fix: solve #3028 — forward DA1 query responses during shell init#3030
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Fish shell sends a DA1 escape sequence (ESC[c) at startup to detect terminal capabilities. The headless emulator (xterm.js) correctly generates a response, but it was being dropped during the "pending" shell-ready state. This caused fish to wait 10 seconds before timing out and disabling optional features like cursor shape and reflow. The fix removes the shellReadyState gate from the headless emulator's onData callback. Unlike renderer-generated responses (which go through session.write() and are correctly dropped to avoid appearing as typed text), headless emulator responses are written directly to the PTY and consumed by the shell as protocol data.
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zombopanda
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The `emulator.onData` callback only forwarded terminal query responses (DA1, DSR) to the PTY subprocess when `attachedClients.size === 0`. When a renderer client is attached (the normal case when viewing a terminal), the headless emulator's DA1 response was silently dropped. This caused fish shell to wait 10 seconds for a DA1 response that never arrived, then print: "warning: fish could not read response to Primary Device Attribute query after waiting for 10 seconds" The previous fix in superset-sh#3030 removed the `shellReadyState === "pending"` guard but left the `attachedClients.size === 0` check intact. The renderer's xterm also generates DA1 responses, but those go through `write()` which drops all escape sequences during shell init — so neither path delivered the response to fish. Remove the `attachedClients.size === 0` condition so the headless emulator always forwards query responses to the subprocess. This is safe because `sendWriteToSubprocess` writes directly to the PTY via IPC, bypassing the renderer's write path entirely. Fixes superset-sh#3028
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This was referenced Mar 31, 2026
Kitenite
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The `emulator.onData` callback only forwarded terminal query responses (DA1, DSR) to the PTY subprocess when `attachedClients.size === 0`. When a renderer client is attached (the normal case when viewing a terminal), the headless emulator's DA1 response was silently dropped. This caused fish shell to wait 10 seconds for a DA1 response that never arrived, then print: "warning: fish could not read response to Primary Device Attribute query after waiting for 10 seconds" The previous fix in #3030 removed the `shellReadyState === "pending"` guard but left the `attachedClients.size === 0` check intact. The renderer's xterm also generates DA1 responses, but those go through `write()` which drops all escape sequences during shell init — so neither path delivered the response to fish. Remove the `attachedClients.size === 0` condition so the headless emulator always forwards query responses to the subprocess. This is safe because `sendWriteToSubprocess` writes directly to the PTY via IPC, bypassing the renderer's write path entirely. Fixes #3028 Co-authored-by: zombopanda <1810282+zombopanda@users.noreply.github.com> Co-authored-by: Kiet Ho <hoakiet98@gmail.com>
MocA-Love
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Apr 5, 2026
…ing shell init (superset-sh#3030)" (superset-sh#3127) This reverts commit 3194568.
MocA-Love
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…rset-sh#3054) The `emulator.onData` callback only forwarded terminal query responses (DA1, DSR) to the PTY subprocess when `attachedClients.size === 0`. When a renderer client is attached (the normal case when viewing a terminal), the headless emulator's DA1 response was silently dropped. This caused fish shell to wait 10 seconds for a DA1 response that never arrived, then print: "warning: fish could not read response to Primary Device Attribute query after waiting for 10 seconds" The previous fix in superset-sh#3030 removed the `shellReadyState === "pending"` guard but left the `attachedClients.size === 0` check intact. The renderer's xterm also generates DA1 responses, but those go through `write()` which drops all escape sequences during shell init — so neither path delivered the response to fish. Remove the `attachedClients.size === 0` condition so the headless emulator always forwards query responses to the subprocess. This is safe because `sendWriteToSubprocess` writes directly to the PTY via IPC, bypassing the renderer's write path entirely. Fixes superset-sh#3028 Co-authored-by: zombopanda <1810282+zombopanda@users.noreply.github.com> Co-authored-by: Kiet Ho <hoakiet98@gmail.com>
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Summary
ESC[c) at startup to detect terminal capabilities, but the response was dropped during the "pending" shell-ready state, causing a 10-second timeoutshellReadyState === "pending"gate from the headless emulator'sonDatacallback so query responses (DA1, DSR, etc.) are forwarded to the subprocess immediatelyRoot cause
In
session.ts, the headless emulator'sonDatacallback had a guard that dropped all terminal query responses whileshellReadyState === "pending". This was intended to prevent responses from appearing as typed text, but the headless emulator writes directly to the PTY (viasendWriteToSubprocess), not through the pre-ready stdin queue. The shell reads these as protocol data, not user input.Fish sends DA1 during this exact "pending" window and waits up to 10 seconds for a reply. Without a response, fish disables cursor shape changes, reflow detection, and other optional features.
Test plan
Closes #3028
Summary by cubic
Forward terminal query responses (DA1, DSR) from the headless emulator during shell init so shells like fish don’t hang for 10s or disable features. Fixes #3028.
shellReadyState === "pending"guard in the headless emulatoronDataso DA1/DSR responses are written to the PTY immediately.Written for commit e807b39. Summary will update on new commits.