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fix(github): route Claude models to Copilot's native format via chatCore #2761

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fix(github): route Claude models to Copilot's native format via chatCore #2761

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136 changes: 21 additions & 115 deletions open-sse/executors/github.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4,8 +4,7 @@ import { OAUTH_ENDPOINTS, GITHUB_COPILOT } from "../config/appConstants.js";
import { HTTP_STATUS } from "../config/runtimeConfig.js";
import { openaiToOpenAIResponsesRequest } from "../translator/request/openai-responses.js";
import { openaiResponsesToOpenAIResponse } from "../translator/response/openai-responses.js";
import { initState, translateRequest, translateResponse } from "../translator/index.js";
import { FORMATS } from "../translator/formats.js";
import { initState } from "../translator/index.js";
import { parseSSELine, formatSSE } from "../utils/streamHelpers.js";
import { proxyAwareFetch } from "../utils/proxyFetch.js";
import { stripUnsupportedParams } from "../translator/concerns/paramSupport.js";
Expand All @@ -19,17 +18,18 @@ export class GithubExecutor extends BaseExecutor {
this.knownCodexModels = new Set();
}

// Claude models get routed to Copilot's Anthropic-native /v1/messages shim (see
// executeWithMessagesEndpoint below) — the only Copilot endpoint that surfaces
// prompt-cache token counts. gpt/gemini/grok models stay on /chat/completions
// (or /responses). Name-pattern check, not a registry field: Copilot's live model
// catalog (services/copilotModels.js) regularly exposes claude-* variants ahead
// of the static registry (registry/github.js).
// Single source of truth for "is this model served by the Anthropic-native shim":
// the registry hook chatCore also uses to pick the target format, so the body shape
// the executor receives and the endpoint it posts to can never disagree.
isClaudeModel(model) {
return /claude/i.test(model || "");
return this.config.resolveTargetFormat?.(model) === "claude";
}

buildUrl(model, stream, urlIndex = 0) {
// Claude models arrive already Anthropic-native (chatCore translated to the
// "claude" target format) — post them to Copilot's /v1/messages shim, the only
// Copilot endpoint that surfaces prompt-cache token counts.
if (this.isClaudeModel(model)) return this.config.messagesUrl;
return this.config.baseUrl;
}

Expand Down Expand Up @@ -96,6 +96,9 @@ export class GithubExecutor extends BaseExecutor {
}

transformRequest(model, body, stream, credentials) {
// Anthropic-native body — none of the OpenAI-shape fixups below apply.
if (this.isClaudeModel(model)) return body;

const transformed = { ...body };
if (this.requiresMaxCompletionTokens(model) && transformed.max_tokens !== undefined) {
transformed.max_completion_tokens = transformed.max_tokens;
Expand Down Expand Up @@ -123,25 +126,23 @@ export class GithubExecutor extends BaseExecutor {
async execute(options) {
const { model, log } = options;

// Claude models: route to Copilot's Anthropic-native /v1/messages shim — the only
// Copilot endpoint that surfaces prompt-cache token counts for Claude. Detected by
// model NAME (not a registry field): Copilot's live model catalog regularly exposes
// claude-* variants the static registry hasn't caught up with yet (see registry/github.js).
if (this.isClaudeModel(model)) {
log?.debug("GITHUB", `Using /v1/messages route for ${model}`);
return this.executeWithMessagesEndpoint(options);
}
// Claude models fall straight through to BaseExecutor.execute(): the body is
// already Anthropic-native and buildUrl() targets /v1/messages, so there is
// nothing left to translate here (chatCore handles both directions).
const isClaude = this.isClaudeModel(model);
if (isClaude) log?.debug("GITHUB", `Using /v1/messages route for ${model}`);

// Only use /responses for models that are explicitly known to need it (e.g. gpt codex models)
// and that the /responses endpoint actually serves (excludes Gemini/Claude, see #1062).
if (this.knownCodexModels.has(model) && this.supportsResponsesEndpoint(model)) {
if (!isClaude && this.knownCodexModels.has(model) && this.supportsResponsesEndpoint(model)) {
log?.debug("GITHUB", `Using cached /responses route for ${model}`);
return this.executeWithResponsesEndpoint(options);
}

