Merge pull request 'feat/release-telemetry-webui' (#28) from feat/release-telemetry-webui into main

Reviewed-on: http://gitea.hansenits.com.au/hits/ExploreDNS/pulls/28

.gitea/workflows/release.yml

@@ -0,0 +1,132 @@
+name: Release
+
+# Builds release artifacts when a version tag (v*) is pushed:
+#   - cross-compiled CLI + server binaries attached to the Gitea release
+#   - version-tagged docker images for the CLI and web server
+# The owner usually creates the Gitea release by hand with notes; this
+# workflow attaches assets to it (creating a bare release only when none
+# exists) and skips assets that are already attached, so re-runs are safe.
+
+on:
+  push:
+    tags: ["v*"]
+
+jobs:
+  binaries:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: 'go.mod'
+          cache: true
+
+      - name: Build release binaries
+        env:
+          GOTOOLCHAIN: local
+        run: |
+          set -euo pipefail
+          TAG="${GITHUB_REF_NAME}"
+          mkdir -p dist
+          for target in linux/amd64 linux/arm64 darwin/amd64 darwin/arm64 windows/amd64; do
+            GOOS="${target%/*}"
+            GOARCH="${target#*/}"
+            EXT=""
+            [ "$GOOS" = "windows" ] && EXT=".exe"
+            OUT="dist/${GOOS}_${GOARCH}"
+            mkdir -p "$OUT"
+            CGO_ENABLED=0 GOOS="$GOOS" GOARCH="$GOARCH" \
+              go build -trimpath -ldflags "-s -w -X main.version=${TAG}" \
+              -o "${OUT}/exploredns${EXT}" ./cmd/exploredns
+            CGO_ENABLED=0 GOOS="$GOOS" GOARCH="$GOARCH" \
+              go build -trimpath -ldflags "-s -w -X main.version=${TAG}" \
+              -o "${OUT}/exploredns-server${EXT}" ./cmd/server
+            if [ "$GOOS" = "windows" ]; then
+              (cd "$OUT" && zip -q "../exploredns_${TAG}_${GOOS}_${GOARCH}.zip" exploredns.exe exploredns-server.exe)
+            else
+              tar -czf "dist/exploredns_${TAG}_${GOOS}_${GOARCH}.tar.gz" -C "$OUT" exploredns exploredns-server
+            fi
+            rm -rf "$OUT"
+          done
+          (cd dist && sha256sum -- * > SHA256SUMS)
+          ls -l dist
+
+      - name: Attach assets to Gitea release
+        env:
+          TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          API: ${{ github.server_url }}/api/v1
+          REPO: ${{ github.repository }}
+        run: |
+          set -euo pipefail
+          TAG="${GITHUB_REF_NAME}"
+          AUTH="Authorization: token ${TOKEN}"
+
+          # Look up the release for this tag; create a bare one only when
+          # none exists (the owner writes release notes by hand).
+          STATUS=$(curl -sS -o release.json -w '%{http_code}' -H "$AUTH" \
+            "${API}/repos/${REPO}/releases/tags/${TAG}")
+          if [ "$STATUS" = "404" ]; then
+            curl -sS -f -o release.json -H "$AUTH" -H 'Content-Type: application/json' \
+              -d "{\"tag_name\":\"${TAG}\",\"name\":\"${TAG}\"}" \
+              "${API}/repos/${REPO}/releases"
+          elif [ "$STATUS" != "200" ]; then
+            echo "release lookup failed with HTTP ${STATUS}" >&2
+            cat release.json >&2
+            exit 1
+          fi
+          RELEASE_ID=$(jq -r '.id' release.json)
+          echo "release id: ${RELEASE_ID}"
+
+          # Existing asset names, so re-runs skip instead of failing.
+          curl -sS -f -H "$AUTH" \
+            "${API}/repos/${REPO}/releases/${RELEASE_ID}/assets" \
+            | jq -r '.[].name' > existing.txt
+
+          for f in dist/*; do
+            NAME=$(basename "$f")
+            if grep -Fxq "$NAME" existing.txt; then
+              echo "skip ${NAME} (already attached)"
+              continue
+            fi
+            echo "upload ${NAME}"
+            curl -sS -f -o /dev/null -H "$AUTH" \
+              -F "attachment=@${f}" \
+              "${API}/repos/${REPO}/releases/${RELEASE_ID}/assets?name=${NAME}"
+          done
+
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Log in to registry
+        uses: docker/login-action@v3
+        with:
+          registry: gitea.hansenits.com.au
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+
+      - name: Build and push CLI image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: Dockerfile.cli
+          push: true
+          build-args: |
+            VERSION=${{ github.ref_name }}
+          tags: |
+            gitea.hansenits.com.au/hits/exploredns-cli:latest
+            gitea.hansenits.com.au/hits/exploredns-cli:${{ github.ref_name }}
+
+      - name: Build and push web image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: Dockerfile.web
+          push: true
+          build-args: |
+            VERSION=${{ github.ref_name }}
+          tags: |
+            gitea.hansenits.com.au/hits/exploredns-web:latest
+            gitea.hansenits.com.au/hits/exploredns-web:${{ github.ref_name }}

Dockerfile.cli

@@ -8,7 +8,8 @@ RUN go mod download
 
 COPY . .
 
-RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -ldflags="-s -w" -o /out/exploredns ./cmd/exploredns
+ARG VERSION=dev
+RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -ldflags="-s -w -X main.version=${VERSION}" -o /out/exploredns ./cmd/exploredns
 
 # Final stage
 FROM alpine:3.21

Dockerfile.web

@@ -8,7 +8,8 @@ RUN go mod download
 
 COPY . .
 
-RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -ldflags="-s -w" -o /out/server ./cmd/server
+ARG VERSION=dev
+RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -ldflags="-s -w -X main.version=${VERSION}" -o /out/server ./cmd/server
 
 # Final stage
 FROM alpine:3.21

Makefile

@@ -3,14 +3,16 @@ SERVER_BINARY_NAME=exploredns-server
 BUILD_DIR=bin
 GO=go
 GOFLAGS=-v
+VERSION?=$(shell git describe --tags --always 2>/dev/null || echo dev)
+LDFLAGS=-ldflags "-X main.version=$(VERSION)"
 
 .PHONY: build build-server build-all test lint clean cover deploy deploy-status
 
 build:
-	$(GO) build $(GOFLAGS) -o $(BUILD_DIR)/$(BINARY_NAME) ./cmd/exploredns
+	$(GO) build $(GOFLAGS) $(LDFLAGS) -o $(BUILD_DIR)/$(BINARY_NAME) ./cmd/exploredns
 
 build-server:
-	$(GO) build $(GOFLAGS) -o $(BUILD_DIR)/$(SERVER_BINARY_NAME) ./cmd/server
+	$(GO) build $(GOFLAGS) $(LDFLAGS) -o $(BUILD_DIR)/$(SERVER_BINARY_NAME) ./cmd/server
 
 build-all: build build-server
 

README.md

@@ -136,6 +136,9 @@ Output Options:
   --show-all-stats        Show statistics after every node (default: false)
   --show-results          Show the results (default: true)
   --show-summary-results  Show the summary results (default: true)
+
+General Options:
+  --version, -V           Print version ("exploredns <version>") and exit
 ```
 
 Every `--show-X` flag can be negated with `--show-X=false` or `--no-show-X`.
@@ -167,8 +170,17 @@ make build-server
 ```
 
 Open `http://localhost:8080` in your browser.  The SPA lets you enter a domain,
-choose a record type, and watch the traversal progress in real time.  When the
-traversal completes the full result tree is displayed in the browser.
+choose a record type, and watch the traversal progress in real time as a live
+detail tree modelled on the dns.squish.net detail page: one node per referral,
+indented per depth, with glue-resolution subtrees collapsed behind per-node
+"show resolve" toggles (a "raw log" toggle reveals the flat event feed for
+debugging).  When the traversal completes the full result list is displayed,
+followed by a Servers section: every nameserver queried during the traversal
+is fingerprinted (`version.bind`) and shown on an OpenStreetMap/Leaflet map
+plus a Country / City / Servers / Software guess table.  Geolocation happens
+client-side in your browser via the free [geojs.io](https://www.geojs.io/)
+API (`get.geojs.io`); servers that cannot be located are still listed with a
+dash location, and the table works without the map when offline.
 
 ### API endpoints
 
@@ -177,7 +189,8 @@ traversal completes the full result tree is displayed in the browser.
 | `POST` | `/api/traverse` | Start an asynchronous traversal |
 | `GET`  | `/api/traverse/{id}` | Poll traversal status and results |
 | `GET`  | `/api/traverse/{id}/stream` | Server-Sent Events live progress stream |
-| `GET`  | `/api/health` | Health check — returns `{"status":"ok"}` |
+| `GET`  | `/api/traverse/{id}/servers` | Fingerprinted list of every server queried |
+| `GET`  | `/api/health` | Health check — returns `{"status":"ok","version":"<build version>"}` |
 
 #### POST /api/traverse
 
@@ -206,7 +219,9 @@ Response (`202 Accepted`):
 #### GET /api/traverse/{id}
 
 Returns a snapshot of the job including the full result list once complete.
-`status` is one of `running`, `complete`, or `error`.
+`status` is one of `running`, `complete`, or `error`.  Once post-traversal
+fingerprinting has finished the snapshot also carries a `servers` array (the
+same list served by `GET /api/traverse/{id}/servers`; omitted before then).
 
 ```json
 {
@@ -228,12 +243,36 @@ Returns a snapshot of the job including the full result list once complete.
 }
 ```
 
+#### GET /api/traverse/{id}/servers
+
+Every `(server name, IP)` pair queried during the traversal — including
+glue-resolution subtree servers — fingerprinted via a `version.bind` CHAOS
+probe once the traversal reaches a terminal state.  Fingerprinting never
+delays the traversal results: while it (or the traversal itself) is still in
+flight the endpoint answers `202 Accepted` with `{"status":"pending"}`.
+Unknown ids answer `404`.  When ready:
+
+```json
+{
+  "status": "complete",
+  "servers": [
+    {"name": "a.iana-servers.net", "ip": "199.43.135.53", "version": ""},
+    {"name": "l.gtld-servers.net", "ip": "192.41.162.30", "version": "..."}
+  ]
+}
+```
+
+`version` is `""` for servers that don't answer the probe.
+
 #### GET /api/traverse/{id}/stream
 
