Problem

web_fetch unconditionally applied the SSRF block list including the RFC 2544 benchmark range (198.18.0.0/15). Clash/mihomo and similar proxy tools use this range for fake-ip mode: DNS queries return virtual IPs in 198.18.x.x that are transparently forwarded to the real destination by the kernel.

This made web_fetch completely unusable for users running a local proxy after the RFC 2544 check was added in 2026.2.22-2.

Furthermore, even though SsrFPolicy.allowRfc2544BenchmarkRange already existed and partial wiring was in web-fetch.ts, the ToolsWebFetchSchema Zod schema used .strict() without including ssrfPolicy — so the config field was silently rejected at validation time with:

Unrecognized key: "ssrfPolicy" at path tools.web.fetch

Additionally, readability and firecrawl sub-config were in the same situation: present in types.tools.ts and schema.help.ts but missing from ToolsWebFetchSchema, causing config validation failures.

Fixes #25215

Changes

• src/config/zod-schema.agent-runtime.ts — Add ssrfPolicy, readability, and firecrawl to ToolsWebFetchSchema (all three caused unrecognized-key errors due to .strict())
• src/agents/tools/web-fetch.ts — Wire ssrfPolicy.allowRfc2544BenchmarkRange through to fetchWithSsrFGuard
• src/config/types.tools.ts — TypeScript type for the new config field
• src/config/schema.help.ts — Help text for tools.web.fetch.ssrfPolicy and tools.web.fetch.ssrfPolicy.allowRfc2544BenchmarkRange
• src/config/schema.labels.ts — UI labels for the new ssrfPolicy fields
• src/agents/tools/web-fetch.ssrf.test.ts — Tests for RFC 2544 range allow/block behavior
• src/config/config.schema-regressions.test.ts — Config regression tests for ssrfPolicy, readability, and firecrawl

Config

Users running Clash/mihomo in fake-ip mode can now add to their config:

{
  "tools": {
    "web": {
      "fetch": {
        "ssrfPolicy": {
          "allowRfc2544BenchmarkRange": true
        }
      }
    }
  }
}

When enabled, the 198.18.0.0/15 range is permitted for web_fetch; all other SSRF protections (private IPs, loopback, cloud-metadata hostnames, etc.) remain active.

Greptile Summary

Added ssrfPolicy.allowRfc2544BenchmarkRange config option to fix web_fetch compatibility with Clash/mihomo proxy fake-ip mode, and fixed schema validation bugs that were silently rejecting ssrfPolicy, readability, and firecrawl config fields.

Key changes:

• Wired ssrfPolicy.allowRfc2544BenchmarkRange through from config to fetchWithSsrFGuard in web-fetch.ts:539
• Fixed ToolsWebFetchSchema missing fields (readability, ssrfPolicy, firecrawl) that caused silent rejection with .strict() validation
• Added comprehensive tests covering RFC 2544 range blocking and allowlist behavior
• Added config regression tests for all three previously-broken fields

Confidence Score: 5/5

• Safe to merge with no blocking issues found
• The implementation correctly wires the new config option through all layers (schema, types, implementation), includes comprehensive tests for all three config fields (ssrfPolicy, readability, firecrawl), and fixes a real schema validation bug where .strict() was silently rejecting valid user config. The security change is conservative (defaults to blocking, requires explicit opt-in), and all SSRF protections remain active when enabled.
• No files require special attention

_{Last reviewed commit: 41ab60b}