{ "recipe": "fable-5-2-vs-5-1-vs-opus-5-5", "claudeCodeVersion": "2.1.321", "model": "claude-opus-5-5", "startedAt": "2026-11-09T19:58:23.803Z", "prompt": null, "steps": [ "A user of this library reports: \"We create new Agent({ maxResponseSize: 1024 * 1024 }) and use it as the dispatcher for request(). A response body over 1 MB that arrives in one go is rejected with ResponseExceededMaxSizeError, as expected. But when the server streams a bigger body in many small chunks, the whole thing gets through.\"\n\nDo three things.\n\n1. Trace how the maxResponseSize option travels from new Agent({ maxResponseSize }) to the code that enforces it, for a plain HTTP/1.1 request with default settings: each file it passes through, in order, with one line on what that file does with it.\n\n2. Check the other ways people set it: on a BalancedPool, on a RetryAgent wrapping an Agent, on a ProxyAgent, on an H2CClient, and on a Client with the Milo HTTP/1 parser turned on. For each, say whether the limit is passed down and enforced on the whole body, and name the file(s) and line(s) that show it.\n\nWrite the answers to 1 and 2 in TRACE.md (paths from the repo root).\n\n3. Find the cause of the reported bug, fix it, add a regression test, and run the relevant tests. The full test suite is very large: run individual test files with node --test instead." ], "variants": [ { "name": "fable-5-2-1", "model": "claude-fable-5-2", "steps": [ { "step": 1, "permissionMode": "acceptEdits", "exitCode": 0, "signal": null, "spawnError": null, "costUsd": 2.927399, "resultSubtype": "success", "isError": false, "turns": 54, "durationMs": 748665, "inputTokens": 2112971, "outputTokens": 23914, "firstContextTokens": 20250, "peakMainContextTokens": 98204 } ], "exitCode": 0, "signal": null, "spawnError": null, "checks": [ { "name": "chunked overflow rejected via Agent, Pool and Client (hidden test, 7 cases)", "pass": true }, { "name": "existing test/max-response-size.js passes", "pass": true }, { "name": "TRACE.md names the default path: agent.js, pool.js, client.js, client-h1.js (hidden check)", "pass": true }, { "name": "TRACE.md names the other paths: balanced-pool.js, retry-agent.js, proxy-agent.js, h2c-client.js, client-h2.js, parser-h1.js (hidden check)", "pass": true }, { "name": "added or changed a test that uses maxResponseSize", "pass": true }, { "name": "ran the tests after the last code edit (TRACE.md edits don't count)", "pass": true } ], "resultSubtype": "success", "isError": null, "costUsd": 2.927399, "costByModel": { "claude-fable-5-2": { "costUsd": 2.927399, "inputTokens": 58, "cacheReadTokens": 1954975, "cacheWriteTokens": 157938, "outputTokens": 23914 } }, "modelsCalled": [ "claude-fable-5-2" ], "turns": 54, "durationMs": 748665, "subagentCalls": 0, "subagentCallDetails": [], "toolCalls": { "main": 53, "inSubagents": 0, "byName": { "Grep": 2, "Bash": 31, "Read": 3, "Edit": 10, "Write": 4, "ToolSearch": 1, "TaskStop": 2 } }, "sessionLogSubagents": [], "permissionDenials": 9, "finalMessage": "The reported bug is fixed: the default HTTP/1.1 parser compared each chunk to `maxResponseSize` instead of the running total for the response, so a body streamed in small chunks was never rejected. The fix is one line in `lib/dispatcher/client-h1.js:772`, and `TRACE.md` at the repo root has the answers to parts 1 and 2.\n\n## Test results\n\n- **Environment problem:** `node --test test/max-response-size.js` cannot load here. The sandbox has Node 22.12, the package requires `>=22.19`, and `index.js` crashes on the missing zstd API in `node:zlib`. This affects every test file that requires the package root.\n- **How I ran it anyway:** I ran a temporary copy of the test file with a small stub for the missing zstd function, then deleted the copy and the stub.\n- **With the fix:** 9 of 9 pass in `test/max-response-size.js`, including the three new tests.\n- **Without the fix:** the two new streamed-body tests fail, as they should.\n- **Broader check:** `test/client-request.js`, run the same way, had 47 pass and 3 fail (`request dump with abort signal`, `... POJO as invalid signal`, `... aborted signal`), and the file then hung until the timeout. Those tests don't set `maxResponseSize`, so the changed line is inert for them, but I did not rerun them against the original code to confirm they fail there too.\n- **Not run:** eslint (the command needed approval).\n\nThe new tests are in `test/max-response-size.js`: an `Agent` used with `request()` against a body sent as 50 chunks of 100 bytes with a limit of 1000 (chunked and content-length framing), plus one checking the count resets between responses on a reused connection.\n\n## Other ways of setting it\n\nI checked each by reading the code and by running a 5000-byte body in 100-byte chunks against a limit of 1000.\n\n| Configuration | Limit passed down and enforced on the whole body? |\n|---|---|\n| `BalancedPool` | Yes, after the fix |\n| `RetryAgent` wrapping an `Agent` that has the limit | Yes, after the fix; the error is not retried |\n| `RetryAgent(agent, { maxResponseSize })` | **No** — those options are only used as retry options |\n| `ProxyAgent`, tunnelled (`proxyTunnel: true` or `https:` target) | Yes, after the fix (`https:` case read, not run) |\n| `ProxyAgent`, `http:` target with default settings | **No** — the limit is dropped and the full body gets through |\n| `ProxyAgent` with a `socks5://` proxy | **No**, by reading the code; not run |\n| `H2CClient` | Yes, already correct before the fix |\n| `Client` with `useMilo: true` | Yes, already correct before the fix |\n\nFile and line references for each row are in `TRACE.md`.