Import the agent-diff wire types from the server

[selfcontained]

What

apps/web/src/hooks/use-agent-diff.ts hand-restated four types that apps/server/src/shared/git/agent-diff.ts already declares. It now type-imports them. One file, +18/-22.

This is sub-item (f) of the server↔web wire-type duplication cluster — (a)–(e) landed in #965, #971, #976, #981 and #985. Only (g) (messages/store.ts vs use-agent-messages.ts) remains.

Headline: this one had real drift

Five of the six prior consolidations found zero drift. This one did not.

The web copy of DiffResponse was:

{ baseRef: string | null; files: DiffFile[] }

The server's is:

{ baseRef: string; files: DiffFile[]; truncatedFileCount?: number }

Both halves of that gap are explained by the route, not by a mistake in either type:

• apps/server/src/routes/agents/lifecycle-routes.ts:394 substitutes { baseRef: null, files: [] } when getAgentDiff returns null. So baseRef really is nullable on the wire, even though the server's own DiffResponse (a function return type) always carries a merge-base SHA. The web type was right; the server type simply isn't the wire type here.
• truncatedFileCount is set at agent-diff.ts:308 when a diff exceeds MAX_FILES (1000) and is sent over the wire. Web's copy dropped it.

So instead of a flat alias, the web type is derived:

export type DiffResponse = Omit<AgentDiffResult, "baseRef"> & { baseRef: string | null };

The nullability stays documented at the one place it's true, and truncatedFileCount — plus any future field — comes across for free.

DiffFileStatus, DiffFile and FileDiffResponse were byte-identical and are plain type-only imports re-exported under their existing names, so every consumer import (changes-file-tree.tsx, changes-diff-section.tsx, changes-tab.test.tsx) is unchanged.

Not fixed here (noted, not in scope)

Nothing in the web app reads truncatedFileCount today, so the "diff truncated at 1000 files" signal is silently dropped by the UI. That's a feature gap, not debt — surfacing it is a UI change and belongs in its own PR. Backlogged.

Deliberate exclusions (near-miss lookalikes left alone)

• agent-diff.ts:55 NumstatEntry and :82's inline { status; oldPath? } map value both share fields with DiffFile, but they are file-private parser intermediates on one side of the boundary — not wire shapes. Left alone.
• The /diff-stats family (use-agent-diff-stats.ts, shared/git/diff-stats.ts) is a separate route and a separate type tree. Untouched.

Why it's tech debt

Two declarations of one wire contract, already measurably drifted apart, with no compiler link between them.

Verification

• pnpm run check:web run before anything created apps/server/src/generated (that directory is absent on a clean tree) — the web program type-checks against the server source without the generated-file side effect. This is the Alias web release/assisted-update wire types to the server definitions #863 trap and it does not apply here.
• pnpm run check, pnpm run finalize:web, pnpm run test:e2e (181 passed), apps/web vitest (1064 passed / 71 files) — all green.
• Completeness grep: oldPath?: string now has 4 declarations, all inside agent-diff.ts (2 wire + 2 parser internals, above); truncated: boolean and truncatedFileCount are 1 declaration each. Zero web copies remain.

Next run

Sub-item (g): apps/server/src/messages/store.ts vs apps/web/src/hooks/use-agent-messages.ts — the last of the cluster.