Langfuse and LangSmith, and Deedglass

Traces show what the agent said. Deedglass's check shows what Postgres did.

Last checked 13 October 2026

The short answer

Langfuse and LangSmith trace LLM applications and agents, and run evaluations.¹²
A trace is the agent's side of the story: each step, prompt and tool call as the application saw it.²
Deedglass checks the system's side: what Postgres committed for each write, sealed into a record.

When to choose Langfuse or LangSmith

You are debugging prompts, comparing models or measuring quality with evaluations.¹²
You want every step of an agent run traced.¹
You want to self-host for free, which Langfuse offers.¹

When Deedglass fits

Your agent writes to Postgres, and a trace that says '1 row updated' isn't enough: triggers and cascades can change hundreds.
You need writes decided before they run, and a record someone else can check offline.

Side by side

Question	Langfuse or LangSmith	Deedglass
Shows each step of an agent run	Yes: traces¹²	Each tool call it governs
Evaluations	Yes¹²	No
Decides before the call	Not described on their pricing pages (checked 13 October 2026)¹	Yes: rules decide each tool call
Checks what Postgres committed	Not described on their pricing pages (checked 13 October 2026)¹	Yes: reads Postgres's change log
Signed record of each action, checkable offline	Not described on their pricing pages (checked 13 October 2026)²	Yes
Self-host	Langfuse: free to self-host¹	Yes: free
Price (checked 13 October 2026)	Free tiers; paid plans on their pricing pages¹²	Free self-host · Pro $49 a month

Use them together

Keep your traces. Deedglass's record of each write carries the action's id, so a trace step and the check of what Postgres committed can be read side by side.

What Deedglass doesn't do

It doesn't trace prompts or model calls, and it doesn't run evaluations.
It sees only the tool calls you put behind it.

Sources

1Langfuse pricing · langfuse.com · checked 13 October 2026
2LangSmith pricing · langchain.com · checked 13 October 2026

Last checked 13 October 2026. We re-check these pages every month. If something is out of date, write to hello@deedglass.com.

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