 An [SSE](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events)
 stream of `ProgressEvent` objects, one per `data:` message.  Past events
 recorded before the client connected are replayed immediately, then live events
-follow.  The stream ends with `event: done`.
+follow.  Two synthetic stages bracket the end of a job: `{"stage":"complete"}`
+when the traversal reaches its terminal status (results are fetchable) and
+`{"stage":"servers"}` when the fingerprinted server list is ready.  The stream
+ends with `event: done`.
 
 ```
 data: {"stage":"start","depth":1,"name":"www.example.com","qtype":"A","bailiwick":"com"}
@@ -256,6 +295,28 @@ variables at startup:
 | `EXPLOREDNS_JOB_TIMEOUT` | `5m` | Hard deadline per traversal (Go duration). Timed-out jobs report `error` with any partial results. |
 | `EXPLOREDNS_MAX_JOBS` | `8` | Maximum concurrent traversals; further `POST /api/traverse` requests get `429`. |
 | `EXPLOREDNS_CORS_ORIGIN` | *(unset)* | Off by default (the SPA is same-origin). Set an origin — or `*` for development — to enable cross-origin API access. |
+| `EXPLOREDNS_RATE_LIMIT` | `30/1h` | Per-client-IP token-bucket limit on `POST /api/traverse` in `N/duration` form (e.g. `10/10m`); invalid values fall back to the default. Over-limit requests get `429`. Buckets refill continuously. Direct localhost connections are exempt (dev loop, tests), but proxied requests are always limited by the real client IP from `Fly-Client-IP` / `X-Forwarded-For`. |
+| `EXPLOREDNS_WEBHOOK_URL` | *(unset)* | Off by default. When set, the server POSTs a usage-reporting JSON event to this URL on every traversal start and completion (see below). |
+
+### Usage reporting
+
+When `EXPLOREDNS_WEBHOOK_URL` is set, the server sends two JSON POSTs per
+traversal, each with header `X-ExploreDNS-Event` naming the event:
+
+- `start` — `{"event":"start","id","domain","query_type","all_roots","client_ip","started_at"}`
+- `complete` — `{"event":"complete","id","domain","query_type","client_ip","started_at","done_at","duration_ms","status","error","result_count","summary"}`
+  where `summary` is the same grouped answers/statuses object returned by
+  `GET /api/traverse/{id}` and `error` is present only for failed jobs.
+
+`client_ip` is the requester's IP (`Fly-Client-IP`, else the first
+`X-Forwarded-For` entry, else the connection address). Delivery is
+fire-and-forget: a 5-second timeout, one retry after 2 seconds, and failures
+are logged without ever affecting the traversal or the API response. On
+Fly.io, configure it as a secret rather than in `fly.toml`:
+
+```sh
+fly secrets set EXPLOREDNS_WEBHOOK_URL=https://example.com/hook
+```
 
 ---
 
@@ -277,13 +338,20 @@ make deploy                     # flyctl deploy --remote-only
 the SPA at `https://<app>.fly.dev/` with `/api/health` as the health check.
 
 Machine placement is imperative rather than part of `fly.toml`; the current
-production topology is one machine in Sydney and one in Virginia:
+production topology is four regions — Sydney, Virginia, Singapore, and
+London — so anycast wake-up behaviour can be observed from anywhere:
 
 ```sh
-flyctl scale count 2 --region syd,iad
+flyctl scale count 4 --region syd,iad,sin,lhr
 ```
 
 `flyctl deploy` preserves existing machines and regions on redeploys.
+`GET /api/health` reports which region served the request (`region` field,
+present only on Fly), making the routing easy to observe:
+
+```sh
+curl -s https://exploredns.hansenits.com/api/health | jq -r .region
+```
 
 ### Continuous deployment
 
@@ -294,14 +362,38 @@ dispatch).  It needs a `FLY_API_TOKEN` repository secret:
 flyctl tokens create deploy -x 999999h
 ```
 
+### Releases
+
+Pushing a `v*` tag triggers the full release pipeline:
+
+1. `.gitea/workflows/release.yml` (`binaries` job) cross-compiles the CLI
+   and server for linux/amd64, linux/arm64, darwin/amd64, darwin/arm64 and
+   windows/amd64, packages them as
+   `exploredns_<tag>_<os>_<arch>.tar.gz` (`.zip` on Windows) plus a
+   `SHA256SUMS` file, and attaches everything to the Gitea release for the
+   tag.  Create the release with notes by hand before (or after) pushing
+   the tag — the workflow attaches assets to an existing release, creates
+   a bare one only when none exists, and skips already-attached assets so
+   re-runs are safe.
+2. `.gitea/workflows/release.yml` (`docker` job) pushes
+   `gitea.hansenits.com.au/hits/exploredns-cli` and `…/exploredns-web`
+   images tagged `<tag>` and `latest`.
+3. `.gitea/workflows/deploy.yml` deploys the web server to Fly.io.
+
+All binaries are stamped with the tag via
+`-ldflags "-X main.version=<tag>"`; check with `exploredns --version` or
+`GET /api/health`.  Local `make build` stamps from
+`git describe --tags --always`.
+
 ### Notes
 
 - Traversal traffic is outbound UDP/TCP port 53, which Fly machines allow;
   upstream root discovery uses Fly's internal resolver via `/etc/resolv.conf`
   and falls back to the built-in IANA root hints.
-- The job timeout, job cap, and same-origin CORS defaults above are what make
-  unauthenticated public exposure reasonable; tighten `EXPLOREDNS_MAX_JOBS`
-  if the app attracts traffic.
+- The job timeout, job cap, per-IP rate limit, and same-origin CORS defaults
+  above are what make unauthenticated public exposure reasonable; tighten
+  `EXPLOREDNS_MAX_JOBS` or `EXPLOREDNS_RATE_LIMIT` if the app attracts
+  traffic.
 
 ---
 

cmd/exploredns/main.go

@@ -13,6 +13,9 @@ import (
 	"gitea.hansenits.com.au/hits/ExploreDNS/internal/traverse"
 )
 
+// version is stamped at build time via -ldflags "-X main.version=...".
+var version = "dev"
+
 func main() {
 	cfg := config.DefaultConfig()
 
@@ -42,6 +45,12 @@ func main() {
 	flag.BoolVar(&dFlag, "debug", false, "Print debug diagnostics to stderr")
 	flag.BoolVar(&ddFlag, "dd", false, "Like -d plus library-level debug")
 
+	// Version: long and short form share the same variable (mirrors
+	// dnstraverse's -V).
+	var showVersion bool
+	flag.BoolVar(&showVersion, "version", false, "Print version and exit")
+	flag.BoolVar(&showVersion, "V", false, "Print version and exit (shorthand)")
+
 	// Quiet: long and short form share the same variable.
 	var quietVal bool
 	flag.BoolVar(&quietVal, "quiet", cfg.Quiet, "Suppress the header block")
@@ -69,6 +78,11 @@ func main() {
 
 	flag.Parse()
 
+	if showVersion {
+		fmt.Printf("exploredns %s\n", version)
+		return
+	}
+
 	args := flag.Args()
 
 	cfg.QueryType = *queryType

cmd/server/main.go

@@ -13,17 +13,21 @@ import (
 	"gitea.hansenits.com.au/hits/ExploreDNS/web/api"
 )
 
+// version is stamped at build time via -ldflags "-X main.version=...".
+var version = "dev"
+
 func main() {
 	addr := flag.String("addr", ":8080", "listen address (host:port)")
 	flag.Parse()
 
 	srv := api.NewServer(*addr)
+	srv.SetVersion(version)
 	if err := srv.Start(); err != nil {
 		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
 		os.Exit(1)
 	}
 
-	log.Printf("ExploreDNS API server listening on %s", srv.Addr())
+	log.Printf("ExploreDNS API server %s listening on %s", version, srv.Addr())
 
 	quit := make(chan os.Signal, 1)
 	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)

internal/config/config.go

@@ -167,6 +167,9 @@ func PrintUsage() {
 			{"--show-results", "Show the results (default true)"},
 			{"--show-summary-results", "Show the summary results (default true)"},
 		}},
+		{"General Options", [][2]string{
+			{"--version, -V", "Print version and exit"},
+		}},
 	}
 
 	for _, group := range flagGroups {

web/api/handler.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io/fs"
+	"net"
 	"net/http"
 	"os"
 	"sort"
@@ -16,6 +17,7 @@ import (
 
 	"gitea.hansenits.com.au/hits/ExploreDNS/internal/config"
 	idns "gitea.hansenits.com.au/hits/ExploreDNS/internal/dns"
+	"gitea.hansenits.com.au/hits/ExploreDNS/internal/fingerprint"
 	"gitea.hansenits.com.au/hits/ExploreDNS/internal/traverse"
 )
 
@@ -38,6 +40,14 @@ const (
 	defaultMaxRunningJobs = 8
 )
 
+// Fingerprinting runs after a traversal reaches a terminal state: bounded
+// concurrency across the unique server IPs, with its own overall deadline so
+// a timed-out or cancelled job context never blocks the server list.
+const (
+	fingerprintConcurrency = 8
+	fingerprintTimeout     = 15 * time.Second
+)
+
 // TraverseRequest is the JSON body for POST /api/traverse.
 type TraverseRequest struct {
 	Domain   string `json:"domain"`
@@ -106,6 +116,14 @@ type Summary struct {
 	ByStatus []SummaryStatus `json:"by_status,omitempty"`
 }
 
+// ServerInfo is one (server name, IP) pair queried during a traversal plus
+// its version.bind fingerprint ("" when the server didn't answer the probe).
+type ServerInfo struct {
+	Name    string `json:"name"`
+	IP      string `json:"ip"`
+	Version string `json:"version"`
+}
+
 // TraversalJob holds all state for a single asynchronous traversal.
 type TraversalJob struct {
 	ID        string          `json:"id"`
@@ -115,13 +133,18 @@ type TraversalJob struct {
 	Results   []ResultItem    `json:"results,omitempty"`
 	Summary   *Summary        `json:"summary,omitempty"`
 	Progress  []ProgressEvent `json:"progress,omitempty"`
+	Servers   []ServerInfo    `json:"servers,omitempty"`
 	Error     string          `json:"error,omitempty"`
 	StartedAt time.Time       `json:"started_at"`
 	DoneAt    *time.Time      `json:"done_at,omitempty"`
 
-	mu     sync.RWMutex
-	subs   []chan ProgressEvent
-	cancel context.CancelFunc
+	mu       sync.RWMutex
+	subs     []chan ProgressEvent
+	cancel   context.CancelFunc
+	clientIP string
+	// serversDone flips once the post-traversal fingerprinting step has
+	// stored Servers (or was skipped); until then GET …/servers is pending.
+	serversDone bool
 }
 
 // subscribeSnapshot atomically registers a subscriber and snapshots the
@@ -224,24 +247,42 @@ func (s *store) cleanup() {
 	}
 }
 
+// versionQuerier is the subset of fingerprint.Fingerprinter the handler
+// uses; tests substitute a fake so no probes leave the process.
+type versionQuerier interface {
+	Query(ctx context.Context, ip net.IP) string
+}
+
 // Handler wires together the HTTP routes and the job store.
 type Handler struct {
 	st         *store
 	mux        *http.ServeMux
 	jobTimeout time.Duration
 	maxRunning int
+	version    string
+	limiter    *rateLimiter
+	webhook    *webhookReporter
+	// fp fingerprints server IPs after each traversal; shared across jobs
+	// so its per-IP cache is reused.
+	fp versionQuerier
 }
 
 func newHandler(ctx context.Context) *Handler {
+	limit, window := parseRateLimit(os.Getenv("EXPLOREDNS_RATE_LIMIT"))
 	h := &Handler{
 		st:         newStore(),
 		mux:        http.NewServeMux(),
 		jobTimeout: envDuration("EXPLOREDNS_JOB_TIMEOUT", defaultJobTimeout),
 		maxRunning: envInt("EXPLOREDNS_MAX_JOBS", defaultMaxRunningJobs),
+		version:    "dev",
+		limiter:    newRateLimiter(limit, window),
+		webhook:    newWebhookReporter(os.Getenv("EXPLOREDNS_WEBHOOK_URL")),
+		fp:         fingerprint.New(),
 	}
 
 	h.mux.HandleFunc("POST /api/traverse", h.startTraversal)
 	h.mux.HandleFunc("GET /api/traverse/{id}/stream", h.streamTraversal)
+	h.mux.HandleFunc("GET /api/traverse/{id}/servers", h.getServers)
 	h.mux.HandleFunc("GET /api/traverse/{id}", h.getTraversal)
 	h.mux.HandleFunc("GET /api/health", h.health)
 
