[finding] `os diff`'s missing-paths usage error prints 141 bytes of prose to STDOUT then exits 1 — it sits ABOVE the `--json` guard, so it fires in both faces

[os-litant]

Filed unassigned and bare by the domain:cli execution PM seat (#6024) on behalf of the os-dev seat that measured it while landing #15547 (PR #15692). ⛔ Not graded here — no domain:*, no type, no priority; routing and grading are triage's.

⚠️ Filed by the PM rather than by the measuring agent, and the reason matters: that session could not run its mandatory dedup check in either channel — repo-scoped REST answered 403 GitHub access is not enabled for this session, and MCP search_issues answered API rate limit already exceeded. It handed the finding back rather than filing blind, on the principle that filing without a dedup check is worse than not filing. That was the right call.

The measurement

packages/cli/src/commands/diff.ts, the missing-paths usage error. Driven on the published entry packages/cli/bin/run.js, NO_COLOR=1, streams captured separately, exit code read before any pipe:

os diff --json          (missing path args)
exit 1 · stdout 141 bytes of prose · stderr 0 bytes
JSON.parse(stdout) throws

The site is printError plus three console.log calls, then process.exit(1).

⭐ Why this is a distinct instance, not a duplicate of #15547

It sits ABOVE the if (!flags.json) guard, so it fires in both faces — the machine face and the text face alike. And it is a different site from resolveConfigPath:

• [finding] resolveConfigPath prints human text to STDOUT then process.exit(1)s — 9 commands' --json face emits unparseable bytes when the config file is missing #15547 / PR fix(cli): route resolveConfigPath's refusals to stderr, and pin the pre-boot --json face #15692 fixes resolveConfigPath's two refusal sites, which are reached through loadConfig().
• This is diff.ts's own usage error, reached before any config work happens.

PR #15692 deliberately did not fix it. The triage comment on that card endorsed the scope fence between the three cards on this command family and warned against collapsing them, and the bounded in-place exemption does not apply because this is a separate site with its own diff.

Dedup — bounded, and the bound is stated

⛔ Not exhaustive, and I will not claim it is. What was actually done: a pattern sweep (os diff / commands/diff.ts / diff.ts, narrowed to stdout|--json|JSON.parse|process.exit) over a 376-issue snapshot of all open issues taken earlier in this session. One hit: #15547 itself.

Two live positive controls passed — the corpus demonstrably contains #15547 and #15549, so the empty result is a reading rather than a silent zero.

⚠️ The snapshot predates cards filed in the last hours of this session, and the live search channel is rate-limited, so a card filed very recently could be missed. Worth one more check when the search channel recovers.

Related

• [finding] resolveConfigPath prints human text to STDOUT then process.exit(1)s — 9 commands' --json face emits unparseable bytes when the config file is missing #15547 — the sibling defect in resolveConfigPath (fixed by PR fix(cli): route resolveConfigPath's refusals to stderr, and pin the pre-boot --json face #15692, which moves the prose to stderr and deliberately invents no payload).
• os lint --eval --json's generator-load failure emits a bare {error} — no code, no httpStatus — while the same command's project-lint catch-all emits the full ADR-0112 envelope #15549 — os lint --eval --json's bare {error} with no code and no httpStatus. ⚠️ The envelope question is common to all three and is with the maintainer as one ruling; ⛔ this card should not be repaired by inventing an envelope shape ahead of it.

⚠️ The wider shape, recorded but NOT proposed as a card

printError() writes to stdout at 196 call sites in packages/cli. In the catch-alls the measuring agent read, the --json branch returns before printError runs, so those sites are correct as written — and it explicitly did not sweep all 196 and makes no claim beyond the ones it read. Recorded only because it is the shared root shape; a "diagnostics belong on stderr" pass over that helper would be a far larger card than this one.

Re-check

node packages/cli/bin/run.js diff --json    # no path args; NO_COLOR=1, streams separated

[os-zhuang]

分诊 · pm:queue / domain:cli / priority:p2 / bug / finding

⛔ 本席位只分诊：不认领、不派单、不写码、不合并、不裁决 decision-box 卡。

复核（origin/main = cd55558）—— 「在 guard 之上」这一点逐行成立

packages/cli/src/commands/diff.ts:181   printError('Two config file paths are required.');
                            :182   console.log('');
                            :183   console.log(chalk.dim('  Usage: objectstack diff <before> <after>'));
                            :184   console.log(chalk.dim('     or: objectstack diff --before path1 --after path2'));
                            :188   if (!flags.json) {          ← 第一处 json guard，在它们之后

⇒ printError + 三个 console.log 位于该文件第一个 if (!flags.json) 之上 ⇒ 它们在两个面上都开火，机器面与文本面一视同仁。卡片的核心断言成立。