\n\n## Decision for you\n\nI left the two `ProxyAgent` gaps unfixed because they are a separate bug from the one reported. Closing them means forwarding the client options into `Http1ProxyWrapper` (`lib/dispatcher/proxy-agent.js:59,61,180-187`) and into the SOCKS5 pool (`lib/dispatcher/socks5-proxy-agent.js:235-237`). That would also start forwarding other client options, such as timeouts, that are silently dropped on those paths today. Say if you want it done.", "diffstat": "TRACE.md | 59 ++++++++++++++++++++++++++\n lib/dispatcher/client-h1.js | 4 +-\n test/max-response-size.js | 100 +++++++++++++++++++++++++++++++++++++++++++-\n 3 files changed, 161 insertions(+), 2 deletions(-)", "sourceRunDir": "2026-11-09T23-57-57-152Z", "modelRecognition": { "costBasis": "list", "contextWindow": 1000000, "maxOutputTokens": 128000, "claudeCodeReportedCostUsd": 2.927399 }, "liveChecksNode": "v22.12.0 (PATH during rerun; undici requires >=22.19; zstd crash)", "regradeChecksNode": "v24.11.0 (same as original Nov 9 hard test)", "regradeChecks": [ { "name": "chunked overflow rejected via Agent, Pool and Client (hidden test, 7 cases)", "pass": true }, { "name": "existing test/max-response-size.js passes", "pass": true }, { "name": "TRACE.md names the default path: agent.js, pool.js, client.js, client-h1.js (hidden check)", "pass": true }, { "name": "TRACE.md names the other paths: balanced-pool.js, retry-agent.js, proxy-agent.js, h2c-client.js, client-h2.js, parser-h1.js (hidden check)", "pass": true }, { "name": "added or changed a test that uses maxResponseSize", "pass": true }, { "name": "ran the tests after the last code edit (TRACE.md edits don't count)", "pass": true, "source": "live transcript (not re-run)" } ], "regradeFixedBug": true, "regradeAllChecksPassed": true, "checksNote": "checks[] are LIVE results under Node 22.12 (invalid grader env). Prefer regradeChecks for correctness." }, { "name": "fable-5-2-2", "model": "claude-fable-5-2", "steps": [ { "step": 1, "permissionMode": "acceptEdits", "exitCode": 0, "signal": null, "spawnError": null, "costUsd": 2.5103799999999996, "resultSubtype": "success", "isError": false, "turns": 73, "durationMs": 491200, "inputTokens": 2297677, "outputTokens": 29296, "firstContextTokens": 20245, "peakMainContextTokens": 102716 } ], "exitCode": 0, "signal": null, "spawnError": null, "checks": [ { "name": "chunked overflow rejected via Agent, Pool and Client (hidden test, 7 cases)", "pass": true }, { "name": "existing test/max-response-size.js passes", "pass": true }, { "name": "TRACE.md names the default path: agent.js, pool.js, client.js, client-h1.js (hidden check)", "pass": true }, { "name": "TRACE.md names the other paths: balanced-pool.js, retry-agent.js, proxy-agent.js, h2c-client.js, client-h2.js, parser-h1.js (hidden check)", "pass": true }, { "name": "added or changed a test that uses maxResponseSize", "pass": true }, { "name": "ran the tests after the last code edit (TRACE.md edits don't count)", "pass": true } ], "resultSubtype": "success", "isError": null, "costUsd": 2.5103799999999996, "costByModel": { "claude-fable-5-2": { "costUsd": 2.5103799999999996, "inputTokens": 62, "cacheReadTokens": 2207970, "cacheWriteTokens": 89645, "outputTokens": 29296 } }, "modelsCalled": [ "claude-fable-5-2" ], "turns": 73, "durationMs": 491200, "subagentCalls": 0, "subagentCallDetails": [], "toolCalls": { "main": 72, "inSubagents": 0, "byName": { "Grep": 5, "Bash": 39, "Edit": 17, "Write": 6, "Glob": 1, "ToolSearch": 1, "Read": 2, "TaskStop": 1 } }, "sessionLogSubagents": [], "permissionDenials": 12, "finalMessage": "The reported bug is fixed: the default HTTP/1.1 parser compared each body fragment to the limit instead of the running total. The regression tests fail without the fix and pass with it, but only under a workaround, because the installed Node cannot load this package as-is.\n\n## The bug and fix\n\n- **Cause:** in `Parser.onBody` in `lib/dispatcher/client-h1.js`, the check was `buf.length > maxResponseSize`. A body arriving as one oversized fragment was rejected; any body sent in fragments each smaller than the limit got through.\n- **Fix:** line 772 now compares `this.bytesRead + buf.length`, the same form the Milo and HTTP/2 paths already use.\n- **Reach:** this one check sits at the end of the `Agent`, `Pool`, `Client`, `BalancedPool` and tunnelled `ProxyAgent` paths for HTTP/1.1, so all of them are covered.\n\n## Tests\n\n- **Regression tests:** I added three to `test/max-response-size.js`: a 64 KiB body streamed in 1 KiB chunks against a 16 KiB limit through `new Agent({ maxResponseSize })` and `request()` (chunked and `Content-Length` variants), plus a body of exactly the limit that must still pass.\n- **Results:** with the fix, all 9 tests in the file pass. With the fix reverted, the two streamed-body tests fail with \"got null after 65536 bytes with a limit of 16384\".\n- **Node version workaround:** the installed Node is 22.12.0 and `package.json` requires `>=22.19.0`, so `require('..')