@@ -255,6 +296,7 @@ func newHandler(ctx context.Context) *Handler {
 				return
 			case <-t.C:
 				h.st.cleanup()
+				h.limiter.sweep()
 			}
 		}
 	}()
@@ -270,11 +312,24 @@ func (h *Handler) registerStatic(sub fs.FS) {
 
 // health handles GET /api/health.
 func (h *Handler) health(w http.ResponseWriter, _ *http.Request) {
-	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
+	body := map[string]string{"status": "ok", "version": h.version}
+	// On Fly.io this identifies which machine served the request —
+	// useful for observing anycast routing and auto-start behaviour.
+	if region := os.Getenv("FLY_REGION"); region != "" {
+		body["region"] = region
+	}
+	writeJSON(w, http.StatusOK, body)
 }
 
 // startTraversal handles POST /api/traverse.
 func (h *Handler) startTraversal(w http.ResponseWriter, r *http.Request) {
+	ip := clientIP(r)
+	if h.limiter != nil && !rateLimitExempt(r) && !h.limiter.allow(ip) {
+		writeError(w, http.StatusTooManyRequests,
+			fmt.Sprintf("rate limit exceeded: %s per client IP", h.limiter))
+		return
+	}
+
 	r.Body = http.MaxBytesReader(w, r.Body, 1<<20) // 1 MB limit
 	var req TraverseRequest
 	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
@@ -310,9 +365,20 @@ func (h *Handler) startTraversal(w http.ResponseWriter, r *http.Request) {
 		QueryType: queryType,
 		StartedAt: time.Now(),
 		cancel:    cancel,
+		clientIP:  ip,
 	}
 	h.st.set(job)
 
+	h.webhook.send(webhookEventStart, webhookStartEvent{
+		Event:     webhookEventStart,
+		ID:        job.ID,
+		Domain:    job.Domain,
+		QueryType: job.QueryType,
+		AllRoots:  req.AllRoots,
+		ClientIP:  ip,
+		StartedAt: job.StartedAt,
+	})
+
 	go h.runTraversal(ctx, job, req.Domain, qtype, req.AllRoots)
 
 	writeJSON(w, http.StatusAccepted, TraverseStartResponse{ID: id, Status: statusRunning})
@@ -337,6 +403,7 @@ func (h *Handler) getTraversal(w http.ResponseWriter, r *http.Request) {
 		Results   []ResultItem    `json:"results,omitempty"`
 		Summary   *Summary        `json:"summary,omitempty"`
 		Progress  []ProgressEvent `json:"progress,omitempty"`
+		Servers   []ServerInfo    `json:"servers,omitempty"`
 		Error     string          `json:"error,omitempty"`
 		StartedAt time.Time       `json:"started_at"`
 		DoneAt    *time.Time      `json:"done_at,omitempty"`
@@ -348,6 +415,7 @@ func (h *Handler) getTraversal(w http.ResponseWriter, r *http.Request) {
 		Results:   job.Results,
 		Summary:   job.Summary,
 		Progress:  job.Progress,
+		Servers:   job.Servers,
 		Error:     job.Error,
 		StartedAt: job.StartedAt,
 		DoneAt:    job.DoneAt,
@@ -357,6 +425,35 @@ func (h *Handler) getTraversal(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, snapshot)
 }
 
+// getServers handles GET /api/traverse/{id}/servers. It answers 202 with a
+// pending body while the traversal or the post-traversal fingerprinting is
+// still in flight, then the fingerprinted server list.
+func (h *Handler) getServers(w http.ResponseWriter, r *http.Request) {
+	id := r.PathValue("id")
+	job, ok := h.st.get(id)
+	if !ok {
+		writeError(w, http.StatusNotFound, "traversal not found")
+		return
+	}
+
+	job.mu.RLock()
+	done := job.serversDone
+	servers := job.Servers
+	job.mu.RUnlock()
+
+	if !done {
+		writeJSON(w, http.StatusAccepted, map[string]string{"status": "pending"})
+		return
+	}
+	if servers == nil {
+		servers = []ServerInfo{}
+	}
+	writeJSON(w, http.StatusOK, struct {
+		Status  string       `json:"status"`
+		Servers []ServerInfo `json:"servers"`
+	}{Status: "complete", Servers: servers})
+}
+
 // streamTraversal handles GET /api/traverse/{id}/stream (SSE).
 func (h *Handler) streamTraversal(w http.ResponseWriter, r *http.Request) {
 	id := r.PathValue("id")
@@ -430,13 +527,21 @@ func (h *Handler) runTraversal(ctx context.Context, job *TraversalJob, domain st
 		if r := recover(); r != nil {
 			now := time.Now()
 			job.mu.Lock()
-			job.Status = statusError
-			job.Error = fmt.Sprintf("panic: %v", r)
-			job.DoneAt = &now
+			if job.DoneAt == nil {
+				job.Status = statusError
+				job.Error = fmt.Sprintf("panic: %v", r)
+				job.DoneAt = &now
+			}
 			job.mu.Unlock()
 		}
+		// Never leave GET …/servers pending: fingerprinting is skipped on
+		// the panic path, so flip the flag here (idempotent otherwise).
+		job.mu.Lock()
+		job.serversDone = true
+		job.mu.Unlock()
 		job.cancel()
 		job.closeSubscribers()
+		h.reportCompletion(job)
 	}()
 
 	cfg := traverse.DefaultTraverserConfig()
@@ -474,6 +579,25 @@ func (h *Handler) runTraversal(ctx context.Context, job *TraversalJob, domain st
 	tr := traverse.NewTraverser(cfg)
 	root, err := tr.Run(ctx, domain)
 
+	h.commitResult(ctx, job, root, err)
+
+	// Tell streaming clients the traversal reached a terminal state so they
+	// can fetch results now; the stream stays open for the servers event
+	// published once fingerprinting (below) finishes.
+	job.mu.Lock()
+	ev := ProgressEvent{Stage: "complete", Status: job.Status}
+	job.Progress = append(job.Progress, ev)
+	job.publishLocked(ev)
+	job.mu.Unlock()
+
+	// Fingerprint the servers queried during the traversal. This runs after
+	// the terminal status is committed, so results never wait on versions.
+	h.fingerprintServers(job, tr.ServersEncountered())
+}
+
+// commitResult stores the traversal outcome and moves the job to its
+// terminal status.
+func (h *Handler) commitResult(ctx context.Context, job *TraversalJob, root *traverse.Referral, err error) {
 	now := time.Now()
 	job.mu.Lock()
 	defer job.mu.Unlock()
@@ -507,6 +631,105 @@ func (h *Handler) runTraversal(ctx context.Context, job *TraversalJob, domain st
 	job.Status = statusComplete
 }
 
+// fingerprintServers turns the traversal's (server, ip) pairs into
+// job.Servers, probing each unique IP's version.bind with bounded
+// concurrency, then publishes a {"stage":"servers"} event so streaming
+// clients know the list is ready without polling. Pseudo "key:" entries and
+// non-address entries are skipped.
+func (h *Handler) fingerprintServers(job *TraversalJob, seen map[string][]string) {
+	type pair struct{ name, ip string }
+	var pairs []pair
+	uniq := make(map[string]bool)
+	var ips []net.IP
+	for name, addrs := range seen {
+		for _, addr := range addrs {
+			if strings.HasPrefix(addr, "key:") {
+				continue
+			}
+			ip := net.ParseIP(addr)
+			if ip == nil {
+				continue
+			}
+			pairs = append(pairs, pair{name: name, ip: addr})
+			if !uniq[addr] {
+				uniq[addr] = true
+				ips = append(ips, ip)
+			}
+		}
+	}
+
+	versions := make(map[string]string, len(ips))
+	if len(ips) > 0 && h.fp != nil {
+		ctx, cancel := context.WithTimeout(context.Background(), fingerprintTimeout)
+		defer cancel()
+
+		var (
+			wg  sync.WaitGroup
+			mu  sync.Mutex
+			sem = make(chan struct{}, fingerprintConcurrency)
+		)
+		for _, ip := range ips {
+			wg.Add(1)
+			go func(ip net.IP) {
+				defer wg.Done()
+				sem <- struct{}{}
+				defer func() { <-sem }()
+				v := h.fp.Query(ctx, ip)
+				mu.Lock()
+				versions[ip.String()] = v
+				mu.Unlock()
+			}(ip)
+		}
+		wg.Wait()
+	}
+
+	servers := make([]ServerInfo, 0, len(pairs))
+	for _, p := range pairs {
+		servers = append(servers, ServerInfo{Name: p.name, IP: p.ip, Version: versions[p.ip]})
+	}
+	sort.Slice(servers, func(i, j int) bool {
+		if servers[i].Name != servers[j].Name {
+			return servers[i].Name < servers[j].Name
+		}
+		return servers[i].IP < servers[j].IP
+	})
+
+	ev := ProgressEvent{Stage: "servers"}
+	job.mu.Lock()
+	job.Servers = servers
+	job.serversDone = true
+	job.Progress = append(job.Progress, ev)
+	job.publishLocked(ev)
+	job.mu.Unlock()
+}
+
+// reportCompletion posts the webhook "complete" event for a job that has
+// reached a terminal state. Fire-and-forget; never blocks the caller.
+func (h *Handler) reportCompletion(job *TraversalJob) {
+	if h.webhook == nil {
+		return
+	}
+	job.mu.RLock()
+	ev := webhookCompleteEvent{
+		Event:       webhookEventComplete,
+		ID:          job.ID,
+		Domain:      job.Domain,
+		QueryType:   job.QueryType,
+		ClientIP:    job.clientIP,
+		StartedAt:   job.StartedAt,
+		Status:      job.Status,
+		Error:       job.Error,
+		ResultCount: len(job.Results),
+		Summary:     job.Summary,
+	}
+	if job.DoneAt != nil {
+		ev.DoneAt = *job.DoneAt
+		ev.DurationMS = job.DoneAt.Sub(job.StartedAt).Milliseconds()
+	}
+	job.mu.RUnlock()
+	h.webhook.send(webhookEventComplete, ev)
+}
+
 // envDuration reads a Go duration from the environment, falling back to
 // def when unset or unparsable.
 func envDuration(name string, def time.Duration) time.Duration {

