[listar2000]

Merge with rebase, not squash

Replaces #49 (same change, renumbered to fix-017 after review).

Outcome

Finished agent runs no longer get thrown away when the server holding their data is slow to hand it back. The trainer now waits up to 30 min (new flag --session-collect-timeout) instead of a fixed 2 min.

Words used below:

• A try is one agent working one task once. Training uses groups of 16 tries on the same task, and scores each try against the others in its group.
• While a try runs, a session on a session server records every model call it makes. When the agent finishes, the trainer collects that record as training samples, then deletes the session.

	Before	After
Wait for a finished try's samples	120 s, fixed	--session-collect-timeout, default 1,800 s
Wait for the session delete	120 s, fixed	the same flag
What a timeout costs	the try is dropped, and with it its whole group of 16	unchanged, but only a stuck server should reach it
3-node DeepSeek-V4.1-Flash overfit run	134 finished tries lost, 15 groups dropped, the next step waited 29 min for its batch	expected: none lost to this

In that run, the 32 session servers ran on the head trainer node. Every one of the 134 timeouts landed while the trainer was running its optimizer step. The head node's optimizer step also took about 30% longer than the other trainer node's, so CPU contention on that node is the likely cause (inferred, not measured per process). All of those tries had finished normally. After this change, a slow session server costs a few minutes, not a whole group.

Patch page: fork/patches/fix-017-session-collect-timeout.md

Contract

• New argument --session-collect-timeout (float, seconds, default 1800). It bounds both the request for a finished session's samples and the session delete. Recipes don't need to set it.
• OpenAIEndpointTracer(..., collect_timeout=120) is a new keyword with the old value as its default, so direct constructions behave as before. OpenAIEndpointTracer.create(args) reads the argument.

Side-effects

• Upstream files touched, all marked [fork fix-017]: miles/rollout/generate_utils/openai_endpoint_utils.py, miles/utils/arguments.py, tests/fast/rollout/generate_utils/test_openai_endpoint_utils.py.
• A session server that is truly stuck now holds its try for up to 30 min before the group is dropped, instead of 2 min. Other groups keep filling the batch in the meantime.
• Not included: moving the session servers off the head trainer node. That would remove the cause, but the session proxy forwards only to the head's address, so it is a separate change that needs a GPU check.
• Both this PR and fix(rollout): score-centering candidates as flat base64 arrays [fork fix-016] #45 add a row to fork/patches/README.md; they merge cleanly in either order.

Done

• Rollout: collect_samples uses self.collect_timeout for both calls, and create() takes it from args.session_collect_timeout.
• Arguments: --session-collect-timeout in the session argument group.
• Tests: create reads the argument, and both calls get the bound.
• Patch page fork/patches/fix-017-session-collect-timeout.md and its README row.

Verification

• python fork/tools/ledger.py check: ok.
• pre-commit run --from-ref c678bbd778 --to-ref HEAD: all hooks pass.
• In the launch image built from this branch (CPU container): pytest tests/fast/rollout/generate_utils/test_openai_endpoint_utils.py tests/fast/rollout/test_fully_async_rollout.py tests/fast/rollout/session gave 416 passed and 3 failed. Two failures are test_session_server_benchmark[v1|v2], which also fail on main c678bbd in the same container. The third, test_post_buffer_no_retry_closes_stalled_body_connection[cancel], is a timing race that fails at random on main and on this branch alike (1 of 3 repeat runs failed on main, 0 of 3 here).
• The two new tests fail on main's code in under 3 s: create() sets no collect_timeout (AttributeError), and the constructor rejects collect_timeout (TypeError).
• No GPU run yet. The next DeepSeek-V4.1 overfit run will show whether any Failed collecting samples lines remain.