fix(cursor): keep checkpoint-suffix history intact through pruning and the envelope - #2940
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Included review availability: Your plan provides up to 10 included reviews per hour; 4 remain after this review. 📝 WalkthroughWalkthroughThe change bounds tool-call lookup by full-history position and passes offsets through Cursor checkpoint continuations. It preserves completed checkpoint suffix pairs, accounts for carried roots, tracks output elision, and falls back to full replay when the envelope is exhausted. ChangesCursor continuation replay
Estimated code review effort: 4 (Complex) | ~60 minutes Merge Risk: 🟡 Moderate · up to The change preserves checkpoint-suffix history and improves cumulative envelope handling, but edge cases remain where native tool-call-only continuations can lose checkpoint context, envelope boundaries can trigger unnecessary full replay, and exhausted checkpoints can be retried until expiry. These may cause repeated work or degraded continuation behavior and require owner follow-up or explicit acceptance before merge. Sequence Diagram(s)sequenceDiagram
participant buildPreparedCursorRunRequest
participant rootPromptMessages
participant conversationTurns
participant callBefore
participant CursorModel
buildPreparedCursorRunRequest->>rootPromptMessages: replay checkpoint suffix with offset and carried roots
rootPromptMessages->>callBefore: resolve preceding tool call
buildPreparedCursorRunRequest->>conversationTurns: replay suffix with full-history offset
conversationTurns->>callBefore: resolve preceding tool call
buildPreparedCursorRunRequest->>CursorModel: emit retained suffix or full replay
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Full details: Docstring CoverageExplanation Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 12 functions across 4 files. (1 skipped: 1 unsupported.) Full details: Title checkExplanation The title clearly summarizes the main change: preserving Cursor checkpoint-suffix history during pruning and envelope enforcement. It is specific, concise, and directly related to the pull request objectives.
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리뷰 · 우선순위 76 / 80이 PR은 지금 쉽게 말하면 이렇다. 작성자가 고치는 방법은 새 문을 하나 더 만들지 않는 것이다. #2936 이 이미 넣은 브랜치 역사에는 이미 테스트는 라인 351 - 메인테이너의 판단이 필요한 지점
너의 추천 이 댓글은 grok-bot이 작성했습니다 |
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Inline comments:
In
`@devlog/_plan/260829_cursor_tool_continuation_pairing/050_phase6_native_turn_orphan.md`:
- Around line 183-185: Reconcile the native-turn scope statements in the phase
plan so they describe a single implementation state: either mark the earlier
all-model scope as superseded or update the later discussion to match it, while
preserving the behavior shown by the protobuf request flow where composer-2.5
turn steps remain unnamed when the turn gate is external-only.
In `@tests/cursor-tool-result-invocation.test.ts`:
- Line 491: Update the test around the turn-step lookup so it asserts that the
replay produces a step before inspecting its content, rather than conditionally
skipping validation when step is absent. Preserve the existing content checks
after this required-existence assertion and add the focused regression coverage
alongside the related cursor tool invocation tests.
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devlog/_plan/260829_cursor_tool_continuation_pairing/040_phase5_checkpoint_suffix_gap.mddevlog/_plan/260829_cursor_tool_continuation_pairing/050_phase6_native_turn_orphan.mddevlog/_plan/260829_cursor_tool_continuation_pairing/060_phase7_positional_bound.mddevlog/_plan/260829_cursor_tool_continuation_pairing/070_phase8_checkpoint_suffix_orphan_strip.mdsrc/adapters/cursor/protobuf-request.tstests/cursor-blob.test.tstests/cursor-tool-result-invocation.test.ts
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| test("the turn step is bounded too", () => { | ||
| const step = turnStepTexts(encode(forwardHistory(), "grok-4.6-high")) | ||
| .find(text => text.startsWith("[Tool Result]")); | ||
| if (step) { |
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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
Require the turn-step fixture to exist.
Line 491 lets this test pass when replay emits no [Tool Result] turn step. That is a failure of the exact turn path this test must protect. Assert that step exists before checking its content.
Proposed fix
- if (step) {
- expect(step).not.toContain("invoked:");
- expect(step).not.toContain("echo LATER");
- }
+ expect(step).toBeDefined();
+ expect(step!).not.toContain("invoked:");
+ expect(step!).not.toContain("echo LATER");As per path instructions, tests/** requires a focused regression test near the existing tests for that subsystem.
