fix(ai): degrade Copilot Responses image detail "original" to auto

The Responses-API "original" image detail is an oh-my-pi extension that
preserves native resolution (snapcompact renders terminal-glyph frames
that do not survive the "auto" downscale). GitHub Copilot's Responses
endpoint rejects detail: "original" with an HTTP 400, so any request
carrying such an image failed outright.

- Add a supportsImageDetailOriginal compat flag in the catalog, resolved
  to false whenever the model resolves to the Copilot host (by provider id
  or base-URL marker, via modelMatchesHost, mirroring the Anthropic compat
  builder) and true for every other host, alongside the existing
  strictResponsesPairing Responses-only flag (same three type touch-points:
  optional on OpenAICompat, omitted from the chat-completions resolved type,
  required on the Responses resolved type).
- Clamp the image detail hint to "auto" when the host does not support
  "original" at both Responses image-emission sites (user content and
  tool-result content). Every other host preserves native-resolution
  frames, so snapcompact is unaffected.

Host-aware detection (rather than a bare provider-string check) keeps the
clamp in force when a model is pointed at the Copilot Responses host under
a different provider id, which would otherwise reintroduce the 400; a
regression test covers that path.

Closes #2822

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/ai/CHANGELOG.md

@@ -67,6 +67,7 @@
 - Fixed Antigravity and Gemini CLI model requests failing with an opaque error when Google requires account verification. Cloud Code Assist `403 VALIDATION_REQUIRED` responses now surface the `validation_url` and the signed-in account email when available, so users see an actionable account-verification message instead of the raw API error body.
 - Fixed MiniMax M3 in-band tool calls by adding a MiniMax dialect that parses `<minimax:tool_call>` wrappers instead of falling back to generic XML. ([#2759](https://github.com/can1357/oh-my-pi/issues/2759))
 - Fixed GitHub Copilot OAuth for Business seats by storing the login-discovered API endpoint and routing model enablement plus chat requests to that endpoint. ([#2876](https://github.com/can1357/oh-my-pi/issues/2876))
+- Fixed GitHub Copilot Responses requests rejecting image inputs that carry the `detail: "original"` hint with an HTTP 400 by degrading the hint to `"auto"` for hosts that do not support it; other hosts still preserve native-resolution frames (snapcompact). ([#2822](https://github.com/can1357/oh-my-pi/issues/2822))
 
 ## [16.0.4] - 2026-06-17
 

packages/ai/src/providers/azure-openai-responses.ts

@@ -297,6 +297,7 @@ function buildParams(
 		model,
 		context,
 		strictResponsesPairing: true,
+		supportsImageDetailOriginal: model.compat.supportsImageDetailOriginal,
 		systemRole,
 		includeThinkingSignatures: true,
 		developerStringContent: true,

packages/ai/src/providers/openai-codex-responses.ts

@@ -3253,7 +3253,15 @@ function convertMessages(model: Model<"openai-codex-responses">, context: Contex
 		}
 
 		if (msg.role === "toolResult") {
-			appendResponsesToolResultMessages(messages, msg, model, false, knownCallIds, customCallIds);
+			appendResponsesToolResultMessages(
+				messages,
+				msg,
+				model,
+				false,
+				model.compat.supportsImageDetailOriginal,
+				knownCallIds,
+				customCallIds,
+			);
 		}
 
 		msgIndex += 1;
@@ -3271,7 +3279,10 @@ function normalizeInputMessageContent(
 		return [{ type: "input_text", text: content.toWellFormed() }];
 	}
 
-	return convertResponsesInputContent(content, model.input.includes("image")) ?? [];
+	return (
+		convertResponsesInputContent(content, model.input.includes("image"), model.compat.supportsImageDetailOriginal) ??
+		[]
+	);
 }
 
