[Bug] ACP harness does not inject agent identity into system prompt — agents can drift to wrong persona under thread context pressure

[cameronhotchkies]

Summary

The ACP harness builds the system prompt as [System]\n<persona_content> but never injects the agent's own display name or pubkey. When a thread contains multiple agents, the LLM can misidentify itself as a different participant — especially when another agent is the most recently active speaker in the conversation context.

Root Cause

crates/buzz-acp/src/pool.rs — framed_system_prompt (around line 1083) constructs the full system prompt from the agent's persona text only. The harness knows the agent's display name and pubkey at spawn time (from the kind:0 profile), but does not expose this to the model.

The conversation context renderer (crates/buzz-acp/src/queue.rs, format_conversation_context around line 1339) lists every thread participant by name and pubkey but includes no marker indicating which participant the agent is. With multiple named agents in a thread, the model receives no ground truth for its own identity.

Observed Behavior

An agent authored messages attributing its responses to a different agent's name — referring to itself in the third person and adopting the other agent's framing. The author pubkey on those messages confirmed the correct agent was running; only the self-identification was wrong.

Impact

• Agent identity confusion in any thread involving two or more agents
• Worse when the non-responding agent is the most recent speaker in the context window
• Affects all agents regardless of how well their persona is written — the persona has no reliable way to self-reference because the harness never tells the model its own name

Suggested Fix

Inject a structured identity block into the system prompt at spawn time, before the persona body:

[Agent Identity]
Your display name is {display_name}.
Your pubkey (hex) is {pubkey_hex}.
In the thread context below, messages attributed to {display_name} ({pubkey_short}...) are your own prior turns.

Location: crates/buzz-acp/src/pool.rs — framed_system_prompt

This makes identity injection automatic and reliable regardless of persona quality, and removes the need for persona authors to manually anchor their agent's name.

Workaround

Adding an explicit You are <AgentName>. opener to the persona file reduces (but does not eliminate) confusion, since the conversation context still lacks a "this is you" marker.

Related

• RC1/RC2/RC3 from the agent detachment investigation (author-gate silent drops, idle timeout visibility, circuit breaker) — separate issue, same thread of user-reported pain