core: redact sensitive headers in the fetch log #1561

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1. cliffhall

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   v2Issues and PRs for v2Issues and PRs for v2

   on Jul 1, 2026
2. cliffhall

   added a parent issue on Jul 1, 2026

   • Tracking: re-implement PR #1510 (spec-conformant Apps host + programmatic review path) as scoped issues #1579
3. cliffhall

   self-assigned this

   on Jul 1, 2026
4. cliffhall

   linked a pull request that will close this issuefeat(core): redact sensitive headers in the fetch log #1585on Jul 1, 2026
5. cliffhall commented on Jul 2, 2026

   

   cliffhall

   on Jul 2, 2026

   MemberAuthor

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   Smoke test & AGENTS.md audit — PR #1585

   Checked out v2/1561-redact-headers (commit 38102706), npm install at root, and exercised the redaction two ways: (1) calling redactSensitiveHeaders directly with a mixed-casing header set, and (2) driving the real entry path through createFetchTracker with a fake fetch and capturing the recorded trackRequest entry. No Playwright — a throwaway tsx script printing real before/after output (included below).

   Smoke method

   • Direct: redactSensitiveHeaders({ Authorization, Cookie, Set-Cookie, Proxy-Authorization, X-Api-Key, x-mcp-remote-auth, Content-Type, X-Trace-Id }) with mixed casing.
   • Entry path: createFetchTracker(fakeFetch, { trackRequest }) → await tracked(url, { headers: { Authorization, x-mcp-remote-auth, Content-Type } }), response carrying Set-Cookie; then inspected the captured entry's requestHeaders / responseHeaders.

   Real output

   === Part A: redactSensitiveHeaders (mixed casing) ===
   REDACTED sentinel = "[REDACTED]"
   
   BEFORE (original object):
   {
     "Authorization": "Bearer super-secret-token",
     "Cookie": "session=abc123",
     "Set-Cookie": "session=abc123; HttpOnly",
     "Proxy-Authorization": "Basic zzz",
     "X-Api-Key": "sk-live-9999",
     "x-mcp-remote-auth": "Bearer inspector-backend-token",
     "Content-Type": "application/json",
     "X-Trace-Id": "trace-42"
   }
   
   AFTER (returned copy):
   {
     "Authorization": "[REDACTED]",
     "Cookie": "[REDACTED]",
     "Set-Cookie": "[REDACTED]",
     "Proxy-Authorization": "[REDACTED]",
     "X-Api-Key": "[REDACTED]",
     "x-mcp-remote-auth": "[REDACTED]",
     "Content-Type": "application/json",
     "X-Trace-Id": "trace-42"
   }
   
   Live/original object untouched? true
   Returned is a different object? true
   
     [OK] Authorization redacted (casing preserved: true)
     [OK] Cookie redacted (casing preserved: true)
     [OK] Set-Cookie redacted (casing preserved: true)
     [OK] Proxy-Authorization redacted (casing preserved: true)
     [OK] X-Api-Key redacted (casing preserved: true)
     [OK] x-mcp-remote-auth redacted (casing preserved: true)
     [OK] Content-Type preserved = "application/json"
     [OK] X-Trace-Id preserved = "trace-42"
   
   Case-insensitivity spot check:
     {"authorization":"[REDACTED]","AUTHORIZATION":"[REDACTED]","x-API-key":"[REDACTED]"}
   
   === Part B: createFetchTracker records a redacted entry ===
   Recorded request headers:
   {
     "authorization": "[REDACTED]",
     "content-type": "application/json",
     "x-mcp-remote-auth": "[REDACTED]"
   }
   Recorded response headers:
   {
     "content-type": "text/plain",
     "set-cookie": "[REDACTED]"
   }
   Entry-path redaction correct? true
   
   ALL SMOKE CHECKS PASSED ✅
   

   Confirmed: all six sensitive headers become [REDACTED] case-insensitively, benign headers and original key casing are preserved, the returned object is a distinct copy, and the live/original header object is untouched. The same holds through the real createFetchTracker entry path for both request and response headers.

   AGENTS.md compliance

   • Mantine: N/A — this is core/ (no React/UI surface in the diff).

   • TypeScript: No any, no @ts-ignore / @ts-expect-error / eslint-disable / v8 ignore anywhere in the diff. redactSensitiveHeaders is fully typed (Record<string, string> → Record<string, string>); SENSITIVE_HEADERS is a ReadonlySet<string>. (The two "any" matches in the diff are prose in the commit message / a code comment, not a type.)

   • Coverage (cd clients/web && npm run test:coverage, full unit + integration suite, 3242 tests passing) — core/mcp/fetchTracking.ts:

     Dimension	%	Covered/Total
     Statements	100	59/59
     Branches	100	33/33
     Functions	100	9/9
     Lines	100	57/57

     All four dimensions ≥ 90 (all at 100). Note: running the fetchTracking.test.ts file in isolation reports Functions 88.88% only because createFetchTracker / isLongLivedStreamResponse are additionally exercised by the transport & integration suites; the full-suite aggregate is 100%.

   Verdict

   ✅ PASS. Redaction works correctly and case-insensitively across all six sensitive headers, preserves casing and benign headers, does not mutate the live object, and the recorded entry is redacted through the real tracker path. Fully typed with no suppressions and 100% per-file coverage. No violations found. Recommend merge.