// Sanitize messages before sending to /chat/completions (gpt/gemini/grok — the
// endpoint rejects non-text/image_url content parts).
const sanitizedOptions = {
// endpoint rejects non-text/image_url content parts). Claude bodies are Anthropic
// shape and must not be touched.
const sanitizedOptions = isClaude ? options : {
...options,
body: this.sanitizeMessagesForChatCompletions(options.body)
};
Expand Down Expand Up @@ -245,101 +246,6 @@ export class GithubExecutor extends BaseExecutor {
};
}

// Claude models arrive here OpenAI-shape (chatCore.js targets "openai" for github —
// see the note in execute() above), so we translate to Anthropic-native ourselves.
// This is what makes prepareClaudeRequest() (translator/formats/claude.js) inject
// cache_control — /chat/completions never gets there, so it never sees cache tokens.
async executeWithMessagesEndpoint({ model, body, stream, credentials, signal, log, proxyOptions = null }) {
const url = this.config.messagesUrl;
const headers = this.buildHeaders(credentials, stream);

// Force stream:true upstream regardless of client preference, same as
// executeWithResponsesEndpoint below — chatCore.js's non-streaming handler already
// knows how to buffer an SSE response into a single JSON reply when the client
// asked for stream:false.
const transformedBody = translateRequest(FORMATS.OPENAI, FORMATS.CLAUDE, model, body, true, credentials, "github");
// _toolNameMap is internal bookkeeping (see openai-to-claude.js) — chatCore.js
// normally strips it before dispatch and threads it into the response state to
// restore original tool names; we must do the same here, or Anthropic's strict
// schema rejects the extra field with a 400.
const toolNameMap = transformedBody._toolNameMap;
delete transformedBody._toolNameMap;

log?.debug("GITHUB", "Sending translated request to /v1/messages");

const response = await proxyAwareFetch(url, {
method: "POST",
headers,
body: JSON.stringify(transformedBody),
signal
}, proxyOptions);

if (!response.ok) {
return { response, url, headers, transformedBody };
}

const state = initState(FORMATS.CLAUDE);
state.model = model;
if (toolNameMap) state.toolNameMap = toolNameMap;

const decoder = new TextDecoder();
let buffer = "";

const emitAll = (controller, chunks) => {
for (const c of chunks) {
controller.enqueue(new TextEncoder().encode(formatSSE(c, "openai")));
}
};

const transformStream = new TransformStream({
async transform(chunk, controller) {
buffer += decoder.decode(chunk, { stream: true });
const lines = buffer.split("\n");

buffer = lines.pop() || "";

for (const line of lines) {
const trimmed = line.trim();
if (!trimmed) continue;

const parsed = parseSSELine(trimmed);
if (!parsed) continue;

if (parsed.done && stream === true) {
controller.enqueue(new TextEncoder().encode(SSE_DONE));
continue;
}

emitAll(controller, translateResponse(FORMATS.CLAUDE, FORMATS.OPENAI, parsed, state));
}
},
flush(controller) {
if (buffer.trim()) {
const parsed = parseSSELine(buffer.trim());
if (parsed && !parsed.done) {
emitAll(controller, translateResponse(FORMATS.CLAUDE, FORMATS.OPENAI, parsed, state));
}
}
}
});

if (!response.body) {
return { response: new Response("", { status: response.status, headers: response.headers }), url, headers, transformedBody };
}
const convertedStream = response.body.pipeThrough(transformStream);

return {
response: new Response(convertedStream, {
status: response.status,
statusText: response.statusText,
headers: response.headers
}),
url,
headers,
transformedBody
};
}

async refreshCopilotToken(githubAccessToken, log, proxyOptions = null) {
try {
const response = await proxyAwareFetch("https://api.github.com/copilot_internal/v2/token", {
Expand Down
7 changes: 5 additions & 2 deletions open-sse/handlers/chatCore.js
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
import { detectFormat, getTargetFormat, resolveTransport } from "../services/provider.js";
import { detectFormat, getTargetFormat, resolveTransport, resolveDynamicTargetFormat } from "../services/provider.js";
import { translateRequest } from "../translator/index.js";
import { stripThinkingSuffix } from "../translator/concerns/thinkingUnified.js";
import { FORMATS } from "../translator/formats.js";
Expand Down Expand Up @@ -58,7 +58,10 @@ export async function handleChatCore({ body, modelInfo, credentials, log, onCred
if (bypassResponse) return bypassResponse;