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Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| if (step) { | |
| expect(step).toBeDefined(); | |
| expect(step!).not.toContain("invoked:"); | |
| expect(step!).not.toContain("echo LATER"); |
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In `@tests/cursor-tool-result-invocation.test.ts` at line 491, Update the test
around the turn-step lookup so it asserts that the replay produces a step before
inspecting its content, rather than conditionally skipping validation when step
is absent. Preserve the existing content checks after this required-existence
assertion and add the focused regression coverage alongside the related cursor
tool invocation tests.
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Inline comments:
In `@src/adapters/cursor/protobuf-request.ts`:
- Around line 364-365: Update the checkpoint suffix budgeting and exhaustion
logic around historyLimit, historyBudget, and the suffix handling near
conversationState so the synthetic default system root is not reserved when
suffixRequest.system is empty; calculate limits only from roots retained in the
assembled request. Preserve suffix-root appending behavior and add
exact-boundary tests for both root-count and byte limits.
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Reviewed exact head 5eedbb3c3159800ec03251a26d07d2671fafb150 against dev@3a9835ca91d34affe97a4028b616d33e86d09d5b.
The Cursor checkpoint-suffix direction is valuable and the live evidence is strong, but this head is not reviewable for merge yet:
-
GitHub reports the branch as conflicted (
mergeable: false,mergeable_state: dirty). It is 15 commits behind currentdevand still carries patch-equivalent predecessor commitsfb56a1a69andc7531ca8a, which already landed through6906049c6andd882caed5. Rebase onto currentdev, drop the duplicated predecessor commits, resolve the overlappingprotobuf-requestchanges, and re-request review on the resulting exact head. The current 1,206-line diff is not the actual incremental patch that would land. -
I independently confirmed the current regression at
tests/cursor-tool-result-invocation.test.ts:488-495can pass without exercising its subject: if no[Tool Result]turn step is emitted,if (step)skips every assertion. Require the step withexpect(step).toBeDefined()and then assert its content. This matters because absence of the step is itself a replay regression. -
Reconcile the contradictory native-turn scope text in
devlog/_plan/260829_cursor_tool_continuation_pairing/050_phase6_native_turn_orphan.md: lines 183-185 say every listed model is affected, while the later section says the external-only gate stays and recordscomposer-2.5as the asymmetry. Mark the earlier design as superseded or rewrite the final state unambiguously so the audit record describes one implementation.
Only hygiene/target checks exist for this conflicted head; there is no exact-head cross-platform test result to rely on. After the rebase and the two bounded test/document fixes, run the focused Cursor suites plus exact-head CI before approval. I am not requesting closure; this remains a strong candidate once the integration state is clean.
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Inline comments:
In `@src/adapters/cursor/protobuf-request.ts`:
- Line 1368: Update the checkpoint validation condition near
suffixRoots.ids.length in the protobuf request handling to apply the
missing-root check only when resultReplayedAsRoot is false. Preserve native
checkpoints whose assistant message contains only a toolCall followed by a
toolResult, and add a cursor/auto regression covering an assistant message with
no text part.
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…phan strip The orphan-strip guard in rootPromptMessages is premised on the replayed history starting where the CONVERSATION starts. That holds for a full replay and not for a checkpoint suffix, which starts at checkpointSuffixStart -- so its first entry is routinely the assistant message whose initiating user turn is inside the checkpoint. The loop read that as an orphan and shifted it off, then the next entry, and kept going: its break fires only once the survivors ARE the active block, so every completed pair was discarded. Measured 2 roots for 1, 2, 3 and 4 pairs in the suffix. Live on cursor/grok-4.6 that meant a growing conversation replayed a constant payload. Three sequential echo commands produced 14 tool executions -- STEP1 and STEP2 seven times each, STEP3 never -- with six was-interrupted narrations and no terminal answer, because the model could not see the output of the command it had just run. Diagnostics showed rawMessages 9,11,13,15,17,19 with rootBlobs pinned at 5. knownCallsOffset already carries the fact the guard was missing: only the checkpoint path passes one, and it passes suffixStart. Naming it suffixContinuesCoveredTurn and skipping the loop when set leaves the #1527 full-replay behaviour and the initiator recovery below it untouched. After the fix the same live run executes each command exactly once, narrates no interrupt, and answers ALLDONE; roots track history at 4, 6, 8, 10. Three assertions added, both mutation directions checked: restoring the unconditional guard turns two red, skipping it unconditionally turns the full-replay orphan case red.