 /** @internal Exported for tests. */

packages/ai/src/providers/openai-responses.ts

@@ -687,6 +687,7 @@ export function buildParams(
 		model,
 		context,
 		strictResponsesPairing,
+		supportsImageDetailOriginal: model.compat.supportsImageDetailOriginal,
 		nativeHistory: {
 			replay: shouldReplayNativeHistory,
 			filterReasoning: policy.reasoning.filterReasoningHistory,

packages/ai/src/providers/openai-shared.ts

@@ -1178,9 +1178,24 @@ export function repairOrphanResponsesToolCalls(input: ResponseInput): ResponseIn
 	return repaired;
 }
 
+/**
+ * Some Responses backends (notably GitHub Copilot) reject the OpenAI image
+ * `detail: "original"` value with a 400. When the model does not advertise
+ * support for it, degrade `"original"` to `"auto"` so the request still goes
+ * through with the closest valid fidelity instead of failing outright. See #2822.
+ */
+function clampResponsesImageDetail(
+	detail: ImageContent["detail"],
+	supportsImageDetailOriginal: boolean,
+): ResponseInputImage["detail"] {
+	const resolved = detail ?? "auto";
+	return resolved === "original" && !supportsImageDetailOriginal ? "auto" : resolved;
+}
+
 export function convertResponsesInputContent(
 	content: string | Array<TextContent | ImageContent>,
 	supportsImages: boolean,
+	supportsImageDetailOriginal: boolean,
 ): ResponseInputContent[] | undefined {
 	if (typeof content === "string") {
 		if (content.trim().length === 0) return undefined;
@@ -1200,7 +1215,7 @@ export function convertResponsesInputContent(
 	for (const item of imageBlocks) {
 		normalizedContent.push({
 			type: "input_image",
-			detail: item.detail ?? "auto",
+			detail: clampResponsesImageDetail(item.detail, supportsImageDetailOriginal),
 			image_url: `data:${item.mimeType};base64,${item.data}`,
 		} satisfies ResponseInputImage);
 	}
@@ -1217,6 +1232,7 @@ export interface BuildResponsesInputOptions<TApi extends Api> {
 	model: Model<TApi>;
 	context: Context;
 	strictResponsesPairing: boolean;
+	supportsImageDetailOriginal: boolean;
 	systemRole?: "system" | "developer";
 	nativeHistory?: {
 		replay: boolean;
@@ -1267,7 +1283,11 @@ export function buildResponsesInput<TApi extends Api>(options: BuildResponsesInp
 				msgIndex++;
 				continue;
 			}
-			const content = convertResponsesInputContent(msg.content, options.model.input.includes("image"));
+			const content = convertResponsesInputContent(
+				msg.content,
+				options.model.input.includes("image"),
+				options.supportsImageDetailOriginal,
+			);
 			if (!content) continue;
 			messages.push({
 				role: "user",
@@ -1318,6 +1338,7 @@ export function buildResponsesInput<TApi extends Api>(options: BuildResponsesInp
 				msg,
 				options.model,
 				options.strictResponsesPairing,
+				options.supportsImageDetailOriginal,
 				knownCallIds,
 				customCallIds,
 			);
@@ -1419,6 +1440,7 @@ export function appendResponsesToolResultMessages<TApi extends Api>(
 	toolResult: ToolResultMessage,
 	model: Model<TApi>,
 	strictResponsesPairing: boolean,
+	supportsImageDetailOriginal: boolean,
 	knownCallIds: ReadonlySet<string>,
 	customCallIds?: ReadonlySet<string>,
 ): void {
@@ -1475,7 +1497,7 @@ export function appendResponsesToolResultMessages<TApi extends Api>(
 		if (block.type === "image") {
 			contentParts.push({
 				type: "input_image",
-				detail: block.detail ?? "auto",
+				detail: clampResponsesImageDetail(block.detail, supportsImageDetailOriginal),
 				image_url: `data:${block.mimeType};base64,${block.data}`,
 			} satisfies ResponseInputImage);
 		}

packages/ai/test/apply-patch-freeform.test.ts

@@ -659,8 +659,17 @@ describe("history replay: custom_tool_call round-trip", () => {
 		};
 		const knownCallIds = new Set<string>(["call_1"]);
 		const customCallIds = new Set<string>(["call_1"]);
+		const model = makeModel();
 