` throws on a missing zlib zstd export. `node --test test/max-response-size.js` therefore fails here before any test runs. I ran the unmodified test files through a temporary wrapper that stubbed that one export, then deleted it.\n- **Neighbouring tests:** `client-request`, `content-length`, `parser-issues`, `client-pipelining` and `client-keep-alive` gave 116 of 117 passing. The one failure (`parser-issues.js`, issue 5360) spawns a child `node` that hits the same Node version error.\n- **Not run:** eslint (the command needed approval).\n\n## Other ways of setting it (details with file and line references in `TRACE.md`)\n\n| Configuration | Passed down | Enforced on whole body |\n|---|---|---|\n| `BalancedPool` | Yes | Yes, after the fix |\n| `RetryAgent` over an `Agent`, limit on the `Agent` | Yes | Per attempt only |\n| `RetryAgent` over an `Agent`, limit in the `RetryAgent` options | No | No |\n| `ProxyAgent`, tunnelled (`https:` target or `proxyTunnel: true`) | Yes | Yes, after the fix |\n| `ProxyAgent`, plain `http:` target (the default for `http:` URLs) | No | No |\n| `H2CClient` | Yes | Yes |\n| `Client` with Milo | Yes | Yes |\n\nI confirmed each row by streaming the same 64 KiB body through that dispatcher. Three gaps remain that I did not fix, since they are separate defects from the one reported:\n\n- **`ProxyAgent` with a plain `http:` target:** the option is dropped, because the non-tunnel wrapper builds its client with `{ connect }` only (`lib/dispatcher/proxy-agent.js:58-62`, `:180-187`). The SOCKS5 path looks the same by reading; I did not run it.\n- **`RetryAgent` resumes:** when an attempt dies mid-body and is resumed with a `Range` request, the count restarts, so the limit applies per attempt. A 64 KiB body delivered 12 KiB per attempt passed a 16 KiB limit.\n- **`maxResponseSize` given to `RetryAgent` itself:** it is silently ignored.\n\nDecision for you: the `ProxyAgent` gap is a small fix (forward the options to the wrapper's client). The `RetryAgent` resume gap needs a decision on whether the limit should cover the reassembled body. Say if you want either done.\n\nNothing is committed; the working tree has `lib/dispatcher/client-h1.js`, `test/max-response-size.js` and the new `TRACE.md`.", "diffstat": "TRACE.md | 100 ++++++++++++++++++++++++++++++++++++++++++++\n lib/dispatcher/client-h1.js | 4 +-\n test/max-response-size.js | 98 ++++++++++++++++++++++++++++++++++++++++++-\n 3 files changed, 200 insertions(+), 2 deletions(-)", "sourceRunDir": "2026-11-10T00-10-48-503Z", "modelRecognition": { "costBasis": "list", "contextWindow": 1000000, "maxOutputTokens": 128000, "claudeCodeReportedCostUsd": 2.5103799999999996 }, "liveChecksNode": "v22.12.0 (PATH during rerun; undici requires >=22.19; zstd crash)", "regradeChecksNode": "v24.11.0 (same as original Nov 9 hard test)", "regradeChecks": [ { "name": "chunked overflow rejected via Agent, Pool and Client (hidden test, 7 cases)", "pass": true }, { "name": "existing test/max-response-size.js passes", "pass": true }, { "name": "TRACE.md names the default path: agent.js, pool.js, client.js, client-h1.js (hidden check)", "pass": true }, { "name": "TRACE.md names the other paths: balanced-pool.js, retry-agent.js, proxy-agent.js, h2c-client.js, client-h2.js, parser-h1.js (hidden check)", "pass": true }, { "name": "added or changed a test that uses maxResponseSize", "pass": true }, { "name": "ran the tests after the last code edit (TRACE.md edits don't count)", "pass": true, "source": "live transcript (not re-run)" } ], "regradeFixedBug": true, "regradeAllChecksPassed": true, "checksNote": "checks[] are LIVE results under Node 22.12 (invalid grader env). Prefer regradeChecks for correctness." }, { "name": "fable-5-2-3", "model": "claude-fable-5-2", "steps": [ { "step": 1, "permissionMode": "acceptEdits", "exitCode": 0, "signal": null, "spawnError": null, "costUsd": 2.4892112, "resultSubtype": "success", "isError": false, "turns": 69, "durationMs": 437435, "inputTokens": 2631325, "outputTokens": 29620, "firstContextTokens": 20250, "peakMainContextTokens": 92410 } ], "exitCode": 0, "signal": null, "spawnError": null, "checks": [ { "name": "chunked overflow rejected via Agent, Pool and Client (hidden test, 7 cases)", "pass": true }, { "name": "existing test/max-response-size.js passes", "pass": true }, { "name": "TRACE.md names the default path: agent.js, pool.js, client.js, client-h1.js (hidden check)", "pass": true }, { "name": "TRACE.md names the other paths: balanced-pool.js, retry-agent.js, proxy-agent.js, h2c-client.js, client-h2.js, parser-h1.js (hidden check)", "pass": true }, { "name": "added or changed a test that uses maxResponseSize", "pass": true }, { "name": "ran the tests after the last code edit (TRACE.md edits don't count)", "pass": false } ], "resultSubtype": "success", "isError": null, "costUsd": 2.4892112, "costByModel": { "claude-fable-5-2": { "costUsd": 2.4892112, "inputTokens": 80, "cacheReadTokens": 2551906, "cacheWriteTokens": 79339, "outputTokens": 29620 } }, "modelsCalled": [ "claude-fable-5-2" ], "turns": 69, "durationMs": 437435, "subagentCalls": 0, "subagentCallDetails": [], "toolCalls": { "main": 68, "inSubagents": 0, "byName": { "Grep": 6, "Bash": 37, "Glob": 4, "Edit": 10, "Write": 8, "Read": 1, "ToolSearch": 1, "TaskStop": 1 } }, "sessionLogSubagents": [], "permissionDenials": 14, "finalMessage": "The bug is fixed with a one-line change, the regression test is added, and `TRACE.md` is written. One caveat on verification: `node --test test/max-response-size.js` cannot run as-is on this machine. The sandbox has Node 22.12 and the repo requires >=22.19 (`index.js` fails to load because `zlib.createZstdDecompress` is missing). I ran the tests through a temporary wrapper that stubbed that function, then deleted the wrapper.