Port: scope /opencode:cancel default to current Claude session

[JohnnyVicious]

Port of openai/codex-plugin-cc#84 (merged)

Problem

handleCancel in plugins/opencode/scripts/opencode-companion.mjs:520-566 resolves the default target via:

const { job, ambiguous } = resolveCancelableJob(state.jobs ?? [], ref);

And resolveCancelableJob in lib/job-control.mjs:138-144 filters only by status === "running" — it does not filter by sessionId. Consequence: if two Claude sessions are running opencode tasks against the same workspace and the user types /opencode:cancel without a job ID in session A, the cancel can target session B's job — silently killing unrelated work.

Contrast with handleStatus at opencode-companion.mjs:483-490, which already filters by sessionId: getClaudeSessionId().

Fix (from upstream diff)

1. Thread sessionId into resolveCancelableJob:

// lib/job-control.mjs
export function resolveCancelableJob(jobs, ref, opts = {}) {
  const running = jobs.filter((j) => j.status === "running");
  const scoped = opts.sessionId
    ? running.filter((j) => j.sessionId === opts.sessionId)
    : running;

  if (!ref) {
    return { job: scoped[0] ?? null, ambiguous: scoped.length > 1 };
  }
  return matchJobReference(scoped, ref);
}

2. Pass the session ID from handleCancel:

async function handleCancel(argv) {
  const { positional } = parseArgs(argv, {});
  const ref = positional[0];

  const workspace = await resolveWorkspace();
  const state = loadState(workspace);
  const sessionId = getClaudeSessionId();

  const { job, ambiguous } = resolveCancelableJob(state.jobs ?? [], ref, { sessionId });
  // ... rest unchanged ...
}

3. Error message refinement — when a session ID is set but no running jobs match it:

if (!job) {
  if (sessionId) {
    console.log("No active OpenCode jobs to cancel for this session.");
  } else {
    console.log("No active job to cancel.");
  }
  return;
}

Escape hatch

If a user explicitly passes a job ID prefix (/opencode:cancel task-xyz), the existing prefix match should still work across sessions — they asked for it by name. Only the default (no argument) is session-scoped.

Test plan

1. Seed two running jobs with different sessionId values. Call cancel with no ref, asserting only the current-session one is returned.
2. Seed two running jobs in the same session. Assert ambiguous: true.
3. Pass an explicit job ID belonging to another session. Assert the explicit path still finds it.
4. Seed one running job in another session, zero in current. Assert error message mentions "for this session".

Upstream reference

openai/codex-plugin-cc#84 (merged 2026-04-08).

[JohnnyVicious]

Consolidated into #31. Default cancel scoping is a subset of the broader result/cancel session-selection issue.