Suppress own-domain tracker attribution

Patterns like "ethereum-https://letaido.com" embed the scanned site's
own origin, appended either by a browser extension (e.g. a wallet
injecting window.ethereum) or by an owner-set tracker. The mapping
agent read that embedded domain and attributed the site to itself as a
third party ("Letaido"), but a site owner is never a third party of its
own site.

Pass the scanned site's eTLD+1 to the agent as a <scanned_site> signal
and instruct it to ignore a domain embedded in the pattern that matches
the site, returning low confidence when that is the only cue. Add a
deterministic backstop that discards any agent attribution whose vendor
name resolves to the site's own domain, so the pattern falls through to
the unmatched fallback regardless of whether the model honored the
prompt. Deterministic catalog, naming, and sibling signals run before
the agent and are untouched, so an independent strong vendor signal
still attributes normally.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/cookiebanner/prompts/tracker_identification.txt.tmpl

@@ -38,7 +38,9 @@ Return a structured JSON response with:
 
 5. The observed domains are useful signals but not conclusive on their own. Many sites load third-party tracker scripts through a first-party reverse proxy (e.g. t.example.com proxying PostHog). When a domain matches the scanned site, it reveals nothing about which third party set the tracker — rely on the naming convention or a database/web search instead. First-party proxy domains are filtered before they reach you, but if you still see the scanned site's own domain, ignore it as evidence. Well-known third-party tracking domains (e.g. doubleclick.net, facebook.com, analytics.google.com) remain strong evidence.
 
-6. Be conservative with third_party_confidence. It measures certainty about the attribution (who set the tracker), nothing else:
+6. A domain or full URL appearing INSIDE the pattern name is NOT a third-party signal when it matches <scanned_site>. It is the site's own first-party origin — commonly a browser extension that appended the page URL to its key (e.g. "ethereum-https://example.com", where the wallet extension suffixes the site origin), or a tracker the site owner set on their own site. The site owner is never a third party of its own site, so you must NOT attribute the scanned site's own brand or domain as a third party. If the embedded own-domain is the ONLY vendor cue, return an empty third_party_name with third_party_confidence below 0.3. A genuine naming convention elsewhere in the key (e.g. _ga, _fbp, _hj) still attributes normally — judge that on its own merits, independent of the embedded site domain.
+
+7. Be conservative with third_party_confidence. It measures certainty about the attribution (who set the tracker), nothing else:
    - 0.9-1.0: exact pattern match found in database, or unmistakable naming convention + matching domain, or a name that embeds the vendor (e.g. "__darkreader__*" -> Dark Reader)
    - 0.7-0.8: strong signal from naming convention or domain, but not a database match
    - 0.5-0.6: reasonable guess based on partial naming patterns
@@ -46,10 +48,10 @@ Return a structured JSON response with:
 
    Do not lower third_party_confidence just because the artifact is a browser-extension key, localStorage entry, or otherwise not a classic web tracker. The goal is to attribute the vendor, not to judge how "tracker-worthy" the artifact is — if the name unambiguously names its source, attribute it with high confidence.
 
-7. If you truly cannot identify who set the tracker, set third_party_name to an empty string and third_party_confidence below 0.3.
+8. If you truly cannot identify who set the tracker, set third_party_name to an empty string and third_party_confidence below 0.3.
 
-8. Only attribute a tracker to a company or service when you have concrete evidence: an exact (perfect) match on the pattern in the database, an unmistakable naming convention where the tracker's meaningful prefix belongs to that vendor (including a vendor name embedded in the key), or a clear web search result whose tracker name shares that meaningful prefix. Absent a shared meaningful prefix or a perfect pattern match, do NOT imagine a vendor — never guess or invent attributions based on vague similarity, a shared generic word, or general knowledge. If no evidence supports a match, return an empty third_party_name with third_party_confidence below 0.3.
+9. Only attribute a tracker to a company or service when you have concrete evidence: an exact (perfect) match on the pattern in the database, an unmistakable naming convention where the tracker's meaningful prefix belongs to that vendor (including a vendor name embedded in the key), or a clear web search result whose tracker name shares that meaningful prefix. Absent a shared meaningful prefix or a perfect pattern match, do NOT imagine a vendor — never guess or invent attributions based on vague similarity, a shared generic word, or general knowledge. If no evidence supports a match, return an empty third_party_name with third_party_confidence below 0.3.
 
