fix(opencode): forking an earlier turn while the thread runs no longer fails by nkoynov · Pull Request #19986 · pingdotgg/t3code

nkoynov · 2026-10-15T18:47:21Z

Forking an earlier completed OpenCode turn failed whenever a later source turn was running. Retrying the fork kept failing until the source finished.

The adapter now forks at the earliest eligible exclusive native history boundary when the prefix is settled. It refreshes observed turns between attempts and waits up to one minute for a safe boundary, then gives actionable retry advice. A stalled history read respects that budget; a native fork already in progress can finish. Budget exhaustion settles the turn immediately instead of repeating the wait through worker retries. Retained reports from older autonomous executions cannot cut away the selected turn. Rollback keeps its existing busy guard.

Continues @nkoynov's work in #19986, preserving the contributor commits and merging current main.

Verification:

Replaced the PR's 6 test declarations / 8 cases with 5 declarations / 6 cases in the existing adapter suite. Main rejects the safe busy fork in the regression check. Added one parameterized service test (two cases) for terminal budget exhaustion versus transient retry. Final suites: 103 adapter and 31 service cases passed; seven focused OpenCode package cases passed.
Scoped server, provider-core, and OpenCode typechecks, targeted lint, formatting, and diff checks passed. After merging newer main, the full PR diff remained byte-identical to the reviewed diff and all 134 service/adapter cases passed again.
Independent full-PR reviews: round 1 found repeated wait budgets and report-boundary ordering; both fixed with regression coverage. Round 2: Sol and Opus returned no confirmed blockers.
Linux web app with actual OpenCode 2.0.29 and an isolated local model endpoint: first source turn completed; later source turn held running; fork of the first turn replied before releasing the source. Read-only native history confirmed the fork preserved the first turn and excluded the later source prompt. The source completed normally after release.
The hard wait and held native fork are covered with controlled response gates and TestClock, without test sleeps.

After: fork replies while the source remains running.

8-second fork flow recording

Before: exact main adapter rejects the same completed-turn fork while the source runs.

Limits: Stop during a waiting fork does not cancel the existing start effect; if the source becomes safe afterward, an unused native fork can remain. This pre-existing cancellation race has a longer window during the bounded wait and was identified by code review, not reproduced live. No real model account, autonomous background-report delivery, remote/relay, macOS, Windows, iOS, Android, or Electron desktop verification. Four simultaneous waiting forks can occupy the existing four effect workers for that minute. The one-minute budget covers inspection and retries after source-gate admission; it does not preempt an operation already holding that gate or a native fork/setup already started. Existing user-prompt cuts inside an autonomous execution and unselected whole-history forks retain their prior behavior. Human review of the concurrency change remains required.

Implemented with Codex GPT-6.1-Sol in T3 Code; tests with Codex GPT-6-Astra; adversarial reviews with Claude Opus 5.5 and Codex GPT-6-Sol.

macroscopeapp · 2026-10-15T18:51:00Z

Approvability

Verdict: Needs Human Approval

Macroscope's review found this PR not approvable — This production change introduces nontrivial history and concurrency handling for forks, including waiting and retry behavior. An unresolved high-severity finding identifies a concrete case where a selected turn and intervening history may be silently omitted.

Needs human approval because:

1 blocking correctness issue found at or above your repo's Minimum Blocking Severity

^{Adjust the Minimum Blocking Severity for this repo — including turning it Off — in Settings. You can add or adjust custom eligibility rules. Learn more.}

coderabbitai · 2026-10-15T18:52:51Z

No actionable comments were generated in the recent review. 🎉

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Reviewing files that changed from the base of the PR and between 022ae59 and 9d23379.

📒 Files selected for processing: 3

apps/server/src/orchestration-v2/Adapters/OpenCode2AdapterV2.test.ts
packages/provider-opencode/src/server/v2/adapter.ts
packages/provider-opencode/src/testing.ts

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📝 Walkthrough

The OpenCode 2 adapter waits for a safe history boundary when a source session is active. It can fork before an active turn’s prompt or report. If the source does not become safe within one minute, the adapter returns OPENCODE_2_FORK_SOURCE_RUNNING. Rollback still rejects active sessions.

Changes: Forking active OpenCode sessions

Layer / File(s)	Summary
Activity and history checks `packages/provider-opencode/src/server/v2/adapter.ts`	The adapter separates working-state checks from rollback rejection. It adds helpers to retrieve session history and identify user and synthetic cut points.
Fork boundary selection `packages/provider-opencode/src/server/v2/adapter.ts`, `apps/server/src/orchestration-v2/Adapters/OpenCode2AdapterV2.test.ts`	The adapter combines supplied and observed turns to select a safe prompt or report boundary. Tests cover completed turns, report boundaries, and history refreshed after an execution ends.
Wait and timeout behavior `packages/provider-opencode/src/server/v2/adapter.ts`, `packages/provider-opencode/src/testing.ts`, `apps/server/src/orchestration-v2/Adapters/OpenCode2AdapterV2.test.ts`	Fork attempts retry under the source-thread gate for up to one minute. The adapter exposes a timeout error. Tests cover delayed forks, server-reported activity, and timeout behavior.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant Caller
  participant OpenCode2Adapter
  participant OpenCodeServer
  Caller->>OpenCode2Adapter: Request fork
  OpenCode2Adapter->>OpenCodeServer: Check source activity and retrieve history
  loop Until the boundary is safe or the wait limit expires
    OpenCode2Adapter->>OpenCodeServer: Refresh activity and history
  end
  OpenCode2Adapter->>OpenCodeServer: Fork at the selected boundary
  OpenCodeServer-->>OpenCode2Adapter: Return forked session
  OpenCode2Adapter-->>Caller: Return session or timeout error

Suggested reviewers: juliusmarminge

Merge Risk: 🔵 Low · up to 9d233

A fork may take longer than one minute to report that its source is still running if a history request stalls. This is a bounded merge risk rather than a reason to block the change.