…n the envelope Audit r8 measured two further paths to the same symptom the orphan-strip fix addressed, and both are closed here. The orphan fix was INERT under byte pressure: 8 pairs of 64 KiB results emitted 2 roots with and without it. The keptPrior loop admits complete TURNS, and a turn starts at a user root -- which a checkpoint suffix does not have, by definition. So turnStart walked to 0, the prior block became one all-or-nothing pseudo-turn, the first budget overrun dropped all of it, and the orphan guard never ran. A suffix that continues a covered turn now admits entries individually: 2 -> 15 roots. Root replay is the only channel carrying suffix history -- conversationTurns opens no turn without a user message, measured 0 turns either way -- so this was a total loss. Restored growth then collided with the cumulative envelope guard, which began throwing a non-retryable 400 where the code used to degrade silently: 50 pairs behind 100 checkpoint roots, 10 behind 180, 4 behind 190, plus a cliff at 96 pairs. Suffix pruning now subtracts the checkpoint's own roots and bytes, and a checkpoint with no room left for its suffix is abandoned for a full replay under a new envelope_exhausted reason. Pruning to fit would have emitted the covered prefix and silently dropped every uncovered message, which is this unit's own defect at the top of the range. All three fixtures now stay at 191 roots, no throw, no cliff. Two tests asserted that throw; they assert the bound now, which is stronger -- the assembled request stays inside the envelope AND keeps its uncovered history. Removing the carriedRoots subtraction turns both red, so this is not a weakened expectation. The plan's live figures were recounted against the completed artifacts: 21 and 133 executions for three commands, not 14, and the turn does terminate. The earlier never-terminates claim came from reading a file mid-run and is withdrawn in the doc.
… cover it Re-audit of the previous commit found the load-bearing half of it untested and one live gap left open. Both are closed here. The claim that the two rewritten envelope tests were mutation-checked against the carriedRoots subtraction was wrong. Both exit through the abandon branch -- the count case uses unmeasurable checkpoint roots, the byte case a checkpoint big enough to trip abandonment -- so neither touched the subtraction. Deleting it reintroduced all three throws with the suite still 97/0 green. A new case reaches it: measurable checkpoint roots, a count three below the limit so abandonment does not fire, and a suffix that only fits if pruning knows what the checkpoint spends. M1 now reddens three tests. The abandon threshold also left a live band. Comparing carried bytes against the raw limit kept the checkpoint a few hundred bytes below it while the suffix budget collapsed, silently dropping the newest tool result -- where the old code at least threw. Adding systemBytes moved the band instead of closing it. The decision now reads what pruning actually did. rootPromptMessages returns the source message index of every surviving root plus the indexes whose output truncation elided entirely, and the caller asks whether the message it is continuing from is in the first set and out of the second. Two earlier predicates are recorded in the devlog because each failed differently: matching the result's output text broke on JSON escaping and made every live turn abandon its checkpoint, and matching roles could not tell the result from the narration beside it. outputElided is set at the one place that can produce an answerless root -- the marker-only fallback, and a cut landing before the envelope's output: line. Both shapes were live in the band. Swept 15 positions from 100 KiB below the byte limit to 100 bytes above it: the newest result is present at every one, where five dropped it before. Live turns still resume from their checkpoint, so the predicate costs nothing on ordinary conversations, and the repro still runs each command exactly once and answers ALLDONE.
