How to give Codex persistent project context with Obsidian

A productive Codex task can learn why an architecture was chosen, which constraint cannot change, what failed previously, and what should happen next. The difficult part comes when a later task starts without that rationale.

PMC solves this by storing selected project knowledge as ordinary Markdown in an Obsidian vault. The goal is not to preserve every conversation. It is to preserve the small amount of reviewed context that future work should trust.

What belongs in project memory

Good durable context includes:

  • accepted decisions and their rationale;
  • non-negotiable requirements and constraints;
  • verified discoveries that change how the system is understood;
  • reusable procedures and debugging lessons;
  • current status, blockers, risks, and next actions.

Transient terminal output, speculative ideas, rejected approaches without lasting relevance, secrets, and complete chat transcripts do not belong in the durable vault.

Set it up with one prompt

Install PMC from the Codex Plugin Directory, open the repository, and enter:

@PMC set up lasting memory for this project in my Obsidian vault

PMC asks whether to create a vault or connect an existing one, confirms the path, registers the repository, and creates a readable Project Home. It can then inspect a small set of repository evidence to capture the project purpose, structure, commands, current state, and likely next actions.

Remember a decision

After making an important decision, enter:

@PMC remember the decision we just made

PMC summarises the proposed durable claim, checks relevant existing notes for duplication or conflict, and asks for clarification when the scope is ambiguous. The resulting note keeps rationale and evidence beside the decision rather than burying them in an old conversation.

Recall it in a new task

In a fresh task, ask:

@PMC what do we already know about authentication?

PMC loads the compact project index and current state, ranks additional notes for the question, and reads only the useful candidates. This keeps context focused rather than loading the whole vault.

Keep the memory honest

Documentation can drift. Ask:

@PMC check this project’s memory

PMC checks structural health and compares important claims with current repository evidence where safe. It distinguishes stale, conflicting, and unverified knowledge. Semantic corrections are proposed for review rather than silently treated as truth.

Why use Markdown

Markdown keeps the knowledge inspectable and portable. You can edit it in Obsidian, version it with Git, sync it using your preferred system, export it, or remove it without depending on PMC. The public plugin has no PMC account, developer server, telemetry, or raw transcript capture.

Start now

Install PMC from the Plugin Directory, then use the one-prompt setup above.

For more detail, see the quickstart and daily workflow.