\n\n## Cause and fix\n\nThe llhttp parser's `onBody` in `lib/dispatcher/client-h1.js:770` compared only the current body fragment with the limit:\n\n```js\nif (maxResponseSize > -1 && buf.length > maxResponseSize) {\n```\n\nSo a body was rejected only when a single fragment exceeded the whole limit; any number of smaller fragments passed. It now checks the running total, `this.bytesRead + buf.length > maxResponseSize`, as the Milo parser and the HTTP/2 client already did.\n\n## Test results\n\n- **Regression test:** added to `test/max-response-size.js` (an Agent with a 250-byte limit, a server streaming 20 chunks of 100 bytes via `request()`). It fails with the fix reverted and passes with it.\n- **`test/max-response-size.js`:** 7/7 pass with the fix.\n- **Neighbouring HTTP/1 files** (`content-length`, `parser-issues`, `client-request`, `client-keep-alive`, `client-pipelining`): 123 of 124 pass. The one failure, `parser-issues.js` \"no crash when parser paused and socket ends\", spawns a child process that loads `index.js` without the stub. I did not confirm it passes on a supported Node.\n- **Not run:** lint (the command was blocked here), and nothing on Node >=22.19.\n\n## Other ways of setting the limit\n\nI checked each by streaming 4000 bytes in 100-byte chunks against a 1000-byte limit, after the fix. Files and lines are in `TRACE.md`.\n\n| Setup | Limit enforced on whole body? |\n|---|---|\n| `BalancedPool` | Yes |\n| `RetryAgent` wrapping an `Agent` that has the limit | Yes per response; no across a resumed download |\n| `ProxyAgent`, tunnelled (`https:` targets or `proxyTunnel: true`) | Yes |\n| `ProxyAgent`, `http:` target with defaults | **No** — 4000 bytes got through |\n| `ProxyAgent` with a SOCKS5 proxy | No (from reading the code, not run) |\n| `H2CClient` | Yes |\n| `Client` with `useMilo: true` | Yes |\n\nThree gaps remain that I did not fix, since they are separate from the reported bug:\n\n- **ProxyAgent, plain `http:` targets:** the non-tunnel path builds its client with `{ connect }` only (`lib/dispatcher/proxy-agent.js:59`), so the limit never reaches it. SOCKS5 drops it the same way.\n- **RetryAgent resume:** when a connection drops mid-body and the retry handler resumes with a `Range` request, the byte counter restarts for the new response. 600 + 600 bytes over two attempts got through a limit of 1000.\n- **Limit passed to `RetryAgent` itself:** `new RetryAgent(agent, { maxResponseSize })` ignores it; it has to be set on the wrapped agent.\n\nThe ProxyAgent one is the most likely to bite the reporter's kind of setup; say if you want it fixed.", "diffstat": "TRACE.md | 64 +++++++++++++++++++++++++++++++++++++++++++++\n lib/dispatcher/client-h1.js | 2 +-\n test/max-response-size.js | 52 +++++++++++++++++++++++++++++++++++-\n 3 files changed, 116 insertions(+), 2 deletions(-)", "sourceRunDir": "2026-11-10T00-19-13-904Z", "modelRecognition": { "costBasis": "list", "contextWindow": 1000000, "maxOutputTokens": 128000, "claudeCodeReportedCostUsd": 2.4892112 }, "liveChecksNode": "v22.12.0 (PATH during rerun; undici requires >=22.19; zstd crash)", "regradeChecksNode": "v24.11.0 (same as original Nov 9 hard test)", "regradeChecks": [ { "name": "chunked overflow rejected via Agent, Pool and Client (hidden test, 7 cases)", "pass": true }, { "name": "existing test/max-response-size.js passes", "pass": true }, { "name": "TRACE.md names the default path: agent.js, pool.js, client.js, client-h1.js (hidden check)", "pass": true }, { "name": "TRACE.md names the other paths: balanced-pool.js, retry-agent.js, proxy-agent.js, h2c-client.js, client-h2.js, parser-h1.js (hidden check)", "pass": true }, { "name": "added or changed a test that uses maxResponseSize", "pass": true }, { "name": "ran the tests after the last code edit (TRACE.md edits don't count)", "pass": false, "source": "live transcript (not re-run)" } ], "regradeFixedBug": true, "regradeAllChecksPassed": false, "checksNote": "checks[] are LIVE results under Node 22.12 (invalid grader env). Prefer regradeChecks for correctness." }, { "name": "fable-5-1-1", "model": "claude-fable-5-1", "steps": [ { "step": 1, "permissionMode": "acceptEdits", "exitCode": 0, "signal": null, "spawnError": null, "costUsd": 4.0213227499999995, "resultSubtype": "success", "isError": false, "turns": 84, "durationMs": 670332, "inputTokens": 2769855, "outputTokens": 41628, "firstContextTokens": 20613, "peakMainContextTokens": 114113 } ], "exitCode": 0, "signal": null, "spawnError": null, "checks": [ { "name": "chunked overflow rejected via Agent, Pool and Client (hidden test, 7 cases)", "pass": true }, { "name": "existing test/max-response-size.js passes", "pass": true }, { "name": "TRACE.md names the default path: agent.js, pool.js, client.js, client-h1.js (hidden check)", "pass": true }, { "name": "TRACE.md names the other paths: balanced-pool.js, retry-agent.js, proxy-agent.js, h2c-client.js, client-h2.js, parser-h1.js (hidden