…isfy it Audit round 3 found the previous commit's predicate correct for external models and wrong for two other cases. Both were measured before changing anything. Native resume models were losing their checkpoint on EVERY tool continuation, including the default cursor/auto. Their result travels in server-side turn state, so echoToolResultInRoot is false and rootPromptMessages emits no toolResult root at all -- asking whether that root survived answers no unconditionally. pendingToolCalls, readPaths and previousWorkspaceUris live only in the checkpoint and full replay does not rebuild them, so this was the unit's own defect relocated to the native path. Measured readPaths 2 -> 0 for auto, composer-2.5-fast and composer-3 while composer-2.5 and grok-4.6 were unaffected, which is exactly the split cursorNeedsExternalToolContinuation draws; the check is gated on it now. Parallel results were protected one at a time. The check read only the last replayed index, and under byte pressure the OLDER results were the ones being emptied -- three calls, one answer, which the code's own comment calls worse than keeping nothing. historyOutputElided already recorded them and nothing read it. The whole trailing run of results is checked now: 628 swept positions went from 10 partial-answer positions to 0. envelope_exhausted reached nothing. It was assigned to a local, so it landed in the debug diagnostic while src/adapters/cursor.ts drops a dead checkpoint by reading request.checkpointInvalidationReason -- the exhausted checkpoint was re-decoded and re-abandoned every turn until TTL. Written back onto the request now, as request-builder.ts already does for every other reason. Three assertions added, each driven red against the implementation it catches. The parallel fixture's 375-byte offset is derived from the sweep, not guessed: it is the one position where a last-index-only check leaves exactly one answer standing.
…aking it Round 3 asked for envelope_exhausted to reach the checkpoint store. The obvious fix -- write the field back onto the request argument, which is what request-builder.ts does -- was implemented in the previous commit and is inert. live-transport.ts prepares a SPREAD COPY of the request, so the write lands on the copy and the outer object src/adapters/cursor.ts reads stays undefined. Measured directly: copy sees envelope_exhausted, outer sees undefined. So the write is removed and the limitation is documented at the site instead. Reaching the store needs the reason threaded back through PreparedCursorRunRequest, a signature change on the shared prepare path that belongs to its own phase. The cost of leaving it is bounded and stated: the checkpoint is re-decoded and re-abandoned each turn until TTL, which is wasted work rather than wrong output. The accompanying test asserted request.checkpointInvalidationReason, which would have passed on the argument while proving nothing about the real path -- the same vacuous coverage round 2 caught. It now asserts what is actually observable: an exhausted checkpoint still assembles a legal full-replay request that carries its own history.
Round 3 gated the result-survival check on cursorNeedsExternalToolContinuation. The abandon condition is a three-way disjunction and only the last term was gated. The middle one -- the suffix produced no history roots at all -- asks the same question, whether a replayed root went missing, so it is equally meaningless for a model whose results never become roots. It fired whenever a native assistant turn was a bare tool call with no narration: no text root, no result root, zero history roots, checkpoint discarded. Measured on that shape, readPaths went 2 -> 0 for auto, composer-1, composer-2.5-fast and composer-3 while composer-2.5 and grok-4.6 were unaffected -- the same split and the same loss as round 3's blocker, one disjunct over. The count-full term stays ungated because it is a real envelope fact independent of who echoes results. The test that let this through was round 3's own: it asserted the native path with narration, so the narration-free shape of that path stayed invisible. It is a cross product now -- four model ids by four assistant shapes (narrated, silent, empty text, whitespace text) -- because that is the axis these bugs keep hiding along. Restoring the ungated disjunct reddens it. Also corrects two counts in the devlog: the four-suite total is 188, not 187, and the three-suite figure is 138 at head rather than the 133 true when written. Both were flagged by the audit; neither matched any commit in the stack.
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historyLimit already subtracted the roots a checkpoint carries, but it was consulted only by the prior-history admission loop. The trailing tool-result block was assembled under byte pressure alone and concatenated with no count check, so for the ordinary checkpoint-continuation shape - empty keptPrior - the payload size was bounded by nothing. truncateToolResultBlob cannot help: it frees bytes, never a root slot. The abandon condition was meant to catch the overflow and tested carried plus system count, which asks whether there is room for ONE more root. A parallel tool-call batch needs active.length of them: 190 carried roots plus a 3-result batch assembled 193 and threw a non-retryable 400, 188 plus 8 threw 196. Reachable by ordinary growth - replaying each turn's state as the next checkpoint, 3 calls per turn died at turn 48 and 5 at turn 32; all shapes now survive 200 turns. Bound active where it is assembled instead of adding a disjunct that must predict the suffix width. Oldest results drop first, matching byte pruning, and one always survives so the abandon check can see the loss through historyMessageIndexes and fall back to a coherent full replay. Sequential fixtures hid this: their trailing run is always length 1, the one width where the old test was exactly right. The parallel sweep used the byte axis, where abandonment fires first. All 188 tests passed with and without the fix; the three new count-by-parallel rows are the first to redden.
