diff --git a/appview/db/migration.go b/appview/db/migration.go
new file mode 100644
index 00000000..0b69d0c8
--- /dev/null
+++ b/appview/db/migration.go
@@ -0,0 +1,18 @@
+package db
+
+import (
+	"context"
+
+	"github.com/bluesky-social/indigo/atproto/syntax"
+	"tangled.org/core/appview/models"
+)
+
+// "migration" for records stored in user's PDS, not AppView DB
+
+// NOTE: each migration row should represent atomic operation.
+
+func ListPDSRecordMigrations(ctx context.Context, e Execer, user syntax.DID) ([]*models.PDSRecordMigration, error) {
+	// select did, name, record from pds_migrations group by (did, name)
+	// merge by (did, name)
+	panic("unimplemented")
+}
diff --git a/appview/migration/migration.go b/appview/migration/migration.go
new file mode 100644
index 00000000..768e8a98
--- /dev/null
+++ b/appview/migration/migration.go
@@ -0,0 +1,154 @@
+package migration
+
+import (
+	"context"
+	"fmt"
+	"html"
+	"net/http"
+
+	comatproto "github.com/bluesky-social/indigo/api/atproto"
+	"github.com/bluesky-social/indigo/atproto/atclient"
+	"github.com/bluesky-social/indigo/atproto/syntax"
+	lexutil "github.com/bluesky-social/indigo/lex/util"
+	"tangled.org/core/api/tangled"
+	"tangled.org/core/appview/db"
+	"tangled.org/core/appview/oauth"
+	"tangled.org/core/appview/pages"
+)
+
+type Migration struct {
+	db    *db.DB
+	oauth *oauth.OAuth
+	pages *pages.Pages
+}
+
+// migration page handler
+func (s *Migration) HandleMigration(w http.ResponseWriter, r *http.Request) {
+	returnURL := r.URL.Query().Get("return_url")
+	if returnURL == "" {
+		returnURL = "/"
+	}
+
+	panic("unimplemented")
+}
+
+// HandleMigrationProgress is migration progress handler
+// This is the place where migration process gets started.
+func (s *Migration) HandleMigrationProgress(w http.ResponseWriter, r *http.Request) {
+	user := s.oauth.GetMultiAccountUser(r)
+	client, err := s.oauth.AuthorizedClient(r)
+	if err != nil {
+		panic("unimplemented")
+	}
+
+	flusher, ok := w.(http.Flusher)
+	if !ok {
+		panic("unimplemented")
+	}
+
+	// start SSE streaming
+	w.Header().Set("Content-Type", "text/event-stream")
+	w.Header().Set("Cache-Control", "no-cache")
+	w.Header().Set("X-Accel-Buffering", "no")
+
+	send := func(event, data string) {
+		fmt.Fprintf(w, "event: %s\ndata: %s\n\n", event, data)
+		flusher.Flush()
+	}
+	sendStepProgress := func(stepName string, curr, max int) {
+		send("StepProgress", fmt.Sprintf(`<span>[%d/%d]: %s</span>`, curr, max, html.EscapeString(stepName)))
+	}
+	sendRecordProgress := func(curr, max int) {
+		percent := 100 * curr / max
+		send("RecordProgress", fmt.Sprintf(`<progress name="migration-progress" value="%d" max="%d"> %d%%</progress>`, curr, max, percent))
+	}
+	sendError := func(msg string) {
+		send("Error", fmt.Sprintf(`<span>%s</span>`, html.EscapeString(msg)))
+	}
+
+	// event:StepProgress   -> <div>[1/3]: adding repository name to migration</div>
+	// event:RecordProgress -> <progress>
+	// event:Done           -> ""
+
+	// <div hx-trigger="sse:Done" hx-whatever="/{return_url}"></div>
+	// or just use js. whatever. just need to handle the event from client side.
+
+	ctx := r.Context()
+
+	migrations, err := db.ListPDSRecordMigrations(ctx, s.db, syntax.DID(user.Active.Did))
+	if err != nil {
+		// 500 maybe?
