Ephemeral previews: capture the worktree diff, guard the silent tool-loop exit, withhold web_search on confined runs

[Evanfeenstra]

Problem

propose_code_change preview runs (Hive → /repo/agent with ephemeral: true) were returning completed with the model's narration as the answer and no diff, even though the edit had landed in the worktree. Confirmed from repo2graph.sphinx logs on swarm38, 2026-09-15.

Root cause chain:

1. The Bifrost gateway rewrites the web_search_20250305 server tool to a newer version on the way to Anthropic (acknowledged by a Bifrost dev on Discord, 2026-07-07: "tool version is the difference").
2. With the newer web tools the API implicitly offers code_execution; Sonnet answered with a server_tool_use for it (text-editor str_replace).
3. @ai-sdk/anthropic only tolerates that when it sent web_search_20260209 itself, so ai marked the call invalid and emitted a tool-error without providerExecuted.
4. The loop's client call/output counts disagreed (1 vs 2), so streamText exited: no error, no stop condition, finish reason tool-calls.
5. get_context saw a last step with tool calls, skipped the stall nudge, fell to extractFinalAnswer's all-text fallback, and reported success.

Changes

tools.ts — withhold web_search on confined runs. create_pr worktrees and ephemeral previews edit files; they have no use for web search, and with no server tool in the request there is nothing for a gateway to rewrite.

agent.ts / utils.ts — guard the silent exit. unresolvedToolCalls finds calls on the last step that are invalid, unregistered, or without an output. get_context retries once with those calls stripped from the transcript (stripToolCallParts; the API rejects a tool_result for a server tool it never ran) plus a nudge naming the unavailable tool, and throws if the retry ends the same way. Also on this path: a mid-run abort now surfaces as AbortError instead of a completed run, and exhausted continuations set incomplete: { reason } on the ContextResult.

git_pr.ts / index.ts — capture the diff from the worktree. captureWorktreeDiff runs git add -A (new files included; git diff HEAD alone omits them) then git diff --cached, with landChange's caps and gitleaks fail-closed scan. The non-stream terminal result reports it as preview, the counterpart of pr on create_pr runs, with the same shape: { ok: true, diff, filesChanged } or { ok: false, failure, error } where failure is one of no_changes, change_too_large, secrets_detected, git_failed. Callers no longer depend on the model pasting a diff into its final message.

Terminal result additions (ephemeral runs)

preview?:    { ok: true, diff, filesChanged } | { ok: false, failure, error }
incomplete?: { reason: "stall" | "length" | "error" }

Testing

• src/repo/**/*.test.ts: 583 passed
• New: unresolved_tools.test.ts (includes the exact production step shape), worktree_diff.test.ts (real git fixtures), and confinement tests asserting web_search is absent on ephemeral and prMode runs
• tsc --noEmit clean on touched files

Notes

• The streaming path (stream_context) is untouched; Hive uses the non-stream path.
• gitleaks is now on the preview path, fail-closed like landChange.
• Companion Hive PR propose_code_change: take the diff from the swarm's worktree capture, refuse incomplete runs hive#5308 consumes preview / incomplete; it is backward compatible with swarms that predate this.