The count bound added for the previous round acts on root entries; the abandon check derived its trailing tool-result run from raw messages. Those spaces diverge on the most ordinary assistant shape there is: a bare tool call with no narration emits no root, so two sequentially-executed results become adjacent roots while raw space still separates them. Both results therefore entered the root-space run, the bound dropped the older one, and the raw-space scan saw a run of length one - the newest result, which survived - and reported "kept". The checkpoint was retained and the request went out with a tool call answered by nothing: measured at 190 carried roots, the first answer was in no root and in no turn, with no throw and no diagnostic. The model's only sensible response is to re-issue the call, which is the loop this unit exists to end. rootPromptMessages now reports activeMessageIndexes, the trailing run as pruning saw it, recorded before pruning can shrink it, and the abandon check reads that instead of re-deriving a run it cannot see. It falls back to the raw scan when the field is empty, so full-replay and native shapes keep their behaviour. The drop was also unnecessary. historyLimit subtracted systemEntryCount on a path where the caller appends only ids.slice(suffixSystemCount) and the checkpoint's own system roots already sit inside carriedRoots.count, so one free slot was charged twice: the limit came out 1 where 2 results fit. Mutation evidence: raw-space check 2 red, double charge 1 red, the previous bound removed 5 red. The first silent-loss test passed with the double charge still present, because that defect abandons the checkpoint and a full replay carries every answer - correct output reached wastefully. Pinning it needed a second case asserting the exact root count at exact fit. Also covers outputElided on the marker-only return, which had none: removing the flag left all 191 tests green.
The trailing-result walk tested only for a toolResult role and started at the very end of history. The repetition breaker appends a synthetic [context note] user root after the transcript when the same output repeats three or more times, and that note stands for no message, so it carries no messageIndex. The walk hit it and stopped: activeStart came out equal to history.length, the trailing run was empty, activeMessageIndexes was empty. Two failures followed, both worse than the one the previous commit fixed. The results lost trailing-run status entirely, falling through to prior history where the keep-at-least-one floor does not apply. And the empty field sent the abandon check into its raw-space fallback, the scan the previous commit exists to avoid: at 186 carried roots the note-armed shape was retained where the identical shape without the note correctly abandoned. The trigger is the worst one available. The note arms on three consecutive identical assistant narrations, which is the runaway-repetition shape this unit exists to end. The walk now skips trailing roots with no messageIndex before looking for the result run, and those roots are re-appended afterwards so the note still reaches the model. A root added after pruning must be paid for during pruning: left uncharged, note-armed continuations at 188-190 carried roots threw the non-retryable 400 for sequential and parallel suffixes alike, so syntheticCount and syntheticBytes are charged in the count bound, the prior-history loop and the byte accounting, and the orphan-strip floor counts them so the strip cannot eat into the run. Also drops chargeableSystemBytes. Review found it had no coverage, and no configuration could be found where relaxing the byte budget changes the payload - six crossings in the deciding band were byte-identical either way. Charging system bytes twice only errs conservative. The count relaxation stays; its case reddens without it. Mutation evidence: messageIndex walk 1 red, syntheticCount in the count bound 1 red, note dropped from the payload 1 red, syntheticCount in the prior loop 2 red. The two charges had no failing test at first, which is the same condition the previous round was caught on.
The previous commit re-appended the note into historyEntries before the pruning blocks ran, so each of them had to recognise a tail it could only identify by position. The initiator-recovery block could not: its floor stops when one entry remains, so with [toolResult, note] it counted the note as the survivor and shifted off the result. With one 600 KB result and three identical narrations instead of two, the model received 193 bytes of "take a DIFFERENT action" and no tool output at all. The result had already been truncated to fit; it was deleted anyway. That is the reported symptom exactly - no output, so the model runs the command again - re-entered through the fix for it. A second mechanism compounded it. activeBytes included syntheticBytes while the equal-share divisor did not, so shares summed to the whole budget and adding the note back always exceeded it. The shrink-instead-of-drop pass became structurally unfittable and fell through to deleting a whole result: 246 bytes of note cost a 200 KB answer. Review measured 166 of 432 byte-pressure configurations losing an answer. Rather than add the tail's length to each floor - which works and leaves the next block to find the same trap - the tail is held out of historyEntries until assembly, and every budget is expressed net of it. historyLimitForReal and historyBudgetForReal are computed once, before the first result is measured, so the pruning blocks reason only about real history. An intermediate version that held the tail out without reserving its bytes committed 51 bytes over the limit, which is why the reservation is separate from the hold-out. Also covers the byte reservation, which review found had no test at all while a sweep against its removal threw 148 envelope errors. Mutation evidence: byte reservation 2 red, count reservation 3 red, note dropped 4 red, messageIndex walk 3 red, and the full r12 defect - re-append plus gross budget - 2 red. Re-appending alone is now harmless because the reservation prevents the loss by itself.
