feat(hook): record an absent response, and assert the capture end to end - #666
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CLOUD-919 Persist every PostToolUse response as a local capture
Why
The bytes are then dropped. Measured against so a structured tool — every MCP call, every Where the capture happens, and why thereIn
Not through
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| Response member | Capture | Provenance row |
|---|---|---|
| absent | none | absence recorded |
| present, empty | a real record of zero bytes | digest of the empty record |
| present, non-empty | the bytes at declared fidelity | digest + fidelity |
facts::rows_in and the Sourced receipt are unchanged and remain a separate consumer reading the same envelope field. They do not read the capture, and the capture does not read them.
Capture failure
CLOUD-917's decision, applied here: hook execution continues, the exit code is unchanged and never 2, a degraded provenance row is written with fidelity = Unavailable and a stable reason id, and the observable signal is that reason id on the doctor and advisory channels — never bytes, never a path. This is the opposite of capture::store's "never a silent skip", and deliberately so: on this surface no Batten failure may block a tool call.
Refinement — Ready
Refinement gate: Definition of Ready & Done. This body carries only specializations.
- Source of truth (§1).
crates/batten/src/lib.rs's post-tool arm inrun_hook— one call site, besiderecord_agent_factat:1881and ahead of it. The store, the handle shape and the fidelity vocabulary are CLOUD-918's and CLOUD-917's; nothing about them is re-decided here. - Computable predicate (§2).
mise run verifygreen with a payload fixture per row of the table above, plus the security predicate end to end: a planted secret is absent from stdout, stderr, every-Jdocument and every file under$GIT_DIR/batten-receipts/, and byte-identical throughbatten capture show <handle> --raw. Failure case: a build that keeps the!command.is_empty()conjunct passes the Bash fixture and reds the structured one — which is why both are required rather than one standing in for the other. - Effect (§3).
hookis already classified. The write is the only new cost and it is a self-declared write on the storecaptureowns; the engine still spawns nothing and builds no runtime, and house-style §5's read promise is untouched because reading a buffer the harness handed over is not execution. - Generated artifacts (§4). None. The wiring is already derived and drift-gated, and this adds no registration.
- Output & exit (§5). Nothing is emitted on the capture path. A post-tool event is not a deny channel on any surveyed host and stays exit
0; a capture failure does not change that. Pointer-only holds structurally: the only new bytes leave the process throughcapture show --raw, which a caller has to name. - Commit / bump (§6).
feat(hook)→ patch until0.1.0. - Test obligation (§7). Over the compiled binary, in
tests/cli.rs's existing idiom beside the CLOUD-776 block at:9114, because the halves live in different processes:-
a Bash fixture and an MCP content-block fixture each persist the authoritative bytes at the declared fidelity;
-
all three aliases —
tool_response,toolResponse,tool_result— reach the capture; -
a present-but-empty response yields a record of zero bytes, and an absent member yields no record and an absence row; a test fails if the two collapse;
-
the planted secret case, both halves — absent from four channels, byte-identical through
--raw; -
spilled, truncated and unavailable responses each produce the specified degraded record rather than a silent full-capture claim, one case per fidelity value;
-
a store that cannot be written leaves the hook at exit
0with a degraded row and a reason id, driven through the state-root seam the suites already use rather than by permission bits (.claude/rules/rust.md: this sandbox runs as root); -
A NEW POST-TOOL BENCH ARM, and this is the row's load-bearing measurement obligation.
mise-tasks/perf.shhas five arms —noop,check,hook,passthrough,wired— andhookandwiredboth feedcrates/batten/tests/fixtures/hooks/claude-code.json, a canned PreToolUse payload, withwired_cmddrawn from.hooks.PreToolUse[]. There is no PostToolUse arm. So the write this row adds — on every post-tool event, therefore on every tool call — is invisible toperf,perf-compare,perf-pairandperf-assert, and runningperf-gateproves nothing about it. This row adds the arm, with its own canned PostToolUse fixture besideclaude-code.jsonandclaude-code-passthrough.json, and publishes the number.Without it the cost is unmeasurable now and unmeasurable later, which is the CLOUD-851 shape exactly: its store acquisition regressed
checkp50 4.76ms → 10.01ms (2.103x) with 2134 cargo tests green across it, because none of them measures invocation cost. CLOUD-875 is the same class.For the arms that already exist:
REGRESSION_RATIOis 1.30, the measured noise floor 1.102, andwiredcarries an exemption to 1.60 until 2026-11-30 (CLOUD-843).perf-pair's two arms are measured sequentially, so concurrent load does not divide out — run it with nothing else in flight. -
perf-assertholds, and a call carrying no response still does less work than--help. -
Shown able to fail per CLOUD-418: restoring the
commandconjunct, and moving the capture after the projection, each turn a named case red.
