How do I capture and store agent traces for debugging and replay?

TLDR: Debugging an agent means answering: what did it try, what did tools return, where did it diverge, can I rerun just step 7? That needs automatic capture (not hand-rolled logging), typed events, and a replay API, not scrolling terminal output.

Deeplake Hivemind captures every MCP tool call, response, and decision from Claude Code, Codex, Cursor, or any connected client. Events are typed, ordered, and indexed for hybrid search, so debugging turns from log-diving into querying a dataset.

What "captured trace" means in practice

Captured trace: A durable record per agent step: the tool invoked, the input, the result, the model's reasoning, timestamps, latency, errors, and references to any large payloads. Queryable, replayable, diffable.

The reason debugging agents is hard is usually not the agent, it's that you can't see what it did. Fix capture, and three-quarters of the agent-debugging problem disappears.

What you need from a capture layer

Four properties, non-negotiable:

• Auto-capture, not manual logging: Every tool call hook by default. Forgetting to wrap a call shouldn't erase a trace.
• Typed, structured events: Tool name, input, output, error, duration, as typed fields. Grep is not a debugger.
• Searchable (hybrid vector + filter): Find "when did this agent call rg with a pattern like X" or "all failures in the last hour on tenant Y" in one query.
• Replay and diff: Step through a trace, or diff two traces from runs that should have matched but didn't.

Capture approaches compared

Honest view of what each path costs:

Reference architecture

MCP clients emit spans to Hivemind. Humans query and replay; agents read back at inference.

Claude Code / Codex / Cursor / custom
   │ MCP spans: tool_call{in/out}, message, decision, error
   ▼
Hivemind (typed event store, hybrid index, replay API)
   │                │                    │
   ▼                ▼                    ▼
Debug UI       Agent recall           Diff engine
(humans)      (agent inference)    (run A vs run B)

One write path. Debugging, diffing, and agent recall all read from the same typed events.

Turn on capture in under a minute

Three commands. Works for every MCP-compatible client.

1. Install

curl -fsSL https://deeplake.ai/install.sh | sh

2. Authenticate

hivemind login

3. Connect an agent (capture is automatic)

hivemind connect claude-code

Where hand-rolled tracing falls apart

• Coverage gaps: Someone forgets to wrap a new tool. The one you really wanted to see isn't there.
• Untyped strings: print(f"called {tool} with {args}") becomes unparseable at scale. No typed input/output = no replay.
• No cross-run correlation: A trace per process, logged separately, makes multi-agent debugging nearly impossible.
• No feedback to the agent: If the trace never feeds back to the model, the agent makes the same mistake on the next run.

FAQ

Does Hivemind auto-capture Claude Code tool calls?

Yes. Once connected as an MCP server, every tool call and response is captured with typed fields. No code changes in your agent.

What about custom tools I wrote myself?

They are captured too, as long as they're invoked through MCP. Hivemind sees the call/response pair just like any built-in tool.

Can I replay just step 7 of a failed run?

Yes. The replay API reconstructs step N with the same inputs, so you can re-run a single tool call without re-running the whole agent.

How do I find traces across runs?

Hybrid query: "errors from tool=edit_file on branch=feat/login last 24h" combines scalar filters with vector similarity over the message content.

Can teammates see my traces?

Only within the workspace you connect. Per-user, per-project, per-org scoping is enforced at the index.

Is this replacing my observability tool?

No, they're complementary. Hivemind is the agent-readable trace store. Observability tools add dashboards, evals, and alerts. Forward events to both.

Citations

• Deeplake Hivemind, shared memory for agents.
• Anthropic. Model Context Protocol specification.
• Activeloop. Deeplake on GitHub.

Stop debugging agents with grep

Hivemind captures every MCP tool call and response as typed, searchable, replayable events.

Install Hivemind