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Fixed a 400 error when using the new Claude code model. #166

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Fixed a 400 error when using the new Claude code model. #166

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9 changes: 4 additions & 5 deletions src/lib/utils.ts
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Original file line number Diff line number Diff line change
@@ -1,9 +1,9 @@
import consola from "consola"

import { getModels } from "~/services/copilot/get-models"
import { getVSCodeVersion } from "~/services/get-vscode-version"
import {getModels} from "~/services/copilot/get-models"
import {getVSCodeVersion} from "~/services/get-vscode-version"

import { state } from "./state"
import {state} from "./state"
Comment on lines +3 to +6
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Copilot AI Jan 5, 2026

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The import statement formatting is inconsistent with the rest of the codebase. The project uses spaces around braces in imports (e.g., import { getModels } rather than import {getModels}). For example, see the consistent pattern in files like src/auth.ts, src/routes/chat-completions/handler.ts, and many others. This inconsistency will likely be flagged by the linter.

Copilot uses AI. Check for mistakes.

export const sleep = (ms: number) =>
new Promise((resolve) => {
Expand All @@ -14,8 +14,7 @@ export const isNullish = (value: unknown): value is null | undefined =>
value === null || value === undefined

export async function cacheModels(): Promise<void> {
const models = await getModels()
state.models = models
state.models = await getModels()
}

export const cacheVSCodeVersion = async () => {
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14 changes: 10 additions & 4 deletions src/routes/messages/non-stream-translation.ts
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Original file line number Diff line number Diff line change
@@ -1,3 +1,5 @@
import consola from "consola"

import {
type ChatCompletionResponse,
type ChatCompletionsPayload,
Expand Down Expand Up @@ -48,11 +50,15 @@ export function translateToOpenAI(

function translateModelName(model: string): string {
// Subagent requests use a specific model number which Copilot doesn't support
if (model.startsWith("claude-sonnet-4-")) {
return model.replace(/^claude-sonnet-4-.*/, "claude-sonnet-4")
} else if (model.startsWith("claude-opus-")) {
return model.replace(/^claude-opus-4-.*/, "claude-opus-4")
if (model.startsWith("claude")) {
const newModel = model.replaceAll(
/(claude-(?:haiku|sonnet|opus)-\d+)-(\d+)(?:[.-]\d+)?/g,
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Copilot AI Jan 5, 2026

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The regex pattern does not match the actual Anthropic Claude model naming format. Anthropic models use the format claude-{version}-{variant}-{date} (e.g., claude-3-5-sonnet-20241022), but this regex expects claude-{variant}-{version}-{date} format.

The pattern /(claude-(?:haiku|sonnet|opus)-\d+)-(\d+)(?:[.-]\d+)?/g would match something like claude-sonnet-4-20250115 but not claude-3-5-sonnet-20241022. This means the regex will not transform most Claude model names as intended, causing them to pass through unchanged when they should be transformed.

Consider updating the regex to match the actual Anthropic model format, or verify what specific model names from Claude Code need to be transformed.

Suggested change
/(claude-(?:haiku|sonnet|opus)-\d+)-(\d+)(?:[.-]\d+)?/g,
/(claude-\d+(?:-\d+)?-(?:haiku|sonnet|opus))-(\d{8})(?:[.-]\d+)?/g,

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"$1.$2",
)
consola.log("Use Model:", model, newModel)
return newModel
Comment on lines +54 to +59
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Copilot AI Jan 5, 2026

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The new model name translation logic lacks test coverage. Given that this PR aims to fix a 400 error with Claude model names, tests should be added to verify that the regex correctly transforms various Claude model name formats (e.g., claude-sonnet-4-20250115 to claude-sonnet-4.20250115). Tests should also verify that models not matching the pattern are passed through unchanged. Consider adding tests in tests/anthropic-request.test.ts that specifically test the translateModelName function with various input formats.

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}
consola.log("Use Model:", model)
Comment on lines +58 to +61
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Copilot AI Jan 5, 2026

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These log statements will be emitted on every request, which could create excessive noise in production logs. Consider using a debug-level log (e.g., consola.debug) instead of consola.log, or removing these logs entirely once the feature is stable. Production logs should typically be reserved for errors, warnings, and important informational messages rather than routine processing details.

Suggested change
consola.log("Use Model:", model, newModel)
return newModel
}
consola.log("Use Model:", model)
consola.debug("Use Model:", model, newModel)
return newModel
}
consola.debug("Use Model:", model)

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return model
}

Expand Down