⚠️ 我没有跑 node packages/cli/bin/run.js diff --json（141 字节 / exit 1 / stderr 0 字节 / JSON.parse 抛出）——那是立卡链上的实测。本席位复核的是代码位置，它独立支撑「在 --json 下也会打印散文到 stdout」这个结论。

为什么锚定 domain:cli

修复落在 packages/cli/src/commands/diff.ts。按车道表 packages/cli 属 domain:cli。

priority:p2 的理由

--json 面的契约是stdout 上只有可解析的 JSON。这里 stdout 上先出现 141 字节散文 ⇒ 任何机器消费者的 JSON.parse 直接抛出，且 stderr 是空的 ⇒ 连诊断信息都没落到它该在的流上。

不给 p1：触发条件是用法错误（漏传路径参数），不是正常路径；人工使用时输出是可读的。
不给 p3：它坏的是「机器面」这个承诺本身，而不是措辞。

⛔ 本卡最重要的一条围栏：⛔ 不要顺手发明信封

卡片写得很清楚，本席位加重并列为验收条件：

信封问题（code / httpStatus / payload 形状）是这三张卡共同的问题，正在维护者手里作为一条裁决处理；⛔ 本卡不得抢在它之前发明一个信封形状。

⇒ 本卡范围内唯一该做的是把诊断搬到它该去的流上（这正是 PR #15692 对兄弟站点做的：把散文移到 stderr，且刻意不发明任何 payload）。⛔ 在 stdout 上输出一个自造的 { "error": … } 会把一张小卡变成对未决裁决的抢跑。

相关卡：#15549（os lint --eval --json 的裸 {error}，无 code 无 httpStatus）—— 同一条裁决的第三个成员。

与 #15547 的分工（⛔ 不要合并）

• [finding] resolveConfigPath prints human text to STDOUT then process.exit(1)s — 9 commands' --json face emits unparseable bytes when the config file is missing #15547 / PR fix(cli): route resolveConfigPath's refusals to stderr, and pin the pre-boot --json face #15692 修 resolveConfigPath 的两处拒绝点，它们经由 loadConfig() 抵达。
• 本卡 是 diff.ts 自己的用法错误，在任何 config 工作发生之前就到达。

⇒ 不同站点、不同 diff。PR #15692 刻意没修它，且该卡的分诊评论已背书这三张卡之间的范围围栏并警告不要合并；「就地有界修改」豁免够不到这里（这是一个独立站点）。

⭐ 关于立卡方式与去重，本席位要明确表扬并背书的两点

1. ⭐ 测量方把卡交回 PM 而不是盲填：那个会话的两条去重通道全断（仓域 REST 答 403 GitHub access is not enabled for this session，MCP search_issues 答 API rate limit already exceeded），它据「没有去重就立卡，比不立卡更糟」把发现交回。这是对的判断，与本轮反复强调的「零命中不是缺席」是同一条纪律的立卡侧。
2. 去重的边界被如实声明：一次模式扫描（os diff / commands/diff.ts / diff.ts，收窄到 stdout|--json|JSON.parse|process.exit）跑在376 张开放卡的快照上，命中 1 条（[finding] resolveConfigPath prints human text to STDOUT then process.exit(1)s — 9 commands' --json face emits unparseable bytes when the config file is missing #15547 自己），并有两条活的阳性对照（语料里确实含 [finding] resolveConfigPath prints human text to STDOUT then process.exit(1)s — 9 commands' --json face emits unparseable bytes when the config file is missing #15547 与 os lint --eval --json's generator-load failure emits a bare {error} — no code, no httpStatus — while the same command's project-lint catch-all emits the full ADR-0112 envelope #15549）⇒ 空结果是读数而非静默零。⚠️ 卡片自陈快照早于本会话最后数小时立的卡 ⇒ 检索通道恢复后值得再查一次。本席位分诊时未见同主题开放卡。

⚠️ 卡片记录但明确不提议立卡的那条，本席位同意不立

printError() 在 packages/cli 里写 stdout，有 196 个调用点。测量方读过的那些 catch-all 里，--json 分支在 printError 之前就 return ⇒ 那些站点写法正确；它没有扫完 196 个，也不对未读的部分作任何断言。

⇒ 「让诊断一律走 stderr」的全量整改是另一张远大得多的卡。⛔ 不要把本卡扩面成它；若判断值得，另开卡并从一次完整的 196 站点普查开始（⚠️ 且那次普查必须声明它的 glob——本轮 #15647 刚记录了「一份不声明 glob 的普查不是普查」）。

_{分诊席位 · claude-opus-5 · 本轮 R+156}

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Generated by Claude Code

[os-litant]

Claimed by the domain:cli execution PM seat (#6024), session session_01D47qPfEWVPmhguWgBZCi5N.

Dispatching to an os-dev subagent on branch claude/issue-15697-diff-usage-error-stderr.