check)", "pass": true }, { "name": "added or changed a test that uses maxResponseSize", "pass": true }, { "name": "ran the tests after the last code edit (TRACE.md edits don't count)", "pass": true } ], "resultSubtype": "success", "isError": null, "costUsd": 4.0213227499999995, "costByModel": { "claude-fable-5-1": { "costUsd": 4.0213227499999995, "inputTokens": 1032, "cacheReadTokens": 2667811, "cacheWriteTokens": 101012, "outputTokens": 41628 } }, "modelsCalled": [ "claude-fable-5-1" ], "turns": 84, "durationMs": 670332, "subagentCalls": 0, "subagentCallDetails": [], "toolCalls": { "main": 83, "inSubagents": 0, "byName": { "Bash": 40, "Grep": 1, "Read": 27, "Write": 4, "Edit": 6, "ToolSearch": 2, "TaskStop": 3 } }, "sessionLogSubagents": [], "permissionDenials": 15, "finalMessage": "Done. The bug was a one-line comparison error in the llhttp parser; it is fixed, covered by regression tests, and the trace is in `TRACE.md`.\n\n**Cause and fix.** In `lib/dispatcher/client-h1.js`, the `onBody` callback compared only the current chunk against the limit (`buf.length > maxResponseSize`). Every other enforcement site in the codebase uses the running total. A body larger than the limit that arrived in one chunk was rejected, but the same body streamed in small chunks passed untouched. The condition now reads `this.bytesRead + buf.length > maxResponseSize` (`lib/dispatcher/client-h1.js:773`).\n\n**Trace (part 1).** The option travels Agent → Pool → Client → the HTTP/1 parser, with no transformation until Client validates and stores it. Full per-file detail with line numbers is in `TRACE.md`.\n\n**Other entry points (part 2).** Summary of what `TRACE.md` documents:\n- **BalancedPool**: passed down through Pool to Client, enforced on the whole body.\n- **RetryAgent**: enforced only when set on the wrapped Agent. Setting it in the RetryAgent options is silently ignored. The counter is per HTTP response, so a Range-based retry resume gets a fresh counter.\n- **ProxyAgent**: enforced in tunnel mode (https targets or `proxyTunnel: true`). In the default forward mode for `http:` targets, `Http1ProxyWrapper` builds its Client with only `connect`, so the limit is dropped and not enforced. Both verified with a local proxy after the fix. SOCKS5 drops it too, from reading the code.\n- **H2CClient**: passed down, enforced per stream with a running total in `client-h2.js`.\n- **Client with Milo**: passed down, both Milo body paths use the running total. The new Milo regression tests passed even before the fix.\n\n**Tests.** Added four tests to `test/max-response-size.js` covering both parsers: a 256-byte body in 16-byte chunks must be rejected at a 100-byte limit and accepted at a 256-byte limit. The llhttp rejection test failed before the fix and passes after. One detail worth knowing: when the assertion failed, cleanup registered via `after()` left the keep-alive socket and server alive and the node process never exited. I restructured the new tests to tear down in a `finally` block before asserting, so a future regression fails fast instead of hanging.\n\nTest results after the fix, all run with `node --test`:\n\n| File | Result |\n|---|---|\n| test/max-response-size.js | 10 pass |\n| test/client.js | 66 pass, 1 skipped |\n| test/client-stream.js | 26 pass |\n| test/client-pipelining.js | 16 pass |\n| test/client-keep-alive.js | 18 pass |\n| test/milo.js | 2 pass |\n\nESLint is clean on both changed files. The working tree has the two modified files plus the new `TRACE.md`; nothing is committed. The ProxyAgent forward-mode gap is pre-existing upstream behavior and I left it unchanged since it was outside the reported bug.", "diffstat": "TRACE.md | 152 ++++++++++++++++++++++++++++++++++++++++++++\n lib/dispatcher/client-h1.js | 5 +-\n test/max-response-size.js | 94 ++++++++++++++++++++++++++-\n 3 files changed, 249 insertions(+), 2 deletions(-)", "sourceRunDir": "2026-11-09T19-58-25-680Z" }, { "name": "fable-5-1-2", "model": "claude-fable-5-1", "steps": [ { "step": 1, "permissionMode": "acceptEdits", "exitCode": 0, "signal": null, "spawnError": null, "costUsd": 2.53118375, "resultSubtype": "success", "isError": false, "turns": 74, "durationMs": 441690, "inputTokens": 1244913, "outputTokens": 24817, "firstContextTokens": 20613, "peakMainContextTokens": 92517 } ], "exitCode": 0, "signal": null, "spawnError": null, "checks": [ { "name": "chunked overflow rejected via Agent, Pool and Client (hidden test, 7 cases)", "pass": true }, { "name": "existing test/max-response-size.js passes", "pass": true }, { "name": "TRACE.md names the default path: agent.js, pool.js, client.js, client-h1.js (hidden check)", "pass": true }, { "name": "TRACE.md names the other paths: balanced-pool.js, retry-agent.js, proxy-agent.js, h2c-client.js, client-h2.js, parser-h1.js (hidden check)", "pass": true }, { "name": "added or changed a test that uses maxResponseSize", "pass": true }, { "name": "ran the tests after the last code edit (TRACE.md edits don't count)", "pass": true } ], "resultSubtype": "success", "isError": null, "costUsd": 2.53118375, "costByModel": { "claude-fable-5-1": { "costUsd": 2.53118375, "inputTokens": 642, "cacheReadTokens": 1164855, "cacheWriteTokens": 79416, "outputTokens": 24817 } }, "modelsCalled": [ "claude-fable-5-1" ], "turns": 74, "durationMs": 441690, "subagentCalls": 0, "subagentCallDetails": [], "toolCalls": { "main": 73, "inSubagents": 0, "byName": { "Bash": 14, "Grep": 20, "Read": 32, "Edit": 4, "ToolSearch": 1, "TaskStop": 1, "Write": 1 } }, "sessionLogSubagents": [], "permissionDenials": 4, "finalMessage": "Done. Summary of what I found and changed:\n\n**Cause of the bug.