+		panic("unimplemented")
+	}
+
+	for i, migration := range migrations {
+		var message string
+		var migrateFn func(context.Context, *atclient.APIClient, syntax.DID, syntax.ATURI) error
+		switch migration.Name {
+		case "add-repo-did":
+			message = `adding <code>repoDid</code> field for all repo-pointing records`
+			migrateFn = s.migrateAddRepoDid
+		case "use-feed-comment":
+			message = `rewriting existing comments to <code>sh.tangled.feed.comment</code> lexicon`
+			migrateFn = s.migrateUseFeedComment
+		default:
+			continue
+		}
+		sendStepProgress(message, i, len(migrations))
+
+		for j, record := range migration.Records {
+			if err := migrateFn(ctx, client, migration.Did, record); err != nil {
+				panic("unimplemented")
+			}
+			sendRecordProgress(j+1, len(migration.Records))
+		}
+	}
+
+	send("Done", "")
+}
+
+func (s *Migration) migrateAddRepoDid(ctx context.Context, client *atclient.APIClient, did syntax.DID, record syntax.ATURI) error {
+	var (
+		collection = record.Collection()
+		rkey       = record.RecordKey()
+	)
+	ex, err := comatproto.RepoGetRecord(ctx, client, "", collection.String(), did.String(), rkey.String())
+	if err != nil {
+		// record doesn't exist, should we fail?
+		panic("unimplemented")
+	}
+
+	// uhhh if it's legacy record, there are pretty high possibility that we lost some data
+	// while unmarshalling it.
+	// so we should not depend on cbor unmarshaller.
+	val := ex.Value.Val
+
+	switch record.Collection() {
+	case tangled.RepoNSID:
+	case tangled.RepoIssueNSID:
+	case tangled.RepoPullNSID:
+	case tangled.RepoCollaboratorNSID:
+	case tangled.RepoArtifactNSID:
+	case tangled.FeedStarNSID:
+	case tangled.ActorProfileNSID:
+	default:
+		return fmt.Errorf("unexpected collection: '%s'", record.Collection())
+	}
+
+	_, err = comatproto.RepoPutRecord(ctx, client, &comatproto.RepoPutRecord_Input{
+		Collection: collection.String(),
+		Repo:       did.String(),
+		Rkey:       rkey.String(),
+		SwapRecord: ex.Cid,
+		Record:     &lexutil.LexiconTypeDecoder{Val: val},
+	})
+	if err != nil {
+		return fmt.Errorf("put record: %w", err)
+	}
+
+	return nil
+}
+
+func (s *Migration) migrateUseFeedComment(ctx context.Context, client *atclient.APIClient, did syntax.DID, record syntax.ATURI) error {
+	panic("unimplemented")
+}
diff --git a/appview/models/migration.go b/appview/models/migration.go
new file mode 100644
index 00000000..ccba61ba
--- /dev/null
+++ b/appview/models/migration.go
@@ -0,0 +1,11 @@
+package models
+
+import (
+	"github.com/bluesky-social/indigo/atproto/syntax"
+)
+
+type PDSRecordMigration struct {
+	Did     syntax.DID
+	Name    string         // name of the migration
+	Records []syntax.ATURI // records that need a migration
+}
diff --git a/flake.nix b/flake.nix
index 9e66decc..bedbd16e 100644
--- a/flake.nix
+++ b/flake.nix
@@ -29,6 +29,10 @@
       url = "https://cdn.jsdelivr.net/npm/htmx-ext-ws@2.0.2";
       flake = false;
     };
+    htmx-sse-src = {
+      url = "https://cdn.jsdelivr.net/npm/htmx-ext-sse@2.2.4";
+      flake = false;
+    };
     lucide-src = {
       url = "https://github.com/lucide-icons/lucide/releases/download/0.536.0/lucide-icons-0.536.0.zip";
       flake = false;