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Stream text/reasoning deltas to ACP and deduplicate using snapshots #2

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Merged
nkosi23 merged 1 commit into from
Mar 1, 2026
Merged

Stream text/reasoning deltas to ACP and deduplicate using snapshots #2

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51 changes: 51 additions & 0 deletions packages/opencode/src/acp/agent.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -137,6 +137,7 @@ export namespace ACP {
private eventStarted = false
private bashSnapshots = new Map<string, string>()
private toolStarts = new Set<string>()
private textSnapshots = new Map<string, string>()
private permissionQueues = new Map<string, Promise<void>>()
private permissionOptions: PermissionOption[] = [
{ optionId: "once", kind: "allow_once", name: "Allow once" },
Expand Down Expand Up @@ -446,6 +447,46 @@ export namespace ACP {
return
}
}

if (part.type === "text" && part.ignored !== true) {
const delta = this.textDelta(part.id, part.text)
if (!delta) return
await this.connection
.sessionUpdate({
sessionId,
update: {
sessionUpdate: "agent_message_chunk",
content: {
type: "text",
text: delta,
},
},
})
.catch((error) => {
log.error("failed to send text update to ACP", { error })
})
return
}

if (part.type === "reasoning") {
const delta = this.textDelta(part.id, part.text)
if (!delta) return
await this.connection
.sessionUpdate({
sessionId,
update: {
sessionUpdate: "agent_thought_chunk",
content: {
type: "text",
text: delta,
},
},
})
.catch((error) => {
log.error("failed to send reasoning update to ACP", { error })
})
return
}
return
}

Expand Down Expand Up @@ -476,6 +517,7 @@ export namespace ACP {
if (!part) return

if (part.type === "text" && props.field === "text" && part.ignored !== true) {
this.textSnapshots.set(part.id, part.text)
await this.connection
.sessionUpdate({
sessionId,
Expand All @@ -494,6 +536,7 @@ export namespace ACP {
}

if (part.type === "reasoning" && props.field === "text") {
this.textSnapshots.set(part.id, part.text)
await this.connection
.sessionUpdate({
sessionId,
Expand Down Expand Up @@ -1085,6 +1128,14 @@ export namespace ACP {
return output
}

private textDelta(id: string, next: string) {
const prev = this.textSnapshots.get(id) ?? ""
this.textSnapshots.set(id, next)
if (!next) return ""
if (next.startsWith(prev)) return next.slice(prev.length)
return next
}

private async toolStart(sessionId: string, part: ToolPart) {
if (this.toolStarts.has(part.callID)) return
this.toolStarts.add(part.callID)
Expand Down
115 changes: 115 additions & 0 deletions packages/opencode/test/acp/event-subscription.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -345,6 +345,121 @@ describe("acp.agent event subscription", () => {
})
})


test("emits text chunks from message.part.updated when delta events are absent", async () => {
await using tmp = await tmpdir()
await Instance.provide({
directory: tmp.path,
fn: async () => {
const { agent, controller, chunks, stop } = createFakeAgent()
const cwd = "/tmp/opencode-acp-test"

const sessionId = await agent.newSession({ cwd, mcpServers: [] } as any).then((x) => x.sessionId)

controller.push({
directory: cwd,
payload: {
type: "message.part.updated",
properties: {
part: {
id: "part_1",
sessionID: sessionId,
messageID: "msg_1",
type: "text",
text: "hello",
},
},
},
} as any)

controller.push({
directory: cwd,
payload: {
type: "message.part.updated",
properties: {
part: {
id: "part_1",
sessionID: sessionId,
messageID: "msg_1",
type: "text",
text: "hello world",
},
},
},
} as any)

await new Promise((r) => setTimeout(r, 20))

expect(chunks.get(sessionId)).toBe("hello world")
stop()
},
})
})

test("does not duplicate chunks when message.part.delta is followed by message.part.updated", async () => {
await using tmp = await tmpdir()
await Instance.provide({
directory: tmp.path,
fn: async () => {
const { agent, controller, chunks, stop } = createFakeAgent()
const cwd = "/tmp/opencode-acp-test"

const sessionId = await agent.newSession({ cwd, mcpServers: [] } as any).then((x) => x.sessionId)

controller.push({
directory: cwd,
payload: {
type: "message.part.delta",
properties: {
sessionID: sessionId,
messageID: "msg_1",
partID: "msg_1_part",
field: "text",
delta: "hello",
},
},
} as any)

controller.push({
directory: cwd,
payload: {
type: "message.part.updated",
properties: {
part: {
id: "msg_1_part",
sessionID: sessionId,
messageID: "msg_1",
type: "text",
text: "hello",
},
},
},
} as any)

controller.push({
directory: cwd,
payload: {
type: "message.part.updated",
properties: {
part: {
id: "msg_1_part",
sessionID: sessionId,
messageID: "msg_1",
type: "text",
text: "hello world",
},
},
},
} as any)

await new Promise((r) => setTimeout(r, 20))

expect(chunks.get(sessionId)).toBe("hello world")
stop()
},
})
})

test("does not create additional event subscriptions on repeated loadSession()", async () => {
await using tmp = await tmpdir()
await Instance.provide({
Expand Down