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- Blockers (§8).
blockedByCLOUD-918 — the store has noStream::Responseand no byte-exact read until it lands, so the security predicate's second half is unassertable before then. Ordered after CLOUD-917 for the fidelity vocabulary this records.relatedToCLOUD-776 (the projection this must leave intact) and CLOUD-777 (the registration this rides, landed — not a blocker).
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In `@crates/batten/src/lib.rs`:
- Around line 3091-3094: Update the absent-response path following
record_absence in the relevant hook handling flow to call
capture::evict_to_budget, matching the normal response capture path. Ensure
absent responses are also constrained by the configured capture budget after
their call row is recorded.
In `@crates/batten/tests/cli.rs`:
- Around line 9781-9786: Update the test assertions around the absence row in
the relevant CLI test to verify that its absent reason equals
capture-response-absent and its fidelity equals unavailable, rather than only
checking field presence. Keep the existing digest assertion and ensure the
absence-row selection targets the row being validated.
- Around line 9645-9649: Update the doctor command invocation in the test to use
the same pinned state home as run_hook_state, ensuring doctor -J inspects the
recorded state under dir rather than the process default state root; preserve
the existing JSON output and assertion flow.
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CLOUD-919's §7 obligations landed short. The capture behaviour was covered by unit tests in `capture.rs` and the reserved-word scan, but four named end-to-end obligations had no test in `tests/cli.rs`, and writing them found a defect the unit tests could not see. ABSENT PRODUCED NO RECORD AT ALL. CLOUD-917 says a post-tool call whose host sends no response member still gets a provenance row carrying `fidelity = Unavailable`; the call site only reached the capture path when the member was present, so absence produced silence. "The host sent nothing" and "no call was ever made" were the same absence — CLOUD-251's collapse on this surface, and exactly what the empty-vs-absent distinction is careful about at the other end. `capture::RESPONSE_ABSENT` is the reason id, and it is deliberately NOT an advisory: five of six harnesses are surveyed `Unavailable`, so pushing a reason id per call would make the ordinary shape look like a fault. The record is the deliverable. Observed red, with the branch dropping the row again: `two calls became 1 row(s)`. THE CLOUD-776 TEST IS RE-SCOPED, NOT DELETED. `no_byte_of_the_result_buffer_is_emitted_or_stored` became false the moment the capture landed, so it is now `..._reaches_stdout_stderr_a_json_document_or_a_receipt`, with the lineage in its doc comment. Five changes, each closing a way it could pass vacuously: a pinned state root, because with none set the bytes went to the AMBIENT root while the assertion searched the fixture and named a place it never looked; a recursive walk, because `read_dir` is one level deep and a nested entry silently emptied the assertion; the `-J` channels it never had (`capture list`, `capture list --calls`, `capture show`, `doctor`); a corrected message; and the capture store excluded BY NAME with everything else under the state root asserted clean, so a later change spraying the bytes into the calls log or a lock file reds it. THE POSITIVE TWIN is what makes that a contract rather than an accident: a build that captured nothing passes every absence assertion. It compares over `Vec<u8>`, never a `String` from a lossy conversion, which would pass over the corruption `--raw` exists to rule out. Observed red with the store handed no bytes: `the replay is not byte-identical to what the host sent`. THE GUARD IS THE RESPONSE MEMBER, NOT THE COMMAND, and a test now says so over the shape that matters: a `Write` payload naming no command. Observed red with CLOUD-776's `!command.is_empty()` conjunct restored on the capture guard — the capture vanishes, which is every structured tool on the hot path. Refs: CLOUD-917, CLOUD-919