   Smoke test script (throwaway, not committed)

   // Smoke test for PR #1585 — redact sensitive headers in the fetch log (issue #1561)
   // Run: cd clients/web && npx tsx smoke-redact-1561.mts
   import {
     redactSensitiveHeaders,
     createFetchTracker,
     REDACTED_HEADER_VALUE,
   } from "../../core/mcp/fetchTracking.ts";
   import type { FetchRequestEntryBase } from "../../core/mcp/types.ts";
   
   const line = (s: string) => console.log(s);
   
   // ---- Part A: direct redactSensitiveHeaders with mixed casing ----
   const original: Record<string, string> = {
     Authorization: "Bearer super-secret-token",
     Cookie: "session=abc123",
     "Set-Cookie": "session=abc123; HttpOnly",
     "Proxy-Authorization": "Basic zzz",
     "X-Api-Key": "sk-live-9999",
     "x-mcp-remote-auth": "Bearer inspector-backend-token",
     "Content-Type": "application/json",
     "X-Trace-Id": "trace-42",
   };
   
   const snapshot = JSON.stringify(original);
   const redacted = redactSensitiveHeaders(original);
   
   line("=== Part A: redactSensitiveHeaders (mixed casing) ===");
   line("REDACTED sentinel = " + JSON.stringify(REDACTED_HEADER_VALUE));
   line("");
   line("BEFORE (original object):");
   line(JSON.stringify(original, null, 2));
   line("");
   line("AFTER (returned copy):");
   line(JSON.stringify(redacted, null, 2));
   line("");
   line("Live/original object untouched? " + (JSON.stringify(original) === snapshot));
   line("Returned is a different object? " + (redacted !== original));
   line("");
   
   const expectRedacted = [
     "Authorization", "Cookie", "Set-Cookie",
     "Proxy-Authorization", "X-Api-Key", "x-mcp-remote-auth",
   ];
   const expectKept = ["Content-Type", "X-Trace-Id"];
   let ok = true;
   for (const k of expectRedacted) {
     const pass = redacted[k] === REDACTED_HEADER_VALUE;
     ok &&= pass;
     line(`  [${pass ? "OK" : "FAIL"}] ${k} redacted (casing preserved: ${k in redacted})`);
   }
   for (const k of expectKept) {
     const pass = redacted[k] === original[k];
     ok &&= pass;
     line(`  [${pass ? "OK" : "FAIL"}] ${k} preserved = ${JSON.stringify(redacted[k])}`);
   }
   
   const caseCheck = redactSensitiveHeaders({
     authorization: "a", AUTHORIZATION: "b", "x-API-key": "c",
   });
   line("");
   line("Case-insensitivity spot check:");
   line("  " + JSON.stringify(caseCheck));
   ok &&=
     caseCheck.authorization === REDACTED_HEADER_VALUE &&
     caseCheck.AUTHORIZATION === REDACTED_HEADER_VALUE &&
     caseCheck["x-API-key"] === REDACTED_HEADER_VALUE;
   
   // ---- Part B: drive the fetch-tracker entry path end-to-end ----
   line("");
   line("=== Part B: createFetchTracker records a redacted entry ===");
   let captured: FetchRequestEntryBase | undefined;
   const fakeFetch: typeof fetch = async () =>
     new Response("pong", {
       status: 200,
       headers: { "Set-Cookie": "sess=leak-me; HttpOnly", "Content-Type": "text/plain" },
     });
   const tracked = createFetchTracker(fakeFetch, {
     trackRequest: (entry) => { captured = entry; },
   });
   
   await tracked("https://example.test/mcp", {
     method: "POST",
     headers: {
       Authorization: "Bearer LIVE-TOKEN-DO-NOT-LOG",
       "x-mcp-remote-auth": "Bearer BACKEND-TOKEN",
       "Content-Type": "application/json",
     },
   });
   
   line("Recorded request headers:");
   line(JSON.stringify(captured?.requestHeaders, null, 2));
   line("Recorded response headers:");
   line(JSON.stringify(captured?.responseHeaders, null, 2));
   
   const reqH = captured?.requestHeaders ?? {};
   const resH = captured?.responseHeaders ?? {};
   const bPass =
     reqH["authorization"] === REDACTED_HEADER_VALUE &&
     reqH["x-mcp-remote-auth"] === REDACTED_HEADER_VALUE &&
     reqH["content-type"] === "application/json" &&
     resH["set-cookie"] === REDACTED_HEADER_VALUE &&
     resH["content-type"] === "text/plain";
   line("Entry-path redaction correct? " + bPass);
   ok &&= bPass;
   
   line("");
   line(ok ? "ALL SMOKE CHECKS PASSED ✅" : "SMOKE CHECKS FAILED ❌");
   process.exit(ok ? 0 : 1);
6. cliffhall commented on Jul 2, 2026

   

   cliffhall

   on Jul 2, 2026

   MemberAuthor

   More actions

   🔗 Implemented by PR #1585. Its code is already integrated into the Wave 1 rollup branch 1579-wave-1 (see rollup PR #1601 / verification #1600). #1585 currently targets v2/main and will auto-show as Merged once the rollup lands in v2/main. The Development panel doesn't link it now because the closing keyword is on a non-default base branch.
7. cliffhall

   closed this as completedon Jul 9, 2026
8. pull

   added a commit that references this issue on Jul 28, 2026

   feat(core): redact sensitive headers in the fetch log (closes modelco…

   ...

   This issue will close once commit 3810270 is merged into the 'main' branch.

   3810270
9. cliffhall

   added this to the v2.0.0 milestone on Jul 28, 2026
10. cliffhall

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    authIssues and PRs related to authorizationIssues and PRs related to authorization

    on Aug 5, 2026