feat(tools): tenant-aware web_fetch domain policy resolution

web_fetch now reads per-tenant policy overrides from
BuiltinToolSettingsFromCtx before falling back to the tool's
default policy. Same per-call resolution pattern as web_search.

- Add resolvePolicy(ctx) with webFetchPolicyOverride struct
- Refactor Execute + doFetch + fetchRawContent to use webFetchPolicy
- InProcessExtractor also resolves policy from ctx
- Remove isDomainAllowed/isDomainBlocked (replaced by matchDomainList)
- 6 new unit tests for tenant policy override scenarios

internal/tools/web_fetch.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"crypto/rand"
 	"encoding/hex"
+	"encoding/json"
 	"fmt"
 	"io"
 	"log/slog"
@@ -79,6 +80,49 @@ func (t *WebFetchTool) UpdatePolicy(policy string, allowed, blocked []string) {
 	slog.Info("web_fetch policy updated", "policy", policy, "allowed", len(allowed), "blocked", len(blocked))
 }
 
+// webFetchPolicy holds the resolved domain policy for a single request.
+type webFetchPolicy struct {
+	mode           string   // "allow_all" | "allowlist"
+	allowedDomains []string
+	blockedDomains []string
+}
+
+// webFetchPolicyOverride is the tenant settings shape for web_fetch
+// (stored in builtin_tool_tenant_configs.settings).
+type webFetchPolicyOverride struct {
+	Policy         string   `json:"policy,omitempty"`
+	AllowedDomains []string `json:"allowed_domains,omitempty"`
+	BlockedDomains []string `json:"blocked_domains,omitempty"`
+}
+
+// resolvePolicy returns the effective domain policy for this request.
+// Checks tenant override via BuiltinToolSettingsFromCtx first; falls back
+// to the tool's default policy when no override is present.
+func (t *WebFetchTool) resolvePolicy(ctx context.Context) webFetchPolicy {
+	if settings := BuiltinToolSettingsFromCtx(ctx); settings != nil {
+		if raw, ok := settings["web_fetch"]; ok && len(raw) > 0 {
+			var override webFetchPolicyOverride
+			if err := json.Unmarshal(raw, &override); err != nil {
+				slog.Warn("web_fetch: failed to parse tenant override, using defaults", "error", err)
+			} else if override.Policy != "" {
+				return webFetchPolicy{
+					mode:           override.Policy,
+					allowedDomains: override.AllowedDomains,
+					blockedDomains: override.BlockedDomains,
+				}
+			}
+		}
+	}
+	// Fall back to tool defaults
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+	return webFetchPolicy{
+		mode:           t.policy,
+		allowedDomains: t.allowedDomains,
+		blockedDomains: t.blockedDomains,
+	}
+}
+
 // matchDomainList checks if a hostname matches any pattern in the list.
 // Supports exact match ("github.com") and wildcard prefix ("*.example.com").
 func matchDomainList(hostname string, patterns []string) bool {
@@ -99,22 +143,6 @@ func matchDomainList(hostname string, patterns []string) bool {
 	return false
 }
 
-// isDomainAllowed checks if a hostname matches the allowlist.
-func (t *WebFetchTool) isDomainAllowed(hostname string) bool {
-	t.mu.RLock()
-	domains := t.allowedDomains
-	t.mu.RUnlock()
-	return matchDomainList(hostname, domains)
-}
-
-// isDomainBlocked checks if a hostname matches the blocklist.
-func (t *WebFetchTool) isDomainBlocked(hostname string) bool {
-	t.mu.RLock()
-	domains := t.blockedDomains
-	t.mu.RUnlock()
-	return matchDomainList(hostname, domains)
-}
-
 func (t *WebFetchTool) Name() string { return "web_fetch" }
 
 func (t *WebFetchTool) Description() string {
@@ -167,18 +195,17 @@ func (t *WebFetchTool) Execute(ctx context.Context, args map[string]any) *Result
 		return ErrorResult(fmt.Sprintf("SSRF protection: %v", err))
 	}
 
+	// Resolve domain policy (tenant override via ctx, or tool defaults)
+	pol := t.resolvePolicy(ctx)
 	hostname := parsed.Hostname()
 
 	// Domain blocklist check (always enforced regardless of policy)
-	if t.isDomainBlocked(hostname) {
+	if matchDomainList(hostname, pol.blockedDomains) {
 		return ErrorResult(fmt.Sprintf("domain %q is blocked by policy", hostname))
 	}
 
 	// Domain allowlist check
-	t.mu.RLock()
-	policy := t.policy
-	t.mu.RUnlock()
-	if policy == "allowlist" && !t.isDomainAllowed(hostname) {
+	if pol.mode == "allowlist" && !matchDomainList(hostname, pol.allowedDomains) {
 		return ErrorResult(fmt.Sprintf("domain %q is not in the allowed domains list", hostname))
 	}
 
@@ -212,7 +239,7 @@ func (t *WebFetchTool) Execute(ctx context.Context, args map[string]any) *Result
 	}
 