-9. For the category field, use one of: {{.Categories}}.
+10. For the category field, use one of: {{.Categories}}.
    Most cookies fall under ANALYTICS or MARKETING.
 </instructions>

pkg/cookiebanner/tracker_mapping_agent.go

@@ -171,9 +171,13 @@ func buildTrackerIdentificationPrompt(
 	)
 }
 
-func buildAgentPrompt(tp coredata.TrackerPattern, domains []string) string {
+func buildAgentPrompt(tp coredata.TrackerPattern, domains []string, siteDomain string) string {
 	prompt := buildTrackerIdentificationPrompt(tp.Pattern, tp.TrackerType, tp.MatchType, tp.MaxAgeSeconds)
 
+	if siteDomain != "" {
+		prompt += fmt.Sprintf("<scanned_site> %s </scanned_site>\n", siteDomain)
+	}
+
 	if len(domains) > 0 {
 		prompt += fmt.Sprintf("<observed_domains> %s </observed_domains>\n", strings.Join(domains, ", "))
 	}

pkg/cookiebanner/tracker_mapping_agent_test.go

@@ -0,0 +1,161 @@
+// Copyright (c) 2026 Probo Inc <hello@probo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package cookiebanner
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"go.probo.inc/probo/pkg/coredata"
+)
+
+func TestNameMatchesSiteDomain(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name       string
+		vendorName string
+		siteOrigin string
+		expected   bool
+	}{
+		{
+			name:       "site brand matches own domain",
+			vendorName: "Letaido",
+			siteOrigin: "https://letaido.com",
+			expected:   true,
+		},
+		{
+			name:       "case and spacing insensitive",
+			vendorName: "  LET AIDO ",
+			siteOrigin: "https://letaido.com",
+			expected:   true,
+		},
+		{
+			name:       "matches against subdomain origin",
+			vendorName: "Letaido",
+			siteOrigin: "https://app.letaido.com",
+			expected:   true,
+		},
+		{
+			name:       "matches full domain form",
+			vendorName: "letaido.com",
+			siteOrigin: "https://letaido.com",
+			expected:   true,
+		},
+		{
+			name:       "unrelated vendor is not the site",
+			vendorName: "Google Analytics",
+			siteOrigin: "https://letaido.com",
+			expected:   false,
+		},
+		{
+			name:       "empty vendor name",
+			vendorName: "",
+			siteOrigin: "https://letaido.com",
+			expected:   false,
+		},
+		{
+			name:       "empty origin",
+			vendorName: "Letaido",
+			siteOrigin: "",
+			expected:   false,
+		},
+		{
+			name:       "unparseable origin",
+			vendorName: "Letaido",
+			siteOrigin: "not a url",
+			expected:   false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(
+			tt.name,
+			func(t *testing.T) {
+				t.Parallel()
+				assert.Equal(t, tt.expected, nameMatchesSiteDomain(tt.vendorName, tt.siteOrigin))
+			},
+		)
+	}
+}
+
+func TestNormalizeAlnum(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{name: "letters lowercased", input: "Letaido", expected: "letaido"},
+		{name: "strips punctuation and spaces", input: "letaido.com - Inc", expected: "letaidocominc"},
+		{name: "keeps digits", input: "auth0", expected: "auth0"},
+		{name: "empty", input: "", expected: ""},
+		{name: "only punctuation", input: "-_.:", expected: ""},
+	}
+
+	for _, tt := range tests {
+		t.Run(
+			tt.name,
+			func(t *testing.T) {
+				t.Parallel()
+				assert.Equal(t, tt.expected, normalizeAlnum(tt.input))
+			},
+		)
+	}
+}
+
+func TestBuildAgentPrompt(t *testing.T) {
+	t.Parallel()
+
+	tp := coredata.TrackerPattern{
+		Pattern:     "ethereum-https://letaido.com",
+		TrackerType: coredata.TrackerTypeLocalStorage,
+		MatchType:   coredata.TrackerPatternMatchTypeExact,
+	}
+
+	t.Run(
+		"emits scanned_site when domain supplied",
+		func(t *testing.T) {
+			t.Parallel()
+
+			prompt := buildAgentPrompt(tp, nil, "letaido.com")
+			assert.Contains(t, prompt, "<scanned_site> letaido.com </scanned_site>")
+		},
+	)
+
+	t.Run(
+		"omits scanned_site when domain empty",
+		func(t *testing.T) {
+			t.Parallel()
+
+			prompt := buildAgentPrompt(tp, nil, "")
+			assert.NotContains(t, prompt, "<scanned_site>")
+		},
+	)
+
+	t.Run(
+		"emits both scanned_site and observed_domains",
+		func(t *testing.T) {
+			t.Parallel()
+
+			prompt := buildAgentPrompt(tp, []string{"doubleclick.net"}, "letaido.com")
+			assert.Contains(t, prompt, "<scanned_site> letaido.com </scanned_site>")
+			assert.Contains(t, prompt, "<observed_domains> doubleclick.net </observed_domains>")
+			assert.Less(t, strings.Index(prompt, "<scanned_site>"), strings.Index(prompt, "<observed_domains>"))
+		},
+	)
+}

