Evidence record / pi-coding-agent
A dated record of one change, kept so the writing that cites it can be checked. Compiled from the sources listed below by the research run, not written for reading. The judgment lives in the issues that cite it, below.
2026-08-10-pi-coding-agent-the-session-and-harness-api-is-replaced-wholesale-with-the-v4-lane
The session and harness API is replaced wholesale with the v4 lane-based model; legacy repositories removed.
v0.84.0 replaces the inherited pi-agent-core harness session model with the v4 lane-based Session, SessionStorage, and SessionRepo APIs, adding durable operation records, global facts, shared sequence numbers, and tree-scoped lane views. The v2 session and AgentHarness API was promoted from pi-agent-core's experimental entrypoint to its default export and the experimental subpaths were removed. The legacy JSONL and in-memory repository APIs are gone; callers must move to v4 JsonlSessionRepo or InMemorySessionRepo, both implementing the new SessionRepo contract. Also breaking in the same release: ModelRegistry.refresh() now takes ModelsRefreshOptions and returns ModelsRefreshResult instead of discarding cancellation and provider errors; ModelRuntime.setRuntimeApiKey() takes auth cancellation options rather than catalog refresh options; config-form extension OAuth refreshToken(credentials, signal) callbacks must honor a concrete abort signal; and dynamic provider refresh store access is replaced by the read-only context.stored snapshot plus a generation-checked context.publish() transaction.
Channel: tagged-release. Ancestry: Documented in the body of the v0.84.0 release under Breaking Changes. v0.84.0 is a stable tag at sha a5f43bf8aff3c55752432655f7334e3dafd1e256 (gh api repos/earendil-works/pi/tags), published 2026-08-06T11:07:05Z with prerelease=false and draft=false per gh api repos/earendil-works/pi/releases. The supporting work is visible as a run of harness-v2 commits in gh api repos/earendil-works/pi/compare/v0.83.0...v0.84.2 dated 2026-08-05 and 2026-08-06 (e.g. 651d5d6a "partial harness v2/json backend (#7611)", 2bb7ba49 "feat: harness v2 r2 (#7669)", a838c069 "harness-v2 jsonl session atomic writes for forks & torn-tail truncation (#7707)").
Operator consequence: Adapt before upgrading, and pin if you embed. If you have wrapped Pi as an agent adapter or built on its SDK, 0.84.0 is not a drop-in minor -- session storage, model-registry refresh, and provider registration contracts all moved at once. The release notes carry before/after migration snippets for the provider refresh path; providers built with createProvider({ fetchModels }) need no change, but handwritten Provider.refreshModels() implementations that touched context.store directly must be rewritten around context.publish(). Budget a migration pass rather than a version bump.
Receipt
Finding metadata
Run: 2026-08-10-weekly-digest-2026-08-03_2026-08-10-frontier-v0
Finding ID: 2026-08-10-pi-coding-agent-the-session-and-harness-api-is-replaced-wholesale-with-the-v4-lane
Source links
Primary links, including exact changelog lines when available.
Versioned source: run artifact