web/api/handler_internal_test.go

@@ -2,6 +2,8 @@ package api
 
 import (
 	"context"
+	"encoding/json"
+	"net"
 	"net/http/httptest"
 	"strconv"
 	"strings"
@@ -147,3 +149,171 @@ func TestSubscribeSnapshot_NoDuplicates(t *testing.T) {
 		t.Error(msg)
 	}
 }
+
+// fakeVersionQuerier returns canned version strings without touching the
+// network.
+type fakeVersionQuerier struct {
+	mu       sync.Mutex
+	versions map[string]string
+	queried  []string
+}
+
+func (f *fakeVersionQuerier) Query(_ context.Context, ip net.IP) string {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.queried = append(f.queried, ip.String())
+	return f.versions[ip.String()]
+}
+
+// TestGetServers_PendingWhileRunning verifies the 202 pending shape while a
+// job has not finished fingerprinting (running or just-completed).
+func TestGetServers_PendingWhileRunning(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	h := newHandler(ctx)
+
+	now := time.Now()
+	jobs := []*TraversalJob{
+		{ID: "running", Status: statusRunning, StartedAt: now},
+		{ID: "fingerprinting", Status: statusComplete, StartedAt: now, DoneAt: &now},
+	}
+	for _, j := range jobs {
+		h.st.set(j)
+	}
+
+	for _, id := range []string{"running", "fingerprinting"} {
+		req := httptest.NewRequest("GET", "/api/traverse/"+id+"/servers", nil)
+		rec := httptest.NewRecorder()
+		h.mux.ServeHTTP(rec, req)
+
+		if rec.Code != 202 {
+			t.Fatalf("%s: want 202, got %d: %s", id, rec.Code, rec.Body.String())
+		}
+		var body map[string]string
+		if err := json.NewDecoder(rec.Body).Decode(&body); err != nil {
+			t.Fatalf("%s: decode: %v", id, err)
+		}
+		if body["status"] != "pending" {
+			t.Fatalf("%s: want status=pending, got %q", id, body["status"])
+		}
+	}
+}
+
+// TestFingerprintServers_StoresServersAndPublishes drives the fingerprint
+// step with a fake querier: (server, ip) pairs become sorted job.Servers with
+// versions, pseudo/invalid entries are skipped, a {"stage":"servers"} event
+// is published, and the endpoint flips from pending to the final list.
+func TestFingerprintServers_StoresServersAndPublishes(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	h := newHandler(ctx)
+	fake := &fakeVersionQuerier{versions: map[string]string{
+		"192.0.2.1": "TestDNS 1.0",
+		"192.0.2.2": "",
+	}}
+	h.fp = fake
+
+	now := time.Now()
+	job := &TraversalJob{ID: "j", Status: statusComplete, StartedAt: now, DoneAt: &now}
+	h.st.set(job)
+	sub, _, _ := job.subscribeSnapshot()
+	defer job.unsubscribe(sub)
+
+	h.fingerprintServers(job, map[string][]string{
+		"b.example.net": {"192.0.2.2"},
+		"a.example.net": {"192.0.2.1", "key:pseudo:entry", "not-an-ip"},
+	})
+
+	want := []ServerInfo{
+		{Name: "a.example.net", IP: "192.0.2.1", Version: "TestDNS 1.0"},
+		{Name: "b.example.net", IP: "192.0.2.2", Version: ""},
+	}
+	job.mu.RLock()
+	got := append([]ServerInfo(nil), job.Servers...)
+	done := job.serversDone
+	job.mu.RUnlock()
+	if !done {
+		t.Fatal("serversDone not set")
+	}
+	if len(got) != len(want) {
+		t.Fatalf("servers = %+v, want %+v", got, want)
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Fatalf("servers[%d] = %+v, want %+v", i, got[i], want[i])
+		}
+	}
+
+	select {
+	case ev := <-sub:
+		if ev.Stage != "servers" {
+			t.Fatalf("published stage = %q, want servers", ev.Stage)
+		}
+	default:
+		t.Fatal("no servers event published")
+	}
+
+	// Endpoint now serves the final list.
+	req := httptest.NewRequest("GET", "/api/traverse/j/servers", nil)
+	rec := httptest.NewRecorder()
+	h.mux.ServeHTTP(rec, req)
+	if rec.Code != 200 {
+		t.Fatalf("want 200, got %d: %s", rec.Code, rec.Body.String())
+	}
+	var body struct {
+		Status  string       `json:"status"`
+		Servers []ServerInfo `json:"servers"`
+	}
+	if err := json.NewDecoder(rec.Body).Decode(&body); err != nil {
+		t.Fatal(err)
+	}
+	if body.Status != "complete" || len(body.Servers) != 2 {
+		t.Fatalf("body = %+v", body)
+	}
+
+	// Snapshot includes servers too.
+	req = httptest.NewRequest("GET", "/api/traverse/j", nil)
+	rec = httptest.NewRecorder()
+	h.mux.ServeHTTP(rec, req)
+	if rec.Code != 200 {
+		t.Fatalf("snapshot: want 200, got %d", rec.Code)
+	}
+	var snap struct {
+		Servers []ServerInfo `json:"servers"`
+	}
+	if err := json.NewDecoder(rec.Body).Decode(&snap); err != nil {
+		t.Fatal(err)
+	}
+	if len(snap.Servers) != 2 {
+		t.Fatalf("snapshot servers = %+v, want 2 entries", snap.Servers)
+	}
+}
+
+// TestFingerprintServers_EmptySeen still terminates the pending state and
+// publishes the servers event for traversals that recorded no servers.
+func TestFingerprintServers_EmptySeen(t *testing.T) {
+	h := &Handler{st: newStore()}
+	job := &TraversalJob{ID: "e", Status: statusError}
+	h.st.set(job)
+	sub, _, _ := job.subscribeSnapshot()
+	defer job.unsubscribe(sub)
+
+	h.fingerprintServers(job, nil)
+
+	job.mu.RLock()
+	defer job.mu.RUnlock()
+	if !job.serversDone {
+		t.Fatal("serversDone not set")
+	}
+	if len(job.Servers) != 0 {
+		t.Fatalf("servers = %+v, want empty", job.Servers)
+	}
+	select {
+	case ev := <-sub:
+		if ev.Stage != "servers" {
+			t.Fatalf("published stage = %q, want servers", ev.Stage)
+		}
+	default:
+		t.Fatal("no servers event published")
+	}
+}

web/api/handler_test.go

@@ -29,6 +29,7 @@ func newTestServer(t *testing.T) *api.Server {
 }
 
 func TestHealth(t *testing.T) {
+	t.Setenv("FLY_REGION", "") // ensure region is absent regardless of host env
 	srv := newTestServer(t)
 	defer srv.Shutdown(5 * time.Second) //nolint:errcheck
 
@@ -48,6 +49,55 @@ func TestHealth(t *testing.T) {
 	if body["status"] != "ok" {
 		t.Fatalf("want status=ok, got %q", body["status"])
 	}
+	if body["version"] != "dev" {
+		t.Fatalf("want version=dev, got %q", body["version"])
+	}
+	if region, ok := body["region"]; ok {
+		t.Fatalf("region should be omitted outside Fly, got %q", region)
+	}
+}
+
+func TestHealthReportsFlyRegion(t *testing.T) {
+	t.Setenv("FLY_REGION", "syd")
+	srv := newTestServer(t)
+	defer srv.Shutdown(5 * time.Second) //nolint:errcheck
+
+	resp, err := http.Get("http://" + srv.Addr() + "/api/health")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+
+	var body map[string]string
+	if err := json.NewDecoder(resp.Body).Decode(&body); err != nil {
+		t.Fatal(err)
+	}
+	if body["region"] != "syd" {
+		t.Fatalf("want region=syd, got %q", body["region"])
+	}
+}
+
+func TestHealthReportsStampedVersion(t *testing.T) {
+	srv := api.NewServer("127.0.0.1:0")
+	srv.SetVersion("v1.2.3")
+	if err := srv.Start(); err != nil {
+		t.Fatalf("start server: %v", err)
+	}
+	defer srv.Shutdown(5 * time.Second) //nolint:errcheck
+
+	resp, err := http.Get("http://" + srv.Addr() + "/api/health")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+
+	var body map[string]string
+	if err := json.NewDecoder(resp.Body).Decode(&body); err != nil {
+		t.Fatal(err)
+	}
+	if body["version"] != "v1.2.3" {
+		t.Fatalf("want version=v1.2.3, got %q", body["version"])
+	}
 }
 
 func TestCORSDisabledByDefault(t *testing.T) {
@@ -205,6 +255,95 @@ func TestGetTraversal_Found(t *testing.T) {
 	}
 }
 
+func TestGetServers_NotFound(t *testing.T) {
+	srv := newTestServer(t)
+	defer srv.Shutdown(5 * time.Second) //nolint:errcheck
+
+	resp, err := http.Get("http://" + srv.Addr() + "/api/traverse/does-not-exist/servers")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusNotFound {
+		t.Fatalf("want 404, got %d", resp.StatusCode)
+	}
+}
+
+// TestGetServers_AvailableAfterCompletion drives a full job through the API:
+// the servers endpoint answers 202 pending while the traversal/fingerprinting
+// is in flight and the fingerprinted list once everything finished.
+func TestGetServers_AvailableAfterCompletion(t *testing.T) {
+	srv := newTestServer(t)
+	defer srv.Shutdown(5 * time.Second) //nolint:errcheck
+
+	startBody := bytes.NewBufferString(`{"domain":"example.com","type":"A"}`)
+	startResp, err := http.Post("http://"+srv.Addr()+"/api/traverse", "application/json", startBody)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer startResp.Body.Close()
+
+	var start struct {
+		ID string `json:"id"`
+	}
+	if err := json.NewDecoder(startResp.Body).Decode(&start); err != nil {
+		t.Fatal(err)
+	}
+
+	deadline := time.Now().Add(90 * time.Second)
+	for {
+		resp, err := http.Get("http://" + srv.Addr() + "/api/traverse/" + start.ID + "/servers")
+		if err != nil {
+			t.Fatal(err)
+		}
+		body, err := io.ReadAll(resp.Body)
+		resp.Body.Close()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		switch resp.StatusCode {
+		case http.StatusAccepted:
+			var pending struct {
+				Status string `json:"status"`
+			}
+			if err := json.Unmarshal(body, &pending); err != nil {
+				t.Fatalf("pending body: %v (%s)", err, body)
+			}
+			if pending.Status != "pending" {
+				t.Fatalf("want status=pending, got %q", pending.Status)
+			}
+		case http.StatusOK:
+			var done struct {
+				Status  string `json:"status"`
+				Servers []struct {
+					Name    string `json:"name"`
+					IP      string `json:"ip"`
+					Version string `json:"version"`
+				} `json:"servers"`
+			}
+			if err := json.Unmarshal(body, &done); err != nil {
+				t.Fatalf("servers body: %v (%s)", err, body)
+			}
+			if done.Status != "complete" {
+				t.Fatalf("want status=complete, got %q", done.Status)
+			}
+			if done.Servers == nil {
+				t.Fatalf("servers key missing or null: %s", body)
+			}
+			return
+		default:
+			t.Fatalf("unexpected status %d: %s", resp.StatusCode, body)
+		}
+
+		if time.Now().After(deadline) {
+			t.Fatal("timed out waiting for servers to become available")
+		}
+		time.Sleep(250 * time.Millisecond)
+	}
+}
+
 func TestStreamTraversal_NotFound(t *testing.T) {
 	srv := newTestServer(t)
 	defer srv.Shutdown(5 * time.Second) //nolint:errcheck
@@ -322,6 +461,71 @@ func TestStaticSPA_TypeOptions(t *testing.T) {
 	}
 }
 