pkg/cookiebanner/tracker_mapping_worker.go

@@ -18,6 +18,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"strings"
 	"time"
 
 	"go.gearno.de/kit/log"
@@ -637,7 +638,9 @@ func (h *trackerMappingHandler) identifyWithAgent(
 
 	domains = uri.FilterFirstPartyDomains(domains, siteOrigin)
 
-	prompt := buildAgentPrompt(tp, domains)
+	siteDomain := uri.ExtractDomain(siteOrigin)
+
+	prompt := buildAgentPrompt(tp, domains, siteDomain)
 
 	agentCtx, cancel := context.WithTimeout(ctx, h.agentTimeout)
 	defer cancel()
@@ -680,11 +683,67 @@ func (h *trackerMappingHandler) identifyWithAgent(
 		return nil, nil
 	}
 
+	// Backstop for the prompt rule that the scanned site is never a third
+	// party of itself: a pattern that embeds the site's own domain (e.g.
+	// an "ethereum-https://example.com" wallet-extension key, or an
+	// owner-set tracker) can lead the agent to attribute the site's own
+	// brand. Discard such attributions outright so the pattern falls
+	// through to the unmatched fallback instead of being mapped to the
+	// site owner.
+	if nameMatchesSiteDomain(identification.ThirdPartyName, siteOrigin) {
+		h.logger.InfoCtx(
+			ctx,
+			"agent attributed scanned site as third party, discarding",
+			log.String("pattern", tp.Pattern),
+		)
+
+		return nil, nil
+	}
+
 	return &agentIdentification{
 		result: identification,
 	}, nil
 }
 
+// nameMatchesSiteDomain reports whether a candidate vendor name refers to
+// the scanned site itself. The site owner is never a third party of its
+// own site, so an attribution whose name resolves to the site's own
+// domain must be rejected. The comparison is alphanumeric-normalised and
+// conservative (equality against the eTLD+1 and its primary label) to
+// avoid suppressing unrelated vendors whose name merely overlaps.
+func nameMatchesSiteDomain(name, siteOrigin string) bool {
+	domain := uri.ExtractDomain(siteOrigin)
+	if domain == "" {
+		return false
+	}
+
+	normalizedName := normalizeAlnum(name)
+	if normalizedName == "" {
+		return false
+	}
+
+	label, _, _ := strings.Cut(domain, ".")
+
+	return normalizedName == normalizeAlnum(domain) ||
+		normalizedName == normalizeAlnum(label)
+}
+
+// normalizeAlnum lowercases s and keeps only ASCII letters and digits,
+// so vendor names and domains can be compared free of spacing,
+// punctuation, and casing differences (e.g. "Letaido" and "letaido.com"
+// both reduce to a comparable form).
+func normalizeAlnum(s string) string {
+	var b strings.Builder
+
+	for _, r := range strings.ToLower(s) {
+		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') {
+			b.WriteRune(r)
+		}
+	}
+
+	return b.String()
+}
+
 // persistAgentIdentification writes a confident agent identification:
 // it resolves or creates the catalog third party and upserts the
 // catalog pattern row that links to it. It runs inside the caller's