…r it The reservation was a subtraction clamped at zero while the append was unconditional, and those are compatible only while the difference is non-negative. Below that the clamp reports that the note costs nothing, every pruning block correctly reasons about a budget of zero and emits nothing, and the note is appended regardless - so the payload lands over the limit by exactly the deficit the clamp erased. With 26 bytes free and a 246-byte note: 220 bytes over, non-retryable 400. Holding the tail out of historyEntries is what made it unrecoverable, since no block below could see it to charge it. Every fixture missed this because the exposed shape is a turn that does not end in a tool result. With a trailing result the abandon check's survival disjuncts rescue the turn; on a plain user interjection they structurally cannot. Across 42 carried-byte positions: 13 throws with the note armed, none without, all on the interjection tail. Affordability is now decided before the reservation, and an unaffordable note is dropped - this unit's own priority order, since a missing instruction is recoverable and a missing tool result restarts the loop. The first version of that test also required a free root slot. It could not be made to matter: 60 boundary positions at and past the root limit behaved identically either way, because the count bound already stops at one surviving result. Removed rather than shipped, for the same reason chargeableSystemBytes was - an envelope condition that cannot fail is indistinguishable from one that is wrong. Also corrects one activeBytes gate that read the gross budget while its body wrote the net one. No behavioural difference, but it is the drift that seeded two earlier rounds. Mutation evidence: affordability removed 3 red, tail appended regardless 3 red.
The previous commit dropped it as inert, reasoning that the count bound below always leaves a slot free because it keeps one result. That holds for every value of historyLimit except 1, where the one free slot is precisely the one the surviving result takes. The note was then judged affordable on bytes alone, the reservation clamped to zero, and the append pushed full replay to 193 roots: four armed-only envelope throws at 191 system prompts, across both tails and both suffix widths, where the same request without the note assembled 192 and succeeded. Full replay has no abandon branch to rescue it. The sweep that supported "inert" varied carried roots on the checkpoint path, where the count-full disjunct abandons long before historyLimit can reach 1. The reachable route is full replay with many system prompts - a different axis. Inert across 60 positions was a true statement about the wrong sixty. Also closes a coverage gap review found in the same area: the affordability check was pinned at the append site only. Neutering syntheticCount and syntheticBytes while leaving the append gated left the suite green, because asserting on the assembled payload cannot separate "the deficit was charged" from "the tail was not appended". Asserting the exact root count at the boundary separates them. Mutation evidence: count conjunct 4 red, byte conjunct 3 red, reservation neutered 6 red, append ungated 7 red.
Review found the bound was only constrained from the loose direction: relaxing historyLimit - syntheticCountRaw >= 1 reddens four cases, but tightening it to >= 2 left all 212 green. Over-conservative is safer than over-eager, but a suite that cannot tell a correct bound from an unnecessarily strict one is the gap that cost the previous round. Two free slots is the tight case - the result takes one, the note takes the other - and the new case asserts both arrive at exactly 192 roots. Relaxing the bound now reddens 4, tightening it reddens 1. Also corrects the record. The previous commit message claimed the reservation had been pinned at the append site only, and that neutering syntheticCount and syntheticBytes left the suite green. On the parent that mutation already reddens 6, all pre-existing cases from earlier rounds. The count-conjunct finding stands on its own evidence; that secondary claim did not. The devlog records the remaining known gap: on the extreme byte axis a ~523 KB system prompt can keep the note while the result truncates to a marker, inverting this unit's priority order. Identical on the parent and far worse on dev, so pre-existing and improved here, but a genuine follow-up.
