixSuggestions []FixSuggestionInfo `json:"fix_suggestions,omitempty"`
+	FixSuggestions []*FixSuggestionInfo `json:"fix_suggestions,omitempty"`
 
 	// The remaining fields are defined by Gerrit but we don't
 	// request their values.
@@ -598,7 +598,7 @@
 	// A list of FixReplacementInfo entities indicating how the
 	// content of one or several files should be modified. Within
 	// a file, they should refer to non-overlapping regions.
-	Replacements []FixReplacementInfo `json:"replacements"`
+	Replacements []*FixReplacementInfo `json:"replacements"`
 }
 
 // FixReplacementInfo describes how the content of a file should be
diff --git a/internal/gerritdocs/sync.go b/internal/gerritdocs/sync.go
index de000cf..2fec090 100644
--- a/internal/gerritdocs/sync.go
+++ b/internal/gerritdocs/sync.go
@@ -146,10 +146,7 @@
 // comments returns file comments for the gerrit change.
 func comments(gr *gerrit.Client, c *changeInfo) ([]*gerrit.CommentInfo, error) {
 	var cmts []*gerrit.CommentInfo
-	cmtsMap, err := gr.Comments(c.project, c.number)
-	if err != nil {
-		return nil, err
-	}
+	cmtsMap := gr.Comments(c.project, c.number)
 	for _, cs := range cmtsMap { // we don't care about comment file locations
 		cmts = append(cmts, cs...)
 	}