v0.9.3

v0.9.3 - three vendors, context files that arrive, and --resume

0.9.2 asked what a stranger's first hour looks like. This release is the
answer, plus two things nobody planned: tau's own system prompt had never
reached a model, and every model was being served over the OpenAI wire
whatever it declared.

Vendors

• tau speaks three wire protocols now: openai-completions (unchanged, still
  the default), anthropic-messages, and google-generative-ai. The two vendor
  SDKs are optional extras — ffwf-tau-llm[anthropic] and ffwf-tau-llm[google]
  — imported lazily on first request, so a plain install pulls neither.
• tau dispatches on Model.api. It used to construct OpenAICompletionsProvider
  unconditionally and read model.api not at all, so a model declaring a
  protocol tau has never implemented was served over the completions wire in
  silence. An unknown api now raises, naming what is registered.
• Model.api, AssistantMessage.api and .provider widen to str. The last was
  pinned to "openai", so a legal Model naming any other vendor raised a
  validation error when the vendor was copied onto the message.
• The Google vendor registers as gemini, matching the backend value config
  entries already carry.
• Reasoning signatures are namespaced by vendor, and the OpenAI writer
  REFUSES a foreign one rather than forwarding a token another vendor will
  reject. A Gemini 3 function-call signature is replayed on every
  reasoning_replay setting including "off" — it is protocol, not
  chain-of-thought, and omitting it is a 400.
• Three capability questions were settled by measurement against the live
  API rather than by reading. Records are in docs/probe-results/.

The system prompt and project context files

• BEFORE THIS RELEASE NEITHER HAD EVER REACHED A MODEL on the TUI or
  headless path. The backend passed a config key straight through and never
  called the loader behind it.
• Discovery now walks the agent dir, then every ancestor of cwd, root-most
  first, one file per directory, first match among AGENTS.override.md,
  AGENTS.md, AGENTS.MD, CLAUDE.md, CLAUDE.MD. CLAUDE.md was not a name tau
  knew at all. A worktree nested in its own repo shadows the repo's copy.
• Context files COMPOSE with system_prompt instead of being switched off by
  it. --no-context-files / -nc turns discovery off.
• A found-but-unreadable file raises, naming the path. Every block is
  wrapped in <project_instructions path="..."> so a prompt cannot carry
  instructions whose origin it does not state.
• A real coding-agent prompt ships, and tau_default_config.json no longer
  carries a system_prompt key.

Sessions

• --resume works. It had been rejected in both modes since it was added,
  with help text saying "TUI only" and an error blaming headless mode.
• A session picker, with fuzzy filter and a Tab that widens the scope from
  this directory to all. --resume, /resume and the command palette are one
  handler with three bindings.
• The sidebar starts closed.
• The branchOf lane tag is gone. Three of its four consumers used it to ask
  "does this belong to the conversation being looked at", which is ancestry
  from the cursor — so a three-way fork returned three mutually exclusive
  alternatives as one conversation.

Backends that are not quite OpenAI-shaped

• Model.stream (default true) — a gateway with no SSE was unreachable
  through any config path.
• Model.request_timeout — 300s read and 10s connect were fixed at client
  construction with no override anywhere.
• context_window and max_tokens are reachable; they were hardcoded at 128000
  and 4096 for every model in existence.
• python -m tau_llm.catalog fills a config entry from models.dev. Nothing
  is vendored; --base-url is required and never guessed.
• Four failures that used to arrive unattributable: a tool call with no name
  was built and executed (now raises, naming the call id, model and base
  URL); an error could carry no content at all; a keepalive frame crashed
  the turn; the timeout was unreachable.

SDK

• create_agent_session takes no_tools ("all" | "builtin" | None) and
  no_context_files. Passing tools= and no_tools= together raises.

JMFTS store

• Stop using a character count as a proxy for a token window; ask the
  server. 1800 characters of base64 is about 1350 tokens against a 512-token
  limit, so dense content took the "short enough to embed whole" path and
  was refused.

Packaging and release

• Python 3.11, 3.12, 3.13 and 3.14 are measured, not claimed.
• dist/ is gitignored.
• The missing-SDK error hint named tau-llm[google], which does not resolve —
  tau imports as tau_llm and publishes as ffwf-tau-llm. Fixed, with a test
  that reads the four distribution names out of the pyproject.toml files.

Upgrade notes

• SessionLog implementors: lane= is gone from the Protocol and every shipped
  store. resolve_cursor is "last entry wins" again. One contract test is
  inverted — a store must not reintroduce a cursor filter.
• The default system prompt changed, and system_prompt is no longer in the
  shipped config.
• A CLAUDE.md or AGENTS.md above your working directory is read now, on
  every run, all the way to /. -nc turns discovery off.
• A gateway that omits function.name now raises on the first call instead of
  burning up to max_turns.
• A model config naming an api tau does not implement now raises.
• create_agent_session(tools=..., no_tools=...) now raises.

Co-Authored-By: Claude Opus 5 (1M context) noreply@anthropic.com