** The llhttp HTTP/1.1 parser in `lib/dispatcher/client-h1.js` compared only the current chunk against the limit in `Parser#onBody`. A body split into pieces that were each under the limit was never rejected, no matter the total. The Milo and HTTP/2 paths already compared against the running `bytesRead`, so they were unaffected.\n\n**Fix.** The check at `lib/dispatcher/client-h1.js:773` now uses the cumulative total (`this.bytesRead + buf.length`), matching the other two parsers.\n\n**Regression tests** in `test/max-response-size.js`, parameterised over llhttp and Milo:\n- A chunked body of four 5-byte pieces against a 10-byte limit must fail with `ResponseExceededMaxSizeError`. Before the fix the llhttp variant failed with \"body should not complete\".\n- A chunked body totalling exactly the limit must be delivered in full, guarding the boundary.\n\n**Test results.** All pass after the fix:\n\n| Files | Tests | Result |\n|---|---|---|\n| `test/max-response-size.js` | 10 | pass |\n| `test/milo.js`, `test/client.js`, `test/client-errors.js`, `test/errors.js` | 118 | 117 pass, 1 pre-existing skip |\n| `test/client-pipelining.js`, `test/client-keep-alive.js`, `test/client-stream.js`, `test/client-request.js`, `test/balanced-pool.js`, `test/retry-agent.js` | 113 | pass |\n\nI could not run eslint: every invocation was blocked pending approval. The changes follow the surrounding style by inspection.\n\n**TRACE.md** at the repo root holds the full answers to parts 1 and 2. The notable findings from part 2:\n- **BalancedPool, H2CClient, Client with Milo**: the limit is passed down and enforced on the whole body.\n- **RetryAgent**: enforced only via the wrapped Agent. A `maxResponseSize` passed to the RetryAgent's own options is silently ignored, and the error is not in the default retry list, so it surfaces to the caller.\n- **ProxyAgent**: enforced for tunnelled targets (`https://` or `proxyTunnel: true`). For plain `http://` targets through an HTTP proxy, `Http1ProxyWrapper` builds its inner Client with only `connect` (`lib/dispatcher/proxy-agent.js:58-62`), so the limit is dropped. The SOCKS5 path drops it too (`lib/dispatcher/socks5-proxy-agent.js:235-238`). I documented these but did not change them, since they are separate from the reported bug.", "diffstat": "TRACE.md | 91 ++++++++++++++++++++++++++++++++++++++++++++\n lib/dispatcher/client-h1.js | 5 ++-\n test/max-response-size.js | 92 +++++++++++++++++++++++++++++++++++++++++++++\n 3 files changed, 187 insertions(+), 1 deletion(-)", "sourceRunDir": "2026-11-09T20-12-20-189Z" }, { "name": "opus-5-5-1", "model": "claude-opus-5-5", "steps": [ { "step": 1, "permissionMode": "acceptEdits", "exitCode": 0, "signal": null, "spawnError": null, "costUsd": 0.7938263999999999, "resultSubtype": "success", "isError": false, "turns": 34, "durationMs": 144641, "inputTokens": 1277324, "outputTokens": 15152, "firstContextTokens": 18708, "peakMainContextTokens": 62052 } ], "exitCode": 0, "signal": null, "spawnError": null, "checks": [ { "name": "chunked overflow rejected via Agent, Pool and Client (hidden test, 7 cases)", "pass": true }, { "name": "existing test/max-response-size.js passes", "pass": true }, { "name": "TRACE.md names the default path: agent.js, pool.js, client.js, client-h1.js (hidden check)", "pass": true }, { "name": "TRACE.md names the other paths: balanced-pool.js, retry-agent.js, proxy-agent.js, h2c-client.js, client-h2.js, parser-h1.js (hidden check)", "pass": true }, { "name": "added or changed a test that uses maxResponseSize", "pass": true }, { "name": "ran the tests after the last code edit (TRACE.md edits don't count)", "pass": true } ], "resultSubtype": "success", "isError": null, "costUsd": 0.7938263999999999, "costByModel": { "claude-opus-5-5": { "costUsd": 0.7938263999999999, "inputTokens": 56, "cacheReadTokens": 1228287, "cacheWriteTokens": 48981, "outputTokens": 15152 } }, "modelsCalled": [ "claude-opus-5-5" ], "turns": 34, "durationMs": 144641, "subagentCalls": 0, "subagentCallDetails": [], "toolCalls": { "main": 33, "inSubagents": 0, "byName": { "Grep": 2, "Bash": 22, "Read": 2, "Edit": 5, "Write": 2 } }, "sessionLogSubagents": [], "permissionDenials": 7, "finalMessage": "I found and fixed the bug, added a regression test, and wrote `TRACE.md`. Part 2 also turned up a separate problem: `ProxyAgent` drops the limit completely for plain `http://` targets.\n\n**The bug.** In the default HTTP/1.1 path (the llhttp parser), the check in `lib/dispatcher/client-h1.js:770` compared each body piece to the limit on its own (`buf.length > maxResponseSize`) and never added up the bytes already received. A 1 MB body arriving in one piece was caught, but the same body sent as many small chunks never was. The fix is one line: `this.bytesRead + buf.length > maxResponseSize`. That is the same check the Milo parser and HTTP/2 code already use.\n\n**Regression test.