fix(text): fail when the chat stream ends without a terminator

[2sumtech]

Summary

mmx text chat --stream treats a dropped connection as a finished response. It
prints the partial answer and exits 0, so a caller cannot distinguish a
truncated reply from a complete one. With --output json it is worse: the
command emits a well-formed, complete-looking {"content": "..."} object that
silently contains only the bytes that arrived.

ERRORS.md already documents the intended behaviour under ## Text Commands →
mmx text chat:

Scenario	Error Message
Stream disconnected mid-response	Stream disconnected before response completed.

That string does not exist anywhere in src/ or test/ — the documented error
is never raised. This is a contract violation against the repo's own error
reference, not a new behaviour proposal.

Root cause

src/commands/text/chat.ts — the SSE consumer exits its loop on whatever ends
the generator, with no notion of a terminator:

for await (const event of parseSSE(res)) {
  if (event.data === '[DONE]') break;
  ...
}
if (inThinking) think.stop();

if (format === 'json') {
  console.log(formatOutput({ content: textContent }, format));   // reached either way
}

parseSSE (src/client/stream.ts) returns normally when the body reader
reports done, which is exactly what a server or proxy closing the connection
early produces. message_stop — a member of the StreamEvent union in
src/types/api.ts — is never inspected, and neither is the absence of
[DONE]. The success path then runs unchanged.

Merged PR #227 (fix: time out stalled streams) covers the stalled case (no
bytes for N seconds) in src/client/http.ts; a stream that closes cleanly but
early never trips that timeout.

Fix

One flag in src/commands/text/chat.ts, set by either terminator the API uses,
checked once after the loop:

let streamCompleted = false;

for await (const event of parseSSE(res)) {
  if (event.data === '[DONE]') { streamCompleted = true; break; }
  ...
  if (parsed.type === 'message_stop') {
    streamCompleted = true;
  } else if (parsed.type === 'content_block_start') {
  ...
}
if (inThinking) think.stop();

if (!streamCompleted) {
  if (!isJsonOutput) resultOut?.write('\n');
  throw new CLIError('Stream disconnected before response completed.', ExitCode.NETWORK);
}

Exit code 6 (ExitCode.NETWORK), per the ### Exit Codes table in ERRORS.md
("Network error") — a dropped stream is a transport failure, not a usage or
content error. Text already streamed to stdout is left as-is (a newline is
added so the shell prompt is not glued to the partial output); the JSON summary
is not printed, so no complete-looking object is produced for an incomplete
response.

Accepting [DONE] as well as message_stop keeps every existing streaming
test green — the repo's sseResponse helper appends data: [DONE].

How tested

New regression test in test/commands/text/chat.test.ts driving the repo's
existing test/helpers/mock-server — no live API call, no API key.

Reproduction (before the fix)

Mock route returns an SSE body with deltas and no terminator:

data: {"type":"content_block_delta","delta":{"type":"text_delta","text":"Hello"}}

data: {"type":"content_block_delta","delta":{"type":"text_delta","text":" wor"}}

mmx text chat --message Hello --stream --output json prints:

{
  "content": "Hello wor"
}

Exit code 0. Expected (per ERRORS.md): Stream disconnected before response completed. with exit code 6.

Test evidence — fails before, passes after

Without the source change (test only):

$ bun test test/commands/text/chat.test.ts
test/commands/text/chat.test.ts:
356 |       ).rejects.toThrow('Stream disconnected before response completed.');
                      ^
error:

Expected promise that rejects
Received promise that resolved: Promise { <resolved> }

(fail) text chat command > should fail when the SSE stream ends without a terminator instead of printing truncated output [7.76ms]

 6 pass
 1 fail
Ran 7 tests across 1 file. [59.00ms]

With the fix:

$ bun test test/commands/text/chat.test.ts
bun test v1.3.13 (bf2e2cec)

 7 pass
 0 fail
 11 expect() calls
Ran 7 tests across 1 file. [216.00ms]

Full suite / typecheck / lint:

$ bun test
 575 pass
 1 fail
 1267 expect() calls
Ran 576 tests across 67 files. [11.92s]

# The single failure is pre-existing and unrelated:
#   (fail) agent installer > times out and terminates the installer process tree
# It reproduces identically on an unmodified `main` checkout under the full
# suite (574 pass / 1 fail) and passes when that file is run on its own.

$ bun run typecheck
$ tsc --noEmit
(no output, exit 0)

$ bun run lint
$ eslint src/ test/
/…/test/sdk/speech.test.ts
  117:39  warning  Unexpected any. Specify a different type  @typescript-eslint/no-explicit-any
✖ 1 problem (0 errors, 1 warning)      # pre-existing, unrelated file

Environment: bun 1.3.13, macOS.

Duplicate check

Run via gh api search/issues (all states) and gh api .../pulls/<n>/files:

Query	Result
repo:MiniMax-AI/cli Stream disconnected	0
repo:MiniMax-AI/cli message_stop	0
repo:MiniMax-AI/cli stream truncated	4 — #206 (truncated downloads), #262, #158, #79; none about SSE termination
repo:MiniMax-AI/cli SSE	16 — all closed; #55/#60/#130 decode audio SSE, #110 adds parseSSE tests, #197 surfaces music stream errors
repo:MiniMax-AI/cli DONE stream	2 — #158, #55; unrelated
repo:MiniMax-AI/cli parseSSE	4 — #110, #55, #60, #122; none add a terminator check
repo:MiniMax-AI/cli text chat stream	13 — closest are #148/#149 (thinking-token UX) and #124 (stream JSON output), both merged, neither checks for completion
repo:MiniMax-AI/cli in:title stream	9 — closest is #227 fix: time out stalled streams (merged, src/client/http.ts): an idle timeout, which a cleanly-closed early stream never trips

All 13 open PRs checked file-by-file (#261, #230, #228, #226, #225, #223, #222,
#221, #219, #209, #207, #204, #186). Only #225 and #204 touch
src/commands/text/chat.ts; neither patch mentions parseSSE, message_stop,
[DONE] or disconnect handling, and neither touches ERRORS.md.

Disclosure: prepared with AI assistance (Claude Code); I reviewed the change and take responsibility for it.

🤖 Generated with Claude Code

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