 	// Fetch
-	result, err := t.doFetch(ctx, rawURL, extractMode, maxChars, policy)
+	result, err := t.doFetch(ctx, rawURL, extractMode, maxChars, pol)
 	if err != nil {
 		errMsg := truncateStr(err.Error(), defaultErrorMaxChars)
 		return ErrorResult(fmt.Sprintf("fetch failed: %s", errMsg))
@@ -223,7 +250,7 @@ func (t *WebFetchTool) Execute(ctx context.Context, args map[string]any) *Result
 	return NewResult(wrapped)
 }
 
-func (t *WebFetchTool) doFetch(ctx context.Context, rawURL, extractMode string, maxChars int, policy string) (string, error) {
+func (t *WebFetchTool) doFetch(ctx context.Context, rawURL, extractMode string, maxChars int, pol webFetchPolicy) (string, error) {
 	// For markdown mode, use the extractor chain (Defuddle → InProcess waterfall)
 	// resolved from builtin_tools settings stored in context.
 	// InProcessExtractor delegates to fetchRawContent (same path as doDirectFetch),
@@ -240,7 +267,7 @@ func (t *WebFetchTool) doFetch(ctx context.Context, rawURL, extractMode string,
 	}
 
 	// Text mode or no chain available — use direct HTTP fetch.
-	return t.doDirectFetch(ctx, rawURL, extractMode, maxChars, policy)
+	return t.doDirectFetch(ctx, rawURL, extractMode, maxChars, pol)
 }
 
 // fetchRawResult holds the output from fetchRawContent.
@@ -254,7 +281,7 @@ type fetchRawResult struct {
 // fetchRawContent performs HTTP GET with full security checks (SSRF, domain policy on
 // redirects) and routes content by type. Returns raw extracted content without formatting.
 // Used by both doDirectFetch (text mode) and InProcessExtractor (chain fallback).
-func (t *WebFetchTool) fetchRawContent(ctx context.Context, rawURL, extractMode string, maxChars int, policy string) (fetchRawResult, error) {
+func (t *WebFetchTool) fetchRawContent(ctx context.Context, rawURL, extractMode string, maxChars int, pol webFetchPolicy) (fetchRawResult, error) {
 	req, err := http.NewRequestWithContext(ctx, "GET", rawURL, nil)
 	if err != nil {
 		return fetchRawResult{}, fmt.Errorf("create request: %w", err)
@@ -280,10 +307,10 @@ func (t *WebFetchTool) fetchRawContent(ctx context.Context, rawURL, extractMode
 				return fmt.Errorf("redirect SSRF protection: %w", err)
 			}
 			redirectHost := req.URL.Hostname()
-			if t.isDomainBlocked(redirectHost) {
+			if matchDomainList(redirectHost, pol.blockedDomains) {
 				return fmt.Errorf("redirect to %q blocked: domain is in blocklist", redirectHost)
 			}
-			if policy == "allowlist" && !t.isDomainAllowed(redirectHost) {
+			if pol.mode == "allowlist" && !matchDomainList(redirectHost, pol.allowedDomains) {
 				return fmt.Errorf("redirect to %q blocked: domain not in allowlist", redirectHost)
 			}
 			return nil
@@ -348,8 +375,8 @@ func (t *WebFetchTool) fetchRawContent(ctx context.Context, rawURL, extractMode
 
 // doDirectFetch wraps fetchRawContent with full HTTP metadata formatting.
 // Used for text mode extraction and as ultimate fallback.
-func (t *WebFetchTool) doDirectFetch(ctx context.Context, rawURL, extractMode string, maxChars int, policy string) (string, error) {
-	raw, err := t.fetchRawContent(ctx, rawURL, extractMode, maxChars, policy)
+func (t *WebFetchTool) doDirectFetch(ctx context.Context, rawURL, extractMode string, maxChars int, pol webFetchPolicy) (string, error) {
+	raw, err := t.fetchRawContent(ctx, rawURL, extractMode, maxChars, pol)
 	if err != nil {
 		return "", err
 	}

internal/tools/web_fetch_extractor_inprocess.go

@@ -16,11 +16,8 @@ func (e *InProcessExtractor) Name() string { return "html-to-markdown" }
 // Extract fetches the URL via the tool's fetchRawContent (full security checks)
 // and returns the raw extracted markdown content.
 func (e *InProcessExtractor) Extract(ctx context.Context, rawURL string) (string, error) {
-	e.tool.mu.RLock()
-	policy := e.tool.policy
-	e.tool.mu.RUnlock()
-
-	raw, err := e.tool.fetchRawContent(ctx, rawURL, "markdown", defaultFetchMaxChars, policy)
+	pol := e.tool.resolvePolicy(ctx)
+	raw, err := e.tool.fetchRawContent(ctx, rawURL, "markdown", defaultFetchMaxChars, pol)
 	if err != nil {
 		return "", err
 	}

