v0.2.1

Tau v0.2.1

User-facing changes since v0.2.0, selected from the full commit descriptions.

Before upgrading

• Rust extension SDK users must update their source. The harness uses protocol
  10.2 and SDK 0.10.0. Configure gains optional-secret absence metadata,
  changing Rust struct construction. The seven packaged external projects remain
  on SDK 0.8.0 / protocol 10.0; they are admitted with the existing
  same-major warning and best-effort behavior, but do not gain the new metadata API.
• Tool-policy lists now merge additively. The six tool name, group and tag
  enable/disable selector lists append unique entries across configuration layers
  and agent/group/role scopes. Use an explicit empty list to clear an inherited
  field; omission inherits it. Review overlays that previously relied on a
  nonempty list replacing an earlier list.
• Credential and configuration refresh still requires a full harness restart.
  An extension-only respawn retains its resolved credential snapshot. This release
  does not activate a new binary or restart any running session for you.

GPT-6.1 Sol and cost estimates

• The ChatGPT/Codex catalog now includes gpt-6.1-sol, with its context/output
  limits, supported reasoning levels and standard short-context API-equivalent
  rates. The shipped default model is unchanged; account access is not guaranteed.
• Sol uses the existing private Function/Custom tool workflow and local-summary
  compaction. Unverified private native/inline compaction, Lite, image tool
  results, phase and verbosity remain unadvertised. The public Responses example
  uses the existing text/Function-only adapter.
• Official OpenAI Chat Completions rejects unsupported Sol tool declarations and
  tool history locally rather than silently dropping them. Custom compatible
  endpoints retain their configured contracts.
• Fixed cost estimates were audited. The retired DeepSeek V4 Flash alias routes
  to V4.1 Flash with conservative peak estimates; the unknown-model fallback is
  labeled GPT-5.5-equivalent. These are estimates, not invoices: long-context,
  tier, regional, tool, subscription and dynamic pricing remain outside the
  scalar base-rate calculation.

Configuration and web tools

• Optional web credentials now behave as declared. Exa, Parallel and You retain
  their anonymous configuration when optional keys are absent; Brave, Tavily and
  Firecrawl leave their configured pools. Missing undeclared or required secrets
  still fail, and both search and fetch must retain a usable provider or the
  entire extension rejects configuration with a pool-specific diagnostic.
• Hosted web activity distinguishes search, page opening and page searching
  without showing queries, URLs or patterns in the activity label. Prompts explain
  when an external fetch is a useful fallback rather than a mandatory duplicate
  read. Cached/index access is not a guarantee of a current live page.
• A complete annotated harness example is linked from the learning guides. It
  includes GPT-6.1 Sol role selections and fictional project-path placeholders;
  adapt it to your setup rather than treating it as the shipped default.

Agent responsiveness

• Completed delegates can receive follow-up prompts and peer messages while older
  background tools continue running. Background results retain their ownership
  and normal delivery; genuine replacement inference or foreground tools still
  protect their active turn.
• Ordinary agent messages admitted during an exact or plural tool wait become
  eligible after 20 seconds, down from 120 seconds by default. Configured
  overrides still apply. This does not cancel tools or impose a global delivery
  deadline; the ordinary-message any-input wait remains five seconds.

Distribution and limits

Tau remains pre-1.0. The native distribution includes Tau and seven independently
versioned external projects, with nine executables including the Telegram gateway.
AMD64 and ARM64 each have individual and tau-full DEB, RPM and tar.gz packages.
tau-full DEB/RPM is an exact-dependency metapackage; its tarball combines payloads.

Native packaging checks compilation, ELF shape, source/version metadata, archive
integrity and a bounded version probe. It does not qualify package-manager
install/uninstall, supervised startup or broad distro/CPU/kernel portability.
The binaries require the conventional glibc loader, glibc 2.34 or newer, libgcc
and CA certificates; NixOS users should use the Nix route. Linux 5.12 remains the
documented mount-API minimum. Assets are checksummed, not signed or independently
attested, and bit-for-bit reproducibility is not claimed.