fix: checkpoint adapter usage and preserve unknown prices (#14991)

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/adapters/opencode-local/src/server/parse.test.ts

@@ -75,3 +75,23 @@ describe("parseOpenCodeJsonl", () => {
     expect(isOpenCodeUnknownSessionError("all good", "")).toBe(false);
   });
 });
+
+describe("OpenCode price availability", () => {
+  it("distinguishes missing cost from reported zero and counts cache writes", () => {
+    const event = { type: "step_finish", part: { tokens: { input: 10, output: 3, cache: { read: 100, write: 20 } } } };
+    expect(parseOpenCodeJsonl(JSON.stringify(event))).toMatchObject({ costUsd: null, usage: { inputTokens: 30, cachedInputTokens: 100, outputTokens: 3 } });
+    expect(parseOpenCodeJsonl(JSON.stringify({ ...event, part: { ...event.part, cost: 0 } })).costUsd).toBe(0);
+    expect(parseOpenCodeJsonl([event, { ...event, part: { ...event.part, cost: 1 } }].map((row) => JSON.stringify(row)).join("\n")).costUsd).toBeNull();
+  });
+});
+
+describe("OpenCode reported usage completeness", () => {
+  it.each([undefined, {}, { input: 1 }, { input: -1, output: 2 }, { input: 1, output: 0.5 }, { input: 1, output: 2, cache: { read: -1 } }, { input: 1, output: 2, cache: { read: null } }, { input: 1, output: 2, reasoning: null }])("preserves unknown usage for incomplete counters %j", tokens => {
+    expect(parseOpenCodeJsonl(JSON.stringify({ type: "step_finish", part: { tokens } }))).toMatchObject({ usageReported: false, usageComplete: false, costUsd: null });
+  });
+  it("accepts explicit zeros but keeps a later missing step incomplete", () => {
+    const line = JSON.stringify({ type: "step_finish", part: { tokens: { input: 0, output: 0 } } });
+    expect(parseOpenCodeJsonl(line)).toMatchObject({ usageReported: true, usageComplete: true, usage: { inputTokens: 0, outputTokens: 0 }, costUsd: null });
+    expect(parseOpenCodeJsonl(line + '\n' + JSON.stringify({ type: "step_finish" }))).toMatchObject({ usageReported: true, usageComplete: false });
+  });
+});