Security architecture risk: 🔵 Low · up to 9d233

The change preserves existing ownership and permission handling while allowing earlier completed work to be forked during later activity. No new access-control weakness was established, but concurrent-fork safety depends on history and snapshot guarantees that could not be independently verified.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

inferred — The changed operation affects the selected source conversation and the newly created target session, including copied conversation state and target permission/location setup. The inspected change does not demonstrate broader tenant, credential, or infrastructure authority.

Trust Boundaries and Controls

inferred — The local source-session gate is not an atomic synchronization boundary with externally initiated OpenCode execution. The activity predicate can rely on local state for a settled loaded session. That predicate and the check-to-fork race already exist in the base, so the race is not established as a new PR security concern.

Resilience and Maintainability Implications

observed — Native creation, local registration, permission updates, and worktree movement remain a multi-step sequence without compensating native-session deletion in the inspected fork block. Failure after creation can leave partial state, but this recovery limitation predates the PR; unsafe polling does not repeat that side-effecting sequence.

Hardening Proposals

proposed — Establish a versioned provider contract or live integration check for strict prefix copying during concurrent execution, history ordering across pagination, and idle finality. This would validate the newly relied-upon safety boundary rather than treating replay fixtures as proof of provider behavior.

Pre-merge checks: 4

Check name	Status	Explanation
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Title check		The title is concise, specific, and accurately describes the main change: allowing forks of earlier OpenCode turns while a later turn runs.
Description check		The description clearly explains the problem, implementation, verification results, limitations, and testing scope. It links the related pull request, but it does not explicitly identify maintainer ap…

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Explanation

The description clearly explains the problem, implementation, verification results, limitations, and testing scope. It links the related pull request, but it does not explicitly identify maintainer approval or explain why the change qualifies without prior approval.

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Inline comments:
Review comments at @packages/provider-opencode/src/server/v2/adapter.ts:
- Around line 4512-4515: Update the polling flow around Effect.repeat and
Schedule.upTo so FORK_WAIT bounds the polling phase even when an isWorking or
historyOf attempt runs past the schedule limit. Apply the deadline after
session.fork completes, preserving the guarantee that an in-progress
session.fork call is not interrupted.

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Reviewing files that changed from the base of the PR and between 3ff452b and 022ae59.

📒 Files selected for processing: 3

apps/server/src/orchestration-v2/Adapters/OpenCode2AdapterV2.test.ts
packages/provider-opencode/src/server/v2/adapter.ts
packages/provider-opencode/src/testing.ts

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A fork's first turn failed with "Cannot fork OpenCode session ... while it is still working" whenever the source thread was running a newer turn, and every retry failed the same way. OpenCode copies only the history before the fork's cut. When the cut is the prompt of a turn after the forked one (or the report a continuation answers) and every execution before it has ended (an `idle` item follows its last output), nothing the running turn writes can reach the fork, so it forks right away. Otherwise it waits up to a minute for the source to go quiet, re-reading the turns, and then says the source is still running and to send the message again. Claude Opus 5.5 in OpenCode

juliusmarminge · 2026-10-19T03:58:01Z

Taking over this one. I will verify the running-thread fork boundary, reduce the tests to the distinct behaviors, and rebuild the waiting path before pushing back here.

…ork-busy-opencode-thread

t3dotgg · 2026-11-12T10:14:54Z

Note

🤖 Claude Opus 5.5 responding on behalf of Theo

Closing. This PR conflicts with main in 5 files, which is more than we will review as a rebase. If the change still matters, open a fresh PR from current main.

github-actions Bot added vouch:unvouched Author is not yet trusted in the VOUCHED list. size:L 100-499 changed lines (additions + deletions). labels Oct 15, 2026

macroscopeapp Bot reviewed Oct 15, 2026

View reviewed changes

Comment thread packages/provider-opencode/src/server/v2/adapter.ts Resolved

coderabbitai Bot reviewed Oct 15, 2026

View reviewed changes

Comment thread packages/provider-opencode/src/server/v2/adapter.ts Resolved

nkoynov force-pushed the fix/fork-busy-opencode-thread branch from 022ae59 to 9d23379 Compare October 16, 2026 06:09

juliusmarminge self-assigned this Oct 19, 2026

juliusmarminge added 6 commits October 19, 2026 03:58

Merge remote-tracking branch 'refs/remotes/op17-main/main' into fix/f…

a03429e

…ork-busy-opencode-thread

test(opencode): tighten busy thread fork regressions

e35c1d9

fix(opencode): bound busy fork reads and preserve selected history

069ed06

test(opencode): cover fork retry and wake boundaries

6508ebe

fix(opencode): settle exhausted forks and use earliest boundary

74f42f5

Merge remote-tracking branch 'refs/remotes/op17-main/main' into fix/f…

92017c0

…ork-busy-opencode-thread

juliusmarminge changed the title ~~fix(server): forking a running OpenCode thread no longer fails~~ fix(opencode): forking an earlier turn while the thread runs no longer fails Oct 19, 2026

ImBIOS mentioned this pull request Oct 23, 2026

fix(opencode): actionable error when a session outgrows the model window #23908

Open

t3dotgg closed this Nov 12, 2026

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fix(opencode): forking an earlier turn while the thread runs no longer fails - #19986

fix(opencode): forking an earlier turn while the thread runs no longer fails#19986
nkoynov wants to merge 7 commits into
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nkoynov:fix/fork-busy-opencode-thread

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