+// TestStaticSPA_DetailTree asserts the SPA ships the live detail tree with
+// its resolve-subtree toggle markup, plus the raw-log fallback feed so the
+// old flat progress view is still reachable for debugging.
+func TestStaticSPA_DetailTree(t *testing.T) {
+	srv := newTestServer(t)
+	defer srv.Shutdown(5 * time.Second) //nolint:errcheck
+
+	resp, err := http.Get("http://" + srv.Addr() + "/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	page := string(body)
+
+	for _, want := range []string{
+		`id="detailTree"`,   // detail-tree container
+		`resolve-toggle`,    // per-node show/hide resolve markup
+		`show resolve`,      // toggle wording mirrors dns.squish.net
+		`id="progressFeed"`, // raw-log fallback feed still present
+		`id="rawToggle"`,    // toggle that reveals it
+	} {
+		if !strings.Contains(page, want) {
+			t.Errorf("index.html missing %q", want)
+		}
+	}
+}
+
+// TestStaticSPA_ServersSection asserts the SPA ships the server map/table
+// section: Leaflet lazy-loaded from unpkg, geojs.io client-side geolocation,
+// and the reference-style table headings.
+func TestStaticSPA_ServersSection(t *testing.T) {
+	srv := newTestServer(t)
+	defer srv.Shutdown(5 * time.Second) //nolint:errcheck
+
+	resp, err := http.Get("http://" + srv.Addr() + "/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	page := string(body)
+
+	for _, want := range []string{
+		`unpkg.com/leaflet@1.9`, // map library CDN
+		`get.geojs.io`,          // client-side geolocation service
+		`id="serversCard"`,
+		`id="serverMap"`,
+		`<th>Country</th><th>City</th><th>Servers</th><th>Software guess</th>`,
+		`/servers`, // fetches the servers endpoint
+	} {
+		if !strings.Contains(page, want) {
+			t.Errorf("index.html missing %q", want)
+		}
+	}
+}
+
 func TestStaticSPA_FallbackToIndex(t *testing.T) {
 	srv := newTestServer(t)
 	defer srv.Shutdown(5 * time.Second) //nolint:errcheck

web/api/ratelimit.go

@@ -0,0 +1,120 @@
+package api
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+// Default per-IP rate limit for POST /api/traverse, overridable via
+// EXPLOREDNS_RATE_LIMIT ("N/duration", e.g. "30/1h" or "10/10m").
+const (
+	defaultRateLimitCount  = 30
+	defaultRateLimitWindow = time.Hour
+)
+
+// rateLimiter is an in-memory token-bucket limiter keyed by client IP.
+// Each bucket starts full with limit tokens and refills continuously at
+// limit tokens per window.
+type rateLimiter struct {
+	limit  int
+	window time.Duration
+
+	mu      sync.Mutex
+	buckets map[string]*tokenBucket
+	now     func() time.Time // overridable in tests
+}
+
+type tokenBucket struct {
+	tokens float64
+	last   time.Time
+}
+
+func newRateLimiter(limit int, window time.Duration) *rateLimiter {
+	return &rateLimiter{
+		limit:   limit,
+		window:  window,
+		buckets: make(map[string]*tokenBucket),
+		now:     time.Now,
+	}
+}
+
+// allow reports whether one request from ip fits within the limit,
+// consuming a token when it does.
+func (rl *rateLimiter) allow(ip string) bool {
+	rl.mu.Lock()
+	defer rl.mu.Unlock()
+
+	now := rl.now()
+	b, ok := rl.buckets[ip]
+	if !ok {
+		b = &tokenBucket{tokens: float64(rl.limit), last: now}
+		rl.buckets[ip] = b
+	} else {
+		refill := now.Sub(b.last).Seconds() * float64(rl.limit) / rl.window.Seconds()
+		b.tokens = min(b.tokens+refill, float64(rl.limit))
+		b.last = now
+	}
+	if b.tokens < 1 {
+		return false
+	}
+	b.tokens--
+	return true
+}
+
+// sweep drops buckets idle for at least one full window; such buckets
+// would be full again anyway, so dropping them loses nothing.
+func (rl *rateLimiter) sweep() {
+	rl.mu.Lock()
+	defer rl.mu.Unlock()
+	cutoff := rl.now().Add(-rl.window)
+	for ip, b := range rl.buckets {
+		if b.last.Before(cutoff) {
+			delete(rl.buckets, ip)
+		}
+	}
+}
+
+// String renders the limit for error messages, e.g. "30 requests per 1h0m0s".
+func (rl *rateLimiter) String() string {
+	return fmt.Sprintf("%d requests per %s", rl.limit, rl.window)
+}
+
+// rateLimitExempt reports whether r may bypass the rate limit: direct
+// connections from loopback (the SPA dev loop, tests, health tooling).
+// Proxied requests are never exempt — when Fly-Client-IP or
+// X-Forwarded-For is present, RemoteAddr is just the proxy, so the real
+// client IP must be limited even though the socket peer is local.
+func rateLimitExempt(r *http.Request) bool {
+	if r.Header.Get("Fly-Client-IP") != "" || r.Header.Get("X-Forwarded-For") != "" {
+		return false
+	}
+	host, _, err := net.SplitHostPort(r.RemoteAddr)
+	if err != nil {
+		host = r.RemoteAddr
+	}
+	ip := net.ParseIP(host)
+	return ip != nil && ip.IsLoopback()
+}
+
+// parseRateLimit parses "N/duration" (e.g. "30/1h"), falling back to the
+// defaults when v is empty or invalid.
+func parseRateLimit(v string) (int, time.Duration) {
+	parts := strings.SplitN(v, "/", 2)
+	if len(parts) != 2 {
+		return defaultRateLimitCount, defaultRateLimitWindow
+	}
+	n, err := strconv.Atoi(strings.TrimSpace(parts[0]))
+	if err != nil || n <= 0 {
+		return defaultRateLimitCount, defaultRateLimitWindow
+	}
+	d, err := time.ParseDuration(strings.TrimSpace(parts[1]))
+	if err != nil || d <= 0 {
+		return defaultRateLimitCount, defaultRateLimitWindow
+	}
+	return n, d
+}

web/api/ratelimit_test.go

@@ -0,0 +1,169 @@
+package api
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestParseRateLimit(t *testing.T) {
+	tests := []struct {
+		in     string
+		limit  int
+		window time.Duration
+	}{
+		{"", defaultRateLimitCount, defaultRateLimitWindow},
+		{"30/1h", 30, time.Hour},
+		{"10/10m", 10, 10 * time.Minute},
+		{"5 / 30s", 5, 30 * time.Second},
+		{"bogus", defaultRateLimitCount, defaultRateLimitWindow},
+		{"0/1h", defaultRateLimitCount, defaultRateLimitWindow},
+		{"-3/1h", defaultRateLimitCount, defaultRateLimitWindow},
+		{"10/-1h", defaultRateLimitCount, defaultRateLimitWindow},
+		{"10/soon", defaultRateLimitCount, defaultRateLimitWindow},
+		{"/1h", defaultRateLimitCount, defaultRateLimitWindow},
+	}
+	for _, tc := range tests {
+		limit, window := parseRateLimit(tc.in)
+		if limit != tc.limit || window != tc.window {
+			t.Errorf("parseRateLimit(%q) = %d, %s; want %d, %s",
+				tc.in, limit, window, tc.limit, tc.window)
+		}
+	}
+}
+
+func TestNewHandlerReadsRateLimitEnv(t *testing.T) {
+	t.Setenv("EXPLOREDNS_RATE_LIMIT", "5/10m")
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	h := newHandler(ctx)
+	if h.limiter.limit != 5 || h.limiter.window != 10*time.Minute {
+		t.Fatalf("limiter = %d/%s, want 5/10m", h.limiter.limit, h.limiter.window)
+	}
+}
+
+// postTraverse sends POST /api/traverse with an empty JSON body so requests
+// that pass the rate limiter fail validation (400) instead of spawning a
+// real traversal. remoteAddr and headers shape the client identity.
+func postTraverse(t *testing.T, h *Handler, remoteAddr string, headers map[string]string) *httptest.ResponseRecorder {
+	t.Helper()
+	req := httptest.NewRequest(http.MethodPost, "/api/traverse", strings.NewReader(`{}`))
+	req.RemoteAddr = remoteAddr
+	for k, v := range headers {
+		req.Header.Set(k, v)
+	}
+	rec := httptest.NewRecorder()
+	h.mux.ServeHTTP(rec, req)
+	return rec
+}
+
+func TestRateLimit_OverLimitReturns429(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	h := newHandler(ctx)
+	h.limiter = newRateLimiter(2, time.Hour)
+
+	hdr := map[string]string{"X-Forwarded-For": "203.0.113.9"}
+	for i := 0; i < 2; i++ {
+		if rec := postTraverse(t, h, "10.0.0.1:1234", hdr); rec.Code != http.StatusBadRequest {
+			t.Fatalf("request %d: want 400 (under limit), got %d: %s", i, rec.Code, rec.Body.String())
+		}
+	}
+	rec := postTraverse(t, h, "10.0.0.1:1234", hdr)
+	if rec.Code != http.StatusTooManyRequests {
+		t.Fatalf("want 429 over limit, got %d: %s", rec.Code, rec.Body.String())
+	}
+	if body := rec.Body.String(); !strings.Contains(body, "2 requests per 1h0m0s") {
+		t.Fatalf("429 body should name the limit, got %s", body)
+	}
+
+	// A distinct client IP has its own bucket and is unaffected.
+	other := map[string]string{"X-Forwarded-For": "203.0.113.10"}
+	if rec := postTraverse(t, h, "10.0.0.1:1234", other); rec.Code != http.StatusBadRequest {
+		t.Fatalf("distinct IP: want 400, got %d: %s", rec.Code, rec.Body.String())
+	}
+}
+
+func TestRateLimit_RefillsContinuously(t *testing.T) {
+	rl := newRateLimiter(2, time.Second)
+	now := time.Now()
+	rl.now = func() time.Time { return now }
+
+	if !rl.allow("a") || !rl.allow("a") {
+		t.Fatal("first two requests should be allowed")
+	}
+	if rl.allow("a") {
+		t.Fatal("third request should be denied")
+	}
+	// Half a window refills half the bucket: one token.
+	now = now.Add(500 * time.Millisecond)
+	if !rl.allow("a") {
+		t.Fatal("request after refill should be allowed")
+	}
+	if rl.allow("a") {
+		t.Fatal("bucket should hold only the refilled token")
+	}
+}
+
+func TestRateLimit_SweepDropsIdleBuckets(t *testing.T) {
+	rl := newRateLimiter(1, time.Minute)
+	now := time.Now()
+	rl.now = func() time.Time { return now }
+
+	rl.allow("stale")
+	now = now.Add(2 * time.Minute)
+	rl.allow("fresh")
+	rl.sweep()
+
+	rl.mu.Lock()
+	defer rl.mu.Unlock()
+	if _, ok := rl.buckets["stale"]; ok {
+		t.Fatal("idle bucket should have been swept")
+	}
+	if _, ok := rl.buckets["fresh"]; !ok {
+		t.Fatal("active bucket should survive the sweep")
+	}
+}
+
+func TestRateLimit_LocalhostExempt(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	h := newHandler(ctx)
+	h.limiter = newRateLimiter(1, time.Hour)
+
+	for _, addr := range []string{"127.0.0.1:5555", "[::1]:5555"} {
+		for i := 0; i < 3; i++ {
+			rec := postTraverse(t, h, addr, nil)
+			if rec.Code != http.StatusBadRequest {
+				t.Fatalf("%s request %d: localhost should be exempt, got %d: %s",
+					addr, i, rec.Code, rec.Body.String())
+			}
+		}
+	}
+}
+
+// TestRateLimit_ProxiedLocalhostNotExempt verifies that a request arriving
+// from a local proxy (RemoteAddr loopback) is still limited by the real
+// client IP carried in Fly-Client-IP / X-Forwarded-For.
+func TestRateLimit_ProxiedLocalhostNotExempt(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	h := newHandler(ctx)
+	h.limiter = newRateLimiter(1, time.Hour)
+
+	hdr := map[string]string{"Fly-Client-IP": "198.51.100.4"}
+	if rec := postTraverse(t, h, "127.0.0.1:5555", hdr); rec.Code != http.StatusBadRequest {
+		t.Fatalf("first proxied request: want 400, got %d", rec.Code)
+	}
+	if rec := postTraverse(t, h, "127.0.0.1:5555", hdr); rec.Code != http.StatusTooManyRequests {
+		t.Fatalf("second proxied request: want 429, got %d", rec.Code)
+	}
+	// The same proxy forwarding a different client is unaffected.
+	other := map[string]string{"Fly-Client-IP": "198.51.100.5"}
+	if rec := postTraverse(t, h, "127.0.0.1:5555", other); rec.Code != http.StatusBadRequest {
+		t.Fatalf("other client via proxy: want 400, got %d", rec.Code)
+	}
+}

web/api/server.go

@@ -27,14 +27,23 @@ var staticFiles embed.FS
 
 // Server is the HTTP API server.
 type Server struct {
-	addr   string
-	srv    *http.Server
-	cancel context.CancelFunc
+	addr    string
+	version string
+	srv     *http.Server
+	cancel  context.CancelFunc
 }
 
