fix(server): isolate rejected parallel history reads

[reachjalil]

Problem

The V1 session proxy starts an upstream history read alongside its workspace-ownership proof. If the upstream transport rejects while that proof is still pending, the read has no rejection observer yet. This produces an unhandled rejection instead of keeping the failure scoped to the request. The concurrency path was introduced in #5075.

Change

• Observe the upstream rejection immediately while retaining the original promise and its eventual error.
• Continue withholding the response until workspace ownership is verified; foreign sessions remain inaccessible.
• Preserve parallel reads, cancellation, and the existing scoped error response. No global exception suppression, additional retries, UI changes, or persistence changes.
• Add four regression cases covering both V1 proxy mounts and owned/foreign sessions in the existing proxy test file.

The production change is one rejection observer plus an explanatory comment.

Validation

Focused local proxy checks: passed with Bun 1.3.14, synthetic workspaces, and a local mock engine:

corepack pnpm --package=bun@1.3.14 dlx bun --conditions=development test apps/server/src/opencode-proxy.e2e.test.ts --test-name-pattern "history transport rejection|v1 session reads dispatch|v1 history disconnect"

• Final candidate on current dev: 7 passed, 0 failed, 20 filtered out; 44 assertions.
• The four new cases failed before the fix, with four unhandled transport-rejection errors.
• Fixed cases assert no unhandled rejection, pending ownership still withholding the response, request-scoped 502 for the owned session, 404 for the foreign session, and healthy /health responses.
• Existing adjacent tests cover foreign-body withholding and V1 disconnect cancellation.
• git diff --check passed.

Scope and limitations

Hosted Web end-to-end proof is incomplete: no browser/Daytona run or deployment verification. The reproduced rejection bug is fixed, but it is not confirmed as the cause of a particular live outage. The test observes unhandled rejections in the test process; it is not proof of default-runtime process termination.

This does not change V2 routing, conversation storage/expiration, sandbox lifecycle, or frontend history-recovery behavior. No visual change; screenshots are not applicable.

[vercel]

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4 Skipped Deployments

Project	Deployment	Actions	Updated
openwork-app	Skipped		Sep 17, 2026 5:17pm UTC
openwork-den	Skipped		Sep 17, 2026 5:17pm UTC
openwork-diagnostics	Skipped		Sep 17, 2026 5:17pm UTC
openwork-landing	Skipped	v0	Sep 17, 2026 5:17pm UTC

[github-actions]

Selected evidence: Incomplete · 12/12 tests · 18/18 assertions · 8 images

Commit 845ed9f0bebebd90eb3aa38517dea371efe1e60a · selected evidence
Required verification is reported separately by the current-head Required verification check.

Open review report

Coverage gaps: Required verification: incomplete. Selected evidence does not satisfy all required specs. No authenticated current-head required plan is available.