refactor(opencode): optimize doom loop detection, summary debounce, parallel plugin events

[AndresCdo]

Issue for this PR

Closes #20302

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Three targeted performance optimizations in the session processing loop:

1. In-memory doom loop detection (session/processor.ts)

Replaces MessageV2.parts(ctx.assistantMessage.id) database call with an in-memory toolCallHistory array tracked in ProcessorContext. The doom loop check already has all the data it needs from the streaming event handler — no need to re-query the database on every tool call.

2. Summary debounce (session/processor.ts)

Runs SessionSummary.summarize() only on the first step of a session. Subsequent steps produce summaries that overwrite the first one with no additional value, wasting CPU and I/O on redundant summary computation.

3. Parallel plugin event handlers (plugin/index.ts)

Replaces sequential for loop with Effect.forEach({ concurrency: "unbounded" }) so slow plugin event handlers don't block the main event stream. Each handler runs in a forked fiber with error isolation via Effect.tryPromise.

How did you verify your code works?

• bun typecheck passes (zero errors in changed files)
• Changes are surgical: +30/-15 lines across 2 files
• Doom loop: same logic, different data source (in-memory vs DB)
• Summary: first step behavior unchanged, subsequent steps skip redundant work
• Plugin handlers: same input, parallel execution with error isolation
• No API changes, no breaking changes

Screenshots / recordings

Not a UI change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Hey! Your PR title perf(opencode): optimize doom loop detection, summary debounce, parallel plugin events doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential Duplicate Found

PR #20288 - refactor(opencode): optimize session loop with message cache, tool cache, doom loop, summary debounce
#20288

Why they're related:

• Both PRs address doom loop detection optimization and summary debounce in the session processing loop
• PR refactor(opencode): optimize session loop with message cache, tool cache, doom loop, summary debounce #20288 appears to be a related refactor that includes similar performance optimizations (message cache, tool cache, doom loop, summary debounce)
• These PRs may be implementing overlapping or conflicting changes to the same code areas

Recommendation: Check PR #20288 to verify if it's addressing the same issue #20302 or if the changes overlap before merging.

[AndresCdo]

Re: duplicate flag from bot

PR #20288 and this PR (#20303) are not duplicates — they target different code structures:

• PR refactor(opencode): optimize session loop with message cache, tool cache, doom loop, summary debounce #20288 (perf/session-loop-optimizations) was branched from an earlier version of dev before the Effect refactoring. It modifies the old Instance.state pattern in prompt.ts with message/tool caching.

• PR refactor(opencode): optimize doom loop detection, summary debounce, parallel plugin events #20303 (perf/doom-loop-summary-plugin) is branched from the current dev (post-effectification). It modifies the new Effect-based ProcessorContext in processor.ts and the Stream.runForEach in plugin/index.ts.

File overlap analysis:

• session/prompt.ts: PR refactor(opencode): optimize session loop with message cache, tool cache, doom loop, summary debounce #20288 adds message/tool cache. PR refactor(opencode): optimize doom loop detection, summary debounce, parallel plugin events #20303 has no changes.
• session/processor.ts: PR refactor(opencode): optimize session loop with message cache, tool cache, doom loop, summary debounce #20288 has no changes (old code). PR refactor(opencode): optimize doom loop detection, summary debounce, parallel plugin events #20303 adds doom loop in-memory and summary debounce.
• plugin/index.ts: Both add parallel hooks but on different code bases (old vs new Effect code).

The changes are complementary and non-conflicting. If both are merged, PR #20288 would need to be rebased onto current dev to apply the message/tool cache to the Effect-based code.