-		appendResponsesToolResultMessages(messages as never, toolResult, makeModel(), true, knownCallIds, customCallIds);
+		appendResponsesToolResultMessages(
+			messages as never,
+			toolResult,
+			model,
+			true,
+			model.compat.supportsImageDetailOriginal,
+			knownCallIds,
+			customCallIds,
+		);
 
 		expect(messages).toHaveLength(1);
 		const item = messages[0] as { type: string; call_id: string; output: string };
@@ -681,8 +690,17 @@ describe("history replay: custom_tool_call round-trip", () => {
 		};
 		const knownCallIds = new Set<string>(["call_2"]);
 		const customCallIds = new Set<string>(); // call_2 not custom
+		const model = makeModel();
 
-		appendResponsesToolResultMessages(messages as never, toolResult, makeModel(), true, knownCallIds, customCallIds);
+		appendResponsesToolResultMessages(
+			messages as never,
+			toolResult,
+			model,
+			true,
+			model.compat.supportsImageDetailOriginal,
+			knownCallIds,
+			customCallIds,
+		);
 
 		const item = messages[0] as { type: string };
 		expect(item.type).toBe("function_call_output");

packages/ai/test/github-copilot-long-context-wire.test.ts

@@ -15,8 +15,12 @@ afterEach(() => {
 	vi.restoreAllMocks();
 });
 
+// Fixed timestamp keeps the wire-body assertions deterministic; the value is
+// never read on the wire, but pinning it avoids any incidental nondeterminism.
+const FIXED_TIMESTAMP = 1_700_000_000_000;
+
 const testContext: Context = {
-	messages: [{ role: "user", content: "hello", timestamp: Date.now() }],
+	messages: [{ role: "user", content: "hello", timestamp: FIXED_TIMESTAMP }],
 };
 