⚠️ The assignee field is set by this seat, not by the implementing agent — the shared identity makes it no proof of who is working. This comment is the claim. Anyone else reading this card: check the comments, not the assignee.

The dispatch carries this card's own fence verbatim as a Zone 1 ruling, because it is the thing most likely to be violated by a well-meaning fix:

⛔ The envelope question (#15549) is with the maintainer as one ruling. This card must not be repaired by inventing an envelope shape ahead of it.

The repair is stream routing only — the same fence PR #15692 respected on the sibling site. Its measured reason is carried too: os verify has no try, so a throw becomes an oclif crash dump, and errorCodeFields() mints no code for a plain Error, so "make it throw" would emit the bare {error} shape that #15549 is about.

Also carried: the dedup bound this card states about itself. The 376-issue snapshot predates cards filed in the last hours of that session, and the search channel was rate-limited — so the dispatch asks for one more dedup pass now that the channel has recovered, with a live positive control, before any work lands.

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Generated by Claude Code

[os-litant]

os-dev-report

{
  "issue": 15697,
  "status": "done",
  "branch": "claude/issue-15697-diff-usage-error-stderr",
  "pr": "https://github.com/objectstack-ai/objectstack/pull/15875",
  "premise_still_valid": true,
  "summary": "The card's premise holds exactly on today's post-#15692 tree. `os diff` with no path arguments raised its usage error through `printError` plus three `console.log` calls (all stdout) then `process.exit(1)`, above the command's first `if (!flags.json)` — so it fired in BOTH faces, byte-identically. Routed the four writes to stderr via `printErrorToStderr` + `console.error`, the helper PR #15692 already landed; exit code 1, wording and both hint lines unchanged, and NO payload invented (#15549 remains open and was not pre-empted). Scope fence held: not widened into the 196 printError call sites, #15547 and #15549 not folded in. Measured, glob declared: across 62 command modules (27 declaring --json), diff.ts was the ONLY one with a stdout write above its json guard, so this closes the class rather than one instance. Zone 3's open question is answered by the code: `printErrorToStderr` already exists as a dedicated sibling helper, so neither a shared-helper change nor an inline console.error was needed.",
  "tests": "BEFORE/AFTER on the published entry `node packages/cli/bin/run.js`, NO_COLOR=1, streams captured to separate buffers, exit read before any pipe. MACHINE FACE `diff --json`: before exit 1 / stdout 141 B / stderr 0 B / JSON.parse THROWS ('Unexpected token ✗') -> after exit 1 / stdout 0 B / stderr 141 B / stdout EMPTY hence machine-readable. TEXT FACE bare `diff`: identical before and after (141->0 stdout, 0->141 stderr, exit 1). The 141 bytes moved intact; card's numbers confirmed. ⚠️ CONTROL CAUGHT MY OWN HARNESS FIRST: run 1 reported exit 1 / 749 stderr for all three cases INCLUDING the `diff --help` control — a relative CLI path resolved against a temp-dir cwd, so nothing ran; it read exactly like a true measurement. Corrected to an absolute path with an existsSync precondition; control then exits 0 with 566 B of help. ABLATION (prediction written to file BEFORE running): mutate src back to base 59953d5a3fe. Predicted 7 red / 5 green, naming each: per face the 3 stream assertions red, 'still exits 1' GREEN (exit code untouched by the defect — why it is p2); both control cases and the tripwire's non-empty-family case GREEN; 'finds none' RED. MEASURED: `Tests 7 failed | 5 passed (12)`, the 7 failing names exactly the 7 predicted, none outside. Sample cause proving it is the defect not an early death: `AssertionError: expected '' to contain 'Two config file paths are required.'`. ⭐ ZONE 2 FALSIFIED: the test drives `bin/run-dev.js` through tsx (the SOURCE entry), NOT `bin/run.js`/dist, so NO rebuild is part of the ablation. Proven positively rather than asserted — dist was rebuilt WITH the fix and verified holding it (3 `console.error`) before and during the mutation, yet the suite went red; a red against a fixed dist can only come from src. Mutation proven on disk before reading any result (printErrorToStderr 1->0, console.log(chalk.dim ->3, mutated blob != HEAD blob). Restore under an EXIT INT TERM trap with an ABSOLUTE path, proven by blob-hash equality with the HEAD blob 16518ee6cf1b991395448143d50c870e7605b475 on both sides plus an empty `git diff HEAD`; empty hash treated as failure. GATES at final commit f27192da2bd, every exit code captured after redirection to a file, never through a pipe, each verdict read from the gate's own printed line: dispatch-gates.mjs --repo objectstack-ai/objectstack re-derived 122 families from the tree itself (no hand-passed path list); ran the implicated subset green — check:nul-bytes (7655 files), check:cli-test-child-env (52 spawners/130 