agent-shared-memory

The persistent blackboard between Claude session A, Codex session B, and Gemini session C — none of which see each other's conversation history natively.

.coord/memory.yml is append-only. Past decisions don't get edited; they get superseded by new entries that reference what they replace. This makes it an audit trail, not a mutable scratchpad.

When to use

Trigger phrases:

• "Update the shared memory with <decision>."
• "Log this open question to shared memory."
• "What have agents decided so far on this project?"
• "What are the open questions blocking us?"
• "Initialize multi-agent shared memory for this project."
• "Give me a primer for a fresh agent session."

Not for:

• Per-task scratch (use .ai/<agent>_task_*.md from

agent-task-splitter).

• Per-round artifacts (use the round-specific files written by

reconciler / acceptance-gate).

• Project-level long-term context (use .research/project_manifest.yml

from research-context-compressor, or .paper/claims.yml from paper-memory-builder).

.coord/memory.yml is specifically the multi-agent coordination layer — short-to-medium-term decisions made during a multi-agent work cycle.

For large or cross-session work, pair this with agent-context-budget to produce .coord/session_primer.md. The primer is the bounded session input; memory.yml remains the append-only source.

Schema

Full schema in references/coord_memory_schema.md. Quick view:

project: "<repo name or research project slug>"
created_utc: "2026-04-28T09:00:00Z"

decisions:
  - id: D1
    date_utc: "2026-04-28T10:30:00Z"
    what: "Use SQLite for shared session state, not Redis"
    why: "Already a project dep; Redis would add infra"
    made_by: "claude"             # which agent / human made it
    supersedes: []                 # IDs of prior decisions this replaces
  - id: D2
    date_utc: "2026-05-02T14:00:00Z"
    what: "Switch to LMDB for shared session state"
    why: "SQLite is locking under concurrent writes from N agents"
    made_by: "user"
    supersedes: [D1]              # D1 is now historical, not current

open_questions:
  - id: Q1
    asked_utc: "2026-04-28T11:00:00Z"
    question: "Should we cache LLM responses?"
    blocker_for: ["T5", "T7"]    # task IDs from .coord/plan.yml
    suggested_next_agent: "claude"
    resolved_by: null              # set to a decision ID when answered
  - id: Q2
    asked_utc: "2026-04-30T09:00:00Z"
    question: "What's the upper bound on concurrent agent sessions?"
    blocker_for: []
    suggested_next_agent: "user"
    resolved_by: D2                # D2's switch to LMDB resolved this

artifacts:
  - path: ".coord/plan.yml"
    round: 1
    produced_by: "agent-task-splitter"
    used_by: ["codex-delegate", "gemini-delegate"]
    timestamp_utc: "2026-04-28T09:30:00Z"
  - path: ".coord/reconciliation_001.md"
    round: 1
    produced_by: "agent-output-reconciler"
    used_by: ["agent-acceptance-gate"]
    timestamp_utc: "2026-04-28T11:45:00Z"

agent_history:
  - agent: codex
    session_id: "abc123"
    started_utc: "2026-04-28T10:00:00Z"
    ended_utc: "2026-04-28T10:25:00Z"
    output_summary: ".ai/codex_result_001_extract-interfaces.md"
    status: "success"
  - agent: gemini
    session_id: "def456"
    started_utc: "2026-04-28T10:30:00Z"
    ended_utc: "2026-04-28T11:15:00Z"
    output_summary: ".ai/gemini_result_001_review-doc-coverage.md"
    status: "success"

Workflow

Read mode: produce a primer

When a new agent session starts (or the user asks "what's the state?"), generate a digest:

[agent-shared-memory] Project state — <project>

Current decisions (3):
  D2 (2026-05-02): Switch to LMDB for shared session state.
       (supersedes D1: SQLite chosen on 2026-04-28)
  D3 (2026-05-04): Use plugin-based auth architecture.
  D4 (2026-05-05): Acceptance gate runs pytest + banned-word audit.

Historical (superseded):
  D1 (2026-04-28): SQLite for shared session state. Replaced by D2.

Open questions (1):
  Q1: Should we cache LLM responses?
       Blocking: T5 (codex), T7 (gemini).
       Suggested next: claude.

Last 3 agent sessions:
  2026-05-04 codex   T8 refactor-config       success
  2026-05-04 claude  T9 review-architecture   success
  2026-05-03 gemini  T6 long-context-review   fallback (test failure)

Files most recently produced:
  .coord/acceptance_002.md (2026-05-04, agent-acceptance-gate)
  .coord/reconciliation_002.md (2026-05-04, agent-output-reconciler)

If .coord/memory.yml doesn't exist yet, say so and offer to initialize.

Append mode: log a new entry

User says "log this decision to memory: we picked LMDB over SQLite because of concurrent-write issues."

