think: align generics with Agent/AIChatAgent + multi-session RFC

[threepointone]

Two related changes to @cloudflare/think in one branch.

1. Align Think generics with Agent / AIChatAgent

Think<Env, Config> becomes Think<Env, State, Props> extending Agent<Env, State, Props>, so subclasses get properly typed this.state, this.setState(), initialState, and this.ctx.props — the same way AIChatAgent does.

The old Config class generic was occupying the slot where Agent / AIChatAgent put State, and only ever typed a single row in the internal assistant_config k/v table. It's replaced with method-level generics on configure<T>() / getConfig<T>() so the config shape lives at the call site instead of consuming a class generic.

Migration:

// Before
export class MyAgent extends Think<Env, MyConfig> {
  getModel() {
    const tier = this.getConfig()?.modelTier ?? "fast";
  }
}

// After
export class MyAgent extends Think<Env> {
  getModel() {
    const tier = this.getConfig<MyConfig>()?.modelTier ?? "fast";
  }
}

Tests, the assistant example, docs, and the cloudflare-docs think.mdx page updated to match. Breaking change captured in a changeset.

2. RFC: Think multi-session via composition (design/rfc-think-multi-session.md)

Proposes how to do multi-session in Think before we ship 1.0, while we still have room for breaking changes:

• One Think DO = one conversation (already how Think is built).
• New Chats parent Agent for the session index + shared state; one directory DO per user/tenant, one Think DO per conversation.
• New generic RemoteContextProvider / RemoteSearchProvider in agents/experimental/memory/session/providers so a Session on one DO can read/write a context block on another DO via RPC.
• New Think#parentAgent<P>() helper.
• New useChats() React hook and examples/chats reference.
• Cleanup: drop the unused _sessionId() stub and session_id column from assistant_config.

Supersedes the unimplemented SessionManager-inside-Think plan from design/think-sessions.md. SessionManager stays available as an advanced primitive in agents/experimental but Think itself will not use it.

Rationale: DOs are single-threaded, so hosting many Sessions inside one DO would serialize inference across a user's chats. Per-chat DOs get true parallelism and scale horizontally; the rest is composition.

Includes an explicit Follow-ups section for everything intentionally left out of v1 (forks, indexed cross-chat search, LLM titles, GC/export, multi-tenant-per-directory, shared workspace across chats, the AgentContextProvider → SqliteContextProvider rename, etc.) so none of it is forgotten.

Status: proposed. Looking for feedback on the shape before any implementation commits.

Test plan

• npm run check — all 74 projects typecheck, oxfmt/oxlint/sherif/exports clean
• @cloudflare/think tests: 249/249 passing
• examples/assistant tsconfig typechecks
• @cloudflare/ai-chat programmatic-turns.test.ts — flaked once in parallel nx run-many test on my machine; passes 3/3 when run in isolation. Unrelated package to my changes; CI will give the final word.

Made with Cursor

---

[changeset-bot]

🦋 Changeset detected

Latest commit: 4c6e75a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@cloudflare/think	Minor

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[devin-ai-integration]

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