diff --git a/docs/ai-coder/ai-bridge/audit.md b/docs/ai-coder/ai-bridge/audit.md
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+# Auditing AI Sessions
+
+AI Bridge groups intercepted requests into **sessions** and **threads** to show
+the causal relationships between human prompts and agent actions. This
+structure gives auditors clear provenance over who initiated what, and why.
+
+## Concepts
+
+| Term             | Definition                                                                                                                                                                                                                                            |
+|------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| **Interception** | A single intercepted request/response pair between client and provider.                                                                                                                                                |                                                                               |
+| **Thread**       | A multi-part interaction starting with a human prompt that triggers one or more tool calls, forming an agentic loop.                                                                                                                                  |
+| **Agentic loop** | A sequence of tool invocations the agent performs to satisfy a request. The model ends its turn with a tool call, the client invokes it, sends the result back, and the cycle repeats until the model has enough information to formulate a response. |
+| **Session**      | A set of threads grouped by a client-provided session key. Claude Code and Codex provide session IDs automatically; other clients may not.                                                                                                            |
+
+## Human vs. Agent attribution
+
+AI Bridge distinguishes between human-initiated and agent-initiated requests
+using the `role` property:
+
+- A message with `role="user"` indicates a human-initiated action (i.e. prompt).
+- A message with `role="assistant"` indicates a message generated by a model.
+- A message with `role="system"` indicates the system prompt for the client.
+
+The `user` role is currently overloaded by clients like Claude Code and Codex;
+they inject system instructions
+within `role="user"` blocks when using agents. AI Bridge applies a heuristic
+of storing only the **last** prompt from a block of `role="user"` messages.
+
+> [!NOTE]
+> AI Bridge cannot declare with certainty whether a request was human- or
+> agent-initiated.
+
+## LLM reasoning capture
+
+AI Bridge captures model reasoning and thinking content when available. Both
+Anthropic (extended thinking) and OpenAI (reasoning summaries) support this
+feature. Reasoning data gives auditors insight into **why** a tool was called,
+not just what was called.
+
+## Navigating the UI
+
+### Sessions list
+
+The sessions page (`http://<deployment-url>/aibridge/sessions`) lists all sessions in
+reverse-chronological order. Each row shows the last prompt, initiator, provider,
+client, token usage, thread count, and timestamp.
+
+Select one to view its full details.
+
+![Sessions](../../images/aibridge/sessions.png)
+
+### Session detail
+
+Click into a session to see a chronological causal chain of events.
+
+Within a thread, each step shows token usage, tool call details (including
+arguments and MCP server URLs), duration, and any errors or warnings.
+
+![Session detail](../../images/aibridge/session_detail.png)
+
+## Conducting a forensic audit
+
+When investigating an incident (policy violation, destructive action, etc.):
+
+1. **Identify the session.** Filter by user, time range, or client to find the
+   relevant session.
+1. **Locate the thread.** Each thread in a session shows the (likely) human prompt
+   that initiated the chain of actions.
+1. **Trace the causal chain.** Expand the thread to see every step in the
+   agentic loop — each tool call and its arguments.
+1. **Review model reasoning.** If extended thinking was enabled, check the
+   model's reasoning at each step to understand why specific tools were called.
+1. **Assess attribution.** The session identifies the human who
+   initiated the action. Subsequent interceptions represent agent-driven actions
+   that stem from that original prompt.
+
+## What we store
+
+AI Bridge captures the following data from each request/response:
+
+- Last user prompt
+- Token usage
+- Tool calls (requests only, not responses)
+  - Responses may be very large, and generally have lower audit value than requests
+  - In future, we will support storing these results
+- Model thinking/reasoning
+
+Model-produced inference text is discarded, as generated text alone
+cannot affect external systems. The retention philosophy prioritizes:
+
+- **Human prompts** — capture intent and detect policy violations or
+  exfiltration attempts.
+- **Tool calls** — record how agents interact with external systems,
+  which is critical for understanding how incidents occurred. For
+  example, an agent might delete and recreate a database because it
+  lacks permissions to satisfy a human request to query a table.
+- **Model reasoning** — preserve thinking content that explains why
+  specific tools were invoked, distinguishing between human instruction
+  and model misunderstanding as the root cause.
+
+See [data retention](./setup.md#data-retention) to configure how long
+session data is kept.
+
+## Next steps
+
+- [Monitoring](./monitoring.md) — Dashboards, data export, and tracing
+- [Setup](./setup.md) — Configure AI Bridge and data retention
+- [Reference](./reference.md) — API and technical reference
diff --git a/docs/ai-coder/ai-bridge/index.md b/docs/ai-coder/ai-bridge/index.md
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+++ b/docs/ai-coder/ai-bridge/index.md
@@ -35,6 +35,7 @@ AI Bridge is best suited for organizations facing these centralized management a
 - [Set up AI Bridge](./setup.md) on your Coder deployment
 - [Configure AI clients](./clients/index.md) to use AI Bridge
 - [Configure MCP servers](./mcp.md) for tool access
+- [Audit AI sessions](./audit.md)
 - [Monitor usage and metrics](./monitoring.md) and [configure data retention](./setup.md#data-retention)
 - [Reference documentation](./reference.md)
 
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diff --git a/docs/manifest.json b/docs/manifest.json
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--- a/docs/manifest.json
+++ b/docs/manifest.json
@@ -1167,6 +1167,11 @@
 										}
 									]
 								},
+								{
+									"title": "Auditing AI Sessions",
+									"description": "How to audit AI sessions",
+									"path": "./ai-coder/ai-bridge/audit.md"
+								},
 								{
 									"title": "Monitoring",
 									"description": "How to monitor AI Bridge",