…ad store The rest of CLOUD-919's §7 list, over the compiled binary. - ALL THREE ALIASES (`tool_response`, `toolResponse`, `tool_result`) reach the capture, asserted together with the content addressing because the two fail in opposite directions: a missed alias loses a row, a broken digest mints a blob per call. Three calls, one blob, three rows. - AN MCP CONTENT-BLOCK RESPONSE concatenates in host order with no framing interleaved into the bytes — which is what makes byte-identical replay possible at all — and the framing appears in the row instead. Its fidelity token is `decoded-content`, never the reserved word. - A SHAPE THE DECODER CANNOT READ is could-not-look: `fidelity = unavailable`, a reason id, no digest, and no blob. `facts::rows_in`'s own distinction, and the collapse would be silent here because the EMPTY case is a real record of zero bytes. - A STORE THAT CANNOT BE WRITTEN leaves exit 0 and a reason id on the advisory channel, pointer-only. Driven through the state-root seam by planting a regular file where the data dir goes, so `create_dir_all` fails with ENOTDIR for root too — a mode-based fixture would assert its own premise before its conclusion in a sandbox that runs as root (CLOUD-249). One §7 item is NOT met and is not fakeable here: "one case per fidelity value". `LexicalBytes` is unreachable at this call site, since `decode` hands `run_hook` an already-parsed value — recorded on CLOUD-928 — and `SpillFile` and `Prefix` need a host that spills or truncates, which no surveyed host does. Writing a case per value would mean constructing a host behaviour nothing produces and asserting the constructor. `DecodedContent` and `Unavailable` are the two values this surface can reach, and both now have cases. `cross-check` caught what the local run could not: every new helper's callers are unix-gated, so on the Windows triple they are dead code and warnings are denied there. Gated to match, with the reason in the re-scoped test's own doc comment rather than left for the next reader to rediscover. Refs: CLOUD-919
Three review findings on f3e0b95 and 1411feb, all valid. THE ABSENT PATH APPLIED NO BUDGET, and it is the path that needs one most. A capture appends a row and mints a blob, so the blob budget eventually brings the store — and with it the call log — back inside its bound. An absence appends a row and mints nothing, so on a host that sends no response for every post-tool call the log grew with no bound at all, and `next_order` scans it on every later call. That is the CLOUD-851 shape rebuilt on the branch that was fixing it. `doctor -J` RAN AGAINST THE AMBIENT STATE ROOT while the capture wrote to the pinned one, so that channel's assertion could pass over a real leak — the same class as the missing state root the re-scope fixed one level up. THE EMPTY-VS-ABSENT TEST CHECKED KEYS, NOT VALUES. A row carrying a storage-failure reason satisfied "has an `absent` key" while recording the wrong fact about the call, which defeats the point of a reason id: it exists to send a reader to one remedy. Both values are asserted now, plus the absence of a digest. Refs: CLOUD-919
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Closes CLOUD-919.
The capture spine landed in #664, but CLOUD-919's §7 obligations landed short: the behaviour was covered by unit tests in
capture.rsand the reserved-word scan, while four named end-to-end obligations had no test intests/cli.rs. Writing them found a defect the unit tests could not see.Absent produced no record at all
CLOUD-917 says a post-tool call whose host sends no response member still gets a provenance row carrying
fidelity = Unavailable. The call site reached the capture path only when the member was present, so absence produced silence — "the host sent nothing" and "no call was ever made" became the same absence. That is CLOUD-251's collapse on this surface, and exactly what the empty-vs-absent distinction is careful about at the other end.capture::RESPONSE_ABSENTis the reason id. It is deliberately not an advisory: five of six harnesses are surveyedUnavailable, so a reason id pushed at the operator on every such call would make the ordinary shape look like a fault. The record is the deliverable, readable on demand and silent otherwise.The CLOUD-776 test is re-scoped, not deleted
no_byte_of_the_result_buffer_is_emitted_or_storedbecame false the moment the capture landed — the bytes are stored, deliberately. It is now..._reaches_stdout_stderr_a_json_document_or_a_receipt, with the CLOUD-776 → CLOUD-919 lineage in its doc comment. Five changes, each closing a way it could pass vacuously:read_diris one level deep, and a nested entry silently emptied the assertion;-Jchannels it never had —capture list,capture list --calls,capture show,doctor;The positive twin
A build that captured nothing passes every absence assertion, which is what makes the twin the thing that turns absence into a contract. It compares over
Vec<u8>, never aStringfrom a lossy conversion — that would pass over exactly the corruption--rawexists to rule out.Shown able to fail (CLOUD-418), one observed red each
two calls became 1 row(s)the replay is not byte-identical to what the host sent!command.is_empty()conjunct on the capture guarda listed response handle; got:— the capture vanishes, which is every structured tool on the hot pathThe third is why the guard is the response member rather than the command, asserted over the shape that matters: a
Writepayload naming no command.Generated by Claude Code