1. Read existing .coord/memory.yml (or initialize if missing).
2. Determine which list to append to (decision / open question /

artifact / agent_history).

1. Generate a new ID (D<N+1> for decisions, Q<N+1> for

questions).

1. If this supersedes prior entries, fill supersedes.
2. Atomic write: rewrite the whole file with the new entry

appended. Use a .coord/memory.yml.lock file to prevent concurrent writes corrupting the YAML:

   # Check lock
   if [ -f .coord/memory.yml.lock ]; then
     echo "memory.yml is being updated by another agent — wait or check stale lock"
     exit 1
   fi
   touch .coord/memory.yml.lock
   # ... write memory.yml ...
   rm .coord/memory.yml.lock

Locks older than 5 minutes are stale (agent crashed) — safe to remove.

Initialize mode

If .coord/memory.yml doesn't exist, ask user for project name and created_utc, then write a minimal skeleton:

project: "<name>"
created_utc: "2026-04-28T09:00:00Z"
decisions: []
open_questions: []
artifacts: []
agent_history: []

Append .coord/ to .gitignore if not already (this is multi-agent state, not project source — versioning the YAML in git is the user's choice; default is gitignore + manual snapshot when valuable).

Promotion rules

Only promote compact coordination facts:

• Decisions: one-sentence what and one-sentence why.
• Open questions: one sentence, blocker, suggested owner.
• Artifacts: relative path plus one-line summary.
• Agent sessions: agent, task ids, status, and result-summary path.

Do not promote raw logs, full diffs, source code, long analysis, or secrets. If a detail is longer than a few sentences, write an artifact file and store only its path plus summary.

Optional agentmemory mirror

If agentmemory is installed, mirror only memory candidates that pass the promotion rules. Treat agentmemory as a searchable cache:

• .coord/memory.yml is canonical.
• agentmemory recall may enrich .coord/session_primer.md.
• Missing or failed agentmemory never blocks the workflow.
• Acceptance decisions must never depend on vector recall alone.

Output to user

Read mode → digest as shown above.

Append mode:

[agent-shared-memory] Appended D5 to .coord/memory.yml:
  D5 (2026-05-08): Adopt LMDB lock-free reads for query path.
       Why: profiling showed read contention bottleneck.
       Supersedes: D4 (which assumed SQLite + WAL was enough).
       Made by: codex (during T12 review session).

Initialize:

[agent-shared-memory] Initialized .coord/memory.yml for project "ai-research-skills".
  Empty: 0 decisions, 0 open questions, 0 artifacts, 0 sessions.
  Add .coord/ to .gitignore (recommended) or commit (if you want
  audit trail in version control).

What NOT to do

• Don't edit existing entries. They're append-only. To "change"

a decision, write a new one with supersedes: [<old-id>].

• Don't read full agent log files. This skill operates on

summaries (the output_summary paths). The reconciler reads logs.

• Don't make memory a transcript. Promote decisions, open

questions, artifact pointers, and session outcomes only.

• Don't store secrets. Memory.yml is YAML in the project repo

— assume any contributor can read it.

• Don't cross domains. This is for **multi-agent coordination

state**, not research project state (.research/) or paper state (.paper/).

• Don't use this for agents that don't share a project root.

If Codex is running in /repo-A and Claude is in /repo-B, they have separate .coord/memory.yml files. This skill operates per-project.

Subagent review (keep main session lean)

When: .coord/memory.yml exceeds 50 entries OR 30 KB, OR a new agent session is about to load memory as primer.

Why: As memory grows, reading it inline in every session is costly. A subagent can pre-digest memory into a compact session primer so the main session only ingests recent + relevant entries, not the full history.

Pattern:

Spawn `general-purpose` subagent (read-only) with:
  - Read .coord/memory.yml in full
  - Filter to: (a) entries from last 14 days; (b) entries tagged
    as `principle` or `decision`; (c) entries referenced by the
    current round's plan.yml
  - Compose memory digest (≤ memory_digest_token_budget from
    context_policy, default 1200 tokens)
  - Return: digest text suitable to paste into session primer +
    promotion-candidate flags (entries that could move to a long-
    term principles file)

Main session uses the digest instead of reading memory.yml directly.

Compaction-by-promotion: if subagent flags entries as long-term principles, run a follow-up step to move them out of memory.yml into a separate principles file, keeping memory.yml bounded.

Commit Boundary

Every agent boundary is a commit boundary (see global rule: ~/.claude/CLAUDE.md → "Commit Discipline for Multi-Agent Work"). This makes multi-agent work auditable (commit log = agent log) and enables surgical rollback via git revert <hash> of just one agent's commit.

Specific to this skill: every promotion to .coord/memory.yml is its own commit with message memory: <decision-summary>. The acceptance-gate skill diffs memory commits to detect inconsistent decisions across agents.