 // NewServer creates a new Server that listens on addr (e.g. ":8080").
 func NewServer(addr string) *Server {
-	return &Server{addr: addr}
+	return &Server{addr: addr, version: "dev"}
+}
+
+// SetVersion records the build version reported by GET /api/health.
+// Call before Start; empty values are ignored.
+func (s *Server) SetVersion(v string) {
+	if v != "" {
+		s.version = v
+	}
 }
 
 // Start builds the HTTP handler, begins listening, and returns when the
@@ -44,6 +53,7 @@ func (s *Server) Start() error {
 	ctx, cancel := context.WithCancel(context.Background())
 	s.cancel = cancel
 	h := newHandler(ctx)
+	h.version = s.version
 
 	sub, err := fs.Sub(staticFiles, "static")
 	if err != nil {

web/api/static/favicon.svg

@@ -0,0 +1,13 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32">
+  <!-- ExploreDNS: delegation tree — root fanning to leaves, green = answered path -->
+  <rect width="32" height="32" rx="5.8" fill="#2563eb"/>
+  <g stroke="#ffffff" stroke-width="1.8" stroke-linecap="round">
+    <line x1="16" y1="7" x2="7" y2="24"/>
+    <line x1="16" y1="7" x2="16" y2="25"/>
+    <line x1="16" y1="7" x2="25" y2="24"/>
+  </g>
+  <circle cx="16" cy="7" r="3.5" fill="#ffffff"/>
+  <circle cx="7" cy="24" r="2.9" fill="#ffffff"/>
+  <circle cx="16" cy="25" r="2.9" fill="#4ade80"/>
+  <circle cx="25" cy="24" r="2.9" fill="#ffffff"/>
+</svg>

web/api/static/index.html

@@ -4,6 +4,8 @@
   <meta charset="UTF-8" />
   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
   <title>ExploreDNS</title>
+  <link rel="icon" type="image/svg+xml" href="/favicon.svg">
+  <link rel="icon" type="image/x-icon" href="/favicon.ico" sizes="16x16 32x32">
   <style>
     /* ── Design tokens ─────────────────────────────────────────────── */
     :root {
@@ -308,6 +310,92 @@
        spacing intact. */
     .pe-text { color: var(--text); white-space: pre; }
 
+    /* ── Detail tree ────────────────────────────────────────────────── */
+    /* Live tree mirroring the dns.squish.net detail page: one node per
+       refid, indented per depth, resolve subtrees collapsed by default. */
+    .detail-tree {
+      font-family: var(--font-mono);
+      font-size: 0.78rem;
+      line-height: 1.7;
+      max-height: 340px;
+      overflow: auto;
+      background: var(--bg);
+      border: 1px solid var(--border);
+      border-radius: var(--radius-sm);
+      padding: 0.6rem 0.75rem;
+      color: var(--text-muted);
+      margin-bottom: 1rem;
+    }
+    .detail-tree:empty::before {
+      content: 'Awaiting traversal…';
+      color: var(--text-dim);
+    }
+    .detail-tree::-webkit-scrollbar { width: 5px; height: 5px; }
+    .detail-tree::-webkit-scrollbar-track { background: transparent; }
+    .detail-tree::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }
+    .tnode-line { display: flex; gap: 0.5rem; align-items: baseline; white-space: nowrap; }
+    .tnode-children, .tnode-resolves {
+      margin-left: 0.9rem;
+      border-left: 1px dotted var(--border);
+      padding-left: 0.6rem;
+    }
+    .tnode-refid { color: var(--text-dim); }
+    .tnode-text  { color: var(--text); white-space: pre; }
+    .tnode-early { color: var(--text-dim); font-style: italic; }
+    .resolve-toggle {
+      background: none;
+      border: 1px dashed var(--border);
+      color: var(--info);
+      border-radius: 3px;
+      font-size: 0.65rem;
+      padding: 0 5px;
+      font-family: inherit;
+      line-height: 1.4;
+    }
+    .resolve-toggle:hover { border-color: var(--info); }
+    .raw-toggle {
+      margin-left: auto;
+      background: var(--bg-input);
+      border: 1px solid var(--border);
+      color: var(--text-muted);
+      border-radius: var(--radius-sm);
+      font-size: 0.7rem;
+      padding: 2px 8px;
+      text-transform: none;
+      letter-spacing: normal;
+    }
+    .raw-toggle:hover { color: var(--text); }
+    .raw-toggle.active { color: var(--primary); border-color: var(--primary); }
+
+    /* ── Servers map + table ────────────────────────────────────────── */
+    .server-map {
+      height: 320px;
+      border: 1px solid var(--border);
+      border-radius: var(--radius-sm);
+      margin-bottom: 1rem;
+      background: var(--bg);
+      z-index: 0; /* keep Leaflet panes under the sticky header */
+    }
+    .servers-table { width: 100%; border-collapse: collapse; font-size: 0.8rem; }
+    .servers-table th {
+      text-align: left;
+      color: var(--text-muted);
+      text-transform: uppercase;
+      font-size: 0.68rem;
+      letter-spacing: 0.05em;
+      padding: 0.4rem 0.6rem;
+      border-bottom: 1px solid var(--border);
+    }
+    .servers-table td {
+      padding: 0.45rem 0.6rem;
+      border-bottom: 1px solid var(--border);
+      vertical-align: top;
+      font-family: var(--font-mono);
+      font-size: 0.75rem;
+      color: var(--text);
+    }
+    .servers-table td.loc { font-family: inherit; color: var(--text-muted); }
+
     /* ── Results tree ───────────────────────────────────────────────── */
     .results-section h2 {
       font-size: 0.9rem;
@@ -515,13 +603,15 @@
 
       <!-- Left: progress + results -->
       <div>
-        <!-- Progress feed -->
+        <!-- Detail tree (raw event log kept behind the toggle for debugging) -->
         <div class="card" id="progressCard" style="margin-bottom:1.25rem;">
           <div class="card-title">
-            ⚡ Live Progress
+            🌳 Traversal Detail
             <span class="badge-count" id="progressCount">0</span>
+            <button class="raw-toggle" id="rawToggle" title="Toggle the raw event log">raw log</button>
           </div>
-          <div class="progress-feed" id="progressFeed"></div>
+          <div class="detail-tree" id="detailTree"></div>
+          <div class="progress-feed hidden" id="progressFeed"></div>
         </div>
 
         <!-- Results -->
@@ -596,6 +686,23 @@
 
     </div><!-- /two-col -->
 
+    <!-- Servers map + table (appears once post-traversal fingerprinting is
+         done; geolocation runs client-side via get.geojs.io, Leaflet loads
+         lazily from unpkg.com/leaflet@1.9 the first time it is needed) -->
+    <div class="card hidden" id="serversCard" style="margin-top:1.25rem;">
+      <div class="card-title">
+        🗺️ Servers
+        <span class="badge-count" id="serversCount">0</span>
+      </div>
+      <div id="serverMap" class="server-map hidden"></div>
+      <table class="servers-table">
+        <thead>
+          <tr><th>Country</th><th>City</th><th>Servers</th><th>Software guess</th></tr>
+        </thead>
+        <tbody id="serversTableBody"></tbody>
+      </table>
+    </div>
+
   </main>
 
   <footer>
@@ -621,6 +728,12 @@
   const errorBox      = document.getElementById('errorBox');
   const progressFeed  = document.getElementById('progressFeed');
   const progressCount = document.getElementById('progressCount');
+  const detailTree    = document.getElementById('detailTree');
+  const rawToggle     = document.getElementById('rawToggle');
+  const serversCard   = document.getElementById('serversCard');
+  const serversCount  = document.getElementById('serversCount');
+  const serverMap     = document.getElementById('serverMap');
+  const serversTableBody = document.getElementById('serversTableBody');
   const resultsContainer = document.getElementById('resultsContainer');
   const resultsEmpty  = document.getElementById('resultsEmpty');
   const resultsCount  = document.getElementById('resultsCount');
@@ -643,8 +756,17 @@
   let startTime     = null;
   let timerInterval = null;
   let progressItems = [];
-  let progressRows  = new Map(); // refid → row elements, updated in place
+  let progressRows  = new Map(); // refid → raw-log row elements, updated in place
   let resultItems   = [];
+  let treeNodes     = new Map(); // refid → detail-tree node, updated in place
+  let resultsFetched = false;
+  let serversFetched = false;
+  let serversRetryTimer = null;
+  let serversRetriesLeft = 0;
+  const geoCache = new Map();    // ip → geo object or null; kept across runs
+  let leafletPromise = null;
+  let mapInstance = null;
+  let mapMarkers  = null;
 
   // ── Theme toggle ──────────────────────────────────────────────────
   const html = document.documentElement;
@@ -710,22 +832,35 @@
       try {
         const ev = JSON.parse(e.data);
         appendProgress(ev);
+        updateTree(ev);
+        // The traversal reaches its terminal state before fingerprinting:
+        // fetch the results immediately, then the servers once ready.
+        if (ev.stage === 'complete') maybeFetchResults();
+        if (ev.stage === 'servers')  fetchServers();
       } catch (_) {}
     });
 
     eventSource.addEventListener('done', () => {
       eventSource.close();
       eventSource = null;
-      fetchResults(id);
+      maybeFetchResults();
+      fetchServers();
     });
 
     eventSource.onerror = () => {
       if (eventSource) { eventSource.close(); eventSource = null; }
       // Fall back to polling
-      fetchResults(id);
+      maybeFetchResults();
+      fetchServers();
     };
   }
 
+  function maybeFetchResults() {
+    if (resultsFetched || !currentJobId) return;
+    resultsFetched = true;
+    fetchResults(currentJobId);
+  }
+
   // ── Fetch final results ───────────────────────────────────────────
   async function fetchResults(id) {
     try {
@@ -793,6 +928,105 @@
     }
   }
 
