refactor(opencode): parallelize git snapshot operations on finish-step

packages/opencode/src/session/processor.ts

@@ -250,31 +250,29 @@ export namespace SessionProcessor {
                   input.assistantMessage.finish = value.finishReason
                   input.assistantMessage.cost += usage.cost
                   input.assistantMessage.tokens = usage.tokens
+                  const tracked = await Snapshot.trackAndPatch(snapshot)
                   await Session.updatePart({
                     id: Identifier.ascending("part"),
                     reason: value.finishReason,
-                    snapshot: await Snapshot.track(),
+                    snapshot: tracked.hash,
                     messageID: input.assistantMessage.id,
                     sessionID: input.assistantMessage.sessionID,
                     type: "step-finish",
                     tokens: usage.tokens,
                     cost: usage.cost,
                   })
                   await Session.updateMessage(input.assistantMessage)
-                  if (snapshot) {
-                    const patch = await Snapshot.patch(snapshot)
-                    if (patch.files.length) {
-                      await Session.updatePart({
-                        id: Identifier.ascending("part"),
-                        messageID: input.assistantMessage.id,
-                        sessionID: input.sessionID,
-                        type: "patch",
-                        hash: patch.hash,
-                        files: patch.files,
-                      })
-                    }
-                    snapshot = undefined
+                  if (tracked.patch && tracked.patch.files.length) {
+                    await Session.updatePart({
+                      id: Identifier.ascending("part"),
+                      messageID: input.assistantMessage.id,
+                      sessionID: input.sessionID,
+                      type: "patch",
+                      hash: tracked.patch.hash,
+                      files: tracked.patch.files,
+                    })
                   }
+                  snapshot = undefined
                   SessionSummary.summarize({
                     sessionID: input.sessionID,
                     messageID: input.assistantMessage.parentID,

packages/opencode/src/snapshot/index.ts

@@ -88,13 +88,16 @@ export namespace Snapshot {
   export async function patch(hash: string): Promise<Patch> {
     const git = gitdir()
     await add(git)
+    return delta(git, hash)
+  }
+
+  async function delta(git: string, hash: string): Promise<Patch> {
     const result =
       await $`git -c core.autocrlf=false -c core.longpaths=true -c core.symlinks=true -c core.quotepath=false --git-dir ${git} --work-tree ${Instance.worktree} diff --no-ext-diff --name-only ${hash} -- .`
         .quiet()
         .cwd(Instance.directory)
         .nothrow()
 
-    // If git diff fails, return empty patch
     if (result.exitCode !== 0) {
       log.warn("failed to get diff", { hash, exitCode: result.exitCode })
       return { hash, files: [] }
@@ -112,6 +115,43 @@ export namespace Snapshot {
     }
   }
 
+  // Runs add once, then write-tree and diff concurrently.
+  export async function trackAndPatch(from?: string): Promise<{ hash?: string; patch?: Patch }> {
+    if (Instance.project.vcs !== "git" || Flag.OPENCODE_CLIENT === "acp") return {}
+    const cfg = await Config.get()
+    if (cfg.snapshot === false) return {}
+    const git = gitdir()
+    if (await fs.mkdir(git, { recursive: true })) {
+      await $`git init`
+        .env({
+          ...process.env,
+          GIT_DIR: git,
+          GIT_WORK_TREE: Instance.worktree,
+        })
+        .quiet()
+        .nothrow()
+      await $`git --git-dir ${git} config core.autocrlf false`.quiet().nothrow()
+      await $`git --git-dir ${git} config core.longpaths true`.quiet().nothrow()
+      await $`git --git-dir ${git} config core.symlinks true`.quiet().nothrow()
+      await $`git --git-dir ${git} config core.fsmonitor false`.quiet().nothrow()
+      log.info("initialized")
+    }
+    await add(git)
+
+    const [tree, patch] = await Promise.all([
+      $`git --git-dir ${git} --work-tree ${Instance.worktree} write-tree`
+        .quiet()
+        .cwd(Instance.directory)
+        .nothrow()
+        .text(),
+      from ? delta(git, from) : Promise.resolve(undefined),
+    ])
+
+    const hash = tree.trim() || undefined
+    log.info("tracking", { hash, cwd: Instance.directory, git })
+    return { hash, patch }
+  }
+
   export async function restore(snapshot: string) {
     log.info("restore", { commit: snapshot })
     const git = gitdir()