 function makeLongContextVariant<TApi extends Api>(spec: Partial<ModelSpec<TApi>> & { api: TApi }): Model<TApi> {
@@ -112,3 +116,109 @@ describe("GitHub Copilot long-context variant wire model id", () => {
 		expect(wireModelIds[0]).toBe("gemini-3.1-pro-preview");
 	});
 });
+
+/**
+ * GitHub Copilot's Responses endpoint rejects the `detail: "original"` image
+ * hint (an oh-my-pi extension that preserves native-resolution snapcompact
+ * frames) with an HTTP 400. The catalog resolves `supportsImageDetailOriginal`
+ * to `false` for Copilot, and the Responses request builder degrades the hint
+ * to `"auto"` so the wire stays valid. Every other host preserves `"original"`.
+ */
+describe("GitHub Copilot Responses image detail clamp (#2822)", () => {
+	const imageContext: Context = {
+		messages: [
+			{
+				role: "user",
+				content: [
+					{ type: "text", text: "describe this frame" },
+					{ type: "image", mimeType: "image/png", data: "ZmFrZQ==", detail: "original" },
+				],
+				timestamp: FIXED_TIMESTAMP,
+			},
+		],
+	};
+
+	// Walk a serialized Responses request body and return the first `input_image`
+	// detail hint it emits (the wire nests it under `input[].content[]`).
+	function firstImageDetail(body: Record<string, unknown>): string | undefined {
+		let found: string | undefined;
+		const walk = (node: unknown): void => {
+			if (found !== undefined || node === null || typeof node !== "object") return;
+			if (Array.isArray(node)) {
+				for (const child of node) walk(child);
+				return;
+			}
+			const obj = node as Record<string, unknown>;
+			if (obj.type === "input_image" && typeof obj.detail === "string") {
+				found = obj.detail;
+				return;
+			}
+			for (const value of Object.values(obj)) walk(value);
+		};
+		walk(body);
+		return found;
+	}
+
+	async function detailOnWire(model: Model<"openai-responses">): Promise<string | undefined> {
+		let body: Record<string, unknown> | undefined;
+		const fetchMock = vi.fn(async (input: string | URL | Request, init?: RequestInit) => {
+			body = await getRequestBody(input, init);
+			return createUnauthorizedResponse();
+		});
+		try {
+			// The mocked fetch returns 401; this test only cares about what was
+			// serialized onto the wire, which `fetchMock` captures into `body`
+			// before `.result()` settles. Tolerate the result rejecting.
+			await streamOpenAIResponses(model, imageContext, {
+				apiKey: "ghu_test_copilot_token",
+				fetch: fetchMock as unknown as typeof fetch,
+			}).result();
+		} catch {
+			// Ignore: the 401 may surface as a rejection on some result paths.
+		}
+		return body === undefined ? undefined : firstImageDetail(body);
+	}
+
+	it("degrades `original` to `auto` for GitHub Copilot, which rejects it with a 400", async () => {
+		const model = makeLongContextVariant({
+			api: "openai-responses",
+			id: "gpt-5.5-1m",
+			requestModelId: "gpt-5.5",
+			name: "GPT-5.5 (1M)",
+		});
+		expect(model.compat.supportsImageDetailOriginal).toBe(false);
+		expect(await detailOnWire(model)).toBe("auto");
+	});
+
+	it("preserves `original` for non-Copilot Responses hosts (snapcompact native frames)", async () => {
+		const model = makeLongContextVariant({
+			api: "openai-responses",
+			provider: "openai",
+			baseUrl: "https://api.openai.com/v1",
+			headers: {},
+			id: "gpt-5.5",
+			requestModelId: "gpt-5.5",
+			name: "GPT-5.5",
+		});
+		expect(model.compat.supportsImageDetailOriginal).toBe(true);
+		expect(await detailOnWire(model)).toBe("original");
+	});
+
+	it("clamps `original` when only the base URL identifies Copilot (provider id differs)", async () => {
+		// A model pointed at the Copilot Responses host but labeled with a generic
+		// provider id must still degrade `original`. Detecting Copilot solely by the
+		// provider field would resolve `supportsImageDetailOriginal: true` here and
+		// reintroduce the HTTP 400 this clamp prevents; host-aware detection keeps it
+		// `false`.
+		const model = makeLongContextVariant({
+			api: "openai-responses",
+			provider: "openai",
+			baseUrl: "https://api.githubcopilot.com",
+			id: "gpt-5.5-1m",
+			requestModelId: "gpt-5.5",
+			name: "GPT-5.5 (1M)",
+		});
+		expect(model.compat.supportsImageDetailOriginal).toBe(false);
+		expect(await detailOnWire(model)).toBe("auto");
+	});
+});

packages/ai/test/issue-967-vision-guard.test.ts

@@ -171,6 +171,7 @@ describe("issue #967 vision guard", () => {
 				{ type: "image", mimeType: "image/png", data: "ZmFrZQ==" },
 			],
 			false,
+			model.compat.supportsImageDetailOriginal,
 		);
 		expect(countTaggedValues(userContent, "input_image")).toBe(0);
 		expect(userContent).toEqual([
@@ -187,6 +188,7 @@ describe("issue #967 vision guard", () => {
 			]),
 			model,
 			true,
+			model.compat.supportsImageDetailOriginal,
 			new Set(["call_1"]),
 		);
 		expect(countTaggedValues(payload, "input_image")).toBe(0);