+  // ── Detail tree ───────────────────────────────────────────────────
+  // One node per refid, indented per depth like the dns.squish.net detail
+  // page. Nodes appear on their first event and update in place; resolve
+  // subtrees (refids entering a ".0." component) are collapsed by default
+  // behind a per-node show/hide toggle. The raw event feed stays available
+  // behind the "raw log" toggle for debugging.
+  rawToggle.addEventListener('click', () => {
+    const showRaw = progressFeed.classList.contains('hidden');
+    progressFeed.classList.toggle('hidden', !showRaw);
+    detailTree.classList.toggle('hidden', showRaw);
+    rawToggle.classList.toggle('active', showRaw);
+  });
+
+  function updateTree(ev) {
+    if (!ev.refid) return; // synthetic stages (complete/servers) have no node
+    let node = treeNodes.get(ev.refid);
+    if (!node) node = createTreeNode(ev.refid);
+
+    const status = ev.status || ev.stage;
+    node.badge.textContent = ev.is_resolve ? 'glue ' + status : status;
+    node.badge.className = 'pe-badge ' + progressBadgeCls(ev);
+
+    let text = ev.server || ev.name || '';
+    text += ' (' + (ev.ips || '') + ')';
+    text += ' <' + (ev.bailiwick || '') + '>';
+    node.text.textContent = text;
+    node.text.title = ev.refid + ' ' + (ev.name || '') + '/' + (ev.qtype || '');
+
+    node.early.textContent = ev.completed_earlier
+      ? ' -- completed earlier (' + ev.completed_earlier + ')' : '';
+  }
+
+  // createTreeNode builds the DOM for refid and attaches it under the node
+  // with the longest existing refid prefix — never assume one dotted
+  // component per level, since multi-childset refids insert an extra digit
+  // (e.g. 1.1.2.1 hanging off 1.1) and resolve refids insert ".0.".
+  function createTreeNode(refid) {
+    const el = document.createElement('div');
+    el.className = 'tnode';
+    const line = document.createElement('div');
+    line.className = 'tnode-line';
+    const badge = document.createElement('span');
+    badge.className = 'pe-badge';
+    const rid = document.createElement('span');
+    rid.className = 'tnode-refid';
+    rid.textContent = refid;
+    const text = document.createElement('span');
+    text.className = 'tnode-text';
+    const early = document.createElement('span');
+    early.className = 'tnode-early';
+    line.appendChild(badge);
+    line.appendChild(rid);
+    line.appendChild(text);
+    line.appendChild(early);
+    el.appendChild(line);
+
+    const node = { refid, el, line, badge, text, early,
+                   childrenEl: null, resolvesEl: null };
+    treeNodes.set(refid, node);
+
+    const parts = refid.split('.');
+    let parent = null, plen = 0;
+    for (let i = parts.length - 1; i >= 1; i--) {
+      const p = treeNodes.get(parts.slice(0, i).join('.'));
+      if (p) { parent = p; plen = i; break; }
+    }
+    if (!parent) {
+      detailTree.appendChild(el);
+      return node;
+    }
+
+    if (parts[plen] === '0') {
+      // Glue-resolution subtree: collapsed container + per-node toggle.
+      if (!parent.resolvesEl) {
+        parent.resolvesEl = document.createElement('div');
+        parent.resolvesEl.className = 'tnode-resolves hidden';
+        // Resolution happens before querying: keep resolves above children.
+        parent.el.insertBefore(parent.resolvesEl, parent.childrenEl);
+        const t = document.createElement('button');
+        t.className = 'resolve-toggle';
+        t.textContent = 'show resolve';
+        t.addEventListener('click', () => {
+          const hidden = parent.resolvesEl.classList.toggle('hidden');
+          t.textContent = hidden ? 'show resolve' : 'hide resolve';
+        });
+        parent.line.appendChild(t);
+      }
+      parent.resolvesEl.appendChild(el);
+    } else {
+      if (!parent.childrenEl) {
+        parent.childrenEl = document.createElement('div');
+        parent.childrenEl.className = 'tnode-children';
+        parent.el.appendChild(parent.childrenEl);
+      }
+      parent.childrenEl.appendChild(el);
+    }
+    return node;
+  }
+
   // ── Results rendering ─────────────────────────────────────────────
   function renderResults(job) {
     detailDomain.textContent  = job.domain || '—';
@@ -942,6 +1176,183 @@
     }
   }
 
+  // ── Servers map + table ───────────────────────────────────────────
+  // Fetched once the backend publishes {"stage":"servers"} (or as a polling
+  // fallback after done/error). Geolocation happens client-side via
+  // get.geojs.io with at most 4 concurrent lookups and an in-page cache;
+  // servers that cannot be located still show in the table with a dash
+  // location, and the section works without the map when offline.
+  function fetchServers() {
+    if (!currentJobId || serversFetched) return;
+    const id = currentJobId;
+    fetch(`/api/traverse/${id}/servers`)
+      .then(async res => {
+        if (id !== currentJobId) return;
+        if (res.status === 202) { scheduleServersRetry(); return; }
+        if (!res.ok) return;
+        const data = await res.json();
+        if (id !== currentJobId || serversFetched) return;
+        serversFetched = true;
+        renderServers(data.servers || []);
+      })
+      .catch(() => { scheduleServersRetry(); });
+  }
+
+  function scheduleServersRetry() {
+    if (serversRetryTimer || serversRetriesLeft <= 0) return;
+    serversRetriesLeft--;
+    serversRetryTimer = setTimeout(() => {
+      serversRetryTimer = null;
+      fetchServers();
+    }, 2000);
+  }
+
+  async function renderServers(servers) {
+    serversCard.classList.remove('hidden');
+    serversCount.textContent = servers.length;
+    serversTableBody.innerHTML = '';
+
+    if (servers.length === 0) {
+      appendServersRow('—', '—', 'No servers recorded.', '—');
+      serverMap.classList.add('hidden');
+      return;
+    }
+
+    appendServersRow('…', '', 'Locating servers…', '');
+    await geolocateAll([...new Set(servers.map(s => s.ip))]);
+    serversTableBody.innerHTML = '';
+
+    // Group servers by geolocation (like the reference servers page); all
+    // unlocatable IPs share the single dash row at the bottom.
+    const groups = new Map();
+    servers.forEach(s => {
+      const geo = geoCache.get(s.ip) || null;
+      const key = geo ? [geo.country, geo.city, geo.latitude, geo.longitude].join('|') : '';
+      if (!groups.has(key)) groups.set(key, { geo, servers: [] });
+      groups.get(key).servers.push(s);
+    });
+
+    const sorted = [...groups.values()].sort((a, b) => {
+      if (!a.geo) return 1;
+      if (!b.geo) return -1;
+      return ((a.geo.country || '') + (a.geo.city || ''))
+        .localeCompare((b.geo.country || '') + (b.geo.city || ''));
+    });
+
+    sorted.forEach(g => {
+      const names = g.servers.map(s => `${s.name} (${s.ip})`).join('\n');
+      const soft  = g.servers.map(s => s.version || '—').join('\n');
+      appendServersRow(
+        g.geo ? (g.geo.country || '—') : '—',
+        g.geo ? (g.geo.city    || '—') : '—',
+        names, soft);
+    });
+
+    const located = sorted.filter(g =>
+      g.geo && isFinite(parseFloat(g.geo.latitude)) && isFinite(parseFloat(g.geo.longitude)));
+    if (located.length === 0) {
+      serverMap.classList.add('hidden');
+      return;
+    }
+    try {
+      await loadLeaflet();
+      drawMap(located);
+    } catch (_) {
+      // Leaflet unavailable (offline / CDN blocked): table already rendered.
+      serverMap.classList.add('hidden');
+    }
+  }
+
+  function appendServersRow(country, city, servers, software) {
+    const tr = document.createElement('tr');
+    [[country, 'loc'], [city, 'loc'], [servers, ''], [software, '']].forEach(([val, cls]) => {
+      const td = document.createElement('td');
+      if (cls) td.className = cls;
+      td.style.whiteSpace = 'pre-line';
+      td.textContent = val;
+      tr.appendChild(td);
+    });
+    serversTableBody.appendChild(tr);
+  }
+
+  // geolocateAll fills geoCache for every ip, max 4 concurrent lookups,
+  // 5 s per lookup; failures cache as null so they are not retried.
+  function geolocateAll(ips) {
+    const queue = ips.filter(ip => !geoCache.has(ip));
+    const worker = async () => {
+      while (queue.length > 0) {
+        const ip = queue.shift();
+        try {
+          const ctrl = new AbortController();
+          const timer = setTimeout(() => ctrl.abort(), 5000);
+          const res = await fetch(
+            `https://get.geojs.io/v1/ip/geo/${encodeURIComponent(ip)}.json`,
+            { signal: ctrl.signal });
+          clearTimeout(timer);
+          const geo = res.ok ? await res.json() : null;
+          geoCache.set(ip, geo && geo.latitude ? geo : null);
+        } catch (_) {
+          geoCache.set(ip, null);
+        }
+      }
+    };
+    const workers = [];
+    for (let i = 0; i < Math.min(4, queue.length); i++) workers.push(worker());
+    return Promise.all(workers);
+  }
+
+  // loadLeaflet injects the Leaflet CSS+JS from unpkg the first time the
+  // map is needed (never on page load).
+  function loadLeaflet() {
+    if (window.L) return Promise.resolve();
+    if (leafletPromise) return leafletPromise;
+    leafletPromise = new Promise((resolve, reject) => {
+      const css = document.createElement('link');
+      css.rel = 'stylesheet';
+      css.href = 'https://unpkg.com/leaflet@1.9.4/dist/leaflet.css';
+      document.head.appendChild(css);
+      const js = document.createElement('script');
+      js.src = 'https://unpkg.com/leaflet@1.9.4/dist/leaflet.js';
+      js.onload = () => resolve();
+      js.onerror = () => { leafletPromise = null; reject(new Error('leaflet failed to load')); };
+      document.head.appendChild(js);
+    });
+    return leafletPromise;
+  }
+
+  function drawMap(groups) {
+    serverMap.classList.remove('hidden');
+    if (!mapInstance) {
+      mapInstance = L.map(serverMap, { scrollWheelZoom: false });
+      L.tileLayer('https://tile.openstreetmap.org/{z}/{x}/{y}.png', {
+        maxZoom: 18,
+        attribution: '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors',
+      }).addTo(mapInstance);
+      mapMarkers = L.layerGroup().addTo(mapInstance);
+    }
+    mapMarkers.clearLayers();
+
+    const bounds = [];
+    groups.forEach(g => {
+      const lat = parseFloat(g.geo.latitude);
+      const lon = parseFloat(g.geo.longitude);
+      bounds.push([lat, lon]);
+      const html = g.servers.map(s =>
+        escapeHtml(`${s.name} (${s.ip})`) +
+        (s.version ? ' — ' + escapeHtml(s.version) : '')).join('<br>');
+      L.marker([lat, lon]).bindPopup(html).addTo(mapMarkers);
+    });
+    mapInstance.invalidateSize();
+    if (bounds.length === 1) mapInstance.setView(bounds[0], 5);
+    else mapInstance.fitBounds(bounds, { padding: [24, 24] });
+  }
+
+  function escapeHtml(s) {
+    return s.replace(/[&<>"']/g, c => ({
+      '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;',
+    }[c]));
+  }
+
   // ── Stats ─────────────────────────────────────────────────────────
   function updateStats(job) {
     const items = job.results || [];
@@ -973,6 +1384,16 @@
     progressItems = [];
     progressRows = new Map();
     progressCount.textContent = '0';
+    detailTree.innerHTML = '';
+    treeNodes = new Map();
+    resultsFetched = false;
+    serversFetched = false;
+    serversRetriesLeft = 30;
+    if (serversRetryTimer) { clearTimeout(serversRetryTimer); serversRetryTimer = null; }
+    serversCard.classList.add('hidden');
+    serversTableBody.innerHTML = '';
+    serversCount.textContent = '0';
+    if (mapMarkers) mapMarkers.clearLayers();
     summaryPre.textContent = '';
     resultItems = [];
     resultsCount.textContent = '0';

