T1.8 — P1 composition gate

Field	Value
Phase	P1 — Walking skeleton
Size	M — 1 to 3 days
Status	Not started
Flags	gate
Spec	inlined below
Blocks	P2

Goal

Prove T1.1–T1.7 compose into one recorded run that re-derives byte-identically, and that the pluggable parts of the skeleton are genuinely pluggable.

Phase gate criterion: one full run is recorded and re-derives byte-identically.

Facts (inlined — no spec read needed)

The walking skeleton is one full run of one workflow against a stub model, in embedded mode, with no network — recorded, verified, and re-derivable from the log. Nothing after it is worth starting until it runs.
Nothing is built before the record is trustworthy: no dashboards and no learning loop until this passes.
The composition properties no single P1 task owns:
- cancellation from any state leaves a legal attempt state and a complete log (T1.1 + T1.3 + T0.2);
- a retry, a cancel and a normal completion all produce episodes that survive drop-and-re-fold (T1.4 + T1.7 + T0.8);
- context partitions and blob refs are present on every model step of every attempt, including failed ones (T1.5 + T1.6 + T1.4).
The serial spine is (TenantId, RunId). Parallelism lives between runs. A composition test with one run cannot see a violation of this.

Steps

Build the run matrix: {clean, one retry, two retries, cancelled mid-step, cancelled during Verifying} × {served from state, served from cold re-fold}.
Assert every cell produces a consistent episode and a legal state sequence.
Swap the stub model script and the verifier implementation without touching executor code — the skeleton must not know which is installed.
Run 50 runs concurrently across 2 tenants; assert per-run ordering and cross-run independence.
Make this the required CI job gating P2.

Acceptance

Every matrix cell is green.
A full run is recorded and re-derives byte-identically.
Swapping the stub script or the verifier requires no executor change.

Verify

Harness: the P0 in-memory ports (T0.9) for speed, plus the real redb path for at least one cell — a composition that only works in memory is not a composition.

Integration test — tests/it_p1_composition.rs:

Matrix: for each of the 10 cells, assert the episode from materialized state and from cold re-fold are byte-identical, and that the run's state sequence is legal under T0.2's table.
Cancel sweep: cancel from Scheduled, Running, Verifying, Grading. For each, assert the attempt lands in Cancelled (no dispatched intent), every spawned task terminated before RunScope returned, and the log is complete up to the cancel.
Capture completeness: across all cells, assert every model-step attempt — including failed ones — carries a context partition and prompt and output refs. Iterate, do not sample.
Immutability under composition: in the two-retry cell, snapshot attempts 1 and 2, run to completion, assert byte equality. Then drop state, re-fold, and assert the attempts are still identical.
Isolation: 50 concurrent runs across 2 tenants. Assert each run's records are totally ordered, no two steps of one run overlap in time, and no record carries the wrong tenant.
Pluggability: run the same matrix with a second stub script and a second verifier. Assert zero changes to executor code — enforce by keeping the executor crate's test-only surface empty.
Regression: re-run every P1 and P0 task suite in the same job.

Command: cargo test -p skeleton --test it_p1_composition

False pass:

Testing only the clean cell. Retry and cancel are where the fold, the scope and the capture paths interact, and each is individually green already.
Step 3 sampling one attempt. A capture path that skips failed attempts passes a sample and discards the entire learning signal.
Step 5 with one run, where serial execution and accidental parallelism are indistinguishable.
Step 1 comparing episodes with PartialEq rather than serialized bytes.

Traps

Declaring the gate green with Verifying/Grading collapsed into function calls. The states must appear in the log, or T4.2's barrier has nowhere to live.
Building any dashboard or grading work before this is green.

Background (not required to do this task): rust-agentic-sys.md §5.2, §5.3, §16, §20 · rust-agentic-task.md

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