Swarm-review follow-ups for the #76 execution layer: security hardening, Windows shims, correctness nits, named test gaps #88

Summary

Consolidated follow-ups from the six-leg swarm review of the #76 final head (6347d1a) — full report + per-finding dispositions on #76. Related: #67–#84 (delivery), PR #85 + #86 + #87 (already-remediated findings), #71 (the capability-registry direction several of these feed).

Security

• S1 (HIGH) — repo-weaponization threat model is undocumented and the opencode permission-abort boundary is event-driven, not policy-enforced. An owned opencode serve runs with cwd = target repo + full process.env; opencode merges the project's opencode.json, so a malicious repo can ship {"permission":{"bash":"allow"}} (no permission.updated event ever fires → the adapter's abort never trips) and hostile mcp entries, while AGENTS.md content flows into the worker prompt. claude/codex workers analogously inherit the repo's .claude/settings.json under the user's trust posture. Options: pin a serve-time restrictive permission policy for owned servers (e.g. --permission scoped to edit-only within the cwd), or document the "ak run only in repos you trust with full user privileges" contract in ADR-0018 + run help. (src/lib/execution/opencode.mjs:158,258-262,285-287)
• S2 (MED) — port-reservation TOCTOU can hand a rogue local process the per-run Basic credential, the full worker prompt, and the ability to fabricate terminal SSE evidence. Probe-bind-close-rebind (defaultReservePort) races under maxConcurrent. Harden: watch child.exitCode during waitForHealth, or serve --port 0 and parse the bound port from child stdout. (src/lib/execution/opencode.mjs:21-30,122-133,255-258)
• S3 (LOW) — SSE per-line buffer is unbounded (memory-DoS amplifier; owned-server context). Cap like the 256 KB subprocess cap. (opencode.mjs:167-169)

Execution correctness

• Windows shim-awareness gap in the execution layer (two reviewers converged): resolveShim (PATHEXT-aware) is used by have() but never exported or applied at launch; bare spawnFn('claude'|'codex'|'opencode') and 'codex' missing from CMD_SHIMS. Windows: readiness passes, launch ENOENTs. Fix: export + apply in subprocess/opencode launch paths, add codex to CMD_SHIMS, add a win32 spawn assertion. (src/lib/exec.mjs:21-38, subprocess.mjs:99, opencode.mjs:258)
• maxTurns is silently dropped by ak run — templates carry per-node caps (6–15) that claude-flow-codex dual honored; no execution adapter reads them. Translate to --max-turns in claude/codex argumentsFor (opencode has no equivalent — document) or drop the field. (routing.mjs:398-424,452)
• $-pattern substitution corrupts the opencode worker prompt — template.replace('{{task}}', worker.prompt) treats $& $` $' as metachars. Use replacer functions. (opencode.mjs:72)
• --timeout has no upper bound — values >2³¹−1 ms are clamped by Node to ~1 ms, turning a huge timeout into an instant timeout for every worker. Cap in positiveInt. (run.mjs:37-41)
• Persisted dualRouting is never validated at load — a hand-edited kit.json with {model:123} crashes plan printing far from the cause. Schema-check in buildRunPlan. (run.mjs, routing.mjs)
• cancel/cleanup HTTP is unbounded — /abort + /instance/dispose have no timeout (a wedged server hangs the runner's timeout branch). Same class as court B4 (launch-phase fetches); fix together. (opencode.mjs:299,307)
• No construction invariant tying canRouteActivities hosts to EXECUTION_ADAPTERS keys — a routable host with no execution adapter loads, validates, and materializes, then every worker fails cli_unavailable at runtime. Same failure class as court A3, one axis over; exactly Architecture: capability-driven host, provider, binding, and observability adapters #71's trap. (execution/adapters.mjs:7-11)

Test coverage gaps (verified — each names the missing assertion)

• Session-isolation: foreign sessionID SSE events must be ignored (currently untested — deleting the filter terminates on any session's idle). (opencode-execution.test.mjs)
• Plan-validation guards: duplicate id / unknown dep / self-dep / bad maxConcurrent / dependency-cycle throw. (execution-runner.test.mjs)
• Materialization capability gate: "cannot materialize… requires canRouteActivities". (routing.test.mjs)
• Readiness-false → cli_unavailable path. (runner suites)
• KILL-fallback signal assertion (['SIGTERM','SIGKILL'], not just the orphan verdict). (opencode-execution.test.mjs:120-137)
• Smaller: auth_required/cancelled categories, session.error mapping, SSE multi-chunk splits, run.mjs exit-1/2 paths, schema type rejections + frozen immutability.

Docs/migration notes (LOW)

• Dyadic projection layer (HOST_PROVIDER duplicated in two places, swapHostModel is two-host-only) — fold into Architecture: capability-driven host, provider, binding, and observability adapters #71's redesign rather than patch.
• Downgrade note landed via PR docs(swarm-review): three coherence nits from the #76 swarm documentation review #87 (opencode routes need the current release). --parallel is silently dropped on ak run (informational).

Acceptance

• S1 disposition: policy pinned for owned servers, or the trust contract documented (ADR-0018 + run help).
• S2/S3 hardening landed.
• Windows shim path fixed + asserted.
• maxTurns / $-prompt / timeout-clamp / dualRouting-load-validation / cancel-cleanup bounds fixed.
• Execution-adapter construction invariant added.
• Named test gaps filled.