const alias = PROVIDER_ID_TO_ALIAS[provider] || provider;
const modelTargetFormat = getModelTargetFormat(alias, model);
// Static per-model targetFormat first (explicit registry entries win), then the
// provider's runtime name-pattern hook for catalogs that outrun the static list.
const modelTargetFormat = getModelTargetFormat(alias, model)
|| resolveDynamicTargetFormat(provider, model);
// Multi-endpoint providers: pick transport matching sourceFormat → zero translation
const runtimeTransport = resolveTransport(provider, sourceFormat);
const targetFormat = modelTargetFormat || runtimeTransport?.format || getTargetFormat(provider);
Expand Down
17 changes: 9 additions & 8 deletions open-sse/providers/registry/github.js
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,14 @@ export default {
userAgent: "GitHubCopilotChat/0.38.0",
apiVersion: "2025-04-01",
},
// Copilot serves Claude models on its Anthropic-native /v1/messages shim (the only
// endpoint that surfaces prompt-cache token counts) and everything else on
// /chat/completions. Decided by model NAME at request time rather than a static
// per-entry targetFormat in models[] below: Copilot's live catalog
// (services/copilotModels.js) ships claude-* variants long before the static list
// catches up — it currently serves claude-sonnet-5, claude-opus-4.8,
// claude-opus-4.8-fast and claude-fable-5, none of which are listed here.
resolveTargetFormat: (model) => (/claude/i.test(model || "") ? "claude" : null),
usage: {
url: "https://api.github.com/copilot_internal/user",
},
Expand All @@ -47,14 +55,7 @@ export default {
{ id: "gpt-5.3-codex", name: "GPT-5.3 Codex" },
{ id: "gpt-5.4", name: "GPT-5.4" },
{ id: "gpt-5.4-mini", name: "GPT-5.4 Mini" },
// Note: routing to Copilot's Anthropic-native /v1/messages shim (see
// executors/github.js) is decided by model-NAME pattern at request time, not by
// a static targetFormat field here — Copilot's live model catalog (see
// services/copilotModels.js) regularly exposes claude-* models this static list
// hasn't caught up with yet (e.g. claude-opus-4.8), and a static per-entry
// targetFormat would silently miss those while also double-translating requests
// for models that ARE listed here (chatCore.js would pre-translate to Claude
// shape, then the executor would translate again). Keep these as plain entries.
// Claude entries stay plain — transport.resolveTargetFormat above routes them.
{ id: "claude-haiku-4.5", name: "Claude Haiku 4.5" },
{ id: "claude-opus-4.5", name: "Claude Opus 4.5" },
{ id: "claude-sonnet-4.5", name: "Claude Sonnet 4.5" },
Expand Down
18 changes: 18 additions & 0 deletions open-sse/services/provider.js
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,24 @@ export function resolveTransport(provider, sourceFormat) {
return transports.find(t => t.format === sourceFormat) || null;
}

// Per-model target format resolved at request time from the model NAME.
// For providers that serve different wire formats per model AND whose live model
// catalog outruns their static models[] list, a static per-entry `targetFormat`
// silently misses the newcomers (github/Copilot: claude-* go to the Anthropic-native
// /v1/messages shim, and the catalog ships claude-* variants well before the registry
// lists them). Providers opt in by exporting transport.resolveTargetFormat(model).
// Returns null when the provider has no hook or the model isn't special-cased.
export function resolveDynamicTargetFormat(provider, model) {
const fn = PROVIDERS[provider]?.resolveTargetFormat;
if (typeof fn !== "function") return null;
try {
return fn(model) || null;
} catch {
// Registry data must never be able to break routing.
return null;
}
}

// Check if last message is from user
export function isLastMessageFromUser(body) {
const messages = body.messages || body.contents;
Expand Down
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