Fix OpenCode free-tier one-shots with temporary sessions

[devin-ai-integration]

Closes #702
Fixes OR-549.

Summary

• Run shared V2 one-shots through temporary sessions so free-tier models can generate titles, starter prompts, skill screening and compaction summaries. Preserve sessionless compatibility only when older servers lack the session routes.
• Preserve provider/session error explanations and clean up known sessions after success, failure or generation timeout, with a separate two-second cleanup deadline.
• Continue @cpa01cmz-beep’s Run OpenCode one-shots through a session so free-tier models work #703 from exact head 70511760093de1b8456f00b9c4bd10ca1474daec, preserving the original commit and author. Original PR remains open.

Merge policy: preserve imported contributor history with a merge commit; do not squash or rebase. No merge authorized.

Test plan

• Reproduced on unmodified main 6285fee7 on Ubuntu 22.04.5 x86_64 with genuine OpenCode v2.0.32 and opencode/nemotron-3.5-super-vl-free: live dashboard chat succeeds, skill-import screening returns the reported 503.
• Latest head 915071862de0748ecfdd74699da74969847397ea: 15 focused V2 tests; full Rust suite (1113 unit and 18 integration tests passed, 3 ignored); formatting, all-target clippy with warnings denied, and style lint. Full-suite execution isolates test Git configuration from VM identity/URL rewriting without changing commit configuration.
• Independent fresh-context scope review: YES. Greptile: 5/5, no findings. CI: 8 passed, 0 failed, 9 skipped on latest head.
• Rebuilt latest head and repeated real-agent Linux workflow in a fresh dev-slot: exact-model CLI preflight and live dashboard reply, then official skill-creator installation and Skills Refresh while recording. A fresh screening decision completed during recording; no 503 or screening error in fresh backend log.
• Freshly fetched main is an ancestor; PR is conflict-free. Original contributor head and author remain preserved.

The skill received a legitimate false/excluded classification, not an accepted import. The persisted decision matched its genuine metadata digest. Older-server fallback, timeout/error cleanup and other one-shot callers are covered by regression tests/code review, not independent live UI runs.

Recordings

Bug reproduction on main — Linux

Post-fix functionality — Linux

Human review

Yes. The shared harness serves several background operations and retains older-server fallbacks; Daniel Kim has the closest surrounding implementation history. Leave open for review and explicit merge approval.

Automation improvements

• OpenCode was initially absent: add optional runtime instructions for official @opencode/cli@2.0.32 installation and exact-model live preflight for OpenCode issues. Blueprint write permission was unavailable, so this remains a recommendation.

Link to Devin session: https://app.devin.ai/sessions/c58486dd1dfe40bcaf8c08954ccdcfc3
Open in Devin Desktop: https://app.devin.ai/desktop/session/c58486dd1dfe40bcaf8c08954ccdcfc3?variant=devin

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; the previous error-reporting issue is fixed.

Summary

Runs V2 one-shot requests through temporary sessions so free-tier models can answer.

• OpenCode V2 one-shots generate text through temporary sessions.

The previous finding is fixed. No new issues were found. Tests were not run during this review.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[One-shot request] --> B[Create temporary session]
  B -->|Created| C[Generate through session]
  B -->|Route missing| D[Use sessionless route]
  C -->|Route missing| D
  C -->|Reply or error| E[Attempt cleanup]
  D --> E
  B -->|Other error| F[Return error explanation]
  E --> G[Return reply or error]

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_{Reviews (2) · Last reviewed commit: "Preserve OpenCode session creation error..." · Reviewed by Greptile}

[devin-ai-integration]

@greptileai Please review latest head 915071862de0748ecfdd74699da74969847397ea. Session creation now uses the shared response decoder to preserve server error explanations, with a regression test for non-404 creation failures.