The eight-phase Cursor tool-continuation unit is finished and its work is visible in public git history: the last phase landed on dev as 62df78d (PR #2940). AGENTS.md puts a unit in _fin once a terminal outcome is recorded and the work it describes is already public, so the unit moves there rather than staying an open plan. 070 gains a Terminal outcome section naming the merge commit, the post-merge remote gate at that commit (exit 0, 16359 pass / 0 fail / 16 skip, so the landed tree is verified and not only the pre-merge head), the round 11 PASS verdict with the two notes it left, and the three items scoped out on purpose - the inert envelope_exhausted propagation, the extreme-byte-axis note ordering, and composer-2.5's hybrid root count, each pre-existing rather than introduced here. No source, build, typecheck or test path reads devlog/, so this changes no runtime behaviour.
2 participants
Summary
Cursor-routed models re-ran the same tool instead of reading its output. Three sequential
echocommands throughcursor/grok-4.6produced 21 tool executions in one live run and 133 in another, with repeated "STEP1 was interrupted" narration and no terminal answer. The checkpoint path collapsed a growing history suffix into a constant payload: 1, 2, 3 and 4 completed call/result pairs all reached the model as the same 2 root blobs, so the model never saw the result of the command it had just run and issued it again.The fix restores the suffix and then keeps the envelope arithmetic honest, which is where the work actually went. Eleven independent audit rounds ran against this branch; the first ten each found a genuine blocker, six of them introduced by the previous round's own fix. The through-line, recorded in the devlog: each fix added a fact to the pruning code without asking which existing block already assumed that fact absent.
What changed, in
src/adapters/cursor/protobuf-request.ts:historyMessageIndexes,historyOutputElided) rather than what it was asked to produce, with a newenvelope_exhaustedreason.activeMessageIndexesnow reports the run as pruning saw it.Verification
Remote gate at the exact head
0340d1759(Linux, full suite):bun x tsc --noEmit0,bun run testexit 0, 16323 pass / 0 fail / 16 skip. CI green at the head on Linux, Windows and macOS.Focused: 213 pass / 0 fail across
cursor-blob,cursor-tool-result-invocation,cursor-tool-continuation,cursor-request-builder(127 incursor-blob).bun run privacy:scanpassed.Live end-to-end on an isolated proxy with a scratch
OPENCODEX_HOME,cursor/grok-4.6, three sequential shell commands: before, 21 executions and no terminal answer; after, 3 commands with one execution each, 0 interrupts, terminalALLDONE, and diagnostics showing root blobs growing 3/4 → 5/6 → 7/8 → 9/10 with the last three turns incheckpointmode.Every production hunk is mutation-verified in isolation, so no assertion is vacuous:
carriedRootssubtraction removednoHistoryRootsdisjunct ungatedmessageIndexwalk removedhistoryEntries+ gross budgetSweeps at this head: 1440-case call-answer invariant across narrated, bare-call, whitespace-text and parallel shapes; 896 note-armed configurations crossed with count and byte pressure; 672-case orphan check; 224-case count sweep; 150 zero-budget boundary cases; 78-position count-by-parallel grid; 42 deficit positions; 5040 checkpoint configurations and a 200-turn feedback-growth simulation from the independent reviewer. Zero envelope overruns, zero orphaned calls, zero lost newest results, zero throws.
Attribution against base
devon identical grids:devloses the newest answer in 372 positions and this head in 232; on a 108-case byte griddevloses 72 answers and throws 24 times where this head loses 4 and throws 0.Two known items are deliberately out of scope and recorded in the devlog:
envelope_exhaustedis not propagated to the checkpoint store (live-transport.tsprepares a spread copy, so writing it here is provably inert — it needs a signature change on the shared prepare path), and on the extreme byte axis a ~523 KB system prompt can keep the note while the result truncates to a marker. That band is identical on the parent commit and far worse ondev, so it is pre-existing and improved here rather than introduced.Checklist
No auth, credential, workflow, or release-automation surface is touched.
devlog/_plan/260829_cursor_tool_continuation_pairing/070_phase8_checkpoint_suffix_orphan_strip.mdrecords all eleven rounds, including the two guards dropped as inert — one correctly, one wrongly and restored.