CONTEXT
CAPSULE
portable context for agent workflows

The context your agents need — nothing they don’t.

Free — 500 capsules/month. No credit card.

Context Capsule

Active
cap_k7x9m2nq4p1r8w3v5
Investigated auth bug in refresh token logic. Root cause: JWT refresh window expired silently. Fixed in auth/refresh.ts with extended 7-day window.
  • Extended refresh window to 7 days over sliding sessions
  • Kept legacy endpoint — 3 downstream consumers depend on it
  • Deploy to staging and run integration suite
  • Notify API consumers about deprecation timeline
> view payload
{
  "files_changed": ["src/auth/refresh.ts"],
  "test_results": "14 pass, 0 fail",
  "related_receipts": ["rct_proof1"]
}
2 Apr 2026 12:00 expires 3 Apr 2026
01
Create

Package your agent’s working context into a capsule — decisions, findings, next steps.

# POST /v1/capsules { "summary": "Investigated auth bug. Fixed in auth/refresh.ts.", "decisions": ["Extended refresh window to 7 days"], "next_steps": ["Deploy to staging", "Notify consumers"], "idempotency_key": "auth-fix-session-42" }
02
Fetch

The next agent loads the capsule. Structured context, no re-discovery, no token waste.

# GET /v1/capsules/cap_k7x9m2nq4p1r8w3v5 { "id": "cap_k7x9m2nq4p1r8w3v5", "summary": "Investigated auth bug. Fixed in auth/refresh.ts.", "decisions": ["Extended refresh window to 7 days"], "next_steps": ["Deploy to staging", "Notify consumers"], "expires_at": "2026-04-03T12:00:00Z" }
03
Expire

Capsules auto-expire. Default 24 hours, up to 7 days. No stale context, no cleanup.

For humans
Shareable URL
Every capsule has a readable page. Share the link to see exactly what context was handed off — decisions, next steps, payload.
For agents
JSON API
Same capsule, machine-readable. Your agent fetches structured context and picks up exactly where the last one left off.
Content negotiation — same URL, different formats.
Full conversation?
50k tokens of noise to find 500 tokens of signal.
A summary?
Lossy. Misses decisions, open questions, structured data.
A shared database?
Couples your agents. No expiry, no structure, no portability.
Context Capsule gives the next agent compressed, structured, expiring context it can act on immediately.
Wasted tokens
Agent B re-discovers everything Agent A already found because the raw conversation was too long to pass.
Without capsules

Agent A spends 50k tokens researching a bug. Agent B gets a one-line summary. Spends another 40k tokens re-investigating the same code paths.

With Context Capsule

Agent A creates a capsule with summary, decisions, and next_steps. Agent B loads 500 tokens of structured context and starts at step 4.

Lost decisions
A handoff agent reverses a critical decision because it was buried in conversation history.
Without capsules

Agent A decided to keep the legacy endpoint. Agent B doesn’t know this, deletes it. Three services break.

With Context Capsule

The capsule’s decisions field explicitly lists “kept legacy endpoint — 3 consumers depend on it.” Agent B reads it and leaves it alone.

Context overflow
An agent’s context window fills up with stale handoff data from three sessions ago.
Without capsules

Each handoff dumps more text into the context window. By session 4, the agent is hallucinating against outdated information from session 1.

With Context Capsule

Each capsule expires. The agent only loads the most recent one. Chain them via parent_capsule_id if you need history. Fresh context, always.

ProofSlip
Verification
Did it happen? Ephemeral receipts your agents verify before they act. Proof of past actions.
Context Capsule
Knowledge
What do I need to know? Structured handoff packets that carry decisions, findings, and next steps forward.
Capsules reference receipts. Receipts prove what capsules describe. proofslip.ai →
npx -y @contextcapsule/mcp-server
Works with Claude Desktop, Cursor, Windsurf, and any MCP client.