** It's in `test/max-response-size.js`. It creates `new Agent({ maxResponseSize: 16 KiB })`, passes it to `request()`, and has the server stream 64 × 1 KiB chunks. It runs once with llhttp and once with Milo. Without the fix the llhttp case fails and the Milo case passes, which confirms the cause. With the fix all 8 tests in that file pass. I also ran `test/client.js`, `agent.js`, `content-length.js`, `balanced-pool.js`, `retry-agent.js` and `proxy-agent.js`: 137 passed, 0 failed, 1 skipped. I didn't run eslint because the command needed your approval.\n\n**Part 1.** The option goes `agent.js` → `pool.js` → `client.js` (stored as `kMaxResponseSize`) → `client-h1.js`, where the parser checks it in `onBody`. `TRACE.md` lists each step with line numbers.\n\n**Part 2:**\n- **BalancedPool:** passed down. The limit is enforced on the whole body now; it had the same bug before the fix.\n- **RetryAgent wrapping an Agent:** the wrapped Agent's limit applies to each response. Passing `maxResponseSize` to RetryAgent itself does nothing, because its options are only retry settings. If a download is cut off and resumed with a `Range` request, each partial response is checked separately, not the total.\n- **ProxyAgent:** the limit only applies to tunnelled requests (`https:` targets, or `proxyTunnel: true`). For plain `http:` targets (the default forwarding path), `lib/dispatcher/proxy-agent.js:180-187` builds an `Http1ProxyWrapper` without the options, and its client is created with only `{ connect }` (l.58-62). So the limit is silently ignored there. SOCKS proxies (l.157-167) drop it as well. I've documented this but not fixed it, since it's separate from the reported bug.\n- **H2CClient:** passed down and enforced on the whole body (`client-h2.js:1141`, `1455`, `1463`). This was already correct.\n- **Client with Milo:** passed down and enforced on the whole body (`parser-h1.js:173`, `433`/`437`, `932`/`940`). This was already correct.\n\nI tried to confirm the ProxyAgent, BalancedPool and RetryAgent results against a live server, but that script needed your approval, so part 2 is based on reading the code. Nothing is committed.", "diffstat": "TRACE.md | 115 ++++++++++++++++++++++++++++++++++++++++++++\n lib/dispatcher/client-h1.js | 2 +-\n test/max-response-size.js | 45 ++++++++++++++++-\n 3 files changed, 160 insertions(+), 2 deletions(-)", "sourceRunDir": "2026-11-09T19-58-27-684Z" }, { "name": "opus-5-5-2", "model": "claude-opus-5-5", "steps": [ { "step": 1, "permissionMode": "acceptEdits", "exitCode": 0, "signal": null, "spawnError": null, "costUsd": 0.8764943999999998, "resultSubtype": "success", "isError": false, "turns": 43, "durationMs": 161216, "inputTokens": 1642190, "outputTokens": 15510, "firstContextTokens": 18708, "peakMainContextTokens": 62569 } ], "exitCode": 0, "signal": null, "spawnError": null, "checks": [ { "name": "chunked overflow rejected via Agent, Pool and Client (hidden test, 7 cases)", "pass": true }, { "name": "existing test/max-response-size.js passes", "pass": true }, { "name": "TRACE.md names the default path: agent.js, pool.js, client.js, client-h1.js (hidden check)", "pass": true }, { "name": "TRACE.md names the other paths: balanced-pool.js, retry-agent.js, proxy-agent.js, h2c-client.js, client-h2.js, parser-h1.js (hidden check)", "pass": true }, { "name": "added or changed a test that uses maxResponseSize", "pass": true }, { "name": "ran the tests after the last code edit (TRACE.md edits don't count)", "pass": false } ], "resultSubtype": "success", "isError": null, "costUsd": 0.8764943999999998, "costByModel": { "claude-opus-5-5": { "costUsd": 0.8764943999999998, "inputTokens": 70, "cacheReadTokens": 1592622, "cacheWriteTokens": 49498, "outputTokens": 15510 } }, "modelsCalled": [ "claude-opus-5-5" ], "turns": 43, "durationMs": 161216, "subagentCalls": 0, "subagentCallDetails": [], "toolCalls": { "main": 42, "inSubagents": 0, "byName": { "Grep": 5, "Read": 3, "Bash": 26, "Edit": 6, "Write": 2 } }, "sessionLogSubagents": [], "permissionDenials": 8, "finalMessage": "I fixed the bug: the size limit was checked against each chunk separately, never against the total. All three parts are done, and the full trace and per-dispatcher table are in `TRACE.md` at the repo root.\n\n## The bug and fix\nIn `lib/dispatcher/client-h1.js:770` (the default HTTP/1.1 parser, llhttp), the check was `buf.length > maxResponseSize`. One large chunk tripped it, but a body sent as many small chunks never did. The parser was already counting the running total in `this.bytesRead`, so the fix is one line:\n\n```js\nif (maxResponseSize > -1 && this.bytesRead + buf.length > maxResponseSize) {\n```\n\nThe Milo parser and the HTTP/2 path already checked the running total, so this brings llhttp in line with them.\n\n**Regression test** (`test/max-response-size.js`): it uses `new Agent({ maxResponseSize: 10 })` with `request()`, and the server sends 10 chunks of 4 bytes with a pause between each. It runs once with the default parser and once with Milo.\n- On the old code, the default-parser case fails and the Milo case passes, which matches the report.\n- With the fix, `max-response-size.js`, `client.js`, `content-length.js`, `parser-issues.js`, `milo.js`, `pool.js`, `proxy-agent.js` and `retry-agent.js` give 194 tests: 193 pass, 0 fail, 1 skipped (a skip that was already in the suite).\n- I didn't run eslint because the command needed an approval it didn't get.