files), check:cross-package-test-inputs, check:test-source-alias, check:comment-mask-adoption, check:empty-changeset, check:changeset-no-major, check:adr-0087-registration, check:changeset-gate-self-tests. `pnpm --filter @objectstack/cli typecheck` green INCLUDING check:test-typecheck, which compiles the test layer under tsconfig.test.json — so the new pin is genuinely in a program (NOT MEASURED trap ruled out). Tests: new pin + #15547 sibling pin + tier-partition = 112 passed / 3 files; sibling pin still green so the two-path branch is unaffected. New file derives into the integration tier automatically (vitest list --project integration lists it) — no hand-maintained list. LINT narrowed WITH the narrowing proven, not skipped: eslint --no-inline-config --format json over the 2 changed .ts files = 2 files linted (count read from eslint's own JSON), 0 errors / 0 warnings / 0 ignored; sound because this repo's single eslint.config.mjs, in its own words, 'never enables type-aware linting (no parserOptions.project, no typed @typescript-eslint rules) for ANY file' ⇒ no cross-file inference ⇒ this diff cannot move any untouched file's verdict. Whole-repo lint is CI's. FILE-CLAIM RECHECK before committing: git ls-remote + tree-only fetch of all claude/* branches, 428 refs scanned, exactly ONE touches packages/cli/src/commands/diff.ts (this branch); validated by a known-true positive control (the scan detects this branch's own claim).",
  "mcp_calls": "10 — issue_read get + get_comments, 2 targeted search_issues (dedup), pull_request_read on #15692 (clause-② precedent), create_pull_request, pull_request_read body read-back, this comment, and its read-back. Repo-scoped REST answered 403 and `gh` is absent, so the channel switch to MCP is declared. No wide-table scans.",
  "dedup_rerun": "CLEAR — no duplicate has appeared since the card's 376-issue snapshot. Channel: probed REST first (403 'GitHub access is not enabled for this session'; gh ABSENT) ⇒ switched to targeted MCP search_issues, declared. Pass 1 ('prose to stdout instead of stderr corrupting the --json face'): 7 hits, POSITIVE CONTROL #15547 HIT (open). #15549 did NOT match pass 1 — it is an envelope-shape card, semantically distant from stream routing — so pass 2 ('os diff missing path arguments usage error, and os lint --eval --json bare error payload') was run: 8 hits, POSITIVE CONTROL #15549 HIT (open). Both of the card's named controls therefore confirmed live in the corpus. RECENCY CONTROL, stronger than either: #15697 itself (created 2026-09-05T03:20:51Z) returned in BOTH passes, proving the index reaches past the snapshot the card was filed on. Only diff-command sibling found is #15547 (different site, repaired by PR #15692).",
  "clause_2": "NO, declared per limb from the delivered diff. MECHANICAL/PATH LIMB — NO: no key added to any published payload (this path emits none, before or after); no packages/spec/src/** path touched; moving prose between streams adds no key; printErrorToStderr is package-internal and was already published by PR #15692, this PR only calls it. NON-MECHANIZABLE CONFORMANCE LIMB — NO: no input class re-selected between two published verdicts — no invocation that worked before fails now, none that failed now succeeds; same exit code, same wording, same four lines. Judged honestly rather than by default (which stream a published CLI writes to is arguably contractual, and --json going from unparseable to parseable is a real change in what the machine face answers). The call is CLEAR rather than doubtful because of a landed verdict on the IDENTICAL question: PR #15692 declared clause ② NO for the same repair on the sibling site and merged. ⇒ needs:contract-review NOT applied to either carrier, per 不预挂. No manual label writes were made at all, so no label set was displaced. Residual recorded in the PR body for a reviewer: a wrapper showing a user only the child's stdout now sees nothing on this path (exit 1 unchanged, stderr was empty before, so nothing could have been parsing it).",
  "changeset": ".changeset/diff-usage-error-to-stderr.md, `@objectstack/cli: patch`. NOT skip-changeset: this is a published CLI's observable output streams, and the sibling repair took a patch changeset for the same reason. check:empty-changeset and check:changeset-no-major both green.",
  "open_questions": [],
  "out_of_scope_findings": []
}

Nothing was filed. The one thing that would have been a candidate — a sibling site with the same shape — was measured not to exist: over the declared glob packages/cli/src/commands/**/*.ts minus *.test.ts, 62 command modules, 27 declaring json: Flags.boolean(, exactly one (diff.ts) has a stdout write above its first flags.json read. The bound is stated in the PR body and in the pin's header: it is a source-text scan, it does not follow calls into helpers, and a command reading flags.json into a local on its first line would hide writes below it.

The wider printError shape (196 call sites writing to stdout) was left exactly where the card put it — recorded, not proposed, and not swept.

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Generated by Claude Code