web/api/webhook.go

@@ -0,0 +1,137 @@
+package api
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net"
+	"net/http"
+	"strings"
+	"time"
+)
+
+// Webhook event names, sent both in the JSON body and in the
+// X-ExploreDNS-Event request header.
+const (
+	webhookEventStart    = "start"
+	webhookEventComplete = "complete"
+)
+
+// webhookStartEvent is posted when a traversal job is accepted.
+type webhookStartEvent struct {
+	Event     string    `json:"event"`
+	ID        string    `json:"id"`
+	Domain    string    `json:"domain"`
+	QueryType string    `json:"query_type"`
+	AllRoots  bool      `json:"all_roots"`
+	ClientIP  string    `json:"client_ip"`
+	StartedAt time.Time `json:"started_at"`
+}
+
+// webhookCompleteEvent is posted when a traversal job reaches a terminal
+// state. Summary reuses the API Summary shape.
+type webhookCompleteEvent struct {
+	Event       string    `json:"event"`
+	ID          string    `json:"id"`
+	Domain      string    `json:"domain"`
+	QueryType   string    `json:"query_type"`
+	ClientIP    string    `json:"client_ip"`
+	StartedAt   time.Time `json:"started_at"`
+	DoneAt      time.Time `json:"done_at"`
+	DurationMS  int64     `json:"duration_ms"`
+	Status      string    `json:"status"`
+	Error       string    `json:"error,omitempty"`
+	ResultCount int       `json:"result_count"`
+	Summary     *Summary  `json:"summary"`
+}
+
+// webhookReporter posts usage events to a configured URL. Sends are
+// fire-and-forget: each runs in its own goroutine with a timeout and a
+// single retry, and failures are logged but never surface to callers.
+type webhookReporter struct {
+	url        string
+	client     *http.Client
+	timeout    time.Duration
+	retryDelay time.Duration
+}
+
+// newWebhookReporter returns a reporter for url, or nil when url is empty
+// (webhook reporting disabled). A nil reporter is safe to call.
+func newWebhookReporter(url string) *webhookReporter {
+	if url == "" {
+		return nil
+	}
+	return &webhookReporter{
+		url:        url,
+		client:     &http.Client{},
+		timeout:    5 * time.Second,
+		retryDelay: 2 * time.Second,
+	}
+}
+
+// send marshals payload and posts it asynchronously with one retry on
+// failure. Errors are logged and never affect the caller.
+func (wr *webhookReporter) send(event string, payload any) {
+	if wr == nil {
+		return
+	}
+	body, err := json.Marshal(payload)
+	if err != nil {
+		log.Printf("webhook: marshal %s event: %v", event, err)
+		return
+	}
+	go func() {
+		err := wr.post(event, body)
+		if err == nil {
+			return
+		}
+		log.Printf("webhook: %s event failed, retrying in %s: %v", event, wr.retryDelay, err)
+		time.Sleep(wr.retryDelay)
+		if err := wr.post(event, body); err != nil {
+			log.Printf("webhook: %s event failed after retry: %v", event, err)
+		}
+	}()
+}
+
+// post performs one synchronous webhook delivery attempt.
+func (wr *webhookReporter) post(event string, body []byte) error {
+	ctx, cancel := context.WithTimeout(context.Background(), wr.timeout)
+	defer cancel()
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, wr.url, bytes.NewReader(body))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("X-ExploreDNS-Event", event)
+
+	resp, err := wr.client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode < 200 || resp.StatusCode > 299 {
+		return fmt.Errorf("webhook returned status %d", resp.StatusCode)
+	}
+	return nil
+}
+
+// clientIP resolves the requesting client's IP: the Fly-Client-IP header if
+// present, else the first entry of X-Forwarded-For, else the host part of
+// RemoteAddr.
+func clientIP(r *http.Request) string {
+	if ip := strings.TrimSpace(r.Header.Get("Fly-Client-IP")); ip != "" {
+		return ip
+	}
+	if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
+		if first := strings.TrimSpace(strings.Split(xff, ",")[0]); first != "" {
+			return first
+		}
+	}
+	if host, _, err := net.SplitHostPort(r.RemoteAddr); err == nil {
+		return host
+	}
+	return r.RemoteAddr
+}

web/api/webhook_test.go

@@ -0,0 +1,241 @@
+package api
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestClientIP(t *testing.T) {
+	tests := []struct {
+		name       string
+		remoteAddr string
+		headers    map[string]string
+		want       string
+	}{
+		{"remote addr only", "192.0.2.7:4711", nil, "192.0.2.7"},
+		{"remote addr no port", "192.0.2.7", nil, "192.0.2.7"},
+		{"fly header wins", "127.0.0.1:80",
+			map[string]string{"Fly-Client-IP": "203.0.113.1", "X-Forwarded-For": "198.51.100.1"},
+			"203.0.113.1"},
+		{"xff first entry", "127.0.0.1:80",
+			map[string]string{"X-Forwarded-For": " 198.51.100.1 , 10.0.0.1"},
+			"198.51.100.1"},
+		{"ipv6 remote", "[::1]:9999", nil, "::1"},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			r := httptest.NewRequest(http.MethodPost, "/api/traverse", nil)
+			r.RemoteAddr = tc.remoteAddr
+			for k, v := range tc.headers {
+				r.Header.Set(k, v)
+			}
+			if got := clientIP(r); got != tc.want {
+				t.Fatalf("clientIP = %q, want %q", got, tc.want)
+			}
+		})
+	}
+}
+
+type webhookHit struct {
+	event string
+	body  map[string]any
+}
+
+// newWebhookHandler builds a Handler whose traversals fail instantly (the
+// per-job context is already expired) and whose webhook posts to url.
+func newWebhookHandler(t *testing.T, url string) *Handler {
+	t.Helper()
+	ctx, cancel := context.WithCancel(context.Background())
+	t.Cleanup(cancel)
+	h := newHandler(ctx)
+	h.jobTimeout = time.Nanosecond
+	h.webhook = &webhookReporter{
+		url:        url,
+		client:     &http.Client{},
+		timeout:    2 * time.Second,
+		retryDelay: 10 * time.Millisecond,
+	}
+	return h
+}
+
+func TestWebhook_StartAndCompleteEventsDelivered(t *testing.T) {
+	hits := make(chan webhookHit, 4)
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if ct := r.Header.Get("Content-Type"); ct != "application/json" {
+			t.Errorf("Content-Type = %q, want application/json", ct)
+		}
+		raw, _ := io.ReadAll(r.Body)
+		var body map[string]any
+		if err := json.Unmarshal(raw, &body); err != nil {
+			t.Errorf("unmarshal webhook body: %v (%s)", err, raw)
+		}
+		hits <- webhookHit{event: r.Header.Get("X-ExploreDNS-Event"), body: body}
+	}))
+	defer ts.Close()
+
+	h := newWebhookHandler(t, ts.URL)
+
+	req := httptest.NewRequest(http.MethodPost, "/api/traverse",
+		strings.NewReader(`{"domain":"example.com","type":"A","all_roots":true}`))
+	req.Header.Set("X-Forwarded-For", "198.51.100.7")
+	rec := httptest.NewRecorder()
+	h.mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusAccepted {
+		t.Fatalf("want 202, got %d: %s", rec.Code, rec.Body.String())
+	}
+	var start TraverseStartResponse
+	if err := json.NewDecoder(rec.Body).Decode(&start); err != nil {
+		t.Fatal(err)
+	}
+
+	// Both events are fired asynchronously; collect them by event name.
+	got := map[string]map[string]any{}
+	for len(got) < 2 {
+		select {
+		case hit := <-hits:
+			got[hit.event] = hit.body
+		case <-time.After(10 * time.Second):
+			t.Fatalf("timed out waiting for webhook events, have %v", got)
+		}
+	}
+
+	startEv := got["start"]
+	if startEv == nil {
+		t.Fatal("no start event received")
+	}
+	for k, want := range map[string]any{
+		"event": "start", "id": start.ID, "domain": "example.com",
+		"query_type": "A", "all_roots": true, "client_ip": "198.51.100.7",
+	} {
+		if startEv[k] != want {
+			t.Errorf("start event %s = %v, want %v", k, startEv[k], want)
+		}
+	}
+	if s, _ := startEv["started_at"].(string); s == "" {
+		t.Error("start event missing started_at")
+	}
+
+	compEv := got["complete"]
+	if compEv == nil {
+		t.Fatal("no complete event received")
+	}
+	for k, want := range map[string]any{
+		"event": "complete", "id": start.ID, "domain": "example.com",
+		"query_type": "A", "client_ip": "198.51.100.7", "status": statusError,
+	} {
+		if compEv[k] != want {
+			t.Errorf("complete event %s = %v, want %v", k, compEv[k], want)
+		}
+	}
+	if msg, _ := compEv["error"].(string); !strings.Contains(msg, "timed out") {
+		t.Errorf("complete event error = %v, want timeout message", compEv["error"])
+	}
+	if _, ok := compEv["duration_ms"].(float64); !ok {
+		t.Errorf("complete event duration_ms = %v, want a number", compEv["duration_ms"])
+	}
+	if d, _ := compEv["done_at"].(string); d == "" {
+		t.Error("complete event missing done_at")
+	}
+	if _, ok := compEv["result_count"].(float64); !ok {
+		t.Errorf("complete event result_count = %v, want a number", compEv["result_count"])
+	}
+	if _, ok := compEv["summary"]; !ok {
+		t.Error("complete event missing summary key")
+	}
+}
+
+// TestWebhook_SlowReceiverDoesNotDelayJob verifies that a webhook receiver
+// stuck for longer than the whole traversal never delays job completion.
+func TestWebhook_SlowReceiverDoesNotDelayJob(t *testing.T) {
+	release := make(chan struct{})
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		<-release // hold every delivery until the test finishes
+	}))
+	defer ts.Close()
+	defer close(release)
+
+	h := newWebhookHandler(t, ts.URL)
+
+	startedAt := time.Now()
+	req := httptest.NewRequest(http.MethodPost, "/api/traverse",
+		strings.NewReader(`{"domain":"example.com"}`))
+	rec := httptest.NewRecorder()
+	h.mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusAccepted {
+		t.Fatalf("want 202, got %d: %s", rec.Code, rec.Body.String())
+	}
+	var start TraverseStartResponse
+	if err := json.NewDecoder(rec.Body).Decode(&start); err != nil {
+		t.Fatal(err)
+	}
+
+	job, ok := h.st.get(start.ID)
+	if !ok {
+		t.Fatal("job not found")
+	}
+	deadline := time.After(5 * time.Second)
+	for {
+		job.mu.RLock()
+		done := job.DoneAt != nil
+		job.mu.RUnlock()
+		if done {
+			break
+		}
+		select {
+		case <-deadline:
+			t.Fatal("job did not reach a terminal state while webhook was stalled")
+		case <-time.After(5 * time.Millisecond):
+		}
+	}
+	// The traversal fails instantly (expired context); reaching terminal
+	// state must not have waited on the stalled webhook receiver.
+	if elapsed := time.Since(startedAt); elapsed > 3*time.Second {
+		t.Fatalf("job completion took %s, webhook receiver must not delay it", elapsed)
+	}
+}
+
+func TestWebhook_RetriesOnceOnFailure(t *testing.T) {
+	var calls atomic.Int32
+	done := make(chan struct{})
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if calls.Add(1) == 1 {
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+		close(done)
+	}))
+	defer ts.Close()
+
+	wr := &webhookReporter{
+		url:        ts.URL,
+		client:     &http.Client{},
+		timeout:    2 * time.Second,
+		retryDelay: 10 * time.Millisecond,
+	}
+	wr.send("start", map[string]string{"event": "start"})
+
+	select {
+	case <-done:
+	case <-time.After(5 * time.Second):
+		t.Fatal("webhook was not retried after a failed delivery")
+	}
+	if n := calls.Load(); n != 2 {
+		t.Fatalf("webhook deliveries = %d, want 2 (initial + one retry)", n)
+	}
+}
+
+// TestWebhook_NilReporterSafe covers the disabled (no URL) path.
+func TestWebhook_NilReporterSafe(t *testing.T) {
+	var wr *webhookReporter
+	wr.send("start", map[string]string{"event": "start"}) // must not panic
+	if newWebhookReporter("") != nil {
+		t.Fatal("empty URL should disable the webhook reporter")
+	}
+}