internal/tools/web_fetch_policy_test.go

@@ -0,0 +1,128 @@
+package tools
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+)
+
+// ctxWithWebFetchSettings returns a ctx with builtin tool settings containing
+// the given web_fetch policy override.
+func ctxWithWebFetchSettings(t *testing.T, override webFetchPolicyOverride) context.Context {
+	t.Helper()
+	raw, err := json.Marshal(override)
+	if err != nil {
+		t.Fatal(err)
+	}
+	settings := BuiltinToolSettings{"web_fetch": raw}
+	return WithBuiltinToolSettings(context.Background(), settings)
+}
+
+func TestResolvePolicy_NoOverride_ReturnsDefaults(t *testing.T) {
+	tool := NewWebFetchTool(WebFetchConfig{
+		Policy:         "allow_all",
+		AllowedDomains: []string{"default.com"},
+		BlockedDomains: []string{"blocked.com"},
+	})
+
+	pol := tool.resolvePolicy(context.Background())
+	if pol.mode != "allow_all" {
+		t.Errorf("mode = %q, want allow_all", pol.mode)
+	}
+	if len(pol.blockedDomains) != 1 || pol.blockedDomains[0] != "blocked.com" {
+		t.Errorf("blockedDomains = %v, want [blocked.com]", pol.blockedDomains)
+	}
+}
+
+func TestResolvePolicy_TenantAllowlist(t *testing.T) {
+	tool := NewWebFetchTool(WebFetchConfig{
+		Policy:         "allow_all",
+		AllowedDomains: []string{"default.com"},
+	})
+
+	ctx := ctxWithWebFetchSettings(t, webFetchPolicyOverride{
+		Policy:         "allowlist",
+		AllowedDomains: []string{"tenant-a.com", "*.api.tenant-a.com"},
+	})
+
+	pol := tool.resolvePolicy(ctx)
+	if pol.mode != "allowlist" {
+		t.Errorf("mode = %q, want allowlist", pol.mode)
+	}
+	if len(pol.allowedDomains) != 2 {
+		t.Errorf("allowedDomains = %v, want 2 entries", pol.allowedDomains)
+	}
+}
+
+func TestResolvePolicy_TenantBlocklist(t *testing.T) {
+	tool := NewWebFetchTool(WebFetchConfig{
+		Policy:         "allow_all",
+		BlockedDomains: []string{"global-blocked.com"},
+	})
+
+	ctx := ctxWithWebFetchSettings(t, webFetchPolicyOverride{
+		Policy:         "allow_all",
+		BlockedDomains: []string{"tenant-blocked.com"},
+	})
+
+	pol := tool.resolvePolicy(ctx)
+	// Tenant override replaces global blocked list
+	if len(pol.blockedDomains) != 1 || pol.blockedDomains[0] != "tenant-blocked.com" {
+		t.Errorf("blockedDomains = %v, want [tenant-blocked.com]", pol.blockedDomains)
+	}
+}
+
+func TestResolvePolicy_MalformedJSON_FallsBack(t *testing.T) {
+	tool := NewWebFetchTool(WebFetchConfig{
+		Policy: "allow_all",
+	})
+
+	settings := BuiltinToolSettings{
+		"web_fetch": []byte(`{not valid json}`),
+	}
+	ctx := WithBuiltinToolSettings(context.Background(), settings)
+
+	pol := tool.resolvePolicy(ctx)
+	if pol.mode != "allow_all" {
+		t.Errorf("mode = %q, want allow_all (fallback)", pol.mode)
+	}
+}
+
+func TestResolvePolicy_EmptyOverride_FallsBack(t *testing.T) {
+	tool := NewWebFetchTool(WebFetchConfig{
+		Policy:         "allowlist",
+		AllowedDomains: []string{"default.com"},
+	})
+
+	// Override exists but has empty policy — should fall back to defaults
+	ctx := ctxWithWebFetchSettings(t, webFetchPolicyOverride{})
+
+	pol := tool.resolvePolicy(ctx)
+	if pol.mode != "allowlist" {
+		t.Errorf("mode = %q, want allowlist (default)", pol.mode)
+	}
+	if len(pol.allowedDomains) != 1 || pol.allowedDomains[0] != "default.com" {
+		t.Errorf("allowedDomains = %v, want [default.com]", pol.allowedDomains)
+	}
+}
+
+func TestResolvePolicy_TenantOverridesGlobal(t *testing.T) {
+	tool := NewWebFetchTool(WebFetchConfig{
+		Policy:         "allowlist",
+		AllowedDomains: []string{"global.com"},
+		BlockedDomains: []string{"global-blocked.com"},
+	})
+
+	ctx := ctxWithWebFetchSettings(t, webFetchPolicyOverride{
+		Policy:         "allow_all",
+		BlockedDomains: []string{"tenant-evil.com"},
+	})
+
+	pol := tool.resolvePolicy(ctx)
+	if pol.mode != "allow_all" {
+		t.Errorf("mode = %q, want allow_all (tenant override)", pol.mode)
+	}
+	if len(pol.blockedDomains) != 1 || pol.blockedDomains[0] != "tenant-evil.com" {
+		t.Errorf("blockedDomains = %v, want [tenant-evil.com]", pol.blockedDomains)
+	}
+}