Follow-up to bug 903. The attach fix made run_tests retries safe, but
agents still observed the underlying MCP transport timeout as a
tool-call error and had to handle it via retry. Implement the proper
fix: MCP `notifications/progress` events keep the client's transport
timer alive so the call never errors from the agent's perspective.
What changed:
server/src/http/mcp/progress.rs (new)
- `ProgressEmitter` (progressToken + mpsc sender) installed in a
`tokio::task_local!` scope by the SSE response path.
- `emit_progress(progress, total, message)` builds a JSON-RPC
`notifications/progress` message and sends it via the channel.
No-op when no emitter is in scope (plain JSON path / tests / API
runtimes), so tool handlers can call it unconditionally.
server/src/http/mcp/mod.rs
- mcp_post_handler now detects `Accept: text/event-stream` AND a
`params._meta.progressToken` on tools/call. When both are present,
routes through `sse_tools_call` instead of the plain JSON path.
- sse_tools_call: spawns the dispatch task with the emitter installed,
builds an SSE stream that interleaves incoming progress events with
the final JSON-RPC response, with a 15s keep-alive interval as a
backstop for tools that don't emit their own progress.
- Plain JSON behaviour is unchanged for non-SSE clients and for
everything other than tools/call.
server/src/http/mcp/shell_tools/script.rs
- tool_run_tests poll loop emits `notifications/progress` every 25s
of elapsed time (well below the typical ~60s MCP transport
timeout). Attached callers (the bug 903 fix path) also emit so
their MCP socket stays alive while waiting for the in-flight job.
- Output filtering: on a passing run the response now returns a
one-line summary ("All N tests passed.") instead of the full
`cargo test` stdout, which was pure noise that burned agent
tokens. Failure output is unchanged (truncated tail with the
`failures:` section and final test_result line). CRDT entry
stores the same filtered value so attached callers see it too.
Tests (3 new):
- emit_progress_no_op_without_emitter — calling outside scope is safe
- emit_progress_sends_notification_when_emitter_installed — full path
- emit_progress_omits_optional_fields — total/message optional
Not changed: coder system_prompts still tell agents to retry on
transport-timeout errors. That advice is now belt-and-braces — if
claude-code's HTTP MCP client honours progress notifications, no agent
will ever observe the error; if not, retry is still safe post-903. We
can drop the retry advice once we've observed the SSE path working in
the field.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Timmy