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[WRONG BRANCH] fix(bridge): decode freeform previews incrementally #165

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[WRONG BRANCH] fix(bridge): decode freeform previews incrementally #165

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99 changes: 64 additions & 35 deletions src/bridge.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -211,29 +211,6 @@ export function bridgeToResponsesSSE(
// the completed custom_tool_call item stays authoritative). Compact `{"input":"...`
// buffers get their string value progressively unescaped; anything else streams raw.
const FREEFORM_WRAP_PREFIX = '{"input":"';
const freeformPartialInput = (args: string): string => {
if (!args.startsWith(FREEFORM_WRAP_PREFIX)) return args;
const body = args.slice(FREEFORM_WRAP_PREFIX.length);
let out = "";
for (let i = 0; i < body.length; i++) {
const c = body[i];
if (c === '"') break; // unescaped closing quote: value complete
if (c === "\\") {
const n = body[i + 1];
if (n === undefined) break; // escape split across chunks: wait for more
i++;
if (n === "n") out += "\n";
else if (n === "t") out += "\t";
else if (n === "r") out += "\r";
else if (n === "u") {
const hex = body.slice(i + 1, i + 5);
if (hex.length === 4 && /^[0-9a-fA-F]{4}$/.test(hex)) { out += String.fromCharCode(parseInt(hex, 16)); i += 4; }
else break; // incomplete \uXXXX: wait for more
} else out += n; // \" \\ \/ etc.
} else out += c;
}
return out;
};
// tool_search_call carries arguments as a JSON object ({query, limit}); parse the model's arg string.
const parseArgsObj = (args: string): Record<string, unknown> => {
try { const o = JSON.parse(args); return o && typeof o === "object" ? o : {}; } catch { return {}; }
Expand Down Expand Up @@ -484,7 +461,14 @@ export function bridgeToResponsesSSE(
// synthetic compaction item's payload on done.
let compactionText = "";
let compactionTextBytes = 0;
let currentToolCall: { itemId: string; outputIndex: number; callId: string; name: string; args: string; argsBytes: number; namespace?: string; freeform?: boolean; toolSearch?: boolean; inputEmitted?: string } | null = null;
let currentToolCall: {
itemId: string; outputIndex: number; callId: string; name: string; args: string; argsBytes: number;
namespace?: string; freeform?: boolean; toolSearch?: boolean;
previewMode?: "prefix" | "wrapped" | "raw" | "done";
previewPrefix?: string;
previewEscape?: boolean;
previewUnicode?: string;
} | null = null;
// Open native web-search cell (between begin and end). Holds the output index allocated on
// begin so the matching done reuses it; closed as `failed` if the stream terminates early.
let currentWebSearch: { itemId: string; eventId: string; outputIndex: number } | null = null;
Expand Down Expand Up @@ -996,19 +980,64 @@ export function bridgeToResponsesSSE(
});
}
if (currentToolCall.freeform) {
// Hold while the buffer is still an ambiguous prefix of the JSON wrapper,
// then stream only the unwrapped input suffix (never rewind on mode flips).
if (!FREEFORM_WRAP_PREFIX.startsWith(currentToolCall.args)) {
const full = freeformPartialInput(currentToolCall.args);
const emitted = currentToolCall.inputEmitted ?? "";
if (full.startsWith(emitted) && full.length > emitted.length) {
emit("response.custom_tool_call_input.delta", {
item_id: currentToolCall.itemId, output_index: currentToolCall.outputIndex,
delta: full.slice(emitted.length),
});
currentToolCall.inputEmitted = full;
// Decode only the newly arrived fragment. Re-decoding the accumulated argument
// buffer here makes one-byte upstream chunks quadratic in total input size.
let pending = event.arguments;
let decoded = "";
currentToolCall.previewMode ??= "prefix";
if (currentToolCall.previewMode === "prefix") {
const prefix = (currentToolCall.previewPrefix ?? "") + pending;
if (FREEFORM_WRAP_PREFIX.startsWith(prefix)) {
currentToolCall.previewPrefix = prefix;
pending = "";
} else if (prefix.startsWith(FREEFORM_WRAP_PREFIX)) {
currentToolCall.previewMode = "wrapped";
currentToolCall.previewPrefix = undefined;
pending = prefix.slice(FREEFORM_WRAP_PREFIX.length);
} else {
currentToolCall.previewMode = "raw";
currentToolCall.previewPrefix = undefined;
pending = prefix;
}
}
if (currentToolCall.previewMode === "raw") {
decoded = pending;
} else if (currentToolCall.previewMode === "wrapped") {
for (const c of pending) {
if (currentToolCall.previewUnicode !== undefined) {
currentToolCall.previewUnicode += c;
if (currentToolCall.previewUnicode.length === 4) {
if (/^[0-9a-fA-F]{4}$/.test(currentToolCall.previewUnicode)) {
decoded += String.fromCharCode(parseInt(currentToolCall.previewUnicode, 16));
currentToolCall.previewUnicode = undefined;
} else {
currentToolCall.previewMode = "done";
break;
}
}
} else if (currentToolCall.previewEscape) {
currentToolCall.previewEscape = false;
if (c === "n") decoded += "\n";
else if (c === "t") decoded += "\t";
else if (c === "r") decoded += "\r";
else if (c === "u") currentToolCall.previewUnicode = "";
else decoded += c;
} else if (c === "\\") {
currentToolCall.previewEscape = true;
} else if (c === '"') {
currentToolCall.previewMode = "done";
break;
} else {
decoded += c;
}
}
}
if (decoded) {
emit("response.custom_tool_call_input.delta", {
item_id: currentToolCall.itemId, output_index: currentToolCall.outputIndex,
delta: decoded,
});
}
}
}
break;
Expand Down
20 changes: 20 additions & 0 deletions tests/bridge.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -655,6 +655,26 @@ describe("Responses bridge reasoning and usage parity", () => {
expect(frames.some(f => f.event === "response.function_call_arguments.done")).toBe(false);
});

test("streaming freeform preview handles large one-byte argument streams incrementally", async () => {
const input = "x".repeat(32_000);
const wrapped = JSON.stringify({ input });
const events: AdapterEvent[] = [
{ type: "tool_call_start", id: "c1", name: "apply_patch" },
...Array.from(wrapped, char => ({ type: "tool_call_delta" as const, arguments: char })),
{ type: "tool_call_end" },
{ type: "done" },
];

const frames = await collectSse(bridgeToResponsesSSE(
replay(events), "model", undefined, new Set(["apply_patch"]),
));
const preview = frames
.filter(frame => frame.event === "response.custom_tool_call_input.delta")
.map(frame => frame.data.delta)
.join("");
expect(preview).toBe(input);
}, 3_000);

test("non-streaming error produces failed status", () => {
const json = buildResponseJSON([
{
Expand Down
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