packages/catalog/CHANGELOG.md

@@ -45,6 +45,7 @@
 - Routed google-antigravity default baseUrl to the stable primary daily endpoint in the catalog generator and all fallback snapshots, resolving connection drops on heavy queries.
 - Fixed MiniMax M3 dialect selection so MiniMax-family OpenAI-compatible models use the MiniMax tool-call dialect instead of generic XML. ([#2759](https://github.com/can1357/oh-my-pi/issues/2759))
 - Fixed GitHub Copilot dynamic discovery to honor plan-specific API endpoints stored in structured OAuth credentials. ([#2876](https://github.com/can1357/oh-my-pi/issues/2876))
+- Added a `supportsImageDetailOriginal` compat flag that resolves to `false` for GitHub Copilot, whose Responses endpoint rejects the `detail: "original"` image hint with a 400, and `true` for every other host. ([#2822](https://github.com/can1357/oh-my-pi/issues/2822))
 
 ## [16.0.4] - 2026-06-17
 

packages/catalog/src/compat/openai.ts

@@ -459,6 +459,12 @@ export function buildOpenAIResponsesCompat(spec: OpenAIResponsesSpecLike): Resol
 		// Azure OpenAI and GitHub Copilot Responses paths require tool results
 		// to strictly match prior tool calls when building Responses inputs.
 		strictResponsesPairing: isAzure || spec.provider === "github-copilot",
+		// GitHub Copilot's Responses endpoint rejects the `detail: "original"`
+		// image hint with a 400; every other host preserves native-resolution
+		// frames (snapcompact relies on `original`). Detect Copilot by provider id
+		// or base-URL host (mirroring the Anthropic compat builder) so a model
+		// pointed at the Copilot host under a different provider id still clamps.
+		supportsImageDetailOriginal: !modelMatchesHost({ provider: spec.provider, baseUrl }, "githubCopilot"),
 		requiresJuiceZeroHack: spec.name.toLowerCase().startsWith("gpt-5"),
 		reasoningEffortMap: {},
 		supportsReasoningParams: true,
@@ -514,6 +520,7 @@ function pickResponsesOnly(compat: ResolvedOpenAIResponsesCompat): ResponsesOnly
 	return {
 		supportsLongPromptCacheRetention: compat.supportsLongPromptCacheRetention,
 		strictResponsesPairing: compat.strictResponsesPairing,
+		supportsImageDetailOriginal: compat.supportsImageDetailOriginal,
 		requiresJuiceZeroHack: compat.requiresJuiceZeroHack,
 		supportsObfuscationOptOut: compat.supportsObfuscationOptOut,
 	} satisfies ResponsesOnlyCompat;

packages/catalog/src/types.ts

@@ -283,6 +283,8 @@ export interface OpenAICompat {
 	alwaysSendMaxTokens?: boolean;
 	/** Whether Responses-API tool-call/result history must be strictly paired. Default: auto-detected (Azure OpenAI, GitHub Copilot). */
 	strictResponsesPairing?: boolean;
+	/** Whether the Responses API accepts the `detail: "original"` image hint. Default: auto-detected (false for GitHub Copilot, which rejects it with a 400). */
+	supportsImageDetailOriginal?: boolean;
 	/**
 	 * Append a trailing `# Juice: 0 !important` developer item when the caller
 	 * did not request reasoning, suppressing default reasoning on models that
@@ -504,6 +506,7 @@ export type ResolvedOpenAICompat = ResolvedOpenAISharedCompat &
 			| "cacheControlFormat"
 			| "thinkingKeep"
 			| "strictResponsesPairing"
+			| "supportsImageDetailOriginal"
 			| "requiresJuiceZeroHack"
 			| "enableGeminiThinkingLoopGuard"
 			| "whenThinking"
@@ -527,6 +530,7 @@ export type ResolvedOpenAICompat = ResolvedOpenAISharedCompat &
 export interface ResolvedOpenAIResponsesCompat extends ResolvedOpenAISharedCompat {
 	supportsLongPromptCacheRetention: boolean;
 	strictResponsesPairing: boolean;
+	supportsImageDetailOriginal: boolean;
 	requiresJuiceZeroHack: boolean;
 	supportsObfuscationOptOut: boolean;
 }