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Respond to DA1 queries to fix fish shell 10s startup delay
Fish 4.x sends a DA1 (Primary Device Attribute) query at startup
and blocks for up to 10s waiting for a response. Add a CSI handler
in PtyServer that intercepts the query and writes back a VT220
response. Add shell integration tests for bash, zsh, and fish.
Closes #5
Based on the approach by @schickling-assistant in #5
Nathan Herald
(Apr 6, 2026, 9:12 PM +0200)
4f7d628b
a5f09b5d
+83
+14
src/server.ts
+14
src/server.ts
···
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}
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);
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// Respond to DA1 (Primary Device Attribute) queries from the child process.
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// Shells like fish 4.x send ESC[c at startup and block for up to 10s waiting
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// for a response. Since xterm-headless doesn't reply, we intercept the query
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// in the output stream and write a VT220 response back to the pty process.
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this.terminal.parser.registerCsiHandler(
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{ final: "c" },
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(params) => {
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if (params.length === 0 || params[0] === 0) {
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this.ptyProcess.write("\x1b[?62;22c");
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}
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return false;
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}
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);
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// ── Event detection ──
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this.terminal.onBell(() => {
+69
tests/shells.test.ts
+69
tests/shells.test.ts
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import { describe, it, expect } from "vitest";
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import { Session } from "../src/testing/index.ts";
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// Shell integration tests — verify that common shells start up,
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// accept input, and produce output when run inside a pty session.
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//
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// bash and zsh use Session.spawn() (direct PTY, no server).
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// fish uses Session.server() (PtyServer) to exercise the DA1 response
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// handler — fish 4.x sends DA1 at startup and blocks 10s without it.
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describe("shell integration", () => {
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describe("bash", () => {
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it("starts up and accepts commands", async () => {
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const session = Session.spawn("bash", ["--norc", "--noprofile"], {
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rows: 24,
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cols: 80,
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});
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await session.waitForText("$", 5000);
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session.type("echo hello-bash\r");
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await session.waitForText("hello-bash", 5000);
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session.press("ctrl+d");
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await session.close();
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}, 15000);
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});
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describe("zsh", () => {
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it("starts up and accepts commands", async () => {
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const session = Session.spawn("zsh", ["--no-rcs"], {
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rows: 24,
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cols: 80,
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env: { PROMPT: "zsh> " },
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});
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await session.waitForText("zsh>", 5000);
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session.type("echo hello-zsh\r");
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await session.waitForText("hello-zsh", 5000);
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session.press("ctrl+d");
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await session.close();
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}, 15000);
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});
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describe("fish", () => {
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it("starts up within 3 seconds (requires DA1 response)", async () => {
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// fish 4.x sends a DA1 query (ESC[c) at startup and blocks for up to
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// 10s waiting for a terminal response. PtyServer must respond to DA1
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// for fish to start promptly. This test uses Session.server() to go
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// through PtyServer.
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const session = await Session.server("fish", ["--no-config"], {
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rows: 24,
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cols: 80,
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});
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await session.attach();
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// If DA1 is not handled, this will timeout at 3s
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await session.waitForText(">", 3000);
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session.type("echo hello-fish\r");
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await session.waitForText("hello-fish", 5000);
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session.type("exit\r");
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await session.close();
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}, 15000);
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});
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});