Charles Session File Format (.chlsx)

Reference for AI agents that need to parse Charles Proxy session files.

File Format

.chlsx is a ZIP archive containing numbered XML files, each representing one HTTP request/response pair.

Structure inside the ZIP

session.chlsx
├── 00001.xml
├── 00002.xml
├── 00003.xml
├── ...
└── 00/
    ├── 00001.xml
    ├── 00002.xml
    └── ...

Files may be flat at the root or grouped in two-digit subdirectories (00/, 01/, etc.) depending on session size.

XML Structure Per File

Each XML file contains:

Request: method, URL, protocol, headers, body
Response: status, protocol, headers, body
Timing: start time, duration

Key XML elements:

<?xml version="1.0" encoding="UTF-8"?>
<session>
  <request>
    <method>GET</method>
    <url>https://discourse.example.com/t/123.json</url>
    <protocol>HTTP/1.1</protocol>
    <header name="Accept">application/json</header>
    <header name="Cookie">_t=abc123</header>
    <body></body>
  </request>
  <response>
    <status>200</status>
    <protocol>HTTP/1.1</protocol>
    <header name="Content-Type">application/json; charset=utf-8</header>
    <body>{"id": 123, "title": "...", "post_stream": {...}}</body>
  </response>
  <timing>
    <start>2026-01-15T10:30:00.000Z</start>
    <duration>450</duration>
  </timing>
</session>

.chls vs .chlsx vs .chlsj

Extension	Format	Notes
`.chls`	Binary	Legacy format, harder to parse
`.chlsx`	ZIP + XML	Prefer this. Most common modern format
`.chlsj`	JSON	Newer, less common; each session is one JSON file with an array of request/response objects

Recommendation: Configure Charles to save as .chlsx (File → Save Session As... → choose .chlsx).

Discourse API Endpoints to Look For

These are the endpoints worth extracting from a Charles session:

Purpose	URL pattern	Parsing target
Topic feed	`/latest.json`	`topic_list.topics[]`
Category topics	`/c/{slug}.json`	`topic_list.topics[]`
Single topic	`/t/{id}.json`	The full topic with posts
Posts in topic	`/t/{id}/{page}.json`	Paginated posts
Search	`/search.json?q=...`	`topics[]`, `posts[]`
User activity	`/u/{username}/activity.json`	User posts/topics

Extraction Strategy for AI

Open the .chlsx as a ZIP (it is not encrypted)
Iterate over all XML files inside
For each XML, check if the request URL matches a Discourse API endpoint
Extract the JSON response body from <response><body>
Parse the JSON and convert to Markdown
Organize by topic ID + title for easy search

Common Pitfalls

Some responses are paginated (/t/{id}.json?page=1). Collect all pages for completeness.
Binary responses (images, JS bundles) should be skipped.
The same topic may appear multiple times in different Charles sessions; deduplicate by topic ID + last updated timestamp.
Session cookies captured in Charles will be expired by the time the AI reads them; only the response data matters.

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