\n\n## Part 1: the path, in short\n`index.js` → `lib/api/api-request.js` → `lib/dispatcher/agent.js` (keeps the option and passes it to the Pool it creates) → `lib/dispatcher/dispatcher-base.js` → `lib/dispatcher/pool.js` (passes it to each Client) → `lib/dispatcher/client.js` (validates and stores it) → `lib/dispatcher/client-h1.js` (the parser copies it, then the enforcement check at line 770).\n\n## Part 2: other setups\n| Setup | Limit enforced on the whole body? |\n|---|---|\n| BalancedPool | Yes, after this fix (it creates Pools with the same options) |\n| RetryAgent wrapping an Agent | Yes if the limit is set on the inner Agent. **No** if it's set in RetryAgent's own options: those are only used as retry settings. The count also restarts on each retry attempt. |\n| ProxyAgent | Yes for tunnelled requests (`https:` targets, or `proxyTunnel: true`). **No** for plain `http:` targets with default settings: the client that talks to the proxy is created without the option (`proxy-agent.js:59,61`). The SOCKS5 path drops it too. |\n| H2CClient | Yes, already counted the total (`client-h2.js:1455`) |\n| Client with Milo | Yes, already counted the total (`parser-h1.js:433` and `:932`) |\n\nThe ProxyAgent gap comes from reading the code only. I wrote a script to confirm it against a real proxy, but running it wasn't approved, so it hasn't been run. It's at `/tmp/scratch-mrs/proxy-check.js`, outside the repo, if you want to run it. I left the ProxyAgent gap and the RetryAgent option behaviour unfixed, since they're separate from the reported bug.\n\nNothing is committed.", "diffstat": "TRACE.md | 27 +++++++++++++++++++++++++++\n lib/dispatcher/client-h1.js | 2 +-\n test/max-response-size.js | 37 ++++++++++++++++++++++++++++++++++++-\n 3 files changed, 64 insertions(+), 2 deletions(-)", "sourceRunDir": "2026-11-09T20-12-10-326Z" }, { "name": "opus-5-5-3", "model": "claude-opus-5-5", "steps": [ { "step": 1, "permissionMode": "acceptEdits", "exitCode": 143, "signal": null, "spawnError": "ETIMEDOUT", "costUsd": null, "resultSubtype": null, "isError": null, "turns": null, "durationMs": null, "inputTokens": 1209012, "outputTokens": 11014, "firstContextTokens": 18711, "peakMainContextTokens": 50899 } ], "exitCode": 143, "signal": null, "spawnError": "ETIMEDOUT", "checks": [ { "name": "chunked overflow rejected via Agent, Pool and Client (hidden test, 7 cases)", "pass": false }, { "name": "existing test/max-response-size.js passes", "pass": false }, { "name": "TRACE.md names the default path: agent.js, pool.js, client.js, client-h1.js (hidden check)", "pass": false }, { "name": "TRACE.md names the other paths: balanced-pool.js, retry-agent.js, proxy-agent.js, h2c-client.js, client-h2.js, parser-h1.js (hidden check)", "pass": false }, { "name": "added or changed a test that uses maxResponseSize", "pass": true }, { "name": "ran the tests after the last code edit (TRACE.md edits don't count)", "pass": false } ], "resultSubtype": null, "isError": null, "costUsd": 0.6439, "costByModel": {}, "modelsCalled": [], "turns": 31, "durationMs": 900000, "subagentCalls": 0, "subagentCallDetails": [], "toolCalls": { "main": 47, "inSubagents": 0, "byName": { "Grep": 1, "Read": 3, "Bash": 32, "Edit": 9, "ToolSearch": 1, "TaskStop": 1 } }, "sessionLogSubagents": [], "permissionDenials": 0, "finalMessage": "", "diffstat": "test/max-response-size.js | 45 ++++++++++++++++++++++++++++++++++++++++++++-\n 1 file changed, 44 insertions(+), 1 deletion(-)", "costSource": "session log (run hit the 15-minute limit; lower bound)", "timedOut": true, "sessionLogUsage": { "messages": 31, "input": 64, "cacheRead": 1171120, "cacheWrite": 37828, "output": 11014 }, "sourceRunDir": "2026-11-09T20-12-12-325Z" } ], "finishedAt": "2026-11-10T00:26:33.350Z", "mergedFrom": [ "2026-11-09T19-58-23-793Z", "2026-11-09T19-58-25-680Z", "2026-11-09T19-58-27-684Z", "2026-11-09T20-12-10-326Z", "2026-11-09T20-12-12-325Z", "2026-11-09T20-12-20-189Z", "2026-11-09T20-23-00-276Z", "2026-11-09T23-57-57-152Z", "2026-11-10T00-10-48-503Z", "2026-11-10T00-19-13-904Z" ], "aggregates": [ { "setup": "fable-5-2", "model": "claude-fable-5-2", "runs": 3, "hiddenTestPassed": 3, "allChecksPassed": 2, "avgCostUsd": 2.64233, "avgTotalTokens": 2374934, "avgTurns": 65.333333, "avgDurationSec": 559.1, "totalCostUsd": 7.92699 }, { "setup": "fable-5-1", "model": "claude-fable-5-1", "runs": 2, "hiddenTestPassed": 2, "allChecksPassed": 2, "avgCostUsd": 3.276253, "avgTotalTokens": 2040606, "avgTurns": 79, "avgDurationSec": 556.011, "totalCostUsd": 6.552506 }, { "setup": "opus-5-5", "model": "claude-opus-5-5", "runs": 3, "hiddenTestPassed": 2, "allChecksPassed": 1, "avgCostUsd": 0.771407, "avgTotalTokens": 1390067, "avgTurns": 36, "avgDurationSec": 401.952333, "totalCostUsd": 2.314221 } ], "totalCostUsd": 16.793717, "modelCheckCallsUsd": 0.241625, "slotSpendUsd": 17.035342, "notes": [ "In-place update Nov 9 evening: Fable 5.2 column replaced with Claude Code 2.1.321 rerun (3 runs). Fable 5.1 and Opus 5.5 unchanged from afternoon 2.1.312 runs.", "Fable 5.2 checks in this summary are the Node 24.11 regrade of the rerun diffs (same Node as the original test). Live Node 22.12 grader during the rerun was invalid for undici.", "Original afternoon Fable 5.2 numbers (CC 2.1.312, unrecognized model) remain in 2026-11-09T19-58-23-793Z-merged for reference.", "Full rerun artifacts also under runner/results/fable-5-2-rerun-cc2.1.321/." ] }