From Controlled Experiments to Trial Use

Working plan, updated 2026-09-22. This document tracks implementation evidence and engineering priorities. Agreed semantics are recorded in the protocol drafts.

Current Assessment

The codec, SDK, terminal Session, and experimental xterm renderer form an executable path. Fixed single-round and multi-round applications run through Windows bundled ConPTY. The pre-trial checklist below is implemented, with recorded tests for each item.

Following the Pi architecture assessment, the Pi session experiment connects the pinned Pi SDK and one read-only tool through SDK bytes, Windows ConPTY, and the experimental xterm host. Both local fixtures and a finite OpenAI subscription trial have browser evidence for completion/search and cancellation. The live source uses SSE after a recorded model WebSocket failure whose root cause remains unresolved. The trial uses a separate plain-text frontend; Pi’s editor and extension UI remain integration work. Other terminals need their own rendering/history integration.

A separate paired Pi reading comparison uses fixed actual Pi sessions and captured pre-PTY output. Both frontends preserved reading during tail streaming. In the tested earlier-tool shrink and resize cases, the protocol frontend preserved reading/selection where Pi’s regular frontend did not. Neither path showed duplication of the checked text.

The entered-prompt multi-round Pi frontend completes the bounded third-stage interactive trial: one in-memory Pi conversation with separate display Contexts per turn. Local-provider ConPTY/xterm checks cover follow-up, assistant/tool cancellation then continuation, old reading/selection/copy, retained search, and orderly exit. Pi’s public stop-after-turn hook avoids preparing another model request after tool cancellation; genuine errors still stop the connection. A separate four-prompt subscription checkpoint observed live context retention and assistant cancellation then continuation.

The coding trial adds a generated project with two readable files, one editable source, and a fixed test command. Local-provider and live subscription runs reproduced three failures, applied a quantity fix, passed all six tests, and repeated the tests in a second turn. Earlier failure output remained searchable and copyable.

Completed Work and Evidence

The linked records provide scenario details, measurements, commands, and limits for each dated checkpoint.

Work	Recorded result	Evidence
Update of the Block being read, 2026-09-14	Replacement-start viewport policy; seven Node and three browser cases	Anchored Update
Full-Block eviction and render failure	Reject mutation of evicted content; stop after injected partial rendering failure	Eviction and containment
Finite multi-round use, 2026-09-15	Three commanded rounds and orderly mid-round quit; separate application checks	Multi-round example
Local queue accumulation, 2026-09-16	Ordering alone does not bound pending pushes; local batch waiting reduces the measured backlog	Ingress pressure
Browser consumption credits, 2026-09-16	Opt-in PTY pause/resume and finite completion; watermark overshoot observed	PTY pressure
Producer waiting, 2026-09-17–18	Synchronous writes waited during paused reading and overlapped the composed browser hold	Isolated probe, composed run
Permanent consumer stall, 2026-09-19	Stop forwarding, request child termination, observe exit, and fail the connection	Stall experiment

The pressure experiments observed producer waiting even with zero stdout drain events, and queues could exceed their high watermark. After partial rendering failure, the host stops with the partial state retained. The anchored-Update experiment uses a terminal-chosen policy; below one screen of content, viewport clamping loses separate off-tail reading intent.

Pre-trial Checklist Completed on 2026-09-19

1. Cleanup failures. Fault-injection tests exercise missing/late exit, failed kill, unresponsive socket closure, trailing output, and failed exit notification. The shared bridge keeps its child slot until both exit and socket closure are observed. Fake events and timers test failure ordering; the real stalled-consumer browser run supplies separate bundled-ConPTY evidence.

2. Resource accounting. Trial budgets bound selected retained content, identity/replay structures, and owned pending input. Content overflow rejects atomically; identity/replay exhaustion stops execution rather than forgetting protocol meaning. Closed and evicted records remain charged. Hosts opt into these local limits; total process memory and reclamation still need separate handling.

3. Application failure handling. Lifecycle tests distinguish unsupported/silent startup negotiation from failure after protocol output starts. Tested runtime failures stop later sends without fallback; cleanup restores input mode and removes handlers. These tests inject failures through synthetic streams.

4. Content samples. The sample report records seven Node and four browser cases for literal code, Chinese, long lines, selected Unicode sequences, and unsupported Tab mapping. Assertions inspect stored Buffer text and Session content; glyph shaping and native interaction for these Unicode sequences need further tests.

That checkpoint passed type checking, 224 Node tests, four affected browser builds, 73 browser endpoint scenarios, two single-round and two multi-round browser checks, and the permanent-consumer-stall check. The latter three fixtures use local Windows bundled ConPTY. Normal examples select the trial budgets but still omit the pressure fixtures’ consumption credits/watchdog.

Remaining Work and Decision Points

• Pi integration scope: the entered-prompt trial and one generated-project coding workflow are complete. Real repository access needs a selected project, explicit permissions, and execution isolation. Stock-UI reuse, a full fallback frontend, and an upstream proposal remain follow-up choices.

• Capacity and retention: partial-Block or unmanaged-row eviction, general snapshot reclamation, and long-session behavior remain open. Full-Block eviction follows the existing semantics.

• Failure and pressure: automatic rollback/recovery, whole-process memory bounds, fairness, and a policy for slow-but-progressing consumers remain open. See the host contract.

• Compatibility: wider Unicode interaction, arbitrary terminal controls, Unix, SSH/tmux, and other terminals need targeted evidence from actual integration requirements.